Biomedical subjects

Jing Chen

Publications and source records attributed to Jing Chen.

At least 73 records · Page 4Linked to original sources

PubMed2006

Differential expression of the intermediate filament protein nestin during renal development and its localization in adult podocytes.

Nestin, an intermediate filament protein, is widely used as stem cell marker. Nestin has been shown to interact with other cytoskeleton proteins, suggesting a role in regulating cellular cytoskeletal structure. These studies examined renal nestin localization and developmental expression in mice. In developing kidney, anti-nestin antibody revealed strong immunoreactivity in vascular cleft of the S-shaped body and vascular tuft of capillary loop-stage glomerulus. The nestin-positive structures also were labeled by endothelial cell markers FLK1 and CD31 in immature glomeruli. Nestin was not detected in epithelial cells of immature glomeruli. In contrast, in mature glomerular, nestin immunoreactivity was observed only outside laminin-positive glomerular basement membrane, and co-localized with nephrin, consistent with podocyte nestin expression. In adult kidney, podocytes were the only cells that exhibited persistent nestin expression. Nestin was not detected in ureteric bud and its derivatives throughout renal development. Cell lineage studies, using a nestin promoter-driven Cre mouse and a ROSA26 reporter mouse, showed a strong beta-galactosidase activity in intermediate mesoderm in an embryonic day 10 embryo and all of the structures except those that were derived from ureteric bud in embryonic kidney through adult kidney. These studies show that nestin is expressed in progenitors of glomerular endothelial cells and renal progenitors that are derived from metanephric mesenchyme. In the adult kidney, nestin expression is restricted to differentiated podocytes, suggesting that nestin could play an important role in maintaining the structural integrity of the podocytes.

Aging↗

PubMed2006

Sophorolipid produced from the new yeast strain Wickerhamiella domercqiae induces apoptosis in H7402 human liver cancer cells.

The effects of sophorolipid on the growth and apoptosis of H7402 human liver cancer cells were investigated. By treatment with sophorolipid, a dose- and time-dependent inhibition of cell proliferation was observed. The cells developed many features of apoptosis, including condensation of chromatin, nuclear fragmentation, and appearance of apoptotic bodies, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling positive cells were stained dark brown. Sophorolipid treatment induced apoptosis in H7402 cells by blocking cell cycle at G1 phase and partly at S phase, activating caspase-3, and increasing Ca2+ concentration in cytoplasm. These findings may suggest a potential use of sophorolipid for liver cancer treatment.

Antineoplastic Agents↗

PubMed2006

FOXO transcription factors cooperate with delta EF1 to activate growth suppressive genes in B lymphocytes.

Forkhead transcription factors regulate many aspects of lymphocyte development and function. The FOXO subgroup of Forkhead factors opposes proliferation and survival, and FOXO inactivation is an important outcome of Ag receptor signaling. FOXO activity at target promoters is modulated by other transcription factors in a manner dependent on cell type and external stimulus. We have investigated the mechanisms by which FOXO proteins activate the promoters of two target genes in murine B lymphocytes, Ccng2 (encoding cyclin G2) and Rbl2 (p130), each of which has been implicated in cell cycle arrest. FOXO proteins bound directly to both promoters in vitro and in vivo, augmented transcriptional activity in reporter assays, and increased expression of the endogenous genes. Each of the promoter sequences has consensus binding sites for the deltaEF1 transcription factor, previously shown to either repress or activate different promoters. deltaEF1 bound to the Ccng2 and Rbl2 promoters in vitro and in vivo and increased reporter activity as well as endogenous mRNA levels for these genes. Strikingly, deltaEF1 synergized with FOXO proteins to strongly activate transcription from both promoters. Coexpression of deltaEF1 enhanced FOXO-induced cell cycle arrest in B lymphoma cells. These findings establish a novel mechanism of FOXO function at target promoters: cooperation with deltaEF1.

Animals↗

PubMed2006

Synthesis of cross-linked enzyme aggregates (CLEAs) in CO2-expanded micellar solutions.

A new method to prepare the cross-linked enzyme aggregates (CLEAs) was developed. Through cross-linking the enzyme (Trypsin) aggregates, which was precipitated from the CO2-expanded reverse micellar solutions, dendritic CLEAs were obtained. The sizes of the CLEAs prepared by this new method were nanometer order of magnitudes and could be tuned by changing the water-to-surfactant ratio (w0) and the concentration of enzyme in the reverse micellar solution. The diameter of CLEAs increased with increasing w0 value of reverse micelles and the concentration of Trypsin. The activity of CLEAs obtained by this method is improved in contrast to those obtained by the conventional method. This method has some advantages in applications and can be easily applied to the synthesis of other cross-linked enzyme aggregates.

