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Biomedical subjects

M Chartier

Publications and source records attributed to M Chartier.

At least 19 recordsLinked to original sources
PubMed1992

Structure of DNA-RecA complexes studied by residue differential linear dichroism and fluorescence spectroscopy for a genetically engineered RecA protein.

The structure of complexes of RecA with double-stranded and single-stranded DNA was studied by linear dichroism spectroscopy, fluorescence quenching and fluorescence anisotropy measurements. One of the two tryptophan residues (Trp291) of RecA was replaced by genetic engineering for an ultraviolet light-transparent threonine. This modified RecA protein shows, within experimental errors, the same DNA-binding kinetics and stoichiometry as the wild-type protein and no significant variation with respect to in vivo repair function was observed between cells with the two protein forms. By comparing the dichroic and fluorescence properties of the wild-type versus the modified protein, when bound to DNA, information about orientation and environment of the Trp291 chromophore in the complex could be obtained. The indole chromophore of Trp291Z was found to be oriented with its pseudo-long axis tilted 61 degrees and the aromatic plane is tilted 27 degrees relative to the fibre axis. Trp291 shows low mobility within the protein and therefore the deduced orientation may be used as a "handle" on the protein at the construction of three-dimensional models of RecA-DNA complexes. Comparison with the orientation for this residue in the crystal structure of the RecA homopolymer fibre indicates no measurable reorientation of the C-terminal subdomain of RecA upon DNA binding. Whereas the accuracy of the orientation determination of tryptophan, in absolute terms, is rather poor, changes of its orientation can be detected with high precision. Thus, similar Trp291 orientations are obtained in the complexes with single-stranded and double-stranded DNA, indicating similar structures of the protein fibres. The fluorescence quenching results indicate that the protein region of Trp291 is not involved in the binding of DNA.

DNA↗
PubMed1991

[Autologous transfusion in heart surgery (apropos of 74 patients)].

The present study uses three techniques of autotransfusion in heart surgery under ECC: peroperative and post-ECC transfusion of blood removed after induction of anaesthesia (group I: 25 patients); postoperative transfusion of extravasated thoracic blood (group II: 24 patients) and a combination of the two (group III: 25 patients). Postoperative bleeding was comparable in all groups; A subset likely to haemorrhage made up of patients who had lost more than one litre of blood was isolated and demonstrated a reduction in the number of homologous red cell concentrates needed for the autotransfused population in comparison with the controls (2.4 +/- 2.6 vs 5.7 +/- 3.5 red cell concentrates, p less than 0.05) and was particularly marked in Group II patients who received 1.9 +/- 2.2 homologous red cell concentrates. None of the techniques caused any side-effects. Combination of the two autotransfusion techniques in heart surgery does not secure any additional advantages compared with postoperative autotransfusion alone.

Blood Transfusion, Autologous↗
PubMed1989

Amoxycillin/clavulanic acid ('Augmentin') compared with a combination of aminopenicillin, aminoglycoside and metronidazole in the treatment of pelvic inflammatory disease.

A randomized, multi-centre trial was carried out in 152 hospitalized women with pelvic inflammatory disease to evaluate the efficacy and tolerability of amoxycillin/clavulanic acid compared with that of a standard regimen using three antimicrobial agents (aminopenicillin, an aminoglycoside and metronidazole). Seventy patients initially received 3 to 4 intravenous doses per day of 1 g amoxycillin/200 mg clavulanic acid (mean 7.7 days) and then 4 to 6 tablets per day of 500 mg amoxycillin/125 mg clavulanic acid (mean 11.2 days). The other group of 82 patients initially received parenteral therapy daily (mean 7.7 days) with a combination of 3 to 4 g amoxycillin or ampicillin, 160 mg gentamicin (or 150 mg dibekacin or tobramycin) and 1.5 g metronidazole, and then oral therapy with 2 to 3 g amoxycillin or ampicillin and 1 to 1.5 g metronidazole daily (11.1 days). Clinical results, assessed at discharge from hospital (mean 10 days in both groups), were comparable in both groups, with 96% complete or partial response and no failures in the amoxycillin/clavulanic acid group, and 90% complete or partial successes and 5 failures with the triple therapy regimen. Both treatments were well tolerated and very few side-effects were reported.

Adult↗
PubMed1988

The membrane channel-forming colicin A: synthesis, secretion, structure, action and immunity.

