Wednesday, 23 October 2013

Show solutions Fill out the chart below. It is information needed to construct an OC curve and AOQ curve for the following sampling plan: ...

Given: 


Size of lot (N)=1900


Sample Size (n) =125


Acceptance Number (c)=2


Proportion defective (p) can be calculated as :


For np=1.8,


 `p=1.8/125=0.0144`


For np=4.2,


 `p=4.2/125=0.0336`


For np=6.0,


 `p=6.0/125=0.048`


So these values of p completes the Column 1 for p.


Now column 2 can be obtained by multiplying p values with 100.


Now let's fill the column 3 (np) values,


For p=0.0016,


 `np=125*0.0016=0.2`


For p=0.008,


`np=125*0.008=1`


 For p=0.012,


`np=125*0.012=1.5`


For p=0.0224,


`np=125*0.0224=2.8`


For p=0.0416,


`np=125*0.0416=5.2`


...

Given: 


Size of lot (N)=1900


Sample Size (n) =125


Acceptance Number (c)=2


Proportion defective (p) can be calculated as :


For np=1.8,


 `p=1.8/125=0.0144`


For np=4.2,


 `p=4.2/125=0.0336`


For np=6.0,


 `p=6.0/125=0.048`


So these values of p completes the Column 1 for p.


Now column 2 can be obtained by multiplying p values with 100.


Now let's fill the column 3 (np) values,


For p=0.0016,


 `np=125*0.0016=0.2`


For p=0.008,


`np=125*0.008=1`


 For p=0.012,


`np=125*0.012=1.5`


For p=0.0224,


`np=125*0.0224=2.8`


For p=0.0416,


`np=125*0.0416=5.2`


For p=0.0512,


`np=125*0.0512=6.4`


Now let's calculate the Probability of acceptance by the cumulative Poisson formula,


`P_a=sum_(x=0)^c(e^(-np)(np)^x)/(x!)`


We have to calculate P_a for each value of p,


For p=0.016


`P_a=P_0+P_1+P_2`


`=(e^(-0.2)(0.2)^0)/(0!)+(e^(-0.2)(0.2)^1)/(1!)+(e^(-0.2)(0.2)^2)/(2!)`


`=0.818730753+0.163746151+0.016374615`


`=0.998851519`


`=~~0.999`


For p=0.008,


`P_a=(e^(-1)(1)^0)/(0!)+(e^(-1)(1)^1)/(1!)+(e^(-1)(1)^2)/(2!)`


`=0.367879441+0.367879441+0.183939721` 


`=0.919698603`


`=~~0.92` 


For p=0.012,


`P_a=(e^(-1.5)(1.5)^0)/(0!)+(e^(-1.5)(1.5)^1)/(1!)+(e^(-1.5)(1.5)^2)/(2!)`


`=0.22313016+0.33469524+0.25102143`


`=0.808846831`


`=~~0.809`


Similarly we can calculate P_a for all values of p, which are shown in the attached image.


Now let' calculate AOQ,


`AOQ=(P_a*p)(N-n)/N`


If `n/N<=0.1`


Then, AOQ `=P_a*p`


Now let's calculate AOQ,


For p=0.0016,


`AOQ=0.0016*0.999=0.0015984`


For p=0.008,


`AOQ=0.008*0.92=0.00736`


Similarly we can calculate AOQ, for other values of p.


Please refer to the attached image, where all calculations are shown.


` `

How can the youth contribute towards strengthening togetherness in a multicultural society?

This is such an important question.  I think that young people need to talk less about tolerance and more about acceptance, that they need to focus more on how people are alike than on how they are different, and that they need to be genuinely interested in the various cultures of those around them. 

As I listen to the discussions swirling around me about multiculturalism, I hear a great deal of discussion of tolerance.  That seems foolish to me.  It implies we are merely putting up with something, which is hardly the road to togetherness.  We should not be putting up with people because they are different from us. We should be accepting them and accepting multiculturalism in general. I don't understand the value in not accepting people who are different from me. They are people, and each must be judged on his or her own merits, not on the basis of difference.  If our youth would abandon this notion of tolerance and start working on acceptance, that would be a very good start. 


Social and professional relationships and communities are built upon commonalities. When we look for ways we are like another person, we can get along with pretty much anyone. When we have an ice-breaking activity in my classes on the first day, I am looking for commonalities, between myself and each student and amongst all the students, so we can have common ground as our foundation for learning. A classroom is a community of learners. Similarly, in the workplace, when a new person comes on board, no matter how that person is different from everyone else, there is something he or she will have in common with others, perhaps similar schooling, perhaps something as superficial as tastes in food or dress. There is always something that we can find in common with others, although it does not mean we should disregard differences. Young people should be working on this. 


We should be interested in differences in others, to learn about another religion, another country, another tradition.  If the interest is genuine, questions will be welcomed, not perceived as rude.  I had a student once who was married in India, and we begged her to bring her wedding photos to class. None of us had ever been fortunate enough to attend an Indian wedding, but we learned so much about the rituals and the beauty of them this way.  If all young people are sincerely interested in learning about others, that is a means of drawing closer together, too.


Perhaps I live in a bit of a bubble, but it does seem to me that the up and coming generation is making a greater contribution to a world of togetherness than previous generations have done. I see young people daily, and for the most part, they all get along very well, at least in the classroom.  I try to urge them to accept, rather than tolerate, to look for common ground, and to be interested in the people around them. 

What is social schemata? |


Introduction

Life would be very complicated if people did not have the ability to store things in memory or to organize the information that did get stored; people would have to relearn information over and over. Because of memories of past experiences, people do not have to relearn what an apple is, for example, or what to do with it each time they come in contact with one.



A well-organized memory system also helps people make educated guesses. People are able to conclude that because of an apple’s texture, it will not make a satisfactory baseball. People are able to make educated guesses because the human brain has the ability to categorize objects and to generalize from past experiences to new experiences. Indeed, social psychologists believe that the brain has not only the ability to categorize but also the tendency to do so. For example, a very young city child who is taken to the zoo may point to a goat and say, “Doggy!”


The brain’s memory system categorizes objects, people, and events by connecting different pieces of related information together. Social psychologists call this collection of related information a schema. The young child knows that “doggies,” for example, have fur, four legs, and wet noses. Somehow, the brain links these pieces of information together. In the child’s mind, there is an idea of the typical characteristics an object must have for it to be a “doggy.”




Types of Social Schemata

All people have many schemata, covering the entire range of topics about which a given person knows things. Some of these topics are social in nature; some are not. If the content of a schema concerns a person, group of people, or social event, the schema is called a social schema. One type of social schema is a script. A script is a schema about a social event, such as a “good party” or “going to class.” Another type of social schema is a stereotype, which is a schema about a group of people. If a person were to list, for example, everything that individual could think of regarding “criminals,” including personal opinions or experiences, that person would have listed the contents of his or her “criminal” stereotype.


A third type of social schema is a self-schema. Each of a person’s many self-schemata combine to make up the person’s overall self-concept, and the self-schema most salient at any given moment is called the working self-concept. A person might, for example, have a self-schema regarding himself or herself as a student, another one as a man or woman, and yet another regarding his or her athletic abilities. Each self-schema might have many, or few, pieces of information. A person’s self-schema as a student, for example, might include information about where the individual goes to school, the classes being taken, the level of enjoyment of student life, memories of the first day in kindergarten, or memorable books. Some of these pieces of information might also be included in other schemata; the information stored in the “student” self-schema might also be stored in a script about school, for example.


