PubMed Health⌕ Search

Biomedical subjects

S S Yang

Publications and source records attributed to S S Yang.

At least 19 recordsLinked to original sources
PubMed2006

Cloning and characterization of the genes for biosynthesis of the compatible solute ectoine in the moderately halophilic bacterium Halobacillus dabanensis D-8(T).

A 11.2-kb fragment containing the ectABC genes of the biosynthetic pathway of ectoine from the Gram-positive, moderately halophilic bacterium Halobacillus dabanensis D-8(T) was obtained by inverse polymerase chain reaction. Subsequently, the entire ectABC cluster was cloned and analyzed. It revealed that the intergenic regions of the ectABC genes from H. dabanensis D-8(T) are more tightly spaced than those of Chromohalobacter salexigens, Halomonas elongata, Marinococcus halophilus, and Salibacillus pasteurii. The amino-acid sequence deduced from ectABC was highly homologous that from Virgibacillus pantethenticus (EctA 52%, EctB 60%, EctC 67%, respectively). The ectABC genes were cloned in the expression plasmid pMXB10 resulting in pMXB10ectABC. The ectoine was detected from cell extract in Escherishia coli ER2566 containing pMXB10ectABC using (13)C nuclear magnetic resonance spectroscopy.

Amino Acid Sequence↗
PubMed2005

Halobacillus dabanensis sp. nov. and Halobacillus aidingensis sp. nov., isolated from salt lakes in Xinjiang, China.

Two moderately halophilic spore-forming bacteria were isolated from salt lakes in the Xinjiang region of China. The two strains, designated AD-6(T) and D-8(T), were aerobic, Gram-positive, rod-shaped and motile by means of peritrichous flagella. Strains AD-6(T) and D-8(T) grew in the presence of 0.5-20% and 0.5-25% (w/v) NaCl in complex medium, respectively. Their cell-wall peptidoglycan was of the L-Orn-D-Asp type. The major menaquinone found in both strains was menaquinone-7 (MK-7). The fatty acid profile contained a large amount of branched fatty acids; the main fatty acids were anteiso-C(15:0), anteiso-C(17:0), iso-C(15:0) and iso-C(16:0). The DNA G+C content of strains D-8(T) and AD-6(T) was 41.4 and 42.2 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains D-8(T) and AD-6(T) were located in the genus Halobacillus. Levels of 16S rRNA gene sequence similarity between the isolated strains and the type strains of Halobacillus species were in the range 96.2-99.5%. DNA-DNA relatedness values of 17.0-52.2% were found between the two strains and other Halobacillus species. The DNA-DNA relatedness value between D-8(T) and AD-6(T) was 50.6%. On the basis of phenotypic and chemotaxonomic properties, phylogenetic analysis and genomic distinctiveness, strains D-8(T) and AD-6(T) should be placed in the genus Halobacillus as two novel species, for which the names Halobacillus dabanensis sp. nov. (type strain=JCM 12772(T)=CGMCC 1.3704(T)) and Halobacillus aidingensis sp. nov. (type strain=JCM 12771(T)=CGMCC 1.3703(T)) are proposed, respectively.

Bacillaceae↗
PubMed2004

Cold perfluorochemical-induced hypothermia protects lung integrity in normal rabbits.

To test the hypothesis that intrapulmonary perfluorochemical (PFC) liquid may induce hypothermia, and to compare the effects of internal (IC), external (EC), and combined cooling techniques (EC + IC), 14 juvenile rabbits were randomized to EC by a cold blanket (4 degrees C, n = 5), IC by intrapulmonary cold PFC liquid lavage (4 degrees C, n = 5), or combined IC with PFC and EC (n = 4). Arterial blood gas, blood pressure, and lung mechanics were monitored, and lung histology was examined by light microscopy. The results showed that cooling rates and the time needed to be cooled down to 30 degrees C were significantly faster in EC and EC + IC than IC (p < 0.05). Blood gas analysis and cardiopulmonary function were within the normal range in all groups. Histological assessment revealed varied atelectasis in all lung regions in EC, whereas PFC-filled lungs (IC and EC + IC) demonstrated more homogenous expansion and no evidence of atelectasis. The results indicate that intrapulmonary PFC may be an effective technique to induce and/or augment hypothermia while supporting gas exchange, lung volume and pulmonary architecture.

Animals↗
PubMed2004

Isolation of salt-sensitive mutants from Sinorhizobium meliloti and characterization of genes involved in salt tolerance.

