PubMed Health⌕ Search

Biomedical subjects

J Park

Publications and source records attributed to J Park.

At least 19 recordsLinked to original sources
PubMed2025

HLA-E and NKG2A Mediate Resistance to BCG Immunotherapy in Non-Muscle-Invasive Bladder Cancer.

Bacillus Calmette-Guérin (BCG) is the first-line therapy for high-grade non-muscle-invasive bladder cancer (NMIBC), yet many patients experience recurrence due to immune evasion. We identify HLA-E and NKG2A as mediators of adaptive resistance involving chronic activation of NK and T cells in BCG-unresponsive tumors. Prolonged IFN-γ exposure enhances HLA-E and PD-L1 expression on recurrent tumors, accompanied by the accumulation of NKG2A+ NK and CD8 T cells. HLA-Ehigh tumor cells preferentially cluster near CXCL12-rich stromal regions with dense effector cell presence, underscoring a spatially segregated tumor architecture. Although cytotoxic lymphocytes retain effector potential, their activity is restrained by HLA-E/NKG2A and PD-L1/PD-1 pathways located in their immediate neighborhood within the bladder tumor microenvironment. These data reveal a spatially organized immune escape program that limits anti-tumor immunity. Our findings support dually targeting NKG2A and PD-L1 checkpoint blockade as a rational, bladder-sparing strategy for patients with BCG-unresponsive NMIBC.

BCG-unresponsive↗
PubMed1995

Immunosuppressive drugs prevent a rapid dephosphorylation of transcription factor NFAT1 in stimulated immune cells.

The immunosuppressive drugs cyclosporin A and FK506 interfere with the inducible transcription of cytokine genes in T cells and in other immune cells, in part by preventing the activation of NF-AT (nuclear factor of activated T cells). We show that transcription factor NFAT1 in T cells is rapidly dephosphorylated on stimulation, that dephosphorylation occurs before translocation of NFAT1 into the cell nucleus, and that dephosphorylation increases the affinity of NFAT1 for its specific sites in DNA. Cyclosporin A prevents the dephosphorylation and the nuclear translocation of NFAT1 in T cells, B cells, macrophages, and mast cells, delineating at least one mechanism that contributes to the profound immunosuppressive effects of this compound.

Animals↗
PubMed1995

Phosphorylation of the transcription factor NFATp inhibits its DNA binding activity in cyclosporin A-treated human B and T cells.

Cyclosporin A (CsA) exerts its immunosuppressive effect by inhibiting the activity of nuclear factor of activated T cells (NFAT), thus preventing transcriptional induction of several cytokine genes. This effect is thought to be largely mediated through inactivation of the phosphatase calcineurin, which in turn inhibits translocation of an NFAT component to the nucleus. Here we report that CsA treatment of Raji B and Jurkat T cell lines yields a phosphorylated form of NFATp that is inhibited in DNA-binding and in its ability to form an NFAT complex with Fos and Jun. Immunoblot analyses and metabolic labeling with [32P]orthophosphate show that CsA alters NFATp migration on SDS-polyacrylamide gel electrophoresis by increasing its phosphorylation level without affecting subcellular distribution. Dephosphorylation by in vitro treatment with calcineurin or alkaline phosphatase restores NFATp DNA binding activity and its ability to reconstitute an NFAT complex with Fos and Jun proteins. These data point to a new mechanism for CsA-sensitive regulation of NFATp in which dephosphorylation is critical for DNA binding.

Alkaline Phosphatase↗
PubMed1995

Human immunodeficiency virus-type 1 replication can be increased in peripheral blood of seropositive patients after influenza vaccination.

Despite considerable evidence that cell activation enhances human immunodeficiency virus-type 1 (HIV-1) replication in vitro, there is very little data on the role of immune activation on in vivo HIV-1 replication. In this study, we examined the effect of influenza vaccination on HIV-1 replication in the peripheral blood of 20 study subjects, and in 14 control subjects who did not receive influenza vaccination. Blood was obtained from each subject on three occasions during the month before vaccination and again on three occasions during the following month. Over the study period, there was little change in levels of proviral DNA in peripheral blood mononuclear cells (PBMCs). However, peak PBMC viral RNA levels after influenza vaccination were significantly increased over the mean of prevaccination values. This change was not observed to the same extent in unvaccinated controls. Therefore, this is the first report showing that HIV-1 replication can increase in temporal association with influenza vaccination. Our results suggest that continued immunologic (antigenic) stimulation may result in increased virus load in vivo. To address the appropriateness of influenza vaccination in HIV-infected patients, expanded studies will be required to examine specific and generalized immune responses to vaccination, and differences in patient response based on disease stage.

