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Biomedical subjects

X Ouyang

Publications and source records attributed to X Ouyang.

At least 19 recordsLinked to original sources
PubMed2006

Rapid eye movement sleep deprivation selectively impairs recall of fear extinction in hippocampus-independent tasks in rats.

Previous studies have shown that rapid eye movement (REM) sleep deprivation (RSD) exerts a detrimental effect on some memory tasks. However, whether post-learning RSD impairs memory for fear extinction, an important model of inhibitory learning, remains to be elucidated. The present study examined the effects of post-extinction RSD from 0 to 6 h and 6 to 12 h on recall of fear extinction tested 24 h after extinction training. We found that RSD from 0 to 6 h significantly increased freezing when recall of extinction of cued fear was tested in the context in which rats received extinction training whereas RSD from 6 to 12 h had no effect (experiments 1 and 2, two hippocampus-independent memory tasks). RSD at either time point had no effect on freezing when recall of extinction of cued fear was tested in the context different from that in which extinction training occurred (experiment 3, a hippocampus-dependent memory task). Additionally, we observed no effect of RSD at either time point on freezing during recall test for extinction of contextual fear (experiment 4, a hippocampus-dependent memory task). These results suggest that the effects of post-extinction RSD on memory for fear extinction are complex. RSD impairs recall of fear extinction in hippocampus-independent tasks, but does not affect recall of fear extinction in hippocampus-dependent tasks. Our findings extend previous research on the effects of RSD on learning and memory and support the notion that REM sleep is involved in memory process of certain tasks.

Acoustic Stimulation↗
PubMed2001

Effect of p53 on centrosome amplification in prostate cancer cells.

Chromosomal instability (CIN) is one of the common features in prostate cancer, especially in advanced stages. Recently, the involvement of p53 in CIN through the regulation of centrosome amplification has been proposed in certain tumor types. In this study, we investigated the relationship between p53 and centrosome amplification in prostate cancer cells. Increased centrosome number and size were observed in DU145 and PC3 containing nonfunctional p53 compared to LNCap which expressed wild-type p53. Transfection of p53 into PC3 cells resulted in a decreased cell growth rate, G2/M arrest and decreased centrosome abnormalities. We provide the first evidence on a correlation between loss of p53 function and centrosome amplification in prostate cancer cells. Our results indicate that p53 may play a role in the regulation of centrosome amplification and loss of p53 may be one of the mechanisms involving CIN in prostate cancer cells.

Centrosome↗
PubMed2001

A comparative study of the effects of magnetic stimulation and electric stimulation on peripheral nerve injury in rat.

The influence of pulsed magnetic stimulation (MS) on the sciatic nerve injury was investigated. Thirty rats were divided into three groups equally: MS group (A), electric stimulation (ES) group (B) and the control group (C). The MS and ES were applied immediately after the first 10 min of the sciatic nerve crush. Sciatic function index (SFI), toe spreading reflex (TSR), muscular weight and volume were measured after the experiment. The TSR of in the groups A and B occurred at 4th day while in the control group it occurs at 10th day. There was statistically significant difference in SFI between groups A and B (P < 0.01). The weight and volume of the gastrocnemius muscle were statistically greater in the groups A and B than in the control group (P < 0.01). The effect of MS was similar to that of ES. It was suggested that the application of MS immediately after the nerve injury might have an important clinical value as it can accelerate functional recovery and prevent or minimize muscle atrophy. The technique is easily to operate, non-invasion, painless and permits tolerance of high intensity output to be used.

Animals↗
PubMed2001

Structural analysis of high resolution in vitro MR images compared to stained grindings.

