A novel quantitative EEG injury measure of global cerebral ischemia.

OBJECTIVE: To develop a novel quantitative EEG (qEEG) based analysis method, cepstral distance (CD) and compare it to spectral distance (SD) in detecting EEG changes related to global ischemia in rats. METHODS: Adult Wistar rats were subjected to asphyxic-cardiac arrest for sham, 1, 3, 5 and 7 min (n=5 per group). The EEG signal was processed and fitted into an autoregressive (AR) model. A pre-injury baseline EEG was compared to selected data segments during asphyxia and recovery. The dissimilarities in the EEG segments were measured using CD and SD. A segment measured was considered abnormal when it exceeded 30% of baseline and its duration was used as the index of injury. A comprehensive Neurodeficit Score (NDS) at 24 h was used to assess outcome and was correlated with CD and SD measures. RESULTS: A higher correlation was found with CD and asphyxia time (r=0.81, P<0.001) compared to SD and asphyxia time (r=0.69, P<0.001). Correlation with cardiac arrest time (MAP<10 mmHg) showed that CD was superior (r=0.71, P<0.001) to SD (r=0.52, P=0.002). CD obtained during global ischemia and 90 min into recovery correlated significantly with NDS at 24 h after injury (Spearman coefficient=-0.83, P<0.005), and was more robust than the traditional SD (Spearman coefficient=-0.63, P<0.005). CONCLUSION: The novel qEEG-based injury index from CD was superior to SD in quantifying early cerebral dysfunction after cardiac arrest and in providing neurological prognosis at 24 h after global ischemia in adult rats. Studying early qEEG changes after asphyxic-cardiac arrest may provide new insights into the injury and recovery process, and present opportunities for therapy.     

Adaptive estimation of QRS complex wave features of ECG signal by the hermite model

The most characteristic wave set in ECG signals is the QRS complex. Automatic procedures to classify the QRS are very useful in the diagnosis of cardiac dysfunctions. Early detection and classification of QRS changes are important in realtime monitoring. ECG data compression is also important for storage and data transmission. An Adaptive Hermite Model Estimation System (AHMES) is presented for on-line beat-to-beat estimation of the features that describe the QRS complex with the Hermite model. The AHMES is based on the multiple-input adaptive linear combiner, using as inputs the succession of the QRS complexes and the Hermite functions, where a procedure has been incorporated to adaptively estimate a width related parameter b. The system allows an efficient real-time parameter extraction for classification and data compression. The performance of the AHMES is compared with that of direct feature estimation, studying the improvement in signal-to-noise ratio. In addition, the effect of misalignment at the QRS mark is shown to become a neglecting low-pass effect. The results allow the conditions in which the AHMES improves the direct estimate to be established. The application is shown, for subsequent classification, of the AHMES in extracting the QRS features of an ECG signal with the bigeminy phenomena. Another application is highlighted that helps wide ectopic beats detection using the width parameter b.     

Effects of defibrillation shock energy and timing on 3-D computer model of heart

We present computer simulations of electrical defibrillation in a three-dimensional model of the ventricles of the heart. In this model, calledHeartSim, the ventricles are represented by 1473 cubic elements with 3 mm sides. The action potential is described by five discrete states; absolutely refractory, three relatively refractory, and repolarized. Activation is propagated to an element's six orthogonal neighbors with the conduction velocity dependent on the refractory state of the neighbor. Delivery of several extra-stimuli with decrementing coupling intervals results in ventricular fibrillation. Following the onset of ventricular fibrillation, we simulate defibrillation using various electrode configurations, shock energies, and timings. The current density distributions in the heart model resulting from the defibrillation shocks are determined from finite element analysis of the electric fields produced by the delivery of high energy shocks. The simulations suggest that successful defibrillation shocks produce a short period of low activation followed by a complete cessation of activation for a duration of 387±162 ms. In contrast, unsuccessful shocks produce a significantly shorter period of low activation (70±12 ms) after which ventricular fibrillation resumes.HeartSim mimics the experimentally reported, highly variable response to near-threshold shocks — the energy for successful defibrillation varies widely (20.8±20.7 J). In addition, the success rate vs. energy curve has a sigmoidal shape that is consistent with experiments. We demonstrate that this variability in the energy requirement results from dynamic variability in the number of elements made refractory by the shock and the relative distribution of the activation pattern at the time of the shock. Further, we show that it may be possible to lower the defibrillation energy requirements by delivery of two successive low energy pulses. The most efficient timing for the second pulse corresponds to the repolarization of the elements that were excited by the first pulse. Thus, when the interval between the two pulses was 85±18 ms, the defibrillation threshold energy (DFE) is reduced by 30.7±10% with pulses of 10 ms duration, and 62.6±7.9% with pulses of 5 ms duration. Our simulations also show that there is a delicate balance of energy between the two pulses that must be reached in order to achieve energy reduction with double pulse defibrillation. In conclusion,HeartSim serves as a tool for studying the underlying mechanisms of the effects of DF shocks on ventricular arrhythmias, and assists in evaluation of improved strategies for shock delivery.     

