What are split-brain studies? |

Introduction

The study of laterality, or the specialized asymmetric functions throughout the body, is not a new and novel field, as might be suggested by the popularization of “left brain-right brain” dichotomies. Lateralization of functions in the brain, sometimes referred to as hemispheric asymmetries, was demonstrated in 1861 by Paul Broca, a well-known physician at the time. He found that patients suffering from damage to certain regions of the left cerebral hemisphere exhibited more frequent speech and language disorders than did those with right cerebral hemisphere damage. Based on these findings, Broca correctly reasoned that the left hemisphere is specialized for speech and language in the vast majority of people. However, these results were quickly transformed into an overly simplistic dichotomization of cerebral functioning in which the left hemisphere was conceptualized as the dominant hemisphere and the right hemisphere as a rather minor, perhaps even unimportant, hemisphere. From split-brain studies performed since 1940, it has become obvious that the right hemisphere is essential for normal visuospatial functioning.

Commissurotomy Effects

Split-brain surgery, sometimes referred to as commissurotomy, was first performed on a human patient by the neurosurgeon William Van Wagenen in 1940 to reduce the severity of life-threatening epileptic seizures. Other early commissurotomies were performed by two neurosurgeons, Philip Vogel and Joseph Bogen. The rationale for commissurotomies is rather simple: By severing the cerebral commissures, the major interconnecting fiber bundles that allow communication between the cerebral hemispheres, surgeons can prevent epileptic seizures from spreading beyond their focal hemisphere. Commissurotomies are performed only as a last resort, after traditional drug therapy fails to control seizure activity.

Surprising as it may seem, commissurotomy patients show few long-term alterations in behavior. All subjects suffer from acute disconnection syndrome, in which they are mute and partially paralyzed on the left side of the body for an interval ranging from a few days to a few weeks. Otherwise, commissurotomy patients exhibit relatively normal behavior. Moreover, the severity and frequency of seizure activity decline, sometimes quite dramatically, in response to this surgical procedure.

Hemispheric Asymmetries in Information Processing

On closer examination with a tachistoscope (an experimental apparatus for presenting visual information very briefly to the right or left visual field, sometimes called a T-scope) of split-brain patients, however, hemispheric asymmetries in information processing are evident. These asymmetries are investigated in T-scope or divided visual field studies. The split-brain patient is required to fixate on a central point, while visual stimulation is presented to the right or left visual field. Assuming that the patient is fixated on the central point, stimulation in the right visual field is projected to the left hemisphere, and left visual field stimulation to the right hemisphere. Once the information is available to the left or right hemisphere of a split-brain patient, it is not able to cross the cerebral commissures, principally the corpus callosum, because those fibers have been partially or completely severed.

The pioneering studies of the divided visual field in split-brain patients are described in The Bisected Brain (1970) by Michael Gazzaniga, who was a coprincipal investigator with Roger Sperry in those studies. In one of their investigations, pictures of common objects were presented to either the right visual field or the left visual field of split-brain patients. All patients were able to identify the information verbally when it was presented in the right visual field (left hemisphere), but not in the left visual field (right hemisphere). These results suggested specialization for verbal tasks in the left cerebral hemisphere but did not address functioning in the right cerebral hemisphere.

To assess the psychological functions of the right cerebral hemisphere, the researchers repeated the procedure described in the previous experiment, except that subjects were asked to reach under a curtain with their left or right hand to select the object from among several alternatives (rather than verbally identifying the picture of the object). Subjects were able to perform this task competently with their left hand, which is controlled primarily by the right cerebral hemisphere. Therefore, stimulation presented to the left visual field is projected to the right cerebral hemisphere, which controls the left hand. The opposite is true for stimulation presented to the right visual field. Correct identification of objects with the left hand indicated right cerebral hemisphere involvement in recognition of nonverbal stimuli.

Support for the superiority of the right hemisphere on visuospatial tasks came from a study in which split-brain patients were required to assemble patterned blocks into particular designs. Even though all patients were right-handed, they were much better at this task with the left hand, presumably because the right cerebral hemisphere controls that hand. Yet another test of the abilities of the left cerebral hemisphere was performed by requesting subjects to copy pictures of line drawings. Again, despite being right-handed, all subjects performed better with the left hand. Their left-handed efforts were rather clumsy, but the spatial dimensions of the line drawings were proportionally correct. Overall, split-brain studies seem to indicate left-hemisphere superiority on verbal tasks and right-hemisphere superiority on nonverbal, visuospatial tasks.

Further proposals for differences between the right and left hemispheres have been suggested from split-brain research. For example, it now appears that the left hemisphere is specialized for verbal tasks, but only as a consequence of its analytical, logical, information-processing style—of which language is one manifestation. Similarly, the right hemisphere is specialized for visuospatial tasks because of its synthetic, holistic manner of processing information. Support for these hemispheric asymmetries was derived from a 1974 study conducted by Jere Levy in which split-brain patients were given ambiguous instructions; they were simply to match similar pictorial stimuli. These pictures could be matched either by their functions, such as a cake on a plate matched with either a spoon or a fork, or by their appearance, such as a cake on a plate matched with a hat with a brim. When the pictures were presented to the right visual field (left hemisphere), matching was accomplished by function, while pictures projected in the left visual field (right hemisphere) were matched according to appearance. Matching by function was construed to involve logical, analytical information processing; matching by appearance was interpreted as involving holistic, synthetic information processing.

Most of the basic findings on hemispheric asymmetries in split-brain patients have been extended to normal subjects whose cerebral commissures are intact, with the exception that right-hemisphere superiority for visuospatial tasks seems to be slightly weaker in normal subjects. Investigations with normal subjects require measurement of reaction time, because information projected to one visual field can quickly and easily transfer to the opposite hemisphere.

In the twenty-first century, Gazzaniga and others have also begun to research how the hemispheres interact with one another in subjects with intact brains. These studies have found that right-hemisphere regions of the brain are more likely to interact across hemispheres, while left-hemisphere regions often interact primarily with each other, and that inter-hemispheral communication is greater when a stimulus is introduced to the side of the brain that is not specialized for it (e.g. if verbal information is introduced to the right hemisphere instead of the left).

Real-World Phenomena

When generalizing basic laboratory research findings to real-world situations, it is important to note that information transfer across the cerebral commissures is nearly instantaneous in normal subjects. In addition, the real-world environment provides prolonged visual stimulation, which is typically scanned with continuous eye movements. In these situations, environmental stimulation is available to both cerebral hemispheres. Therefore, one must be cautious not to overstate the case for a relationship between hemispheric asymmetries and real-world phenomena. The two cerebral hemispheres do work in combination as a unified brain in normal subjects. Even in split-brain patients, the prolonged availability of environmental stimulation and continuous eye scanning movements result, for the most part, in unified overt behavior. Behavioral, perceptual, and motor differences in split-brain patients are evident only with highly specialized and artificial laboratory testing with such instruments as the tachistoscope. Generalizations, then, from divided visual field studies of asymmetry to everyday situations require actual research evidence rather than the speculation that is popular among some segments of both the scientific and lay community.

Stuttering Research

Stuttering
is one real-world phenomenon for which laterality research has practical implications. There is some evidence that stutterers are bilaterally represented for speech and language to a greater extent than are nonstutterers. In one investigation, R. K. Jones, a neurosurgeon, was presented with four stutterers who had blood clots or tumors located near the normal speech center in the left hemisphere. Because of concern that removal of the blood clots or tumors would produce muteness in his patients by damaging the speech center, Jones performed the Wada test to determine where the speech center was located in each patient. This test involves the injection of an anesthetic agent, sodium amobarbital, into the right or left carotid artery. The carotid arteries provide the frontal regions of the brain, where the speech center is located, with oxygenated blood. The sodium amobarbital anesthetizes the particular hemisphere into whose carotid artery the drug is injected. If speech is disrupted by this procedure, either the speech center is located in the opposite hemisphere or the patient is bilaterally represented for speech. Additional testing of the opposite hemisphere will reveal whether the patient is bilaterally represented.

Using this procedure, Jones found that all four stutterers possessed bilateral speech representation. After the surgery, all four patients stopped stuttering and began to speak normally. These findings raise the question as to why stuttering is related to bilateralization of speech functions. One explanation is that stuttering occurs in these patients because, unlike normal people, they have a speech center in one hemisphere that is competitive with the speech center in the opposite hemisphere. Neural impulses from the two speech centers arrive out of synchrony at the muscles that control speech, which produces stuttering. What are the practical implications of these findings? It is quite obvious that producing irreparable damage to the brain for the sole purpose of eliminating a speech disorder, such as stuttering, would be highly unethical at current levels of medical technology and knowledge about the brain. Additional research on the hemispheric basis of stuttering will need to be conducted, and technological advances will be required before stuttering can be eliminated in bilaterally represented patients by means of neurosurgery; however, findings such as these may be increasingly useful in future applications of laterality research.

