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Y Zhou

Publications and source records attributed to Y Zhou.

At least 811 records · Page 45Linked to original sources
PubMed1994

A mass spectrometric solution to the address problem of combinatorial libraries.

The molecular weights of femtomole quantities of small peptides attached to polystyrene beads have been determined with imaging time-of-flight secondary ion mass spectrometry. The analysis is made possible by the selective clipping of the bond linking the peptide to a bead with trifluoroacetic acid vapor before the secondary ion mass spectrometry assay. The approach can be applied to large numbers of 30- to 60-micrometer polystyrene beads for the direct characterization of massive combinatorial libraries.

Amino Acid Sequence↗
PubMed1994

Regulation of interleukin-8 expression in porcine alveolar macrophages by bacterial lipopolysaccharide.

Interleukin (IL)-8 is a macrophage-derived neutrophil chemotactic factor that plays an important role in the recruitment of neutrophils to inflammatory loci. Hence, expression of IL-8 by alveolar macrophages may be a significant factor in host defense in the lung and in the pathogenesis of pneumonia in swine. To initiate molecular studies of IL-8 regulation in pigs, we cloned IL-8 cDNA and examined the regulation of its mRNA in alveolar macrophages. The porcine IL-8 cDNA consists of 1491 base pairs including a coding region of 309 base pairs. The deduced amino acid sequence was 75 and 81% similar to human and rabbit IL-8, respectively. Resting macrophages contained low levels of IL-8 mRNA, which increased markedly after exposure to bacterial lipopolysaccharide (LPS). LPS induction of IL-8 was direct, not mediated through elevation of tumor necrosis factor or interleukin-1. The effect of LPS on IL-8 expression was dose dependent, and induction was observed at a concentration of 10 pg/ml. IL-8 mRNA expression was detectable within 0.5 h after stimulation with LPS, peaked at 3-6 h at about 30-fold higher levels than in resting cells, and was maintained for 24 h. Secreted IL-8, measured by neutrophil chemotaxis, was induced within 4 h by LPS, and accumulated in the media throughout the 24-h period. The mechanism of induction of IL-8 mRNA appeared to involve transcription and RNA processing. Nuclear run-on analysis showed that the IL-8 gene was actively transcribed in noninduced cells; upon stimulation with LPS, the rate of IL-8 transcription was increased about 4-fold. A single mature mRNA species was detected by primer extension analysis. The half-life of IL-8 mRNA transcripts in aveolar macrophages was approximately 2 h and did not change after LPS stimulation. The ability of LPS to induce IL-8 expression was suppressed by recombinant human IL-4 and dexamethasone in a concentration-dependent manner. These observations indicate that the expression of IL-8 is an early event in the sequelae to bacterial infection in the lung.

Amino Acid Sequence↗
PubMed1994

Processing of prodynorphin by the prohormone convertase PC1 results in high molecular weight intermediate forms. Cleavage at a single arginine residue.

Processing of rat prodynorphin (proDyn) by the mouse prohormone convertase PC1 was investigated. Recombinant vaccinia virus vectors were used to coexpress proDyn and PC1 in rat PC12 pheochromocytoma and mouse AtT-20 corticotroph cells. In vitro experiments were also conducted by co-incubating purified proDyn and PC1. The results demonstrate that PC1 cleaves proDyn at pairs of basic residues to yield 10 and 16 kDa high molecular weight (HMW) intermediates. Additionally, PC1 cleaves proDyn at a single arginine residue to yield an 8 kDa product and the C-peptide. This demonstrates that PC1 cleaves proDyn at single and pairs of basic residues.

Amino Acid Sequence↗
PubMed1994

Soluble interleukin-6 receptors released from T cell or granulocyte/macrophage cell lines and human peripheral blood mononuclear cells are generated through an alternative splicing mechanism.

