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H Hyden

Publications and source records attributed to H Hyden.

15 recordsLinked to original sources
PubMed1995

S-100 beta has a neuronal localisation in the rat hindbrain revealed by an antigen retrieval method.

The localisation of S-100 in mammalian CNS neurons has been under debate for more than two decades. We address the question with two polyclonal and two new monoclonal antibodies. The specificity and the distribution in rat brain is based on an antigen retrieval method. We present evidence that aldehyde fixatives mask S-100 beta in neurons, and that the immunoreactivity is retrieved after trypsinisation. Neuronal S-100 beta is also detected in unfixed and ethanol fixed sections. The neuronal immunoreactivity is partly solubilised from unfixed tissue sections with 2.5 mM EDTA and is completely extracted with 2.5 mM EDTA and 1% Triton X-100. Most of the glial S-100 beta is washed out from unfixed tissue sections with saline. S-100 beta has distinct distribution in neurons of the hindbrain, i.e., the brainstem and cerebellum, but is not observed in the forebrain. One of the monoclonal antibodies immunostained neither neurons nor glia when it had been absorbed with S-100 crosslinked to nitrocellulose membranes. The distribution of neuronal S-100 beta differed from that of other neuronal calcium binding proteins, such as calbindin and parvalbumin. It was confined mainly to cholinergic neurons of the hindbrain. The presence of S-100 beta in distinct neuronal populations may indicate neurotrophic effects of S-100 beta. The notion is supported by the capability of S-100 to cause neurite outgrowth in vitro.

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PubMed1992

Further evidence for the presence of gamma-aminobutyric acidA (GABAA) receptors on the cytoplasmic side of Deiters' membrane.

1. The permeation of labeled Cl- across single nerve membranes microdissected from rabbit Deiters' neurons was studied in a microchamber system. The in----out permeation of the ions was evaluated under control conditions and in the presence of either 10(-6) M GABA or 10(-6) M GABA plus 10(-5) M bicuculline methiodide (BMI) on the membrane cytoplasmic side. 2. In 32 experiments, involving one animal each, at least two membranes served as controls and at least two others were studied with the addition of GABA. Within each experiment all the membranes were obtained from the same animal. 3. In an additional 10 experiments, involving one animal each, at least two membranes served as controls and at least two others were studied in the presence of GABA plus bicuculline methiodide on the membrane cytoplasmic side. 4. The data show that 10(-6) M GABA on the Deiters' membrane cytoplasmic side stimulates Cl- permeation in----out by 42% (P = 0.0000001). When 10(-5) M BMI was present together with GABA, no stimulation of Cl- in----out permeation occurred.

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PubMed1986

Asymmetric diffusion into the postsynaptic neuron: an extremely efficient mechanism for removing excess GABA from synaptic clefts on the Deiters' neurone plasma membrane.

Microdissected Deiters' neuron plasma membranes have been used for studying the passage of GABA through the membrane both in the inward and outward direction. Working with 0.2 mM GABA in the compartment simulating the outside of the neurone and with 2.0 mM GABA in the one simulating the inside we found a net transport of GABA towards the inside. This mechanism does not require a Na+ ion gradient across the membrane. The nature of the transport process involved was studied by determining the rate of [3H]-GABA inward passage as a function of GABA concentration (1 nM - 800 microM) on the outward side of the membrane. The results have shown that until 50 microM a diffusion process (v = D1 X C, where D1 = 3.1 X 10(-11) 1/micron 2 X sec) is the sole mechanism involved. Above 50 microM a second diffusion process is activated v = D2 X (C - 50 X 10(-6), where D2 = 2.8 X 10(-11) 1/micron 2 X sec. Taking in account both inward and outward directed diffusion, one can calculate 16 microM as the equilibrium concentration of GABA on the outward side of the membrane. From a kinetic point of view, these diffusion processes are able to reduce GABA concentration in a synaptic cleft from 3 mM to 20 microM within 3 mu sec. These diffusion systems are discussed as extremely efficient in removing the excess of released GABA in the synaptic cleft.

