Biomedical subjects

Guohua Chen

Publications and source records attributed to Guohua Chen.

23 records · Page 2Linked to original sources

PubMed2003

The haemochromatosis protein HFE induces an apparent iron-deficient phenotype in H1299 cells that is not corrected by co-expression of beta 2-microglobulin.

HFE, an atypical MHC class I type molecule, has a critical, yet still elusive function in the regulation of systemic iron metabolism. HFE mutations are linked to hereditary haemochromatosis type 1, a common autosomal recessive disorder of iron overload. Most patients are homozygous for a C282Y point mutation that abrogates the interaction of HFE with beta(2)-microglobulin (beta(2)M) and, thus, impairs its proper processing and expression on the cell surface. An H63D substitution is also associated with disease. To investigate the function of HFE we have generated clones of human H1299 lung cancer cells that express wild-type, C282Y or H63D HFE under the control of a tetracycline-inducible promoter. Consistent with earlier observations in other cell lines, the expression of wild-type or H63D, but not C282Y, HFE induces an apparent iron-deficient phenotype, manifested in the activation of iron-regulatory protein and concomitant increase in transferrin receptor levels and decrease in ferritin content. This phenotype persists in cells expressing wild-type HFE after transfection with a beta(2)M cDNA. Whereas endogenous beta(2)M is sufficient for the presentation of at least a fraction of chimeric HFE on the cell surface, this effect is stimulated by approx. 2.8-fold in beta(2)M transfectants. The co-expression of exogenous beta(2)M does not significantly affect the half-life of HFE. These results suggest that the apparent iron-deficient phenotype elicited by HFE is not linked to beta(2)M insufficiency.

Hemochromatosis↗

PubMed2003

Linear free energy relationships for dechlorination of aromatic chlorides by Pd/Fe.

Reductive dechlorination rate constants for five chlorobenzenes in the presence of Pd/Fe as catalyst were determined experimentally. Linear free energy relationships (LFER) for the dechlorination rate constants of five chlorobenzenes and three chlorophenols were developed by partial least squares (PLS) regression based on quantum chemical parameters computed by PM3 Hamiltonian. The optimal LFER model obtained is logk=-1.63+1.46 x 10(-3)DeltaH(f)-7.69 x 10(-1)E(LUMO)where k stands for the dechlorination rate constants, DeltaH(f) is the standard heat of formation, and E(LUMO) is the energy of the lowest unoccupied molecular orbital. The Q(2)(cum) value of the model is 0.879, indicating good robustness and predictive power of the model.

Chlorides↗

PubMed2002

The prolyl 4-hydroxylase inhibitor ethyl-3,4-dihydroxybenzoate generates effective iron deficiency in cultured cells.

Ethyl-3,4-dihydroxybenzoate (EDHB) is commonly utilized as a substrate analog and competitive inhibitor of prolyl 4-hydroxylases. These iron-dependent enzymes have received a lot of attention for their involvement in crucial biochemical pathways such as collagen maturation and oxygen sensing. Since EDHB is also capable of chelating the enzyme-bound iron, we study here its function as a chelator. We show that the affinity of EDHB for ferric iron is significantly lower than that of desferrioxamine. Nevertheless, EDHB is sufficient to promote effective iron deficiency in cells, reflected in the activation of the iron-responsive element/iron regulatory protein regulatory network. Thus, treatment of B6 fibroblasts with EDHB results in slow activation of iron regulatory protein 1 accompanied by an increase in transferrin receptor levels and reduction of the ferritin pool.

Animals↗

PubMed2002

Novel electrode system for electroflotation of wastewater.

Electroflotation (EF) is an attractive method in wastewater treatment. The heart of EF is the dimensionally stable oxygen evolution anode that is usually expensive. In this paper, we present a stable anode by coating IrOx-Sb2O5-SnO2 onto titanium. Accelerated life test showed that the electrochemical stability of the Ti/IrOx-Sb2O5-SnO2 anode containing only 2.5 mol % of IrOx nominally in the activated coating was even higher than that of the conventional Ti/IrOx anode. Its service life for electroflotation application is predicted to be about 20 yr. Voltammetric investigation demonstrated that the Ti/IrOx-Sb2O5-SnO2 anode could provide fast electron transfer. Moreover, the present anode was designed to be fork-like and arranged interlockingly at the same level as the cathode with a similar shape. Such an innovation in electrode configuration and arrangement allows bubbles produced at both electrodes to be dispersed into wastewater flow quickly and, therefore, enhances the effective contact between bubbles and particles, favorable for high flotation efficiency. In addition, the novel electrode system reduces the interelectrode gap to 2 mm, a spacing that is technically difficult for a conventional electrode system. This small gap results in a significant energy saving. Easy maintenance is found to be another advantage of this novel electrode system.

Coloring Agents↗

PubMed2002

Glass recycling in cement production--an innovative approach.

An innovative approach of using waste glass in cement production was proposed and tested in a laboratory and cement production plant. The laboratory characterization of 32 types of glass show that the chemical composition of glass does not vary significantly with its color or origin but depends on its application. The alkali content of glass, a major concern for cement production varies from 0 to 22%. For the glass bottles mainly found in Hong Kong waste glasses, the alkali content (Na2O) ranges from 10 to 19% with an average around 15%. There is no significant change of the SO2 content in the gas exhaust of the rotary kiln when about 1.8 t/h of glass bottles were loaded along with the 280-290 t/h raw materials. The content of NOx, mainly depends on the temperature of the kiln, does not show significant change either. The SO3 content of the clinker is comparable with that obtained without the loading of glass. The alkaline content shows a slight increase but still within three times the standard deviation obtained from the statistical data of the past year. The detailed analysis of the quality of the cement product shows that there is not any significant impact of glass for the feeding rate tested.

Conservation of Natural Resources↗