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Biomedical subjects

Dan Luo

Publications and source records attributed to Dan Luo.

At least 19 recordsLinked to original sources
PubMed2026

Glutamate metabolic correlation analysis reveals CnP5CS1 contributes to 2-acetyl-1-pyrroline accumulation in aromatic coconut.

Flavor quality, a key sensory attribute of coconut, has consistently been a central breeding objective throughout long-term domestication and varietal improvement efforts. Developing high-aroma varieties requires a clear understanding of their underlying molecular genetic mechanisms. However, research on the metabolic regulatory enzymes involved remains limited, particularly those linked to 2-acetyl-1-pyrroline (2AP), a volatile compound that primarily contributes to the unique scent of aromatic coconuts. We developed contrasting populations and systematically evaluated the role of CnP5CS in 2AP accumulation by examining enzyme activity, metabolic flux, population-level genetic variation, and transcriptional regulatory networks. In the aromatic coconut population, the selected genomic regions were enriched in pathways associated with amino acid metabolism and stress responses. Conspicuously, glutamate (Glu) and its derivatives showed significant correlations within the differentiated populations. The Glu metabolic enzyme P5CS was subjected to strong purifying selection, and haplotype-phenotype association analysis further identified the dominant CnP5CS1 allele genotype. Moreover, we established metabolic marker indicators to assess relative 2AP levels, based on the metabolic profiles of CnP5CS and the substrates and products of its catalyzed reactions. The Y1H assay identified the key transcription factor CnYAB2, which exhibited a strongly correlated expression pattern with CnP5CS1 and major markers of 2AP metabolism. The identification of CnP5CS1 offers a novel perspective on the genetic regulation of 2AP metabolism in aromatic coconuts and establishes a theoretical foundation for developing molecular markers to support the breeding of high-aroma varieties.

Aroma↗
PubMed2006

Involvement of endothelial cell-derived CGRP in heat stress-induced protection of endothelial function.

Previous studies have shown that heat stress possesses cardioprotection, which is related to the synthesis and release of calcitonin gene-related peptide (CGRP) via activation of capsaicin receptor (vanilloid receptor subtype 1, VR1) on the capsaicin-sensitive sensory neurons. The VR1 exists in human umbilical vein endothelial cells (HUVECs). Endothelial cells can synthesize CGRP and CGRP could protect against endothelial dysfunction induced by lysophosphatidylcholine (LPC) or oxidized low-density lipoprotein. In the present study, we explored whether the endothelial cell-derived CGRP is involved in the effect of heat stress on endothelial function in vivo and in vitro. Our results indicated that heat stress significantly increased the plasma concentration of CGRP, which was abolished by pretreatment with capsazepine, a VR1 antagonist. Immunohistochemistry and in situ hybridization showed that the endothelium of mesenteric artery and aorta expressed CGRP. And heat stress increased the expression of CGRP, which was also abolished by capsazepine. LPC attenuated the endothelium-dependent relaxation responses of aorta rings, which were improved by pretreatment with heat stress. In cultured HUVECs, the CGRP secretion was increased after heat stress. LPC increased the lactate dehydrogenase (LDH) activity in the cultured medium and decreased the cell viability, suggesting that LPC injured the HUVECs. However, pretreatment with heat stress attenuated the injurious effects of LPC on HUVECs. And this beneficial effect of heat stress on HUVECs was inhibited by capsazepine or CGRP(8-37), the CGRP receptor antagonist. The present results suggest that the endothelial cell-derived CGRP contributes to the protective effects of heat stress on endothelial function. Our study provides a potential mechanism to explain the protective effect of heat stress on cardiovascular system.

Animals↗
PubMed2006

Enzyme-catalysed assembly of DNA hydrogel.

