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Biomedical subjects

Y Xiao

Publications and source records attributed to Y Xiao.

At least 91 records · Page 5Linked to original sources
PubMed2000

Thyroid hormone coordinates respiratory control maturation and adenine nucleotide translocator expression in heart in vivo.

BACKGROUND: The signal transduction mechanism linking mitochondrial ATP synthesis with cytosolic ATP utilization in heart changes during postnatal development in vivo. This maturational process occurs in parallel with accumulation of mitochondrial adenine nucleotide translocator (ANT), which provides a possible site for respiratory control. We postulated that thyroid hormone regulates these maturational processes. METHODS AND RESULTS: We used (31)P MR spectroscopy to determine the relationship between myocardial high-energy phosphates, phosphocreatine, and ADP and oxygen consumption (MVO(2)) during epinephrine stimulation in 32- to 40-day-old lambs thyroidectomized after birth (THY) and age-matched controls. Steady-state protein and mRNA levels for ANT isoforms and beta-F(1)-ATPase were assessed from left ventricular tissues by Western and Northern blotting. With greater doses of epinephrine, THY attained lower peak MVO(2) than controls (P:<0.05). Controls maintained high-energy phosphate levels, unlike THY, which demonstrated significantly decreased phosphocreatine/ATP and increased cytosolic ADP despite lower peak MVO(2). No significant differences in beta-F(1)-ATPase protein or mRNA occurred between groups. However, ANT isoform mRNA levels were 2-fold greater and protein levels 4-fold greater in control hearts. CONCLUSIONS: These data imply that the maturational shift away from ADP-mediated respiratory control is regulated by thyroid hormone in vivo. Specific thyroid-modulated increases in ANT mRNA and protein imply that this regulation occurs in part at a pretranslational level.

Adenosine Diphosphate↗
PubMed2000

Expression and purification of a recombinant DNA-binding domain of ADR6 protein from Escherichia coli and its secondary structure characterization.

From Saccharomyces cerevisiae, a piece of ADR6 gene that encodes a DNA-binding domain of ADR6 protein was cloned and expressed in Escherichia coli. With Ni-chelating column and high-performance liquid chromatography (HPLC), This recombinant protein (RDB-ADR6) could reach more than 95% purity. The molecular weight (MW) of RDB-ADR6 is 13405 Da with mass spectra technique containing 114 amino acid residues. Structural aspects of RDB-ADR6 were examined by spectroscopic techniques. It contains approximately 25% alpha-helix and 24% beta-turn both with circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). Percent of beta-sheet differs between these two methods in that 22% in CD while 35% in FTIR. RDB-ADR6 contains only one tryptophan residue. Fluorescence studies show that this residue may lie in a hydrophobic circumstance either on or near the surface of the molecule. This was confirmed by a blue shift of 20 nm in the fluorescence emission spectrum as compared to the protein in 6 M guanidine hydrochloride (GuHCl) and by quenching studies with KI. Effects of different pH and SDS in different concentration on the secondary structure of RDB-ADR6 were also studied. A model was obtained by comparative modeling with homologous known structure protein by program Modeller 4.

Amino Acid Sequence↗
PubMed2000

[Evaluation of two-dimensional and color Doppler ultrasonography in diagnosis of peritoneal mesothelioma].

OBJECTIVE: To evaluate diagnostic value of two-dimensional and color Doppler ultrasonography in peritoneal mesothelioma. METHODS: Ten cases of ultrasonograms and color Doppler ultrasonographic manifestations in 3 cases of them were analysed and compared with the outcome of surgery and pathology. RESULTS: Images of 8 cases were showed to be hypoechoic mass which some had no-echoic area; 5 to be ascites; 5 to be peritoneal thickness. With color Doppler, we saw the mass which is rich in the blood flow. CONCLUSION: Combining clinical manifestations, ultrasonography is of benefit to initial diagnosis of peritoneal mesothelioma.

Adult↗
PubMed2000

An immunosuppressive and anti-inflammatory HLA class I-derived peptide binds vascular cell adhesion molecule-1.

