Biomedical subjects

S Y He

Publications and source records attributed to S Y He.

At least 19 recordsLinked to original sources

PubMed2006

Crocetin improves endothelium-dependent relaxation of thoracic aorta in hypercholesterolemic rabbit by increasing eNOS activity.

Our previous studies have proven that crocetin (CCT), extracted from Gardenia jasminoides Ellis, possesses the anti-atherosclerotic effect. Because endothelial dysfunction strongly contributes to the initiation and progression of atherosclerosis, the present study aims to investigate whether CCT is capable of improving this dysfunction and to explore the possible mechanisms. Endothelial dysfunction was induced by in vivo feeding high cholesterol diet (HCD) to rabbit and by in vitro treating bovine aortic endothelial cells (BAECs) with oxidized LDL (oxLDL). Endothelium-dependent relaxation (EDR) evoked by acetylcholine (Ach) and endothelium-independent relaxation (RIDR) mediated by sodium nitroprusside (SNP) of thoracic aorta isolated from rabbit were measured. The results indicated that the EDR in HCD alone treated rabbits was seriously impaired and the maximal relaxation induced by Ach (10(-5.5) M) was only 54% that in control rabbit fed with regular diet. Oral complementation with CCT (15, 30 mg/kg) dose-dependently improved this impairment and restored the maximal relaxation to 68% and 80% that in control group, respectively. However, the EIDR maintained comparable in all groups. Complementation with CCT (15, 30 mg/kg) simultaneously increased serum level of nitric oxide (NO), upregulated vessel activity and mRNA expression of endothelial NO synthase (eNOS) as well as vessel cyclic GMP (cGMP) content compared with those in rabbit treated with HCD alone. Inducible NOS (iNOS) activity remained unchangeable in all groups. In BAECs, oxLDL treatment decreased NO production, downregulated both activity and mRNA expression of eNOS. While those decrease or downregulation were inhibited by co-treatment with CCT (0.1, 1, 10 microM) in a dose-dependent manner. These findings suggested that CCT significantly restored the EDR of thoracic aorta in hypercholesterolemic rabbit, which might be explained by its action to increase the vessel eNOS activity, leading to elevation of NO production.

Animals↗

PubMed2001

Role of the Hrp pilus in type III protein secretion in Pseudomonas syringae.

Bacterial surface appendages called pili and needle-like filaments are associated with protein and/or DNA transfer to recipient plant, human, or bacterial cells during pathogenesis or conjugation. Although it has long been suspected that pili function as a conduit for protein or DNA transfer, direct evidence has been lacking. The Hrp pilus of Pseudomonas syringae is assembled by the type III secretion system. We used an in situ immunogold labeling procedure to visualize the extrusion of an effector protein, AvrPto, from the tip of the Hrp pilus, providing direct evidence that a bacterial pilus can function as a conduit for protein delivery.

Antibodies, Bacterial↗

PubMed2001

Monophosphoryl lipid A-induced delayed preconditioning is mediated by calcitonin gene-related peptide.

The delayed preconditioning of the heart by monophosphoryl lipid A is mediated by endogenous nitric oxide (NO), and the cardioprotection afforded by nitroglycerin is related to stimulation of calcitonin gene-related peptide (CGRP) release. The objective of this study was to explore whether improvement of preservation with cardioplegia by monophosphoryl lipid A is mediated by CGRP. In addition, we examined the effect of monophosphoryl lipid A on the tumor necrosis factor-alpha (TNF-alpha) content of myocardial tissues. The isolated rat heart was perfused in the Langendorff mode. Heart rate, coronary flow, left-ventricular pressure, and its first derivatives (+/-dp/dt(max)) were recorded, and plasma levels of NO and CGRP, the release of creatine kinase in coronary effluent and the content of TNF-alpha in myocardial tissues were measured. Hypothermic ischemia for 4 h caused a decline in cardiac function, and an increase in the release of creatine kinase and in the content of TNF-alpha. Pretreatment with monophosphoryl lipid A (500 microg/kg, i.p.) for 24 h improved the recovery of cardiac function and reduced the release of creatine kinase concomitantly with a decrease in the content of cardiac TNF-alpha. Monophosphoryl lipid A markedly increased plasma concentrations of CGRP and NO. After pretreatment with L-nitroarginine methyl ester (L-NAME), the cardioprotection and the increased release of NO and CGRP induced by monophosphoryl lipid A were abolished. Capsaicin also abolished the cardioprotection and the increased release of CGRP induced by monophosphoryl lipid A, but did not affect the content of NO. The results suggest that monophosphoryl lipid A-induced preconditioning enhances preservation with cardioplegia and that the protective effects of monophosphoryl lipid A are related to stimulation of CGRP release.

