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Biomedical subjects

Feng Li

Publications and source records attributed to Feng Li.

At least 127 records · Page 7Linked to original sources
PubMed2005

Determination of the chronaxie and rheobase of denervated limb muscles in conscious rabbits.

Measurements of the rheobase and chronaxie can be used to define the excitability of nerves and muscles. The aim of this study was to obtain a record over many weeks of changes in the rheobase and chronaxie of denervated rabbit tibialis anterior muscle (TA). A custom-built electronic stimulator was implanted into the peritoneal cavity of New Zealand White rabbits. Large stainless steel electrodes were placed on the denervated TA muscle. Rheobase and chronaxie were measured noninvasively at weekly intervals by means of a laptop PC, which communicated with the stimulator via a radio-frequency link. At each setting the denervated TA was palpated manually to detect the response of the muscle. During the first few days after denervation the rheobase increased transiently to 0.8 +/- 0.13 mA, approximately twice the value for normal innervated muscle, then decreased to normal for the remainder of the experimental period. Chronaxie underwent a significant 3-fold increase from 4.5 +/- 1.1 ms to 14.1 +/- 1.1 ms during the first two weeks of denervation and remained elevated throughout. The custom-built implantable electronic stimulator allowed changes in muscle excitability to be studied over a long period of denervation within individual animals, providing an accurate assessment of the time course of denervation-induced changes in muscle excitability.

Analysis of Variance↗
PubMed2005

Preparation and preliminary application of monoclonal antibodies against Trichokirin-S1, a small ribosome-inactivating peptide from the seeds of Trichosanthes kirilowii.

Trichokirin-S1, a small ribosome-inactivating peptide recently purified from the seeds of Trichosanthes kirilowii, has potential clinical applications because of its small molecular mass. Two stable strains of hybridomas (1F11 and 2A5) that can secrete highly specific monoclonal antibodies (mAbs) against Trichokirin-S1 have been developed using the hybridoma technique. The isotypes of these two mAbs, 1F11 and 2A5, were determined to be IgG2a and IgG1, respectively. The affinity constants, which were measured by non-competitive ELISA, were found to be 2.3 x10(8) M(-1) and 2.8 x 10(8) M(-1), respectively. An immunoaffinity method using 2A5-coupled Sepharose 4B was successfully developed to purify Trichokirin-S1. These two antibodies have also been used to detect Trichokirin-S1 in Western blot.

Animals↗
PubMed2005

Discerning an effective balance between equine infectious anemia virus attenuation and vaccine efficacy.

Among the diverse experimental vaccines evaluated in various animal lentivirus models, live attenuated vaccines have proven to be the most effective, thus providing an important model for examining critical immune correlates of protective vaccine immunity. We previously reported that an experimental live attenuated vaccine for equine infectious anemia virus (EIAV), based on mutation of the viral S2 accessory gene, elicited protection from detectable infection by virulent virus challenge (F. Li et al., J. Virol. 77:7244-7253, 2003). To better understand the critical components of EIAV vaccine efficacy, we examine here the relationship between the extent of virus attenuation, the maturation of host immune responses, and vaccine efficacy in a comparative study of three related attenuated EIAV proviral vaccine strains: the previously described EIAV(UK)DeltaS2 derived from a virulent proviral clone, EIAV(UK)DeltaS2/DU containing a second gene mutation in the virulent proviral clone, and EIAV(PR)DeltaS2 derived from a reference avirulent proviral clone. Inoculations of parallel groups of eight horses resulted in relatively low levels of viral replication (average of 10(2) to 10(3) RNA copies/ml) and a similar maturation of EIAV envelope-specific antibody responses as determined in quantitative and qualitative serological assays. However, experimental challenge of the experimentally immunized horses by our standard virulent EIAV(PV) strain by using a low-dose multiple exposure protocol (three inoculations with 10 median horse infective doses, administered intravenously) revealed a marked difference in the protective efficacy of the various attenuated proviral vaccine strains that was evidently associated with the extent of vaccine virus attenuation, time of viral challenge, and the apparent maturation of virus-specific immunity.

