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Yu Cao

Publications and source records attributed to Yu Cao.

At least 19 recordsLinked to original sources
PubMed2006

Activity-independent prespecification of synaptic partners in the visual map of Drosophila.

Specifying synaptic partners and regulating synaptic numbers are at least partly activity-dependent processes during visual map formation in all systems investigated to date . In Drosophila, six photoreceptors that view the same point in visual space have to be sorted into synaptic modules called cartridges in order to form a visuotopically correct map . Synapse numbers per photoreceptor terminal and cartridge are both precisely regulated . However, it is unknown whether an activity-dependent mechanism or a genetically encoded developmental program regulates synapse numbers. We performed a large-scale quantitative ultrastructural analysis of photoreceptor synapses in mutants affecting the generation of electrical potentials (norpA, trp;trpl), neurotransmitter release (hdc, syt), vesicle endocytosis (synj), the trafficking of specific guidance molecules during photoreceptor targeting (sec15), a specific guidance receptor required for visual map formation (Dlar), and 57 other novel synaptic mutants affecting 43 genes. Remarkably, in all these mutants, individual photoreceptors form the correct number of synapses per presynaptic terminal independently of cartridge composition. Hence, our data show that each photoreceptor forms a precise and constant number of afferent synapses independently of neuronal activity and partner accuracy. Our data suggest cell-autonomous control of synapse numbers as part of a developmental program of activity-independent steps that lead to a "hard-wired" visual map in the fly brain.

Animals↗
PubMed2006

Modulation of voltage-dependent Shaker family potassium channels by an aldo-keto reductase.

The beta subunit (Kvbeta) of the Shaker family voltage-dependent potassium channels (Kv1) is a cytosolic protein that forms a permanent complex with the channel. Sequence and structural conservation indicates that Kvbeta resembles an aldo-keto reductase (AKR), an enzyme that catalyzes a redox reaction using an NADPH cofactor. A putative AKR in complex with a Kv channel has led to the hypothesis that intracellular redox potential may dynamically influence the excitability of a cell through Kvbeta. Since the AKR function of Kvbeta has never been demonstrated, a direct functional coupling between the two has not been established. We report here the identification of Kvbeta substrates and the demonstration that Kvbeta is a functional AKR. We have also found that channel function is modulated when the Kvbeta-bound NADPH is oxidized. Further studies of the enzymatic properties of Kvbeta seem to favor the role of Kvbeta as a redox sensor. These results suggest that Kvbeta may couple the excitability of the cell to its metabolic state and present a new avenue of research that may lead to understanding of the physiological functions of Kvbeta.

Alcohol Oxidoreductases↗
PubMed2006

A Raman-scattering study on the net orientation of biomacromolecules in the outer epidermal walls of mature wheat stems (Triticum aestivum).

BACKGROUND AND AIMS: Raman spectroscopy can be used to examine the orientation of biomacromolecules using relatively thick samples of material, whereas more traditional means of analysing molecular structure require prior isolation of the components, which often destroys morphological features. In this study, Raman spectroscopy was used to examine the outer epidermal cell walls of wheat stems. METHODS: Polarized Raman spectra from the epidermal cell walls of wheat stem were obtained using near-infrared-Fourier transform Raman scattering. By comparing spectra taken with Raman light polarized perpendicular or parallel to the longitudinal axis of the cell, the orientation of macromolecules in the cell wall was investigated. KEY RESULTS: The net orientation of macromolecules varies in the epidermal cell walls of the different components of wheat stem. The net orientation of cellulose is parallel to the longitudinal axis of the cells, whereas the xylan and the phenylpropane units of lignin tend to lie perpendicular to the longitudinal axis of the cells, i.e. perpendicular to the net orientation of cellulose in the epidermal cell walls. CONCLUSIONS: The results imply that cellulose, lignin and xylan form a relatively ordered network that defines the mechanical and structural properties of the cell wall. Such results are likely to have a significant impact on the formulation of definitive models for the static and growing cell wall.

Cell Wall↗
PubMed2006

Preparation and characterization of magnetic microspheres for the purification of interferon alpha-2b.

