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Biomedical subjects

G Sperk

Publications and source records attributed to G Sperk.

At least 109 records · Page 6Linked to original sources
PubMed1982

In vivo synthesis of substance P in the corpus striatum of the rat and its transport to the substantia nigra.

Incorporation of [35S]methionine into substance P in the striatum of the rat and the subsequent transport of the labelled peptide to the substantia nigra has been demonstrated in vivo. After a 4-h infusion of [35S]methionine into the corpus striatum and an additional interval of 4 h radiolabelled substance P was found in the striatum and the substantia nigra of the animals. The criteria for concluding that the labelled product was substance P were: (a) gel chromatography and subsequent ion exchange chromatography of an acetic acid extract of the infused striatum of the ipsilateral substantia nigra yielded a peak of radioactivity co-eluting with endogenous immunoreactive substance P or a sample of synthetic substance P; (b) the radioactive material from this peak also co-chromatographed with synthetic substance P on high-voltage paper electrophoresis or high-pressure liquid chromatography; and (c) bound specifically to the substance antibody. Intracisternal injection of colchicine (70 microgram, i.c.) completely suppressed the appearance of radiolabelled substance P immunoreactive material in the substantia nigra. The data indicate that synthesis of substance P occurs in nerve cell bodies located in the corpus striatum and that substance P is transported to the substantia nigra by a colchicine sensitive mechanism.

Afferent Pathways↗
PubMed1982

Tissue levels of N-n-propylnorapomorphine after treatment with (-)10,11-methylenedioxy-N-n-propylnoraporphine, an orally long-acting prodrug active at central dopamine receptors.

High performance liquid chromatography with electrochemical detection was used to assay N-n-propylnorapomorphine (NPA) and other aporphines. Pretreatment of rats with (-)10,11-methylenedioxy-N-n-propylnoraporphine (MDO-NPA) yielded dose-dependent increases in tissue levels of NPA after oral or parenteral administration. Cerebral levels of NPA significantly paralleled the stereo-typed behavioral effects produced by MDO-NPA at several doses and times. Pretreatment with the microsomal oxidase inhibitor SKF-525A (see Methods) prevented these behavioral effects of MDO-NPA and blocked the formation of NPA in vitro. These results support the suggestion that MDO-NPA is a uniquely orally effective and relatively long-acting aporphine which acts at cerebral dopamine receptors as a prodrug of NPA.

Animals↗
PubMed1982

Capsaicin does not change tissue levels of glutamic acid, its uptake, or release in the rat spinal cord.

Capsaicin treatment (50 mg/kg, subcutaneous) of newborn rats resulted in 1 75% decrease of substance P immunoreactivity in the dorsal spinal cord of the adult animal, but failed to affect levels of the proposed sensory neurotransmitter glutamic acid or to alter high-affinity uptake of [3H]glutamic acid into synaptosomes of the same tissue. Furthermore, capsaicin (30 microM) in vitro had no influence on the release of [3H]glutamic acid from spinal cord P2 fractions of untreated adult rats, but induced a marked release of substance P. The results suggest that, in contrast to substance P fibers, neurons containing glutamic acid are not sensitive to capsaicin. Eleven other neurochemical parameters measured in the spinal cord did not appear to be changed by the treatment with capsaicin, suggesting a considerable neurochemical selectivity of the lesion.

Animals↗
PubMed1982

Characterization of catecholamine-storage organelles in transplantable phaeochromocytoma and adrenal glands of rats.

The properties of the catecholamine-storing organelles from transplantable rat phaeochromocytoma and rat adrenal glands were compared by density gradient centrifugation. It was shown that tumour granules are more heterogeneous and less dense than adrenal granules. Both granule preparations can take up catecholamines and nucleotides by a process driven by an electrochemical proton gradient. Dopamine beta-hydroxylase and glycoprotein III were analysed by immunological techniques. Glycoprotein III was shown to be a specific component of chromaffin granules. Tumour tissue (average weight 700 mg) contains amounts of these antigens comparable to those in 210 adrenals. The biosynthesis of granules in the tumour apparently occurs at a low rate, making turnover studies difficult. The transplantable rat phaeochromocytoma is very useful for studies on the uptake properties and the immunological characteristics of rat catecholamine storage granules because on tumour provides an amount of material that could otherwise be obtained only from a large number of adrenal glands.

Adenosine Triphosphate↗
PubMed1982

Simultaneous determination of serotonin, 5-hydroxindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid by high performance liquid chromatography with electrochemical detection.

A rapid and highly sensitive procedure for simultaneous determination of serotonin, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid is described. After precipitation of proteins with perchloric acid the samples are applied directly to a high performance liquid chromatograph, with electrochemical detection. As little as 20 pg of serotonin, 5-hydroxyindoleacetic acid, and 3,4-dihydroxyphenylacetic acid and 200 pg of homovanillic acid can be detected. One chromatographic run requires less than 10 min.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1981

Kainic acid-induced changes of serotonin and dopamine metabolism in the striatum and substantia nigra of the rat.

