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Biomedical subjects

S W Chang

Publications and source records attributed to S W Chang.

At least 19 recordsLinked to original sources
PubMed2005

Long-term follow-up of giant serpentine MCA aneurysm treated with EC-IC bypass and proximal occlusion.

Giant serpentine aneurysms are a rare but important subset of giant aneurysms, with unique management considerations. We present long-term follow-up clinical and imaging features of a giant serpentine middle cerebral artery lesion treated with extracranial-intracranial bypass and proximal occlusion more than a decade earlier. Calcification of the obliterated aneurysm sac and durability of this management strategy are demonstrated.

Adolescent↗
PubMed2004

Multiple mutagenesis of the Candida rugosa LIP1 gene and optimum production of recombinant LIP1 expressed in Pichia pastoris.

Candida rugosa lipase, a significant catalyst, had been widely employed to catalyze various chemical reactions such as non-specific, stereo-specific hydrolysis and esterification for industrial biocatalytic applications. Several isozymes encoded by the lip gene family, namely lip1 to lip7, possess distinct thermal stability and substrate specificity, among which the recombinant LIP1 showed a distinguished catalytic characterization. In this study, we utilized PCR to remove an unnecessary linker of pGAPZalphaC vector and used overlap extension PCR-based multiple site-directed mutagenesis to convert the 19 non-universal CTG-serine codons into universal TCT-serine codons and successfully express a highly active recombinant C. rugosa LIP1 in the Pichia expression system. Response surface methodology and 4-factor-5-level central composite rotatable design were adopted to evaluate the effects of growth parameters, such as temperature (21.6-38.4 degrees C), glucose concentration (0.3-3.7%), yeast extract (0.16-1.84%), and pH (5.3-8.7) on the lipolytic activity of LIP1 and biomass of P. pastoris. Based on ridge max analysis, the optimum LIP1 production conditions were temperature, 24.1 degrees C; glucose concentration, 2.6%; yeast extract, 1.4%; and pH 7.6. The predicted value of lipolytic activity was 246.9+/-39.7 U/ml, and the actual value was 253.3+/-18.8 U/ml. The lipolytic activity of the recombinant LIP1 resulting from the present work is twofold higher than that achieved by a methanol induction system.

Base Sequence↗
PubMed2004

Cardiac disease due to random mitochondrial DNA mutations is prevented by cyclosporin A.

Mice expressing an error-prone mitochondrial DNA polymerase rapidly accumulate random mutations in mitochondrial DNA. Expression of the transgene in the heart leads to dilated cardiomyopathy accompanied by a wave of apoptosis in cardiomyocytes, and a vigorous and persistent protective response, including upregulation of the anti-apoptotic protein, Bcl-2. To investigate the role of the mitochondrial permeability transition pore in the development of disease, we treated mice with cyclosporin A (CsA), an inhibitor of pore opening. Drug treatment prevented cardiac dilatation, transgene-specific apoptosis, and upregulation of Bcl-2. It also rescued hearts from the profound decrease in connexin 43, which characterizes the dilatated heart. Treatment with FK506, which like CsA inhibits cytoplasmic calcineurin but not the mitochondrial pore, did not affect disease development, suggesting that the relevant target of CsA was the mitochondrial pore. These data implicate breakdowns in the mitochondrial permeability barrier in pathogenesis of elevated frequencies of mtDNA mutations.

Animals↗
PubMed2004

Long term operation of high concentration powdered activated carbon membrane bio-reactor for advanced water treatment.

A pilot scale experiment was conducted to evaluate the performance of a membrane bioreactor filled with high concentration powdered activated carbon. This hybrid system has great potential to substitute for existing GAC or O3/BAC processes in the drinking water treatment train. The system was installed at a water treatment plant located downstream of the Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system which consists of PAC bio-reactor, submerged MF membrane module and air supply facility. PAC concentration of 20 g/L was maintained at the beginning of the experiment and it was increased to 40 g/L. The PAC has not been changed during the operational periods. The membrane was a hollow fiber type with pore sizes of 0.1 and 0.4 microm. It was apparent that the high PAC concentration could prevent membrane fouling. 40 g/L PAC was more effective to reduce the filtration resistance than 20 g/L. At the flux of 0.36 m/d, TMP was maintained less than 40 kPa for about 3 months by intermittent suction type operation (12 min suction/3 min idling). Adsorption was the dominant role to remove DOC at the initial operational period. However the biological effect was gradually increased after around 3 months operation. Constant DOC removal could be maintained at about 40% without any trouble and then a tremendous reduction of DBPs (HAA5 and THM) higher than 85% was achieved. Full nitrification was observed at the controlled influent ammonia nitrogen concentration of 3 and 7 mg/L. pH was an important parameter to keep stable ammonia oxidation. From almost two years of operation, it is clear that the PAC membrane bioreactor is highly applicable for advanced water treatment under the recent situation of more stringent DBPs regulation in Korea.

