Genetic and environmental effects on diurnal dehydroepiandrosterone sulfate concentrations in middle-aged men.

BACKGROUND: Dehydroepiandrosterone sulfate (DHEAS) is important for its association with immune system function and health outcomes. The characterization of the genetic and environmental contributions to daily DHEAS concentrations is thus important for understanding the genetics of health and aging. METHODS: Saliva was collected from 783 middle-aged men (389 complete pairs and 5 unpaired twins) as part of the Vietnam Era Twin Study of Aging. Samples were taken at multiple specified time points across two non-consecutive days in the home and one day at the study sites. A twin modeling approach was used to estimate genetic and environmental contributions for time-specific and average DHEAS concentrations. RESULTS: There was a consistent diurnal pattern for DHEAS concentrations in both at-home and day-of-testing (DOT) measures, which was the highest at awakening and decreased slightly throughout the day. Heritability estimates were significant for measures at 10 am, 3 pm and bedtime for the in-home days and at 10 am and 3 pm on the DOT, ranging between 0.37 and 0.46. CONCLUSIONS: The significant heritability estimates later in the day reflect time-specific genetic effects for DHEAS, compared with prior twin and family designs studies which frequently used averaged morning-only measures. Additive genetic influences on DHEAS concentrations were consistent between at-home and DOT measures.

Vacuolar pathology in the median eminence of the hypothalamus after hyponatremia.

The median eminence of the hypothalamus is an important conduit by which neurosecretory hormones from hypothalamic nuclei are delivered to the pars nervosa (neural lobe) of the pituitary en route to the bloodstream. Dilutional hyponatremia was produced in adult rats to determine the effect on the morphology of the median eminence of the hypothalamus. Hyponatremia was caused by reducing electrolyte and organic osmolyte reserves to block the excretion of water through delivery of the nephrotoxin mercuric chloride (HgCl2). Histological examination of the brain 1 day after a hyponatremic insult revealed vacuolation within the median eminence of the hypothalamus. No other lesions were found in other parts of the brain after hyponatremia. The hyponatremic lesion consisted of a band of closely packed vacuoles that crossed the floor of the third ventricle. Vacuoles associated with hyponatremia were predominantly in the subependymal, fiber, reticular, and palisade layers of the median eminence. Vacuolation was not observed in the tanycyte layer of the median eminence. This study indicates that the median eminence is a potentially vulnerable site in human hyponatremic conditions that should be evaluated further in relevant animal models.

Mitotic figures in the median eminence of the hypothalamus.

The median eminence of the hypothalamus is part of the avenue by which neurosecreted hormones from the hypothalamic nuclei reach the pars nervosa (neural lobe) of the pituitary and eventually the bloodstream. Lithium treatment and osmotic stress increases the transport of neurosecretory hormones to the pituitary in the adult rat. Specialized astrocytes termed pituicytes in the pars nervosa of the pituitary participate in the secretory process and also develop considerable mitotic activity. The present work reveals similar mitotic figures in cells within the median eminence following 3 days of lithium treatment. The location and appearance of these mitoses add to the evidence that pituicytes are present in the median eminence. Moreover, mitoses occur within the ependymal (tanycyte) layer of the median eminence. Thus, the present results suggest that the tanycyte layer may contain pituicytes, indicating that the hypothalamus possesses specialized cells for modulating neurosecretion in response to osmotic challenges.

Genetic and environmental influences on cortisol regulation across days and contexts in middle-aged men.

Cortisol is an indicator of hypothalamic-pituitary-adrenal axis responsivity to stress, but few twin studies have examined the heritability of cortisol concentrations in adults across the diurnal cycle and in different contexts. Saliva samples were provided by 783 middle-aged male twins on one laboratory and two home days as part of the Vietnam Era Twin Study of Aging. Significant cortisol heritability estimates were found for laboratory measures only: awakening (.56); 30 min after awakening (.48); 1000 h (.42); mean output across the day (.43); and mean cortisol awakening response (.64). Twin correlations at home were low. In the laboratory, they were unchanged for fraternal twins, but increased for identical twins. Greater measurement error at home did not appear to account for home-laboratory differences. The results suggest that genetic factors influence cortisol responses to specific environmental stressors. Thus, cortisol levels are correlated in identical twins only when they undergo similar experiences.

