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.     

Complex life cycles and the responses of insects to climate change

Many organisms have complex life cycles with distinct life stages that experience different environmental conditions. How does the complexity of life cycles affect the ecological and evolutionary responses of organisms to climate change? We address this question by exploring several recent case studies and synthetic analyses of insects. First, different life stages may inhabit different microhabitats, and may differ in their thermal sensitivities and other traits that are important for responses to climate. For example, the life stages of Manduca experience different patterns of thermal and hydric variability, and differ in tolerance to high temperatures. Second, life stages may differ in their mechanisms for adaptation to local climatic conditions. For example, in Colias, larvae in different geographic populations and species adapt to local climate via differences in optimal and maximal temperatures for feeding and growth, whereas adults adapt via differences in melanin of the wings and in other morphological traits. Third, we extend a recent analysis of the temperature-dependence of insect population growth to demonstrate how changes in temperature can differently impact juvenile survival and adult reproduction. In both temperate and tropical regions, high rates of adult reproduction in a given environment may not be realized if occasional, high temperatures prevent survival to maturity. This suggests that considering the differing responses of multiple life stages is essential to understand the ecological and evolutionary consequences of climate change.     

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.     

PKG and the neural basis for behavioral phenotypes

Cyclic GMP-dependent protein kinase (PKG) has been implicated in the regulation of diverse aspects of vertebrate and insect behavior, yet the mechanisms underlying these effects are poorly understood. In this issue of Neuron, Fujiwara et al. and L'Etoile et al. address the neural basis for PKG function in C. elegans and demonstrate the power of behavioral genetic analysis in simple systems in the elucidation of neuronal signaling mechanisms in vivo.     

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.     

Canine behavioral genetics: pointing out the phenotypes and herding up the genes

An astonishing amount of behavioral variation is captured within the more than 350 breeds of dog recognized worldwide. Inherent in observations of dog behavior is the notion that much of what is observed is breed specific and will persist, even in the absence of training or motivation. Thus, herding, pointing, tracking, hunting, and so forth are likely to be controlled, at least in part, at the genetic level. Recent studies in canine genetics suggest that small numbers of genes control major morphologic phenotypes. By extension, we hypothesize that at least some canine behaviors will also be controlled by small numbers of genes that can be readily mapped. In this review, we describe our current understanding of a representative subset of canine behaviors, as well as approaches for phenotyping, genome-wide scans, and data analysis. Finally, we discuss the applicability of studies of canine behavior to human genetics.     

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.     

Lipid peroxidation and the life span of Drosophila melanogaster

Studies have been made on the relationship between incubation temperature (20-30 degrees C) of D. melanogaster and the life span as well as the content of various products of lipid peroxidation. It was shown that the increase in the environmental temperature results in the decrease in the life span, the content of unsaturated fatty acids and conjugated hydroxyperoxids; ketodienic content increases. Strong correlation was observed between the life span and the content of peroxidation products. As it is indicated by coefficients of bifactorial linear regression with interaction, conjugated hydroperoxids and ketodiens exert negative influence on the life span. Their combined effect on the life span is less significant than the sum of their separate effects, which indicates the existence of common "canals" of their influences on the life span.     

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.     

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.