Two techniques for end-to-end anastomosis of the small colon were evaluated in each of 6 horses. A simple interrupted suture pattern that excluded the mucosa and was oversewn with an inverting suture was compared with a triangulated double-row pattern of stainless steel staples. Anastomotic sites were evaluated at 2 weeks, 2 months, and 6 months for extent of abdominal adhesions, lumen diameter at anastomotic sites, bursting pressures, and healing response. Clinical postoperative complications were not associated with either technique. At postmortem examination, there was extensive adhesion formation from the mesocolon to the stapled anastomotic site. The suture technique resulted in greater luminal diameters (P less than or equal to 0.05), with good apposition of the tissue layers. Staples were missing as early as 2 weeks after surgery, and their loss was associated with separation of the muscularis at later evaluation periods. Regardless of technique, all but one anastomotic segment burst away from the anastomotic site along the mesenteric taenial band. For the 12 anastomoses performed in normal horses, the suturing technique was better than the stapling technique because of significantly larger lumen diameters, better anastomotic healing, and minimal intra-abdominal adhesion formation.

Effects of age and season on type and occurrence of sperm abnormalities were examined in semen samples collected from 3 groups of Nubian bucks at ages of 4 to 9 months, 10 to 21 months, and 39 to 50 months. The average total percentage of sperm abnormalities at the onset of puberty (141 +/- 4 days) was 64.6 +/- 14.8% (head, 19.5 +/- 13.6%; middle piece, 17.2 +/- 9.3%; and proximal protoplasmic droplets, 14.6 +/- 10.5%), but this improved rapidly and was reduced to 12.5 +/- 7.5% by 8 months of age (head, 1.9 +/- 4.5%; middle piece, 4.6 +/- 2.8%). Further increase in age, at least up to 4 years, did not reveal a significant effect (P less than 0.05) on the type of percentage of total abnormalities. Similar to age, a comparison of data among seasons did not reveal a significant effect on the type or occurrence of sperm abnormalities in 10- to 21-month-old or 39- to 50-month-old bucks. Seemingly, Nubian bucks started producing good quality semen at 8 months of age, and season did not influence sperm abnormalities.

A specialized tip structure in some mycoplasmas facilitates their attachment to host cells. Mycoplasma bovoculi strains FS8-7 and M165/69 did not have specialized membrane structure and did not exhibit capsule when stained with ruthenium red and examined by use of transmission electron microscopy. The organisms attached in vitro to bovine lung fibroblasts, with no apparent specialized structure. Attachment to conjunctival epithelium in vivo was observed (after death) in a calf infected with M bovoculi. Close association between M bovoculi and the host cells was noticed. Mycoplasmal cells pretreated with hyperimmune rabbit serum and labeled with protein A-gold complex had gold particles randomly distributed around the membrane. Gold-labeled monoclonal antibodies, M25.5 and M7.3, which were directed against 2 surface antigens of M bovoculi, also were distributed randomly on the mycoplasmal surface as seen in results of double-labeling experiments.

Cells acquired from lymph node biospy specimens obtained from 58 dogs scheduled to undergo chemotherapy for lymphoma were immunophenotyped, using a microlymphocytotoxicity (MLCT) assay comprising a panel of well-characterized monoclonal antibodies (MAB) specific for canine cell surface antigens. Cells from 54 of the dogs concurrently were tested cytofluorometrically, using surface immunoglobulin (SIg) as a marker for B cells and the MAB DT2 specific for peripheral blood T cells. The MLCT results indicated frequent coexpression of antigens identified by DT2 antibody and, to a lesser extent, by 1A1 antibody on SIg-positive cells, suggesting that these antigens may be associated with other types of less-differentiated lymphoid cells, in addition to being associated with mature T cells. Class-II major histocompatibility antigens, as recognized by MAB H81.98.71, HB10a, and H40.315.7, were detected on most SIg-positive cells, but generally were lacking on SIg-negative, DT2-negative cells. The MAB Wig4, reactive with canine monocytes, recognized relatively few cells (11 of 58). Response to chemotherapy was not correlated with reactivity to MAB DLy6 specific for resting lymphocytes or to MAB W3G10 specific for a polymorphic antigen associated with the canine major histocompatibility complex. The MLCT assay appears to be efficient, rapid, and inexpensive for immunophenotyping cells from lymphoma biopsy specimens.

