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PubMed1989

Hydrodynamic instability of "stroma-free" hemoglobin.

A simple kinetic test with visual observation of hemoglobin solutions under 4 - 10x magnification was used to detect and roughly characterize a rapid formation of fine fibrous inhomogeneities in agitated "stroma-free" hemolyzates (SFH). In parallel SFH samples stored motionless for months, no such precipitate was observed. Hydrodynamic conditions are necessary to provoke a stepwise aggregation of small amounts of unstable filamentous nonhemoglobin molecules originating mostly from the stromata of erythrocytes and from constituents of other lysed blood cells. Numerous screening experiments mentioned here failed to remove significantly the "fiber-forming" substances from SFH or to prevent their precipitation. Development of a hydrodynamically stable and better purified SFH seems to be a prerequisite for further progress in the field of infusable SFH and its chemically modified variants (MSFH).

Chemical Precipitation↗
PubMed1998

The multistep process of homotypic neutrophil aggregation: a review of the molecules and effects of hydrodynamics.

Homotypic adhesion of neutrophils stimulated with chemoattractant is analogous to capture on vascular endothelium in that both processes are supported by L-selectin and beta 2-integrin adhesion receptors. Under hydrodynamic shear, cell adhesion requires that receptors bind sufficient ligand over the duration of intercellular contact to withstand the hydrodynamic stresses. Using cone and plate viscometry to apply a uniform linear shear field to suspensions of neutrophils and flow cytometry to quantitate the size distribution of aggregates formed over the time course of formyl peptide stimulation, we conducted a detailed examination of the affect of shear rate and shear stress on the kinetics of cell aggregation. The efficiency of aggregate formation was fit from a mathematical model based on Smoluchowski's two-body collision theory. Over a range of venular shear rates (400-800 s-1), approximately 90% of the single cells are recruited into aggregates ranging from doublets to grouping larger than sextuplets. Adhesion efficiency fit to the kinetics of aggregation increased with shear rate from approximately 20% at 100 s-1 to a maximum level of approximately 80% at 400 s-1. This increase to peak adhesion efficiency was dependent on L-selectin and beta 2-integrin, and was resistant to shear stress up to approximately 7 dyn/cm2. When L-selectin was blocked with antibody, beta 2-integrin (CD11a,b) supported adhesion at low shear rates (< 400 s-1). Aggregates formed over the rapid phase of aggregation remain intact and resistant to shear up to 120 s. At the end of this plateau phase of stability, aggregates spontaneously dissociate back to singlets. The rate of cell disaggregation is linearly proportional to the applied shear rate. The binding kinetics of selectin and integrin appear to be optimized to function within discrete ranges of shear rate and stress, providing an intrinsic mechanism for the transition from neutrophil tethering to firm but reversible adhesion.

Animals↗
PubMed1982

The hydrodynamic resistance of hyaluronic acid and its contribution to tissue permeability.

An experimental system was developed to measure flow rates and pressure drops across hyaluronic acid solutions. The solutions were contained by membranes in a test cell, and solvent was perfused through the cell at flow rates comparable to physiological conditions. The pressure drop was found to be proportional to a steady flow rate for concentrations up to 1.5%, confirming that Darcy's Law for porous media is valid for hyaluronic acid solutions (and indicating that the polymer chains did not pile up at one end of the test cell). From the flow data, the hydrodynamic permeability of each solution was calculated and found to be 50 times higher that whole tissue having the same hyaluronic acid concentration; hyaluronic acid on its own, therefore, is not the source of resistance to flow in tissue. The results for hyaluronic acid were then used to show that all the glycosaminoglycans together cannot cause the high resistance of ground substance in tissue, and it is argued that mucoproteins are the most likely source. A hydrodynamic model of the polymer chains was developed to predict solution permeability; the theoretical values agree closely with the experimental data.

Biomechanical Phenomena↗
PubMed2005

Antitumor effects of angiostatin K1-3 and endostatin genes coadministered by the hydrodynamics-based transfection method.

