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Initiation
Kinds of Initiation Terms modified by Initiation Selected AbstractsEARLY INITIATION OF PHOSPHATE LOWERING DIETARY THERAPY IN NON-DIALYSIS CHRONIC KIDNEY DISEASE: A CRITICAL REVIEWJOURNAL OF RENAL CARE, Issue 2009M.K. Sigrist SUMMARY Dietary management of hyperphosphatemia and hyperparathyroidism have long been important elements in the clinical management of CKD stage 4 and 5 for the prevention of mineral bone disease. The rationale for phosphate lowering has been further justified, given the accumulating data to support the association of phosphate with vascular damage, in this population who are at high risk of cardiovascular (CV) death. Phosphate is a novel CV risk factor in both CKD and in the general population, and a growing body of literature suggests that high normal serum phosphate may be a risk factor for progression of CKD. Few studies have examined hard outcomes after phosphate lowering. Nonetheless, given the balance of data both in cell, animal and human studies, the use of phosphate lowering strategies at earlier stages of CKD, perhaps even prior to serum phosphate level rising, may well be justified. This review will discuss the complications associated with higher serum phosphate, the potential benefits of early phosphate intervention, practical considerations of low phosphate diets and novel strategies for evaluating these strategies in clinical practice. [source] LANDSLIDE INITIATION, RUNOUT, AND DEPOSITION WITHIN CLEARCUTS AND OLD-GROWTH FORESTS OF ALASKA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2000A. C. Johnson ABSTRACT: More than 300 landslides and debris flows were triggered by an October 1993 storm on Prince of Wales Island, southeast Alaska. Initiation, runout, and deposition patterns of landslides that occurred within clearcuts, second-growth, and old-growth forests were examined. Blowdown and snags, associated with cedar decline and "normal" rates of mortality, were found adjacent to at least 75 percent of all failures regardless of land use. Nearly 50 percent of the landslides within clearcuts occurred within one year following timber harvest; more than 70 percent of these sites had hydrophytic vegetation directly above failures. In following the runout paths of failures, significantly more erosion per unit area occurred within clearcuts than in old-growth forests on slopes with gradients from 9 to 28* (16 to 54 percent). Runout length, controlled by hillslope position within deglaciated valleys, was typically longer in old-growth forests than in second growth and clearcuts (median values were 334, 201, and 153 m, respectively). Most landslides and debris flows deposited in first-and second-order channels before reaching the main stem channels used by anadromous fish. Slide deposits in old-growth forests were composed of a higher proportion of woody debris than deposits derived from slides in second growth or clearcuts. [source] CD40-CD40L COSTIMULATION IS REQUISITE FOR BOTH THE INITIATION OF IMMUNE RESPONSES AND FOR EFFECTOR RESPONSES IN CRESCENTIC GLOMERULONEPHRITIS (GN)NEPHROLOGY, Issue 1 2002A-J Ruth [source] Recurrent Exacerbations of Protein-losing Enteropathy after Initiation of Growth Hormone Therapy in a Fontan Patient Controlled with SpironolactoneCONGENITAL HEART DISEASE, Issue 2 2010Michael J. Grattan MSc ABSTRACT Protein-losing enteropathy (PLE) is a rare, but serious complication in single ventricle patients after Fontan palliation, and is associated with a 5-year mortality of 46%. We describe a patient with PLE after Fontan palliation who achieved remission with high-dose spironolactone (an aldosterone antagonist), but had three exacerbations each temporally correlated with the use of growth hormone (an aldosterone agonist). Because of the opposing mechanisms of action of these two medications, caution might be indicated when using growth hormone for patients with PLE who are successfully treated with spironolactone. [source] Initiation of limb regeneration: The critical steps for regenerative capacityDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2008Hitoshi Yokoyama While urodele amphibians (newts and salamanders) can regenerate limbs as adults, other tetrapods (reptiles, birds and mammals) cannot and just undergo wound healing. In adult mammals such as mice and humans, the wound heals and a scar is formed after injury, while wound healing is completed without scarring in an embryonic mouse. Completion of regeneration and wound healing takes a long time in regenerative and non-regenerative limbs, respectively. However, it is the early steps that are critical for determining the extent of regenerative response after limb amputation, ranging from wound healing with scar formation, scar-free wound healing, hypomorphic limb regeneration to complete limb regeneration. In addition to the