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At least 289 records · Page 16Linked to original sources
PubMed1975

Effect of alterations in extracellular fluid volume on segmental sodium transport.

This review focuses on the segmental handling of sodium during alterations in extracellular fluid volume. There is abundant evidence that proximal tubular sodium reabsorption is inhibited by Ringer loading but there are also unequivocal data demonstrating that inhibition of a more distal nephron segment is required for a maximal natriuretic response. From the evidence at hand presently, it would seem that, of the distal nephron segments, only the collecting duct is inhibited by expansion of the extracellular volume per se.

Animals↗
PubMed1996

Recirculatory pharmacokinetic models of markers of blood, extracellular fluid and total body water administered concomitantly.

Pharmacokinetic models were developed to describe the disposition of markers of extracellular fluid (inulin) and total body water (antipyrine) from the moment of injection to incorporate the intravascular mixing component, determined by a marker of intravascular space (indocyanine green, ICG). The simultaneous dispositions of these markers were characterized in four halothane-anesthetized dogs. After injection of ICG, [14C]-inulin, and antipyrine into the right atrium, femoral arterial blood samples were collected every 3 sec for 1 min and less frequently to 20 min for ICG and to 360 min for inulin and antipyrine. ICG and antipyrine concentrations were measured by high-performance liquid chromatography and [14C]-inulin concentrations were measured by liquid scintillation counting. The marker concentration histories were characterized completely by fully identifiable recirculatory compartmental models. Because neither ICG nor inulin distribute beyond intravascular space before recirculation, their first-pass data were modelled simultaneously to improve confidence in central circulation model parameters. This central circulation model included an estimate of cardiac output that was retained in the recirculatory models of all markers. Three tissue compartments were identified for antipyrine, a lipid soluble marker that equilibrates with tissue (including the lung) and estimates total body water and tissue blood flow. The hydrophilic marker, inulin, diffuses into interstitial fluid so slowly that only two extravascular compartments were identified. These models may be used to determine how cardiac output and its distribution, pulmonary drug uptake, and nondistributive blood flow contribute to variability in patient response to drugs with a rapid onset of effect.

Animals↗
PubMed1986

Extracellular fluid proteins of goldfish brain: evidence for the presence of proteases and esterases.

Preparations of enriched fractions of extracellular fluid (ECF) proteins from goldfish brain were found to contain protease(s) and esterase(s). The N-substituted furanacryloyl (FA) peptides FA-Phe-Gly-Gly and FA-Phe-OMe were used as model substrates for determining protease and esterase activity, respectively, in a spectrophotometric assay. Studies of the profile of substrate specificity and identification of the types of compounds that were effective as inhibitors showed that these ECF enzymes have some distinctive properties. GSH, but not GSSG, and EDTA inhibited the protease(s) without influencing the esterase(s), whereas L-1-tosylamide-2-phenylethylchloromethyl ketone blocked both protease and esterase activities of ECF. Most of the protease and esterase properties of ECF could be bound to concanavalin A-Sepharose affinity chromatographic columns in association with ependymin--a brain extracellular protein. These observations indicate that ECF may contain a metalloprotease(s) and raise the possibility that the ependymins might be a substrate for these ECF enzymes.

Animals↗
PubMed1991

Dynamic changes in extracellular fluid ascorbic acid monitored by in vivo electrochemistry.

Voltammetric carbon fiber electrodes and a measuring protocol were designed to monitor extracellular changes in rat brain ascorbic acid (AA). Very fast variations of AA (less than 60 s in duration) as well as much slower changes can be followed. Basal and stimulated levels of AA, determined with the enzyme ascorbate oxidase (AAO), confirm the detection is selective for AA. Microinjections of glutamate (Glu) into various brain regions gave rise to rapid electrochemical signals ascribed to the efflux of AA into the extracellular fluid.

Animals↗
PubMed1986

Sodium chloride, extracellular fluid volume, and blood pressure regulation.

Data from humans and experimental animals indicate that hypertensive diseases triggered by extracellular fluid volume expansion are characterized, in their chronic phases, by relatively normal blood volume (BV) and heightened pressure-volume relationship may be viewed as corresponding to a condition of "virtual hypervolemia," where BV is inappropriately "high" relative to blood pressure. The limited data available on the phasic relationship between these variables indicate that the BV expansion appears to be a prerequisite to alterations in vascular ion metabolism, that both of these changes precede the rise in blood pressure, and that structures within the central nervous system may be a critical link between the body fluid volumes and vascular functional changes. In contrast, hypertensive diseases triggered by secretion of pressor agents or their precursors appear to be characterized in their chronic phases by low BV. These relationships and the associated alterations in plasma aldosterone and renin levels are summarized for a variety of clinical syndromes, including essential hypertension and pregnancy-induced hypertension. Direct or indirect evidence of a primary or secondary defect in renal function is apparent as an underlying event in many of these diseases.

