The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Vagn Leick - One of the best experts on this subject based on the ideXlab platform.
-
Chemokinesis by tetrahymena in response to bacterial oligopeptides
Journal of Eukaryotic Microbiology, 2007Co-Authors: Vagn Leick, Soren LindemoseAbstract:The ciliate Tetrahymena responds very efficiently by chemoattraction to a group of trichloroacetic acid-soluble oligopeptides isolated from a commercial bioprotein from Methanococcus. When fractionated by reversed phase C18-high-pressure liquid chromatography, this group of very efficient chemoattractants turned out to consist of a heterogeneous group of oligopeptides with molecular weight ranging from 0.2 to 1.5 kDa. The peptides were very rich in the following amino acids: aspartic acid, alanine, glutamic acid, proline, glycine, lysine, and arginine. The term Chemokinesis is used throughout to emphasise that chemoattraction does not necessarily include an element of orientation of cells.
-
tetrahymena cells and the quantitative two phase assay visual assessment of Chemokinesis and gravikinesis
Journal of Eukaryotic Microbiology, 2005Co-Authors: J D Olesen, Per Hellunglarsen, Vagn LeickAbstract:A two-phase assay was used to assess Chemokinesis and gravikinesis of Tetrahymena cells. METHOD: Tetrahymena thermophila cells were cultured without stirring at 36°C in a medium containing proteose peptone, yeast extract, glucose, and MOPS. Growing cells or cells in the stationary phase (1 million cells/ml) were used. Before assay, the cells were diluted 1+1. A semi-microcuvette contained a 1-ml bottom-phase with NycoPrep™ Universal (5% w/v) and MOPS. Carefully, a 1-mL top-phase in the same buffer was layered on top of the bottom-phase. Cells were either in the top- or the bottom-phase. A commercially fed supplement for animals was used as chemoattractant in the phase opposite to the cells (Bioprotein, BP; Norferm, Norway). Changes in cell concentrations were monitored as optical density at 600 nm.RESULTS: (1) cells in top-phase: −BP, 0.0001/30 min;+BP, 0.12/4 min. (2) cells in bottom-phase: top-phase exposed to a stream of nitrogen gas: −BP, 0.07/2 min; +BP 0.05/2 min; top-phase not exposed to a stream of nitrogen gas: −BP, 0.08/2 min; +BP, 0.04/2 min. CONCLUSIONS: The BP proved to be an effective chemoattractant. Gravikinesis was observed with and without the presence of BP. Aerotaxis was not observed. The two-phase assay is a sensitive, reliable, and quick procedure for the assessment of Chemokinesis and gravikinesis.
-
Cilia-Mediated Oriented Chemokinesis in Tetrahymena thermophila
Journal of Eukaryotic Microbiology, 1994Co-Authors: Vagn Leick, Uffe Koppelhus, Jens RosenbergAbstract:The role of the cilia in the locomotion (“gliding”) of Tetrahymena thermophila in a semi-solid medium has been studied when cells were migrating in gradients of attractant. Video recordings and computer-aided motion analysis of migrating cells and their ciliary activity show that Tetrahymena thermophila migrate by swimming forward in semi-solid methyl cellulose, using their cilia. Ciliary reversals occur at certain intervals and cause a termination (“stop”) of cellular migration. Cells with reversed cilia resume forward migration when normal ciliary beating resumes. In gradients of attractants, cells migrating towards the attractant suppress ciliary reversals, which leads to longer runs between stops than in control cells. Cells migrating away from the attractant have a higher frequency of ciliary reversals than the control cells resulting in shorter runs. Stimulated cells adapt to a particular ambient concentration of attractant several times during migration in the gradient. Adaptation is followed by de-adaptation, which occurs during the “stop”. In the presence of cycloheximide, a strong inhibitor of chemoattraction, the attractant-induced suppression of ciliary reversal is abolished (cells become desensitized to the attractant). It is concluded that Tetrahymena has a short-term memory during adaptation. This is important for the efficiency of migration towards an attractant.
-
an improved quantitative assay for Chemokinesis in tetrahymena
The Biological Bulletin, 1994Co-Authors: Uffe Koppelhus, Per Hellunglarsen, Vagn LeickAbstract:This paper presents a quantitative and sen sitive assay for the measurement ofchemosensory behav ior in Tetrahymena. The two-phase assay is easy to per form in large quantities, so a variety of compounds can be screened under comparable conditions. A suspension of 2 X i05 cells m1 ‘?� (the upper phase) is starved for 20â€" 40 h and then gently placed on top of a 5% solution of Metrizamide (the lower phase) in a disposable microcu vette. The optical density ofthe lower phase is monitored at 600 nm with an automated spectrophotometer at se lected time points. Optimum sensitivity of the assay is achieved when the cells slowly but continuously enter the lower phase, so that about 5%ofthem will be in the lower phase within 30 mm. Optimal chemosensory responses occurred in Tetrahymena thermophila at about 25°C. The response was delayed at 15°C and markedly reduced at 35°C. The data suggest three bases for quantifying the response in the assay: (1) initial slope of the absorbance versustime; (2) final maximal absorbancewithin the time period of measurement; and (3) signal-to-noise ratio (5/ N) at a fixed time. We have quantifiedâ€"in terms of 5/ Nâ€"the chemosensory responses in Tetrahymena for the following compounds: /3-endorphin, fibroblast growth factor, insulin, and platelet-derived growth factor (PDGF); these substances were active in nanomolar concentrations, and the maximal S/N was between 3 and 5. 1. Acetylcho line was active only in millimolar concentrations; maxi mal S/N was 4. 1at 1 mM. Glutamic acid, glutamine, gly cine, isoleucine, leucine, methionine, phenylalanine, pro line, serine, threonine, tryptophan, and valine were active in millimolar concentrations, with S/N between 1.5 and
Thomas V Bilfinger - One of the best experts on this subject based on the ideXlab platform.
