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PubMed2005

Non-equilibration of hydrostatic pressure in blebbing cells.

Current models for protrusive motility in animal cells focus on cytoskeleton-based mechanisms, where localized protrusion is driven by local regulation of actin biochemistry. In plants and fungi, protrusion is driven primarily by hydrostatic pressure. For hydrostatic pressure to drive localized protrusion in animal cells, it would have to be locally regulated, but current models treating cytoplasm as an incompressible viscoelastic continuum or viscous liquid require that hydrostatic pressure equilibrates essentially instantaneously over the whole cell. Here, we use cell blebs as reporters of local pressure in the cytoplasm. When we locally perfuse blebbing cells with cortex-relaxing drugs to dissipate pressure on one side, blebbing continues on the untreated side, implying non-equilibration of pressure on scales of approximately 10 microm and 10 s. We can account for localization of pressure by considering the cytoplasm as a contractile, elastic network infiltrated by cytosol. Motion of the fluid relative to the network generates spatially heterogeneous transients in the pressure field, and can be described in the framework of poroelasticity.

Actins↗

PubMed1978

Sedimentation velocity analyses of the effect of hydrostatic pressure on the 30 S microtubule protein oligomer.

Increasing hydrostatic pressure in the analytical ultracentrifuge by increasing rotor velocity and overlayering protein samples with oil caused a depolymerization of the 30 S oligomer of microtubule protein. This results indicates that the reaction of 6 S microtubule protein to form the oligomer was accompanied by a positive volume change. The effect of hydrostatic pressure on the 6 S to 30 S transition was employed to demonstrate the presence of a rapidly reversible equilibrium between these components by showing polymerization or depolymerization of the oligomer during the course of ultracentrifugation. The magnitude of the partial specific volume change accompanying this reaction was estimated from mass fraction measurements of microtubule protein solutions at a variety of hydrostatic pressures to be about 9 X 10(-4) ml g-1.

Animals↗

PubMed2004

Synchronous effects of temperature, hydrostatic pressure, and salinity on growth, phospholipid profiles, and protein patterns of four Halomonas species isolated from deep-sea hydrothermal-vent and sea surface environments.

Four strains of euryhaline bacteria belonging to the genus Halomonas were tested for their response to a range of temperatures (2, 13, and 30 degrees C), hydrostatic pressures (0.1, 7.5, 15, 25, 35, 45, and 55 MPa), and salinities (4, 11, and 17% total salts). The isolates were psychrotolerant, halophilic to moderately halophilic, and piezotolerant, growing fastest at 30 degrees C, 0.1 MPa, and 4% total salts. Little or no growth occurred at the highest hydrostatic pressures tested, an effect that was more pronounced with decreasing temperatures. Growth curves suggested that the Halomonas strains tested would grow well in cool to warm hydrothermal-vent and associated subseafloor habitats, but poorly or not at all under cold deep-sea conditions. The intermediate salinity tested enhanced growth under certain high-hydrostatic-pressure and low-temperature conditions, highlighting a synergistic effect on growth for these combined stresses. Phospholipid profiles obtained at 30 degrees C indicated that hydrostatic pressure exerted the dominant control on the degree of lipid saturation, although elevated salinity slightly mitigated the increased degree of lipid unsaturation caused by increased hydrostatic pressure. Profiles of cytosolic and membrane proteins of Halomonas axialensis and H. hydrothermalis performed at 30 degrees C under various salinities and hydrostatic pressure conditions indicated several hydrostatic pressure and salinity effects, including proteins whose expression was induced by either an elevated salinity or hydrostatic pressure, but not by a combination of the two. The interplay between salinity and hydrostatic pressure on microbial growth and physiology suggests that adaptations to hydrostatic pressure and possibly other stresses may partially explain the euryhaline phenotype of members of the genus Halomonas living in deep-sea environments.

Bacterial Proteins↗

PubMed2003

Hydrostatic pressure effects on vestibular hair cell afferents in fish and crustacea.

