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Biomedical subjects

Lei Zhang

Publications and source records attributed to Lei Zhang.

At least 343 records · Page 19Linked to original sources
PubMed2004

[Detection of residual leukemic cells after complete remission of patients with acute myeloid leukemia].

The aim was to study minimal residual disease (MRD) in blood and bone marrow after complete remission of patients with acute myeloid leukemia (AML) and explore the role of MRD in detecting relapse of acute myeloid leukemia. The blood and bone marrow samples from 33 AML patients who had been in complete remission were determined for residual leukemic cells (RLC) with flow cytometry. The results showed that RLC in AML group of complete remission was higher than that of normal group both in blood by (4.7518 +/- 4.1537)% vs (0.4835 +/- 0.2005)% and bone marrow by (17.9082 +/- 20.4819)% vs (0.7285 +/- 0.2209)%, while the RLC in relapsed group was higher than that in non-relapsed group both in blood by (2.233 +/- 1.5923)% vs (10.2369 +/- 9.4714)% and bone marrow by (4.779 +/- 3.0336)% vs (38.0685 +/- 19.4295)%. In conclusion, early detection of leukemic residual cells with flow cytometry contributes to treatment of relapse in time.

Acute Disease↗
PubMed2004

[Determination and identification of anions and cations in cosmetics].

A method was developed for the determination of anions and cations (Na+, NH4+, K+, Mg2+, Ca2+,Cl-, Br-, NO2- , NO3- and SO4(2-)) in cosmetics by using ion chromatography with conductometric detection. The eluent for determining anions was 1,2,4,5-benzenetetracarboxylic acid (2.0 mmol/L) with 1.0 mL/min flow rate on anion exchange column (ICS-C25), while that for cations was o-phthalic acid (2.5 mmol/L) and trihydroxyaminomethane (2.4 mmol/L ) with 0.6 mL/min flow rate on cation exchange column (Shim-pack IC-Al). The ions had good linear relations in wide range, and the recoveries were from 93% to 102%.

Anions↗
PubMed2004

Intrauterine infections and birth defects.

Intrauterine infection is an important cause of some birth defects worldwide. The most common pathogens include rubella virus, cytomegaloviurs, ureaplasma urealyticum, toxoplasma, etc. General information about these pathogens in epidemiology, consequence of birth defects, and the possible mechanisms in the progress of birth defects, and the interventions to prevent or treat these pathogens' infections are described. The infections caused by rubella virus, cytomegaloviurs, ureaplasma urealyticum, toxoplasma, etc. are common, yet they are proved to be fatal during the pregnant period, especially during the first trimester. These infections may cause sterility, abortion, stillbirth, low birth weight, and affect multiple organs that may induce loss of hearing and vision, even fetal deformity and the long-term effects. These pathogens' infections may influence the microenvironment of placenta, including levels of enzymes and cytokines, and affect chondriosome that may induce the progress of birth defect. Early diagnosis of infections during pregnancy should be strengthened. There are still many things to be settled, such as the molecular mechanisms of birth defects, the effective vaccines to certain pathogens. Birth defect researches in terms of etiology and the development of applicable and sensitive pathogen detection technology and methods are imperative.

Animals↗
PubMed2004

[Analysis of nitrogen, phosphorus nutrients and COD in waters of Yangtze River Estuary].

The characters of the morphological, vertical and spatial distribution of nitrogen and phosphate in the water of Changjiang Estuary were discussed, according to the survey conducted in November 2003. Among the dissolved inorganic nitrogen species, nitrate accounted for 90% in the water of Changjiang Estuary. The concentration of nitrogen nutrients in the Changjiang Estuary show higher level, and 67% of sampling stations attained or exceeded the forth standard level of seawater, according to the national standard of seawater quality. Most of total phosphate in the water of Changjiang Estuary is total dissolved phosphate (TDP), which primary composition is dissolved organic phosphate (DOP). The dramatic changes of salinity in the water of Changjiang Estuary lead to the different distribution characteristics of nutrients. The concentrations of nitrate are higher inside the estuary and lower outside the estuary due to its conservatism. On the contrast, ammonium and phosphate are influenced by the change of particle concentrations and salinity, which are higher outside the estuary and lower inside the estuary. Besides, the contents of COD in the water of Changjiang estuary are very high, and the spatial distribution characteristics are higher inside the estuary and lower outside the estuary.

