Biomedical subjects

S J Chen

Publications and source records attributed to S J Chen.

At least 73 records · Page 4Linked to original sources

PubMed2000

Gene expression networks underlying retinoic acid-induced differentiation of acute promyelocytic leukemia cells.

To elucidate the molecular mechanism of all-trans-retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) cells, the gene expression patterns in the APL cell line NB(4) before and after ATRA treatment were analyzed using complementary DNA array, suppression-subtractive hybridization, and differential-display-polymerase chain reaction. A total of 169 genes, including 8 novel ones, were modulated by ATRA. The ATRA-induced gene expression profiles were in high accord with the differentiation and proliferation status of the NB(4) cells. The time courses of their modulation were interesting. Among the 100 up-regulated genes, the induction of expression occurred most frequently 12-48 hours after ATRA treatment, while 59 of 69 down-regulated genes found their expression suppressed within 8 hours. The transcriptional regulation of 8 induced and 24 repressed genes was not blocked by cycloheximide, which suggests that these genes may be direct targets of the ATRA signaling pathway. A balanced functional network seemed to emerge, and it formed the foundation of decreased cellular proliferation, maintenance of cell viability, increased protein modulation, and promotion of granulocytic maturation. Several cytosolic signaling pathways, including JAKs/STAT and MAPK, may also be implicated in the symphony of differentiation. (Blood. 2000;96:1496-1504)

Antineoplastic Agents↗

PubMed2000

Modulation of endogenous Smad expression in normal skin fibroblasts by transforming growth factor-beta.

Transforming growth factor-beta (TGF-beta) stimulation of collagen synthesis plays a fundamental role in physiological tissue repair as well as pathological fibrosis. Members of the SMAD family of intracellular proteins are phosphorylated by TGF-beta receptors and convey signals to specific TGF-beta-inducible genes. Ligand binding initiates signaling through the SMAD pathway, but it is unknown how signaling is terminated. The expression and regulation of Smads have been characterized mostly in transformed cells using transient expression systems. In this study, we investigated the physiological regulation of endogenous Smads by TGF-beta in nontransformed normal skin fibroblasts in vitro. Treatment with TGF-beta resulted in time- and dose-dependent translocation of SMAD3 and SMAD4 from the cytoplasm to the nucleus. The levels of SMAD3 and Smad3 mRNA were profoundly down-regulated by TGF-beta1 or TGF-beta3 in a time-dependent manner, whereas expression of antagonistic Smad7 was rapidly and transiently induced. The stability of Smad3 mRNA transcripts was unaffected by TGF-beta. Cycloheximide prevented the inhibition of Smad3, but not the induction of Smad7, mRNA expression by TGF-beta1, identifying Smad7 as an immediate-early gene target of TGF-beta in fibroblasts. In Smad4-deficient breast cancer cells, TGF-beta failed to modulate Smad expression, suggesting that SMADs mediate their own regulation in response to ligand. These results demonstrate that TGF-beta not only triggers functional activation of the SMAD signaling cascade in primary skin fibroblasts, but also simultaneously exerts potent effects on endogenous SMAD expression and intracellular trafficking. Taken together with recent reports implicating ubiquitination in SMAD turnover, these findings indicate the existence of multiple levels of control for modulating SMAD-mediated TGF-beta signaling in fibroblasts.

Adult↗

PubMed2000

Concomitant management of airway and its adjacent vascular pathology in addition to repair of congenital cardiac defects.

Respiratory symptoms are often present in infants with congenital cardiac anomalies, but the intrinsic pathology of the airway itself or external compression by abnormal vessels is frequently undetected before cardiac repair. We collected 12 patients with airway pathology from July 1996 to October 1998; all had definite diagnosis of lesions of the airway and its adjacent vessels by preoperative ultrafast computed tomography. Four had intrinsic pathology (one retrotracheal diverticulum, three tracheal stenosis) as well as external compression. Among them, six had complete vascular ring, four partial rings and three had bronchial compression by aneurysmal dilatation of branch pulmonary arteries. Simultaneous airway repair (one diverticulectomy, three patch tracheoplasty) and external decompression were performed in ten cases under cardiopulmonary bypass, nine of ten had simultaneous cardiac repair; the other two were done before cardiac repair. All survived except three. We concluded that ultrafast computed tomography is indispensable for definite diagnosis of airway and adjacent cardiovascular pathology. Mere repair of congenital cardiac defects without rectification of the airway and its adjacent structures is incompatible with survival.

Aorta↗

PubMed2000

IL-13-mediated worm expulsion is B7 independent and IFN-gamma sensitive.

