Thyroid And Aging

Objective: Review physiologic thyroid function changes with aging and emphasize careful interpretation of tests in the aging population.Methods: Literature review.Results: Using age-specific thyroid-stimulating hormone (TSH) reference ranges should minimize or avoid the unnecessary diagnosis of thyroid disease in elderly patients. Subclinical thyroid dysfunction and abnormal TSH with normal thyroid levels may improve with time, so careful monitoring of thyroid function is recommended. Overt thyroid disease should always be treated.Conclusion: Clinical judgement is always warranted to decide how and when to treat subclinical thyroid disease in the elderly.Abbreviations: FT4 = free thyroxine; rT3 = reverse triiodothyronine; T3 = triiodothyronine; T4 = thyroxine; TFT = thyroid function test; TSH = thyroid-stimulating hormone     

Mitochondria and Aging

Cover illustration: Mitochondria and Aging, a special issue edited by Professor Heinz D. Osiewacz (Frankfurt, Germany), devoted to aging research and the involvement of mitochondria “from models to humans”. Depicted are a 3D section of a human cell with mitochondria shown in red (© NIH, see http://ghr.nlm.nih.gov/handbook/illustrations/cellmitochondria) and from top to bottom: micrograph of mitochondria from the model organism Podospora anserina (© C. Scheckhuber, see p. 781), hand with pill (© Photodisc Inc.) and the worm Caenorhabditis elegans with typical senescent morphology (© B. Braeckman, see p. 803).     

Aging in Perennials

Compared with our knowledge of senescence processes in annuals and biennials, relatively little is known about age-related changes in perennials. The study of aging in plants is very complex and there is no consensus in general concepts related to this topic. Furthermore, there is also a problem of scaling up, which makes us wonder whether cells, tissues/organs or whole organisms really age in plants. This is particularly interesting in the case of perennials, which have the ability to make new leaves every year and live for several years or even centuries or millennia. Recent studies indicate that physiological burdens, such as demands on water and nutrient supply, are responsible for reduced growth as plants age. Aside from the extrinsic factors, it is also possible that intrinsic changes in the shoot meristems could occur through repeated cell divisions and could be fixed during plant development, thereby affecting the physiology of leaves that originated from these cells. Additionally, the increased size associated with the aging of woody perennials (trees and shrubs) has also been proposed as a determining factor responsible for the age-related reductions in growth and photosynthetic rates in leaves. This review is aimed at compiling our current understanding of aging in perennials. After defining some fundamental questions and concepts, and introducing the model plants presently used in the study of aging in perennials, the major role meristems play in perenniality and how aging is manifested in the physiology of perennials (changes in phytohormones, water relations, photosynthesis and oxidative stress) are described. Finally, the causes underlying age-related changes in perennials are discussed in detail and a model based on plant plasticity to explain the aging phenomenon in perennials is presented.     

Aging in bacteria

Analysis of senescent Escherichia coli cells reveals a link between protein oxidation and the fidelity of the translational apparatus. This model system has also provided a mechanistic molecular explanation for a trade-off between reproduction and survival activities, which may inspire proponents of the disposable soma theory and antagonistic pleiotropy hypothesis of aging.     

Aging in birds

Rodents are the most commonly used model organisms in studies of aging in vertebrates. However, there are species that may suit this role much better. Most birds (Aves), having higher rate of metabolism, live two-to-three times longer than mammals of the same size. This mini-review briefly covers several evolutionary, ecological, and physiological aspects that may contribute to the phenomenon of birds’ longevity. The role of different molecular mechanisms known to take part in the process of aging according to various existing theories, e.g. telomere shortening, protection against reactive oxygen species, and formation of advanced glycation end-products is discussed. We also address some features of birds’ aging that make this group unique and perspective model organisms in longevity studies.     

Paradoxes of Aging

Insightful articles by Kirkwood and other outstanding scientists reveal paradoxes of aging. The source of paradoxes is an assumption that aging is caused by random accumulation of molecular damage. Here I demonstrate that a concept of TOR-driven program-like aging almost automatically resolves eleven paradoxes of aging. This article discusses why the accumulation of molecular damage does not limit life span, why calorie restriction and inhibition of protein synthesis extend life span, why non-existing ‘program’ for aging is nevertheless robust, why a key gene for aging cannot be found by knocking it out, why low insulin is associated with good health but low insulin response with bad health, why aging is not a disease but can be treated as a disease, why ‘healthy’ aging is slow aging, and how do we know that calorie restriction actually slows aging in humans.     

Data on Aging

Federal payment for hospitalization and partial medical care of certain citizens 65 and over is proposed in H.R. 4222. There are several important aspects of this proposed legislation which merit consideration, notably (1) How great is the actual need? and (2) Who would actually be covered by the proposed measure?1. The need for subsidized hospitalization and medical care is believed to be distinctly limited. A national study of the total life situation of those 65 and over (by Wiggins and Schoeck) showed that 90 per cent of the respondents reported no unmet medical needs of which they were aware. About 96 per cent reported no medical debts. This would leave presumably 4 per cent with such debts.2. The proposed legislation would cover those eligible for benefits under the Social Security Act and the Railroad Retirement Act, but not other elderly persons.The Wiggins-Schoeck Report has been bitterly assailed by supporters of H.R. 4222 as being nonrepresentative and incomplete. Its authors (in a recent letter to Science) point out that it is indeed representative of the older population currently designated in H.R. 4222, and that it intentionally omitted those segments which would not be covered by H.R. 4222. In other words the data on needs of elderly persons as uncovered by Wiggins and Schoeck is pertinent to the legislation at hand. For this reason it is believed that physicians will be interested in reading the reply of these authors to the criticisms of their survey.With the permission of Science and of the authors, it is reprinted herewith.