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Biomedical subjects

L Zhu

Publications and source records attributed to L Zhu.

At least 19 recordsLinked to original sources
PubMed2006

Total fluoride in Guangdong soil profiles, China: spatial distribution and vertical variation.

A total of 260 soil profiles were reported to investigate the fluoride distribution and vertical variation in Guangdong province. The soil fluoride contents followed an approximately lognormal distribution. Although the soil fluoride geometric mean concentration of 407 mg/kg is lower than that of China, its content varied from 87 to 2860 mg/kg. An upper baseline concentration of 688 mg/kg was estimated for surface soils. In A-, B-, and C-horizon soil fluoride spatial distribution presented similar patterns that high fluoride concentration mainly located in limestone, purple shale, and sandshale areas, indicated that soil fluoride spatial distribution was primarily dependent on the regional bedrock properties rather than anthropogenic inputs. From A- to C- horizon soil fluoride geometric mean concentration had an increasing tendency of 407, 448, and 465 mg/kg. This vertical variation was the result of the intensive eluviation under the subtropical hydrothermal condition, and had closely related with soil properties, such as lower organic matters and clay content variations. Moreover, the soil degradation and erosion was also an important pathway of soil fluoride movement, as a result the soil fluoride exported into surface and groundwaters would reach about 4.1x10(4) t year-1 in the study area.

China↗
PubMed2006

The tumor suppressor effect of the glucocorticoid receptor in skin is mediated via its effect on follicular epithelial stem cells.

Glucocorticoids are potent inhibitors of mouse skin tumorigenesis. The glucocorticoid control of cellular functions is mediated via the glucocorticoid receptor (GR), a well-known transcription factor. Recently, we generated transgenic mice overexpressing GR under control of the keratin5 (K5) promoter, and showed that K5.GR animals are resistant to skin carcinogenesis. Follicular epithelial stem cells (SCs), located in the bulge region of the hair follicle, are believed to be one of the target cells for skin carcinogenesis. We found that the number of putative hair follicle SC detected as label-retaining cells was significantly less in the K5.GR transgenics compared to wild type (w.t.) littermates. We also showed that GR overexpression led to a reduction in the clonogenicity of the follicular epithelial SCs. We evaluated the global effect of GR on gene expression in a population of follicular SC-enriched bulge keratinocytes isolated by fluorescence activated cell sorting. We found that GR affected the expression of numerous bulge SC 'signature' genes, genes involved in the maintenance of SC and progenitor cells of non-epidermal origin and proapoptotic genes. Our findings underscore the important role of GR signaling in the homeostasis of follicular epithelial SCs, and suggest that the reduction in their number may underlie the tumor suppressor effect of GR in the skin.

Animals↗
PubMed2006

Glucagon receptor knockout mice are resistant to diet-induced obesity and streptozotocin-mediated beta cell loss and hyperglycaemia.

AIMS/HYPOTHESIS: Under normal physiological conditions, glucagon signalling is important in glucose homeostasis. Hyperglucagonaemia or altered insulin:glucagon ratio plays a role in maintaining hyperglycaemia in subjects with type 2 diabetes. It has been reported that glucagon receptor knockout (Gcgr (-/-)) mice develop normally and have lower plasma glucose on a normal diet. The goal of the current research was to further investigate the role of glucagon signalling in metabolic control and glucose homeostasis. METHODS: Gcgr (-/-) mice were challenged with a high-fat diet (HFD) and with streptozotocin, which induces beta cell damage. They were then analysed for whole-body and serum metabolic phenotypes as well as pancreatic islet morphology. RESULTS: In comparison with wild-type mice, Gcgr (-/-) mice exhibited decreased body weight and food intake, reduced plasma glucose levels, and improved oral and intraperitoneal glucose tolerance. Elevated glucagon-like peptide-1 levels and reduced gastric emptying were also observed in Gcgr (-/-) mice, which also had reduced HFD-induced hyperinsulinaemia and hyperleptinaemia, and were resistant to the development of hepatic steatosis. In addition, Gcgr (-/-) mice were resistant to STZ-induced hyperglycaemia and pancreatic beta cell destruction. CONCLUSIONS/INTERPRETATION: This study demonstrates that blocking glucagon signalling by targeted Gcgr gene deletion leads to an improvement in metabolic control in this mouse model.

