Biomedical subjects

H Y Cho

Publications and source records attributed to H Y Cho.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effects of apolipoprotein E phenotypes on the neuropsychological functions of community-dwelling elderly individuals without dementia.

Studies have demonstrated that different apolipoprotein E (APOE) phenotypes appear to modulate the effects of cognitive aging in Caucasian elderly populations. Few studies have investigated the effects of the common APOE alleles on the neuropsychological functioning in other ethnic elderly populations. We examined the different effects of APOE polymorphism on the neuropsychological functions of 213 community-dwelling Korean elderly individuals without dementia. Individuals with APOE epsilon4 allele performed poorly on memory measures, Recency of the Elderly Verbal Learning Test, Immediate and Delayed Reproductions of the Simplified Rey Figure Test (SRFT), the Primary Memory Index, and the Secondary Memory Index. They also performed worse on the sub-scale assessing executive function on the Korean-Dementia Rating Scale (K-DRS). Subjects with APOE epsilon2 allele performed better on visuo-spatial measures, the Construction sub-scale of the K-DRS, and the Copy and Immediate Reproductions of the SRFT.

Aged↗

PubMed2000

Inhibitory effect of Artemisia asiatica alkaloids on acetylcholinesterase activity from rat PC12 cells.

We screened 42 Korean traditional tea plants to determine the inhibitory effect of acetylcholinesterase and attenuation of toxicity induced by amyloid-beta peptide, which were related to the treatment of Alzheimer's disease (AD). The methanolic extract from Artemisia asiatica among tested 42 tea plants, showed the highest inhibitory effect (48%) on acetylcholinesterase in vitro. The methanolic extract was further separated with n-hexane, chloroform, and ethyl acetate of water, in order. The chloroform solubles, which were high in inhibitory effect of acetylcholinesterase, were repeatedly subjected to open column chromatography on silica gel. From the highest inhibitory fraction (78%) on acetylcholinesterase, the single compound was obtained by the Sep-Pak Cartridge (C18: reverse phase column). This compound was found to react positively on Dragendorff's reagent (potassium bismuth iodide), which typically reacted with the alkaloid. This compound was purified by HPLC (mu-bondapack C18 reverse phase column: 3.9 x 150 mm). The IC50 (the concentration of 50% enzyme inhibition) value of this compound was 23 micrograms/ml and the inhibitory pattern on acetylcholinesterase was mixed with competitive/non-competitive type. We examined the effects of this compound on toxicity induced by A beta (25-35) in rat pheochromocytoma PC12 cells. Pretreatment of the PC12 cells for 2 h with an alkaloid of Artemisia asiatica (1200 microg/ml) reduced the toxicity induced by A beta. This study demonstrated that an alkaloid of Artemisia asiatica, which was metabolized to small molecule in digestive tract and then could pass through the blood-brain barrier, appeared to be an acetylcholinesterase inhibitor with a blocker of neurotoxicity induced by A beta in human brain causing Alzheimer's disease.

Acetylcholinesterase↗

PubMed2000

Role of the glutamate 332 residue in the transglycosylation activity of ThermusMaltogenic amylase.

A sequence alignment shows that residue 332 is conserved as glutamate in maltogenic amylases (MAases) and in other related enzymes such as cyclodextrinase and neopullulanase, while the corresponding position is conserved as histidine in alpha-amylases. We analyzed the role of Glu332 in the hydrolysis and the transglycosylation activity of Thermus MAase (ThMA) by site-directed mutagenesis. Replacing Glu332 with histidine reduced transglycosylation activity significantly, but enhanced hydrolysis activity on alpha-(1,3)-, alpha-(1,4)-, and alpha-(1,6)-glycosidic bonds relative to the wild-type (WT) enzyme. The mutant Glu332Asp had catalytic properties similar to those of the WT enzyme, but the mutant Glu332Gln resulted in significantly decreased transglycosylation activity. These results suggest that an acidic side chain at position 332 of MAase plays an important role in the formation and accumulation of transfer products by modulating the relative rates of hydrolysis and transglycosylation. From the structure, we propose that an acidic side chain at position 332, which is located in a pocket, is involved in aligning the acceptor molecule to compete with water molecules in the nucleophilic attack of the glycosyl-enzyme intermediate.

Acarbose↗

PubMed2000

Molecular characterization of a dimeric intracellular maltogenic amylase of Bacillus subtilis SUH4-2.

