Biomedical subjects

H Zhan

Publications and source records attributed to H Zhan.

At least 19 recordsLinked to original sources

PubMed2001

Analytical solutions of contaminant transport from finite one-, two-, and three-dimensional sources in a finite-thickness aquifer.

Analytical study of contaminant transport from a finite source in a finite-thickness aquifer is most useful in hydrological and environmental sciences and engineering but rarely investigated in previous studies. This paper provides analytical solutions of contaminant transport from one-, two-, and three-dimensional finite sources in a finite-thickness aquifer using Green's function method. A library of unpublished analytical solutions with different finite source geometry is provided. A graphically integrated MATLAB script is developed to calculate the temporal integrations in the analytical solutions and obtain the final solutions of concentration. The analytical solutions are examined by reproducing the solutions of some special cases discussed in previous studies. The sensitivities of the line source solutions to source geometry, dispersion coefficients, and distance to the source are tested. The contaminant concentration in the near field is found to be sensitive to the source geometry and anisotropy of the dispersion coefficients. The contaminant concentration in the far field is found to be much less sensitive to the source geometry. The physical insights of the analytical solutions are interpreted.

Chemical Phenomena↗

PubMed2001

Effects of repeated +Gz exposures on lipid peroxidation of various organs in rats.

OBJECTIVE: To investigate the change of lipid peroxidation in various organs of rats after repeated +10 Gz stress. METHOD: Twenty male Wistar rats were randomly divided into control (+1 Gz) group and +10 Gz group (n = 10 for each group ). The two groups were exposed to +1 Gz or +10 Gz on an animal centrifuge respectively. The onset rate of +Gz was 0.5 G/s; the sustained time at peak +Gz was 30 s each time, with 5 times/d, 1 min intervals, 3 d/wk, 3 wk in total. The rats were decapitated in ice bath on the next day after the last +Gz exposure. The lung, heart, liver and kidney of rats were collected for the following determinations. These organs were made into homogenates and the mitochondria of heart and kidney were isolated from their homogenates. Then malondialdehyde (MDA) content , superoxide dismutase (SOD) activity and glutathion (GSH) concentration in these homogenates and mitochondria were determined individually. RESULT: Compared with the control, MDA concentration in myocardial mitochondria increased significantly (P < 0.01) after repeated +10 Gz exposures, and the SOD activity in liver homogenate and renal mitochondria decreased remarkably (P < 0. 01). But there was no significant difference between GSH concentrations of the two groups. CONCLUSION: Repeated +10 Gz stress induced lipid peroxidation injury of myocardial mitochondria and had some influences on the oxygen radical metabolism of liver and kidney in rats.

Animals↗

PubMed2001

Protective effects of tea polyphenols on myocardial free radical metabolic disorder in mice induced by inhalation of pure oxygen under 5500 m hypobaric condition.

OBJECTIVE: To observe the protective effects of natural antioxidant tea polyphenols(TP) on myocardial free radical metabolic disorder in mice induced by inhalation of hypobaric pure oxygen under 5500 m hypobaric condition. METHOD: Forty-two male Kunming mice were randomly divided into three groups (n = 14 each): group A, normal control; group B, inhalation of pure oxygen (> 96 %) at simulated altitude of 5500 m in an animal altitude chamber; group C (TP protection group), same as group B but 100 mg/kg of TP was given orally before the exposure. The exposure time was 2 h/d, 3 d/wk for a total of 8 wk, and distilled water was given to groups A and B before exposure. After experiment, the mice were decapitated on the next day and the heart was quickly removed. Malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity and nitric oxide (NO) content were measured. In addition, Cu, Zn-SOD and inducible NO synthase (iNOS) enzymatic contents in myocardial tissue were qualitatively examined by immunohistochemical assaying. RESULT: Compared with the control, MDA concentration, SOD activity and Cu, Zn-SOD enzymatic content in group B were significantly increased (P < 0. 05). But in TP protection group, myocardial MDA formation was significantly decreased (P < 0. 01) and SOD activity and Cu, Zn-SOD expression restored to normal. On the contrary, myocardial NO generation and iNOS expression were significantly reduced after repeated inhalation of hypobaric oxygen at 5500 m. NO metabolism regained to normal after repeated administration of TP. CONCLUSION: Natural antioxidant TP had protective effects on myocardial free radical metabolic disorder induced by inhalation of hypobaric pure oxygen under 5500 m hypobaric condition.

Altitude↗

PubMed2001

[Inhibitory effects of tea polyphenols and vitamin C on lipid peroxidation induced by FeSO4- cysteine in isolated human plasma and carbon tetrachloride-induced liver free radical injury in mice].

