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Biomedical subjects

S Yuan

Publications and source records attributed to S Yuan.

At least 163 records · Page 9Linked to original sources
PubMed1993

Androgen-induced inhibition of cell proliferation in an androgen-insensitive prostate cancer cell line (PC-3) transfected with a human androgen receptor complementary DNA.

A full length human androgen receptor complementary DNA was introduced into androgen receptor-negative PC-3 cells to determine if androgen sensitivity could be established in this cell line and to assess what influence, if any, androgen exposure would have on the growth of these cells. The androgen receptor complementary DNA was inserted into pSG5 in the region controlled by the SV40 promoter. This construct was cotransfected with pSR1neo into PC-3 cells and stably transfected cells were selected and screened for the expression of the androgen receptor. Active expression of the receptor was demonstrated by Western blotting using a rabbit anti-androgen receptor antiserum and by [3H]methyltrienolone binding to cytosol extracts. Saturation ligand-binding analysis revealed the presence of a single class, high affinity (Kd = 0.122 nM) androgen-binding site in cytosol extracts of transfected cells but not in extracts from mock-transfected cells. In cells expressing the transfected androgen receptor, androgen decreased the proliferation rate and cloning efficiency and induced a more differentiated phenotype. These results demonstrate that PC-3 cells have retained the mechanisms required to respond to the activated androgen receptor and that the loss of androgen sensitivity in these cells is due to the lack of functional androgen receptor. This also provides a technique for determining whether androgen-resistant tumor cells contain functional androgen receptors or whether androgen sensitivity is due to abnormalities in downstream signaling pathways. The apparent androgen-induced decreased malignant state of these transfected cells suggests new directions for the treatment of prostate cancer.

Animals↗
PubMed1993

Immobilization of high-affinity heparin oligosaccharides to radiofrequency plasma-modified polyethylene.

Oligosaccharides of heparin with high affinity for antithrombin III (ATIII) have been immobilized onto surface-modified NHLBI Primary Reference low density polyethylene (PE). PE was modified by radiofrequency plasma polymerized (< 150 nm thick) films derived from N-vinyl-2-pyrrolidone (PPNVP) or allyl alcohol (PPAA), and coupled by chemical derivatization to either 3-aminopropyltriethoxysilane or amino-terminated poly(ethylene oxide). High affinity heparin oligosaccharides (HA-heparin, anti-factor Xa activity of 592 +/- 120 IU/mg) prepared by partial deaminative cleavage of commercial crude heparin and fractionated by agarose-ATIII affinity chromatography, were immobilized to surface-modified PE by reductive amination. The anticoagulant activity, as determined by a chromogenic assay for the inhibition of factor Xa, was estimated to be 30-70 mIU/cm2, with binding estimated to be 56-119 ng/cm2. The highest activity was obtained for the HA-heparin immobilized to PE modified by PPNVP with a PEO spacer. Visual confirmation of ATIII binding to immobilized HA-heparin was demonstrated by a gold-labeled double antibody method with imaging by SEM.

1-Propanol↗
PubMed1993

Relationship between tissue calcium content and duodenal ulcer in the rat.

Since the effect of cellular calcium on cell injury has been in question, this study focused on the relationship between tissue calcium content and cysteamine-induced duodenal ulcer. Rats treated with cysteamine showed a high frequency and severity of duodenal ulcer, and the calcium content in the duodenal mucosa was elevated. Furthermore, the level of calcium content in duodenal mucosa was positively associated with the severity of the duodenal lesion. Whereas administration of calcium increased duodenal ulcerative response to cysteamine, verapamil afforded protection against ulceration. We conclude that calcium accumulation in duodenal mucosa is related to duodenal ulceration induced by cysteamine.

Animals↗
PubMed1993

Development and validation of a limited sampling strategy for 5-fluorouracil given by bolus intravenous administration.

