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Biomedical subjects

H Nakata

Publications and source records attributed to H Nakata.

At least 361 records · Page 20Linked to original sources
PubMed1982

Computed tomography of mediastinal bronchogenic cysts.

The computed tomographic (CT) findings in seven cases of mediastinal bronchogenic cysts were reviewed. Two showed homogeneous high density masses with CT numbers of 97 and 89 Hounsfield units (HU). One had a CT number of 40 HU. Four cases had low density masses with CT numbers ranging from -3 to 20 HU; however, two of these four low density masses had either high density outer walls or deposits. All but one of the patients' chest radiographs revealed similar water density masses. Radiographic evidence of calcium deposits was previously considered rare, but its demonstration with CT appears to be common in mediastinal bronchogenic cysts.

Adult↗
PubMed1982

Purification and properties of tryptophan 5-monooxygenase from rat brain-stem.

Tryptophan 5-monooxygenase was purified approximately 5,500-fold, to apparent homogeneity with a specific activity of 374 nmol min-1 mg-1 at 30 degrees C, from rat brain-stem using Sepharose CL-6B, DEAE-Sepharose CL-6B and pteridine-agarose chromatography. Two distinct active forms were separable by DEAE-Sepharose CL-6B and designated as form I and form II based on their order of elution from the gel column. The apparent molecular weight of form I was determined to be 300,000 by gel filtration on Ultrogel AcA 34 and 288,000 by gradient polyacrylamide gel electrophoresis. The enzyme gave a single band on sodium dodecylsulfate/polyacrylamide gel electrophoresis, the molecular weight of which was estimated to be 59,000, indicating that the enzyme might be composed of four identical subunits. The tetrameric structure of the enzyme was further suggested by cross-linking studies using dimethyl suberimidate as a bifunctional reagent. The enzyme activity was stimulated approximately 3.5-fold by the addition of Fe2+. Kinetic studies revealed that this activation was associated with an increase of V value. The purified enzyme had an activity of phenylalanine hydroxylation but not an activity of tyrosine hydroxylation.

Animals↗
PubMed1982

Tryptophan 5-monooxygenase from mouse mastocytoma P815. A simple purification and general properties.

Tryptophan 5-monooxygenase was purified 880-fold with a 48% yield from mouse mastocytoma cells (P815) by only a one-step purification procedure of pteridine affinity chromatography. The specific activity of the final preparation was 5280 nmol min-1 mg-1. It gave a single protein band on polyacrylamide gel electrophoresis in the absence and presence of sodium dodecylsulfate. The molecular weight of the enzyme was determined to be 270,000 by gel filtration and 280,000 by gradient polyacrylamide gel electrophoresis. Sodium dodecylsulfate/polyacrylamide gel electrophoresis revealed the enzyme to be composed of identical subunits with a molecular weight of 53,000. Tetrameric structure of the enzyme was suggested by cross-linking studies using dimethyl suberimidate as a bifunctional reagent. The isoelectric point of the enzyme was estimated to be 6.0. Amino acid analysis showed a residue composition similar to that reported for rat liver phenylalanine 4-monooxygenase. The enzyme activity was stimulated approximately fivefold by preincubation with dithiothreitol and Fe2+. The purified enzyme had an activity of phenylalanine hydroxylation and also a weak activity of tyrosine hydroxylation. The kinetic properties of the enzyme are also presented.

Amino Acids↗
PubMed1981

A new activator protein that activates tryptophan 5-monooxygenase and tyrosine 3-monooxygenase in the presence of Ca2+-, calmodulin-dependent protein kinase. Purification and characterization.

