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At least 865 records · Page 48Linked to original sources
PubMed1997

Increase in extracellular calcium in the optic tectum of fish after optic nerve transection.

In this study the extracellular distribution of cytochemically generated calcium reaction product in the denervated optic tectum of a cichild fish (Oreochromis mossambicus) was investigated. The left optic nerve had been transected and the fish (5 per experimental condition) maintained for 2, 10 and 21 days. The amount of the calcium-containing precipitates was estimated using energy-filtering transmission electron microscopy (EFTEM) and image analysis. A special degeneration type of the optic terminals (neurofibrillar hypertrophy) was found which seems to be rare in other teleosts and was therefore chosen for quantification of the calcium deposits. These terminals are surrounded by astroglial processes and the calcium reaction product in the extracellular spaces between these glial processes and the terminals was measured and compared to normal optic terminals in nonoperated controls. A distinct and significant increase in the amount of calcium deposits was found 2 and 10 days after surgery which decreased to control levels after 21 days. This rise of deposits around the degenerating terminals was very local as arbitrarily selected extracellular spaces near these terminals showed values which were at the level of the nonoperated controls. Therefore, a transient and local increase in extracellular calcium precipitates was found after optic nerve transection which affected only the degenerating synapses.

Animals↗
PubMed1992

Production and disposition of 1-methyl-4-phenylpyridinium in primary cultures of mouse astrocytes.

Dopaminergic neurons are a primary target for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity. However, the conversion of MPTP to its neurotoxic 1-methyl-4-phenylpyridinium metabolite (MPP+) is likely to occur in astrocytes via the monoamine oxidase (MAO)-dependent formation of the 1-methyl-4-phenyl-2,3-dihydropyridinium intermediate (MPDP+). The main purpose of this study was to characterize the molecular mechanism(s) by which MPP+, once generated by astrocytes, may reach the extracellular space to become available for the active accumulation into dopaminergic neurons. Primary cultures of mouse astrocytes were used as an in vitro model system. After the addition of MPTP, levels of MPP+ were found to increase at constant rates both intracellularly and extracellularly at time points when no sign of cytotoxicity was evident. In contrast, MPDP+ levels remained quite stable during 4 days of incubation in the presence of MPTP. Finally, when astrocytes were allowed to accumulate MPP+ by pretreatment with either MPTP or MPP+ and then were incubated in fresh medium not containing MPTP or MPP+, intracellular levels of MPP+ rapidly declined and corresponding amounts of this compound were found in the incubation medium. Results of this study are compatible with the following conclusions: 1) the MPP+ accumulated in the extracellular compartment during incubations with MPTP is not released from astrocytes as a consequence of its own cytotoxic effects; 2) MPP+ can be formed extracellularly presumably via autoxidation of MPDP+ after this latter compound has been generated within astrocytes and has crossed astrocyte membranes; and 3) despite its charged chemical structure, MPP+ can cross the plasma membrane toward the extracellular space after being formed within astrocytes.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2006

Measurement of kinetic parameters in skeletal muscle by magnetic resonance imaging with an intravascular agent.

The purpose of this work was to investigate the use of an intravascular contrast agent to determine perfusion kinetics in skeletal muscle. A two-compartment kinetic model was used to represent the flux of contrast agent between the intravascular space and extravascular extracellular space (EES). The relationship between the image signal-to-noise ratio (SNR) and errors in estimating permeability surface area product (Ktrans), interstitial volume (ve), and plasma volume (vp) for linear and nonlinear curve-fitting methods was estimated from Monte Carlo simulations. Similar results were obtained for both methods. For an image SNR of 60, the estimated errors in these parameters were 10%, 22%, and 17%, respectively. In vivo experiments were conducted in rabbits to examine physiological differences between these parameters in the soleus (SOL) and tibialis anterior (TA) muscles in the hind limb. Values for Ktrans were significantly higher in the SOL (3.2+/-0.9 vs. 2.0+/-0.5x10(-3) min-1), as were values for vp (3.4+/-0.8 vs. 2.1+/-0.7%). Differences in ve for the two muscles (8.7+/-2.2 vs. 8.5+/-1.6%) were not found to be significant. These results demonstrate that relevant physiological metrics can be calculated in skeletal muscle using MRI with an intravascular contrast agent.