Animals↗
PubMed1996

[Effect of dl-3-n-butylphthalide (NBP) on purine metabolites in striatum extracellular fluid in four-vessel occlusion rats].

The effects of NBP on concentrations of some purine metabolites in extracellular fluid of rat striatum during global ischemia and reperfusion were studied. Global ischemia was produced by the four-vessel occlusion method. Push-pull cannula was implanted stereotaxically into the striatum of rat and was perfused with Ringer's solution at a flow rate of 2.5 microliters.min-1. The level of adenosine(Ade), inosine(Ino), hypoxanthine(Hyp) and xanthine(Xan) in perfusates were measured with HPLC connected with a UV detector. The results indicate that the levels of ade, ino, hyp and xan were significantly increased (about 3-5 times of initial value) during cerebral ischemia and reperfusion. NBP at the dose of 20 or 40 mg.kg-1 given intra-peritoneally 20 min before ischemia was shown to depress the increase of ade, ino, hyp and xan during ischemia and reperfusion dose dependently. But no change in the level of purine metabolites was found in sham operated rats. It has been known that harmful free radicals were produced when xan and uric acid were formed by xanthine oxidase during reperfusion. This might be important for the development of ischemic injuries. Our findings suggest that the effect of NBP might be beneficial for protection against post-ischemic neuronal damage.

Adenosine↗
PubMed1997

Bioelectrical impedance changes in regional extracellular fluid alterations.

The purpose of this study was to determine whether changes in bioelectrical impedance (BI) can reveal regional extracellular fluid (ECF) alterations. ECF changes were induced by holding various arm positions for ten minutes, and they were evaluated through the measurement of BI in eight normal adult subjects. A low frequency current (100 Hz, 0.50 mA) was applied using an electromyography machine through two current electrodes, and the voltage signals were recorded by two amplitude electrodes. The corresponding BI was calculated by Ohm's law, resistance = voltage/current (R = V/I). There was no significant difference between BI and time interval, but between BI and arm position (two-way ANOVA with replicate, p = 0.954, p < 0.001). BI has a negative correlation with wrist circumference. These results show that this experimental method can be used as reflection of ECF changes and that both position and wrist circumference are major factors for BI in the upper extremity.

Adult↗
PubMed1993

Uterine extracellular fluid volume and blood flow after artificial uterine stimulation to rats differentially sensitized for the decidual cell reaction.

Uterine extracellular fluid volume (ECFV) and blood flow (BF) were assessed after unilateral intrauterine injection of sesame oil to rats given either ideal sensitization for the decidual cell reaction or one of several forms of non-ideal sensitization. The study was intended to determine how changes in uterine ECFV and BF might contribute to the Evans blue dye reaction that can be elicited during early decidualization. Uterine ECFV was determined by the uterine volume of distribution of 51Cr-EDTA after its i.v. injection; BF was determined by the radioactive microsphere technique. ECFV was significantly greater in oil-injected than in control horns by 8 h after deciduogenic stimulation, reaching a maximum of 0.63 +/- 0.06 microliter/mg (p < 0.05) in oil-injected horns at 16 h. Ideal temporal sensitization and sensitization with estrogen both were essential to obtain the significantly increased ECFV in stimulated horns. Although absolute uterine BF increased to oil-injected horns, the increase matched uterine weight gains, making relative uterine BF similar for both horns (3-4 microliters/min/mg) at all times after unilateral deciduogenic stimulation. Ideal sensitization did not significantly alter the relative uterine BF. The increase in ECFV occurs at a similar time and requires the same ideal sensitization as the stimulation-induced increase in endometrial vascular permeability described previously, suggesting that these events are under similar control. We suggest that enzymatic changes to the uterine extracellular matrix may contribute to the Evans blue reaction by creating a larger compartment into which protein-dye complexes may diffuse.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Abnormal relation of extracellular fluid volume and exchangeable sodium with systemic arterial pressure in early borderline essential hypertension.

Interrelations between systemic arterial pressure, extracellular fluid (ECF) volume, exchangeable sodium (Na) and the renin-angiotensin-aldosterone system were studied in 38 young patients with borderline hypertension and in 37 age- and sex-matched control subjects. ECF volume and exchangeable Na were subnormal (not significant) in borderline hypertension. In normal subjects, volume data did not relate to arterial pressure; in contrast, negative correlations were observed between arterial pressure and ECF volume or exchangeable Na in patients with borderline hypertension (in hypertensive women, r greater than or equal to 0.7, p less than 0.01). Plasma renin activity was consistently elevated in borderline hypertension, mainly in the upright posture, and these values were inversely correlated with ECF volume and exchangeable Na. No correlation was observed between arterial pressure and plasma renin activity. These results show that slight elevation of arterial pressure in the early stage of hypertension induces a proportional decrease in ECF volume, suggesting that the phenomenon of pressure-natriuresis is operative in young borderline hypertensive persons. The renin-angiotensin system is activated in these patients, in part to preserve sodium homeostasis.

