Biomedical subjects

H H Zhang

Publications and source records attributed to H H Zhang.

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

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↗

PubMed2005

Role of fascin in the proliferation and invasiveness of esophageal carcinoma cells.

Fascin, an actin-bundling protein, induces membrane protrusions and increases cell motility in various transformed cells. The overexpression of fascin in esophageal squamous cell carcinoma (ESCC) has been described only recently, but the roles and mechanism still remained unclear. Here, by using RNA interference (RNAi), we have stably silenced the expression of the fascin in EC109 cells, an ESCC cell line. Down-regulation of fascin resulted in a suppression of cell proliferation and as well as a decrease in cell invasiveness. Furthermore, we revealed that fascin might have functions in regulating tumor growth in vivo. The effect of fascin on cell invasiveness correlated with the activation of matrix metalloproteases such as MMP-2 and MMP-9. We examined that fascin down-expression also led to a decrease of c-erbB-2 and beta-catenin at the protein level. These results suggested that fascin might play crucial roles in regulating neoplasm progression of ESCC.

Animals↗

PubMed2004

A novel preparation of solid lipid nanoparticles with cyclosporin A for prolonged drug release.

Solid lipid nanoparticles were prepared by a novel solvent diffusion method in an aqueous system. The lipophilic model drug cyclosporin A was incorporated into SLN to study encapsulation efficiency, zeta potential (charge) and drug delivery. Stearylamine and cyclosporin A were dissolved in ethanol and acetone and the resultant organic solution was dropped into water at 60 degrees C. The drug-loaded SLN suspension quickly formed with an azury color. After burst drug release with 18% of the drug over the first 12 hours, a distinctly prolonged release over a monitored period of 16 days was observed, with nearly 4% of the drug being released each day. These results demonstrate the suitability of SLN produced with the proposed method as a prolonged release formulation for lipophilic drugs.

Amines↗

PubMed2002

Preparation of solid lipid nanoparticles with clobetasol propionate by a novel solvent diffusion method in aqueous system and physicochemical characterization.

Solid lipid nanoparticles (SLN) are a colloidal carrier system for controlled drug delivery. Monostearin SLN were prepared by a novel solvent diffusion method in an acidic aqueous system in order to improve the recovery of the method. The lipophilic model drug clobetasol propionate was incorporated to study the recovery of nanoparticles, entrapment efficacy, zeta potential (charge) and drug delivery characterization. The drug and monostearin were dissolved in acetone and ethanol at 50 degrees C in water bath, the resultant organic solution was poured into an acidic aqueous (pH 1.10) containing 1% polyvinyl alcohol (PVA) under mechanical agitation at room temperature. The drug loaded SLN was quickly produced with an aggregation state and easily separated by centrifugation. The recovery of nanoparticles was markedly increased compared to using a usual aqueous (pH 5.73) containing the same concentration of PVA. After burst drug release at the first 3 h, a distinctly prolonged release over a monitored period of 4 days was observed and nearly 6% drug was released in each day. Further, a novel preparation method and the optimized separation parameters in the present research for SLN were established. These results also demonstrate the principle suitability of SLN as a prolonged release formulation for lipophilic drugs.

Algorithms↗

PubMed2001

Dexamethasone inhibits tumor necrosis factor-alpha-induced apoptosis and interleukin-1 beta release in human subcutaneous adipocytes and preadipocytes.

Tumor necrosis factor-alpha (TNF alpha) can decrease adipose tissue mass, but in obesity, adipose tissue hypertrophy persists despite increased TNF alpha expression. The hormonal milieu of obesity may antagonize the adipostat effects of TNF alpha. We examined the effects of insulin and the synthetic glucocorticoid, dexamethasone (Dex), on TNF alpha-induced apoptosis and gene expression in human adipocytes and preadipocytes. Using RT multiplex PCR, the expression of the proapoptotic genes interleukin-1 beta (IL-1 beta)-converting enzyme (ICE) and TNF alpha and the antiapoptotic genes bcl-2, nuclear factor-kappa B (NF kappa B), and NF kappa B inhibitory subunit, I kappa B, were examined. The expression and release of IL-1 beta, a postulated downstream effector of ICE-mediated apoptosis, were also determined. TNF alpha increased the messenger ribonucleic acid levels of ICE, TNF alpha, IL-1 beta, bcl-2, and NF kappa B in preadipocytes and adipocytes (P < 0.01). Dex inhibited TNFalpha-induced messenger ribonucleic acid expression of ICE, TNF alpha, and IL-1 beta (P < 0.01), but not that of bcl-2 and NF kappa B. TNF alpha stimulated IL-1 beta release from preadipocytes and adipocytes up to 20-fold, but the effect was abrogated by Dex. Apoptosis induced by TNF alpha was reduced to control levels (P < 0.01) by Dex. Insulin had no significant effect on TNF alpha-induced apoptosis and gene expression. In obesity, glucocorticoids may reduce TNF alpha actions in adipose tissue by inhibiting TNF alpha-induced apoptosis, IL-1 beta release, and TNF alpha expression.