Dyslexia Research

Yet another phenomenon linked with laterality research is dyslexia, a disorder of reading that is not associated with sensory impairment, retardation, or emotional disturbances. In 1937, a physician by the name of Samuel T. Orton was the first to propose a link between hemispheric asymmetries and dyslexia. He observed mirror-image reversals of letters and words in reading and writing among children with reading problems. Orton also noted that many of these children exhibited unstable hand preferences, often accomplishing tasks normally reserved for a preferred hand with either hand on a given occasion. To account for these observations, Orton proposed that these children were insufficiently lateralized for speech and language functions. In other words, neither hemisphere was specialized for speech and language.

Evidence to support the hypothesis that dyslexia is attributable to incomplete lateralization was generated in 1970 by E. B. Zurif and G. Carson, who compared the performance of fourteen normal readers in the fourth grade with fourteen dyslexic fourth graders on a dichotic listening task. Dichotic listening involves presenting simultaneous, competing verbal stimuli of differing content to each ear through headphones. The subjects’ task is to identify the words, letters, or digits presented to each ear. Since the right ear primarily transmits auditory input to the left hemisphere, and the left ear to the right hemisphere, detectable differences in the processing of verbal stimulation can be used to suggest hemispheric asymmetries. In the foregoing study, presentation of a dichotic digits task showed a significant right-ear (left-hemisphere) advantage for the normal children and a weak, insignificant left-ear (right-hemisphere) advantage for the dyslexic children. Failure to find a significant hemispheric advantage in processing dichotically presented verbal stimulation suggests that dyslexic children may, indeed, be incompletely lateralized for speech and language. Before practical applications of this finding are realized, further explorations on the development of hemispheric asymmetries will be necessary to determine whether lateralization of functions can be influenced by environmental manipulation. Only if such modifications are possible can the development of incomplete lateralization be altered in dyslexics.

Early Roots of Research

Modern research on hemispheric asymmetries has its origins in a short paper read at an 1836 medical conference in Montpellier, France. Marc Dax, an obscure country physician, reported that aphasia
(any loss of the ability to use or understand language) is related to left-hemisphere brain damage and concluded that each hemisphere is specialized for different function. Unfortunately, the paper received little attention and Dax died the following year, never knowing that he had anticipated one of the most exciting and productive research fields to emerge in the twentieth century. Because Dax’s paper was not widely known, credit for the discovery of hemispheric asymmetries was incorrectly given to Broca, who presented a similar paper in 1861 to a meeting of the Society of Anthropology in Paris. Broca does deserve some of the credit for the discovery of hemispheric asymmetries in that he suggested an exact area of the left frontal lobe that produces an expressive aphasia when damaged. Furthermore, Broca presented a much more impressive case for left-hemisphere lateralization of speech and language; his paper was received with enthusiasm and controversy.

In 1868, British neurologist John Hughlings Jackson proposed the idea of a “leading” hemisphere, which preceded the modern concept of “cerebral dominance,” the idea that one hemisphere is dominant for psychological functions over the other hemisphere. By 1870, Carl Wernicke, a German neurologist, had presented evidence that a specific region of the temporal lobe in the left cerebral hemisphere is essential for comprehending language and, when damaged, produces a receptive aphasia. In combination, these findings led to a widely held position that one hemisphere, usually the left, is dominant for verbal tasks and other higher functions, while the opposite hemisphere, usually the right, possesses no special function or only minor, limited functions. Even though the term “cerebral dominance” is still used today, it is generally recognized that there are no “major” or “minor” hemispheres; they are simply specialized for different tasks and information-processing styles.

The strongest early evidence for a specific function mediated primarily by the right hemisphere came from widespread assessment of brain-damaged patients on spatial relationship tests. After testing more than two hundred brain-damaged patients, T. Weisenberg and K. E. McBride concluded in 1935 that the right hemisphere is specialized for spatial relationships. These results refuted the notion of a single dominant hemisphere for all psychological functions.

Modern contributions made by Sperry, Gazzaniga, and their colleagues have been, perhaps, most instrumental in establishing the functions of the cerebral hemispheres. Their results, as well as those of neuropsychologists, have been incorporated into such areas as biological psychology, cognition, and perception. Biological psychologists are concerned with establishing the functions of various brain structures in normal subjects, including the cerebral hemispheres. Neuropsychologists contribute to laterality research by specifying the cognitive, motor, and behavioral deficits that arise following brain damage to a specific region in the cerebral cortex. Laterality research also provides information about hemispheric specialization for cognitive and perceptual processes.

Future explorations on laterality will continue to examine performance for specific tasks and information-processing strategies in each hemisphere, but with greater emphasis on localizing functions to specific brain structures. In addition, more effort will be expended on developing practical applications of laterality research in clinical and educational settings.

Bibliography

Bakker, Lars N., ed. Brain Mapping Research Developments. New York: Nova Biomedical, 2008. Print.

Davidson, Richard J., and Kenneth Hugdahl, eds. Brain Asymmetry. Cambridge: MIT P, 1996. Print.

Doron, Karl W., Danielle S. Bassett, and Michael S. Gazzaniga. "Dynamic Network Structure of Interhemispheric Coordination." Proceedings of the National Academy of Sciences 109.46 (2012): 18661–8. Print.

Gotts, Stephen J., et al. "Two Distinct Forms of Functional Lateralization in the Human Brain." Proceedings of the National Academy of Sciences 110.36 (2013): E3435–44. Print.

Hellige, Joseph B. Hemispheric Asymmetry: What’s Right and What’s Left. Cambridge: Harvard UP, 1993. Print.

Hugdahl, Kenneth, and Richard J. Davidson, eds. The Asymmetrical Brain. Cambridge: MIT P, 2003. Print.

Laureys, Steven, and Giulio Tononi. The Neurology of Consciousness: Cognitive Neuroscience and Neuropathology. London: Academic, 2009. Print.

Springer, Sally P., and Georg Deutsch. Left Brain, Right Brain. 5th ed. New York: Freeman, 1997. Print.

What is HIV/AIDS support? |

Proposed Natural Treatments

Among the many proposed natural treatments for HIV, none has more than preliminary supporting evidence.

Inhibiting viral replication. No natural remedies rival the effectiveness of antiretroviral drugs for inhibiting HIV replication in the body. However, preliminary research suggests that an extract of the leaves and stems of the boxwood shrub may have at least some efficacy. Many other herbs and supplements have been proposed, but there is little evidence that they work.

Boxwood. In a double-blind, placebo-controlled study of 145 people with HIV, French researchers studied the effects of two doses of a preparation made from the evergreen boxwood (Buxus sempervirens). The preparation was given in doses of 990 milligrams (mg) and 1,980 mg per day for periods ranging from four to sixty-four weeks.

When participants started the study, they had no symptoms of HIV and had never taken antiretroviral drugs. They were kept off anti-HIV drugs during the study. (This was before the use of anti-HIV drugs became widespread.) At the end, researchers found that among those taking the lower dose, fewer people developed AIDS, symptomatic HIV, or CD4+ counts below 200 compared with those taking the higher dose or placebo. Additionally, by the end of their treatment period, fewer people in the low-dose group had a large increase in the amount of HIV they carried compared with the other two groups.

The researchers had originally planned the study to continue for eighteen months (seventy-eight weeks). However, as the study progressed, a review committee decided to halt the study early when the average participant had taken boxwood or placebo for only thirty-seven weeks. The review committee felt it was unethical to continue to have some people take placebo, given the positive results among those taking the extract. Nonetheless, further research is necessary to confirm the effectiveness of boxwood extract for HIV, particularly with proven antiviral drugs, which have now become the standard of care for HIV infection.

No severe side effects were reported in this study, and the people taking boxwood had the same overall rate of side effects as those taking placebo. However, there are some safety concerns with this herb. A substance called cycloprotobuxine is believed to be one of the active ingredients in boxwood. High doses of this substance can cause vomiting, diarrhea, muscular spasms, and paralysis. The herb should only be taken under medical supervision. Safety in pregnant or nursing women, young children, and people with liver or kidney disease has not been established. In addition, touching fresh boxwood leaves can occasionally cause skin irritation.

Only a special boxwood extract has been studied as a treatment for HIV infection. One should not try to use raw boxwood leaf because it might not be safe.

Other proposed natural treatments. One of the constituents of the
herb aloe, acemannan, has shown some promise in test-tube and animal studies for
stimulating immunity and inhibiting the growth of viruses. These findings have led
to trials of acemannan (or whole aloe) for the treatment of HIV
infection. However, a double-blind, placebo-controlled trial of acemannan failed
to find any benefits for people with severe HIV infection. (There is some question
whether the effects seen in these studies were actually caused by acemannan or by
a contaminant called aloeride.)

Other substances that have been investigated for possible HIV suppression include bacailin (Chinese skullcap), curcumin, elderberry, schisandra, spirulina, and reishi. However, as with aloe, the evidence that they work is primarily limited to test-tube and animal studies; whether these results translate into real improvement among people with HIV has not been determined.

The herb St.
John’s wort contains a substance called hypericin, which has
been investigated for possible anti-HIV effects. However, contrary to popular
belief, neither hypericin nor St. John’s wort is useful for treating HIV
infection. In addition, St. John’s wort seriously impairs the activity of standard
HIV medications and might lead to treatment failure.

