Peak Response Time Research Articles

Effect of Ibutilide on the Canine Cardiac Conduction System

The objective of the study was to evaluate the effect of ibutilide on canine cardiac sinoatrial and atrioventricular nodes (AVNs). For this purpose, 18 mongrel dogs were injected intravenously with ibutilide and the changes in heart rate, sinus node recovery time, and AVN were measured. Our data show that ibutilide administration caused significant suppression of the sinus atrial node, the peak response time was 20-30 min, and the heart rate was restored to pre-drug administration level. After receiving ibutilide, 1 animal had a 5 s sinus pause, and after 5 min of ibutilide administration, 1 dog showed 2:1 atrioventricular conduction. Therefore, it was concluded that ibutilide had a suppressive effect on the sinoatrial node and AVN.

Tratamiento de hemangiomas infantiles con propranolol en régimen de control ambulatorio. Estudio prospectivo

ObjectiveTo assess the safety and effectiveness of oral propranolol (OP) in the treatment of infantile hemangiomas. Material and methodWe conducted a prospective study of infantile hemangiomas (IHs) treated with oral propranolol between October 2008 and March 2011. We included fast-growing IHs in the proliferative phase, IHs affecting vital structures, ulcerated IHs, and IHs that could cause functional or aesthetic problems after the proliferative phase. The patients received oral propranolol 2mg/kg/d and were monitored on an outpatient basis. Response to treatment was assessed by volume reduction, lightening of color, improvement of symptoms, and parent satisfaction. Time of initial and peak response, as well as side effects and sequelae, were recorded. ResultsWe analyzed 20 IHs, corresponding to 17 girls and 3 boys. The main sites of involvement were around the eyes (20%), the nose (15%), the neck (15%), and the trunk (15%). Ninety percent of the hemangiomas were focal and in the proliferative phase. Treatment was started between the ages of 2 and 19 months and the main reason for starting treatment was rapid growth (50% of cases). Initial response was observed in 70% of cases and only in 2 of them it took over a month. Peak response occurred at 3 months. All the IHs responded to treatment; response was excellent in 55% of cases, good in 35%, and minimal in 10%. The following factors were predictive of response: focal IH, proliferative phase, periorbital location, and ulceration. No serious side effects were observed. ConclusionOral propranolol was clinically effective in reducing the volume and color of infantile hemangiomas, although the reduction was not complete and telangiectasia and scarring persisted after treatment. Oral propranolol also proved to be safe for use in outpatients.

Multisociety sedation curriculum for gastrointestinal endoscopy

Multisociety sedation curriculum for gastrointestinal endoscopy

Pre-Existing Adenovirus Immunity Modifies a Complex Mixed Th1 and Th2 Cytokine Response to an Ad5/HIV-1 Vaccine Candidate in Humans

The results of the recent Step Study highlight a need to clarify the effects of pre-existing natural immunity to a vaccine vector on vaccine-induced T-cell responses. To investigate this interaction, we examined the relationship between pre-existing Ad5 immunity and T-cell cytokine response profiles in healthy, HIV-uninfected recipients of MRKAd5 HIV-1 gag vaccine (HVTN 050, ClinicalTrials.gov #NCT00849732). Participants were grouped by baseline Ad5 neutralizing antibody titer as either Ad5-seronegative (titer ≤18; n = 36) or Ad5-seropositive (titer >200; n = 34). Samples from vaccine recipients were analyzed for immune responses to either HIV-1 Gag peptide pools or Ad5 empty vector using an ex vivo assay that measures thirty cytokines in the absence of long-term culture. The overall profiles of cytokine responses to Gag and Ad5 had similar combinations of induced Th1- and Th2-type cytokines, including IFN-γ, IL-2, TNF-α, IP-10, IL-13, and IL-10, although the Ad5-specific responses were uniformly higher than the Gag-specific responses (p<0.0001 for 9 out of 11 significantly expressed analytes). At the peak response time point, PBMC from Ad5-seronegative vaccinees secreted significantly more IP-10 in response to Gag (p = 0.008), and significantly more IP-10 (p = 0.0009), IL-2 (p = 0.006) and IL-10 (p = 0.05) in response to Ad5 empty vector than PBMC from Ad5-seropositive vaccinees. Additionally, similar responses to the Ad5 vector prior to vaccination were observed in almost all subjects, regardless of Ad5 neutralizing antibody status, and the levels of secreted IFN-γ, IL-10, IL-1Ra and GM-CSF were blunted following vaccination. The cytokine response profile of Gag-specific T cells mirrored the Ad5-specific response present in all subjects before vaccination, and included a number of Th1- and Th2-associated cytokines not routinely assessed in current vaccine trials, such as IP-10, IL-10, IL-13, and GM-CSF. Together, these results suggest that vector-specific humoral responses may reduce vaccine-induced T-cell responses by previously undetected mechanisms.

