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Biomedical subjects

Qiang Li

Publications and source records attributed to Qiang Li.

At least 235 records · Page 13Linked to original sources
PubMed2003

[Erythropoietin increases transferrin receptor expression and the impact of erythropoietin on K562 leukemic cell cycle].

OBJECTIVE: Functionally, erythropoietin (EPO) can promote the proliferation and growth of erythroid progenitor cells, and it is widely used in the treatment of anemia in chronic diseases caused by tumor and inflammation. However, it is unclear whether EPO has any effect on tumor cell iron metabolism and tumor cell proliferation. The purpose of this study was to explore the effects of recombinant human EPO (rhEPO) on the expression of transferrin receptor (TfR, CD(71) antigen) of leukemic cell K562 and its relation to cell cycle. METHODS: In vitro culture of K562 cell was performed with additions of various concentrations of rhEPO and Fe. Treatments were terminated at 24 h and 72 h, respectively. Then each group of cells was incubated with FITC-IgG antibody to CD(71) or PI, a kind of DNA dye. And TfR expression and DNA synthesis status were analyzed by flow-cytometry. RESULTS: (1) The expression of TfR by K562 cells increased significantly when incubated for 72 h with different concentrations of rhEPO. The measurement values of 5 U/ml, 10 U/ml and 20 U/ml groups were 12.2 +/- 1.40, 10.7 +/- 0.99 and 11.1 +/- 0.90, respectively. They were markedly increased when compared with that of control group (6.27 +/- 0.11, P < 0.05). (2) When incubated with rhEPO (5 u/ml) alone or combined with FeCl(3) (100 micro mol/L), the percentages of cells in S phase were 51.1% and 59.6%, respectively. They significantly increased when compared with that of control group (42.9%, P < 0.05). CONCLUSIONS: Iron is very important for the proliferation of both normal cells and leukemic cells. It is essential to the activity of ribonucleotide reductase (RR). The authors hypothesized that rhEPO would increase the expression of TfR and intracellular iron content of leukemic cells, which would enhance the DNA synthesis and cell proliferation. Therefore, the clinical application of rhEPO to promote erythropoiesis of cancer patients should be cautious.

Cell Cycle↗
PubMed2003

[Treatment and pathologic change of pachydermoperiostosis].

OBJECTIVE: To investigate the treatment and possible pathogenesis of pachydermoperiostosis. METHODS: Facelift was performed on five patients with pachydermoperiostosis. Histological studies were performed to check the affected skin for possible pathogenesis. RESULTS: After the surgery of facelift, appearances of the patients were markedly improved. Histological studies revealed significant changes in the skin, characterized by hyperplasia and thickening of the subcutaneous collagen, as well as an increase of PAS-positive substance. CONCLUSION: Alterations of fibroblast bioactivity might be responsible for the pathogenesis of pachydermoperiostosis. There have been no satisfying treatments to the disease. Facelift is a feasible method to improve the aging appearance of the patients.

Adult↗
PubMed2003

[Clinical applications of the buried-guided-suture method in the treatment of facial depression].

OBJECTIVE: To develop a method for the treatment of facial depression without incision scar. METHODS: In repairing the facial depression, the ruptured subdermal adipocellular tissue was approximated and reunite with the buried-guided-suture method through an intraoral or a concealed skin incision. RESULTS: 17 patients with facial depressions from trauma were treated. Postoperative follow-up of 10 patients for one year showed satisfactory results without recurrence. CONCLUSION: The buried-guided-suture method for repair of facial depression from trauma is simple, reliable and worth recommendation.

Adolescent↗
PubMed2002

Tyrosine phosphorylation of I kappa B alpha activates NF kappa B through a redox-regulated and c-Src-dependent mechanism following hypoxia/reoxygenation.

