oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Possible involvement of microtubules and microfilaments of the epididymal epithelial cells in 17beta-estradiol synthesis.  [cached]
Mariola Marchlewicz,Barbara Wiszniewska,Rafa? Kurzawa,Lidia Wenda-Rózewicka
Folia Histochemica et Cytobiologica , 2004, DOI: 10.5603/4663
Abstract: The rat epididymal epithelial cells revealed features of steroidogenic cells and released 17beta-estradiol (E2) into the culture medium. In steroidogenic cells, elements of the cytoskeleton due to their influence on organelle distribution are implicated in the regulation of steroidogenesis. In the present study, the morphology of cultured epididymal epithelial cells in light, scanning and transmission electron microscopes was evaluated. The organization of microtubules and microfilaments revealed by fluorescence microscopy, and the concentration of E2 in cultured medium were also studied. The epididymal epithelial cells were cultured in different conditions: in the medium with or without exogenous testosterone (T) and in the co-culture with Leydig cells as a source of androgens. The cells in co-culture located close to Leydig cells were rich in glycogen, PAS-positive substances and lipid droplets, in higher amount than the cells cultured with addition of exogenous testosterone. Stress fibers and microtubules of epididymal epithelial cells cultured with exogenous T and in co-culture with Leydig cells presented typical structure, and numerous granular protrusions appeared on the surface of the cells. Disorganization of microtubules and shortening of stress fibers as well as the smooth cell surface deprived of granular protrusions were observed in the epididymal epithelial cells cultured without T. Change of the cytoskeleton organization caused by the absence of androgen in culture medium resulted in an increased E2 secretion.
Chronological Reorganization of Microtubules, Actin Microfilaments, and Chromatin during the First Cell Cycle in Swamp Buffalo (Bubalus bubalis) Embryos
Vibuntita Chankitisakul,Theerawat Tharasanit,Kriengsak Tasripoo,Mongkol Techakumphu
Veterinary Medicine International , 2010, DOI: 10.4061/2010/382989
Abstract: This paper aimed to study the dynamics of early embryonic development, in terms of redistribution of cytoskeleton (microtubules, actin microfilaments) and chromatin configurations during the first cell cycle in swamp buffalo embryos. Oocytes were matured and fertilized in vitro, and they were fixed at various time points after IVF. At 6 h after IVF, 44.4% matured oocytes were penetrated by spermatozoa. Partial ZP digestion, however, did not improve fertilization rate compared to control (>.05). At 12 h after IVF, the fertilized oocytes progressed to the second meiotic division and formed the female pronucleus simultaneously with the paternal chromatin continued to decondense. A sperm aster was observed radiating from the base of the decondensing sperm head. At 18 h after IVF, most presumptive zygotes had reached the pronuclear stage. The sperm aster was concurrently enlarged to assist the migration and apposition of pronuclei. Cell cleavage was facilitated by microfilaments and firstly observed by 30 h after IVF. In conclusion, the cytoskeleton actively involves with the process of fertilization and cleavage in swamp buffalo oocytes. The centrosomal material is paternally inherited. Fertilization failure is predominantly caused by poor sperm penetration. However, partial digestion of ZP did not improve fertilization rate.
Incorporation of mammalian actin into microfilaments in plant cell nucleus
Heiti Paves, Erkki Truve
BMC Plant Biology , 2004, DOI: 10.1186/1471-2229-4-7
Abstract: Visualization of microfilaments in onion bulb scale epidermis cells by different techniques revealed that rhodamine-phalloidin stained F-actin besides cytoplasm also in the nuclei whereas GFP-mouse talin hybrid protein did not enter the nuclei. Microinjection of fluorescently labeled actin was applied to study the presence of nuclear microfilaments in plant cells. Ratio imaging of injected fluorescent rabbit skeletal muscle actin and phalloidin staining of the microinjected cells showed that mammalian actin was able to incorporate into plant F-actin. The incorporation occurred preferentially in the nucleus and in the perinuclear region of plant cells whereas part of plant microfilaments, mostly in the periphery of cytoplasm, did not incorporate mammalian actin.Microinjected mammalian actin is able to enter plant cell's nucleus, whereas incorporation of mammalian actin into plant F-actin occurs preferentially in the nucleus and perinuclear area.Actin is an ancient molecule and is believed to find its origin at the onset of eukaryotic life 2 billion years ago [1]. Comparison of amino acid sequences has shown more than 90% homology between mammalian and plant actins [2]. The regions of the actin molecule that are involved in actin-actin contacts (F-actin assembly) are largely conserved, and it has been shown that actins from evolutionally distant organisms are able to copolymerize with mammalian skeletal muscle actin [3], [4]. Thus, it is likely that mammalian actin is able to incorporate into microfilaments in plant cells but there is no experimental evidence until now.Fluorescent analogues of actin and tubulin have been used for studies on cytoskeletal dynamics in animal cells. Mammalian fluorescently labeled neurotubulin has been shown to incorporate into plant microtubules [5], but fluorescent staining of plant microfilaments in living cells has been carried out indirectly, using phalloidin derivates [6], GFP-mouse talin fusion protein [7], and fluorescently labele