accumulation of information on gene expression during limb regeneration, functional analysis of signaling molecules has recently shown important roles of fibroblast growth factor (FGF), Wnt/,-catenin and bone morphogenic protein (BMP)/Msx signaling. Here, the routine steps of wound healing/limb regeneration and signaling molecules specifically involved in limb regeneration are summarized. Regeneration of embryonic mouse digit tips and anuran amphibian (Xenopus) limbs shows intermediate regenerative responses between the two extremes, those of adult mammals (least regenerative) and urodele amphibians (more regenerative), providing a range of models to study the various abilities of limbs to regenerate. [source] Early adolescents show enhanced acute cocaine-induced locomotor activity in comparison to late adolescent and adult ratsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2008Kimberly A. Badanich Abstract Initiation of drug use during adolescence is associated with an increased probability to develop a drug addiction. The present study examined dose,response effects of cocaine (0, 5, 10, or 20 mg/kg, i.p.) on locomotor activity in early adolescent (postnatal day (PND) 35), late adolescent (PND 45), and young adults (PND 60) by measuring total distance moved (TDM) and frequency of start,stops. In response to 20 mg/kg cocaine, early adolescents showed the greatest cocaine-induced increase in TDM in comparison to late adolescent and adult rats. At this same dose, early adolescents showed the greatest cocaine-induced attenuation of start,stops relative to older rats. Results suggest that early adolescents engage in more cocaine-induced locomotor activity and less stationary behavior indicating that early adolescents are more sensitive to locomotor activating effects of high dose cocaine than older rats. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 127,133, 2008. [source] Heroin users in Australia: population trendsDRUG AND ALCOHOL REVIEW, Issue 1 2004C. YALÇIN KAYA Senior Lecturer Abstract The aim of this paper is to identify certain important population trends among heroin users in Australia for the period 1971 , 97, such as: population growth, initiation, i.e. the number who were initiated to heroin in a given year, and quitting, i.e. the number that quit using heroin. For this purpose, we summarize and extract relevant characteristics from data from National Drug Strategy Household Survey (NDSHS 1998) conducted in Australia in 1998. We devise a systematic procedure to estimate historical trends from questions concerning past events. It is observed from our findings that the size of the heroin user population in Australia is in a sharp increase, especially from the early 1980s onwards. The general trend obtained for the period 1971 , 97 is strikingly similar to that obtained by Hall et al. (2000) for the dependent heroin user population in Australia, even though their study was based on different datasets and a different methodology. In our reconstruction of the time history we also detect a levelling-off prior to 1990. Initiation is also observed to be on a sharp increase. The latter trend is accompanied by a similar trend of quitting, perhaps indicating a relatively short heroin use career. A sharp decrease in both initiation and quitting is observed after 1990. In conclusion, in the case of the trend in the population of heroin users a high rate of growth has been identified that is consistent with the existing literature. In the process, we demonstrated that even a static survey such as NDSHS 1998 can, sometimes, be used to extract historical (dynamic) trends of certain important variables. [source] Editor's Note on Initiation of Lay AbstractsEPILEPSIA, Issue 4 2005Epilepsia, Ph.D. Editor-in-Chief, Robert S. Fisher M.D. No abstract is available for this article. [source] Distribution and Initiation of Seizure Activity in a Rat Brain with Subcortical Band HeterotopiaEPILEPSIA, Issue 5 2000Zong-Fu Chen Summary: Purpose: Misplaced (heterotopic) cortical neurons are a common feature of developmental epilepsies. To better understand seizure disorders associated with cortical heterotopia, the sites of aberrant discharge activity were investigated in vivo and in vitro in a seizure-prone mutant rat (tish) exhibiting subcortical band heterotopia. Methods: Depth electrode recordings and postmortem assessment of regional c- fos mRNA levels were used to characterize the distribution of aberrant discharge activity during spontaneous seizures in vivo. Electrophysiologic recordings of spontaneous and evoked activity also were performed by using in vitro brain slices from the tish rat treated with proconvulsant drugs (penicillin and 4-aminopyridine). Results: Depth electrode recordings demonstrate that seizure activity begins almost simultaneously in the normotopic and heterotopic areas of the tish neocortex. Spontaneous