PubMed Health⌕ Search

Biomedical subjects

C A Chen

Publications and source records attributed to C A Chen.

At least 19 recordsLinked to original sources
PubMed2002

Identification and characterization of bone morphogenetic protein 2/4 gene from the starfish Archaster typicus.

A bone morphogenetic protein 2/4 (BMP2/4) gene has been cloned from the starfish, Archaster typicus, for the purpose of investigating the expression pattern of the BMP4 gene in echinoderm embryos which do not produce micromeres. The isolated gene (named AtBMP2/4) contained two exons that encoded the entire coding region. The deduced AtBMP2/4 protein sequence contained 509 amino acids. Sequence comparison showed that it shared high amino acid similarity with sea urchin BMP2/4 and Xenopus BMP2 and BMP4. Northern blot analyses indicated that AtBMP2/4 mRNA initially appears at the blastula stage and has a maximal expression level at the gastrula stage. Whole-mount in situ hybridization revealed that AtBMP2/4 mRNA is expressed in the archenteron, coelomic vesicles, and ectodermal cells of gastrula stage embryos. The observed spatial distribution pattern vastly differs from that of sea urchin SpBMP2/4, which is expressed mainly in the oral ectoderm region of the mesenchyme blastula and early gastrula embryos.

Amino Acid Sequence↗
PubMed2001

The anti-apoptotic role of interleukin-6 in human cervical cancer is mediated by up-regulation of Mcl-1 through a PI 3-K/Akt pathway.

Interleukin-6 (IL-6), a multifunctional cytokine, has recently been implicated in human cervical cancer, though the mechanism remains elusive. This study demonstrates that the anti-apoptotic protein Mcl-1 and IL-6 was concomitantly expressed in human cervical cancer tissues and cell lines, but not in normal cervix tissues. Upon IL-6 treatment, Mcl-1, but not other Bcl-2 family members, was rapidly up-regulated peaking at 4-8 h in human cervical cancer C33A cells. Supporting this observation, using anti-IL-6 or anti-IL-6 receptor antibody to interrupt the IL-6 autocrine loop in SiHa cells significantly reduced cellular level of Mcl-1. This study hypothesizes that the expression of Mcl-1 in cervical cancer cells is regulated by IL-6. The matter of which signaling pathways transduced by IL-6 is responsible for the Mcl-1 up-regulation is further investigated herein. Blocking the STAT3 or MAPK pathway with dominant-negative mutant STAT3F or the MEK inhibitor PD98059 failed to inhibit IL-6-mediated Mcl-1 expression. Meanwhile, the IL-6-induced Mcl-1 up-regulation was effectively abolished by treatment with PI 3-K inhibitors, LY294002. Additionally, overexpression of dominant-negative (dn) Akt in C33A cells could inhibit the IL-6-induced increase of Mcl-1. Finally, overexpression of IL-6 in C33A cells caused a markable resistance to apoptosis induced by doxorubicin or cisplatin. Transient transfection of IL-6-overexpressed cells with a mcl-1 antisense vector, leading to the attenuation of their apoptosis-resistant activity. In conclusion, the data herein suggest that IL-6 regulated the mcl-1 expression via a PI 3-K/Akt-dependent pathway that may facilitate the oncogenesis of human cervical cancer by modulating the apoptosis threshold.

Antineoplastic Agents↗
PubMed2001

Regulation of G proteins by covalent modification.

Heterotrimeric G protein alpha,beta, and gamma subunits are subject to several kinds of co- and post-translational covalent modifications. Among those relevant to G protein-coupled receptor signaling in normal cell function are lipid modifications and phosphorylation. N-myristoylation is a co-translational modification occurring for members of the G(i) family of Galpha subunits, while palmitoylation is a post-translational modification that occurs for these and most other Galpha subunits. One or both modifications are required for plasma membrane targeting and contribute to regulating strength of interaction with the Gbetagamma heterodimer, effectors, and regulators of G protein signaling (RGS proteins). Galpha subunits, including those with transforming activity, are often inactive when unable to be modified with lipids. The reversible nature of palmitoylation is intriguing in this regard, as it lends itself to a regulation integrated with the activation state of the G protein. Several Galpha subunits are substrates for phosphorylation by protein kinase C and at least one is a substrate for phosphorylation by the p21-activated protein kinase. Phosphorylation in both instances inhibits the interactions of these subunits with the Gbetagamma heterodimer and RGS proteins. Several Galpha subunits are also substrates for tyrosine phosphorylation. A Ggamma subunit is phosphorylated by protein kinase C, with the consequence that it interacts more tightly with a Galpha subunit but less well with an effector.

