Inside Capillaries Research Articles

A Protein Toxin from the Sea Anemone Phyllodiscus semoni Targets the Kidney and Causes a Severe Renal Injury with Predominant Glomerular Endothelial Damage

Envenomation by the sea anemone Phyllodiscus semoni causes fulminant dermatitis and, rarely, acute renal failure in humans. Here, we investigated whether the venom extracted from the nematocysts (PsTX-T) was nephrotoxic when administered intravenously in rats and whether PsTX-T induced activation of the complement system. Although small dose of PsTX-T induced acute tubular necrosis in rats resembling pathology seen in patients, kidneys displayed glomerular injury with glomerular endothelial damage, thrombus formation, mesangiolysis, and partial rupture of glomerular basement membrane, accompanied by severe tubular necrosis at 24 hours after administration of 0.03 mg of PsTX-T per animal, similar to the glomerular findings typical of severe hemolytic uremic syndrome. The early stage injury was accompanied by specific PsTX-T binding, massive complement C3b, and membrane attack complex deposition in glomeruli in the regions of injury and decreased glomerular expression of complement regulators. A pathogenic role for complement was confirmed by demonstrating that systemic complement inhibition reduced renal injury. The isolated nephrotoxic component, a 115-kd protein toxin (PsTX-115), was shown to cause identical renal pathology. The demonstration that PsTX-T and PsTX-115 were highly nephrotoxic acting via induction of complement activation suggests that inhibition of complement might be used to prevent acute renal damage following envenomation by P. semoni.

Perfusion of Endothelial Capillary Structure in Tissue Engineered Constructs by In Vitro Inosculation

In the present study we wanted to prove controlled perfusion of endothelial cells capillary channels in a collagen/chitosan/glycosaminoglycan (CCGAG) biopolymer inosculated on to a microfabricated device. This connection between a microfluidic structure, with one inlet and one outlet, and a tissue engineered construct made from human fibroblasts and umbilical vein endothelial cells should allow the generation of flow inside capillaries spontaneously created by endothelial cells within the biopolymer. We used many soft lithographic techniques to create the polycaprolactone-poly (DL-lactide-co-glycolide) acid microfluidic structure. The biopolymer is made by freeze-drying the CCGAG solution, and then cells are seeded and cultured for a total of 31 days. Then the microfluidic structure and the biopolymer are cultured together in a bioreactor where degradation of the top layer of the microfluidic device allows inosculation in this model. We have shown such an inosculation phenomenon in our model by injecting fluorescent microspheres in the microfluidic device, separated the biopolymer from the device and performed confocal microscopy study on 30um thick cryostat sliced sample. Those are promising results for various applications such as tissue engineered vascularized organ substitutes and in vitro pharmacodynamics and angiogenesis studies. Financial support (NRC-CIHR grant 66473)

Branching of Colloidal Chains in Capillary-Confined Nematics

We report on the observation of colloidal chain assembly and branching inside capillaries filled with a nematic liquid crystal. Because of the homeotropic anchoring of liquid crystalline molecules on the capillary and colloidal droplet surfaces, the assembly of droplets along the capillary axis is expected, producing a transformation of the nematic director field from an escape-radial to quasiradial configuration. However, the subsequent over time branching of the straight colloidal chains is counterintuitive. By numerical simulations, we demonstrate that chain branching can occur by overcoming an energy barrier and can at least dwell as a metastable configuration. Moreover, manipulation of colloidal chains by electric fields and their gradients demonstrates various regimes of chain behavior in electric fields.

Investigation of dynamic streaming potential by dimensional analysis

The theory of streaming potential at sinusoidal flow of liquid in a porous medium is a convenient and fruitful tool for determination of the interface properties of materials and also for construction of apparatus for zeta potential measurements and electrokinetic transducers. An investigation of the dynamic streaming potential by the method of dimensional analysis is presented. This method provides a wider approach to the problem under consideration. As a result, relationships between streaming potential in a porous medium and mechanical quantities are established. These quantities include pressure gradient in a liquid inside pores and capillaries, acceleration of capillaries, and the solid part of a porous medium, and the viscous friction force the liquid exerts on the solid part. The corresponding formulas for streaming potential are presented. The relationship between the streaming potential and viscous friction force does not depend on the frequency of oscillation and pore size. All these formulas in particular cases are transformed to known formulas for the streaming potential.