Another type of social schema is the relational schema. Relational schemata are cognitive structures that exist within an interpersonal, interdependent context. Relational schemata are truly social psychological in nature, as they reflect people’s views about themselves and others, not in an isolated context but in the context of others. Relational schemata contain three aspects. First is the self-schema in relation to another person, or how the self is experienced in interaction with another. A good example of this relational self-schema is the distinct self-schema a person has when interacting with a parent or romantic partner. The second component of relational schemata is a partner or particular other schema within the context of an interaction or relationship. For instance, a person holds a distinct schema of a parent, unique to his or her particular parent/child relationship. Finally, relational schemata also include an interpersonal script composed of expectations about how the relationship will and should transpire based on past experiences within the relationship. These three components of relational schemata interact to influence expectations and behavior. As a result, a person having a relational schema with a parent would have a specific self-schema when interacting with the parent (“When I’m with Mom I feel incompetent”), a specific schema of the parent within the interaction (“When Mom is with me, she is very critical”), and, finally, an interpersonal script specific to the parent-child relationship (“If I bring up school, Mom will start yelling at me”).




Social Schemata as Mental Shortcuts

Schemata, whether they are self-schemata, scripts, stereotypes, relational schemata, or other types of schemata, help people organize and understand new events. They function as shortcuts to help people navigate through both their physical and social worlds. Just as a person’s schema for an apple helps the individual recognize and know what to do with an apple, a person’s social schemata help the individual function in social situations. For example, most high school juniors know what to do in a new classroom without having to be told because their “classroom” schema, created during previous semesters, already holds information about how to behave in class. Schemata, then, help people simplify the world; they do not constantly have to relearn information about events, concepts, objects, or people.


To understand how social schemata help people simplify the world, social psychologists study the cognitive processes that schemata affect. This area of study is called social cognition
. Cognitive processes are thinking processes, such as paying attention, that enable the brain to perceive events. Research has shown that schemata affect what people pay attention to, what they store in permanent memory and then later recall, how they interpret events, and even how people behave (although “behaving” is not considered a cognitive process).




Impact on Memory and Interpretation

Research in social cognition shows that having a schema makes it more likely that a person will pay attention to events that are relevant to the schema than to events that are irrelevant. Schemata also make it more likely that a person will store in permanent memory and later recall new information that confirms the beliefs that person already has in his or her schemata.


An interesting study illuminating this tendency had research participants view a videotape of a woman eating dinner with her husband. Half of the participants had previously learned that this woman was a librarian, while the other half had been told that the woman was a waitress. The researchers found that when they later asked participants to recall what they had seen on the videotape, those who had been told the woman was a librarian recalled more information consistent with the “librarian schema,” such as the fact that the woman wore glasses or that she played the piano. Those participants who had been told the woman was a waitress recalled more information consistent with a “waitress schema,” for instance, that the woman had a bowling ball in the room or that there were no bookshelves.


There are exceptions to this general rule. When a schema is either very new or very well established, inconsistent information becomes more important and is often more likely to be recalled than when a schema is only moderately established. For example, if one is just getting to know a new person or if the person is one’s best friend, information inconsistent with one’s schema is more likely to stand out.


Schemata also affect how people interpret events. When people have a schema for an event or person, they are likely to interpret that event or the person’s behavior in a way that is consistent with the beliefs already held in the schema. For example, researchers found that when participants were exposed to either a list of words designed to bring to mind a schema of an adventurous person (brave, courageous, daring) or to invoke the schema of a reckless person (foolish, careless), their later judgments of a paragraph they read about a fictional person named Donald, who loved to go white-water rafting and skydiving, were influenced. Specifically, participants whose adventurous schema had been activated judged Donald positively, while those whose reckless schema had been activated judged Donald negatively.


Finally, people tend to act in ways that are consistent with the schemata they hold in memory, and their actions can affect the actions of others in such a way as to confirm the original beliefs. All these cognitive memory biases result in confirmation of the beliefs that are already held; thus, these biases often produce self-fulfilling prophecies.




The Negative Impact

Although social schemata can facilitate people’s understanding of their social world, they also can bias people’s social perceptions. Often, people are not accurate recorders of the world around them; rather, their own beliefs and expectations, clustered and stored as schemata, distort their perceptions of social events. Such distortions help explain why stereotypes are so difficult to change.


If a person has a schema, a stereotype, about criminals and then meets a man who is introduced as a criminal, perceptions of this person can be biased by the schema. Because schemata affect what people notice, this person will be more likely to notice things about this man that are consistent with his or her schema than things that are irrelevant. Perhaps the person believes that criminals use foul language but has no expectations regarding the type of listening skills a criminal might have. In this case, the person might be more likely to notice when the criminal swears than to notice his empathic listening skills. Then, because schemata affect what is stored in and recalled from memory, the person might be more likely to put into memory, and later remember, the criminal’s swearing. Even if the person did notice his good listening skills, he or she would be less likely to store that in memory, or to recall it later, than to store information about his swearing.


On the other hand, if a person believes that criminals are not very empathic, he or she might be especially likely to notice this new acquaintance’s empathic listening skills. It is unlikely, though, that a person would change his or her schema to fit this new information; what is more likely is that he or she would interpret this information in such a way as to make it fit the stereotype—for example, consider this one criminal to be the exception to the rule, or conclude he developed his listening skills as a con to get out of jail more quickly.


Finally, a person very well might treat a criminal in a way that fits his or her beliefs about him. For example, a person who believes criminals lie might express doubt over things he says. The criminal might then respond to these doubts by acting defensively, which might then confirm the other person’s belief that criminals act aggressively or that they have reasons to feel guilty. The criminal also might respond to doubting comments by actually lying. He might have the attitude, “If you expect me to lie, I might as well.” What has happened, in this case, is this: a person’s beliefs have affected his or her behavior, which in turn has affected the criminal’s behavior, and the criminal’s behavior now confirms the person’s stereotype. This chain of events is one of the problems created by schemata. Very often, negative beliefs make it more likely that a person will find or produce confirmation for these beliefs.


These biases in information processing also can apply to how people perceive themselves, and thus explain why it can be difficult to change a negative self-concept. If a woman sees herself as incompetent, for example, she is likely to notice when her own behavior or thoughts are less than adequate, to store those examples in memory, and to recall such examples from memory. Furthermore, if she engages in an activity and her performance is up for interpretation, she will be more likely to evaluate that performance as incompetent than as competent. Finally, if she believes she is incompetent, this can lead her actually to act that way. For example, her belief may lead her to feel nervous when it is time to perform, and her nervousness might then lead her to perform less competently than she otherwise might have. This provides her with more proof of her own incompetence, another self-fulfilling prophecy.




History of Research

Research in social cognition, the area of social psychology that focuses on social schemata, evolved as a hybrid from two areas of psychology: social psychology and cognitive psychology. In 1924, Floyd Allport published a book titled Social Psychology; this early text was the first to assert that an individual’s behavior is affected by the presence and actions of other individuals. In the 1950s, though, Kurt Lewin asserted that an individual is more influenced by his or her perceptions of other individuals than by what the other individuals actually are doing. For many years after, a popular subfield in social psychology was person perception. Researchers studying person perception discovered many factors that influence people’s judgments and impressions of others. For example, researchers showed that individuals are more influenced by unpleasant than by pleasant information when forming an impression of a stranger. Person perception research focused on how individuals perceive others, rather than on how individuals are influenced by others, and such research provided one of the main foundations for the field of social cognition.