Animals↗
PubMed2005

Myc stimulates nuclearly encoded mitochondrial genes and mitochondrial biogenesis.

Although several genes involved in mitochondrial function are direct Myc targets, the role of Myc in mitochondrial biogenesis has not been directly established. We determined the effects of ectopic Myc expression or the loss of Myc on mitochondrial biogenesis. Induction of Myc in P493-6 cells resulted in increased oxygen consumption and mitochondrial mass and function. Conversely, compared to wild-type Myc fibroblasts, Myc null rat fibroblasts have diminished mitochondrial mass and decreased number of normal mitochondria. Reconstitution of Myc expression in Myc null fibroblasts partially restored mitochondrial mass and function and normal-appearing mitochondria. Concordantly, we also observed in primary hepatocytes that acute deletion of floxed murine Myc by Cre recombinase resulted in diminished mitochondrial mass in primary hepatocytes. Our microarray analysis of genes responsive to Myc in human P493-6 B lymphocytes supports a role for Myc in mitochondrial biogenesis, since genes involved in mitochondrial structure and function are overrepresented among the Myc-induced genes. In addition to the known direct binding of Myc to many genes involved in mitochondrial structure and function, we found that Myc binds the TFAM gene, which encodes a key transcriptional regulator and mitochondrial DNA replication factor, both in P493-6 lymphocytes with high ectopic MYC expression and in serum-stimulated primary human 2091 fibroblasts with induced endogenous MYC. These observations support a pivotal role for Myc in regulating mitochondrial biogenesis.

Animals↗
PubMed2005

p21-activated kinase 1 regulates microtubule dynamics by phosphorylating tubulin cofactor B.

p21-activated kinase 1 (Pak1) induces cytoskeleton reorganization in part by regulating microtubule dynamics through an elusive mechanism. Using a yeast two-hybrid screen, we identified tubulin cofactor B (TCoB) (a cofactor in the assembly of the alpha/beta-tubulin heterodimers) as an interacting substrate of Pak1. Pak1 directly phosphorylated TCoB in vitro and in vivo on serines 65 and 128 and colocalized with TCoB on newly polymerized microtubules and on centrosomes. TCoB interacted with the GTPase-binding domain of Pak1 and activated Pak1 in vitro and in vivo. In contrast to wild-type TCoB, an S65A, S128A double mutant and knock-down of the endogenous TCoB or Pak1 reduced microtubule polymerization, suggesting that Pak1 phosphorylation is necessary for normal TCoB function. Overexpression of TCoB dramatically increased the number of gamma-tubulin-containing microtubule-organizing centers, a phenotype reminiscent of cells overexpressing Pak1. TCoB was overexpressed and phosphorylated in breast tumors. These findings reveal a novel role for TCoB and Pak1 in regulating microtubule dynamics.

Breast Neoplasms↗
PubMed2005

Computer-aided detection of peripheral lung cancers missed at CT: ROC analyses without and with localization.

PURPOSE: To retrospectively evaluate whether a difference-image computer-aided detection (CAD) scheme can help radiologists detect peripheral lung cancers missed at low-dose computed tomography (CT). MATERIALS AND METHODS: Institutional review board approval and informed patient and observer consent were obtained. Seventeen patients (eight men and nine women; mean age, 60 years) with a missed peripheral lung cancer and 10 control subjects (five men and five women; mean age, 63 years) without cancer at low-dose CT were included in an observer study. Fourteen radiologists were divided into two groups on the basis of different image display formats: Six radiologists (group 1) reviewed CT scans with a multiformat display, and eight radiologists (group 2) reviewed images with a "stacked" cine-mode display. The radiologists, first without and then with the CAD scheme, indicated their confidence level regarding the presence (or absence) of cancer and the most likely position of a lesion on each CT scan. Receiver operating characteristic (ROC) curves were calculated without and with localization to evaluate the observers' performance. RESULTS: With the CAD scheme, the average area under the ROC curve improved from 0.763 to 0.854 for all radiologists (P = .002), from 0.757 to 0.862 for group 1 (P = .04), and from 0.768 to 0.848 for group 2 (P = .01). The average sensitivity in the detection of 17 cancers improved from 52% (124 of 238 observations) to 68% (163 of 238 observations) for all radiologists (P < .001), from 49% (50 of 102 observations) to 71% (72 of 102 observations) for group 1 (P = .02), and from 54% (74 of 136 observations) to 67% (91 of 136 observations) for group 2 (P = .006). The localization ROC curve also improved. CONCLUSION: Lung cancers missed at low-dose CT were very difficult to detect, even in an observer study. The use of CAD, however, can improve radiologists' performance in the detection of these subtle cancers.

