A preliminary description of responses of free-ranging rhesus monkeys to brief capture experiences: behavior, endocrine, immune, and health relationships.

A cohort of free-ranging rhesus monkeys has been followed since birth in 1994 on the island of Cayo Santiago, Puerto Rico. At 3 years of age, subjects were trapped and blood samples were collected after capture and prior to release the following day. Blood samples were processed for natural cytotoxicity toward xenogeneic tumors, phenotyping, and plasma hormones. Intestinal parasites were determined from fresh stool samples collected during trapping. Data were also available from the previous year for antibody titers to latent viruses prevalent in this population. Behavioral traits of each monkey were characterized using a previously developed trait scale for rhesus monkeys. Natural cytotoxicity toward both K562 and Raji targets declined from capture until release the following day. Plasma cortisol rose and plasma prolactin and growth hormone fell during the period of captivity; a rise in insulin was significant. It was expected that individual differences in behavioral traits might predict immune and hormone levels at the time of capture or changes in these parameters during the capture period. Although behavioral adjectives tended to cluster along three orthogonal dimensions (Insecurity, Irritability, and Sociability), they bore no relationship to the physiological parameters collected acutely (in vitro immune and endocrine parameters). The individual difference markers of gender and maternal rank were not related to the magnitude of the observed changes in these in vitro parameters, either. However, an in vivo measure (CMV titer) was related to individual differences in Irritability. It was concluded that the magnitude of the stress associated with capture overwhelmed the individual difference effects.

Trait-like immunological and hematological measures in female rhesus across varied environmental conditions.

In this 2-year longitudinal study, 45 2-year-old female rhesus were observed as they were captured and removed from a free-ranging setting (Phase I), single caged for 1 year (Phase II), and housed in small, stable social groups for an additional year (Phase III). During the study, eight blood samples were taken, and hematological, immunological, and hormonal variables were assayed to determine whether 1) any of the measures would exhibit trait-like, inter-individual longitudinal stability, despite fluctuations in population means induced by Phases I, II, and III; 2) plasma concentrations of cortisol, prolactin, and norepinephrine would be lowest in Phase III, and elevated during the periods of acute and chronic stress associated with Phases I and II; and 3) there would be any evidence of immunosuppression associated with Phases I and II. The results suggest that the majority of hematological/immunological variables were trait-like throughout the study in contrast to plasma cortisol, prolactin, and norepinephrine concentrations. Thus, red blood cells, hemoglobin, hematocrit, platelets, mean corpuscular volume and hemoglobin, as well as white blood cells, the absolute number of CD4+ (T-helper/inducer) cells, the absolute number of CD8+ (T-suppressor/cytotoxic) cells, total T cells (CD2+%), total B cells (CD20+%), and the ratio of CD4+/CD8+ cells were trait-like. The hematological measures were changed dramatically by capture and the subsequent single caging, with most not recovering to presumed baselines until after 12-28 weeks. The immune measures were depressed at capture (excepting B cells), and during 7 months of single caging failed to return to normal levels associated with social housing. We thus conclude that single housing can produce significant, long-term features of immunosuppression. Capture produced significant increases in plasma cortisol, prolactin, and norepinephrine concentrations. Long periods of single caging produced significant increases in plasma prolactin concentrations, indicative of stress-induced anxiety, and may also have been associated with down-regulation of plasma norepinephrine and cortisol concentrations.

Enhanced function conferred on low-abundance chemoreceptor Trg by a methyltransferase-docking site.

In Escherichia coli, high-abundance chemoreceptors are present in cellular amounts approximately 10-fold higher than those of low-abundance receptors. These two classes exhibit inherent differences in functional activity. As sole cellular chemoreceptors, high-abundance receptors are effective in methyl-accepting activity, in establishing a functional balance between the two directions of flagellar rotation, in timely adaptation, and in mediating efficient chemotaxis. Low-abundance receptors are not, even when their cellular content is increased. We found that the low-abundance receptor Trg acquired essential functional features of a high-abundance receptor by the addition of the final 19 residues of the high-abundance receptor Tsr. The carboxy terminus of this addition carried a methyltransferase-binding pentapeptide, NWETF, present in high-abundance receptors but absent in the low-abundance class. Provision of this docking site not only enhanced steady-state and adaptational methylation but also shifted the abnormal, counterclockwise bias of flagellar rotation toward a more normal rotational balance and vastly improved chemotaxis in spatial gradients. These improvements can be understood as the result of both enhanced kinase activation by the more methylated receptor and timely adaptation by more efficient methyl-accepting activity. We conclude that the crucial functional difference between the low-abundance receptor Trg and its high-abundance counterparts is the level of methyl-accepting activity conferred by the methyltransferase-docking site.

