Lack of BCR/ABL rearrangement in acute and chronic T cell leukemias.
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Chromosomes, Human, Pair 22↗
Biomedical subjects
B P Simões
Publications and source records attributed to B P Simões.
Racial heterogeneity of DNA polymorphisms linked to the A and the O alleles of the ABO blood group gene.
Except for subgroup A2 and minor A, O and B alleles (Ax, O2 and B(A)), which occur at low frequencies in the population, the major ABO alleles are considered to be homogeneous entities. The present study is the first demonstration of an extensive variability linked to the more common alleles of the blood A and O genes by digestion of the genomic DNA with different restriction enzymes and hybridization with a probe generated by PCR amplification of a segment of the last exon of the glycosyltransferase gene. For group A in Whites, two or three-allele fragment length polymorphisms (RFLP) were demonstrated by Hinc II, Taq I and Hinf I; for group O two to five-allele RFLP were detected in Blacks, Whites and Amerindians with restriction enzymes Hinc II, Bgl I, Kpn I, Taq I and Hinf I. These polymorphisms probably originated by single-base changes, although a length variation due to variable number of tandem repeats cannot be ruled out for some. Allelic association between the different restriction sites permitted the identification of seven O allele haplotypes in Blacks, and two in Whites and Indians. Three different haplotypes were identified for group A in Whites. The greater heterogeneity of the O allele among the Blacks as compared with Whites and Indians is similar to that observed for other gene systems. The polymorphisms of the histoblood group ABH antigen genes seem a useful tool for population genetics, phylogenetics and evolution studies.
ABO Blood-Group System↗
Relative frequencies of the two O alleles of the histo-blood ABH system in different racial groups.
O blood group results from the absence of glycosyltransferase activity, which is due most commonly to a single nucleotide deletion in the glycosyltransferase gene. A second type of O allele resulting from three nucleotide substitutions in the glycosyltransferase gene had its frequency recently determined in a Danish population. However, its frequency among different human populations is not known. The frequencies of the two types of O alleles were determined by DNA analysis of the glycosyltransferase gene of group O individuals of three racial groups (Caucasians, blacks and Amerindians). The mean frequency of carriers of the three-base mutation group O gene among blacks and Caucasians is 4.7%; the mutation was not observed among 100 Amerindian chromosomes. The data reveal the relative frequencies of O alleles in different racial groups, and demonstrate that the origin of this variant predates racial divergence, since it is found equally among blacks and whites.
ABO Blood-Group System↗
Splenic function in acute leukemia.
Spleen function was evaluated in 36 patients with acute leukemia by enumeration of pitted erythrocytes and analysis of clearance from circulation of heat-damaged 99mTc-labelled erythrocytes (HDE). At diagnosis, the mean percentage of pitted erythrocytes was significantly higher in the patient group (4.04 +/- 7.19%) than in the control group (0.41 +/- 0.35%; p < 0.01), suggesting the occurrence of a splenic hypofunction in a high proportion of the patients. Accordingly, the clearance of HDE showed a pattern of splenic hypofunction in 4 out of 7 patients, based on reduced values for the parameters C20 (overall clearing function of the spleen), K (the rate constant of HDE irreversibly trapped) and K/K1 + K (the fraction of HDE entering the spleen undergoing permanent removal). After successful treatment, the pit counts decreased in all reassessed patients, returning to normal values in 10 out of 12 patients with high pit counts at diagnosis. Additionally, two patients with normal pit counts at diagnosis presented borderline results for the parameters C20 and K, which may suggest a slight splenic hyperactivity in these patients. These results demonstrate, for the first time, the presence of functional spleen abnormalities in patients with acute leukemia.
Acute Disease↗
Large DNA inversions, deletions, and TaqI site mutations in severe haemophilia A.
Large DNA inversions caused by an intrachromosomal recombination between homologous regions located in intron 22 and 5' of the factor VIII gene have recently been identified in patients with severe haemophilia A. To evaluate better the prevalence of this large inversion and to estimate the overall sensitivity of the Southern blot/hybridization method we analysed the factor VIII gene of 49 unrelated patients with severe haemophilia A. All patients were screened for the inversion mutation, TaqI site mutations, and deletions. Mutations were identified in 31 (63%) patients, and comprised 24 large inversions, 4 partial deletions, and 3 point mutations. Three different haplotypes were characterised in the patients presenting the inversion mutation, confirming its independent origin. Two novel deletions are reported: a large one spanning from intron 14 to intron 22 and a deletion of 86 bp comprising the 3' region of exon 1 and 39-41 bp of intron 1. DNA sequencing of the deletion junction showed no significant homology between normal 5' and 3' sequences around the breakpoints. A novel missense mutation is also reported: CGA-->GGA, Arg-2209 to Gly. These results confirm that the inversion mutation is the most common cause of severe haemophilia A and indicate that the Southern blot/hybridization assay should be used as the first method for screening of mutations in severe haemophilia A.
Base Sequence↗
Molecular bases of the ABO blood groups of Indians from the Brazilian Amazon region.
Phenotype studies of ABO blood groups in most Amerindian populations revealed the exclusive presence of group O. Since group O is the result of the absence of glycosyltransferase activity, its molecular bases may be heterogeneous. We carried out ABO blood group genotyping by analysis of DNA of 30 Indians from 2 Amazonian tribes (Yanomami and Arara), and compared the findings with other populations (Caucasians and Blacks). Two segments of the glycosyltransferase gene were amplified by PCR and digested with KpnI or AluI to detect deletion or base change at positions 258 and 700, respectively. For all subjects, the gene basis of blood group O is the deletion of a single nucleotide at position 258 of the glycosyltransferase A gene, similar to that observed in Caucasoids and Negroids. DNA sequencing of limited regions of the gene supports this conclusion. This finding does not exclude, however, that a heterogeneity of the O allele may be revealed by a more extensive analysis.
ABO Blood-Group System↗
[Reagudization of Chagas myocarditis inducing exclusive right ventricular failure].
Woman, 42 years-old, receiving immunosuppressive therapy for a lymphoma, presented reagudization of Chagas' disease, from its indeterminate phase. Intense inflammatory visceral aggression, due to extensive intracellular proliferation of the Trypanosoma cruzi, was the likely mechanism for acute myocarditis leading to severe right ventricular failure. Antiparasite chemotherapy was effective in the control of visceral involvement and for the remission of cardiac failure. The clinical course in this case is compatible with the hypothesis of early right ventricular damage in Chagas' disease.
Adult↗
Malignant T gamma/delta lymphoproliferative disease with natural killer lytic activity.
A 17-year-old girl presented with a lymphoproliferative disease involving the bone marrow, peripheral blood, and liver associated with reactive hyperplasia of the spleen. Neoplastic cells were atypical medium-sized lymphoblasts with convoluted nuclei and nucleoli without features of large granular lymphocytes (LGL). The phenotype was CD3+ CD4- CD8-, TCR alpha/beta-, TCR gamma/delta+, delta TCS1-, and CD16+, and these cells exhibited spontaneous natural killer (NK) activity. DNA analysis showed rearrangement of the TCR gamma gene but not of TCR beta or of Ig mu genes. This unusual lymphoproliferative disease may represent the neoplastic expansion of a minor subset of normal T gamma/delta cells with NK activity.
Adolescent↗