Female Marmosets Research Articles

A Novel Directed Seed-Based Connectivity Analysis Toolbox Applied to Human and Marmoset Resting-State fMRI

Estimating the direction of functional connectivity (FC) can help to further elucidate complex brain function. However, the estimation of directed FC at the voxel level in fMRI data, and evaluating its performance, has yet to be done. We therefore developed a novel directed seed-based connectivity analysis (SCA) method based on normalized pairwise Granger causality that provides greater detail and accuracy over ROI-based methods. We evaluated its performance against 145 cortical retrograde tracer injections in male and female marmosets that were used as ground truth cellular connectivity on a voxel-by-voxel basis. The ROC curve was calculated for each injection, and we achieved AUC (Area Under the ROC Curve) of 0.95 for undirected and 0.942 for directed SCA in the case of high cell count threshold. This indicates that SCA can reliably estimate the strong cellular connections between voxels in fMRI data. We then used our directed SCA method to analyze the human default mode network (DMN) and found that dlPFC (dorsolateral prefrontal cortex) and temporal lobe were separated from other DMN regions, forming part of the language-network that works together with the core DMN regions. We also found that the cerebellum (Crus I & II) was strongly targeted by the posterior parietal cortices and dlPFC, but reciprocal connections were not observed. Thus, the cerebellum may not be a part of, but instead a target of, the DMN and language-network. Summarily, our novel directed SCA method, visualized with a new functional flat mapping technique, opens a new paradigm for whole-brain functional analysis.Significant StatementWe developed a novel directed seed-based connectivity analysis (SCA) method. To evaluate its performance, we used 145 retrograde tracer injections into the common marmoset left cortex as ground truth cellular connectivity. These were compared with directed and undirected SCA on a voxel-by-voxel basis. We achieved AUC=0.95 for undirected and AUC=0.942 for directed SCA, thus SCA can estimate strong cellular connections with high accuracy. Then, we analysed the human default mode network (DMN) with directed SCA and found that the dorsolateral prefrontal cortex and temporal lobe were not part of the DMN, but part of the language network. Secondly, our analysis showed that the cerebellum may not be part of, but instead a target of, the DMN and language network.

ARViS: a bleed-free multi-site automated injection robot for accurate, fast, and dense delivery of virus to mouse and marmoset cerebral cortex

Genetically encoded fluorescent sensors continue to be developed and improved. If they could be expressed across multiple cortical areas in non-human primates, it would be possible to measure a variety of spatiotemporal dynamics of primate-specific cortical activity. Here, we develop an Automated Robotic Virus injection System (ARViS) for broad expression of a biosensor. ARViS consists of two technologies: image recognition of vasculature structures on the cortical surface to determine multiple injection sites without hitting them, and robotic control of micropipette insertion perpendicular to the cortical surface with 50 μm precision. In mouse cortex, ARViS sequentially injected virus solution into 100 sites over a duration of 100 min with a bleeding probability of only 0.1% per site. Furthermore, ARViS successfully achieved 266-site injections over the frontoparietal cortex of a female common marmoset. We demonstrate one-photon and two-photon calcium imaging in the marmoset frontoparietal cortex, illustrating the effective expression of biosensors delivered by ARViS.

Distribution pattern of the celiac, cranial mesenteric, and caudal mesenteric arteries to the gastrointestinal tract in the common marmoset (Callithrix jacchus).

Gastrointestinal diseases pose problems to captive common marmosets. Therefore, knowledge of the anatomy of the arterial supply to the gastrointestinal tract is an important prerequisite for implementing appropriate veterinary care. The common marmoset's intestinal tract has a well-developed cecum specialized for the fermentative digestion of tree gums. This specialized gastrointestinal tract may have a unique pattern of arterial distribution. This study aimed to elucidate the species-specific gastrointestinal tract arterial anatomy of the common marmoset. We traced the celiac, cranial mesenteric, and caudal mesenteric arteries in six male and nine female common marmosets using the latex injection method. We found that the celiac artery gave rise to the left gastric, common hepatic, splenic, and caudal pancreaticoduodenal arteries. In addition to these arteries, the celiac artery gave origin to the middle colic or jejunal arteries in seven or one cases, respectively. The branches of the cranial mesenteric artery consisted of 3-6 arteries, including the middle colic, caudal pancreaticoduodenal, jejunal, right colic, ileocolic, and ileal arteries, as well as a common trunk of the ventral cecal and ileal branches, and the dorsal cecal and colic branches. In four cases, the cranial mesenteric artery gave rise to the jejunal, ileocolic, and ileal arteries. In one of the 13 cases, the celiac and cranial mesenteric arteries formed a common trunk. The caudal mesenteric artery branched into the left colic, sigmoid, and cranial rectal arteries in all the cases. These findings provide an anatomical basis for gastrointestinal veterinary care of common marmosets.

