Scanning Compton X-ray microscopy.

X-ray microscopy offers the opportunity to image biological and radiosensitive materials without special sample preparations, bridging optical and electron microscopy capabilities. However, the performance of such microscopes, when imaging radiosensitive samples, is not limited by their intrinsic resolution, but by the radiation damage induced on such samples. Here, we demonstrate a novel, to the best of our knowledge, radio-efficient microscope, scanning Compton X-ray microscopy (SCXM), which uses coherently and incoherently (Compton) scattered photons to minimize the deposited energy per unit of mass for a given imaging signal. We implemented SCXM, using lenses capable of efficiently focusing 60 keV X-ray photons into the sub-micrometer scale, and probe its radio-efficient capabilities. SCXM, when implemented in high-energy diffraction-limited storage rings, e.g., European Synchrotron Radiation Facility Extremely Brilliant Source and PETRA IV, will open the opportunity to explore the nanoscale of unstained, unsectioned, and undamaged radiosensitive materials.

Suppression of ventricular arrhythmias in man by d-propranolol independent of beta-adrenergic receptor blockade.

To investigate the mechanisms of ventricular arrhythmia suppression by propranolol, we determined the antiarrhythmic efficacy of d-propranolol in 10 patients with frequent ventricular ectopic depolarizations (VEDs) and nonsustained ventricular tachycardia. After an initial placebo phase, 40 mg d-propranolol was administered orally every 6 h with dosage increased every 2 d until arrhythmia suppression (greater than or equal to 80% VED reduction), intolerable side effects, or a maximal dosage (1,280 mg/d) was reached. Response was verified by documenting return of arrhythmia during a final placebo phase. Arrhythmia suppression occurred in six patients while two more had partial responses. Effective dosages were 320-1,280 mg/d (mean 920 +/- 360, SD) of d-propranolol with corresponding plasma concentrations of 60-2,280 ng/ml (mean 858 +/- 681). For the entire group, the QTc interval shortened by 4 +/- 4% (P = 0.03). Arrhythmia suppression was accompanied by a reduction in peak heart rate during exercise of 0-29%. To determine whether arrhythmia suppression could be attributed to beta-blockade, racemic propranolol was then administered in dosages producing the same or greater depression of exercise heart rate. In 3/8 patients, arrhythmias were not suppressed by racemic propranolol indicating that d-propranolol was effective via a non-beta-mediated action. By contrast, in 5/8 patients racemic propranolol also suppressed VEDs. We conclude that propranolol suppresses ventricular arrhythmias by both beta- and non-beta-adrenergic receptor-mediated effects.

Antipsychotics and the risk of sudden cardiac death.

BACKGROUND: Case reports link antipsychotic drugs with sudden cardiac deaths, which is consistent with dose-related electrophysiologic effects. Because this association has not been confirmed in controlled studies, we conducted a retrospective cohort study in Tennessee Medicaid enrollees, which included many antipsychotic users; there were also computer files describing medication use and comorbidity. The study was conducted before the introduction of risperidone and, thus, did not include the newer atypical agents. METHODS: The cohort included 481,744 persons with 1,282,996 person-years of follow-up. This included 26,749 person-years for current moderate-dose antipsychotic use (>100-mg thioridazine equivalents), 31,864 person-years for current low-dose antipsychotic use, 37,881 person-years for use in the past year only, and 1 186,501 person-years for no use. The cohort had 1487 confirmed sudden cardiac deaths; from these, we calculated multivariate rate ratios adjusted for potential confounding factors. RESULTS: When current moderate-dose antipsychotic use was compared with nonuse, the multivariate rate ratio was 2.39 (95% confidence interval, 1.77-3.22; P<.001). This was greater than that for current low-dose (rate ratio, 1.30; 95% confidence interval, 0.98-1.72; P=.003) and former (rate ratio, 1.20; 95% confidence interval, 0.91-1.58; P<.001) use. Among cohort members with severe cardiovascular disease, current moderate-dose users had a 3.53-fold (95% confidence interval, 1.66-7.51) increased rate relative to comparable nonusers ( P<.001), resulting in 367 additional deaths per 10,000 person-years of follow-up. CONCLUSIONS: Patients prescribed moderate doses of antipsychotics had large relative and absolute increases in the risk of sudden cardiac death. Although the study data cannot demonstrate causality, they suggest that the potential adverse cardiac effects of antipsychotics should be considered in clinical practice, particularly for patients with cardiovascular disease.

