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At least 343 records · Page 19Linked to original sources
PubMed1976

Normal renin uremic hypertension. Study of cardiac hemodynamics, plasma volume, extracellular fluid volume, and the renin angiotensin system.

Studies were undertaken in 33 uremic patients with or without hypertension, 11 normal subjects, and 15 essential hypertensive patients to assess cardiac hemodynamics, plasma volume, extracellular fluid volume, and peripheral renin levels. Cardiac output and intraarterial blood pressure were measured and peripheral vascular resistance index calculated. These studies suggest that uremic hypertension with normal renin values and hypervolemia is hemodynamically sustained by an increase in peripheral resistance rather than by an increased cardiac output. The renin angiotensin system plays a secondary role as compared to overexpansion in the genesis of hypertension in normoreninemic uremic hypertension.

Adolescent↗
PubMed2004

Increases in extracellular fluid glucose levels in the rat hippocampus following an anesthetic dose of pentobarbital or ketamine-xylazine: an in vivo microdialysis study.

Using in vivo microdialysis, we examined glucose levels in the extracellular fluid (ECF) of the hippocampus and in the blood prior to and during pentobarbital (45 mg/kg) or ketamine-xylazine (66 mg/kg, 7 mg/kg) anesthesia. Anesthesia with either pentobarbital or ketamine-xylazine significantly increased hippocampal ECF glucose levels (mean peak increases of +71% and +85%, respectively). In addition, there were substantial increases in blood glucose levels (mean peak increases of +24% and +30%, respectively). The increased levels of hippocampal ECF glucose during anesthesia complement past evidence for decreases in ECF glucose in the hippocampus observed while rats perform a memory task sensitive to hippocampal damage, providing further support for the view that ECF glucose levels in the hippocampus are dynamically coupled to local neural activity.

Analgesics↗
PubMed1996

[Dynamic changes of amino acids in extracellular fluid in rat hippocampus in cases of cerebral ischemia].

OBJECTIVE: To study the changes of excitatory amino acid (EAA) in patients with cerebral ischemia. METHODS: We observed dynamic changes of EAA in extracellular fluid by intracerebral microdialysis inserted in hippocampus through stereotaxic method with modified Pulsinelli's model of four vessels occlusion. RESULTS: The concentration of Glu was 5.88 +/- 1.40 and 11.2 +/- 1.5 micromol/L in patients with incomplete cerebral ischemia after 30 minutes and 60 minutes, and the concentration of Asp was 2.72 +/- 0.24 and 4.4 +/- 0.6 micromol/L. The concentration of Glu was 15.1 +/- 1.6 micromol/L and 17.9 +/- 1.6 micromol/L in patients with complete cerebral ischemia after 30 minutes and 60 minutes, and the concentration of Asp was 8.2 +/- 1.0 and 12.1 +/- 1.1 micromol/L. The concentration of Glu and Asp was 1.75 +/- 0.88 micromol/L and 0.24 +/- 0.09 micromol/L in the controls. CONCLUSIONS: In this study, the concentration of Glu and Asp in patients with cerebral ischemia was significantly increased than in the controls, and the more serious ischemia was, the more release of EAA. It is suggested that Dansen injection can reduce the release of EAA by cerebral cells in case of ischemia.

Amino Acids↗
PubMed1994

Serum potassium, hydrogen ion and magnesium: neuromuscular regulation by variation of cation concentration in the extracellular fluid?

It is a common clinical observation that changes in serum [K] are frequently associated with changes in serum [H] and/or [Mg]. Thus, hypokalaemia and alkalosis are associated, as are hyperkalaemia and acidosis, and hypokalaemia and hypomagnesaemia. Most investigators would accept that these ions have important roles in the maintenance of neuromuscular excitability. Extracellular potassium exerts its effect by defining the potassium gradient across the cell membrane and therefore the membrane potential in the resting state; magnesium and hydrogen ion 'screen' negative charges on the surface of nerve cells, modulating the local transmembrane potential gradient, to which the voltage-sensitive channels governing the initiation of the action potential respond. It is pointed out here that the changes in ionic concentration observed in pathophysiology are not incompatible with the idea that the associated changes reflect regulatory events in the extracellular fluid designed to preserve excitability.

