Biomedical subjects
Publications and source records attributed to D Loukopoulos.
This paper presents data collected in Europe on 107 prenatal diagnoses of cystic fibrosis (CF) using linked DNA markers. To date, 38 children have been born without CF, as predicted, demonstrating the present rapid move from research to clinical genetic service.
Hb Knossos is a beta-chain variant (beta 27 Ser----Ala) that is unrecognizable by conventional separation methods but detectable by globin electrophoresis on urea-Triton X-acrylamide gels or by IEF. Hb Knossos is characterized by reduced synthesis and by interaction with beta-thalassemia, in which the double heterozygotes display typical features of thalassemia intermedia. The present paper summarizes the salient genetic, clinical, and biochemical characteristics of five such cases hitherto identified in three families along with the same features on 12 heterozygous Hb Knossos carriers. Hb Knossos displays a slightly decreased oxygen affinity; this factor may compensate in part for the severe anemia of the double heterozygotes. Hb Knossos is relatively rare in our population, since a prospective survey on 610 individuals has failed to disclose any heterozygotes. However, the mutation appears to have spread over the Mediterranean countries and may be more common elsewhere.
Interaction of beta zero thalassemia with Hb San Diego [a high affinity hemoglobin variant, alpha 2 beta (2)109(G11)Val----Met] in a 29-year-old Greek male is described. A marked polycythemia with low MCH and MCV, but minor clinical problems were observed. Functional properties of the isolated variant are described.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The hemoglobin content of single erythrocytes was determined by microspectrophotometry as total extinction (TE) at 415 nm in subjects with a wide spectrum of hemoglobin levels and erythrocyte indices. Precise measurements of the cellular area (A) and the ratio TE/A were also recorded. A significant correlation was found between TE and mean corpuscular hemoglobin (MCH), A and mean corpuscular volume, and TE/A and mean cell hemoglobin concentration (MCHC) for the cases studied. In addition, TE, A and TE/A were determined in fetal erythrocytes obtained by fetoscopy at the 20th week of gestation for prenatal diagnosis of beta-thalassemia. The mean red cell TE and TE/A of the group of fetuses diagnosed to have thalassemia major were significantly lower than those of the group of normal controls and with heterozygous beta-thalassemia. The significant differences of TE, A and TE/A between maternal and fetal blood allowed a safe distinction of the latter. The calculated MCH of the fetuses with thalassemia major was 12% less than that of the normal controls; the respective difference of the mean cell size was 5% and that of MCHC 3% lower than normal.
Prenatal diagnosis of thalassemia and of the hemoglobinopathies is now accepted as an effective measure to reduce the impact of these diseases in populations where they occur in high frequencies. The procedure has been carried out on more than 5,000 cases over the past decade. Evaluation of the results shows a significant decrease of the yearly number of affected newborns and reflects a considerable gain in economic and medical resources. Methodology has improved over the years so as to make the procedure safer, faster, and less expensive. Among recent advances, gene mapping on trophoblast DNA (as early as the 9th week of pregnancy) represents a major step which will gradually replace conventional procedures (performed during the 18-20th week of pregnancy) in concerned laboratories.
Hemoglobin beta Knossos (beta 27Ala-Ser) is a cause of beta-thalassemia due to its reduced synthesis. To investigate the basis for this observation, we have isolated the beta Knossos gene and examined its expression in heterologous cells. We have found that some beta Knossos RNA transcripts are abnormally processed, utilizing a cryptic splice sequence that is enhanced by the Knossos substitution. This form of abnormal RNA processing is seen in two other mutations in this region (a silent substitution in codon 24 and the substitution in codon 26 that produces the beta E variant) and most likely contributes appreciably to the reduced synthesis of beta Knossos.
Prevention of thalassemia and hemoglobinopathies is the only solution to efficiently reduce the huge medical, social and economic impact of these diseases in countries where they occur in high frequencies. In Greece, a serious effort has been undertaken towards this goal over the last years. Prevention is carried out at various levels: ample public education, easy provision of the necessary laboratory tests for carrier identification and thorough counseling of the couples at risk. Availability of prenatal diagnosis has contributed significantly to the acceptance by the public of various screening programmes. To date, the experience of the Greek group for prenatal diagnosis totals 1088 cases (June 1977 to December 1982). The number of couples at risk seeking the test prior to having any children is steadily increasing (prospective counseling). The efficacy of the overall prevention programme in Greece is reflected by the fact that the number of babies with thalassemia major admitted for transfusion to the major Units of the country has decreased substantially in the last years. Routine method used for prenatal diagnosis is biosynthesis of hemoglobin in samples of placental blood drawn by fetoscopy. With increasing experience the procedure now is safe (less than 1% of obstetrical complications in the last year) and the prediction accurate (no false diagnoses in the recent years). However, it is anticipated that the conventional method will soon be replaced by studies of amniotic cell DNA, a procedure both safer and less traumatic, or by studies of trophoblast DNA, which will allow prenatal diagnosis at an earlier stage of pregnancy.
