Cortisol responses and social buffering: a study throughout the life span

The ability of specific adult females to moderate plasma cortisol responses throughout the life span was examined in male guinea pigs maintained in large mixed age/sex groups. At four critical life stages of social development (preweaning, periadolescent, sexually but not socially mature, and sexually and socially mature), the same male guinea pigs were exposed to the stressor of exposure to a novel environment for 4 h while either alone, with an unfamiliar adult female, or with a favored adult female, as based on objective criteria from behavioral observation at that life stage. In preweaning males (9-19 days of age), the favored female (biological mother), but not an unfamiliar female, reduced the cortisol response in the novel environment. In periadolescents (49-61 days), an unfamiliar female, but not the favored female, buffered the cortisol response. At the sexually but not socially mature stage (114-126 days), the cortisol response to novelty was depressed in all conditions, and not affected by either female. At the sexually and socially mature stage (270-330 days), the favored female, but not the unfamiliar female, moderated cortisol levels. These results corroborate previous findings in infants and full adults, demonstrate marked age-specific changes in the ability of females to buffer hypothalamic-pituitary-adrenal responses, and identify a heretofore undescribed period of cortisol response suppression in maturing male guinea pigs. The changing pattern of social buffering during the life span described here for the guinea pig might represent a more general pattern for males of other group-living mammals.     

Radioinduced change in life span of laboratory strains of Drosophila melanogaster

Chronic irradiation (accumulated dose 0.6-0.8 Gy) was shown to change the life span in male Drosophila melanogaster. Death was retarded in wild-type strains and accelerated in mutant strains defective in DNA repair and displaying a higher sensitivity to induction of apoptosis.     

Human NK cells display major phenotypic and functional changes over the life span

Aging is generally associated with an increased predisposition to infectious diseases and cancers, related in part to the development of immune senescence, a process that affects all cell compartments of the immune system. Although many studies have investigated the effects of age on natural killer (NK) cells, their conclusions remain controversial because the diverse health status of study subjects resulted in discordant findings. To clarify this situation, we conducted the first extensive phenotypic and functional analysis of NK cells from healthy subjects, comparing NK cells derived from newborn (cord blood), middle‐aged (18–60 years), old (60–80 years), and very old (80–100 years) subjects. We found that NK cells in cord blood displayed specific features associated with immaturity, including poor expression of KIR and LIR‐1/ILT‐2 and high expression of both NKG2A and IFN‐γ. NK cells from older subjects, on the other hand, preserved their major phenotypic and functional characteristics, but with their mature features accentuated. These include a profound decline of the CD56^bright subset, a specific increase in LIR‐1/ILT‐2, and a perfect recovering of NK‐cell function following IL2‐activation in very old subjects. We conclude that the preservation of NK cell features until very advanced age may contribute to longevity and successful aging.     

The shaping of the behavioral act: the problem of intrasystemic heterochrony

According to P.K. Anokhin's conception, the functional system of every behavioural act includes one and the same sequence of basic mechanisms, the main of them are afferent synthesis and making decision, realization of action, achievement of the result and evaluation of its parameters. The present work deals with the question about the extent of coordination in the development of these systemic mechanisms in the process of new behavioural act formation.     

Genetic determinants of human health span and life span: progress and new opportunities

We review three approaches to the genetic analysis of the biology and pathobiology of human aging. The first and so far the best-developed is the search for the biochemical genetic basis of varying susceptibilities to major geriatric disorders. These include a range of progeroid syndromes. Collectively, they tell us much about the genetics of health span. Given that the major risk factor for virtually all geriatric disorders is biological aging, they may also serve as markers for the study of intrinsic biological aging. The second approach seeks to identify allelic contributions to exceptionally long life spans. While linkage to a locus on Chromosome 4 has not been confirmed, association studies have revealed a number of significant polymorphisms that impact upon late-life diseases and life span. The third approach remains theoretical. It would require longitudinal studies of large numbers of middle-aged sib-pairs who are extremely discordant or concordant for their rates of decline in various physiological functions. We can conclude that there are great opportunities for research on the genetics of human aging, particularly given the huge fund of information on human biology and pathobiology, and the rapidly developing knowledge of the human genome.     

