Maternal Weight Gain as a Predictor of Litter Size in Swiss Webster, C57BL/6J, and BALB/cJ mice.

An important task facing both researchers and animal core facilities is producing sufficient mice for a given project. The inherent biologic variability of mouse reproduction and litter size further challenges effective research planning. A lack of precision in project planning contributes to the high cost of animal research, overproduction (thus waste) of animals, and inappropriate allocation of facility resources. To examine the extent daily prepartum maternal weight gain predicts litter size in 2 commonly used mouse strains (BALB/cJ and C57BL/6J) and one mouse stock (Swiss Webster), we weighed ≥ 25 pregnant dams of each strain or stock daily from the morning on which a vaginal plug (day 0) was present. On the morning when dams delivered their pups, we recorded the weight of the dam, the weight of the litter itself, and the number of pups. Litter sizes ranged from 1 to 7 pups for BALB/cJ, 2 to 13 for Swiss Webster, and 5 to 11 for C57BL/6J mice. Linear regression models (based on weight change from day 0) demonstrated that maternal weight gain at day 9 (BALB/cJ), day 11 (Swiss Webster), or day 14 (C57BL/6J) was a significant predictor of litter size. When tested prospectively, the linear regression model for each strain or stock was found to be accurate. These data indicate that the number of pups that will be born can be estimated accurately by using maternal weight gain at specific or stock-specific time points.

Irradiated compared with nonirradiated NSG mice for the development of a human B-cell lymphoma model.

NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice are a superior strain for the engraftment of human tumors, as they provide an ideal model to explore the potency, toxicity, and dosage of therapeutic drugs. Although whole-body nonlethal irradiation is often performed to enhance engraftment, the need for irradiation to establish a human B-cell lymphoma model using the NSG strain has not been addressed. In the current study, a mouse model of B-cell lymphoma was established by intravenous injection of human B-cell lymphoma Z138 cells into mice with and without irradiation. Tumor development, signs of engraftment, survivability of engrafted mice, histopathology, and immunohistochemistry were evaluated. Potential sex-associated variations in the model were assessed also. Irradiation of NSG mice did not enhance tumor cell engraftment, and nonirradiated animals had increased survivability. Mice with irradiation survived for a median of 27 d before being euthanized due to signs of morbidity, whereas those without irradiation had a median survival of 35 d. Both irradiated and nonirradiated mice were normal in activity until 3 wk after the injection of cells. At that time, the mice started to show signs of lymphoma including ruffled fur, decreased activity, and hindlimb paralysis. There were no significant differences in evaluated parameters between male and female mice. Therefore, we conclude that a model of B-cell lymphoma can successfully be established by using Z138 cells in nonirradiated male and female NSG mice.

Hypothermic endpoint for an intranasal invasive pulmonary aspergillosis mouse model.

Immunocompromised mice were infected intranasally with Aspergillus fumigatus as part of a vaccine efficacy study. Although body temperature was measured throughout the study, a formal evaluation of its usefulness as an endpoint criterion was not performed. We retrospectively evaluated survival data and temperature records to determine whether body temperature can be used as an objective predictor of death and included in the humane endpoint criteria for this mouse model. CF1 mice were immunosuppressed with either cortisone acetate or by treatment with antiGR1 (a neutrophil-depleting antibody) and then intranasally challenged with A. fumigatus. Body temperature was measured by using an infrared noncontact thermometer a maximum of 3 times daily until death or euthanasia. A surface body temperature below 29.0 °C was correlated with a poor chance of survival, and using this cutoff point with signs of morbidity (hunched, ruffled fur, respiratory distress) reliably indicates mice for euthanasia without negatively affecting data collection. Using 2 subsequent readings of less than 31.0 °C as an endpoint would have led to premature euthanasia of only one mouse (2.2%). As a single reading, a body temperature of 28.8 °C had a sensitivity of 92.2% and specificity of 90.9%. Hypothermia proved to be a useful addition to the humane endpoint criteria for this mouse model, and veterinary and research groups should discuss their study needs in relation to animal welfare to best determine the most appropriate means of including this parameter.

Assessment of carprofen and buprenorphine on recovery of mice after surgical removal of the mammary fat pad.

The purpose of this study was to determine the level of pain elicited by mammary fat pad removal surgery and the effects of postoperative analgesics on recovery. Female FVB mice were anesthetized, and mammary fat pad removal was performed. After surgery, mice received carprofen, buprenorphine, a combination of carprofen and buprenorphine, or saline treatment. Additional mice received anesthesia but no surgery or treatment. Food and water intake, body weight, wheel running activity, and a visual assessment score were recorded daily for 4 d after surgery and compared with presurgical findings. Corticosterone metabolites in fecal samples were analyzed at 12 and 24 h postsurgically and compared with baseline values. All surgical groups had significantly decreased food intake at 24 h, with a return to baseline by 48 h. The combination treatment resulted in a significantly decreased water intake and body weight at 24 h. All surgical groups had significantly decreased wheel running activity at 24 h only. The visual assessment scores indicated mild pain for all surgical groups, with the buprenorphine treated mice showing the highest pain index scores, as compared with nonsurgical controls. Fecal corticosterone metabolite levels did not differ significantly between any of the groups or across time. The parameters used in this study did not indicate that administration of these analgesic regimens improved recovery as compared with that of saline-treated mice. Care should be taken when using visual assessment scores to evaluate pain in mice, given that analgesics may have side effects that inadvertently elevate the score.

Mode of ethanol administration influences the severity of hemorrhage-induced lactic acidemia in conscious guinea pigs.

