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  • 1
    ISSN: 1432-0878
    Keywords: Choline acetyltransferase ; Enkephalin ; Norepinephrine ; Vasoactive intestinal peptide ; Protein gene product 9.5 ; Enteric nervous system ; Sympathetic nervous system ; Jejunum ; Denervation ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The objective of this study was to examine the effects of two different denervation procedures on the distribution of nerve fibers and neurotransmitter levels in the rat jejunum. Extrinsic nerves were eliminated by crushing the mesenteric pedicle to a segment of jejunum. The myenteric plexus and extrinsic nerves were eliminated by serosal application of the cationic surfactant benzyldimethyltetradecylammonium chloride (BAC). The effects of these two denervation procedures were evaluated at 15 and 45 days. The level of norepinephrine in whole segments of jejunum was initially reduced by more than 76% after both denervation procedures, but by 45 days the level of norepinephrine was the same as in control tissue. Tyrosine hydroxylase (nor-adrenergic nerve marker) immunostaining was absent at 15 days, but returned by 45 days. However, the pattern of noradrenergic innervating axons was altered in the segment deprived of myenteric neurons. Immunohistochemical studies showed protein gene product 9.5 (PGP 9.5)-immunoreactive fibers in whole-mount preparations of the circular smooth muscle in the absence of the myenteric plexus and extrinsic nerves. At 45 days, the number of nerve fibers in the circular smooth muscle increased. Vasoactive intestinal polypeptide (VIP)-immunoreactive fibers, a subset of the PGP 9.5 nerve fibers, were present in the circular smooth muscle at both time points examined. Choline acetyltransferase (CAT) activity and VIP and leucine enkephalin levels were measured in separated smooth muscle and submucosa-musosal layers of the denervated jejunum. VIP and leucine-enkephalin levels were no different from control in tissue that was extrinsically denervated alone. However, the levels of these peptides were elevated two-fold in the smooth muscle 15 and 45 days after myenteric and extrinsic denervation. In the submucosa-mucosa, VIP and leucine enkephalin levels also were elevated two-fold at 15 days, but comparable to control at 45 days. CAT activity was equal to control in the smooth muscle but elevated two-fold in the submucosa-mucosa at both times. These results provide evidence for innervation of the circular smooth muscle by the submucosal plexus. Moreover, these nerve fibers originating from the submucosal plexus proliferate in the absence of the myenteric plexus. Furthermore, the myenteric neurons appear to be essential for normal innervation of the smooth muscle by the sympathetic nerve fibers. It is speculated that the sprouting of the submucosal plexus induced by myenteric plexus ablation is mediated by increased production of trophic factors in the hyperplastic smooth muscle.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Using antisera specific for methionine- and leucine-enkephalin, we studied the characteristics of the release of these peptides from rat striatal slices. Only 2–3% of the total tissue stores of enkephalin could be released by potassium depolarization; similar percentages were released from globus pallidus, thalamus, and nucleus accumbens. Enkephalin release from hippocampus could not be detected. The striatal release of both enkephalins was affected similarly by changes in potassium and calcium levels in the superfusion medium. Lithium has no effect on either basal or potassium-stimulated release; tyr-arg did not affect basal release of either peptide. Striatal enkephalin levels were stable during the short-term incubation periods used in these experiments.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 30 (1978), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Degredation rates of rat brain proteins were measured by following the decay in specific radioactivity of carboxyl labelled aspartate and glutamate over a 17-day period. Initial labelling of these amino acids was achieved by a single intraperitoneal injection 0f NaH14CO3. The non-linear decay curve for total brain proteins could be approximated by assuming that the mixture contained two classes of proteins with half-lives of 3.3 and 8.7 days, respectively. Half-lives of 2.5 and 7.7 days were estimated for such protein classes in the microsomal fraction. The half-lives of soluble proteins, synaptic membranes, cell body and synaptic mitochondria were 3.1, 5.8, 5.6 and 8.4 days, respectively. Identical results were obtained if the change in specific activity of intact protein labeled by NaH14CO3 was followed.Two-fold slower decay rates were obtained when brain proteins were labeled with a pulse of [4,5-3H]leucine or [l-14C]leucine. Half-lives calculated for the two classes of proteins in whole brain were 8.4 and 16.5 days, respectively with [4,5-3H]leucine and 8.9 and 14.2 days, respectively with [1-14C]leucine. These results indicate the very significant reutilization of this amino acid in brain. Sodium [14C]bicarbonate is a more satisfactory isotopic precursor for accurate assessment of rates of protein turnover in brain.