Effects of phenothiazine and thiabendazole on bovine dorsal pedal vein contractility induced by ergonovine and serotonin; Potential for alleviation of fescue toxicity

Phenothiazine and thiabendazole were studied for their ability to antagonize venoconstriction induced by ergonovine, and the biogenic amine serotonin, in the isolated dorsal pedal vein of cattle. The two compounds are commercially available, approved for usage in cattle and have been reported to reverse some of the toxic effects associated with the intake of Acremonium coenophialum-infested fescue forage by cattle. Neither compound had any antagonistic activity against venoconstriction induced by ergonovine. However, thiabendazole did have some activity against venoconstriction induced by serotonin. Ergot alkaloids are known to cause venoconstriction through effects on biogenic amine receptors, including serotonergic receptors, and since thiabendazole has anti-serotonin activity, part of the reported beneficial effects of thiabendazole in alleviating fescue toxicity may be due to the anti-serotonin activity of the drug. Further work is needed to determine if phenothiazine and thiabendazole have any effect on other types of alkaloids that are present in A. coenophialum-infested fescue.     

Cross-reactivity between a monoclonal antibody that recognizes a tumor-associated antigen on bovine lymphosarcoma cells and blood lymphocytes from various mammalian species.

Tumor-associated antigens that are expressed in lymphosarcoma B cells of cattle with enzootic bovine leukosis had been analyzed in terms of their reactivity with 13 monoclonal antibodies (MAB). By use of flow cytometry and radioimmunoprecipitation, 1 of the MAB (c143) that recognized a tumor-associated antigen cross-reacted with blood lymphocytes (BL) from various mammalian species. By use of flow cytometry, the c143 MAB reacted with 10 to 49% of BL derived from human beings, mice, dogs, horses, pigs, llamas, sheep, goats, and cattle. Titer of the c143 MAB with BL from horses, pigs, human beings, and llamas ranged between 1:6.0 x 10(4) and 1:5.3 x 10(5); titer associated with BL of goats and sheep was 1:1.6 x 10(6); and that associated with BL of cattle was 1:4.3 x 10(7). The c143 MAB specifically immunoprecipitated 3 homologous proteins from cell extracts of caprine, ovine, and bovine BL (32-, 34-, and 36- to 37-kDa bovine proteins; 31-, 32-, and 36- to 37-kDa caprine proteins; and 31.5-, 33-, and 36- to 37-kDa ovine proteins), but none was immunoprecipitated from human, murine, canine, porcine, and llama BL. These results indicate that the avidity of the c143 MAB in binding to BL from ruminants (eg, goats, sheep, and cattle) is higher than that to BL from human beings, mice, dogs, horses, pigs, and llamas. In sheep, the c143 MAB could immunoprecipitate the aforementioned proteins from BL of the Suffolk breed, but not BL from the Corriedale breed, whereas the c143 MAB immunoprecipitated apparently identical proteins from BL of 4 breeds of cattle.     

Reactivity of lichen lectins with blood typed canine erythrocytes

Extracts from 69 species of lichens were tested for their ability to agglutinate untreated and enzyme-modified erythrocytes from a panel of blood typed dogs. Forty-three lichen species reacted positively with either untreated or enzyme-modified cells. Many extracts exhibited differential agglutination among red cells tested. The patterns of differential agglutination observed with the lichen extracts did not correspond to known canine blood groups present on the test red cell panel.     

The effect of ticlopidine on canine platelets, fibrinogen, and antithrombin III activity

The effect of ticlopidine on platelet function, platelet number, mean platelet volume, antithrombin III activity, and fibrinogen was evaluated in 10 laboratory beagles. Ticlopidine (62 mg/kg) significantly inhibited ADP- and collagen-induced platelet aggregation within 2 days of the beginning of oral administration. Collagen-induced platelet 14C-serotonin release was not inhibited by day 9 of medication but was inhibited by day 20 in two of three beagles given medication for 32 days. Significant increases in mean platelet number were observed on days 2 and 5. The trend toward increased platelet number continued until day 16, at which time platelet number began to decrease toward baseline in three of three dogs treated for 32 days. Mean platelet volume (MPV) was significantly decreased compared to baseline on days 5 and 9. In three dogs treated for 32 days, the lowest MPV was observed on day 9 in two dogs and on day 12 in one dog. Significant changes were not observed in antithrombin III activity or fibrinogen with ticlopidine treatment.     