The second main foundation was research on cognitive processes. In the 1980s, researchers studying person perception realized they could better understand why people perceive others as they do by learning more about cognitive psychology. Cognitive psychology was first developed to explain how individuals learn—for example, to explain the relationship between a child’s ability to pay attention, put information into memory, and recall information, and the child’s ability to learn information from a textbook. As cognitive psychologists created techniques for studying these cognitive processes, researchers studying person perception realized that the same processes that affect a schoolchild’s ability to learn textbook material also might affect how individuals learn about other individuals. As these new cognitive research techniques began answering many questions in the field of person perception, that field branched into a second field, the field called social cognition.




Practical Applications of Research

In the 1970s and 1980s, Aaron T. Beck
demonstrated that individuals who are depressed have a self-schema for depression and also a hopeless schema about the world in general. Beck’s work has been extremely influential in the understanding of depression. Because of his work, one of the major approaches to treating depression is to help the depressed individual change his or her thoughts and cognitive processes.


Understanding that schemata can bias people’s thinking can help people resist such biases. Resisting the biases can help people change parts of their self-concepts, their stereotypes of others, or even their schemata about their loved ones. If a person sees his or her roommate as messy, for example, that individual might be especially likely to notice and remember the roommate’s messy behaviors and may respond by cleaning up after the roommate, nagging, or joining the roommate in being messy. The roommate might then rebel against all these responses by becoming even more messy, resulting in a downward spiral. If the person’s roommate also is his or her spouse, this can lead to marital problems. Not all self-fulfilling prophecies have these types of unpleasant consequences, but to stop the cycle of those that do, people need to search actively for evidence that disconfirms their schemata.


One of the earliest contributions from the field of social cognition and social schemata research was a better understanding of interracial problems. Before their understanding of social schemata, social psychologists had been interested in discovering the factors that lead to unpleasant feelings toward other racial groups and the conditions that would eliminate such feelings. Research on social schemata helped explain unpleasant intergroup relations by showing that thoughts, that is, schemata, can be resistant to change for reasons that have nothing to do with unpleasant feelings toward a group; the biases in attention, storing information in memory, recalling information, and interpreting events can occur even when unpleasant feelings are not present. Just as a young child’s brain perceives a goat to be a “doggy,” an adult’s brain also tends to perceive new events in ways that fit information already held in memory.


Social psychologists came to understand that cognitive processes also affect many other psychological phenomena that formerly were explained by emotional processes alone. For example, social schemata contribute to psychologists’ understanding of why crime victims do not always receive help, why bullies initiate fights, and why some teenagers are so angry with their parents.


Social schemata, studied by social psychologists, have such far-reaching effects that researchers in areas of psychology other than social psychology also study them. For example, personality psychologists study how social schemata affect self-concept, and clinical psychologists study how social schemata can inhibit or facilitate therapy sessions. Social schemata themselves may simplify people’s understanding of social events, but the study of schemata has greatly enriched the understanding of the social perceiver.




Bibliography


Burns, David D. Feeling Good Together: The Secret of Making Troubled Relationships Work. New York: Broadway, 2008. Print.



Graziano, Michael S. A. Consciousness and the Social Brain. New York: Oxford UP, 2013. Print.



Lassen, Maureen Kirby. Why Are We Still Fighting? How to End Your Schema Wars and Start Connecting with the People You Love. Oakland: New Harbinger, 2000. Print.



Rison, Lawrence P., et al., ed. Cognitive Schemas and Core Beliefs in Psychological Problems: A Scientist-Practitioner Guide. Washington: American Psychological Association, 2007. Print.



Rochat, Philippe, ed. Early Social Cognition. New York: Psychology, 2014. Digital file.



Saltz, Gail. Becoming Real: Defeating the Stories We Tell Ourselves That Hold Us Back. New York: Riverhead, 2004. Print.



Strack, Fritz, and Jens Forster, eds. Social Cognition: The Basis of Human Interaction. New York: Psychology, 2009. Print.



Van Vreeswijk, Michiel, Jenny Broersen, and Marjon Nadort. The Wiley-Blackwell Handbook of Schema Therapy. Malden: Wiley, 2012. Print.

Tuesday, 22 October 2013

Does insurance cover addiction treatment?


History

Although experts have known for some time that rehabilitation treatment is important for sustained
addiction recovery, not until 2008 did health insurers, on a wider scale, begin to cover addiction treatment. Typically, health insurers contract with health care facilities and providers to obtain a discounted reimbursement rate.


Mental health and addiction treatment facilities and providers have been reluctant to contract with health care insurers because they did not want to accept the reduced reimbursement and because many of their patients did not have health insurance covering mental health and addiction treatment. Less than 70 percent of addiction treatment facilities were contracted with public and private insurers. Health insurers, when they did cover addiction services, only covered detoxification. They provided little or nothing for rehabilitation services for the abuser.


A few US states had mandated that health insurers cover addiction treatment. Other states required that health insurers include options for addiction treatment but did not mandate this form of coverage; still other states did not require coverage at all for addiction services. There were exceptions, however. Self-insured employers opted not to cover addiction services, and employers covered by the Employment Retirement Income Security Act of 1974 (ERISA) were exempt from these state requirements.


ERISA is a federal law that sets minimum standards for pensions and health care insurance in private industry, but it does not require pension plans or health care insurance. Many substance abusers were not employed and had no health insurance. This left addiction treatment facilities and providers without any assurance of payment. As a result, addiction treatment facilities and providers frequently required that persons pay in advance for their treatment.




Mental Health and Addiction Coverage

In 2008, after years of lobbying by mental health advocates, the Mental Health Parity and Addiction Equity Act (MHPAE) was signed into law in the United States. This federal legislation requires that health insurance policies with coverage for mental health and substance abuse treatment include coverage at the same level as that for physical treatment. This means that co-payments, co-insurance, out-of-pocket expenses, office visit and days-of-service limitations, and in-network and out-of-network benefits, must be comparable to those for care for physical ailments.


In addition, this law requires equal mental health and substance abuse treatment coverage for self-funded health plans and for ERISA employers’ health plans; exclusions were no longer permitted. However, MHPAE has a large loophole: Health insurers and employers are not required to offer any mental health and addiction coverage.


Upon enactment of MHPAE, the greatest concern among businesses was that the act would increase the cost of health insurance. Few studies have been performed to determine whether this concern is valid. One study utilizing data from federal employees’ health plans has been performed to evaluate this change. Federal employees were granted mental health parity in 2001. The study used claims data from 1999 through 2002. The mental health costs before parity were compared with those after parity. The study found little increase in the utilization and costs of mental health and addiction treatment. However, out-of-pocket costs for members were lowered significantly.


Another flaw in the mental health parity law is the way that health insurers validate and pay for coverage. Often, they have special criteria for claims’ reimbursement that interfere with payments. For example, a health insurer might require that the mental health or substance abuse patient receive outpatient care before inpatient care. Only if the outpatient treatment fails can the person be admitted for care. Also, visits to a psychiatrist or a counselor are often limited in number by calendar year.




Issues

Even with parity for mental health and addiction treatment, additional reimbursement issues arise. First, a majority of addicted persons have no health insurance. Often they have no job or they have a job that does not provide any health insurance. Second, addicted persons often have relapses. Costs for addiction treatment are controlled through limited admissions for treatment, resulting in limited treatment for relapses.


