Quantification of early gait development: Expanding the application of Catwalk technology to an infant rhesus macaque model.

BACKGROUND: Understanding gait development is essential for identifying motor impairments in neurodevelopmental disorders. Defining typical gait development in a rhesus macaque model is critical prior to characterizing abnormal gait. The goal of this study was to 1) explore the feasibility of using the Noldus Catwalk to assess gait in infant rhesus macaques and 2) provide preliminary normative data of gait development during the first month of life. NEW METHOD: The Noldus Catwalk was used to assess gait speed, dynamic and static paw measurements, and interlimb coordination in twelve infant rhesus macaques at 14, 21, and 28 days of age. All macaque runs were labeled as a diagonal or non-diagonal walking pattern. RESULTS: Infant rhesus macaques primarily used a diagonal (mature) walking pattern as early as 14 days of life. Ten infant rhesus macaques (83.3%) were able to successfully walk across the Noldus Catwalk at 28 days of life. Limited differences in gait parameters were observed between timepoints because of the variability within the group at 14, 21, and 28 days. COMPARISON WITH EXISTING METHODS: No prior gait analysis system has been used to provide objective quantification of gait parameters for infant macaques. CONCLUSIONS: The Catwalk system can be utilized to quantify gait in infant rhesus macaques less than 28 days old. Future applications to infant rhesus macaques could provide a better understanding of gait development and early differences within various neurodevelopmental disorders.

Conditioned sexual arousal in a nonhuman primate.

Conditioning of sexual arousal has been demonstrated in several species from fish to humans but has not been demonstrated in nonhuman primates. Controversy exists over whether nonhuman primates produce pheromones that arouse sexual behavior. Although common marmosets copulate throughout the ovarian cycle and during pregnancy, males exhibit behavioral signs of arousal, demonstrate increased neural activation of anterior hypothalamus and medial preoptic area, and have an increase in serum testosterone after exposure to odors of novel ovulating females suggestive of a sexually arousing pheromone. Males also have increased androgens prior to their mate's ovulation. However, males presented with odors of ovulating females demonstrate activation of many other brain areas associated with motivation, memory, and decision making. In this study, we demonstrate that male marmosets can be conditioned to a novel, arbitrary odor (lemon) with observation of erections, and increased exploration of the location where they previously experienced a receptive female, and increased scratching in post-conditioning test without a female present. This conditioned response was demonstrated up to a week after the end of conditioning trials, a much longer lasting effect of conditioning than reported in studies of other species. These results further suggest that odors of ovulating females are not pheromones, strictly speaking and that marmoset males may learn specific characteristics of odors of females providing a possible basis for mate identification.

Pulsatile gonadotropin-releasing hormone release from hypothalamic explants of male marmoset monkeys compared with male rats.

The present study was conducted to quantify in vitro gonadotropin-releasing hormone (GnRH) release parameters in the male marmoset. We established primary cultures of marmoset hypothalamic tissues for approximately 2 days (marmosets) to assess GnRH release profiles in vitro in hypothalamic explants from testis-intact and gonadectomized males. Pulsatile GnRH release profiles were readily demonstrated from in vitro hypothalamic explants isolated from adult male marmoset monkeys. Gonadectomy of male marmosets resulted in elevated mean GnRH and pulse amplitude from hypothalamic explants on the 1st day of culture (day 0). GnRH pulse amplitude increased by day 2 in approximately 67% of hypothalamic explants from testis-intact marmosets, suggesting release from an endogenous regulator of GnRH. We also measured GnRH release profiles in vitro in hypothalamic explants from testis-intact and gonadectomized rats. Male rats showed no changes in any concentration or frequency release parameters for GnRH following gonadectomy or during successive days in culture. The present study represents a unique examination of GnRH release from male marmoset monkey hypothalamic tissue and compares release dynamics directly with those obtained from male rat, suggesting a species difference in feedback regulation of GnRH release.

Glycerol monolaurate does not alter rhesus macaque (Macaca mulatta) vaginal lactobacilli and is safe for chronic use.