Acylation↗
PubMed2001

Cytosol vascular endothelial growth factor in endometrial carcinoma: correlation with disease-free survival.

OBJECTIVE: The aim of this study was to evaluate whether vascular endothelial growth factor (VEGF) could be a marker for disease-free survival in endometrial carcinoma patients. METHODS: Fifty-three patients with endometrial carcinoma undergoing surgery were enrolled. Clinical and pathologic items were recorded. Cytosol VEGF was quantified by enzyme immunoassay. The microvessel density (MVD) of the excised tumors was immunohistochemically assessed. The relationship among MVD, cytosol VEGF concentration of the tumor tissues, and clinicopathologic parameters was analyzed. The risk factors influencing clinical outcome were tested. RESULTS: Higher cytosol VEGF concentrations and MVD values were noted in tumors with advanced stage (more than stage I) (917 versus 125 pg/mg, P = 0.03; 94.1 +/- 37.8 versus 60.8 +/- 38.9, P = 0.008), lymphovascular emboli (917 versus 102 pg/mg, P = 0.001; 94.4 +/- 33.2 versus 62.4 +/- 40.7, P = 0.009), and lymph node metastasis (1032 versus 95 pg/mg, P < 0.001; 116.5 +/- 30.8 versus 56.7 +/- 33.3, P < 0.001). The cytosol VEGF and MVD showed a positive linear correlation (VEGF versus MVD, r = 0.41, P = 0.003). Grade 3 tumor and overexpressed cytosol VEGF (> 800 pg/mg) are independent risk factors for recurrence. There was a trend that patients with grade 1 or 2 tumors and normal-expressed VEGF had the highest probability of disease-free survival, and patients with grade 3 tumors and overexpressed cytosol VEGF had the poorest probability of disease-free survival. CONCLUSIONS: Cytosol VEGF had a good correlation with the disease progression and metastasis in endometrial carcinoma, and it might also be an independent prognostic factor for disease-free survival of endometrial carcinoma patients.

Adult↗
PubMed2001

Interleukin-6 in cervical cancer: the relationship with vascular endothelial growth factor.

OBJECTIVE: Interleukin-6 (IL-6), a central proinflammatory cytokine, has been implicated in cervical cancer, though its role remains elusive. This study was an attempt to elucidate the role of IL-6 in the pathogenesis of cervical cancer, with particular emphasis on tumor angiogenesis. METHODS: Cytosolic IL-6, vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) levels were determined via enzyme immunoassay in 60 FIGO stage IB-IIA cervical cancer patients. Immunohistochemical staining in tissue sections was performed to analyze the distributions of IL-6 and IL-6 receptors. Meanwhile, human papillomavirus (HPV) DNA was detected by polymerase chain reaction-based survey. In vitro studies of two cervical cancer cell lines, C33A and SiHa, for the interaction between IL-6 and VEGF were also performed. RESULTS: Consistently higher expression of IL-6 and VEGF was evident in cancerous tissues than in adjacent noncancer tissues in early-stage cervical cancer patients (P < 0.01). After recombinant human IL-6 was added, VEGF was induced in a time- and dose-dependent manner in cervical cancer cell line C33A. Correspondingly, interrupting the IL-6 autocrine machinery with either anti-IL-6 or anti-IL-6 receptor antibody markedly reduced the expression of VEGF at the transcriptional level in SiHa cells. Significantly higher levels of IL-6 in cancer tissues were observed in patients older than 45 (P < 0.01), patients with tumors >2 cm (P < 0.01), patients with oncogenic HPV-16 or -18 infections (P < 0.01), and patients with squamous cell carcinoma (P = 0.02). Patients with a deeper stromal invasion, vaginal invasion, lymphovascular emboli, or lymph node metastasis appeared to have higher intratumoral IL-6 levels, although the differences were statistically insignificant. CONCLUSIONS: Substantially high microenvironmental IL-6 levels promote tumor angiogenesis and the development of cervical cancer. Thus, inhibition of the biological activity of IL-6 may be potentially beneficial.