Third, addiction treatment programs, both outpatient and inpatient, have patient rules. For example, patients cannot take any drugs while they are in the program. They are tested weekly for the presence of drugs in their urine. If they violate this rule, they can be discharged from the addiction treatment program, even if they have health insurance.


Fourth, insurers may require that substance abusers use in-network (contracted) providers. Often, only a few such facilities and providers exist in a given network, and there may be a waiting period for treatment. Programs using cognitive-behavioral therapy are more likely to accept health insurance for payment. If a patient does not respond well to this type of therapy, their health insurance is of little use to them. Fifth, denial is a common symptom of substance abuse. It can be difficult to get the patient to accept their problem and to go for treatment, even if he or she has health insurance.




Bibliography


“Acceptance of Private Health Insurance in Substance Abuse Treatment Facilities.” 6 Jan. 2011. Web. 21 Feb. 2012. http://www.oas.samhsa.gov/2k11/305/305privateins2k11.htm. Examines data on the extent to which treatment facilities are ready to accept private health insurance for substance abuse treatment services.



“Health Insurance and Substance Use Treatment Need.” Substance Abuse and Mental Health Services Administration. 2007. Web. 21 Feb. 2012. http://www.oas.samhsa.gov/2k7/insurance/insurance.htm. Describes health insurance coverage for mental health and addiction services prior to the passing of the mental health parity legislation.



Johnson, Teddi Dineley. “Mental Health Advocates Laud New Federal Parity Law: Equal Coverage for Mental Health Care.” Nation’s Health 38.10 (2008). Print. This article discusses the features of the Federal Mental Health and Substance Abuse parity legislation.



“Understanding the Federal Parity Law.” Substance Abuse and Mental Health Services Administration. Web. 21 Feb. 2012. http://www.samhsa.gov/healthreform/docs/ConsumerTipSheetParity508.pdf. A brief overview of the Mental Health Parity and Addiction Equity Act of 2008.

Monday, 21 October 2013

What are intersex conditions? |


Early Human Sexual Development

Up to the ninth week of gestation, the external genitalia (external sexual organs) are identical in appearance in both male and female human embryos. There is a phallus that will become a penis in males and a clitoris in females and labioscrotal swelling that will become a scrotum in males and labial folds in females. Sexual differentiation into a male or female is governed by his or her sex chromosomes (the X and Y chromosomes) and hormones. An individual who has two X chromosomes normally develops into a female, and one who has one X and one Y chromosome normally develops into a male. It is the Y chromosome that determines the development of a male. The Y chromosome causes the primitive gonads (the gonads that have not developed into either an ovary or a testis) to develop into testes and to produce testosterone (the male sex hormone). It is testosterone that acts on the early external genitalia and causes the development of a penis and scrotum. If testosterone is not present, or the receptors for it are lacking, regardless of the chromosome constitution of the embryo, female external genitalia will develop.















Intersexuality: Causes and Effects

Intersex individuals have both male and female gonads. At birth, intersex individuals can have various combinations of external genitalia, ranging from completely female to completely male genitalia. Many intersex individuals have external genitalia that are ambiguous (genitalia somewhere between normal male and normal female) and may consist of what appears to be an enlarged clitoris or a small penis, hypospadias (a urinary tract opening at the base of or along the penis or scrotum instead of the tip), and a vaginal opening. The extent to which the genitalia are masculinized depends on how much testosterone was produced and received by the testicular portion of the gonads during development. The gonadal structures of an intersex individual can range from a testis on one side and an ovary on the other side, to testes and ovaries on each side, to an ovotestis (a single gonad with both testicular and ovarian tissue) on one or both sides.


Intersexuality has different causes. The chromosomal or genotypic sex of an intersex individual can be 46,XX, 46,XY, 45 XO (Turner syndrome), 47,XXX (triple X), or 47 XXY (Klinefelter syndrome). Chromosomal mutations can cause intersexuality. The absence or dysfunction of the SRY locus produces an individual with normal female genitalia but a 46,XY karyotype. Individuals with a 46,XX karyotype who have the SRY locus transposed to one of their X chromosomes will have a normal male appearance. Likewise, the genes WT1, SOX9, and SF1 are necessary for normal testicular development.


Some affected individuals have different types of mosaicism, such as 46,XX/47,XXY or 45,X/46,XY. Individuals with a 46,XX/46,XY karyotype are known as chimeras. Chimerism usually occurs through the merger of two different cell lines (genotypes), such as when two separate fertilized eggs fuse together to produce one embryo. This can result in a single embryo with some cells being 46,XX and some being 46,XY. Mosaicism means having at least two different cell lines present in the same individual, but the different cell lines are caused by losing or gaining a chromosome from some cells early in development. An example would be an embryo that starts out with all cells having a 47,XXY chromosome constitution and then loses a single Y chromosome from one of its cells, which then produces a line of 46,XX-containing cells. This individual would have a karyotype written as 46,XX/47,XXY. In a chimera or mosaic individual, the proportion of developing gonadal cells with Y chromosomes determines the appearance of the external genitalia. More cells with a Y chromosome mean that more testicular cells are formed and more testosterone is produced.


Hormones also play a part in determining the sex of an individual. Abnormalities of testosterone production or abnormalities in the testosterone receptor at the cellular level can cause 46, XY intersex (formerly called "male pseudohermaphroditism"). One example is a deficiency in 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT). When there is a deficiency of this enzyme, there will be a deficiency of DHT, which is the hormone primarily responsible for masculinization of external genitalia. An individual who is genetically male but lacks DHT will have female-appearing external genitalia or ambiguous genitalia at birth. Often these individuals are reared as females, but at puberty they will masculinize because of greatly increased production of testosterone. These individuals may actually develop into nearly normal-appearing males. Abnormalities of the testosterone receptor, known as androgen insensitivity syndrome, can also result in a range of different conditions in affected males, from normal female appearance (a totally defective receptor) to ambiguous genitalia (partially defective receptor). These individuals will not masculinize at puberty because no matter how much testosterone or DHT they produce, their bodies cannot respond to the hormones. Similarly, deficiency in aromatase (an estrogen-producing enzyme), overproduction of androgen due to congenital adrenal hyperplasia, and in utero exposure to testosterone can cause 46, XX intersex (formerly "female pseudohermaphroditism").



The cause of intersexuality in the majority of affected individuals is unknown, although it has been postulated that those intersex individuals with normal male or female karyotypes may have hidden chromosome mosaicism in just the gonadal tissue.




Impact and Applications

Intersex individuals with ambiguous genitalia are normally recognized at birth. It is essential that these individuals have a thorough medical evaluation, since some causes of ambiguous genitalia, such as congenital adrenal hyperplasia, can be life-threatening if not recognized and treated promptly. Once intersexuality is diagnosed in a child, the decision must be made whether to raise the child as a boy or a girl. This decision is made by the child’s parents working with specialists in genetics, endocrinology, psychology, and urology. Typically, the karyotype and appearance of the external genitalia of the child are the major factors in deciding the sex of rearing. Previously, most intersex individuals with male karyotypes who had either an absent or an extremely small penis were reared as females. The marked abnormality or absence of the penis was thought to prevent these individuals from having fulfilling lives as males. This practice has been challenged by adults who are 46,XY but were raised as females. Some of these individuals believe that their conversion to a female gender was the wrong choice, and they prefer to think of themselves as male. Intersex individuals with a female karyotype and normal or near-normal female external genitalia are typically reared as females.


