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PubMed1978

Some hemodynamic and hydroelectrolytic alterations of chronic salt deprivation.

Male Wistar rats were fed for 1 month on a low salt diet and compared with control animals. The body fluids are decreased, and this diminution takes place due to the decrease of the total water, extracellular space, intracellular space, plasma volume and interstitial liquid. In the muscle, the alterations in the water composition were similar to the modifications observed in the whole animal. The electrolytic composition of the muscle showed a decrease in the sodium content; no modifications were found in the chloride content and there was a slight decrease in the potassium content. The cardiac rate was increased and the arterial pressure and heart weight also showed a slight augmentation. The infusion of antibodies against angiotensin II provoked a similar decrease in arterial pressure in both groups of animals. These results show an alteration of the hydroelectrolytic metabolism in salt-deprived rats and that the circulatory function is adapted to this new situation.

Angiotensin II↗
PubMed1983

The fluid problem in the critically ill.

Fluid therapy in the critically ill patient must be adjusted to accommodate continuing changes in the plasma volume, interstitial space, and intracellular space. During and after hemorrhagic shock, replacement of crystalloid is needed to replenish the plasma and interstitial spaces during operation and then interstitial and intracellular spaces after operation. Severe sepsis leads to a more pronounced expansion of the interstitial space than that of hemorrhagic shock. Continuing therapy after both hemorrhage and sepsis should be directed toward maintaining effective plasma volume and levels of hemoglobin while the interstitial and intracellular spaces return to normal. Concomitantly, effective circulatory volume must be guided by continuing changes in cardiac, pulmonary, and renal function.

Aged↗
PubMed1983

Estimation of platelet size by measurement of intracellular water space using an oil technique.

The intracellular water space of human platelets has been measured after equilibration with tritiated water and then separating these cells by centrifugation through phthalate oil of density 1.042. The mean intracellular water space of platelets in citrated plasma was 0.52 +/- 0.09 microliter/10(8) cells for 19 normal subjects. The gravimetric water content of platelets was 784 +/- 4 mg water/g cells. From these values the mean platelet volume was calculated to be 6.2 fl which agrees closely with values based on Coulter size distribution and thrombocytocrit. Gel filtration alters platelets such that a mean 19% of the platelets could not be centrifuged through phthalate oils of density 1.031 or 1.042. The measurement of tritiated water space of platelets centrifuged from their own plasma through oil provides a simple and reliable estimate of the mean platelet size.

Blood Platelets↗
PubMed1985

The determination of intracellular water space by NMR.

A new method for the determination of intracellular water space using NMR spectroscopy is described. The method is based on the measurement of 59Co NMR signal intensity of an inert, stable and membrane-impermeable cobalt(III) compound such as Co(CN)3-6 or Co(imidazole)3+6 and the 2H or 1H NMR signal intensities of the freely permeable water. As an example of the method, the variation of the intracellular water space of human erythrocytes as a function of osmolality was measured.

Cobalt Radioisotopes↗
PubMed1979

Potassium, sodium, and the intracellular fluid space of cells from bone.

Cells enzymatically dispersed from fetal rat calvaria were analyzed for sodium and potassium content and intracellular fluid space (ICF). Even when obtained in comparatively high yield, the cells are damaged by the isolation procedure as evidenced by high sodium and low potassium content immediately after isolation. During a post-incubation period potassium is accumulated and sodium extruded to steady-state levels. Although electrolyte content of cells after recovery did not vary as a function of cell yield, ICF was increased in cells obtained in lower yield, suggesting cell swelling as a result of membrane damage. The weighted mean values obtained for the best cell preparations were 117 mM K+ and 27 mM Na+. Based on DNA assay of isolated cells and the whole tissue, 20- to 21-day calvaria were found to have an average of 8.1 x 10(6) cells/calvarium. Combining cell data with analysis of total tissue sodium, potassium, and water, it was concluded that the tissue extracellular sodium is in equilibrium with blood but that the potassium concentraiton is approximately 5-fold higher than blood levels.

Animals↗
PubMed1998

[The clinical application of diffusion weighted magnetic resonance imaging to acute cerebrovascular disorders].

