Nintey nonanesthetized 7- to 16-week-old pigs were studied, using 2-dimensional echocardiography that permits orientation of a targeted M-mode beam perpendicular to structures being studied and allows serial studies of the same cardiac regions. Normative data were obtained and included body weight and measurements of left atrial diameter, mitral valve excursion, aortic root diameter, left ventricular end-diastolic and end-systolic diameters, and left ventricular fractional shortening. A positive correlation was found between body weight and measurements of left atrial diameter, mitral valve excursion, aortic root diameter, left ventricular end-diastolic and end-systolic diameters, and fractional shortening. A correlation was found between body weight and age. Best-fit analysis resulted in all measurements fitting either a first- or second-degree polynomial.

Efficacy of a repositol formulation of melengestrol acetate (MGA) for inhibition of pregnancy was determined in one hundred 14- to 16-month-old beef heifers. Nonpregnant heifers were allocated on the basis of weight into 5 groups of 20 heifers each and were given 0, 30, 60, 90, or 120 mg of repositol MGA, SC, on day 0. Four bulls, determined to be satisfactory potential breeders, were pastured with the heifers from postinjection days (PID) 7 to 177. The day of gesation was estimated for each heifer by rectal palpation at PID 59, 91, 134, 177, and 225. Heifers not pregnant by PID 177 were assigned a day of conception of greater than 177. For heifers given 0, 30, 60, 90, and 120 mg of MGA, respectively, the percentage pregnant at PID 177 was 95, 95, 50, 15, and 15%, and the median day of estimated conception was PID 21, 87, 175, greater than 177, and greater than 177. Repositol MGA significantly (P less than 0.001) affected the distribution of conception times over all doses. Average daily gain (+/- SEM) for 178 days was 0.28 +/- 0.04 kg, 0.24 +/- 0.03 kg, 0.33 +/- 0.04 kg, 0.40 +/- 0.03 kg, and 0.35 +/- 0.03 kg for heifers given 0, 30, 60, 90, and 120 mg of MGA, respectively. Increased dose of repositol MGA was associated with increased average daily gain, but this effect was not apparent when days pregnant were taken into account. Repositol MGA was an effective contraceptive for pastured heifers and the duration of its effect was dose-dependent.

High-speed cinematography was used to record the movements of 12 cutting horses performing a standard test with a mechanical flag. Based on their previous competitive performances, horses were classified into 2 groups: group 1, composed of 5 moderately successful or average performers that had won less than $35,000 in purse money; and group 2, composed of 7 highly successful or elite performers that had amassed greater than $35,000 in competition earnings. Analysis of the results indicated that, compared with horses of the average group, the elite horses had faster reaction times in response to the start and cessation of flag movement (P less than 0.01), and were positioned closer to the flag during all stages of the trial (P less than 0.05). Discriminant analysis was used to construct a mathematical formula that could be used to classify an individual horse into 1 of the 2 alternative groups, based on the set of measurements. Two predictor variables were selected that described the maximal distance between the horse and the flag during the run and the part of the body that was moved first in response to the initial flag movement. The accuracy of the predicted group membership, compared with the actual group membership, was 100%.

Quantitative evaluation of neutrophil chemotaxis was performed on cells obtained by hypotonic-lysis techniques from heparinized blood samples from clinically normal dogs. The techniques resulted in neutrophil recovery rates between 60 and 80%. Chemotaxis comparisons were based on cellular migration in microchambers equipped with polycarbonate membranes with 5-micrometer pores. Chemo-attractant comparisons were based on neutrophil migration to medium, normal canine plasma, zymosan-activated plasma, and xanthine oxidase. Cellular migration to zymosan-activated plasma in buffer (1:100 dilution) was significantly (P less than 0.001) enhanced over random baseline medium migration. Neutrophil migrations to normal canine plasma and xanthine oxidase were quantitatively less than to zymosan-activated plasma, but were equivalent to each other and significantly greater than for random migration. Migration to xanthine oxidase was maximal at concentrations near 1 U/ml within 30 minutes.

The relationship between the palpebral conjunctival oxygen index, mixed venous oxygen tension, and cardiac index were compared, using a canine hemorrhagic shock model. The cardiac output was reduced by reducing the blood volume in 5% increments until the initial cardiac output was reduced by one half. In each of 7 dogs, the palpebral conjunctival oxygen index and mixed venous oxygen tension were found to have good correlation with cardiac index; however, the correlation coefficients were markedly reduced when the data from all of the dogs were combined. It was concluded that the palpebral conjunctival oxygen index provides an excellent means of assessing changes in cardiac index over time in the same dog; however, it cannot be used to estimate cardiac index in an individual dog with a degree of accuracy that would be clinically significant.

Ninety-one equine aortic and cranial mesenteric arterial segments were evaluated ultrasonographically in a water bath. On the basis of pathologic evidence of verminous arteritis, arterial segments were classified into 4 categories, and the ultrasonographic characteristics of each group were evaluated. Normal arteries (class 1) were ultrasonographically characterized by a smooth luminal surface layer and uniform wall thickness and echogenicity. Arteries with only histopathologic evidence of verminous arteritis (class 2) were ultrasonographically characterized by a smooth luminal surface layer, uniform thickness, uniform echogenicity, and the presence of a hyperechoic luminal layer. Arteries with both gross and histopathologic evidence of verminous arterities (class 3) were characterized ultrasonographically by an irregular luminal surface layer, varying wall thickness, varying wall echogenicity, and the presence of a hyperechoic luminal layer. The ultrasonographic characteristics of arteries with luminal thrombosis (class 4) were an irregular luminal surface, varying wall thickness, and nonuniform echogenicity.