The debate over what criteria should be used to decide sex of rearing of a child is ongoing. An increasingly important part of this debate is the concept of gender identity, which describes what makes people male or female in their own minds rather than according to what sex their genitalia are. This is an especially important issue for those individuals with chimerism or mosaicism who have both a male and female karyotype. The decision to raise these individuals as boys or girls is made primarily on the basis of the degree to which their external genitalia are masculinized or feminized.


Those intersex individuals who have normal female or male genitalia at birth are at risk for developing abnormal masculinization in the phenotypic females or abnormal feminization in the phenotypic males at puberty if both testicular and ovarian tissue remains present. Thus, the gonad that is not specific for the assigned sex of the individual may be surgically removed. Gonadal tissue may be also removed because the cells of the gonad(s) that have a 46,XY karyotype are at an increased risk of becoming cancerous. Medical professionals increasingly recommend that surgeries, other than those necessary for urinary function, be delayed until the affected individual is old enough to have input in the decision-making process.




Key terms




ambiguous genitalia


:

external sexual organs that are not clearly male or female




genotype

:

an organism’s complete set of genes




gonad

:

an organ that produces reproductive cells and sex hormones; termed ovaries in females and testes in males




karyotype

:

a description of the chromosomes of an individual’s cells, including the number of chromosomes and a physical description of them (normal female is 46,XX and normal male is 46,XY)




phenotype

:

the physical and biochemical characteristics of an individual based on the interaction of genotype and environment





Bibliography


Donohoue, Patricia A. "Disorders of Sex Development." Nelson Textbook of Pediatrics. Ed. Waldo E. Nelson and Robert Kliegman. Philadelphia: Elsevier/Saunders, 2011. Digital file.



Dreger, Alice Domurat. Hermaphrodites and the Medical Invention of Sex. Cambridge: Harvard UP, 1998. Print.



Gilbert, Ruth. Early Modern Hermaphrodites: Sex and Other Stories. New York: Palgrave, 2002. Print.



Harper, Catherine. Intersex. New York: Berg, 2007. Print.



Holmes, Morgan. Intersex: A Perilous Difference. Selinsgrove: Susquehanna UP, 2008. Print.



Hunter, R. H. F. Sex Determination, Differentiation, and Intersexuality in Placental Mammals. New York: Cambridge UP, 1995. Print.



"Intersex." Medline Plus. US National Library of Medicine, 22 Aug. 2013. Web. 1 Aug. 2014.



Meyer-Bahlburg, Heino. “Intersexuality and the Diagnosis of Gender Identity Disorder.” Archives of Sexual Behavior 23.1 (1994): 21. Print.



Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 9th ed. Philadelphia: Saunders/Elsevier, 2013. Print.



Preves, Sharon E. Intersex and Identity: The Contested Self. 2003. New Brunswick: Rutgers UP, 2005. Print.



Reis, Elizabeth. Bodies in Doubt: An American History of Intersex. Baltimore: Johns Hopkins UP, 2012. Print.



Simpson, J. L. “Disorders of the Gonads, Genital Tract, and Genitalia.” Emery and Rimoin’s Principles and Practice of Medical Genetics. Ed. David L. Rimoin, Reed E. Pyeritz, and Bruce R. Korf. 6th ed. San Diego: Elsevier Science, 2007. Print.



Zucker, Kenneth J. “Intersexuality and Gender Identity Differentiation.” Annual Review of Sex Research 10 (1999): 1–69. Print.

What is Saccharomyces cerevisiae? |


The Organism


Saccharomyces cerevisiae (S. cerevisiae, or baker’s yeast) has been used for millennia as a leavening agent in bread products and for fermentation in beer and wine. Yeast is a simple, one-celled eukaryote with six thousand genes on sixteen chromosomes. It was the first eukaryote to have its entire DNA sequenced.




Yeast can produce offspring using two different methods, a sexual life cycle and an asexual life cycle. In the asexual life cycle, the yeast cell produces the next generation by a process called budding. All genetic components of the mother cell are duplicated, and a small “bud” begins to grow from the mother cell. The bud continues to grow until it is nearly the size of the mother cell. The DNA and other duplicated cellular components are then partitioned into the new bud. The cells undergo cytokinesis and are now separate entities able to grow and continue reproducing independently of one another.


To produce offspring that are not clones of the mother cell, yeast use a sexual life cycle. A yeast cell exists stably as either a diploid or a haploid organism, but only the haploid organism is able to mate and exchange genetic information. Haploid yeast can contain either the MATa or MATalpha gene. These genes produce soluble factors that distinguish them as one of two mating types. An “a” cell (MATa) and an “alpha” cell (MATalpha) mate by sequentially fusing their cell walls, their cytoplasms, and finally their nuclei. This diploid cell now contains two copies of each chromosome that can undergo recombination during meiosis. When all environmental signals are ideal, the diploid yeast will undergo meiosis, allowing exchange and recombination of genetic information brought to the diploid by both haploid cells. The result of meiosis is an ascus that contains four recombinant spores that will grow into haploid yeast cells when environmental conditions are ideal.




A Model Organism

Researchers choose yeast as a model organism to study specific areas of interest for many different reasons. Saccharomyces cerevisiae is nonpathogenic to humans, allowing manipulation in a laboratory with little or no containment required. At a temperature of 30 degrees Celsius (86 degrees Fahrenheit), the yeast population can double in ninety minutes, allowing many experiments to be completed in one day. Among the primary reasons for selection of yeast as a model system is that they offer the possibility of studying the genes and proteins that are required for basic growth functions and cell division. Yeast use many of the same genes and proteins to govern the same processes that animal and plant cells use for growth and division. Each single cell has to take in nutrients, grow, and pass along information to its progeny. In many ways, yeast can be considered a simplified version of a plant or animal cell, in that it lacks all the genes that provide the determinants that are expressed as differences between plants and animals. Another important reason for using yeast is that yeast is amenable to investigation using both genetic and biochemical approaches. This allows for correlation of findings from both approaches and a better understanding of a specific process or activity.


Yeast is also ideal for use as a model system due to at least four well-established techniques and procedures. First, genetics in yeast takes advantage of well-established auxotrophic markers. These markers are usually mutations in biosynthetic pathways that are used to synthesize required cellular components such as amino acids and nucleotides. By using these marker genes, researchers can follow genes and their associated chromosomes from one generation to the next.


Second, yeast is readily transformed by plasmids that function as artificial chromosomes. All that is needed is an auxotrophic marker to follow the plasmid through succeeding generations, a yeast origin of replication to allow replication of the plasmid DNA, and a region into which the gene of interest can be inserted in the plasmid DNA. This allows the researcher to move genes easily from yeast strain to yeast strain and quickly examine the effect of the gene in combination with many other genes.


Third, yeast is easily mutated by chemicals and can be grown in a small space, which allows the researcher quickly to identify mutations in genes that result in a specific phenotype. For example, to define all the genes in the adenine biosynthetic pathway, a researcher would mutate a yeast strain with one of many available mutagenic chemicals, resulting in changes within the DNA. The mutated yeast strains would then be checked to see if the strain was able to grow on media lacking adenine. All of the strains mutant for growth on adenine would be collected and could identify a number of genes involved in the adenine biosynthetic pathway. Further research could establish whether each of these mutations in the yeast identified one gene or many genes.


