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At least 1,495 records · Page 83Linked to original sources
PubMed1995

Intraphagosomal oxygen in stimulated macrophages.

A new electron paramagnetic resonance (EPR)-based method was developed to obtain selective information on pO2 in a specific intracellular compartment (phagosomes). This method did not require the use of a broadening agent thereby eliminating one of the potential sources of experimental error with EPR oximetry. An oxygen-sensitive probe (4-(Trimethylammonium) 2,2,6,6-tetramethylpiperidine-d17-1-oxyl iodide (d-Cat1)) which has a net positive charge, was incorporated selectively into the phagosomes of macrophages stimulated with zymosan. Extracellular oxygen was measured by addition of a neutral nitroxide (4-oxo-2,2,6,6-tetramethylpiperidine-d16-1-oxyl (15N PDT)) to this same sample. Measurements based on EPR linewidths showed the average intraphagosomal oxygen concentration to be 11.2 +/- 3.4 microM lower than that measured from the extracellular compartment when the sample was perfused with air, and this was increased on stimulation of mitochondrial consumption or by increasing the oxygen concentration in the extracellular compartment. These experiments provide what we believe to be the first reported measurements of the oxygen concentration in a specific intracellular location (intraphagosomal) and its comparison with the oxygen concentration in the extracellular space. The observed gradient cannot be explained in terms of known coefficients of diffusion, and these results are consistent with previous reports that a gradient in oxygen concentration can occur between the average intracellular and extracellular concentration of oxygen.

Animals↗
PubMed1985

An ultrastructural study of the vascular alterations within the carotid bodies of spontaneously hypertensive rats (SHR).

Electron microscopic studies of the fine structural changes of the arterioles within the carotid bodies of spontaneously hypertensive rats (SHR) in the established phase of hypertension revealed partly hyperplastic endothelial cells. In the subendothelial space a multiplication of the basal laminae was observed often of a whirl-like shape. The smooth muscle cells of the media were hypertrophied, bizarre and with numerous projections. They exhibited a marked increase in cell organelles. The extracellular space was extensively enlarged and partly vacuolated. It contained a basement membrane-like material which was connected with the basal laminae of the myocytes. All these alterations produced a pad-like thickening of the arteriolar wall which narrowed the vessel lumen. These findings and their possible effects on carotid body function are discussed.

Animals↗
PubMed1995

Vasoactive intestinal peptide regulates extracellular adenosine levels in rat cortical cultures.

Adenosine is an important inhibitory neuromodulator in the cerebral cortex, yet it remains unclear how extracellular adenosine concentrations are regulated. Recently, it has been shown that beta-adrenergic receptor stimulation in rat cortical cultures causes the accumulation of extracellular adenosine derived by enzymatic hydrolysis from adenosine cyclic monophosphate (cAMP) transported into the extracellular space. In this study we show that vasoactive intestinal peptide (VIP), in addition to activating adenylyl cyclase and promoting the accumulation of intracellular cAMP in rat cortical cultures, also causes transport of cAMP and accumulation of extracellular adenosine. We further show that the extracellular accumulation of adenosine in response to VIP can be blocked by inhibition of cAMP transport, cyclic nucleotide phosphodiesterase activity, and 5'-nucleotidase, indicating that extracellular cAMP is the source of the adenosine. Cyclic AMP transport may be a general mechanism by which a variety of neuromodulators that act upon receptors coupled to adenylyl cyclase might regulate extracellular adenosine levels and thereby inhibitory tone in the cerebral cortex.

Adenosine↗
PubMed1980

Effect of prolonged beta-adrenoceptor blockade on heart weight and ultrastructure in young rabbits.

1 Young rabbits were treated for 30 days or 6 weeks with propranolol or oxprenolol to provide dose-levels similar to those used clinically. 2 Relative to litter matched controls the treated rabbits exhibited a reduced rate of growth. 3 Morphometric studies showed that prolonged beta-adrenoceptor blockade had no effect on the myofibrillar volume as a proportion of cell volume. 4 Prolonged beta-blockade increased the proportion of the extracellular space occupied by vascular tissue.

Adrenergic beta-Antagonists↗
PubMed1976

Amino acid uptake by fetal kidney slices.

