Evaluation of Positive Airway Pressure Treatment for Sleep Related Breathing Disorders in Adults

Positive airway pressure (PAP) is used to treat obstructive sleep apnea (OSA), central sleep apnea (CSA), and chronic hypoventilation. This document provides a systematic analysis and grading of peer-reviewed, published clinical studies pertaining to application of PAP treatment in adults. The paper is divided into 5 sections, each addressing a series of questions. The first section deals with whether efficacy and/or effectiveness have been demonstrated for continuous PAP (CPAP) treatment based on a variety of parameters and the level of OSA severity. Next, CPAP titration conducted with full, attended polysomnography in a sleep laboratory is compared with titration done under various other conditions. The third section investigates what can be expected regarding adherence and compliance with CPAP treatment as measured by subjective and objective methods and what factors may influence these parameters. Side effects and the influence of other specific factors on efficacy, effectiveness and safety of CPAP therapy are evaluated in the fourth section. Finally, the use of bilevel PAP therapy is reviewed for both patients with OSA and those with other selected nocturnal breathing disorders. Each section also contains a brief summary and suggestions for future research.

Effect of a targeted obstructive sleep apnea consult to improve access and quality at a sleep disorders center

STUDY OBJECTIVES

We sought to evaluate whether a targeted obstructive sleep apnea (OSA) consult (TOSAC) protocol that reduced sleep-specialist time spent with patients suspected of having OSA would improve quality of care compared with the previous clinical method for evaluation of patients internally referred for suspected OSA.

METHODS

Prospective cohort design. TOSAC patients received oximetry and criteria screening prior to a split-night polysomnography and a 45-minute sleep-specialist consult, while control patients received consult, testing, and a follow-up visit (90 minutes of sleep-specialist time).

RESULTS

We enrolled 186 TOSAC and 94 control patients. TOSAC patients completed their evaluation in a median of 7.0 days compared with 60.0 days for the controls (p < .001). At baseline, the TOSAC group was sleepier (Epworth Sleepiness Scale 13.9+/-4.5 vs 11.0+/-4.3; p < .001) and had a slightly lower quality of life (Functional Outcomes of Sleep Questionnaire 15.0+/-3.0 vs 16.8+/-2.2, p < .001) than controls. The apnea-hypopnea index noted at polysomnography was similar in TOSAC and control patients (28.6+/-29.5 vs 23.1+/-23.9, p = .156), and the prevalence of OSA was similar in both groups (75% vs 72%, p = .616). At 1 month of therapy, improvement in the Epworth Sleepiness Scale and overall patient satisfaction were similar between groups (all p > .10), while TOSAC patients had a slightly greater improvement on the Functional Outcomes of Sleep Questionnaire (p = .010). TOSAC patients reported better subjective continuous positive airway pressure compliance (median 42.0 vs 32.5 hours/week; p = .037).

CONCLUSIONS

A protocol-driven evaluation pathway for OSA that used screening with oximetry and less sleep-specialist time shortened access and produced similar diagnoses, improvements in sleepiness and quality of life, and overall satisfaction.

Search for the Higgs boson in H --> WW(*) decays in pp collisions at square root of 1.96 TeV

We present a search for the standard model Higgs boson in H --> WW(*) decays with e+e-, e+/-mu-/+, and mu+mu- final states in pp collisions at a center-of-mass energy of square root of s = 1.96 TeV. The data, collected from April 2002 to June 2004 with the D0 detector, correspond to an integrated luminosity of 300-325 pb(-1), depending on the final state. The number of events observed is consistent with the expectation from backgrounds. Limits from the combination of all three channels on the Higgs boson production cross section times branching ratio sigma x BR(H --> WW(*) are presented.

Measurement of the lifetime difference in the B0(s) system

We present a study of the decay B0(s) --> J/psiphi. We obtain the CP-odd fraction in the final state at time zero, Rperpendicular = 0.16 +/- 0.10(stat) +/- 0.02 (syst), the average lifetime of the (B0(s), B0(s)) system, tau(B0(s)) = 1.39(+0.13)(-0.16)(stat)(+0.01)(-0.02)(syst) ps, and the relative width difference between the heavy and light mass eigenstates, DeltaGamma/Gamma tripple bond (GammaL - GammaH)/Gamma = 0.24(+0.28)(-0.38)(stat)(+0.03)(-0.04)(syst). With the additional constraint from the world average of the lifetime measurements using semileptonic decays, we find tau(B0(s)) = 1.39 +/- 0.06 ps and DeltaGamma/Gamma = 0.25(+0.14)(-0.15). For the ratio of the B0(s) and B0 lifetimes we obtain tau(B0(s))/tau(B0) = 0.91 +/- 0.09(stat) +/- 0.003(syst).

