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Biomedical subjects

H Roman

Publications and source records attributed to H Roman.

At least 19 recordsLinked to original sources
PubMed1993

Relationships between cell surface protease and acid phosphatase activities of Leishmania promastigote.

A correlation between the ratio of the cell surface protease activity to phosphatase activity and the complexity of the pattern of cell surface exposed polypeptides of Leishmania promastigotes was demonstrated for various strains grown under similar conditions. The ratio of the cell surface protease activity to acid phosphatase activity was high for L. major and L.b. panamensis and it correlates with the expression of a single polypeptide of 63 KDa on their cell surface. Intermediate and lower ratios of these enzymatic activities relate with more complex radio-iodinated patterns: two main bands in L.b. guyanensis (70 and 58 KDa) and L.b. braziliensis (72 and 60 KDa) and three main bands 65, 50, 27 KDa in all L.m. mexicana strains tested. Evidence is presented that the acid phosphatase located on the L.m. mexicana cell surface is not an artifact due to a secondary absorption of the secreted acid phosphatase from the culture medium. These results confirm the Leishmania antigen cell surface heterogeneity. The implications on the biology of Leishmania and the clinical manifestation of leishmaniasis are discussed.

Acid Phosphatase↗
PubMed1990

Mechanisms of gene conversion in Saccharomyces cerevisiae.

In red-white sectored colonies of Saccharomyces cerevisiae, derived from mitotic cells grown to stationary phase and irradiated with a light dose of x-rays, all of the segregational products of gene conversion and crossing over can be ascertained. Approximately 80% of convertants are induced in G1, the remaining 20% in G2. Crossing over, in the amount of 20%, is found among G1 convertants but most of the crossovers are delayed until G2. About 20% of all sectored colonies had more than one genotype in one or the other sector, thus confirming the hypothesis that conversion also occurs in G2. The principal primary event in G2 conversion is a single DNA heteroduplex. It is suggested that the close contact that this implies carries over to G2 when crossing over and a second round of conversion occurs.

Chromosomes, Fungal↗
PubMed1984

Gene conversion at different points in the mitotic cycle of Saccharomyces cerevisiae.

In the Saccharomyces cerevisiae mitotic cycle, the timing of radiation-induced gene conversion has been studied using thermosensitive cell division cycle mutants. The cells were found to perform conversion at different G1 or post-replication steps. A lower yield in induction is found during the G2 phase and is explained by the competition for recombinational repair between sister chromatids and homologous chromosomes. The results are discussed in relation to repair.

Alleles↗
PubMed1983

Gene conversion and associated reciprocal recombination are separable events in vegetative cells of Saccharomyces cerevisiae.

Mitotic gene conversion occurs in both the G1 and G2 phases of cell growth. We postulate that the DNA strand or strands that connect the duplexes in G1 as a consequence of strand transfer are cleaved by an endonuclease. When this takes place in G1, crossing-over occurs in G2 at a frequency that is higher than would be expected from independent events. Conversion and associated reciprocal recombination are therefore separable with respect to the stage in the cell cycle when each occurs and possibly with respect to mechanism.

Cell Cycle↗
PubMed1980

Boris Ephrussi.

Explore the source record for details and available documents.

Animals↗
PubMed1979

Evidence that a single DNA ligase is involved in replication and recombination in yeast.

The possible existence in yeast of different nuclear DNA ligase enzymes led us to ask whether induced recombination (gene conversion) involves the same ligase as that involved in DNA replication. The conditional cdc9 mutant is known to be defective, under restrictive conditions, in the rejoining of Okazaki fragments. We show here that under the same conditions, x-ray-induced convertants within the cdc9 locus are produced with kinetics indicating that most, if not all, of the conversion events require the participation of the cdc9-controlled ligase. Thus, the same DNA ligase is involved in DNA replication and in induced gene conversion.

DNA Ligases↗
PubMed1978

Protein synthesis by synaptosomes from rat brain: the effect of centrifugal forces.

1. Synaptosomal protein synthesis has been found to differ depending on whether synaptosomes are recovered from the sucrose gradients by centrifuging at 20,000 g or at 150,000 g. 2. The fraction obtained at 20,000 g incorporated 60% more amino acid into proteins after 30 min of incubation than the one obtained in the same period of time at 150,000 g. 3. The respiratory capacity of synaptosomes obtained at 20,000 g in the presence or absence of glucose as substrate, is also better preserved than that of those obtained at 150,000 g. 4. It is shown that the yield, enzymic content, and nucleic acid composition is the same in both fractions. 5. These results cannot be explained by the presence of inhibitory factors in the 150,000 g fraction or by the presence of better preserved free mitochondria in the 20,000 g fraction. 6. Our findings are best explained by postulating that the synaptosomal metabolic activity is damaged when synaptosomes are pelleted at too high a speed.

