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At least 505 records · Page 28Linked to original sources
PubMed1988

Time course of release in vivo of PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and TxB2 into the brain extracellular space after 15 min of complete global ischemia in the presence and absence of cyclooxygenase inhibition.

The time-dependent release of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), thromboxane (Tx) B2, and 6-keto-PGF1 alpha (6-keto) from brain was measured before, during, and after a 15-min interval of total ischemia (four-vessel occlusion) in halothane-anesthetized cats using the technique of cerebroventricular perfusion. Resting levels of PGE2, PGF2 alpha, 6-keto, and Tx were: 253 +/- 75, 953 +/- 300, 650 +/- 200, and 550 +/- 170 pg/ml, respectively. During the 15-min ischemia, all prostanoids rose significantly, yet the highest levels were not observed until the first 15-60 min of the reflow at which time levels of PGE2, PGF2 alpha, 6-keto, and Tx, as compared with the preischemic baseline, rose approximately 8, 3.4, 3, and 55-fold, respectively. Significantly, although all prostanoids showed increases relative to baseline, the ratios of PGF2 alpha/6-keto and PGE2/6-keto remained stable throughout the experiment in both groups of animals. In contrast, the Tx/6-keto ratio rose from approximately 1 to approximately 30 during the 60 min after reflow in untreated cats. Treatment with zomepirac sodium (5 mg/kg, i.v.), a cyclooxygenase inhibitor, resulted in highly significant reductions in the levels of all prostanoids during the preischemic period. In zomepirac sodium-treated animals, there were also highly significant reductions in the prostanoid response to ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Effects of clonidine on the stimulation-evoked release of 3H-noradrenaline from superfused rat brain slices as a function of the biophase concentration. Temperature dependent widening of extracellular space.

The influence of clonidine on the stimulation-evoked overflow of tritium was studied in brain slices preincubated with 3H-noradrenaline. The slices were prepared from parietal cortex (Cx), nucleus anterior hypothalami (nah) and nucleus tractus solitarii (nts). After preincubation, the tissues were superfused at 23 degrees C or 37 degrees C with a medium containing the noradrenaline uptake inhibitor desipramine. Electrical field stimulation was applied using stimulation frequencies of 0.3-10 Hz. At 23 degrees C/0.3 Hz, clonidine concentration-dependently inhibited the evoked overflow of tritium in all three brain regions. In contrast, at 23 degrees C/3 Hz the inhibitory effect of the drug in the Cx was abolished and a facilitation was observed in the nah and nts. When tested at increasing frequencies of stimulation in the nts at 23 degrees C, clonidine exerted a dual action, characterized by a reduction of electrically evoked responses at frequencies below 1 Hz and a facilitation at frequencies above 1 Hz. At 37 degrees C, clonidine concentration-dependently decreased the evoked overflow in all brain regions studied, this effect being more pronounced at 0.3 Hz than at 3 Hz. The apparent lack of an effect of clonidine on the stimulation-evoked overflow of tritium in the Cx at 23 degrees C/3 Hz was turned to a facilitation when noradrenaline (0.01 mumol/l) was included in the superfusion medium. Conversely, an inhibitory effect of clonidine was seen when the uptake blocker desipramine (as well as noradrenaline) was omitted from the superfusion medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Kinetic of adjustment of enzyme catalytic concentrations in the extracellular space of the man, the dog and the rat. Approach to a quantitative diagnostic enzymology, V. Communication.

The high degree of constancy of enzyme catalytic activity in the plasma of a given individual is regulated by a complex system of flux equilibria consisting of eight basic processes. Some of these processes are of primarily theoretic importance. Enzymes from all tissues of the body, including the liver, are released via a continuous physiological process into the interstitial space and get into the intravascular space by way of lymphatic transport. The release of enzymes from tissues directly into the intravascular space is of secondary importance as is the exchange of enzyme molecules across capillary membranes from the intravascular to the interstitial space and vice versa. In contrast, enzymes from circulating blood cells are transported directly into the intravascular space. Enzymes are removed from the intravascular space at rates which vary greatly between both enzymes and species. In a review of the literature, half-lives of diagnostically important enzymes in plasma of man, dogs and rats were given and the striking differences in the results for a given enzyme are discussed from a methodological point of view. In a mathematical analysis, data for lymphatic transport of enzymes from dogs and rats (Lindena et al. (1986) this J. 24, 19-33) and of enzyme efflux from in vivo ageing erythrocytes (Lindena et al. (1986) this J. 24, 49-59) into the plasma are related to the elimination rate constants of enzymes from the plasma. The contribution of lymphatically transported enzymes to the basal catalytic activity in plasma (Lindena & Trautschold (1986) this J. 24, 11-18) amounts to 55-80% for lactate dehydrogenase and malate dehydrogenase, 80-90% for adenylate kinase and phosphohexose isomerase, 90-95% for aspartate aminotransferase and aldolase and 99% for creatine kinase. A model of Ca2+ -mediated vesicular transport of enzymes out of ageing erythrocytes is proposed. The importance of lymphatically transported enzymes to total plasma catalytic activity in dogs and rats argues for a similar contribution of lymph transport in man.