Algorithms↗
PubMed2004

Phospholipid metabolism in lung surfactant.

Pulmonary surfactant is a mixture of lipids, mostly phospholipids, and proteins that allows for breathing with minimal effort. The current chapter discusses the metabolism of the phospholipids of this material. Surfactant phospholipids are synthesized in the type II epithelial cells of the lung. The lipids and surfactant proteins are assembled in intracellular storage organelles, called lamellar bodies, and are subsequently secreted into the alveolar space. Within this extracellular space surfactant undergoes several transformations. First the lamellar bodies unravel to form a highly organized lattice-like lipid:protein structure tubular myelin. Second, the organized structures, in particular tubular myelin, adsorb to form a lipid at the air-liquid interface of the alveoli. It is, in fact, this surface tension reducing film that is responsible for the physiological role of surfactant, to prevent lung collapse and allow ease of inflation. Third, the surface film is converted to a small vesicular form. Finally, these small vesicles are taken-up by the type II cells for recycling and degradation and by alveolar macrophages for degradation.

Aged↗
PubMed1976

Distribution of the glio-interstitial system in molluscs. II. Electron microscopy of tonic and phasic muscles in the digestive tract of Aplysia and other opisthobranchs.

The muscular walls of the buccal mass and the oesophagus of Aplysia rosea and Glossodoris tricolor were studied by electron microscopy. The cytological features of the muscle cells, neuro-muscular junctions and a neuro-glial junction are described. This junction between an axon and a teloglial process, in the oesophagus of Aplysia, possesses all the cytological differentiations of a typical molluscan synapse. Particular attention is drawn to the distribution of the glio-interstitial tissue and the size of the extracellular spaces in these muscular organs. The classification of these muscle into 'tonic' and 'phasic' types is discussed. From this study and other data, it is concluded that the development of the glio-interstitial tissue in the muscular organs of molluscs is correlated with the size of the extracellular spaces rather than with the type of contraction of the muscle.

Animals↗
PubMed1997

Enhanced anti-inflammatory effects of Cu, Zn-superoxide dismutase delivered by genetically modified skin fibroblasts in vitro and in vivo.

PURPOSE: The purpose of this work was to evaluate the anti-inflammatory effects of secretable human Cu, Zn-superoxide dismutase (hSOD) delivered by genetically modified skin fibroblasts in vitro and in vivo. METHODS: Rat skin fibroblasts were transfected with pRc/CMV-ILSOD including secretable SOD-coding cDNA. The effects of host and transformants on oxidative stress in vitro models using the xanthine/xanthine oxidase (X/XO) system were examined to study the paracrine SOD action. The anti-inflammatory effects by transplantation of host and transformants were evaluated in an acute inflammation model, carrageenin-induced paw edema, in rats. RESULTS: The transformants (ILSOD cells) secreted SOD protein into the extracellular space, and the extracellular SOD activity in ILSOD cells cultures was significantly increased compared with that in host cell cultures. ILSOD cells diminished the cytotoxic activity by X/XO in a paracrine fashion. These protective effects of ILSOD cells against X/XO-induced cytotoxicity correlated well with the decrease in lipid peroxidation in the damaged cells. The in vivo study showed that transplantation of ILSOD cell suspensions into the hind paw in rats inhibited carrageenin-induced paw edema for at least 7 days, and the degree and the durability of these inhibitory effects were dependent on the number of ILSOD cells transplanted. These inhibitory effects of ILSOD cell suspensions were reduced by co-administration of antiserum for hSOD. Furthermore, the healing of paw edema caused by carrageenin was markedly enhanced by transplantation of ILSOD cells into the edemics hind paw. CONCLUSIONS: The findings suggested that genetically modified skin fibroblasts are a suitable delivery system for obtaining an efficient and continuous supply of SOD to the target site, and this strategy may be a useful drug delivery system for therapeutic proteins.

