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Biomedical subjects

Y Shen

Publications and source records attributed to Y Shen.

At least 145 records · Page 8Linked to original sources
PubMed2001

[Studies on the methods of mating test for Cryptococcus neoformans].

Six media (MA:Mating agar, HA:Hay agar, HCA:Hay cube agar, RSA:Rice shell agar, IHA:additional nutrition in HA and SDA:Sabouraudia dextrose agar) were compared for their efficiencies of the mating test for Cryptococcus neoformans. The positive rates in 2-week-cultivation were 95% (HCA and RSA), 86% (HA), 38% (MA and SDA) and 24% (IHA). The streaking inoculation was equally replaced by the dot inoculation for the mating tests. However, the dot method saves much more materials, and is suitable for testing in large number of isolates. Additionally, the precultivation of the tester and tested isolates in broth medium (YMPDB) could enhance the positive mating rates.

Agar↗
PubMed2001

[Fragile X mental retardation protein interacts with human NDK/Nm23-H2].

OBJECTIVE: To investigate the physiological role of fragile X mental retardation protein (FMRP) and screen the proteins interacting with FMRP in human fetal hippocampus cDNA library. METHODS: Human fetal hippocampus cDNA library was constructed in yeast two-hybrid DAD vector pGAD10. Quality of the library was measured by picking up random colonies as templates for PCR testing. Proteins interacting with FMRP were screened by yeast two-hybrid system. Furthermore, the interaction site of FMRP was mapped in yeast. RESULTS: The average length of inserts of the two-hybrid library was 1.5 kb, and the ratio of recombinant colonies was about 90%. Human NDK/Nm23-H2 was found interacting with FMRP. NDK/Nm23-H2 interacted with FMRP exon 1-12, as well as FMRP isoforms without exon 12, and exons 14-17. NDK/Nm23-H2 couldn't interact with FMRP exon 1-6 and exon 2-7 fragments. CONCLUSIONS: Human NDK/Nm23-H2 can bind FMRP directly. The interaction site of FMRP is located at its exon 1-11. This interaction in vitro might alter the intracellular distribution of NDK/Nm23-H2, and even regulates the transcription and expression of FMRP.

Fragile X Messenger Ribonucleoprotein 1↗
PubMed2001

[Two-photon fluorescence from recombinant green fluorescent protein].

The photoconversion process of recombinant green fluorescent protein (rGFP) was investigated by two-photon excitation. The results indicated that the rGFP had very strong two-photon excitation fluorescence. The changes of two-photon-induced fluorescence polarization suggest that there is a proton transfer process between two different proton states of rGFP chromophores. The conformation of rGFP chromophores could be changed upon illumination, which partly block the energy transfer processes from amino acid residues to chromophores in rGFP, and result in the decrease of two-photon-induced fluorescence intensity. The fluorescence from amino acid residues in rGFP was also observed by three-photon excitation, which resulted from the blocked amino acid residues in rGFP. These results suggested that it is necessary to optimize rGFP excitation and detection for quantitative fluorescence microscopy.

Energy Transfer↗
PubMed2001

[Influence of calcium carbonate on the microstructure of bovine serum albumin].

The influence of calcium carbonate on the microstructure of bovine serum albumin (BSA) in aqueous solution was studied by ultraviolet spectrum and ultraviolet second order derivative spectrum and Fourier transform infrared spectrum. The results showed the changes of the microenvironment of the aromatic amino acid residues and secondary structure of BSA. It was the changes that provided a favorable condition for biomineral formation.

Amino Acids↗
PubMed2001

[Fine structure branching ratio for K-Ar optical collision].

An optically thin gaseous mixture of K and low-density Ar is excited by the fixed frequency line 514.5 nm of the argon ion laser. The excited KAr molecule is dissociated into the K 4P1/2 or K 4P3/2. The branching ratio is defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic K D1 and D2 lines. The branching is determined in the Ar density range between 2 and 8 x 10(17) cm-3. The ratio of the dissociation rates and the fine structure changing cross section are obtained.

Argon↗
PubMed2001

[The clinical assessment of zygomatic complex fracture treated via infraorbital incision and rigid fixation].

