Biomedical subjects

J Fan

Publications and source records attributed to J Fan.

At least 55 records · Page 3Linked to original sources

PubMed2001

Cytoprotection against mechanical forces delivered through beta 1 integrins requires induction of filamin A.

Cells in mechanically active environments can activate cytoprotective mechanisms to maintain membrane integrity in the face of potentially lethal applied forces. Cytoprotection may be mediated by expression of membrane-associated cytoskeletal proteins including filamin A, an actin-binding protein that increases the rigidity of the subcortical actin cytoskeleton. In this study, we tested the hypotheses that applied forces induce the expression of filamin A specifically and that this putative protective response inhibits cell death. Magnetically generated forces were applied to protein-coated magnetite beads bound to human gingival fibroblasts, cells with constitutively low basal levels of filamin A mRNA and protein. Forces applied through collagen or fibronectin, but not bovine serum albumin or poly-l-lysine-coated beads, increased mRNA and protein content of filamin A by 3-7-fold. Forces had no effect on the expression of other filamin isotypes or other cytoskeletal proteins. This effect was dependent on the duration of force and was blocked by anti-beta(1) integrin antibodies. Force also stimulated a 60% increase in expression of luciferase under the control of a filamin A promoter in transiently transfected Rat2 fibroblasts and was dependent on Sp1 transcription factor binding sites located immediately upstream of the transcription start site. Experiments with actinomycin D-treated cells showed that the increased filamin A expression after force application was due in part to prolongation of mRNA half-life. Antisense filamin oligonucleotides blocked force-induced filamin A expression and increased cell death by >2-fold above controls. The force-induced regulation of filamin A was dependent on intact actin filaments. We conclude that cells from mechanically active environments can couple diverse signals from forces applied through beta-integrins to up-regulate the production of cytoprotective cytoskeletal proteins, typified by filamin A.

Animals↗

PubMed2001

Self-assembly of frameworks with specific topologies: construction and anion exchange properties of M3L2 architectures by tripodal ligands and silver(I) salts.

Three five-component architectures, compounds 3, 4, and 5 were obtained by self-assembly of tripodal 1,3,5-tris(imidazol-1-ylmethyl )-2,4,6-trimethylbenzene (6) and 1,3,5-tris(benzimidazol-2-ylmethyl)benzene (7) ligands with silver(I) salts. The structures of these novel complexes have been determined by X-ray crystallography. The results of structural analysis indicate that these frameworks have same M3L2 components, but different structures. Compounds 3 and 4 are both M3L2 type cage-like complexes, while the 5 is an open trinuclear complex. The complex 3 is a cylindrical cage with simultaneous inclusion of a perchlorate anion inside of the cage as a guest molecule. Such guests can be exchanged for other anions through the open edge of the cage as evidenced by crystal structure of 4. The results demonstrate that the molecular M3L2 type cage can act as a host for anions and provide a nice example of supramolecular architectures with interesting properties and possible applications.

Journal Article↗

PubMed2001

[Expression rates of three angiogenic factors in hepatocellular carcinoma and their relation with microvessel density and portal vein tumor thrombosis].

OBJECTIVE: To investigate the expression rates of the three angiogenic factors-basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and platelet-derived endothelial cell growth factor (PD-ECGF) in hepatocellular carcinoma (HCC) and to investigate the relation of their expression rates to the microvessel density (MVD) of the tumor and to the formation of portal vein tumor thrombus (PVTT). METHODS: Immunohistochemical staining was conducted on 61specimens of hepatic cell carcinoma removed in operation. RESULTS: The expression rates of dFGF, VEGF, and PD-ECGF in HCC tissue were 45.9%, 75.4% and 70.5% respectively. The incidence rates of PVTT while all of the 3 angiogenic factor were negatively expressed, one of them was positively expressed, two of them were positively expressed, and all of them were positively expressed were 16.7%, 25.0%, 54.2% and 63.2% respectively (P < 0.05, test for trend). The MVD counts in HCC tissue in the above-mentioned four conditions were 99 +/- 56, 113 +/- 27, 140 +/- 347 and 194 +/- 52 respectively (P < 0.001, ANOVA test). CONCLUSION: As the number of positively expressed angiogenic factors in HCC tissue increases, the angiogenic capability of the tumor enhances greatly, and the incidence rate of PVTT increases too.

