Home About us Contact
|
Home About us Contact | ||
|
|
||
Migration Behavior (migration + behavior)
Selected AbstractsBlockage of voltage-gated calcium signaling impairs migration of glial cells in vivoGLIA, Issue 3 2005Christian Lohr Abstract Migration of glial cells is an essential step in the development of the antennal lobe, the primary olfactory center of insects, to establish well-defined borders between olfactory glomeruli required for odor discrimination. In the present study, we used two-photon microscopy to visualize calcium signaling in developing antennal lobe glial cells of the sphinx moth Manduca sexta. We found a correlation between the upregulation of functional voltage-gated calcium channels and the onset of glial cell migration. In addition, glial cells migrating into the center of the antennal lobe express larger voltage-gated calcium transients than glial cells that remain at the periphery. Migration behavior and calcium signaling of glial cells in vivo were manipulated either by deafferentation, by injection of the calcium channel blockers diltiazem, verapamil, and flunarizine, or by injection of the calcium chelators BAPTA-AM and Fluo-4-AM. In deafferented antennal lobes, glial cells failed to express functional voltage-gated calcium channels and did not migrate. Calcium channel blockage or reducing glial calcium signals by calcium chelators prevented glial cell migration and resulted in antennal lobes lacking glial borders around glomeruli, indicating that voltage-gated calcium signaling is required for the migration of antennal lobe glial cells and the development of mature olfactory glomeruli. © 2005 Wiley-Liss, Inc. [source] Recent developments in peptide stereoisomer separations by capillary electromigration techniquesELECTROPHORESIS, Issue S1 2009Gerhard K. E. Scriba Abstract The stereochemistry of peptides determines their physicochemical and biological activities. Thus, analytical methods that are able to discriminate between peptide stereoisomers are important. As peptides are typically hydrophilic compounds, many methods for the separation of peptide diastereomers and enantiomers have been developed by capillary electromigration techniques. Moreover, peptide enantiomers displayed unique migration behavior such as a pH-dependent change of the enantiomer migration order in CD-mediated enantioseparations in CE making them ideal compounds to study mechanistic effects of enantioseparations. The present short review summarizes recent developments in the separation of stereoisomers of peptide and peptidomimetics by capillary electromigration techniques. Moreover, recent NMR and molecular modeling studies as well as investigation on the effect of buffer additives on complex formation will be discussed as attempts to understand mechanistic aspects of peptide enantioseparations and to analyze the structure of peptide-CD complexes. [source] Retention of proteins and metalloproteins in open tubular capillary electrochromatography with etched chemically modified columns,ELECTROPHORESIS, Issue 18 2008Joseph J. Pesek Abstract Etched chemically modified capillaries with two different bonded groups (pentyl and octadecyl) are compared for their migration behavior of several common proteins and metalloproteins as well as metalloproteinases. Migration times, efficiency and peak shape are evaluated over the pH range of 2.1,8.1 to determine any effects of the bonded group on the electrochromatographic behavior of these compounds. One goal was to determine if the relative hydrophobicity of the stationary phase has a significant effect on proteins in the open tubular format of capillary electrochromatography as it does in HPLC. Reproducibility of the migration times is also investigated. [source] Association of europium(III), americium(III), and curium(III) with cellulose, chitin, and chitosanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Takuo Ozaki Abstract The association of trivalent f-elements,Eu(III), Am(III), and Cm(III),with cellulose, chitin, and chitosan was determined by batch experiments and time-resolved, laser-induced fluorescence spectroscopy (TRLFS). The properties of these biopolymers as an adsorbent were characterized based on speciation calculation of Eu(III). The adsorption study showed that an increase of the ionic strength by NaCl did not affect the adsorption kinetics of Eu(III), Am(III), and Cm(III) for all the biopolymers, but the addition of Na2CO3 significantly delayed the kinetics because of their trivalent f-element complexation with carbonate ions. It also was suggested from the speciation calculation study that all the biopolymers were degraded under alkaline conditions, leading to their masking of the adsorption of Eu(III), Am(III), and Cm(III) on the nondegraded biopolymers. The masking effect was higher for cellulose than for chitin and chitosan, indicating that of the three, cellulose was degraded most significantly in alkaline solutions. Desorption experiments suggested that some portion of the adsorbed Eu(III) penetrated deep into the