Two-layered blood flow in stenosed tubes for different diseases

A two-fluid model for blood flow through a stenosed tube has been developed. The model consists of a core (suspension of RBCs) and peripheral plasma layer. The core is assumed to be represented by a polar fluid and the plasma layer by a Newtonian fluid. The flow is assumed to be steady and laminar, and the fluids incompressible. The flow variables are computed for normal blood and for the cases of polycythemia, plasma cell dyscrasias and for Hb SS diseases. Resistance to flow has been computed for different stenosis length and for different stenosis height. Shear stress distribution along the axial distance has been computed for different stenosis height. The impact of size effects (particle size to tube diameter) on blood diseases is discussed.     

A numerical model for studying the effect of plasma layer on the process of blood oxygenation in the pulmonary capillaries

A two layer model for the blood oxygenation in pulmonary capillaries is proposed. The model consists of a core of erythrocytes surrounded by a symmetrically placed plasma layer. The governing equations in the core describe the free molecular diffusion, convection, and facilitated diffusion due to the presence of haemoglobin. The corresponding equations in the plasma layer are based on the free molecular diffusion and the convective effect of the blood. According to the axial train model for the blood flow proposed by Whitmore (1967), the core will move with a uniform velocity whereas flow in the plasma layer will be fully developed. The resulting system of nonlinear partial differential equations is solved numerically. A fixed point iterative technique is used to deal with the nonlinearities. The distance traversed by the blood before getting fully oxygenated is computed. It is shown that the concentration of O2 increases continuously along the length of the capillary for a given ratio of core radius to capillary radius. It is found that the rate of oxygenation increases as the core to capillary ratio decreases. The equilibration length increases with a heterogeneous model in comparison to that in a homogeneous model. The effect of capillary diameters and core radii on the rate of oxygenation has also been examined.     

A two-phase model for flow of blood in narrow tubes with increased effective viscosity near the wall

A two-phase model for the flow of blood in narrow tubes is described. The model consists of a central core of suspended erythrocytes and a cell-free layer surrounding the core. It is assumed that the viscosity in the cell-free layer differs from that of plasma as a result of additional dissipation of energy near the wall caused by the red blood cell motion near the cell-free layer. A consistent system of nonlinear equations is solved numerically to estimate: (i) the effective dimensionless viscosity in the cell-free layer (beta), (ii) thickness of the cell-free layer (1-lambda) and (iii) core hematocrit (H(c)). We have taken the variation of apparent viscosity (mu(app)) and tube hematocrit with the tube diameter (D) and the discharge hematocrit (H(D)) from in vitro experimental studies [16]. The thickness of the cell-free layer computed from the model is found to be in agreement with the observations [3,21]. Sensitivity analysis has been carried out to study the behavior of the parameters 1-lambda, beta, H(c), B (bluntness of the velocity profile) and mu(app) with the variation of D and H(D).     

Three-dimensional structure of the surface layer protein of Aquaspirillum serpens VHA determined by electron crystallography.

The three-dimensional structure of the protein which forms the S layer of Aquaspirillum serpens strain VHA has been determined by electron microscopy. Structures have been reconstructed to a resolution of about 1.6 nm for single-layered specimens and about 4 nm for two-layered specimens. The structure, which has hexagonal symmetry, consists of a core in the shape of a cup, with six projections arising from the rim of the cup to join adjacent subunits at the threefold symmetry axes. The model is consistent with edge views of the S layer which have been obtained in this and other work. It is now clear from this work and from three-dimensional reconstructions of other bacterial S layers that a wide diversity exists in the morphology of surface layers.     

A semi-empirical model for flow of blood and other particulate suspensions through narrow tubes

A semi-empirical model applicable to the flow of blood and other particulate suspensions through narrow tubes has been developed. It envisages a central core of blood surrounded by a wall layer of reduced hematocrit. With the help of this model the wall layer thickness and extent of plug flow may be calculated using pressure drop, flow rate and hematocrit reduction data. It has been found from the available data in the literature that for a given sample of blood the extent of plug flow increases with decreasing tube diameter. Also for a flow through a given tube it increases with hematocrit. The wall layer thickness is found to decrease with increase in blood hematocrit. A comparison between the results of rigid particulate suspensions and blood reveals that the thicker wall layer and smaller plug flow radius in the case of blood may be attributed to the deformability of the erythrocytes.     