Adult↗
PubMed2001

Steady-state and time-resolved fluorescence studies on wild type and mutant chromatium vinosum high potential iron proteins: holo- and apo-forms.

Detailed circular dichroism (CD), steady-state and time-resolved tryptophan fluorescence studies on the holo- and apo- forms of high potential iron protein (HiPIP) from Chromatium vinosum and its mutant protein have been carried out to investigate conformational properties of the protein. CD studies showed that the protein does not have any significant secondary structure elements in the holo- or apo- HiPIP, indicating that the metal cluster does not have any effect on formation of secondary structure in the protein. Steady-state fluorescence quenching studies however, suggested that removal of the iron-sulfur ([Fe(4)S(4)](3+)) cluster from the protein leads to an increase in the solvent accessibility of tryptophans, indicating change in the tertiary structure of the protein. CD studies on the holo- and apo- HiPIP also showed that removal of the metal prosthetic group drastically affects the tertiary structure of the protein. Time-resolved fluorescence decay of the wild type protein was fitted to a four-exponentials model and that of the W80N mutant was fitted to a three-exponentials model. The time-resolved fluorescence decay was also analyzed by maximum entropy method (MEM). The results of the MEM analysis agreed with those obtained from discrete exponentials model analysis. Studies on the wild type and mutants helped to assign the fast picosecond lifetime component to the W80 residue, which exhibits fast fluorescence energy transfer to the [Fe(4)S(4)](3+) cluster of the protein. Decay-associated fluorescence spectra of each tryptophan residues were calculated from the time-resolved fluorescence results at different emission wavelengths. The results suggested that W80 is in the hydrophobic core of the protein, but W60 and W76 are partially or completely exposed to the solvent.

Apoproteins↗
PubMed2001

Drug design with a new transition state analog of the hydrated carbonyl: silicon-based inhibitors of the HIV protease.

BACKGROUND: Silicon is the element most similar to carbon, and bioactive organosilanes have therefore been of longstanding interest. Design of bioactive organosilanes has often involved a systematic replacement of a bioactive molecule's stable carbon atoms with silicon. Silanediols, which are best known as unstable precursors of the robust and ubiquitous silicone polymers, have the potential to mimic an unstable carbon, the hydrated carbonyl. As a bioisostere of the tetrahedral intermediate of amide hydrolysis, a silanediol could act as a transition state analog inhibitor of protease enzymes. RESULTS: Silanediol analogs of a carbinol-based inhibitor of the HIV protease were prepared as single enantiomers, with up to six stereogenic centers. As inhibitors of this aspartic protease, the silanediols were nearly equivalent to both their carbinol analogs and indinavir, a current treatment for AIDS, with low nanomolar K(i) values. IC(90) data from a cell culture assay mirrored the K(i) data, demonstrating that the silanediols can also cross cell membranes and deliver their antiviral effects. CONCLUSIONS: In their first evaluation as inhibitors of an aspartic protease, silanediol peptidomimetics have been found to be nearly as potent as currently available pharmaceutical agents, in enzyme and cell protection assays. These neutral, cell-permeable transition state analogs therefore provide a novel foundation for the design of therapeutic agents.

Cells, Cultured↗
PubMed2000

Altering expression of alpha3beta1 integrin on podocytes of human and rats with diabetes.

