Laboratory animal science最新文献

Background and purpose: Guinea pigs are used as models for study of ventricular tachyarrhythmias (VT); however, the tachyarrhythmia often is transient and does not persist. We developed an open-thorax guinea pig model of sustained ventricular fibrillation (VF).

Methods: Bilateral thoracotomy was performed on eight guinea pigs weighing 865 to 1,464 g, and two sutures were positioned in the right ventricular apex for the purpose of pacing. Two methods were used to induce VF: a 50-Hz burst (normal pacing), and an initial 15 beats at 70% of the R-R interval followed by a 100-Hz burst for 84 beats (rapid pacing). Fifteen attempts at inducing VF were performed by use of each method. Blood pressure was recorded before and after development of VF, which was defined as VT with mean blood pressure consistently <10 mm Hg. A final observation was obtained using the normal pacing method without defibrillation.

Results: Use of both methods successfully induced VF. A significant relationship between body weight >1,021 g and ability to sustain and survive VF was detected.

Conclusion: The guinea pig is a useful rodent model for the study of VF and defibrillation.

Background and purpose: Peripheral neuropathies, disorders of peripheral nerves, result from genetic alterations or from metabolic, inflammatory, infectious, or chemical insults. Experimental animal models, spontaneous or induced, exist for many of the common human peripheral neuropathies. Recent advances in human genetics have led to identification of several specific gene defects involved in heritable neuropathies and have allowed reproduction of the molecular defects in experimental animals.

Methods: Genetic modifications in mice and rats, similar to those seen in humans, along with animal models of specific gene defects are presented and discussed.

Results and conclusion: Chemotherapeutic agents administered to affected animals mimic the dose-dependent neuropathies similar to those seen in humans. Availability of the experimental animal models has been invaluable to an understanding of the pathogenesis of disease and the development of new treatments.

Objective: Our purpose was to assess the extent to which early weaning and other weaning-management factors affect development of postweaning chronic diarrhea in captive rhesus monkeys at the California Regional Primate Research Center between 1992 and 1995.

Methods: Data for weaning, management, and onset of diarrhea were obtained from daily records. The Cox proportional hazard model was used to assess whether the risk of chronic diarrhea was related to early weaning.

Results: Monkeys that were lighter at weaning had a threefold increase in risk of postweaning chronic diarrhea (P = 0.07), compared with that in heavier monkeys. An episode of preweaning diarrhea increased the risk of postweaning chronic diarrhea twofold (P = 0.08). Relocation of monkeys to outdoor facilities in the fall was associated with a fivefold decrease in risk (P < 0.001), compared with that of other seasons, and weaning in 1993 was associated with a twofold decrease in risk, compared with that of other years (P = 0.04).

Conclusions: Multiple factors need to be considered for prevention of postweaning chronic diarrhea, including weaning weight, preweaning diarrhea, season weaned, and weaning conditions that change from year to year.

Background and purpose: Q fever is a disease of humans. Vaccines to prevent this disease have demonstrated efficacy in rodents and must also be evaluated for efficacy in a nonhuman primate model. Preliminary to vaccine efficacy experiments, cynomolgus and rhesus monkeys were evaluated as suitable experimental models of acute Q fever.

Methods: Both species of monkeys were challenged with aerosolized 10(5) virulent phase-I Coxiella burnetii Henzerling strain, and clinical and serologic responses were determined.

Results: Radiographic changes were observed in seven of eight monkeys of both species; however, changes in cynomolgus monkeys tended to be more significant. Between 7 and 10 days after challenge, all rhesus monkeys and 88% of cynomolgus monkeys were bacteremic. Sequential increases in antibody responses to C. burnetii phase-I and phase-II whole cells and phase-I lipopolysaccharide were observed in both species. Although the maximal rectal temperature increase was similar in both species, duration of fever was slightly longer in rhesus monkeys. Clinical features were similar to those described in human acute Q fever patients.

Conclusions: On the basis of the more pronounced radiographic changes in cynomolgus monkeys, we favor use of this species for future studies of vaccine efficacy.

Background and purpose: Use of rabbits in orthopedic investigations is common. In this study, focus is on factors that influence bone healing and on distraction osteogenesis. Biomechanical characteristics of two external fixator systems (Orthofix device and Hoffmann device) for long bones were tested.

Methods: Twelve freshly dissected tibiae were obtained from six skeletally mature New Zealand White rabbits, and four-point bending stiffness in two planes (90 and 180 degrees to the fixator pins) and torsional stiffness and strength of the bone-fixator complex were evaluated by use of a material testing machine.

Results: In four-point bending, Orthofix device had higher stiffness and strength, compared with Hoffmann device. When the load was applied 180 degrees to the pins, both devices had higher stiffness, compared with that at 90 degrees. In torsional testing, Orthofix device had significantly higher stiffness and strength.

Conclusions: Significant differences in structural properties between the two systems were evident. Loading direction and gap conditions were important factors in determining properties of the systems. Therefore, type of external fixation system and fixation technique should be considered when designing experiments, using the rabbit long bone model.