Enhancing the immune system. In test-tube studies, a number of substances have been found to improve measures of immunity in HIV infection, for example, by elevating CD4+ counts, changing the ratio between CD4+ cells and other immune cells, increasing amounts of other immune chemicals, or enhancing the body’s ability to attack invading substances. However, there is relatively little information on whether they can actually help people with HIV infection.

N-acetylcysteine. One of the natural substances most widely used
by people with HIV in hopes of enhancing immune system function is the antioxidant
N-acetylcysteine (NAC), but evidence that it helps is
somewhat conflicting. NAC is a specially modified form of the dietary amino acid
cysteine. NAC supplements help the body make the important antioxidant enzyme
glutathione. Early human trials, including a double-blind
study of forty-five people, suggest that NAC may increase levels of CD4+ cells in
healthy people and slow CD4+ cell decline in people with HIV infection. Another
study of NAC combined with selenium had mixed results, affecting T-cell counts in
some people but not in others. However, preliminary results of another study found
that NAC had no effect on CD4+ counts or the amount of HIV in the blood. Whey
protein also contains cysteine and may increase glutathione levels, but there is
no evidence of any meaningful benefit.

Other proposed natural treatments. One study found evidence that the amino acid methionine taken at a dose of 2.4 g daily may mildly improve immune function in people with HIV infection. Other natural treatments that are sometimes recommended to boost immunity in HIV include andrographis, trichosanthin (compound Q), lipoic acid, coenzyme Q10, maitake, a component of licorice known as glycyrrhizin, Momordica charantia (an herb also called bitter melon), echinacea, ginseng, omega-6 fatty acids, carnitine, and proteolytic enzymes. However, there is no real evidence that these treatments actually work. Garlic is sometimes recommended too, but for safety reasons it should be avoided by persons with HIV infection.

Fish
oil is also sometimes recommended for enhancing immunity in
HIV infection. However, one six-month, double-blind study found that a combination
of the omega-3 fatty acids in fish oil plus the amino acid arginine was no more
effective than placebo in improving immune function in people with HIV infection.
Another study found that the hormone dehydroepiandrosterone (DHEA) does not
improve immunity in people with HIV infection.

Study results are mixed on whether massage therapy can improve measures of
immune function. A careful review of thirty-five randomized trials found that
relaxation
therapies may be generally helpful at improving the quality
of life of HIV-positive persons and in reducing their anxiety, depression, stress,
and fatigue. These interventions, though, had no significant effect on the growth
of the virus, nor did they influence immunologic or hormonal activity.
Subsequently, however, a small study involving forty-eight persons with HIV found
that mindfulness meditation, a popular method for inducing the relaxation
response, slowed the loss of the specific immune cells destroyed by the virus,
though more research needs to be done to confirm this result.

Treating other symptoms and opportunistic infections. In addition to the foregoing treatments, a number of natural remedies have been proposed for symptoms of HIV or common opportunistic infections. Bovine colostrum has been suggested as a treatment for the chronic diarrhea that commonly occurs in people with HIV or AIDS, but the evidence that it works is weak at best.

Tea tree oil and cinnamon have been suggested as treatments for thrush (oral candida infection). There is some evidence that capsaicin cream applied topically is beneficial for limb pain caused by peripheral neuropathy associated with HIV infection.

DHEA is a hormone that seems to decrease in people with AIDS, possibly because of malnutrition and stress. One small double-blind trial suggests that DHEA (50 mg per day) may improve mood and fatigue scores in people with HIV; another small trial found inconclusive results. A more substantial (145-participant) double-blind study found that DHEA at a dose of 100 to 400 mg daily improved symptoms of dysthymia (minor depression) in people with HIV, without significant adverse effects. DHEA does not appear to provide general benefits for people with HIV, such as improving immunity, suppressing virus levels, or aiding weight maintenance.

Chinese herbal combinations have been investigated for the treatment of HIV, but the results have not been very promising. In a twelve-week, double-blind, placebo-controlled trial, thirty HIV-infected adults with CD4+ counts of 200 to 500 were given a Chinese herbal formula containing thirty-one herbs. The results hint that the use of the herbal combination might have improved various symptoms compared with placebo, but none of the differences were statistically significant. People who believed they were taking the real treatment showed significant benefit regardless of whether they were in the placebo group or the real treatment group.

In another double-blind, placebo-controlled trial, sixty-eight HIV-positive adults were given either placebo or a preparation of thirty-five Chinese herbs for six months. The results indicate that the use of Chinese herbs did not improve symptoms or objective measurements of HIV severity. In fact, people using the herbs reported more digestive problems than those given placebo.

Fighting weight loss. Undesired weight loss is a frequent symptom
of HIV and AIDS. Weight loss can be so extreme that the person seems to “waste
away,” hence the name “AIDS wasting syndrome,” which is technically defined as the
loss of more than 10 percent of body weight combined with either chronic diarrhea
or weakness and fever. Many factors can contribute to this weight loss, including
loss of appetite, nausea, malabsorption of nutrients, and mouth sores.
Supplemental medium-chain triglycerides (MCTs), a particular type of fat,
and glutamine may be helpful for this symptom, although there is no definitive
evidence that they work.

MCTs. Fat malabsorption is particularly common in HIV infection and can lead to both diarrhea and weight loss. MCTs, which are more easily absorbed than ordinary fats (long-chain triglycerides), may help decrease diarrhea and wasting. Two small, double-blind studies have found that MCTs are more easily absorbed than long-chain triglycerides in people with HIV or AIDS. However, there is no direct evidence that MCTs actually help people gain weight. In both of these studies, participants consumed nothing but a special nutritional formula containing MCTs. Taking MCTs in this way requires medical supervision to determine the dose. People with HIV or diabetes should not use MCTs (or any other supplement) without a doctor’s supervision.

Glutamine. Another promising treatment for wasting is the amino
acid glutamine, a substance that plays a role in maintaining the
health of the immune system, digestive tract, and muscle cells. Although research
is still preliminary, one double-blind, placebo-controlled study found that a
combination of glutamine and antioxidants (vitamins C and E, beta-carotene,
selenium, and N-acetylcysteine) led to significant weight gain in people with HIV
who had lost weight. Another small, double-blind trial found that combination
treatment with glutamine, arginine, and beta-hydroxy beta-methylbutyrate could
increase muscle mass and possibly improve immune status.

Other natural treatments. Whey protein is sometimes recommended for weight gain in HIV, but evidence that it works is preliminary at best. One study found that while exercise improved weight gain, whey protein alone or with exercise offered no benefit. Fish oil might be helpful for weight gain, however.

Treating the side effects of medication. Several natural treatments have been proposed to treat side effects from various medications used in the treatment of HIV infection. Reverse transcriptase inhibitors, such as lamivudine and zidovudine, may damage mitochondria, the energy-producing subunits of cells. The supplement CoQ10 has been tried for minimizing side effects attributed to mitochondrial damage. In one study, the use of CoQ10 improved sense of well-being in asymptomatic people with HIV infection; however, it actually worsened pain symptoms in people with peripheral neuropathy.

Taking AZT (zidovudine, formerly called azidothymidine) can lead to
zinc deficiency, which may interfere with immune function. One partially blinded
study found that zinc supplements may benefit people on AZT. In the zinc-treated
group, body weight increased or stabilized, CD4+ count rose, and participants had
significantly fewer opportunistic infections.

Carnitine has also been proposed as a treatment for AZT side
effects, based on early evidence that it may keep AZT from damaging muscle cells.
Other weak evidence hints that the acetyl form of carnitine might reduce
nerve-related side effects caused by HIV drugs in general.

Based on preliminary evidence, vitamin B12 has been suggested as a preventive for blood abnormalities caused by AZT. In one well-designed, double-blind study, the use of the amino acid glutamine at a dose of 30 grams (g) daily significantly reduced the diarrhea caused by the protease inhibitor nelfinavir. Presumably, glutamine would be helpful for other protease inhibitors.

It has been suggested that the supplement NAC might help prevent side effects from the antibiotic TMP-SMX (trimethoprim-sulfamethoxazole). However, two controlled studies found that NAC did not significantly decrease adverse reactions to TMP-SMX. Note, however, that TMP-SMX is known to decrease folate levels in the body, and folate supplements might therefore be useful.

The herb milk thistle is sometimes recommended for preventing liver problems related to the use of HIV medications. While there is no direct evidence that it is helpful for this purpose, there is fairly good evidence that the use of milk thistle does not adversely affect blood levels of indinavir.

General nutrition support. People infected with HIV may be particularly vulnerable to malnutrition because of decreased appetite, poor absorption, or possibly increased requirements for specific nutrients. Studies have found deficiencies of vitamins A, B1, B6, B12, and E, beta-carotene, choline, folate, selenium, and zinc to be common among people with HIV infection. Many deficiencies become more common as the disease worsens. This suggests, but does not prove, that taking supplements of these nutrients may be helpful. One study evaluated whether the use of a multivitamin tablet might reduce infectivity of African women with HIV infection. Researchers unexpectedly found the opposite: Multivitamin tablets increase the levels of HIV in the genital area. The reason for this surprising finding is unknown. It is not clear whether the same response would occur among people living in developed countries who, presumably, have better underlying nutrition.

