Showing papers on "Ultrastructure published in 2004"
TL;DR: The early harbinger of radial asymmetry described here could play a crucial role during basal body maturation by orienting the asymmetric attachment of the various associated fibers and therefore might define the orientation of the basal bodies and, ultimately, the direction of flagellar beating.
Abstract: The biflagellate unicellular green alga Chlamydomonas reinhardtii is a classic model organism for the analysis of flagella and their organizers, the basal bodies. In this cell, the two flagella-bearing basal bodies, along with two probasal bodies and an array of fibers and microtubules, form a complex organelle called the basal apparatus. The ultrastructure of the basal apparatus was analysed in detail by serial thin-section electron microscopy of isolated cytoskeletons and several newly discovered features are described, including a marker for the rotational asymmetry inherent in the basal bodies and probasal bodies. In addition, the complex three-dimensional basal apparatus ultrastructure is resolved and illustrated, including the attachment sites of all basal apparatus elements to specific microtubular triplets of the basal bodies and probasal bodies. These data will facilitate both the localization of novel basal apparatus proteins and the analysis of mutants and RNA interference cells with only subtle defects in basal apparatus ultrastructure. The early harbinger of radial asymmetry described here could play a crucial role during basal body maturation by orienting the asymmetric attachment of the various associated fibers and therefore might define the orientation of the basal bodies and, ultimately, the direction of flagellar beating.
138 citations
TL;DR: Modifications in the chloride (mitochondria-rich) and pavement cells of the gill epithelia of the Adriatic sturgeon Acipenser naccarii after their transfer under hypertonic environmental conditions were examined and indicated enhanced cellular activity.
Abstract: Modifications in the chloride (mitochondria-rich) and pavement cells of the gill epithelia of the Adriatic sturgeon Acipenser naccarii after their transfer under hypertonic environmental conditions (salinity 35) were examined by light and electron microscopy. In contrast to freshwater specimens, seawater-acclimated fish showed a marked increase in the number and size of chloride cells. Ultrastructural modifications included: presence of a slightly invaginated apical crypt, a darker cytoplasm, a more compact tubular system, a major increase in cisternae from Golgi apparatus stacks and flattened-out sacs with dilated ends that produced an increase in lateral and basal cell surfaces. All these changes indicated enhanced cellular activity. Pavement cells, which largely covered the chloride cells on the gill filament and lamella, exhibited a complex system of microridges on their apical surface. Typical features included numerous desmosomes that characterized the intercellular junction, and the presence in the apical cytoplasm of bundles of filaments and of electro-dense vesicles in freshwater fish or clear vesicles in seawater-acclimated animals.
92 citations
TL;DR: The ultrastructure of Mycobacterium tuberculosis cells undergoing division was examined by electron microscopy and two features of cell division were observed and are described here.
Abstract: The ultrastructure of Mycobacterium tuberculosis cells undergoing division was examined by electron microscopy. Two features of cell division were observed and are described here. First, cells are capable of undergoing a type of “snapping” postfission movement. This movement is likely due to a multi-layered cell wall in which the inner layer participates in septum formation while the outer layer ruptures first on one side. A second feature related to cell division is the ability of dividing cells to form transient branching structures.
60 citations
TL;DR: The general morphological properties, ultrastructural organization, and physiological features of cystlike cells formed during the developmental cycle suggest that constitutive dormancy is characteristic of non-spore-forming bacteria.
