Search PubMed⌕ Search

Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 703 records · Page 39Linked to original sources
PubMed2000

HMSH6 alterations in patients with microsatellite instability-low colorectal cancer.

Two microsatellite instability (MSI) phenotypes have been described in colorectal cancer (CRC): MSI-H (instability at >30% of the loci examined) and MSI-L (MSI at 1-30% of the loci examined). The MSI-H phenotype, observed in both hereditary nonpolyposis colon cancer-associated CRC and approximately 15% of sporadic CRC, generally results from mutational or epigenetic inactivation of the DNA mismatch repair (MMR) genes hMSH2 or hMLH1. The genetic basis for the MSI-L phenotype, however, is unknown. Several other proteins, including hMSH3 and hMSH6, also participate in DNA MMR. Inactivating mutations of MSH6 in yeast and human tumor cell lines are associated with an impaired ability to repair single-base mispairs and small insertion-deletion loops but not large insertion-deletion loops. This suggests that hMSH6 mutations are more likely to be associated with a MSI-L phenotype than a MSI-H phenotype in CRC. To explore this possibility, we screened tumors from 41 patients with MSI-L CRC for hMSH6 mutations with conformation-sensitive gel electrophoresis (CSGE) and for hMSH6 protein expression by immunohistochemistry. Alterations found with CSGE were confirmed by DNA sequencing of normal and tumor tissue. One somatic (Asp389Asn) and 15 germ-line changes were found. Of the 15 germ-line changes, 9 were found in an intron (none involving splice junctions), and 6 were found in an exon (Gly39Glu, Leu395Val, and 4 silent alterations). Immunohistochemical staining for hMSH6 performed on 34 of the 41 tumors revealed strong nuclear hMSH6 expression in all of the cases. Overall, our results suggest that hMSH6 mutations do not play a major role in the development of sporadic CRC with a MSI-L phenotype.

Adult↗
PubMed2000

Signal peptide determinants of SecA binding and stimulation of ATPase activity.

A signal peptide is required for entry of a preprotein into the secretory pathway, but how it functions in concert with the other transport components is unknown. In Escherichia coli, SecA is a key component of the translocation machinery found in the cytoplasm and at membrane translocation sites. Synthetic signal peptides corresponding to the wild type alkaline phosphatase signal sequence and three sets of model signal sequences varying in hydrophobicity and amino-terminal charge were generated. These were used to establish the requirements for interaction with SecA. Binding to SecA, modulation of SecA conformations sensitive to protease, and stimulation of SecA-lipid ATPase activity occur with functional signal sequences but not with transport-incompetent ones. The extent of SecA interaction is directly related to the hydrophobicity of the signal peptide core region. For signal peptides of moderate hydrophobicity, stimulation of the SecA-lipid ATPase activity is also dependent on amino-terminal charge. The results demonstrate unequivocally that the signal peptide, in the absence of the mature protein, interacts with SecA in aqueous solution and in a lipid bilayer. We show a clear parallel between the hierarchy of signal peptide characteristics that promote interaction with SecA in vitro and the hierarchy of those observed for function in vivo.

Adenosine Triphosphatases↗
PubMed2000

Effect of retinoic acid on the enhancing effect of acetaldehyde on mouse type I collagen expression.

Acetaldehyde alone and retinoic acid alone have been shown to increase and decrease, respectively, collagen production by stellate cells in culture. In this study the effects of retinoic acid on alpha(1)(I) and alpha(2)(I) collagen expression and its influence on the enhancing effects of acetaldehyde were determined. Retinoic acid decreased the activation of the alpha(2)(I) collagen promoter and decreased the message of alpha(2)(I) collagen in cultured stellate cells, but had no effect on either the activation of the alpha(1)(I) collagen promoter or on the alpha(1)(I) collagen message. This depressant effect of retinoic acid was also evident in the transfected alpha(2)(I) collagen promoter mutated at the retinoic acid response element (RARE). The activation of the alpha(2)(I) collagen promoter by acetaldehyde was not decreased significantly by retinoic acid, but was suppressed by the retinoic acid receptor (RAR) selective retinoid SRI-6751-84. Retinoic acid, however, decreased the acetaldehyde-induced enhancement of the alpha(1)(I) and alpha(2)(I) collagen messages. Acetaldehyde also resulted in a decrease in RAR beta message and RARbeta protein. This study shows that retinoic acid depresses alpha(2)(I) collagen gene expression but that this effect is less pronounced when the expression of this collagen is enhanced by acetaldehyde, which also decreases RARbeta message and protein. Furthermore, the action of retinoic acid in inhibiting alpha(2)(I) collagen gene expression occurs at sites other than the RARE site.