Adsorption↗
PubMed2001

Optimized synthesis of lipase-catalyzed hexyl acetate in n-hexane by response surface methodology.

Hexyl acetate, a short-chain ester with fruity odor, is a significant green note flavor compound and widely used in the food industry. The ability for immobilized lipase from Mucor miehei (Lipozyme IM-77) to catalyze the transesterification of hexanol with triacetin was investigated in this study. Response surface methodology and five-level-five-factor central composite rotatable design were adopted to evaluate the effects of synthesis variables, such as reaction time (2-10 h), temperature (25-65 degrees C), enzyme amount (10-50%; 0.024-0.118 BAUN), substrate molar ratio of triacetin to hexanol (1:1 to 3:1), and added water content (0-20%) on percentage molar conversion of hexyl acetate. The results showed that reaction temperature and substrate molar ratio were the most important parameters and that added water content had less of an effect on percent molar conversion. On the basis of canonical analysis, optimum synthesis conditions were as follows: reaction time, 7.7 h; temperature, 52.6 degrees C; enzyme amount, 37.1% (0.089 BAUN); substrate molar ratio, 2.7:1; and added water, 12.5%. The predicted value was 88.9% molar conversion, and the actual experimental value was 86.6% molar conversion.

Catalysis↗
PubMed2001

Delayed tear clearance in contact lens associated papillary conjunctivitis.

PURPOSE: To study the tear film clearance in contact lens associated papillary conjunctivitis patients. METHODS: Fifty-eight daily-wear soft contact lens wearers completed a questionnaire regarding a survey of their contact lens usage and subjective symptoms. They were grouped according to the size of conjunctival papillae, namely PC1 with no papillae, PC2 with papillae of less than 0.3 mm, and PC3 with papillae of 0.3-1.0 mm in diameter. Tear film breakup time and fluorescein clearance tests were performed. RESULTS: There was a median of 1, 2, and 3 subjective symptoms in PC1, PC2, and PC3 groups respectively (p < 0.001). Patients with larger papillae on their upper tarsus had more subjective symptoms such as burning sensation, discharge, limbal injection, foreign body sensation and dryness sensation (p = 0.018, 0.001, 0.004, 0.005, and 0.036 respectively). They also had shorter tear film breakup time (p = 0.05), delayed tear clearance (p = 0.002) and more corneal neovascularization (p < 0.001). Patients having delayed tear clearance test tended to have more subjective symptoms (p = 0.004) and larger papillae on upper tarsus (p = 0.002). However, neither the way the patients cleaned their contact lenses nor their enzyme cleaning frequency associated with the tear fluorescein clearance (p = 0.528 and 0.394, respectively). Meibomian gland dysfunction and corneal neovascularization did not correlate with the delayed tear clearance either (p = 0.111 and 0.717, respectively). CONCLUSIONS: Tear clearance in contact lens associated papillary conjunctivitis patients was delayed. We proposed that delayed tear clearance might increase the protein and inflammatory mediator concentrations in the tear film and contribute to the pathogenesis or aggravate the severity of contact lens associated papillary conjunctivitis.

Adult↗
PubMed2001

Application of the general health status questionnaire SF36 to patients with gastrointestinal dysfunction: initial validation and validation as a measure of change.

OBJECTIVE: To determine whether the Short Form (SF36) Health Status Survey is a valid measure of health status and health change for patients with irritable bowel syndrome (IBS). METHODS: The SF36 was self-administered by 116 patients with IBS at the commencement and end of a controlled clinical trial. Patients were recruited through two Sydney teaching hospitals and through private gastroenterologists during 1997 and treated with Chinese herbal medicine. RESULTS: The SF36 health concepts demonstrated internal consistency, construct validity and concurrent validity when applied to patients with significant bowel dysfunction. Patient scores on two health scales of the SF36 (bodily pain, general health) correlated significantly with the bowel symptom scores recorded by patients and gastroenterologists at the beginning and end of the trial period. Actively treated patients significantly improved their scores in four out of eight of the health scales of the SF36 and reported overall improvement compared with inactively treated patients. CONCLUSIONS: The SF36 is a valid measure of general health status in IBS patients, is sensitive to the presence of IBS, and is adequately sensitive to gastrointestinal change in IBS patients. IMPLICATIONS: While the SF36 general health measure is used by the Australian Bureau of Statistics and widely overseas, until recently no data have been available on the sensitivity of the SF36 to gastrointestinal dysfunction or numerous other disorders. The SF36 is not only sensitive to the presence of IBS, it also provides a useful adjunct to current methods of evaluating treatment outcomes for IBS, and potentially other disorders.

