introduction: since organophosphorus compounds (op) are toxic and designed to destroy insects and pest species, there are many hazards associated with their use. although, the main target site of these compounds is acetylcholinesterase (ache), however it has become increasingly evident that ops have also other direct effects on cellular processes. in the present study, the effects of low concen...

Introduction: Since organophosphorus compounds (OP) are toxic and designed to destroy insects and pest species, there are many hazards associated with their use. Although, the main target site of these compounds is acetylcholinesterase (AChE), however it has become increasingly evident that OPs have also other direct effects on cellular processes. In the present study, the effects of low con...

The peritrich ciliate Vorticella sp. exhibits cellular contraction of an all-or-nothing type in response to a mechanical stimulus. Many authors have suggested that the contraction may be controlled by the cytosolic level of Ca2+, since glycerol-extracted Vorticella contracts when Ca2+ is added to the external solution. However, no direct evidence for the increase in cytosolic [Ca2+] has yet bee...

Current clamp and modeling studies of low-threshold calcium spikes in cells of the cat's lateral geniculate nucleus. All thalamic relay cells display a voltage-dependent low-threshold Ca2+ spike that plays an important role in relay of information to cortex. We investigated activation properties of this spike in relay cells of the cat's lateral geniculate nucleus using the combined approach of ...

We have examined statistically the actions of thyrotropin-releasing hormone (TRH) and Bay K 8644, an L-type Ca(2+)-channel agonist, on the frequency and shape of cytosolic Ca2+ spikes in individual GH4C1 rat pituitary cells. TRH induced a brief (0-40 s) suppression of Ca2+ spikes followed by a period (40-200 s) of increased spike frequency. TRH treatment reduced the rate of rise and amplitude o...

The action of arginine vasopressin (AVP) on cytosolic free Ca2+ concentration ([Ca2+]i) was investigated in single rat pituitary corticotrophs using indo-1 microfluorimetry, in part in combination with the monitoring of membrane electrical events with the perforated patch-clamp technique. In corticotrophs showing the series of short-lived [Ca2+]i rises (transient pattern) in response to cortico...

Single cardiac ryanodine receptor (RyR) channel adaptation was previously defined with Ca2+ stimuli produced by flash photolysis of DM-nitrophen (caged-Ca+2). Photolysis of DM-nitrophen induced a very fast Ca+2 overshoot (Ca+2 spike) at the leading edge of the Ca+2 stimuli. It has been suggested that adaptation (tau approximately 1.3 s) may reflect Ca+2 slowly coming off the RyR Ca+2 activation...

Inhibitory synaptic transmission between leech heart interneurons consist of two components: graded, gated by Ca2+ entering by low-threshold [low-voltage-activated (LVA)] Ca channels and spike-mediated, gated by Ca2+ entering by high-threshold [high-voltage-activated (HVA)] Ca channels. Changes in presynaptic background Ca2+ produced by Ca2+ influx through LVA channels modulate spike-mediated t...

In rat pituitary cells from estrogen-induced hyperplasia, angiotensin II (ANG II) does not evoke a clear spike elevation of intracellular Ca2+concentration ([Ca2+]i) but induces a plateau increase. The present work was undertaken to establish whether this difference was related to a differential participation of intracellular and/or plasma membrane Ca2+ channels. We first tested the effect of 1...

On fertilisation of mouse oocytes, the fusing spermatozoon triggers a series of repetitive calcium (Ca2+) spikes. The Ca2+ spikes seem to be necessary for successful progression through the cell cycle and are regulated in a cell-cycle-dependent manner. The spikes appear to require the linkage of continuous Ca2+ influx to the periodic release of Ca2+ from intracellular stores by a process of Ca(...