Search results for "Biological clock"
showing 8 items of 28 documents
Novel modes of rhythmic burst firing at cognitively-relevant frequencies in thalamocortical neurons.
2008
It is now widely accepted that certain types of cognitive functions are intimately related to synchronized neuronal oscillations at both low (alpha/theta) (4-7/8-13 Hz) and high (beta/gamma) (18-35/30-70 Hz) frequencies. The thalamus is a key participant in many of these oscillations, yet the cellular mechanisms by which this participation occurs are poorly understood. Here we describe how, under appropriate conditions, thalamocortical (TC) neurons from different nuclei can exhibit a wide array of largely unrecognised intrinsic oscillatory activities at a range of cognitively-relevant frequencies. For example, both metabotropic glutamate receptor (mGluR) and muscarinic Ach receptor (mAchR) …
Three Patterns of Oscillatory Activity Differentially Synchronize Developing Neocortical Networks In Vivo
2009
Coordinated patterns of electrical activity are important for the early development of sensory systems. The spatiotemporal dynamics of these early activity patterns and the role of the peripheral sensory input for their generation are essentially unknown. We performed extracellular multielectrode recordings in the somatosensory cortex of postnatal day 0 to 7 rats in vivo and observed three distinct patterns of synchronized oscillatory activity. (1) Spontaneous and periphery-driven spindle bursts of 1-2 s in duration and approximately 10 Hz in frequency occurred approximately every 10 s. (2) Spontaneous and sensory-driven gamma oscillations of 150-300 ms duration and 30-40 Hz in frequency oc…
Comparison of complex fractionated atrial electrograms at cellular scale using numerical and experimental models.
2010
This study investigates the existence of the pseudo complex fractionated atrial electrogram (CFAE) at cellular level. Our assumptions are based on the fact that CFAEs are linked to the generation of the spiral waves. These are created using a numerical model and an experimental model of in vitro culture of neonatal rats cardiac cells. Pseudo bipolar electrograms resulting from these two models are compared qualitatively and some patterns could be identified as CFAE signature.
Fiat lux: the light became therapy. An overview on the Bright Light Therapy in Alzheimer’s Disease sleep disorders
2020
Background: A system of photosensitive retinal ganglion cells provides ‘non-visual’ information on the circadian sequences of light to the suprachiasmatic nucleus (SCN), which, as the ‘master clock’, synchronizes the chronobiological mechanisms of all the biological clocks. Damage to SCN structure alters circadian behavioral and hormonal rhythms and interferes with a regular sleep-wake pattern. Several studies have shown that, in aging and in Alzheimer’s disease (AD), circadian rhythms change their synchronization with the environment and behavior loses sync with light. Objective: The current overview aims to examine research studies showing the effect of bright light therapy (BLT) on sleep…
Effective target arrangement in a deterministic scale-free graph
2010
We study the random walk problem on a deterministic scale-free network, in the presence of a set of static, identical targets; due to the strong inhomogeneity of the underlying structure the mean first-passage time (MFPT), meant as a measure of transport efficiency, is expected to depend sensitively on the position of targets. We consider several spatial arrangements for targets and we calculate, mainly rigorously, the related MFPT, where the average is taken over all possible starting points and over all possible paths. For all the cases studied, the MFPT asymptotically scales like N^{theta}, being N the volume of the substrate and theta ranging from (1 - log 2/log3), for central target(s)…
Safety and side effects of human and ovine corticotropin-releasing hormone administration in man.
1991
Synthetic human and ovine corticotropin-releasing hormone (hCRH, oCRH) are commonly used as a diagnostic tool of the hypothalamo-pituitary-adrenal axis. In this paper reports about side effects after various modes of CRH-application are analyzed and compared to our corresponding data of human studies with hCRH and oCRH. Generally, CRH is well tolerated after single administration and interval-application of standard doses, although minor side effects appear sometimes after higher doses (greater than 200 micrograms hCRH, oCRH) of CRH-bolus-injections. Predominantly the cardiovascular system (e.g. tachycardia, hypotension, flushing) is affected; neuropsychological symptoms are only seen spora…
Microstructures in shells of the freshwater gastropod Viviparus viviparus: a potential sensor for temperature change?
2013
Abstract Mollusk shells contain a plethora of information on past climate variability. However, only a limited toolkit is currently available to reconstruct such data from the shells. The environmental data of some proxies (e.g. Sr/Ca ratios) is obscured by physiological effects, whereas other proxies, such as δ 18 O, simultaneously provide information on two or more different environmental variables. The present study investigates whether microstructures of the freshwater gastropod Viviparus viviparus provide an alternative means to reconstruct past water temperature. Cold and highly variable temperature regimes resulted in the precipitation of highly unordered first-order lamellae of simp…
Mammalian Pinealocytes: Ultrastructural Aspects and Innervation
2008
In the mammalian pineal gland it is notoriously difficult to relate structure to function. The pineal-specific cells, the pinealocytes, contain only inconspicuous numbers of secretory granules, and the variable amounts of smooth and rough endoplasmic reticulum also do not point to a particular function. In addition to these widely known cellular components, pinealocytes contain organelles, the so-called 'synaptic' ribbons, histophysiological studies of which provide important insights into the structural and functional complexity of the organ. As synaptic ribbons may be involved in neuronal functions of pinealocytes it is notable that these organelles are structurally heterogeneous. Ribbons…