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Biomedical subjects

H Yun

Publications and source records attributed to H Yun.

15 recordsLinked to original sources
PubMed2005

Quantitative analysis of biological effect on membrane fouling in submerged membrane bioreactor.

The objective of this study is to investigate solids concentration and extracellular polymeric substance (EPS) effects on the membrane fouling in the submerged membrane bioreactor. The relationship between the solids retention time (SRT) and the amount of EPS is observed in three lab-scale MBRs. Additionally, the EPS effect on membrane fouling is quantified by calculating the specific cake resistance (alpha) using an unstirred batch cell test. By observing the sludge over a long period under various SRT scenarios, a wide range of EPS and membrane fouling data is obtained. These observations provide sufficient evidence of the functional relationship between SRT, EPS and alpha. As SRT decreases, the amount of EPS bound in sludge floc becomes higher in the high MLSS condition (> 5,000 mg/L). The amount of EPS in the sludge floc has positive influence on alpha. A sigmoid trend between EPS and alpha is observed and the functional relationship obtained by dimensional analysis is consistent with the experimental results.

Bacteria, Aerobic↗
PubMed2003

Purification, characterization, and molecular cloning of a novel amine:pyruvate transaminase from Vibrio fluvialis JS17.

A transaminase from Vibrio fluvialis JS17 showing activity toward chiral amines was purified to homogeneity and its enzymatic properties were characterized. The transaminase showed an apparent molecular mass of 100 kDa as determined by gel filtration chromatography and a subunit mass of 50 kDa by MALDI-TOF mass spectrometry, suggesting a dimeric structure. The enzyme had an isoelectric point of 5.4 and its absorption spectrum exhibited maxima at 320 and 405 nm. The optimal pH and temperature for enzyme activity were 9.2 and 37 degrees C, respectively. Pyruvate and pyridoxal 5'-phosphate increased enzyme stability whereas (S)-alpha-methylbenzylamine reversibly inactivated the enzyme. The transaminase gene was cloned from a V. fluvialis JS17 genomic library. The deduced amino acid sequence (453 residues) showed significant homology with omega-amino acid:pyruvate transaminases (omega-APT) from various bacterial strains (80 identical residues with four omega-APTs). However, of 159 conserved residues in the four omega-APTs, 79 were not conserved in the transaminase from V. fluvialis JS17. Taken together with the sequence homology results, and the lack of activity toward beta-alanine (a typical amino donor for the omega-APT), the results suggest that the transaminase is a novel amine:pyruvate transaminase that has not been reported to date.

Amino Acid Sequence↗
PubMed2001

Duration of efficacy of treatment of latent tuberculosis infection in HIV-infected adults.

BACKGROUND: Treatment of latent infection is needed to protect HIV-infected individuals against tuberculosis. A previous report addressed short-term efficacy of three regimens in HIV-infected adults. We now report on long-term efficacy of the study regimens. METHODS: Three daily self-administered regimens were compared in a randomized placebo-controlled trial in 2736 purified protein derivative (PPD)-positive and anergic HIV-infected adults. PPD-positive subjects were treated with isoniazid (INH) for 6 months (6H), INH plus rifampicin for 3 months (3HR), INH plus rifampicin and pyrazinamide for 3 months (3HRZ), or placebo for 6 months. Anergic subjects were randomized to 6H or placebo. RESULTS: 6H initially protected against tuberculosis in PPD-positive individuals; however, benefit was lost within the first year of treatment. Sustained benefit was observed in persons receiving 3HR and 3HRZ. In a Cox regression analysis, the adjusted relative risk for tuberculosis compared with placebo was 0.67 [95% confidence interval (CI), 0.42-1.07] for 6H, 0.49 (95% CI, 0.29-0.82) for 3HR, and 0.41 (95% CI, 0.22-0.76) for 3HRZ. When the rifampicin-containing regimens were combined, the adjusted relative risk for tuberculosis compared with placebo was 0.46 (95% CI, 0.29-0.71). Among anergic subjects, a modest degree of protection with 6H was present (adjusted relative risk, 0.61; 95% CI, 0.32-1.16). Treatment of latent tuberculosis infection had no effect on mortality. CONCLUSION: Six months of INH provided short-term protection against tuberculosis in PPD-positive HIV-infected adults. Three month regimens including INH plus rifampicin or INH, rifampicin and pyrazinamide provided sustained protection for up to 3 years.

AIDS-Related Opportunistic Infections↗
PubMed2001

XAFS study of copper species stabilized in the interlayer space of layered perovskite oxides.

