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Biomedical subjects

S Yuan

Publications and source records attributed to S Yuan.

At least 109 records · Page 6Linked to original sources
PubMed1998

De novo induction of the organizer and formation of the primitive streak in an experimental model of notochord reconstitution in avian embryos.

We have developed a model system for analyzing reconstitution of the notochord using cultured blastoderm isolates lacking Hensen's node and the primitive streak. Despite lacking normal notochordal precursor cells, the notochord still forms in these isolates during the 36 hours in culture. Reconstitution of the notochord involves an inducer, which acts upon a responder, thereby inducing a reconstituted notochord. To better understand the mechanism of notochord reconstitution, we asked whether formation of the notochord in the model system was preceded by reconstitution of Hensen's node, the organizer of the avian neuraxis. Our results show not only that a functional organizer is reconstituted, but that this organizer is induced from the responder. First, fate mapping reveals that the responder forms a density, morphologically similar to Hensen's node, during the first 10-12 hours in culture, and that this density expresses typical markers of Hensen's node. Second, the density, when fate mapped or when labeled and transplanted in place of Hensen's node, forms typical derivatives of Hensen's node such as endoderm, notochord and the floor plate of the neural tube. Third, the density, when transplanted to an ectopic site, induces a secondary neuraxis, identical to that induced by Hensen's node. And fourth, the density acts as a suppressor of notochord reconstitution, as does Hensen's node, when transplanted to other blastoderm isolates. Our results also reveal that the medial edge of the isolate forms a reconstituted primitive streak, which gives rise to the normal derivatives of the definitive primitive streak along its rostrocaudal extent and which expresses typical streak markers. Finally, our results demonstrate that the notochordal inducer also induces the reconstituted Hensen's node and, therefore, acts like a Nieuwkoop Center. These findings increase our understanding of the mechanism of notochord reconstitution, provide new information and a novel model system for studying the induction of the organizer and reveal the potential of the epiblast to regulate its cell fate and patterns of gene expression during late gastrula/early neurula stage in higher vertebrates.

Animals↗
PubMed1998

[Antimutagenic effects of beta-carotene from Dunaliella salina].

AIM: To study the genotoxic and antimutagenic efficts of beta-carotene from Dunaliella salina (beta-CDS). METHODS: The in vitro micronucleus and chromosomal aberration tests in hunman lymphocytes were adopted. The effect of beta-CDS on mutagensis induced by gamma-rays and mitomycin (Mit) was studied. RESULTS: beta-CDS (1-30 mg.L-1) had no genotoxicity, but inhibited spontaneous and gamma-ray-induced micronucleus fromation and Mit-induced chromosomal aberrations in human lymphocytes in vitro. The genotoxic action of synthetic beta-carotene (S beta C) was suppressed, the antimutagenic effects were heightened when S beta C and beta-carotene oil (beta CO, one of the beta-CDS compositions) were mixed in proportion as 80:27.5. CONCLUSION: beta-CDS is an antimutagenic agent.

Adult↗
PubMed1998

[Chemical constituents of Cichorium intybus L].

OBJECTIVE: To investigate the chemical constituents of Cichorium intybus. METHOD: Constituents were separated by means of solvent extraction and chromatography on silical gel. The structures were established by spectral analysis and chemical evidence. RESULT: Seven compounds were isolated from the roots of C. intybus and four of them were identified as alpha-amyrin, taraxerone, baurenyl acetate and beta-sitosterol. CONCLUSION: All the four compounds were obtained from the plant for the first time.

Cichorium intybus↗
PubMed1998

[Effects of processing on toxicity and pharmacological action of flos Genkwa].

Daphne genkwa can not be taken unless the toxicity is removed. The study on the effect of processing on the toxicity and pharmacological action of Flos Genkwa has shown that the toxicity of vinegar-processed Flos Genkwa is lower than that of the rude drug, but the pharmacological action is better. Both genkwanin and its vinegar-processed imitation have antitussive and expectorant actions without marked difference in efficacy. Both yuanhuacine and its vinegar-processed imitation could cause contraction of the extracorporeal womb and the intestinal canal, and the efficacy is almost similar in the concentration of 1:10(-5)-10(-6). The gestational womb was observed more sensitive than the normal one.

Animals↗
PubMed1998

[Study on the interaction of Et2SnCl2(phen) with DNA].

The absorbance, fluorescence and cyclic voltammetric methods as well as agarose gel electrophoresis were used to study the interaction of the antitumor compound Et2SnCl2(phen) with DNA. The results indicate that Et2SnCl2 (phen) mainly reacts electrostatically with the phosphate backbone of DNA. There also exists an intercalation into the double-helix of DNA through the phenanthroline group of Et2SnCl2(phen). At high concentration Et2SnCl2(phen) can cause unwinding of DNA. The molecular action mechanism of Et2SnCl2(phen) with DNA was first proposed.

