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Boguszewiecz, J. and Braszko, J. J.: The significance of Na⁺ ions in angiotensin II stimulation of acզuisition of active avoidance in rats. Acta physiol. pol., 1989, 40 (4): 409-412. Angiotensin II (1 μg) dissolved in water and given intracerebroventricularly on day 1, 15 min before the first learning session, enhanced rate of learning of active avoidance in rats over the next 7 days. However, the peptide, dissolved in 0.25 M NaCl, and given at the same dose and route,, stimulated learning significantly more than that dissolved in water. A possible involvement of Na⁺ ions in facilitating learning action of A II is discussed.
Gliomas are highly invasive brain tumors with the occurence of numerous microglial cells arround the tumor. The density of these cells positively correlates with the malignancy, invasiveness and grading of gliomas. Sialic acid-binding immunoglobulin superfamily lectins (Siglecs) are members of immunoglobulin superfamily that recognize sialic acid residues of glycoproteins. Siglecs have intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIM), implicating them in the suppression of immunoreceptor signaling. Siglec-F is a CD33-related Siglec that binds to 2.3-, 2.6- and weakly 2.8-linked sialic acid. We analysed distribution and function of sialic acids and their receptor, Siglec-F, in glioma-microglia interactions. We observed Siglec-F gene transcription and Siglec-F protein expression in cultured embryonic stem cells derived microglia as well as high level of sialic acids in the mouse glioma cell line GL261. Flow cytomety analysis showed that sialylated structures expressed at the plasma membrane of glioma cells are recognized by recombinant mouse Siglec-F/Fc chimera. Enzymatic desialylation of the glioma cells with endoneuraminidase and α-neuraminidase significantly decreased binding of Siglec-F protein. Our data demonstrate that activation of immunosuppressive Siglec-F receptor by sialic acids can modulate microglia activity and immune response against malignant cells.
Omega-3 polyunsaturated fatty acids (FAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may slow cognitive decline. DHA plays an important role in neural function. Decreases in plasma DHA are associated with cognitive decline in healthy elderly adults and in patients with Alzheimer’s disease. In this study we tested a hypothesis that DHA - active constituent of cod liver oil alleviates negative impact of prolonged restraint stress on cognititive functions of male Wistar rats. Specifically, we attempted to characterize the preventive action of long-lasting treatment with DHA (daily dose 300 mg/kg, p.o. for 21 days) in comparison with positive control (fluoxetine: 10 mg/ kg daily, p.o. for 21 days) against an impairment caused by chronic restraint stress (2 h daily for 21 days) on recognition memory tested in an object recognition task and on the spatial working memory tested in Morris water maze (MWM). We found that DHA administration statistically significantly prevented deleterious effects of chronic restraint stress both on recognition (p<0.01) and the working spatial memory (p<0.001). In conclusion, the present study demonstrated that prolonged treatment with a standardized high-concentration DHA preparation reduced stress-induced spatial reference and working memory and recognition memory impairments as measured in the MWM and object recognition task. The present findings not only corroborate the sparse literature concerning the behavioral effects of DHA but also demonstrate for the first time that the use of DHA facilitates functional recovery after stress evoked cognitive brain damage with potency comparable with fluoxetine. This effect appears to be sustained over time.
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The neuropeptide angiotensin II (Ang II) has been recently found to be involved in cognitive processes. Both AT1 and AT2 angiotensin receptors seem to mediate this action. However, unspecific behavioural effects of the peptide, particularly motor and emotional, appear to influence the interpretation of cognition-oriented tests and contribute to considerable differences in opinions of various authors on the subject. In this study, aimed specifically at the assessment of these effects, we found small and insignificant changes in motor performance measured in open field after intracebroventricular injections of Ang II and its receptor subtype-specific antagonists; losartan (AT1) and PD 123319 (AT2). However, Ang II was found to increase substantially anxiety measured in elevated 'plus' maze and impair motor coordination measured in 'chimney test'. Interestingly, both antagonists abolished Ang II generated anxiety and only losartan counteracted impaired motor coordination caused by the peptide. The AT2 receptor antagonist PD 123319 impairing motor coordination on its own, nonetheless partly diminished that caused by Ang II. Therefore it appears safe to conclude that mood but not motor effects of AT1 and AT2 receptor affecting drugs may significantly bias interpretation of the cognition - oriented tests on these drugs.
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