Biomedical subjects

J Hong

Publications and source records attributed to J Hong.

At least 127 records · Page 7Linked to original sources

PubMed1998

Distribution of catechol-O-methyltransferase expression in human central nervous system.

Catechol-O-methyltransferase (COMT, EC 2.1.1.6) is a ubiquitous enzyme crucial to catechol metabolism. Two isoforms exist in the human central nervous system (CNS) and they are encoded by two transcripts (1.3 and 1.5 kb) in most human tissues. Using two alpha-32P-labeled probes, we found only the 1.5 kb transcript in all 16 regions of the human CNS using commercially available Northern blots. Spinal cord had the highest and amygdala had the lowest levels of expression. The other CNS regions shared a similar level of expression. The distributions of COMT gene expression relative to whole brain between both probes were significantly correlated. Our study shows that the expression of the 1.5kb transcript is crucial for COMT activity in all regions of the human CNS.

Blotting, Northern↗

PubMed1998

Suppression of adventitious formation of 8-oxoguanine(TMS)4 from guanine during trimethylsilylation.

GC/MS quantitation of 8-oxoguanine derived from DNA may yield artificially high values when trimethylsilylation is used as the technique to form a volatile derivative. Significant quantities of the tetrakis trimethylsilyl-derivative of 8-oxoguanine may be formed from guanine during the derivatization reaction at elevated temperatures. We have screened eight antioxidants in an attempt to identify a substance that will reduce the spurious formation of this product. Whereas several compounds were active, N-phenyl-1-naphthylamine was the most effective agent. Moreover, this compound was sufficiently basic to act as a catalyst for the derivatization reaction. Our data, which are based on the use of an isotopically labeled internal standard, show that the level of the tetrakis trimethylsilyl derivative of 8-oxoguanine remained constant as a function of derivatization heating time when N-phenyl-1-naphthylamine was added to a reaction in which guanine was present. In contrast, the level in control samples increased linearly with reaction time indicating formation of 8-oxoGua during derivatization. The level of 8-oxoguanine was measured in both a synthetic oligodeoxynucleotide containing a single 8-oxo-2'-deoxyguanosine moiety and commercially available calf thymus DNA using this technique.

1-Naphthylamine↗

PubMed1998

Modeling trichloroethylene degradation by a recombinant pseudomonad expressing toluene ortho-monooxygenase in a fixed-film bioreactor

Burkholderia cepacia PR123(TOM23C), expressing constitutively the TCE-degrading enzyme toluene ortho-monooxygenase (Tom), was immobilized on SIRANtrade mark glass beads in a biofilter for the degradation and mineralization of gas-phase trichloroethylene (TCE). To interpret the experimental results, a mathematical model has been developed which includes axial dispersion, convection, film mass-transfer, and biodegradation coupled with deactivation of the TCE-degrading enzyme. Parameters used for numerical simulation were determined from either independent experiments or values reported in the literature. The model was compared with the experimental data, and there was good agreement between the predicted and measured TCE breakthrough curves. The simulations indicated that TCE degradation in the biofilter was not limited by mass transfer of TCE or oxygen from the gas phase to the liquid/biofilm phase (biodegradation limits), and predicts that improving the specific TCE degradation rates of bacteria will not significantly enhance long-term biofilter performance. The most important factors for prolonging the performance of biofilter are increasing the amount of active biomass and the transformation capacity (enhancing resistance to TCE metabolism). Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗

PubMed1998

Presenilin-1 mutations associated with familial Alzheimer's disease do not disrupt protein transport from the endoplasmic reticulum to the Golgi apparatus.

Mutations in genes encoding presenilin-1 (PS1) and presenilin-2 (PS2) have been linked to familial forms of Alzheimer's disease (AD). Cells expressing mutant presenilins produce elevated levels of Abeta42, the major amyloid peptide found in AD plaques. The mechanism whereby this occurs remains unknown, but the localization of presenilins to endoplasmic reticulum (ER) and Golgi compartments has suggested that they may function in intracellular trafficking pathways involved in processing beta-amyloid precursor proteins (APP). To test this possibility, we coexpressed PS1(wt), PS1(M146L), or PS1(L286V) in HEK293 cells together with the LDL receptor, a classic glycoprotein marker that undergoes post-translational O-glycosylation in the Golgi compartment. Pulse-chase analysis of the receptor indicated that mutant presenilins had no effect on ER-->Golgi transport. Similar results were obtained when the studies were carried out with cells expressing the Swedish variant of APP (SWAPP751) instead of the LDL receptor. Moreover, secretion of the soluble exodomain polypeptide fragments of SWAPP751 that arise from alpha-secretase and beta-secretase cleavage was not markedly affected by the PS1 mutants. Despite the lack of discernible effect of the PS1 mutants on trafficking of proteins through the Golgi apparatus, they caused a substantial increase in the proportion of Abeta42 relative to total Abeta in the culture medium. The results suggest that mutant forms of PS1 cause elevated production of Abeta42 by a mechanism that is independent of a major disruption of exocytic trafficking of APP.

