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N Sorgente

Publications and source records attributed to N Sorgente.

71 records · Page 4Linked to original sources
PubMed1977

Proteolysis associated with normal, carcinogen-treated, and transformed rat liver epithelial cells.

A method was developed to distinguish between cell surface-associated and released proteolytic activity. The approach utilizes 125I-labeled protein substrate covalently linked to modified latex beads. These beads are either rolled over the surface of cells grown in culture or next to the cells. Using this method we have studied normal, carcinogen-treated and spontaneously transformed rat liver epithelial cells. Transformed cells always released greater amounts of radioactivity than carcinogen-treated or normal hepatocytes when the beads were presented next to the cells, indicating an enhanced release of proteolytic enzymes. When the substrate was in contact with the viable cell surfaces both the carcinogen-treated and transformed cells released more radioactivity from the beads' surface than the tissue culture-adapted normal cells. This enhanced proteolytic cleavage indicated that there is an altered surface topology or an increased surface-associated enzyme activity on both the carcinogen-treated and transformed cells.

4-Nitroquinoline-1-oxide↗
PubMed1976

Cell surface-associated and released proteolytic activities of bovine aorta endothelial cells.

We have demonstrated cell surface-associated and released proteolytic activity on bovine aorta endothelial cells, representing normal cells with regulated invasive properties. To demonstrate these proteolytic activities on viable cells grown in monolayer cultures, a new method was developed. The method consists of rolling modified plastic beads carrying covalently-linked [125I]-labeled casein in contact with the cell surfaces or adjacent to the cell monolayers without actual contact. The rate of radioactive peptide release is proportional to the proteolytic activity. Released proteases are detected when no contact occurs between the substrate and the cells. When the bead-substrate complex is rolled over the surface of endothelial cells, a significant increase in released labeled peptides is observed which represents a cell surface-associated proteolytic activity. These activities may be relevant to the endothelial cell's invasive capacity and appear to be similar to the neutral proteolytic activity of transformed cells.

Animals↗
PubMed1975

The resistance of certain tissues to invasion. II. Evidence for extractable factors in cartilage which inhibit invasion by vascularized mesenchyme.

If hyaline cartilage is explanted to the chick chorioallantoic membrane, it resists invasion by vascularized mesenchyme of the host. This resistance is diminished if the tissue is extracted with relatively low concentrations (1.0 M) of guanidine HCl. The extracts contain antiproteolytic activity. This molarity of guanidine HCl extracts only small amounts of the major structural components of cartilage extracellular matrix. It, therefore, seems reasonable to suggest that hyaline cartilage is both avascular and resistant to invasion because it contains extractable inhibitors of invasion, perhaps in the form of proteinase inhibitors.

Allantois↗
PubMed1975

The resistance of certain tissues to invasion. III. Cartilage extracts inhibit the growth of fibroblasts and endothelial cells in culture.

Extracts of bovine dermis and cartilage inhibit the growth of bovine endothelial cells more than that of most of the fibroblast types tested. Extracts of cartilage, a tissue rather resistant to invasion, inhibit the growth of endothelial cells more than extracts of dermis do. Since such extracts contain antiproteolytic activity, it is suggested that the inhibition of cell growth they induce is effected by protease inhibitors native to connective tissues.

Animals↗
PubMed1975

Lysozyme in calcifying tissues.

Lysozyme, present in several connective tissues, is synthesized in cartilage by chondrocytes and immediately secreted into the extracellular matrix, where it is bound in the territorial (lacunar) matrix and along collagen fibers. In the epiphyseal growth plate, lysozyme levels increase toward the cartilage-bone junction, but cartilage lysozyme seems to be bound or inactivated by an inhibitor. Parathyroid extract injections decrease bone lysozyme levels. Cartilage lysozyme levels are low in rickets, while vitamin D increases it in both cartilage and aorta, suggesting an association between lysozyme and the calcification process. Although it is cationic and forms salt-like complexes with cartilage proteoglycans and chondroitin sulfate in vitro, lysozyme does not seem to be bound to proteoglycans in the native tissue. Proteoglycans in cartilage exist in a monomeric and aggregated form. Aggregation occurs by an interaction of monomers with hyaluronic acid and spedific link proteins. Aggregated proteoglycans inhibit mineral accretion in vitro. Mammalian cartilage lysozyme but not hen egg white lysozyme seems to inactivate this inhibitory capacity of aggregated proteoglycans, which is probably due to an interaction with hyaluronic acid resulting in a disaggregation. Therefore, we hypothesize that cartilage lysozyme plays an important role in the regulation and initiation of cartilage calcification.