Deciphering social traits and pathophysiological conditions from natural behaviors in common marmosets

Nonhuman primates (NHPs) are indispensable animal models by virtue of the continuity of behavioral repertoires across primates, including humans. However, behavioral assessment at the laboratory level has so far been limited. Employing the application of three-dimensional (3D) pose estimation and the optimal integration of subsequent analytic methodologies, we demonstrate that our artificial intelligence (AI)-based approach has successfully deciphered the ethological, cognitive, and pathological traits of common marmosets from their natural behaviors. By applying multiple deep neural networks trained with large-scale datasets, we established an evaluation system that could reconstruct and estimate the 3D poses of the marmosets, a small NHP that is suitable for analyzing complex natural behaviors in laboratory setups. We further developed downstream analytic methodologies to quantify a variety of behavioral parameters beyond motion kinematics. We revealed the distinct parental roles of male and female marmosets through automated detections of food-sharing behaviors using a spatial-temporal filter on 3D poses. Employing a recurrent neural network to analyze 3D pose time series data during social interactions, we additionally discovered that marmosets adjusted their behaviors based on others' internal state, which is not directly observable but can be inferred from the sequence of others' actions. Moreover, a fully unsupervised approach enabled us to detect progressively appearing symptomatic behaviors over a year in a Parkinson's disease model. The high-throughput and versatile nature of an AI-driven approach to analyze natural behaviors will open a new avenuefor neuroscience research dealing with big-data analyses of social and pathophysiological behaviors in NHPs.

In vitro matured oocytes have a higher developmental potential than in vivo matured oocytes after hormonal ovarian stimulation in Callithrix jacchus

BackgroundThe common marmoset, Callithrix jacchus, is an invaluable model in biomedical research. Its use includes genetic engineering applications, which require manipulations of oocytes and production of embryos in vitro. To maximize the recovery of oocytes suitable for embryo production and to fulfil the requirements of the 3R principles to the highest degree possible, optimization of ovarian stimulation protocols is crucial. Here, we compared the efficacy of two hormonal ovarian stimulation approaches: 1) stimulation of follicular growth with hFSH followed by triggering of oocyte maturation with hCG (FSH + hCG) and 2) stimulation with hFSH only (FSH-priming).MethodsIn total, 14 female marmosets were used as oocyte donors in this study. Each animal underwent up to four surgical interventions, with the first three performed as ovum pick-up (OPU) procedures and the last one being an ovariohysterectomy (OvH). In total, 20 experiments were carried out with FSH + hCG stimulation and 18 with FSH-priming. Efficacy of each stimulation protocol was assessed through in vitro maturation (IVM), in vitro fertilization (IVF) and embryo production rates.ResultsEach study group consisted of two subgroups: the in vivo matured oocytes and the oocytes that underwent IVM. Surprisingly, in the absence of hCG triggering some of the oocytes recovered were at the MII stage, moreover, their number was not significantly lower compared to FSH + hCG stimulation (2.8 vs. 3.9, respectively (ns)). While the IVM and IVF rates did not differ between the two stimulation groups, the IVF rates of in vivo matured oocytes were significantly lower compared to in vitro matured ones in both FSH-priming and FSH + hCG groups. In total, 1.7 eight-cell embryos/experiment (OPU) and 2.1 eight-cell embryos/experiment (OvH) were obtained after FSH + hCG stimulation vs. 1.8 eight-cell embryos/experiment (OPU) and 5.0 eight-cell embryos/experiment (OvH) following FSH-priming. These numbers include embryos obtained from both in vivo and in vitro matured oocytes.ConclusionA significantly lower developmental competence of the in vivo matured oocytes renders triggering of the in vivo maturation with hCG as a part of the currently used FSH-stimulation protocol unnecessary. In actual numbers, between 1 and 7 blastocysts were obtained following each FSH-priming. In the absence of further studies, FSH-priming appears superior to FSH + hCG stimulation in the common marmoset under current experimental settings.