Vitamin A, beta-carotene, and mixed carotenoids.
Vitamin
A and beta-carotene are described together
here because the body uses beta-carotene to produce vitamin A. Substances called
carotenoids are closely related to vitamin A; this family includes lutein and
lycopene.

Vitamin A deficiency may be linked to lower CD4+ counts and to higher death rates among HIV-positive people. A few preliminary studies have raised hopes that beta-carotene supplements might increase or preserve immune function or decrease symptoms among HIV-positive persons. One small, double-blind study suggested that taking beta-carotene might raise white blood cell count in people with HIV infection. However, two subsequent larger controlled trials found no significant differences between those taking beta-carotene or placebo in white blood cell count, CD4+ count, or other measures of immune function.

Two observational studies lasting six to eight years suggest that higher intakes of vitamin A or beta-carotene may be helpful, but they also found that caution is in order with regard to dosage. This group of researchers generally linked higher intake of vitamin A or beta-carotene to lower risk of AIDS and lower death rates, with an important exception: People with the highest intake of either nutrient (more than 11,179 international units [IU] per day of beta-carotene, more than 20,268 IU per day of vitamin A) did worse than those who took somewhat less. Excessive dosages of vitamin A can be toxic to the liver. One should consult with a physician about the right dose.

At one point it was thought that vitamin A supplements might decrease the rate of transmission of HIV from a pregnant woman to her newborn. However, it now appears that the reverse may be true: Vitamin A may increase the chance of such transmission.

One double-blind study found statistically weak evidence that the use of mixed carotenoids by persons with AIDS might prolong life.

B vitamins. An observational study found that HIV-positive men with the highest intakes of vitamins B1, B2, and B6 and niacin had significantly longer survival rates, while a similar study found that those taking the most B1 or niacin had a significantly lower rate of developing AIDS.

Vitamin B12 deficiencies in people infected with HIV have been linked to neurologic symptoms, including slower processing of information in studies of cognitive functioning; early research suggests that restoring B12 levels to normal may decrease these symptoms. Vitamin B12 deficiency has also been linked to lower CD4+ counts and more rapid development of AIDS.

Vitamin B6 deficiency has been linked to impaired immune function in one study of people with HIV infection. Excessive intake of vitamin B6 can cause neurologic problems.

Vitamins C and E. Massive doses of vitamin C
have at times been popular among people with HIV based on preliminary evidence. An
observational study linked high doses of vitamin C with slower progression to
AIDS. High intake of vitamin E was also linked to decreased
risk of progression to AIDS in a different observational study.

However, a double-blind study of forty-nine people with HIV who took combined vitamins C and E or placebo for three months did not show any significant effects on the amount of HIV detected or the number of opportunistic infections. It has been suggested that vitamin E may enhance the antiviral effects of AZT, but evidence for this is minimal.

Choline. The substance choline has been newly added to the
list of essential nutrients. Evidence suggests that people with HIV who are low in
choline may experience more rapid disease progression.

Iron. A study of seventy-one HIV-positive children noted a high rate of iron deficiency. One observational study of 296 men with HIV infection linked high intake of iron to a decreased risk of AIDS six years later. One should not take iron supplements, however, unless one is iron deficient.

Selenium.
Selenium is required for a well-functioning immune system.
Observational studies have linked higher levels of selenium in the blood with
higher CD4+ counts and reduced risk of mortality from HIV disease. Selenium
deficiency may also increase the infectiousness of women who are HIV positive.

In a double-blind, placebo-controlled study of 450 people with HIV, the use of selenium supplementation at a dose of 200 micrograms (mcg) per day appeared to reduce measures of viral load. However, the statistical method used in this study is somewhat questionable. Previous smaller studies using more standard statistical methods failed to find such effects.

In one double-blind, placebo-controlled study, the use of selenium at a dose of 200 mcg decreased anxiety in patients undergoing HAART. Selenium has also been proposed as a preventive or treatment for cardiomyopathy, a disorder of the heart muscle that can affect people with AIDS. Evidence of its benefits is weak.

Zinc. Some studies have found that HIV-positive people tend to be
deficient in zinc, with levels dropping lower in more severe disease. It remains
unclear whether taking zinc will help.

Higher zinc levels have been linked to better immune function and higher CD4+ cell counts, whereas zinc deficiency has been linked to increased risk of dying from HIV infection. One preliminary study among people taking AZT found that thirty days of zinc supplementation led to decreased rates of opportunistic infection over the following two years.

Other research has linked higher zinc intake to more rapid development of AIDS. In another study of HIV-positive people, those with higher zinc intake or those taking zinc supplements in any dosage had a greater risk of death within the following eight years. However, one study found that the use of zinc supplements could reduce diarrhea symptoms in people with HIV infection.

Multivitamins. Because so many nutrients are affected by HIV infection and treatments, multivitamin supplements are a logical choice. A double-blind study of forty people on HAART found that the use of a multinutrient supplement improved CD4 counts and possibly improved neuropathy symptoms. As indicated by a foregoing study that evaluated whether the use of a multivitamin tablet might reduce infectivity of African women with HIV, multivitamin tablets actually increased the levels of HIV in the genital area.

Abrams, D. I., et al. “Dehydroepiandrosterone (DHEA) Effects on HIV Replication and Host Immunity.” AIDS Research and Human Retroviruses 23 (2007): 77-85.

Agin, D., et al. “Effects of Whey Protein and Resistance Exercise on Body Cell Mass, Muscle Strength, and Quality of Life in Women with HIV.” AIDS 15 (2001): 2431-2440.

Austin, J., et al. “A Community Randomized Controlled Clinical Trial of Mixed Carotenoids and Micronutrient Supplementation of Patients with Acquired Immunodeficiency Syndrome.” European Journal of Clinical Nutrition 60 (2006): 1266-1276.

Baeten, J. M., et al. “Selenium Deficiency Is Associated with Shedding of HIV-1-infected Cells in the Female Genital Tract.” Journal of Acquired Immune Deficiency Syndromes 26 (2001): 360-364.

Birk, T. J., et al. “The Effects of Massage Therapy Alone and in Combination with Other Complementary Therapies on Immune System Measures and Quality of Life in Human Immunodeficiency Virus.” Journal of Alternative and Complementary Medicine 6 (2000): 405-414.

Cárcamo, C., et al. “Randomized Controlled Trial of Zinc Supplementation for Persistent Diarrhea in Adults with HIV-1 Infection.” Journal of Acquired Immune Deficiency Syndromes 43 (2006): 197-201.

Creswell, J. D., et al. “Mindfulness Meditation Training Effects on CD4+ T Lymphocytes in HIV-1 Infected Adults.” Brain, Behavior, and Immunity 23 (2009): 184-188.

Diego, M. A., et al. “HIV Adolescents Show Improved Immune Function Following Massage Therapy.” International Journal of Neuroscience 106 (2001): 35-45.

Hurwitz, B. E., et al. “Suppression of Human Immunodeficiency Virus Type 1 Viral Load with Selenium Supplementation.” Archives of Internal Medicine 167 (2007): 148-154.

Kaiser, J. D., et al. “Micronutrient Supplementation Increases CD4 Count in HIV-Infected Individuals on Highly Active Antiretroviral Therapy.” Journal of Acquired Immune Deficiency Syndromes 42 (2006): 523-528.

McClelland, R. S., et al. “Micronutrient Supplementation Increases Genital Tract Shedding of HIV-1 in Women.” Journal of Acquired Immune Deficiency Syndromes 37 (2004): 1657-1663.

Mehta, S., and W. Fawzi. “Effects of Vitamins, Including Vitamin A, on HIV/AIDS Patients.” Vitamins and Hormones 75 (2007): 355-383.

Piscitelli, S. C., A. H. Burstein, and D. Chaitt, et al. “Indinavir Concentrations and St. John’s Wort.” The Lancet 355 (2000): 547-548.

Piscitelli, S. C., A. H. Burstein, and N. Welden, et al. “The Effect of Garlic Supplements on the Pharmacokinetics of Saquinavir.” Clinical Infectious Diseases 34 (2002): 234-238.

Rabkin, J. G., et al. “Placebo-Controlled Trial of Dehydroepiandrosterone (DHEA) for Treatment of Nonmajor Depression in Patients with HIV/AIDS.” American Journal of Psychiatry 163 (2006): 59-66.

Scott-Sheldon, L. A., et al. “Stress Management Interventions for HIV+ Adults.” Health Psychology 27 (2008): 129-139.

Shor-Posner, G., et al. “Psychological Burden in the Era of HAART: Impact of Selenium Therapy.” International Journal of Psychiatry in Medicine 33 (2003): 55-69.

Simpson, D. M., S. Brown, and J. Tobias. “Controlled Trial of High-Concentration Capsaicin Patch for Treatment of Painful HIV Neuropathy.” Neurology 70 (2008): 2305-2313.

