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Y Guo

Publications and source records attributed to Y Guo.

At least 73 records · Page 4Linked to original sources
PubMed2001

MAP2 phosphorylation and visual plasticity in Xenopus.

Microtubule-associated protein 2 (MAP2) has been implicated in activity-dependent structural changes in dendrites. MAP2 regulates the assembly of cytoskeletal proteins such as microtubules and actin, and its function is phosphorylation-dependent. In hippocampus, MAP2 has been reported to be dephosphorylated by activation of the NMDA-type glutamate receptor, a key player in synaptic plasticity. In this work, we used a phospho-specific MAP2 antibody (Ab 305) that recognizes epitopes close to the microtubule-binding domain to investigate the possible role of MAP2 in the Xenopus visual system. The binocular system in Xenopus exhibits activity-dependent synapse rearrangement during a critical period of development. We have found that, in critical period animals, NMDA receptor activation leads to the dephosphorylation of MAP2 at sites recognized by Ab 305 in a dose-dependent manner. We compared the responses of MAP2 to NMDA treatment in animals with high binocular plasticity (critical period juveniles and dark-reared adults) and low plasticity (normal adults). Our results show that, in all groups, NMDA treatment induces the dephosphorylation of MAP2. Tecta from frogs with different degrees of plasticity show no differences in the baseline level of MAP2 phosphorylation or in the NMDA-induced MAP2 dephosphorylation response. These results suggest that activity may modify dendrite structure via the NMDA receptor--MAP2-cytoskeletal protein pathway, but this pathway does not seem to be a determinant of the degree of plasticity.

Aging↗
PubMed2001

[Effect of endostatin gene transfer mediated by electric pulses into skeletal muscles on development of atherosclerotic plaques in mice].

OBJECTIVE: To investigate the effect of endostatin gene transfer mediated by electric pulses into skeletal muscles of mice upon the develpment of atherosclerotic plaques. METHODS: Eukaryotic expression plasmid of mouse endostatin was injected into the muscles of 2 groups of ApoE-deficient mice, group A at the age of 24 weeks, and group B at the age of 36 weeks (named therapy group as a whole). Gene transfer was mediated by electric pulses for ten times. Empty plasmid was used to mice at the same ages as controls. Twenty weeks later, blood-lipid was tested, and the aortas of the experimental animals were taken out to examine the areas of atherosclerotic plaques and count the endothelial cells and microvessels in the plaques. RESULTS: In the 24-week-aged group, the stenosis rate of aorta 16% +/- 4% before the experiment. Twenty weeks later, the stenosis rate was 56% +/- 14% among the control mice, and was 34% +/- 8% among the treated ones with an improvement rate of 54%. In the 36-week-aged group, the stenosis rate of aorta was 30% +/- 6% before the experiment. Twenty weeks after the begining of experiment, the stenosis rate was 64% +/- 12% among the control mice, and was 49% +/- 10% among the treated ones with an improvement rate of 44%. Twenty weeks after the begining of experiment, the endothelial cell count and microvessel appearance rate were less among the therapy group than among the controls. There was no significant difference in blood-lipid between the therapy group and the control group. CONCLUSION: Endostatin gene transfer into skeletal muscle effectively inhibits the development of atherosclerotic plaques.

Animals↗
PubMed2001

Discovery and characterization of the potent, selective and orally bioavailable MMP inhibitor ABT-770.

Modification of the biphenyl portion of MMP inhibitor 2a gave analogue 2i which is greater than 1000-fold selective against MMP-2 versus MMP-1. The stereospecific synthesis of both enantiomers of 2i was achieved beginning with (S)- or (R)-benzyl glycidyl ether. The (S)-enantiomer, 11 (ABT-770), is orally bioavailable and efficacious in an in vivo model of tumor growth.

Administration, Oral↗
PubMed2001

Stabilization of short collagen-like triple helices by protein engineering.

