Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research.

We sought to determine whether sex had a significant effect on the hematologic and serum chemistry analytes in adult sand rats (Psammomys obesus) maintained under normal laboratory conditions. According to the few data available for this species, we hypothesized that levels of hematologic and serum chemistry analytes would not differ significantly between clinically normal male and female sand rats. Data analysis revealed several significant differences in hematologic parameters between male and female sand rats but none for serum biochemistry analytes. The following hematologic parameters were greater in male than in female sand rats: RBC count, hemoglobin, hematocrit, red cell hemoglobin content, and percentage monocytes. Red cell distribution width, hemoglobin distribution width, mean platelet volume, and percentage lymphocytes were greater in female than in male sand rats. The sex of adult sand rats is a source of variation that must be considered in terms of clinical and research data. The data presented here likely will prove useful in the veterinary medical management of sand rat colonies and provide baseline hematologic and serum chemistry analyte information for researchers wishing to use this species.

The goal of the current studies was to determine the risk of transmission of mouse parvovirus (MPV) by caging and husbandry practices. To determine whether MPV can be transmitted during cage changes in a biologic safety cabinet without the use of disinfectants, 14 cages of Swiss Webster mice were inoculated with MPV. Cages containing infected mice were interspersed among 14 cages housing naïve Swiss Webster mice. At 1, 2, and 4 wk after inoculation of the mice, cages were changed across each row. All naïve mice housed adjacent to infected mice remained seronegative. To determine the risk of environmental contamination, nesting pads that were used to sample the room floor during husbandry procedures at 1, 2, 4, and 6 wk after inoculation of the mice were placed in cages with naïve mice. None of the mice exposed to the pads became MPV seropositive. To determine whether components from cages that had housed MPV-infected mice could transmit MPV, Swiss Webster mice were exposed to soiled bedding or used cages, drinking valves, food, cage bottoms, wire bars and filter tops, nesting material, or shelters. With the exception of drinking valves, all mice exposed to other components became MPV seropositive. Fourteen cages that had housed MPV-infected mice were washed but not autoclaved; mice housed in the washed cages did not become MPV seropositive. In conclusion, all cage components can serve as fomites, with the drinking valve being the least risky. Cage washing alone was sufficient to remove or inactivate MPV.

The objective of the current study was to evaluate the effects of cage density, sanitation frequency, and bedding type on animal growth and welfare. At weaning, Sprague–Dawley rats and C57BL/6 mice were allocated to treatment groups according to sex, bedding type (shredded aspen, cellulose, or a 50:50 mixture), and cage density and sanitation frequency (inhouse cage density standards and sanitation procedures measured against Guide recommendations) for an 8-wk period. Body weight, feed disappearance, cage ammonia, ATP concentrations, behavior, morbidity, and mortality were assessed weekly; fecal corticosterone, microbiology, and lung histopathology (rats only) were evaluated at the culmination of the trial. In both rats and mice, parameters indicative of animal health and welfare were not significantly affected by cage density and sanitation frequency or bedding type. Occasional effects of feed disappearance and cage ammonia concentrations due to density and sanitation guidelines were noted in rat cages, and bedding type affected cage ammonia and ATP concentrations. Periodic spikes of cage ammonia and ATP concentrations were recorded in mouse cages maintained according to inhouse compared with Guide standards and in cages containing aspen compared with cellulose or aspen–cellulose mixed bedding. Ongoing studies and historical data support the finding that deviations or exceptions from the cage density and sanitation frequency standards set forth in the Guide do not negatively affect animal health, welfare, or production parameters at our institution. These parameters appear to be credible measures of animal health and wellbeing and may be useful for evaluating performance standards for animal husbandry.

Detection of mouse parvovirus (MPV) and other murine pathogens in research colonies is dependent on the transmissibility of the agents and the sensitivity of sentinels to those agents. Transmissibility is based on several agent-dependent properties including mode of transmission, infectivity, and environmental stability, whereas host susceptibility can vary according to mouse age, strain, and sex. In this study, 4-wk-old, 12-wk-old, and aged Swiss Webster female sentinel mice were compared for their ability to detect infectious agents by using a standardized health surveillance program, to determine whether sentinels should be replaced more frequently to improve the efficiency of detection of infectious agents within a murine colony. Both experimentally and naturally infected mice were used to transmit MPV and other infectious agents from index mice to sentinels. First, Swiss Webster mice were inoculated with MPV, and transmission to 4-, 12-, and 24-wk-old contact and soiled-bedding sentinels was determined. Second, mice naturally infected with 9 infectious agents were obtained from 2 local pet stores, and transmission to 4-wk-old contact sentinels and 4-, 12-, and 44-wk-old soiled-bedding sentinels was determined. For agents that were transmitted via soiled bedding (MPV, mouse hepatitis virus, murine norovirus, Theiler murine encephalomyelitis virus, and pinworms), transmission did not differ in regard to the age of the sentinels. In conclusion, susceptibility to several infectious agents did not differ according to sentinel age in a health-surveillance protocol that used mice older than 12 wk.

