Evaluation of radioadaptive response induced in CHO-K1 cells in a non-traditional model.

PURPOSE: The present study was designed to evaluate the effects of sequential exposures to low doses of gamma-radiation that induce a radioadaptive response to a later high-dose of radiation in CHO-K1 cells. MATERIALS AND METHODS: Cells were cultured in four dilution cycles and grown to confluency. Radiation treatment was performed once per cycle with 0.1 Gy gamma-rays. After the last radiation period (chronic radiation) the culture was irradiated with a higher dose (1 Gy). Each cell culture was immediately divided into two fractions: one of them was used to carry out the comet assay and the other for the structural chromosome aberration test. In the first fraction, genotoxic damage was evaluated by degree of damage in 300 cells per experimental point. The second assay was performed with 400 cells per treatment. The statistical analysis was carried out using the chi(2)-test. RESULTS: Results from these assays demonstrated a genotoxic effect for both the adaptive and acute treatments (p < 0.001). The comet assay showed a significant increase in damage for the combined treatment when compared with 1 Gy treatment (p < 0.001). The frequency of chromosomal aberrations (CA) was lower for the combined treatment than for that using the highest radiation dose. CONCLUSIONS: These results suggest the possible induction of a radioadaptive response after the sequential exposure to very low doses of radiation. The finding of decreased cytogenetic damage after one cell cycle and not immediately after radiation could indicate the eventual potentiation of repair mechanisms.

Assessment of genotoxic damage in lymphocytes of hospital workers exposed to ionizing radiation in Argentina.

The authors aimed to assess genotoxic damage in the lymphocytes of workers chronically exposed to ionizing radiation. The studied population included 15 exposed donors of the radiology unit of a public hospital in La Plata, Argentina. The control group included 15 nonexposed employers from administrative areas that the authors matched by age, sex, and smoking habits. The mean frequency of cytogenetic damage was higher in the exposed group than in the unexposed group for aneuploidy and structural chromosome aberrations. They observed the highest difference when achromatic lesions (or gaps) were considered. The comet assay showed that the frequency of cells with low damage was higher in the exposed group than in the unexposed group. A mean length analysis showed significant differences between exposed and nonexposed people. The results can be considered to be consistent evidence of occupational radiation exposure, and the results indicate that the workers must be advised to avoid or minimize their exposure.

Chlamydia trachomatis and Human papillomavirus infections in cervical disease in Argentine women.

OBJECTIVES: To examine the prevalence of Human papillomavirus and Chlamydia trachomatis DNA in cervical samples among women with normal and abnormal cervical cytology from La Plata, Argentina. METHODS: Two hundred and seventy-nine women (200 with cervical neoplasia or ICC and 79 women with normal cytology) provided cervical samples for the detection of HPV and C. trachomatis DNA by PCR-based assays. RESULTS: HPV DNA increased with the cervical lesion severity, ranging from 30% among women with normal cytology to 99-100% among women with HSIL or ICC. C. trachomatis DNA prevalence increased from low levels in women with normal cytology (11%) to 47% in those with HSIL, but was uncommon among ICC patients (20%). Among women with normal cytology, C. trachomatis prevalence was higher in HPV DNA positive (12.5%) than HPV DNA negative women (10.9%), but this difference was not significant. CONCLUSIONS: HPV prevalence in the general population is slightly higher than those reported for other developing countries. C. trachomatis DNA positivity was associated with a higher risk of both LSIL and HSIL lesions, but not with ICC.

The c-myc activation in cervical carcinomas and HPV 16 infections.

Despite the prominent role for Human Papillomavirus (HPV) infection in the development of genital cancer, other genetic or environmental co-factors have also been involved. Studies of c-myc activation in cervical carcinomas have reported that gene over-expression (mainly gene amplification) are common in cervical squamous cell carcinomas and may correlate with the biologic behavior of the neoplasm. Using PCR based technology, DNAs from 79 normal cervical samples and 225 abnormal cervical tissue scrapes were analyzed for HPV detection and typing and for c-myc gene amplification. Significant differences were found between the different cyto/histology groups (P<0.0001) and also with HPV high-risk infected samples (P<0.0002). In this sense, we showed that the average c-myc copy number increased according to the histological grade of the lesion (OR=6.3, CI=2.1-18.8). Also, the results showed that the infection with HPV 16 was tightly associated with c-myc amplification (OR=10.6, CI=3.1-36). These results could indicate that oncogene amplification take place in pre-invasive stages of cervical disease and could cooperate not only in tumor progression but also in cell transformation. Moreover, the results strongly associate the c-myc gene amplification to the infection with the oncogenic HPV 16, showing that the pattern of virus infection and oncogene activation could be specific for different viral genotypes.

The hyaluronic acid receptor (CD44) is expressed in bovine oocytes and early stage embryos.

