Histomorphometric and scanning electron microscopic analyses were performed on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histologic differentiation of the omasum took place at 33 days of fetal life, with the appearance of first-order laminae. Second-, third-, and fourth-order laminae appeared at 39, 50, and 59 days, respectively. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life, decreasing quantitatively until birth, before subsequently stabilizing in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Growth curves and formulas were constructed for each tissue layer. Initial tests involved multiplicative (y = axb), exponential (y = EXP [a + bx]), linear (y = a + bx), and polynomial models [y = a + bx + cx(2) + dx(3)].

Gastric pH was monitored in neonatal foals from birth to 3 months of age. Background pH decreased, especially during the first week of life. Milk had complex effects that depended on pH prior to sucking, confounded by the age of the foal: nearly neutral background pH tended to be acidified after milk intake; moderately acid background pH tended to be neutralized; low background pH was only slightly increased by milk. Absolute magnitude of the effects of milk decreased with age. Existence of a proulcerative intragastric environment in preweaning foals is postulated, but this must be considered in the context of what probably is a multifactorial pathogenesis.

A 3-year prospective study of large-breed dogs (4 months to 3 years of age) was conducted to evaluate the influence of radiographic positioning and age on coxofemoral joint (hip) laxity, subjective hip score, and development of degenerative joint disease (DJD). The dogs (n = 142) were breeder- or client-owned and represented 14 breeds. With dogs under heavy sedation, hips were radiographed in the standard hip-extended position and in the new compression/distraction position at 4, 6, 12, 24, and 36 months of age. The standard hip-extended radiographic view was evaluated by 3 methods: subjective evaluation by a board-certified veterinary radiologist (WHR), according to the standard 7-point Orthopedic Foundation for Animals (OFA) scoring scheme (OFA/WHR); joint laxity quantitation, using the Norberg angle (NA) method; and subjective scoring by a veterinary orthopedic surgeon for radiographic evidence of DJD. The hips in the distraction radiographic view were evaluated for passive hip laxity, as measured by use of a unitless distraction index (DI). Results of the study indicated that at a specific age (4, 6, 12, 24, or 36 months), all methods of hip evaluation correlated with each other at a moderate level (P < 0.05). The strength of contemporaneous correlation tended to increase with age of evaluation. Longitudinally, the between-method correlations were usually significant (P < 0.05), but not at a sufficiently high level to permit reliable between-method prediction. Prospective intraclass (within-method) statistical analysis of the various hip-scoring methods indicated that DI was superior to NA and OFA/WHR in comparability of score over time. The intraclass correlation coefficient ranged from 0.55 to 0.91 for DI in contrast to 0.40 to 0.78 for NA, and 0.06 to 0.39 for OFA/WHR over the age intervals of the study. For reference, the highest Kappa of 0.39 for the subjective OFA/WHR scoring reflected a maximal level of agreement between time intervals, only slightly better than chance. The associated large error questions the predictive use of the 7-point, subjective hip-scoring scheme, particularly prior to the age of 2 years.

We examined the effect of infusion of lipopolysaccharide (LPS) on serum tumor necrosis factor alpha (TNF alpha) concentration and clinical attitude in 2- to 3-day-old colostrum-fed (CF) and colostrum-deprived (CD) foals. Eleven CF and 8 CD neonatal foals were given a bolus IV infusion of Escherichia coli 055:B5 lipopolysaccharide (0.5 microgram/kg of body weight) in sterile saline (0.9% NaCl) solution. Four CF and 2 CD foals were given saline solution alone. Serum IgG concentration and serum anti-LPS IGG(T) antibody titer were determined for each foal prior to infusion. A depression index was used to score clinical abnormalities. Serum TNF alpha concentration was estimated by use of an in vitro cytotoxicity bioassay that used WEHI 164 clone 13 cells as targets. The cytotoxic serum factor was identified as TNF alpha by immunoprecipitation with caprine antisera raised against the 15 NH2-terminal amino acids of human TNF alpha. Tumor necrosis factor alpha was not detected in any preinfusion serum samples nor in any samples from foals given saline solution alone. Serum TNF alpha concentration increased in all LPS-infused foals and peaked between 60 and 90 minutes after infusion. Serum TNF alpha concentrations, expressed as mean percentage of peak serum TNF alpha concentration, persisted longer in CD foals given LPS than in CF foals given LPS. All LPS-infused foals displayed clinical signs of endotoxemia, but mean depression index scores of the CF and CD foals given LPS were not significantly different at any time. Serum TNF alpha concentrations were correlated with depression index scores in both LPS-infused groups. Mean rectal temperature increased by 1 hour and remained high for 4 hours after infusion in CF foals given LPS. Mean rectal temperature in CD foals given LPS was significantly less than that for CF foals given LPS 1 and 2 hours after infusion and was higher than mean rectal temperature prior to infusion 3 and 4 hours after infusion. Neither preinfusion total serum IgG concentration nor serum anti-LPS IgG(T) antibody titer correlated with peak serum TNF alpha concentration in the 19 LPS-infused foals.