Molecular heterogeneity of protein kinase C expression in human ventricle.

OBJECTIVE: Although activation of protein kinase C (PKC) modulates the function of normal cardiac myocytes and likely plays a role in the pathogenesis of cardiomyopathic disease states, the molecular basis of PKC expression in human ventricle has not been examined in detail. METHODS: We have performed Western analysis and immunohistochemistry on explanted human cardiac tissue from nondiseased and diseased specimens using isoform-specific antibodies directed against all known PKC isozymes. RESULTS: In homogenates from left and right ventricle, all isoforms except PKC-gamma and theta were detected by immunoblotting, with confirmation using a second antibody directed against a different epitope when possible. For PKC-betaII, delta, and epsilon, data indicated that these isoforms were variably phosphorylated in vivo, resulting in multiple bands during immunoblotting. Because of potential antibody cross-reactivity, reverse transcriptase polymerase chain reaction (RT-PCR) was performed which confirmed expression of PKC-alpha, betaI, and zeta. Immunohistochemistry demonstrated that all isoforms detected in ventricular homogenate by Western analysis could be localized to cardiac myocytes. From a methodologic standpoint, significant degradation of PKC isoforms could be demonstrated when samples were either frozen or allowed to remain at room temperature, compared to immediate subcellular fractionation. CONCLUSIONS: These findings indicate that the PKC expression in human ventricular myocytes is remarkably diverse, with multiple conventional, novel, and atypical isoforms present, and highlight the importance of sample preparation in comparative studies of PKC isoform expression.

Mexiletine and tocainide: a comparison of antiarrhythmic efficacy, adverse effects, and predictive value of lidocaine testing.

Thirty patients received one of the lidocaine analogues--mexiletine or tocainide--orally for treatment of symptomatic ventricular arrhythmias. Crossover to the other analogue was allowed if initial drug treatment was unsuccessful, and the controlled use of other marketed oral antiarrhythmic agents was permitted. After follow-up of 7 +/- 3 months (SD), mexiletine was successful in 5 of 13 patients initially and in 5 of 14 patients who failed to respond to tocainide. Tocainide was successful in 1 of 17 patients initially and in 2 of 7 who did not respond to mexiletine. Combination therapy was used in nearly half of all ultimately successful drug trials. A common cause of drug trial failure for both drugs was the occurrence of adverse effects that frequently appeared well after hospital discharge. Response to lidocaine was a sensitive but nonspecific predictor of clinical outcome with mexiletine or tocainide that helped to identify drug-resistant patients. Finally, although mexiletine provided effective antiarrhythmic therapy more often than tocainide, response to one lidocaine analogue did not predict response to the other.

Conventional protein kinase C isoforms and cross-activation of protein kinase A regulate cardiac Na+ current.

We tested the hypothesis that specific isoforms of protein kinase C (PKC) are responsible for modulation of Na+ current (I(Na)) derived from the human cardiac Na+ channel using activators and inhibitors selective for specific PKCs. Experimental results demonstrated that I(Na) suppression was mediated by activation of conventional PKCs (cPKCs) and possibly resulted from channel internalization. In the presence of cPKC inhibition, phorbol ester application unexpectedly increased Na+ current, an effect eliminated by inhibition of protein kinase A. These findings demonstrate complex modulation of cardiac I(Na) by protein kinases and provide further evidence that PKC isoforms have distinct protein targets.

Parsing the genetic and nongenetic variance in children's depressive behavior.

Estimates of the genetic and environmental contributions to depressive behavior were derived using model-fitting analyses with data from a sample of 364 twin pairs, aged 4 to 12 years. Results suggested that genetic and nonshared environmental factors accounted for significant proportions of the variance in children's depressive symptomatology, but estimates differ for boys and girls. Further analyses indicated different genetic and environmental contributions for younger and older children. Analyses of a direct measure of shared and nonshared components of the environment identified specific aspects of children's environments which were associated with depressive behavior.

Effortful control in early childhood: continuity and change, antecedents, and implications for social development.