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Protein turnover in rat brain was measured over a period of 30 days by following the decay in specific radioactivity of acidic amino acids in proteins labelled by a single intraperitoneal injection of [14C]NaHCO3. Two major populations of brain proteins can be identified from the resultant non-linear decay curve—one with an average half-life of 4 days and another with an average half-life of 12 days. The half-lives of total brain, mitochondrial, microsomal and soluble proteins determined over a period of 5 days were 3.4, 5.8, 2.8, and 2.6 days, respectively. Turnover of these same brain subcellular fractions was also measured by continuous infusion of [14C]tyrosine. The estimated half-lives were in close agreement with those obtained from the 5 day measurement of radioactive decay following a pulse label of [14C]NaHCO3.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 32 (1979), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Evidence for multiple forms of the α and β subunits of tubulin isolated from rat brain has been obtained by means of SDS polyacrylamide gel electrophoresis, isoelectric focusing, and SDS hydroxylapatite column chromatography. Fourteen distinct bands, localized near pH 5.4, were formed when tubulin was subjected to isoelectric focusing in a gradient established with a very narrow range ampholyte mixture. Three tubulin subunits, a1., α2, and β, were separated by sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in a second dimension. The β subunit was more acidic than the α subunits. Brain sections were incubated in tissue culture medium containing 32P1 and radiolabeled tubulin was subsequently isolated and subjected to electrophoresis. Only the β subunit was labeled. All radioactivity was associated with two or three adjacent bands on isoelectric focusing gels.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —A method is described for the preparation of glutamate dehydrogenase in a highly purified form from rat brain. Only one protein band was detected when the enzyme was subjected to electrophoresis on SDS polyacrylamide gels. The rat brain enzyme was essentially identical to the rat liver enzyme with respect to electrophoresis on SDS polyacrylamide gels, immunochemical properties and most kinetic parameters. However, the brain enzyme was much less reactive with glutamate, was more sensitive to inhibition by haloperidol, and was considerably more stable than the liver enzyme.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 31 (1978), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The turnover rate of tubulin in rat brain was determined from the decay in specific radioactivity of the protein after pulse-labeling. When precursors were administered by a parenteral route, the shortest half-life, 9.8 days, was obtained with [14C]NaHCO3; the longer half-lives obtained with [U-14C]glucose or [4,5-3H]leucine suggest significant reutilization of label. Furthermore, with leucine as precursor maximal specific radioactivity of tubulin was not obtained until eight days after administration of label. Labeling and decay kinetics obtained with [4,5-3H]leucine were markedly different when the isotope was administered directly into the lateral ventricle. The difference between the turnover rates of the -α and β subunits of tubulin purified by means of high resolution polyacrylamide gel electrophoresis was not statistically significant. A half-life for tubulin of 6.2 days was measured by continuous intravenous infusion of [U-14C]tyrosine.
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  • 8
    ISSN: 1573-2568
    Keywords: mucosal innervation ; mucosal repair ; rat jejunum ; vasoactive intestinal peptide ; neuropeptide Y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the time course of the regeneration of the jejunal mucosa of the rat after it was damaged by exposure to the surfactant, benzalkonium chloride. We placed particular emphasis on assessing the morphology of the nerve fibers within the villi during and after regeneration. The application of benzalkonium chloride resulted in virtually complete loss of villi within the treated segment; however, the crypts were only partially damaged. The mucosa began to regenerate within 6 hr of the insult. The villus lengths and crypt depths returned to pretreatment values within two to four days. The mucosal innervation was assessed through immunohistochemistry for vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and neuron-specific enolase (NSE). At all stages of regeneration, VIP, NPY, and NSE immunopositive fibers within the lamina propria extended to the tips of the villi. The density of the immunopositive fibers in the lamina propria at four days after mucosal insult was similar to that in control tissues regardless of the neuronal marker visualized. We conclude that the nerve fibers innervating the small intestinal mucosa grow at a rate of approximately 100 μm/day and that the entire length of each villus contains nerve fibers throughout the regeneration process. The innervation of the regenerated mucosa appears identical to that of control mucosa.
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