This study provides evidence for the Golgi-like activity of the multilayered interlaced network (MIN) and new ultrastructural observations of the MIN in the sporoplasm of Anncaliia algerae, a microsporidium that infects both insects and humans. The MIN is attached to the end of the polar tubule upon extrusion from the germinating spore. It surrounds the sporoplasm, immediately below its plasma membrane, and most likely maintains the integrity of the sporoplasm, as it is pulled through the everting polar tube.
View Article and Find Full Text PDFThe three-dimensional (3-D) network of the granum-stroma thylakoid assembly of vascular plant chloroplasts exhibits complex structural/functional heterogeneity. A complete understanding of the ultrastructure of this assembly is critical for our understanding of thylakoid function. The prevailing historical model of thylakoid structure, based on information derived from serial section analyses of electron microscopy (EM) images, suggests a helical arrangement of stroma membranes wound around the granum stacks.
View Article and Find Full Text PDFThe C. elegans eat-3 gene encodes a mitochondrial dynamin family member homologous to Opa1 in humans and Mgm1 in yeast. We find that mutations in the C.
View Article and Find Full Text PDFThe role of mitochondria in cell metabolism and survival is controlled by calcium signals that are commonly transmitted at the close associations between mitochondria and endoplasmic reticulum (ER). However, the physical linkage of the ER-mitochondria interface and its relevance for cell function remains elusive. We show by electron tomography that ER and mitochondria are adjoined by tethers that are approximately 10 nm at the smooth ER and approximately 25 nm at the rough ER.
View Article and Find Full Text PDFThe present studies examined the effects of Candida albicans yeast and hyphal morphologies on tissue pathologies and transmigration properties of the fungus in two experimental models: 1) an in vivo, neonatal rat model, and 2) a cell culture model of human brain microvascular endothelial cells (ECs) (BMVEC). We inoculated a hyphae-producing strain (CAI4-URA3) and a non-hyphae-producing strain (CAI4) of C. albicans into 4-10 day old rats and BMVEC cultures.
View Article and Find Full Text PDFMitochondrial encephalomyopathies are common and devastating multisystem genetic disorders characterized by neuromuscular dysfunction and tissue degeneration. Point mutations in the human mitochondrial ATP6 gene are known to cause several related mitochondrial disorders: NARP (neuropathy, ataxia, and retinitis pigmentosa), MILS (maternally inherited Leigh's syndrome), and FBSN (familial bilateral striatal necrosis). We identified a pathogenic mutation in the Drosophila mitochondrial ATP6 gene that causes progressive, adult-onset neuromuscular dysfunction and myodegeneration.
View Article and Find Full Text PDFSporozoites of the apicomplexan Cryptosporidium parvum possess a small, membranous organelle sandwiched between the nucleus and crystalloid body. Based upon immunolabelling data, this organelle was identified as a relict mitochondrion. Transmission electron microscopy and tomographic reconstruction reveal the complex arrangement of membranes in the vicinity of this organelle, as well as its internal organization.
View Article and Find Full Text PDFAnat Rec A Discov Mol Cell Evol Biol
May 2004
Mitochondria of human Leydig cells were reconstructed in three dimension utilizing the technique of electron microscopic tomography to obtain a better understanding of the topology of the internal membrane system and the relationship of these cristae to the inner boundary membrane (IBM). Cristae structure, in many respects, is consistent with previous tomographic studies from typical mitochondria, i.e.
View Article and Find Full Text PDFElectron tomography indicates that the mitochondrial inner membrane is not normally comprised of baffle-like folds as depicted in textbooks. In actuality, this membrane is pleomorphic, with narrow tubular regions connecting the internal compartments (cristae) to each other and to the membrane periphery. The membrane topologies observed in condensed (matrix contracted) and orthodox (matrix expanded) mitochondria cannot be interconverted by passive folding and unfolding.
View Article and Find Full Text PDFThe mechanism during apoptosis by which cytochrome c is rapidly and completely released in the absence of mitochondrial swelling is uncertain. Here, we show that two distinct pathways are involved. One mediates release of cytochrome c across the outer mitochondrial membrane, and another, characterized in this study, is responsible for the redistribution of cytochrome c stored in intramitochondrial cristae.
View Article and Find Full Text PDFThe positional relationships among all of the visible organelles in a densely packed region of cytoplasm from an insulin secreting, cultured mammalian cell have been analyzed in three dimensions (3-D) at approximately 6 nm resolution. Part of a fast frozen/freeze-substituted HIT-T15 cell that included a large portion of the Golgi ribbon was reconstructed in 3-D by electron tomography. The reconstructed volume (3.
