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Biomedical subjects

D Shi

Publications and source records attributed to D Shi.

At least 19 recordsLinked to original sources
PubMed2007

Development of indirect enzyme-linked immunosorbent assay with nucleoprotein as antigen for detection and quantification of antibodies against avian influenza virus.

Avian influenza (AI) is a serious infectious disease caused by avian influenza virus (AIV) belonging to type A Orthomyxovirus. In the present study, we developed an indirect enzyme-linked immunosorbent assay (ELISA) employing E. coli-expressed full-length nucleoprotein (NP) of H9N2 avian influenza virus for the detection and quantification of antibodies against AIV nucleoprotein. The NP-ELISA was compared with the AI agar gel propagation (AGP) test, haemagglutination inhibition (HI) test, and IDEXX-FlockChek ELISA using 263 sera. The NP-ELISA was significantly more sensitive than the AGP and HI tests, and showed 96.2% agreement ratio with IDEXX-FlockChek ELISA. With results obtained using the NP-ELISA, an ELISA titre (ET) prediction equation, with which the ELISA titres of a flock or individual chickens can be determined, was derived from a positive/negative (P/N) ratio standard curve. The NP-ELISA enables an alternative rapid serological diagnosis and is suitable for influenza A antibody screening, especially in species that harbour several influenza subtypes.

Animals↗
PubMed2006

Chaperoning of estrogen receptor and induction of mammary gland proliferation by neuronal protein synuclein gamma.

Synucleins are emerging as central players in the formation of pathologically insoluble deposits characteristic of neurodegenerative diseases. However, synuclein gamma (SNCG), previously identified as a breast cancer specific gene (BCSG1), is also highly associated with breast cancer progression. Using transgenic mouse model, we demonstrated a role of SNCG in induction of highly proliferative pregnancy-like phenotype of mammary epithelial cells and branching morphology. SNCG participated in the heat shock protein-based multiprotein chaperone complex for steroid receptor signaling. Expression of SNCG in mammary epithelium resulted in a significant stimulation of ERalpha transcriptional activity. SNCG-induced mammary gland proliferation can be effectively blocked by antiestrogen and ovariectomy, indicating that the induced proliferation is mediated by ERalpha signaling and requires estrogen stimulation. These data indicate the chaperone activity of SNCG on stimulation of steroid receptor signaling in mammary gland and, thus induces extensive mammary gland proliferation and contributes to the hormonal impact on mammary tumorigenesis.

Animals↗
PubMed2006

hHR23B is required for genotoxic-specific activation of p53 and apoptosis.

Rad23 proteins function in both DNA repair and protein stability regulation. As ubiquitinated forms of p53 are stabilized after DNA damage in concert with p53 functional activation, and human Rad23 proteins (hHR23A and B) regulate p53 stability in unstressed cells, the role of hHR23B in post-genotoxin regulation of p53 was investigated. Depletion of hHR23B by specific short interfering RNA before genotoxic exposure attenuated p53, p21 and bax induction, abrogated the accumulation of ubiquitinated p53 and suppressed apoptosis. Expression of ubiquitin derivatives with all lysines mutated except K48 or K63 demonstrated that K48-linked p53-ubiquitin conjugates were specifically induced after DNA damage. hHR23B, along with native and ubiquitinated p53, accumulated in chromatin after genotoxic exposure, and the accumulation of ubiquitinated p53 in chromatin was prevented by hHR23B depletion. Chromatin immunoprecipitation analysis demonstrated that hHR23B and p53 both localized to the p21 promoter shortly after DNA damage. hHR23B thus plays a critical role in the activation and function of p53 after specific genotoxic exposures.

Apoptosis↗
PubMed2005

Sensitivity analysis applied to the construction of radial basis function networks.

Conventionally, a radial basis function (RBF) network is constructed by obtaining cluster centers of basis function by maximum likelihood learning. This paper proposes a novel learning algorithm for the construction of radial basis function using sensitivity analysis. In training, the number of hidden neurons and the centers of their radial basis functions are determined by the maximization of the output's sensitivity to the training data. In classification, the minimal number of such hidden neurons with the maximal sensitivity will be the most generalizable to unknown data. Our experimental results show that our proposed sensitivity-based RBF classifier outperforms the conventional RBFs and is as accurate as support vector machine (SVM). Hence, sensitivity analysis is expected to be a new alternative way to the construction of RBF networks.