Diffusion is a measure of motion freedom and is a sensitive parameter to characterize the tissue at the microscopic level. The methods of measuring in vivo diffusion by magnetic resonance imaging (MRI) have been based mainly on the addition of two motion-probing gradients (MPG) to the spin echo sequence to produce signal attenuation for the spins moving at random. The resultant MR images reflect the intravoxel incoherent motions (IVIM), which contain both water molecule diffusion and perfusion in the capillary network, and can be quantified by an apparent diffusion coefficient (ADC). Diffusion weighted MRI, acquired from IVIM MR imaging by the addition of the very strong MPG predicate water diffusion and anisotropy. High signal or reduced ADC can be observed in case of the slower diffusion. The anisotropy depends upon the orientation of the subjects and the gradients. Greater signal attenuation (faster diffusion) can be observed when the relative orientation of white matter tracts to the MPG is parallel as compared to that obtained with a perpendicular alignment. This anisotropy may preclude the detection or delineation of an ischemic lesion. Diffusion tensor trace has been designated to eliminate this anisotropy effect. In ischemic animal models, low signal (fast diffusion) and high signal (slow diffusion) have been noted in the vasogenic edema and cytotoxic edema, respectively. High signal appears only in case of cerebral blood flow below 15-20 ml/100 g per minute, a value identical to the threshold of tissue at high energetic metabolism and ion homeostasis. ADC value decreases following the cerebral vessel occlusion, or remains unchanged when collateral circulation develops. It has been speculated that reduction in ADC reflects the water shift from extracellular space to intracellular space due to the membrane permeability and/or intracellular osmolality increase. These results suggest that diffusion weighted MRI correlates well with the cell metabolism, and cytotoxic edema plays an important role in the acute cerebral stroke. In clinical setting of acute cerebral ischemia, diffusion weighted MRI may detect superacute infarction by showing high signal (slower ADC) over the 6 hours following the insult, whereas conventional MRI generally fails to do so. In chronic liquefied cerebral infarction, increased ADC, or attenuated signal are the most frequent findings, suggestive of an elevated diffusion. Therefore, diffusion weighted MRI improves early diagnosis of stroke and help differentiate acute from chronic stroke. One disadvantage of diffusion weighted MRI is motion artifact, which may be reduced by the introduction of a navigator echo to correct for the phase shift caused by the first imaging echo, or by the utility of ultrafast imaging technique, such as echo planar. Another shortcomings is the susceptibility artifact incorporating the diffusion weighted MRI. The eddy current may also result from the strong gradients, producing shiftlike artifact. Such artifacts can be compensated for by appropriate shaping of the current pulses sent into the gradient coils, or by use of shielded gradients. As with rapid progresses in perfusion imaging of ischemia penumbra, misery perfusion and luxury perfusion, new insight into the diffusion weighted MRI will be significant.

Acute Disease↗
PubMedDate not supplied

Hypercapnia and resultant bicarbonate transfer processes in an elasmobranch fish (Scyliorhinus stellaris).

In order to test the effects of hypercapnia on the acid-base status of fish, larger spotted dogfish were exposed to sudden changes of PCO2 in a closed seawater recirculation system. pH, PCO2 and PO2 were determined in arterial blood and seawater. The exchange of bicarbonate between extracellular space (ECS), intracellular space (ICS), and seawater (SW) was obtained from changes of the total bicarbonate amount in ECS and SW. After fourfold increase of PCO2 arterial pH fell markedly, but started to recover immediately towards control values. This was caused by compensatory accumulation of bicarbonate in the ECS. According to the origin of the extracellular bicarbonate increase three periods could be distinguished: 1.-- Bicarbonate transferred from ICS to both ECS and SW; 2. -- Bicarbonate transferred from both SW and ICS to ECS; 3. -- Bicarbonate transferred from SW to both ECS and ICS. After return to normocapnia similar periods occurred with opposite transfer directions and delayed period transitions. In the first period the ICS was found to be the only source for compensatory bicarbonate increases and even in the second period the ICS contributed to compensation of the extracellular pH. Thus bicarbonate exchange with the ICS appears to be an important regulatory mechanism diminishing the extracellular pH variations after changes in PCO2, before other compensatory mechanisms are initiated.

Animals↗
PubMed1994

Water diffusion and acute stroke.

The occlusion of the middle cerebral artery was used as an experimental acute stroke model in 30 cats. The diffusion of water was followed by diffusion-sensitized MRI between 1 and 15 h after induction of stroke. It is demonstrated that images representing the trace of the diffusion tensor provide a much more accurate delineation of affected area than images representing the diffusion in one direction only. The reason is that the strong contrast caused by the anisotropy and orientation of myelin fibers is completely removed in the trace of the diffusion tensor. The trace images show a small contrast between white and gray matter. The diffusion coefficient of white matter is decreased in acute stroke to approximately the same extent as gray matter. It is further shown that the average lifetime of water in extra and intracellular space is shorter than 20 ms both for healthy and ischemic tissue indicating that myelin fibers are permeable to water. The anisotropy contrast did not change before or after induction of stroke, nor after sacrifice. Together, these observations are consistent with the view that the changes in water diffusion during acute stroke are directly related to cytotoxic oedema, i.e., to the change in relative volume of intra- and extracellular spaces. Changes in membrane permeability do not appear to contribute significantly to the changes in diffusion.

