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Biomedical subjects

C Petit

Publications and source records attributed to C Petit.

At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

Nucleotide excision repair: from E. coli to man.

Nucleotide excision repair is both a 'wide spectrum' DNA repair pathway and the sole system for repairing bulky damages such as UV lesions or benzo[a]pyrene adducts. The mechanisms of nucleotide excision repair are known in considerable detail in Escherichia coli. Similarly, in the past 5 years important advances have been made towards understanding the biochemical mechanisms of excision repair in humans. The overall strategy of the repair is the same in the two species: damage recognition through a multistep mechanism involving a molecular matchmaker and an ATP-dependent unwinding of the damaged duplex; dual incisions at both sides of the lesion by two different nucleases, the 3' incision being followed by the 5'; removal of the damaged oligomer; resynthesis of the repair patch, whose length matches the gap size. Despite these similarities, the two systems are biochemically different and do not even share structural homology. E. coli excinuclease employs three proteins in contrast to 16/17 polypeptides in man; the excised fragment is longer in man: the procaryotic excinuclease is not able by itself to remove the excised oligomer whereas the human enzyme does. Thus, the excinuclease mode of action is well conserved throughout evolution, but not the biochemical tools: this represents a case of evolutionary convergence.

DNA Repair↗
PubMedDate not supplied

Production of macrophage-derived cytotoxic factor by N-[3-[(carbamoylmethyl)thio]propionylated] neoglycoproteins.

6-Phosphomannosylated bovine serum albumin (Man6P-BSA), a neoglycoprotein endocytosed by macrophages, bearing either 3-(2-pyridyldithio)propionyl or 3-[(carbamoylmethyl)thio]propionyl residues coming from alkylation of thiol residues by iodoacetamide were prepared and tested for their immunomodulator properties. The supernatants of mouse peritoneal macrophages incubated with Man6P-BSA bearing 3-[(carbamoylmethyl)thio]propionyl groups, and by a lesser extent 3-(2-pyridyldithio)propionyl groups, were cytotoxic to L929 cells, suggesting the presence of a tumor necrosis factor like compound. This macrophage-activation process is linked to the capacity of Man6P-BSA to be endocytosed via membrane lectins of macrophages, because the supernatants of macrophages incubated with unglycosylated conjugates were not cytotoxic. The cytotoxic activity induced by 3-[(carbamoylmethyl)thio]propionyl groups bound onto Man6P-BSA was similar to that induced by Man6P-BSA bearing muramyl dipeptide, indicating that endocytosed neoglycoproteins bearing 3-[(carbamoylmethyl)thio]propionyl residues are potent macrophage activators.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

A sensorineural progressive autosomal recessive form of isolated deafness, DFNB13, maps to chromosome 7q34-q36.

Deafness is the most frequent sensorineural defect in children. The vast majority of the prelingual forms of isolated deafness are highly genetically heterogeneous with an autosomal recessive mode of inheritance. Using linkage analysis, we have mapped the gene responsible for a severe progressive sensorineural hearing loss, DFNB13, segregating in a large consanguineous family living in an isolated region in northern Lebanon. A maximum lod score of 4.5 was detected for markers D7S661-D7S498. Recombination events and homozygosity mapping by descent define a 17 cM gene interval in the chromosome region 7q34-q36, between the markers D7S2468/D7S2505, on the proximal side, and D7S2439, on the distal side.

Chromosome Mapping↗
PubMedDate not supplied

Identification of a locus on chromosome 7q31, DFNB14, responsible for prelingual sensorineural non-syndromic deafness.

In our efforts to identify new loci responsible for non-syndromic autosomal recessive forms of deafness, DFNB loci, we have pursued the analysis of large consanguineous affected families living in geographically isolated areas. Here, we report on the study of a Lebanese family affected with a prelingual profound sensorineural isolated form of deafness. Segregation analysis resulted in a linkage with locus D7S554 to locus D7S2459 on 7q31, with a maximum lod score of 6.3. The causative gene was mapped to a 15 cM interval extending from D7S527 to D7S3074 (on the telomeric side). The distal limit of this interval could be located between D7S496 and D7S3074 which are the closest polymorphic loci flanking the gene underlying Pendred syndrome (PDS) on the centromeric and on the telomeric sides, respectively. To eliminate PDS as a candidate gene, its 21 exons were sequenced. No mutation was detected. This study therefore reports the identification of a novel locus, DFNB14, on chromosome 7q31, in a position proximal to PDS.

Audiometry↗
PubMedDate not supplied

Improvement of zinc intestinal absorption and reduction of zinc/iron interaction using metal bound to the caseinophosphopeptide 1-25 of beta-casein.

Binding zinc (Zn) to soluble caseinophosphopeptides (CN), produced by the hydrolysis of caseins, improves its absorption and could prevent inhibition by other nutrients such as iron (Fe). The absorption of Zn (100 mumol/L) bound to the 1-25 CN (beta-CN(1-25)) of beta-casein, or as ZnSO4 was studied using the isolated, perfused rat intestinal loop system. Fe (Fe-CN or Fe gluconate (Fe Gluc)) was added at Zn/Fe ratios of 2:1, 1:5 and 1:10. Disappearance from the lumen (Q1) and net absorption (ZnAbs) of Zn-CN were statistically greater than for ZnSO4; Zn retention by the mucosa (Q2) did not significantly differ. Fe Gluc reduced Q1, Q2 and ZnAbs for ZnSO4 at ratios of 1:5 and 1:10 and for Zn-CN at a ratio of 1:10. Fe-CN reduced Q1 and ZnAbs of both forms of Zn at a ratio of 1:10; Q2 remained unchanged. Binding Zn to beta-CN(1-25) improved Zn absorption and prevented Fe from inhibiting its absorption.

