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S F Parsons

Publications and source records attributed to S F Parsons.

At least 37 records · Page 2Linked to original sources
PubMed1992

Okadaic acid induces interphase to mitotic-like microtubule dynamic instability by inactivating rescue.

We used high-resolution video microscopy to visualize microtubule dynamic instability in extracts of interphase sea urchin eggs and to analyze the changes that occur upon addition of 0.8-2.5 microM okadaic acid, an inhibitor of phosphatase 1 and 2A (PP1, PP2a) (Bialojan, D., and A. Takai. 1988. Biochem. J. 256:283-290). Microtubule plus-ends in these extracts oscillated between the elongation and shortening phases of dynamic instability at frequencies typical for interphase cells. Switching from elongation to shortening (catastrophe) was frequent, but microtubules persisted and grew long because of frequent switching back to elongation (rescue). Addition of okadaic acid to the extract induced rapid (< 5 min) conversion to short, dynamic microtubules typical of mitosis. The frequency of catastrophe doubled and the velocities of elongation and shortening increased slightly; however, the major change was an elimination of rescue. Thus, modulation of the rescue frequency by phosphorylation-dependent mechanisms may be a major regulatory pathway for selectively controlling microtubule dynamics without dramatically changing velocities of microtubule elongation and shortening.

Animals↗
PubMed1992

New monoclonal antibodies in CD59: use for the analysis of peripheral blood cells from paroxysmal nocturnal haemoglobinuria (PNH) patients and for the quantitation of CD59 on normal and decay accelerating factor (DAF)-deficient erythrocytes.

CD59 is a widely expressed cell surface glycosylphosphatidylinositol (GPI)-linked glycoprotein which acts as an inhibitor of the assembly of the membrane attack complex of autologous complement. Four new monoclonal antibodies to CD59 (2/24, 1B2, BRIC 229, BRIC 257) are described. Competitive binding experiments using these antibodies, two known CD59 antibodies (MEM-43, YTH 53.1) and a previously described antibody LICR-LON-Fib75.1 demonstrated that all seven antibodies see related epitopes on human erythrocyte CD59. In common with other GPI-linked proteins, CD59 (as defined by antibody 2/24) was sensitive to treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) on lymphocytes and monocytes but not on erythrocytes. Flow cytometric analysis using antibody 2/24 identified two populations (CD59 positive and CD59 deficient) of lymphocytes, monocytes and erythrocytes in peripheral blood from a patient with paroxysmal nocturnal haemoglobinuria (PNH). The abundance of CD59 on normal erythrocytes was determined as 21,000 copies/cell when radioiodinated BRIC 229 was used. Other CD59 antibodies gave values of 10,000 (IF5) and 15,000 (2/24) against the same target cells. Radioiodinated Fab fragments of BRIC 229 gave a value of 39,000 copies/cell. Erythrocytes from two individuals with a rare inherited deficiency of decay accelerating factor (DAF), known as the Inab phenotype, expressed normal levels of CD59.

Antibodies, Monoclonal↗
PubMed1991

Immunochemical studies on the differential binding properties of two monoclonal antibodies reacting with Tn red cells.

Two monoclonal antibodies (MoAbs), BRIC 66 (IgM) and BRIC 111 (IgG1), were produced by immunizing mice with ovarian cyst blood group A1 glycoprotein and Tn red cells (RBCs), respectively. Their specificities were determined by inhibitions using Tn sialoglycoproteins (SGPs), mucins (armadillo [ASG] and ovine [OSG] submaxillary glycoproteins), and monosaccharides. BRIC 66 agglutinated both Tn and group A RBCs and reacted immunohistochemically with both the vascular endothelium and tumor cells from a group A adenocarcinoma, BRIC 66 was inhibited by N-acetylgalactosamine (GalNAc), Tn SGPs, and mucins on both hemagglutination inhibition tests and radioimmunoassay. BRIC 111 agglutinated Tn RBCs only, and it specifically stained tumor cells from a group O patient's breast carcinoma and a group A patient's adenocarcinoma. In hemagglutination inhibition tests, BRIC 111 was readily inhibited by Tn SGPs, only partially inhibited by GalNAc, and not inhibited by mucins. In a sensitive radioimmunoassay, BRIC 111 was inhibitable by GalNAc. Tn SGP was 2000-fold more effective as an inhibitor than the mucins (ASG and desialized OSG), which contain a high content of terminal alpha-GalNAc-O-serine (threonine) residues. It is postulated that BRIC 66 is specific for terminal alpha-GalNAc units in carbohydrate chains. The exclusive reaction of BRIC 111 with Tn SGP indicates a combining site larger than GalNAc alpha-1, which probably includes amino acid residues in juxtaposition to GalNAc in Tn SGP. In view of its specific agglutination of Tn RBCs, BRIC 111 is a useful reagent for the examination of polyagglutinable RBCs.