seizures induce c- fos mRNA in normotopic and heterotopic neocortical areas, and limbic regions. The threshold concentrations of proconvulsant drugs for inducing epileptiform spiking were similar in the normotopic and heterotopic areas of tish brain slices. Manipulations that blocked communication between the normotopic and heterotopic areas of the cortex inhibited spiking in the heterotopic, but not the normotopic, area of the cortex. Conclusions: These findings indicate that aberrant discharge activity occurs in normotopic and heterotopic areas of the neocortex, and in certain limbic regions during spontaneous seizures in the tish rat. Normotopic neurons are more prone to exhibit epileptiform activity than are heterotopic neurons in the tish cortex, and heterotopic neurons are recruited into spiking by activity initiated in normotopic neurons. The findings indicate that seizures in the tish brain primarily involve telencephalic structures, and suggest that normotopic neurons are responsible for initiating seizures in the dysplastic neocortex. [source] A Comparison of Conventional Local Approach and the Short Crack Approach to Fatigue Crack Initiation at a Notch,ADVANCED ENGINEERING MATERIALS, Issue 9 2009Narayanaswami Ranganathan Methods to estimate fatigue crack initiation life at a notch tip are compared. The methods used determine the strain amplitudes at the notch tip using Neuber's or Glinka's approximation. In conventional approaches, equivalent-damage levels are determined, using appropriate strain-life relationships coupled with damage-summation models. In the short-crack approach, a crack-like defect is assumed to exist at the notch tip. It is shown that the short-crack concept can be successfully applied to predict crack-initiation behavior at a notch. Model predictions are compared with carefully designed experiments. It is shown that model predictions are very close to experimentally measured lives under an aircraft-wing loading spectrum. [source] Initiation and early growth of fatigue cracks in an aerospace aluminium alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2002S. A. Barter Abstract Material imperfections usually play a substantial role in the early stages of fatigue cracking. This article presents some observations concerning fatigue crack initiating flaws and early crack growth in 7050-T7451 aluminium alloy specimens and in full-scale fatigue test articles with a production surface finish. Equivalent initial flaw size (EIFS) approaches used to evaluate the fatigue implications of metallurgical, manufacturing and service-induced features were refined by using quantitative fractography to acquire detailed information on the early crack growth behaviour of individual cracks; the crack growth observations were employed in a simple crack growth model developed for use in analysing service crack growth. The use of observed crack growth behaviour reduces the variability which is inherent in EIFS approaches which rely on modelling the whole of fatigue life, and which can dominate EIFS methods. The observations of realistic initial flaws also highlighted some of the significant factors in the fatigue life-determining early fatigue growth phase, such as surface treatment processes. Although inclusions are often regarded as the single most common type of initiating flaw, processes which include etching can lead to etch pitting of grain boundaries with significant fatigue life implications. [source] Initiation of JC virus DNA replication in vitro by human and mouse DNA polymerase ,-primaseFEBS JOURNAL, Issue 9 2003Richard W. P. Smith Host species specificity of the polyomaviruses simian virus 40 (SV40) and mouse polyomavirus (PyV) has been shown to be determined by the host DNA polymerase ,-primase complex involved in the initiation of both viral and host DNA replication. Here we demonstrate that DNA replication of the related human pathogenic polyomavirus JC virus (JCV) can be supported in vitro by DNA polymerase ,-primase of either human or murine origin indicating that the mechanism of its strict species specificity differs from that of SV40 and PyV. Our results indicate that this may be due to differences in the interaction of JCV and SV40 large T antigens with the DNA replication initiation complex. [source] Regulation of the initiation of chromosomal replication in bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 4 2007Jolanta Zakrzewska-Czerwi Abstract The initiation of chromosomal replication occurs only once during the cell cycle in both prokaryotes and eukaryotes. Initiation of chromosome replication is the first and tightly controlled step of a DNA synthesis. Bacterial chromosome replication is initiated at a single origin, oriC, by the initiator protein DnaA, which specifically interacts with 9-bp nonpalindromic sequences (DnaA boxes) at oriC. In Escherichia coli, a model