A model of chloroplast growth regulation in mesophyll cells  [PDF]
Kelly M. Paton,Lisa Anderson,Pauline Flottat,Eric N. Cytrynbaum
Quantitative Biology , 2015,
Abstract: Chloroplasts regulate their growth to optimize photosynthesis. Quantitative data shows that the ratio of total chloroplast area to mesophyll cell area is constant across different cells within a single species, and also across species. Wild-type chloroplasts exhibit little scatter around this trend; highly irregularly-shaped mutant chloroplasts exhibit more scatter. Here we propose a model motivated by a bacterial quorum-sensing model consisting of a switch-like signalling network that turns off chloroplast growth. We calculated the dependence of the location of the relevant saddle-node bifurcation on the geometry of the chloroplasts. Our model exhibits a linear trend, with linearly growing scatter dependent on chloroplast shape, consistent with the data. When modelled chloroplasts are of a shape that grows with a constant area to volume ratio (disks, cylinders) we find a linear trend with minimal scatter. Chloroplasts with area and volume that do not grow proportionally (spheres) exhibit a linear trend with additional scatter.
Rapid and dynamic subcellular reorganization following mechanical stimulation of Arabidopsis epidermal cells mimics responses to fungal and oomycete attack
Adrienne R Hardham, Daigo Takemoto, Rosemary G White
BMC Plant Biology , 2008, DOI: 10.1186/1471-2229-8-63
Abstract: Within 3 to 5 minutes of touching the surface of Arabidopsis cotyledon epidermal cells with fine glass or tungsten needles, actin microfilaments, ER and peroxisomes began to accumulate beneath the point of contact with the needle. Formation of a dense patch of actin was followed by focusing of actin cables on the site of contact. Touching the cell surface induced localized depolymerization of microtubules to form a microtubule-depleted zone surrounding a dense patch of GFP-tubulin beneath the needle tip. The concentration of actin, GFP-tubulin, ER and peroxisomes remained focused on the contact site as the needle moved across the cell surface and quickly dispersed when the needle was removed.Our results show that plant cells can detect the gentle pressure of a microneedle on the epidermal cell surface and respond by reorganizing subcellular components in a manner similar to that induced during attack by potential fungal or oomycete pathogens. The results of our study indicate that during plant-pathogen interactions, the basal defence response may be induced by the plant's perception of the physical force exerted by the pathogen as it attempts to invade the epidermal cell surface.Early studies of plant-pathogen interactions documented an increase in the activity of cytoplasmic streaming and accumulation of cytoplasm beneath the invading pathogen cell as the first structural manifestation of the response of plants to microorganisms on their surface [1-4]. Cytoplasmic aggregation is accompanied by reorganization of cytoskeletal and endomembrane components which become focused on the infection site [5-8]. This cytoplasmic reorganization is followed by thickening and strengthening of the cell wall to form wall appositions, or papillae, beneath the invading pathogen [9]. Wall appositions develop as the result of localized deposition of callose and site-directed secretion of other cell wall components and anti-microbial compounds including phenolics, silicon, H2O2 and path
Lifeact-mEGFP Reveals a Dynamic Apical F-Actin Network in Tip Growing Plant Cells  [PDF]
Luis Vidali, Caleb M. Rounds, Peter K. Hepler, Magdalena Bezanilla
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005744
Abstract: Background Actin is essential for tip growth in plants. However, imaging actin in live plant cells has heretofore presented challenges. In previous studies, fluorescent probes derived from actin-binding proteins often alter growth, cause actin bundling and fail to resolve actin microfilaments. Methodology/Principal Findings In this report we use Lifeact-mEGFP, an actin probe that does not affect the dynamics of actin, to visualize actin in the moss Physcomitrella patens and pollen tubes from Lilium formosanum and Nicotiana tobaccum. Lifeact-mEGFP robustly labels actin microfilaments, particularly in the apex, in both moss protonemata and pollen tubes. Lifeact-mEGFP also labels filamentous actin structures in other moss cell types, including cells of the gametophore. Conclusions/Significance Lifeact-mEGFP, when expressed at optimal levels does not alter moss protonemal or pollen tube growth. We suggest that Lifeact-mEGFP represents an exciting new versatile probe for further studies of actin's role in tip growing plant cells.
