Development and usage of eXtension's HorseQuest: an online resource.

eXtension (pronounced e-extension) is an online resource transforming how faculty can collaborate and deliver equine education. As the first Community of Practice launched from eXtension, HorseQuest (HQ) offers free, interactive, peer-reviewed, online resources on a variety of equine-related topics at http://www.extension.org. This group has adapted traditional educational content to the online environment to maximize search engine optimization, to be more discoverable and relevant in the online world. This means that HQ resources are consistently being found on the first page of search results. Also, by researching key words searched by Internet users, HQ has guided new content direction and determined potential webcast topics based on relevance and frequency of those searches. In addition to establishing good search engine optimization, HQ has been utilizing the viral networking aspect of YouTube by uploading clips of existing equine educational videos to YouTube. HorseQuest content appears in mainstream media, is passed on by the user, and helps HQ effectively reach their community of interest (horse enthusiasts). HorseQuest partners with My Horse University to produce webcasts that combine concise knowledge exchange via a scripted presentation with viewer chat and incoming questions. HorseQuest has produced and published content including 12 learning modules, 8 webchats, 21 webcasts, and 572 videos segments. After the official public launch, there was a steady increase in average number of visits/mo and average page views/mo over the 26-mo period. These regressions show a statistically significant increase in visits (P < 0.001) of approximately 450 visits per month and a significant increase in page views (P = 0.004) of about 373 page views per month. HorseQuest is a resource for several state 4-H advancement and competition programs and will continue to be incorporated into traditional extension programs, while reaching and affecting global audiences.

Multidimensional rhythm disturbances as a precursor of sustained ventricular tachyarrhythmias.

Cardiac cycle dynamics reflect underlying physiological changes that could predict imminent arrhythmias but are obscured by high complexity, nonstationarity, and large interindividual differences. To overcome these problems, we developed an adaptive technique, referred to as the modified Karhunen-Loeve transform (MKLT), that identifies an individual characteristic ("core") pattern of cardiac cycles and then tracks the changes in the pattern by projecting the signal onto characteristic eigenvectors. We hypothesized that disturbances in the core pattern, indicating progressive destabilization of cardiac rhythm, would predict the onset of spontaneous sustained ventricular tachyarrhythmias (VTAs) better than previously reported methods. We analyzed serial ambulatory ECGs recorded in 57 patients at the time of VTA and non-VTA 24-hour periods. The disturbances in the pattern were found in 82% of the recordings before the onset of impending VTA, and their dimensionality, defined as the number of unstable orthogonal projections, increased gradually several hours before the onset. MKLT provided greater sensitivity and specificity (70% and 93%) compared with the best traditional method (68% and 67%, respectively). We present a theoretical analysis of MKLT and describe the effects of ectopy and slow changes in cardiac cycles on the disturbances in the pattern. We conclude that MKLT provides greater predictive accuracy than previously reported methods. The improvement is due to the use of individual patterns as a reference for tracking the changes. Because this approach is independent of the group reference values or the underlying clinical context, it should have substantial potential for predicting other forms of arrhythmic events in other populations.

Inhibition of human cytomegalovirus replication in a human retinal epithelial cell model by antisense oligonucleotides.

PURPOSE: The antiviral activity of first and second generation antisense oligonucleotides on human cytomegalovirus (CMV) replication was evaluated in two cell systems, the traditional system on human fibroblasts and on human retinal pigment epithelial (HRPE) cell culture system. METHODS: To evaluate CMV replication strategies within the retina, an HRPE cell system permissive to CMV replication was developed. In this study, the antiviral activity of the antisense oligonucleotides, ISIS 2922 (Vitraven) and ISIS 13312, was evaluated in the traditional fibroblast antiviral assay and in the HRPE cell system. Antiviral activity was measured by evaluating inhibition of virus induced cytopathic effect, virus plaque formation, and virus gene expression. RESULTS: Both oligonucleotides produced concentration-dependent inhibition of CMV cytopathic effect and CMV plaque formation in both human RPE cells and a human fibroblast cell line, MRC-5. The oligonucleotide, ISIS 2922, demonstrated a mean 50% inhibitory concentration (IC(50)) of 0.04 and 0.24 microM in HRPE and MRC-5 cells, respectively. The second-generation oligonucleotide, ISIS 13312, yielded similar results with IC(50) levels of 0.05 and 0.3 microM in HRPE and MRC-5 cells, respectively. Similar findings were obtained with a CMV clinical isolate. In addition, initiation of effective oligonucleotide treatment could be introduced 6 days after CMV infection in HRPE cells, whereas, in the fibroblast cell line, oligonucleotide treatment was only effective up to 3 days after infection. Semiquantitative RT-PCR analysis demonstrated significant inhibition of CMV intermediate early and late mRNAs by both oligonucleotides. CONCLUSIONS: These studies demonstrate that HRPE cells were significantly more sensitive than fibroblasts to the antiviral actions of ISIS 2922 and ISIS 13312. Moreover, the data indicate that the anti-CMV potency of the two oligonucleotides was similar. The enhanced potency of these oligonucleotides in HRPE cells may be associated with a delay in viral gene transcription and slow viral replication and spread in these cells.

