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Y Bai

Publications and source records attributed to Y Bai.

At least 145 records · Page 8Linked to original sources
PubMed1996

Interleukin-1 involvement in the induction of leukemia inhibitory factor mRNA expression following axotomy of sympathetic ganglia.

Axotomy of superior cervical (sympathetic) ganglia (SCG) results in increased neuropeptide gene expression. In vitro, neuropeptide gene expression is similarly increased by exposure to the inflammatory cytokine interleukin-1 (IL-1). The effect of IL-1 in-vitro has been shown to be mediated by leukemia inhibitory factor (LIF). Since IL-1 regulates neuropeptide expression via LIF in vitro, we asked whether axotomy in vivo produces an increase in LIF mRNA, and whether that increase is regulated by IL-1 activity. Within 6 h following axotomy, ganglionic LIF mRNA is substantially elevated. Moreover, axotomy produces a rapid and transient increase in intraganglionic IL-1 beta mRNA, followed rapidly by an increase in ICAM-1 mRNA, thereby suggesting a local source of IL-1 activity. Pretreatment with the anti-inflammatory agent dexamethasone (DEX) reduces the increases of both IL-1 beta and LIF mRNAs following axotomy. mRNA encoding the specific signal-transducing Type I IL-1 receptor is present in unlesioned SCG in vivo, and increases following axotomy. Local application of IL-1 beta in vivo induces LIF mRNA even in uninjured ganglia, though not to the extent seen with axotomy. DEX treatment blocks this IL-1 beta-mediated increase in LIF mRNA. Therefore, DEX blocks the induction of LIF mRNA by inhibiting both the production of IL-1 and its action on LIF gene expression. Axotomy of a homozygous IL-1 receptor type I gene knockout mouse leads to a delayed and/or diminished induction of LIF mRNA in SCG, but does not prevent LIF mRNA expression. We conclude that while IL-1 is likely to be involved in the cascade of gene expression that follows axotomy, it alone is not sufficient to mediate the full induction of LIF mRNA by axotomy.

Animals↗
PubMed1996

[A study on relationship between glutathione S-transferase mu gene deletion and senile cataract susceptibility].

OBJECTIVE: To study the relationship between glutathione S-transferase mu (GST mu) gene deletion and senile cataract (SC) susceptibility. METHOD: Polymerase chain reaction (PCR) method was used to investigate the rates of GST mu gene deletion in 59 cases with SC and 112 healthy controls. RESULTS: The rate of GST mu gene deletion in cases with SC was 69.5% which was significantly higher than that of the controls, 50.9% (P < 0.05). An analysis stratified by smoking and nonsmoking showed that GST mu gene deletion rate in smoking subjects with SC was higher. Because of the small sample size of this study, although the rate of GST mu gene deletion in smoking subjects with SC has reached 72.4%, that is not significantly different from that of the controls statistically (P > 0.05). CONCLUSION: SC correlates with GST mu gene deletion and GST mu gene deletion is one of the hereditary factors for susceptibility to SC.

Aged↗
PubMed1995

Binding sites for transcription factor NTF-1/Elf-1 contribute to the ventral repression of decapentaplegic.

The Dorsal morphogen is a transcription factor that activates some genes and represses others to establish multiple domains of gene expression along the dorsal/ventral axis of the early Drosophila embryo. Repression by Dorsal appears to require accessory proteins that bind to corepression elements in Dorsal-dependent regulatory modules called ventral repression regions (VRRs). We have identified a corepression element in decapentaplegic (dpp), a zygotically active gene that is repressed by the Dorsal morphogen. This dpp repression element (DRE) is located within a previously identified VRR and close to essential Dorsal-binding sites. We have purified a factor from Drosophila embryo extracts that binds to the DRE but not to mutant forms of the DRE that fail to support efficient repression. This protein also binds to an apparently essential region in a VRR associated with the zerknüllt (zen) gene. One of the DREs in the dpp VRR overlaps the binding site for a potential activator protein suggesting that one mechanism of ventral repression may be the mutually exclusive binding of repressor and activator proteins. We have found the DRE-binding protein to be identical to NTF-1 (equivalent to Elf-1, the product of the grainyhead gene), a factor originally identified as an activator of the Ultrabithorax and Dopa decarboxylase promoters. NTF-1 mRNA is synthesized during oogenesis and deposited in the developing oocyte where it is available to contribute to ventral repression during early embryogenesis. Previous studies have shown that overexpression of NTF-1 in the postblastoderm embryo results in a phenotype that is consistent with a role for this factor in the repression of dpp later in embryogenesis.

Animals↗
PubMed1995

Identification and characterization of a TFIID-like multiprotein complex from Saccharomyces cerevisiae.