Measurement of semileptonic branching fractions of B mesons to narrow D** states

Using the data accumulated in 2002-2004 with the D0 detector in proton-antiproton collisions at the Fermilab Tevatron collider with a center-of-mass energy of 1.96 TeV, the branching fractions of the decays B --> D0(1)(2420)mu+ vmuX and B --> D2(*0)(2460)mu+ vmuX and their ratio have been measured: B(b --> B) x B(B --> D0(1)mu+ vmuX) x B(D0(*0) --> D*- pi+) = [0.087 +/- 0.007(stat) +/- 0.014(syst)]%; B(b --> B) x B(B --> D2(*0) mu+ vmuX) x B(D2(*0) --> D*- pi+) = [0.035 +/- 0.007(stat) +/- 0.008(syst)]% and [B(B --> D2(*0)mu+ vmuX) x B(D2(*0) --> D*- pi+)]/[B(B --> D0(1)mu+ vmuX) x B(D0(1) --> D*- pi+)] = 0.39 +/- 0.09(stat) +/- 0.12 (syst), where the charge conjugated states are always implied.

Search for large extra spatial dimensions in dimuon production with the d0 detector

We present the results of a search for the effects of large extra spatial dimensions in pp collisions at sqrt[s] = 1.96 TeV in events containing a pair of energetic muons. The data correspond to 246 pb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Good agreement with the expected background was found, yielding no evidence for large extra dimensions. We set 95% C.L. lower limits on the fundamental Planck scale between 0.85 and 1.27 TeV within several formalisms. These are the most stringent limits achieved in the dimuon channel to date.

Search for supersymmetry via associated production of charginos and neutralinos in final states with three leptons

A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a pp center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three charged leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a data set corresponding to an integrated luminosity of 320 pb-1. Limits on the product of the production cross section and leptonic branching fraction are set. For the minimal supergravity model, a chargino lower mass limit of 117 GeV at the 95% C.L. is derived in regions of parameter space with enhanced leptonic branching fractions.

Search for neutral supersymmetric Higgs Bosons in multijet events at sqrt[s]=1.96 TeV

We have performed a search for neutral Higgs bosons produced in association with bottom quarks in pp collisions, using 260 pb-1 of data collected with the D0 detector in Run II of the Fermilab Tevatron Collider. The cross sections for these processes are enhanced in many extensions of the standard model (SM), such as in its minimal supersymmetric extension at large tanbeta. The results of our analysis agree with expectations from the SM, and we use our measurements to set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV.

Production of WZ events in pp collisions at square root(s) = 1.96 TeV and limits on anomalous WWZ couplings

We present results from a search for WZ production with subsequent decay to l nu l' l' (l and l' = e or mu) using 0.30 fb(-1) of data collected by the D0 experiment between 2002 and 2004 at the Fermilab Tevatron. Three events with WZ decay characteristics are observed. With an estimated background of 0.71 +/- 0.08 events, we measure the WZ production cross section to be 4.5(-2.6)(+3.8) pb, with a 95% C.L. upper limit of 13.3 pb. The 95% C.L. limits for anomalous WWZ couplings are found to be -2.0 < delta kappaZ < 2.4 for form factor scale lambda = 1 TeV, and -0.48 < lambdaZ < 0.48 and -0.49 < delta g(1)(Z) < 0.66 for lambda = 1.5 TeV.

Identification of the structural gene of the PEP-phosphotransferase enzyme I in Bacillus subtilis Marburg

A thermosensitive mutation pt8I1 in the gene coding for the Enzyme I of the PEP-phosphotransferase system pathway has been isolated. The mutant enzyme was shown to be sensitive to high temperature, but this effect is dependent on the ionic strength. The ptsI1 mutation was shown to belong to the previously described ctr locus. Following Lin (1970) it is proposed to retain the symbole ptsI for this locus.

