Biomedical subjects

D S Beardsley

Publications and source records attributed to D S Beardsley.

24 records · Page 2Linked to original sources

PubMed1984

An analogue of the erythroid membrane skeletal protein 4.1 in nonerythroid cells.

Protein 4.1 is a crucial component of the erythrocyte membrane skeleton. Responsible for the amplification of the spectrin-actin interaction, its presence is required for the maintenance of erythrocyte integrity. We have demonstrated a 4.1-like protein in nonerythroid cells. An antibody was raised to erythrocyte protein 4.1 purified by KCl extraction (Tyler, J. M., W. R. Hargreaves, and D. Branton, 1979, Proc. Natl. Acad. Sci. USA, 76:5192-5196), and used to identify a serologically cross-reactive protein in polymorphonuclear leukocytes, platelets, and lymphoid cells. The cross-reactive protein(s) were localized to various regions of the cells by immunofluorescence microscopy. Quantitative adsorption studies indicated that at least 30-60% of the anti-4.1 antibodies reacted with this protein, demonstrating significant homology between the erythroid and nonerythroid species. A homologous peptide doublet was observed on immunopeptide maps, although there was not complete identity between the two proteins. When compared with erythrocyte protein 4.1, the nonerythroid protein(s) displayed a lower molecular weight--68,000 as compared with 78,000-and did not bind spectrin or the nonerythroid actin-binding protein filamin. There was no detectable cross-reactivity between human acumentin or human tropomyosin-binding protein, which are similarly sized actin-associated proteins, and erythrocyte protein 4.1. The possible origin and significance of 4.1-related protein(s) in nonerythroid cells are discussed.

Antigen-Antibody Complex↗

PubMed1984

Platelet membrane glycoprotein IIIa contains target antigens that bind anti-platelet antibodies in immune thrombocytopenias.

The precise pathogenic mechanism of platelet destruction in immune thrombocytopenias is not known, although many investigators have found that platelet-associated IgG is increased in these diseases. We report here the differentiation between specific binding of anti-platelet antibody, associated with platelet destruction, and the ubiquitous presence of nonspecific, platelet-associated IgG. Using an electrophoretic separation and antibody overlay technique, we have identified a specific membrane protein that bears target platelet antigens in immune thrombocytopenias. When posttransfusion purpura serum was studied, antibody binding to the PlA1 antigen on glycoprotein IIIa was readily distinguished from the nonspecific binding of immunoglobulin to a protein of 200,000 mol wt. After reduction of disulfide bonds, the PlA1 antigenicity was not observed, and IgG bound nonspecifically to a protein band with an apparent molecular weight of 45,000. We have also identified anti-platelet antibodies in patients with idiopathic thrombocytopenic purpura and determined their antigenic specificity. Antibodies which bind to a 100,000-mol wt protein were found in nine of thirteen patients with chronic disease. The antigens in three of these cases were studied in detail by using both reduced and nonreduced control and Glanzmann's thrombasthenic platelets. Target antigens were localized to glycoprotein IIIa, but are different from PlA1. The immune thrombocytopenic purpura antigenic system is clearly distinguished from nonspecific platelet-associated IgG. Sera from eight children with acute idiopathic thrombocytopenic purpura were also studied. In all cases, the nonspecific IgG binding to the 200,000-mol wt protein was observed. However, we were unable to demonstrate antibody binding to glycoprotein IIIa, which suggested that the acute childhood form of this disease may have a different pathogenic mechanism than that of the autoimmune chronic cases.

Adolescent↗

PubMedDate not supplied

Storage of platelet concentrates after high-dose ultraviolet B irradiation.

Ultraviolet B (UVB) irradiation of platelet concentrates (PCs) may prevent the development of posttransfusion HLA alloimmunization. As irradiation performed in a blood center or a hospital will probably be associated with a variable postirradiation delay before transfusion, the ability to store PCs after UVB irradiation becomes important. The effects have been studied of a UVB dose of 10,000 mJ per cm2, the dose used in our institution for UVB clinical trials, on PCs pooled and stored for up to 96 hours after irradiation. Results showed that after 96 hours of storage, though there were no changes in pH, platelet count, white cell count, percent discharge of lactate dehydrogenase, or beta-thromboglobulin, there were significant decreases in morphology score and osmotic recovery. These changes, however, were not evident after 24 hours of storage. Similarly, there was a 60-percent decrease in immunoreactive membrane glycoprotein (GP) Ib after 96 hours of storage, but these changes were not seen after 48 hours of storage. No changes were seen in levels of GPIIb/IIIa in either group during the 96 hours of storage. On computer-analyzed two-dimensional polyacrylamide gel electrophoresis, PCs irradiated at 10,000 mJ per cm2 and stored for 72 hours had changes in over 50 platelet proteins as compared to those proteins in nonirradiated age-matched control PCs. It can be concluded that UVB irradiation of PCs at 10,000 mJ per cm2 does not lead to significant platelet deterioration after short-term storage (24-48 hours) but is likely to be deleterious after long-term (72-96 hours) storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Banks↗

PubMedDate not supplied

Safety and efficacy of low-dose intravenous immune globulin (IVIG) treatment for infants and children with immune thrombocytopenic purpura. Low-Dose IVIG Study Group.