Magnetic agarose microspheres (MAMS), magnetic cellulose microspheres (MCMS), and magnetic poly(vinyl alcohol) microspheres (MPVAMS) were prepared by various different preparation methods. MCMS coupled with anti-IFN alpha-2b monoclonal antibodies (mAb) were selected for the purification of interferon alpha-2b (IFN alpha-2b) after performance characterization among microspheres. Parameters of immunomagnetic separation (IMS), including binding mAb, elution behavior, and sample pretreatment conditions, were optimized to improve the purification efficiency of the separation of IFN alpha-2b by MCMS. Size-exclusion HPLC (HPSEC) showed that the IFN alpha-2b was purified from crude cell lysate had an overall purity of 92.9%, while immunological and biological assays showed an activity recovery of 88.5% and specific antiviral activity of 2.7 x 10(8) IU/mg. Identity and molecular mass of purified IFN alpha-2b were confirmed by western blot and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) analysis. This study illustrated the favorable separation media which combined desired properties for the development of magnetic separation of biological materials.

Blotting, Western↗
PubMed2006

Immobilized iminobiotin on magnetic poly (vinyl alcohol) microspheres for single-step purification of streptavidin.

Magnetic poly (vinyl alcohol) microspheres (MPVAMS) immobilized with iminobiotin as the ligand were prepared for the purification of streptavidin. Parameters of magnetic separation, including spacers, NHS-iminobiotin added, elution behavior, and sample treatment, were optimized to improve the purification efficiency to achieve the maximum recovery of the protein. Streptavidin was successfully purified 38-fold from culture supernatant in a single-step by iminobiotin-MPVAMS with an overall recovery of 90.15% and purity of 95.08%. Hence, this study effectively illustrated the favorable application of magnetic microcarriers for the purification of streptavidin.

Bioreactors↗
PubMed2006

Drosophila NMNAT maintains neural integrity independent of its NAD synthesis activity.

Wallerian degeneration refers to a loss of the distal part of an axon after nerve injury. Wallerian degeneration slow (Wld(s)) mice overexpress a chimeric protein containing the NAD synthase NMNAT (nicotinamide mononucleotide adenylyltransferase 1) and exhibit a delay in axonal degeneration. Currently, conflicting evidence raises questions as to whether NMNAT is the protecting factor and whether its enzymatic activity is required for such a possible function. Importantly, the link between nmnat and axon degeneration is at present solely based on overexpression studies of enzymatically active protein. Here we use the visual system of Drosophila as a model system to address these issues. We have isolated the first nmnat mutations in a multicellular organism in a forward genetic screen for synapse malfunction in Drosophila. Loss of nmnat causes a rapid and severe neurodegeneration that can be attenuated by blocking neuronal activity. Furthermore, in vivo neuronal expression of mutated nmnat shows that enzymatically inactive NMNAT protein retains strong neuroprotective effects and rescues the degeneration phenotype caused by loss of nmnat. Our data indicate an NAD-independent requirement of NMNAT for maintaining neuronal integrity that can be exploited to protect neurons from neuronal activity-induced degeneration by overexpression of the protein.

Animals↗
PubMed2006

[Myeloperoxidase in the plasma of patients with acute coronary syndrome].

OBJECTIVE: To determine the diagnostic value and efficacy for risk stratification of myeloperoxidase (MPO) levels in patients with acute coronary syndrome (ACS). METHODS: One hundred and sixty-two patients were enrolled in this study. All patients underwent coronary angiography. They were divided into 3 groups: ACS group (n=54), SAP group (n=54) and control group (n=54). Blood samples were taken from the artery before angiography in all patients and the concentrations of MPO, hsCRP and cTnI were measured. Each subject was asked details of history of hypertension, hyperlipidemia, diabetes and smoking habits. The efficacy of therapy, the cardiovascular events (myocardial infarction, the need for revascularization, or death) were recorded after 6 months of follow-up. RESULTS: The plasma MPO level in ACS group (30.98 ng/mL) was significantly higher than those in the SAP group (14.67 ng/mL) and the control group(14.23 ng/mL)(P<0.01), and the plasma MPO levels in patients of the SAP group and the control group were not significantly different (P=0.74). There was no obvious correlation between the levels of plasma MPO and the serum levels of cTnI, hsCRP,the prevalence of the 4 major risk factors for CHD. Multivariate logistic regression analysis showed that plasma MPO level, free plasma glucose and sex were the significant variables. The risk for subsequent cardiovascular events was higher in the patients with elevated level of MPO. CONCLUSION: Plasma MPO may be a new risk biomarker for ACS and may predict the incidence of subsequent cardiovascular events.

Acute Coronary Syndrome↗
PubMed2005

Improvement of alkali solubility of cellulose with enzymatic treatment.

