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Biomedical subjects

W Yan

Publications and source records attributed to W Yan.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Cloning of the genes associated with the pathogenesis of pregnancy induced hypertension using subtractive hybridization].

OBJECTIVE: To clone the genes related to pregnancy induced hypertension (PIH) for the study of PIH pathogenesis. METHODS: The differential expressed cDNA of PIH and normal pregnant placenta were cloned using modified polymerase chain reaction based subtractive hybridization. The differential cDNA were sequenced. RESULTS: Among 86 clones from subtractive hybridization, 14 clones containing differential expressed gene fragments in PIH and normal placenta were identified, and these might be the genes associated with PIH. Compared with the expressed sequence tags (EST) in dbEST of National Center for Biotechnology Information, it showed that 11 of them were known gene fragments, and three were unknown. The three unknown gene fragments were registered in GenBank, the accession number is AF 232216, AF 232217, AF 233648 respectively. CONCLUSIONS: Fourteen PIH related genes were cloned with subtractive hybridization. A new approach to study on the pathogenesis of PIH is presented.

Cloning, Molecular↗
PubMed2000

Stem cell factor functions as a survival factor for mature Leydig cells and a growth factor for precursor Leydig cells after ethylene dimethane sulfonate treatment: implication of a role of the stem cell factor/c-Kit system in Leydig cell development.

The significance of the interaction between Sertoli cell-produced stem cell factor (SCF) and its receptor, c-kit, on Leydig cells (LCs) during LC development and differentiation is unknown. In the present study, we investigated the potential role of the SCF/c-kit system in LC apoptosis and precursor LC proliferation after ethylene dimethane sulfonate (EDS) treatment in rats. A function-blocking anti-c-kit antibody, ACK-2, was used to block SCF/c-kit interaction at four time points, corresponding to the peak of LC apoptosis and three waves of proliferation of precursor LCs. Blockade of SCF/c-kit interaction by ACK-2 accelerated LC apoptosis and inhibited proliferation of precursor LCs during the first two waves of precursor LC proliferation around days 3-4 and day 10, but not the third wave of precursor LC proliferation around day 20 after EDS treatment. The data suggest that the soluble SCF might act as a survival factor for mature LCs and a growth factor for precursor LCs after EDS-induced LC depletion. This is also supported by a close correlation between the oscillating levels of soluble SCF mRNA and the profiles of LC apoptosis and regeneration. Since regeneration of the LC population after EDS treatment resembles the development of adult-type LCs during prepubertal life, the present findings imply that soluble SCF might participate in regulation of the formation of the LC population during testicular development. Our data also support a model in which delicate and reciprocal regulation exists between soluble SCF production by Sertoli cells, testosterone production by LCs, and pituitary gonadotropins.

Animals↗
PubMed2000

A beta-D-glucan from the sclerotia of Pleurotus tuber-regium (Fr.) Sing.

An alkali-soluble polysaccharide (Hunai polysaccharide, 1) from the fruit body of Pleurotus tuber-regium (Fr.) Sing was shown to be homogeneous by gel permeation chromatography and its molecular weight was approximately 4.3 x 10(5). Complete acid hydrolysis, periodate oxidation, Smith degradation, methylation, FT-IR and 13C NMR analysis, complex formation with Congo Red, indicated that 1 has a beta-(1 --> 3)-linked D-glucopyranosyl backbone with a single beta-D-glucopyranosyl group at O-6 of every third glucose residue.

Carbohydrate Conformation↗
PubMed2000

Involvement of Bcl-2 family proteins in germ cell apoptosis during testicular development in the rat and pro-survival effect of stem cell factor on germ cells in vitro.

