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Biomedical subjects

B Modell

Publications and source records attributed to B Modell.

At least 73 records · Page 4Linked to original sources
PubMed1988

The frequency of consanguineous marriage among British Pakistanis.

An enquiry answered by 100 randomly selected British Pakistani mothers in the postnatal wards of two hospitals in West Yorkshire showed that 55 were married to their first cousins, while in only 33 cases had their mother been married to her first cousin. This suggests an increasing rate of consanguineous marriage in this relatively small group, by contrast with the decreasing rate observed in some other countries. The genetic implications merit further study.

Consanguinity↗
PubMed1988

Distribution and control of some genetic disorders.

The health burden of genetic disorders varies between ethnic groups within the same country or between countries to a large extent because of genotypic differences at the population level. Genetic services should recognize this variability in need and be developed within the traditional context of medical care. All practical approaches require a sound epidemiological basis and underline the importance of early diagnosis for both prevention and treatment. Effective control is now possible for some Mendelian conditions and some congenital malformations and should be incorporated into general health care. The development of genetic services within any country depends on the optimal utilization of available resources, both financial and intellectual.

Chromosome Aberrations↗
PubMed1987

Two unusual cases of first trimester prenatal diagnosis of cystic fibrosis using DNA probes.

There are now several DNA probes which localize the cystic fibrosis mutation (CF) to chromosome 7q2.2-q3.1. The most tightly linked probes, pJ3.11 and met, are useful for first trimester prenatal diagnosis for many families provided that there is at least one living child affected by CF (Farrall et al., 1986). We describe here two families seeking prenatal diagnosis for CF which present unusual counselling problems. The first is an extended family in which there is no living affected member with CF; the second, a consanguinous marriage at risk both for cystic fibrosis and beta-thalassaemia. In both cases first trimester chorionic villus sampling and DNA haplotype analysis predicted that the fetus is a carrier for CF, and in the doubly affected family a carrier for beta-thalassaemia as well. Both pregnancies resulted in live births and subsequent immunoreactive trypsin estimations were both in the normal range.

Chorionic Villi↗
PubMed1987

Association of thalassaemia intermedia with a beta-globin gene haplotype.

We have identified 14 Asian patients with homozygous beta zero thalassaemia who had a mild clinical disorder related to an augmented production of haemoglobin F. None of their parents had an elevated level of Hb F. Restriction fragment length polymorphism analysis of the beta-globin cluster of these patients and a control group of Asian thalassaemia major patients showed that 6/14 of the thalassaemia intermedia patients were homozygous for a particular 5' beta-globin haplotype (-+-++), in contrast to 1/42 of the thalassaemia major patients. Furthermore, the -+-++ beta haplotype is also associated with amelioration of disease severity in beta thalassaemia in an Italian population. This beta haplotype is linked to a DNA sequence variation 5' (at position -158) to the G gamma globin gene which can be detected by the presence (+) of an Xmn I restriction enzyme site. The possible role of the Xmn I-gamma polymorphism in relation to this variant HPFH is discussed. We conclude that much of the observed clinical variability of beta thalassaemia can now be explained by the inheritance of beta thalassaemia chromosomes with different propensities for fetal haemoglobin production.

Adolescent↗
PubMed1987

Human fetal lymphocytes require T cell growth factors for cytotoxic responses.

Lymphocytes isolated from the blood of 17 human fetuses, varying in gestational age between 16 and 26 weeks, were tested for their capacity to generate specific cytotoxic cells after mixed lymphocyte culture (MLC) with allogeneic cells in the presence or absence of exogenous T cell growth factor (TCGF). Blood cells from seven fetuses, distributed throughout the age range, failed to generate cytotoxic cells even when TCGF was added in MLC, whereas six others gave positive responses but only when exogenous TCGF was present during the sensitisation phase. The maturation induced in the latter was not caused solely by a direct, non-specific effect of the TCGF, for control responder cells incubated with TCGF in the absence of allogeneic stimulator cells always responded less strongly or not at all. Fetal blood lymphocytes from the remaining four fetuses gave significant cytotoxic responses that were not augmented by TCGF. It is concluded that there can be a clear dichotomy between proliferative and cytotoxic responses to alloantigens and that the inability of human fetal blood lymphocytes to mount cytotoxic responses at this stage of development might be due to deficiencies in helper cells, cytotoxic precursors or both. For three fetuses it was possible to study, additionally, cytotoxic responses of spleen, liver and thymus with and without TCGF. None of them made specific responses even when TCGF was added, though cells from two spleens and one thymus responded directly to TCGF. To ascertain whether the absence of cytotoxic responses might have been caused by a failure of blood, spleen, thymus or liver cells to proliferate, their mixed lymphocyte reactivity, as detected by the uptake of 3H-thymidine, was studied without exogenous TCGF. Whereas thymus cells from only one of five fetuses responded, cells from all other tissues (including blood) responded consistently.

