The application of radionuclides for the localization of essential trace elements in vivo and the characterization of their binding proteins is a story of intermittently made improvements of the techniques used for their detection. In this study we present the use of neutron activation analysis and different autoradiographic imaging methods including real‐time digital autoradiography to reveal new insights in the hierarchy of selenium homeostasis. Selenoproteins containing the essential trace element selenium play important roles in the CNS. Although the CNS does not show the highest selenium concentration in the case of selenium‐sufficient supply in comparison with other organs, it shows a high priority for selenium uptake and retention in the case of dietary selenium deficiency. To characterize the hierarchy of selenium supply in the brain, in vivo radiotracer labeling with 75Se in rats with different selenium status was combined with autoradiographic detection of 75Se in brain tissue sections and 75Se‐labeled selenoproteins after protein separation by two‐dimensional gel electrophoresis. This study demonstrates significant differences in the uptake of 75Se into the brain of rats with different selenium status. A brain region‐specific uptake pattern of the radiotracer 75Se in selenium‐deficient rats could be revealed and the CSF was identified as a key part of the brain selenium homeostasis.
Selenium is present in various biologically important selenoproteins. The preferential incorporation of selenium into the brain indicates its significance for this organ, but so far knowledge concerning the cerebral selenoproteome is scarce. We therefore investigated the expression of selenoproteins in various regions of the rat brain, various subcellular fractions and several brain cell lines by (75)Se-labelling, gel electrophoretic separation and autoradiography, with the (75)Se tracer as the selenoprotein marker. Quantitative evaluation of the labelled proteins in selenium-deficient rats revealed information regarding preferentially supplied selenoproteins and their distribution; 21 selenoproteins could be distinguished, among them a novel or modified 15-kDa selenoprotein enriched in the cerebellum cytosol. The selenoproteins differed in the degree of their expression among the brain regions and within a region among the subcellular fractions. Some cell-type-specific selenium-containing proteins were found in the cell lines. Differences in the distribution patterns between mono-cultured and co-cultured endothelial cells and astrocytes showed that mediators produced by other cells could affect the selenoprotein expression of a specific cell-type. This effect might play a role in the uptake and distribution of selenium in the brain but could also be of significance in the selenium metabolism of other tissues.
We conclude, that twofold ilio-sacral screw positioning from one side increases the risk for screw misplacement. In this case, alternative techniques like navigation should be considered. Anterior screw perforation represents a common problem with a high incidence and warrants particular attention.
A case of intoxication with Phytosol (an insecticide) in a 29-year-old man is described. Ingestion of Phytosol (suicide attempt) produced signs of cholinergic crisis followed, after 16 days, by features of peripheral neuropathy and later, with the regression of signs of polyneuropathy, gradually increasing spastic paralegia. Electrophysiological investigation of nerves which were clinically moderately involved demonstrated sparing of sensory fibers and damage to motor fibers. There was no change in maximal motor conduction velocity. Histology of the clinically involved sural nerve revealed axonal changes together with demyelination, presumed to be secondary in type. This case shows that the susceptibility to delayed nervous system damage in man is greater than it might be expected from experimental studies and calls for caution in human exposure to these compounds.
By a combination of trace techniques and various biochemical methods, information about the characteristics of a 15-kDa selenoprotein was obtained. After labeling of rats in vivo with [(75)Se]selenite, subcellular fractionation of the homogenates of the prostate, lung, brain, thyroid gland, and large intestine, and gel electrophoretic separation of the proteins and subcellular fractionation, 15-kDa (75)Se was found in the cytosols of the tissues prostate > brain > lung > thyroid gland > large intestine after autoradiography. After coelectrophoresis of the separated 15-kDa labeled band obtained from each cytosolic fraction, the 15-kDa (75)Se band migrated in the same way as the combined bands isolated from the five tissue cytosols. After proteolytic cleavage in the gel of the 15-kDa labeled band obtained from the cytosol of each tissue and re-electrophoresis, the same labeled peptide pattern was found in each gel slice after autoradiography. By means of reversed-phase HPLC, we characterized a selenocysteine-containing protein that has enzymatic activity like that of glutathione peroxidase.
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