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PubMed2001

Influence of hydrostatic pressure and gas content on continuous ultrasound emulsification.

Ultrasound is one means among others of producing emulsions mechanically. Droplet disruption in sonicated liquid-liquid systems is considered to be controlled by cavitation. Both hydrostatic pressure and gas content of the liquids influence the probability and intensity of cavitation. Continuous ultrasound emulsification experiments were carried out to elucidate the effect of these parameters on the result of droplet disruption. Maximum energy density in the apparatus decreases with increasing hydrostatic pressure, probably due to partial suppression of cavitation which is the main mechanism of power dissipation. At constant energy density there is no significant influence of hydrostatic pressure on the emulsification result, however. Corresponding results were obtained for the influence of the gas content. Gas saturation or partial degassing prior to emulsification lead to a shift in maximum energy density. But, again, at constant energy density no clear effect on the droplet size of the emulsion is observed.

Journal Article↗

PubMed1968

The effect of small hydrostatic pressure gradients on the rate of active sodium transport across isolated living frog-skin membranes.

1. The rate of active sodium transport across living isolated skins from Rana temporaria was measured when the skins were bulged inwards and outwards by small constant hydrostatic pressure gradients and by pushing them mechanically in the absence of such gradients. The effect of pressure gradients in the absence of bulging was also studied.2. An apparatus was designed to circulate Ringer solution to each side of the skin at constant temperature, flow and pressure. The pressures were controlled to within 0.5 mm H(2)O.3. It was found that bulging the skins in the absence of hydrostatic pressure gradients had no effect on sodium transport but that pressure gradients of less than 5 mm H(2)O had a marked effect, increasing transport when the pressure was higher on the outside of the skin, and decreasing it when the pressure was higher on the inside.4. It is concluded that increasing surface area does not influence sodium transport, whereas small hydrostatic pressure gradients have a marked effect.5. Possible causes for this phenomenon are discussed and its significance is considered with special reference to sodium reabsorption from the proximal tubule of the kidney.

Animals↗

PubMed1981

Effects of high hydrostatic pressure on normal and neoplastic rat cells in culture.

Four types of rat cells in culture were exposed to hydrostatic pressures in the range 1-1,500 bar. Each applied pressure was constant for half an hour. The morphological effects of pressure application were studied by phase contrast microscopy, and mortality was measured by total cell counts and the trypan blue exclusion test. Morphological changes characterized by cell rounding were observed in secondary fetal brain cells and fibroblasts at about 700 bar. In two permanent neoplastic neurogenic cell lines similar changes occurred at 1,000 to 1,100 bar. When approximately 50% of the cells were rounded, mortality began to increase, as compared with controls. This was gradual in secondary cells and comparatively abrupt in the permanent neoplastic lines. Malignant cells in culture may therefore be more resistant to hydrostatic pressure than their normal counterparts.

Animals↗

PubMed2007

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

OBJECTIVES: This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. METHODS: Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. RESULTS: The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). SIGNIFICANCE: These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

Biomechanical Phenomena↗

PubMed2005

[Expression of integrin alpha5 and actin in the cells of intervertebral disc under cyclic hydrostatic pressure in vitro].

OBJECTIVE: To investigate the expression of integrin alpha5 and actin in the cells of intervertebral disc under cyclic hydrostatic pressure in vitro. METHODS: The porcine lumbar intervertebral disc cells were isolated and cultured in vitro, and the cells underwent cyclic hydrostatic loading. After that, the expression of integrin alpha5 and actin in intervertebral disc cells were studied by means of morphology observing, Western blot and immunohistochemistry staining. RESULTS: The morphology of intervertebral disc cells were changed into smaller and flatten shape, and the expression of integrin alpha5 and actin were decreased after loading. CONCLUSIONS: The expression of integrin alpha5 decreases under cyclic hydrostatic pressure, and the actin is affected at the same time when signals are transferred into the cells by integrin alpha5. That may be one of the important mechanisms of the mechanotransduction in the cells of intervertebral disc.

Actins↗

PubMed2004

Numerical simulation of the mechanics of a yeast cell under high hydrostatic pressure.