Search for Randall-Sundrum gravitons in dilepton and diphoton final states

We report the first direct search for the Kaluza-Klein (KK) modes of Randall-Sundrum gravitons using dielectron, dimuon, and diphoton events observed with the D0 detector operating at the Fermilab Tevatron pp(-) Collider at sqrt[s]=1.96 TeV. No evidence for resonant production of gravitons has been found in the data corresponding to an integrated luminosity of approximately equal to 260 pb(-1). Lower limits on the mass of the first KK mode at the 95% C.L. have been set between 250 and 785 GeV, depending on its coupling to standard model particles.

Study of Zgamma events and limits on anomalous ZZgamma and Zgammagamma couplings in pp collisions at square root s = 1.96 TeV

We present a measurement of the Zgamma production cross section and limits on anomalous ZZgamma and Zgammagamma couplings for form-factor scales of lambda = 750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eegamma (mumugamma) final state using 320(290) pb(-1) of pp(-1) collisions at square root of s = 1.96 TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are /h(10,30)Z/ < 0.23, /h(20,40)Z/ < 0.020, /h(10,30)gamma/ < 0.23, and /h(20,40)gamma/ < 0.019 for lambda = 1000 GeV.

Measurement of inclusive differential cross sections for pp collisions at (square root)s = 1.96 TeV

We present measurements of the inclusive production cross sections of the Gamma(1S) bottomonium state in pp collisions at (square root)s = 1.96 TeV. Using the Gamma(1S) --> mu(+)mu(-) decay mode for a data sample of 159 +/- 10 pb(-1) collected by the D0 detector at the Fermilab Tevatron collider, we determine the differential cross sections as a function of the Gamma(1S) transverse momentum for three ranges of the Gamma(1S) rapidity: 0 < y(Gamma) < or = 0.6, 0.6 < y(Gamma) < or = 1.2, and 1.2 < y(Gamma) < or = 1.8.

Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

Measurement of the ratio of B+ and B0 meson lifetimes

The ratio of the B+ and B0 meson lifetimes was measured using data collected in 2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider. These mesons were reconstructed in B-->mu(+)nuD(*-)X decays, which are dominated by B0 and B-->mu(+)nuD 0X decays, which are dominated by B+. The ratio of lifetimes is measured to be tau(+)/tau(0)=1.080+/-0.016(stat)+/-0.014(syst).

Measurement of the ratio of inclusive cross sections sigma(pp --> Z + b jet)/sigma(pp --> Z + jet) at square root(s) = 1.96 TeV

Using the data collected with the D0 detector at square root(s) = 1.96 TeV, for integrated luminosities of about 180 pb(-1), we have measured the ratio of inclusive cross sections for pp --> Z + b jet to pp --> Z + jet production. The inclusive Z + b-jet reaction is an important background to searches for the Higgs boson in associated ZH production at the Fermilab Tevatron collider. Our measurement is the first of its kind, and relies on the Z --> e+ e- and Z --> mu+ mu- modes. The combined measurement of the ratio yields 0.021+/-0.005 for hadronic jets with transverse momenta pT > 20 GeV/c and pseudorapidities absolute value(eta) < 2.5, consistent with next-to-leading-order predictions of the standard model.

Search for anomalous heavy-flavor quark production in association with W bosons

We search for anomalous production of heavy-flavor quark jets in association with W bosons at the Fermilab Tevatron pp Collider in final states in which the heavy-flavor quark content is enhanced by requiring at least one tagged jet in an event. Jets are tagged using one algorithm based on semileptonic decays of b/c hadrons, and another on their lifetimes. We compare e+jets (164 pb(-1)) and mu+jets (145 pb(-1)) channels collected with the D0 detector at sqrt[s]=1.96 TeV to expectations from the standard model and set upper limits on anomalous production of such events.

Measurement of the WW production cross section in pp collisions at square root[s]=1.96 TeV

We present a measurement of the W boson pair-production cross section in pp collisions at a center-of-mass energy of sqrt[s]=1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224-252 pb(-1) depending on the final state (ee, emu, or mumu). We observe 25 candidates with a background expectation of 8.1+/-0.6(stat)+/-0.6(syst)+/-0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3x10(-7), equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8(+4.3)(-3.8)(stat)+1.2-0.9(syst)+/-0.9(lum) pb, in agreement with predictions from the standard model.

