PubMed Health⌕ Search

Biomedical subjects

R Colah

Publications and source records attributed to R Colah.

18 recordsLinked to original sources
PubMed2005

Three novel polymorphisms in the beta globin gene.

We report on three novel polymorphisms in and around the beta globin gene. Two of them are intronic (IVS2) polymorphisms (IVS 2 nt 200-203 (-CTTT) and IVS2 82-83 (-AG)). The third is a novel G-->C substitution at nt +1707 related to the beta globin cap site. This +1707 G-->C polymorphism was detected in 23.5% of chromosomes among 140 samples from India. It seems to be a novel but common polymorphism among Indians. There was no linkage between these novel polymorphisms and any beta thalassemia mutation.

Adult↗
PubMed2004

An interplay of alleviating mutations in the clinical phenotype of beta-thalassaemia intermedia.

Prediction of a beta-thalassaemia major phenotype from the beta-genotype is generally relatively straightforward. However, despite the ability to accurately define the beta-thalassaemia mutations, prediction of a beta-thalassaemia intermedia phenotype from the genotype sometimes remains problematic and this has important implications in genetic counselling and prenatal diagnosis. We report a 11-year-old Indian male child with a thalassaemia intermedia phenotype. beta-Globin gene analysis of the family showed that he was a compound heterozygote with the -88 (C-->T) beta+-mutation and the IVS1 nt 130 (G-->C) beta0-mutation. Both these mutations are rare among Indians. The propositus was also found to be heterozygous for the XmnI polymorphism and had a normal alpha-genotype. In this family interplay of two alleviating mutations (a milder promoter mutation along with a gene for raised HbF) might have synergistically compensated for lack of globin chains in the patient. Hence, the nature of the beta-genotype as well as the knowledge of the presence or absence of alleviating factors will help the clinician to decide whether early commencement of a regular transfusion regime is necessary.

Child↗
PubMed2001

Molecular pathogenesis and clinical variability of beta-thalassemia syndromes among Indians.

Sixty-four homozygous beta-thalassemia patients comprising 40 patients with beta-thalassemia major and 24 patients with beta-thalassemia intermedia were investigated for the nature of their beta-thalassemia mutations, associated alpha-thalassemia, and XmnI polymorphism in the gamma gene which are known to affect the clinical course of the disease. This study was undertaken to look for the contribution of these associated factors in reducing the clinical severity of homozygous beta-thalassemia from a severe disease to a beta-thalassemia intermedia phenotype. Clinical severity of these patients was assessed by the degree of transfusion dependency and the age at which the patient presented with symptoms. Globin chain synthetic ratio was taken as the biochemical pointer of severity of the disease. Eleven different beta-thalassemia mutations were encountered among 128 beta-thalassemia chromosomes. It was observed that the nature of the beta-thalassemia mutations was not very different between the beta-thalassemia major and beta-thalassemia intermedia groups in our patients, but co-inheritance of one or more alpha-globin gene deletions (-alpha(3.7)) and the presence of the XmnI polymorphism were associated with lesser severity of the disease in Indians.

Adolescent↗
PubMed1999

Variable clinical severity of Hb E beta-thalassemia among Indians.

OBJECTIVE: The aim of this preliminary report was to look at the effect of genetic variations in the alpha, beta and gamma globin genes in 7 cases of hemoglobin E/beta-thalassemia with diverse clinical expression of the disease. METHODS: beta-thalassemia mutations were characterized by PCR and dot blot hybridization. G gamma gene polymorphism (Xmnl) was determined by PCR followed by restriction enzyme digestion and polyacrylamide gel electrophoresis. alpha genotyping was done by Southern blot hybridization. RESULTS: Six cases had a severe beta+ mutation [IVS 1 nt 5 (G-->C)] and one case had a beta zero mutation [F/S 41/42 (-CTTT)]. Hence, the beta-thalassemia mutation does not seem to contribute towards the clinical diversity. alpha-genotyping showed a single alpha-gene deletion of the rightward type in three of the five milder cases. The -158 G gamma (C-->T) substitution was present at least in heterozygous state (+/-) in all the milder cases. CONCLUSIONS: Deletional alpha thalassemia and presence of the -158 G gamma (C->T) substitution are the two factors which appear to be more important in decreasing the severity of the disease rather than the nature of the beta thalassemia mutation.

Adolescent↗
PubMed1998

The influence of alpha-thalassaemia on the haematological & clinical expression of sickle cell disease in western India.

