PubMed Health⌕ Search

Biomedical subjects

V Georgieva

Publications and source records attributed to V Georgieva.

At least 19 recordsLinked to original sources
PubMed2006

Negative ion behavior in single- and dual-frequency plasma etching reactors: particle-in-cell/Monte Carlo collision study.

Particle-in-cell/Monte Carlo simulations are used to simulate the trajectories and energies of randomly sampled F- and CF-(3) ions in capacitively coupled radio-frequency discharges, in order to clarify the movement of the negative ions in the sheaths and plasma in both single- and dual-frequency regimes, as well as in symmetric and asymmetric discharges. In the single-frequency reactor both types of negative ions are confined in the plasma and the main loss mechanism is recombination with positive ions. In the dual-frequency reactor under certain operating conditions when the sheaths are wide and the bulk plasma is narrow the light F- ions move across from one sheath to the other, and they can even be lost at the electrodes. The main loss mechanisms are then electron detachment and absorption at the electrodes. The much heavier CF-(3) ions are still confined in the bulk and represent the major negative charge. In an asymmetric discharge the electric field in the sheath to the smaller (powered) electrode is much stronger than that in the sheath to the grounded electrode. Consequently, the F- ions reach mainly the grounded electrode.

Journal Article↗
PubMed2006

Spastin gene mutations in Bulgarian patients with hereditary spastic paraplegia.

Hereditary spastic paraplegia (HSP) is an extremely heterogeneous group of neurodegenerative disorders affecting the longest axons in the central nervous system. The most common genetic form accounting for about 40% of the autosomal-dominant HSP (ADHSP) cases is spastin gene, SPG4. We performed mutation screening of the spastin gene on 36 unrelated HSP patients from three different ethnic groups (Bulgarian, Turks and Gypsies) and found four new mutations and one already reported. The phenotype-genotype correlations in Bulgarian SPG4 patients showed a great difference in the age at disease onset between patients with missense mutations and those harboring deletions and splice-site mutations. Our study is the first to present corroborative clinical data in favor of the general hypothesis that the clinical course of the disease is related to the type of the spastin mutation. The clinical and genealogical findings in Bulgarian SPG4 patients suggest that a positive family history for inheritance as an autosomal-dominant trait is a strong indication for spastin mutation screening.

Adenosine Triphosphatases↗
PubMed2004

Numerical investigation of ion-energy-distribution functions in single and dual frequency capacitively coupled plasma reactors.

Ion-energy-distribution functions (IEDFs) are numerically investigated in capacitively coupled (cc) radio frequency (rf) Ar/CF(4)/N(2) discharges by a one-dimensional particle-in-cell/Monte Carlo model. The simulation considers electron-neutral collisions, various kinds of collisions of ions (Ar+, CF+3, N+2, F-, and CF-3) with neutral, positive-negative ion, and electron-ion recombination. The influence of pressure, applied voltage amplitude, and applied frequency on the Ar+, CF+3, and N+2 IEDFs is presented. The dependence on the frequency regime is investigated by simulations of the Ar/CF(4)/N(2) mixture in single (13.56 MHz) and dual frequency (2+27 MHz or 1+27 MHz) cc reactors. A comparison of the simulation results with analytical calculations in a collisionless rf sheath is discussed. The results show that the IEDFs shift toward the low energies with increasing pressure or decreasing applied voltage amplitude. The Ar+ and N+2 IEDFs exhibit secondary maxima due to the charge transfer collisions. The CF+3 IEDF has a peak at high energies in consistency with the average sheath potential drop. The IEDFs in the dual frequency regime are broad and bimodal.

Journal Article↗
PubMed2004

[Lansinoh in the treatment of sore nipples in breastfeeding women].