Cartilage resurfacing by chondrocyte transplantation, using porous collagen matrices as a vehicle to secure the cells in cartilage defects, has been used experimentally in animals, This in vitro study evaluated the temporal morphologic features and proteoglycan synthesis of chondrocyte-laden collagen matrices. Forty-two porous collagen disks were implanted with a minimum of 6 X 10(6) viable chondrocytes, covered by a polymerized collagen gel layer, and 6 disks were harvested after 0, 3, 7, 10, 14, 18, or 22 days of incubation in supplemented Ham's F12 medium at 37 degrees C and 5% CO2. Histologic and histochemical evaluation of formalin-fixed segments of the cultured disks indicated that the chondrocytes proliferated in the implant, producing small groups and linear segments of cells by day 14. The collagen framework remained intact over the course of the study with thick areas attributable to depositions of matrix material after day 10. Alcian blue-stained matrix was evident in the pericellular region of chondrocytes in sections of disks harvested on days 14, 18, and 22. Glycosaminoglycan (GAG) assay by dimethylmethylene blue dye binding after papain digestion of the disk segments revealed negligible amounts of GAG at day 0. Significant (P < 0.0001) increase in total GAG content was observed by day 3 (0.329 micrograms/mg of disk) and further increases were observed until a plateau in GAG quantity was seen on day 14. Mean peak GAG content was 0.553 +/- 0.062 micrograms/mg. Secondary treatment of the papain-digested implants with keratanase and chondroitinase ABC yielded similar trends in chondroitin sulfate (CS) and keratan sulfate (KS) concentrations. The CS content significantly (P = 0.0002) increased for the first 14 days of incubation, then a plateau was observed for the remainder of the study. Peak CS content was 0.354 +/- 0.037 micrograms/mg. Concentration of KS reached a plateau earlier than did CS content, with peak amount of 0.193 +/- 0.027 micrograms/mg on day 10. Fluctuations in KS content were not significant until an increase on day 22. Chondrocytes actively populated the collagen implants, increasing in number and synthesizing matrix GAG epitopes over the 22 days of incubation. These results indicate that chondrocyte-laden porous collagen matrices may be suitable cartilage analogue materials and the optimal metabolic time for transfer to cartilage defects is 10 to 14 days.

From 2 to 4.5 months of age, 80 crossbred gilts were reared in a conventional grower unit where they were naturally exposed to mycoplasmal and bacterial pathogens that cause pneumonia and atrophic rhinitis. At 4.5 months of age, gilts were moved to environmentally regulated rooms (4.9 X 7.3 m) and assigned at random to 1 of 2 treatment groups: low aerial concentration of ammonia (4 to 12 ppm; mean, 7 ppm) or moderate aerial concentration of ammonia (26 to 45 ppm, mean, 35 ppm). Low concentration of ammonia was obtained by flushing of manure pits weekly, whereas moderate concentration of ammonia was maintained by adding anhydrous ammonia to manure pits that were not flushed. Gilts were weighed biweekly. Mean daily gain (MDG) was less (P < 0.01) for gilts exposed to moderate concentration of ammonia than for gilts exposed to low concentration of ammonia after 2 weeks in their respective environments. By 4 and 6 weeks, however, MDG was similar between the 2 treatment groups. After 6 weeks in these environments, 20 gilts from each treatment group were slaughtered, and prevalence and severity of lung lesions and snout grades were determined. At slaughter, body weight was greater (P < 0.01) in gilts exposed to low, rather than moderate, ammonia concentration (94.5 vs 86.8 kg; SEM, 3.3 kg). Percentage of lung tissue containing lesions (18 vs 12) and snout grade (2.8 vs 3.1) were similar between gilts exposed to low or moderate concentration of ammonia. The remaining 20 gilts in each treatment group were maintained in their respective environments, exposed daily to mature boars and bred at first estrus. Age at puberty was similar between gilts exposed to low or moderate concentration of ammonia (208 vs 205 days; SEM, 1.3 days), even though weight at puberty was less (P < 0.03) for gilts exposed to low concentration of ammonia than for gilts exposed to moderate concentration of ammonia (109.7 vs 118.2 kg; SEM, 4.5 kg). At day 30 of gestation, number of live fetuses (10.6 vs 11.7), fetal length (2.53 vs 2.57 cm), and fetus-to-corpus luteum ratio (0.85 vs 0.78) were similar between gilts at low and moderate ammonia environments. These data indicate that exposure of gilts to mean aerial ammonia concentration of 35 ppm in environmentally regulated rooms depressed MDG for 2 weeks, but failed to alter onset of puberty or litter size at day 30 of gestation.

