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Biomedical subjects

J W Yang

Publications and source records attributed to J W Yang.

At least 37 records · Page 2Linked to original sources
PubMed2000

A new method to control electrolytes pH by circulation system in electrokinetic soil remediation.

To simultaneously avoid a decrease of electro-osmotic flow by hydrogen ions and to increase heavy metal precipitation due to hydroxide ions, simulated electrokinetic remediation was conducted in saturated kaolinite specimens loaded with lead(II) using an electrolyte circulation method to control electrolyte pH. At an electrolyte circulation rate of 1.1 ml/min, it was possible to increase the anolyte pH from 2 to 4 and decrease the catholyte pH from 12 to 8. Using electrolyte circulation, it was observed that the rate of decrease of clay pH due to the change of electrolyte pH was reduced. As a result, the operable period was extended and the removal efficiency for lead(II) was also increased. It was observed that most of the effluent lead(II) from the cathode compartment was electroplated onto the cathode and that residual effluent lead(II) did not precipitate onto, or adsorb to, the clay at the anode compartment during circulation. Therefore, there was no need to treat the electrolyte because there was virtually no effluent from the cathode compartment in the circulation system. It was also found that the electrolyte volume required to sustain the electrolytic reaction was sufficient for the whole electrokinetic remediation process.

Electrochemistry↗
PubMed2000

Human mini-chromosomes with minimal centromeres.

We have introduced a 6.5 Mb human mini-chromosome with a complex centromere structure into DT40 cells and have used sequence targeting and telomere-directed chromosome breakage to dissect the sequence requirements for centromere function. These experiments proved that a vertebrate centromere with two blocks of functional alphoid DNA separated by 2.5 Mb can exist as a stable structure in some but not all vertebrate cells. Further experiments indicated that recovery of chromosomes with less than approximately 100 kb of alphoid DNA is very inefficient, suggesting that a functional centromere requires a minimum of approximately 100 kb of alphoid DNA. Mini-chromosomes with minimal centromeres segregate accurately in some but not all vertebrate cells and should be useful for the detection of sequence-specific factors required for vertebrate centromere maintenance.

Animals↗
PubMed2000

Reconstruction of pulp defect using a free finger-pulp flap from an excised extra digit.

We present a case of a post-traumatic finger-pulp reconstruction in which we used a free finger-pulp flap elevated from the excised extra digit in a patient with coincidental polydactyly of the thumb that had not been previously corrected. It resulted in satisfactory reconstruction of the defect with a well-padded, sensitive fingertip (static two-point discrimination of 3 mm) and excellent cosmetic appearance with the simultaneous correction of the polydactyly.

Adult↗
PubMed2000

Molecular characterization of multidrug-resistant Streptococcus pneumoniae isolates in Korea. The Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study Group.

Pulsed-field gel electrophoresis, ribotyping, and fingerprinting analysis of 22 invasive isolates of multidrug-resistant (MDR) pneumococci from Korea showed that 59 to 82% were genetically related. DNA sequencing of the PBP 2B gene showed relatively uniform alterations in nucleotides (5.4 to 7.8%) and amino acids (3.0 to 4. 3%), while Asn-276-->Lys, Arg-285-->Cys and Ser-305-->Phe substitutions were unique to Korean MDR strains, suggesting the spread of a few epidemic clones of resistant pneumococci within Korea.

Anti-Bacterial Agents↗
PubMed2000

Triptolide: a potent inhibitor of NF-kappa B in T-lymphocytes.

AIM: To study the effect of triptolide on the activity of nuclear factor-kappa B (NF-kappa B) and gene expression of I kappa B alpha, a major inhibitor of NF-kappa B, in human Jurkat T cell line. METHODS: Jurkat cells treated with or without PMA/PHA were incubated with varied doses of triptolide for different time periods. The activity of NF-kappa B in Jurkat cells was measured with electrophoretic mobility shift assays (EMSA), and the mRNA expression of I kappa B alpha in Jurkat cells was detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: PMA/PHA treatment was found to induce NF-kappa B activation rapidly. Triptolide treatment decreased the activity of NF-kappa B in both PMA/PHA treated and untreated Jurkat cells. This effect of triptolide was in a dose-dependent manner and was more obvious in cells treated with PMA/PHA. The mRNA expression of I kappa B alpha were upregulated by triptolide, while this effect was more potent in cells without PMA/PHA treatment. CONCLUSION: Triptolide is a potent inhibitor of NF-kappa B activation in T lymphocyte and this effect is partly due to the upregulation of I kappa B alpha mRNA expression.