Following the discovery of a hydrostatic pressure sensor with no associated gas phase in the crab, and the knowledge that several systems of cells in culture show long term alterations to small changes in hydrostatic pressure, we show here that vestibular type II hair cells in a well known model system (the isolated elasmobranch labyrinth), are sensitive to hydrostatic pressure. This new finding for the vertebrate vestibular system may provide an explanation for low levels of resting activity in vertebrate hair cells and explain how fish without swim bladders sense hydrostatic cues. It could have implications for humans using their balancing systems in hypobaric or hyperbaric environments such as in aircraft or during space exploration. Although lacking the piston mechanism thought to operate in crab thread hairs which sense angular acceleration and hydrostatic pressure, the vertebrate system may use larger numbers of sensory cells with resultant improvement in signal to noise ratio. The main properties of the crab hydrostatic pressure sensing system are briefly reviewed and new experimental work on the isolated elasmobranch labyrinth is presented.

Action Potentials↗

PubMed1975

Water Stress and Protein Synthesis: II. Interaction between Water Stress, Hydrostatic Pressure, and Abscisic Acid on the Pattern of Protein Synthesis in Avena Coleoptiles.

Water stress causes a reduction in hydrostatic pressure and can cause an increase in abscisic acid in plant tissues. To assess the possible role of abscisic acid and hydrostatic pressure in water stress effects, we have compared the effects of water stress, abscisic acid, and an imposed hydrostatic pressure on the rate and pattern of protein synthesis in Avena coleoptiles. Water stress reduces the rate and changes the pattern of protein synthesis as judged by a double labeling ratio technique, Abscisic acid reduces the rate but does not alter the pattern of protein synthesis. Gibberellic acid reverses the abscisic acid-induced but not the stress-induced inhibition of protein synthesis. The effect of hydrostatic pressure depends on the gas used. With a 19: 1 N(2)-air mixture, the rate of protein synthesis is increased in stressed but not in turgid tissues. An imposed hydrostatic pressure alters the pattern of synthesis in stressed tissues, but does not restore the pattern to that found in turgid tissues. Because of the differences in response, we conclude that water stress does not affect protein synthesis via abscisic acid or reduced hydrostatic pressure.

Journal Article↗

PubMed1969

Initiation of germination and inactivation of Bacillus pumilus spores by hydrostatic pressure.

The effect of hydrostatic pressures as high as 1,700 atm at 25 C on the heat and radiation resistance of Bacillus pumilus spores was studied. Phosphate-buffered spores were more sensitive to compression than spores suspended in distilled water. Measurements of the turbidity of suspensions, the viability, refractility, stainability, dry weight, and respiratory activity of spores, and calcium and dipicolinic acid release were made for different pressures and times. Initiation of germination occurred at pressures exceeding 500 atm and was the prerequisite for inactivation by compression. The rate of initiation increased with increasing pressure at constant temperature. This result is interpreted as a net decrease in the volume of the system during initiation as a result of increased solvation of the spore components.

Bacillus↗

PubMed1997

Hydrostatic pressure influences mRNA expression of transforming growth factor-beta 1 and heat shock protein 70 in chondrocyte-like cell line.

The present study investigated the influence of hydrostatic pressure on the expression of cytokines and heat shock protein 70 in a chondrocyte-like cell line. Chondrocyte-like cells (HCS-2/8) were exposed to hydrostatic pressure by a special pressure apparatus. Total RNA for cytokines (interleukin-1 beta, basic fibroblast growth factor, insulin-like growth factor-I, and transforming growth factor-beta 1) and for heat shock protein 70 was extracted and was analyzed by a polymerase chain reaction method and Northern blotting. An assay for incorporation of [35S]sulfate was performed to assess proteoglycan synthesis. The expression of transforming growth factor-beta 1 mRNA was enhanced after exposure to 5-MPa of hydrostatic pressure and was reduced after 50 MPa, whereas the expression of heat shock protein 70 was enhanced following exposure to 50 MPa of hydrostatic pressure. The incorporation of [35S]sulfate into the cultured cells increased following exposure to 1-5 MPa of hydrostatic pressure and decreased following 10-50 MPa of pressure. These results suggest that hydrostatic pressure at physiologic levels enhances the expression of transforming growth factor-beta 1 mRNA in addition to increasing proteoglycan synthesis in chondrocytes and that excessively high hydrostatic pressure reduces the expression of transforming growth factor-beta 1 mRNA and increases the expression of heat shock protein 70 mRNA while decreasing proteoglycan synthesis.

