Journal of the American Association for Laboratory Animal Science : JAALAS最新文献

To maintain rodent colonies free from harmful infectious agents, laboratory animal care programs frequently employ the use of sterilized caging and supplies. Sterilized caging is important for preventing the spread of infectious pathogens from contaminated fomites, for biocontainment, and for safety. We designed several experiments to determine the effects of commonly encountered processes on steam penetration and substrate heat exposure. We used biologic indicators as a proxy for steam penetration. We used the time bedding spent above 121 °C as a proxy for substrate cumulative heat exposure. This temperature was measured using a high-temperature data logger. We first examined the effect of stacking cages with various bedding types on steam penetration. We then autoclaved soiled bedding and studied the variables of bedding type, bagging style, presence of diet and water in the cage, and amount of time between cage change out on steam penetration and cumulative heat exposure. For clean bedding, we found adequate steam penetration regardless of bedding type, cycle program, or location of the cage in the bulk autoclave. For the soiled bedding experiments, there were no differences between bedding types noted. Placement of cages inside plastic bagging increased the amount of time the bedding spent above 121 °C on average but not significantly. There was no difference in steam penetration of bedding or time spent above 121 °C for 2- or 4-wk cage change-out schedules. When cages were autoclaved with diet and water, the time the bedding spent above 121 °C was significantly less than when autoclaving bedding alone, but there was adequate steam penetration for all cages. This study demonstrates that common practices in the industry are effective. Based on the results of this study, it is recommended that each institution evaluate their autoclaving practices and confirm that those practices are sufficient and effective.

Corynebacterium bovis (Cb), the etiologic agent of Corynebacterium-associated hyperkeratosis (CAH) in nude mice, may impact research outcomes. Little is known about the differences in the course and severity of CAH in different outbred athymic nude mice stocks. Three genetic stocks (designated A, B, and C), 1 of which was obtained from 2 geographically separate colonies with distinct microbiota (A1 and A2), were inoculated topically with 1 × 108 cfu of a pathogenic Cb field isolate (no. 7894; n = 6/stock) or sterile media (n = 2/stock; controls). Clinical signs were assessed daily and scored 0 to 5 based on lesion severity. Mice were euthanized at 14 (A1, A2, B, and C) or 28 (B) days postinoculation (dpi), macroscopic changes were documented, and 6 skin samples per mouse were obtained and histologically scored 0 to 4 based on the presence and severity of hyperkeratosis, acanthosis, inflammation, and bacterial colonies. No stock A1 or control mice developed clinical disease; 1 of 6 stock B mice developed mild CAH (mean peak clinical score [MPCS]: 0.33) at 14 dpi (14-d group); 2 of 6 stock B (28-d group) developed mild CAH at 15 dpi (MPCS: 0.33); and all stock C and A2 mice developed significant clinical signs at 5 dpi (MPCS: 2.5 and 3, respectively), which resolved by 11 dpi. Despite differences in clinical presentation, all Cb-infected mice had hyperkeratosis and/or acanthosis with associated bacterial colonies. Stocks A1 and B, which had minimal or no clinical signs, were colonized with Corynebacterium amycolatum (Ca). In contrast, stocks C and A2 were not colonized with Ca, raising the possibility that Ca and/or other components of the skin microbiota may mitigate clinical signs but not necessarily all histopathologic changes associated with infection. These findings suggest host genetics and/or the skin microbiota can markedly influence the presentation of CAH in nude mice.

Dystocia, a common murine reproductive condition, is classified as either obstructive, a result of fetal factors such as an oversized fetus, or functional, a result of dam factors such as advanced age. Treatment is based on the dam's clinical condition and the underlying etiology, but usually requires euthanasia. A prospective study was conducted to characterize the etiology of murine dystocia to determine if treatment is warranted. The signalment and experimental, clinical, and breeding histories were obtained, and a targeted serum chemistry panel, radiographs, and a gross necropsy were conducted on mice presenting with clinical signs consistent with dystocia. Obstructive dystocia was diagnosed if the pelvic canal width was less than the diameter of the fetal head closest to the cervix or a fetus was lodged in the pelvic canal. Functional dystocia was diagnosed based on clinicopathologic abnormalities. A total of 54 mice were evaluated over 7 mo with 45/54 (83%) confirmed to have dystocia with the remaining 9 (17%) having other reproductive abnormalities. Of the confirmed cases, 27/45 (60%) were C57BL/6 or on a C57BL/6 background, and the average age at presentation was 181 ± 85 d. The number of mice categorized as having an obstructive (n = 16) compared with a functional (n = 11) dystocia was not significantly different than those in which the definitive category could not be ascertained (n = 18). Neither clinical signs nor clinical pathology were significantly different between mice categorized as having an obstructive compared with a functional dystocia. Hunched posture, lethargy, and vaginal discharge were the most common presentation. Azotemia (BUN: 66.6 ± 10.2 mg/dL, mean ± SE), hypoglycemia (96.11 ± 8.5 mg/dL), and hyperglobulinemia (3.13 ± 0.14 mg/dL) were common. Differentiating obstructive from functional dystocia could not be determined cageside with strong confidence.