PURPOSE: This report presents pooled data from two multicenter studies conducted to assess the efficacy, safety, and tolerance of lower-dose intravenous immune globulin (IVIG) regimens of 250 mg/kg/day, 400 mg/kg/day, and 500 mg/kg/day for 2 days, compared to an established higher-dose regimen of 1 g/kg/day for 2 days, in children with immune thrombocytopenic purpura (ITP). PATIENTS AND METHODS: A total of 24 children received IVIG (Gammar i.v.). In Study 1, 10 centers enrolled 12 children between 5 and 12 years old who received IVIG at either 400 mg/kg/day or 1 g/kg/day for 2 days. In Study 2, five centers enrolled 12 infants and children younger than 5 years old who received IVIG at 250 mg/kg/day or 500 mg/kg/day for 2 days. Both studies were prospective and randomized. RESULTS: IVIG treatment was effective (platelets increased at least 30,000/cu mm over baseline) in 94% (16 of 17) of the evaluable patients in the low-dosage group. Platelet increases occurred rapidly: by 48 hours, total platelet counts ranged from 32,000/cu mm to 256,000/cu mm, and peak platelet counts reached 38,000/cu mm to 551,000/cu mm. Adverse events (AEs) were most often mild, lasted less than 3 hours, and were usually those typically associated with immunoglobulin administration-headache, nausea, vomiting, and fever. There were two serious AEs-an anaphylactoid reaction in one patient in the 400 mg/kg group and aseptic meningitis in one patient in the 1 g/kg high-dosage group. Both patients recovered without sequelae and were responders. Although the incidence of AEs varied by dosage groups, this difference was not significant. However, the incidence of AEs was affected by age. AEs were significantly lower in patients younger than 5 years of age. CONCLUSIONS: In this small, randomized trial, low-dose IVIG in 2-day regimens of 250, 400, or 500 mg/kg/day rapidly reversed thrombocytopenia just as effectively as 1 g/kg/day in infants and young children with ITP. Lower-dosage regimens are safe and well-tolerated; the incidence of AEs is lower in children younger than 5 years of age.

Child↗

PubMedDate not supplied

Giant platelets with abnormal surface glycoproteins: a new familial disorder associated with mitral valve insufficiency.

PURPOSE: To study the platelets from a family with a new form of inherited giant platelet disorder. PATIENTS AND METHODS: Two siblings exhibited a hemorrhagic disorder characterized by moderate thrombocytopenia, giant platelets, and markedly prolonged bleeding time. The parents had no discernible platelet defect. Both children also developed mitral regurgitation requiring medication, and one underwent surgical replacement at the age of 3 years. RESULTS: The mean platelet size was greater than 20 microm3. Direct measurements of the two major axes of each of 12 platelets on electron micrographs revealed a range of 2x4 to 4x6 microm. Electron microscopy did not demonstrate any abnormality of granule content. The platelets agglutinated normally with ristocetin and aggregated normally with collagen. However, the aggregation was slightly slower than normal with ADP, epinephrine, and Na arachidonate. Two-dimensional unreduced versus reduced SDS-polyacrylamide gel electrophoresis of surface radioiodinated platelet glycoproteins revealed absence of proteins Ia, Ic, and IIa in both affected children, whereas GP Ib, IIb, and IIIa appeared normal. The 2D gels of platelet glycoproteins from both parents were identical to controls. Western blots demonstrated that GP Ic, Ic', Ib, and Ia/IIa were present. CONCLUSIONS: This disorder represents a new syndrome of thrombocytopenia with giant platelets distinct from Bernard-Soulier, Montreal giant platelets, Swiss cheese platelets, May-Hegglin anomaly, and other previously described syndromes.

Bernard-Soulier Syndrome↗

PubMedDate not supplied

Platelet membrane glycoproteins: role in primary hemostasis and component antigens.

The biochemical details of the platelet surface as they relate to normal platelet function have been elucidated through study of labeled membranes from both normal platelets and those with congenitially defective function. Several cytoadhesive glycoprotein complexes which are integral components of the platelet membrane have been demonstrated to act as important receptors for extracellular matrix macromolecules. Glycoproteins Ia/IIa (collagen receptor), Ic/IIa (fibronectin receptor), and IIb/IIIa (fibrinogen receptor) belong to a family of cytoadhesive complexes called the integrins, while glycoprotein Ib/IX, the major von Willebrand receptor, has different features. These same major glycoproteins comprise all of the alloantigens and most of the autoantigens that have been characterized. Glycoprotein IIb/IIIa contains the alloantigens, PlA (Zw), Bak (Lek), and Pen (Yuk), as well as the most frequent target antigenic sites for anti-platelet autoantibodies. Because a number of platelet alloantigens were discovered independently by more than one group, nomenclature is confusing at present, although a system analogous to that used for histocompatibility antigens has been proposed. Precise identification of the antigenic epitopes has not yet been accomplished for all of the platelet antigens. Current research efforts include characterization of antigenic epitopes, elucidation of mechanisms by which platelet immunization occurs, and determination of the clinical implications of the presence of various platelet antibodies.

Autoantigens↗