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Biomedical subjects

H C Huang

Publications and source records attributed to H C Huang.

At least 73 records · Page 4Linked to original sources
PubMed1997

Decrease in myocardial Na(+)-K(+)-ATPase activity and ouabain binding sites in hypercholesterolemic rabbits.

OBJECTIVES: The purpose of this study was to explore the effect of high dietary cholesterol on the lipid composition, Na(+)-K(+)-ATPase activity and ouabain receptor property of the myocardial sarcolemma. METHODS: Male New Zealand white rabbits were fed with standard chow or standard chow supplemented with 0.5% (w/w) cholesterol and 10% (w/w) coconut oil to induce hypercholesterolemia. After 8 weeks, the rabbits were sacrificed; a myocardial sarcolemma fraction was then prepared from the left ventricular myocardium and analyzed for lipid composition. Assay of Na(+)-K(+)-ATPase activity and 3H-ouabain binding studies were performed in the myocardial sarcolemma from the control and cholesterol-fed rabbits. RESULTS: The cholesterol content, but not the phospholipid content, of the sarcolemma was significantly greater in the cholesterol-fed group, thus, resulting in an increased cholesterol/phospholipid molar ratio in the cholesterol-fed group. In addition, a decrease in Na(+)-K(+)-ATPase activity was also found in this group. The decrease in Na(+)-K(+)-ATPase activity was selective, since the Mg(++)-ATPase and 5'-nucleotidase activities remained unchanged. In the 3H-ouabain binding study, a decrease in the number of maximum binding sites, but not the binding affinity, for 3H-ouabain was found in the cholesterol-fed group. CONCLUSIONS: High dietary cholesterol induces higher levels of cholesterol not only in the plasma, but also in the myocardial sarcolemma. These changes result in decreased myocardial Na(+)-K(+)-ATPase activity mediated by a reduction in the maximum number of binding sites for ouabain but not a change in binding affinity.

5'-Nucleotidase↗
PubMed1997

Cytokeratin-19 associated with apoptosis and chemosensitivity in human cervical cancer cells.

Cytokeratins are one group of intermediate filament proteins responsible for the integrity of cell structure, and have been recently reported to play a role in conferring a drug resistance phenotype. MAb Cx-99 is a monoclonal antibody exhibiting the specificity toward its corresponding antigen which was recently identified as the cytokeratin-19 protein. In the present study, we found that the level of cytokeratin-19 in cervical cancer cells could be decreased by incubation of cancer cells with MAb Cx-99. The reduction of cytokeratin-19 level had a killing effect on cervical carcinoma SIHA and HeLa S3 cell lines. The DNA ladder pattern, convoluted nuclei and blebbing morphology were observed with these cells after exposure to MAb Cx-99 for 72 h, suggesting that the cytotoxic mechanism of reduced cytokeratin-19 was mediated by induction of apoptosis. Moreover, the MAb Cx-99 treatment could increase the cytotoxicities of cancer chemotherapeutic agents such as cisplatin and vinblastine to both cervical carcinoma cell lines. The LD80 values were at least 15-fold reduced when cancer cells were treated with cisplatin or vinblastine in the presence of MAb Cx-99. These results suggest that the functional role of cytokeratin-19 was associated with the apoptosis prevention and drug resistance of cervical cancer cells.

Journal Article↗
PubMed1997

The ATP-dependent HslVU protease from Escherichia coli is a four-ring structure resembling the proteasome.