Glycerol monolaurate (GML) is a fatty acid monoester that inhibits growth and exotoxin production of vaginal pathogens and cytokine production by vaginal epithelial cells. Because of these activities, and because of the importance of cytokine-mediated immune activation in human immunodeficiency virus type 1 (HIV-1) transmission to women, our laboratories are performing studies on the potential efficacy of GML as a topical microbicide to interfere with HIV-1 transmission in the simian immunodeficiency virus-rhesus macaque model. While GML is generally recognized as safe by the FDA for topical use, its safety for chronic use and effects on normal vaginal microflora in this animal model have not been evaluated. GML was therefore tested both in vitro for its effects on vaginal flora lactobacilli and in vivo as a 5% gel administered vaginally to monkeys. In vitro studies demonstrated that lactobacilli are not killed by GML; GML blocks the loss of their viability in stationary phase and does not interfere with lactic acid production. GML (5% gel) does not quantitatively alter monkey aerobic vaginal microflora compared to vehicle control gel. Lactobacilli and coagulase-negative staphylococci are the dominant vaginal aerobic microflora, with beta-hemolytic streptococci, Staphylococcus aureus, and yeasts sporadically present; gram-negative rods are not part of their vaginal flora. Colposcopy and biopsy studies indicate that GML does not alter normal mucosal integrity and does not induce inflammation; instead, GML reduces epithelial cell production of interleukin 8. The studies suggest that GML is safe for chronic use in monkeys when applied vaginally; it does not alter either mucosal microflora or integrity.

Vocalization development in common marmosets for neurodegenerative translational modeling.

Objectives In order to facilitate the study of vocalizations in emerging genetic common marmoset models of neurodegenerative disorders, we aimed to analyze call-type changes across age in a translational research environment. We hypothesized that acoustic parameters of vocalizations would change with age, reflecting growth of the vocal apparatus and a maturation of control needed to make adult-like calls. Methods Nineteen developing common marmosets were longitudinally video- and audio-recorded between the ages of 1-149 days in a naturalistic setting without any vocalization elicitation protocol. Vocalizations were coded for call type (cry, tsik, trill, phee, and trill-phee) and analyzed for duration (sec), minimum and maximum frequency (Hz), and bandwidth (Hz). Mixed model linear regressions were performed to assess the effects of age on call parameters listed above for each call type. Results Cries decreased in duration (P = 0.038), maximum frequency (P = 0.047), and bandwidth (P = 0.023) with age. Tsik calls decreased in duration (P = 0.002) and increased in minimum frequency (P = 0.004) and maximum frequency (P = 0.005) with age. Trill calls increased in duration (P = 0.003), and trillphee bandwidth (P = 0.031) decreased with age. Discussion Our results demonstrate that development of common marmoset vocalizations is call type dependent and that changes in acoustic parameters can be detected without complex vocalization elicitation paradigms or specialized audio recording equipment. Thus, we demonstrate the feasibility of a naturalistic protocol to collect and objectively analyze marmoset vocalizations longitudinally. This approach may be useful for studying vocal communication deficits in genetic models of neurodegenerative disorders.

Sample collection and restraint techniques used for common marmosets (Callithrix jacchus).

The common marmoset (Callithrix jacchus) is a small-bodied, adaptable New World primate from secondary forests in Brazil that is used in various types of research, such as reproductive biology, neuroendocrinology, behavioral research, neuroscience, infectious disease, and drug development. Because of their small body size, adaptability to a variety of conditions, unique physiologic characteristics, family social structure, and calm demeanor, they have become the primate of choice for certain research areas. However, because of their small body size, the amount and type of samples that can be obtained from them can prove to be challenging. The objective of the study reported here is to review some techniques developed for obtaining samples or data from marmoset monkeys in a variety of research settings and includes restraint methods that work well for the type of sample collection required.

Aspects of common marmoset basic biology and life history important for biomedical research.

