Changes In Hydrostatic Pressure Research Articles

The push for a place in the crowd

Cells change shape and volume when they divide — not a simple task, especially when they are confined by surrounding tissue. Experiments now reveal that hydrostatic pressure changes generate the pushing forces that cells need to create space for division.

Hydrogen Degassing in a Vacuum Arc Degasser Using a Three‐Phase Eulerian Method and Discrete Population Balance Model

A three‐phase Eulerian model incorporating slag‐steel interactions to predict the rate of hydrogen removal from molten steel in a full‐scale industrial vacuum arc degasser (VAD) has been developed. The interfacial area for hydrogen transfer is calculated using a bubble population balance model. This accounts for bubble growth due to changes in hydrostatic pressure as well as coalescence and breakup. The predicted velocity field and bubble distribution are compared with experimental data in the literature. The bubble size predictions under atmospheric pressure conditions are sensitive to the initial bubble size, while under vacuum conditions they are relatively independent of the initial size. The omission of the slag layer from the model results in a 12% increase in the hydrogen removal rate. Variation in the slag eye diameter as a function of argon flowrate is simulated and compared with empirical correlations in the literature. Hydrogen measurements from a full‐scale VAD unit at Sheffield Forgemasters International Ltd. steelworks are compared to the model predictions for a series of melts of varying initial hydrogen content. Based on the initial hydrogen content of the liquid steel, the model predicts the amount of hydrogen removed to within ±20% of final experimental measurements obtained from the melt.

Cuffless Estimation of Blood Pressure: Importance of Variability in Blood Pressure Dependence of Arterial Stiffness Across Individuals and Measurement Sites.

Measuring arterial pulse transit time (PTT) to estimate blood pressure (BP) without conventional brachial cuff-based measurement is not new, but is a focus of current wearable technologies research. Much research pertains to efficient, accurate sensing of artery-related waveforms, yet the relationship between PTT and BP receives less attention despite being key for accurate BP estimation. This study investigated BP/PTT calibration by quantifying anatomical site variability (n = 10, 3 female, age 30 9 years) and individual variability ( n = 103, 50 female, age 53 22 years). BP and pulse wave velocity (PWV) were measured in both seated and supine. Carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and carotid-finger-volume PWV (cvPWV) were measured with the wrist and hand positioned at the level of the upper thigh to achieve the same hydrostatic pressure effect across all measurements. The postural change invoked a small (4 7 mmHg) change in brachial diastolic BP with an additional 27 2 mmHg change in hydrostatic pressure. cfPWV decreased in the supine position (1.75 0.17 m s-1, p < 0.001), but crPWV and cvPWV were more variable. The calibration term (BP/PWV) across the sample population varied from 6.6 to 98.3 mmHg sm-1 (mean 22 14 mmHg sm-1) and was correlated with age, heart rate, diastolic and pulse pressure, and weight. These variables did not explain the majority of the variability (R2 = 0.248). There is anatomical site and between-individual variability in the calibration term for BP estimation from PTT. Using and accurately calculating hydrostatic changes in BP within the individual may be one method to increase the accuracy of this calibration term.

Analysis of the thrust deduction in waterjet propulsion – The Froude number dependence

The definition of thrust deduction in waterjet propulsion is different from that of a propeller driven hull and cannot be interpreted in the same way. A particularly interesting feature of the waterjet thrust deduction is the large variation with Froude number. This is well known from experience, but has never been fully explained. The objective of this paper is to use CFD to address the reasons for these large variations. To this end, the thrust deduction fraction is split into resistance increment fraction and jet thrust deduction fraction. The former is due to the self-propelled hull resistance change in comparison with the bare hull resistance and the latter is due to the difference between gross and net thrust. This split reveals that the main reason for the thrust deduction variation is the hull resistance change. Analysis of the resistance increment in different speed ranges is performed by studying the hydrostatic and hydrodynamic pressure changes on the hull as well as the friction change due to the waterjet system. Despite the negative thrust deduction fraction in the intermediate speed range there is no indication of a resistance reduction compared to that of the bare hull at these speeds.

