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Biomedical subjects

D J Brock

Publications and source records attributed to D J Brock.

At least 145 records · Page 8Linked to original sources
PubMed1983

Amniotic fluid alkaline phosphatase isoenzymes in early prenatal diagnosis of cystic fibrosis.

Second-trimester amniotic fluid contains two major alkaline phosphatase (ALP) isoenzymes, one susceptible to inhibition by phenylalanine and the other to inhibition by homoarginine. The proportions of these isoenzymes are constant between 15 and 21 weeks of gestation. In pregnancies where the fetus has cystic fibrosis there is a profound deficiency of the phenylalanine-inhibitable form which is thought to be derived mainly from mucosal cells of the fetal intestine. When phenylalanine and homoarginine were used to define ALP isoenzymes in stored amniotic fluids, 9 of 10 cases of cystic fibrosis were identified, while only 9 of 831 control fluids were scored as false positives. In pregnancies where there is an a priori risk of 1:3 (one or more previous affected children) a positive test indicates a 28:1 risk of cystic fibrosis in the fetus. This method is likely to prove satisfactory for the early prenatal diagnosis of cystic fibrosis.

Alkaline Phosphatase↗
PubMed1983

A simple method for ranking the affinities of monoclonal antibodies.

Measurement of the binding of constant trace amounts of labelled antigen by increasing dilutions of culture supernatant allows the ranking of monoclonal antibodies in the order of their affinity for the antigen. The theoretical basis for this method is discussed and it is illustrated with data from a set of anti-alphafoetoprotein monoclonal antibodies. Hybridomas secreting antibodies of desired affinity for immunoassay, histochemistry or antigen purification can thus be selected at an early stage after fusion.

Animals↗
PubMed1983

Microvillar peptidase activity in amniotic fluid: possible use in the prenatal diagnosis of cystic fibrosis.

The activities of two microvillar peptidases, gamma-glutamyl transpeptidase (GGTP) and aminopeptidase M (APM), have been measured in 132 samples of mid-trimester amniotic fluid. These included samples from 16 pregnancies at risk for cystic fibrosis. The activities of both peptidases were significantly below the normal range in amniotic fluids from the 6 affected pregnancies. This points to early pathological changes in fetal tissues in which microvilli are prominent. In contrast, 4-methylumbelliferylguanidinobenzoate-reactive protease activity in amniotic fluid from the 6 affected pregnancies was normal. Correlation of individual values between GGTP and APM was close in all cases examined, so that when a further 7 samples from cases at risk became available they were tested for GGTP alone. Of these, the 3 affected pregnancies had significantly reduced GGTP activity, particularly in the early weeks of gestation. It is suggested that early amniocentesis and examination of gamma-glutamyl-transpeptidase isoenzyme constitution might make possible the reliable early diagnosis of cystic fibrosis.

Aminopeptidases↗
PubMed1983

Prenatal diagnosis of cystic fibrosis by methylumbelliferylguanidinobenzoate protease titration in amniotic fluid.

Amniotic fluids were obtained from 19 mothers who had previously given birth to a child with cystic fibrosis. Measurement of methylumbelliferylguanidinobenzoate (MUGB) reactive proteases suggested that all 19 would have unaffected babies. Amongst the first 10 cases to come to term there were 5 infants with cystic fibrosis. It is concluded that MUGB protease titration is not suitable for the early prenatal diagnosis of cystic fibrosis.

Amniotic Fluid↗
PubMed1983

Normal second-trimester amniotic fluid alphafetoprotein and acetylcholinesterase associated with fetal sacrococcygeal teratoma.

Amniocentesis was performed at 19 weeks' gestation on a patient with two sequential serum alphafetoprotein values above 2 times median. Ultrasound examination suggested a possible sacrococcygeal teratoma. However, both amniotic fluid alphafetoprotein and acetylcholinesterase were normal, and the patient elected to continue her pregnancy. At 24 weeks fetal demise was confirmed, and prostaglandin induction of labour produced a macerated female fetus with a large sacrococcygeal teratoma.

Acetylcholinesterase↗
PubMed1982

Impact of maternal serum alpha-fetoprotein screening on antenatal diagnosis.

An analysis has been made of indications for amniocentesis in the Edinburgh area from 1979 to 1981. About 5% of all mothers underwent the procedure. Among 2137 amniocenteses, 37% were performed on mothers 35 years old or more, and 30% on patients with raised serum alpha-fetoprotein. The total number of amniocenteses and the categories have been stable for the past three years. As a result of amniocentesis 104 pregnancies were terminated, 66 of which (63%) followed a raised maternal serum alpha-fetoprotein indication, while only 10 (9.6%) were in mothers aged 35 or more. There were a further 12 terminations based on raised serum alpha-fetoprotein but where no amniocentesis had been thought necessary. Even when figures for anencephaly are excluded from the analysis, maternal serum alpha-fetoprotein screening was responsible for detecting 35 out of 63 (56%) abnormal fetuses. This constitutes a strong case for the continuation of alpha-fetoprotein screening programmes.