matrix, being isolated in a cavity-like site. The TRLFS study showed that the coordination environment of Eu(III) is stabilized mainly by the inner spherical coordination in chitin and by the outer spherical coordination in chitosan, with less association in cellulose in comparison to chitin and chitosan. These results suggest that the association of these biopolymers with Eu(III), Am(III), and Cm(III) is governed not only by the affinity of the functional groups alone but also by other factors, such as the macromolecular steric effect. The association of degraded materials of the biopolymers also should be taken into consideration for an accurate prediction of the influence of biopolymers on the migration behavior of trivalent f-elements. [source] Comparison of Cyclodextrin-Dipeptide Inclusion Complexes in the Absence and Presence of Urea by Means of Capillary Electrophoresis, Nuclear Magnetic Resonance and Molecular ModelingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2007Benjamin Waibel Abstract The use of capillary electrophoresis (CE) modified with cyclodextrin (CD) for the separation of stereoisomers of peptides is well established. To increase the solubility of ,-CD, urea is often added to the buffer which may influence the complexation of a CD with a guest molecule. The aim of the present study was to investigate the influence of urea on the complexation between dipeptides and ,-CD using Ala-Phe and Ala-Tyr as model compounds. For this purpose three different analytical methods were employed: capillary electrophoresis (CE), 1H-NMR spectroscopy and molecular dynamics simulations (MD). Electropherograms of the peptide enantiomers were different in the presence and absence of urea. For example, at pH,2.5 in the absence of urea the enantiomers of Ala-Tyr are not separated in contrast to the use of buffers containing urea. Applying "complexation-induced chemical shift (CICS)" in NMR spectroscopy and rotating frame Overhauser enhancement spectroscopy (ROESY) revealed differences in the complexation of the peptide enantiomers by ,-CD in the absence and presence of urea suggesting the stabilization of the complex through the phenolic hydroxyl group of tyrosine. MD simulations for different complexes were carried out with consideration of both water and urea molecules in solution. Simulations were performed for 1 ns. In conclusion, NMR spectroscopy and MD methods help to understand the structure of peptide-CD complexes and the separation and migration behavior in CE. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] PR-39 coordinates changes in vascular smooth muscle cell adhesive strength and locomotion by modulating cell surface heparan sulfate,matrix interactionsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2001John H. Chon PR-39 is proline-rich peptide produced at sites of tissue injury. While the functional properties of this peptide have not been fully defined, PR-39 may be an important regulator of processes related to cell-matrix adhesion since it reportedly upregulates syndecan-4, which is a critical determinant of focal adhesion formation. The ability of PR-39 to modulate the adhesion and chemokinetic migration behavior of arterial smooth muscle cells (SMCs) in a fashion coordinated with syndecan-4 expression was investigated. Treatment of SMCs with PR-39 did not alter syndecan-1 mRNA, but did induce a two-fold increase in syndecan-4 mRNA (P,<,0.0001) and significantly enhanced cell surface expression of both syndecan-4 (P,<,0.01) and heparan sulfate (HS) (P,<,0.05). These observations were consistent with an observed increase in cell-matrix adhesive strength (P,<,0.05) and a reduction in cell speed (P,<,0.01) on fibronectin-coated substrates. Incubation of PR-39 treated cells with a soluble fibronectin derived heparin-binding peptide, as a competitive inhibitor of heparan sulfate/matrix interactions, abolished these effects. These data suggest that PR-39 mediated alterations of cell adhesion and motility may be related, in part, to the increased expression of heparan sulfate glycosaminoglycans (GAGs) that accompany the upregulation of cell surface syndecan-4. Futhermore, this investigation supports the notion that factors which control syndecan-4 expression may play an important role in regulating adhesion related cell processes. © 2001 Wiley-Liss, Inc. [source] 83 Comparative analysis of vertically migrating euglena viridis populations in tidal and non-tidal benthic environmentsJOURNAL OF PHYCOLOGY, Issue 2003M.B. KingstonArticle first published online: 12 JAN 200 Benthic populations of Euglena viridis exhibit vertical migration behavior on high energy intertidal beaches and along the sand banks of freshwater streams. This study examines similarities and differences in the migratory behavior and cell morphology of populations of E. viridis inhabiting Scripps Beach, La Jolla, California and Coble Brook, Burlington, North Carolina. The timing of migration was measured by counting the number of cells in samples collected from the sediment surface throughout the