Angiostatin and endostatin are potent endothelial cell growth inhibitors and have been carefully evaluated for antiangiogenic cancer therapy. Previously, we have shown that subcutaneous administration of angiostatin K1-3 and endostatin genes complexed with liposomal vectors is a more practical treatment procedure than administration of angiostatin and endostatin proteins. This study provides additional conclusive evidence supporting the effectiveness of antiangiogenic cancer gene therapy employing angiostatin K1-3 and endostatin genes. Plasmids encoding a mouse angiostatin K1-3 gene (pFLAG-AngioK1/3) and an endostatin gene (pFLAG-Endo) were introduced by the hydrodynamic transduction method into mice carrying Matrigel plugs or B16BL6 mouse melanoma tumors. A single systemic injection of the two genes exhibited potent antiangiogenic and antitumor activity in the mouse model. Hydrodynamic coadministration of the genes inhibited the B16BL6 mouse melanoma growth and pulmonary metastasis more effectively than administration of either gene alone. Compared with the untreated control group, the mice cotreated with pFLAG-AngioK1/3 and pFLAG-Endo exhibited 75% reduction of tumor growth while those treated with pFLAG-AngioK1/3 or pFLAG-Endo showed 46% and 52% reduction, respectively. The cotreatment inhibited B16BL6 pulmonary metastasis formation by 80% while the inhibition induced by individual treatment with pFLAG-AngioK1/3 or pFLAG-Endo was 68% and 71%, respectively. These results provide additional evidence that systemic expression of angiostatin K1-3 and/or endostatin genes is a viable alternative procedure for antiangiogenic cancer therapy.

Angiogenesis Inhibitors↗
PubMed2006

Hydrodynamic-based delivery of an interleukin-22-Ig fusion gene ameliorates experimental autoimmune myocarditis in rats.

IL-22 is one of several cytokines with limited homology to IL-10. However, the biological activities of IL-22 are mostly unknown. The purpose of this study was to evaluate the effect of IL-22 on rat experimental autoimmune myocarditis (EAM) and elucidate an aspect of the biological activities of IL-22. Rats were immunized on day 0; IL-22-Ig-treated rats were injected with pCAGGS-IL-22-Ig and control rats with pCAGGS-Ig using hydrodynamics-based gene delivery on day 1 or day 6. IL-22-Ig gene therapy administered on day 1 or day 6 after immunization was effective in controlling EAM as monitored by the heart weight to body weight ratio, and the myocarditis area in rats was sacrificed on day 17. Examination of the expression of IL-22-related genes in purified cells from EAM hearts suggested that IL-22-Ig acting target cells were noncardiomyocytic (NC) noninflammatory cells such as fibroblasts, smooth muscle cells, and endothelial cells. Therefore, we examined the effect of rIL-22 or serum containing IL-22-Ig on the expression of immune-relevant genes in IL-1-stimulated NC cells cultured from EAM hearts. Results showed that the expression of immunologic molecules (PGE synthase, cyclooxygenase-2, MIP-2, MCP-1, IL-6, and cytokine-induced neutrophil chemoattractant-2) in IL-1-stimulated NC cells was significantly decreased by rIL-22 or serum containing IL-22-Ig. EAM was suppressed by hydrodynamics-based delivery of plasmid DNA encoding IL-22-Ig, and the reason for this effectiveness may be that IL-22 suppressed gene expression of PG synthases, IL-6, and chemokines in activated NC noninflammatory cells.

Animals↗
PubMed1998

Effects of hydrodynamic pressure on the viability of Trichinella spiralis in pork.

Treatment by hydrodynamic pressure is an attractive alternative for meat tenderization and might also have an effect on foodborne pathogens. Numbers of Trichinella spiralis recovered from infected pork were significantly reduced by treatment with the Hydrodyne process, as compared with untreated, infected pork. However, treatment with the hydrodynamic force described in this paper (55 to 60 MPa) did not eliminate the infectivity of this parasite when the larvae from Hydrodyne-treated meat were inoculated into mice.