A wide range of interindividual variability of 5-fluorouracil (5-FU) pharmacokinetics exists after bolus administration. The degree to which this variability in 5-FU exposure impacts upon the response and toxicity of the drug has not been determined. The area under the concentration time curve (AUC) is a commonly used indicator of exposure, but normally requires the collection of 8-10 timed blood samples after i.v. bolus administration. This presents difficulties if large-scale population samplings are required. This study involved the development and testing of a strategy to estimate AUC from a limited number of blood samples in patients with gastrointestinal and breast cancer. The optimal single time point for AUC estimation was 0.17 h (r2 = 0.954). Addition of the 0.75 h time point significantly improved predictability (r2 = 0.983). Addition of a third or fourth time point did not provide further benefit. These models were then tested separately in a group of women who received a higher dose of 5-FU. The two data points model performed significantly better than the single time point model (r2 = 0.70 and 0.85, respectively). The AUC of standard dose 5-FU after bolus administration can be reliably estimated from two timed samples taken 10 and 45 min after injection.

Adult↗
PubMed1993

Neutralizing monoclonal antibodies that distinguish three antigenic sites on human cytomegalovirus glycoprotein H have conformationally distinct binding sites.

Seven neutralizing murine monoclonal antibodies specific for the glycoprotein H of human cytomegalovirus were produced and used to construct a topological map of two nonoverlapping antigenic sites that are bridged by a third antigenic site. Neutralization assays with 15 laboratory or clinical human cytomegalovirus strains indicated that the monoclonal antibodies recognize three antigenically variable and three conserved epitopes within the three antigenic sites. The variable-domain genes encoding monoclonal antibodies representing each of the three antigenic sites were cloned and sequenced, and molecular models of their binding sites were generated. Conformational differences in the antibody-binding sites suggested a structural basis for experimentally observed differences in gH epitope recognition.

Amino Acid Sequence↗
PubMed1993

Intercellular communication and maintenance of islet cell mass--implications for islet transplantation.

BACKGROUND: The major emphasis in islet transplantation has been the development of methods to enhance islet purity. This focus assumes that islets do not require support from other cellular elements of the pancreas. We chose to examine a possible duct-islet interaction because of the embryologic origin of islets from ductal epithelium. METHODS: Duct and islet cells were prepared by collagenization of hamster pancreas and purified on a bovine serum albumin gradient. Primary duct cultures were passaged twice. Duct-conditioned medium was collected from the tertiary cultures. Three groups of cultures were established: group 1, 100 islets/plate in minimal medium (Dulbecco's modified Eagle medium/F12); group 2, 100 islets + 40 duct fragments/plate in Dulbecco's modified Eagle medium/F12; and group 3, 100 islets/plate+duct-conditioned medium. After a 3-day incubation, tritiated thymidine (1 microCi/ml) was added for 24 hours. The islets were separated from the ducts by handpicking and then sonicated. DNA was measured (microgram) fluorometrically and tritiated thymidine incorporation, a measure of cell proliferation, was determined in trichloroacetic acid-precipitated material by liquid scintillation. Data (mean +/- SEM) were compared by two-tailed Student's t test. RESULTS: Tritiated thymidine incorporation into islet cells in minimal medium (81.1 +/- 24.6 disintegrations per minute [dpm]/microgram DNA [n = 8 plates]) was less than 25% (p < 0.001) of that of islet cells cocultured with ducts (323.2 +/- 54.5 dpm/micrograms DNA [n = 6]) or with duct-conditioned medium (389.7 +/- 27.6 dpm/micrograms DNA [n = 5]). CONCLUSIONS: Pancreatic duct epithelium can stimulate islet cell proliferation in a paracrine manner.

Animals↗
PubMed1992

Comparative study of eight sets of ECG criteria for the localization of the accessory pathway in Wolff-Parkinson-White syndrome.

Eight sets of electrocardiographic (ECG) criteria for the localization of accessory conduction pathway (ACP) were evaluated on 182 patients with a single ACP. The Rosenbaum criteria identified 78.6% of the left-sided and 94.0% of the right-sided ACPs. Four of the other seven sets of criteria demonstrated a sensitivity higher than 70.9% and six showed a specificity higher than 74.9% in the 4-region ACP localization. The ECG feature of the delta wave polarity in lead V1 correctly localized the ACP to one of three broad regions in 162 of 182 patients with an overall specificity of 94.5%. The study indicates that (1) the 12-lead ECG is of practical value for initial ACP localization; (2) a type A ECG is almost invariably associated with a left-sided ACP, while type B may occur with any ACP location; (3) the polarity of the delta wave is the most important ECG feature, and the polarities of the delta wave and main QRS complex in lead V1 play an important role in ACP localization.

