Allostasis, allostatic load, and the aging nervous system: role of excitatory amino acids and excitotoxicity

Depressive symptoms and memory performance among older adults: results from the ACTIVE memory training intervention

BACKGROUND

Cognitive performance benefits from the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study may differ for individuals who exhibit a greater number of depressive symptoms.

METHOD

Using data from ACTIVE memory training and control conditions, we evaluated the effect of depressive symptomatology on memory scores across a 5-year period. Of 1,401 participants, 210 had elevated depressive symptoms at baseline, as measured by a 12-item version of the Center for Epidemiological Studies-Depression Scale (CES-D).

RESULTS

Participants with elevated depressive symptoms scored significantly lower at baseline and had faster decline in memory performance than those exhibiting fewer depressive symptoms. Memory score differences among depressive symptom categories did not differ between training conditions.

DISCUSSION

Findings suggest that elevated depressive symptoms may predict declines in memory ability over time, but do not attenuate gains from training. Training provides a potential method of improving memory which is robust to effects of depression.

Allostasis model facilitates understanding race differences in the diurnal cortisol rhythm

The concept of allostasis suggests that greater cumulative stress burden can influence stress-responsive physiology. Dysregulation of allostatic mediators, including the hypothalamic-pituitary-adrenal (HPA) axis, is thought to precede many other signs of age-related pathology as the persistent burden of stressors accumulates over the individual's life span. We predicted that even in young adulthood, HPA regulation would differ between Blacks and Whites, reflecting, in part, higher rates of stressor exposure and greater potential for stressors to "get under the skin." We examined whether stressor exposure, including experiences with racism and discrimination, explained race differences in waking cortisol and the diurnal rhythm. We also examined whether HPA functioning was associated with mental health outcomes previously linked to cortisol. Salivary cortisol was assayed in 275 young adults (127 Blacks, 148 Whites, 19 to 22 years old), four times a day across 3 days. Hierarchical linear models revealed flatter slopes for Blacks, reflecting significantly lower waking and higher bedtime cortisol levels compared to Whites. Associations of HPA functioning with stressors were typically more robust for Whites such that more stress exposure created an HPA profile that resembled that of Black young adults. For Blacks, greater stressor exposure did not further impact HPA functioning, or, when significant, was often associated with higher cortisol levels. Across both races, flatter slopes generally indicated greater HPA dysregulation and were associated with poor mental health outcomes. These differential effects were more robust for Whites. These findings support an allostatic model in which social contextual factors influence normal biorhythms, even as early as young adulthood.

Reduced expression of MAPK/ERK genes in perinatal arsenic-exposed offspring induced by glucocorticoid receptor deficits

Changes within the glucocorticoid receptor (GR) cellular signaling pathway were evaluated in adolescent mice exposed to 50 ppb arsenic during gestation. Previously, we reported increased basal plasma corticosterone levels, decreased hippocampal GR levels and deficits in learning and memory performance in perinatal arsenic-exposed mice. The biosynthesis of members of the mitogen-activated protein kinase (MAPK) signaling pathway, known to be involved in learning and memory, is modulated by the binding of GR to glucocorticoid response elements (GREs) in the gene promoters. Two genes of the MAPK pathway, Ras and Raf, contain GREs which are activated upon binding of GRs. We evaluated the activity of GRs at Ras and Raf promoters using chromatin immunoprecipitation and real-time PCR and report decreased binding of the GR at these promoters. An ELISA-based GR binding assay was used to explore whether this decreased binding was restricted to in vivo promoters and revealed no differences in binding of native GR to synthetic GREs. The decreased in vivo GR binding coincides with significantly decreased mRNA levels and slight reductions of protein of both H-Ras and Raf-1 in perinatally arsenic-exposed mice. Nuclear activated extracellular-signal regulated kinase (ERK), a downstream target of Ras and Raf, whose transcriptional targets also play an important role in learning and memory, was decreased in the hippocampus of arsenic-exposed animals when compared to controls. GR-mediated transcriptional deficits in the MAPK/ERK pathway could be an underlying cause of previously reported learning deficits and provide the link to arsenic-induced deficiencies in cognitive development.

Successful cognitive aging

Given the rapid rate of population aging, basic science and public health efforts have increasingly focused on the determinants of successful cognitive aging. In this chapter, we review the definition and biological, psychological, and environmental determinants of cognitive health in later life. Successful cognitive aging is a multi-dimensional construct that lacks a consensus operationalized definition, and has been variously conceptualized in an ipsative, normative, or criterion-referenced manner. Nevertheless, there are a number of biomarkers, at the genetic and cellular level, that provide indicators of cognitive health in aging. Functional and structural neuroimaging suggest multiple pathways to successful cognitive aging, by way of brain reserve and cognitive reserve. A number of behavioral and environmental interventions, including dietary restriction, physical activity, and cognitive stimulation, are promising avenues for extending the cognitive healthspan associated with normal aging. Thus, there is a variety of recent findings providing optimism that successful cognitive aging, howsoever defined, will be attainable by more older adults in the future.

Neurobehavioral consequences of stressor exposure in rodent models of epilepsy

Both normal, non-epileptic as well as seizure-prone rodents exhibit a spectrum of anxiogenic-like behaviors in response to stressor exposure. Comparative analysis reveals that the same set of emotionality dependent measures is sensitive to both stress reactivity in normal rodents as well as stress hyperreactivity typically seen in seizure-prone rodents. A variety of unconditioned, exploratory tasks reflect global sensitivity to stressor exposure in the form of behavioral inhibition of locomotor output. Moreover, well chosen stressors can trigger de novo seizures with or without a history of seizure incidence. Seizures may be elicited in response to stressful environmental stimuli such as noxious noises, tail suspension handling, or home cage disturbance. Stress reactivity studies in rodents with a genetic predisposition to seizures have yielded important clues regarding brain substrates that mediate seizure ontogeny and modulate ictogenesis. Brains of seizure susceptible rodents reflect elevated content of the stress-related neuropeptide, corticotropin-releasing factor (CRF) in several nuclei relative to non-susceptible controls and neutralization of brain CRF attenuates seizure sensitivity. Findings outlined in this review support a diathesis-stress hypothesis in which behavioral- and neuro-pathologies of genetically seizure susceptible rodents arise in part due to multifaceted hyperreactivity to noxious environmental stimuli.