Cellulose was treated with different extracellular microbial enzymes. The treatment of cellulose with the enzymes can improve alkaline solubility. Both endoglucanase and crude cellulase decreased the average degrees of polymerization ([see text]) and improved the alkaline solubility of cellulose most efficiently. The composition of the enzyme, the type of cellulosic materials, pretreatment, and the treatment conditions are the key factors for its effective processing, using the enzymes to improve on alkaline solubility of cellulose. The improvement in the alkaline solubility is caused by the decrease in [see text] and hydrogen bond because of enzymatic hydrolysis.

Abies↗
PubMed2005

Expression, physiological action, and coexpression patterns of neuropeptide Y in rat taste-bud cells.

Recent studies have suggested that neuropeptides could play previously unrecognized functional roles in peripheral gustation. To date, two peptides, cholecystokinin and vasoactive intestinal peptide, have been localized to subsets of taste-bud (TB) cells (TBC) and one, cholecystokinin, has been demonstrated to produce excitatory physiological actions. This study extends our knowledge of neuropeptides in TBC in three significant ways. First, using techniques of immunocytochemistry and RT-PCR, evidence is presented for the expression of a third peptide, neuropeptide Y (NPY). Like other peptide expression patterns, NPY expression is circumscribed to a subset of cells within the taste bud. Second, using physiological studies, we demonstrate that NPY specifically enhances an inwardly rectifying potassium current via NPY-Y1 receptors. This action is antagonistic to the previously demonstrated inhibitory effect exerted by cholecystokinin on the same current, thus providing important clues to their signaling roles in the TB. Third, using the technique of double-labeled fluorescent immunocytochemistry, the relationship of three subsets of neuropeptide-expressing TB cells to one another was examined. Remarkably, NPY expressions, although fewer in number than either the cholecystokinin or vasoactive intestinal peptide subsets, overlapped 100% with either peptide. Collectively, these three observations transform previously suggestive roles of neuromodulation by peptides in TB cells to more concrete signaling pathways. The extensive colocalization of these peptides suggests they may be subject to similar presynaptic influences of release yet have antagonistic postsynaptic actions. The convergence or divergence of these postsynaptic actions awaits further investigation.

Animals↗
PubMed2005

The v-ATPase V0 subunit a1 is required for a late step in synaptic vesicle exocytosis in Drosophila.

The V(0) complex forms the proteolipid pore of an ATPase that acidifies vesicles. In addition, an independent function in membrane fusion has been proposed largely based on yeast vacuolar fusion experiments. We have isolated mutations in the largest V(0) component vha100-1 in flies in an unbiased genetic screen for synaptic malfunction. The protein is only required in neurons, colocalizes with markers for synaptic vesicles as well as active zones, and interacts with t-SNAREs. Loss of vha100-1 leads to vesicle accumulation in synaptic terminals, suggesting a deficit in release. The amplitude of spontaneous release events and release with hypertonic stimulation indicate normal levels of neurotransmitter loading, yet mutant embryos display severe defects in evoked synaptic transmission and FM1-43 uptake. Our data suggest that Vha100-1 functions downstream of SNAREs in synaptic vesicle fusion.

Animals↗
PubMed2005

Mutations in Drosophila sec15 reveal a function in neuronal targeting for a subset of exocyst components.

The exocyst is a complex of proteins originally identified in yeast that has been implicated in polarized secretion. Components of the exocyst have been implicated in neurite outgrowth, cell polarity, and cell viability. We have isolated an exocyst component, sec15, in a screen for genes required for synaptic specificity. Loss of sec15 causes a targeting defect of photoreceptors that coincides with mislocalization of specific cell adhesion and signaling molecules. Additionally, sec15 mutant neurons fail to localize other exocyst members like Sec5 and Sec8, but not Sec6, to neuronal terminals. However, loss of sec15 does not cause cell lethality in contrast to loss of sec5 or sec6. Our data suggest a role of Sec15 in an exocyst-like subcomplex for the targeting and subcellular distribution of specific proteins. The data also show that functions of other exocyst components persist in the absence of sec15, suggesting that different exocyst components have separable functions.

Amino Acid Sequence↗
PubMed2005

Improved method for extraction and LC-MS analysis of pyrrolizidine alkaloids and their N-oxides in honey: application to Echium vulgare honeys.