organism used to study the mechanism of DNA replication and its regulation, the control of initiation relies on a reduction of the availability and/or activity of the two key elements, DnaA and the oriC region. This review summarizes recent research into the regulatory mechanisms of the initiation of chromosomal replication in bacteria, with emphasis on organisms other than E. coli. [source] Congress, Presidential Approval, and U.S. Dispute InitiationFOREIGN POLICY ANALYSIS, Issue 4 2008David J. Brulé Do presidents initiate disputes in response to low public approval ratings? Although research on the diversionary use of force finds links between poor economic conditions and military disputes, findings evaluating the effect of presidential approval ratings typically fail to support the diversionary hypothesis. But this research tends to neglect the role of presidential-congressional relations in the president's foreign policy making processes. This paper applies the policy availability argument to the puzzle: legislative constraints on presidential action during periods of low public approval compel the president to pursue alternatives that he can implement largely on his own in order to display his leadership skills,including the use of military force abroad. The argument is tested by examining the interactive effects of congressional support for the president and presidential approval ratings on the propensity to initiate militarized interstate disputes from 1949 to 2000. The results indicate that the president is more likely to use force in response to low presidential approval when faced with low congressional support. [source] Analysis of a microcrack model and constitutive equations for time-dependent dilatancy of rocksGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003Zuan Chen SUMMARY Based on experimental observations and theoretical analyses, the author introduces an ideal microcrack model in which an array of cracks with the same shape and initial size is distributed evenly in rocks. The mechanism of creep dilatancy for rocks is analysed theoretically. Initiation, propagation and linkage of pre-existing microcracks during creep are well described. Also, the relationship between the velocity of microcrack growth and the duration of the creep process is derived numerically. The relationship agrees well with the character of typical experimental creep curves, and includes three stages of creep. Then the damage constitutive equations and damage evolution equations, which describe the dilatant behaviour of rocks, are presented. Because the dilatant estimated value is taken as the damage variable, the relationship between the microscopic model and the macroscopic constitutive equations is established. In this way the mechanical behaviour of rocks can be predicted. [source] The Impact of Welfare Reform on Insurance Coverage before Pregnancy and the Timing of Prenatal Care InitiationHEALTH SERVICES RESEARCH, Issue 4 2007Norma I. Gavin Objective. This study investigates the impact of welfare reform on insurance coverage before pregnancy and on first-trimester initiation of prenatal care (PNC) among pregnant women eligible for Medicaid under welfare-related eligibility criteria. Data Sources. We used pooled data from the Pregnancy Risk Assessment Monitoring System for eight states (AL, FL, ME, NY, OK, SC, WA, and WV) from 1996 through 1999. Study Design. We estimated a two-part logistic model of insurance coverage before pregnancy and first-trimester PNC initiation. The impact of welfare reform on insurance coverage before pregnancy was measured by marginal effects computed from coefficients of an interaction term for the postreform period and welfare-related eligibility and on PNC initiation by the same interaction term and the coefficients of insurance coverage adjusted for potential simultaneous equation bias. We compared the estimates from this model with results from simple logistic, ordinary least squares, and two-stage least squares models. Principal Findings. Welfare reform had a significant negative impact on Medicaid coverage before pregnancy among welfare-related Medicaid eligibles. This drop resulted in a small decline in their first-trimester PNC initiation. Enrollment in Medicaid before pregnancy was independent of the decision to initiate PNC, and estimates of the effect of a reduction in Medicaid coverage before pregnancy on PNC initiation were consistent over the single- and two-stage models. Effects of private coverage were mixed. Welfare reform had no impact on first-trimester PNC beyond that from reduced Medicaid coverage in the pooled regression but separate state-specific regressions suggest additional effects from time and income constraints induced by welfare reform may have occurred in some states. Conclusions. Welfare reform had significant adverse effects on insurance coverage