Adolescent↗
PubMed2001

The cornea in young myopic adults.

AIMS: To further understand the effect of refractive error on the corneal dimensions and function. METHODS: Corneal curvature, corneal thickness, and axial length measurements were performed, as well as specular microscopy and fluorophotometry, on patients with various refractive statuses. 216 subjects, mean age 22.2 (SD 4.2) years, were examined. Patients with previous contact lens wear history, external eye diseases, as well as previous ocular surgeries, were excluded. RESULTS: The corneas were flatter in eyes with longer axial length (r = -0.22, p = 0.003). Eyes with more myopic spherical equivalent had longer axial length (r = -0.90, p <0.001) as well as less corneal endothelial density (r = 0.20, p = 0.037). Corneal endothelial density decreased in eyes with longer axial length (r = 0.24, p = 0.019); however, it correlated neither with corneal thickness (r = -0.06, p = 0.59) nor with corneal curvature (r = -0.07, p = 0.52). The corneas had a mean corneal thickness of 533 (SD 29) microm and were thinner in more myopic eyes (r = 0.16, p = 0.021). The corneas tended to be thinner in eyes with longer axial length. However, the correlation did not reach statistical significance (r = -0.11, p = 0.14). Besides, there was no significant correlation between the corneal thickness and the corneal curvature (r = -0.13, p = 0.093) and the endothelial permeability (r = 0.042, p = 0.69). The corneas with higher endothelial density had larger corneal transfer coefficient (r = 0.26, p = 0.024) and higher permeability to fluorescein molecules (r = 0.28, p = 0.014). Nevertheless, the corneal endothelial permeability did not correlate significantly with either the axial length (r = -0.18, p = 0.11) or the degree of myopia (r = 0.12, p = 0.26). CONCLUSION: Changes in the anterior segments as the eyeball elongates in myopia progression included flatter corneal curvature, decreased corneal thickness, as well as decreased endothelial density. These factors should be considered in refractive surgery.

Adult↗
PubMed2001

Microbial degradation of benzene, toluene, ethylbenzene and xylene isomers (BTEX) contaminated groundwater in Korea.

A mixed culture derived from a gasoline-contaminated aquifer in Korea was enriched on toluene at 25 degrees C. A study was conducted to characterize the substrate interaction of BTEX by toluene-enriched consortia and determine the effects of initial BTEX concentration on BTEX degradation. Substrate degradation patterns in individual aromatics were found to differ significantly from patterns for aromatics in mixtures. In the experiment of a single substrate, toluene was degraded fastest, followed by benzene, ethylbenzene, and the xylenes. In BTEX mixtures, degradation followed the order of toluene, ethylbenzene, benzene, and the xylenes. The studies conducting with toluene-enriched consortia evaluated substrate interactions by the concurrent presence of multiple BTEX compounds and revealed a range of substrate interaction patterns including no interaction, stimulation, inhibition, and cometabolism. The simultaneous presence of benzene and toluene were degraded with a slight inhibitory effect on each other. Ethylbenzene was shown to be the most potent inhibitor of BTEX degradation. p-xylene also inhibited the degradation of benzene, toluene, and ethylbenzene, whereas the presence of either benzene or toluene enhanced the degradation of ethylbenzene and the xylenes.

Benzene↗
PubMed2000

Construction of transgenic mice with tissue-specific acceleration of mitochondrial DNA mutagenesis.

Transgenic mice having rapid accumulation of mitochondrial DNA (mtDNA) mutations specifically in the heart were created. These mice contained a transgene encoding a proofreading-deficient, mouse mitochondrial DNA polymerase (pol gamma) driven by the promoter for the cardiac-specific alpha-myosin heavy chain. Starting shortly after birth greater than 95% of all pol gamma mRNA in the heart was transgene derived; expression in other tissues was low or absent. Mutations in cardiac mtDNA began to accumulate by 7 days after birth. At 1 month of age the frequency of point mutations was 0.014% as determined by DNA sequencing of cloned mtDNA. By long-extension PCR multiple different deletion mutations that had removed several thousand basepairs of genomic sequence were also detected. Sequencing of two deletion molecules showed that one was flanked at the breakpoint by direct repeat sequences. The expression of proofreading-deficient pol gamma had no apparent deleterious effect on mitochondrial DNA and protein content, gene expression, or respiratory function. However, associated with the rise in mtDNA mutation levels was the development of cardiomyopathy as evidenced by enlarged hearts in the transgenic mice. These mice may prove to be useful models to study the pathogenic effects of elevated levels of mitochondrial DNA mutations in specific tissues.

