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Biomedical subjects

W Zheng

Publications and source records attributed to W Zheng.

At least 91 records · Page 5Linked to original sources
PubMed2001

Population-based, case-control study of blood C-peptide level and breast cancer risk.

Insulin resistance has been suggested to be associated with an increased risk of breast cancer. Insulin sensitivity can be measured using blood C-peptide, a marker of insulin secretion. It is thus conceivable that blood C-peptide levels may be associated with breast cancer risk. To evaluate this hypothesis, we analyzed data from a subset (143 case-control pairs matched by age and status of menopause) of women who participated in the Shanghai Breast Cancer Study, a population-based, case-control study conducted in Shanghai during 1996-1998. Fasting blood samples were collected from study subjects to measure C-peptide levels. For cancer patients, the samples were collected before any cancer therapy. Conditional logistic regression was used to estimate adjusted odds ratios and 95% confidence intervals related to C-peptide levels. Breast cancer risk was increased with increasing levels of C-peptide (trend test, P = 0.01), with an odds ratio of 2.7 (95% confidence interval = 1.2-5.9) observed for the highest compared with the lowest tertile of C-peptide concentration after adjusting for body mass index and age at the first live birth. The risk was not altered after fully adjusting for other traditional risk factors for breast cancer. This positive association was observed in both pre and postmenopausal women and regardless of the levels of waist-to-hip ratio or body mass index. The results from this study were consistent with the insulin-resistance hypothesis for breast cancer and suggest that increased levels of C-peptide may contribute to the development of breast cancer.

Adult↗
PubMed2001

Characteristics of spongiform leukoencephalopathy induced by heroin: MRI detection.

OBJECTIVE: To elucidate the imaging characteristics of spongiform leukoencephalopathy induced by heroin and the diagnostic value of MRI examination. METHODS: Eleven cases of heroin addiction were examined by MRI. The sequences included T1-weighted imaging (T1WI), T2-weighted imaging (T2WI) and fast fluid-attenuated inversion recovery pulse sequence (Flair). RESULTS: Bilateral symmetrical lesions were located in the white matter of the cerebrum and cerebellum, the internal capsule in all cases, and the callosum in 6 cases. Elliptical lesions in the mesencephalon were found in two cases. These lesions were shown as hypointense signals on T1WI and hyperintense signals on T2WI and Flair's imaging. Cerebellar white matter suffered more severely, but the dentate nuclei were not invaded. CONCLUSION: Heroin-induced spongiform leukoencephalopathy has characteristic patterns in MRI, which are very specific to this form of the disease.

Adult↗
PubMed2001

[Effect of benzo(a)pyrene on antioxidant enzyme activities in Boleophthalmus pectinirostris liver].

The effect of different BaP concentrations on the activities of superoxide dismutase(SOD), glutathione peroxidase (GPx) and catalase(CAT) in Boleophthalmus pectinirostris liver was studied under experimental condition. The results showed that the activities of antioxidant enzymes did not change too much with BaP exposure in lower concentration, whereas the SOD and GPx activities were increased significantly with BaP exposure in higher concentration. No statistical changes were observed in the effect of BaP exposure in different concentrations on CAT activities throughout the experiment.

Animals↗
PubMed2001

[Microsurgical treatment of 86 cases of intracranial aneurysms].

OBJECTIVE: To summarize the microsurgical experience in the treatment of intracranial aneurysms. METHOD: The clinical materials, surgical modes and prognosis of 86 cases of clipped intracranial aneurysms were retrospectively reviewed. RESULTS: Of the 86 cases, 69 recovered, 10 were moderately disabled, 2 severely disabled, and 5 died. CONCLUSIONS: To avoid rerupture, aneurysms should be treated as soon as possible when the diagnosis was established. Proper management of rupture of aneurysms during operation is the key of success. Multiple aneurysms are better to be clipped in one stage. "de novo" aneurysms could be detected early by long-term angiography.

Adolescent↗
PubMed2001

Impairment of non-specific immunity in patients under persistent vegetative state resulting from trauma.

OBJECTIVE: To investigate the immune response in patients under persistent vegetative state (PVS) resulting from trauma. METHODS: Peripheral blood monocytes were obtained from 12 PVS patients (Group PVS)and individuals in normal control group by density gradient centrifugation; the enzyme linked immunosorbent assay kit was then used to measure monocyte HLA-DR antigen expression on the surface of peripheral blood monocytes before and after monocyte activation with either IFN-gamma or LPS. RESULTS: Compared with normal control group, the peripheral blood monocyte HLA-DR antigen expression in the Group PVC fell significantly in PV S patients (P<0.001); the level of HLA-DR antigen express ion on the monocyte surface rose notably after stimulation with either IFN-gamma or LPS (P<0.01). As for PVS patients, it was still difficult to restore to normal (P<0.05). CONCLUSIONS: The level of HLA-DR antigen expression on the sur face of peripheral blood monocytes in PVS patients decreases obviously. Therefore, the function of non-specific immunity in PVS patients is suppressed.