Three-dimensional structure of the surface protein layer (MW layer) of Bacillus brevis 47

The three-dimensional (3D) structure of one surface protein layer from Bacillus brevis 47, the middle wall (MW) layer, has been reconstructed from tilted-view electron micrographs after correlation averaging to a resolution of 2 nm. The MW layer has p6 symmetry with a center-to-center spacing of 18.3 nm and a minimum thickness of 5.5 nm. The reconstruction reveals a distinct domain structure: the heavier domain of six monomers jointly forms a massive core centered at the sixfold symmetry axis, and lighter domains interconnect adjacent unit cells. In addition, the larger domains collectively form a pore by making contact with each other towards the inner surface, while the smaller domains establish a second connectivity towards the outer surface of the S layer. The MW layer of B. brevis resembles the S layer of Acetogenium kivui in various aspects: they have very similar lattice parameters and highly reminiscent 3D structures; the pores penetrate through the whole core and appear to determine the porosity of the S layers.     

Identification of a putative LPS-associated cation exporter from Rhizobium leguminosarum bv. viciae

A gene, cpaA, with similarity to calcium proton antiporters has been identified adjacent to lpcAB in Rhizobium leguminosarum. LpcA is a galactosyl transferase while LpcB is a 2-keto-3-deoxyoctonate transferase, both of which are required to form the lipopolysaccharide (LPS) core in R. leguminosarum. Mutations in lpcAB result in a rough LPS phenotype with a requirement for elevated calcium concentrations to allow growth, suggesting that truncation of the LPS core exposes a highly negatively charged molecule. This is consistent with the LPS core being one of the main sites for binding calcium in the Gram-negative outer membrane. Strain RU1109 (cpaA::Tn5-lacZ) has a normal LPS layer, as measured by silver staining and Western blotting. This indicates that cpaA mutants are not grossly affected in their LPS layer. LacZ fusion analysis indicates that cpaA is constitutively expressed and is not directly regulated by the calcium concentration. Over-expression of cpaA increased the concentration of calcium required for growth, consistent with CpaA mediating calcium export from the cytosol. The location of lpcA, lpcB and cpaA as well as the phenotype of lpcB mutants suggests that CpaA might provide a specific export pathway for calcium to the LPS core.     

Facile fabrication of gelatin‐based biopolymeric optical waveguides

The rapid development in optical detection techniques for sensing applications has led to an increased need for biocompatible, biodegradable, and disposable optical components. We present a controllable fabrication technique for an entirely biopolymeric planar optical waveguide via simple spin‐coating. The refractive index difference, thermal responsive properties, and inherent biocompatibility of gelatin and agarose were exploited in the fabrication of thin, stacked films that efficiently guide light in a core layer with higher index of refraction. These planar waveguides were fabricated using a simple spin‐coating technique, which resulted in controllable layer thicknesses and smooth layer interfaces. This technique, therefore, offers a path for routine engineering of biopolymer structures with contrasting refractive indices. The thermal stability of the gelatin core layer was improved using two crosslinkers; glutaraldehyde or microbial Transglutaminase. Light guiding in the core layer of the waveguide was demonstrated using a simple He–Ne laser setup. Guiding efficiency was further illustrated by directly embedding fluorescent markers within the core layer and detecting their spectral signature. Combined with the biopolymers' inherent biocompatibility and biodegradability, our simple strategy to fabricate disposable optical components holds the potential for the development of applications in biological sensing and implantable biomedical devices. Biotechnol. Bioeng. 2009;103: 725–732. © 2009 Wiley Periodicals, Inc.     

Tailoring LSPR-Based Absorption and Scattering Efficiencies of Semiconductor-Coated Au nanoshells

Absorption and scattering efficiencies of semiconductor-coated Au nanoshell have been studied by the extended Mie theory for their possible solar cell, optical imaging, and photothermal applications, etc. The effect of Au shell layer thickness, core size, and surrounding medium on the absorption and scattering efficiencies at the localized surface plasmon resonance (LSPR) wavelengths has been reported. It has been found that both the absorption and scattering efficiencies get blue-shifted with an increase in Au shell layer thickness from 2 to 10 nm and with an increase in surrounding refractive index whereas the corresponding LSPR peaks shift towards red. It has also been found that the spectra are red-shifted with an increase in the core radius from 20 to 40 nm while keeping the shell thickness same. The effect of shell thickness on the absorption peak position and absorption linewidth has also been studied. Hence, the optical response of both CdSe- and CdTe-coated Au nanoshells can be tuned and controlled from the visible to the near-infrared (NIR) region of the electromagnetic (EM) spectrum. Finally, the CdSe-coated Au nanoshell exhibits high scattering and absorption efficiencies in comparison to the CdTe-coated nanoshell.     

Photographic demonstration of the annual nature of a varve type common in N. Swedish lake sediments

Several lakes in northern Sweden have laminated sediments, of which many are interpreted as varved (annually laminated). In one of these lakes, a core of the recent sediment has been sampled annually since 1979 (except 1984). These cores verify that one varve, comprising of a thick summer layer (often colour-banded) and a thin winter layer, is formed each year. The cores also show, that, other than compaction, no change in visual appearance of the individual varves takes place after they have been overlain by new varves.     

