Conjoined twins in a rhesus monkey (Macaca mulatta)

Conjoined twinning is an extremely rare occurrence among human and nonhuman primates. The current report describes a case of minimally conjoined omphalopagus rhesus monkey twins that were observed in the breeding colony at the California Regional Primate Research Center. The full-term nonviable male twins were morphologically normal and united in the umbilical region, involving the liver, xiphoid, umbilicus, body wall, and skin. The umbilical cords were separate, but closely aligned, within an ensheathing amnion; each cord contained two arteries and a vein. The closely associated cords were centrally inserted on a large bidiscoid placenta. There were no gross or histologic abnormalities in the viscera, with the exception of enlargement of the left central liver lobes, which constituted the area of attachment. The cause of death was attributed to asphyxia and trauma experienced during parturition.     

The effects of extended time in the laboratory on selected aspects of reproduction in the female rhesus monkey (Macaca mulatta)

Reproduction data from 60 wild-caught and 16 captive-born, hand-reared female rhesus monkeys (Macaca mulatta) were examined. Both groups had been maintained in a controlled laboratory environment, the wild-caught for a minimum of 10 years and the captive-born for a minimum of 5 years. All were bred to wild-caught males. Animals of both sexes were individually caged unless being bred. Data from 662 pregnancies indicated that, although seasonal breeding became attenuated in the laboratory, it did not disappear. Neither pregnancy outcome nor number of matings necessary for conception was affected by increasing parity or prior occurrence of fetal wastage or hysterotomy. Nor did hysterotomy affect the potential for a subsequent vaginal delivery. The number of matings necessary for conception were shown to be a useful predictor of animals that should be culled from the breeding colony. Birthweights of infants of wild-caught females, but only male infants of house-born females, increased with parity of the mother. Parity had only minimal effect on gestation length. Conception was shown to occur infrequently at less than 100 days postpartum even when animals were not lactating and were rebred begining as early as 56 days postpartum. Summary data were presented for pregnancy outcome, gestation length, infant birth weight, and sex for both groups of animals.     

Alopecia areata in a rhesus monkey (Macaca mulatta)

BACKGROUND: A 14-year-old female rhesus monkey (Macaca mulatta) of Chinese origin has been suffering from alopecia universalis since childhood. METHODS: Recently, the health status of the animal was recorded comprehensively by detailed clinical examination including hematology and serology supplemented by histological and immunohistochemical investigations of skin biopsies and molecular biological techniques to clarify the causes of the persistent hair loss. RESULTS AND CONCLUSIONS: The hairless gene (hr) nonsense mutation was ruled out by polymerase chain reaction and by sequencing of the corresponding gene. Histological examinations revealed a prominent chronic lymphocytic perifolliculitis and folliculitis affecting anagen stage hair follicles as well as miniaturized hair follicles. Immunohistochemistry using the antibodies CD3, CD20 and CD4 confirmed the diagnosis of a T-cell-mediated autoimmune disease resembling alopecia areata universalis in humans.     

Corneal biometrics of the rhesus monkey (Macaca mulatta)

Keratometry, retinoscopy, horizontal diameter, and pachymetry were measured in adult and infant rhesus monkeys (Macaca mulatta). The adult monkeys had a mean corneal thickness of 0.47 +/- 0.03 mm (+/- standard deviation), corneal diameters of 10.6 +/- 0.5 mm, keratometry values of 51.90 +/- 1.61 diopters, and subjective refractions of 0.48 +/- 2.36 diopters. Female adult monkeys had smaller corneal diameters by 0.06 mm (P = .02) and steeper corneas by 0.77 diopters (P = .04). Infant female monkeys also had steeper corneas by 2.37 diopters (P = .05). No significant differences were found between right and left eyes in either adult or infant monkeys.     