Long-range projections of oxytocin neurons in the marmoset brain.

The neurohormone oxytocin (OT) has become a major target for the development of novel therapeutic strategies to treat psychiatric disorders such as autism spectrum disorder because of its integral role in governing many facets of mammalian social behavior. Whereas extensive work in rodents has produced much of our knowledge of OT, we lack basic information about its neurobiology in primates making it difficult to interpret the limited effects that OT manipulations have had in human patients. In fact, previous studies have revealed only limited OT fibers in primate brains. Here, we investigated the OT connectome in marmoset using immunohistochemistry, and mapped OT fibers throughout the brains of adult male and female marmoset monkeys. We found extensive OT projections reaching limbic and cortical areas that are involved in the regulation of social behaviors, such as the amygdala, the medial prefrontal cortex, and the basal ganglia. The pattern of OT fibers observed in marmosets is notably similar to the OT connectomes described in rodents. Our findings here contrast with previous results by demonstrating a broad distribution of OT throughout the marmoset brain. Given the prevalence of this neurohormone in the primate brain, methods developed in rodents to manipulate endogenous OT are likely to be applicable in marmosets.

The common marmoset as a translational model of age-related osteoarthritis.

Age-related osteoarthritis (OA) is a degenerative joint disease characterized by pathological changes in nearly every intra- and peri-articular tissue that contributes to disability in older adults. Studying the etiology of age-related OA in humans is difficult due to an unpredictable onset and insidious nature. A barrier in developing OA modifying therapies is the lack of translational models that replicate human joint anatomy and age-related OA progression. The purpose of this study was to determine whether the common marmoset is a faithful model of human age-related knee OA. Semi-quantitative microCTscoring revealed greater radiographic OA in geriatric versus adult marmosets, and the age-related increase in OA prevalence was similar between marmosets and humans. Quantitative assessments indicate greater medial tibial cortical and trabecular bone thickness and heterogeneity in geriatric versus adult marmosets which is consistent with an age-related increase in focal subchondral bone sclerosis. Additionally, marmosets displayed an age-associated increase in synovitis and calcification of the meniscus and patella. Histological OA pathology in the medial tibial plateau was greater in geriatric versus adult marmosets driven by articular cartilage damage, proteoglycan loss, and alteredchondrocyte cellularity. The age-associated increase in medial tibial cartilage OA pathology and meniscal calcification was greater in female versus male geriatric marmosets. Overall, marmosets largely replicate human OA as evident by similar 1) cartilage and skeletal morphology, 2) age-related progression in OA pathology, and 3) sex differences in OA pathology with increasing age. Collectively, these data suggest that the common marmoset is a highly translatable model ofthe naturally occurring, age-related OA seenin humans.

Herpes simplex virus type 1 infection in pet marmoset – case report

A 19-month-old female common marmoset (Callithrix jacchus) was presented with a 4-day history of anorexia and behavioral changes. At presentation, a combination of neurological signs, erosions, and ulcerations of the mucous membranes of the oral mucosa and mucocutaneous junction of the lips were observed, suggesting herpesvirus infection. Although etiological and symptomatic therapy was initiated immediately, the animal died the next day. A necropsy was performed, and gross pathology and pathohistology findings indicated a systemic viral infection. Definitive diagnosis was based on the results of molecular testing that demonstrated the presence of human herpes simplex virus type 1. In conclusion, marmosets are a highly susceptible host for human herpes simplex virus. To reduce the risk of infection and prevent this highly lethal disease in monkeys, contact with humans who have symptomatic or asymptomatic forms of HSV-1 should be limited and accompanied by appropriate hygiene measures.

Sex differences in marmoset neurocognitive aging, a nonhuman primate model for brain aging and age‐related neurodegenerative diseases