Animals↗

PubMed2001

Visualization of secreted Hrp and Avr proteins along the Hrp pilus during type III secretion in Erwinia amylovora and Pseudomonas syringae.

Pili are required for protein and/or DNA transfer from bacteria to recipient plant or bacterial cells, based on genetic evidence. However, it has never been shown directly that the effector proteins or DNA are localized along or inside the pili in situ. Failure to visualize an association of effector proteins/DNA with pili is the central issue in the debate regarding the exact function of pili in protein and DNA transfer. In this study, a newly developed in situ immunogold labelling procedure enabled visualization of the specific localization of type III effector proteins of Erwinia amylovora and Pseudomonas syringae pv. tomato along the Hrp pilus, but not along the flagellum or randomly in the intercellular space. In contrast, PelE, a pectate lyase secreted via the type II protein secretion system, was not associated with the Hrp pilus. These results provide direct evidence that type III secretion occurs only at the site of Hrp pilus assembly and that the Hrp pilus guides the transfer of effector proteins outside the bacterial cell, favouring the 'conduit/guiding filament' model.

Animals↗

PubMed2001

Immunogold labeling of Hrp pili of Pseudomonas syringae pv. tomato assembled in minimal medium and in planta.

Hypersensitive reaction and pathogenicity (hrp) genes are required for Pseudomonas syringae pv. tomato (Pst) DC3000 to cause disease in susceptible tomato and Arabidopsis thaliana plants and to elicit the hypersensitive response in resistant plants. The hrp genes encode a type III protein secretion system known as the Hrp system, which in Pst DC3000 secretes HrpA, HrpZ, HrpW, and AvrPto and assembles a surface appendage, named the Hrp pilus, in hrp-gene-inducing minimal medium. HrpA has been suggested to be the Hrp pilus structural protein on the basis of copurification and mutational analyses. In this study, we show that an antibody against HrpA efficiently labeled Hrp pili, whereas antibodies against HrpW and HrpZ did not. Immunogold labeling of bacteria-infected Arabidopsis thaliana leaf tissue with an Hrp pilus antibody revealed a characteristic lineup of gold particles around bacteria and/or at the bacterium-plant contact site. These results confirm that HrpA is the major structural protein of the Hrp pilus and provide evidence that Hrp pili are assembled in vitro and in planta.

Agar↗

PubMed2001

Role of calcitonin gene-related peptide in nitric oxide-mediated myocardial delayed preconditioning induced by head stress.

AIM: To study the role of calcitonin gene-related peptide (CGRP) in nitric oxide (NO)-mediated myocardial delayed preconditioning induced by heat stress. METHODS: The isolated rat heart was perfused in a Langendorff model. Hearts for all groups were subjected to 4 h hypothermia (4 degrees C) and 40 min reperfusion (37 degrees C). In the hyperthermia-treated group, rats were subjected to whole-body hyperthermia (rectal 42 degrees C, 15 min) 24 h before the experiment. Heart rate, coronary flow, left ventricular pressure, and its derivative (+/- dp/dtmax) were recorded, and calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in plasma and the activity of creatine kinase (CK) in the coronary effluent were measured. RESULTS: Pretreatment with hyperthermia significantly improved the recovery of cardiac protection, reduced the release of CK, and increased plasma concentrations of CGRP. Pretreatment with L-NAME, an inhibitor of NOS, or capsaicin, which selectively depleted sensory neurotransmitter content, abolished the protective effects and the increased level of CGRP elicited by hyperthermia. CONCLUSION: Endogenous NO is involved in the cardioprotection afforded by heat stress, and the beneficial effects of NO are mediated by CGRP in the rat.

Animals↗

PubMed2001

[The development and application of oxypathor of standard atmosphere].

This paper introduces a newly-developed oxypathor under one absolute atmosphere. It provides both oxygen and mixed-oxygen therapies, featuring oxygen-supply and oxygen-inhalation of hyperbaric oxygen chamber, and broaden the clinical applications of oxygen-therapy, which gave shown satisfactory results.

Equipment Design↗

PubMed2000

The gene coding for the Hrp pilus structural protein is required for type III secretion of Hrp and Avr proteins in Pseudomonas syringae pv. tomato.