Hydrodynamics of slug flow inside capillaries

Understanding the motion of long gas bubbles (gas slugs) inside capillaries is a challenging problem that is relevant in many processes of chemical and biological interests. It has been proved by many workers that such long gas bubbles can be used successfully in enhancing mass and heat transfer in many chemical and biological processes. In order to quantify and understand this enhancement a light was shed on the hydrodynamics of such a flow pattern. The volume of fluid method implemented in the commercial CFD package, Fluent, is used for this numerical study. Velocity and bubble profile were obtained as functions of capillary number. Computed values of the bubble velocity and diameter were in excellent agreement with published experimental measurements. The detailed velocity field around the bubble was also computed and compared favourably with those experimental results reported in literature.

Pressure drop in monolith reactors

A theoretical model for the computation of pressure drop in bubble-train flow inside capillaries of square cross-section was developed. The model is based on three contributions: hydrostatics, viscous pressure drop, and capillary pressure drop. Capillary pressure drop is related to the shape of the fronts and ends of the bubbles. The model does not include entrance or exit effects, has no adjustable parameters, and agrees very well with available experimental data.For a given set of flow parameters, bubble velocity and liquid slug average velocity are computed as a function of gas and liquid superficial velocities. The length of the unit cell determines the number of bubbles inside the capillary for a given flow situation. The model requires experimental information of average bubble lengths to compute the length of a unit cell consisting of a bubble and a liquid slug.The three pressure contributions for a unit capillary length are linear functions of the number of bubbles inside the capillary. The length of the bubbles in bubble-train flows is a critical parameter in the computation of pressure drop.

Recalculation of the temperature inside capillaries using high buffer concentrations

Recalculation of the temperature inside capillaries using high buffer concentrations

Joule heating calculations in capillary zone electrophoresis.: Reply to “Recalculation of the temperature inside capillaries using high buffer concentrations” by Zhang et al.

Joule heating calculations in capillary zone electrophoresis.: Reply to “Recalculation of the temperature inside capillaries using high buffer concentrations” by Zhang et al.

Microscope PIV for velocity-field measurement of particle suspensions flowing inside glass capillaries

We assembled an experimental arrangement for the measurement of the velocity field of glycerol suspensions, in the diametric plane, inside glass capillaries with internal diameter of the order of 200 µm. Glass spheres of mean diameter of 10 µm were used to seed the flow. The velocity fields were determined by the particle image velocimetry (PIV) method, whereby, in contrast to the usual implementations of this method based on light-sheet imaging, a forwards-scattering technique with the entire volume flow illuminated was used and the plane of interest was determined by the objective lens of a microscope. Statistical analysis of acquired experimental results was performed and possible limitations of the proposed technique were investigated. The method, with its present implementation, was used to measure velocities up to 4 mm s-1 and seems to be promising for similar measurements in glass capillaries or in microcirculation.

Characterisation of gas–liquid two-phase flow inside capillaries

Continuous gas sparging inside ultrafiltration hollow fibres (with the feed) has been shown to be effective in enhancing permeate flux by reducing particle deposit on the membrane wall. The present study focuses on the hydrodynamic characterisation of gas–liquid two-phase flow inside glass capillaries in order to understand the mechanisms involved in the process improvement. In capillaries of inner diameter less than 4×10 -3 m, experiments showed that the flow consisted of a slug flow: a succession of gas and liquid slugs rising up the pipe. As very few data are available concerning this type of flow, it was visualised inside the glass capillaries so that its characteristics could be observed. Gas slug velocity, which is different from the mean velocity of the flow, was calculated and a linear relationship found between the two velocities. Gas and liquid slug lengths and frequency were determined and plotted versus operating parameters such as gas and liquid superficial velocities, capillary inner diameters and fluid properties.

Microfabrication inside capillaries using multiphase laminar flow patterning

The reaction of species in solutions flowing laminarly (without turbulent mixing) inside capillaries was used as the basis for a broadly applicable method of microfabrication. In this method, patterning occurs as a result of transport of reactive species to interfaces within the capillary by laminar flow. A wide range of chemistries can be used to generate structures with feature sizes of less than 5 micrometers and with spatial localization to within 5 micrometers. The method is applicable to the patterning of metals, organic polymers, inorganic crystals, and ceramics on the inner walls of preformed capillaries, using both additive and subtractive processes.

Flow patterns in liquid slugs during bubble-train flow inside capillaries

Bubble-train flow consists of strings of bubbles separated by liquid slugs flowing cocurrently inside capillaries of circular or square cross section. Bubble-train flows have interesting properties and have been used to enhance heat and mass transfer rates inside capillaries. The quantitative analysis of heat and mass transfer processes related to this flow requires a detailed knowledge of flow patterns inside the liquid slugs. High-speed video imaging was used to characterize liquid flow patterns. Velocity distributions inside liquid slugs were determined by particle imaging velocimetry (PIV). Video images recorded in a reference frame moving with the bubbles indicate the presence of recirculating patterns with a high degree of mixing. Depending on the capillary number of the flow, counter rotating vortices or a complete bypass flow inside the liquid slug were observed. The position and size of these vortices and the magnitude of the liquid velocity can be accurately predicted by theory. Mixing inside the liquid slug can be characterized by the average recirculating time of a particle of fluid trapped in the liquid vortex.

