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At least 307 records · Page 17Linked to original sources
PubMed1987

Plasma, red blood cell, total blood, and extracellular fluid volumes in healthy horse foals during growth.

During the growth interval encompassing age 2 days through 24 weeks, plasma, RBC, total blood, and extracellular fluid (ECF) volumes were determined in 7 healthy, resting foals. Evans blue dye and sodium thiocyanate were used to estimate plasma and ECF volumes, respectively. Absolute plasma volume remained stable from 2 days through 2 weeks of age, then increased progressively through 24 weeks of age. After decreasing between 2 days and 2 weeks of age, absolute RBC and total blood volumes progressively increased. Absolute ECF volume increased progressively from 2 days of age through 24 weeks of age, but plasma, RBC, and total blood volumes decreased relative to body weight increase. During the first 12 weeks of life, ECF volume decreased relative to body weight increase, and then remained stable during the next 12 weeks. There were close correlations between age, as well as body weight, and plasma, RBC, total blood, and ECF volumes. The relationship defined between age and the respective fluid and blood volumes provided a useful tool for evaluation and management of alterations of fluid balance in the foal.

Animals↗
PubMed1989

Urine electrolytes in the assessment of extracellular fluid volume contraction.

The purpose of this study was to determine which urine electrolytes should be measured to confirm that the extracellular fluid (ECF) volume is depleted. ECF volume contraction was induced by furosemide administration to rats consuming an electrolyte-free diet. An external potassium balance was achieved by replacing potassium losses with KHCO3 and KCl so that the sodium and chloride deficits were comparable (equivalent to a 30% reduction in ECF volume). As expected, the urine sodium and chloride concentrations fell to 2 +/- 0.3 mmol/l and 3 +/- 0.3 mmol/l, respectively. Rats were then randomized to receive 50-75% of their sodium or chloride deficit as either: NaCl (control group), NH4Cl or NaHCO3 to mimic clinical situations associated with ECF volume contraction. In the NaCl group, the urine sodium and chloride concentrations remained low (6 +/- 2 mmol/l and 7 +/- 2 mmol/l), consistent with persistent ECF volume contraction. Although the NH4Cl group continued to have a low urine sodium concentration (2 +/- 0.2 mmol/l), there was now a marked increase in the urine chloride concentration (51 +/- 7 mmol/l; p less than 0.01 vs. NaCl group). In contrast, although the NaHCO3 group continued to have a low urine chloride concentration (2 +/- 1 mmol/l), there was a significant increase in the urine sodium concentration (19 +/- 3 mmol/l; p less than 0.01 vs. NaCl group). We conclude that the clinical assessment of ECF volume by urine electrolytes requires an evaluation of both the urine sodium and chloride concentrations.

Ammonium Chloride↗
PubMed1993

[HPLC--detection of hydroxyl radicals in striatum extracellular fluid in rats subjected to reperfusion after cerebral ischemia and the action of vitamin E].

The formation of hydroxyl radical in the extracellular fluid in striatum of rats subjected to 4-vessel occlusion during ischemia and reperfusion was measured by HPLC with UV detector using salicylic acid as a trapping agent. Hydroxyl radicals react with salicylic acid yielding 2,3- and 2,5-dihydroxybenzoic acids which can be separated by liquid chromatography. The striatum was perfused with artificial cerebrospinal fluid containing 0.5 mmol.L-1 salicylic acid at a flow rate of 2.5 microliters.min-1. The results indicate that the concentration of 2,5-dihydroxybenzoic acid in the perfusates was highest during 25 min reperfusion and no change was found during ischemia. Vit E at 30, 60 and 120 mg.kg-1 i.p. 20 min before ischemia was shown to dose dependently suppress the rise of 2,5-dihydroxybenzoic acid after reperfusion. The results suggest that the HPLC method is useful and reliable for the measurement of hydroxy radical in global ischemia in vivo.

Animals↗
PubMed2004

Sustained and generalized extracellular fluid expansion following heat acclimation.

