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1.
As projects progress from pilot studies with few simple variables and small samples, the research process as a whole becomes qualitatively more complex and subject to an array of contamination by errors and mistakes. Data usually undergo a series of manipulations (e.g., recording, computer entry, transmission) prior to final statistical analysis. The process, then, consists of numerous operations only ending with eventual statistical analysis and write-up. We present a means of estimating the impact of process error in the same terms as psychometric reliability and discuss the implications for reducing the impact of errors on overall data quality. 相似文献
2.
Ektoras Hadjipanayi Peer-Hendrik Kuhn Philipp Moog Anna-Theresa Bauer Haydar Kuekrek Lilit Mirzoyan Anja Hummel Katharina Kirchhoff Burak Salgin Sarah Isenburg Ulf Dornseifer Milomir Ninkovic Hans-Günther Machens Arndt F. Schilling 《PloS one》2015,10(8)
Conceptually, premature initiation of post-wound angiogenesis could interfere with hemostasis, as it relies on fibrinolysis. The mechanisms facilitating orchestration of these events remain poorly understood, however, likely due to limitations in discerning the individual contribution of cells and extracellular matrix. Here, we designed an in vitro Hemostatic-Components-Model (HCM) to investigate the role of the fibrin matrix as protein factor-carrier, independent of its cell-scaffold function. After characterizing the proteomic profile of HCM-harvested matrix releasates, we demonstrate that the key pro-/anti-angiogenic factors, VEGF and PF4, are differentially bound by the matrix. Changing matrix fibrin mass consequently alters the balance of releasate factor concentrations, with differential effects on basic endothelial cell (EC) behaviors. While increasing mass, and releasate VEGF levels, promoted EC chemotactic migration, it progressively inhibited tube formation, a response that was dependent on PF4. These results indicate that the clot’s matrix component initially serves as biochemical anti-angiogenic barrier, suggesting that post-hemostatic angiogenesis follows fibrinolysis-mediated angiogenic disinhibition. Beyond their significance towards understanding the spatiotemporal regulation of wound healing, our findings could inform the study of other pathophysiological processes in which coagulation and angiogenesis are prominent features, such as cardiovascular and malignant disease. 相似文献
3.
Trace gas flux and the influence of short-term soil water and temperature dynamics in Australian sheep grazed pastures of differing productivity 总被引:1,自引:0,他引:1
S. J. Livesley R. Kiese J. Graham C. J. Weston K. Butterbach-Bahl S. K. Arndt 《Plant and Soil》2008,309(1-2):89-103
Temperate pastures are often managed with P fertilizers and N2-fixing legumes to maintain and increase pasture productivity which may lead to greater nitrous oxide (N2O) emissions and reduced methane (CH4) uptake. However, the diel and inter-daily variation in N2O and CH4 flux in pastures is poorly understood, especially in relation to key environmental drivers. We investigated the effect of pasture productivity, rainfall, and changing soil moisture and temperature upon short-term soil N2O and CH4 flux dynamics during spring in sheep grazed pasture systems in southeastern Australia. N2O and CH4 flux was measured continuously in a High P (23 kg P ha?1 yr?1) and No P pasture treatment and in a sheep camp area in a Low P (4 kg P ha?1 yr?1) pasture for a four week period in spring 2005 using an automated trace gas system. Although pasture productivity was three-fold greater in the High P than No P treatment, mean CH4 uptake was similar (?6.3?±?SE 0.3 to ?8.6?±?0.4 μg C m?2 hr?1) as were mean N2O emissions (6.5 to 7.9?±?0.8 μg N m?2 hr?1), although N2O flux in the No P pasture did not respond to changing soil water conditions. N2O emissions were greatest in the Low P sheep camp (12.4 μg?±?1.1 N m?2 hr?1) where there were also net CH4 emissions of 5.2?±?0.5 μg C m?2 hr?1. There were significant, but weak, relationships between soil water and N2O emissions, but not between soil water and CH4 flux. The diel temperature cycle strongly influenced CH4 and N2O emissions, but this was often masked by the confounding covariate effects of changing soil water content. There were no consistently significant differences in soil mineral N or gross N transformation rates, however, measurements of substrate induced respiration (SIR) indicated that soil microbial processes in the highly productive pasture are more N limited than P limited after >20 years of P fertilizer addition. Increased productivity, through P fertilizer and legume management, did not significantly increase N2O emissions, or reduce CH4 uptake, during this 4 week measurement period, but the lack of an N2O response to rainfall in the No P pasture suggests this may be evident over a longer measurement period. This study also suggests that small compacted and nutrient enriched areas of grazed pastures may contribute greatly to the overall N2O and CH4 trace gas balance. 相似文献
4.