Animals↗
PubMed2006

Nucleus- and species-specific properties of the slow (<1 Hz) sleep oscillation in thalamocortical neurons.

The slow (<1 Hz) rhythm is an electroencephalogram hallmark of resting sleep. In thalamocortical neurons this rhythm correlates with a slow (<1 Hz) oscillation comprising recurring UP and DOWN membrane potential states. Recently, we showed that metabotropic glutamate receptor activation brings about an intrinsic slow oscillation in thalamocortical neurons of the cat dorsal lateral geniculate nucleus in vitro which is identical to that observed in vivo. The aim of this study was to further assess the properties of this oscillation and compare them with those observed in thalamocortical neurons of three other thalamic nuclei in the cat (ventrobasal complex, medial geniculate body; ventral lateral nucleus) and two thalamic nuclei in rats and mice (lateral geniculate nucleus and ventrobasal complex). Slow oscillations were evident in all of these additional structures and shared several basic properties including, i) the stereotypical, rhythmic alternation between distinct UP and DOWN states with the UP state always commencing with a low-threshold Ca2+ potential, and ii) an inverse relationship between frequency and injected current so that slow oscillations always increase in frequency with hyperpolarization, often culminating in delta (delta) activity at approximately 1-4 Hz. However, beyond these common properties there were important differences in expression between different nuclei. Most notably, 44% of slow oscillations in the cat lateral geniculate nucleus possessed UP states that comprised sustained tonic firing and/or high-threshold bursting. In contrast, slow oscillations in cat ventrobasal complex, medial geniculate body and ventral lateral nucleus thalamocortical neurons exhibited such UP states in only 16%, 11% and 10% of cases, respectively, whereas slow oscillations in the lateral geniculate nucleus and ventrobasal complex of rats and mice did so in <12% of cases. Thus, the slow oscillation is a common feature of thalamocortical neurons that displays clear species- and nuclei-related differences. The potential functional significance of these results is discussed.

Action Potentials↗
PubMed2006

A methodology for investigating new nonprecious metal catalysts for PEM fuel cells.

This paper reports an approach to investigate metal-chalcogen materials as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. The methodology is illustrated with reference to Co-Se thin films prepared by magnetron sputtering onto a glassy-carbon substrate. Scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) have been used, in parallel with electrochemical activity and stability measurements, to assess how the electrochemical performance relates to chemical composition. It is shown that Co-Se thin films with varying Se are active for oxygen reduction, although the open circuit potential (OCP) is lower than for Pt. A kinetically controlled process is observed in the potential range 0.5-0.7 V (vs reversible hydrogen electrode) for the thin-film catalysts studied. An initial exposure of the thin-film samples to an acid environment served as a pretreatment, which modified surface composition prior to activity measurements with the rotating disk electrode (RDE) method. Based on the SAM characterization before and after electrochemical tests, all surfaces demonstrating activity are dominated by chalcogen. XRD shows that the thin films have nanocrystalline character that is based on a Co(1-x)Se phase. Parallel studies on Co-Se powder supported on XC72R carbon show comparable OCP, Tafel region, and structural phase as for the thin-film model catalysts. A comparison for ORR activity has also been made between this Co-Se powder and a commercial Pt catalyst.

Journal Article↗
PubMed2006

Membrane excitability and fear conditioning in cerebellar Purkinje cell.

In a previous study it has been demonstrated that fear conditioning is associated with a long-lasting potentiation of parallel fiber to Purkinje cell synaptic transmission in vermal lobules V and VI. Since modifications of intrinsic membrane properties have been suggested to mediate some forms of memory processes, we investigated possible changes of Purkinje cell intrinsic properties following the same learning paradigm and in the same cerebellar region. By means of the patch clamp technique, Purkinje cell passive and active membrane properties were evaluated in slices prepared from rats 10 min or 24 h after fear conditioning and in slices from control naïve animals. None of the evaluated parameters (input resistance, inward rectification, maximal firing frequency and the first inter-spike interval, post-burst afterhyperpolarization, action potential threshold and amplitude, action potential afterhyperpolarization) was significantly different between the three studied groups also in those cells where parallel fiber-Purkinje cell synapse was potentiated. Our results show that fear learning does not affect the intrinsic membrane properties involved in Purkinje cell firing. Therefore, at the level of Purkinje cell the plastic change associated with fear conditioning is specifically restricted to synaptic efficacy.

