Biomedical subjects

Hongwei Guo

Publications and source records attributed to Hongwei Guo.

16 recordsLinked to original sources

PubMed2007

Blind phase shift estimation in phase-shifting interferometry.

A blind phase shift estimation algorithm that allows simultaneous calculation of phases and phase shifts from three or more interferograms is presented. In phase-shifting interferometry, the phase shift errors introduce specific correlations between the calculated background intensity distribution and the fringe component. These correlations can be measured with a cross-power spectrum. By minimization of an objective function based on this cross-power spectrum, the actual phase shifts are estimated and used for phase recovery. The validity of this algorithm is verified by both the numerical simulation and the experiment results.

Algorithms↗

PubMed2006

Least-squares fitting of carrier phase distribution by using a rational function in fringe projection profilometry [corrected].

A least-squares fitting technique for the carrier phase component in fringe projection profilometry is presented. The carrier phase distribution for an arbitrary measurement system can be perfectly described with a rational function, whose coefficients can be estimated by least-squares fitting to the measured reference phases, so that the restrictions and limitations in the existing techniques are eliminated.

Journal Article↗

PubMed2006

ETHYLENE-INSENSITIVE5 encodes a 5'-->3' exoribonuclease required for regulation of the EIN3-targeting F-box proteins EBF1/2.

Ethylene is a gaseous plant growth regulator that controls a multitude of developmental and stress responses. Recently, the levels of Arabidopsis EIN3 protein, a key transcription factor mediating ethylene-regulated gene expression, have been demonstrated to increase in response to the presence of ethylene gas. Furthermore, in the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F-box proteins, EBF1 and EBF2. Here we report the identification of ETHYLENE-INSENSITIVE5 as the 5'-->3' exoribonuclease XRN4. Specifically, we demonstrate that EIN5 is a component of the ethylene signal transduction cascade acting downstream of CTR1 that is required for ethylene-mediated gene expression changes. Furthermore, we find that the ethylene insensitivity of ein5 mutant plants is a consequence of the over-accumulation of EBF1 and EBF2 mRNAs resulting in the under-accumulation of EIN3 even in the presence of ethylene gas. Together, our results suggest that the role of EIN5 in ethylene perception is to antagonize the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay, which consequently allows the accumulation of EIN3 protein to trigger the ethylene response.

Alleles↗

PubMed2006

Mercaptoethane sulfonate protected, water-soluble gold and silver nanoparticles: Syntheses, characterization and their building multilayer films with polyaniline via ion-dipole interactions.

Mercaptoethane sulfonate protected, water-soluble gold and silver nanoparticles (Au-MES and Ag-MES) are synthesized by one-phase method and characterized by TEM, TGA and XPS techniques, UV-vis and FTIR spectra. Both Au-MES and Ag-MES nanoparticles are soluble in the water up to 2.0 mg/ml and the stability of Au-MES is much better than that of Ag-MES. When dissolved in the water, they behave like a polyanion and can be used to build multilayer films with polyaniline (PANI) by way of layer-by-layer. A new approach is presented to fabricate the multilayer films of Au-MES/PANI and Ag-MES/PANI. The assembly mechanism of these multilayer films is also discussed. We anticipate highly conducting PANI films can be obtained by doping with these nanoparticles.

Journal Article↗

PubMed2006

Sequential deprotonation of meso-(p-hydroxyphenyl)porphyrins in DMF: from hyperporphyrins to sodium porphyrin complexes.

Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (1H NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character. The negative centers generated by deprotonation of pyrrolic-H and phenolic-H are not thoroughly delocalized between the substituents and the porphyrin ring. Thus the negative centers generated by deprotonation of pyrrolic-H only act as electron-donating groups on the porphyrin pi system, and the negative charges of the phenoxide anion are also mainly localized on the peripheral substituents. As a result, the porphyrin pi orbitals cross over the phenoxide anion pi orbital and turn into HOMOs, which turns hyperporphyrin spectra of deprotonated phenolic-H of p-OHTPPH2 into three-banded spectra of regular metalloporphyrins.

Dimethylformamide↗

PubMed2006

Effect of Lycium barbarum polysaccharide on the improvement of antioxidant ability and DNA damage in NIDDM rats.

The effects of polysaccharide extracted from Lycium barbarum (LBP) on blood glucose, oxidative stress and DNA damage in rats with non-insulin dependent diabetes mellitus (NIDDM) were studied. The results show that LBP treatment (10 mg/kg.d) for 4 weeks led to decreased levels of blood glucose, malondialdehyde (MDA) and nitric oxide (NO) in serum of fasting rats; and to increased serum level of superoxidedismutase (SOD). Furthermore, LBP could reduce cellular DNA damage in peripheral lymphocytes of NIDDM rats. The DNA damage was determined by using the single cell gel (comet) assay with alkaline electrophoresis and was quantified by measuring tail length and tail moment. These results suggest that LBP can control blood glucose and modulate the metabolism of glucose, leading to significant improvement of oxidative stress markers (SOD, MDA) in rats with NIDDM. And that, LBP decreases DNA damage possibly via a decrease in oxidative stress levels. In conclusion, LBP as a dietary supplement may prevent the development of complications or even tendency to carcinogenesis in NIDDM rats.

