Axial stability of equine oblique proxidmal phalangeal osteotonies with application of the standard short limb cast or 1 of 3 configurations of transfixation casts was determined in vitro. Transfixation cast methods included use of parallel pins, divergent pins, or parallel pins incorporating a metal walking bar. Displacement at the osteotomy was recorded for each limb at 4,448 N. Standard short limb casts provided significantly (P = 0.0002) less axial stability than did any form of transfixation cast. Significant differences were not found between the 3 transfixation casts.

Placental transfer of enrofloxacin and ciprofloxacin was evaluated, using a rabbit in situ perfusion model. A two-step infusion program was carried out to obtain steady-state maternal plasma concentrations of these drugs. For each compound, the placenta in 5 rabbits was perfused for 200 minutes with Earle's enriched bicarbonate buffer at flow rate of 1.5 ml/min. To assess reliability of the model, most of the determinants of placental transfer (maternal and fetal pH, gas balance, heart status, rectal temperature, and protein binding) were controlled. In addition, the infusion program included administration of antipyrine, a commonly used indicator of placental exchange. Drug concentrations were measured in maternal plasma and perfusate by use of a high-performance liquid chromatographic assay. Plasma protein-binding estimation indicated no differences between the drugs. Placental clearance of the drugs was significantly (P < 0.01) different (0.88 +/- 0.13 ml/min for enrofloxacin and 0.06 +/- 0.02 ml/min for ciprofloxacin). These values accounted for 81 and 5%, respectively, of the placental clearance found for antipyrine. These results indicate that caution must be taken when enrofloxacin is to be used during pregnancy, and suggest the need to extend this type of experiment to species that can be exposed to these drugs used for therapeutic or prophylactic purposes.

Breaking strength (torque at failure) of equine third metacarpal bones, with transfixation pins placed parallel in the frontal plane and 30 degrees divergent from the frontal plane, was determined in vitro. Two transfixation pins were placed through the distal metaphysis, using a jig designed to drill the holes in the assigned configuration. Paired metacarpal bones II through IV from 12 horses were tested in torsion. The torsional moment of the force applied through the transfixation pins at failure was compared for each limb. Metacarpal bones with divergent pins were significantly (P = 0.030) stronger, compared with those with parallel pins. Metacarpal bones with parallel pins failed with longitudinal oblique fractures through a proxidmal bone-pin interface, whereas those with divergent pins failed with more comminuted fractures through multiple bone-pin interfaces.

The left ovary of chicken embryos was removed and incubated in culture medium with a thymidine analogue, bromodeoxyuridine (BrdU), in vitro. In addition, fertile chicken eggs were injected with BrdU via the extraembryonic vessels and incubated for 24 hours. The ovaries were then processed for immunohistochemical localization of calbindin-D28K (a 28-kd vitamin D-dependent calcium-binding protein) and BrdU. Calbindin-D28K was detected in the germinal epithelium and in cells surrounding the oogonia and oocytes (future granulosa cells) of the embryonic chicken ovary. However, Brdu was observed in the nucleus of the oogonia and oocytes of the chicken embryonic ovaries. Comparison of the 2 adjacent sections, immunostained for calbindin-D28K and BrdU consecutively, indicated that BrdU, the marker for cell proliferation was not detected in calbindin-D28K-containing cells, namely, germinal epithelium and future granulosa cells, in the ovary of chicken embryos. These results suggested that calbindin-D28K-containing cells in the ovary were not in the process of cell division during the 24-hour incubation of chicken embryos.

Thirty-two mixed-breed male and female cats were blocked by sex, arranged by body weight from greatest to least, and allocated to 4 groups of 8 (4 male, 4 female) cats, using random numbers. Cats in each of 3 groups were treated orally with a 7% suspension formulation of lufenuron at dosage of 15, 30, or 45 mg/kg of body weight. Cats in the fourth group were treated orally with an excipient suspension without lufenuron. Cats were infested with newly emerged, unfed cat fleas (Ctenocephalides felis felis) on days -7 and -3 before treatment and at approximately weekly intervals after treatment. Flea eggs were collected from beneath each cat on selected days before and after treatment and placed in an artificial rearing medium. Flea eggs and medium were kept for 35 days in an insectary to determine effects of lufenuron or excipient suspension on emergence of adults of the F1 generation. Lufenuron was 100% effective in inhibiting development of C felis at all dosages for 11 days after treatment. Thereafter, efficacy exceeded 92% in all dosages groups, On day 32, when the study was terminated, efficacy for each of the dosage groups was: 15 mg/kg, 95.2%; 30 mg/kg, 98.2%; and 45 mg/kg, 99.6%. Adverse reactions or side effects were not observed in cats, regardless of treatment dosage.

