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Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 523 records · Page 29Linked to original sources
PubMed1999

[The histopathological observation and the clinical significance of invasion of pyriform sinus apex in pyriform sinus carcinoma].

OBJECTIVE: To approach the clinical significance of pyriform sinus carcinoma invading to pyriform sinus apex. METHOD: Forty-three cases of surgical specimens from total laryngectomy and partial hypopharyngectomy of pyriform sinus carcinoma were made with the organ subserial sectioning and pathological study. RESULT: Pyriform sinus apex is the inferior 1/3 region of pyriform sinus. If pyriform sinus carcinoma invades its apex, the cancerous tissue easely infiltrated the adjacent structure and organs. CONCLUSION: The invasion of pyriform sinus apex is the beginning position and the most important sign of invading downward the tissue and surrounding organs in the inferior position of hypopharynx. When surgery treatment is performed, the total laryngectomy and hypopharyngectomy of ill hypopharynx is appropriate and necessary.

Adult↗
PubMed1999

[Excretion ratio of lactulose and mannitol as intestinal permeability index in healthy Chinese volunteers].

OBJECTIVE: To determine lactulose (L)/mannitol (M) excretion ratio with high pressure liquid chromatograph with pulsed electrochemical detection (HPLC-PED) in healthy Chinese volunteers. METHODS: Sixty healthy Chinese volunteers enrolled. For each volunteer the L/M permeability study was performed twice by two different doses, as small dose (1 g mannitol and 2 g lactulose) and regular dose (5 g mannitol and 10 g lactulose). The urine were collected during 6 hours after ingestion of the test solution. The M and L concentrations were analyzed by HPLC with pulsed electrochemical detection. RESULTS: The L/M ratio was 0.026 +/- 0.006 in the small doses tests, and 0.036 +/- 0.008 in the large doses tests. CONCLUSIONS: With HPLC-PED detection, a low doses of lactulose and mannitol can be used to study intestinal permeability. Determination of the L/M ratio may be a way of evaluating intestinal barrier function in clinical practice.

Adult↗
PubMed1999

Study of loss of heterozygosity at DCC and APC/MCC genetic loci of gastric cancer.

In order to assess the role of the changes of DCC and APC/MCC genes in the development and progression of gastric cancer, the loss of heterozygosity (LOH) of these genetic loci was investigated in 45 surgical specimens of gastric cancer with PCR-RFLP. The rate of LOH was 30.0% (9/30) at APC/MCC gene and 33.3% (15/45) at DCC gene. LOH was found in both intestinal and gastric types of gastric cancer and the rate of LOH of DCC gene was significantly higher in stages III to approximately IV gastric cancer (48.0%) than in stages I to approximately II (15.0%) (P<0.05). LOH of APC/MCC gene could be found in both early and advanced stages of gastric cancer. These findings suggest that changes of DCC and APC/MCC genes are involved in the development and progression of the intestinal and gastric types of gastric cancer.

Adenocarcinoma↗
PubMed1999

[Study on catalytic spectrophotometic determination of nitrite with catechol violet system].

A new sensitive method for the determination of trace nitrite was developed, based on nitrite as a catalyst. The optimum kinetic conditions were discussed and the concentration of nitrite was linear in the rang of 0.2-3.5 microg/10mL. The proposed method is simple, rapid, selective and convenient to determine nitrite in water and vegetables with good results.

Catalysis↗
PubMed1999

[Determination of diclofenac sodium and codeine phosphate in shuerfen tablets by CPA-matrix method].

The contents of diclofenac sodium and codeine phosphate in shuerfen tablets may be determined simultaneously by CPA-matrix method without separation of its components. The program was edited by BASIC. The average recoveries and RSD were 99.85%, 0.46% for diclofenac sodium and 99.80%, 0.50% codeine phosphate, respectively. This method is simple and rapid, and the result is accurate.

Codeine↗
PubMed1999

[New solution of simultaneous equations in spectrophotometry for the determination of aspirin and acetaminophen in xiaoer tuishao pian].

The contents of aspirin and acetaminophen in xiaoer tuishao pian were determined by using the new solution of simultaneous equations without any preliminary separation. The average recoveries and variation coefficients of the analysis are 99.95% and 1.74% for aspirin and 100.1% and 0.93% for acetaminophen, respectively. The method was simple, rapid and accurate.