Animals↗

PubMed2005

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite.

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and O2 with Km values of 19.86 microM, 9.43 microM, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and O2), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction. It can be extended to immobilize other enzymes and biomolecules, which will greatly facilitate the development of biosensors, biofuel cells, and other bioelectrochemical devices.

Biosensing Techniques↗

PubMed2005

Structures of the oxidized and reduced forms of nitrite reductase from Rhodobacter sphaeroides 2.4.3 at high pH: changes in the interactions of the type 2 copper.

Nitrite reductase is an enzyme operating in the denitrification pathway which catalyses the conversion of nitrite (NO2(-)) to gaseous nitric oxide (NO). Here, crystal structures of the oxidized and reduced forms of the copper-containing nitrite reductase from Rhodobacter sphaeroides 2.4.3 are presented at 1.74 and 1.85 A resolution, respectively. Whereas the structure of the enzyme is very similar to those of other copper-containing nitrite reductases, folding as a trimer and containing two copper sites per monomer, the structures reported here enable conformational differences between the oxidized and reduced forms of the enzyme to be identified. In the type 1 copper site, a rotational perturbation of the side chain of the copper ligand Met182 occurs upon reduction. At the type 2 copper site, a dual conformation of the catalytic residue His287 is observed in the oxidized structure but is lacking in the reduced structure, such that the interactions of the oxidized type 2 copper ion can be regarded as adopting octahedral geometry. These findings shed light on the structural mechanism of the reduction of a copper-bound nitrite to nitric oxide and water.

Copper↗

PubMed2005

Least-squares algorithm for phase-stepping interferometry with an unknown relative step.

A pointwise least-squares phase-stepping algorithm with an unknown relative phase step is proposed. In phase-stepping interferometry the recorded temporal intensity sequence is a discrete sinusoidal signal biased by a direct-current component. Its value at a certain time can be predicted from its three past samples by use of a recursive formula. Based on this linear prediction property, an unbiased least-squares estimator is deduced to determine the relative phase step from a sequence of intensity values, and the result is used to evaluate the phase value. The validity and performance of this algorithm are verified by computer simulations.

Journal Article↗

PubMed2004

Gamma correction for digital fringe projection profilometry.

Digital fringe projection profilometry utilizes a digital video projector as a structured light source and thus gains great flexibility. However, the gamma nonlinearity of the video projector inevitably decreases the accuracy and resolution of the measurement. We propose a gamma-correction technique based on statistical analysis of the fringe images. The technique allows one to estimate the value of gamma from the normalized cumulative histogram of the fringe images. By iterating the two steps, gamma estimation and phase evaluation, the actual gamma value can be calculated. At the same time the phase distribution of the fringe pattern can be solved with higher accuracy. In so doing, neither photometric calibration nor knowledge of the device is required. Both computer simulation and experiment are carried out to demonstrate the validity of this technique.

Journal Article↗

PubMed2004

The ethylene signaling pathway: new insights.

During the past decade, molecular genetic studies on the reference plant Arabidopsis have established a largely linear signal transduction pathway for the response to ethylene gas. The biochemical modes of action of many of the signaling components are still unresolved. During the past year, however, progress in several areas has been made on several fronts. The different approaches used have included a functional study of the activity of the receptor His kinase, the determination of the ethylene receptor signaling complex at the endoplasmic reticulum and of the regulation of CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) activity by these receptors, the identification of a unique MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) cascade, the cloning and characterization of numerous ETHYLENE INSENSITIVE3 (EIN3)/EIN3-like (EIL) transcription factors from many plant species, and the integration of the ethylene and jasmonate response pathways via the ETHYLENE RESPONSE FACTOR (ERF) family of transcription factors. The elucidation of the biochemical mechanisms of ethylene signal transduction and the identification of new components in the ethylene response pathway in Arabidopsis are providing a framework for understanding how all plants sense and respond to ethylene.

Arabidopsis↗

PubMed2004

[Evaluating dietary quality of type 2 diabetics in Macao by Healthy Eating Index].

