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S Chung

Publications and source records attributed to S Chung.

At least 127 records · Page 7Linked to original sources
PubMed1995

Regulation of T-cell antigen receptor (TCR) alpha-chain expression by TCR beta-chain transcripts.

The TCR is an alpha beta heterodimer, a part of the multimeric structure through which physiological T-cell activation occurs. The expression of TCR alpha chain is greatly diminished in a beta-chain-deficient mutant Jurkat cell line (J.RT3-T3.5). The relationship between the expression of the TCR alpha and beta chains has been examined by stable transfection of a series of TCR beta-chain mutant constructs into this mutant cell line. The level of alpha-chain transcript was dramatically upregulated by the expression of the beta chain and specifically by a transcript of the beta-chain variable region alone, including a transcript in which the ATG start codon was mutated. The downregulation of the endogenous alpha-chain transcripts in mutants cells lacking complete beta-chain transcripts occurred primarily at the posttranscriptional level. This evidence for a regulatory function of the TCR beta-chain gene represents an unusual regulatory pathway in which the transcript of one gene is required for the optimal expression of another gene.

Amino Acid Sequence↗
PubMed1995

Glutathione S-transferase and S-crystallins of cephalopods: evolution from active enzyme to lens-refractive proteins.

Our previous studies have shown that the S-crystallins of cephalopod (Ommastrephes sloani pacificus) eye lenses comprise a family of at least ten members which are evolutionarily related to glutathione S-transferase (GST, EC 2.5.1.18). Here we show by cDNA cloning that there are at least 24 different S-crystallins that are 46-99% identical to each other by amino acid sequence in the squid Loligo opalescens. In each species, all but one S-crystallin (SL11 in O. pacificus and Lops4 in L. opalescens) examined has an inserted central peptide of variable length and sequence. cDNA expression studies conducted in Escherichia coli showed that squid GST (which is expressed little in the lens) has very high enzymatic activity using 1-chloro-2, 4-dinitrobenzene (CDNB) as a substrate; by contrast, SL20-1 of O. pacificus and Lops12 of L. opalescens (which are encoded by abundant lens mRNAs) have no GST activity. Interestingly, SL11 and Lops4 have some enzymatic activity with the CDNB substrate. Site-specific mutations at Y7 or W38, both residues essential for activity of vertebrate GSTs, or insertion of the central peptide present in the inactive SL20-1, reduced the specific activity of squid GST by 30- to 100-fold. These data indicate that the S-crystallins consist of a family of enzymatically inactive proteins (when using CDNB as a substrate) which is considerably larger than previously believed and that GST activity was lost by gradual drift in sequence as well as by insertion of an extra peptide by exon shuffling. The results are also consistent with the idea that SL11 and Lops4 are orthologous crystallins representing the first descendants of the ancestral GST gene in the pathway which gave rise to the extensive S-crystallin family of lens proteins.

Amino Acid Sequence↗
PubMed1995

Manipulation of skin graft rejection in alloimmune mice by anti-VCAM-1:VLA-4 but not anti-ICAM-1:LFA-1 monoclonal antibodies.

C3H mice were immunized by repeated skin grafting with B10.BR tail skin. Ten days after the last immunization mice received 100 micrograms (intravenously) of a variety of different monoclonal antibodies (mAbs: anti-ICAM-1, -LFA-1, -VCAM-1, -VLA-4), alone or in combination, followed by further B10.BR skin grafts. Control animals received injections of saline only. Skin graft survival was monitored daily in all groups. Further injections of antibody were given every second day until graft rejection occurred. In separate studies lymphoid cells were harvested from various tissues of the grafted mice at 6 and 20 days post grafting. Aliquots of each sample were analysed by polymerase chain reaction for mRNA for different cytokines (interleukins IL-2, IL-4, IL-10 and IFN gamma (gamma-interferon)) believed to be important in the regulation of graft rejection. In addition, lymphoid cells were restimulated in vitro with irradiated B10.BR or third-party stimulator cells in the presence or absence of monolayers of C3H-derived endothelial cells (EC), in an attempt to mimic the in vivo environment of the interactions of cells engaged in alloreactivity in these mice. Only anti-VCAM-1 caused significant prolongation of graft survival in immune mice, while in contrast only the combination of anti-ICAM-1 and anti-LFA-1 produced enhanced survival in naive animals. In each case increased survival was associated with decreased activation of Th1 cells (diminished IL-2, IFN gamma) and increased activation of Th2 cells (increased IL-4, IL-10).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Manipulation of xenogeneic skin and/or renal graft survival in the rat-mouse concordant combination by portal vein pretransplant transfusion.

