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Biomedical subjects

T Lu

Publications and source records attributed to T Lu.

At least 91 records · Page 5Linked to original sources
PubMed1998

Desensitization of AMPA receptors on horizontal cells isolated from crucian carp retina.

In horizontal cells freshly dissociated from crucian carp (Carassius auratus) retina, we recorded the whole-cell responses to rapid application of glutamate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate. Currents induced by glutamate and AMPA, but not by kainate, usually showed extremely rapid desensitization. 1-(4-aminophenyl)-3-methylcarbamyl- 4-methyl-7,8-methylenedioxy-3,4-dihydro-5H-2,3-benzodiazepine (GYKI 53655), a selective AMPA receptor antagonist, was found to completely block glutamate- and kainate-induced currents, which were supposed to be mediated by activation of AMPA receptors. We further extensively studied the kinetics of desensitization of glutamate- and AMPA-induced currents in horizontal cells. The time constants for decay of whole-cell currents induced by glutamate and AMPA were 1.9 and 1.4 ms, respectively, and the equilibrium responses to glutamate and AMPA at concentrations over 1 mM were invariably less than 10% of the corresponding peak responses. We have determined the values of EC50 for glutamate and AMPA as 1.08 and 1.05 mM, respectively, which are nearly 100-fold higher than that reported previously. Dose dependence of desensitization was also investigated and the glutamate concentration for a half desensitization was 26 microM, much lower than the EC50. Furthermore, kainate and AMPA interacted at AMPA receptors of horizontal cells in a dual competitive manner: the response to kainate of low concentration (10 microM) was potentiated by the addition of 300 microM AMPA, while the responses induced by kainate of relatively higher doses (300 microM or more) were reduced. We conclude that crucian carp horizontal cells may exclusively express the AMPA subtype of glutamate receptors, which is characterized by extremely rapid desensitization.

Animals↗
PubMed1998

Antimycobacterial matricaria esters and lactones from Astereae species.

Six matricaria esters (MEs) and two matricaria lactones (MLs), isolated from members of the tribe Astereae (Asteraceae), were tested against Mycobacterium tuberculosis and M. avium, using a radiorespirometric bioassay. (2Z,8Z)-ME and (2E-8Z)-ME gave minimum inhibitory concentrations (MICs) of 50 micrograms ml-1 against M. tuberculosis and respective MICs of 25 and 50 micrograms ml-1 against M. avium. The (4Z,8Z)-ML, (2Z)-8-dehydro-ME and (2Z,8Z)-10-angeloyloxy-(2Z,8Z)-ME showed respective MICs of 12.5, 25, 25 micrograms ml-1 against M. tuberculosis and MICs of 50, 25, 25 micrograms ml-1 against M. avium, respectively. The MICs of (2Z,8Z)-10-tigloyloxy-ME and (2E,8Z)-10-angeloyloxy-ME and (4E,8Z)-ML ranged from 50 to > 100 micrograms ml-1 against both pathogenic mycobacteria.

Antitubercular Agents↗
PubMed1998

Direct interaction of Jak1 and v-Abl is required for v-Abl-induced activation of STATs and proliferation.

In Abelson murine leukemia virus (A-MuLV)-transformed cells, members of the Janus kinase (Jak) family of non-receptor tyrosine kinases and the signal transducers and activators of transcription (STAT) family of signaling proteins are constitutively activated. In these cells, the v-Abl oncoprotein and the Jak proteins physically associate. To define the molecular mechanism of constitutive Jak-STAT signaling in these cells, the functional significance of the v-Abl-Jak association was examined. Mapping the Jak1 interaction domain in v-Abl demonstrates that amino acids 858 to 1080 within the carboxyl-terminal region of v-Abl bind Jak1 through a direct interaction. A mutant of v-Abl lacking this region exhibits a significant defect in Jak1 binding in vivo, fails to activate Jak1 and STAT proteins, and does not support either the proliferation or the survival of BAF/3 cells in the absence of cytokine. Cells expressing this v-Abl mutant show extended latency and decreased frequency in generating tumors in nude mice. In addition, inducible expression of a kinase-inactive mutant of Jak1 protein inhibits the ability of v-Abl to activate STATs and to induce cytokine-independent proliferation, indicating that an active Jak1 is required for these v-Abl-induced signaling pathways in vivo. We propose that Jak1 is a mediator of v-Abl-induced STAT activation and v-Abl induced proliferation in BAF/3 cells, and may be important for efficient transformation of immature B cells by the v-abl oncogene.