Fresh Water↗
PubMed2004

[Studies on organic protective coatings for anti-atomic oxygen effects by spectrum analysis].

This paper describes organic protective coatings on space material for anti-AO effects and the experiments to assess properties of the coatings. Organic protection was analyzed after exposures to ground state fast atomic (AO) radiation in the atomic oxygen beam facility for ground simulation experiments. The tests results have been analyzed with advanced FTIR, XPS and SEM. The test indicated that epoxy, alkyd and urethane organic coatings were highly reactive to AO with a strong degradation and changed in morphology of the surface layer. It is evident that siloxane coatings have excellent properties for anti-AO effects. The erosion product has SiO2 left on the surface, thus providing protection from further attack by the energetic oxygen atoms.

Materials Testing↗
PubMed2004

[Study on metronidazole resistance to Helicobacter pylori from three populations with different ethnics in Yunnan].

OBJECTIVE: To evaluate the prevalence of Helicobacter pylori (H.pylori) resistance to metronidazole among three populations in Yunnan. METHODS: Susceptibilities to metronidazole among 109 H. pylori strains (33 H. pylori strains from Han, 31 H. pylori strains from Bai and 45 H. pylori strains from Naxi ethnic populations) were tested by Epsilometer test (E-test). RESULTS: In 109 H. pylori strains, the overall metronidazole resistance rate was 67.89%. There were no significant difference in the metronidazole resistant rates of H. pylori among Han, Bai, Naxi populations Yunnan in terms of the distribution on age and upper gastroduodenal diseases. In the facet of gender, metronidazole resistant rate of H. pylori was significantly lower in Han males than in females (chi2=5.304, P=0.027), but not seen in the Bai or Naxi peoples. CONCLUSION: Metronidazole resistance rate of H. pyloriin Yunnan was high, but no significant difference was found among Han, Bai, Naxi peoples in the province.

Adult↗
PubMed2004

[Influence of different doxorubicin-salt aggregates on the leakage of liposomal doxorubicin in vitro and long circulation in vivo].

AIM: To develop liposomes containing doxorubicin with different salts and to investigate their influence on the stability of liposomal doxorubicin in vitro and in vivo. METHODS: Liposomes were prepared by the film method, treated further by extruded through nuclear membrane. The entrapment efficiency was determined by column chromatography. In vitro drug release experiments were carried out with a dialysis bag (Mw cut-off 12000 - 14000). Reverse-phase HPLC was used to study the pharmacokinetics of liposomal doxorubicin. RESULTS: The particle size of liposomes with glycinate buffer, citrate buffer and ammonium sulfate as the inner water phase were (103 +/- 8), (102 +/- 12) and (97 +/- 8) nm. The zeta potential and the encapsulation ratio were (-21.3 +/- 0.5), (-21.7 +/- 0.4), (-20.9 +/- 0.7) mV and 47.8%, 96.7%, 98.6%, respectively. The leaking rate of doxorubicin from liposomes was related to the pH value of the release medium. The leaking rate increased at lowered pH. Pharmacokinetic study showed that the MRT (mean retention time) of liposomes with glycinate buffer, citrate buffer and ammonium sulfate as the inner water phase were 12.13, 23.31 and 29.79 h, respectively. CONCLUSION: Doxorubicin showed different stability in liposomes with different inner water phases, the weaker the acid in the inner water phase, the stabler the liposome.

Ammonium Sulfate↗
PubMed2004

[Construction of cell lines producing high-titer recombinant retroviruses of message and antisense cDNA of human glucocorticoid receptor beta].

