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At least 199 records · Page 11Linked to original sources
PubMed1986

Cultured capillary endothelial cells from bovine adipose tissue: a model for insulin binding and action in microvascular endothelium.

Capillary endothelial cells were cultured from bovine adipose tissue. The endothelial nature of the cultures was documented by characteristic morphology, uniform presence of factor VIII antigen, and uptake of the endothelial cell marker Dil-Ac-LDL. The capillary cell cultures had specific, high affinity binding sites for insulin, demonstrating time and temperature dependence of binding, pH optimum, analog specificity, and inhibition of insulin binding by anti-insulin receptor antibodies. In both subconfluent and confluent cultures, insulin stimulated thymidine incorporation into DNA; significant stimulatory effects of insulin were observed at insulin concentrations of 1 ng/ml with maximal 8- to 10-fold increases at hormone concentrations of 1,000 to 10,000 ng/ml. Because of the ease of routine preparation, cell purity, presence of high affinity insulin binding sites, and insulin-sensitive metabolic responses, we suggest that the bovine capillary endothelial cultures could serve as a model cell system for the detailed study of insulin interactions with capillary endothelial cells.

Adipose Tissue↗
PubMed1995

Manipulation of a single cell with microcapillary tubing based on its electrophoretic mobility.

Manipulation of a single cell of spherical shape, approximately 5-10 microns in diameter, was performed with capillary tubing and an electrostatic field. A single cell migrates with its electrophoretic mobility into capillary tubing against the flow of electroosmosis coming out of the capillary. After trapping the cell in the capillary, it is pulled out into the other microreservoir with the application of a reverse electric voltage. When we apply a negative voltage to the microreservoir itself, the cell in it can keep floating for a relatively long period due to electrostatic repulsion. The electrophoretic mobility of a single cell is also estimated.

Animals↗
PubMed2001

Interface-mediated oscillatory phenomena.

Oscillatory transport processes which occur in the far from equilibrium region have assumed great significance from the viewpoint of science of complexity. Oscillatory phenomena in the chemical reaction systems have been subjected to intense investigations both from theoretical and experimental angles. In the present review an effort has been made to bring transport processes other than conventional chemical reactions into focus: transport processes mediated by solid-liquid and liquid-liquid interfaces have been discussed. Transport through membranes including liquid membranes, liquid-liquid interfaces and the recently reported hydrodynamic oscillator have been covered. Applications of these systems in areas such as fabrication of sensors, phase transfer catalysis and, of course, the obvious biological action, e.g. excitation of biomembranes and tissues, have been reviewed. Theoretical frameworks proposed to rationalize the phenomena have also been critically reviewed.

Capillary Action↗
PubMed2002

Complete structure of an increasing capillary permeability protein (ICPP) purified from Vipera lebetina venom. ICPP is angiogenic via vascular endothelial growth factor receptor signalling.

The partial sequence of the increasing capillary permeability protein (ICPP) purified from Vipera lebetina venom revealed a strong homology to vascular endothelial growth factor (VEGF)-A. We now report its complete amino acid sequence determined by Edman degradation and its biological effects on mouse and human vascular endothelial cells. ICPP is a homodimeric protein linked by cysteine disulfide bonds of 25115 Da revealed by mass spectrometry. Each monomer is composed of 110 amino acids including eight cysteine residues and a pyroglutamic acid at the N-terminal extremity. ICPP shares 52% sequence identity with human VEGF but lacks the heparin binding domain and Asn glycosylation site. Besides its strong capillary permeability activity, ICPP was found to be a potent in vitro angiogenic factor when added to mouse embryonic stem cells or human umbilical vein endothelial cells. ICPP was found to be as potent as human VEGF165 in activating p42/p44 MAPK, in reinitiation of DNA synthesis in human umbilical vein endothelial cells, and in promoting in vitro angiogenesis of mouse embryonic stem cells. All these biological actions, including capillary permeability in mice, were fully inhibited by 1 microm of a new specific VEGF receptor tyrosine kinase inhibitor (ZM317450) from AstraZeneca that belongs to the anilinocinnoline family of compounds. Indeed, up to a 30 times higher concentration of inhibitor did not affect platelet-derived growth factor, epidermal growth factor, FGF-2, insulin, alpha-thrombin, or fetal calf serum-induced p42/p44 MAPK and reinitiation of DNA synthesis. Therefore, we conclude that this venom-derived ICPP exerts its biological action (permeability and angiogenesis) through activation of VEGF receptor signaling (VEGF-R2 and possibly VEGF-R1).