Fourth, yeast is the model system of choice when examining and identifying proteins that interact with one another in the cell. This technique is called the two-hybrid system.




Two-Hybrid System

The two-hybrid system takes advantage of scientists’ understanding of transcription at the GAL1 gene in yeast. The promoter region of GAL1 contains a binding site for the Gal4p transcription factor. When the cell is grown on the sugar galactose, Gal4p binds to the promoter of GAL1 and activates transcription of the GAL1 gene. Gal4p can be essentially divided into two functional regions: one region that binds to DNA and another region that activates transcription.


The two-hybrid system uses the GAL1-Gal4p transcription system to identify previously unknown proteins that interact with a protein of interest. The system consists of a reporter gene under the control of the GAL1 promoter and two plasmids that produce fusions with the Gal4p transcription factor. The first plasmid contains a gene of interest fused to a DNA-binding domain. This plasmid expresses a protein that is able to bind to the DNA-binding site in the GAL1 promoter of the reporter gene. This plasmid is unable to activate transcription of the reporter gene, since the Gal4p fragment does not contain the information to activate transcription. The second plasmid is provided from a collection of plasmids that consist of unknown or random genes fused to the transcription activation domain of Gal4p. This plasmid by itself is unable to bind to the DNA-binding site in the GAL1 promoter and thus is unable to activate transcription of the reporter gene. If both plasmids contain genes whose protein products physically interact in the cell, the complex is able to bind to the DNA-binding region of the
GAL1 promoter, and since the activation domain of Gal4p is also present in this complex, activation of the reporter gene will occur. The production of the reporter gene serves as a signal that both of the gene products interact in the cell. The yeast strain containing the active reporter gene is then selected and further examined to determine the unknown DNA that resides on the second plasmid by sequence analysis.




Cell Cycle Mutants

The isolation, characterization, and identification of conditional mutations in Saccharomyces cerevisiae has led to great advances in our understanding of the genes involved in the cell cycle. Because cell division is an essential process, null mutations in cell cycle genes are lethal. Thus, an approach to isolate temperature-sensitive mutants, cells that grow at room temperature but not at 36 degrees Celsius (96.8 degrees Fahrenheit), was taken. The observation that the formation of the yeast bud occurs at the beginning of the cell cycle and the bud continues to grow through cell cycle progression facilitated analysis of defects in cell division cycle (CDC). At the permissive temperature (room temperature), cell cultures are asynchronous; however, when the culture is switched to the restrictive temperature, cells with mutations in genes affecting cell cycle progression become synchronously arrested, which can be visualized microscopically. Temperature-sensitive mutants with defects in budding, DNA synthesis, nuclear division cytokinesis, and cell division were analyzed. This approach led to the isolation and characterization of the cell division cycle mutants, each of which undergoes growth arrest at specific points in the cell cycle and essentially represents all the key regulators of cell cycle progression. A fundamental observation that arose from this work was that cell cycle progression is controlled by cell-cycle checkpoints, whereby progression of the cell cycle is dependent upon the successful completion of upstream events. These checkpoints maintain cellular integrity by causing the cell cycle to arrest and initiate repair processes before errors are passed on to daughter cells. One of the genes thought to be most important that was identified using this approach is CDC28, which, like all of the CDCs, has homologues in all eukaryotes, including humans. Cdc28p, a cyclin-dependent kinase, initiates two pathways that lead to cell division. The identification of the CDC genes in yeast and mammalian homologues has led to important insights into defects in cell-cycle checkpoints that ultimately lead to cancer.




Research and Implications

The years of work on yeast as a model system have provided many insights into how genes and their protein products interact to coordinate the many cellular mechanisms that take place in all cells from simple yeast to complicated humans. It is impossible to exhaustively list the different areas of research currently being examined or completely list the new understandings that have come to light through the use of the S. cerevisiae model system. Every major area of cellular research has at one time or another used yeast to ask some of the more difficult questions that could not be asked in other systems. Work in yeast has aided identification of genes and elucidated the mechanism of many different areas of research, including cell-cycle regulation, mechanisms of signal transduction, the process of secretion, DNA replication, transcription of DNA, translation of messenger RNA into proteins, biosynthetic pathways of amino acids and other basic building blocks of cells, and regulation and progression of cells through mitosis and meiosis. Despite all these advances, there is still much to learn from yeast, and it will continue to provide information for years to come.


Outside of its value in genetic research, S. cerevisiae continues to be an important resource in other ways. As implied by its common name of baker's yeast, it is still used as the chief leavening agent for the production of bread products. A different strain of the yeast is also an important factor in the fermentation process used in winemaking and beer brewing. As the craft beer market has expanded, greater attention has been paid to the specific processes used in producing different types and flavors of beer; S. cerevisiae belongs to the group of yeasts often referred to as top fermenting. In 2013 the government of Oregon named S. cerevisiae as the state's official microbe in recognition of its role in the history of brewing and the state's close association with the craft brew movement.




Key terms



ascus

:

the cellular structure that results from meiosis in yeast, containing four recombinant spores that are fully capable of growing into haploid yeast cells




budding

:

the asexual method of duplication used by yeast to create a clone of the original cell




diploid cell

:

a cell that contains two copies of each chromosome




haploid cell

:

a cell that contains one copy of each chromosome




mating type

:

one of two types of yeast cell, depending on a soluble factor that each cell secretes





model organism


:

an organism well suited for genetic research because it has a well-known genetic history, a short life cycle, and genetic variation between individuals in the population





Bibliography


Aggarwal, Monika, and Robert M. Brosh. “Functional Analyses of Human DNA Repair Proteins Important for Aging and Genomic Stability Using Yeast Genetics.” DNA Repair 11.4 (2012): 335–48. Print.



Amberg, D., D. Burke, and J. Strathern. Methods in Yeast Genetics: A Cold Spring Harbor Laboratory Course Manual, 2005 Edition. Cold Spring Harbor: Cold Spring Harbor Laboratory P, 2005. Print.



Broach, J., J. Pringle, and E. Jones, eds. The Molecular and Cellular Biology of the Yeast Saccharomyces. 3 vols. Cold Spring Harbor: Cold Spring Harbor Laboratory P, 1991–97. Print.



Feldmann, Horst. Yeast: Molecular and Cell Biology. Wenheim: Wiley, 2010. Print.



Fields, S., and O. Song. “A Novel Genetic System to Detect Protein-Protein Interactions.” Nature 340 (1989): 245–46. Print.



Hartwell, L. “Yeast and Cancer.” Bioscience Reports 24 (2004): 523–44. Print.



Lodolo, E. J., et al. "The Yeast Saccharomyces Cerevisiae: The Main Character in Beer Brewing." FEMS Yeast Research 8.7 (2008): 1018–36. PubMed. Web. 3 Mar. 2015.



McInerny, Christopher J. “Cell Cycle Regulated Gene Expression in Yeasts.” Advances in Genetics. Ed. Theodore Friedmann, Jay C. Dunlap, and Stephen F. Goodwin. Vol. 73. San Diego: Elsevier, 2011. 51–86. Print.

Sunday, 20 October 2013

What is microscopy? |


Indications and Procedures

Conventional microscopy uses a beam of light to illuminate a thin slice of material to be viewed. The material may be stained to provide contrast among its components. The visible light is aimed through the material and collected in a lens. Additional lenses magnify the image until it is visible to the eye of the viewer.




