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At least 109 records · Page 6Linked to original sources
PubMed2006

Disruption of granules by hydrodynamic force in internal circulation anaerobic reactor.

A process of granule disruption by hydrodynamic force is discussed in this paper. Shear force and attrition among granules originated from hydrodynamic force are the main causes of the disruption. Since it is positively correlated to the attrition force, the shear force is utilized to describe the effect of hydrodynamic force on granule disruption. In the experiment, when increase rate of average shear rate (IRgamma) of the 1st stage is about 0.2 s(-1) x d(-1), the granules are disrupted; while re-granulation could develop when IRgamma is about 0.07 s(-1) x d(-1); even when the shear rate is as high as about 30s(-1), the granulation rate keeps stably at a relatively high level, which shows that granules could bear the high hydrodynamic force only if it increases by low increase rate. The experimental results would be valuable for the operation and controlling of the upflow reactors.

Aerobiosis↗
PubMed2004

Insulin expression in livers of diabetic mice mediated by hydrodynamics-based administration.

AIM: Transfer and expression of insulin gene in vivo are an alternative strategy to improve glycemic control in type 1 diabetes. Hydrodynamics-based procedure has been proved to be very efficient to transfer naked DNA to mouse livers. The basal hepatic insulin production mediated by this rapid tail vein injection was studied to determine its effect on the resumption of glycemic control in type 1 diabetic mice. METHODS: Engineered insulin cDNA was inserted into plasmid vectors under a CMV promoter, and transferred into STZ induced diabetic mice by hydrodynamic procedure. Glucose levels, body weight of treated mice, insulin levels, immunohistology of the liver, and quantity of insulin mRNA in the liver were assayed to identify the improvement of hyperglycemic complication after plasmid administration. Sleeping Beauty, a transposon system, was also used to prolong the insulin expression in the liver. RESULTS: After plasmid administration, Plasma insulin was significantly increased in the diabetic mice and the livers were insulin-positive by immunostaining. At the same time the hyperglycemic complication was improved. The blood glucose levels of mice were reduced to normal. Glucose tolerance of the treated diabetic mice was improved. Body weight loss was also ameliorated. The rapid tail vein injection did not cause any fatal result. CONCLUSION: Our results suggested that insulin gene could be efficiently transferred into the livers of diabetic mice via rapid tail vein injection and it resulted in high level of insulin expression. The basal hepatic insulin production mediated by hydrodynamics-based administration improved the glycemic control in type 1 diabetes dramatically and ameliorated diabetic syndromes. Hydrodynamics-based administration offers a simple and efficient way in the study of gene therapy for type 1 diabetes.

Animals↗
PubMed2005

In vivo hydrodynamic delivery of cDNA encoding IL-2: rapid, sustained redistribution, activation of mouse NK cells, and therapeutic potential in the absence of NKT cells.

In the present study, we have tested the ability of hydrodynamically delivered IL-2 cDNA to modulate the number and function of murine leukocyte subsets in different organs and in mice of different genetic backgrounds, and we have evaluated effects of this mode of gene delivery on established murine tumor metastases. Hydrodynamic administration of the IL-2 gene resulted in the rapid and transient production of up to 160 ng/ml IL-2 in the serum. The appearance of IL-2 was followed by transient production of IFN-gamma and a dramatic and sustained increase in NK cell numbers and NK-mediated cytolytic activity in liver and spleen leukocytes. In addition, significant increases in other lymphocyte subpopulations (e.g., NKT, T, and B cells) that are known to be responsive to IL-2 were observed following IL-2 cDNA plasmid delivery. Finally, hydrodynamic delivery of only 4 mug of the IL-2 plasmid to mice bearing established lung and liver metastases was as effective in inhibiting progression of metastases as was the administration of large amounts (100,000 IU/twice daily) of IL-2 protein. Studies performed in mice bearing metastatic renal cell tumors demonstrated that the IL-2 cDNA plasmid was an effective treatment against liver metastasis and moderately effective against lung metastasis. Collectively, these results demonstrate that hydrodynamic delivery of relatively small amounts of IL-2 cDNA provides a simple and inexpensive method to increase the numbers of NK and NKT cells, to induce the biological effects of IL-2 in vivo for use in combination with other biological agents, and for studies of its antitumor activity.