The recent advancement of high resolution magnetic resonance imaging has opened up new avenues for the determination of structural characteristics of the trabecular network, which may significantly improve the diagnosis of osteoporosis. An analysis of the calcaneus in healthy women has shown similar age-related changes when comparing structural parameters in high resolution MR images and BMD as measured by DXA [1]. Here we undertook an in vitro study to further compare structural measurements in MR images with those from stained grindings. A 3D gradient echo sequence on a 1.5 T scanner was used to obtain four contiguous sagittal MR images with a slice thickness of 1 mm and an in plane pixel size of 195 microns. Twenty-one stained grindings with a slice thickness of 1 micron each were obtained from a 3 mm thick slab of the same volume investigated by MR. The stack of stained grindings was also used to simulate the influence of variations in slice thickness and in plane resolution. Results for structural parameters derived from the high resolution MR images differed considerably from those derived from the stained grindings because the MR images are heavily influenced by partial volume artifacts. This finding was supported by simulations which also revealed that even at a slice thickness of 500 microns and an in plane pixel size of 13 microns, accurate results could not be obtained when a histomorphometric type analysis was applied. Results also depended strongly on the segmentation method. However, contrary to the stained grindings, images averaged over several slices reveal the three-dimensional network character of the trabecular structure. New efforts should be undertaken to develop analysis strategies that are more adequate for in vivo high resolution images instead of using analysis techniques applied in classical histomorphometry.

Cadaver↗
PubMed2001

Association of ErbB2 Ser1113 phosphorylation with epidermal growth factor receptor co-expression and poor prognosis in human breast cancer.

The carboxyterminal domain of the epidermal growth factor receptor (EGFR)--a putative binding site for the ubiquitin ligase Cbl--is the site of serine phosphorylation events which are essential for ligand-dependent EGFR desensitization and degradation. Using a monoclonal antibody (aPS1113) which selectively recognizes the homologous phosphorylated domain in the ErbB2 oncoprotein, we show here that wild-type ErbB2 becomes Ser1113-phosphorylated following treatment of 3T3 cells with growth factors or tyrosine phosphatase inhibitors. In EGFR-overexpressing A431 cells, ligand-inducible aPS1113 immunoreactivity declines more rapidly than other detectable phosphorylation events and is followed by EGFR downregulation. Analysis of 65 ErbB2-expressing primary breast cancers reveals a highly significant relationship between Ser1113 phosphorylation and EGFR overexpression (p < 0.0001) as well as an association with poor prognosis (p = 0.005). We submit that ErbB2 Ser1113 phosphorylation status represents a novel and informative biomarker of cancer cell biology and tumor behavior.

Animals↗
PubMed2001

Multisite phosphotyping of the ErbB-2 oncoprotein in human breast cancer.

BACKGROUND: Overexpression of the ErbB-2 (HER2/neu) receptor tyrosine kinase is one of the most common molecular changes in human cancer, but the functional significance of this phenotype remains uncertain. METHODS AND RESULTS: Using phosphorylation-specific antibodies recognizing different ErbB-2 functional states, we assessed the phosphorylation status of ErbB-2 in 102 human breast cancer specimens. Quantitative ErbB-2 immunoblotting intensity correlated directly with that of immunohistochemistry (r = 0.84). Widely varying phosphorylation profiles were evident in 65 ErbB-2-positive carcinomas, suggesting different ErbB-2 functions in different tumors. In a subset of patients for whom clinical data were obtainable, mortality trends were strongly associated with the quantitative signal intensities of ErbB-2 phosphoantibodies (P < or =.02), but not with those of conventional antibodies to ErbB-2 (P = .147), epidermal growth factor receptor (P = .44), or phosphotyrosine (P = .94). CONCLUSION: Although requiring corroboration in larger prospective clinical studies, these findings suggest that immunophenotyping using phosphorylation-specific antibodies may enable more accurate prediction of cancer behavior than is currently obtainable using conventional reagents.

3T3 Cells↗
PubMed2001

Protective effect of Salvia miltiorrhiza on angiotensin II-induced hypertrophic responses in neonatal rat cardiac cells.