Recombinant expression of collagens and fragments of collagens is often difficult, as their biosynthesis requires specific post-translational enzymes, in particular prolyl 4-hydroxylase. Although the use of hydroxyproline-deficient variants offers one possibility to overcome this difficulty, these proteins usually differ markedly in stability when compared with the hydroxyproline-containing analogs. Here, we report a method to stabilize collagen-like peptides by fusing them to the N terminus of the bacteriophage T4 fibritin foldon domain. The isolated foldon domain and the chimeric protein (GlyProPro)(10)foldon were expressed in a soluble form in Escherichia coli. The recombinant proteins and the synthetic (ProProGly)(10) peptide were characterized by circular dichroism (CD) spectroscopy, differential scanning calorimetry, and analytical ultracentrifugation. We show that the foldon domain, which comprises only 27 amino acid residues, forms an obligatory trimer with a high degree of thermal stability. The CD thermal unfolding profiles recorded from foldon are monophasic and completely reversible upon cooling. Similar Van't Hoff and calorimertic enthalpy values of trimer formation indicated a cooperative all-or-none transition. As reported previously, (ProProGly)(10) peptides form collagen triple helices of only moderate stability. When fused to the foldon domain, however, triple helix formation of (GlyProPro)(10) is concentration independent, and the midpoint temperature of the triple helix unfolding is significantly increased. The stabilizing function of the trimeric foldon domain is explained by the close vicinity of its N termini, which induce a high local concentration in the range of 1 M for the C termini of the collagen-like-peptide. Collagen-foldon fusion proteins should be potentially useful to study receptor-collagen interactions.

Amino Acid Sequence↗
PubMed2001

Nuclear import of histone H2A and H2B is mediated by a network of karyopherins.

The first step in the assembly of new chromatin is the cell cycle-regulated synthesis and nuclear import of core histones. The core histones include H2A and H2B, which are assembled into nucleosomes as heterodimers. We show here that the import of histone H2A and H2B is mediated by several members of the karyopherin (Kap; importin) family. An abundant complex of H2A, H2B, and Kap114p was detected in cytosol. In addition, two other Kaps, Kap121p and Kap123p, and the histone chaperone Nap1p were isolated with H2A and H2B. Nap1p is not necessary for the formation of the Kap114p-H2A/H2B complex or for import of H2A and H2B. We demonstrate that both histones contain a nuclear localization sequence (NLS) in the amino-terminal tail. Fusions of the NLSs to green fluorescent protein were specifically mislocalized to the cytoplasm in kap mutant strains. In addition, we detected a specific mislocalization in a kap95 temperature-sensitive strain, suggesting that this Kap is also involved in the import of H2A and H2B in vivo. Importantly, we show that Kap114p, Kap121p, and Kap95 interact directly with both histone NLSs and that RanGTP inhibits this association. These data suggest that the import of H2A and H2B is mediated by a network of Kaps, in which Kap114p may play the major role.

Active Transport, Cell Nucleus↗
PubMed2001

Gene therapy with extracellular superoxide dismutase protects conscious rabbits against myocardial infarction.

BACKGROUND: Extracellular superoxide dismutase (Ec-SOD) may protect the heart against myocardial infarction (MI) because of its extended half-life and capacity to bind heparan sulfate proteoglycans on cellular surfaces. Accordingly, we used direct gene transfer to increase systemic levels of Ec-SOD and determined whether this gene therapy could protect against MI. METHODS AND RESULTS: The cDNA for human Ec-SOD was incorporated into a replication-deficient adenovirus (Ad5/CMV/Ec-SOD). Injection of this virus produced a high level of Ec-SOD in the liver, which was redistributed to the heart and other organs by injection of heparin. Untreated rabbits (group I) underwent a 30-minute coronary occlusion and 3 days of reperfusion. For comparison, preconditioned rabbits (group II) underwent a sequence of six 4-minute-occlusion/4-minute-reperfusion cycles 24 hours before the 30-minute occlusion. Control-treated rabbits (group III) were injected intravenously with Ad5/CMV/nls-LacZ, and gene-therapy rabbits (group IV) were injected with Ad5/CMV/Ec-SOD 3 days before the 30-minute occlusion. Both groups treated with Ad5 received intravenous heparin 2 hours before the 30-minute occlusion. Infarct size (percent risk area) was similar in groups I (57+/-6%) and III (58+/-5%). Ec-SOD gene therapy markedly reduced infarct size to 25+/-4% (P<0.01, group IV versus group III), a protection comparable to that of the late phase of ischemic preconditioning (29+/-3%, P<0.01 group II versus group I). CONCLUSIONS: Direct gene transfer of the cDNA encoding membrane-bound Ec-SOD affords powerful cardioprotection, providing proof of principle for the effectiveness of antioxidant gene therapy against MI.

