Gray short-tailed opossums (Monodelphis domestica) currently are used in genetic, developmental, oncology, and neurologic research. Little is known about their natural flora or potential for pathogenic infectious disease. The present study aims to improve existing comparative normal blood and organ weight values available to researchers and to describe flora of clinically normal M. domestica to obtain an understanding of potential pathogenic flora in clinically abnormal animals. For evaluation of serum hematology and serum chemistry, clinically normal animals were assigned to 1 of 6 groups stratified by age (younger than 1 y, 1 to 2 y, and 2 to 3 y) and sex. Hemoglobin and phosphorus levels were higher in male than female opossums, whereas monocyte and eosinophil counts were greater in females than males. Hemoglobin concentration decreased with increasing age. The youngest group had significantly higher levels of serum alkaline phosphatase and lower serum protein levels compared with older age groups. Liver and kidney weights of adult animals (1 to 3 y) were greater in female than male opossums. The predominant nasopharyngeal flora in 20 clinically normal animals from the 2- to 3-y-old group were Streptococcus viridans, Escherichia coli, and coagulase-negative Staphylococcus spp.; predominant cecal organisms were Escherichia coli and Citrobacter spp. The availability of reference hematologic values and flora for Monodelphis domestica will aid researchers in comparisons and analysis of experimental data and in diagnosis and evaluation of potential pathogens in clinically ill animals.

Excessive weight gain has been reported to occur in captive cynomolgus macaques with little to no change in diet. Overweight body condition can result in development of hyperglycemia and type 2 diabetes and should be avoided. The purpose of this survey was to assess the prevalence of overweight cynomolgus macaques in North American research facilities, including breeding colonies and short-term and long-term facilities, and to describe current methods used to assess body condition. The survey consisted of 51 questions covering animal population demographics, body weight and body condition scoring, feeding, and behavior. Voluntary participants included veterinarians and animal care managers. Respondents from 13 facilities completed the survey, and information was collected on 17,500 cynomolgus macaques. The majority of surveyed facilities housed juvenile and young adult macaques. The reported prevalence of overweight (greater than 10% of ideal body weight) animals ranged between 0% and 20% and reportedly was more frequent in animals younger than 10 y. Most facilities had weight reduction strategies in place. Despite these programs, a significant proportion of animals were reported as being overweight. The results of this survey demonstrate that most North American facilities housing cynomolgus macaques recognize the importance of tracking body condition regularly. However, implementing effective weight reduction programs may be difficult in captive housing environments. Because of the potential for adverse health effects, facilities should have a means of regularly tracking body weight as well as an action plan for managing overweight animals.

At refrigerated temperatures, mouse embryos can maintain developmental ability for short periods. Previously, we succeeded in transporting vitrified and warmed 2-cell mouse embryos while maintaining developmental ability at refrigerated temperatures for 50 h. Transport of nonfrozen embryos is an easier and more useful means of exchanging genetically engineered mice between laboratories than is transport of cryopreserved embryos. Here we examined the developmental ability of transported 2-cell embryos that were produced through in vitro fertilization using cryopreserved sperm. Results show that 2-cell embryos produced by cryopreserved sperm can develop into blastocysts after cold storage for 24, 48, and 72 h. Transported 2-cell embryos produced by cryopreserved sperm yielded a favorable number of pups in all of the receiving laboratories after transport lasting 48 to 52 h. In summary, cold storage and transport of 2-cell embryos derived from cryopreserved sperm at refrigerated temperatures provides a novel means of transporting genetically engineered mice as an alternative to the transport of cryopreserved embryos and sperm.

Here we describe a new technique for cryopreserving mouse ovaries by using 0.5-mL straws. One advantage of this method is that it uses the same controlled-rate freezer and programming routinely used for the cryopreservation of mouse embryos. Using a 0.5-mL French straw loaded in the same way as for embryo freezing (for example, the one-step dilution method) with 1 M sucrose as an osmotic buffer and 2 M propylene glycol as the cryoprotectant containing the ovary sample, we further standardized the 2 methodologies. Applying this technique, 11 ovarian halves were cryopreserved in straws and stored under liquid nitrogen. Straws containing the frozen ovarian halves were thawed in a water bath at room temperature and the recovered ovaries orthotopically implanted into 11 recipient female mice; 8 of the 11 frozen ovarian halves resulted in functional ovaries. The 73% pregnancy rate resulted in a total of 53 pups born, of which 38 (72%) were generated from cryopreserved ovaries. Ovarian cryopreservation has been demonstrated to be a valid option for banking mouse genetic resources. Unlike frozen embryos, cryopreservation of ovarian tissue preserves haploid gametes. Despite this limitation, ovarian cryopreservation is the only technique that can be used to preserve oocytes from aged or problematic breeders. This advantage is especially important in situations where the only males available in the line are infertile, aged, or problematic breeders.