To detect transcripts encoding the interleukin-6 receptor (IL-6R) molecule lacking the transmembrane (TM) domain, in various cell lines and peripheral blood mononuclear cells (PBMC), we used the polymerase chain reaction (PCR) with primer pairs that flank the TM domain and which were selected to generate a 398-bp fragment. We detected 398-bp and 304-bp DNA molecules in the PCR products of the U1, J22HL60, MT-2, MT-4, U937 and HL60 cell lines and of PBMC isolated from several individuals. The sequencing analysis of both DNA molecules showed that a 94-bp region consisting of the TM domain of IL-6R was deleted in the 304-bp molecule. Moreover, we detected a soluble (s) IL-6R protein of 45 kDa in culture supernatants of the MT-2, MT-4 and U937 cell lines by radioimmunoprecipitation using specific antibodies against sIL-6R. Our results indicate that active deletion of the TM domain by alternative splicing of mRNA represents one mechanism for release of sIL-6R into the culture supernatants of cells, or into serum or urine.

Alternative Splicing↗
PubMed1994

Interleukin-4 suppresses inflammatory cytokine gene transcription in porcine macrophages.

Inflammatory cytokines, including interleukin (IL)-1 alpha, IL-1 beta, IL-8, and tumor necrosis factor alpha (TNF-alpha) are produced by macrophages in response to a variety of pathogenic stimuli. We show here that the expression of inflammatory cytokines is suppressed by IL-4 at the transcriptional level. Interleukin-4, when added together with bacterial lipopolysaccharide (LPS), suppressed LPS-induced increases in mRNA levels of IL-1 alpha, IL-1 beta, IL-8, and TNF-alpha in alveolar macrophages. The level of suppression was dependent on dose and time of exposure and reached a maximum of 75-80% of uninduced values for IL-1 alpha, IL-8, and TNF. Interleukin-1 beta expression was completely inhibited by IL-4. The amount of secreted protein, as determined by TNF-alpha bioassay, was also suppressed by IL-4. Half-maximal suppression occurred at IL-4 concentrations between 0.02 and 0.1 ng/ml for all inflammatory cytokines. Nuclear run-on assays showed that IL-4 suppressed transcriptional activity of all inflammatory cytokines. Messenger RNA stability was not changed by IL-4. The data suggest that IL-4 plays an important transcriptional role in the regulation of alveolar macrophage inflammatory activities in respiratory disease and raise the possibility that IL-4 may function in vivo as a coordinator of inflammatory and immune responses.

Animals↗
PubMed1994

Human cytotrophoblast invasion is up-regulated by epidermal growth factor: evidence that paracrine factors modify this process.

Formation of the human placenta requires a subset of cytotrophoblast stem cells to acquire an invasive phenotype. We examined the effect on cytotrophoblast invasiveness of growth factors that control the differentiation of other cells. Exogenous TGF-beta 1, PDGF-AA, PDGF-BB, and TNF-alpha affected neither cell morphology nor the rate of cytotrophoblast invasion in vitro. In contrast, addition of EGF to first trimester cytotrophoblast cultures produced dramatic changes in morphology and a severalfold increase in invasive capacity. The effects of EGF on later gestation cytotrophoblasts, whose invasive capacity is diminished, were much less pronounced. Next we investigated whether cytotrophoblasts themselves produce ligands that interact with the EGF receptor. A radioimmunoassay and a radioreceptor assay failed to detect EGF receptor ligands in cytotrophoblast-conditioned medium. Likewise, by RT-PCR cytotrophoblasts expressed neither EGF nor TGF-alpha mRNA. In contrast, EGF receptor mRNA was expressed and its protein levels remained constant during the experiment. Immunolocalization using F(ab') fragments of an anti-human EGF antibody failed to detect this growth factor in the chorionic villus. We conclude that maternal ligands that interact with the EGF receptor could play an important role by up-regulating trophoblast invasion, particularly during the early stages of pregnancy.

Becaplermin↗
PubMed1994

Generation and characterization of antibodies to adhesion-related molecules of retinal pigment epithelial cells.