Animals↗
PubMedDate not supplied

Cryopreservation of human platelets with dimethyl sulfoxide: changes in biochemistry and cell function.

BACKGROUND: The shelf life of liquid-stored platelet concentrates is limited to 5 days. Therefore, much work has been carried out in an attempt to establish the optimum method for cryopreservation. Among the various cryoprotectants, dimethyl sulfoxide (DMSO) has been shown to be the most effective. However, DMSO-frozen platelets are characterized by a number of cell lesions. This report describes metabolic and functional changes that should give rise to some concern about the functional integrity of these cells. STUDY DESIGN AND METHODS: Single-donor platelet concentrates were frozen in liquid nitrogen by use of DMSO (5%). After thawing, the cells were washed and resuspended in autologous plasma. Before, during, and after the freezing process, samples for analysis of metabolic measures (e.g., pH; calcium, potassium, and lactate dehydrogenase concentrations; plasma complement factors) and functional measures (e.g., aggregometry, in vitro bleeding time, alpha-granule membrane protein-140 expression) were taken. RESULTS: Mean platelet volume increases during the deep-freezing process. Potassium, calcium, and lactate dehydrogenase are released from the intracellular space to the extracellular space. A strong activation of complement, which is mainly due to the addition of DMSO, is observed. Platelets become activated as indicated by the expression of alpha-granule membrane protein-140. Accordingly, decreased platelet function can be observed. CONCLUSION: DMSO-frozen platelets are characterized by several metabolic and functional changes. Although these cells have been shown to exert hemostatic effects in vivo, it is conceivable that those effects could be improved by further development of platelet-freezing techniques.

Blood Platelets↗
PubMed1998

Molecular modeling of HIV-1 coreceptor CCR5 and exploring of conformational space of its extracellular domain in molecular dynamics simulation.

The chemokine receptor CCR5 functions as a major fusion coreceptor for macrophage-tropic human immunodeficiency virus entry into cell. Here we report a three-dimensional model of CCR5 built using molecular modeling approach. Because the virus binds to extracellular domain of the receptor, special attention was given to conformational flexibility, hydrogen bonding, and environmental polarity properties of this protein part. Such data were obtained in the result of molecular dynamics study of the extracellular domain. It was shown that during the simulation the extracellular segments form a compact globular domain with numerous long-range hydrogen bonds between them. First loop of the receptor stays quite rigid while N-terminal region and loops 2, 3 are rather flexible. A number of amino acid residues disposed in unfavourable environment and, therefore, potentially involved in binding of CCR5 to viral glycoproteins and chemokines, was delineated. Comparison of the results with available experimental data permits a proposal that such residues in loop-1 and N-terminal part of the receptor are important for HIV-1 entry, while those in loops 2 and 3 participate in ligand binding. Perspectives of rational alteration of virus-binding activity of CCR5 are discussed.

Amino Acid Sequence↗
PubMed1996

Uptake characteristics of oligonucleotides in the isolated rat liver perfusion system.

The objective of this study was to examine the hepatic disposition characteristics of 20-mer model phosphodiester oligonucleotide (PO) and its partially phosphorothioated (PS3) and fully phosphorothioated (PS) derivatives in the single-pass isolated rat liver perfusion system. [32P]-labeled oligonucleotides were momentarily introduced into this system through the portal vein as a bolus input mode, and the venous outflow patterns were evaluated using statistical moment analysis. The apparent volumes of distribution of these oligonucleotides were greater than those of reference substances for vascular space (erythrocytes) and extracellular space (human serum albumin), indicating a significant interaction between oligonucleotides and the liver. Significant hepatic uptake of oligonucleotides was also observed. About 20%, 36%, and 52% of the injected dose (3 micrograms/rat) was taken up by the liver during a single passage after bolus injection of PO, PS3, and PS, respectively. In the case of PS injection, slow efflux from the liver was observed in the latter phase of perfusion. This suggests that the hepatic uptake process of these oligonucleotides greatly depended on their types. The results of collagenase perfusion experiments suggest that PS3 oligonucleotides were taken up by both liver parenchymal and nonparenchymal cells. The amount of total recovery in the liver decreased substantially by coadministration of polyinosinic acid, dextran sulfate, polycytidic acid and 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid. This suggests that PS3 was taken up by the liver as an anionic molecule in a nonspecific manner.

