Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracted human deciduous teeth undergoing physiological root resorption were fixed with a mixture of formaldehyde and glutaraldehyde and processed for scanning (SEM) and analytical transmission electron microscopy, as well as acid trimetaphosphatase cytochemistry. The granulated tissues, which are rich in multinucleated odontoclasts and capillary vessels, formed various resorption lacunae on the resorbing dentin surfaces. SEM observations of dentin surfaces treated with sodium hypochlorite revealed two types of resorption lacunae: deep, round lacunae in which the peritubular matrix of dentinal tubules was strongly dissolved; and shallow, irregular lacunae with intact peritubular matrix. In trypsin-treated materials, the resorption surfaces were characterized by the presence of numerous collagen fibers in both the peritubular and intertubular matrices, suggesting demineralization of the surface dentin. Odontoclasts were characterized by the presence of abundant mitochondria, perinuclear stacks of Golgi membranes, various lysosomes, numerous endocytotic vacuoles, and a well-developed ruffled border against the resorption lacunae. Most endocytotic vacuoles were distributed in the cytoplasm between the ruffled border and the nuclei. In undemineralized ultrathin sections, the surface dentin of resorption lacunae consisted of collagen fibers and apatite crystals and had a lower packing density than those in unresorbed, deeper dentin. Many apatite crystals were demonstrated to be present in the extracellular channels of the ruffled border and in adjacent endocytotic vacuoles derived from it. Lysosomes located in the perinuclear cytoplasm of odontoclasts contained amorphous dense material and/or a small amount of crystals. An energy-dispersive x-ray microanalysis of apatite crystals in undemineralized sections indicated that the energy spectrum peaks of Ca and P detected from crystals in resorbing dentin were much lower than those in unresorbed dentin. Similarly, lower spectrum peaks of Ca and P were obtained from crystals found in the ruffled border and endocytotic vacuoles of odontoclasts. A slight trace Ca peak also was detected in the amorphous dense material in lysosomes of odontoclasts. The enzyme cytochemistry of lysosomal acid trimetaphosphatase indicated that odontoclasts had intense enzymatic activity in the Golgi membranes, endoplasmic reticulum cisternae, lysosomes, and endocytotic vacuoles. Dense reaction precipitates of enzymatic activity also were found along the dentin surfaces of resorption lacunae occupied by odontoclast ruffled borders.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Dentin resorption mediated by odontoclasts in physiological root resorption of human deciduous teeth. 285 Dec 63

Natural killer (NK) cells were obtained from C3H mouse spleens according to a modified version of the method of Kuribayashi et al. [Kuribayashi, K., Gillis, S., Dern, D. E. & Henney, C. S. (1981) J. Immunol. 126, 2321-2327]. These cells retain in vitro cytotoxicity against certain model tumor cell targets and appear homogeneous by morphological criteria. NK cells, YAC (tumor) cells, and NK cell-YAC cell conjugates have been examined with scanning (SEM) and transmission (TEM) electron microscopy. SEM experiments have shown that: (i) NK cells are large and possess various shapes in contrast to the YAC target cells which are smaller and round, (ii) YAC cells have uniformly distributed microvilli whereas the NK cell microvilli are most prominent in the area of effector-to-target contact, and (iii) in the absence of target cells, NK cell microvilli are found in a small number (usually 1-3) of cell surface locations. The region of NK cell-tumor cell contact has also been examined with TEM. The cells were stained with ruthenium red/OsO(4). The electron-dense ruthenium red/OsO(4) reaction product was consistently found in regions of close cell-cell contact, suggesting that carbohydrates were not completely cleared from areas of contact and that target and effector membranes do not fuse extensively. TEM observations indicate that NK cells have structurally unique granules. The granules are composed of at least two distinct compartments. The outer compartment contains the lysosome-associated enzymes acid phosphatase and inorganic trimetaphosphatase. No enzymatic activities have been found associated with the inner compartment. NK cells appear to degranulate when incubated with YAC cells. Under those circumstances, limited areas of the NK cytoplasm contain vacuole-like areas possessing granules and apparent granular debris. Degranulation appears to be involved in the cytotoxic function of NK cells.
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PMID:Electron microscopic study of natural killer cell-tumor cell conjugates. 629 Oct 36