OBJECTIVE: To investigate the inhibitory effects of tea polyphenols (TP) and Vitamin C (Vit C) on FeSO4-cysteine induced lipid peroxidation in isolated human plasma and carbon tetrachloride (CCl4) induced liver free radical injury in mice. METHOD: The experiment included two parts: (1) In FeSO4-cysteine induced lipid peroxidation system of isolated human plasma, malondialdehyde (MDA) content was detected after administration of different concentrations of TP (0.3 ~ 8.1 mg/L, as C ~ F group) and Vit C (3 ~ 81 mg/L, as G ~ J group) respectively; (2) Thirty-six male Kunming mice were randomly divided into four groups: control group (A), CCl4 damage group (B), TP protection group (C) and Vit C protection group (D). TP or Vit C (100 mg/kg) was given orally to group C and D respectively, while the same volume of distilled water was given to the other two groups one time every day, continued for three days. Twelve hours after the final treatment, CCl4 (230 mg/kg) was given orally to group B ~ D. Thirty six hours later, all the mice were decapitated and liver homogenate were prepared for measuring MDA content. RESULT: In FeSO4-cysteine induced lipid peroxidation in isolated human plasma, the inhibitory rate of TP (0.3 ~ 8.1 mg/L) was 30.7%, 32.0%, 46.9% and 59.7 %, and the inhibitory rate of Vit C (3 ~ 8.1 mg/L) was 8.3%, 41.4%, 47.7% and 52.7% for various dosages. In the CCl4 induced liver free radical injury system, the inhibitory rate of the same dosage of TP and Vit C was 45.2%, 42.8% respectively. CONCLUSION: TP (0.3 ~ 8.1 mg/L) and Vit C (9 ~ 81 mg/L) had inhibited lipid peroxidation induced by FeSO4-cysteine in isolated human plasma significantly, and the inhibitory effects of TP was superior to that of Vit C at the same dosages. The same dosage of TP and Vit C had remarkable inhibitory effects on the CCl4 induced liver free radical injury, but there was no significant difference between the two groups.

Animals↗

PubMed2001

[Establishment and experimental study on mouse model of Chlamydia pneumoniae pneumonitis].

OBJECTIVE: To evaluate mice as experimental animals for Chlamydia pneumoniae (C. Pneumoniae) infection and investigate the pathogenesis of C. pneumoniae pneumonitis. METHODS: The Icr mice were inoculated with C. pneumoniae, strain CWL-029, by the intranasal or intravenous routes. After a single inoculation, mice were killed on the 1st, 3rd, 7th, 15th, 21th, 28th and 60th day separately. The pathological changes of lung tissue were analyzed. RESULTS: The Icr mice were shown to be susceptible to C. pneumoniae. Inoculation of mice with C. pneumoniae induced a prolonged course of lung infection, as demonstrated by persistence of lung pathology (60 days). In the intranasal inoculation of mice, the lung pathology was characterized by patchy interstitial pneumonitis with predominately neutrophil leukocyte infiltration in the early(7 days) and lyphocytes infiltration in the later stages(14 days later) of infection. After i.v. inoculation, a similarly interstitial pneumonitis was seen, but it was milder and more patchy, especially in the early stage. C. pneumoniae DNA was detected by polymerase chain reaction(PCR) intermittently in the lung tissue. Inoculated mice developed serum IgG antibody responses. CONCLUSIONS: The Icr mice were shown to be susceptible to C. pneumoniae and the pulmonary infection was characterized by interstitial pneumonitis, especially in mice of intranasal inoculation.

Animals↗

PubMed2001

Protective effects of tea polyphenols on mild hypobaric hypoxia induced pulmonary free radical metabolic disorder in mice.

Objective. To observe the protective effects of natural antioxidant tea polyphenols (TP) on repeated mild hypobaric hypoxia induced pulmonary free radical metabolic disorder in mice. Method. Fourty-two male Kunming mice were randomly divided into three groups (n=14 each): normal control (A); 1500 in mild hypobaric hypoxia (B) and TP protection group (C). The exposure time in hypobaric chamber was 2 h/d, 3d/wk, 8 wk in total. Before hypoxic exposure, TP was orally given to group C at a dose of 100 mg/kg, while distilled water was given to the other two groups. After experiment, the mice were decapitated on the next day and the lung was quickly removed. The malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity and nitric oxide (NO) content were measured. In addition, Cu, Zn-SOD and inducible NO synthase (iNOS) enzymatic contents in lung were were qualitatively examined by immunohistochemical assaying. Result. Compared with the control group, pulmonary MDA concentration and NO content were significantly increased after chronic mild hypobaric hypoxic exposures (P<0.01) but the MDA formation and NO generation in TP protection group were restored to normal. Pulmonary SOD activity in group B tended to increase. Cu, Zn-SOD expression in endothelial cells of bronchioli and iNOS contents in endothelial cells of bronchioli and endothelial cells and smooth muscle cells in pulmonary interstitial vessels were significantly elevated after repeated mild hypobaric hypoxic exposure. These enzymatic abnormal expressions regained to normal after administration of TP. Conclusion. Natural antioxidant TP had protective effects on repeated mild hypobaric hypoxia induced pulmonary free radical metabolic disorder.