Social housing remains one of the best forms of environmental enhancement for nonhuman primates (NHPs). The gradual steps (GS) method, a 2-step plan involving an initial phase of limited physical contact (protected contact [PC]) prior to full contact (FC), is widely used for introducing macaque pairs. Recent evidence has suggested that administration of diazepam prior to FC introduction, without a PC phase, improves the success rate of pairings among adult male rhesus macaques (Macaca mulatta). Nevertheless, given the popularity of the standard GS method, there is considerable interest in using diazepam along with this technique. We hypothesized that administering a single dose of diazepam prior to the PC phase would improve the success rates of isosexual pairings of unfamiliar adult macaques. Twelve males and 12 females were studied in each of 3 groups, with 2 different doses of oral diazepam (2.5 or 3.2 mg/kg) and controls introduced without diazepam. Pairs were deemed successful after 14 consecutive days of compatible FC housing. Among males, success rates for the low diazepam, high diazepam, and control groups were 67%, 50%, and 67%, respectively. Among females, the corresponding values were 50%, 33%, and 17%. There were no significant differences in overall introduction success rates for either sex. However, among females, the success rates during the initial PC phase were significantly higher in introductions involving the lower dose of diazepam (83%) than among controls (33%). Descriptively, in both sexes, less severe wounding patterns were observed with the lower dose compared with either the high dose or control groups. Our results suggest that diazepam administration prior to the PC phase of the GS method does not improve pairing outcomes for either sex in rhesus macaques. However, diazepam may have some utility in moderating wounding during unsuccessful introductions.

Soft-pelleted, high-fat diets (HFD) are greasy and crumble easily leading to food wastage and hair coat grease accumulation when mice are fed using commercially available feeders. The ideal HFD feeder design should reduce food wastage, facilitate mouse weight gain, and minimize variables such as hair coat grease accumulation that have the potential to alter scratching behaviors. Our study compared the feeding efficiency of 2 commercially available feeders (feeders A and E) to 4 novel feeder designs (feeders B, C, D, and F). Novel feeders had alterations in feeding aperture size, feeding surface area, feeder configuration, and level of food presentation. Male C57BL/6NCrl mice (n = 120; 4/cage) were randomly assigned to cages containing one of the 6 feeder types and were fed HFD for 12 wk. Feeders and cage bottoms were weighed before use and then weekly at the time of cage change. Mice were weighed before starting the HFD and then biweekly. Scratching behavior was video recorded at 0, 4, 8, and 12 wk. Hair coat grease accumulation was visually scored biweekly. Feeder A use was associated with the highest feed cost due to HFD wastage ($36.98 ± 1.54/cage/wk). Mice fed using Feeder A had the highest average weight gain (23.75 ± 0.8 g, P < 0.005). However, mice also had significantly higher hair coat grease accumulation scores (P < 0.05) and significantly increased scratching frequency at 4 wk (P < 0.05) when compared with mice fed using other feeder types. Novel feeder designs utilized 10 to 21 times less HFD dispensed when compared to feeder A. Mice fed using novel feeders also displayed improved welfare, as evidenced by low hair coat grease accumulation scores, and no significant differences in scratching frequency when compared with baseline behavior.

The Whitten effect is a widely used tool for manipulating the mouse estrous cycle and generating reproductively active females within the laboratory setting. Typically, peak numbers of sexually receptive mice occur following exposure to male pheromones, resulting in a higher number of successful copulations on the third day after exposure. Although this method has improved efficiencies, the percentage of females mated and subsequently deemed to be pregnant/pseudopregnant remains relatively low, around 50%. In experiment 1, we aimed to 1) further understand cyclicity; 2) determine whether the initial cycle stage plays an importance on day 3 receptivity; and 3) identify any repetitive patterns/cycle stabilization. Mice (n = 27) were assigned to group cages according to cycle stage (proestrus, estrus, metestrus, diestrus). Experiment 2 was developed to determine an optimum treatment to promote receptivity by exposure to various pheromone stimuli. Mice (n = 45) were randomly assigned to 5 treatment groups (PBS-treated sham soiled bedding, male soiled bedding, live male, pregnant females, and lactating females). In both experiments, daily vaginal cytology was performed for 21 days to determine the cycle stage. Results from experiment 1 indicate that the initial cycle stage did not contribute to day 3 receptivity, although synchronization within several groups/cages was noted, and that the greatest numbers of estrous animals were obtained on days 6 and 7. Experiment 2 revealed that exposure to live males and lactating females both significantly improved receptivity compared with the PBS, male soiled bedding, and pregnant female groups. These results indicate that current strategies used for routine synchronization could be further improved through alternative housing regimens without compromising animal welfare.

