bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disulfide-linked and transglutaminase-catalyzed protein assemblies in platelets
Authors: Cohen I , Lim CT , Kahn DR , Glaser T , Gerrard JM , White JG 
Published: October 2019

Abstract
Energy depletion induces the formation of disulfide-linked and transglutaminase-catalyzed protein assemblies in platelets. The disulfide type polymers, formed following incubation at 37 degrees C in the absence of adenosine triphosphate (ATP)-generating precursors, are composed of cytoskeletal proteins and are associated with a decrease of reduced glutathione levels accompanying ATP depletion. The maintenance of ATP and reduced glutathione levels to, respectively, 34% and 47% of their original values is sufficient to prevent the formation of both polymer types. The transglutaminase-type cross-links are formed in the presence of calcium in either “energy-depleted” or thrombin stimulated platelets. 125I-surface-labeled membrane proteins, presumably transmembrane proteins, are incorporated into the transglutaminase- catalyzed cross-linked polymer of thrombin-stimulated platelets. Glycoproteins IIb and IIIa are not essential to the polymer formation, since thrombasthenic platelets treated with thrombin exhibit the same type of labeled polymer. The transglutaminase-catalyzed polymer formation following thrombin stimulation of platelets is inhibited by a calcium channel blocker, an intracellular calcium antagonist, as well as other inhibitors such as indomethacin, dibutyryl cyclic AMP, and prostaglandin E1. Although the evidence points to the formation of transglutaminase-catalyzed cross-linking in the cytoplasmic compartment, additional cross-linking of extruded components cannot be excluded.
Acceleration of fibrinolysis by the N-terminal peptide of alpha 2- plasmin inhibitor
Authors: Kimura S , Tamaki T , Aoki N 
Published: October 2019

Abstract
When blood plasma containing the NH2-terminal 12-residue peptide (N- peptide) of alpha 2-plasmin inhibitor (alpha 2PI; alpha 2-antiplasmin) was clotted in the presence of calcium ions, the N-peptide and alpha 2PI were cross-linked to fibrin by activated coagulation factor XIII. The amount of N-peptide cross-linked to fibrin was proportional to the concentration of N-peptide present in plasma. On the other hand, the amount of alpha 2PI cross-linked to fibrin was decreased by the presence of N-peptide, and the decrease was in reverse relationship to the increase of cross-linking of N-peptide. Spontaneous fibrinolysis or fibrinolysis induced by tissue plasminogen activator was accelerated by the presence of N-peptide, and the acceleration was dependent on the concentrations of N-peptide and directly proportional to inhibition of alpha 2PI cross-linking exerted by N-peptide. The acceleration was more pronounced when the clot was compacted by platelet-mediated clot retraction or by a squeeze. Fibrinolysis of an alpha 2PI-deficient or a factor XIII-deficient plasma clot was not accelerated by N-peptide. These findings were substantiated in a purified system and support the previous proposal that alpha 2PI is cross-linked to fibrin at the glutamine residue that is next to the NH2-terminus of alpha 2PI, and this factor XIII-mediated cross-linking of alpha 2PI is significant in inhibition of physiologically occurring endogenous fibrinolysis.
Platelet-derived growth factor promotes human peripheral monocyte activation
Authors: Tzeng DY , Deuel TF , Huang JS , Baehner RL 
Published: October 2019

Abstract
Like in the polymorphonuclear leukocyte (PMN), the platelet-derived growth factor (PDGF) purified to homogeneity is capable of inducing monocyte activation responses as evaluated by generation of superoxide anion (O-.2) from membrane-associated oxidase system, release of granule enzymes, and enhanced cell adherence and cell aggregation. Superoxide anion release was maximized at 10 ng/mL PDGF and was comparable to that induced by 10(-7) mol/L formyl-methionyl-leucyl- phenylalanine. The potency of PDGF to induce this response in monocytes was of the same magnitude as that observed in PMNs. Similarly, lysozyme release and monocyte adherence were also increased in a dose-dependent manner and achieved maximal responses at 40 ng/mL concentration of PDGF. The PDGF concentration required to achieve maximal monocyte aggregation was two-fold (60 ng/mL) of that found for PMNs. In contrast to PMNs, a positive correlation (gamma = .93; P less than .01) was observed between the increases of PDGF concentration and beta- glucuronidase release. These findings indicate that PDGF can induce the full sequence of cell activation events in human monocytes similar to human PMNs.
Near-normal circulatory survival of rabbit red cells exposed to high levels of Ca and ionophore in vitro
Authors: Bookchin RM , Roth EF Jr , Lew VL 
Published: October 2019

