The 7.47-g dose provides short-term advantages over lower doses. However, this benefit is transient and associated with slightly greater toxicity. The use of a cumulative dose of 7.47 g of methylprednisolone provides short-term advantage over lower doses. This may suggest that an intermediate-dose regimen be used in most cases and the high-dose regimen be reserved to most severe cases of GO.
Histogenesis was studied in forebrain cortical areas of two reptiles, Emys orbicularis and Lacerta trilineata, by using tritiated thymidine autoradiography. Four areas were considered: the dorsomedial, the general (dorsal), and the lateral cortices, and the dorsal ventricular ridge (DVR). The bulk of neurogenesis in these four pallial fields proceeds within a short period of 8-9 days, between developmental stages 15 and 18 in Emys and stages 32-34 in Lacerta. Lateral-to-medial as well as anterior-to-posterior tangential gradients of histogenesis are present in both species. Radial neurogenetic gradients are directed from outside to inside, except in the medial cortex of lizards, where no radial gradient is seen. This pattern of histogenesis in the cortex of turtles and lizards is comparable to that in mammals in terms of timing and tangential, areal variations. It might represent a "common denominator" of cortical histogenesis. However, in contrast to the mammalian cortex, which develops according to an inside to outside, "inverted" pattern, radial neurogenesis in the cortex of turtles and lizards follows an outside-to-inside gradient. These observations suggest that the inside-out gradient of cortical neurogenesis has been acquired during evolution of the synapsid radiation from stem reptiles to mammals, and that it may be related to the development of radial cortical architectonics.
Rab proteins are small GTPases that control distinct vesicular transport steps. Along the endocytic pathway, Rab5a is a ratelimiting catalyst of internalization, and Rab7 controls trafficking through late endosomes to lysosomes. The dependence of thyroid hormone production by thyrocytes on thyroglobulin endocytosis and intracellular processing in late endosomes͞lysosomes suggests that its rate can be regulated by the expression or function of these endocytic catalysts. We compared the expression level and membrane recruitment of Rab5a and Rab7 in autonomous thyroid adenomas (where the cAMP cascade is constitutively activated) and surrounding quiescent tissues. The concentrations of Rab5a and Rab7, but not of Rab8, were coordinately increased up to 6-fold in adenomas, and correlated with a proportionate decrease in soluble thyroglobulin content (reflecting colloid depletion by accelerated endocytic uptake in hyperactive tissue). In adenomas, a higher proportion of Rab5a and Rab7 was membrane associated, and the equilibrium density of particulate Rab7 and iodine shifted toward lysosomal fractions, indicating that progression along the degradation pathway also was promoted. In cultures of polarized human thyrocytes from normal patients, thyroid-stimulating hormone or forskolin increased, to a similar extent, Rab5a and Rab7 but not Rab8 expression, apical endocytosis of thyroglobulin and lucifer yellow, and basolateral secretion of T 3 and T4. Taken together, these in vivo and in vitro observations demonstrate that thyroid-stimulating hormone, via cAMP, coordinately enhances the expression of Rab5a and Rab7, which promote Tg endocytosis and transfer to lysosomes, respectively, resulting in accelerated thyroid hormone production.
Progress in biotechnology has provided useful tools for tracing proteins involved in thyroid hormone synthesis in vivo. Mono- or polyclonal antibodies are now available to detect on histological sections the Na(+)/I(-) symporter (NIS) at the basolateral pole of the cell, the putative iodide channel (pendrin) at the apical plasma membrane, thyroperoxidase (TPO), and members of the NADPH-oxidase family, thyroid oxidase 1 and 2 (ThOXs), part of the H(2)O(2)-generating system. The aim of this study was to correlate thyroglobulin (Tg) iodination with the presence of these proteins. Tg, T(4)-containing Tg, NIS, pendrin, TPO, ThOXs, and TSH receptor (TSHr) were detected by immunohistochemistry on tissue sections of normal thyroids and various benign and malignant thyroid disorders. Tg was present in all cases. T(4)-containing Tg was found in the adenomas, except in Hurthle cell adenomas. It was never detected in carcinomas. NIS was reduced in all types of carcinomas, whereas it was detected in noncancerous tissues. Pendrin was not expressed in carcinomas, except in follicular carcinomas, where weak staining persisted. TPO expression was present in insular, follicular carcinomas and in follicular variants of papillary carcinomas, but in a reduced percentage of cells. It was below the level of detection in papillary carcinomas. The H(2)O(2)-generating system, ThOXs, was found in all carcinomas and was even increased in papillary carcinomas. Its staining was apical in normal thyroids, whereas it was cytoplasmic in carcinomas. The TSHr was expressed in all cases, but the intensity of the staining was decreased in insular carcinomas. In conclusion, our work shows that all types of carcinomas lose the capacity to synthesize T(4)-rich, iodinated Tg. In follicular carcinomas, this might be due to a defect in iodide transport at the basolateral pole of the cell. In papillary carcinomas, this defect seems to be coupled to an altered apical transport of iodide and probably TPO activity. The TSHr persists in virtually all cases.
Patients who deteriorate at 6 weeks after ivGCs are unlikely to benefit from continuing ivGCs. Patients unresponsive at 6 weeks still have a significant possibility of improvement later. Accordingly, they may continue ivGC treatment, or, alternatively, possibly stop ivGCs and be switched to a second-line treatment.
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