Biomedical subjects

Feng Li

Publications and source records attributed to Feng Li.

At least 235 records · Page 13Linked to original sources

PubMed2002

Coordinate expression of survival p-ERK and proapoptotic cytochrome c signals in rat brain neurons after transient MCAO.

In order to determine possible coordinate expression of major survival and proapoptotic signals, immunofluorescent analyses for phosphorylated ERK (p-ERK) and cytochrome c were carried out after 90 min of transient middle cerebral artery occlusion (MCAO) in rats. Strong induction of p-ERK was primarily expressed in the ischemic penumbra, while that of cytosolic cytochrome c signal was strongly induced in the ischemic core from 3 min to 3 h of reperfusion. The double-stained cells with strong p-ERK/weak cytochrome c became most apparent at 3 min primarily expressed in the ischemic penumbra, whereas the cells with weak p-ERK/strong cytochrome c were predominantly found in the ischemic core at 3 h. The proportion of double positive cells among the total number of single positive cells decreased in the ischemic core, and increased in the ischemic penumbra. These findings suggest that the coordinate expression of p-ERK and cytochrome c is fundamentally involved in cell survival or death at the early stage of reperfusion, and that they could play roles in different temporal and spatial profiles.

Animals↗

PubMed2002

Potentiation of Akt and suppression of caspase-9 activations by electroacupuncture after transient middle cerebral artery occlusion in rats.

Electroacupuncture (EA) is an effective curative method for diseases including cerebral ischemia. In the current study, we investigated the effects of EA treatment on the activations of survival Akt and proapoptotic caspase-9 after 90 min of transient middle cerebral artery occlusion (tMCAO) in rat. Immunoreactivity of phospho-Akt (p-Akt) increased in the ipsilateral hemisphere after tMCAO with a peak at 8 h, and EA enhanced the Akt expression both in the number and the staining strength mainly in the ischemic penumbra (IP) at 8 and 24 h. Cleaved caspase-9 was strongly induced at 8 h in IP, which was suppressed with EA. The number of terminal deoxynucleotidyl transferase-mediated uridine 5' triphosphate-biotin nick end labelling positive cells reduced at 24 h in the cerebral cortex. These results suggest that EA potentiated the Akt and suppressed the caspase-9 activations, and may have a potential to reduce the number of neuronal cells undergoing apoptotic cell death.

Animals↗

PubMed2002

Heregulin promotes expression and subcellular redistribution of ADP-ribosylation factor 3.

To identify genes whose expression is modulated by heregulin-beta1 (HRG), a regulatory polypeptide for mammary epithelial cells, we performed differential display screening of MCF-7 cell mRNA. One cDNA clone upregulated by HRG was identical to human ADP-ribosylation factor 3 (ARF3), a guanine nucleotide-binding protein functioning in vesicular trafficking, phospholipase D activation and intracellular transport. HRG treatment increased expression of ARF3 mRNA and protein. Also, HRG triggered a rapid redistribution of ARF3, first to cell membranes and then to the nuclear compartment, where ARF3 colocalized with acetylated histone H3 in discrete regions. In addition, the ARF3 protein was developmentally regulated in the mammary gland with the highest levels in virgin and post-weaning glands. Together, these findings suggest for the first time that stimulation of ARF3 expression, subcellular redistribution and interaction with acetylated histone H3 may play a role in the action of HRG in mammary epithelial cells.

ADP-Ribosylation Factors↗

PubMed2002

p21-activated kinase 1 interacts with and phosphorylates histone H3 in breast cancer cells.

