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Biomedical subjects

A Cao

Publications and source records attributed to A Cao.

At least 199 records · Page 11Linked to original sources
PubMed1989

Prenatal diagnosis of beta thalassaemia based on restriction endonuclease analysis of amplified fetal DNA.

In the Mediterranean area, 50% of the beta thalassaemia mutations abolish or create a restriction endonuclease site in the beta globin gene. This study describes a new procedure for prenatal detection of these beta thalassaemia defects based on the direct visualisation, on an ethidium bromide stained polyacrylamide gel, of the discrete DNA fragments produced by restriction endonuclease digestion of fetal DNA, enzymatically amplified using the DNA polymerase from the thermophilus bacterium Thermus aquaticus. We applied this procedure to the Sardinian population to detect the nonsense mutation at codon 39 and the frameshift at codon 6 of the beta globin gene; these are the most frequent beta thalassaemia mutations in this population, accounting for 95% and 2.2% of the beta thalassaemia chromosomes. The main advantages of this procedure are simplicity (no radioactivity), sensitivity (0.2 microgram of DNA), and rapidity (12 hours). The very small amount of fetal material required makes amniotic fluid cell culture unnecessary and may decrease the fetal loss rate associated with trophoblast sampling. By circumventing the use of radioactive and non-radioactive probes, the spread of this technology to the high risk areas will be facilitated.

Amniocentesis↗
PubMed1989

Interaction between deletion delta-thalassemia and beta zero-thalassemia (codon 39 nonsense mutation) in a Sardinian family.

This paper describes individuals of Sardinian descent with heterozygous normal-Hb A2 beta-thalassemia who have a chromosome with a 7.2 Kb deletion in the psi beta/delta globin intergenic region and a chromosome with the codon 39 nonsense mutation. The propositus has the typical thalassemia-like red cell indices with a relatively high Hb level (13.4 g/dl) for a beta-thalassemia carrier, indicating a normal function of the beta-globin gene in cis to the 7.2 Kb deletion. The deletion starts between the psi beta and delta genes and ends in the IVS-2 of the delta-gene. His breakpoints are identical to a previously described deletion detected in the homozygous state in a patient with thalassemia intermedia, homozygous for G-greater than A mutation at position 5 of IVS-1. Because the mutation herein described silences the delta-globin gene and leaves intact the function of the in cis beta-globin gene we propose the definition of deletion delta zero-thalassemia.

Chromosome Deletion↗
PubMed1989

The prevention of thalassemia in Sardinia.

In this paper we review the characteristics and effectiveness of a program aimed at preventing homozygous beta-thalassemia in the Sardinian population. The target population for screening were couples at marriage, conception or early pregnancy. Awareness of the problem and the involvement of the population were achieved via the mass media or by personal approaches through lectures or discussions. Parents' Associations were consulted and have made themselves available to prospective couples in several critical areas. Education on thalassemias was introduced into the school curriculum. Counseling was based on private interviews at which the several options available were discussed with the individual carrier or the couples. Prenatal diagnosis was chosen by the large majority of couples counseled. The introduction of 1st trimester diagnosis resulted in a striking increase of the acceptance rate from 93.2 to 99.1%. Prenatal diagnosis was carried out initially by fetal blood analysis and thereafter by trophoblast or amniocyte DNA analysis. Direct detection of the mutation by oligonucleotide hybridization on agarose gel separated DNA fragments or by dot-blot analysis with allelic specific oligonucleotide probes on enzymatically amplified DNA was used. This program resulted in a decline in thalassemia major births of 90%. The reasons for residual cases were mostly lack of information and, less frequently, misdiagnoses or refusal of fetal diagnosis.

Adult↗
PubMed1989

Molecular pathology and detection of beta-thalassemias.

In this review, we have described the molecular bases accounting for beta, delta beta and gamma delta beta-thalassemias, discussed the molecular mechanisms responsible for the production of mild forms of thalassemia and presented a strategy for detecting beta-thalassemia mutations in each at risk population. The molecular bases of beta-thalassemia are very heterogeneous. The great majority of beta-thalassemias are caused by point mutations affecting the coding region or critical areas of the beta-globin gene and are only rarely produced by gross gene rearrangements. By contrast delta beta and gamma delta beta-thalassemias most commonly result from gross gene deletion. Determinants recognized to date as able to produce mild forms of beta-thalassemias, are beta-thalassemia mutations with a high residual output of beta-globin chain production, coinheritance of alpha-thalassemia or nondeletion HPFH linked or not linked to the beta-globin gene cluster, delta beta thalassemias and specific beta-globin haplotype. Because in each population a restricted number of molecular defect occurs, strategies have been developed to detect the beta-thalassemia mutations in prospective parents in each at risk population. These strategies are based on the direct detection of the mutation by dot blot analysis on enzymatically amplified DNA using a limited number of oligonucleotide probes complementary to the most common mutations in each population.