A large part of germ cells die apoptotically during testicular development in rodents. In the present study, a wave of germ cell apoptosis was observed between days 10 and 30 of postnatal life by in situ 3'-end labeling and DNA fragmentation analysis. To explore the potential involvement of Bcl-2 family members in this process, the expression and localization of some Bcl-2 family proteins (Bcl-2, Bcl-xL, Bcl-w, Bak, Bax, and Bad) and p53 were analyzed during testicular development in the rat by Western blotting and immunohistochemistry. The dynamic changes in the expression profiles of Bcl-2 family proteins are consistent with a model in which germ cells are primed for apoptosis during the first cycle of spermatogenesis by de novo expression of the death effectors Bax and Bad in a p53-dependent manner and these proteins are prevented from triggering further apoptosis after the first spermatogenic cycle has been set up by anti-apoptotic Bcl-2 family proteins Bcl-xL and Bcl-w. To examine whether the pro-survival effect of stem cell factor (SCF) on germ cells in vitro is mediated by Bcl-2 family proteins, the correlation between the pro-survival effect of SCF on germ cells and the expression of the above-mentioned apoptosis-related gene products in the seminiferous tubules at stage XII of the epithelial cycle were also investigated using a tubular culture system. The data suggest that SCF supports germ cell survival during spermatogenesis by up-regulating pro-survival Bcl-2 family proteins, Bcl-w and Bcl-xL, and down-regulating pro-apoptosis Bcl-2 family proteins, e.g. Bax.

Animals↗
PubMed2000

Corin, a transmembrane cardiac serine protease, acts as a pro-atrial natriuretic peptide-converting enzyme.

Atrial natriuretic peptide (ANP) is a cardiac hormone essential for the regulation of blood pressure. In cardiac myocytes, ANP is synthesized as a precursor, pro-ANP, that is converted to biologically active ANP by an unknown membrane-associated protease. Recently, we cloned a transmembrane serine protease, corin, that is highly expressed in the heart. In this study, we examine effects of corin on pro-ANP processing. Our results show that recombinant human corin converts pro-ANP to ANP and that the cleavage in pro-ANP by corin is highly sequence specific. Our findings suggest that corin is the long-sought pro-ANP-converting enzyme and that the corin-mediated pro-ANP activation may play a role in regulating blood pressure.

Animals↗
PubMed2000

G protein-coupled receptor kinase-5 regulates thrombin-activated signaling in endothelial cells.

We studied the function of G protein-coupled receptor kinases (GRKs) in the regulation of thrombin-activated signaling in endothelial cells. GRK2, GRK5, and GRK6 isoforms were expressed predominantly in endothelial cells. The function of these isoforms was studied by expressing wild-type and dominant negative (dn) mutants in endothelial cells. We determined the responses to thrombin, which activates intracellular signaling in endothelial cells by cleaving the NH(2) terminus of the G protein-coupled proteinase-activated receptor-1 (PAR-1). We measured changes in phosphoinositide hydrolysis and intracellular Ca(2+) concentration ([Ca(2+)](i)) in response to thrombin as well as the state of endothelial activation. In the latter studies, the transendothelial monolayer electrical resistance, a measure of the loss of endothelial barrier function, was measured in real time. Of the three isoforms, GRK5 overexpression was selective in markedly reducing the thrombin-activated phosphoinositide hydrolysis and increased [Ca(2+)](i). GRK5 overexpression also inhibited the thrombin-induced decrease in endothelial monolayer resistance by 75%. These effects of GRK5 overexpression occurred in association with the specific increase in the thrombin-induced phosphorylation of PAR-1. In contrast to the effects of GRK5 overexpression, the expression of the dn-GRK5 mutant produced a long-lived increase in [Ca(2+)](i) in response to thrombin, whereas dn-GRK2 had no effect. These results indicate the crucial role of the GRK5 isoform in the mechanism of thrombin-induced desensitization of PAR-1 in endothelial cells.

Cells, Cultured↗
PubMed2000

[Immunological study on the antitumor effects of fungus polysaccharides compounds].