Acute Disease↗
PubMed1996

Biexponential diffusion attenuation in various states of brain tissue: implications for diffusion-weighted imaging.

Diffusion-weighted single voxel experiments conducted at b-values up to 1 x 10(4) smm-2 yielded biexponential signal attenuation curves for both normal and ischemic brain. The relative fractions of the rapidly and slowly decaying components (f1, f2) are f1 = 0.80 +/- 0.02, f2 = 0.17 +/- 0.02 in healthy adult rat brain and f1 = 0.90 +/- 0.02, f2 = 0.11 +/- 0.01 in normal neonatal rat brain, whereas the corresponding values for the postmortem situation are f1 = 0.69 +/- 0.02, f2 = 0.33 +/- 0.02. It is demonstrated that the changes in f1 and f2 occur simultaneously to those in the extracellular and intracellular space fractions (fex, f(in)) during: (i) cell swelling after total circulatory arrest, and (ii) the recovery from N-methyl-D-aspartate induced excitotoxic brain edema evoked by MK-801, as measured by changes in the electrical impedance. Possible reasons for the discrepancy between the estimated magnitude components and the physiological values are presented and evaluated. Implications of the biexponential signal attenuation curves for diffusion-weighted imaging experiments are discussed.

Age Factors↗
PubMed1984

A stopped flow capillary perfusion method to evaluate contraluminal transport parameters of methylsuccinate from interstitium into renal proximal tubular cells.

In order to study the transport of dicarboxylic acids through the contraluminal cell membrane of proximal tubular cells, 3H- methylsuccinate has been synthetized by catalytic hydration of methylfumarate . As the chromatography of radioactive material excreted in the urine after i.v. injection of 3H- methylsuccinate shows, no metabolite is detectable during the first 3 min. After 10 min, less than 10% of the excreted radiolabel is metabolized. To measure the contraluminal influx of 3H- methylsuccinate from the interstitium into cortical tubular cells, the renal vessels were clamped so that the proximal tubular lumina collapsed. Then Ringer solution was injected into the blood capillaries. It contained different concentrations of 3H- methylsuccinate and 14C-inulin as extracellular space marker. After contact times between 1 and 10 s, this fluid was withdrawn from the capillaries and the disappearance of 3H- methylsuccinate relative to 14C-inulin was measured. The morphological compartments in the outer cortex of the clamped glutaraldehyde-fixed kidney were evaluated by a stereological method. For proximal tubular cells a ratio of extracellular water space to intracellular space of 1:3.1 and a ratio extracellular water space to free cell water space of 1:2 was found. It was tested whether the experimental disappearance curves with 4 different starting concentrations of 3H- methylsuccinate fit with the data from four model calculations. It was found that the data and the conditions of transport are consistent with the predictions of a facilitated diffusion model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Dexamethasone treatment during hemorrhagic shock: changes in extracellular fluid volume and cell membrane transport.

Changes in extracellular fluid volume and cell membrane transport during hemorrhagic shock and the effects of dexamethasone treatment on these changes were measured. It is well known that prolonged hemorrhagic shock leads to irreversible changes and a progressive decrease in blood pressure despite reinfusion for lost blood. Pharmacologic doses of glucocorticoids provide some protection against these changes. Therefore, one purpose in the present study was to identify possible sites of glucocorticoid action whicy may prevent the irreversible changes from occurring. The extracellular fluid volume in normal control, nontreated dogs in shock, and dexamethasone-treated dogs in shock were measured by a dilution technique, using [35S] sodium sulfate. Cell membrane cation transport capabilities were measured in liver slices, diaphragm slices, and red blood cells taken from normal control, nontreated rats in shock, and dexamethasone-treated rats in shock. The accumulation of radioactivity by the tissues incubated with 22Na served as an indicator of cell membrane ion transport capabilities. The results indicate that in animals subjected to prolonged hemorrhagic shock, there is a fluid shift from the extracellular space into intracellular spaces, reducing blood volume. Cell membranes are damaged and transport mechanisms are altered; therefore, the cells are unable to extrude ions along with water. Dexamethasone treatment was shown to prevent extracellular fluid volumes from decreasing below that amount due to the plasma lost during hemorrhage. Also, it prevented some cell membrane damage and maintained membrane transport mechanisms near normal. In addition, at the onset of dexamethasone injection, blood pressure increased, and urine output was restored.

