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Biomedical subjects

S Peng

Publications and source records attributed to S Peng.

At least 19 recordsLinked to original sources
PubMed2005

Acclimation of photosynthesis to high irradiance in rice: gene expression and interactions with leaf development.

Rice (Oryza sativa L.) has been used to study the long-term responses of photosynthesis to high irradiance focusing on the composition of the photosynthetic apparatus and leaf morphology. Typical sun/shade differences in chloroplast composition are seen in the fifth leaf following growth in high irradiance compared with low irradiance (1000 and 200 micromol m(-2) s(-1), respectively): higher light-saturated rates of photosynthesis (P(max)), higher amounts of Rubisco protein, and a lower chlorophyll a:b ratio. In addition, leaves were thicker under high light compared with low light. However, responses appear more complex when leaf developmental stage is considered. Using a system of transferring plants from low to high light in the laboratory responses that occur before and after full leaf extension have been studied. Acclimation of photosynthesis is limited by leaf age: the transfer to high light, post-leaf extension, is characterized by alterations in chlorophyll a:b but not in Rubisco protein, which may be limited by leaf morphology. Microarray analysis of gene expression was carried out on plants that were transferred to high light post-leaf extension. A down-regulation of light-harvesting genes was seen. No change in the expression level of Rubisco genes was observed. Up-regulation of genes involved in photoprotection was observed. It was also shown that high-light leaf morphology is established prior to formation of the zone of cellular elongation and division. The endogenous and environmental factors which establish the characteristics of high light acclimation may be important for attaining high rates of assimilation in leaves and crop canopies, and the fifth leaf in rice provides a convenient model system for the determination of the mechanisms involved.

Acclimatization↗
PubMed2005

Cancer immunotherapy using a DNA vaccine encoding a single-chain trimer of MHC class I linked to an HPV-16 E6 immunodominant CTL epitope.

The potency of DNA vaccines may be affected by the efficiency of intracellular processing and MHC class I presentation of encoded antigens. Since a single-chain trimer (SCT) composed of peptide, beta2-microglobulin (beta2m), and MHC class I heavy chain has been shown to bypass antigen processing and lead to stable presentation of peptides, we investigated the efficacy of a DNA vaccine encoding a SCT composed of an immunodominant CTL epitope of human papillomavirus type 16 (HPV-16) E6 antigen, beta2m, and H-2Kb MHC class I heavy chain (pIRES-E6-beta2m-Kb). Transfection of 293 cells with pIRES-E6-beta2m-Kb can bypass antigen processing and lead to stable presentation of E6 peptide. Furthermore, C57BL/6 mice vaccinated with pIRES-E6-beta2m-Kb exhibited significantly increased E6 peptide-specific CD8+ T-cell immune responses compared to mice vaccinated with DNA encoding wild-type E6. Most importantly, 100% of mice vaccinated with pIRES-E6-beta2m-Kb DNA were protected against a lethal challenge of E6-expressing TC-1 tumor cells. In contrast, all mice vaccinated with wild-type E6 DNA or control plasmid DNA grew tumors. Our data indicate that a DNA vaccine encoding a SCT can lead to stable enhanced MHC class I presentation of encoded antigenic peptide and may be useful for improving DNA vaccine potency to control tumors or infectious diseases.

Animals↗
PubMed2004

Discrete molecular dynamics simulations of peptide aggregation.

We study the aggregation of peptides using the discrete molecular dynamics simulations. Specifically, at temperatures above the alpha-helix melting temperature of a single peptide, the model peptides aggregate into a multilayer parallel beta-sheet structure. This structure has an interstrand distance of 4.8 A and an intersheet distance of 10 A, which agree with experimental observations. Our model explains these results as follows: hydrogen-bond interactions give rise to the interstrand spacing in beta sheets, while Gō interactions between side chains make beta strands parallel to each other and allow beta sheets to pack into layers. An important feature of our results is that the aggregates contain free edges, which may allow for further aggregation of model peptides to form elongated fibrils.

Amyloid beta-Peptides↗
PubMed2004

Probe selection algorithm for oligonucleotide array-based medium-resolution genotyping.

