SEARCH · PubMed Health

Results for “Hydrostatic Pressure”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1981

The action of high hydrostatic pressure on the membrane currents of Helix neurones.

1. The actions of high hydrostatic pressure (10.4, 20.8 MPa) on the membrane currents of Helix neurones were examined under voltage clamp. 2. High hydrostatic pressure (20.8 MPa) reduced the maximum inward current to 0.78 and the delayed outward current, measured at the inward current reversal potential, to 0.75 of their value at atmospheric pressure. 3. High hydrostatic pressure shifted the curve relating the inward current conductance to membrane potential to more positive values but the maximum conductance was altered. 4. The rates of activation of the inward and delayed outward currents were slowed by pressure. 5. The steady-state level and time course of inactivation of the inward current was unaffected by high pressure over the investigated range. 6. The effects of high hydrostatic pressure on the fast outward current identified in gastropod neurones by Connor & Stevens (1971) were also examined. 20.8 MPa reduced the current measured at -30 mV to 0.71 of its control value. 7. The rate of activation of the fast outward current was slowed by high pressure but the time constant of inactivation was unchanged. 8. The majority of the effects of high hydrostatic pressure were completely reversible upon decompression. 9. These results are discussed with reference to the known effects of high hydrostatic pressure on the action potential and discharge frequency of gastropod neurones. Possible sites and mechanisms of pressure action on the excitable cell are briefly discussed.

Action Potentials↗

PubMed1986

Hydrostatic pressures in glomeruli and renal vasculature of the hagfish, Eptatretus stouti.

Hydrostatic pressures in the renal vasculature of hagfish have been studied. Estimates of the blood colloid osmotic pressure (COP) have been made. In blood vessels supplying the renal corpuscles, the average hydrostatic pressure is about 1 kPa. The average hydrostatic pressure falls to a value of 0.04 kPa within the postcardinal vein efferent to the renal corpuscle. Within the glomerular capillaries the hydrostatic pressure averages 0.21 kPa. Since the blood COP averages about 1.4 kPa, it is clear that glomerular filtration in the hagfish is not underlain by the hydrostatic pressure of the arterial pulse. In some blood vessels efferent to the renal corpuscles, hydrostatic pressure may be as high as in the afferent supply. Evidence is presented that the glomerular capillaries are shunted by this high pressure vascular pathway.

Animals↗

PubMed1992

Inactivation of herpes viruses by high hydrostatic pressure.

The effects of high hydrostatic pressure on herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV) were examined. Pressure at more than 300 MPa for 10 min at 25 degrees C inactivated these virions and drastically inhibited their infection to cultured cells, and at greater than 400 MPa, reduced infective titers of HSV-1 and HCMV by more than 7 and 4 logs, respectively. Electron microscopic examination illustrated coincidentally that high pressure at 300 MPa damaged the virus envelope and prevented the virus particles from binding to the cells. The findings suggest that treatment at high hydrostatic pressure is promising as a means of inactivating HSV-1, HCMV and other enveloped viruses.

Animals↗

PubMed2000

The role of microtubules in the regulation of proteoglycan synthesis in chondrocytes under hydrostatic pressure.

Chondrocytes of the articular cartilage sense mechanical factors associated with joint loading, such as hydrostatic pressure, and maintain the homeostasis of the extracellular matrix by regulating the metabolism of proteoglycans (PGs) and collagens. Intermittent hydrostatic pressure stimulates, while continuous high hydrostatic pressure inhibits, the biosynthesis of PGs. High continuous hydrostatic pressure also changes the structure of cytoskeleton and Golgi complex in cultured chondrocytes. Using microtubule (MT)-affecting drugs nocodazole and taxol as tools we examined whether MTs are involved in the regulation of PG synthesis in pressurized primary chondrocyte monolayer cultures. Disruption of the microtubular array by nocodazole inhibited [(35)S]sulfate incorporation by 39-48%, while MT stabilization by taxol caused maximally a 17% inhibition. Continuous hydrostatic pressure further decreased the synthesis by 34-42% in nocodazole-treated cultures. This suggests that high pressure exerts its inhibitory effect through mechanisms independent of MTs. On the other hand, nocodazole and taxol both prevented the stimulation of PG synthesis by cyclic 0. 5 Hz, 5 MPa hydrostatic pressure. The drugs did not affect the structural and functional properties of the PGs, and none of the treatments significantly affected cell viability, as indicated by the high level of PG synthesis 24-48 h after the release of drugs and/or high hydrostatic pressure. Our data on two-dimensional chondrocyte cultures indicate that inhibition of PG synthesis by continuous high hydrostatic pressure does not interfere with the MT-dependent vesicle traffic, while the stimulation of synthesis by cyclic pressure does not occur if the dynamic nature of MTs is disturbed by nocodazole. Similar phenomena may operate in cartilage matrix embedded chondrocytes.

