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Biomedical subjects

D Brault

Publications and source records attributed to D Brault.

At least 55 records · Page 3Linked to original sources
PubMed1991

Intravenous immunoglobulin therapy for prevention of infection in high-risk premature infants: report of a multicenter, double-blind study.

The effectiveness of intravenously administered immunoglobulin (Ig) therapy for prophylaxis of infection was evaluated in high-risk preterm infants. Two hundred thirty-five premature newborns were randomly assigned, in a double-blind controlled trial, to treatment and placebo groups. Thirty-five infants (29%) of the Ig group and 29 (25%) of the placebo group had one or more episodes of certain infection. Thirty infants (25%) of the Ig group and 18 (16%) of the placebo group had one or more episodes of probable infection. No significant differences were observed in the incidence of certain or probable infection in treated and control infants. Nevertheless, among the infants who had one or more certain or probable episodes of infection, more of them belonged to the Ig group than to the placebo group. The possible deleterious effect of the administration of large amounts of polyspecific Ig is discussed.

Cross Infection↗
PubMed1991

[Update of a selected technique for uric acid determination in plasma and serum. Experimental study and value of derivative spectrophotometry].

A critical study of the candidate reference method for evaluation of uric acid in plasma proposed by the American Association of Clinical Chemistry is followed by testing in six laboratories. The dispersion of results is wide (CV greater than 5%). The importance of turbidity remaining after the deproteinization by trichloracetic acid is clearly demonstrated. This turbidity is really not reproducible from an operation to another one on the same serum. It is very likely responsible of the great dispersion of the results. After that, other deproteinization methods are tried. Ultrafiltration and ultracentrifugation give both defect errors because uric acid is in part bound to proteins. So it is necessary to find another technic which cancels the effects of turbidity on the absorbance readings in the ultra-violet domain. Experimental studies showed that uric acid may be evaluated with a good accuracy by derivative spectrophotometry, in lipid solutions as well as in cloudy ones. Turbidity was created by intralipid suspension additions. Various parameters hitting the method were examined (linearity, smoothing window...), taking as criterion the measure of overloaded serums at different levels. At last, the method is successfully transferred in several sites. In the case of blood serum, the respective influences of derivation and of repetition of final centrifugations are studied in order to estimate the effect of remaining turbidity. By the use of derivative spectrophotometry the improvement of the method of evaluation of uric acid proposed by A.A.C.C. is very noticeable; it reduces the variation coefficient between sites to less than 2%.

Animals↗
PubMed1990

Physical chemistry of porphyrins and their interactions with membranes: the importance of pH.

The physicochemical properties of dicarboxylic porphyrins are examined with particular emphasis on acid-base equilibria. Interactions with membranes appear to be dominated by the charge of the propionic acid chains and the hydrophobic character of other peripheral substituents. A physicochemical basis for the effect of pH on the incorporation of porphyrins within membranes is given. The effect of lowered tumour pH on the incorporation of porphyrins within membranes and on porphyrin retention is discussed.

Liposomes↗
PubMed1990

Uptake and photodynamic efficiency of hematoporphyrin, hydroxyethylvinyldeuteroporphyrin and hematoporphyrin derivative (Photofrin II): a study with isolated mitochondria.

The uptake of Photofrin II (PFII), hematoporphyrin (Hp) and hydroxyethylvinyldeuteroporphyrin (HVD) by isolated mitochondria was studied using the high performance liquid chromatography (HPLC) technique. The various PFII components show a high affinity for mitochondria. At 5.75 micrograms/ml PFII, their ratio of incorporation was found to be very similar, except for Hp which is about two times less incorporated. These results were reproduced with pure Hp and pure HVD. The uptake of Hp and HVD increases with concentration but, while that of Hp reaches a plateau, the uptake of HVD continues to increase. At a high porphyrin concentration (approximately 10(-5) M), the loss of respiratory control is obtained with the same light dose for Hp and PFII. Taking into account the uptake and the known photophysical parameters of the various porphyrins, the photodynamic efficiency of HVD seems equivalent to that of Hp. The present results and known data on cell photoinactivation suggest that the activity of these porphyrins is mainly dependent on their incorporation.

Animals↗
PubMed1990

["Cis" and "trans" regulator elements of transcription].

The 5'-flanking region of genes is involved in transcription regulaton. Multiple nucleotidic cis-acting sites are spread out over a region of 400 bp, (mostly) upstream of the start point. Examples are given with TATA box, GC box, CCAAT box and some octamers. Transcription factors recognize cis-acting sites and bind to them. Some are required for transcription initiation. Others affect (usually enhance) the rate of initiation. Trans-regulator proteins contain two domains. One is responsible for binding to DNA (as for instance: Zn fingers, Leu zipper, positive homeotic domain). The other one is responsible for activity on transcription (as for instance: rich in Gln, rich in Pro, acidic alpha-helix domain). Some technics used for determination of the site of transcription initiation and of protein fixation on DNA are briefly described. It is hoped that a better comprehension of transcription mechanisms will offer new possibilities of investigation for acting in some varieties of protein synthesis dysfunctionnements.

