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Biomedical subjects

Mei Zhang

Publications and source records attributed to Mei Zhang.

At least 37 records · Page 2Linked to original sources
PubMed2006

Regulation of the mouse protein targeting to glycogen (PTG) promoter by the FoxA2 forkhead protein and by 3',5'-cyclic adenosine 5'-monophosphate in H4IIE hepatoma cells.

The scaffolding protein, protein targeting to glycogen (PTG), orchestrates the signaling of several metabolic enzymes involved in glycogen synthesis. However, little is known concerning the regulation of PTG itself. In this study, we have cloned and characterized the mouse promoter of PTG. We identified multiple FoxA2 binding sites within this region. FoxA2 is a member of the forkhead family of transcription factors that has recently been implicated in the cAMP-dependent regulation of several genes involved in liver metabolism. Using luciferase reporter constructs, we demonstrate that FoxA2 transactivates the PTG promoter in H4IIE hepatoma cells. Nuclear extracts prepared from mouse liver and H4IIE cells were able to bind a FoxA2-specific probe derived within the PTG promoter region. Chromatin immunoprecipitation experiments further demonstrate that FoxA2 binds to the PTG promoter in vivo. Finally, we show that treatment with cAMP analogs activates the PTG promoter and significantly increases PTG levels in H4IIE cells. Our results provide a framework to investigate how additional transcription factors may regulate PTG expression in other cell types.

Animals↗
PubMed2006

The fate of platinum(II) and platinum(IV) anti-cancer agents in cancer cells and tumours.

SRIXE mapping has been used to gain insight into the fate of platinum(II) and platinum(IV) complexes in cells and tumours treated with anticancer active complexes to facilitate the development of improved drugs. SRIXE maps were collected of thin sections of human ovarian (A2780) cancer cells treated with bromine containing platinum complexes, cis-[PtCl(2)(3-Brpyr)(NH(3))] (3-Brpyr=3-bromopyridine) and cis,trans,cis-[PtCl(2)(OAcBr)(2)(NH(3))(2)] (OAcBr=bromoacetate), or a platinum complex with an intercalator attached cis-[PtCl(2)(2-[(3-aminopropyl)amino]-9,10-anthracenedione)(NH(3))]. After 24h the complexes appear to be localised in the cell nucleus with a lower concentration in the surrounding cytoplasm. In cells treated with cis-[PtCl(2)(3-Brpyr)(NH(3))] the concentration of bromine was substantially higher than in control cells and the bromine was co-localised with the platinum consistent with the 3-bromopyridine ligand remaining bound to the platinum. The cells treated with cis,trans,cis-[PtCl(2)(OAcBr)(2)(NH(3))(2)] also showed an increased level of bromine, but to a much lesser extent than for those treated with cis-[PtCl(2)(3-Brpyr)(NH(3))] suggestive of substantial reduction of the platinum(IV) complex. Maps were also collected from thin sections of a 4T1.2 neo 1 mammary tumour xenograft removed from a mouse 3h after treatment with cis,trans,cis-[PtCl(2)(OH)(2)(NH(3))(2)] and revealed selective uptake of platinum by one cell.

Animals↗
PubMed2006

XANES investigation of the Co oxidation state in solution and in cancer cells treated with Co(III) complexes.

XANES spectroscopy has been used to investigate whether it is possible to determine the oxidation state and coordination environment of Co complexes following treatment of cancer cells with Co(III) or Co(II) complexes. Our results show that the variation of the XANES with coordination geometry make it impossible to do this in a completely reliable way which is in contrast to the situation for platinum and chromium. It was established that the XANES spectrum obtained from cells treated with [Co(diNOsar)]Br(3) remained unchanged with respect to its XANES spectrum obtained in solution, demonstrating that the [Co(diNOsar)]Br(3) complex remained intact after 24h in cellular media (diNOsar=1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane). In contrast, the XANES spectra obtained from cells treated with Na[Co(acac)(3)] and [Co(acac)(3)] differed from the XANES spectra of the respective complexes obtained in solution, indicating a change in co-ordination environment for both complexes upon uptake in cells. The similarity of these spectra suggests that appearance of this XANES can be used as an indication of loss of the carrier ligands, a useful indicator in the study of hypoxia selective complexes. The results obtained for Na[Co(acac)(3)] and [Co(acac)(3)] are consistent with the intracellular coordination of cobalt(III) to sulfur ligands upon cellular uptake.