Medium-resolution genotyping has the goal of distinguishing different subgroups instead of each element in a group. An oligonucleotide array provides an inexpensive, high-throughput method to identify differences in DNA sequence among individuals, which is fundamental for genotyping. As the cost and difficulty of designing and fabricating the oligonucleotide array dramatically increase with the number of probes used, it is therefore important to have a design with a minimum number of probes meeting the requirement of medium-resolution genotyping. The first algorithm for designing and selecting probes for oligonucleotide array-based medium-resolution typing is reported. The goal in deriving the algorithm was to select a minimum number of probes from a large probe set on the premise of minimum loss of resolution. The algorithm, which was based on entropy, conditional entropy and mutual information theory, was used to select the minimum number of probes from a large probe set. The algorithm was tested on a human leukocyte antigen (HLA) sequence data set Thirty probes were selected from 390 probes for HLA-A, and 60 probes were selected from 767 probes for HLA-B. Although the number of probes was reduced by almost ten times, the distinguishability was reduced only a little, by 0.45% (from 99.90% to 99.45%) for HLA-A and 0.27% (from 99.84% to 99.57%) for HLA-B, respectively. This is a satisfactory and practical result.

Algorithms↗
PubMed2004

Imaging single cardiac ryanodine receptor Ca2+ fluxes in lipid bilayers.

In this and an accompanying report we describe two steps, single-channel imaging and channel immobilization, necessary for using optical imaging to analyze the function of ryanodine receptor (RyR) channels reconstituted in lipid bilayers. An optical bilayer system capable of laser scanning confocal imaging of fluo-3 fluorescence due to Ca2+ flux through single RyR2 channels and simultaneous recording of single channel currents was developed. A voltage command protocol was devised in which the amplitude, time course, shape, and hence the quantity of Ca2+ flux through a single RyR2 channel is controlled solely by the voltage imposed across the bilayer. Using this system, the voltage command protocol, and concentrations of Ca2+ (25-50 mM) that result in saturating RyR2 Ca2+ currents, proportional fluo-3 fluorescence was recorded simultaneously with Ca2+ currents having amplitudes of 0.25-14 pA. Ca2+ sparks, similar to those obtained with conventional microscope-based laser scanning confocal systems, were imaged in mouse ventricular cardiomyocytes using the optical bilayer system. The utility of the optical bilayer for systematic investigation of how cellular factors extrinsic to the RyR2 channel, such as Ca2+ buffers and diffusion, alter fluo-3 fluorescent responses to RyR2 Ca2+ currents, and for addressing other current research questions is discussed.

Animals↗
PubMed2004

Diffusion of single cardiac ryanodine receptors in lipid bilayers is decreased by annexin 12.

Diffusion of cardiac ryanodine receptors (RyR2) in lipid bilayers was characterized. RyR2 location was monitored by imaging fluo-3 fluorescence due to Ca2+ flux through RyR2 channels or fluorescence from RyR2 conjugated with Alexa 488 or containing green fluorescent protein. Single channel currents were recorded to ensure that functional channels were studied. RyR2 exhibited an apparent diffusion coefficient (DRyR) of 1.2 x 10(-8) cm2 s(-1) and a mean path length of 5.0 microm. Optimal use of optical methods for analysis of RyR2 channel function requires that RyR2 diffusion be limited. Therefore, we tested the effect of annexin 12, which interacts with anionic phospholipids in a Ca2+-dependent manner. Addition of annexin 12 (0.25-4.0 microM) to the trans side of bilayers containing an 80:20 ratio of phosphatidylethanolamine/phosphatidylserine decreased RyR2 diffusion in a concentration-dependent manner. Annexin 12 (2 microM) decreased the apparent DRyR 683-fold from 1.2-10(-8) to 1.8 x 10(-11) cm2 s(-1) and the mean path length 10-fold from 5.0 to 0.5 micro m without obvious changes in the conductance of the native bilayer or in activation of RyR2 channels by Ca2+ or suramin. Thus, annexin 12 may provide a useful tool for optimizing optical analysis of RyR2 channels in lipid bilayers.

Animals↗
PubMed2003

Neuron recognition by parallel Potts segmentation.

Identifying neurons and their spatial coordinates in images of the cerebral cortex is a necessary step in the quantitative analysis of spatial organization in the brain. This is especially important in the study of Alzheimer's disease (AD), in which spatial neuronal organization and relationships are highly disrupted because of neuronal loss. To automate neuron recognition by using high-resolution confocal microscope images from human brain tissue, we propose a recognition method based on statistical physics that consists of image preprocessing, parallel image segmentation, and cluster selection on the basis of shape, optical density, and size. We segment a preprocessed digital image into clusters by applying Monte Carlo simulations of a q-state inhomogeneous Potts model. We then select the range of Potts segmentation parameters to yield an ideal recognition of simplified objects in the test image. We apply our parallel segmentation method to control individuals and to AD patients and achieve recognition of 98% (for a control) and 93% (for an AD patient), with at most 3% false clusters.

