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Results for “Hydrostatic Pressure”

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At least 199 records · Page 11Linked to original sources

PubMed1998

High hydrostatic pressure can reverse aggregation of protein folding intermediates and facilitate acquisition of native structure.

The present work demonstrates that high hydrostatic pressure can increase protein folding by reducing nonspecific aggregation. Protein aggregation is one of the main side reactions that competes with protein folding, and it typically results from interactions among partially folded intermediates. It is known that oligomeric proteins can be dissociated by the application of high hydrostatic pressure. Since protein aggregates can be described as nonspecific protein oligomers, it can be predicted that they can be completely or partially dissociated by pressure. The enzyme rhodanese is prone to slow aggregation in 3.9 M urea, and it is widely used as a model for the folding of a protein which readily aggregates. In the present study, it was demonstrated that this aggregation process could be completely reversed under high hydrostatic pressure. Release of the pressure led to renewed protein aggregation. In addition, it was demonstrated that refolding of urea-denatured rhodanese at 2 kbar pressure led to an increased yield of the native enzyme. The final recovery was increased up to approximately 25% in contrast to approximately 5% recovery observed under ambient pressure. The recovery can be further increased in the presence of 4 M glycerol, where 56% of the protein was recovered by treatment with high pressure. These observations suggest that some protein aggregation can be limited without the use of chemical additives, and they show that the pressures needed to maintain solubility are considerably less than those typically required for dissociation of specific oligomers and unfolding of polypeptide chains.

Buffers↗

PubMed1993

Stress response of Escherichia coli to elevated hydrostatic pressure.

The response of exponentially growing cultures of Escherichia coli to abrupt shifts in hydrostatic pressure was studied. A pressure upshift to 546 atm (55,304 kPa) of hydrostatic pressure profoundly perturbed cell division, nucleoid structure, and the total rate of protein synthesis. The number of polypeptides synthesized at increased pressure was greatly reduced, and many proteins exhibited elevated rates of synthesis relative to total protein synthesis. We designated the latter proteins pressure-induced proteins (PIPs). The PIP response was transient, with the largest induction occurring approximately 60 to 90 min postshift. Fifty-five PIPs were identified. Many of these proteins are also induced by heat shock or cold shock. The PIP demonstrating the greatest pressure induction was a basic protein of 15.6 kDa. High pressure inhibits growth but does not inhibit the synthesis of stringently controlled proteins. Cold shock is the only additional signal which has been found to elicit this type of response. These data indicate that elevated pressure induces a unique stress response in E. coli, the further characterization of which could be useful in delineating its inhibitory nature.

Autoradiography↗

PubMed2000

Effects of hydrostatic pressure and temperature on growth and lipid composition of the inner membrane of barotolerant Pseudomonas sp. BT1 isolated from the deep-sea.

A barotolerant member of the genus Pseudomonas was isolated from deep-sea sediment obtained from the Japan Trench, at a depth of 4418 m. The growth temperature was found to affect the hydrostatic pressure range in which the bacterium could grow; the optimum hydrostatic pressure for growth shifted to a higher pressure with increasing temperature. We examined the lipid composition of the inner membrane of cells grown at various hydrostatic pressures and temperatures. The fatty acid components of the inner membrane lipids were C16:0, C16:1, C18:0, and C18:1. The phospholipid components of the inner membrane were phosphatidylethanolamine, cardiolipin, phosphatidylglycerol, and phosphatidylserine. It is evident that the effects of elevated hydrostatic pressure are comparable to the effects of low temperature on both the fatty acid composition of the inner membrane lipids and the phospholipid composition of the inner membrane of this bacterium.

DNA, Ribosomal↗

PubMed1992

Abscisic Acid increases terrestrial plant cell resistance to hydrostatic pressure.

Cells of the terrestrial plant species bromegrass (Bromus inermis L.) are not naturally adapted to withstand the hydrostatic pressures encountered in aquatic environments. However, after treatment with the natural plant growth hormone abscisic acid (75 micromolar), bromegrass cells survived a hydrostatic pressure of 101.3 megapascals, approximating the limits of ocean depth (10,860 m). The increased resistance to hydrostatic pressure from 1 to 7 days of abscisic acid treatment paralleled the induced elevation of cell tolerance to freezing stress.

