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Quantitative Contribution (quantitative + contribution)
Selected AbstractsMolecular modifiers of T cell antigen receptor triggering threshold: the mechanism of CD28 costimulatory receptorIMMUNOLOGICAL REVIEWS, Issue 1 2003Oreste Acuto Summary:, CD28 was thought to represent a prototypic membrane receptor responsible for delivering the classically defined ,second signal' needed to avoid T cell paralysis when recognizing antigen presented by appropriate antigen presenting cells (APCs). Almost two decades after its molecular identification, the mechanism by which this ,second receptor' facilitates clonal expansion and differentiation upon antigen encounter is still not fully elucidated. There may be at least two reasons for this partially gray picture: the use of nonphysiological experimental conditions to study it and the fact that the action of CD28 may be partly masked by the presence of additional T cell surface receptors that also provide some costimulatory signals, although not equivalent to the one delivered through CD28. Thus, instead of aging, the study of CD28 is still a topical subject. What is appearing through work of recent years is that far from being purely qualitative, the CD28 signal provides a key quantitative contribution to potently boost the T cell antigen receptor (TCR) signal. In other words, CD28 is in part a signaling ,sosia' of the TCR. Also, it is clear now that CD28 operates via multiple molecular effects. Still, what we do not understand is the ,qualitative' part of this signal, perhaps due to lack of identification of unique signaling components and/or pathways activated by CD28 only. Here we review a series of recent findings pointing towards novel avenues to better understand the molecular basis of CD28 function. [source] The contribution of the swimbladder to buoyancy in the adult zebrafish (Danio rerio): A morphometric analysisJOURNAL OF MORPHOLOGY, Issue 6 2008George N. Robertson Abstract Many teleost fishes use a swimbladder, a gas-filled organ in the coelomic cavity, to reduce body density toward neutral buoyancy, thus minimizing the locomotory cost of maintaining a constant depth in the water column. However, for most swimbladder-bearing teleosts, the contribution of this organ to the attainment of neutral buoyancy has not been quantified. Here, we examined the quantitative contribution of the swimbladder to buoyancy and three-dimensional stability in a small cyprinid, the zebrafish (Danio rerio). In aquaria during daylight hours, adult animals were observed at mean depths from 10.1 ± 6.0 to 14.2 ± 5.6 cm below the surface. Fish mass and whole-body volume were linearly correlated (r2 = 0.96) over a wide range of body size (0.16,0.73 g); mean whole-body density was 1.01 ± 0.09 g cm,3. Stereological estimations of swimbladder volume from linear dimensions of lateral X-ray images and direct measurements of gas volumes recovered by puncture from the same swimbladders showed that results from these two methods were highly correlated (r2 = 0.85). The geometric regularity of the swimbladder thus permitted its volume to be accurately estimated from a single lateral image. Mean body density in the absence of the swimbladder was 1.05 ± 0.04 g cm,3. The swimbladder occupied 5.1 ± 1.4% of total body volume, thus reducing whole-body density significantly. The location of the centers of mass and buoyancy along rostro-caudal and dorso-ventral axes overlapped near the ductus communicans, a constriction between the anterior and posterior swimbladder chambers. Our work demonstrates that the swimbladder of the adult zebrafish contributes significantly to buoyancy and attitude stability. Furthermore, we describe and verify a stereological method for estimating swimbladder volume that will aid future studies of the functions of this organ. J Morphol., 2008. © 2008 Wiley-Liss, Inc. [source] Quantitative evaluation of marine protein contribution in ancient diets based on nitrogen isotope ratios of individual amino acids in bone collagen: An investigation at the Kitakogane Jomon siteAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Yuichi I. Naito Abstract Nitrogen stable isotopes analysis of individual bone collagen amino acids was applied to archeological samples as a new tool for assessing the composition of ancient human diets and calibrating radiocarbon dates. We used this technique to investigate human and faunal samples from the Kitakogane shell midden in Hokkaido, Japan (5,300,6,000 cal BP). Using compound-specific nitrogen isotope analysis of individual amino acids, we aimed to estimate i) the quantitative contribution of marine and terrestrial protein to the human diet, and ii) the mean trophic level (TL) from which dietary protein was derived from marine ecosystems. Data were interpreted with reference to the amino acid trophic level (TLAA) model, which uses empirical amino acid ,15N from modern marine fauna to construct mathematical equations that predict the trophic position of organisms. The TLAA model produced realistic TL estimates for the Kitakogane marine animals. However, this model was not appropriate for the interpretation of human amino acid ,15N, as dietary protein is derived from both marine and terrestrial environments. Hence, we developed a series of relevant equations that considered the consumption of dietary resources from both ecosystems. Using these equations, the mean percentage of marine protein in the Kitakogane human diet was estimated to be 74%. Although this study is one of the first systematic investigations of amino acid ,15N in archeological bone collagen, we believe that this technique is extremely useful for TL reconstruction, palaeodietary interpretation, and the correction of marine reservoir effects for radiocarbon dating. Am J Phys Anthropol 143:31,40, 2010. © 2010 Wiley-Liss, Inc. [source] Quantitative Analysis of Pulsatile Flow Contribution to UltrafiltrationARTIFICIAL ORGANS, Issue 1 2009Ki Moo Lim Abstract We evaluated the quantitative contribution of pulsatile flow to ultrafiltration (UF) in terms of fluid power, membrane stretch, and reduction of membrane layering. An in vitro comparison of the UF rate using pulsatile and roller pumps was performed with distilled water and bovine whole blood. The mean transmembrane pressure (TMPm) and UF rate were higher with the pulsatile pump for the same mean flow rate: 6.6 mm Hg and 21.1 mL/min higher on average for distilled water and 34.2 mm Hg and 31.4 mL/min higher on average for blood. The average UF rate was 8.4 mL/min higher with the pulsatile pump for the same TMPm with bovine blood. However, the relationship between the UF rate and the TMPm was independent of the flow configuration for distilled water. We showed that the higher UF rate in the pulsatile pump is mainly due to greater fluid power and reduction of membrane layering, while the membrane stretch was not an important factor. [source] | |||||||||||||