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Biomedical subjects

M I Cho

Publications and source records attributed to M I Cho.

At least 55 records · Page 3Linked to original sources
PubMed1987

3H-mannose utilization by fibroblasts of the periodontal ligament.

The synthesis, intracellular translocation, and secretion of mannose-containing glycoproteins(s) by periodontal ligament fibroblasts have been investigated by means of electron microscopic radioautography. Tritiated mannose was administered to young mice via jugular vein, and radioautographs were prepared at 5, 10, 20, and 35 minutes, 4 and 8 hours after injection. Analysis of electron microscopic radioautographs revealed a maximum labeling (94%) with 3H-mannose of the rough endoplasmic reticulum at 5 minutes. Labeling of the Golgi components started to increase from 10 minutes (14%) and reached a maximum level at 20 minutes (31.2%). At 35 minutes, secretion granules, dense bodies, profiles of intracellular collagen, and the cell surface were labeled. At 8 hours, most labelling (79.2%) was extracellular, and associated either with the collagenous matrix (43.7%) or the cell surface (35.5%). Cytoplasmic vesicles containing dense materials around collagen fibrils were also labeled at 8 hours. It is concluded that mannose is directly incorporated into the rough endoplasmic reticulum (RER), and that mannose-containing glycoprotein(s) are packaged in the Golgi apparatus into secretory granules. Mannose-containing glycoprotein(s) become distributed on the periodontal ligament (PDL) fibroblast cell surface, cytoplasmic dense bodies, and the extracellular matrix.

Animals↗
PubMed1986

A freeze-fracture cytochemical study of filipin-sterol complexes in pulp fibroblasts of the rat incisor.

The sterols in microdomains of the cell membrane of pulp fibroblasts react with the polyene antibiotic, filipin, to form filipin-sterol complexes (FSC). The FSC appear in ultra-thin sections as minute corrugations or deformations of the membrane. In freeze-fracture replicas, individual FSC were 20-30 nm elevations and were abundant on filopodial cell processes. They were not found in the membrane of cell-to-matrix attachment plaques or in cell-to-cell adherens junctions. The findings suggest that stabilization of the membrane at these sites may interfere with FSC formation and conversely that the absence of FSC may be an indication of membrane stabilization.

Animals↗
PubMed1986

Localization of fibronectin in gingival connective tissue of the beagle dog. Ultrastructural detection with ferritin and peroxidase-conjugated antibodies.

Ferritin and peroxidase-conjugated antibodies were used in an indirect antibody method to localize fibronectin in gingival connective tissues. Fibronectin was found in the basal lamina beneath the epithelium and endothelium. Collagen fibrils associated with the basement membranes were also heavily coated by fibronectin. Amorphous patches of fibronectin were found adjacent to the plasma membrane of epithelial cells as well as free in the interepithelial spaces. Fibronectin was present throughout the connective tissue in close association with individual collagen fibrils, apparently serving as an interfibrillar cementing substance. Patches of fibronectin were located at the cell surface of fibroblasts, plasma cells, lymphocytes, endothelial cells, smooth muscle cells, and neutrophils. These amorphous patches were observed to connect adjacent cells across narrow spaces and to connect cells to collagen fibrils. The heavy labeling for fibronectin visualized by fluorescent microscopy around gingival blood vessels (Cho et al., 1985) can be accounted for by a heavy coating of fibronectin on the collagen fibrils and basal laminas associated with endothelial cells, as well as by the presence of abundant deposits of fibronectin along the cell membranes of endothelial cells and in the intercellular spaces of the vessel wall.

Animals↗
PubMed1985

Effects of L-azetidine-2-carboxylic acid on matrix secretion and Golgi structure in fibroblasts and osteoblasts of the mouse.

The effect of a proline analogue, L-azetidine-2-carboxylic acid (LACA), on collagenous matrix secretion by periodontal ligament fibroblasts and alveolar bone osteoblasts was studied by light and electron microscopic radioautography after injection of 3H-glycine; 3H-glycine labeled material accumulated in the cisternae of the rough endoplasmic reticulum and was not secreted for over 4 hours. The Golgi complex of both fibroblasts and osteoblasts showed a marked alteration of its composition after LACA administration. All Golgi saccules and collagen secretion granules disappeared within 2 hours. Flattened Golgi cisternae were still present and appeared to be unaffected by the administration of LACA. These observations indicate that Golgi saccules in collagen-secreting cells are the initial staging areas for the formation of collagen secretory granules and that there is a close correlation between form and function in the Golgi apparatus of collagen-secreting cells.

Alveolar Process↗
PubMed1985

Radioautographic analysis of [3H]-fucose utilization by mouse odontoblasts with emphasis on intracytoplasmic and plasma membrane glycoproteins.

