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Biomedical subjects

A Palm

Publications and source records attributed to A Palm.

At least 37 records · Page 2Linked to original sources
PubMed1987

The effect of antisecretory factor on the permeability of nerve cell membrane to chloride ion.

The antisecretory factor (ASF) is a hormone-like protein (m.w. 60,000) that most effectively counteracts hypersecretion in vivo in the small intestine of pigs and rats. The present report demonstrate that 10(-13) moles of ASF inhibits significantly the 36Cl- permeation through the isolated neuronal plasma membrane of Deiters' cells in rabbits. This effect was enhanced by 0.2 mM gamma-aminobutyric acid (GABA), and quenched by the addition of anti-ASF immunoglobulins; pretreatment of the neuronal membrane with nipecotic acid (10(-6) M) or with bicuculline (10(-3) M) abolished the ASF action whilst picrotoxin (10(-4) M) pretreatment left the inhibitory effect of ASF unaffected. The results suggest that ASF blocks chloride channels in neuronal membranes, including those channels activated by GABA.

Animals↗
PubMed1987

Effect of anti-S-100 serum on 36Cl- ion permeability across the Deiters' neuron plasma membrane.

1. A microtechnique allowing the study of single plasma membranes from the gamma-aminobutyric acid (GABA)-acceptive Deiters' neuron has been utilized in order to assess the effect of both S-100 protein and its antiserum on 36Cl- permeability through such membranes. 2. The results show that both S-100 (in the Ca2+ form) incorporation onto the external side of the membranes and their preincubation with anti-S-100 serum stimulate 36Cl- permeability. 3. These effects are not additive with that of GABA, indicating that both S-100 and anti-S-100 act via the GABAA receptor complexes on Deiters' membranes. 4. When the membranes were incubated first with S-100/Ca2+ and then with anti-S-100, the second treatment resulted in the disappearance of the S-100 effect. However, the anti-S-100 effect was fully displayed.

Animals↗
PubMed1987

GABAA receptor complexes are present on both sides of a GABA-acceptive neuronal membrane.

A micromethod allowing the study of the characteristics of single GABA-acceptive membranes microdissected from Deiters' neurones was used in order to assess the effects of both "extra"- and "intra"-cellular GABA on Cl- permeability. The results indicate that GABA can activate Cl- permeability in the in----out direction when it is present on the cytoplasmic side of the membrane. Moreover, as already described, it can activate Cl- permeability in the opposite direction when present on the "extracellular" side of the membrane. Both these phenomena are blocked by GABAA receptor inhibitors, bicuculline and picrotoxin. The presence of GABAA receptors on both sides of the membrane is discussed as the possible basis for synaptically released GABA hyperpolarising action on these neurones.

Animals↗
PubMed1986

gamma-Aminobutyric acid stimulates chloride permeability across microdissected Deiters' neuronal membrane.

Fluxes of 36Cl- across freshly prepared Deiters' neuronal membranes have been studied in a two-compartment microchamber simulating the extra- and the intracellular space. The rate of 36Cl- influx was enhanced by gamma-aminobutyric acid (GABA) (10(-4) M), the effect being reversed by picrotoxin (10(-4) M) and by bicuculline (10(-5) M). Diazepam (10(-8)-10(-7) M) did not potentiate the response to GABA and rather depressed it. However, a barbiturate site is most probably present in the GABA receptor complexes since pentobarbitone (10(-4) M) was able to stimulate 36Cl- permeability to the same extent as GABA itself.

Animals↗
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.

Animals↗
PubMed1985

An inhibitory protein of intestinal fluid secretion reverses neuronal GABA transport.

Intestinal challenge with cholera toxin induces the synthesis of a hormone-like protein which counteracts intestinal hypersecretion. This study shows that the protein also inhibits GABA transport across the plasma membrane of Deiters' cells in rabbits. The inhibitory action of the protein was dose dependent, and 10(3) times more potent than met 5-enkephalin, hitherto the most effective known inhibitor of GABA transport in vitro. The influence of the protein on the plasma membrane was reversible, and did not affect either postsynaptic binding or uptake of GABA.

Animals↗
PubMed1984

Increased binding of GABA to its post-synaptic carrier sites on the plasma membrane of Deiters' neurons after a learning experiment in rats.

A new micromethod for studying the interaction of gamma-aminobutyric acid (GABA) with its post-synaptic uptake in a defined type of nerve cell is described. The method involves the isolation by free hand microdissection of Deiters' nerve cells from the rabbit lateral vestibular nucleus and their incubation with tritiated GABA in the presence of 100 mM Na+ at 4 degrees C. From the binding data a Kd was calculated for this interaction of 104 nM and a BMax of 8.4 X 10(5) sites/neuron. The method was applied to the study of the modifications of the binding of GABA to Deiters' neurons from control rats and rats trained to balance on a steel wire in order to reach food. This performance is a powerful stimulation to the vestibular system. The results show that, in the binding experiment with 100 nM [3H]GABA, the amount of GABA which specifically binds to the Deiters' neurons is increased by 38% in the trained rats. Analogously, when the incubation with GABA was performed at 37 degrees C, involving an intake of GABA into the neurons, the amount of GABA taken up increases by 50% in the trained group. No GABA-binding or uptake increase was found when animals were subjected to intense vestibular stimulation for a short period without learning. These results indicate that when rats learn a behavioral test which involves an improved vestibular control, there is a specific neurochemical modification in the neurons of the lateral vestibular nucleus. This modification seems to be of importance for the physiology of the neuronal circuits controlling the vestibular function in the rat.

Animals↗
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.

Animals↗
PubMedDate not supplied

UV-transparent, replaceable agarose gels for molecular-sieve (capillary) electrophoresis of proteins and nucleic acids.

Gels of methoxylated agarose (gelling point 25.6 degrees C) and other low-melting agarose derivatives compare favorably with cross-linked polyacrylamide gels for capillary and slab molecular-sieve electrophoresis of proteins and DNA. These agarose gels can be pressed out of the capillary following a run and replaced by an agarose solution with a temperature of 35-40 degrees C. Gelation occurs upon lowering temperature and the same capillary can thus be reused for another analysis with a fresh gel. The methoxylated, non UV-absorbing agarose gels are, accordingly, replaceable, which makes them very attractive for series analyses with modern, automated capillary electrophoresis apparatus. The high resolution of these agarose gels is demonstrated with a separation of an albumin sample into monomers, dimers, trimers, tetramers, pentamers, hexamers, heptamers, and of DNA fragments.

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