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Biomedical subjects

X Yang

Publications and source records attributed to X Yang.

At least 973 records · Page 54Linked to original sources
PubMed1995

[Relation between 5 flavors and channel tropism in some traditional Chinese drugs].

In the present paper, the relationship between five flavors and channel tropism is statistically studied for 261 traditional Chinese drugs which are reported to have only on flavor in the Chinese Pharmacopeia (1990 edition). The results show that in attribution there are considerable differences between the law of bitter and the law of acrid, between the law of sweet and law of salty, and between the law of acrid and the law of salty, while the laws of other pairs of flavors are similar. The laws of channel tropism are considerably affected by the mergence of exterior and interior channels. The relationship between five flavors and channel tropism is thus widely divergent from that held by the traditional theory of five elements.

Drugs, Chinese Herbal↗
PubMed1995

[The effect of furosemide and valium on band 3 protein anion transport function in chronic respiratory failure patients].

In order to explore the effect of drugs on band 3 protein anion transport function and its clinical significance, several common drugs such as furosemide, hydrochlorothiazide, etc, were tested. The results demonstrated that furosemide, hydrochlorothiazide and valium could inhibit rapidly and reversibly the anion transport function of band 3 protein and led to HCO-3/Cl- exchange restriction. The mechanism of action of the drugs was thought to be an interaction between drugs and the two sites of band 3 protein anion transport system. The reason that pulmonary encephalopathy was induced by diuretics and sedatives may be related to the inhibition of anion transport by the drugs and reduced CO2 elimination. It was necessary to be careful in using these drugs in patients with impaired lung function, especially the patients of cor pulmonale with type II respiratory failure.

Aged↗
PubMed1994

A family of proteins containing a conserved domain that mediates interaction with the yeast SNF1 protein kinase complex.

The SNF1 protein kinase is required for the regulatory response to glucose starvation in Saccharomyces cerevisiae. SNF1 is a protein serine/threonine kinase that has been widely conserved in both plants and mammals. Previously, we identified SIP1 and SIP2 as proteins that interact with SNF1 in vivo by the two-hybrid system. We have cloned the SIP2 gene and the encoded protein is homologous to SIP1 and to GAL83, which affects glucose repression of the GAL genes. We show that SIP2 and GAL83, like SIP1, co-immunoprecipitate with SNF1 and are phosphorylated in vitro. An 80 amino acid sequence, designated the ASC domain, is highly conserved at the C-termini of all three proteins. We show that this small domain can mediate protein-protein interaction with the SNF1 kinase complex. Thus, SIP1, SIP2 and GAL83 define a family of homologous proteins that are tightly associated with the SNF1 kinase, probably in alternative forms of the complex. Genetic evidence suggests that the three proteins have distinct, but related, functions in the SNF1 pathway, and deletion of GAL83 dramatically reduces SNF1 activity in immune complex assays. We propose that SIP1, SIP2 and GAL83 act as adaptors that promote the activity of SNF1 towards specific targets.

AMP-Activated Protein Kinases↗
PubMed1994

Cloning of a novel cDNA homologous to CHIP28 water channel from ocular ciliary epithelium.

Water channel protein (CHIP28) has been initially identified from human erythrocyte and subsequently localized in human kidney, rat kidney and bovine corneal endothelium. We report here cloning of homologous cDNA (CHIP29) from an expression cDNA library constructed from bovine ciliary epithelium poly A+ that codes a 271 amino acid, 28.8 kDa protein. At the amino acid level, bovine CHIP29 is 91% identical to the CHIP28 protein. Analysis of the deduced amino acid sequence indicated a hydrophobic protein with six membrane spanning domains, one N-linked glycosylation site, two conserved NPA boxes common to MIP26 family proteins, and conserved amino acid residue cysteine 189 common to water channels. Northern blotting revealed a major mRNA of 2.8 Kb size expressed in bovine ciliary epithelium. The results presented here confirm the presence of water channel gene in the bovine ciliary epithelium, a primary site for the aqueous humor production.

Amino Acid Sequence↗
PubMed1994

Yeast SNF1 is functionally related to mammalian AMP-activated protein kinase and regulates acetyl-CoA carboxylase in vivo.

