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1.  Independent modulation of von Willebrand factor and fibrinogen binding to the platelet membrane glycoprotein IIb/IIIa complex as demonstrated by monoclonal antibody. 
Journal of Clinical Investigation  1985;76(5):1950-1958.
In this study we have used two new monoclonal antibodies, designated LJP5 and LJP9, as well as a previously described one, AP2, all specific for the platelet membrane glycoprotein (GP)IIb/IIIa complex. None of them reacted with dissociated GPIIb or GPIIIa. The monovalent Fab fragment of both LJP5 and LJP9 bound to unstimulated platelets in a saturable manner, but binding was markedly decreased after platelets had been incubated at 37 degrees C in the absence of added extracellular calcium. The binding of LJP9 was not affected by AP2, but was blocked by excess LJP5. On the contrary, the binding of LJP5 was blocked in the presence of both AP2 and LJP9. Thus, these antibodies bound to distinct epitopes of GPIIb/IIIa. At saturation, the binding to unstimulated platelets was between 2.41 and 10.9 X 10(4) molecules/platelet for LJP5 and between 3.47 and 9.1 X 10(4) molecules/platelet for LJP9 (range of 11 and 10 experiments, respectively). Binding increased up to 50% after thrombin stimulation. The estimated association constant, Ka, was 2.7 X 10(7) M-1 for LJP5 and 3.85 X 10(7) M-1 for LJP9. Both LJP5 and LJP9 partially inhibited the association of 45Ca2+ with the surface of unstimulated platelets. Moreover, both antibodies blocked the binding of von Willebrand factor (vWF) to stimulated platelets, whereas only LJP9, but not LJP5, blocked fibrinogen binding. LJP9 was also a potent inhibitor of platelet aggregation, whereas LJP5 was without effect in this regard. The results of the present study demonstrate that independent modulation of vWF and fibrinogen binding to stimulated platelets can be attained with monoclonal antibodies directed against distinct epitopes of GPIIb/IIIa.
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PMCID: PMC424250  PMID: 2414325
2.  Characterization of human platelet vasopressin receptors. 
Journal of Clinical Investigation  1985;76(5):1857-1864.
Using tritiated arginine-8-vasopressin [3H]AVP, vasopressin-specific binding sites were detected on human platelet membranes. One class of high-affinity binding sites was characterized with an equilibrium dissociation constant of 1.01 +/- 0.06 nM and a maximal binding capacity of 100 +/- 10 fmol/mg of protein (n = 12). Highly significant correlations were found between the relative agonistic (r = 0.87, P = 0.002) or antagonistic (r = 0.99, P = 0.007) vasopressor activities of a series of 13 AVP structural analogues and their relative abilities to inhibit [3H]AVP binding to platelet receptors whereas no such relationship existed when antidiuretic activities were considered (r = 0.28, P = 0.47). AVP did not stimulate cyclic AMP production of human platelets; on the contrary, high AVP concentrations (10(-6) M) inhibited cyclic AMP production measured in basal and prostaglandin E1-stimulated conditions. AVP caused intact platelet aggregation with a half-maximal aggregation (EC50) of 28 +/- 2 nM. This effect was more potently reversed by the specific vascular antagonist d(CH2)5Tyr(Me)AVP (pA2 = 8.10 +/- 0.23) than by the specific renal antagonist d(CH2)5IleuAlaAVP (pA2 = 6.67 +/- 0.12). The pA2 values of these two antagonists in platelets are in close agreement with the pKi values obtained in competition experiments (respectively 8.59 and 6.93) and with pA2 values reported in the literature for their in vivo antivasopressor activity (respectively 8.62 and 6.03). The observation that human platelets bear AVP receptors belonging to the vascular class suggests that platelet receptors can be used to further explore the role of vasopressin in cardiovascular homeostasis.
PMCID: PMC424226  PMID: 2997293
3.  Rhinophyma. 
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PMCID: PMC1289847  PMID: 3160857
4.  Human factor VIII procoagulant protein. Monoclonal antibodies define precursor-product relationships and functional epitopes. 
Journal of Clinical Investigation  1985;76(1):117-124.
The human Factor VIII procoagulant protein (VIII:C) purified from commercial Factor VIII concentrate consisted of a polypeptide doublet of 80,000 mol wt, a 92,000-mol wt polypeptide, and additional polypeptides of up to 188,000 mol wt. Thrombin digests contained a doublet of 72,000 mol wt, as well as 54,000- and 44,000-mol wt fragments. Proteolysis studies of purified VIII:C using thrombin and activated protein C have suggested that the 92,000- and 80,000 (or 72,000)-mol wt polypeptides comprise activated VIII:C. We have now used seven monoclonal antibodies raised against purified VIII:C to construct a preliminary epitope map of these VIII:C polypeptides. The specific VIII:C polypeptides with which the monoclonal antibodies reacted were determined by immunoblotting of VIII:C onto nitrocellulose sheets after reduced NaDodSO4-polyacrylamide gel electrophoresis. A minimum of five distinct epitopes were defined by these monoclonal anti-VIII:C antibodies. Identification of polypeptides bearing these epitopes allowed localization of distinct thrombin cleavage sites to the 92,000- and 80,000-mol wt chains, helped define polypeptide chain precursor-product relationships, and suggested that both the 92,000- and 80,000-mol wt polypeptides are necessary for VIII:C function. These data and their interpretation are consistent with the published description of the complete primary structure of VIII:C and its thrombin cleavage products. The 92,000- and 80,000-mol wt chains have been located at the amino- and carboxy-terminal ends of the molecule, respectively.
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PMCID: PMC423722  PMID: 2410456
5.  Airway responsiveness to histamine in man: effect of atropine on in vivo and in vitro comparison. 
Thorax  1985;40(4):261-267.
Airway responsiveness to histamine in man may be determined by the smooth muscle sensitivity to histamine or to the interaction between vagal nerve input and smooth muscle sensitivity. We have compared in vivo responsiveness to histamine with in vitro smooth muscle sensitivity to histamine in 20 non-asthmatic patients and one asthmatic patient undergoing thoracic surgery. Histamine responsiveness was assessed in the first 10 non-asthmatics without atropine pretreatment, in the second 10 after atropine pretreatment, and in the asthmatic patient both with and without atropine. In vivo responsiveness was also measured in 10 normal subjects and 10 asthmatic patients not undergoing surgery. Results were expressed as the provocation concentration (PC) causing a decrease in FEV1 of 20% (PC20FEV1) and in specific airways conductance of 35% (PC35SGaw), and in terms of maximal expiratory flow at 35% vital capacity, measured from the partial (V35(P] and complete (V35(C] flow volume curves of 35% (PC35V35(P); PC35V35(C]. In vitro smooth muscle sensitivity to histamine of bronchial tissue obtained at thoracotomy was expressed as the concentration causing a 50% maximum contraction (EC50) and as the maximum tension generated. There was considerable variation between patients in the in vivo responsiveness but a relatively narrow range for in vitro responses. There was no significant correlation between in vivo responsiveness, either with or without atropine pretreatment, and in vitro results. The asthmatic patient showed hyperresponsiveness in vivo but but not in vitro. These results suggest that in vitro airway smooth muscle sensitivity to histamine is not the sole determinant of in vivo airway responsiveness and that this lack of relationship is not explained by the influence of vagal nerve input on in vivo measurements. The results in the asthmatic patient suggest that airway hyperresponsiveness may be an in vivo phenomenon which is not related to a primary abnormality of airway smooth muscle.
PMCID: PMC460043  PMID: 4023976

Results 1-6 (6)