NF kappa B is a critical transcription factor involved in modulating cellular responses to environmental injuries. Tyrosine 42 phosphorylation of I kappa B alpha has been shown to mediate NF kappa B activation following hypoxia/reoxygenation (H/R) or pervanadate treatment. This pathway differs from the canonical proinflammatory pathways, which mediate NF kappa B activation through serine phosphorylation of I kappa B alpha by the IKK complex. In the present study, we investigated the involvement of c-Src in the redox activation of NFkappaB following H/R or pervanadate treatment. Our results demonstrate that pervanadate or H/R treatment leads to tyrosine phosphorylation of I kappa B alpha and NF kappa B transcriptional activation independent of the IKK pathway. In contrast, inhibition of c-Src by pp2 treatment or in c-Src (-/-) knockout cell lines, demonstrated a significant reduction in I kappa B alpha tyrosine phosphorylation and NF kappa B activation following pervanadate or H/R treatment. Overexpression of glutathione peroxidase-1 or catalase, but not Mn-SOD or Cu,Zn-SOD, significantly reduced both NF kappa B activation and tyrosine phosphorylation of I kappa B alpha. In vitro kinase assays further demonstrated that immunoprecipitated c-Src has the capacity to directly phosphorylate GST-I kappa B alpha and that this I kappa B alpha kinase activity is significantly reduced by Gpx-1 overexpression. These results suggest that c-Src-dependent tyrosine phosphorylation of I kappa B alpha and subsequent activation of NF kappa B is controlled by intracellular H(2)O(2) and defines an important redox-regulated pathway for NF kappa B activation following H/R injury that is independent of the IKK complex.

Hypoxia↗
PubMed2002

Modulation of the human polycystin-L channel by voltage and divalent cations.

Polycystin-L (PCL) is highly homologous in sequence and membrane topology to polycystin-2, the product of the second gene responsible for autosomal dominant polycystic kidney disease (ADPKD). PCL and polycystin-2 were recently shown to be Ca2+-permeable, Ca2+-activated cation channels. Further characterization of polycystins will help in the understanding of cystogenesis and pathogenesis of ADPKD. In the present study, we expressed human PCL in Xenopus oocytes and studied its function utilizing patch-clamp and two-electrode voltage clamp techniques. In addition to its permeability to Ca2+, K+ and Na+, PCL was highly permeable to NH4+ and Cs+ with a permeability ratio NH4+:Cs+:Na+ of 2.2:1.02:1. Voltage modulation of channel properties was studied using cell-attached (C-A) and excised inside-out (I-O) patches. In the C-A mode, the open probability (NP(o)) of PCL at negative potentials (NP(o)=0.22) was higher than at positive potentials (NP(o)=0.05). The mean open time averaged 31.6 ms at negative potentials, and 6.2 ms at positive potentials; single-channel activity exhibited bursts with a mean interburst time of 178 ms. Using I-O patches under symmetrical ionic conditions, single-channel inward conductance was significantly larger than outward conductance, indicating a slight inward rectification. External Mg2+ inhibited the PCL channel currents. The inhibitory effect was voltage-dependent and substantially reduced by depolarization. The time course of inactivation depended on external calcium concentration but was independent of voltage and peak current. This study shows that although PCL is not a voltage-gated channel, its channel activity and inhibition by Mg2+ are modulated by membrane potential.

Animals↗
PubMed2002

Endogenous released ascorbic acid suppresses ethanol-induced hydroxyl radical production in rat striatum.

Previous studies have shown that acute systemic administration of ethanol induced ascorbic acid release in the striatum. However, the pharmacological implications of ethanol-induced striatal ascorbic acid release are unclear. In the present study, ethanol-induced extracellular changes of ascorbic acid and hydroxyl radical levels were detected in rat striatum by using brain microdialysis coupled to high-performance liquid chromatography with electrochemical detection. It was found that both in male and female rats, ethanol (3.0 g/kg, i.p.) increased striatal ascorbic acid release in the first 60 min after ethanol administration. Meanwhile, the extracellular hydroxyl radical levels, detected as 2,3- and 2,5-DHBA, were significantly decreased. However, when the ascorbic acid levels returned to the baseline, hydroxyl radical levels rebounded. Administration of DL-fenfluramine (20 mg/kg, i.p.) had no effect on the basal levels of ascorbic acid and hydroxyl radical, but significantly blocked ethanol-induced ascorbic acid release and increased hydroxyl radical levels significantly. Exogenous administration of ascorbic acid (20 mg/kg, s.c.) increased the extracellular levels of ascorbic acid in the striatum, and inhibited the increase of 2,3- and 2,5-DHBA in DL-fenfluramine plus ethanol group. These results provide first evidence that release of endogenous ascorbic acid in the striatum plays an important role in preventing oxidative stress by trapping hydroxyl radical in the central nervous system.

