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Biomedical subjects

I R Peake

Publications and source records attributed to I R Peake.

At least 73 records · Page 4Linked to original sources
PubMed1990

Family studies in von Willebrand's disease by analysis of restriction fragment length polymorphisms and an intragenic variable number tandem repeat (VNTR) sequence.

We have previously identified a microsatellite variable number tandem repeat region of the nucleotide sequence ATCT within intron 40 of the von Willebrand factor (vWF) gene. By polymerase chain reaction (PCR) amplification of this region, eight major alleles have been demonstrated in the South Wales population, with an overall heterozygosity rate of 75%. Direct sequencing has shown that the alleles correspond to lengths of between six and 14 ATCT repeats. In the present study we describe the use of this variable repeat sequence and previously reported restriction fragment length polymorphisms (RFLP) to study inheritance patterns in families with type I, IIA and severe type III von Willebrand's disease (vWD). The results confirm that analysis of this precisely localized intragenic locus provides a highly informative marker for gene tracking studies in the major forms of vWD.

Base Sequence↗
PubMed1989

Factor IX Cardiff: a variant factor IX protein that shows abnormal activation is caused by an arginine to cysteine substitution at position 145.

Crude barium chloride eluates prepared from 12 unrelated patients with cross-reacting material positive (CRM+) haemophilia B were activated with celite eluate, the reaction products resolved after reduction by 13% SDS-PAGE, and factor IX antigenic material detected by probing with radiolabelled immunopurified rabbit anti-factor IX antiserum followed by autoradiography. Out of the 12, one sample showed faulty activation with the production of a stable reaction product with a MW compatible with that of a putative light chain-activation intermediate. In order to confirm this, two oligonucleotide primers that bracketed exon 6 of the factor IX gene were constructed and used to prime a polymerase chain reaction on DNA isolated from the patient's peripheral blood leucocytes. A single 489 nucleotide DNA fragment was obtained, gel purified, subcloned into M13, and DNA sequencing carried out on both strands. A single C to T transition was discovered that changed the Arg residue at position 145, the first residue of the first bond in the activation peptide, to a Cys, a result that confirmed the inferences drawn from the activation studies.

Antigens↗
PubMed1989

Anti-idiotypes to factor VIII antibodies and their possible role in the pathogenesis and treatment of factor VIII inhibitors.

Studies on the production and characterization of anti-idiotype antibodies (AId) to monoclonal factor VIII antibodies (McFVIIIAb) are reported. Two AIds were produced and one of these exhibited cross-reactivity with two other McFVIIIAb but showed no reactivity with haemophilic and non-haemophilic FVIIIAb. This AId was also active against McFVIIIAb which bound immunologically active forms of factor VIII but it did not neutralize McFVIIIAb directed against procoagulant factor VIII. The in vitro effect of therapeutic pooled human IgG concentrates upon haemophilic and non-haemophilic FVIIIAb was also assessed. Approximately 25% of non-haemophilic FVIIIAb were inhibited following incubation with human IgG whereas the latter had no effect upon haemophilic FVIIIAb activity. Studies on haemophilic sibling pairs of FVIIIAb and non-FVIIIAb producing individuals indicated FVIIIAb neutralizing activity in the non-FVIIIAb producing sibling's IgG fraction which may be of anti-idiotypic origin. These findings lend further support to suggestions that anti-idiotypes have a regulatory role in FVIIIAb production and are of potential therapeutic value.

Antibodies, Anti-Idiotypic↗
PubMed1989

Defective propeptide processing and abnormal activation underlie the molecular pathology of factor IX Troed-y-Rhiw.

