Search PubMed⌕ Search

Biomedical subjects

X Feng

Publications and source records attributed to X Feng.

At least 37 records · Page 2Linked to original sources
PubMed2002

STAT and SMAD signaling in cancer.

STAT and SMAD often exert opposite biological effects on diverse cellular functions. Recent studies have shown that STAT can interface with SMAD at molecular level and that some novel molecules, such as SOCS (also called CIS) and APRO6 (also called TOB), modulate this signaling. A cofactor p300/CBP might act as a bridging molecule to mediate the interface. Thus, STAT and SMAD signaling pathways may crosstalk each other with interweaved regulatory mechanisms. Interestingly, the importance of all the proteins' function has been shown by the increasing evidence of their involvement in cancer. These recent progresses have been made in attributing novel exciting functions. Accordingly, we would like to review the latest advances of those pathways on a cross-section in cancer signaling.

Animals↗
PubMed2001

Mechanistic studies on the nucleophilic reaction of porphyrins with organolithium reagents.

Porphyrins react readily with organolithium reagents under substitution of free meso positions. As this method has proven to be very versatile for the preparation of a wide range of meso substituted porphyrins, a mechanistic study of the reaction was undertaken using 5,15-diaryl- and dialkyl substituted porphyrins, 2,3,7,8,12,13,17,18-octaethylporphyrin, and the respective nickel(II) complexes. A combination of deuteration experiments, electronic absorption spectroscopy of the reactive intermediates, trapping of intermediates with organic electrophiles, and reaction at different pH values showed significant differences in the reaction pathways of free base porphyrins and metalloporphyrins. In both cases the reaction proceeds initially under formation of phlorin like intermediates which are stable in water. For the Ni(II)phlorins a mesomeric carbanionic form with a highly distorted structure exists that can react as a nucleophile with electrophiles such as RI, H+, or D+. In the latter case a protonation-deprotonation equilibrium involving porphodimethen intermediates has to be assumed. Free base phlorins do not react as nucleophiles but can undergo H/D exchange reactions in strongly acidic media.

Journal Article↗
PubMed2001

Strain selection of Metarrhizium anisopliae by image analysis of colony morphology for consistency of steroid biotransformation.

Quantitative description of colony morphological images of the fungus Metarrhizium anisopliae was done by means of computer image analysis based on fractal analysis. Compared with simple fractal analysis, the differences in the morphological features of colonies were expressed more accurately by multifractal analysis. The use of multifractal analysis markedly improved the reliability of colony image analysis, which could be extended to morphological characterization for colony recognition and classification. First, the multifractal spectrum was calculated from each morphological image and 14 features were defined on the spectrum to describe the spectral line profile. Second, three features, alpha-right, alpha-width, and f-start, were selected from the 14 features in two-dimensional feature vector spaces and a feature augmented vector (alpha-right, alpha-width, and f-start, 1)(T) was generated and used for classifier design. Third, a statistical least mean square error (LMSE) algorithm was applied to design a piecewise-linear classifier, which consists of two linear classifiers, d(1)(x) and d(2)(x). Representative colony samples were used as training and test sample sets, which were previously classified into a high-activity class and another class by a training person. After passing the training phase, the piecewise-linear classifier could be used for automated classification of unknown colony samples. A correct recognition rate of 96% was achieved in this manner. Compared with conventional strain selection methods, this new method has the advantage of less subjectivity, reduced labor and time, and improved ability to deal with a large number of colonies.

Algorithms↗
PubMed2001

Coulomb fission event resolved progeny droplet production from isolated evaporating methanol droplets.

An electrodynamic balance was used to levitate a single methanol droplet while it evaporated down to, and just beyond, its first encountered Coulomb fission limit as ascertained by the time dependence of its laser light scatter signal. At its Coulomb limit, the primary droplet fragmented and approximately 81% of its net charge was released in the form of small droplets that are termed progeny. The window of time over which the progeny droplets were ejected from the electrodynamic balance was deltat = 850 ms, indicating that these droplets were formed with a range of mass-to-charge values. An average of 13.2 (+/-4.4) progeny droplets were detected as a result of this fragmentation event. On the assumption that the average initial radius of the progeny droplets were one-tenth the radius of the droplet undergoing the Coulomb fission event, approximately 50% of the total net charge ejected would not have been carried by the 13 progeny droplets detected.

