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Biomedical subjects

Y C Su

Publications and source records attributed to Y C Su.

At least 55 records · Page 3Linked to original sources
PubMed1996

The adaptor protein Nck links receptor tyrosine kinases with the serine-threonine kinase Pak1.

Nck is an adaptor protein composed of a single SH2 domain and three SH3 domains. Upon growth factor stimulation, Nck is recruited to receptor tyrosine kinases via its SH2 domain, probably initiating one or more signaling cascades. In this report, we show that Nck is bound in living cells to the serine-threonine kinase Pak1. The association between Nck and Pak1 is mediated by the second SH3 domain of Nck and a proline-rich sequence in the amino terminus of Pak1. We also show that Pak1 is recruited by activated epidermal growth factor (EGF) and platelet-derived growth factor receptors. Moreover, Pak1 kinase activity is increased in response to EGF in HeLa cells transfected with human Pak1, and the kinase activity was enhanced when Nck was co-transfected. It is concluded that Nck links receptor tyrosine kinases with Pak1 and is probably involved in targeting and regulation of Pak1 activity.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Interaction between the phosphotyrosine binding domain of Shc and the insulin receptor is required for Shc phosphorylation by insulin in vivo.

Stimulation of the insulin receptor (IR) results in tyrosine phosphorylation of the intermediate molecules insulin receptor substrate-1 (IRS-1), IRS-2, and Shc, which then couple the IR to downstream signaling pathways by serving as binding sites for signaling molecules with SH2 domains. It has been proposed that direct binding of IRS-1, IRS-2, and Shc to an NPX-Tyr(P) motif in the juxtamembrane region of the IR is required for tyrosine phosphorylation of these molecules by the IR. In this regard, Shc and IRS-1 contain domains that are distinct from SH2 domains, referred to as the phosphotyrosine binding (PTB) or phosphotyrosine interaction (PI) domains, which bind phosphotyrosine in the context of an NPX-Tyr(P) motif. To further clarify the role of the Shc PTB/PI domain, we identified a mutation in this domain that abrogated binding of Shc to the IR in vitro. Interestingly, this mutation completely abolished Shc phosphorylation by the IR in vivo whereas mutation of the arginine in the FLVRES motif of the Shc SH2 domain did not affect Shc phosphorylation by insulin. In addition, we identified specific amino acids on the IR that are required for the IR to stimulate Shc but not IRS-1 phosphorylation in vivo. As with the PTB/PI domain Shc mutant, the ability of these mutant receptors to phosphorylate Shc correlates with the binding of the PTB/PI domain of Shc to similar sequences in vitro. These findings support a model in which binding of the PTB/PI domain of Shc directly to the NPX-Tyr(P) motif on the IR mediates Shc phosphorylation by insulin.

3T3 Cells↗
PubMed1996

High seroprevalence of IgG against Helicobacter pylori among endoscopists in Taiwan.

A prospective survey to investigate the seroprevalence of IgG against Helicobacter pylori among endoscopists in Taiwan was conducted by analyzing blood samples of 70 study subjects and 64 nonendoscopist physicians with quantitative ELISA. Personal information and the practices of infection control related to gastroscopy examination were obtained by a self-administered questionnaire. Significant differences were detected in the IgG prevalence between study and control subjects (80.0% vs 51.6%; P < 0.05). The serum level of antibody in endoscopists (385.2 +/- 36.1 unit/ml) was significantly higher than that of nonedoscopists (211.8 +/- 33.0 unit/ml; P = 0.018). Endoscopists performing 30 or more sessions of gastroscopy per week had higher seroprevalence than those performing less than 30 sessions (90.9% vs 70.3%; P = 0.0126). In conclusion, endoscopists in Taiwan had a high prevalence of H. pylori infection. The cause might be related to the frequency of gastroscopies performed.

Adult↗
PubMed1996

Detection of staphylococcal enterotoxin H by an enzyme-linked immunosorbent assay.

A double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of a newly identified staphylococcal enterotoxin H (SEH). Peroxidase was conjugated to antibodies specific to the enterotoxin. 2,2'Azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid)(ABTS) in hydrogen peroxide solution was used as the enzyme substrate. A standard curve of purified SEH was prepared with concentrations ranging from 1.3 to 50 ng/ml. SEH at levels equal to 2.5 ng/ml and higher were detected by this procedure. Culture supernatant from the growth of selected Staphylococcus aureus strains was analyzed by using the ELISA. SEH was produced by three of 20 strains that produced one identified enterotoxin. Ten of 21 strains, previously shown to produce substances that induced emesis in monkeys but not any known enterotoxins (A through E), were also positive for SEH production. The other 11 strains gave negative results in the ELISA, indicating that other unidentified serological types of enterotoxin exist.