BACKGROUND: A synthetic peptide corresponding to residues 75-84 of HLA-B2702 modulates immune responses in rodents and humans both in vitro and in vivo. METHODS: We used a yeast two-hybrid screening, an in vitro biochemical method, and an in vivo animal model. RESULTS: Two cellular receptors for this novel immunomodulatory peptide were identified using a yeast two-hybrid screen: immunoglobulin binding protein (BiP), a member of the heat shock protein 70 family, and vascular cell adhesion molecule (VCAM)-1. Identification of BiP as a ligand for this peptide confirms earlier biochemical findings, while the interaction with VCAM-1 suggests an alternative mechanism of action. Binding to the B2702 peptide but not to closely related variants was confirmed by ligand Western blot analysis and correlated with immunomodulatory activity of each peptide. In mice, an ovalbumin-induced allergic pulmonary response was blocked by in vivo administration of either the B2702 peptide or anti-VLA-4 antibody. CONCLUSIONS: We propose that the immunomodulatory effect of the B2702 peptide is caused, in part, by binding to VCAM-1, which then prevents the normal interaction of VCAM-1 with VLA-4.

Amino Acid Sequence↗
PubMed2000

Distinct antitumor properties of a type IV collagen domain derived from basement membrane.

Vascular basement membrane is an important structural component of blood vessels. During angiogenesis this membrane undergoes many alterations and these changes are speculated to influence the formation of new capillaries. Type IV collagen is a major component of vascular basement membrane, and recently we identified a fragment of type IV collagen alpha2 chain with specific anti-angiogenic properties (Kamphaus, G. D., Colorado, P. C., Panka, D. J., Hopfer, H., Ramchandran, R., Torre, A., Maeshima, Y., Mier, J. W., Sukhatme, V. P., and Kalluri, R. (2000) J. Biol. Chem. 275, 1209-1215). In the present study we characterize two different antitumor activities associated with the noncollagenous 1 (NC1) domain of the alpha3 chain of type IV collagen. This domain was previously discovered to possess a C-terminal peptide sequence (amino acids 185-203) that inhibits melanoma cell proliferation (Han, J., Ohno, N., Pasco, S., Monboisse, J. C., Borel, J. P., and Kefalides, N. A. (1997) J. Biol. Chem. 272, 20395-20401). In the present study, we identify the anti-angiogenic capacity of this domain using several in vitro and in vivo assays. The alpha3(IV)NC1 inhibited in vivo neovascularization in matrigel plug assays and suppressed tumor growth of human renal cell carcinoma (786-O) and prostate carcinoma (PC-3) in mouse xenograft models associated with in vivo endothelial cell-specific apoptosis. The anti-angiogenic activity was localized to amino acids 54-132 using deletion mutagenesis. This anti-angiogenic region is separate from the 185-203 amino acid region responsible for the antitumor cell activity. Additionally, our experiments indicate that the antitumor cell activity is not realized until the peptide region is exposed by truncation of the alpha3(IV)NC1 domain, a requirement not essential for the anti-angiogenic activity of this domain. Collectively, these results effectively highlight the distinct and unique antitumor properties of the alpha3(IV)NC1 domain and the potential use of this molecule for inhibition of tumor growth.

Angiogenesis Inhibitors↗
PubMed2000

Human interferon-beta inhibits binding of HIV-1 gp41 to lymphocyte and monocyte cells and binds the potential receptor protein P50 for HIV-1 gp41.

Previous findings have indicated that HIV-1 gp41 like human type I interferon (IFN) could inhibit lymphocyte proliferation and up-modulate MHC class I, II and ICAM-1 molecule expression, and a common epitope exists between gp41 and type I interferon (IFN-alpha and -beta) in the receptor binding regions. To clarify the relationship between human type I interferon and HIV-1 gp41, we tried to inhibit recombinant soluble gp41-binding to human T, B and monocyte cell lines by human IFN-alpha, -beta and -gamma. It was interestingly observed that IFN-beta after preincubating with cells could inhibit the binding of rsgp41 to H9, Raji and U937 cells (T, B and monocyte cell lines), while this binding could not be inhibited by another type I interferon (IFN-alpha) and a type II interferon (IFN-gamma). It was further examined whether human IFN-alpha and -beta bind to the gp41 binding protein P50. In ELISA-assay, the human IFN-beta, but not IFN-alpha, could bind to P50 which was identified as a potential cellular receptor protein for gp41-binding. By the affinity capillary electrophoresis (ACE) analysis, formation of stable IFN-beta-P50 complex was observed. These results indicate that IFN-beta binds the potential receptor protein P50. Based on these experimental evidences and previous studies, it was presumed that the potential cellular receptor protein P50 may be the 51 kDa subunit of human IFN-alpha/beta receptor, which needs to be verified in the future.

