Cat foods containing propylene glycol (PG) induce Heinz body formation in feline erythrocytes. To further study the hematologic importance of dietary PG, 21 adult cats were allotted to 3 groups of 7 each and fed diets containing 0, 6, or 12% PG on a dry-weight basis. Cats fed PG had a dose-related increase in Heinz bodies within 2 weeks, and the increase persisted throughout the study. Although only slight changes occurred in PCV, hemoglobin concentration, and RBC count, punctate reticulocytes were significantly increased in the group fed 12% PG. Mean RBC survival was decreased in the groups fed 6 or 12% PG by 30 and 55%, respectively, compared with the control group. These data indicate that PG-containing diets cause a dose-dependent erythrocyte destruction, even when fed at concentrations as low as 6%.

Pigs from 3 litters kept under gnotobiotic conditions were inoculated orally with virulent transmissible gastroenteritis (TGE) virus, a TGE vaccine, or Hank's balanced salt solution at 2 days of age and then euthanatized at intervals ranging from 1 to 7 days after inoculation. Pigs exposed to the vaccine had clinical evidence of diarrhea and weakness. Lesions resembling those of TGE were revealed grossly, microscopically, and by scanning electron microscopy. Viral antigen was seen in intestinal epithelial cells by the direct fluorescent antibody technique. The disease induced by the vaccine virus had a longer incubation period and lesions were less severe than that induced by the virulent virus.

Ten controlled tests were done between 1972 and 1989, in lambs on pasture, evaluating activity of fenbendazole (FBZ; 5 mg/kg of body weight), oxfendazole (OFZ; 3.5 and 10 mg/kg), oxibendazole (OBZ; 10 mg/kg), pyrantel pamoate (PRT; 25 mg of base/kg), and thiabendazole (TBZ; 44 and 50 mg/kg) against natural infections of helminths, with emphasis on 2 strains (A and B) of Haemonchus contortus. Strain A was phenothiazine-susceptible and strain B was phenothiazine-resistant when isolated in 1955. For approximately 10 years prior to these tests, sheep infected with both strains had been treated periodically each year with several compounds, including thiabendazole, which was used many more times than the other drugs. For this study, 4 (FBZ, OFZ, OBZ, and PRT) of the 5 compounds were evaluated in either 1 or 2 controlled tests. The fifth compound, TBZ, was used for 5 tests. Strain A H contortus was resistant to TBZ for all years tested, but more susceptible to FBZ, OFZ, OBZ, and PRT. Overall, strain B was susceptible to TBZ (with a few exceptions), and also to FBZ, OFZ, OBZ (activity less on immature forms), and PRT. Other abomasal parasites (2 species of Ostertagia and 3 of Trichostrongylus) were found in low numbers, but removal overall was good for the compounds tested. Trichostrongylus axei, found in higher numbers than species of Ostertagia and other species of Trichostrongylus, were effectively removed by all compounds in most cases. Activities of TBZ and PRT were also evaluated against several species of intestinal helminths, most of which were found in low numbers. Cooperia curticei were inconsistently removed by TBZ, but activity of PRT was effective. Both compounds were active on mature Nematodirus spathiger, but TBZ had variable activity on immature forms. Strongyloides papillosus were effectively removed by TBZ. Other parasites found in lower numbers than the aforementioned 3 species were Capillaria spp, Trichuris spp, and Oesophagostomum columbianum; removal was variable for both drugs.

The hemolytic effect of onion consumption in dogs with hereditary high erythrocyte reduced glutathione and potassium concentrations (designated HK dogs) was compared with that in clinically normal dogs. Twelve hours after oral administration of boiled onions (200 g/dog), hemoglobin concentration decreased to 84.4% of the initial value in HK dogs; it decreased only to 90.5% in clinically normal dogs. At 24 hours, methemoglobin concentration was significantly (P < 0.05) higher in HK dogs than in clinically normal dogs. The concentration of erythrocyte oxidized glutathione increased about fivefold at 10 hours in HK dogs, whereas it did not change during the experimental period in clinically normal dogs. In addition, at 12 hours, the proportion of erythrocytes containing Heinz bodies increased to 24.4% in HK dogs, but increased only to 1.2% in clinically normal dogs. Thus, results indicated that HK dogs were more susceptible to the oxidant action of onions than were clinically normal dogs.

