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Biomedical subjects

Z Yao

Publications and source records attributed to Z Yao.

At least 235 records · Page 13Linked to original sources
PubMed1993

Activation of cardiac KATP channels: an endogenous protective mechanism during repetitive ischemia.

The role of KATP channels in myocardial stunning produced by repetitive coronary occlusions was studied in barbital-anesthetized dogs. Regional percent segment function (%SS) was measured by sonomicrometry, and the monophasic action potential (MAP) in the ischemic region was measured by an epicardial probe. Under control conditions, six 5-min periods of coronary occlusion, interspersed with 10-min periods of reperfusion, and ultimately followed by 2 h of reperfusion produced regional segment dysfunction and a similar rate and amount of shortening of the MAP measured at 50% repolarization duration (MAPD50) during each successive ischemic period. Pretreatment with glibenclamide (0.3 mg/kg iv), a KATP channel antagonist, significantly prevented the reduction of MAPD50, particularly during the first occlusion period, and it worsened postischemic dysfunction. In contrast, pretreatment with aprikalim (10 micrograms/kg bolus +/- 0.1 microgram.kg-1.min-1 iv), a KATP channel opener, accelerated the rate and extent of shortening of MAPD50 during each occlusion and markedly improved %SS throughout reperfusion. Pretreatment with d-sotalol (2 mg/kg iv), an antagonist of voltage-dependent K+ channels, significantly prolonged MAPD50 of the ischemic region before coronary occlusion but did not alter the rate of shortening of MAPD50 during ischemia and did not affect the recovery of %SS. These results indicate that activation of KATP channels during ischemia with the resultant shortening of the MAPD50 is an endogenous adaptive mechanism that affords functional myocardial protection during repetitive, brief periods of coronary arterial occlusion.

Action Potentials↗
PubMed1993

Acetylcholine mimics ischemic preconditioning via a glibenclamide-sensitive mechanism in dogs.

The major objectives of the present study were to examine the ability of acetylcholine (ACh) to mimic ischemic preconditioning in dogs and to determine the role of cardiac ATP-sensitive potassium (KATP) channels in mediating its effects. Barbital-anesthetized open-chest dogs were subjected to 60 min of left anterior descending coronary artery (LAD) occlusion followed by 4 h of reperfusion. Preconditioning was elicited by 10 min of LAD occlusion followed by 10 min of reperfusion before the 60-min occlusion period. ACh (10 micrograms/min) or an equivalent volume of saline were infused into the LAD for 10 min followed by a 10-min drug-free period before the 60-min ischemic insult. In another group, the specific KATP channel blocker glibenclamide (0.3 mg/kg iv) was given 15 min before ACh administration. Transmural myocardial blood flow was measured at 30 min of occlusion, and infarct size (IS) was determined by triphenyltetrazolium staining and expressed as a percentage of the anatomic area at risk (AAR). There were no significant differences in hemodynamics, collateral blood flow, or AAR between groups. Preconditioning produced a marked reduction (P < 0.05) in IS (5.3 +/- 3.0 vs. 23.7 +/- 5.9% in the controls). ACh, similar to preconditioning, resulted in a dramatic decrease in IS (10.0 +/- 2.9%), whereas glibenclamide completely abolished its protective effects (20.9 +/- 4.8%). These results are the first to indicate that ACh mimics ischemic preconditioning via a cardiac KATP channel-sensitive mechanism in dogs.

Acetylcholine↗
PubMed1993

ApoA-IV is secreted on discrete HDL particles by the rat hepatoma cell line McA-RH7777 transfected with ApoA-IV cDNA.