Associations between jet lag and cortisol diurnal rhythms after domestic travel.

OBJECTIVE: Millions of adults in the United States travel abruptly across time zones each year. Nevertheless, the impact of traveling over relatively short distances (across 3 or fewer time zones) on diurnal patterning of typical physiological response patterns has yet to be studied in a large, epidemiological sample. DESIGN: The current research focuses on 764 middle-aged men comparing variations in diurnal cortisol regulation based on number of time zones traveled eastward or westward the day before. MAIN OUTCOME MEASURE: Participants provided samples of salivary cortisol at waking, 30-min postwaking, 10 a.m., 3 p.m., and bedtime. RESULTS: Eastward travel was associated with a steeper salivary cortisol awakening response (p < .01) and lower peak (PEAK) levels of salivary cortisol the next morning (p < .05). Westward travel was associated with lower peak levels of cortisol the next morning (p < .05). Effect sizes for these differences ranged from Cohen's d = .29 to .47. Differences were not present for 2 days in their home environment. CONCLUSIONS: The results provide evidence that traveling across time zones is associated with diurnal cortisol regulation and should be studied further to understand the subsequent impacts on health and well-being in large national samples.

Comparing cortisol, stress, and sensory sensitivity in children with autism.

Previously we reported that children with autism show significant variability in cortisol. The current investigation was designed to extend these findings by exploring plausible relationships between cortisol and psychological measures of stress and sensory functioning. Salivary cortisol values for diurnal rhythms and response to stress in children with and without autism were compared to parent-report measures of child stress, the Stress Survey Schedule (SSS), sensory functioning, Short Sensory Profile (SSP), and Parenting Stress Index. In autism, a negative relationship between morning cortisol and the SSS revealed that higher observed symptoms of stress were related to lower cortisol. Lower cortisol is seen in conditions of chronic stress and in social situations characterized by unstable social relationships. Sensory sensitivity painted a more complicated picture, in that some aspects of SSP were associated with higher while others were associated with lower cortisol. We propose that increased sensory sensitivity may enhance the autistic child's susceptibility to the influence of zeitgeibers reflected in variable cortisol secretion. Evening cortisol was positively associated with SSS such that the higher the level of evening cortisol, the higher the child's parent-reported daily stress, especially to changes, such as in daily routine. Regarding the response to stress, the psychological and parent variables did not differentiate the groups; rather, discrete subgroups of cortisol responders and nonresponders were revealed in both the autism and neurotypical children. The results support a complex interplay between physiological and behavioral stress and sensory sensitivity in autism and plausible developmental factors influencing stress reactivity across the groups.

Cortisol and antisocial behavior in early adolescence: the role of gender in an economically disadvantaged sample.

This study examines the relation between adolescents' antisocial behaviors and adrenocortical activity during a laboratory visit in a sample of economically disadvantaged families (N = 116, ages 12-14, 51% female). Pretask cortisol levels indexed adolescents' prechallenge response to the lab visit, whereas adolescents' response to a conflict discussion with their caregivers was indexed with residualized change in pre- to postconflict cortisol levels. A trait measure of antisocial behavior (derived from parent, teacher, and self-reports) was associated with lower pretask cortisol levels but greater cortisol response to the conflict discussion. Gender moderated antisocial adolescents' cortisol response to the conflict discussion with girls who reported more covert risky problem behaviors showing an increased cortisol response. The findings suggest that, although antisocial adolescents had lower pretask cortisol levels, conflict discussions with caregivers present a unique challenge to antisocial girls compared with antisocial boys.

Morning cortisol Levels in preschool-aged foster children: differential effects of maltreatment type.

