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The toxicity of new surfactants containing a β-lactam ring has been established by studying their interaction with a hybridoma cell line. An hour of contact is sufficient to generate an apoptotic signal after two days of culture. Under the experimental conditions chosen for the experiments, surfactants have been divided into three categories: i) biocompatible and non-apogenic; ii) surfactants triggering an apoptotic signal without inducing cell necrosis; iii) surfactants triggering an apoptotic signal at low concentrations and destroying the cells by necrosis at higher concentrations. The necrosis inducing surfactants also had haemolytic properties. These properties were related to the values of the hydrophilic-lipophilic balance of the molecules.

Algal toxins, as Microcystins released in water supplies, may represent a serious health hazard. The behaviour of primary hepatocytes was compared with that of immortalized liver cells, with the intention of providing a new test on Microcystin cellular toxicity. Immortalized liver cells were obtained by transfection with SV40 Large T antigen-bearing plasmids. Primary hepatocytes were used as a reference. Microcystin-LR at 10(-6), 10(-7)and 10(-9)m was added to hepatocytes maintained in suspension or cultured as three-dimensional hepatospheroids for 20 and 90 min at 37 degrees C. Toxic effects were monitored by cytoskeletal disruption ('blebs') using both light and scanning electron microscopy (SEM), lactate dehydrogenase release (LDH) and trypan blue dye exclusion test. Microcystin-LR at all doses induced bleb formation and a loss of microvilli in both primary hepatocytes and immortalized cell suspensions in comparison with controls. A high level of blebbed cells was detected in the absence of increased LDH release. The blebbing phenomenon was readily detectable by light microscopy but its morpho-complexity was unmasked by SEM, with early toxic events being indentified as loss of microvilli prior to bleb formation. Cells of primary hepatospheroids appeared to be less tightly attached to each other and more likely to bleb than immortalized ones. These immortalized cells could limit the use of primary cells and increase the reproducibility of the assay.

Amongst the existing 3-D culture models, the Rotary Cell Culture System (RCCS) enables 3-D growth in a unique environment (increased mass transfer and minimal shear forces). We investigated whether these conditions could generate improved hepatocyte 3-D models as potential tools for in vitro toxicological assays. Cells were seeded into three types of culture vessel which rotate on a horizontal axis and differ in their respective chamber dimensions.

This report represents an investigation into the nature of apoptosis in hybridoma cultures and its significance to their utilization in biotechnology. To this end DNA fragmentation and capillary electrophoresis of genomic DNA was studied during the culture of two hybridoma cell lines. This indicated that the phenomenon of apoptosis was always present even under normal culture conditions. Two DNA fragments not associated with the typical DNA fragmentation ladder were identified in the two hybridoma cultures: a previously unreported DNA fragment of about 100 bp and a large fragment which may correspond to one reported in the literature (Walker et al., 1993). The small fragment was identified as soon as the early exponential growth phase of culture, while the large fragment appeared only in the latter part of the growth curve when there was marked DNA fragmentation. In addition we present evidence that aurintricarboxylic acid, which inhibits apoptosis in neural cells, permits this process in hybridoma cells at levels below 100 microM. This unusual predisposition of hybridoma cultures to undergo apoptosis and their response to inhibitor of apoptosis may have important implications for approaches to the culture of hybridomas and their utilization for monoclonal production.