Journal Article↗
PubMed2001

Transgenic expression of sarcoplasmic reticulum Ca(2+) atpase modifies the transition from hypertrophy to early heart failure.

To examine the contribution of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) to early heart failure, we subjected transgenic (TG) mice expressing SERCA2a gene and wild-type (WT) mice to aortic stenosis (AS) for 7 weeks. At an early stage of hypertrophy (4-week AS), in vivo hemodynamic and echocardiographic indices were similar in TG and WT mice. By 7 weeks of AS, which is the stage of early failure in this model, TG mice with AS had lower mortality than WT mice with AS (6.7% versus 29%). The magnitude of left ventricular (LV) hypertrophy was similar in WT and TG 7-week AS mice. In vivo LV systolic function was higher in TG than in WT 7-week AS mice. In LV myocytes loaded with fluo-3, fractional cell shortening and the amplitude of the [Ca(2+)](i) transients were higher in TG than in WT 7-week AS mice under baseline conditions (0.5 Hz, 1.5 mmol/L [Ca(2+)](o), 25 degrees C). The rates of relengthening and decay in [Ca(2+)](i) were faster in TG than in WT 7-week AS myocytes. In myocytes from WT 7-week AS compared with sham-operated WT mice, contractile reserve in response to rapid pacing was depressed with impaired augmentation of both peak-systolic [Ca(2+)](i) and the SR Ca(2+) load. In contrast, contractile reserve and the capacity to augment SR Ca(2+) load were maintained in TG 7-week AS mice. SERCA2a protein levels were depressed in WT 7-week AS mice, but were preserved in TG 7-week AS mice. These data suggest that defective SR Ca(2+) loading contributes to the onset of contractile failure in animals with chronic pressure overload.

Animals↗
PubMed2001

Preheat treatment for Mycobacterium tuberculosis Hsp16.3: correlation between a structural phase change at 60 degrees C and a dramatic increase in chaperone-like activity.

The in vitro chaperone-like activity of Mycobacterium tuberculosis small heat shock protein Hsp16.3 was found to be dramatically enhanced to the same extent after preheat treatment at or over 60 degrees C. Structural analysis using gel filtration, native pore-gradient PAGE, nondenaturing PAGE, and far-UV CD spectroscopy consistently revealed no significant difference between the native and the preheated Hsp16.3 proteins. However, near-UV CD spectroscopy clearly demonstrated that the tertiary structure of preheated Hsp16.3 is quite similar to its native conformation, with a minor but significant difference. Further analysis using differential scanning calorimetry indicated that Hsp16.3 exhibited a structural transition near 60 degrees C. All these results together indicate that Hsp16.3 suffers a phase change at approximately 60 degrees C, which seem to remove a structural energy barrier for the protein to refold to a conformational status with increased chaperone-like activity.

Bacterial Proteins↗
PubMed2001

Degradation of dye solution by an activated carbon fiber electrode electrolysis system.

Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in the process. Dyes with many -SO3-, COO-, -SO2NH2, -OH, hydrophilic groups, and azo linkages are susceptible to reduction. However, dyes with many -C=O, -NH-and aromatic groups, and hydrophobic groups, tend to be adsorbed. For dyes with -SO3-, COOH and -OH groups, if their molecules linearly spread in solution and have a significant tendency to form colloids by hydrogenous bonding, they also tend to be adsorbed and flocculated. Typical dynamic electrolysis of dye Acid Red B, Vat Blue BO and Disperse Red E-4B shows how the two major mechanisms, degradation and adsorption, act differently during treatment. Reduction occurs evenly during treatment. During the dominant adsorption process, after certain amount of iron is generated, colloid precipitation occurs and TOC and color are rapidly removed.

Adsorption↗
PubMed2001

BDNF dependence in neuroblastoma.

Neuroblastomas are heterogeneous tumors arising from sympathetic precursors in the neural crest. Growth factor stimulation of neuroblastomas promote diverse biological responses (mitogenesis, differentiation, cell death) depending on the particular tumor studied. Here we show that brief treatment with retinoic acid (RA) rendered the human neuroblastoma lines SY5Y, NGP, SMS-KCNR, and SK-N-SH dependent on brain-derived neurotrophic factor (BDNF) for survival. The BDNF- and trkB-expressing line SMS-KCN was dependent on an autocrine BDNF/trkB survival without exposure to RA. We conclude that the BDNF/trkB pathway plays an important role in neuroblastoma survival and speculate on a possible role in tumor pathogenesis.