Animals↗
PubMedDate not supplied

[Hydrodynamic efficiency of various forms of free DNA].

DNA of blood plasma is the factor which corrects hydrodynamic resistance (HR) of blood flow and provides Thomes' effect. As comparative hydrodynamic effectiveness of various plasma DNA forms (nucleoprotein, thread and denaturated DNA isolated standardly from human leukocytes) remains unknown, the in vitro test identified HR of the flow of the above DNA forms weak solutions--10(-6) to 10(-5) g/ml--necessary for achievement of Thomes' effect in strictly similar hydrodynamic conditions warranting a turbulent flow (Re 8000). Thomes' effect was confirmed in blood samples in its absence in low-molecular solutions (glycerine) with the same asymptotic viscosity. It was found that HR of the flow of synthetic polymer solutions producing Thomes' effect depends on its initial concentrations. Hydrodynamic effectiveness in the used solutions of the nucleoprotein and DNA was high being comparable to that of the synthetic polymer widely used in production for obtaining Thomes' effect.

Blood Viscosity↗
PubMed2001

Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep.

Survival to six months for sheep with a non-biostable polyurethane mitral heart valve prosthesis has been reported previously, however, with surface degradation and accumulation of calcified fibrin/thrombus that impaired leaflet motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prostheses of documented hydrodynamic performance, implanted in the mitral position, were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and electron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving leaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve prostheses.

Animals↗
PubMed2001

The influence of ventricular input impedance on the hydrodynamic performance of bioprosthetic aortic roots in vitro.

BACKGROUND AND AIM OF THE STUDY: Hydrodynamic function testing using pulsatile flow simulators provides a valuable means of comparative assessment of heart valves in vitro. The majority of pulsatile flow simulators consist of modular rigid chambers and a positive displacement pump with an infinite input impedance, in which the inertia of the test fluid results in pressure oscillations when the valves under test are opening and closing. For mechanical and stented bioprosthetic valves these pressure oscillations decay quickly. However, due to the highly compliant nature of tissue roots, the resulting pressure and flow oscillations are extreme and extend throughout systole. With increasing interest in the use of free-sewn roots and valves it is most desirable to improve this hydrodynamic model. The aim of this study was to investigate the influence in changes in ventricular input impedance on the hydrodynamic characteristics of free-sewn aortic roots and stented valves. METHODS: The Leeds pulsatile flow simulator was modified to incorporate additional compliance chambers in the form of a viscoelastic impedance adaptor (VIA) at the pump/ventricular interface. Six 23 mm bioprosthetic aortic roots fixed with 0.5% buffered glutaraldehyde at zero pressure, and a size 23 mm stented porcine aortic bioprosthesis were tested in this modified simulator, at the conditions of maximum and minimum input compliance. RESULTS: The pressure and flow waveforms for the fixed aortic roots showed considerable differences at the conditions of maximum and minimum input compliance. Indeed, the extreme pressure oscillations observed at minimum compliance (infinite input impedance) were not present at maximum compliance, and the forward flow waveform was much smoother. In contrast, for the stented valve, the differences in the pressure and flow waveforms between maximum and minimum input compliance were minimal, but this was expected due to the lack of compliance in the stented valve itself. In addition, the flow and pressure waveforms at maximum compliance in the VIA were comparable for the fixed aortic roots and the stented bioprosthesis, thus allowing direct comparison of the characteristics of these two different devices. Using test conditions of maximum input compliance, effective orifice area for the roots was 1.69 cm2 compared with 1.47 cm2 for the stented valve. CONCLUSION: An appropriate physiological model for the hydrodynamic testing of compliant tissue roots has been established.

