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Results for “Hydrostatic Pressure”

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PubMed2000

Hydrostatic pressure stimulates synthesis of elastin in cultured optic nerve head astrocytes.

Elastin is a major component of the extracellular matrix (ECM) of the lamina cribrosa in the optic nerve head in humans and nonhuman primates. The lamina cribrosa appears to be the site of damage to the retinal ganglion cell axons in glaucomatous optic neuropathy, characterized in many patients by elevated intraocular pressure (IOP). Type 1B astrocytes are the major cell type in the lamina, synthesize elastic fibers during development, express increased elastin mRNA, and synthesize abnormal elastin in glaucoma. In this study, we determined the effect of elevated hydrostatic pressure on the synthesis of elastin by type 1B astrocytes in culture. Type 1B astrocytes were exposed to gradients of hydrostatic pressure and tested for proliferation, morphology, synthesis, and deposition of elastin. Trichloroacetic acid (TCA) and immunoprecipitation of radiolabeled protein determined total new protein and elastin synthesis. Proteins from the conditioned media were analyzed by Western blot. Levels of elastin mRNA were determined by in situ hybridization. Cell proliferation increased approximately 2-fold after exposure to pressure for one day, approximately 5-fold after 3 and 5 days of exposure to pressure. Confocal and electron microscopic cytochemistry showed a marked increase in intracellular elastin in astrocytes exposed to pressure, as compared with controls. Intracellular elastin was associated with the RER-Golgi region and with the cytoskeleton. Total protein and elastin synthesis increased significantly (P < 0.05) at 3- and 5-day exposure to pressure, as well as the level of elastin mRNA. Elastin protein in the media increased with the level of pressure. These results indicate that hydrostatic pressure stimulates type 1B astrocytes to synthesize and secrete soluble elastin into the media. In glaucoma, type 1B astrocytes may respond to IOP-related stress with increased expression of elastin and formation of elastotic fibers leading to loss of elasticity and tissue remodeling.

Adolescent↗

PubMed2007

Response of two Salmonella enterica strains inoculated in model cheese treated with high hydrostatic pressure.

The aim of this work was to determine the response to high hydrostatic pressure and the ability for survival, recovery, and growth of 2 strains of Salmonella enterica (Salmonella enteritidis and Salmonella typhimurium) inoculated in a washed-curd model cheese produced with and without starter culture. Inoculated samples were treated at 300 and 400 MPa for 10 min at room temperature and analyzed after treatment and after 1, 7, and 15 d of storage at 12 degrees C to study the behavior of the Salmonella population. Cheese samples produced with starter culture and treated at 300 and 400 MPa showed maximum lethality; no significant differences in the baroresistant behavior of both strains were detected. Nevertheless, when starter culture was not present, the maximum lethality was only observed in cheese samples treated at 400 MPa, in the case of S. enteritidis. Ability to repair and grow was not observed in model cheese produced with starter culture and cell counts of treated samples decreased after 15 d of storage at 12 degrees C. In cheese produced without starter culture, Salmonella cells showed the ability to repair and grow during the storage period, reaching counts over 3 log(10) (cfu/mL) in both applied treatments and serotypes. These results suggest that high hydrostatic pressure treatments are effective to reduce Salmonella population in this type of cheese, but the presence of the starter culture affects the ability of this microorganism to repair and grow during the storage period.

Animals↗

PubMed2005

High hydrostatic pressure inhibits the biosynthesis of eukaryotic elongation factor-2.

High continuous hydrostatic pressure is known to inhibit the total cellular protein synthesis. In this study, our goal was to identify pressure-regulated proteins by using two dimensional gel electrophoresis and mass spectrometry. This analysis showed that under 30 MPa continuous hydrostatic pressure the biosynthesis of eukaryotic elongation factor-2 (eEF-2) was inhibited both in HeLa carcinoma and T/C28a4 chondrocytic cell lines. Western blot analysis of HeLa cells revealed that the cellular protein level of eEF-2 decreased by 40%-50% within 12 h of the pressure treatment. However, the steady-state mRNA level of eEF-2 was not affected by the pressure. Cycloheximide addition after 4 h-pressure treatment suggested that the half-life of eEF-2 protein was shorter in pressurized cells. eEF-2 is responsible for the translocation of ribosome along the specific mRNA during translation, and its phosphorylation prevents the ribosomal translocation. Therefore, increased phosphorylation of eEF-2 was considered as one mechanism that could explain the reduced level of protein synthesis in pressurized HeLa cell cultures. However, Western blot analysis with an antibody recognizing the Thr56-phosphorylated form of eEF-2 showed that phosphorylation of eEF-2 was not elevated in pressurized samples. In conclusion, the inhibition of protein synthesis under high pressure occurs independent of the phosphorylation of eEF-2. However, this inhibition may result from the decrease of cellular eEF-2 protein.

