Biomedical subjects

C H Liao

Publications and source records attributed to C H Liao.

At least 19 recordsLinked to original sources

PubMed2002

A general statistical analysis for fMRI data.

We propose a method for the statistical analysis of fMRI data that seeks a compromise between efficiency, generality, validity, simplicity, and execution speed. The main differences between this analysis and previous ones are: a simple bias reduction and regularization for voxel-wise autoregressive model parameters; the combination of effects and their estimated standard deviations across different runs/sessions/subjects via a hierarchical random effects analysis using the EM algorithm; overcoming the problem of a small number of runs/session/subjects using a regularized variance ratio to increase the degrees of freedom.

Algorithms↗

PubMed2002

Estimating the delay of the fMRI response.

We propose a fast, efficient, general, simple, valid, and robust method of estimating and making inference about the delay of the fMRI response modeled as a temporal shift of the hemodynamic response function (HRF). We estimate the shift unbiasedly using two optimally chosen basis functions for a spectrum of time shifted HRFs. This is done at every voxel, to create an image of estimated delays and their standard deviations. This can be used to compare delays for the same stimulus at different voxels, or for different stimuli at the same voxel. Our method is compared to other alternatives and validated on an fMRI data set from an experiment in pain perception.

Brain↗

PubMed2001

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles.

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Alligators and Crocodiles↗

PubMed2001

Inhibition of the expression of inducible nitric oxide synthase and cyclooxygenase-2 in macrophages by 7HQ derivatives: involvement of IkappaB-alpha stabilization.

Nitric oxide is an important biological mediator associated with multiple pathophysiological phenomena, such as platelet aggregation, vasodilation, septic shock, and autoimmune diseases. Prostaglandins, derived from cyclooxygenases, play prominent roles in homeostasis and inflammation. In this study, we characterized the effects of 7HQ derivatives (7-[(4-methylene-5-oxo-2-R-2-tetrahydrofuranyl) methoxy]-3,4-dihydrocarbostyril, where R is methyl, phenyl, p-fluorophenyl and p-phenylphenyl; 7HQ-1,-2,-3 and-4, respectively) in murine RAW 264.7 cells, a macrophage-like cell line. Lipopolysaccharide, the active component of endotoxin, significantly induced the expression of inducible nitric oxide synthase and cyclooxygenase-2, leading to the accumulation of nitrite and prostaglandin E(2), respectively. These actions of lipopolysaccharide were inhibited by 7HQ derivatives; additionally, the inhibition of the expression, rather than the activity, of inducible nitric oxide synthase correlated well with that of nitric oxide formation. Western blotting and electrophoretic mobility shift assay results demonstrated that the 7HQ derivatives could effectively inhibit IkappaB-alpha degradation and nuclear factor kappaB (NF-kappaB) translocation. At higher concentrations, 7HQ derivatives also inhibited cyclooxygenase-2 enzyme activity. These results suggest that 7HQ derivatives exhibit inhibitory effects on lipopolysaccharide-induced nitric oxide production and expression of inducible nitric oxide synthase and cyclooxygenase-2 through inhibition of IkappaB-alpha degradation and NF-kappaB activation.

Animals↗

PubMed2001

Photodegradation of humic acids in the presence of hydrogen peroxide.

A batch photoreactor was used to evaluate the UV/H2O2 oxidation process for the removal of humic acids in water. A 450-W UV lamp with high-pressure mercury vapor was employed as the light source. The residues of humic acids and hydrogen peroxide were measured for assessment of process performance and understanding of process reaction behavior. The UV photolysis alone can play an important role in the degradation of humic acids. The presence of hydrogen peroxide was found to promote the degradation efficiency. However, excessive dosage of H2O2 does not further improve the degradation of humic acids. On the contrary, the lower the H2O2 dosage the higher the amount of humic acids which can be removed. Aeration with air does not favor the removal efficiency of humic acids as the oxidation lasts for a sufficiently long time. The presence of carbonate species deteriorates the humic acids' removal, whereas it results in a larger amount of H2O2 decomposition.