Animals↗
PubMed1997

Phenotypic modulation of hamster acinar cells by culture in collagen matrix.

The aim of this study was to assess the effect of different culture conditions on the survival and morphological phenotype of cultured acinar cells. Acinar fragments isolated from hamster pancreas were embedded in rat-tail collagen. Four groups were established: Medium 1-5% NuSerum + basic medium (basic medium = DMEM/F12 supplemented with dexamethasone, 3-isobutyl-2-methylxanthine, and antibiotics); Medium 2-10% NuSerum + basic medium. Medium 3-Medium 2 supplemented with epidermal growth factor and cholera toxin; and Medium 4:-Medium 3 supplemented with soybean trypsin inhibitor. Freshly isolated acinar cells were retrieved morphologically intact. In Medium 1, more than 80% of cells retained a normal histological appearance at 34 days in culture. Immunostaining for amylase was observed at the apical pole of the cells. The remaining cells showed variable degrees of degeneration. In Medium 2, approximately 50% of acinar cells appeared normal at 34 days in culture, while the remainder were severely degenerated. A few cystic structures were also observed. Positive immunostaining for amylase was limited to the cells with a normal histological appearance. The cells grown in Media 3 and 4 had similar courses of morphological changes. After 8 days in culture, most acinar fragments disappeared and were replaced by cystic structures, lined by a single layer of cuboidal cells. Some amylase-positive immunoreactive cells were integral components of the cystic wall. Cellular amylase activity was a function of the different culture media, a more rapid decrease in amylase activity being observed in Media 3 and 4. Uptake of [3H]thymidine did not show any significant differences between the media. It was also found that the ductlike cells cultured in Medium 4 had a limited capacity to redifferentiate into acinar cells. This study shows that the acinar cell phenotype can be maintained in vitro for more than 1 month. This study also suggests that ductal-like epithelial structures arise from transformation of acinar cells.

Amylases↗
PubMed1997

Signed value of monophasic action potential duration difference. A useful measure in evaluation of dispersion of repolarization in patients with ventricular arrhythmias.

AIMS: To evaluate the usefulness of the signed value of monophasic action potential duration difference in analysing the cause of dispersion of ventricular repolarization. METHODS AND RESULTS: Monophasic action potentials were simultaneously recorded from the right ventricular apex and outflow tract during programmed stimulation in 36 patients with ventricular arrhythmias. The time difference between the ends of repolarization on the two monophasic action potentials was used as a measure of the dispersion of ventricular repolarization, and the signed value of the monophasic action potential duration difference was used to specify the contributions of the activation time difference and the monophasic action potential duration difference to the dispersion of ventricular repolarization. During right ventricular pacing, single and double programmed stimulation and at the induction of ventricular arrhythmias, the dispersion of ventricular repolarization and the signed value of monophasic action potential duration difference were markedly greater in the 11 patients with polymorphic ventricular tachycardia/ventricular fibrillation induced than in the 13 patients with monomorphic ventricular tachycardia induced, and in the 10 patients with clinical polymorphic ventricular tachycardia/ventricular fibrillation/cardiac arrest than in the 12 patients with sustained monomorphic ventricular tachycardia. This disclosed that the increased dispersion of ventricular repolarization was caused by increases in both the activation time difference and the monophasic action potential duration difference in the former, but mainly by an increased activation time difference in the latter groups. CONCLUSION: The signed value of monophasic action potential duration difference can specify whether an increased dispersion of ventricular repolarization is caused by inhomogeneous repolarization, inhomogeneous conduction or both, and thereby it is useful in study of the mechanism of ventricular arrhythmias.

Action Potentials↗
PubMed1997

Immunization with heat-killed Mycobacterium vaccae stimulates CD8+ cytotoxic T cells specific for macrophages infected with Mycobacterium tuberculosis.

Immune responses to Mycobacterium tuberculosis are analyzed in mice which have been immunized with Mycobacterium vaccae to examine novel ways of altering protective immunity against M. tuberculosis. The spleen cells of mice immunized with M. vaccae proliferate and secrete gamma interferon (IFN-gamma) in response to challenge with live M. tuberculosis in vitro. Immunization with M. vaccae results in the generation of CD8+ T cells which kill syngeneic macrophages infected with M. tuberculosis. These effector cytotoxic T cells (CTL) are detectable in the spleen at 2 weeks after immunization with M. vaccae but cannot be found in splenocytes 3 to 6 weeks postimmunization. However, M. tuberculosis-specific CTL are revealed following restimulation in vitro with heat-killed M. vaccae or M. tuberculosis, consistent with the activation of memory cells. These CD8+ T cells secrete IFN-gamma and enhance the production of interleukin 12 when cocultured with M. tuberculosis-infected macrophages. It is suggested that CD8+ T cells with a cytokine secretion profile of the Tc1 class may themselves maintain the dominance of a Th1-type cytokine response following immunization with M. vaccae. Heat-killed M. vaccae deserves attention as an alternative to attenuated live mycobacterial vaccines.

