Content in Simple Signalling Systems

Our understanding of communication and its evolution has advanced significantly through the study of simple models involving interacting senders and receivers of signals. Many theorists have thought that the resources of mathematical information theory are all that are needed to capture the meaning or content that is being communicated in these systems. However, the way theorists routinely talk about the models implicitly draws on a conception of content that is richer than bare informational content, especially in contexts where false content is important. This article shows that this concept can be made precise by defining a notion of functional content that captures the degree to which different states of the world are involved in stabilizing senders’ and receivers’ use of a signal at equilibrium. A series of case studies is used to contrast functional content with informational content, and to illustrate the explanatory role and limitations of this definition of functional content

The hemo-neural hypothesis : effects of vasodilation on astrocytes in mammalian neocortex

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2011.Cataloged from PDF version of thesis.Includes bibliographical references.Astrocytes play an important role in regulating neuronal activity and local brain states, in part by serving as intermediaries between neurons and vasculature. We postulate that neurons and astrocytes are sensitive to biophysical conditions in their local environment, in addition to their participation in traditional signaling networks with other neurons. Mechanically sensitive astrocytic endfeet ensheathe cerebral blood vessels, which change size in order to regulate blood flow. We found that changes in local biophysical state caused by mechanical perturbations exerted through blood vessels can depolarize astrocytes and some neurons in slice. To test the hemoneural hypothesis in vivo, we developed a means of inducing dilation using the SUR2B receptor agonist pinacidil, which is specific to vascular smooth muscle. It was important to ascertain that pinacidil had no direct effect on astrocytes or neurons, and we confirmed this in whole cell recordings in cortical slices. We then used two-photon imaging to visualize astrocytic calcium dynamics in vivo while manipulating vasodilation in vivo. Pinacidil caused a 10-20% dilation in most vessels, a degree of dilation of similar magnitude to those naturally evoked by persistent sensory stimulation (e.g. in fMRI studies). We found that increases in pial arteriole diameter could occasionally evoke traveling calcium waves in astrocytes. We also saw consistently slow increases (which took tens of seconds to onset, and persisted for minutes) in astrocytic calcium levels at both endfeet and soma in cortical layer 1, corresponding to vessel dilation. When vessels partially reconstricted due to pinacidil washout, calcium levels also showed a relative decrease. At short time scales (from 0.5 - 5 seconds) we saw strong correlations (>0.5) between small fluctuations in astrocytic calcium levels (1-3%) and vessel diameter (1-3%). Fluctuations in vessel diameter predicted similar fluctuations in astrocytic calcium, as often and as strongly as the reverse, suggesting feedback regulation between vascular diameter and astrocytic calcium activation levels.by Rosa Cao.Ph.D

Neuropilin 1 mediates epicardial activation and revascularization in the regenerating zebrafish heart

Unlike adult mammals, zebrafish can regenerate their heart. A key mechanism for regeneration is the activation of the epicardium, leading to the establishment of a supporting scaffold for new cardiomyocytes, angiogenesis and cytokine secretion. Neuropilins are co-receptors mediating signaling of kinase receptors for cytokines known to play critical roles in zebrafish heart regeneration. We investigated the role of neuropilins in response to cardiac injury and heart regeneration. All four neuropilin isoforms nrp1a, nrp1b, nrp2a and nrp2b were upregulated by the activated epicardium and a nrp1a knockout mutant showed a significant delay in heart regeneration and displayed persistent collagen deposition. The regenerating hearts of nrp1a mutants were less vascularized and epicardial-derived cell migration and re-expression of the developmental gene wt1b was impaired. Moreover, cryoinjury-induced activation and migration of epicardial cells in heart explants was reduced in nrp1a mutant. These results identify a key role for Nrp1 in zebrafish heart regeneration, mediated through epicardial activation, migration and revascularization

Tasa Efectiva del Impuesto a la Propiedad Inmueble en Puerto Rico: Análisis de caso de la implementación del impuesto predial en el municipio de Guaynabo