An additional amylase besides the typical alpha-amylase was detected in the cytoplasm of Bacillus subtilis SUH4-2, an isolate from Korean soil. The corresponding gene encoded a maltogenic amylase, which hydrolyzed cyclodextrin or starch to maltose and glucose; pullulan to panose; acarbose to glucose and acarviosine-glucose. Maltogenic amylase of B. subtilis SUH4-2 transferred sugar molecules to form various branched oligosaccharides upon the hydrolysis of substrates. The enzyme existed in a monomer-dimer equilibrium with a molar ratio of 3:2 in 50 mM KH(2)PO(4)-NaOH buffer (pH 7.0). The maltogenic amylase is most likely to be associated with carbohydrate metabolism in the cytoplasm, since the nucleotide sequence of the gene was highly homologous to the yvdF gene of B. subtilis 168, which is located in a gene cluster involved in maltose/maltodextrin utilization.

ATP-Binding Cassette Transporters↗

PubMed2000

Analysis of essential leucine residue for catalytic activity of novel thermostable chitosanase by site-directed mutagenesis.

Bacterial chitosanases share weak amino acid sequence similarities at certain regions of each enzyme. These regions have been assumed to be important for catalytic activities of the enzyme. To verify this assumption, the functional importance of the conserved region in a novel thermostable chitosanase (TCH-2) from Bacillus coagulans CK108 was investigated. Each of the conserved amino acid residues (Leu64, Glu80, Glu94, Asp98, and Gly108) was changed to aspartate and glutamine or asparagine and glutamate by site-directed mutagenesis, respectively. Kinetic parameters for colloidal chitosan hydrolysis were determined with wild-type and 10 mutant chitosanases. The Leu64 --> Arg and Leu64 --> Gln mutations were essentially inactive and kinetic parameters such as Vmax and kcat were approximately 1/10(7) of those of the wild-type enzyme. The Asp98 --> Asn mutation did not affect the Km value significantly, but decreased kcat to 15% of that of wild-type chitosanase. On the other hand, the Asp98 --> Glu mutation affected neither Km nor kcat. The observation that approximately 15% of activity remained after the substitution of Asp98 by Asn indicated that the carboxyl side chain of Asp98 is not absolutely required for catalytic activity. These results indicate that the Leu64 residue is directly involved in the catalytic activity of TCH-2.

Amino Acid Sequence↗

PubMed2000

Scleral melanocytosis and oculodermal melanocytosis (nevus of Ota) in Chinese children.

Two thousand nine hundred fourteen Chinese children (1510 males and 1404 females) were examined for the presence of scleral melanocytosis (SM) and oculodermal melanocytosis in a cross-sectional prevalence survey. SM was found in 4.9% of boys and 4.1% of girls under the age of 1 year. The peak prevalence was at 6 years of age, when 44.6% of boys and 46.6% of girls were affected. At 18 years of age, only 11.1% of boys and 13.2% of girls had SM. The overall prevalence, regardless of age, was 27.6% in boys and 27. 1% in girls. The condition was bilateral in 78% of cases. The medial superior quadrant was the most frequently affected site, and the lateral inferior quadrant was the least frequently affected site. Oculodermal melanocytosis occurred only in one patient; the pigmentation affected the left side of the face and the ipsilateral sclera.

Adolescent↗

PubMed2000

Thermostable chitosanase from Bacillus sp. Strain CK4: cloning and expression of the gene and characterization of the enzyme.

A thermostable chitosanase gene from the environmental isolate Bacillus sp. strain CK4, which was identified on the basis of phylogenetic analysis of the 16S rRNA gene sequence and phenotypic analysis, was cloned, and its complete DNA sequence was determined. The thermostable chitosanase gene was composed of an 822-bp open reading frame which encodes a protein of 242 amino acids and a signal peptide corresponding to a 30-kDa enzyme. The deduced amino acid sequence of the chitosanase from Bacillus sp. strain CK4 exhibits 76.6, 15.3, and 14.2% similarities to those from Bacillus subtilis, Bacillus ehemensis, and Bacillus circulans, respectively. C-terminal homology analysis shows that Bacillus sp. strain CK4 belongs to cluster III with B. subtilis. The gene was similar in size to that of the mesophile B. subtilis but showed a higher preference for codons ending in G or C. The enzyme contains 2 additional cysteine residues at positions 49 and 211. The recombinant chitosanase has been purified to homogeneity by using only two steps with column chromatography. The half-life of the enzyme was 90 min at 80 degrees C, which indicates its usefulness for industrial applications. The enzyme had a useful reactivity and a high specific activity for producing functional oligosaccharides as well, with trimers through hexamers as the major products.

