Enzootic hepatitis A infection in cynomolgus monkeys (Macaca fascicularis)

During a toxicology study in cynomolgus (long-tailed or crab-eating) monkeys (Macaca fascicularis), a randomly distributed incidence of significantly increased hepatic enzyme activity was observed. Premedication hepatic enzyme activity in all monkeys of this study was normal, but increased alanine aminotransferase (ALT) activity was found in 4 of the 24 animals 2 weeks after initiation of the study and in 10 of 24 at 4 weeks. A drug-related effect was considered unlikely initially because the increases were not doserelated, and a 3-year review of 655 cynomolgus monkeys revealed a 15–20% incidence of increased hepatic enzyme activity. Good correlation was subsequently established between increased hepatic enzyme activity, active hepatitis A virus (HAV) infection, and histomorphologic confirmation of hepatitis (chronic periportal inflammation). Follow-up viral serodiagnostic screening of resident macaques revealed an overall incidence of anti-HAV IgG in 80% (155/193) of cynomolgus and in 70% (14/20) of rhesus monkeys. Serial screening demonstrated that several initially negative monkeys became seropositive for anti-HAV IgG, and a few acquired active infection (anti-HAV IgM). Among newly acquired cynomolgus monkeys, 2.5% (2/80) had an acute HAV infection, and 35% (28/80) eventually tested positive for anti-HAV IgG while quarantined in the primate facility. The characterization of an enzootic HAV infection in incoming monkeys posed a significant risk for the primate colony and handlers. Rigorous sanitation, isolation, and quarantine procedures, including personnel training and additional protective clothing for personnel working in the primate colony, reduced tho potential for transmission and arrested the outbreak. Experimenters should be cautious in ascribing toxicity to a test article based solely on increased hepatic enzyme activity associated with chronic periportal inflammation.     

Weight and size of the placenta in cynomolgus monkeys (Macaca fascicularis).

A gross anatomical survey of the placental development was carried out in 24 cynomolgus monkeys (Macaca fascicularis) of 4, 5, 6, 7, 8, 9, 10, 15 and 20 weeks of gestational age. Eight of the 24 placentas examined were found to be single discoidal and the remaining 16 bidiscoidal. The weight and size of placentas of each animal were measured. The average weight of the 20th week placentas was about 94 times heavier than that of the 4th week ones; the average diameter of the former was about 5 times larger than that of the latter.     

Medroxyprogesterone acetate, aggression, and sexual behavior in male cynomolgus monkeys (Macaca fascicularis).

Medroxyprogesterone acetate (MPA) is used clinically to treat male sex offenders, but there are conflicting reports about its effects on aggression. To investigate these matters in a nonhuman primate, four intact male cynomolgus monkeys were studied in a testing paradigm that involved the presence of a caged, aggression-arousing stimulus male either immediately before or during a pair-test with an ovariectomized, untreated female partner. After two 4-week periods of pretreatment baseline, males received weekly injections of 40 mg MPA either alone (two 4-week treatment periods) or in combination with testosterone replacement with sc implants (one period) and additional daily injections of 2 mg testosterone propionate (two periods). MPA was then withdrawn while testosterone replacement continued (three periods). The testing paradigm was effective in maintaining aggression, especially male-male aggression, for many months. Male-male aggression increased with MPA treatment, and increased further with testosterone replacement, whereas male-female aggression tended to change in the opposite direction. As in earlier studies, MPA decreased both plasma testosterone and male sexual activity, but restoring plasma testosterone levels in treated males failed to restore their sexual activity. MPA therefore has behavioral effects that are not mediated primarily by its suppression of circulating androgens.     

Relationship between body weight and hematological and serum biochemical parameters in female cynomolgus monkeys (Macaca fascicularis).