The product of the SNF1 gene is a protein kinase whose activity is essential for transcriptional activation of glucose repressed genes in Saccharomyces cerevisiae. We have cloned a mammalian AMP-activated protein kinase (AMPK) that is 46% identical to the deduced amino acid sequence of SNF1 (Carling, D., Aguan, K., Woods, A., Verhoeven, A.J.M., Beri, R., Brennan, C.H., Sidebottom, C., Davison, M.D., and Scott, J. (1994) J. Biol. Chem. 269, 11442-11448). Mammalian AMPK plays a major role in the control of lipid metabolism and phosphorylating, thereby inactivating both acetyl-CoA carboxylase and 3-hydroxy-3-methylglutaryl-CoA reductase, key regulatory enzymes in the synthesis of fatty acids and cholesterol, respectively. We present evidence indicating that, in common with its mammalian homologue, SNF1 forms part of a protein kinase cascade. SNF1 is inactivated in vitro by treatment with protein phosphatase 2A and can be reactivated using a partially purified preparation of mammalian AMPK kinase. SNF1 undergoes a time-dependent increase in activity during growth in glucose-derepressing conditions, providing the first evidence that SNF1 activity is regulated by the level of available glucose. In wild-type yeast, but not in a snf1 deletion mutant, acetyl-CoA carboxylase shows a reciprocal change in activity compared with SNF1 under glucose derepressing conditions, indicating that SNF1 regulates acetyl-CoA carboxylase in vivo. These results suggest that, in addition to their structural similarity, the role of SNF1 and AMPK in the regulation of fatty acid synthesis has been highly conserved throughout evolution.

AMP-Activated Protein Kinases↗
PubMed1994

The A1 and A1B proteins of heterogeneous nuclear ribonucleoparticles modulate 5' splice site selection in vivo.

Recent in vitro results suggest that the heterogeneous nuclear ribonucleoparticle (hnRNP) A1 protein modulates alternative splicing by favoring distal 5' splice site (5'SS) selection and exon skipping. We used a mouse erythroleukemia (MEL) cell line (CB3C7) deficient in the expression of hnRNP A1 to test whether variations in hnRNP A1 and AlB protein levels affected alternative splicing in vivo. In contrast to A1-expressing MEL cell lines, CB3C7 cells preferentially selected the proximal 13S and 12S 5'SS on the adenovirus E1A pre-mRNA. Transiently expressing the A1 or A1B cDNA in CB3C7 cells shifted 5'SS selection toward the more distal 9S donor site. A1 protein synthesis was required for this effect since the expression of a mutated A1 cDNA did not affect 5'SS selection. These results demonstrate that in vivo variations in hnRNP A1 protein levels can influence 5'SS selection.

Alternative Splicing↗
PubMed1994

Enhanced functional preservation of cold-stored rat heart by a nucleoside transport inhibitor.

This study investigates the hypothesis that inhibition of nucleoside transport during hypothermic storage elevates tissue adenosine (ADO) content and improves the function of the isolated rat heart. The hearts, flushed with a cardioplegic solution containing varying concentrations (0-100 nM) of a nucleoside transport inhibitor, S-(4-nitrobenzyl)-6-thioinosine (NBTI), were immersion-stored at 0 degrees C for 9 hr. Function was assessed after 30 min of working reperfusion. Function of unstored fresh hearts served as controls and poststorage recovery is reported as percentage of control function. Poststorage heart rate in all groups returned to control level after reperfusion. Recovery of other functional parameters in the no-NBTI group was as follows: aortic flow (AF), 56.2 +/- 4.6%; coronary flow (CF), 53.9 +/- 3.2%; cardiac output (CO), 55.5 +/- 4.0%; systolic pressure, 81.6 +/- 2.5%; work, 47.0 +/- 4.2%; and coronary vascular resistance (CVR), 157.1 +/- 7.8% of control. NBTI improved functional recovery in a dose-dependent fashion; the maximal improvement was seen at a dose of 5 nM, in which the recovery was: AF, 78.1 +/- 3.4%; CF, 73.5 +/- 4.4%; CO, 76.7 +/- 3.6%; work, 70.7 +/- 5.0%; and CVR, 127.5 +/- 4.5% of control (P < 0.05 vs. no-NBTI). The ADO A1-receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (0.1 microM) blocked the effects of 5 nM NBTI; the recovery of AF, CF, CO, work, and CVR decreased to 62.8 +/- 8.0%, 58.3 +/- 5.0%, 61.5 +/- 3.9%, 54.4 +/- 4.5%, and 163.8 +/- 12.7% of control, respectively (P < 0.05 vs. 5 nM NBTI). Tissue ADO content in 5 nM NBTI hearts at the end of storage was 0.075 +/- 0.025 mumol/g dry wt, which was significantly elevated from 0.016 +/- 0.004 mumol/g dry wt in no-NBTI hearts. Purine release during initial reperfusion was delayed in 5 nM NBTI hearts, indicating the inhibition of nucleoside transport by NBTI. But NBTI treatment did not improve end-storage or end-reperfusion myocardial ATP. In conclusion, the addition of NBTI to cardioplegic solution enhanced tissue ADO and improved poststorage function of the hypothermically stored rat heart. The effect is ADO A1-receptor mediated without invoking energy conservation.