HslVU is a new two-component protease in Escherichia coli composed of the proteasome-related peptidase HslIV and the ATPase HsIU. We have used electron microscopy and image analysis to examine the structural organization of HslV and HslU homo-oligomers and the active HslVU enzyme. Electron micrographs of HslV reveal ring-shaped particles, and averaging of top views reveal six-fold rotational symmetry, in contrast to other beta-type proteasome subunits, which form rings with seven-fold symmetry. Side views of HslV show two rings stacked together, thus, HslV behaves as dodecamer. The ATPase HslU forms ring-shaped particles in the presence of ATP, AMP-PNP or ADP, suggesting that nucleotide binding, but not hydrolysis, is required for oligomerization. Subunit crosslinking, STEM mass estimation, and analysis of HslU top views indicate that HslU exists both as hexameric and heptameric rings. With AMP-PNP present, maximal proteolytic activity is observed with a molar ratio of HslU to HslV subunits of 1:1, and negative staining electron microscopy shows that HslV and HsIU form cylindrical four-ring structures in which the HsIV dodecamer is flanked at each end by a HslU ring.

ATP-Dependent Proteases↗
PubMed1997

Cloning, expression and isoform classification of a minor oleosin in sesame oil bodies.

The oil bodies of plant seeds contain a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with alkaline proteins termed oleosins. Two distinct oleosins are present in the oil bodies of diverse angiosperms, and classified as high and low Mr isoforms according to their relative molecular masses in each species. In sesame oil bodies, besides the two ubiquitous oleosin isoforms (17 and 15 kDa), an additional minor oleosin (15.5 kDa) was revealed on Tricine SDS-PAGE. A full-length cDNA fragment was cloned, sequenced and deduced to be a putative oleosin of 15,446 Da. The gene was constructed in a fusion or non-fusion vector and then over-expressed with different efficiency in Escherichia coli. All three oleosins purified from sesame oil bodies were subjected to immunoassaying using antibodies raised against the over-expressed oleosin. The results confirmed that this gene encodes the sesame 15.5 kDa oleosin. Sequence comparisons with other known oleosins revealed that sesame 15.5 kDa oleosin does not represent a new oleosin isoform class but may have been derived through gene duplication and truncation of sesame 17 kDa oleosin, and possesses the minimal structure of the high Mr oleosin isoform. A conserved amphipathic alpha-helix is predicted in sesame 15.5 kDa oleosin, which may imply a potential biological function associated with this isoform.

Amino Acid Sequence↗
PubMed1997

Altered localization of HrpZ in Pseudomonas syringae pv. syringae hrp mutants suggests that different components of the type III secretion pathway control protein translocation across the inner and outer membranes of gram-negative bacteria.

Pseudomonas syringae pv. syringae 61 (Pss61) secretes the HrpZ harpin by a type III protein secretion pathway encoded by a cluster of hrp (hypersensitive response and pathogenicity) and hrc genes. The nine hrc genes represent a subset of hrp genes that are also conserved in the type III virulence protein secretion systems of animal pathogenic Yersinia, Shigella, and Salmonella spp. The hrpJ and hrpU operons contain seven hrc genes (counting hrcQ(A) and hrcQ(B) as one gene), all with additional homologs involved in flagellar biogenesis and secretion, and five of which encode predicted inner membrane proteins. The hrpC and hrpZ operons encode HrcC and HrcJ, respectively, which are associated with the outer membrane. Interposon mutants affected in all of the hrc genes in the hrpJ and hrpU operons and TnphoA-induced hrcC and hrcJ mutants were assayed for altered localization of HrpZ in mid-log-phase cultures by immunoblotting sodium dodecyl sulfate-polyacrylamide gels that were run with various cell fractions. The hrpJ and hrpU operon mutants revealed a novel phenotype of partially reduced accumulation of HrpZ in the total culture (despite wild-type levels of hrpZ operon transcription), all of which was cell bound and equivalent in level to that of cell-bound HrpZ in the wild type. The hrcC and hrcJ mutant cultures accumulated the same total amount of HrpZ as the wild type, but the HrpZ was cell bound. Among all the strains tested, only the hrcC mutant accumulated significant amounts of HrpZ in the periplasm, as indicated by selective release through spheroplasting. Analysis of nonpolar mutations in the hrpU and hrpC operons support the results obtained with polar mutations. These observations indicate that a constant pool of HrpZ is maintained in the cytoplasm of Pss61 despite secretion deficiencies, that the hrpJ and hrpU operons encode an alternative to the Sec (general protein export) pathway for translocation across the inner membrane, that genes in the hrpC operon are necessary for translocation across the outer membrane, and that the Pss61 Hrp system permits study of two genetically distinguishable stages in type III protein secretion.