Chelating Agents↗

PubMed2001

Hydroxyl radical scavenging role of chloride and bicarbonate ions in the H2O2/UV process.

Simultaneous effect of inorganic anions, such as chloride and bicarbonate ions, on the scavenging of hydroxyl radicals (HO*) in the H2O2/UV process is the focus of this paper. The model compound of n-chlorobutane (BuCl) was used as the probe of HO*. By changing the pH conditions (2-9) and the concentrations of NaCl (0.25-2500 mM) and NaHCO3 (25 mM), the variation of HO* concentrations and the rate of H2O2 decomposition were compared. In general, the BuCl and H2O2 follow closely the first-order reaction within the first 10 and 40 min, respectively. In the presence of chloride alone at the pH range of 2-6, the HO* concentration in the reaction mixture increases with the increase of pH, and the HO* concentration at pH = 6 is 100 times of that at pH = 2. Including bicarbonate species in the solution, the peak HO* concentration was found at a certain pH, which shifts from 4, 5, to 5-7, as the molar ratios of chloride/bicarbonate species increase from 1 to 100. In addition, without bicarbonate species HO* concentration decreases significantly with increasing chloride concentration but remained rather unchanged beyond 1250 mM. In contrast, the HO* scavenging in the presence of bicarbonate species became relatively significant only when the chloride concentration reached beyond 250 mM. Throughout all experiments of different water quality conditions, the H2O2 decomposition rate remains rather unchanged.

Bicarbonates↗

PubMed2001

Role of cupric ions in the H2O2/UV oxidation of humic acids.

The purpose of this study is to reveal the role of cupric ions as a natural water contaminant in the H2O2/UV oxidation of humic acids. Humic acids are naturally occurring organic matter and exhibit a strong tendency of complexation with some transition metal ions. Chlorination of humic acids causes potential health hazards due to formation of trihalomethane (THM). The removal of THM precursors has become an issue of public concern. The H2O2/UV process is capable of mineralizing humic acids due to formation of a strong oxidant, hydroxyl radicals, in reaction solution. Experiments were conducted in a re-circulated photoreactor. Different cupric concentrations (0-3.8 mg/l) and different pH values (4-9) were controlled to determine their effects on the degradation of humic acids, UV light absorbance at 254 nm, and H2O2. The presence of cupric ions inhibits humic mineralization and decreases the rate of destruction of humic acids which absorb UV light at 254 nm. On the other hand, the higher the cupric concentration, the lower the H2O2 decomposition rate. In the studied pH range, the minimum of total organic carbon (TOC) removal occurs at pH = 6 in the presence of 2.6 mg/l of cupric ions; both acidification (pH = 4) and alkaline condition (pH = 9) lead to a better removal of TOC. It is inferred from this study that the cupric-complexed form of humic acids is more refractory than the non-complexed one.

Copper↗

PubMed2001

Analysis of native microflora and selection of strains antagonistic to human pathogens on fresh produce.

The native microflora of three types of produce (green bell peppers, Romaine lettuce, and prepeeled baby carrots) and two types of sprouting seeds (alfalfa and clover) were investigated. Aerobic plate count (APC) for each produce or seed type as determined on Pseudomonas agar F (PAF) with incubation at 28 degrees C was in the range of 4 to 7 log CFU per g of tissue or seed. There was no significant difference (P > or = 0.05) in APC when the determinations were made with three agar media including PAF, brain heart infusion agar, and plate count agar. However, the APC as determined from plates that were incubated at 28 degrees C was significantly (P < or = 0.05) higher than with incubation at 37 degrees C. Fluorescent pseudomonads accounted for 23 to 73% of APC and 6 to 18% of APC recovered from carrots, pepper, and lettuce were pectolytic. Forty-eight strains of pectolytic bacteria were randomly isolated and identified, respectively, as members of the genera of Pseudomonas, Erwinia, Bacillus, Xanthomonas, or Flavobacterium. Lactic acid bacteria and/or yeast were consistently isolated from baby carrots, lettuce, and sprouting seeds (alfalfa or clover) but not from green bell peppers. Approximately 120 strains of indigenous microflora were tested for their ability to inhibit the growth of Salmonella Chester, Listeria monocytogenes, Escherichia coli, or Erwinia carotovora subsp. carotovora on PAF. Six isolates capable of inhibiting the growth of at least one pathogen were isolated and identified, respectively, as Bacillus spp. (three strains), Pseudomonas aeruginosa (one strain), Pseudomonas fluorescens (strain A3), and yeast (strain D1). When green pepper disks were inoculated with strains A3 and D1, the growth of Salmonella Chester and L. monocytogenes on the disks was reduced by 1 and 2 logs, respectively, over a period of 3 days. Application of strains A3 and D1 as potential biopreservatives for enhancing the quality and safety of fresh produce is discussed.

