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Biomedical subjects

Q Liu

Publications and source records attributed to Q Liu.

At least 325 records · Page 18Linked to original sources
PubMed1999

Coexistence of immune-neuro-endocrine substances in the rat central neurons.

To investigate the expression of interleukin-2 (IL-2), metabotropic glutamate receptor subunit 1 (mGluR1) and estrogen receptor (ER) in neurons of the rat central nervous system (CNS) and identify the coexistence possibility of these immune-neuro-endocrine substances in the central neurons, the tri-labeling immunocytochemical technique with different species-specific primary antibodies (goat anti-IL-2 antibody, rabbit anti-mGluR1 antibody and mouse anti-ER antibody) were used to incubate two serial neighbor sections (one for demonstrating IL-2, another for mGluR1 and ER) of the cerebral cortex, medulla oblongata and spinal cord. There were IL-2-, mGluR1- and ER-immunoreactivity (IR)-positive labeled neurons in the above-mentioned central areas. The IL-2-IR production showed brown color, located in the cytoplasm; In the neighbor serial section, the mGluR1-IR, production showed blue-black color, located on the cell membrane; the ER-IR production also showed brown color, located in the cytoplasm and nuclei. There were mGluR1/ER double-labeled cells in the same section, which accounted for about 50%-60% of the total single and double labeled neurons. It was identified by projection check of serial neighbor sections that had mGluR1/ER/IL-2 tri-labeled cells, which accounted for about 30% of total mGluR1/ER double-labeled neurons. The results indicate that mGluR1, ER and Il-2 can coexist in the same rat central neurons, therefore, providing morphological basis for the theory about immune-neuro-endocrine network at the cellular level for the first time.

Animals↗
PubMed1999

The effect of GHRH, GHRP-2 and somatostatin on GH secretion by fetal pituitary.

Growth hormone releasing peptide (GHRP-2) is a synthetic hexapeptide which specifically stimulates secretion of growth hormone (GH) by fetal pituitary somatotrophs through a new membrane receptor, which is different from growth hormone releasing hormone (GHRH) and somatostatin (SMS) receptors. We used cell cultures of human fetal pituitary somatotroph cells to investigate the effect of GHRH, GHRP-2 and somatostatin on GH secretion. The results showed that the mechanism of GHRH/SMS and GHRP-2 was different. This indicated that a different intracellular signal transduction system might also play a crucial role in the regulation of GH secretion.

Fetus↗
PubMed1999

Effects of the novel GH secretogogue, hexarelin on GH secretion and phosphatidylinositol hydrolysis by human pituitary somatotrophinomas in cell culture.

The effects of the novel GH-releasing hexapeptide, Hexarelin, on cultured human pituitary somatotrophinomas were investigated. Hexarelin (0.01-100 nmol/L) dose-dependently stimulated GH secretion up to 4.6-fold. Maximal effects occurred with 10 nmol/L. These effects were very similar to those observed with GHRP-6. The effects of Hexarelin were reduced by phloretin, an inhibitor of protein kinase C (PKC). The rate of phosphatidylinositol (PI) hydrolysis was markedly increased by Hexarelin in a dose-dependent manner. These results demonstrated that Hexarelin could directly stimulate GH secretion by human pituitary somatotrophs in a PKC-dependent manner, probably via activation of the PI transduction system.

Adenoma↗
PubMed1999

Effect of Salvia Miltiorrhiza on coronary collateral circulation in dogs with experimental acute myocardial infarction.

To evaluate the effect of Salvia Miltiorrhiza on coronary collateral circulation in dogs with experimental acute myocardial infarction, 12 dogs were randomly divided into Salvia Miltiorrhiza group (group D) and control group (group C). Acute myocardial infarction model was established in all dogs, Salvia Miltiorrhiza or saline was administered to the 2 groups respectively for 21 days. Coronary angiography was performed before and after ligation of coronary artery. The capillaries and distribution vessel density in tissue sections of myocardia were assessed. Angiography 2 h and 22 days after ligation of coronary artery revealed significant augmentation of collateral vessels, and capillaries and distribution vessel density in ischemic zone on day 22 showed statistically significant augmentation in group D as compared with that of controls (P < 0.05 and P < 0.01). It is concluded that Salvia Miltiorrhiza might improve the opening and formation of coronary collateral circulation of ischemic myocardia in dogs and thereby protecting myocardia from ischemia.

Animals↗
PubMed1999

Action potential propagation failures in long-term recordings from embryonic stem cell-derived cardiomyocytes in tissue culture.

