Effects of Deslorelin on Testosterone Secretion and Testicular Volume in Male Rhesus Macaques (Macaca mulatta).

Sterility in male NHP has long been achieved through surgical castration or vasectomy. However, these techniques are irreversible, require a surgical procedure, and have potential consequences such as sperm granulomas and long recovery time. Deslorelin is a gonadotropin-releasing hormone agonist that temporarily and reversibly suppresses sex hormone secretion. Our goal in this study was to investigate the effects of deslorelin on testosterone secretion and testicular volume in male rhesus macaques (Macaca mulatta). Male macaques (n = 4) each received two, 4.7-mg deslorelin implants subcutaneously in the interscapular region. Serum testosterone and testicular volume were then monitored at specific time points until 10 mo after treatment. Testosterone suppression was defined as testosterone levels lower than 0.6 ng/mL for a sustained period of at least 30 d. After implantation, mean testicular volume was significantly reduced by day 121. Testosterone suppression was observed in all subjects. However, the time from implantation to testosterone suppression and duration of suppression varied. Two macaques were hormonally suppressed by day 26 after implantation and remained suppressed for at least 6 mo. The other 2 macaques were hormonally suppressed by 2 mo after implantation; of these two, one remained suppressed for 70 days while the other was suppressed for at least 245 days. We conclude that deslorelin can safely suppress testosterone secretion in male rhesus macaques, but individual variation in onset and duration of action should be considered when establishing reimplantation time points and potential return to reproductive activity.

Detrusor underactivity is associated with metabolic syndrome in aged primates.

Lower urinary tract (LUT) dysfunction is prevalent in the elderly population, and clinical manifestations include urinary retention, incontinence, and recurrent urinary tract infections. Age-associated LUT dysfunction is responsible for significant morbidity, compromised quality of life, and rising healthcare costs in older adults, but its pathophysiology is not well understood. We aimed to investigate the effects of aging on LUT function by urodynamic studies and metabolic markers in non-human primates. Adult (n = 27) and aged (n = 20) female rhesus macaques were evaluated by urodynamic and metabolic studies. Cystometry showed detrusor underactivity (DU) with increased bladder capacity and compliance in aged subjects. Metabolic syndrome indicators were present in the aged subjects, including increased weight, triglycerides, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and high sensitivity C-reactive protein (hsCRP), whereas aspartate aminotransferase (AST) was unaffected and the AST/ALT ratio reduced. Principal component analysis and paired correlations showed a strong association between DU and metabolic syndrome markers in aged primates with DU but not in aged primates without DU. The findings were unaffected by prior pregnancies, parity, and menopause. Our findings provide insights into possible mechanisms for age-associated DU and may guide new strategies to prevent and treat LUT dysfunction in older adults.

Hormonal Suppression in Female Rhesus Macaques (Macaca mulatta) Implanted Subcutaneously with Deslorelin.

Providing effective contraception for nonhuman primates (NHP) is challenging. Deslorelin acetate is a commercially available gonadotropin-releasing hormone (GnRH) agonist that may provide a relatively noninvasive, long-lasting, and potentially reversible alternative to standard NHP contraception methods. This study evaluated the duration of suppression of progesterone and estradiol in 6 adult female rhesus macaques (Macaca mulatta) that received a single subcutaneous 4.7 mg deslorelin implant. We hypothesized that deslorelin would suppress production of these hormones for 6 mo with a correspond- ing cessation of menses. Prior to implantation, blood was collected over 1 mo for baseline hormone analyses. Macaques were sedated at the onset of the next menstrual cycle and a 4.7 mg deslorelin implant was placed in the interscapular region. Blood was collected over the subsequent month at the same intervals used for the baseline collection schedule, and then every 7 d thereafter. Results showed that estradiol and progesterone transiently increased 1 to 3 d after implantation, then fell to basal levels within 6 d of implantation. The duration of hormone suppression (progesterone <0.5 ng/mL) varied among animals. Two macaques returned to cyclicity by 96 d and 113 d after implantation, while hormones remained suppressed in the other 4 macaques at 6 mo after implantation. Cessation of menses correlated with hormone suppression except in 1 animal that continued to have sporadic vaginal bleeding despite progesterone remaining below 0.5 ng/mL. This study indicates that deslorelin is a noninvasive and long-lasting contraceptive method in female rhesus macaques. However, individual variation should be considered when determining reimplantation intervals.

