Search PubMed⌕ Search

Biomedical subjects

H C Yang

Publications and source records attributed to H C Yang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Antitumor, genotoxicity and anticlastogenic activities of polysaccharide from Curcuma zedoaria.

The antitumor effect of the partially purified polysaccharide from Curcuma zedoaria was studied in mice transplanted with sarcoma 180 cells. The polysaccharide fraction, CZ-1-III, at dose of 6.25 mg/kg/d showed 50% inhibition in solid tumor growth. When mice were injected with fractions, CZ-1 and CZ-1-III, at the dose of 100.0 mg/kg, 91.6% and 97.1% of tumor growth were inhibited, respectively, indicating that the cytotoxic effect of polysaccharide on sarcoma 180 cells increases upon increasing the amount of polysaccharide administered. To assess the genotoxicity of CZ-1-III fraction, several classical toxicological tests were performed. In Ames test, CZ-1-III did not show any transformation of revertant with or without S-9 metabolic activating system, indicating the lack of mutagenic effect of the compound. To assess clastogenic effect, micronucleus and chromosomal aberration assays were performed using Chinese hamster lung (CHL) fibroblast cells. However, up to 259.0 microg/ml concentration of CZ-1-III, neither micronucleus formation nor chromosomal aberration was induced regardless of the presence of S-9 metabolic activating system. Inhibition of CZ-1-III on micronucleus formation induced by mitomycin C was exhibited in a dose-dependent manner, maximally up to 52.0%. These results strongly suggest that CZ-1-III, the polysaccharide fraction from C. Zedoaria, decreases tumor size of mouse and prevents chromosomal mutation.

Animals↗
PubMed2000

Inhibitory effect of Artemisia asiatica alkaloids on acetylcholinesterase activity from rat PC12 cells.

We screened 42 Korean traditional tea plants to determine the inhibitory effect of acetylcholinesterase and attenuation of toxicity induced by amyloid-beta peptide, which were related to the treatment of Alzheimer's disease (AD). The methanolic extract from Artemisia asiatica among tested 42 tea plants, showed the highest inhibitory effect (48%) on acetylcholinesterase in vitro. The methanolic extract was further separated with n-hexane, chloroform, and ethyl acetate of water, in order. The chloroform solubles, which were high in inhibitory effect of acetylcholinesterase, were repeatedly subjected to open column chromatography on silica gel. From the highest inhibitory fraction (78%) on acetylcholinesterase, the single compound was obtained by the Sep-Pak Cartridge (C18: reverse phase column). This compound was found to react positively on Dragendorff's reagent (potassium bismuth iodide), which typically reacted with the alkaloid. This compound was purified by HPLC (mu-bondapack C18 reverse phase column: 3.9 x 150 mm). The IC50 (the concentration of 50% enzyme inhibition) value of this compound was 23 micrograms/ml and the inhibitory pattern on acetylcholinesterase was mixed with competitive/non-competitive type. We examined the effects of this compound on toxicity induced by A beta (25-35) in rat pheochromocytoma PC12 cells. Pretreatment of the PC12 cells for 2 h with an alkaloid of Artemisia asiatica (1200 microg/ml) reduced the toxicity induced by A beta. This study demonstrated that an alkaloid of Artemisia asiatica, which was metabolized to small molecule in digestive tract and then could pass through the blood-brain barrier, appeared to be an acetylcholinesterase inhibitor with a blocker of neurotoxicity induced by A beta in human brain causing Alzheimer's disease.

Acetylcholinesterase↗
PubMed2000

Decentration, tilt, and near vision of the array multifocal intraocular lens.

PURPOSE: To study the periodic changes in decentration, tilt, and near vision in eyes with the Array(R) multifocal intraocular lens (IOL). SETTING: Department of Ophthalmology, St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea. METHOD: This study comprised 20 eyes of 10 patients older than 60 years who had binocular cataract and bilateral implantation of the Array multifocal IOL. Mean patient age was 66.0 years (range 60 to 75 years). After a clear corneal incision and continuous curvilinear capsulorhexis were made, each eye had phacoemulsification and in-the-bag IOL implantation. The amount of IOL decentration and degree of tilt were evaluated using the EAS-1000 anterior eye segment analysis system 1 day and 1 and 2 months postoperatively. Near and far visual acuities were measured at the same examinations. RESULTS: No statistically significant differences were observed in decentration (P =.13) or tilt (P =.32) throughout the follow-up. Mean uncorrected distance visual acuity was 0.68 +/- 0.27 (SD), and mean uncorrected near acuity was 0.49 +/- 0.15 2 months postoperatively. Uncorrected distance acuity better than 0.5 was achieved in 14 eyes (77.8%), in which the mean uncorrected distance acuity was 0.80 +/- 0.18 and the mean uncorrected near acuity was 0. 53 +/- 0.14 2 months postoperatively. CONCLUSIONS: Tilt and decentration of the Array multifocal IOL showed no significant progression up to 2 months after implantation. For near acuity, the Array IOL may be an effective aid.