Animals↗
PubMed2006

In situ profiling and quantification of cytokines released during ultraviolet B-induced inflammation by combining dermal microdialysis and protein microarrays.

In skin, an evolving inflammatory or immune response is triggered by early release of a cytokine cascade into the extracellular space. Investigation of extracellular cytokine secretion in situ has been limited by low cut-off filtering membranes and sample volume size and the inability to monitor changes in cytokine protein levels in real-time in situ. Here, we combine for the first time the methods of intradermal microdialysis and antibody protein arraying to profile the early cascade of multiple cytokines in a complex inflammatory response exemplified by ultraviolet B (UVB)-induced inflammation. We observed significant differences of the cytokine and growth factor responses after tissue injury by catheter placement and UVB-induced inflammation. UVB irradiation initiates a rapid proinflammatory response followed by a mixed TH1/TH2 response in which ultimately TH2 cytokines IL-4 and IL10 predominated after 24 h. This most likely indicates the termination and self limitation of the inflammatory response. We conclude that the combination of dermal microdialysis and protein microarray offers a powerful tool to analyze in real-time the complex and rapidly changing interstitial protein milieu during cutaneous inflammatory responses.

Adult↗
PubMed1999

Review of mechanisms by which electrical stimulation alters the transmembrane potential.

Electrical stimuli pace, cardiovert, or defibrillate the heart by changing transmembrane potential (deltaVm). Recent simulation studies provide insights into mechanisms by which stimuli establish deltaVm. This review attempts a nonmathematical description of these mechanisms. We start with the cable model in which the intracellular core conductor is bounded by a highly resistive and capacitive membrane that separates the intracellular and extracellular spaces. Intracellular and extracellular resistances are assumed to vary linearly with position. Although this model predicts anodal extracellular stimuli hyperpolarize adjacent tissue and cathodal extracellular stimuli depolarize that tissue, it fails to reproduce regions of opposite deltaVm distant from the electrodes. We then consider the sawtooth model in which microscopic discontinuities in intracellular resistance represent gap junctions. While model studies with such discontinuities demonstrate large deltaVm at cell ends, experimental validation of such deltaVm remains elusive. Extending the analysis to the two- and three-dimensional syncytium, we also consider the bidomain model in which intracellular, extracellular, and interstitial currents are explicitly characterized. Differences in resistance to these currents gives rise to virtual electrodes, which are experimentally observed regions of large deltaVm that arise distant from the stimulating electrode. Distant deltaVm regions are also evident when macroscopic discontinuities in intracellular resistance are introduced into the bidomain model. Such discontinuities are associated with clefts or scars that give rise to "secondary sources." Albeit the cable model offers remarkable insight the bidomain model and the concept of secondary sources provide a more complete understanding of membrane excitation, especially when combined into a unifying activating function.

Action Potentials↗
PubMed1999

Effects of osmotic stress on dextran diffusion in rat neocortex studied with integrative optical imaging.

Effects of osmotic stress on dextran diffusion in rat neocortex studied with integrative optical imaging. This study investigated how dextran (Mr = 3,000) diffused in rat cortical slices when the osmolarity of the bathing artificial cerebrospinal fluid was altered by varying the NaCl content. The apparent diffusion coefficient, D*, was measured in the neocortex region using fluorescent molecules and the integrative optical imaging (IOI) method. The main results were: 1) the value of D* in rat neocortex in the isotonic (300 mOsm) artificial cerebrospinal fluid at 34 degrees C was D* = 0.68 +/- 0. 01 x 10(-6) cm2 s-1 (mean +/- SE, n = 78) and it could be changed within minutes by varying the extracellular osmolarity. 2) Hypotonic stresses up to -100 mOsm decreased D* by 35% and were fully reversible when the slices were returned to the isotonic medium. Further hypotonic stress to -150 mOsm caused further decrease in D* but after removal of the stress, D* overshot its control value. 3) Hypertonic stress of +50 mOsm increased D*, but the maximum reversible increase in D* was only 15%. Further hypertonic stress (to +200 mOsm) did not cause any further increase in D* and, after removal of the stress, D* undershot the control value. The changes in D* are thought to be related to volume changes of cells in tissue: hypotonic solutions caused cell swelling, resulting in reduced extracellular space and compressed extracellular matrix so that the dextran diffusion was more hindered. Hypertonic solutions had the opposite effect. Recordings of extracellular field potentials in the hippocampal CA1 region demonstrated that, on return to the isotonic solution after exposure to an extreme hypotonic or hypertonic stress, the neurons retained their ability to generate synaptic responses.

