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Query: UMLS:C1275122 (TEM)
 21,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Secondary lysosomes of the residual body type are frequent in nondividing cells from phase III cultures of human glial cells. These organelles have previously been shown to be analogous to lipofuscin granules of postmitotic cells in vivo. Most recent studies favor the assumption that residual bodies mainly result from incomplete degradation within the lysosomal vacuome of endogenous cellular components such as mitochondria and endoplasmic reticulum. Since iron occurs in several metalloenzymes produced by such organelles, it should then be possible to demonstrate accumulated iron within residual bodies. X-ray dispersive analysis of sectioned biological material is often hampered by diffusion and dissolution during preparation, as well as by too low a concentration of the elements. In this study we cultured glial cells on Formvar-coated gold grids and studied them unsectioned, after brief glutaraldehyde fixation and freeze-drying, in a transmission electron microscope at 100 kV in TEM and STEM mode. It was then possible to demonstrate iron in residual bodies of aged cells, presumably because the type of preparation utilized does not permit much dissolution.
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PMID:Electron probe X-ray microanalysis of residual bodies in aged cultured human glial cells. 723 72

Granulosa cells from porcine ovarian follicles were cultured in vitro in standard medium and in medium supplemented with HCG. After culture the cellular 3 beta HSD enzymatic activity was evaluated and the cells were studied by TEM and SEM. A stereological evaluation of the smooth and rough endoplasmic reticulum was carried out. The results indicate that the cultured cells undergo a luteinization process which is more evident in the presence of HCG. In fact, in comparison with the controls, in these cells the enzymatic activity is higher, the rough endoplasmic reticulum decreases and the smooth endoplasmic reticulum increases, the cytoplasm shows lipid droplets and vesicular mitochondria. The cell surface develops a number of microvillus-like evaginations.
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PMID:On the structural changes of granulosa cells cultured in vitro. Histochemical, ultrastructural and stereological observations. 733 47

The structure and connexions of Reissner's fibre have been studied in the rat by means of scanning and transmission electron microscopy. The fibre was found to arise from a series of filaments, each of which was formed by a structure forming the juxta-aqueductal surface or lining of the subcommissural organ. This structure was termed 'apical spherical protrusion' and was found to be rich in rough endoplasmic reticulum. The fibre was firmly attached at its rostral end to the subcommissural organ, at its middle to the ventral surface of the termination of the aqueduct and finally to the calamus scriptorius of the fourth ventricle. It was held in a state of considerable tension between these three points and attached to it were numerous cilia from the ependymal lining. In sections examined by TEM the fibre appeared to be totally amorphous in structure, with erythrocytes and other debris attached to it.
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PMID:Reissner's fibre in the rat: a scanning and transmission electron microscope study. 744 Mar 97

The ultrastructural features of the cells and of the oxytalan fibers within the periodontal ligaments of aged rats (2 year old) were quantified and compared with data for tissues obtained from younger animals (8 week old). Sections of the mid-root regions of the mandibular first molars were prepared for examination by TEM. The fibroblasts of the aged rats were found to differ in 3 respects: the areas occupied by endoplasmic reticulum were significantly less, the areas occupied by intracellular collagen profiles were also less, and both the numbers and sizes of intercellular contacts were significantly different (p < 0.05). For the oxytalan fibers, no differences were observed between the periodontal ligaments of the aged and control animals both in terms of numbers of fibers per 50 microns and in terms of area of tissue occupied. Thus, in contrast to the apparent lack of age changes so far determined for the extracellular matrix of the periodontal ligament (collagen fibrils and oxytalan), the periodontal fibroblasts exhibit some age changes as perceived at the ultrastructural level.
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PMID:The effects of aging upon the connective tissues of the periodontal ligament. 755 60