Adult↗

PubMed2001

Experience of 1000 patients who underwent hepatectomy for small hepatocellular carcinoma.

BACKGROUND: Recently, the implementation of screening programs using alpha-fetoprotein (AFP) and ultrasonography in high risk populations has identified increasing numbers of patients with small hepatocellular carcinoma (small HCC). The aim of this study was to summarize the authors' experience in patients who underwent hepatectomy for small HCC and the factors that influence or improve long term survival. METHODS: The study included 1000 patients who underwent hepatectomy for small HCC (< or = 5 cm) and compared them with 1366 patients who underwent hepatectomy for large HCC (> 5 cm) during the same period. A Cox proportional-hazards model was used for multivariate analysis of prognostic factors. RESULTS: Comparison between patients with small HCC (n = 1000 patients) and patients with large HCC (n = 1366 patients) revealed that those with small HCC had a higher resection rate (93.6% [1000 of 1068 patients] vs. 55.7% [1366 of 2451 patients]; P < 0.01), a higher curative resection rate (80.5% [805 of 1000 patients] vs. 60.7% [829 of 1366 patients]; P < 0.01), a lower operative mortality rate (1.5% [15 of 1000 patients] vs. 3.7% [50 of 1366 patients]; P < 0.01), better differentiation of tumor cells (Edmondson Grade 3-4; 14.9% vs. 20.1%; P < 0.01), a higher incidence of single nodule tumors (82.6% vs. 64.4%; P < 0.01), a higher proportion of well encapsulated tumors (73.3% vs. 46.3%; P < 0.01), a lower incidence of tumor emboli in the portal vein (4.9% vs. 20.8%; P < 0.01), and higher survival rates after undergoing resection (5 years: 62.7% vs. 37.1%; P < 0.01; 10 years: 46.3% vs. 29.2%; P < 0.01). No significant difference was found between survival after undergoing minor resection (n = 949 patients) or lobectomy (n = 51 patients) in patients with small HCC (P > 0.05). Reresection for subclinical recurrence or solitary pulmonary metastasis after small HCC resection was undertaken in 84 patients. CONCLUSIONS: Resection is still the modality of first choice for the treatment of patients with small HCC. Minor resection instead of lobectomy was the key to increasing resectability and decreasing operative mortality, and reresection for subclinical recurrence or solitary pulmonary metastasis was important approach to prolonging survival further.

Adolescent↗

PubMed2001

Antibodies to cytoplasmic dynein heavy chain map the surface and inhibit motility.

Polyclonal antibodies have been raised against four 16 residue peptides with sequences taken from the C-terminal quarter of the human cytoplasmic dynein heavy chain. The sites are downstream from a known microtubule-binding domain associated with the "stalk" that protrudes from the motor domain. The antisera were assayed using bacterially expressed proteins with amino acid sequences taken from the human cytoplasmic dynein heavy chain. Every antiserum reacted specifically with the appropriate expressed protein and with pig brain cytoplasmic dynein, whether the protein molecules were denatured on Western blots or were in a folded state. But, whereas three of the four antisera recognized freshly purified cytoplasmic dynein, the fourth reacted only with dynein that had been allowed to denature a little. After affinity purification against the expressed domains, whole IgG molecules and Fab fragments were assayed for their effect on dynein activity in in vitro microtubule-sliding assays. Of the three anti-peptides that reacted with fresh dynein, one inhibited motility but the others did not. The way these peptides are exposed on the surface is compatible with a model whereby the dynein motor domain is constructed from a ring of AAA protein modules, with the C-terminal module positioned on the surface that interacts with microtubules. We have tentatively identified an additional AAA module in the dynein heavy chain sequence, which would be consistent with a heptameric ring.

Amino Acid Sequence↗

PubMed2001

Selective sensitization of retinoblastoma protein-deficient sarcoma cells to doxorubicin by flavopiridol-mediated inhibition of cyclin-dependent kinase 2 kinase activity.