Amino Acid Sequence↗
PubMed2000

Self-Assembly of Hexagonal Rod Arrays Based on Capillary Forces.

A series of well-ordered, extended mesostructures has been generated from hexagonal polyurethane rods (15x3.2 mm) by self-assembly using capillary forces. The surface of one or more sides of the rods was rendered hydrophilic by exposure to an oxygen plasma. This modification determined the pattern of hydrophobic and hydrophilic faces; the hydrophobic sides were coated with a thin film of a hydrophobic lubricant. Agitation of the rods in an approximately isodense aqueous environment resulted in their self-assembly, in a process reflecting the action of capillary forces, into an array whose structure depends on the pattern of hydrophobic sides; capillarity also aligned the ends of the rods. We also carried out experiments in reaction chambers that restricted the motion of the rods; this restriction served to increase the size and regularity of the assemblies. Copyright 2000 Academic Press.

Journal Article↗
PubMed1996

Profilin forms tetramers that bind to G-actin.

Profilin binds to G-actin and affects polymerization. However, regulation of profilin function is generally unknown and controversy exists regarding profilin effects on actin polymerization. Because protein-protein interactions are implicated in many cellular responses, human platelet profilin self-association and actin inter-action was examined. Silver stained SDS-PAGE of poly-l-proline/sepharose 4B column purified profilin revealed the presence of profilin (14.8 kD) and extraneous higher bands (primarily 30 kD and 58.5 kD). Re-electrophoretic analysis of gel electroelution purified profilin yielded predominantly 14.8 kD and 58.5 kD proteins. Rabbit IgG antibodies made against gel electroelution-purified profilin recognized all profilin sizes on immunoblots. Capillary electrophoresis of profilin in solution produced a single peak that resolved into three distinct peaks upon addition of reducing agent or high salt conditions. Further, G-actin did not bind to 14.8 kD profilin on immunoblot overlay assays, but surprisingly bound only to 58.5 kD profilin. The data indicate that monomeric profilin forms tetramers which are the relevant high affinity actin-binding form.

Actins↗
PubMed1991

Analysis of endoproteinase Arg C action on adrenocorticotrophic hormone by capillary electrophoresis and reversed-phase high-performance liquid chromatography.

The specificity and rate of cleavage of adrenocorticotrophic hormone (ACTH) peptide bonds by endoproteinase Arg C were analyzed using capillary electrophoresis (CE) and reversed-phase (C18) high-performance liquid chromatography (HPLC). Acidic cleavage products were readily resolved by CE in uncoated capillaries using low ionic strength electrolytes. However, products predicted to have a net positive charge greater than 2 or more than 4 positively charged groups per peptide did not migrate out from the capillary at low ionic strength. Addition of salts and zwitterions to the electrolyte decreased capillary-peptide interactions such that all of the ACTH peptides examined were eluted with high efficiency separation by CE. Commercially obtained endoproteinase Arg C preparations exhibited peptidase activity at Lys-15-Lys16 and at Lys16-Arg17 in addition to the expected cleavage at Arg-X bonds. ACTH peptide bond cleavage rates for Arg8-Trp9, Arg17-Arg-18, Lys15-Lys16, and Lys16-Arg17 were 1.46, 0.096, 0.57, and 0.029 mumol min-1 mg-1 respectively. CE separations generally exhibited better resolution and were accomplished in shorter times than C18 HPLC separations. These properties make CE a particularly appropriate method for kinetic analysis of proteolytic enzyme action on peptide substrates.

Adrenocorticotropic Hormone↗
PubMed2007

Graded occlusion of perfused rat muscle vasculature decreases insulin action.