Acetaminophen↗
PubMed1999

[Assay of diclofenac sodium and codeine phosphate in tablet by multiwavelength K-factor spectrophotometry].

Assay of diclofenac sodium and codeine phosphate in tablet is reported in this paper. The calibration curves were linear over the range of 11.18-25.40 microg/mL of diclofenac sodium and over the range of 6.785-15.42 microg/mL of codeine phosphate. The average recoveries and relative standard deviations of diclofenac sodium and codeine phosphate were 100.1%, 0.36% and 100.7%, 0.80%, respectively. The method is simple and rapid, and the results are satisfactory.

Codeine↗
PubMed1999

[Determination of the content of aminopyrine in antongding injection by orthogonal function spectrophotometry].

Determination of the content of aminopyrine in the antongding injection by orthogonal function spectrophotometry was reported in this paper. The six wavelengths for the determination are 257, 261, 265, 269, 273 and 277 nm. The concentration of aminopyrine in the range of 5-25 microg x mL(-1) is in a good linear relation to P2, and the regression equation is P2 = + 0.018 - 0.032 9c, r = 0.999 9. The average recovery and relative standard deviation are 100.3% and 0.40%, respectively. On the basis of the data observed it is concluded that this method shows no obvious difference as compared with Hebei province pharmacy regulation.

Aminopyrine↗
PubMed1999

[Measurement of aluminum (III) in crops by synergistic chromatic reaction].

In the presence of OP, a sensitive color reaction of aluminum (III) on pyrocatechol violet and rhodamine 6G has been studied. In a NH4Ac-HAc (pH = 6.5) medium, aluminum (III) ions form an ions-associate complex with pyrocatechol violet and rhodamine 6G. The composition of the complex is Al (III) : PV: Rh6G = 1 : 2 : 4. The maximum absorption of the ions-associate complex is at 580 nm with an apparent molar absorptivity of 6.8 x 10(4) L x mol(-1) x cm(-1). Beer's law is obeyed in the range of 0-7 microg/25 mL of aluminum. The method is highly selective and has been applied to the determination of trace aluminum in crops with satisfactory results.

Aluminum↗
PubMed1999

[Study on the synergistic coloration of tin (II) with pyrocatechol violet and rhodamine B and its application].

In the presence of PVA, a sensitive color reaction of tin (I ) on pyrocatechol violet and rhodamine B has been studied. In a NaAc-HAc (pH = 5.0) medium, tin(II) ions form an ions-associate complex with pyrocatechol violet and rhodamine B. The composition of the complex is Sn (II): PV : RhB = 1 : 2: 4. The maximum absorption of the ions-associate complex is at 560 nm with an apparent molar absorptivity of 1.18 x 10(5) L x mol(-1) x cm(-1). Beer's law is obeyed in the range of 0-15 microg/25 mL of tin. The method is highly selective and has been applied to the determination of trace tin in some objects with satisfactory results.

Benzenesulfonates↗
PubMed1999

[Analysis of 4 metal elements in 11 kidney tonic Chinese traditional medicines].

The contents of Zn, Cd, K and Na in 11 kidney tonic Chinese traditional medicines usually used in clinical practice were determined by FAAS. The results showed that element Zn, which is closely related to yang deficiency of the kidney, and the macro elements K and Na, which are essential to human-body, are very rich, but element Cd is lower. The relations between trace elements and the therapeutic efficacy were discussed, and it is concluded that the results are in agreement with clinical usage of medicines by herbalists.

Cadmium↗
PubMed1998

Cloning and functional expression of a cDNA encoding a pheromone gland-specific acyl-CoA Delta11-desaturase of the cabbage looper moth, Trichoplusia ni.