Animals↗
PubMed1998

[The investigation of children's Helicobacter pylori infection by 13C-urea breath test in Yangzhong area of Jiangsu province].

OBJECTIVE: Yangzhong area in Jiangsu province is one of the places in China with high gastric cancer incidence (73.19/1000,00). In order to investigate the relations between gastric cancer and helicobacter pylori infection rate. METHODS: 13C-urea breath test was conducted for 119 children aged from 4 to 12 years old. RESULTS AND CONCLUSIONS: Total H. pylori infection rate was 73.11%, and 81.08% for boys, 60.00% for girls.

Breath Tests↗
PubMed1998

[Comparison of demineralization of different organic acid to enamel].

The rates of demineralization of 5 organic acids (mathanoic acid, formic acid, propionic acid, Lactic acid, acetic acid, mixed acid) to the bovine enamel were tested and analysed with the self-made calcium ionselective microelectrodes(Ca(2+)-ISME) basing on a neutral carriers of ETH1001. The results showed; 1. The difference between the rates of demineralization of formic acid and lactic acid, formic acid and propionic acid, formic acid and acetic acid, acetic acid and mixed acid, acetic acid and lactic acid, propionic acid and mixed acid, propionic acid and lactic acid, lactic acid and mixed acid were of great significance (P < 0.01); 2. The rates of demineralization of acetic and mixed acid decreased with time, due to saturation of the solution during demineralization; 3. Ca(2+)-ISME was of the advantages of simplicity, rapidity, sensitivity and accuracy. The results suggest that the cariogenic potential is related to different acid products of different cariogenic bacteria, and the degree of mineral saturation within solution affects the rate of demineralization.

Acetic Acid↗
PubMed1998

[The history of Sparganium stoloniferum processing].

Through the study on medical literatures about Sparganium stoloniferum processing from Tang Dynasty to Qing Dynasty and Pharmacopoeias of China and the standards of herbal processing practised in defferent localities in China, the author summed the history of Sparganium stoloniferum processing, and its original meaning and gave suggestions to improve the Sparganium stoloniferum processing.

China↗
PubMed1998

KN-93, an inhibitor of multifunctional Ca++/calmodulin-dependent protein kinase, decreases early afterdepolarizations in rabbit heart.

The multifunctional Ca++/calmodulin-dependent protein kinase II (CaM kinase) mediates Ca++-induced augmentation of L-type Ca++ current (ICa); therefore it may act as a proarrhythmic signaling molecule during early afterdepolarizations (EADs) due to ICa. To investigate the hypothesis that ICa-dependent EADs are favored by CaM kinase activation EADs were induced with clofilium in isolated rabbit hearts. All EADs were rapidly terminated with ICa antagonists. Hearts were pretreated with the CaM kinase inhibitor KN-93 or the inactive analog KN-92 (0.5 microM) for 10 min before clofilium exposure. EADs were significantly suppressed by KN-93 (EADs present in 4/10 hearts) compared to KN-92 (EADs present in 10/11 hearts) (P =.024). There were no significant differences in parameters favoring EADs such as monophasic action potential duration or heart rate in KN-93- or KN-92-treated hearts. CaM kinase activity in situ increased 37% in hearts with EADs compared to hearts without EADs (P =.015). This increase in CaM kinase activity was prevented by pretreatment with KN-93. In vitro, KN-93 potently inhibited rabbit myocardial CaM kinase activity (calculated Ki </= 2.58 microM), but the inactive analog KN-92 did not (Ki > 100 microM). The actions of KN-93 and KN-92 on ICa and other repolarizing K+ currents did not explain preferential EAD suppression by KN-93. These data show a novel association between CaM kinase activation and EADs and are consistent with the hypothesis that the ICa and CaM kinase activation both contribute to EADs in this model.

Animals↗
PubMed1997

Discontinuation of methotrexate treatment in juvenile rheumatoid arthritis.