Alleles↗
PubMed1988

Interaction of heterozygous beta zero-thalassemia with single functional alpha-globin gene.

In this study, we analyzed the phenotypic manifestations resulting from the interaction of heterozygous beta zero-thalassemia(beta zero-39 nonsense mutation) with the functional loss of three alpha-globin structural genes in six subjects, of whom four had the [-alpha/--]alpha-globin genotype and two the [--/alpha Th alpha] alpha-globin genotype. The beta-thalassemia defect was in all cases the nonsense mutation at codon 39. The nondeletion alpha-thalassemia alpha th was the initiation codon mutation (AUG----GUG) of the alpha-2 gene. In all these subjects hypochromia and microcytosis were more marked than in beta zero-thalassemia heterozygotes with a full complement of four alpha-globin genes. All but one had moderate anemia. The alpha:beta globin chain synthesis ratios were consistently decreased. No cases had Hb H on electrophoresis. Subjects with [--/alpha Th alpha] alpha-globin genotype had more severe thalassemia-like manifestations than those with [--/-alpha] alpha-globin genotype.

Adolescent↗
PubMed1988

Problems in prenatal diagnosis of beta-thalassaemia by fetal blood analysis: beta-chain variant comigrating with gamma chains.

This report describes a couple at risk for beta-thalassaemia in which one spouse was heterozygous for classical high Hb A2 beta-thalassaemia while the other had the compound heterozygous state for beta+-thalassaemia and a beta-chain variant. This variant comigrates on carboxymethyl-cellulose columns (CMC) with gamma-chains, indicating that globin separation on CMC columns could not have been used for fetal diagnosis. The beta-chain variant migrates separately from the other globin chains on HPLC and the respective abnormal haemoglobin can be separated by isoelectrofocusing. Oligonucleotide hybridization showed that both parents were carriers of the beta+ IVS-1, nt 6 mutation. Prenatal diagnosis was successfully accomplished by oligonucleotide analysis on trophoblast DNA. This case indicates that an Antenatal Service should have alternative methods to CMC columns so as to carry out prenatal diagnosis of beta-thalassaemia in uncommon cases.

Blood Protein Electrophoresis↗
PubMed1988

Prenatal diagnosis of beta-thalassaemia by second-trimester chorionic villus sampling.

In this study we evaluated the feasibility of second-trimester transabdominal chorionic villus sampling for prenatal diagnosis of beta-thalassaemia in 80 pregnancies at risk presenting in the second trimester at the Antenatal Service. Sampling was carried out from 13 to 20 weeks and was successful in all cases. The amount of chorionic villi obtained varied from 10 to 40 mg, which was sufficient to make fetal diagnosis by oligonucleotide analysis within 10 days from sampling in all cases. No fetal losses occurred. From these results we conclude that transabdominal chorionic villus sampling is a useful procedure for prenatal diagnosis of beta-thalassaemia in those couples presenting after the first trimester.

Biopsy, Needle↗
PubMed1988

Beta-thalassemia mutations in the Portuguese population.

In this study we have carried out haplotype analysis on the beta-globin gene cluster and characterized the beta-thalassemia mutation by oligonucleotide hybridization in 14 patients with thalassemia major and 5 with sickle cell/beta-thalassemia originating from southern Portugal. We found that three mutations, namely the beta(0)-39, beta(0) IVS-1 nt 1 and beta(+) IVS-1 nt 110 are prevalent accounting for 53%, 32% and 10% of the beta-thalassemia chromosomes respectively. In general each mutation was associated with a specific chromosomal haplotype; the beta(0)-39 mutation, however, was linked to three different haplotypes. These results indicate that three oligo-probes complementary to the most common mutations allow prenatal diagnosis by oligonucleotide analysis in 96% of the couples at risk of having offspring with thalassemia major in southern Portugal.

Genotype↗
PubMed1988

Human immunodeficiency virus infection in multi-transfused patients with thalassaemia major.