Mechanisms that limit metabolic acidemia during shock are limited by ethanol (EtOH). This may be due to (1) loss of respiratory compensation, (2) a greater fall in cardiac output, (3) altered removal of plasma lactate by the liver, and (4) alterations in central nervous system orchestration of compensatory responses. We have previously shown that loss of metabolic compensation during hemorrhage is correlated with plasma EtOH concentrations. The present study determines if the mode of ethanol administration influences compensation during hemorrhage. Male guinea pigs were administered EtOH (1 g/kg, 30% wt/vol) via intraperitoneal (IP) or intragastric (IG) routes. After 30 minutes, 60% of the estimated blood volume was removed. Animals remained in shock for 30 minutes were resuscitated with lactated Ringer solution and monitored for 3 hours. Plasma EtOH levels were similar in the 2 groups at the initiation of, and during, hemorrhage and resuscitation. Animals given EtOH IP exhibited more severe acidemia. The mode of EtOH administration may affect hepatic ethanol and lactate metabolism, thus exacerbating acidemia. An altered central nervous system response may impact compensatory responses during shock. Our results indicate that the "history" of the EtOH episode may be an important determinant in the compensation for hemorrhage and resuscitation.

Role of the perifornical hypothalamic monoamine neurotransmitter systems in anorectic effects of endotoxin.

The cachexia-anorexia syndrome, in which patients suffering from chronic illness lack the desire to eat and experience weight loss, creates a serious clinical problem when patients are attempting to overcome the disease process. Endotoxin (ET) has many actions in the brain and peripheral injections can affect regulation of monoamines in brain areas as diverse as the olfactory lobes and the locus coeruleus. Certainly, ET is involved in the febrile process and it plays a prominent role in the regulation of food intake and maintenance of body weight during chronic illnesses. Monoamine neurotransmitters in specific regions of the hypothalamus also participate in the regulation of food intake and body weight and have been well characterized. In this regard, the hypothalamic perifornical nucleus (PFN) is of interest to our lab due to its role in drug-induced anorexia caused by amphetamines. It is also the most sensitive site in the hypothalamic monoaminergic system that involves dopamine (DA) and epinephrine (EPI). DA antagonist, stereotaxically placed in this site, can stimulate feeding, and specific injections of DA or EPI can result in a 70-90% decrease in food intake, even in food-deprived animals. We have shown in our studies that ET in a dose (0.2 mg/kg of lipopolysaccharide) that does not induce noticeable ambulatory (lack of movement) effects (related to malaise) can cause a significant decrease in food intake in lean Zucker rats. We hypothesize that exogenous ET causes an increase in the extracellular concentrations of monoamines in the perifornical hypothalamus, which in turn can mediate the decrease in food intake. Microdialysis was utilized to measure extracellular concentrations of EPI, norepinephrine, 5-hydroxyindoleacetic acid, DA, and serotonin or 5-hydroxytryptamine. These measurements were taken at a post-ET time period that coincides with an ET-induced decrease (4x) in food intake. Extracellular DA and EPI both significantly increased in the PFN in response to injection of ET. Increases in extracellular DA were dose related and were significant (p < 0.05) compared to zero baseline and saline at both doses of ET. No statistically significant differences were found in 5-hydroxyindoleacetic acid, norepinephrine, and serotonin in microdialysates of this part of the hypothalamus. The present data suggest that catecholamines, namely DA and EPI which are known to decrease food intake, in the PFN may be involved in the regulation of decreases in food intake caused by peripherally administered ET. This does not rule out a role for locally produced inflammatory molecules in the brain in this process.

Evaluation of a combination of sodium hypochlorite and polyhexamethylene biguanide as an egg wash for red-eared slider turtles (Trachemys scripta elegans) to suppress or eliminate Salmonella organisms on egg surfaces and in hatchlings.

OBJECTIVE: To evaluate a combination of 2 nonantibiotic microbicide compounds, sodium hypochlorite (NaOCl) and polyhexamethylene biguanide (PHMB), as a treatment to suppress or eliminate Salmonella spp from red-eared slider (RES) turtle (Trachemys scripta elegans) eggs and hatchlings. SAMPLE POPULATION: 2,738 eggs from 8 turtle farms in Louisiana. PROCEDURES: Eggs were randomly sorted into 3 or, when sufficient eggs were available, 4 treatment groups as follows: control, pressure-differential egg treatment with NaOCl and gentamicin, NaOCl and PHMB bath treatment, and pressure-differential egg treatment with NaOCl and PHMB. Bacterial cultures were performed from specimens of eggs and hatchlings and evaluated for Salmonella spp. RESULTS: RES turtle eggs treated with NaOCl and PHMB as a bath (odds ratio [OR], 0.2 [95% confidence interval (CI), 0.1 to 0.3]) or as a pressure-differential dip (OR, 0.01 [95% CI, 0.001 to 0.07]) or with gentamicin as a pressure-differential dip (OR, 0.1 [95% CI, 0.06 to 0.2]) were significantly less likely to have Salmonella-positive culture results than control-group eggs. CONCLUSIONS AND CLINICAL RELEVANCE: Concern over reptile-associated salmonellosis in children in the United States is so great that federal regulations prohibit the sale of turtles that are < 10.2 cm in length. Currently, turtle farms treat eggs with gentamicin solution. Although this has reduced Salmonella shedding, it has also resulted in antimicrobial resistance. Results of our study indicate that a combination of NaOCl and PHMB may be used to suppress or eliminate Salmonella spp on RES turtle eggs and in hatchlings.