We determined the vasoconstrictive effects of selected ergot alkaloids, and a sample containing loline and its derivative alkaloids, on the isolated dorsal pedal vein of cattle, as a model system to study one of the toxic effects that result from cattle ingesting fescue forage infected with the endophytic fungus Acremonium coenophialum. The ergot compounds ergotamine, ergosine, and agroclavine constricted this peripheral vein of cattle, but much less so than did the alpha-adrenergic agonist norepinephrine, which supports the ergots acting as partial agonists for these receptors. However, the sample of loline and loline-derivative alkaloids did not affect the dorsal pedal vein when given at concentrations similar to those of the ergot compounds. Loline and loline-derivative alkaloid sample at high concentrations partially inhibited norepinephrine-elicited vascular contraction, an effect that appeared to be unrelated to alpha-adrenoceptor activity. Thus, in the dorsal pedal vein model in cattle, the ergopeptide alkaloids were more venoconstrictive than were loline and its derivative alkaloids.

Fasting and postprandial gastroesophageal sphincter pressure (GESP) and plasma gastrin immunoreactivity were measured in 6 dogs from 9 through 60 months after treatment for and recovery from gastric dilatation-volvulus (GDV). The GESP was not significantly increased in these dogs, compared with that in clinically normal dogs in either the fasting or postprandial state. Corresponding plasma gastrin immunoreactivity was not significantly increased in dogs of the GDV-recovered group, compared with that in clinically normal dogs (fasting or postprandial). An exaggerated increase in GESP in response to food-induced gastrin release was not observed in dogs of the GDV-recovered group. Exogenously administered pentagastrin (3-micrograms/kg bolus, IV) increased fasting GESP in clinically normal dogs over a 4-minute test period (P = 0.01). Gastric distention in response to oral administration of isosmolar saline solution (500 ml) did not significantly increase GESP or plasma gastrin immunoreactivity in clinically normal dogs. In anesthetized clinically normal dogs, gastric distention in response to use of balloons filled to exert intragastric pressure of 30 mm of Hg also did not cause significant increase in plasma gastrin immunoreactivity. Increased GESP, secondary to hypergastrinemia or gastric distention, is an unlikely cause of eructation failure in dogs with GDV.

Serum from dogs with surgically induced renal impairment was incorporated into the medium for erythroid bone marrow cultures. A significant correlation was found between serum activities of erythropoietin and numbers of erythroid colony-forming units grown in culture. Serum creatinine concentrations had no correlation, and serum parathyroid hormone activities had a negative correlation with numbers of erythroid colony-forming units that was below the level of significance. Purified 1-84 parathyroid hormone added to bone marrow cultures was found to be stimulatory to erythroid colony-forming unit growth in higher concentrations, but decreased the number of burst-forming units. Unmeasured substances in the canine serum appeared to have a greater effect on the canine erythroid bone marrow cultures than did creatinine or parathyroid hormone values.

Hybridomas producing monoclonal antibodies to Ehrlichia risticii were developed to provide a means of molecular investigation of the biochemical and immunopathologic characteristics of the organism. All of 6 stable monoclonal antibodies obtained were IgG isotypes. The ascitic fluid titers induced by the hybridomas ranged from 10(2) to 10(7). Competitive binding experiments conducted by ELISA and binding of labeled protein A to antigen-antibody complexes indicated competition among monoclonal antibodies. Two monoclonal antibodies (HybI and 14D4) were reactive in an indirect fluorescent antibody test; these antibodies also bound a maximum of labeled protein A, indicating recognition of epitopes on the surface of the ehrlichiae. Protein specificity of monoclonal antibodies could not be demonstrated with western blot procedure. HybI monoclonal antibody, however, did precipitate the 28 kD protein from 125I-surface-labeled ehrlichiae and was shown to be specific to E risticii on the basis of nonreactivity with E sennetsu, using the indirect fluorescent antibody test. By use of the different monoclonal antibodies as probes, more definitive molecular studies now will be feasible.

We evaluated the deformability of bovine platelets and contrasted the effects of pharmacologic and thermal perturbations on cytoskeletal structure of human and bovine platelets. Platelets were aspirated into micropipettes (0.7 to 0.8 micromoles in diameter) by stepwise increments in tension. The resulting lengths of the cell extensions were recorded. The cell extensions aspirated from bovine platelets were shorter than the extensions drawn from human platelets. Disassembly of the circumferential microtubule coil allowed human platelets to pass through the pipette, but the same treatments only slightly increased the deformability of bovine platelets. Alteration of the actin filament cytoskeleton caused increased mechanical fragility of human platelets. In contrast, even the combined use of microtubule and actin filament-disrupting agents only modestly increased the deformability of bovine platelets and did not cause premature fragmentation of the cells. Unusual cytoskeletal structure, absence of an open canalicular system, and disparity in granule size may all contribute to the variance in deformability between the platelets of the 2 species. Reduced cell deformability may impair bovine platelet surface interactions by diminishing the ease of cell spreading and formation of areas of contact between the platelet and other cell surfaces.