Action Potentials↗
PubMed2006

Spatial distribution and vertical variation of arsenic in Guangdong soil profiles, China.

Total of 260 soil profiles were reported to investigate the arsenic spatial distribution and vertical variation in Guangdong province. The arsenic concentration followed an approximately lognormal distribution. The arsenic geometric mean concentration of 10.4 mg/kg is higher than that of China. An upper baseline concentration of 23.4 mg/kg was estimated for surface soils. The influence of soil properties on arsenic concentration was not important. Arsenic spatial distributions presented similar patterns that high arsenic concentration mainly located in limestone, and sandshale areas, indicating that soil arsenic distribution was dependent on bedrock properties than anthropogenic inputs. Moreover, from A- to C-horizon arsenic geometric mean concentrations had an increasing tendency of 10.4, 10.7 to 11.3 mg/kg. This vertical variation may be related to the lower soil organic matter and soil degradation and erosion. Consequently, the soil arsenic export into surface and groundwaters would reach 1040 t year-1 in the study area.

Arsenic↗
PubMed2006

Anti-inflammatory effects of inhaled nitric oxide are optimized at lower oxygen concentration in experimental Klebsiella pneumoniae pneumonia.

OBJECTIVE AND DESIGN: To evaluate whether antiinflammatory effects of inhaled nitric oxide (NO) in experimental Klebsiella pneumoniae pneumonia may be affected by oxygen levels in association with cytokine response and NO synthase (NOS) activity. SUBJECTS AND TREATMENT: Healthy adult rats were intratracheally instilled with live Klebsiella pneumoniae to induce pneumonia (P) or with sterile saline as a control (C) group. Group C was allocated to room air (CA) and inhaled NO (CNO, NO = 20 parts per million) groups. Group P was divided into 6 groups (n = 8 - 10) exposed to room air (PA), inhaled NO (PNO), low oxygen (40%, PLO), inhaled NO and low oxygen (PLONO), high oxygen (100%, PHO), and inhaled NO and high oxygen (98%, PHONO). After 24 h exposure, intraalveolar cells, expression of proinflammatory cytokines, nuclear transcription factor (NF-kappaB), myeloperoxidase (MPO) and NOS activities, characteristic of lung inflammatory mechanisms, were measured. RESULTS: All the pneumonia groups had pneumonia whereas CA and CNO had no or mild lung inflammation. Compared to the PA, significantly decreased recruitment of alveolar neutrophils was found in the PNO, along with lower NF-kappaB and MPO activity, tumor necrosis factor-alpha (TNF-alpha) and intercellular adhesion molecule-1 (ICAM-1). Similar trends were found between the PLONO and PLO in alleviation of lung inflammation. However, PHONO significantly enhanced recruitment of alveolar neutrophils and pulmonary MPO activity associated with increased TNF-alpha. Inhaled NO improved bacterial clearance, reduced total proteins in alveoli, and ICAM-1 expression irrespective of oxygen levels. Inhaled NO and/or low and high oxygen partially restored constitutive NOS activity whereas high oxygen or together with inhaled NO depressed inducible NOS activity. CONCLUSIONS: The overall beneficial effects of inhaled NO in anti-inflammation in the mature lungs with K. pneumoniae pneumonia are in favor of a combination with lower level of oxygen, which warrants clinical verification in the treatment of lung inflammatory injury.

Animals↗
PubMed2006

Risk assessment of organic pesticides pollution in surface water of Hangzhou.

Advances in research on pollution of organic pesticides (OPs) in surface water, pollution survey and risk assessments of organochlorine pesticides (OCPs) and organophosphorus pesticides (OPPs) of surface water in Hangzhou are conducted. Total concentrations of dichloro-diphenyl-trichloroethane (DDT) and hexachloride-benzene (HCH) in surface water were observed to be 0-0.270 microg/L and 0-0.00625 microg/L respectively. DDE, as a metabolite of DDT and many species of OPP(S) were determined in some samples of surface water. Parathion, the main pollutant among OPPs in surface water of Hangzhou, was observed to be 0-0.445 microg/L. Based on these experimental results, health risk assessments on the organic pollution are developed. It is observed that the total risk "R (T)" at present time of surface water in Hangzhou is mainly contributed by organophosphorus pesticides, especially Parathion; HCH and DDT are not the main contaminants; on the contrary, organophosphorous pesticides, especially Parathion, must be of concern at the present time.