Fungus polysaccharides compounds (FPC) are the mixture of procyanidins oligomers, glycyrrhetinicacid and polysaccharides of hericium erinaceus, lentinus edodes and poria cocos. The antitumor effects of FPC and its immunity regulating effects as an immunostimulant on the mice burdened with sarcoma 180 (S-180) were studied. FPC (100, 200 and 400 mg/kg BW) was gavaged to mice for 31 days. S-180 was transplanted to these mice on the 21th day. Lentinus edodes group was gavaged 200 mg/kg BW saccharine of lentinus edodes. The results showed that FPC could inhibit the growth of S-180 effectively. The inhibitory rates were 37.74%, 44.73% and 48.32% respectively. The antineoplastic activity of FPC (200 mg/kg. BW) was more effective than polysaccharide of lentinus edodes at the same dose. In S-180 burdened mice, the percentage of L3T4 and the ratio of L3T4/Lyt-2, NK activity and the induced IL-2, IFN-gamma levels were decreased significantly compared with the normal control group. As an immunostimulant, FPC could increase the percentage of L3T4 and the ratio of L3T4/Lyt-2 in S-180 burdened mice, but had no significant effects on the percentage of Lyt-2. Polysaccharide of lentinus edodes alone could also increase the immunity competence of mice burdened with S-180, but was not better than that of FPC at the same dose. It could be concluded that the compound of antineoplastic component could be synergetic.

Adjuvants, Immunologic↗
PubMed2000

Design and synthesis of aryloxyethyl thiocyanate derivatives as potent inhibitors of Trypanosoma cruzi proliferation.

As a part of our project directed at the search of new chemotherapeutic agents against American trypanosomiasis (Chagas' disease), several drugs possessing the 4-phenoxyphenoxy skeleton and other closely related structures employing the thiocyanate moiety as polar end group were designed, synthesized, and evaluated as antiproliferative agents against Trypanosoma cruzi, the parasite responsible for this disease. These thiocyanate analogues were envisioned bearing in mind the potent activity shown by 4-phenoxyphenoxyethyl thiocyanate (compound 8) taken as lead drug. This compound had previously proved to be an extremely active growth inhibitor against T. cruzi with IC(50) values ranging from the very low micromolar level in epimastigotes to the low nanomolar level in the intracellular form of the parasite. Of the designed compounds, the ethyl thiocyanate drugs connected to nonpolar skeletons, namely, arylthio, 2,4-dichlorophenoxy, ortho-substituted aryloxy, and 2-methyl-4-phenoxyphenoxy (compounds 15, 34, 47, 52, 72, respectively), were shown to be very potent antireplicative agents against T. cruzi. On the other hand, conformationally restricted analogues as well as branched derivatives at the aliphatic side chain were shown to be moderately active against T. cruzi growth. The biological activity of drugs bearing the thiocyanate group correlated quite well with the activity exhibited by their normal precursors, the tetrahydropyranyl ether derivatives, when bonded to the same nonpolar skeleton. Compounds having the tetrahydropyranyl moeity as polar end were proportionally much less active than sulfur-containing derivatives in all cases. Drugs 47 and 72 also resulted to be very active against the amastigote form of the parasite growing in myoblasts; however, they were slightly less active than the lead drug 8. On the other hand, compounds 34 and 52 were almost devoid of activity against myoblasts. Surprisingly, the dithio derivative 15 was toxic for myoblasts.

Animals↗
PubMed2000

Cooperative phosphorylation at multiple sites is required to activate p53 in response to UV radiation.

The activity of the tumor suppressor p53 is induced in response to DNA-damaging agents such as UV and gamma radiation. Phosphorylation is one of the key regulatory steps for activating p53 function. Recent reports have shown that p53 is phosphorylated at both serines 15 and 392 in response to UV radiation. Phosphorylation at serine 15 prevents the binding of HDM2, a negative regulator of p53. Phosphorylation at serine 392 induces the DNA-binding function of p53. We examined the requirement for phosphorylation at both serines and show that both these modifications occur on the same molecule of p53. In vitro assays demonstrate that phosphorylation at either one of these sites is not sufficient to yield an active p53. Phosphorylation by DNA-PK, that modifies serines 15 and 37, inhibits HDM2 binding to p53 but does not induce the DNA-binding activity of p53. Phosphorylation at serine 392, on the other hand, stimulates the DNA-binding ability of p53 but does not make it immune to binding and inhibition by HDM2. Thus, our results demonstrate that multiple sites need to be modified to yield a functional p53.