The effect of the root of Salvia miltiorrhiza (SM) on angiotensin II (Ang II)-induced hypertrophic responses was examined in cultured neonatal rat cardiac cells (cardiomyocytes and non-cardiomyocytes). The methanol eluate fraction (SM2) of the water extract and the ethyl acetate-insoluble fraction (SM3) and its soluble fraction (SM4) partitioned from the methanol extract were prepared. Treatment with SM4 (5-80 microg/ml), not SM2 and SM3, for 24 h produced dose-dependent cytotoxicity against cardiac cells relative to the reduction in viability and the morphological injury of cardiomyocytes. SM2 or SM3 in the absence of Ang II affected neither hyperplastic nor hypertrophic growth of both cell types. However, SM3 (40 microg/ml) attenuated the positive chronotropic responsiveness of cardiomyocytes to Ang II (1 nM) stimulation, whereas Ang II-induced increase in non-cardiomyocyte number was decreased only by SM2 (40 microg/ml) treatment. Furthermore, SM3 suppressed Ang II-induced enlargement of cell size by preceding Ang II-induced induction of immediate early response gene (c-jun) expression in cardiomyocytes, while SM2 decreased Ang II-induced DNA synthesis in non-cardiomyocytes. Moreover, three phenolic compounds and tanshinone IIA that differed quantitatively among three SM fractions were identified by reverse-phase high performance liquid chromatography. Thus, the present findings indicate that the root of SM is an effective inhibitor of Ang II action and has a plural effective constituent, which possess different pharmacological activities on Ang II-induced hypertrophy and hyperplasia in cultured neonatal rat cardiac cells.

Angiotensin II↗
PubMed2001

[Effect of hepatitis C virus nonstructural protein NS3 on telomerase activity].

OBJECTIVE: To study the effect of hepatitis C virus nonstructural protein NS3 (HCV NS3) on telomerase activity and its carcinogenesis, and to observe the practical use of in situ telomerase activity labeling. METHODS: NIH3T3 cells were transfected with plasmid pRcHCNS3-5prime prime or minute (expressing HCV NS3 C-terminal deleted protein), pRcHCNS3-3prime prime or minute (expressing HCV NS3 N-terminal deleted protein) and blank plasmid pRcCMV. Positive clones, 11 with plasmid pRcHCNS3-5prime prime or minute, 11 with pRcHCNS3-3prime prime or minute and 8 with plasmid pRcCMV were harvested respectively. Streptavidin-peroxidase conjugated method (SP) was used to detect the expression of HCV NS3 protein in NIH3T3 cells transfected with plasmid pRcHCNS3-5prime prime or minute and pRcHCNS3-3prime prime or minute. Telomerase activity was detected by in situ telomerase activity labeling method and telomerase PCR ELISA technique in the transfected and non-transfected NIH3T3 cells. RESULTS: HCV NS3 protein was expressed in the cells transfected with plasmid pRcHCNS3-5prime prime or minute or plasmid pRcHCNS3-3prime prime or minute. The positive signals of HCV NS3 protein were localized in the cytoplasm of transfected NIH3T3 cells, and the signal intensity of the former was stronger (chi(2) = 6.667 P < 0.05). There was significant difference on telomerase activity between each group (F = 134.083 P < 0.01). Telomerase activity in all 11 clones with plasmid pRcHCNS3-5prime prime or minute was stronger than cells with plasmid pRcHCNS3-3prime prime or minute (P < 0.01), whereas telomerase activity in NIH3T3 cells transfected with the plasmid pRcCMV or non-transfected NIH3T3 cells were weaker than the cells with the plasmid pRcHCNS3-3prime prime or minute. The expression level of HCV NS3 protein were correlated significantly with the strength of telomerase activity (rs = 0.8084 P < 0.01). The results obtained with in situ telomerase activity labeling corresponded to those with telomerase PCR ELISA technique (rs = 0.50196 P < 0.01). CONCLUSIONS: (1) HCV NS3 protein may activate telomerase through endogenous mechanism to induce host cells transformation. (2) The effect of HCV NS3 C-terminal deleted protein on telomerase activity in host cells may be more intense than that of HCV NS3 N-terminal deleted protein. (3) In situ telomerase activity labeling is a reliable technique for studying pathological morphology and telomerase activity in tissues and cells.

3T3 Cells↗
PubMed2001

[Effects of change of crown contour on health of gingiva].