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification.

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.

Child sexual abuse and bulimic symptomatology: relevance of specific abuse variables.

OBJECTIVE: This study examined specific aspects of child sexual abuse in relation to symptom severity among hospitalized patients diagnosed with bulimia nervosa. METHOD: Participants were 45 hospitalized bulimic women who reported a history of child sexual abuse. Structured interviews were conducted in order to obtain detailed information regarding specific features of the abusive event(s). Participants also completed instruments that measured depression and eating pathology. RESULTS: There were no significant differences in severity of depression or eating disturbance among women reporting differing abusive experiences including intrafamilial versus extrafamilial abuse, abuse with or without the use of physical force, one versus multiple incidents, early abuse versus abuse occurring after age 14, contact versus noncontact abuse, disclosed versus undisclosed, and combined physical/sexual abuse versus sexual abuse alone. CONCLUSION: The specific characteristics of child sexual abuse are not related to the level of symptomatology for hospitalized bulimic patients. This study suggests that differences in the nature of the abuse may not be as important as the fact that the abuse occurred in the first place.

Enhancing the precision of ECG baseline correction: selective filtering and removal of residual error.

Reemergence of the problem of baseline correction is related to recent advancements in the electrocardiographic (ECG) analysis of beat-to-beat repolarization changes which play an important role in risk assessment and the prediction of sudden cardiac death. These alterations often have an amplitude of a few microvolts and duration of several milliseconds and their detection requires special accuracy of baseline estimation. Using detailed analysis of various types of residual errors we designed a two-step procedure for selective filtering of ECG and removal of residual error with minimal distortion of cardiac complexes and tested this approach on 100 simulated and 210 real ECG signals. Application of this procedure provided a twofold reduction in the error of baseline estimation and T-wave amplitude measurements compared to high-pass filtering. Selective application of this approach to the segments with low baseline drift allowed analysis of low-amplitude, beat-to-beat changes in repolarization during more than 70% of the recording time.

Defibrillators in nonischemic cardiomyopathy treatment evaluation.

The Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) is a multicenter randomized trial. Patients will have nonischemic cardiomyopathy (LVEF < or = 35%), a history of symptomatic heart failure and spontaneous arrhythmia (> 10 PVCs/hour or nonsustained ventricular tachycardia defined as 3-15 beats at a rate of > 120 beats/min) on Holter monitor or telemetry within the past 6 months. Patients will be randomized to an implantable cardioverter defibrillator (ICD) versus no ICD. All patients will receive standard oral medical therapy for heart failure including angiotensin converting enzyme inhibitors and beta-blockers (if tolerated). Patients will be followed for 2-3 years. The primary endpoint will be total mortality. Quality-of-life and pharmacoeconomics analyses will also be performed. A registry will track patients who meet basic inclusion criteria but are not randomized. We estimate an annual total mortality of 15% at 2 years in the treatment arm that does not receive an ICD. The ICD is expected to reduce mortality by 50%. Approximately 204 patients will be required in each treatment group. Twenty-five centers will be included in a trial designed to last an estimated 4 years.

The GATA-E box-GATA motif in the EKLF promoter is required for in vivo expression.