Alzheimer Disease↗
PubMed2002

Claudin 5 is transiently expressed during the development of the retinal pigment epithelium.

During the development of chick retinal pigment epithelium (RPE), the permeability and selectivity of the epithelium's tight junctions are continuously modulated. Overall paracellular permeability decreases, but selectivity increases. Because the claudin family of transmembrane proteins appears to provide the structural basis for selectivity, we examined the expression of claudins as a function of development in chick RPE. Degenerate primers were used with the reverse transcriptase-polymerase chain reaction (RT-PCR) to obtain complete sequences of chick claudins 3 and 5. Northern blotting and semi-quantitative RT-PCR demonstrated that claudin 5 was expressed in RPE, but claudin 3 was expressed only in the choroid layer of the eye. Northern blotting, semiquantitative RT-PCR and immunoblotting demonstrated that the expression of claudin 5 was transient, with peak levels of expression between embryonic days 10 and 14. Primary cultures were used to demonstrate that factors secreted by the neural retina induced the expression of claudin 5 nearly 3-fold if RPE was isolated from embryonic day 7 embryos. There was little effect if RPE was isolated from embryonic day 14. The upregulation of claudin 5 correlates with permeability changes that occur during the intermediate stage of RPE development. Interestingly, claudin 5 must be replaced during the late stage of development when the number and complexity of tight junctional strands increases. This would imply more changes in selectivity.

Amino Acid Sequence↗
PubMed2001

Synthesis and analgesic effects of kyotorphin-steroid linkers.

Kyotorphin (KTP, H-Tyr-Arg-OH) was covalently bonded with hydrocortisone or estrone to form the corresponding hydrocortisone-21-O-yl-succinyl-Tyr-ArgOH or estrone-3-O-yl-acyl-Tyr-Arg-OH. Their analgesic activities were investigated using the tail flick test. The potency of the two linkers were significantly higher than that of KTP and the mixture of KTP and hydrocortisone or estrone in the CNS and/or the periphery administration.

Analgesics↗
PubMed2001

Formation of novel polymeric nanoparticles.

We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.

Microspheres↗
PubMed2001

Melanocortin-1 receptor gene variants in four Chinese ethnic populations.

There is strong relationship between melanocortin-1 receptor (MC1R) gene variants and human hair color and skin type. Based on a sequencing study of MC1R gene in 50 individuals from the Uygur, Tibetan, Wa and Dai ethnic populations, we discuss the occurrence of 7 mc1r variants consisting of 5 nonsynonymous sites (Val60Leu, Arg67Gln, Val92Met, Arg163Gln and Ala299Val) and 2 synonymous sites (C414T and A942G), among which C414T and Ala299Val were reported for the first time. Confirmation and analysis were also made of 122 individuals at three common point mutations (Val92Met, Arg163Gln, A942G) using PCR-SSCP. The frequency of Arg163Gln variant varies in the four ethnic populations, with percentage of 40%, 85.0%, 66.2% and 72.7%, respectively, while those of Val92Met and A942G are roughly similar in these four populations. The different environments, migration and admixture of various ethnic groups in China might have impact on the observed frequency of Arg163Gln.

Alleles↗
PubMed2001

Indigenization and beyond: methodological relationalism in the study of personality across cultural traditions.

A brief intellectual history of the indigenization movement in Asia leads to the thesis that the generation of psychological knowledge is culture dependent. Indigenous psychologies go further and insist on viewing a target group from the natives' own standpoint. Psychological decentering underlies conceptions of human existence rooted in Asian intellectual traditions, in particular, relatedness between persons predominates in Confucianism. These conceptions demand new approaches to knowledge generation that signify a paradigmatic shift from methodological individualism to methodological relationalism. An implication is that relationships precede situations in the study of personality and social behavior. We define personality as the sum total of common attributes manifest in, and abstracted from, a person's behavior directly or indirectly observed across interpersonal relationships and situations over time. We rely on the notion that there are identifiable levels of cognition to develop a metatheoretical framework for reconstructing selfhood. Confronting the subject-object dichotomy opens the door to investigations of transcendent consciousness; confronting the self-other demarcation underlying Western theories leads to the construction of self-in-relations.

