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441.
R. Bareggi P. Narducci V. Grill F. Mallardi M. Zweyer P. Fusaroli 《Histochemistry and cell biology》1986,84(3):237-240
Summary We used the simple method of direct cytofluorescence to detect the presence of the aminoglycoside, streptomycin, in the inner ear after its systemic administration. In the cochlea, fluorescence was observed in the organ of Corti, the spiral ganglion, the nerve fibres, the vascular stria and Reissner's membrane; in the vestibulum, fluorescence was seen in the crista ampullaris and the planum semilunatum. The localization of the drug was related to the distribution of its specific receptor, triphosphoinositide (TPI); therefore, it is reasonable to assume that aminoglycosides exert their toxic effects by binding to TPI.Supported by grants of Ministero della Pubblica Istruzione, Italy 相似文献
442.
One major parvalbumin each was isolated from the skeletal muscle of two
reptiles, a boa snake, Boa constrictor, and a map turtle, Graptemys
geographica, while two parvalbumins were isolated from an amphibian, the
salamander Amphiuma means. The amino acid sequences of all four
parvalbumins were determined from the sequences of their tryptic peptides,
which were ordered partially by homology to other parvalbumins.
Phylogenetic study of these and 16 other parvalbumin sequences revealed
that the turtle parvalbumin belongs to beta lineage, while the salamander
sequences belong, one each, to the alpha and beta lineages defined by
Goodman and Pechere (1977). Boa parvalbumin, however, while belonging to
the beta lineage, clusters within the fish in all reasonably parsimonious
trees. The most parsimonious trees show many parallel or back mutations in
the evolution of many parvalbumin residues, although the residues
responsible for Ca2+ binding are very well conserved. These most
parsimonious trees show an actinopterygian rather than a crossoptyrigian
origin of the tetrapods in both the alpha and beta groups. One of two
electric eel parvalbumins is evolving more than 10 times faster than its
paralogous partner, suggesting it may be on its way to becoming a
pseudogene. It is concluded that varying rates of amino acid replacement,
much homoplasy, considerable gene duplication, plus complicated lineages
make the set of parvalbumin sequences unsuitable for systematic study of
the origin of the tetrapods and other higher-taxa divergence, although it
may be suitable within a genus or family.
相似文献
443.
Summary In turnip seedlings, anthocyanin synthesis can be induced with light as soon as water uptake enables the seed coat to be removed. In very young seedlings the main site of production is in the cotyledons but this moves to the hypocotyl when the period of dark growth, before transfer to the light, is increased. The total amount of anthocyanin formed decreases as the seedlings become older. It is suggested that a substance stored in the cotyledons is needed for anthocyanin synthesis and that this substance disappears during growth in the dark. It cannot be replaced by known anthocyanin precursors such as phenylalanine, acetate, shikimic acid and sugars.Anthocyanin synthesis in the hypocotyl is almost completely prevented when the cotyledons are excised, or covered: no anthocyanin is formed in the hypocotyl when the cotyledons alone are irradiated. Cotyledons that have been excised from the hypocotyl synthesize about as much anthocyanin as is formed in the whole intact seedling, but covering the hypocotyl does not increase the amount formed in the cotyledons. These results suggest that pigment synthesis begins in the cotyledons, where a light reaction is needed for the formation of a precursor; the precursor is translocated to the hypocotyl where a second photochemical reaction is required for anthocyanin synthesis. If translocation to the hypocotyl is prevented, anthocyanin is formed in the cotyledons. The nature of the transported precursor is not yet known.
With 9 Figures in the Text 相似文献
Zusammenfassung In Keimlingen vonBrassica rapa kann Anthocyansynthese durch Licht induziert werden, sobald es möglich ist, die Samenschale zu entfernen. In den jüngsten Keimlingen sind die Kotyledonen der Ort stärkster Anthocyanbildung, in älteren Keimlingen das Hypokotyl. Die Gesamtmenge an gebildetem Anthocyan nimmt mit zunehmendem Alter der Keimlinge ab. Es wird vermutet, daß eine für Anthocyansynthese notwendige Substanz in den Kotyledonen gespeichert ist und während des Wachstums im Dunkeln abnimmt. Diese Substanz konnte durch bekannte Anthocyanvorstufen wie Phenylalanin, Acetat, Shikimisäure und Zucker nicht ersetzt werden.Anthocyansynthese ist im Hypokotyl fast vollständig unterdrückt, wenn die Kotyledonen entfernt oder verdunkelt werden: Kein Anthocyan wird im Hypokotyl gebildet, wenn die Kotyledonen allein belichtet werden. Isolierte Kotyledonen synthetisieren ungefähr die gleiche Menge Anthocyan wie intakte Keimlinge, aber eine Verdunkelung des Hypokotyls bewirkt keine Steigerung der Anthocyanbildung in den Kotyledonen. Diese Ergebnisse lassen vermuten, daß die Synthese von Anthocyan in den Kotyledonen beginnt, wo eine lichtabhängige Reaktion zur Bildung einer Zwischenstufe notwendig ist; diese Zwischenstufe wird in das Hypokotyl transportiert, wo eine zweite photochemische Reaktion für Anthocyansynthese erforderlich ist. Wird der Transport in das Hypokotyl verhindert, findet Anthocyansynthese in den Kotyledonen statt. Über die Natur dieser Zwischenstufe ist jedoch noch nichts bekannt.
With 9 Figures in the Text 相似文献
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Insulin secretion declines progressively before and during the
course of type 2 diabetes. Evidence indicates that this process is,
in part, secondary to increased requirement for insulin secretion
that is brought about by insulin resistance and by hyperglycemia.
The effects of over-secretion extend far beyond a mere reduction
of available insulin stores and may cause not only functional but
also structural damage. The time is ripe for clinical studies, which
explore the therapeutic potential of reducing over-secretion. 相似文献