OBJECTIVE: To study the effects of different excessive crown contours on the health of periodontium. METHODS: A total of 63 posterior teeth of 12 volunteers were randomly divided into three groups and each group was consisted of 21 teeth. The buccal surfaces of the teeth were overcontoured 0.2 mm, 0.5 mm, and 0.8 mm respectively. At the point of 1 week, 4 weeks and 8 weeks, gingival cervical fluid (GCF) were collected, GCF-aspartate aminotransferase (GCF-AST) and GCF-alkaline phosphatase (GCF-ALP) levels were tested and the debris amount was assessed for three groups. RESULTS: The 0.8 mm group presented most amount of GCF, highest level of GCF-AST, GCF-ALP and most debris. The 0.5 mm group was the second. When the excess was 0.2 mm, all indexes showed no statistically significant change. CONCLUSIONS: Excessive crown contour is unfavourable to periodontium health. The more the teeth are excessively contoured, the more they impair periodontium.

Adult↗
PubMed2000

[Titer and avidity of serum antibody to Porphyromonas gingivalis before and after periodontal therapy].

OBJECTIVE: To observe the changes of titer and avidity of serum antibody to Porphyromonas gingivalis (Pg) before and one month after periodontal therapy, and to observe the correlation of titer and avidity of anti-Pg IgG with clinical indices. METHODS: ELISA and DEA-ELISA were used to determine the titer and avidity of serum IgG antibody to Pg381 before and one month after periodontal treatment in 17 periodontitis patients and 6 healthy control subjects. RESULTS: The titers of anti-Pg IgG antibody were higher in periodontitis patients than in healthy control subjects (P < 0.001). All patients were seropositive (titers to Pg were higher than 2-fold above the median for control subjects). IgG antibody avidity to Pg in periodontitis patients were not found to be significantly lower than that in control group. The titers to Pg decreased significantly at one month after periodontal therapy, but antibody avidity didn't change. Serum anti-Pg antibody titers had a tendency of negative correlation with probing depth. The antibody titers were significant higher in periodontitis patients with < or = 5 mm mean probing depth than in patients with > 5 mm mean probing depth. CONCLUSIONS: It is suggested that the humoral immune response to Pg381 is protective and this protective effect mainly depends on the titer of antibody.

Antibodies, Bacterial↗
PubMed1999

Metabolism-based brain-targeting system for a thyrotropin-releasing hormone analogue.

Gln-Leu-Pro-Gly, a progenitor sequence for the thyrotropin-releasing hormone (TRH) analogue [Leu(2)]TRH (pGlu-Leu-Pro-NH(2)), was covalently and bioreversibly modified on its N- and C-termini (by a 1,4-dihydrotrigonellyl and a cholesteryl group, respectively) to create lipoidal brain-targeting systems for the TRH analogue. The mechanism of targeting and the recovery of the parent peptide at the target site involve several enzymatic steps, including the oxidation of the 1,4-dihydropyridine moiety. Due to the lipid insolublity of the peptide pyridinium conjugate obtained after this reaction, one of the rudimentary steps of brain targeting (i.e., trapping in the central nervous system) can be accomplished. Our design also included spacer amino acid(s) inserted between the N-terminal residue of the progenitor sequence and the dihydrotrigonellyl group to facilitate the posttargeting removal of the attached modification. The release of the TRH analogue in the brain is orchestrated by a sequential metabolism utilizing esterase/lipase, peptidyl glycine alpha-amidating monooxygenase (PAM), peptidase cleavage, and glutaminyl cyclase. In addition to in vitro experiments to prove the designed mechanism of action, the efficacy of brain targeting for [Leu(2)]TRH administered in the form of chemical-targeting systems containing the embedded progenitor sequence was monitored by the antagonistic effect of the peptide on the barbiturate-induced anesthesia (measure of the activational effect on cholinergic neurons) in mice, and considerable improvement was achieved over the efficacy of the parent peptide upon using this paradigm.

Animals↗
PubMed1999

Transforming growth factor-alpha short-circuits downregulation of the epidermal growth factor receptor.