Abstract: Using electron microscopy (ultrathin sections and freeze-fractures), we investigated the ultrastructure of the resting cells formed in cultures of Micrococcus luteus, Arthrobacter globiformis, and Pseudomonas aurantiaca under conditions of prolonged incubation (up to 9 months). These resting cells included cystlike forms that were characterized by a complex cell structure and the following ultrastructural properties: (i) a thickened or multiprofiled cell wall (CW), typically made up of a layer of the preexisting CW and one to three de novo synthesized murein layers; (ii) a thick, structurally differentiated capsule; (iii) the presence of large intramembrane particles (d = 180–270 A), occurring both on the PF and EF faces of the membrane fractures of M. luteus and A. globiformis; (iv) a peculiar structure of the cytoplasm, which was either fine-grained or lumpy (coarse-grained) in different parts of the cell population; and (v) a condensed nucleoid. Intense formation of cystlike cells occurred in aged (2- to 9-month-old) bacterial cultures grown on diluted complex media or on nitrogen-, carbon-, and phosphorus-limited synthetic media, as well as in cell suspensions incubated in media with sodium silicate. The general morphological properties, ultrastructural organization, and physiological features of cystlike cells formed during the developmental cycle suggest that constitutive dormancy is characteristic of non-spore-forming bacteria.
59 citations
TL;DR: The morphology of the midgut epithelium cells of Anticarsia gemmatalis (Hübner) larvae is described by light and transmission electron microscopy.
Abstract: The morphology of the midgut epithelium cells of Anticarsia gemmatalis (Hubner) larvae is described by light and transmission electron microscopy. The midgut of A. gemmatalis is the largest portion of the digestive tract, with three distinct regions: proximal, media and distal. Its wall is formed by pseudostratified columnar epithelial tissue having four cell types: columnar, goblet, regenerative, and endocrine cells. The columnar cells are numerous and long, with the apical portion showing many lengthy microvilli and the basal portion invaginations forming a basal labyrinth. The goblet cells have a large goblet-shaped central cavity delimited by cytoplasmic projections filled with mitochondria. The regenerative cells present electron-dense cytoplasm and few organelles. The endocrine cells are characterized by electron-dense secretory granules, usually concentrated in the cytoplasm basal region.
59 citations
TL;DR: In the two Citrus species the pattern of oil gland development was practically the same, except the different plastid behaviour, which was preceded by an abundant essential oil synthesis.
51 citations
TL;DR: It is concluded that heat shock disrupts microtubule and microfilaments in the two-cell bovine embryo and that these changes are responsible for movement of organelles away from the periphery.
Abstract: Two-cell bovine embryos become arrested in development when exposed to a physiologically relevant heat shock. One of the major ultrastructural modifications caused by heat shock is translocation of organelles toward the center of the blastomere. The objective of the present study was to determine if heat- shock-induced movement of organelles is a result of cytoskeletal rearrangement. Two-cell bovine embryos were cultured at 38.5 degrees C (homeothermic temperature of the cow), 41.0 degrees C (physiologically relevant heat shock), or 43.0 degrees C (severe heat shock) for 6 h in the presence of either vehicle, latrunculin B (a microfilament depolymerizer), rhizoxin (a microtubule depolymerizer), or paclitaxel (a microtubule stabilizer). Heat shock caused a rearrangement of actin-containing filaments as detected by staining with phalloidin. Moreover, latrunculin B reduced the heat-shock-induced movement of organelles at 41.0 degrees C but not at 43.0 degrees C. In contrast, movement of organelles caused by heat shock was inhibited by rhizoxin at both temperatures. Furthermore, rhizoxin, but not latrunculin B, reduced the swelling of mitochondria caused by heat shock. Paclitaxel, while causing major changes in ultrastructure, did not prevent the movement of organelles or mitochondrial swelling. It is concluded that heat shock disrupts microtubule and microfilaments in the two-cell bovine embryo and that these changes are responsible for movement of organelles away from the periphery. In addition, intact microtubules are a requirement for heat-shock-induced swelling of mitochondria. Differences in response to rhizoxin and paclitaxel are interpreted to mean that deformation of microtubules can occur through a mechanism independent of microtubule depolymerization.
46 citations
TL;DR: New observations concerning the median bodies of Giardia lamblia add new data on the scarce literature and to this largely understudied cell structure.