Large increases in systemic and pulmonary arterial pressures of exercising healthy ponies have been observed. Because exercise causes a considerable increase in PCV of ponies, we examined the effect of splenectomy on exercise-induced changes in systemic and pulmonary pressures. These pressures (taken with catheter-tip micromanometers) and indicator dilution cardiac output were determined on 9 healthy ponies that had undergone splenectomy 4 to 9 weeks before the study. Data obtained at rest and during submaximal (10.5 to 11.0 mph) and maximal (14 to 15 mph) exercise from these ponies were compared with similar data from clinically normal ponies. Following splenectomy, PCV increased by only 4 vol% during maximal exercise, but cardiac output of splenectomized ponies reached values similar to those of clinically normal ponies. Despite this similarity in cardiac output, the systemic and pulmonary arterial pressures of exercising splenectomized ponies increased to significantly lower levels than those in clinically normal ponies (P less than 0.01); total pulmonary vascular resistance and total peripheral resistance decreased to values significantly less than those in clinically normal ponies (P less than 0.01). Thus, it appears that increases in blood viscosity induced by increases in PCV may contribute substantially to the pulmonary and systemic hypertension of exercise in clinically normal ponies.

Effects of xylazine (1.1 mg/kg of body weight, IV bolus, plus 1.1 mg/kg/h infusion) and subsequent yohimbine (0.125 mg/kg, IV bolus) administration on the arrhythmogenic dose of epinephrine (ADE) in isoflurane (1.8% endtidal)-anesthetized dogs were evaluated. The ADE was defined as the total dose of epinephrine that induced greater than or equal to 4 premature ventricular contractions within 15 seconds during a 3-minute infusion period or within 1 minute after the end of infusion. Total ADE values during isoflurane anesthesia, after xylazine administration, and after yohimbine injection were 36.6 +/- 8.45 micrograms/kg, 24.1 +/- 6.10 micrograms/kg, and 45.7 +/- 6.19 micrograms/kg, respectively. Intravenous xylazine administration significantly (P less than 0.05) increased blood pressure and decreased heart rate, whereas yohimbine administration induced a significant (P less than 0.05) decrease in blood pressure. After yohimbine administration, the ADE significantly (P less than 0.05) increased above that after isoflurane plus xylazine administration. After yohimbine administration, blood pressure measured immediately before epinephrine-induced arrhythmia was significantly (P less than 0.05) less than the value recorded during isoflurane plus xylazine anesthesia. Heart rate was unchanged among treatments immediately before epinephrine-induced arrhythmia. Seemingly, yohimbine possessed a protective action against catecholamine-induced arrhythmias in dogs anesthetized with isoflurane and xylazine.

Chloramphenicol was administered by constant IV infusion to 7 healthy postpartum cows at rates predicted to approach a steady-state plasma concentration of 5 micrograms/ml. After 8 hours of constant IV infusion, uterine tissues were removed surgically and were assayed for chloramphenicol concentrations. Mean plasma-to-tissue ratios of chloramphenicol concentrations were 3.05, 3.63 (6 cows only), and 3.22 for caruncles, endometrium, and uterine wall, respectively. Plasma-to-tissue ratios of the 3 tissues were not significantly different (P greater than 0.10). Intrauterine (IU) injections of chloramphenicol (20 mg/kg of body weight) were administered to 3 healthy postpartum cows. The mean value of the fraction of the drugabsorbed from the uteri of these cows was 0.04. Mean concentrations of chloramphenicol were 43.8 micrograms/g in caruncles, 34.6 micrograms/g in endometrium, 2.8 micrograms/g in uterine wall, and 2.9 micrograms/ml in plasma 8 hours after IU injections. Chloramphenicol has now been banned for use in food-producing animals in the United States because of its potential for causing toxicosis in human beings. It is illegal to use chloramphenicol in food-producing animals in the United States and in some other countries as well. This includes use by the IU route of administration because chloramphenicol and most drugs are absorbed from the uterus into the bloodstream and are distributed to milk and tissues.