Insulin increases capillary recruitment in vivo and impairment of this may contribute to muscle insulin resistance by limiting either insulin or glucose delivery. In the present study, the effect of progressively decreased rat muscle perfusion on insulin action using graded occlusion with MS (microspheres; 15 mum in diameter) was examined. EC (energy charge), PCr/Cr (phosphocreatine/creatine ratio), AMPK (AMP-activated protein kinase) phosphorylation on Thr(172) (P-AMPKalpha/total AMPK), oxygen uptake, nutritive capacity, 2-deoxyglucose uptake, Akt phosphorylation on Ser(473) (P-Akt/total Akt) and muscle 2-deoxyglucose uptake were determined. Arterial injection of MS (0, 9, 15 and 30 x 10(6) MS/15 g of hindlimb muscle, as a bolus) into the pump-perfused (0.5 ml x min(-1) x g(-1) of wet weight) rat hindlimb led to increased pressure (-0.5+/-0.8, 15.9+/-2.1, 28.7+/-4.6 and 60.3+/-9.4 mmHg respectively) with minimal changes in oxygen uptake. Nutritive capacity was decreased from 10.6+/-1.0 to 3.8+/-0.9 micromol x g(-1) of muscle x h(-1) (P<0.05) with 30 x 10(6) MS. EC was unchanged, but PCr/Cr was decreased dose-dependently to 61% of basal with 30 x 10(6) MS. Insulin-mediated increases in P-Akt/total Akt decreased from 2.15+/-0.35 to 1.41+/-0.23 (P<0.05) and muscle 2-deoxyglucose uptake decreased from 130+/-19 to 80+/-12 microg x min(-1) x g(-1) of dry weight (P<0.05) with 15 x 10(6) MS; basal P-AMPKalpha in the absence of insulin was increased, but basal P-Akt/total Akt and muscle 2-deoxyglucose uptake were unaffected. In conclusion, partial occlusion of the hindlimb muscle has no effect on basal glucose uptake and marginally impacts on oxygen uptake, but markedly impairs insulin delivery to muscle and, thus, insulin-mediated Akt phosphorylation and glucose uptake.

Adenylate Kinase↗
PubMed2000

Clinical efficacy of micronized purified flavonoid fraction (MPFF) in edema.

Swelling is one of the most frequent complaints of patients in daily clinical practice; leg edema is its objective confirmation. It can be associated with several diseases. Micronized purified flavonoid fraction (MPFF) is a phlebotropic drug commonly used to treat the signs and symptoms associated with chronic venous insufficiency (CVI). It has confirmed its clinical efficacy in different groups of patients suffering from edema: idiopathic cyclic edema, CVI-associated edema, postmastectomy lymphedema and might be beneficial in some of drug-induced edema. In a double-blind, placebo-controlled, randomized study including 30 outpatients suffering from idiopathic cyclic edema syndrome, MPFF 1000 mg/day for 6 weeks, normalized the capillary permeability, assessed by the Landis isotope test, in 3 out of 4 patients (p=0.01). The decrease in capillary hyperpermeability led to a clinically significant decrease in weight and edema. In 200 patients with functional or organic venous insufficiency of the lower limbs, a double-blind, placebo-controlled, randomized study with MPFF 1000 mg/day for 2 months provided strong evidence of a marked improvement in symptoms and signs. A significant reduction in supramalleolar edema (assessed by circumference measurement) was observed, whatever the origin of CVI: functional or organic. MPFF efficacy was also demonstrated in another randomized, multicenter controlled trial in 320 patients suffering from chronic venous insufficiency. In this study, a significant decrease in circumference of the most affected leg was observed after 2 months of treatment (p<0.001), whatever the schedule of administration of MPFF (1000 mg once daily or bid). The benefit of MPFF on edema has been further confirmed by the volometer technique (opto-electronic measuring system) which was performed in a population of 30 patients suffering from CVI and treated by MPFF 1000 mg/day over a 6-week period. The mean volume of the more affected lower leg decreased significantly after a 6-week period of treatment, correlating to a significant improvement in clinical symptoms. MPFF has been also tested on another type of edema, upper limb lymphedema secondary to mastectomy, during a double-blind, placebo-controlled, randomized study in 104 patients. MPFF 1000 mg/day improved all lymphoscintigraphic parameters such as half-life and clearance of the labelled colloid. With regard to evolution of lymphedema volume, a tendency in favor of MPFF was observed in the subgroup of patients with more severe lymphedema. Based on its action on capillary hyperpermeability, MPFF has been used with attractive results when combined with classic treatment for a pilot study carried out in patients with advanced breast cancer (n=21) or ovarian carcinoma (n=3), treated with docetaxel, which causes severe edema as a side effect, even when associated with corticoids. Further trials are under way to assess the possible benefit of MPFF in such patients. These results in different types of edema confirm that, by acting on all parameters involved in edema, veins, lymphatics, and microcirculation, MPFF represents a drug of choice for treating CVI-associated edema.