40 citations
TL;DR: Results provide indirect evidence for a metabolic Se requirement in this algal species and various types of inclusions are seen in vacuolar areas and the accumulation of lipid reserves is evident in Se‐deficient cells.
Abstract: The effects of selenium deficiency on the siliceous and nonsiliceous components of the planktonic marine diatom Thalassiosira pseudonana (Hust) Hasle and Heimdal (clone 3H) are examined using light and electron microscopy Selenium deficiency induces elongation along the pervalvar axis initially as a result of chain formation caused by the failure of sibling cells to separate and subsequently by cell elongation via the production of hyaline girdle bands In Se-deficient cultures cell elongation involves the blockage of both mitotic and cytokinetic components of cell division Selenium deficiency results in ultrastructural alterations in the reticular membrane system and in mitochondrial and chloroplast membranes Various types of inclusions are seen in vacuolar areas and the accumulation of lipid reserves is evident in Se-deficient cells These results provide indirect evidence for a metabolic Se requirement in this algal species
38 citations
TL;DR: In this paper, the exact nature of the staining reaction with iodine and to provide insight into the properties and organisation of the wood cell wall was investigated. But the results were limited to tracheid cells.
Abstract: Iodine staining has been used to study the orientation of cellulose microfibrils in wood using light microscopy. The aim of this work was to understand the exact nature of the staining reaction with iodine and to provide insight into the properties and organisation of the wood cell wall. Based on transmission electron microscopy it is apparent that precipitation of the iodine following treatment with nitric acid results in the formation of crystal cavities within the cell wall, which follow the orientation of the cellulose microfibrils. There is no evidence that iodine precipitates within drying checks as previously speculated. High resolution confocal reflectance microscopy of crystal cavity orientation indicates that the microfibril arrangement within pit borders can be both spiral and circular. Crystal cavities are much more abundant within the S1 layer than elsewhere. All of the cells examined had crystal cavities in the S1 region, which may be related to the reduced lignification at the S1/S2 boundary resulting in greater porosity of the cell wall at this location. Within the S2 region, clusters of crystal cavities are randomly distributed and occur in widely varying numbers among adjacent cell walls, suggesting variations in the porosity of the S2 wall within and among adjacent tracheids. Cavities form preferentially within more electron lucent regions of the cell wall. The random nature of crystal cavity formation within S2 clusters probably reflects the underlying random nature of the cell wall nanostructure. We conclude that iodine staining can provide important clues to the nanostructural properties of tracheid cell walls.
36 citations
TL;DR: The effects of the microtubule affecting drugs taxol, nocodazole and colchicine on the cell cycle and ultrastructure of Tritrichomonas foetus, a protist parasite of cattle, were studied.
Abstract: The effects of the microtubule affecting drugs taxol, nocodazole and colchicine on the cell cycle and ultrastructure of Tritrichomonas foetus, a protist parasite of cattle, were studied. Alterations in the cytoskeleton, motility and organellar ultrastructure were followed using anti-tubulin antibodies and fluorescence microscopy, scanning- and transmission-electron microscopy. Flow cytometry was also used to analyze the effect of the drugs on the cell cycle. T. foetus was treated with 10 microM taxol, 15 microM nocodazole or 1.5 mM colchicine for 12 h. The first effect observed was pseudocyst formation and alterations in cell motility. The cell cycle was affected and the cells have blocked cytokinesis, but not karyokinesis. The behavior of Golgi, hydrogenosomes and vacuoles was analyzed. The following effects were seen following drug treatments: (1) cell motility was altered and flagella internalized; (2) microtubules of the pelta-axostyle complex were not depolymerized and the axostyle assumed a curved form; (3) hydrogenosomes were of abnormal size and shape; (4) cells became multinucleate; (5) the division process was blocked in cytokinesis; (6) autophagic vacuoles containing a large amount of microtubules were seen; (7) axoneme organization was altered; (8) zoids were formed; (9) signs of cell death, such as membrane blebbing, were observed.
