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E Recio-Pinto

Publications and source records attributed to E Recio-Pinto.

25 records · Page 2Linked to original sources
PubMed1988

Human brain sodium channels in bilayers.

Sodium channels from human cortex were fused into planar lipid bilayers in the presence of batrachotoxin, and their single channel properties examined. Single channel slope conductance averaged 26 ps; tetrodotoxin block of the channels was voltage dependent with a K1/2 at 0 mV of 51 nM. The channel was asymmetrically selective for sodium over potassium. The permeability ratio (PNa/PK) equalled 3.3 when potassium was present only on the intracellular side of the channel, but it was 5.7 with potassium on the extracellular side. The average channel activation gating midpoint was -91 mV. These results indicate that sodium channels from human brain can be successfully studied both electrophysiologically and pharmacologically with the planar bilayer system.

Batrachotoxins↗
PubMed1987

Purified and unpurified sodium channels from eel electroplax in planar lipid bilayers.

Highly purified sodium channel protein from the electric eel, Electrophorus electricus, was reconstituted into liposomes and incorporated into planar bilayers made from neutral phospholipids dissolved in decane. The purest sodium channel preparations consisted of only the large, 260-kD tetrodotoxin (TTX)-binding polypeptide. For all preparations, batrachotoxin (BTX) induced long-lived single-channel currents (25 pS at 500 mM NaCl) that showed voltage-dependent activation and were blocked by TTX. This block was also voltage dependent, with negative potentials increasing block. The permeability ratios were 4.7 for Na+:K+ and 1.6 for Na+:Li+. The midpoint for steady state activation occurred around -70 mV and did not shift significantly when the NaCl concentration was increased from 50 to 1,000 mM. Veratridine-induced single-channel currents were about half the size of those activated by BTX. Unpurified, nonsolubilized sodium channels from E. electricus membrane fragments were also incorporated into planar bilayers. There were no detectable differences in the characteristics of unpurified and purified sodium channels, although membrane stability was considerably higher when purified material was used. Thus, in the eel, the large, 260-kD polypeptide alone is sufficient to demonstrate single-channel activity like that observed for mammalian sodium channel preparations in which smaller subunits have been found.

Animals↗
PubMed1986

Effects of insulin, insulin-like growth factor-II, and nerve growth factor on neurite formation and survival in cultured sympathetic and sensory neurons.

Insulin and the insulin-like growth factors (IGFs) may directly affect the development of the nervous system. NGF, IGF-II, and insulin's effects on neurite formation and neuronal survival were studied in peripheral ganglion cell cultures from chick embryos. Neurite outgrowth was enhanced in a dose-dependent manner by insulin and IGF-II in sympathetic cell cultures. The half-maximally effective concentration, ED50, was about 0.4-0.6 nM for both polypeptides, and concentrations as low as 10 pM were active. However, in sensory neurons the ED50 for neurite outgrowth was about 30 nM for insulin and 0.1 nM for IGF-II, suggesting that these factors may have selective effects in different neuronal tissues. Neither serum nor the presence of non-neuronal cells was required for the response in sympathetic neurons. The specific anti-NGF antiserum inhibited the neurite outgrowth response to NGF but not to insulin nor IGF-II. Insulin and IGF-II additionally supported survival of sensory and sympathetic neurons; however, insulin was not as efficacious as NGF. The combination of high concentrations of NGF and insulin was no better than NGF alone in supporting sympathetic cell survival, or neurite outgrowth. This indicates that insulin acts on the same, or a subpopulation, of NGF-responsive neurons. These results support the hypothesis that insulin and its homologs belong to a broad family of neuritogenic polypeptides.

Animals↗
PubMed1985

Neurite formation modulated by nerve growth factor, insulin, and tumor promoter receptors.

Until recently, nerve growth factor could be considered the only neurotrophic factor with an established physiological role. We discuss the emerging evidence indicating that the insulinlike factors may constitute a family of related neurotrophic proteins, and the observations suggesting that the receptor for the phorbol ester tumor promoters is closely associated with neuronal differentiation. The emphasis of the discussion is placed on neurite formation under multiple modulation by insulinlike factors, nerve growth factor, and tumor promoter receptors in sensory, sympathetic and human neuroblastoma cells.

Animals↗
PubMed1984

Effects of insulin, insulin-like growth factor-II and nerve growth factor on neurite outgrowth in cultured human neuroblastoma cells.

The identification of biologically important and chemically well-defined substances that can promote axon and dendrite formation would improve present understanding of the development of the nervous system. Physiological concentrations of insulin and insulin-like growth factor-II (IGF-II) reversibly enhanced neurite outgrowth (NTO) in human neuroblastoma SH-SY5Y cells cultured in media with and without serum. Nerve growth factor (NGF), in contrast, did not enhance NTO in serum-free media. Furthermore, anti-NGF antiserum inhibited NGF but not insulin-enhanced NTO. Insulin increased [3H]leucine and [3H]uridine uptake. These increases, together with increased NTO, were inhibited by cycloheximide and actinomycin D, respectively. The inhibition of NTO by cycloheximide was reversible. Human neuroblastoma cell lines that were responsive by NTO to NGF were also responsive to insulin, with the exception of line CHP-270. Moreover, cell lines unresponsive by NTO to NGF, and to tumor promoters, were uniformly unresponsive to insulin. These findings suggest that there are common defects in distal sites, because specific NGF and tumor promotor receptors are present in these lines. Insulin increased [3H]thymidine uptake in SH-SY5Y and CHP-100 cells. However, the enhancement of NTO by insulin and IGF-II in SH-SY5Y cells was independent of the cellular proliferation rate. Our results, together with the observations of others, suggest that insulin and IGF-II may modulate NTO in the nervous system.

Axons↗
PubMed1984

Insulin and insulin-like growth factor II permit nerve growth factor binding and the neurite formation response in cultured human neuroblastoma cells.

In serum-free medium, SH-SY5Y human neuroblastoma cells specifically and reversibly lost the capacity to bind 125I-labeled nerve growth factor (NGF) to the high-affinity sites (slow sites) and to respond by neurite outgrowth, unless physiological concentrations of insulin or insulin-like growth factor II were present. In serum-containing medium, anti-insulin antiserum decreased the neurite formation response to NGF, and insulin supplementation increased the number of available NGF slow sites. The low-affinity NGF fast sites are absent from SH-SY5Y cells and did not emerge on treatment with insulin. Insulin potentiated the induction of neurites by NGF in rat pheochromocytoma PC12 cells also. These results implicate a wider role for insulin and its homologs in the nervous system.

Animals↗