Animals↗
PubMed1998

Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor.

The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems.

Biofilms↗
PubMed2000

[Age-dependent dynamics of biomechanical and hydrodynamic properties of the valve-aortic complex of man].

A comparative analysis of geometrical, biomechanical and hydrodynamic characteristics of the valve-aortic complexes taken from humans of different age has shown a determining role of distensibility of the aortic root in the functioning of valve cusps. An alteration of geometrical relationships of elements of the aortic root, its less distensibility, worse biomechanical and hydrodynamic characteristics of the aortic valve in humans older than 50-60 years of age is established.

Adult↗
PubMedDate not supplied

[Hydrodynamic properties of exopolysaccharide-acrylamide copolymer].

The method for producing copolymer EPAA of exopolysaccharide (EPS)--polyacrylamide (PAA) has been presented which was based on microbial exopolysaccharides (enposane, xampane), their mixture and model EPS (xanthane sigma, rodopol P-23). The copolymer was produced by acrylamide polymerization in 1-2% water solutions of polysaccharides, the concentration of acrylamide in the reaction mixture being 4.7-2% and that of polysaccharides 0.1-1% of the weight. Hydrodynamic parameters of the studied polymers have been determined, their heterogenity as to molecular-weight characteristics has been demonstrated. Molecular-weight distribution of copolymers showed that the content of low-molecular fractions decreased, thus the Mw values were (0.08-0.2) x 10(6) Da in contrast to that of exopolysaccharides possessing Mw (1.2-0.4) x 10(6) Da and of polyacrylamide possessing Mw within (2-30) x 10(6) Da. The value of efficient viscosity of copolymers ranged from 120 to 131 mPa.s that was lower than that of polyacrylamide (500 mPa.s), and higher than that of exopolysaccharides (42 mPa.s), and it depended on the sample, raw material, production conditions. A possibility has been shown to produce a new copolymer based on microbial polysaccharides enposane and xampane in the process of acrylamide polymerization. It has been found out that the studied copolymers EPAA differ from initial ones as to their hydrodynamical properties, which determines their preference: better solubility, good glueing properties, prolonged term of preservation, resistance to bacterial pollution.

Acrylamide↗
PubMed2001

Hydrodynamics-based gene delivery.

The need for a safe and efficient method for gene delivery has stimulated the recent emergence of vectorless methods (e.g., naked DNA) as promising alternatives to the available viral- and non-viral-based systems. Among these methods, hydrodynamics-based gene delivery through systemic injection of DNA offers a convenient, efficient and powerful means for high-level gene expression in mice. This review deals with the background and progress made so far with this new gene delivery method, the potential mechanism underlying the hydrodynamics-based DNA transfer into cells and its potential applications towards gene function analysis, protein expression and gene therapy in whole animals.

Animals↗
PubMed2001

[Ocular hydrodynamics in patients with occluding and stenosing disease of main cerebral vessels after reconstructive surgery of internal carotid and vertebral arteries].

Ocular hydrodynamics was investigated using the tonography method in 58 patients, to whom reconstructive operations on the affected vessels were performed. After reconstructive operation on vertebral arteries ocular hydrodynamics didn't change significantly, on a carotis interna (ACI)--the positive effect was revealed on the side of the operation performed, and if the cerebrum arterial circle function was preserved--on the contralateral side as well. If extra- and intracranial parts of ACI were affected after conduction of reconstructive operation and restoration of the artery's passability occurrence of "ocular reperfusional syndrome" is possible, manifested by intraocular pressure raising due to excessive raising of the aqueous humor production.

Adult↗
PubMed1975

Antifreeze glycoproteins from an Antarctic fish. Quasi-elastic light scattering studies of the hydrodynamic conformations of antifreeze glycoproteins.

