Humoral response to Mycobacterium avium subsp. avium in naturally infected ring-neck doves (Streptopelia risoria).

Creation of a reliable and easy to use serologic test would greatly improve ante mortem diagnosis of Mycobacterium avium subsp. avium and aid in the control of avian mycobacteriosis, particularly in captive birds. In order to determine whether serodiagnostics could be of value in testing ring-neck doves (Streptopelia risoria) for M. a. avium infection, Western blot analysis was used to assess the humoral response of ring-neck doves exposed to M. a. avium, and to evaluate whether an association could be made between the humoral response and necropsy findings, histopathology, culture, and PCR testing. Western blot results were examined for reactivity patterns associating humoral response with infection status, severity and type of lesions (diffuse vs. multifocal granulomatous inflammation) and phenotype (white vs. non-white). A sensitivity of 88.24% and a specificity of 100% were achieved utilizing Western blot analysis to detect M. a. avium infection in ring-neck doves, offering a negative predictive value of 93% and a positive predictive value of 100%. While Western blot analysis results did not reflect lesion severity, lesion type did partially correspond with the humoral response. The findings of the present study indicate that serologic testing can be used as a valuable ante mortem screening tool for identifying ring-neck doves infected with M. a. avium.

Evidence for GABA tolerance in barbiturate-dependent and withdrawn mice.

Mice were rendered tolerant and dependent to barbital by a chronic feeding schedule of barbital over 5 weeks. The behavioural effects of muscimol, imidazole-acetic acid (ImAA), and gamma-hydroxybutyric acid (GHB) were measured in control, barbital-dependent, and mice dependent on barbital 48 hr after withdrawal of the drug. The sedative effects of the GABA-mimetics imidazole-acetic acid and muscimol were increased in dependent mice, but reduced in withdrawn mice. Subanaesthetic doses of barbital, given acutely, also increased the sedative effects of imidazole-acetic acid and muscimol but not of gamma-hydroxybutyric acid. Assay of plasma barbital levels by GLC indicated that a negligible amount of barbital was present 48 hr after withdrawal compared to levels of between 60 and 120 micrograms/ml during chronic treatment with barbital. The binding of [3H]GABA to membrane preparations from brain indicated that the values of Kd and Bmax for low affinity binding were not significantly altered in mice withdrawn from chronic treatment with barbital, but that the Kd for high affinity binding was significantly increased from 4.38 to 6.06 nM in barbital-withdrawn mice. There was no difference in the enhancement of GABA binding by pentobarbital between the two groups. It is concluded that barbital-tolerant and dependent mice are cross-tolerant to GABA and that this is possibly mediated by a change in the affinity of the GABA receptor for its ligand.

Alterations in dopamine and 5-hydroxytryptamine (5-HT) function during barbiturate dependence and withdrawal in mice.

Mice were rendered barbiturate-dependent by chronic feeding with barbital-con taining food. Brain dopamine turnover was significantly increased in barbital withdrawal, whereas 5-hydroxytryptamine (5-HT) turnover was significantly decreased. Severity of with drawal was assessed by measuring the convulsions following a dose of 33 mg/kg mer captopropionate (MPA). The neurotoxins 6-hydroxydopamine and 5,6-dihydroxytryptamine as well as metergoline (5 mg/kg) increased the severity of MPA convulsions. Quipazine (20 mg/ kg) attenuated the convulsions. The results are consistent with the hypothesis that diminished 5-HT function may contribute to the barbital withdrawal syndrome. Behavioural responses to serotonergic drugs were enhanced in barbital-dependent mice compared to controls, but [(3)H]- 5-HT binding to crude membrane fractions was similar in both groups with a single high affinity site.

Prevalence of Neospora antibodies in beef cattle in New Zealand.

AIM: To estimate the prevalence of Neospora infection in a sample of New Zealand beef cattle. METHODS: The prevalence of Neospora caninum infection in New Zealand beef cattle was estimated by collecting blood at slaughter from 499 beef cattle from 40 different farms at 2 slaughter plants in the North Island and 1 in the lower South Island . Sera were tested using an ELISA against Neospora tachyzoite antigen. RESULTS: The prevalence of seropositive cattle was 2.5% (n=120), 3.6% (n=166) and 2.3% (n=213) at the plants surveyed, the overall prevalence being 2.8%. The serologically positive cattle came from 9 farms, 3 of which had more than 1 positive animal. The highest prevalence recorded amongst animals from 1 farm was 4/13 (31%), in a group of young steers. CONCLUSION: Neosporosis appears to be present at a lower level in the New Zealand beef cattle population than in the New Zealand dairy cattle population. Nevertheless, from the high seroprevalence evident amongst young cattle on 1 farm, we suggest that Neospora may be a cause of infertility in beef cattle in this country.