Siddharth G. Adhvaryu

Assessment of genotoxicity of nicotine employing in vitro mammalian test system

Genotoxicity of nicotine was evaluated employing Chinese hamster ovary (CHO) cells. Two cytogenetic endpoints, viz. frequency of sister chromatid exchange (SCE) and chromosome aberration (CA) were considered. Nicotine was found to induce CA and SCE frequency in a dose and duration dependent manner. Statistically significant elevations in CA frequency were observed only with higher concentrations of nicotine, whereas, SCE frequencies were increased significantly by all the doses utilized. It was genotoxic at the concentration, comparable to the saliva levels of nicotine achieved during tobacco chewing. The results obtained by continuous and pulse treatments with nicotine explain the harmful effects of chronic tobacco consumption.

In vitro genotoxic effects of areca nut extract and arecoline

SummaryThe genotoxic potential of the aqueous extract of areca nut as well as arecoline, the major alkaloid of the areca nut, was tested with the help of cytogenetic markers such as sister-chromatid exchanges and chromosome aberrations, utilizing Chinese hamster ovary (CHO) cells. The continuous-treatment and pulse-treatment schedules yielded dose-dependent elevations in the frequencies of sister-chromatid exchange and chromosomal aberration in CHO cells, indicating a genotoxic effect of both the extract and arecoline. The results also imply that, besides arecoline, there may be some other water-extractable substances in the areca nut that make the extract more genotoxic. The chromosome damage was found to be more severe on treating the cells with low concentrations and for longer duration, which mimic the effects of chronic areca nut consumption.

Spontaneous and induced sister chromatid exchange frequencies and cell cycle progression in lymphocytes of patients with carcinoma of the uterine cervix

Thirteen healthy females and thirteen untreated patients with carcinoma of the uterine cervix were studied for spontaneous and mitomycin C (MMC)-induced rates of sister chromatid exchange (SCE) and cell cycle progression. The mean values of spontaneous as well as MMC-induced SCE rates showed no statistically significant difference between groups. For studying cell cycle progression, cells in the M1, M2, and M3 stages were scored from the same samples. The percent values of cells in these stages, identified by the nature of differential sister chromatid staining, were found to be almost identical in normal as well as MMC-treated cultures in controls and patients. It was concluded that the presence of carcinoma of the uterine cervix in human females has no bearing either on spontaneous and MMC-induced SCE rates or on cell cycle progression in PHA-stimulated cultures of peripheral blood lymphocytes.

Chromosome damaging effects of pan masala

Effects of aqueous extracts of a popular brand of pan masala with and without tobacco (PM-T and PM) were studied for short duration treatment employing an in vitro system. Metabolic activation with S9 mix was also included. Frequency of all the three cytogenetic endpoints viz., chromosome aberration (CA); sister chromatid exchange (SCE) and % micronucleated cells (% MNC) were found to be elevated significantly in a dose-dependent manner in cultures without metabolic activation. However, addition of S9 activation system resulted in suppression of chromosomal damage. Our findings indicate that pan masalas contain water soluble direct acting mutagens.

Heteromorphism of C-band positive chromosomal regions in CML patients

The heteromorphism of constitutive heterochromatin in chromosomes #1, #9, and #16 was investigated in 44 chronic myelocytic leukemia patients and 44 controls using bone marrow and peripheral blood lymphocyte cultures. A significant increase in the length of C-band region in all the three chromosome pairs as well as a statistically significant difference in the homologs of chromosome #1 was observed in chronic myelocytic leukemia patients when compared with the controls. The frequency of inversions was also greater in the patients than in the controls. A random translocation of 22q was found on either homolog of chromosome #9.

Pan masala — a genotoxic menace

Cytogenetic markers such as chromosome aberration (CA), sister-chromatid exchange (SCE) and micronucleated cells (MNC) were used to assess the genotoxic potential of dimethyl sulphoxide (DMSO) extract of pan masala with and without tobacco (PM-T and PM). Using in vitro short-term assays, the extracts were tested in the presence or absence of metabolic activation. In cultures without metabolic activation the extracts were found to increase the frequency of all the three parameters tested significantly, however those with activation elicited a weak response, implying that pan masalas contain solvent (DMSO)-soluble direct-acting mutagen.

Genotoxic effects of tobacco extract on Chinese hamster ovary cells

Genotoxic effects of an aqueous extract of Nicotiana tabacum, a variety commonly used in India for chewing purposes, were analysed on CHO cells utilizing two different cytogenetic end-points, namely, chromosome aberration frequency and sister chromatid exchange frequency. Statistically significant elevations in the values of both the markers clearly indicated chromosome damaging effects of the extract. Elevations in chromosome aberration and sister chromatid exchange frequencies are suggestive of intrastrand and interstrand DNA cross-links following exposure to tobacco. The effects observed following treatment with low dose for longer duration are of relevance to the condition of the oral mucosa of the chronic smokeless tobacco users.

Effects of CCNU therapy on human chromosomes.

Peripheral blood lymphocytes of 9 patients under CCNU therapy were examined for frequency of sister-chromatid exchanges (SCEs) and chromosomal aberrations (CAs). 7 out of 9 patients were treated with only CCNU, whereas the remaining 2 were treated with other chemotherapeutic agents in combination with CCNU. Compared to normal individuals, a significantly increased frequency of SCE was observed in the patients before starting anticancer therapy (P less than 0.001). Increased incidences of structural changes in chromosomes were observed in cells from all the treated patients. The most frequent aberrations were of chromatid type. After administration of a single dose of CCNU, an increase in SCE frequencies was observed which remained elevated even after 6 weeks. It was concluded that increases in SCEs and CAs in lymphocytes were caused by CCNU treatment. Further studies are needed to elucidate whether any CAs observed in the present study could participate in the induction of second neoplasm.

Variability of Euchromatic and Heterochromatic Regions of Y Chromosome in Two Types of Cancer Patients

Heteromorphism of Y chromosome was studied in head and neck cancer patients and leukemia patients. The results were compared with similar data obtained for healthy men. It was observed that, compared to the controls, mean lengths of Y chromosome were nonsignificantly higher for leukemia patients and lower for head and neck cancer patients. The euchromatic region of Y chromosome (Y-eu) remained comparable in the controls and the leukemia patients, whereas it was smaller in patients with head and neck malignancies. The heterochromatic region (Y-het) was more or less analogous in controls and head and neck cancer patients, however, it was significantly larger in patients with leukemia (P < 0.02).

Complex translocation involving chromosomes #1, #9, and #22 in a patient with chronic myelogenous leukemia

A case of Philadelphia chromosome positive chronic myelogenous leukemia with a complex translocation involving chromosomes #1, #9, and #22 is described. All cells in the bone marrow showed this rearrangement, and Q-banding analysis showed the predominant karyotype to be 46,XY, t(1;9;22)(p22;q34;q11).