Aided versus implanted speech recognition abilities in severe to profound postlingual deafness.
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Adult↗
Biomedical subjects
M H Chung
Publications and source records attributed to M H Chung.
DNA damage in the kidneys of diabetic rats exhibiting microalbuminuria.
8-Hydroxydeoxyguanosine (8-OHdG), an oxygen radical induced modification of purine residue in DNA, was measured in the liver, pancreas, and kidney of streptozotocin-induced diabetic rats (STZR) exhibiting microalbuminuria. At 4 weeks after the injection of streptozotocin (50 mg/kg, i.v.), the rate of urinary albumin excretion was 0.5 +/- 0.1 and 2.0 +/- 0.2 mg/24 h in age-matched control rats (CR) and STZR, respectively. Compared to CR, STZR also showed a significantly increased level of 8-OHdG in the kidney but not the liver and pancreas. Amounts of 8-OHdG/10(5) dG for CR and STZR were 3.4 +/- 0.3 and 5.1 +/- 0.2 for renal cortices, and 4.1 +/- 0.2 and 20.0 +/- 3.7 for renal papillae. Daily injection of insulin (2 U, SC) starting on the third day after streptozotocin treatment significantly reduced both urinary albumin excretion and papillary 8-OHdG formation, which suggests that these are associated with the diabetic state induced by streptozotocin rather than a direct nephrotoxic effect of the drug. This study suggests that formation of 8-OHdG and, therefore, oxidative damage are closely related in the process of diabetic nephropathy.
8-Hydroxy-2'-Deoxyguanosine↗
Moraxella (Branhamella) catarrhalis-induced experimental otitis media in the chinchilla.
Otitis media was introduced in chinchillas by direct transbullar inoculation with either viable or formalin-inactivated Moraxella (Branhamella) catarrhalis. Both groups of animals developed middle ear fluids (MEF) and severe inflammatory changes in the tubotympanum. Pure cultures of M. catarrhalis were recovered for up to 5 days after inoculation from those animals inoculated with viable bacteria. Significantly elevated anti-M. catarrhalis antibody titers were detected in post-inoculation sera and in MEF or bullar lavages, and an increased number of IgG-bearing cells was also observed in the tubotympanum of these animals. Control chinchillas inoculated with pyrogen-free sterile saline failed to show any signs of otitis media. Our data indicate that viable M. catarrhalis induce acute otitis media in the chinchilla but that the bacteria are rapidly eliminated from the middle ear, precluding its usefulness as a model to study acute otitis media. Moreover, the same concentration of nonviable organisms also induces severe inflammatory changes in the middle ear. These data indicate that the chinchilla may be a useful model for studying the role of nonviable M. catarrhalis or its cell wall components on the induction and persistence of inflammation in the middle ear.
Animals↗
Liver function in Clonorchis sinensis-infected rabbits.
Nine rabbits were fed with Clonorchis sinensis metacercariae (MC) and the blood samples chronologically obtained were analyzed biochemically. Rabbits infected by less than 100 flukes were grouped into Group I, and by 100-250 flukes into Group II. The serum level of alanine aminotransferase (ALT) was increased from 3 weeks after the infection of the metacercariae (AIM) and showed a peak at 8 weeks, and decreased from 12 weeks AIM. The serum level of aspartate aminotransferase (AST) was raised to 92.3 +/- 65.4 U/L at 3 weeks AIM and stayed high until 8 weeks, then lowered thereafter. The serum level of gamma-glutamyl transpeptidase (gamma-GT) was increased rapidly to the highest value (18.9 +/- 14.6 U/L) at 16 weeks AIM, and decreased to the control level after 20 weeks. The serum level of alkaline phosphatase (ALP) was headed down from the early infection to 52 weeks AIM. The serum cholesterol level was increased from 8 weeks and reached at a peak 16 weeks AIM, and decreased thereafter to the control level. It is suggested that serum ALT, AST, ALP and gamma-GT tests be useful to diagnose the early infection of C. sinensis.
Animals↗
Egg positive rates of Clonorchis sinensis and intestinal helminths among residents in Kagye-ri, Saengbiryang-myon, Sanchong-gun, Kyongsangnam-do.
