The vasculature of 22 small colons from dead adult ponies was perfused with latex or barium sulphate solution. The vascular anatomy was studied by use of dissection and alkali digestion of the latex specimens and microangiography of the barium sulphate-perfused specimens. The small colon is supplied by the caudal mesentric artery. The left colic artery arises from the caudal mesenteric artery, which then becomes the cranial rectal artery. Branches from the left colic and cranial rectal arteries form anastomosing arcades that become narrower distally along the length of the small colon. From these arcades arise terminal arteries, which enter the small colon wall and give rise to a subserosal, an intermuscular, and a large submucosal plexus, with frequent anastomoses between them. The venous drainage closely parallels the arterial supply, except near to its origin from the portal vein, when the left colic vein and caudal mesentric vein are separate from the corresponding arteries.

The vasculature of 22 small colons from dead adult ponies was perfused with latex or barium sulphate solution. The vascular anatomy was studied by use of dissection and alkali digestion of the latex specimens and microangiography of the barium sulphate-perfused specimens. The small colon is supplied by the caudal mesentric artery. The left colic artery arises from the caudal mesenteric artery, which then becomes the cranial rectal artery. Branches from the left colic and cranial rectal arteries form anastomosing arcades that become narrower distally along the length of the small colon. From these arcades arise terminal arteries, which enter the small colon wall and give rise to a subserosal, an intermuscular, and a large submucosal plexus, with frequent anastomoses between them. The venous drainage closely parallels the arterial supply, except near to its origin from the portal vein, when the left colic vein and caudal mesentric vein are separate from the corresponding arteries.

The disposition of theophylline in healthy ruminating calves was best described by a first-order 2-compartment open pharamacokinetic model. The drug had a mean elimination half-life of 6.4 hours and a mean distribution half-life of 22 minutes. Total body clearance averaged 91 ml/kg/h. The mean values for the pharmacokinetic volume of the central compartment, pharmacokinetic volume of distribution during the terminal phase, and volume of distribution at steady state were 0.502, 0.870, and 0.815 L/kg, respectively. Theophylline was readily absorbed after oral administration to the ruminating calf, with a mean fraction of 0.93 absorbed. The plasma concentrations after oral dosing peaked in approximately 5 to 6 hours, with a mean absorption half-life of 3.7 hours. A flip-flop model (rate constant of input is much smaller than the rate constant of output) of drug absorption was not found because the elimination process roughly paralleled that of the study concerning IV administration. In a multiple-dose trial that used a dosage regimen based on single-dose pharmacokinetic values, clinically normal calves responded as predicted. However, diseased calves had higher than expected plasma concentrations after being given multiple oral doses of theophylline at 28 mg/kg once daily. Overt signs of toxicosis were not seen, but this aspect of the drug was not formally investigated. Theophylline can be used as an ancillary therapeutic agent to treat bovine respiratory disease, but not without risk. The suggested oral dose of theophylline at 28 mg/kg of body weight once daily should be tailored to each case. Twice daily oral dosing at 20 mg/kg should reduce the plasma peak:trough ratio and provide plasma concentrations more cnsistently within the human therapeutic range of 10 to 20 micrograms/ml. Even then, therapeutic drug monitoring should be done.

The disposition of theophylline in healthy ruminating calves was best described by a first-order 2-compartment open pharamacokinetic model. The drug had a mean elimination half-life of 6.4 hours and a mean distribution half-life of 22 minutes. Total body clearance averaged 91 ml/kg/h. The mean values for the pharmacokinetic volume of the central compartment, pharmacokinetic volume of distribution during the terminal phase, and volume of distribution at steady state were 0.502, 0.870, and 0.815 L/kg, respectively. Theophylline was readily absorbed after oral administration to the ruminating calf, with a mean fraction of 0.93 absorbed. The plasma concentrations after oral dosing peaked in approximately 5 to 6 hours, with a mean absorption half-life of 3.7 hours. A flip-flop model (rate constant of input is much smaller than the rate constant of output) of drug absorption was not found because the elimination process roughly paralleled that of the study concerning IV administration. In a multiple-dose trial that used a dosage regimen based on single-dose pharmacokinetic values, clinically normal calves responded as predicted. However, diseased calves had higher than expected plasma concentrations after being given multiple oral doses of theophylline at 28 mg/kg once daily. Overt signs of toxicosis were not seen, but this aspect of the drug was not formally investigated. Theophylline can be used as an ancillary therapeutic agent to treat bovine respiratory disease, but not without risk. The suggested oral dose of theophylline at 28 mg/kg of body weight once daily should be tailored to each case. Twice daily oral dosing at 20 mg/kg should reduce the plasma peak:trough ratio and provide plasma concentrations more cnsistently within the human therapeutic range of 10 to 20 micrograms/ml. Even then, therapeutic drug monitoring should be done.

