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Biomedical subjects

Y C Wu

Publications and source records attributed to Y C Wu.

At least 37 records · Page 2Linked to original sources
PubMed2001

C. elegans CED-12 acts in the conserved crkII/DOCK180/Rac pathway to control cell migration and cell corpse engulfment.

We have identified and characterized a novel C. elegans gene, ced-12, that functions in the conserved GTPase signaling pathway mediated by CED-2/Crkll, CED-5/DOCK180, and CED-10/Rac to control cell migration and phagocytosis of apoptotic cells. We provide evidence that ced-12 likely acts upstream of ced-10 during cell migration and phagocytosis and that CED-12 physically interacts with CED-5 and forms a ternary complex with CED-2 in vitro. We propose that the formation and localization of a CED-2-CED-5-CED-12 ternary complex to the plasma membrane activates CED-10, leading to the cytoskeletal reorganization that occurs in the polarized extension of cell surfaces in engulfing cells and migrating cells. We suggest that CED-12 counterparts in higher organisms regulate cytoskeleton dynamics, as CED-12 does in C. elegans.

Amino Acid Sequence↗
PubMed2001

Cytotoxic constituents of the fruits of Cananga odorata.

A new guaipyridine sesquiterpene alkaloid, cananodine (1), and two new eudesmane sesquiterpenes, cryptomeridiol 11-alpha-L-rhamnoside (2) and gamma-eudesmol 11-alpha-L-rhamnoside (3), along with gamma-eudesmol (4), were isolated from the fruits of Cananga odorata. The structures of compounds 1-3 were established on the basis of NMR and MS methods. In addition, compounds 1-4 and four previously reported alkaloids, cleistopholine (5), N-trans-feruloyltyramine (6), (+)-ushinsunine-beta-N-oxide (7), and lyscamine (8), were evaluated for cytotoxicity against two human hepatocarcinoma cell lines.

Acetylation↗
PubMed2001

Novel cytotoxic annonaceous acetogenins from Annona muricata.

Seven new annonaceous acetogenins, muricins A-G (1-7), as well as five known compounds, a mixture of muricatetrocin A (8) and muricatetrocin B (9), longifolicin (10), corossolin (11), and corossolone (12), were isolated from the seeds of Annona muricata. The structures of all isolates were elucidated and characterized by spectral and chemical methods. These acetogenins showed significantly selective in vitro cytotoxicities toward the human hepatoma cell lines Hep G(2) and 2,2,15.

Antineoplastic Agents, Phytogenic↗
PubMed2001

The alkaloids of Artabotrys uncinatus.

A novel type of alpha,beta-butenolide alkaloid, uncinine (1), two novel oxoaporphines, artabonatine C (2) and artabonatine D (3), a new oxazoloaporphine, artabonatine E (4), and a new 7,7'-bisdehydroaporphine, artabonatine F (5), along with 25 known alkaloids, were isolated from Artabotrys uncinatus. The structures of 1-5 were determined using NMR and mass spectral data. Atherospermidine and squamolone exhibited cytotoxicity against hepatocarcinoma cancer cell lines (Hep G(2) and 2,2,15), and the activity of some of the alkaloids in an antithrombin assay is also discussed.

Alkaloids↗
PubMed2001

Mechanical effects of liriodenine on the left ventricular-arterial coupling in Wistar rats: pressure-stroke volume analysis.

1. In a recent in vivo study, liriodenine, an aporphine alkaloid, has been identified as a prominent anti-arrhythmic agent that can prevent rats' sudden deaths, even at the dose as low as 10(-7) g kg(-1). The aim of this study was to determine whether liriodenine at its effective anti-arrhythmic dose of 10(-7) g kg(-1) had effects on the left ventricular (LV)-arterial coupling in Wistar rats. 2. LV pressure and ascending aortic flow signals were recorded to construct the ventricular and arterial end-systolic pressure-stroke volume relationships to calculate LV end-systolic elastance (E(es)) and effective arterial volume elastance (E(a)), respectively. The optimal afterload (Q(load)) determined by the ratio of E(a) to E(es) was used to measure the optimality of energy transmission from the left ventricle to the arterial system. 3. Liriodenine at the dose of 10(-7) g kg(-1) showed no significant changes in basal heart rate (HR), cardiac output (CO), LV end-systolic pressure (P(es)), E(a), E(es), and Q(load). 4. By contrast, liriodenine at the dose of 10(-6) g kg(-1) produced a significant fall of 2.0% in HR and a significant rise of 5.8% in CO, but no significant change in P(es). Moreover, liriodenine administration of 10(-6) g kg(-1) to rats significantly decreased E(es) by 8.5% and E(a) by 10.6%, but did not change Q(load). 5. We conclude that liriodenine at the dose of 10(-7) g kg(-1) has no effects on the mechanical properties of the heart and the vasculature and the matching condition for the left ventricle coupled to its vasculature in rats. Even at 10 times the effective anti-arrhythmic dose, liriodenine shows no effects on the efficiency of energy transferred from the left ventricle to the arterial system.