Animals↗
PubMed2001

Activation of enzymes for nonaqueous biocatalysis by denaturing concentrations of urea.

Urea is one of the most commonly used denaturants of proteins. However, herein we report that enzymes lyophilized from denaturing concentrations of aqueous urea exhibited much higher activity in organic solvents than their native counterparts. Thus, instead of causing deactivation, urea effected unexpected activation of enzymes suspended in organic media. Activation of subtilisin Carlsberg (SC) in the organic solvents (hexane, tetrahydrofuran, and acetone) increased with increasing urea concentrations up to 8 M. Active-site titration results and activity assays indicated the presence of partially unfolded but catalytically active SC in 8 M urea; however, the urea-modified enzyme retained high enantioselectivity and was ca. 80 times more active than the native enzyme in anhydrous hexane. Likewise, the activity of horseradish peroxidase (HRP) lyophilized from 8 M urea was ca. 56 times and 350 times higher in 97% acetone and water-saturated hexane, respectively, than the activity of HRP lyophilized from aqueous buffer. Compared with the native enzyme, the partially unfolded enzyme may have a more pliant and less rigid conformation in organic solvents, thus enabling it to retain higher catalytic activity. However, no substantial activation was observed for alpha-chymotrypsin lyophilized from urea solutions in which the enzyme retained some activity, illustrating that the activation effect is not completely general.

Acetone↗
PubMed2001

Card10 is a novel caspase recruitment domain/membrane-associated guanylate kinase family member that interacts with BCL10 and activates NF-kappa B.

BCL10 belongs to the caspase recruitment domain (CARD) family of proteins that regulate apoptosis and NF-kappaB signaling pathways. Analysis of BCL10-deficient mice has revealed that BCL10 mediates NF-kappaB activation by antigen receptors in B and T cells. We recently identified a subclass of CARD proteins (CARD9, CARD11, and CARD14) that may function to connect BCL10 to multiple upstream signaling pathways. We report here that CARD10 is a novel BCL10 interactor that belongs to the membrane-associated guanylate kinase family, a class of proteins that function to organize signaling complexes at plasma membranes. When expressed in cells, CARD10 binds to BCL10 and signals the activation of NF-kappaB through its N-terminal effector CARD domain. We propose that CARD10 functions as a molecular scaffold for the assembly of a BCL10 signaling complex that activates NF-kappaB.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Toxicity studies of Rhizoma Polygonati Odorati.

The toxicity of the water-soluble extract of Rhizoma Polygonati Odorati was studied in the present investigation, which included its acute toxicity, chronic toxicity, and genetic toxicity. The aqueous extract of Rhizoma Polygonati Odorati did not cause seriously abnormal signs or death to animals in the acute toxicity test and in the 6-month chronic toxicity test. Neither was genetic toxicity found in the Ames test, the micronucleus test of bone marrow and the sperm malformation test in mice.

Administration, Oral↗
PubMed2001

Hypoglycemic effects of aqueous extract of Rhizoma Polygonati Odorati in mice and rats.

Water soluble extract of Rhizoma Polygonati Odorati (RPO) was studied for its hypoglycemic effect in diabetic mice and rats. Results showed that RPO significantly lowered hyperglycemia caused by starch loading in both normal and diabetic mice. Four week's administration with RPO reduced fasting blood glucose, decreased glycosylated hemoglobin (GHb), and improved the glucose tolerance in diabetic mice. In diabetic rats complicated with hyperlipemia, RPO prevented and reduced both hyperglycemia and hypertriglyceridemia. The results support the view that RPO may influence glucose or carbohydrate metabolism of diabetic animals in many ways including inhibiting the activity of alpha-glucosidase in digestive canal, and improving the metabolism of glucose and triglyceride.