OBJECTIVE: To construct cell lines producing high-titer recombinant retroviruses of human glucocorticoid receptor beta (hGRbeta). METHODS: The recombinant retrorinal vectors of message and antisense cDNA of hGRbeta were transfected into PA317 cells by liposomes, respectively, and cell colonies were selected with G418. The titers of viruses from the 2 cell culture supernatants were determined by colony numbers produced in NIH3T3 cells. RESULTS: The presence of aimed RNAs in supernatant of the G418-resistant cell cultures were detected by RT-PCR and subsequent sequence analysis. The titers of retroviruses were 2. 0 x 10(5) and 1.8 x 10(5), each for recombinant message and antisense hGRbeta cDNA. CONCLUSION: We demonstrated here the obtaining of transfect PA317 cells that produce recombinant retroviruses containing message and antisense RNAs of hGRbeta with highly infective efficiencies.

3T3 Cells↗
PubMed2003

Repression of vascular endothelial growth factor A in glioblastoma cells using engineered zinc finger transcription factors.

Angiogenic factors are necessary for tumor proliferation and thus are attractive therapeutic targets. In this study, we have used engineered zinc finger protein (ZFP) transcription factors (TFs) to repress expression of vascular endothelial growth factor (VEGF)-A in human cancer cell lines. We create potent transcriptional repressors by fusing a designed ZFP targeted to the VEGF-A promoter with either the ligand-binding domain of thyroid hormone receptor alpha or its viral relative, vErbA. Moreover, this ZFP-vErbA repressor binds its intended target site in vivo and mediates the specific deacetylation of histones H3 and H4 at the targeted promoter, a result that emulates the natural repression mechanism of these domains. The potential therapeutic relevance of ZFP-mediated VEGF-A repression was addressed using the highly tumorigenic glioblastoma cell line U87MG. Despite the aberrant overexpression of VEGF-A in this cell line, engineered ZFP TFs were able to repress the expression of VEGF-A by >20-fold. The VEGF-A levels observed after ZFP TF-mediated repression were comparable to those of a nonangiogenic cancer line (U251MG), suggesting that the degree of repression obtained with the ZFP TF would be sufficient to suppress tumor angiogenesis. Thus, engineered ZFP TFs are shown to be potent regulators of gene expression with therapeutic promise in the treatment of disease.

Cell Line, Tumor↗
PubMed2003

Synthesis and biological evaluation of (-)-laulimalide analogues.

[reaction: see text] The syntheses of five laulimalide analogues are described, incorporating modifications at the C(16)-C(17)-epoxide, the C(20)-alcohol, as well as the C(1)-C(3)-enoate of the parent natural product. The resultant analogues are active in drug-sensitive HeLa and MDA-MB-435 cell lines. Significantly, like laulimalide, these analogues are poor substrates for the drug transport protein P-glycoprotein (Pgp) and are thus effective against Taxol-resistant cell lines.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Synoviolin/Hrd1, an E3 ubiquitin ligase, as a novel pathogenic factor for arthropathy.

Rheumatoid arthritis (RA) is one of the most critical articular diseases with synovial hyperplasia followed by impairment of quality of life. However, the mechanism(s) that regulates synovial cell outgrowth is not fully understood. To clarify its mechanism(s), we carried out immunoscreening by using antirheumatoid synovial cell antibody and identified and cloned "Synoviolin/Hrd1", an E3 ubiquitin ligase. Synoviolin/Hrd1 was highly expressed in the rheumatoid synovium, and mice overexpressing this enzyme developed spontaneous arthropathy. Conversely, synoviolin/hrd1(+/-) mice were resistant to collagen-induced arthritis by enhanced apoptosis of synovial cells. We conclude that Synoviolin/Hrd1 is a novel causative factor for arthropathy by triggering synovial cell outgrowth through its antiapoptotic effects. Our findings provide a new pathogenetic model of RA and suggest that Synoviolin/Hrd1 could be targeted as a therapeutic strategy for RA.

