Some hematological and histopathological effects of the alkaloids gramine and hordenine on meadow voles (Microtus pennsylvanicus).

Meadow voles (Microtus pennsylvanicus) were used to evaluate the relative toxicity of the alkaloids, gramine and hordenine, which are present in reed canarygrass (Phalaris arundinacea) and to assess their effects on the quality of this grass as a forage. One hundred and twenty meadow voles, 31 days of age, were fed gramine (0, 0.125, 0.25, or 0.5% of a nutritionally complete diet) or hordenine sulfate (0, 0.15, 0.31, or 0.62% of the diet) for 21 days. The effects of treatment on growth, mortality, hematology, blood chemistry, and histology of body organs were examined. Approximately one-third of the voles died when fed either 0.25 or 0.50% gramine. Voles that survived on gramine diets had kidney lesions, glycosuria, higher intakes (P less than 0.05), and lower weight gains (P less than 0.01) than control animals. Voles fed 0.25 and 0.50% gramine had increased circulating reticulocyte levels (P less than 0.01) and those fed 0.125% gramine had higher alkaline phosphatase activity (P less than 0.05) than the control voles. Hordenine did not affect vole diet intake, weight gain, or rate of mortality. Voles fed hordenine developed kidney lesions and glucose was detected in the urine of 62% of these animals. Gramine was more toxic than hordenine on a molar equivalent basis.

Effects of halothane and isoflurane on mean arterial blood pressure, heart rate, and respiratory rate in adult Pekin ducks.

Although the cardiovascular and respiratory effects of halothane and isoflurane have been documented in a variety of common mammalian laboratory animals, they have not been investigated in birds. In this study, the effects of halothane and isoflurane anesthesia on respiratory rate, heart rate, heart rhythm, and mean arterial pressure in adult Pekin ducks were evaluated. Both anesthetics significantly increased heart rate and depressed blood pressure and respiration. Halothane induced a more profound alteration in heart rate and respiratory rate. With the ducks under halothane anesthesia, abnormal cardiac rhythms included ventricular fibrillation, ventricular bigeminy, and multifocal ventricular rhythms. Other than cardiac tachycardia, isoflurane induced no changes in cardiac rhythm.

Randomly amplified polymorphic DNA polymerase chain reaction assay for molecular epidemiologic investigation of Pasteurella pneumotropica in laboratory rodent colonies.

After an episode of clinical Pasteurella pneumotropica infection was diagnosed in a C57BL/6N mouse, a randomly amplified polymorphic DNA polymerase chain reaction assay (RAPD-PCR) was developed and used to genetically characterize and differentiate 52 field isolates and laboratory reference strains of P. pneumotropica and related bacteria. A survey of rodents in the facility recovered 36 isolates of P. pneumotropica from 30 mice, six isolates from hamsters, and three isolates from rats during the follow-up investigation. Antibiograms and routine bacteriologic evaluations for morphologic and biochemical characteristics on selective media did not substantively aid in the differentiation of these isolates, but the RAPD-PCR revealed four strains of P. pneumotropica in the colony, two of which were confined to rats and hamsters. The RAPD-PCR unambiguously differentiated Heyl and Jawetz biotypes of P. pneumotropica recovered from mice, identified two additional genetic groups for rat and hamster isolates, and clearly distinguished P. pneumotropica from related bacteria. Most field isolates were genetically consistent with the Jawetz biotype of P. pneumotropica. The RAPD-PCR is a fast, sensitive, and efficient method for identifying genetic differences between strains of the P. pneumotropica complex and can contribute substantially in addressing the epidemiology, pathogenesis, and taxonomic classification of this common opportunistic pathogen.

Pica behavior associated with buprenorphine administration in the rat.

Marked gastric distention was-observed in rats 20 h after they underwent partial hepatectomy under isoflurane anesthesia and received buprenorphine (0.3 mg/kg of body weight) after surgery. Hardwood bedding comprised the bulk of the gastric contents. A study was undertaken to determine the cause of the pica behavior (consumption of non-nutritive substances) and resultant gastric distention. Ten-week-old male Sprague Dawley rats were randomly assigned to one of six groups. Group-1 rats (n = 11) underwent laparotomy under isoflurane anesthesia, with buprenorphine (0.3 mg/kg) administered after surgery. Group-2 rats (n = 12) underwent laparotomy under isoflurane anesthesia with buprenorphine (0.05 mg/kg) administered after surgery. Group-3 rats (n = 24) underwent laparotomy under isoflurane anesthesia, with saline administered after surgery. Isoflurane was administered at the same rate, concentration, and duration for all groups that underwent laparotomy (groups 1 to 3). Buprenorphine or saline was administered subcutaneously as a single injection when anesthesia was discontinued (groups 1 to 3). Group-4 rats (n = 6) received buprenorphine (0.3 mg/kg) only. Group-5 rats (n = 6) received buprenorphine (0.05 mg/kg) only. Group-6 rats (n = 12) received saline only. Rats not undergoing laparotomy (groups 4 to 6) received buprenorphine or saline 18 to 20 h before euthanasia. Rats were housed individually in filter-topped polycarbonate cages containing hardwood bedding. A purified, pelleted diet and water were offered ad libitum. Food and water consumption were measured over the posttreatment period. Eighteen to 20 h after treatment, rats were euthanized, each stomach and its contents were weighed, contents were examined grossly, and wet and dry gastric content weights were recorded. All weights were significantly (P < 0.05) increased in rats receiving buprenorphine administered after surgery (groups 1 and 2), compared with rats of the control group (group 3). Weights of the stomach and contents, wet gastric contents, and dry gastric contents were significantly (P < 0.05) increased in rats receiving 0.3 mg of buprenorphine/kg only (group 4), compared with values for their controls (group 6). Hardwood bedding comprised the bulk of the gastric contents in all groups receiving buprenorphine. Stomachs of rats not receiving buprenorphine contained the purified diet with little or no hardwood bedding. These results indicate that a single injection of buprenorphine at a dosage of 0.05 or 0.3 mg/kg resulted in rats ingesting hardwood bedding, leading to gastric distention. It was concluded that pica behavior associated with administration of buprenorphine should be considered when evaluating experimental data from rats housed on contact bedding.