Oxytetracycline (OTC) pharmacokinetic values in plasma and bile were ascertained after IV administration of the drug. At 6 hours after administration of 1 mg of OTC/kg of body weight, 2.15% of the dose was found in the bile and 37.6% was found in the urine. At 2 hours after administration, the peak bile-to-plasma OTC concentration ratio was 60:1. Bioavailability of OTC was 47.6% when it was administered orally to fasted turkeys and was 9.4% when administered to fed turkeys.

Oxytetracycline (OTC) pharmacokinetic values in plasma and bile were ascertained after IV administration of the drug. At 6 hours after administration of 1 mg of OTC/kg of body weight, 2.15% of the dose was found in the bile and 37.6% was found in the urine. At 2 hours after administration, the peak bile-to-plasma OTC concentration ratio was 60:1. Bioavailability of OTC was 47.6% when it was administered orally to fasted turkeys and was 9.4% when administered to fed turkeys.

Fecal excretion of a particulate marker, ytterbium (Yb), was evaluated in 9 horses before surgery and 3 weeks, 3 months, and 6 months (4 trials) after sham-operation (group 1; n = 3) or extensive large colon resection (group 2; n = 6). Fecal excretion curves of total Yb excretion, log(e) Yb excretion, % Yb excretion, log(e) % Yb excretion, and cumulative % Yb excretion were evaluated, and kinectic analysis was performed on the log(e) Yb excretion curves to detect mixing pools and to calculate the fractional rate of particulate passage, turnover rate, and pool size. Calculations were performed to determined transit time, mean overall retention time, adjusted mean retention time, peak time, and disappearance time. Values were statistically analyzed to determine differences between groups and among trials (P less than 0.05). Group-2 horses had significantly shorter transit, peak, and mean overall retention times, compared with preoperative values and with values for group-1 horses. Two mixing pools were identified: a slower emptying pool of 5.7% hour-1 (k1) and a faster emptying pool of 12.3% hour-1 (k2). The rate of passage from the first pool (k1) was not altered by colon, resection, and was interpreted as being most influenced by the cecum. In further support of this interpretation, the capacity of the k1 pool approximated the capacity of the cecum (17 L). The capacity of the k1 pool significantly expanded by 6 months in the resected horses. The rate of passage from the second pool (k2) significantly increased initially after colon resection (3 weeks and 3 months), but returned to preoperative values by 6 months. This pool was affected by colon resection, and was therefore interpreted as being influenced by a portion of the colon. Despite these changes in rate of passage and capacity of the mixing pools, on all the trials, colon resection decreased intestinal transit time and overall mean retention time because of a decrease in the total large intestinal length or capacity. This decrease in particulate matter retention and transit time may partially or totally explain the decrease in fiber digestion reported in horses with extensive large colon resection.

Pilus-mediated adherence is a virulence attribute of Moraxella bovis. Several pilus types have been shown to exist among strains of this bacterium, but correlation between pilus type and specific field cases of the disease has not been done. During the summer of 1987, an epizootic of infectious bovine keratoconjunctivitis was reported in 7 Iowa counties. Eight isolates of M bovis were secured from 12 episodes studied. All 8 of the isolates were nearly homogeneous in biochemical properties and had the same plasmid biotype. Pilus typing performed by immunofluorescence and immunogold electron microscopy identified a single new pilus type among 5 of the 8 isolates. This pilus type was identified in field cases that developed within a narrow time frame and over large distances. The implication of these findings is that infectious bovine keratoconjunctivitis epizootics may be associated with emergence of a novel pilus type, and that rapid dissemination over wide distances can occur, presumably by transportation of carrier cattle.

Pilus-mediated adherence is a virulence attribute of Moraxella bovis. Several pilus types have been shown to exist among strains of this bacterium, but correlation between pilus type and specific field cases of the disease has not been done. During the summer of 1987, an epizootic of infectious bovine keratoconjunctivitis was reported in 7 Iowa counties. Eight isolates of M bovis were secured from 12 episodes studied. All 8 of the isolates were nearly homogeneous in biochemical properties and had the same plasmid biotype. Pilus typing performed by immunofluorescence and immunogold electron microscopy identified a single new pilus type among 5 of the 8 isolates. This pilus type was identified in field cases that developed within a narrow time frame and over large distances. The implication of these findings is that infectious bovine keratoconjunctivitis epizootics may be associated with emergence of a novel pilus type, and that rapid dissemination over wide distances can occur, presumably by transportation of carrier cattle.

