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S Li

Publications and source records attributed to S Li.

At least 1,045 records · Page 58Linked to original sources
PubMed1997

MyD88: an adapter that recruits IRAK to the IL-1 receptor complex.

IL-1 is a proinflammatory cytokine that signals through a receptor complex of two different transmembrane chains to generate multiple cellular responses, including activation of the transcription factor NF-kappaB. Here we show that MyD88, a previously described protein of unknown function, is recruited to the IL-1 receptor complex following IL-1 stimulation. MyD88 binds to both IRAK (IL-1 receptor-associated kinase) and the heterocomplex (the signaling complex) of the two receptor chains and thereby mediates the association of IRAK with the receptor. Ectopic expression of MyD88 or its death domain-containing N-terminus activates NF-kappaB. The C-terminus of MyD88 interacts with the IL-1 receptor and blocks NF-kappaB activation induced by IL-1, but not by TNF. Thus, MyD88 plays the same role in IL-1 signaling as TRADD and Tube do in TNF and Toll pathways, respectively: it couples a serine/threonine protein kinase to the receptor complex.

Adaptor Proteins, Signal Transducing↗
PubMed1997

In-vitro apatite formation on phosphorylated bamboo.

Natural self-reinforced composite, bamboo, was surface modified by phosphorylation with urea-H3PO4 and NaOH-H3PO4 methods; then precalcification was performed by immersing samples in saturated Ca(OH)2 solution. After that, calcium phosphate can be formed on the surface of bamboo samples in calcification media: simulated body fluid (1.5 SBF) and accelerated calcification solution (ACS). Experimental results reveal that pre-calcification is an inevitable step for the formation of calcium phosphate. The calcium phosphate formed in 1.5 SBF was identified by thin-film X-ray diffraction as apatite which was not well crystallized. Compared with the urea-H3PO4 method, the NaOH-H3PO4 method has the advantages of quicker and continuous apatite formation and stronger adhesive between apatite and bamboo.

Journal Article↗
PubMed1997

Antibody independent crescentic glomerulonephritis in mu chain deficient mice.

The hypothesis that crescent formation in glomerulonephritis (GN) is a delayed type hypersensitivity (DTH)-like lesion, not dependent on a humoral immune response, was addressed using mice with deletion of the mu immunoglobulin heavy chain gene (mu chain deficient mice). Homozygous mu chain deficient mice do not develop mature B cells or produce immunoglobulin, but have intact cell mediated immunity. GN was induced in sensitized mice by a subnephritogenic dose of sheep anti-mouse GBM globulin. Heterozygous mice (mu chain +/-) demonstrated normal antibody and DTH responses to sheep globulin and developed a proliferative GN with proteinuria (6.4 +/- 1.4 mg/24 hr), renal impairment (serum creatinine 32.6 +/- 3.3 mumol/liter) and crescents in 33 +/- 24% of glomeruli, when this antigen was planted in their glomeruli. This lesion was demonstrated to be T cell dependent by in vivo T cell depletion. Homozygous mu chain deficient mice (-/-) also developed proliferative GN, histologically indistinguishable from +/- mice. Proteinuria (3.8 +/- 1.0 mg/24 hr), renal impairment (serum creatinine 24.5 +/- 3.4 mumol/liter) and crescent formation (29 +/- 2% of glomeruli) were no different from =/- mice. Mouse immunoglobulin was absent in their serum and glomeruli, however, cutaneous DTH to sheep globulin was identical to heterozygous mice. These results demonstrate that glomerular crescent formation and injury can occur independent of a humoral immune response to planted glomerular antigen and without glomerular deposition of autologous antibody. This strongly supports the hypothesis that crescent formation is a manifestation of DTH.

Animals↗
PubMed1997

Delivery of a PCR amplified DNA fragment into cells: a model for using synthetic genes for gene therapy.

Synthetic genes offer many potential advantages over conventional plasmid DNA, such as simplicity in purification, absence of endotoxin contamination, and more importantly, flexibility in chemical modifications to render them specific properties. We have used PCR amplified fragments as a model to test the feasibility of using synthetic genes for gene therapy. The CAT reporter gene driven by the CMV promoter (CMV-CAT), ie a nuclear expression system, or by the bacteriophage T7 promoter (T7-CAT), ie a cytoplasmic expression system, was used to evaluate this concept. The expression efficiency of both plasmids (pUCCMV-CAT and pT7-CAT) and their corresponding PCR fragments (fCMV-CAT and fT7-CAT) were compared on a molar basis. Limited expression of CAT was found with fCMV-CAT. However, fT7-CAT consistently gave a CAT activity comparable to that of pT7-CAT. When fT7-CAT was codelivered with pCMV/T7-T7pol (a self-amplifying-T7 RNA polymerase autogene), high CAT activity could be detected up to 9 days. This expression was much longer than the duration of expression with a nuclear expression system. These encouraging results imply that gene therapy with synthetic genes could be both feasible and efficient.