Cellular life span and the Warburg effect

Enhanced glycolysis is observed in most of cancerous cells and tissues, called as the Warburg effect. Recent advance in senescent biology implicates that the metabolic shift to enhanced glycolysis would be involved in the early stage during multi-step tumorigenesis in vivo. Enhanced glycolysis is essential both in the step of immortalization and transformation, as it renders cells resistant to oxidative stress and adaptive to hypoxic condition, respectively. ES, immortalized primary, and cancerous cells display the common concerted metabolic shift, including enhanced glycolysis with reduced mitochondrial respiration by poorly characterized mechanism. Discovery of a novel regulatory mechanism for such a metabolic shift might be essential for the future development of cancer diagnosis and anti-cancer therapy.     

The evolution of plant life span: facts and hypotheses

There are two different views on the evolution of life forms in Cormophyta: from woody plants to herbaceous ones or in opposite direction - from herbs to trees. In accordance with these views it is supposed that life span in plants changed in the course of evolution from many years (perennials) to few years (annuals, biennials), or went in reverse - from few years to many years. The author discusses the problems of senescence and longevity in Cormophyta in the context of various hypotheses of ageing (programmed death theory, mutation accumulation, antagonistic pleiotropy, disposable soma, genes of ageing, genes of longevity). Special attention is given to bio-morphological aspects of longevity and cases of non-ageing plants ("negative senescence", "potential immortality"). It is proposed to distinguish seven models of simple ontogenesis in Cormophyta that can exemplify the diversity of mechanisms of ageing and longevity. The evolution of life span in plants is considered as an indirect result of natural selection of other characteristics of organisms or as a consequence of fixation of modifications (episelectional evolution). It seems that short life span could emerge several times during evolution of one group of plants, thus favoring its adaptive radiation.     

Odor-evoked autobiographical memories: age and gender differences along the life span

Odors are powerful in bringing back old and vivid memories bearing emotional content. This inherent hedonic property of olfactory stimuli makes this sensory modality particularly suitable for studying autobiographical memory. In the present work, adolescents (first experiment), young adults (second experiment), and elderly (third experiment) of both sexes were asked to smell 10 familiar odorants and to report if these odorants evoked personal autobiographical memories or referential memories (i.e., names and objects). The participants were then required to link these memories to triplets of words using the progressive elaboration method of the Loci mnemonic. The aim of the study was to investigate whether 1) odorants evoking autobiographical memories led to faster reaction times (RTs) and to a greater number of correct responses in the recall of the items associated to such memories than do odorants evoking referential memories, 2) females differed from males on the above tasks along with the life span, and 3) the preferential codes (i.e., autobiographical or referential) attributed to the odorants vary according to gender and age. In general, it was observed that the way in which the odorants were encoded affected the subsequent retrieval. Indeed, data analyses have shown that odorants evoking autobiographical memories lead to faster RTs (experiments 2 and 3) and that females outperform males (experiments 1 and 2). However, these effects are greatly age and gender dependent. Furthermore, females are more prone than males to code the odorants autobiographically (as shown by the higher amount of autobiographical experiences that they have provided at all ages relative to males). Results are discussed in terms of developmental differences and odor-emotion links and the possible role of odors and autobiographical memory in learning and retrieval of other items.     

Growth negatively impacts the life span of mammals

A negative intraspecific relationship between growth and longevity was proposed in the early 20th century. Indeed, stunting the growth of rodents by restricting their food dramatically extended life span. Subsequently, however, the hypothesis that growth exacerbates aging rates fell into disfavor. Contributing to this was (a) the establishment of a positive relationship between body size and longevity interspecifically, (b) purported antiaging impacts of growth hormone, and (c) the fact that the longevity of even mature rodents that had completed growth was extended by dietary restriction. Furthermore, intraspecific analytical studies failed to provide any clear resolution. This article presents the first global analyses of maximal longevity versus maximum mature mass for laboratory rats and mice, based on a relatively comprehensive compilation of research across the 20th century. Peak body mass (which reflects juvenile growth rates) was negatively associated with longevity within both species. Proximal mechanisms for impacts of growth on longevity appear congruent with the free radical and immunological theories of aging.     