Adenosine↗
PubMed1994

Characterization of an acetylcholine receptor alpha 3 gene promoter and its activation by the POU domain factor SCIP/Tst-1.

Genes encoding neuronal nicotinic acetylcholine receptors exhibit restricted patterns of expression in the nervous system. We are interested in elucidating the molecular mechanisms responsible for establishing these patterns of expression. This paper presents the characterization of regulatory elements upstream of the neuronal nicotinic acetylcholine receptor alpha 3 gene. We have identified a GC-rich multistart site promoter adjacent to the alpha 3 coding region. Similar alpha 3 start sites were identified in PC12 cells and sympathetic ganglion neurons, suggesting similar control mechanisms in the clonal line and peripheral neurons. The start site region lacks TATA-like sequences but does contain initiator-like sequences. We show, in transient transfection assays, that the POU domain transcription factor, SCIP/Tst-1, specifically activates alpha 3 in a neural context. Other POU domain factors tested only weakly activated or repressed alpha 3. Unexpectedly, we found that alpha 3 basal activity and SCIP/Tst-1 activation of alpha 3 is not dependent on the SCIP/Tst-1 binding sites found upstream of the gene. In addition, mutations in the SCIP/Tst-1 coding region that prevent the factor from binding to DNA with high affinity do not obliterate alpha 3 activation. These results lead us to propose that alpha 3 activation by SCIP/Tst-1 is achieved via protein-protein interactions between SCIP/Tst-1 and a specific complement of transcription factors that act directly on the promoter.

Animals↗
PubMed1994

Cytodifferentiation in Tetrahymena vorax is linked to glycosyl-phosphatidylinositol-anchored protein assembly.

The role of glycosyl-PtdIns (GPI)-anchored proteins in the cytodifferentiation of Tetrahymena vorax was examined. Labelling of cells with [3H]myristate or [3H]palmitate followed by electrophoresis showed an array of proteins carrying covalently bound lipids. Electrophoresis of protein from cells labelled with the GPI-anchor components [3H]Ins and [14C]ethanolamine revealed three polypeptides on fluorograms which have apparent molecular masses of approx. 28, 50 and 82 kDa. Labelled lipid associated with these polypeptides was susceptible to release by in vitro exposure to Bacillus thuringiensis PtdIns-specific phospholipase C (PI-PLC). Using labelled fatty acids, cells induced to differentiate showed altered GPI-anchored protein-labelling patterns in comparison with undifferentiated control cells, with a heavily labelled 32 kDa band appearing upon differentiation. Pre-incubation of cells in 10 mM D-mannosamine, an inhibitor of GPI incorporation into protein, resulted in a reduction of the incorporation of label into the three GPI-anchored proteins, nearly complete inhibition of differentiation and a reduction in the rate of digestive vacuole formation. A 50% inhibition of differentiation was obtained using 500 microM mannosamine. The inhibitory impact of D-mannosamine on differentiation could be competitively and completely reversed by the inclusion of D-mannose, but not D-glucose. Neither glucosamine nor tunicamycin inhibited differentiation. Incubation of cells in PI-PLC (5 units/ml) plus the differentiation inducer resulted in an acceleration of differentiation and generally higher percentages of differentiated cells versus controls.

