Stationary-growth-phase Saccharomyces cerevisiae yeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. In S. cerevisiae stationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Our in vivo analyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficient cox4Δ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth.
This study focused on the attachment strategy, cell structure and the host-parasite interactions of the protococcidian Eleutheroschizon duboscqi, parasitising the polychaete Scoloplos armiger. The attached trophozoites and gamonts of E. duboscqi were detected at different development stages. The parasite develops epicellularly, covered by a host cell-derived, two-membrane parasitophorous sac forming a caudal tipped appendage. Staining with Evans blue suggests that this tail is protein-rich, supported by the presence of a fibrous substance in this area. Despite the ultrastructural evidence for long filaments in the tail, it stained only weakly for F-actin, while spectrin seemed to accumulate in this area. The attachment apparatus consists of lobes arranged in one (trophozoites) or two (gamonts) circles, crowned by a ring of filamentous fascicles. During trophozoite maturation, the internal space between the parasitophorous sac and parasite turns translucent, the parasite trilaminar pellicle seems to reorganise and is covered by a dense fibrous glycocalyx. The parasite surface is organised in broad folds with grooves in between. Micropores are situated at the bottom of the grooves. A layer of filaments organised in bands, underlying the folds and ending above the attachment fascicles, was detected just beneath the pellicle. Confocal microscopy, along with the application of cytoskeletal drugs (jasplakinolide, cytochalasin D, oryzalin) confirmed the presence of actin and tubulin polymerised forms in both the parasitophorous sac and the parasite, while myosin labelling was restricted to the sac. Despite positive tubulin labelling, no microtubules were detected in mature stages. The attachment strategy of E. duboscqi shares features with that of cryptosporidia and gregarines, i.e. the parasite itself conspicuously resembles an epicellularly located gregarine, while the parasitophorous sac develops in a similar manner to that in cryptosporidia. This study provides a re-evaluation of epicellular development in other apicomplexans and directly compares their niche with that of E. duboscqi.
- MeSH
- aktiny ultrastruktura MeSH
- Apicomplexa klasifikace fyziologie ultrastruktura MeSH
- interakce hostitele a parazita MeSH
- Polychaeta parazitologie MeSH
- protozoální proteiny ultrastruktura MeSH
- trofozoiti fyziologie MeSH
- tubulin ultrastruktura MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The yeast strains VKM Y-2977 and VKM Y-2978, derived from the isolate Pa-202, were examined for their physiological properties and mycocin sensitivities and studied by light, phase-contrast, fluorescence, transmission and scanning electron microscopy. The cells of the first strain produced long stalk-like conidiophores, whereas the cells of the second one had the appearance of a typical budding yeast under the light microscope. Transmission and scanning electron microscopy showed the formation of stalk-like conidiophores and long necks in VKM Y-2977, similar in appearance to Fellomyces fuzhouensis. The actin cytoskeleton, microtubules and nuclei were similar as well, but due to presence of a capsule, they were not clearly visible. The second isolate, VKM Y-2978, had very short stalk-like conidiophores, and the neck, microtubules and actin cables were shorter as well. The actin patches, actin cables, and microtubules were similar in VKM Y-2977 and VKM Y-2978 and not clearly visible. The physiological characteristics and mycocin sensitivity patterns, together with the microscopic structures and ultrastructures, led us to conclude that both strains belong to Fellomyces penicillatus, even though they differ in the lengths of their stalk-like conidiophores and necks.
- MeSH
- aktiny ultrastruktura MeSH
- antifungální látky farmakologie MeSH
- Basidiomycota klasifikace účinky léků růst a vývoj ultrastruktura MeSH
- buněčné jádro ultrastruktura MeSH
- cytoplazma ultrastruktura MeSH
- mikroskopie MeSH
- mikrotubuly ultrastruktura MeSH
- spory hub účinky léků růst a vývoj ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Temperature-sensitive actin mutant of Saccharomyces cerevisiae act1-1 was studied at a permissive temperature of 23°C by light, fluorescent and electron microscopy to elucidate the roles of actin cytoskeleton in the cycling eukaryotic cells. Mutant cells that grew slowly at the permissive temperature showed aberrations in the cytoskeleton and cell cycle. Mutant cells contained aberrant 'faint actin cables,' that failed in directing of mitochondria, vacuoles and secretory vesicles to the bud and the stray vesicles delivered their content to the mother wall instead of the bud. Bud growth was delayed. Spindle pole bodies and cytoplasmic microtubules did not direct to the bud, and nucleus failed to migrate to the bud. Repeated nuclear divisions produced multinucleated cells, indicating continued cycling of actin mutant cells that failed in the morphogenetic checkpoint, the spindle position checkpoint and cytokinesis. Thus, a single actin mutation appears to indicate uncoupling in space and time of the 'actin cytoskeleton-dependent cytoplasmic pathway of bud development and organelle positioning and inheritance' from the 'microtubule-dependent nuclear division pathway' in a budding yeast cell cycle.