The erythroid Krüppel-like factor (EKLF) is a key regulatory protein in globin gene expression. This zinc finger transcription factor is required for expression of the adult beta globin gene, and it has been suggested that it plays an important role in the developmental switch from fetal gamma to adult beta globin gene expression. We have previously described a sequence element in the distal promoter region of the mouse EKLF gene that is critical for the expression of this transcription factor. The element consists of an E box motif flanked by 2 GATA-1 binding sites. Here we demonstrate that mutation of the E box or the GATA-1 consensus sequences eliminates expression from the EKLF promoter in transgenic mice. These results confirm the importance of this activator element for in vivo expression of the EKLF gene. (Blood. 2000;95:1652-1655)

Dynamics of low-frequency R-R interval oscillations preceding spontaneous ventricular tachycardia.

BACKGROUND: Increased sympathetic activity is believed to be an important trigger of sustained ventricular tachyarrhythmias (VT) and is believed to be responsible for the increased heart rate that we and others have reported before the onset of spontaneous VT. However, in the patients reported herein, heart rate variability (HRV) indexes that reflect sympathetic activity unexpectedly declined, whereas heart rate increased. To explain this apparent paradoxic behavior, we tested the hypothesis that baseline levels of HRV determine its reaction to short-term autonomic perturbations before the onset of VT. METHODS AND RESULTS: Holter electrocardiograms from 47 patients (ejection fraction 36% +/- 15%) with recorded VT were analyzed. Frequency domain HRV indexes (low-frequency power [LFP] 0. 04 to 0.15 Hz, high-frequency power [HFP] 0.15 to 0.4 Hz, and total power [TP] 0.01 to 0.4 Hz) were studied in 5-minute intervals and over a period of 24 hours. Patients were divided into those with a decrease in LFP in the 2-hour period before VT (group A, n = 32) and those with an increase or no change (group B, n = 15). The data were logarithmically transformed. Heart rate increased 15 minutes before the onset of VT compared with the 24-hour mean in both groups (group A: 80.3 +/- 15.4 to 86.1 +/- 20.0 beats/min, P =.005; group B: 80.6 +/- 13.5 to 86.7 +/- 14.0 beats/min, P =.017). Group A had higher TP, LFP, and LFP/HFP 2 hours before VT, and these variables decreased 15 minutes before the onset of VT (TP from 7.31 +/- 1.28 to 6.88 +/- 1.35, LFP from 6.09 +/- 1.28 to 5.38 +/- 1.33, LFP/HFP from 1.33 +/- 0.89 to 0.96 +/- 0.80, P <.001 for all 3 variables). HFP also decreased 15 minutes before VT compared with 2 hours (from 4.78 +/- 1.05 to 4.49 +/- 1.24, P =.028). In group B, which had lower baseline TP, LFP, and LFP/HFP at 2 hours before VT, these variables increased 15 minutes before the event (TP from 6.41 +/- 1.41 to 6.86 +/- 1.42, P =.004; LFP from 4.59 +/- 1.51 to 4.95 +/- 0.62, P <.001; LFP/HFP from 0.22 +/- 1.22 to 0.52 +/- 1.38, P =.10), whereas HFP did not change significantly (4.40 +/- 0.94 and 4.53 +/- 1.01, P =. 50). CONCLUSIONS: An increase in heart rate and a drop in the low-frequency oscillations of R-R intervals before the onset of VT occurred in patients with higher baseline level of oscillatory activity. These changes suggest a dissociation between the average and rhythmic modulation of R-R intervals. A decline of the low-frequency oscillations in the setting of increasing heart rate could reflect an abnormal response to increased sympathetic activity in most of the patients from the studied group. The different behaviors of the HRV indexes before the onset of VT in the 2 groups suggest that change in the dynamics of R-R intervals, rather than the direction of change, facilitates arrhythmogenesis.

Characterization of the lung Krüppel-like transcription factor gene and upstream regulatory elements.

