Macromolecular permeability of the small intestine was tested in four 3-week-old gnotobiotic pigs inoculated with porcine rotavirus strain RV277 (group A). Pigs were administered 125I-labeled polyvinylpyrrolidone (molecular weight [mol wt], 40,000) orally 1 day before and 2 and 24 hours after virus inoculation, and blood samples were obtained every 6 hours. Eight hours after rotavirus inoculation, pigs had watery diarrhea. Increased permeation of 125I-labeled polyvinylpyrrolidone was not observed after clinical signs of infection had developed. Serum total protein and urea nitrogen concentrations increased slightly at the end of the study, probably as a consequence of dehydration. Differences in blood glucose concentration were not seen. At 48 hours after viral inoculation, macromolecular permeability was tested morphologically by injecting horseradish peroxidase (mol wt, 40,000) into the jejunal lumen just distally to the ligamentum colicoduodenale. After an incubation period of 20 minutes, small segments of jejunum were obtained for stereomicroscopic, histologic, and ultrastructural investigations. Moderate hyperregenerative villus atrophy was found. Ultrastructural changes of the villus epithelium were minor, and increased macromolecular permeation was not observed.

We investigated the influence of parasympathetic tone on the arrhythmogenicity of graded dobutamine infusions in horses anesthetized under clinical conditions. Six horses were used in 9 trials. Two consecutive series of graded dobutamine infusions were given IV; each continuous graded dobutamine infusion was administered for 20 minutes. The dobutamine infusion dosage (5, 10, 15, and 20 microgram/kg of body weight/min) was increased at 5-minute intervals. Isovolumetric saline solution vehicle (v) or atropine (A; 0.04 mg(kg) was administered IV, or bilateral vagotomy (VG) was performed as a treatment before the second series of dobutamine infusions. Treatment was not administered prior to the first dobutamine infusion. Significant interaction between treatment and dosage of dobutamine infusion existed for differences from baseline for mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, heart rate, and cardiac index at dosages of 5 and 10 micrograms of dobutamine/kg/min, given IV and for heart rate at dosage of 15 micrograms of dobutamine/kg/min, given IV. Results for group-V horses were different from those for group-A and group-VG horses, but were not different between group-A and group-VG horses in all aforementioned cases, except for heart rate and cardiac index at dosage of 5 micrograms of dobutamine/kg/min, given IV. Normal sinus rhythm, second-degree atrioventricular block, and bradyarrhythmias predominated during low dobutamine infusion rates during the first infusion series (nontreated horses) and in group-V horses during the second infusion series. Only tachyarrhythmias were observed during the second infusion series in the horses of the A and VG groups. The modulating influence of parasympathetic nervous system activity on hemodynamics and development of arrhythmia was conspicuous during low dobutamine infusion rates. Significant differences were not observed in hemodynamic responses to dobutamine, with respect to parasympathetic influence at high dobutamine infusion rates.