Anthropometry↗
PubMed2003

Carbazochrome sodium sulfonate (AC-17) reverses endothelial barrier dysfunction through inhibition of phosphatidylinositol hydrolysis in cultured porcine endothelial cells.

The effect of carbazochrome sodium sulfonate (AC-17), a hemostatic drug with capillary stabilising action, on the endothelial barrier dysfunction induced by a variety of vasoactive substances or agents that increase the vascular permeability was investigated in the monolayers of cultured porcine aortic endothelial cells (PAECs). The endothelial barrier function was determined by the transendothelial transport of albumin-conjugated Evans blue. AC-17 (0.1-1 M) reversed the barrier dysfunction induced by tryptase, thrombin and bradykinin without affecting the endothelial permeability enhanced by Ca(2+) ionophores such as ionomycin and A23187 or phorbol 12-myristate 13-acetate. Immunofluorescence analysis showed that AC-17 reversed the tryptase-induced formation of actin stress fibres and disruption of VE-cadherin in PAECs. On the other hand, AC-17 (0.1-10 M) reduced concentration-dependently the enhancement of [(3)H]inositol triphosphate formation from [(3)H]myo-inositol induced by bradykinin and thrombin.Therefore, it is suggested that AC-17 reduces the vascular hyperpermeability induced by a variety of vasoactive agents through inhibition of agonist-induced phosphoinositide hydrolysis.

Actins↗
PubMed2000

Capillary interactions between particles bound to interfaces, liquid films and biomembranes.

This article is devoted to an overview, comparison and discussion of recent results (both theoretical and experimental) about lateral capillary forces. They appear when the contact of particles or other bodies with a fluid phase boundary causes perturbations in the interfacial shape. The capillary interaction is due to the overlap of such perturbations which can appear around floating particles, vertical cylinders, particles confined in a liquid film, inclusions in the membranes of lipid vesicles or living cells, etc. In the case of floating particles the perturbations are due to the particle weight; in this case the force decreases with the sixth power of the particle size and becomes immaterial for particles smaller than approximately 10 microm. In all other cases the interfacial deformations are due to the particle wetting properties; the resulting 'immersion' capillary forces can be operative even between very small particles, like protein globules. In many cases such forces can be responsible for the experimentally observed two-dimensional particle aggregation and ordering. An analogy between capillary and electrostatic forces enables one to introduce 'capillary charges' of the attached particles, which characterize the magnitude of the interfacial deformation and could be both positive and negative. Moreover, the capillary interaction between particle and wall resembles the image force in electrostatics. When a particle is moving bound to an interface under the action of a capillary force, one can determine the surface drag coefficient and the surface viscosity supposedly the magnitude of the capillary force is known. Alternative (but equivalent) energy and force approaches can be used for the theoretical description of the lateral capillary interactions. Both approaches require the Laplace equation of capillarity to be solved and the meniscus profile around the particles to be determined. The energy approach accounts for contributions due to the increase of the meniscus area, gravitational energy and/or energy of wetting. The second approach is based on calculating the net force exerted on the particle, which can originate from the hydrostatic pressure, interfacial tension and bending moment. In the case of small perturbations, the superposition approximation can be used to derive an asymptotic formula for the capillary forces, which has been found to agree well with the experiment. Capillary interactions between particles bound to spherical interfaces are also considered taking into account the special geometry and restricted area of such phase boundaries. A similar approach can be applied to quantify the forces between inclusions (transmembrane proteins) in lipid membranes. The deformations in a lipid membrane, due to the inclusions, can be described theoretically in the framework of a mechanical model of the lipid bilayer, which accounts for its 'hybrid' rheology (neither elastic body nor fluid). In all considered cases the lateral capillary interaction originates from the overlap of interfacial deformations and is subject to a unified theoretical treatment, despite the fact that the characteristic particle size can vary from 1 cm down to 1 nm.

Capillary Action↗
PubMed2001

The role of fenestrations and channels on the transverse motion of a soft contact lens.

