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Biomedical subjects

G Lefebvre

Publications and source records attributed to G Lefebvre.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Technics of the use of CO2 laser in microsurgery of sterility. Experimental study. Clinical results].

The authors describe their experience in the use of CO2 laser in microsurgical treatment of tubal sterility. An experimental study was carried out on Fallopian tubes in order to define the parameters for the use of CO2 laser in tubal surgery. Certain microsurgical techniques were altered when CO2 laser was used. The procedures were improved by the ease of surgery and the speed with which it could be carried out. Our clinical experience was on 153 patients who were operated on. In 66 laparotomies the combined use of microscope and CO2 laser seemed to improve the handling of tubal sterility.

Carbon Dioxide↗
PubMed1986

[Triploidy and mole. Apropos of 2 cases continuing to the second trimester].

Triploidy in a common chromosomal abnormality that gives rise to early abortion in most cases. Rarely triploidies carry on past the end of the first trimester. When they do they are always accompanied by severe intra-uterine growth retardation with occasionally molar changes in the placenta. These changes are different from hydatidiform moles but they can become malignant. The formal diagnosis of triploidy depends on the fetal caryotype.

Adult↗
PubMed1986

[Facial paralysis of obstetrical origin. Etiology, evolution].

In the case of 17 obstetrical facial paralyses occurring in a total of 20,409 births, the authors have studied the circumstances of their appearance and the prognosis for this lesion. It is a rare lesion favoured by asymmetric purchase when using articulated forceps. The authors insist that use of Thierry's forceps do not harm the facial nerve. They emphasise the possibility that progression may not always be favourable.

Birth Injuries↗
PubMed1985

[Obstetrical injuries of the newborn infant. Retrospective study apropos of 20,409 births].

We have been able to find 291 cases of obstetric trauma when we analysed the 20,409 deliveries which took place in the Pitié maternity between 1971 and 1980. It has been shown that bony lesions did well in the long and short term but nerve lesions had a far less good prognosis. This pathology should become far less when it is possible to recognize better when the fetus is large and when such traumatising manoeuvres as high forceps and assisted deliveries of large breech babies are stopped.

Birth Injuries↗
PubMed1983

[Not Available].

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Journal Article↗
PubMed1981

Turnover of proteins, cell walls and ribosomal constituents during the growth of actinomycetes.

Biochemical reorganizations occurring during the slowdown of growth following the exponential phase in liquid batch cultures of some species of actinomycetes, have been studied. Three main events occur during the reduction of the growth rate. Firstly, there is a decrease of the ribosomal fraction with a drop in r-RNA and ribosomal proteins, and, secondly, protein turnover occurs. This was indicated by changes in the cell protein content, by the appearance of aminated material in the extracellular medium and by drops of the specific activity of some enzymes. Thirdly, there are changes in the cell envelope with a periodic release into the medium of soluble radioactivity from cells prelabelled with tritiated diaminopimelic acid. These cellular reorganizations may be biochemical mechanisms of adaptation of actinomycetes during the transition from nutrient-rich to poorer environments.

Actinomycetales↗
PubMed1980

[Variations in cyclic AMP level and specific activities of adenylate cyclase and cyclic AMP phosphodiesterase during the cell cycle of an Actinomycete (author's transl)].

The variations in the concentrations of intra- and extracellular cyclic AMP and in he specific activities of adenylate cyclase (EC 4.6.1.1) and cyclic AMP phosphodiesterase (EC 3.1.4.17) have been monitored in synchronized cultures of Nocardia restricta, a prokaryote belonging to the group of Actinomycetes. At the beginning of the cell cycle, during a first period of RNA and protein synthesis, there is an increasing synthesis of adenylate cyclase which can be suppressed in the presence of chloramphenicol or rifampicin. Simultaneously, the specific activity of cyclic AMP phosphodiesterase decreases and the concentrations of intra- and extracellular cyclic AMP rise. After the end of DNA replication, during a second period of RNA and protein synthesis, the specific activity of cyclic AMP phosphodiesterase increases; during the same time, the specific activity of adenylate cyclase and the level of intracellular cyclic AMP drop. It appears that the overall metabolism of cyclic AMP is coordinated so that the cyclic AMP level will be high at the beginning of DNA replication and will fall thereafter. The results are discussed in comparison with known data about the variations of cyclic AMP during the cell cycle of mammalian cells in cultures.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Synthesis of macromolecules in synchronously grown Arthrobacter.

The synchronous growth of Arthrobacter has not yet been studied. We have shown that synchrony of A. crystallopoietes and A. globiformis cultures can be achieved in a liquid synthetic medium by inoculating a fresh medium with cells taken from an advanced stationary phase culture. DNA content measurements and pulsed incorporations of tritiated thymidine have been used to show that DNA synthesis occurs in a stepwise manner in these synchronized cultures. The use of absorbance of cultures as a monitor of synchronized cell growth was especially useful since cells did not separate during the exponential phase. The breaks in the absorbance versus time curve indicated a slow-down in mass synthesis. Protein and RNA synthesis occurred in two waves during the time necessary for a doubling of cell mass: a first increase was observed at the beginning of the DNA replication; after a slow-down, a second sharp increase occurred after the replication of DNA. These results are discussed in relation to previous data on the existence of a differential transcription during the development of A. crystallopoietes.

Arthrobacter↗
PubMed1978

[Demonstration, kinetic study and solubilization of particular adenylate cyclase from Nocardia restricta].

An adenylate cyclase (EC r.6.1.1.) was found in cell-free extracts of several Nocardia species. The enzyme from Nocardia restricta has been specially studied. It is a membrane enzyme which exhibits a strong specific activity, one hundred times greater than that of mammals. It has an optimal pH of 8.5 in Tris buffer and an absolute requirement for divalent ions, Mg++ or Mn++ (Mn++ ions are the most efficient). The kinetic properties of this adenylate cyclase are similar to those that could be expected of an allosteric enzyme having, as a substrate, the ATP-Mg++ complex and, as an activator, free Mn++ ions. Ca++ ions are activators: they set up the maximum velocity without modification of the KM. GTP is a competitive inhibitor (KI = 5.10(-5) M). Fluoride ions have no detectable effect on activity. Non-ionic detergents, Lubrol WX and Triton X 100, are inhibitors of the enzyme which has been partially solubilized by repeated freezing and thawing, following by brief ultra-sonic treatment. Catalytic sites are not modified after the solubilization, but cooperative effects between moles of substrate ATP-Mn++ are diminished: the KM becomes smaller and the sigmoidal shape of the curve v = f (ATP-Mn++) is attenuated.

Adenylyl Cyclases↗