Bacterial Outer Membrane Proteins↗
PubMed1997

Prolongation and enhancement of postischemic c-fos expression after fasting.

BACKGROUND AND PURPOSE: A rapid but transient expression of c-fos after cerebral ischemia has been extensively documented. However, the mechanism of this induction and whether induction of c-fos is neuroprotective or detrimental to the brain after ischemia is presently not clear. Fasting before transient cerebral ischemia has been shown to reduce delayed neuronal necrosis and infarct volume. The purpose of the present study was to examine the effect of preischemic fasting for 24 hours on the expression of c-fos after transient focal cerebral ischemia. METHODS: Focal cerebral ischemia was induced by temporary occlusion of the right middle cerebral artery and both common carotid arteries for 60 minutes. Male Long-Evans rats weighting 250 to 300 g were randomly divided into two groups: fed (control group) and food deprived for 24 hours (fasted group) before ischemic surgery. Infarct volumes were measured on the basis of triphenyltetrazolium chloride-delineated infarct areas, and plasma glucose levels were determined by the glucose oxidase method. Temporal and spatial expression of c-fos was assessed by Northern blot analysis, in situ hybridization, and immunohistochemistry. RESULTS: Fasting for 24 hours before 60 minutes of ischemia resulted in a 26.6% decrease in preischemic plasma glucose levels and a 74.5% reduction in infarct volumes in the fasted group compared with the control group. A rapid but transient induction of c-fos mRNA was observed in the ischemic cortex in control animals after 60 minutes of ischemia. Fasting not only prolonged but also enhanced the intensity of c-fos expression in the ischemic cortex. Regional c-fos expression was also different between these two groups. CONCLUSIONS: The results support the contention that c-fos expression may be compatible with its purported neuroprotective role in selected experimental paradigms. The signaling mechanisms underlying the effect of fasting and subsequent lowering of plasma glucose levels on postischemic c-fos expression remain to be explored.

Animals↗
PubMed1996

Protein tyrosine phosphatase activities are involved in apoptotic cancer cell death induced by GL331, a new homolog of etoposide.

GL331 is a semisynthetic topoisomerase II inhibitor derived from a plant toxin podophyllotoxin. In 72-h exposure assays, LD50 values of GL331 range from 0.5 to 2 microM, which are three- to ten-fold lower than those of its homologous compound etoposide (VP-16), depending on different cancer cell lines including nasopharyngeal, hepatocellular, gastric, cervical and colon cancer types. Apoptotic DNA ladders could be detected when cancer cells were treated with GL331 for 24 h even if the Bcl-2 and Bax protein levels were not altered during the period. Besides acting as topoisomerase II inhibitors, both GL331 and VP-16 decrease the cellular protein tyrosine kinase (PTK) activities in cancer cells. The activities of protein tyrosine phosphatase (PTP) are significantly increased after GL331 treatment but are not affected by VP-16. GL331-induced internucleosomal cleavage can be efficiently prevented by two inhibitors of PTP, sodium orthovanadate and zinc chloride, but not by okadaic acid, which inhibits serine/threonine phosphatase activity. These results indicate that GL331 may induce apoptotic cell death, and that activation of protein tyrosine phosphatases may be involved in this process.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Ischemia-induced alteration of myocardial Na(+)-K(+)-ATPase activity and ouabain binding sites in hypercholesterolemic rabbits.