Animals↗
PubMed1977

Lithium in depression: a biochemical study.

Two groups of depressed subjects, one with a history of recurrent depression, the other with a history of persistent apathy, were given lithium carbonate 1,200 mg q.i.d. and supplementart potassium 1,200 mg t.d.s. for 1 week. Measurements were made before and after the lithium treatment of total body water (tritium space), extracellular fluid (sulphate space), total exchangeable sodium (Nae) and total exchangeable potassium (Ke) using sodium-24 and potassium-42 multiple isotope dilution techniques. Prior to treatment when compared with a group of normal subjects, both depressed groups showed changes in body fluid volumes and electrolyte levels. Total body water, intracellular fluid and intracellular potassium were lowered, while electrolyte levels. Total body water, intracellular fluid and intracellular potassium were lowered, while intracellular sodium was raised. After treatment with lithium the values in the apathetic group showed little change but the group with recurrent depression showed a significant increase in intracellular fluid (p less than 0.025), Ke (p less than 0.001), intracellular potassium (p less than 0.025) and a significant decrease in Nae (p less than 0.05). There was a marked increase in mood in the group with recurrent depression but not in the apathetic group following lithium treatment. These findings suggest that recurrent depression, both in clinical improvement, mood and also correction of water and also correction of water and electrolyte disturbances arise, but not in patients with long-standing apathy.

Aged↗
PubMed1988

Comparison of the action of epinephrine and a respiratory chain uncoupler, 2,4-dinitrophenol, on Ca2+-mobilization in isolated hepatocytes and perfused livers.

The effects of epinephrine and dinitrophenol (DNP) on Ca2+-fluxes and energy metabolism were compared in isolated rat hepatocytes and perfused rat livers. Epinephrine increased the cytosolic free Ca2+ concentration ([Ca2+]i), with Ca2+ being extruded into the extracellular space. DNP also increased [Ca2+]i, but did not cause Ca2+ extrusion into the extracellular space. The maximal change of [Ca2+]i caused by DNP was much larger than that by epinephrine. In the absence of extracellular Ca2+, the transient increase of [Ca2+]i due to epinephrine declined rapidly, while the DNP-induced increase was not affected. Although increased oxygen consumption was detected after the addition of epinephrine or DNP, tissue ATP contents decreased markedly by DNP, but not by epinephrine, suggesting that the Ca2+ extrusion is energy-dependent. DNP could activate glycogenolysis even after the depletion of the epinephrine-responsive Ca2+ store in isolated perfused liver, indicating that this intracellular Ca2+ store differed from the DNP-responsive store.

2,4-Dinitrophenol↗
PubMed2025

Dehydration and rehydration in donkeys: the role of the hind gut as a water reservoir.