Adult↗
PubMed1991

Localization of cardiac arrhythmias: conventional noninvasive methods.

Noninvasive localization of the accessory pathway (AP) in patients with the Wolff-Parkinson-White syndrome and of the site of origin of ventricular tachycardia (VT) is reviewed. 12-lead electrocardiography (ECG) is the most readily available method for localization of both the AP and the site of VT origin. Many published ECG criteria are introduced. The application of body surface potential mapping, vectorcardiography, nuclear phase imaging, echocardiography, computed tomography, nuclear magnetic resonance, and signal-averaged ECG in the localization of these arrhythmogenic substrates is also described. We believe that ECG is the most sensitive noninvasive method for AP localization as well as being convenient and simple; it may be used as the only noninvasive method for the initial evaluation. The left lateral AP, which occurs with an incidence of more than 40%, could be localized preoperatively by noninvasive methods only. For localization of the site of VT origin, none of the noninvasive methods is accurate enough for guiding the surgical and catheter-mediated ablative therapies so far.

Action Potentials↗
PubMed1991

Effect of pentisomide (CM 7857) on myocardial excitation, conduction, repolarization, and refractoriness. An electrophysiological study in humans.

The electrophysiological effects of pentisomide upon the intact human heart were evaluated using programmed stimulation and recording of intracardiac monophasic action potentials (MAP) in 17 patients with various ventricular arrhythmias. After i.v. administration of pentisomide, 85-135 mg, the atrial-His interval increased by 8 +/- 12 ms (p less than 0.05) during sinus rhythm and by 13 +/- 21 ms (p less than 0.05) at atrial pacing of 600 ms cycle length (600 ms pacing). The His-ventricular interval also increased by 6 +/- 10 ms during sinus rhythm (p less than 0.05) and by 5 +/- 9 ms at 600 ms pacing (NS). The QRS duration prolonged by 9 +/- 10 ms (p less than 0.01) and 6 +/- 8 ms (p less than 0.01) during 600 and 500 ms ventricular pacing, respectively. The right ventricular MAP duration to 90% repolarization was significantly shortened, by 20 +/- 21 ms (p less than 0.01) during sinus rhythm, by 16 +/- 17 ms (p less than 0.01) at 600 ms ventricular pacing, and by 11 +/- 16 ms (p less than 0.01) at 500 ms ventricular pacing. The corrected QT interval was shortened by 21 +/- 28 ms (p less than 0.01). The present study supports that pentisomide is a class-I antiarrhythmic agent with a marked effect on depolarization (action of class Ia and Ic) and on repolarization (action of class Ib). This unique combination of cellular electrophysiological properties indicates that the clinical antiarrhythmic efficacy of pentisomide may differ from that of hitherto available antiarrhythmic drugs.

Action Potentials↗
PubMed1991

[Effect of processing of toxic constituents in radix Phytolaceae].

This paper reports the effect of different processing technologies on the main toxic constituents in Radix Phytolaceae using its contents of phytolaccatoxin and histamine as index. The study was carried out to probe into the processing principle and improve the processing technology of Radix Phytolaceae. The result is gratifying.

Drugs, Chinese Herbal↗
PubMed1991

[Effects of processing on toxicity and pharmacological action of Phytolacca americana L].

The experimental results have shown that the toxicity of variously processed Phytolacca americana is lower than that of the original rude drug, i.e. the local irritability tends to decrease by 16.7-83.3%; LD50 to elevate by 1.66-10.47 times; expectoration to increase by 1.10-1.57 times; but diuresis mostly to decrease by 16.0-45.0%. This reveals that the main object of processing Phytolacca americana is to lower toxicity, increase expectoration and relieve diuresis to reduce fluid retention.

Animals↗
PubMed1991

Growth kinetics of Bu3 cells secreting HBsAg in microcarrier culture.

The genetically engineered mammalian cell (Bu3) secreting Hepatitis B surface antigen (HBsAg) was cultured on microcarriers semi-continuously. The growth model of Bu3 cells propagating on microcarriers, glucose consumption and lactate accumulation models were established. It is illustrated that the technology of anchorage-dependent Bu3 cell culture on microcarriers will give high yield and high HBsAg expression.