TL;DR: The deposits of the IP6‐Ca(II) salt are also observed inside membrane vesicles in cells of the germinal layer of the HCW, indicating that IP6 precipitates with calcium within a cellular vesicular compartment and is then secreted to the LL.
Abstract: The ubiquitous intracellular molecule myo-inositol hexakisphosphate (IP6) is present extracellularly in the hydatid cyst wall (HCW) of the parasitic cestode Echinococcus granulosus. This study shows that extracellular IP6 is present as its solid calcium salt, in the form of deposits that are observed, at the ultrastructural level, as naturally electron dense granules some tens of nanometers in diameter. The presence of a calcium salt of IP6 in these structures was determined by two different electron microscopy techniques: (i) the analysis of the spatial distribution of phosphorus and calcium in the outer, acellular layer of the HCW (the laminated layer, LL) through electron energy loss spectroscopy, and (ii) the observation, by transmission electron microscopy, of HCW that were selectively depleted of IP6 by treatment with EGTA or phytase, an enzyme that catalyses the dephosphorylation of IP6. The deposits of the IP6-Ca(II) salt are also observed inside membrane vesicles in cells of the germinal layer (the inner, cellular layer of the HCW), indicating that IP6 precipitates with calcium within a cellular vesicular compartment and is then secreted to the LL. Thus, much as in plants (that produce vesicular IP6 deposits), the existence of transporters for IP6 or its precursors in internal membranes is needed to explain the compound's cellular localisation in E. granulosus. © 2004 Wiley-Liss, Inc.
TL;DR: Energy-filtering transmission electron microscopy by use of an in-column spectrometer is employed as a powerful tool for ultrastructural analysis of plant cells by facilitating the detection of immunomarkers without renunciation of contrast.
Abstract: In the present study energy-filtering transmission electron microscopy by use of an in-column spectrometer is employed as a powerful tool for ultrastructural analysis of plant cells. Images of unstained very thin (50 nm) and thick (140 nm) sections of the unicellular green alga Micrasterias denticulata, as a model system for a growing plant cell, taken by conventional transmission electron microscopy are compared to those obtained from filtering at zero energy loss (elastic bright field) and to those generated by energy filtering below the carbon-specific absorption edge at about 250 eV. The results show that the high-contrast images produced by the latter technique are distinctly superior in contrast and information content to micrographs taken at conventional transmission electron microscopy mode or at elastic bright field. Post- or en bloc staining with heavy metals, which is indispensable for conventional bright-field transmission electron microscopy, can be completely omitted. Delicate structural details such as membranous or filamentous connections between organelles, organelle interactions, or vesicle and vacuole contents are clearly outlined against the cytoplasmic background. Also, immunoelectron microscopic localization of macromolecules benefits from energy-filtering transmission electron microscopy by a better and more accurate assignment of antigens and structures and by facilitating the detection of immunomarkers without renunciation of contrast.
TL;DR: The appearance and the modification of the gill apparatus in Rana dalmatina tadpoles have been described in the different phases of larval development and the morphology and ultrastructure have been studied using light microscopy and both scanning and transmission electron microscopy.