Mean phosphorus (P) content in bovine rib bone was 102.9, 108.3, and 182.7 mg/g of bone on fresh, dry, and ash weight bases, respectively. Values for calcium (Ca) were 194.3, 203.7, and 344.6 mg/g, respectively, and for magnesium (Mg) were 5.3, 5.5, and 9.4 mg/g, respectively. Mean percentage of ash in rib bone was 59.12%. Expected concentrations of Ca, P, and Mg were determined on fresh, dry, and ash weight bases and for 3 age groups, 3 breeds, and bulls, females, and steers. On an ash weight basis, cattle 6 to 18 months old had 185.74 mg of P/g, 372.52 mg of Ca/g, and 12.37 mg of Mg/g. Those 19 to 36 months old had 182.02 mg of P/g, 322.35 mg of P/g, and 8.09 mg of Mg/g. Those > 36 months old had 174.80 mg of P/g, 340.36 mg of Ca/g, and 6.62 mg of Mg/g. Steers had 183.93 mg of P/g, 352.73 mg of Ca/g, and 10.15 mg of Mg/g. Females had 178.47 mg of P/g, 320.28 mg of Ca/g, and 6.5 mg of Mg/g. Males had 176.15 mg of P/g, aH on an ash weight basis. Dairy breeds were found to have 186.08 mg of P/g, 351.25 mg of Ca/g, and 10.47 mg of Mg/g. Cattle of mixed breeding had 177.42 mg of P/g, 341.28 mg of Ca/g, and 6.54 mg of Mg/g. The Africander breed of beef cattle had 167.07 mg of P/g, all on an ash weight basis.

The position, dimensions, and structure of the thyroid gland, the portion of the esophagus in the neck the cervical lymph nodes, and the major blood vessels of the neck were determined via ultrasonography in cattle. The left and right ventral neck regions of 30 healthy Swiss Braunvieh cows were examined ultrasonographically, using 3.5- and 5.0-MHz linear transducers and a 3.5-MHz convex transducer. The external jugular vein was situated directly beneath the skin in the upper and middle parts of the neck and 2.7 to 6.6 cm from the body surface in the lower part of the neck. In contrast, the common carotid artery was located further from the body surface along the entire ventral neck region; depending on the measuring point, this distance varied from 2.6 to 10.9 cm. The external jugular vein narrowed from caudad to craniad. The diameter of the common carotid artery remained fairly constant along its course in the ventral part of the neck and varied from 0.9 to 1.4 cm. The thyroid gland was identified via ultrasonography caudodorsal to the larynx It appeared as an echogenic spindle-shaped structure with finely granular echogenic pattern. The esophagus appeared as a band-shaped structure in longitudinal section, and it could be followed to the thoracic inlet. Its width increased from craniad to caudad, and mean +/- SD diameter was 2.9 +/- 0.23 cm. The medulla, hilus, cortex, and capsule of the cervical lymph nodes could be clearly differentiated via ultrasonography. Mean length and width of the left cervical lymph node were 3.0 +/- 0.45 and 1.8 +/- 0.23 cm, respectively. To determine reproducibility and reliability of the results, 10 cows were examined by ultrasonography 10 times within 2 weeks. The interassay coefficients of variation determined from these examinations varied from 3.0 to 12.3%; most of the coefficients of variation ranged from 5 to 10%. The smallest coefficients of variation were determined for diameter of the common carotid artery, and the largest were for diameter of the external jugular vein. Description of the ultrasonographic appearance of the structures of the ventral neck region in healthy cattle represents the basis for use of diagnostic ultrasonography in cattle with suspected diseases involving this area. The technique is noninvasive and can be performed on cattle in standing position.