Electrokinetic Movement of Settled Spherical Particles in Fine Capillaries

In certain soil remediation schemes using electrical fields, through the soil's porous network there may be transport of colloidal and larger-than-colloidal particles, which can affect remediation in several ways. In the first visual investigation of the electrokinetic motion of particles in fine capillaries, an experi- mental methodology is described for studying the effects of capillary diameter, ionic strength and pH. The technique is applied to the case of negatively charged spherical particles having a diameter of 6.76 μm, after they have been allowed to settle inside cylindrical capillaries with diameters of 10, 110, and 700 μm, respectively. Electrokinetic velocities are reported at several values of applied electric field. In most cases, the direction of the particles' movement is toward the cathode, implying that electroosmotic flow is dominant. At pH 4 and in the 10-μm capillary, the direction of electrokinetic movement depends on the applied field. At low electric fields, the particles move toward the cathode, whereas above some critical value for the electric field, movement takes place toward the anode.

Bubble-train flow in capillaries of circular and square cross section

Ceramic monoliths first developed for their use in automotive catalyst, are used now to perform three-phase, catalyzed reactions. The large mass transfer rates achieved within this type of reactor are the result of large interfacial area and very thin diffusion paths. These enhanced mass transfer rates are credited to the presence of well-developed bubble-train flow. Bubble-train flows consist of trains of long bubbles separated by liquid slugs. The interfacial area is the area of the bubbles and the thin films are the result of the squeezing action of the bubbles as they overtake the liquid slugs. The objective of this paper is to predict the main mass transfer parameters, such as bubble size and shape, bubble velocity, and volume fraction of gas inside capillaries of circular or square cross section, on the basis of the superficial flow rates of gas and liquid in the feed. Experiments are reported here on bubble train flow inside capillaries of circular and square cross section for a large range of capillary numbers. A mass balance model was developed to allow the computation of flow parameters using an iteration scheme.

Scanning electron microscopy of liquid metal infiltration of capillaries

The infiltration front of liquid metals (tin, lead, or copper) inside capillaries (iron, copper, or tungsten) after solidification of the infiltrant metal was examined using scanning electron microscopy. The existence of a precursor film ahead of the bulk liquid front was invariably revealed. The precursor film was seen to advance parallel to the solid walls of the capillaries, which indicates that the microscopic wetting angle of the film tends to zero. The microstructures observed at different stages indicate that the precursor film forms principally under the influence of the infiltrant vapour by a chain of elementary processes suggested to be adsorption, condensation, and surface migration of the condensed atoms on the solid walls. The vapour condensation observed in all the systems investigated is thus an important factor in the mechanism of capillary rise of liquid metals and the amount of condensation was observed to increase with increasing solubility of the solid in the liquid.MST/1388

The structure and properties of tetrakis(tironato)cerate(IV), Na 12[Ce(C 6H 2O 2(SO 3) 2) 4]·9H 2O·6C 3H 7NO

The title complex, prepared in 1 M NaOH, was crystallized from hot N, N-dimethylformamide/ ethanol solutions to give Na 12[Ce(C 6H 2O 2(SO 3) 2) 4]· 9H 2O·6DMF. The purple—brown crystals were examined by X-ray diffraction while inside quartz capillaries filled with DMF, (λ max 425 nm, ϵ 3664; λ sh 520 nm, ϵ 2240) and belong to space group Pbca, Z=8 with a=21.846(4), b=17.348(2), c=43.103- (6) Å, V=16.335(7) Å 3, D c=1.693 gcm t−3, D o=1.725 g cm t−3. Diffractometer data were collected using Mo Kα radiation to 2θ=43 o. For 7331 independent data with F o 2>3σ( F o 2) full matrix least squares refinement converged to unweighted and weighted R factors of 0.072 and 0.110, respectively, with a mixture of anisotropic and isotropic thermal parameters. The disordered DMF atom parameters were not refined. The structure consists of discrete monomeric Ce(C 6H 2S 2O 8) 4 12− units with 12 Na + counter cations and 10 H 2O molecules (two with half occupancy), and 6 DMF molecules of solvation filling up spaces between cations and anions. Cerium(IV) is in a general position with a coordination polyhedron close to the trigonal-faced dodecahedron, D 2d, with the angles between the two BAAB trapezoids of 2.3 o and 3.7 o. The average CeO(A) distance, 2.363(9) Å is longer than the average CeO(B) distance, 2.326(15)Å, with the reverse being true for one of the four tironato ligands. The average ring OCeO angle is 67.9(1) o. The cerium (IV) complex is found by cyclic voltammetry to undergo a quasi-reversible one-electron reduction (in strongly basic solution with excess tiron) with Ef=−497 mV vs. SCE, hence the ratio of the formation constants for tetrakis(tironato)cerate(IV) to that for tetrakis(tironato)cerate(III), K IV/ K III, is 10 33. Characterization of other tiron salts is reported.