Arteriovenous malformation in a rhesus monkey (Macaca mulatta)

A developmental arteriovenous malformation of the right arm was recognized in a 1-year-old rhesus monkey. The diagnosis was based on physical findings, ultrasound, and angiography. Treatment consisting of therapeutic transcatheter embolization using polyvinyl alcohol was performed with partial success. Necropsy revealed a lesion that was limited to the skin and subcutis. An abnormal vascular pattern was present leading to and within the lesion.     

Mandibular growth in the rhesus monkey (Macaca mulatta)

Mandibular growth of 42 rhesus monkeys (Macaca mulatta) was analyzed quantitatively and qualitatively. Four groups of animals were defined according to dentitional age (i.e., infant, juvenile, adolescent, young adult). At each age growth was observed for a 24 week period. Since some animals were observed at more than one stage of development, 57 periods of growth were studied. The growth incremental data were collected by superimposing serial cephalograms on mandibular implants. Growth and remodeling of both the skeletal and dento-alveolar components of the rhesus mandible were greatest in the infant monkeys and were less in successive age groups. Posterior relocation of the ramus was noted in all age groups while bone deposition on the anterior and inferior borders of the mandibular body was greatest in the younger animals. The most pronounced dental changes also occurred in the younger animals while the dentitions of the adolescent and adult animals were generally more stable. This study demonstrates that the rate and direction of normal mandibular growth varies with the age of the animal. Furthermore, mandibular growth is quantified at four defined maturational levels to provide a set of values illustrating normal mandibular growth. These values can also be used as control data for experimental studies.     

Studies of rhesus monkey (Macaca mulatta) hemoglobin.

One hemaglobin was found in the adult rhesus monkey (Macaca mulatta) by the technique of isoelectric focusing. In addition to the adult hemoglobin, one fetal hemaglobin was observed in neonates of the same species. The alpha and non-alpha globins of rhesus monkey hemoglobins showed similar electrophoretic mobilities as those of human hemoglobin A by cellulose acetate membrane electrophoresis. It appeared that the rhesus monkey hemoglobin system is a good model system for the study of human hemoglobin development.     

Behavioral predictors of pairing success in rhesus macaques (Macaca mulatta)

Pair housing is one of the most important components of behavioral management for caged macaques; however, it can result in aggression and injury if partners are incompatible. Knowing when to proceed and when to stop social introductions can be challenging, and can have consequences for the partners. We examined whether behavior early in social introductions predicted success (i.e., partners remained cohoused with full contact for at least 28 days) in 724 female–female and 477 male–male rhesus macaque pairs. We took cage side one–zero focal observations on pairs during the first 2 days of full contact, recording social and aggressive behaviors. The majority of pairs (79.6% of female and 83.0% of male) were successful. The most common behaviors exhibited by pairs during these observations were maintaining proximity, tandem threats, and anxiety. Mounting was also relatively common in male pairs. Grooming and close social contact (e.g., touching) were not common in our study. Several behaviors observed on Day 1 significantly predicted pairing success. For females, these included proximity, tandem threat, rump present, mount, and groom. Day 1 predictors of success for male pairs included proximity, tandem threat, rump present, mount, and social contact. Fewer behaviors predicted success on Day 2. Maintaining proximity on Day 2 predicted success for both sexes, but tandem threat predicted success only for females. Behaviors that predicted incompatibility for females on Day 1 included displace, grimace, threat, bite, and other aggressive contacts. Day 1 predictors of separation for male pairs were displaced, grimace, and abnormal behavior. The only Day 2 behavior that correlated with incompatibility was grimace, which was predictive for males. Interestingly, aggression did not predict incompatibility for male pairs. Identifying behaviors exhibited by monkeys early in the pair introduction that are predictive of long-term compatibility can shape pairing decisions, reducing later stress and potential injury.     