Casein Kinase II↗
PubMed2000

The dimensionality of coping among Chinese health care workers.

The transactional model defines coping as a process that changes on the basis of the context of an environmental encounter. An instrument used to investigate coping in diverse person-environment interactions is the Ways of Coping Questionnaire (WOC; S. Folkman & R. S. Lazarus, 1988). Although evidence exists to support the basic underlying structure of the WOC in Western societies, no research has been conducted on the instrument's dimensionality in non-Western societies. The authors identified 14 factors for the WOC administered to a sample of health care workers in Beijing, China. The 14 factors identified in the present study were similar to the 8 factors identified in the original validation study (S. Folkman, R. S. Lazarus, C. Dunkel-Schetter, A. DeLongis, & R. J. Gruen, 1986), but they were more content specific.

Adaptation, Psychological↗
PubMed2000

Bcl-w forms complexes with Bax and Bak, and elevated ratios of Bax/Bcl-w and Bak/Bcl-w correspond to spermatogonial and spermatocyte apoptosis in the testis.

Bcl-w, a prosurvival member of the Bcl-2 family, is essential for spermatogenesis. However, the mechanisms by which Bcl-w participates in the regulation of apoptosis in the testis are largely unknown. To explore the potential role of Bcl-w in the regulation of apoptosis in the testis, the expression of Bcl-w mRNA and protein during testicular development and spermatogenesis, the dimerization with the proapoptosis members of the Bcl-2 family, and the responses to hormonal stimulation in vitro and apoptosis-inducing signals in vivo were investigated. Both Bcl-w mRNA and protein were detected in Sertoli cells, spermatogonia, and spermatocytes, as well as in Leydig cells. The steady-state levels of Bcl-w mRNA and protein were much higher in Sertoli cells than in spermatogonia and spermatocytes. In the adult rat testis, both Bcl-w mRNA and protein in Sertoli cells displayed a stage-specific expression pattern. Bcl-w could form complexes with Bax and Bak but not with Bad. Bax and Bak were immunohistochemically localized to the same cell types as Bcl-w, but with higher expression levels in spermatocytes and spermatogonia than in Sertoli cells. FSH could up-regulate Bcl-w mRNA levels in the seminiferous tubules cultured in vitro, whereas no effect was observed when testosterone was applied. Three animal models that display spermatogonial apoptosis induced by blockade of stem cell factor/c-kit interaction by a function-blocking anti-c-kit antibody, spermatocyte apoptosis induced by methoxyacetic acid, and apoptosis of spermatogonia, spermatocytes, and spermatids induced by testosterone withdrawal after ethylene dimethane sulfonate treatment were employed to check the changes of Bcl-w, Bax, and Bak protein levels during apoptosis of specific germ cells. In all three models, the ratios of Bax/Bcl-w and Bak/Bcl-w were significantly elevated. The present study suggests that Bcl-w is an important prosurvival factor of Sertoli cells, spermatogonia, and spermatocytes and participates in the regulation of apoptosis by binding proapoptotic factors Bax and Bak. The ratios of Bax/Bcl-w and Bak/Bcl-w may be decisive for the survival of Sertoli cells, spermatogonia, and spermatocytes.

Acetates↗
PubMed2000

Stem cell factor protects germ cells from apoptosis in vitro.