AbstractBackgroundNonhuman primate models of human aging are necessary to understand functional decline and identify vulnerabilities to aging pathologies. Longitudinal studies are critical and common marmosets (Callithrix jacchus) are ideal as they have a short lifespan (∼12 yr) and naturally develop neuropathology relevant to Alzheimer’s disease (AD).MethodWe studied 28 marmosets (14 females) from midlife (∼5 yr old) to old age across four years. Simple discrimination and reversal learning was used to evaluate cognitive performance. Additional yearly tests included motor, stress reactivity, and social behavior assessments. A subset of animals (n = 17, 9 females) were studied for AD‐relevant neuropathology in post‐mortem tissue of the dorsal lateral prefrontal cortex (dlPFC) and CA1 of the hippocampus.ResultMultilevel models revealed age‐related changes for cognitive performance with improved reversal learning during the first three years due to practice followed by decline in the final year with the onset of old age. Cognitive decline was steeper and began earlier for females compared to males. Based on cognitive trajectories which were highly variable across individuals, we categorized marmosets as cognitively impaired or non‐impaired. Mild amyloid β (Aβ) deposition was observed in the dlPFC and CA1 but did not differ between males and females. Aβ burden was higher in cognitively impaired compared to non‐impaired marmosets, but this difference did not reach statistical significance. However, cognitively impaired marmosets showed signs of accelerated brain aging including higher astrogliosis associated with Aβ deposits and dendritic spine loss, both in the dlPFC and hippocampus. In addition, increased activation and changes in microglial phenotypes were observed in the dlPFC.ConclusionLike humans, aging marmosets displayed intra‐individual variability in cognitive decline, neurodegeneration and neuronal aging. Female marmosets showed greater vulnerability to cognitive impairment, which is translationally relevant to the higher prevalence of AD in women. While trajectories of cognitive decline did not strongly map onto Aβ burden for females or males, evidence of accelerated brain aging was found in the impaired marmosets. This study highlights the value of marmosets as a nonhuman primate model of AD to identify vulnerabilities to aging pathologies, such as sex differences.

Impact of prior dengue virus infection on Zika virus infection during pregnancy in marmosets.

Zika virus (ZIKV) infection during pregnancy causes severe developmental defects in newborns, termed congenital Zika syndrome (CZS). Factors contributing to a surge in ZIKV-associated CZS are poorly understood. One possibility is that ZIKV may exploit the antibody-dependent enhancement of infection mechanism, mediated by cross-reactive antibodies from prior dengue virus (DENV) infection, which may exacerbate ZIKV infection during pregnancy. In this study, we investigated the impact of prior DENV infection or no DENV infection on ZIKV pathogenesis during pregnancy in a total of four female common marmosets with five or six fetuses per group. The results showed that negative-sense viral RNA copies increased in the placental and fetal tissues of DENV-immune dams but not in DENV-naïve dams. In addition, viral proteins were prevalent in endothelial cells, macrophages, and neonatal Fc receptor-expressing cells in the placental trabeculae and in neuronal cells in the brains of fetuses from DENV-immune dams. DENV-immune marmosets maintained high titers of cross-reactive ZIKV-binding antibodies that were poorly neutralizing, raising the possibility that these antibodies might be involved in the exacerbation of ZIKV infection. These findings need to be verified in a larger study, and the mechanism involved in the exacerbation of ZIKV infection in DENV-immune marmosets needs further investigation. However, the results suggest a potential negative impact of preexisting DENV immunity on subsequent ZIKV infection during pregnancy in vivo.

Lingual innervation in male and female marmosets

Several gaps in knowledge exists in our understanding of orofacial pain. Some of these include type of peripheral sensory innervation in specific tissues, differences in innervation between sexes and validation of rodent studies in higher order species. The current study addresses these gaps by validating mouse studies for sensory innervation of tongue tissue in non-human primates as well as assesses sex-specific differences. Tongue and trigeminal ganglia were collected from naïve male and female marmosets and tested for nerve fibers using specific markers by immunohistochemistry and number of fibers quantified. We also tested whether specific subgroups of nerve fibers belonged to myelinating or non-myelinating axons. We observed that similar to findings in mice, marmoset tongue was innervated with nerve filaments expressing nociceptor markers like CGRP and TRPV1 as well as non-nociceptor markers like TrkB, parvalbumin (PV) and tyrosine hydroxylase (TH). Furthermore, we found that while portion of TrkB and PV may be sensory fibers, TH-positive fibers were primarily sympathetic nerve fibers. Moreover, number of CGRP, TrkB and TH-positive nerve fibers were similar in both sexes. However, we observed a higher proportion of myelinated TRPV1 positive fibers in females than in males as well as increased number of PV + fibers in females.Taken together, the study for the first time characterizes sensory innervation in non-human primates as well as evaluates sex-differences in innervation of tongue tissue, thereby laying the foundation for future orofacial pain research with new world smaller NHPs like the common marmoset.

