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Biomedical subjects

R Sawa

Publications and source records attributed to R Sawa.

At least 73 records · Page 4Linked to original sources
PubMed1995

Tetrodecamycin and dihydrotetrodecamycin, new antimicrobial antibiotics against Pasteurella piscicida produced by Streptomyces nashvillensis MJ885-mF8. II. Structure determination.

Novel antimicrobial antibiotics against Pasteurella piscicida, tetrodecamycin (1) and weakly active dihydrotetrodecamycin (2) were isolated from a culture broth of Streptomyces nashvillensis MJ885-mF8. The planar structure of 1 was determined to be 2-acyl-4-ylidene tetronic acid alkyl ether containing decaline ring by various NMR spectral data of 1 and its acetyl derivative (3). The structure of 2 was elucidated by comparison with the spectral data of 1 and confirmed by catalytic reduction of 1 into 2. The X-ray crystallography of 2 showed the relative stereochemistry. Their absolute configurations were determined by using modified Mosher's method.

Anti-Bacterial Agents↗
PubMed1995

Azicemicins A and B, new antimicrobial agents produced by Amycolatopsis. II. Structure determination.

A new structural class of antibiotics, azicemicins A (1) and B (2) were isolated from the culture broth of Amycolatopsis sp. MJ126-NF4. Their structures were elucidated from their physico-chemical properties, various NMR experiments and chemical transformations and were shown to be 3-(1-methyl-2-aziridinyl)- and 3-(2-aziridinyl)-3,4-dihydro-3,7,8,10,12b-pentahydroxy-9,12-dimeth oxy-benz [a]anthracene-1,6(2H,5H)-dione, respectively.

Actinobacteria↗
PubMed1994

Plasma adenosine concentration in appropriate- and small-for-gestational-age fetuses.

OBJECTIVE: Our purpose in this study was to investigate the relationship between fetal plasma adenosine concentration and catecholamine concentration, blood gases, and pH in appropriate- and small-for-gestational-age fetuses. STUDY DESIGN: Cordocentesis was performed in 23 appropriate- and 14 small-for-gestational-age fetuses at 30 to 37 weeks' gestation for the measurement of umbilical venous blood plasma adenosine and catecholamine concentrations, blood gases, and pH. RESULTS: In small-for-gestational-age fetuses plasma adenosine concentration was higher, umbilical venous PO2 and pH were lower, and PCO2 was significantly higher than in appropriate-for-gestational-age fetuses. The elevation of plasma adenosine concentration was inversely related to umbilical venous PO2 and pH. CONCLUSION: Some small-for-gestational-age fetuses are exposed to diminished oxygen tension and acidotic blood gas values in utero. We postulate that the accompanying elevation of plasma adenosine may elicit protective adaptation during fetal asphyxia as a stress response.

Adenosine↗
PubMed1994

Aldecalmycin, a new antimicrobial antibiotic from Streptomyces. I. Taxonomy, fermentation, isolation, physico-chemical and biological properties.

A new antibiotic, aldecalmycin, has been discovered in the culture broth of Streptomyces sp. MJ147-72F6. Aldecalmycin was purified by solvent extraction, Diaion HP-20 chromatography, silica gel chromatography, Sephadex LH-20 chromatography, HPLC and centrifugal partition chromatography. The 1H and 13C NMR spectra of aldecalmycin showed the presence of keto-enol tautomers. Aldecalmycin is equipotent in inhibiting the growth of sensitive and methicillin-resistant Staphylococcus aureus (MRSA).

Anti-Bacterial Agents↗
PubMed1994

Aldecalmycin, a new antimicrobial antibiotic from Streptomyces. II. Structure elucidation by NMR studies.

A new antibiotic, aldecalmycin (1) was isolated from the culture broth of Streptomyces sp. MJ147-72F6. The 1H and 13C NMR spectra of 1 were complicated due to the presence of a beta-ketoaldehyde moiety. Therefore, 1 was converted into an ethylene ketal derivative (2) and into a dihydroaldecalmycin (3). These derivatives gave assignable NMR spectra. The planar structure was elucidated by using 1H-1H COSY, 2D-HOHAHA, 1H-13C COSY and HMBC spectra of 2. The conformation of the decalin ring was elucidated by using ID-HOHAHA, NOE difference and NOESY spectra of 3. The geometry of double bond in the side chain was determined by NOE difference and NOESY spectra of 3.

Anti-Bacterial Agents↗
PubMed1994

Aldecalmycin, a new antimicrobial antibiotic from Streptomyces. III. Determination of absolute configuration.

The planar structure of aldecalmycin (1) had been determined in the previous paper, together with the conformations of the substituted trans decalin ring having one double bond and the sugar: beta-glucopyranoside type. The absolute configuration of 1 was a following problem to be solved. X-Ray crystallographic analysis of crystalline 4'-6'-O-benzylidenedihydroaldecalmycin (4) revealed the relative configuration. On the other hand, the stereoisomerism of the sugar was determined to be D by the optical rotation value of tetra-O-acetyl-alpha-methylglucopyranoside derived from 1. These results established the absolute configuration of 1.

Anti-Bacterial Agents↗
PubMed1993

Disappearance of palmitic acid from plasma of fetal and newborn sheep.

These studies were undertaken to measure the kinetic constants that characterize the disappearance of a representative free fatty acid (FFA) from the plasma of fetal and newborn sheep. A bolus of albumin-complexed [14C]palmitic acid was infused intravenously, and during the next 8 min, 24 arterial samples were collected to characterize the disappearance curve. Palmitic acid disappearance from plasma was well described by a double-exponential model. When birth was simulated in utero, kinetic values were not changed by cooling. However, after intrauterine ventilation with O2, the volume of distribution of the FFA increased 29%, its plasma clearance rate decreased 26%, and its apparent half-life in the plasma lengthened from 0.8 to 1.2 min (all P < 0.01, n = 8). After umbilical cord occlusion, plasma clearance rate decreased a further 19% and half-life lengthened to 1.4 min. About 60% of the increase in FFA concentration during simulated birth is explained by increased release from adipose stores, and 40% is explained by decreased clearance. Further experiments tested the influence of FFA concentrations themselves. After infusion of unlabeled FFA, clearance of the tracer decreased 23% (P < 0.05, n = 5), a result consistent with a saturable membrane transporter of FFAs.

Animals↗
PubMed1993

Delaminomycins, novel nonpeptide extracellular matrix receptor antagonist and a new class of potent immunomodulator. II. Physico-chemical properties and structure elucidation of delaminomycin A.

Delaminomycins, novel extracellular matrix receptor antagonists, have been isolated from a culture broth of Streptomyces albulus MJ202-72F3. The structure of delaminomycin A was determined to be 3-[[2-[(3E,5E)-2,8-dihydroxy-7-methyl-3,5-decadienyl]- 1,6,8- trimethyl-1,2,4a,5,6,7,8,8a-octahydro-1-naphthyl]carbonyl]-5- hydroxypyrrolidine-2,4-dione by analyses of spectral properties and chemical studies.

Adjuvants, Immunologic↗