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W Saltzman

Publications and source records attributed to W Saltzman.

17 recordsLinked to original sources
PubMed2004

Social suppression of cortisol in female marmoset monkeys: role of circulating ACTH levels and glucocorticoid negative feedback.

Behaviorally subordinate female common marmoset monkeys (Callithrix jacchus) exhibit pronounced, chronic reductions of circulating cortisol levels. Cortisol suppression in these animals is mediated in part by adrenocortical hyporesponsiveness to adrenocorticotropic hormone (ACTH). In addition, we hypothesized that social subordination may activate a central, neurally mediated mechanism to further inhibit hypothalamo-pituitary-adrenal function. In this study, therefore, we evaluated basal plasma cortisol and ACTH concentrations, as well as cortisol and ACTH responses to dexamethasone (DEX), in dominant and subordinate females to initially characterize such a mechanism. Morning plasma cortisol and ACTH levels were determined before, and 1, 2, and 3 days following administration of DEX (0.5, 1.0, or 5.0 mg/kg, IM) or saline. Baseline cortisol concentrations prior to DEX treatment were significantly lower in subordinate females than in dominants, as previously reported. However, ACTH concentrations in the same blood samples did not differ between the two groups. Furthermore, dominant and subordinate females showed similar cortisol and ACTH responses to DEX. These results indicate that reduced circulating cortisol levels in subordinate females are not associated with either altered circulating ACTH concentrations or enhanced responsiveness to glucocorticoid negative feedback. However, the finding that basal ACTH levels are not elevated in subordinate females as compared to dominants, in spite of low circulating cortisol concentrations, suggests that ACTH secretion in subordinate females is restrained by a steroid-independent inhibitory mechanism operating at the level of the brain or pituitary.

Adaptation, Physiological↗
PubMed2004

Novel restraint system for neuroendocrine studies of socially living common marmoset monkeys.

We describe a novel soft jacket and sling-harness restraint that permits species-typical postures for small-bodied primates, such as the common marmoset (Callithrix jacchus), during long-term (>6 h), continuous restraint. The restraint system is straightforward to use and manipulate, it is easily repaired, and the materials used are readily available. The soft jacket allows for increased versatility and longevity, and the sling-harness provides for greater movement and much longer duration of continuous restraint (up to 3 days) compared to a previously described, more conventional chair restraint for small-bodied primates. The new restraint system prevents the normal diurnal decrease in plasma cortisol levels across the daylight hours; however, it does not disrupt ovulatory cycles. Unlike the previously available techniques, therefore, this new restraint system is applicable to many neurobiological and neuroendocrine studies involving small-bodied, non-human primates and is especially suited to investigations requiring the maintenance of relationships within social groups.

Animals↗
PubMed2003

Are subordinates always stressed? A comparative analysis of rank differences in cortisol levels among primates.

Among primate species there is pronounced variation in the relationship between social status and measures of stress physiology. An informal meta-analysis was designed to investigate the basis of this diversity across different primate societies. Species were included only if a substantial amount of published information was available regarding both social behavior and rank-related differences in stress physiology. Four Old World and three New World species met these criteria, including societies varying from small-group, singular cooperative breeders (common marmoset and cotton top tamarin) to large-troop, multi-male, multi-female polygynous mating systems (rhesus, cynomolgus, talapoin, squirrel monkeys, and olive baboon). A questionnaire was formulated to obtain information necessary to characterize the stress milieu for individuals in particular primate societies. We standardized cortisol values within each species by calculating the ratio of basal cortisol concentrations of subordinates to those of dominants in stable dominance hierarchies and expressing the ratio as a percentage (relative cortisol levels). The meta-analysis identified two variables that significantly predicted relative cortisol levels: subordinates exhibited higher relative cortisol levels when they (1). were subjected to higher rates of stressors, and (2). experienced decreased opportunities for social (including close kin) support. These findings have important implications for understanding the different physiological consequences of dominant and subordinate social status across primate societies and how social rank may differ in its behavioral and physiological manifestations among primate societies.

Aggression↗
PubMed2000

Reduced adrenocortical responsiveness to adrenocorticotropic hormone (ACTH) in socially subordinate female marmoset monkeys.

