Decomposition of Neurological Multivariate Time Series by State Space Modelling

Decomposition of multivariate time series data into independent source components forms an important part of preprocessing and analysis of time-resolved data in neuroscience. We briefly review the available tools for this purpose, such as Factor Analysis (FA) and Independent Component Analysis (ICA), then we show how linear state space modelling, a methodology from statistical time series analysis, can be employed for the same purpose. State space modelling, a generalization of classical ARMA modelling, is well suited for exploiting the dynamical information encoded in the temporal ordering of time series data, while this information remains inaccessible to FA and most ICA algorithms. As a result, much more detailed decompositions become possible, and both components with sharp power spectrum, such as alpha components, sinusoidal artifacts, or sleep spindles, and with broad power spectrum, such as FMRI scanner artifacts or epileptic spiking components, can be separated, even in the absence of prior information. In addition, three generalizations are discussed, the first relaxing the independence assumption, the second introducing non-stationarity of the covariance of the noise driving the dynamics, and the third allowing for non-Gaussianity of the data through a non-linear observation function. Three application examples are presented, one electrocardigram time series and two electroencephalogram (EEG) time series. The two EEG examples, both from epilepsy patients, demonstrate the separation and removal of various artifacts, including hum noise and FMRI scanner artifacts, and the identification of sleep spindles, epileptic foci, and spiking components. Decompositions obtained by two ICA algorithms are shown for comparison.     

Tubulin paracrystals in intermitotic nuclei of the foraminifer Allogromia laticollaris Arnold after treatment with vinblastine

Electron microscopic investigations on the foraminifer Allogromia laticollaris showed that after treatment with 10(-3) M vinblastine tubulin paracrystals can be demonstrated in intermitotic nuclei. As these paracrystals are either membrane coated or lie free in the karyoplasm, and as in the perinuclear cytoplasm, membrane coated paracrystals can be demonstrated as well, it is assumed that the cytoplasmic tubulin which is composing the intranuclear division spindle can transverse the intact nuclear envelope via vesicle transport.     

The transformation of cytoplasmic microtubules into helices and paracrystals by halothane in the foraminifer Allogromia laticollaris Arnold

After treatment of cells of the foraminifer Allogromia laticollaris Arnold (protozoa, rhizopoda) with the volatile anesthetic halothane in concentrations of more than 1 mM no cytoplasmic microtubules are demonstrable. In place of microtubules, other tubulin polymers that are helices or paracrystalline structures, with the same ultrastructure as seen after treatment with vinca alkaloids, can be identified. Below 1 mM halothane, besides loosely arranged paracrystals, single helices, microtubules and transition stages between microtubules and helices can be seen in close juxtaposition. Reasons for the transformation of microtubules and the involvement of microtubules in narcosis are discussed.     

Adenine inhibits microcyst formation inPhysarum flavicomum and affects the cellular level of S-adenosylmethionine

Summary The effect of various purines, pyrimidines and nucleosides on the encystment of haploid cells ofPhysarum flavicomum was determined. Of the compounds tested guanine, guanosine, cytidine, cytosine, 5-methylcytosine and uracil had no effect on encystment. Adenosine, thymine, uridine and 3-methyladenine only slightly delayed encystment and protein degradation. Adenine and, to a lesser extent, hypoxanthine produced a significant inhibition of encystment and greatly increased rates of autolytic protein and RNA degradation, which eventually led to about 75% cell death in the adenine-exposed cells. The inhibition of microcyst formation by adenine was concentration dependent. The incubation of cells with adenine resulted initially in elevated intracellular levels of S-adenosylmethionine up to 3.5 times the level of untreated control cells.