Although the mechanisms of transcriptional regulation by RNA polymerase II are apparently highly conserved from yeast to man, the identification of a yeast TATA-binding protein (TBP)-TBP-associated factor (TAFII) complex comparable to the metazoan TFIID component of the basal transcriptional machinery has remained elusive. Here, we report the isolation of a yeast TBP-TAFII complex which can mediate transcriptional activation by GAL4-VP16 in a highly purified yeast in vitro transcription system. We have cloned and sequenced the genes encoding four of the multiple yeast TAFII proteins comprising the TBP-TAFII multisubunit complex and find that they are similar at the amino acid level to both human and Drosophila TFIID subunits. Using epitope-tagging and immunoprecipitation experiments, we demonstrate that these genes encode bona fide TAF proteins and show that the yeast TBP-TAFII complex is minimally composed of TBP and seven distinct yTAFII proteins ranging in size from M(r) = 150,000 to M(r) = 25,000. In addition, by constructing null alleles of the cloned TAF-encoding genes, we show that normal function of the TAF-encoding genes is essential for yeast cell viability.

Amino Acid Sequence↗
PubMed1995

Proteolysis prevents in vivo chimeric fusion protein import into yeast mitochondria. Cytosolic cleavage and subcellular distribution.

The in vivo import of liver mitochondrial aldehyde dehydrogenase was investigated in yeast by constructing fusion proteins between its leader sequence and beta-galactosidase. Only 7% of the protein was imported. If 21 or 71 amino acids from the mature portion of aldehyde dehydrogenase were included in the construct, 40% was imported. The protein remaining in cytosol was sequenced. When the leader was fused directly to beta-galactosidase, the first 7 residues of the leader were missing. When 21 residues of mature aldehyde dehydrogenase were included, the entire leader plus 6 residues of the mature portion were missing; if 71 residues of mature aldehyde dehydrogenase were included, the first residue found corresponds to the 66th residue of the mature portion. When the leader was fused directly to beta-galactosidase, no processing of the imported protein occurred, and the N-terminal amino acid was blocked, presumably by acetylation. If the 21-amino acid insert was included, processing occurred. A modified leader sequence lacking the three-amino acid linker (RGP) was imported but not processed, just as we found in vitro (Thornton, K., Wang, Y., Weiner, H., and Gorenstein, D.G. (1993) J. Biol. Chem. 268, 19906-19914). The less than 100% import of pre-aldehyde dehydrogenase was due to the action of a post-translational protease attack which prevented import by destroying the leader peptide segment.

Aldehyde Dehydrogenase↗
PubMed1995

Protein folding intermediates: native-state hydrogen exchange.

The hydrogen exchange behavior of native cytochrome c in low concentrations of denaturant reveals a sequence of metastable, partially unfolded forms that occupy free energy levels reaching up to the fully unfolded state. The step from one form to another is accomplished by the unfolding of one or more cooperative units of structure. The cooperative units are entire omega loops or mutually stabilizing pairs of whole helices and loops. The partially unfolded forms detected by hydrogen exchange appear to represent the major intermediates in the reversible, dynamic unfolding reactions that occur even at native conditions and thus may define the major pathway for cytochrome c folding.

Cytochrome c Group↗
PubMed1995

Thermodynamic parameters from hydrogen exchange measurements.

Just as exchangeable hydrogens that are controlled by global unfolding can be used to measure thermodynamic parameters at a global level, hydrogens that are exposed to exchange by local unfolding reactions may be used to obtain locally resolved energy parameters. Results with the hemoglobin system demonstrate the ability of HX methods to locate functionally important changes in a protein and to measure the energetic contribution of each. These results offer the promise that HX measurements may be used to delineate, in terms of definable bonds and their energies and interactions, the network of interactions that Hb and other proteins use to produce their various functions.

Chromatography, High Pressure Liquid↗
PubMed1995

N-oxides of some norditerpenoid alkaloids.

Eight new N-oxides [1-8] of the norditerpenoid alkaloids aconitine, ajacine, delphinine, delphisine, deltaline, heteratisine, lappaconitine, and N-deacetyllappaconitine have been prepared with m-chloroperbenzoic acid. The structures of these compounds were established on the basis of their spectroscopic data (1H, 13C, DEPT, COSY, HETCOR, and selective INEPT nmr experiments). The complete nmr chemical shift assignments for all eight N-oxides are reported. Table 2 shows the differences between the 13C-nmr shifts of the N-oxides compared with those of the parent alkaloids.

Chlorobenzoates↗
PubMed1995

Species-specific activity of rat recombinant interleukin-1 beta.