Animals↗
PubMed1997

[The expression of tumor suppressor gene p53 and Rb gene in nasopharyngeal carcinoma].

In order to observe the relation of tumor supperssor gene p53 and Rb gene to nasopharyngeal carcinoma, we investigated p53 gene mutations in exon 7-8 in 33 cases of nasopharygeal carcinoma (NPC), using single-strand conformation ploymorphism analysis of PCR (PCR-SSCP). The data showed p53 mutations in 7 of 33 specimens at exon 8 (21.2%). No mutation in exon 7 was detected. Analysis of Rb gene in NPC tissues by southern blot revealed the deletion and loss of activity of Rb gene in 11 of 13 cases (86.6%). Our results suggest that Rb gene and p53 gene are closely associated with the tumorigenesis of NPC.

Carcinoma, Squamous Cell↗
PubMed1997

[The effect of Tianma injection on cultured vascular smooth muscle cells proliferation].

The proliferation of vascular smooth muscle cells (VSMC) has been thought to play an important role in the development of hypertension and atherosclerosis. The aim of this study was to investigate the effect of Tianma Injection and its major component Gastrodin on the proliferation of cultured VSMC. VSMC were cultured and randomly divided into the control, Tianma and Gastrodin groups. The results showed that Tianma Injection significantly decreased cell numbers dose-dependently and time-dependently, and it inhibited 3H-TdR incorporation in VSMC. It also increased the content of PGI2 production in VSMC. However, no significant differences of the above measurements were observed between the Gastrodin and control groups. The suggest that Tianma Injection can inhibit VSMC proliferation and the effect possibly results from its increasing PGI2 production content, and that the inhibiting effect of Tianma is irrelated to Gastrodin.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

[The aggregation and kinetics of decomposition reaction of Ga-sulfophthalocyanine].

The aggregation and kinetics of decomposition reaction of Ga-sulfophthalocyanine has been studied by electronic spectroscopy. The effects of pH on the aggregation are discussed. The experimental results show that the rate of decomposition reaction of Ga-sulfophthalocyanine can be expressed as follow: -dcM/dt = 12.279cDcOH-. Where cD and cOH- concentration of GA-sulfophthalocyanine and OH- respectively.

Dimerization↗
PubMed1997

[A study on the infiltration of macrophages and lymphocytes in interrenal tissues in patients with acute renal tubulointerstitial disease].

Renal tissues of 14 patients with acute renal tubulointerstitial disease were studied by using immunohistochemical method. Cells infiltrated in interrenal tissue were observed. The results show that the causes which result in acute renal tubulointerstitial disease are different; the renal tubular and interstitial damages are reversible or irreversible; the major inflammatory cells infiltrated in interrenal tissues are CD68 and CD45ro positive cells. The results suggest that the macrophages and T lymphocytes infiltrated in interrenal tissues play an important role in the progress of acute renal tubulointerstital disease.

Acute Disease↗
PubMed1996

Transdifferentiation of human islets to pancreatic ductal cells in collagen matrix culture.

Transdifferentiation is a change from one differentiated phenotype to another, involving morphological and functional phenotypic markers. Stability of the cellular phenotype is probably related to the extracellular milieu, as well as cytoplasmic and nuclear components that interact to control gene expression, and the conversion of cell phenotype is likely to be accomplished by selective enhancement of gene expression, which controls the terminal developmental commitment of cells. In this paper, we show the induction of cultured human islets cells to alter their usual phenotypic expression and attain morphological and functional characteristics of duct cells. Islets were isolated by collagenase digestion of pancreata that were removed from cadaveric organ donors. The islets were purified on a two-step density gradient of bovine serum albumin and were then placed into a three-dimensional rat-tail collagen gel matrix supplemented with NuSerum epithelial growth factor and cholera toxin. During the initial 96 h of culture, the islets underwent a cystic transformation that was associated with (1) the maintenance of immunoreactivity for neuron-specific enolase, an endocrine cell marker, but a progressive loss of insulin gene expression, (2) a loss of immunoreactivity for insulin protein, and (3) the appearance of CK-19, a marker for ductal cells. After the transformation was complete, the cells had the ultrastructural appearance of primitive duct-like cells. Cyst enlargement after the initial 96 h was associated, at least in part, with cell replication, as reflected in the 1500% increase in the incorporation of tritiated thymidine. These experiments are consistent with the transdifferentiation of an islet cell to a ductal cell. The exact mechanisms involved still need to be fully elucidated.

