Sustained AF in goats leads to predominantly structural changes in the atrial myocytes similar to those seen in ventricular myocytes from chronic hibernating myocardium. These structural changes may explain the depressed contractile function of atrial myocardium after cardioversion. This goat model of AF offers a new approach to study the cascade of events leading to sustained AF and its maintenance.

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Our results suggest that the partial cell fusion-type of heterocellular communication in our co-culture model and the contacts observed in vivo may lead to new insights in cardiovascular disease.

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Cardiomyocyte dedifferentiation, but not extensive degeneration through apoptosis, can be observed in chronic hibernating myocardium and chronic fibrillating atrium. Dedifferentiation may be the best way to survive prolonged exposure to the unfavourable conditions imposed by increased wall stress, a relative lowered oxygen environment, or both.

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Yeast cells exposed to different doses of the antimycotic agent miconazole revealed important cytochemical changes in the topographic distribution of the phosphatases. A strong effect was observed on the behavior of oxidative and peroxidative enzymes. Decreased cytochrome c oxidase and peroxidase activity and increased catalase activity were seen after treatment with a fungistatic dose ofmiconazole, whereas a complete disappearance ofthese enzymes was observed after treatment with a minimal fungicidal dose of miconazole. This was in complete agreement with the quantitative biochemical data. A hypothesis is advanced concerning the possible involvement of peroxidase and catalase in the mechanism of action of this drug., is an imidazole nitrate that has demonstrated broad-spectrum activity against most pathogenic fungi and gram-positive bacteria (7,10,18,19,36). The studies on the uptake and utilization of substances in Candida albicans by Van den Bossche (37) indicated that miconazole induced changes in the permeability of the plasmalemma and the cell wall. At the ultrastructural level, C. albicans cells show changes in a dosedependent manner when grown in the presence of 10`8 to 10-M concentrations of miconazole. These changes range from slight alterations in the cell periphery and increase in the number of peroxisomes and lipid globules, to progressive cytoplasmic deterioration, prominent shape changes, and complete cellular necrosis (11, 12; S. De Nollin, Ph.D thesis, University of Brussels, Brussels, Belgium, 1976). Recent investigations with scanning and transmission electron microscopy (12) on C. albicans cultures treated with a fungicidal dose of miconazole (10-4 M) have shown that the sequence of alterations differs totally from that obtained with lower-dose treatments.The cytochemistry of untreated yeast cells has already been described by several authors (2, 3, 13, 22, 40; S. De Nollin, Ph.D. thesis, 1976). In earlier experiments (16, 13), we tried to optimize the preparatory conditions for the cytochemical examination of yeasts cells by using a modification of the conventional procedure for preservation. This yields, besides a good micromorphology of the cells, sufficient enzyme activities and allows an adequate penetration of substrates and captation ions during the incubation. For the biochemical studies, Van Belle, Goossens, and Van Roy (in preparation) have recently developed a method for obtaining adequate homogenization of the very rigid cells of yeast, thereby yielding reliable enzyme activities that are directly proportional to the number of cells (more than 99.9% of the cells are thoroughly homogenized). Using these modifications of the cytochemical and biochemical preparative techniques, we have tried in this study to evaluate the effects of miconazole on the activities and the distribution pattem of phosphohydrolases and of oxidative and peroxidative enzymes in C. albicans and Saccharomyces cerevisiae. Our particular aim was to see whether there was any correlation between the observed morph...