Carbon Dioxide↗

PubMed2006

Enhanced solubilization of bovine serum albumin in reverse micelles by compressed CO2.

The effect of compressed CO2 on the solubilization of bovine serum albumin (BSA) in water/sodium bis-(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles was studied by observing phase behavior and recording UV-visible spectra under different conditions. The pH values within the water cores of reverse micelles at different CO2 pressures were also determined. The solubilization capacity of the reverse micelles for the protein increased considerably as CO2 pressure increased within the low-pressure range, but decreased at higher CO2 pressures, so that the micelles eventually lost their ability to solubilize the protein. The effect of CO2 on the stability of the reverse micelles played an important role in the relationship between pressure and protein solubility. A "multicomplex" model was proposed to explain these effects. The different solublization capacities within different pressure ranges demonstrates the unique advantage of using compressed CO2 in the extraction of proteins with reverse micelles.

Carbon Dioxide↗

PubMed2006

Body weight and mortality among men and women in China.

CONTEXT: The effect of underweight and obesity on mortality has not been well characterized in Asian populations. OBJECTIVE: To examine the relationship between body mass index (BMI) and mortality in Chinese adults. DESIGN, SETTING, AND PARTICIPANTS: A prospective cohort study in a nationally representative sample of 169,871 Chinese men and women aged 40 years or older. Data on body weight and covariables were obtained at a baseline examination in 1991 using a standard protocol. Follow-up evaluation was conducted in 1999-2000, with a response rate of 93.4% (n = 158,666). MAIN OUTCOME MEASURES: Body mass index and all-cause mortality. RESULTS: After excluding those participants with missing body weight or height values, 154,736 adults were included in the analysis. After adjustment for age, sex, cigarette smoking, alcohol consumption, physical activity, education, geographic region (north vs south), and urbanization (urban vs rural), a U-shaped association between BMI and all-cause mortality was observed (P<.001). Using those participants with a BMI of 24.0 to 24.9 as the reference group, the relative risks of all-cause mortality across categories of BMI were 1.65 (95% confidence interval [CI], 1.54-1.77) for BMI less than 18.5, 1.31 (95% CI, 1.22-1.41) for BMI 18.5 to 19.9, 1.20 (95% CI, 1.11-1.29) for BMI 20.0 to 20.9, 1.12 (95% CI, 1.04-1.21) for BMI 21.0 to 21.9, 1.11 (95% CI, 1.03-1.20) for BMI 22.0 to 22.9, 1.09 (95% CI, 1.01-1.19) for BMI 23.0 to 23.9, 1.00 (95% CI, 0.92-1.08) for BMI 25.0 to 26.9, 1.15 (95% CI, 1.06-1.24) for BMI 27.0 to 29.9, and 1.29 (95% CI, 1.16-1.42) for BMI 30.0 or more. The U-shaped association existed even after excluding participants who were current or former smokers, heavy alcohol drinkers, or who had prevalent chronic illness at the baseline examination, or who died during the first 3 years of follow-up. A similar association was observed between BMI and mortality from cardiovascular disease, cancer, and other causes. CONCLUSIONS: Our results indicate that both underweight and obesity were associated with increased mortality in the Chinese adult population. Furthermore, our findings support the use of a single common recommendation for defining overweight and obesity among all racial and ethnic groups.

Adult↗

PubMed2006

Organochlorine pesticides in soil profiles from Tianjin, China.

Soil cores were collected from soils at five sites in Tianjin area for the determination of hexachlorocyclohexane isomers (HCHs, including alpha-HCH, beta-HCH, gamma-HCH and delta-HCH), dichlorodiphenyltrichloroethane and metabolites (DDXs, including p,p'-DDT, p,p'-DDE and p,p'-DDD) and total organic carbon (TOC). The levels and vertical distributions of HCHs and DDXs are studied. Results show that the application of pesticides in the past years was the major contributor of HCHs and DDXs accumulation in the sampling areas. Significant positive correlations were seen between the residual and application amounts of HCHs and DDXs. Wastewater irrigation did not bring a significant contribution of HCHs or DDXs into the soils. HCHs and DDXs concentrations peak at the surface and decline in soil profile with depth, while fluctuations were observed in the plow layers of some cultivated soils caused by frequent cultivation activities and batch irrigation. Positive correlations were observed between the contents of TOC and HCHs and DDTs. Although the amounts of HCHs application in all sampling sites are larger than DDXs, at surface and near surface layers of most sampling sites, the concentrations of summation operatorHCHs are lower than summation operatorDDXs. The composition of DDXs in the applied pesticides and sampled soils indicates that there is no recent DDT input at the sample areas.

