Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Capillary Action”

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 163 records · Page 9Linked to original sources
PubMed1995

Probing the inner surface of a capillary with the atomic force microscope.

The inner surface of a fused silica capillary for zone electrophoresis was probed by the atomic force microscope (AFM) in the contact mode. Only uncoated surfaces were analyzed, after a simple washing cycle with detergent, NaOH and HCl, and final equilibration in distilled water. Three progressively larger surface areas were probed: 0.5 x 0.5 micron, 2 x 2 microns and 4 x 4 microns. In all cases, it was found that the surface is remarkably smooth, with a median height increasing from 1.3 to 5.6 nm; mean height, from 1.3 to 5.8 nm; root-mean-squared roughness, from 0.35 to 1.5 nm; and average roughness, from 0.28 to 0.67 nm (the lower values referring to the smaller area, the larger to the largest area probed). The lowest "peaks" detected are of the order of 1-2 nm; some scattered peaks as high as 16 nm are occasionally found. It is concluded that the inner surface of a capillary is not a serrate or notchy structure, but is indeed quite smooth. Since the average roughness is comprised within the thickness of the diffuse double layer (> 10 nm) existing on the silica wall as a result of silanol ionization (and, in fact, it is on the average considerably smaller), it is concluded that it cannot possibly influence peak shape and contribute to peak decay in an electrophoretic run.

Capillary Action↗
PubMed1991

Capillary zone electrophoresis for the quantitation of oligosaccharides formed through the action of chitinase.

Capillary zone electrophoresis with fluorescence detection was used to analyze the products formed by chitinase acting on N-acetylchitooligosaccharide-fluorescent conjugates. Six oligosaccharides of the structure [N-acetylglucosamine(1----4)]n (where n = 1-6) were conjugated to 7-amino-1,3-naphthalene disulfonic acid by reductive amination. Each oligosaccharide-fluorescent conjugate was purified by preparative gradient polyacrylamide gel electrophoresis, semi-dry electrotransfer to a positively-charged nylon membrane and recovered by washing the membrane with salt solution. The products formed by treating each oligosaccharide-fluorescent conjugate with chitinase were analyzed by capillary zone electrophoresis. The chitinase treatment hexasaccharide-fluorescent conjugate was also examined kinetically to study the action pattern of this enzyme.

Amination↗
PubMed1998

Extracellular discontinuities in cardiac muscle: evidence for capillary effects on the action potential foot.

It has become of fundamental importance to understand variations in the shape of the upstroke of the action potential in order to identify structural loading effects. One component of this goal is a detailed experimental analysis of the time course of the foot of the cardiac action potential (Vm foot) during propagation in different directions in anisotropic cardiac muscle. To this end, we performed phase-plane analysis of transmembrane action potentials during anisotropic propagation in adult working myocardium. The results showed that during longitudinal propagation there was initial slowing of Vm foot that resulted in deviations from a simple exponential; corollary changes occurred at numerous sites during transverse propagation. We hypothesized that the effect on Vm foot observed in the experimental data was created by the microscopic structure, especially the capillaries. This hypothesis predicts that the phase-plane trajectory of Vm foot will deviate from linearity in the presence of a high density of capillaries, and that a linear trajectory will occur in the absence of capillaries. Comparison of the results of Fast and Kléber (Circ Res. 1993;73:914-925) in a monolayer of neonatal cardiac myocytes, which is devoid of capillaries, and our results in newborn ventricular muscle, which is rich in capillaries, showed drastic differences in Vm foot as predicted. Because this comparison provided experimental support for the capillary hypothesis, we explored the underlying biophysical mechanisms due to interstitial electrical field effects, using a "2-domain" model of myocytes and capillaries separated by interstitial space. The model results show that a propagating interstitial electrical field induces an inward capacitive current in the inactive capillaries that causes a feedback effect on the active membrane (source) that slows the initial rise of its action potential. The results show unexpected mechanisms related to extracellular structural loading that may play a role in selected conduction disturbances, such as in a reperfused ischemic region surrounded by normal myocardium.

Action Potentials↗
PubMed2000

A liquid core waveguide fluorescence detector for multicapillary electrophoresis applied to DNA sequencing in a 91-capillary array.

A new laser-induced fluorescence (LIF) detector for multicapillary electrophoresis is presented. The detection principle is based on waveguiding of the emitted fluorescence from the point of illumination to the capillary ends by total internal reflection (TIR) and imaging of the capillary ends. The capillaries themselves thus act as liquid core waveguides (LCWs). At the illumination point, the capillaries are arranged in a planar array, which allows clean and efficient illumination with a line-focused laser beam. The capillary ends are rearranged into a small, densely packed two-dimensional array, which is imaged end-on with high light collection efficiency and excellent image quality. Wavelength dispersion is obtained with a single prism. Intercapillary optical crosstalk is less than 0.5%, and rejection of stray light is very efficient. The detector is applied to four-color DNA sequencing by gel electrophoresis in a 91-capillary array, with simple fluorescein and rhodamine dyes as fluorophores. Since the imaged two-dimensional array is so compact, the detector has a high potential for very large-scale multiplexing.

Base Sequence↗
PubMed2004

Nonlinear electroosmosis in hierarchical monolithic structures.

