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S Yahara

Publications and source records attributed to S Yahara.

At least 37 records · Page 2Linked to original sources
PubMed1993

Cyclic peptides, acyclic diterpene glycosides and other compounds from Lycium chinense Mill.

The chemical structures of four cyclic peptides, lyciumins A-D (1-4), three acyclic diterpene glycosides, lyciumosides I-III (5-7) and other three compounds, a tryptophan derivative glycoside (8), a monoterpene glycoside (9) and a steroidal glycoside (10) isolated from Lycium chinense, have been elucidated by a combination of chemical, 1H- and 13C-NMR, and mass spectrometric studies. Lyciumins are interesting because of their monocyclic octapeptides containing a novel C-N linkage between tryprophan N1 and glycine C alpha.

Amino Acid Sequence↗
PubMed1991

Structures of two new steroidal glycosides, soladulcosides A and B from Solanum dulcamara.

The structures of two new steroidal glycosides named soladulcosides A and B, isolated from the aerial parts of Solanum dulcamara including new sapogenols, were elucidated as (22R, 25R)-3 beta, 15 alpha, 23 alpha-trihydroxy-5 alpha-spirostan-26-one 3-O-alpha-L-rhamnopyranosyl-(1----2)-beta-D-glucopyranoside and (22R, 25R)-3 beta,23 alpha-dihydroxy-5 alpha-spirostan-26-one 3-O-alpha-L-rhamnopyranosyl-(1----2)-[alpha-L-rhamnopyranosyl-(1----4)]- beta-D-glucopyranoside, respectively.

Glycosides↗
PubMed1989

Studies on lens-aldose-reductase inhibitor in medicinal plants. II. Active constituents of Monochasma savatierii Franch. et Maxim.

The 70% acetone extract of Monochasma savatierii FRANCH. et MAXIM. showed very strong inhibition of rabbit lens aldose reductase (AR). From the active fraction, five iridoid glucosides along with the two phenolic glycosides, acteoside and dehydroacteoside, have been isolated. Among them, acteoside showed the highest activity, being about 2.5 times more potent than baicalein, a known natural inhibitor of AR (IC50 = 9.8 x 10(-7) M). Demethylmussaenoside and 7-O-acetyl-8-epi-loganic acid, which are iridoid glucosides, had weak inhibitory activity.

Aldehyde Reductase↗
PubMed1989

The structure of M-GTFI, an inhibitor of glucosyltransferase from S. mutans, and its inhibitory relationship with other sulfate ester-containing inhibitors.

M-GTFI, an inhibitor of glucosyltransferase from S. mutans was produced by Micromonospora narashinoensis strain No. 731. The isolation procedure for M-GTFI was improved and established for spectroscopic analyses, and some properties of the inhibitor were investigated. The structure of M-GTFI was shown to be trisodium [2-sulphonato-(E)-9-undecenyll-oxacyclotriacont-(E)-3- en-2-one, 16, 18-bis sulphonate. The chemical structure of M-GTFI was therefore similar to that of izumenolide which is a beta-lactamase inhibitor containing sulfate ester groups in its molecule. The inhibitory characteristics of M-GTFI were parallel to that of other inhibitory compounds containing sulphate esters but the spectrum of activity was wider.

Alkanesulfonates↗
PubMed1987

A streptothricin-like antibiotic mixture, A-269A (and A-269A').

A streptothricin-like antibiotic, A-269A (referred to as A-269A hereafter) was isolated from the culture broth of Streptomyces sp., strain No. A-269. In this paper, the characterization of the producer, and the production, isolation, physico-chemical properties and biological properties of A-269A are reported. The structure of the antibiotic was also examined by 1H NMR, 13C NMR and fast atom bombardment mass spectra studies. From the spectroscopic data, A-269A was assumed to be a mixture of antibiotic LL-BL 136 and an isomeric compound in which the carbamoyl group is substituted on C-12' hydroxyl instead of C-10 hydroxyl.

Aminoglycosides↗
PubMed1984

Metabolism of cerebrosides and sulfatides in subcellular fractions of developing rat brain.

Previous studies on myelinating rat brain indicated that microsomes, Golgi-enriched and cytosol fractions may process galactolipids destined for myelin. To extend these findings we labeled brain galactolipids in vivo and determined the specific radioactivity of cerebrosides and sulfatides in several subcellular fractions. 17-day-old rats were treated by intracranial injection with [14C]galactose 60 min prior to and [3H]galactose 15 min prior to killing. Subcellular fractions were prepared from brain stem, and concentrations of cerebrosides and sulfatides were determined, their radioactivity measured and the 3H/14C ratio compared. Our results showed that the heavier Golgi-enriched fraction (designated Fraction 2) is unique in its low galactolipid content and high specific radioactivities of cerebrosides and sulfatides. The low ratio of the specific activity of cerebroside to that of sulfatide in Fraction 2 compared to other fractions indicates that it may be the site of most rapid conversion of newly synthesized cerebrosides to sulfatides. The specific radioactivities of cerebrosides and sulfatides in cytosol are intermediate between those in Golgi-enriched Fraction 2 and microsomes and those in myelin, consistent with the role postulated for cytoplasmic elements in the transport of cerebrosides and sulfatides to myelin.

