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At least 1,783 records · Page 99Linked to original sources
PubMed1978

Intercellular granules and vesicles in prolonged cerebral vasospasm.

Prolonged vasospasm was produced in the dog basilar arteries by introduction of fresh arterial blood or norepinephrine into the chiasmatic cistern. Myonecrosis was limited to a small number of smooth-muscle cells, and a large number of muscle cells appeared intact. The most characteristic change was the appearance of aggregated granules and vesicles in the widened extracellular space between smooth-muscle cells, particularly near the adventitia and the elastic lamina. The granules were spherical, 50 to 100 nm in diameter, often surrounded by a single membrane, and contained a dense osmiophilic core, about 40 to 90 nm in diameter. In addition, the elastic lamina often became loose and corrugated or broken.

Animals↗
PubMed1997

An extracellular insoluble inhibitor of cysteine proteinases in cell cultures and seeds of carrot.

An 18 kDa extracellular insoluble protein (EIP18) was found previously in amorphous particles suspended in the culture medium and in the interspaces of cell clusters of carrot (Daucus carota L.) callus, as well as in the extracellular spaces of carrot seeds, being located both in the embryo and at the inner edge of the endosperm. We purified EIP18 by washing the amorphous particles with the mixture of Triton X-100, NaCl and ethylenediaminetetraacetic acid (EDTA). We determined several partial amino acid sequences, and then we cloned and sequenced a cDNA for EIP18. EIP18 was found to consist of 133 amino acid residues that included a signal sequence, but it did not contain cysteine, sites for N-linked glycosylation or hydrophobic regions. Since its sequence was found to be homologous to that of inhibitors of cysteine proteinases, namely cystatins, EIP18 was renamed EICC (extracellular insoluble cystatin of carrot). EICC expressed in yeast was also found in an insoluble form in yeast cell walls. EICC prepared from the culture medium of carrot cells inhibited commercial cysteine proteinases and a proteinase extracted from germinating carrot seeds. The expression of the gene for EICC was detected in developing seeds, and the level of its transcript was markedly enhanced upon treatment of somatic embryos with abscisic acid.

Amino Acid Sequence↗
PubMed1982

Morphological correlates of permeability in the frog perineurium: vesicles and "transcellular channels".

Lanthanum, applied to the outside of the fixed sciatic nerve of Rana pipiens, did not enter the endoneurium, but was halted by functionally tight junctions at the inner layers of the perineurium. This component of the blood-nerve barrier consists of several concentric layers of cells interspersed with an extracellular matrix of amorphous ground substance, collagen fibrils, and fine filaments. Numerous vesicular profiles are closely associated with the surface membranes of all the cells. The application of lanthanum to fixed tissue revealed that these profiles are attached to the cell surface by narrow necks, and open to the extracellular space. The attenuated cells are filled by the vesicular structures, which often appear to overlap. Stereoscopic electron microscopy showed that these vesicles did not fuse with each other or with the apposing cell surface to form transcellular channels. Channel formation does not appear to contribute significantly to the permeability of any of the perineurial layers.

Animals↗
PubMed1980

Tight junctions in the ependyma of the spinal cord of the urodele Pleurodeles waltlii.

The ependymal junction pattern in the spinal cord of postmetamorphic ribbed newts has been studied, using transmission electron microscopy of ultrathin sections of normal animals and of animals perfused through the IVth ventricle with lanthanum. Contrary to what has been observed in mammalian CNS, the ependyma of the urodelan spinal cord is furnished with tight junctions that seal the luminal border of the terminal bars. These occludens junctions are made up of two to seven punctate fusions of the plasma membranes. Lanthanum tracer remains restricted inside the lumen of the central canal, being stopped at the first punctate fusion on its way through the intercellular clefts. Beyond this point, the extracellular space contains no tracer material. Besides tight junctions, intermediate, desmosomal and gap junctions are also present. Gap junctions and desmosomes are not present in CSF-contacting neurons. It is suggested that ependyma with occluding junctions (special ependyma) overlay the regions of the CNS where the ependymal cells significantly modify the composition of both intercellular and cerebrospinal fluids, through secretory, transporting and permeability control activities.

Animals↗
PubMed1967

Intracellular sodium concentration and resting sodium fluxes of the frog heart ventricle.