Stimulation of p21-activated kinase-1 (Pak1) signaling promotes motility, invasiveness, anchorage-independent growth and abnormal mitotic assembly in human breast cancer cells. Here, we provide new evidence that, before the onset of mitosis, activated Pak1 is specifically localized with the chromosomes during prophase and on the centrosomes in metaphase and moves to the contraction ring during cytokinesis. To identify mitosis-specific substrates of Pak1, we screened a synchronized G2-M expression library by using a glutathione transferase Pak1 solid-phase-based kinase reaction. This analysis identified histone H3 as a substrate of Pak1 both in vitro and in vivo, and it specifically interacted with Pak1 but not Pak2 or Pak3. Site-directed mutagenesis indicated that Pak1 phosphorylates histone H3 on Ser10. Expressions of the wild-type, or catalytically active, Pak1 caused it to appear at the poles corresponding to mitotic centrosomes in a variety of mammalian cells. Together, these results suggest for the first time that Pak1 interacts with and phosphorylates histone H3 and may thus influence the Pak1-histone H3 pathway, which in turn may influence mitotic events in breast cancer cells.

Breast Neoplasms↗

PubMed2002

Members of the C/EBP transcription factor family stimulate expression of the human and rat surfactant protein A (SP-A) genes.

Members of the CCAAT enhancer binding protein (C/EBP) transcription factor family were detected in fetal lung of both human and rat. In rat lung, the level of C/EBPs increased with time of gestation, peaking around birth. In adult rat lung, C/EBPs were localized to the alveolar type II cells. The effect of C/EBPs on pulmonary surfactant protein A (SP-A), which is also expressed late in gestation, was investigated. In contrast to control plasmids, C/EBP delta expressing plasmids reversed the action of a transcriptional silencer just upstream of the rat SP-A promoter. In order to test the effect of C/EBPs on endogenous SP-A gene expression, cells that express SP-A were exposed to a phosphorothioate-substituted, double-stranded oligonucleotide matching the consensus C/EBP binding site (decoy oligonucleotide) at concentrations from 0.5 to 10 microM for 72 h. A mutant oligonucleotide with an 8-base pair (bp) substitution served as a control. The decoy oligonucleotide reduced SP-A mRNA as much as 75% compared to a mutant oligonucleotide both in the human lung cell line, NCI-H441, and in primary human fetal alveolar type II cells. The data indicate that C/EBPs facilitate SP-A gene expression, possibly by overcoming transcriptional silencing.

Animals↗

PubMed2002

Heregulin induces expression, ATPase activity, and nuclear localization of G3BP, a Ras signaling component, in human breast tumors.

We have found using differential display of mRNA that the growth factor heregulin beta 1 (HRG), a combinatorial ligand for human epidermal growth factor receptors (HERs), induced expression of G3BP, the Ras GTPase-activating protein SH3 domain-binding protein, in breast cancer cells. G3BP is a downstream effector protein of Ras signaling with ATP-dependent RNase and helicase activities, which may link Ras signaling with RNA turnover and cell cycle progression. In human breast cancer cells, HRG induced G3BP mRNA and protein expression. Up-regulation of G3BP was found in MCF7 breast cancer cells overexpressing HER2. G3BP was also overexpressed in human breast tumors in parallel with HER2 overexpression and in an estrogen-independent manner, suggesting a role for G3BP in cancer progression. In addition, HRG stimulation of breast cancer cells promoted phosphorylation of G3BP and increased the association of G3BP with GTPase-activating protein, both of which are essential for G3BP activity. G3BP ATPase activity was also significantly increased by HRG treatment. Furthermore, HRG treatment resulted in G3BP translocation to the nucleus and colocalization with acetylated histone H3, a hallmark of active transcription sites. G3BP induction, phosphorylation, ATPase activity, and relocalization after HRG treatment could all be blocked by pretreatment with the anti-receptor HER2 monoclonal antibody Herceptin (trastuzumab), which may suggest additional applications for this therapeutic antibody. These findings demonstrate for the first time the receptor-dependent regulation of G3BP, a downstream effector of Ras signaling, by HRG, a growth factor with diverse functions in breast cancer cells.

Adenosine Triphosphatases↗

PubMed2002

Intraneuronal Alzheimer abeta42 accumulates in multivesicular bodies and is associated with synaptic pathology.