Animals↗
PubMed2000

The frequency of point mutations in mitochondrial DNA is elevated in the Alzheimer's brain.

Using a PCR-based strategy, we found that point mutation frequencies in mitochondrial DNA (mtDNA) were 2- to 3-fold higher in the parietal gyrus, hippocampus, and cerebellum from subjects with Alzheimer's disease (AD) compared to normal controls. In contrast, levels of a commonly studied deletion mutation, mtDNA(4977), were not elevated in AD. The frequency of point mutations did not vary significantly among the three brain areas, whereas the frequency of mtDNA(4977) was 15- to 25-fold lower in the cerebellum in comparison to the cortex; this regional variation was seen in both the normal and Alzheimer's brain. In blood mtDNA, point mutation frequencies were not elevated in AD patients. The elevated frequency of point mutations in all three brain regions is consistent with the idea that increased oxidant stress is associated with AD.

Adult↗
PubMed2000

Benzalkonium chloride and gentamicin cause a leak in corneal epithelial cell membrane.

The purposes of this study are to characterize the pathophysiological effects of benzalkonium chloride and gentamicin on corneal epithelial cells and to determine the concentration dependent effect of these agents on membrane currents of these cells. Rabbit corneal epithelial cells were isolated and subdivided into small, medium and large cells according to their cell capacitance. Using whole cell clamp technique, potassium current of corneal epithelial cells was recorded. Transmembrane current was measured again after bathing in benzalkonium chloride 1, 3, 10, 30 and 100 micrometer ml(-1)for 3 min. The effect of gentamicin was tested at concentrations of 0.4, 1.0, 2.0, 4.0 and 10 mg ml(-1). Synergistic effect of gentamicin of the above mentioned concentrations in the presence of benzalkonium chloride 1 microgram ml(-1)was also measured. We found that small corneal epithelial cells had the highest depolarization-gated, outward potassium current density and large cells had the lowest current density, while medium cells had a current density in between. Benzalkonium chloride induced a concentration dependent increase in the leak current with increasing concentration from 1 to 100 microgram ml(-1). The increase of leak current in medium and large cells was less than that in the small cells. Gentamicin also caused a concentration dependent increase in leak current density from 0.4 to 10.0 mg ml(-1). The increase in leak current density was statistically significant when the concentration was 2.0 mg ml(-1)or higher in small corneal epithelial cells and 1.0 mg ml(-1)or higher in the medium and large cells. Benzalkonium chloride 1.0 microgram ml(-1)augmented the effect of gentamicin on epithelial cell membrane. The extent of enhancement was more prominent in larger than smaller cells. Using whole-cell clamp technique, we were able to determine the threshold concentration of gentamicin and benzalkonium chloride on the integrity of corneal epithelial cell membrane. The toxic action of both agents is mediated by an increase in leak current. We propose that the whole-cell clamp technique is a sensitive and useful tool in determining cytotoxic effects of various agents.

Animals↗
PubMed2000

Wound healing patterns following perforation sustained during laser in situ keratomileusis.

BACKGROUND AND PURPOSE: Corneal perforation during laser in situ keratomileusis (LASIK) may interfere with flap adhesion and wound healing. The purpose of this study was to investigate wound healing patterns following corneal perforation sustained during LASIK in rabbits. METHODS: Forty-two pigmented rabbit eyes underwent LASIK surgery with 5.0-mm excimer laser treatment under the corneal flap. Animals were divided into two groups: group I (n = 19) underwent the regular LASIK procedure with -10.0 D treatment, without perforation; in group II (n = 23), the cornea was perforated with the excimer laser. Treatment was discontinued once perforation was observed, and the corneal flap was replaced without sutures. Slit-lamp biomicroscopy, photography, and scatterometry were performed preoperatively and at 1 and 2 days, 1 week, and weekly up to 1 month, 2 months, and 3 months postoperatively. Animals were killed at 1 day, 1 week, 1 month, and 3 months postoperatively and processed for light microscopic, electron microscopic, and immunohistochemical examinations. RESULTS: In group I, the corneas remained clear throughout the experiment. In all eyes, the interface was not readily discernable clinically or histologically. Corneal wound healing was accompanied by minimal cell infiltration. Epithelial hyperplasia at the flap edge was noted at 1 week. Myofibroblast activation was found at the epithelial wedge where there was an epithelial basement membrane break. In group II, the anterior chamber was shallow with no iris incarceration at the end of surgery. The corneas were clear (n = 6) or showed mild to moderate edema (n = 12). Corneal edema peaked at 3.6 +/- 5.0 days and subsided thereafter. Corneal wounds healed similarly to those in group I except at the perforation site. The break in Descemet's membrane and endothelium was covered with a fibrin plug on day 1, which resolved thereafter. There was no statistically significant difference in the incidence of postoperative infection (p = 1.0) or flap displacement (p = 0.69) rates between the two treatment groups. The scatterometry index peaked at 2 to 3 weeks postoperatively and was significantly higher in group II than in group I (p < 0.001). CONCLUSIONS: Although corneal perforation during LASIK surgery may interfere with immediate postoperative flap adhesion, corneal wound healing following LASIK perforation may be similar to that after an uncomplicated LASIK procedure.

