Pharmacokinetics and bioavailability of rifampin in adult sheep were investigated by use of high-performance liquid chromatography for determination of serum concentrations. Eight adult ewes were given rifampin PO at the rate of 50 mg of rifampin/kg of body weight. Three weeks after the first experiment, the sheep were given rifampin PO and IV at the rate of 20 mg/kg in a cross-over design, with 1 week between treatments. Serum obtained over a 36-hour period was analyzed for rifampin and a potential metabolite, 25-desacetyl-rifampin, using reverse-phase chromatography with uv detection at 254 nm. Data were analyzed by compartmental and noncompartmental models. Analysis by the noncompartmental model of rifampin serum concentrations after IV administration yielded a mean +/- SD total body clearance of 1.16 +/- 0.21 ml/min/kg, apparent volume of distribution at steady state of 0.45 +/- 0.06 L/kg, and terminal elimination rate constant of 0.15 +/- 0.04 hour-1. The harmonic mean of the elimination half-life was 4.56 hours. Because of incomplete and continuing absorption, bioavailability was extremely variable after oral administration. Desacetyl-rifampin was not detected. On the basis of pharmacokinetic values, serum concentrations measured in this study, and published minimal inhibitory concentrations, the dosage of 20 mg of rifampin/kg, PO, every 24 hours should provide adequate serum concentrations for treatment of rifampin-susceptible bacterial infections in sheep.

From Aug 1985 through July 1986, 720 meat turkey flocks on 160 California premises were monitored and outbreaks of fowl cholera (Pasteurella multocida) were investigated. Data from 43 outbreak (case) flocks were compared with data from 43 nonoutbreak (control) flocks. Outbreak flocks, compared with control flocks, were more likely to be located on premises with higher maximal bird capacity and history of fowl cholera outbreaks. The overall impression was that flocks in larger, newer, more intensively managed premises were at greater risk of fowl cholera outbreaks than were other flocks.

The purpose of this study was to evaluate the effect of withdrawal of lactose from the diet for 72 hours on lactase activity in the jejunal mucosa of conventionally raised calves. The descending portion of the duodenum of six Holstein calves < 24 hours old was cannulated. The calves were fed milk except on days 5, 6 and 7 when they were given the same volume of an electrolyte solution. Sequential biopsy specimens of the proximal jejunal mucosa were obtained for three weeks and the lactase activity determined. Lactase activity was highest on day 1 and a trend toward decreased lactase activity from birth until three weeks was observed. Mean lactase activity was significantly (p < 0.05) higher for days 1, and 3 compared to days 9, 13 and 17. The withdrawal of milk and replacement by an electrolyte solution during three days had no significant effect on jejunal mucosal lactase activity in neonatal calves.

Piglets infected intranasally with Bordetella bronchiseptica were injected with two fluorochrome markers. Transverse sections of undecalcified nasal conchae (cut between the third incisor and the third premolar teeth) were examined by microradiography and fluorescence microscopy; surface-stained sections were evaluated by light microscopy. The fluorescent surface of the nasal ventral conchae from the infected piglets was increased as compared with the controls. This was due to an increased amount of fluorescent mineralization fronts as well as to the presence of abnormal fluorescent areas within trabeculae. Trabecular mineral content of the microradiographs was irregular and varied from hypo- to hypermineralized. When compared with the corresponding surface-stained sections, no correlation could be made between the mineral content and the type of tissue. These findings suggest that an increased number of osteoblasts which secrete prebone matrix but are modified so that mineralization does not occur normally.

The purpose of the study was to determine whether there were circadian variations in serum osteocalcin in normal horses and to determine whether it was important to regulate the time of blood sampling in clinical investigations. Osteocalcin or bone Gla-protein (BGP), alkaline phosphatase, total calcium, phosphate and total protein were studied over a 24 h period. Blood samples were taken every 60 min from nine adult Standardbred horses. There was a correlation between serum levels of alkaline phosphatase (r = 0.3, p < 0.01), phosphate (r = 0.42, p < 0.01) and serum osteocalcin levels. There was a very marked individual effect on serum levels of osteocalcin and alkaline phosphatase (p < 0.01). This effect was present for phosphate levels but not significant for total calcium. The individual effect was lower and time effect was higher for serum osteocalcin if the subjects were divided into two age groups, one of horses of five years or less (n = 4) and a second group older than five years (n = 5). In both groups a circadian rhythmicity was observed. Serum osteocalcin showed a biphasic pattern. Levels were constant during daytime (light period) and underwent significant variations during the night (dark period), going through a nadir at 2000 h and through a maximum peak at 0500 h. It was concluded that in normal horses the blood osteocalcin level follows a circadian variation. Also daytime (light period) seems to be the more appropriate period for blood sampling.

Ovulation has been likened to an inflammatory process. Inflammatory cells accumulate in the ovulating follicle, presumably because of chemotactic factors. Chemotactic activity was measured in fluid aspirated from follicles of estrous mares 0, 12, 24, and 36 hours after ultrasonographic detection of a 35-mm follicle and IV treatment with 2,500 IU of human chorionic gonadotropin. Chemotaxis was assessed by measuring directional migration of equine neutrophils under agarose. Follicular fluid acted as a chemoattractant for neutrophils, but there was no significant difference in chemotactic activity among different time intervals after administration of human chorionic gonadotropin. On the basis of results of various treatments, chemotactic properties of serum and follicular fluid were similar. Chemotactic activity was significantly reduced by heating (56 C for 30 minutes) and by trypsinization and was virtually removed by charcoal treatment. Dialyzing the follicular fluid (3,500 and 8,000 molecular weight cut-off) significantly reduced the chemotactic activity of follicular fluid and serum. The importance of chemotactic factors in the process of ovulation in the mare is yet to be established.

