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Biomedical subjects

H Seto

Publications and source records attributed to H Seto.

At least 19 recordsLinked to original sources
PubMed1992

Nucleotide sequence of a carboxyphosphonoenolpyruvate phosphonomutase gene isolated from a bialaphos-producing organism, Streptomyces hygroscopicus, and its expression in Streptomyces lividans.

The carboxyphosphonoenolpyruvate (CPEP) phosphonomutase gene of bialaphos-producing Streptomyces hygroscopicus, which encodes a C-P bond forming enzyme was cloned into Streptomyces lividans and sequenced. The amino acid composition of the protein coded in an open reading frame of 295 codons and its calculated molecular mass, 32,800 Da, coincided well with those of the purified enzyme. Introduction of the CPEP phosphonomutase gene, the expression of which is controlled by the promoter of the aph gene, into S. lividans resulted in the production of this enzyme at a level almost equivalent to that in the parent strain.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of phosphoenolpyruvate phosphomutase from Pseudomonas gladioli B-1.

Phosphoenolpyruvate phosphomutase (PEPPM) catalyzes C-P bond formation by intramolecular rearrangement of phosphoenolpyruvate to phosphonopyruvate (PnPy). We purified PEPPM from a gram-negative bacterium, Pseudomonas gladioli B-1 isolated as a C-P compound producer. The equilibrium of this reaction favors the formation of the phosphate ester by cleaving the C-P bond of PnPy, but the C-P bond-forming reaction is physiologically significant. The C-P bond-forming activity of PEPPM was confirmed with a purified protein. The molecular mass of the native enzyme was estimated to be 263 and 220 kDa by gel filtration and polyacrylamide gel electrophoresis, respectively. A subunit molecular mass of 61 kDa was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that the native protein was a tetramer. The optimum pH and temperature were 7.5 to 8.0 and 40 degrees C, respectively. The Km value for PnPy was 19 +/- 3.5 microM, and the maximum initial velocity of the conversion of PnPy to phosphoenolpyruvate was 200 microM/s/mg. PEPPM was activated by the presence of the divalent metal ion, and the Km values were 3.5 +/- 1.4 microM for Mg2+, 16 +/- 5 nM for Mn2+, 3.0 +/- 1.5 microM for Zn2+, and 1.2 +/- 0.2 microM for Co2+.

Carbon↗
PubMed1992

New redistribution index of nutritive blood flow to skeletal muscle during dynamic exercise.

BACKGROUND: Cardiac output is effectively redistributed to working muscle by regional changes in vascular resistance. However, there has been no suitable method to quantify blood flow distribution to large working and nonworking muscles involved in ergometer or treadmill exercise. METHODS AND RESULTS: To quantify the redistribution of blood flow, we compared thallium activity in a bicycle pedaling leg with that in the contralateral resting leg in 10 normal subjects. The regional thallium activity was expressed as a percentage of the whole-body radioisotope activity. Comparison of thallium activity between legs was performed at rest and at the work rates of anaerobic threshold and peak exercise during one-leg exercise. Thallium distribution of both legs was essentially the same at rest. At the anaerobic threshold, thallium activity increased about threefold to fourfold in the exercising thigh and about twofold in the exercising calf. The thallium distribution in these muscles at peak exercise was the same as at the anaerobic threshold. In the nonexercising calf, thallium distribution during exercise decreased significantly, and it was unchanged in the nonexercising thigh. Consequently, the ratio of thallium activity between the exercising and nonexercising thighs increased from 1.1 +/- 0.1 to 4.0 +/- 0.9 at the anaerobic threshold and to 3.3 +/- 0.6 at peak exercise. Similarly, the ratio between the exercising and nonexercising calves increased from 1.0 +/- 0.0 to 3.8 +/- 1.3 at the anaerobic threshold and to 3.5 +/- 1.0 at peak exercise. The ratios at peak exercise, however, did not differ significantly from those at the anaerobic threshold. CONCLUSIONS: These findings suggest that the redistribution of blood flow occurs predominantly during mild to moderate exercise; therefore, blood flow in the leg during strenuous exercise would depend primarily upon an increased cardiac output. Thus, the thallium activity ratio of exercising and nonexercising legs reflects the difference in vascular tone of each leg and could provide a noninvasive and quantitative index of blood flow redistribution.

Adult↗
PubMed1992

A child with pituitary gigantism and precocious adrenarche: does GH and/or PRL advance the onset of adrenarche?