We studied the dependence of electroosmotic flow (EOF) velocity and separation efficiency for neutral analytes in 100 microm ID capillary monoliths on a variation of the mobile phase ionic strength and applied electrical field strength, i.e., we covered a range for the concentration of Tris buffer from 10(-5) to 10(-2) M and applied electrical field strengths up to 10(5) V/m. The silica-based monoliths are hierarchically structured having intraskeleton mesopores and interskeleton macropores. While a linear dependence of the average EOF velocity on applied field strength could be observed with 5 x 10(-3) M Tris (turning slightly nonlinear at a higher concentration due to thermal effects), this dependence becomes systematically nonlinear as the Tris concentration is reduced towards 10(-4) M. Increased velocities by more than 50% compared to those expected from linear behavior are realized at 10(5) V/m. Concomitantly, as the Tris concentration is reduced from 10(-3) to 10(-4) M, we notice an improvement in plate heights by a factor of more than 2 (they approach 2 microm for ethylbenzoate). We complementary analyzed the onset of the nonlinear EOF dynamics in a hierarchical monolith and the significantly reduced axial dispersion in view of nonequilibrium electrokinetic effects which may develop in porous media due to the presence of ion-permselective regions, e.g., the mesoporous monolith skeleton. In this respect, a decreasing mobile phase ionic strength favors the formation of nonequilibrium concentration polarization in strong electrical fields, and a coupling of the electrostatics and hydrodynamics then may explain nonlinear EOF velocities and increasing separation efficiencies depending on the Tris concentration and applied field strength.

Capillary Action↗
PubMedDate not supplied

Unusual peaks and baseline shifts in capillary electrophoresis.

Emersion peaks, baseline shifts, and spontaneous-marker peaks in CE are documented. These baseline perturbations are observed in a simple CE system that does not employ sample injection and with sodium benzoate as the running electrolyte. Emersion peaks are attributed to the preferential adsorption of electrolyte at the air-solution interface formed upon emersion of the capillary inlet. Baseline shifts are believed to be caused by field-dependent changes in electrolyte concentration entering the capillary. These shifts may be accompanied by spontaneous-marker peaks, which may be caused by diffusion into or out of the capillary inlet between electrophoretic experiments. All baseline perturbations are detected as a change in UV absorbance signal and are transported by electroosmotic flow.

Adsorption↗
PubMedDate not supplied

Separation of two closely related serine protease analogues using HPCE/MECC with SDS in a dynamic mode.

HPCE was evaluated for the identification of different serine protease analogues. This work represents a separation of two serine proteases, Savinase (SAV) (Novo Nordisk A/S, Bagsvaerd, Denmark) and a Savinase analogue, both consisting of 269 amino acids and having identical isoelectric points. The only difference between the two protease variants is that a methionine is substituted with a serine, M222S. The separation was only made feasible by the HPCE/micellar electrokinetic capillary chromatography (MECC) technique using sodium dodecyl sulfate (SDS) dynamically as the surfactant. This paper shows that it is possible to employ HPCE/MECC to separate Savinase and a Savinase variant with no alteration in net charge.

Bacillus↗
PubMed1990

[Capillary permeability under the action of the naphthene hydrocarbons of naphtalane].

During the experiments on rats, the authors studied the influence of cyclopentanoperhydrofenantren of naphthenes; which is one of the active initials of the naphthalan, on the two-side vessel permeability for the radio active phosphorus. After repeated injection of the agent, the increase of the permeability for the indicator is noted. It is supposed that the mechanism of the action is caused by the inclusion of the agent to the biosynthesis of hormones of the suprarenals.

Animals↗
PubMed1990

Capillary permeability: atrial peptide action is independent of "protein effect".

Perfusion of exchange microvessels with the vasoactive hormone, atrial natriuretic peptide (AP), acutely and reversibly elevates hydraulic conductivity (Lp) by mechanisms that are, as yet, unknown. This, the first of two studies to characterize AP responses when perfusate composition was altered, specifically focuses on the action of AP when perfusate albumin was lowered to change the transcapillary barrier properties for water by passive mechanisms (protein effect). Perfusion of frog (Rana pipiens) mesenteric microvessels with 1 nM AP in 10 mg/ml bovine serum albumin (BSA) elevated Lp by a median 2.1-fold (range 1.2-2.7, n = 13) from control levels (10 mg/ml BSA). Reduction of perfusate albumin from 10 to 1 mg/ml elicited a small rise in Lp (1.8-fold, n = 10); Lp rose a further 2.1-fold (n = 6) when 1 nM AP was added to 1 mg/ml BSA. Likewise, protein-free perfusion elevated Lp from a median 2.2 to 5.1 X 10(-7) cm.s-1.cmH2O-1 (n = 11); 1 nM AP in protein-free perfusate elevated Lp a further 2.1-fold (n = 8). Thus, regardless of protein content, the response to the peptide was a consistent, twofold increase in exchange vessel Lp (n = 27). These data are consistent with the suggestion that the AP-activated rise in Lp (twofold) occurs via an increase in the effective area of the transcapillary pathway for water without influencing the selectivity properties of the paracellular, albumin-sensitive portion of the barrier.

Animals↗