Adipocytes↗

PubMed2000

"Emergency" granulopoiesis in G-CSF-deficient mice in response to Candida albicans infection.

Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein believed to play an important role in regulating granulopoiesis both at steady state and during an "emergency" situation. Generation of G-CSF and G-CSF receptor-deficient mice by gene targeting has demonstrated unequivocally the importance of G-CSF in the regulation of baseline granulopoiesis. This study attempted to define the physiologic role of G-CSF during an emergency situation by challenging a cohort of wild-type and G-CSF-deficient mice with Candida albicans. Interestingly, after infection, G-CSF-deficient mice developed an absolute neutrophilia that was observed both in blood and bone marrow. In addition, 3 days after Candida infection increased numbers of granulocyte-macrophage (GM) and macrophage (M) progenitors were observed in the bone marrow of G-CSF-deficient mice. Of the cytokines surveyed, interleukin (IL)-6 levels in serum were elevated; interestingly, levels of IL-6 were higher and more sustained in G-CSF-deficient mice infected with C albicans than similarly infected wild-type mice. Despite the higher levels of serum IL-6, this cytokine is dispensable for the observed neutrophilia because candida-infected IL-6-deficient mice, or mice simultaneously deficient in G-CSF and IL-6, developed neutrophilia. Similarly, mice lacking both G-CSF and GM-CSF developed absolute neutrophilia and had elevated numbers of GM and M progenitors in the bone marrow; thus, G-CSF and GM-CSF are dispensable for promoting the emergency response to candidal infection. (Blood. 2000;95:3725-3733)

Animals↗

PubMed2000

Tumour necrosis factor-alpha exerts dual effects on human adipose leptin synthesis and release.

The acute and chronic effects of tumour necrosis factor-alpha (TNF-alpha) on leptin production by human preadipocytes, differentiated preadipocytes, and mature adipocytes have been examined by competitive RT-PCR of leptin mRNA and by western blotting. In preadipocytes, secreted leptin was detectable after 5-day incubation in differentiation medium and this increased 4-fold by day 20. TNF-alpha blocked leptin synthesis during differentiation. In differentiated preadipocytes and mature adipocytes, TNF-alpha treatment resulted in time-dependent decreases in mRNA for leptin and glycerol-3-phosphate dehydrogenase (G3PD). In contrast, TNF-alpha (4-8-h treatment) resulted in a 4-fold increase in leptin release. This effect was lost at 24 h and leptin accumulation in culture medium was decreased 24-48 h after TNF-alpha addition. We conclude that TNF-alpha stimulates the release of preformed leptin from human mature adipocytes and existing differentiated preadipocytes, which may contribute to obesity/infection-linked hyperleptinemia, and that TNF-alpha inhibits leptin synthesis via inhibition of preadipocyte differentiation and induction of adipocyte dedifferentiation.

Adipocytes↗

PubMed2000

Ceiling culture of mature human adipocytes: use in studies of adipocyte functions.