We measured intra- and extravascular body-fluid compartments in 12 resting males before (day 1; control), during (day 8) and after (day 22) a 3-week, exercise-heat acclimation protocol to investigate plasma volume (PV) changes. Our specific focus was upon the selective nature of the acclimation-induced PV expansion, and the possibility that this expansion could be sustained during prolonged acclimation. Acclimation was induced by cycling in the heat, and involved 16 treatment days (controlled hyperthermia (90 min); core temperature = 38.5 degrees C) and three experimental exposures (40 min rest, 96.9 min (s.d. 9.5 min) cycling), each preceded by a rest day. The environmental conditions were a temperature of 39.8 degrees C (s.d. 0.5 degrees C) and relative humidity of 59.2% (s.d. 0.8%). On days 8 and 22, PV was expanded and maintained relative to control values (day 1: 44.0 +/- 1.8; day 8: 48.8 +/- 1.7; day 22: 48.8 +/- 2.0 ml kg(-1); P < 0.05). The extracellular fluid compartment (ECF) was equivalently expanded from control values on days 8 (279.6 +/- 14.2 versus 318.6 +/- 14.3 ml kg(-1); n= 8; P < 0.05) and 22 (287.5 +/- 10.6 versus 308.4 +/- 14.8 ml kg(-1); n= 12; P < 0.05). Plasma electrolyte, total protein and albumin concentrations were unaltered following heat acclimation (P > 0.05), although the total plasma content of these constituents was elevated (P < 0.05). The PV and interstitial fluid (ISF) compartments exhibited similar relative expansions on days 8 (15.0 +/- 2.2%versus 14.7 +/- 4.1%; P > 0.05) and 22 (14.4 +/- 3.6% versus 6.4 +/- 2.2%; P= 0.10). It is concluded that the acclimation-induced PV expansion can be maintained following prolonged heat acclimation. In addition, this PV expansion was not selective, but represented a ubiquitous expansion of the extracellular compartment.

Acclimatization↗
PubMed1975

The influence of the extracellular fluid volume on the tubular reabsorption of uric acid.

Changes is tubular reabsorption of uric acid in response to alterations in the extracellular fluid volume (ECFV) were examined in rats by clearance studies and by direct intratubular microinjections. Contraction of the ECFV led to a rise in the serum uric acid concentration and a 47% decrease in the clearance of uric acid. The ratio of uric acid to inulin clearance also fell, indicating an increase in the net tubular reabsorption of urate. Volume expansion resulted in an increase in the urate clearance and a 37% decrease in the net tubular reabsorption of uric acid. To localize the site in the nephron where these changes occur, microinjections of [2-14C]urate were performed. The lack of conversion of radioactive urate to allantoin after microinjections was demonstrated by thin-layer chromatography. After contraction of the ECFV, urinary recoveries of uric acid were significantly decreased after microinjections into proximal tubular sites. In contrast, recoveries were increased from these proximal sites after volume expansion. No evidence for distral reabsorption was obtained in any group of animals. These studies demonstrate that net urate reabsorption is influenced by the state of hydration of the ECFV and that these alterations are mediated by changes in the rates of reabsorption in the proximal tubule.

Allantoin↗
PubMed1999

Pharmacokinetics of methotrexate in the extracellular fluid of brain C6-glioma after intravenous infusion in rats.

