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  • 1
    ISSN: 1432-0533
    Keywords: Key words Calcium ; SOD-1 ; Knockout mouse ; Motoneuron ; Parvalbumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract SOD-1-deficient mice demonstrate no loss of motoneurons but are still vulnerable to axotomy and ischemic insults. To investigate possible reasons for vulnerability of motoneuron populations, we studied changes in ultrastructural calcium distribution during maturation in spinal- and oculomotor neurons in SOD-1–/– mice. Between 3 and 11 months the cytoplasmic component of the intracellular calcium changed at a lower rate in spinal motoneurons and motor axon terminals in the interosseus muscle of SOD-1–/– animals compared to wild-type controls. No such dissimilarities were noted in the oculomotor system, or in mitochondrial calcium contents of either cell type. These data suggest that the lack of SOD-1 may be associated with vulnerability to insult by depletion of non-mitochondrial calcium stores selectively in motoneurons lacking parvalbumin and/or calbindin D28K.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Key words Glutamate neurotoxicity ; Mitochondria ; Calcium accumulation ; Neuronal cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of serum proteins on glutamate-induced mitochondrial calcium accumulation was studied in primary cortical and hippocampal cultures using oxalate-pyroantimonate staining with electron microscopy. Cultures were prepared from rat embryos on gestational day 17–19 and cultivated for 8 days in minimal essential medium (MEM) containing 5% native horse serum. At this time cultures were exposed for 5 min to 100 μM or 1.0 mM glutamate, followed by recovery in either serum-free or serum-containing culture medium. Mitochondrial calcium accumulation was assessed before glutamate treatment, at the end of glutamate exposure, and after 5 min, 30 min, 6 h and 24 h of recovery. Under control conditions and at the end of glutamate exposure, mitochondria contained only a few calcium deposits. If cultures were placed in serum-free medium after glutamate treatment, mitochondria were progressively loaded with calcium. At 5 min after glutamate exposure mitochondrial calcium deposits were prominent in both cortical and hippocampal cultures, followed by a further steady increase and neuronal death within 24 h. When cultures were allowed to recover after glutamate treatment in serum-containing MEM, calcium sequestration and ultrastructural changes of mitochondria were essentially absent, and neurons survived. No differences between cortical and hippocampal cultures were observed. The data demonstrate that prevention of glutamate neurotoxicity by serum proteins is associated with prevention of post-glutamate mitochondrial calcium accumulation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0533
    Keywords: Histamine ; Cerebral ventricle ; Pinocytosis ; Brain-blood barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Histamine dihydrochloride (10 μg of 500 μg/ml) was infused during 1 min into the lateral cerebral ventricle of rats, which resulted in a significant stimulation of pinocytosis in the endothelial cells. Systemic injections of mepyramine or metiamide could not prevent this activation. In contrast, ranitidine, injected with histamine was able to inhibit the stimulation of pinocytosis. Albumin exudation from the blood was not found. There was also no change in water and electrolyte contents of the brain tissue. The results suggest that histamine reaching the abluminal membrane can activate the pinocytosis in the cerebral endothelial cells in the reverse direction, i.e., from brain to blood, without opening the blood-brain barrier.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 79 (1983), S. 77-86 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Presynaptic calcium binding sites were demonstrated by means of X-ray microprobe analysis in rat neuromuscular junctions subjected to perfusion with a calcium containing (5 mM) aldehyde fixative. Type A calcium binding sites are triangular structures facing the junctional folds, identical with presynaptic protrusions of the active zone. Since, because of low concentration and disturbing effects, calcium peaks cannot be detected if using the conventional single shot analysis, the spectrum averaging technique was used. While gradual rising of the calcium peak from the background can be established in the course of averaging 9 spectra obtained from several Type A sites, spectra obtained from indifferent areas of the presynaptic membrane exhibited a less intensive phenomenon. The results are in agreement with previous data obtained by means of electron cytochemical methods, suggesting that Type A sites may play an important role in the regulation of calcium influx to the intraaxonal area. Junctional folds of the postsynaptic membrane may funnel calcium ions exactly to these restricted places of the nerve membrane and, at the arrival of nerve action potential, calcium ions may enter directly to the active zone. This way, a relatively small amount of calcium is sufficient to release neurotransmitter from the terminal.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 90 (1988), S. 185-193 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In view of the importance of calcium in the induction of long-term potentiation (LTP), experiments were carried out to localize calcium at the electron microscopic level in the CA1 region of guinea pig hippocampal slices, following high-frequency stimulation of the Schaffer collaterals. Apart from the ultrastructural localization, a semiquantitative method was used to count the calcium-containing deposits in electron micrographs. Significantly more calcium-containing deposits were seen in the dendrites of the stratum radiatum in slices with LTP than in those without it. A moderate increase of the extradendritic deposits was observed, too. The calcium content of the deposits was determined by means of EGTA incubation and X-ray analysis. The presented results, together with the relevant literature data, underline the importance of calcium-activated processes in postsynaptic structures probably involved in the generation of LTP.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous physiological and morphological studies suggested that sodium bromide promotes synaptogenesis of implanted cholinergic nerves in the superior cervical ganglion of adult rats. To check whether sodium bromide also modifies synaptic numbers in the intact ganglion, quantitative electron microscopy was used to determine the total number of synaptic junctions in the superior cervical ganglion of adult rats. Untreated controls were compared with animals which drank water containing 280 mg ml−1 sodium bromide for 7 days. The disector method, an unbiased estimator of volume density of certain particles, has been adapted to this particular case. To accomplish the task, an on-line counting procedure was developed, which permitted the efficient adaptation of the disector method for the superior cervical ganglion, in which the synapses are known to be distributed sparsely. Three pairs of (control and treated) ganglia have been completely processed by three independent examiners. The estimated number of synapses in the ganglia ranged from 4 to 8 million while the volumes of the ganglia varied from 0.65 to 0.90 mm3. Evaluation of the results showed that variations in the total number of synapses were in each case proportional to differences in ganglionic volumes. This suggests that: (1) sodium bromide does not lead to changes in density of intrinsic synapses; and (2) the morphogenetic action of sodium bromide on principal ganglion cells previously described is essentially postsynaptic and requires additional presynaptic elements to increase the number of synapses.
    Type of Medium: Electronic Resource
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