Effects of Ibutilide on Inhibiting Heart Rate and Rapidly Terminating Atrial Flutter in Canine

Ibutilide is a newer class-III antiarrhythmic agent approved for clinical use. We sought to investigate its electrophysiological effects in canines and also the underlying mechanism of conversion of atrial flutter (AFL). For this purpose, 15 male mongrel dogs were anesthetized, intubated with tracheal tube, and heart was exposed and connected to electrodes. Electrophysiologic variables were measured with and without ibutilide (10-min infusion-dose: 0.10mg/kg; 30-min later, maintaining dose: 0.01mg/min) which included heart rate, conduction of intra- and inter-atrium, conduction ratio of isthmus, and ERP. Ibutilide had a significant inhibitory effect on sinus atrial node, peak response time was 20-30min, and heart rate returned to the baseline after 2h. One canine had 5s sinus pause, and the other had 2:1 atrioventricular conduction post-administration. Atrial, ventricular, and pulmonary vein ERP was significantly prolonged (P<0.05). No significant differences were observed regarding conduction of intra-atrium, inter-atrium, and isthmus. It was, therefore, concluded that ibutilide had suppressive effect on sinus atrial and atrioventricular nodes. Ibutilide rapidly terminated AFL due to the reentrant wave front's inability to proceed as the refractory period was protracted and hence caused the whole excitable gap of the reentrant circuit to be affected by refractoriness.

Single-cell NF-κB dynamics reveal digital activation and analogue information processing

Cells operate in dynamic environments using extraordinary communication capabilities that emerge from the interactions of genetic circuitry. The mammalian immune response is a striking example of the coordination of different cell types. Cell-to-cell communication is primarily mediated by signalling molecules that form spatiotemporal concentration gradients, requiring cells to respond to a wide range of signal intensities. Here we use high-throughput microfluidic cell culture and fluorescence microscopy, quantitative gene expression analysis and mathematical modelling to investigate how single mammalian cells respond to different concentrations of the signalling molecule tumour-necrosis factor (TNF)-alpha, and relay information to the gene expression programs by means of the transcription factor nuclear factor (NF)-kappaB. We measured NF-kappaB activity in thousands of live cells under TNF-alpha doses covering four orders of magnitude. We find, in contrast to population-level studies with bulk assays, that the activation is heterogeneous and is a digital process at the single-cell level with fewer cells responding at lower doses. Cells also encode a subtle set of analogue parameters to modulate the outcome; these parameters include NF-kappaB peak intensity, response time and number of oscillations. We developed a stochastic mathematical model that reproduces both the digital and analogue dynamics as well as most gene expression profiles at all measured conditions, constituting a broadly applicable model for TNF-alpha-induced NF-kappaB signalling in various types of cells. These results highlight the value of high-throughput quantitative measurements with single-cell resolution in understanding how biological systems operate.

Global gene expression analysis in the mouse brainstem after hyperalgesia induced by facial carrageenan injection – Evidence for a form of neurovascular coupling?

The present study was carried out to examine global gene expression in the brainstem, in a mouse facial carrageenan injection model of orofacial pain. Mice that received facial carrageenan injection showed increased mechanical allodynia, demonstrated by increased responses to von Frey hair stimulation of the face. The brainstem was harvested at 3 days post-injection, corresponding to the time of peak responses, and analyzed by Affymetrix Mouse Genome 430 2.0 microarrays. We sought to identify common genes that are changed in the respective sides of the brainstem after either right- or left-sided facial carrageenan injection. The result is a relatively small list of genes (22 genes), which were then classified using DAVID software. Many of them fell into the categories of “response to stress”, “defence response”, “response to biotic stimulus”, “cell adhesion” and “leukocyte adhesion”. Of these, increased expression of P-selectin, ICAM-1 and CCL12 after carrageenan injection could be verified by real-time RT-PCR on both the right and left sides, and increased in P-selectin and ICAM-1 further verified by Western blot analysis. P-selectin and ICAM-1 were immunolocalized to endothelial cells, and were double labelled with von Willebrand factor. Intraperitoneal injection of the P-selectin inhibitor KF38789 significantly reduced mechanical allodynia in the facial carrageenan-injected mice. P-selectin mediates the capturing of leukocytes from the bloodstream and rolling of leukocytes along the endothelial surface. We hypothesize that increased nociceptive input to the brainstem could attract circulating macrophages into the brain, resulting in neuroinflammation and pain.