The effect of the rate of hydrostatic pressure depressurization on cells in culture.

Changes in hydrostatic pressure, at levels as low as 10 mm Hg, have been reported in some studies to alter cell function in vitro; however, other studies have found no detectable changes using similar methodologies. We here investigate the hypothesis that the rate of depressurization, rather than elevated hydrostatic pressure itself, may be responsible for these reported changes. Hydrostatic pressure (100 mm Hg above atmospheric pressure) was applied to bovine aortic endothelial cells (BAECs) and PC12 neuronal cells using pressurized gas for periods ranging from 3 hours to 9 days, and then the system was either slowly (~30 minutes) or rapidly (~5 seconds) depressurized. Cell viability, apoptosis, proliferation, and F-actin distribution were then assayed. Our results did not show significant differences between rapidly and slowly depressurized cells that would explain differences previously reported in the literature. Moreover, we found no detectable effect of elevated hydrostatic pressure (with slow depressurization) on any measured variables. Our results do not confirm the findings of other groups that modest increases in hydrostatic pressure affect cell function, but we are not able to explain their findings.

Non-cohesive Soil Direct Shear Strength Affected with Hydrostatic Pressure

This paper presents first results of non­cohesive soil direct shear tests with hydrostatic pressure. To reach this aim, it was chosen the Baltic Sea Klaipėda sand, due to granulometry composition and particles shape. According to this, investigated Baltic Sea sand can be called Lithuanian standard sand for scientific testing. Analysis of results revealed, that when it is increased hydrostatic pressure, the shearing strength is also increasing. Comparing air­ dry sand results with fully saturated sand and affected with 100 kPa of hydrostatic pressure, the angle of internal friction increased for 21,24%. Meanwhile, the cohesion was not changing so dramatically according to hydrostatic pressure change. Obtained results allows to proceed this research work more detailed with different loading types, testing procedures and hydrostatic pressures.

PRESSURE OPTIMISED VISCOELASTIC VIBRATION AND IMPACT INSULATION

&amp;lt;jats:p&amp;gt;Within this contribution we present recently published findings [1] on the new way of utilizing polymeric materials for vibration damping. We present and demonstrate patented dissipative bulk and granular systems technology [2], based on which we have developed granular damping elements (GDE). The damping elements consist of granular viscoelastic material encapsulated and pressurized within a woven container made of basalt, carbon, and/or glass fibres. The hydrostatic pressure changes material properties and consequently the performance of the vibration isolation. Within this contribution, properties of three TPU materials in solid state are investigated, which after granulation are potential candidates for producing new GDE damping elements. We have demonstrated that for the case of TPU materials the stiffness and energy absorption capability of insulation may be increased between 10 to 100 times.&amp;lt;/jats:p&amp;gt;

Pressure dependence of resistivity and magnetic properties in a Mn1.9Cr0.1Sb alloy

We report magnetic-field and hydrostatic pressure dependent electrical resistivity and magnetic properties of a Mn1.9Cr0.1Sb alloy. Upon cooling, the magnetization of Mn1.9Cr0.1Sb exhibits a first-order ferrimagnetic to antiferromagnetic transition at the exchange inversion temperature, TS = 261 K under a 0.1 T magnetic field. Our experimental results show that TS decreases with increasing magnetic field but increase with increasing hydrostatic pressure. The pressure induced transition is accompanied by a large positive baro-resistance of 30.5% for a hydrostatic pressure change of 0.69 GPa. These results show that the lattice parameters as well as the bond distance between Mn-Mn atoms play a crucial role in the magnetic and electronic transport properties of Mn1.9Cr0.1Sb. This sample also exhibits a large inverse magnetocaloric effect with a magnetic entropy change of ΔSm = +6.75 J/kg.K and negative magnetoresistance (44.5%) for a field change of 5 T at TS in ambient pressure which may be useful for magnetic cooling and spintronics applications.

