Chemotherapy of haemobartonellosis in squirrel monkeys (Saimiri sciureus)

Splenectomised Saimiri sciureus squirrel monkeys are being used increasingly as an experimental host for human malarial studies, notably for the assessment of candidate vaccines against Plasmodium falciparum blood-stage infection. Recently, we have reported that colony-reared S. sciureus monkeys are asymptomatic carriers of Haemobartonella sp. and that patent Haemobartonella infection, activated following splenectomy, may interfere with the course of P. falciparum parasitaemia in these animals. For several years, splenectomised S. sciureus monkeys were routinely submitted to oxytetracycline therapy before their use in malarial studies in order to prevent a possible spontaneous Heamobartonella infection. However, we report here that such antibiotic therapy is often ineffective and that neoarsphenamine chemotherapy may be considered as an alternative to cure both latent and patent haemobartonellosis in S. sciureus monkeys.     

Abnormal behaviors in nursery-reared squirrel monkeys (Saimiri sciureus)

Seventeen squirrel monkeys (Saimiri sciureus), 11 nursery-reared and six mother-reared, were monitored to clarify the type and degree of deviant behaviors that result from rearing this species in the nursery. Two observation periods were used: the first when the subjects averaged 6.7 months of age, the second when they averaged 15.5 months. Thirteen activities involving variations of nonnutritive orality, stereotypic posturing, and agitated behaviors were seen in the nursery-reared subjects, but never in the mother-reared subjects. No consistent gender, subspecies, or age differences were evident. Squirrel monkeys, like chimpanzees and some Old World monkeys, do develop atypical self-directed behaviors when deprived of normal stimulation during early development.     

A study of postnatal appendicular skeletal maturation in captive-born squirrel monkeys (Saimiri boliviensis)

This study is based on a mixed longitudinal radiographic sampling of appendicular bones in 82 captive-born squirrel monkeys (Saimiri boliviensis). All appendicular ossification centers had appeared radiographically by 17 weeks of age, and epiphyseal fusion was complete by 47-53 months of age. No statistically significant differences were found between the sexes in comparisons carried out at birth and at 6 and 8 months of age. Valid sex comparisons could not be made at other ages owing to the small size of the sample. The sequence of appearance of the ossification centers (Spearman correlation coefficient of Saimiri vs. Callithrix = 0.68) shows greater interspecies differences than the sequence of fusion (Saimiri vs. Callithrix = 0.88).     

Orthocephalization in the postweaning squirrel monkey

Twenty male squirrel monkeys (Saimiri sciureus boliviensis) raised in captivity were allotted to one of the following groups: weanling control (C6) sampled at 6 months of age; young control (C24) fed ad libitum on a control diet and killed at 24 months of age; and malnourished (M24) fed ad libitum on a low-protein diet and sampled at 24 months of age. Cranial points and the lateral semicircular canals were marked. On each skull, a strict lateral teleradiograph was taken, and the lengths of the midsagittal chords and their angles with respect to the vestibular line were measured. Age changed the lengths in about 70% of the chords and more than 50% of the angles. Malnutrition arrested about 50% of the lengths, but the angles were practically not affected. It is concluded that the postweaning Saimiri sciureus undergoes orthocephalization according to a general pattern already observed in rodents and suggested for pongids. Postweaning malnutrition affected growth in size but not shape changes related to the orthocephalization of the Saimiri skull. © 1996 Wiley-Liss, Inc.     

Seasonality of reproduction in captive squirrel monkeys (Saimiri Sciureus)

Seasonality of reproduction is believed to be influenced by environmental factors such as humidity, temperature, and photoperiod. In primates, there has been much speculation about which environmental factors have the greatest influence on reproductive seasonality. To determine whether environmental factors affect seasonality of reproduction of squirrel monkeys in captivity, I used path analysis to compare number of births and matings per month with monkeys kept in indoor enclosures (maintained at optimal temperatures) and those kept in outdoor enclosures (exposed to the elements). Since a different pattern of seasonality was found to occur, I was able to test whether temperature, rainfall, or photoperiod could explain the temporal variation in reproduction. Squirrel monkeys raised in captivity displayed different patterns of seasonality of reproduction, depending on the conditions in which they are housed ( chi(2)3 25.12, P<0.001; G = 28.10, P<0.001). Temperature seemed to have a large impact on number of births and matings per month (matings: path coefficient = 0.799; births: path coefficient = -1.315). Understanding what factors regulate reproduction for animals and how these factors affect reproduction differently in wild versus captive populations are important to conservation and management of species.     

