Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Capillaries”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed2002

Estimation of sialic acid in a sialoglycan and a sialoglycoprotein by capillary electrophoresis with in-capillary sialidase digestion.

An example of application of in-capillary derivatization for CE, obtained by using the throughout-capillary format, is presented. Introduction of a sialoglycan (N-acetylneuraminyllactose) or a sialoglycoprotein (bovine serum fetuin) sample to a running buffer (pH 5.0) containing N-acetylneuraminidase followed by application of a voltage resulted in the release of N-acetylneuraminic acid (NANA) which could be estimated by CE with UV detection. Two-step application of voltages (5 and 20 kV) was proved to be more effective for rapid estimation of the released NANA. This format (modified throughout-capillary format) allowed differential estimation of the NANA present in the sample as an impurity and the NANA released from the substrate at the picomol level, and thereby reliable micro assay of the sialidase activity. It also allowed estimation of the rate constant of this enzymatic reaction.

Electrophoresis, Capillary↗
PubMed1997

Capillary zone electrophoresis with fluid-impervious polymer tubing inside a fused-silica capillary.

A fused-silica capillary was used as a mold in the in situ formation of, and as a sheath for, a highly crosslinked poly(styrene-divinylbenzene) inner tubing having 3-5 microns wall thickness. This 'tube-in-the-tube' construction with the thin-walled, fluid-impervious polymer inner tubing precluded contact between the aqueous buffer solution and the inner wall of the fused-silica capillary. As a result, this structure withstood long-term treatment with highly alkaline solutions without deterioration. In order to hydrophilize the inner surface of the polymer tube, a polyoxyethylene oligomer was grafted to its inner wall and subsequently crosslinked. The inner tube with such hydrophilic coating was also stable to hydrolytic attack by 1 M NaOH. Although the nonpolar polymeric inner surface generated electrosmotic flow as if it had some fixed negative charges, the flow velocity became almost negligibly small once it had been hydrophilized. As illustrated by electropherograms, the hydrophilization of the polymeric inner tube greatly facilitated the CZE of basic proteins in the pH range from 3 to 6 without the need for additives in the electrophoretic medium to mask the silanol groups at the surface of quartz capillaries.

Chemical Phenomena↗
PubMed1999

Capillary electrophoresis using diol-bonded fused-silica capillaries.

In this paper, 3-glycidoxypropyltrimethoxysilane was used to produce diol-bonded capillaries at room temperature for capillary electrophoresis (CE). A variety of standard reference compounds and authentic biological samples including ribonucleotides, peptides and proteins were used to test the columns. It was found that greatly suppressed electroosmotic flow was measured over a pH range of 3-10. Lower than 1.6% relative standard deviation (> 10 runs) in migration time was observed for the analysis of test proteins. For real samples of ribonucleotides in tumor cell extracts, approximately 1 million theoretical plates and excellent peak shapes were obtained. The high column efficiency and symmetrical peaks allowed the separation of samples with only 0.6% maximum difference in migration times. The diol-bonded fused-silica capillary columns were stable when used in a pH range of 2-8 under typical CE conditions. The column preparation method involved a simple dynamic coating procedure at room temperature, greatly simplifying the more typical static coating methods that require vacuum pumps and ovens.

Amino Acid Sequence↗
PubMed1999

Dynamics of capillary electrochromatography. II. Comparison of column efficiency parameters in microscale high-performance liquid chromatography and capillary electrochromatography.