Abstract
The belief is widely held, on the basis of indirect evidence, that a substantial, even brief elevation of red cell Ca content must result in a marked shortening of circulatory survival. To test this notion directly, we exposed rabbit red cells in vitro to the ionophore A23187 and Ca so as to produce sustained uniform cell Ca levels of 40 to 360 mumol/L cells for one to 60 minutes, and compared the survival of the Ca-loaded cells in vivo with that of ionophore-treated controls, simultaneously, in the same rabbits. Despite marked reductions in cell adenosine triphosphate and dehydration of the Ca-exposed cells prior to reinfusion, the majority of cells, all of which had experienced these high cytoplasmic Ca levels, showed normal or near-normal survival in the circulation.
Fibronectin binding to thrombin-stimulated platelets: evidence for fibrin(ogen) independent and dependent pathways
Authors: Plow EF , Marguerie GA , Ginsberg MH 
Published: October 2019

Abstract
Plasma fibronectin binds in a specific and saturable manner to thrombin- stimulated platelets. gamma-Thrombin stimulated 80% as much fibronectin binding to platelets as alpha-thrombin with conversion of less than or equal to 1% of platelet fibrinogen to fibrin. Afibrinogenemic and normal platelets bound similar quantities of fibronectin in the presence of calcium or magnesium-ethylene glycol tetra-acetic acid (EGTA). These observations indicate that fibronectin can interact with platelets without involvement of fibrin or fibrinogen. Nevertheless, two different effects of fibrin(ogen) on fibronectin binding were observed. First, exogenous fibrinogen inhibited fibronectin binding to thrombin-stimulated platelets. This inhibition was unidirectional, as fibronectin did not inhibit fibrinogen binding to ADP or thrombin- stimulated cells. Second, formaldehyde-fixed cells with surface- associated fibrin bound significant quantities of fibronectin. This interaction required calcium and did not occur on fixed cells with or without surface-bound fibrinogen. A portion of the ligand bound to fixed cells with surface-associated fibrin was modified to form a derivative with a molecular weight identical to that of the fibronectin subunit cross-linked to the alpha-chain of fibrin. This high mol wt derivative was also observed to a variable extent with living cells in the presence of magnesium or calcium but not in the presence of magnesium-EGTA. Thus, fibronectin binds to platelets by at least two mechanisms: (1) a fibrin(ogen)-independent pathway that requires divalent ions and is inhibited by exogenous fibrinogen; and (2) a fibrin-dependent pathway with an absolute calcium requirement. With nonaggregated, thrombin-stimulated platelets, the former pathway appears to predominate.
Modulation of thrombin-mediated activation of factor VIII:C by calcium ions, phospholipid, and platelets
Authors: Hultin MB 
Published: October 2019

Abstract
The activation of factor VIII:C by thrombin appears to be an important prerequisite for the function of factor VIII:C as a cofactor in factor X activation in coagulation. The possible modulation of factor VIII:C activation by potential cofactors such as calcium ions, phospholipid, and platelets was studied systematically. Factor VIII:C activation could not be studied in the complete absence of Ca2+, since factor VIII:C activity decayed rapidly in calcium-free buffers, EDTA, or ethylene glycol tetra-acetic acid (EGTA), with only partial or no recovery of activity after readdition of Ca2+, Mn2+, or Mg2+. Added calcium chloride at 1.25, 2.5, 4, 10, 50, and 200 mmol/L produced progressive inhibition of factor VIII:C activation, with complete inhibition achieved by 50 mmol/L. Crude phospholipid preparations gave varying results, while purified phospholipids either had no effect or inhibited activation. This paper reports the new finding that fresh washed human platelets markedly potentiated factor VIII:C activation by a low concentration of thrombin (0.02 U/mL), even with prostaglandin E1 (PGE1) or dibutyryl cyclic AMP (cAMP) added to the washed platelets. However, the activity of platelets in factor VIII:C activation was inhibited by inclusion of PGE1 or dibutyryl cAMP during platelet washing, and ionophore A23187 increased this platelet activity; these data suggest that platelet stimulation is involved in the development of this activity. When platelets were maximally stimulated by thrombin (0.5 U/mL), the external calcium concentration increased 55 to 160 mumol/L, as measured with murexide, supporting the possible modulation of factor VIII:C activation by a transient increase in Ca2+ at the platelet surface.
The transport of 125I-labeled human high molecular weight urokinase across the intestinal tract in a dog model with stimulation of synthesis and/or release of plasminogen activators
Authors: Sasaki K , Moriyama S , Tanaka Y , Sumi H , Toki N , Robbins KC 
Published: October 2019

