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1.
2.
Winnie W.Y. Lau Marlene M. Martinez 《Journal of experimental marine biology and ecology》2003,295(1):1-21
Hydrodynamic forces can affect survival as well as limit the movement of motile benthic animals. An animal's danger of dislodgement depends on the hydrodynamic forces it experiences in its microhabitat relative to the force required to dislodge it (tenacity) from the substratum. We measured water flow and substratum characteristics in two different habitats of the shore crab Pachygrapsus crassipes: a wave-swept rocky shore and an intertidal mudflat. The maximum water velocities and accelerations in the microhabitats of the crabs at the wave-swept site were three times and two times greater, respectively, than at the mudflat site. In the laboratory, we measured the tenacity of crabs of various sizes on different substrata, and also measured their drag, lift and added-mass coefficients. Using these data, we calculated the flow conditions under which crabs would be overturned or sheared off the substratum in their two habitats. The net horizontal force (drag plus acceleration reaction) required to dislodge a crab on a rugose rock substratum was an order of magnitude greater than on smooth rock and two orders of magnitude greater than on mud. Our calculations indicate that, under non-storm conditions, crabs will not be dislodged from the substratum in either the mudflat or the wave-swept habitat when grasping the substratum with maximum tenacity. Moving crabs have lower tenacity and our calculations predict that hydrodynamic forces will restrict the mobility of large crabs more than that of small ones on smooth, but not on rugose rock. 相似文献
3.
Digital images of ex situ germplasm stored in the Sardinian Germplasm Bank (BG-SAR) were used for the application of image analysis techniques at the Stazione Sperimentale di Granicoltura per la Sicilia. The analysed accessions refer to 148 taxonomic units belonging to 102 genera and 47 families, typical of the Sardinian flora, and of the Mediterranean basin in general.The images of diaspores were acquired by a flatbed scanner and elaborated with a macro specially developed for the morphometric and colorimetric measurements. This method allowed carrying out a database for the characterization of autochthonous germplasm in entry to the bank and the realization of statistic classifiers for the discrimination of genera and species within the following families: Apiaceae, Boraginaceae, Caryophyllaceae, Cistaceae, Fabaceae and Scrophulariaceae. Such classifiers, based on the linear discriminant analysis (LDA) technique and checked by cross-validation, showed a performance included between 74.3% and 96.4%.In addition, for the genus Astragalus, it was possible to elaborate a classifier able to identify very similar taxa of a species complex, obtaining a performance between 83.7% and 100%. Such analysis proved the validity of the methodology also from the taxonomic point of view.Suggestions for subsequent methodological progress, which could offer applications in other research issues, such as ecological analysis, soil seed bank and archaeological botany are proposed. 相似文献
4.
Oscar Fernandez‐Capetillo 《EMBO reports》2010,11(1):32-36
Ageing is an unavoidable corollary to being alive; the most intuitive interpretation of ageing being that it is the consequence of progressive body degeneration. In agreement with this, current models propose that ageing occurs through a stepwise accumulation of DNA damage, which ultimately limits the regenerative capacity of tissues. On the other hand, there is increasing evidence that fetal distress can influence the development of disease in adult life, a phenomenon known as ‘intrauterine programming’. The extent to which an intrauterine exposure to DNA damage can compromise lifespan remains unclear. My group has recently generated a murine model of a human syndrome linked to defective DNA repair and observed that these animals age prematurely, but the accumulation of DNA damage is restricted mostly to the embryonic period. Here, I discuss the implications of this finding and propose that ageing can be influenced by fetal distress. 相似文献
5.
Dominique Martinez Antoine Chaffiol Nicole Voges Yuqiao Gu Sylvia Anton Jean-Pierre Rospars Philippe Lucas 《PloS one》2013,8(4)
Insects and robots searching for odour sources in turbulent plumes face the same problem: the random nature of mixing causes fluctuations and intermittency in perception. Pheromone-tracking male moths appear to deal with discontinuous flows of information by surging upwind, upon sensing a pheromone patch, and casting crosswind, upon losing the plume. Using a combination of neurophysiological recordings, computational modelling and experiments with a cyborg, we propose a neuronal mechanism that promotes a behavioural switch between surge and casting. We show how multiphasic On/Off pheromone-sensitive neurons may guide action selection based on signalling presence or loss of the pheromone. A Hodgkin-Huxley-type neuron model with a small-conductance calcium-activated potassium (SK) channel reproduces physiological On/Off responses. Using this model as a command neuron and the antennae of tethered moths as pheromone sensors, we demonstrate the efficiency of multiphasic patterning in driving a robotic searcher toward the source. Taken together, our results suggest that multiphasic On/Off responses may mediate olfactory navigation and that SK channels may account for these responses. 相似文献
6.