Cartilage, Articular↗

PubMed2004

Entrainment of the circatidal swimming activity rhythm in the cumacean Dimorphostylis asiatica (Crustacea) to 12.5-hour hydrostatic pressure cycles.

The cumacean Dimorphostylis asiatica (Crustacea) exhibits a circatidal swimming activity rhythm. The animals were exposed to a 12.5 hr sinusoidal change of hydrostatic pressure of 0.3 atm amplitude in the laboratory. Under constant dark conditions, most of the specimens were entrained to a daily bimodal swimming activity rhythm by the hydrostatic pressure cycle. A small number of individuals exhibited a unimodal daily rhythm, with no apparent entraining from the administered cycles. A marked feature was a flexible phase relationship between the entrained daily bimodal rhythm and the hydrostatic pressure cycles: the swimming activity of most of the specimens occurred around the pressure-decreasing phase, but for a small number of individuals it coincided with the pressure-increasing phase. Such flexibility suggests a weak entraining effect of hydrostatic pressure on the circatidal rhythm of this species. When exposed to 24 hr light-dark cycles and a hydrostatic pressure cycle simultaneously, the specimens exhibited a rhythmic activity entrained by the hydrostatic pressure cycle during the dark period, which closely resembles the temporal activity pattern of this species in the field. The light cycles entrained the swimming activity via direct inhibition and induction of activity (i.e., masking). Under light-dark conditions, the specimens exhibited activity on the pressure-increasing phase more frequently compared with specimens kept in constant darkness.

Animals↗

PubMed2001

Nitric oxide mediates the change of proteoglycan synthesis in the human lumbar intervertebral disc in response to hydrostatic pressure.

STUDY DESIGN: This in vitro study clarifies the role of nitric oxide (NO) in human lumbar intervertebral disc metabolism. OBJECTIVE: To investigate the effects of NO on proteoglycan synthesis in human lumbar discs and to test the hypothesis that NO is a mediator of the changes in proteoglycan synthesis in response to hydrostatic pressure. SUMMARY OF BACKGROUND DATA: The authors have clarified that hydrostatic pressure has an apparent effect on proteoglycan synthesis as well as matrix metalloproteinase production in the intervertebral disc. The cellular mechanisms underlying the response of disc cells to hydrostatic pressure remain to be clarified. Herniated lumbar discs produce NO in response to interleukin (IL)-1 beta. In articular cartilage, NO mediates the change of proteoglycan synthesis by IL-1 or shear stress. METHODS: Fifty-eight lumbar intervertebral disc specimens were obtained from patients who had undergone posterior discectomy. The specimens were chopped into 1-2-mm cubes and were incubated in a plastic syringe with 1 mL Dulbecco's modified Eagle's medium (DMEM). The syringes were placed in a water-filled pressure vessel kept at 37 C. Hydrostatic pressures of 1 (control), 3, and 30 atmospheres (atm) were applied. Proteoglycan synthesis was determined from (35)S-sulfate incorporation rates. Nitrite (the stable oxidation product of NO) concentration in DMEM was determined by a spectrophotometric method based on the Griess reaction. As a competitive inhibitor of NO synthases, N(G)-methyl-l-arginine (l-NMA, 10-1000 micromol) and as an organic donor of NO, S-nitroso-N-acetylpenicillamine (SNAP, 1-200 micromol) were used. RESULTS: Addition of l-NMA suppressed NO production and increased proteoglycan synthesis rates in the intervertebral disc specimens in a dose-dependent fashion. Addition of SNAP increased exogenous NO content in the medium significantly and suppressed proteoglycan synthesis rates in a dose-dependent fashion. Three-atmosphere hydrostatic pressure stimulated the proteoglycan synthesis rates. Rates were approximately 1.3-fold greater than at 1 atm, whereas 30-atm pressure inhibited proteoglycan synthesis rates. However, the hydrostaticpressure had inverse effect on NO production. At 3 atm, NO production decreased slightly relative to 1 atm, whereas at a pressure of 30 atm, NO production was increased and was approximately 1.32-fold greater than at 1 atm. L-NMA enhanced the 3-atm pressure-induced increase in proteoglycan synthesis and also relieved the suppression of proteoglycan synthesis at a pressure of 30 atm. CONCLUSION: The current study confirmed the previous finding that human herniated lumbar disc cultures spontaneously produce NO. Endogenously generated and exogenously supplied NO inhibited proteoglycan synthesis in the intervertebral disc. Hydrostatic pressure influenced NO production by disc cells, and NO is one of the mediators that changes proteoglycan synthesis in response to hydrostatic pressure. These results may show that autocrine and paracrine mechanisms of NO play an important role in the regulation of disc cell metabolism under mechanical stress and in the pathophysiology of intervertebral disc degeneration.

