Search PubMed⌕ Search

Biomedical subjects

M Charron

Publications and source records attributed to M Charron.

67 records · Page 4Linked to original sources
PubMed1990

DNA topoisomerase II is required for formation of mitotic chromosomes in Chinese hamster ovary cells: studies using the inhibitor 4'-demethylepipodophyllotoxin 9-(4,6-O-thenylidene-beta-D-glucopyranoside).

To study the biochemical processes which DNA topoisomerase II carries out in mammalian cells, which have not been identified, we have examined the effects on chromosome replication in Chinese hamster ovary cells of an agent which traps molecules of topoisomerase II when they are covalently integrated into DNA during their reaction. This agent, 4'-demethylepipodophyllotoxin 9-(4,6-O-thenylidene-beta-D-glucopyranoside) (VM-26), targets this enzyme specifically according to a compelling body of evidence. Using synchronously growing cells, we found that VM-26 at a cytotoxic concentration (0.08 microM) did not affect DNA replication during the S phase. The formation of mitotic chromosomes was delayed by 4 h, and its rate was reduced thereafter, causing a delay in mitosis of greater than 14 h in 65% of the cells; in some cells, the chromatin was aberrantly condensed, forming diffuse chromosomes or particles. Chromosome formation was completely inhibited at 0.32 microM VM-26. DNA fragments derived from topoisomerase II molecules covalently integrated in DNA and trapped by VM-26 were detected by FIGE analysis in the G2 period, but not during the S phase. The delay of chromosome formation appeared to be caused by two factors: first, a delay in the completion of DNA replication, because progress of some cells to mitosis after removal of VM-26 was prevented by aphidicolin, an inhibitor of DNA polymerases alpha and delta; and second, a delay of chromosome formation in cells which had apparently completed DNA replication. The observations reported here show that topoisomerase II carries out reactions which are essential for formation of mitotic chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Quantitative thallium imaging.

There has been much recent interest in quantitative interpretation of 201thallium myocardial imaging. Quantitative analysis can be used as an aid in the more accurate interpretation of myocardial scans. Quantitative analysis is essential to extract information about the kinetics of thallium redistribution. This article briefly reviews the mechanism of uptake and redistribution of 201thallium in the heart and the effect of dipyridamole on uptake and redistribution. Several of the algorithms that have been used to quantitate 201thallium distribution and kinetics on planar studies and the value of quantification on diagnostic accuracy are described. Proper utilization of these methods depends upon a complete understanding of the assumption and the limitations of these algorithms.

Coronary Disease↗
PubMed1988

Focal lung uptake of gallium-67 in patients with acquired immunodeficiency syndrome secondary to pneumocystis carinii pneumonia.

It is generally accepted that the lung uptake of 67Ga in patients with pneumocystis carinii pneumonia (PCP) is diffuse and bilateral. Three cases of focal lung uptake of 67Ga in AIDS patients with PCP but without other opportunistic infection are described. While focal lung uptake is characteristic of opportunistic infections other than PCP, we wish to emphasize that focal uptake of gallium in the chest does not rule out PCP and may represent its earliest stage of presentation.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Viral encephalitis: imaging with SPECT.

SPECT brain imaging performed in two patients with presumed herpes encephalitis demonstrated greater sensitivity and more precise localization than either planar brain imaging or CT scanning.

Adult↗
PubMedDate not supplied

LISS--an effective way to increase blood utilization.

The low ionic strength solution (LISS) of Low and Messeter was compared with both the automated low ionic strength Polybrene and the manual IDAT techniques. A five minute incubation with the LISS was sufficient to detect all significant antibodies. By extending the incubation period to 15 minutes it was possible to increase the sensitivity of the reaction (as measured by titer) beyond that of either of the other methods. This LISS procedure has enabled us to greatly extend the applications of a "standby procedure" for elective surgery. In this procedure routine crossmatching is not done. Rather, the blood is placed on standby and if required, transfusion is provided by using the LISS. In one general hospital this resulted in the reduction by 1,600 units of unneccessary crossmatches and an increase of 10% in the total blood utilization rate over a nine-month period.

Antibodies↗
PubMedDate not supplied

Assessment of biventricular cardiac function in patients with a Novacor left ventricular assist device.

Novacor left ventricular assist devices were implanted in 10 patients. We used blood-pool radionuclide angiography and echocardiography to evaluate the response of the left and right ventricle to the left ventricular assist. Radionuclide angiography was done before and after implantation of the Novacor left ventricular assist devices in all cases. All patients had diffuse left ventricular enlargement; the mean left ventricular ejection fraction before Novacor left ventricular assist device implantation was 17% +/- 7%. After implantation of the Novacor left ventricular assist devices the left ventricular ejection fraction improved to 47% +/- 19%, with the pump on a 1:1 assist ratio (p < 0.005). The right ventricular ejection fraction before the Novacor left ventricular assist device implantation was 21%, which improved to 32% with the Novacor left ventricular assist devices (p < 0.01). Doppler echocardiography was carried out in nine patients with the left ventricular assist devices. In five patients the aortic valve remained closed throughout systole. In four patients partial aortic valve opening was noted. At an assist ratio of 1:3, complete opening of the aortic valve was noted in all cases (n = 9); the left ventricular ejection fraction decreased to 31%. We conclude that the Novacor left ventricular assist device substantially improves both right ventricular ejection fraction and left ventricular ejection fraction, although the aortic valve typically remains closed.

Echocardiography↗