Comparison of Insulins Glargine and Degludec in Diabetic Rhesus Macaques (Macaca mulatta) with CGM Devices.

Treating and monitoring type 2 diabetes mellitus (T2DM) in NHP can be challenging. Multiple insulin and hypoglycemic therapies and management tools exist, but few studies demonstrate their benefits in a NHP clinical setting. The insulins glargine and degludec are long-acting insulins; their duration of action in humans exceeds 24 and 42 h, respectively. In the first of this study's 2 components, we evaluated whether insulin degludec could be dosed daily at equivalent units to glargine to achieve comparable blood glucose (BG) reduction in diabetic rhesus macaques (Macaca mulatta) with continuous glucose monitoring (CGM) devices. The second component assessed the accuracy of CGM devices in rhesus macaques by comparing time-stamped CGM interstitial glucose values, glucometer BG readings, and BG levels measured by using an automated clinical chemistry analyzer from samples that were collected at the beginning and end of each CGM device placement. The CGM devices collected a total of 21,637 glucose data points from 6 diabetic rhesus macaques that received glargine followed by degludec every 24 h for 1 wk each. Ultimately, glucose values averaged 29 mg/dL higher with degludec than with glargine. Glucose values were comparable between the CGM device, glucometer, and chemistry analyzer, thus validating that CGM devices as reliable for measuring BG levels in rhesus macaques. Although glargine was superior to degludec when given at the same dose (units/day), both are safe and effective treatment options. Glucose values from CGM, glucometers, and chemistry analyzers provided results that were analogous to BG values in rhesus macaques. Our report further highlights critical clinical aspects of using glargine as compared with degludec in NHP and the benefits of using CGM devices in macaques.

Sexual dimorphism of detrusor function demonstrated by urodynamic studies in rhesus macaques.

The lower urinary tract (LUT) and micturition reflexes are sexually dimorphic across mammals. Sex as a biological variable is also of critical importance for the development and translation of new medical treatments and therapeutics interventions affecting pelvic organs, including the LUT. However, studies of LUT function with comparisons between the sexes have remained sparse, especially for larger mammals. Detrusor function was investigated by filling cystometry and pressure flow studies in 16 male and 22 female rhesus macaques. By filling cystometry, male subjects exhibited a significantly larger bladder capacity and compliance compared to females. Pressure flow studies showed a significantly higher bladder pressure at voiding onset, peak pressure, and elevation in detrusor-activated bladder pressure from the end of bladder filling to peak pressure in the male subjects. The activation of reflex micturition, with associated detrusor contractions, resulted in voiding in a significantly larger proportion of female compared to male subjects. A higher urethral outlet resistance is suggested in the male subjects. We conclude that sexual dimorphism of detrusor function is prominent in rhesus macaques, shares many features with the human, and merits consideration in translational and pre-clinical research studies of micturition and LUT function in non-human primates.

Ketamine-induced neuromuscular reactivity is associated with aging in female rhesus macaques.

Rhesus macaques represent an important species for translational and pre-clinical research studies across a multitude of disease and injury models, including aging. Ketamine anesthesia is used in humans and non-human primates but may be associated with adverse effects, including neuromuscular reactions. The effects of aging on ketamine adverse effects is not well characterized. Urodynamic recordings and electromyography (EMG) studies were performed in aged (>20 years old) and adult (3.9-14.9 years old) female rhesus macaques under an equal and light plane of sedation by constant rate infusion (CRI) of ketamine. A total of 4 of 41 adult subjects (9.7%) showed clinical signs of ketamine-induced abnormal neuromuscular reactivity, whereas a larger portion of 14 of 26 aged subjects showed similar ketamine-induced neuromuscular reactivity (53.8%; P< 0.001). The ketamine CRI rate was 19.8±0.9 mg/kg/h in adults and lower in aged subjects at 16.5±1.4 mg/kg/h (P<0.05). The ketamine CRI rate was negatively correlated with age (r = -0.30, P<0.05, n = 64). The incidence of ketamine reactivity or CRI rate was not different between aged pre-and post-menopausal females. EMG recordings during neuromuscular reactivity showed coordinated activation of multiple muscles, suggesting a central nervous system (CNS) mechanism for ketamine-associated neuromuscular reactivity. The incidence of ketamine-induced neuromuscular reactivity is age related but not affected by the estrous cycle in female rhesus macaques. A coordinated activation of multiple muscles, innervated by different peripheral nerves, suggests that ketamine-induced neuromuscular reactivity originates in the CNS.

