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Biomedical subjects

A Crevat

Publications and source records attributed to A Crevat.

At least 73 records · Page 4Linked to original sources
PubMed1985

Identification by nuclear magnetic resonance and mass spectrometry of a glucuronic acid conjugate of o-hydroxybenzoic acid in normal urine and uremic plasma.

An endogenous compound (included in the fraction of uremic toxins often called the "uremic middle molecules") was separated from plasma of uremic patients and urine from normal persons. As elucidated by mass spectrometry, enzymatic hydrolysis, and 1H, 13C nuclear magnetic resonance, it appears to be a conjugate of o-hydroxybenzoic acid with glucuronic acid. Its presence in urine of healthy subjects indicates its physiological character.

Adult↗
PubMed1985

Sequential sodium therapy allows correction of sodium-volume balance and reduces morbidity.

We investigated whether individually adjusting Na+ dialysis levels (Na+Di) combined with Na+ and UFR (ultrafiltration rate) programming, and a sodium/volume model (sequential sodium therapy, SST) can improve the end stage renal failure (ESRD) patient's homeostatic equilibrium intra- and interdialytically. One hundred and fifty patients were included in the study over a one year period. The results show that the patients are divided into two groups: 50 patients respond according to the sodium/volume model developed by F. Gotch [1983]. In this group it is possible to predict pre- and post dialysis plasma Na+ concentration (Na+o, Na+t) as a function of Na+Di and it becomes possible to choose Na+Di to allow Na+o and Na+t to virtually coincide, eliminating severe shifts in plasma tonicity. In the second group two subgroups can be distinguished: excess Na+ or excess H2O post dialysis, without possible correction at a single sodium level. SST corrects sodium/volume balance in this group by using sequential intermittent hypo or hypertonic dialysate, combined with fluid removal adapted to each episode. In both groups there was a significant improvement in the clinical condition of the patients who previously were less equilibrated. It is possible to conclude that SST improves tolerance intradialytically and achieves better equilibrium interdialytically. Implementation of SST requires precise control of the concentrate and the water, and equipment adapted for accurate, programmable sequential control of Na+Di and ultrafiltration rate.

Adolescent↗
PubMed1984

The in vitro effect of some nitroimidazoles on microtubule formation.

The in vitro effects of some nitroimidazoles (metronidazole, ornidazole) and their metabolites on microtubule formation have been tested. Cyclic metabolites are without effect. Metabolites proceeding from cleavage of the imidazole ring inhibit microtubule formation and reduce the polymerization rate of tubulin. This inhibitory effect might be correlated to some of the side-effects of these drugs. Isaxonine phosphate corrects this effect.

Animals↗
PubMed1983

Partial purification of a calcium ionophore from human uremic plasma and normal urine.

A fraction is isolated from human uremic plasma and normal urine using a three step chromatographic separation :gel permeation on Sephadex G15, then chromatography on hydroxyapatite and finally desalting operation on Sephadex G15. The fraction thus separated is ninhydrine positive and uncouples mitochondria principally releasing the resting respiration. Calcium potentiates the uncoupling, while red ruthenium and magnesium inhibit it. These results are in good agreement with a ionophorous activity of the isolated fraction. An hypothetic physiological role of this compound is there being discussed.

Animals↗
PubMed1983

Inhibition in vitro of the polymerization of tubulin by uremic middle molecules: corrective effect of isaxonine.

The polymerization of tubulin leads to the formation of microtubules which are one of the components of the axons of nerve cells. This reaction is the limiting factor in the growth of axons. Uremic middle molecules inhibit in vitro the polymerization of tubulin in a dose dependent way. It is possible that a similar phenomenon could occur in vivo in uremic patients, and this might be involved in the development of neuropathy. In addition, isaxonine phosphate counteracts the inhibitory effect of uremic middle molecules on the polymerization of tubulin.

Adult↗
PubMed1982

Microcalorimetric study of magnesium-adenosine triphosphate ternary complex.

Using an original microcalorimetric method, the existence of the Mg2ATP ternary chelate has been studied. The thermodynamic parameters of this complex are delta H = 7.2 +/- 0.5 kJ mole-1 and K = 49 +/- 9 M-1. These values are compared with those previously obtained for binary chelate Mg ATP2-. A possible regulation role of Mg2ATP is discussed.

Adenosine Triphosphate↗
PubMed1982

A study of the cardiotoxicity of uremic middle molecules on embryonic chick hearts.

Ultrafiltrates from uremic patients can induce, in vitro, strong modifications of beating frequency of auricular fragments of the embryonic chick heart. According to concentration, effects increase from tachycardia to cessation of cardiac beats. Complete reversion is always observed after washing with normal medium. Only fraction 7c of middle molecules exhibits this cardiotoxicity, other fractions are without effect, even in high concentration. Uremic middle molecules strongly modify cardiac beats in vitro.

Animals↗
PubMed1981

Some aspects of middle molecules toxicity.

Middle molecules can act on several levels of uremic disease. So, this work is a multidisciplinary one with the participation of nephrologists, hematologists and also pharmacologists, chemists and biophysicians. We present here our results on four different toxic effects found with middle molecules: the energy dependant phenomena, the platelet aggregability, the cardiotoxic, and the neurotoxic effects. Middle molecules were isolated from urine of normal subjects and blood of patients with chronic renal insufficiency and treated by hemodialysis. Separation was done according to Furst's procedure.

Animals↗
PubMed1980

"In vitro" inhibition of platelet aggregation by uremic middle molecules.

"Uremic middle molecules" are isolated from the urine of normal subjects and the blood in chronic renal insufficiency treated by hemodialysis. Their action is tested in vitro on platelets aggregation induced by ADP. Some fractions of these middle molecules (fractions 7b, 7c and 7 "fg") are without any effect. The 7 "de" fractions give an inhibition of platelets aggregation. The percentage variations of first phase inhibition as a function of the middle molecules concentrations is studied.

Adenosine Diphosphate↗
PubMed1979

Action of middle molecules from chronic renal insufficiency treated by hemodialysis on mitochondrial respiration.

"Middle molecules" are isolated both from the urine of normal subjects and from the blood of patients suffering from chronic renal insufficiency treated by hemodialysis. Their action is tested on mitochondrial respiratory activity. Some of these molecular species (fraction 7 f and 7 g) are without any effect. On the other hand the 7 c middle molecules fraction gives a loss of respiratory control due to a decrease of respiratory activity in state 3. A diminution of the P/O ratio is noted and so the available ATP pool is decreased. This action can be compared to the fact that 7 c plasmatic fraction concentration seems to be connected with the patients clinical condition.

Humans↗
PubMed1979

[Interaction of thiamine diphosphate with magnesium ion].

The action of magnesium ion on the exchange rate of the proton in C2 of thiamine and thiamine diphosphate is studied at different values of pD. Above pD 5 the ion Mg2+ increases this exchange rate. The phenomenon is markedly enhanced for TDP rather than thiamine and increases with pD. Below pD 5 magnesium decreases the exchange rate. This decrease is greater for TDP than for thiamine. The maximum effect is reached at a magnesium concentration of 0.5/1 for thiamine and of 1/1 for TDP. T1 measurements are made for different pH values with and without magnesium ion. Results seem to prove that an increase in pD values from 3.9 to 5.9 leads to an accentuation of the molecules "folded" form. Nevertheless for a given pD value the TDP-Mg complex seems to have a more "folded" form than TDP.

Chemical Phenomena↗