To investigate the infection of newborn mice with mouse parvovirus (MPV), a single MPV-infected mouse was added to each of 15 cages, each of which housed an uninfected breeding pair of Swiss Webster mice just before parturition. Seven litters were left with their parents, and the remaining 8 litters were fostered at postpartum day 1. All dams were shedding MPV at 1 and 2 wk after exposure. Soiled-bedding transmission did not differ between cages with and without litters. Half the foster dams but none of the fostered pups seroconverted to MPV. None of the pups left with their birth mothers had MPV DNA in their feces at 3 or 6 wk after exposure, but pups in 6 of 7 litters were MPV seropositive at 6 wk. To investigate MPV infection of older neonatal mice, 9 dams with 7-d-old litters and 9 dams with 14-d-old litters each were exposed to an MPV-infected mouse. At weaning, pups exposed to MPV at 7 or 14 d of age were shedding MPV and were seronegative but became seropositive by 6 wk of age and transmitted the infection to sentinels. In conclusion, fostering of pups had no benefit and may spread infection because the pups may act as fomites, infecting the foster dam. Infection of 7- or 14-d-old mice likely occurred because maternal antibodies had not been transferred to the progeny before they began to ingest MPV-laden feces.

Helicobacter pullorum is an enterohepatic Helicobacter spp. known to infect both chickens and humans. H. pullorum infection has recently been reported in both mice and rats. This study was designed to determine whether standard methods of colony health surveillance using exposure to rodent soiled bedding could detect H. pullorum in Sprague–Dawley rats. We exposed 8 Helicobacter-free Sprague–Dawley rats to bedding from H. pullorum-infected Brown Norway rats. Fecal samples were analyzed by PCR every 2 wk for 22 wk. Dirty bedding transfer resulted in intermittent positive fecal PCR results; however, none of the rats became persistently infected with H. pullorum. Select intestinal tissues collected at necropsy analyzed by PCR were negative for H. pullorum. To determine whether the failure to detect H. pullorum in Sprague–Dawley rats receiving contact bedding was due to resistance of Sprague–Dawley rats to H. pullorum colonization, 10 Helicobacter-free Sprague–Dawley rats were orally dosed with H. pullorum. Fecal samples were analyzed by PCR every 2 wk for 12 wk. At 2 wk after infection, 5 of 10 rats were PCR positive for H. pullorum. By 12 wpi, only 2 rats were persistently colonized with H. pullorum according to culture and PCR results. These data contrast with our previous data, which showed a high frequency of both natural and experimental H. pullorum infection in Brown Norway rats. Sprague–Dawley rats are resistant to experimentally induced H. pullorum gastrointestinal colonization when dosed orally with H. pullorum or exposed to bedding from H. pullorum-infected rats.

Tail biopsy in mice is a common procedure in genetically modified mouse colonies. We evaluated the anesthetic and analgesic effects of various agents commonly used to mitigate pain after tail biopsy. We used a hot-water immersion assay to evaluate the analgesic effects of isoflurane, ice-cold ethanol, ethyl chloride, buprenorphine, and 2-point local nerve blocks before studying their effects on mice receiving tail biopsies. Mice treated with ethyl chloride spray, isoflurane and buprenorphine, and 2-point local nerve blocks demonstrated increased tail-flick latency compared with that of untreated mice. When we evaluated the behavior of adult and preweanling mice after tail biopsy, untreated mice demonstrated behavioral changes immediately after tail biopsy that lasted 30 to 60 min before returning to normal. The use of isoflurane, isoflurane and buprenorphine, buprenorphine, 2-point nerve block, or ethyl chloride spray in adult mice did not significantly improve their behavioral response to tail biopsy. Similarly, the use of buprenorphine and ethyl chloride spray in preweanling mice did not improve their behavioral response to tail biopsy compared with that of the untreated group. However, immersion in bupivacaine for 30 s after tail biopsy decreased tail grooming behavior during the first 30 min after tail biopsy. The anesthetic and analgesic regimens tested provide little benefit in adult and preweanling mice. Given that tail biopsy results in pain that lasts 30 to 60 min, investigators should carefully consider the appropriate anesthetic or analgesic regimen to incorporate into tail-biopsy procedures for mice.

Buprenorphine HCl is a common analgesic for laboratory mice undergoing surgical procedures. The documented duration of action of buprenorphine HCl is as short as 3 to 5 h in mice, potentially necessitating readministration for continued analgesia. A long-acting buprenorphine formulation would reduce handling-associated stress and provide uninterrupted analgesia. This study used the hot-plate assay to assess the antinociceptive effects of a single injection of sustained-release buprenorphine (bup-SR), buprenorphine-HCl (bup-HCl), and saline over 72 h in young adult male BALB/cJ and SWR/J mice. SWR/J mice had shorter baseline latencies than did BALB/cJ mice, possibly reflecting greater sensitivity to thermal nociception. Relative increase from baseline latency (% maximal possible effect) was significant for buprenorphine-SR at 2, 6, and 12 h compared with saline. According to results from a hot-plate assay, the analgesic efficacy of buprenorphine-SR appears to last at least 12 h in male BALB/cJ and SWR/J mice.