Identifying Cardiac Diseases using Cardiac Biomarkers in Rhesus Macaques (Macaca mulatta).

Cardiac biomarkers are an important tool for diagnosing cardiac diseases in both human and veterinary patients. Serum concentrations of N-terminal probrain natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) have been used to indicate the presence of various cardiac diseases including hypertrophic cardiomyopathy (HCM) in various species including humans. However, these cardiac biomarkers have not been established as a diagnostic tool for detecting cardiac disease in rhesus macaques. In the rhesus macaque colony at the California National Primate Research Center, naturally occurring HCM and various other cardiac diseases have been identified. In this study, commercially available assays were used to measure serum cTnI and NT-proBNP concentrations to evaluate their utility as a diagnostic screening tool for cardiac diseases in rhesus macaques. This study revealed that the serum cTnI concentration was significantly higher in animals with echocardiographically apparent cardiac disease as compared with the animals that had no cardiac structural and functional changes (the control group). However, no significant differences were detected between animals with HCM and non-HCM cardiac disease. Because the area under the receiver operating characteristic curve was 0.81 when the serum cTnI was compared between the control and cardiac disease groups, serum cTnI was considered a moderately accurate test to predict the presence of cardiac disease. The optimal cut-off value of serum cTnI concentration for diagnosis of cardiac disease was 0.0085 ng/mL, with a sensitivity of 0.68 and specificity of 0.94. Significant but weak correlations were noted between the serum cTnI concentration and several echocardiographic parameters. Conversely, no significant differences in NT-proBNP concentrations were detected between animals with and without cardiac diseases. In conclusion, measurement of serum cTnI can be used to aid in diagnosing cardiac diseases in rhesus macaques. However, cTnI measurement does not replace echocardiographic evaluation to diagnose cardiac diseases in rhesus macaques due to the poor sensitivity of the assay and the weak correlation to with more established echocardiographic markers for cardiac disease.

Vertebral Heart Score in Rhesus Macaques (Macaca mulatta): Generating Normal Reference Intervals and Assessing its Validity for Identifying Cardiac Disease.

Vertebral heart scoring (VHS) is a semiquantitative method to assess the presence and severity of cardiomegaly by using thoracic radiographs. VHS in rhesus macaques (Macaca mulatta) has not been validated or used routinely in the clinical or research setting. We hypothesized that rhesus macaques with cardiac disease diagnosed by using echocardiography would have higher VHS than animals without cardiac disease. A total of 150 rhesus macaques were enrolled in this study. All animals underwent echocardiography and thoracic radiography (right lateral [RL], dorsoventral [DV], and ventrodorsal [VD] views).According to echocardiography, 121 rhesus macaques had no cardiac disease and were used to establish reference intervals for VHS. The remaining 29 macaques had hypertrophic cardiomyopathy (n = 20) or other cardiac disease (n = 9). Results showed that VHS of RL and VD views were significantly higher in macaques with any of the identified cardiac diseases and in the cardiac disease group that excluded hypertrophic cardiomyopathy. VHS of animals with HCM was not significantly different than that of control animals. In the RL view, VHS was moderately accurate for predicting the presence of cardiac disease, with an AUC of 0.71 and an optimal cut-off value of 10.25 (sensitivity: 62%, specificity: 77%). In the VD view, VHS was a mildly accurate test for cardiac disease, with an AUC of 0.654 and an optimal cut-off value of 10.65 (sensitivity, 66%;specificity, 63%). Study results indicated that VHS could be a useful screening tool for clinically identifying rhesus macaques with cardiac disease. However, VHS is unlikely to replace echocardiographic examination for determining the presence, type,and severity of cardiac disease in this species.

Noninvasive spinal neuromodulation to map and augment lower urinary tract function in rhesus macaques.