Animals↗
PubMed1996

Computed tomography, endoscopic ultrasonography and intraoperative assessment in TN staging of gastric carcinoma.

In a prospective study from November 1989 to December 1993, the accuracy of computed tomography (CT), endoscopic ultrasonography (EUS) and intraoperative surgical assessment were compared for the evaluation of the depth of invasion (T category) and involvement of lymph nodes (N category) in patients with gastric carcinoma. Sixty-nine consecutive patients who received preoperative CT and EUS underwent subsequent surgery. CT and EUS results were compared with histopathologic staging of tumor invasion depth and regional lymph node metastasis (pT and pN categories). T categories were staged correctly in 42% of the cases by CT, 71% by EUS and 55% by intraoperative surgical assessment. CT correctly staged 49% of N1 and N2 lymph nodes compared with 65% for EUS and 45% for intraoperative surgical assessment. CT was more accurate for advanced cancer but had a tendency to understage the T and N categories. EUS was more accurate for serosal cancer and displayed a tendency to overstage T categories and understage N categories. Intraoperative surgical assessment overstaged early T stages, understaged the T4 stage and had a tendency to overstage N categories. CT and intraoperative surgical assessment of T and N categories were of limited value in the staging of gastric carcinoma compared to EUS. EUS is a valuable form of assessment to evaluate gastric cancer staging before surgery.

Adenocarcinoma↗
PubMed1996

Cloning of the tryptophan operon of Brevibacterium divaricatum and its expression in E. coli.

A genomic bank from Brevibacterium divaricatum has been prepared using lambda EMBL3 as a vector. The genomic bank's titers are 2.2 x 10(6) pfu/micrograms. Through screening by plaque hybridization, a 9.6 kb NcoI fragment which contains the entire trp operon has been isolated. Polymerase chain reaction amplification and restriction endonuclease analysis of PCR fragments indicated that there is homology between the coryneform bacteria; however, some genetic diversity among the species still exists. By complementation tests using subcloning of the 9.6 kb NcoI fragments and various E. coli tryptophan auxotrophs, this fragment was found to contain a gene cluster composed of trpE, trpD, trpC, trpB and trpA in this order. This revealed that the tryptophan biosynthesis genes in B. divaricatum may be an operon.

Bacterial Proteins↗
PubMed1995

Identification and purification of a new staphylococcal enterotoxin, H.

A staphylococcal enterotoxin which elicited an emetic response in monkeys but did not share antigenic determinants with any of the identified enterotoxins was identified and purified from Staphylococcus aureus FRI-569. The emetic activity of this new enterotoxin was neutralized only by antibodies specific to it and not by antibodies to enterotoxins A, B, C, D, and E or toxic shock syndrome toxin 1. Immunodiffusion assays did not detect cross-reactivity between this new and all the other identified enterotoxins. The purification procedure involved removal of the enterotoxin from culture supernatant fluids by batch adsorption with CG-50 resin, CM-Sepharose FL ion-exchange chromatography, and Sephacryl 100 HR and Bio-Gel P-30 gel filtration. The molecular weight of this enterotoxin, 27,300, determined by gel filtration on Sephacryl 100 HR agreed with the molecular weight, 28,500, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The apparent migration of this enterotoxin determined by SDS-PAGE did not shift in the presence of a disulfide reducing agent, indicating that it is composed of a single-chain protein. The N-terminal amino acid sequence of the enterotoxin was determined to be Glu-Asp-Leu-His-Asp-Lys-Ser-Glu-Leu-Thr-Asp-Leu-Ala-Leu-Ala-Asn-Ala-Tyr- Gly- Gln-Tyr-Asn-His-Pro-Phe-Ile-Lys-Glu-Asn-Ile, which did not match the N-terminal sequences of any known proteins. The isoelectric point of the enterotoxin determined by isoelectric focusing was about 5.7.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Construction of lysine-producing strains by gene disruption and replacement in Brevibacterium divaricatum.