Amino Acid Sequence↗
PubMed2003

Cerebral microbleeds as a risk factor for subsequent intracerebral hemorrhages among patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Cerebral microbleeds (MBs) detected by gradient-echo MRI are considered evidence of advanced microangiopathy with potential for further bleeding. The goal of this study was to determine whether the presence of MBs is a risk factor for subsequent intracerebral hemorrhage among patients with acute ischemic stroke. METHODS: We prospectively examined patients hospitalized with acute cerebral infarction with gradient-echo T2*-weighted MRI for the presence of MBs. We recorded demographics, medical history, and stroke severity. Patients were then followed up for the development of stroke, other vascular events, and death. RESULTS: One hundred twenty-one consecutive patients with a mean age of 67.96+/-10.97 years were recruited. MBs were present in 43 patients (35.5%). During follow-up of 27.15+/-11.68 months, 16 patients had recurrent stroke. There was no difference between patients with or without MB for the development of ischemic stroke (5 and 6 respectively, P=0.841). However, 4 patients (9.3%) with MBs and 1 patient (1.3%) without an MB had intracerebral hemorrhage during follow-up (P=0.053). Of the 5 patients who developed subsequent intracerebral hemorrhages, 3 were treated with aspirin and 2 with anticoagulation. Two of the intracerebral hemorrhages occurred in the site where asymptomatic MBs were found at baseline. CONCLUSIONS: MBs appear to be a risk factor for subsequent intracerebral hemorrhage among patients with ischemic stroke in this small cohort of Chinese stroke patients. A large cohort study is required to confirm this observation.

Acute Disease↗
PubMed2003

Relations between brain network activation and analgesic effect induced by low vs. high frequency electrical acupoint stimulation in different subjects: a functional magnetic resonance imaging study.

Two- or 100-Hz electrical acupoint stimulation (EAS) can induce analgesia via distinct central mechanisms. It has long been known that the extent of EAS analgesia showed tremendous difference among subjects. Functional MRI (fMRI) studies were performed to allocate the possible mechanisms underlying the frequency specificity as well as individual variability of EAS analgesia. In either frequencies, the averaged fMRI activation levels of bilateral secondary somatosensory area and insula, contralateral anterior cingulate cortex and thalamus were positively correlated with the EAS-induced analgesic effect across the subjects. In 2-Hz EAS group, positive correlations were observed in contralateral primary motor area, supplementary motor area, and ipsilateral superior temporal gyrus, while negative correlations were found in bilateral hippocampus. In 100-Hz EAS group, positive correlations were observed in contralateral inferior parietal lobule, ipsilateral anterior cingulate cortex, nucleus accumbens, and pons, while negative correlation was detected in contralateral amygdala. These results suggest that functional activities of certain brain areas might be correlated with the effect of EAS-induced analgesia, in a frequency-dependent dynamic. EAS-induced analgesia with low and high frequencies seems to be mediated by different, though overlapped, brain networks. The differential activations/de-activations in brain networks across subjects may provide a neurobiological explanation for the mechanisms of the induction and the individual variability of analgesic effect induced by EAS, or that of manual acupuncture as well.

Acupuncture Analgesia↗
PubMed2003

Modulation of cold pain in human brain by electric acupoint stimulation: evidence from fMRI.

The purpose of this study is to investigate the modulation of pain responses in the human brain by electric acupoint stimulation (EAS). Eight healthy subjects were enrolled; each received real or mock EAS treatment in separate sessions. Cool (18 degrees C) and cold (2 degrees C) stimuli were delivered, during which functional magnetic resonance imaging scans were performed, before and after treatment. Real EAS specifically increased the pain-specific activation in bilateral secondary somatosensory area, medial prefrontal cortex, and Brodmann area (BA) 32, while it decreased the activation in contralateral primary somatosensory area, BA7, and BA24. We suggest that EAS may induce an analgesic effect via modulation of both the sensory and the emotional aspect of pain processing.

Adult↗
PubMed2003

The role of the extracellular signal-regulated kinase signaling pathway in mood modulation.