Weber, R., et al. “Randomized, Placebo-Controlled Trial of Chinese Herb Therapy for HIV-1-Infected Individuals.” Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology 22 (1999): 56-64.

Youle, M., and M. Osio. “A Double-Blind, Parallel-Group, Placebo-Controlled, Multicentre Study of Acetyl L-Carnitine in the Symptomatic Treatment of Antiretroviral Toxic Neuropathy in Patients with HIV-1 Infection.” HIV Medicine 8 (2007): 241-250.

What is deafness? |

Causes and Symptoms

To understand deafness, it is first necessary to understand how sound is heard.
The sound waves produced by any noise travel through the air and are funneled down the ear canal by the external ear, which is specially shaped for this function. The sound waves then cause the tympanic membrane
to vibrate, which in turn causes the chain of tiny ossicles to vibrate. This mechanical energy of vibration is then transformed by the cochlea into nerve impulses that travel along the eighth cranial nerve to the spinal cord. These impulses are transmitted to the auditory cortex (center) of the brain, where they are interpreted. The ability to hear depends on all these elements working properly.

Deafness can occur when any particular part of this hearing pathway is not functioning as it should. If the ear canal is blocked with cerumen (earwax), a foreign body, fluid, or the products of infection or inflammation, then the sound waves are unable to travel to the eardrum. If the eardrum has ruptured or become stiff (sclerosed), then it cannot vibrate. If the ossicles have been damaged in any way, then they cannot vibrate. If the middle ear is filled with fluid from inflammation or infection, then the eardrum and ossicles cannot work properly. If the cochlea, auditory nerve, or both have been damaged through trauma, disease, or use of an ototoxic drug, then they cannot do their job of converting vibration into nerve impulses and transmitting them to the brain. If the auditory center of the brain is damaged, then it cannot interpret the nerve impulses correctly.

Hearing loss is classified by the cause: conductive, sensory, or neural. Conductive losses are those that affect the conduction of sound waves; they involve problems with the external ear, ear canal, tympanic membrane, and ossicles. The sensory and neural causes are usually classified together as “sensorineural”; these losses affect the cochlea, auditory nerve, or auditory cortex of the brain.

The most common cause of hearing loss in children is otitis media, or middle-ear infection, which causes fluid to build up behind the tympanic membrane. It is usually reversible with time and treatment. This is a type of conductive loss, as is hearing loss attributable to cerumen impaction (excessive buildup of earwax), which can occur in both children and adults. Sensorineural losses are caused by such things as excessive noise exposure, ototoxic drugs, exposure to toxins in the environment, and diseases such as rubella (German measles). The type of sensorineural loss that many people experience as they get older is called presbycusis, which means “a condition of elder hearing.” Many people with sensorineural losses have a genetic predisposition for hearing loss.

Congenital deafness is deafness that is present at the time a baby is born. Before the widespread availability of immunization against rubella, mothers who contracted the disease during pregnancy were at great risk of having a baby with congenital deafness. Congenital deafness may also be genetic. For example, if a child inherits a defective copy of the GJB2 gene from each parent, then that child will be deaf even if both parents can hear.

Likewise, deafness that occurs after birth may be either acquired or genetic. Deafness associated with exposure to loud noises is acquired, for example, while many forms of deafness that occur in older age are genetic. About one-third of people over the age of sixty-five have hearing loss.

Treatment and Therapy

According to the World Health Organization, as of early 2013, about half of all cases of hearing loss worldwide were preventable. Indeed, the best treatment for deafness is prevention. Immunization against rubella, protection of ears from excessive noise, and avoidance of too much aspirin are all examples of preventative measures.

Once hearing impairment has occurred, determination of the cause is essential. The primary care provider, an otorhinolaryngologist (ear, nose, and throat doctor), an audiologist (hearing specialist), and a neurologist may be involved in this assessment. Reversible causes of deafness or hearing loss can be addressed medically or surgically, as in the removal of earwax. For nonreversible causes, hearing aids
and other assistive hearing devices may be helpful. These devices have become increasingly sophisticated. Some allow the wearer to adjust the hearing aid to specific circumstances, while older versions amplified all sounds equally.

Cochlear implants
are electronic devices that give profoundly deaf persons a sense of sound that helps them understand speech and other noises. A microphone picks up sounds, which are processed, converted to electric impulses, and sent to different areas of the auditory nerve.

In addition to these products, many assistive devices are available to help persons with severe hearing impairment function independently. For example, special telephones, alarm clocks, and doorbells that flash a light or shake the bed in addition to ringing are readily available.

Bibliography

A.D.A.M. Medical Encyclopedia. "Hearing Loss." MedlinePlus, May 22, 2012.

American Medical Association. American Medical Association Family Medical Guide. 4th rev. ed. Hoboken, N.J.: John Wiley & Sons, 2004.

Carmen, Richard, ed. The Consumer Handbook on Hearing Loss and Hearing Aids: A Bridge to Healing. 3d rev. ed. Sedona, Ariz.: Auricle Ink, 2009.

Dillon, Harvey. Hearing Aids. New York: Thieme, 2001.

Komaroff, Anthony, ed. Harvard Medical School Family Health Guide. New York: Free Press, 2005.

National Center on Birth Defects and Developmental Disabilities. "Hearing Loss in Children." Centers for Disease Control and Prevention, March 22, 2013.

National Institute on Deafness and Other Communication Disorders. "Hearing, Ear Infections, and Deafness." National Institutes of Health, September 8, 2011.

Romoff, Arlene. Hear Again: Back to Life with a Cochlear Implant. New York: League for the Hard of Hearing, 1999.

Stoppard, Miriam. Family Health Guide. London: DK, 2006.

World Health Organization. "Millions Have Hearing Loss That Can Be Improved or Prevented." World Health Organization, February 27, 2013.

What is tendinitis? |

Causes and Symptoms

Tendons are fibrous cords that attach muscles to bones. Their function is to transmit force and coordinate the activity between muscles and bones. When too much stress is placed upon the tendons, they may become inflamed (tendinitis), or damaged, or both, from the chronic degeneration of tendon
collagen (tendinosis). The cause of such stress is usually poor technique, overuse, or repetitive movements in sports, recreational, and occupational activities. The injury usually follows the progression of multiple microscopic tears in the tendon tissue, eventually leading to acute inflammation and pain. The areas most commonly affected are the rotator cuff of the shoulder, the elbow (“tennis elbow” or “golfer’s elbow”), the
wrist/thumb (de Quervain’s disease), the knee (“jumper’s knee”), and the ankle (Achilles tendinitis).

Many athletic activities, such as racquet sports, baseball, running, and weight training, involve repetitive movements that may put excessive stress on the tendons. Many occupations also pose a risk; examples include performing assembly line work, playing a musical instrument, and using a keyboard. Tendinitis may also be caused by infection or by a buildup of calcium deposits (calcific tendinitis) or other materials in a joint as a result of a chronic illness such as diabetes or arthritis.

Pain is the usual complaint. It occurs when the patient moves the affected joint but may sometimes persist when the joint is at rest. In severe cases, simple activities such as raising a coffee cup or brushing teeth may cause pain. There may also be swelling, warmth, and redness in the affected area.

Treatment and Therapy

The term “tendinitis” has traditionally been used as a blanket term for all tendinopathies. However, medical professionals emphasize that tendinitis and tendinosis, while often occurring hand-in-hand, are separate conditions and must be treated accordingly. Tendon overuse conditions have been generally considered inflammatory processes (tendinitis), and therapy has been administered based on that conception. However, it is important to recognize that overuse tendon conditions are frequently caused by collagen damage and degeneration of tendon tissue (tendinosis), eventually leading to an acute inflammatory condition. Tendinosis requires a different approach to therapy once the initial inflammation is treated.

True tendinitis conditions are treated with therapy aimed at reducing inflammation. Rest and avoidance of the causative activity, alternative application of ice and heat, compression and elevation of the affected extremity, and immobilization with slings and splints are all helpful measures. Over-the-counter anti-inflammatory medications such as ibuprofen may be suggested. A method exists for delivering medication to inflamed tissue: iontophoresis, whereby a small electrical current delivers anti-inflammatory medication, such as dexamethasone, through the skin to the inflamed tissue. More severe cases may require corticosteroid injections. Tendinitis caused by infection is treated with antibiotics and sometimes surgery if first-course therapy is not effective. Recovery from tendinitis varies from a few to several weeks.

Tendinosis therapy is aimed at allowing the injured tendon tissue to heal. Rest and avoidance of the offending activity is most important. Icing, ultrasound, and electrical stimulation may enhance collagen production. Once the initial inflammation has been treated, anti-inflammatory medications and corticosteroid injections are not indicated and may actually impede healing. Ergonomic changes in the workplace and the correction of improper technique in sports activities are important. Physical therapy and strengthening exercises play key rehabilitative roles by helping to prevent future injury, and they may also improve collagen formation and thus speed healing. Surgery to remove damaged tissue is used only as a last resort when conservative management has failed. Recovery from tendinosis may take up to several months.