Alzheimer Disease↗

PubMed1998

Transition-state theoretical interpretation of the catalytic power of pyruvate decarboxylases: the roles of static and dynamical considerations.

The catalytic power of two thiamin diphosphate (ThDP)-dependent enzymes, yeast pyruvate decarboxylase (the hysteretically regulated enzyme from Saccharomyces cerevisiae, SCPDC) and bacterial pyruvate decarboxylase (the unregulated enzyme from Zymomonas mobilis, ZMPDC), are analyzed by thorough-going application of transition-state theory, i.e. by a static approach that emphasizes the state-function character of the free energy of activation and takes no explicit account of dynamical considerations. The overall catalytic reaction is resolved into manifolds for addition (conversion of free enzyme and substrate to the complex of enzyme with the pyruvate:ThDP adduct), decarboxylation, and elimination (conversion of the complex of enzyme with the acetaldehyde:ThDP adduct formed by decarboxylation into free product and free enzyme). For SCPDC, the addition manifold is most strongly catalyzed (3x1012-fold, corresponding to net transition-state stabilization of 72 kJ/mol, transition-state stabilization of 83 kJ/mol diminished by reactant-state stabilization of 11 kJ/mol), the decarboxylation manifold is least strongly catalyzed (5x107-fold, corresponding to net transition-state stabilization of 41 kJ/mol, transition-state stabilization of 68 kJ/mol diminished by reactant-state stabilization of 27 kJ/mol), and the elimination manifold is catalyzed to an intermediate degree (2x1010-fold, corresponding to net transition-state stabilization of 59 kJ/mol, transition-state stabilization of 76 kJ/mol diminished by reactant-state stabilization of 17 kJ/mol). A similar situation holds for ZMPDC. There is no need to make an explicit analysis of dynamical factors in order to describe the catalytic mechanism and catalytic power of these complex enzymes.

Bacteria↗

PubMed1998

Matrix-assisted laser desorption/ionization for short tandem repeat loci.

Matrix-assisted laser desorption/ionization was used for the detection of four base short tandem repeats (STR) for clinical samples using a time-of-flight mass spectrometer. Since STR plays an important role in genetic disease and human identification, this work indicates that laser desorption mass spectrometry has the potential to achieve rapid DNA typing for both forensic applications and genetic disease diagnosis.

DNA↗

PubMed1998

The effect of ventricular volume reduction surgery in the dilated, poorly contractile left ventricle: a simple finite element analysis.

OBJECTIVES: Ventricular volume reduction surgery has been proposed by Batista to improve cardiac function in patients with dilated cardiomyopathy. However, limited clinical data exist to determine the efficacy of this operation. A finite element simulation is therefore used to determine the effect of volume reduction surgery on left ventricular end-systolic elastance, diastolic compliance, stroke work/end-diastolic volume (preload recruitable stroke work), and stroke work/end-diastolic pressure (Starling) relationships. METHODS: End-diastole and end-systole were represented by elastic finite element models with different unloaded shapes and nonlinear material properties. End-systolic elastance, diastolic compliance, preload recruitable stroke work, and Starling relationships, as well as energy expenditure per gram of unresected myocardium, were calculated. Two different types of volume reduction surgery (apical and lateral) were simulated at 10% and 20% left ventricular mass reduction. RESULTS: Ventricular volume reduction surgery causes diastolic compliance to shift further to the left on the pressure-volume diagram than end-systolic elastance. Volume reduction surgery increases the slope of the preload recruitable stroke work relationship (dilated cardiomyopathy 0.006 J/mL; 20% lateral volume reduction surgery 0.009 J/mL) but decreases the slope of the Starling relationship (dilated cardiomyopathy 0.028 J/mm Hg; 20% lateral volume reduction 0.023 J/mm Hg). For a given amount of resection, lateral volume reduction has a greater effect than apical volume reduction. Ten-percent and 20% lateral volume reduction reduces energy expenditure by 7% and 17%, respectively. CONCLUSION: Ventricular volume reduction surgery shifts end-systolic elastance and diastolic compliance to the left on the pressure-volume diagram. The net effect on ventricular function is mixed. Volume reduction surgery increases the slope of preload recruitable stroke work, but increased diastolic compliance causes a small decrease in the Starling relationship (3 mm Hg difference between dilated cardiomyopathy and volume reduction surgery at stroke work = 0.5 J).