- MeSH
- aktiny genetika metabolismus ultrastruktura MeSH
- aparát dělícího vřeténka genetika metabolismus MeSH
- buněčné dělení MeSH
- cytoplazma metabolismus MeSH
- fluorescenční mikroskopie metody MeSH
- mikrofilamenta genetika metabolismus ultrastruktura MeSH
- mikroskopie elektronová rastrovací transmisní metody MeSH
- mikroskopie elektronová rastrovací metody MeSH
- mikrotubuly genetika metabolismus ultrastruktura MeSH
- mutace MeSH
- Saccharomyces cerevisiae genetika růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Tumors that originate from neural crest-derived cells represent a heterogeneous group of neoplasms including benign and malignant tumors with melanocytic and schwannian differentiation. The immunophenotype of these tumors is well known but little is known about the expression of smooth muscle/myofibroblastic markers in these tumors. A total of 590 neural crest-derived tumors (50 benign schwannomas, five malignant peripheral nerve sheath tumors, 80 neurofibromas, 240 nevocytic nevi, 115 primary melanomas, and 100 melanoma metastases) were studied with respect to alpha-smooth muscle actin and muscle-specific actin expression. alpha-Smooth muscle actin and muscle-specific actin-positive tumor cells with a co-expression of S-100 protein were found in one benign schwannoma, one primary cutaneous melanoma, and four melanoma metastases. Four of these cases were examined ultrastructurally, but typical actin filaments with focal densities were not found in any of the four. Other immunohistochemical markers examined including desmin, h-caldesmon and smooth muscle myosin heavy chain were negative in the tumor cells. The present results suggest that neural crest-derived tumors could show expression of alpha-smooth muscle actin on rare occasion.
- MeSH
- aktiny metabolismus ultrastruktura MeSH
- crista neuralis metabolismus patologie MeSH
- financování organizované MeSH
- lidé MeSH
- melanocyty metabolismus patologie MeSH
- melanom metabolismus sekundární MeSH
- nádorové biomarkery metabolismus MeSH
- nádory nervové pochvy metabolismus patologie MeSH
- neurilemom metabolismus patologie MeSH
- neurofibrom metabolismus patologie MeSH
- pigmentový névus metabolismus patologie MeSH
- Check Tag
- lidé MeSH
Microtubular and actin cytoskeletons were investigated in the lipophilic yeast Malassezia pachydermatis by fluorescence and electron microscopy. To detect microtubules by indirect immunofluorescence using monoclonal anti-tubulin antibody, a prolonged incubation with lysing enzymes was necessary due to its very thick cell wall. Cytoplasmic microtubules were detected in interphase and a spindle with astral microtubules was seen in M-phase. The disintegration of cytoplasmic microtubules and migration of the nucleus to the bud before mitosis were characteristic features of the basidiomycetous yeast Malassezia pachydermatis. The visualisation of F-actin structures (patches, cables and cytokinetic rings) by fluorescence microscopy using both monoclonal anti-actin antibody and rhodamine-phalloidin failed, but actin was detected by electron microscopy with immunogold labelling. Clusters of gold particles indicating actin structures were detected at the plasma membrane of cells with unique cortical ultrastructural features characteristic of the genus Malassezia. A possible association of these with the actin cytoskeleton is suggested.
- MeSH
- aktiny ultrastruktura MeSH
- biologické modely MeSH
- buněčný cyklus MeSH
- cytoskelet metabolismus ultrastruktura MeSH
- financování organizované MeSH
- fluorescenční mikroskopie MeSH
- imunohistochemie MeSH
- Malassezia ultrastruktura MeSH
- mikrotomie MeSH
- mikrotubuly ultrastruktura MeSH
- mrazové lámání MeSH
The distribution of F-actin in the monogenean Entobdella soleae (van Beneden et Hesse, 1864) Johnston, 1929 (Platyhelminthes: Capsalidae) was revealed by staining paraformaldehyde-fixed specimens with FITC-labelled phalloidin. On the ventral surface on the left side of the body, just posterior to the pharynx, a concentrically arranged array of fluorescent fibres was observed, following a circular path around the tiny ventral opening of the vagina. It is assumed that this asymmetrically placed array of actin fibres is contractile and the possible role of these fibres in the assimilation of sperm from an attached spermatophore into the vagina is discussed.
- MeSH
- aktiny ultrastruktura MeSH
- fluorescenční mikroskopie MeSH
- Trematoda ultrastruktura MeSH
- vagina ultrastruktura MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