In capillary electrochromatography (CEC) the flow of the mobile phase is generated by electrosmotic means in high electric field. This work compares band spreading measured experimentally in several packed capillaries with electrosmotic flow (EOF) and viscous flow under otherwise identical conditions. The data were fitted to the simplified van Deemter equation for the theoretical plate height, H = A + B/u + Cu, in order to evaluate parameters A and C in each mode of flow in the different columns. The ratio of these two parameters obtained with the same column in microscale HPLC (mu-HPLC) and CEC was used to quantify the attenuation of their contribution to band spreading upon changing from viscous flow (in mu-HPLC) to electrosmotic flow (in CEC). The capillary columns used in this study were packed with stationary phases of different pore sizes as well as retentive properties and measurements were carried out under different mobile phase conditions to examine the effects of the retention factor and buffer concentration. In the CEC mode, the value of both column parameters A and C was invariably by a factor of two to four lower than in the mu-HPLC mode. This effect may be attributed to the peculiarities of the EOF flow profile in the interstitial space and to the generation of intraparticle EOF inside the porous particles of the column packing. Thus, band spreading due to flow maldistribution and mass transfer resistances is significantly lower when the mobile phase flow is driven by voltage as in CEC, rather than by pressure as in mu-HPLC.

Buffers↗
PubMed1983

Glycogen metabolism in the capillary endothelium. Electron histochemical study of glycogen synthetase and phosphorylase in the pecten capillary of the chick.

Glycogen synthetase and phosphorylase activities in the pecten capillary of the chick were studied electron histochemically. Polyglucose particles synthesized by glycogen synthetase or phosphorylase in the pecten capillary were demonstrated to be amorphous. They were located in the cytoplasmic matrix of the endothelium and expanded it widely. The endothelial cell of the pecten capillary plays a role in glycogenesis as well as glycogenolysis and may require substantial energy to its important transport functions.

Animals↗
PubMed2004

Vascular change of hippocampal capillary is associated with vascular change of retinal capillary in aging.

Vascular deficiency, such as deleterious change of endothelial cells, becomes the prominent feature of hippocampal microvessels during the processes of aging in rodents and it seems to be associated with deficiency of intellectual behavior in aged subjects. The hippocampal microvessels and hippocampal pyramidal neurons form and accumulate intermediates of advanced Maillard reaction (glycation) end products, specifically N()-carboxymethyl lysine (CML) and CML in rodents during the processes of aging. CML facilitates proliferation of endothelial cells in culture. However, further conjugation of CML with the substance(s) seems to occur in the microvessels and pyramidal neurons of hippocampus and it brings about deleterious change of endothelial cells and pyramidal neuron death. This would cause deficiency of recognition and reference memory in rodents during the processes of aging. In man in Alzheimer's disease (AD), one might speculate that formation and accumulation of CML in the hippocampal microvessels initiate the accumulation of amyloid to produce cerebral amyloid angiopathy and it brings about hypoglycemia and hypoxia in the hippocampal pyramidal neurons. Furthermore, formation and accumulation of CML in the hippocampal pyramidal neurons initiate the deposition of neurofibrillary tangles and senile plaques which cause neuronal death. In this way, vascular deficiency of hippocampal microvessels seems to be associated with the demented disease, the atrophic process of the brain and accumulation of amyloid in the brain in man. In terms of vascular deficiency concerns, the vascular change of the retinal capillaries becomes also a prominent feature during the processes of aging and it has a positive correlation with the vascular change of hippocampal capillary. In man during senescence, one might also speculate that vascular change of eye capillaries would become the early market for diagnosis of dementia in AD.

Aging↗
PubMed2000

Capillary electrophoretic separation of proteins and peptides using Pluronic liquid crystals and surface-modified capillaries.

Separation of model mixtures of peptides/proteins carried out in a hydrophilically coated capillary in 10 mmol/l Tris and 75 mmol/l phosphate buffer containing 7.5% (w/w) Pluronic F127 copolymer (apparent pH 2.9) revealed that the separation is predominantly driven by the charge/mass ratio with little or no sieving effect. Using a coated capillary helped to remove current fluctuations that are observed in the fused-silica capillaries in the presence of the Pluronic copolymer. With peptides bearing distinct positive charge (polylysine of Mr around 3300) molecular sieving helps more detailed separation of individual species. Polyamino acids carrying negative charge can be brought to the detector window in the reversed polarity mode, however, no detailed separation of the individual species involved was observed under the conditions used. With a naturally occurring mixture of collagen fragments released by CNBr treatment of the protein the sequence of emerging peptides (positive polarity mode) with no relation to the rel. mol. mass could be revealed. It is concluded that separation of proteins/peptides in the presence of Pluronic in the background electrolyte occur on the charge/mass ratio basis with molecular sieving effects acting as a secondary partition mechanism.