We have generated antisera to pig retinal pigment epithelial (RPE) cells and to their fractionated membrane proteins. The antisera have been screened functionally by adhesion inhibition assays, and morphologically with immunofluorescence microscopy of cultured cells and frozen sections of the retina. From these sera, we have affinity purified five monospecific antibodies to the RPE surface molecules having molecular weights of 220, 180, 110, 85 and 70 kDa, which effectively inhibit cell-substratum attachment. The 220 and 85 kDa antigens are localized to focal contacts of the cultured cells and are seen in patches in the intact RPE layer in frozen sections of eye tissues. Immunofluorescence microscopy shows that the 180, 110 and 70 kDa antigens localize predominantly to cell-cell junctions. Hence, these antigens may participate in both cell-cell and cell-substratum adhesion in RPE cells. Staining patterns obtained with confocal microscopy of frozen sections of the retina demonstrate that these antibodies are RPE-specific. These adhesion-related molecules may play a role in maintenance of the morphological and functional integrity of RPE.

Animals↗
PubMed1994

Estrogen rapidly induces c-jun immunoreactivity in rat striatum.

Estrogen has been reported to exert rapid effects on the function of neurons located in various brain regions, including those where classical estrogen receptors are not abundant, such as the striatum. The mechanism underlying these actions is not well understood, but does not appear to involve classical estrogen receptor-mediated genomic mechanisms. Estrogen has also been shown to regulate expression of immediate-early gene products in many tissues. In the present study, immunohistochemical methods were used to determine whether estrogen modulates the appearance of c-jun immunoreactivity (IR) in the striatum of rats. Administration of estradiol (100 micrograms/rat) to ovariectomized rats for 15 min induced a rapid and transient increase in c-jun-IR in the dorsomedial striatum and the core region of the nucleus accumbens. These data suggest that c-jun may serve as one of the rapidly responding mediators of estrogen action in the striatum and nucleus accumbens.

Animals↗
PubMed1994

Influence of zinc and copper administration on metal disposition in rats with cadmium-metallothionein-induced nephrotoxicity.

Only a few studies have investigated the effects of the interaction between Cu, Zn, and Cd on the toxicity of Cd in vivo and the metabolism of these metals. The present study is concerned with these effects. Observations of the distribution of these metals in liver and renal cortex and of their excretion in urine were made. Sixty male Wistar rats were divided into 10 groups of six (a full factorial design complemented by a center point and a control group) and were administered Zn (0 or 25 mg/kg body mass), Cu (0 or 12.5 mg/kg), and CdMT (cadmium--metallothionein; 0.1 or 0.4 mg Cd/kg) by sc injection. The rats were given Zn and/or Cu 24 hr prior to the CdMT injection. The data were analyzed by linear multiple regression. After CdMT injection, the Cd retention level was markedly reduced in renal cortex and increased in liver by Cu pretreatment, while the urinary excretion of Cd was significantly lower in these rats. The levels of endogenous Zn in renal cortex and liver increased significantly in rats pretreated with Cu. The production of MT in liver and renal cortex was induced more efficiently by Cu than by Zn. The results obtained may be of importance in understanding the mechanism of CdMT toxicity and the potential influence of Zn and Cu on the chronic nephrotoxicity of cadmium.

Animals↗
PubMed1994

trans-activation of the HIV promoter by a cDNA and its genomic clones of human herpesvirus-6.

