Biomedical subjects

S Jung

Publications and source records attributed to S Jung.

At least 109 records · Page 6Linked to original sources

PubMed1998

Primary B cells essentially lack constitutive NF-kappa B activity.

Based primarily on the analysis of B cell lines, mature B cells are considered distinct from non-B cells and immature B cells by having constitutive nuclear NF-kappaB activity. By their comparison to splenic non-B cells or activated B cells we show here that primary resting B cells lack cell-autonomous NF-kappaB activity. This finding indicates that the role of the transcription factor in B cells is similar to that in other cells, namely a common mediator of activation and stress signals. Whereas the absence of constitutive NF-kappaB activity in mature B cells does not argue against a role of NF-kappaB in B cell development, it does not support the notion of the essential function of the factor in maintaining the unique transcriptional activities in B cells.

Animals↗

PubMed1998

Co-stimulation-dependent activation of a JNK-kinase in T lymphocytes.

Previously we implicated c-Jun N-terminal kinase (JNK) as an element that is involved in signal integration during co-stimulation of T lymphocytes. This pathway has now been traced to an upper level, comprising MAPKK SEK1/MKK4/JNKK1 which, similarly to JNK, must receive input both from the TCR and CD28. A large portion of this input is probably integrated at the level of the Rho-family protein CDC42 which, here, activates SEK1 and JNK to the level reached by TCR and CD28 stimulation. We have identified another putative SEK/ JNK pathway regulator, PKCtheta, which in contrast to CDC42, activates SEK and JNK maximally only in conjunction with a calcium signal delivered through calcineurin. Signals originating at the TCR and CD28 may travel down the JNK pathway via PKCtheta, calcineurin, CDC42, MEKK1 and SEK1.

Animals↗

PubMed1998

Prediction of facial nerve displacement in extra large vestibular schwannoma.

The primary objective in the surgery of extra large vestibular schwannoma is the total removal of the tumour mass while preserving the facial nerve. Preservation of the facial nerve in extra large tumours is reported as being notoriously difficult in the majority of cases. This study was undertaken to evaluate the accuracy in predicting displacement of the facial nerve by preoperative radiological imaging studies in 19 cases of extra large vestibular schwannoma. The direction of displacement of the facial nerve was predicted with preoperative axial and coronal MRI scans and verified intraoperatively. We achieved total removal of tumours in 84.2%, facial nerve displacement was predicted in 80% and we accomplished anatomical preservation in 80%. Prediction of displacement was difficult in tumours with little or no intracanalicular components or with severe bony destruction of the internal acoustic meatus. The preoperative prediction of facial nerve displacement in extra large tumours allows safe internal decompression of the tumour and careful dissection near the predicted area of the facial nerve during the operation. Consequently, a high rate of anatomical preservation of the facial nerve can be achieved.

Decompression, Surgical↗

PubMed1998

Characterization of glial filament-cytoskeletal interactions in human astrocytomas: an immuno-ultrastructural analysis.

The role that glial filaments play in cells and tumors of glial origin is not well understood. We therefore undertook the present study to determine the relationships between glial and vimentin intermediate filaments (IFs), actin microfilaments, and CD44, a cell surface glycoprotein important in cell migration and invasion, in human astrocytoma cells. Three astrocytoma cell lines, U343 MG-A (U343), U251 MG (U251), and antisense GFAP-transfected U251 (asU251) were studied using immunofluorescence confocal and immunoelectron microscopy. Furthermore, we studied the phenotypic behaviour of these astrocytoma cell lines by analyzing their migration through Matrigel in vitro. U343 astrocytoma cells had the highest expression levels of glial fibrillary acidic protein (GFAP), whereas asU251 had virtually no expression of GFAP. Parental U251 cells had intermediate expression levels of GFAP. The elimination of GFAP expression in as U251 cells was accompanied by a marked increase in vimentin, actin microfilaments and CD44 levels. Gold labeling density counts of cytoskeletal and cell surface elements demonstrated that the differences between GFAP, actin, CD44 and vimentin levels in the different astrocytoma cell lines were statistically significant (p < 0.05). Results from the in vitro invasion assay revealed that U343 cells demonstrated the least invasive potential, whereas asU251 astrocytoma cells demonstrated the most. Our results show that elimination of GFAP expression by antisense leads to marked alterations in cell morphology and phenotypic behaviour. These data imply that GFAP may be linked spatially and functionally to cytoskeletal elements which may be altered when this IF is deleted in astrocytomas.