Animals↗
PubMed1991

[Serial study on nail fold microcirculation in patients with acute myocardial infarction].

The nail fold microcirculation was studied in 55 patients with acute myocardial infarction (AMI). At 12, 24, 36, 48, 60 hours and 3, 5, 7, 10, 14, 21, 28 days after AMI, sixteen indices of nail fold microcirculation were observed and analysed according to Tian Niu's "Multiple Weighted Evaluation Method of Nail Fold Microcirculation" using microscopic video system. The results showed: (1) The nail fold microcirculatory multiple weighted values were 6.6 +/- 0.8 within 12 hours after AMI, the mean value decreased significantly while the patient got better (P less than 0.0005). Significant difference among the different weighted values after AMI was shown. (2) The multiple weighted values in patients with complication were higher than those without complications (P less than 0.001). The values in patients with cardiogenic shock were much higher than those with cardiac failure or arrhythmia (P less than 0.01, P less than 0.05). (3) The weighted values in patients with multiple infarction were significantly higher than those with single infarction (P less than 0.05). (4) The nail fold multiple weighted values positively correlated with CPK, LDH, GOT (r = +0.82-0.97, P less than 0.0005) respectively. Thus, the higher the weighted value the much more serious condition of patients with AMI was. Continuous nail fold microcirculation observation and electrocardiographic monitoring would be helpful in early diagnosis and treatment of the complications with AMI to reduce the total mortality.

Aged↗
PubMed1990

Biogenesis of transverse tubules: immunocytochemical localization of a transverse tubular protein (TS28) and a sarcolemmal protein (SL50) in rabbit skeletal muscle developing in situ.

To study the biogenesis of transverse tubules, the temporal appearance and distribution of TS28 (a specific marker of transverse tubules absent from the sarcolemma in adult skeletal muscle; 28,000 Mr) and SL50 (specifically associated with the sarcolemma and absent from the region of the transverse tubules in adult rabbit skeletal muscle) (Jorgensen, A.O., W. Arnold, A. C.-Y. Shen, S. Yuan, M. Gaver, and K.P. Campbell. 1990. J. Cell Biol. 110:1173-1185) were determined in rabbit skeletal muscle developing in situ (day 17 of gestation to day 15 newborn) by indirect immunofluorescence labeling. The results presented show that the temporal appearance and subcellular distribution of TS28 is distinct from that of SL50 at the developmental stages examined. TS28 was first detected in some, but not all, multinucleated myotubes on day 17 of gestation. At this stage of development, SL50 and the Ca2(+)-ATPase of the sarcoplasmic reticulum were already present in all myotubes. TS28 first appeared in discrete foci mostly confined to the cell periphery of the myotubes. At subsequent stages of development (days 19-24 of gestation), TS28 was also found in shoft finger-like structures extending obliquely and transversely from the cell periphery towards the center of the myotubes. 1-2 d after birth, TS28 was observed in an anastomosing network composed of transversely oriented chickenwire-like networks extending throughout the cytoplasm and interconnected by longitudinally oriented fiber-like structures. As development proceeded, the transversely oriented network became increasingly dominant. By day 10 of postnatal development, the longitudinally oriented component of the tubular network was not regularly observed. At none of the developmental stages examined was TS28 observed to be uniformly distributed at the cell periphery. SL50, like TS28, first appeared in discrete foci at the cell periphery. However, shortly after its first appearance it appeared to be distributed along the entire cell periphery. Although the intensity of SL50 labeling increased with development, it remained confined to the sarcolemma and was absent from the interior regions of the myofibers, where transverse tubules were present at all subsequent developmental stages examined. Immunoblotting of cell extracts from skeletal muscle tissue at various stages of development showed that SL50 was first detected on day 24 of gestation, while TS28 was not detected until days 1-2 after birth. Comparison of these results with previous ultrastructural studies of the formation of transverse tubules supports the idea that the temporal appearance and subcellular distribution of TS28 correspond very closely to that of the distribution of forming transverse tubules in rabbit skeletal muscle developing in situ.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