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Biomedical subjects

N Sicard

Publications and source records attributed to N Sicard.

At least 19 recordsLinked to original sources
PubMed2007

Non-patient factors related to rates of ruptured appendicitis.

BACKGROUND: Adult rates of ruptured appendicitis vary from 13.2 to 41.9 per cent in urban hospitals, despite controlling for individual factors. This suggests an effect of hospital organization. Surgeons report that appendicectomies may be delayed because of lack of access to operating rooms. METHODS: Combining interviews with hospital personnel and information from medical records for 1998-1999, a cross-sectional study using logistic regression, taking hospital clustering of patients into account, was conducted on 861 patients from 12 hospitals. Hospitals were grouped into organizational models. The diagnostic information was recoded to ensure interhospital validity. RESULTS: Hospitals with high activity and volumes of patients, but without an operating room designated for urgent surgery, were associated with a significantly higher risk of peritonitis (P<0.050). Time to surgery was very long in all hospitals, particularly time after departure from the emergency department and for elderly patients. CONCLUSION: Organizational characteristics, in unfavourable combinations, influence the course of time-dependent diseases such as appendicitis. Difficulties in gaining access to operating rooms, even for urgent operations, have emerged. Delays in treatment must be addressed when planning healthcare reforms.

Adolescent↗
PubMed1995

An Escherichia coli strain deficient for both exonuclease V and deoxycytidine triphosphate deaminase shows enhanced sensitivity to ionizing radiation.

An Escherichia coli mutant lacking deoxycytidine triphosphate deaminase (Dcd) activity and an unknown function encoded by a gene designated ior exhibits sensitivity to ionizing radiation whereas dcd mutants themselves are not sensitive. A DNA fragment from an E. coli genomic library that restores the wild type level of UV and gamma ray resistance to this mutant has been cloned in the multicopy vector pBR322. Comparison of its restriction map with the physical map of the E. coli chromosome revealed complete identity to the recBD genes. ior affects ATP-dependent exonuclease activity, suggesting that it is an allele of recB. This mutation alone does not confer sensitivity to UV and gamma radiation, indicating that lack of Dcd activity is also required for expression of radiation sensitivity.

Chromosome Mapping↗
PubMed1992

Structure of the gene complementing uvr-402 in Streptococcus pneumoniae: homology with Escherichia coli uvrB and the homologous gene in Micrococcus luteus.

The repair ability for UV-induced damage observed for Streptococcus pneumoniae proceeds through a system similar to the Uvr-dependent system in Escherichia coli. The DNA sequence of a gene complementing uvr-402, a mutation conferring UV sensitivity, was determined. Alignments of the deduced amino acid sequence revealed an extensive sequence homology of 55% with the UvrB protein of E. coli and 59% with the UvrB-homologous protein of Micrococcus luteus. Nucleotide-binding site consensus was observed. The high conservation of the uvrB-like gene among these three species suggests that the role of the UvrB protein and excision repair in general might be very important for cell survival.

Amino Acid Sequence↗
PubMed1990

Excision-repair capacity in Streptococcus pneumoniae: cloning and expression of a uvr-like gene.

Although deficient in photoreactivation and some SOS-like functions, Streptococcus pneumoniae has the capacity to carry out excision repair when exposed to UV light. The repair ability and sensitivity to UV irradiation or treatment with chemical agents in the wild type and a UV-sensitive mutant strain indicate that UV-induced pyrimidine dimers might be repaired in pneumococcus by a system similar to the uvr-dependent system in Escherichia coli. A gene complementing the mutation conferring UV sensitivity of the mutant strain has been cloned. The coding region directs the synthesis of a polypeptide with a molecular weight of 78 kDa. The relationship with uvr-like protein in E. coli is discussed.

Bacterial Proteins↗
PubMed1989

Excision-repair capacity of UV-irradiated strains of Escherichia coli and Streptococcus pneumoniae, estimated by plasmid recovery.

Although the biological role of many bacterial repair genes is known, there is still an interest in evaluating the capacity of repair pyrimidine dimers in some strains. For this purpose, we have developed a rapid assay. Cells bearing a plasmid are UV irradiated and incubated to allow recovery. The plasmid DNA is extracted, purified and treated with UV endonuclease from Micrococcus luteus that specifically produces single strand breaks at the site of pyrimidine dimers. The amount of open circular and covalently closed circular forms of the plasmid DNA after treatment and post-incubation provides an estimate of the repair capability of the host strain. The wild type strain and the uvrA mutant of Escherichia coli were used to adjust the assay. The lexA mutant of E. coli has been tested and its repair capability is equivalent to that of wild-type strain. The assay has been extended to Streptococcus pneumoniae, which is naturally deficient in photoreactivation and SOS-like functions. This strain is efficient in the repair of pyrimidine dimers, formed after UV irradiation.

