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Biomedical subjects

S S Yang

Publications and source records attributed to S S Yang.

At least 73 records · Page 4Linked to original sources
PubMed1997

Cross-resistance analysis and molecular modeling of nonnucleoside reverse transcriptase inhibitors targeting drug-resistance mutations in the reverse transcriptase of human immunodeficiency virus.

Oxathlin carboxanilide analogs (UC) and alpha APA, compounds recognized as nonnucleoside reverse transcriptase (RT) inhibitors (NNRTI), were evaluated for activity against the human immunodeficiency virus (HIV-1) and drug-resistant variants. These NNRTIs are structurally diverse but potent inhibitors of HIV-1 with efficacy in the nanomolar to low micromolar concentrations. They interact at a specific site in the pain domain of the p66 subunit of RT. Treatment of HIV-1 infected cell cultures with UC compounds resulted in the selection of drug-resistant viruses bearing specific amino acid changes at 100, 101, 103, 106, and/or 181. Since Y181C and L1001 are the most commonly observed resistance-engendering mutations, RT enzymatic analysis was correlated with molecular modeling to glean information on the structural interactions between these NNRTIs and RT. Information derived from these studies will facilitate rational drug design and the selection of complementary anti-HIV drugs for combination therapy.

Drug Resistance, Microbial↗
PubMed1996

Recent advances in the residue analysis of N-methylcarbamate pesticides.

This paper highlights recent advances in the determination of methylcarbamate residues in water, soil and plant tissues. Chromatographic analyses (e.g., HPLC, GC, supercritical fluid chromatography and TLC) with various sample pretreatment procedures and detection methods are reviewed. More generally, some non-chromatographic techniques such as immunoassay, biosensor and spectrophotometry are included.

Biosensing Techniques↗
PubMed1996

Evaluation of micellar electrokinetic capillary chromatography for the analysis of selected tobacco alkaloids.

Micellar electrokinetic capillary chromatography was evaluated for simultaneous determination of several tobacco alkaloids with similar molecular structure. Satisfactory separation of nicotine, nornicotine, myosmine, anatabine and anabasine extracted from tobacco was achieved by introducing an ionic surfactant, sodium dodecyl sulfate, into the buffer system at a concentration of 100 mM. Sample preparation involved a single extraction with water containing 1% triethanolamine. Separation was performed on a 72 cm long, uncoated fused-silica capillary. Experimental parameters such as applied voltage, pH value, buffer composition and surfactant concentration were optimized. Enhancement of UV absorption of alkaloids in the presence of micelles was also studied.

Alkaloids↗
PubMed1996

Paraganglioma of the interatrial septum.

The case of a patient undergoing successful resection of an interatrial septal paraganglioma is presented. The diagnosis of an interatrial mass was established preoperatively by echocardiography, ultrafast cine computed tomographic scan, and cardiac catheterization. The tumor was excised in total, and the interatrial septum and the roof of the left atrium were reconstructed using a bovine pericardial patch.

Animals↗
PubMed1996

A rare variant of mirror hand: a case report.

Mirror hand is one of the rarest congenital differences of the upper extremity. Typically, there is absence of the radius, duplication of the ulna, and 7 digits in mirrored symmetry about the middle finger. We report a case of a rarer subset of hand duplication in which there is a normal radius and ulna and a hand with 8 digits. The patient underwent surgery to excise the radial 3 digits and to reconstruct the remaining radial digit to function as an opposable, 2 phalanx thumb. Wrist extension was augmented by transferring the digital extensors from the excised fingers to the radial wrist extensors.

Hand Deformities↗
PubMed1996

Electrohydraulic lithotripsy of upper ureteral calculi with semirigid ureteroscope.

Forty-three patients with single ureteral calculi located above the pelvic brim were treated by electrohydraulic lithotripsy (EHL) using a semirigid mini-ureteroscope. Of the 43 calculi, 36 (84%) were fragmented in one procedure. Six calculi (14%) were pushed back to the renal pelvis and treated successfully by complementary extracorporeal shockwave lithotripsy (SWL). The total success rate of ureteroscopic manipulation thus was 98%. The operation time (mean 26.4 minutes) and postoperative hospital stay (mean 2.53 days) were relatively short. Complications were limited to four (9%) minor perforations of the ureter managed by internal stenting. Among these patients with complications, there were no significant ureteral strictures noted on excretory urography or ureteroscopic examination 1 to 3 months after ureterolithotripsy. The costs of ureteroscopy with EHL are lower than that of SWL or ureteroscopic lasertripsy. The total fees for ureteroscopy with EHL are about two thirds those for SWL in Taiwan. Despite the longer learning curve required for ureteroscopy, ureteroscopy associated with EHL is a cost-effective alternative for the treatment of upper ureteral calculi, especially when SWL is not readily available.