Stools of the residents in a village in Saengbiryang-myon, Sanchong-gun, Kyongsangnam-do were examined for the eggs of intestinal helminths. In 1987, infection rate of 76 residents by Clonorchis sinensis was 80.3% with mean eggs per gram of feces (EPG) 27,781. C. sinensis-infected persons were treated once with praziquantel 60 mg/kg, q.i.d. Seventeen persons (22.4%) infected by Metagonimus yokogawai was coinfected with C. sinensis. In 1993, C. sinensis egg positive rate was 48.4% with mean EPG 5,929. Reinfection rate of follow-up cases by C. sinensis was 55.2% during 5 years and 5 months. Infection rate by M. yokogawai was 3.2%. This village was an endemic focus of clonorchiasis occurring reinfection high.
Clonorchiasis↗
General pharmacology of cis-malonato[4R,5R)-4,5-bis-(aminomethyl)-2-isopropyl-1,3- dioxolane]platinum(II).
The general pharmacological properties of cis-malonato-[(4R,5R)-4,5- bis(aminomethyl)-2-isopropyl-1.3-dioxolane]platinum(II) (SKI 2053R, CAS 146665-77-2), a new potential anticancer agent, were investigated in mice, rats, guinea pigs, rabbits, cats and dogs. Intravenous administration of SKI 2053R had no effect on the central nervous system. SKI 2053R had no effect on the autonomic nervous system and smooth muscles except that it slightly inhibited the spontaneous motility of isolated rabbit ileum at a concentration of 5 x 10(-5) g/ml. SKI 2053R did not adversely affect the respiratory-cardiovascular system, gastrointestinal system, neuromuscular junction, or renal function. SKI 2053R did not significantly alter the levels of serum glucose, serum free fatty acid and plasma lactate, and did not induce hemolysis. SKI 2053R did not affect blood coagulation mechanism and liver function. SKI 2053R did not exhibit anti-inflammatory activity. It was observed that SKI 2053R increased the formation of hemolytic plaque by spleen cells of sensitized mice at high doses (10 mg/kg and 35 mg/kg). Therefore, it is concluded from these general pharmacological studies that SKI 2053R at the doses showing antitumor activity does not induce severe adverse effects on the central nervous, autonomic nervous, respiratory-cardiovascular, gastrointestinal, peripheral nervous, and other systems in experimental animals.
Animals↗
Identification of 8-hydroxyguanine glycosylase activity in mammalian tissues using 8-hydroxyguanine specific monoclonal antibody.
Here we report the finding of glycosylase activity in mammalian tissues to remove 8-hydroxyguanine residues from DNA. To detect this activity, a synthetic duplex DNA containing an 8-hydroxyguanine residue was used as the substrate, and before the product was analyzed by HPLC-electrochemical detection (ECD), 8-hydroxyguanine released by the enzymatic action was specifically collected from reactions using immunoaffinity columns of 8-hydroxyguanine specific monoclonal antibody. With the application of immunoaffinity column chromatography, a single peak of 8-hydroxyguanine free from many interfering peaks of unknown origin was clearly demonstrated in HPLC-ECD even with crude tissue extracts used as assay materials. All the tissues of the rats examined showed the activity, suggesting its presence is ubiquitous. The present coupled technique of immunoaffinity column chromatography and HPLC-ECD will be very useful to many future studies of 8-hydroxyguanine glycosylase such as its activity detection, characterization and purification, etc.
Animals↗
Formation, inhibition of formation, and repair of oxidative 8-hydroxyguanine DNA damage.
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Base Composition↗
The alterations of cellular metabolism in the contralateral testis following spermatic cord torsion in rats.
Cellular metabolic study was performed on the contralateral testis after torsion to delineate early testicular changes. In 9-week-old Sprague-Dawley rats the left testicle was rotated and fixed to the scrotum for 3, 8 and 24 hours in 3 groups (I, II and III). Each group was divided into 3 subgroups (a, b and c) by the length of detorsion of 0, 4 hours and 14 days. We measured adenosine triphosphate, total adenosine nucleotides and adenylate energy charge of the contralateral testis by high performance liquid chromatography. Compared to controls, no subgroups showed differences in the histological parameters. Also in subgroups Ia, Ib, Ic and IIa none of the metabolic parameters were significantly altered. However, subgroups IIb and IIc, and group III and its subgroups showed significantly decreased levels of all metabolic parameters. Therefore, it appears that unilateral testicular torsion (greater than 8 hours) and detorsion affect the contralateral testicular metabolism without gross histological changes in rats, and these changes seem to be reversible in terms of cellular recoverability because the maximally decreased level of adenylate energy charge among all subgroups is only 13% compared to controls. These findings suggest that some systemic mechanisms rather than an immunological or local inflammatory process is involved in this early period after torsion.