Sex differences in the impact of social status on hair cortisol concentrations in rhesus monkeys (Macaca mulatta)

Social status impacts stress in primates, but the direction of the effect differs depending on species, social style, and group stability. This complicates our ability to identify broadly applicable principles for understanding how social status impacts health and fitness. One reason for this is the fact that social status is often measured as linear dominance rank, yet social status is more complex than simply high or low rank. Additionally, most research on social status and health ignores the effects of sex and sex-specific relationships, despite known differences in disease risk, coping strategies, and opposite-sex dominance interactions between males and females in many species. We examine the influence of social status, sex, and opposite-sex interactions on hair cortisol concentrations (HCC) in a well-studied species, rhesus macaques, where the literature predicts low ranking individuals would experience more chronic stress. Animals in three captive, seminaturalistic social groups (N = 252; 71 male) were observed for 6 weeks to obtain metrics of social status (rank and dominance certainty [DC]). DC is a measure of one's fit within the hierarchy. Hair samples were collected from each subject and analyzed for HCC. Generalized linear mixed models were used to examine (a) whether rank, DC, or sex predicted HCC; (b) whether same- or opposite-sex dominance relationships differentially impacted HCC; and (c) whether aggressive interactions initiated or received could explain any observed relationships. Results indicated that DC, not rank, predicted HCC in a sex-specific manner. For males, high HCC were predicted by receiving aggression from or having high DC with other males as well as having low DC with females. For females, only high DC with males predicted high HCC. These results likely relate to sex-specific life history pattern differences in inherited versus earned rank that are tied to female philopatry and male immigration.     

Sex differences in adolescent rhesus monkey (Macaca mulatta) Behavior

Sex differences in the behavior of 2.5- to 4.5-year-old rhesus monkeys, living in two social groups approximating natural compositions, were studied over a period of 3 years. Both sexes interacted significantly more often with members of their own sex in agonistic and affiliative interactions even when total rates and durations for male and female subjects did not differ. Strong sexual segregation was also seen in proximity, nonspecific contact, and huddling partners. Males were more involved in play and sex than were females and engaged in these activities primarily with other males. Females did more grooming than males, but groomed both male and female partners. Females also appeared to interact with a wider age range of partners than did males. Although total participation in aggressive interactions did not differ between the two sexes, females used more active forms of agonistic expression than did males. These differences in the behavior of adolescent rhesus are hypothesized to lead to social bonding among adolescent males, while females remain bonded to their matri-lines, including younger males and some fully adult males associated with matrilineal relatives. Adolescent males emigrate from their natal groups but retain sociality and bond to males and females in new groups as they become adult. © 1993 Wiley-Liss, Inc.     

Sebaceous gland adenoma in a rhesus monkey (Macaca mulatta)

A tumor mass was identified below the shoulder region of a 5-year-old male rhesus monkey (Macaca mulatta). The mass was excised and diagnosed as sebaceous gland adenoma based on the microscopic findings. Morphologically it appeared as an elevated, dome-shaped, circumscribed mass of 3.6 x 2.8 x 3.2 cm in dimension with tan speckled color. Histologically, the tumor was composed of mature, sebaceous cells (sebocytes), basal cells arranged in a mass of irregular shapes and sizes, with a characteristic appearance of poly or multilobular structure. Sebocytes were well differentiated with foamy cytoplasm in the center of the lobules and poorly or undifferentiated densely staining basal cells in the periphery of the lobules. Cellular changes in the adjacent lymph node included hyperplasia of plasma cells, macrophages and lymphoid elements with typical mitosis.     

Adenoviral hepatitis in a SIV-infected rhesus monkey (Macaca mulatta)

BACKGROUND: A 5-year-old female rhesus monkey infected with simian immunodeficiency virus became clinically suspicious with anorexia, increasing weakness and apathy eighty-five weeks after the tonsillar virus inoculation and was euthanised due to a poor prognosis. METHODS AND RESULTS: Postmortal examinations revealed a severe multifocal to coalescing necotizing hepatitis with numerous intranuclear basophilic inclusion bodies. Transmission electron microscopy of the liver resulted in the finding of adenovirus like particles arranged in paracrystalline arrays within the nuclei of hepatocytes.CONCLUSION: The SIV infected rhesus monkey suffered from an adenovirus included necortizing hepatitis, an extremely rare organ manifestation of adenovirus infection in nonhuman primates.     