Correlation of CSF 5-HIAA concentration with sociality and the timing of emigration in free-ranging primates.

OBJECTIVE: The purpose of this study was to examine the relationship between behavior and serotonin in nonhuman primates. METHOD: During a routine capture and medical examination, 26 adolescent male rhesus macaques (Macaca mulatta) were selected as subjects from a free-ranging population of 4,500 rhesus monkeys inhabiting a 475-acre sea island. Blood samples (N = 23) and CSF samples (N = 22) were obtained, and each subject was fitted with a radio transmitter collar for rapid location. The subjects were released into their social groups, and quantitative behavioral observations were made over a 3-month period. RESULTS: CSF 5-hydroxyindoleacetic acid (5-HIAA) concentration was positively correlated with three measures of sociality: 1) total time spent grooming others, 2) total time spent in close proximity to other group members, and 3) mean number of neighbors within a 5-m radius. In addition, CSF 5-HIAA concentration was positively correlated with age at emigration from the natal group (in months). CONCLUSIONS: In adolescent male rhesus macaques living in naturalistic settings, CSF 5-HIAA concentration is positively correlated with affiliative sociality. Rhesus males with low CSF 5-HIAA concentrations exhibit less social competence and emigrate from their social groups at a younger age than do males with higher concentrations of CSF 5-HIAA.

Transmembrane signaling characterized in bacterial chemoreceptors by using sulfhydryl cross-linking in vivo.

Transmembrane signaling by bacterial chemoreceptors is thought to involve conformational changes within a stable homodimer. We investigated the functional consequences of constraining movement between pairs of helices in the four-helix structure of the transmembrane domain of chemoreceptor Trg. Using a family of cysteine-containing receptors, we identified oxidation treatments for intact cells that catalyzed essentially complete sulfhydryl cross-linking at selected positions and yet left flagellar and sensory functions largely unperturbed. Constraining movement by cross-links between subunits had little effect on tactic response, but constraining movement between transmembrane segments of the monomer drastically reduced function. We deduce that transmembrane signaling requires substantial movement between transmembrane helices of a monomer but not between interacting helices across the interface between subunits.

Low CSF 5-HIAA concentrations and severe aggression and impaired impulse control in nonhuman primates.

OBJECTIVE: The purpose of this study was to examine the relationship between behavior and serotonin by using a nonhuman primate model of aggression and impulse control. METHOD: During a routine capture and medical examination, 26 adolescent male rhesus macaques (Macaca mulatta) were selected as subjects from a free-ranging population of 4,500 rhesus monkeys inhabiting a 475-acre sea island. Physiological data were obtained from 22-23 of the subjects. Blood and CSF samples were obtained, and each subject was fitted with a radio transmitter collar for rapid location. The subjects were released into their social groups, and quantitative behavioral observations were made over a 3-month period. RESULTS: CSF 5-hydroxyindoleacetic acid (5-HIAA) concentrations were inversely correlated with "escalated" aggression, i.e., a measure of more intense or severe aggression as defined by the ratio of chases and physical assaults to all aggressive acts. CSF 5-HIAA concentrations were significantly lower in those subjects who showed evidence of physical wounding than in subjects with no wounds. Low CSF 5-HIAA concentrations were also correlated with greater risk-taking as determined by an analysis of leaping behaviors in the forest canopy. The ratio of long leaps (leaps that traversed the longest distances at dangerous heights) to all leaps was negatively correlated with CSF 5-HIAA concentrations. CONCLUSIONS: Adolescent male rhesus macaques with low CSF 5-HIAA concentrations are at risk for 1) exhibiting more violent forms of aggressive behavior and 2) loss of impulse control as evidenced by greater risk taking during movement through the forest canopy.