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The metamorphosis of the epibranchial cartilage, a skeletal component of the hyobranchial apparatus, in the salamander Eurycea bislineata entails a combination of the reabsorption of a larval cartilaginous element with the simultaneous genesis of an adult cartilage in the same place. In this study we focus on the fate of the larval chondrocytes. Two hypotheses are considered: one, larval cells simply die off during metamorphosis, or, alternatively, they dedifferentiate and participate in the formation of the adult element. Thyroxine treatment and experimental tissue manipulation coupled with measurements of thyroxine levels using radioimmunoassay show that, within 24 h after T4 treatment, larval chondrocytes in the epibranchials exhibit large autophagocytic vacuoles, disruption of the rough endoplasmic reticulum, abnormally shaped mitochondria, abundance of lysosomes and nuclear degeneration, all symptoms of the onset of cell death. In conclusion, evidence from light microscopy, TEM and SEM show that the larval chondrocytes in response to rising levels of thyroid hormones undergo a process of lysosomal autophagocytosis and do not participate in the formation of adult structures.
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PMID:The fate of larval chondrocytes during the metamorphosis of the epibranchial in the salamander, Eurycea bislineata. 407 41

Isolated rat hepatocytes in early primary culture were incubated in the presence of three substituted nitroimidazoles currently of clinical interest as tumour radiosensitisers. The effects of 3h treatments with Misonidazole (MISO), Desmethylmisonidazole (DESMISO) and the basic compound Ro 03-8799 were monitored both directly from treatment and following a 24h 'recovery' period. Morphological changes were observed by SEM and TEM and included effects on the plasma membrane and the nucleus. The plasma membrane of DESMISO and 03-8799 treated cells was characterised by blebbed regions not present in control cultures, and considered indicative of an early toxic insult. Blebs were most evident in 03-8799 treated hepatocytes where they often contained coils of endoplasmic reticulum within the ground plasma. Blebbed areas were less evident 24h after the removal of the drugs from surviving cells. An increased aggregation of peripherally located heterochromatin within the nucleus was the other main morphological alteration induced by nitroimidazole treatment. This was again more prevalent in 03-8799 and DESMISO exposures; and particularly in cells demonstrating membrane damage. Parallel viability studies indicated an efficacy of the nitroimidazole towards rat liver parenchymal cells in primary culture of Ro 03-8799 greater than DESMISO greater than MISO. This fitted the order predicted from the morphological findings and from previously published clinical data. The validity of monitoring structural parameters as a means of initially indicating lesion sites following drug treatments in the hepatocyte cytotoxic screening model is considered.
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PMID:Morphological changes in rat hepatocytes in primary culture induced by Misonidazole, desmethylmisonidazole and Ro 03-8799. 614 29

Mammary adenocarcinomas from C3H/HeJ mice carrying the mammary tumor virus were studied by means of light, transmission, and scanning electron microscopy. The histological appearance of the tumors was variable; however, 60% were classified as type B adenocarcinomas, while 20% were type A and 20% were composed of equal regions characteristic of both types. Four populations of tumor cells were observed with the TEM. The most abundant of these, primitive glandular cells, were characterized by large, regular, euchromatic nuclei and cytoplasm containing numerous free ribosomes, little rough endoplasmic reticulum, few mitochondria, small Golgi complex and a variable number of type A virus particles. Specialized glandular cells contained highly pleomorphic nuclei, many lysosomes, lipid droplets, multivesicular bodies, profiles of rough endoplasmic reticulum and granules resembling secretory proteins. Myoepithelial cells and dark glandular cells with abundant organelles, large Golgi complexes, dense cytoplasmic matrix and very heterochromatic nuclei were observed infrequently. The SEM revealed tumor cells to be variable in size, shape and surface characteristics. Most cells were rough in texture, displaying irregular ridges, small blebs and a few short microvilli. The contours of some cells were smooth, and a few cells had short, irregular microvilli on limited regions of their surfaces. Cells lining ducts within the tumor had microvilli on their apical surface, but the number, size, shape and distribution of microvilli varied considerably. Cells lining ducts from non-tumor-bearing animals displayed less variation in size, shape and surface morphology.
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PMID:Fine structure analysis and surface characteristics of mouse mammary gland adenocarcinomas. 633 Aug 78