The purpose of this study was to explore the effect of ischemia on the Na(+)-K(+)-ATPase activity and ouabain receptor of the myocardial sarcolemma in hypercholesterolemic rabbits. Male New Zealand white rabbits were fed with either standard chow or standard chow supplemented with 0.5% (w/w) cholesterol and 10% (w/w) coconut oil. After an 8 week feeding period, the rabbits underwent a thoracotomy and myocardial ischemia was induced by occlusion of the coronary artery. Myocardial samples from the ischemic and non-ischemic regions of the left ventricle of control and cholesterol-fed rabbits were taken for study. The cholesterol-fed group showed a decrease in both Na(+)-K(+)-ATPase activity and [3H]ouabain binding sites as compared to the control group. Ischemia caused a reduction in both Na(+)-K(+)-ATPase activity [3H]ouabain bindings sites in both control and cholesterol-fed rabbits. The combination of ischemia and hypercholesterolemia produced an additive effect, with a further decrease in both Na(+)-K(+)-ATPase activity and [3H]ouabain binding sites. Neither the activity of Mg+(+)-ATPase nor the binding affinity for [3H]ouabain was affected by either hypercholesterolemia or ischemia. These findings indicate that hypercholesterolemia may exaggerate certain aspects of functional deterioration arising during myocardial ischemia.

Animals↗
PubMed1996

HslV-HslU: A novel ATP-dependent protease complex in Escherichia coli related to the eukaryotic proteasome.

We have isolated a new type of ATP-dependent protease from Escherichia coli. It is the product of the heat-shock locus hslVU that encodes two proteins: HslV, a 19-kDa protein similar to proteasome beta subunits, and HslU, a 50-kDa protein related to the ATPase ClpX. In the presence of ATP, the protease hydrolyzes rapidly the fluorogenic peptide Z-Gly-Gly-Leu-AMC and very slowly certain other chymotrypsin substrates. This activity increased 10-fold in E. coli expressing heat-shock proteins constitutively and 100-fold in cells expressing HslV and HslU from a high copy plasmid. Although HslV and HslU could be coimmunoprecipitated from cell extracts of both strains with an anti-HslV antibody, these two components were readily separated by various types of chromatography. ATP stimulated peptidase activity up to 150-fold, whereas other nucleoside triphosphates, a nonhydrolyzable ATP analog, ADP, or AMP had no effect. Peptidase activity was blocked by the anti-HslV antibody and by several types of inhibitors of the eukaryotic proteasome (a threonine protease) but not by inhibitors of other classes of proteases. Unlike eukaryotic proteasomes, the HslVU protease lacked tryptic-like and peptidyl-glutamyl-peptidase activities. Electron micrographs reveal ring-shaped particles similar to en face images of the 20S proteasome or the ClpAP protease. Thus, HslV and HslU appear to form a complex in which ATP hydrolysis by HslU is essential for peptide hydrolysis by the proteasome-like component HslV.

ATP-Dependent Proteases↗
PubMed1996

Diarylspiro[2.4]heptenes as orally active, highly selective cyclooxygenase-2 inhibitors: synthesis and structure-activity relationships.

A novel series of 5,6-diarylspiro[2.4]hept-5-enes was shown to provide highly potent and selective cyclooxygenase-2 (COX-2) inhibitors. A study of structure-activity relationships in this series suggests that 3,4-disubstituted phenyl analogs are generally more selective than 4-substituted phenyl analogs and that replacement of the methyl sulfone group on the 6-phenyl ring with a sulfonamide moiety results in compounds with superior in vivo pharmacological properties, although with lower COX-2 selectivity. Several compounds have been shown to possess promising pharmacological properties in adjuvant-induced arthritis and edema analgesia models. The absence of gastrointestinal (GI) toxicity at 200 mpk of several selected compounds in rats and mice corresponds well with the weak potency for inhibition of COX-1 observed in the enzyme assay. Methyl sulfone 55 and sulfonamide 24 were shown to have superior in vivo pharmacological profiles, low GI toxicity, and good oral bioavailability and duration of action.