Adult↗

PubMed1998

Trichosanthin inhibits T cell activation by interfering with the recruitment of ZAP-70 to CD3 zeta chain.

Plant protein Trichosanthin (Tk) has been shown in our previous experiments to suppress antigenic response of T cells. Here we explored its inhibitory mechanisms on the proliferation of human Jurkat leukemia T cell triggered by anti-CD3 McAb. By examination of tyrosine phosphorylation of cell lysate, we were able to show that Tk could interfere with the PTK-related activity in the TCR/CD3-initiated signal transduction in addition to blocking the phosphorylation of PKC. As shown in our experiment, the expression intensity of ZAP-70, a kind of protein tyrosine kinase, was not changed but its phosphorylation could be inhibited. When physical link between CD3 zeta chain and ZAP-70 was further examined by using coimmunoprecipitation after pluse-treatment of the cell line with Tk, the anti-CD3 McAb-induced recruitment of ZAP-70 to CD3 zeta chain was observed to be blocked in some extent. This may account for, at least in part, how Trichosanthin was able to inhibit the TCR-triggered T cell proliferation.

Antibodies, Monoclonal↗

PubMed1998

CADASIL syndrome: a genetic form of vascular dementia.

Mental disorders due to cerebral microvascular disease have been known for over 100 years. Recently, an autosomal dominant form of cerebral arteriopathy (CADASIL) has been described in association with a Notch3 family gene on the short arm of chromosome 19. CADASIL causes subcortical lacunar infarction and dementia in over 80% of cases and depression in a large proportion of patients. Clinically, CADASIL may appear to be very similar to hypertensive microvascular disease (Binswanger's disease), a condition that is seen in the elderly. This article reviews the clinical, pathologic, and genetic features of CADASIL. CADASIL is of interest to neurologists and psychiatrists because it is the first syndrome of vascular dementia and depression with an identified gene. How the gene causes the widespread arteriopathy is not yet known. Insights gained from the study of CADASIL should help us better understand its etiology, as well as the options for treatment of the more common forms of microvascular disease seen in the elderly.

Aged↗

PubMed1998

[The ultrasonic treatment of curved, fine and obstructed root canal].

OBJECTIVE: To investigate and evaluate the method of managing curved, fine, and obstructed root canals during endodontic treatment. METHODS: Ultrasonic treatment of such root canals was used in 73 cases. RESULTS: The root canals were enlarged and filled in 69 cases, with a success rate of 94.5%. Fracture of the tooth, lateral perforation of the canal, and breaking of the reamer were not found. Failure occurred in 4 cases where the canals were obstructed. CONCLUSION: The ultrasonic treatment of root canal is an effective, practical, and safe method. Nevertheless, its use in curved and severely obstructed root canals is limited.

Dental Pulp Cavity↗

PubMed1998

[Effects of freeze on Ca2+ and cyclic 3', 5'-adenosine monophosphate level in cultured human retinal pigment epithelial cells].

OBJECTIVE: To investigate the mechanism of retinal pigment epithelial (RPE) cell migration and proliferation at molecular level by measuring the concentrations of intracellular cyclic 3', 5'-adenosine monophosphate (cAMP) and calcium ion (Ca(2+)) level of frozen cultured RPE cells. METHODS: The culture of human RPE cells was frozen for 0s, 15s, 30s, 45s, 60s respectively at -70 degrees C. The concentrations of cAMP and Ca(2+) in cultured human cells were measured by Fura-2/AM fluorescent technique and endogenous protein combination method. RESULTS: After freeze for 15 s, the contents of cAMP and Ca(2+) in RPE cells were not changed significantly compared with the control (no freeze). After freeze for 30s, 45s, 60s respectively, the level of intracellular cAMP was significantly decreased, while the concentration of cytoplasmic free Ca(2+) was markedly increased, showing that the concentration of cAMP and Ca(2+) being antagonistic to each other. With the re-vitalization of RPE cells for 60 minutes, the intracellular free Ca(2+) gradually reduced. CONCLUSIONS: The decreased concentration of cAMP and increased concentration of free Ca(2+) in RPE cells may be the effective mechanism of RPE cell migration and proliferation after cryotherapy, and it possibly plays an important role in the formation of proliferative vitreoretinopathy.

Adolescent↗

PubMed1998

[Isolation, detection toxicity and structure of toxin from Beauveria bassiana].

