Developmental Patterns of Doublecortin Expression and White Matter Neuron Density in the Postnatal Primate Prefrontal Cortex and Schizophrenia

Postnatal neurogenesis occurs in the subventricular zone and dentate gyrus, and evidence suggests that new neurons may be present in additional regions of the mature primate brain, including the prefrontal cortex (PFC). Addition of new neurons to the PFC implies local generation of neurons or migration from areas such as the subventricular zone. We examined the putative contribution of new, migrating neurons to postnatal cortical development by determining the density of neurons in white matter subjacent to the cortex and measuring expression of doublecortin (DCX), a microtubule-associated protein involved in neuronal migration, in humans and rhesus macaques. We found a striking decline in DCX expression (human and macaque) and density of white matter neurons (humans) during infancy, consistent with the arrival of new neurons in the early postnatal cortex. Considering the expansion of the brain during this time, the decline in white matter neuron density does not necessarily indicate reduced total numbers of white matter neurons in early postnatal life. Furthermore, numerous cells in the white matter and deep grey matter were positive for the migration-associated glycoprotein polysialiated-neuronal cell adhesion molecule and GAD65/67, suggesting that immature migrating neurons in the adult may be GABAergic. We also examined DCX mRNA in the PFC of adult schizophrenia patients (n = 37) and matched controls (n = 37) and did not find any difference in DCX mRNA expression. However, we report a negative correlation between DCX mRNA expression and white matter neuron density in adult schizophrenia patients, in contrast to a positive correlation in human development where DCX mRNA and white matter neuron density are higher earlier in life. Accumulation of neurons in the white matter in schizophrenia would be congruent with a negative correlation between DCX mRNA and white matter neuron density and support the hypothesis of a migration deficit in schizophrenia

Postnatal development of calcium-binding proteins immunoreactivity (parvalbumin, calbindin, calretinin) in the human entorhinal cortex

The entorhinal cortex is an essential component in the organization of the human hippocampal formation related to cortical activity. It transfers, neocortical information (ultimately distributed to the dentate gyrus and hippocampus) and receives most of the hippocampal output directed to neocortex. At birth, the human entorhinal cortex presents similar layer organization as in adults, although layer II (cell islands) and upper layer III have a protracted maturation. The presence of interneurons expressing calcium-binding proteins (parvalbumin, calbindin–D28K (calbindin) and calretinin) is well documented in the adult human entorhinal cortex. In many of them the calcium binding is co-localized with GABA. Parvalbumin-immunoreactive cells and fibers were virtually absent at birth, their presence increasing gradually in deep layer III, mostly in the lateral and caudal portions of the entorhinal cortex from the 5th month onwards. Calbindin immunoreactive cells and fibers were present at birth, mainly in layers II and upper III; mostly at rostral and lateral portions of the entorhinal cortex, increasing in number and extending to deep layers from the 5th month onwards. Calretinin immunoreactivity was present at birth, homogeneously distributed over layers I, II and upper V, throughout the entorhinal cortex. A substantial increase in the number of calretinin neurons in layer V was observed at the 5th month. The postnatal development of parvalbumin, calbindin and calretinin may have an important role in the functional maturation of the entorhinal cortex through the control of hippocampal, cortical and subcortical information

Impacto de la aplicación del fair value en la volatilidad de la banca Brasileña: un estudio empírico

En este paper es analizado el impacto que ha tenido la adopción del valor razonable sobre la volatilidad de los resultados y fondos propios en los bancos de Brasil. La muestra estuvo constituida por 73 bancos que representaban, a Junio del 2002, el 95,93% del total de activos del sistema nacional. Se realizo un análisis comparativo entre las volatilidades, con y sin los efectos de la nueva regulación, e se indago para conocer si existe algún síntoma de utilización de prácticas para el alisamiento de los beneficios, relacionadas con las partidas de ajustes a valor razonable. Los resultados de esta investigación revelan que, al contrario de lo que se espera, el nuevo criterio en cuestión no ha incrementado las volatilidades y, por otro lado, han puesto en manifiesto síntomas de alisamiento de beneficios.<br>In this paper, we analyze the impact of the adoption of fair value on the volatility of the results and reserves of Brazilian banks. The sample consisted of 73 banks, which represented, in June 2002, 95.93% of total assets in the national system. We conducted a comparative analysis between the volatilities, with and without the effects of the new regulation, and investigated if there is some symptom of utilization of practices for smoothing the benefits, related to the items of adjustments to fair value. The results of our research revealed that, as opposed to expectations, the new criterion in question has not increased volatility but, on the opposite, has exhibited symptoms of smoothing of benefits