We examined the effects of flavopiridol (FP), a cyclin-dependent kinase inhibitor, on doxorubicin (DOX)-induced cell killing in an osteosarcoma cell line (SaOs-2) that lacks functional retinoblastoma protein (pRb). The IC50 value for DOX was 7-fold lower when combined with a low dose (100 nM) FP in pRb-deficient SaOs-2 cells than in the absence of FP. In contrast, the IC50 value for DOX was not decreased in the presence of 100 nM FP in pRb-restored SaOs-2 cells. Consistent with this, FP enhanced DOX-induced activation of caspase-3, which correlates with apoptosis, in pRb-deficient cells but not in pRb-restored cells. Additional studies showed that FP decreased DOX-induced cell accumulation in S phase in retinoblastoma-restored cells but not in pRb-deficient cells. An increased expression of p21 and inhibition of cyclin-dependent kinase 2 kinase activity by FP was also observed in pRb-deficient cells but not in retinoblastoma-restored SaOs-2 cells. We conclude that pRb plays a key role in determining whether FP selectively sensitizes DOX-induced cell killing in human sarcoma cells. Because lack of functional pRb is a common abnormality in human cancers, the combination of FP with DOX in tumors lacking pRb would be worthy of further investigation.

Antibiotics, Antineoplastic↗

PubMed2001

Local structures of mechanically alloyed Fe100-xCux solid solutions studied by X-ray absorption fine structure.

The local structures of the immiscible Fe(100-x)Cu(x) alloys (x= 0, 10, 20, 40, 60, 80 and 100) produced by mechanical alloying have been investigated by XAFS. For the Fe(100-x)Cu(x) (x > or = 40) solid solutions, the local structures around Fe atoms change from bcc structure to fcc one and the Cu atoms maintain the original coordination geometry after milling for 160 hours. On the contrary, the local structures around Cu atoms in both of Fe80Cu20 and Fe90Cu10 alloys appear a transition from fcc to bcc structure. We found that the Debye-waller factor sigma of fcc Fe-Cu phase is larger than that of bcc Fe-Cu phase, and the sigma (0.099 A) around Fe atoms is larger than that (0.089 A) of Cu in the Fe(100-x)Cu(x) (x > or = 40) solid solutions. This suggests that the mechanically alloyed Fe(100-x)Cu(x) supersaturated solid solution is not a homogeneous alloy, and consists of Fe-rich and Cu-rich regions for various compositions. A possible mechanism for bcc-to-fcc and fcc-to-bcc changes in Fe(100-x)Cu(x) solid solutions is discussed in relation to the interdiffusion and transition induced by the ball milling.

Journal Article↗

PubMed2001

Structural basis of diverse sequence-dependent target recognition by the 8 kDa dynein light chain.

Dyneins are multi-subunit molecular motors that translocate molecular cargoes along microtubules. Other than acting as an essential component of the dynein motor complex, the 89-residue subunit of dynein light chain (DLC8) also regulates a number of other biological events by binding to various proteins and enzymes. Currently known DLC8 targets include neuronal nitric oxide synthase; the proapoptotic Bcl-2 family member protein designated Bim; a Drosophila RNA localization protein Swallow, myosin V, neuronal scaffolding protein GKAP, and IkappaBalpha, an inhibitor of the NFkappaB transcription factor. The DLC8-binding domains of the various targets are confined within a short, continuous stretch of amino acid residues. However, these domains do not share any obvious sequence homology with each other. Here, the three-dimensional structures of DLC8 complexed with two peptides corresponding to the DLC8-binding domains of neuronal nitric oxide synthase and Bim, respectively, were determined by NMR spectroscopy. Although the two DLC8-binding peptides have entirely different amino acid sequences, both peptides bind to the protein with a remarkable similar conformation by engaging the symmetric DLC8 dimer through antiparallel beta-sheet augmentation via the beta2 strand of the protein. Structural comparison indicates that the two target peptides use different regions within the conformational flexible peptide-binding channels to achieve binding specificity. We have also re-determined the apo-form solution structure of DLC8 in this work. The structures of the DLC8/target peptide complexes, together with the dynamic properties of the protein, provide a molecular basis of DLC8's diverse amino acid sequence-dependent target recognition.

Amino Acid Sequence↗

PubMed2001

Onset of odorant receptor gene expression during olfactory sensory neuron regeneration.