Animals↗
PubMed2006

Hemorrhage and operation cause a contraction of the extracellular space needing replacement--evidence and implications? A systematic review.

BACKGROUND: Hemorrhagic hypotension or operative trauma is believed to cause a contraction of the extracellular fluid volume (ECV) beyond the measured fluid losses. The aim of this review was to explore the evidence and implications of ECV loss. METHODS: We performed a systematic review of original trials measuring ECV changes during hemorrhage or operation. PubMed, relevant periodicals, and reference lists were searched until no further original articles appeared. The quality of both the scientific and the technical methods of the trials were evaluated. RESULTS: A total of 61 original articles were found. The pattern appeared that all investigators reporting shock or operation to cause a disparate reduction of the ECV had measured the ECV with the same method. The ECV was calculated from very few blood samples that were withdrawn after 20 to 30 minutes of equilibration of a tracer (the (35)SO(4)-tracer). Trials calculating ECV from multiple blood samples, after longer equilibration times, or using other tracers did not find a contraction of the ECV. On the contrary, trials using a bromide tracer found the ECV to be expanded after operation. CONCLUSIONS: The evidence supporting the idea that hemorrhage or operation cause a contraction of the ECV is weak, and probably a result of flawed methodology.

Clinical Trials as Topic↗
PubMedDate not supplied

[Muscular dystrophies due to alterations at extracellular space level: congenital muscular dystrophy caused by merosin deficiency].

OBJECTIVE: This is an up-to-date analysis of congenital muscular dystrophies (CMD), especially merosin-deficient-CMD, we also present our center expertise. DEVELOPMENT: CMD are skeletal muscle degenerative hereditary diseases caused by abnormal synthesis of structural or functional muscle proteins. Severe hypotonia, joint deformities and muscle weakness at birth are the main features of CMD. A especial type of CMD caused by absence of alpha 2 chain (or merosin) of laminin 2, a tissue specific protein from muscle basement membrane which anchors extracellular matrix to dystrophin, is the paradigm of a muscular dystrophy produced by extracellular abnormalities. CMD merosin-negative locus was assigned to chromosome 6q2, where is localized the laminin alpha 2 chain gene (LAMA2). Recently, LAMA2 gene mutations producing the disease have been described. Floppy infant syndrome is its earliest symptom and CMD merosin-negative represents the most frequent cause of muscular origin. 40% of our CMD patients are completely merorin-deficient. They had marked delayed motor milestones and never became ambulant but their intelligence remainded normal. Nowadays we can perform a prenatal diagnosis by immunohistochemical analysis in trophoblast. CONCLUSION: CMD merosin-deficient represents a subset of patients with a potentially poor prognosis, thus an early diagnosis is highly convenient in order to establish a correct follow-up [REV NEUROL 1999; 28: 141-9].

Biopsy↗
PubMed2000

BMP-binding modules in chordin: a model for signalling regulation in the extracellular space.

A number of genetic and molecular studies have implicated Chordin in the regulation of dorsoventral patterning during gastrulation. Chordin, a BMP antagonist of 120 kDa, contains four small (about 70 amino acids each) cysteine-rich domains (CRs) of unknown function. In this study, we show that the Chordin CRs define a novel protein module for the binding and regulation of BMPs. The biological activity of Chordin resides in the CRs, especially in CR1 and CR3, which have dorsalizing activity in Xenopus embryo assays and bind BMP4 with dissociation constants in the nanomolar range. The activity of individual CRs, however, is 5- to 10-fold lower than that of full-length Chordin. These results shed light on the molecular mechanism by which Chordin/BMP complexes are regulated by the metalloprotease Xolloid, which cleaves in the vicinity of CR1 and CR3 and would release CR/BMP complexes with lower anti-BMP activity than intact Chordin. CR domains are found in other extracellular proteins such as procollagens. Full-length Xenopus procollagen IIA mRNA has dorsalizing activity in embryo microinjection assays and the CR domain is required for this activity. Similarly, a C. elegans cDNA containing five CR domains induces secondary axes in injected Xenopus embryos. These results suggest that CR modules may function in a number of extracellular proteins to regulate growth factor signalling.

Amino Acid Sequence↗
PubMed1993

Contribution of potassium accumulation in narrow extracellular spaces to the genesis of nicorandil-induced large inward tail current in guinea-pig ventricular cells.

