Low-threshold monopolar motor mapping for resection of primary motor cortex tumors

Microsurgery within eloquent cortex is a controversial approach because of the high risk of permanent neurological deficit. Few data exist showing the relationship between the mapping stimulation intensity required for eliciting a muscle motor evoked potential and the distance to the motor neurons; furthermore, the motor threshold at which no deficit occurs remains to be defined.

Obesity lowers the threshold of allergic sensitization and augments airway eosinophilia in a mouse model of asthma

Clinical and epidemiological studies show a close association between obesity and the risk of asthma development. The underlying cause-effect relationship between metabolism, innate and adaptive immunity, and inflammation remains to be elucidated.

Monitoring and Modeling of the Hydraulic and Sediment Processes at In-Stream Restoration Structures in the Vicinity of a Bridge Crossing

The long-term performance of infrastructure depends on reliable and sustainable designs. Many of Pennsylvania’s streams experience sediment transport problems that increase maintenance costs and lower structural integrity of bridge crossings. A stream restoration project is one common mitigation measure used to correct such problems at bridge crossings. Specifically, in an attempt to alleviate aggradation problems with the Old Route 15 Bridge crossing on White Deer Creek, in White Deer, PA, two in-stream structures (rock cross vanes) and several bank stabilization features were installed along with a complete channel redevelopment. The objectives of this research were to characterize the hydraulic and sediment transport processes occurring at the White Deer Creek site, and to investigate, through physical and mathematical modeling, the use of instream restoration structures. The goal is to be able to use the results of this study to prevent aggradation or other sediment related problems in the vicinity of bridges through improved design considerations. Monitoring and modeling indicate that the study site on White Deer Creek is currently unstable, experiencing general channel down-cutting, bank erosion, and several local areas of increased aggradation and degradation of the channel bed. An in-stream structure installed upstream of the Old Route 15 Bridge failed by sediment burial caused by the high sediment load that White Deer Creek is transporting as well as the backwater effects caused by the bridge crossing. The in-stream structure installed downstream of the Old Route 15 Bridge is beginning to fail because of the alignment of the structure with the approach direction of flow from upstream of the restoration structure.

Enhanced Atlantic subpolar gyre variability through baroclinic threshold in a coarse resolution model

Direct observations, satellite measurements and paleo records reveal strong variability in the Atlantic subpolar gyre on various time scales. Here we show that variations of comparable amplitude can only be simulated in a coupled climate model in the proximity of a dynamical threshold. The threshold and the associated dynamic response is due to a positive feedback involving increased salt transport in the subpolar gyre and enhanced deep convection in its centre. A series of sensitivity experiments is performed with a coarse resolution ocean general circulation model coupled to a statistical-dynamical atmosphere model which in itself does not produce atmospheric variability. To simulate the impact of atmospheric variability, the model system is perturbed with freshwater forcing of varying, but small amplitude and multi-decadal to centennial periodicities and observational variations in wind stress. While both freshwater and wind-stress-forcing have a small direct effect on the strength of the subpolar gyre, the magnitude of the gyre's response is strongly increased in the vicinity of the threshold. Our results indicate that baroclinic self-amplification in the North Atlantic ocean can play an important role in presently observed SPG variability and thereby North Atlantic climate variability on multi-decadal scales.

Predicting spike timing of neocortical pyramidal neurons by simple threshold models

Neurons generate spikes reliably with millisecond precision if driven by a fluctuating current--is it then possible to predict the spike timing knowing the input? We determined parameters of an adapting threshold model using data recorded in vitro from 24 layer 5 pyramidal neurons from rat somatosensory cortex, stimulated intracellularly by a fluctuating current simulating synaptic bombardment in vivo. The model generates output spikes whenever the membrane voltage (a filtered version of the input current) reaches a dynamic threshold. We find that for input currents with large fluctuation amplitude, up to 75% of the spike times can be predicted with a precision of +/-2 ms. Some of the intrinsic neuronal unreliability can be accounted for by a noisy threshold mechanism. Our results suggest that, under random current injection into the soma, (i) neuronal behavior in the subthreshold regime can be well approximated by a simple linear filter; and (ii) most of the nonlinearities are captured by a simple threshold process.

Increased proximal urethral sensory threshold after radical pelvic surgery in women

AIM: To identify factors that potentially influence urethral sensitivity in women. PATIENTS AND METHODS: The current perception threshold was measured by double ring electrodes in the proximal and distal urethra in 120 women. Univariate analysis using Kaplan-Meier models and multivariate analysis applying Cox regressions were performed to identify factors influencing urethral sensitivity in women. RESULTS: In univariate and multivariate analysis, women who had undergone radical pelvic surgery (radical cystectomy n = 12, radical rectal surgery n = 4) showed a significantly (log rank test P < 0.0001) increased proximal urethral sensory threshold compared to those without prior surgery (hazard ratio (HR) 4.17, 95% confidence interval (CI) 2.04-8.51), following vaginal hysterectomy (HR 4.95, 95% CI 2.07-11.85), abdominal hysterectomy (HR 5.96, 95% CI 2.68-13.23), or other non-pelvic surgery (HR 4.86, 95% CI 2.24-10.52). However, distal urethral sensitivity was unaffected by any form of prior surgery. Also other variables assessed, including age, concomitant diseases, urodynamic diagnoses, functional urethral length, and maximum urethral closure pressure at rest had no influence on urethral sensitivity in univariate as well as in multivariate analysis. CONCLUSIONS: Increased proximal but unaffected distal urethral sensory threshold after radical pelvic surgery in women suggests that the afferent nerve fibers from the proximal urethra mainly pass through the pelvic plexus which is prone to damage during radical pelvic surgery, whereas the afferent innervation of the distal urethra is provided by the pudendal nerve. Better understanding the innervation of the proximal and distal urethra may help to improve surgical procedures, especially nerve sparing techniques. Neurourol. Urodynam. (c) 2006 Wiley-Liss, Inc.

Ondansetron does not reduce the shivering threshold in healthy volunteers

BACKGROUND: Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control, and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (triggering core temperatures) in humans. METHODS: Control (placebo) and ondansetron infusions at the target plasma concentration of 250 ng ml(-1) were studied in healthy volunteers on two different days. Each day, skin and core temperatures were increased to provoke sweating; then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction and shivering thresholds after compensating for changes in mean-skin temperature. Data were analysed using t-tests and presented as means (sds); P<0.05 was taken as significant. RESULTS: Ondensetron plasma concentrations were 278 (57), 234 (55) and 243 (58) ng ml(-1) at the sweating, vasoconstriction and shivering thresholds, respectively; these corresponded to approximately 50 mg of ondansetron which is approximately 10 times the dose used for postoperative nausea and vomiting. Ondansetron did not change the sweating (control 37.4 (0.4) degrees C, ondansetron 37.6 (0.3) degrees C, P=0.16), vasoconstriction (37.0 (0.5) degrees C vs 37.1 (0.3) degrees C; P=0.70), or shivering threshold (36.3 (0.5) degrees C vs 36.3 (0.6) degrees C; P=0.76). No sedation was observed on either study day. CONCLUSIONS: /b>. Ondansetron appears to have little potential for facilitating induction of therapeutic hypothermia.