Dysfunction of the lower urinary tract (LUT) is prevalent in neurological disorders, including multiple sclerosis, stroke, spinal cord injury and neurodegenerative conditions. Common symptoms include urgency, incontinence, and urinary retention. Recent advances in neuromodulation have resulted in improved treatments for overactive bladder symptoms of urgency, frequency, and nocturia. However, there are presently no treatments available for the induction of voiding to overcome urinary retention. We demonstrate that transcutaneous spinal cord stimulation (TSCS), a non-invasive intervention, applied over the thoracolumbar spine in neurologically intact rhesus macaques can activate the LUT, including activation of the bladder detrusor muscle, the urethral sphincter and pelvic floor muscles. Urodynamic studies show improved voiding efficiency and decreased post-voiding residual volumes in the bladder, while maintaining coordinated activity in the detrusor and sphincter with physiologic detrusor peak pressure, contraction duration, and urine flow rate remaining unchanged. We conclude that TSCS may represent a novel approach to activate the LUT and enable voiding in select neurological conditions.

Pharmacokinetics of a Long-lasting, Highly Concentrated Buprenorphine Solution after Subcutaneous Administration in Rhesus Macaques (Macaca mulatta).

Opioids are essential for use in rhesus macaques (Macaca mulatta) that require multimodal analgesia or those unable to receive NSAID as part of their pain management plan. The current opioid epidemic has universally limited the availability of these vital analgesics, compelling clinicians to investigate other options including novel opioid formulations. A commercially available injectable, long-lasting, highly concentrated buprenorphine solution (HCBS) provides therapeutic plasma concentrations lasting 24 h after a single dose in cats ( Felis catus). We hypothesized that this same HCBS would achieve therapeutic concentrations (≥0.1 ng/mL) for at least 24 h in rhesus macaques. In the current study, 6 healthy, adult rhesus macaques were included in a randomized, 2-period, 2-treatment crossover study. The low dose (0.24 mg/kg SC) achieved a peak plasma concentration of 19.1 ± 5.68 ng/mL at 0.308 ± 0.077 h, with an AUC of 236.4 ± 22.5 h/ng/mL and terminal elimination half-life of 19.6 ± 4.02 h; for the high dose (0.72 mg/kg SC), these parameters were 65.2 ± 14.7 ng/mL, 0.034 ± 0.004 h, 641.3 ± 79.4 h/ng/mL, and 20.6 ± 2.30 h, respectively. The mean plasma concentrations for the low and high doses in rhesus macaques significantly exceeded the therapeutic threshold for 48 and 72 h, respectively. One macaque showed mild somnolence at both doses, and another showed mild pruritus at both doses. These findings show that subcutaneous administration of HCBS provides prolonged and long-lasting therapeutic plasma levels for 48 to 72 h dosing without problematic adverse effects and thus represents a potential new analgesic alternative.

Modified Dose Efficacy Trial of a Canine Distemper-Measles Vaccine for Use in Rhesus Macaques (Macaca mulatta).

Measles virus causes a highly infectious disease in NHP. Clinical signs range from asymptomatic to fatal, although measles virus is most well-known for its characteristic generalized maculopapular rash. Along with appropriate quarantine practices, restricted human access, and appropriate personal protective equipment, vaccines are used to combat the risk of infection. The canine distemper-measles vaccine (CDMV), administered at the manufacturer's standard dose (1.0 mL IM), has been shown to be effective against clinical measles disease in rhesus macaques (Macaca mulatta). The goal of the current study was to test whether doses smaller than the manufacturer's recommended dose stimulated adequate antibody production to protect against infection. We hypothesized that either 0.25 or 0.5 mL IM of CDMV would stimulate antibody production comparable to the manufacturer's recommended dose. We found that the 0.25-mL dose was less effective at inducing antibodies than either the standard (1.0 mL) or 0.5-mL dose, which both yielded similar titers. The primary implication of this study informs balancing resource allocation and providing efficacious immunity. By using half the manufacturer-recommended dose, the 50% cost reduction may provide sufficient monetary incentive to implement, maintain, or modify measles vaccination programs at NHP facilities.

Rotavirus is associated with decompensated diarrhea among young rhesus macaques (Macaca mulatta).