The objective of this study was to evaluate the effect on litter size of 2 analgesics used perioperatively during mouse embryo transfer surgery. Day 2.5 pseudopregnant CD1 mice (n = 96) were divided equally into 2 analgesic treatment groups and a saline control group. Each mouse received a single, subcutaneous dose of buprenorphine hydrochloride (0.1 mg/kg), flunixin meglumine (2.5 mg/kg), or saline immediately after induction of anesthesia with 2.5% isoflurane. Each mouse then was prepared for aseptic surgery. Blastocysts had previously been collected from C57BL/6NCrl female mice that were synchronized and superovulated by using pregnant mare serum gonadotropin and human chorionic gonadotropin and mated with C57BL/6NTac male mice 3.5 d before collection. Viable blastocysts were pooled, and 8 were selected arbitrarily and transplanted into the right uterine horn of each pseudopregnant CD1 mouse. Mice were monitored throughout pregnancy, and the number of pups at birth was documented. No statistically significant difference was found between the 3 groups. These results indicate that perioperative analgesic treatment with buprenorphine or flunixin in the CD1 mouse undergoing embryo transfer is not associated with increased embryonic loss.

The behavioral, biochemical, and physiologic consequences of 6 wk of environmental enrichment were evaluated in male Long Evans and Sprague–Dawley rats and compared with those of rats in standard single-housing conditions. Standard housing provided little or no social or physical stimulation whereas environmental enrichment comprised group housing for 8 h daily in a 3-story cage equipped with novel stimuli. Dependent measures included performance in the forced swim test, thresholds for brain-stimulation reward, sucrose intake and preference, determination of corticosterone levels before and after brief restraint stress, and rate of weight gain. In forced swimming tests, active behaviors (diving, swimming with struggling, and climbing) tended to dominate over passive behaviors (sinking, floating) in both groups and outbred rat stocks (especially in enriched groups) on the first day. These behaviors were replaced with maintenance behaviors such as grooming and swimming without struggling on the second exposure, with enriched Long Evans rats showing the largest decline in activity. Baseline plasma corticosterone levels were elevated in both rat stocks after 6 wk of enrichment. After restraint stress, hormone levels in enriched animals tended to peak earlier and approach or exceed baseline values more quickly than was observed in the comparable control groups. Rate of body weight gain was greater in enriched Long Evans rats than Sprague–Dawley or control rats. Our observations indicate that stock- and group-associated differences in several indices occur in association with enrichment. The data support the claim that environmental enrichment may render animals more resilient to challenges.

A mouse parvovirus (designated MPV1f) was identified in a commercial laboratory mouse colony in Australia. The infection had not been detected by using an rNS1 parvovirus ELISA antigen even though the virus was genetically similar to other MPV1 variants reported previously. A recombinant biotinylated protein based on a truncated VP1 protein of the MPV1 strain was produced and used as antigen for ELISA and Western immunoblots to detect virus infection and determine the seroprevalence of infection in a colony of approximately 45,000 mice. Antibody-positive mice were detected in 8 of 11 rooms sampled, indicating that infection was widespread in the facility. Antibody was detected in 16.2% of 1161 sera obtained from 20 strains of mice. Seroprevalence varied among mouse strains, suggesting genetic variation in the susceptibility of mice to MPV1 or in their antibody response to infection, as has been reported previously in experimentally infected mice. Seroprevalence was high in some inbred strains, including DBA/2JArc and the random-bred strains Hsd:NIH and Arc:Arc(s). Antibody was not detected inC57BL/6J strains, and BALB/c strains showed low seroprevalence of MPV1f.

The effect of mouse strain and age at infection on viral replication and concurrent antibody response to mouse parvovirus 1 (isolate MPV1f) was evaluated for 305 d after inoculation in 4 strains of mice. The results confirmed previous reports that mouse strain and age at infection are significant factors in viral persistence and antibody development and detection. Randombred Arc:Arc(s) mice originally bred from CD1 stock inoculated as juveniles (4 wk) or adults (8 wk) developed persistent viral infection for 152 d after inoculation and an antibody response that persisted for 295 d. Mice of C57BL/6J background inoculated as juveniles had detectable viral DNA in large intestinal content and tissues for 24 d after inoculation and an antibody response that persisted for 288 d. However, viral DNA was not detected in tissues of C57BL/6J mice inoculated as adults, although an antibody was detected for 111 d after inoculation; these results suggest probable viral replication in adult C57BL/6J mice but at levels below the limits of detection. BALB/cArc mice inoculated as juveniles or adults had detectable virus DNA in tissues for 108 to 242 d after inoculation, but no antibody was detected. Similarly, BALB/c-Foxn1^nu/Arc mice had detectable levels of viral DNA in tissues for 98 to 131 d but no measurable antibody. The difficulty of detecting antibody in mice with a BALB/c background indicates they are unsuitable for routine surveillance of MPV1f infection.

