Temporal variability of glucocorticoid receptor activity is functionally important for the therapeutic action of fluoxetine in the hippocampus.

Previous studies have shown inconsistent results regarding the actions of antidepressants on glucocorticoid receptor (GR) signalling. To resolve these inconsistencies, we used a lentiviral-based reporter system to directly monitor rat hippocampal GR activity during stress adaptation. Temporal GR activation was induced significantly by acute stress, as demonstrated by an increase in the intra-individual variability of the acute stress group compared with the variability of the non-stress group. However, the increased intra-individual variability was dampened by exposure to chronic stress, which was partly restored by fluoxetine treatment without affecting glucocorticoid secretion. Immobility in the forced-swim test was negatively correlated with the intra-individual variability, but was not correlated with the quantitative GR activity during fluoxetine therapy; this highlights the temporal variability in the neurobiological links between GR signalling and the therapeutic action of fluoxetine. Furthermore, we demonstrated sequential phosphorylation between GR (S224) and (S232) following fluoxetine treatment, showing a molecular basis for hormone-independent nuclear translocation and transcriptional enhancement. Collectively, these results suggest a neurobiological mechanism by which fluoxetine treatment confers resilience to the chronic stress-mediated attenuation of hypothalamic-pituitary-adrenal axis activity.

The SH3-domain protein Bem1 coordinates mitogen-activated protein kinase cascade activation with cell cycle control in Saccharomyces cerevisiae.

The mating mitogen-activated protein kinase (MAPK) cascade has three major outputs prior to fusion: transcriptional activation of many genes, cell cycle arrest in the G1 phase, and polarized growth. Bem1 localizes near the cortical actin cytoskeleton and is essential for polarized growth during mating. Here we show that Bem1 is required for efficient signal transduction and coordinates MAPK cascade activation with G1 arrest and mating. bem1delta null mutants are defective in G1 arrest and transcriptional activation in response to mating pheromone. Bem1 protein stimulates Fus3 (MAPK) activity and associates with Ste5, the tethering protein essential for activation of the MAPK kinase kinase Ste11. Bem1-Ste5 complexes also contain Ste11, Ste7 (MAPK kinase), and Fus3, suggesting that Ste5 localizes the MAPK cascade to Bem1. Strikingly, Bem1 also copurifies with Far1, a Fus3 substrate required for G1 arrest and proper polarized growth during mating. These and other results suggest that Bem1 may cross-link the Ste5-MAPK cascade complex to upstream activators and specific downstream substrates at the shmoo tip, thus enabling efficient circuitry for G1 arrest and mating.

Stress-level cortisol treatment impairs inhibitory control of behavior in monkeys.

Most studies of cortisol-induced cognitive impairments have focused on hippocampal-dependent memory. This study investigates a different aspect of cognition in a randomized placebo-controlled experiment with monkeys that were treated with cortisol according to a protocol that simulates a prolonged stress response. Young adult and older adult monkeys were assigned randomly to placebo or chronic treatment with cortisol in a 2 x 2 factorial design (n = 8 monkeys per condition). Inhibitory control of behavior was assessed with a test shown previously in primates to reflect prefrontal cortical dysfunction. Failure to inhibit a specific goal-directed response was evident more often in older adults. Treatment with cortisol increased this propensity in both older and young adult monkeys. Age-related differences in response inhibition were consistent across blocks of repeated test trials, but the treatment effects were clearly expressed only after prolonged exposure to cortisol. Aspects of performance that did not require inhibition were not altered by age or treatment with cortisol, which concurs with effects on response inhibition rather than nonspecific changes in behavior. These findings lend support to related reports that cortisol-induced disruptions in prefrontal dopamine neurotransmission may contribute to deficits in response inhibition and play a role in cognitive impairments associated with endogenous hypercortisolism in humans.

Fus3p and Kss1p control G1 arrest in Saccharomyces cerevisiae through a balance of distinct arrest and proliferative functions that operate in parallel with Far1p.

