Effects of dietary ochratoxin A (OA) and T-2 toxin, fed singly and in combination, were evaluated in growing crossbred pigs. Thirty-six barrows (3 replicates of 3 for each of 4 treatment groups, mean body weight, 18.0 kg) were fed: 0 mg of OA and 0 mg of T-2/kg of feed (control); 2.5 mg of OA/kg of feed; 8.0 mg of T-2/kg of feed; or 2.5 mg of OA plus 8.0 mg of T-2/kg of feed for 30 days. Production performance, serum biochemical, hematologic, immunologic, and pathologic evaluations were made. Body weight and body weight gain were decreased by all toxin treatments, but the combination toxin treatment reduced weight gain more than did either of the toxins administered singly and could be considered additive. Liver weight was decreased by combination treatment, whereas kidney weight was increased by OA treatment. Ochratoxin decreased serum cholesterol, inorganic phosphorus, and alkaline phosphatase values; reduced mean cell volume, hemoglobin concentration, and macrophage phagocytosis; and increased creatinine and total protein values. Consumption of T-2 toxin reduced hemoglobin and serum alkaline phosphatase values. The combination treatment decreased serum cholesterol, gamma-glutamyltransferase, alkaline phosphatase, mean cell volume, hematocrit, and hemoglobin values, as well as lymphoblastogenesis and phagocytosis, and increased serum nine concentration. We concluded that OA and T-2, singly or in combination, can affect clinical performance, serum biochemical, hematologic, and immunologic values, and organ weights of growing barrows. Although some analytes were affected more by the combination than by either toxin alone, the interactions could best be described as additive, not synergistic.

Doxorubicin was encapsulated in canine erythrocytes, treated with 0.32% glutaraldehyde, and administered at a dosage equivalent to 30 mg of free doxorubicin/m(2) of body surface area to dogs with diagnosis of lymphosarcoma. Compared with administration of free doxorubicin, this method of drug delivery substantially reduced peak plasma concentration and prolonged higher plasma concentration of doxorubicin. As such, this method was comparable to continuous IV infusion. Previous studies have indicated this method's potential for reduction in toxic side effects, particularly cardiotoxicosis, while allowing higher total doses of doxorubicin to be administered. In this study, doxorubicin encapsulated in glutaraldehyde-treated erythrocytes induced a triphasic exponential decay of doxorubicin from plasma, the highest relative contribution to the total area of the curve being the terminal phase. The treatment was effective in inducing complete and partial remissions of lymphosarcoma, with minimal acute toxicosis and no evidence of cardiotoxicosis. However, substantial, unanticipated, chronic, nonregenerative myelosuppression developed, and was most strikingly expressed as profound thrombocytopenia. Efforts to ameliorate or circumvent this toxic effect will be required prior to further consideration of this doxorubicin delivery system for treatment of systemic neoplasia.

Growth of Pasteurella haemolytica A1 in RPMI 1640 medium containing 0.5% bovine serum albumin (BSA) for 2.5 hours enhanced culture supernatant leukotoxic activity [30,700 +/- 12,900 toxic units/ml, compared with leukotoxic activity of culture supernatants produced in RPMI 1640 medium alone (120 +/- 40 toxic units/ml)]. Gel filtration chromatography of the leukotoxic activity from RPMI 1640 medium supernatants in buffer containing 50 mM NaCl indicated a single leukotoxic activity peak (peak I) eluting near the gel resin molecular mass exclusion limit (estimated molecular mass of approx 8,000 kd). In contrast, culture supernatants produced in RPMI 1640 plus bovine serum albumin medium (RPMI + BSA) had peak I and 2 additional leukotoxic activity peaks (peaks II and III) with estimated molecular mass of approximately 80 and < 30 kd, respectively. All leukotoxic activity peaks were composed of approximately 100-kd molecular mass leukotoxin protomer, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with a monoclonal antibody against leukotoxin. Subjecting culture supernatant leukotoxic activity produced in RPMI + BSA to gel filtration chromatography in buffer containing 500 mM NaCl or 6M urea resulted in detection of only a single leukotoxic activity peak with estimated approximate molecular mass of 250 and 800 kd, respectively. These findings suggest that P haemolytica exists as a high molecular mass aggregate with low leukotoxic activity which, in the presence of BSA, partially disaggregates to multiple toxin forms with enhanced leukotoxic activity. Some of these leukotoxin forms interact with dextran-based gel resins at low ionic strength.

