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Biomedical subjects

P R Blankenship

Publications and source records attributed to P R Blankenship.

8 recordsLinked to original sources
PubMed1986

HPLC assay of phenylalanine and tyrosine in blood spots on filter paper.

Blood spots on filter paper are used to screen for phenylketonuria. We have developed a high pressure liquid chromatographic assay of phenylalanine and tyrosine after elution of these amino acids from filter paper. The analysis time is 20 min. The amino acids are separated using an ion-exchange resin with post-column ortho-phthalaldehyde derivatization and subsequent fluorescence detection. Other common amino acids do not interfere. The assay is linear from 20 pmol to at least 2,000 pmol with a coefficient of variation of 3%. The assay is as accurate as the determination of phenylalanine by ion-exchange ninhydrin-reactive methods currently in use, but is 100 times more sensitive. The method has the advantages of avoiding venipuncture, is cost effective, has a high sensitivity, and a rapid turnaround.

Adult↗
PubMed1986

Combined xanthine and sulphite oxidase defect due to a deficiency of molybdenum cofactor.

Increased urinary excretion of xanthine, hypoxanthine, sulphite, thiosulphate and decreased serum uric acid were observed in an infant with profound failure to thrive. Other clinical findings included refractory seizures, spastic quadriplegia and profound psychomotor retardation. The patient died at 20 months of age. There were no detectable activities for xanthine oxidase and sulphite oxidase in the postmortem liver. Urothione, which is the metabolic excretory product of the molybdenum cofactor for molybdoenzymes was not present in the urine. A deficiency of the molybdenum cofactor which is common to both xanthine and sulphite oxidase is presumed to be the metabolic defect responsible for the absent activities of both enzymes.

Coenzymes↗
PubMed1986

Increased excretion of histidyl-L-proline diketopiperazine by infants receiving Pregestimil and Nutramigen formulas.

Histidyl-L-proline diketopiperazine is excreted in increased amounts by infants receiving Nutramigen or Pregestimil. When these formulas are discontinued, its excretion becomes undetectable. The compound was isolated from Nutramigen and Pregestimil, as well as from the urine of the infants receiving these formulas, and was identified by comparison with authentic histidyl-L-proline diketopiperazine standard in various chromatographic and electrophoretic systems. A neuropeptide widely distributed in the brain and gut and having a variety of biological functions, histidyl-L-proline diketopiperazine may have as-yet-undetermined effects on infants who are receiving these formulas.

Electrophoresis↗
PubMed1984

Gamma-glutamylornithine excretion in patients with hyperornithinemia.

Gamma-glutamylornithine has been identified in urine from patients with the HHH syndrome (hyperornithinemia, hyperammonemia and homocitrullinuria) and with gyrate atrophy associated with hyperornithinemia. The amount of gamma-glutamylornithine excreted was 10-15 times higher than that excreted in normal subjects. The level of excretion was comparable in the HHH syndrome subjects and the gyrate atrophy subjects despite the fact that the gyrate atrophy subjects excreted more ornithine. A 100 mg/kg oral challenge of ornithine increased the excretion of gamma-glutamylornithine by a factor of three. This increased excretion of gamma-glutamylornithine was observed in hyperornithinemia patients with different etiologies and is therefore presumably due to the hyperornithinemic state, per se, independent of the underlying defect.

Amino Acid Metabolism, Inborn Errors↗
PubMed1979

Hydroxyproline metabolism in two sisters with hydroxyprolinemia.

Hydroxyproline metabolism was evaluated in two sisters with hydroxyprolinemia and their mother. 33 and 21% of an oral hydroxyproline load (200 mg/kg) was excreted by the sisters, 5.4% by the mother, and 1.3% by normal subjects. Plasma and erythrocyte values in the sisters and their mother were elevated, indicating that extra- and intracellular hydroxyproline pools were increased. Analysis for urinary glycolate and oxalate (metabolic products of hydroxyproline) showed no increased excretion by the two sisters, although the mother's excretion was normal. A deficiency of hydroxyproline oxidase in the two sisters was indicated by the lack of delta 1-pyrroline-3-hydroxy-5-carboxylic acid excretion.

Adult↗
PubMed1975

Loss of transferase enzyme activity of transfused erythrocytes in galactosemia.

Rapid loss of erythrocyte galactose-1-phosphate uridyl transferase in hemolysates from an infant 26 days after transfusion led to investigation of the possiblity of an unstable enzyme or other variant of galactosemia. However, the child was found to have the classic type of galactosemia. The seeming transferase instability was attributable to loss of enzyme activity in hemolysates from blood containg aged, transfused cells, the source of the enzyme. Thus when transfusion is necessary, transferase assay for diagnosis of the enzyme deficiency before transfusion avoids confusion attributable to the enzyme supplied in the transfused cells.

Adult↗