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Biomedical subjects

Chao Zhang

Publications and source records attributed to Chao Zhang.

At least 73 records · Page 4Linked to original sources
PubMed2005

[Treatment of rabbit corneal with skin epidermal stem cells].

OBJECTIVE: To construct artificial rabbit corneas with autologous skin epidermal stem cells and allogenic stromal cells in vitro and promote healing of corneal wounds. METHODS: Skin epidermal stem cells were isolated from autologous skin samples. Keratocytes were isolated from newborn cornea biopsies. The cells were combined with acellular porcine corneal stroma scaffold to construct artificial corneas. Then the constructed artificial corneas were used to repair severe vision loss caused by complete loss of corneal epithelial stem cells. RESULTS: Cultured skin epidermal stem cells and keratocytes were in good growth conditions. Cultured artificial corneas consisted of multiplayer epithelial cells growing on stroma equivalent consisting of stromal matrix with incorporated keratocytes. The in vitro constructed artificial corneas were histologically similar to normal rabbit corneas. Three months after transplantation, the cornea wounds were healed and the rabbit cornea became transparent. CONCLUSION: The artificial corneas were constructed successfully in vitro and can be used to repair severe vision loss caused by complete loss of corneal epithelial stem cells.

Animals↗
PubMed2004

Pseudolaric acid B inhibits angiogenesis and reduces hypoxia-inducible factor 1alpha by promoting proteasome-mediated degradation.

PURPOSE: Pseudolaric acid B (PAB), the naturally occurring diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), possesses potent antifungal and pregnancy-terminating effects that may be tightly associated with angiogenesis. This study was to examine its angiogenic inhibition, impact on vascular endothelial growth factor (VEGF) secretion from tumor cells and the possible mechanism of action. EXPERIMENTAL DESIGN: Angiogenesis inhibition was assessed by the human umbilical vascular endothelial cell proliferation, migration, and tube-formation assays, as well as the chorioallantoic membrane assay. ELISA, reverse transcription-PCR, and Western blotting analyses were performed to examine VEGF protein secretion, mRNA expression, and the possible mechanism in hypoxic MDA-MB-468 cells. RESULTS: PAB displayed potent in vitro antiangiogenic activity shown by inhibiting VEGF-stimulated proliferation and migration and fetal bovine serum-stimulated tube formation of human umbilical vascular endothelial cells in a concentration-dependent manner. Moreover, PAB (10 nmol per egg) significantly suppressed in vivo angiogenesis in the chorioallantoic membrane assay. On the other hand, PAB abrogated hypoxia-induced VEGF secretion from MDA-MB-468 cells via reducing HIF-1alpha protein. Additional analyses using LY294002 and U0126 indicated that the increase in hypoxia-inducible factor 1 (HIF-1)alpha protein level was highly dependent on phosphatidylinositol 3'-kinase and p42/p44 mitogen-activated protein kinase activities in hypoxic MDA-MB-468 cells. However, PAB treatment did not affect the active (phosphorylated) forms of Akt and Erk. Interestingly, the selective proteasome inhibitor MG-132 completely reversed the reduction of HIF-1alpha protein in the PAB-treated MDA-MB-468 cells. CONCLUSIONS: PAB displays the dual antiangiogenic activities of directly inhibiting endothelial cells and abrogating paracrine stimulation of VEGF from tumor cells due to reducing HIF-1alpha protein by promoting its proteasome-mediated degradation in MDA-MB-468 cells, which has potential clinical relevance.

Animals↗
PubMed2004

A glutamine switch mechanism for nucleotide selectivity by phosphodiesterases.

Phosphodiesterases (PDEs) comprise a family of enzymes that modulate the immune response, inflammation, and memory, among many other functions. There are three types of PDEs: cAMP-specific, cGMP-specific, and dual-specific. Here we describe the mechanism of nucleotide selectivity on the basis of high-resolution co-crystal structures of the cAMP-specific PDE4B and PDE4D with AMP, the cGMP-specific PDE5A with GMP, and the apo-structure of the dual-specific PDE1B. These structures show that an invariant glutamine functions as the key specificity determinant by a "glutamine switch" mechanism for recognizing the purine moiety in cAMP or cGMP. The surrounding residues anchor the glutamine residue in different orientations for cAMP and for cGMP. The PDE1B structure shows that in dual-specific PDEs a key histidine residue may enable the invariant glutamine to toggle between cAMP and cGMP. The structural understanding of nucleotide binding enables the design of new PDE inhibitors that may treat diseases in which cyclic nucleotides play a critical role.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2004

Effects of bile reflux and intragastric microflora changes on lesions of remnant gastric mucosa after gastric operation.