Aortic Valve↗
PubMed2001

Hepatic uptake and gene expression mechanisms following intravenous administration of plasmid DNA by conventional and hydrodynamics-based procedures.

Hepatic uptake and gene expression mechanisms following intravenous administration of naked plasmid DNA (pDNA) by conventional and hydrodynamics-based procedures were studied in mice. After conventional (normal) intravenous injection, (32)P-labeled pDNA was rapidly eliminated from the circulation and predominantly taken up by the liver nonparenchymal cells while no significant gene expression was observed in this organ. The hepatic uptake process was saturable. Involvement of a specific mechanism was demonstrated since the hepatic uptake of [(32)P]pDNA was dramatically inhibited by cold pDNA, calf thymus DNA, and some polyanions [polyinosinic acid (poly I), dextran sulfate], but not by others (polycytidylic acid, chondroitin sulfate). The liver endothelial cells appeared to be a major contributor because gadolinium chloride (GdCl(3))-induced Kupffer cell blockade did not affect the hepatic uptake. After intravenous injection of naked pDNA with a large volume of saline at a high velocity (hydrodynamics-based procedure), the apparent hepatic uptake profile was similar to that after normal injection. The hepatic uptake was not inhibited by prior administration of polyanions, including poly I, dextran sulfate, and heparin. The hydrodynamics-based procedure resulted in marked gene expression in the liver, which was not inhibited by prior administration of polyanions or GdCl(3) treatment. These results indicate that pDNA uptake is a nonspecific process. This hypothesis was supported by the finding that significant hepatic uptake of bovine serum albumin and immunoglobulin G was observed after the hydrodynamics-based procedure.

Animals↗
PubMed2003

Application of CFD modelling to study the hydrodynamics of various anaerobic pond configurations.

The simulation of hydrodynamics and transport phenomena in waste stabilization ponds is a developing tool worth studying in order to understand their internal processes and interactions. Pond design involves several physical, hydrological, geometric and dynamic variables so as to provide high hydrodynamic efficiency and maximum substrate utilization rates. CFD modelling allows the combination of these factors to predict the behaviour of ponds having different configurations. The two-dimensional depth-integrated model MIKE 21 was used in this study to simulate hydrodynamic and advection-dispersion processes in a full-scale anaerobic pond (AP) located in southwest Colombia. A set of 12 configurations including sludge contents, inlet-outlet positioning, baffling and pond geometry were modelled. Results showed that a crosswise (diagonally opposite) inlet-outlet layout, a length-to-breadth ratio of 2:1, plus provision of two cross baffles at 1/3 L and 2/3 L were the most effective measures to improve overall AP hydrodynamics and dispersion patterns.

Bacteria, Anaerobic↗
PubMedDate not supplied

[Changes in hydrodynamic diameter of myometrium plasmalemma vesicles under artificial creation of transmembrane proton gradients].

A method of laser-correlation spectrophotometry was applied for finding the effect of proton transmembrane gradient on hydrodynamic diameter of plasmalemma smooth muscle vesicles. It is shown, that the building of protons gradient on the membrane of vesicles, pHi = 6.0; pHo = 7.5 (delta pH = 1.5) results in the reliable decrease of their hydrodynamic diameter (from 212 +/- 6 nm in monitoring to 174 +/- +/- 0.25 nm in experiment). The exit of K+ from vesicles (KCl concentration inside vesicles is 150 mM), on the contrary, evokes augmentation of hydrodynamic diameter. The chemical paravariation of COO-, NH(3+)-groups and stabilization of SH-groups of plasmalemma surface results in essential modifications in magnitude of the hydrodynamic diameter of vesicles. On the basis of experimental data a supposition is expressed about the role of modifications of regional position of the functionally important groups of plasmalemma with respect to the membrane surface in mechanisms of H+ transport.

Animals↗
PubMed1978

[Hydrodynamic and radiologic examination of the common bile duct].