Astrocytoma↗

PubMed1998

Sequential expression of transforming growth factor-beta1 by T-cells, macrophages, and microglia in rat spinal cord during autoimmune inflammation.

Transforming growth factor-beta1 (TGF-beta1) is crucially involved in regulating inflammatory events during experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. Despite accumulating evidence for local expression of TGF-beta1 in the inflamed nervous system, uncertainty remains regarding its cellular source. We have investigated the temporospatial distribution of TGF-beta1 gene expression in rat spinal cord during EAE. In actively induced EAE, in situ hybridization revealed strong expression of TGF-beta1 in meningeal and perivascular mononuclear infiltrates at onset of the disease, continued expression in perivascular infiltrates and scattered mononuclear cells at maximal disease severity, and expression in scattered parenchymal cells during recovery. Double labeling studies revealed subpopulations of infiltrating T-cells to be the major source of TGF-beta1 early in the disease, followed by macrophages at peak severity and microglial cells during the recovery phase of EAE. Astrocytes and neurons did not express TGF-beta1. Quantification of mRNA by Northern blot analysis revealed that cellular expression of TGF-beta1 by T-cells, macrophages, and microglia sums up to a long-lasting elevation of TGF-beta1 mRNA extending well into the recovery phase. Our data indicate cellular diversity and suggest functional diversity of TGF-beta1 gene expression during EAE. While TGF-beta1 expressed early in the disease by T-cells may contribute to inflammatory lesion development, microglial cells may potentially contribute to recovery by expressing immunosuppressive TGF-beta1 during remission.

Adoptive Transfer↗

PubMed1998

Tropoelastin and elastin degradation products promote proliferation of human astrocytoma cell lines.

Expression of tropoelastin, the precursor of insoluble elastin and a major component of elastic fibers, has not yet been demonstrated in astrocytomas nor has it been linked to their proliferation. Here we report that human astrocytoma cell lines (U87 MG, U251 MG, U343 MG-A, U373 MG, SF 126, SF188, SF 539), as well as surgical specimens of malignant human astrocytomas, express intracellular tropoelastin. The tropoelastin produced by astrocytoma cells is, however, susceptible to proteolytic trimming to the extent that it cannot be assembled into extracellular elastic fibers. Astrocytoma cells also express the cell surface 67-kDa elastin binding protein (EBP), which binds elastin degradation products, leading to the upregulation of cyclin A and cdk2 and increased incorporation of [3H]-thymidine. The elastin-dependent mitogenic response of astrocytoma cells is abolished by lactose and chondroitin sulfate, factors which cause shedding of this 67-kDa elastin receptor from the cell surface and by blocking anti-EBP antibody. We therefore suggest that, in astrocytomas, endogenous tropoelastin degradation products bind to EBP and generate signals leading to cell cycle progression in an autocrine or paracrine manner. This is the first report implicating elastin-derived peptides as possible mitogens in malignant astrocytomas.

Astrocytoma↗

PubMed1998

[Are glycosaminoglycans responsible for the therapeutic effect of mussel extract? A contribution to the current controversy].

For years the mechanism of action of mussel extract has been explained as due to the presence of glycosaminolgycans (GAG). In this study our aim was to determine the content and type of GAG in mussel extract using the revised more specific DMMB method. Relevant amount of classical GAG could not be detected either in pure mussel extract or in feed supplements containing mussel extract. On the basis of the results of our study and a comprehensive literature search we reach the conclusion that the effects induced by mussel extract can not be mediated by GAG.