Amino Acid Sequence↗

PubMed2026

A chromosomal gtrB homolog and dam differentially contribute to dry-heat and high hydrostatic pressure resistance in Salmonella enterica.

Salmonella enterica can persist in low-moisture foods and shows enhanced dry-heat resistance under low water activity, posing significant food safety challenges. However, the genetic basis of extreme dry-heat resistance and its relationship with other processing stresses remain unclear. In this study, twelve S. enterica strains were screened for dry-heat treatment at 60 °C and 80 °C, with S. Infantis CICC21649 identified as the most resistant strain. Comparative genomics and transcriptional analysis identified candidate genes related to envelope integrity and regulation, including gtrB and dam. Deletion of the chromosomal gtrB homolog reduced dry-heat resistance, producing an additional 0.91-log10 reduction relative to the parent strain at 80 °C. Deletion of dam caused broader stress sensitivity, reducing resistance to both dry heat and high hydrostatic pressure, with the stronger phenotype observed under high hydrostatic pressure. Proteomic analysis of the chromosomal gtrB homolog mutant revealed broad alterations in envelope-associated proteins, transport functions, oxidative stress pathways, and central metabolism under dry-heat stress. These findings indicate that the chromosomal gtrB homolog is an important contributor to extreme dry-heat resistance, whereas dam contributes to resistance against both dry-heat and high hydrostatic pressure, likely through a broader regulatory role in stress adaptation. These results reveal distinct structural and regulatory layers underlying stress adaptation in S. enterica and provide practical guidance for low-moisture food processing by highlighting the need to account for strain-dependent and stress-specific resistance during process validation.

Hydrostatic Pressure↗

PubMed2001

Combination of reduced oxygen tension and intermittent hydrostatic pressure: a useful tool in articular cartilage tissue engineering.

Cartilage cells are normally studied under atmospheric pressure conditions and without loading. However, since cartilage exists in a condition of reduced oxygen and intermittent hydrostatic pressure we hypothesized lower partial oxygen pressures (PO2) and different intermittent hydrostatic pressures (IHP) would increase articular chondrocyte proliferation and matrix production and to stabilize chondrocyte phenotype in vitro. Monolayers of adult bovine articular chondrocytes were cultured under 5% or 21% PO2 in combination with IHP (0.2 MPa amplitude, frequencies 5/5s = 0.1 Hz, 30/2 or 2/30 min on/off loading). We measured proliferation (3H-thymidine incorporation) and collagen secretion (protein-binding assay, collagen type II-ELISA and immunocytochemical staining of pericellular collagen types I, II and IX). Reduced PO2 stimulated proliferation and collagen type II and IX secretion of chondrocytes in comparison to 21% PO2. Additionally, collagen type I expression was delayed by low PO2, indicating a stabilization of the cell phenotype. IHP 5/5s and 30/2 min inhibited proliferation but increased collagen secretion (pericellular collagen type IX was decreased). IHP 30/2 min delayed first expression of collagen type I. In contrast, IHP 2/30 min increased proliferation, but lowered collagen expression. All stimulating or inhibiting effects of PO2 and IHP were additive and vice versa. Reduced PO2 and different settings of IHP increased proliferation, collagen secretion, and phenotype stability of chondrocytes. The oxygen- and IHP-induced effects were additive, suggesting that a combination of these parameters might be a useful tool in cartilage tissue engineering.

Animals↗

PubMed1986

Effects of high hydrostatic pressure on 'passive' monovalent cation transport in human red cells.

The effects of high hydrostatic pressure (up to 400 ATA) on the 'passive' (defined as ouabain + bumetanide + EGTA-insensitive) influx and efflux of radiotracer cations (K+ Rb+, Na+, Cs+) has been studied in human red cells suspended at different medium tonicities giving altered cell volumes. Under all conditions studied, cation permeability was raised at pressure, and at least two distinct components were found to comprise this flux. Thus, increasing pressure caused a generalized increase in cation permeability which was unaffected by the anion present, demonstrated linear concentration dependence, and was reduced with cell swelling, and stimulated a specific KCl pathway which was Cl- dependent, demonstrated saturation kinetics with raised [K]0 and was increased with cell swelling. High hydrostatic pressure caused a significant alteration to red cell morphology from the normal biconcave disc to cup-shaped forms and it is proposed that this is associated with the unmasking of the volume-sensitive KCl system.

