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At least 721 records · Page 40Linked to original sources
PubMed1987

Attenuation of endotoxin-induced increase in glucose metabolism by platelet-activating factor antagonist.

Platelet-activating factor (PAF) has recently been proposed as a putative mediator of various pathophysiologic events during endotoxemia. The aim of the present study was to determine the relative importance of PAF in producing the alterations in carbohydrate metabolism following endotoxin. Chronically catheterized conscious rats were treated with SRI 63-441, a specific PAF receptor antagonist, or saline prior to Escherichia coli endotoxin (100 micrograms/100 g body weight, LD10) administration. Hemodynamic and whole-body glucose kinetic changes, the latter assessed by a constant intravenous infusion of [6-3H] glucose, were determined throughout the 4-hr experimental protocol. Endotoxin induced a transient 30-35% reduction in mean arterial blood pressure (MABP) in animals treated with saline. The PAF-antagonist attenuated this hypotensive effect, and MABP was only reduced by 14-18%. Endotoxin increased plasma glucose and lactate levels, as well as the rate of glucose appearance (Ra) in saline-treated rats. The PAF antagonist reduced the hyperglycemia by 60-75% and tended to prevent the hyperlactacidemia. The endotoxin-induced elevation in glucose Ra was also attenuated by 55%. A similar degree of hyperglucagonemia was observed following endotoxin in both groups, and plasma insulin concentrations were not different. However, plasma catecholamine levels were significantly lower (30-70%) in endotoxemic rats treated with the PAF antagonist. These results suggest that the enhanced production of PAF following endotoxin may be responsible, at least in part, for the early hemodynamic changes. The role of PAF as a mediator of endotoxin-induced glucose dyshomeostasis, however, may be secondary to its hemodynamic effects.

Animals↗
PubMed1987

The sensitivity to trypanocidal drugs of Trypanosoma vivax isolated in Kenya and Somalia.

The drug sensitivity of seven Trypanosoma vivax-isolates from Kenya and Somalia was examined. With the exception of diminazene aceturate all commercially available trypanocidal drugs failed to effect a cure. The results suggest the existence of multiple drug resistance of T. vivax-strains, geographically widely distributed along the East African Coast. The isolates were resistant to the recommended dose rates of isometamidium, homidium and quinapyramine. Isometamidium showed no prophylactic properties when tested against one of the isolates. All were sensitive to diminazene aceturate.

Animals↗
PubMed1987

Evaluation of the effect of a platelet activating factor antagonist on platelet activating factor and Ascaris antigen-induced airway responses in rhesus monkeys.

An acute airway response to aerosolized platelet activating factor (PAF) can be induced in certain rhesus monkeys. This PAF airway response is completely inhibited by the PAF antagonist, SRI 63-441, in normal monkeys. After the completion of these studies showing inhibition of the PAF airway response, we evaluated whether the PAF antagonist could inhibit three types of acute IgE-mediated airway responses to Ascaris suum (A) in rhesus monkeys. The A aerosol test protocols used the following: a single A aerosol challenge system; a threshold dose of A challenge system, which consists of increasing A aerosol exposure until an airway response occurs; and two sequential A challenges in which the response to the second A challenge always occurs if there is a response to the first A challenge. When SRI 63-441 was tested as a potential antagonist of the A airway response in any of these three systems, no inhibition was shown.

Aerosols↗
PubMed1986

Inhibition of PAF-induced systemic responses in the rat, guinea pig, dog and primate by the receptor antagonist SRI 63-441.

Systemic administration of synthetic PAF produces a number of dose-dependent circulatory effects in a variety of species. We have evaluated a novel PAF antagonist, SRI 63-441, for its ability to inhibit PAF-induced effects in the rat, guinea pig, dog and primate. In the rat, a 100 ng kg-1 i.v. PAF challenge produced a (mean +/- 1 S.D.) 39 +/- 5% decrease in carotid blood pressure. Prior injection of SRI 63-441 inhibited this hypotensive response in a dose-dependent manner, with an ED50 of 0.15 mg kg-1 i.v. In the guinea pig, PAF at 100 ng kg-1 elicited a 50 +/- 8% increase in hematocrit and a 50 +/- 11% elevation in bronchial resistance. The ED50 values for inhibition by SRI 63-441 of these two physiological parameters were 0.012 mg kg-1 and 0.035 mg kg-1 i.a., respectively. Dogs challenged with 1.5 micrograms kg-1 PAF i.v. exhibited 28.7 +/- 6.5% increase in hematocrit 10 min after injection. The ED50 value for SRI 63-441 inhibition of hemoconcentration in the dog was 0.18 mg kg-1 i.v. In the primate model of PAF-induced hemoconcentration, controls responded to 3.5 micrograms kg-1 i.v. PAF with a 30 +/- 6% increase in hematocrit. Using the primates in a cross-over design, the ED50 of SRI 63-441 was 0.11 mg kg-1 i.v. At this ED50 value, the ratio of nmol kg-1 PAF used versus nmol kg-1 antagonist is approximately 1:25. The effectiveness of SRI 63-441 in these models suggest potential clinical applications in disease states involving hyperpermeability and pulmonary dysfunction.

Animals↗
PubMed1985

An assay for screening drugs against animal-infective bloodstream forms of Trypanosoma brucei brucei in vitro.

A rapid and simple assay for in vitro drug screening has been established using the mammalian feeder layer cell system for continuous cultivation of infective bloodstream forms of Trypanosoma brucei brucei. A total of 21 trypanocides have been tested. Differences in sensitivity to standard trypanocides were detected among drug-susceptible isolates and strains of T. b. brucei. This assay may thus be of potential use for rapid detection of new drug-resistant isolates of T. b. brucei.

Animals↗
PubMed1985

Quinuronium levels in ovine plasma as determined by an in vitro/in vivo system with Babesia rodhaini.

Quinuronium was shown to have a babesicidal activity in vitro. In vitro/in vivo system with Babesia rodhaini gave an in vitro EC50 for 13.5 ng/ml. Quinuronium levels in ovine plasma increased to a maximum mean of approximately 27 ng/ml at 2 hours with a gradual decay from 8 hours up to almost no detectable levels at 48 hours following administration of therapeutic dose (1 mg/kg s.c.). This study supports previous reports of the use of Babesia rodhaini as an organism in screening antibabesials. The in vitro/in vivo model can be used to monitor quinuronium levels in ovine plasma. Second treatment with quinuronium may be administered after 24 to 48 hours whenever clinically indicated.

Animals↗
PubMed1985

Comparative studies of the effects of quinuronium sulfate and diminazene diaceturate in sheep.

Biochemical parameters in 20 sheep were investigated following administration of quinuronium sulfate or diminazene diaceturate. The usual signs of salivation, micturition, anorexia, depression, muscular tremors and ataxia were observed within 20 min in sheep receiving therapeutic and double doses of quinuronium sulfate. There was an increased dose dependent plasma LDH activity above baseline values following administration of quinuronium sulfate and a non-dose dependent increased trend in diminazene diaceturate treatment. Plasma CK activity had an increased trend (p less than 0.05) above baseline values following administration of the two babesicides. Plasma BUN levels increased significantly (p less than 0.05) following administration of the two drugs. This study indicated that quinuronium sulfate is more organotoxic and hypotensive than diminazene diaceturate at therapeutic and/or above therapeutic dosages.

Amidines↗