Direct evidence linking alkaloids found in endophyte-infected tall fescue forage with the livestock disorder known as fescue toxicosis is lacking. Physiologic effects of fescue toxicosis include reduced serum prolactin concentration in cattle. A monoclonal antibody specific to the lysergic moiety of ergot alkaloids was developed in mice after creating an immunogen by linking lysergol to human serum albumin. The antibody was specific to the lysergic moiety and, therefore, it cross-reacted with ergot alkaloids, lysergic acid, and lysergol. The antibody did not cross-react with alkaloid derivatives that had bromated or hydrogenated lysergic ring moieties. Fescue toxicosis conditions were elicited in yearling Angus steers by permitting them to graze endophyte-infected tall fescue containing > 650 Kg/kg of ergovaline for 60 days. Passive immunization of steers by infusion of the monoclonal antibody increased serum prolactin concentration by 7 ng/ml, beginning immediately after infusion. Control steers did not respond to treatment with bovine serum albumin. Active immunization of yearling Angus heifers with immunogens containing lysergol or ergonovine linked to human serum albumin resulted in an antibody response.

A bolus dose of methimazole (MMI) was administered IV over 1 minute to 5 healthy adult dogs at a dosage (40 mg/kg of body weight) known to impart protection against cisplatin-induced renal disease. Blood and urine samples for pharmacokinetic analysis were collected over a 24-hour period. Physical examination, CBC, determination of serum thyroid hormone concentrations, and serum biochemistry analysis were performed over a 10-day period to evaluate short-term toxicoses. At this dosage, MMI appears to be safe and well tolerated in dogs; only 1 of the 5 dogs had mild and transient increases in serum activity of hepatic enzymes. In addition, MMI did not alter serum thyroid hormone concentrations. Half-life of 8.82 hours and mean residence time of 12.18 hours were determined for MMI. Renal clearance of native MMI, along with sulfate and glucuronide conjugates, represented only 20% of total systemic clearance. Results of this study provide further information concerning clinical use of MMI in dogs and may contribute to better understanding of the mechanism of MMI protection against chemically induced nephrotoxicosis.

Medetomidine, an investigational drug indicated for clinical use as a short-term chemical restraint in dogs, was evaluated for its cardiopulmonary effects, in 10 naturally heartworm-infected (HW+) and 10 noninfected (HW-) Beagles. The drug was randomly administered IV (30 microgram/kg of body weight) and IM (40 microgram/kg) in single injections to all dogs. Heart rate, respiratory rate, ECG, blood gas tensions, blood pH, central venous and arterial pressures were measured at 0, 15, 30, 60, 90, 120, and 180 minutes. Medetomidine induced an immediate significant (P less than or equal to 0.001) increase in mean arterial blood pressure followed by decreased blood pressure that remained below normal throughout the study in both groups, irrespective of route of administration. Medetomidine increased central venous pressure, over time, for both groups and both routes of administration. Heart and respiratory rates were significantly (P less than or equal 0.001) decreased after medetomidine administration and remained reduced for the duration of the study in all dogs. The ECG variables were not significantly different between groups or between routes of administration. The HW+ dogs tended to have higher mean PaO2 than did HW- dogs at several postinjection determination times, particularly when the drug was administered IM. The PaO2 decreased during the first 30 minutes in both groups and tended to increase gradually thereafter. The pH decreased over time for both groups and both routes. A significant (P less than or equal to 0.05) decrease in pH was seen in the HW- dogs, compared with HW+ dogs at each measuring time for both routes. The PaCO2 did not significantly change for groups or routes. In general, bradycardia was the predominant cardiovascular effect seen after medetomidine administration in all dogs, irrespective of route. Lowering of blood pressure and heart rate (after a transient blood pressure increase) was synchronized with sedation in these dogs. The overall clinical response with regard to cardiopulmonary effects in HW+ dogs was similar to that in HW- dogs.