Aged↗
PubMed2005

Synthesis, characterization, and antitumoral activity of polyoxometalate loaded starch nanocomplexes.

Using a reverse-phase microemulsion polymerization method and an encapsulating method, polyoxometalates (POMs) K6SiW11TiO40 incorporating starch microspheres have been prepared and structurally characterized by elemental analyses, IR, UV-vis, and NMR spectroscopy. The size of SiW11TiO40/starch particles is about 40-60 nm. The polyoxometalate encapsulated by a starch microsphere retains the parent structure. The starch microsphere is a good carrier, as it is able to enhance the antitumoral activity of POMs and decrease the toxicity of POMs as well.

Antineoplastic Agents↗
PubMed2005

Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosomes deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1.

A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein encoded by ORF4 may take part in the signal transduction relating to biosynthesis of magnetosomes.

Amino Acid Sequence↗
PubMed2005

[Expression of integrin-linked kinase in prostate cancer and its significance].

OBJECTIVE: To investigate the expression of integrin-linked kinase (ILK) in primary prostate cancer and its clinical significance. METHODS: The expression of ILK was analysed in 50 prostate cancer and 16 benign prostatic hyperplasia samples by immunohistochemical staining. RESULTS: The positive percentage of ILK was 46.0% (23/50) in primary prostate cancer. The higher the grade and the clinical stage of the tumor, the lower the expression of ILK. The positive percentages of ILK were 9.1% (1/11) in the well differentiated type, 56.4% (22/39) in the moderately and poorly differentiated type (chi2 = 12.28, P < 0.01), 24.0% (6/25) in the well and moderately differentiated type, 68.0% (17/25) in the poorly differentiated type (chi2 = 9.74, P < 0.01), 22.6% (7/31) at the A + B stage and 84.0% (16/19) at the C + D stage (chi2 = 11.8, P < 0.01). But in benign prostatic hyperplasia, it was only 6.2% (1/16), significantly lower than in primary prostate cancer (46.0%) (chi2 = 8.27, P < 0.01). CONCLUSION: The abnormal expression of ILK plays an important role in the development of primary prostate cancer, and the detection of ILK may be useful for the judgement of tumor development and prognosis.

Aged↗
PubMed2005

[Epidemiological survey of prevalence of fatty liver and its risk factors in a general adult population of Shanghai].