AIMS: The purpose of our research is to isolate salt-sensitive mutants and to study the genes involved in salt tolerance of the salt-tolerant bacterium Sinorhizobium meliloti 042BM. METHODS: Wild type S. meliloti 042BM bacteria are able to grow at a NaCl concentration of 0.6 mol l(-1). A transposon Tn5-1063a mutagenesis library of S. meliloti 042BM was constructed and eight salt-sensitive mutants were isolated, which were unable to growth on FY plates containing 0.4 mol l(-1) NaCl. SIGNIFICANCE: Our interest is to provide information about the mechanism of salt tolerance in bacteria by studying the genes involved in salt tolerance. Here, seven different genes were identified. These genes include omp10 encoding a cell outer membrane protein, relA encoding (p)ppGpp synthetase, greA encoding a transcription cleavage factor, nuoL encoding NADH dehydrogenase I chain L transmembrane protein, a putative nuclease/helicase gene and two unknown genes. Based on these findings, we suggest that the regulation of salt tolerance of S. meliloti 042BM is complex and on several levels.

Bacterial Proteins↗
PubMed2003

A catalogue of molecular, physiological and symbiotic properties of soybean-nodulating rhizobial strains from different soybean cropping areas of China.

We have analysed 198 fast-growing soybean-nodulating rhizobial strains from four different regions of China for the following characteristics: generation time; number of plasmids; lipopolysaccharide (LPS), nodulation factors (LCOs) and PCR profiles; acidification of growth medium; capacity to grow at acid, neutral, and alkaline pH; growth on LC medium; growth at 28 and 37 degrees C; melanin production capacity; Congo red absorption and symbiotic characteristics. These unbiased analyses of a total subset of strains isolated from specific soybean-cropping areas (an approach which could be called "strainomics") can be used to answer various biological questions. We illustrate this by a comparison of the molecular characteristics of five strains with interesting symbiotic properties. From this comparison we conclude, for instance, that differences in the efficiency of nitrogen fixation or competitiveness for nodulation of these strains are not apparently related to differences in Nod factor structure.

Bacterial Proteins↗
PubMed2003

Predictive factors of the long-term outcome in reflux esophagitis in a low-prevalence gastroesophageal reflux disease region.

BACKGROUND: There are no data concerning the long-term outcome of patients with reflux esophagitis in Taiwan. In this study the outcome and the specific prognostic indicators associated with outcome in patients were assessed retrospectively, 7 years after diagnosis of esophagitis. METHODS: The study comprised a total of 128 patients with endoscopic esophagitis, diagnosed between January and June 1995, at Taichung Veterans' General Hospital. The outcome at 7 years after diagnosis was assessed by outpatient or telephone interview. Factors associated with requiring long-term acid suppression therapy were analyzed. RESULTS: In all, 105 patients were eligible for analysis: 61 patients (58.1%) with LA (Los Angeles classification) grade A, 29 patients (27.6%) with grade B, 11 patients (10.5%) with grade C and 4 patients (3.5%) with grade D esophagitis. Seven years after diagnosis, there were 52 patients (49.5%) with no or occasional reflux symptoms, 8 patients (7.6%) with occasional symptoms requiring treatment with histamine-2 receptor antagonists (H2RAs), 12 patients (11.4%) with occasional symptoms requiring treatment with proton pump inhibitors (PPIs), as needed, and 33 patients (31.3%) with sustained symptoms needing daily maintenance with PPIs. CONCLUSION: Nearly 50% of patients in Taiwan with endoscopic esophagitis still required treatment 7 years after diagnosis. Approximately 31% of patients still required daily acid suppression therapy. Presence of hiatal hernia and the severity of esophagitis at initial endoscopy independently were predictive of those who would require long-term acid suppression therapy.

Adult↗
PubMed2003

Steroid-induced tumor lysis syndrome in a patient with preleukemia.

Tumor lysis syndrome (TLS) is a well recognized complication of chemotherapy and radiotherapy for leukemia, lymphoma as well as rapidly growing malignancies. Less described is the occurrence of TLS following steroid therapy alone. Herein, we report on a 32-year-old male with myelodysplastic syndrome, characterized by refractory anemia with excess blasts in transformation, who developed acute oliguric renal failure 12 hours after methylprednisolone 1.0 g for presumed autoimmune thrombocytopenia. Laboratory investigations revealed typical findings of TLS, including hyperkalemia, marked hyperuricemia, hyperphosphotemia, hypocalcemia and urine uric acid to creatinine ratio 1.8 (> 1.0). Long hemodialysis (8 hours) was initiated for 3 consecutive sessions. Renal function recovered 1 week later. This case high-lights that single-dose steroid administration in a patient with hematological malignancy may cause the potential life-threatening complications of TLS. Prophylactic management prior to the use of steroid therapy for a variety of purposes is absolutely required in high-risk patients.

