The default mode network is functionally and structurally disrupted in amnestic mild cognitive impairment — a bimodal MEG–DTI study

Over the past years, several studies on Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) have reported Default Mode Network (DMN) deficits. This network is attracting increasing interest in the AD community, as it seems to play an important role in cognitive functioning and in beta amyloid deposition. Attention has been particularly drawn to how different DMN regions are connected using functional or structural connectivity. To this end, most studies have used functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET) or Diffusion Tensor Imaging (DTI). In this study we evaluated (1) functional connectivity from resting state magnetoencephalography (MEG) and (2) structural connectivity from DTI in 26 MCI patients and 31 age-matched controls. Compared to controls, the DMN in the MCI group was functionally disrupted in the alpha band, while no differences were found for delta, theta, beta and gamma frequency bands. In addition, structural disconnection could be assessed through a decreased fractional anisotropy along tracts connecting different DMN regions. This suggests that the DMN functional and anatomical disconnection could represent a core feature of MCI.

Los instrumentos convertibles en acciones para la financiación empresarial en un entorno económico de restricción del crédito bancario

(SPA) Los bonos convertibles en acciones son instrumentos de financiación corporativa que en general comparten varias de las características de las emisiones de deuda senior corporativa, como el pago regular y fijado de cupones, vencimiento definido, momento en el que se repaga la totalidad del principal, y prelación en caso de default con respecto a otras obligaciones crediticias. En cambio, el repago del principal se ofrecerá bajo determinadas circunstancias en acciones de la compañía emisora en una proporción acordada previamente. Pero los instrumentos convertibles son instrumentos heterogéneos que suelen incorporar otras características particulares a cada caso, como son repagos anticipados bajo determinadas condiciones, reducción del ratio de conversión a determinados precios de la acción, pagos compensatorios o "make-whole" y otros. Los instrumentos convertibles son ejemplos de activos híbridos que comparten características de deuda y de capital y por tanto tienen impacto específico en la contabilidad de las empresas y en la posible dilución de sus accionistas. En España y otros países de la periferia de Europa, la emisión de bonos convertibles ha aumentado considerablemente desde el inicio de la crisis financiera, fundamentalmente debido a la restricción de otras formas de crédito empresarial, principalmente los créditos bancarios. En el presente artículo se explican algunas de las características comunes a los bonos convertibles emitidos recientemente por empresas españolas, se analizan las ventajas, y las razones para la emisión de estos activos, y se indican sus implicaciones contables. Los instrumentos convertibles pueden ser una alternativa estable a la deuda bancaria y a la renta fija tradicional en los mercados de capitales para la financiación de las compañías medianas, que tienen menos acceso a fuentes de financiación en situaciones de aversión riesgo por parte de los inversores y entidades financieras. (ENG)Convertible bonds share several characteristics with secure corporate debt, such as the regular coupon payments, fixed maturity and similar seniority in case of default. Nevertheless the investor of the convertible bond has the option of receiving the principal amount repayment at maturity in cash or receiving a previously agreed number of shares. But convertible securities can be complex financial instruments that possess exotic or specific features, such as soft calls, put options, cash options, cash top up features, or make whole amounts. Convertible securities are hybrid instruments that share characteristics of both debt and equity, and therefore suffer an specific accounting treatment under International Financial Reporting Standards, where the issuing company must separately identify the debt and equity components in its financial statements In peripheral European countries and in Spain in particular, convertible issuance has significantly increased since the start of the Global Financial Crisis, an increase mainly driven by the restriction of other forms of credit, namely banking loans. This article summarizes some of the common characteristics of convertible securities, analyzes its advantages for both issuers and investors, and introduces the accounting of convertible bonds. Convertible Bonds can become a viable and stable alternative to bank loans and to high yield or investment grade bonds for the funding of mid-sized corporates which normally have a more difficult access to credit in regional banking crisis or credit restrictive environments.

