Mitochondrial granules in the normal and rachitic rat epiphysis

Matthews, James L.; Martin, J. Holmes; Sampson, H. Wayne; Kunin, Arthur S.; Roan, J. H.

doi:10.1007/bf02017539

Cited by 78 publications

(17 citation statements)

References 8 publications

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“…It is shown in this study that cultured bone cells contain about twice the amount of exchangeable Ca++ as compared with cultured fibroblasts under similar conditions. High values of Ca++ have been previously reported in freshly isolated bone cells (Dziak and Brand, 1974) and could also be inferred from histochemical (Kashiwa, 1968) and electron microscope findings (Matthews et al, 1970). Our kinetic analysis indicates that the higher level of Ca++ in bone cells is the result of a n elevated concentration of Cat+ mainly in the "slow-" but also in the "fast-turnover" Ca++ pool.…”

Section: Discussionsupporting

confidence: 84%

Calcium transport and cellular distribution in quiescent and serum‐stimulated primary cultures of bone cells and skin fibroblasts

Eilam

Szydel

1981

Journal Cellular Physiology

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Primary cultures of bone cells and skin fibroblasts were examined for their Ca++ content, intracellular distribution and Ca++ fluxes. Kinetic analysis of 45Ca++ efflux curves indicated the presence of three exchangeable Ca++ compartments which turned over at different rates: a "very fast turnover" (S1), a "fast turnover" (S2, and a "slow turnover" Ca++ pool (S3). S1 was taken to represent extracellular membrane-bound Ca++, S2 represented cytosolic Ca++, and S3 was taken to represent Ca++ sequestered in some intracellular organelles, probably the mitochondria. Bone cells contained about twice the amount of Ca++ as compared with cultured fibroblasts. Most of this extra Ca++ was localized in the "slow turnover" intracellular Ca++ pool (S3). Serum activation caused the following changes in the amount, distribution, and fluxes of Ca++: (1) In both types of cells serum caused an increase in the amount of Ca++ in the "very fast turnover" Ca++ pool, and an increase in the rate constant of 45Ca++ efflux from this pool, indicating a decrease in the strength of Ca++ binding to ligands on cell membranes. (2) In fibroblasts, serum activation also caused a marked decrease in the content of Ca++ in the "slow turnover" Ca++ pool (S3), an increase in the rates of Ca++ efflux from the cells to the medium, and from S3 to S2, as well as a decrease in the rate of influx into S3. (3) In bone cells the amount of Ca++ in S3 remained high in "serum activated" cells, the rate of efflux from S3 to S2 increased, and the rate of influx into S3 also increased. The rate of efflux from the cells to the medium did not change. The results suggest specific properties of bone cells with regard to cell Ca++ presumably connected with their differentiation. Following serum activation we investigated the time course of changes in the amount of exchangeable Ca++ in bone cells and fibroblasts, in parallel with measurements of 3H-thymidine incorporation and cell numbers. Serum activation caused a rapid decrease in the content of cell Ca++ which was followed by a biphasic increase lasting until cell division.

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Section: Discussionsupporting

confidence: 84%

Calcium transport and cellular distribution in quiescent and serum‐stimulated primary cultures of bone cells and skin fibroblasts

Eilam

Szydel

1981

Journal Cellular Physiology

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“…The mechanism or site of nucleation will require further study, but all of the candidates presently proposed as likely nucleation sites for bone are present in toad skin. Mitochondria1 granules have been demonstrated to increase in number as cartilage matures along the growth plate, and to be released at the site of provisional calcification where extracellular sites of mineralization are first seen (Matthews et al, 1970(Matthews et al, , 1971, and they can be identified in the calcifying region of toad skin (Verhaagh & Greven, 1982) (Plate I1 e). Collagen is abundant (Plate I e; Plate I1 e) and would also be available as a possible site of nucleation (Glimcher, 1976;Neuman, 1980), as would the structures appearing to be matrix vesicles or cytoplasm fragments (Plate I e) (Anderson, 1976;Morris, Vaananen & Anderson, 1983).…”

Section: Resultsmentioning

confidence: 99%

The calcified amorphous layer of the skin of Bufo marinus (Amphibia: Anura)

1987

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The integument of Bufo marinus is surveyed. It is similar to that of other anurans and contains the three chromatophores common to anurans. The skin of these toads contains more than 28% minerals deposited as small crystals in a mucopolysaccharide‐positive amorphous layer between the stratum compactum and the stratum spongiosum. These crystals reveal a high content of calcium and phosphorus aggregated in and near membrane‐bound vesicles which have an appearance very similar to matrix vesicles. Electron microscopy gives the appearance that these vesicles are associated with flbroblasts located between alternating bundles of collagen. Histochemical studies indicate that the amorphous layer possesses many of the characteristics commonly associated with mineralized cartilage or bone.

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“…This indicates that 50% or less of the mitochondrial calcium is exchangeable. The unexchangeable fraction could possibly reflect the sequestration of calcium in mitochondria as calcium phosphate precipitates (Peachey 1964;Greenawatt et al 1964;Weinbach and Von Brand 1968;Zadunaisky et al 1968;Lehninger 1970;Matthews et al 1970;Martin and Matthews 1970;Sutfin et al 1971;Ruigrok and Elbers 1972;Sayegh et al 1974) or as organic-inorganic complexes (Barnard and Afzelius 1972;Bonucci et al 1973).…”

Section: Cellular Distribution Of Calciummentioning

confidence: 99%