A crude, whole-body extract of female heartworms was administered IV to 10 dogs with and 13 dogs without heartworm (HW) infection. Shock developed in 8 of 10 infected dogs and 11 of 13 non-infected dogs, and blood coagulopathy was observed in 12 of 19 dogs with shock. Prevalence and severity of blood coagulopathy were proportionate to prevalence and severity of shock. Platelet count decreased in all dogs with shock with or without blood coagulopathy; thus, the decrease in platelet count might be related to shock. In 4 dogs, activated partial thromboplastin time (APTT) was prolonged--192.0 seconds at 30 minutes after HW injection--and prothrombin time (PT) was increased--13.8 seconds at initial collapse. In 8 dogs, APTT was increased--200 seconds for 2 hours after HW injection--and PT was increased--200 seconds at 30 minutes after the injection. The APTT prolongation might have been caused mainly by decreases in activities of factors VIII, IX, XI, and XII of the intrinsic blood coagulation pathway. In dogs with severely prolonged PT, plasma fibrinogen concentration and factor II activity decreased slightly. Prolonged PT was corrected in vitro by addition of normal plasma at high concentration (> 80%), but prolonged APTT could not be corrected in vitro by addition of 80% normal plasma. Serum fibrin degradation products concentration was < 10 microgram/ml, and soluble fibrin monomer complex was negative in all dogs. Thrombi were not found in blood vessels of any organ at necropsy and after histologic study. Therefore, it was suggested that blood coagulopathy resulting from inhibition of coagulation factor activities might develop in shock induced by HW extract.

The effect of mimicking prepartum concentration of estradiol-17 beta on the inflammatory response to endotoxin in gilts was studied. The study was performed in a split-litter design and comprised 5 pairs of littermates. A catheter was inserted into the jugular vein 2 days prior to the start of the study. In each pair, 1 littermate was treated IM with 2.5 mg of estradiol-17 beta/75 kg of body weight, and the other littermate was given peanut oil IM as a control. The day after treatment, all gilts were challenge-exposed with a Salmonella typhimurium-derived endotoxin (1 microgram/kg, IV) and the inflammatory response to challenge exposure was monitored. There was no effect of estradiol treatment on the transient clinical signs of endotoxemia or on the increase in rectal temperature. The increase in blood concentrations of prostaglandin F2 alpha, metabolite and cortisol after endotoxin challenge exposure was not affected by estradiol. Decrease in number of circulating blood mononuclear cells and polymorphonuclear leukocytes was not changed by estradiol treatment. Taken together, mimicking prepartum concentration of estradiol did not affect either the magnitude or the kinetics of the inflammatory response to endotoxin in gilts. Relevance of these findings to development of endotoxin-mediated diseases, such as the postpartum agalactia syndrome, needs further study.

A crude, whole-body extract of female or male heartworms was injected IV into 28 dogs with and 22 dogs without heartworm (HW) infection. The female HW extract caused shock in 22 of 24 dogs with and 12 of 20 dogs without HW infection. The male HW extract induced shock in 4 of 4 dogs with and 1 of 2 dogs without HW infection. Prevalence of shock caused by female HW extract was significantly (P < 0.05) higher in dogs with than without HW infection; shock developed 5 to 30 minutes after HW injection. These signs were observed: marked decrease in blood pressure; collapse (initial collapse); paleness of mucous membranes; weak heart sounds; dyspnea; skin coldness; intestinal hyperperistalsis, and defecation; increases in RBC count, serum total protein concentration, serum osmolality, serum Na and blood glucose concentrations; and decreases in neutrophil, eosinophil, and platelet counts. Alanine transaminase, alkaline phosphatase, and lactate dehydrogenase activities increased substantially from the time of initial collapse to 24 hours after HW injection. Of 39 dogs with shock, 29 recovered from initial collapse, but 5 of the 29 subsequently collapsed again (secondary collapse), with bloody diarrhea followed by death. Of these 39 dogs, 6 died during initial collapse without bloody diarrhea, and 4 were euthanatized during initial collapse. It was confirmed that HW extract had, in fact, induced shock. These clinical, hematologic, and biochemical findings were fundamentally similar to those associated with shock resulting from administration of drugs, such as diethylcarbamazine and milbemycin D, in microfilaremic dogs with HW infection.

Sheep given powdered Ferula communis variety brevifolia at dosage of 2.5 g/kg of body weight/d for 15 days developed classical clinical signs of intoxication: anorexia, somnolence, apparent weakness, and hemorrhage. Marked reduction of vitamin K-dependent coagulation factors and prolongation of prothrombin time and activated partial thromboplastin time were consistent with presence of ferulenol, a toxic coumarinic factor in the plant. Changes induced in the coagulation system developed by the second day of plant administration and were normal within 4 days after dosing was stopped. There was no evidence of primary liver damage or platelet malfunction. Of 6 intoxicated sheep, 2 died with only minimal evidence of hemorrhage.