day. Sediment cores were extracted and sectioned to determine the vertical distribution of the population. Neutral density filters and opaque canisters were used to shade the substratum to 56%, 22%, 2%, and 0% of incident irradiance (Io) to examine the effect of light on cell morphology and migratory behavior. On intertidal beaches, E. viridis exhibited a tidal rhythm in vertical migration with cells migrating below the sediment surface at night (>15 cm) and during daytime high tides. In this habitat, the upward migration response was enhanced at irradiances lower than 100% Io but cell morphology was not altered by shading. On the banks of freshwater streams, E. viridis exhibited a diurnal migratory rhythm with both tear-drop and spherical morphologies observed throughout the day. The population was most concentrated at the surface around solar noon and at night it was located between 1 and 2 cm below the surface. Shading did not enhance upward migration but it did affect cell morphology. These results will be interpreted in the context of the dominant selection pressures in each environment. [source] Capillary electrophoresis with capacitively coupled contactless conductivity detection for low molecular weight organic acids in different samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2007Wai Siang Law Abstract CE with capacitively coupled contactless conductivity detection (CE-C4D) was explored and validated for the identification and quantification of organic acids in various types of samples. The analyses were performed under optimized conditions, using a buffer system composed of 20 mM MES-histidine (His), pH 6.0, 0.1 mM CTAB, 0.025% HP-,-CD, and 10% methanol. The investigation included a study of the effects of buffer pH, concentration of CTAB, type and concentration of organic additives, on the migration behavior, resolution and selectivity of the organic acids. The intra- and interday RSDs (n = 6) obtained for migration time and peak area were typically in the range of 0.12,2% and 0.5,4%, respectively. Linearity, detection limits, and repeatability were evaluated. In order to evaluate the application potential of the developed method, real samples from different sources were analyzed. The results demonstrate that CE-C4D is a versatile tool for analyzing organic acids in beverages, Chinese herbal medicines (CHM) and plants as it allows for their detection, identification, and quantification. [source] Hydrophilization of polypropylene films by using migratory additivesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2007Siqiang Zhu Linear and branched hydrophilic additives of various molecular weights (MWs) were extruded with polypropylene (PP) to make blend films. The surface-modifying additives included polyethylene glycol (PEG), hydroxyl-terminated four-arm polyethylene oxide (PEO), and a commercial hydrophilic additive, Irgasurf HL560. Films were extruded by using a twin-screw microcompounder at 200°C, and the resulting film thickness was 100 ,m. Attenuated total reflectance (ATR)-FTIR spectrometry and water contact angle measurements were performed on the film surfaces over time to investigate the additive migration behavior. Although ATR-FTIR detected concentration increases for all additives in the subsurface region, there was no significant improvement in surface hydrophilicity for the PEGs and four-arm PEOs in the same period of time as water contact angles were measured on the surfaces. Among the linear additives, low MW PEG (1 kDa) was found to migrate faster than the high MW varieties. The linear PEG and four-arm PEO with MW higher than 2 kDa did not exhibit significant migration to the surface within a month. Irgasurf was found to change the surface wettability effectively in a relatively short time. J. VINYL ADDIT. TECHNOL., 13:57,64, 2007. © 2007 Society of Plastics Engineers. [source] Correlation between molecular structures and relative electrophoretic mobility in capillary electrophoresis: AlkylpyridinesCHINESE JOURNAL OF CHEMISTRY, Issue 10 2003Xiao-Jun Yao Abstract The quantitative relationship between relative electrophoretic mobility in capillary electrophoresis for a series of 31 closely related alkylpyridines and their molecular structures was studied by using CODESSA. According to the t -test on the results, we found that the three most important descriptors affecting the mobility are the relative number of rings (NR), Min e-n attraction for a C,-N bond (MEN) and average complementary information index (ACIC). With these structure descriptors a good three-parameter linear model was developed to correlate the mobility of these compounds with their structures. This model can not only correctly predict the migration behavior of these compounds, but also find the structural factors which are responsible for the migration behavior of these compounds, thus can help to explain the separation mechanism of these compounds. The method used in this work can also be extended to the mobility-structure relationship research of other compounds. [source] | |||||||||||||