DNA is a remarkable polymer that can be manipulated by a large number of molecular tools including enzymes. A variety of geometric objects, periodic arrays and nanoscale devices have been constructed. Previously we synthesized dendrimer-like DNA and DNA nanobarcodes from branched DNA via ligases. Here we report the construction of a hydrogel entirely from branched DNA that are three-dimensional and can be crosslinked in nature. These DNA hydrogels were biocompatible, biodegradable, inexpensive to fabricate and easily moulded into desired shapes and sizes. The distinct difference of the DNA hydrogel to other bio-inspired hydrogels (including peptide-based, alginate-based and DNA (linear)-polyacrylamide hydrogels) is that the crosslinking is realized via efficient, ligase-mediated reactions. The advantage is that the gelling processes are achieved under physiological conditions and the encapsulations are accomplished in situ-drugs including proteins and even live mammalian cells can be encapsulated in the liquid phase eliminating the drug-loading step and also avoiding denaturing conditions. Fine tuning of these hydrogels is easily accomplished by adjusting the initial concentrations and types of branched DNA monomers, thus allowing the hydrogels to be tailored for specific applications such as controlled drug delivery, tissue engineering, 3D cell culture, cell transplant therapy and other biomedical applications.

Catalysis↗
PubMed2006

Transfer characteristics of cadmium and lead from soil to the edible parts of six vegetable species in southeastern China.

The transfer characteristics of Cd and Pb from soils to the edible parts of six vegetable species were calculated from plant and corresponding surface soil samples collected from the fields in Fujian Province, southeastern China. The soil-to-plant transfer factors (TF) calculated from both total and DTPA-extractable Cd and Pb in the soils decreased with increasing total or DTPA-extractable Cd and Pb, indicating that the TF values of Cd and Pb depend on the soil metal content. For most plants studied, there was a significant relation between the TF values and the corresponding soil metal concentrations (total or DTPA-extractable) that was best described by an exponential equation (y=axb). We recommend that the representative TF value for a given crop-metal system should be estimated from the regression models between the transfer factors and the corresponding soil metal concentrations and at a given soil metal concentration.

Biological Transport↗
PubMed2006

Short- and long-wave UV light (UVB and UVA) induce similar mutations in human skin cells.

While the mutagenic and carcinogenic properties of longwave UV light (UVA) are well established, mechanisms of UVA mutagenesis remain a matter of debate. To elucidate the mechanisms of mutation formation with UVA in human skin, we determined the spectra of UVA- and UVB-induced mutations in primary human fibroblasts. As with UVB, we found the majority of mutations to be C-to-T transitions also with UVA. For both UVA and UVB, these transitions were found within runs of pyrimidines, at identical hotspots, and with the same predilection for the nontranscribed strand. They also included CC-to-TT tandem mutations. Therefore, these mutations point to a major role of pyrimidine dimers not only in UVB but also in UVA mutagenesis. While some differences were noted, the similarity between the spectra of UVA- and UVB-induced mutations further supports similar mechanisms of mutation formation. A non-dimer type of DNA damage does not appear to play a major role in either UVA or UVB mutagenesis. Therefore, the previously reported increasing mutagenicity per dimer with increasing wavelengths cannot be due to non-dimer DNA damage. Differences in the cellular response to UVA and UVB, such as the less prominent activation of p53 by UVA, might determine a different mutagenic outcome of UVA- and UVB-induced dimers.

Base Sequence↗
PubMed2006

Effect of epigallocatechingallate on ultraviolet B-induced photo-damage in keratinocyte cell line.

One type of traditional Chinese medicines, epigallocatechingallate (EGCG) has been commonly used as a clinical and skin health protective ingredient. It has been known to have photo-protective, anti-inflammatory, and anti-oxidant effects. However, little is known about the mechanisms of EGCG on UV-induced photo-aging and photo-carcinogenesis. In the present study, we investigated the photo-protective mechanisms of EGCG on UVB-induced skin damage, including the potency of EGCG to inhibit the UVB-induced cytotoxicity, secretion of cytokine (IL-6 and TNF-alpha), cellular apoptosis, expression of apoptosis-regulatory genes (p53-p21) and c-fos gene in cultured immortalized human keratinocyte HaCaT cells. EGCG treatment decreased UVB- induced cell cytotoxicity and apoptosis. It also inhibited the mRNA expressions of apoptosis-regulatory gene (p53 and p21) and c-fos gene. These results suggest that EGCG may have an inhibitory effect on UVB-induced photo-damage and apoptosis by blocking the cytokine secretion and the mRNA expressions of p53, p21 and c-fos genes.