Bacterial surface appendages called pili often are associated with DNA and/or protein transfer between cells. The exact function of pili in the transfer process is not understood and is a matter of considerable debate. The Hrp pilus is assembled by the Hrp type III protein secretion system of Pseudomonas syringae pv. tomato (Pst) strain DC3000. In this study, we show that the hrpA gene, which encodes the major subunit of the Hrp pilus, is required for secretion of putative virulence proteins, such as HrpW and AvrPto. In addition, the hrpA gene is required for full expression of genes that encode regulatory, secretion, and effector proteins of the type III secretion system. hrpA-mediated gene regulation apparently is through effect on the mRNA level of two previously characterized regulatory genes, hrpR and hrpS. Ectopic expression of the hrpRS gene operon restored gene expression, but not protein secretion, in the hrpA mutant. Three single amino acid mutations at the HrpA carboxyl terminus were identified that affect the secretion or regulatory function of the HrpA protein. These results define an essential role of the Hrp pilus structural gene in protein secretion and coordinate regulation of the type III secretion system in Pst DC3000.

Amino Acids↗

PubMed2000

Conversion of compatible plant-pathogen interactions into incompatible interactions by expression of the Pseudomonas syringae pv. syringae 61 hrmA gene in transgenic tobacco plants.

The hrmA gene from Pseudomonas syringae pv. syringae has previously been shown to confer avirulence on the virulent bacterium P. syringae pv. tabaci in all examined tobacco cultivars. We expressed this gene in tobacco plants under the control of the tobacco Delta0. 3 TobRB7 promoter, which is induced upon nematode infection in tobacco roots (Opperman et al. 1994, Science, 263, 221-223). A basal level of hrmA expression in leaves of transgenic plants activated the expression of pathogenesis-related genes, and the transgenic plants exhibited high levels of resistance to multiple pathogens: tobacco vein mottling virus, tobacco etch virus, black shank fungus Phytophthora parasitica, and wild fire bacterium Pseudomonas syringae pv. tabaci. However, the hrmA transgenic plants were not significantly more resistant to root-knot nematodes. Our results suggest a potential use of controlled low-level expression of bacterial avr genes, such as hrmA, in plants to generate broad-spectrum resistance to bacterial, fungal and viral pathogens.

Animals↗

PubMed2000

Expression of a functional antizearalenone single-chain Fv antibody in transgenic Arabidopsis plants.

The efficacy of cloning a recombinant mycotoxin antibody in plants was tested using Arabidopsis as a model. An antizearalenone single-chain Fv (scFv) DNA fragment was first cloned in the newly constructed phage display vector (pEY.5) and then recloned in the plant transformation vector pKYLX71::35S(2). After transformation, constructs of antizearalenone scFv were introduced into immature Arabidopsis seeds via Agrobacterium tumefaciens mediation by vacuum infiltration. Only plants transformed with the construct containing a PR-1b signal peptide sequence produced transgenic offspring. The antizearalenone scFv "plantibody" from these transgenic plants bound zearalenone with a high affinity (50% inhibitory concentration, 11.2 ng/ml) that was comparable to that of bacterially produced scFv antibody and the parent monoclonal antibody (MAb). By electron microscopic immunogold labeling, the presence of antizearalenone scFv was detected mainly in the cytoplasm and only occasionally outside the cell. Like bacterially produced scFv antibody, antizearalenone scFv plantibody exhibited greater sensitivity to methanol destabilization than did the parent MAb. The sensitivity of antizearalenone scFv plantibody to acidic disassociation was similar to the sensitivities of bacterially produced scFv antibody and MAb. Expression of specific plantibodies in crops might be useful for neutralizing mycotoxins in animal feeds and for reducing mycotoxin-associated plant diseases.

Antibody Formation↗

PubMed1998

The Pseudomonas syringae pv. tomato HrpW protein has domains similar to harpins and pectate lyases and can elicit the plant hypersensitive response and bind to pectate.

The host-specific plant pathogen Pseudomonas syringae elicits the hypersensitive response (HR) in nonhost plants and secretes the HrpZ harpin in culture via the Hrp (type III) secretion system. Previous genetic evidence suggested the existence of another harpin gene in the P. syringae genome. hrpW was found in a region adjacent to the hrp cluster in P. syringae pv. tomato DC3000. hrpW encodes a 42. 9-kDa protein with domains resembling harpins and pectate lyases (Pels), respectively. HrpW has key properties of harpins. It is heat stable and glycine rich, lacks cysteine, is secreted by the Hrp system, and is able to elicit the HR when infiltrated into tobacco leaf tissue. The harpin domain (amino acids 1 to 186) has six glycine-rich repeats of a repeated sequence found in HrpZ, and a purified HrpW harpin domain fragment possessed HR elicitor activity. In contrast, the HrpW Pel domain (amino acids 187 to 425) is similar to Pels from Nectria haematococca, Erwinia carotovora, Erwinia chrysanthemi, and Bacillus subtilis, and a purified Pel domain fragment did not elicit the HR. Neither this fragment nor the full-length HrpW showed Pel activity in A230 assays under a variety of reaction conditions, but the Pel fragment bound to calcium pectate, a major constituent of the plant cell wall. The DNA sequence of the P. syringae pv. syringae B728a hrpW was also determined. The Pel domains of the two predicted HrpW proteins were 85% identical, whereas the harpin domains were only 53% identical. Sequences hybridizing at high stringency with the P. syringae pv. tomato hrpW were found in other P. syringae pathovars, Pseudomonas viridiflava, Ralstonia (Pseudomonas) solanacearum, and Xanthomonas campestris. DeltahrpZ::nptII or hrpW::OmegaSpr P. syringae pv. tomato mutants were little reduced in HR elicitation activity in tobacco, whereas this activity was significantly reduced in a hrpZ hrpW double mutant. These features of hrpW and its product suggest that P. syringae produces multiple harpins and that the target of these proteins is in the plant cell wall.