A study for about a 30-month period was done to compare strongyle control programs, using per os treatments of ivermectin (IVE) paste exclusively or alternation of 4 antiparasitic paste compounds: IVE, oxfendazole (OFZ), oxibendazole (OBZ), or pyrantel pamoate (PRT). Every 8 weeks, 1 group of horses (barn C; n = 14 to 16) was given IVE paste exclusively, and a second group (barn E; n = 16) was given the 4 antiparasitic pastes on an alternating schedule. Worm eggs and larvae per gram of feces (epg and lpg, respectively) values were determined every 2 weeks during the investigation. This study in grazing horses (mares and fillies), naturally infected with internal parasites, was conducted during the period between Oct 22, 1987 and Feb 8, 1990, with an additional observation on Mar 28, 1990. For barn-C horses, treated exclusively with IVE (200 micrograms/kg of body weight) 14 times, 2-week posttreatment mean strongyle epg and lpg (small strongyle) values were reduced 99 to 100%. Mean strongyle epg and lpg (small strongyle) values for each 2-week sample period remained low (< 20) throughout the study period, except for 1 moderate transient increase in July 1988. For the entire study period, the aggregate mean strongyle epg value was 12 and the lpg value was 6. Two-week posttreatment mean strongyle epg and lpg (small strongyle) values for barn-E horses, treated alternately with therapeutic (approx) dosage of IVE (200 micrograms/kg, 4 times), OFZ (10 mg/kg; 5 times), OBZ (10 mg/kg; 4 times), or PRT (6.6 mg base/kg; 2 times), varied within and between compounds. Posttreatment (2-week) mean epg values were reduced 100% by IVE, 0 to 100% by OFZ, 74 to 100% by OBZ, and 92 to 100% by PRT. Mean small strongyle lpg values at 2 weeks after treatment indicated reduction of: 100% for IVE, 0 to 76% for OFZ, 43 to 100% for OBZ, and 97 to 100% for PRT. For the entire study period, the aggregate mean strongyle epg value was 54 and the lpg value was 64. The epg and lpg reduction values for the 2 benzimidazoles indicated an increase in the benzimidazole-resistant segment of small strongyles. Fecal cultures for horses in both groups contained larvae of large strongyles (Strongylus vulgaris and S edentatus) only at the time of initial treatment. Treatment program evaluations included necropsy of 9 foals (56 to 203 days old), 7 born to barn-C mares and 2 born to barn-E mares. Generally, low numbers of bots (Gasterophilus intestinalis) and Habronema muscae were found in foals of both groups. Intestinal stages of immature and mature ascarids (Parascaris equorum) were also found in foals born to both groups of mares. Mature pinworms (Oxyuris equi) were found in 1 barn-C foal. Only barn-E foals had Strongyloides westeri. Small strongyles were detected in foals of both groups, up to several thousand in some. The latter finding indicates, in particular, that although barn-C mares had low small strongyle epg and lpg values throughout the study, eggs and larvae built up on pasture in sufficiently high numbers for major transmission to foals born there. Small strongyles in foals were composed of 3 genera and 10 species for barn-C foals and of 3 genera and 8 species for barn-E foals. Seasonal transmission of parasites also was observed.

The purposes of this study were to evaluate the efficacy of metoclopramide to aid passage of a flexible endoscope into the duodenum of dogs, and to determine whether the effect of metoclopramide is dependent on dose. In a randomized, blinded, complete-block design, 6 healthy dogs were anesthetized, then each was given saline solution or 1 of 4 doses of metoclopramide on different days. The ease of passage of a flexible, fiberoptic gastroscope through the pylorus was assessed independently by 3 endoscopists. Administration of metoclopramide hydrochloride at a dosage of 0.4 mg/kg of body weight, IV, made passage of a flexible endoscope into the duodenum significantly (P = 0.009) more difficult than when saline solution was administered; however, dosages of 0.1, 0.2 and 0.8 mg of metoclopramide/kg did not (P = 0.489, 0.842, and 0.092 respectively). It was concluded that metoclopramide did not facilitate, and at one dosage hindered, successful passage of a flexible endoscope into the duodenum of healthy dogs under the conditions of the study. Metoclopramide, therefore, cannot be recommended as an aid for passage of a flexible endoscope into the duodenum of dogs.

We compared the effects of bilateral vs unilateral tibial nerve stimulation of percutaneously recorded spinal evoked potentials (SEP) in the lumbar and caudal thoracic area in dogs. The overall amplitude of the SEP is increased by this means. Use of this method could improve legibility of the recordings. Amplitudes of root and interneuronal components of the SEP are doubled as are cranially transmitted depolarizations. However, the amplitude of the SEP component arising from the primary afferents' depolarization was less than doubled. Latencies of the components were unaffected by bilateral stimulation. Careful observation of the latencies disclosed a 0.9-ms delay in transmission of the fastest component in the midlumbar area. This delay was consistant with results of previous cordotomy experiments, and could influence precision of conduction velocity measurement.