Markers of cartilage and bone matrix metabolism differ between the sera of macaque and squirrel monkeys

BACKGROUND: Nonhuman primates develop the characteristic lesions of osteoarthritis, making them attractive biomedical models for the study of environmental factors, such as diet, which may influence the progress of the condition. METHODS AND MATERIALS: We used ELISA assays of potential markers of osteoarthritis which were developed for use in humans to see if we could determined the presence of immunoreactivity in two nonhuman primate genera - Macaca (macaque monkeys) and Saimiri (squirrel monkeys). RESULTS: Inter-generic differences were significant for most markers. Three markers (bone alkaline phosphatase, hyaluronin and YKL-40) were outside the human range and two markers (laminin and C2C) did not yield useful results because they were off-scale high. CONCLUSION: Our results indicate that most of the ELISA assays designed for use with human serum can be used in nonhuman primates. The highly significant differences we observed between the sera of Macaca and Saimiri, suggest that further examination is warranted.     

Effect of hormonal status and metabolic changes of restricted ewes during late pregnancy on their fetal growth and development

This study investigated the effects of hormonal status and metabolic changes of restricted ewes during late pregnancy on the ovine fetus growth and development. One hundred Mongolian ewes, synchronized for oestrus and mated, were divided into three groups and offered 0.175 MJME·kgw^−0.75·d⁻¹ (Restricted Group 1, RG1), 0.33 MJME·kgw^−0.75·d⁻¹ (Restricted Group 2, RG2) and ad libitum access to feed (Control Group, CG) during their late pregnancy respectively. The results suggested that with the supply of exogenous energy decreasing during late pregnancy, maternal body weight and net body weight loss in RG2 and RG1 were lower than those of CG (Ps0.01). The insulin and IGF-1 concentrations of ewes in RG2 and RG1 tended to be lower than those of CG (P>0.05), but the GH concentrations in RG2 and RG1 were enhanced and there was significant difference between RG1 and CG on d 120 of gestation (P<0.05). The glucose concentration of ewes in RG2 and RG1 was decreased throughout the feed restriction period, and the differences were observed between RG1 and CG on d 120 of gestation (P<0.05). In addition, the nonesterified fatty acid (NEFA) and total amino acid (TAA) concentrations of ewes in RG2 tended to increase, but there was no significant difference (P>0.05). However, the NEFA and FAA concentrations of ewes in RG1 were reduced from d 90 to d 120 of gestation, then enhanced from d 120 to d 140 of gestation. During the late pregnancy, with the supply of nutrition decreasing, the negatively physiological and biochemical maternal reactions to restriction became worse, which significantly reduced the average lamb birth weight and daily growth rate of fetus in RG2 (P<0.05) and RG1 (P<0.01).     

Effect of hormonal status and metabolic changes of restricted ewes during late pregnancy on their fetal growth and development

This study investigated the effects of hormonal status and metabolic changes of restricted ewes during late pregnancy on the ovine fetus growth and development. One hundred Mongolian ewes, synchro- nized for oestrus and mated, were divided into three groups and offered 0.175 MJME·kgw-0.75·d-1 (Re- stricted Group 1, RG1), 0.33 MJME·kgw-0.75·d-1 (Restricted Group 2, RG2) and ad libitum access to feed (Control Group, CG) during their late pregnancy respectively. The results suggested that with the sup- ply of exogenous energy decreasing during late pregnancy, maternal body weight and net body weight loss in RG2 and RG1 were lower than those of CG (P<0.01). The insulin and IGF-1 concentrations of ewes in RG2 and RG1 tended to be lower than those of CG (P>0.05), but the GH concentrations in RG2 and RG1 were enhanced and there was significant difference between RG1 and CG on d 120 of gesta- tion (P<0.05). The glucose concentration of ewes in RG2 and RG1 was decreased throughout the feed restriction period, and the differences were observed between RG1 and CG on d 120 of gestation (P<0.05). In addition, the nonesterified fatty acid (NEFA) and total amino acid (TAA) concentrations of ewes in RG2 tended to increase, but there was no significant difference (P>0.05). However, the NEFA and FAA concentrations of ewes in RG1 were reduced from d 90 to d 120 of gestation, then enhanced from d 120 to d 140 of gestation. During the late pregnancy, with the supply of nutrition decreasing, the negatively physiological and biochemical maternal reactions to restriction became worse, which sig- nificantly reduced the average lamb birth weight and daily growth rate of fetus in RG2 (P<0.05) and RG1 (P<0.01).     