We describe a female child with pituitary gigantism and precocious adrenarche. From two years of age she showed unusual overgrowth, and at 5 years old she was 133.5 cm (+ 5.5 SD) tall and weighed 40.5 kg. Her precocious manifestations were public hair, acne vulgaris, hirsutism, and advanced bone age. Endocrinological examination revealed markedly increased serum growth hormone (GH) and prolactin (PRL), which responded paradoxically to a TRH test. In addition, the concentrations of serum dehydroepiandrosterone (DHA) and its sulfate (DHAS) were increased to adult levels, moving in accordance with changes in ACTH, which suggested that these androgens were secreted from the adrenal glands functionally. These androgens seemed to be responsible for her partial precocity. Prior reports have suggested that GH and/or PRL overproduction might have played a role in the induction of adrenarche. Also, in previous reports of 9 gigantism patients under 10 years old, the manifestation of precocious adrenarche was suggested in 8. Further investigation of the influence of GH and PRL on adrenal androgen production in children with pituitary gigantism is required. On the other hand, in short children with normal GH secretion, attention should be paid to whether or not the GH therapy in early childhood induces precocious adrenarche.

Adenoma↗
PubMed1992

Studies on viridenomycin, a novel 24-membered macrocyclic polyene lactam antibiotic.

A new antitumor antibiotic, designated AL081, was obtained from the culture filtrate of an actinomycete identified as Streptomyces gannmycicus, and found to be identical with viridenomycin by direct comparison. The structure of the antibiotic was determined by NMR spectral analysis including a variety of two-dimensional techniques to be a novel 24-membered macrocyclic polyene lactam. Viridenomycin prolonged the survival periods of mice bearing P388 leukemia and B16 melanoma cells.

Animals↗
PubMed1992

A new anthracycline antibiotic, cinerubin R. Taxonomy, structural elucidation and biological activity.

A novel anthracycline antibiotic, cinerubin R, was isolated from the fermentation broth of Streptomyces eurythermus strain H1715MY2. The structure of cinerubin R was elucidated to be 4"-aculosyl-4'-rhodinosyl-7-rhodosaminyl-epsilon-py rromycinone. Cinerubin R was active against Gram-positive bacteria and inhibited the growth of divergent multi-drug-resistant cells to the same extent as their parental cells.

Animals↗
PubMed1992

New polyenic antibiotics active against gram-positive and gram-negative bacteria. IV. Structural elucidation of enacyloxin IIa.

The chemical structure of a unique polyenic antibiotic enacyloxin IIa (former name: fr. 2) produced by Frateuria (formerly Gluconobacter) sp. W-315 has been determined by extensive spectroscopic studies, in particular by NMR spectral analysis. It has a novel non-lactonic structure involving 3,4-dihydroxycyclohexanecarboxylic acid with a chlorine-containing polyenic and polyhydroxy acyl side chain attached as an ester to the 3-hydroxyl substituent of the acid.

Acetobacteraceae↗
PubMed1992

Circumvention of multidrug resistance in human carcinoma KB cells by polyether antibiotics.

We examined the effect of various polyether antibiotics on colchicine resistance in multidrug-resistant KB-C4 cells which exhibit about 4,000-fold resistance to colchicine. As a result, 4 out of 14 polyether antibiotics were found to reverse colchicine resistance. Among them, laidlomycin was the most potent. It potentiated colchicine cytotoxicity on KB-C4 cells about 700-fold at 1 microgram/ml. Degree of potentiation was calculated by dividing of the IC50 value of colchicine in the absence of a polyether antibiotic by the IC50 value of colchicine in the presence of the polyether antibiotic. Monensin, dianemycin, and leuseramycin at 3 micrograms/ml also potentiated the cytotoxicity, about 100-fold. We previously reported that inostamycin is a potent chemosensitizer in KB-C4 cells. Although lysocellin has a structure very similar to that of inostamycin, it didn't reverse colchicine resistance. It slightly increased [3H]vinblastine accumulation in KB-C4 cells and weakly inhibited the [3H]vinblastine binding to KB-C4 plasma membranes.

Anti-Bacterial Agents↗
PubMed1992

Studies on the biosynthesis of bialaphos (SF-1293) 12. C-P bond formation mechanism of bialaphos: discovery of a P-methylation enzyme.