Transforming growth factor-alpha (TGFalpha) is an epidermal growth factor receptor (EGFR) ligand which is distinguished from EGF by its acid-labile structure and potent transforming function. We recently reported that TGFalpha induces less efficient EGFR heterodimerization and downregulation than does EGF (Gulliford et al., 1997, Oncogene, 15:2219-2223). Here we use isoform-specific EGFR and ErbB2 antibodies to show that the duration of EGFR signalling induced by a single TGFalpha exposure is less than that induced by equimolar EGF. The protein trafficking inhibitor brefeldin A (BFA) reduces the duration of EGF signalling to an extent similar to that seen with TGFalpha alone; the effects of TGFalpha and BFA on EGFR degradation are opposite, however, with TGFalpha sparing EGFR from downregulation but BFA accelerating EGF-dependent receptor loss. This suggests that BFA blocks EGFR recycling and thus shortens EGF-dependent receptor signalling, whereas TGFalpha shortens receptor signalling and thus blocks EGFR downregulation. Consistent with this, repeated application of TGFalpha is accompanied by prolonged EGFR expression and signalling, whereas similar application of EGF causes receptor downregulation and signal termination. These findings indicate that constitutive secretion of pH-labile TGFalpha may perpetuate EGFR signalling by permitting early oligomer dissociation and dephosphorylation within acidic endosomes, thereby extinguishing a phosphotyrosine-based downregulation signal and creating an irreversible autocrine growth loop.

3T3 Cells↗
PubMed1999

The effects of Radix Ginseng rubra on cAMP of experimental ischemic myocardium in rats.

The model of SD rats ligated at the proximate left anterior descend (LAD) of coronary was used. The number and dissociation constant of beta receptor were studied by using receptor autoradiography to observe the changes in beta receptor and the effects of Radix Ginseng Rubra on cAMP in experimental ischemic myocardium. The result showed that the number of binding site in simple ligation group (Bmax = 0.279) was obviously higher than that in sham operation group (Bmax = 0.093) and the dissociation constant of simple ligation group (Kd = 12. 431) was higher than that of sham operation group (kd = 1.319). There was a significant difference between the two groups (P < 0.05). It proved that the number of beta receptor was increased and the activity was elevated in myocardial cell membranes after ligation of LAD. The myocardial cAMP level in simple ligation group [(1293.96 +/- 519.36) x 10(-3) nmol/g] was much higher than that in sham operation group [(774.44 +/- 210.55) x 10(-3) nmol/g]; but the level of cAMP in ligation group after receiving Radix Ginseng Rubra treatment (805.02 +/- 362.48 pm/g) was obviously lower than that in simple ligation group (P < 0.01), which was close to the result of sham operation. The results indicated that Radix Ginseng Rubra could decrease the cAMP level in ischemic myocardium.

Animals↗
PubMed1999

Intensification of growth factor receptor signalling by phorbol treatment of ligand-primed cells implies a dimer-stabilizing effect of protein kinase C-dependent juxtamembrane domain phosphorylation.

Protein kinase C (PKC) phosphorylates the juxtamembrane domain of many growth factor receptors, but the physiologic effect of this modification on ligand signalling and desensitisation is unclear. Here we show that PKC-dependent transmodulation of EGFR and ErbB2 signalling is schedule-specific: prolonged pre-treatment of A431 cells with the PKC agonist phorbol dibutyrate potently inhibits subsequent ligand-induced EGFR signalling as expected, but EGF pre-treatment reverses the inhibitory effect of phorbol. The agonist activity of PKC on receptor signalling is even more apparent when cells are treated with phorbol in the presence of a tyrosine phosphatase inhibitor. Because these findings suggested a synergistic interaction between tyrosine- and PKC-dependent phosphorylation events, we sought to define the interactions of tyrosine-phosphorylated and PKC-modified ErbB2 subsets within EGF-inducible hetero-oligomers. Growth factor-dependent PKC transphosphorylation takes place exclusively within endocytosed tyrosine-phosphorylated receptor oligomers. Moreover, phorbol differentially affects two ErbB2 C-terminal autophosphorylation sites: whereas phosphorylation of Tyr1222 is reduced, phosphorylation of Tyr1139 is increased. These results suggest that PKC-dependent phosphorylation of the juxtamembrane domain may contribute positively to both internalisation and signalling of ligand-activated receptors, simultaneously accelerating termination of growth factor action. We propose that transient PKC-dependent signal amplification results from enhanced stability of liganded receptor oligomers due to phosphorylation-dependent juxtamembrane domain interactions, analogous to the protein-protein binding now known to be induced by serine-threonine phosphorylation of CREB and SMAD.