Cobalt↗
PubMed2006

Isolation of an eclosion hormone gene from the cotton bollworm, Helicoverpa armigera: temporal and spatial distribution of transcripts.

The cDNA encoding eclosion hormone (EH), which plays an integral role in triggering ecdysis behavior at the end of each molt, was cloned from the cotton bollworm, Helicoverpa armigera (Har) (Lepidoptera: Noctuidae). The EH polyprotein precursor contains a 26-amino acid signal peptide and a single 62-amino acid mature EH. Compared the mature Har-EH with other known EHs, it shows 94%, 84%, and 59% identities to Manduca sexta, Bombyx mori, and Drosophila melanogaster, respectively. Har-EH mRNA is expressed only in the brain by Northern blot and RT-PCR, but not in other tissues. By in situ hybridization and immunocytochemistry, both Har-EH mRNA and protein are localized in two pairs of neurosecretory cells of the brain. Prior to a molt, expression level of Har-EH gene reaches the highest point, and then drops after molt. EH release is detected both centrally, within the ganglia, and peripherally, into the hemolymph. A peak of the EH titer in hemolymph measured by ELISA presents at ecdysis. These results are consistent with the biological function of Har-EH associated with ecdysis. Furthermore, Har-EH gene is expressed throughout all of the developmental stages examined, implicating that the EH gene may possess other biological functions in post-embryonic development other than triggering ecdysis behavior.

Amino Acid Sequence↗
PubMed2006

Resident stem cells are not required for exercise-induced fiber-type switching and angiogenesis but are necessary for activity-dependent muscle growth.

Skeletal muscle undergoes active remodeling in response to endurance exercise training, and the underlying mechanisms of this remodeling remain to be defined fully. We have recently obtained evidence that voluntary running induces cell cycle gene expression and cell proliferation in mouse plantaris muscles that undergo fast-to-slow fiber-type switching and angiogenesis after long-term exercise. To ascertain the functional role of cell proliferation in skeletal muscle adaptation, we performed in vivo 5-bromo-2'-deoxyuridine (BrdU) pulse labeling (a single intraperitoneal injection), which demonstrated a phasic increase (5- to 10-fold) in BrdU-positive cells in plantaris muscle between days 3 and 14 during 4 wk of voluntary running. Daily intraperitoneal injection of BrdU for 4 wk labeled 2.0% and 15.4% of the nuclei in plantaris muscle in sedentary and trained mice, respectively, and revealed the myogenic and angiogenic fates of the majority of proliferative cells. Ablation of resident stem cell activity by X-ray irradiation did not prevent voluntary running-induced increases of type IIa myofibers and CD31-positive endothelial cells but completely blocked the increase in muscle mass. These findings suggest that resident stem cell proliferation is not required for exercise-induced type IIb-to-IIa fiber-type switching and angiogenesis but is required for activity-dependent muscle growth. The origin of the angiogenic cells in this physiological exercise model remains to be determined.

Adaptation, Physiological↗
PubMed2006

Impact of Chinese guidelines for management of patients with acute myocardial infarction on outcomes of hospitalized patients.