Adenine Nucleotides↗
Cytological and histological changes in the middle ear after inoculation of influenza A virus.
Experimental otitis media induced in the chinchilla by inoculation of influenza A virus into the middle ear resulted in capillary engorgement, subepithelial hemorrhage, tissue edema and acute inflammatory cell infiltration. Quantitative morphometric measurements were made for 28 days. Ciliated cells appeared to be the primary target of this strain of influenza virus and demonstrated the greatest degree of damage. Three weeks were required to restore the ciliated epithelium in the tubotympanum to normal levels.
Animals↗
Ligand binding characteristics of [3H] dihydroalprenolol in cerebral cortical membranes of young and old senescence-accelerated mouse.
1. The values of both Kd and Bmax of [3H] dihydroalprenolol binding in the cerebral cortical membranes of old-aged (12 month old) SAM-P/1 were not significantly different compared with those of young (2 month old) SAM-P/1. 2. The values of Ki of metoprolol in the young and old aged SAM were 119 +/- 39.5 nM and 157 +/- 55 nM, respectively. 3. The values of beta 1/beta 2 ratio of the young and old aged SAM were 1.67 +/- 0.15 and 1.64 +/- 0.13, respectively. 4. These results suggest that there were no significant changes of binding characteristics of beta 1 and beta 2 adrenoceptors during aging in the cerebral cortex of SAM.
Aging↗
DNA strand cleavage at 8-hydroxyguanine residues by hot piperidine treatment.
The two findings indicate that 8-hydroxyguanine(8-OH-Gua) is a hot piperidine-sensitive lesion in DNA. These are cleavages of DNA containing 8-OH-Gua at the site of this residue and decomposition of 8-hydroxydeoxyguanosine when the DNA and nucleoside were treated in 1 M piperidine for 30 min at 90 degrees C. However, no cleavage was observed in DNA containing 8-hydroxyadenine or O6-methylguanine. 8-OH-Gua was found to be different from apurinic sites that are also alkali-labile lesions since the former was more resistant to alkali treatment. This property of 8-OH-Gua can be used as a check for the incorporation of this base into DNA after the synthesis of DNA containing 8-OH-Gua at a specific position or possibly can be one of the markers for the identification of 8-OH-Gua formed in DNA exposed to reactive oxygen species.
Base Sequence↗
Protection of DNA damage by dietary restriction.
Dietary restriction is known to retard the aging processes and delay the onset of age-related neoplastic diseases. The mechanisms underlying these remarkable actions of nutritional intervention are not known in spite of recently intensified research efforts. However, the last couple of years' research on dietary restriction produced strong evidence indicating that its effective antiaging actions might be related to its ability to modulate free radical damage. In the present study, DNA damage and attenuation of the damage by dietary restriction were assessed by measuring 8-hydroxydeoxyguanosine 8-OH dG) in both nuclear DNA (nuDNA) and mitochondrial DNA (mitDNA) fractions. The data show that substantially more damage (approximately 15 times) occurred in mitDNA compared to nuDNA. More interestingly, the DNA damage was significantly attenuated in dietarily restricted rats.
Animals↗
Ubiquitous presence in mammalian cells of enzymatic activity specifically cleaving 8-hydroxyguanine-containing DNA.
Here we report the finding of enzymatic activity that specifically cleaves DNA containing 8-hydroxyguanine (oh8Gua) residues in various mammalian cells. To detect this activity, we used a synthetic double-stranded DNA containing a single oh8Gua at a defined position as the substrate, and analyzed the products of enzymatic digestion by polyacrylamide gel electrophoresis. Two cleavage sites near the oh8Gua residue were detected with partially purified fractions from cow brain and rat liver, and also with preparations from all mammalian tissues examined. These results suggest that enzymatic activity for the removal of oh8Gua from DNA is widely distributed in mammalian cells.
Animals↗
An endonuclease activity in human polymorphonuclear neutrophils that removes 8-hydroxyguanine residues from DNA+.
