Biomedical subjects

J Hong

Publications and source records attributed to J Hong.

At least 91 records · Page 5Linked to original sources

PubMed2000

Aberrant T cell responses to myelin antigens during clinical exacerbation in patients with multiple sclerosis.

Multiple sclerosis (MS) is a demyelinating disease of presumed T cell autoimmunity against self myelin. We hypothesized that if myelin-reactive T cells are associated with the disease processes, they may undergo activation and expansion during acute exacerbation. In this study, we examined the precursor frequency, epitope recognition and cytokine profile of myelin-reactive T cells in 14 relapsing/remitting MS patients during exacerbation and remission. The study revealed that T cells recognizing the immunodominant peptides of candidate myelin antigens, including myelin basic protein (MBP), proteolipid protein and myelin oligodendrocyte glycoprotein, occurred at increased precursor frequency during acute exacerbation. The T cell responses to MBP focused on the immunodominant regions (residues 83-99 and 151-170) during exacerbation and shifted toward other epitopes of MBP at the time of remission. Furthermore, there was a marked increase in the production of T(h)1 cytokines among T cell lines obtained during exacerbation compared to those obtained during remission. The study demonstrated that myelin-reactive T cells underwent selective activation and expansion during acute MS exacerbation. In contrast, myelin-reactive T cells found during remission in the same patients generally resembled those identified in healthy controls with some discrepancies. The findings suggest potential association of aberrant myelin-reactive T cell responses with acute exacerbation in MS, which may reflect transient activation of myelin-reactive T cell populations of pathogenic potential.

Adult↗

PubMed2000

Characterization of soliton damping in the granular chain under gravity

A soliton created in the horizontal granular chain damps due to gravity in the vertical chain. We show that there are two types of propagating modes, quasisolitary and oscillatory, in the vertical chain, depending on the strength of impulse. We find that the type of damping is a power law in depth or time. We also find that the absolute value of the exponent of the power law decreases as the strength of the initial impulse increases in the quasisolitary regime. In the oscillatory regime, however, in which the initial impulse is weak, the power-law exponent is independent of the strength of the initial impulse. We show that the power-law damping is caused by the gravitation which results in the change of the force constant at each contact.

Journal Article↗

PubMed2000

Plasma and tissue levels of tea catechins in rats and mice during chronic consumption of green tea polyphenols.

To understand the relationship between tea consumption and its biological effects, plasma and tissue levels of (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC) were measured after rats and mice were given a 0.6% green tea polyphenol preparation as the drinking fluid for different periods of time. EGC and EC levels in rat plasma increased over time and reached peak values (3 times the Day 1 values) on Day 14. Then the plasma levels of tea catechins decreased, to Day 1 values on Day 28. The plasma concentrations of EGCG were much lower than those of EGC or EC. High levels of EGC and EC were found in urine, whereas high levels of EGCG were found in feces. The changes in the urinary and fecal excretions of tea catechins could not account for the above-described changes in the plasma levels. The amounts of catechins in different tissues reflected the ingestion, absorption, and excretion pattern. When the green tea polyphenol preparation was given to mice, the "increase-and-then-decrease" pattern of catechin levels was also observed in the plasma, lung, and liver; the EGCG levels were much higher than in the rats. The results suggest that consumption of tea by rodents could induce adaptive responses affecting blood and tissue levels of tea catechins with time and that investigation of a similar phenomenon in humans is warranted.

Adaptation, Biological↗

PubMed2000

No correlation of polymorphism of angiotensin-converting enzyme genes with left ventricular hypertrophy in essential hypertension.