Algorithms↗
PubMed2005

Outcome of late surgical treatment in patients with incomplete paraplegia due to spinal degenerative diseases.

STUDY DESIGN: Retrospective analysis. OBJECTIVE: To assess the outcome of late surgical intervention in patients with incomplete paraplegia due to spinal degenerative diseases. SETTING: Three men and four women with cervical or thoracic spinal degenerative diseases, who preoperatively were unable to walk for more than 6 months in Mie prefecture, Japan. METHODS: Review of clinical records and questionnaire survey regarding the walking ability of patients 2 years after surgery. RESULTS: All seven patients were unable to walk postoperatively. CONCLUSION: A late surgical intervention may not lead to functional recovery in patients with spinal degenerative disease who were unable to walk for at least 6 months.

Aged↗
PubMed2003

The incidence of deep vein thrombosis after hip and knee arthroplasties in Japanese patients: a prospective study.

PURPOSE: To document the incidence of proximal deep vein thrombosis and pulmonary embolism in 58 consecutive Japanese patients undergoing total hip arthroplasty or total knee arthroplasty. METHODS: Patients were routinely examined for proximal deep vein thrombosis by B-mode ultrasonography before and after surgery. Those patients who had ultrasonographic findings of deep vein thrombosis were also investigated for pulmonary embolism by ventilation-perfusion lung scan. RESULTS: The incidence of deep vein thrombosis after total hip arthroplasty and total knee arthroplasty were 9.1% and 4.0% respectively, and the incidence of pulmonary embolism were 3.0% and 0%, respectively. There were no cases of fatal pulmonary embolism. CONCLUSION: The incidence of deep vein thrombosis and pulmonary embolism in Japanese patients may have increased over the last few decades.

Aged↗
PubMed2003

Interactions between landscape changes and host communities can regulate Echinococcus multilocularis transmission.

An area close to the Qinghai-Tibet plateau region and subject to intensive deforestation contains a large focus of human alveolar echinococcosis while sporadic human cases occur in the Doubs region of eastern France. The current review analyses and compares epidemiological and ecological results obtained in both regions. Analysis of rodent species assemblages within quantified rural landscapes in central China and eastern France shows a significant association between host species for the pathogenic helminth Echinococcus multilocularis, with prevalences of human alveolar echinococcosis and with land area under shrubland or grassland. This suggests that at the regional scale landscape can affect human disease distribution through interaction with small mammal communities and their population dynamics. Lidicker's ROMPA hypothesis helps to explain this association and provides a novel explanation of how landscape changes may result in increased risk of a rodent-borne zoonotic disease.

Animals↗
PubMed2001

Projection structure and molecular architecture of OxlT, a bacterial membrane transporter.

The major facilitator superfamily (MFS) represents the largest collection of evolutionarily related members within the class of membrane 'carrier' proteins. OxlT, a representative example of the MFS, is an oxalate-transporting membrane protein in Oxalobacter formigenes. From an electron crystallographic analysis of two-dimensional crystals of OxlT, we have determined the projection structure of this membrane transporter. The projection map at 6 A resolution indicates the presence of 12 transmembrane helices in each monomer of OxlT, with one set of six helices related to the other set by an approximate internal two-fold axis. The projection map reveals the existence of a central cavity, which we propose to be part of the pathway of oxalate transport. By combining information from the projection map with related biochemical data, we present probable models for the architectural arrangement of transmembrane helices in this protein superfamily.

Amino Acid Sequence↗
PubMed2001

Crystallization and preliminary X-ray crystallographic studies of wild-type human ornithine transcarbamylase and two naturally occurring mutants at position 277.

Wild-type human ornithine transcarbamylase (OTCase) and two mutants (R277Q and R277W) that cause 'late-onset' hyperammonemia were crystallized and a preliminary structure determination was carried out. The unliganded wild-type enzyme crystallizes in the cubic space group I23, with unit-cell parameters a = b = c = 203.4 A. R277Q crystallizes in two crystal forms under the same crystallization conditions. One crystal form is isomorphous to that of unliganded wild-type crystals, with unit-cell parameters a = b = c = 202.2 A. The second form also belongs to a cubic space group, P4(3)32, but has unit-cell parameters a = b = c = 139.8 A. R277W crystals are isomorphous to the second crystal form of R277Q, with unit-cell parameters a = b = c = 138.7 A. None of these crystal forms is isomorphous to other crystal forms of OTCase that have been studied. The structures in both crystal forms have been solved using molecular replacement. In the first crystal form there are two monomers in the asymmetric unit, corresponding to a solvent content of 75%. Because of its high molecular and crystal symmetry and the presence of non-crystallographic symmetry, this structure could not be solved with AMoRe or X-PLOR, but was solved successfully with COMO. There is only one monomer in the asymmetric unit in the second crystal form, corresponding to a solvent content of 62%. This structure was successfully solved with AMoRe.