Altitude↗

PubMed2001

[The progress on +Gz stress-induced injuries of the cardiac structure and function and their mechanisms].

The heart is the dynamic pump of the circulation. To some extent, high +Gz acceleration exposure can result in injuries on cardiac ultrastructure, metabolism and function. Specifically, repeated +Gz exposures can produce harmful effects on aviators, as reported by French and American researchers. However, the mechanisms of injuries on heart under high +Gz stress have not been studied systematically till now; nor have some protective measures been adopted. In this article, acute and chronic +Gz stress induced injuries on cardiac structure and function in animals and detrimental effects on the hearts of pilots are reviewed. Moreover, the related mechanisms are also explained basing on stress injury, oxidative stress and genetic regulation.

Acceleration↗

PubMed2001

[Effects of repeated high +Gz exposure on several enzyme activities in cardiomyocytes in rats and some protective measures].

Objective. To determine the changes of several myocardial enzymes in rats after repeated high +Gz exposure and the protective effects of preconditioning of low-G exposure and tea polyphenols (TP). Method. Thirty-two male Wistar rats were randomly divided into 4 groups (n = 8 each): control group (group A), +10 Gz group (group B), low-G preconditioning group (group C) and TP protection group (group D). Group B, C and D were exposed to repeated +10 Gz stress (each for 30s, 5 times/d with +1 Gz 1 min intervals, 3 d/wk, 3 weeks in total), but group A was only submitted to +1 Gz for 5 min. Group C was exposed to +2 Gz for 5 min about 1 h prior to +10 Gz stress. Additionally, TP (200 mg/kg) was given orally to group D about 1 h prior to the +Gz experiment, while distilled water was given to groups A, B and C instead. On the next day after the last centrifuge run, the hearts were taken out immediately for making frozen tissue sections. Enzyme histochemical staining and image analysis were carried out for acid phosphatase (ACP), succinate dehydrogenase (SDH), cytochromeoxidase (Cyt aa3) and adenosine triphosphatase (ATPase). Result. As compared with the control, the activities of ACP and SDH in +10 Gz stressed rats decreased significantly (P<0.05), and there was a declining trend for Cyt aa3. But, low-G preconditioning and TP had protective effects on +10 Gz stress-induced reduction of these enzymatic activities (P<0.05). Conclusion. The results showed that repeated high +Gz exposure could bring about decreases of activities in ACP (the marker enzyme of lysosome) and SDH (the marker enzyme of mitochondrial endomembrane), which indicated a reduction of oxidative metabolism in myocardial tissue; but preconditioning with low-G and natural antioxidant TP had protective effects.

Acceleration↗

PubMed2001

[Sequences of 5S-rRNA gene spacer region and comparison of alkaloid content in Fritillaria thunbergii from different habitats].

OBJECTIVE: To study the genetic basis of the formation of indigenous Chinese medicine materials. METHODS: The 5S-rRNA gene spacer regions in F. thunbergii from different habitats were amplified with AS and AS-1 as primers, and then sequenced. Total alkaloid contents were assayed by acid dye colorimetry, and 2 main alkaloid contents were assayed by pre-column derivatization and gas chromatographic method. RESULT: The sequenues of 5S-rRNA gene spacer regions in F. thunbergii from different habitats were same, and the length of them was 588 bp. They had same content total alkaloid. The results of gas chromatography showed that they had same kinds of monomer alkaloids, but the contents of different monomer alkaloids were different. CONCLUSION: The difference of alkaloid content in F. thunbergii from various habitats isn't resulted from base sequence variation, but from microenvironment.

Alkaloids↗

PubMed2000

Crystal structure of human cathepsin V.