Agar↗

PubMed2001

Effect of percent free prostate-specific antigen measurement on improving the specificity of serum prostate-specific antigen testing in Taiwanese patients.

BACKGROUND AND PURPOSE: Measurement of percent free prostate-specific antigen (fPSA) has been shown to enhance the diagnostic performance of traditional serum PSA determination. We sought to determine whether measurement of percent fPSA could improve the specificity of serum total PSA testing in the detection of prostate cancer in Taiwanese patients with intermediate serum PSA concentrations. METHODS: The medical records of 211 patients examined from March 1998 through March 2000 were analyzed retrospectively; all had a serum total PSA concentration of between 4.1 and 20.0 ng/mL and negative digital rectal examination (DRE) findings, and had undergone a prostate biopsy. Biopsy results were correlated with the serum total PSA concentration and percent fPSA, which were determined using a microparticle enzyme immunoassay. Percent fPSA was calculated as the ratio of fPSA to total PSA multiple by 100. The sensitivity and specificity were calculated and the receiver operating characteristic (ROC) curves were generated from different cutoff values of percent fPSA and total PSA. RESULTS: Thirty-four patients (16.1%) had positive biopsy results (prostate cancer). Patients with positive biopsy results had significantly lower percent fPSA values than those with negative results (11.7% vs 16.0%, p < 0.001). Patients with a lower percent fPSA (< 10%) had a higher probability of a positive biopsy result than those with a high percent fPSA (> 20%) (positive biopsy rate, 29% vs 10%, p < 0.05). Using a cutoff value of 25% fPSA or below, the sensitivity, specificity, and positive predictive value in differentiating patients with positive biopsy results from those with negative results were 97%, 13%, and 18%, respectively. Consequently, 27 unnecessary biopsies could have been avoided at the cost of missing one cancer. The area under the ROC curve was 0.68 for percent fPSA and 0.63 for total PSA (p > 0.05). CONCLUSIONS: For Taiwanese patients with a serum PSA concentration of between 4.1 and 20.0 ng/mL, the incidence of prostate cancer is relatively low; measurement of percent fPSA only weakly enhances the specificity of serum PSA testing in detecting prostate cancer.

Aged↗

PubMed2001

Effectiveness of transperitoneal and trans-retroperitoneal laparoscopic adrenalectomy versus open adrenalectomy.