ABO Blood-Group System↗
PubMed1991

New monoclonal antibodies in CD44 and CD58: their use to quantify CD44 and CD58 on normal human erythrocytes and to compare the distribution of CD44 and CD58 in human tissues.

The cell-surface glycoproteins CD44 and CD58 are involved in cell adhesion reactions. In this paper 12 monoclonal antibodies in CD44 and two in CD58 are described. Competitive binding assays using CD44 antibodies identified three distinct epitope groups. Antibodies in Group 1 and, with one exception (BRIC 214), antibodies in group 2, but not antibodies in Group 3, recognized epitopes that are sensitive to reduction and to trypsin or chymotrypsin treatment of intact erythrocytes, and so these epitopes probably reside on the N-terminal disulphide-bonded domain of CD44. Antibodies in CD44 did not inhibit the binding of CD58 antibodies to erythrocytes or vice versa. Quantitative binding studies using radioiodinated IgG measured 1888-5592 copies of CD44 and 1772-3290 copies of CD58 on normal erythrocytes. Similar measurements with radioiodinated Fab fragments gave values of 6508-10,450 (CD44) and 3457-7622 (CD58). Immunocytochemical studies indicated that CD44 is much more widely expressed in non-haemopoietic tissues than CD58. Comparison with previously described CD44 antibodies suggests that antibodies in our Group 1 encompass Hermes 2 and that those in Group 2 encompass Hermes 1. All the CD44 antibodies gave weakened reactions with Lu(a-b-) erythrocytes of the In(Lu) type by one or more methods. BRIC 214 and antibodies in epitope Group 3 were used to demonstrate that CD44 on these variant cells gives membrane-bound trypsin and chymotrypsin cleavage fragments of similar molecular weight to those obtained with normal erythrocytes.

Antibodies, Monoclonal↗
PubMed1989

Studies on the defect which causes absence of decay accelerating factor (DAF) from the peripheral blood cells of an individual with the Inab phenotype.

1. We have studied the peripheral blood cells of an individual with the Inab phenotype who is deficient in decay accelerating factor (DAF). 2. In contrast with the situation in paroxysmal nocturnal haemoglobinuria, membranes from peripheral blood cells of the Inab phenotype individual lack DAF, but retain the other glycosylphosphatidylinositol-linked proteins acetylcholinesterase and LFA-3. 3. Unlike normal Epstein-Barr-virus-transformed lymphoblastoid cell lines (EBV-LCL), DAF was not expressed on EBV-LCL derived from peripheral blood lymphocytes of the Inab individual. 4. No differences in the DAF gene of normal and Inab phenotype individuals could be detected by Southern blotting studies. 5. EBV-LCL derived from the Inab individual had a gross reduction in the level of DAF mRNA compared with normal EBV-LCL. 6. Our results suggest that the DAF gene in the Inab phenotype contains a mutation which affects the transcription or processing of DAF mRNA.

Blood Cells↗
PubMed1989

Epitopes on sialoglycoprotein alpha: evidence for heterogeneity in the molecule.

The binding of 15 125I-labelled mouse monoclonal antibodies to cell-surface sialoglycoprotein alpha (SGP alpha: synonym Glycophorin A) was studied using intact IgG and Fab fragments. It was estimated that the number of sialoglycoprotein alpha (SGP alpha) molecules per red cell is of the order of 1 x 10(6) and the number of sialoglycoprotein delta (SGP delta; synonym Glycophorin B) molecules per red cell is of the order of 1.7-2.5 x 10(5). Competitive binding assays showed that antibodies of the same blood group specificity (four anti-Ns reacting with SGP alpha and SGP delta (BRIC 33, BRIC 115, BRIC 120, BRIC 123) and four anti-Wrbs reacting with SGP alpha (R7, BRIC 14, BRIC 89, BRIC 93) inhibited binding of each other to red cells. Two antibodies (R1.3 reacting with SGP alpha and SGP delta and R18 reacting with SGP alpha) recognized distinct epitopes, and the remaining five antibodies (BRIC 116, BRIC 117, BRIC 119, BRIC 127, R10 reacting with SGP alpha) partially inhibited binding of each other to red cells. This latter observation and the finding that four of these antibodies (BRIC 116, BRIC 117, BRIC 119, BRIC 127) bind to a considerably smaller number of antigen sites (1.69-2.71 x 10(5) for intact IgG) than the maximum value obtained, suggests heterogeneity of glycosylation within SGP alpha molecules. The functional affinities of the IgG antibodies ranged from 1 x 10(5) to 4 x 10(7)M-1.

