Oleksandr Chernyavskiy

Academy of Sciences of the Czech Republic, Praha, Hlavni mesto Praha, Czech Republic

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Publications (9)23.76 Total impact

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    ABSTRACT: Much like other microorganisms, wild yeasts preferentially form surface-associated communities, such as biofilms and colonies, that are well protected against hostile environments and, when growing as pathogens, against the host immune system. However, the molecular mechanisms underlying the spatiotemporal development and environmental resistance of biofilms and colonies remain largely unknown. In this paper, we show that a biofilm yeast colony is a finely tuned, complex multicellular organism in which specialized cells jointly execute multiple protection strategies. These include a Pdr1p-regulated mechanism whereby multidrug resistance transporters Pdr5p and Snq2p expel external compounds solely within the surface cell layers as well as developmentally regulated production by internal cells of a selectively permeable extracellular matrix. The two mechanisms act in concert during colony development, allowing growth of new cell generations in a well-protected internal cavity of the colony. Colony architecture is strengthened by intercellular fiber connections.
    The Journal of Cell Biology 09/2011; 194(5):679-87. · 10.82 Impact Factor
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    ABSTRACT: Within the human testis, Reinke's crystals are found in Leydig cells but their nature and function are poorly understood. The aim of our study was to investigate the properties of Reinke's crystals in man with the normal morphology of the testis (control group) and infertile patients diagnosed with cryptorchidism. 20 biopsies from infertile patients and six biopsies from men with regular spermatogenesis (20-30 years.) were used. Sections of the testis tissue were stained with haematoxylin and eosin and a modified Masson's method. Specimens were observed by bright field, confocal and transmission electron microscopy (TEM). The number of Reinke's crystals in investigated groups was determined applying stereological methods. In both groups, Reinke's crystals were noted within the cytoplasm and nuclei of Leydig cells. Some "free" crystals were found within the interstitial space, outside Leydig cells. Confocal microscopy proved to be very useful in the assessment of the shape and 3D reconstruction of the crystal. TEM analysis confirmed a hexagonal form of the crystal, while crystallographic data on sections of 70-300 nm thickness provided a better insight into the organization of the crystal lattice. Stereological analysis revealed a significant increase in the number of crystals in cryptorchid testes when compared with controls. Increased number of crystals in cryptorchid specimens leads to the assumption that the prolonged exposure to higher (abdominal) temperature might stimulate enzymes involved in the synthesis of the proteins of the crystal. However, the exact molecular nature of the crystal lattice remains in both normal and cryptorchid testis obscure.
    Histochemie 02/2011; 135(2):215-28. · 2.61 Impact Factor
  • O. Chernyavskiy, L. Kubínová, X.-W. Mao
    Microscopy and Microanalysis 01/2010; 16:286-287. · 2.50 Impact Factor
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    ABSTRACT: Yeasts, when growing on solid surfaces, form organized multicellular structures, colonies, in which cells differentiate and thus possess different functions and undergo dissimilar fate. Understanding the principles involved in the formation of these structures requires new approaches that allow the study of individual cells directly in situ without needing to remove them from the microbial community. Here we introduced a new approach to the analysis of whole yeast microcolonies either containing specific proteins labelled by fluorescent proteins or stained with specific dyes, by two-photon excitation confocal microscopy. It revealed that the colonies are covered with a thin protective skin-like surface cell layer which blocks penetration of harmful compounds. The cells forming the layer are tightly connected via cell walls, the presence of which is essential for keeping of protective layer function. Viewing the colonies from different angles allowed us to reconstruct a three-dimensional profile of the cells producing ammonium exporter Ato1p within developing microcolonies growing either as individuals or within a group of microcolonies. We show that neighbouring microcolonies coordinate production of Ato1p-GFP. Ato1p itself appears synchronously in cells, which do not originate from the same ancestor, but occupy specific position within the colony.
    Environmental Microbiology 06/2009; 11(7):1866 - 1877. · 6.24 Impact Factor
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    ABSTRACT: We investigated possibilities of the combination of the one- and two-photon excitation microscopy for examination of the experimental melanoma tissue in vivo, in mice under general anesthesia, and ex vivo on freshly harvested specimens. Our aim was to obtain sufficiently informative images of unstained tumor tissues and their modifications after hyperthermia treatment. The mouse experimental melanoma structure was studied and compared with normal tissue from the same animal by using confocal and nonlinear microscopy techniques based on (i) one-photon excitation (1PE) fluorescence, (ii) 1PE reflectance, (iii) second harmonic generation imaging, and (iv) two-photon excitation autofluorescence. We checked different spectral conditions and other settings of image acquisition, as well as combinations of the above imaging modalities, to fully exploit the potential of these techniques in the evaluation of treated and untreated cancer tissue morphology. Our approach enabled to reveal the collagen fiber network in relation with the other tissues, and to identify invasive tumor cells. It also proved to be useful for the examination of interrelationships between functional and morphological aspects based on optical properties of the tissues, especially in studies of changes between the tumor and control tissue, as well as changes induced by physical treatments, e.g., delivery of microwave hyperthermia treatment. These differences were also evaluated quantitatively, when we found out that the maximum Euler-Poincaré characteristic reflects well the melanoma morphological structure. The results showed that the proposed investigative approach could be suitable also for a direct evaluation of tissue modifications induced by clinical interventions.
    Microscopy Research and Technique 03/2009; 72(6):411-23. · 1.59 Impact Factor
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    ABSTRACT: Newly developed confocal techniques are perspective for potentially clinical applications (mainly skin pathologies). The new repertoire of tissue, cell and vessel imaging produced by these approaches needs to be understood in its significance. More than one confocal method could be used to improve the diagnostic value. To investigate these possibilities, we performed observations of cancer tissue in vivo in totally anesthetized animals, and ex vivo on freshly harvested specimens. Murine B16F10 melanoma cells were SC inoculated in syngeneic mice. When tumors developed into up to 15-20 mm in diameter, they were studied either directly or after hyperthermia (microwave treatment).
  • 38:45-45.
  • European Journal Of Clinical Investigation. 38:45-45.
  • O. Chernyavskiy, L. Kubínová
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    ABSTRACT: Confocal fluorescence microscopy with one-photon excitation (1PE) or two-photon excitation (2PE) has become a powerful tool, which is extensively used in biomedical research. Its optical sectioning capabilities can be exploited for measurements of geometrical characteristics of biological structures and their 3D reconstructions, enabling spatial characterization of tissue organization and morphology. Further, in the last two decades, confocal microscopy finds increasing utilization in various quantitative microscopic techniques. By means of FRAP, FLIP, FRET techniques based on fluorescence intensity measurements, biological studies of cell membrane diffusion and protein binding, spatial and temporal distribution of protein associations inside living cells [1, 2] are possible.