The course, antecedents, and implications for social development of effortful control were examined in this comprehensive longitudinal study. Behavioral multitask batteries and parental ratings assessed effortful control at 22 and 33 months (N = 106). Effortful control functions encompassed delaying, slowing down motor activity, suppressing/initiating activity to signal, effortful attention, and lowering voice. Between 22 and 33 months, effortful control improved considerably, its coherence increased, it was stable, and it was higher for girls. Behavioral and parent-rated measures converged. Children's focused attention at 9 months, mothers' responsiveness at 22 months, and mothers' self-reported socialization level all predicted children's greater effortful control. Effortful control had implications for concurrent social development. Greater effortful control at 22 months was linked to more regulated anger, and at 33 months, to more regulated anger and joy and to stronger restraint.

Meeting the health care needs of rural elderly: client satisfaction with a university-sponsored nursing center.

Responding to health care needs of the elderly has presented great challenges for health care professionals. These problems are compounded in rural communities by physical and social isolation, increased poverty, and lack of transportation. An innovative approach to meeting health needs of rural elderly is through nursing centers. Through an emphasis on health promotion and maintenance of optimal level of functioning, these primary health care facilities can foster independence and self-care for this targeted population. In addition, nursing centers serve as clinical sites for student learning experiences and settings for nursing research. This article focuses on a nursing center established at Edinboro University of Pennsylvania (EUP), which tailors its services to the elderly living in Edinboro. Results of a client satisfaction survey, based on the Risser Patient Satisfaction Instrument, are described in addition to patterns of nursing center usage, general categories of care, teaching interventions, referrals, counseling, and frequency of visits. Findings from the survey indicated a general high client satisfaction level with nursing care received at the center. Discussion also includes plans to expand services to elderly in the community through home visits.

Musical backgrounds, listening habits, and aesthetic enjoyment of adult cochlear implant recipients.

This paper describes the listening habits and musical enjoyment of postlingually deafened adults who use cochlear implants. Sixty-five implant recipients (35 females, 30 males) participated in a survey containing questions about musical background, prior involvement in music, and audiologic success with the implant in various listening circumstances. Responses were correlated with measures of cognition and speech recognition. Sixty-seven implant recipients completed daily diaries (7 consecutive days) in which they reported hours spent in specific music activities. Results indicate a wide range of success with music. In general, people enjoy music less postimplantation than prior to hearing loss. Musical enjoyment is influenced by the listening environment (e.g., a quiet room) and features of the music.

Mother-child mutually responsive orientation and conscience development: from toddler to early school age.

We examined whether positive implications of mother-child mutually responsive orientation, demonstrated earlier at toddler and preschool age, extend longitudinally into early school age. The focus of the present study was on the long-term consequences of mutually responsive orientation for the development of conscience. Mutually responsive orientation encompassed shared cooperation and shared positive affect between mother and child. It was measured as a composite of those qualities observed in dyadic naturalistic interactions and reported by mothers, at toddler and preschool age. Children's conscience was assessed at early school age (N = 83) using multiple measures, including observations of moral behavior, alone and in the peer context, and moral cognition. Mother-child mutually responsive orientation at toddler and preschool ages predicted children's future conscience, even after controlling for the developmental continuity of conscience. Model-fitting analyses revealed that mutually responsive orientation at toddler age had a direct effect on future conscience, not mediated by such orientation at preschool age. The findings extend those of earlier work that revealed the importance of mother-child mutually responsive orientation for socialization, and they confirm the value of the relationship approach to social development, including long-term outcomes.

The development of self-regulation in the first four years of life.

This study examined longitudinally the development of self-regulation in 108 young children during the first 4 years of life. Children's committed compliance (when they eagerly embraced maternal agenda) and situational compliance (when they cooperated, but without a sincere commitment) were studied. Both forms of compliance were observed in "Do" contexts, in which the mothers requested that the children sustain unpleasant, tedious behavior, and in "Don't" contexts, in which they requested that the children suppress pleasant, attractive behavior. Children's internalization while alone in the similar contexts was also studied. Parallel assessments were conducted when the children were 14, 22, 33, and 45 months of age. At all ages, the Do context was much more challenging for children than the Don't context. Girls surpassed boys in committed compliance. Both forms of compliance were longitudinally stable, but only within a given context. Children's fearfulness and effortful control, observed and mother reported, correlated positively with committed compliance, but mostly in the Don't context. Committed, but not situational, compliance was linked to children's internalization of maternal rules, observed when the children were alone in the Do and Don't contexts. These links were both concurrent and longitudinal, context specific, and significant even after controlling for maternal power assertion. There was modest preliminary evidence that committed compliance may generalize to interactions with adults other than the mother.