Amino Acid Sequence↗

PubMed2000

Neutrophil-dependent and neutrophil-independent alterations in the nasal epithelium of ozone-exposed rats.

Ozone induces epithelial hyperplasia and mucous cell metaplasia (MCM) in nasal transitional epithelium (NTE) of rats. A transient neutrophil influx accompanies upregulation of mucin messenger RNA (mRNA) before the onset of MCM. The present study was designed to examine the role of neutrophils in ozone-induced epithelial changes in the NTE of rats. Fourteen hours before inhalation exposure, male F344/N rats were injected intraperitoneally with antirat neutrophil antiserum to deplete circulating neutrophils, or were injected with normal (control) serum. Rats were then exposed to 0 ppm (filtered air) or 0.5 ppm ozone (8 h/d) for 1 or 3 d. Maxilloturbinates lined with NTE were analyzed to determine the epithelial labeling index; numeric densities of neutrophils, total epithelial cells, and mucous secretory cells; amount of stored intraepithelial mucosubstances; and steady-state ratMUC-5AC (mucin) mRNA levels. At 2 h after 3 d of exposure, rats treated with antiserum had 90% fewer circulating neutrophils than did rats treated with control serum. Antiserum-treated, ozone-exposed rats had 87% fewer infiltrating neutrophils than did control serum-treated, ozone-exposed rats. At 4 d after 3 d of exposure, antiserum-treated, ozone-exposed rats had 66% less stored intraepithelial mucosubstances and 58% fewer mucous cells in their NTE than did control serum-treated, ozone-exposed rats. Antiserum treatment had no effects on ozone-induced epithelial cell proliferation or mucin mRNA upregulation. The results of this study indicated that ozone-induced MCM was neutrophil-dependent, whereas ozone-induced epithelial cell proliferation and mucin gene upregulation were neutrophil-independent.

Animals↗

PubMed1999

Effects of pre-existing rhinitis on ozone-induced mucous cell metaplasia in rat nasal epithelium.

Ozone causes rhinitis and nasal epithelial alterations. The toxicity of ozone on nasal airways with pre-existing rhinitis has not been investigated. The present study was designed to determine the effect of endotoxin-induced rhinitis on ozone-induced epithelial alterations, especially mucous cell metaplasia (MCM), in the nasal transitional epithelium (NTE) of rats. Six h prior to daily inhalation exposure, male F344/N rats were intranasally instilled with saline or endotoxin (100 microgram/day). Rats were killed 2 h or 4 days after 3-day (8 h/day) exposure to ozone (0.5 ppm) or filtered air (0 ppm). The maxilloturbinate from one nasal passage was processed for morphometric analyses of the numbers of neutrophils and epithelial cells and the amount of intraepithelial mucosubstances (IM) in the NTE. The maxilloturbinate from the other nasal passage was processed for a mucin-specific (rMuc-5AC) mRNA analysis. At 2 h postexposure, endotoxin/ozone-exposed rats had 48 and 3 times more neutrophils in the NTE than did saline/air- and saline/ozone-exposed rats, respectively. Ozone-exposed rats had 35% more NTE cells and 2-fold more mucin mRNA than did saline/air-exposed rats, independent of endotoxin exposure. At 4 days postexposure, endotoxin/ozone-exposed rats had 5 and 2 times more IM and mucous cells, respectively, than did saline/air- and saline/ozone-exposed rats. Though endotoxin/air-exposed rats killed at 2 h postexposure had more neutrophils (40-fold), epithelial cells (27%) and mucin mRNA (2-fold) in the NTE than did saline/air-exposed rats, no MCM was present in those rats killed at 4 days postexposure. The results of the present study indicated that pre-existing rhinitis augments ozone-induced MCM.

Animals↗

PubMed1999

Kinetics of inactivation of Bacillus subtilis spores by continuous or intermittent ohmic and conventional heating.