The operative study of the common bile duct was carried out with the hydrodynamics methods (flow and resting pressure) in 433 patients and with the operative cholangiography in 383 patients. The hydrodynamics explorations pointed-out a margin of mistake due to falses positives and negatives of the 2.7% and the operative cholangiographies of the 8.6%. The association of both methods, hydrodynamics and radiologycs, allowed us to estimate that the diagnostic mistake is reduced to 0%. It is established in this work the necessity of carring out the flow, the measure of the resting pressure and the cholangiographies; in all the patients that are operated on the biliary tract because the diagnostic accuracy is the 100%. It is discussed the value of the diameter of the common bile duct for affirming the eventual existence of obstruction of the lower part of the common bile duct and the values are correlated, measured in mm., with pathological founds. It is considered the value of the hydrodynamics methods in the diagnostic of the stenosis of the sphincter of Oddi.

Adolescent↗
PubMed2004

[Hydrodynamic investigations of the current mechanical artificial heart valves].

The work presents results of comparative investigations of the integral hydrodynamic characteristics of the best for today domestic mechanical heart valve (MHV) Medinzh-2 (MI-2) and the turn-disk domestic MHV--LIKS-2, EMIKS (E) and foreign MHV--Medtronic-Hall, Bjork-Shiley (BS), Sorin (SO) and bicuspid valves--St. Jude Medical (SJ), Carbomedics in the stationary and in the pulsatile flows. It was found that according to the main hydrodynamic characteristics including the outlet flow structure, MHV MI-2 was substantially superior to MHV E, BS and SO, and by certain characteristics it approximated to the best foreign MHV SJ. Like all mechanical heart valves, the valve MI-2 disturbs the uniformity of the inlet flow and forms a complex non-stationary flow with detached zones, areas of great shear stresses, with vortex structures of different types, and hence the task of hydrodynamic optimization of its construction is thought to become actual. The comparison of clinical parameters of work of the valve MI-2 with its hydrodynamic characteristics confirms its high hemodynamic effectiveness and thrombo-resistance in patients at long-term periods of follow-up, taking into account the adequate correction of disbalance of hemostasis.

Heart Valve Prosthesis↗
PubMed1984

Electron microscopy and hydrodynamic properties of blood clotting factor V and activation fragments of factor V with phospholipid vesicles.

The electron microscopic and hydrodynamic properties of factor V and factor Va-vesicle complexes were determined. Images of negatively stained factor V bound to vesicles showed the protein as a relatively large globular domain (9.5 nm diameter) connected to the membrane through a narrow protein region 0.5-3 nm in length. This connecting region was not always visible and was measured as the distance between the globular region and the apparent vesicle edge. Factor V protein alone usually appeared as two connected globular regions of 10.2 and 6.5 nm diameter. The two-domain protein structure appeared consistent with both the image of factor V alone and bound to the membrane. Factor V had no biological activity in a phospholipid-free prothrombinase assay system used. The proteolytically activated form of factor V generated by digestion with thrombin (factor Va) was at least 30,000 times more active. The electron microscopic images of factor Va-vesicle complexes showed a smaller protein that was more closely associated with the vesicle surface than was factor V. The light chain (Mr about 80,000) component of factor Va also bound to the surface of the vesicles and appeared to be largely external to the membrane. Protein-induced hydrodynamic radius changes for the factor V-vesicle and factor Va-vesicle complexes were 12.8 and 6.3 nm, respectively. The images observed in the electron microscope were used to calculate protein-induced radius changes. Comparison of these values with the experimentally determined hydrodynamic radius changes showed approximate agreement for factor Va-membrane complexes. However, the images of factor V-vesicle complexes suggested smaller hydrodynamic radius changes than were actually observed.

Animals↗
PubMedDate not supplied

[Experimental study of hydrodynamics of artificial heart valves].