Adolescent development, hypothalamic-pituitary-adrenal function, and programming of adult learning and memory

Chronic exposure to stress is known to affect learning and memory in adults through the release of glucocorticoid hormones by the hypothalamic-pituitary-adrenal (HPA) axis. In adults, glucocorticoids alter synaptic structure and function in brain regions that express high levels of glucocorticoid receptors and that mediate goal-directed behaviour and learning and memory. In contrast to relatively transient effects of stress on cognitive function in adulthood, exposure to high levels of glucocorticoids in early life can produce enduring changes through substantial remodeling of the developing nervous system. Adolescence is another time of significant brain development and maturation of the HPA axis, thereby providing another opportunity for glucocorticoids to exert programming effects on neurocircuitry involved in learning and memory. These topics are reviewed, as is the emerging research evidence in rodent models highlighting that adolescence may be a period of increased vulnerability compared to adulthood in which exposure to high levels of glucocorticoids results in enduring changes in adult cognitive function.

A pilot study on perceived stress and PTSD symptomatology in relation to four dimensions of older women's physical health

OBJECTIVES

The authors examined whether selected demographic and psychological factors would predict physical health dimensions in a sample of 53 cognitively high-functioning and ethnically diverse women (age 65-105 years).

METHOD

Predictors encompassed posttraumatic stress disorder (PTSD) symptomatology and perceived stress (of a nontraumatic nature and beyond health status) in relation to four dimensions of physical health. Age and income, well-known correlates of health in the target population, were included as potential predictors. The authors first tested the relationship between potential predictors and health dimensions via a canonical correlation analysis, and then employed full multiple regression analyses to simultaneously test the predictors in each health dimension model.

RESULTS

Perceived stress was a significant predictor of lower levels of general health (GH), but not of physical role limitations or physical functioning (PF). Conversely, PTSD symptomatology predicted more limitations in role fulfillment (and, to a lesser extent, impaired PF), but not lower levels of GH. As expected, age and income were predictive of some physical health dimensions. The hypothesized predictors failed to account for a significant portion of variance in pain scores.

CONCLUSION

PTSD symptomatology and perceived stress might influence older women's physical health dimensions differentially; additional research on larger samples is needed to corroborate these findings.

Aging-related gene expression in hippocampus proper compared with dentate gyrus is selectively associated with metabolic syndrome variables in rhesus monkeys

Age-dependent metabolic syndrome (MetS) is a well established risk factor for cardiovascular disease, but it also confers major risk for impaired cognition in normal aging or Alzheimer's disease (AD). However, little is known about the specific pathways mediating MetS-brain interactions. Here, we performed the first studies quantitatively linking MetS variables to aging changes in brain genome-wide expression and mitochondrial function. In six young adult and six aging female rhesus monkeys, we analyzed gene expression in two major hippocampal subdivisions critical for memory/cognitive function [hippocampus proper, or cornu ammonis (CA), and dentate gyrus (DG)]. Genes that changed with aging [aging-related genes (ARGs)] were identified in each region. Serum variables reflecting insulin resistance and dyslipidemia were used to construct a quantitative MetS index (MSI). This MSI increased with age and correlated negatively with hippocampal mitochondrial function (state III oxidation). More than 2000 ARGs were identified in CA and/or DG, in approximately equal numbers, but substantially more ARGs in CA than in DG were correlated selectively with the MSI. Pathways represented by MSI-correlated ARGs were determined from the Gene Ontology Database and literature. In particular, upregulated CA ARGs representing glucocorticoid receptor (GR), chromatin assembly/histone acetyltransferase, and inflammatory/immune pathways were closely associated with the MSI. These results suggest a novel model in which MetS is associated with upregulation of hippocampal GR-dependent transcription and epigenetic coactivators, contributing to decreased mitochondrial function and brain energetic dysregulation. In turn, these MSI-associated neuroenergetic changes may promote inflammation, neuronal vulnerability, and risk of cognitive impairment/AD.

Greater resistance to inflammation at adulthood could contribute to extended life span of p66(Shc-/-) mice

Evidence is mounting that reactive oxygen species (ROS) produced because of stressful challenges could interfere with the proper functioning of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in greater vulnerability to aging and neurodegeneration. Here we tested the hypothesis that p66(Shc-/-) mice, which have been described to have an extended life span and a high resistance to oxidative stress, might be less susceptible to the effects of inflammatory insults at adulthood. Although adrenocortical reactivity in response to bacterial endotoxin (lipopolysaccharide, LPS) did not differ as a function of the genotype, a hyperdrive of the HPA axis was revealed following treatment with a synthetic glucocorticoid agonist. When measuring changes in hippocampal oxidative status following LPS, only wild-type (WT) subjects showed increased levels of F(2)-isoprostanes, an index of lipid peroxidation and free radical formation. At the same time, the neurotrophin brain-derived neurotrophic factor was selectively increased in WT subjects, while levels of prostaglandin E(2) were decreased in the mutants. Overall, the greater resilience to inflammation-induced changes in the p66(Shc-/-) mutants might underlie the better health status and the longevity characterizing these mice.