A central question in Alzheimer's disease concerns the mechanism by which beta-amyloid contributes to neuropathology, and in particular whether intracellular versus extracellular beta-amyloid plays a critical role. Alzheimer transgenic mouse studies demonstrate brain dysfunction, as beta-amyloid levels rise, months before the appearance of beta-amyloid plaques. We have now used immunoelectron microscopy to determine the subcellular site of neuronal beta-amyloid in normal and Alzheimer brains, and in brains from Alzheimer transgenic mice. We report that beta-amyloid 42 localized predominantly to multivesicular bodies of neurons in normal mouse, rat, and human brain. In transgenic mice and human Alzheimer brain, intraneuronal beta-amyloid 42 increased with aging and beta-amyloid 42 accumulated in multivesicular bodies within presynaptic and especially postsynaptic compartments. This accumulation was associated with abnormal synaptic morphology, before beta-amyloid plaque pathology, suggesting that intracellular accumulation of beta-amyloid plays a crucial role in Alzheimer's disease.

Aging↗

PubMed2002

Discrimination of subtypes of small adenocarcinoma in the lung with thin-section CT.

We studied the usefulness of thin-section CT in discriminating two categories of adenocarcinoma in the lung. Thin-section CT findings, such as, lesion size, ground-glass opacity (GGO) areas of lesion and presence or absence of lobulation, coarse spiculation, air bronchogram, small air space, or pleural tag of lesion in 62 consecutive patients with 62 adenocarcinomas (35 type A or B tumors (Noguchi's classification) and 27 type C tumors) of < or =20 mm, including 36 women and 26 men with a mean age of 64 years were analyzed. We performed stepwise logistic modeling using all the CT findings as independent variables to estimate the significant factors for discriminating type C from type A or B tumor. Lesion size in type C tumors was significantly (P<0.001) greater than that in type A or B tumors. GGO areas in type C tumors were significantly (P<0.001) smaller than that in type A or B tumors. The prevalence of coarse spiculation, air bronchogram, and pleural tag in type C tumors was significantly greater (P=0.001, 0.010, and <0.001, respectively) than that in type A or B tumors. Logistic modeling revealed that the GGO area was the only significant factor for discriminating two categories (P<0.001). Using the percentage of GGO areas for predicting type C tumor, 40% or less showed the highest accuracy of 85% with 70% sensitivity and 97% specificity. GGO areas of 30% or less had no false-positive diagnosis (100% specificity) with 81% accuracy but its sensitivity was low (56%). Thin-section CT was useful in discriminating two categories of adenocarcinoma in the lung.

Adenocarcinoma↗

PubMed2002

Filamin is essential in actin cytoskeletal assembly mediated by p21-activated kinase 1.

The serine/threonine kinase p21-activated kinase 1 (Pak1) controls the actin cytoskeletal and ruffle formation through mechanisms that are independent of GTPase activity. Here we identify filamin FLNa as a Pak1-interacting protein through a yeast two-hybrid screen using the amino terminus of Pak1 as a bait. FLNa is stimulated by physiological signalling molecules to undergo phosphorylation by Pak1 and to interact and colocalize with endogenous Pak1 in membrane ruffles. The ruffle-forming activity of Pak1 is functional in FLNa-expressing cells but not in FLNa-deficient cells. In FLNa, the Pak1-binding site involves tandem repeat 23 in the carboxyl terminus and phosphorylation takes place on serine 2152. The FLNa-binding site in Pak1 is localized between amino acids 52 and 132 in the conserved Cdc42/Rac-interacting (CRIB) domain; accordingly, FLNa binding to the CRIB domain stimulates Pak1 kinase activity. Our results indicate that FLNa may be essential for Pak1-induced cytoskeletal reorganization and that the two-way regulatory interaction between Pak1 and FLNa may contribute to the local stimulation of Pak1 activity and its targets in cytoskeletal structures.

Actins↗

PubMed2002

Characterizing CGI-94 (comparative gene identification-94) which is down-regulated in the hippocampus of early stage Alzheimer's disease brain.

