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Kevin H. J. Park John Meitzen Ignacio T. Moore Eliot A. Brenowitz David J. Perkel 《Developmental neurobiology》2005,64(2):181-191
Many animals exhibit seasonal changes in behavior and its underlying neural substrates. In seasonally breeding songbirds, the brain nuclei that control song learning and production undergo substantial structural changes at the onset of each breeding season, in association with changes in song behavior. These changes are largely mediated by photoperiod‐dependent changes in circulating concentrations of gonadal steroid hormones. Little is known, however, about whether changes in the electrophysiological activity of neurons accompany the dramatic morphological changes in the song nuclei. Here we induced seasonal‐like changes in the song systems of adult white‐crowned sparrows and used extracellular recording in acute brain slices from those individuals to study physiological properties of neurons in the robust nucleus of the arcopallium (RA), a pre‐motor nucleus necessary for song production. We report that: RA neurons from birds in breeding condition show a more than twofold increase in spontaneous firing rate compared to those from nonbreeding condition; this change appears to require both androgenic and estrogenic actions; and this change is intrinsic to the RA neurons. Thus, neurons in the song circuit exhibit both morphological and physiological adult seasonal plasticity. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 相似文献
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Eliot M. Herman Brian W. Tague Leslie M. Hoffman Susanne E. Kjemtrup Maarten J. Chrispeels 《Planta》1990,182(2):305-312
Soluble proteins that reside in the lumen of the endoplasmic reticulum are known to have at their carboxyterminus the tetrapeptides KDEL or HDEL. In yeast and mammalian cells, these tetrapeptides function as endoplasmic reticulum (ER)-retention signals. To determine the effect of an artificially-introduced KDEL sequence at the exact carboxyterminus of a plant secretory protein, we modified the gene of the vacuolar protein phytohemagglutinin-L (PHA) so that the amino-acid sequence would end in LNKDEL rather than LNKIL, and expressed the modified gene in transgenic tobacco with a seed-specific promoter. Analysis of the glycans of PHA showed that most of the control PHA had one endoglycosidase H-sensitive and one endoglycosidase H-resistant glycan, indicating that it had been processed in the Golgi complex. On the other hand, a substantial portion of the PHA-KDEL (about 75% at mid-maturation and 50% in mature seeds) had two endoglycosidase H-sensitive glycans. Phytohemagglutinin with two endoglycosidase H-sensitive glycans is normally found in the ER. Using immunocytochemistry we found that a substantial portion of the PHA-KDEL was present in the ER or accumulated in the nuclear envelope while the remainder was found in the protein storage vacuoles (protein bodies). We interpret these data to indicate that carboxyterminal KDEL functions as an ER retention-retardation signal and causes protein to accumulate in the nuclear envelope as well as in the ER. The incomplete ER retention of this protein which is modified at the exact carboxyterminus may indicate that structural features other than carboxyterminal KDEL are important if complete ER retention is to be achieved.Mention of trademark, proprietary product, or vendor, does not constitute a guarantee or warrenty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.Abbreviations endoH
endoglycosidase H
- ER
endoplasmic reticulum
- Mr
relative molecular mass
- PHA
phytohemagglutinin
- SDS
sodium dodecyl sulfate
- PAGE
polyacrylamide gel electrophoresis
- TBST
Tris-buffered saline containing Tween 20
We thank Debra Donaldson for her contribution to the PHA gene constructions. This work has been supported by grants from the National Science Foundation (Cell Biology) and the Department of Energy (DE-FG03-86ER13497) to Maarten J. Chrispeels. The assistance of the staff of the Electron Microscope Laboratory, USDA, Beltsville is gratefully acknowledged. 相似文献
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Synopsis A combined biochemical, histochemical and cytochemical study was made of cardiac glycogen distribution following intravenous infusions of varying doses of isoproterenol in anaesthetized, open-chested dogs. There was a dose-dependent decrease in glycogen levels in biopsies of the posterolateral wall of the left ventricle which also exhibited a transmural gradient with the endocardial third the most severely affected. Periodic acid-Schiff (PAS) histochemical studies also suggested a transmural gradient. There was, however, a marked variability within each layer, particularly the large amounts in the conduction system fibres. The ultrastructural studies exhibited a marked variation in glycogen content from one cell to the next. This was particularly evident in the complete absence of granules in the contraction band lesions of isoproterenol cardiotoxicity yet substantial amounts were retained in neighbouring cells. Isoproterenol, therefore, produces a heterogenous depletion of cardiac glycogen related to the scattered catecholamine-induced myocardial cellular lesions. These relationships have not previously been documented or emphasized. 相似文献