Adipocytes contain large lipid droplets in their cytoplasm. When cultured, they float on top of the medium, clump together, and do not gain equal and sufficient access to the medium. Morphological changes cannot be observed and the majority of adipocytes undergo cell lysis within 72 h of isolation. We have used a ceiling culture method for human mature adipocytes which uses their buoyant property to allow them to adhere to a floating glass surface, where they remain viable for several weeks. Using confocal immunofluorescence microscopy we showed the cellular expression and subcellular localization of leptin in ceiling-cultured adipocytes. The secretion of leptin was increased from ceiling cultures following tumour necrosis factor-alpha treatment. Proliferation of mature human adipocytes in serum-containing medium was demonstrated by incorporation of bromodeoxyuridine, 2% of adipocytes showing positive incorporation after 4 h labelling. Proliferation was also evident from the budding of daughter cells. Apoptosis in the ceiling cultures was increased by 48 h serum deprivation (30-35 vs 10-15% in the control) and was assayed by propidium iodide staining and terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick-end labelling. Lipolysis, analysed by liquid scintillation counting, was increased by forskolin (10 microM for 90 min) and lipogenesis, shown by autoradiography, was stimulated by insulin (10 and 100 nM for 4 h). These findings indicate that ceiling-cultured adipocytes maintain adipocyte-specific functions and that ceiling culture, which overcomes the shortcomings of adipocyte suspension culture, can be used to study adipocyte cell biology.

Adipocytes↗

PubMed2000

[Complexity analysis of surface EMG signals].

OBJECTIVE: Since the neurophysiological system is a highly nonlinear dynamic system, nonlinear dynamic information of EMG signals were extracted to describe its characteristics. METHOD: Two-channel surface EMG signals were extracted and analyzed to reflect the complexity degree of the dynamics of the neurophysiological system. RESULT: Complexity measures of four kinds of forearm motions were calculated and compared. They showed a good separability. CONCLUSION: Experimental results proved that this measure, having a simple algorithm, is suitable for short data sets and suitable for real time processing. It provides a new measurable index for both physiological and pathological analysis.

Electromyography↗

PubMed2000

[A surface EMG signal identification method based on short-time Fourier transform].

A surface EMG signal identification method based on short-time fourier transform is presented in this paper. To fully utilize the nonstationary character of the EMG signal, short-time fourier transform is employed to get the signal's time-frequency representation. Singular value decomposition is then used in the spectrogram to extract feature vector for pattern identification. Four types of movement of forearm, hand grasp, hand extension, wrist pronation and wrist supination can be identified from surface EMG signals. Experimental results show that it is a stable and efficient method for extracting features.

Electromyography↗

PubMed1999

Investigation of the anomalous spectroscopic features of the copper sites in chicken ceruloplasmin: comparison to human ceruloplasmin.

Chicken ceruloplasmin has been previously reported to display a number of key differences relative to human ceruloplasmin: a lower copper content and a lack of a type 2 copper signal by electron paramagnetic resonance (EPR) spectroscopy. We have studied the copper sites of chicken ceruloplasmin in order to probe the origin of these differences, focusing on two forms of the enzyme: "resting" (as isolated by a fast, one-step procedure) and "peroxide-oxidized". From X-ray absorption, EPR, and UV/visible absorption spectroscopies, we have shown that all of the copper sites are oxidized in peroxide-oxidized chicken ceruloplasmin and that none of the type 1 copper sites display the EPR features typical for type 1 copper sites that lack an axial methionine. In the resting form, the type 2 copper center is reduced. Upon oxidation, it does not appear in the EPR spectrum at 77 K, but it can be observed by using magnetic susceptibility, EPR at approximately 8 K, and magnetic circular dichroism spectroscopy. It displays unusually fast relaxation, indicative of coupling with the adjacent type 3 copper pair of the trinuclear copper cluster. From reductive titrations, we have found that the reduction potential of the type 2 center is higher than those of the other copper sites, thus explaining why it is reduced in the resting form. These results provide new insight into the nature of the additional type 1 copper sites and the redox distribution among copper sites in the different ceruloplasmins relative to other multicopper oxidases.

Animals↗

PubMed1999

A parallel distributed processing model of stimulus-stimulus and stimulus-response compatibility.

A parallel distributed processing (PDP) model is proposed to account for choice reaction time (RT) performance in diverse cognitive and perceptual tasks such as the Stroop task, the Simon task, the Eriksen flanker task, and the stimulus-response compatibility task that are interrelated in terms of stimulus-stimulus and stimulus-response overlap (Kornblum, 1992). In multilayered (input-intermediate-output) networks, neuron-like nodes that represent stimulus and response features are grouped into mutually inhibitory modules that represent stimulus and response dimensions. The stimulus-stimulus overlap is implemented by a convergence of two input modules onto a common intermediate module, and the stimulus-response overlap by direct pathways representing automatic priming of outputs. Mean RTs are simulated in various simple tasks and, furthermore, predictions are generated for complex tasks based on performance in simpler tasks. The match between simulated and experimental results lends strong support for our PDP model of compatibility.