In the present study, the synthesis and secretion of transfected apolipoprotein (apo) A-IV was investigated in rat hepatoma McA-RH7777, a cell line that does not express apoA-IV mRNA or protein. An expression plasmid that contained the rat apoA-IV cDNA was transfected into the cells; five stable transformants were selected that harbor different copy numbers of the apoA-IV construct and secrete different amounts of apoA-IV. Gel filtration column chromatography and density gradient ultracentrifugation, combined with gel electrophoresis and electron microscopy techniques, demonstrated that (1) the secreted apoA-IV associated mainly with high-density lipoproteins (HDLs) and only a trace amount of apoA-IV was associated with very-low-density lipoproteins; (2) overexpression of apoA-IV resulted in an increased number of disk-shaped structures (thickness, approximately 8.0 nm and diameter, approximately 22 nm); and (3) the electrophoretic mobilities of the apoA-IV-containing particles differed from those of apoA-I-containing HDL. Expression of apoA-IV exerted no discernible effect on the density distribution or the secretion efficiency of apoB-100. Additionally, secretion of apoB-100 and apoA-IV exhibited opposite responses to serum: apoB-100 secretion was stimulated eightfold after addition of serum, whereas apoA-IV secretion was inhibited by 40%. These results suggest that synthesis of apoA-IV may lead to the formation of a subclass of HDL with a different metabolic fate than that of lipoproteins containing either apoA-I or apoB.

Animals↗
PubMed1993

Glibenclamide antagonizes adenosine A1 receptor-mediated cardioprotection in stunned canine myocardium.

BACKGROUND: The main objective of the present study was to determine the role of adenosine in the development of myocardial stunning following multiple, brief periods of coronary artery occlusion as well as the subtype of adenosine receptor (A1 or A2) involved. A second objective was to determine if there was an interaction between the adenosine A1 receptor and the ATP-dependent K channel (KATP). METHODS AND RESULTS: The effects of the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and agonist cyclopentyladenosine (CPA), the selective A2 receptor agonist CGS 21680, and the KATP channel blocker glibenclamide on myocardial stunning produced by repetitive coronary artery occlusions were studied in barbital-anesthetized dogs. Regional segment function was measured with sonomicrometry. Under control conditions, six 5-minute periods of coronary occlusion interspersed with 10-minute periods of reperfusion and ultimately followed by 2 hours of reperfusion produced regional segment dysfunction. Pretreatment with intravenous infusion of CPA (2.0 micrograms.kg-1.min-1) improved percent segment shortening throughout reperfusion, whereas pretreatment with DPCPX (1.0 mg/kg i.v. bolus) significantly worsened the recovery of postischemic contractile function. In contrast, neither DPCPX nor CPA had any effect on the recovery of contractile function when administered before the second coronary occlusion. Furthermore, pretreatment with CGS 21680 (0.2 micrograms.kg-1.min-1) did not affect the recovery of percent segment shortening. In addition, pretreatment with a low dose of glibenclamide (0.1 mg/kg) had no effect on percent segment shortening by itself but completely abolished the beneficial effect of CPA. Importantly, the effects of the various agents on percent segment shortening were independent of difference in systemic hemodynamics, collateral blood flow, or ischemic bed size. CONCLUSIONS: These results suggest that stimulation of myocardial adenosine A1 receptors, particularly when induced by the initial coronary artery occlusion, is cardioprotective during repetitive, brief periods of coronary artery occlusion and that these beneficial actions may be partially mediated via a glibenclamide-sensitive mechanism, possibly opening of myocardial KATP channels.

Adenosine↗
PubMed1993

Role of nitric oxide, muscarinic receptors, and the ATP-sensitive K+ channel in mediating the effects of acetylcholine to mimic preconditioning in dogs.

