Quantitative Analysis of Electrotonic Structure and Membrane Properties of NMDA-Activated Lamprey Spinal Neurons

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK), and leakage (IL) currents. Both the passive cable properties and the voltage dependence of ion channel kinetics were estimated, including the electrotonic structure of the cell, the steady-state gating characteristics, and the time constants for particular voltage- and time-dependent ionic conductances. An alternate kinetic formulation was developed that consisted of steady-state values for the gating parameters and their time constants at half-activation values as well as slopes of these parameters at half-activation. This procedure allowed independent restrictions on the magnitude and slope of both the steady-state gating variable and its associated time constant. Quantitative estimates of the voltage-dependent membrane ion conductances and their kinetic parameters were used to solve the nonlinear equations describing dynamic responses. The model accurately predicts current clamp responses and is consistent with experimentally measured TTX-resistant NMDA-induced patterned activity. In summary, an analysis method is developed that provides a pragmatic approach to quantitatively describe a nonlinear neuronal system

Validation of Non-Invasive CO\u3csub\u3e2\u3c/sub\u3e Tolerance Field Test

INTRODUCTION: Breathwork, or the specific act of controlling breathing to elicit a desired outcome, is not only a potential way to improve one’s mental well-being but also to alter adaptative responses through gas exchange at the capillary level. Increasing tolerance to carbon dioxide (CO2) has been positively correlated with improvement in athletic performance and reduction of stress and anxiety. However, there does not exist a validated non-invasive test to accurately measure one’s tolerance to CO2. PURPOSE: The purpose of this study was to validate the only currently known CO2 tolerance (CO2T) field test against measured maximal dissolved CO2 and maximal ventilatory carbon dioxide (V̇CO2max) in endurance athletes. HYPOTHESIS: It was hypothesized that the novel CO2T field test would have a strong positive correlation to clinical CO2 measurements, there would be no observable differences in comparative values between the CO2T field test and clinical CO2 measurements between sexes, and there would be a negative correlation between anaerobic capacity and CO2T. METHODS: Twenty-eight (n=28, 19 males, 9 females) participants reported to the Human Performance Laboratory on two separate occasions, separated by 48 hours, for testing. Peak CO2 levels were generated via repeated 30-second Wingate anaerobic power intervals with two minutes of rest in-between. Participants continued the Wingate tests until a plateau of peak power was achieved or volitional fatigue. CO2 data were recorded at the end of each interval. Day one consisted of a study orientation, informed consent, anthropometric measurements, CO2T field test, and ventilatory CO2 measurements during the repeated Wingate tests. Day two consisted of a second CO2T field test, end-tidal CO2 (EtCO2), and lactate (BL) measurements during the repeated Wingate tests. STATISTICS: Repeated measures ANOVA and paired t-test were used to determine if differences existed between CO2T times, EtCO2, anaerobic capacity (AC), and blood BL values. Pearson correlation coefficient analysis was used to determine if there was a relationship between CO2T times and all primary research variables. RESULTS: The CO2T field test showed to have a very high degree of intra-rater reliability but did not show any validity to CO2 measurements. Statistical analysis showed a high positive correlation between CO2T tests one and two (r = 0.989, p \u3c 0.01) and no significant difference so an average score was used for analysis. A moderate positive correlation to HRpeak for CO2Tavg (r = 0.38, p \u3c 0.05), and an indirect correlation to EtCO2(1) (r = -0.342, p \u3c 0.05). Correlations between CO2T tests and all other variables did not reach statistical significance. CONCLUSION: While reliable, the novel CO2T field test does not seem to be a valid measurement of physiological levels of CO2. The test was shown to have a high degree of intra-rater reliability and could be used to show trends over time but does not give an accurate portrayal of actual CO2 production, accumulation, and tolerance

Kinematic reducibility of multiple model systems

This paper considers the relationship between second order multiple model systems and first order multiple model systems. Such a relationship is important to, among other things, studying path planning for mechanical control systems. This is largely due to the fact that the computational complexity of a path planning problem rapidly increases with the dimension of the state space, implying that being able to reduce a path planning problem from TQ to Q can be helpful. Not surprisingly, the necessary and sufficient condition for such a reduction is that each model constituting a multiple model control system be reducible. We present an extensive example in order to illustrate how these results can provide insight into the control of some specific physical systems

Smooth feedback control algorithms for distributed manipulators

This paper introduces a smooth control algorithm for controlling fully actuated distributed manipulation systems that operate by frictional contact. The control law scales linearly with the number of actuators and is simple to implement. Moreover, we prove that control law has desirable robustness properties in the presence of the nonsmooth mechanics inherent in distributed manipulation systems that rely upon frictional contact. This algorithm has been implemented on an experimental distributed manipulation test-bed, whose structure is briefly reviewed. The experimental results confirm the validity and performance of the algorithm

Predicting Academic Success for NCAA Division I Student-Athletes

Demographic data were obtained on the population of all freshmen student-athletes admitted to the University of Florida (UF) during 1995 (N=91). Demographic data included gender, race, age, distance from home, and several subjective measures. The researchers analyzed the relationship between UF's predictive index and student-athletes' actual Grade Point Average (GPA) and found a significant correlation (r(89)=.60). The correlation between athletes' High School GPA (HSGPA) and their UF GPA was also significant (r(89)=.61). No correlation was found between UF GPA and any of the subjective measures administered to the athletes. Recommendations are made for future testing and prediction of academic success for National Collegiate Athletic Association (NCAA) Division I student-athletes