Biological Transport, Active↗

PubMed2000

Biological response of rats fed with tofu treated with high hydrostatic pressure.

Emerging technologies for food preservation have arisen in recent years, such as high-pressure (HP) hydrostatic treatment, and the biological response for this kind of food preservation is not well-known. Forty female rats (six weeks old) were used in the experiment to evaluate the biological effects of HP treatment of tofu. The animals were divided into groups that were fed with tofu (untreated), tofu treated with HP, and conventional food (as control) for 28 days. The glucose level, mineral content (calcium, potassium, zinc, and magnesium), shinbone maximum shear force, weight of the body, and weight of organs (heart, liver, spleen, and kidneys) were analyzed. The biological response for the rats was that significant differences were found in the calcium amount determined on the serum of the rats fed with untreated tofu and those fed with tofu treated with HP, and the calcium amount was lower on the rats fed with tofu treated with HP. Also, there were significant differences in the weight of the liver, and it was lower in the rats fed with tofu treated with HP. It was quite remarkable how the weight of the body and organs were smaller in the rats fed with tofu in comparison to the weight of the control rats. In the other components assayed no significant differences were found. HP produces a potential effect on tofu as it is observed in the rats response to the tofu treated with HP.

Animals↗

PubMed1979

Action potentials in single axons: effects of hyperbaric air and hydrostatic pressure.

Resting potential and action potential parameters of crayfish (Procambarus acutus) single axon were examined under hyperbaric air and hydrostatic pressure to 8.6 atmospheres absolute to determine if evidence for the basis of neurological dysfunctions that may occur in diving in this pressure range is detectable at the membrane level. Hyperbaric air increased the maximum rates of depolarization and repolarization of the action potential by (2.2 +/- 0.2) and (2.1 +/- 0.2)%/atm, respectively. Hydrostatic pressure had an opposite effect, decreasing the maximum rates of depolarization and repolarization by (0.57 +/- 0.13) and (0.9 +/- 0.3)%/atm, respectively. Action potential duration was decreased (0.91 +/- 0.19)%/atm by hyperbaric air. Action potential amplitude, resting potential, and threshold were unchanged by increasing pressure. Increasing the nitrogen tension alone produced results consistent with hyperbaric air compression. Thus, increased hydrostatic and nitrogen pressures oppositely affect the rates of polarization of the action potential in a reversible manner at pressures in the range encountered by human divers.

Action Potentials↗

PubMed2006

Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of electrodes.

A novel sample injection method for chip CE was presented. This injection method uses hydrostatic pressure, generated by emptying the sample waste reservoir, for sample loading and electrokinetic force for dispensing. The injection was performed on a double-cross microchip. One cross, created by the sample and separation channels, is used for formation of a sample plug. Another cross, formed by the sample and controlling channels, is used for plug control. By varying the electric field in the controlling channel, the sample plug volume can be linearly adjusted. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip, without any electrode or external pressure pump, thus allowing a sample injection with a minimum number of electrodes. The potential of this injection method was demonstrated by a four-separation-channel chip CE system. In this system, parallel sample separation can be achieved with only two electrodes, which is otherwise impossible with conventional injection methods. Hydrostatic pressure maintains the sample composition during the sample loading, allowing the injection to be free of injection bias.

Electrodes↗

PubMed2005

Adaptation of Saccharomyces cerevisiae to high hydrostatic pressure causing growth inhibition.

Genome-wide mRNA expression profiles of Saccharomyces cerevisiae growing under hydrostatic pressure were characterized. We selected a hydrostatic pressure of 30 MPa at 25 degrees C because yeast cells were able to grow under these conditions, while cell size and complexity were increased after decompression. Functional characterization of pressure-induced genes suggests that genes involved in protein metabolism and membrane metabolism were induced. The response to 30 MPa was significantly different from that observed under lethal conditions because protein degradation was not activated under 30 MPa pressure. Strongly induced genes those that contribute to membrane metabolism and which are also induced by detergents, oils, and membrane stabilizers.

Adaptation, Physiological↗

PubMed2003

Inactivation of classical swine fever virus: association of hydrostatic pressure and ultraviolet irradiation.

Reversible pressure-induced disassembly of several viruses has suggested the idea of using hydrostatic pressure to suppress virus infectivity. In this study, the effects of high hydrostatic pressure and ultraviolet (UV) irradiation were investigated on classical swine fever virus (CSFV) in an attempt to eliminate residual infectivity. The structural modifications were followed by intrinsic fluorescence and biological activity assays. The kinetics of CSFV inactivation showed that pressure-induced inactivation was not enough to eliminate viral infectivity. However, when pressure was applied in association with UV irradiation no infectious focus was observed. The application of these two methods against CSFV can be an attractive inactivation strategy for the development of a vaccine.