and first-trimester PNC initiation among our nation's poorest women of childbearing age. Improved outreach and insurance options for these women are needed to meet national health goals. [source] Lipoprotein (a) in Chronic Renal Failure: Effect of Maintenance HemodialysisHEMODIALYSIS INTERNATIONAL, Issue 4 2003Om Prakash Kalra Background:,Coronary artery disease accounts for significant morbidity and mortality in patients with chronic kidney disease (CKD). Besides the higher prevalence of traditional risk factors, several uremia-related factors may play a role in accelerated atherosclerosis, such as elevated levels of lipoprotein (a) (Lp(a)). The effect of maintenance hemodialysis (MHD) on Lp(a) levels is not well understood. The present work was carried out to study the Lp(a) levels in Stage 4 and Stage 5 CKD patients as well as the effect of MHD on Lp(a) levels in patients with Stage 5 CKD. Methods:,The study subjects included 15 patients with Stage 4 CKD, 15 patients with Stage 5 CKD, and 15 age- and sex-matched healthy controls. Plasma Lp(a) was measured by ELISA in all the subjects at the time of entry into the study and after 4 weeks of MHD in patients with Stage 5 CKD. Patients on MHD were dialyzed two to three times weekly for 4 hr during each session. Results:,Mean Lp(a) levels were significantly higher in patients with CKD than in control patients. In patients with Stage 4 CKD, the Lp(a) level was 34.0 ± 19.5 mg/dL, whereas in Stage 5 CKD the level was 49.0 ± 30.9 and in healthy controls it was 22.2 ± 16.4. In patients with Stage 5 CKD, 4 weeks of MHD led to a significant fall in Lp(a) levels by 23.6% (P < 0.001). Conclusions:,The results of this study show that increases in Lp(a) levels start early during the course of CKD and become more pronounced with increased severity of disease. Initiation of MHD lowers Lp(a) levels and may have a long-term beneficial effect on cardiovascular morbidity and mortality. [source] Initiation of TCR signaling: regulation within CD3 dimersIMMUNOLOGICAL REVIEWS, Issue 1 2003Balbino Alarcón Summary: The number of possible T cell activation outcomes resulting from T cell receptor (TCR) engagement suggests that the TCR is able to differentially activate a myriad of signaling pathways depending on the nature of the stimulus. The complex structural organization of the TCR itself could underlie this diversity of responses. Assembly and stoichiometric studies have helped us to shed some light on the initiation of TCR signaling. The TCR is composed of TCR and CD3 dimers. Changes in the interaction between CD3 subunits within the CD3 dimers and in the interaction of these dimers with the TCR heterodimer could be the triggering mechanism that initiates the first activation events. One of the hallmarks of these early changes in TCR conformation is the induced recruitment of the adapter protein Nck to a proline-rich sequence of the cytoplasmic tail of CD3,, but there may be others. According to our most recent observations, the TCR is organized in pre-existing clusters within plasma membrane microdomains, exhibiting a complexity above and beyond that of dimer composition complexity. How the presence of TCR in clusters influences TCR avidity and propagation of TCR signals is something that has yet to be investigated. [source] Mechanism of Repolarization Change During Initiation of Supraventricular TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2004YENN-JIANG LIN M.D. Introduction: Previous literature has documented the association between narrow QRS supraventricular tachycardia (SVT) and pronounced ST-T segment change. The aim of this study was to evaluate repolarization changes during SVT initiation and demonstrate the possible mechanism. Methods and Results: Fifty-one consecutive patients (20 men and 31 women; mean age 46.1 ± 16.4 years) with narrow QRS SVT (32 patients with AV nodal reentrant tachycardia and 19 patients with AV reentrant tachycardia) were included. We retrospectively analyzed the intracardiac recordings and ST-T segment changes on 12-lead surface ECGs during SVT initiation. Twenty-six (51%) patients developed ST segment repolarization changes during SVT initiation. Patients with shorter baseline sinus cycle length, shorter tachycardia cycle length, elevated systolic blood pressure before tachycardia induction, and greater reduction of systolic blood pressure had a higher incidence of repolarization changes. However, multivariate analysis showed that reduction of systolic blood pressure after SVT induction was the only independent predictor of repolarization changes. Furthermore, the maximal degree of ST segment depression during SVT correlated with the reduction of systolic blood pressure (r = 0.75, P < 0.001). Conclusion: Repolarization changes during SVT initiation were caused mainly by concurrent hemodynamic change after SVT initiation with abrupt cycle