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Biomedical subjects

A Iolascon

Publications and source records attributed to A Iolascon.

At least 73 records · Page 4Linked to original sources
PubMed1998

Mutational screening of thrombopoietin receptor gene (c-mpl) in patients with congenital thrombocytopenia and absent radii (TAR).

Thrombocytopenia with absent radii (TAR) is a rare autosomal recessive disease characterized by hypomegakaryocytic thrombocytopenia and bilateral radial aplasia. We performed mutational screening of coding and promoter regions of the c-mpl gene, encoding thrombopoietin (TPO) receptor, by sequence analysis in four unrelated patients affected by TAR syndrome. Our results indicate that c-mpl gene mutations are not a common cause of thrombocytopenia in TAR syndrome.

Adolescent↗
PubMed1998

Genomewide search for dehydrated hereditary stomatocytosis (hereditary xerocytosis): mapping of locus to chromosome 16 (16q23-qter).

Dehydrated hereditary stomatocytosis, also known as "hereditary xerocytosis," is caused by a red blood cell-membrane defect characterized by stomatocytic morphology, increased mean corpuscular hemoglobin concentration, decreased osmotic fragility, increased permeability to the univalent cations Na+ and K+, and an increased proportion of phosphatidylcholine in the membrane. The clinical presentation is heterogeneous, ranging from mild to moderate hemolytic anemia associated with scleral icterus, splenomegaly, and choletithiasis. Iron overload may develop later in life. The disease is transmitted as an autosomal dominant trait. We recruited a large three-generation Irish family affected with DHS and comprising 23 members, of whom 14 were affected and 9 were healthy. Two additional, small families also were included in the study. The DNA samples from the family members were used in a genomewide search to identify, by linkage analysis, the DHS locus. After the exclusion of a portion of the human genome, we obtained conclusive evidence for linkage of DHS to microsatellite markers on the long arm of chromosome 16 (16q23-q24). A maximum two-point LOD score of 6.62 at recombination fraction .00 was obtained with marker D16S520. There are no recombination events defining the telomeric limit of the region, which therefore is quite large. No candidate genes map to this area.

Anemia, Hemolytic↗
PubMed1998

Resistance to activated protein C in thalassaemic patients: an underlying cause of thrombosis.

We evaluated 81 thalassaemia major and 4 thalassaemia intermedia patients (48 M, 37 F), median age 17 years; 62/85 patients were HCV-positive, 3/85 HIV-positive, 19/85 were splenectomized. Forty normal healthy children were recruited as the control group. The number of thrombotic events was studied retrospectively. Platelet poor plasma was filtered and quick-frozen at -70 degrees C until time of assay. APC resistance was measured in an activated thromboplastin time and results were expressed as normalized ratio. All tests were done with diluted 1 in 5 (v/v) factor V deficient plasma and with undiluted plasma. Molecular genetic investigation of factor V gene was performed with polymerase chain reaction, followed by digestion of amplified products with restriction enzyme Mnl I. Data obtained with molecular investigation revealed the presence of 4 heterozygous subjects for factor V Leiden (4.7%). Functional tests were able to detect all heterozygotes for factor V Leiden both with undiluted and with diluted plasma, and there were no false negative subjects. However, undiluted plasma revealed a greater number of false positive subjects (n=15) than did diluted plasma. Therefore, tests done with undiluted and diluted plasma revealed a 100% sensitivity, while specificity was 81% for undiluted plasma and 97% for diluted plasma. Only one thrombotic event was observed in one of the 85 studied patients, as a case of stroke in a thalassaemia intermedia patient with APC resistance. In the same patient an additional thrombogenic risk factor was represented by a pronounced haematocrit increase at the beginning of her transfusion regimen.

Adolescent↗
PubMed1998

Maternal and neonatal lead exposure in southern Italy.