Data were collected for 3,636 full-term pigs born in a commercial swine herd to determine the effects of birth weight and clinical disease on survival during the first 3 weeks of life. Logistic regression models were constructed for 7-day survival for all live-born pigs, and for 21-day survival for pigs surviving the first week of life. Estimates of birth weight and disease effects were adjusted simultaneously for other risk factors including litter size, parity, and within-litter variation in birth weight. The 7-day survival model indicated that survival odds improved significantly with increasing birth weight. Maximal survival, relative to pigs weighing less than 601 g at birth, was evident in pigs weighing greater than 2 kg atbirth (odds ratio [OR] = 349). Diarrhea (OR = 2.7) and splayed limbs (splay leg; OR = 37.3) significantly (P less than 0.05) reduced 7-day survival. Models of 21-day survival indicated a smaller, but still significant, effect of birth weight on survival. Adjusted survival odds for pigs in the heaviest weight group (greater than 2 kg) were 20.1 times higher than pigs weighing less than 801 g. Diarrhea (OR = 2.7) and lameness (OR = 2.6, 2 limbs) significantly (P less than 0.05) decreased 21-day survival.

Embryos were harvested at the blastocyst stage from nontreated outbred mice and were grown in vitro for 4 days. Embryos cultured in control medium hatched and grew to the egg cylinder stage. Purified zearalenone (ZEN) added to the culture medium at concentrations of 8.5 to 68 microgram/ml decreased the number of embryos growing, with a 50% decrease in the number growing in 32 micograms of ZEN/ml of medium. Embryos growing in ZEN had decreased numbers of cells derived from the inner cell mass, normal growth of the trophoblast, less cellular differentiation than was seen in control embryos, and increased numbers of phagosomes. Undifferentiated cells of the inner cell mass of control and treated embryos were of the same size, as determined by morphometric analysis. Addition of 25 micrograms of estradiol/ml of culture medium caused no decrease in number of embryos growing or in embryonic size. Saturation of culture medium with ZEN (68 microgram/ml) did not inhibit the growth of a tissue culture line of goat synovial cells. Seemingly, ZEN at concentrations near saturation inhibited the growth of mouse embryos in vitro. This effect was not duplicated with similar concentrations of estradiol and was not manifested in culture-adapted cells.

Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light microscopic observation, using standard histologic methods. In sections from 6 horses, injection replicas were made by perfusing the vessels with 2 types of plastics. The results of microangiography, light microscopy, and scanning electron microscopy of vascular replicas were correlated, providing acomprehensive documentation of the microvasculature of the ascending colon at the pelvic flexure. Arteries branched from mesenteric colic vessels approximately every 2 cm toward the colonic tissue. Immediately after branching, arterial vessels formed an anastomotic plexus, the colonic rete. However, each branch from the colic vessel eventually continued into the colonic tissue. A second set of vessels originated from the colonic rete and supplied the mesenteric lymph nodes. Arterial vessels penetrated the tunica muscularis into the sub-mucosa 3 to 4 cm toward the antimesenteric border forming a submucosal vascular network. From the submucosal arterioles, branching took place at right angles to supply the mucosal capillaries. Capillaries surrounded the colonic glands and anastomosed at the luminal surface, forming a superficial luminal honeycomb-appearing vascular plexus. Venules, sparsely distributed, drained the superficial plexus. Arterial venous anastomoses were not observed within the mucosa.

Exogenously administered vasopressors (sympathomimetics) were evaluated in halothane-anesthetized dogs to determine the effects of these drugs on cardiovascular function before and after hemorrhage. Six dogs were anesthetized with thiamylal sodium (20 mg/kg of body weight) and halothane (1.25 minimal alveolar concentration) in 100% oxygen. After instrumentation, cardiac output, systemic arterial blood pressure (SAP), heart rate (HR), left ventricular pressure, pulmonary arterial pressure, and an index of cardiac contractility (dP/dT) were measured. Stroke volume, cardiac index (CI), stroke index (SI), rate-pressure product, and systemic vascular resistance (SVR) were calculated. Epinephrine (0.1, 0.3, and 0.5 micrograms/kg/min [low, medium, and high doses, respectively]) and dobutamine (1, 5, and 10 micrograms/kg/min [low, medium, and high doses, respectively]) were infused. Methoxamine was given in a bolus of 0.22 mg/kg, IV. All measurements were taken at 2.5 minutes after infusion, and were repeated after removal of 40% of the estimated blood volume. Dobutamine administered at the low dose before hemorrhage increased SAP and dP/dT. At the high and medium dose, dobutamine significantly increased CI, dP/dT, and SAP with no significant change in HR or SVR. The medium dose of epinephrine was the most effective dose of epinephrine at increasing key variables (CI, SI, dP/dT). The response of CI and SI to this dose was not significantly different from the changes seen with high-dose administration of dobutamine. The dP/dT was significantly lower with epinephrine than with dobutamine, and SVR and HR were unchanged with epinephrine, except at the low dose, which decreased SVR. Methoxamine significantly decreased CI, SVR, and HR, whereas SVR and SAP were increased significantly. After hemorrhage, the only variables that had a significant change in the absolute magnitude of the response to a drug, relative to the response before hemorrhage, were a significantly reduced ability of dobutamine and methoxamine to increase SAP, and a significantly decreased ability of methoxamine to decrease CI. We concluded that dobutamine and epinephrine provide beneficial short-term support of the cardiovascular system in the halothane-anesthetized dog during acute hypovolemia.