China↗

PubMed2006

Fluence-to-absorbed dose conversion coefficients for use in radiological protection of embryo and foetus against external exposure to protons from 100 MeV to 100 GeV.

In the literature, no conversion coefficients are available for use in radiological protection of embryo and foetus against external exposure to protons. This study used the Monte Carlo code MCNPX to determine mean absorbed doses to the embryo and foetus when the mother is exposed to proton fields. Monoenergetic protons ranging from 100 MeV to 100 GeV were considered. The irradiation geometries include antero-posterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT) and isotropic (ISO). At each of these standard irradiation geometries, absorbed doses to the foetal brain and body were calculated for the embryo of 8 weeks and the foetus of 3, 6 or 9 months. Proton fluence-to-absorbed dose conversion coefficients were derived for the four prenatal ages.

Body Burden↗

PubMed2006

AMPK regulation of mouse oocyte meiotic resumption in vitro.

We have previously shown that the adenosine analog 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), an activator of AMP-activated protein kinase (AMPK), stimulates an increase in AMPK activity and induces meiotic resumption in mouse oocytes [Downs, S.M., Hudson, E.R., Hardie, D.G., 2002. A potential role for AMP-activated protein kinase in meiotic induction in mouse oocytes. Dev. Biol, 245, 200-212]. The present study was carried out to better define a causative role for AMPK in oocyte meiotic maturation. When microinjected with a constitutively active AMPK, about 20% of mouse oocytes maintained in meiotic arrest with dibutyryl cAMP (dbcAMP) were stimulated to undergo germinal vesicle breakdown (GVB), while there was no effect of catalytically dead kinase. Western blot analysis revealed that germinal vesicle (GV)-stage oocytes cultured in dbcAMP-containing medium plus AICAR possessed elevated levels of active AMPK, and this was confirmed by AMPK assays using a peptide substrate of AMPK to directly measure AMPK activity. AICAR-induced meiotic resumption and AMPK activation were blocked by compound C or adenine 9-beta-d-arabinofuranoside (araA, a precursor of araATP), both inhibitors of AMPK. Compound C failed to suppress adenosine uptake and phosphorylation, indicating that it did not block AICAR action by preventing its metabolism to the AMP analog, ZMP. 2'-deoxycoformycin (DCF), a potent adenosine deaminase inhibitor, reversed the inhibitory effect of adenosine on oocyte maturation by modulating intracellular AMP levels and activating AMPK. Rosiglitazone, an anti-diabetic agent, stimulated AMPK activation in oocytes and triggered meiotic resumption. In spontaneously maturing oocytes, GVB was preceded by AMPK activation and blocked by compound C. Collectively, these results support the proposition that active AMPK within mouse oocytes provides a potent meiosis-inducing signal in vitro.

AMP-Activated Protein Kinases↗

PubMed2006

Mobilization as a preparative regimen for hematopoietic stem cell transplantation.

Current myeloablative conditioning regimens for hematopoietic stem cell (HSC) transplantation are associated with significant morbidity and mortality. Thus, alternative strategies to promote engraftment of infused HSCs with increased safety warrant investigation. Using parabiotic mice, we determined that, after mobilization with AMD3100 (a CXCR4 antagonist), HSCs exited from marrow, transited blood, and engrafted in open niches in partner marrow. We then hypothesized that mobilization before transplantation might vacate niches and improve HSC engraftment. When PeP3(b) mice were treated with AMD3100 at 2 hours before the transplantation of 4 x 10(7) marrow cells, donor cell engraftment was higher (4.6% +/- 1.1%) than in control animals (no AMD3100; 1.0% +/- 0.24%, P < .001). When mice received weekly injections of AMD3100 on 3 consecutive weeks and marrow cells were transplanted 2 hours after each mobilization, donor cell engraftment further increased (9.1% +/- 1.7%, P = .001). In contrast, in similar experiments with Balb/cByJ mice that mobilize poorly, there was no difference between the donor cell engraftment of AMD3100-treated and control recipients. These results indicate that the number of available niches regulates the number of HSCs. In addition, mobilization with AMD3100 may provide a safer preparative approach for HSC transplantation in genetic and other nonmalignant disorders.

Animals↗

PubMed2006

Threshold estimation in children using auditory steady-state responses to multiple simultaneous stimuli.

