Co-expression of ovine LPS receptor CD14 with Mannheimia haemolytica leukotoxin receptor LFA-1 or Mac-1 does not enhance leukotoxin-induced cytotoxicity

Leukotoxin (Lkt) and LPS are the major virulence determinants of Mannheimia haemolytica that contribute to the pathogenesis of bovine and ovine pneumonic pasteurellosis. We have previously identified bovine and ovine CD18 as the functional receptor for Lkt. LPS complexes with Lkt resulting in increased thermal stability and enhanced cytotoxic activity of Lkt. Cellular recognition of LPS involves several different molecules including CD14. We hypothesized that expression of ovine CD14 together with LFA-1 or Mac-1 would enhance Lkt-induced cytotoxicity. Ovine cDNA for CD14 was amplified by PCR and cloned into mammalian expression vectors. The 1122 bp cDNAs for bighorn sheep (BHS) and domestic sheep (DS) CD14 encode 373 amino acids which exhibit 99% identity with each other. Ovine CD14 plasmids were transfected either into HEK-293 cells, or previous HEK-293 transfectants stably expressing ovine LFA-1 or Mac-1. Flow cytometric analysis of transfectants confirmed the cell surface expression of CD14. The transfectants expressing LFA-1 or Mac-1 and the transfectants co-expressing CD14 with LFA-1 or Mac-1 did not show any significant difference in Lkt-induced cytotoxicity when incubated with LPS complexed Lkt. In contrast, incubation of the LFA-1 or Mac-1 and LFA-1/CD14 or Mac-1/CD14 transfectants with Lkt which lacks LPS, resulted in reduced cytotoxicity. None of the above transfectants showed any difference in [Ca2+](i) elevation when incubated with both types of Lkt preparations. Lkt did not induce any cytotoxicity or [Ca2+](i) elevation in ovine CD14 transfectants or parent HEK-293 cells. Based on these findings, we conclude that expression of CD14 together with LFA-1 or Mac-1 does not enhance Lkt-induced cytotoxicity, whereas LPS enhances cytotoxicity by complexing with Lkt.     

Uptake of zinc from zinc sulfate and zinc proteinate by ovine ruminal and omasal epithelia

Uptake and transport of Zn from (65)Zn-labeled ZnSO(4) and Zn proteinate (ZnProt) by ruminal and omasal epithelia were examined by using a parabiotic chamber system. Uptake was measured during a 4-h incubation with 10, 20, or 200 microM Zn as ZnSO(4) or ZnProt in the mucosal buffer (pH 6.0, Krebs-Ringer phosphate). Zinc uptake and transport were also evaluated after simulated ruminal digestion. Buffered ruminal fluid contained a feed substrate and 10 or 200 microM added Zn as ZnSO(4) or ZnProt. In a preliminary experiment, uptake of Zn by omasal tissue was low; thus, the remaining experiments were conducted solely with ruminal epithelium. Incubations to determine the effect of time on Zn uptake from mucosal buffer containing 20 microM added Zn as ZnSO(4) or ZnProt resulted in increased (P < 0.01) Zn uptake as incubation time increased from 30 to 240 min. Zinc uptake was also greater (P = 0.02) from mucosal buffer containing ZnProt compared with ZnSO(4). Zinc uptake from incubations containing 10 or 200 microM was affected by source x concentration (P = 0.05) and concentration x time (P < 0.01) interactions. With 10 microM Zn, uptake was not influenced by Zn source, whereas when 200 microM Zn was added, Zn uptake from ZnProt was greater than from ZnSO(4). Increasing incubation time resulted in increased Zn uptake with 200 microM Zn in the mucosal buffer; however, with 10 microM Zn, uptake did not change after 30 min. After simulated ruminal fermentation, the proportion of Zn in a soluble form was influenced by a source x concentration interaction (P = 0.03). After 18 h of incubation, the proportion of Zn that was soluble was not different between ZnProt and ZnSO(4) in buffered ruminal fluid that contained 10 microM added Zn, but was greater for ZnProt compared with ZnSO(4) with 200 microM Zn in the incubation. Zinc uptake from the aqueous fractions of simulated ruminal digestions containing 200 microM added Zn was greater (P < 0.01) than from those containing 10 microM added Zn. Zinc transport, based on detection of (65)Zn in serosal buffer, did not occur in any of the experiments. The results of the current experiments suggest that absorption of Zn into the bloodstream does not occur from the ruminant foresto-mach; however, Zn uptake occurs in ruminal tissue and is greater from ZnProt than from ZnSO(4).     