Segregation of Heterotrimeric G Proteins in Cell Surface Microdomains: Gq Binds Caveolin to Concentrate in Caveolae, whereas Gi and Gs Target Lipid Rafts by Default

Select lipid-anchored proteins such as glycosylphosphatidylinositol (GPI)-anchored proteins and nonreceptor tyrosine kinases may preferentially partition into sphingomyelin-rich and cholesterol-rich plasmalemmal microdomains, thereby acquiring resistance to detergent extraction. Two such domains, caveolae and lipid rafts, are morphologically and biochemically distinct, contain many signaling molecules, and may function in compartmentalizing cell surface signaling. Subfractionation and confocal immunofluorescence microscopy reveal that, in lung tissue and in cultured endothelial and epithelial cells, heterotrimeric G proteins (Gi, Gq, Gs, and Gβγ) target discrete cell surface microdomains. Gq specifically concentrates in caveolae, whereas Gi and Gs concentrate much more in lipid rafts marked by GPI-anchored proteins (5′ nucleotidase and folate receptor). Gq, apparently without Gβγ subunits, stably associates with plasmalemmal and cytosolic caveolin. Gi and Gs interact with Gβγ subunits but not caveolin. Gi and Gs, unlike Gq, readily move out of caveolae. Thus, caveolin may function as a scaffold to trap, concentrate, and stabilize Gq preferentially within caveolae over lipid rafts. In N2a cells lacking caveolae and caveolin, Gq, Gi, and Gs all concentrate in lipid rafts as a complex with Gβγ. Without effective physiological interaction with caveolin, G proteins tend by default to segregate in lipid rafts. The ramifications of the segregated microdomain distribution and the Gq-caveolin complex without Gβγ for trafficking, signaling, and mechanotransduction are discussed.

Medial prefrontal cortex and self-referential mental activity: Relation to a default mode of brain function

Medial prefrontal cortex (MPFC) is among those brain regions having the highest baseline metabolic activity at rest and one that exhibits decreases from this baseline across a wide variety of goal-directed behaviors in functional imaging studies. This high metabolic rate and this behavior suggest the existence of an organized mode of default brain function, elements of which may be either attenuated or enhanced. Extant data suggest that these MPFC regions may contribute to the neural instantiation of aspects of the multifaceted “self.” We explore this important concept by targeting and manipulating elements of MPFC default state activity. In this functional magnetic resonance imaging (fMRI) study, subjects made two judgments, one self-referential, the other not, in response to affectively normed pictures: pleasant vs. unpleasant (an internally cued condition, ICC) and indoors vs. outdoors (an externally cued condition, ECC). The ICC was preferentially associated with activity increases along the dorsal MPFC. These increases were accompanied by decreases in both active task conditions in ventral MPFC. These results support the view that dorsal and ventral MPFC are differentially influenced by attentiondemanding tasks and explicitly self-referential tasks. The presence of self-referential mental activity appears to be associated with increases from the baseline in dorsal MPFC. Reductions in ventral MPFC occurred consistent with the fact that attention-demanding tasks attenuate emotional processing. We posit that both self-referential mental activity and emotional processing represent elements of the default state as represented by activity in MPFC. We suggest that a useful way to explore the neurobiology of the self is to explore the nature of default state activity.

Default taxonomy: Ernst Mayr’s view of the microbial world

This perspective is a response to a taxonomic proposal by E. Mayr [“Two empires or three?” (1998) Proc. Natl. Acad. Sci. USA 95, 9720–9723]. Mayr has suggested that the now accepted classification of life into three primary domains, Archaea, Bacteria, and Eucarya—originally proposed by myself and others—be abandoned in favor of the earlier Prokaryote–Eukaryote classification. Although the matter appears a taxonomic quibble, it is not that simple. At issue here are differing views as to the nature of biological classification, which are underlain by differing views as to what biology is and will be—matters of concern to all biologists.