To investigate the correlation of polymorphism of angiotensin-converting enzyme (ACE) genes with left ventricular hypertrophy in essential hypertension, 151 patients with essential hypertension were studied. ACE genotypes were determined by PCR technology and diastolic left ventricular diameter (DLVd), systolic left ventricular diameter (SLVd), interseptal ventricular thickness (IVS), and left ventricular posterior wall thickness (LVPW) were scanned by echocardiography. Left ventricular mass (LVM) and the left ventricular mass index (LVMI) were calculated from echocardiographic findings. Results revealed that DLVd, SLVd, IVS, LVPW, LVM, and LVMI of the DD genotype group were 49.9 +/- 5.6 mm, 30.5 +/- 6.5 mm, 11.2 +/- 1.6 mm, 11.7 +/- 1.5 mm, 259.5 +/- 62.1 g, 92.7 +/- 23.5 g/m2, respectively. DLVd, SLVd, IVS, LVPW, LVM, and LVMI of the ID genotype group were 8.9 +/- 5.3 mm, 31.5 +/- 5.2 mm, 11.4 +/- 1.7 mm, 11.9 +/- 1.6 mm, 261.3 +/- 70.3 g, and 94.9 +/- 25.8 g/m2, respectively, and DLVd, SLVd, IVS, LVPW, LVM, and LVMI of the II genotype group are 48.9 +/- 5.5 mm, 31.8 +/- 6.5 mm, 11.1 +/- 1.9 mm, 11.5 +/- 1.8 mm, 250.8 +/- 82.5 g and 90.8 +/- 30.1 g/m2 respectively. There was no significant difference between the ID, DD and II genotype groups as regards DLVd, SLVd, IVS, LVPW, LVM, and LVMI (p > 0.05). These findings indicate that there is no association between the ACE gene and left ventricular hypertrophy in essential hypertension occurring in the Chinese population.

Aged↗

PubMed2000

Forskolin increases the expression of the pancreatic tumor antigen, Nd2, and uptake of Nd2 antibody.

Nd2 antibody recognizes an antigen that is tumor specific in pancreas. It has been used successfully in clinical radioimmunodetection studies to identify exocrine pancreatic tumors. In the present study we show that the uptake of radiolabeled Nd2 antibody by SW1990 pancreatic carcinoma cells was increased by the adenyl cyclase activator, forskolin. Dibutyryl cyclic AMP and forskolin were both effective in increasing the level of Nd2 antigen in SW1990 cells. Immunoprecipitation studies showed that the Nd2 epitope is associated with MUC1 mucin. Forskolin increased Nd2/MUC1 antigen in both a membrane fraction and a high buoyant density mucin-like fraction. Nd2 immunoreactivity was reduced by treatment of mucins with proteases and beta-mercaptoethanol. Immunohistochemical studies showed that periodate catalyzed beta-elimination greatly reduced Nd2 immunoreactivity. These results suggest that the Nd2 epitope is unusual in having characteristics of both a peptide and a carbohydrate, protease and conformation sensitivities and involvement of O-linked oligosaccharides. Nd2 antibody does not react with several known pancreatic cancer antigens. In summary, activation of the cyclic AMP pathway increased cellular uptake of Nd2 antibody and the cellular expression of the tumor-specific, mucin-associated Nd2 antigen. These results suggest a means of improving the effectiveness of monoclonal antibodies in targeting tumor antigens for the diagnosis and treatment of malignancy.

Amino Acid Sequence↗

PubMed2000

[Clinic analysis of retinopathy in gestosis patients].

PURPOSE: To explore the relationship between degree of retinopathy and degree of gestosis, hypertension, and fetal death rate by examing eye fundus of 115 gestosis patients. METHOD: We compared the degree of retinopathy with the degree of gestosis, the degree of hypertension, and the fetal death rate respectively. RESULTS: The degree of retinopathy is postively related with the degree of gestosis, the degree of hypertension and the fetal death rate. CONCLUSION: Eye fundus examination in gestosis patients is an significant guideline for clinical treatment.

Adult↗

PubMed2000

Role of DIC in multiple organ failure.

BACKGROUND: Disseminated intravascular coagulation (DIC) is a severe and complex coagulopathy resulting from excessive thrombin formation. Although there is a final common pathway, consumption coagulopathy and multiple organ failure (MOF), the early pathophysiology differs depending on the underlying disease. AIM: The aim of this study is to elucidate the pathophysiology of septic DIC, and also to assess logical diagnostic and therapeutic procedure. METHODS: Blood samples were collected from septic patients. Coagulant, fibrinolytic and vascular markers were analyzed. RESULTS AND CONCLUSION: Damaged vascular endothelial cells overproduce plasminogen activator inhibitor 1, which, with excess production of thrombin, leads to fibrnolysis-suppressive DIC and fibrin formation in the microvasculature. These changes characterize the septic coagulopathy, which is often complicated by MOF; however, a bleeding tendency is relatively rare. The platelet count and fibrinogen/fibrin degradation products are most useful for the diagnosis of septic DIC. However, since the specificity is not sufficient with these screening tests, other tests including molecular markers should be added. Since endothelial damage plays an important role in the pathophysiology in septic DIC, treatment should be focused not only on abnormal coagulopathy but also on vascular damage. Protease inhibitors and antithrombin III are both effective treatments for DIC. Although heparin is a standard drug for the treatment of DIC, the use of heparin is not recommended in case of septic DIC.