B7 costimulation is a required component of many type 2 immune responses, including allergy and protective immunity to many nematode parasites. This response includes elevations in Th2 cytokines and associated effector functions including elevations in serum IgG1 and IgE and parasite expulsion. In studies of mice infected with Trichuris muris, blocking B7 ligand interactions inhibited protective immunity, suppressed IL-4 production, and enhanced IFN-gamma production, but unexpectedly did not inhibit production of the Th2 cytokine, IL-13. Blocking both IFN-gamma and B7 restored protective immunity, which was IL-13 dependent, but did not restore IL-4 or associated IgE responses. Although IL-13 was required for worm expulsion in mice in which both IFN-gamma and B7 were blocked, IL-4 could mediate expulsion in the absence of both IL-13 and IFN-gamma. These studies demonstrate that 1) B7 costimulation is required to induce IL-4, but not IL-13 responses; 2) IL-13 is elevated in association with the IFN-gamma response that occurs following inhibition of B7 interactions, but can only mediate IL-4-independent protection when IFN-gamma is also inhibited; and 3) increased IL-13 production, in the absence of increased IL-4 production, is not associated with an IgE response, even in the absence of IFN-gamma.

Abatacept↗

PubMed2000

No evidence of correlation between mutation at codon 531 of src and the risk of colon cancer in Chinese.

The protein tyrosine kinase activity of c-src proto-oncogene product, pp60(c-src), is elevated in a number of human cancers, including colon cancer. Phosphorylation of human pp60(c-src) carboxy-terminal tyrosine 530 suppresses its kinase activity. A recent report suggested that the risk of colon cancer is higher for those who carry a C-->T transition mutation on codon 531 (Gln-531-->Amber-531) of src gene. This mutation caused a prematured translation termination and up-regulated the kinase activity. To examine whether this mutation could be a risk factor for colon carcinoma in the Chinese population, we used the same PCR-based assay to analyze src genotypes of 131 colon cancers and other various types of carcinoma. No mutation was detected in all specimens that were screened in this study. Thus, mutation at Gln-531 of src gene does not seem to be involved in the development of colon cancer in Chinese ethnicity.

China↗

PubMed2000

Direct in vivo evidence demonstrating neointimal migration of adventitial fibroblasts after balloon injury of rat carotid arteries.

BACKGROUND: Clinical and experimental evidence suggest that the adventitia participates in the response to endoluminal vascular injury. The current study used a direct approach to test the hypothesis that, after balloon injury of the rat carotid artery, adventitial fibroblasts migrate in a luminal direction and contribute to neointima formation. METHODS AND RESULTS: Primary syngeneic adventitial fibroblasts were stably transduced with retroviral particles coordinating expression of beta-galactosidase (LacZ) and introduced into the adventitia of right carotid arteries of rats immediately after balloon injury. At defined times after injury and fibroblast implantation, rats were euthanized, and arterial tissue was examined for detection of LacZ mRNA (reverse transcription polymerase chain reaction), DNA (polymerase chain reaction), and in situ enzymatic activity. LacZ expression was detected in the media 5 days postinjury and in both media and neointima at 7, 10, and 14 days postinjury. LacZ was undetectable in injured vessels that had not been seeded with transduced fibroblasts and was restricted to the adventitia in seeded vessels that were not injured. CONCLUSIONS: These observations provide direct demonstration of adventitial fibroblast migration into neointima of arteries after endoluminal injury.

Animals↗

PubMed2000

RNA folding energy landscapes.

Using a statistical mechanical treatment, we study RNA folding energy landscapes. We first validate the theory by showing that, for the RNA molecules we tested having only secondary structures, this treatment (i) predicts about the same native structures as the Zuker method, and (ii) qualitatively predicts the melting curve peaks and shoulders seen in experiments. We then predict thermodynamic folding intermediates. For one hairpin sequence, unfolding is a simple unzipping process. But for another sequence, unfolding is more complex. It involves multiple stable intermediates and a rezipping into a completely non-native conformation before unfolding. The principle that emerges, for which there is growing experimental support, is that although protein folding tends to involve highly cooperative two-state thermodynamic transitions, without detectable intermediates, the folding of RNA secondary structures may involve rugged landscapes, often with more complex intermediate states.

Base Sequence↗

PubMed2000

Interaction of smad3 with a proximal smad-binding element of the human alpha2(I) procollagen gene promoter required for transcriptional activation by TGF-beta.

