Biomedical subjects

T Nikolova

Publications and source records attributed to T Nikolova.

18 recordsLinked to original sources

PubMed2001

Frequency of HPRT mutants in humans exposed to vinyl chloride via an environmental accident.

The mutant frequency (MF) in the hypoxanthine-guanine-phosphoribosyl-transferase (HPRT) locus of peripheral blood T-lymphocytes was measured in a population environmentally exposed to vinyl chloride - a toxic and carcinogenic substance through an accidental release into the atmosphere. It was compared to MF in a control group of unexposed individuals. Both groups were re-investigated in a follow-up study, 2 years later. No significant difference could be observed in MF between exposed and controls either at the accident nor in the follow-up study. Approximately the same mean HPRT mutant frequencies were observed for both groups in T-lymphocytes from blood samples obtained shortly after the accident and from the follow-up blood samples. Both groups showed a higher mean MF in the re-investigation samples which is most probably due to the significantly lower average cloning efficiency (CE) under non-selective conditions and because of the inverse relationship between CE and MF. The exposed population showed a higher mean T-cell CE at the initial blood sampling as compared to the control group. The concurrent cytogenetic analyses of peripheral lymphocytes showed a significant increase in cells with aberrations in the exposed population. Clastogenic but not mutagenic activity of vinyl chloride was observed in our study.

Adult↗

PubMed1999

Chromosomal aberrations in humans as genetic endpoints to assess the impact of pollution.

The chromosomal aberration assay with peripheral blood lymphocytes has been used routinely during the last three decades to survey exposure of humans to various genotoxic agents. A large number of biomonitoring studies are based on this genetic endpoint. A great deal of data exists on occupational, life-style or medical exposure situations but less evidence of the validity of the assay is available with regards to environmental exposure. In the present paper we report our investigations on the impact of pollution in two different populations using chromosomal aberrations in human peripheral blood lymphocytes as a biomarker of chronic exposure to heavy metals and dioxins/furans for a long period and as a biomarker of acute exposure to accidentally released vinyl chloride in the air. In order to study genotoxic effects (chromosomal aberrations) of heavy metals and dioxins/furans, 52 exposed individuals from a polluted area were compared to 51 matched controls from a distant non-industrialized area. A statistically significant increase was observed in the frequency of chromosomal aberrations in peripheral blood lymphocytes from the exposed population (1.90% aberrant cells vs. 1.11% for the controls). In the case of the vinyl chloride accident, chromosomal aberrations were analyzed in peripheral blood lymphocytes from 29 potentially exposed and 29 non-exposed individuals (matched controls). The exposed group showed a statistically significant increase in the frequency of aberrant cells (1.47% vs. 1.07% for the controls).

Accidents, Occupational↗

PubMed1999

A follow-up study on chromosomal aberrations in lymphocytes of alcoholics during early, medium, and long-term abstinence.

The frequencies of structural chromosomal aberrations were analyzed in peripheral blood lymphocytes of 31 chronic alcoholics at the beginning of an intensive outpatient treatment program at a neuropsychiatric clinic and were compared with 31 controls matched for gender, age, smoking habits, and nondrinkers. A statistically significant difference was observed in the level of chromosomal aberrations in somatic cells from alcoholics when compared with controls (3.01% vs. 1.28%, p < or = 0.001). A follow-up study was carried out for a subset of the patients after 3 months (8 subjects) and 12 months (14 subjects) of controlled abstinence. A statistically significant increase in the mean frequency of cells with aberrations was observed in the group of 14 subjects reinvestigated after 12 months of abstinence when compared with the mean value of the first blood samples immediately after hospitalization (4.61% vs. 3.01%; p < or = 0.001). An excessive increase in cigarette consumption during alcohol abstinence, reflected by a dramatic elevation of CO-hemoglobin levels, may, at least in part, account for this finding. In conclusion, chronic alcoholism leads to genotoxic effects that, instead of recovering after 1 year of alcohol abstinence, are even enhanced, most likely due to the "shift in addictive behavior."

Adult↗

PubMed1998

Cytogenetic analysis of peripheral lymphocytes in a population exposed to vinyl chloride through an accidental release into the environment.

On the first of June, 1996 an environmental accident occurred in Schönebeck, Germany in which free vinyl chloride was evaporated into the atmosphere. Thereby, the human population living in this area was exposed to vinyl chloride and its byproducts. Chromosomal aberrations were measured in peripheral blood lymphocytes from 29 potentially exposed and 29 non-exposed (control) individuals. Both groups were matched regarding age, gender and smoking habits. Two hundred metaphases were analysed for chromosomal aberrations per each individual. The exposed group showed a statistically significant increase in the mean frequency of aberrant cells (1.47% versus 1.07% in the control group). Chromosomal aberrations in peripheral lymphocytes have been shown to be a very sensitive biomarker of genotoxic effects not only for occupational exposure to vinyl chloride as reported several times during the last 20 years, but also for an accidental environmental exposure. A follow-up cytogenetic study is recommendable.

Accidents, Occupational↗

PubMed1996

Adaptive and synergistic effects of a low-dose ENU pretreatment on the frequency of chromosomal aberrations induced by a challenge dose of ENU in human peripheral blood lymphocytes in vitro.

N-Ethyl-N-nitrosourea (ENU) is an alkylating agent whose mutagenic and carcinogenic potential has been extensively studied but its ability to induce cytogenetic adaptive responses in normal human cells has not been investigated so far. The aim of our present experiments was to study the effect of a pretreatment with a low concentration of ENU (2 x 10(-5) M) on the frequency of chromosomal aberrations induced by a subsequent 50 times higher concentration of ENU (10(-3) M) in human lymphocytes isolated from buffy coats of 4 donors. Two different inter treatment times and three harvesting times were applied to the lymphocytes from each donor. A cytogenetic adaptive response was shown by the lymphocytes of one donor only when the time span between the low adapting and the higher challenging concentration was 4 h. The other three donors did not respond with significant differences in the yield of cells with aberrations. The complex interaction between the ENU-induced multiple primary DNA lesions and various DNA repair mechanisms as well as the influence of cell cycle effects on the induction of clastogenic adaptive response are discussed.

Alkylating Agents↗

PubMed1992

Plant extracts induce chromosome aberrations and sister-chromatid exchanges in Chinese hamster ovary cells and human lymphocytes.

Effects of extracts from Vicia faba were compared with those of Zea mays for the induction of sister-chromatid exchanges (SCEs) and of chromosome aberrations (CAs) in Chinese hamster ovary (CHO) cells. CA induction by the maize extract was also tested in human lymphocytes. The extracts from roots and leaves of Vicia faba induced CAs and SCEs in CHO cells. The extracts from maize leaves also induced SCEs and CAs in CHO cells, and CAs in human lymphocytes. Maize extracts were more potent in inducing SCEs than Vicia extracts and the SCE- and CA-inducing capacity of maize extracts decreased during preincubation before addition to cells.

Adult↗

PubMed1979