Aged↗
PubMed2000

Cognitive stimulation in brainstorming.

Research on group brainstorming has demonstrated that it is less effective for generating large numbers of ideas than individual brainstorming, yet various scholars have presumed that group idea sharing should enhance cognitive stimulation and idea production. Three experiments examined the potential of cognitive stimulation in brainstorming. Experiments 1 and 2 used a paradigm in which individuals were exposed to ideas on audiotape as they were brainstorming, and Experiment 3 used the electronic brainstorming paradigm. Evidence was obtained for enhanced idea generation both during and after idea exposure. The attentional set of the participant and the content of the exposure manipulation (number of ideas, presence of irrelevant information) influenced this effect. These results are consistent with a cognitive perspective on group brainstorming.

Adult↗
PubMed2000

Laparoscopic-assisted renal biopsy: an alternative to open approach.

An open renal biopsy frequently is performed when the conventional percutaneous approach is contraindicated. Although many of the surgical procedures, previously performed by a traditional open technique, are now successfully accomplished by laparoscopic technique, there remains a paucity of reports on laparoscopic kidney biopsy. We describe the use of laparoscopic technique in performing native kidney biopsy in three patients and review the potential safety and accuracy of this approach. To date, laparoscopic-assisted renal biopsy has been reported in six patients. The average length of stay in our small series was 1.3 days, and there were no major or catastrophic complications. Adequate numbers of glomeruli for confirmation of microscopic diagnosis were obtained in all cases. The review of literature, in addition to our encouraging preliminary results of a small group of patients, shows a possible role of laparoscopic-assisted renal biopsy in place of an open renal biopsy.

Aged↗
PubMed1999

A retention mechanism for distribution of mitochondria during cell division in budding yeast.

Mitochondria are indispensable for normal eukaryotic cell function. As they cannot be synthesized de novo and are self-replicating, mitochondria must be transferred from mother to daughter cells. Studies in the budding yeast Saccharomyces cerevisiae indicate that mitochondria enter the bud immediately after bud emergence, interact with the actin cytoskeleton for linear, polarized movement of mitochondria from mother to bud, but are equally distributed among mother and daughter cells [1] [2] [3]. It is not clear how the mother cell maintains its own supply of mitochondria. Here, we found that mother cells retain mitochondria by immobilization of some mitochondria in the 'retention zone', the base of the mother cell distal to the bud. Retention requires the actin cytoskeleton as mitochondria colocalized with actin cables in the retention zone, and mutations that perturb actin dynamics or actin-mitochondrial interactions produced retention defects. Our results support the model that equal distribution of mitochondria during cell division is a consequence of two actin-dependent processes: movement of some mitochondria into the daughter bud and immobilization of others in the mother cell.

Actins↗
PubMed1999

Group-specific assays that distinguish between the four major types of mammalian phospholipase A2.

Phospholipase A2 (PLA2) constitutes a diverse superfamily of enzymes which catalyze the deacylation of phospholipids. At least four types of PLA2 are potentially involved in arachidonic acid release in cells and tissues. Since all of them catalyze the same enzymatic reaction, it is difficult to distinguish between them in mixtures of enzymes normally present in biological samples. Utilizing specific properties of each PLA2, we have designed distinct assay procedures which selectively and sensitively detect each type: Group VI Ca2+-independent PLA2, Group IV cytosolic Ca2+-dependent PLA2, Groups V and IIA secreted PLA2s. Each specific assay procedure is selective for a particular PLA2 type by at least fourfold and as high as four orders of magnitude relative to the other three enzymes. All assays can detect PLA2 activity with as low as subnanogram quantities of enzyme. Importantly, these assays are able to differentiate and quantitate the biochemically and structurally related enzymes, Group IIA and V sPLA2s in crude biological samples. Employing this system, we have found that iPLA2 is the dominant PLA2 in rat brain, and cPLA2 is the most abundant PLA2 in P388D1 macrophages and human amnionic WISH cells.

Animals↗
PubMed1999

A specific human lysophospholipase: cDNA cloning, tissue distribution and kinetic characterization.