Adult↗
PubMed1996

Morphogenesis, ATP content and oxytetracycline production by Streptomyces rimosus in solid substrate cultivation.

On agar plates, mycelia of Streptomyces rimosus TM-55 had a slender and smooth surface at 24 h, developed a shorter form and rough surface at 116 h, and lysed after 504 h incubation. Oxytetracycline potency reached a maximum at 94 h. During cultivation on solid substrate, mycelia rarely occurred on the surface at 24 h. The organism appeared as short rods at 166 h, and formed spores at 504 h. The ATP content was maximal at 166 h, while energy charge varied between 0.63 and 0.77 during cultivation. The oxytetracycline potency was maximal at 166 h and each gram of substrate produced 11 mg of antibiotic. ATP content and energy charge of mycelia showed a positive correlation with cell activity and oxytetracycline production.

Adenosine Triphosphate↗
PubMed1996

Identification of the mitogen-activated protein kinase phosphorylation sites on human Sos1 that regulate interaction with Grb2.

The Son of sevenless proteins (Sos) are guanine nucleotide exchange factors involved in the activation of Ras by cytoplasmic and receptor tyrosine kinases. Growth factor stimulation rapidly induces the phosphorylation of Sos on multiple serine and threonine sites. Previous studies have demonstrated that growth factor-induced Sos phosphorylation occurs at the C-terminal region of the protein and is mediated, in part, by mitogen-activated protein (MAP) kinase. In this report, we describe the identification of five MAP kinase sites (S-1137, S-1167, S-1178, S-1193, and S-1197) on hSos1. We demonstrate that four of these sites, S-1132, S-1167, S-1178, and S-1193, become phosphorylated following growth factor stimulation. The MAP kinase phosphorylation sites are clustered within a region encompassing three proline-rich SH3-binding sites in the C-terminal domain of hSos1. Replacing the MAP kinase phosphorylation sites with alanine residues results in an increase in the binding affinity of Grb2 to hSos1. Interestingly, hSos2 contains only one MAP kinase phosphorylation site and, as demonstrated previously, has an increased affinity toward Grb2 compared with hSos1. These results suggest a role for MAP kinase in the regulation of Grb2-Sos interactions. Since the binding of Grb2 is important for Sos function, the phosphorylation-dependent modulation of Grb2-Sos association may provide a means of controlling Ras activation.

Adaptor Proteins, Signal Transducing↗
PubMed1996

DNA flow cytometric analysis of chest-wall chondroma and chondrosarcoma.

DNA flow cytometric analysis was performed for prediction of malignancy potential, and hence of outcome, in 17 patients aged 29-76 (mean 52) years with cartilaginous tumour of the chest wall. Histologically there were nine chondromas and eight chondrosarcomas. The chondrosarcomas (3 grade I, 4 grade II, 1 grade III) were significantly larger than the chondromas (13.6 +/- 7.8 vs 4.2 +/- 2.0 cm, p < 0.001). DNA flow cytometry was performed on paraffin-embedded blocks of resected tumour. In eight of the 17 tumours (6 chondromas, 1 grade I and 1 grade II chondrosarcoma) measurement of DNA content failed because of low cellularity and severe calcification. Aneuploid DNA content was detected only in three chondrosarcomas (2 grade II, 1 grade III). The synthetic phase fraction was less than 15% in all the studied chondromas, but exceeded 25% in four of six chondrosarcomas. This case series though small, may indicate a trend towards association between higher histologic grading and greater incidence of aneuploidy with higher synthetic phase fraction. Tumour size, histologic grade, DNA ploidy and adequacy of surgical resection are the main influences on prognosis.

Adult↗
PubMed1996

Effect of vapor phase corrosion inhibitor on microbial corrosion of aluminum alloys.

Vapor phase corrosion inhibitors were used to investigate the antimicrobial activities and anticorrosion of aluminum alloy. Aspergillus flavus, A. niger, A. versicolor, Chaetomium globosum and Penicillium funiculosum had moderate to abundant growth on the aluminum alloy AA 1100 at Aw 0.901, while there was less growth at Aw 0.842. High humidity stimulated microbial growth and induced microbial corrosion. Dicyclohexylammonium carbonate had a high inhibitory effect on the growth of test fungi and the microbial corrosion of aluminum alloy, dicyclohexylammonium caprate and dicyclohexylammonium stearate were the next. Aluminum alloy coating with vapor phase corrosion inhibitor could prevent microbial growth and retard microbial corrosion.