The antipsychotic drug trifluoperazine (TFP) causes a reversible rounding of cells of the rat liver epithelial cell line, WIRL. We have investigated the cytoplasmic organization of these cells after TFP treatment using SEM, TEM and immunofluorescence and have observed significant differences between the control and treated cells. Mitochondria are converted to the condensed configuration with distended cristae and the endoplasmic reticulum becomes tubular with distended cisternae. Intermediate filaments, visualized with a monoclonal antibody, are aggregated to a cap on the nucleus in an arrangement different from that induced by colcemid.
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PMID:Alterations of the cytoplasmic organization of WIRL cells induced by trifluoperazine. 636 51

Immature, Stage VI oocytes of Xenopus laevis fail to activate (i.e., to propagate a cortical reaction and elevate a fertilization envelope) when pricked or exposed to A23187. We determined the times during maturation when immature oocytes treated with progesterone in vitro developed the capacity to respond to pricking and to ionophore. Responsiveness to ionophore first appears at about 3.5-4.5 hr after progesterone treatment; all oocytes are activated by 8-9 hr after progesterone. The capacity to respond to pricking appears about 1.0-1.5 hr after first signs of ionophore responsiveness. We examined the cortical endoplasmic reticulum (CER) by TEM to determine whether the morphology of this component could be correlated with the development of responsiveness during maturation. Fully mature oocytes exhibit an extensive CER that (1) forms a "shell" around most cortical granules, (2) appears to interconnect cortical granules, and (3) forms junctions with the plasma membrane. The CER-plasma membrane junctions are especially obvious in preparations of isolated cortex. The elaborate CER is not present in immature oocytes. It first appears during maturation of progesterone-treated oocytes at 4.5-5.0 hr, coincident with the time when maturing oocytes develop their responsiveness to ionophore and to pricking. This temporal correlation is consistent with the hypothesis that the CER is one of the components required for regulation of intracellular free calcium in oocytes.
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PMID:The onset of activation responsiveness during maturation coincides with the formation of the cortical endoplasmic reticulum in oocytes of Xenopus laevis. 642 40

Samples of teleost cerebellar cortex (Arius Spixii and Salmo Trout) fixed by immersion and vascular perfusion techniques were processed for light microscopy, SEM and TEM. SEM fractographs of endothelial cell nuclear, organelle and peripheral cytoplasmic zones have been compared with their corresponding TEM images. A simultaneous three-dimensional view of the luminal surface of endothelial cells at the nuclear zone, and inner details of heterochromatin structure was obtained. Chained micropinocytotic vesicles and deep cytoplasmic invaginations were observed. Surface connected micropinocytotic vesicles or vacuoles show stomas open to the luminal surface. Clear and dense endothelial micropinocytotic vesicles and vacuoles were observed at TEM level. The dense plasma substance can be used as an endogenous electron dense tracer for permeability studies. At SEM level the rough endoplasmic reticulum appears as a trabecular continuous system. The endothelial cytosol exhibits a smooth, glass surface appearance. The endothelial luminal surface changes its aspect according to the fixation procedure. The SEM and TEM aspect of endothelial junctions further supports their role as the morphological counterpart of blood-brain barrier. The basement membrane exhibited a homogeneous matrix and short or long neuropilar projections. Clear perivascular astrocytes with anastomotic processes form the main framework of perivascular neuropile. Like the peripheral endothelial cytoplasm, they exhibited dense and clear micropinocytotic vesicles and vacuoles, providing evidence for their transport function between capillaries and neighbouring brain parenchyma. The SEM appearance of their outer surface further supports their barrier function.
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PMID:Light, scanning and transmission electron microscopy study of fish cerebellar capillaries. 663 43

Pancreas, double-fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin was cut into sections 0.5-1 micron thick. The sections were surface-etched in an oxygen plasma produced by exciting oxygen with a radio frequency generator. Structural components of exocrine and endocrine cells were morphologically investigated in the secondary electron image mode of the SEM. Moreover, in order to identify some cell components such as endocrine granules, the morphological image obtained of the etched surface by the SEM were compared with those seen in a TEM, using the serial sections from the same tissue block and at the same cellular level. For a microanalytical investigation, tissues were fixed with glutaraldehyde alone. The structural components of exocrine and endocrine cells were analyzed by SEM/EDX. A better resolution under the SEM was obtained of 0.5-0.8 micron thick sections after surface-etching in an oxygen plasma for 1 minute. Intracellular structures such as nuclear membranes, nucleolus, mitochondria, rough endoplasmic reticulum and zymogen granules were readily identifiable. Moreover, the internal structure of organelles such as cristae of mitochondria was recognized. In the serial sections, the mode of arrangement of intracellular structures in the SEM was well consistent with those in the TEM. The peaks of phosphorus, sulphur and calcium were clearly detected from the intracellular components such as nucleolus, nuclear membranes and secretory granules.
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PMID:Scanning electron microscopy and EDX analysis of exocrine and endocrine gland cells of rat pancreas surface-etched in an oxygen plasma. 676 46

