1,721,026 research outputs found
Avvelenamenti da fitofarmaci: aspetti tossicologici ed indagini diagnostiche nelle intossicazioni da organofosforici e carbamati
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The muscarinic modulation of [3H]D-aspartate efflux and [Ca2+](i) levels in rat cerebellar granule cells
No full textThe effects of ACh on [3H]D-aspartate efflux and on calcium levels ([Ca2+]i) were studied at the same time in sister cultures of rat cerebellar granule cells stimulated with electrical pulses (5-20 Hz) or depolarized with KCl (15-40 mM). ACh, 0.3-1000 nM, greatly facilitated the 10-Hz-evoked tritium efflux while its effect on 20 mM KCl-evoked efflux was significantly smaller. ACh, 10-1000 nM, enhanced [Ca2+]i levels to a limited extent under both experimental conditions. Therefore, ACh facilitation was evident above all on the electrically evoked [3H]D-aspartate efflux. The ACh-mediated responses depended on the activation of M3-muscarinic receptors since these responses were blocked by 4-DAMP. ACh, 50 microM, reduced the [Ca2+]i plateau, determined by prolonged electrical or KCl stimulation. This effect was due to its action of M2-receptors being blocked by AF-DX 116. In conclusion, at very low concentrations, ACh greatly facilitated the electrically evoked [3H]D-aspartate efflux through M3-receptors, while at a higher concentrations, it inhibited, through M2-receptors, the rise in [Ca2+]i caused by prolonged cell depolarization
A difficult choice for tiny pests:host-seeking behaviour in Xenos vesparum triungulins
Full text linkThe first-instar larvae of strepsipteran parasites, commonly referred to as otriungulinso, are the host-seeking stage: they must locate, invade and successfully develop in the new host, in order to start their parasitic cycle. Little information is available about the behaviour of Xenos vesparum triungulins. They emerge in batches from the endoparasitic female infecting Polistes dominulus, the primary host, and reach the nest through a vector (a foraging wasp or the parasitised wasp itself). Once there, they have the possibility to penetrate into wasp immatures at different developmental stages. In this study, we performed preliminary analyses aimed to investigate which cues are important to direct triungulin movements during their brief stay in wasp nests. In laboratory conditions we selectively presented different stimuli to Xenos larvae: apparently, the host larva itself is attractive in an open arena, but not inside a confined space, nor are epicuticular compounds of wasp larvae able to control triungulin movements. These are more likely oriented by their gregarious behaviour, whereas light (positive phototaxy) may at a previous stage enhance their emergence via the brood canal opening in the female cephalothorax
Fluorimetric determination of electrically evoked increase in intracellular calcium in cultured cerebellar granule cells
No full textA technique is described to measure the electrically evoked increase in intracellular calcium in cerebellar granule cells cultured on glass coverslips and preloaded with FURA-2. To minimize light scattering, the coverslip containing the granules was placed in the fluorimeter cuvette at a 30° angle to the exciting light beam. The cuvette was provided with 2 platinum electrodes so as to stimulate the neurons with a tangential field. The [Ca2+]itransients were maximized by omitting Mg2+. The fluorescence peaks were directly related to the pulse (1 ms, 100 mA) frequency and to the train length. The responses were completely tetrodotoxin- and [Ca2+]o-dependent and could be replicated 5-6 times at 5-min intervals. At the stimulation rate of 20 Hz for 5 s, a condition ensuring submaximal peaks, the [Ca2+]irose from the basal levels of 41 ± 2.7 nmol/l to 89.6 ± 5.8 nmol/1. The participation of various membrane channels in the electrically induced [Ca2+]iincrease was demonstrated. 4-Aminopyridine (1 mM) increased the height of the peaks to 240%. Both nifedipine (10 Î1⁄4M) and Ï-conotoxin (1 Î1⁄4M) reduced the transients by about 25%. The residual response (in the absence of Mg2+) depended mostly on the release of endogenous glutamate as it proved sensitive to NMDA, AMPA and t-ACPD receptor antagonists. Since a technique to measure the electrically evoked release of d-[3H]aspartate is presently available, the parallel determination of release and of [Ca2+]iin twin populations of cultured granule cells is possible. © 1994