Electron microscopy is a procedure in which a beam of electrons, rather than visible light, is projected toward an object to be viewed. The object is prepared by coating it with a fine layer of metal, frequently gold, that is one or two atoms thick. The electrons reflect off the coated object and hit a screen. The image on the screen is magnified and becomes visible to the human eye. An alternative procedure involves a very thin section of material that is dried and put into a vacuum chamber. A beam of electrons is directed through the prepared specimen. A coated screen receives the electron beam and transforms the image into one visible to the human eye.


Fluorescence microscopy is a procedure that is based on the fact that fluorescent materials emit visible light when they are irradiated with ultraviolet light, which is outside the spectrum visible to the human eye. Some materials manifest this property naturally; others may have to be treated with fluorescent solutions in a process similar to staining. When the absorption of the specimen is in the relatively long ultraviolet range, two filters are also used. The first is placed over the light source to eliminate all but the desired long ultraviolet rays. The second is placed over the eyepiece. The result is a field that becomes dark and allows any red or yellow fluorescence to be visible.




Uses and Complications

Microscopy has extended the range of understanding for physical objects. Intracellular organelles are routinely made visible. Microscopy has made possible the science of microbiology. Fluorescence allows immunoglobulins to be routinely assayed. Viruses are too small to be seen with a light microscope, but electron microscopy has enabled virologists to view and classify viruses.


The drawbacks of current microscopy techniques are primarily that only small samples of material can be viewed at a time. Usually, the material must be destroyed while it is being prepared. Living tissue may be viewed, but only at levels of magnification below those possible at the limits of normal microscopy and far below those possible with electron microscopy.


Electron microscopy allows the greatest amount of magnification for objects. Because the wavelength of electrons is thousands of times shorter than that of visible light, the resulting magnification is several thousand times greater than that possible with visible light. The use of subatomic particles theoretically increases the potential of magnification, but a continuous source of subatomic particles is difficult and quite expensive to supply.




Bibliography


Black, Jacquelyn G., and Laura J. Black. Microbiology. Hoboken, N.J.: Wiley, 2013.



Hawkes, Peter W., and John C. H. Spence, eds. Science of Microscopy. New York: Springer, 2007.



Madigan, Michael T., and John M. Martinko. Brock Biology of Microorganisms. 13th ed. San Francisco: Pearson/Benjamin Cummings, 2012.



Murray, Patrick R., Ken S. Rosenthal, and Michael A. Pfaller. Medical Microbiology. 6th ed. Philadelphia: Mosby/Elsevier, 2009.



Singleton, Paul, and Diana Sainsbury. Dictionary of Microbiology and Molecular Biology. Rev. 3d ed. Hoboken, N.J.: John Wiley & Sons, 2007.



Spector, David L., and Robert D. Goldman, eds. Basic Methods in Microscopy: Protocols and Concepts from Cells—A Laboratory Manual. Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press, 2006.

Discuss dehumanisation in Heart of Darkness. Refer to Enlightenment philosophy in your discussion.

In the Belgian colony that serves as the setting of Joseph Conrad's Heart of Darkness, then called the Congo Free State, narrator Marlow consistently witnesses the dehumanization of the Congolese people. Belgian officials ruthlessly exploited and abused the people of the Congo in order to extract their natural resources for profit. For the Belgians who ruled in the Congo, the Congolese were merely tools to be used in the pursuit of profit; this is emphasized...

In the Belgian colony that serves as the setting of Joseph Conrad's Heart of Darkness, then called the Congo Free State, narrator Marlow consistently witnesses the dehumanization of the Congolese people. Belgian officials ruthlessly exploited and abused the people of the Congo in order to extract their natural resources for profit. For the Belgians who ruled in the Congo, the Congolese were merely tools to be used in the pursuit of profit; this is emphasized in the scene where Marlow discovers the place where Africans were left to die when they were deemed too sick to continue constructing the railroad. Another example of dehumanization is performed by Marlow himself, who does not interact with or personally acknowledge the Congolese people he sees. To him they are a foil that he projects his own philosophical struggles on; Marlow seems to view them and their suffering as a cause for personal contemplation, but doesn't  perceive them as being fully human.


Dehumanization in Heart of Darkness could be examined through the lens of Enlightenment philosophy with an emphasis on humanism. Humanism, a philosophical tenet of Enlightenment ideology, argued for the inherent value of humanity and promoted the use of uniquely human intellectual abilities, such as rationality. The dehumanization of the Congolese would be an affront to humanism, because it would deprive people the value inherent to their humanity. Denying humans access to their humanity through brutalization and slavery does not respect the inherent value of their humanity, so it is at odds with Enlightenment philosophy.

What kind of poem is "The Secret Heart"?

"The Secret Heart" by Robert Peter Tristam Coffin is a lyric verse. A lyric poem is one in which the speaker in the poem expresses strong feelings about an experience or idea. Although we might think of the word "lyric" as referring to the words of a song, in poetry it refers to a poem that uses rhythm, rhyme, meter, and sound devices to create a lyrical effect. The term "verse" means that the...

"The Secret Heart" by Robert Peter Tristam Coffin is a lyric verse. A lyric poem is one in which the speaker in the poem expresses strong feelings about an experience or idea. Although we might think of the word "lyric" as referring to the words of a song, in poetry it refers to a poem that uses rhythm, rhyme, meter, and sound devices to create a lyrical effect. The term "verse" means that the poem rhymes and has a regular rhythm and meter. 


This poem expresses the speaker's feelings about a boy and his father, especially the boy's memory of his father checking on him after he has gone to bed. The father's actions and the boy's memories are described in warm, loving, and appreciative terms. The poem uses the visual of the heart shape the father formed with his hands to portray the father's love for his son. Such symbolism and/or metaphor is a common device in lyric poetry. The poem is written in one stanza composed of eleven couplets, or pairs of rhyming lines. Most of the lines are iambic tetrameter, although there is some variation. The poem uses soft alliterative sounds like repeated /s/ and /h/ sounds to create a pleasant and quiet sound. 


When you find a poem that makes use of traditional rhythm, meter, rhyme, and other poetic devices and that does not fit into any other category of poetry (see link below), you may categorize it as lyric verse. 


Saturday, 19 October 2013

What is salmonella? |


Definition


Salmonella are gram-negative, motile, non-spore-forming,
nonencapsulated, facultative-anaerobic rods that cause several diseases, primarily
enteric (intestinal), in humans and other animals.





Natural Habitat and Features

The genus Salmonella was named for Daniel E. Salmon, an American veterinary pathologist and bacteriologist. The type strain, originally named S. choleraesuis, was discovered by Salmon’s research associate, Theobald Smith. The genus is closely related to Escherichia coli (E. coli) and was initially subdivided into hundreds of species named for the diseases it caused and for the host organism: for example, S. typhi (typhoid fever), S. enteritidis (gastroenteritis), S. typhimurium (mouse typhoid), and S. choleraesuis (hog cholera).



After further genetic testing and after scientists determined that most Salmonella spp. are not very host specific, most of the original species were combined into a single species, S. enterica. This species was then divided into five subspecies and more than two thousand strains or serovars; for example, S. enterica subsp. enterica serovar Typhi has replaced S. typhi, S. enterica subsp. enterica serovar Enteritidis has replaced S. enteritidis, and S. enterica subsp. arizonae has replaced S. arizonae. Only S. bongori was deemed distinct enough to stand alone as a different species. The older designations are still frequently used in both professional journals and the popular press.