Journal Article↗

PubMed1976

Hydrostatic pressure treatment for carcinoma of the bladder. A clinical and urodynamic evaluation of the effect on bladder hemorrhage and fibrosis in irradiated patients.

Hydrostatic pressure treatment as described by Helmstein was given to 12 patients with hematuria secondary at irradiation for carcinoma of the bladder. The bladder function was evaluated on the basis of urodynamic examinations before and after the treatment. The study includes examination of the effect on the renal function. In 6 patients, hemostasis was obtained for a period averaging 10 months. No serious complications occurred. Following irradiation, the patients showed a characteristic micturition pattern with a small bladder capacity and a marked increase in pressure during the filling phase. The micturition took place partly by use of the abdominal musculature; the detrusor pressure was falling during the whole voiding time. The voiding was almost complete, and the flow values were slightly reduced. The hydrostatic pressure treatment resulted in no demonstrable changes in this micturition pattern. Evaluated from the creatinine clearance, the renal function was unchanged after the treatment, and neither polyuria nor an increased excretion of sodium was demonstrated during the first hours after the treatment. We conclude that before major surgery is decided on, hydrostatic pressure treatment should be given to patients with hemorrhage following irradiation for carcinoma of the bladder. No improvement can be expected in patients where the often pronounced pollakiuria is due to fibrosis of the bladder secondary to irradiation.

Aged↗

PubMed1998

[The effect of elevated hydrostatic pressure on expression level of type III collagen mRNA by lamina cribrosa cells in vitro].

OBJECTIVE: To investigate the effect of elevated hydrostatic pressure on the expression level of type III collagen mRNA by lamina cribrosa cells (LCCs) and approach the action of changes of extracellular stroma on glaucomatous optic nerve damage. METHODS: LCCs were cultured and submitted to elevated hydrostatic pressure (4.67 - 5.33 kPa). We observed collagen type III mRNA level by dot-blot hybridization and computer imaging analysis. RESULTS: Under the pressure for 3 days, the amounts of collagen III mRNA were 0.5828 +/- 0.0517 in optical density (OD), compared with the same period controls (0.2832 +/- 0.0613), the difference was statistically significant (P < 0.05). When exposed to pressure up to 6 days, the collagen III mRNA level remained somewhat higher than that of the control, but there was no significant difference (P > 0.05). After 9 to 12 days of exposure to pressure, the mRNA amounts were decreased respectively to 0.3246 +/- 0.0957 and 0.2164 +/- 0.0171 in OD that were lower than that of the control in the respective same periods, and the differences between the experimental and the control had no significance (P > 0.05). CONCLUSION: Elevated hydrostatic pressure may increase expression level of collagen III mRNA by LCCs in a certain period.

Collagen Type III↗

PubMed1976

An improved plethysmograph with servo control of hydrostatic pressure.

One limitation of the conventional fluid displacement plethysmograph is that the hydrostatic pressure varies as recordings of volume change are obtained. Thus, use of this instrument can lead to inaccuracies that are proportional to the compliance of the biological system under study. This paper describes an improved design which utilizes a servo-control system and an open, mobile reservoir to ensure that the hydrostatic pressure is maintained constant as volume changes are recorded. The result is a device that succeeds in combining stability, sensitivity and accuracy in a fluid displacement plethysmograph.

Compliance↗

PubMed1997

Increased renal interstitial hydrostatic pressure causes c-fos expression in the rat's spinal cord dorsal horn.