Crystallization↗
PubMed2001

Human ornithine transcarbamylase: crystallographic insights into substrate recognition and conformational changes.

Two crystal structures of human ornithine transcarbamylase (OTCase) complexed with the substrate carbamoyl phosphate (CP) have been solved. One structure, whose crystals were prepared by substituting N-phosphonacetyl-L-ornithine (PALO) liganded crystals with CP, has been refined at 2.4 A (1 A=0.1 nm) resolution to a crystallographic R factor of 18.4%. The second structure, whose crystals were prepared by co-crystallization with CP, has been refined at 2.6 A resolution to a crystallographic R factor of 20.2%. These structures provide important new insights into substrate recognition and ligand-induced conformational changes. Comparison of these structures with the structures of OTCase complexed with the bisubstrate analogue PALO or CP and L-norvaline reveals that binding of the first substrate, CP, induces a global conformational change involving relative domain movement, whereas the binding of the second substrate brings the flexible SMG loop, which is equivalent to the 240s loop in aspartate transcarbamylase, into the active site. The model reveals structural features that define the substrate specificity of the enzyme and that regulate the order of binding and release of products.

Amino Acid Sequence↗
PubMed2001

Surface water phosphorus dynamics in rice fields receiving fertiliser and manure phosphorus.

A long-term randomised block field experiment was established in 1997 to study the dynamics of total P and dissolved P in the surface waters of rice fields receiving two application rates of fertiliser P and one rate of combined fertiliser and manure P. Preliminary results from the first two crops show that concentrations of both total P and dissolved P in the surface waters increased significantly following P application, especially during the first 2 weeks after application. P concentrations subsequently declined sharply within about 10 days, then declined steadily and remained almost constant from about 1 month after application. The initial increase in P concentration of surface waters was higher with increasing rate of fertiliser P, and the P concentration at the highest fertiliser rate peaked within about 1 week of application. The elevated P concentrations following fertiliser P application declined more rapidly than those following the combined application of fertiliser and manure P. When fertiliser and manure P were applied together, about 7 days later the surface water P concentrations were significantly higher than when the same rate of P (or double) was applied as fertiliser only. Disturbance of the surface soil by hand harrowing further increased the P concentrations in surface waters, with a subsequent decline to a steady value after about 1 week. Application of P fertiliser to the high P status soil in this experiment gave no crop yield response and may have increased the risk of pollution of adjacent surface waters through drainage from heavy rainfall events during the rice growing season. Therefore, fertiliser P should not be applied to such soils. If, however, fertiliser or manure P is applied, the application should be made during the dry winter to reduce P losses. Manure should be applied with particular care because of the higher risk of P losses to surface water arising from the relatively long period of high P concentrations in surface waters and the potential for greater release of P to field surface waters from the soil. Hand harrowing should also be avoided during wet weather to protect water quality.

Animals↗
PubMed2001

The clinically variable R40H mutant ornithine carbamoyltransferase shows cytosolic degradation of the precursor protein in CHO cells.

Ornithine carbamoyltransferase (OCT) deficiency is now frequently found in adults with hyperammonaemia affected by mutations that cause partial deficiency of this urea cycle enzyme. One of these mutations (R40H) has occurred in several families and has been found also in asymptomatic relatives. To better understand the phenotypic heterogeneity of this recurrent mutation, we investigated the biological properties of the mutant protein. Using 35S labelling, the import and processing of the R40H mutant OCT protein was investigated in intact CHO cells and in isolated rat liver mitochondria and compared to the wild type and R141Q mutant that causes complete enzyme deficiency. The R40H OCT protein seems to be imported and processed by the mitochondria in a manner similar to that of wild type. However, it is consistently degraded to a smaller fragment in the intact cells, unlike the wild type and R141Q mutant. The mature form of the enzyme is not susceptible to degradation. These data, obtained in CHO cells, suggest that deficiency in OCT enzymatic function conferred by the R40H mutation is likely caused by enhanced degradation of the preprotein in the cytosol. We propose therefore that variation in the rate of OCT turnover is responsible for the heterogeneity of the clinical phenotype in these patients.