OBJECTIVE: To investigate the prevalence and major risk factors of fatty liver among adult residents in Shanghai. METHODS: A cross-sectional survey with multiple-stage stratified cluster and random sampling was performed. All residents aged 16 and above were invited to participate in the survey; they came from four communities of Yangpu District and Pudong New District. Questionnaire, physical examination, serum lipid-profile, and 75 gram oral glucose tolerance test and ultrasonographic examination of liver were undertaken. Analysis of data was performed through SPSS 11.0 for Windows statistical package. RESULTS: A total of 3175 residents took part in the survey, which was 75% of adult residents of the investigated communities and 2.26/10 000 of Shanghai municipal residents. Of the 3175, 1218 were males and 1957 were females. The mean age of the participants was 52.4+/-15.1 years and ranged from 16 to 88 years. Fatty liver was detected with ultrasound examination in 661 participants (20.82%), among which 3.48% had alcoholic fatty liver, 4.08% had suspected alcoholic fatty liver, and 92.43% had nonalcoholic fatty liver. The age-adjusted, sex-adjusted prevalence of fatty liver in Shanghai adult residents was 17.29%, the prevalence of alcoholic fatty liver, suspicious alcoholic fatty liver, and nonalcoholic fatty liver in Shanghai adult residents were 0.79%, 1.15%, and 15.35%, respectively. The prevalence of fatty liver was increased with aging in males and in females. Among participants younger than 50 years old, the prevalence of fatty liver in males was significantly higher than that in females, but in participants older than 50 years the case was just the opposite, higher in females. The mean age (years), body mass index (BMI), waist circumference, blood pressure, fasting and two hour serum glucose level, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and the presence of obesity, diabetes mellitus, hypertension, dyslipidemia, and gallstones in the fatty liver group was significantly higher than those in the group without fatty liver, but the high-density lipoprotein cholesterol (HDL-C) level and the educational level were both lower in the fatty liver group. Logistic regression analysis demonstrated that the prevalence of fatty liver was only positively correlated to nine risk factors, including male sex, educational level, waist circumference, BMI, fasting glucose level, HDL-C, TG, hypertension and diabetes mellitus. In heavy drinkers, obesity increased the risk for fatty liver by 4.8-fold, but heavy drinking only increased the risk for fatty liver 1.5-fold (95% CI 0.9-2.6, P=0.1685). CONCLUSION: There is a high prevalence of fatty liver among adult residents in Shanghai, and nonalcoholic fatty liver is the major type. Metabolic disorders such as obesity and diabetes mellitus, hypertension and hyperlipidemia are more closely associated with fatty liver than heavy drinking in Shanghai.

Adolescent↗
PubMed2005

HIV-1 assembly and budding as targets for drug discovery.

Research conducted during the past several years has led to an increased understanding of the roles played by the viral protein Gag and specific cellular factors in HIV assembly/budding. The identification of compounds that interfere with this process validates this late step in virus replication as a target for HIV therapeutic discovery. In this review, current understanding of HIV-1 assembly/budding is described and several developmental stage drugs that target this process are reviewed.

Capsid↗
PubMed2005

[Detection of RNA interference in nasopharyngeal carcinoma cell lines using reporter genes].

BACKGROUND & OBJECTIVE: RNA interference (RNAi) technique is now widely used in studies of gene function, signal transduction pathway, and gene therapy because it can effectively and specifically inhibit gene expression. This study was designed to synthesize small interfering RNA (siRNA) by in vitro transcription, and construct retrovirus vectors to express small hairpin RNA (shRNA), detect RNAi in nasopharyngeal carcinoma cell lines, and to develop a RNAi technique platform. METHODS: siRNAs targeting green fluorescent protein (GFP) and luciferase (Luc) were synthesized by in vitro transcription, while shRNAs targeting GFP and Luc were constructed from pSUPER.retro. Cervical cancer cell line HeLa, nasopharyngeal carcinoma cell lines CNE1, CNE2, and 5-8F were co-transfected with siRNAs or shRNAs and reporter gene pEGFP-N1 or pGL3. The expression of GFP was detected by fluorescent microscopy and Western blot. The activity of luciferase was measured by Luciferase Enzyme Assay System. RESULTS: siRNA duplexes with 3' UU overhangs and shRNA specifically silenced GFP expression, while antisense RNA and siRNA without 3' UU overhangs did not trigger RNA interference of GFP. Quantitative luciferase activity analysis showed that siRNA inhibited Luc expression in HeLa, CNE1, CNE2, and 5-8F cell lines with inhibition rates of 91.43%, 78.01%, 90.30%, and 62.85%, respectively. Similarly, the inhibition rate was 78.22% when shRNA targeting Luc was co-transfected into HeLa cell line. CONCLUSIONS: Both siRNAs and shRNAs can induce RNAi. 3' UU overhangs of siRNA may play a role in RNAi. RNAi can be triggered in both nasopharyngeal carcinoma cell lines and HeLa cell line.