Adult↗
PubMed1995

Cloning and functional expression of a rat kidney extracellular calcium/polyvalent cation-sensing receptor.

The maintenance of a stable extracellular concentration of ionized calcium depends on the integrated function of a number of specialized cells (e.g., parathyroid and certain kidney epithelial cells). We recently identified another G protein-coupled receptor (BoPCaRI) from bovine parathyroid that responds to changes in extracellular Ca2+ within the millimolar range and provides a key mechanism for regulating the secretion of parathyroid hormone. Using an homology-based strategy, we now report the isolation of a cDNA encoding an extracellular Ca2+/polyvalent cation-sensing receptor (RaKCaR) from rat kidney. The predicted RaKCaR protein shares 92% identity with BoPCaR1 receptor and features a seven membrane-spanning domain, characteristic of the G protein-coupled receptors, which is preceded by a large hydrophilic extracellular NH2 terminus believed to be involved in cation binding. RaKCaR cRNA-injected Xenopus oocytes responded to extracellular Ca2+, Mg2+, Gd3+, and neomycin with characteristic activation of inositol phospholipid-dependent, intracellular Ca(2+)-induced Cl- currents. In rat kidney, Northern analysis revealed RaKCaR transcripts of 4 and 7 kb, and in situ hybridization showed localization primarily in outer medulla and cortical medullary rays. Our results provide important insights into the molecular structure of an extracellular Ca2+/polyvalent cation-sensing receptor in rat kidney and provide another basis on which to understand the role of extracellular divalent cations in regulating kidney function in mineral metabolism.

Amino Acid Sequence↗
PubMed1995

Neurotoxicity of acute glutamate transport blockade depends on coactivation of both NMDA and AMPA/Kainate receptors in organotypic hippocampal cultures.

Excessive activation of glutamate receptors is neurotoxic, contributing to brain injury caused by cerebral ischemia. The pharmacology of glutamate neurotoxicity is difficult to study in animals because it is efficiently cleared from the extracellular space by a family of glutamate transporters. We have investigated the receptor specificity of endogenous glutamate's toxic effects in organotypic cultures of the hippocampus by acute blockade of these transporters. The organotypic cultures used in these transporters. The organotypic cultures used in these experiments preserve the intrinsic connections and regional differentiation of the hippocampus in long term culture and may more closely reproduce the pharmacology of the mature brain region. Membrane injury was measured with digital fluorescence imaging of the vital dye, propidium iodide, 24 h after a 30-min exposure to glutamate receptor agonists or to antagonists of glutamate transport. Confirming our previous results, bath-applied, exogenous glutamate caused dose-dependent neuronal injury. Glutamate was less potent than the selective agonists NMDA, AMPA, and quisqualate. Blockade of glutamate transport with the selective antagonists threo-hydroxy-aspartate and pyrrolidine-dicarboxylic acid also caused dose-dependent neuronal injury. Endogenous or exogenous glutamate toxicity was caused by a coactivation of both NMDA and AMPA/kainate receptors; blockade of either was sufficient to substantially prevent neuronal injury. Protective effects of combined application of antagonists were generally less than additive. We conclude that AMPA/kainate receptors play a more prominent role in glutamate neurotoxicity in organotypic cultures than in dissociated cortical or hippocampal cultures, acting together with NMDA receptors to cause neuronal injury.

ATP-Binding Cassette Transporters↗
PubMed1995

Navigator: tools for informal structure-activity relationship discovery.