Individual olfactory sensory neurons are thought to express only one odorant receptor gene from a repertoire of hundreds to thousands of genes. How do these sensory neurons choose just one specific odorant receptor to express during their differentiation? As an initial attempt toward understanding the process of odorant receptor gene regulation, we studied when odorant receptor expression is activated during sensory neuron regeneration. We find that receptor gene expression is activated in postmitotic neurons and can occur in the absence of the olfactory bulb. These results suggest that receptor expression is restricted to the terminal stages of olfactory neuron differentiation, and sensory neurons do not simply inherit the odorant receptor that is already expressed in mitotic precursor cells. Our results also support a model in which odorant receptor gene expression occurs independent of the olfactory bulb.

Animals↗

PubMed2001

Role of the oncogenic Raf-1 in orchestration of discrete nuclear factor-kappaB-activating pathways.

Raf-1, a key kinase in the Ras signaling pathway, plays critical roles in cell differentiation, proliferation, and tumorigenesis. However, knowledge of the Raf-1 in inflammation is limited. Using an inducible oncogenic Raf-1, we show that the Raf-1 orchestrates the discrete NF-kappaB activating pathways. While the Raf-1 activation induces a modest IkappaB degradation by enhancing the basal IkappaB kinase activity, it contradictorily suppresses the proinflammatory cytokine inducible IkappaB kinase complex, leading to an inhibition of TNF-alpha- and IL-1beta-induced NF-kappaB activation. Despite considerable degrees of overlap, LPS signaling is not affected by Raf-1. By either conditionally reducing Raf-1 activity or completely disrupting the Raf-1 signaling by PD98059, a specific inhibitor of MEK1, the otherwise inhibited cytokine responses can be restored. Moreover, when the activity of Raf-1 is up-regulated during the cell cycle progression from the G(0) phase to the late G(1) phase, the enhanced Raf-1 activity suffices to shift the TNF-alpha response from the sensitive to the insensitive state. Together, these studies elucidate a mechanism by which signaling outputs are shaped by the intracellular Raf-1, thus explaining the "cellular context"-dependent cytokine response.

Animals↗

PubMed2001

Regulated ectopic expression and allelic-replacement mutagenesis as a method for gene essentiality testing in Staphylococcus aureus.

Conditional expression systems were utilized for the ectopic induction of essential genes in Staphylococcus aureus. Resulting strains were then subjected to allelic-replacement mutagenesis of the native allele under inducing conditions for expression of the ectopic copy of the gene. This strategy produced test strains whereby cellular viability was uniquely dependent on the presence of inducer and provided a direct and absolute confirmation of genetic essentiality for each locus. The procedure is particularly useful for genes that are difficult to analyze by conventional inactivation strategies due to either small size or complex genomic organization.

Alleles↗

PubMed2001

The potential of plasma thrombomodulin as a biomarker of portal vein tumor thrombus in hepatocellular carcinoma.

PURPOSE: To study the relationship between thrombomodulin (TM) plasma levels and the formation of portal vein tumor thrombus (PVTT) in patients with hepatocellular carcinoma (HCC). METHODS: Pre- and-postoperative plasma TM levels of 45 patients with HCC and six patients with benign liver-occupying lesion were measured by enzyme-linked immunosorbent assay (ELISA), and the expression of TM in human HCC tissues was determined by immunohistochemistry assay. RESULTS: The preoperative plasma TM level of patients with HCC (10.2+/-5.7 ng/ml) was significantly higher than that of those patients with benign liver-occupying lesion (6.1+/-2.2 ng/ml) and that of normal controls (5.7+/-1.0 ng/ml), respectively (P<0.05). The postoperative TM level of 40 patients with HCC whose tumors had been removed decreased significantly than the preoperative TM level (10.8+/-5.3 ng/ml versus 7.6+/-4.2 ng/ ml, P < 0.05), whereas there was no significant difference between the preoperative and postoperative TM level of six patients with benign liver-occupying lesion (6.1+/-2.2 ng/ml versus 5.9+/-1.8 ng/ml, P>0.05). The preoperative plasma TM level of patients with single HCC (11.5+/-5.9 ng/ml) or no PVTT (11.4+/-5.6 ng/ml) was significantly higher than that of those patients with multiple HCC (8.1+/-4.6 ng/ml) or PVTT (6.9+/-4.5 ng/ ml), respectively (P<0.05). The preoperative plasma TM level of the patients with HCC tissue that stained positive for TM was significantly higher than those with tissue that stained negative for TM (12.2+/-6.5 ng/ ml versus 8.7+/-4.6 ng/ml, P<0.05). The postoperative plasma TM level showed no difference between the patients with HCC tissue stained positive and negative for TM (8.3+/-4.1 ng/ml versus 7.6+/-4.4 ng/ml, P>0.05). There was also no significant difference between the plasma TM level and other clinicopathological futures. CONCLUSIONS: Plasma TM increases in patients with HCC and can be a biomarker of the formation of PVTT.