Animals↗
PubMed1983

Monoclonal antibodies to hepatitis B surface antigen (HBsAg) as a tool for the automated HBsAg screening.

Hybridomas secreting monoclonal antibodies to hepatitis B surface antigen (HBsAg) were established by fusion of the spleen cells from mice immunized with purified HBsAg with the mouse myeloma cell line P3-NSI/1-Ag4-1. The monoclonal antibodies to the group-specific antigen (a) produced by one of them were used for the automated screening of HBsAg on the Groupamatic 360 (Kontron International). Its sensitivity is almost equal, but slightly inferior, to the system employing polyclonal horse antibodies to HBsAg; it barely detects 6 ng/ml of HBsAg. It is also as highly specific as the system with polyclonal antibodies; the incidence of false-positive reactions is 0.2%. These results indicate that the monoclonal antibodies will become a practical source for the HBsAg screening on the Groupamatic.

Animals↗
PubMed1982

A change in the cerebrosides and sulfatides in a demyelinating nervous system. Development of the methodology and study of multiple sclerosis and Wallerian degeneration.

This report described a new method for the microanalysis of sphingolipids and its application for the characterization of cerebrosides and sulfatides in multiple sclerosis brain and rat sciatic nerves undergoing Wallerian degeneration. Tissue was extracted with isopropanol/hexane (20:78), and the total lipids obtained were subjected to benzoylation-desulfation. A portion of this was directly analyzed by silica-column high performance liquid chromatography for the determination of nonhydroxycerebroside, hydroxycerebroside, nonhydroxysulfatide, and hydroxysulfatide. Another portion was fractionated by thin-layer chromatography, and the spots corresponding to the sphingolipid derivatives were eluted. The material from each spot was analyzed by reverse phase high performance liquid chromatography for its homolog composition. With this new procedure the concentrations and homolog compositions of cerebrosides and sulfatides were measured in plaque, periplaque, and normal-appearing white matter from brains of multiple sclerosis patients and Wallerian degenerated rat sciatic nerves distal to the nerve transection. One piece of plaque studied contained only 1.86, 2.76, 0.60, and 0.45 nmol of nonhydroxycerebroside, hydroxycerebroside, nonhydroxysulfatide and hydroxysulfatide/mg of protein, respectively. These concentrations are less than 1% of those found in normal white matter. Periplaques were found to contain concentrations of these sphingolipids between those of plaque and normal white matter. The levels of these sphingolipids in degenerative nerves were 10-20% below normal the third day after the nerve was severed and about 70% below normal after 10 days. The rate of decrease lessened from ten days to 55 days. The homolog compositions of these sphingolipids in both multiple sclerosis brain and degenerating nerves were similar to those in the control. The implications of these findings and the advantages of this new analytical method are discussed.

Adult↗
PubMed1981

Levels and syntheses of cerebrosides and sulfatides in subcellular fractions of jimpy mutants.

During the period of brain development, the levels of nonhydroxy- and hydroxycerebrosides in the cytosol from brains of jimpy mutants were determined by high-performance liquid chromatography and compared to those in the rest of the particulates from the same brains as well as those in the littermate controls. The concentrations of cerebrosides in jimpy brain preparations were much lower than in controls at all ages. In another experiment, [U-14C]glucose was injected intraperitoneally into jimpy mutants and their littermate controls. The amounts of radioactivity incorporated into cerebrosides and sulfatides in brain cytosol, the microsome-rich fraction, and the rest of the heavier particles were determined. Although the total radioactivity incorporated into these lipids was much lower in jimpy, the specific activities were 2-3 times the control value in all subcellular fractions.

Animals↗
PubMed1981

Characterization of alkylgalactolipids from calf brain by high performance liquid chromatography.

Minor nonpolar galactolipids were isolated from the total lipids of calf brain stem by column chromatography and were separated by preparative thin-layer chromatography into four groups. The material recovered from the bottom band of the thin-layer chromatography consisted of monogalactosyl diglyceride and its 1-0-alkyl isomer, alkylgalactolipid, present in a molar ratio of 11:9. After perbenzoylation, they were separated by preparative thin-layer chromatography and characterized. The fatty acid compositions of these lipids were similar to each other and to those of the ester-linked fatty acids of cerebroside esters. The major alkyl group of alkylgalactolipid was palmityl, and the other, minor componenents were oleyl, myristyl, and stearyl ethers. Perbenzoylated derivatives of these lipids were further separated by reverse-phase high performance liquid chromatography. The chromatograms from these two lipids were similar; however, most of the peaks were still mixtures of homologs containing different fatty acids or an alkyl group.

Animals↗
PubMed1980

A method for the automated screening for hepatitis B surface antigen.

A reverse passive hemagglutination (RPHA-G) technique for the automated screening of hepatitis B surface antigen (HBsAg) on the Groupamatic 360 (Kontron International, Zürich, Switzerland) has been developed. It is more sensitive than manual RPHA (RPHA-M) and nearly as sensitive as radioimmunoassay (RIA); it detects 6 ng/ml of HBsAg, compared to 3 ng/ml by RIA and 25 ng/ml by RPHA-M. Although it is slightly inferior to the other two methods in respect of specificity, the incidence of false-positive reactions was only 0.34%. The test can also be performed manually without the Groupamatic.

Automation↗