Search PubMed⌕ Search

Biomedical subjects

A Chartier

Publications and source records attributed to A Chartier.

6 recordsLinked to original sources
PubMed1998

A Drosophila RNA helicase gene, pitchoune, is required for cell growth and proliferation and is a potential target of d-Myc.

This article describes the characterization of a new Drosophila gene that we have called pitchoune (pit) (meaning small in Provence) because mutations in this gene produce larvae that cannot grow beyond the first instar larval stage although they can live as long as 7-10 days. All the tissues are equally affected and the perfectly shaped larvae are indistinguishable from first instar wild-type animals. Analysis of mutant somatic clones suggests a function in cell growth and proliferation, which is supported by the fact that cell proliferation is promoted by pit overexpression. Tagged-Pit, when transfected in S2 cells, localizes mainly to the nucleolus, pointing towards a possible role in ribosome biogenesis and, consequently, in protein biosynthesis. pit encodes a DEAD-box RNA helicase, a family of proteins involved in the control of RNA structure in many cellular processes and its closest homologue is a human DEAD-box RNA helicase, MrDb, whose corresponding gene transcription is directly activated by Myc-Max heterodimers (Grandori, C., Mac, J., Siëbelt, F., Ayer, D. E. and Eisenman, R. N. (1996) EMBO J. 15, 4344-4357). The patterns of expression of d-myc and pit are superimposable. Ectopic expression of myc in the nervous system drives an ectopic expression of pit in this tissue indicating that in Drosophila as well, pit is a potential target of d-Myc. These results suggest that myc might promote cell proliferation by activating genes that are required in protein biosynthesis, thus linking cell growth and cell proliferation.

Amino Acid Sequence↗
PubMed1995

Accurate measurements of organic dye solutions by use of pulsed laser photothermal deflection spectroscopy.

Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothermal signals magnitudes when pulsed laser excitation is used. These anomalous signals can be due to optical bleaching of the electronic singlet states with subsequent optical absorption within the triplet spin state manifold. A model based on excitation and excited state relaxation rate expressions is derived and applied to the analysis of excitation laser irradiance-dependent photothermal signal magnitude data. The model is found to fit the experimental results very precisely. It is subsequently used to correct the photothermal signal at high irradiances and to deduce photodynamic parameters from the studied molecule. Regression of the model to the excitation irradiance-dependent data allows determination of the T2-->T1 relaxation rate constant and the triplet state cross absorption section. Model regression is applied to the analyses of erythrosin in water and ethanol solvent and of eosin and 1,1'-diethyl-2,2'-cyanine iodide dyes in ethanol solutions. A method for quantitative determination of analyte concentration is developed.

Coloring Agents↗
PubMed1994

[What is the place of conventional radiology in the exploration of esophageal dyskinesia and hiatal hernia?].

Esophageal dyskinesias are due to various aetiologies and sometimes present with marked clinical symptoms. The barium swallow remains the preferred first-line examination. Upper GI endoscopy and manometry are useful to confirm the functional nature and eliminate any concomitant or secondary mucosal lesions of these motor disorders. The clinical signs of hiatus hernia are essentially due to complications related to gastro-esophageal reflux. They can be asymptomatic or may present in the form of atypical, sometimes extra-gastrointestinal, symptoms. Although conventional radiology allows the diagnosis of hiatus hernia by specifying the type, the morphology and the anatomical relations, it may fail to detect the consequences of gastro-esophageal reflux, especially ulcerated lesions. Upper gastrointestinal endoscopy appears to be the first-line examination of choice for the diagnosis of hiatus hernia. Barium swallow is useful in cases of failure of endoscopy and in the context of preoperative assessment, as these two investigations are often complementary.

Esophageal Achalasia↗
PubMed1994

[Megaesophagus].

Although it was first described a long time ago, the pathophysiology of megaesophagus, a primary esophageal motor disorder due to an abnormality of the esophageal sphincter reflex ("achalasia"), remains poorly understood. Our paper shows that it may also be missed clinically for a long time, sometimes for psychological reasons.

Adult↗