The adhesion molecule integrin alpha3beta1 is the major receptor of podocyte to the glomerular capillary basement membrane (GBM). Since progressive alteration of the glomerular extracellular matrix (ECM) compartment leading to GBM thickening is common in diabetic nephropathy, we investigated the cellular distribution of alpha3beta1 integrin in podocytes of patients with diabetic nephropathy and streptozotocin-induced diabetic rats, and we evaluated the effects of high glucose on the cultured rat podocytes. Both human and rat kidneys were stained using the immunoelectron microscopy and immunoperoxidase technique with mouse monoclonal antibodies to human integrin alpha3 subunit. The results showed that both the number of immunogold particles and the staining of integrin alpha3 subunit on podocytes were weaker in patients with diabetic nephropathy than those of control kidneys. The staining of alpha3 on podocytes in the poorly-controlled diabetic rats was also weaker after one and three months of hyperglycemia. However, the staining was identical to controls in rats with only one week of hyperglycemia. High glucose (25 mM) but not streptozotocin in vitro suppressed the alpha3 expression of cultured rat podocytes. Our results demonstrated that the expression of integrin alpha3beta1 on podocytes was suppressed in both human and rats with diabetes, possibly due to the effects of hyperglycemia, and the suppression became more severe with the duration of diabetes.

Adult↗
PubMed2000

Regulation of galpha i palmitoylation by activation of the 5-hydroxytryptamine-1A receptor.

Nearly all alpha subunits of heterotrimeric GTP-binding regulatory proteins (G proteins) are palmitoylated at cysteine residues near the N terminus. A regulated cycle of palmitoylation could provide a mechanism for modulating G protein signaling by affecting protein interactions and localization of the subunit. In the present studies we utilized both [(3)H]palmitate incorporation and pulse-chase techniques to address the dynamics of alpha(i) palmitoylation in Chinese hamster ovary cells. Both techniques demonstrated a dose- and time-dependent change in [(3)H]palmitate labeling of alpha(i) upon activation of stably expressed 5-hydroxytryptamine-1A receptors by the agonist (+/-)-2-dipropylamino-8-hydroxy-1,2,3, 4-tetrahydronaphthalene hydrobromide (DPAT), with an EC(50) of approximately 10 nm. For the incorporation assay, DPAT elicited an approximate doubling in labeling at the earliest time point measured. For the pulse-chase assay, DPAT promoted a significant loss of radiolabel almost equally as fast. These data demonstrate that the exchange of palmitate on alpha(i) is increased upon stimulation of 5-hydroxytryptamine-1A receptors through the combined processes of depalmitoylation and palmitoylation. These results provide the basis for extending the concept of regulated exchange of palmitate beyond G(s) and provide a framework for exploring the specific functional attributes of the palmitoylated and depalmitoylated forms of subunit.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2000

Angiogenesis of endometrial carcinomas assessed by measurement of intratumoral blood flow, microvessel density, and vascular endothelial growth factor levels.

OBJECTIVE: To evaluate the relationship between blood flow in the tumor assessed by color Doppler ultrasound, microvessel density, and vascular endothelial growth factor levels in endometrial carcinoma. METHODS: Forty-nine patients undergoing surgery for endometrial carcinoma were enrolled. Transvaginal color Doppler ultrasound was performed preoperatively and the lowest resistance index (RI) in the tumor was recorded for analysis. Vascular endothelial growth factor in the tumor was quantified by enzyme immunoassay. The microvessel density of the excised tumor was assessed immunohistochemically. The relationships between the corresponding RI, microvessel density, and vascular endothelial growth factor level of the tumor tissues and clinical and pathologic parameters were analyzed. RESULTS: Significantly lower RIs were noted in tumors of stage II or greater (0.37 compared with 0.50, P <.001), of high histologic grade (grade 3) (0.34 compared with 0.49, P =.004), with deep myometrial invasion (one-half depth or greater) (0.39 compared with 0.49, P =.002), with lymphovascular emboli (0.38 compared with 0.49, P <.001), or with lymph node metastasis (0.30 compared with 0.49, P <.001) compared with stage I tumors and tumors of histologic grade 1 or 2, with superficial myometrial invasion, without lymphovascular emboli, or with no lymph node metastasis. Increased vascular endothelial growth factor levels and microvessel density (x200 field) also were detected in tumors of stage II or greater (975 compared with 129 pg/mg, P =.014; and 88 compared with 61, P =.018, respectively), with lymphovascular emboli (1138 compared with 120 pg/mg, P =.002; and 86 compared with 63, P =.023), or with lymph node metastasis (1011 compared with 95 pg/mg, P <.001; and 98 compared with 61, P =. 019). Resistance index, microvessel density, and vascular endothelial growth factor levels in the tumor showed linear correlations (RI compared with microvessel density: r = -.32, P =. 03; RI compared with vascular endothelial growth factor levels: r = -.40, P =.004; microvessel density compared with vascular endothelial growth factor levels: r =.36, P =.011). CONCLUSION: Blood flow assessed by color Doppler ultrasound has histologic and biologic correlations with angiogenesis and vascular endothelial growth factor levels and might play an important role in predicting tumor progression and metastasis in endometrial carcinoma.