Animals↗
PubMed1986

Extracellular fluid volume during pneumothorax and hypoxemia in rabbits.

This study was designed to test the hypothesis that persistent pneumothorax of greater than or equal to 6 days duration causes a decrease of extracellular fluid volume (ECF). Such changes are of interest as they may be causally related to persistent hypotension that has occurred in humans following pneumothorax evacuation. Experiments were done in rabbits to determine the effect on ECF of persistent pneumothorax with or without systemic hypoxemia. Animals were divided into four treatment groups: 1) pneumothorax with hypoxemia [fractional concentration of O2 in inspired gas (FIO2) = 0.21, n = 30], 2) pneumothorax without hypoxemia (FIO2 = 0.40, n = 25), 3) hypoxemia alone (FIO2 = 0.14, n = 11), and 4) normal controls (FIO2 = 0.21, n = 15). Measurements of ECF were made in the base-line control state and after 6 days of treatment using the dilution volume of thiocyanate sodium as an estimate of ECF volume. We found a reduction of ECF in 53% of animals with pneumothorax plus hypoxemia (range -47% to +13%) and in 54% of animals with hypoxemia alone (range -26% to +25%). ECF declined in only 7% of normal controls and 20% of animals with pneumothorax without hypoxemia. Arterial O2 tensions after 6 days of treatment were 58 +/- 12.6, 141 +/- 28, 60 +/- 5.1, and 97 +/- 9.3 Torr (mean +/- SD) in groups 1-4, respectively. The results suggest that pneumothorax with hypoxemia or hypoxemia alone may contribute to depletion of ECF, but this response is variable and unpredictable in individual animals.

Animals↗
PubMed1999

Age-dependent differences in the relationship between plasma and brain extracellular fluid concentrations of magnesium after MgSO4 infusions in miniswine.

Magnesium is a potential neuroprotective agent in the treatment of head injury and ischemia whose efficacy is likely determined by increases in brain extracellular fluid (ECF) magnesium, which in turn depends on its concentration in plasma. The objectives of this study were to: 1) examine the effects of increasing plasma magnesium concentration ([Mg]plasma) to 4-6 mM on brain ECF magnesium concentration ([Mg]ECF) and 2) determine whether maturational changes occur in the transfer of magnesium into brain ECF for newborn and more mature (approximately 1 month old) miniswine. Increases in [Mg]plasma by systemic administration of MgSO4 resulted in similar maximal elevations in brain [Mg]ECF for both age groups (193+/-76% versus 253+/-106% of control for newborn and 1-month-old miniswine, respectively). Calculations of half-lives (t1/2) for the increase and decrease in magnesium concentration (t1/2 uptake and t1/2 clearance) were used to characterize magnesium kinetics in plasma and brain ECF. Plasma magnesium uptake was shorter in 1-month-old (t1/2 = 11.1+/-0.9 min) compared with newborns (12.9+/-1.7 min, p < 0.05). The faster increase in [Mg]plasma probably contributed to a faster uptake of brain [Mg]ECF in 1-month-old compared with newborn swine (t1/2 uptake = 27.9+/-12.8 versus 46.0+/-20.9 min, respectively, p < 0.05). Although plasma magnesium clearance was shorter in 1-month-old swine compared with newborn (t1/2 = 34.3+/-7.0 versus 74.7+/-33.7 min, respectively, p < 0.05), the clearance of magnesium from the brain ECF was similar for each age group. Reductions in blood pressure and heart rate occurred during hypermagnesemia and were similar in each age group. This study shows that acute elevations in [Mg]plasma to 4-6 mM result in similar relative increases in brain [Mg]ECF for both newborn and 1-month-old miniswine. However, there are maturational differences, as demonstrated by the faster rate of magnesium uptake into the ECF observed in the older miniswine.

