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Showing papers on "Cellular compartment published in 1968"


Journal ArticleDOI
TL;DR: The results suggest that parathyroid hormone influences the cellular calcium balance by mobilizing calcium from the extracellular fluids in order to increase its concentration in some cellular compartment and it is proposed that these effects can enhance calcium transport.
Abstract: Calcium metabolism was investigated in HeLa cells. 90% of the calcium of the cell monolayer is bound to an extracellular cell coat and can be removed by trypsin-EDTA. The calcium concentration of the naked cell, freed from its coat, is 0.47 mM. The calcium concentration of the medium does not affect the concentration of the naked cell calcium. However, the calcium of the cell coat is proportional to the calcium concentration in the medium. Calcium uptake into the cell coat increases with increasing calcium concentration of the medium, whereas uptake by the naked cell is independent of the calcium of the medium. Anaerobic conditions and metabolic inhibitors do not inhibit calcium uptake by the cell, a fact suggesting that this transfer is a passive phenomenon. The calcium in the extracellular cell coat, was not affected by parathyroid hormone. In contrast, the hormone increased the cellular calcium concentration by stimulating calcium uptake or by enhancing calcium binding to some cell components. These results suggest that, contrary to current thinking, parathyroid hormone influences the cellular calcium balance by mobilizing calcium from the extracellular fluids in order to increase its concentration in some cellular compartment. It is proposed that these effects can enhance calcium transport.

135 citations


Journal ArticleDOI
TL;DR: Electron microscope autoradiography was used to study cartilage from regenerating limbs of adult newts, Triturus, after intraperitoneal injections of proline‐3H to indicate that a large part of the radioactive secretion probably leaves the cell after having been in only one cellular compartment.
Abstract: Electron microscope autoradiography was used to study cartilage from regenerating limbs of adult newts, Triturus, after intraperitoneal injections of proline-3H. The labeling in the endoplasmic reticulum, small vesicles, Golgi vacuoles, ground cytoplasm and extracellular matrix was compared during the secretion of radioactive products. The data appear to indicate that a large part of the radioactive secretion probably leaves the cell after having been in only one cellular compartment. Although this compartment may be the endoplasmic reticulum, a considerable amount of radioactivity fluxes through the ground cytoplasm and the possibility cannot be excluded that some secretory components leave the cell directly from the ground cytoplasm. The data appear incompatible with the hypothesis that all the radioactivity seen in the extracellular matrix arrived there via a single pathway involving first the endoplasmic reticulum and then the Golgi vacuoles. It is not, however, incompatible with a hypothesis that a fraction of the radioactive product uses this pathway.

65 citations