Apoptosis↗
PubMed2006

A dendrimer-like DNA-based vector for DNA delivery: a viral and nonviral hybrid approach.

DNA can be used as a generic delivery vector in addition to its genetic role as a antigen expression vector. This is inspired in part by the fact that DNA molecules are true polymers. Surprisingly, DNA molecules have not been used as a delivery vector material. This is probably due to the fact that almost all DNA have only two shapes: linear or circular. This chapter details our efforts in fabricating highly branched dendrimer-like DNA (DL-DNA) that may serve as a multivalent DNA delivery vector. Just like chemical dendrimers, DL-DNA is multi-valent and monodisperse. However, unlike traditional chemical dendrimers, DL-DNA is much larger (~100 nm, generation 4) and can be designed to be nonsymmetric as well. Most importantly, DL-DNA possesses two unique properties: anisotropicity and biodegradability, making multiple, specific conjugations of viral peptides possible. Our method suggests that viral-pep-tide conjugated DL-DNA vectors can deliver genes into cells without any other transfection reagents. This viral-nonviral hybrid system can be further tailored to specific cells by conjugating specific ligands. We believe that such a DL-DNA-based, viral, and nonviral hybrid assembly will provide a new platform for drug delivery in general and gene delivery in particular.

Dendrimers↗
PubMed2006

Multiplexed molecular detection using encoded microparticles and nanoparticles.

Signal-encoded microparticles and nanoparticles have been used to label many reactions simultaneously for target identification in assays, and thus are an indispensable part of multiplex technologies. With the increasing demand for multiplexed molecular detection, encoded particles have evolved from pattern encoding to signal-intensity encoding, and also from signal-molecule encapsulation to signal-molecule tagging. The fabrication and utilization of such nano- and microparticles should advance multiplexed analysis. This short review focuses on how these encoded particles work and briefly touches on their applications in multiplexed molecular detection.

Biological Assay↗
PubMed2006

[Expression and localization of estrogen receptor ERalpha and the kinds of ERbeta mRNA on placenta].

OBJECTIVE: To investigate the kinds of ERa, ERbeta mRNA and the localization of ERa, ERbeta on normal human placenta. METHODS: The expression and localization of ERa,ERbeta on normal human placenta were detected by reverse transcription-ploymerase chain reaction (RT-PCR) and immunhistochemistry (SP-assay). RESULTS: There was mRNA expression of ERalpha and ERbeta on human term placenta, and ERbeta was identified with ERbeta5. The ERa immunoreactivity on human term placenta was in villous cytotrophoblastic nucleus, and that of ERbeta was in syncytiotrophoblastic cytoplasm. CONCLUSION: The findings indicate that ERbeta5 is the kind of ERbeta on placenta. It is localizated in the cytoplasm of syncytiotrophoblast and is probably connected with the production of estrogen.

Adult↗
PubMed2005

Nucleoside phosphocholine amphiphile for in vitro DNA transfection.

A new transfection reagent based on nucleoside phosphocholine amphiphile leading to high transfection efficacy and low cytotoxicity is described. TEM, ethidium bromide displacement assays, agarose gel electrophoresis and SAXS studies support the formation of lipoplexes for the transfection of CHO cells.

Animals↗
PubMed2005

Multiplexed detection of pathogen DNA with DNA-based fluorescence nanobarcodes.

Rapid, multiplexed, sensitive and specific molecular detection is of great demand in gene profiling, drug screening, clinical diagnostics and environmental analysis. One of the major challenges in multiplexed analysis is to identify each specific reaction with a distinct label or 'code'. Two encoding strategies are currently used: positional encoding, in which every potential reaction is preassigned a particular position on a solid-phase support such as a DNA microarray, and reaction encoding, where every possible reaction is uniquely tagged with a code that is most often optical or particle based. The micrometer size, polydispersity, complex fabrication process and nonbiocompatibility of current codes limit their usability. Here we demonstrate the synthesis of dendrimer-like DNA-based, fluorescence-intensity-coded nanobarcodes, which contain a built-in code and a probe for molecular recognition. Their application to multiplexed detection of the DNA of several pathogens is first shown using fluorescence microscopy and dot blotting, and further demonstrated using flow cytometry that resulted in detection that was sensitive (attomole) and rapid.

