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Urokinase is a chymotrypsin-like serine protease and an endogenous extrinsic plasminogen activator that is important in conversion of the circulating proenzyme plasminogen into the active serine protease plasmin. 1 Urokinase is a single

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in American Journal of Veterinary Research

thrombophilia. 2 A study 2 in humans has revealed that exercise results in activation of coagulation and subsequent counter-regulation of the previously initiated coagulation reaction. Exercise-induced activation of the coagulation system is possibly caused by

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in American Journal of Veterinary Research

laminar tissues are similar to those in organs at risk of failure in humans with sepsis. 5,9 These changes include leukocyte and endothelial activation that results in induction of a number of proinflammatory mediators, which alter endothelial

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in American Journal of Veterinary Research

activation in these vessels and whether PKC contributes differentially to agonist-induced constriction in laminar veins and arteries. Protein kinase C was among the first protein kinases to be identified. 12 It has been found to be a key player in a

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in American Journal of Veterinary Research

Abstract

Objective

To test the hypothesis that platelet-activating factor (PAF) induces inositol phosphate turnover through a receptor-linked, pertussis toxin-sensitive guanine nucleotide-binding (G) protein-dependent pathway in porcine alveolar macrophages.

Design

Randomized complete block design was used with 2 or 3 replicates/block.

Animals

Porcine alveolar macrophages were obtained by lavage of excised lungs from Yorkshire-type pigs (mean ± SEM, 21 ± 2 kg).

Procedure

Phospholipase C activation was assessed, using anion exchange chromatography to measure accumulation of inositol phosphates in [3H)myo-inositol-labeled alveolar macrophages. Macrophages were incubated with saline solution, pertussis toxin (4.75 nM), or B-oligomer (4.75 nM) for 2 hours. Cells then were washed and incubated for 5 minutes with PAF (0, 0.1, 1.0, or 10 μM; n = 15). Results were expressed as total inositol phosphates (inositol monophosphate, bisphosphate, trisphosphate, and tetrakisphosphate).

Results

Concentrations of total inositol phosphates were significantly (P < 0.05) increased to 162 ± 7, 172 ± 4, and 194 ± 9% of control in response to 0.1, 1.0, and 10 μM PAF, respectively. Pertussis toxin attenuated the PAF-induced increase in total inositol phosphates by approximately 50% (P < 0.05). The B-oligomer of pertussis toxin failed to modify PAF-induced increases in total inositol phosphates. The specific PAF receptor antagonist WEB 2086 markedly attenuated PAF-induced (10 μM) increase in inositol phosphates.

Conclusions

We conclude that PAF stimulates accumulation of inositol phosphates through a specific receptor and that a pertussis toxin-sensitive G protein is involved in the signal transduction process leading to activation of phospholipase C in porcine alveolar macrophages. (Am J Vet Res 1996;57:574-579)

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in American Journal of Veterinary Research

SUMMARY

The role of platelet-activating factor in mediating the cardiovascular and peripheral cellular responses to large-colon ischemia and reperfusion, was explored in anesthetized ponies. A specific platelet-activating factor (PAF) antagonist (WEB 2086) was administered to a group of 6 ponies, and another 6 ponies (controls) were given an equivalent volume of saline solution, prior to 1 hour of large-colon torsion. After correction of the torsion, ponies were monitored during the reperfusion period. Significant (P < 0.05) hypotension and metabolic acidosis developed in all ponies after correction of colonic torsion, cardiac index increased initially, but then decreased significantly (P < 0.05) over the study period. Mean times between correction of torsion and onset of cardiac failure and death were not different between groups. Significant (P < 0.05) thrombocytopenia developed during the reperfusion period in control ponies, but not in WEB-treated ponies. Blood leukocyte concentration in control ponies was more variable and significantly (P < 0.05) decreased immediately upon reperfusion, compared with that in WEB-treated ponies. We conclude that although the cardiovascular responses to colonic ischemia and reperfusion are not prevented by use of a specific paf-antagonist, specific peripheral cellular responses are mediated by paf.

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in American Journal of Veterinary Research

Summary

Labor and delivery stimulate increased release of catecholamines and endogenous opioid peptides in neonates. Catecholamines promote adaptation to the extrauterine environment after birth. Enkephalins are stored together with catecholamines in the adrenal medulla and have an inhibitory effect on catecholamine release. We investigated the influence of labor and neonatal hypoxia on epinephrine, norepinephrine, and met-enkephalin release in calves. Blood samples were taken from the umbilical artery before rupture of the umbilical cord and from the jugular vein repeatedly after birth. Highest plasma norepinephrine concentration was found in calves delivered at the end of gestation (term calves) before umbilical cord rupture. In calves delivered before the physiologic end of gestation (preterm calves), norepinephrine values increased after cord rupture, but remained lower than values in term calves. Epinephrine release followed a similar pattern, but norepinephrine was clearly predominant. In term calves, met-enkephalin values were significantly higher than values in preterm calves. In calves of both groups, met-enkephalin release increased after cord rupture. During birth, the increase in catecholamine release seems to take place earlier than that of enkephalins. Norepinephrine-dominated stimulation during expulsion of the calf might be followed by increasing enkephalinergic inhibition after cord rupture and onset of respiration. Reduced release of catecholamines and enkephalins in preterm calves may be connected with delayed adaptation to the extrauterine environment.

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in American Journal of Veterinary Research

This approach is also widely advocated for disorders of myocardial failure (eg, dilated cardiomyopathy). 2–8 Administration of the loop diuretic furosemide can result in activation of the RAAS in dogs, which calls into question its use as a lone

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in American Journal of Veterinary Research

provide at least some of the hemostatic properties. 16 In vitro studies have revealed that various saponins are capable of inducing a strong activation response in human platelets. 17,18 Moreover, preliminary clinical trials of humans have indicated some

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in American Journal of Veterinary Research

vessels. The 2 principal determinants of vascular smooth muscle tone are the [Ca 2+ ] i and the sensitivity of the contractile apparatus to [Ca 2+ ] i . Increases in [Ca 2+ ] i elicit contraction primarily via activation of calcium

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in American Journal of Veterinary Research