El análisis contenido en este artículo examina el comportamiento y los factores que afectan la tasa efectiva del impuesto sobre la propiedad inmueble en Puerto Rico, con la intención de establecer su impacto en la equidad del sistema impositivo. Los hallazgos del análisis son generalmente aplicables a aquellas jurisdicciones que no actualizan el proceso por el cual valorizan las propiedades inmuebles para fines contributivos, ni implementan mecanismos de corrección a sus ineficiencias. Entre los resultados más significativos se encuentra que la tasa efectiva del impuesto sobre la propiedad no es fija entre los inmuebles; específicamente, ésta penaliza a las propiedades con una mayor edad de haber sido construida y muestra un comportamiento regresivo

Genome-wide association analysis for fumonisin content in maize kernels

Background: Plant breeding has been proposed as one of the most effective and environmentally safe methods to control fungal infection and to reduce fumonisin accumulation. However, conventional breeding can be hampered by the complex genetic architecture of resistance to fumonisin accumulation and marker-assisted selection is proposed as an efficient alternative. In the current study, GWAS has been performed for the first time for detecting high-resolution QTL for resistance to fumonisin accumulation in maize kernels complementing published GWAS results for Fusarium ear rot. Results: Thirty-nine SNPs significantly associated with resistance to fumonisin accumulation in maize kernels were found and clustered into 17 QTL. Novel QTLs for fumonisin content would be at bins 3.02, 5.02, 7.05 and 8.07. Genes with annotated functions probably implicated in resistance to pathogens based on previous studies have been highlighted. Conclusions: Breeding approaches to fix favorable functional variants for genes implicated in maize immune response signaling may be especially useful to reduce kernel contamination with fumonisins without significantly interfering in mycelia development and growth and, consequently, in the beneficial endophytic behavior of Fusarium verticillioides.Xunta de Galicia | Ref. IN607A/013Ministerio de Economía | Ref. AGL2015–67313-C2–1-RMinisterio de Economía | Ref. AGL2015–67313-C2–2-

Defensive changes in maize leaves induced by feeding of Mediterranean corn borer larvae

Bioassays raw data. (XLSX 33 kb

Neutralizing antibody response during acute and chronic hepatitis C virus infection

Little is known about the role of Abs in determining the outcome of hepatitis C virus (HCV) infection. By using infectious retroviral pseudotypes bearing HCV glycoproteins, we measured neutralizing Ab (nAb) responses during acute and chronic HCV infection. In seven acutely infected health care workers, only two developed a nAb response that failed to associate with viral clearance. In contrast, the majority of chronically infected patients had nAbs. To determine the kinetics of strain-specific and crossreactive nAb emergence, we studied patient H, the source of the prototype genotype 1a H77 HCV strain. An early weak nAb response, specific for the autologous virus, was detected at seroconversion. However, neutralization of heterologous viruses was detected only between 33 and 111 weeks of infection. We also examined the development of nAbs in 10 chimpanzees infected with H77 clonal virus. No nAb responses were detected in three animals that cleared virus, whereas strain-specific nAbs were detected in six of the seven chronically infected animals after approximately 50 weeks of infection. The delayed appearance of high titer crossreactive nAbs in chronically infected patients suggests that selective mechanism(s) may operate to prevent the appearance of these Abs during acute infection. The long-term persistence of these nAbs in chronically infected patients may regulate viral replication

Regime mapping and the role of the intermediate region in wall-coated microreactors

Operation of a wall-coated microreactor can occur in several mass transfer-reaction regimes. We define these regimes analytically in several planes of a multi-parametric map, taking into account the different degrees of concentration profile development, as well as the influence of non-unity orders of reaction and reactant inhibition in the kinetic law. It was found that the regions where conversion can be calculated from simplified mass transfer models are not discriminated by common results for entrance-length. We also illustrate the trade-offs that exist across this operating map concerning the catalyst design (costs associated with loading and volume) and overall system performance (evaluated in terms of reactant conversion, flow efficiency and microreactor effectiveness). It is shown that under certain conditions, the existence of moderate mass transfer resistance can be advantageous (even if internal limitations cannot be avoided), clarifying the role of the intermediate transport-reaction region