Lysophospholipases are critical enzymes that act on biological membranes to regulate the multifunctional lysophospholipids; increased levels of lysophospholipids are associated with a host of diseases. Herein we report the cDNA cloning of a human brain 25 kDa lysophospholipid-specific lysophospholipase (hLysoPLA). The enzyme (at both mRNA and protein levels) is widely distributed in tissues, but with quite different abundances. The hLysoPLA hydrolyzes lysophosphatidylcholine in both monomeric and micellar forms, and exhibits apparent cooperativity and surface dilution kinetics, but not interfacial activation. Detailed kinetic analysis indicates that the hLysoPLA binds first to the micellar surface and then to the substrate presented on the surface. The kinetic parameters associated with this surface dilution kinetic model are reported, and it is concluded that hLysoPLA has a single substrate binding site and a surface recognition site. The apparent cooperativity observed is likely due to the change of substrate presentation. In contrast to many non-specific lipolytic enzymes that exhibit lysophospholipase activity, hLysoPLA hydrolyzes only lysophospholipids and has no other significant enzymatic activity. Of special interest, hLysoPLA does not act on plasmenylcholine. Of the several inhibitors tested, only methyl arachidonyl fluorophosphonate (MAFP) potently and irreversibly inhibits the enzymatic activity. The inhibition by MAFP is consistent with the catalytic mechanism proposed for the enzyme - a serine hydrolase with a catalytic triad composed of Ser-119, Asp-174 and His-208.

Amino Acid Sequence↗
PubMed1999

Regional distribution, ontogeny, purification, and characterization of the Ca2+-independent phospholipase A2 from rat brain.

We purified an 80-kDa Ca2+-independent phospholipase A2 (iPLA2) from rat brain using octyl-Sepharose, ATP-agarose, and calmodulin-agarose column chromatography steps. This procedure gave a 30,000-fold purification and yielded 4 microg of a near-homogeneous iPLA2 with a specific activity of 4.3 micromol/min/mg. Peptide sequences of the rat brain iPLA2 display considerable homology to sequences of the iPLA2 from P388D1 macrophages, Chinese hamster ovary cells, and human B lymphocytes. Under optimal conditions, the iPLA2 revealed the following substrate preference toward the fatty acid chain in the sn-2 position of phosphatidylcholine: linoleoyl > palmitoyl > oleoyl > arachidonoyl. The rat brain iPLA2 also showed a head group preference for choline > or = ethanolamine >> inositol. The iPLA2 is inactivated when exposed to pure phospholipid vesicles. The only exception is vesicles composed of phosphatidylcholine and phosphatidylinositol 4,5-bisphosphate. Studies on the regional distribution and ontogeny of various phospholipase A2 (PLA2) types in rat brain indicate that the iPLA2 is the dominant PLA2 activity in the cytosolic fraction, whereas the group IIA secreted PLA2 is the dominant activity in the particulate fraction. The activities of these two enzymes change during postnatal development.

Animals↗
PubMed1999

New strategies using 'low-dose' mycophenolate mofetil to reduce acute rejection in patients following kidney transplantation.

CONTEXT: Tacrolimus, microemulsion cyclosporine (Neoral), and mycophenolate mofetil (MMF) at 2 and 3 grams daily have demonstrated superior immunosuppressive properties in several recent clinical trials involving solid-organ transplants. An effective immunosuppression may be maintained with lower doses of MMF administered with either tacrolimus or microemulsion cyclosporine. OBJECTIVE: To compare tacrolimus plus "low-dose" MMF-based immunosuppressive regimen (TMBIR) with Neoral plus "low-dose" MMF-based immunosuppressive regimens (NMBIR) among kidney transplant recipients. DESIGN: Prospective, randomized study. PATIENTS: 53 consecutive adult recipients of kidney transplant. Both groups (TMBIR and NMBIR) were equally matched on demographic characteristics. INTERVENTIONS: Participants were randomized to receive orally either tacrolimus (0.08 mg/kg twice daily) (n = 27) or Neoral (4 mg/kg twice daily) (n = 26). Both regimens were started before surgery and continued when allograft demonstrated no postoperative acute tubular necrosis. Both groups received similar "low-dose" MMF (500 mg twice daily) and prednisone (2 mg/kg/day to taper off after 1 year). Switch from tacrolimus to Neoral or vice versa was allowed after refractory rejection or serious adverse events. MAIN OUTCOME MEASURE: Acute rejection and patient and graft survival 1 year following kidney transplant. RESULTS: One-year patient survival rates were 88.9% for the TMBIR group and 100% for the NMBIR group; 1-year graft survival rates were 88.9% for the TMBIR group and 96.1% for the NMBIR group. No significant differences were found in the incidence of biopsy-confirmed acute rejection (14.8% TMBIR vs 23% NMBIR). Steroid-resistant rejections requiring cytolytic antibody therapy were higher in the NMBIR group (50% vs 25%). Three patients crossed over from NMBIR to TMBIR for refractory rejections and 1 patient crossed over from TMBIR to NMBIR for new onset seizure. Three episodes of cytomegalovirus infection were observed in the TMBIR group. Other adverse events were similar in both groups. CONCLUSIONS: Both tacrolimus and microemulsion cyclosporine combined with "low-dose" MMF and corticosteroids provide effective immunosuppression and have similar adverse events in kidney transplant recipients.