The aims of the current study were to examine the efficacy of acetylcholine (ACh) to mimic ischemic preconditioning in dogs and to determine the role of nitric oxide (NO), muscarinic receptors, and ATP-sensitive K+ (KATP) channels in mediating its effects. Barbital-anesthetized open-chest dogs were subjected to 60 minutes of left anterior descending coronary artery (LAD) occlusion followed by 4 hours of reperfusion. Preconditioning was elicited by 10 minutes of LAD occlusion followed by 10 minutes of reperfusion before the 60-minute occlusion period. ACh (3 or 10 micrograms/min) or an equivalent volume of saline was infused into the LAD for 10 minutes, followed by a 10-minute drug-free period before the 60-minute ischemic insult. In other groups, the specific NO synthesis inhibitor NG-monomethyl-L-arginine (L-NMMA, 4 mg/min), the muscarinic receptor antagonist-NO synthesis inhibitor nitro-L-arginine methyl ester (L-NAME, 3 mg/min), or the specific KATP channel blocker 5-hydroxydecanoate (5-HD, 3 mg/min) was infused with ACh into the LAD for 10 minutes. The infusion of L-NAME, L-NMMA, or 5-HD was started 2 minutes before ACh infusion. Transmural myocardial blood flow was measured at 5 minutes of occlusion, and infarct size was determined by triphenyltetrazolium staining and expressed as a percentage of the area at risk. There were no significant differences in collateral blood flow or the area at risk between groups. Preconditioning produced a marked reduction (P < .05) in infarct size (6.2 +/- 3.0% versus 26.1 +/- 5.7% in the control group).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

[Evaluation of a cytokeratin 19 assay kit "BALL ELSA CYFRA21-1"].

We evaluated "BALL ELSA CYFRA21-1" kit, an immunoradiometric assay kit for cytokeratin 19. Monoclonal antibodies KS19-1 and BM19-21 are used for immunoadsorbent and indicator, respectively. There was no problems in reproducibility, dilution test and recovery test. Minimum detectable concentration was 0.42 ng/ml. The antigen measured by this kit was immunologically cross-reactive with tissue polypeptide antigen (TPA) and CYFRA21-1 concentration was closely correlated with TPA concentration in patient's serum. One of twenty-six healthy subjects showed serum concentration over a cut-off value of 2.0 ng/ml. Serum CYFRA21-1 concentration elevated in 5 of 10 esophageal cancer patients, 5 of 10 gastric cancer patients, 7 of 10 colorectal cancer patients and 6 of 10 pancreatic cancer patients. Positive rate in patients with benign disease including hepatopathy was low. BALL ELSA CYFRA21-1 kit is reliable and CYFRA21-1 could be a useful tumor marker in gastrointestinal cancer.

Adult↗
PubMed1993

[Expression of human multidrug resistance gene (mdr1) cDNA in murine ES cells and in chimeric mice].

Human multidrug resistance gene (mdr1) was introduced into mouse embryonic stem cells (ES-5 line) by calcium phosphate mediated transfection, and transfected ES-5 cells were then selected by stepwise increase in colchicine concentration (30, 50, 100, and 200 ng/ml respectively). Finally, we obtained 4 clones that could be stably grown in culture medium with colchicine at 200 ng/ml and designated as ES-mdr1 clones A, B, C, and D. Southern blot analysis of DNA from ES-mdr1 A and D cells digested by Hind III and hybridized with mdr1 cDNA 5 A probe was shown in Fig. 3. Characteristic 4.8 and 2.4 kb fragments of mdr1 gene were found as expected and their amplification under increased concentration of colchicine in culture medium was also evident from the figure. Slot blot and Northern analysis of total RNA and poly A+ RNA extracted from ES-mdr1 cells were shown in Fig. 4 and 5, demonstrating that ES-mdr1 cells could express mdr1 mRNA. Indirect immunofluorescence analysis with antibodies against p170 glycoprotein indicated that p170 protein translated from mdr1 mRNA was present at the surface of ES-mdr1 cells (Plate I, Fig. 2). The biological characteristics of ES-mdr1 cells cultured in medium containing 200 ng/ml colchicine were investigated. The cells maintained their undifferentiated morphology and grew in nests (Plate I, Fig. 1), like the parental ES-5 cells. When ES-mdr1 cells were cultured in suspension in vitro, these cells were still capable of producing simple and cystic embryoid bodies. ES-mdr1 cells injected subcutaneously into 129 mice formed tumor-like outgrowths giving a great variety of cell types (Plate I, Fig. 4). These results indicated that the integration and expression of human mdr1 gene and selection against colchicine did not affect the pluripotency of ES-mdr1 cells both in vitro and in vivo. However, ES-mdr1 cells, unlike their parental ES-5 cells, could no longer be induced to differentiate by either RA or HMBA (Plate I, Figs. 3a, 3b), indicating that the human mdr1 gene transfected ES cells had changed their competence of inducible response to differentiation in vitro. The details and possible significance of such change require further studies. From the above preliminary data, we are of the opinion that ES-mdr1 cells may serve as a model to study the mode of action of p170 glycoprotein at cellular level and to screen possible means to counteract the action of mdr1 gene.(ABSTRACT TRUNCATED AT 400 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