OBJECTIVE: To investigate the clinical effect of zygomatic complex (ZC) fracture via infraorbital incision and rigid fixation. METHODS: To clinically classify 65 cases with ZC fractures,which treated with open reduction and minor titanium-plate internal fixation. RESULTS: (1) The operated area can be widely exposed via infraorbital incision. (2) ZC fractures can be reducted timely and correctly. (3) The fragments can be fixed rigidly with minor Ti-plaets. No injury to the facial nerve.The satisfactory rate of recovery was 95.4% (63/65). CONCLUSION: Operation through infraorbital incision is suitable to ZC fractures.

English Abstract↗
PubMed2000

B7 requirements for primary and secondary protein- and polysaccharide-specific Ig isotype responses to Streptococcus pneumoniae.

The requirements for B7 costimulation during an in vivo humoral response to an intact extracellular bacteria have not been reported. In this study we immunized mice with Streptococcus pneumoniae (R36A) to determine the B7 requirements for induction of Ig, specific for two determinants on R36A, the phosphorylcholine (PC) determinant of C-polysaccharide and pneumococcal surface protein A (PspA). We show that the primary anti-PspA response, the development of PspA-specific memory, and the induction of the secondary anti-PspA response in primed mice were completely dependent upon B7 costimulation. Of note, costimulation was required only briefly after the secondary immunization compared with after the primary immunization for optimal induction of Ig. Blockade of B7 costimulation at the time of secondary immunization also completely abrogated the established state of memory, but did not induce tolerance. In contrast to the anti-PspA response, the primary anti-PC response involved only a very short period of B7 costimulation. Whereas B7-2 alone was required for induction of the primary anti-PspA and anti-PC responses, a redundant role for B7-1 and B7-2 was noted for the PspA-specific secondary response. CTLA4Ig blocked both the anti-PC and anti-PspA responses equally well over a wide range of bacterial doses. These studies demonstrate a critical, but variable, role for B7-dependent costimulation during an Ig response to an extracellular bacteria.

Abatacept↗
PubMed2000

Permutation tests for comparing marginal survival functions with clustered failure time data.

We propose a class of two-sample non-parametric permutation tests to compare the marginal survival distributions of two groups when the failure times are correlated within cluster, with clusters nested within each group. The permutation distribution effectively takes into account the correlation between failure times within a cluster. The method is able to handle data with clusters of either fixed or variable sizes. Moreover, this class of test statistics is sensitive to various alternatives. The size and power of the proposed tests are assessed by a series of simulation studies. The method is illustrated by application to data from the Hypertension Detection and Follow-up program trial.

Adult↗
PubMed2000

InIB-dependent internalization of Listeria is mediated by the Met receptor tyrosine kinase.

The Listeria monocytogenes surface protein InlB promotes bacterial entry into mammalian cells. Here, we identify a cellular surface receptor required for InlB-mediated entry. Treatment of mammalian cells with InlB protein or infection with L. monocytogenes induces rapid tyrosine phosphorylation of Met, a receptor tyrosine kinase (RTK) for which the only known ligand is Hepatocyte Growth Factor (HGF). Like HGF, InlB binds to the extracellular domain of Met and induces "scattering" of epithelial cells. Experiments with Met-positive and Met-deficient cell lines demonstrate that Met is required for InlB-dependent entry of L. monocytogenes. InlB is a novel Met agonist that induces bacterial entry through exploitation of a host RTK pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Deficiency of complement defense protein CD59 may contribute to neurodegeneration in Alzheimer's disease.

Complement defense 59 (CD59) is a cell surface glycophosphoinositol (GPI)-anchored protein that prevents complement membrane attack complex (MAC) assembly. Here, we present evidence from ELISA assays that CD59 protein levels are significantly decreased in the frontal cortex and hippocampus of Alzheimer's disease (AD) compared with nondemented elderly (ND) patients, whereas complement component 9, a final component to form MAC, is significantly increased. To further confirm the CD59 deficit, PI-specific phospholipase C (PIPLC) was used to cleave the CD59 GPI anchor at the cell surface in intact slices from AD and ND cortex. CD59 released by PIPLC cleavage was significantly reduced in AD compared with ND samples. By the use of a ribonuclease protection technique, amyloid beta-peptide was found to downregulate CD59 expression at the mRNA level, suggesting a partial explanation of CD59 deficits in the AD brain. To evaluate the pathophysiological significance of CD59 alterations in neurons, we exposed cultured NT2 cells, which normally underexpress CD59, and NT2 cells transfected to overexpress CD59 to homologous human serum. Lactic acid dehydrogenase assays revealed significant complement-induced cell lysis in CD59-underexpressing NT2 cells and significant protection from such lysis in CD59-overexpressing NT2 cells. Moreover, cells expressing normal levels of CD59 showed no evidence of MAC assembly or damage after exposure to homologous serum, whereas pretreatment of these cells with a CD59-neutralizing antibody resulted in MAC assembly at the cell surface and morphological damage. Taken together, these data suggest that CD59 deficits may play a role in the neuritic losses characteristic of AD.

