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Short Episodes (short + episode)
Selected AbstractsProlonged Atrial Action Potential Durations and Polymorphic Atrial Tachyarrhythmias in Patients with Long QT SyndromeJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2003PAULUS KIRCHHOF M.D. Introduction: Prolongation of the QT interval and torsades de pointes tachycardias due to altered expression or function of repolarizing ion channels are the hallmark of congenital long QT syndrome (LQTS). The same ion channels also contribute to atrial repolarization, and familial atrial fibrillation may be associated with a mutated KVLQT1 gene. We therefore assessed atrial action potential characteristics and atrial arrhythmias in LQTS patients. Methods and Results: Monophasic action potentials (MAPs) were simultaneously recorded from the right atrial appendage and the inferolateral right atrium in 10 patients with LQTS (8 with identifiable genotype) and compared to 7 control patients. Atrial arrhythmias also were compared to MAPs recorded in patients with persistent (n = 10) and induced (n = 4) atrial fibrillation. Atrial action potential durations (APD) and effective refractory periods (ERP) were prolonged in LQTS patients at cycle lengths of 300 to 500 msec (APD prolongation 30,41 msec; ERP prolongation 26,52 msec; all P < 0.05). Short episodes of polymorphic atrial tachyarrhythmias (polyAT, duration 4,175 sec) occurred spontaneously or during pauses after pacing in 5 of 10 LQTS patients, but not in controls (P < 0.05). P waves showed undulating axis during polyAT. Cycle lengths of polyAT were longer than during persistent and induced atrial fibrillation. Afterdepolarizations preceded polyAT in 2 patients. The electrical restitution curve was shifted to longer APD in LQTS patients and to even longer APD in LQTS patients with polyAT. Conclusion: This group of LQTS patients has altered atrial electrophysiology: action potentials are prolonged, and polyAT occurs. PolyAT appears to be a specific arrhythmia of LQTS reminiscent of an atrial form of "torsades de pointes."(J Cardiovasc Electrophysiol, Vol. 14, pp ***-***, October 2003) [source] Short episodes of water stress increase barley root resistance to radial shrinkage in a dehydrating environmentPHYSIOLOGIA PLANTARUM, Issue 4 2006Jorge Hugo Lemcoff Although plant shoots can be ,hardened' by abiotic stresses, little is known about such changes in roots. In order to investigate possible induction of root-hardening in response to short water-stress episodes, barley seedlings (Hordeum vulgare L) hydroponically grown under a controlled environment were moderately water-stressed by addition of a non-penetrating osmoticum, polyethylene glycol (PEG) 6000 at ,0.4 MPa water potential, to the aerated nutrient solution. Seedlings were then hydrated in dilute nutrient solution without PEG before excision and assay of the seminal roots. Previous water stress treatments for 72 h, 12 h, or even 6 h induced an apparent root-hardening process. Thus, root radial shrinkage during subsequent exposure to strongly dehydrating conditions was remarkably decreased. The root hardening was related to biophysical adjustments: turgor-pressure increased while osmotic potential decreased from ,0.45 ± 0.02 MPa to ,0.60 ± 0.02 MPa. Moreover, the maximum bulk volumetric modulus of elasticity, ?max determined by pressure,volume analysis, increased from 2.1 ± 0.4 MPa to 3.7 ± 0.4 MPa, i.e. root elasticity was decreased. Root hardening in response to episodes of water stress may have ecological significance for barley plants in regions where intermittent drought episodes are frequent. [source] Effects of meconium aspiration in isolated perfused rat lungsPEDIATRIC PULMONOLOGY, Issue 4 2005Wlodzimierz M. Wisniewski MD Abstract Our objective was to study meconium-induced lung injury in isolated perfused rat lungs exposed to anoxia. Our working hypothesis was that meconium-induced lung injury is independent of preexisting hypoxia, and that hypoxia will increase severity of lung injury observed after meconium aspiration. We comparde five different groups of animals (n,=,5) for pulmonary arterial pressure (PAP), weight lung changes, and TNF, expression. Group I had lungs instilled with 4 ml of normal saline. Group II had lungs exposed to 5 min of anoxia. Group III had lungs instilled with 4 ml of 30% filtered human meconium. Group IV had lungs exposed to 5 min of anoxia and then instilled with 4 ml of 30% filtered human meconium. Group V had lungs instilled with 4 ml of 30% unfiltered human meconium. Our subjects were adult Sprague-Dawley rats. The isolated rat lung model was prepared according to Levey and Gast (J Appl Physiol 1966;21:313,316). Lungs were ventilated with room air. Anoxia was caused by the use of N2. The pulmonary artery was cannulated, and pulmonary arterial pressure and lung weight were measured. Lung weight and pulmonary arterial pressure were monitored for 120 min, and TNF, levels were measured in effluent at 15, 30, 60, and 120 min. Experiments were done at the Michael Reese Hospital (Chicago, IL). At the end of the experiment, PAP reached its highest values in group V (10.0,±,1.7 mmHg). Final PAPs in groups I,IV were: 4.85,±,0.3, 4.99,±,0.4, 5.93,±,0.3, and 7.25,±,0.51 mmHg, respectively). Lung wet weight increased significantly only in groups IV and V vs. group I; at 120 min, they were: 0.96,±,0.3 g, P,<,0.01, and 1.5 g,±,0.2 g, P,<,0.01, respectively. TNF, levels did not change significantly over time in group I. TNF, is a marker as well as proprietor of pulmonary inflammatory response. TNF, reached its highest levels in groups IV and V: 595 and 753 pg/ml at 120 min, respectively. In conclusion, a short episode of anoxia prior to meconium aspiration may increase lung sensitivity to meconium-induced lung injury. This effect may be moderated by the TNF, present in the pulmonary circulation. Pediatr Pulmonol. 