Adult↗

PubMed2001

Genes and attention deficit hyperactivity disorder.

The initial molecular genetic studies of attention deficit hyperactivity disorder (ADHD) evaluated two candidate genes (DAT and DRD4) suggested by dopamine theories of this common disorder and its treatment with stimulant medication. The initial reports of weak associations with ADHD have been replicated by many (but not all) investigators, as is expected for genes with small effects. This literature is reviewed, along with emerging literature generated by active research groups investigating additional genes that might contribute to the genetic basis of this complex disorder.

Attention Deficit Disorder with Hyperactivity↗

PubMed2001

Photosonochemical degradation of phenol in water.

The combination of ultrasound (US) and photochemistry has been used to degrade an aqueous solution of phenol. It was considerably more effective than ultrasound or ultraviolet (UV) light alone. Based on the results of total organic carbon (TOC) removal, it was shown that the synergistic action of ultrasound and ultraviolet light existed. Identification of the first intermediates of the reaction (hydroquinone, catechol, benzoquinone and resorcin) indicates that OH radicals are involved in the photosonochemical degradation mechanisms. The effects of parameters such as pH, saturating gases, and Fe2+ on the photosonochemical degradation have been studied. The experimental results have shown that lower pH and higher concentration of dissolved oxygen favor the phenol degradation and that the presence of Fe2+ enhanced TOC removal of phenol solutions.

Disinfectants↗

PubMed2001

Photosonochemical degradation of trichloroacetic acid in aqueous solution.

The degradation of trichloroacetic acid (TCA) was studied with ultraviolet (UV) photolysis, ultrasound (US) sonolysis and their combination. It was found that the degradation in the combined processes was more significant than in the UV photolysis or sonolysis alone. The effects of pH and dissolved gases on the rate of photosonochemical degradation of TCA were investigated and the degradation kinetics, mechanism and possible degradation products were discussed in detail.

Caustics↗

PubMed2001

The p38-MAPK/SAPK pathway is required for human keratinocyte migration on dermal collagen.

Human keratinocyte motility plays an important role in the re-epithelialization of human skin wounds. The wound bed over which human keratinocytes migrate is rich in extracellular matrices, such as fibrin, fibronectin, and collagen, and serum factors, such as platelet-derived growth factor and transforming growth factor beta 1. Extracellular matrices and the serum factors bind to cell surface receptors and initiate a cascade of intracellular signaling events that regulate cell migration. In this study, we identified an intracellular signaling pathway that mediates collagen- driven motility of human keratinocytes. Pharmaco logic inhibition of the activation of p38-alpha and p38-beta mitogen-activated protein kinase activation potently blocked collagen-driven human keratinocyte migration. Transfection of the same keratinocytes with the kinase-negative mutants of p38-alpha or p38-beta mitogen-activated protein kinase markedly inhibited keratinocyte migration on collagen. Attachment of keratinocytes to collagen activated p38 mitogen- activated protein kinase, as well as p44/p42 ERKs. Interestingly, activation of the p38 mitogen-activated protein kinase cascade by overexpressing the constitutively active MKK3 and MKK6, MKK3b(E) and MKK6b(E), could neither initiate migration in the absence of collagen nor enhance collagen-driven migration. This study provides evidence that the p38-MAPK/SAPK pathway is necessary, but insufficient, for mediating human keratinocyte migration on collagen.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed2001

Calcium oxalate crystallization in undiluted postprandial urine of healthy male volunteers as influenced by citrate.