Aged↗
PubMed2000

Capillary isoelectric focusing of yeast cells.

In the present work, capillary isoelectric focusing (CIEF) methods were developed for the separation and identification of yeast cells. Yeast cells (approximately 4-microm diameter) cultured to various phases of growth were shown to be reproducibly resolved by CIEF using 100-microm-i.d. fused-silica capillaries coated with hydroxypropyl methylcellulose. Separation efficiencies corresponding to peak capacities of >4000 were obtained. The suitable cell concentration range for obtaining repeatable elution in CIEF separations was found to be quite low (<3 cells/microL). CIEF experiments showed that yeast cell populations at early log, mid log, and stationary growth phases differ in isoelectric point, with values ranging from 5.2 to 6.4. The broader application of CIEF are projected for microorganism identification and separation based upon growth conditions.

Isoelectric Focusing↗
PubMed2000

Detection of complement alternative pathway mRNA and proteins in the Alzheimer's disease brain.

Previous research on complement activation in the Alzheimer's disease (AD) brain has focused almost exclusively on the classical complement pathway. The alternative pathway represents another important arm for complement activation, converging with the classical cascade at the C5 cleavage step. Here, we show that mRNA for a critical alternative pathway component, factor B, is present in AD frontal cortex and that the factor D cleaved split products of factor B, Bb and Ba, are significantly increased, indicating alternative pathway activation. By contrast, the two major inhibitors of alternative pathway activation, factor H and factor I, are present at the level of mRNA and protein but are not significantly upregulated. Immunohistochemical analysis reveals significant positive staining in AD sections for all three components. Taken together with previous reports demonstrating alternative pathway activation by amyloid beta peptide, these findings suggest that conditions conducive to chronic alternative pathway activation may exist in the AD brain.

Aged↗
PubMed2000

Overexpression of a dominant negative CREB protein in HT-1080 cells selectively disrupts plasminogen activator inhibitor type 2 but not tissue-type plasminogen activator gene expression.

The tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type 2 (PAI-2) genes are differentially regulated by 12-phorbol 13-myristate acetate (PMA) in HT-1080 fibrosarcoma cells. PMA transcriptionally down-regulates the t-PA gene in HT-1080 cells, while the PAI-2 gene is simultaneously induced by this agonist. The t-PA and PAI-2 gene promoters harbour a cAMP-response element (CRE) which influences the expression of both genes. We have compared the binding activity of nuclear factors that recognise these CRE sites. We show that CREB (CRE binding protein) recognises each CRE and that the degree of constitutive Ser119-phosphorylated t-PA CRE-bound CREB was greater than for PAI-2 CRE bound CREB. Stable transfection of HT-1080 cells with a plasmid containing a CREB that could not be phosphorylated on Ser119 (pCI-CREB(ala119)) did not influence PMA-mediated suppression of t-PA mRNA, but markedly impaired PMA-mediated induction of PAI-2 mRNA. Our results demonstrate that the Ser119 residue of CREB plays a crucial role in PMA-mediated induction of PAI-2 gene expression, whereas PMA-mediated suppression of t-PA in HT-1080 cells requires a different process.

Cyclic AMP Response Element Modulator↗
PubMed2000

Striatal extracts promote the survival and phenotypic expression of rat fetal dopaminergic neurons in vitro.

To begin to identify novel protein(s) that acts on nigral dopaminergic (DA) neurons, we characterized trophic effects of DA-depleted striatum on survival of fetal DA neurons in the present study. Treatment of ventral mesencephalic cultures with the striatal extracts delayed DA cell death in a dose-dependent manner. This effect was partially dependent on brain-derived neurotrophic factor (BDNF), but not glial cell line-derived neurotrophic factor (GDNF), present in the extracts. Furthermore, we addressed the hypothesis that the striatum-derived substances can elicit DA phenotypic expression of striatal cells in cultures. The striatal extract was found to be able to induce expression of tyrosine hydroxylase in cultured striatal cells in the presence of dopamine. These data suggest that denervation of the striatum resulted in production of neurotrophic factors, including BDNF and as-yet-unidentified trophic substances, which may be responsible for the increased survival and DA phenotype expression in DA neurons.