Analysis of Variance↗
PubMed2001

Duodenal reflux induces cyclooxygenase-2 in the esophageal mucosa of rats: evidence for involvement of bile acids.

BACKGROUND & AIMS: Reflux of duodenal contents including bile acids is believed to contribute to esophageal injury and Barrett's esophagus. Cyclooxygenase (COX)-2, an inducible form of COX, has been implicated in both inflammation and carcinogenesis. In this study, we investigated the effects of bile acids and duodenal reflux on COX-2 expression in cultured esophageal cells and tissue, respectively. METHODS: Immunoblotting and Northern blotting were used to assess the effects of bile acids on COX-2 expression in esophageal cell lines. Immunoblotting and immunohistochemistry were performed to evaluate the effects of duodenal reflux on COX-2 expression and cell proliferation in esophageal tissue. RESULTS: Unconjugated bile acids were about fivefold more potent inducers of COX-2 messenger RNA, COX-2 protein, and prostaglandin synthesis than conjugated bile acids. Acidifying the culture medium sensitized esophageal cells to bile acid-mediated induction of COX-2. The induction of COX-2 by bile acids was mediated by phosphatidylinositol-3 kinase and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases. In experimental animals, duodenoesophageal reflux led to esophagitis, marked thickening of the esophageal mucosa, and enhanced expression of COX-2. Increased immunoreactivity for Ki-67 and cyclin D1 indicated that enhanced cell proliferation contributed to mucosal thickening. CONCLUSIONS: Reflux of duodenal contents into the esophagus led to increased COX-2 expression and mucosal thickening. Bile acids are likely to contribute to these effects.

Animals↗
PubMed2001

Flow cytometry compared with indirect immunofluorescence for rapid detection of dengue virus type 1 after amplification in tissue culture.

Dengue virus (DV) was detected early in infected mosquito C6/36 cells by using indirect immunofluorescence (IF) in conjunction with flow cytometry. Three fixation-permeabilization methods and three DV serotype 1 (DEN-1)-specific monoclonal antibodies, 8-8 (anti-E), 16-4 (anti-NS1), and 15F3-1 (anti-NS1), were evaluated for the detection of DEN-1 in infected C6/36 cells. We found that these three monoclonal antibodies were capable of detecting DV in C6/36 cells as early as 24 h postinoculation by using a conventional indirect IF stain. Both 8-8 and 16-4 detected DV earlier and showed a greater number of DV-positive cells than 15F3-1. In flow cytometry, 3% paraformaldehyde plus 0.1% Triton X-100 with 16-4, the best fixation-permeabilization method for testing DV, showed higher sensitivity (up to 1 PFU) than indirect IF stain. The higher sensitivity of 16-4 in detecting DEN-1 was found with both IF and flow cytometry. Flow cytometry, which had a sensitivity similar to that of nested reverse transcription-PCR, was more sensitive in detecting DV in the infected mosquito cells 10 h earlier than the conventional IF stain. When clinical specimens were amplified in mosquito C6/36 cells and then assayed for DV using flow cytometry and conventional virus isolation at day 7 postinfection, both methods had 97.22% (35 out of 36) agreement. Moreover, among 12 positive samples which were detected by conventional culture method, the flow cytometry assay could detect DV in 58.33% (7 out of 12) of samples even at day 3 postinfection. In conclusion, both monoclonal antibodies 8-8 and 16-4 can be used for the early detection of DEN-1-infected C6/36 cells, with 16-4 (anti-NS1) being the best choice for the rapid diagnosis of DV by both the IF staining and flow cytometry methods.

Animals↗
PubMed2001

A novel mutation in the calcium-sensing receptor gene in a Chinese subject with persistent hypercalcemia and hypocalciuria.

Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant disorder characterized by high penetrance of relatively benign, lifelong persistent hypercalcemia and hypocalciuria. By contrast, neonatal severe hyperparathyroidism represents a life-threatening form of hypercalcemia that can cause the early newborn mortality if immediate intervention is not undertaken. Both disorders are due to inactivation mutation of the human calcium-sensing receptor (CaSR) gene on chromosome 3q21-24. Up to now, more than 30 mutations in the CaSR gene associated with FHH have been described. In this study, we analyzed one 79-yr-old male with hypocalciuric hypercalcemia without siblings or children to compare with an additional group of 50 normal Chinese subjects in Taiwan. DNA sequence analysis of the CaSR gene was performed. The result showed that the proband had a heterozygous nonsense mutation in exon 7 of the CaSR gene at codon 648 (CGA-->TGA/Arg-->Ter). This mutation, located in the COOH-terminal of the first intracellular loop of the CaSR, predicts a markedly truncated protein. We have identified a novel R648X mutation in the CaSR gene in one patient with FHH in Taiwan

Aged↗
PubMed2001

UCN-01 suppresses E2F-1 mediated by ubiquitin-proteasome-dependent degradation.

E2F-1 regulates the transcription of genes required for DNA synthesis. Previously, we have reported that UCN-01 suppresses E2F-1 protein expression without any noticeable effect on its mRNA level in gastric cancer cell line SK-GT5 (Clin. Cancer Res., 4: 2201-2206, 1998). In this study, we investigated the mechanism responsible for the suppression of E2F-1 expression by UCN-01 in SK-GT5 cells. After 24-h exposure to 1 microM UCN-01, E2F-1 protein expression was decreased by >99%. The suppressive effect of UCN-01 could be reversed by ubiquitin-dependent proteasome inhibitors such as calpain inhibitor I and lactacystin. Transfection experiments using expression plasmids encoding full-length E2F-1 or truncated E2F-1 with deletion of the COOH-terminal region (which is required for eliciting ubiquitination and protein degradation) revealed that the expression of truncated E2F-1 was not affected by UCN-01. Other cell-cycle-related and ubiquitin-proteasome-regulated proteins such as p21, p27, and cyclin B1 were not repressed by UCN-01 in E2F-1-overexpressing cells. In vitro-translated, full-length E2F-1 degraded more rapidly upon incubation with extracts from UCN-01-treated cells when compared with truncated E2F-1. Taken together, these data indicate that UCN-01 suppresses E2F-1 protein expression mediated by the ubiquitin-proteasome pathway in a specific manner.

Acetylcysteine↗
PubMed2000

NUC-1, a caenorhabditis elegans DNase II homolog, functions in an intermediate step of DNA degradation during apoptosis.

One hallmark of apoptosis is the degradation of chromosomal DNA. We cloned the Caenorhabditis elegans gene nuc-1, which is involved in the degradation of the DNA of apoptotic cells, and found that nuc-1 encodes a homolog of mammalian DNase II. We used the TUNEL technique to assay DNA degradation in nuc-1 and other mutants defective in programmed cell death and discovered that TUNEL labels apoptotic cells only during a transient intermediate stage. Mutations in nuc-1 allowed the generation of TUNEL-reactive DNA but blocked the conversion of TUNEL-reactive DNA to a subsequent TUNEL-unreactive state. Completion of DNA degradation did not occur in the absence of cell-corpse engulfment. Our data suggest that the process of degradation of the DNA of a cell corpse occurs in at least three distinct steps and requires activities provided by both the dying and the engulfing cell.

Animals↗
PubMed2000

Power Doppler angiographic appearance and blood flow velocity waveforms in invasive cervical carcinoma.

OBJECTIVES: The aim of this study was to investigate the effectiveness of transvaginal power Doppler angiography in predicting cervical malignancy by detecting intratumoral blood flow and to understand the relationship between squamous cell carcinoma (SCC) serum levels and intratumoral blood flow analysis of invasive cervical carcinoma before treatment. METHODS: Thirty-eight patients with cervical carcinoma (35 with stages Ia to IVb invasive carcinoma, 3 with cervical carcinoma in situ) were enrolled for the evaluation of tumor flow using transvaginal ultrasound accompanied with power Doppler angiography before surgery. The pulsatility, resistance index, and vascular index of tumor flow were measured. Thirty patients with proven healthy cervices were used as the control group. Pretreatment SCC serum levels were obtained in 34 women with cervical carcinoma. RESULTS: The pulsatility index and resistance index were significantly lower in the study group than in the control group (P < 0.0001). The vascular index was also significantly lower in the study group than in the control group (P < 0.0001). There were no significant differences among patients with SCC type and non-SCC type cervical carcinoma (P > 0.05) among the six parameters. There was no significant correlation between the pretreatment SCC serum levels with any of the six parameters obtained from the intratumoral blood flow analysis in the SCC group. CONCLUSIONS: Transvaginal ultrasound with power Doppler angiography is a valuable diagnostic tool for differentiating benign tumors of the cervix from malignant ones. Intratumoral blood flow of the cervix supplied us with practical diagnostic information before surgery and may aid in early prediction and management of cervical carcinoma. The use of transvaginal ultrasound with power Doppler angiography in the grading of vascularity ratio within cervical masses provided more sonographic characteristics among the different subclassifications of cervical cancer and is more useful than color Doppler imaging in the visualization of sonographic morphology.

