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Biomedical subjects

K Furuhata

Publications and source records attributed to K Furuhata.

At least 19 recordsLinked to original sources
PubMed1992

Chlorination of cellulose with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in lithium chloride-N,N-dimethylacetamide.

Microcrystalline cellulose was chlorinated with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in LiCl-N,N-dimethylacetamide. At the early stage of the reaction only replacement of the 6-hydroxyl groups with chlorine was observed, and 3-hydroxyl groups were replaced at a lower rate with Walden inversion. The effects of reaction conditions on the extent of chlorination were studied in detail. More than two equivalents of chlorination reagents per glucose residue were necessary to attain a high degree of substitution (ds) by chlorine, and the maximum ds attained was 1.86. Chlorinated disaccharides were found in the hydrolyzates of chlorodeoxycelluloses hydrolyzed under mild conditions, and their structures were studied by mass spectrometry.

Acetamides↗
PubMed1991

Studies on glycosylation of the mitomycins. Syntheses of 7-N-(4-O-glycosylphenyl)-9a-methoxymitosanes.

Two new derivatives of glycosyl mitomycin C, 7-N-[4-O-(beta-D-glucopyranosyl and alpha-sialosyl)phenyl]-9a- methoxymitosanes, were synthesized, and their structures were elucidated by analysis of the nuclear magnetic resonance spectra. Field desorption mass spectrometry was successfully used for the confirmation of these structures. The cytotoxic, antibacterial, and antitumor activities of 7-N-(4-glycosylphenyl)-9a- methoxymitosanes were also examined.

Animals↗
PubMed1990

4-Methylumbelliferyl-alpha-glycosides of partially O-acetylated N-acetylneuraminic acids as substrates of bacterial and viral sialidases.

4-O-Acetylated, 7-O-acetylated, and 9-O-acetylated 4-methylumbelliferyl-alpha-N-acetyl-neuraminic acids (Neu4,5Ac2-MU, Neu5,7Ac2-MU, Neu5,9Ac2-MU) were tested as substrates of sialidases of Vibrio cholerae and of Clostridium perfringens. Both sialidases were unable to hydrolyse Neu4,5Ac2-MU. This compound at 1 mM concentration did not inhibit significantly the cleavage of Neu5Ac-MU, the best substrate tested. The 4-O-acetylated sialic acid glycoside is hydrolysed slowly by the sialidase from fowl plague virus. The relative substrate specificity, reflected in V/Km of the Vibrio cholerae sialidase is Neu5Ac-MU much greater than Neu5,7Ac2-MU approximately Neu5,9Ac2-MU and of the clostridial enzyme it is Neu5Ac-MU greater than Neu5,9Ac2-MU greater than Neu5,7Ac2-MU. The affinities of both enzymes for the side-chain O-acetylated sialic acid derivatives are higher than for Neu5Ac-MU. The artificial, well-defined substrates, described here, provide the opportunity to quantify the influence of sialic acid O-acetylation on the hydrolysis of sialoglycoconjugates without the side effects introduced by other parts of more complex glycans.

Acetylation↗
PubMed1989

Determination of mono-O-acetylated N-acetylneuraminic acids in human and rat sera by fluorometric high-performance liquid chromatography.

A simple, rapid, and highly sensitive fluorometric high-performance liquid chromatographic method for the determination of N-acetylneuraminic acid and its mono-O-acetyl derivatives in human and rat sera is described. The neuraminic acids, released by hydrolysis of serum in 2 M acetic acid, are converted with 1,2-diamino-4,5-methylenedioxybenzene, a fluorogenic reagent for alpha-keto acids, to highly fluorescent derivatives without the occurrence of O-acetyl migration and de-O-acetylation. The derivatives are separated isocratically within 25 min by reversed-phase chromatography using a TSK gel ODS-120T column. The limits of detection are 57-192 fmol in a 10-microliters injection volume at a signal-to-noise ratio of 3. This sensitivity permits precise determination of the neuraminic acids in 5 microliters of human and rat sera.

Animals↗
PubMed1989

Studies on sialic acids. XIII. Isolation of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN) from chum salmon, Oncorhynchus keta.

