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Biomedical subjects

D L Pierson

Publications and source records attributed to D L Pierson.

At least 73 records · Page 4Linked to original sources
PubMed1980

Human carbamylphosphate synthetase I. Stabilization, purification, and partial characterization of the enzyme from human liver.

Carbamylphosphate synthetase I from human liver was stabilized, purified, and partially characterized. The labile enzyme was stabilized in cell-free extracts by the presence of MgATP and dithiothreitol at pH 7.8. The stabilized enzyme was purified by a rapid procedure consisting of ion exchange chromatograhy and electrofocusing The native molecular weight of the enzyme was determined by gel filtration to be 190,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a monomeric molecular weight of 165,000. The isoelectric point of the purified enzyme was 6.05, and only one species of active enzyme was observed during electrofocusing of both purified enzyme preparations and crude liver homogenates. The enzyme exhibited a pH optimum of 7.8. The apparent Michaelis constants for NH4+, HCO3-, MgATP, and the activator, N-acetyl-L-glutamic acid, were 0.8, 6.7, 1.1, and 0.1 mM, respectively.

Adenosine Triphosphate↗
PubMed1980

A rapid colorimetric assay for carbamyl phosphate synthetase I.

A rapid, reproducible, and sensitive colorimetric assay for carbamyl phosphate synthetase I was presented. A four-fold increase in sensitivity and reduced assay time were afforded by this procedure. The method utilized the chemical conversion of carbamyl phosphate to hydroxyurea by the action of hydroxylamine instead of employing a coupling enzyme. The hydroxyurea was quantitated in 15 min by an improved colorimetric assay for ureido compounds by measuring the absorption of the resulting chromophore at 458 nm. Optimum conditions for both the formation and quantitation of hydroxyurea were established. Activity measurements of carbamyl phosphate synthetase I obtained by this uncoupled method were identical with those obtained by the ornithine transcarbamylase coupled assay.

Carbamoyl-Phosphate Synthase (Ammonia)↗
PubMed1980

A glomus tumor mimicking a peripheral neuropathy.

A patient was found to have a solitary glomus tumor near the posterior cutaneous branch of the ulnar nerve at a wrist. For years, his symptoms mimicked a peripheral neuropathy. The location, color, and soft vascular consistency of the lesion helped us to make the correct diagnosis in this case and simple ablation of the lesion effected a cure.

Aged↗
PubMed1980

Stabilization and purification of ornithine transcarbamylase from Neisseria gonorrhoeae.

Ornithine transcarbamylase was stabilized in cell-free extracts by the presence of either carbamyl phosphate or glycerol. The enzyme was rapidly purified by a procedure consisting of ion-exchange chromatography and electrofocusing. The native molecular weight of the enzyme was determined by gel filtration to be 110,000. A subunit molecular weight of 36,000 was determined by polyacrylamide electrophoresis under dissociating conditions. These findings indicated a trimeric quaternary structure for the enzyme. The isoelectric point of the purified enzyme was 4.75, and no evidence of multiple forms of active enzyme was found in either crude or purified preparations. An inactive form of the enzyme appeared upon storage in the absence of stabilization buffer.

Cell-Free System↗
PubMed1980

Selective deficiency of a T cell subpopulation in active atopic dermatitis.

The T cell subpopulation bearing a receptor for the Fc fragment of IgM (T mu) or the Fc fragment of IgG (T gamma) were studied in 12 patients with active atopic dermatitis (AD) and elevated IgE (5678 I.U./ml +/- 1382) and compared with a control group with normal IgE (33 +/- 17). Values for the total lymphocytes and for absolute and relative numbers of total T and T mu cells were comparable in both groups. However, AD patients had markedly reduced relative T gamma levels, 1.8% +/- 0.4%, compared with normals, 10.5% +/- 0.7% (p less than 0.001). The patients also had reduced absolute T gamma levels, 29 +/- 7, compared with 181 +/- 36 (p less than 0.0005). This abnormality was not indicative of allergic disease in general, nor did it appear to be caused directly by serum factors. The T gamma cell deficit did reflect disease activity and correlated inversely with the levels of serum IgE in the AD patients. Thus, patients with active AD and elevated IgE have a selective reduction in circulating T gamma cells.

Adolescent↗
PubMed1979

Trichilemmoma.

Trichilemmoma is an uncommon cutaneous neoplasm that originates in the outer hair sheath. We are reporting two cases, one of lobular pattern, the other a massing of cells of the follicular infundibulum. In each case, the clinical appearance was nonspecific and the mistaken clinical diagnosis was basal-cell carcinoma.

Aged↗
PubMed1979

Cutaneous inoculation tuberculosis: prosector's wart occurring in a physician.

Cutaneous inoculation tuberculosis may occur either a primary or secondary infection. When the condition occurs in medical or laboratory personnel after contact with tuberculous material the term "prosector's wart" is often used. A case is reported in a physician following trauma during an autopsy on a tuberculous patient.

Adult↗
PubMed1977

Human ornithine transcarbamylase. Purification and characterization of the enzyme from normal liver and the liver of a Reye's syndrome patient.