Bacillus subtilis spores were suspended in 0.1% NaCl solution (ca. 10(7) CFU/mL) and treated by conventional or ohmic heating under identical temperature histories. Temperatures tested were in the range of 88 to 99 degrees C. Survival curves and calculated D values showed significantly higher lethality for spores by ohmic than conventional heating. The z or Ea values corresponding to the two heating methods, however, were not significantly different. Spores of B. subtilis were suspended in nutrient broth and treated with conventional and ohmic heating through a single- or a double-stage treatment. In case of double-stage treatment, heating was interrupted by a 20 min of incubation at 37 degrees C to induce a Tyndallization effect. Spore inactivation during double-stage treatment was greater for ohmic than conventional heating. The enhanced spore inactivation by ohmic, compared with conventional, heating resulted from a greater rate of spore death during the first stage of heating and greater decrease in count of viable spores immediately after the incubation period that intervened the heating process. Thus it is concluded that spore inactivation during ohmic heating was primarily due to the thermal effect but there was an additional killing effect caused by the electric current.

Bacillus subtilis↗

PubMed1999

Inflammatory and epithelial responses during the development of ozone-induced mucous cell metaplasia in the nasal epithelium of rats.

Rats repeatedly exposed to high ambient concentrations of ozone develop mucous cell metaplasia (MCM) in the nasal transitional epithelium (NTE). The present study was designed to determine the temporal relationships of ozone-induced inflammatory and epithelial responses and their correlation with subsequent MCM in the NTE of rats. Male F344/N rats were exposed to 0.5 ppm ozone, 8 h/day for 1, 2, or 3 days. Two h prior to sacrifice, all the rats were injected intraperitoneally with 5'-bromo-2-deoxyuridine (BrdU) to label epithelial cells undergoing DNA synthesis. Rats exposed to ozone for 1 or 2 days were killed 2 h after the exposure. Rats exposed to ozone for 3 days were killed 2 h or 1, 2, or 4 days after the exposure. Control rats were killed after a 7-day exposure to filtered air. One nasal passage from the anterior nasal cavity of each rat was fixed and processed for light microscopy to morphometrically determine the numeric densities of epithelial cells, neutrophils, and mucous cells, and the amount of intraepithelial mucosubstances in the NTE. The maxilloturbinate from the other nasal passage was processed for analysis of an airway mucin-specific gene (i.e., rMuc-5AC mRNA). Acute ozone exposure induced a rapid increase in rMuc-5AC mRNA levels prior to the onset of MCM, and the increased levels of rMuc-5AC mRNA persisted with MCM. Neutrophilic inflammation coincided with epithelial DNA synthesis and upregulation of rMuc-5AC, but was resolved when MCM first appeared in the NTE. The results of the present study suggest that upregulation of mucin mRNA by acute ozone exposure may be associated with the concurrent neutrophilic inflammation and epithelial hyperplasia in the NTE. Ozone-induced MCM may be dependent on these important pre-metaplastic responses (i.e., mucin mRNA upregulation, neutrophilic inflammation, and epithelial proliferation).

Administration, Inhalation↗

PubMed1999

Hypohidrosis in children.

Hypohidrosis has many causes. The condition may be generalised or segmental, acute or progressive and central or peripheral in origin. Most of the causes can be diagnosed from the history and physical examination. Laboratory investigations are usually not necessary. Treatment should be directed at the underlying cause whenever possible.

Child↗

PubMed1999

Nocturnal leg cramps in children: incidence and clinical characteristics.

The records of 2527 healthy children seen in an ambulatory care clinic were evaluated for nocturnal leg cramps in the preceding 12 months, frequency and duration of the cramps, whether the cramps affected one leg or both legs at a time, whether there was associated muscle cramps in feet, whether the cramps occurred when the child was awake or asleep, and whether there was residual tenderness in the affected muscles. Nocturnal leg cramps were present in 185 children for an overall incidence of 7.3%. Leg cramps were noted only in children aged > or = 8 years. The incidence increased at 12 years and peaked at 16 to 18 years of age. A majority (81.6%) of the affected children had nocturnal leg cramps 1 to 4 times per year. The mean duration of episodes was 1.7 minutes. Leg cramps were unilateral in 98.9% of cases and the ipsilateral foot also was involved in 18.9% of cases. One hundred thirty-five (73%) children had leg cramps while asleep, and the remaining 23 (12.4%) children had leg cramps in either state. Fifty-seven (30.8%) children had residual tenderness in the affected muscles. The mean duration of residual tenderness was 33.2 minutes (range: 2 minutes-1 day). We conclude that nocturnal leg cramps are common in children aged > 12 years. A majority of the affected children have leg cramps 1 to 4 times per year. The cramps are usually unilateral and occur when the children are asleep. Normal duration of the leg cramp is < 2 minutes. Residual tenderness is present in approximately 30% of the affected children. Residual tenderness, if present, usually lasts for half an hour.