In vivo bioluminescent imaging (BLI) is a sensitive and reliable technique for studying gene expression, although experiments must be controlled tightly to obtain reproducible and quantitative measurements. The luciferase reaction depends on the availability of the reaction substrate, oxygen, and ATP, the distribution of which can vary markedly in different tissues. Here we used in vivo fiber optic technology, combined with stereotaxis-assisted surgery, to assess luciferase reaction kinetics in response to 2 anesthetic regimens, isoflurane and ketamine–xylazine. Transgenic rats that expressed luciferase under the control of the human prolactin promoter were used as a model organism. Anesthesia had a marked effect on luciferase reaction kinetics. The rise time to peak emission differed by 20 min between isoflurane and ketamine–xylazine. Optical imaging using a charge-coupled–device camera confirmed this delay. These results demonstrate that different anesthetics can have substantial effects on luciferase reaction kinetics and suggest that the timing of image acquisition after substrate injection should be optimized in regard to experimental conditions and the tissues of interest.

Intraarterial chemotherapy (IAC) is considered effective for the treatment of solid tumors with high local doses of systemically toxic chemotherapeutics. Osteosarcoma, which is often located in the extremities, is a potential target for IAC. However, the efficacy of this treatment modality has varied, and standardized protocols are difficult to establish due to tumor heterogeneity and the limited numbers of patients available for clinical trials. Reproducible experimental models are needed to further investigate IAC in osteosarcoma. Here, we describe a new microsurgical technique for repeated infusion of drugs into the mouse femoral artery for local treatment of experimental intratibial metastasizing osteosarcoma. We successfully achieved 5 catheterizations at 3-d intervals in 70% of the mice tested. Laser speckle imaging indicated a maximal 50% reduction in blood flow around the ankle region of catheterized legs infused with 0.5 mg/kg cisplatin. However, blood flow in the front feet was affected only minimally. Histologic examination of catheterized arteries of saline control or cisplatin-treated mice showed circular fibrinoid media necrosis and partial thrombosis, but total occlusion of the arteries was not observed. The method we describe for repeated transient catheterization of the mouse femoral artery likely will be useful in future studies comparing the efficacies of intraarterial and systemic cisplatin treatment of intratibial metastasizing osteosarcoma in mice under standardized conditions.

Perioperative treatment of several rats in our facility with ketoprofen (5 mg/kg SC) resulted in blood loss, peritonitis, and death within a day to a little more than a week after surgery that was not related to the gastrointestinal tract. Published reports have established the 5-mg/kg dose as safe and effective for rats. Because ketoprofen is a nonselective nonsteroidal antiinflammatory drug that can damage the gastrointestinal tract, the putative diagnosis for these morbidities and mortalities was gastrointestinal toxicity caused by ketoprofen (5 mg/kg). We conducted a prospective study evaluating the effect of this therapeutic dose of ketoprofen on the rat gastrointestinal tract within 24 h. Ketoprofen (5 mg/kg SC) was administered to one group of rats that then received gas anesthesia for 30 min and to another group without subsequent anesthesia. A third group was injected with saline followed by 30 min of gas anesthesia. Our primary hypothesis was that noteworthy gastrointestinal bleeding and lesions would occur in both groups treated with ketoprofen but not in rats that received saline and anesthesia. Our results showed marked gastrointestinal bleeding, erosions, and small intestinal ulcers in the ketoprofen-treated rats and minimal damages in the saline-treated group. The combination of ketoprofen and anesthesia resulted in worse clinical signs than did ketoprofen alone. We conclude that a single 5-mg/kg dose of ketoprofen causes acute mucosal damage to the rat small intestine.

Long-term oral administration of immunosuppressive agents to transplanted rhesus monkeys (Macaca mulatta) is one of the major challenges in such studies. To avoid the drawbacks of gavage, we tested an alternative method for oral dosing of sirolimus in rhesus monkeys by adding sirolimus, a commonly used immunosuppressant, to gelatin to create drug-containing gelatin 'treats' that our macaques would accept voluntarily. We evaluated the oral bioequivalence of the oral solution and drug-containing gelatin and assayed the whole-blood levels of sirolimus after long-term drug delivery. We found that time to peak concentration but not peak concentration itself or the area under the time–concentration curve differed between the 2 groups. Although the maximal concentration data did not fit the condition of bioequivalence, those for the time–concentration curves from 0 to 24 h and from 0 h to infinity did; therefore the extent of sirolimus absorption did not differ significantly between the 2 formulations. The sirolimus levels for long-term drug delivery were equivalent at 2.97 ± 1.91 ng/mL in the gelatin group and 3.13 ± 2.03 ng/mL in the solution group. The gelatin dosing technique we describe here is convenient and effective for oral administration of sirolimus in rhesus monkeys and likely can be adapted for other drugs.