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Minireview: aging and anti-aging effects of hormones

Article Abstract:

This review discusses experiments with rats which demonstrate that hormones can either promote or delay aging, depending on the specific situation. Reduction of hormone levels can be achieved by destroying endocrine glands which secrete them or by restricting food intake, which reduces hormone secretion as well. These interventions in young or adult rats over a long period of time appear to prevent disease and tumor development and to increase the life span. Thus, lowered hormone levels have an anti-aging effect. But raising hormone levels in old rats also can have anti-aging effects. Administering female hormones to old female rats stimulates the estrous cycle; giving old male rats testosterone leads to increases in protein synthesis, thymus size, and growth hormone secretion. In women, estrogen supplementation after menopause can inhibit the bone loss that typically occurs with aging. Yet it is also important to note that abnormally high or low hormone levels can have adverse effects on body functions. Reduced hormone levels in rats can have anti-aging effects, but can also cause poor growth in young animals and weight loss in adult rats. Metabolism slows down so that body temperature and blood glucose levels are depressed; some of these effects appear to actually promote, rather than inhibit, aging. Thus, the physiological effects of hormones are complex, and their interaction with the aging process is not always readily predictable. (Consumer Summary produced by Reliance Medical Information, Inc.)

Models, Reports, Physiological aspects, Hormones, Endocrinology, Hormone research

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Minireview: age-related changes in the anatomy of the normal human heart

Article Abstract:

The anatomy of the heart undergoes various changes with age. For example, the weight of the heart increases, especially in women, and the walls of the lower chambers of the heart (ventricles) thicken and the circumference of the valves increases. In the heart muscle (myocardium) itself, the amount of fat, collagen and elastin, as well as a brownish pigment, absent in young hearts but present in older hearts, called lipofuscin increases. The shape of the heart changes with aging, too. The heart valves get thicker, there is less collagen, lipids accumulate, and calcium salts accumulate in the tissues (calcification). The coronary arteries widen (dilate), become twisted, and develop calcifications in specific places. In the conduction tissue of all of the chambers (atria and ventricles), the tissue diminishes in size (atrophies) and thus some of the tissue through which the electrical impulses pass is lost. Some of these changes may simulate disease, and so the distinction between the effects of aging and the effects of disease may be blurred. Nonetheless, the changes that accompany aging can still predispose the elderly to heart failure; heart disease from hypertension; stiff (stenotic), leaky (regurgitant) valves; and changes in heart rhythms (arrhythmias). (Consumer Summary produced by Reliance Medical Information, Inc.)

Heart, Anatomy

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Minireview: on size and survival: progress and pitfalls in the allometry of life span

Article Abstract:

Allometry refers to the relationship between body size and various other physical characteristics, including maximum life span (MLS) and life history variation. G.A. Sacher's 1959 discovery of a 1/4 slope in the relationship between longevity and body size led to discoveries of a similar relationship for many other traits, but the reason is not clear. E.L. Charnov's model may unite the allometric explanation of MLS with adaptational explanations. Future studies of life history and morphology will need to consider such matters as alternative measures of longevity.

Health aspects, Research, Allometry, Body size, Body weights and measures, Longevity

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