Animals↗

PubMed2002

The interactions of nucleic acids at elevated hydrostatic pressure.

The application of elevated hydrostatic pressure on the order of a few thousand bar provides insight into the molecular forces responsible for stabilizing the conformations and non-covalent interactions of biological molecules in aqueous solution. In particular, the parameters derived from these studies have enabled researchers to glean information regarding the importance of hydration in the energetics and kinetics of these systems. This review presents data concerned with the application of hydrostatic pressure to study the thermodynamics, kinetics, and structure of nucleic acids and the interactions between nucleic acids and proteins, enzymes, and drugs. These complexes often form extremely stable non-covalent complexes in which electrostatic interactions play an important role. The sensitivity of these interactions to pressure offers a valuable experimental tool for investigating the energetics of the complexes.

Animals↗

PubMed1975

Cellular immunity to transitional cell carcinoma of the urinary bladder. III. Effects of hydrostatic pressure therapy.

The effects of hydrostatic pressure therapy on in vitro cellular cytotoxicity responses have been studied in 19 patients with transitional cell carcinoma of the bladder (TCC). Cytotoxicity was quantitated against allogeneic targets in a microplate assay or by 51chromium isotope release. Two types of reactivity were detected, the most common being a differential cytotoxicity for targets derived from TCC, in either short-term or long-term tissue culture. This reaction is operationally termed "tumor-specific". Less frequently, a general cytotoxicity for targets of diverse histogenic origins was observed. For the present, this is termed "non-specific". Nine patients were tested before pressure therapy and of these only two gave a specific reaction and one a non-specific reaction, while six were non-reactive. Eighteen patients were tested at varying intervals after treatment and of these 11 gave a specific reaction and one a non-specific effect, while six were non-reactive. Three individuals who were non-reactive prior to therapy had a specific reaction post therapy. Two who reacted specifically before therapy became non-reactive post therapy. The results of serial in vitro testing for cytotoxicity are presented with individual case histories, tumor staging and grading and the clinical outcome of hydrostatic pressure therapy.

Adult↗

PubMed2005

Behavior of Yersinia enterocolitica strains inoculated in model cheese treated with high hydrostatic pressure.

The effects of high hydrostatic pressure treatment and the ability for survival, repair, and growth of three human pathogenic serotypes (O:1, O:3, O:8) of Yersinia enterocolitica were investigated in washed-curd model cheese made with pasteurized bovine milk. Samples were treated at 300, 400, and 500 MPa for 10 min at 20 degrees C and analyzed at 0, 1, 7, and 15 days to assess the viability of the Yersinia population. A long-term study (up to 60 days of ripening after high hydrostatic pressure treatment) was also undertaken. Treatments at 400 and 500 MPa caused maximum lethality, and only the treatment at 300 MPa showed significant differences (P < 0.05) between serotypes; the most baroresistant was O:3. Ability to repair and grow was not observed after 15 days of storage at 8 degrees C. Yersinia counts in untreated cheese samples also decreased below the detection limit at day 45 in the long-term study. These results suggest that the cheese environment did not allow recovery of injured cells or growth. A primary contributing factor to this effect seemed to be the low pH resulting from the production of lactic acid during cheese ripening.

Animals↗

PubMed1993

Fixation of biological specimens by high hydrostatic pressure.