Effects of glucocorticoids on mood, memory, and the hippocampus. Treatment and preventive therapy

Corticosteroids, such as prednisone and dexamethasone, are commonly prescribed medications that suppress the immune system and decrease inflammation. Common side effects of long-term treatment with corticosteroids include weight gain, osteoporosis, and diabetes mellitus. This paper reviews the literature on psychiatric and cognitive changes during corticosteroid therapy and potential treatment options. Hypomania and mania are the most common mood changes during acute corticosteroid therapy, although depression has also been reported. However, depression is reported to be more common than mania during long-term treatment with corticosteroids. A decline in declarative and working memory is also reported during corticosteroid therapy. Corticosteroids are associated with changes in the temporal lobe, detected by structural, functional, and spectroscopic imaging. The mood and cognitive symptoms are dose dependent and frequently occur during the first few weeks of therapy. Other risk factors are not well characterized. Controlled trials suggest that lithium and phenytoin can prevent mood symptoms associated with corticosteroids. Lamotrigine and memantine also have been shown to reverse, at least partially, the declarative memory effects of corticosteroids. Uncontrolled trials suggest that antipsychotics, anti-seizure medications, and perhaps some antidepressants can also be useful for normalizing mood changes associated with corticosteroids. Thus, both the symptoms and treatment response are similar to those of bipolar disorder. Moreover, corticosteroid-induced mood and cognitive alterations have been shown to be reversible with dose reduction or discontinuation of treatment.

A pilot study on perceived stress and PTSD symptomatology in relation to four dimensions of older women's physical health

OBJECTIVES

The authors examined whether selected demographic and psychological factors would predict physical health dimensions in a sample of 53 cognitively high-functioning and ethnically diverse women (age 65-105).

METHOD

Predictors encompassed posttraumatic stress disorder (PTSD) symptomatology and perceived stress (of a nontraumatic nature and beyond health status) in relation to all dimensions of physical health of the Medical Outcome Study 36-item Short Form Health Survey (MOS SF-36); (Ware, J.E., & Sherbourne, C.D., 1992). The MOS 36-item short-form health survey (SF-36): I. Conceptual framework and item selection. Medical Care, 30(6), 473-483). Age and income, well-known correlates of health in the target population, were included as potential predictors. The authors first tested the relationship between potential predictors and health dimensions via a canonical correlation analysis, and then employed full multiple regression analyses to simultaneously test the predictors in each health dimension model.

RESULTS

Perceived stress was a significant predictor of lower levels of general health (GH), but not of role limitations or physical functioning (PF). Conversely, PTSD symptomatology predicted more limitations in role fulfillment (and, to a lesser extent, impaired PF), but not lower levels of GH. As expected, age and income were predictive of some physical health dimensions. The hypothesized predictors failed to account for a significant portion of variance in pain scores.

CONCLUSION

PTSD symptomatology and perceived stress might influence older women's physical health dimensions differentially; additional research on larger samples is needed to corroborate these findings.

Biological mechanisms of disease and death in Moscow: rationale and design of the survey on Stress Aging and Health in Russia (SAHR)

BACKGROUND

Prior research has revealed large differences in health and mortality across countries, socioeconomic groups, and individuals. Russia experiences one of the world's highest levels of all-cause and cardiovascular mortality, great mortality differences within the population, and a heavy burden of ill health. Psychological stress has been suggested as a likely explanation of health loss and premature death in Russia and Eastern Europe. However, physiological mechanisms connecting stress with health in Russia remain unclear since existing epidemiological data are scarce and limited to conventional risk factors.

METHOD AND DESIGN

The survey on Stress Aging and Health in Russia (SAHR) is addressing this knowledge gap by collecting an unusually rich database that includes a wide range of reported information, physical and cognitive health outcomes, and biomarkers in a sample of Muscovite men and women aged 55 and older. The total planned sample size is 2,000 individuals. The sample was randomly selected from epidemiological cohorts formed in Moscow between the mid-1970s and the 1990s and from medical population registers. The baseline data collection was carried out from December 2006 to June 2009. Interviews and medical tests were administered at hospital or at home according to standardized protocol. Questionnaire information includes health, socio-demographic characteristics, economic well-being, cognitive functioning, and batteries on stress and depression. Biomarkers include anthropometry, grip strength, resting ECG, conventional cardiovascular factors of risk such as lipid profile and blood pressure, and other biochemical parameters such as those related to inflammation, glucose and insulin resistance, coagulation, fibrinolysis, and stress hormones. In addition to these measurements, SAHR includes dynamic biomarkers provided by 24-hour ECG (Holter) monitoring. This method continuously registers the beat-to-beat heart rate in naturalistic conditions without restrictions on normal daily activities. It provides information about heart functioning, including heart rate variability and ischemic and arrhythmic events.Re-examination of the study subjects will be conducted in 2009-2011 and will focus on health, functional status, economic conditions, behaviors, and attitudes towards aging. The subjects are also followed up for mortality and non-fatal health events.

DISCUSSION

The SAHR will produce a valuable set of established and novel biomarkers combined with self-reported data for the international research community and will provide important insights into factors and biological mechanisms of mortality and health losses in Russia.

Investigations of HPA function and the enduring consequences of stressors in adolescence in animal models

Developmental differences in hypothalamic-pituitary-adrenal (HPA) axis responsiveness to stressors and ongoing development of glucocorticoid-sensitive brain regions in adolescence suggest that similar to the neonatal period of ontogeny, adolescence may also be a sensitive period for programming effects of stressors on the central nervous system. Although research on this period of life is scarce compared to early life and adulthood, the available research indicates that effects of stress exposure during adolescence differ from, and may be longer-lasting than, effects of the same stress exposure in adulthood. Research progress in animal models in this field is reviewed including HPA function and the enduring effects of stress exposures in adolescence on sensitivity to drugs of abuse, learning and memory, and emotional behaviour in adulthood. The effects of adolescent stress depend on a number of factors, including the age, gender, the duration of stress exposure, the type of stressor, and the time between stress exposure and testing.