Gene Expression↗
PubMed1997

Selection and use of ligands for receptor-mediated gene delivery to myogenic cells.

Identification of myogenic cell targeting ligands is a critical step in the development of synthetic vectors for gene delivery to skeletal muscle. Here we describe the screening of six potential targeting ligands (insulin, insulin-like growth factor I, iron transferrin, gallium transferrin, alpha-bungarotoxin and carnitine) for their ability to bind dystrophin-deficient myotubes in vitro. Those ligands showing high levels of binding to myotubes were then tested on fully differentiated, isolated, viable myofibers. Of the ligands tested, transferrin showed the most promise based on high levels of binding to myogenic cells, high levels of receptor observed in regenerating fibers of patients with Duchenne muscular dystrophy and the ability to direct a large enzyme conjugate to the cytoplasm of myotubes. Finally, we show that incorporation of transferrin into an artificial virus consisting of poly-L-lysine-condensed DNA coated with a lipid shell (LPDII formulation) results in ligand-directed delivery of DNA to myogenic cells. This is the first report of gene transfer to myogenic cells using a ligand-directed synthetic vector. These results suggest that rational design of ligand-directed, fully synthetic, gene delivery vehicles is a viable approach to skeletal muscle vector development.

Animals↗
PubMed1997

In vivo gene transfer via intravenous administration of cationic lipid-protamine-DNA (LPD) complexes.

A novel LPD formulation has been developed for in vivo gene transfer. It involves the interaction of plasmid DNA with protamine sulfate, a cationic polypeptide, followed by the addition of DOTAP cationic liposomes. Compared with DOTAP/DNA complexes, LPD offers better protection of plasmid DNA against enzymatic digestion and gives consistently higher gene expression in mice via tail vein injection. When a luciferase reporter gene was employed, gene expression was found in all tissues examined including lung, heart, spleen, liver and kidney with the highest expression in the lung. The in vivo efficiency of LPD was dependent upon charge ratio and was also affected by the lipid used. Increasing the amount of DNA delivered induced an increase in gene expression. The optimal dose was approximately 50 micrograms per mouse at which concentration approximately 20 ng luciferase protein per milligram extracted tissue protein could be detected in the lung. Increasing the DNA to 100 micrograms per mouse resulted in toxicity and death of the animal. Gene expression in the lung was detected as early as 1 h after injection, peaked at 6 h and declined thereafter. High expression was also found in the spleen 6 h after injection but dropped very rapidly thereafter. The in vivo gene expression by LPD was dependent upon the route of administration since intraportal injection of LPD led to about a 100-fold decrease in gene expression in the lung as compared with i.v. injection. Using lacZ as a reporter gene, it was shown that endothelial cells were the primary locus of transgene expression in both the lung and spleen. No sign of inflammation in these organs was noticed. Since protamine sulfate has been proven to be nontoxic and only weakly immunogenic in humans, this novel vector may be useful for clinical gene therapy.

Animals↗
PubMed1997

Involvement of neurosteroids in the effect of the endogenous benzodiazepine receptor ligand octadecaneuropeptide (ODN) on gonadotropin-releasing hormone gene expression in rat brain.

We have recently demonstrated that different activators of the GABAA receptor complex including reduced progesterone metabolites and the endozepine octodecaneuropeptide (ODN) exert an inhibitory influence on GnRH gene expression. In order to investigate the possible involvement of neurosteroids, especially progesterone metabolites in the effect of ODN, we have evaluated in adrenalectomized and castrated male rats the influence of pretreatment with an inhibitor of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) trilostane (TRIL) and an inhibitor of 5 alpha-reductase MK-906 on GnRH mRNA levels in ODN-treated rats. TRIL completely prevented the inhibitory influence of ODN on GnRH mRNA. It was also found that the inhibitor of 3 beta-HSD as well as pregnenolone sulfate (PREG-S), which has been shown to be increased following TRIL treatment, could induce an increase in GnRH mRNA. MK-906 could also completely reverse the negative influence of ODN. When administered alone, this antagonist of 5 alpha-reductase induced an increase in GnRH mRNA. These results clearly indicate that the inhibition of two key enzymes for the synthesis of reduced progesterone metabolites can completely prevent the inhibitory influence of the endozepine ODN, suggesting that the effect of this endogenous ligand might be completely or partially mediated by an activation of the synthesis of active progesterone metabolites. On the other hand, it remains possible that, as a consequence of enzymatic inhibition, an increase in some precursors known as antagonists of GABAA may play a role in the prevention of the ODN effect by the two enzyme antagonists.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Differential agonist regulation of the human kappa-opioid receptor.