UNLABELLED: The aim of the study was to assess the efficacy and side effects of purified lanolin (Lansinoh) in the prophylactics and treatment of sore nipples. Fifty-seven women aged 20-35 years have been treated - 41 (72%) with phototype III-IV and 16 (28%) with phototype I-II. Thirty-seven (65%) of them were primiparous and 20 (35%) were multiparous. Pre-delivery preparation of the breast has been performed in 16 (28%) of the women. Two groups of patients were formed: I gr. - 10 women (17,5%) with no complaints applying the preparation with preventive aim and II gr. - 47 (82,5%) women with sore nipples of different severity. Therapeutic efficacy was assessed according to the nipple attribute score. In the first group of patients due to the application of Lansinoh the skin remained smooth and elastic and breast-feeding was not disturbed. In the II group Lansinoh lead to a statistically significant difference in the nipple attribute score before and after treatment. The improvement was most pronounced in patients with light and moderate forms of inflammation, in women with phototype III-IV, in multipara and in patients with pre-delivery preparation of the breast. CONCLUSION: Lansinoh is purified lanolin suitable for prophylactics and treatment of sore nipples.

Administration, Topical↗
PubMed2000

[The transfer of genes for Brown Rust resistance from Aegilops umbellulata Eig. to wheat (Triticum aestivum L.) genome].

The potential of a genome-substituted form Avrolata (AABBUU) as a genetic system in genomic and chromosome manipulations for gene transfer from the wild species Aegilops umbellulata Eig. (UU) to cultivated wheat was studied. It was shown that plants combining resistance to leaf brown rust with high productivity may be produced from this form by classical hybridization procedures. The resistance gene introduced to line R-12 is dominant and probably identical to the Lr9 gene. By N-banding, chromosome staining technique and gliadin electrophoresis, the structural changes in chromosomes 1A, 2A, 4B, 6B, 7B, 1D, and 2D of the resistant line R-12 were revealed.

Gene Transfer Techniques↗
PubMed1996

Gene mapping in Gypsies identifies a novel demyelinating neuropathy on chromosome 8q24.

Founder effect and linkage disequilibrium have been successfully exploited to map single gene disorders, and the study of isolated populations is emerging as a major approach to the investigation of genetically complex diseases. In the search for genetic isolates ranging from Pacific islands to Middle East deserts, the 10 million Gypsies resident in Europe have largely escaped the attention of geneticists. Because of their geographical ubiquity, lack of written history and the presumed social and cultural nature of their isolation, Gypsies are construed as not meeting the criteria for a well defined founder population. Gypsy society has a complex structure with subdivisions and stratifications that are incomprehensible to the surrounding populations. Marginalization by the health care systems in most countries results in a lack of information on causes of morbidity and mortality and little is known about hereditary disorders or the population genetic characteristics of Gypsies. This study is the first example of mapping a disease gene in endogamous Gypsy groups. Using lod score analysis and linkage disequilibrium, we have located a novel demyelinating neuropathy to a narrow interval on chromosome 8q24. We show that the disease, occurring in Gypsy groups of different identity and history of migrations, is caused by a single mutation whose origin predates the divergence of these groups.

Adolescent↗
PubMed1994

Comparative analysis of sister-chromatid exchanges in plant and human chromosomes.

Species specificity concerning the two main SCE characteristics, namely frequency and localization, of "spontaneous" SCEs in plant cells (root tips of Crepis capillaris) and in human lymphocytes was investigated under comparable conditions. The FPG technique was used for detection of SCEs after bifilar incorporation of BrdU into DNA (TB-BB). Data of parallel experiments showed that the frequency of SCEs in plant cells was considerably higher than that observed in human lymphocytes--13.2 and 7.3 SCEs per cell respectively. The difference was even more pronounced when the SCE frequency was estimated on the basis of DNA content/cell (pg). Analysis of SCE distribution was limited to SCEs localized in the centromere, since contradictory results most frequently concerned this chromosome region. The data of the present experiments showed that the frequency of SCEs localized in the centromere regions of plant chromosomes was considerably lower than that observed in human chromosomes. Compared with the relative sizes of the centromere regions in the two genomes, however, these frequencies proved to be quite similar. In both systems the centromeres were involved in SCE, as could be expected for random distribution, along the length of the chromosomes.