A method for analysis of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN) by high-performance liquid chromatography (HPLC) with a strongly basic anion-exchange resin was developed. The method was applied to detect free KDN in water used to rinse of fertilized eggs of chum salmon, Oncorhynchus keta. Furthermore, KDN was isolated from the water as a fully protected derivative.

Animals↗
PubMed1989

[Bone drilling simulation by three-dimensional imaging].

The three-dimensional display technique has a wide range of medical applications. Pre-operative planning is one typical application: in orthopedic surgery, three-dimensional image processing has been used very successfully. We have employed this technique in pre-operative planning for orthopedic surgery, and have developed a simulation system for bone-drilling. Positive results were obtained by pre-operative rehearsal; when a region of interest is indicated by means of a mouse on the three-dimensional image displayed on the CRT, the corresponding region appears on the slice image which is displayed simultaneously. Consequently, the status of the bone-drilling is constantly monitored. In developing this system, we have placed emphasis on the quality of the reconstructed three-dimensional images, on fast processing, and on the easy operation of the surgical planning simulation.

Computer Simulation↗
PubMed1988

The S.pombe mei2 gene encoding a crucial molecule for commitment to meiosis is under the regulation of cAMP.

The complete nucleotide sequence of the mei2 gene of Schizosaccharomyces pombe, which is essential for initiation of meiosis, is presented and four transcriptional start sites assigned. Transcription of mei2 and other genes involved in life cycle control of S. pombe, which is inducible by nitrogen starvation, is inhibited by addition of cAMP, suggesting that cAMP can mediate the signal of nitrogen supply in S.pombe. mei2 is the furthest downstream among target genes regulated by cAMP and genetic or physiological factors so far shown to block uncontrolled meiosis in S.pombe, which is provoked by inactivation of the part1 gene product, are either mutations at the mei2 locus or inhibitors of its expression. Cooperation of two regulatory pathways, one leading to the inactivation of pat1 activity and the other to the supply of the mei2 product, appears to commit cells to meiosis in S.pombe.

Base Sequence↗
PubMed1987

Synthesis of 9-O-acyl- and 4-O-acetyl-sialic acids.

Various 9-O-acyl derivatives of N-acetyl- and N-glycoloyl-neuraminic acid, and O-(5-acetamido-3,5-dideoxy-D-glycero-alpha- and beta-D-galacto-2-nonulopyranosylonic acid)-(2----6)-O-beta-D-galactopyranosyl-(1----4)-D-glucopyranose were regioselectively synthesized by use of ortho esters. In addition, 5-acetamido-4-O-acetyl-D-glycero-D-galacto-2-nonulopyranosonic acid was prepared starting from the benzyl and methyl esters of N-acetylneuraminic acid.

Carbohydrate Conformation↗
PubMed1983

Reduced drug metabolism in isolated hepatocytes from adjuvant arthritic rats.

Viable hepatocytes were isolated from the livers of rats with adjuvant arthritis by the collagenase-perfusion method and measured for activities of drug-metabolizing enzymes. These cells produced radioactive metabolites from 14C-aminopyrine and 14C-aniline to a much lesser extent than the control hepatocytes that were derived from pair-fed normal rats. On the other hand, 14C-aminopyrine was scarcely metabolized by non-parenchymal cells other than hepatocytes, even when incubated with those from control rats. Although there were no significant differences in cell yield, viability and oxygen consumption, the cellular uptake of indocyanine green was significantly slower in the arthritic hepatocytes than the control hepatocytes. Morphologically, the freshly isolated arthritic hepatocytes demonstrated the disappearance of the microvilli, the appearance of bleb-like protrusions in the plasma membrane and the widespread distribution of the rough endoplasmic reticulum associated with a relatively decreased area of the smooth endoplasmic reticulum in the cytoplasma. Biochemically, these cells showed a significantly higher RNA/DNA ratio and an ability to incorporate 14C-leucine into proteins more rapidly, as compared to the control hepatocytes. A possible relationship between the reduction of the drug metabolizing activity and the production of the acute phase proteins in rat hepatocytes after an inflammatory stimulus was discussed.

Aminopyrine↗