Navigator is a molecular database visualization system, designed to support exploratory data analysis and informal structure-activity relationship studies. In addition to the operations commonly found in chemical database systems, it provides new tools that facilitate substituent analysis and help elucidate the relationships among similar molecules and between related assays. Navigator's capabilities include two ways of displaying the relationships between analogs, mouse-sensitive charts of sets of molecules, mouse-sensitive plots of assay relationships, and access to a system for three-dimensional quantitative structure-activity relationship discovery. Navigator's mouse-based user interface provides a one-object/one-window paradigm that makes data manipulation easy even for inexperienced users. Navigator runs on Silicon Graphics workstations.

Computer Graphics↗
PubMed1995

Detection of water proximity to tryptophan residues in proteins by single photon radioluminescence.

We recently developed a single photon radioluminescence (SPR) technique to measure submicroscopic distances in biological samples [Bicknese et al., and Shahrokh et al., Biophys. J., 63 (1992) 1256-1279]. SPR arises from the excitation of a fluorophore by the energy deposited from a slowing beta decay electron. The purpose of this study was to detect 3H2O molecules near tryptophan residues in proteins by tryptophan SPR. To detect small SPR signals, a sample compartment with reflective ellipsoidal optics was constructed, and amplified signals from a cooled photomultiplier were resolved by pulse-height analysis. A Monte Carlo calculation was carried out to quantify the relationship between SPR signal and 3H2O-tryptophan proximity. Measurements of tryptophan SPR were made on aqueous tryptophan; dissolved melittin (containing a single tryptophan); native and denatured aldolase; dissolved aldolase, monellin, and human serum albumin; and the integral membrane proteins CHIP28 (containing a putative aqueous pore) and MIP26 using 3H2O or the aqueous-phase probe 3H-3-O-methylglucose (OMG). After subtraction of a Bremsstrahlung background signal, the SPR signal from aqueous tryptophan (cps.microCi-1 mumol-1 +/- SE) was 8.6 +/- 0.2 with 3H2O and 7.8 +/- 0.3 with 3HOMG (n = 8). With 3H2O as donor, the SPR signal (cps.microCi-1 mumol-1) was 9.0 +/- 0.3 for monomeric melittin in low salt (trytophan exposed) and 4.6 +/- 0.8 (n = 9) for tetrameric melittin in high salt (tryptophans buried away from aqueous solution). The ratio of SPR signal obtained for aldolase under denaturing conditions of 8 M urea (fluorophores exposed) versus non-denaturing buffer (fluorophores buried) was 1.53 +/- 0.07 (n = 6). Ratios of SPR signals normalized to fluorescence intensities for monellin, aldolase, and human serum albumin, relative to that for d-tryptophan, were 1.42, 1.09, and 1.04, indicating that the cross-section for excitation of fluorophores in proteins is greater than that for tryptophan in solution. For the CHIP28 and MIP26 proteins in membranes, the ratio of SPR signal obtained with 3H2O versus 3HOMG was 1.35 +/- 0.13 (CHIP28, n = 5) and 0.99 +/- 0.02 (MIP26). These data are consistent with the existence of an aqueous channel through CHIP28 that excludes small solutes. We conclude that tryptophan radioluminescence in proteins is measurable and provides unique information about the presence of local aqueous compartments.

Evaluation Studies as Topic↗
PubMed1995

Localization of the epitope in methamphetamine and its antibody use for the detection of methamphetamine and benzphetamine by polarization fluoroimmunoassay.

An antibody was prepared, using a four carbon-bridged methamphetamine molecule as an immunogen in order to develop a polarization fluoroimmunoassay for urine screening of methamphetamine and benzphetamine. Also, its binding characteristics were investigated to locate epitope sites of methamphetamine. The study showed that the antibody was highly capable of eliciting a polarization fluoroimmunoassay response. However, the detection limit was much greater for benzphetamine (0.05 ppm) than for methamphetamine (0.2 ppm) and weakly antibody binding was found with methamphetamine. This difference in sensitivity may reflect the similarity of benzphetamine to the immunogen used to produce the antibody. Both benzphetamine and the immunogen have a tertiary amine attached to a carbon bridges whereas methamphetamine has only a secondary amine and amphetamine has a primary amine group. The difference of cross-reactivity data between phenylethylamine drugs and beta-hydroxyl phenylethylamine drugs indicates that the beta-carbon position have a major influence on the antibody interaction. Thus, the substitution of hydroxyl group on beta-carbon resulted in virtually no antibody affinity, even if a tertiary amine or secondary amine group was present in the molecule. This suggests that the beta-carbon chain plays a primary role as the epitope site with cooperative binding site of tertiary amine or secondary amine in alpha-carbon position. A hydroxyl group at the beta-carbon position plays an important inhibitory role to the antibody binding.