The mechanism of nicorandil-induced large inward tail current (Itail) in single guinea-pig ventricular cells was investigated using the whole-cell patch-clamp technique. In the presence of 0.5-1.0 mM nicorandil, an activator of adenosine 5'-triphosphate (ATP)-sensitive K+ current (IKATP), a depolarization pulse causing a large outward current was followed by a large inward Itail on the repolarization step to the holding potential at -85 mV. The larger the outward current, the greater the Itail. The amplitude of Itail increased as a single exponential function (tau = 74.9 ms) as the duration of preceding depolarization was prolonged. Both the outward current and Itail were inhibited nearly completely after application of glibenclamide (1 microM), a specific blocker of IKATP. Substitution of K+ with Cs+ in both the external and internal solutions resulted in a virtual elimination of Itail. Itail was well preserved under the condition where Ca2+ entry during the preceding depolarization was largely inhibited or where external Na+ was replaced by Li+. A transient positive shift of reversal potential for the net current was observed at the peak of Itail). At 30 mM external K+ concentration, Itail was almost eliminated. From these findings, its is concluded that the Itail is a K+ current associated with an alteration of the K+ equilibrium potential (EK) following a substantial K+ efflux. This EK change is most likely explained by an accumulation of K+ in transverse tubules (T-tubules) since Itail was not induced in atrial cells in which T-tubules are poorly developed.

Adenosine Triphosphate↗
PubMed1988

Expansion of extracellular tracer spaces in the isolated heart perfused with crystalloid solutions: expansion of extracellular space, trans-sarcolemmal leakage, or both?

Comparisons of the distributions of tracers putatively confined to the myocardial extracellular space (ECS) in vivo and in isolated hearts perfused with crystalloid solutions via their coronaries, generally indicate that ECS markedly expands--both absolutely and relative to cellular space (ICS)--over a period of in vitro perfusion. Quantification of the expansion is problematic, however, because of the difficulty of distinguishing between a true increase in anatomical ECS and expansion of tracer space due to penetration of the plasma membrane. This difficulty in turn renders an assessment of the distribution of electrolytes and other substances unreliable. In the present study a combined morphometric-tracer distribution analysis is applied towards distinguishing between ECS expansion and tracer leakage in the rat Langendorff preparation perfused with a modified Krebs-Henseleit solution. The results demonstrate that both ICS and ECS expanded with the first few minutes of perfusion, with the ICS remaining constant thereafter and the ECS increment declining slowly. Although the expansion of the ECS initially is disproportionately greater relative to that of the ICS, this relative difference disappears in about 1 h, i.e., the uptake of water by the myocardium is nearly homogeneous. An apparent increase of ECS relative to ICS, by more than one-third the initial space after 90 min perfusion, was found to be entirely artifactual and apparently due to a non-specific increase in sarcolemmal permeability.

Animals↗
PubMed1997

Cellular uptake of 3H-bestatin in tissues of mice after its intravenous injection.

Bestatin, a dipeptide analog, is a potent aminopeptidase inhibitor of bacterial origin. We have previously shown that bestatin inhibits cytosolic exopeptidases in mammalian cells, and results in the accumulation of di- and tripeptide intermediates in cellular protein degradation. Our primary interest is the uptake of bestatin in liver and muscle, 10 min after its intravenous injection into mice. In this short interval, peptide intermediates accumulate linearly in these tissues and permit an estimate of their rates of cellular protein breakdown. Male, CD-1 adult mice received the intravenous injection of 3H-bestatin and 14C-sucrose. The disappearance of 3H-bestatin from the plasma, when normalized by the injected radioactivity, was indistinguishable from that of 14C-sucrose. They both drop rapidly during the first 10 min after the injection, followed by a slower exponential disappearance of 3.4% per min, which extrapolates to an apparent volume of distribution of 25 ml/100 g body weight. In two mice, 3 hr after the injection, the urine contained 77.4% and 79.8% of the injected 14C-sucrose, and 70.9% and 73.9% of the injected 3H-bestatin. Other mice were killed 10 min after the injection of 5 mg of bestatin, and the concentration of 3H-bestatin and 14C-sucrose was determined in the plasma and various tissues. Using sucrose as a nonpermeant marker of the extracellular space, extracellular 3H-bestatin was calculated and subtracted from the total to estimate the cellular uptake of bestatin. Bestatin was taken up readily in the liver (383-452 microg/g), kidneys (175-191 microg/g), and intestine (137-179 microg/g), but much less in red cells (11 microg/g) or skeletal muscle (4.8 microg/g). Bestatin also entered slowly into erythrocytes in vitro (0.3%/min) by a nonsaturable process. It is suggested that bestatin is taken up through transporter-mediated processes in some cells but not others.

Animals↗