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PubMed1982

The cells of Boettcher in the bat, Pteronotus p. parnellii.

The structural characteristics, distribution and intercellular relationships of the cells of Boettcher were studied in the mustache bat, Pteronotus P. parnellii. The cells of Boettcher have many structural features similar to those described in other mammals, but in Pteronotus they are distributed throughout the cochlea and are associated with relatively large amounts of secretory and/or absorptive material. Much of this material seems to be derived from or contribute to, a darkly staining upper layer of the basilar membrane. This material accumulates in elaborate microvillus-filled intercellular channels which are restricted to an area near the basilar membrane. The channels communicate with the basilar membrane surface through wide intercellular spaces and through small canals. The microvillus-filled channels are confluent with large extracellular spaces between Boettcher's cells and a single row of cells which form the floor of the outer tunnel. The latter have irregular shaped nuclei, contain many vacuoles and like Boettcher's cells, are associated with large amounts of basilar membrane-like material. Observations on Pteronotus, as well as other species of bats, do not support concepts relating Boettcher's cells to hair cell innervation patterns or to high frequency hearing.

Animals↗
PubMed1988

Effects of arginine vasopressin on the sequestration of albumin in extravascular space in the rat.

1. The effect of Arginine-Vasopressin (AVP) and phenoxybenzamine on regional sequestration of albumin in the extracellular space was studied in anesthetized (Na-Thiopentone) rats using a dual albumin labelling technique. 2. Low AVP dose (400 microU/kg) resulted in increased albumin sequestration, particularly in cutaneous and skeletal muscle extravascular space. In higher AVP doses this effect was not pronounced. 3. Phenoxybenzamin resulted in increased albumin sequestration, mostly in cutaneous and skeletal muscle extravascular space. 4. The effect of AVP, a potent pressoric hormone, on albumin sequestration resembles that of a vasodilator drug and contrasts with its pressoric nature.

Animals↗
PubMed1991

Intra- and extracellular pH of the brain in vivo studied by 31P-NMR during hyper- and hypocapnia.

Studies were performed to determine the pH relationships among the extracellular, intracellular, and arterial blood compartments in the brain in vivo. Resolution of the extracellular monophosphate resonance peak from the intracellular peak in 31P nuclear magnetic resonance (NMR) spectra of sheep brain with the calvarium intact enabled pH measurement in these respective compartments. Sheep were then subjected to both hyper- and hypoventilation, which resulted in a wide range of arterial PCO2 and pH values. Linear regression analysis of pH in these compartments yielded slopes of 0.56 +/- 0.05 for extracellular pH (pHe) vs. arterial pH, 0.43 +/- 0.078 for intracellular pH (pHi) vs. pHe, and 0.23 +/- 0.056 for pHi vs. arterial pH. These data indicate that CO2 buffering capacity is different and decreases from the intracellular to extracellular to arterial blood compartments. Separation of the extracellular space from the vascular space may be a function of the blood-brain barrier, which contributes to the buffering capability of the extracellular compartment. A marked decrease in the pH gradient between the extracellular and intracellular space occurs during hypercarbia and may influence mechanisms of central respiratory control.

Animals↗
PubMed2003

A direct mass-action mechanism explains capacitative calcium entry in Jurkat and skeletal L6 muscle cells.

We examined capacitative calcium entry (CCE) in Jurkat and in L6 skeletal muscle cells. We found that extracellular Ca2+ can enter the endoplasmic reticulum (ER) of both cell types even in the presence of thapsigargin, which blocks entry into the ER from the cytosol through the CaATPase. Moreover, extracellular Ca2+ entry into the ER was evident even when intracellular flow of Ca2+ was in the direction of ER to cytosol due to the presence of caffeine. ER Ca2+ content was assessed by two separate means. First, we used the Mag-Fura fluorescent dye, which is sensitive only to the relatively high concentrations of Ca2+ found in the ER. Second, we transiently expressed an ER-targeted derivative of aequorin, which reports Ca2+ by luminescence. In both cases, the Ca2+ concentration in the ER increased in response to extracellular Ca2+ after the ER had been previously depleted despite blockade by thapsigargin. We found two differences between the Jurkat and L6 cells. L6, but not Jurkat cells, inhibited Ca2+ uptake at very high Ca2+ concentrations. Second, ryanodine receptor blockers inhibited the appearance of cytosolic Ca2+ during CCE if added before Ca2+ in both cases, but the L6 cells were much more sensitive to ryanodine. Both of these can be explained by the known difference in ryanodine receptors between these cell types. These findings imply that the origin of cytosolic Ca2+ during CCE is the ER. Furthermore, kinetic data demonstrated that Ca2+ filled the ER before the cytosol during CCE. Our results suggest a plasma membrane Ca2+ channel and an ER Ca2+ channel joined in tandem, allowing Ca2+ to flow directly from the extracellular space to the ER. This explains CCE; any decrease in ER [Ca2+] relative to extracellular [Ca2+] would provide the gradient for refilling the ER through a mass-action mechanism.

