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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 73 records · Page 4Linked to original sources
PubMed2001

[A survey on blood lipid levels among newborns and healthy inhabitants in urban Shanghai from 1997 to 1999].

OBJECTIVE: To analyze the blood lipid levels among inhabitants of different ages in urban Shanghai by the end of 1990 and compare the results with those in 1970 s and 1980 s. METHODS: Venous blood samples were collected from 3647 persons undergoing annual health examination, including workers and staff members, employees, functionaries, and students of factories, governmental organizations, institutions, enterprises, and schools. Umbilical blood samples were collected from 88 newborns. Serum TC, TG, LDL-C, and HDL-C were determined. RESULTS: 3647 blood samples were collected in total. It is found that: (1) The levels of blood lipids increased along with the age. The levels of TC and LDL-C among females over their fifty were higher that those among the males in the same age groups. The level of TG among females over fifty was similar to that among the males in the same age groups. The levels of LDL-C were higher in families in all of the age groups than those in the males of the same ages. (2) In comparison to those in 1970 s the levels of TC and TG in 1990 s were significantly higher by 6.79% - 17.69% and 21.95% - 45.53% respectively, and the level of HDL-C decreased by 8.02% - 29.19%. (3) The percentage of persons over forty with their TC levels over the upper normal limit was much larger in 1990 s than in 1970 s (for TC 11.57% vs. 4.40% among males and 16.02% vs. 5.40% among females, for TG 21.83% vs. 5.20% among males and 13.32% vs. 5.70% among females). and (4) The percentage of persons with their TC/HDL-C >or= 4 and TG >or= 1.70 mmol/L was much larger among persons over forty than among persons under forty (20.74% vs. 10.99% among males and 13.32% vs. 2.05% among females). CONCLUSION: The mean serum TC, TG, and LDL-C levels increased and the HDL-C level decreased significantly among healthy inhabitants in urban Shanghai in 1990 s. Along with the rise of living standards of people, their mean lipid level increases too. Nutrition education is necessary.

Adolescent↗
PubMed2001

Interwoven metal-organic framework on a periodic minimal surface with extra-large pores.

Interpenetration (catenation) has long been considered a major impediment in the achievement of stable and porous crystalline structures. A strategy for the design of highly porous and structurally stable networks makes use of metal-organic building blocks that can be assembled on a triply periodic P-minimal geometric surface to produce structures that are interpenetrating-more accurately considered as interwoven. We used 4,4',4"-benzene-1,3,5-triyl-tribenzoic acid (H(3)BTB), copper(II) nitrate, and N,N'-dimethylformamide (DMF) to prepare Cu(3)(BTB)(2)(H(2)O)(3).(DMF)(9)(H(2)O)(2) (MOF-14), whose structure reveals a pair of interwoven metal-organic frameworks that are mutually reinforced. The structure contains remarkably large pores, 16.4 angstroms in diameter, in which voluminous amounts of gases and organic solvents can be reversibly sorbed.

Journal Article↗
PubMed2001

Regulation of an endogenous locus using a panel of designed zinc finger proteins targeted to accessible chromatin regions. Activation of vascular endothelial growth factor A.

We have mapped conserved regions of enhanced DNase I accessibility within the endogenous chromosomal locus of vascular endothelial growth factor A (VEGF-A). Synthetic zinc finger protein (ZFP) transcription factors were designed to target DNA sequences contained within the DNase I-hypersensitive regions. These ZFPs, when fused to either VP16 or p65 transcriptional activation domains, were able to activate expression of the VEGF-A gene as assayed by mRNA accumulation and VEGF-A protein secretion through a range exceeding that induced by hypoxic stress. Importantly, multiple splice variants of VEGF-A mRNA with defined physiological functions were induced by a single engineered ZFP transcription factor. We present evidence for an enhanced activation of VEGF-A gene transcription by ZFP transcription factors fused to VP16 and p65 targeted to two distinct chromosomal sites >500 base pairs upstream or downstream of the transcription start site. Our strategy provides a novel approach for dissecting the requirements for gene regulation at a distance without altering the DNA sequence of the endogenous target locus.

Cell Line, Transformed↗
PubMed2001

Replicative response, immunophenotype, and functional activity of monocyte-derived versus CD34(+)-derived dendritic cells following exposure to various expansion and maturational stimuli.