OBJECTIVE: To Evaluate dietary quality of type 2 diabetics in Macao with Healthy Eating Index and try to know whether the result from quantitative food frequency survey reflect the result from 24 hour recall dietary survey. METHODS: We randomly drew samples from file of registered type 2 diabetics on a Health Center of Macao. The diabetics have been investigated with both 24 hour dietary recall and quantitative food frequency dietary survey methods. According to the calculational method of healthy eating index, the result of dietary survey was transferred to Healthy Eating Index and evaluate the diet quality with it. RESULTS: There was a significant correlation between both results, including Healthy Eating Index, total energy and the percentages of energy from the three major nutrients, were obtained with 24 hour recall and quantitative food frequency. The Healthy Eating Index was 66.0. The minimum score of HEI components was milk. Total Energy of the diabetics was 5407.9 kJ (1287.6 kcal). And the percentages of energy from carbohydrate, total fat and protein were 59.4%, 25.8% and 16.1%, respectively. The intake of dietary fiber and calcium were 9.9 g and 340 mg respectively. CONCLUSION: For this population, the results of both dietary survey methods can reflect each other well. According to the criteria of Healthy Eating Index, diet quality of 80% patients were among "need improvement". The situation of milk consumption was the worst. The consumption of fruits, grains and vegetable were too low and the consumption of sodium was too high. The percentages of energy from the three major nutrients were within the recommended range but the intake of total energy was too low. The intake of thiamin and riboflavin were not enough. Intake of dietary fiber and calcium were severely low.

Adult↗

PubMed2003

Plant responses to ethylene gas are mediated by SCF(EBF1/EBF2)-dependent proteolysis of EIN3 transcription factor.

Plants use ethylene gas as a signal to regulate myriad developmental processes and stress responses. The Arabidopsis EIN3 protein is a key transcription factor mediating ethylene-regulated gene expression and morphological responses. Here, we report that EIN3 protein levels rapidly increase in response to ethylene and this response requires several ethylene-signaling pathway components including the ethylene receptors (ETR1 and EIN4), CTR1, EIN2, EIN5, and EIN6. In the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F box proteins, EBF1 and EBF2. Plants containing mutations in either gene show enhanced ethylene response by stabilizing EIN3, whereas efb1 efb2 double mutants show constitutive ethylene phenotypes. Plants overexpressing either F box gene display ethylene insensitivity and destabilization of EIN3 protein. These results reveal that a ubiquitin/proteasome pathway negatively regulates ethylene responses by targeting EIN3 for degradation, and pinpoint EIN3 regulation as the key step in the response to ethylene.

Arabidopsis↗

PubMed2003

[Study on the role of glucosamine hydrochloride in the pathogenesis of osteoarthritis].

The role of glucosamine hydrochloride in the pathogenesis of osteoarthritis in animal models of sponge granuloma, Kaolin arthritiaand and adjuant arthritis was studied. The results showed that glucosamine hydrochloride inhibited granulation, delayed immunoreactivity, immunological-reative arthritis in daily doses of 0.25-0.75 g/kg BW orally and vascular oozing, tissue swelling and cell isolating in daily doses of 0.5-1.5 g/kg BW orally, indicating that glucosamine hydrochloride might have a preventive and theraputic effect on osteoarthritis.

Animals↗

PubMed2002

Regulation of Arabidopsis cryptochrome 2 by blue-light-dependent phosphorylation.

Cryptochromes are blue/ultraviolet-A light receptors that mediate various light responses in plants and animals. But the initial photochemical reaction of cryptochrome is still unclear. For example, although most photoreceptors are known to undergo light-dependent protein modification such as phosphorylation, no blue-light dependent phosphorylation has been reported for a cryptochrome. Arabidopsis cryptochrome 2 (cry2) mediates light regulation of seedling development and photoperiodic flowering. The physiological activity and cellular level of cry2 protein are light-dependent, and protein protein interactions are important for cry2 function. Here we report that cry2 undergoes a blue-light-dependent phosphorylation, and that cry2 phosphorylation is associated with its function and regulation. Our results suggest that, in the absence of light, cry2 remains unphosphorylated, inactive and stable; absorption of blue light induces the phosphorylation of cry2, triggering photomorphogenic responses and eventually degradation of the photoreceptor.

Arabidopsis↗

PubMed2002

[Effects of dietary lipids on serum lipid levels of hypertensive patients].

OBJECTIVE: To survey the intake of dietary lipids and analyze serum lipid levels in hypertensive patients, and to study the effects of changing dietary lipids intake on the serum lipid levels. METHODS: To estimate the intake of dietary fat and to measure the level of serum lipids in hypertensive patients before and after intervention. RESULTS: The baseline survey showed that the intake of dietary fat and cholesterol were high in those patients. Their fat intake is more than 30% of the total energy intake; serum total cholesterol (TC), triglycerides (TG) and LDL-cholesterol (LDL-C) levels were higher than the normal level. Correlation analysis showed that body mass index (BMI) and saturated fatty acid (SFA) intake were positively correlated with serum TC, TG and LDL-C; serum HDL-C/TC ratio was positively correlated with monounsaturated fatty acid (MUFA) intake, and negatively correlated with BMI and SFA. The results implicated that MUFA is the protective factor against hypertension and hyperlipidemia. After one-year community-based nutrition intervention, the serum TC and LDL-C levels of the intervened subjects were reduced dramatically. CONCLUSION: The results indicate that reducing the intake of dietary fat and cholesterol and properly increasing dietary MUFA intake have significant effects on lowering serum lipids levels and controlling blood pressure in hypertensive patients.

Aged↗