Levels of the putative neurotransmitters serotonin (5-HT) and dopamine (DA) and their respective metabolites 5-hydroxyindoleacetic acid (5-HIAA) and dihydroxyphenylacetic acid (DOPAC) was determined in the rat striatum after unilateral intrastriatal injection of the convulsive neurotoxin kainic acid. Two days after intrastriatal kainic acid injection, levels of the 5-HT metabolite 5-HIAA were increased by abut 200% in the injected striatum and by about 150% in the contralateral striatum. An elevated striatal 5-HIAA content was still detectable 10 days after the kainate lesion, but approached normal values 10 weeks after the injection of the neurotoxin. Two days after the lesion, but not at the other time intervals, a moderate increase of 5-HIAA also occurred bilaterally in other brain areas such as the substantia nigra, frontal cortex and hypothalamus. Levels of 5-HT were decreased significantly in the injected striatum 2 days after the intrastriatal application of kainic acid and increased by about 40% after 10 weeks. The 5-HT concentration in the contralateral striatum or in the three other brain areas examined was unchanged at all time intervals. Levels of the DA metabolite DOPAC and DA turnover were increased in the lesioned striatum 2 days after kainic acid injection; concomitantly the DOPAC level was increased in the substantia nigra of the contralateral side. DOPAC levels of the contralateral striatum were unchanged or slightly reduced 2 days after the injection. Ten days as well as 10 weeks after the lesion there was a slightly increased DOPAC concentration in both striata. The levels of DA were not altered at any time interval after the injection of kainic acid.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1981

Measurement of gamma-aminobutyric acid in human cerebrospinal fluid: radioreceptor assay using [3H]muscimol.

A method is described for the determination of gamma-aminobutyric acid (GABA) levels in human cerebrospinal fluid by modification of the radioreceptor assay utilizing [3H]muscimol as labelled ligand. This method is compared with the radioreceptor assay using [3H]GABA as labelled ligand. Although the [3H]muscimol assay is less sensitive than the [3H]GABA method, it offers the advantage of being more rapid due to the use of a filtration step instead of the usual, more time-consuming centrifugation of the samples. Samples of CSF of patients with various neurological or psychiatric disturbances were analysed. There was a satisfactory correlation between the GABA values obtained by the two assays.

Animals↗
PubMed1981

Striatal ganglioside levels in the rat following kainic acid lesions: comparison with Huntington's disease.

Ganglioside and DNA levels were estimated in the striatum of rats 10 days and 6 weeks after lesioning by intrastriatal injection of kainic acid. There was a moderate, 21-24% decrease of the ganglioside concentration per unit protein on the side of the lesion, which can be ascribed to the loss of the intrinsic striatal neurons following the injection of kainic acid. On the other hand, there was a 131 and 60% increase of DNA per unit protein in the kainate injected side 10 days and 6 weeks after the lesions, respectively; these changes apparently reflected the gliotic reaction brought about by the neurotoxin. Qualitatively similar findings--a decrease of ganglioside and an increase of DNA levels per unit protein--were also found in the brain of patients with Huntington's disease; however, as compared with the corresponding control material, the decrease of the ganglioside concentration was more pronounced in the striatum of Huntington's disease (by 38% in the caudate nucleus and by 46% in the putamen) than in the kainate lesioned rat striatum. This difference could be due to the different proportions of the intrinsic and extrinsic neuronal plasma membranes in the striatum of the two species; however, the possibility of a more generalized affection of neuronal plasma membranes in Huntington's disease may also be envisaged.

Animals↗
PubMed1981

Evidence for neuronal localization of histamine-N-methyltransferase in rat brain.

There is evidence that histamine may be a neurotransmitter in mammalian brain. Histamine in neurons of the central nervous system is easily released and rapidly turned over. The cellular localization of histamine-N-methyltransferase, the proposed histamine-inactivating enzyme, was investigated by measuring its activity in rat striatum after applying neurochemical or electrolytic lesions. The results indicate a major neuronal localization of the enzyme in this area.

Animals↗
PubMed1980

A sensitive and reliable assay for dopamine beta-hydroxylase in tissue.

A new assay procedure for dopamine beta-hydroxylase (DBH) in tissue extracts is described. Solubilized DBH was adsorbed from crude extracts on Concanavalin A-Sepharose (Con A-Sepharose), resulting in enrichment of the enzyme as well as removal of endogenous catecholamines and inhibitory substances. The enzymatic assay was carried out with DBH still adsorbed to Con A-Sepharose. The adsorption of the DBH to Con A-Sepharose offers three advantages over previous assay procedures. (1) Because of removal of the endogenous inhibitory substances, a single Cu2+ concentration can be used for the determination of DBH activity, regardless of the tissue dilution or inhibitor content of the analysed sample. Using this procedure, the optimal Cu2+ concentration for DBH of bovine adrenal gland extracts was 3 microM and for rat brain 10 microM. (2) Because of removal of endogenous catecholamines, dopamine, the main physiological substrate of DBH in noradrenergic neurons, can be used for the assay. The enzymatic reaction product, noradrenaline, was determined by high performance liquid chromatography and electrochemical detection (hplc-ec). This procedure resulted in an approx. 10-fold increase in sensitivity of the assay compared with other procedures, e.g., the radioenzymatic assay. (3) Direct determination of the immediate product of the enzymatic reaction (noradrenaline) permits kinetic analysis. It was found that the Michaelis constants for the substrate (dopamine) and co-factor (ascorbic acid) (2 mM and 0.65 mM, respectively) determined in bovine adrenal tissue extracts by the described procedure were identical with the values for the purified DBH preparation.

Adrenal Glands↗
PubMed1980

Evidence of H2 receptor activity on glomerular cells.

The role of histamine in physiological and pathological states has not been fully elucidated. In the pathological state histamine release can be induced by several mechanisms. The most frequent events are IgE-mediated release, complement-mediated release and release by chemical agents. During inflammation histamine is set free and contributes to the course of inflammatory processes, either enhancing or inhibiting inflammatory reactions. In order to look for a target in the glomerulum we examined H2 receptor binding to isolated glomerular cells using 3H-cimetidine as ligand. Two binding sites were detected, a low affinity site with a kD = 6.3 microM and a high affinity site exhibiting a kD = 0.18 microM. These findings are comparable to properties of 3H-cimetidine receptor binding to brain membranes.

Animals↗