Bacterial Outer Membrane Proteins↗

PubMed1998

Type III protein secretion systems in plant and animal pathogenic bacteria.

Among many interesting and sophisticated mechanisms used by bacterial pathogens to subvert eukaryotic hosts is a class of specialized protein secretion systems (known as type III protein secretion systems) that deliver bacterial virulence proteins directly into the host cell. Recent studies have revealed four important features of these secretion systems. First, they are widespread among plant and animal bacterial pathogens, and mutations affecting type III protein secretion often eliminate bacterial virulence completely. Second, at least eight type III secretion components share sequence similarities with those of the flagellar assembly machinery and flagellum-like structures are associated with type III secretion, raising the possibility that these secretion systems are derived from the presumably more ancient flagellar assembly apparatus. Third, type III secretion is activated in vivo upon contact with host cells. Fourth, the type III secretion mechanism is Sec-independent and the effector proteins may possess mRNA-based targeting signals. This review highlights the similarities and differences among type III secretion systems of selected model plant and animal pathogenic bacteria.

Journal Article↗

PubMed1997

Hrp pilus: an hrp-dependent bacterial surface appendage produced by Pseudomonas syringae pv. tomato DC3000.

Hypersensitive response and pathogenicity (hrp) genes control the ability of major groups of plant pathogenic bacteria to elicit the hypersensitive response (HR) in resistant plants and to cause disease in susceptible plants. A number of Hrp proteins share significant similarities with components of the type III secretion apparatus and flagellar assembly apparatus in animal pathogenic bacteria. Here we report that Pseudomonas syringae pv. tomato strain DC3000 (race 0) produces a filamentous surface appendage (Hrp pilus) of 6-8 nm in diameter in a solid minimal medium that induces hrp genes. Formation of the Hrp pilus is dependent on at least two hrp genes, hrpS and hrpH (recently renamed hrcC), which are involved in gene regulation and protein secretion, respectively. Our finding of the Hrp pilus, together with recent reports of Salmonella typhimurium surface appendages that are involved in bacterial invasion into the animal cell and of the Agrobacterium tumefaciens virB-dependent pilus that is involved in the transfer of T-DNA into plant cells, suggests that surface appendage formation is a common feature of animal and plant pathogenic bacteria in the infection of eukaryotic cells. Furthermore, we have identified HrpA as a major structural protein of the Hrp pilus. Finally, we show that a nonpolar hrpA mutant of P. syringae pv. tomato DC3000 is unable to form the Hrp pilus or to cause either an HR or disease in plants.

Bacterial Proteins↗

PubMed1997

Hrp-controlled interkingdom protein transport: learning from flagellar assembly?

Plant pathogenic bacteria appear to deliver avirulence and virulence proteins through the cell wall and into the host cells via an Hrp (hypersensitive reaction and pathogenicity)-encoded type III secretion system. Recent results suggest that there is a similarity between this secretion system and the flagellum assembly apparatus.

Animals↗

PubMed1996

hrp gene-dependent induction of hin1: a plant gene activated rapidly by both harpins and the avrPto gene-mediated signal.