Analysis of Variance↗
PubMedDate not supplied

Contribution of DFNB1 and DFNB2 loci to neurosensory deafness in affected Tunisian families.

Classical studies have demonstrated genetic heterogeneity for nonsyndromic autosomal recessive congenital neurosensory deafness. The first two DFNB1 and DFNB2 locations were found using two consanguineous Tunisian families respectively from north and south. We tested these loci for cosegregation with deafness in twenty four southern families with nonsyndromic presumed congenital sensorineural deafness and a pedigree structure consistent with autosomal recessive inheritance. Only in our families, did deafness cosegregate with DFNB1. Although our families are from the south, none of them showed linkage to DFNB2.

Chromosome Segregation↗
PubMedDate not supplied

[Antibody producing cells and immunoglobulin synthesizing cells lacking antibody function].

After primary immunization the first immunoglobulin-synthesizing cells which appeared, contained immunoglobulins devoided of antibody function. These cells were progressively replaced by antibody synthesizing cells. The results we reported here demonstrated that except the repartition of Ig between IgM and IgG, there are no differences in the molecular composition and in the rate of biosynthesis between these two populations of cells.

Animals↗
PubMedDate not supplied

Development of immuneeoglobulin and antibody-forming cells in different stages of the immun response.

After primary immunization of mice, rats and rabbits with antigens (horse radish peroxidase, bovine serum albumin and muchroom tyrosinase) emulsified in complete or incomplete Freund's adjuvant, both cells synthesizing immunoglobulin without detectable antibody function and antibody-producing cells were detected. The first cells which appeared were synthesizing and secreting IgG and IgM immunoglobulins without antibody function. These cells were progressively replaced by cells synthesizing and secreting antibodies. In some plasma cells of mice, rats and rabbits immunized with peroxidase, antibody activity was detected only in restricted areas of the cytoplasm ; the remainder contained antigenic determinants of immunoglobulins. After secondary immunization the results were the following: in mice, both cells containing immunoglobulins without antibody function and antibody-containing cells appeared simultaneously and they were present in equal amount; in rats, only the antibody-containing cells were present in high number. Immunizations performed using different protein antigens (horse radish peroxidase, human and bovine serum albumin, aggregated and desaggregated human IgG, and ovalbumin) injected as a solution in saline have shown that after antigenic stimulation both populations of cells appeared, their number depending on the dose of the antigen injected. Further experiments carried out with tolerant mice, with germ-free animals and with "B" mice have shown that the appearance or not of antibody-producing cells was always related with respectively the presence or absence of cells synthesizing immunoglobulins without detectable antibody function. Finally experiments performed on rabbits have shown that some cells containing immunoglobulins without antibody function share idiotypic determinants in common with cells synthesizing antibodies.

Animals↗
PubMedDate not supplied

Direct detection of idiotypic determinants on blotted monoclonal antibodies.

The protein-blotting technique has been tested as a mean to study the expression of idiotypic determinants. A monoclonal BALB/c antipoly (Glu60-Ala30-Tyr10) GAT antibody (G5) was caused to migrate on SDS gel and transferred to a nitrocellulose filter. To facilitate the renaturation of the idiotypic determinants, the blotted proteins were incubated in NP40 buffer, immediately after the transfer. The ability of two anti-idiotypic sera to detect two defined idiotypic specificities of the blotted G5 molecules was investigated. When G5 was electrophoresed on SDS gel under non-reducing conditions, a specific detection of two idiotypic specificities of the G5-blotted molecules was obtained. On the other hand, when G5 was migrated under reducing conditions, none of the two antiidiotypic sera gave a staining of the heavy and the light chains. This result indicates that molecules expressing conformational idiotypic determinants can be detected by protein-blotting technique after migration on SDS gel. Moreover, this suggests the possible interest of this technique to analyse non-antibody molecules bearing idiotypic determinants.

Animals↗
PubMedDate not supplied

[Massive edema of the ovary. A clinicopathologic study of one case and review of the literature (author's transl)].

The first observation of a massive ovarian edema with frozen-section examination of a biopsy specimen and ovarian preservation is related. A 27-year-old woman had a 12 cm right ovarian mass on twisted pedicle. After the ovary was untwisted and biopsied and while waiting for the frozen section study, the ovary returned to normal size and aspect. Ovarian preservation was decided. The elements of histopathologic diagnosis, in particular for a frozen-section examination of ovarian biopsy, are listed and discussed. Diagnostic difficulties must be solved by : clinical and peroperative macroscopic findings, a large biopsy specimen, allowing several frozen-section studies, in order to detect ovarian follicles scattered by the edema, which alone allows the affirmation of the diagnosis.

Adolescent↗