Opiates are potent analgesics used clinically in the treatment of pain. A significant drawback to the chronic use and clinical effectiveness of opiates is the development of tolerance. To investigate the cellular mechanisms of tolerance, the cloned human kappa-opioid receptor was stably expressed in human embryonic kidney (HEK 293) cells, and the effects of opioid agonist treatment were examined. The receptor-expressing cells showed specific high-affinity membrane binding for a kappa-selective opioid, 3H-labeled (+)-(5alpha,7alpha,8beta)-N-methyl-N-[7-(1-pyrrolidiny l)-1-oxaspiro [4,5] dec-8-yl] benzeneacetamide ([3H]U69,593), and a nonselective opioid antagonist, [3H]diprenorphine. Pretreatment with pertussis toxin or guanosine 5'-O-(3-thiotriphosphate) reduced [3H]69,593 binding, indicating that the human K receptor coupled to G proteins of the Gi or Go families in HEK 293 cells. The receptor-mediated inhibition of adenylyl cyclase was abolished by pertussis toxin pretreatment and was blocked by a kappa-selective antagonist, norbinaltorphimine. A 3-h pretreatment with a kappa-selective agonist, (+/-)-trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide (U50,488), caused receptor down-regulation, whereas no receptor down-regulation was found after levorphanol pretreatment. U50,488 or dynorphin A(1-17) pretreatments (3 h) desensitized the ability of U50,488 or dynorphin A(1-17) to inhibit cyclic AMP accumulation, as evidenced by a decrease in functional potency. Also, U50,488 pretreatment desensitized the ability of levorphanol to inhibit forskolin-stimulated cyclic AMP accumulation. In contrast, pretreatment of cells with either levorphanol or a potent nonselective opioid, etorphine, resulted in no apparent receptor desensitization. Taken together, these results demonstrate that the human kappa receptor is differentially regulated by selective and nonselective opioid agonists, with selective agonists able to desensitize the receptor.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1997

Salt-induced folding of alkaline denatured creatine kinase under high pH conditions.

The conformational changes of creatine kinase during alkaline unfolding and salt-induced folding at high pH have been followed by fluorescence emission and circular dichroism spectra. The results obtained show that at low ionic strength, with increasing pH value, creatine kinase denatured gradually to reach the ultimate unfolded conformation in the vicinity of pH 12.7. With the increase of pH from 9.0 to 12.7, the fluorescence emission maximum red shifted from 337 to 355 nm, indicating complete exposure of the buried tryptophan residues to the solvent. The far-UV CD spectra show that even at pH 12.7, the apparently fully denatured enzyme retains a great part of ordered secondary structure. At pH 12.7 by adding the salt, the relatively unfolded state of denatured enzyme changes into a compact conformational state by hydrophobic collapsing. Folded state induced by salt bound ANS strongly, indicating the existence of increased hydrophobic surface. The above results suggest that the salt-induced folded state at high pH may be the folded intermediate which exists in the general protein folding, and the larger residual ordered secondary structure might become folded being point on the salt-induced folding.

Anilino Naphthalenesulfonates↗
PubMed1997

Linkage analysis of 49 high-risk families does not support a common familial prostate cancer-susceptibility gene at 1q24-25.

