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Biomedical subjects

Y C Liu

Publications and source records attributed to Y C Liu.

At least 307 records · Page 17Linked to original sources
PubMed1982

The conformational transition of horse heart porphyrin c.

The heme iron of horse heart cytochrome c was selectively removed using anhydrous HF. The product, porphyrin c, exhibits the viscosity, far ultraviolet circular dichroic, and fluorescence properties characteristic for native cytochrome c. However, porphyrin c is more susceptible to denaturation by guanidine hydrochloride and by heat than is the parent cytochrome. All of the conformational parameters of porphyrin c exhibit a common reversible transition centered at 0.95 m guanidine hydrochloride at 23 degrees C and pH 7.0. Guanidine denatured porphyrin c refolds in two kinetic phases having time constants of 20 and 200 ms as detected by stopped flow absorbance or fluorescence measurement, with about 80% of the observed change in the faster phase. The kinetics of porphyrin c refolding are not significantly altered by increasing the viscosity of the refolding solvent 15-fold by addition of sucrose. We suggest that the folding of guanidine denatured cytochrome c is not a diffusion-limited process and that the requirement for protein axial ligation elicits the slow (s) kinetic phase observed in the refolding of cytochrome c.

Amino Acids↗
PubMed1977

Conformational prediction for snake venom toxins and laser Raman scattering of a cardiotoxin from Taiwan cobra (Naja naja atra) venom.

Secondary structure regions in snake venom toxins were predicted using the prediction method of Chou and Fasman (Chou, P. Y., and Fasman, G. D. (1974), biochemistry 13,222) and an averaging scheme assuming structural homology in each type of toxins. The results indicate that, in general, snake toxins contain only some beta-sheet regions and beta bends. The content of secondary structures thus predicted does vary to some extent. The predicted results correlate well with conclusions from physicochemical studies. Interestingly, beta-bend regions predicted for the two types of neurotoxins, short-neurotoxin-type and long-neurotoxin-type, are primarily located in the middle of disulfide loops in spite of large differences in primary sequences. Comparisons between predicted results and the crystal structure of erabutoxin b determined at 2.75 A resolution suggest that the two types of neurotoxin are both sequencely and conformationally related while cardiotoxins could have an entirely different molecular topology. The Raman spectrum of a Taiwan cobra cardiotoxin indicates that the content of beta-pleated-sheet structure could be greater than that in neurotoxins.

Amino Acid Sequence↗
PubMedDate not supplied

Differences in gastric emptying between highly selective vagotomy and posterior truncal vagotomy combined with anterior seromyotomy.

Gastric emptying has been reported to be both delayed and unchanged following posterior truncal vagotomy combined with anterior seromyotomy (PTV + AS). When compared to highly selective vagotomy (HSV), our clinical experience was that PTV + AS not uncommonly produced postprandial distress. We studied gastric emptying of both liquids and solids 3 and 12 months following HSV and PTV + AS to determine what if any differences there were in gastric emptying between the two procedures. We compared these results with those from studies done in both normal subjects and unoperated duodenal ulcer patients. In 26 duodenal ulcer patients with perforation (n = 18) or bleeding (n = 8), who were treated with HSV (n = 10) or PTV + AS (n = 16), gastric emptying of liquids and solids was evaluated at 3 months and 12 months postoperatively. At 3 months, gastric emptying of liquids was delayed in both the HSV and PTV + AS groups as compared to values in both normal subjects and unoperated duodenal ulcer patients. The emptying of solids was markedly delayed by PTV + AS in contrast to HSV at 3 months (167.1 +/- 28.4 minutes vs. 79.9 +/- 16.7 minutes; P <0.05). The lag duration was not affected. A limited number of patients studied at 12 months showed similar and near-normal emptying of solids in both the HSV and PTV + AS groups (67.5 +/- 7.0 minutes vs. 70 +/- 6.6 minutes). PTV + AS in contrast to HSV produces more marked delayed emptying of liquids and solids at 3 months; with time (1 year) these values return to near normal.

Gastric Emptying↗
PubMedDate not supplied

Immobilization of reducing sugars as toxin binding agents.

A simple and economical procedure for the attachment of reducing sugars to aminated solid supports has been developed. Reaction of the amino groups on the solid support with p-nitrophenyl chloroformate, followed by 1,6-hexanediamine, yields a chain-extended amine to which reducing sugars can be attached while remaining accessible to macromolecules. Immobilization of the reducing sugars involves a simple incubation followed by trapping of the resulting glycosylamine with acetic anhydride and recovery of the unreacted sugar by filtration. This technique was used to immobilize lactose and sialyllactose onto silylaminated Chromosorb P, producing solid supports that effectively neutralized the activity of cholera toxin from Vibrio cholerae and heat-labile enterotoxin of enterotoxigenic Escherichia coli. The general applicability of such solid supports for toxin neutralization was further demonstrated by immobilization of the enzymatically synthesized alpha Gal(1-3) beta Gal(1-4)Glc trisaccharide, which produced a support that efficiently neutralized toxin A of Clostridium difficile. The results from this study suggest that these solid supports have the potential to serve as inexpensive therapeutics for bacterial toxin-mediated diarrheal diseases.

Animals↗
PubMedDate not supplied

Field comparison of impingers and treated filters for sampling of total aliphatic isocyanates with the MAP reagent.