Body fluid distribution was measured in three donkeys, fully hydrated, following dehydration and after being rapidly rehydrated. In twenty other donkeys that were slaughtered to supply food for predators in a safari zoo, the water content in the different compartments of the gastrointestinal tract (GIT) was assessed. Prior to being slaughtered, four of the animals were fully hydrated, four dehydrated and 12 dehydrated, rehydrated and then slaughtered and examined, four at 1, for at 3 and four at 5 hours following drinking. When the body mass of dehydrated donkeys dropped to 75.4 +/- 2.4% of their initial value, total body water of the animals (HTO space), extracellular volume (SCN space) and plasma volume (EB space) were reduced to 76.6 +/- 5.3%, 80.9 +/- 10.6% and 73.2 +/- 8.3% of their initial values, respectively. The amount of water retained in the GIT of the fully hydrated donkeys amounted to 15.9 +/- 3.4 1, 19% of total body water. In the dehydrated donkeys it was only 7.4 +/- 1.3 1. The calculated total intracellular volume in the dehydrated donkeys was only 14% lower than in the fully hydrated animals. When drinking was allowed, dehydrated donkeys consumed 17.6 +/- 2.4 1 of water. The increase in the water content in the gut of newly rehydrated donkeys matched this volume, 80% of which was retained in the hind gut. During the five hours after drinking, only slow and moderate changes in the volume of the hind gut were recorded. Changes in plasma volume were also suppressed. It is suggested that the hind gut of the donkey, similar to the rumen of goats and sheep, plays a role as a water reservoir that helps maintain the osmotic stability of the body.

Animals↗
PubMed1982

[Morphofunctional study of human pericardial macrophages].

Human pericardial macrophages have been studied with the light and electron microscope. The cells showed high activities of acid phosphatase and of non-specific and acid esterases. The macrophages are able to pinocytosis the extracellular space marker--horseradish peroxidase. The network of intracytoplasmic cavities, continuous with the extracellular space, has been documented by applying two different methods of visualization of the cellular surface. A possible role of these cavities in pinocytosis is discussed.

Adult↗
PubMed1977

A potassium gradient in smooth muscle segment of the opossum esophagus.

Sodium and potassium content were determined in the smooth muscle segment of the opossum esophagus. Extracellular space measurements were also made using inulin and mannitol as markers. The muscle also made using inulin and mannitol as markers. The muscle was sampled at five sites spaced equally along the esophageal segment. On site in the stomach was also examined. The mean tissue sodium content was 36.6 +/- 10.7 meg/kg, and the mean tissue sodium content was 83.5 +/- 2.9 meg/kg wet wt. The mean inulin space was 184 +/- 34 ml/kg, and the mean mannitol space was 249 +/- 20 ml wet wt. The tissue potassium content was found to decline from 48.4 /- 10.1 meg/kg at the proximal site to 23.6 +/- 8.0 meg k/g at the distal site. The slope of electrolyte values from sites 1 through 5 was significant for both potassium and sodium. Extracellular space volume did not differ significantly from one end of the smooth muscle segment to the other.

Animals↗
PubMed1987

The volume and ionic composition of cells in incubated slices of rat renal cortex, medulla and papilla.

The apparent extracellular space in incubated slices of rat renal cortex, medulla and papilla has been measured using three differently sized marker molecules, mannitol, sucrose and inulin. Cellular volumes have been estimated by following the efflux of 3-O-methyl-D-glucose from equilibrated slices. Sucrose appears to be the most accurate extracellular marker in each of the regions examined, in that the sum of its volume of distribution plus cellular volume approximates most closely to the total slice fluid volume. Inulin has the same volume of distribution as sucrose in cortical slices, but under-penetrates medullary and papillary tissue. Mannitol overestimates the extracellular space in all three regions, although its larger volume of distribution, relative to that of sucrose, was not statistically significant in papillary slices. When cell volume and composition are estimated (a) using sucrose as extracellular marker and (b) making appropriate allowance for the presence of bound tissue electrolytes, it is found that cells in each region have low Na+ and high K+ concentrations and contents. When papillary slices are incubated in medium of very high osmolality (NaCl plus urea, 2000 mosmol/kg H2O) there is a moderate (approx. 23%) decrease in cell volume and an increase in cell fluid Na+ and Cl- concentrations equal to approx. 50% of the increase in the extracellular concentrations. Cell K+ concentrations remain unchanged. The results show that cells in renal slices are able to maintain high K+-to-Na+ ratios when incubated in isosmotic (cortex) or moderately hyperosmotic media (medulla and papilla), and suggest that regulation of papillary cell volume following hyperosmotic shock can only partly be ascribed to uptake of extracellular electrolytes.

3-O-Methylglucose↗