Cross-Cultural Comparison↗
PubMed2001

[The development of multi-lead EEG telemetry and tele-monitoring system].

This paper introduces a kind of EEG Telemetry and Tele-monitoring system. With the use of the public telephone network to transport signals and the portable EEG recording system as the sender of system, the EEG data of 20 standard leads can be transmitted to the receiver of system (monitoring center) synchronously. And at the monitoring center, the waves can be displayed real-time, freezing, stored, reviewed, analyzed and printed, thus providing aid in remote diagnosis and treatment consultations.

Computer Communication Networks↗
PubMed2001

[Association of apolipoprotein E gene polymorphism with early-onset coronary heart disease and its effect on plasma lipid levels].

OBJECTIVE: To detect the association of apolipoprotein E(apoE) gene polymorphism with early-onset coronary heart disease(CHD) and to evaluate the effect of apoE gene polymorphism on plasma lipid levels. METHODS: The apoE genotypes of 52 early-onset CHD patients (aged 38-55 years), 161 aged CHD patients and 180 controls were determined by PCR-RFLP. Plasma lipid levels were measured by using routine methods. RESULTS: Five genotypes of apoE, E3/3, E4/4, E3/2, E4/3 and E4/2 were detected in this study. Statistically differences in apoE4/3 and epsilon4 frequencies between early-onset and aged CHD patients and controls were seen (P<0.05). The frequency of epsilon4 in the early-onset CHD patients was higher than that in the aged CHD patients. epsilon4 and epsilon2 alleles also differently affected the plasma total cholesterol and low density lipoprotein cholesterol levels. CONCLUSION: These results suggest that apoE gene polymorphism is in association with the occurrence and development of early-onset CHD and it affects the plasma lipid levels.

Adult↗
PubMed2001

[Influence of elevated atmospheric CO2 concentration on photosynthesis and leaf nitrogen partition in process of photosynthetic carbon cycle in Musa paradisiaca].

The photosynthetic rate (Pn) in leaves of Musa paradisiaca grown under elevated CO2 concentration (700 +/- 56 microliters.L-1) for one week was 5.14 +/- 0.32 mumol.m-2.s-1, 22.1% higher than that under ambient CO2 concentration, while under elevated CO2 concentration for 8 week, the Pn decreased by 18.1%. It can be inferred that the photosynthetic acclimation to elevated CO2 concentration and the Pn inhibition occurred in leaves of M. paradisiaca. The respiration rate in light (Rd) was lower in leaves under higher CO2 concentration, compared with that under ambient CO2 concentration. If the respiration in light was not included, the difference in CO2 compensation point for the leaves of both plants was not significant. Under higher CO2 concentration for 8 weeks, the maximum carboxylation rate(Vcmax) and electron transportation rate (J) in leaves decreased respectively by 30.5% and 14.8%, compared with that under ambient CO2 concentration. The calculated apparent quantum yield (alpha) in leaves under elevated CO2 concentration according to the initial slope of Pn/PAR was reduced to 0.014 +/- 0.010 molCO2.mol-1 quanta, compared with the value of 0.025 +/- 0.005 molCO2.mol-1 quanta in the control. The efficiency of light energy conversion also decreased from 0.203 to 0.136 electrons.quanta-1 in plants under elevated CO2 concentration. A lower partitioning coefficient for leaf nitrogen in Rubisco, bioenergetics and thylakoid light-harvesting components was observed in plants under higher CO2 concentration. The results indicated that the multi-process of photosynthesis was suppressed significantly by a long-term (8 weeks) higher CO2 concentration incubation.

Carbon Dioxide↗
PubMed2001

[Species and species diversity in relation with restoration and persistence of degraded ecosystem functions].

Species diversity is an important character of an ecosystem, and keeps it to function. Species diversity and their communities provide human with essential ecosystem services, including nutrient cycling, biological productivity, trophic function, etc. Species diversity is tightly related with the ecosystem's ability to withstand stress and disturbance. Increasing biodiversity could enhance system stability. Compared to individual species and species number, functional group and functional diversity impose larger impact on system functioning, and are good approaches used to measure stability and to predict community change. Several forms with which the species act on ecosystem functioning were proposed and discussed in this paper. Understanding the relationship between species diversity and ecosystem function could guide the practice of restoring degraded ecosystem and maintaining its functions. Particularly, it provides basic ecological theories for "species assemblage" at initial stage of restoration.

Ecosystem↗