Unnecessary and excessive fluid therapy increases the risk of adverse effects such as pulmonary edema. To prevent this, a mini-fluid challenge (MFC) has been utilized to predict whether fluid therapy will improve circulatory dynamics in human intensive care medicine. The study described here investigated whether MFC is also efficacious in pigs. Thirty-two domestic pigs anesthetized and maintained under mechanical ventilation were treated with successive IV fluid administrations of 2, 1, 1, and 2 mL/kg over a 10-min period for a total dose of 6 mL/kg of Ringer lactate. The percentage increase in mean arterial pressure (MAP) at 2, 3, and 4 mL/kg of cumulative fluid administration was examined to determine whether responders could be identified that would benefit hemodynamically from higher doses of fluids. For the purposes of this study, a 10% increase or more in MAP after 6 mL/kg of fluid administration defined responders, and an increase of less than 10% in MAP was used to define nonresponders. The percentage increase in MAP at 2, 3, and 4 mL/kg fluid administration was evaluated to determine whether this could predict responder status. Eleven of the 32 animals were determined to be responders. Responder status was predicted with high accuracy by the administration of 3 mL/kg (AUC = 0.98) and was moderately predicted with administration of 2 mL/kg (AUC = 0.80), as well as pulse pressure variation (AUC = 0.75). Thus, MFC may be helpful to maintain tissue perfusion in pigs through the use of managed fluid therapy.

Mice are the most commonly used models of infectious disease, and disease in mice is similar to that of humans. As a consequence, standard hematology and biochemistry reference values in mice are essential to evaluate functional changes caused by experimental treatments, although very few data in the literature provide a comparative reference range. The aim of this investigation was to establish the reference intervals for major hematology and biochemistry analytes in 2 inbred mouse strains, BALB/c and C57BL/6, at 3 different age ranges. Parameters were assessed in 600 mice (300 male and 300 female) of BALB/c and C57BL/6 strains at 6 to 8 wk, 10 to 14 wk, and 6 to 9 mo of age. Reference intervals were calculated by nonparametric or robust methods according to sample size, and statistical analyses were performed to assess the changes in relation to sex, age, and strain. The data demonstrate that strain, sex, and age have significant effects on the hematologic and biochemical profiles of mice. Hemoglobin, Hct, MCH, MCHC, neutrophils, eosinophils, and ALP were found to be significantly greater in BALB/c mice. In contrast, WBC, lymphocytes, basophils, glucose, total protein, albumin, and urea were found to be significantly greater in C57BL/6 mice in all age ranges. Lymphocytes and ALP progressively decreased with age, while neutrophils increased with age in both strains. The study successfully defined and established reference intervals for hematologic and biochemical analytes in 2 inbred mouse strains at 3 different age ranges. The reference values reported here could be useful in characterizing the phenotype of experimental mice and assessing the changes caused by investigational treatments.

Peromyscus species have been used in research for decades, yet there are no specific reports of mite infestations in the laboratory setting despite many reports of various mite species found in wild Peromyscus. This study documents P. californicus infestation with Radfordia lemnina in an academic research setting. During the colony quarantine period, deer mice tested positive on a general mite PCR but negative on all species-specific mite PCR assays. Tape tests were performed on a subset of cages, and 21% were positive for adult mites or viable eggs. Mites were sent for sequencing and identified as R. lemnina, for which the natural host is Microtus pennsylvanicus. The entire colony was treated with selamectin, applied topically to the nape of the neck, and repeated one month later. All deer mice were successfully treated using a novel method of restraint, and no gross adverse reactions to selamectin treatment were noted. Tape tests were performed weekly to biweekly on a subset of deer mice, and PCR was used to confirm negative tape test results. PCR was positive at 14 wk posttreatment, and tape tests were intermittently positive for egg casings for 27 wk, indicating continued presence of genetic material but not necessarily an active infection. Weaned offspring were tape test and/or PCR negative at 12 and 21 wk posttreatment, providing further support for successful treatment. At 31 wk, 2 rounds of tape tests and PCR were both negative. This report documents a safe and effective treatment method for mites in P. californicus.