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At least 55 records · Page 3Linked to original sources
PubMed1978

Determination of cellular shape by the extracellular matrix and its correlation with the control of cellular growth.

Although the problem of cellular proliferation may seem at first glance to be tremendously complex, the mechanisms which control it may be extremely simple. One of the primary factors which regulates the mitogenic response of a given cell type to a given class of mitogenic agents seems to be the cellular shape. We have found that corneal epithelial cells, for example, adopt a flattened configuration when maintained in vitro on plastic and are very sensitive to fibroblast growth factor, but not to epidermal growth factor. When maintained on collagen, on the other hand, they become tall and columnar and respond primarily to epidermal growth factor. The cellular shape is dictated in vivo by the extracellular material upon which the cells rest and in vitro by the substrate upon which the cells are maintained. The substrate itself may, in turn, induce the cells to manufacture their extracellular material and specific cell surface proteins which control the cellular shape.

Animals↗
PubMed1977

Extracellular matrix synthesis in blastula and gastrula stages of normal and hybrid frog embryos. II. Autoradiographic observations on the sites of synthesis and mode of transport of galactose- and glucosamine-labelled materials.

Pulse-chase labelling experiments and light- and electron-microscopic autoradiography were used to examine the sites of synthesis, mode of transport, and sites of deposition of galactose- and glucosamine-labelled materials in different developmental stages of normal developing Rana pipiens embryos and interspecific hybrid embryos formed by fertilizing the eggs of R. pipiens with the sperm of R. catesbeiana. In both normal and hybrid embryos, after 15-min pulse, grains are closely associated with juxtanuclear and cytoplasmic collections of membrane-bound vesicles which resemble the Golgi apparatus. In normal embryos following a 15-30 min pulse and a 60-min chase, grains are largely cleared from the cytoplasmic vesicles and deposited in the extracellular spaces or along cell surfaces where the extracellular spaces are relatively large. In contrast, arrested hybrid embryos given a 15-30-min pulse and a 60-min chase show a marked accumulation of grains over cytoplasmic structures such as the Golgi apparatus and vesicular elements in the cell cortex. Finally, early gastrula stage normal embryos are most active in the synthesis of galactose-labelled materials in cells above the dorsal lip of the blastopore, where cell migration is initiated.

Animals↗
PubMed1977

Scanning electron microscope study of the extracellular matrix between presumptive lens and presumptive retina of the chick embryo.

The three-dimensional architecture of the intercellular matrix contained in the interspace between the presumptive lens and optic vesicle of the chick embryo was examined by scanning electron microsocpy. The fibrous structure of the basement membranes lining the space was demonstrated. The space was shown to be filled with a dense fibrous meshwork. The reaction of basement membranes and interspace contents to enzymic digestion is described. The functional significance of the arrangement of fibres in the interspace is discussed.

Animals↗
PubMed1977

Extracellular matrix synthesis in blastula and gastrula stages of normal and hybrid frog embryos. III. Characterization of galactose- and glucosamine-labelled materials.

Normal Rana pipiens gastrulae show more incorporation of isotopically-labelled galactose and glucosamine into TCA-insoluble materials than blastulae. Interspecific hybrid embryos which undergo developmental arrest at the onset of gastrulation often synthesize reduced amounts of galactose- and glucosamine-labelled materials. These materials are high-molecular weight, but not collagen. After pronase digestion, labelled materials elute in the void volume of Sephadex G-50. Labelled materials migrate slowly on cellulose acetate, bind to several kinds of anion exchangers and elute at low ionic strength, are precipitated by cetyl pyridinium chloride (CPC) when mixed with carrier compounds, and are not degraded by Clostridium neuraminidase or Streptomyces, leech, and bovine testicular hyaluronidases.

Animals↗
PubMed1978

Extracellular matrix synthesis in blastula and gastrula stages of normal and hybrid frog embryos. IV. Biochemical and autoradiographic observations on fucose-, glucose-, and mannose-labelled materials.

Normal Rana pipiens gastrulae show more incorporation of isotopically labelled fucose, glucose, and mannose into TCA-insoluble materials than blastulae. Interspecific hybrid embryos which undergo developmental arrest at the onset of gastrulation often synthesize reduced amounts of fucose-, glucose- and mannose-labelled materials. These materials are high-molecular weight and are degraded by Pronase into fragments which are included in Sepharose CL-4B but excluded from Sephadex G-50. Labelled materials contain label predominantly in fucose and galactose with little label in glucose or mannose. Labelled materials migrate slowly on cellulose acetate, bind to DEAE-cellulose and elute at low ionic strength and are precipitated by cetyl pyridinium chloride (CPC) without the addition of carrier compounds. Pulse-chase labelling experiments and light- and electron-microscopic autoradiography were used to examine the site of synthesis, mode of transport, and sites of deposition of fucose-, glucose- and mannose-labelled materials in different developmental stages of normal developing Rana pipiens embryos and interspecific hybrid embryos formed by fertilizing the eggs of R. pipiens with the sperm of R. catesbeiana. In both normal and hybrid embryos, after a 15-30-min pulse, grains are closely associated with juxtanuclear and cytoplasmic collections of membrane-bound vesicles which resemble the Golgi apparatus. In normal embryos following a 15-30-min pulse and a 60-min chase, grains are largely cleared from the cytoplasmic vesicles and deposited in the extracellular spaces or along cell surfaces. In contrast, arrested hybrid embryos given a 15-30-min pulse and a 60-min chase show a marked accumulation of grains over cytoplasmic structures such as the Golgi apparatus and vesicular elements in the cell cortex. Certain interesting features of regional variation in synthetic activity in developing normal embryos are also described.

Animals↗
PubMed1978

Extracellular matrix metabolism by chondrocytes. VI. Concomitant depression by exogenous levels of proteoglycan of collagen and proteoglycan synthesis by chondrocytes.

The synthesis of collagen and proteoglycans by cultured chondrocytes, as measured by the incorporation of L-[3H]proline into hydroxyproline and [3H]acetate into glycosaminoglycans, was shown to be depressed by 58% and 39%, respectively, by the addition of exogenous proteoglycan at a concentration of 10 mg/ml growth media. The incorporation of L-[3H]proline into acid-insoluble protein remained unaltered in the presence of the proteoglycan. It was concluded that the effect was depressing the activity on the enzymatic steps, associated with the endoplasmic reticulum, which are responsible for the post-translational modification of collagen and proteoglycan.

Acetates↗
PubMed1978

Extracellular matrix metabolism by chondrocytes. 4. Role of glutamine in glycosaminoglycan synthesis in vitro by chondrocytes.

The rate of synthesis of glycosaminoglycans by cartilage was shown to be dependent on an exogenous source of L-glutamine. In the absence of L-glutamine the tissue and cellular levels of this amino acid were rapidly depleted. The levels of nucleotide sugars and their precursors were measured after separation on Dowex 1 (formate form) in cartilage incubated with and without L-glutamine. It was found that the levels of N-acetylhexoamine 6-phosphate and UDP-N-acetylhexosamine were decreased by 27 and 40% respectively. This demonstrates that L-glutamine is required as the amido group donor in the synthesis of glucosamine 6-phosphate and that the decrease in glycosaminoglycan synthesis is due to the limitation in synthesis of UDP-N-acetylhexoamine.

Animals↗