-
neuropeptide y inhibits human and invertebrate immunocyte chemotaxis Chemokinesis and spontaneous activation
Cellular and Molecular Neurobiology, 1993Co-Authors: Paul Erby Dureus, Dahla Louis, Anthony V Grant, Thomas V Bilfinger, George B StefanoAbstract:1. In a concentration-dependent manner neuropeptide Y was found to be a potent inhibitor of the spontaneous activation of human granulocytes and macrophages as well asMytilus edulis immunocytes. 2. Neuropeptide Y also inhibited the chemotaxic response of these immunocytes to the chemoattractant f-MLP. 3. Incubation of both the human and the invertebrate immunocytes in f-MLP (10−9M) causes “activation” as noted by random locomotion (Chemokinesis). Neuropeptide Y also blocked f-MLP-induced Chemokinesis. 4. The results suggest that neuropeptide Y may, in addition to other functions, serve as an endogenous regulator of immunocyte function.
-
human neutrophil and macrophage Chemokinesis induced by cardiopulmonary bypass loss of dame and il 1 chemotaxis
Journal of Neuroimmunology, 1993Co-Authors: George B Stefano, Thomas V BilfingerAbstract:Cardiopulmonary bypass (CPB) induces both cellular immunosuppression and an inflammatory response. In an effort to better characterize CPB-induced immune dysfunction, we examined the chemotaxic ability of human granulocytes and macrophages to D-Ala2-Met-enkephalin (DAME) and interleukin (IL)-1 alpha with computer-assisted microscopic image analysis before, during and after CPB. Spontaneous granulocyte and macrophage activation increased from 6% and 8% (before) to 52% and 44% (during) and then 39% and 31% after (38 h) CPB, respectively. These activated cells, characterized by conformational changes and locomotion, exhibited Chemokinesis. Furthermore, no direct response to either DAME or IL-1 alpha was observed in the bypass and postoperative specimens. Cellular velocity was 0.14 and 0.07 microns s-1 for control spontaneously activated granulocytes and macrophages, respectively, and equal to the velocity observed for DAME and IL-1 alpha exposed cells, during and after CPB. CPB-unexposed cells, influenced only by the chemotaxic agents, exhibited a 3-4-fold increase in their velocity. Additionally, the migratory path of the activated cells obtained during and after CPB exhibited Chemokinesis, rather than chemotaxis, when placed in a concentration gradient of either signal molecule. Cells exposed to fentanyl, the anesthetic agent, exhibited the same behavior as controls, as did those treated with morphine sulphate. However, at higher concentrations (> or = 10 ng ml-1) fentanyl and morphine reduced granulocyte and macrophage activity, demonstrating that CPB caused the opposite effect of fentanyl and also that CPB exposure overcame the pharmacological inhibitory effect of the mu opiate ligands.(ABSTRACT TRUNCATED AT 250 WORDS)
George B Stefano - One of the best experts on this subject based on the ideXlab platform.
-
neuropeptide y inhibits human and invertebrate immunocyte chemotaxis Chemokinesis and spontaneous activation
Cellular and Molecular Neurobiology, 1993Co-Authors: Paul Erby Dureus, Dahla Louis, Anthony V Grant, Thomas V Bilfinger, George B StefanoAbstract:1. In a concentration-dependent manner neuropeptide Y was found to be a potent inhibitor of the spontaneous activation of human granulocytes and macrophages as well asMytilus edulis immunocytes. 2. Neuropeptide Y also inhibited the chemotaxic response of these immunocytes to the chemoattractant f-MLP. 3. Incubation of both the human and the invertebrate immunocytes in f-MLP (10−9M) causes “activation” as noted by random locomotion (Chemokinesis). Neuropeptide Y also blocked f-MLP-induced Chemokinesis. 4. The results suggest that neuropeptide Y may, in addition to other functions, serve as an endogenous regulator of immunocyte function.