The mechanical effects of the compression of a yeast cell (Saccharomyces cerevisiae) under high hydrostatic pressure used for the processing of food and food ingredients are modelled and simulated with the finite-element method. The cell model consists of a cell wall, cytoplasm a lipid filled vacuole and the nucleus. Material parameters have been taken from literature or have been derived from thermodynamic relationships of water and lipids under high hydrostatic pressure. The model has been validated for a pressure load up to 250 MPa. Comparison of the volume reduction to in situ experimental observations reveals very good agreement. Dimensional analysis of the governing equations shows that transient pressure application in a high-pressure food process does not enhance structural inactivation (mechanical damage), unless pressure oscillation frequencies of 700 MHz are applied. The deformation of the cell under pressure deviates strongly from isotropic volume reduction. Especially, organelle membranes exhibit large effective strain values. Hydrostatic stress conditions are preserved in the interior part of the cell. A pressure load of 400 MPa, which is critical upon disruption of cell organelle membranes, generates an effective strain up to 80%. In the cell wall, the stress state is heterogeneous. Von-Mises stress reaches the critical value upon failure of the cell wall of 70+/-4 MPa at a pressure load between 415 and 460 MPa.

Biomechanical Phenomena↗

PubMed1998

Three-dimensional changes of the cytoskeleton of vascular endothelial cells exposed to sustained hydrostatic pressure.

The three-dimensional changes in the cytoskeleton and in cell proliferation of bovine pulmonary artery endothelial cells when exposed to sustained hydrostatic pressure were investigated in vitro using laser scanning confocal microscopy. Subconfluent endothelial cells on rigid substrates were exposed to 1.5, 5 and 10 cm H2O pressure under hydrostatic heads of culture medium for up to seven days. Confocal microscopic images were taken at distances of 0.4 micron through the thickness of the sample and visualised in multiplanar, stereopair and 90 degrees rotation formats. The results of the study provide evidence of: increased proliferation after exposure to 10 cm H2O pressure for five and seven days; cell bilayering after exposure to 1.5 and 5 cm H2O pressure and trilayering after exposure to 10 cm H2O pressure for seven days; and F-actin filament reorganisation into centrally located, parallel, stress fibres in confluent cells, into peripheral bands in subconfluent, multilayered cells, and into multilayers in the plane perpendicular to the applied force.

Animals↗

PubMed1975

Stability of Escherichia coli polysomes at high hydrostatic pressure.

The stability of Escherichia coli polysomes at increased hydrostatic pressure was investigated in actively growing cells, in which the initiation of transcription was blocked by rifampin. In these cells, [3-H]uridine incorporation into messenger ribonucleic acid and the subsequent degradation of the message (and therefore of polysomes) by ribonuclease could be observed. Evidence is presented that the activity of the RNases is unaffected by a pressure of 680 atm, that protein synthesis is completely inhibited at 680 atm but immediately resumes at the 1 atm rate on release of pressure, and that no degradation of messenger ribonucleic acid in polysomes occurs at 680 atm. The effects of pressure; puromycin, and chloramphenicol on polysomal degradation are discussed. These results indicate that, contrary to some previous reports, polysomes are probably stabilized by high pressures. Therefore, we consider that polysomal instability is not a factor in the inhibition of protein synthesis by high pressures.

Amino Acids↗

PubMed1999

In vivo effects of hydrostatic pressure on interstitium of abdominal wall muscle.

Fluid loss from the peritoneal cavity to surrounding tissue varies directly with intraperitoneal hydrostatic pressure (Pip). According to Darcy's law [Q = -KA(dPif/dx)], fluid flux (Q) across a cross-sectional area (A) of tissue will increase with an increase in either hydraulic conductivity (K) or the interstitial fluid hydrostatic pressure gradient (dPif/dx, where x is distance). Previously, we demonstrated that in the anterior abdominal muscle (AAM) of rats, dPif/dx increases by only 40%, whereas K rises fivefold between Pip of 1.5 and 8 mmHg. Because K is a function of interstitial volume (thetaif), we hypothesized that perturbations of Pip would change Pif and expand the interstitium, increasing thetaif. To test this hypothesis, we used dual-label quantitative autoradiography (QAR) to measure extracellular fluid volume (thetaec) and intravascular volume (thetaiv) in the AAM of rats within the Pip range from -2.8 to +8 mmHg. thetaif was obtained by subtraction (thetaec - thetaiv). dPif/dx was measured with a micropipette and a servo-null system. Local thetaiv did not vary with Pip and averaged 0.010 +/- 0.002 ml/g, and thetaif averaged 0. 19 +/- 0.01 ml/g at Pif </=1.2 mmHg. However, thetaif doubled between Pif of 1.2 and 4.2 mmHg (from 0.20 +/- 0.00 to 0.39 +/- 0.01 ml/g, respectively) but did not increase with further increases in Pif. This nonlinear pressure-volume relationship does not explain the fivefold increase in K with Pip. Because the interstitial matrix contributes to the interstitial resistance to fluid flow, and because hyaluronan (HA) is the only component of the matrix that is not anchored to the tissue, we hypothesized that the loss of interstitial HA was responsible for the continued decrease in interstitial resistance to fluid flow. We determined HA concentration in the rat AAM and adjacent subcutaneous tissue (SC) at Pip = 0 mmHg and after 2 h of dialysis at constant Pip = 6 mmHg. The HA content (normalized to dry weight) in the AAM was reduced from 487 +/- 16 to 360 +/- 27 micrograms/g dry tissue (n = 4, P < 0.05) and increased from 528 +/- 72 to 1,050 +/- 136 mg/g dry tissue (n = 4, P > 0.001) in the SC. We conclude that the mechanisms responsible for the increase in K with Pip include expansion of the interstitium, dilution of interstitial macromolecules, and washout from the AAM to SC of interstitial macromolecules responsible for resistance to fluid flow.