Measurement of the Lambda0b lifetime in the decay lambda0b--> J/psiLambda0 with the D0 detector

We present measurements of the Lambda(0)(b) lifetime in the exclusive decay channel Lambda(0)(b)--> J/psiLambda(0), with J/psi--> mu(+)mu(-) and Lambda(0)--> ppi(-), the B0 lifetime in the decay B0-->J/psiK(0)(S) with J/psi--> mu(+)mu(-) and K(0)(S)-->pi(+)pi(-), and the ratio of these lifetimes. The analysis is based on approximately 250 pb(-1) of data recorded with the D0 detector in pp collisions at sqrt[s] = 1.96 TeV. The Lambda(0)(b) lifetime is determined to be tau(Lambda(0)(b)) = 1.22(+0.22)(-0.18)(stat) +/- 0.04(syst) ps, the B0 lifetime tau(B0) = 1.40(+0.11)(-0.10)(stat) +/- 0.03(syst) ps, and the ratio tau(Lambda(0)(b))/tau(B0) = 0.87(+0.17)(-0.14)(stat) +/- 0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the Lambda(0)(b) lifetime based on a fully reconstructed decay channel.

Search for Wbb and WH production in pp collisions at square root [s]=1.96 TeV

We present a search for Wbb production in pp collisions at sqrt[s]=1.96 TeV in events containing one electron, an imbalance in transverse momentum, and two b-tagged jets. Using 174 pb(-1) of integrated luminosity accumulated by the D0 experiment at the Fermilab Tevatron collider, and the standard-model description of such events, we set a 95% C.L. upper limit on Wbb production of 6.6 pb for b quarks with transverse momenta p(b)(T)>20 GeV and bb separation in pseudorapidity-azimuth space DeltaR(bb)>0.75. Restricting the search to optimized bb mass intervals provides upper limits on WH production of 9.0-12.2 pb for Higgs-boson masses of 105-135 GeV.

Search for the flavor-changing neutral current decay B0s--> mu(+) mu(-) in pp Collisions at sqrt[s] = 1.96 TeV with the D0 detector

We present the results of a search for the flavor-changing neutral current decay B(0)(s)--> mu(+) mu(-) using a data set with integrated luminosity of 240 pb(-1) of pp collisions at sqrt[s] = 1.96 TeV collected with the D0 detector in run II of the Fermilab Tevatron collider. We find the upper limit on the branching fraction to be B(B(0)(s)--> mu(+) mu(-)) < or= 5.0 x 10(-7) at the 95% C.L. assuming no contributions from the decay B(0)(d)--> mu(+) mu(-) in the signal region. This limit is the most stringent upper bound on the branching fraction B(0)(s)--> mu(+) mu(-) to date.

Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

Nutrient transport in a restored riparian wetland

We determined the water quality effect of a restored forested riparian wetland adjacent to a manure application area and a heavily fertilized pasture in the Georgia Coastal Plain. The buffer system was managed based on USDA recommendations and averaged 38 m in width. Water quality and hydrology data were collected from 1991-1999. A nitrate plume in shallow ground water with concentrations exceeding 10 mg NO3-N L(-1) moved into the restored forested riparian wetland. Along most of the plume front, concentrations were less than 4 mg NO3-N L(-1) within 25 m. Two preferential flow paths associated with past hydrologic modifications to the site allowed the nitrate plume to progress further into the restored forested riparian wetland. Surface runoff total N, dissolved reactive phosphorus (DRP), and total P concentrations averaged 8.63 mg N L(-1), 1.37 mg P L(-1), and 1.48 mg P L(-1), respectively, at the field edge and were reduced to 4.18 mg N L(-1), 0.31 mg P L(-1), and 0.36 mg P L(-1), respectively, at the restored forested riparian wetland outlet. Water and nutrient mass balance showed that retention and removal rates for nitrogen species ranged from a high of 78% for nitrate to a low of 52% for ammonium. Retention rates for both DRP and total P were 66%. Most of the N retention and removal was accounted for by denitrification. Mean annual concentrations of total N and total P leaving the restored forested riparian wetland were 1.98 mg N L(-1) and 0.24 mg P L(-1), respectively.