1. Using (24)Na to label the exchangeable sodium in the tissue and either [(35)S]sulphate or [(14)C]sucrose to label the extracellular spaces, the intracellular sodium concentration of frog heart ventricles was determined and found to be between about 5 and 10 m-mole/kg cell water.2. The intracellular potassium concentration, obtained by flame-photometric analysis, was approximately 163 m-mole/kg cell water.3. Two different methods were employed to study the sodium tracer efflux of resting heart ventricles. One involved a double-tracer technique, using (24)Na to indicate the release of the exchangeable tissue sodium, and (35)SO(4) to indicate, approximately, the release of extra-myocardial sodium. In the other a comparison was made of the sodium release from the tissue when it contained sodium either at the normal concentration or at a concentration enhanced by exchange with intracellular potassium.4. The magnitude of the sodium efflux from heart fibres as measured by both methods was of the order 50-100 p-mole/cm(2) sec. Simultaneously with this cellular efflux a substantial amount of sodium was released from extra-myocardial spaces and tissues.5. The net efflux of potassium ions from heart cells that occurred when heart ventricles were perfused with potassium-depleted fluids was determined. The results were used to obtain an indirect estimate, of about 2-3 p-mole/cm(2) sec, for the resting sodium influx.6. The significance of these different values of sodium efflux and influx is discussed.

Animals↗
PubMed1994

Dynamics of retinotectal synaptogenesis in normal and 3-eyed frogs: evidence for the postsynaptic regulation of synapse number.

Quantitative stereological methods were used to determine if the number, density, and types of synaptic connections formed during development are regulated by presynaptic input or by postsynaptic target cells in the optic tectum of normal and 3-eyed Rana pipiens tadpoles and frogs. Our analysis indicates that the number and size of synapses is approximately the same in both tecta of 3-eyed tadpoles and frogs, even though one tectal lobe is receiving input from twice the normal complement of retinal ganglion cells. Moreover, the number and size of synapses in the tectal lobes of 3-eyed animals did not differ significantly from values determined for normal tadpoles and frogs of the same developmental stage. These data suggest strongly that developing tectal cells regulate the number of synaptic contacts they will form. Differences in several morphological features between singly and doubly innervated tecta, however, including synapse density, distribution and complexity, amount of extracellular space, and number of myelin figures, suggest that the presence of supernumerary input retards tectal maturation. We propose that the noncorrelated activity of retinal ganglion cell terminals in the doubly innervated tectum results in fewer stabilized synapses per unit volume of neuropil and in the delayed maturation of the tectal neuropil. Taken together, our data suggest a complex dynamic interaction between retina and tectum during development.

Animals↗
PubMed1978

[Cefamandol: pharmacokinetics with normal and impaired renal function (author's transl)].

1.0 g cefamandol was injected in 25 patients with various degrees of renal function. Half-life and distribution volume of this antibiotic and the glomerular filtration rate (GFR) were then measured. The distribution volume was 18.5 +/- 3.5% of body weight, similar to the extracellular space. Half-life and GFR were related in a way which could be expressed in the formula: half-life = 400 sqaure root GFR. Levels of blood concentration of cefamandol could be estimated from half-life and GFR, with the construction of "isoconcentration dosages", by which it is possible to achieve levels similar to those in normal subjects receiving a normal dosage.

Body Weight↗
PubMed1967

The distribution of [14C]sucrose within the skeletal muscle of the rat in vitro.

1. The distribution of [(14)C]sucrose within the plantaris muscle of the rat has been examined by suspending muscles in oxygenated Ringer containing this marker and subsequent analysis of the muscle.2. Histological examination of sections of muscle treated in this way indicates considerable distortion of muscle fibre pattern; this has been held to cast doubt upon the validity of such a method as a means of extracellular space examination.3. The rate of K(+) loss from muscles under these conditions has been examined by flame photometry. Up to 50% of the original muscle K(+) has been shown to be lost by efflux within approximately 1 hr from the commencement of soaking.4. It is considered that these findings indicate severe deterioration in the physiological condition of the muscle, and it is suggested that tissue hypoxia is chiefly responsible for this.

Animals↗
PubMedDate not supplied

[Differential ultrastructural elements in human cytomegalovirus and Herpes simplex virus replication in cultures of human cells].

Differential ultrastructural features in the replicative cycle between a strain of human cytomegalovirus (CMV) and two strains (types 1 and 2) of herpes simplex virus (HSV) have been studied by electron microscopy. Either on the same or different host cell system four differential aspects have been constantly observed: a) presence in CMV infected cells of a large nuclear inclusion, lacking in HSV infected cells; b) envelopment of CMV capsids by microvescicular systems near the nuclear membrane, whereas HSV (types 1 and 2) takes envelope from the inner lamina of the nuclear membrane; c) presence in the cytoplasm of CMV infected cells of homogeneous dense material and dense microbodies, lacking in HSV infected cells; d) in extracellular space homogenous dense microbodies are present only in CMV infected cell cultures. Diagnostic usefulness of the above reported ultrastructural differences and their meaning on the basis of most recent data of the literature are discussed, with special concern to envelopment of two viruses and to the nature of homogeneous dense material observed in CMV infected cells.