Linkage of a putative prostate cancer-susceptibility locus (HPC1) to chromosome 1q24-25 has recently been reported. Confirmation of this linkage in independent data sets is essential because of the complex nature of this disease. Here we report the results of a linkage analysis using 10 polymorphic markers spanning approximately 37 cM in the region of the putative HPC1 locus in 49 high-risk prostate cancer families. Data were analyzed by use of two parametric models and a nonparametric method. For the parametric LOD-score method, the first model was identical to the original report by Smith and coworkers ("Hopkins"), and the second was based on a segregation analysis previously reported by Carter and coworkers ("Seattle"). In both cases, our results do not confirm the linkage reported for this region. Calculated LOD scores from the two-point analysis for each marker were highly negative at small recombination fractions. Multipoint LOD scores for this linkage group were also highly negative. Additionally, we were unable to demonstrate heterogeneity within the data set, using HOMOG. Although these data do not formally exclude linkage of a prostate cancer-susceptibility locus at HPC1, it is likely that other prostate cancer-susceptibility loci play a more critical role in the families that we studied.

Adult↗
PubMed1997

Purification, staphylolytic activity, and cleavage sites of alpha-lytic protease from Achromobacter lyticus.

Alpha-lytic protease (alp) was purified from a bacteriolytic agent, Achromopeptidase from Achromobacter lyticus M497-1, and has been shown to possess staphylolytic activity. Cleavage sites of this enzyme on the peptidoglycan of Staphylococcus aureus were determined by N-terminal amino acid sequence and amino acid composition analyses. Alp cleaved the N-acetylmuramoyl-L-alanine amide bond, the junction between the polysaccharide and peptide moieties, in addition to the D-Ala-Gly and Gly-Gly peptide bonds, implying that this enzyme recognizes the amino acid of D-configuration at the P1 site and possesses N-acetylmuramoyl-L-alanine amidase activity. However, alp could not cleave the D-Ala-Gly peptide bond in a synthetic peptide, suggesting that this hydrolytic activity of alp is peptidoglycan-specific. The results obtained from different consecutive actions of alp and glycosidase on S. aureus peptidoglycan indicate that the presence of polysaccharide in the peptidoglycan is necessary for the bacteriolytic activity of alp.

Alcaligenes↗
PubMed1997

Alpha2-adrenergic receptor-mediated Ca2+ influx and release in porcine myometrial cells.

We studied the mechanisms underlying alpha2-adrenergic receptor (AR)-mediated increase in intracellular free calcium ([Ca2+]i) in freshly dispersed myometrial cells from sows in the luteal phase of the estrous cycle. After the blockade of beta-ARs with propranolol, epinephrine increased [Ca2+]i dose-dependently in both the presence and absence of extracellular Ca2+. The rank order of alpha antagonists in inhibiting [Ca2+]i response to epinephrine was yohimbine > WB4101 >> prazosin in both the presence and absence of extracellular Ca2+, suggesting that epinephrine acts on alpha(2A)-ARs to increase Ca2+ influx as well as Ca2+ release from intracellular stores. Thapsigargin, the blocker of the Ca2+ pump in the sarcoplasmic reticulum, abolished the release but did not affect the influx. Pertussis toxin (PTX) inhibited the influx but failed to change the release. Nimodipine, an L-type Ca2+ channel blocker, nearly abolished the influx. The peak increase in [Ca2+]i caused by epinephrine was reached within 20 sec of administration. Intracellular cAMP concentrations were also decreased at 20 sec post-epinephrine. Epinephrine enhanced the L-type Ca2+ channel current, whereas forskolin suppressed it. Maximization of intracellular cAMP content by applying 8-bromo-cAMP (100 microM) blocked the effect of epinephrine on the current. U-73122, a phospholipase C inhibitor, reduced the Ca2+ release by epinephrine and oxytocin. Our results suggested that 1) activation of alpha2-ARs induces Ca2+ influx through opening L-type Ca2+ channels as well as inducing Ca2+ release from intracellular stores, and 2) a PTX-sensitive G protein couples negatively to adenylyl cyclase, leading to a decrease in cAMP formation which may be involved in the activation of Ca2+ channels. In addition, our results are consistent with the coupling of alpha2-ARs to a PTX-insensitive G protein (G(q)) to release Ca2+ from intracellular stores.

Adenylate Cyclase Toxin↗
PubMed1997

Glutamate transporter alterations in Alzheimer disease are possibly associated with abnormal APP expression.