We evaluated the blood lead levels in 159 pregnant women and in their healthy newborns at birth. The blood lead levels were higher in mothers as compared with neonates, with a linear correlation between maternal and neonatal levels. The blood lead levels were also higher in neonates as compared with infants aged 6-12 months, and, besides, 2.5% of the newborns had blood lead levels > 10 microg/dl, the actual level of concern according to the Center for Disease Control. The study of blood and urinary lead levels during the 1st week of life showed a steady decrease of blood lead levels, together with increasing levels of urinary lead. The mechanism of renal elimination is important to avoid persistently high free blood lead levels, with possible deposition in tissues with high lead affinity, such as bone. In newborns, the possibility of a functional renal insufficiency during the first days of life suggests that newborns with high cord blood lead levels and impaired renal function could be at high risk of lead toxicity, so that it could be advisable to perform a careful and prolonged follow-up.

Environmental Exposure↗
PubMed1998

Structural and functional analysis of cyclin-dependent kinase inhibitor genes (CDKN2A, CDKN2B, and CDKN2C) in neuroblastoma.

The status of the CDKN2A gene family, including CDKN2A, CDKN2B, and CDKN2C, was investigated in 24 cases of neuroblastoma. These genes were selected on the basis of 1) high incidence of their inactivation in several human cancers and 2) their localization on chromosomal regions (9p and 1p) frequently rearranged in neuroblastomas. Detailed molecular analyses indicated the absence of homozygous deletions and point mutations involving these genes in all investigated tumor samples. However, when loss of heterozygostity for chromosome 9p21 (the region where CDKN2A and CDKN2B are localized) was investigated, 16% of cases showed abnormalities in an area telomeric to the CDKN2A locus. To study transcriptional silencing of the CDKN2A gene, the methylation status of exon 1 was examined. In about 35% of cases, a partial methylation was evidenced. Analysis of the CDKN2A mRNA expression, however, did not show any relationship between methylation status and gene transcription. Finally, expression of the CDKN2B gene was demonstrated in all stage IV neuroblastomas, whereas none of stage I tumors expressed this gene. This finding suggests the occurrence of a correlation between CDKN2B transcription and tumor phenotype.

Brain Neoplasms↗
PubMed1998

Hereditary spherocytosis: from clinical to molecular defects.

Resistance and elastic deformability of red cells are due to a protein network (cytoskeleton) that laminates the lipid bilayer and to proteins that span the latter. All proteins are interconnected. Their structure as well as the structure of the corresponding genes are now well known. Hereditary spherocytosis (HS) is the most common hemolytic anemia due to a red cell membrane defect. It derives from alterations of the following genes: ANK1, EPB3, ELB42, SPTA1 and SPTB. This condition is clinically, biochemically and genetically heterogeneous. The osmotically fragile spherocytes are selectively trapped in the spleen and destroyed. Increased red blood cell destruction causes the three main clinical signs of HS: anemia, jaundice and splenomegaly. In this review we analyze the most recent advances concerning the molecular basis and the clinical course of HS. In particular, we examine the major individual proteins that constitute the skeleton, which are now known to play an essential role in the pathogenesis of HS. This paper also includes a review of the therapeutical approach to HS. Concerning the diagnosis we provide a flow chart from the clinical aspects to the molecular diagnosis.

Erythrocytes↗
PubMed1998

Decision making at the bedside: diagnosis of hereditary spherocytosis in a transfused infant.

A large group of hereditary spherocytosis (HS) patients manifest the clinical signs of this condition during the neonatal period and most of them require transfusions. The authors describe a clinical case of a neonate that was transfused. They demonstrated that the splenectomized mother had an HS due to a de novo mutation of one ankyrin allele. By means of this molecular approach, they were able to perform a diagnosis of HS in the newborn. The administration of rhEpo during the first months of life created a condition of transfusion-independence and, after six months, they were able to demonstrate the biochemical defect on the red cell membrane.

Erythrocyte Transfusion↗
PubMed1998

[Blood lead levels during pregnancy in th the newborn period. Study of the population of Bari].