Cathepsin V is a lysosomal cysteine protease that is expressed in the thymus, testis and corneal epithelium. We have determined the 1.6 A resolution crystal structure of human cathepsin V associated with an irreversible vinyl sulfone inhibitor. The fold of this enzyme is similar to the fold adopted by other members of the papain superfamily of cysteine proteases. This study provides a framework for understanding the structural basis for cathepsin V's activity and will aid in the design of inhibitors of this enzyme. A comparison of cathepsin V's active site with the active sites of related proteases revealed a number of differences, especially in the S2 and S3 subsites, that could be exploited in identifying specific cathepsin V inhibitors or in identifying inhibitors of other cysteine proteases that would be selective against cathepsin V.

Binding Sites↗

PubMed2000

Expression, purification, and characterization of deglycosylated human pro-prostate-specific antigen.

Wild-type and deglycosylated forms of human prostate-specific antigen were expressed in Chinese hamster ovary (CHO) cells as zymogens. ProPSA was collected from conditioned medium and purified using a single cation-exchange chromatographic step for the deglycosylated form and cation-exchange followed by gel filtration chromatography for the wild-type form. Recombinant wild-type proPSA produced in CHO cells has an average MW of 34.5 kDa, whereas the deglycosylated proPSA has a MW of 32.4 kDa. Both forms of proPSA were activated in vitro and the kinetic properties measured for the deglycosylated PSA are very similar to those of the wild-type recombinant PSA and the native PSA isolated from seminal fluid. These results suggest that deglycosylated PSA is likely to be very similar to native PSA with respect to its three-dimensional structure and will provide a homogeneous protein preparation necessary for X-ray crystallographic analysis.

Animals↗

PubMed1999

A method for quick measurement of protein binding to unilamellar vesicles.

A general method for measuring interaction of liposome-protein (or potentially small molecules) was developed. This method utilizes biotinylated liposomes to incubate with interactants. Streptavidin-coated paramagnetic resins were then added and the liposomes (along with bound materials) can be quickly separated under a magnetic field or by low speed centrifugation. Subsequently, concentration of unbound materials (in the supernatants) can be directly determined. The described method is particularly useful for proteins or compounds that are not very soluble under certain assay conditions.

Animals↗

PubMed1999

Conformation of the diphtheria toxin T domain in membranes: a site-directed spin-labeling study of the TH8 helix and TL5 loop.

The isolated T domain of diphtheria toxin was mutated by cysteine-scanning mutagenesis at 28 consecutive sites (residues 328-355) that comprise the TH8 helix and the TL5 interhelical loop in the native toxin. After derivatizing the mutant proteins with a sulfhydryl-selective nitroxide reagent, we examined the mobility of each nitroxide and its accessibility to polar and nonpolar paramagnetic reagents, before and after insertion into phospholipid bilayers. The data obtained with the proteins in solution at pH 8 are generally consistent with predictions from the crystal structure of the toxin. Upon membrane binding at pH 4.6, a major structural reorganization of the domain was seen, which dramatically reduced the accessibility of most residues in this region to the polar reagent nickel(II)-ethylenediaminediacetate complex (NiEDDA). Many of these residues also showed reduced accessibility to the nonpolar reagent O(2). Periodic accessibility of the nitroxide side chains along the sequence to these reagents shows that TH8 remains largely helical in the membrane-bound state, with one surface associated with protein and the other facing the hydrophobic interior of the bilayer. In addition, the TL5 loop also appears to become alpha-helical in the membrane, with one surface in contact with protein and the other in contact with the bilayer interior. These findings provide a structural framework for understanding how the T domain forms a transmembrane channel and mediates translocation of diphtheria toxin's enzymic moiety across a membrane.

Chelating Agents↗

PubMed1999

Effects of mutations in proline 345 on insertion of diphtheria toxin into model membranes.

Translocation of the catalytic domain of diphtheria toxin (DT) across the endosomal membrane to the cytoplasm of mammalian cells requires the low-pH-dependent insertion of a hydrophobic helical hairpin (TH8-TH9) that is buried within the T domain of the native protein. Mutations of Pro345, which terminates helix TH8, have been reported to block toxicity for Vero cells. We found that mutant toxins in which Pro345 had been replaced by Cys, Glu, or Gly were profoundly defective at low pH in forming channels in planar phospholipid bilayers and in permeabilizing phospholipid vesicles to entrapped fluorophores. Experiments with isolated T domain containing a polarity-sensitive fluorophore attached to Cys at position 332 suggest that the P345E mutation blocks membrane insertion. None of the Pro345 mutations shifted the pH-dependence of binding in solution of the hydrophobic fluorophore, 2-p-toluidinyl-naphthalene 7-sulfonate. The results indicate that proline at position 345 is required for the T domain to insert into phospholipid bilayers or to adopt a functional conformation within the bilayer.