The crystallization of calcium oxalate (CaOx) in undiluted urine of healthy male volunteers, collected 3 h after intake of a test meal, was evaluated. In two experiments in vitro either the urinary total citrate concentration was increased (urine A) or the urinary pH was elevated (urine B). In one clinical trial the bioequivalence of orally taken potassium citrate (PC) or potassium-sodium citrate (PSC) (n = 9) was studied, in two other trials the dose-response effects of oral PC (n = 8) and oral calcium-sodium citrate (CSC; n = 8). Elevation of urinary citrate (urine A) decreased CaOx crystallization (nucleation, growth, agglomeration time), the crystal content of calcium and oxalate was low and the one of citrate was high. Elevation of urinary pH (urine B) also inhibited CaOx crystallization, the calculated molar ratio free (ionised) citrate/free (ionised) calcium at pH 7.0 was about twice the value observed at pH 5.5, and the ratio complexed citrate/complexed calcium was low. PC and PSC, leading to high urinary citrate and pH, inhibited CaOx crystallization, the former at the stages nucleation, growth and agglomeration, the latter largely beyond nucleation. CSC increased calciuria and crystal growth, but left crystal agglomeration time unchanged. The urinary molar ratio total calcium/total citrate appeared to indicate the state of crystallization, as influenced by alkali containing citrate. It was concluded that 1) application of a technically simple test allows to study CaOx crystallization in undiluted urine; 2) changes in urinary pH and citrate manifest as altered CaOx crystallization, presumably inhibiting this process, the stage of nucleation included, via the action of free citrate and the formation of a calcium citrate complex (stoichiometry < 3:2); 3) oral intake of PC, PSC or CSC modulate differently CaOx crystallization. The significance of these findings, especially with CSC, for renal stone risk is uncertain, but awaits clarification by long-term studies using the described techniques and the calcium/citrate ratio in postprandial urine.

Adult↗

PubMed2001

Synergistic induction of IL-10 by hypertonic saline solution and lipopolysaccharides in murine peritoneal macrophages.

BACKGROUND: Liver injury after ischemia/reperfusion is an important cause of morbidity in surgical patients. We have shown that the preconditioning of animals that were subjected to liver ischemia/reperfusion with hypertonic saline solution (HTS) prevented injury by inhibiting Kupffer cell tumor necrosis factor (TNF) production. We postulated that the induction of anti-inflammatory interleukin-10 (IL-10) by HTS might contribute to protection. METHODS: Murine thioglycolate--elicited peritoneal exudative macrophages (PEMs) were used to model the effects of HTS on IL-10 release from Kupffer cells. Cells were preconditioned with 500 mOsm HTS (or isotonic saline medium) for 2 hours and then stimulated with lipopolysaccharide (LPS; 1 microg/mL) or vehicle for 4 hours under isotonic conditions. TNF-alpha and IL-10 were measured in the culture supernatant by enzyme-linked immunosorbent assay; TNF, IL-10, and SOCS-3 messenger RNA expression were assessed by Northern blot. NF-kappa B activation was examined by electrophoretic mobility shift assay and Western blot for I kappa B degradation. RESULTS: In the absence of LPS, isotonic medium--and HTS-pretreated PEMs produced little IL-10 (24.9 +/- 66.0 and 0 pg/mL, respectively); however, stimulation of PEMs with LPS increased IL-10 (134.9 +/- 72.2 pg/mL). Preconditioning with HTS significantly augmented LPS-induced IL-10 production, resulting in a 2-fold increase in IL-10 compared with the isotonic solution LPS group (270.7 +/- 106.8 pg/mL; P <.01). HTS alone increased IL-10 mRNA levels and markedly augmented levels induced by LPS alone. To determine whether IL-10 accounted for HTS-induced TNF inhibition, cells from IL-10 knockout animals were studied. A lack of IL-10 did not reverse the inhibitory effect of HTS on LPS-induced TNF. NF-kappa B activation was the same in HTS-and isotonic solution--pretreated groups after LPS. CONCLUSIONS: HTS augments IL-10 induction by LPS at the gene level. Although TNF is reduced, it is not causally related to increased IL-10 or altered NF-kappa B signaling. HTS might exert its beneficial effects by independently modulating pro- and anti-inflammatory molecules, accounting for the potent immunomodulation exerted by HTS in vivo.

Animals↗