Pseudodominant inheritance of spondylocostal dysostosis type 1 caused by two familial delta-like 3 mutations

Spondylocostal dysostoses (SCD) are a heterogeneous group of disorders of axial skeletal malformation characterized by multiple vertebral segmentation defects and rib anomalies. Sporadic cases with diverse phenotypes, sometimes including multiple organ abnormalities, are relatively common, and monogenic forms demonstrating autosomal recessive (AR) and, more rarely, autosomal dominant (AD) inheritance have been reported. We previously showed that mutations in delta-like 3 (DLL3), a somitogenesis gene that encodes a ligand for the notch signaling pathway, cause AR SCD with a consistent pattern of abnormal segmentation. We studied an SCD family previously reported to show AD inheritance, in which the phenotype is similar to that in AR cases. Direct DLL3 sequencing of individuals in two generations identified the affected father as homozygous for a novel frameshift mutation, 1440delG. His two affected children were compound heterozygotes for this mutation and a novel missense mutation, G504D, the first putative missense mutation reported in the transmembrane domain of DLL3. Their two unaffected siblings were heterozygotes for the 1440delG mutation. Pseudodominant inheritance has been confirmed, and the findings raise potential consequences for genetic counseling in relation to the SCD disorders.     

Early restitution of electrocorticogram predicts subsequent behavioral recovery from cardiac arrest.

Previous studies have shown that parameters of EEG restitution reflect the severity of global hypoxic-ischemic brain injury. Here, the hypothesis is tested that patterns of EEG restitution during the first 4 hours predict later behavioral recovery. Time course and correlations between behavior, electrocorticogram (EcoG), and neuronal injury were investigated in a rodent model of asphyctic cardiac arrest. Forty Wistar rats were subjected to 5 minutes of asphyxia and cardiopulmonary resuscitation. Behavior was assessed by repeated scoring of neurodeficits and open field activity until euthanasia at 48 hours. Electrocorticographic bursting occurred at 13.2 +/- 4 minutes after resuscitation. Bursts increased in frequency and duration until the EcoG reverted to a continuous signal. The resuscitation-continuous EcoG interval correlated with the first appearance of spontaneous movements (r = 0.80, P < 0.05). Larger intervals were associated with hyperactivity in the open field at 24 hours (r = 0.61, P < 0.05), indicating a more severe behavioral deficit. Larger intervals were also associated with worse 48-hour neurodeficit scores (P < 0.05). Neuronal damage in the hippocampus correlated with the degree of open field hyperactivity at 14 hours (P < 0.05). These findings demonstrate a close temporal and prognostic relationship between electrical and behavioral recovery after hypoxic-ischemic brain injury.     

Fetal in vivo continuous cardiovascular function during chronic hypoxia

AbstractAlthough the fetal cardiovascular defence to acute hypoxia and the physiology underlying it have been established for decades, how the fetal cardiovascular system responds to chronic hypoxia has been comparatively understudied. We designed and created isobaric hypoxic chambers able to maintain pregnant sheep for prolonged periods of gestation under controlled significant (10% O₂) hypoxia, yielding fetal mean P_aO2 levels (11.5 ± 0.6 mmHg) similar to those measured in human fetuses of hypoxic pregnancy. We also created a wireless data acquisition system able to record fetal blood flow signals in addition to fetal blood pressure and heart rate from free moving ewes as the hypoxic pregnancy is developing. We determined in vivo longitudinal changes in fetal cardiovascular function including parallel measurement of fetal carotid and femoral blood flow and oxygen and glucose delivery during the last third of gestation. The ratio of oxygen (from 2.7 ± 0.2 to 3.8 ± 0.8; P < 0.05) and of glucose (from 2.3 ± 0.1 to 3.3 ± 0.6; P < 0.05) delivery to the fetal carotid, relative to the fetal femoral circulation, increased during and shortly after the period of chronic hypoxia. In contrast, oxygen and glucose delivery remained unchanged from baseline in normoxic fetuses. Fetal plasma urate concentration increased significantly during chronic hypoxia but not during normoxia (Δ: 4.8 ± 1.6 vs. 0.5 ± 1.4 μmol l⁻¹, P<0.05). The data support the hypotheses tested and show persisting redistribution of substrate delivery away from peripheral and towards essential circulations in the chronically hypoxic fetus, associated with increases in xanthine oxidase‐derived reactive oxygen species.