Genetic and molecular features of Su(P), a gene that interacts with ref(2)P in male fertility of Drosophila melanogaster

The ref(2)P gene is involved in the control of sigma rhabdovirus multiplication in Drosophila melanogaster. ref(2)P activity is also necessary for male fertility. However, in one-third of laboratory strains tested, males that lacked ref(2)P activity were fertile. In all such strains studied, the male sterility phenotype was abolished due to the presence of a particular allele at the Su(P) locus, at 73B1-2. These spontaneous suppressor alleles were dominant. We were able to induce dominant suppressor alleles at the Su(P) locus by X-ray mutagenesis and hybrid dysgenesis, suggesting that null alleles of Su(P) confer the dominant suppressor phenotype. The Su(P) gene was cloned by P element tagging. The P element-tagged alleles identified a Su(P) transcript as a 1.4-kb mRNA produced in the soma of both males and females, which is also abundant in ovaries.

Block of human cardiac Kv1.5 channels by loratadine: voltage-, time- and use-dependent block at concentrations above therapeutic levels

OBJECTIVE

The aim of this study was to analyze the effects of loratadine on a human cardiac K+ channel (hKv1.5) cloned from human ventricle and stably expressed in a mouse cell line.

METHODS

Currents were studied using the whole-cell configuration of the patch-clamp technique in Ltk- cells transfected with the gene encoding hKv1.5 channels.

RESULTS

Loratadine inhibited in a concentration-dependent manner the hKv1.5 current, the apparent affinity being 1.2 +/- 0.2 microM. The blockade increased steeply between -30 and 0 mV which corresponded with the voltage range for channel opening, thus suggesting that the drug binds preferentially to the open state of the channel. The apparent association and dissociation rate constants were (3.6 +/- 0.5) x 10(6).M-1.s-1 and 3.7 +/- 1.6.s-1, respectively. Loratadine, 1 microM, increased the time constant of deactivation of tail currents elicited on return to -40 mV after 500 ms depolarizing pulses to +60 mV from 36.2 +/- 3.4 to 64.9 +/- 3.6 ms (n = 6, P < 0.01), thus inducing a 'crossover' phenomenon. Application of trains of pulses at 1 Hz lead to a progressive increase in the blockade reaching a final value of 48.6 +/- 4.3%. Recovery from loratadine-induced block at -80 mV exhibited a time constant of 743.0 +/- 78.0 ms. Finally, the results of a mathematical stimulation of the effects of loratadine, based on an open-channel block model, reproduced fairly well the main effects of the drug.

CONCLUSIONS

The present results demonstrated that loratadine blocked hKv1.5 channels in a concentration-, voltage-, time- and use-dependent manner but only at concentrations much higher than therapeutic plasma levels in man.

Comparative effects of nonsedating histamine H1 receptor antagonists, ebastine and terfenadine, on human Kv1.5 channels

The effects of ebastine and terfenadine, long-acting nonsedating histamine H1 receptor antagonists, were studied on hKv1.5 channels using the whole-cell voltage-clamp configuration of the patch-clamp technique in Ltk- cells transfected with the gene encoding the hKv1.5 channel. Upon depolarization to +60 mV, terfenadine, 1 microM and 3 microM, inhibited the hKv1.5 current by 42.4 +/- 6.4% and 69.3 +/- 4.2% (P < 0.01). In contrast, at the same range of concentrations, ebastine-induced inhibition of this K+ current averaged 6.5 +/- 2.0% and 13.0 +/- 2.0 (P < 0.05). At the highest concentration tested (3 microM) neither terfenadine carboxylate nor carebastine significantly modified hKv1.5 current. All these results suggest that ebastine could represent a safer alternative to terfenadine in the clinical practice.

Effects of ropivacaine on a potassium channel (hKv1.5) cloned from human ventricle

BACKGROUND

Ropivacaine, a new amide local anesthetic agent chemically related to bupivacaine, is able to induce early after depolarizations in isolated cardiac preparations. The underlying mechanism by which ropivacaine induces this effect has not been explored, but it is likely to involve K+ channel block.