Human herpesvirus 6 (HHV-6) is a lymphotropic herpesvirus, and in vitro, it can productively infect human CD4+ T cells as HIV-1. Co-infection of T cells by HIV-1 and HHV-6 can lead to both activation of the HIV-1 promoter and acceleration of the cytopathic effects. An HHV-6 (GS) cDNA clone, pCD41, encoding for a 41-kDa nuclear protein was identified and characterized previously (Chang and Balachandran, J. Virol. 65, 2884-2894 and 7085, 1991). Sequence analyses show that this protein has significant homology with the human cytomegalovirus UL44 gene coding for the ICP36 family of early-late-class phosphoprotein. Using this cDNA as the probe, a 3.8-kb EcoRI genomic fragment encoding the HHV-6(GS)P41 was cloned and designated as pGD41. When cotransfected with the HIV LTR CAT into CV-1 cells, both the pCD41 and pGD41 clones trans-activated the HIV LTR. Sequence analyses of pCD41 indicate that there are two potential open reading frames (ORFs), A and B, which are homologous to the ORFs found in the genomic clone pGD41. Deletion constructs of the pCD41 clone demonstrated that ORF-A was critical for the HIV LTR activation. Deletion analyses of the pCD41 ORF-A and the use of promoter constructs further mapped an internal functional promoter within the pCD41 sequence that can direct the synthesis of the trans-activating protein. By using HIV LTR deletion mutants, the NF-kappa B binding sites were found to be critical for response to the pCD41 trans-activation.

Amino Acid Sequence↗
PubMed1994

Effects of peptone on hybridoma growth and monoclonal antibody formation.

Hybridoma WuT3 secreting a monoclonal antibody against T lymphocytes was grown in RPMI 1640 medium supplemented with 1% human serum. The effect of the concentration of peptone, as an additive, was investigated on cell growth, monoclonal antibody formation, and cell metabolism over 0-10 g l-1 range. It was found that 1-5 g l-1 peptone can significantly promote the growth of cells and increase the formation of monoclonal antibody, especially at 3-5 g l-1, when both the accumulating level and secretion rate of monoclonal antibody are higher than that at other peptone concentrations. Based on glucose, lactate and ammonia analysis data, the efficiency of glycolysis was assessed and the utilization of amino acids was more efficient at 3-5 g l-1 peptone. The cell growth and monoclonal antibody formation were inhibited at higher peptone concentrations, e.g. 10 g l-1.

Amino Acids↗
PubMed1994

Clinical application of SPECT to the localization of corticoepileptogenic focus of intractable epilepsy.

This paper presented 51 cases of intractable epilepsy, of which 36 were males, and 15 females, with a mean age of 21. They were all verified through CT/MRI, among which 17 were proved to have lesions on the brain, and 34 to have no lesion. Before operation all the patients were identified by SPECT and cerebral blood flow imaging (CBF). During the operation they were monitored under subdural strip electrode ECoG for the localization of corticoepileptogenic focus. The results showed that the sensitivity rate of localization with SPECT for corticoepileptogenic focus location was 97.87%.

Adolescent↗
PubMed1994

Enhanced preservation of acutely ischemic myocardium with transseptal left ventricular assist.

Mechanical support for acute regional ischemia without hemodynamic collapse may be achieved percutaneously with an intraaortic balloon pump (IABP) or with transseptal left ventricular assist (TLVA) while awaiting revascularization. The relative benefits of these two percutaneous transfemoral techniques for the treatment of ischemia were compared in a representative animal model. During 90 minutes of regional coronary occlusion, four groups of 8 pigs were treated with either no support (control), IABP, TLVA, or both IABP and TLVA. Cardioplegic arrest for 30 minutes to simulate coronary grafting was followed by 180 minutes of global reperfusion on bypass. In all groups regional wall motion and interstitial pH in the area at risk were significantly depressed with ischemia, but wall motion fully recovered after reperfusion. However, histochemical staining of the area of necrosis/area at risk was significantly reduced with IABP versus control (20.2% versus 34.1%; p < 0.05) and further significantly reduced with TLVA and IABP + TLVA (10.7% and 6.7% versus IABP alone; p < 0.05). We conclude that in supporting even a modest-sized myocardial region at risk (12% of the left ventricle) the area that went on to infarction was significantly reduced with the use of TLVA over IABP. Regional wall motion and myocardial pH measurements did not reflect this difference in the early reperfusion period. The benefit of TLVA over IABP during more extensive or prolonged ischemia may have real clinical significance.

Acute Disease↗
PubMed1994

Study of propagation along nonuniform excitable fibers.

