Laboratory animal science最新文献

Background and purpose: Sendai virus nasal vaccines inactivated with various chemicals induce complete protection against contact-challenge exposure with the Nagoya strain. The study reported here was to reevaluate the efficacy of the inactivants by determining the protective index (PI) in mice, using the more virulent MN strain.

Methods: Mice were given each of 22 inactivated vaccines intranasally three times. After challenge exposure with 10(-2) to 10(6) MID50 of virus, infection of cells of the respiratory tract was determined by immunofluorescence.

Results: Twelve vaccines induced PI > or = 2.0 in the nasal mucosa and were classified as group 1. The first half of the preceding vaccines that induced PI > or = 3.2 in the larynx were classified subgroup a, and the rest were classified subgroup b. Of the other 10 vaccines, 6 that induced PI < or = 2.0 in the larynx and 4 that induced intermediate PI in the nasal mucosa and larynx were ranked as groups 3 and 2, respectively; PI of the trachea decreased by numeric order of groups. Serum hemagglutination inhibition titer induced by intranasal vaccination was low in general.

Conclusion: On the basis of PI values, 6 of the 22 nasal vaccines provided the strongest defense in the respiratory tract.

Background and purposes: The purpose of the study was to document diurnal variation of autonomic nervous functions by use of power spectral analysis of heart rate (HR) variability.

Methods: To clarify characteristics of power spectral analysis of HR variability, electrocardiogram (ECG), blood pressure (BP), and respiratory (Resp) waveform simultaneously were recorded.

Results: Two major spectral components were examined at low (LF)- and high (HF)-frequency bands for HR variability. Coherence between HR and Resp variabilities and HR and BP variabilities was maximal at approximately 0.14 and 0.03 Hz, respectively. On the basis of these data, two frequency bands of interest--LF (0.01 to 0.07 Hz) and HF (0.07 to 1.0 Hz)--were defined. Autonomic blockade studies indicated that the parasympathetic system mediated the HF and LF components, whereas the sympathetic system mediated only the LF component; HR had a diurnal pattern. The LF and HF bands in the dark phase tended to be higher than those in the light phase. The LF-to-HF ratio had a diurnal pattern similar to that of the HR.

Conclusion: Parasympathetic nervous activity in miniature swine may be predominant in the dark phase. The characteristics of power spectra and diurnal variations of autonomic nervous functions are almost the same as those of humans. Therefore, miniature swine may be a useful animal model for future biobehavioral and pharmacotoxicologic studies.

Background and purpose: Development of the rhesus monkey model of Helicobacter pylori has been hampered by problems with serodetection and by the difficulty of identifying specific-pathogen (Helicobacter)-free animals. Our purpose was to determine whether detection could be improved and to determine if pathogen-free monkeys could be derived by nursery rearing.

Methods: An enzyme-linked immunoabsorbent assay (ELISA) and a [14C]urea breath test were compared to endoscopy to determine H. pylori infection status in rhesus macaques; 18 animals were hand raised in the nursery to determine whether pathogen-free animals could be selected.

Results: Helicobacter pylori infection was common in colony-raised young rhesus monkeys and was nearly universal by adulthood. Serodetection, using antigen from rhesus-derived H. pylori strains, was 95% sensitive and 94% specific. The [14C]urea breath test was 96% sensitive and 88% specific for detection of chronic Helicobacter infection in rhesus monkeys. Segregation of newborn animals within the first 24 h of life was a reliable method to obtain pathogen-free rhesus monkeys.

Conclusion: Isolation of specific-pathogen-free animals, together with better detection methods, may improve the value of the rhesus monkey model for the study of H. pylori pathogenesis, immune response, and vaccine development.

Background and purpose: In mice, genetic engineering involves two general approaches-addition of an exogenous gene, resulting in transgenic mice, and use of knockout mice, which have a targeted mutation of an endogenous gene. The advantages of these approaches is that questions can be asked about the function of a particular gene in a living mammalian organism, taking into account interactions among cells, tissues, and organs under normal, disease, injury, and stress situations.

Methods: Review of the literature concentrating principally on knockout mice and questions of unexpected phenotypes, lack of phenotype, redundancy, and effect of genetic background on phenotype will be discussed.

Conclusion: There is little gene redundancy in mammals; knockout phenotypes exist even if none are immediately apparent; and investigating phenotypes in colonies of mixed genetic background may reveal not only more phenotypes, but also may lead to better understanding of the molecular or cellular mechanism underlying the phenotype and to discovery of modifier gene(s).

Background and purpose: After myocardial necrosis and fibrosis was observed in five rabbits which had been anesthetized a variable number of times, the potential relationship of these lesions and anesthesia was evaluated in 35 other rabbits.

Methods: Anesthesia was induced by intramuscular administration of ketamine and xylazine followed by infusion of lactated Ringer's solution also containing ketamine and xylazine. Group A rabbits (n = 9) were subjected to multiple anesthesias and were evaluated by echocardiography, thoracic radiography, electrocardiography, determination of serum coronavirus titer, vitamin E concentration, and complete necropsy. Prior to a single acute procedure followed by necropsy, group B rabbits (n = 11) were evaluated by echocardiography only. Group C rabbits (n = 10) had never been anesthetized and were necropsied after euthanasia. Group D rabbits (n = 5) had intermediate anesthesia exposure history and were evaluated by echocardiography only. Myocardial fibrosis was scored semi-quantitatively on a scale of 0 to 4.

