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Biomedical subjects

S L Wu

Publications and source records attributed to S L Wu.

At least 91 records · Page 5Linked to original sources
PubMed1991

Ascitic fluid analysis in peritoneal carcinomatosis: comparison of various biochemical tests with ascitic cirrhotics.

Owing to the high false-negative rate of cytological examinations, various biochemical tests have been investigated to search for an alternative method to differentiate between the most frequent causes of ascites formation, i.e. cirrhosis of the liver and peritoneal carcinomatosis. For this purpose, serum and ascitic fluid samples of 71 ascitic patients (54 due to cirrhosis of the liver and 17 due to peritoneal carcinomatosis) were prospectively and simultaneously collected. Eleven major parameters were analyzed, and, of them, ascitic fluid protein, albumin, cholesterol, fibronectin and serum-ascitic gradient of protein and albumin were found to be useful. The serum-ascitic fluid albumin gradient was not as useful as described in the literature and, if clinically applied, the best cut-off value should be raised up to 1.5 gm/dl. Neither as useful was the serum-ascitic fluid protein gradient. Ascitic cholesterol and ascitic fibronectin were more accurate than the ascitic total protein, ascitic albumin and serum-ascitic gradient of protein and albumin in the diagnosis of peritoneal carcinomatosis. Of these tests, an ascitic fluid fibronectin concentration greater than 40 micrograms/ml was the most accurate parameter (diagnostic accuracy 96.2%) that could solely help to establish the diagnosis of peritoneal carcinomatosis.

Adult↗
PubMed1990

Capillary gel electrophoresis for DNA sequencing. Laser-induced fluorescence detection with the sheath flow cuvette.

Capillary polyacrylamide gel electrophoresis separation of dideoxycytidine chain-terminated DNA fragments is reported. A post-column laser-induced fluorescence detector based on the sheath flow cuvette was used to minimize background signals due to light scatter from the gel and capillary. A preliminary mass detection limit of 10(-20) mol of fluorescein-labeled DNA fragments was obtained. The system was used to analyze an actual DNA sequencing sample. Theoretical plate counts of 2 x 10(6) were produced. Gel stability limits the performance of the current system.

Base Sequence↗
PubMed1990

Use of high-performance capillary electrophoresis to monitor charge heterogeneity in recombinant-DNA derived proteins.

The separation of charge variants of recombinant DNA-derived (rDNA) proteins by high-performance capillary electrophoresis (HPCE) has been explored with the following examples: human growth hormone (rhGH), a soluble form of a T4 receptor protein (rCD4) and tissue plasminogen activator (rt-PA). The separation of rhGH and deamidated variants were examined over the range of low pH (less than 2.5) to high pH (8.0) on a coated silica capillary. No resolution was observed at pH 2.5 while at pH values of 6.5 or greater the deamidated species were separated. At pH 3.5 the variant was partially resolved but no detector signal was observed at pH 4.5 and 5.0. HPCE was also used to monitor a glycoprotein (rt-PA) with charge heterogeneity presumably due to variable sialic acid content. At a pH value of 4.5, the charge heterogeneity was only observed as peak broadening. For rCD4 multiple peaks were observed at pH 5.5 but no signal was observed at pH 6.5 or above (the pI of rCD4 is 8). These results suggest that HPCE will prove to be a valuable technique for the analysis of charged variants present in rDNA products either as a consequence of natural microheterogeneity or due to degradative processes such as deamidation.

CD4 Antigens↗
PubMed1990

The hypotensive and negative chronotropic effects of dehydroevodiamine.

