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Median lethal dose (LD50) testing in mice is the 'gold standard' for evaluating the lethality of snake venoms and the effectiveness of interventions. As part of a study to determine the murine LD50 of the venom of 3 species of rattlesnake, temperature data were collected in an attempt to more precisely define humane endpoints. We used an 'up-and-down' methodology of estimating the LD50 that involved serial intraperitoneal injection of predetermined concentrations of venom. By using a rectal thermistor probe, body temperature was taken once before administration and at various times after venom exposure. All but one mouse showed a marked, immediate, dose-dependent drop in temperature of approximately 2 to 6°C at 15 to 45 min after administration. The lowest temperature sustained by any surviving mouse was 33.2°C. Surviving mice generally returned to near-baseline temperatures within 2 h after venom administration, whereas mice that did not survive continued to show a gradual decline in temperature until death or euthanasia. Logistic regression modeling controlling for the effects of baseline core body temperature and venom type showed that core body temperature was a significant predictor of survival. Linear regression of the interaction of time and survival was used to estimate temperatures predictive of death at the earliest time point and demonstrated that venom type had a significant influence on temperature values. Overall, our data suggest that core body temperature is a useful adjunct to monitoring for endpoints in LD50 studies and may be a valuable predictor of survival in venom studies. more...

Ulcerative dermatitis (UD) is a common syndrome of unknown etiology that results in profound morbidity in C57BL/6 mice and lines on a C57BL/6 background. The lesions are due to severe pruritus-induced self-trauma, progressing from superficial excoriations to deep ulcerations. UD may be behavioral in origin, with ulcerative lesions resulting from self-mutilating behavior in response to unresolved inflammation or compulsion. Alternatively, abnormal oxidative damage may be a mechanism underlying UD. To evaluate whether UD behaves similarly to normal wounds, consistent with a secondary self-inflicted lesion, or is a distinct disorder with abnormal wound response, we evaluated expression levels of genes representing various arms of the oxidative stress response pathway UD-affected and unwounded C57BL/6J mice. No evidence indicated that UD wounds have a defect in the oxidative stress response. Our findings are consistent with an understanding of C57BL/6 UD lesions as typical rather than atypical wounds. more...

Ulcerative dermatitis (UD) is a genetically linked syndrome that affects the neck, torso, and facial regions of C57BL/6 mice and strains with C57BL/6 background. In this study, 96 mice with skin ulcerations in 3 different regions of the body and 40 control animals without ulcerated lesions were evaluated histologically for the presence of hair-induced inflammation in the oronasal cavity. We found that 73.5% (100 of 136) of the mice had hair-induced periodontitis, glossitis, or rhinitis regardless of the presence or absence of UD. Of those mice with UD, 93.9% had hair-induced oronasal inflammation. The mandibular incisors were the most commonly affected site (64.6%), followed by the maxillary molars (20.8%), maxillary incisors (16.7%), tongue (16.7%), nasal cavity (10.4%), and mandibular molars (7.3%). In addition, oronasal hair-induced inflammation occurred in 25% (10 of 40) of the control mice. Here we show a significant association between UD and hair-induced inflammatory lesions of the oronasal cavities. more...

The etiologic agent of mandibulofacial and maxillofacial abscesses in mice is reportedly coagulase-positive Staphylococcus aureus. Although suggested to be through the oral cavity, the exact route of entry has not been documented. Among the clinical cases of mandibulofacial and maxillofacial abscess we report here, each case that was cultured yielded coagulase-positive S. aureus. Histologically, all of the abscesses examined were directly associated with intralesional hair shafts, both vibrissae and pelage, that were introduced into the submucosa via the maxillary or mandibular molar gingival sulci. Grossly, a variable amount of hair was imbedded in the lingual, buccal, or mesial gingival sulci of the maxillary or mandibular molars or both. Computed tomography revealed that the presence of the hair resulted in inflammation and resorption of alveolar bone. With these findings, we propose that mandibulofacial and maxillofacial abscesses are induced by the mastication and fragmentation of hair ingested during the barbering process. From the resulting foreign body periodontitis, abscess formation originates at the maxillary lingual, buccal, or mesial gingival sulci, resulting in infection of the maxillary molar tooth roots with swelling or rupture through the skin inferior to the eye, or at the mandibular lingual, buccal, and or mesial gingival sulci, resulting in infection of the mandibular molar tooth roots and osteomyelitis with drainage through the skin of the ventral mandible. more...