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Biomedical subjects

J C Vincent

Publications and source records attributed to J C Vincent.

10 recordsLinked to original sources
PubMed1992

An enzymatic determination of hydrogen peroxide by using spectrophotometry.

A new spectrophotometric method for determining low hydrogen peroxide concentrations by using horseradish peroxidase in the presence of NADH at pH 7.5 has been described. Both total NADH consumption and initial reaction rate may be used for the determination. Using the NADH consumption, a linear response with respect to hydrogen peroxide was observed in the concentration range 7 x 10(-8)-2.5 x 10(-6) M. Due to the presence of superoxide dismutase, hydrogen peroxide is partly regenerated and an amplification of the signal results, which explains the sensitivity.

Horseradish Peroxidase↗
PubMed1992

Gram-scale enzymatic synthesis of a peptide bond.

The synthesis reaction of the peptide, N-Cbz-L-tryptophanyl-glycineamide, catalyzed by alpha-chymotrypsin was performed in a 20% water/80%, 1,4-butanediol mixture. The synthesis yield reached 90.9% at the end of the reaction and 72.3% after purification. The effects on the yield of both pH and the ratio between total initial concentrations of glycineamide and N-Cbz-L-tryptophan are examined. The high yield, specificity, simplicity and reproducibility of this method make it complementary of the chemical methods.

Catalysis↗
PubMed1991

Euthanasia.

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Attitude of Health Personnel↗
PubMed1991

Stiripentol.

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Animals↗
PubMed1988

Angiotensin-converting enzyme inhibition, anti-hypertensive activity and hemodynamic profile of trandolapril (RU 44570).

Trandolapril (RU 44570), a new non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor chemically related to enalapril, and its diacid (RU 44403), were investigated for their ability to inhibit angiotensin-converting enzyme. Trandolapril attenuated angiotensin I (Ang I)-induced pressor responses following i.v. administration to rats and dogs with ID50 values of 13.1 +/- 1.3 and 21.1 +/- 2.3 micrograms/kg. RU 44403 produced corresponding values of 9.9 +/- 0.7 and 7.2 +/- 2.3 micrograms/kg. Trandolapril (3-300 micrograms/kg) produced a dose-related attenuation of Ang I-induced pressor responses (ID50 30 micrograms/kg) following oral administration to rats. Oral administration of trandolapril (30-1000 micrograms/kg) to dogs inhibited Ang I pressor responses for over 6 h. The depressor action of bradykinin in the rat was potentiated by i.v. trandolapril and RU 44403 with ED50 values of 5.5 +/- 0.8 and 4.9 +/- 0.3 micrograms/kg respectively. Trandolapril was 2.3-10-fold more potent than enalapril in all experiments, depending on species or route of administration. RU 44403 and MK 422 were approximately equipotent, implying that trandolapril was more readily hydrolysed than enalapril. Trandolapril (0.3-30 mg/kg) produced dose-related, long-lasting (greater than 24 h) reductions in blood pressure (BP) in spontaneously hypertensive rats (SHR) following oral administration. The anti-hypertensive effect was potentiated significantly in hydrochlorothiazide-pretreated SHR when the plasma renin activity was increased. Enalapril was 10-fold less potent than trandolapril in reducing BP. The anti-hypertensive action of trandolapril (3 mg/kg) was abolished in SHR that were bilaterally nephrectomized 24 h beforehand, but was maintained in SHR pretreated by indomethacin (5 mg/kg p.o.). Trandolapril (1 mg/kg i.v.) produced a modest and transient reduction in BP in anesthetized dogs. Trandolapril produced dose-related (30-1000 micrograms/kg) reductions in BP, total peripheral resistance and heart work in dogs pretreated with hydrochlorothiazide to increase plasma renin activity.

Angiotensin I↗
PubMed1988

How a soluble enzyme can be forced to work as a transport system: description of an experimental design.

The cellular transport systems which have been studied up to now have been found to be based on the functioning of specialized proteins anchored asymmetrically in cell membranes. In the present paper we show that a single soluble enzyme inserted at random in a gel slab can drive an uphill transport, provided that asymmetrical boundary conditions force the reversible reaction catalyzed by this enzyme to work forward on one face of the gel slab and backward on the other face. Experimentally, we have used a yeast alcohol dehydrogenase to induce an uphill transport of NADH. It cannot be excluded that comparable structurally symmetrical transport systems also exist in living cells. Such systems would be particularly well suited to preserving cell homeostasis with regard to small solutes.

Alcohol Dehydrogenase↗
PubMed1987

Immobilized cycling enzyme active transport systems. pH feedback control.

Active transport can be induced by applying a pH gradient across a membrane containing a homogeneous mixture of two cycling enzymes. When the two reactions are inversely 'pH active', one producing protons and the other consuming them, a pH feedback control of the functional structure occurs and the active transport function of the membrane can be either stabilized or inhibited according to whether the endogenic pH modifications tend to enhance or reduce the exergonic pH gradient. When it is stabilized, the system looks like a thin active layer surrounded by two diffusive layers, leading to a fairly good model for biological transport systems. Under particular conditions, signals can be emitted.

Biological Transport, Active↗
PubMed1985

Gastric cytoprotective, antisecretory and antiulcer activities of (E)-4-oxo-4-(3,4,5-trimethoxyphenyl)-2-butenoic acid (RU 38086).

As a result of trials of a large series of compounds, RU 38086 (E)-4-oxo-4-(3,4,5-trimethoxyphenyl)-2-butenoic acid) was selected because of its cytoprotective, antisecretory and antiulcer properties. In pylorus-ligated rats, RU 38086 dose-dependently decreased the total acid output, at 2.5, 5 and 10 mg/kg orally and at 10 and 50 mg/kg intraduodenally. In the perfused rat stomach, 1.2 mg/kg RU 38086 in situ inhibited acid secretion stimulated by histamine or pentagastrin but was inactive against carbachol. In the same test 5 mg/kg intravenously did not antagonize pentagastrin-induced acid secretion. In the cat Heidenhain pouch, 0.6 mg/kg RU 38086 was also antisecretory, reducing the acid concentration when in contact with the mucosa of the pouch. In ulcers induced in rats by ligature of the pylorus plus acetylsalicylic acid, RU 38086 at 2.5 and 5 mg/kg demonstrated much more striking activity after oral than after intraduodenal administration. It also had antiulcer activity against stress ulcers (restraint plus cold), starting at a dose of 5 mg/kg orally. RU 38086 had marked gastric cytoprotective activity in rats against the necrotizing effects of ethanol from the low dose of 0.3 mg/kg orally. This cytoprotective activity was not significantly affected by indomethacin pre-treatment. At 4 and 20 mg/kg orally, RU 38086 strongly increased prostaglandin E2 levels in gastric juice of pylorus-ligated rats and in stomach tissue of normal rats. These data indicate that RU 38086 is an orally effective cytoprotective, antisecretory and antiulcer agent.

Animals↗
PubMed1977

[Regulation and electric excitation of enzyme membranes in vitro].

Enzyme membranes can be activated or inhibited by applying continuous or alternating electrical fields. The field can modify the transport or reaction term of the transport-reaction by action on the displacement of charged species including those giving pH effects or inducing volume flows. A first experimental example is given: the progressive supression of the inhibition of hexokinase by the product when increasing alternating fields are applied. In the same way the apparent optimal pH approaches that of the soluble enzyme. In addition to its theoretical and practical implications electrical regulation can lead to the monitoring of enzyme reaction-driven mechanochemical fibers.

Electric Stimulation↗