Correlato neural de la lectura en bilingües

This paper does not intend to carry out a systematic or complete review of the literature, but rather aims to offer a critical view by the authors about the functional brain organization during reading in bilinguals. Firstly, a critical analysis of different theoretical proposals about the reading process is presented, with particular emphasis on the Dual-Route Cascade Model for being the most influential theory in the field. Then, we analize the main theoretical proposals about the neurobiological substrate based mainly on functional neuroimage studies. The main factors that influence this neural correlate during reading in bilinguals are extracted and the findings regarding them of the most recent studies are presented. Finally, a critical analysis is made about the main limitations of the research on this topic and challenges and future research lines in the field are discussed.Este artículo no pretende realizar una revisión sistemática ni completa de la literatura, sino que tiene como objetivo ofrecer una visión crítica por parte de los autores, acerca de la organización funcional cerebral durante la lectura en personas bilingües. Primeramente se presenta un análisis crítico de diferentes propuestas teóricas acerca del proceso lector, haciendo particular énfasis en el modelo de doble ruta en cascada por ser el más influyente. Luego se analizan las principales propuestas teóricas acerca del sustrato neurobiológico basado fundamentalmente en estudios de imágenes funcionales. Se extraen los principales factores que influyen sobre este correlato neural durante la lectura en bilingües y se presentan los hallazgos de los estudios más recientes. Finalmente, se hace un análisis crítico acerca de las principales limitaciones de las investigaciones en este tema y se describen los retos y líneas de investigación futuras que el campo tiene por delante

Clay minerals, oxyhydroxide formation, element leaching and humus development in volcanic soils

A weathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100–115,000 years in the Etna region served as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements. Although the soils were influenced by ash depositions during their development and the soil on the oldest lava flow developed to a great extent under a different climate, leaching of elements and mineral formation and transformation could still be measured. Leaching of major base cations coupled with a corresponding passive enrichment of Al or Fe was a main weathering mechanism and was especially pronounced in the early stages of soil formation due to mineral or glass weathering. With time, the weathering indexes (such as the (K + Ca)/Ti ratio) tend to an asymptotic value: chemical and mineralogical changes between 15,000 and 115,000 years in the A and B horizons were small. In contrast to this, the accumulation of newly formed ITM (imogolite type materials) and ferrihydrite showed a rather linear behaviour with time. Weathering consisted of the dissolution of primary minerals such as plagioclase, pyroxenes or olivine, the breakdown of volcanic glass and the formation of secondary minerals such as ITM and ferrihydrite. The main mineral transformations were volcanic glass ➔ imogolite ➔ kaolinite (clay fraction). In the most weathered horizons a very small amount of 2:1 clay minerals could be found that were probably liberated from the inner part of volcanic glass debris. The rate of formation and transformation of 2:1 clay minerals in the investigated soils was very low; no major changes could be observed even after 115,000 years of soil evolution. This can be explained by the addition of ash and the too low precipitation rates. In general, soil erosion played a subordinate role, except possibly for the oldest soils (115,000 years). The youngest soils with an age < 2000 years had the highest accumulation rate of organic C (about 3.0 g C/m2/year). After about 15,000 years, the accumulation rate of organic C in the soils tended to zero. Soil organic carbon reached an asymptotic value with abundances close to 20 kg/m2 after about 20,000 years. In general, the preservation and stabilisation of SOM were due to poorly crystalline Al- and Fe-phases (pyrophosphate-extractable), kaolinite and the clay content. These parameters correlated well with the organic C. Imogolite-type material did not contribute significantly to the stabilisation of soil organic matter

Giant Sertoli cell nodule of the testis: distinction from other Sertoli cell lesions

The case of a 33‐year‐old man with a clinically suspected testicular neoplasm is reported here. The radical orchidectomy specimen showed a sharply demarcated, firm, yellow–white 1‐cm nodule beneath the tunica albuginea at the upper pole. Microscopical examination showed the encapsulated nodule to be composed of tubules lined by immature Sertoli cells with interspersed spermatogonia and an interwoven network of hyalinised basement membrane having foci of calcification. Immunohistochemical studies verified the fetal phenotype of the Sertoli cells and the non‐neoplastic nature of the germ cell component. Except for the large size, the findings were identical to those of a Sertoli cell nodule—a typically microscopic, unencapsulated lesion commonly detected in cryptorchid testes. The term “giant Sertoli cell nodule” is used for this unique, hitherto undescribed lesion and its distinction from other Sertoli cell lesions of the testis is considered here