AIM: To investigate the effects of bile reflux and intragastric microflora changes on lesions of remnant gastric mucosa after gastric operation. METHODS: Concentration of bile acid and total bacterial counts (TBC) in gastric juice were measured in 49 patients with peptic ulcer before and after gastrectomy. One year after the operation, sample of gastric mucosa taken from all the patients were used for histological examination. RESULTS: The concentration of gastric bile acid was significantly increased in group B-I, or B-II and SV+A than that in group HSV (P<0.05-0.01). The abnormal histological changes in the remnant gastric mucosa were more common in the first 2 groups than in the last group. CONCLUSION: The type of gastrectomy can affect bile reflux. The abnormal histological changes in the remnant gastric mucosa are closely related to the elevation of bile acid concentration and increase of TBC in gastric juice. HSV can effectively prevent bile reflux and keep the gastric physiological functions stable.

Adult↗
PubMed2004

Simultaneous determination of alpha-fetoprotein and free beta-human chorionic gonadotropin by element-tagged immunoassay with detection by inductively coupled plasma mass spectrometry.

BACKGROUND: An inductively coupled plasma mass spectrometry (ICP-MS)-based immunoassay has been proposed independently by Baranov et al. (Anal Chem 2002;74:1629-36) and our group, but the applicability of this method for multianalyte analysis in clinical samples has not been fully illustrated. We developed a dual-label immunoassay method for the simultaneous determination of alpha-fetoprotein (AFP) and free beta-human chorionic gonadotropin (hCGbeta) in human serum. METHODS: Monoclonal antibodies immobilized on microtiter plates captured AFP and hCGbeta, which were detected by use of Eu(3+)-labeled anti-AFP and Sm(3+)-labeled anti-hCGbeta monoclonal antibodies. Eu(3+) and Sm(3+) were dissociated from the immunocomplex with HNO(3) solution (10 mL/L) and delivered by peristaltic pump to the ICP mass spectrometer. RESULTS: The measurable ranges of AFP and hCGbeta were 4.6-500 and 5.0-170 microg/L, respectively, with detection limits of 1.2 and 1.7 microg/L (3 SD above mean of zero calibrator), respectively. The intraassay imprecision (CV) for AFP was 8.3%, 4.0%, and 2.7% at 16.3, 86, and 354 microg/L, respectively, and the interassay CV was 10%, 5.7%, and 3.5%. For hCGbeta, the intraassay CV was 5.4%, 6.4%, and 3.1%, respectively, at 10.5, 45.2, and 105 microg/L, and the interassay CV was 7.2%, 8.0%, and 3.7%. Comparison with IRMAs for AFP and hCGbeta yielded correlation coefficients (r(2)) of 0.97 and 0.95. CONCLUSIONS: Two proteins can be measured simultaneously by immunoassays using two rare earth elemental tags (Eu(3+) and Sm(3+)) and ICP-MS detection. The multielement capability and the multiple potential elemental labels make ICP-MS attractive for multianalyte immunoassays. Implementation of ICP-MS-linked immunoassays may be relatively straightforward because the labeling and immunoreaction procedures have been well developed for clinical time-resolved immunofluorometric assays.

Antibodies, Monoclonal↗
PubMed2004

Extraction of protoporphyrin disodium and its inhibitory effects on HBV-DNA.

AIM: To explore an ideal method for extracting protoporphyrin disodium (PPN) from unanticoagulated animal blood, and to study the inhibitory effects of PPN on HBV-DNA duplication and its cytotoxicity to 2.2.15 cell strain. METHODS: Protoporphyrin methyl ester and other intermediate products were prepared with protoheme separated from protein hydrolysates of coagulated animal blood, which were finally made into PPN and detected quantitatively with an ultraviolet fluorescent analyzer. Ten microg/ml, 20 microg/ml, 40 microg/ml, 80 microg/ml and 160 microg/ml of PPN-aqueous solution were added into culture medium for 2.2.15 cells respectively. Eight days later, the drug concentration in supernatant from the culture medium was detected when inhibition rate of HBeAg, cell survival rate when inhibition rate of HBeAg was 50% (ID50), and when survival cells in experimental group were 50% of those in control group (CD50), and the therapeutic index (TI) was also detected. PPN with different concentration of 10 microg/ml, 20 microg/ml, 40 microg/ml, 80 microg/ml and 160 microg/ml was respectively mixed and cultivated with HepG2 2.2.15 cell suspension, and then the inhibition of PPN against HBV-DNA was judged by PCR. RESULTS: The extract of henna crystal was identified to be PPN. When the concentrations of PPN were 160 microg/ml and 80 microg/ml, the inhibition rates of HBeAg were 89.8% and 82.4%, and the cell survival rates were 98.7% and 99.2%. CONCLUSION: It is suggested that PPN can be extracted from unanticoagulated animal blood. PPN can inhibit HBV-DNA expression and duplication in vitro, and has no cytotoxicity to liver cells. Further study and application of PPN are warranted.