Animals↗
PubMed2000

Differential expression of mRNAs of GDNF family in the striatum following 6-OHDA-induced lesion.

Changes of mRNA levels of GDNF and its recently discovered congeners persephin, neurturin, artemin in the striatum of lesioned side following 6-hydroxydopamine (6-OHDA) lesion in rodents were investigated with semi-quantitative RT-PCR. Two weeks after the lesions were made, mRNA levels of GDNF family members, except for neurturin, were significantly increased in the striatum on the side ipsilateral to the lesion compared with equivalent tissue of sham control. This increase reached a maximal level 5-7 weeks post-lesion. The marked increase of BDNF mRNA expression was also observed in the ipsilateral striatum with similar time course. These findings suggest that 6-OHDA-induced lesions can change gene expression in denervated target tissue, and that mRNA levels of GDNF family members in striatal cells may be modulated by afferent dopaminergic input in a slow-rising and long-lasting fashion.

Animals↗
PubMed2000

Structural and functional similarities in the ADP-forming amide bond ligase superfamily: implications for a substrate-induced conformational change in folylpolyglutamate synthetase.

Comparison of the three-dimensional structures of folylpolyglutamate synthetase (FPGS) and the bacterial cell wall ligase UDP-N-acetylmuramoyl-l-alanine:d-glutamate ligase (MurD) reveals that these two enzymes have a remarkable structural similarity despite a low level of sequence identity. Both enzymes have a modular, multi-domain structure and catalyse a similar ATP-dependent reaction involving the addition of a glutamate residue to a carboxylate-containing substrate, tetrahydrofolate in the case of FPGS, and UDP-N-acetylmuramoyl-l-alanine in the case of MurD. Site-directed mutations of selected residues in the active site of Lactobacillus casei FPGS (P74A, E143A, E143D, E143Q, K185A, D313A, H316A, G411A and S412A) showed that most of these changes resulted in an almost complete loss of activity. Several of these amino acid residues in FPGS are found in structurally equivalent positions to active-site residues in MurD. Some insights into the function of these residues in FPGS activity are proposed, based on the roles surmised from the structures of two MurD. UDP-N-acetylmuramoyl-l-alanine.ADP complexes and a MurD. UDP-N-acetylmuramoyl-l-alanine-d-glutamate complex. Furthermore, the comparison has led us to propose that conformational changes induced by substrate binding in the reaction mechanism of FPGS result in a movement of the domains towards each other to more closely resemble the orientation of the corresponding domains in MurD. This relative domain movement may be a key feature of this new family of ADP-forming amide bond ligases.

Adenosine Diphosphate↗
PubMed2000

Tumor-specific CD4(+) suppressor T-cell clone capable of inhibiting rejection of syngeneic sarcoma in A/J mice.

Elimination of CD4(+) T cells by anti-CD4 antibody caused regression of a methylcholanthrene-induced S713a sarcoma growing in syngeneic A/J mice, and the tumor regression was essentially required for CD8(+) T cells. A CD4(+) T-cell clone, designated T595B1, was established to elucidate the characteristics of CD4(+) suppressor T cells. T595B1 expressed CD3, T-cell receptor (TCR)beta, TCR-Vbeta2, CD4, CD25, CD45RB, CD44, LFA-1, and ICAM-1 molecules on its cell surface and showed MHC class II I-E(k)-restricted tumor antigen-specific proliferation. T595B1 cells specifically suppressed in vitro CTL induction of S713a in a dose-dependent manner. Furthermore, culture supernatant of T595B1 cells also suppressed in vitro CTL induction, but its suppressive activity was not specific. Cytokine analyses revealed that T595B1 cells secreted IL-4, IL-5, IL-6, and IL-10 but not IFN-gamma, IL-2, TNF, or TGFbeta, indicating that this clone belongs to the so-called T helper 2 (Th2) type. However, the suppressive activity of the culture supernatant to the in vitro CTL induction was not abrogated by any neutralizing antibody to IL-4, IL-5, IL-6, IL-10, or TGF-beta. Repeated adoptive transfer of T595B1 cells into syngeneic immune mice entirely impaired their capacity to reject S713a sarcoma, resulting in progressive tumor growth in these mice.

Adoptive Transfer↗