Modifications in growth and morphology of ovine jejunal and ruminal epithelia as affected by inert dietary substances

Thirty-two lambs were used to study the effects of a nondegradable material in the alimentary tract on growth and morphology of ruminal and jejunal epithelia. Lambs were fed isoenergetic rations that differed only by addition of ground polyethylene. Eight of the lambs receiving each diet were given polyurethane cubes orally that were confined to the rumen. Lambs were slaughtered after 30 d; morphological and growth characteristics of the anterior-ventral and posterior-dorsal ruminal epithelia and jejunal epithelia were examined. Weights of the stomach complex were greater (P less than .05; 1.57 vs 1.48 kg) for lambs fed the polyethylene diet. Polyurethane cubes had no effect on weights of the stomach complex and small intestines. Deoxyribonucleic acid levels and both height and width of papillae were greater (P less than .05) in ruminal epithelial from lambs fed the diet with polyethylene than in those from lambs given the control diet. Protein and DNA levels in jejunal epithelia also were affected (P less than .05) by diet, averaging 8.2 mg/cm2 and 510 micrograms/cm2, respectively, for lambs fed the polyethylene diets vs 7.3 mg/cm2 and 417 micrograms/cm2 for lambs fed the control diet, respectively. Average villus height was greater (P less than .05) in jejunal epithelia of lambs fed the control diet than in jejunal epithelia of those given the polyethylene diet (553 vs 466 microns). Polyurethane cubes did not affect growth or morphological characteristics of either ruminal or jejunal epithelia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absorption of 2-hydroxy-4-(methylthio)butanoic acid by isolated sheep ruminal and omasal epithelia

Alimet (Novus Inter., Inc., St. Louis, MO) feed supplement (an 88% aqueous solution of 2-hydroxy-4-(methylthio) butanoic acid; HMB) is a source of L-Met commonly used in nonruminants and ruminants. The absorption of HMB across ovine omasal and ruminal epithelia was evaluated in this study. Ruminal and omasal epithelia were collected from eight lambs (BW = 67.6 kg +/- 9.1) and mounted in parabiotic chambers that were repeatedly sampled throughout a 60-min incubation. The appearance of HMB (using DL-[5-14C]-HMB as a radiolabeled marker) in serosal buffers increased quadratically (P < .004) with time in both tissues. More (P < .001) HMB appeared in the serosal buffers with omasal than with ruminal epithelia. Both tissues responded similarly, and, after 60 min of incubation, the accumulation of HMB within the tissues increased linearly (P < .001) as substrate concentration (.375, .75, 1.5, 3.0, 6.0, and 12.0 mM) increased in mucosal buffers. As the concentration of HMB in the mucosal buffers increased, there was a quadratic (P < .001) increase in the appearance of HMB in the serosal buffer of the omasal epithelium, indicating some saturation of the system. The increase in serosal appearance of HMB was linear (P < .001) with ruminal tissue. The results indicate that there are probably multiple mechanisms involved in the absorption of HMB. Because saturation was observed in the omasum, it is likely that mediated transport accounts for at least a portion of the absorption of HMB in the omasum. Other mechanisms (e.g., diffusion and(or) paracellular absorption) are responsible for the balance of the absorption. Omasal epithelium appears to have a greater capacity for HMB absorption than ruminal epithelium. The enzymes involved in the conversion of HMB to 2-keto-4-(methylthio)butanoic acid were found in ruminal and omasal epithelia, liver and kidney. These results indicate that HMB can be absorbed across ruminal and omasal epithelium and that HMB can be used as a source of L-methionine.     