[3H]-fucose utilization by odontoblasts was studied by light and electron microscopic radioautography. At 10 min after injection, fucose label was concentrated in the Golgi area. By 20-30 min, there was a progressive decline in Golgi labelling with label present at the plasma membrane, terminal web, odontoblast process and predentine matrix. At 4 h, the predentine and the predentine-dentine junction were heavily labelled. At the ultrastructural level, Golgi labelling at 10 min was mostly localized to cisternal elements and at 20 and 30 min secretory granules and dense bodies were also labelled. Most of the silver grains observed in the terminal web were associated with microfilaments near the plasma membrane. In the predentine, the matrix itself accounted for 23.0 per cent of the label at 4 h and the plasma membrane of the odontoblast process accounted for 19 per cent. The results indicate that odontoblasts, in addition to secreting glycoproteins into the dentinal matrix, also continuously manufacture glycoproteins for incorporation into the cell surface, the lysosomal system and the terminal web.

Animals↗
PubMed1985

Ultrastructural and cytochemical studies of the fate of unsecreted collagen precursors after administration of colchicine to mice.

The administration of colchicine disrupts the normal organization of the Golgi complex and blocks the secretion of collagen precursors in periodontal ligament fibroblasts of the mouse. The fate of the unsecreted collagen precursors contained in Golgi-derived saccules and newly formed dense bodies was followed by electron microscopy. A progressive condensation of saccule content along with phase separation of electron-dense and electron-lucent material was observed. Fusion of saccules with dense secretory bodies gave rise to larger inclusions (zebra bodies; ZB) filled with a combination of electron-dense and electron-lucent material. In some ZB, these materials appeared to polymerize into fibrillar units. The fibrillar units stained with silver methenamine like normal collagenous fibrils. These results suggest that unsecreted collagen precursors accumulate in vesicular compartments within which partial polymerization can occur. This finding may explain some reports of intracellular collagenous fibrils in fibroblasts of pathologically altered connective tissues.

Animals↗
PubMed1985

Localization of fibronectin in gingival connective tissue of the beagle dog. Immunofluorescent light microscopic findings.

Affinity purified antibodies to plasma fibronectin were used to localize fibronectin in the connective tissues of inflamed and noninflamed beagle gingiva. In noninfiltrated gingival connective tissue, fibronectin was demonstrated in the basement membrane beneath gingival epithelium and around blood vessels as a uniform and intensely stained band about 3 to 10 micron thick. Fibronectin was also distributed throughout the connective tissue in association with collagen fibrils as a more diffuse, less intensely stained pattern. The inflamed gingiva included in this study was characterized by proliferation of epithelial pegs, heavy infiltration of plasma cells and loss of collagen within the subepithelial connective tissue. In these sites, fibronectin was present as an intensely stained band around blood vessels and at the crest of connective tissue papillae nearest the sulcular space. The fibronectin in the basement membrane beneath the epithelium appeared diminished and less uniformly distributed. A delicate network of fibronectin was present around plasma cells and the remaining collagen fibers.

Animals↗
PubMed1984

Formation of multinucleated fibroblasts in the periodontal ligaments of old mice.

Multinucleated cells were observed to account for more than 17% of all cells in the periodontal ligament (PDL) of 20-month-old mice. The number of nuclei contained in sections of these cells ranged from 2 to 17, with over 50% of the multinucleated cells containing four or more nuclei within the plane of section. The multinucleated cells contained several cytoplasmic features resembling those previously described by the authors as characteristic of PDL fibroblasts. The multinucleated cells did not resemble osteoclasts or foreign body giant cells. It is suggested that fibroblasts develop a tendency to fuse and form multinucleated cells in the aged PDL. Similar cells were not observed in the PDL of young (5-week-old) mice or in the tail tendon at any age.

Aging↗
PubMed1984

The effect of beta-aminoproprionitrile on the periodontal ligament: II. Radioautographic study of collagen secretion from fibroblasts.

Fibroblasts are distributed evenly throughout the periodontal ligament (PDL) of normal mice. In mice fed beta-aminoproprionitrile (beta-APN) the fibroblasts undergo aggregation to form palisades of closely juxtaposed cells abutting pools of acellular collagenous matrix. Individual fibroblasts within these aggregates retain their polarized cytoplasmic organization and continue to synthesize and secrete collagen. However, unlike normal PDL fibroblasts, the beta-APN-treated cells appear immobilized by well-developed cell-to-cell adherens-type junctions along their lateral surfaces. We studied collagen secretion from beta-APN-treated fibroblasts by light and electron microscopic radioautography after injection of 3H-proline. Newly synthesized collagen was secreted from the distal ends of the beta-APN-aggregated fibroblasts as a distinct band of labeled material, resembling the pattern of matrix deposition seen in osteogenesis and dentinogenesis. The radioactive band of collagenous matrix was displaced further away from the fibroblasts at 2 and 4 days after 3H-proline injection as more collagen was secreted. This pattern of radiolabeled collagen secretion confirmed previous observations that PDL fibroblasts are highly polarized and that collagen secretory granules are extruded from the distal or secretory pole of the cell. In normal PDL the even distribution of fibroblasts and the complex interrelationship of their distal cell processes leads to a diffuse pattern of silver grain deposition, masking the oriented flow of new collagen from the distal ends of individual fibroblasts. Analysis of electron microscopic radioautographs revealed that newly synthesized collagen was packaged and secreted from beta-APN-treated fibroblasts via the normal cytoplasmic pathways but at a slower rate.