View Article and Find Full Text PDFMultiple apoptotic pathways release cytochrome c from the mitochondrial intermembrane space, resulting in the activation of downstream caspases. In vivo activation of Fas (CD95) resulted in increased permeability of the mitochondrial outer membrane and depletion of cytochrome c stores. Serial measurements of oxygen consumption, NADH redox state and membrane potential revealed a loss of respiratory state transitions.
View Article and Find Full Text PDFCubic membranes occur in a variety of membrane-bound organelles in many cell types. By transmission electron microscopy (TEM) these membrane systems appear to consist of highly curved periodic surfaces that fit mathematical models analogous to those used to describe lipidic cubic phases. For the first time, a naturally occurring cubic membrane system has been reconstructed in three dimensions by electron microscopic tomography, and its periodicity directly characterized.
View Article and Find Full Text PDFElectron microscopic observations were made from tissues apposing titanium and ceramic root form and blade implants. The tissue was serially sectioned from the most coronal epithelium, through the gingival connective tissue, to the osseous support tissues, and directly to the most apical tissue support. Of the thousands of sections analyzed for each implant, 500 micrographs were routinely viewed for each of the implants analyzed by this study.
View Article and Find Full Text PDFBlood vessels from the vasculature of mouse brains during postnatal development and from human brain tumors (hemangiomas) removed at biopsy were examined immunocytochemically by transmission electron microscopy (TEM) or high-voltage transmission electron microscopy (HVEM) to determine the expression of intercellular adhesion molecule-1 (ICAM-1). In the mouse brains, ICAM-1 was shown to be initially expressed on the luminal and abluminal endothelial cell (EC) surfaces on day 3 after birth. ICAM-1 intensity increased on the luminal EC surfaces and labeled vesiculotubular profiles (VTS, defined in the present report) between days 5 and 7.
View Article and Find Full Text PDFElectron microscopic tomography can provide a complete three-dimensional range of information about subcellular structures. Applied to mitochondria, it has shown that the conventional textbook model of this organelle is incorrect. The infoldings of the inner membrane (called cristae) are connected by narrow tubular regions to each other and to the outside, suggesting that internal diffusion of ions, metabolites and proteins may be restricted.
View Article and Find Full Text PDFArachidonic acid is essential for antibody-mediated phagocytosis but its role in this process has not been defined. The phospholipase A2 inhibitor bromoenol lactone decreases arachidonic acid release and arrests phagocytosis; this effect is bypassed by the addition of arachidonic acid to bromoenol lactone-treated cells. In this morphological study, monocytes treated with bromoenol lactone accumulate electronlucent vesicles in the cytoplasm underlying bound targets.
View Article and Find Full Text PDFInt J Oral Maxillofac Implants
September 1997
Correlated transmission electron and high-voltage electron microscopic analyses examined the undecalcified bone and associated support tissues of 60 endosseous titanium blade and titanium and ceramic root-form implants in dogs. The implants supported fixed partial dentures for up to 2 years. Data obtained from this investigation suggest that a range of tissues, both mineralized and unmineralized, support osseointegrated dental implants.
View Article and Find Full Text PDFKinetochore microtubules (kMts) are a subset of spindle microtubules that bind directly to the kinetochore to form the kinetochore fiber (K-fiber). The K-fiber in turn interacts with the kinetochore to produce chromosome motion toward the attached spindle pole. We have examined K-fiber maturation in PtK1 cells using same-cell video light microscopy/serial section EM.
View Article and Find Full Text PDFTreponema denticola is an anaerobic, motile, oral spirochete associated with periodontal disease. We found that the periplasmic flagella (PFs), which are located between the outer membrane sheath and cell cylinder, influence its morphology in a unique manner. In addition, the protein composition of the PFs was found to be quite complex and similar to those of other spirochetes.
View Article and Find Full Text PDFTrends Biochem Sci
February 1997
We used laser microsurgery to cut between the two sister kinetochores on bioriented prometaphase chromosomes to produce two chromosome fragments containing one kinetochore (CF1K). Each of these CF1Ks then always moved toward the spindle pole to which their kinetochores were attached before initiating the poleward and away-from-the-pole oscillatory motions characteristic of monooriented chromosomes. CF1Ks then either: (a) remained closely associated with this pole until anaphase (50%), (b) moved (i.
View Article and Find Full Text PDFSpirochetes are an evolutionary and structurally unique group of bacteria. Outermost is a membrane sheath (OS), and within this sheath are the protoplasmic cell cylinder (PC) and periplasmic flagella (PFs). The PFs are attached at each end of the PC and, depending on the species, may or may not overlap in the center of the cell.
View Article and Find Full Text PDFFidelity of tomographic reconstructions is improved and reconstruction artifacts are reduced, without increasing the number of projections, by combining tilt series taken around two orthogonal axes. Test reconstructions were made from high-voltage EM of rat liver mitochondria in a 0.6 micron thick plastic section.
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