Acute Disease↗
PubMed1998

Blockage of apoptotic signaling of transforming growth factor-beta in human hepatoma cells by carboxyfullerene.

Transforming growth factor-beta (TGF-beta) has been shown to induce apoptosis in normal hepatocytes and hepatoma cells both in vivo and in vitro. However, the mechanism by which TGF-beta induces apoptosis is not clear. The antiapoptotic activity of antioxidants including N-acetyl-L-cysteine (Ac-Cys), ascorbic acid and a novel free radical scavenger, carboxyfullerene (C60) on TGF-beta-treated human hepatoma Hep3B cells was examined. Only the water-soluble hexacarboxylic acid derivative of C60 was found to prevent TGF-beta-induced apoptosis. Antiapoptotic activity of C60 correlated its ability to eliminate TGF-beta-generated reactive oxygen species (ROSs). However, C60 did not interfere with TGF-beta-activated PAI-1 promoter activity in the Hep3B cells. These results indicate that the signaling pathway of TGF-beta-induced apoptosis may be related to the generation of ROSs and may be uncoupled from the TGF-beta-activated gene promoter activity. Furthermore, the regioisomer of C60 with a C3 symmetry was more potent in protecting cells from apoptosis than that with a D3 symmetry, and the C3 isomer had stronger interactions with lipid bilayers than the D3 isomer. The spectroscopic analysis revealed that the C3 isomer had stronger interactions with artificial lipid bilayers than the D3 isomer. Therefore, our study indicates that C60 may interact with membrane to eliminate TGF-beta-induced ROSs and to prevent apoptosis occur in human hepatoma cells.

Acetylcysteine↗
PubMed1998

Peloisis hepatis due to Bartonella henselae in transplantation: a hemato-hepato-renal syndrome.

BACKGROUND: Bacillary peliosis hepatis is an uncommon but well recognized disease due to disseminated Bartonella infections occurring predominantly in immunocompromised individuals infected with human immunodeficiency virus, type 1. A similar condition in the absence of Bartonella infection when described in organ transplant patients was felt to be secondary to azathioprine and/or cyclosporine. METHODS: Herein, we report the first case of bacillary peliosis hepatis due to systemic Bartonella henselae infection in a patient after kidney transplant. The patient presented with severe anemia, persistent thrombocytopenia, and hepato-renal syndrome. DNA-based polymerase chain reactions (PCR), which allowed direct detection of both B henselae and quintana DNA in patient's peripheral blood and liver tissue, were used. Indirect immunofluorescence assay for Bartonella serology was performed on peripheral blood. RESULTS: Histopathology of the liver biopsy demonstrated peliosis hepatis. Indirect immunofluorescence assay for Bartonella serology was positive, and B henselae DNA was identified by PCR in the peripheral blood and liver tissue. Treatment with a 3-month course of oral erythromycin resulted in an excellent clinical response. CONCLUSIONS: The present case suggests that although various anti-rejection therapies and opportunistic infections are associated with hepatic and renal dysfunction along with bone marrow suppression, the diagnostic evaluation in this situation should include liver biopsy and a careful search for evidence of systemic Bartonella infection, e.g., exposure to cats, Bartonella serology, and Bartonella DNA by PCR. A reduction in immunosuppression and prolonged therapy with antibiotics such as erythromycin will often result in early recovery.

Adult↗
PubMed1998

Intestinal immune system modulating polysaccharides from rhizomes of Atractylodes lancea.

