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Results for “Osmotic Pressure”

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At least 19 recordsLinked to original sources
PubMed1990

Hydrostatic pressure versus osmotic pressure in the development of vasogenic brain edema induced by cold injury.

The role of hydrostatic pressure and osmotic pressure gradient in the development of vasogenic brain edema induced by cold lesion made in the parietal cortex was studied in cats under ketamine anesthesia and blood pressure monitoring. The animals were divided into a hypertensive group and a normotensive group and were kept alive for 6 hr. The brain was removed and cut coronally at the lesion for tissue sampling from various areas of edematous white matter to measure both the SG and the amount of extravasated serum albumin in the same samples. Our result showed that the edema confined in the area containing extravasated serum albumin and the increase of water content correlated linearly with the amount of extravasated serum albumin both in the normotensive group and hypertensive group. However, the slope of the regression line indicated albumin content in the edema fluid was significantly different between the two groups. The slope became lower as the MABP during the experiment became higher, indicating that protein concentration in the edema fluid became lower when hypertension sustained. Thus, both hydrostatic and osmotic pressure gradient regulate the extravascular accumulation of edema fluid in the cold lesion edema.

Albumins↗
PubMed1995

Antagonistic effects of hydrostatic pressure and osmotic pressure on cytochrome P-450cam spin transition.

The combined effects of hydrostatic pressure and osmotic pressure, generated by polyols, on the spin equilibrium of fenchone-bound cytochrome P-450cam were investigated. Hydrostatic pressure indices a high spin to low spin transition, whereas polyols induce the reversed reaction. Of the four solutes used, glycerol, glucose, stachyose, and sucrose, only the last two would act on the spin transition by osmotic stress. The spin volume changes measured by both techniques are different, 29 and -350 ml/mol for hydrostatic pressure and osmotic pressure, respectively. It suggests that even if the two are perturbing water molecules, different properties are probed. From the volume change induced by osmotic stress, 19 water molecules are deduced that would be implicated in the spin transition of the fenchone-bound protein. This result suggests that water molecules other than the well defined ones located in the active site play a key role in modulating the spin equilibrium of cytochrome P-450cam.

Camphor 5-Monooxygenase↗
PubMed1980

Measurement of tissue osmotic pressure.

Osmotic pressure measured by a modified pressure-volume method was compared with that of the mixed sap expressed from frozen and thawed tissue. The error in the latter technique averaged 11 and 16% (too dilute) for greenhouse and field leaves of Zea mays L. at all growth stages. These errors were not consistently calculated by a model of simple mixing between the matric and osmotic fractions, both of which decreased with plant age. Some other alternatives to the pressure-volume method are discussed which are based on a more rapid estimate of the zero turgor point.

Journal Article↗
PubMed1994

Hydrostatic pressure reverses osmotic pressure effects on the specificity of EcoRI-DNA interactions.

To characterize the role of water in protein-DNA interactions, we have studied the specificity of the EcoRI restriction endonuclease as a function of osmotic and hydrostatic pressure. The extent of cleavage by the enzyme at noncanonical ("star") sites is shown to depend uniquely upon the osmotic pressure in the reaction as controlled by the addition of a wide variety of neutral solutes. Alteration of cleavage specificity ("EcoRI* activity") is not uniformly correlated with any other colligative solvent property such as dielectric constant, viscosity, or water concentration. The application of hydrostatic pressure reverses the effects of osmotic pressure, restoring the natural selectivity of the enzyme for its canonical site GAATTC. This combination of observations provides compelling evidence that the site-specific recognition of canonical site DNA by EcoRI is mediated by discretely bound water molecules and that the release of these waters induces a fundamental change in the specificity of the interaction, leading to cleavage at alternative sites. This comprehensive analysis of solvent effects facilitates the unambiguous identification of structurally and functionally specific waters involved in macromolecular recognition events.

DNA↗
PubMed1987

The direct measurement of plasma colloid osmotic pressure is superior to colloid osmotic pressure derived from albumin or total protein.

Plasma colloid osmotic pressure (COP) has been calculated from both serum albumin concentration and plasma total protein concentration. These values have been compared to those measured directly using a membrane-transducer oncometer in a group of normal subjects, in a group of critically-ill patients with a variety of primary diagnoses and in a group of hypovolaemic patients before and after plasma volume replacement with 6% hydroxyethyl starch solution. In the normal samples, COP calculated from albumin (COPalb) underestimated the measured COP (COPm) by mean of 2.0 mmHg (p less than 0.002), with correlation coefficient r = 0.39(n/s). Similarly, the COPalb underestimated COPm by a mean of 5.7 mmHg (p less than 0.001) in the critically ill patient group; r = 0.38 (p less than 0.02). Furthermore, in the patients receiving plasma volume replacement serum albumin concentration fell by 13.1% (p less than 0.001) whilst COPm increased by 11.5% (p less than 0.002). In the normal subjects COP calculated from total protein concentration (COPtp) underestimated the COPm by 1.5 mmHg (p less than 0.02) with r = 0.65 (p less than 0.01). Conversely, in the patient samples, mean COPtp overestimated COPm by 3.5 mmHg (p less than 0.001) with r = 0.73 (p less than 0.002). We conclude that COPalb is an inadequate estimate of COPm particularly in patients where its use may have important clinical consequences. COPtp provides a reasonable estimate of COPm in normal subjects but in patients samples, where albumin: globulin ratio is low COPtp overestimates substantially in many cases. We advocate the direct measurement of COP in critically-ill patients.