Animals↗
PubMed2006

In vivo protein transduction to the CNS.

Proteins and peptides are useful research and therapeutic tools, however applications are limited because delivery to the desired location is not easily achievable. There are two hurdles in protein/peptide delivery to the brain: the blood-brain barrier and intracellular penetration. Penetration to both brain and the intracellular space can be achieved by adjusting hydrophilicity, and small molecule pharmacological agents have been successfully developed using this approach. But with proteins and peptides, it is difficult to modify the hydrophilicity without influencing biological functions. Trans-acting factor protein from the human immunodeficiency virus contains a highly conserved cationic peptide sequence necessary for transduction across the cell membrane. While trans-acting factor peptide has been used for in vitro protein transduction, its in vivo application is very limited because it is rapidly degraded by proteolysis. Polyethylenimine is a chemically synthesized small molecule cationization agent; the charge density is greater than a peptide-based cationic cluster such as trans-acting factor, and it is resistant to proteolysis in vivo. We first tested intracellular protein transduction following direct brain injection in mice using polyethylenimine-conjugated green fluorescence protein and beta-galactosidase (molecular weights 29 and 540 kDa, respectively). Polyethylenimine-conjugates penetrated to the intracellular space immediately surrounding the injection site within one hour. We further tested polyethylenimine-mediated protein transduction following intranasal administration, which bypasses the blood-brain barrier. Polyethylenimine-conjugates in pH 7.5 solution did not reach the brain, probably because the polyethylenimine-conjugates penetrated into the intracellular space where first exposed to the tissue, i.e. at the nasal mucosae. We temporarily reduced the electrostatic interaction between cationized polyethylenimine-conjugates and cellular surfaces by adjusting the pH to 4.5; solution rapidly reached the brain and penetrated to the intracellular space. This study suggests that polyethylenimine is a useful protein transduction agent in the brain in vivo, and adjusting cationic charge interaction can determine the extent of brain penetration.

Administration, Intranasal↗
PubMed1982

Extra- and intracellular water spaces in muscles of man at rest and with dynamic exercise.

A method was established to analyze the extracellular water space (H2Oe) in small muscle tissue samples as [3H]inulin distribution space. After initial experiments on rats, the method was applied on 13 men and 6 women. Muscles with different fiber compositions (soleus, S; vastus lateralis, (VL; gastrocnemius, G; triceps brachii, TB) were studied at rest. The total water content was the same for all muscles, 320 (313-330) ml/100 g dry wt. However, differences were demonstrated for H2Oe, with 26-34 ml/100 g dry wt in VL and 38-54 ml/100 g dry wt in S, (P less than 0.05); the values for G and TB were in between those for VL and S. The differences in H2Oe were not related to the fiber composition of the muscles. During 3 x 3 min of intense bicycle exercise demanding about 120% VO2 max (6 men), total water content increased in VL from 313 to 359 ml/100 g dry wt and H2Oe increased from 34 to 60 ml/100 g dry wt (P less than 0.05), In TB, which is relatively inactive during bicycle exercise, no such changes occurred. The calculated intracellular lactate concentration increased in VL from 5.7 to 30.6 mmol/l H2Oi. The extracellular lactate concentration amounted to 13.6 mmol/l H2Oe at the end of exercise. The concentration gradient for lactate of 2 from intra- to extracellular space favored a flux of water to the intracellular space. The relative large increase in H2Oe may then be caused by a hydrostatic rather than an osmotic factor.U

Adult↗
PubMed1994

Intracellular and extracellular spaces and the direct quantification of molar intracellular concentrations of phosphorus metabolites in the isolated rat heart using 31P NMR spectroscopy and phosphonate markers.

To quantify metabolite and cation concentrations using NMR spectroscopy, the volumes of intracellular and extracellular spaces must be known. We describe a simple 31P NMR spectroscopic method that employs dimethyl methylphosphonate (DMMP) as a marker of total water space and phenylphosphonate (PPA) as a marker of extracellular space to determine intracellular and extracellular space volumes in the isolated, perfused rat heart. In vivo and in vitro radiolabel studies were used to verify this method. The difference between the total and extracellular water spaces, determined as milliliters/heart, gave the intracellular volume and allowed direct calculation of myocardial creatine phosphate, ATP, and inorganic phosphate concentrations, which were 13.4 mM, 10.1 mM, and 3.4 mM, respectively, for the glucose-perfused rat heart. The extracellular volume decreased by 84% in hearts subjected to 28 min total, global ischemia and increased by 15% during reperfusion. The method described allows the determination of intracellular energy metabolite concentrations in perfused rat heart directly from a single, fully relaxed 31P NMR spectrum.