Genes, Regulator↗
PubMed1989

Singlet molecular oxygen quenching by saturated and unsaturated fatty-acids and by cholesterol.

The rate constants of molecular singlet oxygen quenching by saturated and unsaturated fatty-acids and by cholesterol-membrane critical components - membrane critical components - have been measured by time resolved detection of the 1270 nm phosphorescence of singlet molecular oxygen [O2(1deltag)]. We have determined (i) an increment of 5.7 x 10(2)M(-1)s(-1) per -CH2- in C6D6 and CD3OD for saturated fatty acids between C4 and C20, (ii) an increment of 3 x 10(4)M(-1)s(-1) per non-conjugated cis-double bond for C18 unsaturated fatty acids, identical in C6D6 and DC3OD, (iii) a lower quenching rate constant by a factor of 2.7 for the trans-C16 and trans-C18 as compared to the corresponding cis-monounsaturated fatty acids, (iv) a rate constant of O2x(1deltag) quenching by cholesterol of 5.7 x 10(4)M(-1)s(-1) in benzene. These rate constants are compared to those obtained for other membrane cellular components.

Cholesterol↗
PubMed1989

Photofrin II uptake by atheroma in atherosclerotic rabbits. Fluorescence and high performance liquid chromatographic analysis on post-mortem aorta.

Atherosclerotic lesions were induced in normal and Watanabe rabbits by atherogenic diet and stripping of aorta endothelium. The rabbits were injected with Photofrin II and sacrificed two days later. Atheromatous aorta as well as normal aorta from control animals were characterized by their fluorescence spectra using front face excitation. Characteristic emission peaks at 631 and 694 nm were displayed at atheromatous plaques. The excitation spectrum shows a strong band at 394 nm and weaker bands at 446, 504, 536 and 574 nm. Although no fluorescence of normal aorta can be seen by visual inspection, emission with a maximum at 626 nm was detected by spectrofluorimetry. Normal phase high performance liquid chromatography analysis of extracts from atheroma and control aorta were also carried out. The specific labelling of atheroma involves mainly protoporphyrin, hematoporphyrin and also minor components of Photofrin II which are accumulated. Some other components are accumulated but do not appear to be specifically retained by atheroma.

Animals↗
PubMed1989

[Spontaneous perforation of the bile ducts].

Spontaneous perforation of the extra-hepatic bile ducts in infancy is rare and of unknown etiology. Its finding at laparotomy in a 2 month-old premature with artificial ventilation allows to underline that the diagnosis may be difficult and may necessitate ultrasonography and even hepatobiliary scintigraphy.

Bile Duct Diseases↗
PubMed1989

[A recommended method for determination of uric acid in serum].

SFBC work group on uric acid propose a method for evaluation in blood serum which is modeled on the one defined by American Association for Clinical Chemistry. Serum is deproteinized by trichoracetic acid and the supernatant, buffered to pH 8.5, is submitted to uricase action. The disappearing of the strong band of uric acid in UV is measured by derivative spectrophotometry; this procedure vanished the effect of trouble which remains in the supernatant. This spectrophotometric technic permit to reach, in multiple sites, a variation coefficient near of 1 p. cent.

Analysis of Variance↗
PubMed1987

Normal-phase high-performance liquid chromatography of free acid dicarboxylic porphyrins and hematoporphyrin derivative on silica.

The isocratic separation of dicarboxylic porphyrins (hematoporphyrin, hydroxyethylvinyl-deuteroporphyrin and protoporphyrin) and their isomers by normal-phase high-performance liquid chromatography is described. The stationary phase is unmodified silica and the mobile phase consists of acetone-ethyl acetate (1:1, v/v) mixtures containing water and inorganic acids. Retention (capacity factor, k') was found to decrease exponentially with the mole fraction of water (NH2O) and to increase linearly with the concentration of hydrochloric acid, following the relation k' = A [HCl] NH2O-4.85, where A is a constant characteristic of the porphyrin. The effects of the concentration and the nature of the acid used strongly suggest that retention involves a form of the porphyrin in which the inner nitrogens are protonated. The retention is thus partly determined by the basicity of the inner nitrogens, which depends on the electron-donating power of the porphyrin side-chains. Good resolution of the various components of hematoporphyrin derivative was obtained. In comparison with reversed-phase chromatography this method shows a different retention mechanism, appears to yield results of comparable reproducibility and provides complementary information. Possible retention mechanisms based on partition or adsorption equilibria are discussed.

Chromatography, High Pressure Liquid↗
PubMed1987

Rate constants for one-electron oxidation by the CF3O2., CCl3O2., and CBr3O2. radicals in aqueous solutions.