Abstract: The appearance and the modification of the gill apparatus in Rana dalmatina tadpoles have been described in the different phases of larval development. The morphology and ultrastructure have been studied using light microscopy and both scanning and transmission electron microscopy. The organization of the gills during the initial phases of development (external gills or transient gills) brings to mind the characteristics of Urodela larvae in which the gills appear to consist of three tufts of filaments supported by the gill arches III, IV and V. The cellular composition of the transient gills appears to be extremely simple and the presence of specialized cells is not noted. Basal cells, pavement cells and ciliated cells form the thin mono- or bilayered epithelium. In the persistent gills (or internal gills) of the R. dalmatina tadpole (Orton’s larval type 4) the gill arches carry four rows of gill tufts branching out to the ventral region. Meanwhile, from the dorsal portion of the arch the gill filters present an axial portion from which there is much branching out, which confers a characteristic appearance on this part of the gills. The cellular composition of the gill tufts and of the filters is different: in the gill tufts basal cells, pavement cells, ciliated cells, cubic cells and mitochondria-rich cells (MRCs) have been recognized, while in the gill filters the last cellular type does not appear. The MRC has highly variable forms and dimensions and is characterized by the presence of numerous mitochondria in the cytoplasm. Often the MRCs manifest themselves grouped together, in groups of three or more. The pavement cells and the cubic cells demonstrate identical ultrastructural characteristics and have an external surface area characterized by the presence of short superficial microridges and numerous vacuoles in the apical cytoplasm.
TL;DR: Both treatments with DEC in vitro and in vivo had a direct mechanism of action on the microfilariae of W. bancrofti, including organelle damage and apoptosis.
Abstract: An ultrastructural study of microfilariae of Wuchereria bancrofti was performed after treatment in vitro and in vivo with diethylcarbamazine citrate (DEC). The morphological alterations produced by treatment in vitro with 5 µg/ml of DEC were the loss of microfilarial sheaths and lysis of the cytoplasm, with the destruction of all organelles and the formation of several vacuoles, the contents of which presented various degrees of electron-density, or showed an empty appearance. Some of these vacuoles seemed to be extruding from the cytoplasm as apoptotic bodies and others presented organelles inside. Similar alterations were observed after in vivo treatment. At 40 min after treatment of a microfilaremic individual with DEC, almost all microfilariae observed had lost their sheaths; and, in some of them, remains of the microfilarial sheath on the larval surface could be detected. Numerous vacuoles were observed, mainly in the hypodermis and somatic cells, showing organelles inside or an empty appearance. Condensed chromatin was also observed in some somatic cells. At 1 h after treatment of a microfilemic individual with DEC, microfilariae presented drastic morphological alterations, with large vacuoles within somatic cell cytoplasm and complete lysis of all cellular organelles. Therefore, both treatments with DEC in vitro and in vivo had a direct mechanism of action on the microfilariae of W. bancrofti, including organelle damage and apoptosis.
TL;DR: Spore morphology, gross structure and wall ultrastructure are compared to that of extant and fossil plant groups, and it is concluded that the spores of O. catheta are highly distinctive and do not conform closely to any plant group, although they show most in common with the fungus of the progymnosperms.
TL;DR: Comparative analysis of cyst wall structure with other dinoflagellate species showed this three layered structure is common among refractive cysts, and that the principal components of the Cyst wall surface were sulphur and silica.
Abstract: Light, scanning and transmission electron microscopy were carried out on Alexandrium tamarense and A. fundyense hypnozygotes (cysts) from cultures and marine sediments. Transmission electron microscopy protocols were adapted to improve the quality of ultrathin sections. Cell contents of hypnozygotes were reduced compared to vegetative stages and were largely made up of storage vesicles in a dense, granular matrix. Chloroplasts and other organelles (Golgi bodies, endoplasmic reticulum and mitochondria) were observed as whorls of undifferentiated membranes and the nucleus was compressed with strongly condensed, granular chromosomes. Two types of accumulation bodies were found, some composed of dense amorphous material and others containing polygonal crystalline inclusions. Both types contained numerous membrane profiles. In cross section, the hypnozygote wall was made up of three layers divided by membranes: an outer layer with a thin electron-dense distal surface and membrane that formed the interface with the environment; a wide middle layer of striated material and membrane (possibly involved in deposition of cyst wall material); and a narrow unstructured inner layer and membrane lying close to the cytoplasmic membrane of the cell. Comparative analysis of cyst wall structure with other dinoflagellate species showed this three layered structure is common among refractive cysts. Energy dispersive X-ray analysis of the cyst wall surface demonstrated that the principal components of the cyst wall were sulphur and silica.