New intercalation compounds with Cu2+ ions in the interlayer of layered perovskite oxides, OA(1-x)Ca(2-x)La(x)Nb3O10) (OA = n-octylammonium ion, 0 < or = x < 1), have been prepared by ion-exchange reaction, and characterized by means of XRD and XAS. For the detail elucidation of the fine structure of the Cu K-edge XANES spectra, polarized XAS was applied for the [Cu(en)2]2+ and Cu2+ ions intercalated to the single crystal. According to the XANES and EXAFS spectra measured at Cu K-edge, copper ions are four coordinated. In addition, XANES spectra have shown that the charge transfer from host layer to intercalated ions influences on the chemical state of copper ion.

Journal Article↗
PubMed2001

Postantibiotic effects and postantibiotic sub-MIC effects of erythromycin, roxithromycin, tilmicosin, and tylosin on Pasteurella multocida.

When intermittent dosing is used during treatment, the concentrations of antibiotics fluctuate and subinhibitory concentrations may occur between doses. Postantibiotic effects (PAEs) and postantibiotic subinhibitory effects (PA SMEs) on bacteria may provide additional, valuable information for the rational use of a drug in clinical practice. In this study tilmicosin was the most active antibiotic tested against P. multocida type D with MICs ranging from 4-16 mg/l. Roxithromycin and tilmicosin induced a statistically significantly longer PAE than did tylosin against P. multocida types A and D (P < 0.05). The duration of PAEs and PA SMEs were proportional to the concentrations of drugs used for exposure. The PA SMEs were substantially longer than PAEs on P. multocida. Tilmicosin had a longer PA SME compared with erythromycin, roxithromycin and tylosin for P. multocida. The computerized incubator used in the present study provided an efficient and convenient determination of PAE and PA SME, allowing frequent measurements of the bacterial growth.

Anti-Bacterial Agents↗
PubMed2001

Statistical advances in AIDS therapy trials.

This paper reviews recent statistical advances in HIV/AIDS therapy trials. Our emphasis is on three emerging areas that address key challenges in AIDS research: the determination of optimal treatment sequences, estimating efficacy of intended treatment, and inference for repeated measures with dependent censoring. A common theme of these topics is the use of observational data within clinical trials to answer questions not addressed by the conventional intent-to-treat analysis. We also give a brief overview of some recent contributions to other topics relevant to AIDS clinical trials, including modelling of treatment compliance data, modelling of repeated measures, and group sequential testing.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Determination of roxithromycin residues in the flounder muscle with electrospray liquid chromatography-mass spectrometry.

A highly sensitive and specific method for the determination of roxithromycin in the flounder muscle by LC-MS was developed and validated. A dichloromethane extract of the sample was separated on C18 reversed-phase column with acetonitrile-50 mM ammonium acetate (80:20, v/v) as the mobile phase and analyzed by LC-MS via atmospheric pressure ionization/electrospray ionization interface. The limit of detection and limit of quantitation were 0.01 and 0.1 ng/g, respectively. Mean recoveries from spiked muscles were 81.1% (ranged from 71.0 to 90.3%) for roxithromycin. The method has been successfully applied to determine roxithromycin in the flounder muscle.

Animals↗
PubMed1998

[Seeds collecting of Ephedra sinica and treatment before sown].

Seeds collecting of Ephedra sinica and treatment before sown were studied. These results indicated that time collecting seeds and treating such as threshing, washing, drying, storing at low temperature and immersing seeds with chemical were available measures. Which could supply a reference for the culture of E. sinica.

Desiccation↗
PubMed1996

Vascularity of uterine myomas: assessment by color and pulsed Doppler ultrasound.

OBJECTIVE: To evaluate the effects of different clinical and anatomical factors on the vascularity of uterine myomas METHODS: The study group included 195 patients, 153 premenopausal and 42 postmenopausal. Four hundred five myomas, 316 in the first group and 89 in the second, were studied by color Doppler ultrasound. Differences in the visualization of blood flow and resistance index (RI) were analyzed according to several factors, including: menopausal status, phase of menstrual cycle, duration of menopause, size and location of the myomas, and secondary changes within the myomas. RESULTS: The size of myomas was the most important single factor in determining both visualization of blood flow and RI. A higher blood flow visualization rate (BFVR) and a lower RI were found: (1) in the premenopausal compared with the postmenopausal patients (P < 0.05), (2) in the group of larger myomas compared with the group of smaller myomas (P < 0.0001), and (3) in submucosal and subserosal myomas compared with intramural myomas (P < 0.05). Other above-mentioned factors did have some, but not significant, influence on the visualization of blood flow and resistance to blood flow. CONCLUSION: Differences in the vascularity and resistance to blood flow in uterine myomas may limit the clinical use of color Doppler ultrasound.