Abstract
In an attempt to elucidate the mechanism of fibrinolytic enhancement by orally administered urokinase, studies on the intestinal transport of urokinase were carried out, using 125I-labeled human high mol wt urokinase, administered intraduodenally in the experimental dog model with a saphenous vein thrombus. Using the plasma sample obtained from blood 45 minutes after intraduodenal administration of the urokinase, protein fractions were isolated by a sequential two-step affinity chromatography method, first with [N alpha-(epsilon-aminocaproyl)-DL- homoarginine hexylester]-Sepharose followed by a specific anti-human low mol wt urokinase rabbit IgG-Sepharose (adsorbed-eluted and unadsorbed). Each of the isolated protein fractions was further purified by gel filtration on Sephacryl S-300. The proteins isolated by the two-step affinity chromatography method were transported human urokinase with radioactivity in the adsorbed-eluted fraction, and newly synthesized and/or released dog plasminogen activators, probably urokinase-type and tissue-activator type, without radioactivity. In an antibody quenching assay, dog urokinase and the immuno-affinity unadsorbed fraction were not neutralized, but the immuno-affinity adsorbed-eluted fraction was completely neutralized by the specific anti-urokinase IgG antibody. Proteins isolated from control plasma (after administration of saline) by the two-step affinity chromatography method in the unadsorbed fraction had negligible amounts of activator activity. In these studies, we were able to show that synthesis of plasminogen activators was stimulated, with the activators being released, from either the liver or the vascular endothelium. Also we showed that urokinase is transported across the intestinal tract in the dog model.
Liquid preservation of human neutrophils stored in synthetic media at 22 degrees C: controlled observations on storage variables
Authors: Glasser L , Fiederlein RL , Huestis DW 
Published: October 2019

Abstract
The purpose of this study was to use a chemically defined medium to identify essential substances and optimal conditions for the liquid storage of neutrophils at 22 degrees C. Several commercially available synthetic media were evaluated: L-15, McCoy's 5a, M199, minimum essential medium, Dulbecco's MEM, NCTC135, and RPMI 1640. Proteins, glucose, pH, and neutrophil concentration were systematically studied. Neutrophils were harvested by centrifugal cell separators or phlebotomy, and their maintenance was evaluated by monitoring cell counts, dye exclusion, phagocytosis, bacterial killing, and chemotaxis. Neutrophils stored equally well in all synthetic media except L-15; however, chemotaxis was poorly maintained in synthetic media as compared with autologous plasma. RPMI 1640 was arbitrarily selected as a basal medium to evaluate storage variables. RPMI 1640 supplemented with albumin to a concentration of 1% improved chemotaxis and was equivalent to plasma as a storage medium with regard to the in vitro functions tested. Cohn fractions IV-1, IV-4, and gamma globulin were not effective substitutes for albumin. Glucose is essential for neutrophil storage; its absence from the medium correlated with poor cell function. Optimal glucose requirements depend on the cell concentration. High glucose concentrations were toxic to neutrophils; at 1,000 mg/dL, chemotaxis was depressed by 58%. Glucose utilization was dependent on the initial pH of the medium and on the cell concentration. A wide range of hydrogen ion concentrations was tolerated, and the optimum pH range was 7.2 to 7.8. Cell concentration is an important variable because it affects the pH of the medium as well as glucose utilization.
Type IIB Tampa: a variant of von Willebrand disease with chronic thrombocytopenia, circulating platelet aggregates, and spontaneous platelet aggregation
Authors: Saba HI , Saba SR , Dent J , Ruggeri ZM , Zimmerman TS 
Published: October 2019

