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Biomedical subjects

D A Rigas

Publications and source records attributed to D A Rigas.

18 recordsLinked to original sources
PubMed1980

Biphasic radiosensitization of human lymphocytes by diethyldithiocarbamate: possible involvement of superoxide dismutase.

A biphasic radiosensitization of human lymphocytes by diethyldithiocarbamate (DDC), a metal chelator, was observed. The first phase occurred at 10(-5) M and the second at 10(-3) MDDC. The biphasic radiosensitization coincided with the previously reported biphasic toxicity of DDC. Inhibition of superoxide dismutase (SOD) occurred only in the second phase, suggesting that it may be a contributing cause of this phase. The mechanism of the first radiosensitization phase is not known. The radiation survival curves indicated the presence of at least two lymphocyte populations differing in their radiosensitivity and representing 40 per cent and 60 per cent of the cells. Both cell populations were biphasically radiosensitized by DDC.

Cell Survival↗
PubMed1976

Respiratory characteristics of blood from Basenji dogs with classical erythrocyte pyruvate kinase deficiency.

The oxygen affinities of blood from eight Basenji dogs homozygous for classical erythrocyte pyruvate kinase deficiency and four dogs heterozygous for the defect were compared with blood from 14 Labrador retrievers and two normal Basenji dogs. The homozygous dogs showed significant anemia compared to heterozygous and normal dogs (P is less than 0.01). The average blood P50 value (at 38C and plasma pH of 7.40) for both homozygous and heterozygous dogs was significantly higher (P is less than 0.01) than for normal dogs (33.6+/-0.4 and 31.8+/-0.7 vs 30.8+/-0.6 mm Hg). The concentrations of 2,3-DPG in the blood of both heterozygous and homozygous dogs were significantly higher than normal values. Four months after splenectomy P50 values declined to normal in four homozygous Basenji dogs without any change in the degree of anemia or blood 2,3-DPG concentrations. Iron kinetic studies showed a shorter plasma clearance time in a homozygous than in a normal dog with the heterozygote falling midway between. The red cell life span in the normal and heterozygous dogs was approximately 120 days. The 59Fe studies on the homozygous dog indicate markedly different survival characteristics which can be attributed to the existence of three populations of red cells differing in their life spans.

Animals↗
PubMed1967

Hemoglobin Portland 1: a new human hemoglobin unique in structure.

A new hemoglobin (Hb), Portland 1, has been found in a newborn infant having multiple congenital anomalies and complex autosomal chromosomal mosaicism. The new hemoglobin has a unique tetrameric structure (molecular weight, 66,000) composed of two pairs of different types of chains, neither of which is alpha, gamma(2)x(2). The x-chain of Hb Portland 1 may be a new type of hemoglobin chain, but the available evidence suggests that it may be identical with the epsilon chain. We suggest that Hb Portland 1 is an embryonic hemoglobin that persisted until after birth in relatively large amounts in this patient.

Blood Protein Electrophoresis↗
PubMed1967

Electrolyte-labile increase of oxygen affinity during in vivo aging of hemoglobin.

Normal human erythrocytes were separated according to in vivo age by ultracentrifugation. The "young" and "old" erythrocytes had mean cell ages of approximately 40 and 79 days, respectively. "Young" erythrocytes had a lower oxygen affinity and a higher heme-heme interaction than did "old" erythrocytes. This indicates an impairment of the oxygen-carrying function of erythrocyte hemoglobin with age."Young" and "old" erythrocytes were hemolyzed yielding "young" and "old" hemoglobins. "Young" hemoglobin had a comparably lower oxygen affinity than did "old" hemoglobin when the hemolysates were dialyzed against electrolyte-free water. Exposure to sodium chloride completely obliterated this difference between the oxygen affinities and buffer values of "young" and "old" free hemoglobin. Similar exposure to potassium chloride resulted in partial obliteration of the difference between the oxygen affinities of "young" and "old" hemoglobin. Subsequent removal of sodium chloride by dialysis did not restore the pre-electrolyte differences between the oxygen affinities of "young" and "old" hemoglobin. This evidence indicates that in vivo aging is accompanied by a conformational change of the hemoglobin molecule, which is probably due to an alteration of electrostatic interactions involving the hemoglobin molecule and which is retained after hemolysis and dialysis against water but is obliterated by addition of electrolyte. It is not possible, however, to decide from the available evidence whether this molecular change occurs independently or as a result of influences by other substances, such as 2,3-diphosphoglycerate, which also change during in vivo aging of the erythrocyte.

Adult↗