Persistence of maternal effects in baboons: Mother's dominance rank at son's conception predicts stress hormone levels in subadult males

Dominance status and reproductive experience are maternal characteristics that affect offspring traits in diverse taxa, including some cercopithecine primates. Maternal effects of this sort are widespread and are sources of variability in offspring fitness. We tested the hypothesis that maternal dominance rank and reproductive experience as well as a male's own age and dominance rank predicted chronic fecal glucocorticoid (fGC) concentrations in 17 subadult wild male baboons, Papio cynocephalus (median age 6.5 years), in the Amboseli basin, Kenya. Among these variables, maternal dominance rank at a subadult male's conception was the sole significant predictor of the male's fGC and accounted for 42% of fGC variance; sons of lower ranking mothers had higher fGC than did those of high-ranking mothers. This result is striking because subadult male baboons are approximately 4-6 years past the period of infant dependence on their mothers, and are larger than and dominant to all adult females. In addition, many males of this age have survived their mothers' death. Consequently, the influence of maternal dominance rank persisted well beyond the stage at which direct maternal influence on sons is likely. Persistence of these major maternal influences from the perinatal period may signal organizational effects of mothers on sons' HPA axis. Although short-term, acute, elevations in GC are part of adaptive responses to challenges such as predators and other emergencies, chronically elevated GC are often associated with stress-related pathologies and, thereby, adverse effects on fitness components.

Modulation of microglia and CD8(+) T cell activation during the development of stress-induced herpes simplex virus type-1 encephalitis

The central nervous system (CNS) has been shown to be vulnerable to a variety of insults in animals exposed to glucocorticoids. For example, psychological stress, a known inducer of glucocorticoid production, enhances the susceptibility of mice to herpes simplex virus type-1 (HSV-1) infection and results in the development of HSV-1 encephalitis (HSE). To determine the immune mechanisms by which stress promotes the development of HSE, we examined the role of the glucocorticoid receptor (GR) and the N-methyl-d-aspartate (NMDA) receptor in the development of HSE. Our findings demonstrate that blockade of either the GR or the NMDA receptor enhances survival following HSV-1 infection in stressed mice to levels similar to non-stressed mice. Subsequent studies determined the effect of GR and NMDA receptor blockade on immune function by specifically examining both microglia and CD8(+) T cell activation. Stress inhibited the expression of MHC class I by microglia and other brain-derived antigen presenting cells (CD45(hi)) independent of either the glucocorticoid receptor or the NMDA receptor, suggesting that stress-induced suppression of MHC class I expression in the brain does not affect survival during HSE. Blockade of the NMDA receptor, however, diminished HSV-1-induced increases in class I expression by CD45(hi) cells, suggesting that blockade of the NMDA receptor may limit CNS inflammation. Also, while CD8(+) T cell activation and function in the brain were not affected by stress, the number of CD8(+) T cells in the superficial cervical lymph nodes (SCLN) was decreased in stressed mice via GR-mediated mechanisms. These findings indicate that stress-induced hypocellularity is mediated by the GR while NMDA receptor activation is responsible for enhancing CNS inflammation. The combined effects of GR-mediated hypocellularity of the SCLN and NMDA receptor-mediated CNS inflammation during stress promote the development of HSE.

Resilience and aging

This article summarizes the literature on resilience to stress and aging. Key concepts and definitions of resilience are identified, and psychosocial and biological factors contributing to resilience that are universal across ages, as well as those that are unique to aging, are reviewed. Current and potentially useful intervention approaches to promote resilience and wellbeing are also reviewed. Views on future directions in resilience research and interventions targeting resilience are offered.

HPA function in adolescence: Role of sex hormones in its regulation and the enduring consequences of exposure to stressors

The hypothalamic-pituitary-adrenal (HPA) axis is one of the physiological systems involved in coping with stressors. There are functional shifts in the HPA axis and its regulation by sex hormones over the lifespan that allow the animal to meet the challenges of the internal and external environment that are specific to each stage of development. Sex differences in HPA function emerge over adolescence, a phenomenon reflecting the concomitant initiation of regulatory effects of sex hormones. The focus of this review is recent research on differences between adolescents and adults in HPA function and the enduring effects of exposure to stressors in adolescence. During adolescence, HPA function is characterized by a prolonged activation in response to stressors compared to adulthood, which may render ongoing development of the brain vulnerable. Although research has been scarce, there is a growing evidence that exposure to stressors in adolescence may alter behavioural responses to drugs and cognitive performance in adulthood. However, the effects reported appear to be stressor-specific and sex-specific. Such research may contribute toward understanding the increased risk for drug abuse and psychopathology that occurs over adolescence in people.

From Malthus to motive: how the HPA axis engineers the phenotype, yoking needs to wants

The hypothalamo-pituitary-adrenal (HPA) axis is the critical mediator of the vertebrate stress response system, responding to environmental stressors by maintaining internal homeostasis and coupling the needs of the body to the wants of the mind. The HPA axis has numerous complex drivers and highly flexible operating characterisitics. Major drivers include two circadian drivers, two extra-hypothalamic networks controlling top-down (psychogenic) and bottom-up (systemic) threats, and two intra-hypothalamic networks coordinating behavioral, autonomic, and neuroendocrine outflows. These various networks jointly and flexibly control HPA axis output of periodic (oscillatory) functions and a range of adventitious systemic or psychological threats, including predictable daily cycles of energy flow, actual metabolic deficits over many time scales, predicted metabolic deficits, and the state-dependent management of post-prandial responses to feeding. Evidence is provided that reparation of metabolic derangement by either food or glucocorticoids results in a metabolic signal that inhibits HPA activity. In short, the HPA axis is intimately involved in managing and remodeling peripheral energy fluxes, which appear to provide an unidentified metabolic inhibitory feedback signal to the HPA axis via glucocorticoids. In a complementary and perhaps a less appreciated role, adrenocortical hormones also act on brain to provide not only feedback, but feedforward control over the HPA axis itself and its various drivers, as well as coordinating behavioral and autonomic outflows, and mounting central incentive and memorial networks that are adaptive in both appetitive and aversive motivational modes. By centrally remodeling the phenotype, the HPA axis provides ballistic and predictive control over motor outflows relevant to the type of stressor. Evidence is examined concerning the global hypothesis that the HPA axis comprehensively induces integrative phenotypic plasticity, thus remodeling the body and its governor, the brain, to yoke the needs of the body to the wants of the mind. Adverse side effects of this yoking under conditions of glucocorticoid excess are discussed.