Alcohol-Induced Disorders, Nervous System↗
PubMed2002

NMDA receptor antagonists disinhibit rat posterior cingulate and retrosplenial cortices: a potential mechanism of neurotoxicity.

NMDA receptor antagonists produce region-specific neurodegeneration by an undetermined mechanism, but one proposed mechanism involves disinhibition. In certain areas of the brain, NMDA receptors mediate excitatory drive onto inhibitory interneurons. Thus, NMDA receptor/channel antagonists may reduce inhibition (i.e., produce "disinhibition"). If a sufficient level of disinhibition is produced, enhanced vulnerability to excitotoxicity may result. Furthermore, if there are region-specific differences in NMDA antagonist-induced disinhibition, this could underlie region-specific NMDA antagonist-induced neurotoxicity. In the present study, we tested this hypothesis by exposing rat brain slices to the NMDA receptor antagonist dizocilpine maleate (MK-801) and measuring MK-801-induced disinhibition in areas of higher and lower vulnerability to neurodegeneration [posterior cingulate/retrosplenial cortices (PCC/RSC) and parietal cortex, respectively]. Using whole-cell patch-clamp techniques, bicuculline-sensitive GABA(A) receptor-mediated IPSCs were measured in biocytin-labeled pyramidal neurons in the PCC/RSC and parietal cortex. In the PCC/RSC, bath-applied MK-801 (10-40 microm) produced disinhibition, shown as a concentration-dependent decrease in spontaneous IPSC frequency and amplitude; MK-801 (40 microm) also reduced evoked IPSC amplitudes. In parietal cortex, MK-801 produced significantly less disinhibition. To determine whether disinhibition is caused by presynaptic or postsynaptic mechanisms, we tested the effects of MK-801 (40 microm) against miniature IPSC (mIPSC) frequency and amplitude in tetrodotoxin (TTX; 0.5 microm)-treated slices and found that MK-801 did not alter mIPSC frequency or amplitude. Taken together, these results suggest that NMDA receptors regulate activity of inhibitory interneurons and, consequently, GABA release in certain cortical areas. This region-specific reduction in inhibitory input to pyramidal cells could underlie the region-specific neurotoxicity of NMDA antagonists.

Animals↗
PubMed2002

The calcium-binding EF-hand in polycystin-L is not a domain for channel activation and ensuing inactivation.

Polycystin-L (PCL) shares high homology with polycystin-2, the product of polycystic kidney disease gene-2. It was previously shown that the PCL forms a non-selective cation channel activated by calcium influx. However, it remains unclear whether calcium activates/inactivates PCL by binding to the EF-hand motif located on the cytoplasmic carboxyl-terminus. Here we obtained two PCL splice variants from liver (PCL-LV, lacking the EF-hand) and testis (PCL-TS, lacking 45 amino acids on the carboxyl tail) using PCR-based approaches. When expressed in Xenopus oocytes and studied using electrophysiology both splice variants exhibited basal cation channel activity and calcium-induced channel activation. While PCL-TS displayed similar activation to PCL, PCL-LV exhibited a three-fold increased activation. All five PCL C-terminal artificial truncation mutants also exhibited basal and calcium-activated channel activities, in particular the mutant T622X lacking the EF-hand was associated with increased activation. Our data demonstrate that the EF-hand and other parts of the carboxyl tail of PCL are not determinants of channel activation/inactivation although the EF-hand seems to be involved in the modulation of these processes.

Alternative Splicing↗
PubMed2002

v-Ha-ras mitogenic signaling through superoxide and derived reactive oxygen species.