Socially subordinate female common marmoset monkeys undergo pronounced, chronic reductions in basal plasma cortisol levels, which appear to result both from socially induced suppression of reproductive hormones and from direct effects of social subordination. In this study, we tested the hypothesis that this cortisol suppression is mediated by reduced adrenocortical responsiveness to adrenocorticotropic hormone (ACTH). Dominant, subordinate, and ovariectomized females were given dexamethasone (5 mg/kg, IM), followed the next morning by human ACTH(1-39) (10 microg/kg, IV) or sterile saline (0.5 ml/kg, IV); blood samples were collected at -20 through 150 min from ACTH or saline treatment and assayed for cortisol. ACTH, but not saline, caused a marked elevation of plasma cortisol levels. Prior to ACTH treatment, dominant females tended to have higher dexamethasone-suppressed cortisol levels than subordinate and ovariectomized females. After ACTH treatment, dominant females had significantly higher cortisol concentrations, as well as higher peak and net integrated cortisol responses to ACTH, than did subordinate and ovariectomized animals; the latter two groups showed comparable cortisol responses to ACTH. These results suggest that dampened adrenocortical responsiveness to ACTH contributes to chronic reductions in cortisol levels in subordinate female marmosets and may be mediated by suppression of reproductive hormones.

Adrenal Cortex↗
PubMed1999

Annual physiological changes in individually housed squirrel monkeys (Saimiri sciureus).

This study investigated whether annual changes in physiology occur in individually housed squirrel monkeys (Saimiri sciureus). Physiological measures were monitored for 20 months. Over the course of the study, all individually housed males and females exhibited clear annual changes in gonadal and adrenal hormone levels, and males exhibited species-typical changes in body weight. Females exhibited a typical pattern of hormonal changes, with elevations in gonadal steroids occurring during the same months as elevations in cortisol. Males, however, exhibited an atypical pattern, as elevations in hormone levels were not synchronized with each other; rather, elevations in testosterone occurred out of phase with changes in cortisol and body weight. The timing of annual events in individually housed subjects was compared to that in nearby social groups, in which the timing of the breeding season from year to year was determined by social group formations and was outside the naturally occurring breeding season. Elevations of ovarian and adrenocortical hormones in individually housed females were synchronized with indices of breeding in heterosexual social groups. Similarly, weight gain in males was associated with elevations in cortisol and, as with socially housed males, tended to precede seasonal breeding in the social groups. In contrast, annual testosterone elevations for individually housed males were not synchronized with breeding in nearby social groups. We conclude that direct physical interaction is not required for the annual expression of breeding readiness. Synchrony of seasonality among squirrel monkeys may be accomplished by distant social cues in females, but males may require physical interaction for complete synchrony of annual physiological changes.

Adrenal Cortex Hormones↗
PubMed1999

Social determinants of reproductive failure in male common marmosets housed with their natal family.

Postpubertal male common marmosets, Callithrix jacchus, engage in little or no sexual behaviour while living with their natal families. The social mechanisms underlying this phenomenon have not been identified but have been assumed to include reproductive suppression by dominant males and/or avoidance of mating with closely related females. We evaluated these two possible components of male reproductive failure. Seven postpubertal males and their fathers underwent a series of 45-min sex tests, in which the son, the father, or the son and father together were allowed to interact freely with the mother/mate or with an unfamiliar, unrelated adult female. We measured testosterone, luteinizing hormone and cortisol concentrations in blood samples collected from males immediately following each test, and in basal blood samples collected on three different occasions. Sons, but not fathers, engaged in very low rates of sexual behaviour when tested with the mother/mate. When tested with unrelated females, however, sons engaged in significantly more sexual behaviour than they had when tested with their mothers and showed no differences from their fathers. When sons and fathers were tested together, both males performed significantly less sexual behaviour than when tested alone with a female; however, they showed no overt competition for females and engaged in little agonism. Hormone levels did not differ significantly between fathers and sons. These results indicate that avoidance of mating with familiar females and possibly father-son competition, but not specific, rank-related suppression, contribute to reproductive failure among postpubertal male marmosets living with their natal family. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Suppression of cortisol levels in subordinate female marmosets: reproductive and social contributions.