-
human neutrophil and macrophage Chemokinesis induced by cardiopulmonary bypass loss of dame and il 1 chemotaxis
Journal of Neuroimmunology, 1993Co-Authors: George B Stefano, Thomas V BilfingerAbstract:Cardiopulmonary bypass (CPB) induces both cellular immunosuppression and an inflammatory response. In an effort to better characterize CPB-induced immune dysfunction, we examined the chemotaxic ability of human granulocytes and macrophages to D-Ala2-Met-enkephalin (DAME) and interleukin (IL)-1 alpha with computer-assisted microscopic image analysis before, during and after CPB. Spontaneous granulocyte and macrophage activation increased from 6% and 8% (before) to 52% and 44% (during) and then 39% and 31% after (38 h) CPB, respectively. These activated cells, characterized by conformational changes and locomotion, exhibited Chemokinesis. Furthermore, no direct response to either DAME or IL-1 alpha was observed in the bypass and postoperative specimens. Cellular velocity was 0.14 and 0.07 microns s-1 for control spontaneously activated granulocytes and macrophages, respectively, and equal to the velocity observed for DAME and IL-1 alpha exposed cells, during and after CPB. CPB-unexposed cells, influenced only by the chemotaxic agents, exhibited a 3-4-fold increase in their velocity. Additionally, the migratory path of the activated cells obtained during and after CPB exhibited Chemokinesis, rather than chemotaxis, when placed in a concentration gradient of either signal molecule. Cells exposed to fentanyl, the anesthetic agent, exhibited the same behavior as controls, as did those treated with morphine sulphate. However, at higher concentrations (> or = 10 ng ml-1) fentanyl and morphine reduced granulocyte and macrophage activity, demonstrating that CPB caused the opposite effect of fentanyl and also that CPB exposure overcame the pharmacological inhibitory effect of the mu opiate ligands.(ABSTRACT TRUNCATED AT 250 WORDS)
Sara M Rankin - One of the best experts on this subject based on the ideXlab platform.
-
mechanisms of acute eosinophil mobilization from the bone marrow stimulated by interleukin 5 the role of specific adhesion molecules and phosphatidylinositol 3 kinase
Journal of Experimental Medicine, 1998Co-Authors: Roger T Palframan, P D Collins, Nicholas J Severs, Stephen Rothery, T J Williams, Sara M RankinAbstract:Mobilization of bone marrow eosinophils is a critical early step in their trafficking to the lung during allergic inflammatory reactions. We have shown previously that the cytokine interleukin (IL)-5, generated during an allergic inflammatory reaction in the guinea pig, acts systemically to mobilize eosinophils from the bone marrow. Here, we have investigated the mechanisms underlying this release process. Examination by light and electron microscopy revealed the rapid migration of eosinophils from the hematopoietic compartment and across the bone marrow sinus endothelium in response to IL-5. Using an in situ perfusion system of the guinea pig hind limb, we showed that IL-5 stimulated a dose-dependent selective release of eosinophils from the bone marrow. Eosinophils released from the bone marrow in response to IL-5 expressed increased levels of β2 integrin and a decrease in L-selectin, but no change in α4 integrin levels. A β2 integrin–blocking antibody markedly inhibited the mobilization of eosinophils from the bone marrow stimulated by IL-5. In contrast, an α4 integrin blocking antibody increased the rate of eosinophil mobilization induced by IL-5. In vitro we demonstrated that IL-5 stimulates the selective Chemokinesis of bone marrow eosinophils, a process markedly inhibited by two structurally distinct inhibitors of phosphatidylinositol 3-kinase, wortmannin and LY294002. Wortmannin was also shown to block eosinophil release induced by IL-5 in the perfused bone marrow system. The parallel observations on the bone marrow eosinophil release process and responses in isolated eosinophils in vitro suggest that eosinophil Chemokinesis is the driving force for release in vivo and that this release process is regulated by α4 and β2 integrins acting in opposite directions.
Jens Rosenberg - One of the best experts on this subject based on the ideXlab platform.
-
Cilia-Mediated Oriented Chemokinesis in Tetrahymena thermophila
Journal of Eukaryotic Microbiology, 1994Co-Authors: Vagn Leick, Uffe Koppelhus, Jens RosenbergAbstract:The role of the cilia in the locomotion (“gliding”) of Tetrahymena thermophila in a semi-solid medium has been studied when cells were migrating in gradients of attractant. Video recordings and computer-aided motion analysis of migrating cells and their ciliary activity show that Tetrahymena thermophila migrate by swimming forward in semi-solid methyl cellulose, using their cilia. Ciliary reversals occur at certain intervals and cause a termination (“stop”) of cellular migration. Cells with reversed cilia resume forward migration when normal ciliary beating resumes. In gradients of attractants, cells migrating towards the attractant suppress ciliary reversals, which leads to longer runs between stops than in control cells. Cells migrating away from the attractant have a higher frequency of ciliary reversals than the control cells resulting in shorter runs. Stimulated cells adapt to a particular ambient concentration of attractant several times during migration in the gradient. Adaptation is followed by de-adaptation, which occurs during the “stop”. In the presence of cycloheximide, a strong inhibitor of chemoattraction, the attractant-induced suppression of ciliary reversal is abolished (cells become desensitized to the attractant). It is concluded that Tetrahymena has a short-term memory during adaptation. This is important for the efficiency of migration towards an attractant.