Adult↗
PubMed1975

Time course of exchanges between red cells and extracellular fluid during CO2 uptake.

A stopped-flow rapid-reaction apparatus was used to follow the time course of extracellular pH in a human red cell suspension following a sudden increase in PCO2. The extracellular pH change was slow (t1/2 similar to 3.5 s) considering the presence of carbonic anhydrase in the cells. When carbonic anhydrase was added to the extracellular fluid, the half-time was reduced to less than 20 ms. The explanation for these phenomena is that the equilibration of H+ across the red cell membrane is rate-limited by the uncatalyzed reaction CO2 plus H2O formed from H2CO3 outside the cells. A theoretical model was developed which successfully reproduced the experimental results. When the model was used to simulate CO2 exchange in vivo, it was determined that blood PCO2 and pH require long times (greater than 50 s) to approach equilibrium between cells and plasma after leaving an exchange capillary. We conclude that cell-plasma equilibrium may never be reached in vivo, and that in vitro measurements of these quantities may not represent their true values at the site of sampling.

Carbon Dioxide↗
PubMed2002

Striking differences in glucose and lactate levels between brain extracellular fluid and plasma in conscious human subjects: effects of hyperglycemia and hypoglycemia.

Brain levels of glucose and lactate in the extracellular fluid (ECF), which reflects the environment to which neurons are exposed, have never been studied in humans under conditions of varying glycemia. The authors used intracerebral microdialysis in conscious human subjects undergoing electrophysiologic evaluation for medically intractable epilepsy and measured ECF levels of glucose and lactate under basal conditions and during a hyperglycemia-hypoglycemia clamp study. Only measurements from nonepileptogenic areas were included. Under basal conditions, the authors found the metabolic milieu in the brain to be strikingly different from that in the circulation. In contrast to plasma, lactate levels in brain ECF were threefold higher than glucose. Results from complementary studies in rats were consistent with the human data. During the hyperglycemia-hypoglycemia clamp study the relationship between plasma and brain ECF levels of glucose remained similar, but changes in brain ECF glucose lagged approximately 30 minutes behind changes in plasma. The data demonstrate that the brain is exposed to substantially lower levels of glucose and higher levels of lactate than those in plasma; moreover, the brain appears to be a site of significant anaerobic glycolysis, raising the possibility that glucose-derived lactate is an important fuel for the brain.

Adolescent↗
PubMed2000

Distribution of gacyclidine enantiomers in spinal cord extracellular fluid.

PURPOSE: Determination of the pharmacokinetics of gacyclidine enantiomers, a non-competitive NMDA antagonist, in plasma and spinal cord extracellular fluid (ECF) of rats. METHODS: Implantation of microdialysis probes in spinal cord (T9). Serial collection of plasma samples and ECF dialysates over 5 hours after IV bolus administration of (+/-)-gacyclidine (2.5 mg/kg). Plasma protein binding determined in vivo by equilibrium dialysis. Chiral GC/ MS assay. RESULTS: Plasma concentrations of (+)-gacyclidine were approximately 25% higher than those of (-)-gacyclidine over the duration of the experiment in all animals. Plasma concentrations decayed in parallel in a biphasic manner (t1/2alpha approximately 9 min; t1/2beta approximately 90 min) with no significant difference between enantiomers. Clearance and volume of distribution of (-)-gacyclidine were approximately 20% higher than those of its optical antipode (CL: 248 vs 197 ml.kg(-1)x min(-1); Vdbeta: 31.6 vs 23.5 1/kg). Protein binding (approximately 90%) was not stereoselective. Both gacyclidine enantiomers were quantifiable in spinal cord ECF 10 min after drug administration and remained stable over the duration of the experiment in spite of changing blood concentrations. Penetration of (-)-gacyclidine was significantly higher (approximately 40%) than that of (+)-gacyclidine in all animals. Yet, exposure of spinal cord ECF was similar for both enantiomers, and not correlated with plasma AUCs. CONCLUSIONS: The disposition of gacyclidine enantiomers is stereoselective. Both enantiomers exhibit a high affinity for spinal cord tissue and their distribution may involve a stereoselective and active transport system. This hypothesis could also explain the discrepancy between drug concentrations in plasma and spinal cord ECE

Animals↗
PubMed1988

Differentiation of dopamine overflow and uptake processes in the extracellular fluid of the rat caudate nucleus with fast-scan in vivo voltammetry.