Activation of protein kinase A modulates trafficking of the human cardiac sodium channel in Xenopus oocytes.

Voltage-gated Na(+) channels are critical determinants of electrophysiological properties in the heart. Stimulation of beta-adrenergic receptors, which activate cAMP-dependent protein kinase (protein kinase A [PKA]), can alter impulse conduction in normal tissue and promote development of cardiac arrhythmias in pathological states. Recent studies demonstrate that PKA activation increases cardiac Na(+) currents, although the mechanism of this effect is unknown. To explore the molecular basis of Na(+) channel modulation by beta-adrenergic receptors, we have examined the effects of PKA activation on the recombinant human cardiac Na(+) channel, hH1. Both in the absence and the presence of hbeta(1) subunit coexpression, activation of PKA caused a slow increase in Na(+) current that did not saturate despite kinase stimulation for 1 hour. In addition, there was a small shift in the voltage dependence of channel activation and inactivation to more negative voltages. Chloroquine and monensin, compounds that disrupt plasma membrane recycling, reduced hH1 current, suggesting rapid turnover of channels at the cell surface. Preincubation with these agents also prevented the PKA-mediated rise in Na(+) current, indicating that this effect likely resulted from an increased number of Na(+) channels in the plasma membrane. Experiments using chimeric constructs of hH1 and the skeletal muscle Na(+) channel, hSKM1, identified the I-II interdomain loop of hH1 as the region responsible for the PKA effect. These results demonstrate that activation of PKA modulates both trafficking and function of the hH1 channel, with changes in Na(+) current that could either speed or slow conduction, depending on the physiological circumstances.

Stereoselective interactions of the enantiomers of chromanol 293B with human voltage-gated potassium channels.

Selective inhibitors of the slow component of the cardiac delayed rectifier K(+) current, I(Ks), are of interest as novel class III antiarrhythmic agents and as tools for studying the physiologic roles of the I(Ks) current. Racemic chromanol 293B is an inhibitor of both native I(Ks) and its putative molecular counterpart, the KvLQT1+minK ion channel complex. We synthesized the (+)-[3S,4R] and (-)-[3R,4S] enantiomers of chromanol 293B using chiral intermediates of known absolute configuration and determined their relative potency to block recombinant human K(+) channels that form the basis for the major repolarizing K(+) currents in human heart, including KvLQT1+minK, human ether-a-go-go-related gene product (hERG), Kv1.5, and Kv4.3, corresponding to the slow (I(Ks)), rapid (I(Kr)), and ultrarapid (I(Kur)) delayed rectifier currents and the transient outward current (I(To)), respectively. K(+) channels were expressed in mammalian cells and currents were recorded using the whole-cell patch-clamp technique. We found that the physicochemical properties and relative potency of the enantiomers differed from those reported previously, with (-)-[3R,4S]293B nearly 7-fold more potent in block of KvLQT1+minK than (+)-[3S,4R]293B, indicating that the original stereochemical assignments were reversed. K(+) current inhibition by (-)-293B was selective for KvLQT1+minK over hERG, whereas the stereospecificity of block for KvLQT1+minK and Kv1.5 was preserved, with (-)-293B more potent than (+)-293B for both channel complexes. We conclude that the (-)-[3R,4S] enantiomer of chromanol 293B is a selective inhibitor of KvLQT1+minK and therefore a useful tool for studying I(Ks).

Voltage clamp of the cardiac sodium current at 37 degrees C in physiologic solutions.