The cardiovascular effects of dehydroevodiamine, an alkaloid isolated from Evodia rutaecarpa Jussieu, were studied in both in vivo and in vitro experiments. The in vivo experiments revealed that i.v. administration of dehydroevodiamine elicited a slight but significant reduction in blood pressure and a marked decrease in heart rate which was confirmed by an increased cycle length of the electrocardiogram. However, a hemodynamic experiment with microspheres showed that the total peripheral resistance was not altered by dehydroevodiamine. The blood flows of various organs were not significantly changed except those of kidney and skin, in which blood flow was decreased. In vitro, the spontaneously beating atria were significantly suppressed by dehydroevodiamine in a dose-dependent manner. These findings suggested an important effect of dehydroevodiamine in suppressing the heart, which may largely contribute to the hypotensive effect of this alkaloid. However, its vasodilator effect on hindquarter muscles cannot be neglected.

Alkaloids↗
PubMed1990

Application of high-performance hydrophobic-interaction chromatography to the characterization of recombinant DNA-derived human growth hormone.

This publication analyzes different preparations of recombinant human growth hormone (rhGH) by hydrophobic-interaction chromatography (HIC). The effect of temperature on the separation was investigated as well as a series of commercially available HIC columns (TSK-phenyl-5PW, TSK-ether-PW, Beckman CAA-HIC and polypropyl A). The TSK-ether column gave the best results in the analysis of rhGH samples at different temperatures, as well as allowing an efficient separation of methionyl-hGH from rhGH. The TSK-phenyl column can be effectively used in the examination of different human growth hormone variants. The details of sample preparation have been demonstrated to be important in HIC analysis of hGH on the TSK-ether-5PW column. Injection volume and the solvent used to dissolve the protein sample are both crucial factors in this analysis. Also protein aggregation may play a role in these observations. The effect of temperature, protein concentration and spectroscopic data on the eluted protein suggest, however, that aggregation is not the cause of frontal peaks.

Chromatography, High Pressure Liquid↗
PubMed1990

Automated evaluation of tryptic digest from recombinant human growth hormone using ultraviolet spectra and numeric peak information.

UV spectra were successfully employed in identifying peptide fragments from a tryptic digest of recombinant-DNA-derived human growth hormone (r-hGH). It was possible to distinguish very similar peptides utilizing a digital comparison of the UV spectra. An automated procedure was developed to generate a calibration library for the tryptic digest of a reference standard. The calibration library was then evaluated for reproducibility and selectivity and found to provide superior performance in correctly identifying ambiguous peaks as compared to the use of a conventional calibration table. Spectral match factors together with numerical information, derived from peak retention time, area and height, were used to arrive at a "peak score" descriptive of the similarity between standard and sample peaks. "Peak scores" could be combined to calculate a "sample score" indicative of overall similarity between an unknown and a standard. The scoring procedure was automated to generate a final report without operator intervention and successfully assigned appropriate scores to similar as well as dissimilar samples, e.g., native and oxidized r-hGH.

Algorithms↗
PubMed1990

Capillary zone electrophoresis separation and laser-based detection of both fluorescein thiohydantoin and dimethylaminoazobenzene thiohydantoin derivatives of amino acids.

Capillary zone electrophoresis is employed for the separation and analysis of both fluorescein thiohydantoin and dimethylaminoazobenzene thiohydantoin derivatives of amino acids. Detection of minute amounts of these amino acid derivatives is an important milestone in the development of a high sensitivity protein sequencer. Current detection limits for the fluorescein derivative is on the order of 10(-21) moles whereas detection limits for the dimethylaminoazobenzene derivative is on the order of 10(-16) moles.

Amino Acids↗
PubMed1990

Effect of parathyroid hormone on portal pressure in portal hypertensive rats.

Conflicting results have been common in the pharmacological treatments of portal hypertension. In an attempt to seek better management of portal hypertension, we studied the effect of the synthetic parathyroid hormone (PTH) fragment, [bPTH-(1-34)], in portal hypertensive rats (partial portal vein ligation). PTH, 10 U/kg, administered via the jugular vein resulted in a reduction of both mean arterial blood pressure (MAP) and portal pressure (PP) to a similar extent (18.9% and 16.9%, respectively). A higher dose (40 U/kg) of PTH lowered the PP by 27.8% and MAP by 43.2%. Hemodynamic experiments, performed with labelled microspheres, demonstrated that PTH decreased the blood flow of the splanchnic and hepatic portal collateral vascular beds. To determine whether there is a direct vasodilatory effect on the venous vasculature, the effect of PTH on the isolated portal vein was examined. PTH was capable of inhibiting both spontaneous and drug (methacholine 10(-7) mol/l or KCl 40 mmol/l-induced contraction in a dose-dependent manner. Therefore, it can be assumed that some of the effect of PTH on portal pressure is due to a selective effect on the portal vein.

