33 research outputs found
A single serine residue confers tetrodotoxin insensitivity on the rat sensory-neuron-specific sodium channel SNS
AbstractSensory neurons express a sodium channel (SNS) that is highly resistant to block by tetrodotoxin (IC50=60 μM). SNS is 65% homologous to the cardiac sodium channel, in which a single hydrophilic residue in the SS2 segment is critical for tetrodotoxin resistance. By site-directed mutagenesis, we have substituted phenylalanine for serine at the equivalent position in SNS: this mutated (S356F) SNS channel is functionally similar to wild-type SNS when expressed in Xenopus oocytes, but is potently blocked by tetrodotoxin and saxitoxin with IC50s of 2.8 nM and 8.2 nM, respectively. These data provide clues to the rational design of selective blockers of SNS with potential as analgesic drugs
Nonlinear dynamics of soft boson collective excitations in hot QCD plasma III: bremsstrahlung and energy losses
Within of the framework of semiclassical approximation a general formalism
for deriving an effective current generating bremsstrahlung of arbitrary number
of soft gluons (longitudinal or transverse ones) in scattering of higher-energy
parton off thermal parton in hot quark-gluon plasma with subsequent extension
to two and more scatterers, is obtained. For the case of static color centers
an expression for energy loss induced by usual bremsstrahlung of lowest-order
with allowance for an effective temperature-induced gluon mass and finite mass
of the projectile (heavy quark), is derived. The detailed analysis of
contribution to radiation energy loss associated with existence of effective
three-gluon vertex induced by hot QCD medium, is performed. It is shown that in
general, the bremsstrahlung associated with this vertex have no sharp direction
(as in the case of usual bremsstrahlung) and therefore here, we can expect an
absence of suppression effect due to multiple scattering. For the case of two
color static scattering centers it was shown that the problem of calculation of
bremsstrahlung induced by four-gluon hard thermal loop (HTL) vertex correction
can be reduced to the problem of the calculation of bremsstrahlung induced by
three-gluon HTL correction. It was shown that for limiting value of soft gluon
occupation number all higher processes of
bremsstrahlung of arbitrary number of soft gluons become of the same order in
coupling, and the problem of resummation of all relevant contributions to
radiation energy loss of fast parton, arises. An explicit expression for matrix
element of two soft gluon bremsstrahlung in small angles approximation is
obtained.Comment: 68 pages, 9 EPS figures; added new sections 8, 10 and reference
Knockdown of zebrafish Nav1.6 sodium channel impairs embryonic locomotor activities
[[abstract]]Although multiple subtypes of sodium channels are expressed in most neurons, the specific contributions of the individual sodium channels remain to be studied. The role of zebrafish Nav1.6 sodium channels in the embryonic locomotor movements has been investigated by the antisense morpholino (MO) knockdown. MO1 and MO2 are targeted at the regions surrounding the translation start site of zebrafish Nav1.6 mRNA. MO3 is targeted at the RNA splicing donor site of exon 2. The correctly spliced Nav1.6 mRNA of MO3 morphants is 6% relative to that of the wild-type embryos. Nav1.6-targeted MO1, MO2 and MO3 attenuate the spontaneous contraction, tactile sensitivity, and swimming in comparison with a scrambled morpholino and mutated MO3 morpholino. No significant defect is observed in the development of slow muscles, the axonal projection of primary motoneurons, and neuromuscular junctions. The movement impairments caused by MO1, MO2, and MO3 suggest that the function of Nav1.6 sodium channels is essential on the normal early embryonic locomotor activities.[[notice]]補æ£å®Œç•¢[[journaltype]]國