Kidney slices of 7-17-week-old human fetuses were incubated for 90 min or less in Krebs-Ringer solution containing aminoisobutyric acid (AIB). Cell to medium ratios of AIB decrease with increasing fetal age. Uptake rate is slower than for mature human tissue. Both water content and extracellular space is high in embryonic tissue as compared to adult.

Age Factors↗
PubMed1991

A discrete helicoid of collagenous fibrils: the cuticle of deep-sea hydrothermal vent worms (Riftia pachyptila).

The fibrillar organization of the collagenous cuticle of the hydrothermal vent worm Riftia pachyptila is described. Fibrils in the posterior part of the cuticle are organized in a classical orthogonal plywood consisting of successive layers of fibrils: in this case, fibrils are oriented in only two directions which are orthogonal, as for pogonophoran. Our new data on the plume of Riftia pachyptila show a new type of fibrillar arrangement of the cuticle: 1) three sets of fibrils are arranged in an hexagonal pattern; 2) fibrils in successive plies are rotated by 60 degrees, and the organization of the fibrillar network is interpreted as a discrete helicoid when compared to continuously twisted plywoods; 3) a fourth set of fibrils crosses the hexagonally arranged plies and is oriented perpendicular to the surface of the body. X-ray diffraction studies of the cuticular fibrils reveal a triple helix which is characteristic of collagen molecules. Results obtained by differential scanning calorimetry (DSC) show that the denaturation temperature of the molecule is 54.7 degrees C for Riftia; whereas it is 58.9 degrees C for type I collagen measured under the same conditions. We discuss the origin of this plywood with respect to biomechanical constraints, self assembly processes, and compartmentation of the extracellular space. The involvement of the cell membrane in the fibrillogenesis of collagen is also discussed.

Animals↗
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↗
PubMed1989

Extracellular cAMP accumulation and degradation in rat cerebral cortex in dissociated cell culture.

Norepinephrine (NE) stimulated the accumulation of cAMP in embryonic rat cerebral cortex in dissociated cell culture. After exposure to NE for 10 min, the intracellular cAMP content of these cultures went from 22 +/- 12 to 202 +/- 75 pmol/mg protein. Using selective culturing techniques, evidence was obtained supporting the hypothesis that NE-stimulated production of cAMP is a property associated with the glial rather than the neuronal component of these cultures. Beta adrenergic agonist stimulation of cortical cultures also resulted in the efflux of cAMP into the medium. At the peak of extracellular accumulation of cAMP (following a 40-min exposure to isoproterenol), 180 pmol cAMP/mg protein had been transported into the extracellular medium. The fate of extracellular cAMP was investigated using thin-layer chromatography. Extracellular cAMP was degraded to AMP and adenosine; this degradation did not seem to be due to the presence of serum or serum components, suggesting the existence of an extracellular phosphodiesterase. In response to NE stimulation of glia, in particular astrocytes, cAMP or its metabolites may accumulate at high enough concentrations in the extracellular space in cerebral cortex to affect neuronal function, possibly via adenosine receptors.

Animals↗
PubMed1976

Pathway of sodium moving from blood to intestinal lumen under the influence of oxyphenisatin and deoxycholate.

The transfer of (51)CrEDTA and inulin--substances which are distributed only in the extracellular space--across the rat colonic mucosa in vivo is increased by oxyphenisatin O (3.5 times 10(-5)M) and deoxycholate D(3 times 10(-3)M). O and D do not change the size of the intra- and extracellular fluid compartments of the mucosa as measured with (51)CrEDTA from the blood side. The sodium and potassium content of the mucosal tissue is not altered. Therefore the calculated intracellular concentrations of sodium and potassium remain constant. The time course of the (22)Na uptake into the mucosal epithelium is not influenced by O and D up to 5 min after i.v. injection. The specific activity of sodium, however, in the luminal fluid increases under the influence of O(twofold) and D(fivefold). The uptake of (22)Na into the mucosal tissue after administration of (22)Nainto the intestinal lumen is not changed in presence of O and D. We conclude that the net transport of sodium and water from blood to lumen under the influence of O and D occurs mainly via the intercellular way.

Animals↗
PubMed1994

Pregnancy-associated major basic protein: deposition of protein and expression of mRNA at the maternal-fetal junction in early and late gestation.