A quasi-elastic light-scattering technique was used to study the hydrodynamic conformations of antifreeze glycoproteins from an Antarctic fish. Antifreeze glycoprotein is composed of repeating units of Ala-Ala-Thr, with each threonine O-linked to a disaccharide, and it exists as several polymers of different numbers of this repeating unit. Molecular weights of the two major active polymers are 10,500 and 17,500 by such methods as centrifugation and osmotic pressure, but smaller than 20 by freezing-point depression. Translational diffusion coefficients at 20 degrees were 8.35 times 10-7 cm2 s-1 and 6.15 times 10-7 cm2 s-1 for the M-r-10,500 and 17,500 polymers, respectively. Measurements at -0.2 degrees in the presence of ice crystals did not indicate any conformational changes that might be related to the lowering of the freezing temperature. Lowering the temperature of these glycoprotein solutions close to temperatures of freezing caused a decrease in the effective hydrodynamic radius of both active and inactive glycoprotein components.

Animals↗
PubMed2001

Different types of aortic stenosis and simulation of their morphological-hydrodynamic interdependence--in vitro study with allografts and stenotic valve models.

Biological valves display a dependence of valve resistance and valve area on flow and a phase shift between systolic flow through the valves and pressure difference across the valves. The pressure-flow relations of stenosed valves raise questions about the "best measure of stenosis". There is a need for quantitative evaluation of the hydrodynamic performance of homografts and allografts. In the present paper, we report on in vitro studies of the hydrodynamic behavior of homografts from human donors, allografts from different animal species as well as three valve models. Valve model I was designed to simulate flow-dependence of valve area, valve model II was designed to simulate restricted valve opening independent of flow, and valve model III was designed to simulate a flow-dependent movement of valve root in flow direction. Among other aspects, the effect of increased viscosity of the test fluid on the pressure difference and the effects of water absorption by valve tissue on valve characteristics were investigated. The results of the present studies clearly indicate that any biological valve may be modelled as a serial connection of a model I type valve and a model II type valve. From the results, the dependence of the characteristic pressure-flow relationship of a valve on valve size and valve distensibility can be clearly seen and the clinical significance of the characteristic coefficients of the pressure-flow relationship of a valve can be elucidated. Further, it was shown that the characteristic phase shift between flow and pressure difference displayed by biological valves is due to their movable valve plane similar to that of valve model III.

Animals↗
PubMed2001

[Effects of implantation technique on hydrodynamic and biomechanical characteristics of stentless aortic valve bioprostheses in experiments].

A comparative analysis of experiments with biomechanics and hydrodynamic stentless xenografts implanted into the subcoronary position with completely (n = 7) and partially (n = 7) scalloped sinuses was made. The implantation was performed into the human aortic root complexes in vitro. Factors of the influence on biomechanical and hydrodynamic performances of xenografts before and after implantation have been established. Subcoronary implantation of stentless bioprostheses with the completely scalloped sinuses proved to result in better flow and biomechanical characteristics than the implantation technique with the saved noncoronary sinus.

Animals↗
PubMed2002

Improved statistical characterization of prosthetic heart valve hydrodynamics using a performance index and regression analysis.

BACKGROUND AND AIMS OF THE STUDY: The ISO 5840 Standard (Cardiovascular implants - Cardiac valves) currently requires a minimum of three test samples per size for hydrodynamic testing. Typically, the only statistical analysis performed is a descriptive analysis, with the mean (+/- SE) given for each size and cardiac output (CO). The study aim was to develop better statistical methods, incorporating regression analysis of a performance index, equal to the effective orifice area divided by the tissue annulus area. The analysis is performed on the full dataset, with size and CO as independent variables. METHODS: Hydrodynamic data of Ionescu-Shiley pericardial valves from a published study were used to compare the two analysis methods. Three samples each of size 19, 23 and 27 mm valves were tested at COs of 4.2, 5.6, 7.0 and 8.4 l/min. Descriptive statistics were performed for each size and CO. Regression analysis was also performed on the full dataset. Confidence intervals (CI) were calculated for each statistical method and compared. RESULTS: The regression equation that best fitted the data was: Performance Index (PI) = -1.63 + (0.011 x CO) + (0.167 x size) - (0.0036 x size2). All four parameter estimates were significantly different from zero (p <0.02). The SE of the mean was 0.015 for COs of 4.2 or 8.4 l/min, and 0.013 for COs of 5.6 or 7.0 l/min, less than that of nine of 12 of the individual descriptive analysis. CI for the regression analysis were substantially tighter, averaging one-third the width of those of the descriptive statistics. CONCLUSION: The tighter CI resulting from the regression analysis allows a better comparison of the PI to an objective performance criterion. Such methods should be considered for inclusion in the new version of the ISO 5840 standard for prosthetic heart valves.