We have constructed expression clones for mature rat interleukin-1 beta (IL-1 beta). Using these clones, rat recombinant IL-1 beta (rrIL-1 beta) was prepared and purified by a single-step cation-exchange chromatography method. In addition, synthetic rrIL-1 beta mRNA was transcribed and used to synthesize radiolabeled 35S-rrIL-1 beta for binding studies. The rrIL-1 beta produced was demonstrated to have IL-1 bioactivity in a mouse thymocyte proliferation assay, in which it could be blocked by inclusion of human recombinant IL-1 receptor antagonist (hrIL-1Ra). Similarly, rrIL-1 beta induced LIF mRNA expression in cultured rat sympathetic ganglia. In each case, the maximal dose of rrIL-1 beta was similar to that of human IL-1 beta. However, the peak response in rat tissue was twofold higher with rat IL-1 beta than with human IL-1 beta. The expression of rrIL-1 beta provides a useful tool for studying IL-1 receptors in rat, in which human and mouse IL-1 beta have been found to bind poorly. Species-specific activity of rat IL-1 beta may correlate with compensatory ionic properties of rat IL-1 receptor.

Amino Acid Sequence↗
PubMed1995

[Applied study on MRI diagnosis of the oral and maxillofacial masses.].

38 cases of Oral and Maxillofacial masses were selected to be studied by MRI,combined with fine neddle aspiration cytologic examination,compared with CT scan.The authors thought that MRI was clear,high resolving power of soft tissue,able to find out the bone infiltration of the Oral Maxillofacial masses and hemangioma or lymphoangioma etc,those which were suspected to invade the crania base,tip of orbit,pterygopalatine fossa,parapharyngeal,the vital blood vessel of the neck,primary study on MRI supervising local recur after the maxillofacial tumors being resected was also done.

English Abstract↗
PubMed1995

Effects of MK-447 on thrombin-induced aggregation, secretion of ATP, and [Ca2+]i mobilization in rabbit platelets.

AIM: To study the effects of MK-447 on aggregation release reaction and intracellular calcium mobilization by thrombin. METHODS: Aggregation and release reaction were assessed by light transmission and ATP content in rabbit citrate platelet-rich plasma (PRP), and cytosolic-free calcium was measured by fluorescence and imaging. RESULTS: MK-447 (2-aminomethyl-4-t-butyl-6-iodophenol hydrochloride) induced a decrease in light transmission (DLT), so called platelet shape change, without detectable aggregation and secretion of ATP, and increased intracellular calcium concentration ([Ca2+]i) slightly in washed single platelet loaded with Fura 2, the peak value being about 160 nmol.L-1. These effects were not inhibited by egtazic acid 3 mmol.L-1 or indometacin 3 mumol.L-1. The pretreatment of PRP with MK-447 700 mumol.L-1 reduced the DLT by thrombin, potentiated and enhanced thrombin-induced aggregation and secretion of ATP in a concentration-dependent manner. Thrombin-induced [Ca2+]i mobilization (peak value: 369 +/- 45 nmol.L-1) was further enhanced by the administration of MK-447 at 2 min before the addition of thrombin, and the peak value reached 623 +/- 121 nmol.L-1 (P < 0.01). CONCLUSION: MK-447-induced platelet shape change was involved in intracellular calcium release in this preparation. MK-447 enhanced thrombin-induced aggregation and release reaction and these effects of MK-447 on aggregation and release reaction by thrombin might result from the synergistic effect of intracellular calcium mobilization.

Adenosine Triphosphate↗
PubMed1995

[Prognosis of Graves disease treated with different modalities of therapy].

A retrospective study on the prognosis of Graves disease was carried out. 224 cases, whose treatment has been stopped for 6 months to more than 10 years, were divided into 3 groups. 82 cases received long-term antithyroid drug therapy, 100 cases were treated with radioactive 131I and 42 cases had subtotal thyroidectomy. The prognosis was evaluated for 4 items according to clinical and laboratory investigations. The cured rate of long-term drug therapy in this study was higher than that reported by most of other authors, 131I therapy was the best among the 3 modalites of therapy. The incidence of permanent hypothyroidism was fairly low in the thyroidectomy group. 97.3% of the patients with exophthalmos showed improvement after treatment in all the 3 groups.

Adolescent↗
PubMed1995

Relationship between platelet density and platelet aggregation, ATP release, and cytosolic-free calcium mobilization in rabbits.