The tarsocrural joints of 11 horses were inoculated with 1.2 to 2.16 x 10(6) viable Staphylococcus aureus organisms susceptible to a trimethoprim-sulfadiazine (TMP-SDZ) combination with minimal inhibitory concentration (MIC) of 0.25 microgram of TMP/ml and 4.75 microgram of SDZ/ml. Antimicrobial treatment consisted of oral administration of a TMP-SDZ combination-30 mg/kg of body weight given once daily (group-1 horses) or 60 mg/kg given as 30 mg/kg every 12 hours (group-2 horses). Paired serum and synovial fluid samples were obtained before intra-articular inoculation with the S aureus, after inoculation with S aureus but before antimicrobial treatment, and after inoculation at various hourly intervals after oral administration of the TMP-SDZ combination. The TMP-SDZ combination was administered daily in the 2 dosages for 21 days. Samples were collected after day 3 of repetitive drug administration so that drug steady-state concentration would have been achieved. Serum and synovial fluid samples were analyzed for TMP and SDZ concentrations. Administration of the TMP-SDZ combination at a dosage of 30 mg/kg once daily was not effective in maintaining TMP or SDZ concentrations above the MIC of TMP-SDZ for the S aureus (0.25 and 4.75 microgram/ml for TMP and SDZ, respectively) in the infected synovial fluid or in maintaining adequate TMP concentration in the serum. The alternative use of the TMP-SDZ combination at a dosage of 60 mg/kg given as 30 mg/kg every 12 hours was effective in maintaining serum and synovial fluid concentrations of TMP and SDZ that were greater than the MIC for the infective organism. Sulfadiazine concentration was significantly (P less than or equal to 0.05) lower in the infected synovial fluid sample than that in the corresponding serum sample. We concluded that administration of 60 mg of TMP-SDZ/kg given as 30 mg/kg every 12 hours is more effective than 30 mg/kg given once daily for the treatment of equine infectious arthritis caused by organisms for which the MIC of TMP-SDZ is less than or equal to 0.25-4.75 microgram/ml.

Five mature Holstein cows and 6 first-lactation Holstein cows were administered 100 mg of glucose/kg of body weight, IV, over a 20-minute period on postpartum day 30. A series (preinfusion, glucose infusion, and postinfusion) of blood samples was collected at -15, -10, -5, 5, 10, 15, 20, 30, 45, 60, 75, 90, 105, and 120 minutes from the start of the infusion. Serum was obtained and was assayed for glucose, immunoreactive insulin (IRI) growth hormone (GH), and free fatty acid concentrations. Baseline glucose and free fatty acid concentrations were similar in cattle of both groups throughout the sample collection period. Both groups of cattle disposed of the infused glucose in a similar manner. The first-lactation cows secreted significantly (P < 0.0001) more IRI to utilize the glucose load than did the mature cows, 71 +/- 13 microU/ml vs 38 +/- 7 microU/ml, respectively (mean +/- SEM). Preinfusion and glucose infusion GH concentrations were similar in cattle of both groups. In the postinfusion period, GH values were significantly (P < 0.0002) higher in the first-lactation cows (8.7 +/- 1.8 ng/ml) than in the mature cows (5.8 +/- 1.6 ng/ml). Compared with that in the mature cows, the higher IRI concentration required by the first-lactation cows to utilize approximately the same glucose load suggested that first-lactation cows were insulin resistant. The increased insulin response to increased glucose concentration may be one reason first-lactation cows produce less milk than do mature cows. Other factors, such as variation in the ability of the mammary gland to synthesize milk cannot be excluded.

Cardiovascular effects and pulmonary gas exchange were compared during conventional mechanical ventilation (CMV) and interrupted high-frequency, positive-pressure ventilation (IHFPPV) in 6 anesthetized ponies in dorsal recumbency. When the peak airway pressure (Paw) was held constant at control values attained during CMV (18 to 20 cm of H2O), and the ventilator frequency of IHFPPV was varied over the range, 2.5 to 12.5 Hz, significant (P less than 0.05) changes from control values were observed only in the ratio of dead-space volume to tidal volume (VD/VT) and in the respiratory minute volume (VE). The mean +/- SEM) carbon dioxide excretion (VCO2) was 2.12 +/- 0.1 ml/kg/min during IHFPPV. Dead-space ventilation ranged from 40 to 73.7% of total ventilation and increased directly with increasing frequency. The VE also increased, from 89 ml/kg/min at a ventilatory frequency of 2.5 Hz to 145 ml/kg/min at a frequency of 12.5 Hz. Maintaining the frequency of IHFPPV constant at 12.5 Hz and increasing the Paw over the range of 5 to 30 cm of H2O caused significant (P less than 0.05) changes in arterial partial pressure of O2 (PaO2), VCO2, pulmonary shunt fraction (QS/QT), VE, arterial-alveolar differences in oxygen tension (AaDO2), VD/VT, and cardiac output, compared with CMV. The PaO2 and the VCO2 increased linearly with increasing Paw. With increasing Paw, VD/VT decreased directly with increasing Paw from 98 to 69.3%. Gas exchange at a Paw of 15 cm of H2O during IHFPPV was equivalent to conditions at Paw of 20 cm of H2O during CMV. At a higher Paw during IHFPPV, improvements over control values were observed in gas exchange.