BACKGROUND: The first Chinese guidelines for the diagnosis and management of patients with acute myocardial infarction (AMI) were issued by the Cardiovascular Branch of the Chinese Medical Association, the Editorial Board of the Chinese Journal of Cardiology, and the Editorial Board of the Chinese Circulation Journal in December 2001. However, it is still unclear whether these guidelines have produced a major impact on clinical practice and patient outcomes. The purpose of this study was to evaluate the impact of these guidelines on the management and prognosis of Chinese patients with AMI. METHODS: A retrospective study was carried out in patients with AMI who were admitted to Qilu Hospital of Shandong University from January 1994 to December 2004. Patients were divided into two groups: group A included patients admitted from January 1994 to December 2001, and group B comprised those admitted from January 2002 to December 2004. Therapeutic approaches and the occurrence rate of angina pectoris, reinfarction, heart failure and death during hospitalization were compared between two groups. RESULTS: A total of 1783 patients including 1208 cases in group A and 575 cases in group B were enrolled in this study. No significant difference was found in baseline characteristics between group A and group B patients (all P > 0.05). There were more patients undergoing reperfusion therapy within the first 24 hours after symptom onset in group B than in group A (35.8% vs 21.7%, P < 0.001). Administration of beta-blockers, angiotensin-converting-enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), statins, and heparins were more commonly seen in group B than in group A (P < 0.001). There were no significant differences in the use of nitrates or antiplatelet drugs between groups A and B (98.8% vs. 97.9%, P = 0.172, and 97.4% vs 98.6%, P = 0.113, respectively). In-hospital angina pectoris, heart failure and death were all lower in group B than in group A (32.2% vs 41.2%, P < 0.001; 17.2% vs 26.2%, P < 0.001; and 6.4% vs 9.4%, P = 0.038, respectively). There was no significant difference in the rate of reinfarction between group A and B patients (2.2% vs 1.7%, P = 0.492). CONCLUSIONS: Chinese guidelines for the management of patients with AMI issued in December 2001 resulted in changes in therapy that led to a significant improvement of in-hospital outcomes but not in the rate of reinfarction in patients with AMI.

Adrenergic beta-Antagonists↗
PubMed2006

Synthesis of substituted benzylamino- and heterocyclylmethylamino carbodithioate derivatives of 4-(3H)-quinazolinone and their cytotoxic activity.

A new series of substituted benzylamino- and heterocyclylmethylamino carbodithioate derivatives of 4-(3H)-quinazolinone were synthesized via four steps starting from 2-amino-5-methylbenzoic acid and initially screened against A-549 (human non-small cell lung cancer), HCT-8 (human colon cancer), and Bel-7402 (human liver cancer) cell lines at the single concentration of 5 microg/mL using the colorimetric MTT assay. The IC50 values were determined for the compounds reaching > or = 70% inhibition in primary screening by serial dilution. Among the newly synthesized compounds, 9n exhibited potent in vitro cytotoxicity against A-549, HCT-8, and Bel-7402 cell lines with the IC50 values of 1.65, 0.93, and 1.43 microM, respectively.

Antineoplastic Agents↗
PubMed2006

Joint capsule matrix turnover in a rabbit model of chronic joint contractures: Correlation with human contractures.

To evaluate changes in matrix molecules of the joint capsule, the right knees of 24 skeletally mature female NZW rabbits were immobilized while the contralateral limb served as an unoperated control. The immobilization was discontinued at 8 weeks and the rabbits were divided among four groups (n = 6) based on the number of weeks the right knees were remobilized: 0, 8, 16, or 32. Three rabbits (six knees) that did not have operations provided normal control joint capsules. The mRNA levels for collagen types I, II, and III, and MMP-1 and -13 were significantly increased in the joint capsules of the contracture knees in all groups when compared to normal and contralateral limb joint capsules. In contrast, the mRNA levels for TIMP-1, -2, and -3 were decreased in the joint capsules of the contracture knees in all groups when compared to normal and contralateral limb joint capsules. The mRNA levels for lumican and decorin were increased in the joint capsules of the contracture knees in all groups when compared to normal capsules. Many of the changes observed in this animal model are similar to those observed in human joint capsules from posttraumatic elbow contractures, supporting the value of this rabbit model.