Pathogenicity and Clinical Significance

According to the Centers for Disease Control and Prevention (CDC) in 2015, 2,500 different strains (serotypes) of Salmonella had been identified, with fewer than 100 responsible for most human disease. S. enterica subsp. enterica contains the majority of disease-causing strains. Salmonellosis is the second most common cause of gastroenteritis, surpassed only by Campylobacter spp. infections. Infections caused by Salmonella spp. are considered zoonotic because many strains of this bacterium can be transferred from humans to animals and from animals to humans.


Most cases of salmonellosis are the result of fecal to oral contamination caused by ingestion of fecal-contaminated food. Because Salmonella spp. are so widespread and can survive several weeks in water or on vegetation and more than two years in soil, transmission is relatively easy. For example, during butchering and processing, raw meats can become contaminated with the intestinal contents of the butchered animals. Shellfish are easily contaminated when raw sewage makes its way into aquatic habitats. An infected chicken can deposit Salmonella into her eggs before shell deposition or on the shell as the egg is laid. Irrigating or washing crop plants in water contaminated by Salmonella can contaminate the crops. Food preparers with poor hygiene can also contaminate food.


After a multistate outbreak of Salmonella Heidelberg that involved more than six hundred Americans was sourced to chicken parts that had been packaged by Foster Farms, the US Department of Agriculture's Food and Safety Inspection Service (FSIS) determined that regulations and standards needed to be set for individual chicken parts as well as whole chickens. In 2015, the FSIS proposed the new standards designed to decrease consumer exposure to Salmonella in all chicken products.


In addition to food contamination, pets, especially birds, reptiles, and amphibians, can harbor Salmonella, which can easily be transferred from their cloacae to their feathers or skin.


The best way to prevent salmonellosis is to always wash one’s hands after using the toilet, handling raw meat, cleaning up feces, and handling a bird, reptile, or amphibian. In addition, cooking all food to an internal temperature of 167° Fahrenheit (75° Celsius) and boiling water for a minimum of one minute kills Salmonella. Freezing, however, will usually not kill all Salmonella in contaminated food or water. Cutting boards used for raw meat should also be cleaned thoroughly, preferably with bleach.


In humans, one of the most serious forms of salmonellosis is typhoid fever caused by S. enterica sub. enterica serovar Typhi, also called S. typhi. This bacterium is highly adaptable and can produce stress-related proteins that allow the bacterium to survive better under environmental stresses (such as increased temperatures, acidic conditions, and the presence of antibiotics). Unlike many Salmonella strains, this bacterium has only one animal reservoir: humans. It is usually transmitted through contaminated water and undercooked, contaminated food. Because of this, it causes most problems in developing countries with poor sanitation.



S. typhi can also be transmitted by food-service workers who were previously infected. About 5 percent of all persons who had typhoid fever retain infective bacteria and can pass these along. In the United States, food service workers who have had typhoid fever are required to be free of the typhoid bacterium (as measured by fecal swabs) before they can return to work.


Diarrhea is the most common symptom of salmonellosis, but bacteria can enter
the intestinal epithelium and migrate to other areas of the body, causing fever,
headache, rose-colored spots on the upper chest, and organ inflammation. Humans
heterozygous for cystic fibrosis may have lowered susceptibility to typhoid
fever because the changes in the cell membrane of heterozygotes decrease the
likelihood of bacterial invasion.


As of 2013, the CDC reported that approximately 5,700 cases of typhoid fever occur in the United States each year, and most of these cases are contracted outside the country. Also according to the CDC, in the developing world, nearly twenty-two million cases of typhoid are seen each year. Most typhoid deaths are caused by dehydration, so rehydration therapy is critical in treating this or any other salmonellosis.




Drug Susceptibility

Bacterial strains resistant to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole, and streptomycin are so common that these antibiotics are no longer used. Ciprofloxacin is the drug of choice, but strains resistant to it are on the rise. Cephtriaxone and cephotaxime are being used more often, especially in areas with multiple resistance. Both oral and injectable vaccines are available, but these are only 50 to 70 percent effective. A very similar, but less common disease is paratyphoid fever, which is caused by the Paratyphoid serovar.



S. enterica serovar Enteritidis is the most frequent cause of Salmonella gastroenteritis in humans. Many other serovars can also cause gastroenteritis. The most common symptoms are diarrhea, abdominal cramps, and nausea. Unlike typhoid fever, gastroenteritis in healthy persons rarely lasts more than one week, although in rare cases it can become systemic. It is usually treated with rehydration therapy and is not always treated with antibiotics unless it is severe.




Bibliography


Braden, Christopher R. “ Salmonella enterica Serotype Enteritidis and Eggs: A National Epidemic in the United States.” Clinical Infectious Diseases 43 (2006): 512–17. Print.



Garrity, George M., ed. Bergey’s Manual of Systematic Bacteriology. 2nd ed. Vol 2. New York: Springer, 2005. Print.



Madigan, Michael T., and John M. Martinko. Brock Biology of Microorganisms. 12th ed. Upper Saddle River: Pearson, 2010. Print.



Romich, Janet A. Understanding Zoonotic Diseases. Clifton Park: Thomson, 2008. Print.



"Typhoid Fever." Centers for Disease Control and Prevention. US Dept. of Health and Human Services, 14 May 2013. Web. 31 Dec. 2015.



"USDA Proposes New Measures to Reduce Salmonella and Campylobacter in Poultry Products." United States Department of Agriculture. USDA, 21 Jan. 2015. Web. 31 Dec. 2015.

Friday, 18 October 2013

How does Friar Lawrence change plans when he finds out that Romeo did not get his message?

In Act V, Scene 2 of Shakespeare's Romeo and Juliet, the audience learns that Friar Lawrence's message to Romeo was never delivered because Friar John was delayed by a plague threat in Verona. Friar Lawrence's letter details his plans for Juliet to fake her death, be entombed in Capulet's vault and for Romeo to retrieve her at the hour of her awakening. The couple would then proceed back to Mantua where they will remain...

In Act V, Scene 2 of Shakespeare's Romeo and Juliet, the audience learns that Friar Lawrence's message to Romeo was never delivered because Friar John was delayed by a plague threat in Verona. Friar Lawrence's letter details his plans for Juliet to fake her death, be entombed in Capulet's vault and for Romeo to retrieve her at the hour of her awakening. The couple would then proceed back to Mantua where they will remain until tempers die down and the friar is able to announce their marriage. Once he learns that Romeo never receives the letter, he becomes quite apprehensive and instructs Friar John to procure a crow bar so he can force his way into the tomb before Juliet wakes up. He also says he will attempt to get another message to Romeo before bringing Juliet back to his "cell":



Now must I to the monument alone.
Within this three hours will fair Juliet wake.
She will beshrew me much that Romeo
Hath had no notice of these accidents.
But I will write again to Mantua,
And keep her at my cell till Romeo come.
Poor living corse, closed in a dead man’s tomb!



Unfortunately, Romeo's servant witnesses Juliet's funeral and tells Romeo, who vows to commit suicide by her side. Friar Lawrence is too late arriving at the tomb as Romeo has already taken poison. The friar is unable to convince Juliet to leave as she too is bent on suicide after seeing Romeo dead and she ultimately kills herself with Romeo's dagger.

How can a 0.5 molal solution be less concentrated than a 0.5 molar solution?

The answer lies in the units being used. "Molar" refers to molarity, a unit of measurement that describes how many moles of a solu...