PURPOSE: This study compared the effectiveness of laparoscopic adrenalectomy, using either a transperitoneal or trans-retroperitoneal approach, with that of open adrenalectomy in patients with benign adrenal tumors. METHODS: From February 1995 to April 2000, laparoscopic adrenalectomy was performed on 31 patients with adrenal tumors, including 16 aldosteronomas, 10 Cushing's adenomas, three nonfunctioning tumors, and two pheochromocytomas. A lateral trans-retroperitoneal approach was used for the first 16 patients and a lateral transperitoneal approach was used for the last 15 patients. Twenty-one patients who received open adrenalectomy during the same period served as a control group. Comparisons were made between laparoscopy and open groups, and between transperitoneal and trans-retroperitoneal groups. RESULTS: Conversion to open adrenalectomy was necessary in two cases--both in the trans-retroperitoneal group during the first 2 years of the study period. No other intraoperative complications occurred and blood transfusion was not used. Compared with the open group, the laparoscopic group had less blood loss (71 vs 124 mL), resumed oral feeding earlier (28 vs 60 hr), required less postoperative narcotics (45 vs 120 mg meperidine), and had shorter postoperative hospital stays (4.9 vs 7.6 days) (all p < 0.05). The mean operative time was longer in the laparoscopic group (203 vs 123 min, p < 0.001). There were no significant differences between the transperitoneal and trans-retroperitoneal laparoscopy groups in any of the studied parameters, except that the operative time was longer in the trans-retroperitoneal laparoscopy group (244 vs 166 minutes, p < 0.01). CONCLUSIONS: Decreased blood loss, less postoperative pain, earlier resumption of oral feeding, and shorter hospital stays were achieved in patients undergoing laparoscopic adrenalectomy. These findings indicate that laparoscopic adrenalectomy is the treatment of choice for benign adrenal tumors. The transperitoneal approach yielded shorter operative time than the trans-retroperitoneal approach, because it offered a clearer view and familiar landmarks.

Adrenalectomy↗

PubMed2001

Correlation of cervical vertebra maturation with hand-wrist maturation in children.

The purpose of this study was to evaluate the reliability of cervical vertebra maturation as an indicator of skeletal age during the circumpubertal period. This was determined by correlating cervical vertebra maturation to hand-wrist maturation. The vertebral skeletal age was assessed using lateral cephalometric radiographs according to maturity indicators modified from Lamparski. The hand-wrist skeletal age was evaluated in radiographs with the system developed by Fishman. The sample consisted of 503 subjects (244 boys and 259 girls), aged 8 through 18 years. The Spearman rank correlation coefficients and Wilcoxon sign rank test showed that a statistically significant relationship existed between the two assessments. Both the intra- and inter-judge tests of reliability displayed no significant differences. The results of this study indicate that skeletal age assessment made from the maturational changes of cervical vertebrae were reliable, reproducible and valid.

Adolescent↗

PubMed2001

Influence of pH on the dewatering of activated sludge by Fenton's reagent.

The specific filtration resistance, moisture, and SVI were used to evaluate the influence of pH on the filtration and dewatering efficiencies when applying Fenton's reagent to treat the excess sludge. The excess sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Results show that initial pH has no significant effect on the filtration efficiency of sludge by using the Fenton (Fe2+/H2O2) system as the treatment process. However, the reduction of specific resistance by Fenton-like (Fe3+/H2O2) process decreased suddenly to a level similar to that obtained from the control experiment at initial pH > 4.5. For the moisture of cake sludge, both Fenton and Fenton-like systems have the same tendency; the moisture of cake sludge increased slightly with increasing the initial pH. The SVI values for Fenton process decreased with increasing the initial pH, but the opposite result was obtained from the Fenton-like and control system; higher pH was not favorable for the sludge settling.

Filtration↗

PubMed2000

Decolorization of textile wastewater by photo-fenton oxidation technology.

This paper describes the use of photo-fenton process for color removal from textile wastewater stream. The wastewater sample to be treated was simulated by using colorless polyvinyl alcohol (PVA) and reactive dyestuff of R94H. As a result, the hydroxyl radical (HO*) oxidation can effectively remove color, but the chemical oxygen demand (COD) was removed in a slight degree. The color removal is markedly related with the amount of HO* formed. The optimum pH for both the OH* formation and color removal occurs at pH 3-5. Up to 96% of color can be removed within 30 min under the studied conditions. Due to the photoreduction of ferric ion into ferrous ion, color resurgence was observed after 30 min. The ferrous dosage and UV power affect the color removal in a positive way, however, the marginal benefit is less significant in the higher range of both. PVA as the major background COD of a textile wastewater stream inhibits the color removal insignificantly as its concentration increases.