Animals↗

PubMed1998

K+ currents of encephalitogenic memory T cells decrease with encephalitogenicity while interleukin-2 (IL-2) receptor expression remains stable during IL-2 dependent cell expansion.

Previous studies revealed a linkage between increased K+ current and lymphocyte activation upon non-specific stimulation with mitogenic lectins and antibodies. So far no information is available about the behaviour of K+ currents in specifically autoantigen-stimulated lymphocytes. Therefore, we have investigated K+ currents in encephalitogenic T line cells, specifically stimulated with myelin basic protein, using the whole-cell patch-clamp technique. In parallel, the T cell activation marker interleukin-2 (IL-2) receptor was measured quantitatively by flow cytometry. Outward currents were observed in response to depolarizing voltage steps from a holding potential of -80mV. The peak current density increased with more positive membrane potentials, where the current threshold was about -40mV and the maximum conductance was 1.22nS/pF. This current was characterized by a fast activation and a fast inactivation with half maximal inactivation at -67mV. The sensitivity of the peak current to K+ channel blocking agents was as follows: 4-aminopyridine (4-AP) had a half blocking concentration of 0.4mM and a maximal block of 83.7% at 10mM 4-AP, tetraethyl-ammonium caused a block of 6% at 0.1mM, 15% at 1mM and 40% at 10mM, charybdotoxin blocked 90% at 100nM, whereas iberiotoxin had no effect (all values at a clamped membrane potential of +30mV). The encephalitogenic T cells used in our study reach their highest encephalitogenic potency on day 3 to 4 after the onset of restimulation. Furthermore, K+ currents were measured during the whole course of an in vitro restimulation cycle. The peak currents normalized to cell capacitance reached their maximum on day 2 (326+/- 52.8pA/pF, n = 4) and decreased thereafter as follows: day 3: 139.7 +/- 7.87pA/pF (n = 27), day 4: 85.4 +/- 8.95pA/pF (n = 28) and day 5: 40.9 +/- 7.45pA/pF (n = 17). The activation and inactivation characteristics of the current and its responses to selective blockers were similar at all days after restimulation. In contrast to the K+ current, IL-2 receptor expression was maintained on > 95% of cells until day 6 after restimulation. In conclusion, the K+ currents measured in rat encephalitogenic T cells resemble n-type voltage-gated K+ currents described in mice and man. The comparison of K+ current, IL-2 receptor expression and encephalitogenic potency let us suppose that the observed K+ current represents an early event of specific T cell activation and can serve as a parameter of high functional activity of T cells corresponding to their encephalitogenicity.

Animals↗

PubMed1997

Inhibition of NF-kappa-B cellular function via specific targeting of the I-kappa-B-ubiquitin ligase.

Activation of the transcription factor NF-kappa B is a paradigm for signal transduction through the ubiquitin-proteasome pathway: ubiquitin-dependent degradation of the transcriptional inhibitor I kappa B in response to cell stimulation. A major issue in this context is the nature of the recognition signal and the targeting enzyme involved in the proteolytic process. Here we show that following a stimulus-dependent phosphorylation, and while associated with NF-kappa B, I kappa B is targeted by a specific ubiquitin-ligase via direct recognition of the signal-dependent phosphorylation site; phosphopeptides corresponding to this site specifically inhibit ubiquitin conjugation of I kappa B and its subsequent degradation. The ligase recognition signal is functionally conserved between I kappa B alpha and I kappa B beta, and does not involve the nearby ubiquitination site. Microinjection of the inhibitory peptides into stimulated cells abolished NF-kappa B activation in response to TNF alpha and the consequent expression of E-selectin, an NF-kappa B-dependent cell-adhesion molecule. Inhibition of NF-kappa B function by specific blocking of ubiquitin ligase activity provides a novel approach for intervening in cellular processes via regulation of unique proteolytic events.

