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Biomedical subjects

L Xue

Publications and source records attributed to L Xue.

At least 109 records · Page 6Linked to original sources
PubMed1996

[Inhibition of experimental metastasis and cell adhesion of B16 murine melanoma cells by protein kinase C inhibitor CJ9111].

Treatment of B16 murine melanoma cells with different concentration of CJ9111 for various time in culture and subsequent i.v. injection of the cells into C57BL/6 mice resulted in dose and time dependent inhibition of lung metastasis. The 50% inhibition concentration (IC50) of metastasis with CJ9111 was 8 micrograms/ml, a value similar to that for the inhibition of B16 cell membrane-associated PKC (IC50 = 63 micrograms/ml). B16 cells treated with CJ9111 for 24 h were less adherent than untreated cells to endothelial cells. These results suggest that PKC may be a key element in regulating tumor-cell metastasis and PKC inhibitors may be promising agents in the control of metastasis.

Animals↗
PubMed1996

[The diagnostic value of thoracoscopy in pleural mesothelioma].

OBJECTIVE: To analyse the diagnostic value of thoracoscopy in pleural mesothelioma. METHODS: The image features under thoracoscopy and the histology of 32 patients with pleural mesothelioma were reported. And the diagnostic rate of thoracoscopy was compared with those of chest X-ray, CT, effusion fluid cytology, tomography and the percutaneous needle pleural biopsy. RESULTS: The diagnostic rate of thoracoscopy in pleural mesothelioma was 100%, and the histologic subtypes were the benign fibrous (5 cases), epithelial (9 cases), fibrosarcoma (12 cases) and the mixed (6 cases). The positive rates of chest X-ray, tomography, pleurography, CT, effusion fluid cytology and the percutaneous needle pleural biopsy were 13%, 33%, 38%, 61%, 15% and 24% respectively. CONCLUSION: Thoracoscopy was found to be the best method for diagnosing pleural mesothelioma, by which all pleural lesions could be observed and biopsied directly.

Adolescent↗
PubMed1996

[Autoimmune thyroiditis diagnosis and erroneous diagnosis].

36 cases of autoimmune thyroiditis were studied by BUS, radioisotopic scan, laboratory test and cytological test, 20 patients were confirmed pathologically. Two cases were complicated with carcinoma. We analysed the causes of the misdiagnosis and considered the importance of TGAb and TMAb pasitive; cytological and pathological examinations are of key importance.

Adult↗
PubMed1995

Dual effects of trimebutine on electrical responses of gastric smooth muscles in the rat.

The effects of trimebutine on the electrical properties of smooth muscle membranes were studied in the isolated rat stomach, the objective being to elucidate the dual actions of this drug on gastric motility. Transmural nerve stimulation elicited a cholinergic excitatory junction potential (e.j.p.) and a nonadrenergic noncholinergic inhibitory junction potential (i.j.p.), and trimebutine inhibited the e.j.p. more than the i.j.p., with no significant change in the acetylcholine-induced depolarization. Trimebutine reduced the interval and, at high concentrations, the amplitude of slow waves. In enzymatically dispersed single cells, the Ca2+ current elicited by depolarization of the membrane was also inhibited by trimebutine. Thus, trimebutine increases slow wave frequency and inhibits cholinergic transmission and Ca2+ influx. The former would enhance while the latter two would depress gastric motility.

Animals↗
PubMed1995

Excitation and inhibition by cisapride of spontaneous and evoked electrical responses in smooth muscles of guinea-pig stomach.

In isolated circular smooth muscles of the guinea-pig stomach, cisapride depolarized the membrane, increased the amplitude and interval of slow waves, and enhanced the cholinergic excitatory junction potential, with no change in the nonadrenergic noncholinergic inhibitory junction potentials. Methysergide mimicked the excitatory actions of cisapride on junction potentials. Results showed that cisapride has dual actions on gastric muscles; excitation by facilitating the release of ACh possibly via 5-HT receptor blockade and also by depolarizing the smooth muscle membrane, and inhibition by reducing the frequency of slow waves, possibly by acting directly on the pacemakers.

Acetylcholine↗
PubMed1995

Prospective studies on the relationship between the 50 g glucose challenge test and pregnant outcome.

The 50 g oral glucose challenge test (50gGCT) was performed on 622 pregnant women, and 75 g oral glucose tolerance test (75gGTT) was further done on subjects with screening tests value of > or = 7.78 mmol/L. The results showed that there were 16.56% (103/622) women with screening value of > or = 7.78 mmol/L, among whom, 32 were identified as having gestational impaired glucose tolerance (GIGT) and 12, gestational diabetes mellitus (GDM) by confirmatory test of 75gGTT. The sensitivity of 50gGCT was 42.72%(44/103). The incidences of edema-proteinuria-hypertension syndrome (EPH-syndrome), premature rupture of membranes, fetal macrosomia, operative deliveries and perinatal morbidity were higher in women with GIGT/GDM than in women without GIGT/GDM. It suggests that 50gGCT is an ideal method of screening for GDM and should be performed on all pregnant women.

