Search results for "Calcium"
showing 10 items of 1740 documents
Carbonic anhydrase activity in a calcium-mobilizing epithelium of the crustacean Orchestia cavimana during molting
1987
We investigated the involvement of the enzyme, carbonic anhydrase, in the calcification-decalcification processes occurring in the posterior caeca of the midgut of the terrestrial crustacean, Orchestia cavimana, before and after exuviation. This enzyme was ultrahistochemically localized throughout the membranes of the caecal epithelium as well as extracellularly, i.e., within pre-exuvial calcareous concretions and postexuvial calcified spherules. During the molt cycle, the pattern of carbonic anhydrase activity in the posterior caeca was correlated with the calcium content at this level. Acetazolamide treatment in vivo inhibited about 50% of the calcium uptake during both pre-exuvial secret…
Acetylsalicylic acid reduces heat responses in rat nociceptive primary sensory neurons – evidence for a new mechanism of action
2002
Acetylsalicylic acid (ASA) is thought to exert its peripheral analgesic effects via inhibition of cyclooxygenase. We now studied the effects of ASA on heat responses in primary nociceptive neurons by whole-cell patch-clamp and calcium microfluorimetry experiments. Heat-evoked inward currents in acutely dissociated rat dorsal root ganglion neurons were significantly reduced by ASA in a dose-dependent and reversible manner (IC(50) 375 nM, Hill slope -2.2, maximum effect 55%). Heat-evoked calcium transients (measured with FURA-2) were reversibly reduced by 53+/-14% (P0.05) by co-application of 1 microM ASA. The low IC(50) value, the rapid occurrence, and the reversibility of the observed effec…
Changes in cytosolic calcium in response to noxious heat and their relationship to vanilloid receptors in rat dorsal root ganglion neurons.
2001
Heat transduction mechanisms in primary nociceptive afferents have been suggested to involve a vanilloid receptor channel with high calcium permeability. To characterize the changes in free cytosolic calcium evoked by noxious heat stimuli (< or =51 degrees C, 10s), we performed microfluorometric measurements in acutely dissociated small dorsal root ganglion neurons (< or =32.5 microm) of adult rats using the dye FURA-2. Only neurons that responded with a reversible increase in intracellular calcium to high potassium were evaluated. Heat-induced calcium transients (exceeding mean + 3S.D. of the temperature dependence of the dye) were found in 66 of 105 neurons. These transients increased non…
Acute effects of antidepressant drugs on long-term potentiation (LTP) in rat hippocampal slices.
1991
The actions of three clinically effective antidepressant drugs with different pharmacological profiles were investigated in the CA1 area of rat hippocampal slices. Imipramine and (+) or (-)-oxaprotiline had negligible effects on population spikes evoked by stratum radiatum stimulation, but reduced postsynaptic excitability in low Ca high Mg medium after an exposure of more than 15 min. Imipramine and (+)-oxaprotiline at 10 mumol/l enhanced long-term potentiation (LTP) when a lower stimulation strength was applied while (+)-oxaprotiline reduced LTP when a higher stimulus amplitude was used to evoke population spikes. (-)-oxaprotiline (levoprotiline) had a similar effect which was, however, n…
Spontaneous release of endogenous 5-hydroxytryptamine and 5-hydroxyindoleacetic acid from the isolated vascularly perfused ileum of the guinea-pig
1987
The spontaneous release of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid from the enterochromaffin cells of the small intestine into the portal circulation was investigated in vitro using the vascularly perfused ileum of the guinea-pig. The release of 5-hydroxytryptamine decreased by 70% in a calcium-free medium and by 35% in the presence of tetrodotoxin. Inhibition of monoamine oxidase activity by pargyline (100 microM) had no effect on the spontaneous release of 5-hydroxytryptamine although it caused a 75% reduction in the outflow of 5-hydroxyindoleacetic acid. Imipramine (1 microM), an inhibitor of neuronal uptake of 5-hydroxytryptamine, reduced the 5-hydroxyindoleace…