Characterization of Gilbert-like syndrome in squirrel monkeys (Saimiri sciureus)

Bolivian squirrel monkeys, unlike those of Brazilian origin, exhibit a marked fasting hyperbilirubinemia (FH) similar to that observed in Gilbert's syndrome in man. Since no delays in the hepatic clearance of sulfobromophthalein or indocyanine green are present, the Bolivian monkey appears to be similar to Gilbert's type I syndrome. FH can be significantly decreased by either phenobarbital or tin-protoporphyrin pretreatment. Nicotinic acid-induced hyperbilirubinemia and delayed tolbutamide clearance were not observed as in the human syndrome.     

Methods for timing of pregnancy and monitoring of fetal body and brain growth in squirrel monkeys

In order to obtain timed pregnancies in squirrel monkeys and to monitor development of the size of the fetus and its brain, tests were made of various combinations of vaginal examination, bioassay of chorionic gonadotropin (CG), measurement of maternal body weight and uterine fundus height during pregnancy, and determination of fetal biparietal diameter by ultrasonography and magnetic resonance imaging. The usefulness of these methods in developmental and teratological studies is discussed.     

Demography of squirrel monkeys (Saimiri sciureus) in captive environments and its effect on population growth

Understanding which life-history variables have the greatest influence on population growth rate has great ecological and conservation importance. Applying models of population regulation and demographic mechanisms can aid management and conservation of both wild and captive populations. By comparisons of sensitivity, elasticity, and life-table response analyses, we identified demographic processes that were most likely to produce changes in population size (via prospective analyses) and the traits that actually influenced population changes (via retrospective analyses) among sexes, zoological facilities, and generations of captive squirrel monkey populations (Saimiri sciureus). Variation in life-history traits occurs within each group analyzed. Those traits that vary the most include age at maturity, age at last reproduction, and fertility. Zoos with increasing population growth rates maintain earlier ages of maturity, later ages of last reproduction, high rates of juvenile and adult survival, and most importantly greater fertility, reflecting shorter inter-birth intervals. Using prospective analyses, juvenile and adult survivals were predicted to be demographic traits with the greatest effect on population growth. Surprisingly, and despite predictions, retrospective analyses revealed that fertility was the life-history characteristic trait that contributed the most to changes in population size.     

Effect of separation distance on isolation call structure in squirrel monkeys (Saimiri sciureus)

Isolation calls of captive squirrel monkeys were recorded by separating infants from their natal group members and then permitting vocal contact between the “lost” baby and the group at systematically varied distances. Separated infants gave longer calls at greater separation distances from their natal group members, and responding adults and juveniles similarly extended the length of their vocalizations. In the longer variants, a highfrequency element was prolonged, which is considered to be an example of the net advantage of a “frequency window” in the ambient noise of environments.     

Modeling dichromatic and trichromatic sensitivity to the color properties of fruits eaten by squirrel monkeys (Saimiri sciureus)

Most platyrrhines have a visual polymorphism that is characterized by the presence of multiple alleles of the M/LWS gene on the X chromosome. This polymorphism is probably maintained by selection. There are two possible mechanisms by which this can be explained: First, heterozygous females may have perceptual advantages over dichromats, such that trichromacy would be favored via the existence of different visual pigments. This is known as selection by heterosis. Second, dichromacy may be advantageous in some situations, with polymorphism being maintained by frequency-dependent selection. In this study the reflectance spectra of fruits and flowers eaten by a troop of squirrel monkeys (Saimiri sciureus) in Eastern Amazon were measured using a spectrophotometer. S. sciureus have an SWS cone with a spectral tuning of approximately 430 nm, and three M/LWS alleles with spectral tunings of 535 nm, 550 nm, and 562 nm. Based on the spectral tunings of the different phenotypes and the spectral data obtained from the food items, the responses of the different visual systems to the measured objects were modeled and then compared. The model predicted that trichromatic phenotypes would have an advantage over dichromats in detecting fruits and flowers from background foliage, which suggests that heterosis is the mechanism for maintaining polymorphism in S. sciureus. On the other hand, a large proportion of fruits could not be detected by any of the phenotypes. Additional studies are necessary to determine whether other important aspects of the primates' visual world, such as prey, predator, and conspecific detection, favor tri- or dichromacy.     