Socially subordinate female common marmosets (Callithrix jacchus) have markedly lower plasma cortisol levels than dominant females. Subordinate females also undergo hypoestrogenemic anovulation, and estrogen can elevate glucocorticoid levels. Therefore, we previously hypothesized that this cortisol difference is mediated by rank-related differences in reproductive hormones, probably estradiol. To test this possibility, we characterized the effects of the ovarian cycle and ovariectomy on plasma cortisol concentrations. Beginning in the early follicular phase, basal blood samples were collected from seven cycling female marmosets daily for 16 days and at 2- to 3-day intervals for another 16 days. Samples were collected identically from seven anovulatory subordinate females and seven long-term ovariectomized females. Cortisol levels changed reliably across the ovarian cycle, with levels in the mid- to late follicular, peri-ovulatory, and early luteal phases higher than those in the remainder of the cycle. Cortisol levels of cycling females were significantly higher than those of subordinates at all parts of the cycle, but were significantly higher than those of ovariectomized females only during the midcycle elevation. Unexpectedly, subordinates had significantly lower cortisol levels than ovariectomized females, as well as higher estradiol and estrone levels and lower progesterone and luteinizing hormone (LH) levels. These results confirm that circulating cortisol concentrations are modulated by reproductive function in female marmosets but also indicate that low cortisol levels in subordinate females cannot be attributed simply to hypoestrogenemia. Instead, other factors, such as direct effects of social subordination or suppression of LH levels, contribute to suppression of cortisol in subordinates.

Animals↗
PubMed1998

Adaptations to subordinate status in female marmoset monkeys.

In singular cooperatively breeding mammals, social status is a key determinant of female reproductive success. Usually only one dominant female breeds in a social group. In the common marmoset (Callithrix jacchus), a cooperatively breeding primate, adaptations to nonbreeding subordinate status appear to parallel those found in social insect societies which demonstrate similar skew to the marmoset in female reproductive success. Female marmosets exhibit rank-related polyethism in behavior, reproductive neuroendocrinology and non-reproductive physiology, and subordinates participate in alloparental care and territory defense. Olfactory, visual and behavioral cues from dominant female marmosets provide important proximate cues regulating ovarian inhibition in female subordinates. Cooperatively breeding marmosets, therefore, appear to have developed specific neural and neuroendocrine adaptations to subordinate social status analogous to those found in social insects such as the lower wasps, bees and termites. Such parallel developments probably reflect the outcome of repeated convergent evolutionary attempts at adapting to environmental conditions not readily conducive to dispersal and independent breeding.

Adaptation, Psychological↗
PubMed1997

Behavioral and social correlates of escape from suppression of ovulation in female common marmosets housed with the natal family.

Although female common marmosets typically do not breed while housed with their natal families, up to half ovulate at least once while housed with the intact natal family, and a similar proportion conceive if an unrelated adult male is present in the group. In this study, we investigated the behavioral and social correlates of escape from suppression of ovulation by daughters housed in intact natal families or in families in which the father had been replaced by an unrelated adult male. Focal-animal behavioral data were collected from daughters that were (N = 7) or were not (N = 10) undergoing ovulatory cycles while housed with the natal family and from daughters that were (N = 5) or were not (N = 3) cycling or pregnant in families containing an unrelated male. Additionally, four cyclic and six acyclic females housed in intact natal families underwent simulated "prospecting" tests. Cyclic and acyclic daughters in intact natal families did not engage in sexual interactions with the father and showed few differences from one another in their interactions with the parents. Moreover, cyclic and acyclic daughters did not differ in their willingness to leave the family for short periods or to investigate an unfamiliar family in "prospecting" tests. However, daughters that underwent ovarian cycles in the presence of an unrelated male showed numerous behavioral differences from those in intact natal families, including frequent courtship and sexual behaviors with the male, reduced affiliative interactions with the mother, and elevated frequencies of aggressive display behavior. Moreover, these females were less likely to behave submissively towards the mother or the adult male. These findings suggest that both suppression of ovulation and inhibition of sexual behavior normally contribute to reproductive failure in female marmosets living with their natal families, and that the two components of suppression may become dissociated under specific social conditions.

Agonistic Behavior↗
PubMed1997

Familial influences on ovulatory function in common marmosets (Callithrix jacchus).

Previous studies have indicated that many, but not all, female common marmosets (Callithrix jacchus) housed with their natal families undergo social suppression of ovulation. In this study, we further characterized ovulatory activity in common marmoset daughters to determine the prevalence of social suppression of ovulation and to elucidate familial influences on daughters' ovarian activity. Blood samples were collected twice weekly from each of 46 daughters for 5-12 months, usually beginning when the daughters were 12 months of age. Plasma progesterone concentrations indicated that 46.3% of daughters in intact natal families ovulated at least once, with the age at first ovulation averaging 17.2 months; however, none of these daughters became pregnant. Daughters' ovulatory cycles showed several significant differences from those of older females housed with unrelated adults, including longer periods between successive luteal phases, shorter luteal phases, and lower peak and mean luteal-phase progesterone levels. Daughters were significantly more likely to ovulate in families in which the mother was experimentally prevented from sustaining pregnancies, and in families in which the father had been replaced by an unrelated adult male and when the daughter was approximately 10-11 months of age. Daughters in families containing an older sister never ovulated; in contrast, those with a female littermate were not less likely to ovulate than were other daughters, but had more sporadic ovarian cycles and significantly lower mean luteal-phase progesterone levels. These results confirm and extend previous findings that up to half of female common marmosets may ovulate while housed with the natal family but that virtually none sustain pregnancies, suggesting that suppression of ovulation is only one of several components of reproductive failure. Furthermore, these results demonstrate that daughters' likelihood of ovulating, as well as the endocrine profiles of their ovulatory cycles, can be modulated by numerous social influences within the family.