METHODS

Cloned human cardiac K+ channels (hKv1.5) were stably transfected in Ltk cells, and the effects of ropivacaine on the expressed hKv1.5 currents were assessed using the whole-cell configuration of the patch-clamp technique.

RESULTS

Ropivacaine (100 microM) did not modify the initial activation time course of the current, but induced a fast subsequent decline to a lower steady-state current level with a time constant of 12.2 +/- 0.6 ms. Ropivacaine inhibited hKv1.5 with an apparent KD of 80 +/- 4 microM. Block displayed an intrinsic voltage-dependent, consistent with an electrical distance for the binding site of 0.153 +/- 0.007 (n = 6) (from the cytoplasmic side). Ropivacaine reduced the tail current amplitude recorded at -40 mV, and slowed the deactivation time course, resulting in a "crossover" phenomenon when control and ropivacaine tail currents were superimposed.

CONCLUSIONS

These results indicate that: (1) ropivacaine is an open channel blocker of hKv1.5; (2) binding occurs in the internal mouth of the ion pore; and (3) unbinding is required before the channel can close. These effects explain the ropivacaine availability of induction early after depolarizations and could be clinically relevant.

Lamotrigine high-dose tolerability and safety in patients with epilepsy: a double-blind, placebo-controlled, eleven-week study

PURPOSE

This study was undertaken to evaluate the dose tolerability and safety of a chronic ascending twice-daily (b.i.d.) dosage regimen of < or = 700 mg/day lamotrigine (LTG) and to include determination of the LTG pharmacokinetic profile at doses > or = 500 mg/day in patients receiving concomitant enzyme-inducing antiepileptic drugs (AEDs).

METHODS

Twelve adult male epileptic patients treated with enzyme-inducing AEDs received < or = 700 mg/day (b.i.d.) oral LTG (n = 8) or placebo (controls, n = 4). For 3 weeks, as outpatients they had their LTG dosage increased from 100 to 400 mg/day. Then, in a clinical research study unit, patients received regimens of 500, 600, and 700 mg/day for 1 week each. Controls received matching placebo in the same sequence. At study end, dosages were tapered in 2 weeks. Follow-up evaluations were made 7 days later.

RESULTS

Five LTG patients tolerated 700 mg/day for 1 week. LTG was reduced to 600 mg/day in a patient with mild diplopia and to 500 mg/day in a patient with mild oscillopsia and diplopia. One patient discontinued 300 mg/day therapy with a moderately intense diffuse papular skin rash, attributed to LTG. Headache, drowsiness, faintness, and diplopia, the common adverse events (AEs), were mild to moderate in intensity and occurred in 50-75% of patients in both groups (except for diplopia, occurring only with LTG). Concomitant AED plasma concentrations were not markedly changed by LTG. LTG pharmacokinetics were linear over the range of 500-700 mg/day.

CONCLUSIONS

LTG doses < or = 700 mg/day can be tolerated in patients receiving concomitant enzyme-inducing AEDs.

Class III antiarrhythmic effects of zatebradine. Time-, state-, use-, and voltage-dependent block of hKv1.5 channels

BACKGROUND

Zatebradine is a bradycardic agent that inhibits the hyperpolarization-activated current (I(f)) in the rabbit sinoatrial node. It also prolongs action potential duration in papillary muscles in guinea pigs and in Purkinje fibers in rabbits. The underlying mechanism by which zatebradine induces this effect has not been explored, but it is likely to involve K+ channel block.

METHODS AND RESULTS

Cloned human cardiac K+ delayed rectifer currents (hKv1.5) were recorded in Ltk- cells transfected with their coding sequence. Zatebradine 10 mumol/L did not modify the initial activation time course of the current but induced a subsequent decline to a lower steady-state current level with a time constant of 109 +/- 16 ms. Zatebradine inhibited hKv1.5 with an apparent KD of 1.86 +/- 0.14 mumol/L. Block was voltage dependent (electrical distance delta = 0.177 +/- 0.003) and accumulated in a use-dependent manner during 0.5- and 1-Hz pulse trains because of slower recovery kinetics in the presence of the drug. Zatebradine reduced the tail current amplitude, recorded at -30 mV, and slowed the deactivation time course, which resulted in a "crossover" phenomenon when control and zatebradine tail currents were superimposed.