Dendritic cells (DCs), generated ex vivo from blood mononuclear cells (PBMC) or CD34(+) stem cells, are being used to develop novel immunotherapies. To establish optimal DC generation, a direct comparison of the optimal cell source, culture conditions, and maturation stimuli was performed, utilizing phenotypic and functional assays as end points. Plastic adherent monocytes from PBMC were expanded in a serum-free medium (X-Vivo 10) for 7 days using GM-CSF/IL-4; CD34(+) cells were expanded for 14 days using GM-CSF/IL-4/ Flt3L, in either X-Vivo 10 alone or with albumin or autologous plasma. Expanded DC from both cell sources were matured for 7 days with CD40L or IFN-alpha/TNF-alpha. Starting from 2 x 10(7) monocytes, the optimal expansion/maturation process yielded 1.73 +/- 0.52 x 10(6) CD86(+) DC. Optimal expansion of CD34(+) cells (83.9 +/- 25.0-fold) was achieved using X-Vivo 10 with 5% plasma, matured with CD40L, and yielded 10.68 +/- 2.72 x 10(6) CD86(+) DC from 1 x 10(6) CD34(+) cells. Mature DC from PBMC or CD34(+) cells had similar enhanced expression of MHC class II HLA-DR, CD80, CD83, and CD86 and were potent stimulators of mixed lymphocyte reactions. Prior to maturation, all groups of DC actively phagocytosed apoptotic melanoma cells (approximately 50% of HLA-DR(+)). CD34(+) DC matured with CD40L or IFN-alpha/TNF-alpha had reduced phagocytic capability (34 and 31% of HLA-DR(+) DC, respectively). Similar expansion and functional activity was found using cryopreserved DC precursors, cultured in gas permeable bags. We conclude that both cell lineages produce potent mature DC, permitting exploration of the optimal clinical strategy to trigger anti-tumor immune responses in patients with malignancies.

Antigens, CD↗
PubMed2001

Electroretinographic abnormalities in a rat glaucoma model with chronic elevated intraocular pressure.

The purpose of this study was to determine the ability of electroretinographic (ERG) measurements to document progression of the retinopathy in a rat glaucoma model. Thirty four rats with a chronic intraocular pressure (IOP) elevation induced in one eye by cautery of three episcleral/extra-orbital veins were studied in four separate groups. ERGs were recorded sequentially in Group A rats (n = 12) at baseline, and after approximately 20, 40 and 60 days of high IOP, and in three additional groups of rats (n = 6 or 10 per group) after approximately 58, 30 and 175 days of high IOP, respectively. Scotopic ERG parameters recorded simultaneously from both eyes in Group A rats were: a- and b-wave amplitudes, implicit times, oscillatory potential amplitudes (OPs) determined at three different light-flash intensities, and the light-adapted (photopic) ERG b-wave amplitude. In the other groups of rats, only scotopic ERG a-wave, b-wave and OP amplitudes were measured.In Group A rats that were followed sequentially, all the ERG parameters recorded with attenuated stimuli showed significant time-dependent changes in glaucomatous eyes relative to their contralateral normal eyes, with OPs showing the earliest significant difference after only 3 weeks of high IOP. When different groups of unilateral glaucomatous rats were compared beyond 8 weeks of elevated IOP only the OPs showed a continued decrease with time and good discrimination between glaucoma and normal eyes. Over a 25 week period of high IOP the scotopic OPs measured with attenuated light stimuli declined at the rate of approximately 1.5% per week and provided the best ERG measure to monitor progression of retinal pathophysiology in the vein-occlusion rat glaucoma model.

Adaptation, Ocular↗
PubMed2001

Sesquiterpenoids from the fruits of Ferula kuhistanica and antibacterial activity of the constituents of F. kuhistanica.

Ethyl acetate extracts of the air-dried fruits of Ferula kuhistanica afforded three daucane esters: kuhistanicaol H, I and J, together with nine other known compounds. Their structures were established on the basis of spectroscopic evidence. Isolated compounds in this paper and previously reported compounds from the roots and stems of F. kuhistanica were tested for antibacterial activity. Some of them were selectively toxic against Gram-positive bacteria, including methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA).

Anti-Bacterial Agents↗
PubMed2001

Film-pore diffusion modeling for the sorption of metal ions from aqueous effluents onto peat.