A challenge-exposure model was developed for dose-dependent induction of subclinical (moderate) atrophic rhinitis (AR) in conventionally raised Dutch Landrace and Large White pigs, about 4 weeks old. Under favorable climatic and housing conditions, pigs were intranasally challenge-exposed with Pasteurella multocida-derived toxin (Pm-T) 3 days after pretreatment by inoculation with 1% acetic acid. Pigs were challenge-exposed with 1 of the following Pm-T doses: 0 (control), 5, 13, 20, or 40 microgram of Pm-T/ml of phosphate-buffered saline solution (PBSS), 0.5 ml/ nostril/d on 3 consecutive days. Five weeks after challenge exposure, subclinical moderate) AR status was defined as intermediate conchal atrophy (grade 2 for ventral conchae on a 0 to 4 scale and grade 1 or 2 for dorsal conchae on a 0 to 3 scale, respectively) and perceptible difference in change in brachygnathia superior (CBS) between control and challenge-exposed pigs between the beginning and end of the study. All Pm-T-exposed pigs had nasal damage that was dose-dependent. The higher Pm-T doses resulted in higher ventral conchae atrophy and dorsal conchae atrophy scores. The CBS increased with applied Pm-T dose, resulting in significant (P < 0.05) differences between controls (3.88 mm) and the 13-, 20-, and 40-microgram Pm-T-treated groups (7.77, 6.58, and 7.98 mm, respectively). In response to the applied dose, weight gain per week for Pm-T-exposed pigs was lower than that of controls after week 3 (P < 0.01). Difference from controls was 32, 54, 52, and 96 g/d/pig for 5-, 13-, 20-, and 40-microgram Pm-T-treated groups respectively, in the last 2 weeks. For Dutch Landrace and Large White pigs, intranasally administered Pm-T mimicked the pathogenic effect of in vivo infection with toxigenic Pm strains. The optimal model to induce subclinical AR appeared to be 13 microgram of Pm-T/ml (0.5 ml/nostril/d) on 3 consecutive days. Our model should enable studies of exogenous and endogenous factors involved in development of AR, independent of the colonizing ability of the Pm strain used.

The effect of interleukin 1 (IL-1) on equine articular cartilage was investigated, using a cartilage explant culture system. Measurement of [35S]O4 incorporation revealed synthesis of matrix proteoglycan by cartilage to be decreased 45, 59.7, and 37.5% after 1, 3, and 5 days, respectively, in culture in the presence of 5 U of IL-1/ml. There was no change in proteoglycan degradation as determined by measurement of [35S]O4 release into the culture medium. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cartilage-conditioned medium indicated that exposure of cartilage to IL-1 caused a decrease in total protein synthesis by 45, 68, and 87% after 1, 3, and 5 days, respectively, in culture while selectively inducing synthesis of the 57-kd neutral metalloproteinase stromelysin (matrix metalloproteinase-3) in young and adult horses. Identification of stromelysin was confirmed by functional characterization and immunoprecipitation. Baseline total protein synthesis, as well as specific synthesis of stromelysin in cartilage from adult and aged horses, was markedly less than that of young horses. The IL-1-induced induced reduction in total protein synthesis may not be a characteristic of equine articular cartilage from affected joints of horses with naturally acquired osteoarthritis as indicated by an overall increase in protein synthesis by osteoarthritic explants. Introduction of IL-1 into an equine articular cartilage explant culture system resulted in decrease of matrix component synthesis and increase in specific degradative enzyme synthesis and activity. Articular cartilage from aged horses had markedly less overall metabolic activity, compared with cartilage from young horses. Articular cartilage from affected joints of horses with naturally acquired osteoarthritis did not have metabolic alterations identical to those of IL-1-stimulated normal articular cartilage from the same individual, necessitating reevaluation of the validity of the IL-1-induced model of osteoarthritis. Osteoarthritis is a common, naturally acquired disease of horses, and tissue from animals of all ages and stages of osteoarthritis is available. The equine model of osteoarthritis may afford an important means of studying the alterations in articular cartilage metabolism as a function of age and disease severity.

A murine monoclonal antibody (MAB) 6G7 generated against tachyzoites of Neospora caninum recognized 8 major and several minor antigens, as observed by western blot analysis. Relative rate of migration of the 8 major antigens ranged from 31 to 97.4 kd. In addition, MAB 6G7 recognized a Toxoplasma gondii tachyzoite antigen with a relative rate of migration of 107 kd. Immunogold labeling of N caninum tachyzoites grown in human foreskin fibroblast cells indicated that MAB 6G7 binds to micronemes, dense granules, basal portions of rhoptries, and intravacuolar tubules within the parasitophorous vacuole. Monoclonal antibody 6G7 also bound to micronemes and basal portions of rhoptries within tachyzoites of T gondii. Monoclonal antibody 6G7 did not significantly inhibit development of tachyzoites in vitro.