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G Giraud

Publications and source records attributed to G Giraud.

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

Molecular study of the retrovirus-like transposable element 412, a 20-OH ecdysone responsive repetitive sequence in Drosophila cultured cells.

Used at a physiological concentration, the steroid hormone 20-hydroxyecdysone (20-OHE) induces, in Kc cultured Drosophila melanogaster cells, important and specific changes. Modifications occur at morphological and enzymatical levels. Variations in specific protein synthesis are observed. At the molecular level, 20-OHE particularly induces a decrease in expression of the mobile dispersed genetic element 412. This repeated element which belongs to the "copia-like" family is more widely represented in Kc cells (80 fold) compared to fly cells (25 fold). 412 transcripts are heterogeneous in size, essentially polyadenylated and restricted to the nucleus. A minimal concentration of 10(-8) M and a time treatment of 16 hours are necessary to obtain a strong decrease in 412 expression. The decrease is at least an effect on these sequences at the transcriptional level. Structural similarities between the 412 element and the proviral forms of vertebrate retroviruses are strengthened by the characterization of extrachromosomal circular DNA forms revealed by the 412 probe. Quantifying experiments have shown that the steady state level of such forms is not affected by the steroid treatment.

Animals↗
PubMed1985

[Radiologic diagnosis of acoustic neurinoma. Apropos of 130 patients].

Diagnostic value of radiologic examinations was assessed in a homogeneous series of 130 cases of neurinoma of acoustic nerve seen over the last 10 years. Radiologic exploration is conceived and used at the present time for two purposes. Firstly, it enables selection of patients with suspected acoustic nerve neurinoma. Radiotomography appears to be currently an accessory examination because of the discriminative performance of early auditory evoked potentials tests on the brain stem. Secondly, radiology is necessary for confirmation of diagnosis. Visualization of the tumoral syndrome can be obtained only by a scan or possibly opaque or gas meatocisternography.

Brain Stem↗
PubMed1983

Actin gene expression is modulated by ecdysterone in a Drosophila cell line.

The steroid hormone ecdysterone induced characteristic and specific changes of morphology, enzymatic activities and protein synthesis in a Kc 0% Drosophila melanogaster cell line. To study the ecdysterone action at a molecular level, a Drosophila genomic library was screened by differential hybridization to poly(A)+ RNA from control and ecdysterone-treated cells. Two recombinant phages were selected for hybridizing very intensively with poly(A)+ RNA of ecdysterone-treated cells and very weakly with poly(A)+ RNA of untreated ones. These two clones (lambda Dm 1632 and lambda Dm A5A1) mapped at the 5 C locus on polytene chromosomes; they overlap for a 9000 base-pair sequence that contains an abundantly transcribed region in ecdysterone-treated cells of about 2000 base-pairs. This region permits the selection of mRNA that gives, after translation in vitro, two polypeptides identified as cytoplasmic actin II and III. We demonstrated that these two recombinant phages, hybridizing preferentially with poly(A)+ RNA of ecdysterone-treated cells, contain the 5 C actin gene. Poly(A)+ RNA prepared from various times of treatment of cells were electrophoresed on agarose gels, transferred to nitrocellulose paper and then hybridized with the cloned actin probe. Results of these experiments indicate that there is a sharp increase in the level of RNA coding for actin after ecdysterone treatment of the cell, and that there are two forms of actin-specific RNA in the D. melanogaster cells. Using genomic blots with specific probes derived from lambda Dm 1632, we show that there are six actin genes per haploid Drosophila cell genome contained on six EcoRI fragments, as in Drosophila embryos, indicating that there is no rearrangement of these sequences in cultured cells. Our results suggest that the expression of actin genes in D. melanogaster Kc 0% cells is modulated by ecdysterone.

Actins↗
PubMed1980

Use of a specific mesenteric vasodilator peptide, urotensin I, to reduce afterload in the dog.

The authors have previously demonstrated that urotensin I, a peptide derived from the urophysis of bony fish, reduced arterial blood pressure of anesthetized dogs by selective dilation of the mesenteric vascular bed. In the present experiments, intravenous infusions of urotensin I produced a sustained increase in cardiac output and decrease in peripheral resistance. The magnitude of the hypotensive response and of reflex effects on the heart appeared to be limited quantitatively by the unique mechanism of action. Coronary artery flow was maintained in spite of a decrease in coronary filling pressure, presumably as a consequence of coronary autoregulation and the increased cardiac output. No direct cardiac effects were observed on close-arterial injection into a coronary artery. An agent with these characteristics which will decrease left ventricle afterload is of interest in the management of myocardial failure and possibly of cardiogenic shock. In dogs in which minimal myocardial injury was produced by injection of thrombin into a coronary artery, intravenous infusions of urotensin I restored minimal but statistically significant elevations in right and left ventricular end-diastolic pressures to preinsult levels.

Animals↗