DNA Repair↗
PubMed1985

Characterization of a mutation conferring radiation sensitivity, ior, located close to the gene coding for deoxycytidine deaminase in Escherichia coli.

The isolation and characterization of a new mutation conferring radiation sensitivity in Escherichia coli is described. This mutation is located close to the gene coding for deoxycytidine deaminase, in the chromosomal region of the gat operon. It is very sensitive to gamma rays and exhibits a decrease in recombination ability. The expression of radiation sensitivity seems to result from the additive effect of the dcd mutation and another mutation of unknown function.

Cytidine Deaminase↗
PubMed1983

Possible correlation between transformability and deficiency in error-prone repair.

We have investigated the relationship between UV-induced mutability (as a measure of an error-prone repair process) and the genetic transformability of transformable and nontransformable bacterial strains. The data suggest a correlation between chromosomal transformability and a deficiency in an error-prone repair system in bacteria.

Bacillus subtilis↗
PubMed1980

Lack of SOS repair in Streptococcus pneumoniae.

Wild-type strains of Streptococcus pneumoniae were non-mutable by UV radiation and thymidine starvation. Moreover, UV-irradiated pneumococcal omega 2 phages were not reactivated in an irradiated host. This suggests that, in pneumoococcus, there is no efficient inducible repair process similar to the SOS repair described in detail for E. coli. We also report that mutations cannot be induced by a process thought to be linked to competence during transformation with isogenic wild-type DNA either on wild-type strains or in strains in which the hex function of excision and repair of mismatched bases is inactive.

Bacteriophages↗
PubMed1977

Thymineless death in Escherichia coli dnaB mutants and in a dnaB dnaG double mutant.

The interference of dnaB mutations of Escherichia coli with thymineless death is described. All the isogenic Thy- dnaB mutants of E. coli we have tested show a remarkable immunity towards cell death induced by thymine deprivation at the nonpermissive temperature. We have also constructed and tested an isogenic double dnaB dnaG mutant. It loses its viability in the absence of thymine at both permissive and nonpermissive temperatures. The role of the dnaB gene product is discussed.

DNA, Bacterial↗
PubMed1976

Size and transforming activity of deoxyribonucleic acid in Diplococcus pneumoniae during thymidine starvation.

The transforming activity and the molecular structure of DNA from cells of Diplococcus pneumoniae during thymidine starvation have been analyzed and the effects of thymidine starvation have been compared with the effects of single-strand breaks produced by deoxyribonucleases in DNA of unstarved cells. The decrease in transforming activity of lysates from starved cells as a function of the size of DNA particles, measured by centrifugation in neutral and alkaline sucrose gradients, does not follow the kinetics observed after enzymatic degradation of DNA of unstarved cells. Moreover, a strain lacking exo- and endonuclease activities is not protected from thymineless death. These results suggest that the basic lethal mechanism of thymidine starvation might have an origin other than the activation of nucleases.

Centrifugation, Density Gradient↗
PubMed1975

Interference of dna ts mutations of Escherichia coli with thymineless death.

Thermosensitive mutants of Escherichia coli in which deoxyribonucleic acid replication is inhibited at high temperature have been assayed for their response to thymine deprivation at permissive and nonpermissive temperatures. The survival rate of mutants in which initiation of replication is defective at 42 C (dnaA and dnaC-D) is much higher at nonpermissive temperatures than at 32 C. By contrast, thymineless death is not hindered at 42 C in two elongation mutants (dnaE and dnaG). Bacterial strains belonging to the dnaB class exhibit both types of behavior. These results are in accordance with the model linking thymineless death to a disruption of an active replication fork. We discuss the possibility that the dnaB protein takes part in this process of cell decay.

Chloramphenicol↗
PubMed1970

Lethal effects of electric current on Escherichia coli.

An attempt has been made to use low-voltage alternating current to kill microorganisms such as Escherichia coli. The bactericidal effect depends on the energy passing through the suspension and on the time during which the cells are left standing in the medium after the treatment. Most of the toxicity is due to an indirect effect developed with unalterable electrodes in the presence of chlorides in the medium. This method might be applied to eliminate pollution of natural waters.

Albumins↗