Animals↗

PubMed2006

Renal interstitial hydrostatic pressure and natriuretic response to high doses of angiotensin II in pregnant rats.

BACKGROUND: Administration of high doses of angiotensin II (Ang II) results in natriuretic and diuretic responses that are mediated by increases in renal perfusion pressure (RPP). Elevations in renal interstitial hydrostatic pressure (RIHP) caused by increases in mean arterial pressure (MAP) or RPP are associated with significant increases in urinary sodium excretion (U(Na)V) and urine flow rate (V). In pregnant rats the renin-angiotensin system (RAS) is activated and basal RIHP is reduced. The exact relationship among MAP, RIHP, U(Na)V, and V in response to a high pressor dose of Ang II during normal pregnancy is not known. METHODS: The objective of this study was to evaluate the relationship between MAP and RIHP, and determine the role of RIHP in the natriuretic and diuretic responses to administration of high dose of Ang II in midterm pregnant (MP) and nonpregnant (NP) Sprague-Dawley (SD) rats. RESULTS: Intravenous infusion of Ang II (200 ng/kg/min) significantly increased MAP (DeltaMAP), DeltaU(Na)V, and DeltaV in anesthetized MP and NP rats. The DeltaMAP, DeltaU(Na)V, and DeltaV were 12 +/- 2 mm Hg, 27.9 +/- 2.7 microEq/min, and 197 +/- 23 microL/min for MP rats and were similar (15 +/- 3 mm Hg, 34.1 +/- 4.3 microEq/min, and 242 +/- 34 microL/min, respectively) for NP rats. The RIHP decreased significantly (P < .05) with Ang II infusion in NP (from 6.1 +/- 0.2 to 3.9 +/- 0.4 mm Hg) but not in MP (from 3.3 +/- 0.3 to 4.1 +/- 0.4 mm Hg) groups of rats. Acute renal decapsulation eliminated the change in RIHP mediated by high doses of Ang II infusion in the NP group, but did not affect MAP or the natriuretic and diuretic responses to Ang II in either the MP or NP groups of rats. CONCLUSIONS: The natriuretic and diuretic responses to high doses of Ang II are not mediated by changes in RIHP in pregnant or nonpregnant rats.

Angiotensin II↗

PubMed2005

Pathologically elevated cyclic hydrostatic pressure induces CD95-mediated apoptotic cell death in vascular endothelial cells.

We describe cyclic hydrostatic pressure of 200/100 mmHg with a frequency of 85/min as a hemodynamically relevant pathological condition enforcing apoptosis in endothelial cells (EC) after 24 h of treatment. This went along with an increase of CD95 and CD95L surface expression, shedding of CD95L into the supernatant, cleavage of caspase-3 and caspase-8, and elevated JNK-2, c-Jun, and CD95L mRNA expression. Furthermore, increased DNA-binding activity of the AP-1 transcription factor family members FRA-1 and c-Jun was observed. This activation was reduced by inhibition of JNK, which subsequently prevented elevated CD95L mRNA expression. Caspase inhibitors and a CD95L-neutralizing antibody also reduced EC apoptosis. Most of the pressure-induced events were most prominent at 24 and 48 h. However, after 48 h, the CD95/CD95L expression pattern switched back to CD95-/CD95L+ and the specific death rate decreased. Cyclic pathological hydrostatic pressure is a novel type of stress to EC that renders them susceptible to CD95/CD95L-mediated autoapoptosis and/or paracrine apoptosis accompanied by upregulation of intracellular molecules known to trigger both apoptosis and survival.

Aorta↗

PubMed2000

Application of hydrostatic pressure facilitates ex vivo adenovirus gene transfer into rabbit aortas.

We investigated whether application of hydrostatic pressure facilitates ex vivo adenovirus gene transfer into rabbit aortas. Assay of beta-galactosidase activity was performed in the aortas subjected to adenovirus encoding LacZ gene (Ad-LacZ) transfer. Application of hydrostatic pressure at 8 atmospheres during Ad-LacZ gene transfer (10(10) pfu/mL, 10 min) to aortic segments resulted in an approximately 4.5-fold increase in transgene efficiency. X-Gal staining showed predominant beta-galactosidase activity in the endothelial and the adventitial cells in the aorta subjected to pressure-supported Ad-LacZ gene transfer. Then we examined the effect of heme oxygenase-1 (HO-1), which catabolizes heme to carbon monoxide and biliverdin, by transferring adenovirus encoding HO-1 (Ad-HO-1) into rabbit aortas using this pressurization system. The Ad-HO-1-infected aortic segment showed a significantly decreased contractile response to phenylephrine compared to the Ad-LacZ-infected aortic segment. Pressure-supported adenovirus gene transfer may increase the feasibility of exploiting intraoperative adenovirus-mediated gene transfer.