Desaturation of coenzyme-A esters of saturated fatty acids is a common feature of sex pheromone biosynthetic pathways in the Lepidoptera. The enzymes that catalyze this step share several biochemical properties with the ubiquitous acyl-CoA Delta9-desaturases of animals and fungi, suggesting a common ancestral origin. Unlike metabolic acyl-CoA Delta9-desaturases, pheromone desaturases have evolved unusual regio- and stereoselective activities that contribute to the remarkable diversity of chemical structures used as pheromones in this large taxonomic group. In this report, we describe the isolation of a cDNA encoding a pheromone gland desaturase from the cabbage looper moth, Trichoplusia ni, a species in which all unsaturated pheromone products are produced via a Delta11Z-desaturation mechanism. The largest ORF of the approximately 1,250-bp cDNA encodes a 349-aa apoprotein (PDesat-Tn Delta11Z) with a predicted molecular mass of 40,240 Da. Its hydrophobicity profile is similar overall to those of rat and yeast Delta9-desaturases, suggesting conserved transmembrane topology. A 182-aa core domain delimited by conserved histidine-rich motifs implicated in iron-binding and catalysis has 72 and 58% similarity (including conservative substitutions) to acyl-CoA Delta9Z-desaturases of rat and yeast, respectively. Northern blot analysis revealed an approximately 1,250-nt PDesat-Tn Delta11Z mRNA that is consistent with the spatial and temporal distribution of Delta11-desaturase enzyme activity. Genetic transformation of a desaturase-deficient strain of the yeast Saccharomyces cerevisiae with an expression plasmid encoding PDesat-Tn Delta11Z resulted in complementation of the strain's fatty acid auxotrophy and the production of Delta11Z-unsaturated fatty acids.

Amino Acid Sequence↗
PubMed1998

Mechanism of allosteric regulation of the rod cGMP phosphodiesterase activity by the helical domain of transducin alpha subunit.

The G protein alpha subunit (Galpha) is composed of two distinct folding domains: a GTP-binding Ras-like domain and an alpha helical domain (HD). We have recently reported that the helical domain (HDt) of the vertebrate visual transducin alpha subunit (Galphat) synergizes activation of retinal cyclic GMP phosphodiesterase (PDE) by activated Galphat (Liu, W., and Northup, J. K., (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 12878-12883). Here, we examine the molecular basis for this HD-based signaling regulation, and we provide a new model for the activation of the target effector. The HD proteins derived from visual transducin or taste gustducin alpha subunits, but no other Galpha HD proteins, each attenuate the PDE catalytic core (Palphabeta) and synergize Galphat stimulation of the holoPDE (Palphabetagamma2) with similar apparent affinities. The data from studies of both HDt-mediated attenuation and stimulation indicate that the HDt and the PDE inhibitory subunit (Pgamma) interact with PDE at independent sites and that Palphabeta contains the binding sites for HD. The saturation of both processes by HDt displays positive cooperativity with Hill coefficients of 1.5 for the attenuation of Palphabeta activity and 2.1 for synergism of holoPDE activation. Our data suggest the that Galphat-HDt regulates PDE by allosterically decreasing the affinity of Palphabeta for Pgamma and thus simultaneously facilitating the interaction of the activated Galphat-Ras-like domain with Pgamma. Thus, we propose a new model for the high efficiency of PDE activation as well as deactivation, and, overall, a novel mechanism for controlling fidelity, sensitivity, and efficacy of G protein signaling.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1998

[Association of VNTR region of the human serotonin transporter gene with bipolar disorder among the Han Chinese].

OBJECTIVE: The serotonin transporter gene (SERT) plays an important role in the serotonin uptake into neurons. This paper reports a population and association study among the Han Chinese. METHODS: DNA were extracted from peripheral blood samples of 50 patients with bipolar disorder (DSM-IIIR), 170 unrelated healthy Han Chinese individuals and 10 healthy trios for polymerase chain reaction. The VNTR locus was amplified and PCR products were separated on the 2% agrose gel. RESULTS: All the three alleles(9,10 and 12 copies of repeat unit) reported in other studies were observed in this study with frequency 0.0029, 0.0676 and 0.9294, respectively. Four genotypes distributed in Caucasian: 12/12, 12/10, 12/9 and 10/10 were also found in the Han Chinese population. A significant difference in the allele frequency between the Han Chinese and Caucasian populations was found(P 0.000000001). No disequilibrium was observed after checking the Hardy-Weinberg equilibrium (P=0. 9995). The hereditary stability of this locus in accordance with the rules of Mendelian inheritance was demonstrated in the analysis of ten trios. In addition, a significant increase of frequency of the allele 10 in female patients with bipolar disorder was found (P=0. 043). CONCLUSION: The data of association study might indicate a different mechanism of aetiology of bipolar disorder in male and female.

Asian People↗
PubMed1998

Identification and chromosomal localization of CTNNAL1, a novel protein homologous to alpha-catenin.