Antibodies↗
PubMed2001

Transgenic targeting of a dominant negative corepressor to liver blocks basal repression by thyroid hormone receptor and increases cell proliferation.

Unliganded thyroid hormone receptors (TRs) interact with corepressors and repress basal transcription of target genes in cotransfection and in vitro studies. Currently, little is known about the function of corepressors in vivo. We thus used a mouse albumin promoter to generate several transgenic mouse lines that overexpressed a dominant negative mutant corepressor, NCoRi, in liver. The transgenic mice had normal liver weight, appearance, and minimal changes in enzyme activity. To study the effects of NCoRi on transcription of hepatic target genes, we examined T3-regulated gene expression of hypo- and hyperthyroid transgenic mice. In hypothyroid mice, hepatic expression of Spot 14, Bcl-3, glucose 6-phosphatase, and 5'-deiodinase mRNA was higher in transgenic mice than littermate controls whereas these genes were induced to similar levels in T3-treated mice. Derepression was not observed for malic enzyme mRNA expression in hypothyroid mice. Thus, NCoRi selectively blocked basal transcription of several thyroid hormone-responsive genes but had no effect on ligand-mediated transcription. Additionally, compensatory increases in endogenous SMRT and NCoR mRNA were observed in hypothyroid transgenic mice. Interestingly, hepatocyte proliferation as detected by BrdUrd incorporation was increased in transgenic mice. The gene profile in transgenic mouse livers was studied by cDNA microarray, and several genes related to cell proliferation were induced. In summary, our studies show that NCoR plays important roles in mediating basal repression by TRs and may prevent cellular proliferation in vivo.

Animals↗
PubMed2001

[Abnormalities of tumor suppressor genes at chromosome 3p in lung cancer].

OBJECTIVE: To investigate the allelic loss of heterozygosity in three tumor suppressor genes, Fhit, hMLH1 and VHL, located at three corresponding regions 3p14-cen, 3p21.3-22 and 3p25-26 with a high fregnency in lung cancer and to evaluate the expression of Fhit protein in the tumor tissue of lung cancer. METHODS: Microsatellite analysis was performed by using the primers that amplified polymorphic sequences inside or flanking to the three genes in the tumor tissues collected from 45 cases of primary lung cancer. Immunohistochemical staining was performed to detect the expression of Fhit protein in the tumor tissues from 17 out of the 45 cases. RESULTS: For loci D3S1234, D3S1300 and D3S4103 that are located in the intron of Fhit gene, LOH was found in informative cases as 62.9%, 63.6% and 59.5%, respectively. In D3S1561 and D3S1612 that are linked with hMLH1 gene, LOH was detected in 54.5% and 63.2% of informative cases, respectively. LOH was found in 64.3% and 41.7% of informative cases, at D3S1038 and D3S1283, respectively, which are flanked to VHL gene. Expression of Fhit protein was down regulated in tumor tissues of 11 out of 17 cases (64.7%); among 10 of the 11 samples, LOH was detected at one or more of the microsatellite loci tested. CONCLUSION: High frequency loss of one allele in tumor suppressor genes Fhit, hMLH1 and VHL was observed in the tumor tissues of lung cancer, indicating that it may play a role in carcinogenesis of human lung, and may provide some new approaches to early gene detection for lung cancer. Loss of one allele of Fhit gene may be one of the mechanisms for down regulation of Fhit protein expression in lung cancer.

Acid Anhydride Hydrolases↗
PubMed2001

Transcriptional mechanisms of bone morphogenetic protein-induced osteoprotegrin gene expression.

Osteoprotegerin (OPG), an osteoblast-secreted decoy receptor, specifically binds to osteoclast differentiation factor and inhibits osteoclast maturation. Members of the transforming growth factor-beta superfamily including bone morphogenetic proteins (BMPs) stimulate OPG mRNA expression. In this study, we have characterized the transcription mechanism of BMP-induced OPG gene expression. Transfection of Smad1 and a constitutively active BMP type IA receptor ALK3 (Q233) stimulated the OPG promoter. Deletion analysis of the OPG promoter identified two Hoxc-8 binding sites that respond to BMP stimulation. Glutathione S-transferase-Hoxc-8 protein binds to these two Hox sites specifically. Consistent with the transfection results of the native promoter, ALK3 or Smad1 linker region, which interacts with Hoxc-8, stimulated the activation of the reporter construct with the two Hox sites. Overexpression of Hoxc-8 inhibited the induced promoter activity. When the two Hox binding sites were mutated, ALK3 or Smad1 linker region no longer activated the transcription. Importantly, Smad1 linker region induced both OPG promoter activity and endogenous OPG protein expression in 2T3 osteoblastic cells. The medium from cells transfected with Smad1 linker region expression plasmid effectively inhibited osteoclastogenesis. Collectively, our data indicate that Hox sites mediate both OPG promoter construct activity and endogenous OPG gene expression in response to BMP stimulation.

