Cortisol metabolism in the Bolivian squirrel monkey (Saimiri boliviensis boliviensis)

New World squirrel monkeys (Saimiri spp.) have high circulating cortisol levels but normal electrolytes and blood pressures. The goal of the present study was to gain insight into adaptive mechanisms used by Bolivian squirrel monkeys to minimize the effects of high cortisol on mineralocorticoid receptor (MR) activity and electrolyte and water balance. Aldosterone levels in serum from 10 squirrel monkeys were 17.7 +/- 3.4 ng/dl (normal range in humans, 4 to 31 ng/dl), suggesting that squirrel monkeys do not exhibit a compensatory increase in aldosterone. The squirrel monkey MR was cloned and expressed in COS-7 cells and found to have similar responsiveness to cortisol and aldosterone as human MR, suggesting that squirrel monkey MR is not inherently less responsive to cortisol. To determine whether altered metabolism of cortisol might contribute to MR protection in squirrel monkeys, serum and urinary cortisol and cortisone were measured, and a comprehensive urinary corticosteroid metabolite profile was performed in samples from anesthetized and awake squirrel monkeys. The levels of cortisone exceeded those of cortisol in serum and urine, suggesting increased peripheral 11beta-hydroxysteroid dehydrogenase 2 activity in squirrel monkeys. In addition, a significant fraction (approximately 20%) of total corticosteroids excreted in the urine of squirrel monkeys appeared as 6beta-hydroxycortisol, compared with that in man (1%). Therefore, changes in cortisol metabolism likely contribute to adaptive mechanisms used by Bolivian squirrel monkeys to minimize effects of high cortisol.     

Hepatocellular carcinoma in a squirrel monkey (Saimiri sciureus)

Abstract: A well-differentiated hepatocellular carcinoma of the liver was diagnosed in a female squirrel monkey. The lesion showed trabecular, solid and glandular features that are characteristics of malignant liver tumours.     

Tonic immobility in the squirrel monkey (Saimiri sciureus)

Tonic immobility and several accompanying behavioral changes were examined in the squirrel monkey (Saimiri sciureus). It was found that either the occurrence of a loud noise immediately before induction or the presence of a stuffed Cooper's hawk increased the duration of immobility in some subjects. Subspecies differences in durations of immobility were also found. The number of inductions required to produce immobility in squirrel monkeys were unusually large, and were negatively correlated with duration of the response. Behavioral variables accompanying tonic immobility showed qualitative differences when compared to what is known concerning their relation to immobility in other species. The findings support the belief that tonic immobility evolved as a predator defense in squirrel monkeys or one of their ancestors, but suggest that it no longer plays an active role in their survival.     

Carcinosarcoma of the maxilla in a squirrel monkey (Saimiri sciureus)

We present the first, to our knowledge, described case of carcinosarcoma of the maxilla in a squirrel monkey. Carcinosarcomas are rare tumors of the upper aerodigestive tract, and consist of carcinomatous and sarcomatous tissue. Histologic analysis revealed a neoplasm composed of an adenocarcinomatous component (epithelial element) and a mesenchymal component (sarcomatous element). Metastatic growth was documented in the lung tissue and the submandibular lymph node. The histolopathologic findings, the pattern of metastasis, and the clinical progression closely resembled those of carcinosarcoma involving salivary glands in humans.     

Stillbirth of twins in a squirrel monkey (Saimiri boliviensis peruviensis)

This is the first published report of twinning in a squirrel monkey (genus Saimiri). The mother survived but the twins, both male and close to full term, were stillborn     

Somatic chromosomes of squirrel monkey (Saimiri sciureus)

The chromosome complement of 2 male and 15 female adult squirrel monkeys (Saimiri sciureus) have been studied in peripheral blood and kidney cultures and bone marrow preparations. The diploid chromosome number is 44. Six of the chromosome pairs are metacentric (isobrachial), 9 pairs submetacentric (heterobrachial) and the remaining 6 pairs are acrocentric (cephalobrachial). The X chromosome is the longest submetacentric (heterobrachial), ranking 5 in order of decreasing size. The Y chromosome is the smallest acrocentric (cephalobrachial) of the complement.A female and male karyotype is presented.Supported, in part, by Grant HDO 1952-03 from the United States Public Health Service.     

Neonatal activity and state control differences among three squirrel monkey subspecies (Saimiri sciureus sciureus,S. boliviensis boliviensis,and S. boliviensis peruviensis)

Squirrel monkeys are a long-standing biomedical model, with multiple species and subspecies housed in research facilities. Few studies have examined the developmental differences between these subspecies, which may affect research outcomes. The primate neonatal neurobehavioral assessment was completed at 2 weeks of age with 279 dam-reared squirrel monkeys (188 Saimiri boliviensis boliviensis, 45 S. b. peruviensis, and 46 Saimiri. sciureus sciureus). Activity, orientation to stimuli, state control, and motor maturity scores, as well as startle responses and number of vocalizations were compared across subspecies and sex using factorial analysis of covariance (ANCOVAs) controlling for birthweight. There were no differences in orientation or motor maturity scores (p > .05) among the three subspecies or between sexes; however, there were significant subspecies differences in motor activity and state control scores. Of the three subspecies, S. s. sciureus has the lowest state control and activity scores (p < .05). They also had the most exaggerated startle response/aversion to a sudden loud noise, vocalized significantly less, and were less likely to resist restraint during the assessment (p < .05). The three subspecies of squirrel monkeys did not differ in motor development and attention to external stimuli but were significantly different in state control and activity levels. Overall S. s. sciureus were less active, agitated, irritable, and easier to console compared to S. b. boliviensis and S. b. peruviensis. This supports field research on socioecology which documented different social structure and behavior in wild populations of S. s. sciureus compared to S. b. boliviensis and S. b. peruviensis.     