Animals↗
PubMed1994

Repertoire diversity of antibody response to bacterial antigens in aged mice. IV. Study of VH and VL gene utilization in splenic antibody foci by in situ hybridization.

Mouse Abs against a bacterial epitope, the phosphorylcholine (PC) hapten are encoded by the T15 genes VH1(S107) and V kappa 22. It has been shown that PC-specific hybridomas from aged animals often express IgV gene families other than T15. To determine the extent of this age-dependent molecular shift in the anti-PC response, we examined antibody-forming cells (AFC) in individual young (2 to 4 month) and aged (20 to 24 month) mice by an in situ RNA hybridization. Mice were immunized either with PC coupled to keyhole limpet hemocyanin or with a Streptococcus pneumoniae strain R36a vaccine. Frozen splenic sections were prepared, and the clusters of PC-specific AFC (i.e., antibody foci) were identified by immunocytochemical staining. The adjacent splenic sections were hybridized with digoxigenin-labeled VH1(S107) and V kappa 22 DNA probes and with a C mu DNA probe as a control. The splenic sections were examined for 1) the number of Ab foci hybridized with the T15 probes, and 2) the estimated proportion of VH1+ and V kappa 22+ AFC within each focus. The results were comparable regardless of the form of PC Ag administered. Virtually all Ab foci (> 85%) in young mice hybridized with the T15 probes and were occupied by the VH1+/V kappa 22+ AFC. In aged mice, the fraction of PC-binding Ab foci that hybridized with a given T15 probe varied from 35% to > 85%; T15+ AFC always represented a minor population of the focus (< 50%), the remaining PC-specific AFC being C mu + but T15-. Also, there appeared to be a greater loss of the V kappa 22 expression relative to the VH1(S107). Thus it appears that the T15+, PC-reactive B cells in aged mice responded to the Ag but that they could not dominate the response. The possibility of an intrinsic molecular change in the aging B cells in discussed.

Aging↗
PubMed1994

Analysis of the SIP3 protein identified in a two-hybrid screen for interaction with the SNF1 protein kinase.

The Saccharomyces cerevisiae SIP3 gene was identified in a two-hybrid screen for proteins that interact in vivo with the SNF1 protein kinase, which is necessary for release of glucose repression. We showed that the C-terminal part of SIP3, recovered through its ability to interact with SNF1, strongly activates transcription when tethered to DNA. We have cloned and sequenced the entire SIP3 gene. The predicted 142-kD SIP3 protein contains a putative leucine zipper motif located in its C terminus. The native SIP3 protein also interacts with DNA-bound SNF1 and activates transcription of a target gene. A complete deletion of the SIP3 gene did not confer phenotypes characteristic of snf1 mutants. However, in a mutant deficient for the SNF1 kinase activity due to loss of the SNF4 stimulatory function, increased dosage of SIP3 partially restored expression of the glucose-repressible SUC2 gene. Overexpression of the C terminus of SIP3 caused defects in growth and SUC2 expression which were remedied by overexpressing SNF1. Taken together, these genetic data suggest that SIP3 is functionally related to the SNF1 protein kinase pathway.

Amino Acid Sequence↗
PubMed1994

Arachidonic acid release in renal proximal tubule cell injuries and death.

Arachidonic acid release and the effect of phospholipase inhibitors on various types of cell injuries and death to rabbit renal proximal tubule suspensions were determined. Proximal tubules were exposed to the mitochondrial inhibitor antimycin A (0.1 microM), the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (1 microM FCCP), the oxidant tert-butyl hydroperoxide (0.5 mM TBHP), or the calcium ionophore ionomycin (5 microM) in the absence or presence of the putative phospholipase inhibitors dibucaine, mepacrine, chlorpromazine, or U-26384. The phospholipase inhibitors had no effect on the proximal tubule lactate dehydrogenase (LDH) release (a marker of cell death) produced by FCCP, antimycin A, or ionomycin after 1,2, or 2 hours of exposure, respectively. Only dibucaine and mepacrine decreased LDH release in TBHP-treated proximal tubules without decreasing TBHP-induced lipid peroxidation. Antimycin A and ionomycin did not release arachidonic acid from proximal tubules prelabeled with [1-14C] arachidonic acid. In contrast, TBHP released arachidonic acid from proximal tubules prior to the onset of cell death, and dibucaine and mepacrine decreased the TBHP-induced release. Thus, phospholipase inhibitors were cytoprotective in those injuries that produced arachidonic acid release. These results suggest that arachidonic acid release and phospholipase A2 activation play a contributing role in oxidant-induced renal proximal tubule cell injury and death but not in mitochondrial inhibitor- or calcium ionophore-induced proximal tubule cell injury and death.