Maltreated foster children are subjected to a range of early adverse experiences, including neglect, abuse, and multiple caregiver disruptions. Research suggests that such disturbances alter the development and subsequent functioning of the hypothalamic-pituitary-adrenocortical system. The current study was designed to investigate morning cortisol levels in 117 foster children and 60 low-income, nonmaltreated children. Maltreatment and foster care placement experiences were coded from official records. Analyses revealed that the foster children were significantly more likely than the nonmaltreated children to have low morning cortisol levels. Additionally, specific maltreatment experiences were significantly associated with the foster children's morning cortisol levels. Foster children with low morning cortisol levels experienced more severe physical neglect than the other foster children. In contrast, foster children with high morning cortisol levels experienced more severe emotional maltreatment. These results suggest that specific early adverse experiences have differential effects on the functioning of the hypothalamic-pituitary-adrenocortical system.

Systemic pathology in aged mouse models of Down's syndrome and Alzheimer's disease.

Down's syndrome (DS) in humans is caused by trisomy of chromosome 21 (HSA 21). DS patients have a variety of pathologies, including mental retardation and an unusually high incidence of leukemia or lymphoma such as megakaryocytic leukemia. Individuals with DS develop the characteristic neuropathological hallmarks of Alzheimer's disease (AD) in early adulthood, generally by the fourth decade of life. There are several mouse models of DS that have a segmental trisomy of mouse chromosome 16 (MMU 16) with triplicated genes orthologous to HSA 21. These mice display neurodegeneration similar to DS. Although brain pathology in DS models is known, little information is available about other organs. We studied the extraneural pathology in aged DS mice (Ts65Dn, Ts2 and Ts1Cje aged 8 to 24 months) as well as other mouse models of neurodegeneration, including presenilin (PS), amyloid-beta precursor protein (APP), and tau (hTau and JNPL) transgenic mice. An increased incidence of peripheral amyloidosis, positive for amyloid A (AA) but not amyloid-beta peptide (A beta), was found in APP over-expressing and tauopathic mice as compared to non-transgenic (ntg) littermates or to DS mouse models. A higher incidence of lymphoma was found in the DS models, including Ts1Cje that is trisomic for a small segment of MMU 16 not including the App gene, but not in the APP over-expressing mice, suggesting that high APP expression is not the cause of lymphoma in DS. The occurrence of lymphomas in mouse DS models is of interest in relation to the increased incidence of malignant conditions in human DS.

Different inflammatory reactions to vitamin D3 among the lateral, third and fourth ventricular choroid plexuses of the rat.

The four choroid plexuses in the brain ventricles are not identical, but differences among them have rarely been studied. The present work concerns the inflammatory and hemorrhagic choroid plexitis produced in Lewis rats by a single gavage of cholecalciferol (vitamin D(3)) or related steroids with vitamin D activity. Plexitis was very severe in the fourth ventricular plexus, somewhat less severe in the lateral ventricular plexuses, and almost absent in the third ventricular plexus. These findings were compared to the scanty data from the literature on differences among the plexuses.

Variable cortisol circadian rhythms in children with autism and anticipatory stress.

OBJECTIVE: Autism is characterized by impairment in communication and social interaction, by repetitive behaviours and by difficulty in adapting to novel experiences. The objective of the current investigation was to replicate and extend our previous findings showing variable circadian rhythm and significant elevations in cortisol following exposure to a novel stimulus (mock magnetic resonance imaging [MRI]). METHODS: Circadian rhythms of cortisol were estimated in 22 children with and 22 children without autism via analysis of salivary samples collected in the morning, afternoon and evening over 6 separate days. We assessed hypothalamic-pituitary-adrenal (HPA) responsiveness by examining changes in salivary cortisol in response to a mock MRI. One-half of the children were re-exposed to the MRI environment. RESULTS: Children with autism showed a decrease in cortisol in the morning over 6 days while maintaining higher evening values. Children with autism also showed more within-and between-subject variability in circadian rhythms. Although the cortisol values tended to be higher in some of the children with autism, a statistically significant elevation in cortisol in response to the initial mock MRI was not observed. Rather, both groups showed heightened cortisol at the arrival to the second visit to the imaging centre, suggesting an anticipatory response to the re-exposure to the mock MRI. CONCLUSION: Children with autism showed dysregulation of the circadian rhythm evidenced by variability between groups, between children and within individual child comparisons. Both groups demonstrated increased salivary cortisol in anticipation of re-exposure to the perceived stressor.