Intravenous pentoxifylline does not enhance the pulmonary haemodynamic efficacy of frusemide in strenuously exercising thoroughbred horses

The present study was carried out to examine whether pentoxifylline administration to horses premedicated with frusemide would attenuate the exercise-induced pulmonary arterial, capillary and venous hypertension to a greater extent than frusemide alone, thereby affecting the occurrence of exercise-induced pulmonary haemorrhage (EIPH). Using established techniques, we determined right heart and pulmonary vascular pressures in 6 healthy, sound Thoroughbred horses at rest and during exercise performed at maximal heart rate at a workload of 14 m/s on 3.5% uphill grade in the control (no medications), frusemide (250 mg i.v., 4 h pre-exercise)-control, and the frusemide (250 mg i.v., 4 h pre-exercise) + pentoxifylline (8.5 mg/kg bwt i.v., 15 min preexercise) treatments. Sequence of the 3 treatments was randomised for every horse and 7 days were allowed between them. In the control study, galloping at 14 m/s on 3.5% uphill grade elicited significant right atrial as well as pulmonary arterial, capillary and venous hypertension and all horses experienced EIPH as detected by the presence of fresh blood in the trachea on endoscopic examination. Frusemide administration was not attended by changes in heart rate at rest or during exercise. Although in the frusemide-control experiments, a significant reduction in mean pulmonary arterial, capillary and wedge pressures was observed both at rest and during galloping at 14 m/s on 3.5% uphill grade, all horses still experienced EIPH. Pentoxifylline administration to standing horses premedicated with frusemide caused nervousness, muscular fasciculations, sweating and tachycardia. Although these symptoms had largely abated within 15 min, there were no significant changes in the right atrial or pulmonary vascular pressures. Exercise in the frusemide + pentoxifylline experiments also caused significant right atrial as well as pulmonary arterial, capillary and venous hypertension, but these data were not found to be significantly different from the frusemide-control experiments. All horses in the frusemide + pentoxifylline experiments also experienced EIPH. In conclusion, our data indicate that pentoxifylline (8.5 mg/kg bwt i.v., 15 min pre-exercise) is ineffective in modifying the pulmonary haemodynamic effects of frusemide in exercising horses. It should be noted, however, that we did not examine whether erythrocyte plasticity was altered by the administration of pentoxifylline. Since the intravascular force exerted onto the blood-gas barrier of exercising horses premedicated with frusemide remained unaffected by pentoxifylline administration, it is concluded that concomitant pentoxifylline administration is unlikely to offer additional benefit to horses experiencing EIPH.     

The effects of butyrate and glucagon on the proliferation of ruminal epithelial cells in culture

When the rate of ruminal epithelial cell proliferation was measured on the basis of ³H-thymidine incorporation into the cellular DNA, butyrate dose-dependently reduced ³H-thymidine incorporation. In contrast, glucagon at 10 and 100 pg/ml had a slight stimulatory effect on the incorporation, but only in the absence of butyrate.     

Clenbuterol administration does not enhance the efficacy of furosemide in attenuating the exercise-induced pulmonary capillary hypertension in Thoroughbred horses

The stimulation of pulmonary beta2-adrenergic receptors causes a decrease in vascular resistance. Thus, the present study was carried out to examine whether concomitant administration of clenbuterol-a beta2-adrenergic receptor agonist, to horses premedicated with furosemide would attenuate the exercise-induced pulmonary capillary hypertension to a greater extent than furosemide alone, and in turn, affect the occurrence of exercise-induced pulmonary hemorrhage (EIPH). Experiments were carried out on six healthy, sound, exercise-trained Thoroughbred horses. All horses were studied in the control (no medications), furosemide (250 mg i.v., 4 h pre-exercise)-control, and furosemide (250 mg i.v., 4 h pre-exercise)+clenbuterol (0.8 microg/kg i.v., 11 min pre-exercise) experiments. The sequence of these treatments was randomized for every horse, and 7 days were allowed between them. Using catheter-tip-transducers whose in-vivo signals were referenced at the point of the left shoulder, pulmonary vascular pressures were determined at rest, sub-maximal exercise, and during galloping at 14.2 m/s on a 3.5% uphill grade--a workload that elicited maximal heart rate. In the control study, incremental exercise resulted in progressive significant (P<0.05) increments in heart rate, right atrial as well as pulmonary arterial, capillary and venous (wedge) pressures, and all horses experienced EIPH. Furosemide administration caused a significant (P<0.05) reduction in mean right atrial as well as pulmonary capillary and venous pressures of standing horses. Although exercise in the furosemide-control experiments also caused right atrial and pulmonary vascular pressures to increase significantly (P<0.05), the increment in mean pulmonary capillary and wedge pressures was significantly (P<0.05) attenuated in comparison with the control study, but all horses experienced EIPH. Clenbuterol administration to standing horses premedicated with furosemide caused tachycardia, but significant changes in right atrial or pulmonary vascular pressures were not discerned at rest. During exercise in the furosemide+clenbuterol experiments, heart rate, mean right atrial as well as pulmonary arterial, capillary and wedge pressures increased significantly (P<0.05), but these data were not different from the furosemide-control experiments, and all horses experienced EIPH as well. Thus, it was concluded that clenbuterol administration is ineffective in modifying the pulmonary hemodynamic effects of furosemide in standing or exercising horses. Because the intravascular force exerted onto the blood-gas barrier of horses premedicated with furosemide remained unaffected by clenbuterol administration, it is believed that concomitant clenbuterol administration is unlikely to offer additional benefit to healthy horses experiencing EIPH.     