Animals↗
PubMed1996

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.

Animals↗
PubMed1995

Behavioral and hormonal changes in female naked mole-rats (Heterocephalus glaber) following removal of the breeding female from a colony.

Colonies of naked mole-rats (Heterocephalus glaber) contain a single dominant, breeding female, or "queen", which suppresses reproduction in subordinate females. In this study, the queen and breeding male were removed from a colony at Brookfield Zoo. We examined behavioral and endocrine changes in the remaining colony females. Behavioral observations were conducted weekly and urine samples were collected beginning 3 months prior to the planned removal of animals. Prior to the removal, only the queen displayed the high frequencies of aggressive shoving typical of breeding females. In the first 2 months following removal of the queen, three non-breeding females markedly increased their frequencies of shoving. Urinary progesterone showed that one of three females had probably ovulated both before and after queen removal. Histological examination following fatal agonistic interactions confirmed ovulatory function in two of these three females. Similar behavioral and endocrinological results were obtained for three more females, following the combat deaths of the first three females. These findings suggest that ovarian activation facilitates intrasexual aggression in female naked mole-rats and might contribute to attainment of breeding status.

Aggression↗
PubMed1994

Social and reproductive influences on plasma cortisol in female marmoset monkeys.

Subordinate female common marmosets (Callithrix jacchus) undergo ovulation suppression and exhibit low plasma cortisol levels compared to the dominant, breeding female. To determine whether this cortisol difference is mediated by the differential reproductive consequences of social status, we monitored plasma progesterone and cortisol in 32 adult female marmosets while they were housed in heterosexual pairs, during the first 3 days of heterosexual group formation, and while animals were housed in established social groups. Cortisol levels prior to group formation were significantly higher in females exhibiting cyclic ovulatory activity than in anovulatory females but were not predictive of social status. Subsequently, when animals were housed in established social groups, dominant (cyclic) females had significantly higher cortisol levels than did subordinate (anovulatory) females. Cortisol levels differed between the pre and postgroup formation conditions only in animals that underwent a corresponding onset or termination of ovulatory cyclicity. Cortisol differences between dominant and subordinate female marmosets therefore appear to be associated with differences in reproductive function rather than with social status per se.

Animals↗
PubMed1993

Children's exposure to community violence: following a path from concern to research to action.

This paper discusses the antecedents and current progress of an ongoing program of research on the nature, extent, and consequences of children's direct and indirect exposure to violent events and settings. Involvement in such research has sensitized the authors to difficult ethical and methodological challenges that, we believe, merit consideration by mental health scientists and policy markers. Resolution of those challenges has substantive implications for both subsequent research and the application of resultant findings.

Adolescent↗
PubMed1991

Sociophysiology of relationships in squirrel monkeys. I. Formation of female dyads.

Physiological and behavioral consequences of formation of female-female relationships were investigated in adult squirrel monkeys. Plasma cortisol, heart rate, and behavior were evaluated during confinement in a test cage while animals were housed alone, during the first hour of isosexual pair formation, and while animals were housed as isosexual dyads. In addition, basal cortisol levels were assessed both before and after pair formation, as were behavioral and cardiovascular responses to social and nonsocial stimulus presentations. Basal cortisol levels underwent a marked and sustained reduction following formation of pairs, independent of both dominance status and the quality of social interactions between pairmates. In contrast, adrenocortical responsiveness was not altered by social conditions, apart from a modest and transitory difference between dominant and subordinate females in their initial response to pair formation. Heart rate declined sharply during each test session, but did not reliably differentiate social conditions, stimulus conditions, or dominance status. These findings contrast with results of a parallel study of male squirrel monkeys and suggest that isosexual relationships in males and females are associated with different sociophysiological processes.

Animals↗