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PubMed1980

Natriuretic factor in rats acutely expanded by Ringer's versus albumin solution.

Previous studies have shown that it is possible to extract a natriuretic factor from the renal tissue of rats. This substance, which can be isolated by fractionation through a G-25 Sephadex column, shows a strong correlation with sodium elimination by the kidney. The present work was designed to compare the effects of expansion by a Ringer's solution versus an albumin solution on the presence of this factor and the natriuretic response in the rat. Albumin-expanded rats, like control nonexpanded rats, which have no natriuretic response, do not exhibit any active natriuretic factor in their kidneys. In contrast, significant activity of the natriuretic factor is found in the kidneys of Ringer-expanded rats, which also respond by a significant natriuresis (P less than 0.001). We conclude that the expansion of the extracellular fluid volume, as opposed to the expansion of the intravascular volume, only determines both the presence of the natriuretic factor and the physiologic natriuretic response. As the difference in the sodium transport by the renal tubule in these two modes of expansion takes place in the collecting duct, we suggest that the natriuretic factor acts at this level.

Albumins↗

PubMed1988

Regulation of Na+-K+ pump activity in erythrocytes and blood pressure in anephric rats.

This study was designed to explore factors involved in the regulation of Na-K pumps in erythrocytes and blood pressure in anephric Sprague-Dawley female rats. Twenty-four hours following bilateral nephrectomy, the rats were given a 1-h infusion of 1 ml of either 0.9% or 5.4% saline, or 5% or 30% glucose. At the completion of the infusion, tail blood pressure was determined and blood was drawn for the measurement of the ouabain-furosemide-sensitive sodium efflux rate constant in erythrocytes. Infusion of 5.4% saline or 30% glucose caused a significant reduction in the erythrocyte sodium efflux rate constant, more pronounced with the former, and an elevation in blood pressure. Nephrectomy or infusion of 0.9% saline or 5% glucose had no effect on either parameter. These findings suggest that in anephric rats (1) extracellular fluid hyperosmolality rather than extracellular fluid volume expansion inhibits the Na-K pump in all cells; (2) a Na-K pump inhibitor is involved in the genesis of hypertension.

Animals↗

PubMed2001

Disturbances of cerebrospinal fluid flow attributable to arachnoid scarring cause interstitial edema of the cat spinal cord.

OBJECTIVE: Spinal arachnoid scarring may be caused by trauma, inflammation, surgery, spinal instability, degenerative diseases, or malformations and may lead to progressive neurological deficits and syringomyelia. We wanted to investigate the effects of focal arachnoid scarring in the cervical spinal canal of cats on pressures in the subarachnoid space and spinal cord tissue, as well as on spinal cord histological features. METHODS: Twenty-nine adult cats were used for this study. Nine animals served as control animals, whereas 20 animals received a focal arachnoid scar at C1-C2, which was produced by placement of a kaolin-soaked fibrin sponge on the posterior surface of the spinal cord. After 4 months, pressure recordings above and below the scar, in the subarachnoid space and spinal cord, were performed. Elasticity measurements were performed with small bolus injections. Morphometric analyses of brain and ventricle volumes, sizes of the central canal, and sizes of the perivascular spaces in gray and white matter were also performed. RESULTS: No animal developed clinical or neurophysiological evidence of neurological symptoms at any time. In the kaolin-treated group, pressure recordings revealed a significant increase in the subarachnoid pressure at C1, because of the cerebrospinal fluid flow obstruction. Pressure gradients tended to increase at all measuring points. A significant difference was detected between the spinal cord and subarachnoid space at C2, where the intramedullary pressure exceeded the subarachnoid pressure. Elasticity was significantly increased in the spinal cord at C2. Intracranially, no evidence of hydrocephalus was observed. In the spinal cord, perivascular spaces were significantly enlarged in the posterior white matter above the arachnoid scar and in the central gray matter below the area of scarring in the cervical cord. CONCLUSION: Arachnoid scarring at C1-C2 produces an interstitial type of edema in the central gray matter below the area of scarring in the cat cervical cord, because of altered cerebrospinal fluid and extracellular fluid flow dynamics. These changes may be interpreted as the initial stage in the development of syringomyelic cavities.