Gene disruption and replacement techniques were applied to block the biosynthesis of threonine and methionine and thus to construct genetically stable lysine producers in a glutamate-producing bacteria, Brevibacterium divaricatum. The homoserine dehydrogenase gene (hom), homoserine kinase gene (thrB) and hom-thrB operon were amplified as 1.8, 1.25 and 2.8 kb fragments from B. divaricatum by polymerase chain reaction (PCR) and cloned in an E. coli-coryneform bacteria shuttle vector, pSUMN18. These genes were disrupted by inserting a kanamycin resistant gene (kan) from pUC4-KISS into the structural genes. Integrative plasmids were constructed and transformed into B. divaricatum. Integrative transformants could be obtained only when the integrative plasmids were constructed from the plasmids which had escaped from the restriction barrier of the hosts. The resulting integrative transformants showed kanamycin resistance and contained no plasmids. About 1-10% of the transformants were auxotrophs. By checking the nutritional requirement, it was found that all of these transformants required threonine and/or homoserine as expected. Southern blot analysis confirmed the integrations, and both single and double crossover homologous recombination mechanisms were proposed to explain the integration and replacement. These auxotrophic integrative transformants which were derived from double crossover events accumulated 1-3% lysine in culture broth only when the added threonine was limited. Integrative transformants which were site-specifically inactivated in hom or hom-thrB genes produced more lysine than did those only inactivated at the thrB gene. These transformants were extremely stable, and the reversion frequency was below 10(-9) per generation. It is suggested that this technique will be useful in the construction of stable auxotrophic mutants.

Actinomycetales↗
PubMed1995

Does Helicobacter pylori infection play a role in the pathogenesis of non-ulcer dyspepsia--a study of gastric emptying time.

UNLABELLED: To investigate the relationship between gastric motility and Helicobacter pylori infection in patients with non-ulcer dyspepsia, 28 patients and 10 asymptomatic healthy persons underwent gastroduodenal endoscope examinations and scintigraphic test of solid phase gastric emptying time using Chinese fried rice as a test meal. Clinical symptoms were also recorded using questionnaires for scoring. Half emptying times for ingested food (t1/2) between H. pylori infected (190.86 +/- 112.53 minutes) and uninfected patients (227.69 +/- 179.29 minutes) were not different statistically. Seven of the 15 patients with H. pylori infection (46.6%) had delayed gastric emptying time (t1/2 > 197.7 minutes), compared to 4 out of 13 without infection (30.07%) (p > 0.05). There was also no association between the status of H. pylori infection and severity of clinical symptoms (total symptoms scores: H. pylori positive: 10.07 +/- 3.84; H. pylori negative: 7.62 +/- 2.25) (p > 0.05). Seven patients from whom H. pylori was found to have been eradicated using triple therapy (colloid bismuth subcitrate 120 mg q i d, tetracycline 500 mg q i d and metronidazole 250 mg q i d for 14 days) did not show significant changes in gastric emptying time (before: 171.14 +/- 128.13; after: 158.57 +/- 182.49 minutes) but showed improvement in total symptoms scores (before: 9.28 +/- 3.85; after: 3.85 +/- 4.22) (p = 0.0277). CONCLUSIONS: infection by H. pylori in patients with non-ulcer dyspepsia did not influence solid phase of gastric emptying time and was not associated with clinical symptoms. Eradication of H. pylori infection relieved the clinical symptoms of the patients with non-ulcer dyspepsia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Evaluation of the severity of Helicobacter pylori infection with urease test: its correlation with histopathology and bacterial density.

In 69 patients, the severity of Helicobactor pylori (H. pylori) infection was evaluated by bacterial density of tissue implants and inflammatory responses by histology. The specimens were taken from gastric angle and antrum (greater and lesser curvature sides) by gastroduodenal endoscopy. In urease test, the severity was measured in 3 grades according to color change of the agar: those change are within 30 minutes (grade 3), 30 minutes to 3 hours (grade 2), and 3 to 6 hours (grade 1), respectively; while the grade 0 indicated no color change occurring 6 hours after tissue inoculation. The severity of infection was assessed according to the bacterial density under high power microscopic fields (Gram's stain). Grade 0 indicated no bacterium seen; grade 1, only 1 to 10 bacteria at all fields; grade 2, 1 to 3 bacteria in each high power field; and grade 3 was 4 bacteria or more on average in each high power field. The degree of inflammatory response was evaluated by inflammatory cell infiltration (H & E stain) and classified into grade 0, 1 and 2, which indicated the inflammatory cell infiltration below 50%, between 50% and 75%, and above 75%, respectively. There are no positive relationships among urease test reaction time, bacterial density grading and degrees of inflammatory cell infiltration. Clinically, the reaction time of urease test cannot reflect the severity of H. pylori infection semi-quantitatively, either in terms of bacterial density or cellular inflammatory response.