We previously described the isolation and characterization of the cDNA for lung Krüppel-like factor (LKLF), a zinc finger transcription factor that is predominately expressed in the lung of adult mice. In this study, we report the complete structure and nucleotide sequence of the mouse LKLF gene, which is comprised of three exons and two small introns. Moreover, the identification of critical sequence elements required for expression is described using reporter constructs with the LKLF promoter transfected into LA-4 lung cells. Results from these constructs reveal an important region for transcriptional activity that lies between the -490/-72bp upstream sequence. This region contains two canonical Sp1 binding sites that affect expression levels in a non tissue-specific manner. In addition, using a base-pair mutagenesis strategy, a region from -157/-72bp was found to be necessary for upregulating expression. In transfection assays, mutations of the -138/-111bp region resulted in approximately 70-80% loss of promoter activity. This cis-element does not appear to correspond to any known transcription factor consensus sequence. Moreover, mutations within this cis-region disrupt the binding of a protein complex from nuclear extracts of various tissues.

Distinctive RR dynamics preceding two modes of onset of spontaneous sustained ventricular tachycardia. (ESVEM) Investigators. Electrophysiologic Study Versus Electrocardiographic Monitoring.

INTRODUCTION: We hypothesized that autonomic activity preceding spontaneous sustained monomorphic ventricular tachycardia (VTsm) as assessed by heart rate (HR) and RR interval variability (RRV) differs between type 1 VTsm which is initiated by morphologically distinct, early cycle, possibly triggering premature ventricular complexes (PVCs) and type 2 VTsm in which the initial complex has a QRS waveform identical to subsequent complexes. METHODS AND RESULTS: Baseline Holter tapes (1,646) from a clinical trial were scanned for VTsm. QRS complexes of VTsm were compared by two-lead cross-correlation to distinguish type 1 and type 2 VTsm. Frequency domain RRV index were estimated over 5 minutes, 15 minutes, and 24 hours. Type 1 and type 2 VTsm were present in 15 (group 1) and 33 (group 2) of 48 patients, respectively. HR did not change in group 1 (88.4+/-15.2 to 89.7+/-13.0 beats/min, P = 0.89), but increased before the onset of VTsm in group 2 (74.3+/-16.3 to 81.2+/-18.0 beats/min, P < 0.001). RRV index were severely depressed in both groups. No RRV index changed significantly before the onset of type 1 VTsm, whereas significant changes occurred before type 2 VTsm from 24-hour average to 30 minutes before VTsm in very low (very low-frequency power [VLFP]: 6.62+/-1.53 to 6.20+/-2.07 ln msec2, P = 0.036), low (low-frequency power [LFP]: 5.61+/-1.43 to 5.28+/-1.59 ln msec2, P = 0.004), normalized low (normalized low-frequency power [LFPn]: -0.48+/-0.58 to -0.55+/-0.64 normalized units [nu], P = 0.05) and the ratio of LFP to high-frequency power (HFP) (LFP/HFP: 4.20+/-3.47 to 3.45+/-2.53, P = 0.017). Declines in RRV index between 2 hours to the 30-minute period before VTsm occurred in group 2 but not group 1 in LFP (5.85 +/- 1.42 to 5.28 +/- 1.59 In msec, P = 0.043) and HFP (4.94 +/- 5.14 to 3.46 +/- 2.52 In msec2, P = 0.008), with a downward trend in LFP/HFP (4.94+/-5.14 to 3.45+/-2.53, P = 0.127) and LFPn (-0.38+/-0.36 to -0.55+/-0.64, P = 0.15), while HFPn tended to rise (-1.47+/-0.65 to -1.27+/-0.64, P = 0.15). CONCLUSIONS: HR and RRV did not change before type 1 VTsm, suggesting that short-term changes in autonomic activity were not essential to initiation of apparent PVC-triggered VTsm. In contrast, RR interval dynamics before type 2 VTsm suggested that short-term changes in neurohormonal activity contributed to arrhythmia initiation. Heterogeneities in arrhythmia onset may reflect distinct triggers and substrate properties that could provide a basis for effective therapeutic targets.

Inhibition of translation of hepatitis C virus RNA by 2-modified antisense oligonucleotides.