Adolescent↗

PubMed1998

Pruritus in children.

Pruritus is the most common of all dermatological complaints. Although pruritus is usually due to a primary skin disease, it may be a manifestation of a systemic illness. The majority of causes can be diagnosed from the history and physical examination. Laboratory investigations are usually not necessary. Treatment should be directed at the underlying cause whenever possible.

Child↗

PubMed1997

Hydrogen peroxide inhibits gap junctional intercellular communication in glutathione sufficient but not glutathione deficient cells.

Cell to cell communication via gap junctions is essential in the maintenance of the homeostatic balance of multicellular organisms. Aberrant intercellular gap junctional communication (GJIC) has been implicated in tumor promotion, neuropathy and teratogenesis. Oxidative stress has also been implicated in similar pathologies such as cancer. We report a potential link between oxidative stress and GJIC. Hydrogen peroxide, a known tumor promoter, inhibited GJIC in WB-F344 rat liver epithelial cells with an I50 value of 200 microM. Inhibition of GJIC by H2O2 was reversible as indicated by the complete recovery of GJIC with the removal of H2O2 via a change of fresh media. Free radical scavengers, such as t-butyl alcohol, propylgallate, and Trolox, did not prevent the inhibition of GJIC by H2O2, which indicated that the effects of H2O2 on GJIC was probably not a consequence of aqueous free radical damage. The depletion of intracellular GSH reversed the inhibitory effect of H2O2 on GJIC. The treatment of glutathione-sufficient cells with H2O2 resulted in the hyperphosphorylation of connexin43, which is the basic subunit of the hexameric gap junction protein, as determined by Western blot analysis. TPA, a well-known tumor promoter, also inhibits GJIC via hyperphosphorylation of GJIC, which is a result of protein kinase-C activation. However, H2O2 also induced hyperphosphorylation in GSH-deficient cells that had normal rates of GJIC. Therefore, the mechanism of GJIC inhibition must be different from the TPA-pathway and involves GSH.

Animals↗

PubMed1997

Leg cramps in children.

Most leg cramps are benign and self-limited. Idiopathic nocturnal leg cramp is the most common from of cramps. Occasionally, leg cramps may signify a significant systemic disorder. Investigations are usually not necessary unless indicated by the history or physical examination. Symptomatic treatment consists of stretching the affected calf muscle by forcible dorsiflexion of the foot.

Child↗

PubMed1996

Constipation in children.

Constipation is a common childhood condition, estimated to occur in 5 to 10 percent of children. In most cases, the cause is functional. However, constipation may occasionally indicate a significant organic disorder, which can usually be determined by a thorough history and physical examination. Constipation that is present from birth or that begins in the neonatal period is most likely to be congenital in origin. Acute constipation usually has an organic cause, while chronic constipation usually has a functional cause. Failure to thrive and gross distention of the abdomen suggest the diagnosis of Hirschsprung's disease. Rectal examination of a child with constipation usually reveals a distended rectum that is full of stool. In patients with Hirschsprung's disease, the rectum is usually empty and tight. Laboratory investigations are usually not necessary in patients with mild constipation. Treatment should be directed at the underlying cause. Functional constipation can be managed by changes in diet, regular bowel habits and, if necessary, pharmacologic therapy and biofeedback training.

Cathartics↗

PubMed1988

Thermostable dipeptidase from Bacillus stearothermophilus: its purification, characterization, and comparison with aminoacylase.

Dipeptidase (dipeptide hydrolase [EC 3.4.13.11]) has been purified to homogeneity and crystallized from the cell extract of Bacillus stearothermophilus IFO 12983. The enzyme has a molecular weight of about 86,000, and is composed of two subunits identical in molecular weight (43,000). The enzyme contains 2 g atoms of zinc per mol of protein. A variety of dipeptides consisting of glycine or only L-amino acids serve as substrates of the enzyme; Km and Vmax values for L-valyl-L-alanine are 0.5 mM and 68.0 units/mg protein, respectively. The enzyme is significantly stable not only at high temperatures but also on treatment with protein denaturants such as urea and guanidine hydrochloride. The enzyme also catalyzes hydrolysis of several N-acylamino acids with Vmax values 3-30% of those for the hydrolysis of dipeptides. The thermostable dipeptidase shares various properties with bacterial aminoacylase [EC 3.5.1.14]: their subunit molecular weight, metal content and requirement, amino acid composition, and amino acid sequence in the N-terminal region are very similar.

Amidohydrolases↗