Best Evidence Medical and Health Professional Education (BEME) collaboration: A moving spotlight

Early this year, a Massachusetts Institute of Technology professor of philosophy presented a new theory of time that caught our interest. One of the key concepts that Professor Skow presented is the “moving spotlight” theory. As Skow asserts, the experiences had a year ago or 10 years ago are still just as real, they’re just “inaccessible” because they are now in a different part of spacetime. This was felt to be an elegant notion to inform this ‘spotlight’ piece on BEME (www.bemecollaboration.org).     

Intratelencephalic projections of the avian visual dorsal ventricular ridge: Laminarly segregated,reciprocally and topographically organized

Recent reports have shown that the avian visual dorsal ventricular ridge (DVR) is organized as a trilayered complex, in which the forming layers—the thalamo-recipient entopallium (E), an overlaying nidopallial stripe called intermediate nidopallium (NI), and the dorsally adjacent mesopallium ventrale—appear to be extensively interconnected by topographically organized columns of reciprocal axonal processes running perpendicular to the layers, an arrangement highly reminiscent to that of the sensory cortices of mammals. In the present report, we implemented in vivo anterograde and retrograde tracing techniques aiming to elucidate the organization of the connections of this complex with other pallial areas. Previous studies have shown that the efferent projections of the visual DVR originate mainly from the NI and E, reaching several distinct associative and premotor nidopallial areas. We found that the efferents from the visual DVR originated solely from the NI, and confirmed that the targets of these projections were the pallial areas described by previous studies. We also found novel projections from the NI to the visual hyperpallium, and to the lateral striatum. Moreover, we found that these projections were reciprocal, topographically organized, and originated from different cell populations within the NI. We conclude that the NI constitutes a specialized layer of the visual DVR that form the core of a dense network of highly specific connections between this region and other higher order areas of the avian pallium. Finally, we discuss to what extent these hodological properties resemble those of the mammalian cortical layers II/III.     

Natural estrogens enhance the engraftment of human hematopoietic stem and progenitor cells in immunodeficient mice

Hematopoietic stem and progenitor cells (HSPC) are crucial in the maintenance of lifelong production of all blood cells. These stem cells are highly regulated to maintain homeostasis through a delicate balance between quiescence, self-renewal and differentiation. However, this balance is altered during the recovery after HSPC transplantation. Transplantation efficacy can be limited by inadequate hematopoietic stem cell number, poor homing, low level of engraftment, or limited self-renewal. As recent evidence indicates that estrogens are involved in regulating hematopoiesis, we sought to examine whether natural estrogens (estrone or E1, estradiol or E2, estriol or E3 and estetrol or E4) modulate human HSPC. Our results show that human HSPC subsets express estrogen receptors, and that signaling is activated by E2 and E4 on these cells. Additionally, these natural estrogens cause different effects on human progenitors in vitro. We found that both E2 and E4 expand human HSPC. However, E4 was the best tolerated estrogen and promoted cell cycling of human hematopoietic progenitors. Furthermore, we found that E2 and, more significantly, E4 doubled human hematopoietic engraftment in immunodeficient mice without altering other HSPC properties. Finally, the impact of E4 on promoting human hematopoietic engraftment in immunodeficient mice might be mediated through the regulation of mesenchymal stromal cells in the bone marrow niche. Collectively, our data demonstrate that E4 is well tolerated and enhances human reconstitution in immunodeficient mice directly, by modulating human hematopoietic progenitor properties, and indirectly, by interacting with the bone marrow niche. This might have particular relevance for improving hematopoietic recovery after myeloablative conditioning, especially when limited numbers of HSPC are available.     

Estudio epidemiológico de la tinea capitis en una población de Santiago de Chile. La aparición de Trichophyton tonsurans como agente etiológico

Introduction

Tinea capitis (TC) is a dermatophytosis that affects the hair and scalp. The epidemiology of TC depends on the different geographical areas and is variable over time. Direct microscopic examination and fungal culture are essential to confirm the diagnostic suspicion and to identify the germ involved.