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Mechanisms Necessary (mechanism + necessary)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

An improved force-restore method for soil temperature prediction

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008
Z. Gao
Summary The force-restore method originally developed to enable soil temperature predictions assumes that soil is uniform with depth (i.e. the vertical gradient of thermal diffusivity is zero in soil) and that thermal conduction is the only heat transfer mechanism necessary for prediction of soil temperature. These assumptions hamper the applicability of the force-restore method to many natural soil conditions. The main objective of this study is to revise the force-restore method by extending it to include the possibility of soil heterogeneity with depth (i.e. non-zero vertical gradient of thermal diffusivity in soil) and to include the possible occurrence of convective heat transfer as well as conductive heat transfer in soil. Soil temperatures calculated by the current and the revised force-restore methods for a shallow soil layer were compared with measured soil temperatures at a bare soil site in the China Loess Plateau from 22 to 26 July 2005. Results showed that the revised method improved on the current force-restore method, which overestimated either the diurnal amplitude or the phase shift for the shallow soil layer. These results indicate that the revised force-restore method is more applicable than the current force-restore method for predicting soil temperatures in naturally occurring non-uniform soil. The revised force-restore method has potential application within many land-atmosphere numerical models. [source]

A Mu-class glutathione S -transferase from gills of the marine shrimp Litopenaeus vannamei: Purification and characterization

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2007
Carmen A. Contreras-Vergara
Abstract Glutathione S -transferases (GSTs) are a family of detoxifying enzymes that catalyze the conjugation of glutathione (GSH) to electrophiles, thereby increasing the solubility of GSH and aiding its excretion from the cell. In this study, a glutatione S -transferase from the gills of the marine shrimp Litopenaeus vannamei was purified by affinity chromatography using a glutathione,agarose affinity column. GST was purified to homogeneity as judged by reducing SDS-PAGE and zymograms. This enzyme is a homodimer composed of ,25-kDa subunits and identified as a Mu-class GST based on its activity against 1-chloro-2,4-dinitrobenzene (CDNB) and internal peptide sequence. The specific activity of purified GST was 440.12 ,mol/(min mg), and the Km values for CDNB and GSH are very similar (390 and 335 ,M, respectively). The intersecting pattern of the initial velocities of this enzyme in the Lineweaver,Burke plot is consistent with a sequential steady-state kinetic mechanism. The high specific activity of shrimp GST may be related to a highly effective detoxification mechanism necessary in gills since they are exposed to the external and frequently contaminated environment. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:62,67, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20162 [source]

Cryopreservable neutrophil surrogates: Granule-poor, motile cytoplasts from polymorphonuclear leukocytes home to inflammatory lesions in vivo

CYTOSKELETON, Issue 5 2006
Stephen E. Malawista
Abstract Cytokineplasts (CKP) are anucleate, motile, granule-poor fragments induced from polymorphonuclear leukocytes on surfaces by the brief application of heat. Derived from the peripheral cytoplasm and membranes of PMN, they retain the sensing, transducing, and effector mechanisms necessary for chemotaxis and phagocytosis, and appear to represent a functional, self-purification of the motile apparatus. Unlike their parent PMN, CKP are cryopreservable. We have shown that they can adhere to endothelial cell monolayers, open interendothelial cell junctions, and migrate to the abluminal side when stimulated by a chemoattractant. Employing an animal model, we now show that, given intravenously, they can home to an inflammatory target lesion in vivo. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source]

Late postnatal maturation of excitatory synaptic transmission permits adult-like expression of hippocampal-dependent behaviors

HIPPOCAMPUS, Issue 5 2005
Theodore C. Dumas
Abstract Sensorimotor systems in altricial animals mature incrementally during early postnatal development, with complex cognitive abilities developing late. Of prominence are cognitive processes that depend on an intact hippocampus, such as contextual,configural learning, allocentric and idiocentric navigation, and certain forms of trace conditioning. The mechanisms that regulate the delayed maturation of the hippocampus are not well understood. However, there is support for the idea that these behaviors come "on line" with the final maturation of excitatory synaptic transmission. First, by providing a timeline for the first behavioral expression of various forms of learning and memory, this study illustrates the late maturation of hippocampal-dependent cognitive abilities. Then, functional development of the hippocampus is reviewed to establish the temporal relationship between maturation of excitatory synaptic transmission and the behavioral evidence of adult-like hippocampal processing. These data suggest that, in rats, mechanisms necessary for the expression of adult-like synaptic plasticity become available at around 2 postnatal weeks of age. However, presynaptic plasticity mechanisms, likely necessary for refinement of the hippocampal network, predominate and impede information processing until the third postnatal week. © 2005 Wiley-Liss, Inc. [source]

How to build a fungal fruit body: from uniform cells to specialized tissue

MOLECULAR MICROBIOLOGY, Issue 4 2007
Silke Busch
Summary It is a challenge in biology to explore the molecular and cellular mechanisms necessary to form a complex three-dimensional structure composed of different cell types. Interesting models to study the underlying processes are fungi that can transform their wire-like hyphal filaments into complex and sometimes container-like fruit bodies. In the past, the role of developmental triggers and transcription factors was a major focus of research on fungal model organisms. In this issue of Molecular Microbiology, Nowrousian and collaborators report that fruit body development of the model organism Sordaria macrospora includes a novel player, a specific membrane protein of the endoplasmic reticulum that is not required for vegetative growth. This finding represents an important step towards connecting regulation of development with the co-ordinated changes in cellular compartments. [source]