Transcription of the alpha2(I) collagen gene (COL1A2) in fibroblasts is potently induced by transforming growth factor-beta (TGF-beta). Smad family proteins function as intracellular signal transducers for TGF-beta that convey information from the cell membrane to the nucleus. In the present study, we establish the functional requirement for endogenous Smad3 and Smad4 in TGF-beta-stimulated COL1A2 transcription in human skin fibroblasts in vitro. Furthermore, using transfections with a series of 5' deletions of the human COL1A2 promoter, we identify a proximal region between -353 and -148 bp, which is required for full stimulation of transcription by a constitutively active TGF-beta type I receptor. This region of the COL1A2 promoter contains a CAGA motif also found in the promoter of the plasminogen activator inhibitor-1. Substitutions disrupting this sequence decreased the binding of nuclear extracts or recombinant Smad3 to the CAGACA oligonucleotide, and markedly reduced the transcriptional response to TGF-beta or overexpressed Smad3 in transient transfection assays. The insertion of tandem repeats of CAGACA conferred TGF-beta stimulation to a heterologous minimal promoter-reporter construct. Inhibition of endogenous Smad expression in fibroblasts by antisense oligonucleotides or cDNA against Smad3 or Smad4, and transfection of COL1A2 promoter constructs into Smad4-deficient breast adenocarcinoma cells, indicated the critical role of Smads for the full TGF-beta response. The importance of Smad binding to the CAGACA box of COL1A2 was further established by transcriptional decoy oligonucleotide competition. Taken together, the results identify a functional Smad-binding element of the COL1A2 promoter harboring a CAGACA consensus sequence that is both necessary and sufficient for stimulation by TGF-beta, and demonstrate that interaction of this Smad-binding element with endogenous Smads is required for the full TGF-beta response in fibroblasts.

Adenocarcinoma↗

PubMed2000

Right lung agenesis with left pulmonary artery sling.

We report on a 2-month-old infant girl who had right pulmonary agenesis and an unusual course of the left pulmonary artery. Computed tomography and cardiac catheterization showed that the left pulmonary artery arose from the main pulmonary artery, crossing the midline, and reaching the left lung via an aberrant course between the esophagus and trachea. The coexistence of right pulmonary agenesis and left pulmonary sling is extremely rare. Unlike in other reports, our patient remained symptom-free and in good health, with normal growth and development until age 2 years, when she died from complications during an attack of bronchiolitis caused by respiratory syncytial virus.

Bronchiolitis↗

PubMed2000

Allatotropic activity in the suboesophageal ganglia and corpora cardiaca of the adult male loreyi leafworm, Mythimna loreyi.

Allatotropic activity was found in the methanolic extract of the suboesophageal ganglia (SOG) and the corpora cardiaca (CC) of the Mythimna loreyi virgin males. No allatotropic activity was observed in the extract of brain or corpora allata (CA). Although CA can be activated by the SOG and CC extract, respectively, CC extract inhibited the response to the SOG extract. A significant in vitro allatotropic effect was exerted by the SOG and CC extract within 10 and 15 min, respectively, and this effect can be sustained for several hours even after transferring to fresh medium without extracts. The time course pattern of the CA activation ratio in both the SOG and CC extract-treated group is very similar to, but with significantly higher level than, that in the control group, suggesting the existence of an intrinsic pacemaker or an in vitro effect that controls the fluctuation of the CA biosynthetic activity. Synthetic Manduca sexta allatotropin had no significant effect on the M. loreyi CA. The results of treatment with the adenylate cyclase activator forskolin, the phosphodiesterase inhibitor IBMX, and the cAMP analogue dibutyryl-cAMP did not indicate that cAMP might be involved in the allatotropic control of CA. Arch.

1-Methyl-3-isobutylxanthine↗

PubMed2000

In vivo selection of hepatocytes transduced with adeno-associated viral vectors.

A murine model for hereditary tyrosinemia Type I (HTI) was evaluated for in vivo gene therapy with adeno-associated viral (AAV) vectors expressing the enzyme fumarylacetoacetate hydrolase. Transduction of a limited number of hepatocytes was accomplished following infusion of vector into the portal circulation. Corrected hepatocytes were expanded in vivo by withdrawing a drug which prevents the accumulation of toxic metabolites. The liver was eventually repopulated with hepatocytes harboring a functional and apparently integrated AAV provirus. Recipient animals regained normal liver function and architecture and the underlying metabolic derangements were normalized. After 9 months, vector-treated animals showed benign hepatomas, whereas in untreated animals areas of marked dysplasia were present within hepatomas.

