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R C Speth

Publications and source records attributed to R C Speth.

At least 91 records · Page 5Linked to original sources
PubMed1983

Evidence for the existence of a family of biologically active angiotensin I-like peptides in the dog central nervous system.

A family of angiotensin I-like peptides has been derived from endogenous precursors present in dog cerebrospinal fluid after incubation with species homologous renin. These peptides are immunologically and pharmacologically similar to [Ile5]angiotensin I, and have molecular weights ranging between 1300 and 2200 daltons. The presence of precursors in the cerebrospinal fluid able to generate various biologically active angiotensin I-like peptides dissimilar to plasma angiotensin I supports the concept of a local angiotensin I-forming system in the brain.

Angiotensin I↗
PubMed1981

Brain renin: localization in rat brain synaptosomal fractions.

The distribution of brain renin activity was determined in subcellular fractions of rat brain prepared by discontinuous density gradient centrifugation. The highest amounts of brain renin activity occurred in both the light and heavy synaptosomal fractions, while the activity of choline acetyltransferase was elevated only in the light synaptosomal fraction. These results indicate an intraneuronal localization of brain renin.

Animals↗
PubMed1981

Neuronal localization of benzodiazepine receptors in the murine cerebellum.

Selective genetic and chemical lesions which affect specific neuronal populations in the cerebellum were studied for changes in benzodiazepine receptors. Destruction of cerebellar climbing fibers with 3-acetylpyridine, did not affect cerebellar benzodiazepine receptors. Destruction of Purkinje, basket and stellate cells with intracerebellar kainic acid, caused moderate decreases in benzodiazepine receptor density. Destruction of Purkinje cells with chronic high doses of phenytoin also caused a significant decrease in benzodiazepine receptor density. In "weaver" mice, which have a severe loss of granule cells, benzodiazepine receptor density was unchanged, while the absolute number of benzodiazepine receptors decreased by 57%. In "staggerer" mice which have diminished Purkinje cells dendritic thickenings at their synapses with parallel fibers and subsequent granule cell loss, there was a 45% decrease in benzodiazepine receptor density and a 90% decrease in the absolute number of benzodiazepine receptors. These results suggest that benzodiazepine receptors exist on cerebellar Purkinje cells, that they probably also occur on cerebellar granule cells, and that they do not appear to be present on cerebellar glial cells or on climbing fibers.

Animals↗
PubMed1980

Sodium-dependent, high-affinity taurine transport into rat brain synaptosomes.

Taurine uptake into rat brain synaptosomal fractions appears to occur by two saturable transport processes and by bulk diffusion. The transport requires the presence of sodium ions. The dependence of the transport on temperature and cellular respiration implies that the uptake is an active process. The active process is specific for taurine and closely related amino acids. Brain regions differ in their ability to transport taurine. Uptake is not due to mitochondrial contamination of the synaptosomal fractions. However, glial contamination might partly contribute to the uptake. Kainic acid lesions of rat corpus striatum and cerebellum reduce taurine uptake implying that the uptake is, at least partly, into neurons.

Animals↗
PubMed1980

The benzodiazepine receptor of mammalian brain.

There exists a saturable, high-affinity, stereospecific, regionally and pharmacologically specific, neuronally localized benzodiazepine receptor in mammalian brain, which has a development profile similar to other neurotransmitter receptors. This receptor appears to be modulated by gamma-aminobutyric acid and selected divalent cations, and chloride ions increase the affinity of the receptor for benzodiazepines. Several benzodiazepines were shown to bind irreversibly to the receptor upon exposure to ultraviolet light and these agents can be used to facilitate solubilization and purification of the benzodiazepine receptor. Although several substances have been suggested to be the endogenous ligand, none has achieved the acceptance given to other neurotransmitters or neuromodulators, e.g., enkephalins and endorphins.

Affinity Labels↗
PubMed1979

On the ability of choline and its analogues to interact with muscarinic cholinergic receptors in the rat brain.

Choline displaced [3H]QNB binding from rat brain muscarinic receptors competitively, (Ki = 460 microM) but it was only 1/1000th as potent as ACh. Deanol was an extremely weak displacer of [3H]QNB binding while hemicholinium-3 was 50 times more potent than choline. Although brain levels of choline are well below its Ki value for muscarinic receptors, choline may directly interact with rat brain muscarinic receptors in some circumstances.

Animals↗
PubMed1979

Benzodiazepine receptors: effect of tissue preincubation at 37 degrees C.

[3H]Flunitrazepam binding to rat brain homogenates was assayed in two ways: by 37-0 degrees C incubations or 0 degrees C only incubations. The affinity of brain benzodiazepine receptors for [3H]flunitrazepam was significantly greater in 37-0 degrees C incubated samples than in 0 degrees C incubated samples, while there was no change in the number of benzodiazepine receptors. The possible mechanisms for this enhanced binding affinity as well as the methodological implications for this observation are discussed.

Animals↗