length shortening. [source] Ventricular Repolarization Change During Initiation of Supraventricular TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2003YENN-JIANG LIN M.D. No abstract is available for this article. [source] Role of Autonomic Tone in the Initiation and Termination of Paroxysmal Atrial Fibrillation in Patients Without Structural Heart DiseaseJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2003Takeshi Tomita M.D. Introduction: Previous studies have suggested that paroxysmal atrial fibrillation (PAF) of vagal origin often occurs at night and PAF of sympathetic origin occurs during the daytime; however, autonomic tone after spontaneous termination of PAF has not been determined. The aim of this study was to evaluate by heart rate variability (HRV) analysis the relationship between the time of PAF onset and autonomic tone before and after PAF. Methods and Results: Twenty-three patients (65 ± 2years) who underwent 24-hour ambulatory monitoring, had one or more episodes of PAF (>30 min), and had maintained normal sinus rhythm for >60 min before/after PAF were enrolled in this study. Mean duration of PAF was6.2 ± 1.2hours. HRV parameters were analyzed in a 10-minutes section at 60 minutes, 20 minutes, and immediately before the onset of PAF and after its termination. PAF began at night in 14 patients (group N) and during the daytime in 9 patients (group D). In group N, the high-frequency (HF) component and low-frequency (LF) component showed a significant decrease after PAF; PAF was preceded by a gradual increase in HF and LF. Changes in the LF/HF ratio, however, did not occur before or after PAF. Conversely, group D showed a significant increase in the LF/HF ratio before PAF and a decrease in LF and the LF/HF ratio after PAF, but no changes in HF. These changes in HRV parameters were not influenced by the duration or termination time of PAF. Conclusion: This study suggests that the autonomic nervous system plays an important role in both the initiation and termination of PAF. Furthermore, the time of PAF onset influences the autonomic tone at the initiation and termination of PAF. (J Cardiovasc Electrophysiol, Vol. 14, pp. 559-564, June 2003) [source] Characterization of Paroxysmal and Persistent Atrial Fibrillation in the Human Left Atrium During Initiation and Sustained EpisodesJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2002GJIN NDREPEPA M.D. Characterization of AF in the LA.Introduction: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes. Methods and Results: The study population consisted of 21 patients (15 men and 6 women; mean age 58 ± 9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF. Mapping of the LA during sustained episodes and the onset of AF was performed with a 64-electrode basket catheter. At the onset of AF, repetitive beats starting with atrial premature complexes and ending with generation of the earliest fibrillatory activity were defined as intermediary rhythm. Patients with paroxysmal AF had longer AF cycle lengths and more pronounced regional differences than patients with persistent AF. In total, AF cycle lengths in the LA in patients with persistent AF were 20% shorter than in patients with paroxysmal AF. Initiation of AF was preceded by an intermediary rhythm of 5.5 ± 2.5 cycles (6.3 ± 2.7 cycles in paroxysmal AF vs 4.2 ± 1.0 cycles in persistent AF; P = 0.026). At the onset of AF, the earliest generators of fibrillatory activity were located more frequently in the posterior wall of the LA. Conclusion: AF in the LA displays substantial regional differences in terms of AF cycle lengths and degree of organization. Patients with persistent AF have shorter cycle lengths and a higher degree of disorganized activity than patients with paroxysmal AF. Intermediary rhythms play an important role in initiation of AF via activation of generator regions in the LA. [source] Role of Wavelength Adaptation in the Initiation, Maintenance, and Pharmacologic Suppression of ReentryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2001STEVEN D. GIROUARD Ph.D. Wavelength Adaptation and Reentry.Introduction: The stability of reentry is thought to depend on a critical balance between the spatial extent of refractory tissue in a reentrant wave (i.e., wavelength ,) and the reentrant path length. Because considerable evidence suggests that , changes continuously in space and time during abrupt rate changes associated with the onset of tachycardia, we hypothesized that beat-by-beat adaptation of , to the dimensions of the reentrant path plays a central role in the mechanism of initiation of reentry. Methods and Results: To investigate the dynamic relationship between , and path length during initiation of reentry, optical mapping with voltage-sensitive dyes was used in a guinea pig model of reentrant ventricular tachycardia (VT). In this model, a computer-guided laser