Animals↗

PubMed1990

Failure of 1,25-(OH)2-vitamin D3 to affect calcium flux across sheep rumen wall mucosa in vitro.

Isolated pieces of mucosa from the sheep rumen wall mounted between half-chambers were used in conventional incubation studies (1 h, 39 degrees C) with buffer solutions resembling rumen fluid (= mucosal fluid) and extracellular fluid (= serosal fluid), respectively. The mucosal-to-serosal (ms) flux of calcium was studied by use of 45CaCl2 with and without 1,25-(OH)2-vitamin D3 in the serosal incubation fluid. Different concentrations of the vitamin had no effect on Ca ms-flux.

Animals↗

PubMed1994

Surgical results of 100 intramedullary tumors in relation to accompanying syringomyelia.

During the period from 1977 to August 1992, 100 intramedullary tumors in 94 patients were operated on in the Department of Neurosurgery at the Nordstadt Hospital in Hannover, Germany. Of these, 45% presented with associated syringes. A syrinx was more likely to be found above (49%) than below (11%) the tumor level. In 40%, a syrinx could be identified above and below the tumor level. Ependymomas and hemangioblastomas were the most common tumor types to be associated with syringes. Astrocytomas tended to demonstrate syringes less often. Regardless of histology, the higher the spinal level, the more likely a syrinx was encountered. In general, the presence of an associated syrinx favored the resectability of the tumor, because it indicated a displacing rather than an infiltrating tumor. Patients with syringomyelia tended to recover from surgery sooner. However, surgical results and long-term prognosis were not influenced significantly by an associated syrinx. The most important factor determining long-term outcome was the preoperative level of neurological function. We propose that factors independent of the tumor, disturbances of cerebrospinal fluid and extracellular fluid flow in particular, have major roles in the pathogenesis of syrinx formation associated with intramedullary tumors.

Adolescent↗

PubMed1999

Bioelectrical impedance analysis revisited.

Although total limb volume measurements are used to track the progress of lymphedema and its treatment, these measurements can be confounded by changes other than fluid excess namely muscle or fat gain. Bioelectrical impedance analysis (BIA) is a technique that specifically quantifies both total body fluid and extracellular fluid in extremities. Whereas BIA has potential as a quick, inexpensive, and quantitative technique to measure directly fluid gain or loss from lymphedema, it also has certain shortcomings that must be addressed before it can be validated. this paper examines the back-ground that explains why measuring total limb volume is insufficient to quantify the extent of peripheral lymphedema and explores the advantages and drawbacks of using BIA for this purpose.

Electric Impedance↗

PubMed1989

[The remarkable accomplishments of the kidney--from molecular mechanisms to organ function].

The kidneys control chemical composition and volume of the extracellular fluid. Total extracellular volume passes about 10 times per day through the kidneys. Only 1% is excreted including metabolic waste products and excess intake by nutrition. While the proximal tubules are adapted to mass transport, the distal tublar cells are specialized to selectively retain or reject water and electrolytes, controlled by exrenal hormonal factors. For these purposes an optimal adjustment of morphologic, encymatic, physico-chemical and molecular features has developed in the course of evolution. With modern experimental techniques it is possible to demonstrate the mode of operation of single protein molecules in the cell membranes as sites of active or passive transport processes. This enables us to describe the basic mechanism of kidney function and to better understand the sequence of events leading to pathological disturbances of this organ.

Aldosterone↗

PubMed1996

[The role of adenosine in the central nervous system].

Adenosine is one of the normal elements in body fluid including extracellular fluid within the CNS. Its normal level is 0.03-0.3 mumol/L. When ATP's metabolism loses balance, for example, during ischemia, the level of adenosine increases dramatically, may reach as much as 1000 times of the normal. Adenosine plays many physiological and pathological roles in CNS via its receptors. It is recognized as an inhibitory neuromodulator playing a neuroprotective role in CNS.

Adenosine↗

PubMed1991

Interstitial lactate, inosine and hypoxanthine in rat kidney during normothermic ischaemia and recirculation.