To describe a sympathetic afferent circuit, interstitial hydrostatic pressure in the left kidney was increased in anesthetized rats for 1.5 h to activate renal mechanoreceptor afferents. Following renal afferent stimulation, the number of immunocytochemically stained cells for the immediate early gene c-fos was increased within the dorsal horn of the spinal cord. Relative to the surgical control procedure, increasing renal interstitial hydrostatic pressure produced more immunocytochemically stained cells per tissue section in laminae I and II of the dorsal horn both ipsilateral and contralateral to the stimulated kidney in the three most caudal thoracic spinal segments. Further, the number of c-fos immunocytochemically stained cells per section in the dorsal horn ipsilateral to the stimulated kidney was 28% greater than the number of stained cells contralateral to it. The staining patterns in the dorsal horns of stimulated and control animals were similar with most labeled cells in laminae I and II. These results indicate that (1) c-fos immunocytochemical staining may be useful for tracing specific sympathetic afferent pathways, (2) sensory pathways affected by increased renal interstitial hydrostatic pressure include spinal neurons located at lower thoracic levels, and (3) some of this sympathetic afferent pathway is located contralateral to the stimulated kidney. Neurons in the contralateral dorsal horn activated by renal stimulation may mediate renorenal reflexes.

Animals↗

PubMed1983

Effect of hydrostatic pressure on translational fidelity.

We have used the application of hydrostatic pressure to modify the misreading of polyuridylate template. Pressure was used to test ribosomes isolated from Escherichia coli strains containing mutations in the S12 ribosomal protein which lead to streptomycin-resistance and -dependence. The incorporation of phenylalanine into polypeptide, at a given pressure, was found to vary with the source of ribosomes and was found to correlate with S12-dependent changes in rates of incorporation suggesting a role of the S12 ribosomal protein in the pressure effect. Streptomycin partially alleviated the increased pressure-resistance in those cases where control rates of incorporation were found to be stimulated by the addition of streptomycin. In contrast, the misincorporation of isoleucine was substantially more sensitive to pressure application, regardless of ribosome source or the presence of streptomycin. These results suggest that the application of hydrostatic pressure affects at least two distinct ribosomal reactions important to the discrimination of these two amino acids.

Escherichia coli↗

PubMed2005

A nature of conformational changes of yeast tRNA(Phe). High hydrostatic pressure effects.

We analysed conformational changes of yeast tRNA(Phe) induced by high hydrostatic pressure (HHP) measured by Fourier-transform infrared (FTIR) and fluorescence spectroscopies. High pressure influences RNA conformation without other cofactors, such as metal ions and salts. FTIR spectra of yeast tRNA(Phe) recorded at high hydrostatic pressure up to 13 kbar with and without magnesium ions showed a shift of the bands towards higher frequencies. That blue shift is due to an increase a higher energy of bonds as a result of shortening of hydrogen bonds followed by dehydration of tRNA. The fluorescence spectra of Y-base tRNA(Phe) at high pressure up to 3 kbar showed a decrease of the intensity band at 430 nm as a consequence of conformational rearrangement of the anticodon loop leading to exposure of Y-base side chain to the solution. We suggest that structural transition of nucleic acids is driven by the changes of water structure from tetrahedral to a cubic-like geometry induced by high pressure and, in consequence, due to economy of hydration.

Codon↗

PubMed2003

Sedimentation behaviour of sludge particles in a biogas tower reactor and the function of a hydrostatically pressurized sedimenter.

It was found that anaerobic sludge particles contain gas bubbles. Due to the compressibility of the bubbles, which are entrapped in the sludge agglomerates, a pressure-dependent sedimentation characteristic of the sludge particles was found and mathematically described. Enhanced hydrostatic pressure results in a considerable increase of the settling velocity of sludge particles. On this basis the concept of a hydrostatically pressurized sedimenter is presented and its performance analyzed. Due to the hydrostatical pressurization of the sedimenter the produced gas is kept in the liquid phase until the liquid phase is saturated. To avoid a degassing of the liquid which results in the undesired release of gas bubbles a maximum liquid dwell time in the sedimenter must not be exceeded.

Bacteria, Anaerobic↗

PubMed1977

Influence of hydrostatic pressure gradients on net transfer of sodium and water across isolated rat colonic mucosa.