[Research on hemostatic constituents in carbonized Schizonepeta tenuifolia Brig].

It has been shown that the fatsoluble extract SeE from carbonized Schizonepeta tenuifolia has an obvious hemostatic action. In a given range of dose there is a significant linear correlation between the logarithms of its doses and the reciprocal of the bleeding and coagulating times in mice. Obvious hemostatic action was observed after mice had been administered in ip and po respectively for 0.5h and 1h. The hemostatic time of the former was 6h and the latter 12h. The LD50 of StE in po was 2.652 +/- 0.286 g/kg, while in ip 1.945 4/- 0.207 g/kg.

Animals↗
PubMed1993

[The production and significance of interleukin-4 in patients with idiopathic nephrotic syndrome].

Samples of serum and PBMC were collected at the same time from 42 pediatric patients with idiopathic nephrotic syndrome (INS) and 28 age-matched healthy individuals. The level of IgE in serum was detected and IL4 in supernatant of PHA-activated PBMC assayed by sandwich ELISA. The level of IL4 and IgE in healthy individuals was 400-500 pg/ml and 50-100 U/ml respectively, and that of IL4 and IgE in the INS patients was on the average 1,080-4,000 pg/ml and 380-1,000 U/ml. Positive correlations were noted between the levels of IL4 and IgE, IL4, and quantity of proteinuria in 24 hours in the INS patients. It is suggested that the elevated IgE in the INS patients was induced by the elevated IL4, and that the imbalanced function of T cells and IL4 was contributable to INS.

Adolescent↗
PubMed1992

Nerve growth factor promotes collateral sprouting of cholinergic fibers in the septohippocampal cholinergic system of aged rats with fimbria transection.

Nerve growth factor (NGF) was injected intraventricularly into aged (24 months) rats with unilateral fimbria transection. Controls received intraventricular injections of cytochrome c. A quantitative analysis of acetylcholinesterase (AChE)-positive fibers was used to evaluate whether the NGF treatment can stimulate regeneration and reinnervation of the cholinergic axons in the septohippocampal system of aged rats with fimbria transection. A marked increase in the density of AChE-positive fibers was observed in the lateral septum, the dorsal fornix and the dorsal hippocampus of the NGF-treated animals, as compared to the controls. In the lateral septum, the increase was observed in the 2-month NGF-treated animals but not in the 15-day NGF-treated animals. In the dorsal fornix at the level of the dorsal hippocampus, the increase was observed on both the lesioned and unlesioned sides of both the 15-day and 2-month NGF-treated animals. In the denervated (lesioned side) hippocampus, the increase took place in the dorsal hippocampus but not in the ventral hippocampus of both the 15-day and 2-month NGF-treated animals. There was no recovery of AChE-positive fibers on the lesioned side of the fimbria distal to the lesion site even in the 2-month NGF-treated animals. These results demonstrate that intraventricular injections of NGF can stimulate collateral sprouting of intact cholinergic axons in the septohippocampal system and promote cholinergic reinnervation of the denervated hippocampus of aged rats with fimbria transection.