Antibody Affinity↗
PubMed1995

Role of Ca2+ and calmodulin in ehrlichial infection in macrophages.

Replication of Ehrlichia risticii was inhibited in P388D1 cells and murine peritoneal macrophages when a calmodulin antagonist (W-7, chlorpromazine, or trifluoperazine); a Ca2+ channel blocker (verapamil, diltiazem, nifedipine, or flunarizine); an extracellular Ca2+ chelator, EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid]; an inhibitor of intracellular Ca2+ mobilization, TMB-8; or Ca2+ ionophore A23187 was added after internalization of the organism at 3 h postincubation. When intracellular ehrlichiae at their logarithmic stage of growth were treated with these reagents, not only was further proliferation prevented but also there was significant reduction in numbers of intracellular ehrlichiae. These reagents prevented spreading of E. risticii from P388D1 cells to THP-1 cells. None of these reagents prevented binding of [35S]methionine-labeled E. risticii to P388D1 cells, but all of these reagents prevented internalization of [35S]methionine-labeled E. risticii. Protein kinase C inhibitors, H-7 and staurosporin, had no effect. 14CO2 production from L-[14C]glutamine in Percoll-density-gradient-purified E. risticii was inhibited by A23187 but not by W-7 or verapamil, suggesting that Ca2+ but not calmodulin directly regulates ehrlichials glutamine oxidation. Pretreatment of E. risticii with W-7 or verapamil did not reduce its infectivity. These results indicate that calmodulin and Ca2+ are essential for ehrlichial internalization, replication, and spreading in macrophages but are not essential for binding.

Animals↗
PubMed1995

Src activity increases and Yes activity decreases during mitosis of human colon carcinoma cells.

Src and Yes protein-tyrosine kinase activities are elevated in malignant and premalignant tumors of the colon. To determine whether Src activity is elevated throughout the human colon carcinoma cell cycle as it is in polyomavirus middle T antigen- or F527 Src-transformed cells, and whether Yes activity, which is lower than that of Src in the carcinoma cells, is regulated differently, we measured their activities in cycling cells. We observed that the activities of both kinases were higher throughout all phases of the HT-29 colon carcinoma cell cycle than in corresponding phases of the fibroblast cycle. In addition, during mitosis of HT-29 cells, Src specific activity increased two- to threefold more, while Yes activity and abundance decreased threefold. The decreased steady-state protein levels of Yes during mitosis appeared to be due to both decreased synthesis and increased degradation of the protein. Inhibition of tyrosine but not serine/threonine phosphatases abolished the mitotic activation of Src. Mitotic Src was phosphorylated at novel serine and threonine sites and dephosphorylated at Tyr-527. Two cellular proteins (p160 and p180) were phosphorylated on tyrosine only during mitosis. Tyrosine phosphorylation of several other proteins decreased during mitosis. Thus, Src in HT-29 colon carcinoma cells, similar to Src complexed to polyomavirus middle T antigen or activated by mutation at Tyr-527, is highly active in all phases of the cell cycle. Moreover, Src activity further increases during mitosis, whereas Yes activity and abundance decrease. Thus, Src and Yes appear to be regulated differently during mitosis of HT-29 colon carcinoma cells.

Aphidicolin↗
PubMed1995

Muscarinic M3 receptor-mediated release of gastrin from canine antral G cells in primary culture.