Diarrhea with secondary decompensation is the main cause of morbidity and mortality in captive young rhesus macaque (Macaca mulatta) colonies. Approximately 25% of diarrhea cases with secondary decompensation are considered to be idiopathic chronic diarrhea. The purpose of this study was to investigate the suspected but not systematically examined association between rotavirus infection and diarrhea with secondary decompensation among young rhesus macaques at the California National Primate Research Center (CNPRC). Blood and stool samples were collected from 89 randomly selected young animals (age range: 6 months to 1.5 years) and were tested for the presence of rotavirus antibody, and rotavirus antigen, respectively, using enzyme-linked immunosorbent assays (ELISA's). Test and clinical data were analyzed using Fisher's exact tests and multivariate logistic regression model. Our analysis indicates that rotavirus is endemic among young outdoor-housed rhesus macaques at the CNPRC. Although the relationship between detectable rotavirus antigen in stool and symptomatic diarrhea with secondary decompensation was not significant, there was a significant association between rotavirus seropositivity and a history of diarrhea with secondary decompensation within the past 6 months. While our cross-sectional and case-control study suggests an association between rotavirus infection and diarrhea with secondary decompensation among captive rhesus macaques, more extensive longitudinal studies on larger cohorts and with more intensive sample collection are needed to confirm these findings.

EMG characteristics of the external anal sphincter guarding reflex and effects of a unilateral ventral root avulsion injury in rhesus macaques ( Macaca mulatta).

The external anal sphincter (EAS) is important for the maintenance of bowel continence and may be compromised by a variety of neuropathic conditions. However, large animal models for the study of EAS functions have been sparse. The EAS guarding reflex was examined by electromyography (EMG) in neurologically intact rhesus macaques ( n = 6) and at 4-6 wk after a unilateral EAS denervation from an L6-S3 ventral root avulsion (VRA) injury ( n = 6). Baseline EAS EMG recordings were quiescent in all subjects, and evoked responses showed an initial large-amplitude EMG activity, which gradually returned to baseline within 1-2 min. At 4-6 wk postoperatively, the EAS guarding reflex showed a significantly reduced EMG response duration of 47 ± 15 s and area under the curve (AUC) of 0.198 ± 0.097 mV·s compared with the corresponding evoked EAS EMG duration of 102 ± 19 s and AUC of 0.803 ± 0.225 mV·s ( P < 0.05) in the control group. Detailed time- and frequency-domain analysis of the evoked EAS EMG responses for the first 40 s showed no difference between groups for the maximum amplitude but a significant decrease for the mean amplitude across the study period and an early AUC reduction for the first 10 s in the VRA injury group. Time-frequency analysis and power spectrum plots indicated decreased intensity and a narrower midrange of frequencies in the VRA injury group. We conclude that the EAS guarding reflex in rhesus macaques shows characteristic EMG features in control subjects and signs of partial target denervation after a unilateral L6-S3 VRA injury. NEW & NOTEWORTHY The external anal sphincter guarding reflex showed initial large-amplitude peaks and a gradual return to a quiescent baseline after a rectal probe stimulus in rhesus macaques. At 4-6 wk after a unilateral ventral root avulsion (VRA) injury, the electromyography duration, mean amplitude, and area under the curve measurements were decreased. Time-frequency analysis and power spectrum plots indicated decreased intensity and a narrowed midrange of frequencies in the VRA injury cohort.

Intraamniotic Zika virus inoculation of pregnant rhesus macaques produces fetal neurologic disease.

Zika virus (ZIKV) infection of pregnant women can cause fetal microcephaly and other neurologic defects. We describe the development of a non-human primate model to better understand fetal pathogenesis. To reliably induce fetal infection at defined times, four pregnant rhesus macaques are inoculated intravenously and intraamniotically with ZIKV at gestational day (GD) 41, 50, 64, or 90, corresponding to first and second trimester of gestation. The GD41-inoculated animal, experiencing fetal death 7 days later, has high virus levels in fetal and placental tissues, implicating ZIKV as cause of death. The other three fetuses are carried to near term and euthanized; while none display gross microcephaly, all show ZIKV RNA in many tissues, especially in the brain, which exhibits calcifications and reduced neural precursor cells. Given that this model consistently recapitulates neurologic defects of human congenital Zika syndrome, it is highly relevant to unravel determinants of fetal neuropathogenesis and to explore interventions.

Noninvasive neurophysiological mapping of the lower urinary tract in adult and aging rhesus macaques.