Animals↗
PubMed2006

Hearing loss with stapedotomy and treated otitis media.

OBJECTIVE: To determine if treated Pseudomonas aeruginosa otitis media (PA OM) increases the risk of sensorineural hearing loss (SNHL) with stapedotomy. STUDY DESIGN AND SETTING: PA OM was induced in 28 guinea pigs. Half of the animals underwent unilateral stapedotomy before antibiotic therapy (untreated), and half underwent stapedotomy after treatment (treated). Control animals underwent saline injections followed by stapedotomy. Electrocochleographic thresholds were measured before and after stapedotomy. Temporal bones were analyzed histomorphologically. RESULTS: Less SNHL was seen after stapedotomy in treated ears than in untreated ears (P = 0.0268). SNHL after stapedotomy in treated ears was similar to controls (P = 0.9370). Severe damage to cochlear outer hair cells was found in untreated ears. CONCLUSIONS: Ears with PA OM treated previously are not at increased risk of SNHL with stapedotomy. SIGNIFICANCE: Stapedotomy may be carried out with caution in the setting of inactive, chronic OM.

Animals↗
PubMed2006

Scalable purification of Bacillus anthracis protective antigen from Escherichia coli.

The anthrax toxin consists of three proteins, protective antigen (PA), lethal factor, and edema factor that are produced by the Gram-positive bacterium, Bacillus anthracis. Current vaccines against anthrax use PA as their primary component. In this study, we developed a scalable process to produce and purify multi-gram quantities of highly pure, recombinant PA (rPA) from Escherichia coli. The rPA protein was produced in a 50-L fermentor and purified to >99% purity using anion-exchange, hydrophobic interaction, and hydroxyapatite chromatography. The final yield of purified rPA from medium cell density fermentations resulted in approximately 2.7 g of rPA per kg of cell paste (approximately 270 mg/L) of highly pure, biologically active rPA protein. The results presented here exhibit the ability to generate multi-gram quantities of rPA from E. coli that may be used for the development of new anthrax vaccines and anthrax therapeutics.

Antigens, Bacterial↗
PubMed2006

In vivo and in vitro inhibitory effect of amniotic extraction on neovascularization.

PURPOSE: To prepare amniotic extraction (AE) and to test its antiangiogenic effect in vivo and in vitro. METHODS: AE was prepared and diluted to 50, 100, and 200 microg/mL concentrations. Alkali burn-induced corneal neovascularization (NV) was produced and topically treated with different concentrations of AE or 0.1% dexamethasone for 7 days. Normal saline was used as a control. Corneal NV was visualized by heart perfusion of Chinese ink and quantified as the percentage of corneal NV area to the whole corneal area. Human umbilical vein endothelial cells (HUVECs) were primarily cultured. The effects of AE on proliferation and tube formation of HUVECs were tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and in vitro angiogenesis assay. Pigment epithelium-derived factor (PEDF) in AE was detected by Western blot. RESULTS: Relative corneal NV area in the control group was 56.6% +/- 9.9%, which was significantly reduced by 50 microg/mL AE (47.6% +/- 6.9%; P = 0.043) and 200 microg/mL AE (34.3% +/- 7.8%; P < 0.001) and by 0.1% dexamethasone (21.1% +/- 1.8%; P < 0.001). HUVEC cell proliferation was significantly decreased after treatment with AE at concentrations of 50 and 100 microg/mL compared with control (P = 0.036 and 0.001, respectively). The tube formation was significantly suppressed by 100 microg/mL AE (70.03% +/- 4.35%) compared with control (100% +/- 4.84%; P = 0.002). No expression of PEDF was detected in AE. CONCLUSION: AE inhibits NV induced by alkali burn. This effect may be elicited at least in part through the inhibiting activity of blood vessel endothelial cells and is not associated with PEDF.