Servais P Martinez J Billen G Vives-Rego J 《Applied and environmental microbiology》1987,53(8):1977-1979
Determination of [H] thymidine incorporation into bacterial DNA versus other macromolecules is usually achieved by NaOH and hot trichloroacetic acid hydrolysis. This procedure was found not to be specific enough. An alternative method founded on DNase treatment is proposed. Under the new method, the fraction of thymidine incorporated into DNA ranged from 10 to 83%. 相似文献
7.
Endosymbiotic origin and codon bias of the nuclear gene for chloroplast glyceraldehyde-3-phosphate dehydrogenase from maize 总被引:19,自引:0,他引:19
Henner Brinkmann Pascal Martinez Françoise Quigley William Martin Rüdiger Cerff 《Journal of molecular evolution》1987,26(4):320-328
Summary The nuclei of plant cells harbor genes for two types of glyceraldehyde-3-phosphate dehydrogenases (GAPDH) displaying a sequence divergence corresponding to the prokaryote/eukaryote separation. This strongly supports the endosymbiotic theory of chloroplast evolution and in particular the gene transfer hypothesis suggesting that the gene for the chloroplast enzyme, initially located in the genome of the endosymbiotic chloroplast progenitor, was transferred during the course of evolution into the nuclear genome of the endosymbiotic host. Codon usage in the gene for chloroplast GAPDH of maize is radically different from that employed by present-day chloroplasts and from that of the cytosolic (glycolytic) enzyme from the same cell. This reveals the presence of subcellular selective pressures which appear to be involved in the optimization of gene expression in the economically important graminaceous monocots. 相似文献
8.
The rate of hydrolysis of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene (BPDE) to tetrahydroxy derivatives (tetrols) in the presence of various subcellular fractions of rat liver was investigated. Microsomes and nuclei increased the half-life of BPDE in a concentration-dependent manner whereas cytosol had no such effect. The presence of 1 mg microsomal protein/ml increased the half-life of BPDE from 4 to 60 min at 22 degrees C and from 1.5 to 20 min at 37 degrees C. Nuclei equivalent of 500 micrograms DNA/ml increased the half-life from 1.9 to 3.6 min at 37 degrees C. Liposomes prepared from microsomal lipids mimicked the effect of microsomes indicating that BPDE is stabilized primarily by interacting with lipids. The significance of these interactions for the stability of BPDE in an intact cell system was evaluated by using isolated hepatocytes. In these cells the half-life of BPDE was substantially shorter (1 min at 5 X 10(6) cells/ml) than in buffer (3 min). However, hydrolysis of BPDE to tetrols was a minor reaction (less than or equal to 3% of added BPDE at a cell density greater than or equal to 5 X 10(6) cells/ml) and the main route of elimination (greater than or equal to 75%) was through conjugation with glutathione. 相似文献
9.
J. Ruiz-Herrera J. P. Martinez M. Casanova M. L. Gil R. Sentandreu 《Archives of microbiology》1987,149(2):156-162
Cells from the slime variant of Neurospora crassa were broken in isotonic conditions by use of triethanolamine buffer plus EDTA. After removal of large membranous structures by low-speed centrifugation, chitosomes and secretory vesicles were separated by means of gel filtration, precipitation of membranous contaminants with Concanavalin A, and centrifugation in sucrose or glycerol gradients. Polypeptidic composition of fractions enriched in secretory vesicles or chitosomes was found to be distinct. By these criteria we concluded that chitosomes and secretory vesicles represent different populations of microvesicles. Both microvesicular populations appeared free of endoplasmic reticulum and vacuolar contaminants as demonstrated by determination of appropriate enzymatic markers.Abbreviations ER
Endoplasmic reticulum
- UDP-GlcNAc
uridine-5-diphosphate N-acetyl glucosamine
- GlcNAc
N-acetyl glucosamine
- SDS
sodium dodecyl sulfate
- PMSF
phenyl methyl sulfonyl fluoride
- EDTA
ethylene diamino tetraacetic acid
Investigador Nacional de Mexico. On leave from the Centro de Investigacion y Estudios Avanzados (IPN), and the Universidad de Guanajuato, Gto., Mexico 相似文献
10.
Acetyl-cholinesterase and fluoride-resistant acid phosphatase activities in dorsal root ganglia in the rat 总被引:1,自引:0,他引:1
J A Vega C Rodriguez M Medina A Martinez Telleria M E Bengoechea A Perez-Casas 《Cellular and molecular biology, including cyto-enzymology》1989,35(1):39-46
Acetylcholinesterase and fluoride-resistant acid phosphatase activities were contrasted in alternative serial sections of rat dorsal root ganglia. The morphometric analysis demonstrated no correlation between cellular size and enzymatic activity. Differences with previous works in this area are discussed. 相似文献