The effect of chamber restraint (with or without lower body positive pressure) on hematopoiesis (particularly erythropoiesis) in squirrel monkeys (Saimiri sciureus)

Squirrel monkeys, restrained in lower body positive pressure (LBPP) chambers in attempts to model the space flight-induced hematological consequences of a cephalad fluid shift, showed a decrease in red blood cell mass which was largely independent of actual LBPP. The only LBPP-specific hematological effect was an alteration in red blood cell (RBC) survival. This monkey model represents the second, ground-based animal system in which this phenomenon has been recorded and shown to be unique to a cephalad fluid shift. These data suggest a re-evaluation is necessary of the role of altered RBC clearance as a contributing factor to the anemia of space flight in humans.     

A study of correlates of hand preferences in squirrel monkeys (Saimiri sciureus)

The purpose of this study was to test the influence of sex, age, social rank, matriline membership, posture, and visual and tactual motor control on manual preferences inSaimiri sciureus. A well-established social group of 12 squirrel monkeys, aged 2 to 14 yrs and consisting of two matrilines with social rank known for each animal, was presented with four different food-reaching tasks and assessed for hand preferences with a minimum of 100 reaches per animal. Frequency of occurrence of hand preferences at the group level and degree of hand preferences at the individual level depended on posture and on whether the reaching act took place under visual or tactual guidance. Sex, age, social rank, and matriline membership were not found to determine frequency of occurrence, direction or degree of hand preferences with the exception of one task in which a significant negative correlation between the degree of hand preference and age was found. Nine out of 12 monkeys showed task-dependent changes in the hand they used preferentially while only three animals preferred the same hand in all four tasks. Significant preferences for the use of right or left hand on a given task were distributed almost equally between individuals. Thus, the results of this study suggest task-specific demands like posture and/or whether reaching was visually or tactually guided to be the major correlates of hand preferences in food-reaching tasks in squirrel monkeys.     

The choice of amniotic fluid in metabolomics for the monitoring of fetus health - update

Introduction: In recent years, several studies have highlighted the promising role of metabolomics in the analysis of amniotic fluid (AF), to describe and characterize the interactions occurring between the mother and the fetus during prenatal development.

Among the available biological fluids, AF represents an ideal substrate to provide dynamic information regarding fetal organogenesis and metabolism through pregnancy, since it originates from both maternal and fetal tissues and contains substances derived from placenta, fetal skin, lungs, gastric fluid, and fetal urine.

Areas covered: In this paper, we provide an update reporting the most recent results on AF metabolomics in the assessment of feto-maternal health, regarding physiological pregnancies but even fields such as prematurity, bronchopulmonary dysplasia, fetal malformations, chromosomopathies, maternal diseases, placental inflammation or infections, maternal diet or exposure to exogenous substances, according to the literature found on MEDLINE since 2015.

Expert opinion: Metabolomics shows a promising role in describing both physiology and disease; the goal would be the identification of biomarkers able to precociously and efficaciously detect pathological conditions, allowing the identification of complicated pregnancy and improving their management. However, this field is under development and its reliability still needs to be clarified, especially through more numerous and accurate studies.     

Seasonal changes of serum concentrations of estradiol and progesterone in Bolivian squirrel monkeys (Saimiri sciureus)

Serial measurements of estradiol (E2) and progesterone (P) were used to describe the ovarian cycle of the Bolivian squirrel monkey. Group-caged, sexually mature female squirrel monkeys, housed with males, were sampled daily between 0900 and 1100 hr. Sampling was carried out during the breeding and nonbreeding seasons, for periods of 19–20 days from September 1981 to May 1982. Seasonal differences in serum concentrations of E2 and P were found with low levels of E2 and P and an absence of preovulatory surges of E2 during the nonbreeding season. This pattern was also observed in some animals during the breeding season. An abrupt increase in serum P concentrations in December appeared to signal the onset of cycling. Cycling animals had well-defined peaks of E2 (450–9,500 pg/ml) followed by increasing levels of P, which were >200 ng/ml in some animals. After the breeding season, E2 and P levels returned to their initially low levels. Levels of both steroids in cycling animals were higher than those reported for other primates and for previous measurements made in squirrel monkeys. Cycle length based on time interval between consecutive E2 peaks varied from 6–12 days.