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991.
Pascale Calabrese Pierre Baconnier Aicha Laouani Julie Fontecave-Jallon Pierre-Yves Guméry André Eberhard Gila Benchetrit 《Acta biotheoretica》2010,58(2-3):265-275
To study the interaction of forces that produce chest wall motion, we propose a model based on the lever system of Hillman and Finucane (J Appl Physiol 63(3):951–961, 1987) and introduce some dynamic properties of the respiratory system. The passive elements (rib cage and abdomen) are considered as elastic compartments linked to the open air via a resistive tube, an image of airways. The respiratory muscles (active) force is applied to both compartments. Parameters of the model are identified in using experimental data of airflow signal measured by pneumotachography and rib cage and abdomen signals measured by respiratory inductive plethysmography on eleven healthy volunteers in five conditions: at rest and with four level of added loads. A breath by breath analysis showed, whatever the individual and the condition are, that there are several breaths on which the airflow simulated by our model is well fitted to the airflow measured by pneumotachography as estimated by a determination coefficient R 2 ≥ 0.70. This very simple model may well represent the behaviour of the chest wall and thus may be useful to interpret the relative motion of rib cage and abdomen during quiet breathing. 相似文献
992.
Keratin intermediate filaments (IFs) fulfill an important function of structural support in epithelial cells. The necessary mechanical attributes require that IFs be organized into a crosslinked network and accordingly, keratin IFs are typically organized into large bundles in surface epithelia. For IFs comprised of keratins 5 and 14 (K5, K14), found in basal keratinocytes of epidermis, bundling can be self-driven through interactions between K14's carboxy-terminal tail domain and two regions in the central α-helical rod domain of K5. Here, we exploit theoretical principles and computational modeling to investigate how such cis-acting determinants best promote IF crosslinking. We develop a simple model where keratin IFs are treated as rigid rods to apply Brownian dynamics simulation. Our findings suggest that long-range interactions between IFs are required to initiate the formation of bundlelike configurations, while tail domain-mediated binding events act to stabilize them. Our model explains the differences observed in the mechanical properties of wild-type versus disease-causing, defective IF networks. This effort extends the notion that the structural support function of keratin IFs necessitates a combination of intrinsic and extrinsic determinants, and makes specific predictions about the mechanisms involved in the formation of crosslinked keratin networks in vivo. 相似文献
993.
994.
Martin FL Kelly JG Llabjani V Martin-Hirsch PL Patel II Trevisan J Fullwood NJ Walsh MJ 《Nature protocols》2010,5(11):1748-1760
Infrared (IR) spectroscopy of intact cells results in a fingerprint of their biochemistry in the form of an IR spectrum; this has given rise to the new field of biospectroscopy. This protocol describes sample preparation (a tissue section or cytology specimen), the application of IR spectroscopy tools, and computational analysis. Experimental considerations include optimization of specimen preparation, objective acquisition of a sufficient number of spectra, linking of the derived spectra with tissue architecture or cell type, and computational analysis. The preparation of multiple specimens (up to 50) takes 8 h; the interrogation of a tissue section can take up to 6 h (~100 spectra); and cytology analysis (n = 50, 10 spectra per specimen) takes 14 h. IR spectroscopy generates complex data sets and analyses are best when initially based on a multivariate approach (principal component analysis with or without linear discriminant analysis). This results in the identification of class clustering as well as class-specific chemical entities. 相似文献
995.
996.
Audrey Coreau Sébastien Treyer Pierre‐Olivier Cheptou John D. Thompson Laurent Mermet 《Oikos》2010,119(8):1364-1376
In a mainly experimental science based traditionally on hypothesis testing such as ecology, studying futures may be difficult. However, in the last few decades, predicting the consequences of global changes on the dynamics and function of ecological systems has become a major challenge in ecological research. To study how ecological scientists deal with potential difficulties in studying futures, we adopted a reflexive viewpoint on how scientists address the study of ecological futures. To do so we questioned a panel of ecological scientists on their practical involvement and point of view. Quantitative and qualitative analyses of their responses showed that predictions or predictive models were the dominant theme. Many quantitative models, based on statistical correlations, empirical rules or processes have been developed and their methodological limitations explored by the researchers we interviewed. In a small proportion of studies, qualitative scenarios have been elaborated to explore the range of possible futures. Interviewees emphasized the problem of dealing with ecological complexity and multiple future possibilities. Specificities of futures compared to past or present events were not fully identified. In fact, researchers studying futures mainly adopted a reductionist approach, trying to simplify complex ecological systems. But methods and tools promoted by such an approach to science may not always be appropriate to deal with future ecological complexity. Indeed, an emphasis on prediction prevents ecologists from acknowledging the multiplicity and undetermined nature of futures. 相似文献
997.
998.
999.
Tiziana Gigliobianco Bernard Lakaye Pierre Wins Benaïssa El Moualij Willy Zorzi Lucien Bettendorff 《BMC microbiology》2010,10(1):148
Background
E. coli cells are rich in thiamine, most of it in the form of the cofactor thiamine diphosphate (ThDP). Free ThDP is the precursor for two triphosphorylated derivatives, thiamine triphosphate (ThTP) and the newly discovered adenosine thiamine triphosphate (AThTP). While, ThTP accumulation requires oxidation of a carbon source, AThTP slowly accumulates in response to carbon starvation, reaching ~15% of total thiamine. Here, we address the question whether AThTP accumulation in E. coli is triggered by the absence of a carbon source in the medium, the resulting drop in energy charge or other forms of metabolic stress. 相似文献1000.
Tailane Sant’Anna Moreira Valéria Pereira de Sousa Maria Bernadete Riemma Pierre 《AAPS PharmSciTech》2010,11(2):621-629
Transdermal delivery of non-steroidal anti-inflammatory drugs may be an interesting strategy for delivering these drugs to
the diseased site, but it would be ineffective due to low skin permeability. We investigated whether oleic acid (OA), a lipid
penetration enhancer in poloxamer gels named poloxamer-based delivery systems (PBDS), can improve lumiracoxib (LM) delivery
to/through the skin. The LM partition coefficient (K) studies were carried out in order to evaluate the drug lipophilicity grade (K
octanol/buffer), showing values >1 which demonstrated its high lipophilicity. Both in vitro percutaneous absorption and skin retention studies of LM were measured in the presence or absence of OA (in different concentrations)
in PBDS using porcine ear skin. The flux of in vitro percutaneous absorption and in vitro retention of LM in viable epidermis increased in the presence of 10.0% (w/w) OA in 25.0% (w/w) poloxamer gel. In vivo cutaneous irritation potential was carried out in rabbits showing that this formulation did not provide primary or cumulative
cutaneous irritability in animal model. The results showed that 25.0% poloxamer gel containing 10.0% OA is potential transdermal
delivery system for LM. 相似文献