Adult↗
PubMed2000

Vascular endothelial growth factor and prognosis of cervical carcinoma.

OBJECTIVE: To evaluate vascular endothelial growth factor (VEGF) as a marker for predicting lymph node metastasis and an independent prognostic factor of early-stage cervical carcinoma. METHODS: One hundred thirty-five women with stage IB-IIA cervical carcinoma had radical abdominal hysterectomies and pelvic lymph node dissections. Intratumoral cytosol VEGF concentrations were assayed with enzyme immunoassay. Histopathologic items and cytosol VEGF-influencing clinical outcomes were compared. RESULTS: Twenty-two women (16.3%) who had disease recurrence had higher levels of cytosol VEGF (1020 versus 112 pg/mg protein, P <.001) than those without recurrence. Using a cutoff value of 400 pg/mg protein resulted in best sensitivity of 75%, best specificity of 70%, positive predictive value of 41%, and negative predictive value of 92%. Only overexpressed cytosol VEGF (hazard ratio 6.44, P <.001) was an independent prognostic factor of disease-free survival. The overexpressed cytosol VEGF (hazard ratio 4.50, P =.021) and positive lymphovascular emboli (hazard ratio 4.11, P =.045) were independent prognostic factor of overall survival. CONCLUSION: Cytosol VEGF might be a biomarker for the status of pelvic lymph nodes in early-stage cervical carcinoma and an independent prognostic indicator of its outcome.

Adult↗
PubMed2000

Effects of arousal and sleep state on systemic and pulmonary hemodynamics in obstructive apnea.

During obstructive sleep apnea (OSA), systemic (Psa) and pulmonary (Ppa) arterial pressures acutely increase after apnea termination, whereas left and right ventricular stroke volumes (SV) reach a nadir. In a canine model (n = 6), we examined the effects of arousal, parasympathetic blockade (atropine 1 mg/kg iv), and sleep state on cardiovascular responses to OSA. In the absence of arousal, SV remained constant after apnea termination, compared with a 4.4 +/- 1.7% decrease after apnea with arousal (P < 0.025). The rise in transmural Ppa was independent of arousal (4.5 +/- 1.0 vs. 4.1 +/- 1.2 mmHg with and without arousal, respectively), whereas Psa increased more after apnea termination in apneas with arousal compared with apneas without arousal. Parasympathetic blockade abolished the arousal-induced increase in Psa, indicating that arousal is associated with a vagal withdrawal of the parasympathetic tone to the heart. Rapid-eye-movement (REM) sleep blunted the increase in Psa (pre- to end-apnea: 5.6 +/- 2.3 mmHg vs. 10.3 +/- 1.6 mmHg, REM vs. non-REM, respectively, P < 0.025), but not transmural Ppa, during an obstructive apnea. We conclude that arousal and sleep state both have differential effects on the systemic and pulmonary circulation in OSA, indicating that, in patients with underlying cardiovascular disease, the hemodynamic consequences of OSA may be different for the right or the left side of the circulation.

Animals↗
PubMed2000

Neural and local effects of hypoxia on cardiovascular responses to obstructive apnea.