OBJECTIVE: It was the aim of this study to explore the use of auditory steady-state response (ASSR) to multiple simultaneous stimuli for threshold estimation in young children. METHOD: The subjects consisted of 40 children, aged from 6 months to 5 years, with variant degrees of sensorineural hearing loss. Simultaneous tonepips (0.5, 1, 2 and 4 kHz) with an amplitude modulated at different rates from 77 to 103 Hz were presented to both ears by insert phones. All children were tested with ASSR and age-appropriate behavioral tests. RESULTS: We found that (1) ASSR thresholds were usually higher than behavioral thresholds with a difference of 8-15 dB, (2) the behavioral thresholds were significantly correlated with ASSR thresholds (p = 0.000), and (3) there was a great difference between ASSR thresholds and behavioral thresholds found in a child with auditory neuropathy. CONCLUSION: Being objective, frequency specific and well correlated with behavioral thresholds, ASSR to multiple simultaneous stimuli was proven to be a good tool to predict behavioral hearing thresholds.

Acoustic Stimulation↗

PubMed2006

Using anti-VEGF McAb and magnetic nanoparticles as double-targeting vector for the radioimmunotherapy of liver cancer.

To study the biodistribution of a new radioimmunoconjugate-131I-anti-VEGF monoclonal antibody (Sc-7269)-Dextran Magnetic Nanoparticles (DMN) in nude mice bearing human liver cancer where an external magnetic field was focused on, and to evaluate its therapeutic effects and safety. Tumor Growth Delay (TGD) and tumor inhibition rate were observed as antitumor effect. Peripheral white blood cells counts and the loss of body weight were tested as an indicator of systemic toxicity. The results suggests that the radioimmunotherapy of intratumoral injection of 131I-Sc-7269-DMN may be safe and efficient for the treatment of liver cancer. Furthermore, the radioimmunotherapy using DMN as a 'carrier system' may be a highly potential approach in the treatment of other kind of tumors.

Animals↗

PubMed2006

Investigation of proton density for measuring tissue temperature.

PURPOSE: To examine the temperature dependence of the proton density (PD) in both adipose and muscle tissues, and the application of the PD as a thermometry parameter in breast tissues. MATERIALS AND METHODS: Porcine fat samples and bovine muscle samples were successively heated to temperatures ranging from 30 degrees C to 76 degrees C and then cooled. They were then imaged with a dual-echo spin-echo sequence. T1 and T2 effects were carefully corrected from the images. The apparent PD (APD) in regions of interest (ROIs) and the sum of the APD in all pixels (Sum_APD) were measured and analyzed by linear regression. RESULTS: APD in adipose tissue is linear and reversible, and changes with a 0.3%/ degrees C to 0.45%/ degrees C temperature variation. The temperature coefficient of Sum_APD in adipose tissue is approximately 0.29%/ degrees C, as predicted from the Boltzmann distribution. However, the results in muscle tissue are more variable. There is an offset in both APD and Sum_APD between heating and cooling phases, as well as different temperature coefficients between these two phases. CONCLUSION: The Sum_APD in adipose tissue validates the 1/T dependence on temperature. The APD is a potentially useful parameter for fat thermometry; however, its application in muscle tissue requires further investigation.

Adipose Tissue↗

PubMed2006

Induction of meiotic maturation in mouse oocytes by adenosine analogs.

In this study we have examined the meiosis-inducing influence of adenosine analogs in mouse oocytes. When a varied group of nucleosides and nucleotides were tested on overnight cultures of hypoxanthine-arrested, cumulus cell-enclosed oocytes (CEO), halogenated adenosine nucleosides, but not native adenosine, exhibited a significant meiosis-inducing capability. When tested under a variety of conditions, meiotic induction by 8-bromo-adenosine (8-Br-Ado) and a second adenosine analog, methylmercaptopurine riboside (MMPR), was especially potent in denuded oocytes (DO) compared to CEO and was not dependent on the type of inhibitor chosen to maintain meiotic arrest. Germinal vesicle breakdown (GVB) was stimulated with rapid kinetics and was preceded by an increase in AMP-activated protein kinase (AMPK) activity. Moreover, compound C, an inhibitor of AMPK, blocked the meiosis-inducing activities of both adenosine analogs. When tested for an effect on meiotic progression to metaphase II (MII) in spontaneously maturing CEO, 8-Br-Ado and the AMPK activator, 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR), increased the percentage of MII-stage oocytes, but MMPR decreased this number. Adenosine and inhibitors of de novo purine synthesis had no effect on the completion of maturation, while compound C suppressed this process. These results support the proposition that oocyte AMPK mediates the positive influence of AICAR and 8-Br-Ado on both the initiation and completion of meiotic maturation. The role of AMPK in MMPR action is less clear.

AMP-Activated Protein Kinases↗

PubMed2006

Illumina universal bead arrays.

