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Biomedical subjects

O David

Publications and source records attributed to O David.

At least 19 recordsLinked to original sources
PubMed1991

Inhibition of hexose monophosphate shunt in young erythrocytes by pyrimidine nucleotides in hereditary pyrimidine 5' nucleotidase deficiency.

Recent reports have suggested that haemolytic anaemia in pyrimidine 5' nucleotidase (P5'N) deficiency might be due to impaired erythrocyte hexose monophosphate shunt (HMS). To investigate the relationship between pyrimidine accumulation, HMS impairment and shortened red-cell survival, we tested glucose 6-phosphate dehydrogenase (G-6PD), HMS, P5'N activities and the UV spectrum in whole red cells and in red cells of different age from 2 P5'N-deficient patients with different degrees of haemolytic anaemia. In whole red cells we found a reduction of both G-6PD and stimulated HMS activity in the presence of a variable amount of pyrimidine nucleotides (37.79 and 17.88 mumol/gHb respectively). A drastic inhibition of stimulated HMS activity was already present in the lightest red-cell fractions from patient 1, who presented a more severe haemolytic anaemia. The variable degree of pyrimidines found among red cell fractions, with a minor accumulation in the older red cells, supports the hypothesis that pyrimidine accumulation and HMS impairment occur in the younger erythrocytes of P5'N-deficient patients.

5'-Nucleotidase↗
PubMed1989

Increased erythrocyte adenosine deaminase activity in children with perinatal human immunodeficiency virus infection.

Erythrocyte adenosine deaminase (ADA) activity was assessed in 33 children born to human immuno-deficiency virus (HIV)-positive mothers. The enzyme values were significantly increased in infected, symptom-free children compared with a control group of HIV-negative subjects (mean +/- SD: 0.34 +/- 0.01 unit/ml red blood cells (RBC) vs. 0.25 +/- 0.04 unit/ml RBC, P less than 0.01) and a further significant increase was found in symptomatic children (0.45 +/- 0.02 unit/ml RBC, P less than 0.01 vs. infected, symptom-free children). ADA values were slightly enhanced also in the group of infants in whom the state of HIV infection was indeterminate (0.29 +/- 0.03 unit/ml RBC, P not significant vs. controls). These data indicate that increased erythrocyte ADA activity may be a useful though indirect marker of HIV infection in children at risk and be of possible prognostic relevance. Since increased values were present also in children without overt infections or hematologic disorders, and ADA activity of erythrocytes obtained from healthy donors did not increase after 1 hour incubation with patients' serum, HIV could induce large amounts of cellular enzyme infecting directly erythroid precursor cells.

Adenosine Deaminase↗
PubMed1989

Pyrimidine 5'-nucleotidase acquired deficiency in beta-thalassemia: involvement of enzyme-SH groups in the inactivation process.

Pyrimidine 5'-nucleotidase (P5'N) partial deficiency has been described in several hematological disorders and also in the beta-thalassemic trait. To check if the P5'N deficiency in thalassemia was acquired we used thalassemic red cells (from either homo- or heterozygous subjects), whose P5'N activity was lower than in control cells. After separation on a density gradient, activity in lighter cells was similar to controls and less than 50% in denser cells. The most probable mechanism for this faster inactivation involves enzyme -SH groups modification by oxidation and reaction with monofunctional aldehydes produced by membrane lipid peroxidation. In vitro challenge of thiol enzymes as pyruvate kinase (PK), adenylate kinase (AK) and P5'N with increasing concentrations of GSSG, hexanal (HEX) and 4-hydroxynonenal (HNE), showed that HNE is the most powerful among the enzyme inhibitors tested and that P5'N activity is a more sensitive index of -SH groups damage, when compared to PK and AK.

5'-Nucleotidase↗
PubMed1989

[Use of semisynthetic human insulin in juvenile insulin-dependent diabetes mellitus].

A study was conducted on 28 paediatric patients with insulin-dependent diabetes mellitus (IDDM), followed up for 2 years from onset of the disease. In this group, 14 were treated with semisynthetic human insulin, 14 with monocomponent porcine insulin. No statistically significant difference was found between the clinical and metabolic parameters examined in the two groups.

Child↗
PubMed1980

gamma chain composition in five Italian newborns heterozygous for Hb F Malta G gamma-117 His leads to Arg.

The percentage of Hb F Malta G gamma-177 His replaced by Arg and the gamma chain composition have been evaluated at birth and at different times after birth in five Italian newborns heterozygous for this variant. The percentage of Hb F Malta ranged at birth from 24% to 31% of the total Hb F, while the average G gamma/A gamma chain ratio was about 7/3, overlapping the values observed in normal newborns. T gamma chains were detected in three out of five newborns, with a percentage of about 10% of the total Hb F. After birth the Hb F Malta declined faster than the total Hb F; thus, the Hb F decrease during the first 45 d of life is mainly due to the switch-off of the G gamma locus containing the Hb F Malta gene.

Aging↗
PubMed1978

Interaction between Hb Hasharon and alpha-thalassemia: an approach to the problem of the number of human alpha loci.

We report the case of an Italian infant girl from Polesine (Po delta region in northern Italy) who was heterozygous for Hb Hasharon and alpha-thalassemia, did not synthesize any normal HbA, and had 3% HbH on electrophoresis. Hematologic and biosynthetic studies on Hb Hasharon carriers of the propositus' family suggest the possibility that the Hb Hasharon gene is linked to an alpha-thalassemia gene. On the other hand, in the Askenazy carriers of Hb Hasharon, Hb Harsharon is probably linked to a normal alpha gene. In comparing Hb Hasharon's behavior with that of other alpha variants, particularly HbG Philadelphia, frequent recombinations between alpha structural genes were suggested. The possible identity between the single alpha locus and the alpha2-thalassemia genotype is discussed.

Female↗
PubMed1977

Regulation of NAD and NADP synthesis in human red cell.

NAD is synthesized in red cell from nicotinic acid and PRPP through the formation of nicotinate mononucleotide and desamido-NAD. Synthesis of one mole of NAD requires two moles of ATP. NADP comes from NAD phosphorylation by NAD-kinase (EC.2.7.1.23). NAD and NADP analysis on a population with ATP level ranging from 800 to 2500 nmoles/ml red cells showed a close correlation between ATP and pyridine cofactors. Moreover, NADP level appeared to be dependent of the redox-state of NADP/NADPH couple. Subjects with low NADPH (G-6-PD) deficient red cells, Hb Köln) showed lower NADtot/NADPtot ratio, suggesting a NAD-kinase equilibrium shift toward NADP related to lower levels of the negative effector NADPH, as already described in rat liver.

Adenosine Triphosphate↗
PubMed1976

Low lead levels and mental retardation.

Borderline and mildly retarded children attending the hospital developmental evaluation clinic were divided into two groups on the basis of the presence or absence of a pred with a paediatric control group using blood-lead concentration as the independent variable. Children with a history of diagnosed lead posisoning were excluded from the study. The group of mentally retarded children "aetiology unknown" had statistically significantly raised blood-lead concentrations but the mentally retarded sample with "probable aetiology" showed no significant difference in lead concentrations from those of the normal controls. It is concluded that the association between lead and mental retardation extends over a much wider range than hitherto suspected and that the nature of this association is independent of a history of "encephalopathic" lead poisoning. It is suggested that physicians should consider raised lead levels in their examination of all children suspected of mental retardation and that the numerical definition of lead toxicity should be re-evaluated.

Child↗
PubMed1976

Cognitive style and the Perky effect.

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.

Adult↗