Disseminated Intravascular Coagulation↗

PubMed1999

Structure and organization of hemolytic and nonhemolytic diastereomers of antimicrobial peptides in membranes.

Recently, we reported on a new group of diastereomers of short-model peptides (12 amino acids long) composed of leucine and lysine with varying ratios, possessing several properties that make them potentially better than native or de novo-designed all L-amino acid antimicrobial peptides. Preliminary studies have revealed that modulating the hydrophobicity and positive charges of these diastereomers is sufficient to confer antibacterial activity and cell selectivity. However, the relationship between their biological function, structure, and mode of action was not investigated. Here we synthesized and investigated three types of linear model diastereomers (12 amino acids long) with varying lysine:leucine (or tryptophan) ratios (i.e., K(3)L(8)W, K(5)L(6)W, and K(7)L(4)W), which confer different levels of lytic activities. For each K:L ratio, tryptophan was introduced in the middle or the N- or C-terminus of the peptides, as an intrinsic fluorescent probe. Only the hemolytic peptide K(3)L(8)W binds to both negatively charged and zwitterionic phospholipid membranes. K(5)L(6)W and K(7)L(4)W bind similarly, but only to negatively charged membranes, despite the fact that K(5)L(6)W is substantially more lytic to bacteria than K(7)L(4)W. Interestingly, although K(3)L(8)W contains 33% D-amino acids, ATR-FTIR spectroscopy revealed a structure of approximately 90% alpha-helix in both types of membranes. In addition, K(5)L(6)W contains approximately 40% 3(10)-helix and K(7)L(4)W is predominantly a random coil in membranes. Polarized ATR-FTIR and tryptophan-quenching experiments, using brominated phospholipids, revealed a similar depth of penetration and an orientation that was parallel to the membrane surface for all the peptides, but with K(3)L(8)W affecting the lipid order more than the others. The results provide insight into the mode of action of this group of diastereomeric peptides, and the effect of hydrophobicity and positive charges on their membrane structure, function, and cell selectivity. Moreover, this research should assist in the development of suitable diastereomeric peptide antibiotics for therapeutic use that would overcome the problem the increasing resistance of bacteria to conventional antibiotics.

Acinetobacter calcoaceticus↗

PubMed1999

Th1 and Th2 deviation of myelin-autoreactive T cells by altered peptide ligands is associated with reciprocal regulation of Lck, Fyn, and ZAP-70.

Th0 clones recognizing an immunodominant peptide of myelin basic protein (residues 83-99) were derived from patients with multiple sclerosis. We demonstrate that analogue peptides with alanine substitution at Val86 and His88 had a unique partial agonistic property in inducing Th0 -->Th1 and Th0 -->Th2 deviation of the myelin basic protein-reactive T cell clones, respectively. Th0 to Th1 deviation induced by peptide 86V-->A correlated with up-regulation of Fyn and ZAP-70 kinase activities. Conversely, Th0 to Th2 deviation induced by peptide 88H-->A was associated with complete failure to activate Fyn and ZAP-70 kinases. The observed Th1 and Th2 shift also correlated, to a lesser extent, with Lck kinase activity that was down-regulated with Th1 deviation and increased with Th2 deviation in some T cell clones. We demonstrated that the Th1 and Th2 shift induced by the analogue peptides was a reversible process, as the T cell clones previously exposed to either 86V-->A or 88H-->A peptide could revert to an opposite phenotype when rechallenged reciprocally with a different analogue peptide. The study has important implications in our understanding of regulation of TCR-associated tyrosine kinases by altered peptide ligands and its role in cytokine regulation of autoreactive T cells.

Alanine↗

PubMed1999

Purification and cloning of amyloid precursor protein beta-secretase from human brain.