Mechanisms underlying the inhibitory effects induced by pituitary adenylate cyclase-activating peptide in mouse ileum
2005
Abstract The aim of this study was to investigate the signal transduction mechanisms underlying the inhibitory effect induced by pituitary adenylate cyclase activating peptide (PACAP-27) on the spontaneous contractile activity of longitudinal muscle of mouse ileum. Mechanical activity of ileal segments was recorded isometrically in vitro. PACAP-27 produced apamin-sensitive reduction of the amplitude of the spontaneous contractions. 9-(Tetrahydro-2-furanyl)-9H-purin-6-amine (SQ 22,536), adenylate cyclase inhibitor, or genistein and tyrphostin 25, tyrosine kinase inhibitors, had negligible effects on PACAP-27-induced inhibition. PACAP-27 effects were significantly inhibited by U-73122, phopho…
Effect of hypolipidemic treatment on emerging risk factors in mixed dyslipidemia: a randomized pilot trial
2012
Background The effects of different hypolipidemic treatment strategies on emerging atherosclerosis risk factors remain unknown. Materials and methods This is a prespecified analysis of a prospective, randomized, open-label, blinded end point (PROBE) study (ClinicalTrials.gov identifier: NCT01010516). Patients (n = 100) with mixed dyslipidaemia on a standard statin dose who had not achieved lipid targets were randomized to switch to the highest dose of rosuvastatin (40 mg/day) or to add-on-statin extended release nicotinic acid (ER-NA)/laropiprant (LRPT) or to add-on-statin micronized fenofibrate for a total of 3 months. Results Following 3 months of treatment, low-density lipoprotein (LDL) …
Adrenaline, DB-c-AMP and myocardial 45Ca exchange. Comparative studies in rat and guinea-pig auricles
1973
The positive inotropic effect of adrenaline has been assumed to result from an increase in the intracellular level of c-AMP which, in turn, might enhance the permeability of the cardiac cell membrane to Ca2+. In order to further test this hypothesis, the effects of cyclic N6-2′-O-dibutyryl-adenosine-3′,5′-monophosphate (DB-c-AMP; 10−3 M) on mechanical performance, 45Ca uptake and total tissue calcium concentration were investigated in electrically stimulated (120 beats/min) left auricles isolated from female rats weighing 180–220 g. The experiments were performed in Tyrode solution containing 0.9 mM CaCl2; the duration of 45Ca exposure was 3–60 min. In this study, DB-c-AMP markedly enhanced…
RELATIONSHIP BETWEEN THEOPHYLLINE UPTAKE AND INOTROPIC EFFECT IN THE GUINEA-PIG HEART
1974
1 The time course of the positive inotropic effect of theophylline was compared with the time course of the uptake and release of [(3)H]-theophylline in guinea-pig isolated, electrically driven hearts perfused by the Langendorff method.2 Formation of theophylline metabolites could not be detected under the experimental conditions used.3 Theophylline entered myocardial tissue very rapidly in two different phases. The first process (half-time 21 s) amounted to 93% and the second (half-time 5 min 50 s) to 7% of the total uptake. The development of the positive inotropic effect of theophylline was about four times faster than even the rapid component of the uptake of the drug into the myocardiu…
Synthesis, configuration, and calcium modulatory properties of enantiomerically pure 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylates.
1992
Enantiomerically pure hexahydroquinolinones of the structural type 9 were prepared by a variation of the Hantzsch synthesis in which an optically active acetoacetate served as a chiral auxiliary reagent. Determinations of the de and ee values are described. The absolute configurations of the optically pure products were characterized by single-crystal X-ray analysis. The antipodes 9a and 9b exhibited calcium antagonistic activities on smooth musculature; the (S)-(-)-enantiomer 9b was the more potent compound with regard to the EC50 values which differed by a factor of 100; the intrinsic activity of 9b was 1.2, compared with a value of 0.54 for 9a. On the other hand, R-(+)-9a exerted positiv…