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Six nontrained mares were subjected to steady-state, submaximal treadmill exercise to examine the effect of exercise on the plasma concentration of atrial natriuretic peptide (ANP) in arterial, compared with mixed venous, blood. Horses ran on a treadmill up a 6 degree grade for 20 minutes at a speed calculated to require a power equivalent to 80% of maximal oxygen uptake (VO2MAX). Arterial and mixed venous blood samples were collected simultaneously from the carotid and pulmonary arteries of horses at rest and at 10 and 20 minutes of exercise. Plasma was stored at -80 C and was later thawed; ANP was extracted, and its concentration was determined by radioimmunoassay. Exercise caused significant (P < 0.05) increases in arterial and venous plasma ANP concentrations. Mean +/- SEM arterial ANP concentration increased from 25.2 +/- 4.4 pg/ml at rest to 52.7 +/- 5.2 pg/ml at 10 minutes of exercise and 62.5 +/- 5.2 pg/ml at 20 minutes of exercise. Mean venous ANP concentration increased from 24.8 +/- 4.3 pg/ml at rest to 67.2 +/- 14.5 pg/ml at 10 minutes of exercise and 65.3 +/- 13.5 pg/ml at 20 minutes of exercise. Significant differences were not evident between arterial or mixed venous ANP concentration at rest or during exercise, indicating that ANP either is not metabolized in the lungs or is released from the left atrium at a rate matching that of pulmonary metabolism.  相似文献   
85.
Ruminant pharmacology.   总被引:1,自引:0,他引:1  
Aspects of drug disposition, metabolism, and toxicity in the ruminant animal are discussed, and illustrative examples are provided. The effects of the reticulo-rumen on drug disposition in the ruminant are highlighted.  相似文献   
86.
Muscle glycogen synthesis depends on glucose availability. This study was undertaken to determine the glycemic and insulinemic response of horses to equal amounts of hydrolyzable carbohydrates (starch and sugar) in the form of one of three grain meals or intragastric administration of a glucose solution. In a randomized crossover design, seven horses were fed each of three grain meals (cracked corn, steamed oat groats, or rolled barley) or were infused intragastrically with glucose solution at 2 g of hydrolyzable carbohydrate (starch plus sugar) per kilogram of BW. The quantity of hydrolyzable carbohydrate ingested was not different among all treatments (P = 0.70). Plasma glucose concentration peaked in all four treatments by 1.5 to 2 h after feeding. Plasma glucose concentration remained higher than baseline in oat groats or barley-fed horses throughout 8 h, whereas plasma glucose returned to baseline by 5 to 6 h in corn-fed horses or after glucose administration. Meal consumption was slower in oat groats-fed horses than in corn-fed ones, which may confound the glycemic and insulinemic responses observed after grain feeding. Plasma glucose area under the curve (AUC) was 63% both in corn and oat groats and 57% in barley-fed horses compared with that of horses administered glucose (P = 0.13). Serum immunoreactive insulin concentration peaked between 2 and 3 h after feeding or glucose administration, and barley-fed horses had lower serum immunoreactive insulin concentration by 3 to 4 h than corn-fed horses or after glucose administration (P < 0.05). We conclude, in horses, ingestion of oat groats, corn, and barley result in similar plasma glucose AUC and, compared with the glycemic index of 100 as the glucose reference, corn, oat groats, and barley had a glycemic index of approximately 60.  相似文献   
87.
OBJECTIVE: To determine components of the increase in oxygen consumption (VO2) and evaluate determinants of hemoglobin saturation (SO2) during incremental treadmill exercise in unfit horses. ANIMALS: 7 unfit adult mares. PROCEDURES: Horses performed 1 preliminary exercise test (EXT) and 2 experimental EXT. Arterial and mixed venous blood samples and hemodynamic measurements were taken during the last 30 seconds of each step of the GXT to measure PO2, hemoglobin concentration ([Hb]), SO2, and determinants of acid-base state (protein, electrolytes, and PCO2). RESULTS: Increased VO2 during exercise was facilitated by significant increases in cardiac output (CO), [Hb], and widening of the arteriovenous difference in O2. Arterial and venous pH, PaO2, and PvO2 decreased during exercise. Arterial PCO2, bicarbonate ([HCO3-])a, and [HCO3-] decreased significantly, whereas PVCO2 and increased. Arterial and venous sodium concentration, potassium concentration, strong ion difference, and venous lactate concentration all increased significantly during exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in CO, [Hb], and O2 extraction contributed equally to increased VO2 during exercise. Higher PCO2 did not provide an independent contribution to shift in the oxyhemoglobin dissociation curve (OCD) in venous blood. However, lower PaCO2 shifted the curve leftward, facilitating O2 loading. The shift of ODC resulted in minimal effect on O2 extraction because of convergence of the ODC at lower values of PO2. Decreased pH appeared responsible for the rightward shift of the ODC, which may be necessary to allow maximal O2 extraction at high blood flows achieved during exercise.  相似文献   
88.