Hydrograph separation for karst watersheds using a two-domain rainfall–discharge model

Highly parameterized, physically based models may be no more effective at simulating the relations between rainfall and outflow from karst watersheds than are simpler models. Here an antecedent rainfall and convolution model was used to separate a karst watershed hydrograph into two outflow components: one originating from focused recharge in conduits and one originating from slow flow in a porous annex system. In convolution, parameters of a complex system are lumped together in the impulse-response function (IRF), which describes the response of the system to an impulse of effective precipitation. Two parametric functions in superposition approximate the two-domain IRF. The outflow hydrograph can be separated into flow components by forward modeling with isolated IRF components, which provides an objective criterion for separation. As an example, the model was applied to a karst watershed in the Madison aquifer, South Dakota, USA. Simulation results indicate that this watershed is characterized by a flashy response to storms, with a peak response time of 1 day, but that 89% of the flow results from the slow-flow domain, with a peak response time of more than 1 year. This long response time may be the result of perched areas that store water above the main water table. Simulation results indicated that some aspects of the system are stationary but that nonlinearities also exist.

The role of natural killer cells in resistance to coccidiosis: investigations in a murine model.

Natural killer (NK) activity, detected by the lysis of Yac-1 target cells, was examined in splenic and mesenteric lymph node (MLN) cells throughout the course of infection with Eimeria vermiformis in BALB/c and C57B1/6 (B6) mice. These strains are, respectively, relatively resistant and susceptible to primary infections, which render them equally, and completely, resistant to challenge. Resting levels of NK activity were higher in B6 than in BALB/c, and B6 responded earlier in the course of infection than BALB/c, but splenic peak values were higher in BALB/c; the pattern of response in MLN cells was similar in both strains, but the peak was higher in BALB/c. At the time (7 days p.i.) of peak NK response in BALB/c mice there was, depending upon the choice of NK-resistant/lymphokine-activated killer (LAK)-sensitive target cells, either little (P388D1), or no (P815) splenic LAK activity. Challenge of immunized BALB/c mice did not evoke a detectable NK response. Although the higher NK activity in BALB/c mice correlated with greater control of primary infection, depletion of NK activity (demonstrated in splenic cells) in vivo by treatment with anti-asialo GM1 antibodies did not greatly affect the course of infection. Furthermore, this treatment did not augment the exacerbation of infection produced by treatment with anti-interferon-gamma (IFN-gamma) MoAb, indicating that, at least in this system, NK cells are not a fundamentally important source of this controlling cytokine of eimerian infections. The results suggest that NK cells may not greatly influence the outcome of coccidial infections.

Rams with poor feed efficiency are highly responsive to an exogenous adrenocorticotropin hormone (ACTH) challenge

An animal's response to a stressor is to increase metabolic rate, and thus energy consumption through the activation of the hypothalamic–pituitary–adrenal axis. Changes to energy use by an animal are likely to influence the efficiency with which it is utilised. In this study, we tested the hypothesis that less efficient sheep are more responsive to exogenous administration of adrenocorticotropin hormone. This was done by firstly determining the appropriate dose (0.4, 1.6 or 6.4 μg/kg LW) and peak serum cortisol response time (45 min) to exogenous administration of adrenocorticotropin hormone in a pilot study ( n = 3 sheep). Following this, adrenocorticotropin hormone (2.0 μg/kg LW) stimulated cortisol levels were measured in a larger group of sheep ( n = 50) of known feed efficiency (feed conversion ratio and residual feed intake values). Less efficient sheep (more positive residual feed intake values) were found to have a greater ( P < 0.001) increase in cortisol concentration in comparison to more efficient animals. Those sheep which had higher levels of cortisol also had a greater proportion ( P < 0.001) of fat tissue. These data clearly demonstrated that efficiency of energy use, when measured as residual feed intake, is significantly related to an animal's stress response. These findings have important implications for understanding the physiological mechanisms underpinning efficiency of energy use, and may be useful in successfully identifying animals which are superior in terms of feed efficiency.