Acetaldehyde↗
PubMed2000

The role of ClC-3 in volume-activated chloride currents and volume regulation in bovine epithelial cells demonstrated by antisense inhibition.

1. A chloride current with mild outward rectification was induced in the native bovine non-pigmented ciliary epithelial (NPCE) cells by a 23 % hypotonic solution. The current showed no or little inactivation at depolarized steps. 2. ATP blocked 88 and 61 % of the outward and inward components of the volume-activated chloride current (ICl,vol) with an IC50 of 5.3 and 9.6 mM, respectively. 3. The volume-activated chloride current was decreased and the activation of the current was delayed by inhibiting endogenous ClC-3 expression using a ClC-3 antisense oligonucleotide. The inhibition of the current as a function of antisense concentration was asymptotic with a maximum about 60 %. The remaining current was probably not derived from ClC-3 and was inhibited by ATP. 4. ClC-3 expression in the bovine NPCE cells was verified by immunofluorescence studies. ClC-3 immunofluorescence was distributed throughout the cells but with the predominant location within the nucleus. The expression of ClC-3 protein was diminished by the ClC-3 antisense oligonucleotide with the greatest diminution occurring in the nuclear region. 5. The size of the volume-activated chloride current was positively correlated with the ClC-3 immunofluorescence level. 6. Regulatory volume decrease of the NPCE cells was reduced by ClC-3 antisense oligonucleotide. 7. We conclude that endogenous ClC-3 is associated with the volume-activated chloride current and is involved in cell volume regulation, but that it can only contribute towards a proportion of the current in NPCE cells. 8. The nuclear predominance of ClC-3 immunofluorescence in NPCE cells, the absence of basal activity of chloride current and the marked pharmacological differences between IClC-3 and ICl,vol argue against ClC-3 being the only, or even the main, volume-activated chloride channel in NPCE cells.

Adenosine Triphosphate↗
PubMed2000

A low-voltage droplet charging circuit with simulative cell-sorting function for flow cytometer-cell sorter.

BACKGROUND: Flow cytometer cell sorters have become important tools in many biological laboratories. Commercial electrically-deflected cell sorters that deflect wanted cells in electrically charged droplets need high-voltage amplifiers which are expensive and difficult to obtain. Effort was made to build an alternative droplet charging circuit with low-voltage amplifiers that are much easier to get and have more reasonable price. METHODS: A low-voltage charging circuit was designed. Every time a cell was to be separated, a pair of complementary charging pulses were produced: one was positive and the other was negative with equal amplitude. These were enlarged by two low-voltage charging amplifiers to drive two charging electrodes respectively. RESULTS: Due to the effect of addition, the voltage between the two electrodes was double as high as the output of either amplifier. The result of test experiment proved that the cell sorter with low-voltage amplifiers, which was cheaper and easier to obtain, could separate cells as efficiently as the instrument with high-voltage ones that were more expensive and more difficult to make. In addition, a simulative cell-sorting function was provided. CONCLUSIONS: This low-voltage, easily-built and low-price charging circuit for flow cytometer cell sorter is a good alternative to the commonly used high-voltage one, especially to researcher who hopes to build his own personal instrument.

Animals↗
PubMed2000

High affinity blockade of the HERG cardiac K(+) channel by the neuroleptic pimozide.

Pimozide is an antipsychotic agent also used to treat facial tics. Pimozide can cause acquired long QT syndrome and ventricular arrhythmias. To elucidate the mechanism behind these clinical findings, we examined the effects of pimozide on the cloned human cardiac K(+) channels HERG (human ether-a-go-go-related gene; rapid component of delayed rectifier), Kv1.5 (ultra-rapid delayed rectifier) and KvLQT1/minK (slow component of delayed rectifier). Using patch clamp electrophysiology, we found that pimozide was a potent inhibitor of HERG displaying an IC(50) value of 18 nM. In contrast, pimozide (10 microM) was a weak inhibitor of KvLQT1/minK and Kv1.5. We conclude that pimozide is a specific, high affinity antagonist of HERG, and that this interaction leads to prolongation of cardiac repolarization.

Animals↗
PubMed2000

Severe B cell hyperplasia and autoimmune disease in TALL-1 transgenic mice.