Aortic Valve↗
PubMed2002

Modelling the hydrodynamic resistance of bordered pits.

Previous studies of the hydrodynamics of plant stems have shown that resistance to flow through bordered pits on the side walls of tracheids makes up a significant proportion of their total resistance, and that this proportion increases with tracheid diameter. This suggests a possible reason why tracheids with a diameter above around 100 microm have failed to evolve. This possibility has been investigated by obtaining an estimate for the resistance of a single pit, and incorporating it into analytical models of tracheid resistance and wood resistivity. The hydrodynamic resistance of the bordered pits of Tsuga canadensis was investigated using large-scale physical models. The importance of individual components of the pit were investigated by comparing the resistance of models with different pore sizes in their pit membrane, and with or without the torus and border. The estimate for the resistance of a real bordered pit was 1.70x10(15) Pa s m(-3). Resistance of pits varied with morphology as might be predicted; the resistance was inversely proportional to the pore size to the power of 0.715; removing the torus reduced resistance by 28%, while removal of the torus and border together reduced it by 72%. It was estimated that in a 'typical tracheid' pit resistance should account for 29% of the total. Incorporating the results into the model for the resistivity of wood showed that resistivity should fall as tracheid diameter increases. However, to minimize resistance wider tracheids would also need to be proportionally much longer. It is suggested that the diameter of tracheids in conifers is limited by upper limits to cell length or cell volume. This limitation is avoided by angiosperms because they can digest away the ends of their cells to produce long, wide vessels composed of many short cells.

Algorithms↗
PubMed2002

Simulation of biofilm growth, substrate conversion and mass transfer under different hydrodynamic conditions.

The hydrodynamic conditions and the substrate load in biofilm systems are two main parameters which influence the biofilm growth in particular the structure, density and thickness. In a long term study on heterotrophic biofilms in biofilm tube reactors the investigation has focussed on mass transfer at the bulk/biofilm interface, the biofilm density and the substrate conversion rates. To study the mass transfer phenomena at the bulk/biofilm interface oxygen profiles have been measured directly in tube reactors with microelectrodes. Microelectrode studies, substrate conversion rates and biofilm densities were used to formulate model equations for the simulation of biofilm growth under different hydrodynamic and substrate conditions. It can be shown that the mass transfer at any time is strongly coupled with the growth conditions during the biofilm cultivation. On the one side the calculated Sherwood numbers were coupled to the present hydraulic conditions, on the other side in addition the growth conditions such as growth rate and Reynolds number during biofilm cultivation were considered.

Biofilms↗
PubMedDate not supplied

Experimental studies on osmotic mechanisms and vegetative regulations of intraocular hydrodynamics as well as the distribution of elecrolytes and amino-acids in refractive environments of the eye.

The studies were carried out on the influence of hyperosmolar loading with glycerol and hypoosmotic glucose, as well as on the effect of pharmacological stimulation of the adrenergic system after sympathetic decentralization of the eyes, and of the cholinergic stimulation, on intraocular hydrodynamics, and on the distribution of electrolytes and amino-acids in refractive environments. The results showed a dependence between the changes in blood osmolality and osmotic intraocular activity, and the secretion and flow of the aqueous humor, as well as the distribution of electrolytes and amino-acids. No specific, antagonistic influence of the adrenergic and cholinergic stimulation on the hydrodynamics and the distribution of electrolytes and amino-acids in refractive environments has been found. The opposite reactions to stimulation of adrenergic alpha or beta-receptors have been observed.

Amino Acids↗