PubMed Health⌕ Search

Biomedical subjects

Z Feng

Publications and source records attributed to Z Feng.

At least 37 records · Page 2Linked to original sources
PubMed2003

A randomized phase III clinical trial of autologous blood stem cell transplantation comparing cryopreservation using dimethylsulfoxide vs dimethylsulfoxide with hydroxyethylstarch.

Hematopoietic stem cells intended for autologous transplantation are usually cryopreserved in solutions containing 10% dimethylsulfoxide (DMSO, v/v) or 5% DMSO in combination with 6% hydroxyethylstarch (HES, w/v). We performed a single-blinded, randomized study comparing these cryoprotectant solutions for patients undergoing autologous peripheral blood stem cell (PBSC) transplantation. A total of 294 patients were evaluable; 148 received cells frozen with 10% DMSO and 146 received cells frozen in 5% DMSO/6% HES. Patients who received cells frozen with the combination cryoprotectant recovered their white blood cell count >or=1.0 x 10(9)/l at a median of 10 days, one day faster than those who received PBSC frozen with DMSO alone (P=0.04). Time to achieve neutrophil counts of >or=0.5 x 10(9) and >or=1.0 x 10(9)/l were similarly faster for the recipients of the cells frozen in the combination solution. This effect was more pronounced for patients who received quantities of CD34+ cells higher than the median for the population. Median time to discontinuation of antibiotic use was also one day faster for the recipients of cells cryopreserved with DMSO/HES (P=0.04). In contrast, median times to recovery of platelet count >or=20 x 10(9)/l were equivalent for each group (10 days; P=0.99) and the median numbers of red cell and platelet transfusions did not differ.

Adolescent↗
PubMed2003

Investigation on the mechanical properties of contracted collagen gels as a scaffold for tissue engineering.

In this article the mechanical properties of contracted collagen gels were investigated thoroughly by means of uniaxial tensile test. Large type I collagen-Dulbecco's Modified Eagle Medium (DMEM) gels (each was 26 ml in volume, 1.67 mg/ml collagen concentration), each populated with about 2.5 x 106 human fibroblasts, were made in 100 mm diameter plastic dishes precoated with albumin for floating the gels in DMEM. Such identically treated gels were divided into three groups for the mechanical measurements at different culture periods (2, 4, and 10 weeks). Rapid contraction occurred within the first 3 days and then the contraction went slowly in the rest period until it reached about 13% of its original size. The stress-strain curve of the contracted collagen gels demonstrated an exponential behavior at low stress region, followed by linear region, a point of yielding, and finally an ultimate stress point at which the maximum stress was reached. The mechanical strength increased in the first few weeks and then decreased as the culture went on. It is obvious that the collagen fibrils formed and were forced to orientate to the tensile direction after the test. The stress relaxation and cyclic creep phenomena were observed. Based on the morphological analysis of transmission electron microscopy (TEM) of the gels, a nonlinear visco-elastic-plastic constitutive formula was proposed, which was able to reproduce the rheological phenomena of the gels. This experiment shows that the human fibroblasts significantly contracted collagen gels so as to achieve certain mechanical strength, which makes it possible to be a scaffold for tissue engineering. However, a further method to reinforce the mechanical strength by several folds must be considered. Meanwhile, the rheological phenomena should be taken into account in the fabrication and application of the structure.

Bioprosthesis↗
PubMed2002

A baseline study of importance of bovines for human Schistosoma japonicum infections around Poyang Lake, China: villages studied and snail sampling strategy.

An epidemiologic survey among four administrative villages around Poyang Lake, in Jiangxi Province, China (two experimental and two controls) is being conducted to determine if bovine infections are responsible for the persistence of human schistosomiasis transmission on Yangtze River marshlands. A previously published paper presented the experimental design and baseline data for humans and bovines. This paper presents basic data for the four villages using remote sensing, and baseline data for snails that includes geographic information systems and remote sensing technology to classify the areas of bovine grazing ranges and habitats suitable for snails. A new method for sampling Oncomelania snails in China is used to determine the distribution, density, and infection rates of snails throughout the grazing ranges from season to season over a four-year period. Hypothetically, treating bovines should reduce infection rates in snails to below the critical number necessary to maintain infections in man and bovines.