Animals↗
PubMed2001

Altered expression of a-type but not b-type synapsin isoform in the brain of patients at high risk for Alzheimer's disease assessed by DNA microarray technique.

Using a cDNA microarray representing 6794 distinct human genes, we identified candidate genes whose expression is altered in cerebral cortex of cases of early Alzheimer's disease (AD); among these was the synaptic vesicle protein synapsin II, which plays an important role in neurotransmitter release. While other candidate genes are presently under investigation in our lab, in this study we discuss the regulation of synapsin gene expression during the transition from normal cognitive function to early AD. We found a selective decrease in the expression of the synapsin splice variants I-III of the a-type isoform in the entorhinal (EC, BM36) but not visual cortex (VC, BM17) of cases characterized by the earliest clinically detectable stage of AD. In contrast, we found no changes in synapsin splice variant II of the b-type isoform. Alteration of synapsin expression at the earliest clinical stage of AD may suggest novel strategies for improved treatment.

Aged↗
PubMed2001

Human casein kinase Idelta phosphorylation of human circadian clock proteins period 1 and 2.

Casein kinase Iepsilon (CKIepsilon), a central component of the circadian clock, interacts with and phosphorylates human period protein 1 (hPER1) [Keesler, G.A. et al. (2000) NeuroReport 5, 951-955]. A mutation in CKIepsilon causes a shortened circadian period in Syrian Golden hamster. We have now extended our previous studies to show that human casein kinase Idelta (hCKIdelta), the closest homologue to hCKIepsilon, associates with and phosphorylates hPER1 and causes protein instability. Furthermore, we observed that both hCKIdelta and hCKIepsilon phosphorylated and caused protein instability of human period 2 protein (hPER2). Immunohistochemical staining of rat brains demonstrates that CKIdelta protein is localized in the suprachiasmatic nuclei, the central location of the master clock. These results indicate that CKIdelta may play a role similar to CKIepsilon, suggesting that it may also be involved in regulating circadian rhythmicity by post-translation modification of mammalian clock proteins hPER1 and 2.

Animals↗
PubMed2001

Comparison of the expression of two forms of glutamic acid decarboxylase (GAD67 and GAD65) in the visual cortex of normal and dark-reared cats.

In normal development, there are dramatic changes in both the level and the laminar pattern of expression of the two forms of glutamate decarboxylase (GAD67, GAD65), the synthetic enzyme for gamma-aminobutyric acid (GABA). We have used antibodies to determine whether these normal postnatal changes in the expression of the two GADs depend on visual input by comparing normal and dark-reared cat visual cortex. Western blot analysis showed no significant differences in the levels of expression of the two enzymes between rearing conditions at either 5 or 20 weeks. Immunohistochemistry was used to compare the laminar distribution of the GADs in the two rearing conditions. At 1 week of age, both GAD67 and GAD65 immunoreactivity is concentrated in deep layers of visual cortex. At 5 and 20 weeks in both rearing conditions, GAD67-stained cells bodies were distributed rather uniformly across all cortical layers. GAD65 primarily labeled puncta (synaptic terminals) and these were also distributed rather uniformly across all visual cortical layers in both rearing conditions. Counts of GAD67-positive cell bodies and GAD65-positive puncta also revealed no differences between the rearing conditions. Thus, both GAD67, which produces the basal pool of GABA, and GAD65, which is specialized to respond to short-term increases in demand in synaptic terminals, developed normal levels of expression and normal intracellular and laminar distributions in the absence of visual input. Physiological studies suggest immaturity in the GABA system of dark-reared visual cortex. The present results indicate that such abnormalities are not due to presynaptic alterations in GABA synthetic enzymes.

Animals↗
PubMed2001

Magnesium deprivation decreases cellular reduced glutathione and causes oxidative neuronal death in murine cortical cultures.