Blood lead levels during pregnancy and in neonates immediately after birth have been evaluated, showing higher values in mothers compared to neonates (5.81 +/- 3.05 vs 4.87 +/- 3.60 micrograms/100 ml) and a positive correlation between maternal and neonatal levels (r = 0.82). On the basis of the results derived from the population examined, it has been observed that 6% of newborns have blood lead levels higher than 10 micrograms/100 ml a value recently identified by the Centers for Disease Control (CDC, Atlanta, USA) as a limit for toxicity in children. Moreover, neonatal Pb levels were higher than those found in infants from 6 to 12 months (4.87 +/- 3.60 vs 2.24 +/- 0.54 micrograms/100 ml). During the first week of life there is a steady decrease of blood lead levels, together with increasing renal lead excretion. This study was carried out at the "Dipartimento di Biomedicina dell'Età Evolutiva" University of Bari, southern Italy.

Environmental Monitoring↗
PubMed1998

Decreased band 3 anion transport activity and band 3 clusterization in congenital dyserythropoietic anemia type II.

Congenital dyserythropoietic anemia type II (CDA-II) is the most common form of inherited dyserythropoiesis. Erythroid precursor and red blood cells (RBCs) show characteristic morphological abnormalities. Biochemical studies have shown that this disease is associated with reduced glycosylation activity, which endows band 3 (anion transporter) with peculiar characteristics. The life span of RBCs may be shortened in patients with CDA-II, a phenomenon that has been ascribed to this membrane defect. We analyzed seven unrelated patients with CDA-II and five control subjects. In all of the CDA-II patients, erythrocytes presented a band 3 that was thinner than usual and also migrated slightly faster on SDS-PAGE. Analysis of anion transport function in CDA-II RBC samples demonstrated decreased anion exchange activity per band 3 molecule. Furthermore, we observed that the CDA-II RBCs contained larger amounts of aggregate band 3 than control erythrocytes. Aggregate band 3 has been reported to bind naturally occurring antibodies that mediate the phagocytic removal of RBCs. We provide evidence that both the phagocytic index (RBCs/macrophage) and the amount of membrane-bound immunoglobulin (IgG) are elevated in CDA-II erythrocytes. Our results suggest that the mild hemolysis observed in patients with CDA-II may be ascribed to clusterization of band 3, which leads to IgG binding and phagocytosis, and not to a secondary modification of the cytoskeletal structure of RBCs.

Anemia, Dyserythropoietic, Congenital↗
PubMed1998

Expression of cell cycle regulatory genes in chronic myelogenous leukemia.

BACKGROUND AND OBJECTIVE: Cell cycle regulatory genes are frequently altered in a variety of malignancies. The structure and pattern of expression of eight genes involved in cell division cycle control were studied in leukemic cell samples prepared from bone marrow of patients affected by chronic myelogenous leukemia. DESIGN AND METHODS: Ten cell preparations were obtained from patients in the chronic phase, five from those in myeloid blast crisis and five from those in the lymphoid acute phase. Moreover, bone marrow CD34+ cells, purified from healthy subjects and patients with chronic myelogenous leukemia (both during chronic and acute phases), were analyzed. The investigated genes were RB1, p53 and six cyclin-dependent kinase inhibitor genes (p15INK4B, p16INK4A, p18INK4C, p21WAF1/CIP1, p27Kip1, p57Kip2). RESULTS: We found that none of these genes is structurally altered in either the chronic or acute phases, with the single exception of the p16INK4A gene, which was homozygously deleted in 1 case of lymphoid evolution. p57Kip2 expression is down-regulated during the evolution towards the blast crisis both in malignant and CD34+ cells. In addition, a significant up-regulation of p15INK4B gene expression is observable during the development of the acute phase of malignancy. INTERPRETATIONS AND CONCLUSIONS: The transcriptional modulation of some cyclin-dependent kinase inhibitors might contribute to the fatal blast crisis of chronic myelogenous leukemia.

Blast Crisis↗
PubMed1997

Exclusion of three candidate genes as determinants of congenital dyserythropoietic anemia type II (CDA-II).

Congenital dyserythropoietic anemia type II (CDA-II) is the most common form of inherited dyserythropoiesis. Previous studies have shown that the anion transporter (band 3) is narrower and it migrates faster on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE); this aspect was related to insufficient glycosylation. Biochemical data support the hypothesis that this disease is due to a deficiency of N-acetylglucosaminyltransferase II (GnT II) or alpha-Mannosidase II (alpha-Man II), which represent the key to glycosylation. In addition, a third candidate gene is alpha-Man IIx, which shows a strong homology with alpha-Man II. The knowledge of the chromosomal localization of these putative genes allowed us to perform a linkage study using three sets of microsatellite markers flanking the candidate genes. Six families with two or more affected children were enrolled in this study. The data obtained exclude linkage to all three candidate genes. In consideration of the biochemical data (reduction of enzymatic activity) of the same enzymes, our results suggest the hypothesis that a defect in an unknown transcriptional factor is involved in CDA-II.