Aequorin↗
PubMed1990

Effect of endothelin-1 on cytosolic calcium ions in cultured human endothelial cells.

The effects of endothelin-1 on cytosolic Ca2+ and inositol 1,4,5-triphosphate (IP3) levels were investigated in cultured, untreated human endothelial cells and in endothelial cells pretreated with anti-endothelin-1 serum for 24 h to exclude the effect of endogenous endothelin-1. Endothelin-1 was found to increase the intracellular Ca2+ level, either in the presence or absence of extracellular Ca2+, in endothelial cells pretreated with antiserum by the fura-2 fluorescence technique. IP3 levels immediately started to rise following endothelin-1 stimulation. Resting intracellular Ca2+ levels were significantly lower when the cells were pretreated with antiserum than without antiserum pretreatment. Following stimulation by endothelin-1, intracellular Ca2+ and IP3 levels in endothelial cells pretreated with antiserum increased significantly compared to those in untreated endothelial cells. Endothelin-1 also increased 45Ca influx from the extracellular space. These results suggest that endothelin-1 increases intracellular Ca2+ in endothelial cells through extracellular Ca2(+)-dependent mechanisms and by the release of Ca2+ from intracellular stores, this presumably being induced by IP3 formation.

Calcium↗
PubMed1981

Intracellular retention of lysosomal enzymes in cystic fibrosis.

Multiple leakage of lysosomal enzymes from cystic fibrosis fibroblasts into the extracellular space has been suggested to occur but was not observed in these experiments. Both extracellular and intracellular levels of enzyme activity were within the normal range. The release of lysosomal enzymes from individual cell lines was seen to be affected both by intrinsic properties of each cell line and by many external factors.

Adolescent↗
PubMed1990

Blockade of the noradrenaline carrier increases extracellular dopamine concentrations in the prefrontal cortex: evidence that dopamine is taken up in vivo by noradrenergic terminals.

The effect of systemic administration of desmethylimipramine (DMI) and oxaproptiline (OXA), two inhibitors of the noradrenaline (NA) reuptake carrier, on the in vivo extracellular concentrations of dopamine (DA) was studied by transcerebral dialysis in the prefrontal cortex and in the dorsal caudate of freely moving rats. In the NA-rich prefrontal cortex, either drug increased extracellular DA concentrations whereas in the dorsal caudate neither was effective. Haloperidol increased extracellular DA concentrations more effectively in the dorsal caudate than in the prefrontal cortex. Pre-treatment with DMI or OXA, which failed to modify the effect of haloperidol in the dorsal caudate, potentiated its action in the prefrontal cortex. 6-Hydroxydopamine lesioning of the dorsal NA bundle prevented the ability of OXA to increase DA concentrations. The results suggest that reuptake into NA terminals in an important mechanism by which DA is cleared from the extracellular space in a NA-rich area such as the prefrontal cortex. The elevated extracellular concentrations of DA resulting from blockade of such mechanism by tricyclic antidepressants may play a role in the therapeutic effects of these drugs.

Animals↗
PubMed1972

Mechanical response with reversed electrical response to noradrenaline by Ca-deprived arterial smooth muscle.

1. When sheep carotid arteries had become electrically active after 30 min in Ca-free saline, noradrenaline 0.1 mM caused almost as much contraction as it did with Ca 1.25 mM present; it also caused slight electrical depolarization, usually with increased spike frequency, followed by electrical quiescence.2. In Ca-free saline with EDTA the arteries became profoundly depolarized, and their mechanical responses greatly reduced, within a few minutes. The mechanical responses to noradrenaline that remained were accompanied by electrical repolarization or, after longer periods in EDTA, by no electrical change.3. This residual mechanical responsiveness to noradrenaline, always tested at 36 degrees C, declined on average 26 times as rapidly during exposure to EDTA at 36 degrees C as at 5 degrees C and was not reduced by increasing the concentration of EDTA from 1.25 to 12.5 mM. This temperature-sensitivity was significantly too high to be explained by a diffusion-limited process.4. The results suggest that most of the tissue Ca responsible for contractility in simple Ca-free saline was either free in the extracellular space or in cellular stores that were discharged within a few minutes when free extracellular Ca was removed. They also indicate a small resistant Ca store which did not communicate with the exterior by diffusion, and part of which noradrenaline could utilize for contraction by means not dependent on depolarization conducted from the cell membrane.