Stimulated overflow of dopamine (DA) into the extracellular fluid of the rat caudate nucleus was measured with fast-scan cyclic voltammetry. DA concentrations were sampled in less than 10 ms at 100-ms intervals with a Nafion-coated, carbon-fiber microelectrode. Overflow of DA was induced by electrical stimulation of the medial forebrain bundle with 300-microA pulses of various duration and frequency. Stimulated overflow was measured as a function of stimulus duration before and after administration of benztropine, bupropion, and amphetamine. These results were correlated with simulated curves based on a simple uptake/overflow model. The observed overflow was assumed to be a function of [DA]p, the concentration of DA which overflows per stimulus pulse, and the kinetics of cellular uptake of DA. Correlation of experimental with stimulated results was obtained at the 95% confidence limit for the duration studies; however, it was not possible to distinguish between the effects of pharmacological agents on uptake and overflow. In contrast, modulation of stimulus frequency did permit such distinction. Simulations of an increase in [DA]p fit results following dihydroxyphenylalanine methyl ester at 95% confidence limits, whereas an equivalent change in the apparent Km did not fit. An increase in the apparent value of Km correlated with results obtained at different frequencies following nomifensine and bupropion administration at the 95% confidence limit, whereas an equivalent increase in [DA]p did not fit. The effects of GBR 12909 best correlated with an increase in the DA available for overflow.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2003

Measurement of both native and inactivated forms of alpha1 proteinase inhibitor in human inflammatory extracellular fluids.

BACKGROUND: Inactivation of the elastase inhibitor, alpha1 proteinase inhibitor (alpha1PI), may be of pathogenic significance in inflammatory diseases like periodontal disease. Two key mechanisms of inactivation appear to be (a) the formation of an alpha1PI-elastase complex and (b) proteolytic cleavage by elastase or other enzymes such as metalloproteinases of host origin or enzymes of bacterial origin. Based on the different heat stabilities of the intact, complexed and proteolytically cleaved forms of alpha1PI, an enzyme-linked immunosorbent assay (ELISA) that allowed the simultaneous measurement of native and inactive forms of alpha1PI was developed. METHODS: The ELISA method described employs a commercially available antibody and represents a rapid, reproducible and sensitive method for studying alpha1PI inactivation in human inflammatory diseases. The assay was applied to normal human plasma and to human extracellular fluids obtained from patients with inflammatory diseases such as adult periodontitis and rheumatoid arthritis. Samples from patients with osteoarthritis, a "non-inflammatory" joint disease, were also studied. RESULTS: The findings expressed as the mean percentage (+/-SD) of the total alpha1PI that was inactivated were as follows: gingival crevicular fluid from adult periodontitis patients: 73.5+/-16.6% (n=12); normal human plasma: 8.4+/-4.9% (n=13); knee-joint synovial fluid (SF) from rheumatoid arthritis patients: 12.5+/-4.5% (n=15); plasma from rheumatoid arthritis patients: 8.0+/-1.8% (n=15); knee-joint SF from osteoarthritis patients: 8.6+/-8.2% (n=14); plasma from osteoarthritis patients: 5.7+/-4.8% (n=14). The results obtained by ELISA were in good agreement with those obtained by the semi-quantitative method of SDS-PAGE and Western blotting. CONCLUSIONS: We have shown that the differential heat stability of alpha1PI may be utilised as the basis for a rapid, sensitive and reproducible ELISA assay of alpha1PI inactivation. In gingival crevicular fluid from periodontal disease patients, alpha1PI is mainly inactivated and the extent of this inactivation is much higher than in inflammatory fluids from other chronic diseases such as rheumatoid arthritis. This assay could be useful in monitoring the progression of periodontal disease.

Adult↗
PubMed1979

[Plasma renin activity, plasma volume extracellular fluid volume and cardiac output in essential hypertension (author's transl)].

The plasma renin activity (PRA), the plasma volume (PV), the extracellular fluid volume (ECV), the cardiac output and the peripheral vascular resistance (TPR) were determined in 51 patients (14 women, 37 men) with essential hypertension of varying severity. The following findings were achieved: 1. In 9 of the 51 patients with essential hypertension (approximately 18%) a low and non-sensitive PRA was detected. 2. PV, ECV, cardiac output and the calculated peripheral vascular resistance of the essential hypertensive patients with low and non-sensitive PRA did not differ significantly from those of the essential hypertensive patients with normal or elevated PRA. 3. The hypertensive patients with low and nonsensitive PRA had the highest average arterial pressure. From these findings it can be concluded that the essential hypertensive patients with low PRA are not an homogeneous group. It is assumed that in a subgroup the elevated blood pressure may be the cause of the renin suppression.

Adult↗