Animals↗

PubMed2000

Prolonged correction of hyperlipidemia in mice with familial hypercholesterolemia using an adeno-associated viral vector expressing very-low-density lipoprotein receptor.

Adeno-associated viral vectors were used to deliver the gene for very-low-density lipoprotein (VLDL) receptor (VLDLR) to liver of a murine model of familial hypercholesterolemia (FH). Infusion of adeno-associated virus-VLDLR into the portal circulation of FH mice resulted in a 40% reduction in serum cholesterol and triglyceride that was stable for the duration of the study (30 weeks). Fractionation of serum lipids revealed a reduction of both VLDL and low-density lipoprotein. Expression of transgene-derived VLDLR was confirmed in livers of recipient animals by Western blot analysis and immunohistochemistry; vector DNA was present at 1 copy/cell. Vector-treated animals had significantly less lipid accumulation in liver and reduced atherosclerosis in the aorta.

Animals↗

PubMed2000

Attenuation of pulmonary vascular hypertension and cardiac hypertrophy with sitaxsentan sodium, an orally active ET(A) receptor antagonist.

Effects of sitaxsentan (TBC11251), an orally active, highly selective antagonist of endothelin A receptors, were examined on the development and maintenance of pulmonary hypertension, pulmonary vascular remodeling, and cardiac hypertrophy in the rat. The pulmonary vasoconstrictor response to acute hypoxia (10% O(2)for 90 min) was prevented with sitaxsentan (5 mg/kg infused iv 10 min prior to the onset of hypoxia) while BQ-788 (a specific endothelin B receptor antagonist) was without effect. The same dose of sitaxsentan delivered iv 50 min after the onset of hypoxia reversed the established pulmonary vasoconstriction. In a 2-week model of hypoxia using 10% O(2), treatment with sitaxsentan (15 mg/kg per day in drinking water) attenuated pulmonary hypertension and the associated right ventricular hypertrophy, and prevented the remodeling of small pulmonary arteries (50-100 microM) without affecting systemic arterial blood pressure or heart rate. Institution of sitaxsentan treatment (15 and 30 mg/kg per day in drinking water) for 4 weeks after 2 weeks of untreated hypoxia produced a significant, dose dependent reversal of the established pulmonary hypertension, right heart hypertrophy, and pulmonary vascular remodeling despite continued hypoxic exposure. Sitaxsentan blocked increased plasma endothelin levels in the prevention protocol but did not affect the established elevated levels in the intervention study. Sitaxsentan dose dependently (10 and 50 mg/kg per day in the drinking water) attenuated right ventricular systolic pressure, right heart hypertrophy, and pulmonary vascular remodeling observed 3 weeks after a single subcutaneous injection of monocrotaline. These findings support the hypothesis that endothelin-1 plays a significant role in the development of pulmonary hypertension, pulmonary vascular remodeling, and the associated cardiac hypertrophy, and further suggest that specific endothelin-A receptor blockade may be useful in the treatment of pulmonary hypertension of diverse etiologies.

Animals↗

PubMed2000

Mechanisms of all-trans retinoic acid-induced differentiation of acute promyelocytic leukemia cells.

Retinoic acids (RA) play a key role in myeloid differentiation through their agonistic nuclear receptors (RAR alpha/RXR) to modulate the expression of target genes. In acute promyelocytic leukemia (APL) cells with rearrangement of retinoic acid receptor a (RAR alpha) (including: PML-RAR alpha, PLZF-RAR alpha, NPM-RAR alpha, NuMA- RAR alpha or STAT5b-RAR alpha) as a result of chromosomal translocations, the RA signal pathway is disrupted and myeloid differentiation is arrested at the promyelocytic stage. Pharmacologic dosage of all-trans retinoic acid (ATRA) directly modulates PML-RAR alpha and its interaction with the nuclear receptor co-repressor complex, which restores the wild-type RAR alpha/RXR regulatory pathway and induces the transcriptional expression of downstream genes. Analysing gene expression profiles in APL cells before and after ATRA treatment represents a useful approach to identify genes whose functions are involved in this new cancer treatment. A chronologically well coordinated modulation of ATRA-regulated genes has thus been revealed which seems to constitute a balanced functional network underlying decreased cellular proliferation, initiation and progression of maturation, and maintenance of cell survival before terminal differentiation.

Antineoplastic Agents↗

PubMed2000

Cytotoxic constituents of Polyalthia longifolia var. pendula.