Hyaluronic acid (HA) is a high molecular weight polysaccharide found in the extracellular matrix of most animal tissues, that exerts a profound influence on cell behavior. HA is one of the most abundant glycosaminoglycans (GAGs) in the uterine, oviductal and follicular fluids in mouse, pig, human and cattle. CD44, the principal cell membrane receptor for HA, is expressed from the 1- to 8-cell stage in human embryos, during post-implantation mouse embryogenesis and on the surface of differentiated embryonic stem cells. In the present study, we have analyzed by immunofluorescence, whether CD44 is present in bovine oocytes, fertilized oocytes and early stage embryos. Bovine cumulus-oocyte complexes (COCs) were aspirated from follicles (2-5mm) and were selected for IVM and incubated for 24h. Oocytes showing an expanded cumulus (generally 90-95%) were used for IVF. Fertilized oocytes were separated for immunofluorescence assay after 16h of sperm incubation in order to fix the eggs at the pronuclear stage. The embryos were cultured for 8 days and the different stages of development for immunofluorescence assay were separated every 24h of culture. The CD44 receptor was detected at every observation time examined. Fluorescence-tagged HA for the internalization assay was prepared by mixing fluorescein amine, Isomer I and 1mg of HA from umbilical cord. Fluorescence-tagged HA was internalized in 2-, 4-, 8- and 16-cell-stage embryos, morulae and blastocysts. CD44 is expressed on the surface and in the cytoplasm of bovine oocytes and embryos in different stages of development.

Amplificación del proto-oncogén HER-2/neu asociada a la infección por VPH de bajo riesgo en citología exfoliativa cervical / HER-2/neu prot-oncogen amplification related to low risk VPH infection in cervical exfoliative cytology

Se analizaron 69 muestras positivas para el virus papiloma humano (VPH) tipos -6, -16 y -18, y 24 muestras con citología cervical normal negativas para el VPH como grupo control. El análisis de la amplificación génica del proto-oncogén HER-2/neu se realizó utilizando la técnica de coamplificación con locus de referencia. Se encontró una asociación entre la amplificación del gen HER-2/neu y el grupo viral de "bajo riesgo" (VPH-6) (p < 0.005). Dentro de este grupo, se observó una asociación entre la amplificación del proto-oncogén y el status citopatológico CIN I (p < 0.01). Debido a que la mayoría de las muestras CIN I analizadas presentaron un patrón coilocítico, la amplificación de HER-2/neu parecería estar relacionada con este tipo de alteración celular. Por otra parte, sería importante estudiar la amplificación génica y la expresión de HER-2/neu en los diferentes estadios de las neoplasias intraepiteliales cervicales a fin de poder evaluar su papel en la progresión del cáncer cervical.

Protective effect of butylated hydroxytoluene (BHT) against the clastogenic acitivity of cadmium chloride and potassium dichromate in hamster ovary cells

The effect of butylated hydroxytoluene (BHT), a widely used food additive, on chromosomal alterations induced by cadmium chloride (CC) and potassium dichromate (PD) in Chinese hamster ovary (CHO) cells was studied both at metaphase and anaphase-telophase. CHO cells were cultured for 15-16 h in the presence of PD (6.0, 9.0 or 12.0 mM), BHT (1.0 mg/ml), or PD plus BHT as well as CC (0.5, 1.0 and 2.0 mM), BHT or CC plus BHT for the analysis of chromosomal aberrations. To perform the anaphase-telophase test, cells were cultured in cover glasses and treated 8 h before fixation with the same chemicals. An extra dose of CC (4 mM) was used in this test. Both metal salts significantly increased chromosomal aberration frequencies in relation to untreated controls, and to DMSO- and BHT-treated cells. Post-treatment with BHT decreased the yield of chromosomal damage in relation to treatments performed with CC and PD. However, chromosomal aberration frequencies were significantly higher than those of the controls. In the anaphase-telophase test, CC significantly increased the yield of lagging chromosomes with the four doses employed and the frequency of lagging fragments with the highest dose. In combined treatments of CC and BHT, frequencies of the two types of alterations decreased significantly in relation to the cells treated with CC alone. No significant variation was found in the frequencies of chromatin bridges. Significant increases of numbers of chromatin bridges, lagging chromosomes and lagging fragments were found in cells treated with PD. The protective effect of BHT in combined treatments was evidenced by the significant decrease of chromatid bridges and lagging chromosomes in relation to PD-treated cells. Whereas BHT is able to induce chromosomal damage, it can also protect against oxidative damage induced by other genotoxicants.

Analysis of sister chromatid exchanges (SCE) in human population studies

A análise das frequências da troca de cromátides irmäs (SCE) em estudos de populaçöes humanas é discutida levando em conta: as frequências de SCE em uma populaçäo de floricultores expostos á pesticidas; 2) a distribuiçäo das frequências de SCE; 3) o numero de células contadas por indivíduo e 4) a proporçäo com altas frequências de SCE (HFC). Dados sobre SCE foram obtidos a partir de uma amostra de 14 floricultores com sintomas de intoxicaçäo crônica e 13 sem. Esses resultados foram comparados com aqueles obtidos de uma amostra de doadores näo expostos. Para a análise das frequências de SCE em floricultores sintomáticos e näo sintomáticos, o uso de testes estatísticos paramétricos e näo paramétricos, bem como uma comparaçäo das curvas de distribuiçäo das frequências de SCE säo discutidas. Sendo que nenhum aumento da frequência de SCE seria esperado em estudos de populaçöes, a utilidade dos diferentes métodos combinados com a comparaçäo das curvas de distribuiçäo é demonstrada para a detecçäo de pequenas diferenças significativas. Nos floricultores e nos doadores näo expostos, as frequências de SCE seguiram uma distribuiçäo binomial negativa, tendo pouca correlaçäo com a distribuiçäo de Poisson. Isto confirma a utilidade dos testes estatísticos para a análise dos dados obtidos. As frequências de SCE de 20 indivíduos após 20, 25, 30 e 50 células foram analisadas para determinar se o numero de células a serem contadas por indivíduo dependem do tamanho da amostra da populaçäo. Finalmente a detecçäo das células com altas frequências de SCE pode ser usada com uma grande amostra e um grande numero de células examinadas por indivíduo