Dobutamine-induced augmentation of cardiac output does not enhance respiratory gas exchange in anesthetized recumbent healthy horses

The influence of pharmacologic enhancement of cardiac output on the alveolar-to-arterial oxygen tension (difference (P[A-a]O2), physiologic right-to-left shunt fraction (Qs/Qt), and physiologic dead space-to-tidal volume ratio (VD/VT) ws studied in halothane-anesthetized horses in left lateral, right lateral, and dorsal recumbencies. Adult horses were anesthetized, using xylazine (2.2 mg/kg, IM), guaifenesin (50 mg/kg, IV), thiamylal (4.4 mg/kg, IV), and halothane (1.5% to 2% inspired) in 100% O2. Mechanical ventilation was controlled to maintain arterial eucapnia (PaCO2) 35 to 45 mm of Hg) for a period lasting at least 1 hour. Dobutamine was administered at dosages of 1, 3, and 5 micrograms/kg/min, IV, on a randomized basis. The P(A-a)O2, Qs/Qt, and VD/VT were calculated during equilibration and after each dobutamine infusion was given. The P(A-a)O2 and Qs/Qt were significantly (P less than 0.05) greater and VD/VT tended to be greater in horses in dorsal recumbency, compared with those values in horses in left lateral or right lateral recumbency. Cardiac output was similar in all horses, regardless of body position (recumbency). The qualitative relationship between horses in the 3 recumbent positions were not altered by dobutamine. Cardiac output was significantly (P less than 0.05) increased by 3 or 5 micrograms of dobutamine/kg/min in all horses, whereas P(A-a)O2, Qs/Qt, and VD/VT were not significantly altered by dobutamine. The results of the present study failed to substantiate our clinical observations of decreased P(A-a)O2 and Qs/Qt in anesthetized compromised horses given dobutamine.     

Both butyrate incubation and hypoxia upregulate genes involved in the ruminal transport of SCFA and their metabolites

Butyrate modulates the differentiation, proliferation and gene expression profiles of various cell types. Ruminal epithelium is exposed to a high intraluminal concentration and inflow of n‐butyrate. We aimed to investigate the influence of n‐butyrate on the mRNA expression of proteins involved in the transmembranal transfer of n‐butyrate metabolites and short‐chain fatty acids in ruminal epithelium. N‐butyrate‐induced changes were compared with the effects of hypoxia because metabolite accumulation after O₂ depletion is at least partly comparable to the accumulation of metabolites after n‐butyrate exposure. Furthermore, in various tissues, O₂ depletion modulates the expression of transport proteins that are also involved in the extrusion of metabolites derived from n‐butyrate breakdown in ruminal epithelium. Sheep ruminal epithelia mounted in Ussing chambers were exposed to 50 mM n‐butyrate or incubated under hypoxic conditions for 6 h. Electrophysiological measurements showed hypoxia‐induced damage in the epithelia. The mRNA expression levels of monocarboxylate transporters (MCT) 1 and 4, anion exchanger (AE) 2, downregulated in adenoma (DRA), putative anion transporter (PAT) 1 and glucose transporter (GLUT) 1 were assessed by RT‐qPCR. We also examined the mRNA expression of nuclear factor (NF) κB, cyclooxygenase (COX) 2, hypoxia‐inducible factor (HIF) 1α and acyl‐CoA oxidase (ACO) to elucidate the possible signalling pathways involved in the modulation of gene expression. The mRNA expression levels of MCT 1, MCT 4, GLUT 1, HIF 1α and COX 2 were upregulated after both n‐butyrate exposure and hypoxia. ACO and PAT 1 were upregulated only after n‐butyrate incubation. Upregulation of both MCT isoforms and NFκB after n‐butyrate incubation could be detected on protein level as well. Our study suggests key roles for MCT 1 and 4 in the adaptation to an increased intracellular load of metabolites, whereas an involvement of PAT 1 in the transport of n‐butyrate also seems possible.     