Giant barocaloric effects over a wide temperature range in superionic conductor AgI

Current interest in barocaloric effects has been stimulated by the discovery that these pressure-driven thermal changes can be giant near ferroic phase transitions in materials that display magnetic or electrical order. Here we demonstrate giant inverse barocaloric effects in the solid electrolyte AgI, near its superionic phase transition at ~420 K. Over a wide range of temperatures, hydrostatic pressure changes of 2.5 kbar yield large and reversible barocaloric effects, resulting in large values of refrigerant capacity. Moreover, the peak values of isothermal entropy change (60 J K−1 kg−1 or 0.34 J K−1 cm−3) and adiabatic temperature changes (18 K), which we identify for a starting temperature of 390 K, exceed all values previously recorded for barocaloric materials. Our work should therefore inspire the study of barocaloric effects in a wide range of solid electrolytes, as well as the parallel development of cooling devices.

RESEARCH OF HYDRAULIC IMPACT ON THE TECHNOLOGICAL STABILITY OF SHALLOW METROTUNNEL IN DREDGING MASSIVES

Purpose. On the basis of the results analysis of the computer simulation and laboratory studies it is necessary to determine the changes impact dependence of the hydraulic level of groundwater on the tunnels processing stability in the underground due to the deformations development of the surrounding dredging massif. Methodology. The methodological basis of the research complex consists of the analysis, generalization of known scientific results and practical experience of forecasting and preconditioning of deformations of tunnel and surrounding soil mass processing, as well as computer simulation of the critical stress-strain state of the tunnel processing at changes in the hydraulic level of groundwater. Findings. In the process of technological construction and under the non-pressure groundwaters impact, when operating tunnels of subway lines of shallow foundation, the stability of all-section machining is ensured due to the uniform hydrostatic reduction of processing. At this the sediments are within the permissible values. The results of the research show that different levels of hydrostatic pressure can occur when the groundwater level changes from both sides of the tunnel. At the same time, there is a redistribution of stresses of the soil mass around the cross section of the tunnel, which, in turn, leads to the appearance of additional non-uniform deformations and the opening of cracks in the tunnels during operation. Originality. The authors of the work firstly established the effect of changes in hydrostatic pressure, which may arise due to fluctuations in the level of groundwater on the whole-section processing of tunnels of metro lines of shallow foundation due to secondary sedimentation. The conditions of occurrence of the secondary sediment have been determined and the nature of the deformation course has been established during the operation of the shallow subway. Practical value. At the stage of designing the metro lines of the shallow foundation, it is necessary to take into account the possibility of uneven precipitation from the action of hydrostatic pressure during operation. This will avoid additional deformations during the seasonal period, reduce the number of current repairs, increase reliability and the useful life of the tunnel processing structures.

A Pulse Wave Velocity Based Method to Assess the Mean Arterial Blood Pressure Limits of Autoregulation in Peripheral Arteries

Background: Constant blood flow despite changes in blood pressure, a phenomenon called autoregulation, has been demonstrated for various organ systems. We hypothesized that by changing hydrostatic pressures in peripheral arteries, we can establish these limits of autoregulation in peripheral arteries based on local pulse wave velocity (PWV).Methods: Electrocardiogram and plethysmograph waveforms were recorded at the left and right index fingers in 18 healthy volunteers. Each subject changed their left arm position, keeping the right arm stationary. Pulse arrival times (PAT) at both fingers were measured and used to calculate PWV. We calculated ΔPAT (ΔPWV), the differences between the left and right PATs (PWVs), and compared them to the respective calculated blood pressure at the left index fingertip to derive the limits of autoregulation.Results: ΔPAT decreased and ΔPWV increased exponentially at low blood pressures in the fingertip up to a blood pressure of 70 mmHg, after which changes in ΔPAT and ΔPWV were minimal. The empirically chosen 20 mmHg window (75–95 mmHg) was confirmed to be within the autoregulatory limit (slope = 0.097, p = 0.56). ΔPAT and ΔPWV within a 20 mmHg moving window were not significantly different from the respective data points within the control 75–95 mmHg window when the pressure at the fingertip was between 56 and 110 mmHg for ΔPAT and between 57 and 112 mmHg for ΔPWV.Conclusions: Changes in hydrostatic pressure due to changes in arm position significantly affect peripheral arterial stiffness as assessed by ΔPAT and ΔPWV, allowing us to estimate peripheral autoregulation limits based on PWV.