1. The dependence of net transfer of water and sodium on hydrostatic pressure gradients from the serosal to the mucosal side was investigated in everted sacs of the stripped mucosa of the rat colon. 2. In the range of 3-20 cm H2O both, net sodium and water transfer were linearly dependent on hydrostatic pressure. The hydraulic permeability coefficient was 1.1 ml per gram dry weight, hour and cm H2O. At a pressure gradient of 5.8 cm H2O the net movement of water from the mucosal to the serosal side ceased. Above this pressure a net movement in the opposite direction occurs. Sodium net movement from the mucosal to the serosal side ceased at 11 cm H2O. The fluid, which appears-driven by higher values of hydrostatic pressure-on the mucosal side, is hypotonic. 3. Oxyphenisation increases the hydraulic permeability of the colonic epithelium. The fluid, which appears--driven by the hydrostatic pressure gradient--on the mucosal side, is isotonic.

Animals↗

PubMed1997

Effect of hydrostatic pressure on water penetration and rotational dynamics in phospholipid-cholesterol bilayers.

The effect of high hydrostatic pressure on the lipid bilayer hydration, the mean order parameter, and rotational dynamics of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) cholesterol vesicles has been studied by time-resolved fluorescence spectroscopy up to 1500 bar. Whereas the degree of hydration in the lipid headgroup and interfacial region was assessed from fluorescence lifetime data using the probe 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), the corresponding information in the upper acyl chain region was estimated from its effect on the fluorescence lifetime of and 3-(diphenylhexatrienyl)propyl-trimethylammonium (TMAP-DPH). The lifetime data indicate a greater level of interfacial hydration for DPPC bilayers than for POPC bilayers, but there is no marked difference in interchain hydration of the two bilayer systems. The addition of cholesterol at levels from 30 to 50 mol% to DPPC has a greater effect on the increase of hydrophobicity in the interfacial region of the bilayer than the application of hydrostatic pressure of several hundred to 1000 bar. Although the same trend is observed in the corresponding system, POPC/30 mol% cholesterol, the observed effects are markedly less pronounced. Whereas the rotational correlation times of the fluorophores decrease in passing the pressure-induced liquid-crystalline to gel phase transition of DPPC, the wobbling diffusion coefficient remains essentially unchanged. The wobbling diffusion constant of the two fluorophores changes markedly upon incorporation of 30 mol% cholesterol, and increases at higher pressures, also in the case of POPC/30 mol% cholesterol. The observed effects are discussed in terms of changes in the rotational characteristics of the fluorophores and the phase-state of the lipid mixture. The results demonstrate the ability of cholesterol to adjust the structural and dynamic properties of membranes composed of different phospholipid components, and to efficiently regulate the motional freedom and hydrophobicity of membranes, so that they can withstand even drastic changes in environmental conditions, such as high external hydrostatic pressure.

1,2-Dipalmitoylphosphatidylcholine↗

PubMedDate not supplied

[Effect of elevated hydrostatic pressure on the activity of catabolic enzymes in barotolerant bacteria].

The effect of elevated hydrostatic pressure on catabolic enzymes was studied with four strains of barotolerant bacteria isolated from ooze at high depth of the Pacific Ocean. Pseudomonas aeruginosa 0798 and Ps. sociovivum 0913, tolerant to a pressure of 500 atm, have more active catabolic enzymes than Ps. nonliquefaciens 0613 and Ps. acuta 039, which do not grow at a pressure of 500 atm. Changes in the activity of the enzymes caused by elevated hydrostatic pressure are similar to changes caused by the process of the culture aging.

Bacteria↗

PubMed2004

Improving post-thaw survival of cryopreserved mouse blastocysts by hydrostatic pressure challenge.

