A model for demonstrating the adhesion of Actinobacillus seminis to epithelial cells.

The objective of this study was to demonstrate that a field isolate of Actinobacillus seminis (As8C) will adhere to epithelial cells and that this adhesion can be inhibited by pretreating the bacteria with mouse serum containing polyclonal antibodies (PoAbs) prepared against this isolate. An indirect fluorescent antibody test, transmission electron microscopy, and phase-contrast microscopy confirmed the adhesion of As8C to an established culture of bovine kidney epithelial cells (BKECs). In a bacterial adhesion assay, 40 As8C were estimated to adhere to each BKEC after 60 min. Using a bacterial inhibition assay, PoAbs diluted 10(-2) or 10(-3) inhibited the adhesion of As8C to BKECs by approximately 90%. Bacterial inhibition decreased to about 50% when the PoAbs were diluted to 10(-4). There was less than 10% inhibition of adhesion of As8C to BKECs when higher dilutions of PoAbs were used. The inhibition of As8C adhesion to BKECs was less than 20% following pretreatment of BKECs with 10(-2) to 10(-5) dilutions of PoAbs. Moreover, pretreatment of As8C with a 10(-2) dilution of PoAbs did not appear to adversely affect bacterial growth on agar. It is likely that the PoAbs interrupted the adhesion of As8C to BKECs by sterically interfering with a bacterial adhesin-epithelial cell receptor interaction.

Effects of mycotoxins in cultured kidney cells: cytotoxicity of aflatoxin B1 in Madin-Darby and primary fetal bovine kidney cells.

The cytotoxicity of aflatoxin B1, a fungal metabolite and an important food contaminant, was evaluated in an established cell line, Madin-Darby bovine kidney (MDBK) cells, and in primary fetal bovine kidney (PFBK) cells. Cells were grown in monolayers and treated with media containing AFB1 for 24 hr. Both culture systems were sensitive to the chemical; the PFBK cultures were approximately four times more susceptible to the cytotoxic effect. Cell multiplication decreased in both systems in long-term cultures. Adherence of MDBK cells was only slightly reduced at the toxic concentrations of the chemical. Electron microscopy revealed condensation of chromatin, separation of nuclei from the cytoplasm, cytoplasmic vacuolization, and loss of surface microvilli. Results indicated differential sensitivity of the two culture systems.

Vanadium accumulation and subcellular distribution in relation to vanadate induced cytotoxicity in vitro.

A bovine kidney cell culture system was used to assess the relationship of vandium uptake and subcellular distribution to orthovanadate induced cytotoxicity. Twenty-four hr incubations with 20-1000 microM vanadium elicited 15-75% cytotoxicity. Concentration-related morphological changes from the control polygonal shape to the treated biopolar appearance were detected. Vanadium accumulated in cells via a multiphasic process; peak accumulation was achieved by 1 hr post-treatment and was followed by apparent decline, completed by 3 hr. A slower second phase of accumulation occurred during the remainder of the 24 hr incubation period. A concentration-dependent accumulation resulted in a 50-fold increase in cellular vanadium content. Near maximum toxicity was achieved at a cellular vanadium burden of approximately 5 nmoles/10(6) cells; further accumulation (up to 35 nmoles/10(6) cells) resulted in only a slight increase in the degree of toxicity. Subcellular distribution studies indicated 90% accumulation of vanadium in the soluble supernatant fraction (105,000xg supernatant) at varying stages of cytotoxicity. It was concluded that the multifaceted dependency of vanadium cytotoxicity on its cellular content may have resulted from a cellular balancing between proposed regulatory functions for vanadium and the interactions incurred with an excessive content.

Ultrastructural study of schizogony of Eimeria bovis in cell cultures.

First-generation schizogony of Eimeria bovis in bovine cell culture was studied by electron microscopy. The intracellular sporozoite retained its structure for at least 6 days at which time it rounded up and lost its apical complex. Although the refractile body underwent certain morphologic changes, it was retained throughout the parasite's growth. The beginning of mitosis was marked by the formation of a cytoplasmic funnel which traversed the nucleus opening on each side toward a pair of centrioles. Subsequently, there developed an intranuclear spindle. Separation of the daughter nuclei was preceded by the formation of typical centrocones. Differentiation of merozoites was accomplished by exogenesis during the last mitotoc division. A dense fiber, interpreted as a link connecting the merozoite anlage with its nucleus, extended from the developing apical complex to the nearest division pole. In the anlage, the inner membrane complex was at first composed of patches associated with pairs of subpellicular microtubules. Rhoptries appeared early in merogenesis, whereas micronemes formed at the time the merozoites detached from the residuum. The level of amylopectin, low in schizonts, rose at the beginning of merozoite formation.