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PubMed1986

Synthesis of rat brain DNA during acquisition of an appetitive task.

We have examined the incorporation of [3H-methyl]thymidine into DNA extracted from several brain regions of rats learning a reverse handedness task, of control rats allowed to use their preferred paw, and of control rats left in their home cages. In learning animals, decrements in percent incorporation were observed in the visual cortex, remaining brain, hippocampus and entorhinal cortex. In the latter two regions less marked decreases were present in the active control group. No variation occurred in the sensory-motor cortex. In learning rats the specific radioactivity of neuronal DNA was markedly decreased in the hippocampus and remaining brain. In the former region, a less marked decrease was present in active control rats. In subcellular fractionation studies it was observed that decreases in DNA specific radioactivity prevailed in the mitochondrial fraction isolated from the hippocampus and visual cortex of learning rats. Brain radioactive DNA was widely distributed among fractions differing in their degree of repetitiveness. Its pattern of distribution did not coincide with that of bulk DNA and differed significantly among behavioural groups. The results suggest a non random origin of newly-synthesized brain DNA and its involvement in learning.

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PubMed1985

A calculation method for evaluating the time course of GABA removal from a synaptic cleft by presynaptic uptake systems.

A calculation method for evaluating the time course of gamma-aminobutyric acid (GABA) removal from a synaptic cleft by presynaptic uptake is suggested. The evaluation of the actual time required to remove GABA requires the knowledge of: (a) KM's and Vmax's (mol/min/mg protein) of the synaptosomal uptake systems in a certain brain area; (b) the synaptosomal volume per mg of protein in the synaptosomal preparation used; (c) the mean sphere diameter for synaptic boutons in the brain area considered and the proportion of GABAergic nerve terminals.

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PubMed1984

Inhibition by sodium valproate of the transport of GABA through the Deiters' neurone plasma membrane.

The transport of GABA through the microdissected plasma membrane Deiters' neurone reflects the physiological event of postsynaptic uptake of GABA by its uptake carrier. Sodium valproate at concentrations greater than or equal to 2.4 mM was able to decrease markedly (57%) such a transport. This effect, which reduces the efficiency of the GABA postsynaptic inactivation process, might be a mechanism for the potentiation by valproate of the synaptic action of GABA.

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PubMed1982

Labeling of poly(A) associated RNA in synaptosomes and the other subcellular fractions of rat cerebral cortex in basal conditions and during training.

The labeling of total and poly(A) associated RNA from the subcellular fractions of cerebral cortex was studied after a 1-hour 3H-uridine pulse in control and trained rats. In the control animals, the fraction of newly synthesized brain cortex RNA which is found in synaptosomes is the minimal one. However, in synaptosomes the proportion of poly(A)+ RNA within newly synthesized RNA is maximal. Training of the rats does not influence total incorporation of label into RNA in the brain cortex and the distribution of newly synthesized RNA within the subcellular fractions. The proportions of poly(A)+ RNA within total labeled RNA in the various fractions are also unaffected.

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PubMed1977

A comparison of poly (A)-associated RNA from synaptosomes and cytoplasmic subcellular fractions of rat brain.

Oligo(dT)-cellulose binding poly(A)-RNA from rat brain microsomes, mitochondria and synaptosomes was isolated and analysed. Synaptosomes and mitochondria appeared to contain a higher proportion of such RNA than microsomes. Poly(A)-RNA from the three fractions was then electrophoretically fractionated in two different gel systems. Mitochondrial and microsomal poly(A)-RNA presented different fractionation patterns. Synaptosomal poly(A)-RNA also presented a characteristic patterns of its own which could not be entirely explained as a mixture of the previous two. Its main feature was the presence of a prominent band with an SE value of around 7. Such species, absent in microsomes, was present as well in mitochondria but in smaller concentration. On the basis of the present evidence and of previous results, it appears that such 7 SE species, although a mitochondrial messenger RNA in origin, becomes accumulated in vivo into synaptic membranes.

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