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Biomedical subjects

A N Schechter

Publications and source records attributed to A N Schechter.

195 records · Page 11Linked to original sources
PubMed1970

Measurement of fast biochemical reactions.

In the 4 years since Hammes (87) reviewed, in this journal, the application of flow and relaxation techniques to the study of primary processes in chemical reactions these methods have been applied to a wide range of biochemical problems. These applications have been facilitated by advances in stopped flow and temperature jump instrumentation, especially with respect to the range of physical properties that may be observed during a reaction, and the availability of instruments.

Alcohol Oxidoreductases↗
PubMed1970

Kinetics of folding of staphylococcal nuclease.

Staplhylococcal nuclease undergoes a reversible structural transition between (p)h3 and 4 which be mesured by changes in tryptoham fluorescence. A stopped-flow spectrofluorometer was used to study the kinetics renaturation of nuclease from the acidified form on neutralization, the refolding is fast and the data can be described as a sequence of two first-order processes with half times of about 55 and 350 milliseconds, respectively.

Enzymes↗
PubMed1968

Mitochondrial malate dehydrogenase: reversible denaturation studies.

The malate dehydrogenase isoenzymes from the mitochondria of chicken hearts have been partially resolved into separate pools. Reversible denaturation, in concentrated guanidine hydrochloride, does not change the isoenzyme distribution in each pool. This result suggests that the electrophoretic differences among the isoenzymes are not solely conformational in origin.

Animals↗
PubMedDate not supplied

Pathophysiology of a sickle cell trait mouse model: human alpha(beta)(S) transgenes with one mouse beta-globin allele.

As a potential model for sickle cell trait (AS), we examined mice containing one normal mouse beta-globin allele in combination with a human hemoglobin S (h(alpha)beta(S)) transgene (m(beta)/hS). The mice segregated into two subpopulations containing low and high proportions of hemoglobin S (m(beta)/hS1 and m(beta)/hS2, respectively) that was associated with one or two human h(alpha)beta(S) transgenes. We noted striking kidney pathology (cortical cysts, hyperplastic tubules, and glomerulonephritis), increasing with age and with greater severity in m(beta)/hS1. mBeta/hS2 animals were largely tolerant to 5% O(2) for 1 h, whereas 80% of m(beta)/hS1 mice died, exhibiting acute sequestration of erythrocytes in spleen, liver, and heart. These pathologies appear to result from a decreased oxygen affinity of the hybrid (human alpha/mouse beta) hemoglobins with a mild beta-thalassemia phenotype. Thus, these mouse models of sickle trait seem to manifest their renal pathology and sensitivity to hypoxia by mechanisms related to low tissue oxygen delivery and are different from the human syndrome. Analyses of parameters such as P(50), red cell indices, and genetic background are necessary in establishing potential relevance of any mouse model of the sickle cell syndromes.

Alleles↗
PubMedDate not supplied

Effects of superoxide anions on red cell deformability and membrane proteins.

The effect of superoxide anions (O2-) on red blood cells (RBC) deformability and membrane proteins was investigated using hypoxanthine-xanthine oxidase system. Exposure of RBC to O2- caused a marked decrease in RBC deformability with a concomitant increase in cell volume and shape changes. The RBC exposed to O2- also displayed pronounced degradation of membrane proteins such as band 3 protein and spectrin; new bands of low molecular weight products appeared as the original membrane proteins tended to diminish, without the appearance of high molecular weight products. Since the membrane proteins are involved in processes regulating membrane properties such as permeability and viscoelasticity, the decreased deformability induced by O2- may be attributable to changes in membrane proteins. Interestingly, resealed ghosts exposed to O2- did not show any significant change in membrane proteins, which suggests the existence of further generation of O2- and subsequent production of other active oxygen species mediated by O2(-)-initiated autoxidation of hemoglobin in intact RBC. Furthermore, electrophoretic analysis suggested that active oxygens increased the endogenous proteolytic susceptibility of RBC. In conclusion, a close linkage was suggested between RBC deformability and the membrane proteins.

Anion Exchange Protein 1, Erythrocyte↗
PubMedDate not supplied

Impaired deformability of Heinz body-forming red cells.

Although a decrease in the deformability of red blood cells (RBCs) has been suspected in Heinz body-forming hemolytic anemia, it remains uncertain whether the formation of Heinz bodies themselves impairs RBC deformability or not. To elucidate this question, we used RBCs treated with phenylhydrazine and RBCs from patients with unstable hemoglobin (Hb) disease (Hb Yokohama) to investigate the effect of Heinz body formation on deformability in terms of RBC filterability through nickel mesh and viscosity of the RBC suspension. The phenylhydrazine-treated RBCs exhibited a marked decrease in deformability in a dose-dependent manner. The Heinz body-forming RBCs from the patients also showed a marked decrease in deformability. Thus we confirmed that Heinz body formation impairs RBC deformability. Further, both phenylhydrazine-treated RBCs and RBCs from the patient showed a degradation of spectrin without any cross-linking of membrane proteins, thereby suggesting that the impaired deformability is associated with the oxidative degradation of the cytoskeletal framework. In summary, this study supports the conclusion that RBC deformability is impaired by the presence of Heinz bodies as well as the related oxidative damage involved in their formation.

Anemia, Hemolytic↗