Adult↗
PubMed1994

Distribution and regulation of rab3C, a small molecular weight GTP-binding protein.

We have investigated the expression and regulation of rab3C in rat tissues and rat pheochromocytoma PC12 cells by using a polyclonal antibody that specifically recognizes this protein. Rab3C was expressed in the neuroendocrine systems, as is its highly homologous family member, rab3A. Strong immunoreactivity of rab3C was also observed in testis, heart and 3 different adipose tissues. In addition, induction of neuronal differentiation in PC12 cells, which causes an increase in catecholamine secretion, also led to an increase in rab3C expression. In summary, our data demonstrate a defined pattern of rab3C expression in the rat; such expression is not limited to the neuroendocrine systems. Regulated secretion of various hormones occurs from all of these rab3C-containing tissues. Our results provide important insight into understanding the potential role of rab3C in regulated exocytosis.

Adrenal Medulla↗
PubMed1994

Reappraisal of gastroduodenal lesions after transcatheter arterial chemoembolization of liver neoplasms--selective versus superselective method.

Twenty-six patients with liver neoplasm receiving transcatheter arterial chemoembolization (TAE) therapy underwent gastroduodenal endoscopic examinations before and after TAE. The balloon was inflated in the common hepatic artery before chemoembolization if superselective cannulation beyond the gastroduodenal artery could not be done. Sixteen of the 26 patients (61.5%) showed new gastroduodenal lesions, with superficial gastritis in six, one or more erosions in nine, and hemorrhagic gastritis in five. The frequency of lesions detected was no different when the common hepatic artery was obstructed (60.0%) than when superselective embolization was done in more peripheral branch(es) (60.0%). No clinical events indicating upper gastrointestinal bleeding were noticed after TAE. The presence of esophageal and/or gastric varices and session(s) of TAE performed before did not affect the occurrence of gastroduodenal lesion(s). We conclude that TAE produces erosive gastroduodenal lesions that are detected by endoscopic examination but are clinically unimportant; balloon catheter occlusion of the common hepatic artery did not result in more frequent gastroduodenal complications than the ordinary superselective chemoembolization method.

Adult↗
PubMed1994

[Distal blood pressure changes after ligation of the femoral artery or vein in the rat].

In the rat, immediately after ligation of the femoral artery below the profundus branch, the intraluminal pressure at the distal part dropped from 15.80kPa to 4.82kPa, and continued to decrease even after seven days. For the femoral vein, the distal intraluminal pressure rose from 0.67kPa to 3.91kPa in one minute. After one hour it dropped slowly and reached 1.25kPa after 24 hours. After seven days it was 0.74kPa. The author consider that it is unsuitable for the distal cut end of an artery or a vein to be used as the feeding vessel in microvascular free tissue transfer, because lowered blood pressure might result in inadequate tissue perfusion. When a big artery of limb was injured, it should be repaired no matter whether the collateral branch can maintain the distal circulation of the limb or not.

Animals↗
PubMed1994

[Screening and rapid identification of Bacillus thuringiensis mutants].

Mutants of Bacillus thuringiensis subsp. kurstaki NTU 9 and Bt 158, which were isolated previously for using the diamondback moth as a target insect in Taiwan, were screening by either protein electrophoresis of intracellular proteins or enzyme-linked immunosorbent assay (ELISA). The optimal conditions of effective protein electrophoresis were (1) 24-hour cells harvested from nutrient broth were crashed by petite glass beads followed by centrifugation. And (2) the supernatant pretreated by heating at 60 degrees C for 2 minutes was electrophoresed with 7.5% native PAGE at 110 voltages. On ELISA, the antiserum used was obtained from rabbits immunized with Bt 158 crystal protein. Optimal antigen coating concentration of ELISA, attained by chequer-board titration method, was 10 micrograms/ml. Antigens (crystal protein) in samples were detected by competitive inhibition method with antiserum diluted to 10(4) fold. By using protein electrophoresis and ELISA methods, two isolates A 71 and BN 11, were denoted respectively as qualitative and quantitative mutants of Bacillus thuringiensis.