Ornithine transcarbamylase was purified and characterized from normal human liver. The properties of this enzyme were compared to those of ornithine transcarbamylase purified from the liver of a patient with Reye's syndrome. The enzyme isolated from both sources appeared virtually identical for a variety of biochemical characteristics. The native molecular weight of ornithine transcarbamylase is 110,000 as determined by gel filtration. Electrophoresis of the enzyme, dissociated by sodium dodecyl sulfate, indicated that the enzyme exists as a trimer of identical or similar subunits of 36,500 daltons. Ornithine transcarbamylase from normal liver has an isoelectric point of 7.95, and the value for the enzyme from the Reye's syndrome liver was 8.05. No evidence of multiple species was found during the purification or subsequent characterization of the enzyme. The enzyme exhibited normal Michaelia-Menten kinetics, and the apparent Michaelis constants for L-ornithine and carbamyl phosphate are 0.20 mM and 0.09 mM, respectively. Inhibitor studies established the structural requirements for L-ornithine antagonists. L-Norvaline is the best competitive inhibitor of the enzyme with respect to L-ornithine. This study indicated that the reduced level of ornithine transcarbamylase activity commonly observed in Reye's syndrome is not necessarily due to structural or functional alterations of the enzyme.

Female↗
PubMed1977

Isolation and preparation of pretyrosine, accumulated as a dead-end metabolite by Neurospora crassa.

Pretyrosine is an amino acid intermediate of phenylalanine and/or tyrosine biosyntheses in a variety of organisms. A procedure for the isolation of high-quality pretyrosine as the barium salt is described. Stable solutions of ammonium pretyrosine that are suitable for use as substrate in enzyme assays can be prepared in good yield with relatively few purification steps. A triple mutant of Neurospora crassa, bearing genetic blocks corresponding to each initial enzyme step of the three pathway branchlets leading to the aromatic amino acids, accumulates prephenate and pretyrosine. Although the time courses of prephenate and pretyrosine accumulations were found to be parallel in any given experiment, the ratios of the two metabolites varied as much as 100-fold depending upon such variables as carbon source, temperature of growth, accumulation, and especially the presence of aromatic pathway metabolites. Under appropriate nutritional conditions of accumulation, pretyrosine concentrations in excess of 4 mM in culture supernatant fluids were obtained. Strains individually auxotrophic for phenylalanine or tyrosine accumulate lesser amounts of prephenate and pretyrosine. The metabolic blocks of the mutant result in high intracellular levels of prephenate, which is then partially transaminated to pretyrosine. In N. crassa, pretyrosine is a dead-end metabolite since it is not enzymatically converted to phenylalanine or tyrosine. At a mildly acidic pH, pretyrosine is quantitatively converted to phenylalanine in a nonenzymatic reaction.

Amino Acids, Dicarboxylic↗
PubMed1976

Hidrotic ectodermal dysplasia in a black mother and daughter.

Hidrotic ectodermal dysplasia is a rare genodermatosis with clinical hallmarks of alopecia, nail dystrophy, and palmoplantar hyperkeratosis. This report calls attention to the first reported cases, to our knowledge, of hidrotic ectodermal dysplasia in a black mother and daughter.

Adolescent↗
PubMed1973

Channel-shuttle mechanism for the regulation of phenylalanine and tyrosine synthesis at a metabolic branch point in Pseudomonas aeruginosa.

A bifunctional protein complex was partially purified from Pseudomonas aeruginosa. Catalytic activities for chorismate mutase and prephenate dehydratase coeluted from gel filtration and DEAE-cellulose chromatography columns. The protein complex had a molecular weight of approximately 134,000, as determined by gel filtration. In crude extracts or in partially purified preparations about one-half of the chorismate utilized by the complex is converted to phenylpyruvate, and the other half accumulates as prephenate. The chorismate mutase activity is strongly product-inhibited by prephenate, competitively with chorismate. Accordingly, the first reaction of the complex can be sufficiently retarded by prephenate so that all of the reaction product is phenylpyruvate. Chorismate mutase activity is also competitively inhibited by phenylalanine. Although phenylalanine is effective at low concentrations, maximal inhibition is only 50 to 60%. Inhibition of chorismate mutase by phenylalanine was completely lost after gel filtration. The prephenate dehydratase activity of the protein complex is nearly completely inhibited by 0.1 mm phenylalanine in either crude extracts or partially purified preparations. A second species of prephenate dehydratase was separated from the prephenate dehydratase-chorismate mutase aggregate by gel filtration or anion exchange chromatography. The second prephenate dehydratase had an estimated molecular weight of 76,000, a high affinity for prephenate, and was insensitive to feedback inhibition by phenylalanine. The physiological role of the latter enzyme is uncertain. The other regulatory enzymes of tyrosine and phenylalanine biosynthesis, prephenate mutase aggregate by gel filtration or anion exchange chromatography. The other regulatory enzymes of tyrosine and phenylalanine biosynthesis, prephenate dehydrogenase (molecular weight of 120,000) and 3-deoxy-d-arabino-heptulosonate-7-phosphate synthetase (molecular weight of 52,000), elute from Sephadex G-100 columns as fractions which are distinct from both the chorismate mutase-prephenate dehydratase complex and from the low-molecular-weight species of prephenate dehydratase. A shuttle mechanism governing the metabolic fate of prephenate (to phenylalanine or to tyrosine) is proposed in the context of a model which also accommodates several previously puzzling findings: (i) the dominating role of tyrosine in the control of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthetase and (ii) the lack of feedback control of prephenate dehydrogenase by tyrosine.

Aldehyde-Lyases↗