Abbreviations

HIF

hypoxia‐inducible factor

IUGR

intrauterine growth restriction

NO

nitric oxide

•O₂⁻

superoxide anion

ROS

reactive oxygen species

XO

xanthine oxidase

     

Neurological recovery by EEG bursting after resuscitation from cardiac arrest in rats

INTRODUCTION: The return of neurological function during the early period after resuscitation from cardiac arrest (CA) has not been evaluated systematically. We report the temporal analysis of EEG bursting pattern during the very early periods after resuscitation. DESIGN/METHOD: A balanced group of good and poor outcome animals was selected from a population of rats subjected to either 5 or 7 min of asphyxial cardiac arrest (ACA) on the basis of a single criteria: 24 h neurobehavioral function based on the neurodeficit score (NDS). The EEGs of six consecutive good outcome rats (NDS > or = 60) and six consecutive poor outcome rats (NDS < 60) were selected for the study. The EEGs of these animals were given to two EEG examiners who were blinded to the selection process, the experimental conditions and the neurobehavioral recovery. The EEG bursting characteristics, such as rate, peak and duration of bursting were studied. RESULTS: There was significantly higher EEG bursting in the good outcome animals (P < 0.05) and the burst complexes evolved into continuous activity by 90 min. Lower frequency bursting that persisted and failed to evolve into continuous activity was observed in the poor outcome group. CONCLUSION: Increased EEG bursting during first 30-40 min after resuscitation from moderate to severe ACA was observed in rats with good neurological outcome at 24 h. Early EEG bursting patterns may provide additional prognostication after resuscitation from CA.     

Multiexposure laser speckle contrast imaging of the angiogenic microenvironment

We report the novel use of laser speckle contrast imaging (LSCI) at multiple exposure times (meLSCI) for enhanced in vivo imaging of the microvascular changes that accompany angiogenesis. LSCI is an optical imaging technique that can monitor blood vessels and the flow therein at a high spatial resolution without requiring the administration of an exogenous contrast agent. LSCI images are obtained under red (632 nm) laser illumination at seven exposure times (1-7 ms) and combined using a curve-fitting approach to obtain high-resolution meLSCI images of the rat brain vasculature. To evaluate enhancement in in vivo imaging performance, meLSCI images are statistically compared to individual LSCI images obtained at a single exposure time. We find that meLSCI reduced the observed variability in the LSCI-based blood-flow estimates by 30% and improved the contrast-to-noise ratio in regions with high microvessel density by 41%. The ability to better distinguish microvessels, makes meLSCI uniquely suited to longitudinal imaging of changes in the vascular microenvironment induced by pathological angiogenesis. We demonstrate this utility of meLSCI by sequentially monitoring, over days, the microvascular changes that accompany wound healing in a mouse ear model.     

Subcutaneous peripheral injection of cationized gelatin/DNA polyplexes as a platform for non-viral gene transfer to sensory neurons.

Selective modulation of sensory neuron gene expression could have numerous applications for the peripheral nervous system. Here, we report that subcutaneous peripheral injection of plasmid DNA complexed with a non-viral cationized gelatin (CG) vector led to transgene expression in rat lumbar dorsal root ganglia (DRGs). CG/DNA polyplexes appeared to undergo rapid retrograde transport through sciatic and spinal nerves, with reporter gene messenger RNA (mRNA) expression detectable in L4 and L5 DRGs within 60 hours. Maximum transgene expression was observed for polyplexes formed at 7.5:1 CG-to-DNA weight ratio under salt-free conditions, which generated 615 +/- 112 nm nanoparticles with zeta-potential of 9.4 +/- 0.19 mV. Six days after injection of the CG/DNA polypex, reporter gene protein immunofluorescence was observed in 1,164 +/- 176 DRG neurons, representing an estimated transfection rate of 47% of targeted neurons. Reporter gene expression was not detected in heart, lung, or liver tissues, suggesting a lack of systemic uptake. Measurements of tactile sensitivity indicate that CG/DNA injection did not cause behavioral toxicity. The injection platform was further used for plasmid-driven short hairpin RNA-mediated suppression of glyceraldehyde-3-phosphate dehydrogenase. This non-invasive gene delivery system could be used for the mechanistic study and targeted molecular evaluation of peripheral nervous system pathologies such as neuropathic pain.