We investigated whether or not high hydrostatic pressure could be used as a new method of histological fixation. Various high hydrostatic pressures from 200 to 800 MPa (Mega Pascal) were applied to fresh organs including heart, liver, intestine and kidney of mice, and the gross and light microscopic findings were compared with those of organs fixed with formalin and those without fixation. The specimens processed with pressure were firm, elastic and pale, somewhat resembling the formalin fixed ones. Light microscopic examination revealed well preserved fine structures in the heart and intestine subjected to approximately 450 MPa for 15 min at room temperature, although the fine structures of the liver and kidney were not well preserved. The enzyme activity of alkaline phosphatase was rarely preserved in the formalin-fixed kidney, but could be easily detected in kidneys processed with a pressure of 450 MPa. We conclude that high hydrostatic pressure can be used as a fixative, both for preserving the basic tissue structure in certain organs and for retaining the biological activity of an enzyme. In addition, the fixation is uniform, the processing is fast, and the materials can be handled safely. At present, however, its application is limited to specific organs.

Alkaline Phosphatase↗

PubMed2006

Folding studies of two hydrostatic pressure sensitive proteins.

High hydrostatic pressure combined with various spectroscopies is a powerful technique to study protein folding. An ideal model system for protein folding studies should have the following characteristics. (1) The protein should be sensitive to pressure, so that the protein can be unfolded under mild pressure. (2) The folding process of the protein should be easily modulated by several chemical or physical factors. (3) The folding process should be easily monitored by some spectroscopic parameters. Here, we summarized the pressure induced folding studies of two proteins isolated from spinach photosystem II, namely the 23-kDa and the 33-kDa protein. They have all the characteristics mention above and might be an ideal model protein system for pressure studies.

Hydrostatic Pressure↗

PubMed1996

In vitro stimulation of articular chondrocyte mRNA and extracellular matrix synthesis by hydrostatic pressure.

This study tested the effects of hydrostatic pressure (10 MPa) on adult articular chondrocyte mRNA and extracellular matrix synthesis in vitro. High density primary cultures of bovine chondrocytes were exposed to hydrostatic pressure applied intermittently at 1 Hz or constantly for 4 hours in serum-free medium or in medium containing 1% fetal bovine serum. mRNAs for aggrecan, types I and II collagen, and beta-actin were analyzed by Northern blots and quantified by slot blots. Proteoglycan synthesis was quantified by 35SO4 uptake into cetylpyridinium chloride-precipitable glycosaminoglycans, and cell-associated aggrecan and type-II collagen were detected by immunohistochemical techniques. In serum-free medium, intermittent pressure increased aggrecan mRNA signal by 14% and constant pressure decreased type-II collagen mRNA signal by 16% (p < 0.05). In the presence of 1% fetal bovine serum, intermittent pressure increased aggrecan and type-II collagen mRNA signals by 31% (p < 0.01) and 36% (p < 0.001), respectively, whereas constant pressure had no effect on either mRNA. Intermittent and constant pressure stimulated glycosaminoglycan synthesis 65% (p < 0.001) and 32% (p < 0.05), respectively. Immunohistochemical detection of cell-associated aggrecan and type-II collagen was increased in response to both intermittent and constant pressure. These data support the hypothesis that physiologic hydrostatic pressure directly influences the extracellular matrix metabolism of articular chondrocytes.

Aggrecans↗

PubMed1997

Membrane lipid order of human red blood cells is altered by physiological levels of hydrostatic pressure.

The effect of hydrostatic pressure at levels applied in diving or hyperbaric treatment (thus considered "physiological") on the order of lipid domains in human red blood cell (RBC) membrane was studied. Membrane order was determined by measuring 1) the fluorescence anisotropy (FAn) of lipid probes, 2) the resonance energy transfer from tryptophan to lipid probes, and 3) spectral shifts in Laurdan fluorescence emission. It was found that the application of mild pressure (< 15 atm) 1) increased, selectively, the FAn of lipid probes that monitor the membrane lipid core, 2) increased the tryptophan FAn, 3) increased the resonance energy transfer from tryptophan to lipid probes residing in the lipid core, and 4) induced changes in the Laurdan fluorescence spectrum, which corresponded to reduced membrane hydration. It is proposed that the application of pressure of several atmospheres increases the phase order of membrane lipid domains, particularly in the proximity of proteins. Because the membrane lipid order ("fluidity") of RBCs plays an important role in their cellular and rheological functions, the pressure-induced alterations of the RBC membrane might be pertinent to microcirculatory disorders observed in humans subjected to elevated pressure.