The paper presents the results of examining the hydrodynamics of artificial heart valves (AHVs) manufactured in Russia and foreign countries. All the AHVs under study have been used in clinical practice for over 10 years and they are different in design. The hydrodynamics of AHVs was examined under static and pulsating flow through the valve. Photochromic imaging (PCI) was used for flow imaging. PCI is based on preparation of simulating blood (model physiological solution) in the medium, colour labels under laser radiation. The recording of colour label movement in the flow behind the valve using a speed camera makes it possible to follow flow hydrodynamics behind AHVs. The advantage of PCI over other methods is that the instant structure of flow behind the valve can be recorded just in the same section at any moment of an operating cycle. Based on the experimental data obtained by PCI, a procedure for comparative analysis of the hydrodynamic characteristics of AHVs was developed.

Heart Valve Prosthesis↗
PubMed1997

Simulation of electrostatic and hydrodynamic properties of Serratia endonuclease.

We analyze the electrostatic and hydrodynamic properties of a nuclease from the pathogenic gram-negative bacterium Serratia marcescens using finite-difference Poisson-Boltzmann methods for electrostatic calculations and a bead-model approach for diffusion coefficient calculations. Electrostatic properties are analyzed for the enzyme in monomeric and dimeric forms and also in the context of DNA binding by the nuclease. Our preliminary results show that binding of a double-stranded DNA dodecamer by nuclease causes an overall shift in the charge of the protein by approximately three units of elementary charge per monomer, resulting in a positively charged protein at physiologic pH. In these calculations, the free enzyme was found to have a negative (-1 e) charge per monomer at pH 7. The most dramatic shift in pKa involves His 89 whose pKa increases by three pH units upon DNA binding. This shift leads to a protonated residue at pH 7, in contrast to the unprotonated form in the free enzyme. DNA binding also leads to a decrease in the energetic distances between the most stable protonation states of the enzyme. Dimerization has no significant effect on the electrostatic properties of each of the monomers for both free enzyme and that bound to DNA. Results of hydrodynamic calculations are consistent with the dimeric form of the enzyme in solution. The computed translational diffusion coefficient for the dimer model of the enzyme is in very good agreement with measurements from light scattering experiments. Preliminary electrooptical calculations indicate that the dimer should possess a large dipole moment (approximately 600 Debye units) as well as substantial optical anisotropy (limiting reduced linear electric dichroism of about 0.3). Therefore, this system may serve as a good model for investigation of electric and hydrodynamic properties by relaxation electrooptical experiments.

Endonucleases↗
PubMed2003

Modeling of scale-down effects on the hydrodynamics of expanded bed adsorption columns.

Expanded-bed adsorption (EBA) is a technique for primary recovery of proteins starting from unclarified broths. This process combines centrifugation, concentration, filtration, and initial capturing of the proteins in a single step. An expanded bed (EB) is comparable to a packed bed in terms of separation performance but its hydrodynamics are that of a fluidized bed. Downstream process development involving EBA is normally carried out in small columns to minimize time and costs. Our purpose here is to characterize the hydrodynamics of expanded beds of different diameters, to develop scaling parameters that can be reliably used to predict separation efficiency of larger EBA columns. A hydrodynamic model has been developed which takes into account the radial liquid velocity profile in the column. The scale-down effect can be characterized in terms of apparent axial dispersion, D(axl,app), and plate number, N(EB), adapted for expanded bed. The model is in good agreement with experimental results obtained from 1- and 5-cm column diameters with buffer solutions of different viscosities. The model and the experiments show an increase of apparent axial dispersion with an increase in column diameter. Furthermore, the apparent axial dispersion is affected by an increase in liquid velocity and viscosity. Supported by visual observations and predictions from the model, it was concluded that operating conditions (liquid viscosity and superficial velocity) resulting in a bed-void fraction between 0.7 and 0.75 would provide the optimal separation efficiency in terms of N(EB).

Adsorption↗
PubMed2006

Disruption of Brewers' yeast by hydrodynamic cavitation: Process variables and their influence on selective release.