Animals↗
PubMed1989

Characterization of human growth hormone by capillary electrophoresis.

Production of proteins by recombinant DNA technology for use as pharmaceuticals requires the use of the most powerful tools of analytical protein chemistry in order to confirm purity and identity of the product and reliability of the process. Capillary electrophoresis is an emerging technology that shows high sensitivity and selectivity and may have promise in this application. The technique combines the instrumental control and quantification features of high-performance liquid chromatography with the separating power of electrophoresis, and thereby has attracted broad interest. In this report, human growth hormone expressed in bacteria has been analyzed by both free zone electrophoresis and isoelectric focusing in a coated capillary to demonstrate the separation of the native molecule from its deamidated variant. A capillary zone electrophoretic tryptic map has also been developed and characterized. This map complements the widely employed reversed-phase high-performance liquid chromatography tryptic mapping systems that are important in protein characterization. Certain drawbacks to capillary zone electrophoresis compared to other analytical methods are noted, including relatively poor reproducibility and low sample tolerance. For applications as demonstrated here, however, the speed, separating power and sensitivity of the technique compensate for these shortcomings.

Chromatography, Ion Exchange↗
PubMed1989

[Treatment of refractory multiple myeloma with vincristine, adriamycin, and dexamethasone].

Ten patients with multiple myeloma (two refractory and eight relapsing) received vincristine and adriamycin infusion therapy with oral high-dose dexamethasone (VAD regimen). Reduction in monoclonal immunoglobulin in serum exceeding 75 per cent was noted in three patients and reduction from 50 per cent to 75 per cent in four patients. Total response rate was 70 per cent. It was as high as the results reported in other countries. The responses to VAD regimen occurred rapidly. Most of them needed only one course. The side effects of VAD were not severe and were mainly reversible depression of leukocyte and infection of various kinds. All patients tolerated well. The probable mechanisms for increased response to VAD regimen are as follows. 1. Instead of administration as a bolus, vincristine and adriamycin were infused continuously and were given several times; therefore there was a prolonged unchanged concentration of the drugs in blood and exerting a possibly superior antitumor effect. 2. high-dose dexamethasone.

Adult↗
PubMed1988

A two-year study of acceptability, side effects, and effectiveness of Norplant and Norplant-2 implants in the People's Republic of China.

A large scale, phased investigation of NORPLANT contraceptive systems was conducted in the People's Republic of China. The first phase comprehended 1,200 women in four cities. Expanded trials included 11,918 women at 12 major centers and at sub-centers by 31 May 1987. At that date 4,676 NORPLANT capsule subjects and 1,089 rod subjects had completed one year of use, 1,381 capsule acceptors had completed two years as had 197 rod users. Gross pregnancy rates were less than 0.1 per 100 for each implant type both at one and at two years. Continuation rates were 94 per 100 for each implant type at one year, and were 82.0 and 83.6 per 100 among users of NORPLANT capsule and rod implants, respectively, at two years. Disruption of menstrual function was the dominant reason for termination, but mean hemoglobin levels increased in each of the nine centers reporting values at admission and at one year. First year gross cumulative termination rates for medical reasons were 1.2 to 1.3 per 100, reaching 3.8 and 5.6 per 100 for capsule and rod implants, respectively, at two years. Microdose contraception with these levonorgestrel-releasing implants appears to be a highly acceptable and effective modality suitable for Chinese women. NORPLANT implants are now approved by the national drug regulatory agency for general use in China.