We have examined whether portal venous pretransplant transfusion, which has been shown to produce prolongation of rodent vascularized (small intestine, kidney) and nonvascularized (skin) allografts, in the absence of other nonspecific immunosuppression, can produce similar graft prolongation in animals receiving vascularized or nonvascularized xeno- (not allo-) grafts. Rat kidney or skin grafts were transplanted into mice after portal venous pretreatment with rat or mouse spleen cells. Animals in some groups received additional immunosuppressive regimens including drug therapy (methotrexate, cyclosporin A) or monoclonal antibody treatment (anti-CD4, anti-CD8). Animal survival and serum creatinine was followed daily, and lymphoproliferation, cytokine production (including cytokine mRNA in grafted mice) and anti-xenograft antibody production was measured at distinct time points postgrafting. Both portal venous pretransplant transfusion and anti-CD4 monoclonal antibody treatment led to increased graft survival. However, unlike the rodent allograft model, graft survival in these animals was not simply explained by altered Th1/Th2 ratios. Other mechanism(s), possibly including xenoantibody production, are likely of importance in the regulation of xenograft rejection.

Animals↗
PubMed1995

Pattern of disease after murine hepatitis virus strain 3 infection correlates with macrophage activation and not viral replication.

Murine hepatitis virus strain (MHV-3) produces a strain-dependent pattern of disease which has been used as a model for fulminant viral hepatitis. This study was undertaken to examine whether there was a correlation between macrophage activation and susceptibility or resistance to MHV-3 infection. Peritoneal macrophages were isolated from resistant A/J and susceptible BALB/cJ mice and, following stimulation with MHV-3 or lipopolysaccharide (LPS), analyzed for transcription of mRNA and production of interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-alpha), transforming growth factor beta (TGF-beta), mouse fibrinogen-like protein (musfiblp), tissue factor (TF), leukotriene B4, and prostaglandin E2 (PGE2). Macrophages from BALB/cJ mice produced greater amounts of IL-1, TNF-alpha, TGF-beta, leukotriene B4, and musfiblp following MHV-3 infection than macrophages from resistant A/J mice, whereas in response to LPS, equivalent amounts of IL-1, TNF-alpha, TGF-beta, and TF were produced by macrophages from both strains of mice. Levels of mRNA of IL-1, TNF-alpha, and musfiblp were greater and more persistent in BALB/cJ than in A/J macrophages, whereas the levels and kinetics of IL-1, TNF-alpha, and TF mRNA following LPS stimulation were identical in macrophages from both strains of mice. Levels of production of PGE2 by MHV-3-stimulated macrophages from resistant and susceptible mice were equivalent; however, the time course for induction of PGE2, differed, but the total quantity of PGE2 produced was insufficient to inhibit induction of musfiblp, a procoagulant known to correlate with development of fulminant hepatic necrosis in susceptible mice. These results demonstrate marked differences in production of inflammatory mediators to MHV-3 infection in macrophages from resistant A/J and susceptible BALB/cJ mice, which may explain the marked hepatic necrosis and fibrin deposition and account for the lethality of MHV-3 in susceptible mice.

Animals↗
PubMed1995

The p53-mediated G1 checkpoint is retained in tumorigenic rat embryo fibroblast clones transformed by the human papillomavirus type 16 E7 gene and EJ-ras.

Rat embryo fibroblast clones transformed with the human papillomavirus type 16 E7 gene and the H-ras oncogene (ER clones) fall into two groups on the basis of endogenous p53 genotype, wild type or mutant. We have compared these clones with the aim of indentifying physiological differences that could be attributed to p53 protein function. We show that all ER clones, regardless of p53 gene status, are tumorigenic and metastatic in severe combined immunodeficiency mice. We demonstrate that only the wild-type p53 protein expressed in ER clones is functional on the basis of its site-specific double-stranded DNA-binding activity and its ability to confer a G1 delay on cells following treatment with ionizing radiation. These data indicate that disruption of the p53 growth-regulatory pathway is not a prerequisite for the malignant conversion of rat embryo fibroblasts expressing the E7 gene and mutant ras. Differences in phenotype that were correlated with loss of p53 protein function included the following: serum-independent growth of ER clones in culture, decreased tumor doubling time in vivo, and increased radioresistance. In addition, we demonstrate the p53-dependent G1 checkpoint alone does not determine radiosensitivity.

Animals↗
PubMed1995

Modulation of the inactivation of voltage-dependent potassium channels by cAMP.