The neurobiological underpinnings of mood modulation, molecular pathophysiology of manic-depressive illness, and therapeutic mechanism of mood stabilizers are largely unknown. The extracellular signal-regulated kinase (ERK) pathway is activated by neurotrophins and other neuroactive chemicals to produce their effects on neuronal differentiation, survival, regeneration, and structural and functional plasticity. We found that lithium and valproate, commonly used mood stabilizers for the treatment of manic-depressive illness, stimulated the ERK pathway in the rat hippocampus and frontal cortex. Both drugs increased the levels of activated phospho-ERK44/42, activated phospho-ribosomal protein S6 kinase-1 (RSK1) (a substrate of ERK), phospho-CREB (cAMP response element-binding protein) and phospho-B cell lymphoma protein-2 antagonist of cell death (substrates of RSK), and BDNF. Inhibiting the ERK pathway with the blood-brain barrier-penetrating mitogen-activated protein kinase (MAP kinase)/ERK kinase (MEK) kinase inhibitor SL327, but not with the nonblood-brain barrier-penetrating MEK inhibitor U0126, decreased immobility time and increased swimming time of rats in the forced-swim test. SL327, but not U0126, also increased locomotion time and distance traveled in a large open field. The behavioral changes in the open field were prevented with chronic lithium pretreatment. SL327-induced behavioral changes are qualitatively similar to the changes induced by amphetamine, a compound that induces relapse in remitted manic patients and mood elevation in normal subjects. These data suggest that the ERK pathway may mediate the antimanic effects of mood stabilizers.

Affect↗
PubMed2003

Growth temperature downshift induces antioxidant response in Saccharomyces cerevisiae.

A rapid downshift in the growth temperature of Saccharomyces cerevisiae from 30 to 10 degrees C resulted in an increase in transcript levels of the antioxidation genes SOD1 [encoding Cu-Zn superoxide dismutase (SOD)], CTT1 (encoding catalase T), and GSH1 (encoding gamma-glutamylcysteine synthetase). The cellular activities of SOD and catalase were also increased, indicating that the temperature downshift caused an antioxidant response. In support of this, a simultaneous increase in the intracellular level of H(2)O(2) was observed. The level of YAP1 mRNA, encoding a transcription factor critical for the oxidative stress response in this yeast, was also increased by the temperature downshift. However, deletion of YAP1 did not reduce the elevated mRNA levels of the antioxidant genes. This suggests that the temperature downshift-induced increase in the mRNA level of anti-oxidant genes is YAP1-independent.

Antioxidants↗
PubMed2003

Cloning, expression, characterization, and interaction of two components of a human mitochondrial fatty acid synthase. Malonyltransferase and acyl carrier protein.

The possibility that human cells contain, in addition to the cytosolic type I fatty acid synthase complex, a mitochondrial type II malonyl-CoA-dependent system for the biosynthesis of fatty acids has been examined by cloning, expressing, and characterizing two putative components. Candidate coding sequences for a malonyl-CoA:acyl carrier protein transacylase (malonyltransferase) and its acyl carrier protein substrate, identified by BLAST searches of the human sequence data base, were located on nuclear chromosomes 22 and 16, respectively. The encoded proteins localized exclusively in mitochondria only when the putative N-terminal mitochondrial targeting sequences were present as revealed by confocal microscopy of HeLa cells infected with appropriate green fluorescent protein fusion constructs. The mature, processed forms of the mitochondrial proteins were expressed in Sf9 cells and purified, the acyl carrier protein was converted to the holoform in vitro using purified human phosphopantetheinyltransferase, and the functional interaction of the two proteins was studied. Compared with the dual specificity malonyl/acetyltransferase component of the cytosolic type I fatty acid synthase, the type II mitochondrial counterpart exhibits a relatively narrow substrate specificity for both the acyl donor and acyl carrier protein acceptor. Thus, it forms a covalent acyl-enzyme complex only when incubated with malonyl-CoA and transfers exclusively malonyl moieties to the mitochondrial holoacyl carrier protein. The type II acyl carrier protein from Bacillus subtilis, but not the acyl carrier protein derived from the human cytosolic type I fatty acid synthase, can also function as an acceptor for the mitochondrial transferase. These data provide compelling evidence that human mitochondria contain a malonyl-CoA/acyl carrier protein-dependent fatty acid synthase system, distinct from the type I cytosolic fatty acid synthase, that resembles the type II system present in prokaryotes and plastids. The final products of this system, yet to be identified, may play an important role in mitochondrial function.

Acyl Carrier Protein↗