Copyright © (2004) International Phycological Society. Reprinted by permission of Alliance Communications Group, a division of Allen Press, Inc.
Journal Article•
TL;DR: Describing of the fine structure of cells and fibres of the central nervous system presented below is based on classical textbooks as well as on the authors' personal experience.
Abstract: Since the articles in this supplement describe ultrastructural changes in diseases of the nervous system, for better understanding of these papers dealing with pathology of the this system, basic elements of the ultrastructure of the central nervous system are presented in this survey. Description of the fine structure of cells and fibres of the central nervous system presented below is based on classical textbooks as well as on the authors' personal experience. The details of ultrastructure of nerve cells (their nucleus and cytoplasm, including cell organelles: abundant granular endoplasmic reticulum, prominent Golgi apparatus, mitochondria, lysosomes, as well as other cell components including: neurofilaments, lipid droplets, multivesicular bodies, lipid droplets, lipofuscin granules, and in some cells melanin granules, and also cell processes), the interneuronal chemical synapses (specialized site of interneuronal communication) as well as all types of neuroglial cells (a class of non-neuronal supporting cells): astrocytes (fibrous and protoplasmic), oligodendrocytes, and microglia neuroglial cells are described.
TL;DR: The ultrastructure of microbial cells was studied in situ in natural biotopes by high-resolution transmission electron microscopy using the known methods of cryofractography, thin sectioning, and the negative staining of total cell specimens, as well as the new methods of the low-temperature fractionation of microbes.
Abstract: The ultrastructure of microbial cells was studied in situ in natural biotopes by high-resolution transmission electron microscopy using the known methods of cryofractography, thin sectioning, and the negative staining of total cell specimens, as well as the new methods of the low-temperature fractionation of microbial cells (providing for the recovery of cells from natural sources and their concentration), the preparation of micromonoliths, and aimed electron microscopy. Among the natural biotopes studied were permafrost ground and oil sludge. Most of the microorganisms found in the 1- to 3-million-year-old permafrost ground were represented by resting forms (spores, cysts, and cystlike cells with specific organomineral envelopes). Oil sludge older than 35 years contained bacteria of atypical morphology and ultrastructure, including various resting forms and ultramicrobacteria. The data obtained is indicative of considerable promise of high-resolution electron microscopy for studying microbial communities in situ.
TL;DR: Analysis by transmission electron microscopy of trophozoites recovered from experimental amebic liver lesions in hamsters revealed two types of cytoplasmic changes, which resemble the encystation vesicles of Entamoeba invadens and Giardia lamblia.
TL;DR: In this study the treatment of cells with dilute Triton X-100 detergent prior to fixation has improved preservation of the ultrastructure of both Paradermamoeba species.
TL;DR: The ultrastructural localization of ryanodine receptors (RyR) in sinus endothelial cells of the rat spleen was examined by confocal laser scanning and electron microscopy by using isoform-specific antibodies to each of the RyR isoforms.
Abstract: The ultrastructural localization of ryanodine receptors (RyR) in sinus endothelial cells of the rat spleen was examined by confocal laser scanning and electron microscopy by using isoform-specific antibodies to each of the RyR isoforms. Immunofluorescence microscopy of tissue cryosections revealed RyR3 to be localized, with a strand-like form, in the superficial layer and within the cytoplasm of endothelial cells. Antibodies to RyR1 and RyR2 did not react indicating RyR3 was the predominant isoform. RyR3 was observed over the cortical layer of actin filaments in the apical part and beneath stress fibers in the basal part of the endothelial cells. The distribution of Ca2+-storing tubulovesicular-structures within endothelial cells was established by tissue sections treated with osmium ferricyanide selectively to stain the sarcoplasmic reticulum and transverse tubules in muscle cells; electron microscopy revealed densely stained tubulovesicular structures located throughout the sinus endothelial cells and interconnected at various sites. These structures closely apposed the plasma membrane at the apical, lateral, and basal surfaces of the cells and occasionally ran closely parallel to the plasma membrane and near to the mitochondria. Immunogold electron microscopy revealed RyR in the membranes of the nucleus, tubulovesicular structures, and subplasmalemmal cisternae. In the subplasmalemmal cisternae at the apical, lateral, and basal surfaces, RyR was detected on the membranes near to the plasma membrane. Labeling was also present on the membranes of tubulovesicular structures near to caveolae and on the cristae of the mitochondria. Thus, RyR probably participates in Ca2+ signal transduction and/or mechanosignal transduction in sinus endothelial cells.