Acetylcholinesterase↗
PubMed1992

Synthesis and secretion of apolipoprotein E occur independently of synthesis and secretion of apolipoprotein B-containing lipoproteins in HepG2 cells.

The synthesis and secretion of apolipoprotein (apo) E, a major protein component of very low density lipoproteins, were examined in the human hepatoma cell line HepG2 under metabolic conditions known to stimulate lipogenesis and the production of apoB-containing lipoproteins. When HepG2 cells were incubated in the presence of fetal bovine serum (5 or 10%) or canine chylomicron remnants (5 or 10 micrograms of protein), the secretion of triglycerides and cholesteryl esters of lipoproteins of d less than 1.063 g/ml increased, as determined by the incorporation of [14C]acetate. Determination of the distribution of apoE among media lipoproteins by agarose column chromatography showed that the majority of secreted apoE was associated with large lipoproteins when cells were incubated with fetal bovine serum. However, immunoblot analysis of total media apoE revealed that incubating cells with or without the lipogenic factors had no effect on the amount of apoE secreted. Pulse-chase and continuous labeling experiments demonstrated that the synthesis and secretion of apoE did not vary under the different metabolic conditions, even though there was a 5-fold increase in apoB secretion in response to increased lipogenesis. Neither apoE nor apoB mRNA levels responded to the lipogenic stimuli. We conclude that the synthesis and secretion of apoE are independent of the production of apoB-containing lipoproteins in HepG2 cells.

Acetates↗
PubMed1992

Acetylation of O-specific lipopolysaccharides from Shigella flexneri 3a and 2a occurs in Escherichia coli K-12 carrying cloned S. flexneri 3a and 2a rfb genes.

Most of the Shigella flexneri O-specific serotypes result from O-acetyl and/or glucosyl groups added to a common O-repeating unit of the lipopolysaccharide (LPS) molecule. The genes involved in acetylation and/or glucosylation of S. flexneri LPS are physically located on lysogenic bacteriophages, whereas the rfb cluster contains the biosynthesis genes for the common O-repeating unit (D.A.R. Simmons and E. Romanowska, J. Med. Microbiol. 23:289-302, 1987). Using a cosmid cloning strategy, we have cloned the rfb regions from S. flexneri 3a and 2a. Escherichia coli K-12 containing plasmids pYS1-5 (derived from S. flexneri 3a) and pEY5 (derived from S. flexneri 2a) expressed O-specific LPS which reacted immunologically with S. flexneri polyvalent O antiserum. However, O-specific LPS expressed in E. coli K-12 also reacted with group 6 antiserum, indicating the presence of O-acetyl groups attached to one of the rhamnose components of the O-repeating unit. This was confirmed by measuring the amounts of acetate released from purified LPS samples and also by the chemical removal of O-acetyl groups, which abolished group 6 reactivity. The O-acetylation phenotype was absent in an E. coli strain with an sbcB-his-rfb chromosomal deletion and could be restored upon conjugation of F' 129, which carries sequences corresponding to a portion of the deleted region. Our data demonstrate that E. coli K-12 strains possess a novel locus which directs the O acetylation of LPS and is located in the sbcB-rfb region of the chromosomal map.

Acetylation↗
PubMed1992

High-level expression of recombinant protein A in Escherichia coli.

A high-level expression plasmid pPA-3 was constructed, which yielded up to 20% of soluble cell proteins as recombinant Protein A in E. coli DH5 alpha strain by heat shock induction. The recombinant Protein A contained only the five domains of native Protein A that bind with the Fc part of IgG. The molecular weights of the recombinant Protein A expressed in E. coli were determined to be 33kDa, 32.2kDa, 29.5kDa and 28.6kDa by SDS-PAGE and Western-blotting. The diversity of the molecular weights may be due to proteolysis, and a possible cleavage site is proposed. Some of the protein was purified with coupled human IgG by one-step affinity chromatography. The reactivity of the protein was compared with that of native Protein A and found that this protein could bind with more IgG than native Protein A in equal quantities of proteins.