Pregnancy-associated major basic protein (pMBP) has previously been isolated from human placenta and localized to the X cell. Here we used immunofluorescence staining and in situ hybridization to determine the distribution of pMBP and pMBP mRNA throughout the maternal-fetal junction in both early gestation tissues and at term. In early gestation tissues, pMBP was present only at the placental insertion site. Specifically, pMBP was present in (a) the decidua basalis (in the extracellular space, in interstitial pools and inside endometrial glands) and (b) intracellularly within extravillous interstitial trophoblasts in the decidua, in the myometrium and surrounding but not within luminal cells of spiral arteries. At term, the placental bed showed intense extracellular pMBP staining with little intracellular pMBP. In situ hybridization showed the presence of pMBP mRNA in both the early and late gestational tissues. pMBP mRNA was present in cells in the decidua, at the decidual-myometrial junction and in cell islands. Quantitative image analysis showed statistically significant hybridization signals with the pMBP antisense probe as compared to the control/sense probe. These results indicate that pMBP mRNA is expressed and pMBP is extensively deposited at the maternal-fetal junction in early pregnancy and at term.

Adult↗
PubMed2003

Metabolism of extracellular pyrophosphate.

Accumulation of excess inorganic pyrophosphate in cartilage matrix leads to calcium pyrophosphate dihydrate crystal deposits. Recent animal and human studies now support a role for physiologic extracellular pyrophosphate levels in preventing ectopic apatite calcification in joints and extracellular tissues. Extracellular pyrophosphate is likely generated by ectoenzymes and/or is a consequence of transport of intracellular pyrophosphate to the extracellular space. Generation of pyrophosphate by chondrocytes is modulated by aging, several soluble growth factors and cytokines, and transglutaminase. The transduction mechanisms involved in regulating pyrophosphate metabolism include protein kinase C and adenylyl cyclase. It appears that regulation of extracellular pyrophosphate levels within a narrow range is complex and necessary for appropriate mineral homeostasis in articular and nonarticular tissues.

Animals↗
PubMed1977

Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa.

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as 0.435 +/- 0.019 and 0.176 +/- 0.018 microliter/microliter tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of 2.63 +/- 0.25, 2.28 +/- 0.16, and 1.86 +/- 0.08 times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.

Animals↗
PubMed1993

Diffusion analysis of valproate and trans-2-en-valproate in agar and in cerebral cortex of the rat.

The diffusion of valproate (VPA) and trans-2-en-valproate were studied in agar gel and in the cerebral cortex of the rat using pressure microejection and VPA-selective microelectrodes. From the agar measurements a free diffusion coefficient for VPA of 6.52 x 10(-6) cm2.s-1 and for trans-2-en-VPA of 5.25 x 10(-6) cm2.s-1 for 37 degrees C was determined. The tortuosity value in the cortex was 1.92 for VPA and 1.67 for trans-2-en-VPA. The tortuosity values suggest that VPA and trans-2-en-VPA diffuse mainly in the extracellular space of the brain.

Agar↗
PubMed1987

Use of osmium tetroxide-potassium ferricyanide in reconstructing cells from serial ultrathin sections.

We describe a technique, modified from Langford and Coggeshall [Anat. Rec., 197 (1980) 297-303; J. Comp. Neurol., 203 (1981) 745-750], for enhancing membrane contrast and defining cellular boundaries, that is useful for reconstructing individual cells from ultrathin sections. The cells of interest in our study were neuronal germinal cells and their differentiated progeny in the retinas of young goldfish. These cells were labeled by pulse injections of [3H]thymidine, and they were subsequently identified in EM autoradiographs by the presence of silver grains overlying their nuclei. In tissue prepared by traditional procedures (fixation in mixed aldehydes, postfixation in osmium tetroxide) it was difficult to follow the processes of these cells through the complex, dense network of cells in the differentiated retina. However, in tissue postfixed with a mixture of osmium tetroxide and potassium ferricyanide, the contrast of the cell membranes was improved and, in favorable preparations, a dense precipitate was formed in the extracellular spaces, serving to outline individual cells. This greatly faciliated the preparation of reconstructions from serial ultrathin sections.

Animals↗
PubMed2004

Distribution and possible roles of aquaporin 9 in the brain.