The treatment of Alzheimer's disease (AD) remains a major challenge because of the incomplete understanding of the triggering events that lead to the selective neurodegeneration characteristic of AD brains. Here we describe a new protein, CGI-94, that is down-regulated at the mRNA level in the hippocampus of early stage AD brain. Transfection experiments with CGI-94 as a green fluorescent protein (GFP)-fusion-protein show that this protein is translocated into the nucleus of the cell. The finding that this protein, which has a bipartite nuclear localization signal, is also observed in the cytoplasm and extracellular space points to a multifunctional protein. Immunohistochemical analyses reveal that CGI-94 is mainly expressed in neurons of the hippocampal formation and the cortex but not in the cerebellar nucleus. In conclusion, the expression of the nucleolar phosphoprotein CGI-94 appears to be disturbed in early processes of neuronal degeneration.

Aged↗

PubMed2002

Treatment and outcome of sinus of valsalva aneurysm.

BACKGROUND: In order to understand the long-term outcome after surgical repair of sinus of Valsalva aneurysms or fistulas (SVAF), the operative results for patients treated at Shanghai Chest Hospital were retrospectively assessed. METHODS: Between 1960 and 1999, 216 patients were operated on for SVAF. Of these 143 (66.2%) had a ventricular septal defect (VSD), 60 (28.0%) had aortic regurgitation and of these 12 underwent aortic valve replacement (AVR). RESULTS: There were eight in-hospital deaths (3.7%). Another patient had aortic regurgitation postoperatively requiring AVR. CONCLUSION: Resection and repair of SVAF entails an acceptably low operative risk and yields long-term freedom from symptoms. Early, aggressive operation is recommended to prevent development of complications.

Journal Article↗

PubMed2002

XY99-5038 promotes long-term survival of cultured retinal neurons.

We have previously reported that XY99-5038, a preparation from a specific formula of Traditional Chinese Medicine, could effectively inhibit hydrogen peroxide-induced retinal cell death. In the present study, we investigated the possibility of XY99-5038 to prolong neuronal survival in a long-term retinal neuronal culture. Basic fibroblast survival factor (bFGF), a potent neurotrophic factor, was employed as comparable agent. Retinas of 0-2 days old Sprague-Dawley rats were isolated and dissociated. The cells were maintained in tissue culture for up to 9 weeks in a synthetic serum-free media. XY99-5038 (100 ng/ml) or a vehicle was added to culture every 3-4 days, starting at the first week of culturing. The number of cells were counted and compared for each time point and treatment. Cell viability was also determined by MTT assay, whereas apoptotic cell death was evaluated by the TUNEL assay. XY99-5038 treatment significantly reduced cell loss, increased cell viability, and inhibited apoptosis in this long-term retinal neuronal culture. Our data also show that the protective effect of XY99-5038 is more potent than that of bFGF. Our data suggest that XY99-5038 could be beneficial to the prolongation of neuron survival.

Aging↗

PubMed2002

Characterization of von Willebrand factor interaction with collagens in real time using surface plasmon resonance.

von Willebrand factor (vWf) binding to subendothelial collagens is an initial step in thrombus formation. We have characterized the binding of vWf multimers to human pepsin-digested collagen I, III, and VI using surface plasmon resonance (BIAcore). Based on vWf subunit molecular weight (250 KDa), normal vWf multimers (nvWf) purified from human cryoprecipitate, which containing the entire range of multimers found in normal plasma, bound to human pepsin-digested collagen III with an association rate of 2.88+/-0.01 x 10(5) M(-1) s(-1), a dissociation rate of 5.85+/-0.10 x 10(-4) s(-1) and an equilibrium dissociation constant KD of 2.03+/-0.04 nM. These nvWf multimers bound to human pepsin-digested collagen I with a five fold lower binding capacity and a ten fold higher equilibrium dissociation constant. There was no detectable binding between the vWf multimers and human pepsin-digested collagen VI. The purified vWf A3 domain, vWf preparations enriched in either relatively small vWf (svWf) multimers or in unusually large vWf (ulvWf) multimers were also studied on collagen III surfaces. Our results demonstrate that the vWf dissociation rates are dependent on the vWf molecular mass and the duration of interactions. We conclude that vWf-collagen binding interactions involve multiple bond processes.

