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Biomedical subjects

Y H Kuo

Publications and source records attributed to Y H Kuo.

At least 91 records · Page 5Linked to original sources
PubMed1994

Inhibition of platelet thromboxane formation and phosphoinositides breakdown by diisoeugenol.

Diisoeugenol inhibited the platelet aggregation and ATP release of rabbit platelets caused by ADP, arachidonic acid, platelet-activating factor (PAF), collagen and thrombin. Prolongation of the incubation time of platelets with diisoeugenol did not cause further inhibition and the aggregability of platelets could not be restored after washing. In human platelet-rich plasma, diisoeugenol inhibited the biphasic aggregation and ATP release induced by adrenaline and ADP in a concentration-dependent manner. Thromboxane B2 formation caused by arachidonic acid, collagen and thrombin was markedly inhibited by diisoeugenol in a concentration-dependent manner. Diisoeugenol also inhibited the formation of inositol monophosphate caused by collagen, PAF and thrombin. The cAMP level of washed platelets was not changed by diisoeugenol. It is concluded that the antiplatelet effect of diisoeugenol is due to the inhibition of thromboxane formation and phosphoinositides breakdown.

Adenosine Diphosphate↗
PubMed1993

Daphnoretin, a new protein kinase C activator isolated from Wikstroemia indica C.A. Mey.

Daphnoretin, a biologically active principle isolated from Wikstroemia indica C.A. Mey., caused platelet aggregation in washed rabbit platelets, platelet-rich plasma and whole blood. The aggregation of and ATP release from platelets induced by daphnoretin were similar to phorbol ester- and diacylglycerol-induced aggregation and release. The EC50 values of daphnoretin-, phorbol 12,13-dibutyrate (PDBu)- and 1-oleoyl-2-acetylglycerol (OAG)-induced platelet aggregation in washed rabbit platelets were 17.2 +/- 2.8 microM, 20.6 +/- 2.1 nM and 38.6 +/- 1.7 microM respectively. Platelet aggregation induced by daphnoretin and PDBu was not inhibited by indomethacin, BN52021 or sodium nitroprusside. ADP-scavenging systems, apyrase and phosphocreatine/creatine kinase, showed weak inhibition of the aggregation, and EGTA, triflavin, verapamil and prostaglandin E1 markedly inhibited the aggregation. Staurosporine, a potent protein kinase C inhibitor, suppressed daphnoretin-, PDBu- and OAG-induced aggregation and ATP release in a concentration-dependent manner. The IC50 values of staurosporine on daphnoretin (50 microM)-, PDBu (100 nM)- and OAG (50 microM)-induced aggregation were 37.7 +/- 8.3, 52.2 +/- 6.3 and 42.8 +/- 8.9 nM respectively. Daphnoretin did not cause significant thromboxane B2 formation in rabbit platelets. Neither daphnoretin nor PDBu caused [3H]inositol monophosphate formation or an increase in intracellular Ca2+ concentration in myo-[3H]inositol-labelled and Fura-2-loaded platelets. Platelet cytosolic protein kinase C was activated by daphnoretin and PDBu in a concentration-dependent manner with an EC50 of 12.4 +/- 1.2 microM and 18.7 +/- 1.4 nM respectively. Membrane-associated protein kinase C activity was increased by either daphnoretin or PDBu. [3H]PDBu binding to washed rabbit platelets was inhibited by daphnoretin in a concentration-dependent manner with an IC50 value of 45.2 +/- 5.2 microM. These results indicate that daphnoretin is a protein kinase C activator in rabbit platelets.

Animals↗
PubMed1993

Analysis of the neurotoxin beta-ODAP and its alpha-isomer by precolumn derivatization with phenylisothiocyanate.

A method is presented for determining 3-N-oxalyl-2,3-diaminopropanoic acid (beta-ODAP), the most potent neurotoxic substance of the seeds and seedlings of Lathyrus sativus, and its much less toxic 2-isomer (alpha-ODAP). The separation of the two forms is achieved after derivatization with phenylisothiocyanate employing a HPLC system. This method was used to monitor the isomerization of beta-ODAP to alpha-ODAP at different time intervals and to quantify the toxin level in seed extracts.