Cerebrovascular response time to a breath-holding challenge

To evaluate the timecourse of cerebrovascular reserve response to breath-holding. Using simultaneous bilateral transcranial Doppler (TCD) recordings from the MCA during a breath-holding challenge, we measured the time interval between baseline and peak blood flow velocity values in 25 patients with critical unilateral internal carotid artery (ICA) stenosis (> 85% lumen diameter reduction), in 9 patients with a non-critical (70-85%) ICA-stenosis and in 27 normal controls. Normal controls and patients with non-critical stenosis reached peak MCA velocities on both sides almost simultaneously. For the patients with critical stenosis the peak response time ipsilateral to the stenosis was delayed 2.40 +/- 3.43 sec compared to the opposite side. This delay resolved after carotid endarterectomy. In response to a breath-holding challenge unilateral critical ICA stenosis is associated with a significant ipsilateral prolongation of the rise time from baseline to peak MCA velocity.

Localized glucoprivation of hindbrain sites elicits corticosterone and glucagon secretion

Glucose is required for brain energy metabolism. Decerebration, aqueduct occlusion, and cannula mapping studies have established that glucose-sensing cells capable of eliciting feeding and adrenal medullary responses to glucoprivation are localized in the hindbrain. Glucoprivation also evokes corticosterone and glucagon secretion, but the location of receptors mediating these responses is unknown. To determine whether glucoreceptive sites controlling these responses are present in the hindbrain, we administered the antiglycolytic agent, 5-d-thioglucose (5TG, 24 microg in 200 nl) into brain stem sites through implanted cannulas and examined plasma concentrations of corticosterone and glucagon. Both hindbrain and hypothalamic sites were tested. Blood was collected remotely from intra-atrial catheters at 0, 30, 60, 90, 120, 180, and 240 min after 5TG or control injection. Caudal hindbrain 5TG injections potently increased circulating corticosterone and glucagon concentrations. For corticosterone, the mean peak response (maximum concentration minus time 0 concentration) elicited at positive sites (23 of 40 sites) was 391 ng/ml (SE = 16). For glucagon, the mean peak response at positive sites (27 of 40 sites) was 46 pg/ml (SE = 6). Glucoprivically evoked glucagon secretion was abolished by the ganglionic blocker, hexamethonium, but not by adrenal denervation. Six of twenty-five hypothalamic sites were positive for corticosterone secretion, yielding plasma levels of 279 +/- 23 ng/ml, but none of the hypothalamic injection sites elevated glucagon concentrations. Results demonstrate that receptor cells responsive to glucose deficit and capable of increasing corticosterone and glucagon concentrations exist within the hindbrain, thus further delineating central glucoregulatory neural circuitry.

砂防ダムを含む山地小流域の水文諸量と出水遅延効果について

砂防ダムを含む山地小流域の水文諸量と出水遅延効果について

Laser induced thermoelectric voltage effect in La0.67Pb0.33MnO3 thin films doped with Ag

The La0.67Pb0.33MnO3 (LPMO) thin films doped with Ag on vicinal-cut LaAlO3 substrates were prepared using standard pulsed laser deposition technique, in which laser induced thermoelectric voltage (LITV) effect was found. With Ag doping level x (x is defined as,x=massAg/massLPMO) increasing from 0.00 to 0.10, the response time of LITV signals in LPMO thin films firstly decreases (reaching minimum at 0.06), and then increases (still less than that with zero Ag doping). Further, an optimal film thickness was found, at which the peak voltage and response time of LITV signals to reaches maximum and minimum, respectively. The response time of LITV in the LPMO thin films are substantially smaller than that of La0.67Ca0.33MnO3 thin films at the same Ag doping level.

Runoff peak response time in the torrent with the frequent occurrences of debris flows

Runoff peak response time in the torrent with the frequent occurrences of debris flows

Spatial extent of oxygen metabolism and hemodynamic changes during functional activation of the rat somatosensory cortex

The spatial extent of the changes in oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR), total hemoglobin concentration (HbT), cerebral blood flow (CBF), and the cerebral metabolic rate of oxygen (CMRO 2) in response to forepaw and whisker stimulation were compared in the rat somatosensory cortex using a combination of multi-wavelength reflectance imaging and laser speckle contrast imaging of cerebral blood flow. The spatial extents of the response of each hemodynamic parameter and CMRO 2 were found to be comparable at the time of peak response, and at early times following stimulation onset, the spatial extent of the change in HbR was smaller than that of HbO, HbT, CBF, and CMRO 2. In addition, a slight spatial dependence was found in the power law coefficient relating changes in CBF and HbT. Although the CMRO 2 response is a metabolic measure and thus expected to have a more localized response than the hemodynamic parameters, the results presented here suggest that this may not be the case in general, possibly due to the increased sensitivity of optical imaging techniques to superficial cortical layers where the lateral extent of the metabolic and neuronal activation is larger compared to that in layer IV. In addition, we found that the measured spatial extent of the CMRO 2 changes was insensitive to assumptions made in the calculation of the CMRO 2 changes such as baseline hemoglobin concentrations, vascular weighting constants, and wavelength dependence of tissue scattering. Multi-parameter full field imaging of the functional response provides a more complete picture of the hemodynamic response to functional activation including the spatial and temporal estimation of CMRO 2 changes.