The ras proto-oncogene is frequently mutated in human tumors and functions to constitutively stimulate signal transduction cascades, resulting in unchecked proliferation and malignant transformation. In certain cells, superoxide functions as a signal-transduction messenger, mediating the downstream effects of ras and rac. We demonstrated previously that v-Ha-ras-transfected rat kidney epithelial cells (RECs) overproduced superoxide anion and that this superoxide production was mediated by ras. In the present study, we further demonstrated that v-Ha-ras overexpression transformed immortal nonmalignant RECs into malignant cancer cells; v-Ha-ras-transfected cells formed clones in soft agar, had high plating efficiency, and formed tumors in nude mice. Our data suggest that superoxide radical plays a role in ras-induced transformation; modulation of intracellular superoxide level by overexpression of manganese-containing superoxide dismutase or copper- and zinc-containing superoxide dismutase inhibited ras-induced transformation, as evidenced by in vitro studies of plating efficiency and by in vivo studies of tumor formation in nude mice. Overexpression of catalase (CAT) alone was found to have little effect on tumor cell growth, but overexpression of glutathione peroxidase 1 (GPx1) completely suppressed tumor cell growth in nude mice. This finding suggests that peroxides removed by GPx1, but not by CAT, are also involved in ras-induced transformation.

Animals↗
PubMed2002

Expression and purification of Rhizobium leguminosarum NodD.

A Rhizobium expression system was constructed via introducing strong transcriptional elements to an IncP broad host range plasmid pKT230. Using this system, the nodD gene of Rhizobium leguminosarum biovar viciae was overexpressed in its own in vivo environment. Western blot showed that the NodD yield of the newly constructed expression vector pKNDT was much higher than that of a reported vector pIJ1518. Based on the result from quantitative gel retardation assay, the specific DNA-binding activity of NodD was estimated to increase by about 80-fold. Purification of NodD was performed by the sequential steps: polyethyleneimine treatment, ammonium sulfate fractional precipitation, and cellulose phosphate P11 chromatography. About 26 mg NodD with a purity about 90% was obtained from 14 g wet weight cell pellet within 2 days.

Bacterial Proteins↗
PubMed2002

Identification of transcripts expressed under functional differentiation in primary culture of cerebral cortical neurons.

In this study, we utilized primary cultures of cerebral cortical neurons and RNA arbitrarily primed polymerase chain reaction (RAP-PCR) to identify differentially expressed transcripts in neurons of different culture ages. Eleven cDNA fragments with high sequence similarity to known genes and Expressed Sequence Tags (ESTs) were cloned. From the National Center for Biotechnology Information (NCBI) sequence database, two clones were shown to be identical to known sequences, Mus musculus HP1-BP74 protein mRNA and Mus musculus KRAB-containing zinc finger protein, both were up-regulated. These genes have never before been shown to be involved in neuronal functional maturation. Among the remaining clones, clone 8-14 (239 bp) was very similar to Rattus norvegicus rS-Rex-b mRNA, which was further confirmed by sequencing its shortest isoform (1.5 kb) obtained by computer cloning. This study has identified eleven potential genes and transcripts, which might be involved in the development and differentiation of GABAergic neurons in culture.

Animals↗
PubMed2002

Histone acetyltransferase activities of cAMP-regulated enhancer-binding protein and p300 in tissues of fetal, young, and old mice.

CBP, a protein that binds to cyclic adenosine monophosphate-regulated enhancer-binding protein, and homologue protein, p300, have histone acetyltransferase (HAT) activity and are important in gene transcription, although their physiological functions in vivo remain to be further elucidated. By using immunoprecipitation and HAT activity assay we have found that p300 and CBP have similar tissue patterns of HAT activities, with the highest level in the brain, a relatively high level in the lung, spleen, and heart, an intermediate level in testes and muscle, and a lower level in liver and kidney; that HAT activities of p300 and CBP are relatively stable with advancing age in most examined tissues, but in liver, muscle, and testes, the activities are attenuated with aging; and that HAT activities of p300 and CBP are high in the brain and liver of E14 fetal and newborn mice. These data suggest that the HAT activities of p300 and CBP are important for gene transcription involved in tissue-specific expression, aging, and developing processes.