Three-dimensional cell aggregates (embryoid bodies, EBs) containing clusters of spontaneously beating cardiomyocytes were derived from permanent mouse embryonic stem (ES) cells. Extracellular recordings of the population action potentials of cardiomyocyte clusters were made using permanently mounted silver wire electrodes and microelectrode arrays integrated into the bottom of the culture dish. These techniques allowed long-term recordings (for up to several weeks) from individual EBs under cell culture conditions. The normal electrical activity consisted of regular spiking with a frequency of 0.5-5 Hz. However, most EBs (87%) spontaneously developed temporary or persistent complex activity patterns because of intermittent block of action potential propagation at narrow pathways connecting larger beating areas. Similar propagation blocks could also be reversibly induced in regularly spiking EBs by nimodipine (NDP). In addition to a slowing of pacemaker activity, NDP (20-200 nM) induced a stepwise decrease of the action potential frequency at the recording site. Perforated patch-clamp recordings from enzymatically isolated ES-cell-derived cardiomyocytes showed that similar activity patterns do not occur at the single-cell level. We suggest that this novel approach may provide a useful tool for in vitro studies of chronotropy and phenomena of propagation failure similar to AV block.

Action Potentials↗
PubMed1999

The maize mutant polymitotic affects cell cycle events during microspore development

The maize (Zea mays L.) male-sterile mutant polymitotic (po) was analyzed utilizing in-vitro cell culture and immunocytochemistry methods to better understand the relationship between the mutant phenotype and cell cycle events during microspore development. Using a live meiocyte culture system, initiation and progression through abnormal post-meiotic cell cycles at the end of meiosis II was documented in the po mutant with a CCD camera and a computer image analysis system. Our results showed that premature chromosomal condensation precedes abnormal post-meiotic cell cycle progression in the po mutant at the end of meiosis II. Temporal analysis of the po mutant in-vitro revealed that unsynchronized post-meiotic divisions occurred immediately following the end of meiosis II and did not require interaction with the surrounding somatic tissue. Furthermore, the altered distribution of p34(cdc2) protein kinase from a nuclear to a cytoplasmic location was identified in tetrads during onset of the unsynchronized divisions in the po mutant. In contrast, a predominantly nuclear location of p34(cdc2) was observed during interphase of the wild-type tetrads at the same stage.

Journal Article↗
PubMed1999

The effect of lexipafant on bacterial translocation in acute necrotizing pancreatitis in rats.

Bacterial translocation (BT) from the gastrointestinal tract to mesenteric lymph nodes (MLNs) and other extra intestinal organs is an important source of infection in acute pancreatitis (AP). Lexipafant (BB-882) is a potent platelet-activating factor receptor antagonist that has an anti-inflammatory effect. To examine whether BB-882 could affect BT in acute necrotizing pancreatitis, 48 male Sprague Dawley rats (250-350 g) were studied. AP was induced in Group I and Group II by pressure injection of 3% taurocholate and trypsin into the common biliopancreatic duct (1 mL/kg of body weight). Group I rats received BB-882 (10 mg/kg, i.p. qd) and Group II rats received a similar volume of normal saline as a placebo postoperatively for 2 days. Group III and Group IV received BB-882 and placebo, respectively, after an exploratory laparotomy. At 48 hours postoperatively, blood was drawn for culture, serum amylase, and tumor necrosis factor (TNF)-alpha determinations. Specimens from MLNs, spleen, liver, pancreas, and cecum were harvested for culture of gram-positive, gram-negative, and anaerobic bacteria. Quantitative cecal cultures of gram-positive, gram-negative, and anaerobic bacteria were obtained. A point scoring system for five histological features that include interstitial edema, inflammatory cellular infiltration, fat necrosis, parenchymal necrosis, and hemorrhage was used to evaluate the severity of pancreatitis. There was no difference in serum amylase levels (2415 +/- 127 IU/L versus 2476 +/- 170 IU/L), serum TNF-alpha levels (7820 +/- 1396 pg/mL versus 7318 +/- 681 pg/mL), and the mean pancreatic histology score (5.9 +/- 1.2 versus 6.5 +/- 1.1) between Group I and Group II, respectively (P > 0.05). Seven of 12 Group I rats had BT to MLNs, compared with 11 of 12 rats in Group II (P > 0.05). Five of 12 Group I rats had BT to distant sites such as pancreas, spleen, liver, and/or blood, compared with 11 of 12 rats in Group II (P < 0.05). BB-882 treatment decreases bacterial spread to distant sites, but does not reduce serum amylase levels and serum TNF-alpha levels or ameliorate pancreatic damage in rats with AP.