Perspective and Prospects

Tendinopathies have been regarded as conditions that are often recalcitrant to therapy, becoming chronic or frequently reoccurring. It is possible that this difficulty is in part attributable to the lack of distinction between tendinitis and tendinosis. It has been postulated that some of the therapies for tendinitis, when used on tendinosis, may cause further tissue deterioration and thus contribute to the chronic nature of the disorder. Additionally, once the initial inflammation is treated and pain is no longer felt, the injured individual will often begin the offending activity before healing is complete. This leads to further damage and weakened tissue, creating a frustrating cycle. It is therefore crucial that a proper diagnosis is made before treatment begins and that the injured individual follow the full course of therapy and rest to ensure optimal healing.

The investigation of new treatment modalities is ongoing. Extracorporeal shock wave therapy has been shown to have some positive benefits for both tendinosis and calcific tendinitis. The use of ultrasound and electrical stimulation has gained acceptance with some professionals.

Preventive measures can greatly reduce the risk of developing overuse tendinopathies. This approach is becoming more evident in the workplace, where proper ergonomic environments help to decrease employee injury, increase productivity, and reduce injury and absences. Conditioning and emphasis on correct technique in sports and recreational activities will greatly reduce the incidence of tendon overuse disorders.

Bibliography

Khan, Karim M., et al. “Overuse Tendinosis, Not Tendinitis: A New Paradigm for a Difficult Clinical Problem.” Physician and Sports Medicine 28, no. 5 (May, 2000): 38–45.

Khan, Karim M, et al. “Time to Abandon the ’Tendinitis’ Myth: Painful, Overuse Tendon Conditions Have a Non-inflammatory Pathology.” British Medical Journal 324, no. 7338 (March 16, 2002): 626–627.

Leach, Robert E., and Teresa Briedwell. "Tendinopathy." Health Library, Mar. 18, 2013.

Porter, Robert S., et al., eds. The Merck Manual Home Health Handbook. Whitehouse Station, N.J.: Merck Research Laboratories, 2009.

Standish, William D., Sandra Curwin, and Scott Mandell. Tendinitis: Its Etiology and Treatment. New York: Oxford University Press, 2000.

"Tendinitis." MedlinePlus, May 9, 2013.

"Tendinitis and Bursitis." American College of Rheumatology, Feb. 2013.

"What Are Bursitis and Tendinitis?" National Institute of Arthritis and Musculoskeletal and Skin Diseases, Apr. 2011.

What are plyometrics? |

Plyometrics is exercise that rapidly and repeatedly stretches and contracts muscles in order to develop explosive muscle power. Also known as jump training, it is considered a form of calisthenics and is used by athletes and exercisers who want to increase their agility, strength, speed, and endurance. It is especially useful for training athletes in sports that require jumping, dodging, and charging activities, such as basketball, volleyball, and tennis.

Once the domain of professional athletes, plyometrics has become popular among student athletes, weekend warriors, and fitness advocates who want to improve their performance and get results beyond other drill training. While research has shown many benefits from performing this type of strength training, it is not without risk. It causes great stress on the joints and needs to be done correctly and under supervision.

Brief History

Coaches began using plyometric exercises in Eastern European countries during the 1920s to train track-and-field athletes. In the 1960s, Yuri Verkhoshansky, a Russian track-and-field coach, researched the movements of running and jumping and designed a training method to increase the speed and explosiveness of track-and-field athletes. He called his training method, which emphasizes the depth jump, the "shock method." In this exercise, an athlete drops from a great height. The impact upon landing creates a shock, or force, that causes the muscles to rapidly contract and then extend, giving the athlete the explosive burst of power to make a powerful jump. Verkhoshansky expanded his shock method training to other sports, such as volleyball, and found that it increased these athletes’ maximal strength as well. The shock method quickly gained popularity and was adopted by coaches throughout Eastern Europe.

In the 1970s, Verkhoshansky’s training method came to the attention of Western athletes and training coaches as Eastern European athletes earned Olympic medals in track-and-field events, gymnastics, and other sports. Fred Witt, a US Olympic coach, coined the term "plyometrics" to describe this training method and introduced jump training to US trainers and coaches. Like their Russian counterparts, American coaches who incorporated jumping exercises into athletes’ training programs noted improvements in strength and endurance.

Over time, plyometrics came to be defined as any training method that incorporated jumping exercises and other workouts that cause the muscles to rapidly lengthen and shorten. Verkhoshansky’s shock method is still used by a small number of professional athletes, but it is less common than other types of plyometrics due to the extreme intensity and training required.

Overview

Plyometric movements are a part of everyday life. Examples include jumping, leaping, hopping, skipping, running, and throwing. Plyometric drills focus on these and other movements that cause the muscles to quickly stretch and then contract. The faster the muscle expands, the faster it contracts, which strengthens the muscle and allows it to develop explosive power. Plyometrics emphasizes exercises that teach the muscles to react quickly and train the neuromuscular system to respond in a certain way.

A person can engage in plyometric workouts to train for a specific sport; to develop a specific skill or combination of skills, such as speed or push-pull power; or to improve overall strength and fitness. Plyometric drills are progressive, and users should move gradually from low-intensity activities to more intense ones. Not only is it helpful to master a skill before performing a more advanced one, but for many exercises, the muscles need to develop full strength in order to complete them properly.

Different sets of exercises are used to develop lower body and upper body explosiveness as well as sports-specific skills. For example, a soccer player is likely to engage in exercises such as jumping over cones and skipping to develop the ability to quickly change direction. A golfer, in contrast, would benefit more from activities such as a lunging rotating pass that develop explosive power in hip and trunk rotation.

Plyometric exercises are categorized into five groups based on the skill focus: speed, jump, push-pull power, rotational power, and change of direction.

Speed is a necessary part of many sports, while straight-ahead explosive speed is especially beneficial to skiers and hockey players. Standing broad jumps, depth jumps, and box jumps help to develop this kind of speed.

Jumping is crucial for volleyball and basketball players. Exercises that help to develop explosive jumping skills include wood chops, hopping over cones, and tuck jumps.

Push-pull power is the ability to move something with force. It is an essential skill for swimmers and basketball players. High pulls and squat throws help athletes develop this skill.

Rotational power is a key part of many sports, including sprinting and golfing. Rotational slams and lunging rotating passes help develop this skill.

Change of direction is crucial to ice skaters, soccer players, and football players. Useful exercises are box jumps, tuck jumps, and slalom hops.

Research shows that the correct use of plyometrics results in improved speed, strength, and endurance. It can also help to condition individuals to prevent injuries. Plyometrics builds on the elasticity of the muscles and strengthens the muscle fibers and tendons. It helps to train the neuromuscular system by strengthening the communications between the muscles and brain. This helps individuals develop explosive power and increases their ability to run, jump, hit, and move with power.

Its success has made plyometrics an integral part of college athletic training programs, professional training programs, and specialty training programs, such as that for Navy SEALs. Plyometrics has also moved beyond these special training programs to become a part of mainstream exercise and fitness programs. It is incorporated in many high-intensity interval-training programs, such as CrossFit.

Because of the high risk of jumping activities, which put great stress on the joints, fitness coaches and exercise physiologists recommend that individuals only perform plyometrics under supervision and with correct training. Workouts should be limited to twice per week, even for advanced exercisers, to allow the muscles time to recover.

Plyometrics is not for everyone. Older persons and those with osteoarthritis are more susceptible to joint damage and should avoid this type of exercise.

Bibliography

Bangma, Kristina. "Fitness: Plyometrics More Than a Buzz Word for Jumping." Vancouver Courier. LMP, 12 Apr. 2013. Web. 15 June 2015.

Chu, Donald A., and Gregory Myer. Plyometrics. Champaign: Human Kinetics, 2013. Print.

Hickman, Justin. "Plyometrics." NW Fitness Magazine. NW Fitness Magazine, 18 Mar. 2015. Web. 15 June 2015.

Internicola, Dorene. "Plyometrics Leaps into Mainstream—but Experts Urge Caution." Huffington Post. HuffingtonPost.com, 16 Sept. 2013. Web. 15 June 2015.

Leicht, Laurel. "6 Plyometrics Exercises for a Better Workout in Less Time." Huffington Post. TheHuffingtonPost.com, 28 Dec. 2014. Web. 15 June 2015.

Pire, Neal. Plyometrics: For Athletes at All Levels. Berkeley: Ulysses, 2006. Print.

"Plyometrics: Controlled Impact/Maximum Power." ACE. Amer. Council on Exercise, n.d. Web. 15 June 2015.

Radcliffe, James, and Robert Farentinos. High-Powered Plyometrics. 2nd ed. Champaign: Human Kinetics, 2015. Web. 15 June 2015.

What is Bloom syndrome? |

Risk Factors

BS is rare, with only several hundred confirmed cases, but it is least rare among the Ashkenazi Jewish population. According to the Center for Jewish Genetics (2014), in this population, approximately 1 percent are carriers of BS. The US National Library of Medicine reports that roughly one out of three people with the disease have one or both parents of Ashkenazi Jewish descent.

