Age-related changes in muscle mass (sarcopenia) and functional properties are the result of a very complex hierarchical system of basic cell aging processes and cell adaptive responses. A basic aging mechanism pertains to mitochondrial production of free radicals and their associated secondary effects. From this basic aging mechanism many other cellular changes can be explained as direct effects or compensatory changes. Altered skeletal muscle cell biochemical and functional properties during aging resulting from intrinsic mechanisms and from changes in hormonal or local signals that influence phenotype maintenance, are reviewed. The effect of skeletal muscle cell senescence on the cellular response to exercise, and the effect of dietary restriction on muscle cell senescence can also be explored from this perspective.

Skeletal muscle and aging

Coenzyme Q10 and differences in coronary heart disease risk in Asian Indians and Chinese.

Background Children adopted from orphanages or other such institutions tend to display blunted reactivity to stressors - even years after arriving in their generally supportive and highly resourced postadoption homes. Puberty, a proposed sensitive period for environmental influences on stress-mediating systems, may provide an opportunity for postinstitutionalized children to recalibrate stress response systems in accordance with their now more supportive living situations. Methods This cross-sectional study examined the hypothalamic-pituitary-adrenocortical (HPA)-axis reactivity of 280 children ages 7 through 14 years; 122 children were adopted from institutions in 14 countries between the ages of 6 months and 5 years, after spending an average of 95% of their lives in institutional care, and 158 children of similarly high socioeconomic status in their biological families served as the nonadopted comparison group. All of the children were assessed by nurses for Tanner stage and, on a different day, completed the Trier Social Stress Test for Children. Results Using a linear mixed-effects model and seven measures of salivary cortisol, results indicated that early-pubertal postinstitutionalized children showed blunted HPA axis reactivity compared to nonadopted children, but mid/late-pubertal postinstitutionalized children displayed higher reactivity similar to the nonadopted comparison children. Conclusions This is the first evidence of possible pubertal recalibration of HPA axis reactivity to a psychosocial stressor in postinstitutionalized children, which provides a promising avenue for future research regarding the protective factors of the postadoption environment and subsequent physiological, behavioral, and psychopathological outcomes.

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Pubertal recalibration of cortisol reactivity following early life stress: a cross-sectional analysis.

The temperature–mortality relationship follows a well-known J-V shaped pattern with mortality excesses recorded at cold and hot temperatures, and minimum at some optimal value, referred as Minimum Mortality Temperature (MMT). As the MMT, which is used to measure the population heat-tolerance, is higher for people living in warmer places, it has been argued that populations will adapt to temperature changes. We tested this notion by taking advantage of a huge migratory flow that occurred in Italy during the 1950s, when a large number of unemployed people moved from the southern to the industrializing north-western regions. We have analyzed mortality–temperature relationships in Milan residents, split by groups identified by area of birth. In order to obtain estimates of the temperature-related risks, log-linear models have been used to fit daily death count data as a function of different explanatory variables. Results suggest that mortality risks differ by birthplace, regardless of the place of residence, namely heat tolerance in adult life could be modulated by outdoor temperature experienced early in life. This indicates that no complete adaptation might occur with rising external environmental temperatures.

The effect of birthplace on heat tolerance and mortality in Milan, Italy, 1980-1989.

History of Biological Anthropology

This review traces some of the developments in population physiology based on contributions to the Annals over the last 25 years. Two broad themes are evident, physiological systems variation and adaptation, and by way of introduction an historical perspective of their relationship within human ecology is explored. Studies of physical fitness and work capacity, and the efforts to create standardized field procedures make up a number of the early papers. Longitudinal studies have provided reliable reference standards for Westernized populations, but are virtually non-existent for primitive groups. The relative importance of phenotypic and genotypic variations in working capacity have yet to be clearly defined. The level of habitual activity during childhood contributes to the development of ventilatory capacity though constitutional influences are of major importance. Variability in strength and motor performance of skeletal muscles are shown to have a direct bearing on aspects of growth, development and biological maturation. Physical and psychological stress in communities have been investigated. These and other studies contribute valuable data on the issue of stress, hypertension and cardiovascular morbidity and mortality. On the theme of human adaptability, high altitude populations, variations in thermal tolerance and adaptations in ageing populations have all received recent investigation. Highland people of all ages have considerably larger lung volumes than coastal dwellers. Haematological, biochemical and pulmonary function show adaptive phenomena that vary in different highland groups. In the tropical biome, more recent work includes the functional consequences of malnutrition, ethnic and cultural differences in work capacity, and the effects of endemic disease on physical performance. Annals of Human Biology papers have more recently contributed to investigations on morphological and physiological changes with human ageing. Though there is a decline in the ability to adapt to environmental stresses with age this may be met by changes in adaptational strategy in physiological systems.

Collins Kj

Papers

Physiological variation and adaptability in human populations