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D Amrani

Publications and source records attributed to D Amrani.

4 recordsLinked to original sources
PubMed1989

Fibrinogen-mediated epidermal cell migration: structural correlates for fibrinogen function.

Previously we showed that epidermal cells are able to use fibrinogen (FGN) as a migration substratum during wound closure. The goal of the present study was to determine the structural features of FGN that allow this migration. Pieces of glass coated with native, fragmented, or other modified forms of FGN were implanted into full-thickness skin wounds of adult newts such that migrating epidermal cells would encounter the implant. In this system, a coating of FGN allowed considerably more migration than a coating of BSA. At high concentrations, heat-denatured FGN supported as much migration as the same amount of intact FGN. Fraction I-9, a circulating form of FGN missing a 20-30K (K = 10(3) Mr) carboxy-terminal segment of the A alpha chain, was no less effective than intact FGN. Comparison of the isolated D1 and E fragments of FGN showed migration only on D1, but never to the extent seen on intact FGN containing the same amount of D1. Plasmin digestion of D1 in the presence of EDTA, a process which produces D3, a fragment differing from D1 by the loss of the carboxy-terminal 109 amino acids of the gamma chain, caused a significant loss of activity in the D fragment. Migration was good on implants coated with relatively high concentrations of purified A alpha chains but gamma chains were inactive. Migration over intact FGN was almost totally blocked by 230 microM-Arg-Gly-Asp-Ser (RGDS), a peptide known to interact with integrin-type receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1983

Hormonal regulation of fibrinogen synthesis in cultured hepatocytes.

Most of what was originally known of the effects of hormones on fibrinogen synthesis was based, as noted above, on experiments involving surgical removal of endocrine glands. Some caution should be exercised when using such in vivo experiments to derive the hormonal requirements of fibrinogen synthesis, however, since multiple hormonal alterations often occur in these animals. The development of a variety of ex vivo systems has allowed investigators to more carefully control the hepatocellular environment. The work of several laboratories, including our own, has now made it clear that hormones and other agents directly stimulate hepatocellular synthesis of fibrinogen. From the studies summarized here, using chick embryo hepatocytes as a model, several generalizations emerge: Fibrinogen synthesis may be considered to be a "constitutive" liver function, since hepatocytes cultured without serum, hormones or other macromolecular supplements synthesize this protein at a basal rate for several days. Addition of certain hormones (e.g. T3, dexamethasone, insulin), individually and in physiological concentrations, elicits an increase in fibrinogen production, varying with each agent in onset, dose, minimum exposure required and accompanying effects on the synthesis of other plasma proteins. Glucocorticoids and thyroid hormones are similar in the selectivity of their stimulation (neither affects albumin or transferrin synthesis) but differ in that thyroid hormones need to be present for just a short "triggering" period. The stimulation of fibrinogen synthesis by insulin occurs only following prolonged exposure to concentrations 10-times higher than the very low doses to which albumin synthesis responds rapidly.

Adrenocorticotropic Hormone↗
PubMed1981

Receptors for cold-insoluble globulin (plasma fibronectin) on human monocytes.

This investigation focused on the role played by cold-insoluble globulin (CIg, plasma fibronectin) in monocyte function. Surface-bound CIg mediated a concentration-dependent of human blood monocytes to gelatin-coated surfaces. CIg also mediated the binding of gelatin-coated particles such as latex beads or tanned erythrocytes to surface-bound human monocytes. However, CIg did not mediate particle ingestion. Subfractionated CIg that was highly enriched in monomeric forms (zone II CIg, mol wt 190,000-235,000) was less effective than were fractions enriched in dimeric forms (zone I CIg, mol wt 450,000) in promoting monocyte attachment. Binding of CIg to a gelatin or plastic surface occurred in the absence of divalent cations, but monocyte attachment to CIg-coated surfaces required divalent cations, Mg++ being much more effective than Ca++. Cation-dependent cell attachment was reversible in that bound cells could be released by treatment with EDTA. Serum-mediated binding of monocytes to gelatin-coated plastic dishes was a result of its content of CIg because the binding activity was abolished by removal of CIg from serum, and could be restored by readdition of purified CIg. Treatment of monocytes with trypsin abolished subsequent cell attachment to CIg-gelatin surfaces or particles. Expression of certain other known monocyte membrane receptors (Fc and C3b) was markedly enhanced as a result of CIg-monocyte interaction. These several observations indicate that monocytes bear membrane receptors (termed receptor cold-insoluble globulin) for surface-bound CIg.

Cations, Divalent↗