Adult↗
PubMed1986

First-trimester fetal diagnosis for haemoglobinopathies: report on 200 cases.

First-trimester prenatal diagnosis by DNA analysis was found to be possible in 224 (80%) of 281 families at risk of having a child with beta-thalassaemia major. 200 prenatal diagnoses, mainly for beta-thalassaemia or sickle-cell anaemia, were made by means of chorionic villus sampling and fetal DNA analysis. The overall fetal loss rate was 6.7%, the majority being in the first half of the programme. There was one misdiagnosis. Prenatal diagnosis was also carried out successfully for both pairs of twins in two pregnancies. Comparison of these results with 53 prenatal diagnoses made with DNA prepared from amniotic fluid suggests that the first-trimester procedure is more reliable. If further experience confirms that chorionic villus sampling has an acceptably low risk for both mother and fetus it will largely replace other methods for prenatal diagnosis of the haemoglobin disorders and other single-gene conditions.

Amniotic Fluid↗
PubMed1986

Meiotic recombination between two polymorphic restriction sites within the beta globin gene cluster.

Analysis of beta globin gene haplotypes for prenatal diagnosis of beta thalassaemia has revealed a recombination event within the beta globin gene cluster. Both a change in the AvaII polymorphic site within the beta globin gene and a change in the phenotype of the beta globin gene were observed. Paternity was established by the pedigree analysis of hypervariable 'minisatellite' DNA polymorphisms and the most probable explanation of the recombination event is a crossover between the psi beta globin gene and the beta globin gene. The data provide direct evidence in support of a DNA region 3' to the beta globin gene with a recombination frequency much higher than expected, and have important implications for the prenatal diagnosis of beta thalassaemia by linked restriction fragment length polymorphisms.

Alleles↗
PubMed1985

Diagnostic fetal blood sampling for the haemoglobinopathies--10-year experience.

The development of methods for fetal blood sampling in the second trimester of pregnancy offers the possibility of fetal diagnosis for couples at risk for having children with a haemoglobinopathy. We review the evolution of 10 years' experience of fetal blood sampling for 681 patients. The obstetric risk associated with the procedure has fallen from an initial 15% (in the first 87 pregnancies) to about 3%, in parallel with increased experience, improved ultrasound control, identification of the causes of complications and implementation of simple steps to avert them.

Diseases in Twins↗
PubMed1984

Effect of fetal diagnostic testing on birth-rate of thalassaemia major in Britain.

A programme of prospective heterozygote detection and counselling, fetal diagnostic testing, and abortion of fetuses affected by thalassaemia major introduced in Britain in 1977 has proved highly acceptable to at-risk couples of Cypriot and East African Asian origin, but less so to couples of Pakistani origin. However, many at-risk couples are still not detected prospectively, the proportion of thalassaemia-major births prevented was only 32% by the end of 1981, and there is little evidence of a further fall since then. The thalassaemia-major birth-rate had fallen by 60% in Cypriots and by 20% in East African Asians, but it had not fallen at all in Pakistanis. Improved approaches to fetal diagnosis of thalassaemia major are becoming available, so a concerted effort is needed to inform all the at-risk ethnic groups of the existence of the problem and the possibility of detection of affected fetuses.

Africa, Eastern↗
PubMed1984

Population and genetic studies suggest a single origin for the Indian deletion beta thalassaemia.

In a study of beta thalassaemia in the Asian Indian immigrant populations in the U.K., 23 out of 125 beta-thalassaemic chromosomes (18%) were of the Indian deletion beta type (600 bp deletion involving the 3' end). The individuals with beta thalassaemia had originated from various parts of India and Pakistan. However, all those individuals with deletion beta thalassaemia were from Sind and the adjacent area of Gujarat. Analysis of restriction fragment length polymorphisms in the beta globin gene cluster showed that all the 23 deletion beta thalassaemia chromosomes had an identical haplotype. These findings suggest a single origin for the Indian deletion beta thalassaemia.

Chromosome Deletion↗
PubMed1984

Feasibility of antenatal diagnosis of beta thalassaemia by DNA polymorphisms in Asian Indian and Cypriot populations.

The feasibility of using restriction fragment length polymorphisms ( RFLPs ) for the antenatal diagnosis of beta thalassaemia in the U.K.-resident Cypriot and Asian Indian populations has been determined. Seven polymorphic restriction endonuclease sites in the beta globin gene cluster were analysed in 20 Cypriot and 42 Asian patients and their parents and the combination of polymorphic sites (haplotype) for each chromosome determined. It was found that 76% of the Asian and 35% of the Cypriot families had DNA polymorphisms which would allow antenatal diagnosis of a homozygous beta thalassaemic fetus, and that in the majority of the remaining families there was a 50% chance of a successful diagnosis of either a normal or a heterozygous fetus. These results indicate that RFLP analysis of fetal DNA is a useful method for antenatal diagnosis of beta thalassaemia in families with either a normal or homozygous beta thalassaemia child, especially in the Asian population in the U.K.

Child↗