Bacillus anthracis↗
PubMed2005

Diffusion of single star-branched dendrimer-like DNA.

We report a single-molecule fluorescence study on the diffusion of star-branched polymer dendrimer-like DNA (DL-DNA). The DL-DNA molecules were synthesized from ligating Y-shaped DNA to the fourth generation. It was found through single particle tracking that the diffusion coefficient of DL-DNA changes in a nonmonotonic fashion with its increased concentration possibly due to arm arrest and arm retraction. The diffusion of DL-DNA in linear lambda DNA solution displayed a monotonic concentration dependence 1 order of magnitude greater than the diffusion of DL-DNA in DL-DNA solution. This difference is attributed to the different conformation of DL-DNA and lambda DNA and the entanglement of lambda DNA with a large radius of gyration. Our diffusion study facilitates DL-DNA transportation for drug delivery.

Benzoxazoles↗
PubMed2005

Interactions of sympathetic nerves with capsaicin-sensitive sensory nerves: neurogenic mechanisms for phenol-induced hypertension in the rat.

BACKGROUND: Previous investigations have shown that norepinephrine is capable of inhibiting neurotransmission in capsaicin-sensitive sensory nerves via a prejunctional mechanism. The alteration in the activity of sympathetic or capsaicin-sensitive sensory nerves in the development of phenol-induced hypertension was observed separately in rats. METHODS: In the present study, we examined interactions of adrenergic nerves with capsaicin-sensitive sensory nerves in phenol-induced hypertensive rats. Blood pressure, the synthesis and release of calcitonin gene-related peptide (CGRP) and the content of nerve growth factor in (NGF) arteries were determined. RESULTS: Intrarenal injection of phenol caused a permanent elevation of blood pressure concomitantly with a decrease in the concentration of CGRP in plasma, the content of CGRP in dorsal root ganglia and the density of CGRP-containing nerves in the mesenteric artery, and vascular NGF content. Chronic treatment with prazosin (an alpha1-adrenoreceptor antagonist, 3 mg/kg per day) failed to alter the synthesis and release of CGRP and vascular NGF content, even though it completely normalized blood pressure. However, treatment with yohimbine (an alpha2-adrenoreceptor antagonist, 5 mg/kg per day) significantly increased CGRP level and vascular NGF content. Combined administration of prazosin and yohimbine not only significantly elevated the synthesis and release of CGRP and arterial NGF content, but also completely normalized blood pressure. CONCLUSION: These results indicate that the decreased production and release of CGRP and reduced vascular NGF content are attributed to the activation of alpha2-adrenoreceptors in phenol-induced hypertensive rats.

Animals↗
PubMed2005

The impact of NiO on microstructure and electrical property of solid oxide fuel cell anode.

Ni-Ce(0.8)Sm(0.2)O(1.9) (Ni-SDC) cermet was selected as anode material for reduced temperature (800 degrees C) solid oxide fuel cells in this study. The influence of NiO powder fabrication methods for Ni-SDC cermets on the electrode performance was investigated so that the result obtained can be applied to make high-quality anode. Three kinds of NiO powder were synthesized with a fourth kind being available in the market. Four types of anode precursors were fabricated with these NiO powders and Ce(0.8)Sm(0.2)O(1.9) (SDC), and then were reduced to anode wafers for sequencing measurement. The electrical conductivity of the anodes was measured and the effect of microstructure was investigated. It was found that the anode electrical conductivity depends strongly on the NiO powder morphologies, microstructure of the cermet anode and particle sizes, which are decided by NiO powder preparation technique. The highest electrical conductivity is obtained for anode cermets with NiO powder synthesized by NiCO(3).2Ni(OH)(2).4H(2)O or Ni(NO(3))(2).6H(2)O decomposition technique.

Electric Impedance↗
PubMed2005

Asymmetric dimethylarginine is not involved in ovariectomy-induced osteopenia in rats.