An endonuclease that specifically removes 8-hydroxyguanine (oh8Gua) from DNA has been isolated from Escherichia coli. As the amount of oh8Gua produced in DNA of X-ray-irradiated mice is known to decrease with time after irradiation, an attempt was made to find a similar activity in human polymorphonuclear neutrophils (PMNs) using a synthetic dsDNA containing oh8Gua as a substrate. The PMN enzyme was isolated free of other DNases, and found to cleave the substrate DNA simultaneously at 2 sites, the phosphodiester bonds 5' and 3' to oh8Gua, producing free hydroxyl and phosphate groups, respectively. The enzyme showed almost no activity on DNAs containing other kinds of modified base tested or mismatched DNA. Thus human cells also contain an endonuclease that specifically removes oh8Gua residues from DNA.
Base Sequence↗
8-oxoguanine (8-hydroxyguanine) DNA glycosylase and its substrate specificity.
Substrate specificities of FPG protein (also known as formamidopyrimidine DNA glycosylase) and 8-hydroxyguanine endonuclease were compared by using defined duplex oligodeoxynucleotides containing single residues of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxodA), and 2,6-diamino-4-hydroxy-5-(N-methyl)formamidopyrimidine (Me-Fapy). Duplexes containing 8-oxodG positioned opposite dC, dG, or dT were cleaved, whereas single-stranded DNA and duplexes containing 8-oxodG.dA or 8-oxodA positioned opposite any of the four DNA bases were relatively resistant. Both enzymes cut duplexes containing 8-oxoG.dC 3' and 5' to the modified base but failed to cleave duplex DNA containing synthetic abasic sites, mismatches containing dG, or unmodified DNA. 8-Oxoguanine, identified by HPLC-electrochemical detection techniques, was released during the enzymatic reaction. Apparent Km values for FPG protein acting on duplex substrates containing a single Me-Fapy or 8-oxodG residue positioned opposite dC were 41 and 8 nM, respectively, and those for 8-hydroxyguanine endonuclease were 30 and 13 nM, respectively. Comparison of the properties of the two enzyme activities suggest that they are identical. In view of the widespread distribution of 8-oxodG in cellular DNA, the demonstrated miscoding and mutagenic properties of this lesion, and the existence of a bacterial gene coding for FPG protein, we propose that 8-oxodG DNA is the primary physiological substrate for a constituent glycosylase found in bacteria and mammalian cells.
Base Sequence↗
An endonuclease activity of Escherichia coli that specifically removes 8-hydroxyguanine residues from DNA.
An enzyme that specifically removes an 8-hydroxyguanine (8-OH-Gua) residue in DNA has been purified from Escherichia coli. To assay the enzymatic activity, a synthetic double-stranded DNA (dsDNA) containing 8-OH-Gua at a defined position was used as a substrate. The substrate DNA was simultaneously cleaved at 2 sites, i.e., the phosphodiester bonds 5' and 3' to 8-OH-Gua, leaving a phosphate at each of the neighboring deoxynucleosides. The cleavage was observed only in dsDNA, but not with single-stranded DNA containing 8-OH-Gua. This enzyme showed almost no activity on DNAs containing other kinds of modified bases such as 8-hydroxyadenine, O6-methylguanine and N7-methylguanine. Also DNAs containing mismatches (A/G or C/T) were not cleaved. Studies on several other properties of this enzyme indicate that it differs from endonucleases previously isolated from E. coli, indicating that it is likely to be an endonuclease which specifically recognizes 8-OH-Gua in dsDNA.
Base Composition↗
Monte Carlo calculation and silicon detector measurement of the hot particle dose.
In our study, we quantitatively compared the hot particle dose calculated by our microcomputer Monte Carlo electron transport code, Eltran3, with the values calculated by the VARSKIN code. For a weightless source, the VARSKIN code overestimated the skin dose by 14% to 37% because the VARSKIN code is based on the data table for point sources in an unbounded medium. Five 60Co hot particles were measured in the current and pulse mode operations of an ion-implanted silicon detector. The measurements were converted to skin dose rates and compared by use of Eltran3 and VARSKIN calculations. Measured values of the skin dose rates for four of the five hot particles agreed well with expected values. The skin dose rate per kBq of the four hot particles ranged from 0.70 to 0.85 mGy h-1 kBq-1. One of the five hot particles showed the presence of a pure beta-emitting radionuclide, which was not detected through gamma-ray measurements.
Cobalt Radioisotopes↗