1,862 research outputs found

    The Relationship Between M in “Calibrated fMRI” and the Physiologic Modulators of fMRI

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    The “calibrated fMRI” technique requires a hypercapnia calibration experiment in order to estimate the factor “M”. It is desirable to be able to obtain the M value without the need of a gas challenge calibration. According to the analytical expression of M, it is a function of several baseline physiologic parameters, such as baseline venous oxygenation and CBF, both of which have recently been shown to be significant modulators of fMRI signal. Here we studied the relationship among hypercapnia-calibrated M, baseline venous oxygenation and CBF, and assessed the possibility of estimating M from the baseline physiologic parameters. It was found that baseline venous oxygenation and CBF are highly correlated (R2=0.77, P<0.0001) across subjects. However, the hypercapnia-calibrated M was not correlated with baseline venous oxygenation or CBF. The hypercapnia-calibrated M was not correlated with an estimation of M based on analytical expression either. The lack of correlation may be explained by the counteracting effect of venous oxygenation and CBF on the M factor, such that the actual M value of an individual may be mostly dependent on other parameters such as hematocrit. Potential biases in hypercapnia-based M estimation were also discussed in the context of possible reduction of CMRO2 during hypercapnia

    Simulation of all-scale atmospheric dynamics on unstructured meshes

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    The advance of massively parallel computing in the nineteen nineties and beyond encouraged finer grid intervals in numerical weather-prediction models. This has improved resolution of weather systems and enhanced the accuracy of forecasts, while setting the trend for development of unified all-scale atmospheric models. This paper first outlines the historical background to a wide range of numerical methods advanced in the process. Next, the trend is illustrated with a technical review of a versatile nonoscillatory forward-in-time finite-volume (NFTFV) approach, proven effective in simulations of atmospheric flows from small-scale dynamics to global circulations and climate. The outlined approach exploits the synergy of two specific ingredients: the MPDATA methods for the simulation of fluid flows based on the sign-preserving properties of upstream differencing; and the flexible finite-volume median-dual unstructured-mesh discretisation of the spatial differential operators comprising PDEs of atmospheric dynamics. The paper consolidates the concepts leading to a family of generalised nonhydrostatic NFTFV flow solvers that include soundproof PDEs of incompressible Boussinesq, anelastic and pseudo-incompressible systems, common in large-eddy simulation of small- and meso-scale dynamics, as well as all-scale compressible Euler equations. Such a framework naturally extends predictive skills of large-eddy simulation to the global atmosphere, providing a bottom-up alternative to the reverse approach pursued in the weather-prediction models. Theoretical considerations are substantiated by calculations attesting to the versatility and efficacy of the NFTFV approach. Some prospective developments are also discussed

    Molecular and Cellular Approaches for Diversifying and Extending Optogenetics

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    Optogenetic technologies employ light to control biological processes within targeted cells in vivo with high temporal precision. Here, we show that application of molecular trafficking principles can expand the optogenetic repertoire along several long-sought dimensions. Subcellular and transcellular trafficking strategies now permit (1) optical regulation at the far-red/infrared border and extension of optogenetic control across the entire visible spectrum, (2) increased potency of optical inhibition without increased light power requirement (nanoampere-scale chloride-mediated photocurrents that maintain the light sensitivity and reversible, step-like kinetic stability of earlier tools), and (3) generalizable strategies for targeting cells based not only on genetic identity, but also on morphology and tissue topology, to allow versatile targeting when promoters are not known or in genetically intractable organisms. Together, these results illustrate use of cell-biological principles to enable expansion of the versatile fast optogenetic technologies suitable for intact-systems biology and behavior

    The Unique Cysteine Knot Regulates the Pleotropic Hormone Leptin

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    Leptin plays a key role in regulating energy intake/expenditure, metabolism and hypertension. It folds into a four-helix bundle that binds to the extracellular receptor to initiate signaling. Our work on leptin revealed a hidden complexity in the formation of a previously un-described, cysteine-knotted topology in leptin. We hypothesized that this unique topology could offer new mechanisms in regulating the protein activity. A combination of in silico simulation and in vitro experiments was used to probe the role of the knotted topology introduced by the disulphide-bridge on leptin folding and function. Our results surprisingly show that the free energy landscape is conserved between knotted and unknotted protein, however the additional complexity added by the knot formation is structurally important. Native state analyses led to the discovery that the disulphide-bond plays an important role in receptor binding and thus mediate biological activity by local motions on distal receptor-binding sites, far removed from the disulphide-bridge. Thus, the disulphide-bridge appears to function as a point of tension that allows dissipation of stress at a distance in leptin

    Data set for transcriptome analysis of pituitary galnd in cattle breeds

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    Transcriptome data presented in this article is associated with the research article entitled “Single nucleotide polymorphism discovery in bovine pituitary gland using RNA-seq technology” published in PLOS One [1]. Herein, we provide raw and analysed RNA-seq data of pituitary gland tissues from three cattle breeds, viz., Polish-HF, Polish Red and Hereford cattle breeds. Bioinformatics pipelines of high-quality RNA-seq data includes the FastQC tools for quality controls, Trimmomatic cutadapt tools for trimming RNA-seq data, and BWA version 0.7.5-r404 for mapping and alignment to the Bos taurus reference genome, SAMtools for SNPs identifications in bovine pituitary gland transcriptome. Raw FASTq files for the RNA-seq libraries of bovine pituitary gland were deposited in the NCBI Sequence Read Archive (SRA) and have been assigned BioProject accession PRJNA312148

    Data set for transcriptome analysis of liver in cattle breeds

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    Transcriptome analysis using high-throughput next-generation sequencing (HT-NGS) technology provides the capability to understand global gene expression variations through a wide range of tissue samples in domesticated animals. We provide raw and analysed data for transcriptomic analysis of liver tissues from Polish-HF, Polish Red and Hereford cattle breeds, obtained by RNA-seq. High-quality sequencing data have been analysed using our bioinformatics pipeline which consists of FastQC for quality controls, Trimmomatic for trimming, and BWA version 0.7.5-r404 for alignment to the Bos taurus reference genome, SAMtools for SNPs identifications, and differentially expressed genes (DEGs) identification using DEseq and edgeR pipelines after adjustment for false-discovery rate (FDR) with adjusted two-sided p values &lt;0.01 and the trimmed mean of M values (TMM) normalisation method. The data accompanying the published manuscript describing the SNPs and DEGs identification in the bovine liver transcriptome of cattle breeds. Raw FASTq files for the RNA-seq libraries are deposited in the NCBI Sequence Read Archive (SRA) and have been assigned BioProject accession PRJNA312148. Raw and processed RNA-seq data were deposited and made publicly available on the Gene Expression Omnibus (GEO; GSE114233)
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