Abstract
Type IIB von Willebrand disease is characterized by enhanced ristocetin- induced platelet aggregation and absence of large von Willebrand factor multimers from plasma. An alteration of the von Willebrand factor molecule resulting in increased reactivity with platelets appears to be the basis for these abnormalities. We have now identified a new variant of type IIB von Willebrand disease in a family in which the four affected members also have chronic thrombocytopenia, in vivo platelet aggregate formation, and spontaneous platelet aggregation in vitro. In spite of repeatedly prolonged bleeding times and persistent thrombocytopenia, their bleeding diathesis is only moderate.
The effect of hydroxyurea on hemoglobin F in patients with myeloproliferative syndromes
Authors: Alter BP , Gilbert HS 
Published: October 2019

Abstract
Fetal hemoglobin (Hb F) may increase in patients receiving chemotherapeutic drugs, a result of potential use in patients with symptomatic hemoglobinopathies. We examined Hb F in 13 patients with myeloproliferative disease (six polycythemia vera, five polycythemia vera with myeloid metaplasia, one agnogenic myeloid metaplasia, and one chronic myelogenous leukemia) who were treated with hydroxyurea. Four patients showed an increase in Hb F from less than 1% to between 5% and greater than 8% while on hydroxyurea, and a decline to less than 1% when the drug was discontinued. This group of “responders” received a higher average daily dose of hydroxyurea, which was administered continuously rather than intermittently, when compared to the “nonresponders.” Mean corpuscular volumes (MCVs) rose in most patients, and i antigen remained elevated or decreased; neither parameter correlated with Hb F levels. Both responders and nonresponders had therapeutically desirable suppression of WBCs and platelets, and almost all had no depression of reticulocytes or Hb.
Treatment of baboon with vinblastine: insights into the mechanisms of pharmacologic stimulation of Hb F in the adult
Authors: Veith R , Papayannopoulou T , Kurachi S , Stamatoyannopoulos G 
Published: October 2019

Abstract
Vinblastine was administered to anemic baboons to test whether stimulation of Hb F takes place following distortion of erythropoiesis by an M-stage-specific compound. The treatments elicited erythroid cell cytoreduction followed by regeneration. During the phase of reticulocyte reduction, gamma/gamma + beta biosynthetic ratios increased without increment in F reticulocytes, suggesting that there was increased production of Hb F per F cell. The phase of reticulocyte regeneration was associated with sharp increments in relative (percentage) and absolute F reticulocytes. These data suggest that perturbations of erythropoiesis underlie the stimulation of Hb F synthesis by vinblastine. Accelerated or abnormal precursor maturation may account for the release of shift F reticulocytes with higher Hb F content, during the reduction phase. Accelerated total erythroid differentiation/maturation may account for the increment in F reticulocyte numbers during the phase of regeneneration.
Surface phenotypes of human hemopoietic progenitor cells defined by monoclonal antibodies
Authors: Ferrero D , Gabbianelli M , Peschle C , Lange B , Rovera G 
Published: October 2019

Abstract
A panel of ten monoclonal antibodies which react with antigens present on the surface of myeloid leukemic cells was used to investigate the distribution of these antigens on normal hemopoietic stem cells and progenitor cells at various stages of maturity. A population of immature cells, possibly stem cells, that are capable of regenerating CFU-GM in long-term marrow cultures reacts with four antibodies recognizing antigens abundantly expressed in leukemic cells, but does not react with antibodies against Ia-like molecules or against carbohydrate determinants specific for myeloid cells. Progenitor cells that form mixed colonies in semisolid medium (CFU-GEMM), early erythroid (BFU-E) and early myelomonocytic (type 1 CFU-GM) progenitors retain the antigens present on the hypothetical stem cell population and begin to express Ia-like antigens. As they differentiate, myeloid and erythroid progenitors undergo a series of quantitative and qualitative shifts in surface phenotype. They begin to express stage- related, lineage-specific antigens and cease expressing antigens common to early cells of different lineages. The identification of antigens present on very immature normal progenitor cells should be valuable in future studies aimed at the detailed characterization of this relatively little-known hemopoietic cell population.
SFL 23.6: a monoclonal antibody reactive with CFU-E, erythroblasts, and erythrocytes
Authors: Gupta AD , Samoszuk MK , Papayannopoulou T , Stamatoyannopoulos G 
Published: October 2019