OBJECTIVE: Children with juvenile rheumatoid arthritis (JRA) treated with methotrexate (MTX) were examined for their course after the discontinuation of the drug to define the relapse and remission rates and to identify predictors of relapse. METHODOLOGY: A retrospective chart review of all patients with JRA was conducted in two pediatric rheumatology centers. A total of 101 patients being treated with MTX were identified. Dose, response to the drug, and length of time until reaching a state of complete control were noted. The outcome of patients with a complete response in whom the drug was discontinued was examined with regards to length of time to relapse or continued remission. RESULTS: In 25 patients, MTX was discontinued after reaching complete control of the disease. There were no statistically significant predictors of response to MTX identified. Of 25 whose MTX was discontinued, relapse occurred in 13 (52%) after a mean of 11 months after discontinuation. There was no significant difference among patients who relapsed or those who remained in remission as to sex, subtype of JRA, number of months to complete control, or number of months in complete control until discontinuing MTX. Patients younger than 41/2 years at diagnosis were found to be more likely to relapse than patients diagnosed at a later age. In 10 of the patients who relapsed, complete control was induced within a mean of 7 months after restarting MTX. CONCLUSION: The optimal time for discontinuing MTX in children with JRA who have achieved complete control is unknown. Relapse occurred in approximately half of the patients in whom MTX was discontinued. Because response to reinstitution of the drug is good, it is reasonable to discontinue MTX after prolonged complete control. It remains to be seen whether the relapse rate can be improved by waiting for longer periods of time in complete control before its discontinuation.

Adolescent↗
PubMed1997

[AMPA receptor desensitization and fast excitatory synaptic transmission].

AMPA(alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor, an ionotropic glutamate receptor subtype, mediates fast excitatory synaptic transmission in central nervous system. Recently, the distinct characteristics of AMPA receptor desensitization have been gradually revealed and a number of chemicals which selectively modulate AMPA receptor desensitization have been developed. Many lines of physiological and pharmacological evidence show that AMPA receptor desensitization plays an important role in fast excitatory synaptic transmission by affecting transmission efficacy of individual synaptic bouton, integrative functions of neuron, and synapse plasticity.

Benzothiadiazines↗
PubMed1997

[The research on analgestic and anti-inflammatory action of different processed products of Achyranthes bidentata].

Analgestic effect of different processed products of Achyranthes bidentata in mice was observed in hot plate and acetic acid induced writhing test. The experiment results showed that water extract of Achyranthes bidentata and its processed products could inhibit the pain. The analgestic effect of its product processed with wine is the most powerful and lasting. The results showed that Achyranthes bidentata could obviously inhibit the ear inflammation of mice which was led by croton fruit oil. The anti-inflammatory effect of its product processed with wine is the most powerful.

Acetic Acid↗
PubMed1997

[Study of interaction between cytochrome C and cystine using synchronours fluorescence spectroscopy].

The interaction of cytochrome C with cystine as promoter was studied by synchronous fluorescence spectroscopy. After cystine was added into cytochrome C solution, the synchronous flurorescence spectra of tyrosine and tryptophan residues in cytochrome C were monitered with time. The results indicated that the lysine residues in cytochrome C molecules combine with cystine slowly. It induced the small conformational change of cytochrome C molecules.

Animals↗
PubMed1997

Platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) tyrosine phosphorylation state changes during vasculogenesis in the murine conceptus.

Vasculogenesis, the differentiation of mesodermal cells to angioblasts and the subsequent formation of blood islands and blood vessels by angioblasts in the conceptus, is a dynamic process modulated, in part, by cell-extracellular matrix and cell-cell interactions in the presence of a variety of growth factors and morphogens. In this report we demonstrate differential tyrosine phosphorylation of platelet-endothelial cell adhesion molecule-1 (PECAM-1) during the formation of blood islands and vessels from clusters of extraembryonic and embryonic angioblasts in the murine conceptus. In addition, we identify the phosphorylation of a particular tyrosine residue in the PECAM-1 cytoplasmic domain, Tyr686, which has the potential of mediating binding to Src homology 2 domain-containing proteins, affecting PECAM-1 cellular localization and endothelial cell migration.