Amylases↗
PubMed1999

Molecular cloning and sequence analysis of cDNA encoding haemorrhagic toxin acutolysin A from Agkistrodon acutus.

By means of reverse transcription polymerase chain reaction, a full-length cDNA of 1632 bp is amplified from the snake venom gland total RNA of Agkistrodon acutus. Analysis of the nucleotide sequence indicates that the amplified cDNA contains a complete open reading frame encoding 413 amino acid residues including signal peptide sequence, zymogen sequence and proteinase domain. The zymogen sequence contains PKMCGVT motif which is highly conserved in almost all venom metalloproteinases. The metalloproteinase domain contains the conserved signature zinc-binding motif HEXXHXXGXXH in the catalytic region. The predicted amino acid sequence of the metalloproteinase domain is identical to the crystallographic sequence of acutolysin A and also shares high homology with other class I snake venom haemorrhagic toxins.

Agkistrodon↗
PubMed1999

In vivo airway eosinophil accumulation does not enhance antigen- or propranolol-induced bronchoconstriction in guinea pigs.

BACKGROUND: Chronic airway eosinophil accumulation is characteristic of asthma. However, it remains unclear whether airway eosinophils enhance or reduce release of chemical mediators and/or action of the released mediators in the airways in vivo, because previous investigators have indicated that eosinophil-derived factors such as histaminase and arylsulfatase may alter the allergic reaction by metabolizing chemical mediators. Recently, we have developed a guinea pig model of propranolol-induced bronchoconstriction (PIB), which is mediated by lipid mediators such as thromboxane A2 (TxA2), cysteinyl leukotrienes (cLTs) and platelet activation factor (PAF). This study was conducted to explain the influence of airway eosinophil accumulation on antigen-induced bronchoconstriction and the following PIB, both of which are mediated by lipid mediators. METHODS: Guinea pigs were transnasally treated with 75 microg/kg of polymyxin-B or vehicle twice a week for a total of 3 weeks. Guinea pigs were anesthetized and treated with diphenhydramine hydrochloride, and then artificially ventilated 24 h after the last administration of polymyxin-B or vehicle followed by passive sensitization. Propranolol at a concentration of 10 mg/ml was inhaled 20 min after an aerosolized antigen challenge. RESULTS: The proportion of eosinophils in bronchoalveolar lavage fluid obtained 15 min after the propranolol inhalation was significantly increased in guinea pigs treated with polymyxin-B compared with the vehicle. The polymyxin-B treatment did not affect antigen-induced bronchoconstriction or the following PIB. CONCLUSIONS: We conclude that eosinophils accumulated in the airways by polymyxin-B does not affect release of chemical mediators induced by antigen or propranolol inhalation, or action of released mediators in vivo.

Administration, Inhalation↗
PubMed1999

How prevalent are Plasmodium ovale and P. malariae in East Asia?

Plasmodium ovale and Plasmodium malariae, two of the four human malaria parasites, are usually found at very low prevalence in East Asia, even in areas with intense malaria transmission. In this article, Fumihiko Kawamoto, Qing Liu, Marcelo Ferreira and Indah Tantular review data obtained in recent field surveys, using alternative diagnostic methods such as acridine orange staining and PCR-based methods, to evaluate the prevalence of these two malaria species in East Asia. They argue that these species might be much more prevalent in East Asia than reported previously. In addition, they discuss the implications of sequence variations found in the small subunit ribosomal RNA genes of the two species targeted by diagnostic PCR and compare morphological criteria for speciation of malaria parasites stained with Giemsa and acridine orange.

Animals↗
PubMed1999

Progress toward demonstration of a surface based DNA computation: a one word approach to solve a model satisfiability problem.

A multi-base encoding strategy is used in a one word approach to surface-based DNA computation. In this designed DNA model system, a set of 16 oligonucleotides, each a 16mer, is used with the format 5'-FFFFvvvvvvvvFFFF-3' in which 4-8 bits of data are stored in eight central variable ('v') base locations, and the remaining fixed ('F') base locations are used as a word label. The detailed implementations are reported here. In order to achieve perfect discrimination between each oligonucleotide, the efficiency and specificity of hybridization discrimination of the set of 16 oligonucleotides were examined by carrying out the hybridization of each individual fluorescently tagged complement to an array of 16 addressed immobilized oligonucleotides. A series of preliminary hybridization experiments are presented and further studies about hybridization, enzymatic destruction, read out and demonstrations of a SAT problem are forthcoming.