Animals↗

PubMed1999

Engineering a soluble extracellular erythropoietin receptor (EPObp) in Pichia pastoris to eliminate microheterogeneity, and its complex with erythropoietin.

The extracellular ligand-binding domain (EPObp) of the human EPO receptor (EPOR) was expressed both in CHO (Chinese Hamster Ovary) cells and in Pichia pastoris. The CHO and yeast expressed receptors showed identical affinity for EPO binding. Expression levels in P. pastoris were significantly higher, favoring its use as an expression and scale-up production system. Incubation of EPO with a fourfold molar excess of receptor at high protein concentrations yielded stable EPO-EPObp complexes. Quantification of EPO and EPObp in the complex yielded a molar ratio of one EPO molecule to two receptor molecules. Residues that are responsible for EPOR glycosylation and isomerization in Pichia were identified and eliminated by site-specific mutagenesis. A thiol modification was identified and a method was developed to remove the modified species from EPObp. EPObp was complexed with erythropoietin (EPO) and purified. The complex crystallized in two crystal forms that diffracted to 2.8 and 1.9 A respectively. (Form 1 and form 2 crystals were independently obtained at AxyS Pharmaceuticals, Inc. and Amgen, Inc. respectively.) Both contained one complex per asymmetric unit with a stoichiometry of two EPObps to one EPO.

Animals↗

PubMed1999

Effects of tea polyphenols on cerebral lipid peroxidation, liver and renal functions in rats after repeated +Gz stress.

OBJECTIVE: To observe the effects of repeated +10 Gz stress on cerebral lipid peroxidation, liver and renal function in rats and the prophylactic effects of antioxidant tea polyphenols (TP). METHOD: Twenty-four male Wistar rats were randomly divided into three groups (n = 8, each): group A (control), group B (+10 Gz), and group C (TP). Group B and C were exposed to repeated +10 Gz stress (each for 30s, onset rate about 0.5 G/s, 3 times/d with +1 Gz 1 min intervals, 3 d/wk, 4 weeks in total), but group A was only submitted to +1 Gz. TP (200 mg/kg) was given orally in group C about 1 h prior to the +Gz experiment, while distilled water was given in group A and B. Lipid peroxidation in the brain, liver and renal functions and serum lipids were determined. RESULTS: As compared with the control, lipid peroxidation in rat cerebral homogenate, mitochondria and cytoplasm was significantly increased (P < 0. 05), and serum creatinine concentration was markedly elevated after repeated +10 Gz stress (P < 0. 01). But, TP had significant inhibitory effect on +10 Gz stress induced peroxidative injury in rat brain and reduced the serum creatinine level. There were no differences of serum triglyceride and total cholesterol concentrations and glutamic-pyruvic transaminase activity among the three groups. CONCLUSION: These results indicated that repeated high +Gz stress could bring about peroxidative injury in brain and harmful effect on renal function, and natural antioxidant TP had significant protective effects.

Acceleration↗

PubMed1999

[Effects of tea polyphenols on microcirculation and antioxidation in aircrew].

OBJECTIVE: To study the effects of tea polyphenols (TP) on bulbi conjunctiva microcirculation (BCM) and antioxidation in aircrew and find out the proper antioxidant for the health protection of aircrew. METHOD: Fourty healthy aircrew were divided into TP group (TP 600 mg/d.po) and control group (placebo) randomly. The effects of TP on microcirculation and antioxidation in aircrew were tested after 20 days. RESULT: Red blood cell (RBC) superoxide dismutase (SOD) activity and GSH-PX (Whole blood glutathione peroxidase)/MDA (serum malondialdehyde) ratio in TP group were significantly higher than those in control (P<0.01), and serum MDA level was significantly decreased after TP administration (P<0.05). The numbers of capillaries and blood flow in micrangium were significantly increased, RBC aggregation, ischemia area and A (arteriole)/V (venule) ratio were remarkably decreased in TP group (P<0.01). The total integral value of microcirculation in TP group was significantly reduced in comparison with that in the control group. CONCLUSION: TP can significantly increase the antioxidative ability of aircrew, decrease the BCM disturbance and improve the microcirculatory function.

Adult↗

PubMed1999

[Isozyme electrophoresis of Fritillaria puqiensis during bulb organogenesis in vitro].

OBJECTIVE: Inquiring into the mechanism of bulb organogenesis of Fritillaria puqiensis. METHOD: Time course studies of the soluble protein, peroxidase and esterase were performed during the new bulb organogenesis by electrophoresis. RESULT: The atlas of electrophoresis changed greatly during the phase of differentiation and the formation of the new bulb. CONCLUSION: Different enzymes are associated with organogenesis and express activity at different times.

Culture Techniques↗