Normal brain ageing: models and mechanisms

Normal ageing is associated with a degree of decline in a number of cognitive functions. Apart from the issues raised by the current attempts to expand the lifespan, understanding the mechanisms and the detailed metabolic interactions involved in the process of normal neuronal ageing continues to be a challenge. One model, supported by a significant amount of experimental evidence, views the cellular ageing as a metabolic state characterized by an altered function of the metabolic triad: mitochondria-reactive oxygen species (ROS)-intracellular Ca2+. The perturbation in the relationship between the members of this metabolic triad generate a state of decreased homeostatic reserve, in which the aged neurons could maintain adequate function during normal activity, as demonstrated by the fact that normal ageing is not associated with widespread neuronal loss, but become increasingly vulnerable to the effects of excessive metabolic loads, usually associated with trauma, ischaemia or neurodegenerative processes. This review will concentrate on some of the evidence showing altered mitochondrial function with ageing and also discuss some of the functional consequences that would result from such events, such as alterations in mitochondrial Ca2+ homeostasis, ATP production and generation of ROS.

The Detrimental Effects of Allostasis: Allostatic Load as a Measure of Cumulative Stress

Since its inception in the 1980s, through further developments during the 1990s, and continuing today, the paradigm of allostatic load (AL) has becomed an important paradigm for predicting senescence and mortality. AL is a cumulative measure of the effects of multiple stressors and the process of responding to stressors on the soma. AL measurements of individuals is being tested on various samples and species and being reported across a variety of medical and social science journals. From the ISI Web of Science, all articles published between January 2000 and June 2005 with AL in any default category were obtained and transferred to Endnote. These articles, categorized as theory/review or data-driven, human or animal, and variability in risk factors used to estimate AL, are reviewed here. Only two of 90 reports were published in anthropological journals, likely, at least partly, because research on AL has focused more on western, industrialized populations where data are more easily obtained. From 2000-2005, 12 of 42 data-driven reports focused on elderly humans. Studies of animal models also are common (0 in 2000, but 4 in 2004 covering 21 species). During the last year, multiple additional potential physiological variables have been tested as measures of AL (10 to 20 in any one article). In the past half decade, AL also has been introduced to a wide range of disciplines, including psychology, anthropology, gerontology, veterinary medicine, and medical specialties, as a viable research theme. AL appears to provide a useful method for determining cumulative somatic stress such as that seen with senescence and frailty at older ages.

Social relationships, sleep quality, and interleukin-6 in aging women

This study examined the interplay of social engagement, sleep quality, and plasma levels of interleukin-6 (IL-6) in a sample of aging women (n = 74, aged 61-90, M age = 73.4). Social engagement was assessed by questionnaire, sleep was assessed by using the NightCap in-home sleep monitoring system and the Pittsburgh Sleep Quality Index, and blood samples were obtained for analysis of plasma levels of IL-6. Regarding subjective assessment, poorer sleep (higher scores on the Pittsburgh Sleep Quality Index) was associated with lower positive social relations scores. Multivariate regression analyses showed that lower levels of plasma IL-6 were predicted by greater sleep efficiency (P < 0.001), measured objectively and by more positive social relations (P < 0.05). A significant interaction showed that women with the highest IL-6 levels were those with both poor sleep efficiency and poor social relations (P < 0.05). However, those with low sleep efficiency but compensating good relationships as well as women with poor relationships but compensating high sleep efficiency had IL-6 levels comparable to those with the protective influences of both good social ties and good sleep.

Na+,K(+)-ATPase activity is reduced in hippocampus of rats submitted to an experimental model of depression: effect of chronic lithium treatment and possible involvement in learning deficits

This study was undertaken to verify the effects of chronic stress and lithium treatments on the hippocampal Na+,K(+)-ATPase activity of rats, as well as to investigate the effects of stress interruption and post-stress lithium treatment on this enzyme activity and on spatial memory. Two experiments were carried out; in the first experiment, adult male Wistar rats were divided into two groups: control and submitted to a chronic variate stress paradigm, and subdivided into treated or not with LiCl. After 40 days of treatment, rats were killed, and Na+,K(+)-ATPase activity was determined. In the second experiment, rats were stressed during 40 days, and their performance was evaluated in the Water Maze task. The stressed group was then subdivided into four groups, with continued or interrupted stress treatment and treated or not with lithium for 30 additional days. After a second evaluation of performance in the Water Maze, rats were killed and Na+,K(+)-ATPase activity was also measured. Results showed an impairment in Na+,K(+)-ATPase activity and in Water Maze performance of chronically stressed rats, which were prevented by lithium treatment and reversed by lithium treatment and by stress interruption. These results suggest that the modulation of Na+,K(+)-ATPase activity may be one of the mechanisms of action of lithium in the treatment of mood disorders.

A protective role of 27-kDa heat shock protein in glucocorticoid-evoked apoptotic cell death of hippocampal progenitor cells

Hippocampus is one of the most vulnerable tissues to glucocorticoid (GC). In the present study, we demonstrate that dexamethasone (DEX), a synthetic GC, induces apoptotic cell death in hippocampal progenitor HiB5 cells without any additional insult. Interestingly, expression of 27-kDa heat shock protein (HSP27) was markedly induced by DEX in time- and dose-dependent manners. This induction was dependent on the production of reactive oxygen species (ROS), suggesting that DEX-evoked oxidative damage to HiB5 cells is responsible for the HSP27 induction. To evaluate a possible role of HSP27, we generated two mutant HiB5 cell lines, in which expression of HSP27 was inhibited or enhanced by the over-expression of HSP27 cDNA with antisense or sense orientation (AS-HSP27 and S-HSP27, respectively). DEX-induced apoptotic cell population was significantly increased in AS-HSP27 HiB5 cells and evidently decreased in S-HSP27 cells. These results indicate that HSP27 protects hippocampal progenitor cells from GC-induced apoptotic cell death.