Animals↗
PubMed1999

Surface-based DNA computing operations: DESTROY and READOUT.

DNA computing on surfaces is where complex combinatorial mixtures of DNA molecules are immobilized on a substrate and subsets are tagged and enzymatically modified (DESTROY) in repeated cycles of the DNA computation. A restriction enzyme has been chosen for the surface DESTROY operation. For the READOUT operation, both cycle sequencing and PCR amplification followed by addressed array hybridization were studied to determine the DNA sequences after the computations.

Animals↗
PubMed1999

Simple spectrophotometric method for the estimation of algal polysaccharide concentrations.

A rapid and simple spectrophotometric method is described for the estimation of microgram quantities of algal polysaccharides following the formation of soluble complexes with methylene blue dye. The binding of the dye to algal polysaccharides causes the absorption maximum (664 nm) to decrease, which is almost linear over the range of 0-30 microg for the algal polysaccharides studied. The absorbance at 664 nm can be measured immediately after the mixing of algal polysaccharides and dye solution and is stable over a period of 2 h. No heating, centrifugation, lengthy equilibration, or sophisticated instrumentation, which hamper other methods, is required. The interference due to individual monosaccharides, neutral polysaccharides, bovine serum albumin, sodium dodecyl sulfate, and high concentrations of inorganic salts is discussed.

Animals↗
PubMed1999

Recombinant expression of late genes agno-2a and agno-2b of avian polyomavirus BFDV.

Budgerigar fledgling disease virus (BFDV) genome contains two times two (two pairs) open reading frames (agnogenes) at the 5' end of the late coding region. Recombinant influenza A viruses were constructed to express the second pair of BFDV agnoproteins, agno-2a and agno-2b, with a fusion of a histidine-tag at their carboxy-termini, respectively. Specific proteins were detected in Western blot analysis using anti histidine-tag monoclonal antibody. By indirect immunofluorescence experiments agno-2a and agno-2b were shown to be located on the surface and in the perinuclear and cytoplasmic areas of infected cells. Comparisons of the expression patterns of BFDV agno-2a and agno-2b with that of simian virus 40 agnoprotein reveal high similarity, suggesting that they might have the same function(s) in polyomavirus infectious cycle.

Amino Acid Sequence↗
PubMed1999

Improving plant drought, salt, and freezing tolerance by gene transfer of a single stress-inducible transcription factor.

Plant productivity is greatly affected by environmental stresses such as drought, salt loading, and freezing. We reported previously that a cis-acting promoter element, the dehydration response element (DRE), plays an important role in regulating gene expression in response to these stresses. The transcription factor DREB1A specifically interacts with the DRE and induces expression of stress tolerance genes. We show here that overexpression of the cDNA encoding DREB1A in transgenic plants activated the expression of many of these stress tolerance genes under normal growing conditions and resulted in improved tolerance to drought, salt loading, and freezing. However, use of the strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive expression of DREB1A also resulted in severe growth retardation under normal growing conditions. In contrast, expression of DREB1A from the stress inducible rd29A promoter gave rise to minimal effects on plant growth while providing an even greater tolerance to stress conditions than did expression of the gene from the CaMV promoter.

Arabidopsis↗
PubMed1999

ATP does not affect fibrinogen binding to platelet GPIIbIIIa in systems free of signal transduction.

Recent studies have suggested that the platelet fibrinogen (Fg) receptor, platelet membrane glycoprotein IIbIIIa (GPIIbIIIa, or integrin alpha(IIb)beta(3)) is also an adenosine triphosphate (ATP) binding site, and that the binding of ATP can directly inhibit the Fg-binding function of GPIIbIIIa. However, any direct effect of ATP on GPIIbIIIa function in intact fresh platelets is difficult to distinguish from indirect inhibitory effects via competition with ADP or elevation of platelet cyclic AMP levels. We therefore studied effects of ATP on Fg binding to activated GPIIbIIIa on the following model particles: externally activated and fixed platelets, as well as latex particles and liposomes containing functionally competent activated GPIIbIIIa receptors for Fg. These particles have 'normal', activated GPIIbIIIa in terms of: (1) binding affinity, (2) specificity to Fg, and (3) conformational change(s) after Fg binding. These particles neither require nor respond to further activation in order to bind Fg. With these model particles, we showed that ATP does not have any direct effect on the binding of Fg to platelet GPIIbIIIa and platelet aggregation. These simplified model particles are useful tools in the mechanistic study of platelet GPIIbIIIa function and the interaction between platelet GPIIbIIIa and its ligands.

Journal Article↗