Effects of an attachment-based intervention on the cortisol production of infants and toddlers in foster care.

Studies with nonhuman primates and rodents, as well as with human children, have suggested that early separations from caregivers are often associated with changes in the functioning of the hypothalamus-pituitary-adrenal (HPA) axis. On the basis of these findings, we designed a relational intervention that was intended to normalize HPA functioning among children in foster care. This paper presents findings from a randomized clinical trial that assessed the effectiveness of a relational intervention (Attachment and Biobehavioral Catch-up [ABC]) with regard to HPA functioning. The ABC intervention was intended to enhance children's ability to regulate physiology and behavior. The control intervention (Developmental Education for Families) was intended to enhance children's cognitive skills. A comparison group of children who had never been in foster care was also included. Children's cortisol production was assessed upon arrival at the lab, and 15 and 30 min following the Strange Situation. Random effects analyses of variance were performed to assess differences in initial values and change between children in the two intervention groups. Children in the ABC intervention and comparison group children showed lower initial values of cortisol than children in the treatment control group, considering arrival at lab as initial values (p < .05). Groups did not differ significantly in change over time. These results suggest that the ABC intervention is effective in helping children regulate biology in ways more characteristic of children who have not experienced early adversity.

Hormonal and metabolic rhythms associated with the daily scheduled nursing in rabbit pups.

Young rabbits are nursed every 24 h for a period of 3-5 min. As a consequence, pups are synchronized to this nursing event; this synchronization is characterized by increased locomotor activity and a peaking of core temperature and plasma corticosterone in anticipation of the daily meal. Ghrelin is a hormone suggested to play a role in meal initiation and to promote food intake. The present study explored the role of ghrelin in food-entrained conditions. Newborn rabbits were maintained in constant darkness and nursed once daily at 1000 by the lactating dam. On postnatal day 7, rabbits were killed at six different time points to complete a 24-h cycle. All pups developed locomotor rhythms entrained by mealtime and exhibited anticipatory activity. Food-entrained rhythms in plasma corticosterone and free fatty acids were observed even if two meals were omitted. In contrast, daily food-driven rhythms in stomach weight, plasma glucose, liver glycogen, and ghrelin did not persist when two meals were omitted. Peak ghrelin levels were observed at the moment in the cycle when the stomach weight was lowest, i.e., before initiation of anticipation. The present data are in agreement with previous data from rabbit pups maintained in light-dark conditions and provide evidence that 7- to 9-day-old rabbits in constant darkness can exhibit metabolic and hormonal rhythms mainly driven by the restricted daily nursing.

Lithium increases gastrointestinal tract weight of male or female rats but it increases body weight only in females.

Lithium treatment of patients and laboratory animals causes increased body weight but no single organ or system has been found responsible. In the present work, we showed that lithium increased the weight of the female rat's gastrointestinal (GI) tract including its contents. The weight gain of the female rat GI tract was the same order of magnitude as the weight gain of the whole body of the females. All three parts of the GI tract (stomach, small intestine, colon) participated in the weight gain. Lithium treatment of male rats also increased GI tract weight, but lithium did not increase their overall body weight because of loss of weight at other sites.

GABAergic circuits and the stress hyporesponsive period in the rat: ontogeny of glutamic acid decarboxylase (GAD) 67 mRNA expression in limbic-hypothalamic stress pathways.