Intracellular products, not secreted from the microbial cell, are released by breaking the cell envelope consisting of cytoplasmic membrane and an outer cell wall. Hydrodynamic cavitation has been reported to cause microbial cell disruption. By manipulating the operating variables involved, a wide range of intensity of cavitation can be achieved resulting in a varying extent of disruption. The effect of the process variables including cavitation number, initial cell concentration of the suspension and the number of passes across the cavitation zone on the release of enzymes from various locations of the Brewers' yeast was studied. The release profile of the enzymes studied include alpha-glucosidase (periplasmic), invertase (cell wall bound), alcohol dehydrogenase (ADH; cytoplasmic) and glucose-6-phosphate dehydrogenase (G6PDH; cytoplasmic). An optimum cavitation number Cv of 0.13 for maximum disruption was observed across the range Cv 0.09-0.99. The optimum cell concentration was found to be 0.5% (w/v, wet wt) when varying over the range 0.1%-5%. The sustained effect of cavitation on the yeast cell wall when re-circulating the suspension across the cavitation zone was found to release the cell wall bound enzyme invertase (86%) to a greater extent than the enzymes from other locations of the cell (e.g. periplasmic alpha-glucosidase at 17%). Localised damage to the cell wall could be observed using transmission electron microscopy (TEM) of cells subjected to less intense cavitation conditions. Absence of the release of cytoplasmic enzymes to a significant extent, absence of micronisation as observed by TEM and presence of a lower number of proteins bands in the culture supernatant on SDS-PAGE analysis following hydrodynamic cavitation compared to disruption by high-pressure homogenisation confirmed the selective release offered by hydrodynamic cavitation.

Alcohol Dehydrogenase↗
PubMed2003

Electrophoretic separations on chips with hydrodynamically closed separation systems.

This review focuses on capillary electrophoretic separations performed on capillary electrophoresis chips (CE chips) with hydrodynamically closed separation systems in a context with transport processes (electroosmotic flow (EOF)) and hydrodynamic flow (HDF)) that may accompany the separations in these devices. It also reflects some relevant works dealing with conventional CE operating under such hydrodynamic conditions. The use of zone electrophoresis (ZE), isotachophoresis (ITP) and their on-line combination (ITP-ZE) on the single-column and column-coupling CE chips with the closed separation systems and related problems are key topics of the review. Some attention is paid to sample pretreatment in the separations performed on the CE chips. Here, mainly potentialities of the ITP-ZE combination in trace analysis applications of the miniaturized systems are discussed in a broader extent. Links between the ZE separation and detection provide a frame for the discussion of current status of the detection on the CE chips. Analytical applications illustrate potentialities of the CE chips operating with the closed separation systems (suppressed HDF and EOF) to the determination of small ions present in various matrices by ZE, ITP and ITP-ZE.

Electrophoresis, Capillary↗
PubMed2005

Nanoparticle-filled capillary electrophoresis for the separation of long DNA molecules in the presence of hydrodynamic and electrokinetic forces.

We report the analysis of long DNA molecules by nanoparticle-filled capillary electrophoresis (NFCE) under the influences of hydrodynamic and electrokinetic forces. The gold nanoparticle (GNP)/polymer composites (GNPPs) prepared from GNPs and poly(ethylene oxide) were filled in a capillary to act as separation matrices for DNA separation. The separations of lambda-DNA (0.12-23.1 kbp) and high-molecular-weight DNA markers (8.27-48.5 kbp) by NFCE, under an electric field of -140 V/cm and a hydrodynamic flow velocity of 554 microm/s, were accomplished within 5 min. To further investigate the separation mechanism, the migration of lambda-DNA was monitored in real time using a charge-coupled device (CCD) imaging system. The GNPPs provide greater retardation than do conventional polymer media when they are encountered during the electrophoretic process. The presence of interactions between the GNPPs and the DNA molecules is further supported by the fluorescence quenching of prelabeled lambda-DNA, which occurs through an energy transfer mechanism. Based on the results presented in this study, we suggest that the electric field, hydrodynamic flow, and GNPP concentration are the three main determinants of DNA separation in NFCE.

Bacteriophage lambda↗