Bacteriolysis↗
PubMed1973

The resistance of certain tissues to invasion: penetrability of explanted tissues by vascularized mesenchyme.

If puppy tissues are explanted onto the chick chorioallantoic membrane, those tissues which normally have a blood supply are rapidly invaded by vascularized mesenchyme of host origin. Hyaline cartilage, a tissue virtually devoid of blood vessels, is impenetrable by proliferating mesenchyme of the host, while calcified cartilage, which normally is vascularized, is penetrable. The stroma of the cornea, another normally avascular tissue, is readily penetrable, but Descemet's membrane forms a barrier to invasion by host tissues. The experimental system used permits the design of experiments in which the study of factors responsible for the resistance of tissues such as cartilage to invasion can be undertaken.

Animals↗
PubMed1973

Collagen-proteoglycan relationships in epiphyseal cartilage.

Columnar and hypertrophic zones of calf scapular cartilage were studied before and after extraction with 3 M guanidinium chloride (GuCl) and digestion with enzymes which degrade various components of the extracellular matrix. Morphologic and chemical analysis suggests that there are at least two anatomic pools of proteoglycan in this tissue. One, which resides between collagen fibrils, is extractable with GuCl. Another appears attached to collagen by strong bonds and is apparently not extractable with GuCl. This type of collagen-proteoglycan relationship is possibly restricted to epiphyseal cartilage. The morphology of the lacuna is different in the columnar and hypertrophic zones. Proteoglycans in the distal hypertrophic zone are less resistant to GuCl extraction.

Animals↗
PubMed1971

Organization of extracellular matrix in epiphyseal growth plate.

Three cations of varying size and charge density, egg-white lysozyme, protamine and ruthenium red, were used to stain the extracellular matrix of epiphyseal cartilage growth plate. With these stains, it was possible to distinguish three types of proteoglycans or materials associated with them, which may well have as their major differences the type of cross linking to the tissue. One type was stained by ruthenium red and protamine but not by lysozyme, was extractable with 3 M guanidinium chloride and was relatively uniformly dispersed throughout the matrix of the growth plate. The other two types were stained by all three cations, were not extractable with 3 M guanidinium chloride and were intimately associated with fibrils. One of these was found on the collagen fibrils, was relatively scanty in the resting zone near the articular surface, relatively restricted to the extralacunar area in the columnar zones and appeared to diminish in amount in the hypertrophic zone. This material often had a 640-A periodic array on the surface of collagen fibrils. The third type also was stained by all three cations and was not extractable with 3 M guanidinium chloride. It was distinguished from the other class of lysozyme-reactive matrix components by the larger volume of distribution occupied by the stained material. It also had a different distribution in that it was widely dispersed in the resting zone, was restricted to the lacuna in the columnar zone and was absent in the hypertrophic zone. Thus, cartilage matrix as well as the chondrocytes undergo differentiation in the epiphyseal growth plate.

Animals↗
PubMedDate not supplied

The ground substance of the arterial wall. Part 1. Extractability of glycosaminoglycans and the isolation of a proteoglycan from bovine aorta.

Water and glycosaminoglycan contents were measured in upper and lower thoracic aortas of claves and steers. The ability of various molarities of guanidine hydrochloride to extract glycosaminoglycans from these tissues was assessed. Some glycosaminoglycans seem to be more resistant to extraction than others. A procedure is described for the isolation of a proteoglycan. The molecule appears to contain both dermatan sulfate and chondroitin sulfate. It also seems to be less dense than cartilage proteoglycans extracted by similar methods as assessed by its behavior in centrifugal fields. The properties, locus and biological activities of this molecule are currently being studied.

Age Factors↗
PubMedDate not supplied

Antiproliferative drugs in the treatment of experimental proliferative vitreoretinopathy.

We used an experimental model of proliferative vitreoretinopathy (PVR) and cell-induced traction retinal detachment to study the therapeutic value of six cytotoxic drugs (actinomycin C, colchicine, cytosine arabinoside hydrochloride, 5-fluorodeoxyuridine, vinblastine sulfate, and daunomycin). Pigmented rabbits were injected with 2.5 X 10(5) cultured homologous dermal fibroblasts. At the same time, cytotoxic drugs were injected into the vitreous in an attempt to inhibit cellular proliferation. The sensitivity of the cells to the drug was also tested in vitro before injection. Daunomycin at a dose of 10 nmol per eye stopped cellular proliferation and subsequent traction retinal detachment in vivo. The electroretinogram (ERG) showed no evidence of drug-induced retinal toxicity with this dose of daunomycin. No alteration in frequency or severity of vitreal membranes and retinal detachment was observed after injection of equivalent doses of the other drugs.

Animals↗