Electrophoresis, Capillary↗
PubMed1997

Capillary zone electrophoresis and ion-exchange capillary electrochromatography: analytical tools for probing the Hanford nuclear site environment.

Ion-exchange capillary electrochromatography (IE-CEC) is a relatively new separation technique based on the combination of ion-exchange chromatographic and electrophoretic separation mechanisms. IE-CEC offers both the efficiency of capillary electrophoresis and the selectivity and sample capacity of ion-exchange chromatography. The utility of the method was examined with I- and IO3-, which are common constituents of nuclear wastes at Hanford, Washington and other U.S. Department of Energy (DoE) sites, and ReO4-, a surrogate for TcO4-. The advantages and limitations of IE-CEC relative to capillary zone electrophoresis (CZE) are explored. The chief advantages are increased loading capacity and an alternative selectivity to that of CZE, in addition to increased efficiency (relative to conventional ion-exchange chromatography). The run-to-run reproducibility of IE-CEC, however, was found to be a limitation of the technique.

Chromatography, Ion Exchange↗
PubMed1997

Separation of components of human globulins by capillary zone electrophoresis using a linear polyacrylamide-coated capillary.

Eleven commercially available protein preparation from human serum were subjected to capillary zone electrophoresis (CZE) using a linear polyacrylamide-coated capillary at pH 7.4. Transferrin, complement C3 and C-reactive protein were each separated into one major peak and several minor peaks. alpha 1-Antitrypsin was separated into two major peaks and three minor peaks. alpha 2-HS-glycoprotein showed four major peaks with a leading shoulder. Haptoglobin, alpha 2-macroglobulin, alpha 1-acid-glycoprotein and prealbumin were detected as relatively wide peaks. Ceruloplasmin showed one major peak with notches, and two minor and several notched peaks. Only low density lipoprotein showed no peaks. A mixture of five of the protein preparations was separated into individual components, as well as individual isoforms. When the same mixture was analyzed by CZE using an uncoated capillary, a much poorer resolution was obtained. Application of this CZE system to albumin-depleted serum demonstrated that it is very useful for analyzing globulin components in serum.

Acrylic Resins↗
PubMed1999

Separation of bovine serum albumin and its monoclonal antibody from their immunocomplexes by sodium dodecyl sulfate-capillary gel electrophoresis and its application in capillary electrophoresis-based immunoassay.

A non-competitive immunoassay was performed by sodium dodecyl sulfate-capillary gel electrophoresis with UV detection using bovine serum albumin (BSA) and monoclonal anti-BSA. BSA, anti-BSA and their immunocomplexes were well resolved under non-denaturing conditions. A linear calibration curve was obtained and can be used for the quantification of anti-BSA. The limit of detection of anti-BSA was 0.1 microM under the present conditions. Compared with capillary zone electrophoresis, we believed that this method has the potential to be used as a more general format for performing capillary electrophoresis-based immunoassay of medium- and large-sized analytes.

Antibodies, Monoclonal↗
PubMed1997

Selected applications of capillaries with dynamic or permanent anodal electroosmotic flow in chiral separations by capillary electrophoresis.

The techniques for a dynamic and permanent reversal of the electroosmotic flow (EOF) were used for the reversal of the enantiomer migration order (EMO) of neutral and cationic analytes in chiral capillary electrophoresis (CE). Native beta-Cd and an anionic CD derivative, CM-beta-CD were used in both, bare silica- and positively coated capillaries. Advantages and disadvantages of a dynamic and permanent modification of the capillary inner surface are briefly discussed.

Benzoin↗
PubMed2002

Determination of ciprofloxacin, enrofloxacin and flumequine in pig plasma samples by capillary isotachophoresis--capillary zone electrophoresis.