The study of colicin release from producing cells has revealed a novel mechanism of secretion. Instead of a built-in 'tag', such as a signal peptide containing information for secretion, the mechanism employs coordinate expression of a small protein which causes an increase in the envelope permeability, resulting in the release of the colicin as well as other proteins. On the other hand, the mechanism of entry of colicins into sensitive cells involves the same three stages of protein translocation that have been demonstrated for various cellular organelles. They first interact with receptors located at the surface of the outer membrane and are then transferred across the cell envelope in a process that requires energy and depends upon accessory proteins (TolA, TolB, TolC, TolQ, TolR) which might play a role similar to that of the secretory apparatus of eukaryotic and prokaryotic cells. At this point, the type of colicin described in this review interacts specifically with the inner membrane to form an ion channel. The pore-forming colicins are isolated as soluble proteins and yet insert spontaneously into lipid bilayers. The three-dimensional structures of some of these colicins should soon become available and site-directed mutagenesis studies have now provided a large number of modified polypeptides. Their use in model systems, particularly those in which the role of transmembrane potential can be tested for polypeptide insertion and ionic channel gating, constitutes a powerful handle with which to improve our understanding of the dynamics of protein insertion into and across membranes and the molecular basis of membrane excitability. In addition, their immunity proteins, which exist only in one state (membrane-inserted) will also contribute to such an understanding.

Amino Acid Sequence↗
PubMed1988

The complete nucleotide sequence of the colicinogenic plasmid ColA. High extent of homology with ColE1.

The complete nucleotide sequence of the colicinogenic plasmid ColA has been determined. The plasmid DNA consists of 6720 bp (molecular weight 4.48 X 10(6]. Fifteen putative biological functions have been identified using the functional map previously determined. These include 11 genes and 3 DNA sites. Nine genes encode proteins of which 3 have been fully characterized. The replication region of ColA coding for RNAI and RNAII is highly homologous to that of ColE1 and Clo DF13. The same holds true for the site-specific recombination region containing palindromic symmetry and involved in stable maintenance of the plasmids. A high percentage of homology has been detected for putative mobility proteins encoded by ColA and ColE1. The exclusion proteins are also highly homologous.

Amino Acid Sequence↗
PubMed1988

Plasma corticosteroid patterns in the fetus.

In umbilical vein blood samples collected in 137 fetuses between 19 and 31 weeks of gestation, cortisol (F), cortisone (E), 17-hydroxyprogesterone (17-OHP) and 11-deoxycortisol (S) were radioimmunoassayed after column chromatography on Sephadex LH-20 of plasma extracts. While F levels plateaued throughout the period considered those of E displayed an increasing pattern which appeared to be comparable with that of unbound F in pregnant women. The declining pattern of S and more particularly of 17-OHP would suggest an increasing utilization and metabolization of these F precursors by the maturing fetus. E was not correlated with either 17-OHP or S but showed a significant correlation with F. S and 17-OHP were correlated with each other and with F. The significance of these correlations was discussed according to the different origin of these steroids and to their metabolic relationships. The application of this method for the prenatal diagnosis of inborn errors of steroid biogenesis is suggested.

17-alpha-Hydroxyprogesterone↗
PubMed1987

Serum growth-promoting activity in normal and hypotrophic fetuses at midpregnancy.

Blood from 24 human fetuses aged 19-24 wk was collected by ultrasound-guided puncture of the umbilical cord in utero, performed for prenatal diagnosis of mother to fetus transmissible infections. Fetal serum growth-promoting activity (thymidine activity) was measured by its effect on 3H-thymidine incorporation into human lectin-activated lymphocytes. Ten blood samples were obtained at 19-22 wk of pregnancy and 14 at 23-24 wk. The pregnancies were maintained and the fetuses delivered, free of infection, at 38-40 wk, nine of them being small for date and 15 having a normal weight for gestation age. The bioassayable thymidine activity was significantly lower in the hypotrophic (0.84 +/- 0.04 U/ml) than in the normal fetuses (1.28 +/- 0.09 U/ml) whatever the time of sampling. Thymidine activity was significantly negatively correlated with gestational age in the normal for date fetuses, not in the small for date. It is suggested that early measurement of thymidine activity in fetal blood might be of value in the assessment of fetal growth despite the fact that the tissue growth factors may be more important in fetus than are the serum factors.

Adult↗
PubMed1985

Prenatal diagnosis of congenital toxoplasmosis.

Prenatal diagnosis of congenital toxoplasmosis was attempted by means of fetal blood sampling at 20-24 weeks' gestation. It was possible to detect in fetal blood samples non-specific laboratory signs of fetal infection, specific antibodies of fetal origin (IgM), and parasitaemia by inoculation of the sample into mice. Amniotic-fluid samples were also inoculated into mice and parasites were often present when the fetus was infected. Ultrasound examination of the fetus was done repeatedly, mainly to detect any enlargement of the cerebral ventricles. Together the results of these examinations allowed a reliable diagnosis, which was confirmed by the presence of necrotic foci of toxoplasmic encephalitis in the fetus in every case. Only 1 case of congenital toxoplasmosis occurred among 209 cases with negative prenatal diagnoses.