Energy Transfer↗

PubMed2000

Effect of hydrostatic pressure on regional bond strengths of compomers to dentine.

OBJECTIVES: The aim of this study was to evaluate the effect of hydrostatic pressure on the regional bond strengths of compomers to dentine. METHODS: Thirty freshly extracted molars were ground flat to expose the dentine and randomly divided into two groups for bonding: no hydrostatic pressure and hydrostatic pressure of 15cm H(2)O. Xeno CF, Dyract AP and F 2000 were applied to dentine surfaces pretreated by the respective bonding systems following the manufactures' instructions, and then restored with Clearfil AP-X. After 24h storage in water, the teeth were sectioned into 0.7-mm thick slabs and visually divided into three regional subgroups: the region communicating with the pulp through dentinal tubules (pulp horn); the region between the pulp horns (center); and the region between the pulp horn and DEJ (periphery). The specimens were trimmed to a cross-sectional area of 1mm(2) and subjected to the micro-tensile bond test. The data were analyzed by one- and three-way ANOVA, and Fisher's PLSD (p<0.05). RESULTS: There were no significant regional differences of bond strengths for all the compomers tested (p>0.05). However, hydrostatic pressure significantly decreased the bond strength of F 2000 to all regions (p<0.05), while the bond strength of Dyract AP significantly decreased only at the pulp horn region (p<0.05). On the other hand, the bond strengths of Xeno CF seemed not to be affected by hydrostatic pressure (p>0.05). For Dyract AP and F 2000, the fracture modes were affected by hydrostatic pressure, while, for Xeno CF, there were no significant differences between the fracture modes with non- or positive hydrostatic pressure. SIGNIFICANCE: Simulated pulpal pressure of 15cm H(2)O had a greater influence on the bond strengths of compomers to dentine than did dentine regions. Therefore, when measuring the bond strengths of compomers to dentine under the simulated in vivo conditions, the wetness of the dentine surface, as well as the intrinsic properties of each material should be seriously considered.

Analysis of Variance↗

PubMed2006

Microscopy under pressure--an optical chamber system for fluorescence microscopic analysis of living cells under high hydrostatic pressure.

High hydrostatic pressure (HHP) becomes more and more interesting for life science research, since it can be employed to inactivate various cells. To directly monitor "cells under pressure," the development of an optical high-pressure chamber is required. Therefore, an optical pressure chamber that can be used for up to 300 MPa was constructed. This chamber has already been described as a tool for in situ observation of dynamic changes of microscopic structures in bright field as well as phase contrast. In combination with an inverted microscope, we obtained brilliant microscopic color pictures with an optical resolution more than 0.56 microm. Here, we demonstrate the capabilities of the HHP cell, in combination with epifluorescence microscopy. Using a nonadherent human B-cell line (Raji, ATCC CCL 86), stained with the fluorescent dyes propidium iodide, Hoechst 33342, or dihexyloxacarbocyanine iodide, we were able to show that the system is suitable to perform fluorescence microscopic analyses, with pressures up to 300 MPa, with viable mammalian cells.

B-Lymphocytes↗

PubMed1997

A stable partly denatured state of trypsin induced by high hydrostatic pressure.

The effect of hydrostatic pressure on the unfolding of trypsin was studied by fluorescence spectroscopy under pressure from 1 to 7000 bar. It was found that, at pH 3.0 or pH 7.3, a stable partly denatured state of trypsin was obtained when the applied pressure was about 6.5 kbar. This transient denatured state did not show any enzymatic activity and was different from that denatured by 8 M urea or high temperature in both intrinsic fluorescence spectrum and 8-anilino-1-naphtalene sulfonate (ANS) binding, having some obvious characteristics of 2 molten globule state of protein. It was also found that the formation of this partly denatured state of trypsin was temperature dependent. Energenic values of the process were also given.

Anilino Naphthalenesulfonates↗

PubMed2005

In vitro effect of hydrostatic pressure exposure on hydroxyl radical production in fish red muscle.