Animals↗
PubMedDate not supplied

Effect of intracellular unstirred layer on apparent reflection coefficient for urea in inner medullary collecting duct: a computer simulation.

In the vasopressin-stimulated inner medullary collecting duct (IMCD), urea is transported through a pathway which is distinct from a water channel. Therefore, no frictional interaction between urea and water should occur at the membrane level, and the reflection coefficient for urea must be close to unity. However, the presence of unstirred layers in the vicinity of membranes causes solute concentration polarization, leading to an underestimation of the reflection coefficient (apparent reflection coefficient). When the value is determined across the perfused renal tubular wall, the intracellular space also constitutes an unstirred layer. The profile of solute and water transport across the system consisting of two membranes and the interposed intracellular space was simulated by a computer to examine the effect of unstirred layer on the value of apparent reflection coefficient. The model demonstrated that the imposed osmotic gradient across the tubular epithelial is decreased at each membrane interface. Under conditions of minimal unstirred layers in the bathing fluid, the existence of the intracellular constraints to diffusion cause considerable underestimation of the reflection coefficient. The higher the membrane permeability of urea and the smaller the diffusion coefficient of urea in the intracellular space, the greater becomes the magnitude of the underestimation. Thus, the measured apparent reflection coefficient for urea may become significantly less than the estimated value, leading to a reduction of the effective transmural osmotic driving force.

Animals↗
PubMed1972

A compartmental analysis of 24 Na kinetics in rat cerebrum, sciatic nerve and cerebrospinal fluid.

1. The kinetics of (24)Na exchange in rat cerebrospinal fluid, brain and sciatic nerve were studied during steady-state plasma isotope conditions. The entrance of (24)Na into brain and sciatic nerve was found to fit a three compartmental model. Using newly derived equations for compartmental analysis, the first compartment (24)Na space of brain was found to be about 22% and the second compartment space about 6%; the corresponding sciatic nerve spaces were 26 and 11%, respectively. In the discussion, arguments are presented that suggest that the first compartment is the extracellular space (ECS) and the second compartment is the intracellular space. The t((1/2)) for compartmental equilibration between plasma and brain ECS was 2 hr and from ECS to intracellular space 14 hr; in nerve the respective t((1/2))'s were (2/3) hr and 10 hr.2. A third compartment of 18% was found in sciatic nerve which was interpreted to be anatomically confined to the epi- and perineurium; in brain the corresponding space was 2% and was felt to be anatomically and kinetically an inactive closed compartment in parallel with the blood.3. There were two t((1/2))'s for plasma-c.s.f. (24)Na equilibration of less than 10 min and 2 hr.4. Profiles of brain, from cortex to ventricle, at 6 min, demonstrated a gradient of decreasing (24)Na radioactivity from ventricle to cortex.

Animals↗
PubMed1989

Plasma reciprocal pool specific activity predicts that of intracellular free leucine for protein synthesis.

We previously proposed that, during the infusion of either labeled leucine or its alpha-ketoacid, alpha-ketoisocaproate (KIC), the plasma specific activity (SA) of the transaminated product of the infused tracer ("reciprocal pool SA") may better reflect the intracellular leucine SA than the plasma SA of either infused tracer ("primary pool SA"). To test this hypothesis, 14 dogs were simultaneously infused intravenously with [3H]leucine and [14C]KIC, and blood and tissue compartments were sampled. The ratios of [3H]-leucine to [14C]leucine [( 3H]/[14C]leucine) in mixed tissue proteins and in the intracellular space of striated muscle were the same as the ratio of the isotope infusion rates and similar, although slightly lower (P less than 0.01), than [3H]KIC/[14C]leucine SA (ratio of reciprocal pool SA) in plasma. Plasma [3H]KIC/[14C]leucine SA were essentially identical to the [3H]/[14C] of leucine in 1) mixed liver proteins, 2) intrahepatic free leucine, and 3) fibrin. The [3H]/[14C]leucine in mixed renal proteins and in the intracellular space of kidney and erythrocytes were similar to those of the venous plasma [3H]/[14C]leucine SA. The plasma [3H]KIC and [14C]leucine SA (the reciprocal pool SA) were similar to the SA of [3H]- and [14C]leucine in the intracellular space of all organs investigated with the exception of kidney. Therefore, in postabsorptive dogs, the plasma SA of the transaminated product of the infused labeled KIC or leucine is an excellent predictor of the intracellular leucine SA in all tissues investigated with the exception of kidney.

Animals↗