Cell Line↗
PubMed2000

[Measurement of the inferior vena cava diameter for estimating fluid status in hemodialysis patients].

OBJECTIVE: To investigate the clinical application of inferior vena cava diameter (VCD) for estimating fluid status. METHODS: VCD were measured during the expiratory phase (VCD-E) in 64 patients before hemodialysis (hypervolemia) and 71 normovolemia cases by ultrasonography, meanwhile collapsibility index (CI) were calculated. RESULTS: (1) VCD-E was (10.69 +/- 2.18) mm, CI was (26.24 +/- 6.34)% in normovolemic group; and (13.78 +/- 2.95) mm, (19.28 +/- 6.24%) in hypervolemic group respectively. There were significant differences in both (P < 0.01). (2) Change of VCD-E between pre- and post-dialysis was related with the amount of ultrafiltration during hemodialysis (r = 0.38, P < 0.01). The ratio was (2.0 +/- 1.2) mm.kg-1. (3) By using VCD-E to estimate hypervolemia, receiver operating characteristic (ROC) curve showed if VCD-E > or = 13.0 mm, the sensitivity was 87.0% and the specificity was 87.5%. CONCLUSION: VCD-E in postdialysis patients would approach (10.7 +/- 2.2) mm, which could be interpreted as being close to the dry weight. Thus VCD appears to be a valuable tool in estimating fluid status.

Adult↗
PubMed2000

Ligand binding and structural properties of segments of GABAA receptor alpha 1 subunit overexpressed in Escherichia coli.

The gamma-aminobutyric acid, type A (GABA(A)), receptor is the target for numerous therapeutic compounds. In the present study, the Gln(28)-Leu(296), Gln(28)-Arg(276), Gln(28)-Arg(248), and Gln(28)-Glu(165) (numbering of bovine precursor protein) segments of its alpha(1) subunit were overexpressed in Escherichia coli, along with Cys(166)-Leu(296) produced previously, for structural analysis by circular dichroism and ligand binding studies by fluorescence spectroscopy. Results showed that the protein segments were rich in beta-sheet structures. Binding of the fluorescent benzodiazepine Bodipy-FL Ro-1986 was evident from fluorescence resonance energy transfer and fluorescence anisotropy measurements. The binding affinity was in the micromolar range. The binding was attributable more to Cys(166)-Leu(296) than to Gln(28)-Glu(165) and was inhibited by known central benzodiazepine site ligands. Three point mutations, Y187A, T234A, and Y237A, were found to perturb protein secondary structures. Studies with the single Trp mutants W198Y and W273Y indicated that Trp(273) was closer to the binding site than Trp(198).

Amino Acid Sequence↗
PubMed2000

[Effects of dietary lipids on serum cholesterol of elder hypercholesterolemic patients].

The intake of dietary lipids of 167 elder hypercholesterolemic patients was collected by a three-day recorded dietary survey. At the mean time, their serum total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels were detected and analyzed. The results showed the effects of dietary lipids and body mass index (BMI) were great on serum cholesterol levels; BMI, dietary cholesterol and saturated fatty acid were positively related to serum TC and LDL-C; serum HDL-C and HDL-C/TC ratio were positively related with dietary monounsaturated fatty acid, and negatively related with BMI. The results indicate that decreasing the intake of dietary cholesterol and saturated fatty acid, controlling body weight and increasing dietary monounsaturated fatty acid intake will have important benefits on the prevention and treatment of hypercholesterolemia and cardiovascular diseases.

Adult↗
PubMed2000

Dox-dependent SIVmac with tetracycline-inducible promoter in the U3 promoter region.