The functional role of the cholinergic nervous system in regulating gastrin release was investigated using enriched canine antral G cells. Gastrin content was 30.1 +/- 2.9 pmol per well and basal gastrin release was 900 +/- 27 fmol per well (n = 45). Carbachol (10(-8) to 10(-5) M) dose-dependently stimulated gastrin release with a maximal stimulatory response achieved at a concentration of 10(-5) M (330% over basal). To characterize the muscarinic receptor which mediates gastrin release from antral G cells, we examined the effect of three muscarinic receptor antagonists on carbachol-stimulated gastrin release; atropine (nonselective muscarinic receptor antagonist), pirenzepine (M1 muscarinic receptor antagonist) and 4-DAMP (M3 muscarinic receptor antagonist). Atropine (10(-9) to 10(-6) M), pirenzepine (10(-8) to 10(-5) M) and 4-DAMP (10(-9) to 10(-6) M) had no effect on the basal gastrin release. However, carbachol (10(-5) M)-stimulated gastrin release was effectively inhibited by atropine and 4-DAMP with Ki values of 0.48 and 0.66 nM, respectively. Pirenzepine at a high concentration (10(-5) M) also inhibited carbachol-stimulated gastrin release with a Ki value of 46.3 nM. These results suggest that the cholinergic nervous system directly stimulates gastrin release via M3 muscarinic receptors located on antral G cells.

Animals↗
PubMed1995

Influence of Helicobacter pylori colonization on histological grading of chronic gastritis in Korean patients with peptic ulcer.

OBJECTIVES: We conducted an analysis of correlation between histological grading of chronic gastritis and the presence of H. pylori infection to investigate if H. pylori influences histological severity of chronic gastritis in Korean patients with peptic ulcers. METHODS: Gastroscopic antral biopsy specimens and peripheral venous blood were taken from 80 patients with gastric or duodenal ulcers. H. pylori was identified microscopically in sections with Giemsa staining and quantitative grading of cultured H. pylori was reported on a scale 0 to 3. The histopathological features of biopsy specimens were reported according to the Sydney classification of chronic gastritis. Serum gastrin and pepsinogen concentrations were measured by radioimmunoassay. RESULTS: H. pylori was identified in 62.5%(20 of 32 GU, 30 of 48 DU) of the study group. Gastric clonization rate of H. pylori did not increased with age. Forty of 50 biopsy specimens with H. pylori and also 23 of 30 biopsy specimens without H. pylori showed active chronic gastritis. There was no significant correlation overall between the presence of H. pylori and histological grading of chronic gastritis, including activity, and also no association was found between the quantitative grading of H. pylori and the histological grading of chronic gastritis. With and without H. pylori, a mean of serum gastrin concentration(79.4 +/- 4.30 pg/ml and 80.2 +/- 31.9 pg/ml)showed no significant difference, but a mean of serum pepsinogen concentration(87.7 +/- 41.6 ng/ml and 119 +/- 34.4 ng/ml) showed significant difference between the populations with and without H. pylori(p = 0.001). CONCLUSIONS: The influence of H. pylori on histological grading of chronic gastritis in Korean is less than that in prior studies of Western countries, and further investigation of pathogenesis of H. pylori in chronic gastritis and peptic ulceration is necessary.

Adolescent↗
PubMed1994

Stopped lower buffer flow electrofractionation: simple electrofractionation for complex protein mixture.

The standard electrofractionation technique simulated the liquid chromatography to create a continuous elution system. Though this continuous lower buffer flow electrofractionation system served as an excellent model for preparative electrophoresis, the restricted current flow caused by electric resistance arising from the column holder prevented the application to the purification of complex protein mixtures. To overcome the electric current problem, the stopped lower buffer flow electrofractionation (SFE) system is designed to work without using a column holder and use prestained markers as the detection tool of protein position during the electrofractionation process. Through this improvement, the SFE system widens the availability of electrofractionation to the purification of complex and low-concentration protein mixtures. In this report, the efficiency of this technique is shown through the partial purification of a 32P-labeled protein in the rat liver microsome.

Animals↗
PubMed1994

Beta 3-adrenoceptor agonist-induced down-regulation of Gs alpha and functional desensitization in a Chinese hamster ovary cell line expressing a beta 3-adrenoceptor refractory to down-regulation.