Adenocarcinoma↗
PubMed2000

Analysis of programmed cell death in the nematode Caenorhabditis elegans.

The nematode Caenorhabditis elegans has been shown to be an excellent model organism with which to study the mechanisms of programmed cell death because of its powerful genetics and the ability to study cell death with single-cell resolution. In this chapter, we describe methods that are commonly used to examine various aspects of programmed cell death in C. elegans. These methods, in combination with genetic analyses, have helped identify and characterize many components of the C. elegans cell death pathway, illuminating the mechanisms by which these components affect programmed cell death.

Animals↗
PubMed2000

ent-kaurane diterpenoids from Annona glabra.

Three new kaurane diterpenoids, annoglabasin C (16alpha-acetoxy-ent-kauran-19-oic acid-17-methyl ester) (1), annoglabasin D (16alpha-acetoxy-ent-kauran-19-al-17-methyl ester) (2), and annoglabasin E (16alpha-hydro-19-ol-ent-kauran-17-oic acid) (3), and a new norkaurane diterpenoid, annoglabasin F (16alpha-acetoxy-19-nor-ent-kauran-4alpha-ol-17-methyl ester) (4), along with 13 known kaurane derivatives were isolated from the stems of Annona glabra. 16alpha-Methoxy-ent-kauran-19-oic acid (5) and 16alpha-hydro-ent-kauran-17,19-dimethyl ester (6) were obtained for the first time as natural products. The structures of compounds 1-6 were characterized by spectral analysis.

Diterpenes↗
PubMed2000

Aristolactams and dioxoaporphines from Fissistigma balansae and Fissistigma oldhamii.

Investigation of extracts of Fissistigma balansae and Fissistigma oldhamii resulted in the isolation of 11 aristolactams-stigmalactam (1), piperolactam A (2), piperolactam C (3), aristolactam AII (4), aristolactam AIIIa (5), aristolactam BII (6), aristolactam BIII (7), aristolactam FII (8), goniothalactam (9), enterocarpam I (10), and velutinam (11)-as well as two dioxoaporphines, noraristolodione (12) and norcepharadione B (13). The new compound 1 was identified by spectral data interpretation. Compounds 1-13 were subjected to antiplatelet aggregation testing.

Animals↗
PubMed2000

Cytotoxic constituents of Polyalthia longifolia var. pendula.

A new halimane diterpene, 3beta,5beta, 16alpha-trihydroxyhalima-13(14)-en-15,16-olide (1), and a new oxoprotoberberine alkaloid, (-)-8-oxopolyalthiaine (2), along with 20 known compounds, were isolated from a methanolic extract of Polyalthia longifolia var. pendula. The structures of compounds 1 and 2 were established by spectroscopic analysis. Several of these compounds were evaluated for cytotoxicity toward a small panel of human cell lines.

Alkaloids↗
PubMed2000

Tupichigenin A, a new steroidal sapogenin from Tupistra chinensis.

From the underground parts of Tupistra chinensis, a novel polyhydroxylated spirostanol sapogenin, tupichigenin A [(20S, 22R)-spirost-25(27)-ene-1beta,2beta,3beta,5beta- tetraol] (1), was isolated and determined structurally on the basis of spectroscopic methods. Also isolated was the known steroidal sapogenin (20S, 22R)-spirost-25(27)-ene-1beta,2beta,3beta,4beta, 5beta, 7alpha-hexaol-6-one (2).

China↗
PubMed2000

New alkaloids from Annona purpurea.

Three new alkaloids, promucosine (1), romucosine F (2), and romucosine G (3), along with 28 known compounds, were isolated from the MeOH extract of stems of Annona purpurea. The structures of 1-3 were determined on the basis of spectral data and chemical evidence.

Alkaloids↗