Two classes of bacterial genes are involved in the elicitation of the plant hypersensitive response (HR) in resistant plants: hrp genes and avr genes. hrp genes have been shown to be involved in the production and secretion of a new class of bacterial virulence/avirulence proteins, including harpin of Erwinia amylovora and harpinPss of Pseudomonas syringae. The ability of avr genes in the elicitation of the HR/resistance is dependent on functional hrp genes. The relationships between harpins and avr gene products are not known. This study investigates the plant genes induced by harpins and the effect of avr genes on the expression of such plant genes. A tobacco gene highly induced by harpins was isolated by a subtractive hybridization method. Induction of hin1 by P.s. pv. syringae 61 (Pss61) was found to be dependent on functional bacterial hrp genes. P. fluorescens (a saprophyte) or hrp mutants defective in the Hrp secretion pathway did not induce hin1 significantly. A hin 1-related gene in tomato cv. Rio Grande-PtoR was found to be rapidly induced by P. s. pv. tomato T1 (a virulent bacterium on Rio Grande-PtoR) containing the avrPto gene, which mediates the elictation of the HR/resistance in a Pto plant resistance gene-dependent manner. The induction of hin1 by bacteria correlates with production of harpins in planta. The putative open reading frame of hin1 encodes a novel protein of 221 amino acids. The data suggest that harpins and the avrPto-mediated signal induce a common plant gene in the elicitation of the HR.

Amino Acid Sequence↗

PubMed1996

Cardiac muscle lesions associated with chronic administration of methamphetamine in rats.

Cardiovascular complications associated with methamphetamine abuse have increasingly been reported. However, chronic cardiotoxicity of methamphetamine is not experimentally well documented. In this study, methamphetamine (1 mg/kg/day) was subcutaneously injected into 5-week-old male Wistar Kyoto rats (n = 30). Age- and sex-matched Wistar Kyoto rats served as controls (n = 30). After 14 and 56 days, hearts were examined by light and electron microscopy. Foci of myocytic degeneration and necrosis appeared in the sub-endocardial areas on day 14 of methamphetamine exposure. Myocytic degeneration and necrosis became more extensive on day 56. At this stage, myocytolysis, contraction bands, atrophied myocytes, and spotty fibrosis were patchily distributed throughout the myocardium in most of rats treated with methamphetamine. The accompanying ultrastructural features included marked degeneration of cardiac mitochondria with fractured and disrupted cristae, hypercontraction of myofibrils, and loss of myofilament. In contrast, cardiac myocyte lesions were not observed in control rats. These myocardial lesions in rats treated with methamphetamine for 56 days resemble the cardiomyopathy associated with methamphetamine abuse in humans.

Animals↗

PubMed1996

Expression of the Pseudomonas syringae avirulence protein AvrB in plant cells alleviates its dependence on the hypersensitive response and pathogenicity (Hrp) secretion system in eliciting genotype-specific hypersensitive cell death.

The nonpathogenic bacteria Pseudomonas fluorescens and Escherichia coli can elicit a genotype-specific hypersensitive response (HR) in plants if they express both the HR and pathogenesis (Hrp) protein secretion system and the HrpZ harpin from P. syringae pv syringae 61 and a P. syringae avirulence (avr) gene whose presence is recognized by a corresponding disease resistance gene in the plant. We have found that the recognition event appears to require transfer of the Avr protein into the plant cell. Elicitation of a genotype-specific HR was observed with avrB+ P. fluorescens in soybean and Arabidopsis plants carrying resistance genes RPG1 and RPM1, respectively, and with avrPto+ E. coll in tomato plants carrying resistance gene PTO, but only if the Hrp secretion system, HrpZ, and the appropriate Avr proteins were produced in the same bacterial cell. The failure of avrB hyperexpression and exogenous AvrB or HrpZ to alleviate these requirements in soybean and Arabidopsis suggests that the site of AvrB action is not in the bacterial cell or plant apoplast. An Arabidopsis rps3 (rpm1) glabrous1 mutant was transformed with constructs expressing avrB and was crossed with an Arabidopsis ecotype Columbia (RPM1 GLABROUS1) plant. F1 seedlings (identified by their kanamycin-resistant, pubescent phenotype) exhibited extensive necrosis on cotyledon leaves 10 days postgermination. Ecotype Columbia and rps3-1 leaves biolistically cobombarded with plasmids expressing the beta-glucuronidase (GUS) gene and avrB failed to produce GUS activity (indicative of cell death) only when RPM1 and avrB were present in the leaf. Thus, both stable and transient expression of avrB in Arabidopsis resulted in RPM1-dependent necrosis, and the only demonstrable site of action for AvrB was inside plant cells.

Arabidopsis↗

PubMed1996

The Pseudomonas syringae Hrp regulation and secretion system controls the production and secretion of multiple extracellular proteins.

Pseudomonas syringae pv. tomato DC3000 produces seven to eight major extracellular proteins (EXPs) in a minimal medium inducing hrp genes. Using a polyclonal antibody against DC3000 EXPs, we have determined that the production and secretion of five EXPs (EXP-60, EXP-45, EXP-43, EXP-22, and EXP-10) are under the control of the Hrp regulation and secretion system.

Amino Acid Sequence↗