Search results for "Calcium in biology"
showing 10 items of 65 documents
Nitric oxide, via activation of guanylyl cyclase, suppresses alpha2-adrenoceptor-mediated 5-hydroxytryptamine release from neuroendocrine epithelial …
1998
Isolated tracheae of newborn rabbits were incubated in vitro and the outflow of 5-hydroxytryptamine (5-HT) was determined by HPLC with electrochemical detection. Evidence has previously been provided that this 5-HT outflow derives from neuroendocrine epithelial (NEE) cells of the airway mucosa. Phenylephrine, at a maximally effective concentration of 10 microM, caused a transient increase in 5-HT outflow by about 250%, an effect mediated by alpha2B-adrenoceptors, as previously shown. The phenylephrine-induced 5-HT release remained unchanged in calcium-free medium, but was reduced by 75% when the tracheae were incubated in calcium-free medium which contained 0.5 mM EDTA, a treatment known to…
[3H]-DA release evoked by low pH medium and internal H+ accumulation in rat hypothalamic synaptosomes: involvement of calcium ions
2003
The pH fluctuations have been often interpreted as an insufficient regulation or as a consequence of the onset of pathological events, such as ischemia, in which a significant decrease in pH levels occurs. Neurotransmitter release appears to be affected by pH drop significantly. In this study, we investigated the effect of an extracellular and an intracellular acidification on tritiated dopamine release ([3H]-DA release), from superfused rat hypothalamic synaptosomes. When compared to basal release, extracellular acidification, due to a reduction in the external pH of the nominally carbonic-free superfusion media, provoked a significant increase in [3H]-DA release that showed a sensitivenes…
Actions of alpha-adrenoceptor blocking agents on two types of intracellular calcium stores mobilized by noradrenaline in rat aorta.
1993
In isolated rat aortic strips noradrenaline induces a biphasic contractile response in Ca-free medium, associated with two different intracellular calcium pools, one of which is common to caffeine. We analyzed the mechanisms involved in the depletion and repletion of both intracellular Ca pools sensitive to noradrenaline in different experimental procedures in presence of prazosin, phentolamine and yohimbine. At 37 degrees C the alpha-adrenergic blocking agents inhibited contractile responses to noradrenaline in Ca-free medium, with prazosin being highly selective. alpha 2-adrenoceptors probably do not participate in the release of Ca from internal stores, as no contractile response was obs…
Dynamic studies on living cells with an atomic force fluorescence microscope
2001
Analysis of the reaction of bone structure to mechanical stimulation is a key issue in understanding the origins of osteoporosis and mechanical adaptation of living bone to external forces. This is thought to be regulated on a cellular level. We have investigated quantitative mechanical stimulation of single bone cells and their immediate intracellular calcium responses using a combination of an atomic force microscope (AFM) and a fluorescence microscope, developed in our laboratory. The force stimulation system can apply quantified forces in the pico- and nano-newton regime on exactly defined positions of a cell. We present here the first measurements using this system on the mechanically …
Imbalance of Neuronal Excitability as a Cause of Psychic Disorder
1989
Electrical activity of neurons is characterized by an equilibrium between excitation and inhibition, maintained by negative feedback mechanisms at the cellular, synaptic and neurohumoral level. A central mechanism is the interaction between excitatory calcium currents and inhibitory potassium currents, linked by intracellular calcium concentration. These conductances are located in the somato-dendritic part of the neuron and fundamentally influence spontaneous activity and the processing of synaptic input. The electrical equilibrium is altered by different neuromodulators, such as biogenic amines, peptides, and steroids and by several drugs. Neuromodulatory desequilibration towards increase…
Calcium signaling in plant cell organelles delimited by a double membrane.
2006
AbstractIncreases in the concentration of free calcium in the cytosol are one of the general events that relay an external stimulus to the internal cellular machinery and allow eukaryotic organisms, including plants, to mount a specific biological response. Different lines of evidence have shown that other intracellular organelles contribute to the regulation of free calcium homeostasis in the cytosol. The vacuoles, the endoplasmic reticulum and the cell wall constitute storage compartments for mobilizable calcium. In contrast, the role of organelles surrounded by a double membrane (e.g. mitochondria, chloroplasts and nuclei) is more complex. Here, we review experimental data showing that t…
Endoplasmic Reticulum Stress Inhibition Protects against Excitotoxic Neuronal Injury in the Rat Brain
2007
Elevated brain glutamate with activation of neuronal glutamate receptors accompanies neurological disorders, such as epilepsy and brain trauma. However, the mechanisms by which excitotoxicity triggers neuronal injury are not fully understood. We have studied the glutamate receptor agonist kainic acid (KA) inducing seizures and excitotoxic cell death. KA caused the disintegration of the endoplasmic reticulum (ER) membrane in hippocampal neurons and ER stress with the activation of the ER proteins Bip, Chop, and caspase-12. Salubrinal, inhibiting eIF2α (eukaryotic translation initiation factor 2 subunit α) dephosphorylation, significantly reduced KA-induced ER stress and neuronal deathin vivo…
Morphologic Damage and Changes of Intracellular Calcium-Binding Sites after Acute Noise Trauma in the Organ of Corti of the Guinea Pig
1993
In guinea pigs, an acute acoustic trauma was created by 6 consecutive gunshots. The sound pressure at the ear drum was 156 +/- 4 dB, the frequency maximum was between 4 and 6 kHz. Sixty hours after the noise trauma, the animals were decapitated, and the cochleae were prepared for microscopic analysis of the resulting trauma to the organ of Corti. During the process of fixation, the potassium-pyroantimonate precipitation reaction was performed to localize calcium-binding sites. The pattern of cell morphology and the distribution of calcium-binding sites was compared to that of normal control animals. Morphologic changes of the cells in the organ of Corti correlated with changes of the cellul…
The cAMP Pathway Sensitizes VR1 Expressed in Oocytes from <i>Xenopus laevis</i> and in CHO Cells
2003
The vanilloid receptor 1 (VR1) is a heat-activated cation channel which also responds to capsaicin and other chemical stimuli. Protein kinase C has a stimulatory effect on VR1 activity, either alone or after activation with capsaicin. The influence of the cAMP-signaling pathway on the effects of capsaicin is controversial. To clarify this, the actions of capsaicin and the modulatory effects of forskolin, pCPT-cAMP, and isobutylmethylxanthine were studied in <i>Xenopus laevis</i> oocytes expressing rat VR1 and in CHO cells expressing human VR1. Capsaicin activated the VR1 channel and increased the intracellular calcium concentration. The effects of capsaicin were enhanced by fors…
Optogenetically Controlled Activity Pattern Determines Survival Rate of Developing Neocortical Neurons
2021
A substantial proportion of neurons undergoes programmed cell death (apoptosis) during early development. This process is attenuated by increased levels of neuronal activity and enhanced by suppression of activity. To uncover whether the mere level of activity or also the temporal structure of electrical activity affects neuronal death rates, we optogenetically controlled spontaneous activity of synaptically-isolated neurons in developing cortical cultures. Our results demonstrate that action potential firing of primary cortical neurons promotes neuronal survival throughout development. Chronic patterned optogenetic stimulation allowed to effectively modulate the firing pattern of single ne…