Animals↗
PubMed1988

Acute changes in extracellular fluid volume modify the antroduodenal flow of saline in dogs: a possible physiological role.

The antroduodenal (AD) flow of saline was measured in anesthetized dogs following two different protocols of acute changes in extracellular fluid (ECF) volume. ECF expansion by iv infusion of saline before or after hemorrhage decreased the AD flow; conversely, hemorrhage before or after expansion increased flow. These alternating modifications in the AD flow are independent of the sequence of volemic changes and may constitute part of the homeostatic responses of the gut to confront life-threatening situations such as accidental hyperhydration or hemorrhage.

Animals↗
PubMed1978

Changes in plasma volume and extracellular fluid volume after addition of prazosin to propranolol treatment in patients with hypertension.

In fifteen patients with hypertension, inadequately controlled during treatment with propranolol alone (mean dosage 333 mg/day), plasma volume (PV) and extracellular fluid volume (ECV) were determined. After addition of prazosin for 3 months (mean dosage 9 mg/day) there was a significant increase in PV and ECV, on average 8 and 5%, respectively. The decrease in supine blood pressure, systolic as well as diastolic, was very modest, on average 11 mmHg (SD +/- 12) and 4 mmHg (SD +/- 7), respectively. The changes in standing blood pressure were more pronounced. It is assumed that the expansion of PV and ECV contributes to the inadequate blood pressure response found in the present study.

Adult↗
PubMed1984

Extracellular fluid filtration as the reason for the viscoelastic behaviour of the passive myocardium.

The experimental results are described confirming the hypothesis that the viscous properties of the passive cardiac muscle are connected with the extracellular fluid filtration in the elastic medium formed by the connective tissue network and myocytes. It is shown that the relaxation properties are more pronounced in cold-blooded animals myocardium (frog, turtle) than in that of warm-blooded (cat, rabbit), which correlates with the smaller connective tissue content and larger porosity of myocardium in cold-blooded animals. The decrease in porosity of the cardiac muscle samples by reducing the osmosis of the surrounding solution or squeezing the fluid out of the samples by mechanical torsion results in the slowing down of the stress relaxation, the increase in porosity of the muscle in the hyperosmotic solution results in its speeding up. The increase of the surrounding solution viscosity by adding saccharose to it leads to the proportional stress relaxation deceleration, which agrees quantitatively and qualitatively with the advanced hypothesis.

Animals↗
PubMed1985

Extracellular fluid volume and distribution in relation to changes in plasma colloid osmotic pressure after major surgery. A randomized study.

This prospective randomized study deals with the changes in magnitude and distribution of the extracellular fluid volume (ECV) and the relation between such changes and the plasma colloid osmotic pressure (COPP) in patients having abdominal aortic surgery. Two groups of thirteen patients each received whole blood to replace the blood loss. One group (ALB) had additionally 80 g albumin administered on the day of operation and 20 g the following 3 days, the other group (NON-ALB) did not receive extra albumin. In the ALB group ECV decreased from 9.3 +/- 1.71 (= 147 ml/kg) to 8.4 +/- 2.01 (NS) on the first postoperative day (p.o.d.) and to 9.2 +/- 2.5 1 (NS) on the fourth p.o.d. In the NON-ALB group the preoperative ECV of 8.1 +/- 1.11 (= 125 ml/kg) was unchanged on the first p.o.d. and 8.4 +/- 1.41 (NS) on the fourth p.o.d. The differences between the groups were non-significant. The post-operative changes observed in ECV were not related to COPP in the range 33 mmHg to 21 mmHg. The ratio between plasma volume (PV) and ECV was 0.35 +/- 0.06 preoperatively in both groups. Postoperative changes were non-significant and no correlation between COPP and PV/ECV could be found. In the present study the distribution of ECV between plasma and interstitium was found to be independent of COPP in the interval 33-21 mmHg. Furthermore, no obligatory contraction or expansion of ECV occurred after major elective surgery.

Aorta, Abdominal↗
PubMed1994

Concentrations of amino acids in extracellular fluid after opening of the blood-brain barrier by intracarotid infusion of protamine sulfate.