Cell Line, Tumor↗
PubMed2005

[Correlation of expression of connexin to growth and progression of cervical carcinoma in situ].

BACKGROUND & OBJECTIVE: Gap junction intercellular communication (GJIC), mediated by connexin (CX), is the unique type of intercellular communication in carcinoma in situ (CIS). Changes in expression of CXs and function of GJIC may play roles in carcinogenesis of cervical cancer and progression of CIS. This study was to investigate the expression of CXs in normal epithelium (NE), hyperplasia, CIS, and invasive carcinoma (IC) of cervix, to explore correlation of expression of CXs to pathogenesis and progression of cervical CIS. METHODS: Expression of CX43 (mRNA, protein), CX26 (mRNA), and Ki-67 (protein) in 30 specimens of cervical NE, 22 specimens of cervical hyperplasia, 30 specimens of cervical CIS, and 26 specimens of cervical IC were detected by immunohistochemistry and in situ hybridization. RESULTS: In cervical NE, hyperplasia, CIS, and IC, positive rates of CX43 protein were 83%, 55%, 50%, and 30%, respectively, and positive rates of CX43 mRNA were 97%, 64%, 58%, and 46%, respectively; positive rates of CX26 mRNA was 93%, 68%, 55%, and 42%, respectively. Positive rates of CX43 (mRNA, protein) and CX26 (mRNA) were gradually decreased. Positive rate of CX was significantly lower in CIS group than in NE group (P < 0.05). The expressions of CX26 and CX43 were weaker in CIS group than in NE groupu their expressions were obviously decreased, or even vanished in the area of CIS adjacent to NE. Proliferating index (PI), indicated by expression of Ki-67 protein, was increased gradually in NE (5%), hyperplasia (12%), CIS (30%), and IC (62%)u the differences were significant (P < 0.05) between CIS group and other groups. CONCLUSIONS: CX26 and CX43 may play important roles in carcinogenesis of cervical cancer. CXs may inhibit tumorigenesis and cell proliferation; it might be key factors in earlier stages when cellular malignant phenotypes have been established, or NE has been transformed into CIS.

Carcinoma in Situ↗
PubMed2005

[Effect of antioxidant on hepatic stellate cell proliferation and apoptosis during recovery from liver fibrosis].

OBJECTIVE: Effects of dietary supplementation of vitamin E and selenium on proliferation and apoptosis of activated hepatic stellate cell(HSC) were investigated in the rat model of liver fibrosis induced by intraperitoneal injection with CCl4. METHODS: Activated HSC was determined by alpha-smooth muscle actin immunohistochemistry staining and apoptotic HSC determined by dual staining both of the terminal deoxynucleotidyl transferase UTP nick end labeling(TUNEL) and of alpha-smooth muscle actin immunohistochemistry. RESULT: During fibrosis recovery, the number of activated HSCs both in pathological group and in intervention group went down gradually,meanwhile, both the number of apoptotic HSCs and the collagen liver also descend little by little. These data confirmed that HSCs had the core effect on liver fibrogenesis and apoptosis may be a major factor regulating HSCs numbers during the injury-fibrosis-recovery sequence. At each time point, the number of activated HSCs in pathological group is more than intervention group, while apoptotic HSCs are less, which suggested dietary supplement with antioxidative nutrients had effect on HSC apoptosis but more studies are necessary to make the mechanism clearer. CONCLUSION: Dietary supplement with proper vitamin E and selenium can effectively lighten the hepatic fibrosis and promote the recovery of hepatocyte and the degradation of the existing collagens, ie, it is beneficial to the recovery of hepatic fibrosis.

Animals↗
PubMed2005

[Quantitative and localized detection of Epstein-Barr virus infectious status in nasopharyngeal carcinoma tissue].

