Automatic smoothing and estimation in single index Poisson regression

We address the problem of smoothing parameter selection when estimating the direction vector and the link function in the context of semiparametric, single index Poisson regression. The single index Poisson model differs from the classical nonparametric setting in two ways: first, tire errors are heteroscedastic, and second, the direction parameter is unknown and has to be estimated. Based on this model, we propose two simple, automatic rules for simultaneously estimating the direction vector and the bandwidth. The first criterion, called weighted least squares, estimates the Kullback-Leibler risk function and has a penalty term to prevent undersmoothing in small samples. Tire second method, termed double smoothing, is based on the estimation of an La approximation of the Kullback-Leibler risk and makes use of a double smoothing idea. Simulations are used to investigate the behavior of various criteria in the single index Poisson model. Our weighted least squares and double smoothing methods outperform both a Kullback-Leibler version of cross-validation and the weighted least squares cross-validation criterion proposed by Hardle, Hall and Ichimura (1993)

Pathophysiologic mechanisms underlying dobutamine- and exercise-induced wall motion abnormalities.

BACKGROUND: Dobutamine and exercise echocardiography are accepted as tests of comparable efficacy for the diagnosis of coronary artery disease. Although dobutamine has been classified as "exercise simulating," the mechanisms of ischemia with dobutamine and exercise have not been well studied. This study sought to compare the determinants of myocardial oxygen consumption. METHODS AND RESULTS: We studied 54 patients with coronary artery disease undergoing dobutamine and exercise stress. A subgroup of 13 patients with comparable degrees of wall motion abnormalities and ST-segment changes during both stresses were selected to compare the determinants of ischemia in comparable circumstances. Dobutamine was infused to a mean maximal dose of 32+/-8 microg/kg/min, and exercise was stopped at an average of 135+/-25 W. The mean regional wall motion score was not statistically different between the two protocols (p = 0.27). At the onset of wall motion abnormalities and peak stress, the heart rate increased significantly less during dobutamine than during exercise (106+/-23 vs 126+/-19 beats/min, p < 0.001). The same was true of systolic blood pressure (155+/-21 vs 205+/-24 mm Hg, p < 0.001) and the rate-pressure product (16.5+/-4.6 vs 25.9+/-5, p < 0.001). Cardiac volumes were similar during both tests. CONCLUSIONS: Ischemia occurs at a lower level of external cardiac work during dobutamine than during exercise stress. We suspect that additional mechanisms, such as the oxygen wasting effect of dobutamine, may be responsible for this observation

Abnormal synaptic morphology and neuronal Ca2+-homeostasis in migraine mutant mice

Assessing neuronal structure and intracellular Ca 2+ levels at baseline, during and after cortical spreading depression in transgenic mice for familial hemiplegic migrain

Abnormal Synaptic Morphology and Neuronal Ca2+-Homeostasis in Migraine Mutant Mice

Paroxysmal Cerebral Disorder