Amnion↗
PubMed2006

Effects of a smoke-free law on hair nicotine and respiratory symptoms of restaurant and bar workers.

OBJECTIVE: Bar and restaurant workers' exposure to secondhand smoke (SHS) was compared before and 3 and 6 months after implementation of a smoke-free ordinance. METHODS: Hair nicotine, self-reported exposure to SHS, and respiratory symptoms were assessed on 105 smoking and nonsmoking workers from randomly selected establishments in Lexington, Kentucky. Thirty-eight percent were current smokers with more than half smoking 10 or fewer cigarettes per day. Workers provided a hair sample at baseline and at the 3-month interview. RESULTS: There was a significant decline in hair nicotine 3 months postlaw when controlling for cigarettes smoked per day. Bar workers showed a significantly larger decline in hair nicotine compared with restaurant workers. The only significant decline in SHS exposure was in the workplace and other public places. Regardless of smoking status, respiratory symptoms declined significantly postlaw. CONCLUSIONS: Hospitality workers demonstrated significant declines in hair nicotine and respiratory symptoms after the law. Comprehensive smoke-free laws can provide the greatest protection to bar workers who are the most vulnerable to SHS exposure at work.

Adolescent↗
PubMed2006

Quantification of infant exposure to celecoxib through breast milk.

AIMS: To determine the milk-to-plasma (M/P) concentration ratio of celecoxib, and estimate likely infant exposure. METHODS: Blood and milk were sampled for 48 h after oral administration of celecoxib 200 mg to six lactating volunteers. The M/P ratio was derived from the area under the concentration-time curves (0-infinity) and the infant 'dose' estimated from celecoxib concentrations in milk. RESULTS: The median (range) M/P ratio was 0.18 (0.15-0.26). The median (range) infant 'dose' was 0.23% (0.17-0.30%) of the maternal dose, adjusted for weight. CONCLUSION: The relative 'dose' of celecoxib to which infants are exposed via milk is very low, suggesting that breastfeeding during routine dosing would pose minimal risk.

Administration, Oral↗
PubMed2006

Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother-infant pairs.

AIMS: To determine infant exposure to 6-thioguanine and 6-methylmercaptopurine nucleotides (6-TGN and 6-MMPN, respectively) during maternal use of azathioprine in breastfeeding. METHODS: Mother-infant pairs provided blood for determination of 6-TGN and 6-MMPN concentrations, and TPMT genotype. RESULTS: Four women taking azathioprine 1.2-2.1 mg kg(-1) day(-1) and their infants were studied. All had the wild-type TPMT genotype. Maternal 6-TGN and 6-MMPN concentrations ranged from 234 to 291 and 284 to 1178 pmol per 8 x 10(8) red blood cells, respectively, and were consistent with those associated with improved therapeutic outcomes. Neither 6-TGN nor 6-MMPN was detected in any of the infants, despite a sensitive assay. CONCLUSIONS: The data suggest that azathioprine may be 'safe' during breastfeeding in patients with the wild-type TPMT genotype ( approximately 90% of caucasian patients) taking 'normal' doses.

Adult↗
PubMed2006

Balance of purines may determine life or death of retinal ganglion cells as A3 adenosine receptors prevent loss following P2X7 receptor stimulation.