Alloys↗
PubMed1996

Microbial corrosion of aluminum alloy.

Several microbes were isolated from the contaminated fuel-oil in Taiwan and the microbial corrosion of aluminum alloy A356-T6 was tested by MIL-STD-810E test method. Penicillium sp. AM-F5 and Cladosporium resinac ATCC 22712 had significant adsorption and pitting on the surface of aluminum alloy, Pseudomonas acruginosa AM-B5 had weak adsorption and some precipitation in the bottom, and Candida sp. AM-Y1 had the less adsorption and few cavities formation on the surface. pH of the aqueous phase decreased 0.3 to 0.7 unit for 4 months of incubation. The corrosion of aluminum alloy was very significant in the cultures of Penicillium sp. AM-F2, Penicillium sp. AM-F5 and C. resinac ATCC 22712. The major metabolites in the aqueous phase with the inoculation of C. resinac were citric acid and oxalic acid, while succinic acid and fumaric acid were the minors.

Alloys↗
PubMed1996

[Gastric emptying in non-insulin dependent diabetic patients].

Disordered gastrointestinal motility is an often overlooked clinical problem. Delayed gastric emptying of solid and/or liquid meal in patients with both type 1 and type 2 diabetes mellitus occurs in approximately 50% of these patients. Gastric emptying time (GET) was studied in seventy four non-insulin dependent (type 2) diabetic out-patients by using radionuclide gamma-photography with Tc-99m phytate solid experimental meal. Thirty nine of them received Tc-99m phytate liquid test meal on the next day. Forty six normal healthy volunteers acted as controls. The results showed that solid GET in patients with type 2 diabetes mellitus was significantly delayed (149.44 +/- 64.0 min) as compared with that in the control group (88.7 +/- 14.2 min) (p < 0.001). Fifty three among these 74 diabetic patients had delayed solid GET, accounting for 71.6%. Only 5 of 39 (12.8%) diabetic patients showed delayed liquid GET (average 38.7 +/- 35.3 min; control 46.2 +/- 11.1 min). There were no differences in sugar control, duration of the disease, and upper gastrointestinal symptoms between patients with delayed GET and those with normal GET. We concluded that delayed gastric emptying is very common in patients with non-insulin dependent diabetes mellitus and which has no direct correlation to blood sugar control, duration of the disease, and upper gastrointestinal symptoms. Radionuclide solid gastric emptying test is a both safe (low radioactivity) and convenient (non-invasive) diagnostic tool in non-insulin dependent diabetic gastroparesis.

Adult↗
PubMed1996

Multiple carpometacarpal dislocations. A case report and review of treatment.

Carpometacarpal dislocations of the ulnar four joints are rare injuries that are usually associated with high-energy trauma. Given the small number of cases reported, there exists some controversy regarding their optimal management. The case of a 27-year-old man who sustained a dorsal dislocation (without associated fractures) of the ulnar four carpometacarpal joints as a result of a fall from a height is presented. The literature regarding these hand injuries is reviewed, and the need for anatomic reduction and stabilization is discussed.

Acetabulum↗
PubMed1995

Differential interactions of human Sos1 and Sos2 with Grb2.

The guanine nucleotide exchange factor Son of sevenless (Sos) performs a crucial step in the coupling of receptor tyrosine kinases to Ras activation. Mammalian cells contain two related but distinct Sos proteins, Sos1 and Sos2. Although they share a high degree of overall similarity, it is not known to what extent their biological and biochemical properties overlap. In the present study, we have compared the interactions of the two human homologues of Sos, hSos1 and hSos2, with the adaptor protein Grb2. We show that hSos2 interacts with Grb2 via its proline-rich COOH-terminal domain and that this interaction is dependent on the SH3 domains of Grb2. In general, these characteristics are similar to the ones reported previously for the interaction of hSos1 with Grb2. However, the apparent binding affinity of hSos2 for Grb2 is significantly higher relative to that of hSos1 both in vitro and in vivo. The region conferring this higher binding affinity has been mapped to residues 1126-1242 of the hSos2 COOH-terminal domain. These results suggest that Sos1 and Sos2 may differentially contribute to receptor-mediated Ras activation.

Adaptor Proteins, Signal Transducing↗