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Biomedical subjects

C Chevalier

Publications and source records attributed to C Chevalier.

At least 37 records · Page 2Linked to original sources
PubMed1988

Occupational exposure to radionuclides in French nuclear power plants: five years excretion monitoring results.

In the French Nuclear Power Plants, monitoring of individual internal exposures is accomplished by lung counting by the medical service of the plant, and on request of the physician by analysis of biological samples in the Saint-Denis Laboratory. A description of the various methods used in the Laboratory for measuring low level activity samples is given. In particular, the performance of routine contamination monitoring by gamma spectrometry of urines with a semiconductor detector is discussed. An automatic system, designed for Marinelli beaker analysis, made up of a sample changer, a germanium detector and a computerized multichannel analyser is presented. The same device is used for counting faecal ashes and nose blows sampled after an incident. The estimation of the incorporated activities is achieved by using a computer program originating from the compartmental metabolic model of the ICRP. This paper presents a survey of routine monitoring of excretions over a period of 5 years, and a discussion of the ICRP Cobalt metabolic models based on the study of its elimination kinetics after occupational intake.

Body Burden↗
PubMed1987

A physico-mathematical model for the human femur, with and without a prosthesis, under the static constraints of one-legged stance.

The authors present a physico-mathematical model of a human femur, under "monopodal" static constraints, using the finite elements method. Three examples are considered: a normal femur, a femur implanted with a short-stem prosthesis without cement, and a femur implanted with a long-stem prosthesis without cement. The lines of isoconstraints were compared in the three examples, as well as the main constraints (direction and intensity). From the results, the authors suggest that a prosthesis made of titanium is currently best even though its YOUNG's modulus differs from that of the bone. A prosthesis of composite material is possible in the future. While the intensity of the constraints is nearly the same at the level of the epiphysis for the short-stem and long-stem prosthesis it seems that the short-stem prosthesis fitted accurately without cement is the best solution. The introduction of a hip prosthesis modifies the normal curve of the loaded femur by changing the center of this curve.

Biomechanical Phenomena↗
PubMed1987

Spiroplasmas: gene structure and expression.

Upon sequencing of the SpV4 genome, eight putative open reading frames (ORFs) including that for the 65-kilodalton (kDa) capsid protein were detected. They involve all three reading frames. Three promoter sequences were found, as well as a transcription terminator and the initiation site for complementary strand synthesis. Ribosome binding sites and regulatory sequences are closely related to those of Eubacteria. Codon usage analysis showed that A and T terminated codons are preferably used. UAA is the major termination codon. Upon cloning of the full-size SpV4 replicative form, the capsid protein gene could not be expressed in Escherichia coli, whereas the spiralin gene cloned in the same bacterium is expressed. These results suggest that in spiroplasmas, as in Mycoplasma capricolum, UGA is not a termination codon, but very probably codes for tryptophan. Spiralin contains no tryptophan. Hence, its gene contains no UGA codons and can thus be expressed in E. coli. On the other hand, the gene for capsid protein has nine UGA codons and cannot be fully expressed in the bacterium. Our results fully support the bacterial origin of spiroplasmas.

Bacteria↗
PubMed1985

Study of the deformations of the isolated mandible under static constraints by simulation on a physicomathematical model.

The authors have studied the deformations of a mandible isolated from its muscular environment and submitted to statical constraints, with the help of a "modified model" and the finite elements method: the general deformation of the mandible and its modifications according to the direction of the application of the pressure, the rotation phenomenon or "torsion" in cross sections (identified by computer) of the mandible, the respective deformations of the internal and external corticals have successively been calculated. Particular mechanical phenomenons corresponding to the areas where the anatomo-clinical forms of the mandibular fractures take place have clearly been shown. The authors draw the conclusion that the mandible behaves mechanically in a similar way to a tridimensional composite.

Humans↗
PubMed1985

Study of the mandible under static constraints by holographic interferometry. New biomechanical deductions.

In order to try to determine the nature of the mechanical structure of the mandible, the authors have compared, with the help of holographic interferometry, the behavior of the fresh mandible of a corpse, of a representative iron angle, and of a block of carbon-carbon under static constraint. There are no similarities between the behavior of the human mandible and that of a polycrystalline steel. On the contrary, the behavior of the mandible and of the carbon-carbon block are very similar. It would be hasty to state that bones are a heterogeneous composite. We can only prove, in a first approach, that they behave similarly under identical experimental conditions. The authors also demonstrated that the mandible presents a "mechanical hysteresis" phenomenon. This means that, when subjected to a small strain, its shape changes, but this change tends to neutralize itself in part in the course of time.

Aged↗
PubMed1983

[Electromyographic study of 4 lip muscles and acoustic findings in parkinsonian dysarthria].

The articulatory E.M.G. activity of lower lip muscles was investigated in 3 patients with Parkinson's disease and compared with normal subjects. Four paired muscles were recorded because of their antagonist function: 1) Orbicularis oris inferioris and depressor labii inferioris; 2) mentalis and buccinator. All patients evidenced well defined E.M.G. abnormalities. These consisted in the impairment of the functional organization of the antagonist muscles (lack of reciprocal inhibition), the existence of both a resting activity between utterances and a sustained hypertonic background activity during the utterance. This study was focused on the E.M.G. activity without concomitant observation of lip movement. Parallel oscillographic records of speech acoustic signals confirmed the characteristics of the voice of parkinsonian patients: low and uniform intensity, poor timbre, irregular speech rate and abnormalities of pitch.

Aged↗
PubMed1979

[Modification of the deep pineal after ablation of the superficial epiphysis in the golden hamster].

In various species (among Rodents: Mesocricetus auratus, Cricetus cricetus, Mus musculus, Meriones libycus, M. shawi et M. crassus; among Cheiroptera: Artibeus jamaicensis etc), the pineal complex is formed by two different portions one superficial situated under the cerebral dura and one deep portion situated between the habenular and posterior commissures. Superficial and deep portions are separated by a tractus of fibers and some pineal cells. Superficial epiphysectomy in the Mesocricetus auratus determines an increase in volume of the deep pineal. The nuclear diameter is also enlarged in this case. The functions of both superficial and deep pineal seem to be closely related. Superficial epiphysectomy is not followed by involution or hypoactivity of the deep pineal. Superficial epiphysectomy also determines changes in the subcommissural and subfornical organs.

Animals↗