In this experiment, the crude toxin from the metabolite of Beauveria bassiana was isolated and its toxicity was detected. The result shows that indicates toxin has toxicity on larva of Aedesalbopictus obvious. Though it with low toxicity to larva of Heliothis zea when swallowed, but has high toxicity when injected into the blood. For bacteria it only inhibites G+. When it applied to cultured cells of Spodoptera frugiperda sf-21, the regression equation of toxicity is y = 2.03 + 2.39x. The half lethal concentration (LC50) is 0.01751%. 95% believable limit is 0.01517-0.0202%. There are three substances which have similar atomic group when analysed by HPLC and infrared spectrum.

Aedes↗

PubMed1998

[Study of the effect of zine-oxide phosphorate base on preventing leakage in intracoronal bleaching]

OBJECTIVE: To study the effect of zine-oxide phosphorate base on preventing hydrogen peroxide leakage in intracoronal bleaching. METHODS: Intracoronal bleaching was given to exsomatized teeth,and the amounts of penetrated hydrogen peroxide was determind by spectro-photo-metry. RESULTS: Placement of a zinc oxide phosphorat protective base at CEJ level decreased hydrogen peroxide. penetration dramatically. CONCLUSION: The zine oxide phosphorate base was a kind of effective measure to prevent post-bleaching external cervical ersorption.

Journal Article↗

PubMed1998

[Effect of diazepam on delayed nausea and vomiting caused by anticancer agents].

We conducted an evaluation of the usefulness of antiemetics (5-Hydroxy-tryptamine 3 receptor antagonism, 5HT3RA) combined with diazepam for delayed nausea and vomiting due to anticancer agents in 17 patients with various malignancies (such as lung Ca, breast Ca, esophagus Ca, gastric Ca, colon Ca, and non Hodgkin's disease) for whom chemotherapy was performed with different regimens in the Dept. of Oncologic Chemotherapy, People's Hospital, Beijing Medical University. Antiemetics (5HT3RA) combined with diazepam were given only to cases that had symptoms of nausea and vomiting induced by anticancer agents in the 1st course and invalidity with antiemetics (5HT3RA) alone in this study. Antiemetic (5HT3RA) agents + Dexamethasone were dosed before chemotherapy and also diazepam 5 mg orally after 24 hours (namely, when nausea was observed). Nausea was reduced and vomiting decreased after the antiemetic treatment with 5HT3RA + Dexamethasone and diazepam. These results indicated that 5HT3RA and diazepam combination therapies were more effective than 5HT3 RA + Dexamethasone alone for delayed nausea and vomiting. Further, the antiemetics had characters that a short adminiter time, few times and a take not over dose. The only side effect related to this antiemetic therapy was light somnolence. Antiemetics combined with diazepam might be a useful therapy against delayed nausea and vomiting induced by anticancer agents.

Adult↗

PubMed1997

Suppression of potyvirus infection by coexpressed closterovirus protein.

A tobacco etch virus (TEV)-based expression vector has been used for insertion of several ORFs derived from the unrelated beet yellows virus (BYV). Hybrid TEV variants expressing the BYV capsid protein, 20-kDa protein, or HSP70 homolog systemically infected Nicotiana tabacum and stably retained BYV sequences. In contrast, insertion of the ORF encoding BYV leader proteinase (L-Pro) resulted in severely impaired systemic transport and accumulation of recombinant TEV. Progeny of this virus underwent various deletions affecting the L-Pro sequence and mitigating the defects in virus spread. Model experiments involving several spontaneous and engineered mutants indicated that the central domain of BYV L-Pro was responsible for the defect in hybrid virus accumulation, whereas full-size L-Pro was required for maximal debilitation of systemic transport. Strikingly, BYV L-Pro expression did not debilitate systemic infection of hybrid TEV in Nicotiana benthamiana plants. No major defects in replication or encapsidation of recombinant RNA were revealed in N. tabacum protoplasts. These results indicated that BYV L-Pro specifically interfered with TEV systemic transport and accumulation in a host-dependent manner and suggested a potential utility of closterovirus L-Pro as an inhibitor of potyvirus infection. In addition, it was demonstrated that the 107-amino-acid-residues-long N-terminal part of the TEV helper component proteinase is not essential for systemic infection.

Closterovirus↗

PubMed1997

A repertoire of novel antibacterial diastereomeric peptides with selective cytolytic activity.

