Laboratory animal science最新文献

Background and purpose: Medetomidine is a selective, specific, and potent alpha2-adrenergic receptor agonist that has been utilized successfully as a sedative/analgesic agent in a variety of domestic and nondomestic animals. The objective of this study was to document the physiological effects of the intravenous administration of medetomidine in rhesus macaques (Macaca mulatta).

Methods: Fifteen healthy rhesus macaques (Macaca mulatta), 5 to 15 years old and weighing 5.5 to 11.8 kg, were given four dosages of medetomidine (50, 100, 150, and 200 microg/kg of body weight) intravenously, and cardiovascular, respiratory, thermoregulatory, sedative, and analgesic effects were determined.

Results: All four doses of medetomidine induced a similar and significant decrease in mean arterial pressure, as well as a transient but significant increase in respiratory rate followed by a longer-lasting significant decrease. Bradycardia, hypotension, and loss of thermoregulatory ability accompanied by a biphasic respiratory response and inconsistent sedation, analgesia, and muscular relaxation were observed. Heart rate decrease was rapid for all doses, but was significantly lower and of shorter duration after administration of the 50 microg/kg dosage.

Conclusion: The inconsistency of the anesthetic plane induced by intravenous administration of medetomidine precludes it from being used alone to sedate rhesus macaques.

Objective: Mouse strains carrying endogenous ecotropic murine leukemia viruses (MuLV) are capable of expressing infective virus throughout life. Risk of transplacental transmission of MuLV raises concerns of embryo infection and induction of pathogenic effects, and postnatal MuLV infection may lead to tumorigenesis.

Methods: Endogenous ecotropic MuLV-negative SWR/J embryos were implanted into Akv-infected viremic SWR/J mice, into spontaneously provirus-expressing AKR/J mice, and into noninfected SWR/J control mice; virus integration and virus expression were investigated at 14 days' gestation. Tumor development was monitored over 18 months.

Results: Of 111 embryos, 20 (18%) recovered from Akv-infected SWR/J mice, which had developed normally, were infected. New proviruses were detected in 10 of 111 (9%) embryos from Akv-infected SWR/J mice, and in 2 of 60 (3%) embryos from AKR/J mice; none expressed viral protein. Of 127 embryos recovered from Akv-infected SWR/J mice, 16 (13%) were dead; 4 of 5 (80%) were infected and expressed viral protein. Of 71 embryos from AKR/J mice, 11 (15%) were dead, and 2 of 2 had virus integration; virus expression was not detected. Numbers of dead embryos recovered from experimentally infected, viremic SWR/J mice and from spontaneously endogenous MuLV-expressing AKR/J mice were significantly higher, compared with numbers from nonviremic SWR/J control mice, and embryo lethality was significantly associated with prenatal provirus expression. Postnatal inoculation of Akv induced lymphoblastic lymphomas in 15 of 24 (61%) SWR/J mice within mean +/- SD latency of 14 +/- 2.4 months. Only 3 of 39 (8%) control mice developed lymphomas (P < 0.005).

Conclusion: Embryos in MuLV-viremic dams are readily infected, and inappropriate prenatal expression of leukemogenic endogenous retroviruses may play a critical role in embryo lethality and decreased breeding performance in ecotropic provirus-positive mouse strains.

Background and purpose: Rat coronaviruses (RCVs) are common natural pathogens of rats that cause clinical illness, necrosis, and inflammation of respiratory, salivary, and lacrimal organs. The aim of the study was to determine whether antigenically different strains of RCV vary in their pathogenic potential in rats.

Methods: Neutralization groups were identified by use of RCV strain-specific antisera. Sprague Dawley rats were inoculated oronasally with RCV-SDA, RCV-BCMM, or RCV-W. Histologic examination, immunohistochemical analysis, and reverse transcriptase-polymerase chain reaction analysis were performed on tissues from infected rats.

Results: Clinical illness was not evident in any of the inoculated rats. The RCV-SDA strain caused mild lesions in the exorbital gland of one rat. The RCV-BCMM strain caused severe lesions in the Harderian and parotid glands and mild lesions in the exorbital glands, lungs, and nasal mucosa. The RCV-W strain caused severe lesions in the Harderian, exorbital, and parotid glands and mild lesions in the submandibular glands, lungs, and nasal mucosa. The RNA concentration was highest in the Harderian, parotid, and exorbital glands of RCV-BCMM- and RCV-W-infected rats at postinoculation day 7.

Conclusions: Although RCV-SDA, RCV-BCMM, and RCV-W caused different degrees and patterns of lesions, neutralization groups are not useful for predicting the pathogenic potential of a new RCV isolate.

Background and purpose: Standard treatment for massive hemorrhage in dogs is infusion of whole blood or of packed red blood cells with fresh frozen plasma if whole blood is not available. Although most whole blood is collected using a citrate-based anticoagulant, knowledge of citrate's relevant non-anticoagulant effects is not widespread. Citrate's anticoagulant activity is achieved through chelation of divalent metal cations (e.g., magnesium, calcium), which may exacerbate cardiovascular and metabolic insults attributable to hemorrhage.

Methods: Blood pressures, gas tensions, metabolites, and electrolytes; myocardial metabolites, pressures, and contractility; cardiac output; and left cranial descending and circumflex coronary artery flows were measured in 21 anesthetized dogs after hemorrhage was induced by collection of blood into a citrated reservoir to mean arterial pressure of 45 mm Hg for approximately 60 min (until arterial lactate concentration was 7.0 mmol/L), followed by a 1-h transfusion and 2 h of maintenance.

Results: Arterial ionized calcium concentration, total peripheral resistance, and myocardial function decreased significantly during hemorrhage. All aforementioned responses but myocardial function continued to decrease during the initial 20 min of transfusion, then began to recover. Total peripheral resistance and end-systolic elastance were the only factors significantly related to calcium concentration.

Conclusion: Transfusion with citrated whole blood may significantly alter calcium concentration, negatively affecting myocardial and vascular function.

Background and purpose: Degenerative diseases of the central nervous system are a heterogenous group of slowly progressive disorders. A common feature of this group, which includes Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, is gradual loss of specific populations of neurons.

Methods: A series of reports about neurodegenerative diseases and their relevant animal models, as well as a brief overview of the normal neuron and mechanisms of neuronal degeneration and death, is presented.

Conclusion: Study of the aforementioned animal models, spontaneously occurring and experimentally induced, have provided important insights into the pathogenesis of these disorders and the development of effective therapeutic strategies.

Background and purpose: The anatomic position of the ileum is such that use of simple, noninvasive sampling techniques is difficult. Sampling of ileal contents by use of a cannula provides information about those contents-digestibility and fermentation patterns; however, complications with use of cannulas in horses and dogs have been reported. Therefore, cats were chosen as a laboratory model in which to study ileal cannulation.

Methods: Simple T-piece cannulas were surgically placed in the ileum of six adult cats.

Results: Postsurgical complications included cannula displacement and leakage, with subsequent abscessation and skin inflammation. Owing to these complications, the cannulas were removed from four of the six cats. Similar complications developed after removal of the cannulas. In the only attempt to collect a sample, obtaining a 0.5-ml sample of ileal fluid from one cannula took 3 h. Of the six cats, four died or were euthanized.

Conclusion: Use of cannulas is not a viable technique of collecting ileal fluid samples in cats.