Development of the hypothalamo-pituitary-adrenocortical (HPA) axis is marked by a diminution in stress responsiveness early in the postnatal period (days 4-14 in the rat). This 'stress hyporesponsive period' (SHRP) is thought to be at least in part centrally mediated. To investigate central mechanisms underlying the SHRP, this study assessed expression of glutamic acid decarboxylase (GAD) 67 in key stress-regulatory regions in the forebrain following acute stress with or without prior maternal deprivation. This isoform of GAD is known to be induced by stress in the adult and is believed to be a major contributor to production of the inhibitory neurotransmitter GABA under stimulated conditions. Expression of GAD67 mRNA was increased in the hippocampus, central amygdala and dorsomedial hypothalamus in pups tested early in the SHRP (day 6) or after its conclusion (day 18). In contrast, restraint caused a down-regulation of GAD67 mRNA in these structures when tested later in the SHRP (day 12). GAD67 mRNA expression was not affected by prior maternal deprivation in these regions. Reduced GABA production in the hippocampus (interneurons) is consistent with enhanced HPA axis inhibition, whereas reduced amygdalar expression predicts impaired stress excitation. Expression of GAD67 mRNA in the bed nucleus of the stria terminalis (BST) was minimally affected by acute restraint or maternal deprivation during the SHRP. However, older animals showed down-regulation of basal expression following maternal deprivation and substantial GAD67 mRNA up-regulation in both deprived and non-deprived groups following acute restraint. In contrast, non-responsiveness of the BST during the SHRP suggests either that BST GABA circuits are not actively engaged by stressors during this period or that circuits regulating BST GAD67 production are not yet in place. Overall, the data implicate forebrain GABA circuits in inhibition of HPA axis activity during the SHRP.

A procedure for inducing sustained hyperlipemia in rats by administration of a surfactant.

Tyloxapol (Triton WR 1339) is a non-ionic detergent that inhibits lipoprotein lipase and thereby raises levels of serum lipids. It is used frequently for acute studies on lipids in rats but not for subacute or chronic studies. In the present work, we found that tyloxapol must be injected intravenously three times each week in order to have high and sustained levels of serum cholesterol and triglycerides for 1, 2, or 3 weeks. These results make it possible to extend the use of tyloxapol into chronic studies of hyperlipemia and vascular disease.

Brain corticotropin-releasing hormone (CRH) circuits in the developing rat: effect of maternal deprivation.

Early in life, there is a delicate and critical balance aimed to maintain low hormone responses derived from the stress responsive hypothalamic-pituitary-adrenal axis (HPA). However, in the infant rat hypothalamic corticotrophin-releasing hormone (CRH) stress responses to environmental events are clearly seen even though other elements of the HPA axis may have limited responses. In view of the role of CRH in mediating behavior associated with stress and anxiety, we considered the ontogeny and the effects of prolonged maternal deprivation (DEP) in brain areas that express CRH-related molecules outside the hypothalamus. We hypothesized that DEP would alter the ontogeny of CRH, CRH binding protein and CRH receptor 1 in prefrontal cortex, amygdala, septum and hippocampus, areas that are part of the CRH extra hypothalamic system, and that a differential modulation would be observed in response to restraint. We compared non-deprived animals to animals subjected to 24 h of DEP at 6, 12 and 18 days of life. We found (1) developmental patterns, which were idiosyncratic to the anatomical area examined, and (2) a temporal response of mRNA levels which was also site specific. The genomic changes are not always related to maternal deprivation status, in fact DEP enhanced, suppressed or had no consequence on the underlying ontogenic progression and restraint response of these CRH-related molecules. We conclude that the extra hypothalamic CRH system is a dynamic system responding to developmental and environmental demands challenging the basic assumption of stress hypo responsiveness in the infant rat. This modulation may have important repercussions on morphological organization and events leading to neuroprotection.

Hypothalamic-pituitary-adrenal axis response to sustained stress after major burn injury in children.