A mathematical model of transmural transport of oxygen to the retina.

A mathematical model of transmural transport of oxygen to a metabolizing retina is presented based on the equations of fluid dynamics. The equations of oxygen transfer are derived and then solved subject to the condition that the capillaries begin to transport oxygen at an initial time. The resulting transient analysis gives us insight into how diffusive and filtrative processes lead to the oxygen distributions both inside and outside capillaries. On the other hand, the steady state solution allows us to predict the cutoff intraocular pressure above which no oxygen is transferred to retinal tissue. It also gives quantitative relationships which allow us to postulate how intracapillary hypertension counterbalances elevated intraocular pressures and how low pressure glaucoma may arise from ineffective diffusive and filtrative processes of oxygen transport.

BOVINE BABESIOSIS: COMPARISON OF FLUORESCENT ANTIBODY AND GIEMSA STAINING IN POST‐MORTEM DIAGNOSIS OF INFECTION

SUMMARY Following experimental infections of cattle, Babesia argentina was detected in smears of heart, lung and kidney, immediately, and up to 8 hours post‐mortem (PM), using Giemsa staining, while smears of brain were positive for up to 28 hours after death. Direct fluorescent antibody (DFA) staining detected B. argentina in heart and lung smears for 12 hours, in kidney smears for 16 hours, and in brain smears for 28 hours after death. Following experimental infections with B. bigemina, this organism could be recognised morphologically in smears of heart, lung and kidney immediately after death, but by one hour and up to 8 hours PM, its morphology resembled B. argentina in Giemsa stained films. A few red blood cells inside and outside brain capillaries were infected with organisms resembling B. argentina up to 16 hours after death. DFA staining detected B. bigemina in heart and lung smears for 12, and in kidney smears for 16 hours after death. A few infected red blood cells inside and outside capillaries were also seen in brain smears 16 hours after death. Organ smears could be held at 22°C for 5 days and both species of Babesia detected by either Giemsa or DFA staining.B. argentina was diagnosed by Giemsa staining of organ smears from 27 field cases of babesiosis. DFA confirmed B. argentina in 22, identified B. bigemina in 3 and failed to detect parasites in the other 2 cases. B. argentha was diagnosed by Giemsa staining in 10 and B. bigemina in 1 blood film from field cases. DFA confirmed B. argentina in 4 cases and B. bigemina in the 1 case. Serum from 5 of 12 animals which died in the field from natural B. argenfina infec‐ tions, had fluorescent antibody titres 2 64. After an experimental primary blood infection with B. argentina and while parasites were still detectable, 18 of 72 cattle had titres 2 64. Because there was no significant statistical difference between these results, it was con‐ cluded that the 12 field cases were due to primary infections, not recrudescences or hetero‐ logous strains or variants.

The contractile basis of amoeboid movement *1IV. The viscoelasticity and contractility of amoeba cytoplasm in vivo

Abstract The viscoelasticity and contractility of amoeba cytoplasm has been studied in vivo and in vitro. A gradient of increasing viscoelasticity and contractility was identified in the endoplasm of intact cells from the uroid (tail) to the fountain zone (tip of advancing pseudopod). Anterior endoplasm, as well as all of the ectoplasm, contracted in response to the microinjection of a threshold calcium ion concentration (ca 7.0 × 10 −7 M). In contrast, there were only delayed weak contractions in the uroid endoplasm upon the microinjection of a threshold calcium ion concentration. Contractions induced in the ectoplasm by microinjecting the contraction solution readily caused the endoplasm to stream. However, the endoplasm at the tips of the extending pseudopods were also contractile and transmitted applied tensions. Furthermore, the microinjection of subthreshold calcium ion concentrations caused the loss of distinct endoplasmic structure and the cessation of streaming in both the uroid and the anterior third of the cell. In addition, the relationship between contractility and cytoplasmic streaming was characterized in “relaxed” cytoplasm placed in a gradient of calcium ion concentration inside quartz capillaries. The results of these experiments demonstrated that the mechanochemical conversion of endoplasm to ectoplasm caused the cytoplasm to become more structured and contractile. Therefore, physiological contractions are possible during and after the conversion of endoplasm to ectoplasm.