Chinese hamster ovary (CHO) cells transfected to express human beta 2- or beta 3-adrenoceptors (beta 2-CHO and beta 3-CHO cells) were exposed to the beta-adrenoceptor agonist isoprenaline at various concentrations and for differing times. Sustained exposure of the beta 2-CHO but not beta 3-CHO cells to isoprenaline resulted in a time- and concentration-dependent down-regulation of the receptor as measured by a reduction in specific binding of [125I]cyanopindolol. Such maintained exposure of cells expressing either receptor to the agonist produced a marked down-regulation of immunologically detectable levels of the alpha subunit of the stimulatory guanine-nucleotide-binding protein Gs. This effect was specific for Gs because levels of both G12 alpha and Gq alpha/G11 alpha were unaltered by isoprenaline treatment of both beta 2-CHO and beta 3-CHO cells. The effect of isoprenaline on Gs alpha down-regulation was some 30-fold more potent in the beta 2-CHO than in the beta 3-CHO cells. Time courses of isoprenaline-induced down-regulation of Gs alpha were not different, however, in the two cell lines. Isoprenaline treatment of the beta 3-CHO cells produced a desensitization of agonist-mediated regulation of adenylyl cyclase, manifested by a 4-fold reduction in the potency and a 30% reduction in maximal effect of the agonist, whereas desensitization of the beta 2-CHO cells was considerably greater (25-fold reduction in potency and 70% reduction in maximal effect). These results demonstrate that agonist-induced down-regulation of the G-protein which interacts with a receptor can be produced by both beta 2- and beta 3-adrenoceptors. Despite apparent concurrence of down-regulation of receptors and G-proteins in other systems [e.g. Adie, Mullaney, McKenzie and Milligan (1992) Biochem. J. 285, 529-536], agonist-induced receptor down-regulation does not appear to be a prerequisite for down-regulation of the G-protein. Furthermore, the results suggest that agonist-induced down-regulation of a G-protein may be sufficient, in the absence of receptor regulation, to induce some agonist desensitization of effector function.

Amino Acid Sequence↗
PubMed1994

Regulation of endocytic trafficking and acidification are independent of the cystic fibrosis transmembrane regulator.

Cystic fibrosis is associated with mutations of the cystic fibrosis transmembrane regulator (CFTR), a cAMP-regulated plasma membrane Cl- channel. Mutations in the CFTR have been reported to not only impair Cl-transport at the plasma membrane but also inhibit organelle acidification and disrupt cAMP-regulated plasma membrane recycling. Comparisons of cultured pancreatic adenocarcinoma cells expressing the delta 508 mutant CFTR (CFPAC-1 cells) with genetically matched CFPAC-1 cells transfected with the wild-type CFTR demonstrate that expression of wild-type CFTR restores cAMP-mediated plasma membrane Cl- transport, but has no effect on pH regulation of endosomes labeled with either transferrin or wheat germ agglutinin. Endosome pH was, in all cases, similar in the two cell lines and unaffected by treatment with the cAMP agonist forskolin. Forskolin treatment had no effect on transferrin internalization, but increased recycling by 30-40% in both cell lines. The kinetics of wheat germ agglutinin recycling were negligibly affected by forskolin in either cell line. These results demonstrate that endocytic acidification and cAMP-mediated endocytic protein redistribution are similar in genetically matched CFPAC-1 cells which differ only in the expression of mutant or wild-type CFTR.

Adenocarcinoma↗
PubMed1994

Regulation of amelogenin gene expression during tooth development.

The amelogenins are the predominant matrix proteins in developing enamel and are crucial for proper enamel mineralization. Transgenic mice were constructed in order to identify the segment of the amelogenin gene required for specific expression in enamel organ cells. A 3.5 kb fragment of the bovine X-chromosomal amelogenin gene that includes a TATA box, the transcription initiation site, and 32 bp of exon 1 was linked to the beta galactosidase gene and injected into fertilized mouse eggs. Newborn transgene positive mice expressed beta galactosidase activity in developing teeth treated with the chromogenic substrate Xgal. Foci of ameloblasts were positive in newborn mice; stain intensity and number of positive ameloblasts increased in 1-day and 2-day postnatal mice. Some of the adjacent stratum intermedium cells also were positive in the later stages. Targeting of the transgene to the enamel organ was specific; the only other cells observed to be positive were macrophages, which have endogenous beta galactosidase activity.

Ameloblasts↗