A marmoset model for Mycobacterium avium complex pulmonary disease.

Mycobacterium avium complex, is the most common nontuberculous mycobacterial respiratory pathogen in humans. Disease mechanisms are poorly understood due to the absence of a reliable animal model for M. avium complex pulmonary disease. The objectives of this study were to assess the susceptibility, immunologic and histopathologic responses of the common marmoset (Callithrix jacchus) to M. avium complex pulmonary infection. 7 adult female marmosets underwent endobronchial inoculation with 108 colony-forming units of M. intracellulare and were monitored for 30 or 60 days. Chest radiograph was assessed at baseline (prior to infection) and at the time of sacrifice (30 days for 3 animals and 60 days for 4 animals), and bronchoalveolar lavage cytokines, histopathology and cultures of the bronchoalveolar lavage, lungs, liver and kidney were assessed at time of sacrifice. Serum cytokines were monitored at baseline and weekly for 30 days for all animals and at 60 days for those alive. Group differences in serum cytokine measurements between those that tested positive versus negative for the M. intracellulare infection were assessed using a series of linear mixed models. Five of seven animals (two at 30 days and three at 60 days of infection) had positive lung cultures for M. intracellulare. Extra-pulmonary cultures were positive in three animals. All animals appeared healthy throughout the study. All five animals with positive lung cultures had radiographic changes consistent with pneumonitis. At 30 days, those with M. intracellulare lung infection showed granulomatous inflammation, while at 60 days there were fewer inflammatory changes but bronchiectasis was noted. The cytokine response in the bronchoalveolar lavage fluid was uniformly greater in the animals with positive M. intracellulare cultures than those without a productive infection, with greater levels at 30-days compared to 60-days. Similarly, serum cytokines were more elevated in the animals that had positive M. intracellulare cultures compared to those without a productive infection, peaking 14-21 days after inoculation. Endobronchial instillation of M. intracellulare resulted in pulmonary mycobacterial infection in marmosets with a differential immune response, radiographic and histopathologic abnormalities, and an indolent course consistent with M. avium complex lung infection in humans.

Use of the ovariectomy technique in female marmosets of the Callithrix spp. gender

In Brazil, the surgical sterilization procedures performed in marmosets from the Callithrix spp. gender are relatively common, since these species are particularly popular as pets and the São Paulo State Infrastructure and Environment Secretariat (Secretaria de Infraestrutura e Meio Ambiente do Estado de São Paulo-SIMA/SP) requires that all of them are sterilized before selling. Due to this reality, a study was conducted in order to determine the efficiency of the ovariectomy technique in these procedures, providing means of making the recovery period easier for the patients. This way, thirty females were submitted to the procedure and monitored until they were sold, providing evidence that the technique brings satisfactory results related to the pre, trans e postoperative periods.

RF10 | PMON216 Aromatase Inhibition Fails to Exaggerate Weight Gain and Induce Bone Loss in Ovariectomized Female Marmosets

Abstract Declining serum estradiol (E2) levels during the menopausal transition are associated with increased central adiposity and heightened risk for metabolic disease. Ovarian estradiol, E2, supports female metabolic function. While ovariectomy (OVX) in rodents enables obesity, OVX in nonhuman primates (NHPs) inconsistently alters weight gain. We therefore hypothesized that in female NHPs, extra-ovarian E2 provides key support for metabolic homeostasis. To test this, we employed aromatase inhibition to eliminate extra-ovarian E2 biosynthesis together with diet-induced obesity (DIO) to enhance weight gain. Thirteen adult female marmoset monkeys were OVX and received: (1) E2-containing capsules and daily oral treatments of vehicle (E2; n=5); empty capsules and daily oral treatments of either vehicle (VEH, 1ml vehicle/kg, n=4), or (3) letrozole (LET, 1 mg/kg in 1ml vehicle/kg, n=4). After 6-7 months, VEH and LET compared to E2 females demonstrated increased % body weight gain (p=0.01) and increased caloric intake VEH (p<0.001) and LET (p<0.001) corrected for fat-free mass. Dual energy x-ray absorptiometry (DXA)-determined body composition at 6 months showed no between female group differences in total fat mass or fat mass in validated body regions of interest. Total body (p=0.014), abdominal region (p=0.002) and upper leg region (p=0.025) DXA-determined fat free mass, however, increased ∼5-10% in all female groups. In addition, lumbar spine and total body DXA-determined bone mineral density (BMD) and bone mineral content (BMC) were comparable across all female groups. Relative circulating E2 levels were E2>>>VEH>LET, while those in hypothalamus ranked E2=VEH>LET, confirming aromatase inhibition of local hypothalamic E2 in LET females. Our findings demonstrate ovarian E2 and extra-ovarian E2 depletion induce comparable increases in DIO weight gain without bone loss in female marmoset monkeys and highlight E2 as a key regulator of female metabolic homeostasis in NHPs. Presentation: Saturday, June 11, 2022 1:48 p.m. - 1:53 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Individual variations and effects of birth facilities on the fecal microbiome of laboratory-bred marmosets (Callithrix jacchus) assessed by a longitudinal study.