Regulation of the life span in unicellular eukaryotes

The review considers the mechanisms of nucleic and mitochondrial control of the life span of unicellular eukaryotes. Special attention is given to analysis of the mechanisms of functioning of telomerase complex, the mechanisms of varied expression of the genes regulating the cell cycle, and the mitochondrial retrograde pathway.     

Comparing plant life histories using elasticity analysis: the importance of life span and the number of life-cycle stages

Recent studies have used transition matrix elasticity analysis to investigate the relative role of survival (L), growth (G) and fecundity (F) in determining the estimated rate of population increase for perennial plants. The relative importance of these three variables has then been used as a framework for comparing patterns of plant life history in a triangular parameter space. Here we analyse the ways in which the number of life-cycle stages chosen to describe a species (transition matrix dimensionality) might influence the interpretation of such comparisons. Because transition matrix elements describing survival (stasis) and growth are not independent, the number of stages used to describe a species influences their relative contribution to the population growth rate. Reduction in the number of stages increases the apparent importance of stasis relative to growth, since each becomes broader and fewer individuals make the transition to the next stage per unit time period. Analysis of a test matrix for a hypothetical tree species divided into 4–32 life-cycle stages confirms this. If the number of stages were defined in relation to species longevity so that mean residence time in each stage were approximately constant, then the elasticity of G would reflect the importance of relative growth rate to . An alternative, and simpler, approach to ensure comparability of results between species may be to use the same number of stages regardless of species longevity. Published studies for both herbaceous and woody species have tended to use relatively few stages to describe life cycles (herbs: n=45, ; woody plants: n=21, ) and so approximate this approach. By using the same number of stages regardless of longevities, the position of species along the G-L side of the triangular parameter space largely reflects differences in longevity. The extent of variation in elasticity for L, G and F within and between species may also be related to factors such as successional status and habitat. For example, the shade-tolerant woody species, Araucaria cunninghamii, shows greater importance for stasis (L), while the gap-phase congener species, Araucaria hunsteinii, shows higher values for G (although values are likely to vary with the stage of stand development).     

The altered responses of a new mutant long life span 1 to cytokinin in Arabidopsis thaliana

Cytokinins are a class of essential plant hormones regulating plant growth and development.Although the two-component phosphorelay pathway of cytokinin has been well characterized,the intact cytokinin responses regulation picture still needs to be fully depicted.Here we report a new mutant,long life span 1(lls1),which displays dwarf stature,curled leaves,numerous axillary branches and nearly 5-month life span.Exogenous cytokinin could not recover the phenotypes of the mutant.Moreover,mutation in lls1 suppressed the cytokinin-responsive phenotypes,including root and hypocotyl growth inhibition,anthocyanin accumulation,metaxylem promotion in primary root development.The induction of cytokinin-responsive genes,ARR5,AHP5,and CKX3,was also suppressed in lls1.According to quantitative RT-PCR(qRT-PCR) and microarray results,the basal expression of positive factors AHP5,ARR1,and ARR10 were down-regulated,while the negative factors ARR4 and ARR5 were up-regulated.Our results suggested that LLS1 gene might be involved in the regulation of cytokinin signaling.It was mapped to chromosome 4 where no other cytokinin relevant gene has been reported.     

Exercise, brain, and cognition across the life span

This is a brief review of current evidence for the relationships between physical activity and exercise and the brain and cognition throughout the life span in non-pathological populations. We focus on the effects of both aerobic and resistance training and provide a brief overview of potential neurobiological mechanisms derived from non-human animal models. Whereas research has focused primarily on the benefits of aerobic exercise in youth and young adult populations, there is growing evidence that both aerobic and resistance training are important for maintaining cognitive and brain health in old age. Finally, in these contexts, we point out gaps in the literature and future directions that will help advance the field of exercise neuroscience, including more studies that explicitly examine the effect of exercise type and intensity on cognition, the brain, and clinically significant outcomes. There is also a need for human neuroimaging studies to adopt a more unified multi-modal framework and for greater interaction between human and animal models of exercise effects on brain and cognition across the life span.