TL;DR: Smooth endoplasmic reticulum was abundant in the secretory cells of physogastric queens, indicating that these cells produce lipid secretion that is stored in granules with multi-lamellar bodies.
TL;DR: The extreme similarity in motile cell ultrastructure revealed in this interspecific comparison parallels that similarity revealed in intergeneric comparisons.
Abstract: Cephaleuros parasiticus Karsten, an endophyte of Magnolia grandiflora L. has been examined with light, and scanning and transmission electron microscopy. The discoid thalli are composed of filaments which ramify throughout the leaf tissues beneath the epidermis. Algal filaments do not penetrate host cells, but do produce black leaf spots which have been mistaken for those caused by the fungus Glomerella cingulate (Ston.) Spauld. and Schrenk. Two distinct thallus types occur, often simultaneously on a single leaf. One bears clusters of zoosporangiate branches which seasonally emerge through the ventral (and rarely, dorsal) surface of the leaf. In contrast, the other thallus type bears gametangia which break through the dorsal leaf surface. Zoosporangia and gametangia have never been found on the same thallus. The zoosporangia are smaller than, but almost identical in shape to, those of C. virescens Kunze. Simple plasmodesmata are present in crosswalls and acetolysis indicates that little or no sporopollenin is present in the cell walls. The ultrastructure of biflagellate gametes and quadriflagellate zoospores is virtually indistinguishable from that reported for C. virescens and similar to that reported for Phycopeltis and Trentepohlia. In both gametes and zoospores there are keeled flagella, overlapping and parallel basal bodies, two 3-layered multilayered structures with microtubular splines, and two medial compound microtubular roots. Pyrenoids, eyespots, flagellar and body scales, striated roots (or rhizoplasts), and distal bands are absent. Two presumptive mating structures are present in each biflagellate gamete, and flagellar collars occur in both types of motile cells. The extreme similarity in motile cell ultrastructure revealed in this interspecific comparison parallels that similarity revealed in intergeneric comparisons.
TL;DR: The intestinal epithelium of third-stage larvae and adults of Cystidicoloides ephemeridarum from haemocoel of mayflies and stomach of brown trout was studied by electron microscopy and cytochemistry to suggest that the intestine may function in digestion and absorption during both stages.
Abstract: The intestinal epithelium of third-stage larvae and adults of Cystidicoloides ephemeridarum from haemocoel of mayflies and stomach of brown trout was studied by electron microscopy and cytochemistry. In section, the intestine of both stages is composed of a single layer of about ten undifferentiated intestinal cells in a ring. A labyrinth of deep invaginations is present in the basal region of each cell. The apical surface is modified into well developed, regularly arranged microvilli. These, together with numerous organelles engaged in metabolism and a well defined gut lumen filled with unidentifiable material suggest that the intestine may function in digestion and absorption during both stages. The adults seem to feed upon the semifluid content of the stomach of brown trout. Fortuitous oral infection with undetermined bacteria in vitro led to degenerative changes in the intestinal tissue and probably caused death of the infected specimens. Up to 75% of the cell volume in the L3 is occupied by glycogen deposits. In the adults, a minor portion of glycogen, together with lipid droplets, has been observed. The adults are considered to rely more on aerobic metabolism, whereas anaerobic metabolism (glycolysis) may prevail in L3.