Aspects on the Physiological and Biochemical Foundations of Neurocritical Care.

Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood–brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the information from all monitoring techniques should be presented bedside online. Accordingly, in the future, the chemical variables obtained from microdialysis will probably be analyzed by biochemical sensors.

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City, China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow, resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as “instability - translational slide - tension fracture - collapse” and the formation mechanism as “translational landslide induced by heavy rainfall”. The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research on potential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.

Survival of marine heterotrophic flagellates isolated from the surface and the deep sea at high hydrostatic pressure: Literature review and own experiments

Although the abyssal seafloor represents the most common benthic environment on Earth, eukaryotic microbial life at abyssal depths is still an uncharted territory. This is in striking contrast to their potential importance regarding the material flux and bacteria consumption in the deep sea. Flagellate genotypes determined from sedimentary DNA deep‐sea samples might originate from vital deep‐sea populations or from cysts of organisms sedimented down from surface waters. The latter one may have never been active under deep‐sea conditions. We wanted to analyze the principal ability of cultivable heterotrophic flagellates of different phylogenetic groups (choanoflagellates, ancyromonads, euglenids, kinetoplastids, bicosoecids, chrysomonads, and cercozoans) to survive exposure to high hydrostatic pressure (up to 670bar). We summarized our own studies and the few available data from literature on pressure tolerances of flagellates isolated from different marine habitats. Our results demonstrated that many different flagellate species isolated from the surface waters and deep-sea sediments survived drastic changes in hydrostatic pressure. Barophilic behavior was also recorded for several species isolated from the deep sea indicating their possible genetic adaptation to high pressures. This is in accordance with records of heterotrophic flagellates present in environmental DNA surveys based on clone libraries established for deep‐sea environments.

Effect of Upper Body Position on Arterial Stiffness: Influence of Hydrostatic Pressure and Autonomic Function

Conventional markers of arterial stiffness, such as carotid beta‐stiffness index, are traditionally obtained in the supine position. In the seated position, it is not known if correcting for hydrostatic pressure is an adequate adjustment for estimation of beta‐stiffness index or if other factors need to be considered, such as autonomic modulation.ObjectiveTo determine if the change in arterial stiffness in a seated position is due to the effects of gravity alone or if there is an additional effect of autonomic modulation after correcting for changes in hydrostatic pressure.MethodsThirty young participants (male=15, 24 ± 4 years, 25.6 ± 3.9 kg/m2) were randomly positioned at 0°, 45°, and 72° angles (semi‐recumbent position). Beat‐to‐beat blood pressure, carotid blood pressure (cBP), beta‐stiffness index, and carotid diameters were measured at each position after 5 min rest. The gravitational height correction was determined by measuring the vertical fluid column distance (mmHg), between the heart and the carotid artery. Beta‐stiffness index was calibrated using three different methods: 1) non‐height corrected cBP of each position, 2) height corrected cBP of each position, 3) height corrected cBP of the supine position (theoretical model). Method 3 was implemented under the assumption that pressures from the supine to the seated position only change due to the effects of gravity. LFSAP was analyzed as a marker of sympathetic activity.ResultsSee table. Beta stiffness did not increase if not corrected for hydrostatic pressure changes. Arterial stiffness indices based on method 2 were not significantly different from the one based on method 3(p=0.65). LFSAP increased in more upright positions (p&lt;0.05) but diastolic diameter relative to diastolic pressure did not change (p&gt;0.05).ConclusionsThe change in arterial stiffness in Method 2 did not differ from Method 3, presumably indicating that the beta stiffness index increases with change in position are pressure dependent, despite the apparent increase in vascular sympathetic modulation. This is supported by the lack of change in diameter relative to diastolic pressure. 0° 45° 72° Heart rate, bpm 58 (9)a 61 (11) 62 (11) Height Correction, mmHg 0 (0)a −11 (3)b −16 (3) Carotid SBP, mmHg (Method 1) 116 (13)a 122 (15) 122 (12) Carotid DBP, mmHg (Method 1) 74 (8)a 78 (7) 78 (6) Carotid SBP height corrected, mmHg (Method 2) 116 (13)a 110 (15)b 105 (12) Carotid DBP height corrected, mmHg (Method 2) 74 (8)a 66 (7)b 61 (6) Carotid SBP theoretical. mmHg (Method 3) 116 (13)a 105 (13)b 99 (13) Carotid DBP theoretical, mmHg (Method 3) 74 (8)a 63 (8)b 58 (8) Beta stiffness (Method 1) 4.1 (1.3) 4.0 (1.5) 4.0 (1.2) Beta stiffness height corrected (Method 2) 4.1 (1.3)b 4.6 (1.7) 4.8 (1.5) Beta stiffness theoretical (Method 3) 4.1 (1.3)a 4.7 (1.6)b 5.0 (1.7) Diastolic diameter, mm 6.1 (0.8)a 5.7 (0.7)b 5.6 (0.7) Diastolic diameter/Carotid DBP height corrected, mm/mmHg 0.08 (0.02) 0.09 (0.01) 0.09 (0.01) Relative diameter, % 11.7 (3.3) 11.7 (3.1) 12.2 (3.7) LFSAP 6.4 (4.7)a 11.6 (6.6) 13.1 (10.1) significantly different from all other positions, p&lt;0.05 significantly different from 72°, p&lt;0.05 Data presented as mean (SD). SBP: systolic blood pressure; DBP: diastolic blood pressure