obstacle precisely controlled the position and dimensions of the reentrant path. Under control perfusion and after addition of 15 , M d-sotalol, , was monitored during steady-state pacing, premature stimulation, and the initiating beats leading to nonsustained and sustained VT. During control perfusion, reentrant VT was reproducibly induced in 8 of 8 hearts, whereas in the presence of d-sotalol, reentry could only be initiated in 1 of 8 hearts due primarily to the failure of , to adapt to the reentrant path length. During successful initiation of VT, a consistent sequence was observed. The sequence was characterized by antidromic and orthodromic propagation around both sides of the anatomic obstacle, followed by unidirectional block of the antidromic impulse and persistence of reentry only if the , of the orthodromic impulse adapted to the reentrant path (, < path length). d-Sotalol prevented initiation of VT by altering , adaptation of the orthodromic wave; however, it failed to terminate ongoing VT because reverse use-dependence developed after several beats of tachycardia. Conclusion: In an experimental model where ,, path length, and cellular action potentials were monitored during initiation of reentry, we found that, in contrast to termination, the initiation of reentry and the transition from nonsustained to sustained VT is strongly dependent on beat-to-beat adaptation of , to the dimensions of the reentrant path. [source] Role of Autonomic Influences in the Initiation and Perpetuation of Focal Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2001CHING-TAI TAI M.D. [source] Analysis of the Pattern of Initiation of Sustained Ventricular Arrhythmias in Patients with Implantable DefibrillatorsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2000ERIC TAYLOR M.D. Initiation of Sustained Ventricular Arrhythmias. Introduction: The purpose of this study was to analyze the pattern of initiation of sustained ventricular arrhythmias in patients with varying types of underlying structural heart disease. Methods and Results: The study group consisted of 90 patients with an implantable cardioverter defibrillator. Cardiovascular diagnoses included coronary artery disease in 64 patients (71%). The patients were divided into four groups based on the type and severity of structural heart disease. Two hundred sixty episodes of sustained ventricular arrhythmias were analyzed. The mean coupling interval of the initiating heat of all ventricular arrhythmias was 523 ± 171 msec. The coupling interval of the initiating beat was longer in patients with impaired ventricular function, particularly those with nonischemic dilated cardiomyopathy. The prematurity index was similar regardless of the type of underlying structural heart disease. However, the prematurity index was shorter in patients with polymorphic ventricular tachycardia (VT) compared to those with monomorphic VT. A pause was observed more commonly before the onset of polymorphic VT/ventricular fibrillation than sustained monomorphic VT. Two hundred twenty-two (85%) of the arrhythmia episodes were initiated by a late-coupled premature beat, 33 (13%) were initiated by an early-coupled premature beat, and 5 episodes (2%) were initiated with a short-long-short sequence. The patttern of initiation of the ventricular arrhythmias was similar in all patient groups and for both monomorphic and polymorphic tachycardias. Conclusion: These findings demonstrate that sustained ventricular arrhythmias typically are initiated by late-coupled ventricular premature depolarizations, regardless of the type or severity of underlying structural heart disease or resultant arrhythmia. [source] Role of fibrinogen-, factor VIII- and XIII-mediated clot propagation in gelatin haemodilutionACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2009A. A. SCHRAMKO Background: Gelatin solution impairs coagulation. The mechanism of coagulopathy is incompletely defined. The purpose of this study was to evaluate the capacity of single coagulation factors to reverse gelatin-promoted whole-blood coagulation disorders in vitro. Methods: Venous blood was withdrawn from 12 volunteers in a crossover study. Four percent succinylated gelatin was added to citrated whole-blood samples to make a 40 vol% end-concentration of gelatin. The baseline and 40 vol% samples, and samples with addition of fresh-frozen plasma (FFP), fibrinogen, coagulation factors XIII (FXIII) or VIII, together with the von Willebrand factor (FVIII+vWF), were analysed by thromboelastometry (ROTEM®). Coagulation was initiated by tissue thromboplastin (ExTEM®) with and without cytochalasin to determine the functional component of fibrinogen (FibTEM®). Results: Initiation of coagulation and fibrin formation were delayed at 40 vol% gelatin dilution. At this stage, the median (25th,75th percentiles) maximum clot firmness (MCF) was 76.3 (65.9,80.0) and 