Animals↗
PubMed1994

Nuclear dynamics of parthenogenesis of bovine oocytes matured in vitro for 20 and 40 hours and activated with combined ethanol and cycloheximide treatment.

Bovine oocytes matured in vitro (IVM) for 20 hr vs. 40 hr were treated for activation with 7% ethanol in Dulbecco's phosphate-buffered saline for 5 min followed by incubation in M199 + 7.5% fetal calf serum containing cycloheximide (10 micrograms/ml). Treated IVM oocytes and the controls (no ethanol and cycloheximide exposures) were fixed after 0, 1, 2, 3, 4, 5, 7, 10, and 20 hr of incubation and stained 24 hr later with 1% acetoorcein to examine nuclear events. Different stages of nuclear development of the activated oocytes were identified on the basis of nuclear and chromosomal morphology. Pronuclear development was classified into four stages (PN I, II, III, and IV) according to pronuclear progression in chromatin decondensation, nucleoplasm appearance, and nuclear size. The results demonstrated that the combined activation treatment effectively drove the IVM oocytes, both young (20 hr) and aging (40 hr), out of metaphase arrest. The activation rates for young oocytes examined immediately after 0, 1, 2, 3, 4, 5, 7, 10, and 20 hr of incubation with cycloheximide were, respectively, 7%, 24%, 77%, 96%, 92%, 97%, 98%, 93%, and 98%. For aging oocytes (40 hr) the corresponding activation values at the same time intervals were 6%, 84%, 100%, 100%, 100%, 100%, 98%, 100%, and 100%, respectively. These values were significantly higher than those for the corresponding controls. The activated aging oocytes achieved peak activation response more rapidly than did young oocytes. In addition, nuclear events in aging oocytes proceeded faster than those in young ones. Spontaneous activation rates of the aging oocytes were also higher (6-57%) than those of the young ones (0-14%).

Anaphase↗
PubMed1994

Parthenogenetic development of bovine oocytes matured in vitro for 24 hr and activated by ethanol and cycloheximide.

This research was undertaken to improve development of parthenogenetic embryos following various combined treatments of ethanol and cycloheximide. In Experiment 1 in vitro matured oocytes (IVM, 24 hr) were treated with 7% ethanol for 5 min followed by incubation in 10 micrograms/ml cycloheximide in Medium 199 for 0 (control), 5, 10, and 20 hr. Development to 2-8 cells following culture for 3 days was similar among treated groups (32-41%; P > 0.05), which was higher than that of controls (6%; P < 0.05). Experiment 2 compared pre-ethanol exposures for 0, 1, 2.5, and 5 min, followed by 5 hr cycloheximide treatment on activation development. One- to 5-min groups resulted in 42-44% cleavage contrasted to 1-12% for controls (P < 0.05). Experiment 3 examined the effect on oocyte development of ethanol and different concentrations of cycloheximide (0, 1, 5, and 10 micrograms/ml). Cleavage to 2-8 cells was similar among the 5 and 10 micrograms/ml cycloheximide groups (36% and 42%, P > 0.05) but lower (P < 0.05) for the 1 micrograms/ml group (24%) and the controls (2-13%). When 5 micrograms/ml cycloheximide was used (Experiment 4), pre-exposure to ethanol (1, 2.5, and 5 min) resulted in more oocytes cleaved (38-41%) than in the cycloheximide alone group (0%) or the control (0%, P < 0.05). Experiment 5 tested blastocyst development of the activated oocytes with or without cytochalasin B treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Surface alterations of the bovine oocyte and its investments during and after maturation and fertilization in vitro.

