Biomedical subjects

M Leon

Publications and source records attributed to M Leon.

203 records · Page 12Linked to original sources

PubMedDate not supplied

Augmentation of the expression of proangiogenic genes in cardiomyocytes with low dose laser irradiation in vitro.

BACKGROUND AND OBJECTIVE: Several reports suggest that low power red laser light (LPRLL) is capable of affecting cellular processes in the absence of significant thermal effect. The objective of the present study was to determine the effect of LPRLL on proliferation of fetal cardiomyocytes in vitro and on the expression of proangiogenic genes, transforming growth factor-beta (TGF-beta), and vascular endothelial growth factor (VEGF). STUDY DESIGN/MATERIALS AND METHODS: All cell cultures were irradiated with single-dose LPRLL using a He-Ne continuous wave laser (632 nm) with different doses. The effect of LPRLL on new DNA synthesis was studied by 3H thymidine-incorporation assay. VEGF and TGF-beta expression by cardiomyocytes was studied by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: We observed that a dose-dependent increase in cardiomyocytes proliferation can be obtained with LPRLL and that there is a significant increase in VEGF and TGF-beta mRNA expression by cardiomyocytes. CONCLUSIONS: These data may have significant importance leading to the establishment of new methods for myocardial photoangiogenesis and photoregeneration as well as in vitro proliferation of cardiac myocytes.

Base Sequence↗

PubMedDate not supplied

Effects of intracoronary radiation on thrombosis after balloon overstretch injury in the porcine model.

BACKGROUND: The main complications of PTCA remain thrombosis and restenosis. Recent studies have demonstrated reduction in the neointimal hyperplasia after intracoronary radiation (IR) with doses of 10 to 25 Gy of ionizing radiation delivered by either beta- or gamma-emitters to injured vessels. The purpose of this study was to examine the effect of ionizing radiation on the thrombosis rate (TR) of injured porcine coronary arteries. METHODS AND RESULTS: Thirty-four juvenile swine (63 coronary arteries) were subjected to overstretch balloon injury followed by IR with doses of 0 to 18 Gy of either beta- or gamma-radiation. Two weeks after treatment, tissue sections were perfusion-fixed, stained with hematoxylin-eosin and Verhoeff-van Gieson's stain, and analyzed for presence of a thrombus, thrombus morphology, and neointima formation by computer-assisted histomorphometry techniques. Although the overall TR increased dose-dependently from 0 to 18 Gy prescribed dose, luminal thrombi decreased. Thrombus area also decreased with increasing radiation dose, whether assessed at the prescription point or at the luminal surface, which corresponded to decreased intimal area. Furthermore, luminal thrombi present after IR tended to consist mostly of fibrin and thus were less organized than in controls. CONCLUSIONS: These results suggest that IR induces thrombosis but does not necessarily compromise the lumen. Strategies for reducing TR may further decrease intimal area as well as increasing the safety of this therapy.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

Hormonal regulation of rat testicular gamma-glutamyl-transpeptidase "in vivo" and "in vitro".

The hormonal regulation of gamma-glutamyl transpeptidase (gamma-GTP), an enzyme marker of Sertoli cells, was studied in immature rats that received 50 micrograms/day of testosterone propionate (TP) during 6 days to suppress pituitary LH and FSH. Suppression of LH was monitored indirectly by the determination of intratesticular levels of testosterone and suppression of FSH by radioimmunoassay of serum FSH. Enzyme activity in the testis decreased in parallel to intratesticular testosterone suppression, and it did recover up to control values when animals received 500 micrograms/day of TP, a dose that was able to maintain intratesticular testosterone at normal levels. beta-glucuronidase, another enzyme marker of Sertoli cells, was not affected by these treatments. A significant decrease in gamma-GTP was detected 24h after significant suppression of intratesticular testosterone and it returned to control levels 2 days after increasing the dose of TP to 500 micrograms/day. Administration of FSH to rats with depletion of intratesticular testosterone was able to maintain testicular gamma-GTP at control levels. An stimulatory action of FSH could also be demonstrated in primary Sertoli cell cultures. It is concluded that testicular gamma-GTP is under the regulation of both androgens and FSH while beta-glucuronidase is not. Eventhough the function of gamma-GTP in the testis is not known, the key role that it plays in other tissues suggests that it might be important in the regulation of Sertoli cell-germ cell interactions.

Animals↗

PubMedDate not supplied

Analysis of ras gene mutations in hepatocellular carcinoma in southern African blacks.

Paired samples of hepatocellular carcinoma and non-tumorous liver tissue from 12 southern African blacks were examined for mutations in codons 12, 13, and 61 of the three ras proto-oncogenes (H-, K-, and N-ras). Deoxyribonucleic acid was isolated from carcinoma and non-tumorous tissues and amplified with the polymerase chain reaction. Using the single-stranded conformational polymorphisms method, products of the polymerase chain reaction amplification of codons 12, 13, and 61 of H-, K-, and N-ras were analysed for mutations. Mobility shifts were not detected except in one tumour in the region of codon 61 of K-ras. By sequencing the relevant polymerase chain reaction products, this sequence of deoxyribonucleic acid was proved to be normal, indicating that the single-stranded conformational polymorphisms result was an artifact of the polymerase chain reaction. Thus, no mutations were detected in the regions of interest in any of the tumours studied. These results indicate that activation of ras proto-oncogenes by mutations in codons 12, 13, and 61 does not play an important role in hepatocellular carcinogenesis in southern African Blacks despite the fact that dietary exposure to aflatoxin B1 is a risk factor in this population.

Artifacts↗

PubMedDate not supplied

Loss of heterozygosity in chromosome 4q12-q13 in hepatocellular carcinoma in southern African blacks.

Paired samples of hepatocellular carcinoma and non-tumorous hepatic tissue from 12 southern African blacks were examined for loss of heterozygosity at two loci (D4S409 and D4S392) in chromosome 4q12-q13 (mapping to the same region as the locus for the gene for alpha-fetoprotein). Deoxyribonucleic acid was extracted from carcinoma and non-tumorous tissues and amplified using the polymerase chain reaction. The primers used were based on flanking regions of minisatellite DNA specific for the loci. Products of PCR amplification were separated by denaturing polyacrylamide gel electrophoresis and analysed for allelic losses. At the D4S409 locus one of seven informative samples showed loss of heterozygosity, whereas none of eight informative samples showed loss of heterozygosity at the D4S392 locus. If these findings are considered together with those previously reported in hepatocellular carcinomas from black Africans, the prevalence of loss heterozygosity in chromosome 4q12-q13 in hepatocellular carcinoma in southern African blacks (33 per cent) is the same as that in tumours from Japanese patients. Loss of heterozygosity at chromosome 4q12-q13 is infrequent during hepatocellular carcinogenesis in southern African blacks.

Alleles↗