Animals↗
PubMed1999

Preliminary assessment of extrastriatal dopamine D-2 receptor binding in the rodent and nonhuman primate brains using the high affinity radioligand, 18F-fallypride.

We have identified the value of 18F-fallypride [(S)-N-[(1-allyl-2-pyrrolidinyl)methyl]-5-(3-[18F]fluoropropyl)-2, 3-dimethoxybenzamide], as a dopamine D-2 receptor radiotracer for the study of striatal and extrastriatal receptors. Fallypride exhibits high affinities for D-2 and D-3 subtypes and low affinity for D-4 (3H-spiperone IC50s: D-2 = 0.05 nM [rat striata], D-3 = 0.30 nM [SF9 cell lines, rat recombinant], and D-4 = 240 nM [CHO cell lines, human recombinant]). Biodistribution in the rat brain showed localization of 18F-fallypride in striata and extrastriatal regions such as the frontal cortex, parietal cortex, amygdala, hippocampus, thalamus, and hypothalamus. In vitro autoradiographic studies in sagittal slices of the rat brain showed localization of 18F-fallypride in striatal and several extrastriatal regions, including the medulla. Positron emission tomography (PET) experiments with 18F-fallypride in male rhesus monkeys were carried out in a PET VI scanner. In several PET experiments, apart from the specific binding seen in the striatum, specific binding of 18F-fallypride was also identified in extracellular regions (in a lower brain slice, possibly the thalamus). Specific binding in the extrastriata was, however, significantly lower compared with that observed in the striata of the monkeys (extrastriata/cerebellum = 2, striata/cerebellum = 10). Postmortem analysis of the monkey brain revealed significant 18F-fallypride binding in the striata, whereas binding was also observed in extrastriatal regions such as the thalamus, cortical areas, and brain stem.

Animals↗
PubMed1999

Fractal analysis of radiographs: assessment of trabecular bone structure and prediction of elastic modulus and strength.

The purpose of this study was to determine whether fractal dimension of radiographs provide measures of trabecular bone structure which correlate with bone mineral density (BMD) and bone biomechanics, and whether these relationships depend on the technique used to calculate the fractal dimension. Eighty seven cubic specimen of human trabecular bone were obtained from the vertebrae and femur. The cubes were radiographed along all three orientations--superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP), digitized, corrected for background variations, and fractal based techniques were applied to quantify trabecular structure. Three different techniques namely, semivariance, surface area, and power spectral methods were used. The specimens were tested in compression along three orientations and the Young's modulus (YM) was determined. Compressive strength was measured along the SI direction. Quantitative computed tomography was used to measure trabecular BMD. High-resolution magnetic-resonance images were used to obtain three-dimensional measures of trabecular architecture such as the apparent bone volume fraction, trabecular thickness, spacing, and number. The measures of trabecular structure computed in the different directions showed significant differences (p<0.05). The correlation between BMD, YM, strength, and the fractal dimension were direction and technique dependent. The trends of variation of the fractal dimension with BMD and biomechanical properties also depended on the technique and the range of resolutions over which the data was analyzed. The fractal dimension showed varying trends with bone mineral density changes, and these trends also depended on the range of frequencies over which the fractal dimension was measured. For example, using the power spectral method the fractal dimension increased with BMD when computed over a lower range of spatial frequencies and decreased for higher ranges. However, for the surface area technique the fractal dimension increased with increasing BMD. Fractal measures showed better correlation with trabecular spacing and number, compared to trabecular thickness. In a multivariate regression model inclusion of some of the fractal measures in addition to BMD improved the prediction of strength and elastic modulus. Thus, fractal based texture analysis of radiographs are technique dependent, but may be used to quantify trabecular structure and have a potentially valuable impact in the study of osteoporosis.

Biomechanical Phenomena↗