Acute Kidney Injury↗
PubMed2002

Determination of tobacco alkaloids by gas chromatography with nitrogen-phosphorus detection.

An improved method, gas chromatography (GC) with nitrogen-phosphorus detection (NPD), has been used for determination of alkaloids in green and cured tobacco. Tobacco alkaloids of interest included nicotine, nornicotine, myosmine, anabasine, and anatabine. Tobacco samples were treated with a small quantity of aqueous ammonia solution to "loosen" tobacco tissue and to adjust pH, then extracted with solvent. The composition of the extraction solvent solution affected recoveries of the alkaloids, particularly nornicotine, and also contributed to other phenomena such as carry-over in the injection liner and "quenching" of the nitrogen-phosphorus detector. Use of a packed injection liner (e.g. with Carbowax-KOH on Chromosorb) to reduce carry-over was studied. Quenching of the nitrogen-phosphorus detector was eliminated by reducing the injection volume (i.e. increasing the split ratio), by use of a packed injection liner, and by reducing the amount of pretreatment with aqueous ammonia. A narrow bore capillary column (i.e. 0.18 mm id) was used to improve sensitivity and resolution and to increase the speed of GC analysis. An internal standard, 2,4'-dipyridyl, was used for quantitative measurement of these tobacco alkaloids.

Alkaloids↗
PubMed2002

Optimization of headspace sampling using solid-phase microextraction for volatile components in tobacco.

Solid-phase microextraction (SPME) was evaluated as a tool for headspace sampling of tobacco samples. Several experimental parameters (e.g. sampling temperature, pH, moisture, and the type of SPME fibers) were optimized to improve sampling efficiency in two aspects; maximum adsorption and selective adsorption of volatile components onto SPME fibers. The effect of these parameters was often dominated by the physical and chemical nature (e.g. volatility, polarity) of target compounds, thus, SPME sampling conditions can be adjusted to favor a selected group of compounds, such as organic acids in tobacco.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

Effect of pH and soybean cultivars on the quantitative analyses of soybean rhizobia populations.

Quantitative analyses of fast- and slow-growing soybean rhizobia populations in soils of four different provinces of China (Hubei, Shan Dong, Henan, and Xinjiang) have been carried out using the most probable number technique (MPN). All soils contained fast- (FSR) and slow-growing (SSR) soybean rhizobia. Asiatic and American soybean cultivars grown at acid, neutral and alkaline pH were used as trapping hosts for FSR and SSR strains. The estimated total indigenous soybean-rhizobia populations of the Xinjiang and Shan Dong soil samples greatly varied with the different soybean cultivars used. The soybean cultivar and the pH at which plants were grown also showed clear effects on the FSR/SSR rations isolated from nodules. Results of competition experiments between FSR and SSR strains supported the importance of the soybean cultivar and the pH on the outcome of competition for nodulation between FSR and SSR strains. In general, nodule occupancy by FSRs significantly increased at alkaline pH. Bacterial isolates from soybean cultivar Jing Dou 19 inoculated with Xinjiang soil nodulate cultivars Heinong 33 and Williams very poorly. Plasmid and lipopolysaccharide (LPS) profiles and PCR-RAPD analyses showed that cultivar Jing Dou 19 had trapped a diversity of FSR strains. Most of the isolates from soybean cultivar Heinong 33 inoculated with Xinjiang soil were able to nodulate Heinong 33 and Williams showed very similar, or identical, plasmid, LPS and PCR-RAPD profiles. All the strains isolated from Xinjiang province, regardless of the soybean cultivar used for trapping, showed similar nodulation factor (LCO) profiles as judged by thin layer chromatographic analyses. These results indicate that the existence of soybean rhizobia sub-populations showing marked cultivar specificity, can affect the estimation of total soybean rhizobia populations indigenous to the soil, and can also affect the diversity of soybean rhizobial strains isolated from soybean nodules.

China↗
PubMed2001

Determination of the chemical structure of the capsular polysaccharide of strain B33, a fast-growing soya bean-nodulating bacterium isolated from an arid region of China.

