PubMed Health⌕ Search

Biomedical subjects

R Krishnamoorthy

Publications and source records attributed to R Krishnamoorthy.

At least 163 records · Page 9Linked to original sources
PubMed1987

Expression of a beta thalassemia gene with abnormal splicing.

Expression of a cloned human beta thalassemia gene with a single base change at position 5 of IVS 1 has been analyzed 48 hours after transfer of the gene into HeLa cells (transient expression). Little or no normal beta globin mRNA accumulates in the presence of the abnormal beta gene in contrast to significantly more normal beta mRNA produced with other mutations at this same position. By contrast, large amounts of an abnormal beta globin mRNA are present; this is due to the use of a cryptic 5' splice site in exon 1 rather than the normal 5' splice site of IVS 1. The results indicate the variability of the effect on RNA splicing of different single base defects within IVS.

Base Sequence↗
PubMed1987

A novel approach to study of the structural basis of enzyme polymorphism. Analysis of carboxylesterase B of Escherichia coli as model.

In order to understand the structural basis of charge differences among enzyme variants without undertaking purification and sequencing of the protein, an original approach was developed. The approach is applicable to any enzyme or protein provided that there is a specific staining procedure. This consists, as a first step, in the projection of electrophoretically obtained mobility values versus pI of all variants into a two-dimensional profile. In a second step, starting from the most common variant, various theoretical possibilities of substitutions are envisaged, taking into consideration the pH of the electrophoretic conditions, pI of the variants and range of variations of the pK values of several amino acid side chains. In a third step, verification of the theoretical data is obtained through comparative protein titration curves by combined isoelectrofocusing-electrophoresis of several pairs of relevant variants. The validity of this approach is tested on the highly polymorphic carboxylesterase B enzyme of Escherichia coli and is found to provide valuable information.

Carboxylesterase↗
PubMed1987

The hematologic characteristics of sickle cell anemia bearing the Bantu haplotype: the relationship between G gamma and HbF level.

Previous work has demonstrated that the HbS gene has appeared and expanded three times in Africa in three separate geographic locations and that these three distinct mutational events can be identified by linked DNA polymorphic sites (haplotypes) surrounding the abnormal gene. We have reported that the Senegalese and Beninian haplotypes differ in G gamma expression, mean percentage of HbF, and percentage of dense cells. We now report on the third haplotype, the Bantu, and find that it has intermediate features, namely, the high mean percentage of HbF and low percentage of dense cells associated with the Senegalese haplotype, but with a low percentage of G gamma expression similar to the Beninian haplotype. The distribution of percent HbF is quite different from Senegal haplotype-bearing sickle cell anemia patients since it covers a much wider range. The low G gamma expression is also different from the Beninians since it contains a significant and unique cluster of individuals with lower than 38% G gamma. Interestingly, among the Bantu there is a strong correlation between HbF levels and G gamma expression, which is not seen with the other haplotypes. These findings open the possibility that among the Bantu haplotype-bearing individuals two chromosomal types exist that define different levels of G gamma and HbF expression. Further structural exploration of these two potential subhaplotypes is needed.

Anemia, Sickle Cell↗
PubMed1987

[Analysis of the recombination zone in hereditary persistence of fetal hemoglobin with fetal gene rearrangement of the G gamma-G gamma-A gamma type].