DNA-Binding Proteins↗
PubMed1999

Huperzine A protects rat pheochromocytoma cells against hydrogen peroxide-induced injury.

The effects of Huperzine A (HupA), a novel acetylcholinesterase inhibitor, on hydrogen peroxide (H2O2) induced cell lesion, level of lipid peroxidation and antioxidant enzyme activities were investigated in rat pheochromocytoma line PC12. Following a 6-h exposure of the cells to H2O2 (200 microM), a marked reduction in cell survival and activities of glutathione peroxidase and catalase, as well as increased production of malondialdehyde (MDA) were observed. Pretreatment of the cells with HupA (0.1-10.0 microM) prior to H2O2 exposure significantly elevated the cell survival and antioxidant enzyme activities and decreased the level of MDA. Our results indicated that in addition to its anticholinesterase effects, HupA had protective effects against free radical-induced cell toxicity, which might be beneficial for the treatment of Alzheimer's disease.

Alkaloids↗
PubMed1997

The effect of oxidizing cholesterol on gastrointestinal absorption, plasma clearance, tissue distribution, and processing by endothelial cells.

Little is known about the absorption or metabolism of oxysterols. Toward better appreciating the metabolic consequences of oxidizing cholesterol, we compared labeled cholesterol with the labeled oxysterols 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, and 7-ketocholesterol prepared from [4-14C]cholesterol, [26,26,26,27,27,27-2H6]cholesterol, and [23,24,25,26,27-13C5] cholesterol. Gastrointestinal absorption of oxysterols in rats was 91.5 +/- 0.3% compared with 75 +/- 1.1% for cholesterol, determined by fecal collection (P < .001). When injected intravenously and followed by gas chromatography/mass spectrometry, 7 alpha-hydroxycholesterol was cleared at 23 times the rate of cholesterol. After 5 minutes, only 1.2 +/- 0.2% of 7 alpha-hydroxycholesterol remained in the plasma, whereas 28.0 +/- 1.7% of cholesterol and 40.0 +/- 2.5% of a triglyceride emulsion injected simultaneously were still present. [14C]7 alpha-Hydroxycholesterol injected intravenously was also rapidly cleared from plasma, was widely distributed in tissues and organs, and showed evidence of extensive metabolism at 5 minutes. The fractional rate of uptake of radiolabeled oxysterols by cultured endothelial cells was 15.7 times that of cholesterol (P < .001), and the fractional rate of efflux was 3.4 times that of cholesterol (P < .001). Oxysterols passed through endothelial cells grown on transwell membranes at a rate 4.3 times that of cholesterol (P < .001). Fractional oxysterol transport across the endothelial cell monolayer was increased 62 +/- 17% when HDL was added to the medium in the lower chamber (P = .003). Oxysterols were extensively metabolized to even more polar metabolites during endothelial cell transit. These properties of oxysterols potentially provide a mechanism for enhancing transport of cholesterol through tissues and preventing accumulation of cholesterol in those cells that can oxidize it.

Animals↗
PubMed1997

Malakoplakia of the prostate: a case report.

Malakoplakia is an unusual chronic inflammatory disease that was first discovered in the urinary bladder but has subsequently been described in other sites. Characteristic gross and microscopic features of the lesions have been well described. The diagnosis of this tumor-like lesion can only be established by pathologic examination of the involved tissue. A case of prostatic malakoplakia with characteristic gross and microscopic features is reported in a 59-year-old man who presented with urinary frequency and a diminished urinary stream. Clinically the condition mimicked carcinoma of the prostate gland and the patient underwent a radical retropubic prostatectomy. Postoperative recovery was uneventful. The clinical and pathological findings, differential diagnosis and pertinent literature are reviewed. Preoperative needle biopsy or intraoperative frozen section for tissue diagnosis is recommended to avoid unnecessary radical surgery for this type of tumor-like lesion.

Humans↗
PubMed1996

Relation between plasma leptin concentration and body fat, gender, diet, age, and metabolic covariates.