Aminopropionitrile↗
PubMed1984

Comparative radioautographic study of the effects of L-azetidine-2-carboxylic acid on matrix secretion and Golgi of the mouse incisor.

The effect of a proline analog, L-azetidine-2-carboxylic acid (LACA), on protein matrix secretion by odontoblasts and ameloblasts was compared by light and electron microscopic radioautography after injection of 3H-glycine in young mice. LACA inhibited the secretion of dentin matrix with consequent accumulation of 3H-glycine labeled procollagen in the cisternae of the rough endoplasmic reticulum. In contrast, LACA had no apparent effect on ameloblasts as enamel matrix continued to be packaged in the Golgi apparatus and secreted from Tomes' process within 30 min after injection of the radioprecursor. Electron microscopy revealed that LACA did not cause any change in ameloblast ultrastructure but produced a marked alteration of the odontoblast Golgi complex. All odontoblast Golgi saccules and collagen secretion granules disappeared within 2 h after LACA administration. Odontoblast Golgi cisternae, however, appeared not to be affected. These observations confirm previous studies conducted in this laboratory showing that Golgi saccules in collagen-secreting cells are the initial staging areas for the formation of secretory granules. These results also indicate that a close correlation exists between form and function in the Golgi apparatus of collagen-secreting cells.

Ameloblasts↗
PubMed1984

A freeze-fracture study of the papillary layer of the rat incisor enamel organ.

After tooth enamel has been secreted it undergoes maturation or hardening. This process is mediated by ruffled and smooth-ended ameloblasts and associated papillary layer cells. The cells of the papillary layer are characterized by large numbers of mitochondria, coated vesicles, microvilli, and gap junctions. These features have led numerous investigators to speculate that the papillary layer is an ion-transporting epithelium. We have conducted freeze-fracture studies of the rat papillary layer in order to better characterize the surface features of these cells. The cell membranes of the papillary cells contained large numbers of intramembrane particles of various sizes ranging from 4 to 9 nm in diameter. Gap junctions were present at the cell surface and in the cytoplasm in the form of annular gap junctions. The intramembrane particles or connexons of both types of gap junctions were about 8-9 nm wide and were either packed randomly or present in the so-called 'crystallized' state. At the interface between smooth-ended ameloblasts and papillary layer cells, a well-developed zonula occludens was present along the basal surfaces of the ameloblasts and several large gap junctions were formed between the two cell types. The capillary network associated with the papillary layer was characterized by a thin endothelium containing large numbers of fenestrations.

Animals↗
PubMed1984

In vitro and in vivo studies of cellular lysis of oral bacteria by a lysozyme-protease-inorganic monovalent anion antibacterial system.

Compared with anion-activated cell lysis of oral bacteria damaged with either lysozyme or trypsin, cells which were treated with both of these enzymes showed a far greater degree of lysis. This was true regardless of whether turbidimetric, DNA release, or electron microscopic assays were used to monitor the lytic process. At an acidic pH of 5.2 and an NaHCO3 concentration of 100 mM, the kinetics of lysis for two different serotype c strains of Streptococcus mutans were similar. At 0 to 100 mM bicarbonate, however, differences in the lytic susceptibilities of the two strains were evident. At pH 5.2, NaHCO3, but not NaSCN, NaCl, or NaF, was effective in promoting cell lysis of the oral bacteria. At apparent sublytic concentrations of NaHCO3, lysis was achieved by adding appropriate concentrations of NaSCN, NaCl, or NaF to the lysozyme-protease-damaged cells. In in vivo studies, hamsters given a combination of NaHCO3, NaCl, and NaSCN were found to have significantly reduced levels of S. mutans on their molar teeth compared with that found in controls or animals exposed to any one of the salts alone or to a combination of chloride and thiocyanate only. The results suggest that bicarbonate is an essential anion which, together with the other major salivary inorganic monovalent anions, plays an active role in the lysis and ultimate elimination of cariogenic bacteria.

Actinomyces↗