Results: Canine coronavirus test results were negative; hypovitaminosis E was evident, and fibrosis scores were significantly increased in group A, compared with group B or group C, rabbits.

Conclusion: Etiologic differentials included alpha2-agonist-mediated coronary vasoconstriction with associated myocardial hypoperfusion, hypovitaminosis E and free radical injury, and other anesthetic-induced physiologic trespass.

Background and purpose: Traumatic spinal cord injury causes initial mechanical disruption of tissue, leading to a complex secondary sequence of pathophysiologic changes and neurologic impairment. These sequelae depend on the impact force delivered to the spinal cord at the time of injury. Successful clinical evaluation of the efficacy of any therapeutic regimen depends on the reliability and reproducibility of an experimental animal model. We describe a trauma device and the biomechanical parameters required to induce severe or moderate spinal cord contusion injury in cats and rats.

Methods: Recovery after injury was determined by behavioral, electrophysiologic, and histologic evaluations.

Results: Behavioral and electrophysiologic tests after injury clearly identified the experimental groups. A stable severe paraplegic state (defined as 6 months for cats and 8 weeks for rats), without evidence of behavioral or electrophysiologic recovery, was induced by a 65-Newton (N) load for cats and a 35-N load for rats. Moderate spinal cord contusion injury, from which cats and rats partially recovered after approximately 3 months and 4 weeks, respectively, was induced by a 45- and 25-N load, respectively.

Conclusion: Use of these injury conditions provides reliable animal models for studies designed to evaluate potential therapeutic regimens for spinal cord injury.

Background and purpose: The gastrointestinal tract is a common portal of entry for Encephalitozoon cuniculi, one of several microsporidial organisms emerging as opportunistic pathogens in immunocompromised humans. Although most human microsporidial pathogens can be propagated in vitro and in a variety of laboratory animals, an experimental animal system to specifically study intestinal uptake and systemic spread of these organisms does not exist.

Methods: Paired segments of near-term fetal rabbit small intestine were implanted subcutaneously into 25 athymic nude or 10 severe combined immune deficient mice. Five weeks after surgery, 65 xenografts were inoculated intraluminally with E. cuniculi (n = 14), E. intestinalis (n = 27), E. hellem (n = 20), or RK-13 cells (n = 2), or were left uninoculated (n = 2).

Results: Intestinal xenograft infection with E. cuniculi (n = 11), E. intestinalis (n = 17), and E. hellem (n = 18) was determined by light microscopy; control xenografts remained uninfected. Extraintestinal infection with E. cuniculi developed in host mouse brain, respiratory tract, spleen, salivary glands, and gastrointestinal tract (3 of 3 mice), and infection with E. intestinalis developed in the liver (8 of 15 mice).

Conclusion: Intestinal xenografts provide a unique, sterile, and biologically relevant animal model system for studying host enterocyte/parasite interactions, mechanisms of microsporidial pathogenicity, antimicrosporidial chemotherapeutic agents, and immune effector mechanisms. This model provides evidence for persistent graft infection with three Encephalitozoon spp., and for intestinal spread of E. cuniculi and E. intestinalis from infected enterocytes in immunoincompetent mice.

Objective: To characterize monoclonal antibody production parameters of five hybridoma cell lines in murine ascites for correlation with clinicopathologic changes in mice.

Methods: Five hybridoma cell lines were grown in groups of 20 mice. Fourteen days prior to inoculation with 10(6) hybridoma cells, mice were primed with 0.5 ml of pristane given intraperitoneally. Ascites fluid was collected a maximum of three times by abdominal paracentesis; volume was measured and antibody concentration was determined by ELISA for each sample.

Results: Trends differed among cell lines when comparing ascites volumes and antibody concentrations over time from the first to the third tap. Antibody production was greatest at tap 1 for Groups 2B11 and 2C6D9; tap 2 for Group 3C9; and tap 3 for Groups RMK and 3D6. Total antibody production ranged from 422.90 to 996.64 mg; total ascites fluid volume ranged from 74.2 to 115.7 ml; and mean antibody concentration for taps 1, 2, and 3 ranged from 2.50 to 15.03 mg/ml among cell lines.

Conclusion: Production characteristics were significantly different among hybridoma cell lines. Determination of production characteristics of hybridomas and correlation with clinicopathologic changes in mice may be valuable in making recommendations for managing mice with ascites.

Old World primates are often studied to model human skeletal physiology. An important advantage of monkeys over other animal models (i.e., rodents) is the presence of cortical bone Haversian remodeling. Seventy-five female rhesus monkeys (Macaca mulatta) were subjected to bone biopsy. With monkeys in lateral decubitus position, the tenth rib was surgically exposed and freed from periosteum by use of careful sharp and blunt dissection. The rib section was resected, using bone cutters, and the surgical wound was closed. This procedure was repeated for the contralateral rib at a later time point in 65 monkeys. There was no mortality or appreciable morbidity. The bone specimens were (mean +/- SD) 2.50 +/- 0.25 cm long, with 5.5 +/- 1.0 mm2 total cross-sectional area. They were adequate for histologic, immunohistochemical, and quantitative histomorphometric examinations. Prevalence of pneumothorax was approximately 8.0% for the 140 procedures. This complication was immediately and successfully corrected by insertion of a small thoracic tube, evacuation of pneumothorax, and closure of the incision. This well-tolerated, repeatable procedure yields excellent specimens for performance of cortical bone histologic examination without euthanasia, allowing longitudinal evaluation.