Behavior and physiology of social stress and depression in female cynomolgus monkeys.

The hypothesis that social subordination is stressful, and results in a depressive response in some individuals, was examined in socially housed female cynomolgus monkeys. Social status was manipulated such that half of the previously subordinate females became dominant and half of the previously dominant females became subordinate. Current subordinates hypersecreted cortisol, were insensitive to negative feedback, and had suppressed reproductive function. Current subordinates received more aggression, engaged in less affiliation, and spent more time alone than dominants. Furthermore, they spent more time fearfully scanning the social environment and displayed more behavioral depression than dominants. Current subordinates with a history of social subordination were preferentially susceptible to a behavioral depression response. The results of this experiment suggest that the stress of social subordination causes hypothalamic-pituitary-adrenal and ovarian dysfunction, and support the hypothesis that chronic, low-intensity social stress may result in depression in susceptible individuals.

Effects of isoflurane anesthesia on glucose tolerance and insulin secretion in Yucatan minipigs.

Isoflurane's effect on intravenous glucose tolerance and insulin secretion was studied in six Yucatan minipigs. Unanesthetized animals, with previously placed indwelling venous catheters, were tested while resting comfortably in slings. The same animals were then retested during isoflurane anesthesia. Serum glucose and insulin concentrations were measured at predetermined times in response to an intravenous bolus of dextrose. The glucose disappearance rate (k), baseline plasma insulin concentration, the area under the insulin response curve, and the insulinogenic index were significantly lower in the anesthetized animals than in controls. The results of this study indicate that anesthesia with isoflurane significantly alters the glucose/insulin response to an intravenous glucose tolerance test and, therefore, is unsuitable for studies when glucose tolerance is to be assessed.

Assessment of abdominal fat deposition in female cynomolgus monkeys.

Computed tomography (CT) was used to assess abdominal fat distribution in adult, female cynomolgus macaques (Macaca fascicularis). The technique used was similar to that applied in human beings and allowed intra-abdominal, subcutaneous and total abdominal fat to be quantitated in 1 cm thick sections. Correlations between single scans and the average of scans at several levels ranged from r = 0.96 to r = 1.00, indicating that a single scan is representative of abdominal fat distribution. Significant positive correlations were found between body mass index (BMI) and intra-abdominal fat (r = 0.89), subcutaneous fat (r = 0.91) and total abdominal fat (r = 0.90). As BMI increased, fat was preferentially deposited subcutaneously versus intra-abdominally. A unique fat depot, not previously described, was identified dorso-laterally between the internal abdominal oblique and the transversalis muscle. This fat depot was also positively correlated with BMI (r = 0.79). These results indicate that CT can be used in cynomolgus monkeys to quantitate regional fat deposits and that these monkeys resemble human beings in their abdominal fat patterning.

T-cell lymphosarcoma in a female African green monkey (Cercopithecus aethiops).

A female African green monkey developed a generalized lymphosarcoma spontaneously that clinically and pathologically resembled malignant lymphoma in human beings infected with human T-lymphotropic virus type I. The monkey was serologically positive for simian T-lymphotropic virus. Immunocytochemical analysis of routinely fixed and paraffin embedded tumor tissue demonstrated neoplastic cells that stained positive with antihuman monoclonal UCHL1 which recognized a T-cell-restricted isotype of leukocyte common antigen.

Fatal fatty liver-kidney syndrome in obese monkeys.

A fatal syndrome associated with brief periods of anorexia or acute weight loss was noted in monkeys. Affected monkeys died unexpectedly or after a very short illness. Consistent gross findings at necropsy were enlarged, pale yellow livers, pale tan to yellow kidneys, abundant deposits of body fat and empty gastrointestinal tracts. Fatty change of the liver and kidney was the predominant and characteristic lesion found microscopically. Most of the monkeys were female Macaca fascicularis greater than 8 years of age. However, monkeys of other species and ages, and one male also died of this syndrome. Affected monkeys generally had losses of 8-33% of body weight (last measured weight--weight at death). In some animals, this syndrome was associated with a location change forcing new social interactions. A common clinical pathologic finding was azotemia. These findings suggest that obese monkeys may be prone to a fatal syndrome characterized by fatty change of the liver and kidney, and weight loss.