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Biomedical subjects

A S Keitt

Publications and source records attributed to A S Keitt.

15 recordsLinked to original sources
PubMed1988

The variant fetal hemoglobin F Texas I is abnormally acetylated.

Two related infants with indistinct slow-moving minor hemoglobin bands were detected by electrophoretic cord blood screening. The variant separated into a major and a minor band on isoelectric focusing (IEF), anion exchange chromatography (AEC), and high-performance liquid chromatography (HPLC). Analysis of the products of tryptic hydrolysis of the abnormal chain revealed a truncated A gamma T-1 peptide containing a glu----lys substitution at position 5, identifying the variant as Hb F Texas I. Microsequencing of the major early peak from AEC confirmed the substitution. However, gamma chains from the minor peak resisted Edman degradation and were shown to be acetylated by fast atom bombardment mass spectrometry (FABMS). Acetylation of HbF Texas I was nearly three times that of normal HbF measured in the same hemolysate, and this ratio remained constant for over 1 year in the proband. This represents the first demonstration of increased N alpha-acetylation of a variant fetal hemoglobin.

Acetylation↗
PubMed1983

Biochemical characterization of three mutant isozymes of erythrocyte pyruvate kinase: PK-"Gainesville," PK-"San Juan," and PK-"Cape Canaveral".

Pyruvate kinase was partially purified from erythrocytes of three unrelated, nonconsaguineous patients with chronic hemolytic anemia of differing clinical severities. Characterization of the defective PK isozymes by internationally standardized criteria indicated that one (PK-"Gainesville") had severely impaired substrate affinity, another (PK-"San Juan") had markedly reduced residual activity, and the third (PK-"Cape Canaveral") had a combination of milder defects. Each appears representative of subsets emerging from the heterogeneous molecular defects that make up pyruvate kinase deficiency.

Adenosine Triphosphate↗
PubMed1983

Studies of the efficacy and potential hazards of methylene blue therapy in aniline-induced methaemoglobinaemia.

The similarity between poison and antidote was known to the ancient Greeks who used the same word, pharmakon, for both. This paper presents evidence that aniline (the toxin) and methylene blue (ther therapy) are in fact remarkably similar and additive in some of their effects on erythrocytes. Studies were prompted by a case of aniline-induced methaemoglobinaemia in which two injections of methylene blue did not rapidly eliminate cyanosis and were followed by severe, delayed haemolysis. Interactions between aniline and methylene blue were studied in cats which, although showing important differences from man in their haemoglobin and splenic vasculature, represent a useful model. Methylene blue potentiated the oxidative denaturation of haemoglobin by aniline as judged by the size and number of Heinz bodies and their turbidity in haemolysate. It also aggravated and prolonged the fall in erythrocyte reduced glutathione content which occurred at a time of maximum Heinz body production. While methylene blue in judicious dosage will reduce the content of methaemoglobin after aniline exposure, it may not eliminate visible cyanosis. Repeated injections of methylene blue can markedly aggravate subsequent haemolysis without further lowering methaemoglobin content.

Adult↗
PubMed1983

Pyrimidine nucleotidase deficiency with active dephosphorylation of dTMP: evidence for existence of thymidine nucleotidase in human erythrocytes.

Erythrocytes from a patient with classical pyrimidine nucleotidase (PyN) deficiency had less than 10% residual PyN activity with uridine 5'-monophosphate (UMP) or cytidine 5'-monophosphate (CMP) as substrate, but exhibited brisk nucleotidase activity with thymidine 5'-monophosphate (dTMP). This strongly suggests the existence of separate enzymes or isozymes of PyN in normal human erythrocytes--an hypothesis that should be tested by similar studies in other cases of severe PyN deficiency, whether induced by genetic defects or lead toxicity.

5'-Nucleotidase↗
PubMed1978

Cryopathic gangrene with an IgM lambda cryoprecipitating cold agglutinin.

Immunochemical and serologic studies of cold agglutinis in patients with chronic cold agglutinin disease (CCAD) have shown the almost exclusive occurrence of IgM kappa antibodies with specificity for the I antigen of red cells. An unusual subgroup of patients has been delineated in which the cryoprotein is IgM lambda, frequently lacks I specificity and often cryoprecipitates. Studies of such a protein from a patient with an unusual array of immunoproliferative disorders including Grave's disease with exophthalmos and Waldenstrom's macroglobulinemia indicate that the cryoprecipitating and cold agglutinating properties probably derive from the sam protein. The occurrence of this type of antibody should suggest the presence of a more aggressive lymphoproliferative disorder than simple CCAD.

Adult↗
PubMed1969

Hemolytic anemia with impaired hexokinase activity.

Analyses of key glycolytic intermediates in freshly drawn red cells from six related individuals suggest that decreased hexokinase activity underlies the hemolytic process in the two members with overt hemolysis. Low red cell glucose 6-phosphate (G6P) was observed not only in the anemic patients but in the presumptive heterozygotes as well and served as a useful marker for the presence of the trait. Hexokinase activity was labile in distilled water hemolysates but was only slightly low when protected by glucose, mercaptoethanol, and ethylenediaminetetraacetate (EDTA). Normal red cell hexokinase was demonstrated to be dependent on glucose for maintenance of activity after heating to 45 degrees C. The cells of the proposita are unable to utilize glucose efficiently at glucose concentrations lower than 0.2 mmole/liter whereas normal cells maintain linear glucose consumption to at least 0.05 mM glucose. These qualitative abnormalities could result from the presence of a mutant hexokinase with an abnormally reactive sulfhydryl group and altered substrate affinity in the red cells of this kindred.

Adenosine Triphosphate↗