Integrable open boundary conditions for the Bariev model of three coupled X Y spin chains

The integrable open-boundary conditions for the Bariev model of three coupled one-dimensional XY spin chains are studied in the framework of the boundary quantum inverse scattering method. Three kinds of diagonal boundary K-matrices leading to nine classes of possible choices of boundary fields are found and the corresponding integrable boundary terms are presented explicitly. The boundary Hamiltonian is solved by using the coordinate Bethe ansatz technique and the Bethe ansatz equations are derived. (C) 2001 Elsevier Science B.V. All rights reserved.

On the intersection problem for 1-factorizations and near 1-factorizations of K-v

The number of 1-factors (near 1-factors) that mu 1-factorizations (near 1-factorizations) of the complete graph K-v, v even (v odd), can have in common, is studied. The problem is completely settled for mu = 2 and mu = 3.

Height discordance in monozygotic females is not attributable to discordant inactivation of X-linked stature determining genes

We tested the hypothesis that X-linked genes determining stature which are subject to skewed or non-random X-inactivation can account for discordance in height in monozygotic female twins. Height discordant female monozygotic adult twins (20 pairs) were identified from the Australian Twin Registry, employing the selection criteria of proven monozygosity and a measured height discordance of at least 5 cm. Differential X-inactivation was examined in genomic DNA extracted from peripheral lymphocytes by estimating differential methylation of alleles at the polymorphic CAG triplet repeat of the Androgen receptor gene (XAR). There were 17/20 MZ pairs heterozygous at this locus and informative for analysis. Of these, 10/17 both had random X-inactivation, 5/17 showed identical X-inactivation patterns of non random inactivation and 2/17 (12%) showed discordant X-inactivation. There was no relationship between inactivation patterns and self-report chorionicity. We conclude that non-random X-inactivation does not appear to be a major contributor to intra-pair height discordance in female MZ twins.

Regulation and properties of KCNQ1 (K(v)LQT1) and impact of the cystic fibrosis transmembrane conductance regulator

The K+ channel KCNQ1 (K(V)LQT1) is a voltage-gated K+ channel, coexpressed with regulatory subunits such as KCNE1 (IsK, mink) or KCNE3, depending on the tissue examined. Here, we investigate regulation and properties of human and rat KCNQ1 and the impact of regulators such as KCNE1 and KCNE3. Because the cystic fibrosis transmembrane conductance regulator (CFTR) has also been suggested to regulate KCNQ1 channels we studied the effects of CFTR on KCNQ1 in Xenopus oocytes, Expression of both human and rat KCNQ1 induced time dependent K+ currents that were sensitive to Ba2+ and 293B. Coexpression with KCNE1 delayed voltage activation, while coexpression with KCNE3 accelerated current activation. KCNQ1 currents were activated by an increase in intracellular cAMP, independent of coexpression with KCNE1 or KCNE3. cAMP dependent activation was abolished in N-terminal truncated hKCNQ1 but was still detectable after deletion of a single PKA phosphorylation motif. In the presence but not in the absence of KCNE1 or KCNE3, K+ currents were activated by the Ca2+ ionophore ionomycin. Coexpression of CFTR with either human or rat KCNQ1 had no impact on regulation of KCNQ1 K+ currents by cAMP but slightly shifted the concentration response curve for 293B. Thus, KCNQ1 expressed in Xenopus oocytes is regulated by cAMP and Ca2+ but is not affected by CFTR.

Cloning and function of the rat colonic epithelial K+ channel K(V)LQT1

K(V)LQT1 (K(V)LQ1) is a voltage-gated K+ channel essential for repolarization of the heart action potential that is defective in cardiac arrhythmia. The channel is inhibited by the chromanol 293B, a compound that blocks cAMP-dependent electrolyte secretion in rat and human colon, therefore suggesting expression of a similar type of K+ channel in the colonic epithelium. We now report cloning and expression of K(V)LQT1 from rat colon. Overlapping clones identified by cDNA-library screening were combined to a full length cDNA that shares high sequence homology to K(V)LQT1 cloned from other species. RT-PCR analysis of rat colonic musoca demonstrated expression of K(V)LQT1 in crypt cells and surface epithelium. Expression of rK(V)LQT1 in Xenopus oocytes induced a typical delayed activated K+ current. that was further activated by increase of intracellular cAMP but not Ca2+ and that was blocked by the chromanol 293B. The same compound blocked a basolateral cAMP-activated K+ conductance in the colonic mucosal epithelium and inhibited whole cell K+ currents in patch-clamp experiments on isolated colonic crypts. We conclude that K(V)QT1 is forming an important component of the basolateral cAMP-activated K+ conductance in the colonic epithelium and plays a crucial role in diseases like secretory diarrhea and cystic fibrosis.

Expression and function of colonic epithelial K(v)LQT1 K+ channels

1. K(V)LQT1 (KCNQ1) is a voltage-gated K+ channel essential for repolarization of the heart action potential Defects in ion channels have been demonstrated in cardiac arrhythmia. This channel is inhibited potently by the chromanol 293B, The same compound has been shown to block cAMP-dependent electrolyte secretion in rat and human colon, Therefore, it was suggested that a K+ channel similar to K(V)LQT1 is expressed in the colonic epithelium. 2, In the present paper, expression of K(V)LQT1 and its function in colonic epithelial cells is described. Reverse transcription-polymerase chain reaction analysis of rat colonic mucosa demonstrated expression of K(V)LQT1 in both crypt cells and surface epithelium. When expressed in Xenopus oocytes, K(V)LQT1 induced a typical delayed activated K+ current. 3, As demonstrated, the channel activity could be further activated by increases in intracellular cAMP. These and other data support the concept that K(V)LQT1 is forming a component of the basolateral cAMP-activated Kf conductance in the colonic epithelium.