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The elongation rate, the gradient of the local elongation rate and the surface pH of maize roots were measured over 12 h. A data bank was constituted by storing these values. By sorting these results on the basis of different elongation rates, different classes of root were obtained. Two classes were chosen: the low-growth roots and the high-growth roots. The mean growth of these two root classes was stable with time and differed significantly from one another. The surface pH of the elongation zone was the same for the roots of these two classes, but the roots selected for their higher growth rate had a larger acid efflux in this zone. 相似文献
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Antoine Wystrach Sebastian Schwarz Patrick Schultheiss Guy Beugnon Ken Cheng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):167-179
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants)
to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised
natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through
the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations
between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the
positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants
(translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants
might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of
landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable. 相似文献
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A. A. Gheyas R. D. Houston J. C. Mota-Velasco D. R. Guy A. E. Tinch C. S. Haley J. A. Woolliams 《Animal genetics》2010,41(5):531-536
In a previous study, three significant quantitative trait loci (QTL) associated with resistance to Infectious Pancreatic Necrosis (IPN) disease were identified by analysing challenge data from one sub-population of Landcatch Atlantic salmon (Salmo salar) smolt. While these QTL were shown to affect the resistance in seawater, their effect in freshwater was unknown. This study investigates the effect of these QTL on IPN resistance in salmon fry in freshwater. Twenty families with intermediate levels of IPN mortality were analysed from a freshwater challenge trial undertaken on a different sup-population of LNS salmon to that studied previously. Only the QTL from linkage group 21 (LG21) appeared to have a significant and large effect on resistance in freshwater; the same QTL was found to have the largest effect in seawater in the previous study. Variance component analysis showed a high heritability for the QTL: 0.45 ± 0.07 on the liability scale and 0.25 ± 0.05 on the observed scale. In a family where both parents were segregating for the QTL, there was a 0% vs. 100% mortality in homozygous offspring for resistant and susceptible QTL alleles. The finding that the same QTL has major effect in both freshwater and seawater has important practical implications, as this will allow the improvement of resistance in both phases through marker assisted selection by targeting this QTL. Moreover, the segregation of the LG21 QTL in a different sub-population gives further evidence of its association with IPN-resistance. 相似文献
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G R Guy J Gordon R H Michell G Brown 《Biochemical and biophysical research communications》1985,131(1):484-491
Resting human tonsillar B cells were stimulated to divide by heat killed Staphylococcus aureus Cowan strain 1 which was shown to induce hydrolysis of phosphatidylinositol 4, 5-bisphosphate known to give rise to diacylglycerol and an increase in cytosolic free calcium. Addition of the diacylglycerols, 1-oleoyl-2 acetyl glycerol or sn-1, 2-dioctanoylglycerol, together with the calcium ionophore ionomycin to B cell cultures induced marked cell proliferation whereas these agents were ineffective when used alone. Both diacylglycerols were shown to compete with [3H] phorbol 12,13 dibutyrate in binding to protein kinase C. These data support the hypothesis that synergism between cytosolic calcium and endogenous diacylglycerol, which activates protein kinase C, is involved in signal transduction in the proliferation of human B cells. 相似文献
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Véronique Lavoie Anne‐Elen Kernaleguen Guy Charron Nada Farhat Mariève Cossette Aida M. Mamarbachi Bruce G. Allen Eric Rhéaume Jean‐Claude Tardif 《Obesity (Silver Spring, Md.)》2011,19(4):722-728
Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen‐coated dishes. Three sub‐populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub‐populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub‐population. We also demonstrated that EPCs, particularly one sub‐population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub‐populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin. 相似文献
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The basic mechanisms underlying chemically-mediated neurotransmission at synapses are well established. Synaptic vesicles release their contents of neurotransmitter by exocytosis, and are then recycled and refilled before re-priming for re-release. It is less clear, however, what determines the differences in the quantitative aspects of this process at synapses with different in vivo activity patterns, and the extent to which they can be adapted to changing patterns of usage. The neuromuscular junction is particularly suited to investigations of these issues, due to the presence of distinctive muscle fibre types, with well-differentiated physiological roles and hence, activity patterns. The relative accessibility of NMJs means that chronic recording and manipulation of in vivo activity patterns of single motor neurones are possible. Several laboratories around the world now examining how transmitter release at NMJs is adapted to maintain (or not) release under these identified activity patterns. This review will cover the current state of knowledge and briefly highlight areas where more research is required. For example, current knowledge is largely derived from invertebrate preparations, indicating a need for more detailed comparisons at mammalian NMJs with different activity patterns. Finally, it is not yet clear in any species whether adaptations observed with imposed activity can be driven to complete transformation, with appropriate stimulus regimes. 相似文献