Aquaporin 9 (AQP9) is a member of the aquaporin channel family involved in water flux through plasma membranes and exhibits the distinct feature of being also permeable to monocarboxylates, such as lactate, and various solutes, including glycerol, carbamides, purines, pyrimidines, and urea. AQP9 is constitutively expressed at high levels in the liver. In the brain under physiological conditions, AQP9 was first observed in tanycytes, and then in astrocytes. Only recently, its expression was also shown in neurons. Neurons expressing AQP9 are catecholaminergic and glucose sensitive. The expression of neuronal AQP9 can be negatively regulated by insulin and in diabetic animals an increase in AQP9 expression is observed in the catecholaminergic nuclei of the hindbrain, similar to the regulation of AQP9 by insulin in the liver. Furthermore, after transient brain ischemia, AQP9 expression is increased in astrocytes and its regulation may implicate the MAP-kinase pathways stimulated in such pathological conditions. Despite these new data, the exact role of AQP9 in the brain is still unclear. However, we may hypothesize that AQP9 is implicated in brain energy metabolism, as a neutral solute channel. AQP9 could facilitate the diffusion of lactate from the astrocyte to the neuron. In glucose sensitive neurons, diffusion of lactate and glycerol could stimulate these neurons in a similar manner to glucose and could regulate the energy balance. In pathological conditions, induction of AQP9 in astrocytes could participate in the clearance of excess lactate in the extracellular space. These hypotheses concerning the function of brain AQP9 are still speculative and open new areas of investigation.

Animals↗
PubMed1993

Inhibition of acidification rate in cultured fibroblasts by glucocorticoids. Application of silicon microphysiometry to endocrinology.

A recently-developed semiconductor-based instrument, the silicon microphysiometer, allows for realtime, sensitive quantification of cellular metabolism in small numbers of cultured cells with relative case. This is accomplished by detecting the extrusion into the extracellular space of acidic metabolic products of glycolysis, respiration, and ATP hydrolysis, including lactic acid, CO2, and protons. In the present report, we use microphysiometry to observe that glucocorticoids inhibit metabolic rate (as assessed indirectly by a change in the extracellular acidification rate) in fibroblasts (minimal effective dose of 1 nM of corticosterone), whereas 1 microM each estradiol, progesterone and testosterone failed to do so. We suggest that this inhibition of metabolism is secondary to the well-established inhibition of glucose transport and of protein synthesis in fibroblasts by glucocorticoids.

Acids↗
PubMed2005

Increased extracellular local levels of estradiol in normal breast in vivo during the luteal phase of the menstrual cycle.

Estrogen exposure is a major risk factor for breast cancer. Tissue estrogen originates from the ovaries but a significant portion is also produced by enzyme activity locally in the breast itself. How these enzymes are regulated is not fully understood. The extracellular space, where the metabolic exchange and cell interactions take place, reflects the environment that surrounds the epithelium but there has been no previous study of hormone concentrations in this compartment. In the present study microdialysis was used to measure extracellular estrogen concentrations in breast tissue and abdominal subcutaneous fat in 12 healthy women in vivo. It was found that women with high plasma progesterone levels had significant increased levels of estradiol in breast tissue compared with fat tissue (breast tissue 168+/-6 pM; subcutaneous fat, 154+/-5 pM; P<0.05), whereas women with low plasma progesterone exhibited no difference. Moreover, there was a significant correlation between local breast tissue estradiol and plasma progesterone levels (r=0.709, P<0.01). There was no difference in estrone sulphate in breast and fat tissue regardless of progesterone levels. Estrone was not detectable. The results in this study suggest that progesterone may be one regulator in the local conversion of estrogen precursors into potent estradiol in normal breast tissue.

Adult↗
PubMed1990

[Changes in fluid spaces in patients with heart failure under the effects of isolated ultrafiltration].

The study was undertaken to examine 22 patients with chronic heart failure of Stages IIB-III according to the classification developed by V. Kh. Vasilenko and N.D. Strazhesko. In patients with severe heart failure accompanied by the edematous syndrome, sessions of isolated ultrafiltration was found to result in substantially lower volumes of circulating plasma, extracellular and interstitial fluids and in increased total protein and hematocrit. When decreased just after each session of isolated infiltration, the volume of circulating plasma increased later due to fluid transfer from the extracellular space into the vascular bed. On day 20 of treatment the volume of circulating plasma reached the baseline values by altering the qualitative composition of plasma.

Aged↗