The purpose of the experiments was to study the effect of high hydrostatic pressure treatment prior to vitrification to the survival of expanded mouse blastocysts. High hydrostatic pressure has been reported to induce the production of "shock proteins" in bacteria, which can provide a possibility of cross-protection to other environmental stresses. The possible beneficial effects of this alleged principle was examined on embryo vitrification. First, the behaviour of blastocysts was studied at altered pressure conditions. In the second part of the study, pressure treatment was combined with a cryopreservation protocol. Our results indicate that the survival of pressurized mouse embryos depends on the magnitude and the duration of pressure applied. We demonstrated that a preceding pressure treatment strikingly increases the survival of the frozen blastocysts as well as the speed of resumption of the development, and hatching rate.

Animals↗

PubMed1994

Histochemical and morphological studies on Trichinella spiralis larvae treated with high hydrostatic pressure.

Histochemical and morphological observations were made on Trichinella spiralis larvae treated with hydrostatic pressures of 100, 150, 200 and 300 MPa using hematoxylin-eosin (HE), periodic acid-Schiff (PAS) and Azan staining. Few histochemical changes were observed in HE and PAS stained larvae after pressurization at 200 MPa and under. However, red staining by Azan changed to blue in the anterior stichosome of larvae and skeletal muscle of mice, when the hydrostatic pressure was raised from 150 to 300 MPa. At 150 and 200 MPa, boundaries among stichocytes were indistinct or irregular, and unstained areas were observed in stichocytes of larvae using Azan staining. At 300 MPa, all tissues of larvae and mouse muscle stained blue with Azan. At the same pressure, decrease in PAS positive staining of stichocytes and dilation of muscular cells were observed in larvae. It is assumed that these histochemical and morphological changes in pressurized larvae might be related to the loss of infectivity of larvae.

Animals↗

PubMed1995

Influence of short-term hydrostatic pressure on organization of stress fibers in cultured chondrocytes.

The present study describes changes in the organization of stress fibers that occur in articular cartilage chondrocytes subjected to hydrostatic pressure. Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hydrostatic pressure at 37 degrees C. The pressure was applied continuously or cyclically at two frequencies: 0.125 Hz (4 seconds of pressure and 4 seconds of no pressure) or 0.05 Hz (1 second of pressure and 19 seconds of no pressure) for a period of 2 hours. Control chondrocytes showed a polygonal form with prominent stress fibers extending across the cells. The exposure of cells to 30 MPa pressure caused a nearly total disappearance of stress fibers and retraction of the cells from each other. With pressure at 15 MPa or cyclic pressure, the number of cells with stress fibers was decreased. In cells subjected to 5 MPa pressure, the stress fibers resembled those in control chondrocytes. The pressure effects were reversible after 2 hours. Pressure had no effect on the staining pattern of vinculin, which suggests that microfilaments are more vulnerable to pressure than vinculin. The results indicate that cytoskeletal changes may be an integral part of the response of chondrocytes to hydrostatic pressure.

Animals↗

PubMed1985

Cardiovascular responses to elevation of intra-abdominal hydrostatic pressure.

Intra-abdominal fluid volume and hydrostatic pressure were elevated by positive pressure infusion of Tyrode solution into the peritoneal cavity of anesthetized dogs. The compliance of the peritoneal cavity fell from 10.8 to 0.56 ml X mmHg-1 X kg-1 of body wt as intra-abdominal pressure increased from 0 to 40 mmHg. Intrathoracic pressure also increased as elevated peritoneal pressure caused diaphragmatic bulging. Cardiac output and stroke volume were reduced by 36% after an intra-abdominal pressure rise of 40 mmHg; in contrast, heart rate did not change. Flow in the celiac, superior mesenteric, and renal arteries was reduced by 42, 61, and 70%, respectively. Pressure in the femoral vein increased to 46 mmHg, while flow in the femoral artery decreased by 65%. Whole-body O2 consumption, pH, and arterial PO2 decreased as intra-abdominal pressure rose. The peritoneal cavity, with its high initial compliance, affords the body an ideal location for the temporary accumulation of small to moderate volumes of fluid during episodes of increased vascular pressure or permeability. The marked alterations in the hemodynamic properties of the cardiovascular system are indicative of the physiological changes that occur when intra-abdominal fluid accumulation becomes excessive and peritoneal pressure rises to high levels.

Abdomen↗