Proteolytic processing of the amyloid precursor protein (APP) generates amyloid beta (Abeta) peptide, which is thought to be causal for the pathology and subsequent cognitive decline in Alzheimer's disease. Cleavage by beta-secretase at the amino terminus of the Abeta peptide sequence, between residues 671 and 672 of APP, leads to the generation and extracellular release of beta-cleaved soluble APP, and a corresponding cell-associated carboxy-terminal fragment. Cleavage of the C-terminal fragment by gamma-secretase(s) leads to the formation of Abeta. The pathogenic mutation K670M671-->N670L671 at the beta-secretase cleavage site in APP, which was discovered in a Swedish family with familial Alzheimer's disease, leads to increased beta-secretase cleavage of the mutant substrate. Here we describe a membrane-bound enzyme activity that cleaves full-length APP at the beta-secretase cleavage site, and find it to be the predominant beta-cleavage activity in human brain. We have purified this enzyme activity to homogeneity from human brain using a new substrate analogue inhibitor of the enzyme activity, and show that the purified enzyme has all the properties predicted for beta-secretase. Cloning and expression of the enzyme reveals that human brain beta-secretase is a new membrane-bound aspartic proteinase.

Amino Acid Sequence↗

PubMed1999

Interferon beta induces T-helper 2 immune deviation in MS.

OBJECTIVE: To define the in vitro effects of interferon beta la (IFN-beta1a) on myelin basic protein (MBP)-reactive T cells and to determine its regulatory mechanism on cytokine networks in patients with MS. METHODS: The proliferation and cytokine production of MBP-reactive T-cell clones were measured in thymidine uptake assays and ELISA respectively. The precursor frequency of MBP-reactive T cells was estimated in a microwell culture system. RESULTS: IFN-beta inhibited the proliferation of established MBP-reactive T-cell clones, which correlated with enhanced production of anti-inflammatory interleukin (IL)-4 and IL-10, and a decrease in tumor necrosis factor alpha (TNF-alpha) and IFN-gamma. When examined with peripheral blood mononuclear cells (PBMCs), IFN-beta was found to reduce the in vitro T-cell responses to MBP, as indicated by the significantly decreased frequency of MBP-reactive T cells. The decreased frequency of MBP-reactive T cells corresponded to an augmented production of IL-4 and IL-10. Although the level of TNF-alpha and IFN-gamma was generally unaltered or decreased, IFN-beta appeared to enhance the production of IFN-gamma in PBMCs derived from some individuals with MS. CONCLUSION: Interferon beta la (IFN-beta) suppresses myelin basic protein (MBP)-reactive T cells and induces immune deviation toward the production of T-helper 2 cytokines, which may contribute to its therapeutic benefit in MS. The study also suggests some heterogeneity in MBP-reactive T-cell responses to IFN-beta in different individuals with MS.

Cell Division↗

PubMed1999

Zinc-dependent structural stability of human Sonic hedgehog.

The role of the zinc site in the N-terminal fragment of human Sonic hedgehog (ShhN) was explored by comparing the biophysical and functional properties of wild-type ShhN with those of mutants in which the zinc-coordinating residues H140, D147, and H182, or E176 which interacts with the metal ion via a bridging water molecule, were mutated to alanine. The wild-type and E176A mutant proteins retained 1 mol of zinc/mol of protein after extensive dialysis, whereas the H140A and D147A mutants retained only 0.03 and 0.05 mol of zinc/mol of protein, respectively. Assay of the wild-type and mutant proteins in two activity assays indicated that the wild-type and E176A mutant proteins had similar activity, whereas the H140A and D147A mutants were significantly less active. These assays also indicated that the H140A and D147A mutants were susceptible to proteolysis. CD, fluorescence, and (1)H NMR spectra of the H140A, D147A, and E176A mutants measured at 20 or 25 degrees C were very similar to those observed for wild-type ShhN. However, CD measurements at 37 degrees C showed evidence of some structural differences in the H140A and D147A mutants. Guanidine hydrochloride (GuHCl) denaturation studies revealed that the loss of zinc from the H140A and D147A mutants destabilized the folded proteins by approximately 3.5 kcal/mol, comparable to the effect of removing zinc from wild-type ShhN by treatment with EDTA. Thermal melting curves of wild-type ShhN gave a single unfolding transition with a midpoint T(m) of approximately 59 degrees C, whereas both the H140A and D147A mutants displayed two distinct transitions with T(m) values of 37-38 and 52-54 degrees C, similar to that observed for EDTA-treated wild-type ShhN. Addition of zinc to the H140A and D147A mutants resulted in a partial restoration of stability against thermal and GuHCl denaturation. The ability of these mutants to bind zinc was confirmed using a fluorescence-based binding assay that indicated that they bound zinc with K(d) values of approximately 1.6 and approximately 15 nM, respectively, as compared to a value of </=100 pM for wild-type ShhN. The properties of the E176A mutant were indistinguishable from those of wild-type ShhN in all biophysical and functional assays, indicating that this residue does not contribute significantly to stabilization of the zinc-binding site and that ShhN does not require hydrolase activity for in vitro biological function.

