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Biomedical subjects

D C Sun

Publications and source records attributed to D C Sun.

At least 19 recordsLinked to original sources
PubMed1984

Effect of concanavalin A on lymph node macrophages: stimulation of endocytic cisternae.

Incubation of isolated lymph node macrophages with concanavalin A (Con A) resulted in a dense and continuous labeling of the plasmalemma and filopodia which were closely adherent to each other and the cell surface. Within a short time period (3-5 min), membranes of the closely apposed filopodia became invaginated into the cytoplasm to form numerous interconnecting cisternae. After 10 min the system of internalized membranes had migrated into the deeper cytoplasm and was closely associated with numerous actin filaments and other components of the cytoskeleton. The internalized plasmalemma remained in the cytoplasm up to 24 hr without fusing with lysosomes. Concomitant with plasmalemmal invagination and the formation of cisternae there were also changes in the Golgi apparatus. These appeared in the form of hypertrophied Golgi saccules and the accumulation of numerous vesicles around the Golgi. Treatment of isolated lymph node macrophages with either succinylated Con A, alpha-methyl-D-mannoside, or ferritin particles alone failed to produce the cisternal structures. The results suggested that the tetravalency of Con A may be responsible for the binding of adjacent Con A-labeled membranes to each other and for maintaining a crosslinking of membranes during invagination and internalization. It is suggested that this process of extensive membrane internalization represents a specialized form of endocytosis. At 24 hr after incubation with Con A, cisternal structures in close proximity to the Golgi vesicles showed signs of degradation. By 48 hr there was a breakdown of cisternal membranes with a release of Con A marker particles into large phagocytic vesicles, which also showed reaction product for acid phosphatase, suggesting a fusion with lysosomes.

Animals↗
PubMed1983

Cultivation of human osteosarcoma cell lines in serum-free hormone supplemented medium.

Two human osteosarcoma cell lines (TE-85, LM-1) were adapted to grow in serum-free hydrocortisone supplemented medium. Human osteosarcoma associated antigens were detected both on the cell membrane as well as in the concentrated culture medium. TE-85 cells produced bone specific alkaline phosphatase and LM-1 cells produced both bone specific and placental-like alkaline phosphatases when cultured in this medium. Successful proliferation of human osteosarcoma cell lines in serum-free medium is valuable in human osteosarcoma research.

Alkaline Phosphatase↗
PubMed1982

Concanavalin A receptor sites on lymph node cells in vivo and in vitro.

The distribution and density of receptors for concanavalin A (Con A) on the surfaces of cells of intact and isolated popliteal and axillary lymph nodes were investigated in the rabbit. Intact lymph nodes were perfused via the subcapsular (marginal) sinus with either Con A peroxidase or Con A ferritin, fixed with glutaraldehyde, and processed for electron microscopy. Both Con A peroxidase and Con A ferritin were distributed on the plasmalemma of lymphocytes, macrophages, neutrophils, plasma cells, reticular endothelial cells, and the vascular endothelium. Counts of Con A-conjugated ferritin particles indicated that the density of Con A receptors was generally similar for lymphocytes, macrophages, and neutrophils but lower on plasma cells. When lymph node cells were isolated by mechanical methods and exposed to Con A ferritin, the label was homogenously distributed on the cell surfaces of most cells. However, Con A binding was significantly higher on the surface of isolated cells than in the intact node. It is suggested that the increase in density of Con A binding sites on isolated cells may possibly be due to an unmasking of cell surface moieties in which additional Con A receptor sites become available as a result of the isolation procedure. The density of Con A ferritin binding sites was also significantly lower on the surface of isolated plasma cells than the lymphocyte and macrophage, suggesting that the density distribution of cell surface saccharides is different for various lymphoid cells.

Animals↗
PubMed1978

Effect of a new antacid on basal and meal-stimulated gastric secretion.

Our study of the comparative neutralizing effectiveness of four antacids on the acidity and pH of the basal gastric secretion in 32 patients showed that using the conventional doses of two tablets of Rolaids, two tablets of Di-Gel, 15 ml. of Maalox liquid or two tablets of Conquel, they are equal in their acid neutralizing capacity. The duration of action for 45-60 minutes. Conquel, in a dose of two tablets, was a potent buffer for the peptone-meal stimulated secretion. The duration of action lasted for longer than two hours.

Aluminum Hydroxide↗
PubMed1977

Augmented histamine test--diagnostic and prognostic values.

The results of the augmented histamine test in 107 controls, 48 patients with gastric ulcer and 141 patients with duodenal ulcer are presented. The mean basal acid secretion and maximal acid output (MAO) were significantly higher in duodenal ulcer patients than in normal subjects. Ulcers of the body of the stomach were associated with lower than normal levels of secretion, whereas ulcers of the prepyloric region were associated with higher than normal levels. In this study of 141 patients with duodenal ulcer, 101 patients or 72% had an MAO above the upper limit of normal (20.4 mEq./hr.). Conversely, a patient with an MAO of less than 12.4 mEq./hr. is unlikely to have duodenal ulcer disease. The use of the ratio of MAO to actual body weight did not increase the diagnostic discrimination between normal subjects and those with duodenal ulcer. Duodenal ulcer patients with complications had a significantly higher MAO to histamine than those without complication. The finding of an MAO greater than 40 mEq./hr. is highly suggestive of the presence or the imminence of a complication.

Adult↗