CONCLUSIONS

These results indicate that (1) zatebradine is an open-channel blocker of hKv 1.5, (2) binding occurs in the internal mouth of the ion pore, (3) unbinding is required before the channel can close, and (4) zatebradine-induced block is use dependent because of slower recovery kinetics in the presence of the drug. These effects may explain the prolongation of the cardiac action potential and could be clinically relevant.

Mechanisms of block of a human cloned potassium channel by the enantiomers of a new bradycardic agent: S-16257-2 and S-16260-2

1. The effects of S-16257-2 (S57) and S-16260-2 (R60), the two enantiomers of a new bradycardic agent, were studied on human cloned K+ channels (hKv1.5) stably expressed in a mouse L cell line using the whole-cell configuration of the patch-clamp technique. 2. S57 and R60 did not modify the sigmoidal activation time course of the current but reduced the amplitude and increased the rate of the decay of the current during the application of depolarizing pulses. Both, S57 and R60 produced a concentration-dependent block of hKv1.5 channels with apparent KD values of 29.0 +/- 1.9 microM and 40.9 +/- 4.0 microM, respectively. Thus, S57 was 1.4 fold more potent than R60 in blocking hKv1.5 channels. 3. The blockade produced by S57 and R60 was voltage-dependent and increased steeply between -30 and 0 mV, which corresponded with the voltage range for channel opening. This result indicated that both enantiomers block the hKv1.5 channels, preferentially, when they are in the open state. Between 0 and +60 mV the blockade exhibited a shallow voltage-dependence which was described by an electrical distance of 0.18 +/- 0.002 and 0.19 +/- 0.004 for S57 and R60, respectively. 4. S57 and R60 also increased the rate of decline of the current during the application of depolarizing pulses. The time constant of such decline (tau Block) was faster in the presence of R60 than in the presence of S57 (16.2 +/- 1.5 ms vs. 24.0 +/- 2.6 ms; P < 0.01). The apparent association rate constants (k) were similar for S57 and R60 ((0.52 +/- 0.13) x 10(6) M-1 s-1 and (0.66 +/- 0.13) x 10(6) M-1 s-1, respectively), whereas the dissociation rate constant (l) was faster for R60 than for S57 (25.8 +/- 1.8 s-1 and 13.0 +/- 2.4 s-1, respectively). 5. Both enantiomers slowed the deactivation of the tail currents elicited upon repolarization to -40 mV, thus inducing a 'crossover' phenomenon. These results suggested that drug unbinding is required before hKv1.5 channels can close. 6. It is concluded that R60 and S57 produced a similar time- voltage- and state-dependent block of hKv1.5 channels that can be interpreted as open channel block by the charged form of each enantiomer. The main difference between R60 and S57 were linked to the apparent dissociation rate constants.

Electromechanical effects of zatebradine on isolated guinea pig cardiac preparations

The effects of zatebradine on rate and contractile force and transmembrane action potentials were studied in isolated guinea pig atria and ventricular papillary muscles. In spontaneously beating right atria, zatebradine, 10(-7)-10(-4) M, produced a negative chronotropic effect (IC50 = 6.5 +/- 3.0 x 10(-6) M) and prolonged the recovery of the sinus function. In addition, it produced a biphasic effect on the atrial contractility, so that at concentrations up to 10(-5) M, it exerted a positive inotropic effect, whereas at higher concentrations, a negative inotropic effect was observed (IC50 = 9.0 +/- 0.3 x 10(-5) M). In electrically driven left atria, zatebradine produced a negative inotropic effect, though no changes were observed in the total contraction time or the time to peak tension. In papillary muscles, zatebradine > or = 5 x 10(-6) M caused a significant decrease in the maximum upstroke velocity (Vmax) without altering the resting membrane potential and exerted biphasic effects on the action potential duration (APD). At concentrations up to 5 x 10(-5) M, it prolonged the APD, whereas at higher concentrations, it shortened the APD. In addition, zatebradine, 10(-4) M, significantly reduced the amplitude and Vmax of the slow action potentials elicited by isoproterenol in K(+)-depolarized papillary fibres. In the presence of zatebradine, trains of stimuli at rates between 0.5 and 3 Hz led to an exponential decline in Vmax (frequency-dependent Vmax block), which was augmented at higher rates of stimulation. The time constant for the recovery of Vmax from the frequency-dependent block was 2.9 s.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the two enantiomers, S-16257-2 and S-16260-2, of a new bradycardic agent on guinea-pig isolated cardiac preparations