A new technique for sampling fetal blood in twin pregnancies using two fetoscopes simultaneously is described. Two fetoscopes were inserted, one after the other, into both amniotic cavities and fetal blood samples were obtained from either the chorionic plate vessels or the umbilical cord insertion area. The observation of the bright tip of the second fetoscope behind the septum using the first fetoscope assured the successful entry of the two fetoscopes into the two different amniotic sacs. This technique was performed on 15 out of 17 patients. In all patients the fetuses were at risk of beta-thalassemia major. Sampling was successful in all cases. Double simultaneous fetoscopy seems to be a safe and accurate technique without technical problems or complications. The simultaneous use of two fetoscopes opens new possibilities in intrauterine fetal surgery and research.
Recent studies from this department have suggested that the level of 2,3-DPG may be determined in part by the volume of the erythrocyte; this conclusion was reached on the basis of the finding of significantly elevated values of 2,3-DPG in heterozygous beta-thalassemia, even in the absence of anemia. In order to test the role of microcytosis in the formation of 2,3-DPG levels, a study was undertaken on a different patient material characterized by microcytosis without anemia or hypoxia, namely on cases of polycythemia vera (PV) rendered microcytic through therapeutic venesection (or blood loss) and on appropriate controls. Five cases of untreated PV (mean HB 18.36 +/- 1.53 g/dl, mean MCV 94.4 +/- 3.9 fl) had 2,3-DPG levels slightly lower than normal controls (13.67 +/- 0,75 mumoles/g Hb vs 14.18 +/- 1.41 mumoles/g Hb). Six microcytic iron deficient PV's (mean Hb 17.42 +/- 2.34 g/dl, mean MCV 74.5 +/- 6.2 fl) had very significantly increased 2,3-DPG levels (17.73 +/- 1.75 mumoles/g Hb). Similar high levels were obtained in five cases venesected in the past and maintained with cytostasis (mean Hb 15.22 +/- 0.67 g/dl, MCV 82.5 +/- 7.5 fl, 2,3-DPG 17.04 +/- 2.44 mumoles/g Hb). A strong linear negative correlation was obtained between 2,3-DPG values and the MCV (r = -0.736, P less than 0.001). It is concluded that microcytosis of other etiology and not only of beta-thalassemia may also lead, per se, to increased levels of 2,3-DPG. The different levels of 2,3-DPG in PV undergoing venesection vs untreated patients may explain some discrepant reports on the behavior of this metabolite in PV.
Explore the source record for details and available documents.
A new electrophoretically silent hemoglobin variant is described that produces the classical phenotype of beta thalassemic intermedia in association with beta thalassemia trait. This variant has the expression of a silent beta thalassemia trait. The abnormal hemoglobin was detected by acid-urea-Triton-acrylamide electrophoresis and further demonstrated by isoelectric focusing. The amount of the variant in carrier is approximately 30% of the total hemoglobin. No instability was found. Absence of hemoglobin A in the propositus blood facilitated structural studies. Peptides maps were normal but analysis of individual peptide spots showed an Ala leads to Ser substitution in the beta T3. This variant has been previously called Hb Knossos (beta 27 (B9) Ala leads to Ser).
In a Greek family three cases of beta-thalassaemia intermedia were diagnosed as resulting from the interaction of a typical high HbA2-beta-thalassaemia with an atypical (silent) beta-thalassaemia gene. Following electrophoresis of globins on an acid-urea-Triton-acrylamide system, an otherwise silent beta-like variant was revealed in the carriers of the atypical thalassaemia gene and in the intermediates; it amounted to 33% of the non-alpha chains in the former and to c. 75% in the latter. The provisional name Hb Knossos is suggested for this abnormality.
Explore the source record for details and available documents.
We describe three patients who had typical features of hairy cell leukemia (HCL) and multiple myeloma (MM) at the same time. In two, both diagnoses were made within a short period of time, and in the third, HCL had been present for 2 yr before the appearance of a paraprotein, bone lesions, and plasma-cell infiltrates established the diagnosis of MM. Although this association has not been previously reported, cases of HCL with osteolytic lesions or a paraprotein band have been described. The cases described may represent clinical manifestations of closely related disorders arising from divergent differentiation from a common B-cell precursor rather than a chance association.