Amino Acids, Diamino↗
PubMed1993

Toxins in the seedlings of some varieties of grass pea (Lathyrus sativus).

The major toxin present in the dry seeds and seedlings of Lathyrus sativus is the neurotoxin 3-N-oxalyl-L-2,3-diaminopropanoic acid (beta-ODAP). The presence of one additional neurotoxin and an osteotoxin in the seedlings increases the overall toxicity. Isolation, purification, and detection of these toxins are described.

Fabaceae↗
PubMed1992

Regulation of alpha-amylase-encoding gene expression in germinating seeds and cultured cells of rice.

Four alpha-amylase-encoding cDNA (alpha Amy-C) clones were isolated from a cDNA library derived from poly(A)+RNA of gibberellic acid (GA3)-treated rice aleurone layers. Nucleotide sequence analysis indicates that the four cDNAs were derived from different alpha Amy genes. Expression of the individual alpha Amy gene in germinating seeds and cultured suspension cells of rice was studied using gene-specific probes. In germinating seeds, expression of the alpha Amy genes is positively regulated by GA3 in a temporally coordinated but quantitatively distinct manner. In cultured suspension cells, in contrast, expression of the alpha Amy genes is negatively and differentially regulated by sugars present in the medium. In addition, one strong and one weak carbohydrate-starvation-responsive alpha Amy genes have been identified. Interactions between the promoter region (HS501) of a rice alpha Amy gene and GA3-inducible DNA binding proteins in rice aleurone cells were also studied. A DNA mobility-shift assay showed that the aleurone proteins interact with two specific DNA fragments within HS501. One fragment is located between nt -131 to -170 and contains two imperfect directly repeated pyrimidine elements and a putative GA3-response element. The other fragment is located between nt -92 to -130 that contains a putative enhancer sequence. The interactions between aleurone proteins and these two fragments are sequence-specific and GA-responsive.

Base Sequence↗
PubMed1991

Metabolic derepression of alpha-amylase gene expression in suspension-cultured cells of rice.

We present evidence to show that the alpha-amylase gene family in rice is under two different modes of regulation: 1) hormonal regulation in germinating seeds, and 2) metabolic repression in cultured cells by available carbohydrate nutrients. Expression of alpha-amylase genes in deembryoed rice seeds is known to be induced by exogenous gibberellic acid. On the other hand, expression of alpha-amylase genes in suspension-cultured cells is induced by the deprivation of carbohydrate nutrient. A lag period of 2-4 h is required for the induction of alpha-amylase mRNA in sucrose-depleted medium. The induction of alpha-amylase expression is extraordinarily high and levels of alpha-amylase mRNA can be increased 8-20-folds after 24 h of sucrose starvation. The synthesis and secretion of alpha-amylase is also dependent upon the level of carbon source. The derepression or repression of alpha-amylase synthesis can be readily reversed by the deprivation or replenishment of sucrose in the medium, respectively. Glucose and fructose exert a repression on the alpha-amylase synthesis similar to that of sucrose. A hypothesis that explains the induction of alpha-amylase synthesis by carbohydrate starvation is proposed. Our data have suggested a hitherto undiscovered, potentially important control mechanism of carbohydrate metabolism in higher plants.

Blotting, Northern↗
PubMed1991

Biosynthesis of beta-(isoxazolin-5-on-2-yl)alanine, the precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid.

beta-(Isoxazolin-5-on-2-yl)alanine (BIA), a biosynthetic precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (ODAP), was confirmed to be derived from O-acetyl-L-serine (OAS) and isoxazolin-5-one by cysteine synthase in higher plants. Some properties of this enzyme in the biosynthesis of BIA are described.

Alanine↗
PubMed1990

Antitumor agents. 111. New 4-hydroxylated and 4-halogenated anilino derivatives of 4'-demethylepipodophyllotoxin as potent inhibitors of human DNA topoisomerase II.