Treatment with aspirin or clopidogrel does not affect equine platelet expression of P selectin or platelet-neutrophil aggregates

Inflammation-induced P-selectin (CD62P) expression on platelets and endothelial cells facilitates interactions among platelets and polymorphonuclear leukocytes (PMN), and can also promote coagulation. The effects of clopidogrel and aspirin (ASA) on equine platelet CD62P expression were investigated. Six horses were treated in a cross-over design with clopidogrel (2mg/kg PO q 24) or ASA (5mg/kg PO q 24h) for 5 days. Platelets collected at 24, 72, 96, 120, and 168h after the initiation of therapy were stimulated using 0.1μg/mL thrombin, followed by flow cytometric analysis using anti-CD41/61 and anti-equine CD62P antibodies. Platelet-PMN aggregates were also enumerated. Baseline CD62P positive platelet numbers were not different between groups (mean±SD): 4254±1785 (clopidogrel) and 3600±1780 (ASA, P=0. 435). Although expression tended to decrease, there were no significant changes in CD62P+platelets after treatment with either drug (clopidogrel P=0.139, ASA P=0.161). There was also no difference in platelet-PMN aggregates during or after treatment with ASA (P=0.513) or clopidogrel (P=0.543). Due to small numbers of horses, this study may have been underpowered to detect a true decrease in expression, and differences between therapies may have been more pronounced if this study had evaluated horses with systemic inflammation.     

丁酸钠对兔离体回肠运动的影响

试验研究了不同剂量（0.025%、0.05%、0.1%、0.15%、0.2%）的丁酸钠对兔离体回肠运动性能（张力和频率）的影响,并探讨其对肠道平滑肌收缩的影响机制。结果表明,丁酸钠对兔离体回肠的收缩张力及收缩频率均有显著地促进作用（P〈0.05）,并且剂量越大促进作用越明显。试验结果还表明丁酸钠对兔离体回肠的收缩活动的促进作用与丁酸钠对肠道pH的影响无关。     

Novel papillomavirus isolated from the oral mucosa of a polar bear does not cluster with other papillomaviruses of carnivores

Papillomatosis has been documented in several carnivores, and papillomavirus (PV) types have been characterized from lesions in a number of carnivore species: the canine oral PV (COPV), the Felis domesticus PV type 1 (FdPV-1) isolated from a Persian cat, the Procyon lotor PV type 1 (PlPV-1) isolated from a raccoon, the canine PV type 2 (CPV-2) from a dog's foot pad lesion and the canine PV type 3 (CPV-3) associated with a canine epidermodysplasia verruciformis - like disease. A tissue sample was taken from a papillomatous lesion on the oral mucosa of a polar bear (Ursus maritimus). Extracted DNA was used as a template for multiply primed rolling-circle amplification (RCA), and restriction enzyme analysis of the RCA product indicated the presence of papillomaviral DNA. The genome of this PV was cloned and the complete genomic sequence was determined. The Ursus maritimus PV type 1 (UmPV-1) genome counts 7582 basepairs and is smaller than that of other papillomaviruses from carnivore species. UmPV-1 contains the typical noncoding region NCR1, but unlike the carnivore PVs of the Lambda genus, UmPV-1 does not possess a second noncoding region NCR2. Phylogenetic analysis based on a nucleotide sequence alignment of the L1 ORF of UmPV-1 and 51 other PV types indicates that UmPV-1 does not cluster with any of the other carnivore PVs, but branches off near the root of the common branch of the genus Alphapapillomavirus.     