Color↗

PubMed2000

Differential expression of four human dynamin-like protein variants in brain tumors.

Dynamin-like protein, a large GTP-binding protein, has recently been cloned, and studies have suggested that it is involved in the formation of coated vesicles. In this report, the differential expression of four human dynamin-like protein splice variants (HdynIV-wildtype [WT], -11, -26, and -37) from various brain tumors was identified by reverse transcription/polymerase chain reaction (RT-PCR). One novel variant (HdynIV-11), not described previously, was identified. The four alternatively spliced variants exhibited tissue specificity in normal tissues. The HdynIV-WT was strongly expressed in the brain, whereas HdynIV-37 was expressed in all tissues examined. Moreover, HdynIV-26 was dominant in the liver and apparently overexpressed in all astrocytomas and most meningiomas and adenomas. This report suggests that HdynIV-26 may cause aberrant protein trafficking and alter vesicle formation in brain tumors. Our results also suggest that dynamin-like protein is associated with various brain tumors and, more importantly, that aberrant expression of the HdynIV-26 variant may play a role in brain tumorigenesis.

Adenoma↗

PubMed2000

Antiplatelet effect of marchantinquinone, isolated from Reboulia hemisphaerica, in rabbit washed platelets.

Platelet activation is involved in serious pathological situations, including atherosclerosis and restenosis. It is important to find efficient antiplatelet medicines to prevent fatal thrombous formation during the course of these diseases. Marchantinquinone, a natural compound isolated from Reboulia hemisphaerica, inhibited platelet aggregation and ATP release stimulated by thrombin (0.1 units mL(-1)), platelet-activating factor (PAF; 2 ng mL(-1)), collagen (10 microg mL(-1)), arachidonic acid (100 microM), or U46619 (1 microM) in rabbit washed platelets. The IC50 values of marchantinquinone on the inhibition of platelet aggregation induced by these five agonists were 62.0 +/- 9.0, 86.0 +/- 7.8, 13.6 +/- 4.7, 20.9 +/- 3.1 and 13.4 +/- 5.3 microM, respectively. Marchantinquinone inhibited thromboxane B2 (TxB2) formation induced by thrombin, PAF or collagen. However, marchantinquinone did not inhibit TxB2 formation induced by arachidonic acid, indicating that marchantinquinone did not affect the activity of cyclooxygenase and thromboxane synthase. Marchantinquinone did inhibit the rising intracellular Ca2+ concentration stimulated by the five platelet-aggregation inducers. The formation of inositol monophosphate induced by thrombin was inhibited by marchantinquinone. Platelet cAMP and cGMP levels were unchanged by marchantinquinone. The results indicate that marchantinquinone exerts antiplatelet effects by inhibiting phosphoinositide turnover.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2000

Attachment and growth of Salmonella Chester on apple fruits and in vivo response of attached bacteria to sanitizer treatments.

Attachment and growth of Salmonella Chester on fresh-cut apple disks and in vivo response of attached bacteria to sanitizer treatments were investigated. Apple disks (14 mm in diameter and 3 to 4 mm in thickness) were immersed in a bacterial suspension that contained 8.17 log CFU/ml of Salmonella Chester and air dried at room temperature for 10 min. After two rinses, the population of Salmonella Chester retained on apple disks that contained no skin was 13 to 19% higher than that retained on disks that contained skin, indicating that Salmonella Chester attached more firmly to the surfaces of injured tissue than to the unbroken skin. The number of bacteria attached to the disk was not affected by the immersion time but was directly proportional to the concentration of bacteria in the suspension. The distribution of artificially inoculated Salmonella Chester on the surfaces of three different parts of whole fruit was determined; 94% of attached bacteria was found on the stem and calyx cavity areas and 6% on the skin of the remaining area of the fruit. Despite their acidic pH (4.1), apple disks supported the growth of Salmonella Chester at 20 degrees C but not at 8 degrees C. All four sanitizers tested in the study, including 6% hydrogen peroxide, 2% trisodium phosphate, 0.36% calcium hypochlorite, and 1.76% sodium hypochlorite, were effective in reducing the population of Salmonella Chester on apple disks by 1 to 2 logs. However, 5 to 13% of bacteria survived the sanitizer treatments. Hydrogen peroxide, which reduced the population of Salmonella Chester on skin by 3 to 4 logs and the population of bacteria on stem or calyx by 1 to 2 logs, was the most effective among the four sanitizers tested. Firm attachment of bacteria on calyx, stem, and injured tissue and partial resistance of attached bacteria to sanitizer treatments are two major obstacles to be considered when developing methods for cleaning and decontaminating apple fruits destined for juice production and fresh consumption.