Amino Acid Sequence↗
PubMed1992

[Stability of shuang huanglian aerosol].

The contents of chlorogenic acid and baicalin in shuang huanglian aerosol were determined by HPLC. The process of chemical kinetics of the aerosol was studied by constant temperature acceleration tests, and the stability of the drug predicted. The results appeared close to those from the stored sample method. pH changes during degradation of the drug were also observed.

Aerosols↗
PubMed1991

Characterization of a membrane-associated glycoprotein (gp 43) on human hepatocellular carcinoma by a monoclonal antibody.

A monoclonal antibody, Hepama-1, produced by immunizing mice with cells of a human hepatocellular carcinoma cell line, has been used to identify and characterize a previously unreported antigen present on the surface of human hepatocellular carcinoma cells. The antigen occurred on the membranes of human hepatoma cell lines and tumor biopsies but was not detectable in tumors of other origin or normal tissues. Binding was determined by enzyme-linked immunoabsorbent assay and immunofluorescence on cell lines and by immunoperoxidase staining of tissue sections. In immunofluorescence studies, Hepama-1 antibodies stained five out of six human hepatoma cell lines, showed only slight binding to breast tumor cell lines, but failed to stain colon tumor or normal cell lines. The antihepatoma antibody exhibited positive immunoperoxidase staining of human liver tumor sections but did not stain tumors of other origin. Hepama-1 bound specifically to a membrane glycoprotein with an approximate molecular weight of 43,000. Western blot and solid phase enzyme-linked immunoabsorbent assay analysis showed that the 43-kD antigen occurred on five of six human hepatoma cell lines and was expressed by every human hepatocellular carcinoma biopsy tested. This cell surface molecule represents a potentially useful target for immunotherapy and localization of human hepatocellular carcinomas.

Antibodies, Monoclonal↗
PubMed1991

[Induced differentiation of mouse embryonic stem cells by retinoic acid and dibutyryl cyclic adenosine monophosphate].

In vitro induced differentiation of mouse embryonic stem cells (ES-5 cells), derived from 5-day 129 mouse blastocyst was studied with retinoic acid (RA) and dibutyryl cyclic adenosine monophosphate (dB-cAMP). RA only or RA with dBcAMP together can both induce monolayer ES-5 cells to differentiate into cells of two types: neuron-like cells and fibroblast-like cells. After treated with 10(-6)mol/L RA for 6 days, the differentiated cells were about 80% of all cells, among which most cells were fibroblast-like cells and others were neuron-like cells. While after 6 days of treatment with 10(-6)mol/L RA and 1 mmol/L dBcAMP, the ratio of differentiated cells can be up to 90-95%, and most cells (about 90-95% of differentiated cells) are neuron-like cells. Immunocytochemical analysis of phenotypic markers, especially GFAP and laminin, showed that the neuron-like cells were glia cells. DBcAMP affected the direction and efficiency of induction by RA. The induced differentiation by RA on attached aggregated ES-5 cells was studied as well. In this case, more cell types appeared, such as epitheloid cells, fibroblast-like cells and spindle shaped cells and so on. The exact nature of these differentiated cells was not identified. After attached culture for about 15 days, rhythmically contracting cardiac-like muscle cells were most attractive among those several differentiated cell types. The change of phenotypic markers during induced differentiation of ES-5 cells in monolayer and aggregated state was summarized in table 1. Transforming growth factor-beta 1 (TGF-beta 1) was also examined in undifferentiated and differentiated cells. Untreated ES-5 cells showed positive immunofluorescent reaction to TGF-beta 1 and various differentiated cells showed different reactions. Glia cells and cardiac-like cells displayed a much stronger TGF-beta 1 reaction. These results indicate that the exact role played by TGF-beta 1 during induced differentiation needs further investigation. The different effect of RA on monolayer and aggregated ES cells and the possible significance of cell to cell interaction in the latter case are discussed.

Animals↗