We measured plasma leptin concentrations by RIA in 204 normal weight and obese subjects, aged 18-80 yr, using full-length recombinant human leptin as a standard. Fasting levels between 1.2-97.9 ng/mL were observed. The plasma leptin concentration was highly correlated with percent body fat (r = 0.710; P < 0.0001) and was 3 times as high in women as in men (17.1 vs. 5.8 ng/mL; P < 0.0001). Circulating leptin was inversely related to age and was reduced 53% in subjects over age 60 yr. A statistical model containing percent body fat, gender, and age accounted for 65% of the variance in plasma leptin levels. Leptin was not independently related to abdominal fat distribution, plasma lipids and lipoproteins, chronic energy intake, diet composition, plasma insulin, or maximum oxygen consumption. However, plasma leptin was reduced by 26% in 5 obese subjects who consumed a 1000-Cal diet for 10 days (P = 0.004). We conclude that circulating leptin rises continuously with increasing adiposity. Gender, age, and short term caloric restriction may be important secondary regulators of plasma leptin.

Adipose Tissue↗
PubMed1995

Lagophthalmos in a multibacillary population under multidrug therapy in the People's Republic of China.

Lagophthalmos may be the most common potentially blinding ocular condition in leprosy. The magnitude of the problem among multibacillary patients has not been determined. We sought to ascertain the magnitude of lagophthalmos in a multibacillary leprosy patient population under multidrug therapy (MDT) (both newly diagnosed and with a prior history of dapsone monotherapy) in China and assess factors associated with its presence. In a survey of 640 multibacillary patients 3.8% of the newly diagnosed patients and 10.2% of the patients with prior dapsone monotherapy had lagophthalmos. Corneal disease and vision loss were common in both groups. Poor compliance with MDT, duration between onset and diagnosis, and duration on dapsone monotherapy were associated with the presence of lagophthalmos. Our findings suggest that there may be a threshold at which MDT must be maintained to prevent lagophthalmos. Early leprosy diagnosis and treatment would also lessen the incidence of lagophthalmos in these patients. The high proportion of lagophthalmos patients with corneal disease suggests that there has been inadequate eye care for these patients.

Adult↗
PubMed1995

A 5' splice-region mutation and a dinucleotide deletion in the lysosomal acid lipase gene in two patients with cholesteryl ester storage disease.

Cholesteryl ester storage disease (CESD) results from inherited deficiencies of the lysosomal hydrolase, acid lipase (LAL; E.C. 3.1.1.13). To establish the molecular defects in LAL deficiency, two unrelated probands with severely reduced LAL activity were examined. DNA amplification by reverse-transcription polymerase chain reaction and subsequent sequence analysis of LAL cDNA identified two mutant alleles. Patient 1, presenting with hepatosplenomegaly, mildly elevated liver function tests, and hyperlipidemia, was homozygous for a deletion of nucleotides 823 to 894 of the LAL cDNA. This 72-bp deletion maintained the reading frame and resulted in a loss of 24 amino acids from the LAL protein. Analysis of genomic DNA revealed that the 72 bp corresponded to an exon of the LAL gene. A single G to A point mutation at the last exon position was observed in the genomic DNA of patient 1, indicating a splicing defect with consecutive exon skipping underlying the 72-bp deletion. Patient 2 was a compound heterozygote for the 72-bp deletion and a dinucleotide deletion at positions 967 and 968. This deletion resulted in a shifted reading frame carboxyterminal of codon 296, and 43 random amino acids followed the frame shift. A premature stop at codon 339 truncated the mutant LAL protein by 34 amino acids. Allele-specific hybridization confirmed that patient 1 was homozygous for the 72-bp deletion mutation, and that patient 2 was a compound heterozygote for the 72-bp deletion and the 2-bp deletion.

Adult↗
PubMed1994

Differentiation of human bone marrow osteogenic stromal cells in vitro: induction of the osteoblast phenotype by dexamethasone.

Human bone marrow stromal cells were examined for their osteogenic potential in an in vitro cell culture system. Dexamethasone (Dex) treatment induced morphological transformation of these cells from an elongated to a more cuboidal shape, increased their alkaline phosphatase activity and cAMP responses to PTH and prostaglandin E2, and was essential for mineralization of the extracellular matrix. Dex-induced differentiation of human bone marrow stromal cells was apparent after 2-3 days of treatment and reached a maximum at 7-14 days, as judged by alkaline phosphatase activity, although induction of osteocalcin by 1,25-dihydroxyvitamin D3 was attenuated by Dex. Withdrawal of Dex resulted in an enhancement of the 1,25-dihydroxyvitamin D3-induced secretion of osteocalcin, whereas alkaline phosphatase activity and the cAMP response to PTH remained at prewithdrawal levels. The steady state mRNA level of osteonectin was not affected by Dex. Our results, which demonstrate that Dex conditions the differentiation of human bone marrow osteogenic stromal cells into osteoblast-like cells, support the hypothesis of a permissive effect of glucocorticoids in ensuring an adequate supply of mature osteoblast populations. Furthermore, the established human bone marrow stromal cell culture provides a good model of an in vitro system to study the regulation of differentiation of human bone osteoprogenitor cells.