This article evaluates the influence of an opening of the blood-brain barrier (BBB) on compounds in brain extracellular fluid. The concentrations of amino acids and some other primary amines were determined in dialysates sampled from the right parietal cortex of rats before and after an intracarotid infusion of protamine sulfate. Extravasated plasma proteins were visualized by Evans blue/albumin and immunohistochemistry. CSF albumin--an indicator of blood-CSF barrier opening--was quantified with immunoelectrophoresis. The brains were macroscopically edematous after 10 mg but not after 5 mg of protamine sulfate. The higher dose led to a 50% death rate. The concentrations of amino acids did not change 10 min after the BBB opening. No significant alterations in the amino acid concentrations were observed after the lower dose. The concentrations of glutamate, aspartate, GABA, glycine, taurine, and phosphoethanolamine increased significantly within 50-80 min after the infusion of 10 mg of protamine sulfate. CSF albumin levels were significantly increased 1 h after infusion. We conclude that a dysfunction of the BBB, of a degree known to induce brain edema (10 mg of protamine sulfate), significantly increases the extracellular concentration of excitatory amino acids, GABA, taurine, and phosphoethanolamine in the extracellular space.

Amino Acids↗
PubMed1988

Brain stem extracellular fluid pH and respiratory drive during hypoxia in newborn pigs.

In response to moderate hypoxia many newborn animals are capable of increasing ventilation only transiently. To examine the hypothesis that changes in brain stem extracellular fluid (ECF) pH explain this transient ventilatory response, we measured brain stem ECF pH and respiratory drive during hypoxia in newborn pigs. The animals were anesthetized with alpha-chloralose-urethan, paralyzed, vagotomized, and mechanically ventilated with a servo-controlled ventilator to regulate end-tidal CO2. Hypoxic ventilation for 6 min was achieved by changing inspired gas from 100% to 10-15% O2. Respiration, measured as integrated phrenic nerve activity, showed a range of responses. In 13 trials increased phrenic activity early in the hypoxic period was sustained or further augmented for the duration of the period. In contrast, in eight other trials phrenic activity increased and then declined. Regardless of the respiratory response, ECF pH (measured with a flat-surface electrode) increased slightly (0.009 +/- 0.002 U) during the first 2.5 min of hypoxia and then declined 0.061 +/- 0.017 U by the 6th min. This acidotic shift in ECF pH is inconsistent with the hypothesis that an alkalotic shift causes the nonsustained respiratory response of newborn pigs.

Animals↗
PubMedDate not supplied

Blood and extracellular fluid volume in whole body and tissues of the Pacific hagfish, Eptatretus stouti.

Whole-body and 20 individual-tissue (51)Cr-RBC (red cell space; RCS) and (99)Tc-diethylenetriaminepentaacetic acid (extracellular space; ECS) spaces were measured in seven unanesthetized Pacific hagfish (Eptatretus stouti). Volume indicators were administered via a dorsal aortic cannula implanted the previous day. Blood samples were collected at 6, 12, 18, and 24 h after injection. Tissues were removed at 24 h and radioactivity was measured; tissue water content (percent of wet weight) was determined by desiccation at 95 degrees C for 48 h. Mixing rates of both indicators were identical and were essentially complete by 12 h, indicating that blood convection is the rate-limiting process. At 24 h, the whole-body RCS was 19.3+/-2.1 mL kg(-1) body weight, and the ECS was 338.5+/-15.2 mL kg(-1) body weight. Blood volume estimated from the 24-h RCS and the mean central hematocrit (14%) was 137.9 mL kg(-1) body weight. Liver RCS (118.6+/-30.5 microL g(-1) tissue weight) was twice that of any other tissue and was also the most variable, ranging from 59 to 263 microL g(-1), whereas liver ECS (406.0+/-34.3 microL g(-1)) was in the range of other tissues, and water content (66.9%+/-3.5%) was low. Gill RCS (55.9+/-5.7 microL g(-1)), ECS (415.3+/-37.7 microL g(-1)), and percent water (83.1%+/-0.8%) were higher than most other tissues. RCS, ECS, and percent water were consistently lowest in ovum (1.1+/-0.02 microL g(-1), 111.1+/-4.3 microL g(-1), 51.3%+/-3.5%, respectively). Tongue, notocord, and myotome had generally lower RCS (2.1+/-0.4, 2.2+/-0.5, 7.1+/-0.1 microL g(-1), respectively) and ECS (121.2+/-7.0, 246.3+/-17.4, 185.3+/-16.7 microL g(-1), respectively), although their water content was in the midrange (74.7+/-0.5, 81.2+/-1.6, 74.4%+/-0.6%, respectively). Skin had a low RCS (6.8+/-1.1) and midrange ECS (387.5+/-28.0) but very low water content (61.2%+/-2.1%). These findings confirm that hagfish blood volume is at least twice as large as other fish, whereas our estimate of extracellular fluid volume is larger than previously reported and more in line with the predicted interstitial volume. RCS, ECS, and water content vary, often independently, between tissues, which may perhaps be indicative of specific tissue needs or functions. A distinct spleen is lacking in hagfish, and the liver appears to serve this function by sequestering red cells. To our knowledge, this is the first report of tissue ECS in Myxiniformes.

