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PubMed2005

Experimental dermatophytosis in calves caused by Trichophyton verrucosum culture.

Microconidia suspension of Trichophyton verrucosum virulent culture isolated originally from the mycotic lesions of cattle was inoculated epicutaneously to calves in various doses. Four application methods were selected, namely, onto the sheared and gently scarified skin, onto the sheared and non-scarified skin, onto the non-sheared and gently scarified skin, and onto the non-sheared and non-scarified skin. The inoculated area was 10 x 10 cm for all cases mentioned. When the application was performed onto the sheared and scarified skin, at least 18,000 microconidia of T. verrucosum per one animal had to be used to induce the mycotic disease in 100% of animals. This value was 10 times higher when the application was performed onto the non-sheared and scarified skin, 100 times higher in the case of the sheared and non-scarified skin and 1,000 times higher in the case of the non-sheared and non-scarified skin. The minimum infectious dose still capable of inducing dermatophytosis was 180 microconidia per 100 cm(2) of the scarified skin, 18,000 microconidia per 100 cm(2) of the sheared and non-scarified skin, and 180,000 microconidia per 100 cm(2) of the non-sheared and non-scarified skin.

Animals↗

PubMed2002

Renewal of the culture medium induces a temporary decrease in the gap junctional communication accompanied by degradation and re-establishment of gap junctions in the V79-4 Chinese hamster cell line.

To replace the culture medium with a fresh one is a routine action of the mammalian cell culture technique. It is generally assumed that this act per se does not cause any significant physiological response of a cell population that would significantly interfere with the experimental procedures in culture. However, in this series of experiments we demonstrate that the exchange of the culture medium for a fresh one may induce a significant temporary decrease in the GJIC, assessed by the dye coupling method in the V79-4 Chinese hamster cell line. This effect is accompanied by a degradation of gap junctions and their re-establishment assessed by the semi-quantitative immunocytochemistry of connexin43. The minimum value of GJIC was reached 45 min after the exchange of the medium. Afterwards, GJIC grew up again, reaching the standard value 3 or 4 h later. This effect does not just result from the exchange of medium as a mechanical action, is not caused by the change of pH and is of quantitative character. The fresh medium loses its capability to reduce GJIC after 3 h of conditioning with the same cells. We found that the value of the early inhibition of GJIC observed during the first 2 h of treatment with the inhibitor of GJIC-EG (applied together with a fresh culture medium)--was indistinguishable from the effect of the exchange of medium itself. Only after that point of time is the EG-induced inhibition of GJIC definitely distinguishable. The results demonstrate that a simple exchange of the culture medium, which is generally implemented in various experiments in culture, may cause serious physiological, biochemical and even morphological responses of cells and thus affect the final results of experiments in culture, especially regarding the early effects of drugs. Consequently, to avoid an undesirable response of the cell population reported in this paper we recommend to apply or remove drugs using a medium conditioned with the same cells for at least 3 h.

Animals↗