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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet alpha-granules contain a factor that stimulates the proliferation of arterial smooth muscle cells and may play a role in atherogenesis. We have studied the role of arachidonic acid in mediating the release of the platelet-derived growth factor (PDGF) from human platelets. PDGF was assayed by stimulating of [(3)H]thymidine incorporation into DNA of mouse 3T3 cells. Platelet aggregation and the release of platelet factor 4,beta-thromboglobulin, and serotonin were also studied. A biphasic response pattern was observed when gel-filtered platelets were incubated with arachidonate over the concentration range 0.01-0.4 mM. At low arachidonate levels (approximately 0.025-0.1 mM), specific concentration-dependent aggregation and release of PDGF and of the other components were observed. This effect was not seen with any of five other fatty acids tested and was suppressed by indomethacin (25 muM). At higher arachidonate concentrations (approximately 0.15-0.35 mM), a concentration-dependent turn-off of both aggregation and release occurred. At these concentrations the platelets remained functional, and no release of lactate dehydrogenase was observed. A similar biphasic pattern of arachidonate-induced aggregation and release was observed with platelet-rich plasma, over a similar range of arachidonate to albumin mole ratios. These studies demonstrate that PDGF and other alpha-granule constituents can be released from platelets specifically by arachidonate via an indomethacin-sensitive pathway, most probably involving the platelet cyclooxygenase and conversion of arachidonate to prostaglandin metabolities. The mechanisms responsible for the turn-off of the specific arachidonate-mediated responses at higher arachidonate concentrations remain to be defined.
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PMID:Release of platelet-derived growth factor from human platelets by arachidonic acid. 29 Oct 68

Some early changes associated with atypical nevi, presumed to be progressing toward malignancy, include chromosomal abnormalities and altered production of growth factors, and/or growth factor receptors. Though normal epidermal melanocytes require a number of exogenous growth factors, nevi require fewer growth factors, and most metastatic melanomas are frequently capable of growing without an exogenous supply of growth factors. This is apparently caused by endogenous production of essential growth factors. Our laboratory focuses on melanoma growth stimulatory activity (MGSA), one of the endogenously produced growth factors, and the role it plays in tumor progression. MGSA is a member of the beta-thromboglobulin super family. These genes code for cytokines, which modulate the inflammatory response. The MGSA protein is highly chemotactic for neutrophils and competes with 125I-interleukin-8 for binding sites on neutrophil receptors. When normal immortalized mouse melanocytes are manipulated so that they overexpress the MGSA gene, the melanocytes form large colonies in soft agar and melanoma tumors in nude mice. These data suggest that the MGSA protein can potentially play a role in melanoma tumor progression.
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PMID:The pathogenic role of growth factors in melanoma. 193 74

Mathematical model of the beta-thromboglobulin (BTG) release from alpha-granules stimulated with ADP is compared with experimental data. Secretion of BTG was analysed using platelets washed by different procedures in the presence or absence of inhibitors of platelet activation. The release of BTG was monitored in response to 5-100 microM ADP. The rate constant of the release of BTG (K = 1.83 X 10(3) M-1 min-1) and efficient amount of ADP molecules secreted by a single platelet (W = 5.2 X 10(-18) mole) were estimated. The model precisely describes the release of BTG associated with the isolation of platelets (blood collection, washing procedure) and allows to estimate the extent of activation of blood platelets in the suspension.
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PMID:Kinetics of the beta-thromboglobulin release from alpha-granules of blood platelets activated by ADP. 295 17

Evidence is presented for in vitro high affinity binding of serotonin (5-HT) by beta-thromboglobulin (beta TG) and platelet factor 4 (PF4) from human blood. Results include: 1) identification by radioimmunoassay of PF4 in specifically bound material obtained by 5-HT affinity chromatography of human platelet extracts; 2) binding of 72% and 6% of radiolabelled PF4 on 5-HT and control affinity columns, respectively; and 3) binding of approximately 8 moles of 5-HT per mole of purified beta TG in the presence of ferrous ion and heparin in ultrafiltration studies, with Scatchard analysis indicating a dissociation constant of about 4 X 10(-8) M.
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PMID:Evidence for serotonin binding in vitro by platelet factor 4 and beta-thromboglobulin. 618 40