While common marmosets are increasingly used as alternative primate models in biomedical research, their life history, specialized behavior and unique physiology are not well known. This paper describes important marmoset attributes that are particularly relevant for biomedical research, including reproduction, neurobiology, immunology, endocrine signaling, obesity and aging, in addition to fetal and postnatal development. While common marmosets exhibit characteristic anthropoid primate traits, they clearly differ from Old World primates and humans in a variety of functions, including reproduction, endocrine signaling and immunology. These differences, however, permit the use of common marmosets in unconventional research strategies targeted on human pathology.

Social odours, sexual arousal and pairbonding in primates.

We describe the role of social odours in sexual arousal and maintaining pairbonds in biparental and cooperatively breeding primates. Social odours are complex chemical mixtures produced by an organism that can simultaneously provide information about species, kinship, sex, individuality and reproductive state. They are long lasting and have advantages over other modalities. Both sexes are sensitive to changes in odours over the reproductive cycle and experimental disruption of signals can lead to altered sexual behaviour within a pair. We demonstrate, using functional magnetic resonance imaging (fMRI), that social odours indicating reproductive state directly influence the brain areas responsible for sexual behaviour. Social odours also influence other brain areas typically involved in motivation, memory and decision making, suggesting that these signals have more complex functions in primates than mere sexual arousal. We demonstrate a rapid link between social odours and neuroendocrine responses that are modulated by a male's social status. Recent work on humans shows similar responses to social odours. We conclude with an integration of the importance of social odours on sexual arousal and maintaining pairbonds in socially biparental and cooperatively breeding species, suggesting new research directions to integrate social behaviour, neural activation and neuroendocrine responses.

Pregnancy weight gain: marmoset and tamarin dads show it too.

Paternal behaviour is critical for the survival of offspring in many monogamous species. Common marmoset (Callithrix jacchus) and cotton-top tamarin (Saguinus oedipus) fathers spend as much or more time caring for infants than mothers. Expectant males of both species showed significant increases in weight across the pregnancy whereas control males did not (five consecutive months for marmoset males and six months for cotton-top tamarin males). Expectant fathers might be preparing for the energetic cost of fatherhood by gaining weight during their mate's pregnancy.

Neuroendocrine response to female ovulatory odors depends upon social condition in male common marmosets, Callithrix jacchus.

Male mammals show rapid behavioral and hormonal responses to signals from sexually receptive females. However, rapid endocrine responses to female signals have not been observed in a nonhuman primate. Here, we tested the behavioral and hormonal response of male common marmosets (Callithrix jacchus) to isolated scent secretions from ovulatory females or to vehicle control scent. Fifteen males were tested in their home cage for behavioral and hormonal responses. These males showed increased investigative and arousal behaviors to the ovulatory scent compared to the vehicle scent. Time sniffing the scent substrate and the duration of erections were significantly elevated in relation to the vehicle scent. Thirty minutes after presentation of ovulatory scent, males showed a significant increase in testosterone compared to the vehicle, but there was no difference in cortisol values. To better control for scent presentation, 15 additional males were tested under a controlled scent exposure. Current social housing condition influenced the male's testosterone response to the ovulatory scent. Single and paired males showed significant increases in testosterone levels with the ovulatory scent but did not increase cortisol levels. Single males also showed the highest change in testosterone with the ovulatory scent, but fathers showed no changes. These results indicate that a rapid hormonal response to sexually arousing cues occurs in marmosets, and the data suggest that a male's social condition influences how he responds to sexually relevant cues.

Reproductive output, maternal age, and survivorship in captive common marmoset females (Callithrix jacchus).