Animals↗
PubMed1981

High-performance liquid chromatographic methods for base and nucleoside analysis in extracellular fluids and in cells.

High-performance liquid chromatography based methods for the study of the metabolism of purine and pyrimidine bases and nucleosides have been developed. These methods, using 200--50 microliter samples of extracellular fluids and employing isocratic separations, can measure a wide range of compounds. Hypoxanthine, xanthine and uridine concentrations in plasma from normal men are relatively stable. Species differences have been detected: concentrations of cytidine are higher in rat and mouse serum than in man, since the concentrations of uridine are similar; purine/pyrimidine ratios may be different. Fetal calf serum used for tissue culture contains about a 40 times higher concentration of hypoxanthine than the less-effective calf serum. Use of the methods appears to be justified in the assessment of the metabolic damage due to severe hypoxia and/or ischaemia.

Animals↗
PubMed1982

The extracellular fluid volume in normal man determined as the distribution volume of [51Cr] EDTA.

The precision of a simplified single injection method for determination of the distribution volume of [51Cr] EDTA, as an estimate of the extracellular fluid volume (ECV), was determined in 49 patients (17 men and 32 women, aged 19-75 years) who had ECV determined twice with an interval of 1-5 days. The glomerular filtration rate (GFR) can be determined by the same method. The total day-to-day variation (coefficient of variation) of ECV was 11.4% and that of GFR 4.5%. ECV differed significantly between men and women so that ECV on average was 14% (P less than 0.001) and 7% (P less than 0.05) higher in men than in women for the same body weight and body surface area, respectively. Regression equations of ECV on body weight and body surface area in 44 normal men and in 40 normal women are presented.

Adult↗
PubMed1980

[Renal excretion of urea and electrolytes in sheep after extracellular fluid expansion with an isotonic solution of sodium chloride].

Sheep of the Merino breed, given 10.11 g nitrogen daily (after Czechoslovak Standard CSN 46 7007) were studied for the effect of the expansion of the extracellular fluid (ECF) by an infusion of an isotonic solution of NaCl (at a rate of 5% of live weight), as exerted on the renal excretion of urea and on the sodium and potassium electrolytes. The high natriuresis, induced by the expansion of ECF, resulted in a statistically significant increase in the clearance of urea, free water, and solutions, and in higher diuresis. An increase was observed in the excretion of urea with urine (UureaV; P < 0.005) and in the excretion of the studied electrolytes of sodium (UNaV; P < 0.001) and potassium (UKV; P < 0.005) by the same route. No variation was recorded in the clearance of inulin as a measure of the glomerular filtration rate (GFR). The fractional excretion of urea, sodium, and potassium also showed a significant increase. The results imply that the fractional excretion of urea increases under the conditions of artificially induced natriuresis.

Animal Feed↗