The lower urinary tract (LUT) may be activated by spinal cord stimulation, but the physiological mapping characteristics of LUT activation with noninvasive transcutaneous spinal cord stimulation (TSCS) are not known. The effects of aging on the contractile properties of the detrusor are also not well understood. Therefore, TSCS was applied over the T10/T11 to L6/L7 spinous processes in adult ( n = 6) and aged ( n = 9) female rhesus macaques. A combination of urodynamic studies and electromyography recordings of the external urethral sphincter (EUS), external anal sphincter (EAS), and pelvic floor muscles was performed. Distinct functional maps were demonstrated for TSCS-evoked detrusor and urethral pressures and for the activation of the EUS, EAS, and pelvic floor muscles. The magnitude of responses for each peripheral target organ was dependent on TSCS location and strength. The strongest detrusor contraction was observed with TSCS at the L1/L2 site in adults and the L3/L4 site in aged subjects. TSCS-evoked bladder pressure at the L1/L2 site was significantly higher for the adults compared with the aged subjects ( P < 0.05). Cumulative normalized TSCS-evoked pressures, calculated for five consecutive sites between the T11/T12 and L3/L4 levels, were significantly lower for aged compared with adult subjects ( P < 0.05). The aged animals also showed a caudal shift for the TSCS site that generated the strongest detrusor contraction. We conclude that natural aging in rhesus macaques is associated with decreased detrusor contractility, a finding of significant translational research relevance as detrusor underactivity is a common occurrence with aging in humans. NEW & NOTEWORTHY Transcutaneous spinal cord stimulation (TSCS) was used to map lower urinary tract function in adult and aged rhesus macaques. Aging was associated with decreased peak pressure responses to TSCS, reduced cumulative normalized evoked bladder pressure responses, and a caudal shift for the site generating the strongest TSCS-induced detrusor contraction. We demonstrate the utility of TSCS as a new diagnostic tool for detrusor contractility assessments and conclude that aging is associated with decreased detrusor contractility in primates.

Evaluation of a Zinc Gluconate Neutralized with Arginine Product as a Nonsurgical Method for Sterilization of Rhesus Macaques (Macaca mulatta).

Because rhesus macaques (Macaca mulatta) are prolific breeders, overpopulation can be problematic in both research and feral populations. Currently, the most effective contraceptive methods are hormonal control in female macaques and vasectomies in males. These methods each come with innate challenges, the foremost being the alteration of necessary hormonal patterns. In this study, we assessed the use of zinc gluconate neutralized with arginine as a novel, nonsurgical alternative to male contraception in 12 rhesus macaques. This FDA-approved product for dogs is given as a one-time, intratesticular injection to cause permanent infertility yet theoretically spare the testosterone-producing Leydig cells of the testis. CBC counts, serum biochemistry analyses, testosterone levels, and testicular widths were evaluated at the time of injection and at 1 wk, 1 mo, 2 mo, or 3 mo afterward. Daily postinjection observations revealed transient scrotal enlargement in 8 of the 12 macaques but no indications of pain. In addition, full necropsies including testicular histopathology were assessed at study endpoints. Although some portion of every testis had evidence of seminiferous tubule loss, normal spermatogenesis was present in 22 of the 24 testes. In conclusion, chemical castration with the tested zinc gluconate neutralized with arginine product is not an effective method for sterilization of male rhesus macaques.

Generalized convulsive seizures are associated with ketamine anesthesia in a rhesus macaque (Macaca mulatta) undergoing urodynamic studies and transcutaneous spinal cord stimulation.

A female rhesus macaque developed two episodes of generalized convulsions during transcutaneous spinal cord stimulation (TSCS) and urodynamic studies under ketamine anesthesia. The seizures took place in the absence of active TSCS and bladder pressure elevation. Ketamine anesthesia remains the primary risk factor for the convulsions during these experimental procedures.

Pharmacokinetics of a Novel, Transdermal Fentanyl Solution in Rhesus Macaques (Macaca mulatta).