Acetylcholine↗

PubMed2000

Effects of hydrostatic pressure on the structure and biological activity of infectious bursal disease virus.

The effects of high hydrostatic pressure on the structure and biological activity of infectious bursal disease virus (IBDV), a commercially important pathogen of chickens, were investigated. IBDV was completely dissociated into subunits at a pressure of 240 MPa and 0 degrees C revealed by the change in intrinsic fluorescence spectrum and light scattering. The dissociation of IBDV showed abnormal concentration dependence as observed for some other viruses. Electron microscopy study showed that morphology of IBDV had an obvious change after pressure treatment at 0 degrees C. It was found that elevating pressure destroyed the infectivity of IBDV, and a completely pressure-inactivated IBDV could be obtained under proper conditions. The pressure-inactivated IBDV retained the original immunogenic properties and could elicit high titers of virus neutralizing antibodies. These results indicate that hydrostatic pressure provides a potential physical means to prepare antiviral vaccine.

Anilino Naphthalenesulfonates↗

PubMed2002

[Effect of high hydrostatic pressure on water imbibition, cooking times and microstructure of Phaseolus vulgaris].

The effect of high hydrostatic pressure (HHP) on water imbibition, cooking times, and microstructure of cotyledons and seed coats of black beans was evaluated. High pressure treatments at 275, 410, 550 or 690 MPa and 25 degrees C for 5 min increased the rate of water imbibition of black beans. The saturation degree of HHP treated black beans was reached 50% faster than the saturation degree of untreated black beans. High hydrostatic pressure treatments reduced the cooking times (CT) of unsoaked black beans by 25% to 39%, similar to black beans soaked for 3 h. The microstructure of HHP treated beans exhibited protein aggregation in cell protoplasm and swelling of cell walls and starch granules. Seed coats of HHP treated black beans were less smooth than seed coats of untreated black beans. The swelling of palisade, hourglass, and parenchyma cells was also observed in HHP treated black beans such as soaked beans. High hydrostatic treatment is an alternative for reducing the preparation long times of Phaseolus vulgaris.

Absorption↗

PubMed2003

[The study of the behavior of exciton and photon within semiconductor microcavity under hydrostatic pressure].

We studied, for the first time, the strong coupling between exciton and cavity mode within semiconductor microcavity under hydrostatic pressure, and measured the Rabi splitting. The strong coupling between exciton and cavity mode, and so Rabi splitting appear clearly as the applied pressure reaches 0.37-0.41 GPa. The experiment result shows that hydrostatic pressure not only can tune the coupling between exciton and cavity mode effectively, but also can keep exciton property almost unchanged during the whole tuning procedure in contrast to other tuning method (temperature field et al). Our result agrees with the related theory very well. The Rabi splitting, extracted from fitting the measured mode-energy vs pressure curves with correspending theoretical model, is equal to 6 meV.

Chemical Phenomena↗

PubMed2000

Combined effects of hydrostatic pressure, temperature, and the addition of allyl isothiocyanate on inactivation of Escherichia coli.

Combined effects of hydrostatic pressure, temperature, and the addition of allyl isothiocyanate (AIT) on the inactivation of Escherichia coli, including type O157, were investigated. Inactivation to undetectable levels by hydrostatic pressure alone requires 400 to 600 MPa. E. coli growth was delayed with increasing of applied pressure and the AIT concentration added subsequently. The antibacterial effects of AIT vapor increased on JCM 1649 and IFO 3301 after pressurization. The bactericidal effects of pressurization with the addition of AIT at 4 degrees C or 40 degrees C were greater than at 20 degrees C, and all bacteria tested were effectively killed at 200 or 250 MPa with 10 to 80 microg/ml of AIT. We tried to apply the combined treatment to a food product "Asazuke" (low salt vegetables), and it was confirmed that E. coli inoculated into the product was inactivated the same as in the in vitro test. We also studied the inactivation mechanism behind pressurization with AIT from the relationship between pressure resistance and precultivation temperature, and it was suggested that destruction of membrane structure caused bacterial kill.

Animals↗