Abortion, Eugenic↗
PubMed1982

Enzyme-linked immunospecific assays for human alphafetoprotein using monoclonal antibodies.

Two sandwich-type enzyme-linked immunospecific assays for human alphafetoprotein (AFP) have been developed. In both assays monoclonal antibodies were immobilised by absorption to the wells of microtitre plates and used to trap AFP in the samples offered. Bound AFP was then quantitated by completing the sandwich with peroxidase-conjugated anti AFP, which was either of polyclonal or monoclonal type. The monoclonal to monoclonal sandwich enable AFP measurements to be made in the range 100 to 1000 kU/l. The polyclonal to monoclonal sandwich covered an AFP range of 10 to 1000 kU/l. Both assays were rapid and robust and extremely sparing in the use of antibody.

Antibodies, Monoclonal↗
PubMed1982

Controlled trial of serum isoelectric focusing in the detection of the cystic fibrosis gene.

Three independent observers assessed the discriminating power of serum isoelectric focusing in detecting the presence of the cystic fibrosis gene. On the basis of average scores, four out of 23 cystic fibrosis patients, six out of 22 heterozygotes, and three out of 16 controls were misclassified. However, the mean scores for the cystic fibrosis and heterozygote groups were significantly different to that for the control group. It is concluded that isoelectric focusing is insufficiently reliable to be used for diagnosis or heterozygote detection in cystic fibrosis, but that it does provide evidence for the presence of a protein associated with the mutant gene.

Blood Proteins↗
PubMed1982

Monoclonal antibodies to human alpha-foetoprotein: analysis of the behaviour of three different antibodies.

Three mouse monoclonal antibodies directed to different epitopes on human alpha-foetoprotein have been produced. Two are of IgG1 subclass and the third is IgA. The polyethylene glycol-dependent immunoprecipitation system, designed for conventional antisera, had to be adapted before reproducible results could be obtained with the reagents. In this adapted system, as well as in a radioimmunoassay using solid-phase second antibody, a mixture of the 3 monoclonal antibodies exhibits cooperativity. However, the sensitivity of the radioimmunoassay with pooled monoclonals is not good as that of conventional antiserum. Low affinity monoclonal antibodies have been used for immunopurification of the antigen, whilst the high affinity one is useful for antigen quantitation in a labelled antibody-dependent system which requires absolute antibody specificity.

Animals↗
PubMed1982

Monoclonal antibodies for use in an immunoradiometric assay for alpha-foetoprotein.

The advantages offered by a mouse IgG1 monoclonal antibody to human alpha-foetoprotein (AFP) for the preparation of [125I]antibody for use in an immunoradiometric assay (IRMA) have been investigated. The antibody was isolated from ascites fluid by sodium sulphate precipitation followed by gel filtration on Sephadex G-200. The freeze-dried powder and solutions thereof were stable and were used for iodination to 1 atom 125I/molecule antibody by the chloramine-T procedure. At high antigen concentrations 70-80% of the added [125I]Ab was present in the sandwich. Linear response curves in the range 1-100 micrograms antigen/l incubate were obtained when [125I]Ab was in slight excess. In this region an Ag : Ab ratio of 1.9 : 1 was obtained which is consistent with the saturation of a bifunctional antibody. Although non-specific binding (in the absence of antigen) was consistently less than 0.1% of added [125I]Ab, this was the main factor in determining assay detection limits. The serum AFP levels from both non-pregnant and pregnant subjects as measured by the IRMA using the [125I]monoclonal Ab and by radioimmunoassay (RIA) using a sheep antiserum to AFP were in excellent agreement. The IRMA was manipulatively simple, employed a shorter incubation time (2 h), required shorter counting times than the RIA and gave a much wider working range. The provision of a monoclonal antibody for labelling removes the one major practicability barrier which otherwise limits the development and use of the potentially superior IRMA system.

Animals↗
PubMed1982

Quantitative immunoassays for diagnosis and carrier detection in cystic fibrosis.

Quantitative immunoprecipitation and immunoradiometric assays have been developed for a protein present in the serum of cystic fibrosis homozygotes, and to a lesser extent in the serum of heterozygotes. When tested on a panel of sera from 14 cystic fibrosis patients, 29 heterozygotes and 23 controls, the immunoprecipitation assay allowed correct assignments to be made on 94% of occasions with one batch of antiserum and 95% with another. With the same panel of sera, the immunoradiometric assay allowed 94% correct assignments. It is suggested that such accuracy is the maximum that can be expected in the present state of knowledge of cystic fibrosis.

Blood Proteins↗
PubMed1982

Maternal plasma alpha-fetoprotein and low birthweight: a prospective study throughout pregnancy.

Maternal plasma alpha-fetoprotein (AFP) was measured serially between 15 weeks gestation and term in 520 patients. Thirty-seven of these women were delivered of normal singleton infants with birthweights less than 2.5 kg. The median plasma AFP values in this group of women were highest between 15 and 20 weeks gestation and then declined steadily towards term. It is concluded that the use of maternal plasma or serum AFP in the early detection of low birthweight babies is optimal in the period most suitable for screening for fetal neural tube defects.

Female↗