Abdominal Muscles↗

PubMed1990

Subepithelial hydrostatic pressure may regulate plasma exudation across the mucosa.

This study demonstrated in guinea pig tracheal tubes in vitro that small increases in serosal hydrostatic pressure caused significant mucosal crossing of serosal macromolecules. Reversibility and repeatability of this passage agree with inflammatory stimulus-induced appearance of exuded plasma in airway lumen in vivo. Bradykinin, histamine, and terbutaline, which induce and inhibit, respectively, plasma exudation in vivo, were without effect on the present in vitro permeability. Carbachol, similar to histamine, contracted the trachea, and did not increase, but rather decreased the pressure-induced luminal entry of serosal macromolecules. It is proposed that a plasma-exudation-induced hydrostatic pressure load transiently separates epithelial cells, providing a direction-selective and non-injurious intercellular pathway for passage of bulk plasma exudate into the airway lumen. This mechanism would allow potent plasma protein systems to operate on mucosal surfaces at sites of insults without compromising the mucosa as a barrier to luminal solutes.

Animals↗

PubMed1959

The influence of high hydrostatic pressure on cocaine and veratrine action in a vertebrate nerve.

The application of high hydrostatic pressure to toad sciatic nerve causes a gain in sodium and a loss of potassium which are not affected by cocaine. However, cocaine action is enhanced by high pressure when counteracting veratrine depolarization and when blocking the action potential. Various effects of elevated pressure on the after-potentials are presented and the role of ions in these processes is discussed.

Action Potentials↗

PubMed1988

Effect of hydrostatic pressure on the mitochondrial ATP synthase.

The effects of hydrostatic pressure on three different preparations of mitochondrial H+-ATPase were investigated by studies of the hydrolytic activity, of the spectral shift and quantum yield of the intrinsic protein fluorescence, and of filtration chromatography. Both membrane-bound and detergent-solubilized forms of the mitochondrial F0-F1 complex were reversibly inactivated in the pressure range of 600-1800 bar, whereas with soluble F1-ATPase the inactivation was irreversible. Pressure inactivation of soluble F1-ATPase was facilitated by decreasing the protein concentration, indicating that dissociation is an important factor. In the presence of 30% glycerol, soluble F1-ATPase becomes inactivated by pressure in a reversible fashion, recovering the original activity. ATPase activity measured in an aqueous medium returns to the original values when incubated under high pressure in a glycerol-containing medium without substrate and is even enhanced when Mg-ATP is present. ATP hydrolysis returns to 80% of its original value in the case of the F0-F1 complex. Fluorescence studies under pressure revealed a red shift in the spectral distribution of the emission of tyrosine fluorescence of soluble F1-ATPase. A decrease in the quantum yield of intrinsic fluorescence was also observed upon subjection to pressure. The fluorescence intensity decreased monotonically as a function of pressure when the sample was in an aqueous medium, whereas it presented a biphasic behavior in a 30% glycerol medium. Gel filtration studies demonstrated that the hydrodynamic properties of the F1-ATPase are preserved if the enzyme is subjected to pressure in the presence of glycerol but they are modified when the same procedure is performed in an aqueous medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

Effect of high hydrostatic pressure on the barrier properties of polyamide-6 films.