An ammonium sulfate-soluble fraction of Taenia hydatigena cyst fluid (ThFAS) was further evaluated for use in the immunodiagnosis of cysticercosis. Analysis of ThFAS by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and protein immunoblot analysis confirmed earlier reports of a highly specific, low molecular weight antigen in this preparation; in contrast, other components of ThFAS were shown to react nonspecifically. Antibodies against the < 12-kD diagnostic antigen were detected in sera from 10 cattle and 4 swine inoculated with metacestodes of T saginata and T solium, respectively, but not in animals inoculated with Fasciola hepatica, Trichinella spiralis, Brucella abortus, or Toxoplasma gondii, or in noninoculated controls. Isolation and immobilization of the < 12-kD antigen on a hydrophobic transfer membrane resulted in development of an unambiguous dipstick assay capable of correctly identifying fully developed (10-week) experimentally induced infections in cattle and swine. In addition, the dipstick assay was highly specific for diagnosis of the disease in human beings, and offers the potential of distinguishing between human clinical cases of cysticercosis and taeniasis. A similar reactive antigen of diagnostic potential was also identified and isolated from T crassiceps and T taeniaeformis cyst fluids.

A flow cytometric method was developed to perform differential leukocyte counts on bovine blood. Blood specimens from 50 healthy Holstein cows were analyzed by use of a flow cytometer. The method entailed diluting blood with phosphate-buffered, hypotonic saline solution containing acridine orange, and performing a step-wise, 3-parameter analysis on the bases of cell size, cellular granularity, and granulocyte fluorescence. Initially, proportions of monocytes, granulocytes, and lymphocytes were determined by creating appropriate windows on dot plots of cell size (determined by forward light scatter) vs cellular granularity (determined by the logarithm of side light scatter). Eosinophils were resolved by analysis of granulocytes as dot plots of logarithms of green vs red fluorescence ascribed to acridine orange. Proportions of eosinophils and neutrophils were computed from data so generated. Microclumps of platelets spuriously affected counts of some granulocytes, particularly eosinophils. Differential leukocyte counts determined by flow cytometry generally compared favorably with those obtained by use of the conventional microscopic method, using Wright-stained blood films. Mean neutrophil and eosinophil counts determined by the 2 methods did not differ significantly, but lymphocyte counts determined by flow cytometry were significantly higher than those determined by microscopy (P < 0.01). Correlation coefficients for counts of neutrophils, eosinophils, and lymphocytes determined by the 2 methods ranged from 0.519 to 0.833. Correlation between monocyte counts was low (r = 0.147), although mean monocyte counts determined by the 2 methods did not differ significantly. Total leukocyte counts determined by flow cytometry were significantly lower (P < 0.01) than counts determined by use of an automated cell counter; correlation between the 2 counts was low (r = 0.350).

The area of skin supplied by the afferent fibers in one cutaneous nerve is called the cutaneous area (CA) for that nerve. The CA of peripheral branches of lumbar and sacral spinal nerves responsive to the stimulation of hair follicle mechanoreceptors were mapped in 27 dogs. The amount of overlap among the CA was similar to that found for other CA of the body. The CA of peripheral branches of the sciatic nerve were restricted to the lateral, cranial, and caudal aspects of the pelvic limb distal to the stifle. The CA of the saphenous nerve was located on the medial side of the limb, except for a small area located on the lateral side of the crus. The distal part of the CA of the saphenous nerve was completely overlapped in the hind paw by branches of the superficial peroneal nerve laterally and the medial plantar branch of the tibial nerve medially. The CA for the deep peroneal nerve was located on the dorsal surface of the webbing between digits 2 and 3 and the adjacent skin of these digits. The CA of the plantar branches of the tibial nerve were small in comparison with the diameter of the nerve, suggesting that these branches contained nerve fibers supplying other, deeper structures in the hindpaw and that damage to these nerves would interfere with cutaneous sensation in only a small region on the plantar surface of the hindpaw. Knowledge of the CA of the various branches of the sciatic nerve allows more accurate localization of injury to the sciatic nerve or its branches by using areas of anesthesia.

The lateral distribution and temporal changes in the eye standing potential of 15 dogs with normal eyes (as determined by use of an ophthalmoscope and electroretinography) were measured by use of noninvasive methods. The standing potential was converted to an alternating potential by controlled eye movement. The light peak occurred 6 minutes after a stimulus intensity increase of 4 log units. The ratios of the highest measured voltage after the light step divided by the voltage measured immediately before the light step ranged from 1.27 to 2.07 (mean 1.74 +/- SEM, 0.064). The responses typically decayed slowly after the light peak. The potential after the light peak did not return to prelight step values during the observation period. The field potential of the standing potential decreased nonlinearly in temporal direction from the outer canthus.