In Saccharomyces cerevisiae, mating pheromones activate two MAP kinases (MAPKs), Fus3p and Kss1p, to induce G1 arrest prior to mating. Fus3p is known to promote G1 arrest by activating Far1p, which inhibits three Clnp/Cdc28p kinases. To analyze the contribution of Fus3p and Kss1p to G1 arrest that is independent of Far1p, we constructed far1 CLN strains that undergo G1 arrest from increased activation of the mating MAP kinase pathway. We find that Fus3p and Kss1p both control G1 arrest through multiple functions that operate in parallel with Far1p. Fus3p and Kss1p together promote G1 arrest by repressing transcription of G1/S cyclin genes (CLN1, CLN2, CLB5) by a mechanism that blocks their activation by Cln3p/Cdc28p kinase. In addition, Fus3p and Kss1p counteract G1 arrest through overlapping and distinct functions. Fus3p and Kss1p together increase the expression of CLN3 and PCL2 genes that promote budding, and Kss1p inhibits the MAP kinase cascade. Strikingly, Fus3p promotes proliferation by a novel function that is not linked to reduced Ste12p activity or increased levels of Cln2p/Cdc28p kinase. Genetic analysis suggests that Fus3p promotes proliferation through activation of Mcm1p transcription factor that upregulates numerous genes in G1 phase. Thus, Fus3p and Kss1p control G1 arrest through a balance of arrest functions that inhibit the Cdc28p machinery and proliferative functions that bypass this inhibition.

Early life stress and inherited variation in monkey hippocampal volumes.

BACKGROUND: Opportunities for research on the causes and consequences of stress-related hippocampal atrophy are limited in human psychiatric disorders. Therefore, this longitudinal study investigated early life stress and inherited variation in monkey hippocampal volumes. METHODS: Paternal half-siblings raised apart from one another by different mothers in the absence of fathers were randomized to 1 of 3 postnatal conditions that disrupted diverse aspects of early maternal care (n = 13 monkeys per condition). These conditions were previously shown to produce differences in social behavior, emotional reactivity, and neuroendocrine stress physiology. Hippocampal volumes were subsequently determined in adulthood by high-resolution magnetic resonance imaging. RESULTS: Adult hippocampal volumes did not differ with respect to the stressful postnatal conditions. Based on paternal half-sibling effects, the estimated proportion of genetic variance, ie, heritability, was 54% for hippocampal size. Paternal half-siblings with small adult hippocampal volumes responded to the removal of all mothers after weaning with initially larger relative increases in cortisol levels. Plasma cortisol levels 3 and 7 days later, and measures of cortisol-negative feedback in adulthood were not, however, correlated with hippocampal size. CONCLUSIONS: In humans with mood and anxiety disorders, small hippocampal volumes have been taken as evidence that excessive stress levels of cortisol induce hippocampal volume loss. Results from this study of monkeys suggest that small hippocampi also reflect an inherited characteristic of the brain. Genetically informed clinical studies should assess whether inherited variation in hippocampal morphology contributes to excessive stress levels of cortisol through diminished neuroendocrine regulation.

Stress inoculation modeled in mice.

Stress inoculation entails intermittent exposure to mildly stressful situations that present opportunities to learn, practice and improve coping in the context of exposure psychotherapies and resiliency training. Here we investigate behavioral and hormonal aspects of stress inoculation modeled in mice. Mice randomized to stress inoculation or a control treatment condition were assessed for corticosterone stress hormone responses and behavior during open-field, object-exploration and tail-suspension tests. Stress inoculation training sessions that acutely increased plasma levels of corticosterone diminished subsequent immobility as a measure of behavioral despair on tail-suspension tests. Stress inoculation also decreased subsequent freezing in the open field despite comparable levels of thigmotaxis in mice from both treatment conditions. Stress inoculation subsequently decreased novel-object exploration latencies and reduced corticosterone responses to repeated restraint. These results demonstrate that stress inoculation acutely stimulates glucocorticoid signaling and then enhances subsequent indications of active coping behavior in mice. Unlike mouse models that screen for the absence of vulnerability to stress or presence of traits that occur in resilient individuals, stress inoculation training reflects an experience-dependent learning-like process that resembles interventions designed to build resilience in humans. Mouse models of stress inoculation may provide novel insights for new preventive strategies or therapeutic treatments of human psychiatric disorders that are triggered and exacerbated by stressful life events.