Affected members of a South Wales haemophilia B family (from Troed-y-Rhiw) were shown by Western blotting and immunoperoxidase detection to have a factor IX molecule of higher than normal molecular weight which also shows impaired calcium binding. Gene cloning and DNA sequencing revealed the same arginine to glutamine mutation at position -4 of the propeptide that has been found in two previously described factor IX variants which circulate with the propeptide still attached. The mutation also abolishes a HaeIII restriction enzyme recognition site. A potential carrier was shown to be normal both by Western blotting and DNA studies. The way in which the attached propeptide interferes with normal factor IX function was investigated by activation studies with crude normal and patient factor IX Troed-y-Rhiw preparations using Western blotting and detection with iodinated immunopurified polyclonal antifactor IX serum. We demonstrate that the -4 mutation appears to block cleavage between the Arg145-Ala146 peptide bond in the activation peptide, thus preventing the normal activation of factor IX Troed-y-Rhiw. A small amount of normally processed factor IX is produced, implying that the -4 mutation does not completely prevent propeptide cleavage, thus accounting for the low levels of factor IX activity measured in the plasma of affected family members.

Base Sequence↗
PubMed1988

Carrier detection in 50 haemophilia A kindred by means of three intragenic and two extragenic restriction fragment length polymorphisms.

Carrier detection was attempted in 50 haemophilia A kindred by means of restriction fragment length polymorphism (RFLP) analysis using two linked and three intragenic probes. The sample comprised 330 individuals including 70 haemophiliacs, 45 obligate carriers and 100 possible carriers. Non-related haplotypes contained within the sample group were used to tabulate the intragenic RFLP allele frequencies. The linkage disequilibrium existing between the XbaI and Bc1I RFLP was shown to be less than previously reported, such that 69% of women are informative for at least one of these two polymorphisms. 36 women were subsequently diagnosed as carriers and 37 as being normal: in 52 of these, diagnosis was based either on intragenic RFLPs or linked RFLP plus strong phenotypic data, and was considered to be unequivocal; in the remaining 21, diagnosis was based on linked RFLPs alone and was considered to be probabilistic, with a 5-10% possible error rate. 27 of the possible carriers, either from families with sporadic haemophilia or from families where missing members precluded haplotype analysis, remained unassigned. 72% of the obligate carriers and firmly diagnosed carriers were heterozygous and phase known for at least one intragenic RFLP, whereas 6% were uninformative for the RFLPs for which they were examined. In 54 informative meioses, three recombinations between the factor VIII locus and the DX13 and/or ST14 loci were observed, giving a recombination rate of 5.5%. 15 prenatal diagnoses were carried out. Of the 11 male fetuses, six were shown to be affected and five to be normal. In three of four prenatal diagnoses where only a linked RFLP was informative, the result was confirmed by fetoscopy, fetal blood sampling, and factor VIII assay.

Alleles↗
PubMed1988

The combined use of monoclonal antibody-based enzyme-linked immunosorbent assays (ELISA) for factor VIII antigen (VIII:Ag) and von Willebrand factor antigen (vWF:Ag) for the detection of carriers of haemophilia A.

Enzyme-linked immunosorbent assays (ELISA) for factor VIII antigen (VIII:Ag) and von Willebrand factor antigen (vWF:Ag) have been developed, each employing monoclonal antibodies. In the majority of severe haemophilic plasmas tested, VIII:Ag was undetectable by ELISA and also by immunoradiometric assay (IRMA) using haemophilic VIII:C antibodies. In haemophilic plasmas with mild/moderate deficiency of coagulant factor VIII (VIII:C), there was no significant difference between the two immunoassays although there was a general trend for ELISA VIII:Ag results to be higher. Assay of von Willebrand's disease (vWd) plasmas with the ELISA for vWF:Ag demonstrated reduced levels of this antigen in type I vWd, normal levels in type IIA, and a severe reduction of vWF:Ag in type III vWd. The discrimination of obligate carriers of haemophilia from normal was determined using ratios of factor VIII/vWF. Factor VIII antigen/von Willebrand factor antigen measured by IRMA and Laurell immunoelectrophoresis respectively, gave a superior discriminant to that of VIII:C/vWF:Ag (Laurell), but optimal discrimination was obtained with the combination of ELISAs for VIII:Ag and vWF:Ag.