TALL-1/Blys/BAFF is a member of the tumor necrosis factor (TNF) ligand superfamily that is functionally involved in B cell proliferation. Here, we describe B cell hyperplasia and autoimmune lupus-like changes in transgenic mice expressing TALL-1 under the control of a beta-actin promoter. The TALL-1 transgenic mice showed severe enlargement of spleen, lymph nodes, and Peyer's patches because of an increased number of B220+ cells. The transgenic mice also had hypergammaglobulinemia contributed by elevations of serum IgM, IgG, IgA, and IgE. In addition, a phenotype similar to autoimmune lupus-like disease was also seen in TALL-1 transgenic mice, characterized by the presence of autoantibodies to nuclear antigens and immune complex deposits in the kidney. Prolonged survival and hyperactivity of transgenic B cells may contribute to the autoimmune lupus-like phenotype in these animals. Our studies further confirm TALL-1 as a stimulator of B cells that affect Ig production. Thus, TALL-1 may be a primary mediator in B cell-associated autoimmune diseases.

Animals↗
PubMed2000

The correlation between P300 alterations and regional cerebral blood flow in non-demented Parkinson's disease.

P300 was evoked by a visual oddball and an S1-S2 task in 22 non-demented Parkinson's disease (PD) patients (13 in the early stage, nine in the late stage) and 18 normal controls. Reaction time was also measured. All patients undertook the (99)Tc-ECD SPECT examination. Quantitative regional cerebral blood flow (rCBF) was obtained by overlying SPECT image on the 3D-magnetic resonance image. In the PD patients in the late stage, P300 latency to S2-same and reaction time were significantly prolonged, while rCBF at bilateral frontal, temporal, and the right parietal lobes was decreased. P300 latency to S2-same was significantly correlated with the rCBF at bilateral temporal lobes. Reaction time was significantly correlated with the rCBF at the right frontal and parietal lobes, as well as the temporal and occipital lobes. The results suggest that P300 changes in non-demented PD in the late stage could be related to the temporal lobe dysfunction.

Aged↗
PubMed2000

Glucose starvation reduces IGF-I mRNA in tumor cells: evidence for an effect on mRNA stability.

The purpose of this study was to characterize the mechanisms by which glucose regulates IGF-I gene expression in rat C6 glioma cells and in rat GH3 pituitary adenoma cells. Glucose starvation for periods of 12 to 48 h decreased IGF-I mRNA levels. In contrast, there was no stimulation of IGF-I mRNA by medium glucose between 1 and 25 mM over a 24-h period. Studies with hexoses and glycolytic metabolites suggested that glucose metabolism was required to maintain IGF-I mRNA. Glucose starvation lowered IGF-I mRNA half-life in both C6 and GH3 cells. Protein synthesis inhibition lowered IGF-I mRNA by about 20% in glucose-fed C6 and GH3 cells, while potently increasing IGF-I mRNA in glucose-starved C6 cells and not altering IGF-I mRNA in glucose-starved GH3 cells. Our results suggest that in these tumor cells, IGF-I mRNA stability is reduced by glucose starvation, secondary to a deficiency in intracellular glucose metabolism. Ongoing protein synthesis is not required for this mRNA de-stabilizing effect in GH3 cells. Rather, in glucose-starved C6 cells, decreased IGF-I mRNA stability may result from the action of a labile protein.

Animals↗
PubMed2000

Synthesis of N-(Hydroxy)amide- and N-(Hydroxy)thioamide-containing peptides.

Methods developed with N-(benzoyloxy)amines and hydroxamic acids were used in the synthesis of N-(hydroxy)amide-containing pseudopeptides. Acylation of N-(benzoyloxy)phenethylamine with the acid chloride of N(alpha)-Fmoc-L-leucine provided a N(alpha)-Fmoc-N-(benzoyloxy)-L-leucinamide in 90% yield. Deprotection of the benzoyl group (using 10 vol % NH(4)OH/MeOH) provided the N(alpha)-Fmoc-N-(hydroxy)-L-leucinamide in 87% yield. In general, the appended Fmoc group allowed for further elaboration of the N-hydroxy-N-(alkyl)amides using classic peptide-coupling methods. A practical synthetic strategy was developed, and racemization issues were addressed using diastereomeric Val-Leu derivatives. In addition, N-(hydroxy)thioamides were generated from the corresponding N-(benzoyloxy)thioamides. N-(Benzoyloxy)thioamides were obtained in moderate yields (53-76%) from the reaction of the corresponding N-(benzoyloxy)amides with Lawesson's reagent (i.e., 2, 4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disu lfide). In summary, this new technology allows for the introduction of either N-hydroxyamide or N-(hydroxy)thioamide linkages into pseudopeptide chains without racemization.