Common marmosets (Callithrix jacchus) demonstrate significant variation in reproductive output on both a yearly and lifetime basis in comparison to other anthropoid primates. We explore the factors that may be most important in determining reproductive variation in captive common marmosets. Studies have found that maternal age, maternal condition, and dam survivorship are related to reproductive output; however, these reports are not in agreement and are far from conclusive. With the use of a large, multicolony, demographic database pooling data across five marmoset colonies, we examined litter information for 1,649 litters, and reproductive summaries for 400 dams to assess 1) how reproductive output variation (total production, total weaned production) is determined by litter size, interbirth interval (IBI), age at first birth, and dam survival age; 2) the relationship between maternal age and reproductive output variables; and 3) relationship between the reproductive output variables and survival. We used stepwise regression procedures to describe the amount of variation in lifetime reproductive output among dams, and found that mean litter size accounted for 18% of the variance in total production, survival age accounted for 10.6%, age at first birth accounted for 8.8%, and mean IBI accounted for 5%. For total (nonzero) weaned production, survival age accounted for 7.6% of variance, age at first birth accounted for 7.2%, mean IBI accounted for 2%, and mean litter size accounted for 1.6%. We identified significant effects (P<0.05) of maternal age on litter size and IBI length, but no effect of dam age on weaned litter size. Cox proportional hazards regression analyses revealed significant effects (P<0.01) of number of litters, age at first birth, and site on dam survivorship. Dams that produced more litters showed higher survivorship. Age at first birth showed a positive relationship with dam survivorship, i.e., dams that delayed first reproduction had higher survival. Our findings about reproductive variation in marmosets may have practical applications for the management of marmoset breeding colonies.

Human adenovirus Ad-36 promotes weight gain in male rhesus and marmoset monkeys.

Although obesity has multiple etiologies, an overlooked possibility is an infectious origin. We previously identified two viruses, SMAM-1, an avian adenovirus (Ad), and Ad-36, a human adenovirus, that produce a syndrome of visceral obesity, with paradoxically decreased serum cholesterol and triglycerides in chickens and mice. In the two studies presented in this paper, we used nonhuman primates to investigate the adiposity-promoting potential of Ad-36. In study 1, we observed spontaneously occurring Ad-36 antibodies in 15 male rhesus monkeys, and a significant longitudinal association of positive antibody status with weight gain and plasma cholesterol lowering during the 18 mo after viral antibody appearance. In study 2, which was a randomized controlled experiment, three male marmosets inoculated with Ad-36 had a threefold body weight gain, a greater fat gain and lower serum cholesterol relative to baseline (P <0.05) than three uninfected controls at 28 wk postinoculation. These studies illustrate that the adiposity-promoting effect of Ad-36 occurs in two nonhuman primate species and demonstrates the usefulness of nonhuman primates for further evaluation of Ad-36-induced adiposity.

Activation of neural pathways associated with sexual arousal in non-human primates.

PURPOSE: To evaluate brain activity associated with sexual arousal, fully conscious male marmoset monkeys were imaged during presentation of odors that naturally elicit high levels of sexual activity and sexual motivation. MATERIAL AND METHODS: Male monkeys were lightly anesthetized, secured in a head and body restrainer with a built-in birdcage resonator and positioned in a 9.4-Tesla spectrometer. When fully conscious, monkeys were presented with the odors of a novel receptive female or an ovariectomized monkey. Both odors were presented during an imaging trial and the presentation of odors was counterbalanced. Significant changes in both positive and negative BOLD signal were mapped and averaged. RESULTS: Periovulatory odors significantly increased positive BOLD signal in several cortical areas: the striatum, hippocampus, septum, periaqueductal gray, and cerebellum, in comparison with odors from ovariectomized monkeys. Conversely, negative BOLD signal was significantly increased in the temporal cortex, cingulate cortex, putamen, hippocampus, substantia nigra, medial preoptic area, and cerebellum with presentation of odors from ovariectomized marmosets as compared to periovulatory odors. A common neural circuit comprising the temporal and cingulate cortices, putamen, hippocampus, medial preoptic area, and cerebellum shared both the positive BOLD response to periovulatory odors and the negative BOLD response to odors of ovariectomized females. CONCLUSION: These data suggest the odor-driven enhancement and suppression of sexual arousal affect neuronal activity in many of the same general brain areas. These areas included not only those associated with sexual activity, but also areas involved in emotional processing and reward.