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141.
Résumé La teneur en glutamine dans le cerveau des chatons nouveau-nés au cours de la maturation cérébrale est comparable à celle des animaux adultes. Les concentrations en acide glutamique et en GABA augmentent et vers la fin du premier mois postnatal correspondent au niveau des adultes. 相似文献
142.
Summary On the basis of experimental evidence, it is proved that phthalyl urea has the structure II, and not structure I, proposed byPiutti and generally accepted by other investigators. 相似文献
143.
G. Nikezić A. Horvat N. Nedeljković J. V. Martinović 《Cellular and molecular life sciences : CMLS》1996,52(3):217-220
Effects of 17-estradiol (E2) in vitro on Na-dependent Ca2+ efflux from, and depolarization-induced Ca2+ uptake into, the nerve cell were studied with the use of synaptosomes isolated from the brain stem, mesencephalic reticular formation (MRF), caudate nucleus and the hippocampus of long-term ovariectomized adult female rats. It was found that E2 (1) at a concentration of 10 nM or lower, stimulates Na-dependent Ca2+ efflux in the caudate nucleus and hippocampus, and does not affect the efflux in MRF and brain stem; (2) at concentrations above 10 nM has no effect on the Ca2+ efflux in any of the four structures investigated; and (3) produces a biphasic effect on the depolarization-induced Ca2+ uptake, increasing it in all structures except MRF at 10 nM concentration, and decreasing it at concentrations higher than 10 nM, irrespective of the structure investigated. These results suggest that E2, acting at extranuclear sites, modulates synaptic transmission via alterations of Ca2+ transport mechanisms in nerve endings. 相似文献
144.
Summary Thymectomized, lethally irradiated rats reconstituted with syngeneic bone marrow were injected with rat brain in complete Freund adjuvant mixture. Both, they and sham-thymectomized, irradiated and bone marrow protected rats displayed a higher incidence of leg paralysis than normal non-irradiated animals. Thymectomy lowered the incidence of the disease.Supported by the Research Fund of Croatia (Zagreb). 相似文献
145.
A2 adenosine receptors were characterized in human glomerular mesangial cells using [3H] 5-N-ethylcarboxamidoadenosine (NECA) as a tracer. There was a single group of receptor sites with a KD of 184 nM, and a number of sites of 317 fmol/mg of cell protein. Adenosine agonists increased 5-nucleotidase activity via A2 receptor stimulation. The specific A2 agonist-NECA, at 0.1 and 1 m, was a potent inhibitor of DNA synthesis. 相似文献
146.
The answer to the fine-tuning problem of the universe has been traditionally sought in terms of either design or multiverse. In philosophy circles, this is sometimes expanded by adding the option of explanatory nihilism—the claim that there is no explanation for statements of that high level of generality: fine-tunings are brute facts. In this paper, we consider the fourth option which, at least in principle, is available to us: co-evolution of the universe and observers. Although conceptual roots of this approach could be found already in ancient stoicism, it is still the least investigated explanatory option for resolving the problem of empirical fine tunings. We offer two preliminary models along which the co-evolution hypothesis could be developed further. They are still on the level of speculative metaphysics, but there are opportunities along the way to generate predictions which are in principle testable, especially in the domain of large-scale numerical simulations. 相似文献
147.
Nikola Vesović Ljubodrag Vujisić Vesna Perić-Mataruga Gordana Krstić Marija Nenadić Mirjana Cvetković 《Journal of Natural History》2017,51(9-10):545-560
Although all ground beetles have pygidial glands homologous in structure and function, there are many differences among species, often significant, in terms of chemical composition of the secretion and morphology of the gland components. In this paper, two predatory ground beetle species of the genus Carabus, namely C. (Tomocarabus) convexus and C. (Procrustes) coriaceus, were subjected to chemical, morphological and histological study of their pygidial glands and the glands’ secretions. Altogether, three carboxylic acids were isolated, and the pygidial gland reservoir and other glandular parts are morphologically described in the study. We also tested whether there exist differences in chemical content of the secretion obtained by upsetting the beetles in a traditional way and that obtained directly from intact reservoirs. Detailed data on morphology of the pygidial glands of both species are presented, as well as updated information about the chemical components of the glandular secretions. Apart from tiglic and methacrylic acids, which are typical for Carabus pygidial secretions, we also found benzoic acid as a minor component of the secretion in both species. In addition, a chemotaxonomic overview of Carabus taxa is given in the paper. 相似文献
148.
Hinke CB Böhmer M Boutachkov P Faestermann T Geissel H Gerl J Gernhäuser R Górska M Gottardo A Grawe H Grębosz JL Krücken R Kurz N Liu Z Maier L Nowacki F Pietri S Podolyák Z Sieja K Steiger K Straub K Weick H Wollersheim HJ Woods PJ Al-Dahan N Alkhomashi N Ataç A Blazhev A Braun NF Čeliković IT Davinson T Dillmann I Domingo-Pardo C Doornenbal PC de France G Farrelly GF Farinon F Goel N Habermann TC Hoischen R Janik R Karny M Kaşkaş A Kojouharov IM Kröll T Litvinov Y Myalski S Nebel F 《Nature》2012,486(7403):341-345
The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During β(+)-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy for the decay of (100)Sn, the heaviest doubly magic nucleus with equal numbers of protons and neutrons. In the β-decay of (100)Sn, a large fraction of the strength is observable because of the large decay energy. We determine the largest Gamow-Teller strength so far measured in allowed nuclear β-decay, establishing the 'superallowed' nature of this Gamow-Teller transition. The large strength and the low-energy states in the daughter nucleus, (100)In, are well reproduced by modern, large-scale shell model calculations. 相似文献
149.
150.
The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences, with direct implications for planet-forming processes in pre-planetary disks. The recent detection of four propeller-shaped features in Saturn's A ring proved the presence of large boulder-sized moonlets in the rings. Their existence favours ring creation in a catastrophic disruption of an icy satellite rather than a co-genetic origin with Saturn, because bodies of this size are unlikely to have accreted inside the rings. Here we report the detection of eight new propeller features in an image sequence that covers the complete A ring, indicating embedded moonlets with radii between 30 m and 70 m. We show that the moonlets found are concentrated in a narrow 3,000-km-wide annulus 130,000 km from Saturn. Compared to the main population of ring particles (radius s < 10 m), such embedded moonlets have a short lifetime with respect to meteoroid impacts. Therefore, they are probably the remnants of a shattered ring-moon of Pan size or larger, locally contributing new material to the older ring. This supports the theory of catastrophic ring creation in a collisional cascade. 相似文献