A new halimane diterpene, 3beta,5beta, 16alpha-trihydroxyhalima-13(14)-en-15,16-olide (1), and a new oxoprotoberberine alkaloid, (-)-8-oxopolyalthiaine (2), along with 20 known compounds, were isolated from a methanolic extract of Polyalthia longifolia var. pendula. The structures of compounds 1 and 2 were established by spectroscopic analysis. Several of these compounds were evaluated for cytotoxicity toward a small panel of human cell lines.

Alkaloids↗

PubMed2000

Esophageal varices in congenital heart disease with total anomalous pulmonary venous connection.

Total anomalous pulmonary venous connection (TAPVC) is an uncommon congenital anomaly in which the anatomical presentations vary widely among patients. We hereby present two newborns with TAPVC associated with asplenia syndrome; both had severe esophageal varices due to infradiaphragmatic pulmonary venous drainage. Ultrafast computed tomography (CT) scanning was superior to color Doppler echocardiography and cardiac catheterization as it provided a detailed portrait of the pulmonary drainage. The remarkable radiographic manifestations are presented.

Cardiac Catheterization↗

PubMed2000

Abnormal activation of K(+) channels in aortic smooth muscle of rats with endotoxic shock: electrophysiological and functional evidence.

1. This study examined the role of K(+) channels in vascular hyporeactivity of rats with endotoxic shock ex vivo. 2. At the end of the in vivo experiments, thoracic aortas were removed from endotoxaemic and control rats. After removal of the endothelium, aortic segments were mounted in myographs for recording of isometric tension and smooth muscle membrane potential. 3. Membrane potentials recorded from endotoxaemic rats were hyperpolarized compared to those of the controls. This hyperpolarization was partially reversed by tetraethylammonium, charybdotoxin or glibenclamide, but not significantly affected by apamin. The hyperpolarization was also partially attenuated by N(omega)-nitro-L-arginine methyl ester (L-NAME) or 1H:-[1,2,4]oxadiazolo[4,3-a]quinoxalin-l-one (ODQ). 4. In phenylephrine-contracted aortic rings, both agonists of K(+) channels, NS1619 and pinacidil, induced greater relaxations and re-polarizations in the preparations obtained from endotoxaemic rats. The NS1619-induced relaxation and re-polarization in arteries from endotoxaemic rats were partially inhibited by tetraethylammonium and completely inhibited by charybdotoxin, L-NAME or ODQ, but not significantly affected by apamin. Similarly, the greater relaxation and re-polarization induced by pinacidil in arteries from endotoxaemic rats were also inhibited by glibenclamide, L-NAME or ODQ. However, these inhibitors had no significant effect on relaxations and re-polarizations induced by NS1619 and pinacidil in arteries from controls. 5. This study provides the electrophysiological and functional evidence showing an abnormal activation of K(+) channels in vascular smooth muscle in animals with endotoxic shock. Our observations suggest that overproduction of nitric oxide causes an activation of large conductance Ca(2+)-activated K(+) channels and ATP-sensitive K(+) channels which contributes to endotoxin-mediated vascular hyporeactivity.

Animals↗

PubMed2000

The impact of differential binding of wild-type RARalpha, PML-, PLZF- and NPM-RARalpha fusion proteins towards transcriptional co-activator, RIP-140, on retinoic acid responses in acute promyelocytic leukemia.

Retinoic acid receptor (RA) heterodimer (RAR/RXR) activities have been shown to be repressed by transcriptional co-repressor, SMRT/N-CoR, in the absence of the ligand while upon all-trans retionic acid (ATRA) treatment, SMRT/N-CoR is dissociated from RARalpha leading to gene expression by the recruitment of transcriptional co-activators to the transcriptional complex. The difference in response to ATRA therapy between acute promyelocytic leukemia (APL) patients with PML-RARalpha fusion and PLZF-RARalpha fusion has recently been found to be partially due to the strong association of the transcriptional co-repressor, SMRT/N-CoR, with PLZF domain. We demonstrate that SMRT association, as with PML-RARalpha, can be released from NPM-RARalpha at pharmacological concentration of ATRA (10-6 M). Moreover, we show for the first time that the interaction between the transcriptional co-activator, RIP-140, and PML-, PLZF- or NPM-RARalpha fusion proteins can be positively stimulated by ATRA although they are less sensitive as compared with the wild-type RARalpha. Our results suggest that the dissociation of transcriptional co-repressors, SMRT/N-CoR, and recruitment of co-activators, eg RIP-140, to APL-associated fusion proteins constitute a common molecular mechanism in APL and underlie the responsiveness of the disease to RA therapy. Leukemia (2000) 14, 77-83.

Dimerization↗