The aim of this study was to determine the potential value of extracellular fluid (ECF) lactate, inosine and hypoxanthine for monitoring the disturbance in energy metabolism associated with kidney ischaemia and recirculation, using intrarenal microdialysis as sampling technique. Normothermic ischaemia was produced in rats by clamping of the left renal pedicle. Microdialysis probes were implanted into the renal cortex and the medulla, respectively. Dialysates were collected in 10-minute fractions before, during 20 (Group A) or 40 minutes (Group B) ischaemia and 2 hours of recirculation. Samples were analysed by HPLC for lactate, inosine and hypoxanthine. Ischaemia caused a dramatic increase of extracellular fluid lactate, inosine and hypoxanthine in both groups, reflecting the disturbance of energy metabolism. The basal extracellular fluid level of lactate as well as that during ischaemia was markedly higher in the medulla compared to cortex, whereas the relative change in lactate concentration was similar (i.e. about 4-fold). In group A all three metabolites returned to the pre-ischaemic level within 20 minutes after reperfusion. However, while inosine and hypoxanthine returned promptly to base line in Group B, recovery of lactate varied dramatically between animals suggesting a persistent metabolic disturbance in some rats. Our results indicate that extracellular fluid lactate, inosine and hypoxanthine, measured by intrarenal microdialysis, may be useful for monitoring of the energy state of the kidney during normothermic ischaemia and that extracellular fluid lactate may be a sensitive indicator of post-ischaemic disturbances in energy metabolism.

Animals↗

PubMed1981

Renal filtration fraction, effective vascular compliance, and partition of fluid volumes in sustained essential hypertension.

Extracellular fluid volume, hemodynamic parameters, total effective compliance, and renal indices were measured in 58 patients with sustained essential hypertensive in comparison with 56 normotensive subjects of the same age and sex. All subjects had a balanced sodium intake and urinary output with inulin clearance and extracellular fluid volume within normal ranges. In patients with hypertension, the ratio between plasma volume (PV) and interstitial fluid volume (IFV) was decreased (P less than 0.01) and was negatively correlated with the filtration fraction (FF) (r = -0.43; P less than 0.001). Total effective compliance was significantly reduced (P less than 0.001) and was positively correlated with the PV/IFV ratio (r = 0.73; P less than 0.001) and negatively correlated with FF (r = -0.56; P less than 0.001. The study provides evidence that the relationships between PV/IFV, FF, and vascular compliance reflect an alteration of the postcapillary segment of the circulation in hypertension.

Adult↗

PubMed1986

Neural mechanisms in body fluid homeostasis.

Under steady-state conditions, urinary sodium excretion matches dietary sodium intake. Because extracellular fluid osmolality is tightly regulated, the quantity of sodium in the extracellular fluid determines the volume of this compartment. The left atrial volume receptor mechanism is an example of a neural mechanism of volume regulation. The left atrial mechanoreceptor, which functions as a sensor in the low-pressure vascular system, is located in the left atrial wall, which has a well-defined compliance relating intravascular volume to filling pressure. The left atrial mechanoreceptor responds to changes in wall left atrial tension by discharging into afferent vagal fibers. These fibers have suitable central nervous system representation whose related efferent neurohumoral mechanisms regulate thirst, renal excretion of water and sodium, and redistribution of the extracellular fluid volume. Efferent renal sympathetic nerve activity undergoes appropriate changes to facilitate renal sodium excretion during sodium surfeit and to facilitate renal sodium conservation during sodium deficit. By interacting with other important determinants of renal sodium excretion (e.g., renal arterial pressure), changes in efferent renal sympathetic nerve activity can significantly modulate the final renal sodium excretion response with important consequences in pathophysiological states (e.g., hypertension, edema-forming states).

Afferent Pathways↗

PubMed1987

Fluid and sodium loss in whole-body-irradiated rats.