The hypothalamic-pituitary-adrenal (HPA) axis is responsible for stress response after injury, yet its function after severe burn injury in children is unclear. The purpose of this study was to define the effects of burn injury on the HPA axis and to evaluate the utility of total serum cortisol in measuring adrenal function in children with major burns in the 2 months after injury. Children ages 0 to 17 years who were admitted within 72 hours to our pediatric burn center with 20% TBSA or greater full-thickness burns were eligible for the study. Serum total cortisol, adrenocorticotropic hormone (ACTH), dehydroepiandrosterone, vasopressin, Pediatric Risk of Mortality (PRISM) score, serum albumin level, and electrolytes were obtained on admission and weekly for 8 weeks. An ACTH stimulation test (250 microg for children >2 years, 125 microg for children < or =2 years) was administered weekly at 8:00 am. Total serum cortisol was measured before and 60 minutes after the administration of ACTH. Twenty-five children with mean age 7.6 +/- 1.1 years and TBSA burn 41.8 +/- 3.8% were enrolled in the study. Baseline total serum cortisol was 12.4 +/- 0.7 microg/dl in the 8 weeks after injury and increased to 24.4 +/- 0.8 microg/dl after the administration of ACTH. Cortisol level did not correlate with PRISM score, albumin, vasopressin, ACTH, or mortality. Although the adrenal response to acute and chronic stress is intact after severe burn injury, the ACTH/adrenal feedback loop is disrupted. Random total serum cortisol measurements overestimate adrenal dysfunction; thus, ACTH stimulation testing should be used to assess adrenal function before the administration of exogenous steroids.

Dual circuitry for odor-shock conditioning during infancy: corticosterone switches between fear and attraction via amygdala.

Rat pups must learn maternal odor to support attachment behaviors, including nursing and orientation toward the mother. Neonates have a sensitive period for rapid, robust odor learning characterized by increased ability to learn odor preferences and decreased ability to learn odor aversions. Specifically, odor-0.5 mA shock association paradoxically causes an odor preference and coincident failure of amygdala activation in pups until postnatal day 10 (P10). Because sensitive-period termination coincides with a declining "stress hyporesponsive period" when corticosterone release is attenuated, we explored the role of corticosterone in sensitive-period termination. Odor was paired with 0.5 mA shock in either sensitive-period (P8) or postsensitive-period (P12) pups while manipulating corticosterone. We then assessed preference/aversion learning and the olfactory neural circuitry underlying its acquisition. Although sensitive-period control paired odor-shock pups learned an odor preference without amygdala participation, systemic (3 mg/kg, i.p.; 24 h and 30 min before training) or intra-amygdala corticosterone (50 or 100 ng; during training) permitted precocious odor-aversion learning and evoked amygdala neural activity similar to that expressed by older pups. In postsensitive-period (P12) pups, control paired odor-shock pups showed an odor aversion and amygdala activation, whereas corticosterone-depleted (adrenalectomized) paired odor-shock pups showed odor-preference learning and activation of an odor learning circuit characteristic of the sensitive period. Intra-amygdala corticosterone receptor antagonist (0.3 ng; during training) infused into postsensitive-period (P12) paired odor-shock pups also showed odor-preference learning. These results suggest corticosterone is important in sensitive-period termination and developmental emergence of olfactory fear conditioning, acting via the amygdala as a switch between fear and attraction. Because maternal stimulation of pups modulates the pups' endogenous corticosterone, this suggests maternal care quality may alter sensitive-period duration.

Foster children's diurnal production of cortisol: an exploratory study.

Young children in foster care have often experienced inadequate early care and separations from caregivers. Preclinical studies suggest that early inadequate care and separations are associated with long-term changes in regulation of the hypothalamic-pituitary-adrenal (HPA) axis. In this study, the daytime pattern of cortisol production was examined among 55 young children who had been placed into foster care and 104 children who had not. Saliva samples were taken at wake-up, in the afternoon, and bedtime for 2 days. Average salivary cortisol values for each time of day were computed. A group (foster vs. comparison) time (morning, afternoon, night) interaction emerged, reflecting less decline in levels across the day for foster than comparison children. Daytime patterns were categorized as typical, low, or high. Children who had been in foster care had higher incidences of atypical patterns of cortisol production than children who had not. These differences suggest that conditions associated with foster care interfere with children's ability to regulate neuroendocrine functioning.