Neuropathologic findings associated with seizures in FVB mice.

The FVB mouse is used extensively in transgenic research because of its defined inbred background, superior reproductive performance, and prominent pronuclei, which facilitate microinjection of genomic material. Seizures associated with a known mutation and seizure-susceptible inbred strains are well documented in mice; however, to the authors' knowledge, seizures in the FVB strain have not been evaluated. Affected nonmanipulated FVB/N (n = 5) and transgenic FVB/N mice generated, using eight unrelated transgenic constructs (n = 63), were submitted for pathologic examination. Most cases were detected during routine observations in animal rooms; however, seizure induction by tail tattooing, fur clipping, and fire alarms has been observed. The majority of mice were female (62 of 68), with mean age of 5.8 months (range, 2 to 16 months). Observations made during seizure presentation in 12 of 68 mice included facial grimace, chewing automatism, ptyalism with matting of the fur of the ventral aspect of the neck and/or forelimbs, and clonic convulsions that frequently progressed to tonic convulsions and death. Four mice were dead at presentation, with matting of the fur of the neck and forelimbs. The remainder of the mice had nonspecific signs of disease, such as lethargy, moribundity, or matting of the fur. Vendor and in-house animal health surveillance reports indicated that mice were seronegative to all murine pathogens. Results of gross pathologic examination were unremarkable. Microscopic findings were limited to the brain and liver. In all mice, neuronal necrosis was present in the cerebral cortex, hippocampus, and thalamus. Concurrent astrocyte hypertrophy, as evidenced by an increase in glial fibrillary acidic protein staining, was detected. Acute coagulative necrosis of centrilobular hepatocytes was present in the liver of some cases (19 of 68). Infective agents were not detected in selected brain specimens submitted for electron microscopy or in brain and liver specimens evaluated by use of special stains. Cytopathologic effect was not observed in 3T3, Vero, and BHK-21 cell lines inoculated with brain and liver specimens. The ischemic neuronal necrosis observed in these mice is consistent with lesions associated with status epilepticus in humans. The hepatocellular changes are interpreted to be agonal and associated with terminal hypoxia in seizuring animals. These results provide evidence of a previously unrecognized, often lethal epileptic syndrome in FVB mice that may have a major impact on transgenic research and other disciplines using this mouse strain.

Efficacy of various therapeutic regimens in eliminating Pasteurella pneumotropica from the mouse.

Pasteurella pneumotropica, a gram-negative opportunistic pathogen, can be isolated from the oropharynx, intestinal tract, and reproductive tract of clinically normal mice and has been associated with various clinical syndromes, including conjunctivitis, infections of the reproductive tract, otitis, and subcutaneous abscess formation. Enrofloxacin, a fluoroquinolone bactericidal antimicrobial, has been shown to be effective in eliminating P. multocida from rabbits. We sought to determine whether enrofloxacin would eliminate P. pneumotropica from mice known to be asymptomatically infected with the agent. Pasteurella pneumotropica-positive (culture and immunofluorescence assay) male (n = 55) and female (n = 55) C57BL/6N mice were randomly assigned to one of seven treatment groups or to a control group. These groups were designed to evaluate the efficacy of enrofloxacin administered orally via the drinking water or parenterally at three dosages (8.5, 25.5, and 85.0 mg/kg of body weight per day) over a 14-day treatment period. A tetracycline-treated group (60 mg/kg per day) and an untreated control group were included for comparisons. Repeated oropharyngeal swab and fecal specimens were obtained for culture through posttreatment day 30, and specimens from numerous enteric and reproductive organs collected during necropsy were used to evaluate group differences. Enrofloxacin eliminated evidence of P. pneumotropica from all sites when administered at 25.5 or 85 mg/kg but not at 8.5 mg/kg by either route for at least 30 days after treatment. Tetracycline-treated and control groups remained consistently culture-positive throughout the study. We concluded that the oral route may be a more practical method for treating large numbers of mice. Enrofloxacin may be a practical and inexpensive alternative to cesarian rederivation or embryo transfer for the elimination of P. pneumotropica in mice.

Phytoestrogen content of purified, open- and closed-formula laboratory animal diets.

BACKGROUND AND PURPOSE: Phytoestrogens exert estrogenic effects on the central nervous system, induce estrus, and stimulate growth of the genital tract of female animals. Over 300 plants and plant products, including some used in laboratory animal diets, contain phytoestrogens. Therefore, the source and concentration of phytoestrogens in rodent diets were determined. METHODS: Twelve rodent diets and six major dietary ingredients were assayed for phytoestrogens (daidzein, genistein, formononetin, biochanin A, and coumestrol), using high-performance liquid chromatography. Three rodent diets recently formulated to reduce phytoestrogen content also were assayed. RESULTS: Formononetin, biochanin A, and coumestrol were not detected. Soybean meal was the major source of daidzein and genistein; their concentrations were directly correlated to the percentage of soybean meal in each diet. CONCLUSIONS: High, variable concentrations of daidzein and genistein are present in some rodent diets, and dietary phytoestrogens have the potential to alter results of studies of estrogenicity. Careful attention should be given to diet phytoestrogen content, and their concentration should be reported. A standardized, open-formula diet in which estrogenic substances have been reduced to levels that do not alter results of studies that are influenced by exogenous estrogens is recommended.