Capsid↗
PubMed1984

Plasma EC-superoxide dismutase activity in insulin-dependent diabetic children.

Toxic oxygen-centered radicals have been linked to beta-cell damage brought about by some chemicals and might conceivably also be of importance in the pathogenesis of spontaneous insulin-dependent diabetes mellitus (IDDM). In several model systems, superoxide dismutase has been protective. The major protector against superoxide radicals in the extracellular space appears to be a recently discovered superoxide dismutase, EC-superoxide dismutase. This enzyme was analysed in plasma from children with insulin-dependent diabetes mellitus. The specimens were obtained from 8 patients with disease of recent onset and from 15 patients with disease of longer duration. There was no significant difference in EC-superoxide dismutase between the patients and controls.

Adolescent↗
PubMed1994

Changes in the extracellular concentrations of amino acids in the rat striatum during transient focal cerebral ischemia.

Although considerable evidence supports a role for amino acids in transient global cerebral ischemia and permanent focal cerebral ischemia, effects of transient focal cerebral ischemia on the extracellular concentrations of amino acids have not been reported. Accordingly, our study was undertaken to examine the patterns of changes of extracellular glutamate, aspartate, GABA, taurine, glutamine, alanine, and phosphoethanolamine in the striatum of transient focal cerebral ischemia, as evidence to support their pathogenic roles. Focal ischemia was induced using the middle cerebral artery occlusion model, with no need for craniotomy. Microdialysis was used to sample the brain's extracellular space before, during, and after the ischemic period. One hour of middle cerebral artery occlusion followed by recirculation caused neuronal damage that was common in the frontoparietal cortex and the lateral segment of the caudate nucleus. During 1 h of ischemia, the largest increase occurred for GABA and moderate increases were observed for taurine, glutamate, and aspartate. Alanine, which is a nonneuroactive amino acid, increased little. After recirculation, the levels of glutamate and aspartate reverted to normal baseline values right after reperfusion. Despite these rapid normalizations, neuronal damage occurred. Therefore, uptake of excitatory amino acids can still be restored after 1 h of middle cerebral artery occlusion, and tissue damage occurs even though high extracellular levels of glutamate are not maintained.

Amino Acids↗
PubMed1992

Age-related white matter atrophy in the human brain.

Aging of the brain involves not only appreciable shrinkage of the cortex and other gray matter structures but above all loss of white matter. This could be due to a decline in the number of myelinated fibers or to a loss of water. To assess the role played by each of these factors we studied brains from 33 neurologically intact subjects at autopsy representing three different age groups: 15-50, 51-70, and 71-93 years. The precentral gyrus, gyrus rectus, and corpus callosum were selected for investigation, with staining for alkaline phosphatase on native cryostat sections to visualize the capillary network, and staining for myelin on semithin sections for nerve fiber visualization. Atrophy was objectified by measuring the number of capillaries, the intercapillary distance, and capillary length, since the capillary network remains constant throughout normal life. A mean difference of 16-20% was found, representing white matter atrophy, between the oldest and youngest age-groups. The cortex of the corresponding gyri, on the other hand, showed a difference of less than 6%. Morphometric investigation of sections stained for myelin showed that the brains with a mean age of 78.7 +/- 6.6 years had 10-15% fewer myelinated fibers. This was only partly offset by an increase in the volume of extracellular space. Our findings show that the age-related decline in brain volume is much more a question of white matter atrophy than of brain cortex atrophy. White matter atrophy could be an indirect indicator of nerve cell loss, since the volume of a nerve cell is much smaller than its myelinated fiber.

Adolescent↗
PubMed1975

Non-ionic diffusion of pentobarbital across human chorion laeve.

Diffusion of the weak organic acid, pentobarbital, across human chorion laeve in vitro shows an inverse correlation with pH, when corrected for extracellular space permeation by the concurrent measurement of membrane permeability to the lipid insoluble molecule, p-aminohippurate. The temperature dependence of pentobarbital diffusion at different pHs supports the concept that the additional net flux of solute at lower pH occurs by transcellular permeation by the non-ionized moiety, the observed increase corresponding roughly to the dissociation curve for pentobarbital.

Biological Transport↗
PubMed1980

Modulation of extracellular calcium and its functional implications.