Antibodies, Monoclonal↗
PubMed1987

Monoclonal antibodies to factor VIII: their application in immunoblotting for the visualization of factor VIII in therapeutic concentrates and plasma.

Two monoclonal antibodies (McAb) termed 12A4 and 19C1 have been raised against human factor VIII. In immunoassays 12A4 bound to factor VIII antigen (VIII:Ag) in plasma but not serum whilst 19C1 bound to VIII:Ag in both plasma and serum. Both McAb were shown by immunoblotting to react with the carboxy (C) terminal polypeptide of factor VIII which appeared as a doublet with a molecular weight (Mr) of 77,000/75,000. The C terminal factor VIII polypeptide was detectable by immunoblotting in each of 12 therapeutic factor VIII concentrates, from six different manufacturers, although its level was variable. Factor VIII was visualized in plasma by immunoblotting following its immunoadsorption and elution from agarose-bound monoclonal antibodies. No Mr 77,000/75,000 bands were detectable in plasma obtained from 13 unrelated CRM- haemophiliacs whilst 11 CRM+ haemophilic plasmas from seven kindred were shown to have a C terminal factor VIII polypeptide of normal molecular size.

Antibodies, Monoclonal↗
PubMed1987

Heterogeneity of the factor IX locus in nine hemophilia B inhibitor patients.

DNA from nine hemophilia B patients who produce anti-factor IX inhibitors (antibodies), including two brothers, was analyzed by the Southern blotting method and hybridization with factor IX cDNA, intragenomic, and 3'-flanking probes. Two inhibitor patients were shown to have total deletions of the factor IX gene. Two other inhibitor patients, the brothers, were shown to have a presumably identical complex rearrangement of the factor IX gene involving two separate deletions. The first deletion is of approximately 5.0 kb and removes exon e. The second deletion is between 9 and 29 kb and removes exons g and h but leaves exon f intact. An abnormal Taq I fragment at one end of the deletion junctions acted as a marker for the inheritance of hemophilia B in the patients' family. Five other inhibitor patients have a structurally intact factor IX gene as detected by this method. Our studies indicate that whereas large structural factor IX gene defects predispose hemophilia B patients to developing an anti-factor IX inhibitor, the development of an inhibitor can be associated with other defects of the factor IX gene.

DNA↗
PubMed1986

Comparison of phenotypic assessment and the use of two restriction fragment length polymorphisms in the diagnosis of the carrier state in haemophilia B.

Carrier detection in haemophilia B has previously involved pedigree analysis and assessment of the coagulation phenotype. At best using these methods, carrier evaluation may be made with about 80% certainty (Orstavik et al, 1981). With isolation and cloning of the factor IX gene, DNA probes are now available to detect intragenic nucleotide changes. This study uses one such probe which detects restriction fragment length polymorphisms with the restriction endonucleases Taq 1 and Xmn 1. Seventy-eight individuals from eight haemophilia B kindred were initially evaluated for factor IXC and factor IXAg levels. DNA from these individuals was then digested with the two restriction enzymes and after Southern blotting, analysed for restriction fragment length polymorphisms (RFLPs) with the radiolabelled genomic probe. Four kindred proved informative with RFLP linkage assessment. In three families evaluation was possible with both Taq 1 and Xmn 1 polymorphic markers but in the fourth pedigree only Xmn 1 was informative. Using these techniques five potential carriers have been definitively assigned as either normal or carriers of the haemophilia B gene defect. Problems of phenotypic assessment are well illustrated in pedigree 4 where polymorphic linkage positively identified a carrier whose coagulation data were normal.

DNA Restriction Enzymes↗
PubMed1985

The application of a monoclonal antibody to factor VIII related antigen (VIIIRAg) in immunoradiometric assays for factor VIII.