Animals↗
PubMed2004

[Evaluate the effect of Nd:YAG laser in treatment of obstructive sleep apnea-hypopnea syndrome].

OBJECTIVE: To observe the effect of laser in treatment of obstructive sleep apnea-hypopnea syndrome (OSAHS). METHOD: Eighty-nine cases of OSAHS were treated by Laser assisted uvulopalptoplasty (LAUP). Among the cases, the soft palate and uvula were partly resected. The cureiform incise was made into the soft palate along the each side of uvula. RESULT: The follow-up period was six months, 76 cases received the detection of polysomnography. Eight cases were cured; 36 cases had notable effects; 25 cases had effects; 7 cases had no effects. The total ratio of validity was 90.8%. CONCLUSION: It has clinical value to use LAUP in treatment of OSAHS, and its advantage include hemostasia, solidfication, penetrability, clear visual threshold, lower complication and shortening the surgery time.

Adult↗
PubMed2004

[Bioinformatics studies on photosynthetic system genes in cyanobacteria and chloroplasts].

This study compared homology of base sequences in genes encoding photosynthetic system proteins of cyanobacteria (Synechocystics sp. PCC6803, Nostoc sp. PCC7120) with these of chloroplasts (from Marchantia Polymorpha, Nicotiana tobacum, Oryza sativ, Euglena gracilis, Pinus thunbergii, Zea mays, Odentella sinesis, Cyanophora paradoxa, Porphyra purpurea and Arabidopsis thaliana) by BLAST method. While the gene sequence of Synechocystics sp. PCC6803 was considered as the criterion (100%) the homology of others were compared with it. Among the genes for photosystem I, psaC homology was the highest (90.14%) and the lowest was psaJ (52.24%). The highest ones were psbD (83.71%) for photosystem II, atpB (79.58%) for ATP synthase and petB (81.66%) for cytochrome b6/f complex. The lowest ones were psbN (49.70%) for photosystem II, atpF (26.69%) for ATP synthase and petA (55.27%) for cytochrome b6/f complex. Also, this paper discussed why the homology of gene sequences was the highest or the lowest. No report has been published and this bioinformatics research may provide some evidences for the origin and evolution of chloroplasts.

Chloroplast Proton-Translocating ATPases↗
PubMed2004

[Long-term follow-up observation of clinical therapy for laryngeal carcinoma recurrence and cervical metastasis].

OBJECTIVE: To observe the long-term effects of clinical treatment for laryngeal carcinoma recurrence and cervical metastasis, and discuss the operative therapy method for laryngeal carcinoma recurrence and cervical metastasis. METHOD: Retrospective analysis the 70 patients with laryngeal carcinoma recurrence and cervical metastasis who was cured in our hospital from 1990 to 1998, including 31 local recurrence, 15 stomal recurrence and 24 cervical lymph node metastasis. RESULT: Sixty-four cases were observed over 3 years and 41 cases were studied over 5 years. Twenty-eight patients who received the second-time operation survived over 5 years. In 31 patients with local recurrence, 19 patients received total laryngectomy and 15 patients of them are now living, but 12 patients who did not accept surgical therapy were died in 1-3 years separately; 9 patients with stomal recurrence received the second-time operation and 5 of them lived 5 years longer, however, the 6 patients with stomal recurrence who did not accept the second-time operation all died in 18 months; In 24 patients with cervical lymph node metastasis, 15 patients received the neck dissection and 8 of them are now alive, but the rest patients who did not accept the operation died in 2 years. CONCLUSION: Regular re-examination and systemic clinical follow-up studying are very important for early detection and early treatment in laryngeal carcinoma recurrence and cervical metastasis; Second-time surgical operation is an effective therapeutic method for laryngeal carcinoma recurrence and cervical metastasis; Radiotherapy and chemotherapy play a limited role in clinical therapy for laryngeal carcinoma recurrence and cervical metastasis.