Lipid composition of squirrel monkey (Saimiri sciureus) saliva

The content and composition of lipids in saliva of healthy caries-free squirrel monkeys were investigated. The dialyzed and lyophilized saliva on extraction with chloroform/methanol yielded 8.0 +/- 0.9 mg of lipids/100 ml of saliva. Following fractionation on silicic acid column, 30.9% of lipids were found in the neutral lipid fraction, 58.8% in the glycolipid fraction, and 10.3% in the phospholipid fraction. The neutral lipids exhibited high content of free fatty acids (58.8%) and triglycerides (23.3%), the glycolipids consisted mainly of neutral and sulfated glyceroglucolipids (95%), while the phospholipids were rich in sphingomyelin and phosphatidylcholine. The results show that squirrel monkey saliva, while displaying lipid content similar to that of caries-susceptible humans, contains 50% less lipids than saliva of periodontal disease-prone marmoset.     

The brachial plexus in the squirrel monkey (Saimiri sciureus)

Based on the statistical data obtained from 37 squirrel monkeys, the standard type of the brachial plexus was determined. Each of the superior (C6, normally also C5), middle (C7), and inferior (C8 and T1, rarely with rudimentary T2) trunks gives off the anterior and posterior divisions. The lateral cord composed of the superior and the middle anterior divisions usually breaks up immediately into the musculocutaneous nerve and the lateral root of the median nerve. The medial cord (generally the peripheral extension of the inferior anterior division itself) terminates in the ulnar nerve and in the medial root of the median nerve. The dorsal cord formed by the union of the 3 posterior divisons extends peripherally as the radial nerve; the axillary nerve arises before the union of the 3 posterior divisons is completed. The frequently encountered aberrant connecting branches, the musculocutaneous nerve tending to separate from the plexus, and the long lateral root of the median nerve characterize the feature of the plexus.The data were compared with previous findings about the plexus of other primates.This investigation was conducted during the tenure of a postdoctoral fellowship in the Department of Anatomy, UCLA School of Medicine, Los Angeles, California, U.S.A.     

Malignant lymphoma in a squirrel monkey (Saimiri sciureus).

A juvenile male Saimiri sciureus died of a tumor diagnosed as a histiocytic type of malignant lymphoma. The neoplasm presented as a thoracic mass occupying the posterior mediastinum and infiltrating the contiguous structures without involving distant nodes, the liver or spleen. The tumor tissue consisted of sheets or poorly defined clusters of fairly large cells with a vesicular nucleus and a variably abundant cytoplasm. The tumor cells were laid out in a poorly developed stroma of fine argyrophilic fibers. This is the first report of a spontaneous malignant lymphoma in a primate of this species. The speculation is put forth that the reported tumor is probably the first known example of the long sought after correlate of squirrel monkeys to Burkitt lymphoma in man.     

Retrobulbar primitive neuroectodermal tumor in a squirrel monkey (Saimiri sciureus)

Background A 2.8‐year‐old female captive‐bred common squirrel monkey (Saimiri sciureus) showed exophthalmos of the right eye, and the eye was surgically enucleated. A tumor mass was found in the eye. Methods Formalin‐fixed tumor samples were examined histopathologically and immunohistochemically for diagnosis. Results The retrobulbar tumor mass adhered to the sclera and infiltrated the choroid. Histopathologically, tumor cells were pleomorphic, arranged in a sheet pattern, and mimicked primitive neuroectodermal cells. The tumor cells were strongly positive for precursor neuronal cell markers (beta III tubulin, neuron‐specific enolase, vimentin, nestin, doublecortin, oligo2, and S‐100), but negative for mature cell markers (cytokeratin, neurofilament, and glial fibrillary acidic protein) and a retinoblastoma marker (rhodopsin). Conclusions This is the first reported case for the retrobulbar location of primitive neuroectodermal tumor in non‐human primates.     

Elevation in plasma glucagon levels in response to stress in squirrel monkeys: comparisons of two subspecies (Saimiri sciureus boliviensis and Saimiri sciureus sciureus)

Bolivian (Bo) and Brazilian (Br) squirrel monkeys (SMs) were captured and restrained to determine patterns of glucagon and glucose response. In both subspecies, plasma glucagon and glucose levels rose rapidly in response to restraint procedures; glucagon levels in BrSMs and glucose levels in both subspecies returned to basal values in 15 minutes. The magnitude of the glucagon and glucose responses differed significantly between BoSMs and BrSMs.