Morphodynamics of oocyte follicle cells association during the development of human ovarian follicles were studied by transmission electron microscopy and high resolution scanning electron microscopy including the ODO method. For this study primordial, primary, growing preantral and antral follicles were systematically analysed in a total of 20 adult and fetal (3-8 months and at term) ovaries. In early stages of follicle development (primordial and primary stages) the flattened and/or polyhedral cells, closely associated with the growing oocyte, project an increasing number of microvillous processes. These are in apposition with the oolemma, and form bulbous terminals presenting attachment zones such as zonula adherens, desmosomes and communicating junctions (gap junctions). "Focal contacts" between oolemma, and lateral microvillous extensions of follicle cells were also present. Unusual forms of contact between follicle cell microvilli and oocytes in the early stages of growing primordial and primary follicles were also observed. These consist of long, thin extensions penetrating into the oocyte through deep invaginations of the oolemma. The aid of high resolution SEM of specimens subjected to the ODO method clearly reveals their 3-D arrangement within the ooplasm. They appear as long tortuous microvilli coming very close to the nucleus, and in their course are closely associated with a variety of organelles such as Golgi vesicles, endoplasmic reticulum membranes and nascent forms of smooth endoplasmic reticulum. Using integrated observations by TEM and SEM, there may be as many as 3-5 "intraooplasmic processes" even in only one plane of fracture of an oocyte. Therefore, if the total volume of the oocyte and associated cells is considered, their amounts appear to be higher than previously reported. Thus, they have to be considered as normal devices of deep contact between the ooplasm and associated follicle cell extensions. The presence of such structures within the ooplasm in early developing follicles well coincides with the great increase in volume of the oocyte. Although it is commonly believed that the activation of the growing oocyte may depend on the numerous contacts between the oolemma and follicle cells (mostly via gap junctions), the finding of these additional intraoocytic extensions suggests that they may in someway contribute to the initiation of growth in the human. In fact, these microvilli penetrate deep into the ooplasm, much like a sword in its sheath.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Oocyte follicle cells association during development of human ovarian follicle. A study by high resolution scanning and transmission electron microscopy. 788 May 91

By fluorescence ratio imaging of large and small inert tracer particles in living cells, we have previously shown that particles 24 nm in radius are excluded from otherwise uncharacterized compartments in the distal and perinuclear cytoplasm (Luby-Phelps, K. and Taylor, D.L., 1988. Cell Motil. Cytoskel. 10, 28-37). In this study we examined the cytoarchitecture of these compartments. Whole-mount TEM showed that distal size-excluding compartments were devoid of membrane-bounded organelles and were filled with a dense cytomatrix consisting of numerous, long bundles of thin filaments interconnected by a more random meshwork of short thin filaments. The mean diameter of void spaces in the cytomatrix of distal excluding compartments was 31 nm, compared to 53 nm in adjacent non-excluding domains. The height of the distal excluding compartments was generally < or = 50% of the height in the adjacent non-excluding compartment. An electron-dense structure having the same projected outline as the perinuclear size-excluding compartment was visible by whole-mount TEM, but the cells were too thick and osmiophilic in this region to resolve any detail. Immunofluorescence localization of cytoskeletal proteins in distal excluding compartments indicated the presence of filament bundles containing F-actin nonmuscle filamin (ABP280) and alpha-actinin. F-actin and ABP280, but not alpha-actinin, were found also in between these filament bundles. Microtubules and vimentin generally were rare or absent from distal excluding domains. Staining of living cells with DMB-ceramide revealed that the perinuclear size-excluding compartment consisted of a compact, juxtanuclear domain coinciding with the trans-Golgi, surrounded by a more diffuse domain coinciding with a perinuclear concentration of endoplasmic reticulum. Intense immunofluorescence staining for vimentin was also observed in the perinuclear size-excluding compartment. We propose that the most likely mechanism for exclusion from distal compartments is molecular sieving by a meshwork of actin filament bundles interconnected by an F-actin/ABP280 gel network, while exclusion from the perinuclear compartment may be due to close apposition of cisternae in the trans-Golgi and a network or basket of vimentin filaments in the centrosomal region of the cell.
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PMID:Cytoarchitecture of size-excluding compartments in living cells. 798 Jul 39

At the onset of the mineralization of bone, small membranous matrix vesicles are often observed. The information available on the production and release of these vesicles is limited. When treated with 10-20 nM of the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the human osteosarcoma cell line U-2 OS developed long cytoplasmic processes connecting adjacent cells. SEM and TEM show that TPA triggers a production and release of matrix vesicle-like membrane vesicles, mainly from the cellular processes. Tetracycline HCl was used to label intracellular bound calcium. The tetracycline HCl label was primarily localized to the end-feet of the cytoplasmic processes, indicating that these contain high concentrations of Ca2+, and to endoplasmic reticulum-like structures in the cell bodies. Together with our previous demonstration of the release of alkaline phosphatase-containing vesicles into the culture medium (Ringbom-Anderson T, Akerman KEO 1992 Calcif Tissue Int 50:533-540), the results presented here indicate that TPA induces a rapid induction of the primary steps of mineralization in U-2 OS osteosarcoma.
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PMID:Production and release of matrix vesicles in the cell processes of TPA-treated human osteoblast-like cells. 805 95


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