Stress-induced elevation of glucocorticoids increases microglia proliferation through NMDA receptor activation

The immunosuppressive nature of glucocorticoids has been well documented both in vitro and in vivo. This glucocorticoid-mediated immunosuppression has also been observed in immune cells within the central nervous system (CNS). For example, microglia have previously been shown to exhibit decreased proliferation, cytokine production, and antigen presentation upon treatment with glucocorticoids in vitro. Despite these in vitro findings, the impact of glucocorticoids on microglia function in vivo has not been fully investigated. To determine the interaction between glucocorticoids and microglia within the CNS, we used a restraint model of psychological stress to elevate corticosterone levels in mice. Quantification of microglia from stressed mice indicated that four sessions of stress induced the proliferation of microglia. This proliferation was a function of corticosterone-induced activation of the N-methyl-D-aspartate (NMDA) receptor within the CNS since blockade of corticosterone synthesis, the glucocorticoid receptor, or the NMDA receptor each prevented stress-induced increases in microglia number. In addition, the NMDA receptor antagonist MK-801 prevented increases in microglia following exogenous corticosterone administration to non-stressed mice. We conclude that activation of the NMDA receptor and subsequent microglia proliferation is a downstream effect of elevated corticosterone levels. These findings demonstrate that elevated levels of glucocorticoids are able to activate microglia in vivo and suggest that stress is able to induce a pro-inflammatory response within the CNS. A pro-inflammatory microglia response may be a contributing factor in the development of various stress-induced inflammatory conditions in the CNS.

Coronary Artery Disease and Risk Factors in People With Posttraumatic Vision Loss

OBJECTIVE

To examine the prevalence of coronary artery disease (CAD) and its risk factors in people with posttraumatic vision loss (PTVL).

DESIGN

Cross-sectional, controlled study.

SETTING

The general community.

PARTICIPANTS

Study groups included 82 subjects with PTVL, 49 siblings, 58 blind subjects with retinitis pigmentosa (RP), and the general population in Israel.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Sociodemographic and biomedical data collected by using a structured questionnaire and medical records.

RESULTS

The prevalence of CAD among subjects with PTVL (24%) was 2 to 3 times higher than the control groups ( P <.001). However, the prevalence of the CAD risk factors in these subjects was similar to or lower than those in the control groups. For example, significantly fewer subjects with PTVL were physically inactive (16%) than patients with RP (55%, P <.01). The only variable that was significantly associated with CAD prevalence was the cause of blindness-that is, trauma versus disease; the odds of having CAD after traumatic vision loss was 3.75 times higher than after RP.

CONCLUSIONS

People with PTVL exhibit elevated rates of risk for CAD similar to those of other groups with physical disability. The traumatic injury that caused vision loss might be an important factor underlying that risk.

Measures of brain morphology and infarction in the framingham heart study: establishing what is normal

Numerous anatomical and brain imaging studies find substantial differences in brain structure between men and women across the span of human aging. The ability to extend the results of many of these studies to the general population is limited, however, due to the generally small sample size and restrictive health criteria of these studies. Moreover, little attention has been paid to the possible impact of brain infarction on age-related differences in regional brain volumes. Given the current lack of normative data on gender and aging related differences in regional brain morphology, particularly with regard to the impact of brain infarctions, we chose to quantify brain MRIs from more than 2200 male and female participants of the Framingham Heart Study who ranged in age from 34 to 97 years. We believe that MRI analysis of the Framingham Heart Study more closely represents the general population enabling more accurate estimates of regional brain changes that occur as the consequence of normal aging. As predicted, men had significantly larger brain volumes than women, but these differences were generally not significant after correcting for gender related differences in head size. Age explained approximately 50% of total cerebral brain volume differences, but age-related differences were generally small prior to age 50, declining substantially thereafter. Frontal lobe volumes showed the greatest decline with age (approximately 12%), whereas smaller differences were found for the temporal lobes (approximately 9%). Age-related differences in occipital and parietal lobe were modest. Age-related gender differences were generally small, except for the frontal lobe where men had significantly smaller lobar brain volumes throughout the age range studied. The prevalence of MRI infarction was common after age 50, increased linearly with age and was associated with significantly larger white matter hyperintensity (WMH) volumes beyond that associated with age-related differences in these measures. Amongst men, the presence of MRI infarction was associated with significant age-related reductions in total brain volume. Finally, statistically significant associations were found between the volume of MRI infarcts in cubic centimeters and all brain measures with the exception of parietal lobe volume for individuals where the volume of MRI infarctions was measured. These data serve to define age and gender differences in brain morphology for the Framingham Heart Study. To the degree participants of the Framingham Heart Study are representative the general population, these data can serve as norms for comparison with morphological brain changes associated with aging and disease. In this regard, these cross-sectional quantitative estimates suggest that age-related tissue loss differs quantitatively and qualitatively across brain regions with only minor differences between men and women. In addition, MRI evidence of cerebrovascular disease is common to the aging process and associated with smaller regional brain volumes for a given age, particularly for men. We believe quantitative MRI studies of the Framingham community enables exploration of numerous issues ranging from understanding normal neurobiology of brain aging to assessing the impact of various health factors, particularly those related to cerebrovascular disease, that appear important to maintaining brain health for the general population.

Molecular endocrinology and physiology of the aging central nervous system

Aging is associated with a progressive decline in physical and cognitive functions. The impact of age-dependent endocrine changes regulated by the central nervous system on the dynamics of neuronal behavior, neurodegeneration, cognition, biological rhythms, sexual behavior, and metabolism are reviewed. We also briefly review how functional deficits associated with increases in glucocorticoids and cytokines and declining production of sex steroids, GH, and IGF are likely exacerbated by age-dependent molecular misreading and alterations in components of signal transduction pathways and transcription factors.