A study was conducted to compare immunogenicity of a Brucella abortus lipopolysaccharide (LPS) and the duration of infection in 5 strains of mice. Mice of strains CBA/NJ, BALB/c, CD-1, C3H/HeN, and C3H/HeJ were allotted into 2 large groups (vaccinated with proteinase K-treated LPS or nonvaccinated) and 6 subgroups based on the intervals between challenge exposure to B abortus strain 2308 and the week the response data were obtained. Criteria used in comparing responses between the various strains of mice as well as betweeen vaccinated and nonvaccinated mice were splenomegaly, colony-forming units (CFU) from spleens, and antibody titers. Responses were evaluated at 1, 2, 3, 5, 8, and 12 weeks after challenge exposure. Results indicated that all strains of mice became infected and maintained infection throughout the 12-week period, the percentages of mice infected were significantly (P less than 0.05) less in vaccinated mice for the first 5 weeks after challenge exposure, and there were no direct correlations between increased immunoglobulins (IgM and IgG titers) and reduction in CFU. Vaccinated mice of strains BALB/c, CD-1, C3H/HeN, and C3H/HeJ had increased titers when challenge exposed and also had significantly (P less than 0.05) smaller spleens and lower CFU. Vaccinated CBA/NJ mice did not have marked antibody titers. The overall results indicated that vaccination with LPS offers some initial protection against B abortus strain 2308 infection, but this protection disappears gradually and in various degrees in the 5 strains of mice studied.

Dermal microfilariae recovered form specimens obtained from umbilical and cervical sites of cattle infected with adult Onchocerca gutturosa alone or with adults of O gutturosa and O lienalis were measured and compared with uterine microfilariae obtained directly from gravid female worms of each species. Uterine microfilariae of O gutturosa were longer than dermal microfilariae obtained from cattle harboring only adults of O gutturosa. Dermal microfilariae were recovered from umbilical and cervical sites in these cattle. Those found at the cervical site had lengths equal to or greater than lengths of microfilariae recovered from the umbilical site. There was a significant (P less than 0.0001) shift in length across populations of microfilariae of O gutturosa from various sites in its bovine host, with a progressive decrease in length between microfilariae recovered from the worm's uterus, microfilariae from the cervical dermis, and microfilariae from the umbilical dermis, respectively. A similar direct comparison was not possible for microfilariae of O lienalis, because none of the cattle was infected with only adult worms of this species. In an indirect comparison, microfilariae of O lienalis were identified at the umbilicus, but their presence in the cervical region could not be determined unequivocally because of confounding of microfilariae length by concurrent infection with O gutturosa. Uterine microfilariae from O lienalis were longer than uterine microfilariae of O gutterosa, although a degree of overlap in the range of measurements existed between species.

Serum uric acid concentrations were determined in horses known to be carriers of combined immunodeficiency gene(s) and in presumed noncarrier horses. Uric acid concentrations were significantly higher (P < 0.005) in carrier horses than in presumed noncarrier horses. However, there was some overlap in serum uric acid concentrations between carrier and presumed noncarrier horses.

Tracheal mucus transport rates were measured over a 10-minute period in 20 healthy horses twice in 24 hours. The mean rate was 1.93 +/- 0.55 cm/min on day 1 and 1.99 +/- 0.49 cm/min 24 hours later. The mean difference between day 1 and day 2 (0.06 +/- 0.42 cm/min) was not significant (P = 0.55). The range on day 1 was 1.12 to 2.9 cm/min and 1.11 to 2.89 cm/min on day 2.

Ruminal microorganisms in cattle at a Florida agriculture research station did not have the ability to detoxify leucaena by degradation of 3-hydroxy-4(lH)-pyridone (3,4,-DHP), but a DHP isomer (2,3-DHP) was degraded in some cattle. Cattle with microorganisms that degraded 2,3-DHP were mostly Senepol cattle imported from St. Croix, US Virgin Islands, where leucaena is an indigenous species. Hereford cattle at the research station in Florida generally did not degrade 3,4-DHP or 2,3-DHP. An experiment was conducted in which a pure culture of 3,4-DHP-degrading bacteria was inoculated into Hereford cattle (with ruminal fistula) grazing leucaena. The bacteria successfully colonized the rumen of recipient cattle and persisted through the following winter when there was no leucaena in the diet.