The lipoxygenase metabolites of arachidonic acid have an important role in lymphocyte activation. We used a specific 5-lipoxygenase inhibitor, A-63162, to examine the role of 5-lipoxygenase (5-LO) in equine blood mononuclear cell (BMC) proliferation and leukotriene B4 (LTB4) synthesis after stimulation with mitogen (phytohemagglutinin, PHA) or calcium ionophore (A23187). The A-63162 inhibited PHA-induced equine BMC proliferation and, at the same concentration, also inhibited A23187-induced LTB4 synthesis. The presence of exogenous interleukin 2 (IL-2) or the cyclooxygenase inhibitor indomethacin, failed to reverse the immunosuppression caused by A-63162. Further, we found that A-63162, at the concentration that inhibited BMC proliferation and LTB4 synthesis, had no effect on BMC viability. The addition of the specific protein kinase C inhibitor, H-7, did not inhibit A23187-induced LTB4 synthesis. Results indicate that 5-lipoxygenase metabolites may have an important role in equine lymphocyte activation and that protein kinase C has no role in regulating LTB4 production after A23187 stimulation.

Isoelectric focusing was performed on the soluble proteins of whole-body and excretory-secretory products (ESP) of Fasciola hepatica and Fascioloides magna. Adult F hepatica flukes were recovered from experimentally infected sheep and ESP obtained from the flukes; portions of liver were cut and frozen at -70 C. Fascioloides magna adults were collected from naturally infected white-tailed deer and ESP obtained; portions of liver were collected from noninfected white-tailed deer. Adult flukes and their host tissues were homogenized and centrifuged; protein concentrations with their ESP were determined and adjusted to < 2.50 mg/ml. Seven ESP samples from F hepatica and 1 from Fascioloides magna were subjected to isoelectric focusing with the 2 species of fluke and their respective host liver homogenates. After separation, gels were stained with silver and scanned on a laser densitometer. Protein banding patterns of the 2 species of flukes were dissimilar. In the pH range of 3.5 to 9.6, the body protein had approximately 30 peaks and ESP about 23 peaks in both species. Overall banding patterns of the body protein and ESP of both species were distinct from those of respective host tissues. Of the peaks reported as dominant, 3 of the body protein and 2 of ESP were shared between the 2 species. Fascioloides magna had more dominant peaks than F hepatica. This technique of soluble protein isoelectric focusing is simple and reproducible, and the 2 fluke species can easily be differentiated by this technique, as well as by morphologic characteristics.

Development of age-dependent resistance to enterotoxigenic Escherichia coli was studied, using isolated enterocytes and brush border membranes (BBM) from 7-day-old and 7-week-old pigs. Binding of 125I-labeled heat-stable (125I-STa) enterotoxin to enterocytes and BBM was specific, temperature- and time-dependent, saturable, and partially reversible. Scatchard analysis revealed a single class of receptors. Mean +/- SD avidity of binding (apparent affinity constant, Ka) of 125I-STa to enterocytes from 7-day-old and 7-week-old pigs was 2.14 +/- 0.29 X 10(8) and 2.72 +/- 0.25 X 10(8) L/mol, respectively. Numbers of STa receptors were calcuated to be 64,903 +/- 2,900/enterocyte for 7-day-old pigs and 53,029 +/- 3,117/enterocyte for 7-week-old pigs. Numbers of STa receptors expressed per milligram of BBM protein from 7-day-old pigs were 2.66 X 10(11), compared with 2.29 X 10(11) for BBM from 7-week-old pigs. By 5 minutes after addition of STa to reaction mixtures, intracellular cyclic guanosine monophosphate concentration increased 13.9-fold in enterocytes from 7-day-old pigs and 8.7-fold in enterocytes from 7-week-old pigs. The particulate guanylate cyclase activity associated with BBM from 7-week-old pigs was slightly more sensitive to low amounts of STa, compared with BBM from 7-day-old pigs; however, differences were not observed at intermediate and high amounts. These data indicate that lack of a secretory response to STa by older pigs is not attributable either to decreased numbers of STa receptors or to decreased signal response between the STa receptor and membrane-bound guanylate cyclase. Development of age-dependent resistance by porcine small intestine to STa appears to be attributable to steps in the secretory pathway that respond to increased concentration of cyclic guanosine monophosphate.