Whole-body and organ fluid compartment sizes and plasma sodium concentrations were measured in conventional, GI decontaminated, bile duct ligated, and choledochostomized rats at different times after various doses of gamma radiation. In addition, sodium excretion was measured in rats receiving lethal intestinal radiation injury. After doses which were sublethal for 3-5 day intestinal death, transient decreases occurred in all the fluid compartments measured (i.e., total body water, extracellular fluid space, plasma volume). No recovery of these fluid compartments was observed in rats destined to die from intestinal radiation injury. The magnitude of the decreases in fluid compartment sizes was dose dependent and correlated temporally with the breakdown and recovery of the intestinal mucosa but was independent of the presence or absence of enteric bacteria or bile acids. Associated with the loss of fluid was an excess excretion of 0.83 meq of sodium between 48 and 84 h postirradiation. This represents approximately 60% of the sodium lost from the extracellular fluid space in these animals during this time. The remaining extracellular sodium loss was due to redistribution of sodium to other spaces. It is concluded that radiation-induced breakdown of the intestinal mucosa results in lethal losses of fluid and sodium as evidenced by significant decreases in total body water, extracellular fluid space, plasma volume, and plasma sodium concentration, with hemoconcentration. These changes are sufficient to reduce tissue perfusion leading to irreversible hypovolemic shock and death.

Amine Oxidase (Copper-Containing)↗

PubMed1987

Transthoracic electrical impedance at 1 and 100 kHz--a means for separating thoracic fluid compartments?

The electrical impedance of biological tissues varies with their water and electrolyte contents. Alternating current above 5-10 kHz passes both intra- and extracellular fluid, and lower frequency current preferentially extracellular fluid. In an attempt to evaluate thoracic fluid in different compartments, transthoracic electrical impedance (TEI) was measured at 1 and 100 kHz in 15 consecutive patients, without overt left heart failure and under haemodynamic surveillance, during the first two days of myocardial infarction. To achieve different states of hydration the patients were given i.v. furosemide, either 40 mg t.i.d. (high dose group--HDG) or 20 mg once daily (low dose group--LDG). Effects of altered body position and the respective furosemide injections, were evaluated on both days. Mean 24-h-diuresis was 3.9 l in the HDG and 2.5 l in the LDG. After 24 h mean pulmonary arterial diastolic pressure had decreased by 30% in the HDG but remained almost unchanged in the LDG. By then mean basal TEI was increased only in the HDG, by 17% at 1 kHz and 13% at 100 kHz. On Day 1, within one hour after furosemide, TEI increased temporarily by 3-5%, at both frequencies and in both groups. On Day 2, this short-term increase was similar in the LDG at both frequencies and in the HDG at 100 kHz, but not at 1 kHz, consistent with a major extracellular fluid loss in the HDG. TEI at 1 and 100 kHz may thus reflect extracellular and total thoracic fluid, respectively.

Acute Disease↗

PubMed1971

A new approach for determining the volume of cerebral cellular fluid and demonstration of its communication with C.S.F.

1. A new technique is presented for determining the volume of extracellular space in bowfin (Amia calva) brain during in vitro incubation. It consists of solving simultaneous equations which are applied to determine the volume of extracellular space as well as intracellular marker concentration. This technique allows for a better insight into the redistribution of marker between incubation medium and extracellular space as well as between extracellular and intracellular space.2. Na(+), K(+) and Cl(-) equilibrated within 10-15 min between incubation medium and extracellular space. There was no evidence of a homoeostatic mechanism controlling the concentration of these ions in the extracellular fluid, which appeared to be in equilibrium with cerebrospinal fluid. The extracellular spaces of these ions were identical: Na(+), 23.4; K(+), 23.3 and Cl(-), 23.2%.3. Sorbitol equilibrated with the extracellular fluid within 45 min and indicated an extracellular space of 22.6%, nearly identical with that for electrolytes.4. Vastly different ;spaces' were obtained for [(3)H]methoxy inulin, which equilibrated within 45 min with a 13% space and [(14)C]carboxyl inulin, which showed a 46% space value for only 30 min. The difference may be explained by marker decomposition. The 9% difference between the [(3)H]methoxy inulin and sorbitol spaces may be explained by a ;packing' factor attributable to molecular size.

Animals↗

PubMed1990

Protease-mediated degradation of lignin peroxidase in liquid cultures of Phanerochaete chrysosporium.