The cellular response induced in the host animal by endotoxin contributes greatly to the morbidity and mortality of gram-negative infections in bovine neonates. We characterized the temporal sequence, magnitude, and duration of mediator release during endotoxemia and evaluated the effect of endotoxin dose and method of administration. Thromboxane B2 (TxB2), and 6-keto prostaglandin F(1 alpha) (PGF 1 alpha) concentrations and tumor necrosis factor (TNF), and interleukin-1 beta (IL-1 beta) activities were measured in 34 newborn calves given Escherichia coli endotoxin at dosage of 0 (saline solution), 0.2, 2.0, or 20 micrograms/kg of body weight, either by IV administered bolus or infusion over 50 minutes. In all groups and at each lipopolysaccharide dosage, mediators peaked in this sequence; TxB2 and TNF, followed by PGF 1 alpha, then IL-1 beta. Neither dose nor method of administration affected the sequence of mediator release. The magnitude of eicosanoid response to endotoxin was dose-dependent. During induced endotoxemia, duration and/or magnitude of mediator response reflected the dose of endotoxin administered, indicating that the outcome of endotoxemia, in neonatal calves, may be related to the amount of circulating endotoxin.

Effects of phenylbutazone (PBZ) and furosemide (FUR) on the respiratory tract of horses were evaluated, focusing on bronchial responsiveness. Four healthy Thoroughbreds were used and data were analyzed by use of a Latin square design. Histamine provocation tests (0.5, 1, 2, and 4 micrograms/kg/min, IV) were done: (1) without prior treatment with PBZ or FUR, (2) 30 minutes after administration of PBZ (8 mg/kg, IV), (3) 1 hour after administration of FUR (1 mg/kg, IV), and (4) after administration of PBZ plus FUR. Pulmonary function tests (dynamic compliance, resistance, respiratory frequency, and tidal volume) and heart rate were monitored throughout the experiments. Phenylbutazone did not influence basal pulmonary function test results, whereas FUR caused a significant (P < 0.05) increase in dynamic compliance and decrease in resistance. Histamine infusion resulted in a dose-dependent decrease in dynamic compliance and a dose-dependent increase in resistance, respiratory frequency, and heart rate. Phenylbutazone administration significantly (P < 0.05) attenuated most of the changes induced by histamine, whereas FUR had less protective action. Administration of PBZ plus FUR before administration of histamine was less effective than administration of PBZ alone.

Effects of intraluminal distention (25 cm of H2O, 120 minutes) and subsequent decompression (60 minutes) on intramural vascular patterns of the small intestine was evaluated in 7 anesthetized horses. Intraluminal distention (25 cm of H2O, 120 minutes) was created in 2 jejunal segments in each horse. Experimental and control segments were removed either immediately after the experimental period or after 60 minutes of decompression. The vascular system of experimental and control jejunal segments was lavaged with NaCl, then was injected with a blue-colored radiopaque medium for microangiography or with a diluted methyl methacrylate for scanning electron microscopy of microcorrosion vascular casts. After angiographic evaluation, tissue sections were prepared for light microscopic evaluation to assess vascular filling and tissue morphology. The distended segments had short villi, which were separated by expanded crypts, and had mesothelial cell loss, neutrophil infiltration, and edema in the seromuscular layer. The number of perfused vessels was significantly (P < 0.05) decreased in the seromuscular layer and, to a lesser extent, in the mucosal layer of the distended segments, compared with controls. After decompression, the morphologic lesions progressed in mucosal and serosal layers and the number of observed vessels increased in all intramural layers; however, vascular density did not return to the predistention state. These results identify altered intramural vascular patterns in the equine jejunum during luminal distention and subsequent decompression.

Age, species, and disease state may substantially alter the disposition and clearance of pharmacologic agents. This is particularly important when drugs with low therapeutic index are used in ill neonates. Pharmacokinetic variables for phenylbutazone were determined in 24- to 32-hour-old healthy and endotoxemic calves after IV administration of a single dose (5 mg/kg of body weight, IV). Elimination halflife was 207 and 168 hours, and clearance was 0.708 and 0.828 ml/kg/h in healthy and endotoxemic calves, respectively. Intravenous infusion of endotoxin at the dose (2 micrograms/kg over 4 hours) given did not significantly alter any of the calculated pharmacokinetic variables. Serum thromboxane B2 concentration was significantly (P = 0.05) suppressed for 3 hours after phenylbutazone administration in healthy calves and for 4 hours in endotoxin-challenged calves. Daily administration of phenylbutazone (10 mg/kg loading, then 5 mg/kg for 9 days) to healthy and endotoxemic calves failed to induce any lesions consistent with nonsteroidal anti-inflammatory drug toxicosis.