Inhibition of hepatitis C virus (HCV) gene expression by antisense oligonucleotides was investigated using both a rabbit reticulocyte lysate in vitro translation assay and a transformed human hepatocyte cell expression assay. Screening of overlapping oligonucleotides complementary to the HCV 5' noncoding region and the core open reading frame (ORF) identified a region susceptible to translation inhibition between nucleotides 335 and 379. Comparison of 2'-deoxy-, 2'-O-methyl-, 2'-O-methoxyethyl-, 2'-O-propyl-, and 2'-fluoro-modified phosphodiester oligoribonucleotides demonstrated that increased translation inhibition correlated with both increased binding affinity and nuclease stability. In cell culture assays, 2'-O-methoxyethyl-modified oligonucleotides inhibited HCV core protein synthesis with comparable potency to phosphorothioate oligodeoxynucleotides. Inhibition of HCV core protein expression by 2'-modified oligonucleotides occurred by an RNase H-independent translational arrest mechanism.

A gene encoding an intestinal-enriched member of the Krüppel-like factor family expressed in intestinal epithelial cells.

The Krüppel-like factors make up a multigene family of transcription factors that have discrete patterns of expression, implying they play important biological roles in the tissues in which they are expressed. We have identified and characterized the cDNA for a novel murine transcription factor that is an additional member of the Krüppel-like family of transcription factors, named intestinal-enriched Krüppel-like factor (IKLF). This gene appears to be a homolog of the human BTEB-2 gene, although it exhibits a different pattern of tissue expression and the translated product is larger. IKLF is expressed in a limited number of tissues; the highest levels of IKLF expression are found in the digestive tract. IKLF shows temporal changes in expression during embryogenesis indicating that this gene is developmentally regulated. In addition, IKLF expression is limited to the epithelial lining of the intestine and is localized primarily to the base of the crypts in the adult intestine. The IKLF cDNA encodes for a 446 amino acid protein and is able to transactivate by binding specific DNA elements that are also recognized by other members of the Krüppel-like family. In addition, mutations in the activation domain attenuate the ability of this protein to function as a transcription factor. Collectively, these findings show that we have identified a transcription factor that is expressed predominantly in the epithelial crypt cells of the gastrointestinal tract and is a member of the Krüppel-like family of transcription factors.

Antisense oligonucleotide inhibition of hepatitis C virus (HCV) gene expression in livers of mice infected with an HCV-vaccinia virus recombinant.

Hepatitis C virus (HCV) is the major cause of non-A, non-B hepatitis worldwide. Current treatments are not curative for most infected individuals, and there is an urgent need for both novel therapeutic agents and small-animal models which can be used to evaluate candidate drugs. A small-animal model of HCV gene expression was developed with recombinant vaccinia virus vectors. VHCV-IRES (internal ribosome entry site) is a recombinant vaccinia viral vector containing the HCV 5' nontranslated region (5'-NTR) and a portion of the HCV core coding region fused to the firefly luciferase gene. Intraperitoneal injection of VHCV-IRES produced high levels of luciferase activity in the livers of BALB/c mice. Antisense oligonucleotides complementary to the HCV 5'-NTR and translation initiation codon regions were then evaluated for their effects on the expression of these target HCV sequences in BALB/c mice infected with the vaccinia virus vector. Treatment of VHCV-IRES-infected mice with 20-base phosphorothioate oligonucleotides complementary to the sequence surrounding the HCV initiation codon (nucleotides 330 to 349) specifically reduced luciferase expression in the livers in a dose-dependent manner. Inhibition of HCV reporter gene expression in this small-animal model suggests that antisense oligonucleotides may provide a novel therapy for treatment of chronic HCV infection.

Changes in autonomic activity and ventricular repolarization.

An increase in sympathetic activity, manifested by shortening of RR intervals (RRi) and changes in RRi variability, precedes and possibly triggers ventricular tachyarrhythmias (VTAs) by altering repolarization. We examined the effects of autonomic activity on the projection of repolarization as detected by body surface potential maps (BSPMs). We recorded 32 lead/192-point BSPMs during passive head-up tilt, tilt + infusion of isoproterenol, rapid atrial pacing, and atrial pacing + infusion of isoproterenol. Changes in QT; recovery time; activation-recovery interval (ARi); T-wave amplitude; and QT, QRST, and ST integrals and their dispersion were analyzed. Autonomic effects on sinus node were inferred from the Fourier transform-derived low and high frequency powers of RRi variability. Patients were divided into those with (SHD) and without structural heart disease (NSHD). Heart rate increased, whereas QT interval and ARi declined with tilt in both groups. RRi variability indices of sympathetic activity increased in NSHD but did not change in SHD. T-wave amplitudes declined in NSHD but did not change in SHD, suggesting altered responsiveness of ventricular repolarization to autonomic stimulation. Tilt and rapid atrial pacing during infusion of isoproterenol resulted in a paradoxical increase in T-wave amplitudes in some patients, similar to that observed before the onset of spontaneous arrhythmias. We conclude that altering autonomic activity by head-up tilt and/or infusion of sympathomimetic agents results in significant changes in the body surface projection of cardiac repolarization, which differ in patients with SHD from those without SHD. Similar paradoxical changes in the T-wave amplitude have been observed before the onset of spontaneous VTA, suggesting that abnormal response of repolarization to autonomic stimulation predisposes to arrhythmogenesis.