Adolescent↗

PubMed2004

Inactivation of selected picornaviruses by high hydrostatic pressure.

The potential of high hydrostatic pressure processing (HPP) to inactivate Aichi virus (AiV), human parechovirus-1 (HPeV-1), and the coxsackievirus strains A9 and B5 was investigated. For coxsackievirus A9 (CAV9), a 5-min HPP treatment in minimum essential growth medium (MEM) supplemented with 10% fetal bovine sera (FBS) resulted in 3.4-, 6.5-, and 7.6-log(10) tissue culture infectious dose (50%) (TCID(50)) reductions at 400, 500, and 600megaPascals (MPa), respectively. For HPeV-1, a 5-min treatment in MEM with 10% FBS resulted in reductions of 1.3-, 4.3-, and 4.6-log(10) TCID(50) at 400, 500, and 600MPa, respectively; however, AiV and coxsackievirus B5 (CBV5) in MEM supplemented with 2 and 10% FBS, respectively, remained fully infectious after a 5-min treatment at 600MPa. These data establish that different picornaviruses have widely variable pressure inactivation thresholds in response to HPP.

Culture Media↗

PubMed2003

A culture device demonstrates that hydrostatic pressure increases mRNA of RGS5 in neuroblastoma and CHC1-L in lymphocytic cells.

Previous studies demonstrated that mechanical forces affect a wide range of cellular behaviors. These forces regulate important cellular responses in the human body and consist of gravity, hydrostatic pressure, stretch, and shear stress, which is exerted on the vascular system by the passage of blood flow. We reasoned that these forces might be significant and dynamic regulators of cellular functions within the human body. While cellular effects of stretch and shear stress have been studied particularly with endothelial cells, little is known about the effects of gravity and hydrostatic pressure to cells. To examine the direct effect of hydrostatic pressure, we developed a culture device to confer hydrostatic pressures to cells ranging from 0 to 1,000 psi. We subjected human neuroblastoma cells and rIL-2-activated lymphocytes to a constant pressure of 20 or 100 psi for 48 h and attempted to identify genes regulated by hydrostatic pressure. Genes of regulator of G-protein signaling 5 in neuroblastoma cells and CHC1-L in lymphocytes increased after exposure to hydrostatic pressure. The results demonstrated that hydrostatic pressure directly regulates the expression of specific genes in mammalian cells. Moreover, there may be some underlying mechanisms that have common effects in altered physical environments. Our in vitro culture system may provide some insight into the mechanisms through the intracellular processes affected by mechanical forces.

Cell Culture Techniques↗

PubMed1998

Interaction of hydrostatic pressure, time and temperature of pressurization and pediocin AcH on inactivation of foodborne bacteria.