The purines ATP and adenosine can act as a coordinated team of transmitters. As extracellular adenosine is frequently derived from the enzymatic dephosphorylation of released ATP, the distinct actions of the two purines can be synchronized. In retinal ganglion cells (RGCs), stimulation of the P2X7 receptor for ATP leads to increased intracellular Ca2+ and death. Here we define the contrasting effects of adenosine and identify protective actions mediated by the A3 receptor. Adenosine attenuated the rise in Ca2+ produced by the P2X7 agonist 3'-O-(4-benzoylbenzoyl)ATP (BzATP). Adenosine was also neuroprotective, increasing the survival of ganglion cells exposed to BzATP. The A3 adenosine receptor agonist 2-chloro-N6-(3-iodobenzyl)-adenosine-5'-N-methyluronimide (Cl-IB-MECA) mimicked the inhibition of the Ca2+ rise, whereas the A3 antagonist 3-Ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191) reduced the protective effects of adenosine. Both Cl-IB-MECA and a second A3 receptor agonist IB-MECA reduced the cell loss triggered by BzATP. The actions of BzATP were mimicked by ATPgammaS, but not by ATP. In summary, adenosine can stop the rise in Ca2+ and cell death resulting from stimulation of the P2X7 receptor on RGCs, with the A3 adenosine receptor contributing to this protection. Hydrolysis of ATP into adenosine and perhaps inosine shifts the balance of purinergic action from that of death to the preservation of life.

Adenosine Triphosphate↗
PubMed2006

Effect of resveratrol on NF-kappaB activity in rat peritoneal macrophages.

This study was to investigate the inhibitive effect of resveratrol (RESV) on nuclear factor kappa B (NF-kappaB) expression and activity induced by lipopolysaccharide (LPS) in rat peritoneal macrophages (PMA). Male Sprague-Dawley (SD) rats were randomly divided into 7 groups, including control group, LPS group and RESV I-V group. In the LPS group, PMA were incubated in DMEM containing LPS (10 microg/ml), whereas in control group, PMA were incubated in DMEM only. In the RESV I-V groups, PMA were incubated in DMEM containing LPS (10 microg/ml) and different concentrations of RESV. After 24 hours of incubation, NF-kappaB activity in PMA, and the levels of tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1) and nitric oxide (NO) in the culture medium were measured. In the concentrations of 1.25-5 microg/ml, RESV had a dose- dependent inhibitive effect on NF-kappaB activity in PMA as well as the expressions of TNF-alpha, IL-1 and NO in the culture medium contrasted with the LPS group. There was no significant difference in the levels of these pro-inflammatory factors between the groups of 5 microg/ml and 10 microg/ml RESV. In conclusion, RESV has the potential for the future application of preventing inflammatory diseases involving PMA.

Animals↗
PubMed2006

ERK, p38, and Smad signaling pathways differentially regulate transforming growth factor-beta1 autoinduction in proximal tubular epithelial cells.

Transforming growth factor (TGF)-beta1 is a mediator of the final common pathway of fibrosis associated with progressive renal disease, a process in which proximal tubular cells (PTCs) are known to play an important part. The aim of the current study was to examine the mechanism of PTC TGF-beta1 autoinduction. The addition of TGF-beta1 led to increased amounts of TGF-beta1 mRNA and increased de novo protein synthesis. The addition of TGF-beta1 led to increased phosphorylation of R-Smads and activation of extracellular signal-regulated kinase mitogen-activated protein (MAP) kinase and p38 MAP kinase pathways. Use of a dominant-negative Smad3 (Smad3 DN) expression vector, Smad3 small interfering RNA, and inhibition of extracellular signal-regulated kinase and p38 MAP kinase pathways with the chemical inhibitors PD98059 or SB203580 suggested that activation of these signaling pathways occurred independently. Smad3 DN expression, Smad3 small interfering RNA, or the addition of PD98059 inhibited TGF-beta1-dependent stimulation of TGF-beta1 mRNA. Furthermore, Smad3 blockade specifically inhibited activation of the transcription factor AP-1 by TGF-beta1, whereas PD98059 prevented TGF-beta1-dependent nuclear factor-kappaB activation. In contrast inhibition of p38 MAP kinase inhibited de novo TGF-beta1 protein synthesis but did not influence TGF-beta1 mRNA expression or activation of either transcription factor. In summary, in PTCs, TGF-beta1 autoinduction requires the coordinated action of independently regulated Smad and non-Smad pathways. Furthermore these pathways regulate distinct transcriptional and translational components of TGF-beta1 synthesis.

Cells, Cultured↗