Differential temperature measurement between interscapular brown adipose tissue (BAT, Tbat), rectum (Trect) and a subcutaneous point in the back left of the vertebral column (Tsc) was useful for examination of BAT-thermogenesis in glutamate-induced obese Wistar-rats. Positive temperature gradients Tbat-Tsc pointed to a basal BAT-thermogenesis, whereas negative temperature gradients Tbat-Trect did not indicate that heat production in lean and obese rats. One may conclude from this, that inclusion of subcutaneous points outside the BAT improves sensitivity of differential temperature measurements for BAT-thermogenesis. Basal temperatures Tbat, Trect and Tsc were reduced in obese rats compared to lean rats, although thermoinsulation of obese rats is improved on account of their high fat content. This points to a diminished heat production in obese rats. Cold exposure at 4 degrees C elicited an increase of temperature gradients Tbat-Trect in lean as well as in obese rats, with positive values found only in lean rats. However, positive values Tbat-Tsc were calculated for both groups. Increases were noted only in lean rats. Injection of noradrenaline (0.5 mg/kg i.m.) was followed by positive temperature gradients Tbat-Trect and increased positive values for Tbat-Tsc, pointing to a remarkable activation of BAT-thermogenesis in lean and obese rats. These findings confirm, that glutamate-induced obese rats preserved the ability to activate BAT-thermogenesis. There were, however, hints of reduced heat production in BAT of obese rats, thus contributing to obesity despite normophagia. 相似文献
5.
Therapeutic angiogenesis promises to aid the healing and regeneration of tissues suffering from a compromised vascular supply. Ischaemia therapy has so far primarily focused on delivering isolated angiogenic growth factors. The limited success of these strategies in clinical trials, however, is increasingly forcing researchers to recognize the difficulties associated with trying to mimic the angiogenic process, due to its natural complexity. Instead, a new school of thought is gradually emerging, focusing on how to induce angiogenesis at its onset, by utilizing hypoxia, the primary angiogenic stimulus in physiological, as well pathological states. This shift in therapeutic approach is underlined by the realization of the importance of depressed HIF-1 α-mediated gene programming in non-healing ischemic tissues, which could explain their apparent habituation to chronic hypoxic stress and the limited capacity to generate adaptive angiogenesis. Hypoxia-based strategies, then effectively aim to override the habituated angiogenic cellular response, re-start the regenerative process and drive it to completion. Here we make a distinction between those strategies that utilize hypoxia in vitro as a preconditioning tool to optimize the angiogenic potential of tissue/cells before transplantation, vs. strategies that aim to induce hypoxia-induced signaling in vivo, directly, through pharmacological means or gene transfer. We then discuss possible future directions for the field, as it moves into the phase of clinical trials. 相似文献
6.
Faezeh Shah Salani Hartmut Arndt Klaus Hausmann Frank Nitsche Frank Scheckenbach 《The ISME journal》2012,6(4):713-723
Knowledge of the spatial scales of diversity is necessary to evaluate the mechanisms driving biodiversity and biogeography in the vast but poorly understood deep sea. The community structure of kinetoplastids, an important group of microbial eukaryotes belonging to the Euglenozoa, from all abyssal plains of the South Atlantic and two areas of the eastern Mediterranean was studied using partial small subunit ribosomal DNA gene clone libraries. A total of 1364 clones from 10 different regions were retrieved. The analysis revealed statistically not distinguishable communities from both the South-East Atlantic (Angola and Guinea Basin) and the South-West Atlantic (Angola and Brazil Basin) at spatial scales of 1000–3000 km, whereas all other communities were significantly differentiated from one another. It seems likely that multiple processes operate at the same time to shape communities of deep-sea kinetoplastids. Nevertheless, constant and homogenous environmental conditions over large spatial scales at abyssal depths, together with high dispersal capabilities of microbial eukaryotes, maintain best the results of statistically indistinguishable communities at larger spatial scales. 相似文献
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Claire Farrell Christopher Szota Nicholas S. G. Williams Stefan K. Arndt 《Plant and Soil》2013,372(1-2):177-193