A white cocoon membrane emanating from an inferotemporal focus in the iris stroma totally ensheathed a Binkhorst four-loop iris plane lens 18 months after implantation. The membrane was removed and studied by scanning (SEM) and transmission (TEM) electron microscopy. By SEM the external surface of the membrane was characterized by a fibrillar meshwork, with only an occasional scattered spindle-shaped or rounded inflammatory cell occupying the surface. One-micron plastic sections revealed both spindle and polyhedral heavily pigmented cells in the outer aspect of the membrane, and compressed elongated nonpigmented spindle cells scattered throughout the central portions. By TEM cells clinging to the outermost aspects were bipolar iris stromal melanocytes with small melanosomes, inactive fibroblasts, or histiocytes with cytoplasmic ruffles. The larger rounded pigmented cells in the superficial region were viable or degenerated iris pigment epithelial cells or macrophages. Most of the substance of the membrane was composed of collagen fibrils 100-500 A in diameter with and without 640 A periodicity; these fibrils were generally oriented parallel to the spindle cells but did not display distinct bundling or a lamellar architecture. The spindle cells in the center of the lesion were active fibroblasts with abundant rough-surfaced endoplasmic reticulum and scattered actin myofilaments; they contained rare small and large melanin granules indicative of phagocytosis. It has been concluded that the membrane was produced predominantly by iris stromal fibroblasts probably activated by the haptics of the IOL or McCanell suture.
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PMID:The ultrastructure of an IOL "cocoon membrane". 687 72

Using electron microscopy and cytochemical techniques, the authors determined the distribution of acid phosphatase (AcPase) within the organelles of lymphocytes from blood rosetted with either neuraminidase-treated sheep erythrocytes (En) or sheep erythrocytes coated with antibody and complement (EACs). Subsequently, the various reactive organelles of the rosetted lymphocytes were counted, affording a comparison of T and B cells. It was found that AcPase was present in approximately 80% of T cells and 45% of B cells and was most frequently observed in secondary lysosomes of varying size and content. Although more T cells than B cells were reactive for AcPase, the extent of reaction in some B cells clearly precludes the use of AcPase for differentiating the two cell lines. It should be recognized that while the En rosetting procedure detects T cells in a nonselective manner, the EAC rosette is a marker of a major subpopulation of B lymphocytes, ie, those bearing complement receptors. We believe that the distribution of lysosomal enzymes in B and T lymphocytes probably reflects the functional state of individual cells rather than being a reliable indicator of cell lineage. A surprising finding (which could be established only by a fine-structural study) was the fact that 20% of circulating "resting" T cells contained reaction product for AcPase within endoplasmic reticulum and the perinuclear cisterna indicating that these cells are actively synthesizing AcPase, probably due to a foregoing inductive event. Such stimulus could be the result of recent endocytosis of surface receptors in combination with antigen, antibody, or immune complexes and/or recent mitosis, or possibly some unrelated autophagic incident.
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PMID:Ultrastructural localization of acid phosphatase in rosetted T and B lymphocytes of normal human blood. 697 May 26

The cement gland of Rhodnius prolixus is an epidermally derived tubular gland consisting of a distal synthetic region and a proximal muscular duct region. The synthetic region consists of numerous secretory units joined to a central chitinous duct via cuticular ductules. Proteinaceous secretion, synthesized by the goblet-shaped secretory cell, passess through the delicate cuticular lattice of a ductule-end apparatus and out through fine ductules to the central duct. Secretory cells are rich in rough endoplasmic reticulum and mitochondria. Light microscopy, SEM and TEM reveal the delicate lattice-like end apparatus structure, its formation and relationship to the secretory cell. The secretory cell associates via septate junctions with a tubular ductule cell that encloses a cuticle-lined ductule by forming an elaborate septate junction with itself. The ductules are continuous with the cuticle lining of the large central duct that conveys secretion to the proximal area. The proximal muscular duct has a corrugated cuticular lining, a thin epithelium rich in microtubules and thick longitudinal, striated muscles which contrast during oviposition, forcing the secretion out. Histochemistry and electrophoresis reveal the secretion as proteinaceous.
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PMID:The ultrastructure of the female accessory gland, the cement gland, in the insect Rhodnius prolixus. 700 76


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