PURPOSE: Establishment of the pharmacokinetic profile of methotrexate (MTX) in the extracellular fluid (ECF) of a brain C6-glioma in rats. METHODS: Serial collection of plasma samples and ECF dialysates after i.v. infusion of MTX (50 or 100 mg/kg) for 4 h. HPLC assay. RESULTS: Histological studies revealed the presence of inflammation, edema, necrosis, and hemorrhage in most animals. In vivo recovery (reverse dialysis) was 10.8 +/- 5.3%. MTX concentrations in tumor ECF represented about 1-2% of the plasma concentrations. Rapid equilibration between MTX levels in brain tumor ECF and plasma. ECF concentrations almost reached steady-state by the end of the infusion (4 h), then decayed in parallel with those in plasma. Doubling of the dose did not modify MTX pharmacokinetic parameters (t1/2alpha, t1/2beta, MRT, fb, Vd, and CL(T)), except for a 1.7-fold increase of AUC(Plasma) and a 3.8-fold increase in AUC(ECF), which resulted in a 2.3-fold increase in penetration (AUC(ECF)/AUC(Plasma)). In spite of an important interindividual variability, a relationship between MTX concentrations in plasma and tumor ECF could be established from mean pharmacokinetic parameters. CONCLUSIONS: High plasma concentrations promote the penetration of MTX into brain tissue. However, free MTX concentrations in tumor ECF remain difficult to predict consistently.

Animals↗
PubMed2002

Zidovudine concentration in brain extracellular fluid measured by microdialysis: steady-state and transient results in rhesus monkey.

We measured zidovudine concentrations in blood, muscle, and brain extracellular fluid (ECF) by microdialysis and in serum ultrafiltrate and cerebrospinal fluid (CSF) samples during a continuous intravenous infusion (15 mg/kg/h) and after bolus dosing (50-80 mg/kg over 15 min) in nonhuman primates to determine whether CSF drug penetration is a valid surrogate for blood-brain barrier penetration. Recovery was estimated in vivo by zero net flux for the continuous infusion and retrodialysis for the bolus dosing. In vivo recovery was tissue-dependent and was lower in brain than in blood or muscle. Mean (+/-S.D.) steady-state blood, muscle, and brain zidovudine concentrations by microdialysis were 112 +/- 63.8, 105 +/- 51.1, and 13.8 +/- 10.4 microM, respectively; and steady-state serum ultrafiltrate and CSF concentrations were 81.2 +/- 40.2 and 14.1 +/- 8.0 microM, respectively. Brain ECF penetration (microdialysis brain/blood ratio) and CSF penetration (standard sampling CSF/serum ratio) at steady state were 0.13 +/- 0.06 and 0.17 +/- 0.02, respectively. With bolus dosing the mean (+/-S.D.) zidovudine area under concentration-time curve (AUC) normalized to a dose of 80 mg/kg was 577 +/- 103 microM. h in blood, 528 +/- 202 microM. h in muscle, and 108 +/- 74 microM. h in brain (brain/blood ratio of 0.18 +/- 0.10) by microdialysis. Serum ultrafiltrate AUC was 446 +/- 72 microM. h and the CSF AUC was 123 +/- 4.7 microM. h (CSF/serum ratio of 0.28 +/- 0.06). In conclusion, recovery was tissue-dependent. CSF and brain ECF zidovudine concentrations were comparable at steady state, and the corresponding AUCs were comparable after bolus injection. Thus, zidovudine penetration in brain ECF and CSF in nonhuman primates is limited to a similar extent, presumably by active transport, as in other species.

Animals↗
PubMed1990

[A compartment analysis of the significance of extracellular fluid volume for body fluid dynamics].

The curve of a reduction in plasma concentration of the indicator substance creatinine for a period of 120 to 240 min was investigated after single intravenous administration of creatinine in a dose of 150 mg/kg on dogs. A model for two compartment distribution of the indicator substance was used as the first compartment was intravasal, but the second--interstitial space of body fluids. The following parameters were estimated: renal clearance, volume of distribution, glomerular filtration, intercompartment clearance and velocity constants of transport between the two compartments. An increase of the volume of extracellular fluid (ECF) was induced by intravenous infusion of 2% of sodium chloride solution in the amount of 30 ml/kg. A reduction in the volume of ECF was caused by peritoneal dialysis with isotonic solution of glucose in the amount of 5% of the body mass. After an increase of the volume of ECF there was an increase in the volume of distribution, elevation of glomerular filtration and a reduction in the velocity constant of transport from the intravasal to interstitial fluid. There was a reduction in the volume of distribution, limitation of glomerular filtration and increment of velocity constant of the transport. The established changes in the velocity constants of the transport showed changes in the dynamics of body fluids, which could be due to vasoconstriction or vasodilation as a mechanism of myogenic autoregulation during changes in the volume of ECF.