We have determined the structure of a polysaccharide from strain B33, a fast-growing bacterium that forms nitrogen-fixing nodules with Asiatic and American soya bean cultivars. On the basis of monosaccharide analysis, methylation analysis, one-dimensional 1H- and 13C-NMR and two-dimensional NMR experiments, the structure was shown to consist of a polymer having the repeating unit -->6)-4-O-methyl-alpha-D-Glcp-(1-->4)-3-O-methyl-beta-D-GlcpA-(1--> (where GlcpA is glucopyranuronic acid and Glcp is glucopyranose). Strain B33 produces a K-antigen polysaccharide repeating unit that does not have the structural motif sugar-Kdx [where Kdx is 3-deoxy-D-manno-2-octulosonic acid (Kdo) or a Kdo-related acid] proposed for different Sinorhizobium fredii strains, all of them being effective with Asiatic soya bean cultivars but unable to form nitrogen-fixing nodules with American soya bean cultivars. Instead, it resembles the K-antigen of S. fredii strain HH303 (rhamnose, galacturonic acid)n, which is also effective with both groups of soya bean cultivars. Only the capsular polysaccharide from strains B33 and HH303 have monosaccharide components that are also present in the surface polysaccharide of Bradyrhizobium elkanii strains, which consists of a 4-O-methyl-D-glucurono-L-rhamnan.

Carbohydrate Conformation↗
PubMed2001

Structure-based mutagenesis reveals distinct functions for Ras switch 1 and switch 2 in Sos-catalyzed guanine nucleotide exchange.

Ras GTPases function as binary switches in signaling pathways controlling cell growth and differentiation. The guanine nucleotide exchange factor Sos mediates the activation of Ras in response to extracellular signals. We have previously solved the crystal structure of nucleotide-free Ras in complex with the catalytic domain of Sos (Boriack-Sjodin, P. A., Margarit, S. M., Bar-Sagi, D., and Kuriyan, J. (1998) Nature 394, 337-343). The structure demonstrates that Sos induces conformational changes in two loop regions of Ras known as switch 1 and switch 2. In this study, we have employed site-directed mutagenesis to investigate the functional significance of the conformational changes for the catalytic function of Sos. Switch 2 of Ras is held in a very tight embrace by Sos, with almost every external side chain coordinated by Sos. Mutagenesis of contact residues at the switch 2-Sos interface shows that only a small set of side chains affect binding, with the most important contact being mediated by tyrosine 64, which is buried in a hydrophobic pocket of Sos in the Ras.Sos complex. Substitutions of Ras and Sos side chains that are inserted into the Mg(2+)- and nucleotide phosphate-binding site of switch 2 (Ras Ala(59) and Sos Leu(938) and Glu(942)) have no effect on the catalytic function of Sos. These results indicate that the interaction of Sos with switch 2 is necessary for tight binding, but is not the critical driving force for GDP displacement. The structural distortion of switch 1 induced by Sos is mediated by a small number of specific contacts between highly conserved residues on both Ras and Sos. Mutations of a subset of these residues (Ras Tyr(32) and Tyr(40)) result in an increase in the intrinsic rate of nucleotide dissociation from Ras and impair the binding of Ras to Sos. Based on this analysis, we propose that the interactions of Sos with the switch 1 and switch 2 regions of Ras have distinct functional consequences: the interaction with switch 2 mediates the anchoring of Ras to Sos, whereas the interaction with switch 1 leads to disruption of the nucleotide-binding site and GDP dissociation.

Amino Acid Substitution↗
PubMed2001

Microbial ecology of soils surrounding nuclear and thermal power plants in Taiwan.

This paper reports a study of the effect of three nuclear and one thermal power plants on the microbial ecology of soils. Populations of bacteria, actinomycetes, fungi, cellulolytic microbes, phosphate-solubilizing microbes and nitrogen-fixing microbes in the soil in the vicinity of each plant were studied. Soils were acidic at three sites, and moisture contents of the power plant soils were lower than those of the surrounding areas. Microbial populations of the topsoils (0-20 cm deep) were higher than the subsoils (21-40 cm deep), and only 10-15% of them showed significant difference (P < .05). Thirty-three percent of the samples from the surrounding areas had higher microbial population than those from the power plant areas, but 19% was the reverse. Populations of cellulolytic, phosphate-solubilizing and nitrogen-fixing microbes varied with sampling locations, season and environmental conditions. Ratios of cellulolytic, phosphate-solubilizing and nitrogen-fixing microbes to total viable counts in some samples of the surrounding areas were significantly higher than in the power plant areas. Although the microbial populations of power plant soil and its surrounding area were somewhat different, it cannot be attributed as an effect of power plant operation, as the differences were not consistent.

Environmental Monitoring↗
PubMed2001

Natural product-based anti-HIV drug discovery and development facilitated by the NCI developmental therapeutics program.