Alkaline Phosphatase↗

PubMed1999

A common TCR V-D-J sequence in V beta 13.1 T cells recognizing an immunodominant peptide of myelin basic protein in multiple sclerosis.

T cell responses to the immunodominant peptide (residues 83-99) of myelin basic protein are potentially associated with multiple sclerosis (MS). This study was undertaken to examine whether a common sequence motif(s) exists within the TCR complementarity-determining region (CDR)-3 of T cells recognizing the MBP83-99 peptide. Twenty MBP83-99-reactive T cell clones derived from patients with MS were analyzed for CDR3 sequences, which revealed several shared motifs. Some V beta 13.1 T cell clones derived from different patients with MS were found to contain an identical CDR3 motif, V beta 13.1-LGRAGLTY. Oligonucleotides complementary to the shared CDR3 motifs were used as specific probes to detect identical target CDR3 sequences in a large panel of T cell lines reactive to MBP83-99 and unprimed PBMC. The results revealed that, in contrast to other CDR3 motifs examined, the LGRAGLTY motif was common to T cells recognizing the MBP83-99 peptide, as evident by its expression in the majority of MBP83-99-reactive T cell lines (36/44) and PBMC specimens (15/48) obtained from randomly selected MS patients. The motif was also detected in lower expression in some PBMC specimens from healthy individuals, suggesting the presence of low precursor frequency of T cells expressing this motif in healthy individuals. This study provides new evidence indicating that the identified LGRAGLTY motif is preferentially expressed in MBP83-99-reactive T cells. The findings have important implications in monitoring and targeting MBP83-99-reactive T cells in MS.

Amino Acid Sequence↗

PubMed1999

Methylation of CpG in a small region of the hMLH1 promoter invariably correlates with the absence of gene expression.

Microsatellite instability (MSI) has been described in tumors from patients with hereditary nonpolyposis colorectal cancer, sporadic colorectal cancer, and other types of cancers. MSI is caused by the dysfunction of mismatch repairs genes. Loss of expression and mutation in one of the major mismatch repair genes, hMLH1, and the methylation of CpG sites in its promoter occur frequently in primary tumors and cell lines of colorectal cancer with MSI. To understand the mechanisms involved in the silencing of hMLH1 expression by methylation, we examined the methylation status of all CpG sites in the hMLH1 promoter in 24 colorectal cancer cell lines by the NaHSO3-sequencing method. We identified a small proximal region (-248 to -178, relative to the transcription start site) in the promoter in which the methylation status invariably correlates with the lack of hMLH1 expression. This correlation was further supported by the observation that cell lines that showed methylation-suppressed hMLH1 expression can be induced to reexpress hMLH1 by a methyl transferase inhibitor, 5-aza-2'-deoxycytidine, and the small region that we identified exhibited significant demethylation in all cell lines examined.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Effects of epidermal growth factor on MDA-MB-468 breast cancer cells: alterations in polyamine biosynthesis and the expression of p21/CIP1/WAF1.