Monoamines modulate the electrically-evoked efflux of 3H-choline from slices of guinea pig nucleus basalis magnocellularis
No full textThe influence exerted by monoamines on acetylcholine release was studied in electrically stimulated slices of guinea pig nucleus basalis magnocellularis (nbM) prelabelled with 3H-choline (3H-Ch). Noradrenaline, 30 μM, and clonidine, 1 μM, reduced the evoked 3H-Ch efflux by about 50%, but phenylephrine, 100 μM. did not; idazoxan, 0.1 μM. but not prazosin, 1 μM, antagonized these effects. pointing to the involvement of alpha2 receptors. Apomorphine, 1 or 30 μM. reduced 3H-Ch efflux from nbM slices as well. The effect was shared by quinpirole, 1 or 10 μM, but not by 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benz-azepine (SKF 38393). 10 μM, and was antagonized by sulpiride, 1 μM, but not by R-(+)-8-chloro-2,3,4,5-tetra-hydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol (SCH 23390). 1 μM, suggesting the involvement of the D2 receptor subtype. 5-hydroxytryptamine (5-HT) 0.3-30 μM, and alphamethyl-5-HT, 10 μM, significantly increased 3H-Ch efflux from nbM slices; the 5-HT2 antagonist ritanseri..
Non-sibling parasites (Strepsiptera) develop together in the same paper wasp
No full textHost discrimination by immature host-seeking endoparasites is a complex and somewhat unexplored topic. In the case of multiple infections, conflicts among conspecifics may occur to monopolize space and resources in the same host. Two or more 1st instar larvae of Xenos vesparum (Strepsiptera, Stylopidae) may enter into a Polistes dominulus (Hymenoptera, Vespidae) larva and develop together until the adult stage of both parasite and host. We carried out a screening of mitochondrial haplotypes in X. vesparum individuals extracted from superparasitized wasps taken in 5 naturally infected nests from different areas of Tuscany (Italy), to assess whether non-sibling parasites may infect the same colony and host. In total, we obtained 12 different haplotypes out of 122 genotyped individuals of both sexes: 17 of 34 superparasitized wasps hosted parasites that originated from females differing in their haplotypes. To date, this is the first described case of superparasitism with non-sibling host-seeking larvae infecting a single individual hymenopteran host. In addition, at least in heavily infected colonies, there is evidence of a male-biased sex-ratio and synchronous development of the parasites, regardless of their haplotypes. Finally, the distribution of haplotypes per nest is consistent with either phoretic infection or larvipositing on nests by means of superparasitized wasp
Effect of adenosine, adenosine triphosphate, adenosine deaminase, dipyridamole and aminophylline on acetylcholine release from electrically-stimulated brain slices
No full textThe effect of adenosine on release of acetylcholine (ACh) was investigated in slices of rat cortex perfused with Krebs solution, at rest and during electrical stimulation at frequencies between 0.2 and 20 Hz. Electrical stimulation brought about a linear increase in release of ACh. Adenosine, in concentrations ranging from 1 to 100 microM, reduced in a dose-dependent manner the release of ACh and was more active on the stimulated than on the resting release. However, the fractional reduction by adenosine of stimulated release of ACh did not vary with increasing stimulation rate. Adenosine triphosphate was less active than adenosine in reducing release of ACh. The inhibitory effect of adenosine was antagonized by aminophylline (0.5 mM) and did not occur when the stimulated release of ACh was enhanced by blocking muscarinic autoreceptors with atropine (15 nM). Aminophylline (0.1 and 0.5 mM) itself exerted a biphasic effect on release of ACh, increasing it at rest and during stimulation at low frequencies, and decreasing it at higher stimulation rates. The manipulation of endogenous adenosine concentrations by adding adenosine deaminase or diphyridamole, an inhibitor of adenosine uptake, had little effect on release of ACh. Dipyridamole, (4 microM), only significantly decreased release of ACh at the 20 Hz stimulation rate
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