Effect of increasing ruminal butyrate absorption on splanchnic metabolism of volatile fatty acids absorbed from the washed reticulorumen of steers

Four steers fitted with a ruminal cannula and chronic indwelling catheters in the mesenteric artery, mesenteric vein, hepatic portal vein, hepatic vein, and the right ruminal vein were used to study the absorption and metabolism of VFA from bicarbonate buffers incubated in the temporarily emptied and washed reticulorumen. Portal and hepatic vein blood flows were determined by infusion of p-aminohippurate into the mesenteric vein, and portal VFA fluxes were calibrated by infusion of isovalerate into the ruminal vein. The steers were subjected to four experimental treatments in a Latin square design with four periods within 1 d. The treatments were Control (bicarbonate buffer) and VFA buffers containing 4, 12, or 36 mmol butyrate/kg of buffer, respectively. The acetate content of the buffers was decreased with increasing butyrate to balance the acidity. The butyrate absorption from the rumen was 39, 111, and 300 +/- 4 mmol/h for the three VFA buffers, respectively. The ruminal absorption rates of propionate (260 +/- 12 mmol/h), isobutyrate (11.4 +/- 0.7 mmol/h), and valerate (17.3 +/- 0.7 mmol/h) were not affected by VFA buffers. The portal recovery of butyrate and valerate absorbed from the rumen increased (P < 0.01) with increasing butyrate absorption and reached 52 to 54 +/- 4% with the greatest butyrate absorption. The liver responded to the increased butyrate absorption with a decreasing fractional extraction of propionate and butyrate, and with the greatest butyrate absorption, the splanchnic flux was 22 +/- 1% and 18 +/- 1% of the absorbed propionate and butyrate, respectively. The increased propionate and butyrate release to peripheral tissues was followed by increased (P < 0.05) arterial concentrations of propionate (0.08 +/- 0.01 mmol/kg) and butyrate (0.07 +/- 0.01 mmol/kg). Arterial insulin concentration increased (P = 0.01) with incubation of VFA buffers compared with Control and was numerically greatest with the greatest level of butyrate absorption. We conclude that the capacity to metabolize butyrate by the ruminal epithelium and liver is limited. If butyrate absorption exceeds the metabolic capacity, it affects rumen epithelial and hepatic nutrient metabolism and affects the nutrient supply of peripheral tissues.     

Supplemental soybean oil or corn for beef heifers grazing summer pasture: effects on forage intake, ruminal fermentation, and site and extent of digestion.

Nine Angus x Gelbvieh heifers (average BW = 347 +/- 2.8 kg) with ruminal and duodenal cannulas were used in a split-plot designed experiment to determine the effects of soybean oil or corn supplementation on intake, OM, NDF, and N digestibility. Beginning June 8, 1998, heifers continually grazed a 6.5-ha predominantly bromegrass pasture and received one of three treatments: no supplementation (Control); daily supplementation of cracked corn (Corn) at 0.345% of BW; or daily supplementation (0.3% of BW) of a supplement containing cracked corn, corn gluten meal, and soybean oil (12.5% of supplemental DM; Oil). Soybean oil replaced corn on a TDN basis and corn gluten meal was included to provide equal quantities of supplemental TDN and N. Three 23-d periods consisted of 14 d of adaptation followed by 9 d of sample collections. Treatment and sampling period effects were evaluated using orthogonal contrasts. Other than crude fat being greater (P = 0.01) for supplemented heifers, chemical and nutrient composition of masticate samples collected via ruminal evacuation did not differ (P = 0.23 to 0.56) among treatments. Masticate NDF and ADF increased quadratically (P < or = 0.003) and N decreased linearly (P = 0.0001) as the grazing season progressed. Supplementation did not influence (P = 0.37 to 0.83) forage OM intake, total and lower tract OM digestibility, ruminal and total tract NDF digestibility, or total ruminal VFA; however, supplemented heifers had lower ruminal molar proportions of acetate (P = 0.01), higher ruminal molar proportions of butyrate (P = 0.007), and greater quantities of OM digested in the rumen (P = 0.10) and total tract (P = 0.02). As the grazing season progressed, total tract OM and N and ruminal NH3 concentrations and NDF digestibility decreased quadratically (P < or = 0.04). Microbial N flow (P = 0.09) and efficiency (P = 0.04) and postruminal N disappearance (P = 0.02) were greater for Control heifers and declined linearly (P < or = 0.02) as the grazing season advanced. Depressed microbial N flow seemed to be more pronounced for Oil than for the Corn treatment. Although total digestible OM intake increased with supplementation, metabolizable protein supply was reduced in supplemented heifers. Therefore, feeding low levels of supplemental grain with or without soybean oil is an effective strategy to increase dietary energy for cattle grazing high-quality forages, but consideration should be given to reduced supply of metabolizable protein.     