Adult↗
PubMed1994

Nuclear structure and the microdistribution of radiation damage in DNA.

Evidence for the roles of proteins and metal ions in the microheterogeneity of DNA damage is reviewed. Decondensation of chromatin in hypotonic buffers markedly sensitizes the DNA to radiation, while treatment of nuclei with hypertonic buffers strips the DNA of histones and other nuclear proteins and enhances the radiosensitivity of the DNA with respect to double-strand break (dsb) formation. Addition of the radical scavenger DMSO reduces the yield of strand breaks, but dehistonized chromatin remains approximately 2.5 times more sensitive to radiation than does native chromatin at 0.1 M DMSO. DNA-protein crosslink (DPC) formation is relatively unaffected by the removal of the majority of histones from chromatin. Most DPC form at or near the nuclear matrix, and matrix is stabilized and radiosensitized by Cu++. To elucidate the role of Cu++, the induction of dsb and DPC by gamma-radiation has been compared with that by hydroxyl radical from Fe(++)-EDTA, or Cu++ catalysed Fenton reactions. Data comparing the size of DNA fragments produced, the effect of expanding or dehistonizing chromatin, and the effects of radical scavengers suggest that gamma-radiation and Fe(++)-EDTA produce dsb at open chromatin sites, whereas Cu(++)-generated dsb are similar to radiation-induced DPC in their location at the nuclear matrix. Both metal ions appeared to produce damage by site-specific generation of hydroxyl radicals. The nuclear matrix, the proteinaceous skeleton which anchors chromosomal loops and provides sites for DNA replication and transcription, binds metal ions and matrix-attachment DNA regions (MARs) consisting of 300 + bp of AT-rich DNA. The interaction of cloned MARs with isolated nuclear matrices has been found to be hypersensitive to crosslinking upon gamma-irradiation, in comparison with associations formed by similarly sized DNA fragments lacking MAR sequences. Thus, the non-random distribution of radiation damage is partially explained by the protection of DNA afforded by histones and chromatin structure and partially by the hypersensitivity of DNA-nuclear matrix associations.

Binding Sites↗
PubMed1994

Sorting signals in the MHC class II invariant chain cytoplasmic tail and transmembrane region determine trafficking to an endocytic processing compartment.

Targeting of MHC class II molecules to the endocytic compartment where they encounter processed antigen is determined by the invariant chain (Ii). By analysis of Ii-transferrin receptor (TR) chimera trafficking, we have identified sorting signals in the Ii cytoplasmic tail and transmembrane region that mediate this process. Two non-tyrosine-based sorting signals in the Ii cytoplasmic tail were identified that mediate localization to plasma membrane clathrin-coated pits and promote rapid endocytosis. Leu7 and Ile8 were required for the activity of the signal most distal to the cell membrane whereas Pro15 Met16 Leu17 were important for the membrane-proximal signal. The same or overlapping non-tyrosine-based sorting signals are essential for delivery of Ii-TR chimeras, either by an intracellular route or via the plasma membrane, to an endocytic compartment where they are rapidly degraded. The Ii transmembrane region is also required for efficient delivery to this endocytic processing compartment and contains a signal distinct from the Ii cytoplasmic tail. More than 80% of the Ii-TR chimera containing the Ii cytoplasmic tail and transmembrane region is delivered directly to the endocytic pathway by an intracellular route, implying that the Ii sorting signals are efficiently recognized by sorting machinery located in the trans-Golgi.

Amino Acid Sequence↗
PubMed1993

Cytotoxic and antimalarial bisbenzylisoquinoline alkaloids from Cyclea barbata.

An alkaloid extract derived from the roots of Cyclea barbata demonstrated cytotoxic and antimalarial activities, and five bisbenzylisoquinoline alkaloids, (+)-tetrandrine [1], (-)-limacine [2], (+)-thalrugosine [3], (+)-homoaromoline [4], and (-)-cycleapeltine [5], were isolated as the active principles. The complete and unambiguous assignments of the 1H- and 13C-nmr data of these substances were made by 1D and 2D nmr techniques (COSY, phase-sensitive ROESY, HETCOR, and FLOCK).

Alkaloids↗
PubMed1992

Inhibitory actions of MCI-154 on guinea-pig femoral artery and vein preparations.