An Experimental Study of the Effects of External Physiological Parameters on the Photoplethysmography Signals in the Context of Local Blood Pressure (Hydrostatic Pressure Changes).

A comprehensive study of the effect of a wide range of controlled human subject motion on Photoplethysmographic signals is reported. The investigation includes testing of two separate groups of 5 and 18 subjects who were asked to undertake set exercises whilst simultaneously monitoring a wide range of physiological parameters including Breathing Rate, Heart Rate and Localised Blood Pressure using commercial clinical sensing systems. The unique finger mounted PPG probe equipped with miniature three axis accelerometers for undertaking this investigation was a purpose built in-house version which is designed to facilitate reproducible application to a wide range of human subjects and the study of motion. The subjects were required to undertake several motion based exercises including standing, sitting and lying down and transitions between these states. They were also required to undertake set arm movements including arm-swinging and wrist rotation. A comprehensive set of experimental results corresponding to all motion inducing exercises have been recorded and analysed including the baseline (BL) value (DC component) and the amplitude of the oscillation of the PPG. All physiological parameters were also recorded as a simultaneous time varying waveform. The effects of the motion and specifically the localised Blood Pressure (BP) have been studied and related to possible influences of the Autonomic Nervous System (ANS) and hemodynamic pressure variations. It is envisaged that a comprehensive study of the effect of motion and the localised pressure fluctuations will provide valuable information for the future minimisation of motion artefact effect on the PPG signals of this probe and allow the accurate assessment of total haemoglobin concentration which is the primary function of the probe.

Annual variability and regulation of methane and sulfate fluxes in Baltic Sea estuarine sediments