Actins↗
PubMed2000

Klebsiella pneumoniae renal abscess.

BACKGROUND: The clinical characteristics of renal abscess caused by Klebsiella pneumoniae have not been previously reported in case-series studies. The purpose of this study is to demonstrate the clinical characteristics of K pneumoniae renal abscess for early diagnosis and to identify the clinical risk factors associating with poor prognosis. METHODS: We retrospectively reviewed the medical records of 24 patients with K pneumoniae renal abscess, from April, 1982 through February, 1998. The clinical presentations, including the demographic characteristics, predisposing disorders, initial signs and symptoms, laboratory test results, diagnostic radiology studies, therapeutic modalities and risk factors associated with mortality were studied. RESULTS: The mean age was 58.7 years and the male to female ratio was 10:14. The most common predisposing factors were diabetes mellitus (58%), urolithiasis (25%) and immunosuppression (17%). Fever, chills and flank pain were the most common symptoms and signs, whereas pyuria, elevation of leukocyte count, glucose, blood urea nitrogen and creatinine were the common laboratory features. The distinct complications of K pneumoniae renal abscess were bacteremia in 13 (54%), emphysematous pyelonephritis in five (21%), and metastatic septic infection in three (12.5%). The cure rate was 52% (11/21) in patients treated with a combination of antibiotics and percutaneous drainage; however, six (35%) patients who survived required another surgical procedure for complete recovery. The overall mortality rate was 25%. The clinical factors of elderly age (>65 years) at presentation, lethargy, elevation of serum blood urea nitrogen and pulmonary complications were associated with poor prognoses. CONCLUSIONS: Focusing on the early diagnosis of K pneumoniae renal abscess and recognition of the prognostic factors for a poor prognosis, we highlight the specific clinical characteristics that include elderly age, lethargy, impairment of renal function, metastatic septic lesions and pulmonary complications. All patients with K pneumoniae renal abscesses should receive empiric antibiotics and percutaneous drainage or aspiration, and surgical intervention as necessary for patients with intractable disease.

Abscess↗
PubMed1999

Outcomes of penetrating keratoplasty with imported donor corneas.

PURPOSE: To analyze factors influencing the surgical success of penetrating keratoplasty and long-term graft survival when using imported donor corneas. METHODS: Sixty-three donor corneas imported to Taipei from the Cincinnati Eye Bank from July 1992-June 1993 were used for penetrating keratoplasty. The corneal endothelium was examined using specular microscopy on arrival in Taiwan. The endothelial morphology and endothelial cell density (ECD) were compared with the photograph of the same cornea taken in the United States. The relationships of the surgical success rate with donor age, death to enucleation time, death to surgery time, and ECD were analyzed. The long-term graft survival and ECD of clear grafts were analyzed 4 years after surgery. RESULTS: On specular microscopic examination. the imported corneas showed diminished endothelial reflection, blurred cellular borders, and increased dark areas, which were markedly different from the pictures of the corneal endothelium taken in the United States. The average ECD before transportation was 2,525+/-267/mm2 and decreased to 1,934+/-250/mm2 after transportation (p < 0.001), with an average endothelial cell loss of 590+/-247/mm2. The overall surgical success rate was 89% and did not correlate with any of the donor factors tested except death to surgery time. The surgical success rate decreased when the time from death to surgery was >7 days (p = 0.05), mainly because of poor reepithelialization. Four years after surgery, 24 grafts remained clear. The ECD had decreased by 72+/-5% in the clear grafts. CONCLUSIONS: Our findings show that endothelial changes in imported donor corneas do occur after transportation, but the surgical success rate may not be influenced significantly if the penetrating keratoplasty is performed within 7 days after donor death. However, the ECD in the clear grafts 4 years after surgery is low.

Adult↗