The effects of hydrostatic pressure on reactive oxygen species (ROS) production have been studied in vitro on fish red muscle fibres. In the eel, Anguilla anguilla, previous studies have shown that hydrostatic pressure acclimatization improves oxidative phosphorylation efficiency together with a supposed concomitant decrease in electron leak and ROS production. In order to test the hypothesis of an electron leak decrease under pressure, hydroxyl radical (HO*) production and oxygen consumption were measured on fish red muscle fibres directly exposed to hydrostatic pressure. Experiments were performed under two conditions--atmospheric pressure and hydrostatic pressure (16.1 MPa)--on eel and trout (which exhibit low- and high-pressure sensitivity, respectively). This work has permitted, first, the validation of an indirect HO* measurement (in vitro) on fish red muscle and the documentation of reference values for fish. Second, at atmospheric pressure, results show higher oxygen consumption for trout (+40%) than for eel which is accompanied by higher HO* production (+90%); in addition, both species present a positive relationship between HO* production and oxygen consumption. Hydrostatic pressure exposure reverses this relationship for eel but not for trout. These preliminary results only partially verify the proposed hypothesis and further experiments are needed.

Acclimatization↗

PubMed1992

High-pressure, high-temperature bioreactor for comparing effects of hyperbaric and hydrostatic pressure on bacterial growth.

We describe a high-pressure reactor system suitable for simultaneous hyperbaric and hydrostatic pressurization of bacterial cultures at elevated temperatures. For the deep-sea thermophile ES4, the growth rate at 500 atm (1 atm = 101.29 kPa) and 95 degrees C under hydrostatic pressure was ca. three times the growth rate under hyperbaric pressure and ca. 40% higher than the growth rate at 35 atm.

Bacteria↗

PubMed1989

Role of prostaglandins in proximal tubule sodium reabsorption: response to elevated renal interstitial hydrostatic pressure.

Previous studies have shown that the elevation of renal interstitial hydrostatic pressure by the direct expansion of renal interstitial volume increases urinary sodium excretion. The objective of the present study was to investigate whether proximal tubules respond to the elevated renal interstitial hydrostatic pressure and whether the inhibition of prostaglandin synthesis would alter the effect of elevated renal interstitial hydrostatic pressure on proximal sodium reabsorption. Expansion of renal interstitial volume by injecting 100 microliters of 2.5% albumin solution through a chronically implanted matrix increased renal interstitial hydrostatic pressure similarly in control rats (n = 8) and in indomethacin (n = 8) or meclofenamate-treated (n = 7) rats. In the absence of prostaglandin synthesis inhibition, renal interstitial volume expansion significantly increased the fractional delivery of sodium at the superficial late proximal tubules from 56.5 +/- 6.1 to 67.0 +/- 6.5% (p less than 0.01) with an accompanying increase in fractional excretion of sodium from 2.1 +/- 0.5 to 3.0 +/- 0.4% (p less than 0.01). In the presence of indomethacin or meclofenamate, renal interstitial volume expansion failed to augment the fractional delivery of sodium and the fractional excretion of sodium. In summary, these studies demonstrate that the synthesis of prostaglandins plays a role in the regulation of sodium reabsorption by the proximal tubules in response to elevated renal interstitial hydrostatic pressure.

Animals↗

PubMed2003

Low-fat set yogurt made from milk subjected to combinations of high hydrostatic pressure and thermal processing.

The combined use of high hydrostatic pressure (300 to 676 MPa, 5 min) and thermal treatment (85 degrees C, 30 min) in milk for the manufacture of low-fat yogurt was studied. The objective was to reduce syneresis and improve the rheological properties of yogurt, reducing the need for thickeners and stabilizers. The use of high hydrostatic pressure alone, or after thermal treatment, reduced the lightness and increased the viscosity of skim milk. However, milk recovered its initial lightness and viscosity when thermal treatment was applied after high hydrostatic pressure. The MALDI-TOF spectra of skim milk presented monomers of whey proteins after a treatment of 676 MPa for 5 min. Yogurts made from skim milk subjected to 400 to 500 MPa and thermal treatment showed increased yield stress, resistance to normal penetration, and elastic modulus, while having reduced syneresis when compared to yogurts from thermally treated or raw milks. The combined use of thermal treatment and high hydrostatic pressure assures extensive whey protein denaturation and casein micelle disruption, respectively. Although reaggregation of casein submicelles occurs during fermentation, the net effect of the combined HHP and thermal treatment is the improvement of yogurt yield stress and reduction of syneresis.

Animals↗