The decline of lignin peroxidase (LiP) activity observed after day 6 in cultures of Phanerochaete chrysosporium was found to be correlated with the appearance of idiophasic extracellular protease activity. Daily addition of glucose started on day 6 resulted in low protease levels and in turn in stable LiP levels. Addition of cycloheximide to day 6 cultures resulted in virtually no change of LiP activity and extracellular protein and negligible levels of protease activity, indicating that this protease is synthesized de novo. LiP activity was found to be stable upon removal of the fungal pellets on day 6 and incubation of the extracellular fluid alone. An almost complete disappearance of LiP activity and LiP proteins and high levels of protease activity were observed upon incubation of 6-day extracellular fluid in the presence of fungal pellets. Moreover, incubation of crude or purified LiP isoenzymes with protease-rich extracellular fluid of day 11 or 11-day cell extracts resulted in a marked loss of activity. In contrast, incubation of crude LiP with boiled and clarified extracellular fluid of day 11 cultures resulted in virtually no loss of activity. These results indicate that protease-mediated degradation of LiP proteins is a major cause for the decay of LiP activity during late secondary metabolism in cultures of P. chrysosporium.

Basidiomycota↗

PubMed1975

Separate roles of sodium ion concentration and fluid volumes in salt-loading hypertension in sheep.

The goal of these studies was to determine whether the hypertension caused by excessive salt loading results from sodium-induced expansion of the extracellular fluid volume or whether the salt increases the pressure in some other way, such as by causing vascular constriction. In one group of sheep, a combination of total nephrectomy and hemodialysis was used to produce and maintain step increases in extracellular fluid volume for 1 wk without a significant change in sodium ion concentration. In a 2nd group, unilateral nephrectomy, dialysis, and DOCA administration were used to cause step increases in sodium ion concentration while the extracellular fluid volume was held as close to normal as possible. The results showed a 41% increase in arterial pressure in the high-volume sheep and only a 4% increase in pressure in the high-sodium sheep. In both instances the total exchangeable sodium increased almost equally--a 21% increase in the high-sodium sheep. The data support the concept that sodium retention causes hypertension almost entirely because of sodium-induced expansion of the extracellular fluid volume.

Animals↗

PubMed1977

Distribution of water and electrolytes in normal and thermally damaged skin.

The alterations in contents of Na, K and water in thermally injuried explants of guinea-pig flank skin involve changes in both the cells and the interstitial material of the tissue. A full interpretation of the distribution of such changes can only be obtained if the volumes of cellular and extracellular fluid are known. This work examines the techniques of measuring extracellular fluid volume using 14C-inulin and 51Cr EDTA. Although it was found that the inulin preparation was excluded from a considerable part of the extracellular fluid of the skin explants, the space which it defined altered with increasing severity of thermal damage. The relationship of the inulin space with total water and with 51Cr EDTA space, which probably measures the total extracellular volume, provides an insight into the possible importance of changes in the nature of connective tissue in trauma. Alterations in fluid and cation balance between cells and their environment have been discussed in relation to increasing thermal damage. A clear sequence of events following the onset of the injury can be observed.

Animals↗

PubMed1983

Renal response in low-birth-weight neonates. Results of prolonged intake of two different amounts of fluid and sodium.

Changes in renal function and extracellular fluid volume during the first ten days of life were studied in two groups of low-birth-weight neonates receiving different fluid and sodium intakes from the third to the tenth day. Group 1 neonates received less fluid and sodium and fewer calories than group 2 neonates. Renal function and inulin space were measured before (day 2) and after (day 8) the neonates received the different fluid and sodium managements. Group 2 neonates (on the eight day) had less weight loss, lower plasma sodium and osmolal concentrations, and a similar inulin space per kilogram of body weight as on day 2. Group 1 neonates had more weight loss and a smaller inulin space on day 8 compared with day 2. Low-birth-weight neonates receiving high fluid and sodium loads from days 2 through 8 did not have a contraction of extracellular fluid volume as did those receiving lower fluid and sodium intakes during this period; as a result, the former group had a dilutional decrease in the plasma sodium level and osmolality.

Extracellular Space↗