Recent studies have shown that deficient functioning of glutamate transporters (GTs) in Alzheimer disease (AD) might lead to neurodegeneration. The main objectives of the present study were to determine which GT subtype is most affected in AD and to asses to what extent altered GT function is associated with abnormal amyloid precursor protein (APP) expression. While EAAT2-immunoreactivity (IR) was decreased in AD frontal cortex, EAAT1- and EAAT3-IR were unaffected; mRNA levels for all 3 GTs were not affected. Decreased EAAT2-IR was associated with decreased GT activity. EAAT2-IR inversely correlated with EAAT2 mRNA levels, suggesting that in AD, GT expression alterations occur due to disturbance at the post-transcriptional level. EAAT2-IR was inversely correlated with APP770 mRNA. In addition, GT activity directly correlated with APP695 mRNA and total APP protein levels, and inversely correlated with APP751/770 mRNA levels. This study supports the notion that astroglial EAAT2 is affected in AD and abnormal functioning and/or processing of APP might play an important role in this process.

ATP-Binding Cassette Transporters↗
PubMed1997

Lipopolysaccharide-responsive protein kinase C isotypes in the adult rat aorta.

Previous studies have shown that protein kinase C (PKC) activity increases in cardiovascular tissue exposed to lipopolysaccharide (LPS). The objective of these experiments was to identify the PKC isotypes that respond to LPS treatment in the adult rat aorta. We found that PKC alpha, -delta, -epsilon, and -zeta isotypes are present in endothelium-intact aortas. The PKC alpha and -epsilon isotypes show two- to threefold increases in abundance after 3 h treatment with 100 ng/mL LPS, while PKC delta and -zeta levels do not increase. In contrast, mRNA for all of the PKC isotypes increased 3.5 to 12-fold during LPS treatment. Both PKC isotype and mRNA levels gradually diminished during 20 h of continuous LPS exposure. Concurrent treatment of the vessels with LPS plus 50 microM cycloheximide caused PKC alpha, -epsilon, and -zeta, but not -delta, isotypes to rapidly decrease in abundance while blunting the increase in PKC isotype mRNA. The major source for all of the PKC isotypes in the vessel is the vascular smooth muscle cells. These results indicate that LPS treatment induces time-dependent increases in PKC isotype mRNA expression and isotype-specific PKC activation and synthesis in vascular tissue.

Age Factors↗
PubMed1997

Cancer mortality in a Chinese population exposed to hexavalent chromium in water.

This report is a clarification and further analysis of our previously published mortality study regarding groundwater contamination with hexavalent chromium (Cr+6) in the JinZhou area of China between 1965 and 1978. In our previous report, we stated that a significant excess of overall cancer mortality was observed (P = 0.04) in five Cr(+6)-contaminated villages combined. Further analysis revealed no clear statistical increase in cancer mortality in the three villages adjacent to the source of the contamination (P = 0.25), where 57% of the wells exceeded the European Community safe drinking water standard of 0.05 ppm Cr+6. These results do not indicate an association of cancer mortality with exposure to Cr(+6)-contaminated groundwater, but might reflect the influence of lifestyle or environmental factors not related to Cr+6. Further follow-up of this cohort is recommended.

Carcinogens, Environmental↗
PubMed1997

A physical map of the Mamestra configurata nucleopolyhedrovirus genome and sequence analysis of the polyhedrin gene.

The genome structure of a nucleopolyhedrovirus (NPV) isolated from the bertha armyworm, Mamestra configurata Walker (Lepidoptera: Noctuidae) (MacoNPV) was analysed with six restriction endonucleases (REN): BamHI, EcoRI, HindIII, PstI, SmaI and Xhol. More than 70 MacoNPV REN fragments were cloned into plasmids pUC18 and pBluescript SK(+). The physical map with 112 restriction sites for the above REN was constructed using double digests and Southern blot hybridization analysis of the MacoNPV DNA clones. The size of the DNA genome of the MacoNPV-90/2 isolate used for this study was estimated at 156 kbp based on REN fragment sizes. The position of the polyhedrin gene, which has by convention been used as the zero point of the REN maps of NPV, was determined by hybridizing the Autographa californica multicapsid nucleopolyhedrovirus HindIII-V fragment clone, which contains most of the polyhedrin gene, with genomic blots of MacoNPV. The cloned MacoNPV fragments identified as containing the polyhedrin gene were sequenced and an ORF coding for a 246 amino acid polypeptide with 98.7% sequence identity with Panolis flammea nucleopolyhedrovirus (PaflNPV) polyhedrin protein was identified. The putative polyhedrin gene sequence had 97.2% and 91.2% identity with the PaflNPV and Mamestra brassicae multicapsid nucleopolyhedrovirus polyhedrin gene sequences, respectively, and also contained an upstream region identical to the highly conserved 12 bp consensus sequence TGTAAGT-AATTT typical of NPV very late genes.

Amino Acid Sequence↗