Analgesics↗
PubMed1996

Large-scale preparation of a ribonuclease from Rana catesbeiana (bullfrog) oocytes and characterization of its specific cytotoxic activity against tumor cells.

Rana catesbeiana ribonuclease (RC-RNase) is a pyrimidine-guanine sequence-specific ribonuclease found only in R. catesbeiana (bullfrog) oocytes, but not in other organs. The protein is localized in the yolk granules of oocytes but not in other organelles, as detected by immunohistochemistry. More than 99% of RC-RNase was found in the yolk granule pellet when a mild separation method was employed under physiological conditions. The ribonuclease was purified by precipitation of yolk granules, extraction of RC-RNase with 0.09 M NaCl, selective removal of impurities by Hepes buffer, and chromatographies on phosphocellulose and carboxymethyl cellulose columns. Three milligrams of RC-RNase was purified from a 1-g pellet of yolk granules prepared from 2 g of ovary tissue. Therefore, 150 milligrams of RC-RNase could be obtained from a mature female bullfrog (600 g in weight) which had 100 g of ovary tissue. The properties of RC-RNase isolated from yolk granules tested so far are identical to those of RC-RNase isolated from the cytosolic fraction and similar to those of a sialic acid-binding lectin from bullfrog oocytes. To investigate the possible role of RC-RNase in the regulation of cell growth and differentiation during embryogenesis, its cytotoxic activity against various cell lines was examined. The degradation of ribosomal RNA was found in RC-RNase-treated HeLa cells. However, both events were not found in RNase A-treated HeLa cells. Therefore, RC-RNase is proposed to have both ribonucleolytic and cytotoxic activity and a specific receptor on the tumor cell surface is suspected to be involved in the recognition and binding, and possibly entry of RC-RNase.

Amino Acid Sequence↗
PubMed1996

Characterization of hsr201 and hsr515, two tobacco genes preferentially expressed during the hypersensitive reaction provoked by phytopathogenic bacteria.

During an incompatible interaction between tobacco and the bacterial phytopathogen Pseudomonas solanacearum, 2 classes of genes, the so-called hsr (hypersensitivity-related) genes, activated preferentially during the hypersensitive reaction, and the str (sensitivity-related) genes, expressed strongly during compatible and incompatible interactions, have been identified. In this report, two hsr cDNA clones, hsr515 and hsr201, as well as their expression patterns are presented. Hsr515 was found to encode a P450 monooxygenase and is most similar to the ripening-related avocado gene CYP71A1 (40.6% amino acid identity). Hsr201 presents 58.6% amino acid identity with pTom36, a tomato gene expressed during fruit maturation. The putative functions of the hsr gene products appear to be quite diverse and their characteristics of activation were found to be very conserved: accumulation of the corresponding mRNAs primarily in leaf areas in contact with the avirulent P. solanacearum strain or with a Pseudomonas fluorescens strain containing the hrpZ gene encoding a necrotizing polypeptide, harpin and absence of expression during normal plant development. Our results also suggest that, in a tobacco line expressing NahG, a lower level of salicylic acid, a compound associated with systemic acquired resistance, and also possibly involved in the development of necrotic lesions characteristic of the HR, does not affect the hsr gene expression.

Amino Acid Sequence↗
PubMed1996

Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy.