2005; 39:368,373. © 2005 Wiley-Liss, Inc. [source] Regulation of retinal ganglion cell gene expression by bHLH transcription factors in the developing and ischemic retinasACTA OPHTHALMOLOGICA, Issue 2009JM MATTER Purpose The loss of retinal ganglion cells (RGC) in the glaucomatous retina exhibits similarities to the pattern of neuronal degeneration detected after experimental ischemia. However, a short episode of retinal ischemia does not provoke damage but rather triggers an endogenous form of neuroprotection. HIFs are bHLH proteins that regulate hypoxic response in ischemic retinas and they are involved in neuroprotection. Hypoxic environments also occur in the developing embryo and create specific niches controlling cell differentiation. Genetic analyses of HIF functions have revealed the importance of oxygen as a key regulator of ontogeny. We have compared the transcriptomes of RGCs in ischemic versus developing retinas. Methods Genome-wide screens were conducted to identify genes which are expressed in newborn RGCs and growing optic nerve axons and which are up- or down-regulated after venal occlusion by photodynamic thrombosis in the rat retinas. Results Atoh7 is a bHLH protein which is central to the transcriptional network regulating the production of RGCs. Among the targets of Atoh7 there are genes involved in the general metabolism and energy supply , e.g., alpha-enolase (ENO1), glucose-6 -phosphate isomerase (GPI). These glycolytic enzymes are also targets of HIFs and they are upregulated during hypoxia. To investigate the linkage of glycolysis and mitochondrial activity in RGCs, we monitored by confocal time-lapse imaging the dynamic distribution of mitochondria in the cell bodies and axons of RGCs that express HIF/Atoh7 targets in developing and ischemic retinas. Conclusion Some gene expression programs involved in differentiating RGCs might be reinitiated in neuroprotection. [source] Dynamic changes in the direction of the theta rhythmic drive between supramammillary nucleus and the septohippocampal systemHIPPOCAMPUS, Issue 6 2006Bernat Kocsis Abstract Neurons in the supramammillary nucleus (SUM) of urethane-anesthetized rats fire rhythmically in synchrony with hippocampal theta rhythm. As these neurons project to the septum and hippocampus, it is generally assumed that their role is to mediate ascending activation, leading to the hippocampal theta rhythm. However, the connections between SUM and the septohippocampal system are reciprocal; there is strong evidence that theta remains in the hippocampus after SUM lesions and in the SUM after lesioning the medial septum. The present study examines the dynamics of coupling between rhythmic discharge in the SUM and hippocampal field potential oscillations, using the directionality information carried by the two signals. Using directed transfer function analysis, we demonstrate that during sensory-elicited theta rhythm and also during short episodes of theta acceleration of spontaneous oscillations, the spike train of a subpopulation of SUM neurons contains information predicting future variations in rhythmic field potentials in the hippocampus. In contrast, during slow spontaneous theta rhythm, it is the SUM spike signal that can be predicted from the preceding segment of the electrical signal recorded in the hippocampus. These findings indicate that, in the anesthetized rat, SUM neurons effectively drive theta oscillations in the hippocampus during epochs of sensory-elicited theta rhythm and short episodes of theta acceleration, whereas spontaneous slow theta in the SUM is controlled by descending input from the septohippocampal system. Thus, in certain states, rhythmically firing SUM neurons function to accelerate the septal theta oscillator, and in others, they are entrained by a superordinate oscillatory network. © 2006 Wiley-Liss Inc. [source] Culturally diverse patient,nurse interactions on acute care wardsINTERNATIONAL JOURNAL OF NURSING PRACTICE, Issue 6 2006Jane Cioffi RN PhD The nurse,patient interaction is central to providing nursing care. This qualitative study explores nurses' and culturally diverse patients' experiences within nurse,patient relationships in acute care wards. Eight nurses and their respective patients volunteered to join the study and were interviewed. The three themes identified in relationships between nurses and culturally diverse patients were shared tension, perceived difference and held awareness. It is concluded from the study that relationships between nurses and culturally diverse patients in acute care wards during short episodes of hospitalization are not easy for nurses and need to receive deeper consideration as to how they can be developed more effectively. It is recommended that educational support be provided to develop more effective interactions between nurses and patients with research being carried out to investigate factors that can strengthen culturally diverse patient,nurse interactions in acute care settings. [source] | |||||||||||||