Animals↗
PubMed1978

Saline-induced natriuresis in the dog without prior exposure of the kidney to the physical effects of expansion of the extracellular fluid compartment.

1. Experiments were carried out in dogs in which renal perfusion pressure was reduced 40 min before beginning expansion of the extracellular fluid space by 10% with isotonic sodium chloride solution. Sodium excretion increased up to 590% of control values in spite of the fact that the filtered load of sodium was below that of the control period and circulating mineralocorticoids were not suppressed. 2. The findings indicate that, in the dog, prior exposure of the kidney to the volume-expanded state is not a prerequisite for natriuresis to occur.

Animals↗
PubMedDate not supplied

Extracellular fluid distribution in rats with chronic one- and two-kidney Goldblatt hypertension.

1. The influence of the intact kidney on blood pressure, extracellular fluid volume (ECF, ferrocyanide space) and ECF volume distribution was studied in rats 60 days after constriction of the contralateral renal artery. 2. Renal artery constriction increased both blood pressure and ECF levels. The rise of both variables was more pronounced in rats with the contralateral kidney removed (one-kidney rats) than with the contralateral kidney intact (two-kidney rats). 3. The interstitial fluid volume increased similarly in both experimental groups, the more pronounced ECF increase in the more severly hypertensive one-kidney rats being due to increased plasma volume. In the less hypertensive two-kidney group the plasma volume was not increased significantly but correlated positively with the blood pressure levels. 4. The plasma volume/interstitial fluid volume ratio was decreased in the two-kidney group but did not differ from control values in the one-kidney group thus resembling the ECF partition reported in the hypo-and hypervolaemic type of essential hypertension, respectively. 5. It is suggested that the antihypertensive influence of the intact kidney may be partly due to its ability to escape from the sodium-retaining mechanism activated by renal artery stenosis, which determines the degree of plasma volume expansion and, in connection with this, also the degree of blood pressure elevation.

Animals↗
PubMed2001

Age-related differences in hippocampal extracellular fluid glucose concentration during behavioral testing and following systemic glucose administration.

Recent evidence indicates that the level of glucose in the brain's extracellular fluid (ECF) is not constant, as traditionally thought, but fluctuates. We determined the effect of aging on hippocampal ECF glucose before, during, and after spatial memory testing. Fischer-344 rats (24 months old) showed a greater decrease in ECF glucose than 3-month-old rats (48% vs 12%); the decrease seen in 24-month-old rats persisted for much longer following testing. These changes were associated with an age-related deficit in spontaneous alternation performance. Following systemic glucose administration, the decrease in ECF glucose was reversed in both aged and young rats, and performance in aged versus young rats following glucose administration did not differ. These findings suggest that increased susceptibility to depletion of ECF glucose in aged rats may contribute to age-related deficits in learning and memory and that administration of glucose may enhance memory by providing additional glucose to the brain at times of increased cognitive demand.

Aging↗
PubMed1984

Respiratory effects of carbon dioxide-induced changes of medullary extracellular fluid pH in cats.

Acute and steady-state responses to hypercapnia of respiratory output, measured as integrated phrenic nerve activity, and medullary extracellular fluid (e.c.f.) pH, measured directly, were determined in paralysed, vagotomized and glomectomized cats. Medullary e.c.f. pH responds within seconds to an acute change of alveolar and arterial PCO2. The respiratory response closely and inversely matches the e.c.f. pH change, but not the cerebrospinal fluid pH change. The medullary e.c.f. pH change following a rapid step-change in end-tidal PCO2 requires at least 5 min for a new steady state to be achieved. Steady-state studies in twenty-six cats show: (a) that the respiratory response to progressive hypercapnic stimulation of the central chemoreceptors is curvilinear (Eldridge, Gill-Kumar & Millhorn, 1981), (b) that the relationship between increasing end-tidal PCO2 and medullary hydrogen ion concentration [(H+]) or changes of pH is linear (r = 0.995); a doubling of PCO2 causes 0.260 units pH change, (c) there is a curvilinear relationship between e.c.f. [H+] and the respiratory response that is the same as that found with CO2. We conclude that medullary e.c.f. pH measured by means of a surface electrode accurately reflects the CO2-induced [H+] stimulus to respiration. The decreasing respiratory responses to identical changes of central chemoreceptor input are due to progressive neuronal saturation of a central pathway between the chemoreceptors and the respiratory controller.