Amino Acid Sequence↗

PubMed1997

Propentofylline and iloprost suppress the production of TNF-alpha by macrophages but fail to ameliorate experimental autoimmune encephalomyelitis in Lewis rats.

Intracellular cAMP levels can be elevated by activation of cAMP-generating adenylate cyclase (AC) or inhibition of cAMP-cleavage by phosphodiesterases. Elevation of intracellular cAMP levels in immune cells inhibits production of some Th1-cytokines, particularly TNF-alpha, and results mainly in downregulation of the immune response. Experimental autoimmune encephalomyelitis (EAE) of Lewis rats is a disease mediated by type 1 T helper lymphocytes and macrophages and serves as a model of multiple sclerosis. In EAE we therefore tested the immunomodulatory potency of an AC-activating, stable prostacyclin analogue, iloprost, and of a potent and non-selective inhibitor of phosphodiesterases, propentofylline, which also has neuroprotective properties. Preventive treatment of Lewis rats with propentofylline (2 x 10 or 12.5 mg/ kg/d), iloprost (2 x 10 or 12.5 micrograms/kg/d), or both did not significantly ameliorate clinical or histological signs of EAE actively induced by immunization with myelin basic protein (MBP) in complete Freund's adjuvant. Furthermore, adoptive transfer EAE (AT-EAE), passively induced by injection of encephalitogenic MBP-specific Th1 lymphocytes, was not altered in its course by the combined application of iloprost (2 x 10 micrograms/kg/d) and propentofylline (2 x 20 mg/kg/d) starting on the day of cell transfer. In vitro assays demonstrated that iloprost strongly and propentofylline moderately inhibited the production of TNF-alpha by macrophages and that iloprost in vivo similarly suppressed TNF-alpha secretion, although this effect was limited to a few hours after a single injection. In contrast to macrophages, TNF-alpha production by antigen-activated encephalitogenic T helper line cells in vitro was completely resistant to modulation by these agents. In addition, the presence of iloprost, propentofylline, or both drugs during activation of the line cells in vitro did not impair their encephalitogenicity in vivo. The findings delineate immunomodulatory effects of both substances, particularly of iloprost, but fail to support a possible therapeutic role of these agents in autoimmune inflammation of the central nervous system.

Animals↗

PubMed1997

Cytogenetic abnormalities related to histopathologic grade of astrocytic tumors.

Cytogenetic analysis was performed on 7 low-grade astrocytomas, 10 anaplastic astrocytomas, and 14 glioblastomas. Abnormal chromosome numbers were noted in all cases of high-grade astrocytomas but were rarely noted in low-grade astrocytomas (28%). The most consistent changes in high-grade astrocytomas were complete loss of chromosome 10 (61%), gain of chromosome 7 (56%), and loss of chromosome 17 (28%). Certain structural abnormalities, such as marker chromosomes and double minutes (33%), and the deletion and translocation of chromosomes 1 (33%) and 17 (17%), were also noted. These results indicate that changes in the number and/or structure of chromosomes with related inactivation of tumor suppressor gene or oncogene activation might play a critical role in the formation and anaplastic progression of astrocytic tumors.

Adolescent↗

PubMed1997

[Estimation of radiation exposure and radiation risk for employees of a heart catheterization laboratory].

The staff at interventional radiological procedures is exposed to high levels of ionizing radiation. This applies especially to measures at cardiac catheterization laboratories. In this study the annual radiation exposure to the staff was estimated by measuring the dose rate under characteristic conditions. It could be shown that the resulting radiation exposure was strongly dependent on the radiation protection measures and is also dependent on the operation conditions of the x-ray-tube. The effective dose for the physician wearing a lead apron and thyroid shield was determined to about 1.7 mSv/a. Without a thyroid shield an effective dose of about 3.5 mSv/a resulted. This corresponds to approximately the natural background radiation of about 2.4 mSv/a in the Federal Republic of Germany. From the number of procedures performed we could derive an effective dose of approximately 1-2 microSv per application for the physician, averaged over all types of procedures. Further, it could be shown that the readings of the film badges, usually worn by the staff, underestimate the effective dose by approximately a factor of two. This is because the film badges do not include the contribution of the unshielded parts of the body to effective dose. From the estimated annual effective dose, a lifetime dose of 68 mSv was estimated for a 40-year working career. The corresponding lifetime risk for induced fatal cancer due to radiation exposure was determined to 0.3% applying the ICRP risk factor of 4 x 10(-2) Sv-1. Considering the NCRP recommendations for a safe occupation, working in a cardiac catheterization laboratory can be considered as safe when applying all radiation protection measures. However, changing the protection measures and modifying the parameters of the x-ray-tube can lead to strong changes of the radiation exposure and the resulting risk estimation.