A series of C-4 hydroxylated and halogenated anilino derivatives of epipodophyllotoxin or 4'-demethylepipodophyllotoxin have been synthesized and evaluated for their inhibitory activity against the human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. Compounds 11-17 and 22 are more potent than etoposide in causing DNA breakage, while compounds 11-13, 15, 16, and 20 are as active or more active than etoposide in their inhibition of the human DNA topoisomerase II. The cytotoxicity in KB cells appears to have no direct correlation with their ability to inhibit DNA topoisomerase II and to cause protein-linked DNA breaks in cells.

Antineoplastic Agents↗
PubMed1990

Antitumor agents. 113. New 4 beta-arylamino derivatives of 4'-O-demethylepipodophyllotoxin and related compounds as potent inhibitors of human DNA topoisomerase II.

A number of 4'-O-demethylepipodophyllotoxin derivatives possessing various 4 beta-N-, 4 beta-O- or 4 beta-S-aromatic rings have been synthesized and evaluated for their inhibitory activity against the human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. The results indicated, that for DNA topoisomerase II, a basic unsubstituted 4 beta-anilino moiety is structurally required for the enhanced activity. Substitution on this moiety with CN, COOCH3, COOC2H5, OH and COOCH3, OCH3, COCH3, CH2OH, OCH2O, OCH2CH2O, phenoxy, morpholino, NO2, and NH2 either at the para and/or the meta position yielded compounds which are as potent or more potent than etoposide. Substitution with COOC2H5 and OH at the ortho position afforded inactive compounds. Replacement of the aryl nitrogen with oxygen or sulfur gave compounds which are much less active or inactive. However, replacement of the phenyl ring with a pyridine nucleus furnished compounds which are as active or slightly more active than etoposide. There is a lack of correlation between the ability of these compounds in inhibiting DNA topoisomerase II and in causing protein-linked DNA breaks.

Antineoplastic Agents↗
PubMed1989

Studies on several naturally occurring lignans.

Form the bark of Taiwania cryptomerioides, the flower buds of Magnolia fargesii, the wood of Juniperus formosana, and the nutmeg of Myristica fragrans and Myristica cagayanensis, eleven new kinds of lignans and neoli gnans were isolated. The structures of these compounds were elucidated by physical and chemical methods.

Chemical Phenomena↗
PubMed1989

[Natural product research in Taiwan (II)].

The results of natural product research of the field of pharmaceutics and others (other than the field of chemistry) in Taiwan were described in this review and 290 research papers (until 1985) were collected. The review introduced the studies of chemical constituents of 270 maybe species of plants, one species of animal and one species of metabolite of fungus, from which 136 kinds of new compounds were isolated and elucidated.

Animals↗
PubMed1982

Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings.

Seeds of Pisum sativum L. cv Finale and Lathyrus odoratus L. cv Spencer were germinated aseptically in moistened sand in the dark. At several stages, the amino acid composition of the exudate and of the corresponding roots was analyzed. A number of common amino acids, including homoserine, were exuded by the growing seedling root in an early stage and were partly reabsorbed later. A number of uncommon amino acids, including several isoxazolin-5-one derivatives, uracil alanines, l-gamma-glutamyl-d-alanine, and alpha-aminoadipic acid were exuded at different rates.

Journal Article↗
PubMed1980

Demonstration of a software package for the reconstruction of the dynamically changing structure of the human heart from cone beam x-ray projections.

The Dynamic Spatial Reconstructor (DSR) is a device constructed at the Biodynamics Research Unit of the Mayo Clinic for (among other things) the visualization of the beating heart inside the intact thorax. The device consists of 28 rotating X-ray sources arranged on a circular arc at 6 degrees intervals (total span 162 degrees) and a matching set of 28 imaging systems. The whole thorax of the patient is projected onto the two-dimensional screen of the imaging systems by cone beams of X rays from the sources. All of the X-ray sources are switched on and off within a total period of 10 milliseconds. The Medical Image Processing Group at the State University of New York at Buffalo has developed a software package for the design and evaluation of algorithms to be used by the DSR. In this paper we illustrate the operation of the package and a particular algorithm for the reconstruction of the dynamically changing structure of the heart from data collected by the DSR.

Computers↗