The sorption of three metal ions, namely, copper, nickel and lead onto sphagnum peat moss has been studied using an agitated batch sorber system. The equilibrium isotherms were determined and kinetic runs were performed over a range of concentrations for each metal ion. A film-pore diffusion mass transfer model has been developed based on a single effective diffusion coefficient for each system. Error analysis of the experimental and theoretical data indicated relatively large errors at low initial metal ion concentrations. Therefore the model was modified to introduce a surface coverage concentration dependent effective diffusivity to account for a contribution from surface diffusion.

Adsorption↗
PubMed2001

A modified glass bead compartment cultivation system for studies on nutrient and trace metal uptake by arbuscular mycorrhiza.

A modified glass bead compartment cultivation system is described in which glass beads continue to be used in the hyphal compartment but are replaced by coarse river sand in the compartments for host plant roots and mycorrhizal hyphae. Arbuscular mycorrhizal (AM) associations were established using two host plant species, maize (Zea mays L.) and red clover (Trifolium pratense L.) and two AM fungi, Glomus mosseae and G. versiforme. When the standard and modified cultivation systems were compared, the new method yielded much more fungal tissue in the hyphal compartment. Using G. versiforme as the fungal symbiont, up to 30 mg of fungal dry matter (DM) was recovered from the hyphal compartment of mycorrhizal maize and about 6 mg from red clover. Multi-element analysis was conducted on samples of host plant roots and shoots and on harvested fungal biomass. Concentrations of P, Cu and Zn were much higher in the fungal biomass than in the roots or shoots of the host plants but fungal concentrations of K, Ca, Mg, Fe and Mn were similar to or lower than those in the plants. There were also significant differences in nutrient concentrations between the two AM fungi and these may be related to differences in their proportions of extraradical mycelium to spores. The high affinity of the fungal mycelium for Zn was very striking and is discussed in relation to the potential use of arbuscular mycorrhiza in the phytoremediation of Zn-polluted soils.

Biomass↗
PubMed2001

Risk assessment under FQPA: case study with chlorpyrifos.

Key science policies have had significant impact on the evolving implementation of the Food Quality and Protection Act (FQPA) (PL 104-170, 1996) by the US Environmental Protection Agency (EPA). The impact offour of these policies will be examined using the risk assessment for chlorpyrifos as a case study. These policies are selection of a regulatory endpoint, use of animal data without consideration of human data for setting the reference dose, a 10 FQPA safety factor and use of the 99.9 percentile of modeled consumer exposure in the acute dietary assessment. Each of these policy decisions had individual impact that was then compounded as cumulative impact on the revised risk assessment for chlorpyrifos conducted by the US EPA in 2000 [Federal Register Notice 65(159) (2000) 49982]. But embedded within each science policy, there are assumptions which may be too conservative and which together have resulted in a very large multiplicative reduction in the allowable exposure limits for chlorpyrifos in the US. These new exposure limits are quite different from other regulatory standards around the world. There is third party opposition to many of these policies and many believe the understanding of the relationship between exposure and what is known about human and animal responses to chlorpyrifos has been clouded. These changes in policy insert a new level of conservatism into the scientific statement of risk and create confusion that threatens to weaken the credibility of the regulatory process.

Animals↗
PubMed2001

"Bite-and-Switch" approach using computationally designed molecularly imprinted polymers for sensing of creatinine.

A method for the selective detection of creatinine is reported, which is based on the reaction between polymerised hemithioacetal, formed by allyl mercaptan, o-phthalic aldehyde, and primary amine leading to the formation of fluorescent isoindole complex. This method has been demonstrated previously for the detection of creatine using creatine-imprinted molecularly imprinted polymers (MIPs) Since MIPs created using traditional methods were unable to differentiate between creatine and creatinine, a new approach to the rational design of a molecularly imprinted polymer (MIP) selective for creatinine was developed using computer simulation. A virtual library of functional monomers was assigned and screened against the target molecule, creatinine, using molecular modelling software. The monomers giving the highest binding score were further tested using simulated annealing in order to mimic the complexation of the functional monomers with template in the monomer mixture. The result of this simulation gave an optimised MIP composition. The computationally designed polymer demonstrated superior selectivity in comparison to the polymer prepared using traditional approach, a detection limit of 25 microM and good stability. The "Bite-and-Switch" approach combined with molecular imprinting can be used for the design of assays and sensors, selective for amino containing substances.