Acetylation↗
PubMed2002

Automated computerized scheme for distinction between benign and malignant solitary pulmonary nodules on chest images.

A novel automated computerized scheme has been developed to assist radiologists for their distinction between benign and malignant solitary pulmonary nodules on chest images. Our database consisted of 55 chest radiographs (33 primary lung cancers and 22 benign nodules). In this method, the location of a nodule was indicated first by a radiologist. The difference image with a nodule was produced by use of filters and then represented in a polar coordinate system. The nodule was segmented automatically by analysis of contour lines of the gray-level distribution based on the polar-coordinate representation. Two clinical parameters (age and sex) and 75 image features were determined from the outline, the image, and histogram analysis for inside and outside regions of the segmented nodule. Linear discriminant analysis (LDA) and knowledge about benign and malignant nodules were used to select initial feature combinations. Many combinations for subgroups of 77 features were evaluated as input to artificial neural networks (ANNs). The performance of ANNs with the selected 7 features by use of the round-robin test showed Az = 0.872, which was greater than Az = 0.854 obtained previously with the manual method (P= 0.53). The performance of LDA (Az = 0.886) was slightly improved compared to that of ANNs (P = 0.59) and was greater than that of the manual method (Az = 0.854) reported previously (P = 0.40). The high level of its performance indicates the potential usefulness of this automated computerized scheme in assisting radiologists as a second opinion for distinction between benign and malignant solitary pulmonary nodules on chest images.

Adult↗
PubMed2002

Development of a computerized method for identifying the posteroanterior and lateral views of chest radiographs by use of a template matching technique.

In picture archiving and communications systems (PACS) or digital archiving systems, the information on the posteroanterior (PA) and lateral views for chest radiographs is often not recorded or is recorded incorrectly. However, it is necessary to identify the PA or lateral view correctly and automatically for quantitative analysis of chest images for computer-aided diagnosis. Our purpose in this study was to develop a computerized method for correctly identifying either PA or lateral views of chest radiographs. Our approach is to examine the similarity of a chest image with templates that represent the average chest images of the PA or lateral view for various types of patients. By use of a template matching technique with nine template images for patients of different size in two steps, correlation values were obtained for determining whether a chest image is either a PA or a lateral view. The templates for PA and lateral views were prepared from 447 PA and 200 lateral chest images. For a validation test, this scheme was applied to 1,000 test images consisting of 500 PA and 500 lateral chest radiographs, which are different from training cases. In the first step, 924 (92.4%) of the cases were correctly identified by comparison of the correlation values obtained with the three templates for medium-size patients. In the second step, the correlation values with the six templates for small and large patients were compared, and all of the remaining unidentifiable cases were identified correctly.

Databases as Topic↗
PubMed2002

Detection of lung nodules on digital chest radiographs: potential usefulness of a new contralateral subtraction technique.

PURPOSE: To evaluate the potential usefulness of a contralateral subtraction technique developed for radiologists' performance in the detection of subtle lung nodules on chest radiographs. MATERIALS AND METHODS: Fifty chest radiographs (25 normal and 25 abnormal with a subtle lung nodule) that were digitized with a 0.175-mm pixel size and 4,096 gray levels were used. Twelve radiologists (10 attending and two residents) participated in observer tests and read both original and contralateral subtraction images with a sequential testing method. Radiologists' performance was evaluated by means of receiver operating characteristic analysis with use of a continuous rating scale. The beneficial and detrimental effects of the contralateral subtraction technique on the radiologists' performance were also evaluated. RESULTS: The area under the receiver operating characteristic curve values obtained without and with contralateral subtraction images were 0.926 and 0.962, respectively. Results indicated that the contralateral subtraction images significantly (P <.05) improved diagnostic accuracy, particularly for radiologists with limited experience. CONCLUSION: The contralateral subtraction technique can assist radiologists in the correct identification of subtle lung nodules on chest radiographs.

Humans↗