Animals↗
PubMed2001

Identification of the type II Na(+)-Pi cotransporter (Npt2) in the osteoclast and the skeletal phenotype of Npt2-/- mice.

We previously reported that a type II sodium phosphate (Na(+)-Pi) cotransporter (Npt2) protein is expressed in osteoclasts and that Pi limitation decreases osteoclast-mediated bone resorption in vitro. We also demonstrated that mice homozygous for the disrupted Npt2 gene (Npt2-/-) exhibit a unique age-dependent bone phenotype that is associated with significant hypophosphatemia. In the present study, we sought to identify the Npt2 cDNA in mouse osteoclasts and characterize the impact of Npt2 gene ablation on osteoclast function and bone histomorphometry. We demonstrate that the osteoclast Npt2 cDNA sequence is identical to that of the proximal renal tubule and, thus, not an isoform or splice variant thereof. Histomorphometric analysis revealed that, at 25 days of age, Npt2-/- mice exhibited a reduction in osteoclast number and eroded perimeters, relative to wild-type mice. Moreover, although the number of metaphyseal trabeculae was reduced in 25-day-old Npt2-/- mice, trabecular bone volume was normal due to increased trabecular width. At 115 days of age, the decrease in osteoclast index persisted in Npt2-/- mice relative to wild-type littermates. However, mineralizing and osteoblast surfaces and bone formation rates were increased, and, although trabecular number was still reduced, trabecular bone volume was higher than that of wild-type mice. These data demonstrate a link between osteoclast activity and trabecular development in young Npt2-/- mice, and suggest that an age-related adaptation to Npt2 deficiency is apparent in osteoclast and osteoblast function and bone formation.

Animals↗
PubMed2001

gC1q-R/p33, a member of a new class of multifunctional and multicompartmental cellular proteins, is involved in inflammation and infection.

Human gC1q-R (p33, p32, C1qBP, TAP) is a ubiquitously expressed, multiligand-binding, multicompartmental cellular protein involved in various ligand-mediated cellular responses. Although expressed on the surface of cells, an intriguing feature of the membrane-associated form of gC1q-R is that its translated amino acid sequence does not predict the presence of either a sequence motif compatible with a transmembrane segment or a consensus site for a glycosylphosphatidylinositol anchor. Moreover, the N-terminal sequence of the pre-pro-protein gC1q-R contains a motif that targets the molecule to the mitochondria and as such was deemed unlikely to be expressed on the surface. However, several lines of experimental evidence clearly show that gC1q-R is present in all compartments of the cell, including the extracellular cell surface. First, surface labeling of B lymphocytes with the membrane-impermeable reagent sulfosuccinimidyl 6-(biotinamido)hexanoate shows specific biotin incorporation into the surface-expressed but not the intracellular form of gC1q-R. Second, FACS and confocal laser scanning microscopic analyses using anti-gC1q-R IgG mAb 60.11 or 74.5.2, and the fluorophore Alexa 488-conjugated F(ab')2 goat anti-mouse IgG as a probe, demonstrated specific staining of Raji cells (>95% viable). Three-dimensional analyses of the same cells by confocal microscopy showed staining distribution that was consistent with surface expression. Third, endothelial gC1q-R, which is associated with the urokinase plasminogen activator receptor, and cytokeratin 1 bind 125I-high molecular weight kininogen in a specific manner, and the binding is inhibited dose-dependently by mAb 74.5.2 recognizing gC1q-R residues 204-218. Fourth, native gC1q-R purified from Raji cell membranes but not intracellular gC1q-R is glycosylated, as evidenced by a positive periodic acid Schiff stain as well as sensitivity to digestion with endoglycosidase H and F. Finally, cross-linking experiments using C1q as a ligand indicate that both cC1q-R and gC1q-R are co-immunoprecipitated with anti-C1q. Taken together, the evidence accumulated to date supports the concept that in addition to its intracellular localization, gC1q-R is expressed on the cell surface and can serve as a binding site for plasma and microbial proteins, but also challenges the existing paradigm that mitochondrial proteins never leave their designated compartment. It is therefore proposed that gC1q-R belongs to a growing list of a class of proteins initially targeted to the mitochondria but then exported to different compartments of the cell through specific mechanisms which have yet to be identified. The designation 'multifunctional and multicompartmental cellular proteins' is proposed for this class of proteins.