Animals↗

PubMed1999

Genetic and biochemical characterization of an exopolygalacturonase and a pectate lyase from Yersinia enterocolitica.

Yersinia enterocolitica, an invasive foodborne human pathogen, degrades polypectate by producing two depolymerizing enzymes, pectate lyase (PL) and polygalacturonase (PG). The gene encoding the PG activity, designated pehY, was located in a 3-kb genomic fragment of Y. enterocolitica ATCC 49397. The complete nucleotide sequence of this 3-kb fragment was determined and an open reading frame consisting of 1803 bp was predicted to encode a PG protein with an estimated M(r) of 66 kDa and pI of 6.3. The amino acid sequence of prePG showed 59 and 43% identity to that of the exopolygalacturonase (exoPG) of Erwinia chrysanthemi and Ralstonia solanacearum, respectively. The Y. enterocolitica PG overproduced in Escherichia coli was purified to near homogeneity using perfusion cation exchange chromatography. Analysis of the PG depolymerization products by high performance anion-exchange chromatography and pulsed amperometric detection (HPAEC-PAD) revealed the exolytic nature of this enzyme. The Y. enterocolitica PL overproduced in E. coli was also partially purified and the M(r) and pI were estimated to be 55 kDa and 5.2, respectively. HPAEC-PAD analysis of the PL depolymerization products indicated the endolytic nature of this enzyme. Southern hybridization analyses revealed that pehY and pel genes of Y. enterocolitica are possibly encoded in the chromosome rather than in the plasmid. Purified exopolygalacturonase (over 10 activity units) was unable to macerate plant tissues.

Amino Acid Sequence↗

PubMed1999

Influence of soft rot bacteria on growth of Listeria monocytogenes on potato tuber slices.

Growth of Listeria monocytogenes on potato tuber slices and its interaction with four representative species of soft rot bacteria (Pseudomonas fluorescens, P. viridiflava, Erwinia carotovora subsp. carotovora, and Xanthomonas campestris) were investigated. When potato tuber slices were inoculated with one of two L. monocytogenes strains (Scott A and ATCC 15313), an increase in numbers of 3 to 4 logs per gram of tissue was observed with samples that were stored at 20 degrees C for 6 days. However, an increase of about 2 logs was observed with samples that were stored at 8 degrees C for 12 days. When potato slices were simultaneously inoculated with L. monocytogenes and one of the four soft rot bacteria, the growth of L. monocytogenes was inhibited in the presence of P. fluorescens or P. viridiflava but was not significantly affected in the presence of E. carotovora or X. campestris. The antagonism of the two pseudomonads to L. monocytogenes was also observed in potato tuber extract and in culture media. Formation of inhibition zones was observed only in iron-deficient media but not in the medium supplemented with FeCl3. In addition, production of fluorescent siderophore (pyoverdin) by these two pseudomonads was demonstrated. L. monocytogenes was unable to colonize macerated plant tissue induced by soft-rotting bacteria 2 days before inoculation of the pathogen. These results indicate that growth of L. monocytogenes on potato tuber slices is differentially affected by soft rot bacteria and that antagonism of fluorescent pseudomonads to L. monocytogenes is possibly caused by the production of iron-chelating siderophore by these pseudomonads.

Colony Count, Microbial↗