Laboratory animals are used for scientific research in various fields. In recent years, there has been a concern that the gut microbiota may differ among laboratory animals, which may yield different results in different laboratories where in-vivo experiments are performed. Our knowledge of the gut microbiota of laboratory-reared common marmosets (Callithrix jacchus) is limited; thus, in this study, we analyzed the daily changes in fecal microbiome composition, individual variations, and effects of the birth facility in healthy female laboratory-reared marmosets, supplied by three vendors. We showed that the marmoset fecal microbiome varied among animals from the same vendor and among animals from different vendors (birth facility), with daily changes of approximately 37%. The fecal microbiome per vendor is characterized by alpha diversity and specific bacteria, with Bifidobacterium for vendor A, Phascolarctobacterium for vendor B, and Megamonas for vendor C. Furthermore, we found that plasma progesterone concentrations and estrous cycles were not correlated with daily fecal microbiome changes. In contrast, animals with an anovulatory cycle lacked Megamonas and Desulfovibrio bacteria compared to normal estrous females. This study suggests that the source of the animal, such as breeding and housing facilities, is important for in-vivo experiments on the marmoset gut microbiota.

Natural SARS-CoV-2 Infection in a Free-Ranging Black-Tailed Marmoset (Mico melanurus) from an Urban Area in Mid-West Brazil

The emergence of spillover pathogens such as SARS-CoV-2 is a risk to vulnerable human populations. We report natural SARS-CoV-2 infection in a free-ranging adult female black-tailed marmoset (Mico melanurus) from an urban area of Cuiabá, Mato Grosso State, Brazil. The animal was found after a motor vehicle collision without previous clinical history. Necropsy confirmed polytrauma. Severe multifocal to coalescent haemorrhage and mild multifocal peribronchial lymphocytic hyperplasia were seen in lung sections. The alveolar septa were multifocally expanded by a few lymphocytes. Mild lymphocytic periportal hepatitis and interstitial nephritis were found. The lymphoid nodules of the large intestine showed marked lymphocytic hyperplasia. Infection by SARS-CoV-2 was established by viral RNA detection in a pool of nasopharyngeal and oropharyngeal swabs and liver samples. Immunohistochemistry detected the viral nucleocapsid protein in sections of lung, liver, spleen, lymph nodes and large intestine, and spike protein antigen in lung tissue. This is the first report of naturally occurring SARS-CoV-2 infection in a New World monkey. Platyrrhine species should be included as potential hosts of natural infection of SARS-CoV-2.

Aromatase Inhibition Eliminates Sexual Receptivity Without Enhancing Weight Gain in Ovariectomized Marmoset Monkeys.

ContextOvarian estradiol supports female sexual behavior and metabolic function. While ovariectomy (OVX) in rodents abolishes sexual behavior and enables obesity, OVX in nonhuman primates decreases, but does not abolish, sexual behavior, and inconsistently alters weight gain.ObjectiveWe hypothesize that extra-ovarian estradiol provides key support for both functions, and to test this idea, we employed aromatase inhibition to eliminate extra-ovarian estradiol biosynthesis and diet-induced obesity to enhance weight gain.MethodsThirteen adult female marmosets were OVX and received (1) estradiol-containing capsules and daily oral treatments of vehicle (E2; n = 5); empty capsules and daily oral treatments of either (2) vehicle (VEH, 1 mL/kg, n = 4), or (3) letrozole (LET, 1 mg/kg, n = 4). ResultsAfter 7 months, we observed robust sexual receptivity in E2, intermediate frequencies in VEH, and virtually none in LET females (P = .04). By contrast, few rejections of male mounts were observed in E2, intermediate frequencies in VEH, and high frequencies in LET females (P = .04). Receptive head turns were consistently observed in E2, but not in VEH and LET females. LET females, alone, exhibited robust aggressive rejection of males. VEH and LET females demonstrated increased % body weight gain (P = .01). Relative estradiol levels in peripheral serum were E2 >>> VEH > LET, while those in hypothalamus ranked E2 = VEH > LET, confirming inhibition of local hypothalamic estradiol synthesis by letrozole.ConclusionOur findings provide the first evidence for extra-ovarian estradiol contributing to female sexual behavior in a nonhuman primate, and prompt speculation that extra-ovarian estradiol, and in particular neuroestrogens, may similarly regulate sexual motivation in other primates, including humans.