Changes in [Ca2+]0 are known to affect axonal excitability and synaptic transmission. Ca2+ is also a major component of dendritic action potentials, and changes in [Ca2+]0 may therefore influence dendritic function. Use of the Ca2+-specific ion-selective microelectrode has shown that significant decreases in [Ca2+]0 occur in stimulated neuronal ensembles. Such changes are greatly enhanced during spreading depression and anoxia. The changes appear to be the result of Ca2+ entry into cells during activity, since the diffusion characteristics of Ca2+ in the extracellular space are not unusual. Decreases in [Ca2+]0 would lower the threshold for neuronal excitability but reduce synaptic transmission; rough numerical estimates of these effects are compiled. These are sufficiently large under some conditions to suggest, but not prove, possible modulatory effects of changes in [Ca2+]0. Variation in [Ca2+]0, however, is seen to be a valuable indicator of Ca2+-mediated processes in the nervous system.

Animals↗
PubMed1979

CNS changes in hyperbilirubinemia. Functional implications.

Hyperbilirubinemia is a recognized etiologic factor in motor and hearing disorders associated with cerebral palsy. Its role in more subtle forms of neurological impairment is more controversial. Using a mutant animal model, which develops symptoms and signs closely resembling the human kernicterus syndrome, neurons of hippocampus, cerebral cortex, cochlear nuclei, losuc ceruleus, and olfactory bulb were examined by electron microscopy. Pathological changes, observed in all areas studied, consisted of mitochondrial and endoplasmic enlargement and vacuolation, with glycogen deposition; increased extracellular space; myelin figures; and degenerating changes in nerve terminals. If we make the assumption that pathologic changes in the human infant with neonatal jaundice are similar to changes in the animal model, then the widespread involvement of CNS neurons in all cortical areas examined may well help to explain the syndromes of minimal cerebral dysfunction reported in clinical studies.

Age Factors↗
PubMed1994

In vivo serotonin release and learned helplessness.

Learned helplessness, a behavioral depression caused by exposure to inescapable stress, is considered to be an animal model of human depressive disorder. Like human depression, learned helplessness has been associated with a defect in serotonergic function, but the nature of this relationship is not entirely clear. We have used in vivo microdialysis brain perfusion to measure serotonin (5-hydroxytryptamine, 5HT) in extracellular space of medial frontal cortex in conscious, freely moving rats. Basal 5HT levels in rats perfused before exposure to tail-shock stress did not themselves correlate with subsequent learned helplessness behavior. However, 5HT release after stress showed a significant increase with helpless behavior. These data support the hypothesis that a cortical serotonergic excess is causally related to the development of learned helplessness.

Animals↗
PubMed1996

Short-range signaling by candidate morphogens of the TGF beta family and evidence for a relay mechanism of induction.

The specification and patterning of cell fates by a morphogen gradient is a unifying theme of developmental biology, yet little evidence exists for the presence of gradients in vivo or to show how such putative gradients form. Vg1 and activin are candidate morphogens involved in Xenopus mesoderm induction. This study suggests that these TGF beta family members act on adjacent cells but do not travel through the intact extracellular space to induce distant cells directly. Moreover, we present evidence for the presence of secondary inducing signals that could be involved in relaying signals to distant cells. These results suggest that if a localized cellular source of an inducer acts to pattern mesodermal cells at a distance in Xenopus embryos, it does so by a relay mechanism.

Activins↗
PubMed1999

Neuroprotective effect of mild hypothermia cannot be explained in terms of a reduction of glutamate release during ischemia.

An exogenous glutamate injection into the hypothermic hippocampal CA1 during 5-min ischemia produced the same extent of extracellular glutamate levels as observed in the normothermic CA1 during 5-min ischemia; however, neuronal death was not induced in the hypothermic CA1. Glutamate is released excessively into the extracellular space during ischemia, and is thought to induce brain injury by its neurotoxicity. It has been reported that the massive glutamate release is reduced by mild hypothermia, and it has been proposed that the reduction of ischemia-induced glutamate release exerts the neuroprotective effect on postischemic neuronal death. In the present study, to determine whether the neuroprotective effect of mild hypothermia on postischemic hippocampal CA1 neuronal death is due to the reduction of ischemia-induced glutamate release, gerbils were subjected to 5-min ischemia under hypothermic condition at 31 degrees C and were simultaneously injected exogenously with L-glutamate, so that the hypothermic CA1 around a microdialysis probe was exposed to the same extracellular glutamate levels as seen during normothermic ischemia, and the histological outcome was examined. An injection with 1 mM L-glutamate into the hypothermic CA1 during 5-min ischemia produced a similar extent of increased glutamate (17-fold increase) to that observed in the normothermic CA1 during 5-min ischemia (16-fold increase). However, neuronal death was not induced in the hypothermic CA1. This result indicates that the neuroprotective effect of mild hypothermia cannot be explained in terms of a reduction of glutamate release during ischemia.

Animals↗