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141.
M a Belen'ki? S Bountzioukas G Gonzales D Ko K Lederis A L Polenov 《Zhurnal evoliutsionno? biokhimii i fiziologii》1990,26(3):340-346
A significant increase of the content of corticosterone in the blood collected from intravenous cannula or by intracardiac punction has been detected using radioimmunoassay in non-operated and adenohypophysectomized frogs Rana catesbeiana subjected to dehydration in 6.2% mannitol solution during 24 hours. The osmolality of the blood plasma of these animals also increases although less significantly than the growth of plasma corticosterone content. There is a tendency to substantial increase of plasma arginine-vasotocin level prior to the growth of corticosterone level, already after 6 hours of dehydration. Based on the present results and literature data, it is suggested that in adenohypophysectomized frogs lacking endogenous ACTH just the increase of blood arginine-vasotocin level results in a substantial activation of corticosteroid-producing cells of the interrenal gland and in the growth of plasma content of corticosterone. 相似文献
142.
4-Aminopyridine is a powerful convulsant that induces the release of neurotransmitters, including glutamate. We report the effect of intrahippocampal administration of 4-aminopyridine at six different concentrations through microdialysis probes on EEG activity and on concentrations of extracellular amino acids and correlate this effect with histological changes in the hippocampus. 4-Aminopyridine induced in a concentration-dependent manner intense and frequent epileptic discharges in both the hippocampus and the cerebral cortex. The three highest concentrations used induced also a dose-dependent enhancement of extracellular glutamate, aspartate, and GABA levels and profound hippocampal damage. Neurodegenerative changes occurred in CA1, CA3, and CA4 subfields, whereas CA2 was spared. In contrast, microdialysis administration of a depolarizing K+ concentration and of tetraethylammonium resulted in increased amino acid levels but no epileptic activity and no or moderate neuronal damage. These results suggest that seizure activity induced by 4-aminopyridine is due to a combined action of excitatory amino acid release and direct stimulation of neuronal firing, whereas neuronal death is related to the increased glutamate release but is independent of seizure activity. In addition, it is concluded that the glutamate release-inducing effect of 4-aminopyridine results in excitotoxicity because it occurs at the level of nerve endings, thus permitting the interaction of glutamate with its postsynaptic receptors, which is probably not the case after K+ depolarization. 相似文献
143.
Mayra Domínguez-Pérez Arturo Simoni-Nieves Patricia Rosales Natalia Nuño-Lámbarri Mónica Rosas-Lemus Verónica Souza Roxana U. Miranda Leticia Bucio Salvador Uribe Carvajal Jens U. Marquardt Daekwan Seo Luis E. Gomez-Quiroz María Concepción Gutiérrez-Ruiz 《Journal of cellular physiology》2019,234(5):7213-7223
144.
The present paper describes and illustrates the new speciesAverrhoidium dalyi and provides a key to the species ofAverrhoidium. The new species is known from lowland, terra firme forest in the Purus River basin, in Acre, Brazil, and from Manu National
Park in Madre de Dios, Peru.
Resumen En el presente artículo se describe, discute e ilustra la nueva especieAverrhoidium dalyi coleccionada en la cuenca del Río Purus en el estado de Acre, Brasil y en el Parque Nacional del Manu en el departamento Madre de Dios, Peru. También en el presente se provee una clave para las especies deAverrhoidium.相似文献
145.
146.
María del Mar Rueda Sara Pasadas-del-Amo Beatriz Cobo Rodríguez Luis Castro-Martín Ramón Ferri-García 《Biometrical journal. Biometrische Zeitschrift》2023,65(2):2200035
Web surveys have replaced Face-to-Face and computer assisted telephone interviewing (CATI) as the main mode of data collection in most countries. This trend was reinforced as a consequence of COVID-19 pandemic-related restrictions. However, this mode still faces significant limitations in obtaining probability-based samples of the general population. For this reason, most web surveys rely on nonprobability survey designs. Whereas probability-based designs continue to be the gold standard in survey sampling, nonprobability web surveys may still prove useful in some situations. For instance, when small subpopulations are the group under study and probability sampling is unlikely to meet sample size requirements, complementing a small probability sample with a larger nonprobability one may improve the efficiency of the estimates. Nonprobability samples may also be designed as a mean for compensating for known biases in probability-based web survey samples by purposely targeting respondent profiles that tend to be underrepresented in these surveys. This is the case in the Survey on the impact of the COVID-19 pandemic in Spain (ESPACOV) that motivates this paper. In this paper, we propose a methodology for combining probability and nonprobability web-based survey samples with the help of machine-learning techniques. We then assess the efficiency of the resulting estimates by comparing them with other strategies that have been used before. Our simulation study and the application of the proposed estimation method to the second wave of the ESPACOV Survey allow us to conclude that this is the best option for reducing the biases observed in our data. 相似文献
147.
Short cationic antimicrobial peptides (AMPs) are believed to act either by inducing transmembrane pores or disrupting membranes
in a detergent-like manner. For example, the antimicrobial peptides aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1,
despite being closely related, appear to act by fundamentally different mechanisms depending on their length. Using molecular
dynamics simulations, the structural properties of these four peptides have been examined in solution as well as in a variety
of membrane environments. It is shown that each of the peptides has a strong preference for binding to regions of high membrane
curvature and that the structure of the peptides is dependent on the degree of local curvature. This suggests that the shorter
peptides aurein 1.2 and citropin 1.1 act via a detergent-like mechanism because they can induce high local, but not long-range
curvature, whereas the longer peptides maculatin 1.1 and caerin 1.1 require longer range curvature to fold and thus bind to
and stabilize transmembrane pores. 相似文献
148.
149.
Insulin-expressing cells that have been differentiated from human pluripotent stem cells in vitro lack the glucose responsiveness characteristic of mature beta cells. Beta-cell maturation in mice was studied to find genetic markers that enable screens for factors that induce bona fide beta cells in vitro. We find that functional beta-cell maturation is marked by an increase in the glucose threshold for insulin secretion and by expression of the gene urocortin 3. 相似文献
150.
Synaptosomes were isolated from cerebrums of rats fed standard (20% protein) or protein-free diets for 30 days. Arrhenius plots of their (Na+/K+)ATPase activities revealed a transition temperature of 25.5°C for control rats and 23.4°C for rats on protein-free diet, indicating that the latter increases synaptosomal membrane fluidity. The only change observed in the composition of the synaptosomal membranes was a 26% decrease of sialic acid. In synaptosomes from rats on protein-free diet the uptake of tyrosine was slightly reduced while that of glutamate was not affected. However, the exit of glutamate was reduced. 相似文献