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M Charron

Publications and source records attributed to M Charron.

17 recordsLinked to original sources
PubMed1991

Chromosome recombination and defective genome segregation induced in Chinese hamster cells by the topoisomerase II inhibitor VM-26.

We found that 4'-demethylepipodophyllotoxinthenylidene-beta-D-glucoside (VM-26; Teniposide), which specifically inhibits the enzyme DNA topoisomerase II, induces the formation of quadriradial chromosomes in Chinese hamster ovary cells. VM-26 traps topoisomerase II molecules when they are covalently integrated into DNA during their reaction. Quadriradial chromosomes are formed by reciprocal exchange of double-stranded DNA between single chromatids of two different chromosomes. Using synchronised cells, we found that they were formed after a single replication cycle in the presence of VM-26 at a low concentration (0.008 micro M), which does not affect DNA replication, and occurred in 50% of the mitotic cells at a concentration of 0.16 micro M. They were also formed when VM-26 was present for only 1.5 h before mitosis, after the completion of S-phase DNA replication. Chromatids bearing a translocated segment of another chromatid, which were derived from recombined chromosomes, were observed in late metaphase cells. Segregation of the daughter genomes was defective in many mitotic cells, probably because chromatids with two or no centromeres and kinetochores, formed from chromosomes recombined between their centromeres, could not be segregated. In the light of evidence that topoisomerase II molecules covalently integrated in DNA are trapped and therefore more abundant in the presence of VM-26, and that this enzyme can effect recombination of double-stranded DNA in vitro, we interpret these observations as evidence that topoisomerase II can mediate chromosome recombination in vivo.

Animals↗
PubMed1991

Phantom kidney: a CT correlation.

The phantom kidney is a "kidney-like" apparition which may be seen in dynamic renal scintigraphy typically in post-nephrectomy patients or in patients with unilateral renal agenesis. We report a case of a phantom kidney demonstrated in the angiographic phase of renal scintigraphy with 99mTc-dimercaptosuccinic acid (99mTc-DMSA) in a patient who was nephrectomized 14 years previously. After comparison with the CT images, we conclude that our patient's finding was caused by an increased mesenteric vascularity, possibly postprandial. Several conditions which may cause the phantom kidney effect, have been reported, but increased mesenteric vascularity seems to be the most common cause.

Adult↗
PubMed1991

De novo mania among elderly people.

De novo mania is defined as the occurrence of a first manic episode in a patient with no history of mood disorder, after exclusion of organic etiologies. Although it is believed to be rare in elderly populations, the authors nonetheless report 6 cases encountered over a 2-year period. The literature regarding mania among elderly people is reviewed, and the authors formulate their recommendations in view of more frequent recognition and better management of these patients.

Aged↗
PubMed1991

A comparison of the renal effects (ERPF, GFR, and FF) of FK 506 and cyclosporine in patients with liver transplantation.

1. The mean "cost" in milliliters per minute of ESLD alone, prior to transplantation, was 35% + 23% (1 SD). In GFR it was 15%. 2. The additional burden of CyA + OLT increases the loss in ERPF an additional 18%; in GFR, it increases loss another 10%. Thus, the total loss in CyA-treated patients was 53% and 25%, respectively. 3. The decrease imposed by FK 506 + OLT on ERPF was only 7%, with no decrease in GFR. 4. Therefore, from the renal point of view, FK 506 would appear to be the superior drug. 5. The large error around mean values underlines the desirability of performing these tests on the individual patient rather than on information from groups, since many values fall near the threshold of the azotemic range (ERPF approximately 175 mL/min). 6. As renal mass was compromised, ie, fall in the ERPF, the GFR increased relatively, ie, the renal filtering membrane became more permeable and the FFs gradually increased. 7. The loss of renal function was significantly less in OLT patients on FK 506 than CyA. However, the greatest loss in expected renal function was due to the basic ESLD itself.

Adult↗
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↗