Action Potentials↗
PubMed1984

Quantitative and temporal characterization of the extracellular H2O2 pool generated by human neutrophils.

The extracellular H2O2 concentration surrounding stimulated human neutrophils was continuously quantitated with a sensitive, H2O2-detecting electrode. Following stimulation of neutrophils with phorbol myristate acetate, opsonized zymosan particles, or N-formyl-Met-Leu-Phe, the extracellular H2O2 concentration rapidly increased and maintained steady state conditions before falling to undetectable levels in a manner that was dependent on the triggering agent used. Total extracellular H2O2 accumulation for each stimulus was quantitated as the integral of the H2O2 concentration with respect to time. H2O2 accumulation in the extracellular milieu was unaffected by the addition of superoxide dismutase, whereas exogenous catalase or myeloperoxidase completely consumed the released H2O2. Analysis of H2O2 metabolism by neutrophils revealed that stimulus-dependent differences in the size of the extracellular H2O2 pool may be partially attributable to differences in hypochlorous acid generation by the H2O2, myeloperoxidase, chloride system. Finally, both the concentration of H2O2 in the extracellular space and its utilization by myeloperoxidase could be diminished in the presence of an extracellular target cell. These data indicate that the ability of a triggering agent to stimulate the neutrophil to generate H2O2 and release myeloperoxidase, coupled with the characteristics of a target cell population, control H2O2 metabolism in effector-target cell interactions.

Catalase↗
PubMed1982

The fine structure of the deep muscle lamellae and their sarcoplasmic reticulum in Branchiostoma lanceolatum.

The ultrastructure of the deep lamellae of Branchiostoma's trunk muscle was investigated electron microscopically using quantitative morphometry and extracellular markers. Earlier measurements by Flood [7] were mostly confirmed and further extended. The controversy about the arrangement of the sarcoplasmic reticulum (SR) was widely resolved. The extracellular space occupies only 4.0% of the whole muscle volume and is freely accessible to extracellular markers (ferritin, lanthanum). The SR consists of cisternae without tubular interconnections. It occupies 5 to 11% of the cell volume. A junctional gap of 11 to 15 nm width separates the cisternae from the surface membrane and is bridged by typical junctional feet, 11 nm long and 10 to 20 nm in diameter. A Markham rotation analysis revealed a well defined tetragonal pattern with a centre-to-centre feet distance of 34 to 38 nm. A transverse tubular system is absent in the main part of the sheet-like muscle cells. However in basal regions with double layers of myofibrils, extracellular channels surrounded by SR cisternae could be detected within the muscle cells. The results show that there are no principal differences in membranal contacts between the diads of Branchiostoma and vertebrate triads. From these data and physiological findings [23, 24] it seems unlikely that main differences exist in the mode of excitation-contraction coupling between these muscle cells.

Animals↗
PubMed1980

The antihypertensive effect of prazosin on mild to moderate hypertension, changes in plasma volume, extracellular volume and glomerular filtration rate.

Changes in blood pressure, plasma volume (PV) (125I-albumin space), extracellular volume (ECV) (82Br-space) and glomerular filtration rate (GFR) (51Cr-EDTA clearance) were measured in 12 patients with mild to moderate essential hypertension on placebo and during long-term treatment with prazosin. During the study, BP decreased from an average of 172/107 to 166/102 mmHg (n.s.). PV increased from 3278 to 3324 ml (n.s.) and ECV from 18360 to 18639 ml (n.s.). GFR was almost unchanged, 95 and 93 ml/min, prespectively. An inverse significant correlation was found between the changes in mean BP and changes in ECV, i.e. fluid retention was demonstrated in patients with the smallest BP reduction. It is concluded that inadequate BP response during treatment with prazosin may in part be due to fluid retention. It is therefor suggested that prazosin should in principle be used together with a diuretic in order to prevent fluid retention.

Adult↗
PubMed1975

Developmental morphology of the subarachnoid space and contiguous structures in the mouse.