China↗
PubMed2006

Feasibility of extracting velocity distribution in choriocapillaris in human eyes from ICG dye angiograms.

Indocyanine green (ICG) dye angiography has been used by ophthalmologists for routine examination of the choroidal vasculature in human eyes for more than 20 years. In this study, a new approach is developed to extract information from ICG dye angiograms about blood velocity distribution in the choriocapillaris and its feeding blood vessels. ICG dye fluorescence intensity rise and decay curves are constructed for each pixel location in each image of the choriocapillaris in an ICG angiogram. It is shown that at each instant of time the magnitude of the local instantaneous dye velocity in the choriocapillaris is proportional to both the slope of the ICG dye fluorescence intensity curve and the dye concentration. This approach leads to determination of the absolute value of blood velocity in the choriocapillaris, assuming an appropriate scaling, or conversion factor can be determined. It also enables comparison of velocities in different regions of the choriocapillaris, since the conversion factor is independent of the vessel location. The computer algorithm developed in this study can be used in clinical applications for diagnostic purposes and for assessment of the efficacy of laser therapy in human eyes.

Algorithms↗
PubMed2006

Amelogenins in human developing and mature dental pulp.

Amelogenins are a group of heterogenous proteins first identified in developing tooth enamel and reported to be present in odontoblasts. The objective of this study was to elucidate the expression and function of amelogenins in the human dentin-pulp complex. Developing human tooth buds were immunostained for amelogenin, and mRNA was detected by in situ hybridization. The effects of recombinant amelogenins on pulp and papilla cell proliferation were measured by Brd U immunoassay, and differentiation was monitored by alkaline phosphatase expression. Amelogenin protein was found in the forming dentin matrix, and amelogenin mRNA was localized in the dentin, presumably in the odontoblast processes. Proliferation of papilla cells was enhanced by recombinant human amelogenin rH72 (LRAP+ exon 4), while pulp cells responded to both rH72 and rH58 (LRAP), with no effect by rH174. These studies suggest that odontoblasts actively synthesize and secrete amelogenin protein during human tooth development, and that low-molecular-weight amelogenins can enhance pulp cell proliferation.

Alternative Splicing↗
PubMed2006

Ammonia removal in the catalytic wet air oxygen process of landfill leachates with Co/Bi catalyst.

Oxidation of ammonia in landfill leachates in the catalytic wet air oxidation (CWAO) process was investigated with Co/Bi catalyst. The characterization of the Co/Bi catalyst was carried out by the X-ray diffraction technique. Studies of ammonia removal from the landfill leachates by CWAO showed that Co/Bi catalyst exhibited higher activities for both total organic carbon (TOC) and ammonia with removal levels of 99% for TOC and 98% for ammonia, respectively. Results also indicated that large amounts of ammonia were produced during the elimination of nitrogenous organic compounds in the CWAO process and the further oxidation of ammonia gave off essentially N2 under 240 degrees C. When the system temperature reached above 240 degrees C, ammonia oxidation rate was much higher with nitrate dominating in the effluent; a very small amount of nitrite was observed in the reaction process, it possibly acts as the intermediate of nitrate ion and molecular nitrogen formation, showing that the system temperature had significant effects on the ammonia oxidation and reaction selectivity towards the production of molecular nitrogen or nitrate.

Ammonia↗
PubMed2005

Integrated microfluidic UV absorbance detector with attomol-level sensitivity for BSA.

An integrated UV absorbance detection system employing a novel silicon-in-plastic technology to seamlessly integrate bare UV photodiode chips into polymer microfluidic systems has been developed. Detection platforms fabricated using this approach exhibit exceptionally low concentration and mass detection limits down to 15 nM and 9.8 amol, respectively, for bovine serum albumin (BSA) as a model protein. In addition to providing high sensitivity, sub-nanoliter detection volumes are enabled by the use of direct photodiode integration. The fabrication methodology is detailed, and system performance metrics including detection limits, detection volume, dynamic range, and linearity are reported.