Adult↗
PubMed1994

Increased low density lipoprotein receptor expression mediated through the insulin-like growth factor-I receptor in cultured fibroblasts.

Plasma insulin-like growth factor-I (IGF-I) levels are inversely correlated with apolipoprotein B and low density lipoprotein (LDL) cholesterol in humans. To identify a molecular basis for this observation, the effects of IGF-I on LDL receptor expression in fibroblasts were studied. IGF-I increased LDL receptors in cultured human skin fibroblasts at concentrations greater than 25 ng/ml. However, IGF-I effects were not easily quantitated due to secretion of inhibitory IGF-binding proteins by the cells. To circumvent this difficulty, QAYL, an IGF-I analog that binds to the IGF-I receptor but not to IGF-binding proteins, was used. QAYL increased LDL receptor number 56-72% with half-maximum effect at 0.6 ng/ml. alpha-IR3, a monoclonal antibody directed toward the IGF-I receptor, blocked this effect. QAYL treatment increased synthesis of LDL receptor protein without increasing LDL receptor mRNA levels or altering protein stability. Both QAYL and IGF-I increased LDL receptors prominently in cells that had been treated with physiological amounts of LDL cholesterol. IGF-I, acting through the IGF-I receptor and modulated by IGF-binding proteins, may contribute to the regulation of LDL metabolism by increasing translation of LDL receptor message.

Amino Acid Sequence↗
PubMed1993

[Effects of Rheum on renal hypertrophy and hyperfiltration of experimental diabetes in rat].

Renal hypertrophy and elevated glomerular filtration rate (GFR) appeared in early stage of diabetic nephropathy (DN). In order to investigate the effect of Rheum officinale (RO) on the renal hypertrophy, streptozotocin induced diabetic rats with moderate hyperglycemia were divided into two groups, receiving RO (RO-DN) or not (DN), and one group of non-diabetic control (C) was set up. At the 28th day, DN group exhibited heavier kidney weight (+61%), more protein (+133%) and DNA (+94%) contents in the kidney and higher GFR (+94%) than the control. RO-DN rats showed much less above mentioned changes. In addition, lipid abnormalities were ameliorated in RO-DN group. This result suggest that RO is beneficial to the diabetes in terms of renal hypertrophy and GFR changes at early stage and is recommended in the treatment of diabetic nephropathy.

Animals↗
PubMed1993

Blockage of clonidine-induced platelet aggregation in rabbits by procainamide.

Procainamide was capable of blocking the alpha 2-adrenergic receptor agonist clonidine-induced platelet aggregation, giving an antagonistic index, pA2, of 5.0 +/- 0.6 and half antagonistic concentration, A2, of 10.4 mumol.L-1. Clonidine showed half efficacy concentrations (EC50) of 44, 82, 182, 485, and 662 nmol.L-1, and affinity parameter (pD2) of 7.4, 7.1, 6.7, 6.3, and 6.2 respectively when different concentrations of procainamide were used as blocking reagent. The results indicated that the mechanism of inhibitory effect of procainamide on clonidine-induced platelet aggregation was to competitively antagonize activating alpha 2-receptors and others of clonidine on platelet membrane.

Animals↗
PubMed1991

Characterisation of the specific p-nitrophenylphosphatase gene and protein of Schizosaccharomyces pombe.

Cloning and sequencing of the pho2 gene which codes for a specific p-nitrophenylphosphatase from Schizosaccharomyces pombe is described. The gene has an open contiguous reading frame of 269 amino acids corresponding to a protein with a molecular mass of 29.5 kDa and a calculated pI of 6.6. The sequence reveals four regions that share significant sequence similarity with the corresponding gene PHO13 of Saccharomyces cerevisiae. Purification of the enzyme to apparent homogeneity is reported. The amino acid composition of the purified protein matches well the values predicted from the nucleotide sequence. On SDS/polyacrylamide gels, the enzyme runs as a protein with a molecular mass of 33 kDa, and by Sephadex chromatography under nondenaturing conditions as 70 kDa. This indicates that the enzyme is a homodimer in its native form. The enzyme is not glycosylated. Its activity is stimulated by Mg2+ and inhibited by Zn2+. The available data on p-nitrophenylphosphatase do not give any clues to its biological role and its physiological substrates.

4-Nitrophenylphosphatase↗