Obesity is a risk factor triggering a variety of metabolic diseases. Cynomolgus monkeys (Macaca fascicularis) exhibit spontaneous onset of obesity in adulthood, similar to such onset exhibited by humans. To clarify the characteristics accompanying obesity in female cynomolgus monkeys, we used simple and multiple regression analyses to determine the relationship between body weight and hematological and serum biochemical parameters as well as obesity-related hormones, namely, leptin and insulin. Simple regression analysis showed that body weight was significantly (P < 0.05) correlated with leptin level, insulin level, hemoglobin concentration, hematocrit values, mean corpuscular volume, glucose concentration, and triglyceride concentration. In addition, a multiple regression model containing leptin level, insulin level, mean corpuscular volume, and red blood cell count explained 66.9% of the variance in body weight. Therefore, female cynomolgus monkeys show similar obesity characteristics to humans, i.e., obesity is associated with enhanced synthesis and excretion of leptin in adipocytes, high risk of diabetes mellitus, and high levels of hematocytes. Our results indicate that female cynomolgus monkeys are good models for studying obesity in humans.     

Comparison of experimental Rickettsia tsutsugamushi infections in silvered leaf (Presbytis cristatus) and cynomolgus (Macaca fascicularis) monkeys.

Both silvered leaf and cynomolgus monkeys were infected with the Gilliam, Karp and Kato strains of Rickettsia tsutsugamushi. The two species developed similar clinical syndromes, but the antibody responses were greater in cynomolgus monkeys. In both species of monkeys, the Gilliam strain induced more severe clinical manifestations. At 10 months post-infection, silvered leaf monkeys were immune to homologous intradermal (id) challenge. Cynomolgus monkeys, at 15 months post-infection, were relatively resistant to homologous intravenous challenge, but not to a homologous or heterologous id challenge.     

Estrogen and androgen receptors in the liver of cynomolgus monkeys (Macaca fascicularis)

Estrogen receptors (ER) and androgen receptors (AR) were evaluated in the hepatic cytosol from cynomolgus macaques to determine if there were differences associated with gender and endogenous hormone secretion. Saturable, high affinity binding (Kd = 0.2-0.8 nM) was demonstrated for both ER and AR from either male or female monkeys. Displacement of tritiated estradiol from the ER was estrogen specific (including ethinyl estradiol). Both androgens and the synthetic progestins (levonorgestrel and norethindrone) displaced tritiated mibolerone from the AR. Both 8S and 4S molecular forms of ER and AR were demonstrated on 5-20% sucrose density gradients. The ER levels were higher in females in the follicular phase of the menstrual cycle (40.5 +/- 1.9 fmol/mg protein) than levels in males (26.4 +/- 4.8 fmol/mg protein; P less than 0.01) or levels in luteal phase females (31.8 +/- 2.4 fmol/mg protein; P less than 0.05). AR levels were not different between females during different phases of the menstrual cycle (65.8 +/- 4.6 and 69.5 +/- 4.3 fmol/mg protein, follicular and luteal, respectively), but there was a tendency (P less than 0.10) for the levels in males (54.4 +/- 6.6 fmol/mg protein) to be lower than female levels. The demonstration of saturable, high affinity binding of androgens and estrogens in liver tissue of these primates, along with differences associated with gender and the stage of the menstrual cycle, suggests that hepatic receptors are functional and may play an important role in hepatic protein secretion.     

Serum estradiol and progesterone during pregnancy and the status of the corpus luteum at delivery in cynomolgus monkeys (Macaca fascicularis).

Levels of estradiol and progesterone in peripheral serum of seven cynomolgus monkeys (Macaca fascicularis) were measured from about the 30th day of pregnancy until parturition. Although the pattern of each steroid in circulation differed somewhat from the respective patterns in rhesus monkeys (Macaca mulatta), there were basic similarities. On the day of delivery, the corpus luteum was excised and in vitro incubation of dispersed luteal cells was performed. Isolated luteal cells produced progesterone under control conditions and responded to the addition of HCG with enhanced steroidogenesis. Accordingly, "rejuvenation" of the corpus luteum may occur during advanced gestation in cynomolgus monkeys. These findings, along with establishing the efficacy of the Subhuman Primate Pregnancy Test kit to diagnose pregnancy in this macaque, extend previous evidence for utility of cynomolgus monkeys as a primate model for study of steroid hormones in pregnancy.     