An increased synthesis of fetal hemoglobin in adult life is a common feature of the genetically determined severe disorders like beta thalassemia and sickle cell anemia. A continued synthesis of fetal hemoglobin in adults is also characteristic of clinical or subclinical syndromes like respectively delta beta thalassemia or hereditary persistence of fetal hemoglobin (HPFH). These disorders are highly heterogeneous with respect to their molecular defects as well as to the composition of Hb F. We report here a novel case of hereditary persistence of fetal hemoglobin in heterozygous state discovered by chance, in a young perfectly healthy french man. The gamma chain of his fetal hemoglobin was almost entirely composed of G gamma chains. Molecular analysis of the DNA revealed the existence of triplicated gamma genes on one chromosome with the genotype arrangement of G gamma-G gamma-A gamma. A polymorphic Xmn I restriction site (at position -158 5' to the cap site) was present in 5' of both of these G gamma genes. The presence of this site in front of G gamma gene had previously been shown to be associated both with high G gamma phenotype constitutively and also with high fetal hemoglobin level only in case of anemic stress. In the absence of any anemic stress in this individual, the constitutive increase of both fetal hemoglobin and G gamma chains could be due to the presence of a chromosome with triplicated arrangement of gamma genes. The classical triplication (G gamma-A gamma-G gamma-A gamma) does not result in HPFH phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Beta thalassemia due to a novel mutation in IVS 1 sequence donor site consensus sequence creating a restriction site.

During a systematic screening of Algerian thalassemics by determining the DNA polymorphism haplotypes in the beta globin gene cluster, a novel haplotype was identified. The DNA of a homozygous individual was cloned and sequenced. The mutation, a G----A change, at position 5 of the small intervening sequence, probably interferes with normal splicing events, and, moreover, creates a new Eco RV restriction site that provides a useful diagnostic tool for detecting this condition.

Base Sequence↗
PubMed1986

Differences in DNase I sensitivity and methylation within the human beta-globin gene domain and correlation with expression.

We have analysed the chromatin features of DNA regions encompassing human epsilon, G gamma, A gamma, delta and beta globin structural genes in fetal and adult erythroid cells on the one hand and adult lymphocytes on the other. Highly purified nuclei from these cells were submitted to DNase I digestion and the kinetic data were obtained from the percentage of residual hybridization of defined regions in Southern blots. Our results, as others have shown by different approaches, indicate that the structural genes of the beta-globin cluster are generally more sensitive to DNase I in the erythroid cells than in non-erythroid cells. Thus a domain of DNase I sensitivity related to the committed state is defined. In addition we show that within this DNase-I-sensitive beta cluster domain, individual genes of the cluster are arranged in subdomains of differential DNase I sensitivity, which correlate with their expression status. Furthermore the differential expression of the two fetal genes in the fetal stage is shown to be directly proportional to the degree of hypomethylation of these genes.

Adult↗
PubMed1986

Haplotype VI associated beta + thalassaemia intermedia. First Italian case.

We report the study of a family originating from eastern Sicily with mild beta thalassaemia intermedia which is similar both at a molecular level and in clinical form to that called "beta + thalassaemia intermedia-Portuguese type". Our patients were homozygous beta + thalassaemics with high HbA2 and low HbF levels. The mild clinical course was as a result of their age and because regular blood transfusion was established only in adulthood. All of the heterozygote parents were asymptomatic with a blood picture and haemoglobin pattern typical of beta thalassaemia. Studies at a molecular level revealed no abnormalities in the beta-like globin gene cluster and excluded the presence of a deletional form of alpha thalassaemia. Restriction enzyme site polymorphisms around the beta gene cluster showed that all patients were homozygous for the haplotype described as VI. Comparison of these homozygous haplotypes with the Portuguese ones revealed a clear difference in the polymorphic Pvu II site. In all Sicilian homozygous cases, this site was present on one chromosome and absent on the other. Therefore our hypothesis is that Portuguese beta + thalassaemia intermedia is different from the Sicilian type.

Adult↗
PubMed1984

A leftward deletional alpha+ thalassemia found in East Sicily in conjunction with heterozygous beta-thalassemia.

Two types of alpha+ thalassemia (-alpha l) have been described, respectively termed leftward and rightward, which correspond to nonhomologous crossing-over in different homology zones X and Z within the alpha-globin gene cluster. Up to now the leftward type has been described only in Asiatic populations, whereas the rightward type is universally distributed. We report here a first case of leftward deletion observed in a Sicilian male. This raises the question of an identical or not crossing-over event.