The in vitro and in vivo binding of a monoclonal antibody (MAB) that recognizes a tumor-associated carbohydrate antigen was studied in dogs. Monoclonal antibody 155H.7 was raised in response to inoculation of mice with beta-galactose(1-3)betaN-acetylgalactosamine conjugated to human serum albumin. Avidin-biotin-complex immunohistochemical staining of cryostat sections of normal and neoplastic canine tissue specimens revealed heterogenous binding of MAB 155H.7 to the cells of many canine mammary and lung carcinomas and homogenous staining of many sarcomas, including osteogenic sarcoma. In addition, there was variable staining of a variety of normal tissues including some ductual epithelium, peripheral nerve fibers, and some endothelial cells and fibroblasts. Immunoscintigraphy with 131I-labeled MAB 155H.7 was used to study the in vitro distribution of the antibody. The 131I-labeled MAB 155.H.7 was administered to 1 clinically normal dog, 7 dogs with osteogenic sarcoma, 1 dog with undifferentiated sarcoma, and 2 dogs with mammary tumor. Scintigraphy revealed concentration of radioactivity in 8 of 10 tumor sites within 24 hours after MAB administration. The ratio of 131I in tumor sites to 131I in the surrounding normal tissues, compared with the similar ratio of 99mTc-labeled erythrocytes ranged from 1.1 to 4.3 in tumor vs normal tissue with a mean value of 2, confirming tumor localization of the radiolabeled MAB in excess of that associated with enhanced tumor vascularization.

The in vitro and in vivo binding of a monoclonal antibody (MAB) that recognizes a tumor-associated carbohydrate antigen was studied in dogs. Monoclonal antibody 155H.7 was raised in response to innoculation of mice with beta-galactose(1-3)betaN-acetylgalactosamine conjugated to human serum albumin. Avidin-biotin-complex immunohistochemical staining of cryostat sections of normal and neoplastic canine tissue specimens revealed heterogenous binding of MAB 155H.7 to the cells of many canine mammary and lung carcinomas and homogenous staining of may sarcomas, including osteogenic sarcoma. In addition, there was variable staining of a variety of normal tissues including some ductual epithelium, peripheral nerve fibers, and some endothelial cells and fibroblasts. Immunoscintigraphy with 131I-labeled MAB 155H.7 was used to study the in vitro distribution of the antibody. The 131I-labeled MAB 155.H.7 was administered to 1 clinically normal dog, 7 dogs with osteogenic sarcoma, 1 dog with undifferentiated sarcoma, and 2 dogs with mammary tumor. Scintigraphy revealed concentration of radioactivity in 8 of 10 tumor sites within 24 hours after MAB administration. The ratio of 131I in tumor sites to 131I in the surrounding normal tissues, compared with the similar ratio of 99mTc-labeled erythrocytes ranged from 1.1 to 4.3 in tumor vs normal tissue with a mean value of 2, confirming tumor localization of the radiolabeled MAB in excess of that associated with enhanced tumor vascularization.

Foals with the Ca blood group antigen on their RBC were given colostrum with anti-Ca antibodies (6 foals) or colostrum without anti-Ca antibodies (6 foals). The PVC were determined at birth and 2, 4, and 6 days after birth for the foals in each group. Significant differences were not observed for the PCV between the 2 groups, indicating that foals were not adversely affected by ingesting colostrum with the anti-Ca antibody. Standardbred mares without the Aa blood group antigen were evaluated to determine whether production of anti-Ca antibodies influenced production of anti-Aa antibodies. Of 266 mares without the Aa antigen, 3 of 61 (5%) mares without the Ca blood group antigen produced anti-Aa antibodies and 43 of 205 (21%) with the Ca blood group antigen produced anti-Aa antibodies. These 2 groups of mares were significantly (p = 0.006) different; Ca-negative mares were less likely to produce antibodies to Aa than were mares with the Ca blood group antigen. This observation was consistent with a hypothesis of antibody-mediated immunosuppression of immune response to the As blood group antigen by antibodies to the Ca blood group antigen, ie, when a mare is exposed to her foal's RBC and already has antibodies to the Ca blood group antigen on the foal's RBC, then she is less likely to initiate an immune response to the Aa blood group antigen also on the foal's RBC.

Foals with the Ca blood group antigen on their RBC were given colostrum with anti-Ca antibodies (6 foals) or colostrum without anti-Ca antibodies (6 foals). The PVC were determined at birth and 2, 4, and 6 days after birth for the foals in each group. Significant differences were not observed for the PCV between the 2 groups, indicating that foals were not adversely affected by ingesting colostrum with the anti-Ca antibody. Standardbred mares without the Aa blood group antigen were evaluated to determine whether production of anti-Ca antibodies influenced production of anti-Aa antibodies. Of 266 mares without the Aa antigen, 3 of 61 (5%) mares without the Ca blood group antigen produced anti-Aa antibodies and 43 of 205 (21%) with the Ca blood group antigen produced anti-Aa antibodies. These 2 groups of mares were significantly (p = 0.006) different; Ca-negative mares were less likely to produce antibodies to Aa than were mares with the Ca blood group antigen. This observation was consistent with a hypothesis of antibody-mediated immunosuppression of immune response to the As blood group antigen by antibodies to the Ca blood group antigen, ie, when a mare is exposed to her foal's RBC and already has antibodies to the Ca blood group antigen on the foal's RBC, then she is less likely to initiate an immune response to the Aa blood group antigen also on the foal's RBC.