Development of pia-arachnoidal membranes in the mouse occurs in four stages: the first (prenatal days 10-13) follows closure of the neural tube and is a period of initial vascularization of the developing telencephalon; the second (prenatal days 14-16) is a period of delineation during which the limits of the subarachnoid space are defined; the third (prenatal day 17 to birth) is a period of ensheathment of pia-arachnoidal blood vessels; and the fourth (birth to postnatal day 21) includes addition of smooth muscle to larger vessels, the appearance of macrophages in the subarachnoid space, and a general increase in extracellular collagenous and elastic fibers. The mesenchyme over the telencephalic surface in the 10-day fetus has a typically large extracellular space. By the 13th fetal day cerebrospinal fluid begins to seep into and replace it. The mesenchymal extracellular compartment is reduced peripherally, resulting in a compacted pia-arachnoidal tissue which limits the peripheral extent of the subarachnoid space. By the 21st postnatal day a subarachnoid space typical of the adult animal has been established.

Animals↗
PubMed1981

Oxidation of ruthenium red for use as an intercellular tracer.

When ruthenium red (RR) is combined with OsO4, an electron-opaque complex forms which readily binds to the cell surface coat. However, the RR-OsO4 complex is often excluded from intercellular spaces in many cell types, and thus is not dependable as a tracer of regions continuous with the extracellular space. Postfixation of erythrocytes agglutinated by the lectin helix (Helix promatia) and intact carotid artery endothelium with a freshly prepared mixture of 1% OsO4 containing 0.1% ruthenium red (RR) resulted in a dense surface deposit of these cells, but intercellular regions were penetrated to a minimal degree by the stain. When a similar mixture of RR-OsO4 was allowed to stand 3 h before use, RR is oxidized by OsO4 to yield a ruthenium compound that has a spectrophotometric absorbance maximum at 365 nm. This RR molecule has a reduced number of cationic sites due to binding with osmium dioxide OsO2=. Postfixation of agglutinated RBCs and carotid artery endothelium with this oxidized ruthenium-OsO4 mixture resulted in a 50-80% decrease in surface deposition but markedly enhanced penetration into intercellular regions. The enhanced penetration is attributed to decreased binding affinity of the oxidized ruthenium for anionic surface membrane components, permitting effective stain penetration of cell-to-cell contact rather than extensive surface deposition. These studies indicate that the ruthenium compound formed by OsO4 oxidation of ruthenium red may be a useful tracer for ultrastructural visualization of intercellular spaces and junctions.

Animals↗
PubMed1982

Synthesis and use of radio cobaltic EDTA as an extracellular marker in rabbit heart.

A new gamma-labeled marker for extracellular space is the cobaltic form of 58Co-ethylenediaminetetraacetic acid (58Co-EDTA). The cobaltic ion has a much higher affinity for EDTA than the cobaltous ion; it is prepared as a potassium salt, K+(58Co3+-EDTA4-), and is apparently biologically inert. Testing by equilibration in intact rabbits and comparing the myocardial content with that of [14C]sucrose give values of the volume of distribution in the myocardium of 0.294 +/- 0.052 ml/g for 58Co-EDTA and 0.303 +/- 0.051 ml/g for [14C]sucrose (SD, n = 130, for two hearts), with the ratios of 58Co-EDTA/sucrose averaging 0.973 +/- 0.043 (n = 130). The average value of the extracellular fluid measured in isolated rabbit interventricular septum using Co-EDTA was 0.51 +/- 0.05 ml/g (SD, n = 16) and 0.46 +/- 0.04 ml/g using [14C]sucrose as an extracellular fluid space (ECF) marker. Flushing with a high concentration of nontracer Co-EDTA does not reveal any release from binding sites. The gamma-energy (811 KeV), long half-life (71.4 days), stability, and lack of binding to tissue components make 58Co-EDTA a useful marker for ECF.

Animals↗
PubMed1996

Quantitative examination of dynamic interneuronal coupling via single-spike extracellular potassium ion transients.