High hydrostatic pressure, because it can kill microorganisms, is being investigated for potential use as a nonthermal food preservation method. The objective of this study was to determine the hydrostatic pressurization parameters, pressure, time, and temperature, and a bacteriocin that in combination would destroy 7 to 8 log cycles of pathogenic and spoilage bacterial populations. We suspended cells of Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, Escherichia coli O157:H7, Lactobacillus sake, Leuconostoc mesenteroides, Serratia liquefaciens, and Pseudomonas fluorescens in peptone solution and exposed them to the combination of treatments. The combined parameters used were hydrostatic pressure (138 to 345 MPa), time (5 to 15 min), temperature (25 to 50 degrees C), and pediocin AcH (3,000 AU/ml, final concentration). In general, cell death increased as the pressure, time, or temperature increased; however, the cells developed proportionately greater sensitivity as the pressure increased to 276 MPa and higher and the temperature increased above 35 degrees C. Pressurization for longer than 5 min, especially at lower pressure and temperature ranges, had very little added benefit. Among the four gram-negative species, E. coli O157:H7 was the most resistant to pressurization while among the four gram-positive species, L. sake and L. mesenteroides had greater resistance. The death rate at high pressure (345 MPa) and high temperature (50 degrees C) in combination followed first-order kinetics; at lower pressure and temperature combination it showed a late tailing effect. Estimated D value data indicated that even at 345 MPa and 50 degrees C an 8-log-cycle viability loss could not be achieved within 5 min for all eight species. However, when pediocin AcH was included during pressurization this loss was achieved.

Bacteria↗

PubMed1986

Promotion of tumor antigenicity in EL-4 leukemia cells by hydrostatic pressure.

Subjection of EL-4-leukemia cells to hydrostatic pressure of 1200-1500 atm for 15 min increased their weak basal immunogenicity to a potent practical level. Injection of such pressure-treated and irradiated EL-4 cells into syngeneic naive C57Bl/6 mice significantly delayed tumor development and increased survival after subsequent challenge with untreated EL-4 cells. Application of pressure of 1500 atm for a longer period of time (e.g., 120 min) resulted in cell death and a smaller increase in tumor immunogenicity which could be partially accounted for by passive shedding of membrane material. Unlike previously studied tumor cells, incorporation of cholesteryl hemisuccinate (CHS) into the plasma membrane of EL-4 cells increased their apparent tumor immunogenicity only slightly. In addition, isolated EL-4 plasma membranes, untreated, CHS-treated or pressure-treated, as well as the material shed thereof by hydrostatic pressure, were all of weak immunogenicity. Modulation in the projection of surface antigens upon pressure treatment could account for the observed increase in tumor immunogenicity and was monitored via the Thy 1.2 antigen. Fluorescence cell sorting analysis indicated that upon application of 1500 atm for different periods of time the projection of Thy 1.2 progressively and irreversibly increased to a maximal level of about 140% at 15 min. At longer pressurization the availability of Thy 1.2 to antibody binding decreased sharply to levels below that of the untreated cells. It is suggested that pressure promotion of tumor immunogenicity is induced by changes in projection and surface distribution of the relevant antigens.

Animals↗

PubMed1975

Protein concentration and hydrostatic pressure in subcutaneous tissue of rats in hypoproteinemia.

Protein concentration and hydrostatic pressure were measured in subcutaneous tissue of rats during development of aminonucleoside nephrosis. Samples of interstitial fluid for protein analysis were collected from subcutaneous tissue by a wick method, and hydrostatic pressure was measured by a modified Scholander technique. When the serum protein concentration was reduced from 6.1 to 4.8 g/100 ml, interstitial fluid protein concentration fell from 3.0 to 1.1 g/100 ml. This corresponds to a reduction of calculated oncotic pressures from 18.0 to 13.0 mm Hg and from 7.8 to 3.0 mm Hg in serum and interstitial fluid, respectively, thus leaving a nearly constant net transcapillary oncotic pressure. When serum protein concentration was further reduced to 3.8 g/100 ml, interstitial fluid protein concentration was reduced to 0.5 g/100 ml, reducing net transcapillary oncotic pressure by 2-3 mm Hg. The average hydrostatic pressure in subcutis was 1.0 mm Hg subatmospheric under control conditions and did not change during hypoproteinemia. The results indicate that a reduction of interstitial protein concentration is an important factor in preventing edema formation in hypoproteinemia.

Animals↗

PubMed2003

Activation and inactivation of Talaromyces macrosporus ascospores by high hydrostatic pressure.