Adult↗
PubMed2001

[Expression of recombinant human Flt3 ligand in Escherichia coli and its purification and characterization].

OBJECTIVE: To establish a highly efficient expression system of recombinant human Flt3 ligand (rhFL) in E. coli and a suitable purification method of the expressed products. METHOD: Human FL encoding cDNA was introduced into pProEXHT plasmid to express a 6 x His-FL fusion protein in E. coli. The fusion protein expressed in inclusion body was isolated, solubilized and refolded, and then purified by chromatography on a metal-chelating affinity column (MCAC). Its activity was detected by stimulating the proliferation of CD(34)(+) cells. RESULT: The amount of rhFL expressed was about 15% of total bacterial proteins and the purity of rhFL was 90% after MCAC. The combination of rhFL, granulocyte colony-stimulating factor and erythropoietin could stimulate CD(34)(+) cells to a 400 fold expansion. CONCLUSION: The purified rhFL had a potent activity to stimulate hematopoietic stem cells to expanse in vitro.

Cell Proliferation↗
PubMed2001

Progress in DNA chip technology.

DNA chip technology employs light-directed in situ oligonucleotide synthesis and/or DNA microarray printing device to produce arrays of large number of probes in the tiny surface of silicon substrates, which makes it possible that the gene detection be conducted efficiently with high speed and sensitivity. The DNA chip may take important part in genome research, gene diagnoses and so on.

Animals↗
PubMed2000

Cell injury releases endogenous adjuvants that stimulate cytotoxic T cell responses.

General immunostimulants (adjuvants) are essential for generating immunity to many antigens. In bacterial infections, adjuvants are provided by components of the microorganism, e.g., lipopolysaccharide. However, it is unclear what provides the adjuvant effect for immune responses that are generated to tumors and many viruses. Here we show that cell injury and death of tumor or even normal cells provide a potent adjuvant effect for the stimulation of cytotoxic T lymphocyte responses. This adjuvant activity is constitutively present in the cytoplasm of cells and is increased in the cytoplasm of cells dying by apoptosis. The release of these components stimulates immune responses both locally and at a distance, and provides a simple mechanism to alert the immune system to potential danger in almost all pathological situations.

3T3 Cells↗
PubMed2000

Patients with intractable epilepsy have low melatonin, which increases following seizures.

Melatonin, which is used to treat sleep disorders, has anticonvulsant properties. The authors measured salivary melatonin and cortisol, at baseline and following seizures, in patients with intractable temporal lobe epilepsy and controls. Melatonin was reduced in patients with epilepsy at baseline compared with controls, and increased threefold following seizures. Cortisol also increased following seizures. Patients with intractable epilepsy have low baseline melatonin levels that increase dramatically following seizures.

Adult↗
PubMed2000

A simple copper(II)-L-histidine system for efficient hydrolytic cleavage of DNA.

Copper(II)-L-histidine complexes effectively promote the cleavage of plasmid DNA and dideoxynucleotide dApdA at physiological pH and temperature. Studies of the mechanism of plasmid DNA cleavage by added radical scavengers, using rigorously anaerobic experiments, analyses for malondialdehyde-like products, religation assays, and HPLC analyses, indicate that DNA cleavage mediated by Cu(L-His) occurs via a hydrolytic path. The hydrolytic cleavage rate constants at 37 degrees C are estimated to be 0.76 h-1 for the decrease of form I and 0.25 h-1 for the increase of form III. The phosphoimager picture reveals that Cu(L-His) cleaves DNA with a certain sequence specificity (preferentially at 5'-GT-3'). The dinucleotide hydrolysis shows, with [Cu(L-His)] = 0.8 mM, rate enhancement factors of > 10(8). Interestingly, histidine-metal ion interactions (with Cu(II), Ni(II), Zn(II), etc.) have been used for various applications, e.g., protein purification, cross-linking, and targeting proteins to lipid bilayers. Our findings may provide the basis for developing new applications and new ways to design more effective and useful catalysts for DNA cleavage. Cu(L-His) is one of only a few well-defined metal complexes demonstrated to hydrolytically cleave dideoxynucleotides and DNA.

Animals↗
PubMed2000

Traces of learning in the auditory localization pathway.

One of the fascinating properties of the central nervous system is its ability to learn: the ability to alter its functional properties adaptively as a consequence of the interactions of an animal with the environment. The auditory localization pathway provides an opportunity to observe such adaptive changes and to study the cellular mechanisms that underlie them. The midbrain localization pathway creates a multimodal map of space that represents the nervous system's associations of auditory cues with locations in visual space. Various manipulations of auditory or visual experience, especially during early life, that change the relationship between auditory cues and locations in space lead to adaptive changes in auditory localization behavior and to corresponding changes in the functional and anatomical properties of this pathway. Traces of this early learning persist into adulthood, enabling adults to reacquire patterns of connectivity that were learned initially during the juvenile period.