Case-Control Studies↗
PubMed1980

Effect of somatostatin and calcium deprivation on cholecystokinin or caerulein-induced insulin and glucagon release from the isolated perfused rat pancreas.

The present experiments were undertaken to investigate the effect of alteration in on extracellular calcium concentration and of somatostatin on cholecystokinin-(CCK)- and caerulein-induced insulin and glucagon release from the isolated perfused rat pancreas. In control studies using perfusate containing 2.5 mM CaCl2 and 50 mg/dl glucose, CCK and caerulein caused insulin and glucagon release in a dose-related fashion. During perfusion with calcium free medium, insulin release was markedly inhibited. Subsequent introduction of 2.5 mM CaCl2 to the medium restored insulin response toward control levels. Extracellular calcium depletion, however, had no effect on CCK- or caerulein-induced glucagon release. The output of glucagon in the absence of calcium was comparable to that seen in the control experiments. On the other hand, somatostatin abolished the increase in glucagon secretion, but not the increase in insulin secretion, when perfused simultaneously with CCK or caerulein. However, pretreatment for 10 min with somatostatin blocked even insulin secretion. However, pretreatment for 10 min with somatostatin blocked even insulin secretion. The effects of somatostatin on hormonal discharge are suggested to be related to an alteration in the handling of or response to calcium. Recently, somatostatin has also been shown to inhibit calcium uptake by islets. Thus, the present results indicate a differential sensitivity of CCK- and caerulein-stimulated alpha and beta cell to extracellular calcium depletion and to the effect of somatostatin.

Animals↗
PubMedDate not supplied

Alterations in cardiovascular function during neurolept anesthesia for surgery on the coronary vessels.

Induction of anesthesia for aortocoronary bypass surgery was accomplished by the administration of droperidol, morphine, oxygen and nitrous oxide-oxygen in 20 patients. They ranged from 40 to 69 years of age. Premedication consisted of diphenhydramine and morphine. Cardiovascular stability was the most important aspect of the technique. Heart rate changes were insignificant. Cardiac index increased substantially after droperiodol and remained unchanged after morphine. It stayed around control levels for the rest of the induction. A substantial decrease was observed while using mechanical ventilation. Mean arterial pressure dropped significantly after droperidol and again after morphine, then rose about 17% after oxygen to near control levels, where it stayed thereafter. Peripheral vascular resistance dropped substantially after droperidol. A significant increase occurred after oxygen, reaching almost control levels at this point. Mechanical ventilation caused a significant increase, similar to the decrease in the cardiac index. Decreased oxygen availability was compensated for by decreased oxygen consumption. Induction of neurolept anesthesia in the manner described appears to be void of the undesirable effects of either large doses of morphine, or nitrous oxide-oxygen following such morphine doses. Amnesia was complete in every patient.

Adult↗
PubMedDate not supplied

Sulfamethazine as a model compound to assess sex hormone-dependent cytochrome P-450 activity in rats.

Plasma disposition and urinary recovery of sulfamethazine (SMZ), its N4-acetylated metabolite (N4AcSMZ), and two of its hydroxylated metabolites [5-hydroxysulfamethazine (5OHSMZ) and 6-hydroxymethylsulfamethazine (6CH2OHSMZ)] were determined in male and female rats, in castrated males, and in rats pretreated with various steroid hormones. Male rats had a 2-fold higher SMZ plasma clearance than females, castrates, and males treated with flutamide (a testosterone antagonist). When castrated male rats were treated with testosterone or trenbolone, SMZ plasma clearance returned to normal values. Higher SMZ plasma clearance rates in the presence of androgens went together with higher urinary recoveries of the 6CH2OHSMZ metabolite. In hepatic microsomes of male rats lower apparent KM values, and higher Vmax values for 6CH2OHSMZ and 5OHSMZ formation were found than in microsomes of female rats. Castration or treatment of male rats with flutamide markedly reduced microsomal SMZ hydroxylation rates. Pretreatment of male or female rats with phenobarbital or triacetyl-oleandomycin had no effect on microsomal SMZ hydroxylation, whereas a continuous infusion with bovine somatotropin in male rats caused a marked decrease in SMZ hydroxylation rate. Finally, SMZ hydroxylation to 6CH2OHSMZ and 5OHSMZ in hepatic microsomes from male rats was strongly inhibited by monoclonal antibodies against P-4502C11. These results suggest that the male-specific P-4502C11 enzyme plays an important role in the hydroxylation of SMZ to 6CH2OHSMZ and 5OHSMZ in rats. SMZ seems a useful model compound to assess hormone effects on oxidative biotransformation (in vivo and in vitro) in rats.

Animals↗