Quinolones are a group of synthetic antibiotics that are widely used in veterinary medicine. Their residues may remain in tissues, milk, etc. intended for human consumption. The European Union fixes the maximum residue limits (MRLs) of veterinary medicinal products in foodstuffs of animal origin. Analytical methods are therefore needed to determine them in biological samples. In this study, we describe capillary isotachophoresis-capillary zone electrophoresis (ITP-CZE) to analyze three quinolones, enrofloxacin (ENR), ciprofloxacin (CPR) and flumequine (FLU), in pig plasma samples. We used solid-phase extraction with Oasis HLB cartridges as a sample pretreatment clean-up step. Capillary zone electrophoresis (CZE) requires low amounts of sample and is not as sensitive as one would wish. ITP-CZE is an easy way to increase the sample loadability and sensitivity. With this system sensitivity increases 40-fold. The detection limits for CPR, ENR and FLU were 70, 85 and 50 microg l(-1), respectively, which were lower than their MRLs in different kinds of samples. This method is simple and sensitive, and is therefore an alternative tool to the existing HPLC methods for analyzing the residuals of these quinolones in biological samples.

Animals↗
PubMed2002

Use of surface-modified capillaries in the separation and characterization of metallothionein isoforms by capillary electrophoresis inductively coupled plasma mass spectrometry.

The separation of metallothionein (ML) isoforms using capillary electrophoresis (CE) has been improved by applying surface-modified capillaries, and the metal composition of MTs has been characterized by subsequent inductively coupled plasma sector field mass spectrometry (ICPSFMS). Nine MT complexes in a commercial preparation from rabbit liver were successfully separated on an anionic polymer-coated column, prepared by immobilizing poly(2-acrylamido-2-methyl-1-propanesulfonic acid) on the fused-silica surface via a linking agent. On uncoated capillaries or those coated dynamically with cationic materials, only three complexes could be separated. Online isotope dilution analysis combined with CE/ICPSFMS indicated the stoichiometric molar metal contents in the MT complexes.

Animals↗
PubMed2002

Capillary-electrode alignment by an optical-fiber connector for amperometric detection in capillary electrophoresis.

We describe here an electrochemical cell ideal for routine analysis of CE-EC experiments (capillary electrophoresis coupled with electrochemical detection). The cell was modified from a fiber-optic connector, named MT, which allowed frequent change and fast alignment between a pair of 4-strand fiber ribbons. The relative standard deviations of the current response and migration time for 100 microM dopamine were, respectively, 3.7 and 0.5% in five repetitive routines of disconnecting, polishing, and assembling the CE cell. The time required for alignment of the separation capillary and the working electrode was < 10 s, once all components were assembled in an MT fiber-optic plug. These features enabled CE-EC users to polish the working electrode and reassemble the EC cell as in HPLC-EC. However, to accommodate the channel dimensions of the commercially available MT, a special order capillary with outer diameter of 125 microm is necessary at this stage.

Catecholamines↗
PubMed1997

Behavior and use of nonaqueous media without supporting electrolyte in capillary electrophoresis and capillary electrochromatography.

Five nonaqueous solvents (acetonitrile, methanol, N,N-dimethylformamide, dimethyl sulfoxide, formamide) and deionized water were investigated for their ability to support electroosmotic flow (EOF) without electrolytic additives. In general, flow was found to be equal to or greater than flow with typical CE buffer systems. The magnitude of EOF was determined for each solvent by open tubular capillary electrophoresis (CE) and related to viscosity (eta), dielectric constant (epsilon), and the ratio of dielectric constant to viscosity (eta/epsilon). Zeta potentials (zeta) were derived indirectly from flow data and tabulated. Comparisons of flow behavior and zeta were made between pure solvents and conventional CE buffers, and questions of equilibrium and reproducibility were addressed. Similar experiments were performed using hydroorganic mobile phases (ACN/water, MeOH/water) across the complete compositional range (100% water-100% organic), with flow characteristics and zeta reported for each mobile phase system. Packed capillary columns (5-microns ODS) were evaluated for flow and retention stability under capillary electrochromatographic (CEC) conditions. A separation of 11 polycyclic aromatic hydrocarbons was performed in under 13 min by CEC with an ACN/water mobile phase. Reduced plate heights (h) were calculated between 2.5 and 3.0 for solutes with capacity factors (k') up to 4.5 for the most retained solute.