Acylation↗
PubMed2000

Cell wall structure of a mutant of Mycobacterium smegmatis defective in the biosynthesis of mycolic acids.

A mutant strain of Mycobacterium smegmatis defective in the biosynthesis of mycolic acids was recently isolated (Liu, J., and Nikaido, H. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 4011-4016). This mutant failed to synthesize full-length mycolic acids and accumulated a series of long chain beta-hydroxymeromycolates. In this work, we provide a detailed characterization of the localization of meromycolates and of the cell wall structure of the mutant. Thin layer chromatography showed that the insoluble cell wall matrix remaining after extraction with chloroform/methanol and SDS still contained a large portion of the total meromycolates. Matrix-assisted laser desorption/ionization and electrospray ionization mass spectroscopy analysis of fragments arising from Smith degradation of the insoluble cell wall matrix revealed that the meromycolates were covalently attached to arabinogalactan at the 5-OH positions of the terminal arabinofuranosyl residues. The arabinogalactan appeared to be normal in the mutant strain, as analyzed by NMR. Analysis of organic phase lipids showed that the mutant cell wall contained some of the extractable lipids but lacked glycopeptidolipids and lipooligosaccharides. Differential scanning calorimetry of the mutant cell wall failed to show the large cooperative thermal transitions typical of intact mycobacterial cell walls. Transmission electron microscopy showed that the mutant cell wall had an abnormal ultrastructure (without the electron-transparent zone associated with the asymmetric mycolate lipid layer). Taken together, these results demonstrate the importance of mycolic acids for the structural and functional integrity of the mycobacterial cell wall. The lack of highly organized lipid domains in the mutant cell wall explains the drug-sensitive and temperature-sensitive phenotypes of the mutant.

Calorimetry, Differential Scanning↗
PubMed2000

Comparison of three treatment options for single brain metastasis from lung cancer.

Whole brain radiotherapy (WBRT), stereotactic radiosurgery (SRS), and the combination of both treatment methods were used for the management of single brain metastasis from lung cancer. The purpose of this study is to compare these three different treatment options in terms of local response, survival, and quality of life. From June 1995 to July 1998, 70 lung cancer patients with new diagnosed single brain metastasis were treated with either WBRT alone (n = 29), or SRS alone (n = 23), or the combination of both methods (n = 18). Multiple endpoints, including survival, freedom from local progression (FFLP), freedom from new brain metastasis (FFNBM), local control, Karnofsky performance status (KPS), and causes of death, were measured from the date of treatment completion and compared using univariate and multivariate analyses. For patients treated with WBRT-alone, SRS-alone, and SRS+WBRT, the median survivals were 5.7, 9.3, and 10.6 months, the median FFLP were 4.0, 6.9, and 8.6 months, the median FFNBM were 4.1, 6.7, and 8.6 months, and the local response rates were 55.6, 87.0, and 88.9%, respectively. Four of the 29 patients treated with WBRT-alone continued with progression of disease. The post treatment KPS showed improvement in 41.4, 82.6, and 88.9% of patients treated with WBRT-alone, SRS-alone, and SRS+WBRT, respectively. The progression of new and/or recurred metastatic brain tumor as the cause of death accounted for 51.7%, 50. 0%, and 28.3% of the patients treated with WBRT-alone, SRS-alone, and SRS+WBRT, respectively. Univariate analyses showed that the significant differences among the three treatment arms were observed based on all of the above mentioned endpoints. However, the comparison between SRS-alone and SRS+WBRT groups indicated that adding WBRT only improves FFNBM (P = 0.0392). Cox regression analyses revealed no significant difference in both of the KPS (P = 0.1082) and causes of death (P = 0.081) among the three arms. Both SRS alone and SRS+WBRT seem better in prolonging life and improving quality of life than WBRT alone for patients with single brain metastasis from lung cancer. But the combined therapy did not show significant advantage over SRS alone in improving survival, enhancing local control, and quality of life except for a more favorable FFNBM. Further investigation via a randomized trial is needed to access the value of adding WBRT to SRS in the management of this group of patients. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 37-45 (2000).

Adult↗
PubMed2000

Fos induction in selective hypothalamic neuroendocrine and medullary nuclei by intravenous injection of urocortin and corticotropin-releasing factor in rats.