TL;DR: The probable connection to nerve cells and the connection to the cushion-like structures in the outer cuticular layer make it likely that the organs described here are sensory in function.
Abstract: Schmidt-Rhaesa, A. 2004. Ultrastructure of an integumental organ with probable sensory function in Paragordius varius (Nematomorpha). — Acta Zoologica (Stockholm) 85 : 15 -19 The cuticle of late parasitic stages of Paragordius varius (Leidy, 1851) is composed of a layer with large fibres and a second layer (often named the areolar layer) distal from it. In this paper, organs are described that start at the basal side of the epidermis, pass the epidermis and the fibrous layer of the cuticle and merge with large, cushion-like structures in the distal layer of the cuticle. The epidermal part of the organs is composed of darkly stained cells, which are probably in contact with the basi-epidermal nervous system. Up to four processes of this cell traverse the cuticle. These processes might include cilia, because they contain microtubule-like structures. The probable connection to nerve cells and the connection to the cushion-like structures in the outer cuticular layer make it likely that the organs described here are sensory in function.
TL;DR: Pleuropodia of the invaginated type were observed on the first abdominal segment in 8-d-old embryos of Thermobia domestica (Packard) and indicates that the cells of this organ perform transport and secretory functions.
Abstract: Pleuropodia of the invaginated type were observed on the first abdominal segment in 8-d-old embryos of Thermobia domestica (Packard). The pleuropodium is formed by a cytoplasmatic internal part and a mushroom-like cavity. The latter is filled with fluid and is composed of a stem protruding through the epidermis and a vesicle-like copula. The arrangement of membrane folds, mitochondria, and lipid drops was observed on electron micrographs (TEM) of pleuropodium cells. The position and structure of these organelles indicates that the cells of this organ perform transport and secretory functions.
TL;DR: The midgut epithelium of Wirenia argentea Odhner is composed of two cell types: dorsal ciliary cells and digestive cells, which show a plasticity in digestive cell size and contents, depending on the amount of absorbed food material.
Abstract: The midgut epithelium of Wirenia argentea Odhner is composed of two cell types: dorsal ciliary cells and digestive cells. Ciliary cells bear simple locomotory cilia with a pair of rootlets and without an accessory centriole. Digestive cells are the site of intracellular digestion and are characterized by an extensive endosomal and lysosomal system. The midgut epithelium shows a plasticity in digestive cell size and contents, depending on the amount of absorbed food material. Additionally, digestive cells produce membrane-bound mineralized granules as well as glandular vesicles, which most probably contain extracellular digestive enzymes. Four stages within the digestive cycle are defined. Cell types and cell cycles are compared with those known for digestive epithelia of other molluscs.
Journal Article•
TL;DR: It is demonstrated that parthenogenetic embryos had significantly altered ultrastructure, indicating extensive subcellular damages, as well as physiological and functional findings.
Abstract: Early bovine precompacted embryos (at 1- to 8-blastomere stage) were analyzed by electron microscopy. The volume density of cellular components was determined by morphometric analysis to quantify the ultrastructure of early bovine embryos produced either in vivo or parthenogenetically after stimulation of oocytes by electric pulse AC/DC. In embryos obtained in vivo, most of cellular volume was occupied by cytoplasm (82.93%). The relative volume of lipids, vacuoles, mitochondria was relatively low (5.46; 5.07; 3.78%, respectively), and the relative volume of Golgi apparatus and cell inclusions was the lowest (1.51%). AC/DC-derived parthenogenotes had a relative high area occupied by vacuoles and lipids (18.68 vs. 14.33%) and a significantly lower relative volume was occupied by cytoplasm (60.63%) when compared with the control in vivo embryos. These observations demonstrated that parthenogenetic embryos had significantly altered ultrastructure, indicating extensive subcellular damages. These findings are discussed from the physiological and functional point of view.