A method for analyzing honey samples was developed that enabled the simultaneous detection and identification of pyrrolizidine alkaloids and their N-oxides. Honey samples were treated with methanol or dilute sulfuric acid and then centrifuged to remove insoluble material. Subsequent strong cation exchange, solid-phase extraction of the supernatant provided a fraction that was analyzed for the presence of pyrrolizidine alkaloids and their N-oxides using high-pressure liquid chromatography coupled to electrospray ionization mass spectrometry. The procedure was validated using extracts of Echium plantagineum and authenticated standards of pyrrolizidine alkaloids and their N-oxides from other plant sources. Of several variations of the solid-phase extraction method assessed in this study, the best combination for generic use involved the dilution of honey with 0.05 M sulfuric acid and the subsequent application of the centrifuged solution to solid-phase extraction columns at the rate of a maximum of 10 g of honey per solid-phase extraction column. The method was applied to the analysis of nine floral honeys, five of which were attributed by the apiarist to Echium vulgare. Seven of the honey samples were positive for pyrrolizidine alkaloids and N-oxides characteristic of E. vulgare.

Chromatography, High Pressure Liquid↗
PubMed2005

Palmitoylation regulates GDP/GTP exchange of G protein by affecting the GTP-binding activity of Goalpha.

The effect of palmitoylation on the GTP-binding activity and conformation of Goalpha protein in hydrophobic and hydrophilic environments was studied. The binding assay was performed with an isotope labeled analog of GTP, GTP-gamma-35S, and its fluorescent analog, BODIPY FL-GTPgammaS was used to detect conformational change in the GTP-binding domain of Goalpha. Investigation of the GTP-gamma-35S binding activity of Goalpha shows that in a hydrophobic environment, mimicked by the presence of detergent, the apparent dissociation constant for palmitoylated Goalpha (K(D)=25.5x10(-9)+/-1.7x10(-9)M) increased threefold compared with that of non-palmitoylated Goalpha (K(D)=9.9x10(-9)+/-0.8x10(-9)M), while in an aqueous environment without detergent there is no significant difference between palmitoylated (K(D)=50.1 x 10(-9)+/-5.2x10(-9)M) and non-palmitoylated (K(D)=65.5x10(-9)+/-7.6x10(-9)M) Go(. This indicates that in a membrane environment palmitoylation may weaken the GTPgammaS binding ability of Go(. Fluorescent quenching studies using BODIPY FL-GTPgammaS as a probe showed that the conformation of the GTP-binding domain of Go( tends to become more compact after palmitoylation. These results imply that palmitoylation may regulate the GTP/GDP exchange of Goalpha by influencing the GTP-binding activity of Goalpha and facilitating the on-off switch function of the G protein in G protein-coupled signal transduction.

Electrophoresis, Polyacrylamide Gel↗
PubMed2005

Effects of synchronous or asynchronous electroacupuncture stimulation with low versus high frequency on spinal opioid release and tail flick nociception.

Electroacupuncture stimulation (EAS) is known to change brain neurotransmitter release. In the present study, we investigated the effects of synchronous or asynchronous electroacupuncture stimulation with low versus high frequency on spinal opioid release and tail flick nociception. Rats were given "2/100 Hz" EAS, which stands for an asynchronous mode of stimulation, in which 2 Hz was alternated with 100 Hz, each lasting for 3 s, or "(2 + 100) Hz" EAS, a mode of stimulation in which 2 Hz stimulation was applied to the left hind leg simultaneously with 100 Hz stimulation on the right hind leg. The rats were subjected to the same total number of electrical stimulations in these two modes. Results were as follows: (1) 2/100 Hz EAS was 40% more potent than (2 + 100) Hz EAS (P < 0.01) in producing an anti-nociceptive effect. (2) Intrathecal (i.t.) injection of the mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr amide (CTOP) blocked in a dose-dependent manner the anti-nociceptive effect produced by 2/100 Hz EAS but not by (2 + 100) Hz EAS, whereas i.t. injection of the kappa-opioid receptor antagonist norbinaltorphimide (Nor-BNI) blocked the anti-nociceptive effect induced by both modes of EAS. (3) I.t. injection of endomorphin-2 antiserum blocked in a dose-dependent manner the anti-nociceptive effect of 2/100 Hz EAS but not that of (2 + 100) Hz EAS, whereas i.t. injection of dynorphin antiserum blocked the anti-nociceptive effect induced by both modes of stimulation. (4) 2/100 Hz EAS increased the release of both endomorphin-2 and dynorphin, whereas (2 + 100) Hz EAS increased the release of dynorphin but not of endmorphin-2. We conclude that the more potent anti-nociceptive effect induced by 2/100 Hz EAS, as compared with that of (2 + 100) Hz EAS, was due, at least partly, to the synergistic interaction of endomorphin-2 and dynorphin in rat spinal cord.