Animals↗
PubMed2002

Preparation and evaluation of poly (D, L-lactic acid) (PLA) or D, L-lactide/glycolide copolymer (PLGA) microspheres with estradiol.

PLA/PLGA was used for biodegradable and biocompatible carriers to achieve sustained release of estradiol. Microspheres were formed by an emulsification-solvent evaporation method, and then their properties and in vitro drug release behavior were examined including amongst others the effects of the concentration of PVA in the aqueous phase, the concentration of PLA in the organic phase, the stirring speed, the volume ratio of O/W, the weight ratio of E2/PLA fed, and the type and molecular weight of the polymers.

Drug Compounding↗
PubMed2001

A comparison of generalized linear mixed model procedures with estimating equations for variance and covariance parameter estimation in longitudinal studies and group randomized trials.

Response data in longitudinal studies and group randomized trials are gathered on units that belong to clusters, within which data are usually positively correlated. Therefore, estimates and confidence intervals for intraclass correlation or variance components are helpful when designing a longitudinal study or group randomized trial. Data simulated from both study designs are used to investigate the estimation of variance and covariance parameters from the following procedures: for continuous outcomes, restricted maximum likelihood (REML) and estimating equations (EE); for binary outcomes, restricted pseudo-likelihood (REPL) and estimating equations (EE). We evaluate these procedures to see which provide valid and precise estimates as well as correct standard errors for the intraclass correlation coefficient or variance components. REML seems the better choice for estimating terms related to correlation for models with normal outcomes, especially in group randomized trial situations. Results for REML and EE are mixed when outcomes are continuous and non-normal. With binary outcomes neither REPL nor EE provides satisfactory estimation or inference in longitudinal study situations, while REPL is preferable for group randomized trials.

Cluster Analysis↗
PubMed2001

Analyses of micronuclei in exfoliated epithelial cells from individuals chronically exposed to arsenic via drinking water in inner Mongolia, China.

The groundwater in Bayingnormen (Ba Men), located in Central West Inner Mongolia, China, is naturally contaminated with arsenic at concentrations ranging from 50 microg/L to 1.8 mg/L. Various adverse health effects in this region, including cancer, have been linked to arsenic exposure via drinking water. A pilot study was undertaken to evaluate frequencies of micronuclei (MN), as measures of chromosomal alterations, in multiple exfoliated epithelial cell types from residents of Ba Men chronically exposed to arsenic via drinking water. Buccal mucosal cells, airway epithelial cells in sputum, and bladder urothelial cells were collected from 19 residents exposed to high levels of arsenic in drinking water (527.5 +/- 24 microg/l), and from 13 control residents exposed to relatively low levels of arsenic in drinking water (4.4 +/- microg/L). Analytical results from these individuals revealed that MN frequencies in the high-exposure group were significantly elevated to 3.4-fold over control levels for buccal and sputum cells, and to 2.7-fold over control for bladder cells (increases in MN frequency significant at p < .001 for buccal cells; p < .01 for sputum cells; p < .05 for bladder cells). When smokers were excluded from high-exposure and control groups the effects of arsenic were observed to be greater, although only in buccal and sputum cells; approximately 6-fold increases in MN frequency occurred in these tissues. The results indicate that residents of Ba Men chronically exposed to high levels of arsenic in drinking water reveal evidence of genotoxicity in multiple epithelial cell types; higher levels of induced MN were observed in buccal and sputum cells than in bladder cells.

Adult↗
PubMed2001

On the nature of conformational openings: native and unfolded-state hydrogen and thiol-disulfide exchange studies of ferric aquomyoglobin.