Possible role of peripheral CD14low monocytes in the development of collagen-induced arthritis in cynomolgus monkeys (Macaca fascicularis).

The changes in levels of peripheral major lymphocyte subsets were monitored with 10 adult cynomolgus monkeys (5 females and 5 males) during the 9 weeks after immunization with chick type-II collagen in Freund's complete adjuvant. Three females and 3 males developed overt arthritis determined by swelling of small joints and increase of plasma alkaline phosphatase as well as C-reactive protein. An increase of CD16+ NK cells was observed in four non-arthritis-developed monkeys (two females and two males). There was no significant difference in the fluctuation pattern of CD4+ T cell, CD8+ T cell and CD20+ B cell levels between arthritis-developed monkeys and non-developed ones. In addition, the percentages of CD45RA+ CD4+ T cells to total CD4+ T cells, CD28- CD8+ T cells to total CD8+ T cells, and IgD- B cells to total B cells did not significantly differ between them. On the other hand, a significant increase was demonstrated in CD14-positive cells at 3 weeks after immunization in only arthritis-developed monkeys regardless of sex. The expression of CD14 antigen on the surface of increased cells was low in comparison with those appearing in blood obtained before immunization. In addition, increased CD14low cells showed no response to LPS stimulation. However, there was no significant difference in antibody titer to both chick type-II and monkey type-II collagen between arthritis-developed monkeys and non-developed ones. These results suggest that an increase in number of CD14low monocytes with immature function might be a part of the autoimmune response, and that the appearance of these cells is of pathogenic importance in the arthritic process in cynomolgus monkeys regardless of the production of autoantibody.     

Herpesvirus simiae (B virus) antibody response and virus shedding in experimental primary infection of cynomolgus monkeys.

Four cynomolgus monkeys (Macaca fascicularis) were inoculated in the lips and tongues with B virus. Virus shedding and antibody responses were monitored for up to 50 days postinfection. Virus was isolated from the oral cavities of all monkeys at 6 days postinfection despite the absence of observable lesions. Virus was not isolated from genital swabs or serum. Antibodies to both B virus and herpes simplex virus were detected by neutralization between days 8 and 12. Virus-specific IgM and IgG antibodies were measured by antibody capture radioimmunoassay. IgM was first detected on day 6; by contrast, IgG did not appear until day 12. Antibodies reactive in a competitive radioimmunoassay appeared by day 12 and peaked at 30 to 40 days postinfection. This study provides data on which to base the diagnosis of primary B virus infection in cynomolgus monkeys.     

Hematological and serum biochemical effects of nursing on the mother in cynomolgus monkeys (Macaca fascicularis)]

The effects of nursing on maternal hematological and serum biochemical values were analyzed in cynomolgus monkeys reared in indoor cages at Tsukuba Primate Center. In our breeding system, infants are usually separated from their mothers at the age of 121 to 180 days. Mother monkeys of such infants were studied hematologically and biochemically (Group B), as were mother monkeys who happened to have nursed their infants past 181 days after parturition (Group A). During the period with their infants, mother monkeys in the latter group showed lower white blood cell counts (WBC) and higher red blood cell counts (RBC), hematocrit values (Ht) and blood urea nitrogen concentrations (BUN) than the mother monkeys who had been separated from their infants. Also, serum calcium concentrations (Ca) were decreased with prolonged nursing periods, indicating that lactation by the mother monkey probably continues even for a period from 181 days to about one year after parturition if she nurses her infant. Lactation during this period may accelerate hematogenesis and protein metabolism in the mother monkey.