Diagnosis and treatment of macrocytic anemia in a perinatal common marmoset: a case report

BackgroundThe common marmoset is widely used in current biomedical research for various research fields. We observed macrocytic anemia in a perinatal common marmoset with gradual weight loss and diarrhea. The objective of this case report is to describe the diagnosis and treatment of macrocytic anemia in a perinatal common marmoset.Case presentationA 7-year-old female common marmoset showed clinical signs of gradual weight loss and intermittent diarrhea beginning 3 months after giving birth. Macrocytic anemia was diagnosed due to a decreased red blood cell (RBC) count, low hemoglobin level, and increased mean corpuscular volume (MCV). Multivitamins containing cobalamin and folate were administered for 7 days, and the patient’s RBC count recovered to near the normal range with this treatment.ConclusionsMacrocytic anemia can be diagnosed by evaluating the MCV on a complete blood count (CBC) and cobalamin or folate levels and be treated by supplementation with cobalamin and folate. Such supplements may be needed during pregnancy and lactation in female common marmosets and/or in animals with chronic diarrhea.

Light microscopic and heterogeneity analysis of astrocytes in the common marmoset brain.

Astrocytes are abundant cells of the central nervous system (CNS) and are involved in processes including synapse formation/function, ion homeostasis, neurotransmitter uptake, and neurovascular coupling. Recent evidence indicates that astrocytes show diverse molecular, structural, and physiological properties within the CNS. This heterogeneity is reflected in differences in astrocyte structure, gene expression, functional properties, and responsiveness to injury/pathological conditions. Deeper investigation of astrocytic heterogeneity is needed to understand how astrocytes are configured to enable diverse roles in the CNS. While much has been learned about astrocytic heterogeneity in rodents, much less is known about astrocytic heterogeneity in the primate brain where astrocytes have greater size and complexity. The common marmoset (Callithrix jacchus) is a promising non‐human primate model because of similarities between marmosets and humans with respect to genetics, brain anatomy, and cognition/behavior. Here, we investigated the molecular and structural heterogeneity of marmoset astrocytes using an array of astrocytic markers, multi‐label confocal microscopy, and quantitative analysis. We used male and female marmosets and found that marmoset astrocytes show differences in expression of astrocytic markers in cortex, hippocampus, and cerebellum. These differences were accompanied by intra‐regional variation in expression of markers for glutamate/GABA transporters, and potassium and water channels. Differences in astrocyte structure were also found, along with complex interactions with blood vessels, microglia, and neurons. This study contributes to our knowledge of the cellular and molecular features of marmoset astrocytes and is useful for understanding the complex properties of astrocytes in the primate CNS.

Welfare Improvement by Enrichment Programs in Common Marmoset Females Under Social Isolation

ABSTRACT Animal welfare is critical to buffer stress in captive animals and to ensure the reliability of data from studies. The most usual environmental enrichment technique (EE) for social non-human primates is the social enrichment. However, some experimental protocols require keeping individuals isolated, thus demanding other types of EE. We tested in six adult Callithrix jacchus females, single housed for experimental purpose, the stress buffering efficacy of a structural enrichment protocol (SEP) and SEP in combination with a foraging enrichment (FSEP) using fecal cortisol and behaviors to infer stress levels. Both types of EE improved welfare in different ways, while cortisol levels decreased with both EE as compared to the baseline, autogrooming, and piloerection increased after FSEP probably due to the new foods. Therefore, these findings support alternative practices of EE when social animals are living in isolation and reinforce the positive role of structural and food enrichment for decreasing stress markers. It also encourages studies on welfare with females, since its use as an animal model has increased.