Short-term effects of repetitive arm work and dynamic exercise on glucose metabolism and insulin sensitivity

AIM

To determine whether repetitive arm work, with a large component of static muscle contraction alters glucose metabolism and insulin sensitivity.

METHOD

Euglycemic clamps (2 h) were started in ten healthy individuals 15 min after 37 min periods of: (1) repetitive arm work in a simulated occupational setting; (2) dynamic concentric exercise on a cycle ergometer at 60% of VO(2max) and (3) a resting regime as a control. During the experimental periods, blood samples were collected, blood pressure was measured repeatedly and electrocardiogram (ECG) was recorded continuously. During the clamps, euglycemia was maintained at 5 mmol l(-1) and insulin was infused at 56 mU m(-2) min(-1) for 120 min.

RESULTS

The insulin-mediated glucose disposal rate (M-value) for the steady-state period (60-120 min) of the clamp, tended to be lower following arm work than for both cycling and resting regimes. When dividing the steady-state period into 20-min intervals, the insulin sensitivity index (ISI) was significantly lower for arm work compared with the resting control situation between 60-80 min (P = 0.04) and 80-100 min (P = 0.01), respectively. Catecholamines increased significantly for arm work and cycling compared with resting regime. Data from heart rate variability (HRV) measurements indicated significant sympathetic activation during repetitive arm work.

CONCLUSION

The results indicate that repetitive arm work might acutely promote insulin resistance, whereas no such effect on insulin resistance was produced by dynamic concentric exercise.

Biological basis of determinants of health

Clinical medicine and health policy planning find common cause as they seek to define the determinants of health. There is substantial recent interest in the social ecology in which health is embedded. However, biology is where these contributing environmental factors are translated. I provide a new conceptual framework for the biological determinants of health. The old public health rubric of host, agent, and environment as the features that define the root elements of health is an impoverished scheme, because it does not represent our new appreciation of genetic and aging contributions to phenotypic health. I propose genes, external agency, internal agency, and aging as more operationally helpful determinants that effectively describe the biological experience of the organism. This scheme has the advantage of differentiating those agencies that are practically approachable, and therefore deserving of increased attention and investment, and those that are currently intractable.

Adverse effect of the combination of hypothyroidism and chronic psychosocial stress on hippocampus-dependent memory in rats

Both hypothyroidism and stress interfere with cognitive function in patients. This study examined the effect of hypothyroidism and stress on hippocampus-dependent learning and memory in rats using the novel radial arm water maze (RAWM), which measures spatial working memory. Hypothyroidism was accomplished by thyroidectomy and 2 weeks later a form of intruder stress was used as the chronic psychosocial stressor. After 4-6 weeks of stress, rats were trained to learn (during the acquisition phase; four trials) and then remember (during two memory test trials occurring 15 and 120 min after the acquisition phase) the within-day location of a hidden escape platform, which was in different arm every day. The number of errors (entry into arms other than the platform arm) was noted. Within-day learning of the platform location was largely unaffected by the experimental manipulations, indicating that rats in all groups were equally capable of finding the platform to escape from the water with similar numbers of errors (P > 0.005). The number of days a rat took to reach a criterion (DTC; a maximum of one error in three consecutive days) indicated that chronic stress or hypothyroidism, alone, resulted in a mild impairment of spatial memory, and the combination of chronic stress and hypothyroidism resulted in a more severe and long-lasting memory impairment. The data indicated that the combination of stress and hypothyroidism produced more deleterious effects on hippocampal function than either chronic stress or hypothyroidism alone.

A broader view of trauma: A biopsychosocial-evolutionary view of the role of the traumatic stress response in the emergence of pathology and/or growth

The main goal of this paper is to articulate a biopsychosocial evolutionary approach to understanding the traumatic stress response. The secondary goal of this paper is to draw out the general clinical implications of this approach. I articulate seven interconnected and overlapping empirically grounded theoretical conclusions: (1) Stress is best understood as a prerational form of biopsychological feedback regarding the organism's relationship with its environment; (2) The normal outcome of traumatic stress is growth, rather than pathology; (3) Most psychopathology is a function of the maladaptive modulation of the stress response; (4) Trauma always leaves the individual transformed on a biological, as well as psychological, level; (5) The general biological process underlying stress responses is universal, but the specific dynamics are always a function of the unique sociocultural environment and psychological makeup of the individual; (6) The biology underlying stable psychopathological symptoms may change even as the psychological symptoms remain the same; and (7) Rationality is humanity's evolutionarily newest and most sophisticated stress-reduction behavioral mechanism, and the most important aspect of restoring psychological health to the trauma victim.

Mood disorders and allostatic load

The brain controls both the physiologic and the behavioral coping responses to daily events as well as major stressors, and the nervous system is itself a target of the mediators of those responses through circulating hormones. The amygdala and hippocampus interpret what is stressful and regulate appropriate responses. The amygdala becomes hyperactive in posttraumatic stress disorder (PTSD) and depressive illness, and hypertrophy of amygdala nerve cells is reported after repeated stress in an animal model. The hippocampus expresses adrenal steroid receptors. It undergoes atrophy in several psychiatric disorders and responds to repeated stressors with decreased dendritic branching and reduction in number of neurons in the dentate gyrus. Stress promotes adaptation ("allostasis"), but a perturbed diurnal rhythm or failed shutoff of mediators after stress ("allostatic state") leads, over time, to wear and tear on the body ("allostatic load"). Neural changes mirror the pattern seen in the cardiovascular, metabolic, and immune systems, that is, short-term adaptation versus long-term damage. Allostatic load leads to impaired immunity, atherosclerosis, obesity, bone demineralization, and atrophy of nerve cells in brain. Allostatic load is seen in major depressive illness and may also be expressed in other chronic anxiety disorders such as PTSD and should be documented.