Native-state amide hydrogen exchange (HX) of proteins in the presence of denaturant has provided valuable details on the structures of equilibrium folding intermediates. Here, we extend HX theory to model thiol group exchange (SX) in single cysteine-containing variants of sperm whale ferric aquomyoglobin. SX is complementary to HX in that it monitors conformational opening events that expose side-chains, rather than the main chain, to solvent. A simple two-process model, consisting of EX2-limited local structural fluctuations and EX1-limited global unfolding, adequately accounts for all HX data. SX is described by the same model except at very low denaturant concentrations and when the bulky labeling reagent 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) is used. Under these conditions SX can occur by a novel denaturant-dependent process. This anomalous behavior is not observed when the smaller labeling reagent methyl methanethiosulfonate is employed, suggesting that it reflects a denaturant-induced increase in the amplitudes of local structural fluctuations. It also is not seen in heme-free apomyoglobin, which may indicate that local openings are sufficiently large in the absence of denaturant to allow DTNB unhindered access. Differences in SX kinetics obtained using the two labeling reagents provide estimates of the sizes of local opening reactions at different sites in the protein. At all sequence positions examined except for position 73, the same opening event appears to facilitate exchange of both backbone amide and side-chain thiol groups. The C73 thiol group is exposed by a low-energy fluctuation that does not expose its amide group to exchange.

Amides↗
PubMed2001

NF-kappa B activation mediates doxorubicin-induced cell death in N-type neuroblastoma cells.

Neuroblastoma is the most common extracranial solid tumor of childhood. N-type neuroblastoma cells (represented by SH-SY5Y and IMR32 cell lines) are characterized by a neuronal phenotype. N-type cell lines are generally N-myc amplified, express the anti-apoptotic protein Bcl-2, and do not express caspase-8. The present study was designed to determine the mechanism by which N-type cells die in response to specific cytotoxic agents (such as cisplatin and doxorubicin) commonly used to treat this disease. We found that N-type cells were equally sensitive to cisplatin and doxorubicin. Yet death induced by cisplatin was inhibited by the nonselective caspase inhibitor z-Val-Ala-Asp-fluoromethylketone or the specific caspase-9 inhibitor N-acetyl-Leu-Glu-His-Asp-aldehyde, whereas in contrast, caspase inhibition did not prevent doxorubicin-induced death. Neither the reactive oxygen species nor the mitochondrial permeability transition appears to play an important role in this process. Doxorubicin induced NF-kappa B transcriptional activation in association with I-kappa B alpha degradation prior to loss of cell viability. Surprisingly, the antioxidant and NF-kappa B inhibitor pyrrolidine dithiocarbamate blocked doxorubicin-induced NF-kappa B transcriptional activation and provided profound protection against doxorubicin killing. Moreover, SH-SY5Y cells expressing a super-repressor form of I-kappa B were completely resistant to doxorubicin killing. Together these findings show that NF-kappa B activation mediates doxorubicin-induced cell death without evidence of caspase function and suggest that cisplatin and doxorubicin engage different death pathways to kill neuroblastoma cells.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Methylated CpG dinucleotides are the preferential targets for G-to-T transversion mutations induced by benzo[a]pyrene diol epoxide in mammalian cells: similarities with the p53 mutation spectrum in smoking-associated lung cancers.

A large fraction of the p53 mutations in lung cancers from smokers are G-to-T transversions, a type of mutation that is infrequent in lung cancers from nonsmokers and in most other tumors. Previous studies have indicated that there is an association between G-to-T transversion hotspots in lung cancers and sites of preferential formation of polycyclic aromatic hydrocarbon adducts along the p53 gene. p53 codons containing methylated CpG sequences are preferential targets for formation of adducts by (+/-) anti-7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). To assess the role of CpG methylation in induction of mutations by BPDE, we analyzed BPDE mutagenesis in three CpG methylated target genes: a supF shuttle vector and the cII and lacI transgenes in embryonic mouse fibroblasts. After methylation of the shuttle vector at all CpG sequences, 42% of all G-to-T transversions were at CpG sites compared with 23% in unmethylated DNA. In the cII transgene, which is methylated at CpG sequences in vivo, 83 of 147 (56%) of the BPDE-induced mutations were G-to-T transversions, and 58% (48 of 83) of all G-to-T transversions occurred at methylated CpG sequences. In the lacI gene, 68% (75 of 111) of the BPDE-induced mutations were G-to-T events, and 58 of 75 (77%) of these occurred at methylated CpG sequences. The occurrence of transversion hotspots at methylated CpGs correlated with high levels of BPDE adducts formed at such sites. This situation mirrors the one in the p53 gene in lung cancers from smokers where 236 of 465 (51%) of the G-to-T transversions occurred at methylated CpG sites. These findings further strengthen a link between polycyclic aromatic hydrocarbons present in cigarette smoke and lung cancer mutations and provide evidence that mutational processes other than C-to-T transition mutations can occur selectively at methylated CpG sequences.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed2001

Identification of a secreted superoxide dismutase in Mycobacterium avium ssp. paratuberculosis.

