Biomedical subjects
Publications and source records attributed to O David.
Depending on inner versus outer frames of reference in Witkin's sense parallels a subject's tendency to distinguish between internal images and external percepts. A rank-order correlation of .69 (N = 22) was found between scores on a task designed to test the latter tendency and scores on the rod-and-frame task.
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Previous studies have reported erythrocyte macrocytosis in adults and children with Down syndrome (DS), the significance of which remains unclear. We compared hematological parameters of 50 DS children aged 2 to 15 years, divided into three age groups, with those of 68 aged-matched healthy children. Patients with DS had a significantly increased mean corpuscular volume (MCV) and hemoglobin in all groups when compared with the controls. Erythrocyte creatine content, hexokinase (Hk) activity, erythrocyte and serum folates, vitamin B12, haptoglobin, serum iron, and ferritin were tested. All of these parameters were not significantly different from those of the control group. We conclude that macrocytosis may not be an expression of reduced red cell survival but rather of an altered folate remethylation pathway, secondary to enhanced cystathionine beta-synthase (CBS) activity, the gene for which is present on chromosome 21.
Aim of this study was to evaluate the influence of the red cell aging process on insulin receptor binding. In erythrocytes from 8 children with high reticulocyte count and 9 healthy age-matched subjects we studied insulin receptor binding in correlation with pyruvate kinase (PK) activity and creatine levels. Moreover maximum 125I-insulin bound % and PK activity were tested in four red cell fractions of different age. Our data show a significant correlation between 125I-insulin bound and either PK activity or creatine levels. In vitro experiments on red cell fractions of different age (as tested by creatine levels) evidence a lower decay of PK activity than insulin bound (p less than 0.05). Our results indicate that creatine content is the best marker of red cell age for insulin receptor studies.
Pyrimidine 5' nucleotidase (P5'N) acquired deficiency has been found in several hematologic disorders including beta-thalassemia. Our previous studies suggested that the aldehydes produced during membrane lipid peroxidation could play a role in P5'N inactivation in thalassemia. To evaluate the effects of the thalassemic "environment" on transfused red blood cells, we tested P5'N, pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G-6PD) activity, creatine content, reduced glutathione (GSH) levels and the hexose monophosphate shunt (HMS) in the red cells of homozygous transfusion-dependent thalassemic children, immediately following and again one month after transfusion. In red cells aged in thalassemic plasma, P5'N activity, creatine level, GSH stability and stimulated HMS flux were significantly decreased. These results fit in with the presence in thalassemic plasma of molecules interfering with antioxidant red cell defenses. Normal red cells incubated in thalassemic plasma display a significant stimulation of the basal HMS (p less than 0.01). Transfused red cell metabolic alterations could be explained by the plasma pro-oxidant activity and may contribute to reducing red cell survival in the host plasma.
Several carbonyls more toxic than malonaldehyde (MDA) are also generated during the propagation of lipid peroxidation stimulated "in vitro" in human erythrocytes. As regards thalassaemia, after "in vitro" treatment with tert-butyl hydroperoxide (TBHP), the total amount of aldehydes formed (MDA plus the other carbonyls) is significantly increased in the red cells from homozygous as compared to heterozygous and normal subjects. These findings lead to the conclusion that the extent of lipid peroxidation in erythrocytes is actually wider than that measurable in terms of malonaldehyde only, and that aldehydes of the hydroxyalkenal class in particular may play a role in the pathogenesis of reduced red cell survival in haemolytic anaemias.
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The purpose of this report is to present an overview on vitamin E distribution, requirements, absorption and biochemical and nutritional aspects. A continuous interest in biochemical functions is recently developed and vitamin E certainly plays an important role throughout the body. The best known of its effects and still actively considered in recent years is the role as an important biological antioxidant. The red blood cell is an ideal model for studying the antioxidant role of vitamin E in cell membranes. Nutritional deprivation is a rare occurrence in developed countries. In prematurely delivered newborns the deficiency is due to marginal stores and to transient malabsorption but it can also be iatrogenic. In infants and adults vitamin E deficiency does occur in syndromes characterized by increased consumption or reduced absorption. Various gastrointestinal disorders induce, with steatorrhoea, marked alteration of vitamin E levels. Cystic fibrosis (CF), the commonest cause of pancreatic insufficiency during the first decades of life, is of particular interest. The fat malabsorption, often severe, may not well respond to pancreatic therapy and the hepatobiliary disease, increased in frequency with improved survival, induce a further reduction in intestinal bile salt concentration. Several manifestations have been attributed to vitamin E deficiency in CF and, although overt neurological complications seem to be relatively uncommon, it is recommended to maintain an adequate supplementation.
Deficiency in human G-6PD is a widespread X-linked disorder, which is mainly characterized by susceptibility to hemolytic anaemia after the ingestion of certain drugs or toxic substances (e.g. pyrimidine derivates contained in fava beans). G-6PD deficiency in hemizygous males in easily detectable since enzymatic activity is almost absent. In heterozygous subjects the determination of enzymatic activity on red cell lysate cannot detect a partial G-6PD deficiency. Cytochemical methods as methemoglobin reduction test or tetrazolium reduction test are more sensitive than spectrophotometric quantitative test, but are not suitable for screening purposes. We measured both G-6PD activity and 6-PGD activity in G-6PD heterozygous females and we evaluated the G-6PD/6PGD ratio. We tested this ratio also in thalassemic traits and in G-6PD heterozygotes with thalassemic trait in order to detect the interference of thalassemic pathology with the phenotypic expression of the gene for G-6PD. We found that the mean G-6PD values were statistically reduced in G-6PD heterozygous females; on the contrary the measurement of true G-6PD activity alone is not a good tool for discriminating heterozygous subjects with and without thalassemic trait. Actually 100% and 79% of values observed were in the normal range +/- 2 DS respectively. The mean G-6PD/6-PGD ratio in heterozygotes for G-6PD deficiency with and without thalassemic trait was lower than normal and the individual values of G-6PD/6-PGD ratio were in the normal range +/- 2 DS only in a few subjects (8.3% and 10.7% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
The Authors studied the HbF in an 8-year-old-girl with Fanconi's anemia. At the admission the patient was anemic (Hb 7,1 g%), thrombocytopenic and leucopenic, HbF was 23% (1,8 g%) with heterocellular distribution. Globin chain synthesis in the peripheral blood displayed an alpha/non alpha ratio of. 1,05. gamma-Chain analysis was performed: at position 136 the gamma G/gamma A ratio was 3:1 at positions 75 threonine was present in the 30% of the chains. The girl was transfused and oximetholone therapy was started. After 2 months of treatment, an increase of the Hb levels was observed. This improvement lasted about 5 months. The amount of HbF remained constant throughout the management. It may be suggested that androgens work only on HbA synthesis while the HbF-producing-cells are irresponsive to the hormonal stimulation.
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