Antibodies, Monoclonal↗
PubMed1988

Effect of endoglycosidase F-peptidyl N-glycosidase F preparations on the surface components of the human erythrocyte.

Endo-N-acetyl-beta-D-glucosaminidase F-Peptidyl N-glycosidase F preparations (abbreviated Endo F) and endo-beta-D-galactosidase were used to study the major human erythrocyte membrane glycoproteins and the components carrying the blood group A, B, Rhesus (D), and Duffy (Fya) antigens. The results are consistent with the known presence of an N-glycosyl-linked oligosaccharide on sialoglycoprotein alpha and the absence of such an oligosaccharide from sialoglycoprotein delta. Under the conditions used, only a portion of the N-glycosyl-linked oligosaccharides on band 3 molecules were cleaved by Endo F alone or by Endo F in combination with endo-beta-D-galactosidase. Immunoblotting experiments showed that treatment of red cells with Endo F alone had little effect on the components carrying blood group A and B antigen activity. However, Endo F used in combination with endo-beta-D-galactosidase caused a substantial reduction in the binding of monoclonal anti-A and anti-B antibodies. The results clearly show that sialoglycoproteins alpha and delta carry little or no blood group A or B activity. Endo F alone, or in combination with endo-beta-D-galactosidase, had no effect on the electrophoretic mobility of the Rh(D) polypeptide, supporting previous suggestions that this membrane polypeptide is unusual in not being glycosylated. Endo F had a dramatic effect on the electrophoretic mobility of the component(s) carrying blood group Fya activity. The diffuse Fya component of Mr 38,500-90,000 was sharpened to a band of Mr 26,000. Either endo-beta-D-galactosidase or neuraminidase treatment reduced the Mr of the Fya component(s) but did not significantly sharpen the bands, suggesting that the Fya component contains between 40-50% by mass of N-glycosyl-linked oligosaccharides.

Electrophoresis, Polyacrylamide Gel↗
PubMed1988

Monoclonal antibodies that recognize different membrane proteins that are deficient in Rhnull human erythrocytes. One group of antibodies reacts with a variety of cells and tissues whereas the other group is erythroid-specific.

1. Rhnull human erythrocytes lack all of the antigens of the Rh and LW blood group systems and have abnormal shape and an increased osmotic fragility. In this paper two murine monoclonal antibodies raised against intact human erythrocytes were used to investigate further the abnormalities in these cells. BRIC 125 reacts weakly with Rhnull erythrocytes and BRIC 69 does not react at all. The results showed that BRIC 125 reacts with a component of Mr 47,000-52,000 which has a substantial content of N-glycans. In contrast, BRIC 69 reacted with a band of Mr 31,000 together with a very diffuse band of Mr 35,000-52,000. Treatment of BRIC 69 immunoprecipitates with endoglycosidase F/peptidyl-N-glycosidase F resulted in the loss of both BRIC 69 reactive components and the appearance of a new band of Mr similar to that of the Rh(D) polypeptide. 2. BRIC 125 had a broad reactivity with cells in peripheral blood, whereas the reactivity of BRIC 69 was confined to erythrocytes. BRIC 125, but not BRIC 69, reacted with human kidney tissue and bound to endothelium in peritubular capillaries, arteries and veins as well as the epithelial tissue of distal tubules. BRIC 125 stained haemopoietic cells, foetal hepatocytes and megakaryocytes in foetal liver and sinusoidal cells, hepatocytes and portal tracts in adult liver. In contrast, BRIC 69 reactivity was confined to haemopoietic cells in foetal liver. The BRIC 125 epitope has a wide tissue distribution, suggesting the occurrence of a related group of polypeptides which have a general functional role on cell surfaces. 3. Rhnull erythrocytes are deficient in at least four different membrane polypeptides.

Antibodies, Monoclonal↗
PubMed1988

A Japanese family with two sisters apparently homozygous for Mk.