Little is known about the barrier properties of polymer films during high pressure processing of prepackaged foods. In order to learn more about this, we examined the influence of high hydrostatic pressure on the permeation of raspberry ketone (dissolved in ethanol/water) through polyamide-6 films at temperatures between 20 and 60 degrees C. Permeation was lowered by increasing pressure at all temperatures. At 23 degrees C, the increasing pressure sequence 0.1, 50, 100, 150, and 200 MPa correlated with the decreasing permeation coefficients P/(10(9) cm(2) s-1) of 6.2, 3.8, 3.0, 2.2, and 1.6. Analysis of the permeation kinetics indicated that this effect was due to a reduced diffusion coefficient. Pressure and temperature acted antagonistically to each other. The decrease in permeation at 200 MPa was compensated for by a temperature increase of 20 degrees C. After release of pressure, the former permeation coefficients were recovered, which suggests that this 'pressure effect' is reversible. Taken together, our data revealed no detrimental effects of high hydrostatic pressure on the barrier properties of polymer films.

Butanones↗

PubMed2001

Optical chamber system designed for microscopic observation of living cells under extremely high hydrostatic pressure.

A novel pressure chamber system has been developed for the study of living cells under conditions of extremely high hydrostatic pressure up to 100 MPa (1 atm = 0.101325 MPa). The temperature in the chamber is thermostatically controlled in the range from 2 degrees to 80 degrees C. Two high-pressure pumps are employed for continuous perfusion of the chamber with culture medium and a chemical solution under high hydrostatic pressure conditions. The chamber has a 2-mm-thick glass window 2 mm in diameter, with a minimum working distance of 3.8 mm. The chamber system is designed to be adaptable to a variety of microscopic and imaging techniques. Using this chamber system, we successfully carried out real-time observations of elongated Escherichia coli and rounded HeLa cells under pressure.

Cell Culture Techniques↗

PubMed2004

Hydrodynamic stimulation and long term cultivation of nucleus pulposus cells: a new bioreactor system to induce extracellular matrix synthesis by nucleus pulposus cells dependent on intermittent hydrostatic pressure.

A novel bioreactor system was constructed to induce extracellular matrix (ECM) synthesis by intervertebral disc (ID) cells due to intermittent hydrostatic pressure. The developed system is completely sterilizable and reusable. It is viable for cultivation, immobilization, and stimulation of various other cell types and tissues especially for cartilage. The custom made lid allows long-run cultivation through semi-continuous operation. Manual interferences and therefore the risk of contamination are reduced. Sampling, medium changing and addition of supplements are easily performed from the connected conditioning vessel, which could be placed in an incubator. For the present investigations nucleus pulposus cells from pigs were taken and immobilized in agarose to obtain three-dimensional cell matrix constructs which were subjected to intermittent hydrostatic pressure. Afterwards the construct was biochemically examined. The proven constituents of ECM were found to be released in dependence of the magnitude and profile of the applied pressure.

Animals↗

PubMed1998

Effect of high hydrostatic pressure on Pacific whiting surimi.

The effects of high hydrostatic pressure (HHP) on gel strength, microbial numbers, proteolytic activity, color and pH of Pacific whiting surimi gels were investigated. Strong gels without the use of protease inhibitors were formed with HHP treatments from 1-4 kBars. Gel strength was not affected by holding time. Total plate counts showed that destruction of vegetative cells was accomplished with 4 kBar. Proteolytic activity was diminished but not eliminated with pressure treatments. The color of the surimi gels treated were translucent while the heat-treated gels were opaque. The pH was increased slightly with HHP treatment. HHP was an effective processing method for making high quality surimi gels from Pacific whiting.

Animals↗

PubMed1983

The subcapsular hydrostatic pressure of allogeneic kidney grafts: a new clinical method for postoperative transplant monitoring.

A method for the measurement of the subcapsular hydrostatic pressure in human kidney grafts is described. This method permits follow-up studies over periods up to 4 weeks. First results indicate that the method is a useful tool to monitor the condition of renal allografts in the early postoperative period. It allows the early recognition of acute rejection episodes and predicts their course and reversibility. The subcapsular hydrostatic pressure is a particularly valuable parameter in the differentiation of acute rejection and acute tubular necrosis.

Acute Kidney Injury↗

PubMed1980

Experience with the use of an intravesical hydrostatic pressure balloon.

Treatment with the use of an intravesical hydrostatic pressure balloon has been undertaken on 34 occasions in 24 patients. The procedure can be of great benefit in seriously ill patients with intractable hemorrhage of the bladder in whom alternative treatment methods either have failed or are too great a risk to attempt. It can also provide a useful treatment adjunct in the management of patients with massive low grade, noninvasive tumors of the bladder in whom endoscopic resection is not technically possible.

Cystitis↗