Contemporary topics in laboratory animal science最新文献

Two replicate lines of mice, selected for hyperactivity and hypoactivity after ethanol administration, had been enzootically infected with mouse hepatitis virus (MHV) for over a decade. A cessation of breeding program (also known as a "burnout") was implemented to eradicate the virus and was successful in only one of the four lines. Subsequent investigation demonstrated persistent shedding of MHV in two lines of mice for at least 7 weeks. To the author's knowledge, this is the first documented case of clinically inapparent persistent shedding of MHV in mice that are not genetically engineered.

The induction and maintenance of general anesthesia can lead to profound alterations of many organ systems, especially the cardiovascular, pulmonary, and nervous systems. Moreover, distinct from their cardiopulmonary effects, certain anesthetics can induce physiologic and behavioral changes, which may persist after recovery from anesthesia. Knowledge of the effects of anesthesia and anesthetic agents on hematologic measurements is important. Although the effects of anesthesia were clinically unapparent, the effect on levels of circulating blood elements was an important determinant for the results of our study. We sought to evaluate the effect of anesthesia and vehicle injection on the levels of circulating blood elements in C3H/HeN male mice. We used an automated hematology system to obtain complete blood counts with differentials in anesthetized and unanesthetized mice receiving subcutaneous injections of polyethylene glycol (PEG-400). Two days after a 30-min exposure to isoflurane anesthesia, mean white blood cell counts had deceased by 15.4%, mean neutrophil counts had decreased by 26.9%, and mean platelet counts by 11.2% compared with levels in unanesthetized mice. Our results indicate that the effect of anesthesia is an important consideration when circulating blood elements in mice must be measured.

In this study, we compared two endotracheal tubes (cuffed [Murphy Eye type] and uncuffed [Cole type]) and a pediatric laryngeal mask airway (LMA) with respect to their ease of use in rabbits and their capacities to limit waste isoflurane emissions. Animals (New Zealand White, 3.3 to 5.0 kg, n = 8) were sedated with intramuscular ketamine (50 mg/kg) and xylazine (10 mg/kg). After 5 min, the larynx was numbed with cetocaine, an intubation device was positioned, and anesthesia was maintained with isoflurane (2%) in oxygen (1 liter/min). Real-time atmospheric isoflurane emissions were assessed at the rabbit's oral commissure and in the operator's breathing zone (45 cm from the rabbit's nose) by using a portable infrared spectrophotometer. The LMA was placed more easily than was either endotracheal tube, especially by novices. The cuffed tube was positioned more readily than was the uncuffed variant. All three devices emitted isoflurane. The concentrations measured at the oral commissure for the LMA (mean +/- standard error, 8.4 +/- 0.6 ppm) were modestly higher than those acquired for the cuffed (6.7 +/- 0.5 ppm) and uncuffed (6.3 +/- 0.4 ppm) endotracheal tubes; the difference between the LMA and uncuffed tube was significant (P = 0.012). Isoflurane was not detected in the operator's breathing zone. These data show that the uncuffed endotracheal tube (usually used to anesthetize birds and reptiles) and the pediatric LMA can be used in rabbits as readily as a cuffed tube. In addition, our findings indicate that tradeoffs will be required in selecting a delivery system for this species, as the easiest apparatus (the LMA) also emits the most isoflurane waste.

A variety of environmental factors can affect the outcomes of studies using laboratory rodents. One such factor is bedding. Several new bedding materials and processing methods have been introduced to the market in recent years, but there are few reports of their performance. In the studies reported here, we have assessed the cage micro-environment (in-cage ammonia levels, temperature, and humidity) of mice housed on various kinds of bedding and their combinations. We also compared results for bedding supplied as Nestpaks versus loose bedding. We studied C57BL/6J mice (commonly used) and NOD/LtJ mice (heavy soilers) that were maintained, except in one study, in static duplex cages. In general, we observed little effect of bedding type on in-cage temperature or humidity; however, there was considerable variation in ammonia concentrations. The lowest ammonia concentrations occurred in cages housing mice on hardwood bedding or a mixture of corncob and alpha cellulose. In one experiment comparing the micro-environments of NOD/LtJ male mice housed on woodpulp fiber bedding in static versus ventilated caging, we showed a statistically significant decrease in ammonia concentrations in ventilated cages. Therefore, our data show that bedding type affects the micro-environment in static cages and that effects may differ for ventilated cages, which are being used in vivaria with increasing frequency.

Vitamin A toxicosis and vitamin E deficiency was diagnosed in a commercial rabbit-breeding colony and was associated with reproductive abnormalities, abortions, and poor survivability of kits in the breeding colony. Paresis and muscular dystrophy were noted in juvenile rabbits. Another group of New Zealand White rabbits from the same commercial colony was used to assess the effect of vitamin E-based therapy on clinical signs, reproduction, and vitamin A and E serum and liver levels. Blood samples were taken before and after dietary changes and vitamin E therapy. Serum vitamin E remained low after feeding a diet containing the recommended levels of vitamin E. Administration of vitamin E for 2 weeks lowered the serum vitamin A levels and increased the vitamin E serum and liver levels. In conclusion, vitamin E therapy appears to be an effective treatment for hypervitaminosis A.

A female cynomolgus monkey presented clinically with a caudal abdominal mass noted on a prestudy physical examination. No other clinical abnormalities were noted. An ultrasound examination revealed a mass approximately 2 cm in diameter, which contained fluid with a granular "free-floating" appearance. Within a month the mass enlarged and was visible from external examination. Exploratory laparotomy revealed a mass encompassing the uterus, both ovaries, bladder, and rectum. The animal was euthanized under anesthesia, and the mass was removed, examined, and submitted for histopathology. A diagnosis of vaginal and cervical atresia was made. To the author's knowledge, this is the first description of vaginal and cervical atresia in a laboratory nonhuman primate.

Mouse parvovirus (MPV) has been increasingly prevalent in laboratory animal facilities, and the source of infection often can be difficult to determine. After 4 years of sporadic MPV detected in our sentinel mice and continual failure to identify index cases in colony mice, we developed a regimen to house newly arrived vendor mice in large sterile cages with a high stocking density. Some of these mice were retained in isolation after the remaining mice were deployed as sentinels. After detecting MPV seropositive sentinel mice 4 weeks after introduction to the mouse colonies in one facility, the remaining naïve mice that had been previously housed with those sentinels also tested positive for MPV, despite never having been exposed to colony mice. These results suggest that commercially bred mice intended for use as sentinels may, in fact, arrive at animal facilities already infected with MPV. Depending upon numerous factors, including the health surveillance methods used, it is possible that a low prevalence of MPV may exist undetected at rodent vendors.