We recently developed a pig model with naturally occurring hypertrophic cardiomyopathy (HCM). To further characterize the biochemical features of high frequency of sudden death affected by this disease, the protein profiles of ventricular tissues were analyzed on normal, HCM, and HCM with sudden-death pigs. By sodium dodecylsulfate-polyacrylamide gel electrophoresis, a protein corresponding to an apparent molecular mass of 90 kDa (p90) was found to be markedly decreased in the HCM-affected tissues of sudden-death pigs, but not in HCM or normal pigs. Further study showed that the primary decrease of p90 in HCM pigs with sudden death was located mainly in the interventricular septum. As determined by the molecular mass and isoelectric point on 2-dimensional gels and Western immunoblot with a specific 90 kDa heat shock protein (HSP90) monoclonal antibody, the unknown protein was identified as HSP90. Our findings indicate for the first time that substantially decreased heart HSP90 is associated with HCM pigs with sudden death. Although the role that HSP90 may play in protecting pigs with HCM from sudden death is still nuclear, the model itself may provide further insight into understanding the role of heat shock proteins in cardiac sudden death.-Lee, W.-C., Lin, K.-Y., Chiu, Y.-T., Lin, J.-H., Cheng, H.-C., Huang, H.-C., Yang, P.-C., Liu, S.-K., Mao, S. J. T. Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy.

Animals↗
PubMed1996

Food-borne disease outbreaks in Taiwan, 1994.

In 1994, 102 outbreaks of food-borne disease involving 4,726 cases were reported to the Taiwan Department of Health. This is the highest number of outbreaks and cases in recent years in Taiwan. Of these outbreaks, 72.5% (74/102) were caused by bacterial pathogens, with Vibrio parahaemolyticus responsible for 56.7% (42/74), Staphylococcus aureus 20.3% (15/74), Bacillus cereus 14.9% (11/74) and Salmonella spp other than S. typhi and S. paratyphi 8.1% (6/74). V. parahaemolyticus has been a leading cause of problems in Taiwan for many years. Contamination of seafood with this organism has been reported frequently, particularly in the warmer months. In 1994, small outbreaks (fewer than 5 cases) and large outbreaks (more than 50 cases) represented 31.4% (32/102) and 12.7% (13/102), respectively, of the total. The median outbreak size was 10 cases. A high proportion (54%, 7/13) of the large outbreaks was associated with commercial lunch-boxes supplied to elementary and junior high schools. Health education to improve food sanitation and supervision of food sanitation practices need to be strengthened.

Bacillus cereus↗
PubMed1996

Legionella pneumophila infection in Taiwan: a preliminary report.

Legionella pneumophila infection has been recognized as an important cause of pneumonia. However, epidemiologic baseline data about the occurrence of legionella-related pneumonia and the distribution of legionellae in aquatic environments are still not available in Taiwan. A survey conducted by the National Institute of Preventive Medicine found that 8.6% of 487 pneumonia patients studied were positive for the L. pneumophila serologic test (indirect fluorescent test, IFA) and 32.0% of the 25 water samples were positive for isolation of legionellae. In conclusion, this survey supported the existence of Legionnaires' disease in Taiwan, indicated a preliminary prevalence of L. pneumophila antibodies among pneumonia patients and identified the prevalence of legionellae in water environments.

Adult↗
PubMed1995

Identification of a potential regulator of early transcriptional responses to mesoderm inducers in the frog embryo.

The activin/transforming growth factor-beta (TGF-beta) family of peptide growth factors plays a central role in the induction of mesoderm during early Xenopus embryogenesis. Immediate transcriptional responses to mesoderm-inducing signals have been described, but the signal transduction steps leading to these early responses are unknown. We describe here the first pre-transcriptional response to activin/TGF-beta mesoderm inducers in the early embryo. We have identified a cellular factor which binds to a 50 bp portion of the promoter for an activin/TGF-beta early response gene. This factor is activated within 4 min of treatment of embryonic prospective ectoderm with mesoderm-inducing factors, making it the earliest response to these factors described in early embryos. This factor can be activated throughout early cleavage and blastula stages, is activated by mesoderm inducers of the activin/TGF-beta superfamily but not the fibroblast growth factor (FGF) family, and does not appear to require an endogenous FGF signal for activation. Characterization of this factor provides a powerful tool for studying the early steps in the induction of mesoderm by members of the activin/TGF-beta superfamily.

Activins↗