Four diets were formulated to contain: 16% protein and 0.4% phosphorus-diet 1; 16% protein and 1.4% phosphorus-diet 2; 32% protein and 0.4% phosphorus-diet 3; and 32% protein and 1.4% phosphorus-diet 4. Forty-eight dogs were fed diet 1 for 3 months after surgical reduction of renal mass, then were allotted to 4 groups of 12 dogs each, with equal mean values for glomerular filtration rate (GFR). Dog of groups 1-4 were fed diets 1-4, respectively, for 24 months. Data collected from the dogs during and at termination of the study were analyzed statistically for effects of dietary protein, phosphorus (P), time, and interactions between these factors. During the 24 months of study, 24 dogs developed uremia and were euthanatized for necropsy. Necropsy also was performed on the remaining 24 dogs after they were euthanatized at the end of the study. Dog survival was significantly enhanced by 0.4% P diets (vs 1.4% P diets), but survival was not significantly influenced by amount of dietary protein. The 0.4% P diets (vs 1.4% P diets) significantly increased the period that GFR remained stable before it decreased, but dietary protein did not have significant effect. Significant blood biochemical changes attributed to P, protein, and time were identified during the study. Terminally, plasma parathyroid hormone concentration was significantly increased from prediet values in all groups of dogs. Urine protein excretion was not significantly affected by dietary amount of either protein or P, when measured by either timed urine collection or urine protein-to-creatinine ratio. A tendency was seen for increased protein excretion with passage of time. Histologic and mineral analyses of kidneys removed at necropsy revealed some significant difference attributable to diet, but differences were more marked when diet was ignored, and the 24 surviving dogs were compared with the 24 that developed uremia. Overall, amount of dietary P was more important than amount of dietary protein for preventing adverse responses. However, because renal damage specifically attributable to either dietary component was not obvious, it is possible that the effects of P were manifested by extrarenal mechanisms.

Incidence of seroconversion to caprine arthritis-encephalitis virus (CAEV) was determined for 1,194 goats on 11 dairies, using 2 repeated annual herd tests for CAEV. Current life table methods were used to compare age-specific incidence of seroconversion for pasteurized milk-raised and unpasteurized milk-raised goats. Logistic regression models were used to determine the risk factors associated with CAEV seroconversion, and to estimate odds ratios for seroconversion for various factor levels. Goats raised by unpasteurized milk-feeding methods were 2.5 to 6.7 times more likely to seroconvert than were goats raised by pasteurized milk-feeding methods, depending on the method of comparison. Similarly, 61.6 to 85.0% of seroconversions in yearling goats possibly were attributable to unpasteurized milk feeding. Among yearling goats, CAEV seroconversion was associated with feeding method, breed, and source of goat (herd of origin) when the effect of dairy was considered. In addition to the 6.7 times greater risk of seroconversion for unpasteurized milk-raised goats, yearling goats of the Saanen and Toggenburg breeds were 2.2 and 3.3 times, respectively, more likely to seroconvert than were Alpine yearling goats. Yearling goats purchased from another source were less likely to seroconvert than were yearlings raised on the dairy where they were studied. Among goats > 1 year old, age was associated with risk of seroconversion. Goats that were 3 years old or were > 4 years old were 1.7 and 3.2 times, respectively, more likely to seroconvert than were 2-year-old goats, when adjusted for effect of dairy. The effects of dairy were significant (P less than or equal to 0.001) in yearling and older goats.