Animals↗
PubMed1985

[Method of determining glomerular filtration rate and extracellular fluid volume in the perioperative phase].

In the course of an investigation concerning the renal response in abdominal surgery, we paid special attention to the precision of determination of the glomerular filtration rate (GFR) and extracellular fluid volume (ECF). The influence of the applied mathematical model on calculation using slope techniques was examined. ECF and GFR were measured by single injection of the radioactive tracer 51Cr-EDTA; plasma samples were taken during the first 4 h postinjection. The results were computed according to the compartmental and noncompartmental model. The correlation between two-compartmental and noncompartmental GFR and ECF values was highly significant. However, values calculated from two-compartmental model were significant lower (p less than 0.01) and differences up to 20% were observed. Calculating ECF by the most widely used approximative method (assuming an early equilibrium between the extra- and intravascular part of ECF) yields incredible high values and correlation to other methods was poor. Based on our data, we conclude that GFR and ECF values obtained by compartmental analysis depend on flow rates between the theoretical compartments. Also the use of two or three exponential components for the plasma curve in the course of noncompartmental analysis (as done by most authors) is not any better than compared conventional compartmental analysis. Noncompartmental analysis should be preferred especially when small changes in ECF and GFR are observed, as it is the more accurate.

Body Fluid Compartments↗
PubMed1979

Brain metabolism and the acquisition of new behaviors. III. Evidence for secretion of two proteins into the brain extracellular fluid after training.

Immunochemical and double labeling experiments were used to demonstrate that at least two out of three brain cytoplasmic proteins, whose metabolism is markedly influenced by behavior, are products which are secreted into the extracellular fluid (ECF) of goldfish brain. Even after 1 h of labeling, the extracts of goldfish brains with 0.32 M sucrose were found to contain highly labeled proteins. Electrophoretic analyses of the proteins, on SDS polyacrylamide gels, indicated that an increased incorporation of [3H]valine occurs for trained animals as compared to untrained controls ([14C]valine) at specific protein bands migrating at 32,000 and 26,000 daltons. The proteins in the ECF gave identical precipitin bands to goldfish brain proteins whose metabolism was responsive to the acquisition of new patterns of behavior and to proteins in CSF. These results are consistant with the hypothesis that the cells which contain the proteins and whose location in the ependymal zone was determined by immunohistochemistry can secrete the products into ECF. It is therefore quite possible that the functional sites of the proteins are away from the locus of their synthesis.

Animals↗
PubMed2002

The redox state of glutathione, cysteine and homocysteine in the extracellular fluid in the skin.

Glutathione, the most abundant low-molecular weight thiol in the skin, has been shown to protect the skin from both photobiological and chemical injury. The thiols, glutathione in particular, have also been shown to be crucially involved in defence against contact allergens. Since the levels of extracellular thiol concentrations are important determinants of intracellular thiol status, we have compared the normal concentrations and the redox status of the main low-molecular weight thiol components in the extracellular fluid at the dermo-epidermal junction with the corresponding plasma levels. In their sulfhydryl form, all three thiols, i.e. glutathione, cysteine and homocysteine, were more abundant in experimental skin blister fluid than in plasma, as were the free disulfides of glutathione and homocysteine, whereas the free disulfides of cysteine were about the same in blister fluid and in plasma. Protein mixed disulfide levels were higher in plasma than in blister fluid. The present results provide information concerning the extracellular defence in the skin.

Blister↗