Biosensing Techniques↗
PubMed2001

Identification of mood stabilizer-regulated genes by differential-display PCR.

An increasing body of evidence demonstrates that lithium and valproate have a regulatory effect on signal transduction pathways. Alteration of signalling molecules triggers changes in gene expression which are thought to contribute to the therapeutic effects of these drugs on bipolar disorder. Differential-display PCR was used to identify genes in rat cerebral cortex that are regulated by chronic treatment with lithium and valproate. One novel lithium-regulated gene was identified and was characterized and studied further with 5'-RACE-PCR and library screening. We also found that valproate regulated the expression of the 78-kDa glucose-regulated protein (GRP78). Chronic treatment with valproate has also been found to increase gene transcription, mRNA and protein levels of GRP78. These results suggest novel targets for lithium and valproate that may be relevant to their mechanism of action. The data further our understanding of the mechanism of the action of mood stabilizers, and help identify new targets for genetic studies and therapeutic strategies in bipolar disorder.

Animals↗
PubMed2001

Modular chemistry: secondary building units as a basis for the design of highly porous and robust metal-organic carboxylate frameworks.

Secondary building units (SBUs) are molecular complexes and cluster entities in which ligand coordination modes and metal coordination environments can be utilized in the transformation of these fragments into extended porous networks using polytopic linkers (1,4-benzenedicarboxylate, 1,3,5,7-adamantanetetracarboxylate, etc.). Consideration of the geometric and chemical attributes of the SBUs and linkers leads to prediction of the framework topology, and in turn to the design and synthesis of a new class of porous materials with robust structures and high porosity.

Carboxylic Acids↗
PubMed2001

Analysis of the effects of cell spacing and liquid depth on nitric oxide and its oxidation products in cell cultures.

A series of reaction-diffusion models was developed to describe spatial and temporal variations in the concentrations of NO and related species (O(2)(-), peroxynitrite, and N(2)O(3)) in a cell culture configuration that is commonly used to study the toxicity and/or mutagenicity of NO. In the analysis, adherent cells that generate NO and O(2)(-) (e.g., macrophages) were assumed to be present in sub-monolayer quantities at the bottom of a culture dish, with a stagnant layer of culture medium separating them from the incubator gas. It was assumed also that the level of O(2)(-) production is lower than that of NO, consistent with the available data. These conditions were found to yield a distinctive spatial segregation among the extracellular reactions, which permits considerable simplifications in modeling events at both the macroscopic (culture medium depth) and microscopic (cell spacing) length scales. Whereas NO and N(2)O(3) were predicted to be present throughout the liquid medium, O(2)(-) and peroxynitrite were each confined to small regions near the cells. It was found that such systems reach a steady state in a small fraction of typical experimental times, so diffusional transients are unimportant. In contrast to the usual assumption made in experimental studies, NO loss to the headspace was found to be very significant. Thus, using the rate of accumulation of NO(2)(-) and NO(3)(-) (the nonvolatile end products of NO oxidation) to infer the cellular rate of NO production may significantly underestimate that rate. Moreover, it was found that varying the cell number density had very different influences on the relative exposures of the cells to NO, O(2)(-), peroxynitrite, and N(2)O(3). These results suggest that previously reported decreases in macrophage viability with increasing cell number density are more likely to be the result of exposure to NO and/or N(2)O(3) than to O(2)(-) or peroxynitrite.

Animals↗
PubMed2001

A phase II trial evaluating the safety and effectiveness of the AastromReplicell system for augmentation of low-dose blood stem cell transplantation.