We examined the effects of epidermal growth factor (EGF) on MDA-MB-468 cells to understand its mechanism of action in an EGF receptor-rich breast cancer cell line. EGF inhibited the growth of MDA-MB-468 cells with an IC50 of 1.5 +/- 0.5 nM, as determined by measurements of DNA content of cells in culture over a period of 4 to 6 days. This growth inhibition included apoptosis 24 h after EGF addition, as detected by an enzyme-linked immunosorbent assay (ELISA) and Hoechst 33342 staining. In EGF-treated cells, peak activities of two key enzymes of polyamine biosynthesis, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC), were reduced by 57% and 83%, respectively. EGF treatment also caused a 30 to 50% decrease in cellular putrescine at all time points tested (12 to 48 h). EGF-induced inhibition of DNA synthesis was also partially reversed by the addition of putrescine or spermidine, but not by spermine. Western blot analysis of cell cycle regulatory proteins showed that EGF-mediated growth inhibition was associated with the induction of p21, an inhibitor of cyclin-dependent kinases. However, EGF had no significant effect on the expression of cyclin D1 or cyclin E. Furthermore, putrescine reversal of EGF effects was associated with the down-regulation of EGF-induced p21. These results suggest that the mechanism of growth inhibition by EGF in MDA-MB-468 cells include a down-regulation of polyamine biosynthesis and the induction of p21. Identification of growth regulatory pathways in breast cancer cells might be useful in the development of novel targets for therapeutic intervention.

Benzimidazoles↗

PubMed1999

Rapid colorimetric assay of urinary beta-galactosidase and N-acetyl-beta-D-glucosaminidase with Cobas Mire Auto-analyzer.

A rapid and simple colorimetric method for the assay of urinary beta-galactosidase (GAL) and N-acetyl-beta-D-glucosaminidase (NAG) using 4-nitrophenyl-glycosides as the substrates and a Cobas Mire Auto-analyzer is described. Optimal conditions for this method including substrate concentration, ionic strength, pH and incubation time were characterized. Endogenous substances in urine did not interfere with the assays. Incubation time could be shortened to 10 minutes. A small volume of an alkaline buffer to terminate the enzyme reaction achieved better sensitivity and accuracy. Buffer-substrate solutions were stable for at least one week at 4 degrees C. Normal values of the two urinary enzymes are also reported.

Acetylglucosaminidase↗

PubMed1999

Impaired apoptotic deletion of myelin basic protein-reactive T cells in patients with multiple sclerosis.

T cell responses to myelin basic protein (MBP) may play an important role in the pathogenesis of multiple sclerosis (MS). If MBP-reactive T cells are involved in the disease processes and undergo clonal activation and expansion, their precursor frequency would be increased in patients with MS. The frequency of MBP-reactive T cells is also influenced by regulatory mechanisms in vivo, including apoptotic deletion. In this study, we examined changes in the frequency of MBP-reactive T cells in patients with MS as a function of the apoptotic deletional mechanism in vivo, using a cell culture-based assay. A significantly increased frequency of MBP-reactive T cells was found in patients with MS relative to healthy individuals only when Fas-ligand antibody was used to block apoptosis. This result indicates that a significant proportion of MBP-reactive T cells are sensitive to apoptosis and are not deleted in vivo in patients with MS, as opposed to healthy individuals, thus suggesting a functional deficit in apoptotic deletional mechanism. Surviving Fas-sensitive MBP-reactive T cell lines represent distinct subpopulations preferentially recognizing the 111-139 region of MBP and exhibiting a Th2 cytokine profile. The findings are relevant to our understanding of regulation of MBP-reactive T cells in vivo in MS.

Antibodies, Monoclonal↗

PubMed1999

Identification of acylated glycoglycerolipids from a cyanobacterium, Synechocystis sp., by tandem mass spectrometry.

Acylated glycoglycerolipids were identified in the total lipid extract from cyanobacterium Synechocystis sp. PCC 6803. These compounds have a palmitoyl group esterified to the hydroxyl group at the C-6 position of the terminal glycosyl moiety of digalactosyl monoacylglycerol and digalactosyl diacylglycerol. Their structural elucidation was accomplished by tandem mass spectrometry coupled with fast atom bombardment ionization. Acylated digalactosyl monoacylglycerol has a structure of 1-hydroxy-2-palmitoyl-3-O-[(6-O-palmitoyl)-alpha-D-galactopyranosyl -(1-->6)-beta-D-galactopyranosyl]-sn-glycerol. This compound has not been reported previously.

Acylation↗