Aged↗
PubMed1983

Monosaccharides bound to hemoglobins in normal and diabetic individuals. Evidence for glucose, mannose and galactose as sugars released by methanolysis of the different hemoglobin components.

Direct evidence is given for the presence of glucose, mannose and galactose as the products of hydrolysis of hemoglobins A1a1, A1a2, A1b, A1c and A0. The presence of galactose cannot be explained by the earlier hypothesis of Amadori rearrangement and suggests the existence of further complex rearrangements. Monosaccharide content of the different hemoglobin components varies from 0.2-2.0 mol/mol of alpha beta dimer with an increase of 1.5-2.0-times in diabetic components. This increase is not accompanied by net charge differences, suggesting that additionally bound sugars are not responsible for the pI modification of these hemoglobins. The pattern of glucose, mannose and galactose ratio in normal individuals divides these hemoglobins into two classes, hemoglobins A1b, A1c and A0 (ratio 0.60:0.25:0.15) on one hand and hemoglobins A1a1 and A1a2 (ratio 0.40:0.40: 0.20) on the other. These findings suggest that diverse mechanisms for sugar binding might exist between these two classes of glycosylated hemoglobins. This difference disappears in diabetic components suggesting that the non-NH2-terminal sites are glycosylated in all components by a common mechanism. Increase in glucose at the expense of mannose and galactose, as observed in diabetics, could be an indicator of recent glycosylation.

Blood Glucose↗
PubMed1983

Characterization of weak alleles at the DIA1 locus (Mustapha 1, Mustapha 2, and Mustapha 3) in the Algerian population.

One percent of the Algerian population carries a weak allele at the DIA1 locus, responsible for a 50% decrease of red cell soluble cytochrome b5 reductase activity. Quantitative abnormalities of the soluble and the membrane-bound enzyme have been investigated in the red cells and in the leukocytes of seven subjects considered to be heterozygous at the DIA1 locus. Conventional electrophoretic or isoelectrophoretic studies did not show any qualitative abnormality. However, continuous titration obtained by combined IEF-electrophoresis displayed in five out of seven subjects a discrete abnormal line on the titration curve compatible with an Arg leads to His substitution. In fact, at least three types of weak alleles could be defined by combining the qualitative and quantitative results obtained with the erythrocyte (soluble and membrane-bound) and leukocyte enzyme. We call these subgroups DIA Mustapha1, DIA Mustapha2, and DIA Mustapha3.

Algeria↗
PubMed1983

Influence of thyroid status on hemoglobin A2 expression.

We studied the electrophoretic pattern of hemoglobin (Hb) and red blood cell indices in 128 women divided into four groups: group I, 36 nonanemic hyperthyroid women, divided in two subgroups: 36 with untreated hyperthyroidism (subgroup IA) and 9 made euthyroid by antithyroid drug therapy (subgroup IB); group II, 12 nonanemic women with untreated hypothyroidism; group III, 30 women known to be heterozygous for beta-thalassemia; and group IV, 50 healthy women. The mean (+/- SEM) HbA2 level was higher (P less than 0.001) in subgroup IA (3.21 +/- 0.06%) than in subgroup IB (2.42 +/- 0.09%) and group IV (2.48 +/- 0.04%), but lower (P less than 0.001) than in group III (5.26 +/- 0.12%). The mean HbA2 level was lower (P less than 0.001) in group II (1.99 +/- 0.08%) than in group IV. Hb fetal was detectable in eight patients of subgroup IA and undetectable in subgroup IB and groups II and IV. The mean cellular volume was lower (P less than 0.001) in subgroup IA than in other nonanemic groups. The mean cellular volume was higher (P less than 0.001) in group II than in group IV. Follow-up of nine patients who became euthyroid with treatment showed the normalization of these erythrocyte parameters. These results suggest that thyroid hormones can modulate the synthesis of delta- and gamma-globin chains.

Adult↗