Mycobacterium avium ssp. paratuberculosis (M. paratuberculosis), the causative agent of Johne's disease, is an important animal pathogen that has also been implicated in human disease. The major proteins expressed by M. paratuberculosis were analyzed by two-dimensional gel electrophoresis, and a superoxide dismutase (Sod) was identified from this protein profile. The M. paratuberculosis Sod has a molecular mass of 23 kDa and an isoelectric point of 6.1. Sequence analysis of the corresponding sodA gene from M. paratuberculosis indicates that this protein is a manganese-dependent enzyme. We show that the M. paratuberculosis Sod is actively secreted, suggesting that it may elicit a protective cellular immune response in the host during infection.

Amino Acid Sequence↗
PubMed2001

Effects of habitat destruction and resource supplementation in a predator-prey metapopulation model.

We developed a mean field, metapopulation model to study the consequences of habitat destruction on a predator-prey interaction. The model complements and extends earlier work published by Bascompte and Solé (1998, J. theor. Biol.195, 383-393) in that it also permits use of alternative prey (i.e., resource supplementation) by predators. The current model is stable whenever coexistence occurs, whereas the earlier model is not stable over the entire domain of coexistence. More importantly, the current model permits an assessment of the effect of a generalist predator on the trophic interaction. Habitat destruction negatively affects the equilibrium fraction of patches occupied by predators, but the effect is most pronounced for specialists. The effect of habitat destruction on prey coexisting with predators is dependent on the ratio of extinction risk due to predation and prey colonization rate. When this ratio is less than unity, equilibrial prey occupancy of patches declines as habitat destruction increases. When the ratio exceeds one, equilibrial prey occupancy increases even as habitat destruction increases; i.e., prey "escape" from predation is facilitated by habitat loss. Resource supplementation reduces the threshold colonization rate of predators necessary for their regional persistence, and the benefit derived from resource supplementation increases in a nonlinear fashion as habitat destruction increases. We also compared the analytical results to those from a stochastic, spatially explicit simulation model. The simulation model was a discrete time analog of our analytical model, with one exception. Colonization was restricted locally in the simulation, whereas colonization was a global process in the analytical model. After correcting for differences between nominal and effective colonization rates, most of the main conclusions of the two types of models were similar. Some important differences did emerge, however, and we discuss these in relation to the need to develop fully spatially explicit analytical models. Finally, we comment on the implications of our results for community structure and for the conservation of prey species interacting with generalist predators.

Animals↗
PubMed2001

Induction of unspliced c-fos messenger RNA in rodent brain by kainic acid and lipopolysaccharide.

The c-fos transcriptional factor forms an activator protein-1 (AP-1) complex with proteins from the Jun family, which plays an important role in the central nervous system. The responses of AP-1 transcriptional factors induced by kainic acid (KA) treatment have been well studied, although the transcriptional regulation of these KA-induced factors has not been clearly characterized. To investigate the role of different stimuli in controlling of the splicing of c-fos mRNA, we performed reverse transcriptional polymerase chain reaction. The results showed that spliced and unspliced c-fos is present in rat brain following KA treatment and in lipopolysaccharide (LPS)-treated primary mouse cortical brain cell cultures. Furthermore, tyrosine kinase and protein phosphatase inhibitors alter the preponderance of c-fos transcripts following LPS treatment.

Animals↗
PubMed2001

Synthesis of enantiopure 7-[3-azidopyl]indolizidin-2-one amino acid. A constrained mimic of the peptide backbone geometry and heteroatomic side-chain functionality of the ala-lys dipeptide.

