Dr. Paul Tabor
1. Amongst the numerous physiological changes that are regulated by the endocrine system is the regulation by our bodies' activities on a day-and-night cycle. Almost all systems in our bodies have these circadian rhthyms . What differences do you recognize in your own physiology that are related to whether it is morning or night? You can probably think of many businesses that would be interested to know more about the changes that occur in our physiology over the period of a 24 hour day. For example, when are people most productive? Why would the military have an interest in circadian rhythms (you can select any of the reference numbers at this site to see the abstracts of the papers)? Are you an athlete? Can these circadian rhythms influence your performance? If our daily activities are in response to circadian rhythms, what happens when our daily routines are disrupted? Can environmental forces disrupt circadian rhythms as well? Recently, the genes that are responsible for controlling the circadian rhythms have been isolated. As you geneticists know, most genes are isolated because mutants are found that have some altered characterisitc related to the function of interest. Are there circadian rhythm mutants that have no day-and-night cycles or have longer or shorter cycles than normal? The discovery of the per and tim genes is fascinating. Take some time to read about it. The regulation of per and tim control keep the clock of our bodies going. But how is the clock set? Can our bodies' clock be reset if we move to Japan? The endocrine gland in the brain that can be thought of as the timing device is the pineal gland. What is the environmental cue during the 24-hour cycle that tells us to wake-up in the morning rather than wake up at 8:00 PM? The pineal gland evolved from a third, light-sensing organ in ancient fish. The pineal gland in our bodies now receives its signals from the phtoreceptors in the retina of the eye. So, we have an endocrine hormone whose synthesis is regulated by daylight? Aaron Lerner discovered melatonin in 1958. The retina itself also produces melatonin. Retinal cells that are grown in tissue culture and are exposed to light retain the ability to produce melatonin and continue circadian rhythms.
Would you be interested in using melatonin as a diet supplement if it could reset your biological clock instead of having jetlag or sleep disorder? Everyone has a somewhat higher tendency to be depressed in the winter. But many people suffer from a serious seasonal depression that is triggered by shorter daylight hours. Could this depression be a hormonal disorder? Could a treatment that would stimulate melatonin production be effective? Is light therapy effective in treating SAD? What correlation do you expect between melatonin levels and diminishing SAD (select abstract #12 at tis site) when light therapy is successful? There is a list of melatonin resources on the world wide web
Do you think that other organisms have circadian rhythms that are set by light? If you have found circadian rhythms fascinating and want to find more information, here is a circadian rhythm bibliography for you. There is a circadian rhythms website .
We have focused on circadian rhythms, but we perceive much shorter time intervals. For example we "know" what it feels like to wait an hour versus waiting for five minutes. Do our bodies also have an interval timing system - a sort of a biological stop watch as well?
2. The anterior pituary is the master gland. It produces six hormones that essentially control other organs and glands of the endocrine system. The most famous or, perhaps, most infamous hormone of the pituary is growth hormone (GH). Human growth hormone is not a large or complex protein and was one of the first products of recombinant DNA technology to be approved for use in replacement therapy for the congenital pituitary dwarfism. Serious legal battles resulted from biotech companies racing for the approval of their own recombinant GH. Do you know if males or females are more likely to have pituitary dwarfism? Can trauma to hypothalamus or pituitary in the fetus or infant at birth cause dwarfism? As treatment for dwarfism has advanced, a question has been raised: Is dwarfism a disability? You can get an idea of the opinions advanced from information at dwarfism resource sites. There also is a site that can answer other questions you may have about dwarfism. As the synthetic hormone was readily available and very effective, it was applied to other growth-related problems. It is known that GH production naturally decreases as people age. What would happen if GH could be replaced? Although there seems to be some vanity in this use of GH, there are important applications. There are some acquired GH deficiencies which would be life-threatening without GH therapy. How does the loss of GH affect adult physiology? A heart disease, myocardiopathy, is characterized by loss of heart muscle mass. Can GH be an affective treatment by causing the heart muscles to grow? GH has been used experimentally to treat AIDS victims in hope of slowing the loss of body mass or wasting of the body that is so debilitating. Do you know that some treatments for AIDS victims are "fast-tracked" for approval by the FDA? GH treatment for AIDS victims is one of these. With so much interest in and so many varieties of treatments using GH, there is a GH homepage that provides information. Doesn't it seem that the growth of muscle tissue and increased cardiovascular rates from GH treatments could result in the abuse of GH as a body building drug - just like anabolic steriods are abused? Can we learn anything about the effects of too much GH from natural afflictions that are caused by overproduction of GH? What is done to manage this condition? It appears that there would be a temptation to have children treated with GH not because they have a GH deficiency but simply because they are shorter than the norm. Here is another opinion on the use of GH in response to peer pressure. What do you think?
GH, more frequently called somatotropin in non-humans, can also increase meat production and milk porduction in livestock. The recombinant bovine somatotropin is claimed to not be able to affect humans. However, there are concerns about the use of growth additives and the affects on livestock that have not been determined. Are you surprised to find out who is an advocate against the use of bovine somatotropin?