The Golgi Apparatus

Clones of nontransformed hormone-responsive bone cells have been isolated in vitro from mixed cell populations of fetal rat calvaria. In several independent isolations, microscopically visible colonies appeared at plating efficiencies of 5-10% of the starting cell numbers. Of these clones, approximately 10% grew to mass populations which could be assayed for a number of growth and biochemical properties. Although some similarities existed among the clones, they could be distinguished from each other and from the mixed cell populations. Population-doubling times (tDs) and saturation densities varied over a wide range: e.g., tDs of 24-72 h and saturation densities of 0.4-5 x 10(5) cells/cm2. Morphologies varied from roughly polygonal multilayering cells to typically spindle-shaped monolayering cells. Hormone responsiveness, as measured by stimulation of cAMP by hormones, indicated that some clones were responsive to both parathyroid hormone (PTH) and prostaglandin E2 (PGE2), while others responded to PTH only. Analysis of extracellular matrix components revealed that all clones produced type I and type III collagens, though in different proportions. Similarly, although all clones synthesized four glycosaminoglycans (hyaluronic acid, heparan sulfate, chondroitin sulfate, and dermatan sulfate), the quantities of each were distinctive from clone to clone. Further investigation of such clones is continuing to define more precisely the heterogeneity of clonal bone cell populations in vitro. They represent an important step in the study of the endocrinology and differentiation of bone.

/pdf/isolation-of-bone-cell-clones-with-differences-in-growth-4srgp0pv3v.pdf

Isolation of bone cell clones with differences in growth, hormone responses, and extracellular matrix production.

At 19â€”20 h of age, the Ciona intestinalis ascidian tadpole has six developed organ systems (tunic, epidermis, notochord, tail musculature, adhesive organ, and nervous system) and approximately four organ system rudiments (including: pn mordial pharynx, atrial primordia, gut primordium, and mesodermal pockets). Con temporarylight and electron microscopic descriptions of the anatomy and the his tology of these tissues support the old contention, originated by Kowalevsky in 1866, that the body plans of tunicate tadpole and of vertebrate larvae are homologues.

Comparative anatomy of the tunicate tadpole, ciona intestinalis

Characterization of a chondroitin 4 -sulfate proteoglycan carrier for heparin neutralizing activity (platelet factor 4 ) released from human blood platelets.

1. The effects of acid mucopolysaccharides and acid mucopolysaccharide-proteins on the size and rate of formation of fibril aggregates from collagen solutions in pH7.6 buffers were studied by turbidimetric and light-scattering methods. 2. Serum albumin, orosomucoid, methylated cellulose, chondroitin sulphate A and chondroitin sulphate C of molecular weight less than 20000, and hyaluronate of molecular weight less than 40000 did not influence rates of fibril formation. Chondroitin sulphate A, chondroitin sulphate C and hyaluronate of high molecular weight retarded the rate of fibril formation. This effect of high-molecular-weight chondroitin sulphate C decreased with increasing ionic strength. Heparin, though of low molecular weight (13000), was highly effective, as was also heparitin sulphate. The chondroitin sulphate-proteins of very high molecular weight were highly effective, despite the fact that for some preparations the component chondroitin sulphate chains had molecular weights much less than 20000. 3. Agents that had delayed fibril formation were also effective in producing an increase in degree of aggregation of fibrillar collagen, as indicated by dissymmetry changes observed in light-scattering experiments at low collagen concentrations. Methylated cellulose and heparin at 2.5mug./ml. were unusual in decreasing aggregation, but heparin at 0.25mug./ml. increased aggregation. Electron microscopy of gels showed fibrils and fibril aggregates with ;normal' collagen spacing and dimensions consistent with the light-scattering results. 4. The rates of electrical transport of agents and of solvent (electro-osmosis) through collagen gels indicated a contribution of molecular entanglement that increased with increase in molecular size of the agents. Electrostatic binding of heparin to collagen was noted. Binding to collagen during fibril formation was also found for heparitin sulphate and a chondroitin sulphate with extra sulphate groups. 5. Electrostatic binding of acid mucopolysaccharide-proteins to collagen may be an important factor in the organization and functioning of connective tissues at all stages of growth and development. Excluded-volume (molecular-entanglement) effects may also be important. These factors operate simultaneously and interact mutually so that precise assessment of their relative importance is difficult.

The effect of acid mucopolysaccharides and acid mucopolysaccharide–proteins on fibril formation from collagen solutions

Introduction . . . . . (I) General considerations . (2) Methodology . . . The tissues . . . . . Collagen . . . . . (I) Characterization . . . (2) Comparative biochemistry of collagen . . . . Glycoproteins . . . . Elastin . . . . . Acid mucopolysaccharide-proteins . ( I ) Characterization . . . (2) The linkage region . . (3) Amino acid composition . (4) Macromolecular structure and taxonomy . . . . (5) Immunology . . . Acid mucopolysaccharides of cartilage andnotochord . . . ( I ) Biological significance of cartilage and bone . . . (2) Notochord . . . . (3) Invertebrates . . . (4) Vertebrates . . . .

M. B. Mathews

Papers

Macromolecular evolution of connective tissue