Modulation of voltage-dependent potassium currents can alter the shape and timing of action potentials, thereby altering neurotransmitter release. To examine the effect of a cAMP analog on potassium currents in metabolically intact cells, perforated-patch and cell-attached patch recordings were carried out using the GH4C1 pituitary cell line. A major component of voltage-dependent potassium current in these cells inactivates slowly, with a time constant of several seconds. Application of dibutyryl cAMP decreased this current at voltages positive to -10 mV and increased the rate of inactivation by approximately twofold. Single channel recordings revealed two channel types whose voltage dependence and kinetics of inactivation match those of the macroscopic current. One of these, the smaller conductance (7.5 pS) channel, was sensitive to the cAMP analog, which decreased the latency of the channel to enter a long-lasting inactivated state. Ensemble averages of the activity of this channel showed that, consistent with its effect on the macroscopic current, dibutyryl cAMP increased its rate of inactivation. Somatostatin, an agent that is known to activate a serine/threonine phosphatase in these cells, completely reversed the effect of dibutyryl cAMP on the channel, while the cyclic GMP analog, dibutyryl cyclic GMP was without effect. In contrast, the rate of inactivation of the larger conductance (approximately 19 pS) channel was not accelerated by dibutyryl cAMP. These studies indicate that different channel subtypes expressed in a single cell respond differently to elevations of cAMP, and suggest that the overall response of potassium currents to second messengers may be determined by the ratio of different channel subtypes.

Animals↗
PubMed1995

Endoscopic sphincterotomy-induced hemorrhage: a study of risk factors and the role of epinephrine injection.

BACKGROUND: We studied the incidence and relative risk factors for postsphincterotomy bleeding and the efficacy of epinephrine injection in hemostasis. METHODS: We retrospectively analyzed the incidence of postsphincterotomy bleeding in 983 consecutive patients with sphincterotomy for common duct stones and risk factors for such bleeding, i.e., presence of coagulopathy, stone impaction, periampullary diverticulum, extension of previous sphincterotomy, and use of needle knife precut sphincterotomy in sphincterotomy-induced bleeding. Epinephrine irrigation was performed for mild bleeding, and injection with 1:10,000 epinephrine was performed to control more severe bleeding. RESULTS: 119 patients (12.1%) developed postsphincterotomy bleeding; 114 patients had immediate bleeding and 5 had delayed hemorrhage. Stone impaction at the papilla, periampullary diverticulum, and extension of a previous sphincterotomy were independent variables that increased the risk of bleeding. Forty-six percent of 119 patients with mild bleeding responded to epinephrine irrigation. The remaining required injection therapy with 1:10,000 epinephrine. Initial hemostasis was achieved in all. Rebleeding occurred in 5 patients but all responded to conservative management. None required emergency surgery and there was no mortality related to uncontrolled hemorrhage. CONCLUSION: Epinephrine injection is a safe treatment for sphincterotomy-induced bleeding.

Adult↗
PubMed1995

[Choristoma of the gastric mucosa: report of a case].

Choristomas are tumor like masses consisting of tissues that are histologically normals but in abnormal location. These are rare in oral cavity and occur generally in tongue. There are seven categories of choristomas on the basis of types of tissues recognized. The presenting case in a gastric mucosal choristoma type, and the treatment was surgical excision. No recurrence of the mass was revealed. Special care should be taken with lingual thyroïd choristoma, because 86% of the cases is the only functional thyroide tissue in the body.

Child↗
PubMed1994

Functional three-domain single-chain T-cell receptors.

T-cell receptors (TCRs) are membrane anchored heterodimers structurally related to antibody molecules. Single-chain antibodies can be engineered by linking the two variable domains, which fold properly by themselves. However, proper assembly of the variable domains of a human TCR (V alpha and V beta) that recognize the HLA-DR2b/myelin basic protein-(85-99) peptide complex was critically dependent on the addition of a third domain, the constant region of the TCR beta chain (C beta), to the single-chain construct. Single-chain molecules with the three-domain design, but not those with the two-domain design, expressed in a eukaryotic cell as chimeric molecules linked either to glycosyl phosphatidylinositol or to the transmembrane/cytoplasmic domains of the CD3 zeta chain were recognized by a conformation-sensitive monoclonal antibody. The chimeric three-domain single-chain TCR linked to CD3 zeta chain signaled in response to both the specific HLA-DR/peptide and the HLA-DR/superantigen staphylococcal enterotoxin B complexes. Thus, by using this three-domain design, functional single-chain TCR molecules were expressed with high efficiency. The lipid-linked single-chain TCR was solubilized by enzymatic cleavage and purified by affinity chromatography. The apparent requirement of the constant domain for cooperative folding of the two TCR variable domains may reflect significant structural differences between TCR and antibody molecules.

Amino Acid Sequence↗
PubMed1994

Prolongation of rat small bowel or renal allograft survival by pretransplant transfusion and/or by varying the route of allograft venous drainage.

Lewis rats show prolongation of survival of LBNF1 renal allografts when those grafts are drained by the portal vein, or if recipients are treated with LBNF1 bone marrow cells infused via the portal venous route peritransplantation. The longest survival was seen in animals in which both portal venous transfusion and graft drainage by the portal route were performed. When the same manipulations were performed for Lewis rats receiving heterotopic small bowel transplants, only in the "combined treatment" group was there significantly enhanced graft or animal survival relative to control rats. In separate studies, we examined the mixed leukocyte proliferation response in vitro, and IL-2 production, from rats treated as above and receiving renal or small bowel transplants. In both organ transplant models, there was a good correlation between enhanced graft survival in vivo and decreased in vitro responses to specific allostimulation.