A two site solid phase immunoradiometric assay (IRMA) for VIIIRAg has been developed using a monoclonal antibody as both the solid phase ligand and the radiolabelled antibody. A range of normal plasmas and von Willebrand's disease (vWd) plasmas has been assayed for VIIIRAg by this method and compared with VIIIRAg values measured by an IRMA using polyclonal antibodies and by immunoelectrophoresis and with ristocetin cofactor activity (VIIIRiCoF). It was found that the monoclonal IRMA correlated well with the polyclonal IRMA and the immunoelectrophoretic assay, but the correlation with the VIIIRiCoF assay was relatively poor, in spite of the strong inhibitory effect of the antibody on VIIIRiCoF activity.

Antibodies, Monoclonal↗
PubMed1985

Laboratory support in the diagnosis of coagulation disorders.

In spite of recent advances in knowledge concerning the detailed biochemistry of blood coagulation, the diagnosis of haemostatic disturbances remains an important problem of clinical judgement in many instances. Laboratory support relies initially on a series of screening tests designed to investigate the general nature of blood clotting. Recent interest in these aspects is centred on standardization and quality assurance of methods and results. Procedures have been recommended in an attempt to unify data. Several aspects of conventional laboratory investigations have been modified and the reliability of diagnostic information has been improved. Some relatively recent findings have extended the application to coagulation studies. For example, the discovery of protein C, a potent physiological inhibitor of blood coagulation, has clarified the nature of the clotting disorder in some patients with hereditary thrombosis disease. In addition, close analysis of plasma from patients with systemic lupus erythematosus has stimulated interest in the association between the haemostatic, neurological and immunological abnormalities recorded in these patients. More recently, sophisticated techniques for the diagnosis of many coagulation factor defects have been developed. Carrier detection of the sex-linked disorders is undertaken widely with reasonable success and reliable prenatal diagnosis procedures have been established in specialized centres. Unequivocal information regarding the diagnosis of carrier status in some families is obtained by the use of gene analysis and linked polymorphisms. Precise details of the genes for several clotting factors have been recorded. Future development in this field is likely to improve the clinical course of many coagulation disorders.

Autoantibodies↗
PubMed1984

Heterogeneity of human procoagulant factor VIII (VIIIC) antibodies in their reaction with factor VIII related antigen (VIIIRAG).

Human inhibitors to procoagulant factor VIII (VIIIC) were tested for possible reactivity with factor VIII related antigen (VIIIRAg) by a modified VIIIRAg immunoradiometric assay (IRMA). Inhibitor IgG's were screened for anti-VIIRAg by competition with I125 labelled VIIIRAg antibodies for common antigenic determinants using either an VIIIRAg concentrate from which factor VIII coagulant antigen (VIIICAg) had been dissociated, or normal plasma (containing VIIIRAg and VIIICAg) as an antigen source. There was no evidence of VIIIRAg antibodies in the five haemophilic VIIIC inhibitor IgG's tested but low titre VIIIRAg antibodies were detected in one spontaneous VIIIC inhibitor IgG.

Antibodies↗
PubMed1984

Carrier detection by direct gene analysis in a family with haemophilia B (factor IX deficiency).

DNA from a patient with severe factor IX deficiency (haemophilia B) in whom an inhibitor to factor IX had developed was studied with four genomic gene probes specific for the factor IX gene. All gave a negative result, indicating at least a partial gene deletion. Eight female relatives, covering four generations, were also studied. Restriction-enzyme-fragmented DNA was probed in each case and the level of binding assessed by darkening of the autoradiograph. The DNA of this patient's sister and mother had reduced signals, when compared with that of normal female subjects, indicating the presence of the defective gene. However, the other six female subjects (grandmother, great-grandmother, maternal aunt, and three female cousins) had normal signals. Levels of factor IX and factor IX antigen were also normal in these subjects. By direct gene analysis in this family, the point of mutation has been identified (mother) and diagnosis of the sister as a carrier confirmed.

Autoradiography↗