Animals↗
PubMed2005

Q2 dependence of the neutron spin structure function g2(n) at low Q2.

We present the first measurement of the Q2 dependence of the neutron spin structure function g2(n) at five kinematic points covering 0.57 (GeV/c)2 < or = Q2 < or = 1.34 (GeV/c)2 at x approximately = 0.2. Though the naive quark-parton model predicts g2 = 0, nonzero values occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses, or orbital angular momentum. When scattering from a noninteracting quark, g2(n) can be predicted using next-to-leading order fits to world data for g1(n). Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g1(n) are consistent with next-to-leading order fits to world data.

Journal Article↗
PubMed2005

Recoil polarization for delta excitation in pion electroproduction.

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

Journal Article↗
PubMed2005

A meta-analysis of case-control studies on the combined effect of hepatitis B and C virus infections in causing hepatocellular carcinoma in China.

We investigated whether concurrent infection by hepatitis B virus (HBV) and hepatitis C virus (HCV) in China, a hyperepidemic area for these infections, was associated with a higher risk of causing hepatocellular carcinoma (HCC) than each infection alone in a meta-analysis in China, 32 case-control studies involving 3201 cases and 4005 controls, identified from a computer-based literature search from 1966 to 2004. The pooled odds ratio and 95% confidence interval (CI) for HBsAg positivity was 14.1 (95% CI: 10.6-18.8); for anti-HCV/HCV RNA positivity was 4.6 (95% CI: 3.6-5.9); for HBsAg positivity and anti-HCV/HCV RNA negativity were 15.6 (95% CI: 11.5-21.3); for HBsAg negativity and anti-HCV/HCV RNA positivity were 8.1 (95% CI: 5.0-13.0); and positivity for both HBsAg and anti-HCV/HCV RNA was 35.7 (95% CI: 26.2-48.5). We conclude that HBV and HCV infections are important independent risk factors for HCC in China, and that dual infection by HBV and HCV is associated with a higher risk of causing HCC than each infection alone, suggesting a synergism between HBV and HCV.

Carcinoma, Hepatocellular↗
PubMed2005

Effects and mechanisms of total glucosides of paeony on joint damage in rat collagen-induced arthritis.

OBJECTIVE AND DESIGN: To investigate the therapeutic effects and mechanisms of total glucosides of paeony (TGP), an effective compound of Chinese traditional herbal medicine (CTM), on collagen -induced arthritis (CIA) in rats. MATERIALS: CIA was induced in male Sprague-Dawley rats immunized with chicken type II collagen in Freund's complete adjuvant. TREATMENT: TGP (25, 50, 100 mg/kg/d) was orally administered to rats from day 14 to 28 after immunization. METHODS: Arthritis was evaluated by hind paw swelling, polyarthritis index, and histological examination. Activities of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) were determined and the ultrastructure of synoviocytes was observed. The proliferation and the production of vascular epidermal growth factor (VEGF), basic fibroblast growth factor (bFGF), matrix metalloproteinase 1 (MMP-1) and MMP-3 in fibroblast-like synoviocytes (FLS) were detected. RESULTS: The administration of TGP (25, 50, 100 mg/kg, ig x 14 days) suppressed secondary inflammatory reactions and histological changes in CIA model. The ultrastructure of synoviocytes from CIA rats was changed, and the level of IL-1 and TNF alpha produced by macrophage-like synoviocytes (MLS) from CIA rats was elevated. TGP (50, 100 mg/kg, ig x 14 days) inhibited above changes significantly. The MLS supernatants of CIA rats induced more cell proliferation and more production of VEGF, bFGF, MMP-1 and MMP-3 in FLS of CIA than those supernatants from CIA rats treated with TGP (50, 100 mg/kg, ig x 14 days). CONCLUSION: These results indicate that TGP exerts a suppressive effect on joint destruction in rat CIA. The therapeutic effect of TGP could be associated with its ability to ameliorate the secretion and metabolism of synoviocytes and to inhibit the abnormal proliferation and VEGF, bFGF, MMP-1 and MMP-3 production by FLS.

Animals↗