Animals↗
PubMed1993

Effect of hypoxia on release of vasoactive substances from cultured pulmonary arterial and aortic endothelial cells.

The effect of hypoxia on the production and release of vasoactive substances from endothelial cells of pulmonary artery (PAECs) and aorta (AECs) was studied. The results indicated that the overall effect of the long half-life vasoactive substances released from PAECs and AECs was vasoconstrictive. The long half-life lipid-soluble substances produced by PAECs and AECs were vasodilative, and did not change in hypoxia. However, the long half-life water-soluble heat-unstable and heat-stable ones were vasoconstrictive. Hypoxia could reduce the release of the former and promote that of the latter which might be peptides. The PAECs could release specific long half-life mediator which was pulmonary artery-constrictive, water-soluble, heat-unstable, and not related to hypoxia. Hypoxia inhibited the production of PGI2, a short half-life vasodilator, in PAECs, but not in AECs.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Recovery and properties of a fructooligosaccharides-producing beta-fructofuranosidase from Aspergillus japonicus CCRC 38011.

The fungus (Aspergillus japonicus CCRC 38011) was found to be able to produce beta-fructofuranosidase with high transfructosylating activity (Ut), a key enzyme involved in synthesis of fructooligosaccharides from sucrose. The Ut productivities of this microorganism were 191.5 units/ml broth in a 6-L jar-fermentor and 256.1 units/ml broth in a 1000-L pilot-fermentor in a modified medium containing 8% sucrose as a carbon source. Most of the Ut of this microorganism was found to be bound with mycelia. Incubation and sonication treatment extracted this enzyme from mycelia with maximum efficiencies of 66.3% and 44.3%, respectively. On the other hand, homogenization and freeze-thawing treatment had only a small effect on enzyme extraction. The soluble enzyme extracted from mycelia by incubation at pH 5.0 and 40 degrees C for 3 hours could be easily recovered and purified by acetone precipitation. The recovery of Ut from the crude enzyme solution was 99.5% by mixing the solution with an equal volume of acetone at 4 degrees C, followed by centrifugation. The purification factor of acetone precipitation was 15.8. The optimum pH and temperature of Ut was 5.0 and 65-70 degrees C, respectively. The enzyme was stable at a pH between 4.0 and 5.0 and at a temperature below 60 degrees C.

Aspergillus↗
PubMed1993

[The hemodynamic and ventilatory effects between Trendelenburg and reverse Trendelenburg position during laparoscopy with CO2-insufflation].

Thirty ASA class I female patients underwent gynecologic pelvioscopy and laparoscopic cholecystectomy were included in this study. All of them received general anesthesia and certain volume of CO2 pneumoperitoneum. We evaluated the effect of positioning (Trendelenburg as group I and reverse Trendelenburg as group II) on hemodynamic parameters and ventilation. The hemodynamic parameters, ventilation, and arterial blood gas were determined at the following stages: (1) after 10 minutes of normoventilation and before CO2 pneumoperitoneum (as control), (2) 5 minutes after CO2 pneumoperitoneum and positioning, (3) 25 minutes after positioning, (4) 50 minutes after positioning, (5) 10 minutes after resumption of supine position and decompression of abdomen. Arterial blood pressure, heart rate, minute volume, end-tidal CO2, oxygen saturation and blood gas analysis were taken during normoventilation. We found that there was no statistical difference between either group in respect to hemodynamic parameters. For the ventilation, both groups had appropriate SpO2 during the period of CO2 pneumoperitoneum, but PaCO2 was significantly increased in group I 25 min after CO2 pneumoperitoneum and Trendelenburg positioning. Nonetheless, end-tidal CO2 was not significantly increased. pH value and PaCO2 did respectively decrease and increase significantly in group I 50 min after Trendelenburg position. However, no change was found in end-tidal CO2. All data were not significantly different after resumption of supine position and decompression of abdomen. Conclusively, except that pH and PaCO2 had changed after a period of Trendelenburg positioning with CO2 pneumoperitoneum, the patients who underwent laparoscopic surgery with normoventilation have no hemodynamic and respiratory change.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