Molecular correlates of impaired prefrontal plasticity in response to chronic stress

Disturbed adaptations at the molecular and cellular levels following stress could represent compromised neural plasticity that contributes to the pathophysiology of stress-induced disorders. Evidence illustrates atrophy and cell death of stress-vulnerable neurones in the prefrontal cortex. Reduced plasticity may be realized through the destabilized function of selective proteins involved in organizing the neuronal skeleton and translating neurotrophic signals. To elucidate the mechanisms underlying these effects, rats were exposed to chronic footshock stress. Patterns of c-fos, phospho-extracellular-regulated protein kinases 1/2 (ERK1/2), calcineurin and phospho-cyclic-AMP response-element binding protein (CREB) expression were subsequently investigated. The results indicate chronic stress-induced impairments in prefrontal and cingulate signal transduction cascades underlying neuronal plasticity. The medial prefrontal cortex, demonstrated functional hyperactivity and dendritic phospho-ERK1/2 hyperphosphorylation, while reduced c-fos and calcineurin immunoreactivity occurred in the cingulate cortex. Significantly reduced phospho-CREB expression in both cortical regions, considering its implication in brain-derived neurotrophic factor (BDNF) transcription, suggests reduced synaptic plasticity. This data confirms the damaging effect of stress on cortical activity, on a molecular level. Due to the association of these markers in the regulation of BDNF signalling, these findings suggest a central role for intracellular neurotrophin transduction members in the pathways underlying cellular actions of stress in the brain.

Environmental conditions unexpectedly affect the long-term extent of cell death following an hypoxic episode

Previously we reported delayed cell death, defined by clear-cut cell loss 60 days after a nitrite-induced hypoxic episode. The loss of cells was not apparent two weeks after the treatment, although some changes in cellular appearance were observed at that time. A similar delayed loss of neurons in the hippocampus after hypoxia induced by blood vessel occlusion has also been found. In addition, we reported that the amount of methemoglobinemia induced by the sodium nitrite can be reduced by the stress produced by handling and the injection of saline 2 or 24 h before the nitrite administration. The degree of methemoglobin formed is directly related to cell death in certain areas of the brain, including regions within the hippocampus. Considering the many effects that can be produced by chronic and acute stress of several kinds and the length of time during which these effects manifest themselves, we undertook to determine the histologic effects of the stresses of transport on the neuroanatomic effects of sodium nitrite administration 60 days post administration. Comparisons were made of the effects of two methods of transport from the laboratory in which the animals (male CD-1 mice) were injected with the sodium nitrite or saline (Tufts Medical School) to the laboratory in which the histologic evaluations were made (Binghamton University). The animals began their travel several hours after the injections. One transport method was by commuter airline and the other was by automobile. All animals had the same transport from the supplier to the Boston location (truck). Thus, the stress of experimental interest occurred after the nitrite administration. Upon arrival at Binghamton University, the animals were housed at the University in their own colony room for 60 days before sacrifice. After sacrifice, sections from their brains were subjected to a number of histologic staining procedures, including PTAH, the Bielschowsky silver method, GFAP, and the standard Nissl procedure. Although special attention was paid to hippocampal areas, changes in cells in the habenulae and the linings of ventricular areas were also prominent. Surprisingly, the nitrite treatment before transport to Binghamton offered partial protection against the very substantial and lasting effects of the injections, transport, and handling found in the control animals. Differential effects caused by the two methods of transport were also noted.

Hippocampal cytochrome P450s synthesize brain neurosteroids which are paracrine neuromodulators of synaptic signal transduction

Hippocampal pyramidal neurons and granule neurons of adult male rats are equipped with a complete machinery for the synthesis of pregnenolone, dehydroepiandrosterone, 17beta-estradiol and testosterone as well as their sulfate esters. These brain neurosteroids are synthesized by cytochrome P450s (P450scc, P45017alpha and P450arom) from endogenous cholesterol. Synthesis is acutely dependent on the Ca(2+) influx attendant upon neuron-neuron communication via N-methyl-D-aspartate (NMDA) receptors. Pregnenolone sulfate, estradiol and corticosterone rapidly modulate neuronal signal transduction and the induction of long-term potentiation via NMDA receptors and putative membrane steroid receptors. Brain neurosteroids are therefore promising neuromodulators that may either activate or inactivate neuron-neuron communication, thereby mediating learning and memory in the hippocampus.

The stress-vulnerability hypothesis in psychotic disorders: focus on the stress response systems

The vulnerabilty stress model is an intriguing concept to look into the etiology of psychotic disorders and, in particular, into the "nature nurture" principle. That stress affects a vulnerable nature may be obvious, but its mechanism is not well understood, and many questions remain to be answered, let alone how to define "vulnerability". The present review tries to focus on the core issues of the vulnerability stress concept--identifying vulnerability, the way stress interferes with it, and the possiblilities of modulating their interaction. Attention is drawn to the biologic stress response systems, the autonomic nervous system (ANS), the hypothalamic pituitary adrenal (HPA) system, and the immune system, and highlights the plasticity of the HPA system as the mediator of adaptation.

Developmental neurobiology of childhood stress and trauma

Severe early stress and maltreatment produces a cascade of events that have the potential to alter brain development. The first stage of the cascade involves the stress-induced programming of the glucocorticoid, noradrenergic, and vasopressin-oxytocin stress response systems to augment stress responses. These neurohumors then produce effects on neurogenesis, synaptic overproduction and pruning, and myelination during specific sensitive periods. Major consequences include reduced size of the mid-portions of the corpus callosum; attenuated development of the left neocortex, hippocampus, and amygdala along with abnormal frontotemporal electrical activity; and reduced functional activity of the cerebellar vermis. These alterations, in turn, provide the neurobiological framework through which early abuse increases the risk of developing post-traumatic stress disorder (PTSD), depression, symptoms of attention-deficit/hyperactivity, borderline personality disorder, dissociative identity disorder, and substance abuse.