Effects of Ostertagia ostertagi infection on secretion of insulin, pancreatic glucagon, cortisol, gastrin, and pepsinogen were studied in calves inoculated with 100,000 (group 1) or 10,000 (group 2) O. ostertagi infective larvae weekly for 14 weeks. Plasma insulin concentrations in both inoculated groups were lower than those in a noninfected (group 3) control group. The differences between group 1 and group 3 were significant (P < 0.05) at 2 and 12 weeks after initial inoculation. Plasma pancreatic glucagon and cortisol concentrations of groups 1 and 2 did not differ significantly from those of the control group, although plasma pancreatic glucagon concentration was consistently lower in group-1 calves from 4 weeks to the end of the study. Plasma pepsinogen and serum gastrin concentrations also increased significantly (P < 0.05) in both groups that received inoculations. We concluded that decreased plasma insulin concentrations are contributory to changes in postabsorptive protein metabolism, and that serum gastrin concentrations are more representative of the pathologic changes in the abomasum than are plasma pepsinogen concentrations.

Mechanisms responsible for the positive inotropic effects of dopexamine were investigated in 8 halothane-anesthetized horses. The hemodynamic effects of increasing infusions of dopexamine (5, 10, 15 microgram/kg of body weight/min) were determined before and after sequential administration of specific antagonists. Using glycopyrrolate and chlorisondamine, and atenolol and ICI 118,551, muscarinic and nicotinic ganglionic, and beta, and beta-adrenergic receptor blockade, respectively, was induced. Dopexamine infusions induced increase in heart rate, cardiac output, systolic and mean arterial blood pressure, and maximal rate of left ventricular pressure development (+dP/dt(max)). Right atrial pressure and systemic vascular resistance decreased. Parasympathetic and ganglionic blockade attenuated cardiac output, systolic and mean aortic blood pressures, and +dP/dt(max) responses to dopexamine infusion. Dopexamine-induced increase in heart rate was potentiated by parasympathetic and ganglionic blockade. beta-Adrenergic receptor blockade decreased heart rate, cardiac output, arterial blood pressure, and +dP/dt(max) from baseline values and markedly reduced the response to dopexamine infusion. beta-Adrenergic receptor blockade induced further decrease in hemodynamic variables from baseline values and completely abolished the cardiostimulatory effects of dopexamine on +dP/dt(max) These data indicate that baroreflex activity, beta- and beta 2-adrenergic receptor stimulation may be an important cause of dopexamine's positive inotropic effects in horses.

A study was performed to determine whether equine peritoneal macrophages produce interleukin 6 (IL-6) in vitro in response to endotoxin. Peritoneal fluid was collected from 14 clinically normal adult horses and was used as the source of peritoneal macrophages. Macrophages from each horse were isolated and cultured separately in vitro in the absence or presence of various concentrations (0.5, 5, or 500 ng/ml) of endotoxin (lipopolysaccharide from Escherichia coli 055:B5). Culture medium supernatants were collected after 3, 6, 12, and 24 hours' incubation and were frozen at - 70 C until assayed for IL-6 activity. Supernatant IL-6 activity was determined by use of a modified colorimetric assay and the murine hybridoma cell line B13.29 clone B.9, which is dependent on IL-6 for survival. Results indicated that equine peritoneal macrophages produce IL-6 in vitro and that supernatant medium IL-6 activity was significantly (P < 0.05) increased by exposure to endotoxin. Significant (P < 0.05) time and treatment effects on macrophage IL-6 production were apparent. The IL-6 activity peaked at 6 or 12 hours' incubation, then remained high through 24 hours' incubation, regardless of endotoxin exposure. Medium IL-6 activity during 3 and 6 hours' incubation was significantly (P < 0.05) greater in macrophages exposed to 5 or 500 ng of endotoxin/ml than in those exposed to 0.5 ng of endotoxin/ml; however peak IL-6 activity was similar among all endotoxin concentrations. Endotoxin concentration did not have an effect on medium IL-6 activity from macrophages exposed to endotoxin for 12 or 24 hours.