The vulnerability of cultured cortical neurons to oxidative injury is an inverse function of the extracellular Mg2+ concentration. In order to test the hypothesis that depolarization-enhanced release of reduced glutathione (GSH) contributes to this phenomenon, we assessed the effect of Mg2+ deprivation on cellular and medium glutathione levels. Incubation of mixed neuronal and glial cultures in Mg2+-free medium resulted in a decline in cellular total glutathione (GSx) within 8 h, without change in oxidized glutathione (GSSG); no effect was seen in pure glial cultures. This decrease in cellular GSx was associated with a progressive increase in GSx but not GSSG in the culture medium. Cellular GSH loss was not attenuated by concomitant treatment with antioxidants (ascorbate, Trolox, or deferoxamine), but was prevented by the NMDA receptor antagonist MK-801. Mg2+ deprivation for over 24 h produced neuronal but not glial death, with release of about 40% of neuronal lactate dehydrogenase by 48-60 h. Most of this cytotoxicity was prevented by treatment with either antioxidants or MK-801. These results suggest that Mg2+ deprivation causes release of neuronal reduced glutathione via a mechanism involving excessive NMDA receptor activation. If prolonged, cellular GSH depletion ensues, leading to oxidative neuronal death.

Animals↗
PubMed2001

CARD11 and CARD14 are novel caspase recruitment domain (CARD)/membrane-associated guanylate kinase (MAGUK) family members that interact with BCL10 and activate NF-kappa B.

The caspase recruitment domain (CARD) is a protein-binding module that mediates the assembly of CARD-containing proteins into apoptosis and NF-kappaB signaling complexes. We report here that CARD protein 11 (CARD11) and CARD protein 14 (CARD14) are novel CARD-containing proteins that belong to the membrane-associated guanylate kinase (MAGUK) family, a class of proteins that functions as molecular scaffolds for the assembly of multiprotein complexes at specialized regions of the plasma membrane. CARD11 and CARD14 have homologous structures consisting of an N-terminal CARD domain, a central coiled-coil domain, and a C-terminal tripartite domain comprised of a PDZ domain, an Src homology 3 domain, and a GUK domain with homology to guanylate kinase. The CARD domains of both CARD11 and CARD14 associate specifically with the CARD domain of BCL10, a signaling protein that activates NF-kappaB through the IkappaB kinase complex in response to upstream stimuli. When expressed in cells, CARD11 and CARD14 activate NF-kappaB and induce the phosphorylation of BCL10. These findings suggest that CARD11 and CARD14 are novel MAGUK family members that function as upstream activators of BCL10 and NF-kappaB signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Analysis of genetic alterations in primary nasopharyngeal carcinoma by comparative genomic hybridization.

To identify genetic alterations associated with the development and progression of human nasopharyngeal carcinoma (NPC), 57 tumors were analyzed by comparative genomic hybridization (CGH). In 47 cases, chromosomal imbalances were found. Several recurrent chromosomal abnormalities were identified in the present study. The most frequently detected chromosomal gains involved chromosome arms 12q (24 cases, 51%), 4q (17 cases, 36%), 3q (16 cases, 34%), 1q (15 cases, 32%), and 18q (15 cases, 32%). Common regions of gain involved 12q13--q15, 4q12--q21, and 3q21--q26. High-copy-number increases of chromosomal materials were detected in four chromosomal regions, 3q21--q26.2, 4p12--q21, 8p, and 12q14--q15. The most frequently detected loss of chromosomal materials involved chromosome arms 16q (26 cases, 55%), 14q (21 cases, 45%), 1p (20 cases, 43%), 3p (20 cases, 43%), 16p (19 cases, 40%), 11q (17 cases, 36%), and 19p (16 cases, 34%). The most common regions of loss involved 14q24--qter, 1pter--p36.1, 3p22--p21.3, 11q21--qter, and the distal region of 19p. Genomic alterations detected by CGH were compared and found to be largely consistent with those identified in banding analysis and loss of heterozygosity studies. However, several previously unrecognized recurrent alterations were also identified in the present study, including gain of 4q and 18q, and loss of 16q, 14q, and 19p. In addition, gain of 1q, 8q, 18q, and loss of 9q showed a statistically significant association with advanced clinical stages (P < 0.05). Identification of recurrent sites of chromosomal gain and loss identify regions of the genome that may contain oncogenes or tumor suppressor genes, respectively, which may be involved in the tumorigenesis of NPC. Published 2000 Wiley-Liss, Inc.

Adult↗