AIM: To study the relationship of platelet density and platelet functions, including aggregation, ATP release, and intracellular calcium mobilization. METHODS: Platelet density was evaluated by discontinuous gradients of Percoll and cytosolic-free calcium concentration in single platelets was measured by fluorescence and imaging. RESULTS: Rabbit platelets were assorted into 3 subpopulations using discontinuous gradients of Percoll: high density (HD, > 1.062, 20%-30%), intermediate density (ID, around 1.057, 40%-50%) and, low density (LD, < 1.051, 10%-15%). The sizes of platelets in these subpopulations were widely different (HD: 725 +/- 76; ID: 443 +/- 47; and LD: 307 +/- 46) and well correlated with the density (r = 0.988, P < 0.01). Thrombin 0.5 U-induced aggregations in the 3 subpopulations were 78 +/- 8%, 69 +/- 4%, and 62 +/- 3%, respectively and a difference was found between HD and LD (P < 0.05). The amounts of ATP released during aggregation were 4.7 +/- 0.9, 3.4 +/- 1.0, and 2.6 +/- 0.6 mumol/4 x 10(5) platelets in HD, ID, and LD groups, respectively. Thrombin 150 U-induced [Ca2+]i mobilization in HD (990 +/- 130 nmol L-1) was different (P < 0.01) from those in ID (410 +/- 80 nmol L-1) and LD (400 +/- 40 nmol L-1). Serotonin (5-HT) 3 mumol L-1 also caused [Ca2+]i mobilization in single-washed platelet subpopulations and results were similar to those of thrombin although it did not induce any detectable aggregation or release reaction. CONCLUSION: Platelet functions and intracellular calcium concentraotion were increased with platelet density in rabbits.

Adenosine Triphosphate↗
PubMed1995

[Effects of some physical and chemical factors on CGRP release from mesenteric arterial bed].

We have shown that calcitonin gene-related peptide (CGRP) is released into the circulation during endotoxin or hemorrhagic shock. In the present study, it was observed that low pH, elevated levels of lactic acid, hypertonic NaCl and hypertonic sucrose caused CGRP release from isolated mesenteric arterial bed (MAB) of rat. All the responses were blocked when MAB was pretreated with capsaicin. Ruthenium red, an inhibitor of Ca(2+)-induced Ca2+ release from intracellular Ca2+ pools, significantly inhibited the release of CGRP. In Ca2+ free medium, low pH, lactic acid and hypertonic solutions became no longer capable of inducing the release of CGRP. The above results suggest that the observed release of CGRP in MAB was mediated by capsaicin-sensitive sensory nerve endings, as a result of Ca(2+)-induced Ca2+ release from the intracellular Ca2+ store which is sensitive to ruthenium red.

Animals↗
PubMed1994

Yeast Taf170 is encoded by MOT1 and exists in a TATA box-binding protein (TBP)-TBP-associated factor complex distinct from transcription factor IID.

Our characterization of the Saccharomyces cerevisiae TATA box-binding protein (TBP) has led to the identification of nine specific yeast TBP-associated factors (TAFs) ranging in size from 170 to 25 kDa. The amino acid sequence derived from a purified TAF with an apparent M(r) of 170,000 indicates that yeast Taf170 is encoded by the essential yeast gene MOT1. We describe in this report a series of experiments that demonstrate that the protein encoded by MOT1 is a bona fide yeast TAF and that Taf170 forms a separate complex with TBP distinct from the RNA polymerase II-specific multisubunit transcription factor IID TBP-TAF complex. The significance of this unique TBP-Taf170 complex regarding transcriptional regulation is discussed.

Adenosine Triphosphatases↗
PubMed1994

Hydrogen bond strength and beta-sheet propensities: the role of a side chain blocking effect.

Amino acid side chains can enhance peptide group hydrogen bond strength in protein structures by obstructing the competing hydrogen bond to solvent in the unfolded state. Available data indicate that the steric blocking effect contributes an average of 0.5 kJ per residue to protein hydrogen bond strength and accounts for the intrinsic beta-sheet propensities of the amino acids. In available data for helical models, the contribution to alpha-helix propensities is obscured especially by large context-dependent effects. These issues are all related by a common side chain-dependent steric clash which disfavors peptide to water H-bond formation, peptide to catalyst complexation in hydrogen exchange reactions (Bai et al., Proteins 17:75-86, 1993), and peptide to peptide H-bonding in the helical main chain conformation (Creamer and Rose, Proc. Natl. Acad. Sci. U.S.A. 89:5937-5941, 1992) but not in beta-strands.

Hydrogen Bonding↗
PubMed1994

Protein stability parameters measured by hydrogen exchange.

The hydrogen exchange (HX) rates of the slowest peptide group NH hydrogens in oxidized cytochrome c (equine) are controlled by the transient global unfolding equilibrium. These rates can be measured by one-dimensional nuclear magnetic resonance and used to determine the thermodynamic parameters of global unfolding at mild solution conditions well below the melting transition. The free energy for global unfolding measured by hydrogen exchange can differ from values found by standard denaturation methods, most notably due to the slow cis-trans isomerization of the prolyl peptide bond. This difference can be quantitatively calculated from basic principles. Even with these corrections, HX experiments at low denaturant concentration measure a free energy of protein stability that rises above the usual linear extrapolation from denaturation data, as predicted by the denaturant binding model of Tanford.

Amines↗