Although cats are less susceptible to infection with Dirofilaria immitis than are dogs, the possibility of severe consequences from infection or adulticidal treatment renders preventive treatment a desirable alternative in endemic areas. To evaluate the efficacy of milbemycin oxime as a chemoprophylactic agent in cats, 48 cats were inoculated with infective D immitis larvae. Single oral treatment with 2.3 mg of milbemycin oxime (0.5 to 0.9 mg/kg of body weight) at 30 or 60 days after inoculation with infective larvae gave strong but incomplete protection. Treatment at 60, as well as 90, days after inoculation with infective larvae was completely effective in preventing development of infection. A control group of inoculated, but untreated, cats was monitored biweekly for hematologic changes and for changes in parasite-specific serum antigen and antibody concentrations. Pronounced increases in total leukocyte counts and eosinophil numbers were associated with the estimated time of in vivo molting from fourth- to fifth-stage larvae. Antibody reactivity correlated with infection status, but serum antigen concentrations through 161 days after inoculation were undetectable.

Six untrained mares were subjected to incremental treadmill exercise to examine exercise-induced in plasma renin activity (PRA) and plasma aldosterone (ALDO) and plasma arginine vasopressin (AVP) concentrations. Plasma renin activity, ALDO and AVP concentrations, and heart rate (HR) were measured at each step of an incremental maximal exercise test. Mares ran up a 6 degrees slope on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s each minute until HR reached a plateau. Plasma obtained was stored at - 80 C and later was thawed, extracted, and assayed for PRA and ALDO and AVP values by use of radioimmunoassay. Exercise caused significant increase in HR from 40 +/- 2 beats/min (mean +/- SEM) at rest to 206 +/- 4 beats/min (HRmax) at speed of 9 m/s. Plasma renin activity increased from 1.9 + /- 1.0 ng/ml/h at rest to a peak of 5.2 +/- 1.0 ng/ml/h at 9 m/s, paralleling changes in HR. Up to treadmill speed of 9 m/s, strong linear correlations were obtained between exercise intensity (and duration) and HR (r = 0.87, P < 0.05) and PRA (r = 0.93, P < 0.05). Heart rate and PRA reached a plateau and did not increase when speed was increased from 9 to 10 m/s. Plasma ALDO concentration increased from 48 +/- 16 pg/ml at rest to 191 +/- 72 pg/ml at speed of 10 m/s. Linear relation was found between exercise intensity (and duration) and ALDO concentration (r = 0.97, P < 0.05). Plasma AVP concentration increased from 4.0 +/- 3.0 pg/ml at rest to 95 +/- 5.0 pg/ml at speed of 10 m/s. The relation between AVP concentration and exercise intensity (and duration) appeared to be curvilinear, and was described by an exponential function (r = 0.92, P < 0.05). These data indicate that PRA and ALDO and AVP concentrations increase in horses during progressive treadmill exercise.

Five studies were performed to determine factors affecting progesterone concentration in skim milk. Results of the first study indicated that progesterone concentration was higher in skim milk of samples kept 16 hours in an ice bath (0 C) than of those left at room temperature (21 C). In the second study, this temperature effect was found to be reversible, with skim milk progesterone concentration increasing when whole milk samples were cooled prior to centrifugation. In the third study, [3H]-labeled progesterone was used to determine the relationship between fat content of foremilk (the first milk obtained from the teats), midmilk (milk obtained through milking), and strippings (milk obtained immediately after milking machines have been removed) samples and temperature (4 C and 21 C) on the percentage of progesterone in the skim milk fraction. The relationship between percentage of butterfat and percentage of progesterone in skim milk was linear when the log of these variables was used for calculations. In the fourth study, assayable progesterone in the skim milk fraction of foremilk, midmilk, and strippings was affected by temperature. In the fifth study, a multiple-regression procedure was used to determine the amount of variation in percentage of radioactive progesterone in the skim milk fraction. Independent variables (whole milk butterfat and temperature of incubation [1, 3, 13, 22, 37, and 50 C]) and the natural log of each variable, were entered into a stepwise multiple-regression analysis. The log of the temperature and percentage of butterfat of whole milk at the time of centrifugation accounted for 89.2% (r2 = 0.892) of the variation in the log of the progesterone concentration in the skim milk fractions. The equation describing this relationship was: log percentage of progesterone in the skim milk fraction = 4.046 - 0.144 X (log of temperature of whole milk sample) - 0.688 X (log percentage of butterfat in whole milk sample). The loss of progesterone from skim milk fractions of warm whole milk samples is possibly a physical phenomenon dependent on the temperature of the sample and its percentage of butterfat. A nomograph was created to allow others to use these variables in making adjustments in progesterone concentrations.