Adolescent↗
PubMed1987

[Brain metastasis from lung cancer--analysis of 53 patients].

From 1976 to 1985, 53 patients with brain metastasis from lung cancer were treated. The most common histologic type was adenocarcinoma (47.4%). All patients presented neurologic symptoms, and 29 were first admitted into the Department of Neurology. CT scan and angiography were most valuable for diagnosis. Metastasis occurred most frequently in frontal, temporal and parietal lobes. In this series, chemotherapy alone was ineffective but resection of the brain foci prolonged the survival in 90.9% of the patients. The authors believe that in order to facilitate radiotherapy or/and chemotherapy, resection of the brain foci should be given more consideration.

Adenocarcinoma↗
PubMed1986

Protein conformational effects in hydrophobic interaction chromatography. Retention characterization and the role of mobile phase additives and stationary phase hydrophobicity.

We have studied the conformational behavior of alpha-lactalbumin (alpha-LACT) in hydrophobic interaction chromatography (HIC). Retention characterization in terms of Z (slope of plot of ln k' vs. ln phi B, where k' is the capacity factor and phi B is the volume fraction of mobile phase B) has been explored, and the relationship of Z to other slopes, such as S (slope of the plot of ln k' vs. phi B) has been derived. The reasons for the sensitivity of Z to conformational change are discussed. The enhanced broadening of alpha-LACT in a temperature transition region of conformational change has been studied by spectral analysis using on-line photodiode array detection. The influence of Ca2+ and Mg2+ addition to the mobile phase is further explored. Since alpha-LACT is a calcium binding protein, addition of this metal leads to stabilization, i.e. higher column temperatures are required for conformational change. On the other hand, addition of Mg2+ appears to destabilize the protein. We have explored the use of a more hydrophobic support, C2-(ethyl) ether phase, for the elution of alpha-LACT. In this case, two widely separated peaks are observed. By spectral analysis the first peak is shown to be native and the later eluted, broad second peak to be an unfolded mixture of species. As previously observed in reversed-phase liquid chromatography, the second peak grows at the expense of the first, as the column temperature is raised. The second peak also grows as the contact time of the protein with the surface increases. This behavior can be ascribed to the conformational change of alpha-LACT in the column, the late eluted species under the second peak binding significantly more strongly to the phase than the native peak. Reinjection of the late eluted fraction reveals that reformation of the native species takes place in solution within 30 min. As before, addition of Ca2+ reduces the extent of unfolding under any specific condition. These results add further to our understanding and ability to control conformational changes in high-performance liquid chromatography.

Animals↗
PubMed1986

Thermal behavior of proteins in high-performance hydrophobic-interaction chromatography. On-line spectroscopic and chromatographic characterization.

The thermal behavior of a series of standard proteins in hydrophobic interaction chromatography on a previously developed weakly hydrophobic ether-bonded phase column has been studied. Depending on the temperature and protein, conformational changes can occur in the chromatographic system. Methods for recognizing these conformational effects are presented, including retention and peak width variations with temperature, and Z values (the slope of the plot of log k' vs. log %B solvent. The Z value is shown to be a general index characterizing protein retention as a function of salt concentration. In addition, on-line UV spectroscopic analysis, (absorbance ratios and second derivative spectroscopy) with a photodiode array detector, is shown to corroborate chromatographic trends. Lysozyme maintains a stable conformation over the temperature range 10-40 degrees C, whereas beta-lactoglobulin A has a conformational transition between 25 degrees C and 40 degrees C. Calcium-depleted alpha-lactalbumin, a rather labile species, maintains a stable conformation up to ca. 20 degrees C, and then undergoes structural changes. Finally, cytochrome c appears to be relatively stable up to ca. 65 degrees C. Since conformational changes for this protein occur at ca. 35 degrees C on more hydrophobic phases, the extent of hydrophobicity of the stationary phase is important for maintenance of the native state. Based on this work, hydrophobic-interaction chromatography at sub-ambient temperatures appears promising.

Chromatography↗