Chromosome Probes at the University of TorontoUploaded: November 29, 1986.Sensitive chromosome probes recently discovered by a University of Toronto geneticist will make it easier to detect certain types of genetic and prenatal diseases, as well as being used to determine paternity and provide forensic evidence in criminal cases.
Probes are short pieces of DNA which bind to, and actually pinpoint, particular sites on a chromosome. Because these new probes are actually repeated hundreds or thousands of time at a particular site, they are much more sensitive than previously available onesOf the 23 pairs of human chromosomes, Dr. F.H. Willard has discovered repeated probes or markers for six plus the gender determining X and Y chromosomes.
“What we’re trying to decide now is whether to isolate probes for the other chromosomes, or whether we should utilize the eight we have,” he says. Dr. Willard is currently negotiating with an American company to develop prenatal diagnostic tests, which, because the current tests are time consuming and technically difficult to do, are restricted to women over 35 and those who have a family history of chromosomal abnormalities. Prenatal tests using Willard’s probes would be much simpler and faster to perform and could be available to all pregnant women who wish to take advantage of the technology.Current prenatal testing involves growing fetal cells in vitro and examining them, over one or two months, to see if there are two copies of a particular chromosome, which is normal, or one or three, which is abnormal. A test using Willard’s probes would require only a few cells and a few days to detect abnormalities. “I don’t think it’s beyond the realm of possibility that these kinds of tests could eventually be done by an obstetrician in the office during the early stages of pregnancy,” he adds. The determination of gender is another possible use for the probes.
Many diseases, such as Duschene’s muscular dystrophy, show up on the X chromosome, manifesting only in boys. Willard thinks it is possible to develop a test which would quickly indicate the fetus’ sex. This would benefit parents whose only option is to have no children or to have only girls. Confirming gender in children with ambiguous genitalia is another medical reason for using the test. A quick examination of the X and Y chromosomes of the child would indicate whether genetically the child is male or female. As yet, Willard has been unable to develop a probe for chromosome 21. Down’s Syndrome results from three copies of chromosome 21 (trisomy 21).
“I think we’ll know within a year whether a test to detect trisomy 21 is feasible, ” he says hopefully. The other six chromosome probes which Willard has developed do not immediately lend themselves to diagnostic tests, except for certain cancers, he says. “We have a probe for chromosome 7 and we know that trisomy 7 is a signal for certain types of cancer. Chromosome abnormalities of all kinds are a signpost of tumors.” Theoretically, an oncologist could use a chromosome probe test to examine tissue and obtain a reading for a specific cancer.
” It wouldn’t suggest a mode of therapy,” he points out, “but would be a speedy test and would have prognostic implications for the kind of tumor discovered.” As a basic research tool, Willard’s probes could be used to develop a genetic linkage map for human chromosomes. “It’s important to know the location of genes in the human genome, particularly disease genes.
The leading approach to try to sort out disease genes is to use genetic linkage. Because our sequences are at the centromere it would allow us to develop a map.” The third application for the probes is in forensic biology. Willard believes his markers are as unique to each each individual as are fingerprints. According to the geneticist, it will be possible to make a DNA ‘fingerprint’ from blood or sperm, which could be used as evidence in rape or murder cases. “We haven’t yet done the analysis which confirms that our probes are DNA fingerprints, but once we do, we will make them available for development into tests.” As research progresses in all these areas, Willard hopes to collaborate with other departments at the U of T to conduct clinical trials.
His work is funded by the March of Dimes, the Hospital for Sick Children Foundation and the Medical Research Council.ContentsIntroductionOverview of Diabetes Type I What is diabetes type IHealth implications of diabetes type IPhysical Activity What is physical activity? Why do we need physical activity in our lives?Physical Activity and Diabetes (Epidemiology)ConclusionBibliographyIntroduction For our seminar topic “physical activity and disease” we chose diabetes as the focus of our research. Since diabetes is such a complex disease with many different forms, we decided to focus on diabetes type I. This is known as insulindependent diabetes mellitus (IDDM). This type of diabetes includes people who are dependant on injections of insulin on a daily basis in order to satisfy the bodies insulin needs, they cannot survive without these injections.OVERVIEW OF DIABETES TYPE I What is diabetes type I? In order to understand the disease we firstly need to know about insulin. Insulin is a hormone. The role of insulin is to convert the food we eat into various useful substances, discarding everything that is wasteful.
It is the job of insulin to see that the useful substances are put to best use for our wellbeing. The useful substances are used for building cells, are made ready for immediate expenditure as energy and also stored for later energy expenditure. The cause of diabetes is an absolute or lack of the hormone insulin. As a result of this lack of insulin the processes that involve converting the foods we eat into various useful substances does not occur. Insulin comes from the beta cells which are located in the pancreas. In the case of diabetes type I almost all of the beta cells have been destroyed. Therefore daily injections of insulin become essential to life.Health implications of diabetes type I One of the products that is of vital importance in our bodies is glucose, a simple carbohydrate sugar which is needed by virtually every part of our body as fuel to function.
Insulin controls the amount of glucose distributed to vital organs and also the muscles. In diabetics due to the lack of insulin and therefore the control of glucose given to different body parts they face death if they don’t inject themselves with insulin daily. Since strict monitoring of diabetes is needed for the control of the disease, little room is left for carelessness. As a result diabetic patients are susceptible to many other diseases and serious conditions if a proper course of treatment is not followed. Other diseases a diabetic is open to: Cardiovascular disease, stroke, Peripheral artery disease, gangrene, kidney disease, blindness, hypertension, nerve damage, impotence etc. Basically there is an increased incident of infection in diabetic sufferers. Therefore special care needs to be taken to decrease the chances of getting these other serious diseases.PHYSICAL ACTIVITYWhat is physical activity? (Bouchard 1988) States that physical activity is any bodily movement produced by skeletal muscles resulting in energy expenditure.