Afferent Pathways↗
PubMed2005

Resveratrol induces apoptosis and differentiation in acute promyelocytic leukemia (NB4) cells.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a naturally occurring phytoalexin found in grapes and wine, and has been reported to exert a variety of important pharmacological effects. We have investigated the activity of resveratrol on proliferation and differentiation of the acute promyelocytic leukemia cell line NB4. The growth inhibitory properties of resveratrol appear to be due to its induction of apoptotic cell death, as determined by morphological changes, DNA fragmentation, increased proportion of the subdiploid cell population and decreased mitochondrial transmembrane potential (Deltapsi(m)). Colorimetric assay for activity of caspase-3 showed an obvious increase in caspase-3 activity in cells after treatment with resveratrol. However, the expression levels of protein Bcl-2 and Bax show no significant change in response to resveratrol treatment. These results suggest that apoptosis of NB4 cells induced by resveratrol requires caspase-3 activation and is related to the mitochondrial transmembrane potential. The combination of resveratrol and all-tran-retinoic acid (ATRA) induced 100% of the NB4 cells to become NBT-positive, whereas only a small part of cells became positive for NBT after a similar exposure to either resveratrol or ATRA alone. Thus, resveratrol may be useful in treating acute promyelocytic leukemia.

Anticarcinogenic Agents↗
PubMed2005

Anti-angiogenic activity of resveratrol, a natural compound from medicinal plants.

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a naturally occurring phytoalexin found in grapes and wine, possesses cancer-preventive activity. Angiogenesis is a crucial step in the growth and metastasis of cancers. We have investigated the effect of resveratrol on angiogenesis in vitro and ex vivo, and found that resveratrol directly inhibited human umbilical vein endothelial cell growth and decreased the gelatinolytic activities of matrix metalloproteinase-2. Tube formation was inhibited by treatment with resveratrol after plating endothelial cells on Matrigel. Resveratrol treatment also inhibited endothelial cell attachment to basement membrane components fibronectin and laminin, and displays similar behavior on cell chemotaxis. In addition, resveratrol has been found to be an angiogenesis inhibitor in the rat aorta matrix culture model. Therefore, inhibition of angiogenesis associated with cancer may be a novel mechanism for the anticancer activity of resveratrol.

Angiogenesis Inhibitors↗
PubMed2005

[Proatherogenic effects of immune complexes of human oxLDL in vitro].

OBJECTIVE: To observe the effects of immune complexes (IC) prepared from human oxidized density lipoprotein (oxLDL) antibodies and human oxLDL on the foam cell forming and the macrophage activation, and to further uncover the possible mechanisms of immune complexes contributing to the atherosclerosis occurrence. METHODS: The immune complexes of human oxLDL and purified human oxLDL antibodies were added to culture U937 cells by protocols: polyethylene glycol-precipitated insoluble IC (PEG-IC) and IC immobilized by absorption to red blood cells (RBC-IC). With oxLDL as controls and heat-aggregated gamma globulin as an inhibitor of Fc gamma receptor, we measured the cholesterol ester, total cholesterol of the cellular extracts, and quantified the secreted MMP-1 of supernatants from U937 cells. RESULTS: A significant increase of MMP-1 release [(0.769 +/- 0.030) ng/ml vs (0.513 +/- 0.034) ng/ml, P < 0.01] and a higher level of cholesterol ester accumulation [(20.271 +/- 1.668) microg/mg protein vs (17. 226 +/- 1.298 ) microg/mg protein, P < 0.05] in U937 cells incubated with RBC-IC were observed, compared with those incubated with RBC-oxLDL. However, the above quantative difference between the cholesterol ester accumulation induced by oxLDL and insoluble PEG-IC was even more striking, and cholesterol ester accumulation was dosage-dependent. Heat-aggregated gamma globulin (10 mg/ml) as an inhibitor of Fc gamma receptors competitively inhibited cholesterol ester accumulation and decreased PEG-IC stimulating MMP-1 secretion to 71%. CONCLUSION: Immune complexe of ox-LDL can transform macrophages into foam cells and activted macrophages. The immunological function of oxLDL is involved in the process of atherosclerosis occurrence.

Antibodies↗