Adult↗
PubMed1977

The endothelial damage of pulsatile renal preservation and its relationship to perfusion pressure and colloid osmotic pressure.

To evaluate the effects of pulsatile preservation, 34 heterotopic renal autografts with immediate contralateral nephrectomy were divided into four groups with either the pulsatile preservation or cold storage technique. Group I had pulsatile preservation with plasma-albumin perfusate at a mean pressure of 60 mm. Hg and a colloid osmotic pressure (COP) of 20 to 50 cm. H2O. Group II had pusatile preservation with the same plasma-albumin perfusates as in Group I, but at a mean pressure of 30 mm. Hg. Group III had pulsatile preservation with albumin-phosphate buffer solution at a mean pressure of 30 mm. Hg. Group IV used cold storage technique. Group I demonstrated severe endothelial destruction and denuding of basement membrane. The changes were inversely related to COP. None of these kidneys functioned and, following transplantation, had persistent severe tubular damage and plugging of glomerular capillary loops with platelets, fibrinogen, and white cells. In Groups II and III, there were minimal changes, consisting of widening of the endothelial pores and focal endothelial damage. All of these kidneys functioned following reimplantation with minimal ultrastructural alterations. Group IV had no glomerular changes following preservation or following transplantation. All preservation techniques produced proximal tubular damage. There is a definite mechanical lesion associated with pulsatile preservation, which can be minimized by utilizing low perfusion pressures and solutions of high colloid osmotic pressure and which has the potential of producing a picture resembling hyperacute rejection following transplantation.

Animals↗
PubMed1980

[Influence of surgery and hemodilution on the colloid osmotic pressure].

Colloid osmotic pressure was measured pre- and postoperatively in 75 patients. It could be demonstrated that the level of the colloid osmotic pressure inaccurately corresponded to the serum protein concentration. This fact can be neglected in those patients that are infused for short-term periods. However, many patients receive large amounts of colloids during long-term parenteral nutrition and in those cases an abnormal increase of plasma volume has to be expected. This might be harmful to the cardiopulmonary function and can be avoided by infusing colloids according to the level of the colloid osmotic pressure.

Adult↗
PubMed1981

Colloid osmotic pressure in newborn infants: variations with birth weight, gestational age, total serum solids, and mean arterial pressure.

Colloid osmotic pressure (COP) of blood was measured directly at birth with the Wescor membrane colloid osmometer (model 4100) in 91 appropriately grown, 11 large, and nine small for gestational age "well" newborn infants. COP correlated directly with birth weight (r = .726, P less than .00001) and gestational age (r = .753, P less than .00001). COP values for small for gestational age (SGA) and large for gestational age (LGA) infants were found to fall within the 95% prediction interval with regard to birth weight and gestational age for appropriate for gestational age (AGA) infants. Simultaneous measurements of COP, total serum solids, and central arterial mean blood pressure were made. The results showed that COP correlated directly with total serum solids (r = .89, P less than .0001) and mean arterial blood pressure (r = .660, P less than .001). Among the factors evaluated, total serum solids was the best predictor of COP.

Birth Weight↗
PubMed2003

Theoretical and experimental studies on freezing point depression and vapor pressure deficit as methods to measure osmotic pressure of aqueous polyethylene glycol and bovine serum albumin solutions.

For survival in adverse environments where there is drought, high salt concentration or low temperature, some plants seem to be able to synthesize biochemical compounds, including proteins, in response to changes in water activity or osmotic pressure. Measurement of the water activity or osmotic pressure of simple aqueous solutions has been based on freezing point depression or vapor pressure deficit. Measurement of the osmotic pressure of plants under water stress has been mainly based on vapor pressure deficit. However, differences have been noted for osmotic pressure values of aqueous polyethylene glycol (PEG) solutions measured by freezing point depression and vapor pressure deficit. For this paper, the physicochemical basis of freezing point depression and vapor pressure deficit were first examined theoretically and then, the osmotic pressure of aqueous ethylene glycol and of PEG solutions were measured by both freezing point depression and vapor pressure deficit in comparison with other aqueous solutions such as NaCl, KCl, CaCl(2), glucose, sucrose, raffinose, and bovine serum albumin (BSA) solutions. The results showed that: (1) freezing point depression and vapor pressure deficit share theoretically the same physicochemical basis; (2) theoretically, they are proportional to the molal concentration of the aqueous solutions to be measured; (3) in practice, the osmotic pressure levels of aqueous NaCl, KCl, CaCl(2), glucose, sucrose, and raffinose solutions increase in proportion to their molal concentrations and there is little inconsistency between those measured by freezing point depression and vapor pressure deficit; (4) the osmotic pressure levels of aqueous ethylene glycol and PEG solutions measured by freezing point depression differed from the values measured by vapor pressure deficit; (5) the osmotic pressure of aqueous BSA solution measured by freezing point depression differed slightly from that measured by vapor pressure deficit.

Freezing↗