Autoradiography↗
PubMed1996

Generation and application of monoclonal antibody to human pancreatic carcinoma.

An IgG1 mouse monoclonal antibody (MAb) YPC3 against human pancreatic carcinoma was generated by a hybridoma technique. When human tissue sections were examined with immunohistochemical staining, YPC3 MAb reacted with 28 of 32 (87.5%) cases of pancreatic carcinoma tissue; it failed to react with all 11 cases of normal pancreas examined. When 99mTC-radiolabeled YPC3 MAb was administrated intravenously to the nude mice bearing xenograft of pancreatic carcinoma, clear scintigraphic visualization of tumor xenograft was found with SPECT 24 h after injection. Administration of either YPC3 MAb or LAK cells combined with YPC3 MAb could inhibit the growth of the xenografts in nude mice. These results suggest that YPC3 MAb might be an ideal carrier for radioimmunolocalization and immunotherapy of human pancreatic carcinoma.

Animals↗
PubMed1996

Dispersion of repolarization following double and triple programmed stimulation. A clinical study using the monophasic action potential recording technique.

To study the dispersion of ventricular repolarization following double and triple programmed stimulation and its correlation with the inducibility of ventricular arrhythmias, monophasic action potentials were simultaneously recorded from the right ventricular apex and outflow tract during programmed stimulation in 12 patients with ventricular arrhythmias and a normal QT interval. The time difference between the ends of the two monophasic action potentials were used as a measure of the dispersion of ventricular repolarization, which consists of the activation time difference and the monophasic action potential duration difference. During double and triple programmed stimulation, the dispersion of ventricular repolarization increased significantly with the shortening of the coupling interval but decreased slightly with the shortening of the preceding interval. The induction of the ventricular arrhythmias in these patients was invariably associated with a marked increase in the dispersion of ventricular repolarization. The maximal dispersion of ventricular repolarization was significantly larger in the seven patients with polymorphic ventricular tachycardia and/or ventricular flutter/fibrillation induced than in the four patients with monomorphic ventricular tachycardia induced. Analysis of the two components of the dispersion of ventricular repolarization revealed that the increased dispersion of ventricular repolarization was mainly caused by an increase in the activation time difference in the monomorphic ventricular tachycardia subgroup, and by increases in both the activation time difference and monophasic action potential duration difference in the polymorphic ventricular tachycardia/fibrillation subgroup. These findings suggest that increased dispersion of ventricular repolarization is one of the underlying mechanisms accounting for the myocardial vulnerability to ventricular arrhythmias and that repolarization disturbance is important for the genesis of polymorphic ventricular tachycardia/fibrillation.

Action Potentials↗
PubMed1996

Clinical application of a microcomputer system for analysis of monophasic action potentials.

UNLABELLED: Computerized analysis of monophasic action potentials (MAPs) has rarely been reported in clinical setting. We developed a computer system featuring on-line acquisition and user-monitored automatic measurement of multichannel MAPs with the capability of manual corrections. This system has been used in 34 patients in whom two-channel MAPs and 1-lead ECG were digitized during sinus rhythm, pacing, and programmed stimulation (PS). In total, 41, 413 MAPs in 212 data files were measured. The correct determination rate was 100% for MAP onset and plateau, 99.78% (95.76% during PS) for MAP baseline, and 99.96% (54.29% during PS) for QRS onset. The comparison between the computerized and manual measurements in 292 MAPs showed that the former highly agreed with the latter, with the limits of agreement, defined as mean difference +/- 2 SD, being from -4.8-4.9 ms for activation time and from -4.1-6.0 ms for MAP duration measurements. Using this system, two-channel MAPs of more than 300 consecutive beats can be measured in a few minutes, which made it possible to determine the steady state of MAP duration individually, and evaluate the MAP changes during intervention in detail. The clinical routine procedure for testing the effective refractory period and several new MAP parameters were also evaluated using this system. CONCLUSION: The MAP measurement using this computer system is reliable, rapid and accurate; it can therefore replace the manual method and provide more useful information for clinical research.

Action Potentials↗
PubMed1996

[Determination of genkwanin in flos Genkwa by HPLC].

In this paper, the method for determining genkwanin in Flos Genkwa was established by HPLC. Detected at 332nm on a Lichrosorb 5 RP-18 column with a mobile phase of methanol-water-acetic acid (65:35:5), the content of genkwanin in Flos Genkwa was determined to be 0.16%. The recovery rate was 95.46% and RSD 1.15%.

Antitussive Agents↗