Persistent truncus arteriosus in a rhesus monkey (Macaca mulatta)

A 47-day-old female rhesus macaque (Macaca mulatta) was examined because of a severe holosystolic heart murmur (grade 5/6) and signs of congestive heart failure. Results of physical examination, thoracic radiography, and cardiac ultrasonography confirmed an advanced stage of congestive heart failure. Due to the animal's age and clinical signs of disease, a congenital heart defect was suspected. Necropsy revealed a rare congenital heart defect known as persistent (common) truncus arteriosus.     

Late DNA replication in rhesus monkey (Macaca mulatta) chromosomes

A study of the pattern of late DNA replication in rhesus monkey chromosomes showed evident similarities with man. This must be a consequence of the evolutionary conservation of replication patterns in primate chromosomes, as it has been demonstrated in the great apes, in Cebus, and man. However, the pattern of late replication of the allocyclic X chromosome in lymphocytes of female rhesus monkey was identical with the fibroblast pattern in man, and with the pattern found in only 5 to 20% of human lymphocytes.     

Oxytocin is luteolytic in the rhesus monkey (Macaca mulatta)

Oxytocin (10 mi.u./microliter/h) or vehicle (0.5% chlorobutanol in saline, 1 microliter/h) was chronically infused directly into the corpus luteum of normally cyclic rhesus monkeys, by means of an Alzet pump-ovarian cannula system. Infusion of oxytocin (N = 6) or vehicle (N = 5) began 6 days after the preovulatory oestradiol surge, and daily peripheral blood samples were taken. Oxytocin caused a significant (P less than 0.05) decrease in progesterone, beginning 1 day after treatment, and oestradiol after 4 days; progesterone and oestradiol remained significantly depressed until menstruation. However, peripheral LH concentrations remained unchanged. The duration of the luteal phase, menstrual cycle and the onset of menses from the initiation of oxytocin infusion were significantly (P less than 0.01) shorter when compared to those of vehicle-treated controls. These results show that oxytocin can induce functional luteolysis in the primate and supports the hypothesis that oxytocin of luteal origin may play a role in spontaneous luteolysis.     

Juvenile rheumatoid arthritis in a rhesus monkey (Macaca mulatta)

A juvenile rhesus macaque (Macaca mulatta) developed a symmetrical erosive polyarthritis involving both large and small diarthrodial joints. Neither an infectious nor a metabolic etiology could be determined. This case shares many clinical and pathological features with the polyarticular form of human juvenile rheumatoid arthritis.     

Social interactions among female rhesus macaques (Macaca mulatta) during the nonbreeding season: Responses to the introduction of males

When rhesus monkeys are observed in social groups during the breeding season, increases in interfemale aggression coincide with midcycle increases in sexual activity between males and females. However, some investigators have suggested that both aggressive and affiliative interactions between females are influenced by the presence or absence of males, irrespective of menstrual cycle stage. In the present study, social interactions among members of a captive group of rhesus females were measured during the non-breeding season in response to the introduction of rhesus males. Ovariectomized rhesus females (estrogen-treated or untreated) served as stimulus controls. Tests with males were characterized by significantly decreased interfemale proximity and grooming and significantly increased aggression from that seen in tests with stimulus females or in the absence of stimulus animals. Only interfemale proximity declined significantly during stimulus female tests, but results suggest that this may merely reflect a decline in this behavior that occurs across the course of the day. Estrogen treatment did not alter either the aggressive or affiliative behavior of stimulus females or group female response to stimulus females. The possibility is discussed that changes in interfemale interactions during tests with males reflect female interest in interacting with the male, particularly under social conditions that may limit such interactions.