Sodium butyrate (NaB) was shown to induce growth inhibition and apoptosis in a human pancreatic cancer cell line (AsPC-1). To identify the genes that are differentially regulated by NaB, we generated subtracted EST libraries highly enriched for up- or down-regulated transcripts using the suppression subtraction hybridization technique. One of the ESTs identified in the down-regulated library showed significant homology to human alpha-catenin. A cDNA of 2.45 kb that codes for a putative protein of 734 aa was cloned. The cloned cDNA was used as a template in an in vitro transcription-translation reaction. This produced a protein product of about 82 kDa in size. The gene designated as CTNNAL1 (catenin (cadherin-associated protein), alpha-like 1) was found to be ubiquitously expressed in many tissues including pancreas, heart, and skeletal muscle. A human BAC clone containing the gene was isolated and used as a probe for fluorescence in situ hybridization (FISH). Both radiation hybrid and FISH analysis mapped the gene to chromosome band 9q31.2, a region where frequent abnormalities have been observed in bladder carcinoma, esophageal cancers, and several other tumors.

Amino Acid Sequence↗
PubMed1998

N-termini of EcoRI restriction endonuclease dimer are in close proximity on the protein surface.

The N-terminal region of EcoRI endonuclease is essential for cleavage yet is invisible in the 2.5 A crystal structure of endonuclease-DNA complex [Kim, Y., Grable, J. C., Love, R., Greene, P. J., Rosenberg, J. M. (1990) Science 249, 1307-1309]. We used site-directed fluorescence spectroscopy and chemical cross-linking to locate the N-terminal region and assess its flexibility in the absence and presence of DNA substrate. The second amino acid in each subunit of the homodimer was replaced with cysteine and labeled with pyrene or reacted with bifunctional cross-linkers. The broad absorption spectra and characteristic excimer emission bands of pyrene-labeled muteins indicated stacking of the two pyrene rings in the homodimer. Proximity of N-terminal cysteines was confirmed by disulfide bond formation and chemical cross-linking. The dynamics of the N-terminal region were determined from time-resolved emission anisotropy measurements. The anisotropy decay had two components: a fast component with rotational correlation time of 0.3-3 ns representing probe internal motions and a slow component with 50-100 ns correlation time representing overall tumbling of the protein conjugate. We conclude that the N-termini are close together at the dimer interface with limited flexibility. Binding of Mg2+ cofactor or DNA substrate did not affect the location or flexibility of the N-terminal region as sensed by pyrene fluorescence and cross-linking, indicating that substrate binding is not accompanied by folding or unfolding of the N-terminus.

Binding Sites↗
PubMed1998

The helical domain of a G protein alpha subunit is a regulator of its effector.

The alpha subunit (Galpha) of heterotrimeric G proteins is a major determinant of signaling selectivity. The Galpha structure essentially comprises a GTPase "Ras-like" domain (RasD) and a unique alpha-helical domain (HD). We used the vertebrate phototransduction model to test for potential functions of HD and found that the HD of the retinal transducin Galpha (Galphat) and the closely related gustducin (Galphag), but not Galphai1, Galphas, or Galphaq synergistically enhance guanosine 5'-gamma[-thio]triphosphate bound Galphat (GalphatGTPgammaS) activation of bovine rod cGMP phosphodiesterase (PDE). In addition, both HDt and HDg, but not HDi1, HDs, or HDq attenuate the trypsin-activated PDE. GalphatGDP and HDt attenuation of trypsin-activated PDE saturate with similar affinities and to an identical 38% of initial activity. These data suggest that interaction of intact Galphat with the PDE catalytic core may be caused by the HD moiety, and they indicate an independent site(s) for the HD moiety of Galphat within the PDE catalytic core in addition to the sites for the inhibitory Pgamma subunits. The HD moiety of GalphatGDP is an attenuator of the activated catalytic core, whereas in the presence of activated GalphatGTPgammaS the independently expressed HDt is a potent synergist. Rhodopsin catalysis of Galphat activation enhances the PDE activation produced by subsaturating levels of Galphat, suggesting a HD-moiety synergism from a transient conformation of Galphat. These results establish HD-selective regulations of vertebrate retinal PDE, and they provide evidence demonstrating that the HD is a modulatory domain. We suggest that the HD works in concert with the RasD, enhancing the efficiency of G protein signaling.

3',5'-Cyclic-GMP Phosphodiesterases↗