Hot water extract (ALR-0) of rhizomes of Atractylodes lanceo DC. was fractionated into MeOH-soluble fraction (ALR-1), supernatant fraction of EtOH precipitation (ALR-3 + 4), and crude polysaccharide fraction (ALR-5). Among these fractions, only ALR-5 showed potent stimulating activity for proliferation of bone marrow cells mediated by Peyer's patch cells. ALR-5 gave three potently active carbohydrate-rich fractions (ALR-5IIa, 5IIb, and 5IIc) by anion-exchange chromatography on DEAE-Sepharose CL-6B, and three active polysaccharides (ALR-5IIa-1-1, ALR-5IIb-2-2, and ALR-5IIc-3-1) were further purified from the respective fractions. The order of activity was revealed to be ALR-5IIb-2-2 > or = ALR-5IIa-1-1 > ALR-5IIc-3-1, ALR-5IIa-1-1, 5IIb-2-2, and 5IIc-3-1 each was eluted as a single peak on HPLC and their molecular weights were estimated to be 74,000, 3,100, 16,000, respectively. ALR-5IIa-1-1 consisted mainly of Ara and Gal (molar ratio; 0.6: 1.0) in addition to a trace amount of uronic acid whereas ALR-5IIb-2-2 and ALR-5IIc-3-1 mainly comprised Ara, Gal, GlcA, and GalA (molar ratio; 0.2: 1.0: 0.2: 0.8, and 0.5: 1.0: 0.7: 1.5, respectively). Methylation analysis indicated that ALR-5IIa-1-1 consisted mainly of terminal Araf, 4- or 5-linked Ara, 3.4- or 3.5-branched Ara, and 3-linked, 4-linked, and 3,6-branched Gal. ALR-5IIb-2-2 and ALR-5IIc-3-1 were composed mainly of terminal Araf, 4- or 5-linked Ara, 4-linked Gal, 4-linked GalA, and terminal GlcA. In addition, ALR-5IIb-2-2 mainly comprised 4-linked Xyl whereas ALR-5IIc-3-1 consisted mainly of 2,4-branched Rha. Single radial gel diffusion indicated that ALR-5IIa-1-1 showed a strong reactivity with beta-glucosyl-Yariv antigen, whereas ALR-5IIb-2-2 and ALR-5IIc-3-1 did not show the reactivity with the antigen. Treatments of ALR-5IIa with NalO4, NaClO2 and pronase did not reduce the stimulating activity for Peyer's patch cells, however combination of exo-alpha-L-arabinofuranosidase and exo-beta-D-(1-->3)-galactanase digestions of ALR-5IIa-1-1 significantly decreased its activity.

Adjuvants, Immunologic↗
PubMed1998

Colorimetric MTT assessment of antifungal activity of D0870 against fluconazole-resistant Candida albicans.

The in vitro antifungal activity of D0870 against eight isolates of fluconazole-resistant Candida albicans was compared with that of itraconazole, ketoconazole and miconazole. The colorimetric MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] assay was used to assess the antifungal activities. The 50% minimum inhibitory concentration (MIC50) of D0870 was below 0.031 microgram ml-1 for seven isolates and 0.25 microgram ml-1 for one isolate. The activity of D0870 was superior to that of the other azoles. Ketoconazole was the most effective azole next to D0870. Therefore, the new bis-triazole, D0870, is expected to be promising for the therapy of fluconazole-resistant candidosis. The present data also confirmed that the MTT assay may be useful for evaluation of resistance and detection of resistant C. albicans.

Antifungal Agents↗
PubMed1998

Imidazole-induced morphological abnormalities of mitochondria of Candida albicans.

The mitochondrial morphology of live Candida albicans samples treated with several imidazoles (miconazole, econazole and clotrimazole) was observed with a fluorescent carbocyanine probe, 3,3'-dihexyloxacarbocyanine [diO-C6-(3)], under a fluorescence microscope. Nearly all non-treated C. albicans cells carried only long tubular mitochondria. Treatment with antimycotics at half the minimum inhibitory concentrations (MIC100) rapidly induced mitochondrial cleavage or fragmentation, which was followed by recovery to the normal tubular morphology within 1 h. Exposing the yeast to drugs at concentrations higher than the MICs resulted in the development of swollen mitochondria or amorphous bodies. These phenomena were concentration dependent. The fluorescence images were also compared with ultrastructural images obtained by transmission electron microscopy.

Antifungal Agents↗
PubMed1997

Involvement of phospholipase A2 in neurodegeneration.

Phospholipases A2 are a heterogeneous class of enzymes that hydrolyse fatty acids from the sn-2 2 position of membrane phospholipids. Prolonged stimulation of phospholipase A2 may damage membrane integrity, not only because of the loss of essential phospholipid from the lipid bilayer but also as a result of an uncontrollable Ca2+ influx. The increased levels of intracellular Ca2+ may be responsible for enhanced lipolysis, proteolysis and DNA fragmentation. This process along with the accumulation of lipid peroxidation products may be associated with neurodegeneration in acute neural trauma (ischemia, head and spinal cord injuries) and neurodegenerative diseases (Alzheimer's disease).

Animals↗