The cardiac sodium current was studied in guinea pig ventricular myocytes using the cell-attached patch voltage clamp at 37 degrees C in the presence of 145 mM external sodium concentration. When using large patch pipettes (access resistance, 1-2 M omega), the capacity current transient duration was typically 70 microseconds for voltage clamp steps up to 150 mV. At 37 degrees C the maximum inward sodium current peaked in approximately 200 microseconds after the onset of a clamp step and at this strong depolarization, less than 10% of the sodium current developed during the capacity transient. The sodium current developed smoothly and the descending limb of the current-voltage relationship usually spanned a range of 40 mV. Moreover, currents reduced by inactivation of sodium channels could be scaled to superimpose on the maximum current. Current tails elicited by deactivation followed a monoexponential time course that was very similar for currents of different sizes. Data obtained over a range of temperatures (15 degrees-35 degrees C) showed that the steady-state inactivation and conductance-voltage curves were shifted to more negative voltages at lower temperatures. These results demonstrate the feasibility of investigating the sodium current of mammalian cardiac cells at 37 degrees C in normal physiological solutions.

Intravenous 3-methoxy-O-desmethyl-encainide in reentrant supraventricular tachycardia: a randomized double-blind placebo-controlled trial in patients undergoing EP study.

Encainide is an agent effective in atrioventricular and atrioventricular nodal reentrant tachycardia. The metabolites O-desmethyl encainide and 3-methoxy-O-desmethyl encainide (MODE) are responsible for the clinical effects of encainide in most patients. In this study, intravenous MODE was evaluated in eight patients with reentrant supraventricular tachycardia undergoing electrophysiological testing. After tachycardia was induced at least twice to ensure reproducibility, MODE (30 micrograms/kg/min x 15 min, then 7.5 micrograms/kg/min) or placebo was administered in a double-blind fashion. If tachycardia remained inducible, the infusion was unblinded; in nonresponding subjects who received placebo, MODE was then administered. Placebo was ineffective in 3/3 patients. MODE prevented tachycardia induction in 5/8 patients and increased the tachycardia cycle length from 302 +/- 38 to 413 +/- 67 msec in the other three. At a mean concentration of 774 +/- 229 ng/ml, MODE prolonged PR, AH, HV, QRS, and QT intervals, right ventricular and accessory pathway effective refractory periods, and slowed or blocked antegrade accessory pathway conduction. Changes in intracardiac conduction were rate independent between cycle lengths 400 to 600 msec, while changes in ventricular effective refractory periods were most pronounced at rapid pacing rates. No adverse effects, hemodynamic changes, or conduction disturbances occurred. Thus, MODE can modify or suppress induction of reentrant atrioventricular or atrioventricular nodal tachycardia. The study design used here is well suited for the evaluation of newer antiarrhythmic agents by electrophysiological testing.

Psychological change over 54 months of cochlear implant use.

OBJECTIVE: To determine the long-term psychological outcome of postlingually deafened adults who received multichannel cochlear implants and to relate the psychological outcome to audiological outcome. DESIGN: Thirty-seven recipients of multichannel cochlear implants who participated in a prospective clinical trial completed psychological assessments before implantation and at regularly scheduled follow-ups through 54 mo of implant use. Standardized measures of affect, social function, and personality were used, and scores on these measures were correlated with asymptotic scores on several audiological measures. RESULTS: Evidence of significant improvement on measures of loneliness, social anxiety, and distress were obtained within a year after implantation and throughout the duration of the follow-up period. For measures of assertiveness and marital satisfaction, improvement was apparent only after long-term implant use. Although favorable changes on the Minnesota Multiphasic Personality Inventory (MMPI) Depression Scale were evidenced only in the initial follow-up period, improvements on the MMPI Paranoia and Social Introversion Scales persisted throughout the 54 mo follow-up. CONCLUSION: Multichannel cochlear implant use is associated with long-term psychological benefit. Correlations between audiological outcome and psychological outcome, however, suggested that the relation between audiological benefit and psychological benefit is not simple.

A randomized, double-blind, placebo-controlled, dose-ranging study of dofetilide in patients with inducible sustained ventricular tachyarrhythmias.