Abstract. Marine methane emissions originate largely from near-shore coastal systems, but emission estimates are often not based on temporally well-resolved data or sufficient understanding of the variability of methane consumption and production processes in the underlying sediment. The objectives of our investigation were to explore the effects of seasonal temperature, changes in benthic oxygen concentration, and historical eutrophication on sediment methane concentrations and benthic fluxes at two type localities for open-water coastal versus eutrophic, estuarine sediment in the Baltic Sea. Benthic fluxes of methane and oxygen and sediment pore-water concentrations of dissolved sulfate, methane, and 35S-sulfate reduction rates were obtained over a 12-month period from April 2012 to April 2013. Benthic methane fluxes varied by factors of 5 and 12 at the offshore coastal site and the eutrophic estuarine station, respectively, ranging from 0.1 mmol m−2 d−1 in winter at an open coastal site to 2.6 mmol m−2 d−1 in late summer in the inner eutrophic estuary. Total oxygen uptake (TOU) and 35S-sulfate reduction rates (SRRs) correlated with methane fluxes showing low rates in the winter and high rates in the summer. The highest pore-water methane concentrations also varied by factors of 6 and 10 over the sampling period with the lowest values in the winter and highest values in late summer–early autumn. The highest pore-water methane concentrations were 5.7 mM a few centimeters below the sediment surface, but they never exceeded the in situ saturation concentration. Of the total sulfate reduction, 21–24 % was coupled to anaerobic methane oxidation, lowering methane concentrations below the sediment surface far below the saturation concentration. The data imply that bubble emission likely plays no or only a minor role in methane emissions in these sediments. The changes in pore-water methane concentrations over the observation period were too large to be explained by temporal changes in methane formation and methane oxidation rates due to temperature alone. Additional factors such as regional and local hydrostatic pressure changes and coastal submarine groundwater flow may also affect the vertical and lateral transport of methane.

Time Optimizing near the Pay Zone

Well control techniques are used in oil and gas drilling operations to control bottom hole pressure and avoid any fluid influx from formation to the well. These techniques are highly important near the pay zone in term of time. Controlling formation fluid pressure and thereby the formations behavior in a predictable fashion will help toward more optimized environmental friendly drilling operation. Time consumed to control the formation fluid pressure will range between few hours to many days. This paper discusses hydrostatic pressure distribution and changes near the pay zone for one oil blocks in Kurdistan, in the northern part of Iraq. Obtaining homogeneous increase in some drilling fluid properties will help the engineer to better interpret sampling of the lithological columns and reduce potential hole problems and operation time.

Role of twins in variations in the conductivity characteristics of single-crystal HoBa2Cu3O7-δ during reversible changes in hydrostatic pressure

The in-plane electrical resistivity of single-crystal HoBa2Cu3O7-δ (Tc = 62–66 K) is studied at temperatures Tc–300 K under conditions such that the measurement current flows parallel to twins or at an angle of 45° to them during reversible changes in hydrostatic pressure. The variations in Tc, in the parameters of the Bloch-Grueneisen equations, and in the parameters of the Aslamasov-Larkin model for fluctuation conductivity are analyzed. Application of a pressure facilitates the formation of a second phase with lower Tc that shows up more clearly when the measurement current flows across the twinning plane. In this case, the transverse coherence length and the interval within which the fluctuation conductivity exists are smaller than in the first configuration. The relaxation of the parameters characterizing the scatting of charge carriers on phonons and defects is related to the redistribution of oxygen between the two phases.

The difference in endolymphatic hydrostatic pressure elevation induced by isoproterenol between the ampulla and the cochlea.

The purpose of the study was to investigate the difference in the responses of endolymphatic hydrostatic pressure to isoproterenol, β-adrenergic receptor agonist, between pars superior and pars inferior. The hydrostatic pressure of endolymph and perilymph and endolymphatic potential in the ampulla and the cochlea during the intravenous administration of isoproterenol were recorded using a servo-null system in guinea pigs. The hydrostatic pressure of endolymph and perilymph in the ampulla and cochlea was similar in magnitude. Isoproterenol significantly increased hydrostatic pressure of ampullar and cochlear endolymph and perilymph with no change in the ampullar endolymphatic potential and endocochlear potential, respectively. The isoproterenol-induced maximum change of endolymphatic hydrostatic pressure in ampulla was significantly (p<0.01) smaller than that in the cochlea. In ears with an obstructed endolymphatic sac, the action of isoproterenol on endolymphatic hydrostatic pressure in the ampulla disappeared like that in the cochlea. Isoproterenol elevates endolymphatic hydrostatic pressure in different manner between the vestibule and the cochlea.