Adult↗
PubMed2004

[Selective quantitation of analgin by flow injection chemiluminescence method].

A new chemiluminescence-based method was proposed for selective quantitation of analgin in pharmaceutical preparation. The CL emission was generated by mixing analgin, polyethylene glycol-400 and rhodamine 6G in acidic medium. The analgin content could be determined by the CL intensity. No oxidants were used in the system, so it was difficult to explain why the CL emission was produced. The mechanism of CL emission remains under investigation. One of the advantages of this method is highly selective. No other pharmaceutical compounds and chemicals could produce CL emission whether they contain sulfuric group or not in the experiment. There was no disturbance in this method, which was different from others. Another advantage is high sensitivity. The quantitation range is from 0.01 to 10 microg x mL(-1) with a detection limit of 0.003 microg x mL(-1) for analgin. This is the lowest detection limit of any CL methods currently available for analgin determination. The proposed method was applied to the selective quantitation of analgin in pharmaceutical preparation.

Dipyrone↗
PubMed2003

Combinatorial efficacy achieved through two-point blockade within a signaling pathway-a chemical genetic approach.

Whether the apparent efficacy of a specific kinase inhibitor is attributable solely to inhibition of its primary target, or to combined inhibition of additional unidentified kinases, is a critical issue in cancer therapy. We used a chemical genetic approach to generate a selective inhibitor of v-erbB [a transforming allele of epidermal growth factor receptor (EGFR)] and interrogated inhibition in known downstream signaling pathways. On the basis of this analysis, we hypothesized that dual inhibition of v-erbB and phosphatidylinositol 3' (PI3) kinases could show improved potency. We, therefore, used two different cell lines to examine the effects of v-erbB or EGFR inhibitors, in combination with PI3 kinase inhibitors, in mouse models for EGFR-driven cancers. When treated with NaPP1, v-erbB-as1-transformed fibroblasts showed cell-cycle arrest and decreased activity of Akt kinase. Inhibitors of v-erbB-as1 and of PI3 kinase showed enhanced efficacy in treating established 3T3:v-erbB-as1 tumor allografts. We extended these results to the human glioma cell line U87:MG transduced with DeltaEGFR, a tumor-derived activated allele, treating tumor-bearing mice with vehicle, the EGFR inhibitor ZD1839, LY294002, or ZD1839 plus LY294002. In human glioma xenografts, inhibition of EGFR cooperated similarly with inhibition of PI3 kinase. Our experiments provide a preclinical mechanistic basis for combining biologically based therapies directed against two targets within a complex signaling cascade.

Animals↗
PubMed2003

Development of a porous poly(L-lactic acid)/hydroxyapatite/collagen scaffold as a BMP delivery system and its use in healing canine segmental bone defect.

A hydroxyapatite/collagen (HAC) composite was produced to mimic the natural extracellular matrix of bone, with the collagen serving as a template for apatite formation. A three-dimensional highly porous scaffold was developed by mixing HAC with poly(L-lactic acid) (PLA) using a thermally induced phase separation technique. Naturally derived bovine bone morphogenetic protein (bBMP) was incorporated into the porous HAC-PLA scaffolds, and the composite then was implanted in diaphyseal defects (2 cm in radius) of adult beagle dogs. Controls were implanted with scaffolds without BMP. The dogs were sacrificed at 6 months, at which time biocompatibility, biodegradability, and osteoinduction were evaluated by histologic and radiologic examination and by bone mineral density (BMD) measurements. All defects healed after treatment with BMP combined with HAC-PLA, and BMD at the site of the defect was higher than the BMD of the intact radius. Fibrous union developed in the control group animals. Histologic observation indicated that the presence of BMP not only promoted osteogenesis but that it also accelerated degradation of the biomaterials. Optimized design parameters of a three-dimensional porous biomaterial would give full scope to the role of BMP as an osteoinductive growth factor.

Animals↗
PubMed2003

Mek1 kinase activity functions downstream of RED1 in the regulation of meiotic double strand break repair in budding yeast.