Animals↗

PubMed2002

Functional replacement and positional dependence of homologous and heterologous L domains in equine infectious anemia virus replication.

We have previously demonstrated by Gag polyprotein budding assays that the Gag p9 protein of equine infectious anemia virus (EIAV) utilizes a unique YPDL motif as a late assembly domain (L domain) to facilitate release of the budding virus particle from the host cell plasma membrane (B. A. Puffer, L. J. Parent, J. W. Wills, and R. C. Montelaro, J. Virol. 71:6541-6546, 1997). To characterize in more detail the role of the YPDL L domain in the EIAV life cycle, we have examined the replication properties of a series of EIAV proviral mutants in which the parental YPDL L domain was replaced by a human immunodeficiency virus type 1 (HIV-1) PTAP or Rous sarcoma virus (RSV) PPPY L domain in the p9 protein or by proviruses in which the parental YPDL or HIV-1 PTAP L domain was inserted in the viral matrix protein. The replication properties of these L-domain variants were examined with respect to Gag protein expression and processing, virus particle production, and virus infectivity. The data from these experiments indicate that (i) the YPDL L domain of p9 is required for replication competence (assembly and infectivity) in equine cell cultures, including the natural target equine macrophages; (ii) all of the functions of the YPDL L domain in the EIAV life cycle can be replaced by replacement of the parental YPDL sequence in p9 with the PTAP L-domain segment of HIV-1 p6 or the PPPY L domain of RSV p2b; and (iii) the assembly, but not infectivity, functions of the EIAV proviral YPDL substitution mutants can be partially rescued by inclusions of YPDL and PTAP L-domain sequences in the C-terminal region of the EIAV MA protein. Taken together, these data demonstrate that the EIAV YPDL L domain mediates distinct functions in viral budding and infectivity and that the HIV-1 PTAP and RSV PPPY L domains can effectively facilitate these dual replication functions in the context of the p9 protein. In light of the fact that YPDL, PTAP, and PPPY domains evidently have distinct characteristic binding specificities, these observations may indicate different portals into common cellular processes that mediate EIAV budding and infectivity, respectively.

Amino Acid Sequence↗

PubMed2002

Budding of equine infectious anemia virus is insensitive to proteasome inhibitors.

The only retrovirus protein required for the budding of virus-like particles is the Gag protein; however, recent studies of Rous sarcoma virus (RSV) and human immunodeficiency virus have suggested that modification of Gag with ubiquitin (Ub) is also required. As a consequence, the release of these viruses is reduced in the presence of proteasome inhibitors, which indirectly reduce the levels of free Ub within the cell. Here we show that the budding of equine infectious anemia virus (EIAV) from infected equine cells is largely unaffected by these drugs, although use of one inhibitor (MG-132) resulted in a dramatic block to proteolytic processing of Gag. This lack of sensitivity was also observed in transiently transfected avian cells under conditions that greatly reduce RSV budding. Moreover, insensitivity was observed when the EIAV Gag protein was expressed in the absence of all the other virus products, indicating that they are not required for this phenotype. An activity that enables EIAV to tolerate exposure to proteasome inhibitors was mapped to the C-terminal p9 sequence, as demonstrated by the ability of an RSV Gag-p9 chimera to bud in the presence of the drugs. Intriguingly, the p9 sequence contains a short sequence motif that is similar to a surface-exposed helix of Ub, suggesting that EIAV Gag may have captured a function that allows it to bypass the need for ubiquitination. Thus, the mechanism of EIAV budding may not be substantially different from that of other retroviruses, even though it behaves differently in the presence of proteasome inhibitors.

Animals↗

PubMed2002

Lung cancers missed at low-dose helical CT screening in a general population: comparison of clinical, histopathologic, and imaging findings.