During the decade 1987-1996, the Developmental Therapeutics Program (DTP) of the National Cancer Institute (NCI) provided infrastructure support for both intramural and extramural anti-HIV (human immunodeficiency virus) drug discovery research and development. This retrospective review describes some of the anti-HIV lead discovery and development that took place under DTP auspices or which was substantially facilitated by resources made available through the DTP. Examples highlighted include leads identified through the initial screening of pure natural product derived compounds and those derived from bioassay-guided fractionation of crude natural product extracts, and these are classified according to the mechanism of action targeting the critical steps within the replication cycle of HIV.

Amino Acid Sequence↗
PubMed2001

The effect of jejunal meal feeding on gastroesophageal reflux.

BACKGROUND: Postprandial gastric distention is frequently associated with transient lower esophageal sphincter relaxation and gastroesophageal reflux (GER). Since the role of nutrient perfusion into the jejunum in inducing GER is not well understood, we studied the effect of jejunal feeding on GER through a percutaneous gastrojejunal tube in patients with and without reflux esophagitis. METHODS: Nine stroke patients with reflux esophagitis were fed through a percutaneous gastrojejunal tube with either a liquid meal (2 kcal/2 ml/min) or saline for 2 h randomly on 2 separate days. An esophageal pH probe was placed 5 cm above the gastroesophageal junction to detect acid reflux. Six stroke patients without esophagitis were enrolled as controls. RESULTS: In both the patients with esophagitis and the controls, esophageal acid exposure (15.3% (4.9%-28.2%) versus 2.7% (0.0%-10.8%), P=0.003; 5.9% (0.5%-6.7%) versus 0.0% (0.0%-1.5%), P = 0.01) and events of acid reflux (5 (1-16) versus 2 (0-8), P = 0.02; 12 (3-17) versus 1 (0-4), P = 0.02) were significantly greater during jejunal meal feeding than during saline infusion. Furthermore, in the reflux patients, but not in the controls, acid clearance time was also greater during jejunal meal feeding than during saline infusion (2.9 min (0.5-9.6 min) versus 0.7 min (0.0-4.3 min), P = 0.04). CONCLUSIONS: We therefore conclude that jejunal nutrient infusion without gastric distention can induce GER in both patients with reflux esophagitis and controls. This implies that GER induced by jejununal nutrients may in part explain the incapability of jejunal tube feeding to prevent gastropulmonary aspiration in patients at risk.

Aged↗
PubMed2001

Small intestinal bacterial overgrowth versus antimicrobial capacity in patients with spontaneous bacterial peritonitis.

BACKGROUND: Spontaneous bacterial peritonitis (SBP) is a serious infection in cirrhotic patients with ascites. Both defects in the host defense mechanisms and the enhancement of the offensive factor (small intestinal bacterial overgrowth (SIBO)) may contribute to the development of SBP. Therefore, the aim of this study was to evaluate the role of SIBO versus various antimicrobial capacities in the pathogenesis of SBP in cirrhotic patients. METHODS: Forty-five cirrhotic patients were enrolled in this study. Bacterial overgrowth was evaluated by breath hydrogen test (BH2T). The hepatic reticuloendothelial system phagocytic index (HRESPI) was measured by intravenously injected colloid suspensions. RESULTS: The Child-Pugh scores in the SBP group were higher than in the non-SBP group (10.5 +/- 2.0 versus 8.0 +/- 1.8, P < 0.01). The ascitic protein concentration was significantly lower in the SBP group than in the non-SBP group (897 +/- 425 mg/l versus 1,325 +/- 453 mg/l, P < 0.01). Furthermore, the serum C3 concentration was lower in the SBP group than in the non-SBP group (43.1 +/- 13.6 ng/dl versus 73.2 +/- 26.4 ng/dl, P < 0.01). The serum C4 concentration was also lower in the SBP group than in the non-SBP group (12.4 +/- 4.0 ng/dl versus 16.9 +/- 6.6 ng/dl, P < 0.05). The incidence of SIBO was higher in the SBP group than in the non-SBP group (68.2% versus 17.4%, P < 0.01). HRESPI values were significantly higher in the two groups of cirrhotic patients than in the normal reference. However, there were no statistical differences in HRESPI between the two groups (8.4 +/- 2.8 min in the SBP group versus 7.9 +/- 2.8 min in the non-SBP group). CONCLUSIONS: The results of this study showed that the hepatic reticuloendothelial function is impaired in cirrhotic patients, but the degree of impairment does not differ between patients with and without previous history of SBP. Lower ascitic total protein, lower serum C3 and C4 concentrations, and presence of SIBO are all risk factors for SBP. Based on the results of our study, defects in the host defense mechanisms and the enhancement of the offensive factor (SIBO) may act in concert for the development of SBP.

Ascitic Fluid↗