Biomedical subjects

N E Brownson

Publications and source records attributed to N E Brownson.

3 recordsLinked to original sources

PubMed1996

Adhesion of platelets to chemotactically responsive and non-responsive neutrophils.

Aims-To investigate the heterotypic adhesion of unactivated platelets to chemotactically responsive (migrated) and non-responsive (non-migrated) polymorphonuclear neutrophils (PMN).Methods-Platelets and PMN were isolated from autologous, normal blood. Migrated and non-migrated PMN were separated after N-formylmethionyl-leucylphenylalanine (FMLP) stimulation. Platelets were labelled with a fluorescent monoclonal antibody directed against CD41 (GPIIb-IIIa). Platelets (3 x 10(8)/ml) and PMN (3 x 10(6)/ml) were incubated together. Heterotypic cell adhesion was measured in isolated PMN and PMN co-incubated with platelets by flow cytometric analysis of platelet marker fluorescence in PMN gated events. Platelet-PMN adhesion was also visualised by fluorescence microscopy.Results-In studies of isolated PMN, contaminating platelets were bound to 16-34% of unstimulated PMN, 7-22% of stimulated PMN, 2-4% of migrated PMN, and 17-24% of non-migrated PMN. When platelets were co-incubated with migrated or non-migrated PMN, 15-78% of PMN bound one or two platelets.Conclusions-Unactivated platelets adhere to isolated PMN in vitro. Fewer unactivated platelets were adhered to migrated PMN than to non-migrated PMN in isolated PMN preparations. These results indicate that platelets adhering to PMN are removed during PMN migration.

Journal Article↗

PubMed1996

Amphotericin B induced abnormalities in human platelets.

Aims-To investigate in vitro the effect of amphotericin B on platelets in order to understand poor platelet recovery in patients receiving platelet transfusions and amphotericin B simultaneously.Methods-Washed platelets were isolated from platelet concentrates and exposed to amphotericin B (4 mug/ml) for one hour. Platelet function was assessed by aggregation response to thrombin (0-0.6 U/ml), serotonin release, response to hypotonic stress, and mean platelet volume. The expression of surface membrane glycoprotein (GP) Ib-IX complex, GPIIb-IIIa complex and CD62P (P-selectin) was examined by flow cytometry using fluorescence labelled monoclonal antibodies. Heterotypic cell adhesion was measured in amphotericin B treated platelets coincubated with isolated, autologous polymorphonuclear leucocytes (PMN) by flow cytometric analysis.Results-Amphotericin B induced platelet dysfunction. The rate of aggregation by thrombin, serotonin uptake and thrombin induced release of serotonin, and the response of platelets to hypotonic stress were inhibited. There was up to a two-fold increase in the mean platelet volume. The expression of platelet surface GPIb-IX and GPIIb-IIIa was not affected. P-selectin, normally expressed only on the surface of activated platelets, was also expressed on unactivated platelets. Amphotericin B increased platelet adherence to PMN and the number of platelets bound per PMN.Conclusions-In vitro, amphotericin B induces P-selectin expression on the surface of unactivated platelets and increases platelet adhesion to PMN, which is exacerbated by storage. Platelet dysfunction resulting from exposure to amphotericin B may contribute to poor platelet recovery in vivo when amphotericin B is administered concomitantly with platelet transfusion.

Journal Article↗

PubMed1994

Laminin peptides stimulate human neutrophil motility.

Laminin, isolated from Engelbreth-Holm-Swarm tumor, and 10 chemically synthesized peptides, corresponding to various regions of the laminin A and B1 chains, were compared for their abilities to stimulate human peripheral blood polymorphonuclear leukocyte (PMN) chemotaxis and chemokinesis through polycarbonate membrane filters in a 48-well microchemotaxis assay. Peptides F-9, F-11, F-12, and F-13 were derived from the B1 chain of laminin at the intersection of the cross, and six peptides were derived from the laminin A chain: peptide TG-1 from the amino-terminal top globule; peptides GD-1, GD-3, GD-6, and GD-7 from the carboxyl-terminal globular domain; and peptide AG-1 from above the carboxyl-terminal globular domain. Laminin and the peptides were evaluated over a concentration range of 1 to 200 micrograms/ml in motility assays. Six of the peptides, F-9, F-12, GD-1, GD-3, GD-6, and TG-1, stimulated human PMN migration in the absence of a gradient (chemokinesis). A fluorescein conjugate of the most active laminin peptide, GD-1, exhibited nonspecific, nonsaturable binding to PMN. Intact laminin and the other peptides failed to stimulate human PMN migration. In contrast, intact Engelbreth-Holm-Swarm laminin stimulated rabbit peripheral blood PMN chemokinesis. These results demonstrate that rabbit and human peripheral blood PMNs have divergent migratory responses to intact laminin. These findings suggest that intact basement membrane laminin does not directly stimulate human blood PMN motility in vivo, but that selected laminin peptide sequences, which may be generated during proteolytic digestion of laminin, can activate human PMN migration.

Amino Acid Sequence↗