Assessing silver nanoparticles behaviour in artificial seawater by mean of AF4 and spICP-MS.

The use of nanotechnology-based products is constantly increasing and there are concerns about the fate and effect on the aquatic environment of antimicrobial products such as silver nanoparticles. By combining different characterization techniques (asymmetric flow field-flow fractionation, single particle ICP-MS, UV-Vis) we show that it is possible to assess in detail the agglomeration process of silver nanoparticles in artificial seawater. In particular we show that the presence of alginate or humic acid differentially affects the kinetic of the agglomeration process. This study provides an experimental methodology for the in-depth analysis of the fate and behaviour of silver nanoparticles in the aquatic environment.

Socioregulatory effects on squirrel monkey pituitary-adrenal activity: a longitudinal analysis of cortisol and ACTH.

Squirrel monkeys show unusually prolonged elevations in plasma cortisol when separated from like-sex social companions. To determine whether this hypersecretion of cortisol reflects a deficiency in feedback mechanisms that normally inhibit the prolonged activation of the pituitary-adrenal axis, we simultaneously measured plasma cortisol and corticotropin (ACTH) in 30 juvenile monkeys housed in established groups, individual cages, and newly formed groups. As found in recent longitudinal studies of adults, when juveniles were living without companions, mean cortisol titers were consistently higher than those observed when the same juveniles were living in like-sex social groups. When cortisol was elevated, however, ACTH titers were significantly and chronically reduced. These results suggest that elevated cortisol does inhibit ACTH synthesis or release, and that hypercortisolism in squirrel monkeys living without companions is not a consequence of chronic elevations in ACTH. Similar peculiarities in pituitary-adrenal activity are evident in a number of affective disorders in human beings.

Separation induced changes in squirrel monkey hypothalamic-pituitary-adrenal physiology resemble aspects of hypercortisolism in humans.

When separated from groups, squirrel monkeys respond with significant increases in plasma cortisol and adrenocorticotropic hormone (ACTH). While cortisol remains elevated above pre-separation levels, significant reductions occur in ACTH. Monkeys that respond with greater increases in cortisol subsequently exhibit greater reductions in ACTH, which suggests that reductions in ACTH are mediated by corticosteroid feedback. Monkeys that respond with greater increases in cortisol also tend to exhibit greater cerebrospinal fluid levels of the dopamine metabolite HVA, but not the norepinephrine metabolite MHPG, or corticotropin-releasing factor (CRF). Attenuation of corticosteroid feedback with metyrapone results in significant increases in circulating ACTH, and in older monkeys increases plasma HVA. Similar findings in humans have been reported in clinical studies of hypercortisolism and major depression.

Early environmental regulation of glucocorticoid feedback sensitivity in young adult monkeys.

Variations in maternal care induce in neonatal rodents life-long changes in glucocorticoid feedback regulation of the hypothalamic-pituitary-adrenal axis. This aspect of plasticity in neuroendocrine development has not been established in primates. We assessed, in young adult squirrel monkeys, postnatal rearing effects on cortisol-induced suppression of corticotropin-releasing factor (CRF) stimulated secretion of adrenocorticotropic hormone (ACTH). Offspring of randomly bred monkeys were periodically removed from natal groups between 13 and 21 weeks of age. In two other postnatal rearing conditions, systematic differences in maternal availability were produced by manipulating the effort required of lactating mothers to successfully find food. All offspring were subsequently administered, 3-5 years later on two occasions, an intravenous ovine CRF injection preceded 60 min earlier by placebo or cortisol pretreatment. The difference between CRF-stimulated time-integrated secretion of ACTH following placebo vs cortisol pretreatment served as an index of glucocorticoid negative feedback. Difference scores were greatest in monkeys previously separated from natal groups. This finding was not attributable to significant rearing condition differences in plasma cortisol levels achieved following pretreatment with exogenous cortisol, nor plasma ACTH levels produced when the CRF injection was preceded by pretreatment with placebo. The results suggest that postnatal experiences altered glucocorticoid feedback in monkeys at least through early adulthood. This conclusion supports retrospective reports indicating that, for humans with major mood and anxiety disorders, systematic differences in glucocorticoid feedback may reflect neural mechanisms in development linking early life stress with psychopathology in adulthood.