This chapter describes an accurate, scalable, and flexible microarray technology. It includes a miniaturized array platform where each individual feature is quality controlled and a versatile assay that can be adapted for various genetic analyses, such as single nucleotide polymorphism genotyping, DNA methylation detection, and gene expression profiling. This chapter describes the concept of the BeadArray technology, two different Array of Arrays formats, the assay scheme and protocol, the performance of the system, and its use in large-scale genetic, epigenetic, and expression studies.

Animals↗

PubMed2006

Y-chromosome genotyping and genetic structure of Zhuang populations.

Zhuang, the largest ethnic minority population in China, is one of the descendant groups of the ancient Bai-Yue. Linguistically, Zhuang languages are grouped into northern and southern dialects. To characterize its genetic structure, 13 East Asian-specific Y-chromosome biallelic markers and 7 Y-chromosome short tandem repeat (STR) markers were used to infer the haplogroups of Zhuang populations. Our results showed that O*, O2a, and O1 are the predominant haplogroups in Zhuang. Frequency distribution and principal component analysis showed that Zhuang was closely related to groups of Bai-Yue origin and therefore was likely to be the descendant of Bai-Yue. The results of principal component analysis and hierarchical clustering analysis contradicted the linguistically derived north-south division. Interestingly, a west-east clinal trend of haplotype frequency changes was observed, which was supported by AMOVA analysis that showed that between-population variance of east-west division was larger than that of north-south division. O* network suggested that the Hongshuihe branch was the center of Zhuang. Our study suggests that there are three major components in Zhuang. The O* and O2a constituted the original component; later, O1 was brought into Zhuang, especially eastern Zhuang; and finally, northern Han population brought O3 into the Zhuang populations.

Alleles↗

PubMed2006

Bundle-shaped cyclodextrin-Tb nano-supramolecular assembly mediated by C60: intramolecular energy transfer.

A bundle-shaped nano-supramolecular assembly possessing numerous luminescent cyclodextrin-Tb polyads and photosensitizing C(60) units has been constructed through the end-to-end inclusion complexation of cyclodextrin cavities with C(60)s, and its properties have been comprehensively characterized. Further investigations on the luminescence properties of the cyclodextrin-Tb polyad and the bundle-shaped assembly demonstrate that a pyridine --> Tb --> C(60) intramolecular energy transfer process is operative when a solution of the assembly is exposed to UV light.

Crystallization↗

PubMed2006

Assessment and management of residential radon health risks: a report from the health Canada radon workshop.

Epidemiologic studies of uranium miners and other underground miners have consistently shown miners exposed to high levels of radon to be at increased risk of lung cancer. More recently, concern has arisen about lung cancer risks among people exposed to lower levels of radon in homes. The current Canadian guideline for residential radon exposure was set in 1988 at 800 Bq/m(3). Because of the accumulation of a considerable body of new scientific evidence on radon lung cancer risks since that time, Health Canada sponsored a workshop to review the current state-of-the-science on radon health risks. The specific objectives of the workshop were (1) to collect and assess scientific information relevant to setting national radon policy in Canada, and (2) to gather information on social, political, and operational considerations in setting national policy. The workshop, held on 3-4 March 2004, was attended by 38 invited scientists, regulators, and other stakeholders from Canada and the United States. The presentations on the first day dealt primarily with scientific issues. The combined analysis of North American residential radon and lung cancer studies was reviewed. The analysis confirmed a small but detectable increase in lung cancer risk at residential exposure levels. Current estimates suggest that radon in homes is responsible for approximately 10% of all lung cancer deaths in Canada, making radon the second leading cause of lung cancer after tobacco smoking. This was followed by a perspective from an UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) working group on radon. There were two presentations on occupational exposures to radon and two presentations considered the possibility of radon as a causative factor for cardiovascular disease and for cancer in other organs besides the lung. The possible contribution of environmental tobacco smoke to lung cancers in nonsmokers was also considered. Areas for future research were identified. The second day was devoted to policy and operational issues. The presentations began with a perspective from the U.S. Environmental Protection Agency, followed by a history of radon policy development in Canada. Subsequent presentations dealt with the cost-effectiveness of radon mitigation, Canadian building codes and radon, and a summary of radon standards from around the world. Provincial representatives and a private consultant were given opportunities to present their viewpoints. A number of strategies for reducing residential radon exposure in Canada were recognized, including testing and mitigation of existing homes (on either a widespread or targeted basis) and changing the building code to require that radon mitigation devices be installed at the time a new home is constructed. The various elements of a comprehensive national radon policy were set forth.

Air Pollutants, Radioactive↗