Stem cell factor (SCF) plays an important role in migration, adhesion, proliferation, and survival of primordial germ cells and spermatogonia during testicular development. However, the function of SCF in the adult testis is poorly described. We have previously shown that, in the presence of SCF, there were more type A spermatogonia incorporating thymidine at stage XII of rat seminiferous tubules cultured in vitro than in the absence of SCF, implying that the increased DNA synthesis might result from enhanced survival of spermatogonia. To explore the potential pro-survival function of SCF during spermatogenesis, the seminiferous tubules from stage XII were cultured in the presence or absence of SCF (100 ng/ml) for 8, 24, 48, and 72 hours, respectively, and apoptosis was analyzed by DNA laddering and in situ 3'-end labeling (ISEL) staining. Surprisingly, not only spermatogonia, but also spermatocytes and spermatids, were protected from apoptosis in the presence of SCF. Apoptosis took place much later and was less severe in the SCF-treated tubules than in the controls. Based on previous studies showing that FSH prevents germ cells from undergoing apoptosis in vitro, and that SCF level is increased dramatically in response to FSH stimulation, we also tested if the pro-survival effect of FSH is mediated through SCF by using a function-blocking monoclonal antibody, ACK-2, to block SCF/c-kit interaction. After 24 hours of blockade, the protective effect of FSH was partially abolished, as manifested by DNA laddering and ISEL analyses. The present study demonstrates that SCF acts as an important survival factor for germ cells in the adult rat testis and FSH pro-survival effect on germ cells is mediated partially through the SCF/c-kit pathway.

Animals↗
PubMed2000

Improved PCR-based subtractive hybridization strategy for cloning differentially expressed genes.

An improved PCR-based subtractive hybridization strategy was used to clone apoptosis-related genes induced by all-trans retinoic acid (ATRA) from human promyelocytic leukemia cell line HL-60 cells. The protocol used the cap-finder method, long-distance PCR, streptavidin magnetic bead-mediated subtraction and spin column chromatography. Twenty-seven clones related to apoptosis were identified by reverse dot blot assay. Seventeen were known genes, of which seven have been reported to be apoptosis related. The remaining 10 were unknown genes, five of which were sequenced and named apr-1 to apr-5. apr-1, apr-2, apr-3 and TNF were reidentified by reverse dot blot, and it is suggested that they might be related to apoptosis. The results suggest that this strategy might be efficient for large-scale cloning of differentially expressed genes in target cells.

Apoptosis↗
PubMed2000

Smad protein expression and activation in transforming growth factor-beta refractory human squamous cell carcinoma cells.

In contrast to nonneoplastic keratinocytes, human squamous carcinoma cell lines are able to proliferate in the presence of transforming growth factor-beta (TGF-beta) in vitro. This has raised the question whether, how frequently, by which mechanism, and at which stage of development squamous carcinomas escape from TGF-beta control in vivo. We have developed a method to rapidly identify the most common molecular alterations in the TGF-beta signaling pathway by combining measurements of the levels and the activation state of Smad signaling intermediates with DNA-based diagnostic assays. In this report, we demonstrate the validity of this approach using a panel of seven squamous cell carcinoma (SCC) lines known to be refractory to TGF-beta-mediated cell cycle arrest. Each of the SCCs expressed the pathway-restricted Smad proteins, Smad2 and-3. Furthermore, treatment with TGF-beta induced phosphorylation of Smad2 in each of the SCCs with the exception of the two cell lines that carry inactivating mutations of the TGF-beta type II receptor. Three of the remaining SCC lines failed to express the common mediator Smad4, two on the basis of loss of transcription and one by a posttranscriptional mechanism. Thus, a mechanism for TGF-beta resistance was identified in five of the seven tumor cell lines. Interestingly, in the two remaining lines, no abnormalities of signaling intermediates were found, and TGF-beta was able to activate TGF-beta-responsive promoters. This suggests that the ability of these two cell lines to grow in the presence of TGF-beta is due to factors extraneous to the TGF-beta pathway itself. Application of our protein-based strategy to interrogate the TGF-beta signaling pathway should allow us to determine whether or not and, if so, how and at which stage human squamous cell carcinomas become TGF-beta resistant in vivo.

Carcinoma, Squamous Cell↗
PubMed2000

Legislation concerning management of medical institutions in China's health reform.

The establishment of China's socialist market economy has called for the management legislation of China's medical institutions. This article gives a brief introduction of the main contents China's legislation concerning management of medical institutions, which includes regional health program, licensing system, and quality management system of medical institutions and systems concerning evaluation and assessment of medical institutions. Besides, the article also put forward some suggestions on further improving the legislation concerning management of medical institutions.

China↗