32.5 (27.4,45.0)% of the pre-dilution value in ExTEM® and FibTEM® thromboelastometry, respectively. Coagulation time was corrected by addition of fibrinogen and FFP in ExTEM® and FibTEM® analysis, whereas FVIII or FXIII had minimal effects. MCF was partly restored only by FFP in ExTEM®. In FibTEM® analysis, MCF improved more by fibrinogen than by FVIII+VWF, FXIII or FFP. Conclusions: Gelatin-induced whole-blood coagulation disorder in vitro is mainly dependent on the initial fibrinogen,fibrin interaction. The proposed mechanism might suggest not to reverse gelatin coagulopathy solely by fibrinogen administration. The administration of FFP, a mixture of different coagulation factors, reversed the gelatin-induced in vitro coagulopathy the best. [source] Sexual Reproduction in Higher Plants I: Fertilization and the Initiation of Zygotic ProgramJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2008Yong-Feng Fan Abstract Sexual plant reproduction is a critical developmental step in the life cycle of higher plants, to allow maternal and paternal genes to be transmitted in a highly regulated manner to the next generation. During evolution, a whole set of signal transduction machinery is developed by plants to ensure an error-free recognition between male and female gametes and initiation of zygotic program. In the past few years, the molecular machineries underlying this biological process have been elucidated, particularly on the importance of synergid cells in pollen tube guidance, the Ca++ spike as the immediate response of fertilization and the epigenetic regulation of parental gene expressions in early zygotic embryogenesis. This review outlines the most recent development in this area. [source] Parenting and Adolescents' Sexual InitiationJOURNAL OF MARRIAGE AND FAMILY, Issue 4 2009Monica A. Longmore This study draws on social control and social learning theories to examine the role of dating-specific attitudes and practices as predictors of adolescents' sexual initiation. We include attention to the adolescent's reaction to control attempts as a further means of assessing family dynamics (i.e., frequency of dating disagreements). The study uses longitudinal data from 697 adolescents who were not sexually active at the first interview as well as separate interviews with parents. In models that include all parenting variables, parental caring, parents' preferences that the child should delay sex, and the frequency of dating disagreements were significant predictors of initiation of teen sexual activity. [source] The Association of Couples' Relationship Status and Quality With Breastfeeding InitiationJOURNAL OF MARRIAGE AND FAMILY, Issue 5 2007Christina M. Gibson-Davis Using data from the Fragile Families and Child Wellbeing Survey (N= 3,567), we examine the links between relationship status, relationship quality, and race and ethnicity in breastfeeding initiation. We consider four relationship types: married, cohabiting, romantically involved but not cohabiting (termed visiting), and nonromantically involved mothers. We find that even after adjusting for a wide range of sociodemographic factors, married mothers were more likely to breastfeed than unmarried mothers and that racial and ethnic differences in breastfeeding do not result from differences in marriage rates. Among unwed mothers, paternal provision of money or other assistance during pregnancy decreases the likelihood of breastfeeding. We conclude that relationship status, above and beyond demographic characteristics, is an important correlate of breastfeeding. [source] Electrospray ionization mass spectrometric study of end-groups in peroxydicarbonate-initiated radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Michael Buback Abstract Initiation by diethyl peroxydicarbonate (E-PDC), di- n -tetradecyl peroxydicarbonate (nTD-PDC), di- n -hexadecyl peroxydicarbonate (nHD-PDC), and di-2-ethylhexyl peroxydicarbonate (2EH-PDC) of free-radical polymerizations of methyl methacrylate in benzene solution was studied by end-group analysis via electrospray ionization mass spectrometry (ESI-MS). Unambiguous assignment of ESI-MS peaks allows for identification of the type of radical that starts chain growth. In case of initiation by dialkyl peroxydicarbonates with linear alkyl groups, almost exclusively alkoxy carbonyloxyl species, which are the primary fragments from initiator decomposition, occur as end-groups. With 2EH-PDC, however, both the primary 2-ethylhexoxy carbonyloxyl fragment and a second moiety, which is formed by decarboxylation of the 2-ethylhexoxy carbonyloxyl radical, are clearly observed as end-groups. The decarboxylation process is described by a concerted mechanism which involves a 1,5-hydrogen shift reaction. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6071,6081, 2008 [source] | ||||||||||||||||||||||||||||||||||||||||||||||