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Biomedical subjects

L Chrobak

Publications and source records attributed to L Chrobak.

8 recordsLinked to original sources
PubMed1996

Characterization of 13 novel band 3 gene defects in hereditary spherocytosis with band 3 deficiency.

Hereditary spherocytosis (HS) is a common hemolytic anemia of variable clinical expression. Pathogenesis of HS has been associated with defects of several red cell membrane proteins including erythroid band 3. We have studied erythrocyte membrane proteins in 166 families with autosomal dominant HS. We have detected relative deficiency of band 3 in 38 kindred (23%). Band 3 deficiency was invariably associated with mild autosomal dominant spherocytosis and with the presence of pincered red cells in the peripheral blood smears of unsplenectomized patients. We hypothesized that this phenotype is caused by band 3 gene defects. Therefore, we screened band 3 DNA from these 38 kindred for single strand conformational polymorphisms (SSCP). In addition to five mutations detected previously by SSCP screening of cDNA, we detected 13 new band 3 gene mutations in 14 kindred coinherited with HS. These novel mutations consisted of two distinct subsets. The first subset included seven nonsense and frameshift mutations that were all associated with the absence of the mutant mRNA allele from reticulocyte RNA, implicating decreased production and/or stability of mutant mRNA as the cause of decreased band 3 synthesis. The second group included five substitutions of highly conserved amino acids and one in-frame deletion. These six mutations were associated with the presence of comparable levels of normal and mutant band 3 mRNA. We suggest that these mutations interfere with band 3 biosynthesis leading thus to the decreased accumulation of the mutant band 3 allele in the plasma membrane.

Alleles↗
PubMed1995

Mutations of conserved arginines in the membrane domain of erythroid band 3 lead to a decrease in membrane-associated band 3 and to the phenotype of hereditary spherocytosis.

To elucidate the molecular basis of band 3 deficiency in a recently defined subset of patients with autosomal dominant hereditary spherocytosis (HS), we screened band 3 cDNA for single-strand conformation polymorphism (SSCP). In 5 of 17 (29%) unrelated HS subjects with band 3 deficiency, we detected substitutions R760W, R760Q, R808C, and R870W that were all coinherited with the HS phenotype. The involved arginines are highly conserved throughout evolution. To examine whether or not the product of the mutant allele is inserted into the membrane, we studied one HS subject who was doubly heterozygous for the R760Q mutation and the K56E (band 3sMEMPHIS) polymorphism that results in altered electrophoretic mobility of the band 3 Memphis proteolytic fragments. We detected only the band 3MEMPHIS in the erythrocyte membrane indicating that the protein product of the mutant, R760Q, band 3 allele is absent from the red blood cell membrane. These findings suggest that the R760Q substitution, and probably the other arginine subsitutions, produce band 3 deficiency either by precluding incorporation of the mutant protein into the red blood cell membrane or by leading to loss of mutant protein from differentiating erythroid precursors.

Alleles↗
PubMed1993

Hb Hradec Kralove (Hb HK) or alpha 2 beta 2 115(G17)Ala-->Asp, a severely unstable hemoglobin variant resulting in a dominant beta-thalassemia trait in a Czech family.

We have identified through sequencing of amplified DNA a GCC-->GAC mutation in codon 115 of the beta-globin gene in a mother and daughter of a small Czech family. This base change was confirmed by hybridization with a 32P-labeled specific oligonucleotide probe and by gene mapping because it creates a new Ava II site. The mutation results in an Ala-->Asp replacement at beta 115(G17); this beta chain is severely unstable and could not be identified either as chain or as hemoglobin variant by isoelectrofocusing and various high performance liquid chromatography methods. Stability tests were mildly positive in freshly prepared lysates, but an unstable hemoglobin could not be detected in older lysates with these methods. Its presence results in a dominant type of beta-thalassemia in the two heterozygotes, with moderate anemia, reticulocytosis, nucleated red cells, target cells, and other red cell changes, Heinz body formation, and splenomegaly; the oldest of the two patients was splenectomized. Both subjects had a marked increase in fetal hemoglobin synthesis.

Adult↗
PubMed1992

Molecular characterization of beta-thalassemia in Czechoslovakia.

We have identified different beta-thalassemia mutations in 93 members of 34 families of Czech or Slovakian descent using gene amplification, hybridization with specific 32P-labeled oligonucleotide probes, sequencing of amplified DNA, and gene mapping. The G----A mutation at IVS-I-1 was found in 18 families; other Mediterranean mutations were IVS-II-1 (G----A), IVS-II-745 (C----G), IVS-I-110 (G----A), and codon 39 (C----T); these were present in 9 additional families. The G----T mutation at codon 121, known to cause Heinz-body beta-thalassemia, was present in 3 families, and the frameshift at codons 82/83 (-G), first described in the Azerbaijanian population, in 2 families. A newly discovered allele was a frameshift at codons 38/39 (-C). One beta-thalassemia allele was incompletely characterized. We observed in 2 families a T----C mutation at position +96 UTR (untranslated region) relative to the termination codon; this mutation likely is a rare polymorphism. alpha-Thalassemia was rare; only one person carried the -alpha 3.7 heterozygosity, and one other had a yet to be identified alpha-thalassemia-1, while seven had the alpha alpha alpha anti 3.7 triplication.

Base Sequence↗
PubMed1992

A short multilingual quality of life questionnaire--practicability, reliability and interlingual homogeneity.

International cooperative clinical trials require a multilingual quality of life questionnaire. The 'International Society for Chemo- and Immunotherapy' therefore designed a study to develop and test a 'health accentuated' quality of life questionnaire in the eight languages spoken in this society. The objective was to examine practicability, reliability and interlingual homogeneity. Versions of the questionnaire in Czech, German, Hungarian, Italian, Kroatian, Polish, Romanian and Slovakian have been prepared. The results are based on data of 1,104 adult patients. They demonstrate that the developed questionnaire is practicable. Patients need 10-15 min to answer it, usually without assistance. The proportion of missing values is for all but two questions less than 3%. The questionnaire also found high acceptance reflected by only 2.7% refusals. It is reasonably reliable in each language. Interlingual homogeneity could be shown by demonstration of strong structural similarities between the different versions using multidimensional scaling, factor analysis and comparison of mean profiles.

Adolescent↗