Etiology and Genetics

BS was first described by David Bloom in 1954 and belongs to a class of human diseases called the chromosome breakage syndromes. A person affected with BS carries two mutant BLM genes, one inherited from each parent. When both parents carry the mutant BLM gene, there is a 25 percent chance for each pregnancy that the offspring will have BS. The BLM gene is on chromosome 15 and has been traced to band q26.1. The normal BLM gene encodes a protein belonging to the RecQ DNA helicase family. DNA helicases are enzymes that unwind the two complementary spiral strands comprising a DNA molecule. These enzymes are crucial for unwinding before DNA can be replicated in cell division. However, BLM gene mutations lead to changes in helicase enzyme activity, affecting the unwinding and copying of DNA as it is replicated.

During normal replication, each chromosome—made up of tightly coiled DNA as well as proteins—makes two identical DNA structures, called sister chromatids. Sister chromatids normally exchange some small sections of DNA during replication in a process called sister chromatid exchange (SCE). When the BLM gene is mutated, more errors occur during replication. In BS, there is an increased level of spontaneous SCEs—as many as ten times the amount of SCEs seen in normal cells. In addition to excessive amounts of SCEs, increased breaks and rearrangements between nonhomologous chromosomes (chromosomes that are not of the same pair) are also observed. This chromosome instability and hyperrecombination is thought to contribute to the increased risk of cancer and other features of BS, although the mechanisms linking chromosomes and cancer are not fully understood.

According to the US National Library of Medicine, more than seventy BS-causing mutations in the BLM gene have been identified. However, one particular mutation causes almost all cases of BS among those of Ashkenazi Jewish descent. This founder deletion/insertion mutation, referred to as blm

Ash
, has reached a carrier frequency of roughly 1 percent in the Ashkenazi Jewish population.

Symptoms

BS is physically characterized by proportional, but unusually small prenatal and postnatal size (although the brain and head are disproportionately small) and sun-sensitive skin lesions that are limited to the face and the back of the hands and forearms. The other most important clinical characteristic, which is not physically observable, is a striking predisposition to cancer. Tumors can be benign or malignant. They may arise at an early age, and with great frequency in a large variety of body locations and cell types. Leukemias, lymphomas, and carcinomas are particularly common. Individuals with BS also usually experience decreased fertility (males are infertile), increased predisposition to multiple infections because of a compromised immune system, and sometimes diabetes.

Screening and Diagnosis

Diagnosis can be presumed based on clinical features associated with BS and is confirmed or ruled out by chromosome analysis. Cells from patients will show a significant (up to tenfold) increase in SCEs compared with cells from normal individuals, as well as increased chromosome breakage and rearrangements, and increased presence of chromosome structures called quadriradicals.

The identification of the BLM gene and the specific BLM gene mutation responsible for BS in Ashkenazi Jews have made carrier testing possible for this population. Prenatal diagnosis of BS is also available for couples who carry BLM gene mutations that have already been identified.

Treatment and Therapy

There is no direct effective treatment for BS. Mutations will continue to arise in excess, but the life span of affected individuals may be maximized by early diagnosis and systematic management. Avoiding the sun (especially in infancy and youth), treating bacterial infections promptly, treating diabetes if it arises, and avoiding environmental exposures or therapies that may further damage chromosomes (such as X rays) are all measures that may increase life span and improve the quality of life of affected individuals. Most important, those with BS should be in close communication with an experienced physician, who can develop a cancer surveillance program.

Prevention and Outcomes

There is no effective means of prevention for BS. Genetic counseling should be available for parents of an affected child, and prenatal screening is an option for parents who are carriers. The Bloom's Syndrome Registry comprises the files of 265 people with BS and shows cancer as the most common cause of death. Within the registry, data from 2009 show that the mean age at death was 26 years, with a range of less than 1 to 49.

Bibliography

"Bloom Syndrome." Genetics Home Reference. National Institutes of Health, 21 July 2014. Web. 28 July 2014.

"Bloom's Syndrome." Center for Jewish Genetics. Center for Jewish Genetics, 2014. Web. 28 July 2014.

"Data from the Bloom's Syndrome Registry." Bloom's Syndrome Registry. Weill Cornell Medical College, 2009. Web. 29 July 2014.

Klug, William S., Michael R. Cummings, Charlotte Spencer, and Michael A. Palladino. Concepts of Genetics. 10th ed. San Francisco: Benjamin Cummings, 2012. Print..

Parker, Philip M. Bloom Syndrome: A Bibliography and Dictionary for Physicians, Patients, and Genome Researchers. San Diego: ICON Group International, 2007. Print.

Victor Center. "Ashkenazi Jewish Genetic Diseases." Jewish Virtual Library. American-Israeli Cooperative Enterprise, 2014. Web. 31 July 2014.

What is testicular torsion? |

Causes and Symptoms

Testicular torsion is most commonly found in infants, adolescents, or young adult males. Roughly half of the cases occur in the early hours of the morning, and cases usually occur on the left side rather than the right. The condition can occur during sleep, rest, game playing, or hard physical activity, but it is more likely to be caused by direct injury. Testicular torsion may also result if the testicle is unusually mobile within its covering in the scrotum because of inadequate connective tissue.

Testicular torsion makes itself known by pain of varying degrees either in the lower part of the abdomen or in the scrotum itself. The pain intensifies rapidly and is occasionally accompanied by nausea as the testicle becomes swollen and very tender and the scrotal skin becomes discolored. A diagnosis can be made by physical examination.

Treatment and Therapy

Immediate treatment of testicular torsion is necessary. The testicle must be untwisted immediately and blood flow restored to the testicle, the epididymis, and other structures. Otherwise, complete blockage of the blood supply (ischemia) for six hours or more may result in gangrene (tissue death) of the testicle. Even a partial loss of circulation can produce atrophy.

Manual untwisting should be followed by surgery within six hours of the onset of symptoms to ensure that the torsion has been undone successfully and that there is no recurrence. An incision is made in the scrotal skin, and the testicle is secured to the scrotum by small stitches. If irreversible damage has been done, the testicle must be removed. The other testicle, which usually remains capable of producing active sperm, is also anchored to prevent torsion on that side. Prompt surgery generally ensures a complete recovery.

Bibliography:

Behrman, Richard E., Robert M. Kliegman, and Hal B. Jenson, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia: Elsevier/Saunders, 2011.

Montague, Drogo K. Disorders of Male Sexual Function. Chicago: Year Book Medical, 1988.

Rajfer, Jacob, ed. Urologic Endocrinology. Philadelphia: W. B. Saunders, 1986.

Rifkin, Matthew D., and Dennis L. Cochlin. Imaging of the Scrotum and Penis. Florence, Ky.: Taylor & Francis, 2002.

Swanson, Janice M., and Katherine A. Forrest. Men’s Reproductive Health. New York: Springer, 1984.

Taguchi, Yosh, and Merrily Weisbord, eds. Private Parts: An Owner’s Guide to the Male Anatomy. 3d ed. Toronto: McClelland & Stewart, 2003.

“Testicular Torsion.” Urology Care Foundation, Jan. 2011.

What are Maslow's hierarchy of needs?

Introduction

The concept of a hierarchy of needs became the central organizing principle in
Abraham Maslow’s theory of human motivation. A research psychologist who began his career in the 1940’s with a series of studies on motivation, culminating with his book Motivation and Personality (1954), Maslow greatly furthered the understanding of human motives. When Maslow began his research, psychology largely regarded hunger as the paradigm for all other motives and examined motivation through animal studies, behaviorist theory, or both. Maslow rejected these early theories as insufficient to account for the human dimensions of motivation. He supplemented experimental study with clinical evidence and redirected the focus from drives to goals and from isolated determinants to a sense of the person as an integrated and dynamic whole.

The most important aspect of Maslow’s theory of motivation was the notion of a hierarchy of needs. Maslow first articulated this theory in his early works, including “A Theory of Human Motivation,” which appeared in Psychological Review in 1943, and he would continue to develop his theory over time. He first identified and differentiated among various clusters of motives. The five clusters he identified were as follows:

•physiological needs

•safety needs

•belongingness or love needs

•esteem needs

•need for self-actualization

He noted that, in the order listed, the clusters formed a hierarchy from lower to higher motives. He pointed out that there is no final satiation point at which the person is no longer motivated, but rather that as a particular motivation is sufficiently gratified, another, higher motive will emerge more prominently. In Maslow’s terms, the higher motives are therefore “prepotent” with regard to the lower ones. Furthermore, there is a basic directionality in the order in which each motivational cluster becomes prominent.

Later Developments

In 1955, following the success of his early studies, Maslow was invited to present his work at the prestigious Nebraska Symposium on Motivation. There he advanced his thesis by making a key distinction between deficiency motivation and growth motivation. The first four clusters of motives tend to be motivating precisely when they are lacking, when there is a deficit or empty hole that must be filled. In contrast, people who are very healthy psychologically have sufficiently gratified their basic needs. This does not mean they have obtained more in an objective sense, but rather that their experience is not structured by a sense of lack. With this experienced sense of sufficiency, healthy people are free to develop their motive toward
self-actualization, which Maslow defined as an “ongoing tendency toward actualizing potentials, capacities and talents . . . of the person’s own intrinsic nature.” Thus self-actualization can be seen as a trend toward fulfillment and integration. He described thirteen specific observable characteristics of such self-actualizing people, including being more perceptive, more accepting of the self and others, more spontaneous, more autonomous, more appreciative, and more creative, and having a richer emotional life and more frequent peak experiences.