1. The electromechanical effects of two enantiomers, S-16257-2 (S57) and S-16260-2 (R60), were studied and compared in guinea-pig isolated atria and ventricular papillary muscles. The possible stereoselectivity of the interaction on the cardiac Na+ channel was analysed by comparing the effects of the two enantiomers on the onset and recovery kinetics of the frequency-dependent Vmax block. 2. In spontaneously beating right atria, S57 and R60 (10(-8)M-10(-4M) exerted a negative chronotropic effect (pIC50 = 5.07 +/- 0.19 and 4.76 +/- 0.18, respectively) and prolonged the sinus node recovery time, this effect being more marked with S57. In electrically driven left atria, S57 decreased (P < 0.05) contractile force only at 10(-4M) and R60 at concentrations > or = 5 x 10(-5M), whereas in papillary muscles the negative inotropic effect appeared at concentrations > 10(-5M). 3. In papillary muscles driven at 1 Hz, S57 and R60 at concentrations higher than 5 x 10(-6M) produced a concentration-dependent decrease in the maximum upstroke velocity (Vmax) and amplitude of the cardiac action potential without altering the resting membrane potential or the action potential duration. S57 and R60 had no effect on the characteristics of the slow action potentials elicited by isoprenaline in ventricular muscle fibres depolarized in high K+ (27 mM) solution. 4. At 5 x 10(-5M), S57 and R60 produced a small tonic Vmax block. However, in muscles driven at rates between 0.5 and 3 Hz both enantiomers produced an exponential decline in Vmax (frequency-dependent Vmax block) which augmented at higher rates of stimulation. The onset and offset rates of the frequency-dependent Vmax block were similar for both drugs. Both S57 and R60 prolonged the recovery time constant from the frequency-dependent block from 20.1 +/- 2.9 ms to 2-3 s.5. At 5 x 10-5 M, S57 and R60 shifted the membrane responsiveness curve in a hyperpolarizing direction.6. It can be concluded that S57 and R60, the two enantiomers of the new bradycardic agent, produced a similar frequency-dependent Vmax block which indicated that the interaction with the Na+ channel was not stereospecific. The analysis of the onset and offset kinetics of the frequency-dependent Vmax block suggested that both enantiomers can be considered as Na+ channel blockers with intermediate kinetics,e.g., class IA antiarrhythmic drugs.

Localization of domains within the Drosophila Ref(2)P protein involved in the intracellular control of sigma rhabdovirus multiplication

The ref(2)P gene of Drosophila melanogaster interferes with sigma rhabdovirus multiplication. This gene is highly variable, and the different alleles are considered permissive or restrictive according to their effects on virus replication. In all cases, the mechanisms involve intracellular interactions between the sigma virus and Ref(2)P proteins. We showed that the N-terminal domain of the Ref(2)P protein was required for its activity in vivo. The protein was inactive in the null p(od)2 mutant when its first 82 amino acids were deleted. The p delta n gene was constructed so that the first 91 amino acids coded for by the restrictive alleles could be expressed in vivo. It was active in a transformed line. This sequence was sufficient to impart a restrictive phenotype to an adult D. melanogaster fly after it was injected with the virus. However, the truncated protein expressed by p delta n did not have an effect on the hereditary transmission of the sigma virus to the offspring of the infected flies, even though it contained the restriction site. The native Ref(2)P protein has been previously shown to have conformation-dependent epitopes common with some of those of the viral N protein. We demonstrated the following. (i) These epitopes were found in a domain of the Ref(2)P protein distinct from the site involved in restriction. (ii) They were modified in the N protein of the haP7 sigma virus mutant selected as being adapted to the restrictive alleles of the ref(2)P gene; only one mutation in the N gene, leading to an amino acid substitution, distinguished the haP7 mutant from the original virus. (iii) The virus strains partially or totally adapted to the effects of the full restrictive protein expressed by pp were always found to multiply to a lesser extent in the presence of the protein expressed by p delta n. These data suggest that two distinct domains of the Ref(2)P protein are involved in the control of sigma virus multiplication.