Multi-Objective Optimization of the Handling Performances of a Road Vehicle: A Fundamental Study on Tire Selection

The optimization of the handling behavior of road vehicles is dealt with in this paper. Both a linear and a nonlinear model have been considered. A number of analytical solutions to the equations of motion have been derived for the linear model. The objective functions (i.e. performance indices) to be optimized for a steering step input maneuver were the sideslip angle gain, the yaw velocity peak response time, the yaw velocity overshoot and the initial yaw acceleration. The front and rear tire cornering stiffness have been considered as the design variables to be optimized. The derived optimal solutions can be used during preliminary design for the definition of the best vehicle handling performance. The tire cornering stiffness of a number of actual road vehicles comply with the corresponding values coming from the optimization process proposed in the paper.

A three-dimensional model of vocal fold abduction/adduction.

A three-dimensional biomechanical model of tissue deformation was developed to simulate dynamic vocal fold abduction and adduction. The model was made of 1721 nearly incompressible finite elements. The cricoarytenoid joint was modeled as a rocking-sliding motion, similar to two concentric cylinders. The vocal ligament and the thyroarytenoid muscle's fiber characteristics were implemented as a fiber-gel composite made of an isotropic ground substance imbedded with fibers. These fibers had contractile and/or passive nonlinear stress-strain characteristics. The verification of the model was made by comparing the range and speed of motion to published vocal fold kinematic data. The model simulated abduction to a maximum glottal angle of about 31 degrees. Using the posterior-cricoarytenoid muscle, the model produced an angular abduction speed of 405 degrees per second. The system mechanics seemed to favor abduction over adduction in both peak speed and response time, even when all intrinsic muscle properties were kept identical. The model also verified the notion that the vocalis and muscularis portions of the thyroarytenoid muscle play significantly different roles in posturing, with the muscularis portion having the larger effect on arytenoid movement. Other insights into the mechanisms of abduction/adduction were given.

Salivary cortisol as indicators of pain in preterm infants: a pilot study.

Assessment and management of pain in preterm infants is critical and complicated. The addition of salivary cortisol measurement may improve the specificity of assessment and guide care to alleviate pain. The purpose of this study was fourfold: (a) assess the feasibility of a method of saliva collection in premature infants, (b) assess reliability of a method of measuring salivary cortisol in response to heelstick, (c) identify relationships between salivary cortisol and a measure of pain behavior (using CRIES) following heelstick, and (d) identify peak response times for elevations of salivary cortisol following heelstick in preterm infants. This was a prospective, descriptive pilot study. Serial saliva samples were collected from eight healthy infants 30 to 36 weeks' gestational age in a Newborn Intensive Care Unit. Cortisol levels were determined using enzyme-immune assay. Samples were collected without use of stimulants. Sample means supported peak and trough patterns previously described in the literature. Behavioral measures of pain did not correlate well with peak cortisol levels.

Cortisol concentrations in 12- to 18-Month-Old infants: stability over time, location, and stressor

Background Sparse information on early development of hypothalamic pituitary adrenal (HPA) axis responsivity in human infants limits our understanding of stress hormone regulation and vulnerability to psychopathology. We considered whether infant cortisol stress response (CSR) is a suitable endocrine phenotype for developmental stress research. Methods We assessed stability of key CSR parameters across time, location, and stressor through saliva samples taken before and then 20 and 40 min following exposure to two stressors administered 1 week apart in 27 infants aged 12 to 18 months. Time-matched home samples were collected to control for circadian rhythm and to evaluate baseline stability. Results Baseline cortisol concentrations, peak percent change, and area under the curve (AUC) were stable across time and stressors. Following both stressors, half the infants exhibited peak cortisol concentrations at 20 min poststress; half peaked at 40 min poststress. For 56% of the infants, peak response time was inconsistent across stressors. Conclusions In humans, baseline and CSR are stable by 12 to 18 months. Variation in CSR time course across stressors indicates that infant CSR should be sampled beyond 30 min. Results support using infant CSR, particularly as measured by AUC, as a valid endocrine phenotype for developmental stress research.