We evaluated the clinical and haematological features of 29 sickle cell anaemia patients with associated alpha-thalassaemia and 22 sickle cell homozygotes with a normal alpha-globin genotype from western India. The presence of alpha-thalassaemia resulted in significantly higher haemoglobin (Hb), haematocrit (HCT), red blood cells counts (RBC) and haemoglobin A2 (HbA2) levels but lower mean cell haemoglobin (MCH) and mean cell volume (MCV). The clinical presentation in these patients was also milder with fewer episodes of painful crisis, chest syndromes, infections, requirement of hospitalization and blood transfusions. However, splenomegaly was more common as compared to the patients with a normal alpha-globin genotype. It is evident from the present study that alpha-thalassaemia could be an important genetic factor modulating the clinical expression and haematological severity of sickle cell anaemia in this region.

Adolescent↗
PubMed1998

Trimodal distribution of HbS levels in sickle heterozygotes--an useful predictor of the alpha-genotype for population screening.

The trimodal distribution of HbS levels in sickle heterozygotes has been used as an indirect approach to determine the prevalence of alpha-thalassaemia in different population groups. We used this approach to predict the alpha-genotypes of 124 sickle cell heterozygotes where the HbS concentration varied from 20 to 46 per cent with antimodes at 28.0 and 33.0. The alpha-genotypes in these individuals were also determined by Southern blot hybridization. We predicted homozygous (-alpha/-alpha) or heterozygous (-alpha/alpha alpha) alpha-thalassaemia-2 in 78 subjects by the trimodal distribution of HbS. However, actual genotyping showed that 75 patients had alpha-thalassaemia. Forty six of the 47 subjects with a normal alpha-globin genotype (alpha alpha/alpha alpha) could be predicted indirectly. The overall sensitivity was 100 per cent and specificity was 94.2 per cent with a positive predictive value of 96.2 per cent and negative predictive value of 100 per cent. As alpha-genotyping is very expensive and not feasible in most laboratories in India, we conclude that the trimodal distribution of HbS levels is a suitable method for screening for alpha-thalassaemia in population studies.

Adolescent↗
PubMed1997

Factor VIII and IX gene polymorphisms and carrier analysis in Indian population.

The efficacy of the three common intra- and extragenic polymorphic sites of the factor VIII and IX genes has been examined in the Indian population, with an aim to develop a strategy that would be accurate and informative, yet economical. The approach for hemophilia A carrier detection includes tests for BclI, XbaI, and TaqI polymorphic sites for introns 18 and 22 and the extragenic locus St 14, respectively, whereas for hemophilia B, tests include detection of TaqI, DdeI, and HhaI polymorphic sites for introns 4 and 1, and the 3' flanking region of the factor IX gene, respectively. In hemophilia A, the cumulative efficiency of these three polymorphisms has been found to be 100%, since all 37 tested families were informative for at least one of these three polymorphisms. It is of interest to note that a case of recombination between St 14 and the factor VIII gene was also observed. Of the 47 unrelated X chromosomes examined (normal = 10, factor VIII:C deficiency = 37), heterozygosity for BclI, XbaI, and St 14 was found to be 47%, 36%, and 86%, respectively, in the factor VIII gene. However, when 37 unrelated X chromosomes (normal = 10, factor IX:C = 27) were analyzed for polymorphism with TaqI, DdeI, and HhaI, it was found that the polymorphism detection rate was only 18% for the TaqI site but 45% each for the DdeI and HhaI sites, in the factor IX gene. This indicates a low effectiveness of the TaqI restriction site in carrier analysis of hemophilia B families in our population.

Alleles↗
PubMed1995

Clinical heterogeneity of silent-gene b-thalassemia among Indians.

This paper describes six Indian families in which silent-gene beta-thalassemia was encountered by us in the past 2 years. This stresses the importance of globin-chain synthesis in the diagnosis of beta-thalassemia. Of these six cases, five were diagnosed retrospectively when they had a homozygous beta-thalassemia offspring. The beta/alpha synthetic ratios ranged from 0.45 to 0.60. Four belong to group-I silent beta-thalassemia and two cases to group II. The severity of thalassemia major in the offspring of these silent carriers cannot be predicted.

Adult↗
PubMed1992

Characterization of G6PD Rohini--a new class III Indian variant.

A new Indian G6PD variant was detected in a 15 yr old Maratha male during a population screening programme in high school children in Bombay (India). The propositus and two family members having the same variant were apparently healthy. This enzyme variant has a mild erythrocyte G6PD deficiency and a slow electrophoretic mobility. It is characterized by a high Michaelis-Menton constant for G6P, a bimodal curve for pH optima and a slight decrease in the thermostability. The rate of utilization of substrate analogue is similar to that of normal. These observations suggest identification of a new class III variant, designated as G6PD Rohini.

Adolescent↗
PubMedDate not supplied

Beta-thalassemias: expression, molecular mechanisms and mutations in Indians.

The beta-thalassemias are a heterogenous group of inherited disorders of hemoglobin (Hb) synthesis characterized by a reduction (beta+) or absence (beta zero) of synthesis of the beta globin chains of Hb, resulting in an imbalanced chain synthesis. To understand their expression and molecular basis in Indians, it is essential to review briefly the genetic control of normal Hb production and the structure, organization and regulation of different globin genes. The Indian beta-thalassemia mutations and strategies for prevention are described.