CRF and urocortin, administrated systemically, exert peripheral biological actions which may be mediated by brain pathways. We identified brain neuronal activation induced by intravenous (i.v.) injection of CRF and urocortin in conscious rats by monitoring Fos expression 60 min later. Both peptides (850 pmol/kg, i.v.) increased the number of Fos immunoreactive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, central amygdala, nucleus tractus solitarius and area postrema compared with vehicle injection. Urocortin induced a 4-fold increase in the number of Fos-positive cells in the supraoptic nucleus and a 3.4-fold increase in the lateral magnocellular part of the paraventricular nucleus compared with CRF. Urocortin also elicited Fos expression in the accessory hypothalamic neurosecretory nuclei, ependyma lining the ventricles and choroid plexus which was not observed after CRF. The intensity and pattern of the Fos response were dose-related (85, 255 and 850 pmol/kg, i.v.) and urocortin was more potent than CRF. Neither CRF nor urocortin induced Fos expression in the lateral septal nucleus, Edinger-Westphal nucleus, dorsal raphe nucleus, locus coeruleus, or hypoglossal nucleus. These results show that urocortin, and less potently CRF, injected into the circulation at picomolar doses activate selective brain nuclei involved in the modulation of autonomic/endocrine function; in addition, urocortin induces a distinct activation of hypothalamic neuroendocrine neurons.

Amygdala↗
PubMed2000

Improvement of the enantioselectivity of lipase-catalyzed naproxen ester hydrolysis in organic solvent.

A method is presented to improve the enantioselectivity of lipase-catalyzed hydrolysis of naproxen methyl ester in water-saturated isooctane. It is shown that coupling of the enantioselective hydrolysis of Naproxen methyl ester with the photo-dissociation methanol leads to the photocatalytic conversion of methanol into water, by which the equilibrium constant (K) of the lipase-catalyzed hydrolysis was changed. The equilibrium yield and enantiomeric excess are increased. Because the lipase would not dissolve in the organic solvent, it was adsorbed on photocatalyst particles, which may facilitate the isolation of enzyme from reaction system.

Journal Article↗
PubMed2000

Gi-mediated translocation of GLUT4 is independent of p85/p110alpha and p110gamma phosphoinositide 3-kinases but might involve the activation of Akt kinase.

Activation of phosphoinositide 3-kinase (PI-3K) is essential for insulin-stimulated translocation of GLUT4 and glucose transport in insulin target tissues. A novel p110gamma PI-3K was reported to be activated by G(i)-coupled receptors via Gbetagamma subunits. We asked whether the stimulation of G(i)-coupled receptors would trigger GLUT4 translocation and glucose uptake by the activation of Gbetagamma-dependent p110gamma PI-3K. We find that this translocation and glucose uptake can be induced by the ligand stimulation of G(i)-coupled alpha(2A) adrenergic receptor and fMet-Leu-Phe receptor in cells stably expressing these receptors. The noradrenaline ('noradrenaline')- and fMet-Leu-Phe-stimulated GLUT4 translocations were abolished by pretreatment with pertussis toxin. Pretreatment with wortmannin or genistein also inhibited the G(i)-mediated GLUT4 translocation. On ligand stimulation of these two kinds of G(i)-coupled receptor, although there was a slight increase in PtdIns(3,4,5)P(3) production, activation of either the p85/p110alpha PI-3K or Gbetagamma-dependent p110gamma PI-3K was not observed even in Chinese hamster ovary cells stably overexpressing exogenous p101/p110gamma. The G(i)-mediated GLUT4 translocation was accompanied by activation of the serine-threonine kinase Akt; the inhibitory effects of pertussis toxin, wortmannin and genistein on G(i)-mediated GLUT4 translocation paralleled their inhibitory effects on Akt activation. In contrast, the activation of some other G(i)-coupled receptors, such as prostaglandin EP3alpha receptor and platelet-activating factor receptor, did not cause either pertussis-toxin-sensitive translocation of GLUT4myc or activation of Akt kinase. These results indicate that the ligand stimulation of some G(i)-coupled receptors triggers GLUT4 translocation that occurs independently of p85/p110alpha-type and p110gamma-type PI-3Ks but might involve the activation of Akt kinase.

Adrenergic alpha-Agonists↗
PubMed2000

[Effects of local vibration on the levels of plasma endothelin and nitric oxide in rabbits].

In order to explore the effects of local vibration on plasma endothelin(ET) and nitric oxide (NO) and the relations with vibration-induced vascular impairment(VVI), plasma ET and NO levels of rabbits were measured after exposure to different vibration power and different exposure period. The results showed an increasing tendency in plasma ET levels, and a decreasing tendency in plasma NO levels in experiment groups, while lasting vibration exposure and enhancing vibration power. It suggested that local vibration could result in the increasing of plasma ET level and decreasing of plasma NO level, which might be one of the mechanisms of vibration-induced vascular impairment.

Animals↗