An enzymatic activity catalyzing P-methylation of N-acetyldemethylphosphinothricin, a biosynthetic intermediate of the herbicide bialaphos, was detected in a cell extract of Streptomyces hygroscopicus SF-1293, a bialaphos producing organism. The gene coding for this P-methylation enzyme in the bialaphos biosynthetic gene cluster was also expressed in Streptomyces lividans. The methyl donor of the reaction was determined to be methylcobalamin. The P-methylation enzyme utilized both N-acetyldemethylbialaphos and N-acetyldemethylphosphinothricin as substrates.

Herbicides↗
PubMed1992

Adipostatins A and B, new inhibitors of glycerol-3-phosphate dehydrogenase.

As a result of screening for inhibitors of glycerol-3-phosphate dehydrogenase, which may be effective to prevent corpulence, we isolated two inhibitors named adipostatin A and adipostatin B from the culture broth of Streptomyces cyaneus 2299-SV1. Their structures have been established to be 5-n-pentadecylresorcinol and 5-isopentadecylresorcinol, respectively. Adipostatin A and adipostatin B inhibited glycerol-3-phosphate dehydrogenase at the IC50 values of 4.1 microM and 4.5 microM, respectively. These compounds prevented triglyceride accumulation in 3T3-L1 cells at a concentration of the microM level.

3T3 Cells↗
PubMed1992

Total and regional bone mineral density by dual photon absorptiometry in patients on maintenance hemodialysis.

To evaluate bone loss in renal osteodystrophy, we measured total and regional (head, trunk, pelvis, leg and arm) bone mineral density (BMD) by dual photon absorptiometry in 72 patients on maintenance hemodialysis (HD). We also examined the validity of serum carboxy-terminal parathyroid hormone (C-PTH) and intact-PTH as an indicator of secondary hyperparathyroidism. Total BMD correlated inversely with age in female patients (r = -0.57, p less than 0.01), but not in male patients. Female patients older than 50 years were omitted from analysis to exclude the effect of menopause on bone. Among clinical and biochemical parameters, only trunk BMD correlated inversely with the duration of HD (r = -0.26, p less than 0.05). Head, trunk and total BMD correlated inversely with serum alkaline phosphatase, C-PTH and intact-PTH, while pelvis BMD did not. Leg and arm BMD also correlated inversely with serum intact-PTH, but not with serum C-PTH. The serum level of C-PTH correlated positively with the duration of HD (r = 0.40, p less than 0.005), while intact-PTH did not. As compared with 18 control male volunteers aged 25-42 years, trunk, pelvis, leg, arm and total BMD were significantly lower in male patients on HD aged 22-49 years, whereas head BMD did not differ significantly between the two groups. The percent decrease of BMD was most prominent in the trunk (-19.6%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1991

Determination of a guanosine-malonaldehyde adduct in urine by high-performance liquid chromatography with a thiobarbituric acid reaction detector.

A new method for the determination of a guanosine-malonaldehyde adduct, beta-D-ribofuranosylpyrimido[1,2-a]purin-10(3H)-one (GMA), in rat and human urine is described. The method involves rapid pretreatment using, in sequence, polyamide, ion-exchange and reversed-phase cartridges; determination is by means of high-performance liquid chromatography with a thiobarbituric acid reactor in series with a fluorescence detector. This device can quantitatively determine the adduct at the sub-picomole level. This rapid, selective and sensitive method is suitable for the determination of guanine-malonaldehyde adducts in biological samples, such as human and rat urine. A semi-preparative method for the extraction and purification of these adducts from rat urine and for their identification by mass spectrometry and high-performance liquid chromatography with ultraviolet detection is also reported.

Animals↗
PubMed1991

Metastatic angiosarcoma of the brain.

Two patients with metastatic angiosarcoma of the brain are described. In one, a 17-year-old man, the tumor was located at the pineal region and exhibited significant vascularity. It was sensitive to radiation therapy and disappeared after radiation of 50 Gy; however, it recurred after 1 year and a new lesion was found in the liver. The other patient is a 31-year-old woman who experienced sudden onset of headache. Computed tomography scan revealed three separate masses in the brain. One tumor was surgically removed. The other two were sensitive to radiation therapy and disappeared after radiation of 40 Gy. A new lesion was found in the femur 16 months after the operation. Brain metastasis from angiosarcoma is exceedingly rare. Both patients developed symptoms with intracranial hemorrhage. The diagnosis of the metastatic lesions preceded diagnosis of the primary lesion by 12 and 16 months, respectively. Ulex europaeus 1 lectin and factor VIII were very useful in establishing the diagnosis of angiosarcoma.

Adolescent↗