Impaired transactivation of the glucocorticoid receptor cloned from the Guyanese squirrel monkey.

Squirrel monkeys are among a diverse group of New World primates that demonstrate unusually high levels of circulating corticosteroids and glucocorticoid receptor (GR) insensitivity. Recent evidence suggests that overexpression of an immunophilin impairs dexamethasone binding to GR in the Bolivian squirrel monkey (Saimiri boliviensis). Here we describe the cloning, expression, and functional characterization of GR from the closely related Guyanese squirrel monkey (S. sciureus). The cloned Guyanese squirrel monkey GR (gsmGR) cDNA closely resembles human GR (hGR) cDNA, and yields a high affinity dexamethasone binding receptor when expressed in COS-1 cells. Transactivation analysis of hGR and gsmGR expressed in CV-1 cells and cultured squirrel monkey kidney (SMK) cells indicates that: (1) SMK cells elaborate a functional high activity GR from human GR cDNA; (2) gsmGR is an order of magnitude less efficient than hGR at transactivation in CV-1 and SMK cells; and (3) maximal transactivation by gsmGR is attenuated in both cell lines. Glucocorticoid resistance in S. sciureus is at least partly attributable to a naturally occurring mutation in the GR gene that results in impaired GR transactivation.

Psychobiological consequences of social relationships.

Social separations can induce long-lasting increases in cortisol, whereas companionship can result in social buffering. Preliminary evidence from studies of squirrel monkeys suggests that social separation-induced hypersecretion of cortisol is initially driven by hypersecretion of ACTH. From 1-21 days postseparation, however, cortisol remains elevated above pre-separation controls, while ACTH levels are consistently reduced. Hypercortisolism is maintained despite reductions in ACTH, because adrenal responsiveness to ACTH is enhanced. Low circulating ACTH, in turn, is maintained by robust feedback mechanisms that apparently inhibit biosynthesis or release of pituitary ACTH. These findings are consistent with neuroendocrine interactions known or hypothesized to occur during major depressive disorders in humans and raise unique possibilities for comparative research in human and nonhuman primates.

Glucocorticoid and mineralocorticoid receptor mRNA expression in squirrel monkey brain.

Corticosteroids have been implicated in hippocampal atrophy in patients with severe psychiatric disorders, but little is known about receptor expression for corticosteroids in human or nonhuman primate brain. Both the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) were surveyed in this study of squirrel monkey brain using in situ hybridization histochemistry. Regions of high GR mRNA levels included CA1 and CA2 of hippocampus, dentate gyrus, paraventricular hypothalamus, lateral geniculate, lateral>medial amygdala, and cerebellum. Western analysis confirmed that GR immunoreactivity in squirrel monkey brain tissue most likely reflects the alpha isoform. Regions of high MR mRNA levels included all hippocampal pyramidal cell fields, dentate gyrus granule cell layer, lateral septum, medial>lateral amygdala, and to a lesser extent, cerebellum. Low levels of MR were also expressed in caudate and putamen. Receptor expression for corticosteroids in deep brain structures and the hippocampal formation was similar to that previously reported in rodents, but GR and MR mRNA were expressed at higher levels in squirrel monkey cerebral cortex. GR expression was evident in all cortical layers, particularly the pyramidal cell-rich layers II/III and V. MR expression was restricted to the more superficial cortical layers, and was only moderately represented in layer V. Laminar patterns were apparent in all regions of cortex for GR expression in squirrel monkeys, but low MR mRNA levels were found in dorsomedial prefrontal cortex (PFC). Different subregional distributions and distinctive laminar patterns suggest specialized functions or coordinated interactions between GR and MR mediated functions in primate PFC.

Frustrative nonreward and pituitary-adrenal activity in squirrel monkeys.