Anemia, Dyserythropoietic, Congenital↗
PubMed1997

Expression of G1-phase cell cycle genes during hematopoietic lineage.

Characterization of proteins that control the passage through the G1 phase of the cell cycle is of particular interest because virtually all stimuli regulating cell proliferation or differentiation act primarily during this phase. We have analyzed the G1 phase proteic machinery, including cyclin D types, cyclin-dependent kinases (CDKs) and CDK inhibitors, of cell populations obtained at different stages of hematopoietic cell lineage. In particular, five cellular phenotypes, namely CD34+ cells (which contain stem cells), BFU-E, CFU-E, CFU-GM and peripheral lymphocytes were studied as representatives of distinct differentiation pathways. The results obtained indicated that all the cellular preparations express cyclin D2 and D3, while cyclin D1, which is the major cyclin D occurring in mesenchimal tissues, is not expressed. Moreover, CDK6 (but not CDK4) was detectable in all the populations investigated. Among the CDK inhibitors studied, p18INK4C and p19INK4D signals were clearly evidentiable in the various cell types. Interestingly, high levels of p15INK4B, a putative tumor suppressor protein, were detectable especially in granulocyte-monocyte precursors. Our results indicate that a specific hematopoietic G1 phase machinery occurs, which is conserved during the various steps of the different maturation processes.

Carrier Proteins↗
PubMed1997

Membrane cation and anion transport activities in erythrocytes of hereditary spherocytosis: effects of different membrane protein defects.

Hereditary spherocytosis (HS) is due to different membrane protein defects (i.e., deficiency of spectrin and ankyrin, band 3, or band 4.2). In order to gain new insight into the relationships between band 3 function and proteins associated with the cytoskeleton, we studied erythrocyte anion transport activity in HS characterized by different membrane protein defects. Anion transport activity was increased in HS due to partial band 4.2 deficiency or to band 4.2 absence, while in HS associated with deficiency of spectrin + ankyrin or band 3, the anion transport results were normal or decreased, respectively. Moreover, since HS erythrocytes are characterized by an increased Na and a decreased K, we studied the principal membrane cation transport pathways. Activity of the Na/K pump was increased in all HS studied, while no changes in Na/K/2Cl cotransport and Na/Li exchange were evident between control and HS as well as between forms of HS associated with different membrane protein defects. K/Cl cotransport activity was decreased in all HS studied compared to normal red cells. In all HS, passive membrane permeability to Na and K was increased compared to normal erythrocytes. The increased Na and the low K content can be attributed to the abnormal membrane permeability to cations, which is not related to a specific membrane protein defect.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1997

Restriction fragment length polymorphism analysis reveals different allele frequency and a linkage disequilibrium at locus D1S94 in neuroblastoma patients.

Deletion of chromosome 1p and MYCN amplification have been reported as frequent abnormalities in human neuroblastoma. We studied loss of heterozygosity (LOH) in 50 (48 informative) Italian neuroblastoma patients by restriction fragment length polymorphisms (RFLPs) analysis using anonymous and hypervariable region (HVR) sequences. Twelve cases (25%) showed LOH at one or more loci. Locus D1S94 was the most frequently involved in LOH events (8/12) of deleted cases (66.6%). MYCN amplification was observed in 20% of patients which showed a significantly lower event-free survival probability (EFSp) (P = 0.004). We also studied the allelic distribution in the constitutional DNA of neuroblastoma patients (n = 44) and a matched group of healthy Italian subjects (n = 79) for loci D1S112 and D1S94. A significantly (P = 0.01) different allele frequency was detected for the two groups at locus D1S94, but not at D1S112. Moreover, the neuroblastoma population did not confirm the Hardy-Weinberg expectations at the former locus. This observation suggests the existence of an allelotype associated with neuroblastoma susceptibility.