Acetonitriles↗
PubMed2006

Comprehensive protein profiling by multiplexed capillary zone electrophoresis using cross-linked polyacrylamide coated capillaries.

We have recently developed a new process to create cross-linked polyacrylamide (CPA) coatings on capillary walls to suppress protein-wall interactions. Here, we demonstrate CPA-coated capillaries for high-efficiency (>2 x 10(6) plates per meter) protein separations by capillary zone electrophoresis (CZE). Because CPA virtually eliminates electroosmotic flow, positive and negative proteins cannot be analyzed in a single run. A "one-sample-two-separation" approach is developed to achieve a comprehensive protein analysis. High throughput is achieved through a multiplexed CZE system.

Acrylic Resins↗
PubMed2001

Large-volume sample stacking for on-capillary sample enrichment in the determination of naphthalene- and benzenesulfonates in real water samples by capillary zone electrophoresis.

We investigated the on-line preconcentration of a test mixture of 15 substituted and unsubstituted naphthalene(NSs) and benzenesulfonates (BZSs) by large-volume sample stacking (LVSS). Analyses were carried out by capillary zone electrophoresis (CZE) with on-column UV detection. In particular, we focused on how experimental variables such as the inside diameter of the capillary, the volume of sample introduced and polarity switching influenced the enrichment procedure. The best results were obtained when 300 nl were injected and stacked using a bubble cell capillary. Under these conditions, LVSS increased the detector response of conventional hydrodynamic injection by a factor of 40. The limits of detection of the method were between 5 and 10 microg l(-1). Determinations were reproducible, in terms of peak area and migration time, under such conditions. The performance of the method was examined by determining NS and BZS in real samples, such as tap, river and surface waters and inflow/outflow waters from a water treatment plant. Real samples were injected directly into the CZE column with little or no preparation.

Benzenesulfonates↗
PubMed1968

Studies on blood capillaries. I. General organization of blood capillaries in muscle.

THE WALL OF THE BLOOD CAPILLARIES OF SKELETAL MUSCLES (DIAPHRAGM, TONGUE, HIND LEGS) AND MYOCARDIUM OF THE RAT, GUINEA PIG, AND HAMSTER CONSISTS OF THREE CONSECUTIVE LAYERS OR TUNICS: the endothelium (inner layer), the basement membrane with its associated pericytes (middle layer), and the adventitia (outer layer). The flattened cells of the endothelium have a characteristic, large population of cytoplasmic vesicles which, within the attenuated periphery of the cells, may attain a maximum frequency of 120/micro(2) of cell front and occupy approximately 18% of the cytoplasmic volume; these values decrease as the cells thicken toward the perikaryon. The vesicles are 650-750 A in over-all diameter and are bounded by typical unit membranes. They occur as single units or are fused to form short chains of two to three vesicles. Each configuration may lie entirely within the cytoplasm or open onto the cell surface. In the latter case, the unit membrane of the vesicle is continuous, layer by layer, with the plasmalemma. Chains of vesicles opening simultaneously on both the blood and tissue fronts of the endothelial tunic have not been observed either in sections or in a tridimensional reconstruction of a sector of endothelial cell cytoplasm. Adjacent endothelial cells are closely apposed to one another and appear to be joined over a large part of their margins, possibly over their entire perimeter, by narrow belts of membrane fusion (zonulae occludentes). Except for tongue capillaries, patent intercellular gaps are rare or absent. The middle layer is formed by a continuous basement membrane ( approximately 500 A thick) and by pericytes which lie in between leaflets of this membrane. The tips of the pericyte pseudopodia penetrate through the inner leaflet of the basement membrane and join the endothelium in maculae occludentes. The adventitia is a discontinuous layer comprising cellular (macrophages, fibroblasts, mast cells) and extracellular (fibrils, amorphous matrix) elements. The same general type of construction appears to be used along the entire length of the capillary.

Animals↗