Acetylcholinesterase↗
PubMed1977

Genetic evidence for inducibility of recombination competence in yeast.

Recombination between unirradiated chromosomes was induced by UV or x-ray irradiation of haploids followed by a mating with heteroallelic diploids of Saccharomyces cerevisiae. The selected event of intragenic recombination did not involve the participation of the irradiated chromosome and apparently was not caused by lesions introduced into the unirradiated chromosomes by some indirect process. The results favor the idea that recombination is repressed in the majority of vegetative cells and that one effect of radiation is the release of some factor(s) necessary for recombination. Consequently, the proportion of competent cells (i.e., cells able to recombine) in the population increases. This competent state seems necessary not only for the recombinational repair of radiation-induced lesions but also, since recombinants are produced in the absence of such lesions, for spontaneous recombination. Photoreactivation of the UV-irradiated haploids led to a decrease in the production of recombinants. Hence, lesions in the DNA appear to be responsible for the induction of the recombinational ability.

Chromosomes↗
PubMed1976

Recombination in Saccharomyces cerevisiae: a DNA repair mutation associated with elevated mitotic gene conversion.

A mutant haploid strain of Saccharomyces cerevisiae has been isolated that is sensitive to the alkylating agent methyl methanesulfonate at a concentration of 0.01% (vol/vol). The strain also shows sensitivities to x-rays and ultra-violet light, which cosegregate with sensitivity to methyl methanesulfonate as a single gene defect. An analysis of the sensitivity to ultraviolet light indicates that the mutation interferes with the excision of pyrimidine dimers. Diploids homozygous for the mutant gene exhibit elevated frequencies of spontaneous mitotic recombination at the ade6 locus. The results indicate that all the events are due to gene conversion. Mitotic recombination was also found to be elevated for three loci other than ade6. Thus, the recombinational effect seems not to be locus specific. Linkage and allelism tests indicate that the mutation is an allele of the known radiation-sensitive gene rad18. The various effects of this new rad18 allele (rad18-3) are discussed in terms of a defect in DNA repair mechanisms.

Alleles↗
PubMedDate not supplied

[Breast cancer in men].

In 20 years we registered 10 observations of male breast cancer (MBC), representing 1.3% out of 767 patients with breast cancer. Two observations of gynecomastia have been noted as a possible risk factor for MBC. A tumoral mass behind the areola suggested the diagnosis in 9 patients, whether in one case the attention was drawn by a bloody nipple discharge. In 3 cases we noted local aggravation clinical signs, and 6 observations presented homolateral palpable adenopathy. Diagnosis was completed by radiology, scintigraphy and pathology. As for clinical staging, we had 1 case in stage I,3 patients in stage II, 5 in stage III and I case in stage IV. Surgical treatment was the major therapeutical mean of the complex oncological procedure. We performed radical mastectomy in 4 cases. MBC prognosis was poor. Only one patient of the 6 ones in stage III and IV survived to five years; among other 4 observations in stage I and II, 2 patients have survived to five years, and other 2 being followed-up through the oncological network.

Aged↗
PubMedDate not supplied

[Difficult laparoscopic cholecystectomy].

The study analyses different situations encountered throughout the authors personal operative experience, susceptible to generate technical and tactical difficulties during laparoscopic cholecystectomy such as: postoperative perivisceritis, obesity, difficult liver mobilization, lipomatosis, acute and scleroatrophic cholecystitis, "porcelain gallbladder". They also point out different causes capable of generating important bleeding during the operation: cirrhosis, accidental adhesion tearing, anatomical arterial variations. Above all, the study presents the possible technical and tactical solutions which they applied when dealing with the already mentioned critical situations.

Acute Disease↗
PubMedDate not supplied

[Treatment with Ginkor Fort in varicose veins].

The study shows the experience acquired in our clinic concerning Ginkor fort administration in varicose veins pathology. The research comprises 32 patients who were treated by the well-known classical procedures (hygienic-dietetic, contention, surgery) and by Ginkor fort administration. The study rendered 71% good results consisting in evident amelioration of symptomatology, both subjective and objective.

Adult↗