In this study we compared rat (n = 16) responses to euthanasia with either gradual-fill CO₂ or rapid induction argon gas by evaluating the animals' heart rate via radiotelemetry, behavior, and vocalizations. We also evaluated the histologic effects of the gases. Rats were placed in an open test chamber 24 h before the start of the experiment. During baseline tests, rats were exposed to oxygen to evaluate the effects of the noise and movement of gas entering the chamber; 1 wk later, rats were euthanized by gas displacement with either 10%/min CO₂ or 50%/min argon gas. Rats tended to have higher heart rats and were more active during the baseline test, but these parameters were normal before the euthanasia experiment, suggesting that the rats had acclimated to the equipment. Heart rate, behavior, and ultrasonic vocalizations were recorded for 2 min after gas introduction in both groups. All rats appeared conscious throughout the test interval. The heart rates of rats exposed to argon did not change, whereas those of rats exposed to CO₂ declined significantly. Unlike those exposed to CO₂, rats euthanized with argon gas gasped and demonstrated seizure-like activity. There were no differences in the pulmonary lesions resulting from death by either gas. Our results suggest that argon as a sole euthanasia agent is aversive to rats. CO₂ using a 10%/min displacement may be less aversive than more rapid displacements. Future research investigating methods of euthanasia should allow sufficient time for the rats to acclimate to the test apparatus.

A safe and reliable method for anesthetizing rats has long been a leading concern of biomedical researchers. We recently found that the intraperitoneal administration of propofol combined with medetomidine and fentanyl is safe for mouse anesthesia. Here we studied whether the same combination could be used for general anesthesia in rats. We used male Wistar rats to test 10 combinations of propofol, medetomidine, and fentanyl administered intraperitoneally and reversed with intraperitoneal atipamezole 30 min after induction. The depth of anesthesia, induction time, loss of pedal withdrawal reflex, pulse rate, and respiratory rate were evaluated, along with the duration and quality of induction, surgical anesthesia, and recovery. The combination of propofol and medetomidine provided a predictable induction and sufficient hypnosis and muscle relaxation, but surgical anesthesia (loss of pedal withdrawal reflex) was difficult to achieve with this protocol. The addition of fentanyl increased analgesia, making it possible to achieve surgical anesthesia. In conclusion, combination of propofol (100 mg/kg), medetomidine (0.1 mg/kg), and fentanyl (0.1 mg/kg) is a safe and practical technique for intraperitoneal anesthesia in rats, providing a surgical window of 25 min and restraint for 30 min, with rapid recovery after administration of atipamezole.

The objective of this prospective study was to determine the duration of anesthesia in Xenopus laevis frogs of different body weights relative to exposure time in a eugenol (350 μL/L) bath. Two groups of 5 female frogs each weighing 7.5 ± 2.1 g (small frogs) or 29.2 ± 7.4 g (medium frogs) were used. The acetic acid test (AAT), withdrawal reflex, righting reflex, heart rate, and blood oxygen saturation were used to evaluate CNS depression after eugenol bath administration. No responses to the AAT, withdrawal reflex, and righting reflex were seen for 1 h (small frogs) or 0.5 h (medium frogs) after immersion in a eugenol bath for 5 or 10 min, respectively. Oxygen saturation was not affected by anesthesia, but heart rate was depressed for as long as 1 h in both groups of frogs. Surgical anesthesia evaluated by using skin and abdominal incisions revealed that small frogs were anesthetized for a maximum of 15 min compared with 30 min in medium frogs. Frogs showed no ill effects 24 h after eugenol bath administration. These results suggest that body weight is an important parameter to consider when using a eugenol bath for anesthesia of Xenopus frogs.

This study compared torcetrapib-induced blood pressure (BP) changes simultaneously obtained by high-definition oscillometry (HDO) and telemetry. Male beagles (n = 6) received single oral doses of vehicle or torcetrapib at 10 or 30 mg/kg; BP were acquired simultaneously by HDO and telemetry from 2 h before dosage until 7 h afterward. Systolic, diastolic, and mean arterial pressures (MAP) and heart rate were compared by using Altman-Bland agreement analysis. Dogs were allocated into subgroups according to temperament and baseline MAP (less than 110 mm Hg and 110 mm Hg or greater). Both methods demonstrated high precision. HDO recordings exhibited higher variability for all parameters (inclusive MAP SDs were 7.0 ± 2.7 mm Hg for HDO compared with 3.4 ± 1.9 mm Hg for telemetry), accompanied by a positive bias for all pressures (systolic, 10.4 mm Hg; diastolic, 5.7 mm Hg; MAP, 1.9 mm Hg). Both methods detected similar maximal increases in MAP with 30 mg/kg torcetrapib (HDO, 15.8 ± 10.4 mm Hg; telemetry, 15.8 ± 5.3 mm Hg). No significant effects were noted for heart rate. Torcetrapib elicited a dose-dependent increase in BP in dogs with baseline MAP of less than 110 mm Hg, whereas increases were maximal with 10 mg/kg in the other group, and dose-dependence was no longer observed. BP changes were influenced by animal temperament, demonstrating that HDO results must be interpreted with caution. HDO may provide a useful and accurate method for noninvasive BP measurements in canine studies.

