A study was made on the in vitro action of the antimycotic miconazole on Candida albicans yeast cells with scanning electron microscopy, and the effects were compared with those seen on the yeast cells by means of transmission electron microscopy. It was found that cells exposed to fungistatic and minimal fungicidal doses of miconazole (10-7 M and 10-6 M) presented rough surfaces and had multiple, desoriented buds and bud scars. Whereas in control cultures the cells were well separated, the treated ones formed small clusters of interconnected cells. After exposure to a fungicidal concentration (10-' M) of the drug, most of the remaining cells showed smooth surfaces and were covered with numerous vesicular structures probably representing cytoplasmic remnants derived from broken cells. This has been substantiated by the presence of abundant fragments of cell walls and confirmed by examination of similarly treated cultures in the transmission electron microscope. Moreover, the cells with an apparently intact surface when examined with scanning electron microscopy were shown with transmission electron microscopical examination to be completely necrotic inside.

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...

The progressive micromorphological changes in Taenia taeniaeformis cysticerci, induced by a single parenteral treatment of the infected mice with mebendazole, are described. The time-related alterations concerned the tegument and tegumental cells and were successively: disappearance of microtubules, accumulation of secretory substances in the Golgi areas, decrease in number to complete loss of microtriches, "ballooning" of all tegumental cells with subsequent burst, vacuolization and degeneration of the tegument, and finally necrosis of the pseudoproglottids. Similar but less pronounced injuries were seen in the scolices, although microtubules disappeared as early as in the pseudoproglottids. Microtubules from the host tissues remained intact. The meaning of the apparent primary interference of mebendazole with the microtubular system in relation to the subsequently observed death of the cysticercoids is discussed.

The application of a new preparation method for demonstrating the activities of hydrolytic and oxidative enzymes in Candida albicans is reported. The problem of inadequate penetration of fixatives into yeast cells has been solved by sectioning solidified pellets of the cells in the presence of glutaraldehyde, a procedure that yields a fairly well preserved ultrastructure and sufficient enzyme activities. The subcellular distribution of most specific and nonspecific phosphatases and of peroxidases is at variance with that found in mammalian cells. The activities toward beta-glycerophosphate, p-nitrophenylphosphate, adenosine triphosphate, adenosine monophosphate, thiamine pyrophosphate and glucose 6-phosphate are almost exclusively confined to the central vacuolar apparatus. Oxidative and peroxidative activities are demonstrated only in mitochondria. Specific marker enzymes for endoplasmic reticulum, plasmalemma, Golgi apparatus and peroxisomes in C. albicans are not found. The possible function of the various subcellular organelles in relation to their enzymatic content is discussed.

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The structural correlates of 'chronic hibernating myocardium' in man consist of myocardial cells which transformed from a functional state (rich in contractile material) to a surviving state (poor in contractile material, rich in glycogen). Since the calcium-handling organelles such as SR, sarcolemma and mitochondria underwent structural changes in cells so affected, the distribution of calcium was investigated in biopsies obtained from 'hibernating' areas. The material was processed for microscopic localization of total calcium (laser microprobe mass analysis, LAMMA) and of exchangeable calcium (phosphate-pyroantimonate precipitation method, PPA). Subcellular distribution of total calcium as assessed by LAMMA revealed that in the structurally affected cells the areas in which sarcomeres were replaced by glycogen contained significantly more calcium than all other areas probed such as mitochondria, remaining sarcomeres at the cell periphery and subcellular areas of normally structured cells. Calcium precipitate, obtained after PPA assessment, was localized at the sarcolemma but was virtually absent in the mitochondria of affected cells. The high calcium content in the myolytic areas of affected cells most probably belongs to a pool of bound calcium. The observations that calcium is retained at the sarcolemma and that mitochondria are devoid of precipitate favour the hypothesis that cells structurally affected as such are not ischaemic and are still able to regulate their calcium homeostasis.

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Electron microscopic examination on Candida albicans yeast cells after exposure in vitro to different doses ofmiconazole revealed that it exerts its effect primarily on the plasmalemma and the cell wall. After exposing cultures to drug concentrations of 10-nM and 10-sM progressive degradation of plasmalemma and cytoplasmic organelles were seen. Injured parts of cellular material were sequestered from the rest of the cytoplasm and extruded into the central vacuole. A similar degradation occurred at the cell periphery. Cell death, characterized by the loss of normal shape, dissolution of the plasmalemma and by severe alterations of all cytoplasmic organelles, was evident at the 5 × 10-nM and 10-SM dose levels. From the morphologic point of view a clear dose relationship could be established.