PURPOSE: Ineffectual removal of potentially harmful species from the postlens tear film (POLTF) may lead to adverse responses among extended wearers of soft contact lenses. It is apparently important to remove bacteria, cell debris, and metabolic products from the postlens tear film to the outer tear lake; the flushing or dispersion rate of these species is enhanced by increasing fluid movement in the tear film driven by periodic lens motion. The contact lens moves laterally (up-down) and transversally (in-out) due to the action of the eyelid forces during blinking. Viscous drag in the POLTF resists lens motion. Consequently, any design change in the lens that reduces viscous drag increases motion and improves flushing of unwanted species from the POLTF. We investigate quantitatively the effect of channels cut on the back surface of the lens and fenestrations (holes) drilled through the lens on transverse lens motion. METHODS: We model the lens as a curved solid body with a periodic arrangement of channels/holes. The cornea is treated as a flat surface, and the hydrodynamic equations of motion are solved for Newtonian fluid transport in the POLTF assuming lubrication and creeping flow. POLTF pressure profiles, obtained by solving these equations, are integrated to determine the lens settling velocity in the transverse direction for a given amount of applied lid force. Lens settling velocity is then compared with the same velocity in the absence of channels/fenestrations. Further, we calculate the total transverse motion in a blink for lenses with and without channels/fenestrations to estimate the possible enhancement in transverse motion due to the channels/fenestrations. RESULTS: Variables that affect the fluid mixing in the POLTF are the postlens tear film thickness, lens thickness, channel length, depth and spacing, and the hole diameter, location, and spacing. We study the effect of each of these variables on the enhancement of transverse motion for channels and holes of diameters varying from 0.1 to 2 mm with spacing varying from 1 to 5 mm. CONCLUSIONS: We demonstrate that incorporation of channels and holes reduces viscous resistance and increases transverse lens motion, and thus increases fluid mixing and dispersive flushing from the POLTF. The increase in transverse motion depends strongly on the postlens tear film thickness. Enhancement of the transverse motion varies from a factor of about 2 to 20 depending on the particular lens design and the postlens tear film thickness. Because fluid mixing increases up to the square of the transverse motion, channels/holes are expected to render flushing of the POLTF considerably more effective. We find that channels and/or fenestrations, when appropriately designed, can provide significant improvement in flushing from the POLTF. This work provides a new quantitative tool for the efficient design of channels/holes in soft contact lenses.

Biomechanical Phenomena↗
PubMed1975

The Dalkon Shield controversy. Structural and bacteriological studies of IUD tails.

The recent report of 209 cases of septic spontaneous abortion and 11 maternal deaths in the United States in women using the Dalkon Shield intrauterine device (IUD) raised the question about a possible causal relationship between the IUD and pelvic sepsis. It is essential to determine whether or not this sipsis is unique to the Dalkon Shield or generic to all types of IUDs. Our studies permit the conclusion that the tail of the Dalkon Shield is structurally and functionally different from the tails of the four other IUDs tested. The unique characteristics of the Dalkon tail theoretically could provide a mechanism whereby pathogenic bacteria from the vagina enter the uterine cavity and cause sepsis.

Abortion, Septic↗
PubMed1997

Electrophoresis of proteins in semidilute polyethylene glycol solutions: mechanism of retardation.

The retardation of proteins in the M(r) range of 15-500 kDa in capillary electrophoresis conducted in semidilute solutions of the polymer polyethylene glycol (M(r) range 0.2-8.0 X 10(6)), was measured. The purpose was to test the predictions of the scaling theory with regard to the relation of retardation to (a) the M(r) of the polymer, (b) the concentration of the polymer, and (c) the radius of the protein particles. These predictions derive from a mechanism that relates retardation to the screening length of the polymer solution, viewed as the average distance between the entanglement points of polymer chains. For the molecular weight range from 60 to 500 kDa of (near) spherical proteins, the retardation was found to be related to polymer concentration c as mu/mu(0) = exp(-Ac0.69) where mu/mu(0) is the retardation expressed as the ratio between the mobility in polymer solution and that in free solution. The value of the exponent of 0.69 is in close agreement with the value of 0.75 predicted by the scaling theory. Parameter A was found (a) to scale as the 0.04th power of M(r) (polymer), approximating the predicted value of 0; and (b) to be proportional to particle radius as predicted. All measured values of retardation were independent of electric field strength in the range of 37-370 V/cm. Thus, experimental findings are consistent with the mechanism relating electrophoretic retardation to the screening length of the polymer network in the specified molecular weight range of proteins. Under the same conditions, log(mu/mu(0)) of proteins with M(r)'s less than 60 kDa (a) scales as the -0.06th power of M(r) (polymer), and (b) is proportional to polymer concentration, suggesting a retardation mechanism that is not related to the screening length.

Capillary Action↗