Amino Acid Motifs↗
PubMed2001

Investigation of microcontact transfer of proteins from a selectively plasma treated elastomer stamp by fluorescence microscopy and force microscopy.

Selective plasma treatment of the recessed regions of the elastomer stamps is shown to alter the resultant protein patterns. Fluorescence microscopy is demonstrated to be an excellent tool to discriminate between regions of microcontact printed fluorescent dye-labelled albumin in polystyrene. Atomic force microscopy and shear force microscopy are used to provide high-resolution images of the patterned protein layers. The formation and characteristics of the patterns formed by these alternative strategies is discussed.

Animals↗
PubMed2001

Serum vitamin A concentrations and growth in children and adolescents in Gansu Province, China.

The association between serum vitamin A concentration and growth was assessed in a random sample of 650 children aged 0-14 years and 143 adolescents aged 15-19 years from the four prefectures of Jiayuguan, Linxia, Lanzhou and Tianshui in Gansu Province, China. Serum vitamin A concentrations were measured using a high performance liquid chromatograph. Height and weight were measured with standard methods. The results show that serum vitamin A concentration appeared to be the lowest in the age group 5-9 years which was only 0.28 mg/mL (95% confidence interval [CI]: 0.27-0.30) in males and 0.30 mg/mL (95% CI: 0.28-0.32) in females; and then it gradually increased with age. There was no statistically significant difference between males and females in any of the age groups. There were statistically significant correlations between vitamin A and weight (r = 0.37; P <0.001) and body mass index (r = 0.26; P < 0.001). This study suggests that serum vitamin A concentrations in children and adolescents may affect child growth. Concerted efforts to improve vitamin A status from a very early age become increasingly important if vitamin A has a genuine impact on child growth.

Adolescent↗
PubMed2001

Depletion of CD4(+) T cells aggravates glomerular and interstitial injury in murine adriamycin nephropathy.

BACKGROUND: CD4(+) T cells play an important role in various types of immunologic renal disease, including lupus nephritis, IgA nephropathy, and crescentic glomerulonephritis. CD4(+) T cells are also major infiltrating lymphocytes in chronic tubulointerstitial inflammation associated with nonimmunological renal diseases. We suspected that CD4(+) T cells might contribute to disease progression and loss of renal function in chronic proteinuric renal disease (CPRD). To investigate this possibility, the effect of monoclonal antibody against CD4(+) lymphocytes (anti-CD4) was studied in a murine model (adriamycin nephropathy) of CPRD. METHODS: Adriamycin nephropathy was produced in male BALB/c mice by a single intravenous injection of adriamycin (11 mg/kg). Anti-CD4 was given by intraperitoneal injection following the development of proteinuria at days 5, 6, 7, 21, and 37 after adriamycin. After six weeks, renal function and histology were studied by histomorphometry, immunohistochemistry, and flow cytometry. RESULTS: Flow cytometric analysis showed a marked decrease in the number of CD4(+) T cells in blood and spleen of the antibody-treated animals (N = 7, P < 0.01). Adriamycin plus CD4(+) depletion mice had significantly greater mesangial expansion, glomerular sclerosis, and interstitial expansion than the mice on adriamycin alone. Interstitial infiltration with macrophages and CD8(+) cells was significantly increased in adriamycin plus CD4(+) depletion mice. Creatinine clearance (17.5 +/- 0.54 vs. 29.2 +/- 0.89 microL/min, P < 0.001) was significantly worse in the adriamycin plus CD4(+) depletion mice than in adriamycin alone mice and correlated with histologic change in glomeruli and interstitium. CONCLUSIONS: Depletion of CD4(+) T cells promotes glomerular and interstitial injury in mice with established adriamycin nephropathy. These findings suggest that CD4(+) T cells have a protective role against the progression of adriamycin nephropathy.

Animals↗