Results of a comparative field study on the performance of 25-mm inhalable samplers (Institute of Occupational Medicine [IOM]) and midget impingers for the collection of total isocyanates in air using the 1-(9-anthracenylmethyl)piperazine (MAP) reagent are presented. Air sampling and analysis was performed according to the National Institute for Occupational Safety and Health MAP draft method 5525. Midget impingers filled with 15 mL of 1 x 10(-4) M MAP in butyl benzoate were operated at 1 L/min. IOM cassettes loaded with 25-mm quartz fiber filters impregnated with 500 microg MAP, were operated at 2 L/min. Filters were field extracted with 10 mL of 1 x 10(-4) M MAP in acetonitrile. Thirty-four impinger-IOM pairs were collected in three autobody shops during spray painting tasks. Regression analysis [Ln (IOM) = 1.0 Ln (impinger), R2 = 0.98] and a paired t-test (Pr > 0.9) demonstrated that impingers and IOMs perform equally in their collection efficiency for the monomer and total oligomeric hexamethylene diisocyanate (HDI). IOM performance did not deteriorate at longer sampling times compared with the impinger performance. Within-sampler variability was calculated from the individual coefficients of variation (CV) of the 17 pairs of like samplers. The mean of CVs (SD)% for the monomer and total oligomeric HDI was approximately 12 (12)% and 15 (13)% for the IOM and the impinger sampler, respectively. Poor correlation (Pearson correlation coefficient < 0.3) and statistically nonsignificant differences (P > 0.74 two-sided) were found for the between-sampler CVs. Factors that might have influenced the observed sampler agreement are also discussed. It is concluded that MAP impregnated filters can be successfully used for sampling of slow curing total aliphatic isocyanates in air.

Air Pollutants, Occupational↗
PubMedDate not supplied

Antibacterial activity of cefprozil in vitro.

Cefprozil is a new orally active cephalosporin which is undergoing in vitro and in vivo evaluations. Using the standard agar dilution method we compared the in vitro activity of this drug with other oral cephalosporins and ciprofloxacin against 637 recent clinical isolates from the Kaohsiung Veterans General Hospital, Taiwan. Against Escherichia coli and Klebsiella pneumoniae, cefprozil showed good activity, inhibiting over 80% of these isolates at 8 mg/l. Like other oral drugs of its class, it had little activity against Pseudomonas aeruginosa and Acinetobacter spp. Against Haemophilus influenzae, irrespective of beta-lactamase production, its activity was similar to comparable drugs. Against methicillin-susceptible Staphylococcus aureus, cefprozil showed high activity, inhibiting 90% of these isolates at 4 mg/l, whereas against methicillin-resistant S. aureus, its activity was higher than that of other oral cephalosporins tested and was similar to that of ciprofloxacin. Of enterococci tested, 57.7% were inhibited by 8 mg/l of cefprozil. Against beta-hemolytic streptococci, its activity was superior to all other drugs tested. The results of this in vitro study indicate that oral administration of cefprozil might be efficacious in the treatment of community-acquired cutaneous, respiratory and urinary tract infections.

Bacteria↗
PubMedDate not supplied

Antibacterial activity of cefpodoxime in vitro.

Cefpodoxime proxetil is a new orally administered prodrug which is absorbed and de-esterified by the intestinal mucosa to release the third-generation cephalosporin, cefpodoxime, and which is undergoing in vitro and in vivo evaluations. Using the standard agar dilution method, we compared the in vitro activity of this drug with other oral cephalosporins and quinolones against 637 recent clinical isolates from Kaohsiung Veterans General Hospital in Taiwan. Against Escherichia coli and Klebsiella pneumoniae, cefpodoxime showed excellent activity, inhibiting over 90% of these isolates at 1 mg/l. Like other oral drugs of its class, it had little activity against Pseudomonas aeruginosa and Acinetobacter spp. Against Haemophilus influenzae, irrespective of beta-lactamase production, its activity was similar to comparative drugs. Against methicillin-susceptible Staphylococcus aureus, cefpodoxime showed moderate activity, inhibiting 90% of these isolates at 4 mg/l, whereas it was inactive against methicillin-resistant S. aureus. However, all cephalosporins have shown little in vivo activity against methicillin-resistant S. aureus regardless of in vitro results. Cefpodoxime was inactive against Enterococcus spp. Against other streptococci, its activity was similar to other oral cephalosporins and quinolones tested. The results of this in vitro study indicated that oral administration of cefpodoxime should be an ideal agent in the empirical outpatient treatment for community-acquired cutaneous, respiratory and urinary tract infections.

Anti-Bacterial Agents↗
PubMedDate not supplied

Fine needle aspiration cytology of appendiceal mucinous cystadenoma: a case report.

BACKGROUND: Fine needle aspiration (FNA) of the appendiceal mucocele is generally avoided because of fear that puncture of a distended viscus will lead to rupture or seeding of neoplastic cells and result in localized or diffuse pseudomyxoma peritonei. Cytologic reports regarding FNA of appendiceal mucoceles are virtually nonexistent. CASE: A 55-year-old male with a preoperative diagnosis of an infectious process with interloop abscess formation underwent computed tomography-guided aspiration of the mass. FNA showed clusters of intestinal type epithelium with mild nuclear crowding, hyperchromasia and atypia in a mucinous background. CONCLUSION: The differential diagnosis of a neoplastic appendiceal cystic tumor based on the FNA findings could be difficult and should be made only in conjunction with clinical findings. FNA of an appendiceal mucocele may be safe when a small-gauge needle and retroperitoneal approach are utilized.

Appendiceal Neoplasms↗