An attenuated live vaccine is a candidate in developing vaccines against human immunodeficiency virus type 1 (HIV-1). The study using macaques and simian immunodeficiency virus (SIVmac) showed an attenuated virus to be more effective than any other vaccine candidate. However, development of a safer vaccine is required for clinical application. In this study, we constructed pSIVmac Delta nef with tetracycline inducible promoter (pTet) and tried to control viral expression in a drug-dependent manner. Promoter/enhancer motifs in the U3 region of the long terminal repeats (LTRs) were serially deleted and replaced with pTet. In mutant LTRs, which lack NF-kappaB and Sp1 binding sites, TATA box motifs, and the 5' half of the U3 region, promoter activity was stringently controlled by doxycycline (Dox). Their activities were similar to or higher than that of wild-type LTR in the presence of Dox, based on the transient chloramphenicol acetyltransferase reporter assay. Three of these mutant LTRs were introduced into the pSIVmac239 Delta nef genome. Viral protein from these viruses was efficiently expressed in a Dox-dependent manner after transfection to a HeLa cell, which expresses reverse tetracycline transactivator (rtTA). The 2-LTR-form viral DNA of these viruses could be detected in M8166 cells that had been infected with supernatants from the transfected rtTA HeLa cell. These results suggest that pSIVmac Delta nef containing mutant LTRs can proceed through one viral replication cycle consisting of transcription, formation of viral particles, infection to cells, and reverse transcription. Although continuous replication of these Dox-dependent viruses requires a supply of rtTA as a constituent for the pTet-On viral genome, the successful replacement of the original promoter with a drug-dependent promoter suggests a new possibility for developing a safer attenuated live virus.

Doxycycline↗
PubMed2000

Partial uncoupling of the mitochondrial membrane by a heterozygous null mutation in the gene encoding the gamma- or delta-subunit of the yeast mitochondrial ATPase.

Prior genetic studies indicated that the yeast mitochondrial ATP synthase can be assembled into enzyme complexes devoid of the gamma-, delta-, or epsilon-subunits (Lai-Zhang, J., Xiao, Y., and Mueller, D. M. (1999) EMBO J. 18, 58-64). These subunit-deficient complexes were postulated to uncouple the mitochondrial membrane thereby causing negative cellular phenotypes. This study provides biochemical and additional genetic data that support this hypothesis. The genetic data indicate that in a diploid cell, a heterozygous deletion mutation in the gene encoding the gamma- or delta-subunit of the ATPase is semidominant negative due to a decrease in the gene number from 2 to 1. However, the heterozygous atp2Delta mutation is epistatic to the heterozygous mutation in the gene encoding gamma or delta, suggesting that the semidominant negative effect is because of a gain of activity in the cells. Biochemical studies using mitochondria isolated from the yeast strains that are heterozygous for a mutation in gamma or delta indicate that the mitochondria are partially uncoupled. These results support the hypothesis that the negative phenotypes are caused by the formation of a gamma- or delta-less ATP synthase complex that is uncoupled.

Adenosine Triphosphatases↗
PubMed2000

Chromosome-specific telomeric associations in Chinese hamster embryonic cells.

Telomeric associations (TAs) represent an important cytogenetic marker of human tumor cells. It has been thought that the primary cause of TAs is telomere shortening. However, we report here a surprising aspect of telomere maintenance in primary Chinese hamster embryonic (CHE) cells: relatively high frequencies of TAs in spite of normal telomere length. These TAs are present in both interphase and metaphase cells, suggesting that metaphase TAs may be relics of interphase chromosome organization. In addition, some TAs observed here are chromosome-specific and recurrent in at least three consecutive cell cycles in two different CHE cell strains. In spite of relatively high frequencies of TAs, none of the CHE strains show chromosome instability resulting from breakage-fusion-bridge cycles, as would be expected from tumor cell studies. It appears that TAs in CHE cells may be reversible events. These results are discussed in light of current understanding of telomere biology.

Animals↗
PubMed2000

Influence of microgravity on ultrastructure and storage reserves in seeds of Brassica rapa L.

