Cell aggregation: role of acid mucopolysaccharides

Ultrastructural studies on the external surface coat of epidermal cells: alcian blue-lanthanum nitrate staining during wound healing

The external surface coat on mouse epidermal cells has been studied during epidermal wound healing in suction-induced intact subepidermal blisters. By sequentially incorporating the cationic dye Alcian blue and the electron opaque tracer lanthanum nitrate into the primary and secondary fixatives for electron microscopy (AB/LN staining), we have demonstrated a selective staining of the epidermal surface coat. At 12 and 24 h after wounding, AB/LN staining always occurred on opposing cell membranes of adjacent epidermal cells. No staining was seen along epidermal cell plasmalemmas exposed to the blister cavity or opposite the basal lamina. The full significance of this differential AB/LN staining during wound healing is not presently known. It is suggested that the presumed anionic sites that are binding the AB/LN stain may play a role in maintaining integrity during wound healing.

The major cell surface glycoprotein of chick embryo fibroblasts is an agglutinin

A major cell surface protein, CSP, of chick embryo fibroblasts has been shown to constitute up to 3% of total cell protein, and to be decreased after viral transformation. Its role in normal cell behavior is not known. We have isolated CSP from chick embryo fibroblasts by extraction with 1 M urea and find that these preparations of CSP agglutinate formalinized sheep erythrocytes at protein concentrations of under 2 mug/ml. In extracts of chick embryo cells, the quantity of such hemagglutinating activity parallels that of CSP determined by electrophoresis, and both are substantially decreased in chick cells transformed by the Bryan hightiter strain of Rous sarcoma virus. Both CSP and hemagglutinating activity are progressively adsorbed onto erythrocytes and can be released by 1 M urea. An antiserum to purified CSP specifically blocks the agglutination. The agglutinating activity is destroyed by boiling or treatment with proteases. The agglutination reaction is inhibited by the chelating agents EDTA and EGTA [ethyleneglycol-bis(beta-aminoethyl ether)N,N'-tetraacetic acid]. Agglutination is also inhibited to a lesser degres by amino sugars and other amines, increased osmolarity, and urea. Other monosaccharides, hyaluronidase, DNase, and RNase have little or not effect on the agglutination reaction. This demonstration that CSP has an agglutinating activity that is sensitive to proteases and that requires divalent cations suggests that this molecule may play a role in cell adhesion.

Calcium binding to D-glucuronate residues: crystal structure of a hydrated calcium bromide salt of D-glucuronic acid

Three-dimensional X-ray diffraction data were used to determine the crystal structure of alpha-D-glucuronate CaBr times 3H20, a model system for investigating the factors involved in the binding of calcium ions to D-glucuronate residues of oligo-and poly-saccharides. Crystals of the salt are monoclinic, space group P21, having a = 6.410 (1), b = 10.784 (2), c = 8.879 (1) A, betta = 92.07 (1)degrees, and Z = 2. Instensity data for 1082 reflections were measured with an automated diffractometer. A trial structure, obtained by the heavy-atom method, was refined by least squares to R = 0.025. The absolute configuration was confirmed by anomalous-dispersion effects. An outstanding feature of the crystal packing is the interaction of D-glucuronate anions with calcium ions. The calcium ion is coordinated to three symmetry-related D-glucuronate anions and to two water molecules. The D-glucuronate anion binds calcium cations through three chelation sites: one that involves a carboxyl-oxygen atom combined with O-5; one that includes the second carboxyl-oxygen atom acting in concert with O-4, and one composed of the O-1-O-2 pair of hydroxyl groups.

Purification and characterization of the retina-specific cell-aggregating factor

The tissue-specific, cell-aggregating component of embryonic neural retina cells was purified from the retina cell-aggregating factor and characterized as a glycoprotein. Its molecular weight in solution is in the range of 50,000, and it contains 10-15% carbohydrate. The amino-acid and carbohydrate compositions have been determined. The glycoprotein is produced by embryonic neural retina cells in primary monolayered cultures and is released into the medium. Its tissue-specific, cell-aggregating effect requires integrity of the polypeptide portion, but not of the carbohydrate portion. We suggest that the isolated molecule is a specific determinant of the embryonic retina cell-surface and that it is involved in mediating self-recognition and selective adhesiveness of these cells.