INTRODUCTION: Dofetilide is a new antiarrhythmic agent with potent IK blocking properties in vitro. We developed a dose-ranging, placebo-controlled study design to define the range of effective doses and to evaluate the clinical electrophysiology of intravenous dofetilide in patients in whom sustained ventricular tachycardia or fibrillation was reproducibly inducible at baseline electrophysiologic testing. METHODS AND RESULTS: The initial four patients received low doses that were increased in subsequent groups of four if adverse effects were absent. In each group of four patients, one patient was randomly assigned to placebo (double blind). Twenty-four patients were studied at six incremental loading and maintenance infusion regimens. Dofetilide (0.1 to 8.0 ng/mL) produced concentration-related increases in the % delta of QT (r = 0.79, P < 0.001), QTc (r = 0.60, P = 0.02), RR (r = 0.62, P < 0.02), and right ventricular effective refractory period (cycle length 600 msec; r = 0.68, P = 0.04). Placebo produced no changes in any of these measurements. Sustained ventricular tachycardia or ventricular fibrillation was no longer inducible in 1 of 6 patients receiving placebo and 8 of 18 receiving dofetilide (4 to 13 sec nonsustained ventricular tachycardia was induced in 4 of these 8). One patient developed torsades de pointes at a high concentration (5.3 ng/mL). CONCLUSIONS: We conclude that: (1) dofetilide produces concentration-related IK blocking effects in patients; (2) an incremental dose-ranging study design aids in identifying the range of doses demonstrating electrophysiologic effects and efficacy; (3) a concomitant placebo group provides important data to assess reproducibility of results over time; and (4) further studies of dofetilide's efficacy and toxicity should be conducted.

Modulation of an inactivating human cardiac K+ channel by protein kinase C.

The transient outward current (ITO) is an important repolarizing component of the cardiac action potential. In native cardiac myocytes, ITO is modulated after activation of protein kinase C, although the molecular nature of this effect is not well understood. A channel recently cloned from human ventricular myocardium (Kv1.4, HK1) produces a rapidly inactivating K+ current, which has phenotypic similarities to the 4-aminopyridine-sensitive component of ITO. Therefore, we examined whether this recombinant channel was also modulated by protein kinase C activation by investigating the effects of the diacylglycerol analogue phorbol 12-myristate 13-acetate (PMA) on Kv1.4 K+ current expressed in Xenopus oocytes. At a concentration of 10 nmol/L, PMA caused a biphasic response with an initial increase (14 +/- 4%, mean +/- SEM) in current, which peaked in 14 minutes. This was followed by a significant reduction (40 +/- 11%) in the current within 30 minutes. There was no significant change in cell membrane electrical capacitance with 10 nmol/L PMA (1 +/- 1% decline in 30 minutes), demonstrating that loss of cell membrane surface area did not explain the reduction in K+ current, although cell capacitance did decrease when using a higher concentration of PMA (81 nmol/L). The inactive stereoisomer, 4 alpha-PMA, had no effect on Kv1.4 current, whereas preincubation with the protein kinase inhibitor staurosporine or protein kinase C-selective chelerythrine prevented the effects of PMA. When purified from a stably transfected mammalian cell line by using immunoprecipitation, the channel protein was readily phosphorylated in vitro by purified protein kinase C.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein kinase A phosphorylation alters Kvbeta1.3 subunit-mediated inactivation of the Kv1.5 potassium channel.

The human Kv1.5 potassium channel forms the IKur current in atrial myocytes and is functionally altered by coexpression with Kvbeta subunits. To explore the role of protein kinase A (PKA) phosphorylation in beta-subunit function, we examined the effect of PKA stimulation on Kv1.5 current following coexpression with either Kvbeta1.2 or Kvbeta1.3, both of which coassemble with Kv1.5 and induce fast inactivation. In Xenopus oocytes expressing Kv1.5 and Kvbeta1.3, activation of PKA reduced macroscopic inactivation with an increase in K+ current. Similar results were obtained using HEK 293 cells which lack endogenous K+ channel subunits. These effects did not occur when Kv1.5 was coexpressed with either Kvbeta1.2 or Kvbeta1.3 lacking the amino terminus, suggesting involvement of this region of Kvbeta1.3. Removal of a consensus PKA phosphorylation site on the Kvbeta1.3 NH2 terminus (serine 24), but not alternative sites in either Kvbeta1.3 or Kv1.5, resulted in loss of the functional effects of kinase activation. The effects of phosphorylation appeared to be electrostatic, as replacement of serine 24 with a negatively charged amino acid reduced beta-mediated inactivation, while substitution with a positively charged residue enhanced it. These results indicate that Kvbeta1.3-induced inactivation is reduced by PKA activation, and that phosphorylation of serine 24 in the subunit NH2 terminus is responsible.