Successful plant reproduction under spaceflight conditions has been problematic in the past. During a 122 d opportunity on the Mir space station, full life cycles of Brassica rapa L. were completed in microgravity in a series of three experiments in the Svet greenhouse. Ultrastructural and cytochemical analyses of storage reserves in mature dry seeds produced in these experiments were compared with those of seeds produced during a high-fidelity ground control. Additional analyses were performed on developing Brassica embryos, 15 d post pollination, which were produced during a separate experiment on the Shuttle (STS-87). Seeds produced on Mir had less than 20% of the cotyledon cell number found in seeds harvested from the ground control. Cytochemical localization of storage reserves in mature cotyledons showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in ground control seeds. Protein bodies in mature cotyledons produced in space were 44% smaller than those in the ground control seeds. Fifteen days after pollination, cotyledon cells from mature embryos formed in space had large numbers of starch grains, and protein bodies were absent, while in developing ground control seeds at the same stage, protein bodies had already formed and fewer starch grains were evident. These data suggest that both the late stage of seed development and maturation are changed in Brassica by growth in a microgravity environment. While gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.

Brassica↗
PubMed2000

A centralized dose calculation system for radiation therapy.

Centralization of treatment planning in a radiation therapy department is a realistic strategy to achieve an integrated and quality-controlled planning system, especially for institutions with numerous affiliations. The rapid evolution of computer hardware and software technology makes this a distinct possibility. However, the procedure of three-dimensional treatment planning involves a number of steps, such as: (1) input of patient computed tomography (CT) images and contour information; (2) interactions with local devices such as a film digitizer; and (3) output of beam information to be integrated with the record and verify the system. A full-fledged realization of the web-based centralized three-dimensional treatment planning system will require an extensive commercial development effort. We have developed and incorporated a web-based Timer/Monitor Unit (MU) program as a first step towards the full implementation of a centralized treatment planning system. The software application was developed in JAVA language. It uses the internet server and client technology. With one server that can handle multiple threads, it is a simple process to access the application anywhere on the network with an internet browser. Both the essential data needed for the calculation and the results are stored on the server, which centralizes the maintenance of the software and the storage of patient information.

Computer Systems↗
PubMed2000

Gravity independence of seed-to-seed cycling in Brassica rapa.

Growth of higher plants in the microgravity environment of orbital platforms has been problematic. Plants typically developed more slowly in space and often failed at the reproductive phase. Short-duration experiments on the Space Shuttle showed that early stages in the reproductive process could occur normally in microgravity, so we sought a long-duration opportunity to test gravity's role throughout the complete life cycle. During a 122-d opportunity on the Mir space station, full life cycles were completed in microgravity with Brassica rapa L. in a series of three experiments in the Svet greenhouse. Plant material was preserved in space by chemical fixation, freezing, and drying, and then compared to material preserved in the same way during a high-fidelity ground control. At sampling times 13 d after planting, plants on Mir were the same size and had the same number of flower buds as ground control plants. Following hand-pollination of the flowers by the astronaut, siliques formed. In microgravity, siliques ripened basipetally and contained smaller seeds with less than 20% of the cotyledon cells found in the seeds harvested from the ground control. Cytochemical localization of storage reserves in the mature embryos showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in the ground control seeds. While these successful seed-to-seed cycles show that gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.

Brassica↗
PubMed2000

HIV-2 transmembrane protein gp36 binds to the putative cellular receptor proteins P45 and P62.

Based on the findings that two cellular proteins of 45 kDa (P45) and 62 kDa (P62) serve as the putative receptor molecules for binding of HIV-1 transmembrane protein gp41 to human T, B lymphocytes and monocytes, we examined whether HIV-2 gp36 and HIV-1 gp41 share the putative receptor proteins P45 and P62. In SPR-assay (SPR: surface plasmon resonance), the recombinant soluble gp36 (rsgp36: Env aa518-678 from clone ROD) like the recombinant soluble gp41 (rsgp41: Env aa539-684 from clone BH10) was binding to P45 and P62. By affinity capillary electrophoresis (ACE)-analysis, formation of stable rsgp36-P45 and rsgp36-P62 complexes were confirmed, and the interactions of rsgp36 with P45 and P62 is quite strong with a fast association rate and a slow dissociation rate. These results indicate that HIV-2 gp36 and HIV-1 gp41 have the common putative cellular receptor proteins P45 and P62, and the binding of gp36 to human lymphocytes and monocytes could be based on the interaction between gp36 and P45 and P62.

Amino Acid Sequence↗