Previous studies have indicated that the plasma concentration of nitric oxide synthase inhibitor, asymmetric dimethylarginine (ADMA), was increased in postmenopausal women. In the study reported here, we tested the relationship between the decrease of bone mineral density (BMD) and ADMA concentration in ovariectomized (OVX) rats. Ovariectomized rats at 8 months of age were treated with 17beta-estradiol (10 or 30 microg/kg of body weight/day, s.c.) or L-arginine (300 mg/kg/day, i.p.) for 12 weeks (n = 10 for each group). Pre- and posttreatment total BMD, posttreatment plasma nitrite/nitrate and ADMA concentrations, and posttreatment BMD in the lumbar part of the spine (L4-L6), femurs, and tibias were examined. Ovariectomy caused a significant decrease in several BMD indexes, which was reversed by estrogen treatment (P < 0.05). Plasma nitrite/nitrate concentration was significantly decreased in OVX rats, but was restored by estrogen treatment (P < 0.05). There were no differences in the plasma concentration of ADMA in OVX or estrogen-treated rats. L-Arginine had no effect on plasma nitrite/nitrate concentration and BMD in OVX rats. These results suggest that ovariectomy does not influence the plasma concentration of ADMA, and that ADMA is not involved in ovariectomy-induced osteopenia in rats.

Animals↗
PubMed2004

A new arginine substitution mutation of DSRAD gene in a Chinese family with dyschromatosis symmetrica hereditaria.

BACKGROUND: Dyschromatosis symmetrica hereditaria (DSH) is a pigmentary genodermatosis of autosomal dominant inheritance characterized by a mixture of hyperpigmented and hypopigmented macules distributed on the dorsal aspects of the hands and feet. To date, only three articles testified that DSH is caused by the mutations of DSRAD gene (also called ADAR1) encoding for RNA-specific adenosine deaminase. OBJECTIVE: To identify mutations of DSRAD as the disease-causing gene and recognize different mutations giving a clue to insight into the mechanism of DSH. METHODS: We collected a Chinese DSH family consisting of a total of 11 individuals including five DSH patients (three males and two females). The whole coding region of DSRAD was amplified by polymerase chain reaction and products analyzed by direct sequencing. RESULTS: We detected a transition, 3463 C>T, leading to a missense mutation (R1155W) in genomic DNAs of five patients, and the point mutation was not found in normal individuals in this DSH family and in 100 unrelated, population-match control individuals. CONCLUSION: Our data suggests that R1155W missense mutation is a new mutation in exon 15 of DSRAD gene and further testify that DSRAD gene is the pathogenic gene of DSH.

Adenosine Deaminase↗
PubMed2004

Delayed preconditioning by cardiac ischemia involves endogenous calcitonin gene-related peptide via the nitric oxide pathway.

Previous investigations have shown separately that calcitonin gene-related peptide (CGRP) or nitric oxide (NO) is involved in mediation of ischemic preconditioning. In the present study, we tested interactions of CGRP with NO in mediation of delayed preconditioning. In Sprague-Dawley rats, ischemia-reperfusion injury was induced by 45-min occlusion followed by 3-h reperfusion of coronary artery, and preconditioning was induced by four cycles of 3-min ischemia and 5-min reperfusion. Infarct size, plasma creatine kinase activity, the plasma level of NO and CGRP, and the expression of CGRP mRNA in dorsal root ganglion were measured. Pretreatment with preconditioning significantly reduced infarct size and the release of creatine kinase during reperfusion, and caused a significant increase in the expression of CGRP mRNA, concomitantly with an elevation in the plasma level of CGRP and NO. The effects of preconditioning were completely abolished by administration of L-nitroarginine methyl ester (L-NAME, 10 mg/kg, i.p.), an inhibitor of NO synthase. Pretreatment with capsaicin (50 mg/kg, s.c.), which depletes transmitters in capsaicin-sensitive sensory nerves, also blocked the cardioprotection of preconditioning and reduced the synthesis and release of CGRP, but did not affect the concentration of NO. The present results suggest the delayed protection afforded by ischemic preconditioning is also mediated by endogenous CGRP via the NO pathway in rat heart.

Animals↗