Intracellular pH topography of Penicillium cyclopium protoplasts. Maintenance of delta pH by both passive and active mechanisms

The intracellular pH distribution in protoplasts of Penicillium cyclopium has been studied using the recently developed fluorescent probe microscopic technique. The technique gives detailed pH maps of the interior of the protoplasts with the exception of vacuoles (no fluorescence signal from vacuoles was observed). In the cytoplasm two separate layers were distinguished: a thinner outer layer with acidic pH (around 5) and the larger core region with near neutral pH. The pH of the core region is decreased by the addition of uncouplers, inhibitors of respiration and during the uptake of L-phenylalanine. These compounds do not change the pH of the surface layer, which is, however, acidified by addition of vanadate, an inhibitor of the proton pump of the plasmalemma. We suggest that the pH of the surface layer is maintained by the combined effects of a Donnan distribution of protons (bound to postulated anion binding proteins) and the proton extrusion via the plasmalemma proton pump. This mechanism explains the protection of the cytoplasmic core of acidophilic eukaryotes from the influence of the usually acidic environment.     

Electron microscopy of two subcellular fractions isolated from cerebral cortex homogenate

The sporulation process in Bacillus subtilis has been studied principally with KMnO(4) fixation, but also, for the purpose of comparison, with OsO(4) and mixtures of both fixatives. At a very early stage, the pre-spore is seen to consist of what seems to be the nuclear material and granular substance, surrounded by a layer of dense material destined to become the innermost layer of the spore coat. At a subsequent stage, a light interspace is observed that is destined to become the spore cortex. The mature spore shows a very complex structure. The spore coat is composed of three layers, the middle layer of which consisted of 5 to 8 lamellae of thin membranes and interspaces, both about 20 to 25 A thick. Between the inner layer of the spore coat and the spore cortex, a thin membrane with an affinity to the cortex can be observed. The spore coat is enclosed within two envelopes, one loosely surrounding the core, and the other adhering to it. The process of spore maturation has been studied in detail. Certain peculiar cellular structures have been observed that seemed to represent features of abnormal sporulation processes.     

Intracellular pH topography of Penicillium cyclopium protoplasts. Maintenance of Δ pH by both passive and active mechanisms

The intracellular pH distribution in protoplasts of Penicillium cyclopium has been studied using the recently developed fluorescent probe microscopic technique. The technique gives detailed pH maps of the interior of the protoplasts with the exception of vacuoles (no fluorescence signal from vacuoles was observed). In the cytoplasm two separate layers were distinguished: a thinner outer layer with acidic pH (around 5) and the larger core region with near neutral pH. The pH of the core region is decreased by the addition of uncouplers, inhibitors of respiration and during the uptake of l-phenylalanine. These compounds do not change the pH of the surface layer, which is, however, acidified by addition of vanadate, an inhibitor of the proton pump of the plasmalemma. We suggest that the pH of the surface layer is maintained by the combined effects of a Donnan distribution of protons (bound to postulated anion binding proteins) and the proton extrusion via the plasmalemma proton pump. This mechanism explains the protection of the cytoplasmic core of acidophilic eukaryotes from the influence of the usually acidic environment.     

Fine Structure of Bacillus subtilis : II. Sporulation Progress

The sporulation process in Bacillus subtilis has been studied principally with KMnO₄ fixation, but also, for the purpose of comparison, with OsO₄ and mixtures of both fixatives. At a very early stage, the pre-spore is seen to consist of what seems to be the nuclear material and granular substance, surrounded by a layer of dense material destined to become the innermost layer of the spore coat. At a subsequent stage, a light interspace is observed that is destined to become the spore cortex. The mature spore shows a very complex structure. The spore coat is composed of three layers, the middle layer of which consisted of 5 to 8 lamellae of thin membranes and interspaces, both about 20 to 25 A thick. Between the inner layer of the spore coat and the spore cortex, a thin membrane with an affinity to the cortex can be observed. The spore coat is enclosed within two envelopes, one loosely surrounding the core, and the other adhering to it. The process of spore maturation has been studied in detail. Certain peculiar cellular structures have been observed that seemed to represent features of abnormal sporulation processes.     