Autonomic nervous system activity and the spontaneous initiation of ventricular tachycardia. ESVEM Investigators. Electrophysiologic Study Versus Electrocardiographic Monitoring Trial.

OBJECTIVES: We hypothesized that neurohormonal activity contributes to the initiation of sustained ventricular tachycardia (VT) as reflected in indices of heart rate variability (HRV). BACKGROUND: Autonomic nervous system activity participates in experimental arrhythmias but clinical studies have been inconsistent. METHODS: Holter electrocardiograms from 53 patients with VT were analyzed. Heart rate variability indices were determined over 5 and 15 min and 24 h and examined for changes before the onset of VT. Heart rate variability indices in the frequency domain included ultra low frequency power (FP) (ULFP): 0-0.0033 Hz; very low FP (VLFP): 0.0033-0.04 Hz; low FP (LFP): 0.04-0.15 Hz; high FP (HFP): 0.15-0.4 Hz; total power (TP); normalized LFP (LFPn); normalized HFP (HFPn), and the ratio: LFP/HFP. RESULTS: Heart rate variability indices were severely diminished: TP: 12,009+/-11,076 ms2; ULFP: 10,087+/-9,565 ms2; VLFP: 1,416+/-1,571 ms2; LFP: 544+/-620 ms2; HFP: 161+/-176 ms2, and LFP/HFP: 3.68+/-2.83. Heart rate increased before VT (80.4+/-17.3 to 85.3+/-17.4 bpm, p < 0.001). Several HRV variables declined 30 min before VT compared to 24-h values (VLFP: -5.89+/-17.81%, p = 0.031; LFP: -5.23+/-14.3%, p = 0.003; HFP: -4.35+/-13.7%, p = 0.04). LFPn and the LFP/HFP ratio decreased significantly before the onset of VT (-17.7+/-46.9%, p = 0.035 and -8.24+/-38.8%, p = 0.037, respectively), whereas HFPn increased slightly (4.29+/-29.9%, p = 0.097). CONCLUSIONS: Heart rate rose, whereas LFP, LFPn and LFP/HFP fell before the onset of VT. This pattern of changes could be explained by a rise in sympathetic activity and saturation of the HRV signal resulting in dissociation of the average and rhythmical effects of sympathetic activity. These findings suggest that alterations in autonomic activity contributed to arrhythmogenesis in this group of patients.

Multiple proteins binding to a GATA-E box-GATA motif regulate the erythroid Krüppel-like factor (EKLF) gene.

Erythroid Krüppel-like factor (EKLF) is a zinc finger transcription factor required for beta-globin gene expression and is implicated as one of the key factors necessary for the fetal to adult switch in globin gene expression. In an effort to identify factors involved in the expression of this important erythroid-specific regulatory protein, we have isolated the mouse EKLF gene and systematically analyzed the promoter region. Initially, a reporter construct with 1150 base pairs of the EKLF 5'-region was introduced into transgenic mice and shown to direct erythroid-specific expression. We continued the expression studies in erythroid cells and have identified a sequence element consisting of two GATA sites flanking an E box motif. The three sites act in concert to elevate the transcriptional activity of the EKLF promoter. Each site is essential for EKLF expression indicating that the three binding sites do not work additively, but rather function as a unit. We further show that GATA-1 binds to the two GATA sites and present evidence for binding of another factor from erythroid cell nuclear extracts to the E box motif. These results are consistent with the formation of a quaternary complex composed of an E box dimer and two GATA-1 proteins binding at a combined GATA-E box-GATA activator element in the distal EKLF promoter.