Bromodeoxyuridine↗
PubMed1993

[Changes in the cell cycle of cultured lymphocytes from patients subjected to halothane anesthesia].

The effect of halothane anesthesia on the proliferative activity of peripheral blood lymphocytes was analyzed. Included in the study were 7 patients. Lymphocyte cultures were prepared by standard methods with blood samples obtained immediately before the operation, after the effect of halothane anesthesia was over and 24 hours later. 5-bromodeoxyuridine in concentration 10 micrograms/ml was used for labelling cells which had passed 1, 2 or more mitotic cycles within the cultivation time. Cell proliferation rate was evaluated by the proportion of metaphases from I, II and III mitotic cycle. Lymphocyte proliferation in the cultures was shown to be inhibited after halothane anesthesia. Inhibition was particularly strong in the first post-halothane sample, but kept on being strong also 24 hours later. The first mitotic cycle was markedly prolonged--to such a degree that subsequent cycles within the 72-hour cultivation period were fully absent. The results were discussed in the light of the overall effect of halothane in the process of its metabolism, its effect on DNA synthesis and eventual implication of additional immunologic mechanisms.

Adult↗
PubMed1993

[The clastogenic effect of halothane on the lymphocytes from patients operated on under halothane anesthesia].

The clastogenic effect of halothane anesthesia on peripheral blood lymphocytes from operated patients was studied. Chromosomal aberrations and sister chromatic exchanges in lymphocyte cultures of 7 patients were analyzed. Blood samples were obtained before the operative intervention, immediately after the effect of anesthesia was over and 24 hours later. To differentiate sister chromatids in the culture medium, on the 24th cultivation hour bromodeoxyuridine in final concentration 10 micrograms/ml was added. Increased incidence of structural chromosomal aberrations was recorded in lymphocyte cultures of patients after anesthesia--6.43 per cent cells with aberrations in the first post-halothane culture and 8.28 per cent in the second. Comparison of the cell affection index with the total number of affected cells revealed a continuous clastogenic effect pattern within the study period. Reliable evidence for induction of sister chromatid exchanges after the anesthesia was not found. The results were debated in the light of the possible mechanisms of clastogenicity of halothane anesthesia, the initial state of the patients and the consequences for them.

Adult↗
PubMed1990

Genotoxic activity of benomyl in different test systems.

Benomyl (methyl-1-[butylcarbamoyl]-2-benzimidazole carbamate), a benzimidazole derivative fungicide, was tested in the Ames test for point mutations; in human lymphocyte cultures for cell division disturbances, chromosomal aberrations, and SCE; in rat bone marrow cells in vivo for micronuclei; and in rats in vivo for dominant lethals. Benomyl was negative in the Ames test. In human lymphocytes, benomyl at concentrations of 0.5, 1.0, and 2.0 micrograms/ml decreased the number of cells undergoing third division whereas at the concentrations of 0.25 to 4.0 micrograms/ml it strongly increased the number of aneuploid cells. Benomyl was also shown to induce sister chromatid exchanges and micronuclei but not chromosome aberrations. Benomyl decreased the number of female rats with implants but did not cause any dominant lethals.

Aneuploidy↗
PubMed1989

Cytogenetic investigations of human subjects occupationally exposed to chemicals from the petroleum-processing industry.

A cytogenetic investigation was carried out of 55 workers from the petroleum-processing industry and of 30 control subjects. The frequencies of both structural and numerical chromosome aberrations and of sister chromatid exchanges were determined simultaneously and the relationship among these cytogenic indices were analyzed. The incidence of chromosome aberrations and sister chromatid exchanges among the petroleum workers was higher than that among the controls. The cytogenic indices demonstrated a clear dependence on the working environment of the subjects and a correlation with the existence of some reproductive failures in the families of the exposed workers. Our results indicate the presence of some mutagenic risk in the working environment of some of the divisions in the petroleum-processing industry due to the genotoxic influence on the somatic cells of the exposed workers at a cytogenetic level. This potential risk is mainly associated with the presence of some heavy oil-fractions and polycyclic aromatic hydrocarbons in the working environment.

Adult↗