1,721,089 research outputs found
Scanning force microscopy on live cultured cells: Imaging and force‐versus‐distance investigations
No full textExtensive measurements with the scanning force microscope on living cells in their native liquid environment are described with the purpose of critically assessing the extent of the interaction between the SFM tip and the (soft) cell materials and the effect of such interaction on topographic information. Images are obtained under various force conditions and systematically correlated with force‐versus‐distance curves. As a result, detailed indications about tip indentation are given, thickness estimates deduced and identification of submembranous cytoplasmic structures suggested. 1994 Blackwell Science Lt
Activity-driven computational strategies of a dynamically regulated integrate-and-fire model neuron
No full textActivity-dependent slow biochemical regulation processes, affecting intrinsic properties of a neuron, might play an important role in determining information processing strategies in the nervous system. We introduce second-order biochemical phenomena into a linear leaky integrate-and-fire model neuron together with a detailed kinetic description for synaptic signal transduction. In this framework, we investigate the membrane intrinsic electrical properties differentiation, showing the appearance of activity-dependent shifts between integration and temporal coincidence detection operating mode, for the single unit of a network
Electrophysiological activity to cell metabolism signal transduction: Possible feedback regulatory biochemical pathway
No full textIntracellular free calcium concentration [Ca 2+ ] IN has been extensively studied as a major feedback element, transducing endogenous levels of electrical activity into an intracellular signal, in the context of modeling activity-dependent changes of ionic conductances of a neuronal membrane patch through slow biochemical subcellular mechanisms. However, distinct patterns of activity may induce similar mean levels in [Ca 2+ ] IN so that a multiple sensing mechanism, integrating and matching the features of calcium temporal dynamics over various time scales, is needed to overcome such ambiguous situations. In the present research, we investigate the possible role of a metabolic sensor, related to the power dissipated by the passive ion transport through channels, as an alternative candidate in intracellular calcium independent signal transduction of the electrophysiological activity
Mechanical and morphological properties of living 3T6 cells probed via scanning force microscopy
No full textScanning Force Microscopy (SFM) is utilized to study living confluent 3T6 cells. Images based on mechanical contrast are obtained and related morphological details, mostly regarding the cell cytoskeleton, are analyzed. Moreover, numerical estimates of the local mechanical properties of the living cells are given, by extensive use of the 'force-vs.-distance' operation mode. On the basis of the results obtained, the potentialities of SFM as an optimal new technique available for probing the cell cytoskeleton of unstained living cells, and assessing related models, are shortly discussed
Fast calculation of short-term depressing synaptic conductances
No full textAn efficient implementation of synaptic transmission models in realistic network simulations is an important theme of computational neuroscience. The amount of CPU time required to simulate synaptic interactions can increase as the square of the number of units of such networks, depending on the connectivity convergence. As a consequence, any realistic description of synaptic phenomena, incorporating biophysical details, is computationally highly demanding. We present a consolidating algorithm based on a biophysical extended model of ligand-gated postsynaptic channels, describing short-term plasticity such as synaptic depression. The considerable speedup of simulation times makes this algorithm suitable for investigating emergent collective effects of short-term depression in large-scale networks of model neurons
Insulin release at the molecular level: Metabolic-electrophysiological modeling of the pancreatic beta-cells
No full textThe role of pancreatic β-cells is fundamental in the control endocrine system, maintaining the blood glucose homeostasis in a physiological regime, via the glucose-induced release of insulin. An increasing amount of detailed experimental evidences at the cellular and molecular biology levels have been collected on the key factors determining the insulin release by the pancreatic β-cells. The direct transposition of such experimental data into accurate mathematical descriptions might contribute to considerably clarify the impact of each cellular component on the global glucose metabolism. Under these perspectives, we model and computer-simulate the stimulus-secretion coupling in β-cells by describing four interacting cellular subsystems, consisting in the glucose transport and metabolism, the excitable electrophysiological behavior, the dynamics of the intracellular calcium ions, and the exocytosis of granules containing insulin. We explicit the molecular nature of each subsystem, expressing the mutual relationships and the feedbacks that determine the metabolic-electrophysiological behavior of an isolated β-cell. Finally, we discuss the simulation results of the behavior of isolated β-cells as well as of population of electrically coupled β-cells in Langerhans islets, under physiological and pathological conditions, including noninsulin-dependent diabetes mellitus (NIDDM) and hyperinsulinemic hypoglycaemia (PHHI)
Curative surgery for colorectal cancer: long-term results and life expectancy in the elderly.
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Vascular endothelial growth factor, KDR, and cycloxygenase-2 expression in reversal reaction
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