To reduce the number of apheresis procedures and maintain the usual rate of hematopoietic recovery in patients treated with high-dose chemotherapy, we studied the effect of adding a small volume of ex vivo expanded bone marrow to low doses of CD34(+) blood stem cells. Thirty-four patients with breast cancer received G-CSF (10 microg/kg/day) priming followed by a limited volume (50-100 ml) bone marrow aspiration and standard 10-liter aphereses. Marrow was expanded ex vivo using the AastromReplicell system and infused along with low doses of blood-derived CD34(+) cells, collected in one apheresis. Thirty-one evaluable patients received a median CD34(+) blood stem cell dose of 0.7 x 10(6)/kg (range, 0.2-2.5) and 4.7 x 10(7) nucleated cells/kg (range, 1.98-8.7) of ex vivo expanded marrow. All patients recovered with normal blood counts and engrafted 500 neutrophils/microl and 20 000 platelets/microl in a median of 10 and 13 days, respectively. Multivariate analysis revealed that, in addition to CD34(+) lineage negative cell quantity, the quantity of stromal progenitors contained in the ex vivo expanded product correlated with engraftment outcome (r = 0.551, P = 0.004). Our results indicate that ex vivo expanded bone marrow is capable of facilitating engraftment when combined with low doses of mobilized blood derived CD34(+) cells.

Adult↗
PubMed2001

Determination of total and EDTA extractable metal distributions in the colloidal fraction of contaminated soils using SdFFF-ICP-HRMS.

Newly developed methods involving an on-line combination of sedimentation field-flow fractionation-inductively coupled plasma-high resolution mass spectrometry (SdFFF-ICP-HRMS) have been used to study the distributions of extractable heavy metals in a soil which had been treated with sewage sludge contaminated with Cu or Pb. The relationship of these metals with other elements in the colloidal fraction was also investigated. The colloidal fraction from the soil was obtained by repeated gravitational sedimentation and extracted with 0.11 M acetic acid, 0.1 M hydroxylamine hydrochloride, 0.05 M ethylenediaminetetraacetic acid disodium salt (EDTA) or aqua regia to assess the potential availability of the metals Cu and Pb. Large proportions of the Cu and Pb were extracted by EDTA, approaching that removed by aqua regia, whereas < 10% of the aqua regia extractable metals were removed by acetic acid and hydroxylamine chloride. The distributions of the heavy metals, the major mineral forming element (Al) and the elements forming sesquioxides (Fe and Mn) within different size classes (0.05-1 microm) of the colloidal fraction were measured using SdFFF-ICP-HRMS before and after extraction with EDTA. This information provides an insight into the composition of the colloids and the distributions of metal contaminants. In the contaminated soil colloids, the concentration of Fe, Mn and Pb is greatest in the smaller particles (<0.2 microm). In contrast, the Cu concentration is constant over the size range studied. Iron oxide surface coatings probably play a significant role in Pb adsorption on soil particles, but may be less important for Cu. The combination of selective chemical extraction, SdFFF and ICP-HRMS provides a means of determining the distribution of potentially available heavy metals within the colloidal fraction of contaminated soils.

Chelating Agents↗
PubMed2001

Oxyhemoglobin induces caspase-mediated cell death in cerebral endothelial cells.

Damaged endothelium is one of the pathological changes of the cerebral vasospastic vessels following subarachnoid hemorrhage. Our recent study shows that oxyhemoglobin (OxyHb) induces apoptosis in vascular endothelial cells. Apoptosis generally requires the action of various classes of proteases, including a family of cysteine proteases, known collectively as the caspases. This study was undertaken to investigate the activation of caspases and the efficacy of caspase inhibitors, z-IETD-fmk and z-LEHD-fmk, for oxyhemoglobin-induced apoptosis in vascular endothelial cells. Cultured bovine brain microvascular endothelial cells (passages 5-9) were used for this study. OxyHb (10 micromol/L) was added during the 24-72 h incubation with and without caspase-8 or - 9 inhibitors (z-IETD-fmk and z-LEHD-fmk). Counting surviving cells, DNA laddering, western blotting of poly(ADP-ribose) polymerase, and measurement of caspase activities were employed to confirm the cytotoxic effects of OxyHb and the protective effects of the caspase inhibitors. OxyHb produced cell detachment in a time-dependent manner and increased caspase-8 and -9 activities in the cells. z-IETD-fmk and z-LEHD-fmk (100 micromol/L) attenuated OxyHb-induced cell loss, DNA laddering, and proteolytic cleavage of PARP, although a lower concentration (10 micromol/L) of caspase inhibitors showed partial effects. OxyHb activates caspase-8 and -9 in cultured vascular endothelial cells, and blocking the action of the caspases with the inhibitors efficiently prevents loss of vascular endothelial cells from OxyHb-induced apoptosis in vitro. These results suggest that the caspase cascade participates in OxyHb-induced apoptosis.

Animals↗