Animals↗
PubMed1997

[Nucleotide sequence of gltB gene encoding the large subunit of Rhodobacter sphaeroides glutamate synthase].

The complete nucleotide sequence of a 5.4-kb chromosomal EcoRI-SalI fragment was determined, which contains the structural gene (gltB) for the large subunit of Rhodobacter sphaeroides glutamate synthase, as well as the 5'- and 3'- flanking regions. A open reading frame of 4636 base pairs was identified as R. sphaeroides gltB gene. The MW of the large subunit, as deduced from the nucleotide sequence, was estimated as 164kD. Comparision of the nucleotide sequences revealed a high similarity among gltB genes of R. sphaeroides, Azospirillum brasilense and Escherichia coli. The deduced amino acid sequence of R. sphaeroides GltB showed a high similarity with that of A. brasilense GltB.

Amino Acid Sequence↗
PubMed1996

Alternative splicing of the pyruvate kinase M gene in a minigene system.

The M1-type and M2-type isozymes of pyruvate kinase are produced from a single gene by mutually exclusive use of exons 9 and 10. Selection of exon 10 generates the M2 type, which occurs in most tissues, whereas the M1 type is expressed by use of exon 9 only in skeletal muscle, heart and brain. We investigated the mechanism by which exon 10, but not exon 9 is selected in M2-expressing cells by transfecting minigenes containing exon 9 and/or exon 10 in cells and by analyzing the transcripts using reverse-transcriptase polymerase chain reaction. Deletion of the most conserved region in intron 8 did not affect selection of exon 10 in dRLh-84 cells, which express only the M2 type. Exclusion of exon 10 from the minigene resulted in two major spliced products. One included correctly spliced exon 9 and the other skipped this exon. Similar splicing patterns were observed when these minigenes were transfected in hepatocytes which express the L type, but not M1 or M2 types. The 5' splice site but not the 3' splice site of exon 9 was found to be hardly recognized by the splicing machinery in dRLh-84 cells. Mutation of the 5' splice site sequence of exon 9 to that of exon 10 and vice versa did not change the splicing patterns. However, mutation of this site of exon 9 to a perfectly complementary sequence of U1 snRNA resulted in selection of exon 9 correctly spliced to exon 10. A 9-10 fusion exon (constructed by substitution of 68 bases of the 3' portion of exon 9 and 33 bases of the 5' portion of intron 9 for the corresponding regions of exon 10 and intron 10) was also correctly incorporated into a major product together with exon 10. Thus, we propose that exon 9 is not recognized in non M1-expressing cells due to the weak signal of its 5' splice site and that, although the 5' splicing signal of exon 10 also appears to be weak, this exon can be recognized in these cells because the 5' recognition signal may be relatively strengthened by cis-acting element(s) which may be present in the 3' portion of exon 9 and the 5' portion of intron 9 and/or the corresponding regions of exon 10 and intron 10.

Alternative Splicing↗
PubMed1996

Antimycobacterial cycloartanes from Borrichia frutescens.

In a bioassay-guided search for antimycobacterial compounds from higher plants of the southeastern United States, we have chemically investigated the sea daisy (Borrichia frutescens) from coastal marshes of Louisiana for their active constituents. Bioactive chromatographic fractions provided two new triterpenes, (24R)-24,25-epoxycycloartan-3-one (1) and (23R)-3-oxolanosta-8,24-dien-23-ol (4), and (3 alpha H, 24R)-24,25-epoxycycloartan-3-ol (3a). Compound 3a had been previously isolated as a mixture of C-24 epimers. The structures of 1, 3a, and 4 were established by spectroscopic methods and chemical transformations, and the molecular structures of 1 and 4 were determined by single-crystal X-ray diffraction. In a radiorespirometric bioassay against Mycobacterium tuberculosis, the epoxycycloartanes 1 and 3a exhibited minimum inhibitory concentrations of 8 micrograms/mL. In contrast, the lanostadiene-type triterpene 4 showed no significant inhibition at 128 micrograms/mL, as did the acetate 3b. Cytotoxicity for Vero cells gave IC50 values of 71.8, 39.8, and 103.6 micrograms/mL for triterpenes 1, 3a, and 4, respectively.

Acetylation↗