The peroxyl radicals CF3O2., CCl3O2. and CBr3O2. were produced by radiolysis of aerated aqueous-alcohol solutions of CF3Br, CF3Cl, CCl4 or CBr4. Kinetic spectrophotometric pulse radiolysis experiments were carried out in the presence of various substrates: urate, ascorbate, xanthine, hydroquinone, p-methoxyphenol, phenol and chlorpromazine. Absolute rate constants for one-electron oxidation of these substrates by the alkylperoxyl radicals were found to vary from less than 10(5) to greater than 10(9) M-1 s-1, depending to some extent on the redox potential of the substrate. For all substrates the order of reactivity was CF3O2. greater than CBr3O2. greater than CCl3O2. . Because of its high reactivity, CF3O2., may have deleterious effects on biological systems. Its likely environmental precursor, CF3Br, which is used as a fire extinguisher and a refrigerant, was found to be reduced by a ferrous porphyrin model for cytochrome P-450 only very slowly and thus is not expected to have a major toxic effect if inhaled.

Free Radicals↗
PubMed1986

Spectrofluorimetric study of porphyrin incorporation into membrane models--evidence for pH effects.

The effects of hydrophobicity and charges of dicarboxylic porphyrins upon their interactions with membrane model systems are investigated. Four protonation steps are evidenced from fluorescence emission studies of hematoporphyrin IX and its more hydrophobic parent compound lacking of alcoholic chain, deuteroporphyrin IX. They are attributed to the successive protonations of the inner nitrogens of the porphyrin cycle (pK = 4.7 and 2.9 for hematoporphyrin and 4.4 and 2.7 for deuteroporphyrin) and successive deprotonations of propionic groups (pK approximately equal to 5.0 and 5.5 for hematoporphyrin and 5.4 and 6.0 for deuteroporphyrin). These porphyrins, as well as their dimethyl ester forms, are shown to incorporate as monomers into the hydrophobic bilayer of egg phosphatidylcholine small unilamellar vesicles, although the esterified forms are highly aggregated in aqueous solutions. In the case of the non-esterified forms, the incorporation of the porphyrins into the lipidic bilayer is reversible and strongly pH-dependent. A theoretical model is presented which takes into account the various protonation steps and the partition equilibria of the porphyrin between the vesicle lipidic phase and the water medium. The neutral form of the porphyrin (i.e., carboxylic groups protonated) presents the higher affinity, with constants of K approximately equal to 2 X 10(5) and K approximately equal to 6 X 10(6) M-1 (relative to lipid concentration) for hematoporphyrin and deuteroporphyrin, respectively. Protonation of one inner nitrogen leading to the monocationic form is sufficient to prevent incorporation into the hydrophobic bilayer. On the other hand, deprotonation of the peripheral propionic chains leading to anionic forms is less effective. These interactions between vesicles and porphyrins lead to shifts of the apparent pK of nitrogens and carboxylic groups, the latter one being now in the range of physiological pH. These results are discussed with regards to the hypothesis of a possible role of pH in the preferential uptake of porphyrins by tumors.

Hydrogen-Ion Concentration↗
PubMed1986

Fundamental aspects in tumor photochemotherapy: interactions of porphyrins with membrane model systems and cells.

Some molecular aspects underlying photochemotherapy and photodiagnosis of tumors with porphyrins are reviewed. The nature of the clinically used photosensitizer HpD is first presented along with structures of molecules found to be efficient in vitro. The possible role of pH in the preferential retention of dicarboxylic porphyrins by tumors is discussed in light of results obtained with membrane models. The uptake of dicarboxylic porphyrins by cells most likely involves passive mechanisms. Cell photoinactivation using a purified porphyrin does not depend upon the incubation time but only on the intracellular concentration of the dye. This likely reflects a poor specificity of the photoinactivation processes with regard to the cellular localization of the dye. The properties which should be presented by more efficient photosensitizers are discussed.

Blood Proteins↗
PubMed1985

Model studies in cytochrome P-450-mediated toxicity of halogenated compounds: radical processes involving iron porphyrins.

Haloalkane toxicity originates from attack on biological targets by reactive intermediates derived from haloalkane metabolism by a hemoprotein, cytochrome P-450. Carbon-centered radicals and their peroxyl derivatives are most likely involved. The reactions of iron porphyrin--a model for cytochrome P-450--with various carbon-centered and peroxyl radicals generated by pulse radiolysis are examined. Competition between iron porphyrin and unsaturated fatty acids for attack by peroxyl radicals is pointed out. These kinetic data are used to derive a model for toxicity of haloalkanes with particular attention to carbon tetrachloride and halothane. The importance of local oxygen concentration and structural arrangement of fatty acids around cytochrome P-450 is emphasized.

Animals↗
PubMed1985

[Acute pancreatitis and biochemical markers. Isoamylase].

Amylase activity in blood and urine, lipase activity in blood, and amylase/creatinine clearance ratio have been prospectively compared in order to test these parameters against estimation of pancreatic isoamylase. Pancreatic isoamylase had been evaluated by inhibition methodology and not by electrophoresis. One hundred patients admitted for strictly sus-umbilical abdominal pain in emergency unit have been studied. Results show that we do not have in blood specific biochemical marker for acute pancreatitis. Lipase and P isoamylase activity evaluation have about the same specificity. In emergency situation the choice of routine investigation will be rather based on methodological simplicity and lower cost.

Acute Disease↗