Animals↗
PubMed1994

Binding of soluble natural ligands to a soluble human T-cell receptor fragment produced in Escherichia coli.

An Escherichia coli expression system has been developed to produce milligram quantities of the variable domains of a human T-cell receptor from a cytotoxic T cell that recognizes the HLA-A2-influenza matrix peptide complex as a single polypeptide chain. The recombinant protein was purified by metal-chelate chromatography and then refolded in a redox buffer system. The refolded protein was shown to directly bind both Staphylococcus aureus enterotoxin B and the major histocompatibility complex protein-peptide complex using a BIAcore biosensor. Thus this preparation of a single-chain, variable-domain, T-cell receptor fragment can bind both of its natural ligands and some of it is therefore a functional fragment of the receptor molecule.

Amino Acid Sequence↗
PubMed1994

The human sorbitol dehydrogenase gene: cDNA cloning, sequence determination, and mapping by fluorescence in situ hybridization.

The cDNA for human sorbitol dehydrogenase (SORD) has been cloned and sequenced. It translates into a peptide of 356 amino acid residues, one more than the sequence previously reported from peptide analysis. An extra alanine was found at the acetyl-blocked N-terminal, between positions 1 and 4. This matches the rat cDNA, which also has 356 amino acids, with an extra proline at position 3. Four other mis-matches were also observed, but these are all amino acid substitutions that occur outside proposed functionally important regions. Further work must be performed to determine whether these discrepancies represent polymorphic forms of the enzyme. The SORD gene was mapped by fluorescence in situ hybridization and found to occupy a single site on chromosome 15q15, indicating that it is a single-copy gene. This was confirmed by Southern blot hybridization. SORD is thought to be involved in the etiology of diabetic complications, and its deficiency has been linked to congenital cataracts. The cloned gene could be used as a probe to study the role of this enzyme in the pathogenesis of these diseases.

Amino Acid Sequence↗
PubMed1994

Nahm et al. reply.

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Journal Article↗
PubMed1994

Expression of HSP70 mRNA in the embryonic chicken lens: association with differentiation.

The heat shock protein, HSP70 is constitutively expressed in the embryonic chicken lens. The present study investigates the localization of HSP70 mRNA in the lens as a function of developmental age to determine whether the state of proliferation or differentiation of the cells is correlated with expression of this gene. Using reverse transcription and quantitative PCR for HSP70 mRNA in RNA samples derived from microdissected regions of the lens, we have found that the concentration of HSP70 mRNA is highest in the annular pad cells at 6 days of development, and in the annular pad and fiber cells at 14 and 19 days of development, suggesting that expression is associated with fiber cell formation. This association was confirmed by studies of HSP70 transcription and HSP70 mRNA levels in cultured explants of 6 day embryonic chicken lens epithelia differentiating in culture. Nuclear run-on transcription experiments indicated that transcription of HSP70 is elevated after 5 and 24 hr of differentiation in vitro. Other genes whose transcription was monitored, c-myc and delta-crystallin, showed distinct patterns of transcriptional regulation, indicating that the changes in HSP70 transcription are specific. RNA extracted from cultured explants at these same times showed increased levels of a 3.4 kb mRNA which hybridized at high stringency to a chicken HSP70 cDNA probe. These results demonstrate that HSP70 mRNA in the embryonic chicken lens is associated primarily with cells in the early stages of fiber formation, and that increased transcription of this gene is part of the differentiation process.

Animals↗
PubMed1994

Family characteristics and offspring growth in various countries. II. Stature of offsprings in various families in Japan and Korea.

The stature of 1219 offspring was examined in 578 families in Japan, and of 672 offspring in 265 families in Republic of Korea. Several traits of parents were investigated, on which using factor analysis four latent factors were extracted. In Japan they consisted of parent's age at child birth (F1), culture level and income (F2), family and apartment size (F3), and genetic factor (F4). The same factors were identified in Korea, but the first two in reverse order. The value of each factor was coded as one when below the median and as 2 when above the median. Using this code, 16 family types were distinguished ranging from 1111 to 2222. The stature of offspring was recalculated in age-independent T-scores. In Japan, family types "maximizing" the stature of offspring were 1122 for boys and 1222 for girls, whereas in Korea 1222 for both sexes, opposite were "minimizing". In the rich populations representing the civilization of the Far East, the factors promoting tall stature of offspring included the low culture-income factor and large family, thus the factors promoting short stature in poor Polish populations belonging to the Western civilization. It is not clear whether this could have been related to the economic status or to different civilization systems.

Adolescent↗