Applications

As Maslow continued working, he began more and more to examine the lives of “self-actualizers,” those people whom he identified as exemplary of being directed by self-actualizing motivation. He saw that a person’s psychological life is lived differently when that individual is oriented not to the gratification of deficiency needs but to growth. This emphasis on growth soon became the focus of an emerging paradigm, known as
humanistic psychology, studied by many other psychologists, including Carl R. Rogers. This emphasis on personal growth reoriented the study of psychology, focusing it not on issues of disease and negativity but rather on themes of personal enrichment and fulfillment, and of living an intrinsically meaningful life. Maslow’s book Toward a Psychology of Being (1962) is one of the hallmarks of this movement, which swept beyond academic psychology into pop psychology.

Maslow’s theory of motivation also influenced other disciplines, such as education and business. Mark Zimmeran’s emotional literacy education project, for example, explicitly draws from Maslow’s motivational theory. Research continues into the role of Maslow’s hierarchy of needs in the fields of business, management, leadership, entrepreneurship, organizational development, and marketing. Issues such as optimally motivating workplace environments and incentives for employees continue to be particularly engaging topics for these studies. Though many of the specific applications often oversimplify Maslow’s theory, the hierarchy of needs is still widely used, especially as the basis for management theories based on a vision of employees as most productive when synergistically and cooperatively engaged through opportunities for self-directed creativity rather than when subjected to authoritarian structures. Maslow himself considered this application important and contributed to it with his book Eupsychian Management: A Journal (1965). Maslow’s position was that the more psychologically healthy people became, the more important such enlightened management would be for any competitive business.

Bibliography

DeCarvalho, Roy Jose. The Growth Hypothesis in Psychology: The Humanistic Psychology of Abraham Maslow and Carl Rogers. San Francisco: Mellen Research UP, 1991. Print.

King, Daniel, and Scott Lawley. Organizational Behavior. Oxford: Oxford UP, 2013. Print.

Lowry, Richard. A. H. Maslow: An Intellectual Portrait. Monterey: Brooks/Cole, 1973. Print.

Moss, Donald, ed. Humanistic and Transpersonal Psychology. Westport: Greenwood, 1999. Print.

Stephens, Deborah C., ed. The Maslow Business Reader. New York: Wiley, 2000. Print.

What is the relationship between psychosis and substance abuse?

Substance Abuse and Psychosis

Clinical studies and community surveys document high rates of substance use disorders (SUD) in persons with psychotic symptoms. The lifetime prevalence of substance abuse among persons with psychotic illnesses such as schizophrenia and bipolar disorder is much higher than in the general population.

This comorbidity is most often associated with being male, single, young, and having a conduct or antisocial personality disorder. Persons with psychosis also tend to abuse multiple substances. The overlapping biological substrates responsible for this co-occurrence include structural brain abnormalities, genetic vulnerabilities, and early exposure to stress or trauma.

A high prevalence of substance abuse in persons with schizophrenia has been reported in numerous studies conducted in developed countries. According to the US National Institute of Mental Health, schizophrenia carries a 10.1 percent risk of drug abuse, and SUD may constitute the most common comorbidity of schizophrenia. Apart from tobacco and cannabis (the preferred substances), these persons also abuse alcohol, cocaine, and amphetamines.

When a person presents to mental health professionals with recent-onset psychosis associated with substance abuse, it becomes essential to establish whether the substance use caused the symptoms. Psychosis is considered to be independent of the SUD if the psychosis occurred before the substance use or if the psychosis persisted during long substance-free periods. An absence of disorientation (which occurs in substance-induced delirium) also may point to a distinct psychosis.

In practice, the aforementioned features can be difficult to ascertain. Persons with psychosis often do not remember the exact sequence of events that contributed to the development of their disorder. Therefore, it becomes difficult to pinpoint the temporal relationship of psychotic symptoms and substance abuse. In addition, the patients may not experience significant substance-free periods. The diagnosis dilemma is further amplified by the similarity of symptoms, such as paranoia and auditory hallucinations, occurring both in independent psychosis and in psychosis induced by substances (especially stimulants). For this reason, persons with comorbid psychosis and SUD need to be thoroughly assessed at presentation, detoxified, treated immediately by interdisciplinary teams (using pharmacotherapy and cognitive behavioral-therapy among other approaches), and then monitored.

Overall, coexisting SUD imparts a more severe character and a poorer outcome to psychotic disorders, with frequent relapses and hospitalizations. Studies show, for example, that persons with defined comorbid SUD and first-episode psychosis are likely to have poorer treatment response than those with psychosis alone.

Psychosis Triggers

Alcohol and illegal drugs (cannabis, amphetamines, cocaine, hallucinogens, and opiates) can cause psychosis, both during use and as a consequence of withdrawal. Severe psychiatric disorders appear to correlate with earlier and longer exposure to stimulants. This suggests the presence of a critical developmental stage, or a threshold effect, of the drug on psychosis development.

Up to 15 percent of cannabis users report psychotic symptoms immediately after use. The hypothesis that cannabis abuse also causes chronic schizophrenia-like psychosis has not been ruled out, although evidence remains insufficient. An increasing body of literature points to early exposure to cannabis as generating psychosis later in life. Cannabis use during adolescence is an independent risk factor for the onset of psychosis in adulthood (especially in at-risk subjects) and associates with an earlier onset of schizophrenia. Studies also suggest that heavy cannabis use precipitates psychotic relapses in persons with schizophrenia who previously achieved remission.

Psychotic symptoms with paranoia and suspiciousness are reported during cocaine use and withdrawal. The propensity to experience cocaine-induced psychosis has been linked to mutations in genes coding for proteins involved in dopaminergic transmission.

Methamphetamine use is commonly associated with psychiatric conditions such as psychosis and depression. During both abstinent and intoxicated circumstances, persons who are methamphetamine-dependent are more likely to report psychotic symptoms than are cocaine addicts. Drug-induced psychotic syndromes are both positive (auditory hallucinations, persecutory delusions) and negative (poor speech, flattened affect). These psychotic states persist after the pharmacological effects of the methamphetamine have subsided, and they reappear upon reinjection. Furthermore, under stressful conditions, persons with a history of methamphetamine psychosis undergo spontaneous recurrence of their psychotic symptoms. Methamphetamine psychosis might therefore associate with persistent structural or functional brain damage caused by repeated drug administration.

Psychosis Can Lead to Substance Abuse

It has been suggested that persons with schizophrenia may self-medicate with tobacco, alcohol, and drugs. The substances of abuse are often perceived as alleviating negative symptoms (such as depression and withdrawal), improving hallucinations and paranoid delusions, lessening adverse effects of medications (such as restlessness), and providing an avenue for social interaction. This causal relationship remains unclear, as some studies have contradicted the self-medication hypothesis for this comorbidity.

Bibliography

Emmelkamp, Paul M. G., and Ellen Vedel. Evidence-Based Treatment for Alcohol and Drug Abuse: A Practitioner’s Guide to Theory, Methods, and Practice. New York: Routledge, 2006. Print.

Tamminga, Carol A., et al., eds. Deconstructing Psychosis: Refining the Research Agenda for DSM-V. Arlington: Amer. Psychiatric Assn., 2010. Print.

Thakkar, Vatsal G. Addiction. New York: Chelsea, 2006. Print.

Volkow, Nora D. “Substance Use Disorders in Schizophrenia: Clinical Implications of Comorbidity.” Schizophrenia Bulletin 35 (2009): 469–72. Print.

How did Rome become politically unstable?

There are a plethora of reasons why Rome, one of history's longest-lasting and most powerful empires, finally fell.  Although the reasons and their level of importance are highly debated among historians, most agree that there were certain factors that clearly led to the Roman empire's demise.

Rome had always struggled against invasions by Germanic tribes, but in 476 the Roman emperor Romulus Augustulus was deposed by Germanic leader Odoacer.  After this happened, no Roman emperor ever...

There are a plethora of reasons why Rome, one of history's longest-lasting and most powerful empires, finally fell.  Although the reasons and their level of importance are highly debated among historians, most agree that there were certain factors that clearly led to the Roman empire's demise.

Rome had always struggled against invasions by Germanic tribes, but in 476 the Roman emperor Romulus Augustulus was deposed by Germanic leader Odoacer.  After this happened, no Roman emperor ever again ruled from a post in Italy.

Rome also began to struggle economically due to its constant wars and overspending on outside conquests. Its over-expansion made it difficult to administer and run the empire across such great distances, while military overspending emptied its treasury.  These problems were exacerbated by the rampant corruption that existed in the Roman government.  Roman citizens began to lose trust in their leadership, setting the stage for civil revolt.