Rhesus macaques (Macaca mulatta) are the most commonly used NHP biomedical model and experience both research and clinical procedures requiring analgesia. Opioids are a mainstay of analgesic therapy. A novel, transdermal fentanyl solution (TFS) has been developed as a long-acting, single-administration topical opioid and was reported to provide at least 4 d of effective plasma concentrations in beagles (Canis familiaris). To evaluate the pharmacokinetic profile of TFS in healthy adult rhesus macaques, we used a 2-period, 2-treatment crossover study of a single topical administration of 1.3 (25) and 2.6 mg/kg (50 µL/kg) TFS. TFS was applied to the clipped dorsal skin of adult rhesus macaques (n = 6; 3 male, 3 female) under ketamine sedation (10 mg/kg IM). We hypothesized that TFS in rhesus macaques would provide at least 4 d of effective plasma concentrations (assumed to be ≥ 0.2 ng/mL, based on human studies). Plasma fentanyl concentrations were determined by liquid chromatography-tandem mass spectrometry before drug administration and at 0, 0.5, 1, 2, 4, 8, 12, 24, 36, 48, 60, 72, 96, 120, 144, 168, 240, 336, 408, and 504 h afterward. Noncompartmental pharmacokinetic analysis was performed. For each dose (1.3 and 2.6 mg/kg), respectively, the maximal plasma concentration was 1.95 ± 0.40 and 4.19 ± 0.69 ng/mL, occurring at 21.3 ± 4.1 and 30.7 ± 8.7 h; the AUC was 227.3 ± 31.7 and 447.0 ± 49.1 h/ng/mL, and the terminal elimination half-life was 93.7 ± 7.1 and 98.8 ± 5.4 h. No adverse effects were noted after drug administration at either dose. Macaques maintained plasma fentanyl concentrations of 0.2 ng/mL or greater for at least 7 d after 1.3 mg/kg and at least 10 d after 2.6 mg/kg topical administration of TFS. A single TFS dose may provide efficacious analgesia to rhesus macaques and reduce stress, discomfort, and risk to animals and personnel.

Zika Virus Tissue and Blood Compartmentalization in Acute Infection of Rhesus Macaques.

Animal models of Zika virus (ZIKV) are needed to better understand tropism and pathogenesis and to test candidate vaccines and therapies to curtail the pandemic. Humans and rhesus macaques possess similar fetal development and placental biology that is not shared between humans and rodents. We inoculated 2 non-pregnant rhesus macaques with a 2015 Brazilian ZIKV strain. Consistent with most human infections, the animals experienced no clinical disease but developed short-lived plasma viremias that cleared as neutralizing antibody developed. In 1 animal, viral RNA (vRNA) could be detected longer in whole blood than in plasma. Despite no major histopathologic changes, many adult tissues contained vRNA 14 days post-infection with highest levels in hemolymphatic tissues. These observations warrant further studies to investigate ZIKV persistence and its potential clinical implications for transmission via blood products or tissue and organ transplants.

Radiographic and Magnetic Resonance Imaging Identification of Thoracolumbar Spine Variants with Implications for the Positioning of the Conus Medullaris in Rhesus Macaques.

The anatomy of the vertebral column in mammals may differ between species and between subjects of the same species, especially with regards to the composition of the thoracolumbar spine. We investigated, using several noninvasive imaging techniques, the thoracolumbar spine of a total of 44 adult rhesus macaques of both genders. Radiographic examination of the vertebral column showed a predominant spine phenotype with 12 rib-bearing thoracic vertebrae and 7 lumbar vertebrae without ribs in 82% of subjects, whereas a subset of subjects demonstrated 13 rib-bearing thoracic vertebrae and 6 lumbar vertebrae without ribs. Computer tomography studies of the thoraco-lumbar spine in two cases with a pair of supernumerary ribs showed facet joints between the most caudal pair of ribs and the associated vertebra, supporting a thoracic phenotype. Magnetic resonance imaging (MRI) studies were used to determine the relationship between the lumbosacral spinal cord and the vertebral column. The length of the conus medullaris portion of the spinal cord was 1.5 ± 0.3 vertebral units, and its rostral and caudal positions in the spinal canal were at 2.0 ± 0.3 and 3.6 ± 0.4 vertebral units below the thoracolumbar junction, respectively (n = 44). The presence of a set of supernumerary ribs did not affect the length or craniocaudal position of the conus medullaris, and subjects with13 rib-bearing vertebrae may from a functional or spine surgical perspective be considered as exhibiting12 thoracic vertebrae and an L1 vertebra with ribs. Anat Rec, 300:300-308, 2017. © 2016 Wiley Periodicals, Inc.