Three meiosis-specific chromosomal components in budding yeast, Mek1, Red1, and Hop1, are required for recombination, proper segregation of homologs, and the meiotic recombination checkpoint. Mek1 is a protein kinase. Mutations that increase the size of the ATP binding pocket of Mek1 (mek1-as1) sensitize the kinase to specific small molecule inhibitors. Experiments using mek1-as1 demonstrate that the requirement for Mek1 kinase activity coincides with the formation of double strand breaks (DSBs) and that this activity is necessary after DSB formation to prevent repair by DMC1-independent pathways. Contrary to previous reports, Red1 is not a substrate for Mek1. Instead, RED1 is required for wild-type levels of Mek1 kinase activity. In addition, activation of Mek1 requires HOP1, the formation of Red1/Hop1 complexes and a functional Mek1 FHA domain. The requirement for RED1 to produce active kinase can be bypassed by a mek1 mutation that creates a constitutively active Mek1 kinase. We propose that Red1 is phosphorylated by a kinase other than MEK1 and that phosphothreonines on Red1 then interact with the Mek1 FHA domain to recruit the kinase to sites of DSBs where Mek1 is activated to prevent DMC1-independent DSB repair.

Adenosine Triphosphate↗
PubMed2003

Bypassing a kinase activity with an ATP-competitive drug.

Unfolded proteins in the endoplasmic reticulum cause trans-autophosphorylation of the bifunctional transmembrane kinase Ire1, which induces its endoribonuclease activity. The endoribonuclease initiates nonconventional splicing of HAC1 messenger RNA to trigger the unfolded-protein response (UPR). We explored the role of Ire1's kinase domain by sensitizing it through site-directed mutagenesis to the ATP-competitive inhibitor 1NM-PP1. Paradoxically, rather than being inhibited by 1NM-PP1, drug-sensitized Ire1 mutants required 1NM-PP1 as a cofactor for activation. In the presence of 1NM-PP1, drug-sensitized Ire1 bypassed mutations that inactivate its kinase activity and induced a full UPR. Thus, rather than through phosphorylation per se, a conformational change in the kinase domain triggered by occupancy of the active site with a ligand leads to activation of all known downstream functions.

Adenosine Diphosphate↗
PubMed2003

Dynamic phosphoregulation of the cortical actin cytoskeleton and endocytic machinery revealed by real-time chemical genetic analysis.

We used chemical genetics to control the activity of budding yeast Prk1p, which is a protein kinase that is related to mammalian GAK and AAK1, and which targets several actin regulatory proteins implicated in endocytosis. In vivo Prk1p inhibition blocked pheromone receptor endocytosis, and caused cortical actin patches to rapidly aggregate into large clumps that contained Abp1p, Sla2p, Pan1p, Sla1p, and Ent1p. Clump formation depended on Arp2p, suggesting that this phenotype might result from unregulated Arp2/3-stimulated actin assembly. Electron microscopy/immunoelectron microscopy analysis and tracking of the endocytic membrane marker FM4-64 revealed vesicles of likely endocytic origin within the actin clumps. Upon inhibitor washout, the actin clumps rapidly disassembled, and properly polarized actin patches reappeared. Our results suggest that actin clumps result from blockage at a normally transient step during which actin assembly is stimulated by endocytic proteins. Thus, we revealed tight phosphoregulation of an intrinsically dynamic, actin patch-related process, and propose that Prk1p negatively regulates the actin assembly-stimulating activity of endocytic proteins.

Actins↗
PubMed2003

Safety evaluation of organoarsenical species in edible Porphyra from the China Sea.

A study was carried out to determine arsenic species in Porphyra seaweed originating from the China Sea. Information about arsenic species in Porphyra was provided by HPLC-ICP-MS and ES-MS-MS. The total arsenic concentrations of Porphyra samples from five different producing areas ranged from 2.1 to 21.6 mg/kg. The analysis report also showed that arsenosugars were the only arsenic species that could be detected in all of the extracts of samples. Arsenosugar PO(4) was the major compound in most samples (0.3-13.9 mg/kg of dry weight), followed by arsenosugar OH (0.7-6.2 mg/kg of dry weight). A further experiment was done to investigate the stability of arsenosugars in the process of being heated. It was observed that the arsenosugars were stable during a short-term heating at 100 degrees C. Their stability in human ingestion was also studied. A substantial increase of dimethylarsinic acid (DMA) was detected in urine samples collected from six volunteers after the consumption of this seaweed. The results obtained indicated that arsenosugars had been metabolized to DMA, which is more toxic than arsenosugars. From this point of view, consumers should consider the possible adverse effects of edible Porphyra on human health and choose those Porphyra having lower arsenic concentrations.

Arsenates↗