Obstructive sleep apnea (OSA) acutely increases systemic (Psa) and pulmonary (Ppa) arterial pressures and decreases ventricular stroke volume (SV). In this study, we used a canine model of OSA (n = 6) to examine the role of hypoxia and the autonomic nervous system (ANS) in mediating these cardiovascular responses. Hyperoxia (40% oxygen) completely blocked any increase in Ppa in response to obstructive apnea but only attenuated the increase in Psa. In contrast, after blockade of the ANS (20 mg/kg iv hexamethonium), obstructive apnea produced a decrease in Psa (-5.9 mmHg; P < 0.05) but no change in Ppa, and the fall in SV was abolished. Both the fall in Psa and the rise in Ppa that persisted after ANS blockade were abolished when apneas were induced during hyperoxia. We conclude that 1) hypoxia can account for all of the Ppa and the majority of the Psa response to obstructive apnea, 2) the ANS increases Psa but not Ppa in obstructive apnea, 3) the local effects of hypoxia associated with obstructive apnea cause vasodilation in the systemic vasculature and vasoconstriction in the pulmonary vasculature, and 4) a rise in Psa acts as an afterload to the heart and decreases SV over the course of the apnea.

Animals↗
PubMed2000

Laparoscopic cystectomy of a twisted, benign, ovarian teratoma in the first trimester of pregnancy.

Adnexal torsion is an unusual, but serious complication in pregnancy. The treatment is surgical, but this may increase the risk of pregnancy loss in the first trimester. The use of laparoscopic surgery, which is less invasive than traditional laparotomy, has been limited by diagnostic and technical difficulties including determination of ovarian tumor nature and spillage of cyst contents intraoperatively. A 25-year-old woman in her 11th week of pregnancy had acute severe left lower-abdominal pain, which was diagnosed as left ovarian teratoma with torsion. She underwent emergency laparoscopic surgery with unwinding of the twisted fallopian tube and ovary and cystectomy of the teratoma. The patient subsequently delivered a full-term baby, without complications. Accurate ultrasound and cytologic diagnoses along with copious intraoperative warm, normal saline irrigation were likely contributing factors to the successful outcome of this case.

Adult↗
PubMed1999

N-Myristoylation and betagamma play roles beyond anchorage in the palmitoylation of the G protein alpha(o) subunit.

Many of the alpha subunits of heterotrimeric GTP-binding regulatory proteins (G proteins) are palmitoylated, a modification proposed to play a key role in the stable anchorage of the subunits to the plasma membrane. Palmitoylation of alpha subunits from the G(i) family is preceded by N-myristoylation, which alone or together with betagamma probably supports a reversible interaction of the alpha subunit with membrane as a prerequisite to the eventual incorporation of palmitate. Previous studies have not addressed, however, the question of whether membrane association alone, carried out through N-myristoylation, interaction with betagamma, or other events, is sufficient for palmitoylation. We report here for alpha(o) that it is not. We found that N-myristoylation is required for palmitoylation at least in part because it supports events subsequent to membrane attachment. Mutants of alpha(o) designed to target the subunit to membrane without an N-myristoyl group are unable to be palmitoylated as evaluated by incorporation of [(3)H]palmitate. Mutants of alpha(o) unable to interact normally with betagamma yet still attach to membrane demonstrate that betagamma, in contrast, is not required for palmitoylation. betagamma becomes necessary, however, when the N-myristoyl group is absent. Our results suggest that N-myristoylation and betagamma, while almost certainly relevant to the reversible interaction of alpha(o) with membrane, also play at least partly overlapping, post-anchorage roles in palmitoylation.

Adenosine Diphosphate Ribose↗
PubMed1999

Sea urchin TgBMP2/4 gene encoding a bone morphogenetic protein closely related to vertebrate BMP2 and BMP4 with maximal expression at the later stages of embryonic development.

We have cloned a gene fragment (named TgBMP2/4) that encodes a protein homologous to vertebrate bone morphogenetic protein (BMP) 2 and BMP4 in the sea urchin Tripneustes gratilla. This peptide sequence contains 204 amino acids with 7 conserved cysteine residues at the C-terminus of the coding region and a cluster of basic amino acids that may serve as a signal for proteolytic cleavage. Sequence comparison and phylogenetic analyses reveal that TgBMP2/4 is closely related to vertebrate BMP2 and BMP4 as well as to amphioxus BMP2/4, with similarity levels ranging from 90% to 94% at the mature C-terminal domain. Northern blot analyses show that a 6.3-kb TgBMP2/4 mRNA appears first at the mesenchyme blastula stage and increases to a maximal level at the gastrula and pluteus stages. This expression pattern is different from that of a BMP2/4-related gene previously found in sea urchin.

Amino Acid Sequence↗