Rat brain tryptophan 5-monooxygenase was activated by incubation with ATP, Mg2+, calmodulin, and micromolar concentrations of Ca2+. The activating activity was resolved into two distinct peaks upon gel filtration on Sepharose CL-6B: one, Ca2+-, calmodulin-dependent protein kinase, and the other, a heat-labile activator protein. The activator protein was purified to apparent homogeneity from rat brain by a procedure involving calmodulin-Sepharose 4B, Sephadex G-150, and phenyl-Sepharose CL-4B column chromatography. The molecular weight of the activator protein was determined to be 70,000 by sedimentation equilibrium and by gel filtration on Sephadex G-150. The protein gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of which was estimated to be 35,000, indicating that the protein might be composed of two identical subunits. Analysis of cross-linked activator protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis also suggested that the protein might be a dimer of identical subunits. Some other molecular properties of the activator protein were: sedimentation coefficient, 4.3 S; Stokes radius, 3.6 nm; diffusion coefficient, 6.0 x 10(-7) cm2/s; frictional ratio, 1.32; and partial specific volume, 0.73 cm3/g. The activator protein activated tyrosine 5-monooxygenase as well as tryptophan 5-monooxygenase in the presence of ATP, Mg2+, Ca2+, calmodulin, and Ca2+-, calmodulin-dependent protein kinase.

Adrenal Medulla↗
PubMed1981

Simple and rapid purification of tryptophan 5-monooxygenase from rabbit brain by affinity chromatography.

A simple and rapid method for isolating tryptophan 5-monooxygenase [L-tryptophan, tetrahydropteridine:oxygen oxidoreductase (5-hydroxylating), EC 1.14.16.4] was reported. The method involves adsorption on calcium phosphate gel and affinity chromatography on agarose coupled with dimethyltetrahydropteridine. Tryptophan 5-monooxygenase was purified 1,100-fold from a rabbit brain extract to a specific activity of 15.9 nmol/min.mg, which is far higher than that of the highly purified preparation reported by Tong and Kaufman ((1975) J. Biol. Chem. 250, 4152-4158). It was also demonstrated that this method was applicable to the purification of rat brain tryptophan 5-monooxygenase.

Adsorption↗
PubMed1981

Choledochal cyst.

The computed tomographic (CT) appearance of a choledochal cyst is reported. Although the appearance on the precontrast scan was highly suggestive of this diagnosis, the definitive was made on CT following the intravenous administration of a biliary contrast agent.

Adolescent↗
PubMed1980

Purification and characterization of phenylalanine 4-monooxygenase from rat liver.

Phenylalanine 4-monooxygenase (L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1) was purified approx. 600-fold to apparent homogeneity with a 48% yield from rat liver. Two distinct active forms were separable by calcium phosphate gel chromatography and numbered based on their order of elution from the gel column. The predominant form, Form I, had an estimated molecular weight of about 240 000. The enzyme gave a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis, the molecular weight of which was estimated to be approx. 51 000, indicating that the enzyme might be composed of four identical subunits. The molecular properties of Form I were: sedimentation coefficient, 10.1 S; Stokes radius, 55 A degrees; diffusion coefficient, 3.90 x 10(-7) cm2/s; frictional ratio, 1.33 and isoelectric point, pH 5.6. The enzyme contained approx. 0.6 mol of iron and 0.3 mol of phosphate/mol of subunit of the enzyme. No significant differences in kinetic properties of the two forms, Form I and Form II, were observed. Amino acid analysis studies revealed that the amino acid composition of Form I was essentially identical with that of Form II, indicating that both forms might be the products of the same gene. There were, however, minor differences in the phosphate content and the isoelectric point between the two forms.

Amino Acids↗
PubMed1980

Radiological diagnosis of acute gastric anisakiasis.

The radiological and clinical features of 41 cases of acute gastric anisakiasis, a form of visceral larva migrans caused by eating poorly cooked fish containing Anisakis larvae, are reviewed. The most important radiological finding, present in 31 patients (76%), was the demonstation of a thread-like filling defect approximately 30 mm long. Suggestive but indeterminate findings such as coarse, broad gastric folds due to mucosal edema were demonstrated in 10 patients (24%). In no case was the radiological examination negative. Once the presence of this larva is suspected, it can often be demonstrated radiologically using careful technique and interpretation.

Adult↗