Development of Chloroplast in the Mesophyll Cells of Satsuma Mandarin Foliar Sprayed with Urea  [PDF]
Socorro E. Aguja,Pear Mohammad,Masaya Shiraishi
Pakistan Journal of Biological Sciences , 1999,
Abstract: The development of chloroplasts in the mesophyll cells of control and urea-applied satsuma mandarin leaves were studied. At 20 days after budding (DAB) active differentiation of chloroplasts in urea-applied trees was evident. However, on a length times width basis, chloroplasts were small in both palisade (1.99x0.70μ m2) and spongy (2.78x1.50μ m2) layers that contained few small (0.53 - 0.72x0.39 - 0.57 μm2) starch grains. The thylakoid layers per chloroplast were lesser (2.80) in this treatment compared to control (3.72). At 40 DAB, both control and urea-applied trees reached chloroplast maturity, but control trees had bigger chloroplast (4.87x2.39μ m2) in the palisade layer cells which contained extremely large and numerous starch grains with few dilated thylakoid layers. Degenerating chloroplasts in the spongy layer cells of control trees were characterized by the disappearance of the outer membrane. While urea-applied trees had smaller chloroplast (4.56x2.39μ m2) in the palisade layer. Further, few small starch grains, thylakoid-filled stroma and many lipid droplets were found. Moreover, thylakoid layers were about to dilate but outer membrane of the chloroplasts remained intact in both palisade and spongy layer cells. Compared to the palisade layer cells, chloroplasts in the spongy were bigger (5.32x1.95μ m2).
FUNCTION OF MALATDEHYDROGENASE COMPLEX OF MAIZE MESOPHYLL AND BUNDLE SHEATH CELLS UNDER SALT STRESS CONDITION  [PDF]
Еprintsev А.Т.,Fedorina О.S.
Journal of Stress Physiology & Biochemistry , 2006,
Abstract: Salt-induced changes in malatdehydrogenase system activity make the essential contribution to cell adaptation to stress condition. The enzyme systems of C4-plants are most interesting due to their ability for adaptation to environment conditions. The role of separate components of malatdehydrogenase complex of mesophyll and bundle sheath cells of corn in formation of adaptive reaction in stressful conditions is investigated in presented work.The activation of all enzymes of malatdehydrogenase system and the subsequent decrease in their activity was observed in mesophyll durring the first stage of adaptation to salt influence. In bundle sheath cells such parameters are differed from control less essentially. Fast accumulation of piruvate in cells and malate in both investigated tissues was induced. The further salinity led to falling of concentration this intermediate. The concentration of piruvate was below control level, and it was raised by the end of an exposition.The results show that sodium chloride causes induction of Krebs-cycle in mesophyll and bundle sheath cells of corn and intensification of Hatch-Slack cycle. The described differences in function malatdehydrogenase systems of mesophyll and bundle sheath cells of leaves of corn under salinity mainly consist of the activity of enzymes of a studied complex in bundle sheath cells is subject to the minimal changes in comparison with mesophyll. Role of this enzymesystem in mechanisms of adaptive reaction of various tissues of corn to salt stress is discussed.
Regulation of the inward K+-channels in stomatal guard cells by cytoskeletal microtubules
Ximing Zhou,Weihua Wu,Ming Yuan,Xuechen Wang
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02885065
Abstract: Patch clamp techniques were applied to investigating the regulation of the inward K+-channels inVicia stomatal guard cells by cytoskeletal microtubules. The intracellular addition of either microtubule-disassembling reagent amprophos-methyl (APM) or microtubule-stabilizing reagent taxol resulted in significant inhibition of the inward K+-currents across the plasma membranes ofVicia stomatal guard cells. The results suggest that the activation of the inward K+-channels in stomatal guard cells requires proper dynamic organization of cytoskeletal microtubules. The regulation of the inward K+-channels in guard cells by microtubules may mediate the regulation of stomatal movements by cytoskeleton.
Regulation of the inward K~+-channels in stomatal guard cells by cytoskeletal microtubules

Ximing Zhou,Weihua Wu,Ming Yuan,Xuechen Wang,

科学通报(英文版) , 1999,
Abstract: Patch clamp techniques were applied to investigating the regulation of the inward K+-channels inVicia stomatal guard cells by cytoskeletal microtubules. The intracellular addition of either microtubule-disassembling reagent amprophos-methyl (APM) or microtubule-stabilizing reagent taxol resulted in significant inhibition of the inward K+-currents across the plasma membranes ofVicia stomatal guard cells. The results suggest that the activation of the inward K+-channels in stomatal guard cells requires proper dynamic organization of cytoskeletal microtubules. The regulation of the inward K+-channels in guard cells by microtubules may mediate the regulation of stomatal movements by cytoskeleton.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.