Micellar subunit assembly in a three-layer model of oligomeric alpha-crystallin

Differential scanning calorimetry was performed to monitor the heat-induced changes that occur in the structural domain of lens alpha-crystallin. Circular dichroism and fluorescence also were used to resolve the controversial issue of the quaternary structure of alpha-crystallin. Based on the thermal behavior as monitored by these techniques, a model is proposed that can account for all previous data as well as the currently reported thermal data. The proposed model of native alpha-crystallin has a three-layer structure in which the inner layer (core) is a micelle containing 12 subunits arranged in cuboctahedral symmetry. The apolar region is directed inward constituting a hydrophobic core similar to a micelle and adding structural stability. A second layer of six subunits has a similar but not identical structure to the first layer, directing its apolar face toward the hydrophobic core. Thus, these two layers constitute a micelle-like structure with octahedral symmetry. The third layer adds more subunits for a total of not more than 24. Differential scanning calorimetry, circular dichroism, and fluorescence studies indicated that the inner two-layer structure of molecular mass 360 kDa is highly stable and is most likely of the alpha m form. The three-layer structure of the native protein, however, is rather unstable. At 35-45 degrees C the outer layer dissociates from the inner two layers, and at higher temperatures rapidly reassociates to a slightly modified two-layer structure with a stability similar to that of alpha m. The proposed model does not require any specific assembly of the alpha A and alpha B subunits in each layer, but the fluorescence results suggest that the native inner two layers probably contain mostly alpha A.     

A mapping technique for probing the structure of proteoglycan core molecules

Our previous work showed that treatment of chick embryo cartilage proteoglycan (PG-H) with chondroitinase-AC II and keratanase yielded a protein-rich core fraction having enzymatically modified linkage oligosaccharides. The core sample has now been analyzed by tryptic peptide mapping, in which the isolated core sample contained in a single Coomassie blue-staining band from a dried slab gel is radioiodinated and treated with trypsin, and the resultant tryptic peptides are displayed two-dimensionally on a silica gel thin layer plate. The map thus obtained exhibited 22 major peptide spots, the resolution and location of which were reproducible. In order to identify regions of the core polypeptide from which the tryptic peptides are derived, PG-H was cleaved with clostripain under conditions that yield a hyaluronic acid-binding fragment with an apparent Mr = 150,000 and chondroitin sulfate-peptide clusters of smaller molecular sizes. Although the peptide maps of the two size classes of clostripain fragments differed significantly from each other, the patterns of spots, as a whole, were extensively similar to those observed with the intact core molecule. These results have provided additional evidence that PG-H has a single, nonvariable core protein structure. In addition, the technique used here will provide a versatile method for the identification of genetic types in this increasingly complex family of matrix macromolecules.     

Surface Plasmon Resonance-Based Tapered Fiber Optic Sensor: Sensitivity Enhancement by Introducing a Teflon Layer Between Core and Metal Layer

Surface plasmon resonance (SPR)-based tapered fiber optic sensor with Teflon as a dielectric sandwiched between metal and tapered fiber core is proposed. The sensitivity of the sensor has been maximized using different combinations of metal and Teflon layer thicknesses for a given taper ratio. The study shows that the sensitivity of the sensor with the introduction of dielectric (Teflon) increases with the increase in the taper ratio. The maximum sensitivity achieved for a given taper ratio is around 15 times higher than the general SPR-based fiber optic sensor.     

Forming the phosphate layer in reconstituted horse spleen ferritin and the role of phosphate in promoting core surface redox reactions.

Apo horse spleen ferritin (apo HoSF) was reconstituted to various core sizes (100-3500 Fe3+/HoSF) by depositing Fe(OH)3 within the hollow HoSF interior by air oxidation of Fe2+. Fe2+ and phosphate (Pi) were then added anaerobically at a 1:4 ratio, and both Fe2+ and Pi were incorporated into the HoSF cores. The resulting Pi layer consisted of Fe2+ and Pi at about a 1:3 ratio which is strongly attached to the reconstituted ferritin mineral core surface and is stable even after air oxidation of the bound Fe2+. The total amount of Fe2+ and Pi bound to the iron core surface increases as the core volume increases up to a maximum near 2500 iron atoms, above which the size of the Pi layer decreases with increasing core size. M?ssbauer spectroscopic measurements of the Pi-reconstituted HoSF cores using 57Fe2+ show that 57Fe3+ is the major species present under anaerobic conditions. This result suggests that the incoming 57Fe2+ undergoes an internal redox reaction to form 57Fe3+ during the formation of the Pi layer. Addition of bipyridine removes the 57Fe3+ bound in the Pi layer as [57Fe(bipy)3]2+, showing that the bound 57Fe2+ has not undergone irreversible oxidation. This result is related to previous studies showing that 57Fe2+ bound to native core is reversibly oxidized under anaerobic conditions in native holo bacterial and HoSF ferritins. Attempts to bury the Pi layer of native or reconstituted HoSF by adding 1000 additional iron atoms were not successful, suggesting that after its formation, the Pi layer "floats" on the developing iron mineral core.     

Fluorescence studies of possible protein-protein interactions in model lipoprotein complexes

Summary The structure of model lipoprotein complexes, extracted from an aqueous phase into isooctane, has been investigated using a fluorescence technique. The technique is based on the transfer of excitation energy from one protein (or DNS-labelled protein) to a second protein containing a fluorescence quencher, such as a haem group. The results obtained with model complexes in isooctane are consistent with a structure comprised of an inner protein core, and an outer layer of phospholipids.