The effect of high hydrostatic pressure treatment (with pressures of up to 700 MPa) on Talaromyces macrosporus ascospores was investigated. At 20 degrees C, pressures of > or = 200 MPa induced the activation and germination of dormant ascospores, as indicated by increased colony counts for ascospore suspensions after pressure treatment and the appearance of germination vesicles and tubes. Pressures of > 400 MPa additionally sensitized the ascospores to subsequent heat treatment. At pressures of > 500 MPa, activation occurred in a few minutes but was followed by inactivation with longer exposure. However, even with the most extreme pressure treatment, a fraction of the ascospore population appeared to resist both activation and inactivation, and the maximal achievable reduction of ascospores was on the order of 3.0 log10 units. Pressure-induced ascospore activation at 400 MPa was temperature dependent, with minimum activation at 30 to 50 degrees C and > or = 10-fold higher activation levels at 10 to 20 degrees C and at 60 degrees C, but it was not particularly pH dependent over a pH range of 3.0 to 6.0. Pressure inactivation at 600 MPa, in contrast, was pH dependent, with the inactivation level being 10-fold higher at pH 6.0 than at pH 3.0. Observation of pressure-treated and subsequently dried spores with the use of light and scanning electron microscopy revealed a collapse of the spore structure, indicating a loss of the spore wall barrier properties. Finally, pressure treatment sensitized T. macrosporus ascospores to cell wall lytic enzymes.

Colony Count, Microbial↗

PubMed1991

The effects of hydrostatic pressure on matrix synthesis in articular cartilage.

The direct effects of hydrostatic pressure on matrix synthesis in articular cartilage can be studied independently of the other factors that change during loading. We have found that the influence of hydrostatic pressure on incorporation rates of 35SO4 and [3H]proline into adult bovine articular cartilage slices in vitro depends on the pressure level and on the time at pressure. Pressures in the "physiological" range (5-15 MPa) applied for 20 s or for 5 min could stimulate tracer incorporation (30-130%) during the following 2 h, but higher pressures (20-50 MPa) had no effect on incorporation rates. The degree of stimulation in cartilage obtained from different animals was found to vary; in some animals none was seen. Stimulation also varied with position along the joint. Physiological pressures (5-10 MPa) applied continuously for the 2-h incubation period also stimulated incorporation rates, but pressures greater than 20 MPa always produced a decrease that was related to the applied pressure and that was reversible. These results suggests that the hydrostatic pressure that occurs during loading is a signal that can stimulate matrix synthesis rates in articular cartilage.

Animals↗

PubMed1977

The induction of cytoplasmic petite mutants of Saccharomyces cerevisiae by hydrostatic pressure.

This study demonstrates that hydrostatic pressure is a potent inductive agent of the petite mutation in cultures of Saccharomyces cerevisiae. The inductive capacity of this mutagen is dependent on the magnitude and the duration of the pressure treatment. Furthermore, the extent of petite induction varies with the growth stage of the culture. Induction occurs in pressure-treated (1-4 X 1-(4) lbf in.-2 or 9-66 X 10(4) kN m-2 for 4 h) log growth cultures but not in stationary or lag phase cultures. Petite induction and cell survival are also dependent on the particular strain of yeast which is pressure-treated. Tetrad analysis and complementation assays demonstrate that pressure-induced petite cells are cytoplasmic in nature. Moreover, induced petite cells show a wide range of suppressivity (2--99%) with a large proportion of the petite cells being highly suppressive.

Cell Survival↗

PubMed1991

Growth inhibition of lysozyme crystals at high hydrostatic pressure.

The influence of high hydrostatic pressures on the crystallization of hen egg-white lysozyme has been determined by growing lysozyme crystals with a capillary technique adapted to high pressure conditions and monitoring the residual protein concentration remaining in the supernatant. Pressure is found to reduce the rate of crystallization and to enhance the solubility of lysozyme in 1 M NaCl, pH 4.66. The volume change calculated from the latter result amounts to 12.5 ml/mol. This value is too small to be detectable by comparison of total molar volumes.

Animals↗