Little is known about frustration-induced changes in stress physiology in humans and nonhuman primates. Here we assess in two experiments with squirrel monkeys plasma levels of pituitary-adrenal stress hormones in conditions designed to provoke frustrative nonreward. In the first experiment 18 prepubertal monkeys were trained to feed from one of eight sites, and then tested without food at any of the sites. These monkeys responded with significant increases in cortisol and adrenocorticotropic hormone (ACTH). In the second experiment 18 adult monkeys were trained to feed from one of eight sites, and then tested after food was moved to a different foraging site. Nine monkeys found food at the relocated site, discontinued foraging at the previously baited site, and responded with decreases in cortisol. The other nine monkeys failed to find the relocated site, initially increased their visits to the previously baited site, and responded with elevations in cortisol and ACTH. In keeping with comparable findings in rats, our observations indicate that frustrative nonreward elicits ACTH-stimulated secretion of cortisol in primates.

Social modulation of pituitary-adrenal responsiveness and individual differences in behavior of young domestic goats.

The effects of three variables known to influence pituitary-adrenal activity were examined in kid goats who were accompanied by adult goats in standard goat-human encounters. Serum corticosteroid concentrations in bold kids who characteristically spent above average amounts of time closely interacting with the person were never significantly different from control values. Corticosteroids in timid kids who spent little time near the person depended on the adult goat's behavior toward the person and the nature of the social relationship between the kid and the adult goat. When timid kids were accompanied by adult goats (familiar pen-mates or strangers) who behaved as if they were fearful of the person, their corticosteroids were significantly greater than control values. In contrast, bold pen-mates or bold strangers effectively reduced pituitary-adrenal responsiveness in timid kids. Only mothers unconditionally reduced kid pituitary-adrenal responsiveness and systematically affected kid behavior toward the person. The functioning of behavioral and pituitary-adrenal systems in young goats was influenced by consistent individual differences in responsiveness and the differing capacities of social companions to modulate this responsivity.

Seasonality in squirrel monkeys (Saimiri sciureus): social facilitation by females.

The extent to which social living arrangements influenced seasonal changes in physiology and behavior was examined in adult squirrel monkeys (Saimiri sciureus). Data were collected over 20 months (encompassing two breeding seasons) from animals that were housed in three mixed-sex social configurations that varied in the number of heterosexual and isosexual social partners. For both sexes, the presence of multiple females was found to facilitate reproduction. Females housed with other females were more likely to exhibit seasonal ovarian cyclicity and tended to have higher conception rates. Social facilitation of reproduction was particularly prominent for subordinate females. The presence of same-sex companions also resulted in reduced adrenocortical output in females during the first nonbreeding season. In males, the availability of multiple females increased plasma testosterone levels, except in the presence of more dominant males. Seasonal increases in male weight coincided with increased cortisol levels and were most prominent in social groups containing multiple females. The influence of multiple females on male seasonality occurred despite the finding that male-female interactions were infrequent and, in fact, occurred less frequently when isosexual partners were available. Unexpectedly, affiliative social interactions between same-sex and opposite-sex partners occurred less frequently during the breeding season. As expected, behaviors associated with sex tended to increase during the breeding season. Very little agonism was observed during the course of the study and there was no evidence of interanimal competition for mates.

Sexual segregation in squirrel monkeys (Saimiri sciureus): a transactional analysis of adult social dynamics.

Female agonism against males and male interventions in social transactions between the sexes are 2 explanations for the low rates of social engagement observed between male and female squirrel monkeys (Saimiri sciureus). These possibilities were evaluated by comparing the frequency, structure, and content of transactions between the sexes in 3 experimental social units: male-female pairs, single-male-multifemale groups, and multimale-multifemale groups. Affiliative transactions between the sexes occurred 3-5 times less often in multimale-multifemale groups than in male-female pairs and in single-male-multifemale groups. Intermale agonism in the multimale-multifemale groups often coincided with ongoing transactions between the sexes, whereas female agonism against males was rather uncommon in all social units. The results failed to support the female agonism hypothesis and indicate a need for more detailed studies of intermale social dynamics.