Adult↗
PubMed2001

Visualizing filamentous actin on lipid bilayers by atomic force microscopy in solution.

The surface structure of actin filaments (F-actin) was visualized at high resolution, by atomic force microscopy (AFM) in aqueous solution, in large paracrystals prepared on positively charged lipid monolayers. The increased stability of these closely packed specimens allowed us to show that both the long pitch (38 nm) and the monomer (5.8 nm) can be directly resolved by AFM in the contact mode. The right-handed helical surface, distinguishable in high resolution images, was compared with reconstructed models based on electron microscopy. The height of the rafts, a measure of the actin filament diameter, was 10 +/- 1 nm, whereas the smaller inter-filament distance, 8 +/- 1 nm, was consistent with interdigitation of the filaments. The 10 +/- 1 nm F-actin diameter is in good agreement with the results of fibre X-ray diffraction. As such specimens are relatively easy to prepare without specialized equipment, this method may allow the study of the thin filaments in which F-actin-associated proteins are also present.

Actin Cytoskeleton↗
PubMed2001

[Determination of podophyllotoxin lignans in Dysosma and its allied plants].

The existence of podophyllotoxin lignans in Dysosma versipellis and its allied plants was analyzed by twice developing TLC, and the content by chromotropic-colorimetric assay. The results showed that podophyllotoxin lignans exist in the rhizoma, radix, stem and leaf of Dysosma versipellis and its allied plants. The total lignans content is 2%-7%, and there is a big variation between different species. The total lignans content of Dysosma versipellis is related to the habitat.

Berberidaceae↗
PubMed2001

[Quantitative analysis of the expression of insulin receptor and tyrosine protein kinase of patients with hepatic cirrhosis].

OBJECTIVE: To investigate the relationship between the expression of insulin receptor (IR) and the content of tyrosine protein kinase (TPK) in patients with hepatic cirrhosis. METHODS: Glucose tolerance test (GTT), insulin, c-peptide, insulin antibodies in serum, the expression of IR and TPK were quantitively analysed in patients with hepatic cirrhosis. The amount of IR and TPK was evaluated by immunohistochemical quantitative analysis using image analyzer in 12 patients with positive HBV marks and cirrhosis. Insulin and c-peptide in serum were determined by immunoenzymemetric assay (IEMA) and insulin antibodies in serum determined by RIA. RESULTS: IR amount in normal and abnormal GTT patients with hepatic cirrhosis was signifficantly less than that in control group (P<0.01). TPK amount in liver of patitents with abnormal GTT was less than that of normal GTT (P<0.01). CONCLUSIONS: IR decreases in cirrhotic patients. Abnormal GTT has relation to reducing TPK activity.

Antibodies↗
PubMed2001

[Experimental study on repair of bile duct defects with expanded polytetrafluoroethylene].

OBJECTIVE: To explore the possibility of repair of the extensive bile duct injuries with expanded polytetrafluoroethylene (ePTFE). METHODS: A total of 36 local healthy hybrid dogs were employed to establish bile duct injury models by means of partial removal of bile duct (group A, 14 dogs), excision of a segmental duct (group B, 10 dogs), and ligation of the lower part of common bile duct(group C, 5 dogs; group D, 7 dogs). Group A were patched with ePTFE mesh, group B replaced by ePTFE tube. Interposition of the grafts between gallbladder and duedenum or jejunum was performed on group C and group D. The animals' postoperative performance status were evaluated. Cholangiography was used to define the patency of bile ducts. Tissues of bile ducts and liver were taken at 3 days, 2, 4, 8, 12 and 52 weeks for microscopic and ultrastructural examination to observe the healing process of bile duct and morphological changes in the liver. RESULTS: Group A with ePTFE patch covered by epithelium had a high patency rate of 75%(9/12) and pathological damages were not found in the liver. The patency rate of group B was merely 40%(4/10), to some extent, accompanying damages in the liver. The grafts of group C and group D were fully expelled, ultimately leading to cystic-duodenal or cystic-jejunal fistulas formation. CONCLUSION: The study suggests that application of ePTFE patch to repair bile duct defects is feasible.

Animals↗