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 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

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

Spermatogenesis in a parthenogenetic type of P. westermani (Kerbert 1878) called P. pulmonalis (Baelz 1880) throughout this study, was observed by light microscopy (LM), scanning (SEM), and transmission (TEM) electron microscopy. During spermatogenesis, most of the cells became degenerated or malformed as a result of aberrations during spermatogenesis. Vacuolated cells were often found in the testicular lumen. In some nuclei of spermatocytes, synaptonemal complexes were formed and this indicated that some pairing of homologous chromosomes did occur, but only rarely. Cytophores in some rosettes were broken down into small fragments and the cells separated from each other. Norman spermatozoa were very rarely found in the testis and never in the seminal receptacle, where egg and vitelline cells were present instead. Throughout spermatogenesis, Golgi complexes, mitochondria, ribosomes, and endoplasmic reticulum were not abundant, and this suggested that cell activities and protein synthesis were greatly reduced.
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PMID:Ultrastructural studies on spermatogenesis in a parthenogenetic type of Paragonimus westermani (Kerbert 1878) proposed as P. pulmonalis (Baelz 1880). 709 41

In long-term cultures of bone marrow, the adherent stromal cells provide support for the proliferation and maintenance of hemopoietic stem cells. These stromal cells and their interactions were characterized by means of scanning (SEM) and transmission (TEM) electron microscopy in correlation with functional studies. Cultures were initiated by establishing the adherent stromal layer as a "soil" which was then "seeded" after 3 weeks by the addition of another marrow-cell suspension. Clonal assay of the supernatant demonstrated the continuous proliferation of the hemopoietic stem cell. The stroma essentially consisted of two cell types, macrophages and epithelioid cells. Macrophages were smaller, 10-15 microns, phagocytosed latex and carbon particles, and contained lysosomes. Their surface did not stain with polycationic ferritin (PCF). Epithelioid cells were much larger, more than 100 microns; contained numerous thin, elongated mitochondria; did not phagocytose latex particles; but did display strong surface staining with PCF. The appearance of epithelioid cells in TEM depended on their state of development and whether the section was parallel or perpendicular to the substratum. Epithelioid cells displayed a maturational spectrum, at two ends of which were synthetic and storage phases. In the synthetic phase, the cell contained numerous profiles of rough endoplasmic reticulum, and in the storage phase, numerous storage granules. These two phases were best appreciated in sections perpendicular to the substratum, demonstrating synthetic cells on top settling over the substratum upon maturation into the storage cells. Both macrophages and epithelioid cells contained fat globules which increased in number and size with the addition of hydrocortisone to the culture medium. A distinct fat-cell type, as has been claimed, was not found in this study. Granulopoiesis was observed in the culture system in the absence of colony-stimulating activity in the supernatant, suggesting direct cellular interaction or short-range factors in the induction of granulopoiesis. Widespread cellular interactions were noted between macrophages and epithelioid cells, the latter often completely embracing the former and both extending cytoplasmic processes toward each other. This is reminiscent of the cooperative interaction of endoderm and mesoderm in chick embryo hemopoiesis and may be necessary for the maintenance of stem cells in these cultures.
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PMID:Morphological studies on long-term culture of marrow cells: characterization of the adherent stromal cells and their interactions in maintaining the proliferation of hemopoietic stem cells. 710 79

A study in rats demonstrated that morphologic changes in the bone osteocytes and osteoblasts are produced following parathyroid hormone (PTH) injection into thyroparathyroidectomized animals. It further showed that similar changes occur in normal rats as the result of of extended fasting. Plasma calcium concentrations were determined at sacrifice to ascertain that these changes in bone occurred at times when plasma calcium is rising as the result of parathyroid hormone stimulation. Tibias from these animals were removed and prepared for morphologic observation using both transmission (TEM) and scanning (SEM) electron microscopy. Specific structural features characterized bone cells stimulated by exogenous or endogenous PTH. The most significant morphologic alterations involved surface microvilli and blebs as determined by SEM. TEM studies showed alterations in the cisternae of the rough endoplasmic reticulum (RER). Additionally, cell shape varied markedly from the control cuboidal morphology. These morphologic changes occurred during peak periods of plasma calcium change and returned to control morphology as plasma calcium levels normalized. Use of an extracellular electron-dense tracer (lanthanum) confirmed the patency of the intercellular channels and the presence of a fluid space between the bone cell plasma membranes and the mineralized surface. PTH stimulation modified cell activity such that the tracer material entered the cell more readily, possibly by inducing increased pinocytosis (endocytosis). This study supports the concept that the osteocytes and lining cells on the surface of bone play a role in maintenance of plasma calcium concentrations.
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PMID:Influence of parathyroid hormone on bone cell ultrastructure. 722 63


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