Abstract
A cytotoxic (IgG2b) monoclonal antibody (McAb) for a novel erythroid differentiation antigen was generated by hyperimmunizing young mice with mononuclear cells obtained from livers of 20- to 22-week-old fetuses. This McAb, designated SFL 23.6, shows an extremely well- defined reactivity with the cells of the erythroid lineage at all stages of maturation as evident from the labeling of morphologically identifiable erythroid precursors and of erythrocytes present in peripheral blood, bone marrow, and fetal liver, and from its reactivity with culture-derived erythroblasts. The nonerythroid cells present in these and other tissue preparations were not labeled by SFL 23.6. The erythroid lineage specificity of McAb SFL 23.6 was confirmed by a cell- sorting experiment in which 97% of the cells in the fluorescent fraction sorted from SFL 23.6-treated bone marrow cells were erythroid precursors at various stages of maturation. Complement-mediated cytotoxicity and progenitor cell-sorting experiments showed that most (greater than 90%) of the late erythroid progenitors (CFU-E) and only a small proportion of the early erythroid progenitors (BFU-E) express the antigenic determinant identified by SFL 23.6. The myeloid progenitors (CFU-GM) and multilineage progenitors (CFU-GEMM) were negative for the SFL 23.6 antigenic determinant. The antigen recognized by SFL 23.6 has not been determined as yet. Because of the pattern of its reactivity and its dependence on sialic acid residues, the possibility of its relationship to glycophoria A was entertained. However, previous work using antiglycophorin McAbs (R-10) has shown that this determinant is not expressed in CFU-E. Therefore, among the erythroid lineage-specific McAbs described thus far, SFL 23.6 is unique in its reactivity with CFU- E and the mature erythron. Reagents with such specificity may be useful in studies of erythroid differentiation and commitment.
Comparison of inhibitory and binding characteristics of an antibody causing acquired von Willebrand syndrome: an assay for von Willebrand factor binding by antibody
Authors: Fricke WA , Brinkhous KM , Garris JB , Roberts HR 
Published: October 2019

Abstract
An acquired inhibitor of von Willebrand factor (vWF) activity occurring in a patient with benign gammopathy and von Willebrand syndrome (vWS) has been partially characterized. The inhibitor-induced syndrome resulted in low to undetectable plasma levels of vWF/ristocetin, vWF/botrocetin, FVIIIR:Ag, and FVIII:C with a normal to slightly prolonged bleeding time. Platelet vWF was normal. Intensive and continuous infusion of a heat-treated factor VIII concentrate (Hemofil- T, Hyland, Glendale, Calif) elevated the FVIII:C plasma levels to about 100%, with an increase in FVIIIR:Ag levels to about 340% and vWF/ristocetin levels to about 40%, much lower than expected based on the dose of Hemofil-T and its content of vWF and FVIII:C activities. The inhibitor bound to staphylococcal protein A (SpA) with high affinity, indicating an IgG antibody (Ab). An assay for the vWF-binding capacity was developed on the basis of absorption of the Ab from serially diluted plasma by SpA and removal of vWF and FVIII:C activities from normal plasma by the SpA-Ab complex. The Ab-binding site was on the vWF component of the factor VIII complex. The Ab was unable to bind isolated FVIII:C. The combined use of the new vWF- binding assay and a battery of tests for inhibition of vWF-dependent platelet aggregation with ristocetin (which detects high molecular weight vWF), with botrocetin (which detects high and low molecular weight vWF), and with platelet-aggregating factor (which detects high molecular weight vWF) provided a means of analysis of Ab effect on in vitro vWF function. Using these tests, a comparison was made of the effects of the vWS Ab with those of an Ab inhibitor occurring in homozygous von Willebrand's disease. The Ab of the vWS patient had weak inhibitory action on vWF/ristocetin without having an effect on vWF/botrocetin and platelet-aggregating factor, a high titer vWF- binding capacity, and no anamnestic response following concentrate therapy. These findings contrasted with those of the Ab occurring in inhibitor von Willebrand's disease in which vWF inhibitor and binding values were similar, with a strong anamnestic response. The findings indicate that the vWS Ab binds to an epitope on the molecular vWF in such a way that causes only limited inhibition of vWF/ristocetin function and no inhibition of vWF/botrocetin function, suggesting that these two functional domains are at separate sites.