Computer Simulation↗

PubMed1999

Renaturation of recombinant Treponema pallidum rare outer membrane protein 1 into a trimeric, hydrophobic, and porin-active conformation.

We have previously observed that while native Treponema pallidum rare outer membrane protein 1 (Tromp1) is hydrophobic and has porin activity, recombinant forms of Tromp1 do not possess these properties. In this study we show that these properties are determined by conformation and can be replicated by proper renaturation of recombinant Tromp1. Native Tromp1, but not the 47-kDa lipoprotein, extracted from whole organisms by using Triton X-114, was found to lose hydrophobicity after treatment in 8 M urea, indicating that Tromp1's hydrophobicity is conformation dependent. Native Tromp1 was purified from 0.1% Triton X-100 extracts of whole organisms by fast-performance liquid chromatography (FPLC) and shown to have porin activity in planar lipid bilayers. Cross-linking studies of purified native Tromp1 with an 11 A cross-linking agent showed oligomeric forms consistent with dimers and trimers. For renaturation studies of recombinant Tromp1 (rTromp1), a 31,109-Da signal-less construct was expressed in Escherichia coli and purified by FPLC. FPLC-purified rTromp1 was denatured in 8 M urea and then renatured in the presence of 0.5% Zwittergent 3,14 during dialysis to remove the urea. Renatured rTromp1 was passed through a Sephacryl S-300 gel exclusion column previously calibrated with known molecular weight standards. While all nonrenatured rTromp1 eluted from the column at approximately the position of the carbonic anhydrase protein standard (29 kDa), all renatured rTromp1 eluted at the position of the phosphorylase b protein standard (97 kDa), suggesting a trimeric conformation. Trimerization was confirmed by using an 11 A cross-linking agent which showed both dimers and trimers similar to that of native Tromp1. Triton X-114 phase separations showed that all of renatured rTromp1, but none of nonrenatured rTromp1, phase separated exclusively into the hydrophobic detergent phase, similar to native Tromp1. Circular dichroism of nonrenatured and renatured rTromp1 showed a marked loss in alpha-helical secondary structure of renatured rTromp1 compared to the nonrenatured form. Finally, renatured rTromp1, but not the nonrenatured form, showed porin activity in planar liquid bilayers. These results demonstrate that proper folding of rTromp1 results in a trimeric, hydrophobic, and porin-active conformation similar to that of the native protein.

Bacterial Proteins↗

PubMed1999

Intrinsic site-specific differences in the expression of leptin in human adipocytes and its autocrine effects on glucose uptake.

Leptin, the ob gene product of adipocytes, regulates body weight by actions on the satiety center in the hypothalamus, but it may also have peripheral effects on the metabolic actions of insulin. In human mature adipocytes isolated from omental (OM) and s.c. tissue, we found that leptin (10 and 100 ng/mL) significantly reduced insulin-mediated glucose uptake by 40% (P<0.05). The effects were rapid and sustained. A U-shaped dose-response curve was obtained, and high leptin concentrations (>100 ng/mL) were without effect. Leptin did not affect basal glucose uptake in adipocytes and had no effect on insulin-stimulated glucose uptake in human preadipocytes. Because leptin may thus have autocrine effects, we examined leptin production from OM and s.c. adipocytes. Western blotting of leptin from 96-h conditioned medium showed greater leptin secretion from s.c. than OM adipocytes, with a ratio of 3.2 (SE +/-0.3, P<0.01). Long-term ceiling cultures were used to examine intrinsic differences in leptin expression under closely controlled conditions. Confocal immunofluorescence microscopy of 12- to 16-day-old ceiling-cultured adipocytes showed that sc adipocytes contained 3.4-fold more leptin (SE +/-0.5, P<0.01) than OM adipocytes, indicating an intrinsic site-specific difference in leptin production. The autocrine effects of leptin to inhibit insulin-stimulated glucose uptake and subsequent lipogenesis in adipose tissue may, therefore, be less in OM adipocytes and may play a role in determining visceral obesity.