PURPOSE: To compare clinical, histopathologic, and imaging features of lung cancers missed at low-radiation-dose helical computed tomography (CT). MATERIALS AND METHODS: Eighty-three primary lung cancers were found during an annual low-dose CT screening program and confirmed histopathologically at either surgery or biopsy. Thirty-two of these lung cancers were missed on 39 CT scans: on 23 scans owing to detection errors and on 16 owing to interpretation errors. The clinical characteristics, CT features, and histopathologic findings of these missed lung cancers were correlated. RESULTS: All missed cancers were intrapulmonary, and 28 (88%) were stage IA. All 20 detection errors occurred in cases of adenocarcinoma, 17 (85%) of which were well-differentiated tumors and 11 (55%) of which were in nonsmoking women. The mean size of cancers missed owing to detection error, 9.8 mm, was smaller than that of cancers missed owing to interpretation error, 15.9 mm (P <.001). In the detection error group, the percentages of nodules with ground-glass opacity (91%) or judged to be subtle (91%) were greater than those of nodules in the interpretation error group (38% and 25%, respectively) (P <.001). In the detection error group, 83% (19/23) of cancers were overlapped with, obscured by, or similar in appearance to normal structures such as pulmonary vessels. On 14 of the 16 CT scans with which there were interpretation errors, the CT findings mimicked benign disease, and the patients also had underlying lung disease, such as tuberculosis, emphysema, or lung fibrosis. CONCLUSION: The lung cancers missed at low-dose CT screening in this series generally were very subtle and appeared as small faint nodules, overlapping normal structures, or opacities in a complex background of other disease.

Adenocarcinoma↗

PubMed2002

Lung cancer: performance of automated lung nodule detection applied to cancers missed in a CT screening program.

PURPOSE: To evaluate the performance of a fully automated computerized method for the detection of lung nodules in computed tomographic (CT) scans in the identification of lung cancers that may be missed during visual interpretation. MATERIALS AND METHODS: A database of 38 low-dose CT scans with 50 lung nodules was obtained from a lung cancer screening program. Thirty-eight of the nodules represented biopsy-confirmed lung cancers that had not been reported during initial clinical interpretation. A computer detection method that involved the use of gray-level thresholding techniques to identify three-dimensionally contiguous structures within the lungs was applied to the CT data. Computer-extracted volume was used to determine whether a structure became a nodule candidate. A rule-based scheme and a cascaded automated classifier were applied to the set of nodule candidates to distinguish actual nodules from areas of normal anatomy. Overall performance of the computer detection method was evaluated with free-response receiver operating characteristic (FROC) analysis. RESULTS: At a specific operating point on the FROC curve, the method achieved a sensitivity of 80% (40 of 50 nodules), with an average of 1.0 false-positive detection per section. Missed cancers were detected by the computerized method with a sensitivity of 84% (32 of 38 nodules) and a false-positive rate of 1.0 per section. CONCLUSION: With an automated lung nodule detection method, a large fraction (84%, 32 of 38) of missed cancers in a database of low-dose CT scans were detected correctly.

Aged↗

PubMed2002

[Development of an image processing scheme for chest radiographs using a dot printer].

The performance of dot printers has recently been improved. Images output by dot printers can provide simple, economical medical reference images if important diagnostic information is not lost. We developed an image processing scheme for chest radiographs that employed a dot printer. We used two types of pixel value conversions, a nonlinear pixel value correction using a lookup table and a linear pixel value conversion using histogram analysis. The density distribution of chest radiographs was analyzed and classified into high-density and low-density images. The two types of pixel value conversions were used depending on the density of chest radiographs. Converted pixel value had density characteristics that were adapted to the output image of the dot printer, and thus the density distributions of the lungs of radiographs became comparable. In addition, an adaptive unsharp masking technique with processing parameters optimized for each of the lungs and mediastinum was applied. An ROC study for the detection of lung nodules was carried out to evaluate the performance of dot printer images. The area under the ROC curve (A(z)) for dot printer images was 0.816, while sensitivity and specificity were 77.6% and 75.2%, respectively. The performance indicated the usefulness of our image processing scheme.

Humans↗