Alleles↗
PubMed1997

Loss of heterozygosity for chromosome 1p in familial neuroblastoma.

Loss of heterozygosity (LOH) and deletion of chromosome 1p are very often found in sporadic neuroblastoma. Nevertheless, very few data are available concerning 1p LOH in familial neuroblastoma. Families with recurrent neuroblastoma are rare and analysis of chromosome 1p in these families might give useful information for identifying the putative neuroblastoma suppressor gene. We used combined cytogenetic and molecular techniques to study 1p LOH in two neuroblastoma families. Family M has 2 out of 3 children with neuroblastoma and family C has 2 children, 1 of whom has neuroblastoma and type 1 neurofibromatosis (NF1). All patients of both families showed tumour cells with chromosome 1p deletion (1pdel), but only the patient from family C also had MYCN gene amplification. In all cases the deleted chromosome 1 was of maternal origin.

Abdominal Neoplasms↗
PubMed1997

Frequent clonal loss of heterozygosity (LOH) in the chromosomal region 1p32 occurs in childhood T cell acute lymphoblastic leukemia (T-ALL) carrying rearrangements of the TAL1 gene.

Deletions and chromosomal translocations involving the 1p32 region, are frequently observed in T cell acute lymphoblastic leukemia (T-ALL). One of the most common genetic changes is the breakage of the TAL1 gene, which was originally described to be involved in the T-ALL carrying the t(1;14)(p32;q11) translocation. Site-specific deletions in the TAL1 gene are reported to occur in 12-26% of T-ALL with apparently normal karyotype. In order to investigate the presence of other subkaryotypic abnormalities involving the 1p32 chromosomal region, where TAL1 gene is mapped, we assessed losses of heterozygosity (LOH) for microsatellite markers, in a series of 22 children with T-ALL. Microsatellite polymorphic markers flanking the TAL1 gene (D1S211, D1S197, D1S200 and D1S220) were analyzed to detect LOH. Eight patients displayed LOH for at least one of the markers, suggesting the existence of hot spot regions at the short arm of chromosome 1. Two out of 11 with no molecular evidences of TAL1 gene involvement, compared to six out of 11 in the group of TAL1 rearranged gene, showed LOH at 1p32. TAL1 gene rearrangements and clonal LOH may represent two independent events, but could be related to the same causes. For the first time this study provides evidences that LOH at 1p32 region, occurs in T-ALL in the same region known to be involved in chromosomal deletions and translocations. LOH mapping may help to define the location of a new putative tumor-suppressor gene implicated in the transformation and progression of children T-ALL.

Adolescent↗
PubMed1997

Novel band 3 variants (bands 3 Foggia, Napoli I and Napoli II) associated with hereditary spherocytosis and band 3 deficiency: status of the D38A polymorphism within the EPB3 locus.

We report three novel variants of band 3 associated with hereditary spherocytosis: band 3 Foggia (311delC; ACCCAC-->ACCAC), band 3 Napoli I (447insT; TCT-->TTCT) and band 3 Napoli II (1783N; ATC-->AAC). The first two mutations resulted in premature termination of translation, making one haploid set of band 3 mRNA unavailable. Since it affected a highly conserved position at the terminal end of transmembrane domain 11, the third mutation prevented one haploid set of band 3 from becoming incorporated or stabilized into the membrane. These three mutations resulted in a reduction of the band 3 level in the red cell membrane (by 20-25%) and were dominantly transmitted. The D38A substitution (GAC-->GCC) is a low frequency change of band 3. In one compound heterozygote D38A/Napoli II, a markedly aggravated picture required early splenectomy. In contrast, the D38A change was not associated with deterioration in another compound heterozygote, carrying in trans, the previously recorded R760W mutation (CGG-->TGG). In the aggravated case, SSCP analysis did not exhibit any additional change in the two EPB3 alleles. Nor did it show any alteration in the exons of the two ANK1 alleles, and the aggravating factor remained elusive. The D38A alteration should be regarded as an innocuous polymorphism.

Anion Exchange Protein 1, Erythrocyte↗