Studies with electron microscopic autoradiography of thyroxine 125 I in organotypic cultures of the CNS. II. Sites of cellular localization of thyroxine 125 I.
نویسنده
چکیده
Thlyroxine, important in the metamorplhosis of amphibians, as well as in the (lifferentiation of mammalian tissues, exerts its effects on suclh diverse tissues as cartilage, liver and brain(l). Effects of thyroxinie at the celltular level have been variously ascribed to its uncoupling of oxidlative phosphorylation(2), its direct interaction with enzymes(3,4), and its stimulation of mitochondrial dependent protein synthesis(5); it has also been implicated in the transcription of both mDNA and rDNA(6-8), and it has been assumed to have a role in nuclear transport(9) and attaclhment of ribosomes to membranes(I0). Perlhaps one of the most fascinating controversies centers on the "primary action" of thyroxine(5); Sokoloff et al., lhave claimed that the mitochondria is tlle first and crucial focus of its effects; Tata has claimed the hormone's primary, albeit tardy tlhrust is in the nucleus(9). MIore specifically, Sokoloff has demonstrated that the early enlhancement of protein syntlhesis by thyroxine (2 h) requires mitocliondria(5), and he postulated that thyroxine may not even participate directly in the (lelayed response of increased nuclear RNA that occurs at 15 to 30 h. Tata on the otlher hand has considered the mitochondrial effects to be "toxic" or "catabolic" manifestations of hiighl doses of the lhormone, that may be entirely separable from its actions on growtlh and development(9,1 1). The present experiments are concerned witlh the ultrastructural localization of tlhyroxine in the cell, wlhiclh has not lheretofore been described. Mfore specifically, cells of the (leveloping nervous system known to be responsive to thyroid hormonies(12-14) were studied. The localization of thyroxine 1251 at early (15 min)
منابع مشابه
Studies with electron microscopic autoradiography of thyroxine 125 I in organotypic cultures of the CNS. I. Fixation of thyroxine 125 I.
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عنوان ژورنال:
- The Yale Journal of Biology and Medicine
دوره 45 شماره
صفحات -
تاریخ انتشار 1972