Therefore this includes sports and leisure activities of all forms.Why do we need physical activity in our lives? Physical activity and exercise helps tune the “human machine”, our bodies. Imagine a car constantly driven only to stop for fuel. It would be a client for all sorts of damage, rusting, oil leaking, dehydration and the chances are most likely it would die in the middle of the road not long after. This is what the body would be like if we didn’t exercise at all. We would be and as a result of todays lifestyle many of us are, the perfect target to all kinds of diseases and infections. For those of us who are carrier of some disease or illness we are still encouraged to exercise by our physicians if we have the strength to.
This is to help make our organs, muscles, bones and arteries more efficient and better equipped to fight against the disease or illness. This is our way of counter attacking. And if we are still healthy then we reduce the chances of getting an illness or a disease. PHYSICAL ACTIVITY AND DIABETES (EPIDEMIOLOGY) Recently insulin injections have become available to dependant patients.
However in the preinsulin era physical exercise was one of the few therapies available to physicians in combating diabetes. For an IDDM carrier to benefit from exercise they need to be well aware of their body and the consequences of exercising. If an IDDM carrier has no real control over their situation and just exercise without considering their diet, time of insulin intake, type of exercise, duration of the exercise and the intensity, then the results can be very hazardous to the patient. In the first journal article that I used for this part of the research (Sutton 1981) had conducted an investigation on “drugs used in metabolic disorders”. The article is designed to provide some background information on previous beliefs and research conducted early this century. As well as his own investigations conducted during the beginning of the 1980’s. He has compared the results and came to the same conclusion as the investigations done early in this century. Sutton’s findings show that decrease in blood glucose following an insulin injection was magnified when the insulin was followed by physical activity/exercise (see figure 1).
This shows that if a person gets involved in physical activity or exercise after insulin the volume of glucose drops dramatically. This leads to symptoms of hypoglycemia. The reason this occurs is that glucose uptake by muscles increase during exercise, in spite of no change or even a diminishing plasma insulin concentration. As a result of this type of information we know now that if a patient is not controlled through a good diet and program then they could put themselves in danger.
A person who might be poorly maintained and ketotic will become even more ketotic and hypoglycimic. Good nutrition is of great importance to any individual especially one that exercises. In the case of diabetes even more consideration must go into the selection of food before and after exercise. Doctors suggest large intakes of carbohydrates before exercise for diabetes carriers to meet the glucose needs of the muscles.
The second article that I used was that of Konen, et al. He and his colleagues conducted testing and research on “changes in diabetic urinary and transferrin excretion after moderate exercise”. This article was a report of the way the research was conducted and it’s findings. The researched found that urinary proteins, particularly albumin, increase in urinary excretion after moderate exercise. Albumin which is associated with micro and macrovascular diseases in diabetic patience was found to increase significantly in IDDM patients, while remaining normal in nondiabetics. (See table 1 and 2 for results) These results cannot be conclusive to say that this shows that exercise causes other micro and macrovascular diseases in diabetics.
Since albumin is not associated with any disease in nondiabetics then the same may be the case for diabetics as well. However further research is required to find out why such a significant increase occurs in diabetic patients and what it really means. It obvious that there are many very complicated issues associated with diabetes which cannot be explained at this stage.
Therefore much more research is required and it’s only a matter of time for these complications to resolved. Although there are no firm evidence to suggest that exercise will improve or worsen diabetes still it is recommended by physicians. Aristotle and the Indian physician, Sushruta, suggested the use of exercise in the treatment of diabetic patients as early as 600 B.C. And during late last century and early this century many physician claimed that the need for insulin decreased in exercising patients.
The benefits of exercise in nondiabetic individuals is well known. For example reduce the risk of heart disease. This makes exercise very important to diabetic carriers since they are at a greater risk of getting heart disease than nondiabetics. Unquestionably, it’s important for diabetics to optimise cardiovascular and pulmonary parameters as it is for nondiabetic individual. Improved fitness can improve one’s sense of wellbeing and ability to cope with physical and psychological stresses that can be aggravated in diabetes. In well controlled exercise programs the benefits are many, as shown on table 3.CONCLUSION In conclusion we can see that although there are many factors that need to considered when a diabetic person exercises, still there are many benefits when an IDDM carrier controls and maintains a good exercise program. The risks of other disease such as heart disease and obesity are reduced.
Bibliography 1. Sutton, J.R, (1981), Drugs used in metabolic disorders, Medicine and Science in Sports and Exercise, Vol 13, pages 266271. 2. Konen, J.C, (1993), Changes in diabetic urinary transferrin excretion after moderate exercise, Medicine and Science in Sports and Exercise, pages 11101114. 3.
Bouchard, C, (1990), Exercise, Fitness and Health, Human Kinetics Publishers. 4. Burke, E.J, (1980), Exercise, Science and Fitness, Mouvement Publishers. 5.
Sanborn, M.A, (1980), Issues in Physical Education, Lea and Febiger. 6. Marble, A, (1985), Joslin’s Diabetes Mellitus, Twelfth Edition, Lea and Febiger. 7. Kilo, C, (1987), Diabetes The facts that let you regain control of your life, John Wiley and Sons, Inc. 8. Seefeldt, V, (1986), Physical Activity and Wellbeing, American Alliance for Health, Physical Education, Recreation and Dance.