BACKGROUND & OBJECTIVE: Epstein-Barr virus (EBV) closely relates to nasopharyngeal carcinoma (NPC). Whether EBV is a causative viral agent or a by-stander in the carcinogenesis of NPC needs further study. The latent status of EBV during carcinogenesis of NPC remains unknown nowadays. This study was to explore the infectious status of EBV in NPC, and analyze the correlation of EBV to carcinogenesis of NPC. METHODS: Carcinoma tissues,adjacent tissues, and contralateral normal nasopharyngeal tissues from 47 patients with poorly-differentiated nasopharyngeal squamous cell carcinoma were prepared simultaneously. Nasopharyngeal tissues from 10 healthy subjects were used as control. EBV DNA copies levels in the specimens were tested using real-time quantitative polymerase chain reaction (PCR); localization of EBV was detected by in situ hybridization [digoxigenin-labeled EBV-encoded RNA 1 (EBER-1) probe]. RESULTS: Infectious rate of EBV was 80.0% in nasopharyngeal tissues of healthy subjects (mean EBV DNA copies of 6.7x10(2)/microg DNA), 100% in carcinoma tissues and adjacent tissues of NPC patients, and 72.3% in contralateral normal nasopharyngeal tissues of NPC patients (mean EBV DNA copies of 6.9x10(5)/microg DNA, 1.5x10(5)/microg DNA, and 9.8x10(3)/microg DNA, respectively). There was no significant difference in infectious rate and level of EBV between controlateral normal nasopharyngeal tissues of NPC patients and nasopharyngeal tissues of healthy subjects (P>0.05); infectious level of EBV was significantly higher in carcinoma tissues than in adjacent tissues (P<0.05), and significantly higher in adjacent tissues than in contralateral normal nasopharyngeal tissues of NPC patients (P<0.01). Using in situ hybridization, EBER-1 expression signal was not detected in contralateral normal nasopharyngeal epithelia of NPC patients, weak in atypical hyperplastic cells in adjacent tissues, and strong in carcinoma cells. CONCLUSIONS: EBV latent infection is a common phenomenon in nasopharyngeal tissues of both NPC patients and healthy persons. The enhancement of EBV infection plays an important role during carcinogenesis of NPC.

Carcinoma, Squamous Cell↗
PubMed2005

[Repair of bone defect with allograft demineralized bone containing basic fibroblast growth factor in rabbits].

OBJECTIVE: To evaluate the ability of inductive osteogenesis of allograft demineralized bone containing basic fibroblast growth factor (bFGF/ALB) in repairing bone defect. METHODS: Thirty-two New Zealand white rabbits were randomly divided into four groups (groups A,B,C and D, n=8). A segmental bone defect of 15 mm in length was made on the bilateral radius respectively and the defects filled with ALB/bFGF in group A, with ALB in group B, with bFGF in group C and without any materials in group D serving as blank control. At 2, 4, 6 and 8 weeks after operation, all restored bones were evaluated by roentgenography, histological observation and Ca2+ detection of osteotylus. RESULTS: The X-ray films showed that groups A and B had a little shadow of bone formation at 2 weeks, while groups C and D had transparent shadow; that group A had denser shadow and new bone formation at 4 weeks and 6 weeks, groups B and C had a little increase of shadow and group D had little shadow at fractured ends; and that group A had formation of bone bridge at 8 weeks, the new formed bone in fractured ends of group B closed with each other, the gap still existed in group C, and the defects filled with the soft tissue in group D. The Ca2+ content of group A was higher than that of groups B, C and D at 4 weeks (P<0.05) and 8 weeks (P<0.01). The histological observation showed that the degree of bone restoration of group A was superior to that of groups B, C and D. CONCLUSION: bFGF/ALB is a good material to improve bone restoration.

Absorbable Implants↗
PubMed2005

[Optical detection system for micro biochemical analyses].

For the need of biochemical chip, which consumes fewer specimens and is easy to integrate with micro-fluid chip, two kinds of spectrophotometric analysis methods are described in the present paper. Both the direct detection method and evanescent wave detection method are used in the experiments with visible light (460-800 nm). The experimental results proved that the direct detection is simple and evident; on the other hand the evanescent wave detection method consumes much less reagent and is easy to integrate with microchips.

Microfluidic Analytical Techniques↗