A computer simulation developed to examine activity-dependent, transient variations of local extracellular potassium ion concentration in the central nervous system is extended to a consideration of depolarizing interactions between an active (primary) neuronal membrane and adjacent quiescent neuronal membranes. A class of potassium-mediated depolarizing interactions is described and quantified in relation to the local histologic fine structure. With a relatively open and rapidly equilibrating extracellular environment, the interactions are in the millivolt range and thus are largely subthreshold. However, with a sufficiently restricted extracellular microenvironment and without additional dynamic mechanisms for enhanced potassium clearance, a single action potential is shown to be capable of producing secondary suprathreshold depolarization of the primary membrane. Such potassium-mediated self-excitation evolves to "autogenic" paroxysmal discharge, that is, a burst of activity terminating in sustained depolarization block. Similar suprathreshold ionic coupling between the primary membrane and its adjacent neuronal membranes can likewise yield "cooperative" paroxysmal discharge, wherein the burst of action potentials from the referential primary membrane interdigitates with homologous bursts in adjacent neuronal elements. The partitioning of the local extracellular space by fine cellular processes, fundamental to determining the magnitude of single-spike local extracellular potassium transients, is a basic determining factor for such putative potassium-mediated suprathreshold events. Of more general relevance is the existence of a class of robust but highly localized, subthreshold potassium-mediated ionic interactions that can support non-synaptic dynamic modulation of neuronal activity. Thus, in addition to providing a quantitative theory for the initiation and propagation of non-synaptic epileptiform events, the model suggests a mechanism for potassium-mediated and activity-dependent proximity modulation of neuronal network throughout that can be significant at normal levels of neuronal activity and normal histologic fine structure.

Action Potentials↗
PubMed1994

Free fatty acid liberation and cellular swelling during cerebral ischemia: the role of excitatory amino acids.

We previously demonstrated the occurrence of cellular swelling during cerebral ischemia in vivo using microdialysis. 14C-Sucrose was pre-perfused into the extracellular space (ECS) as an ECS marker, and cellular swelling was detected as an increase in extracellular concentration of 14C-sucrose. In the present study, we examined in rats the time courses of the increase in FFA in relation to the occurrence of cellular swelling, and the role of excitatory amino acids (EAAs) in these events. A pair of microdialysis probes were placed in the hippocampus bilaterally. One probe was perfused with modified Ringer solution containing kynurenic acid (KYN, 10 mM), a broad-spectrum EAA antagonist, and the other with Ringer solution as a control. At 30 minutes after the initiation of perfusion, ischemia was induced by decapitation. The brain was subjected to microwave irradiation at 0-8 minutes after decapitation, and the FFA levels in the dorsal hippocampus were measured by high performance liquid chromatography. The time course of cellular swelling was determined in a separate group of animals using the previously described method. It was found that arachidonic and stearic acids began to demonstrate a rapid increase during the period from 1 to 2 minutes following ischemia induction. The levels of oleic and palmitic acids demonstrated similar but less marked increase. The rate of increase became less rapid after 4 minutes, suggesting a transient rapid increase superimposed on a background slow increase. The rapid increase roughly corresponded in timing to the occurrence of the early cellular swelling.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Relationship between local changes in cortical blood flow and extracellular K+ during spreading depression.

Change of local cerebral blood flow in response to a single cortical spreading depression of Leão was studied in the brain. During a spreading depression, potassium briefly accumulates in the brain extracellular space. The cortical blood flow was normal during the maximal rate of increase of the extracellular potassium concentration. The blood flow doubled during the subsequent period of normalization of potassium and remained high for one minute thereafter. Thus, potassium cannot be the immediate mediator of the blood flow increase.

Animals↗
PubMed1993

Kinetic properties of a slow apamin-insensitive Ca(2+)-activated K+ current in guinea pig vagal neurons.

1. The calcium-activated outward current (gKCa,2) following an action potential was recorded from neurons in the guinea pig dorsal motor nucleus of the vagus (DMV). gKCa,2 was activated after a delay after the action current and had a distinct rising phase in contrast to the apamin sensitive calcium-activated current in rat DMV neurons (gKCa,1). 2. The time course of gKCa,2 was well described by function of the form A*[exp(t/tau 1)-exp(t/tau 2)], where tau 1 = 1.42 +/- 0.05 (SE) s and tau 2 = 555 +/- 24 ms. 3. Increasing calcium influx by firing multiple action currents lead to an increase in the peak amplitude of gKCa,2 with no change in its kinetics. In cells loaded with low concentrations of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), gKCa,2 was smaller in amplitude but its time course was similar to that in cells not loaded with EGTA. 4. When preceded by a conditioning influx of calcium, the amplitude and time course of gKCa,2 was identical to one with no conditioning influx. These results show that, after influx of calcium, a potassium current with stereotyped amplitude and kinetics is generated. 5. These data are consistent with the idea that the source of calcium for activation of gKCa,2 is not the extracellular space.

Action Potentials↗