DNA damage kinetics and apoptosis in ivermectin-treated Chinese hamster ovary cells.

A comet assay was used to analyze DNA damage kinetics in Chinese hamster ovary (CHO-K1) cells induced by antiparasitic ivermectin (IVM) and the IVM-containing technical formulation Ivomec® (IVO; 1% IVM). Cells were treated with 50 µg ml(-1) IVM and IVO for 80 min, washed and re-incubated in antiparasiticide-free medium for 0-24 h until assayed using the single-cell gel electrophoresis assay (SCGE). Cell viability remained unchanged up to 3 h of incubation. After 6 h of treatment, cell survival decreased up to 75% and 79% in IVM- and IVO-treated cultures, respectively, remaining unchanged within 12-24 h after treatment. For both anthelmintics, biphasic behavior in DNA damage occurred during the incubation time. A time-dependent increase of IVM- and IVO-induced DNA damage was observed within 0 to 3 h after pulse treatment, revealed by a progressive decrease of undamaged cells and an increase in slightly damaged and damaged cells. Finally, a time-dependent decrease in IVM- and IVO-induced DNA damage was revealed by a progressive decrease of slightly damaged cells and the absence of damaged cells simultaneously with an increase in the frequency of undamaged cells during the final 18 h of incubation. Flow cytometry analysis revealed that both compounds are able to induce a marked increase in early and late apoptosis. Based on our observations, we could conclude that the decrease in DNA lesions is mostly related to IVM-induced cytotoxicity rather than attributable to a repair process.

Testing genotoxicity and cytotoxicity strategies for the evaluation of commercial radiosterilized fetal calf sera.

Effects of 18 commercial lots of fetal calf serum (FCS) after gamma-irradiation and their non-irradiated counterparts were comparatively analyzed on CHO-K1 and MDBK MDL1 cells for genotoxicity [sister chromatid exchange (SCE), micronuclei (MNi), and single cell gel electrophoresis (SCGE)], cytotoxicity [cell-cycle progression (CCP), proliferative replication index (PRI), mitotic index (MI), growth promotion (GP), and plating efficiency (PE)], and microbiological properties (mycoplasma and bovine viral diarrhea virus contamination). SCE and SCGE were the most informative end-points for genotoxicity since significant differences were found in 44.4% (P<0.05-0.001, Student's t-test) and 61.1% (P<0.05-0.001, chi(2) test) samples, respectively. MI was the cytotoxicity assay revealing the greatest variation, showing differences in 66.7% (P<0.05-0.001, chi(2) test) samples. Thus, these three end-points for screening bioproducts such as FCS were found most suitable for detecting potential geno-cytotoxicants in biological samples; their simultaneous use could be strongly recommended.

Genotoxic and cytotoxic effects of carbofuran and furadan on Chinese hamster ovary (CHOK1) cells.

The in vitro geno- and cytotoxicity exerted by the N-methylcarbamate pesticide carbofuran (CF) and its commercial formulation furadan (F) were studied in Chinese hamster ovary (CHO(K1)) cells by several bioassays for both genotoxicity (e.g., the sister chromatid exchange (SCE) and micronuclei (MNi) frequencies), and cytotoxicity (e.g., cell-cycle progression, mitotic index (MI), 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and neutral red (NR)). Both CF and F activities were tested within the range of 5-100 microg/ml. CF within a 10-100 microg/ml concentration-range induced a significant dependent increase of SCE frequency and MNi over control values. At the same concentration-range, F increased significantly the SCE frequencies over control values although in a non-dependent manner while only an enhanced frequency of MNi was found in those 50 microg/ml-treated cultures. No binucleated cytokinesis-block cells were found in 100 microg/ml F-treated cultures. The NDI index revealed a delay in the onset of cell-division with 50 and 100 microg/ml of CF and F, respectively. The delayed rate of nuclear division induced by 100 microg/ml of F was higher than that induced by an equal concentration of CF. CF and F induced both a significant concentration-dependent delay in cell-cycle progression and a decrease in the proliferative replication index within 5-100 microg/ml and 50-100 microg/ml concentration-range, respectively. Decreased cell viability was found in up to 26% and 47% in 100 microg/ml CF- and F-treated cultures, respectively. The NR and MTT assays revealed a clear cell growth inhibition when concentrations of 50 and 100 microg/ml of either CF or F were employed. Accordingly, the results highlight that CF by itself and F, even in a greater extend exerts both genotoxicity and cytotoxicity in mammalian cells in culture, at least in CHOK1 cells.

Susceptibility of Enterococcus faecalis to twelve antibiotics, time-kill assays, and high-level aminoglycoside resistance in a university hospital in Argentina

Se estudiaron 201 cepas de Enterococcus faecalis, aisladas de diferentes materiales biológicos para: (I) establecer su perfil de sensibilidad, (II) determinar el porcentaje de cepas con alto nivel de resistencia (CIM) > 2.000 *g/ml) a cinco aminoglucósidos y (III) demostrar si la combinación de penicilina o ampicilina con un aminoglucósido es sinérgica cuando la CIM de los mismos se encuentra entre los límites de sensibilidad y 2.000 *g/ml (bajo nivel de resistencia). La eritromicina fue muy poco activa, con CIM90 > *g/ml. La pefloxacina y norfloxacina tuvieron actividad intermedia con valores de CIM50 = 4*g/ml y CIM90 = 8*g/ml. El 94% de las cepas fueron sensibles a trimetoprima-sulfametoxazol (1:20) con CIM < ou = 2*g/ml y el 87,6% a concentraciones < ou = 0,5*g/ml. La ampicilina, penicilina y piperacilina fueron los agentes más activos; el 90% de las cepas fueron inhibidas con 1*g/ml de ampicilina y 4*g/ml de penicilina (Cuadro 1). Las cepas de E. faecalis estudiadas fueron relativa o totalmente resistentes a los aminoglucósidos. Noventa y seis (47,8%) fueron altamente resistentes por lo menos a uno de ellos. El alto nivel de resistencia a estreptomicina fue el más frecuente con 47,3%, y amicacina el menos frecuente con 4,5%, obteniéndose valores intermedios para gentamicina (45,3%), tobramicina (35,3%) y netilmicina (11,9%) (Cuadro 2). Treinta y una cepas de E. faecalis fueron seleccionadas para el estudio de curvas de muerte. Los resultados mostraron que no hubo sinergia entre penicilina o ampicilina y el aminoglucósido en las cepas con alto nivel de resistencia, excepto en tres de ellas: una presentaba alto nivel de resistencia a estreptomicina, otra a netilmicina y amicacina y la tercera a amicacina. Entre las cepas con bajo nivel de resistencia a los aminoglucósidos sólo presentaron sinergia el 36,2% de las combinaciones con penicilina y el 39,7% de las combinaciones con ampicilina (Cuadros 3 y 4). Estos resultados que no se asegura sinergia entre ß-lactámicos y aminoglucósidos en cepas con CIM < 2.000 *g/ml para estos últimos