Intravenous pentoxifylline does not affect the exercise-induced pulmonary arterial, capillary or venous hypertension in Thoroughbred horses

The present study was carried out to examine whether intravenously administered pentoxifylline-a phosphodiesterase inhibitor which increases red blood cell deformability and decreases blood viscosity-would attenuate the magnitude of exercise-induced pulmonary capillary hypertension in healthy, fit Thoroughbred horses and in turn, diminish the occurrence of exercise-induced pulmonary hemorrhage (EIPH). Experiments were carried out on six healthy, sound, exercise-trained Thoroughbred horses. Hemodynamic data were collected at rest, and during exercise performed at 8 and 14 m/sec on 3.5% uphill grade in the control (no medications) and the pentoxifylline (8.5 mg/kg, i.v.) experiments. The sequence of treatments was randomized for every horse and 7 days were allowed between treatments. Galloping at 14 m/sec on 3.5% uphill grade elicited maximal heart rate. In both treatments, simultaneous measurements of phasic and mean right atrial and pulmonary arterial, capillary and wedge pressures were made using catheter-tip-manometers whose signals were carefully referenced at the point of the left shoulder. In the control study, exercise resulted in progressive significant increments in heart rate, right atrial and pulmonary arterial, capillary and venous pressures; thereby, confirming that exercising Thoroughbreds develop significant pulmonary hypertension. All horses experienced exercise-induced pulmonary hemorrhage (EIPH) in the control experiments. Pentoxifylline administration to standing horses caused anxiety, tachycardia, muscular fasciculations/tremors and mild sweating, but statistically significant changes in right atrial and pulmonary arterial, capillary and venous pressures were not detected. Exercise in the pentoxifylline treatment also resulted in progressive significant increments in heart rate and right atrial as well as pulmonary vascular pressures, but these data were not statistically significantly different from those in the control study and the incidence of EIPH remained unchanged. Thus, it was concluded that i.v. pentoxifylline is ineffective in attenuating the exercise-induced pulmonary arterial, capillary and venous hypertension in healthy, fit Thoroughbred horses.     

Jaagsiekte sheep retrovirus found in milk macrophages but not in milk lymphocytes or mammary gland epithelia of naturally infected sheep

Jaagsiekte sheep retrovirus (JSRV) causes ovine pulmonary adenocarcinoma. JSRV can be transmitted via infected colostrum or milk, which contain somatic cells (SCs) harboring JSRV provirus. Nevertheless, the cell types involved in this form of transmission and the involvement of the mammary gland remain unknown. We separated adherent cells (macrophages and monocytes) by plastic adherence, and lymphocytes (CD4+ and CD8+ T cells, and B cells) by flow cytometry, from SCs in milk samples from 12 naturally infected, PCR blood test JSRV–positive, subclinical ewes. These cell populations were tested by PCR to detect JSRV provirus. The ewes were euthanized, and mammary gland samples were analyzed immunohistochemically to detect JSRV surface protein. We did not detect JSRV provirus in any milk lymphocyte population, but milk adherent cells were positive in 3 of 12 sheep, suggesting a potential major role of this population in the lactogenic transmission of JSRV. Immunohistochemistry did not reveal positive results in mammary epithelial cells, pointing to a lack of participation of the mammary gland in the biological cycle of JSRV and reducing the probability of excretion of free viral particles in colostrum or milk.     

Buprenorphine in combination with naloxone at a ratio of 15:1 does not enhance antinociception from buprenorphine in healthy cats

Naloxone can enhance the antinociceptive/analgesic effects of buprenorphine in humans and rats. The antinociceptive effects of a patented 15:1 buprenorphine:naloxone combination was investigated in cats using a thermal and mechanical nociceptive model. Twelve cats received buprenorphine 10 μg/kg, naloxone 0.67 μg/kg or a buprenorphine-naloxone combination intramuscularly in a randomised cross over study. Using thermal and mechanical analgesiometry validated in the cat, pre-treatment baselines were measured. Following test drug administration, thresholds were studied for the next 24h. Naloxone did not enhance the thermal antinociceptive effect of buprenorphine. The results from this study are in agreement with previously published work showing that naloxone antagonises the effects of clinically analgesic doses of buprenorphine. Mechanical nociceptive thresholds were not affected by buprenorphine.