OBJECTIVE: To compare effects of low and high intensity warm-up exercise on oxygen consumption (VO2) and carbon dioxide production (VCO2) in horses. ANIMALS: 6 moderately conditioned adult Standard-breds. PROCEDURES: Horses ran for 2 minutes at 115% of maximum oxygen consumption (VO2max), 5 minutes after each of the following periods: no warm-up (NoWU); 10 minutes at 50% of VO2max (LoWU); or 7 minutes at 50% VO2max followed by 45-second intervals at 80, 90, and 100% VO2max (HiWU). Oxygen consumption and VCO2 were measured during exercise, and kinetics of VO2 and VCO2 were calculated. Accumulated O2 deficit was also calculated. RESULTS: For both warm-up trials, the time constant for the rapid exponential increase in VO2 was 30% lower than for NoWU. Similarly, the rate of increase in VCO2 was 23% faster in LoWU and HiWU than in NoWU. Peak values for VO2 achieved during the high-speed test were not significantly different among trials (LoWU, 150.2 +/- 3.2 ml/kg/min; HiWU, 151.2 +/- 4.2 ml/kg/min; NoWU, 145.1 +/- 4.1 ml/kg/min). However, accumulated O2 deficit (ml of O2 equivalents/kg) was significantly lower during LoWU (65.3 +/- 5.1) and HiWU (63.4 +/- 3.9) than during NoWU (82.1 +/- 7.3). CONCLUSIONS AND CLINICAL RELEVANCE: Both the low- and high-intensity warm-up, completed 5 minutes before the start of high-intensity exercise, accelerated the kinetics of VO2 and VCO2 and decreased accumulated O2 deficit during 2 minutes of intense exertion in horses that were moderately conditioned.  相似文献   
89.
Frusemide reduces pulmonary vascular pressures in resting horses and attenuates exercise-induced increases in these pressures in exercising horses. The mechanism underlying these effects of frusemide is unclear. We tested the hypothesis that the haemodynamic effects of frusemide are dependent on diuresis by examining the effect of frusemide in anaesthetised horses in which diuresis was prevented by ligation of ureters. Twenty four horses were assigned randomly to one of 4 treatments: 1) frusemide (1 mg/kg bwt i.v.) and intact ureters; 2) frusemide and ligated ureters; 3) saline placebo and ligated ureters; and 4) frusemide and phenylbutazone (4.4 mg/kg bwt i.v. 12 h and 15 min before frusemide) and ligated ureters. Frusemide administration to anaesthetised horses with intact ureters increased plasma total protein concentration and reduced mean right atrial, pulmonary artery and aortic pressures. There was no significant effect of frusemide administration on haemodynamic variables or plasma total protein concentration in horses with ligated ureters. The combination of frusemide and phenylbutazone increased mean right atrial, pulmonary artery and aortic pressures in horses with ligated ureters. This study demonstrates that, in anaesthetised horses, the haemodynamic effect of frusemide is dependent upon diuresis. We interpret these results as providing further evidence that the haemodynamic effect of frusemide in horses is attributable to a reduction in plasma and blood volume.  相似文献   
90.
Medical records of 101 blood culture-confirmed bacteremic foals were reviewed to determine whether foals with Actinobacillus sp. bacteremia are affected at an earlier age, have more severe signs of disease, and have a worse prognosis than do foals with bacteremia of other causes. Thirty percent (30/101) of bacteremic foals had Actinobacillus sp. cultured, and these were 2 times more likely to die (crude odds ratio [OR(CR)] 0.8, 4; P = .14), with a survival rate of 43% (13/30) compared to the overall survival rate of 55% (56/101). When compared to other bacteremic foals, foals with actinobacillosis were 7 times more likely to have been sick from birth (adjusted odds ratio [OR(ADJ)] 2, 26; P = .003) and 6 times more likely to have diarrhea (OR(ADJ) 1, 22; P = .009). By bivariate analysis. foals with Actinobacillus sp. bacteremia were 5 times more likely to have a sepsis score >11 (OR(CR) 1, 18; P = .007), 6 times more likely to be obtunded (OR(CR) 2, 20; P = .005), and 3 times more likely to have pneumonia (OR(CR) 1, 7; P = .03). Furthermore, Actinobacillus sp. bacteremic foals were 27 times more likely to have a segmented neutrophil count <3.3 X 10(9) cells/L (OR(ADJ) 4, 166: P < .0001) and were 4.5 times more likely to have a band neutrophil count >0.46 x 10(9) cells/L (OR(ADJ) 1, 17; P = .02) when compared to foals that had bacteremia caused by either gram-negative enteric or gram-positive organisms. Sepsis score was < or = 11 in 49% (29/59) of bacteremia foals aged <13 days for which a discernible sepsis score was calculable. Results of this study should improve the diagnostic sensitivity of clinical examinations of neonatal foals, thereby facilitating treatment decisions.  相似文献   
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