Two Japanese sisters with consanguineous parents have M-N- En(a-) Wr(a-b-) S-s-U- red cells and are therefore apparently homozygous for Mk; the third reported family with members of this genotype. The serum of the proposita (ORCMK) contained anti-EnaTS, anti-EnaFR and possibly anti-Wrb, whereas the serum of her MkMk sister contained no atypical antibodies. Total absence of sialoglycoproteins alpha and delta from red cell membranes of an Mk homozygote was demonstrated by lactoperoxidase-catalysed radioiodination of accessible tyrosine residues with subsequent SDS polyacrylamide gel electrophoresis and autoradiography, and by use of a monoclonal antibody directed at the cytoplasmic portion of alpha-sialoglycoprotein.

Adult↗
PubMed1988

Evidence for the occurrence of human erythrocyte membrane sialoglycoproteins in human kidney endothelial cells.

Several mouse monoclonal antibodies recognising different epitopes on human erythrocyte sialoglycoproteins alpha and beta (syn: glycophorins A and C, respectively) react with human renal endothelium. Those monoclonal anti-blood group M and anti-blood group N antibodies which recognised the M/N epitopes on sialidase-treated human erythrocytes also reacted with human renal endothelium whilst those which recognise the M/N epitopes on native, but not on sialidase-treated human erythrocytes were not reactive with human renal endothelium. These results provide evidence for the occurrence of alpha and beta molecules in renal endothelium and suggest that alpha in renal endothelium is incompletely sialylated.

Antibodies, Monoclonal↗
PubMed1988

The Ina and Inb blood group antigens are located on a glycoprotein of 80,000 MW (the CDw44 glycoprotein) whose expression is influenced by the In(Lu) gene.

The Ina and Inb blood group antigens were found to be located on an erythrocyte membrane glycoprotein of 80,000 MW by immunoblotting with human anti-Ina and anti-Inb antibodies under non-reducing conditions. This glycoprotein is shown here to be identical to that defined by monoclonal antibodies to CDw44, and a new murine monoclonal antibody (BRIC 35) is added to this cluster. Experiments with endo-beta-galactosidase and Endo F preparations suggest that the glycoprotein contains one or more N-glycans but that these oligosaccharides do not contain extensive poly-N-acetyllactosaminyl sequences. Experiments using membranes prepared from sialidase-treated normal erythrocytes, from Tn erythrocytes and from Cad erythrocytes suggest that the glycoprotein does not contain a substantial content of O-glycans. The Inb antigen and the epitope defined by a murine monoclonal antibody (BRIC 35) show reduced expression on Lu(a-b-) erythrocytes which result from the effect of the dominant inhibitor gene In(Lu). Evidence is presented here that the Inb antigen is expressed on normal granulocytes and lymphocytes and on the haemopoietic cell lines HEL, K562 and HL-60, a lymphoblastoid cell line and lymphocytes from two patients with B-CLL.

Antibodies, Monoclonal↗
PubMed1987

Estimation of the number of binding sites for a murine monoclonal anti-Lub on human erythrocytes.

The number of Lub antigen sites on the human erythrocyte membrane, as recognised by the murine monoclonal antibody BRIC-108, has been determined. The number of antibody molecules bound per cell on one example of cells of the phenotype Lu(a-b-) with recessive inheritance was an average of around 200 in replicate determinations, which probably represents non-specific antibody binding. A similar number of antibody molecules to this bound to trypsin- or pronase-treated normal cells or cells of the Lu(a-b-) phenotype associated with the inheritance of the X-borne gene, XS2. The number of binding sites on three examples of cells of the phenotype Lu(a-b-) with dominant inheritance was from 440 to 690. A variation in the number of binding sites per cell from 1,640 to 4,070 was found in five individuals with the phenotype Lu(a-b+) and from 850 to 1,820 in four individuals with the phenotype Lu(a+b+). Four individuals with the Lu(a+b-) phenotype had an average of 480 binding sites per cell. The Lub antigen therefore appears to a have low-site density and a variable level of expression on the erythrocyte surface.

Animals↗
PubMed1987

A human cell-surface glycoprotein that carries Cromer-related blood group antigens on erythrocytes and is also expressed on leucocytes and platelets.

A new human erythrocyte glycoprotein has been identified by immunoblotting with murine monoclonal antibodies under non-reducing conditions. The glycoprotein has a MW of 70,000 and carries Cromer-related blood group antigens. The monoclonal antibodies also react with normal peripheral blood leucocytes and platelets and several haemopoietic cell lines. The glycoprotein has a reduced MW after sialidase treatment. The MW is markedly reduced in Tn erythrocyte membranes and slightly increased in Cad erythrocyte membranes. These results suggest that the glycoprotein has a substantial content of O-glycans. The glycoprotein appears to be absent from, or grossly altered in, the erythrocytes of two individuals with the rare Inab phenotype.

Antibodies, Monoclonal↗