Two related reaction diffusion systems that support traveling wave solutions when parameters are constant are studied when there are jump discontinuities in the diffusion coefficient. The first system represents a classical axon model where the fiber had a jump in diameter at discrete locations and the membrane dynamics represent those of barnacle muscle (which we call Morris-Lecar dynamics). The second model represents a passive cable with a uniform density of spines that have Morris-Lecar dynamics. Conditions under which echo waves form are studied, as well as conditions when wave blocking takes place with a thickening of the fiber.

Action Potentials↗
PubMed1994

Interaction of methyl benzoate as a model odorant with a series of free-base amino acids and some amino-acid hydrochlorides.

The interactions of methyl benzoate as a model odorant with a series of free-base amino acids: lysine, tryptophan, arginine, proline, histidine, cysteine, leucine, threonine and phenylalanine, were studied by gas-phase adsorption on solid amino-acid samples. DL-, D- and L-isomers were investigated for all of the amino acids with the exception of cysteine where only DL- and D- were studied. Langmuir adsorption isotherms show that the strongest interactions are with lysine. Correlation of the relative interaction strength with the chemical structures suggests that binding is strongest to the remote amino groups in the amino-acid side-chain and involves a nucleophilic attack of a lone pair of electrons on the epsilon-nitrogen of lysine to the carbon of the carbonyl group of the methyl benzoate. This suggestion is supported by studies on hydrochlorides of lysine where the side-chain amino groups are protonated and thus cannot participate in a lone-pair interaction. Arginine mono-hydrochloride was found to adsorb more methyl benzoate than even the lysine free-base, an observation which is not fully understood.

Amino Acids↗
PubMed1994

Variations in the management and outcome of non-small cell lung cancer in Ontario.

Prospectively gathered information in the Ontario Cancer Foundation's computerized clinical database was analysed to provide a description of the management of 12,399 patients with unresected non-small cell lung cancer (NSCLC) registered at seven regional cancer centres in Ontario between 1982 and 1991. Overall, 44% received initial thoracic radiotherapy, 19% received initial radiotherapy to metastatic sites, and 36% received no immediate radiotherapy. Of those who received thoracic radiation 41% received doses > or = 40 Gy and 59% received doses < 40 Gy. Among the seven centres, the proportion of patients receiving initial thoracic radiotherapy ranged from 41% to 56% (p < 0.001), and the proportion of those receiving doses > or = 40 Gy ranged from 30% to 68% (p < 0.001). Between 1982 and 1991, the overall proportion of patients who received initial thoracic radiotherapy decreased from 48% to 38%, the proportion of those receiving high dose treatment decreased from 55% to 28%, and the mean number of fractions given to the chest decreased from 17 to 10. Only 10% received chemotherapy at any time, and that proportion ranged from 3% to 21% (p < 0.001) among the seven centres. Between 1982 and 1991 the proportion of patients receiving chemotherapy decreased significantly from 15% to 8% (p < 0.001) across the Cancer Foundation as a whole. These wide variations in management policies were not associated with any significant differences in survival, which was similar at all seven centres, and remained constant between 1982 and 1991.

Adenocarcinoma↗
PubMed1994

Establishing a resuscitation model in rabbits with closed-thoracic cardiopulmonary by-pass.

This study aims to establish an animal model of resuscitation in rabbits by using closed-thoracic cardiopulmonary by-pass (CTCPB). The rabbits were randomly divided into four groups according to cardiac arrest times which were 8, 10, 12, and 15 min. Neurologic outcome and blood lactate were determined within 150 min after resuscitation. It was indicated that the rabbits' neurologic functions were progressively injured with prolonged cardiac arrest time. The threshold of circulatory arrest time that induced a vegetative state in the rabbits was between 10 and 12 min. There were no significant differences in cardiac resuscitability among the four groups, as was so for plasma lactate, although it increased significantly from the control levels. The establishment of a small-animal model of resuscitation by using CTCPB, and the problems in dealing with it are also described and discussed in detail in this paper. Our experience indicated that this is a simple, convenient, and economical animal model for the study of resuscitation.

Animals↗