In guinea-pig femoral artery and vein preparations, the effects of MCI-154 were investigated on: (1) membrane depolarizations produced by 29.6 mM [K+]0 (high-K) solution and noradrenaline (NA) and on e.j.p.s produced by perivascular nerve stimulation; (2) contractions produced by NA, high-K and perivascular nerve stimulation; and, (3) endothelium-dependent relaxation produced by acetylcholine (ACh). In both femoral artery and vein preparations, MCI-154 (up to 10(-5) M) did not change the resting membrane potential or the depolarization produced by high-K. In preparations of femoral vein but not femoral artery, MCI-154 reduced NA-induced depolarization. The contractions produced by NA and high-K were reduced by MCI-154, the former more than the latter. The actions of MCI-154 were more pronounced in the vein than in the artery. The excitatory junction potential and contractions produced by perivascular nerve stimulation in guinea-pig saphenous artery preparations were inhibited by MCI-154 (greater than 10(-7) M). ACh-induced relaxations of guinea-pig femoral artery preparations precontracted with high-K were not affected by MCI-154. It was concluded that MCI-154 is an antagonist at postjunctional alpha 2-adrenoceptors, and, at high concentrations, inhibits voltage-dependent Ca2+ influx in vascular smooth muscle cells. These actions may contribute to the hypotensive effect of this drug.

Animals↗
PubMed1991

Stereochemistry of the concerted enolization catalyzed by delta 5-3-ketosteroid isomerase.

The reaction catalyzed by delta 5-3-ketosteroid isomerase has been shown to occur via the concerted enolization of the delta 5-3-ketosteroid substrate to form a dienolic intermediate, brought about by Tyr-14, which hydrogen bonds to and protonates the 3-keto group, and Asp-38, which removes and axial (beta) proton from C-4 of the substrate, in the same rate-limiting step [Xue, L., Talalay, P., & Mildvan, A.S. (1990) Biochemistry 29, 7491-7500; Kuliopulos, A., Mildvan, A.S., Shortle, D., & Talalay, P. (1989) Biochemistry 26, 3927-3937]. Since the axial C-4 proton is removed by Asp-38 from above the substrate, a determination of the complete stereochemistry of this rapid, concerted enolization requires information on the direction of approach of Tyr-14 to the enzyme-bound steroid. The double mutant enzyme, Y55F + Y88F, which retains Tyr-14 as the sole Tyr residue, was prepared and showed only a 4.5-fold decrease in kcat (12,000 s-1) and a 3.6-fold decrease in KM (94 microM) for delta 5-androstene-3, 17,dione, in comparison with the wild-type enzyme. Deuteration of the aromatic rings of the 10 Phe residues further facilitated the assignment of the aromatic proton resonances of Tyr-14 in the 600-MHz TOCSY spectrum at 6.66 +/- 0.01 ppm (3,5H) and at 6.82 +/- 0.01 ppm (2,6H). Variation of the pH from 4.9 to 10.9 did not alter these shifts, indicating that the pKa of Tyr-14 exceeds 10.9. Resonances assigned to the three His residues titrated with pKa values very similar to those found with the wild-type enzyme. The binding of 19-nortestosterone, a product analogue and substrate of the reverse isomerase reaction, induced downfield shifts of -0.12 and -0.06 ppm of the 3,5-and 2,6-proton resonances of Tyr-14, respectively, possibly due to deshielding by the 3-keto group of the steroid, but also induced +0.29 to -0.41 ppm changes in the chemical shifts of 8 of the 10 Phe residues and smaller changes in 10 of the 12 ring-shifted methyl resonances, indicating a steroid-induced conformation change in the enzyme. NOESY spectra in H2O revealed strong negative Overhauser effects from the 3,5-proton resonance of Tyr-14 to the overlapping 2 alpha-, 2 beta-, or 6 beta-proton resonances of the bound steroid but no NOE's to the 4- or 6 alpha-protons of the steroid.(ABSTRACT TRUNCATED AT 400 WORDS)

Escherichia coli↗
PubMed1990

Effects of the heat-tonification method on the surface temperature of the body observed by infra-red thermography.

With the infra-red thermography, 73 tests of the effect of Heat-Tonification maneuvers on body surface temperature were made. The experiments showed that application of Heat-Tonification produced marked elevation of temperature at the site of puncture, over the face and the front of the neck. The differences between pre- and post-needling temperatures were statistically significant (P less than 0.02 and P less than 0.01). Furthermore, 44.8% of the tests showed elevation of temperature over the trunk and extremities, and the distribution of temperature elevation followed the course of the meridians mostly. The findings demonstrated that the Heat-Tonification method mobilized Qi and activated Blood through influence over the vegetative nervous system that led to readjustment of blood circulation.

Acupuncture Therapy↗
PubMed1989

[The effects of pyrrole aldehydephenyl semicarbazone on experimental gastric peptic ulcer models in rats].