Thromboxane and prostacyclin production in ponies with colonic volvulus.

Effects of 1 hour of colonic volvulus and 3 hours of reperfusion on concentrations of thromboxane (TXB2) and prostacyclin (6-keto-PGF1 alpha) in portal, pulmonary arterial, and jugular blood were determined by radioimmunoassay to assess the site of production and clearance of these eicosanoids from the circulation in 5 anesthetized ponies. Colonic volvulus had no significant effect on mean arterial pressure or TXB2 concentrations, but significantly (P less than 0.05) increased 6-keto-PGF1 alpha concentrations in all blood samples. Immediately after colonic reperfusion, all eicosanoid concentrations were significantly (P less than 0.05) increased. Then, TXB2 returned to baseline values, whereas 6-keto-PGF1 alpha concentrations remained significantly (P less than 0.05) high for the remainder of the study. Eicosanoid concentrations were significantly (P less than 0.05) greater in portal blood than in pulmonary arterial and jugular blood samples at all periods. This suggests that the splanchnic circulation is the primary site of eicosanoid production during and after colonic volvulus and the liver appears to provide most of the circulatory clearance of thromboxane and prostacyclin.     

Manually assisted ejaculation in a stallion with erectile dysfunction subsequent to paraphimosis.

A Thoroughbred stallion with erectile dysfunction following paraphimosis was managed to allow consistent ejaculation. Ejaculation was elicited in this stallion by applying manual stimulation to the base of the penis. This technique allowed consistent ejaculation, and the stallion was able to return to natural service. Historically, stallions with this degree of penile dysfunction have been considered incapable of ejaculation and unable to continue as breeding animals.     

Intestinal myxosarcoma in a thoroughbred mare.

A large fibrotic mass originating from the cecal base was discovered upon surgical exploration of the abdomen in a Thoroughbred mare with a history of chronic colic and weight loss. The mass protruded intraluminally resulting in partial obstruction. Surgical excision was not feasible due to the location of the mass and the inability to exteriorize it adequately from the abdominal cavity. The mass was fibrous with a shiny, gelatinous material present throughout the neoplasm. Histologically, large confluent spaces filled with mucopolysaccharides were identified by staining with Alcian blue. The diagnosis of myxosarcoma was based upon finding of atypical fibroblastic cells, mucinous stroma, local invasiveness, and metastasis to the regional lymph nodes. Myxomatous tumors have not previously been documented to occur in the equine intestinal tract.     

Genetic diversity among Australian and New Zealand isolates of Leptospira interrogans serovar pomona

Restriction endonuclease analysis of 16 Australian and 4 New Zealand isolates of Leptospira interrogans serovar pomona showed that they could be divided into 3 genetic groups. Most of the isolates closely resembled the serovar kennewicki reference strain, and they all differed from the reference strain of serovar pomona. Based on these findings, it is suggested that vaccine manufacturers re-evaluate their choice of serovar pomona vaccine strain.     

Field experiments to evaluate the feasibility of eradication of Aujeszky's disease virus by different vaccination schedules.

In the present report, the extent of the reduction in Aujeszky's disease virus (ADV) dissemination achieved when pigs were intensively vaccinated with gI-deleted vaccines under field circumstances, was examined. On widely dispersed breeding-fattening farms, a gI-negative status was most rapidly obtained and the rate of new waves of infections was lowest when the attenuated Bartha strain was administered to both the sows and the fatteners. It was more difficult not only to reach but also to keep a gI-negative status on farms on which the sows were vaccinated with an inactivated vaccine and the fatteners with the attenuated Bartha strain or when the fattening pigs were not vaccinated at all. In a densely populated area, 9 of the 17 farms had gI-positive fatteners at the start of the intensive vaccination programme in which the attenuated Bartha strain was given to both the sows and the fatteners. Antibodies were not detected in the sera of the fatteners of each farm at some time during the experiments, but the fatteners on 7 of the 18 farms still showed antibodies against gI after 20 months of vaccination. At the end of the experiment, the percentage of fatteners with antibodies on these farms was markedly reduced compared with the percentage at the start of the experiment. Therefore, elimination of field virus may be feasible if intensive vaccination is carried out over a sufficiently long period of time. However, the high rate of reinfections experienced either due to reintroduction of the virus or to recrudescence should be a warning against too much optimism, particularly in regions with a dense swine population.