Enantiopure N-(BOC)amino-7-[3-azidopropyl]indolizidin-2-one acid 1 has been synthesized by displacement of the methanesulfonate of its 7-hydroxypropyl counterpart 11 with sodium azide and subsequent ester hydrolysis. N-(BOC)Amino-7-[3-hydroxypropyl]indolizidin-2-one ester 11 was obtained from a sequence commencing with the alkylation of (2S,8S)-di-tert-butyl 5-oxo-2,8-di-[N-(PhF)amino]azelate 5 (PhF = 9-(9-phenylfluorenyl)). Stereoselective allylation of 5, regioselective olefin hydroboration, selective primary alcohol protection as a silyl ether, and oxidation of the secondary alcohol gave (2S,4R,8S)-di-tert-butyl 4-[3-tert-butyldimethylsiloxypropyl]-5-oxo-2,8-di-[N-(PhF)amino]azelate 9 as a pure diastereomer in 33% overall yield. Linear ketone 9 was then converted into the indolizidinone heterocycle by a route featuring reductive amination, lactam cyclization, and isolation by way of a silyl ether which provided the (6S,7R)-isomer of 11.

Amino Acids↗
PubMed2001

The PDB data uniformity project.

The Protein Data Bank (PDB; http://www.rcsb.org/pdb/) is the single worldwide archive of structural data of biological macromolecules. This paper describes the data uniformity project that is underway to address the inconsistency in PDB data.

Databases, Factual↗
PubMed2001

Seattle 5 a Day worksite program to increase fruit and vegetable consumption.

BACKGROUND: 5 a Day for Better Health is a simple message encouraging people to eat more fruits and vegetables. The Seattle 5 a Day worksite investigators designed and evaluated an intervention, organized on stages of behavioral change, to increase worksitewide fruit and vegetable consumption. METHODS: We recruited 28 worksites with cafeterias and randomized 14 to intervention and 14 to control. The intervention addressed both changes in the work environment and individual level behavior change. In each worksite, an employee advisory board, with study interventionist assistance, implemented the program. By surveying cross-sectional samples of 125 employees per worksite, we compared worksite mean fruit and vegetable consumption at 2-year follow-up with that at baseline. Unobtrusive site-level indicators including plate observation and cafeteria checklist were also used. RESULTS: The difference at 2 years was 0.5 for the intervention worksites and 0.2 for the control worksites, with an intervention effect of 0.3 daily serving (P < 0.05). Other measures of fruit and vegetable consumption, including unobtrusive indicators, supported the effectiveness of the intervention. CONCLUSIONS: This simple 5 a Day intervention is feasible and acceptable for use in worksites with cafeterias. There was a significant differential increase in fruit and vegetable consumption in the intervention worksites. This kind of worksite intervention can achieve important health benefits on a population basis, because of its potential to reach large numbers of people.

Adult↗
PubMed2001

The binding ability analysis of the normal VLDL receptor and its mutant.

The ligand-binding domain of VLDL receptor contains eight imperfectly similar repeats. To discuss the contribution of each repeat to ligand binding, the RT-PCR technique was used to clone the VLDLR-cDNA from the heart muscle of Chinese people. Two recombinants were further constructed, which contained the full-length cDNA of VLDLR and the mutant lacking repeats 1-5. CHO cell line was transfected with two recombinants. The expression of VLDLR gene could be detected by RT-PCR from the CHO cells transfected with pCD-VR. The results of binding experiments showed that the ability of the CHO cells transfected with the full-length cDNA of VLDL-R binding DiI-labeled beta-VLDL was higher than that of the CHO cells transfected with the mutant. Our findings indicated that human VLDL-R gene could be expressed effectively on CHO cells, and the receptor was almost inactivated when repeats 1-5 were deleted.

Animals↗
PubMed2001

Study on the preparation of recombinant human HSP70 and its presenting-antigen function.

The preparation of recombinant human HSP70 and its presenting-antigen function were investigated. Cultured in glucose-free M9ZB medium and induced with IPTG and lactose at a final concentration of 0.02 mmol/L and 5 mmol/L respectively, the engineered bacteria carrying expression vector of human HSP70 gene expressed rHSP70 at an efficiency fo 60%. After the purification with DEAE ion-exchange chromatography, HSP70 with a purity of higher than 90% was obtained. The purified product could bind tumor-antigen peptide in vitro, and the binding was identified by native PAGE containing 5% glycerol. HSP70-peptide complex could activate lymphocytes to produce specific cytotoxicity to tumor cells, suggesting that the recombinant human HSP70 could be used as an antigen-presenting reagent in tumor therapy.

Animals↗