Albumin, fibrinogen and transferrin synthesis in isolated rat hepatocyte suspensions. A model for the study of plasma protein synthesis

A system using hepatocyte suspensions in vitro was developed for studying the synthesis of albumin, fibrinogen and transferrin. Conditions for optimum survival of the hepatocyte and for synthesis of these plasma proteins were defined for this system. These conditions included the use of horse serum (17.5 percent, v/v, heat-inactivated), an enriched medium (Waymouth's MB 752/1), an O2 tension of between 18.7 times 10(3) and 26.7 times 10(3) Pa and constant stirring. Albumin, fibrinogen and transferrin synthesis rates were obtained of 0.32 p 0.094(10), 0.12 p 0.030(11) and 0.097 p 0.017(10) [mean p S.D. (n)]mg/h per g of hepatocytes respectively. These rates were maintained for the first 12h of study and synthesis continued at a diminished rate up to 48h. The synthesis of albumin was decreased in a medium containing less amino acids and glucose, but that of fibrinogen was substantially unaffected. ATP concentrations up to 12h and RNA/DNA ratios up to 24h were comparable with values in vivo. The ability to study cells up to 48h permitted us to find that the addition of a mixture of hormones consisting of glucagon, cortisol, tri-iodothyronine and growth hormone enhanced fibrinogen synthesis. Addition of insulin to the above mixture resulted in increased synthesis for albumin and transferrin but not for fibrinogen.

Transformation of chick embryo neuroretinal cells by Rous sarcoma virus in vitro: induction of cell proliferation

Neuroretinal cells from 7-day-old chick embryos are transformed and induced to proliferate after infection with Rous sarcoma virus in vitro. Susceptibility of neuroretinal cells to the virus is also dependent on the stage of development since infection of cells from 10-day-old embryos is uneffective.

Breast cancer: induction of differentiation by embryonic tissue

A mouse mammary tumor, adenocarcinoma BW 10232, was maintained in vitro for 14 days, separated from embryonic mammary mesenchyme by a Millipore filter. Tubules developed in the tumor; deoxyibonucleic acid synthisis declined; and a presumptive acid mucopolysaccharide matrix, not evident in the controls, appeared.

Studies on cell adhesion. 3. Adhesion of baby hamster kidney cells

Normal and transformed baby hamster kidney (BHK) cells attach to Falcon polystyrene with the same first order rate constant. The longer the cells are attached to the bottles, the more difficult they are to remove. Sulfhydryl (-SH) binding reagents inhibit both the attachment of BHK cells and the increase in adhesive strength of attached cells. Attached BHK cells bind fewer molecules of [1-(14)C]N-ethylamleimide (an -SH binding reagent) than do suspended cells. Incubation of cells with high concentrations of trypsin results in a reversible loss of cell adhesiveness. The recovery of adhesiveness of trypsin-treated cells is inhibited by cycloheximide.

Structural and functional characterization of isolated pancreatic exocrine cells

Viable isolated exocrine cells have been obtained from guinea-pig pancreas by a tissue dissociation procedure using crude collagenase (EC 3.4.4.19) and hyaluronidase (EC 3.2.1.35), chelation of divalent cations, and mild shearing forces. Cell yields are 50-60%, based on recovered DNA, and about 90% of the population consists of exocrine cells which, although rounded up, retain their in situ polarity with regard to regional distribution of zymogen granules and specialization of the former luminal plasmalemma. The isolated cells incorporate labeled amino acids into proteins at linear rates for at least 4 hr at levels comparable to pancreatic slices in vitro; more than 95% of the exocrine cell population is active in this process, as shown by autoradiography. In response to secretogogues at optimal doses (100 muM carbamylcholine; 0.1 muM pancreozymin, or 0.01 muM caerulein), the cells discharge up to 30% of their content of pulse-labeled secretory proteins to the medium over a 3-hr period; in the same time, the controls release about 5% of their content. The results indicate that isolated exocrine cells are capable of synthesizing the processing secretory proteins, and of responding directly to cholinergic and peptidic secretogogues.