The increase in infectious diseases and bacterial resistance to antibiotics has resulted in intensive studies focusing on the use of linear, alpha-helical, cytolytic peptides from insects and mammals as potential drugs for new target sites in bacteria. Recent studies with diastereomers of the highly potent cytolytic peptides, pardaxin and melittin, indicate that alpha-helical structure is required for mammalian cells lysis but is not necessary for antibacterial activity. Thus, hydrophobicity and net positive charge of the polypeptide might confer selective antibacterial lytic activity. To test this hypothesis, a series of diastereomeric model peptides (12 amino acids long) composed of varying ratios of leucine and lysine were synthesized, and their structure and biological function were investigated. Peptide length and the position of D-amino acids were such that short peptides with stretches of only 1-3 consecutive L-amino acids that cannot form an alpha-helical structure were constructed. Circular dichroism spectroscopy showed that the peptides do not retain any detectable secondary structure in a hydrophobic environment. This enabled examination of the sole effect of hydrophobicity and positive charge on activity. The data reveal that modulating hydrophobicity and positive charge is sufficient to confer antibacterial activity and cell selectivity. A highly hydrophobic diastereomer that permeated both zwitterionic and negatively charged phospholipid vesicles, lysed eukaryotic and prokaryotic cells. In contrast, a highly positively charged diastereomer that only permeated slightly negatively charged phospholipid vesicles had low antibacterial activity and could not lyse eukaryotic cells. In the boundary between high hydrophobicity and high positive charge, the diastereomers acquired selective and potent antibacterial activity. Furthermore, they were completely resistant to human serum inactivation, which dramatically reduces the activity of native antibacterial peptides. In addition, a strong synergistic effect was observed at nonlethal concentrations of the peptides with the antibiotic tetracycline on resistant bacteria. The results are discussed in terms of proposed mechanisms of antibacterial activity, as well as a new strategy for the design of a repertoire of short, simple, and easily manipulated antibacterial peptides as potential drugs in the treatment of infectious diseases.

Amino Acid Sequence↗

PubMed1997

Solution structure of recombinant human interleukin-6.

Interleukin-6 (IL-6) is a 185 amino acid cytokine which exerts multiple biological effects in vivo and whose dysregulation underlies several disease processes. The solution structure of recombinant human interleukin-6 has now been determined using heteronuclear three and four-dimensional NMR spectroscopy. The structure of the molecule was determined using 3044 distance and torsion restraints derived by NMR spectroscopy to generate an ensemble of 32 structures using a combined distance geometry/simulated annealing protocol. The protein contains five alpha-helices interspersed with variable-length loops; four of these helices constitute a classical four-helix bundle with the fifth helix located in the CD loop. There were no distance violations greater than 0.3 A in any of the final 32 structures and the ensemble has an average-to-the-mean backbone root-mean-square deviation of 0.50 A for the core four-helix bundle. Although the amino-terminal 19 amino acids are disordered in solution, the remainder of the molecule has a well defined structure that shares many features displayed by other long-chain four-helix bundle cytokines. The high-resolution NMR structure of hIL-6 is used to rationalize available mutagenesis data in terms of a heteromeric receptor complex.

Antigens, CD↗

PubMed1997

Metal-catalyzed oxidation of histidine in human growth hormone. Mechanism, isotope effects, and inhibition by a mild denaturing alcohol.

Metal-catalyzed oxidation of proteins represents an important pathway of post-translational modification. We utilized human growth hormone (hGH), a protein with a well defined metal-binding site, to study the detailed mechanism of metal-catalyzed oxidation by ascorbate/Cu(II)/O2. Particularly His18 and His21 within the metal-binding site were oxidized, predominantly to 2-oxo-His with the incorporated oxygen originating from molecular oxygen, based on amino acid analysis, tryptic mapping, mass spectrometry, isotopic labeling, and 1H NMR. The anaerobic reduction of a hGH/Cu(II) mixture by ascorbate generated a hGH-Cu(I) complex with NMR spectral features different from those of native hGH and hGH/Cu(II). The anaerobic reaction of this hGH-Cu(I) complex with hydrogen peroxide resulted in the oxidation of His18 and His21, suggesting that a fraction of Cu(I) was bound at the metal-binding site of hGH. Site-specific oxidation of hGH required an intact metal-binding site and could largely (about 80%) be inhibited by the presence of >/=28% (v/v) 1-propanol which appears (i) to perturb the metal-binding site and (ii) to interact with a reactive oxygen species formed at the perturbed metal-binding site. The inhibition by 1-propanol-d7 (CD3CD2CD2OH) was significantly lower than that by 1-propanol-h7 with [residual hGH]1-propanol-h7/[residual hGH]1-propanol-d7 = 1.95 at 30% (v/v) 1-propanol, reflecting a kinetic isotope effect close to that for the reaction of a hydroxyl radical with Calpha-H/D bonds of methanol, suggesting the involvement of a hydroxyl radical-like species in the oxidation of His.

1-Propanol↗