Antibodies↗
PubMed1985

Lysis protein encoded by plasmid ColA-CA31. Gene sequence and export.

A gene, cal, coding for a polypeptide needed for the release of colicin A from Escherichia coli cells has been identified by transposon insertion. The cal gene was located on the ColA plasmid map adjacent to cai, the gene coding for colicin A immunity protein, and therefore 592 bases downstream from caa, the structural gene for colicin A. Transcription of cal is in the same direction as caa, that is in the opposite direction to cai. Its sequence has been determined and the predicted amino acid composition features a basic N-terminal end followed by a serie of hydrophobic residues similar to the signal sequence in precursors of exported proteins. The C-terminal part also contains a core of hydrophobic residues. The overall amino acid sequence of the cal protein is homologous to that of lytic proteins encoded by the related plasmids pColE1, and pCloDF13. The cal protein has been identified on urea-SDS-polyacrylamide gels by selective labelling with various radioactive amino acids and its synthesis is co-induced with that of colicin A. The cal protein undergoes slow processing with loss of the N-terminal "signal" region and the mature form is released into the medium together with colicin A.

Amino Acid Sequence↗
PubMed1984

Prenatal diagnosis of congenital rubella.

In an attempt at prenatal diagnosis of fetal infection after primary rubella infection before 18 weeks of pregnancy fetal blood was taken by direct puncture under ultrasound guidance at 20-26 weeks of pregnancy from eighteen patients. Total IgM was assayed by radial immunodiffusion and rubella-specific IgM by IgM capture immunoassay. Rubella-specific IgM was detected in twelve of the eighteen fetuses. The parents decided whether to continue or terminate the pregnancy on the basis of the time of onset of maternal rubella. All six pregnancies in which rubella occurred before 12 weeks of gestation were terminated. Of the six with rubella after 12 weeks two were terminated. Among the six fetuses negative for rubella-specific IgM, five had no rubella-specific IgM at birth and no persistent IgG but one was found to be infected at birth; this false-negative diagnosis was due to sampling too early during pregnancy.

Antibody Specificity↗
PubMed1983

Complete nucleotide sequence of the structural gene for colicin A, a gene translated at non-uniform rate.

The complete nucleotide sequence of the structural gene for colicin A has been established. This sequence consists of 1776 base-pairs. According to the predicted amino acid sequence, the colicin A polypeptide chain comprises 592 amino acids and has a molecular weight of 62,989. The amino-terminal part is rich in proline and glycine and accordingly secondary structure prediction indicates that this region (1 to 185) is beta-structured. The rest of the molecule (residues 186 to 592) is very rich in alpha-helix. An uncharged amino acid sequence of 48 residues is located in the C-terminal part of the molecule, which is involved in the membrane depolarization caused by colicin A. A similar region has been found in colicin E1, which has the same mode of action as colicin A. Three peptides of these bacteriocins were found to be homologous, but a comparison of the bacteriocin genes did not reveal any significant homology out of the corresponding regions. The codon usage of both genes, however, exhibits some similarity and is quite different from that of genes coding for highly or weakly expressed proteins of Escherichia coli.

Amino Acid Sequence↗
PubMed1983

Nucleotide sequence of promoter, operator and amino-terminal region of caa, the structural gene of colicin A.

The nucleotide sequence of 378 bp covering the promoter-operator regions and the region coding for the N-terminal portion of the colicin A gene was determined. These assignments were made possible by the determination of the N-terminal 12 amino acids of the colicin A protein. DNA sequence homologies between operator regions of recA, lexA, uvrA, uvrB, cea and caa genes are discussed.

Amino Acid Sequence↗
PubMed1979

Measurement of plasma human chorionic gonadotropin (hCG) and beta-hCG activities in the late luteal phase: evidence of the occurrence of spontaneous menstrual abortions in infertile women.

Plasma luteinizing hormone (LH-human chorionic gonadotropin (hCG) and beta-hCG activities were measured during the late luteal phase in 321 cycles of 147 infertile women. In 71 cycles the hCG measurement permitted the diagnosis of pregnancy between the 10th and 14th days after the thermal nadir. The slope of the regression line derived from hCG levels during the first 22 days of pregnancy was significantly lower in pregnancies which aborted before the 60th day than in normal pregnancies (P less than 0.01). Among 72 cycles ended by apparently normal menses which exhibited an LH-hCG activity at least equal to 7 mIU of hCG/ml during the late luteal phase, the beta-hCG activity was measured in 49 cycles during which hCG had not been given. Significant beta-hCG activity (greater than or equal to 4 mIU of hCG/ml) was detected in 19 cases. This finding supports the assumption that secretory trophoblastic tissue had been present and that spontaneous menstrual abortions had occurred in these women.

Abortion, Spontaneous↗