Surface characteristics of the bovine oocyte and its investments before, during, and after maturation, and fertilization in vitro were evaluated by scanning electron microscopy (SEM). Oocyte diameters were also measured during SEM analysis of the oocyte. The cumulus cells manifested a compact structure with minimal intercellular spaces among them in the immature oocytes. These became fully expanded with increased intercellular spaces after maturation in vitro, but contracted again after fertilization. The zona pellucida (ZP) showed a fibrous, open mesh-like structure in the maturing and matured oocytes. The size and number of meshes on the ZP decreased dramatically after fertilization. The vitelline surface of immature oocytes was characterized by distribution of tongue-shaped protrusions (TSPs) varying in density. After 10 and 22 hr of maturation incubation, oocyte surface microvilli (MV) increased to become the predominant surface structure, and TSPs decreased substantially. The vitelline surface of fertilized oocytes (at 6 and 20 hr) was similar to that of the matured oocytes, but unfertilized oocytes had less dense MV than did fertilized oocytes (at 20 hr). The diameter of the oocytes decreased from 99 to 80 microns during maturation and increased to 106 microns after insemination (P < 0.05). Membrane maturation was characterized by surface changes from a TSP-predominant pattern to a MV-predominant pattern. Thus, the bovine oocyte maturation process was found to involve the expansion of cumulus cells and the maturation of the ZP, which changes dramatically upon fertilization. Also, volumetric changes occurred in ooplasm processed for SEM following oocyte maturation and insemination.

Animals↗
PubMed1994

Antifreeze glycoproteins from antarctic notothenioid fishes fail to protect the rat cardiac explant during hypothermic and freezing preservation.

The antarctic notothenioid fishes avoid freezing through the action of circulating antifreeze glycoproteins (AFGPs). This study investigated whether AFGPs could serve as cryoprotectants for the isolated rat heart under three different storage conditions. (1) Hearts were flushed with 15 mg AFGP/ml cardioplegic solution (CP) and stored for 9 h at 0 degrees C. This AFGP concentration has been reported to protect pig oocytes during hypothermic storage. (2) Hearts were flushed with 10 mg AFGP/ml CP-14 and stored frozen at -1.4 degrees C for 3 h. At this concentration the AFGPs significantly reduce the solution freezing point and also change the crystal morphology from dendritic to spicular. (3) Hearts were flushed with 10 micrograms AFGP/ml CP-15 and stored frozen at -1.4 degrees C for 5 h. At this low concentration the AFGPs have a strong inhibitory effect on ice recrystallization, but have little effect on the freezing point and less apparent effect on the crystal habit. After hypothermic or freezing storage, the functional viability was assessed by determining cardiac output (CO) during working reperfusion. No difference in CO was found between AFGP-treated and untreated hearts after 9 h of 0 degree C storage. CO in hearts frozen in CP-14 without AFGPs recovered to 50% of the freshly perfused control hearts. Hearts frozen in the presence of high concentrations of AFGPs (10 mg/ml CP-14) failed to beat upon thawing and reperfusion, although their tissue ice content was less than that found in hearts without AFGP treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The complete DNA sequence and replication analysis of the plasmid pCB2.4 from the cyanobacterium Synechocystis PCC 6803.

Both strands of small plasmid pCB2.4 from the unicellular cyanobacterium Synechocystis PCC 6803 have been sequenced and analyzed. pCB2.4 contains 2345 bp and 57% A+T. Three open reading frames (ORFs) were identified in the nucleotide sequence of one strand of pCB2.4. ORF1 and ORF3 may encode basic proteins with calculated pI values of 7.71 and 9.96, respectively. The products of these ORFs have been compared to published protein sequences in databases and do not show significant homology to other proteins including replication proteins. pCB2.4 is not similar at the global DNA level to another 2.4-kbp plasmid, pCA2.4, present in the same cells, which has been found to replicate by a rolling-circle mechanism via a single-stranded intermediate. However, a short region (37 bp) is similar in pCA2.4 and pCB2.4. This region contains a potential nicking site (GATA) for replication proteins encoded by a group of plasmids that replicate by a rolling-circle mechanism and might be used as the origin of replication for these plasmids. Detection of a low level of single-stranded intermediate for pCB2.4 in the Synechocystis 6803 suggests that pCB2.4 may also replicate by a rolling-circle mechanism.

Amino Acid Sequence↗