Pyrrole aldehydephenyl semicarbazone was shown to be an effective anti-ulcer agent in five experimental models in rats, namely, the indomethacin-induced, acetic acid-induced, pyloric ligation-induced and 0.6 mol HCl, absolute alcohol-induced ulcers, at doses of 40-100 mg/kg. Its anti-ulcer activity and characteristics are similar to those of furazolidone. Its oral acute toxicity in mouse is much lower than furazolidone. This compound exhibited mild inhibitory effects on gastric pepsin secretion, caused increases in hexosamine level and decreases of DNA content in gastric juice. It showed no influence on gastric acid secretion and was considered to have "cytoprotective action" on the gastric mucosa. However, this compound was found to be ineffective against the stress-restraint gastric ulcer model.

Animals↗
PubMed1989

[HPLC determination of prostaglandins with small-bore ODS column].

Several prostaglandins can be separated and identified with 2.6mm small bore ODS column-HPLC at 204 nm. The mobile phase used was 26% acetonitrile at the flow rate of 0.3 ml/min. The PGs studied were 6-keto-PGF1 alpha, TXB2, PGF2 alpha, PGE2 and 13,14-dihydro PGF2 alpha with retention times of 3.3, 5.6, 7.8, 8.8 and 11 minutes, respectively. Rabbit gastric mucosa was homogenized, incubated with 14C-AA (33 nmol) for 20 min and then extracted with ethyl acetate. The organic phase was dried under nitrogen, the residue was dissolved in 25% acetonitrile and injected into the HPLC system. Fractions of effluent were collected every 20 seconds and the radioactivity was measured. The results show that the peaks of radioactivity coincided well with those of the PG standard samples. When indomethacin was added to the incubation system, the radioactivity counts decreased significantly.

Animals↗
PubMedDate not supplied

Channel catfish, Ictalurus punctatus rafinesque, neutrophil adhesion to selected extracellular matrix proteins, lipopolysaccharide, and catfish serum.

Adhesion of leukocytes to endothelium and extracellular matrix proteins is an important step in the inflammatory process. Therefore, the adhesion of channel catfish neutrophils to a surface coated with extracellular matrix proteins, LPS, and non-immune catfish serum was evaluated. Stimulation of neutrophils with phorbol dibutyrate (PDBU) resulted in at least two-fold increases in cellular adhesion to all substrates tested except laminin. When EDTA was included during or after PDBU stimulation, neutrophil adhesion to fibrinogen and LPS coated surfaces was reduced to the level of unstimulated neutrophils or to 50-60% of that for stimulated neutrophils. Similarly, EDTA and Ca2+/Mg2+ deficient medium reduced homotypic aggregation of PDBU stimulated neutrophils to background levels. Adhesion of stimulated neutrophils to fibrinogen coated surfaces was inhibited 44, 33, and 50% when soluble fibrinogen, fibronectin, and serum, respectively, were used to block the adhesion assay. The tripeptide integrin adhesion recognition sequence, Arg-Gly-Asp (RGD), caused 83% reduction and the fibrinogen-binding inhibitor protein caused 10% reduction in binding of stimulated neutrophils to fibrinogen coated surfaces. Two hexapeptides tested did not reduce neutrophil adhesion to fibrinogen. The binding of channel catfish neutrophils to the matrices used in the present study is suggestive that integrin mediated adhesion occurs during biological and pathological processes of teleosts.

Animals↗
PubMedDate not supplied

Identification of a channel catfish, Ictalurus punctatus (Rafinesque), leukocyte-specific leucine zipper protein.

Five clones isolated from a channel catfish cDNA library were each reactive with monoclonal antibodies (mAbs) C3-1 and 51A only. The size of the cDNA inserts from C3-1 and 51A positive clones was 2.5 Kb and identical based on sequence analysis. Monoclonal antibodies C3-1 and 51A specifically reacted with the expressed product of the 2.5 Kb cDNA clone. The complete DNA sequence indicated that the 2.5 Kb cDNA encoded an approximately 50 Kd protein molecule consisting of 445 amino acids. Sequence analysis showed that this putative protein was a potential leucine-zipper DNA binding protein. Comparison of the deduced amino acid sequence demonstrated homology (14.6 to 19.5%) throughout the sequence of the catfish protein with a group of cytoplasmic-leucine zipper containing proteins of humans; paraneoplastic cellebellar degeneration related (cdr) antigen 2 and 3 with 39.8 to 56.3% homology in the leucine-zipper motif (amino acids 52 through 175 in the catfish protein). This protein was detected in nuclear extracts. cytoplasmic membrane preparations and cytosolic extracts of neutrophils and lymphocytes when reacted with mAbs C3-1 and 51A in an ELISA. However, the intensity of the reactions was dependent upon the cell type and cellular component. The putative cdr protein was not detected with any appreciable intensity in preparations from other cell types. This finding strongly suggests that this protein is expressed in a leukocyte-specific manner and is unique among the cdr group in that it is being expressed in a site that is not immune privileged.

Amino Acid Sequence↗