We investigated the incidence, clinical and immunological characteristics of human immuno-deficiency virus (HIV) infection in a group of multi-transfused patients with thalassaemia major who were exposed to transfusion-associated HIV infection. Seropositivity to HIV by Western blot and immunofluorescence analysis was detected in 26 out of 590 patients. At a follow up 21-40 months later, none of these seropositive patients had developed acquired immuno-deficiency syndrome (AIDS), and six manifested the AIDS related complex (ARC). ARC was unusually mild and consisted of moderate laterocervical and submandibular lymph node enlargement associated with hypergammaglobulinaemia and a reduced CD4/CD8 ratio resulting from the decreased number of CD4 lymphocytes. These findings suggest that multi-transfused patients with thalassaemia major are relatively resistant to the development of severe manifestations of HIV infection, presumably because their immune status is relatively better preserved than that of other infected populations. Longer follow up is, however, necessary to determine whether the incidence of AIDS will be lower in this population or whether overt AIDS merely takes longer to develop.

AIDS-Related Complex↗
PubMed1988

Effect of ethanol on dimyristoylphosphatidylcholine large unilamellar vesicles investigated by quasi-elastic light scattering and vibrational spectroscopy.

The gel-like liquid phase transition of dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles prepared by reverse phase evaporation has been investigated in buffers containing ethanol by quasi-elastic light scattering (QLS) and vibrational (infrared and Raman) spectroscopy. With the QLS technique, the relative change in the vesicles area (which is related to the molecular cross-sectional area of lipid molecules) was followed versus both temperature and ethanol concentration. When the latter was low, the depression of the transition point was a linear function of the alcohol concentration, c, but the vesicles area was practically unmodified. At alcohol concentration 10% v/v, an abrupt change of the vesicles area was observed and for c greater than 10% the depression of the transition point was a non-linear function of c. The infrared and Raman spectra showed a perturbation of the hydrophobic regions, including the terminal methyl groups of the acyl tails.

Chemical Phenomena↗
PubMed1988

Pitfalls in genetic counselling for beta-thalassemia: an individual with 4 different thalassemia mutations.

This paper describes a complex combination of four thalassemia genes (delta(+), beta(0), nondeletion and deletion alpha-thalassemia) in the spouse of a typical high Hb A2 beta-thalassemia carrier presenting for genetic counselling. This complex gene combination resulted in a hematological phenotype, characterized by thalassemia-like red cell indices, normal Hb A2 and Hb F levels and slightly reduced alpha/beta globin chain synthesis ratio, and therefore not indicative for the presence of beta-thalassemia trait. Family studies in combination with alpha-globin gene mapping, haplotype analysis at the beta-globin gene cluster and definition of the beta-thalassemia mutation by oligonucleotide hybridization led us to identify a beta-thalassemia mutation, to define the molecular basis for this phenotype and give the appropriate genetic counselling.

Female↗
PubMed1988

Depletion of trace elements and acute ocular toxicity induced by desferrioxamine in patients with thalassaemia.

High doses of intravenous desferrioxamine infused over a short period of time induce a large faecal and urinary iron excretion but also produce retinal abnormalities that are characterised by decreased amplitude on electroretinography and defective dark adaptation. This regimen also results in high faecal iron, zinc, and copper excretion, and reduced granulocyte zinc concentrations and alkaline phosphatase activity. The retinal abnormalities may be related to the zinc and copper deficiency and/or iron depletion 'per se' which interferes negatively with critical iron dependent enzymes.

Adolescent↗
PubMed1988

Prenatal diagnosis of beta thalassaemia by oligonucleotide analysis in Mediterranean populations.

We have used four oligonucleotide probes and two restriction enzymes to detect the beta thalassaemia mutation in a group of 61 couples of Italian descent who were prospective parents. We have been able to define the beta thalassaemia mutation in both parents in 47 couples and in only one parent in 12 couples. Prenatal diagnosis was accomplished successfully either by amniocyte (two) or trophoblast (26) DNA analysis in 28 couples in which the pregnancy was in progress. These results indicate that direct identification of the mutation by oligonucleotide or restriction endonuclease analysis is a practical and useful method for prenatal diagnosis of beta thalassaemia in childless couples.

Amniocentesis↗
PubMed1988

Beta thalassaemia mutations in Turkish Cypriots.

Using oligonucleotide hybridisation or restriction endonuclease analysis, we have characterised the molecular defect in 94 patients with thalassaemia major and four with thalassaemia intermedia of Turkish Cypriot descent. We found that four mutations, namely beta+ IVS-1 nt 110, beta zero IVS-1 nt, beta+ IVS-1 nt 6, and beta+ IVS-2 nt 745 were prevalent, accounting for 69.9%, 11.7%, 8.7%, and 5.6% respectively of the beta thalassaemia chromosomes. This information may help in the organisation of a large scale prevention programme based on fetal diagnosis of beta thalassaemia by DNA analysis in the Turkish population.

Cyprus↗