Cardiac Catheterization↗

PubMed1997

Interindividual differences in degradation of sodium monofluorophosphate by saliva in relation to oral health status.

The enzymatic degradation of sodium monofluorophosphate by whole saliva in patients with differing oral health status was compared Ten patients each with good or poor oral health were selected. Assessment of oral health status included indices of the amount of dental plaque, caries experience and counts of Streptococcus mutans and lactobacilli. Whole-saliva samples were collected under standardized conditions and monofluorophosphatase (MFPase) activity was measured in 2-ml saliva samples during 2 h of incubation at 37 C with 1 ml of monofluorophosphate solution (equivalent 31.5 mmol/1 F). MFPase activity was found in all the saliva samples. The values ranged from 0.6 to 17.8 nmol F/ml saliva per min. High MFPase activities correlated well with large amounts of plaque with the D component of the DMFT index and with high counts of salivary S. mutans and lactobacilli. The results show a wide range of MFPase activity in individuals and a statistically significant correlation (p < 0.05) between high MFPase activity and poor oral health status.

Adolescent↗

PubMed1997

Pancreatoblastoma.

BACKGROUND: Pancreatoblastoma is a rare pancreatic tumor with distinct acinar and squamoid cell differentiation that generally affects infants and young children. Just over 50 cases have been reported in the literature. METHODS: Five cases of pathologically proven pancreatoblastoma treated at Seoul National University Hospital from 1984 to 1994 were reviewed. There were three girls and two boys who were 2 years to 5 years of age. All cases came to medical attention because of an abdominal mass. RESULTS: Abdominal pain was observed in one case and anorexia, vomiting, and weight loss in one case. There was marked elevation of serum alpha-fetoprotein (27,000 ng/mL) in one case of liver metastases. Complete excision was performed in two cases in which the tumors were located in the tail of the pancreas. Partial excision was performed in two patients who had unresectable tumors of the head of the pancreas. One patient had an unresectable tumor at diagnosis and needle aspiration biopsy was carried out under ultrasound guidance. Electron microscopy was performed on pathological specimens of three cases and showed zymogen granules but not neuroendocrine granules. Immunocytochemical studies for alpha-fetoprotein, insulin, glucagon and somatostatin were performed in one patient, and results were all negative. Of two patients who underwent complete excision, one patient presented with liver metastases 4 months after operation and received chemotherapy, but died of tumor 6 months after operation. The other patient had local recurrence 1 year after operation. Reoperation and chemotherapy were performed, and the child is now alive without evidence of disease for 32 months. All three patients who had unresectable tumor died of tumor despite adjuvant radiotherapy and chemotherapy. CONCLUSIONS: The authors emphasize that the diagnosis of pancreatoblastoma in childhood should be suspected with palpation of an abdominal mass, and the chance for cure may be determined by complete excision of the tumor.

Child, Preschool↗

PubMed1997

T-cell receptor V beta-element expression in peripheral nerves of Lewis rats suffering from experimental autoimmune neuritis.