Adipocytes↗

PubMed1999

Use of PCR/DNA probes to identify circumsporozoite genotype of Plasmodium vivax in China.

The paper reports the result of identifying cirumsporozoite (CS) genotype of Plasmodium vivax by using PCR/DNA probe labeled with biotin. The sensitivity of this method to detect patient blood samples was 0.2 parasite/microl and also with high specific to P. vivax. CS genes from 52 blood samples collected from patients with P. vivax in Hainan and Yunnan Provinces were amplified by PCR and 49 were positive by gel-e electrophoresis analysis, positive rate was 94%. Then the amplified CS genes further were probed with special oligoprobes (PV210 and PV247) that hybridized with the predominant CS repeat region and the variant CS repeat region. The results showed 46 (88.5%) PV210 positive and 6 (11.5%) PV247 positive; 2 hybridized with both probes. The variant genotype was present only in samples from Yunnan Province. The above results showed that the PCR/DNA probe labeled with biotin was highly sensitive and specific to P. vivax and found a CS variant genotype of P. vivax in Yunnan Province of China.

Animals↗

PubMed1998

Spectroscopic and magnetic studies of human ceruloplasmin: identification of a redox-inactive reduced Type 1 copper site.

Ceruloplasmin is unique among the multicopper oxidases in that in addition to the usual copper stoichiometry of one Type 1 copper site and a Type 2/Type 3 trinuclear copper cluster, it contains two other Type 1 sites. This assignment of copper sites, based on copper quantitation, sequence alignment, and crystallography, is difficult to reconcile with the observed spectroscopy. Furthermore, some chemical or spectroscopic differences in ceruloplasmin have been reported depending on the method of purification. We have studied the resting (as isolated by a fast, one-step procedure) and peroxide-oxidized forms of human ceruloplasmin. Using a combination of X-ray absorption spectroscopy, a chemical assay, magnetic susceptibility, electron paramagnetic resonance spectroscopy, and absorption spectroscopy, we have determined that peroxide-oxidized ceruloplasmin contains one permanently reduced Type 1 site. This site is shown to have a reduction potential of approximately 1.0 V. Thus, one of the additional Type 1 sites in ceruloplasmin cannot be catalytically relevant in the form of the enzyme studied. Furthermore, the resting form of the enzyme contains an additional reducing equivalent, which is distributed among the remaining five copper sites as expected from their relative potentials. This may indicate that the resting form of ceruloplasmin in plasma under aerobic conditions is a four-electron oxidized form, which is consistent with its function in the four-electron reduction of dioxygen to water.

Binding Sites↗

PubMed1998

Biochemical characterization of mutant EGF receptors expressed in the hemopoietic cell line BaF/3.

The Epidermal Growth Factor (EGF) receptor appears to require a fully active tyrosine kinase domain to transmit mitogenic signals. However, waved-2 mice carrying a mutation in the alpha-helix C of their EGF-R, which abolishes tyrosine kinase activity, only display a mild phenotype and are fully viable. This suggests that the mutant EGF-R signals through heterodimerization with endogenous, kinase active members of the EGF-R family such as ErbB-2 or ErbB-4. We have examined the biochemistry of EGF-Rs carrying mutations in the alpha-helix C of the human EGF-R (V741G and Y740F), in the ATP binding site (K721R) and at the C-terminus (CT957), by expression in BaF/3 cells which are devoid of EGF-R family members. The in vitro kinase activity of the alpha-helix C EGF-R mutants was severely impaired as a result of reduced phosphotransfer activity without appreciable changes in the affinity for either ATP or peptide substrate. Surprisingly, EGF stimulation of cells carrying the different mutant or wild type EGF-Rs resulted in tyrosine phosphorylation of EGF-R proteins; this phosphorylation was abolished in crude plasma membrane preparations, and appears to be due to activation of a membrane-associated or a cytosolic kinase. Receptor-mediated internalization of EGF was profoundly suppressed in the V741G, K721R and CT957 receptor mutant, and high affinity EGF binding was undetectable in the V741G and K721R receptors. We conclude that specific residues in the C-helix of the EGF-R kinase are essential for full kinase activity; mutations in this region do not affect ATP binding, but impair the receptors' phosphotransfer ability. High affinity binding of EGF is not dependent on tyrosine kinase activity or sequences in the C-terminus.

Adenosine Triphosphate↗