Animals↗
PubMed2000

Association of menstrual and reproductive factors with breast cancer risk: results from the Shanghai Breast Cancer Study.

The incidence of breast cancer among women in Shanghai, a traditionally low-risk population, has increased substantially over the past 20 years. To evaluate the association of menstrual and reproductive factors with breast cancer risk and the influence of these factors on the temporal trend of breast cancer incidence, we analyzed data from the Shanghai Breast Cancer Study, a population-based case-control study of breast cancer recently completed among Chinese women in urban Shanghai. In-person interviews were completed for 1,459 women newly diagnosed with breast cancer between ages 25 and 64 and for 1,556 controls frequency-matched to cases by age. Unconditional logistic regression was employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) related to menstrual and reproductive factors. Earlier menarcheal age, nulliparity, and later age at first live birth were associated with increased risk of breast cancer among both pre- and post-menopausal women, while never having breast-fed and later age at menopause were associated with elevated risk only among post-menopausal women. Among controls, 32% of younger women (</=40 years) and 24% of older women (>40 years) reported starting menarche at age of 13 or younger, and this factor contributed to 44% of cases diagnosed among younger women and 26% to 28% of cases in older women. Older age at first live birth or at menopause explained a considerable portion of cases diagnosed in older, but not younger, women. Our study suggests that the changes in menstrual and reproductive patterns among women in Shanghai have contributed to the recent increase in breast cancer incidence, particularly among younger women.

Adult↗
PubMed2000

Role of the guanosine triphosphatase Rac2 in T helper 1 cell differentiation.

T helper 1 (TH1) cells mediate cellular immunity, whereas TH2 cells potentiate antiparasite and humoral immunity. We used a complementary DNA subtraction method, representational display analysis, to show that the small guanosine triphosphatase Rac2 is expressed selectively in murine TH1 cells. Rac induces the interferon-gamma (IFN-gamma) promoter through cooperative activation of the nuclear factor kappa B and p38 mitogen-activated protein kinase pathways. Tetracycline-regulated transgenic mice expressing constitutively active Rac2 in T cells exhibited enhanced IFN-gamma production. Dominant-negative Rac inhibited IFN-gamma production in murine T cells. Moreover, T cells from Rac2-/- mice showed decreased IFN-gamma production under TH1 conditions in vitro. Thus, Rac2 activates TH1-specific signaling and IFN-gamma gene expression.

Animals↗
PubMed2000

The Missing Link: Early Methane ("T") Dwarfs in the Sloan Digital Sky Survey.

We report the discovery of three cool brown dwarfs that fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands in the 1-2.5 µm range, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water. The newly discovered objects were detected as very red objects in the Sloan Digital Sky Survey imaging data and have JHK colors between the red L dwarfs and the blue Gl 229B-like T dwarfs. They show both CO and CH(4) absorption in their near-infrared spectra in addition to H(2)O, with weaker CH(4) absorption features in the H and K bands than those in all other methane dwarfs reported to date. Due to the presence of CH(4) in these bands, we propose that these objects are early T dwarfs. The three form part of the brown dwarf spectral sequence and fill in the large gap in the overall spectral sequence from the hottest main-sequence stars to the coolest methane dwarfs currently known.

Journal Article↗
PubMed2000

Imparting biomimetic ion-gating recognition properties to electrodes with a hydrogen-bonding structured core-shell nanoparticle network.

This paper presents findings of the creation of biomimetic ion-gating properties with core-shell nanoparticle network architectures. The architectures were formed by hydrogen-bonding linkages via an exchange-cross-linking-precipitation reaction pathway using gold nanoparticles capped with thiolate shell and alkylthiols terminated with carboxylic groups as model building blocks. Such network assemblies have open frameworks in which void space is in the form of a channel or chamber with the nanometer-sized cores defining its size, the geometric arrangement defining its shape, and the shell structures defining its chemical specificity. The formation of the network linkages via head-to-head hydrogen-bonded carboxylic terminals and the reversible pH-tuned structural properties between neutral and ionic states were characterized using infrared reflectance spectroscopic technique. The biomimetic ion-gating properties were demonstrated by measuring the pH-tuned network "open-close" responses to charged redox probes. Such redox responses were shown to depend on the degree of protonation-deprotonation of carboxylic groups at the interparticle linkages, core sizes of the nanoparticles, and charges of the redox probes. Differences in structural networking, pH-tuning, and electrochemical gating properties were identified between the network films derived from nanoparticles of two different core sizes (2 and 5 nm). The mechanistic correlation of these structural properties was discussed. These findings have added a new pathway to the current approaches to biomimetic molecular recognition via design of core-shell nanoparticle architectures at both nanocrystal and molecular scales.

Alum Compounds↗