Child↗
PubMedDate not supplied

Is cellulose acetate electrophoresis a suitable technique for detection of Hb Bart's at birth?

Symptomatic alpha-thalassemia (alpha-thal) as found in South-East Asia is uncommon in India. However, the presence of Hb Bart's in cord blood samples has been reported from different parts of India and the prevalence of alpha-thal has ranged from 0.5 to 18% by different electrophoretic techniques. The methodology utilised has ranged from paper electrophoresis to isoelectric focussing (IEF). We screened 798 cord bloods for the presence of Hb Bart's by cellulose acetate electrophoresis and found a prevalence rate of alpha-thal of 15.3% in a heterogenous population in Bombay. A comparison of four different electrophoretic techniques for detection of Hb Bart's in 138 neonates showed that cellulose acetate and starch gel electrophoresis were by and large comparable and only a little less sensitive than IEF. Paper electrophoresis used at many centers in India was most insensitive. As alpha-genotyping is not possible at most centers in the country, it is suggested that a simple cellulose acetate electrophoresis would be the method of choice for screening neonates for alpha-thal in India. As a part of our follow-up study, alpha-genotyping was done by Southern blot hybridization in 24 cases who had shown variable levels of Hb Bart's at birth. The rightward deletion (-alpha3.7/) either in a heterozygous or homozygous condition was the only gene defect encountered in this preliminary study. However, 7 of 24 cases (29.17%) showed no correlation between Hb Bart's level and alpha-genotypes.

Electrophoresis↗
PubMedDate not supplied

Prenatal diagnosis of haemophilia: a preliminary report.

BACKGROUND: Haemophilia A is the most common congenital bleeding disorder seen in man, affecting one in 5000 to 10,000 males. Because of the large size and heterogeneity of mutations in the factor VIII gene, direct detection of mutations is not practically feasible, except the recently detected intron 22 inversions. Hence, the indirect method of gene tracking using various polymorphic markers is the method of choice. Using this approach, we have performed antenatal diagnosis in four haemophilia A families. METHODS: The four families included 21 subjects who were used for gene-tracking analysis. Two families had a positive history with more than one member affected, while the remaining two families had a negative history with only one affected son. In all four families, the propositi and their affected relatives had severe haemophilia A with factor VIII:C less than 1%. All were negative for inhibitors. The polymorphic markers used were IVS 18 Bcl I, IVS 19 Hind III and the extragenic DXS 52 St 14 of the factor VIII gene. Prior to polymorphism analysis, the sex of the foetus was determined using Y chromosome-specific primers. All the analyses were carried out by polymerase chain reaction. RESULTS: Antenatal diagnosis in the four families showed three normal male foetuses and one normal female foetus. Two families provided evidence with only IVS 18 Bcl I and St 14 markers. One family provided information with only intron 19 Hind III marker. The fourth family provided information with all three markers. The coagulation parameters were almost in agreement with the results of DNA analysis. CONCLUSION: All three polymorphic markers yielded information. This suggests that these three markers can be effectively used in the antenatal diagnosis of haemophilia A in Indian families.

Chorionic Villi Sampling↗
PubMedDate not supplied

Assessment of transcervical chorion villus aspiration biopsy in early pregnancy.

BACKGROUND: Chorionic villus sampling for prenatal diagnosis is a relatively new technique and variable success rates have been reported by different authors depending on the methods and instruments used. We describe our experience with chorionic villus sampling in Bombay. METHODS: The procedure was attempted on 62 women before termination of their pregnancy via the transcervical route, under constant real-time ultrasound guidance. A metallic cannula was negotiated through the cervix into the uterine cavity to reach the chorionic frondosum and chorionic villi were aspirated by creating a negative pressure in the syringe attached to the cannula. The villus tissue was checked under a dissecting microscope. We calculated the success rate for obtaining a sample depending on the site of the chorionic frondosum, the physique of the mother, the position of the uterus and the size of the cannula. RESULTS: Villus tissue was aspirated in 47 of the 62 cases. The success rates of sampling at the first and second attempts were 48% and 27% respectively. The factors which were associated with a higher success rate were when the chorionic frondosum was situated posteriorly rather than anteriorly (61% v. 48%; p < 0.01), when the patient was thin rather than fat (58% v. 25%; p < 0.001), when the uterus was anteverted rather than retroverted (53% v. 41%). The commonest complication was bleeding which occurred in 15% of patients. CONCLUSION: Transcervical chorionic villus sampling is associated with a high success rate except in fat women with a retroverted uterus and in those with the chorionic frondosum situated in the fundus.

Abortion, Induced↗