In experimental autoimmune neuritis (EAN), peripheral nerves are infiltrated by T-lymphocytes and macrophages. By RT-PCR and sequence analysis we characterized TCR V beta-element usage in sciatic nerve tissue of Lewis rats suffering from EAN induced by immunization with peripheral myelin antigens. Several TCR V beta-chain sequences were detected, which did not show homology to sequences of P2-reactive T cells published so far. In EAN induced with peripheral nerve myelin, but not with P2-protein or P2 peptide aa 53-78, TCR V beta 8.2 sequences identical to sequences of encephalitogenic myelin basic protein (MBP) reactive T-cells were identified. These results provide further evidence for a contribution of MBP-directed T-cell reactivity to the pathogenesis of myelin induced EAN and may have implications for the pathogenesis of human demyelinating neuropathies.

Animals↗

PubMed1997

Modulation of experimental autoimmune neuritis in Lewis rats by oral application of myelin antigens.

Experimental autoimmune neuritis (EAN) in Lewis rats is a T cell-mediated disease and serves as an animal model of human inflammatory demyelinating neuropathies. EAN can be induced by immunization with complete bovine peripheral nerve myelin (BPM), the myelin protein P2 or its neuritogenic peptide, each emulsified in complete Freund's adjuvant (CFA). The present study evaluates the effect of oral tolerization with BPM or P2 protein on the development of actively induced EAN. Oral administration of BPM strongly suppressed clinical and histological signs of EAN subsequently induced by BPM/CFA, but feeding of P2 protein alone did not affect its course. In contrast, feeding of BPM did not mitigate the course of EAN subsequently induced by immunization with neuritogenic P2 peptide/CFA. Oral therapy with BPM after onset of myelin-induced EAN only slightly ameliorated the further course of disease, but significantly reduced lethality of this severe form of disease. The findings suggest that immunogenicity of the antigens fed determine strength of tolerance, that downregulation of EAN occurs at the site of immunization and not in the nerve, and that active suppression rather than specific anergization is operative in mediating resistance to EAN. However, only partial tolerance to myelin-induced EAN was achieved in naive animals by transfer of spleen/LN cells from rats orally tolerized with BPM. Although methodic factors may have limited the effect of the cells, the result is suggestive of some contribution of anergy to oral tolerance in the present model. Cholera toxin and LPS were identified as oral adjuvants for BPM and prolonged the state of tolerance. However, LPS exhibited proinflammatory properties if EAN was induced early after BPM/LPS-feeding. Thus, oral application of a mixture of myelin components in combination with cholera toxin may be a useful treatment for chronic inflammatory neuropathies considered autoimmune in nature.

Adjuvants, Immunologic↗

PubMed1997

B cell development under the condition of allelic inclusion.

Mice whose IgH alleles are engineered to encode two distinct antibody heavy (H) chains generate a normal-sized B cell compartment in which most cells stably express the two heavy chains. This demonstrates that "toxicity" of bi-allelic H chain expression and cell-autonomous mechanisms of silencing in-frame IgH gene rearrangements do not significantly contribute to allelic exclusion at the IgH locus. Notwithstanding, the stability of the various engineered IgH loci during B cell development in the bone marrow differed substantially from each other.

Alleles↗

PubMed1997

Improving in vivo folding and stability of a single-chain Fv antibody fragment by loop grafting.

The complementary determining regions (CDRs) from the fluorescein-binding antibody 4-4-20, which yields almost no soluble protein in periplasmic expression in Escherichia coli, were transplanted to the framework of the humanized antibody 4D5. The resulting single-chain Fv fragment (scFv) 4D5Flu showed both a dramatic improvement in soluble expression, even at 37 degrees C, and an improved thermodynamic stability. Antigen affinity was maintained upon this engineering by paying attention to crucial framework-CDR contacts. This demonstrates that the use of superior frameworks is a robust strategy to improve the physical properties of scFv fragments. We also report that the grafted version was selected in phage display over several competing variants of the same antibody with identical binding constant but poorer folding or stability properties. The selection required four panning rounds and a temperature of 37 degrees C and we show that the underlying reason for this selection is a higher fraction of phages carrying functional scFv molecules.

Amino Acid Sequence↗