Percutaneous vascular access options in preclinical models are often smaller than the relevant structures in humans or undersized for early-prototype research devices. Here we describe the surgical approaches and results for surgical vascular access sites in preclinical swine and sheep models. Fourteen adult miniature swine underwent successful 18-French vascular access by means of thoracotomy to the brachiocephalic artery. In addition, 11 swine and 10 sheep underwent successful 22-French vascular access by means of retroperitoneal laparotomy to the abdominal aorta. The relevancy of approach angles and vessel tortuosity should be considered when selecting appropriate preclinical models and techniques. The techniques described are effective for delivery of large-caliber devices in preclinical testing.

Alterations in neutrophil extravasation are seen in disease states and in response to therapeutics. To investigate neutrophil extravasation during the acute inflammatory response, a skin-window technique used in humans was adapted for use in cynomolgus macaques (Macaca fasicularis). Modulation of neutrophil extravasation was attempted with systemic methotrexate and local application of the anaphylatoxin recombinant C5a (rC5a). On day 1, skin windows were created in 4 ketamine-anesthetized monkeys on both forearms by mildly abrading the skin and then overlaying the abrasions with filter paper either saturated in saline or rC5a for 6 h. At 2.5 h prior to generation of new skin windows on day 2, the monkeys received 4.5 mg methotrexate IM, and skin windows and treatment with saline or rC5a were repeated on new forearm sites on each monkey. All papers were analyzed for albumin, neutrophil number, and the neutrophil chemoattractant IL8. Day 1 albumin levels did not differ between groups, indicating consistent abrasion. Methotrexate given prior to the day 2 abrasions reduced neutrophil extravasation and IL8 levels compared with those on day 1. rC5a partially abrogated the methotrexate-induced reduction in neutrophil extravasation and IL8 production. The skin-window technique was well tolerated by the monkeys and successfully accommodated measurement of changes in neutrophil extravasation in response to inflammatory modulators.

Staphylococcus xylosus typically is described as a nonpathogenic common inhabitant of rodent skin. Reports of S. xylosus as a primary pathogen in human and veterinary medicine are scarce. Here we report 37 cases, affecting 12 strains of laboratory mice, of spontaneous infections in which S. xylosus was isolated and considered to be the primary pathogen contributing to the death or need for euthanasia of the animal. Infection with S. xylosus was the major cause of death or euthanasia in 3 strains of mice deficient in the production of phagocyte superoxide due to defects in NADPH oxidase. NADPH-oxidase–deficient mice (n = 21) were most susceptible to spontaneous S. xylosus infections. The infections were characterized by abscesses and granulomas in soft tissues, with bacterial migration to internal organs (primarily regional lymph nodes and lungs and, to a lesser degree, muscle, bone, and meninges). In contrast, 9 strains of phagocyte-superoxide–producing mice (n = 16) also had S. xylosus infections, but these were largely confined to eyelids, ocular conjunctiva, and skin and rarely involved other tissues or organs. Because exhaustive bacterial culture and isolation may not be performed routinely from mouse abscesses, S. xylosus infections may be underdiagnosed. S. xylosus should be considered in the differential diagnosis in laboratory mice with abscesses and other skin lesions. This report expands the range of mouse strains and tissues and organs susceptible to spontaneous S. xylosus infection and compares the pathology among various mice strains.

Horses and ponies are used infrequently in research but may be valuable animal models for studying both equine-specific diseases and biomedical applications. We report here 2 cases of pediculosis in random-source ponies. Infestation and clinical signs were not present during a 4-wk quarantine period or for 3 to 9 mo thereafter but became apparent coincident with the ponies' movement from pasture to indoor housing. These 2 geldings presented with pruritus associated with excoriating lesions on the neck, and infestation with Bovicola (Werneckiella) equi Denny, 1842 was diagnosed. Ponies were treated successfully with standard wound care and a spray containing 2.0% permethrin and 0.05% pyriproxyfen. These cases highlight the importance of recognizing the possibility of louse infestation, even in healthy, well-cared-for animals, and the need for personnel to be aware of early behavioral signs of infestation, such as rubbing and agitation.