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Decrease or growth of population comes from the interplay of death and birth (and locally, migration). We revive the logistic
model, which was tested and found wanting in early-20th-century studies of aggregate human populations, and apply it instead
to life expectancy (death) and fertility (birth), the key factors totaling population. For death, once an individual has legally
entered society, the logistic portrays the situation crisply. Human life expectancy is reaching the culmination of a two-hundred
year-process that forestalls death until about 80 for men and the mid-80's for women. No breakthroughs in longevity are in
sight unless genetic engineering comes to help. For birth, the logistic covers quantitatively its actual morphology. However,
because we have not been able to model this essential parameter in a predictive way over long periods, we cannot say whether
the future of human population is runaway growth or slow implosion. Thus, we revisit the logistic analysis of aggregate human
numbers. From a niche point of view, resources are the limits to numbers, and access to resources depends on technologies.
The logistic makes clear that for homo faber, the limits to numbers keep shifting. These moving edges may most confound forecasting
the long-run size of humanity. 相似文献
3.
P D Ellis P S Marchetti P Strang J D Potter 《The Journal of biological chemistry》1988,263(21):10284-10288
The binding of cadmium to the calcium binding subunit of skeletal troponin (STnC) has been reinvestigated using direct binding methods and fluorescent derivatives. These data provide straightforward explanations of the observed titration behavior in the 113Cd NMR (Ellis, P.D., Strang, P., and Potter, J.D. (1984) J. Biol. Chem. 259, 10348-10356). Further, fluorescent derivatives of skeletal troponin C provide an excellent means of establishing a sequence assignment for the resonances observed in the 113Cd NMR. The results of these experiments demonstrate that sites I and II, the Ca2+ regulatory sites, can be assigned to resonances at -108.5 and -101.5 ppm, respectively. Sites III and IV, the structural sites, are assigned to resonances -112.8 and -106.8 ppm, respectively. These data are discussed in terms of recent structural findings and speculations. 相似文献
4.
Studies on the folate coenzyme metabolism in the castrated rat and treated with 17 -estradiol 总被引:1,自引:0,他引:1
5.
Arhamatoulaye Ma?ga Jon Merlin Elodie Marcon Céline Rouget Maud Larregola Bernard Gilquin Carole Fruchart-Gaillard Evelyne Lajeunesse Charles Marchetti Alain Lorphelin Laurent Bellanger Roger J. Summers Dana S. Hutchinson Bronwyn A. Evans Denis Servent Nicolas Gilles 《PloS one》2013,8(7)
ρ-Da1a is a three-finger fold toxin from green mamba venom that is highly selective for the α1A-adrenoceptor. This toxin has atypical pharmacological properties, including incomplete inhibition of 3H-prazosin or 125I-HEAT binding and insurmountable antagonist action. We aimed to clarify its mode of action at the α1A-adrenoceptor. The affinity (pKi 9.26) and selectivity of ρ-Da1a for the α1A-adrenoceptor were confirmed by comparing binding to human adrenoceptors expressed in eukaryotic cells. Equilibrium and kinetic binding experiments were used to demonstrate that ρ-Da1a, prazosin and HEAT compete at the α1A-adrenoceptor. ρ-Da1a did not affect the dissociation kinetics of 3H-prazosin or 125I-HEAT, and the IC50 of ρ-Da1a, determined by competition experiments, increased linearly with the concentration of radioligands used, while the residual binding by ρ-Da1a remained stable. The effect of ρ-Da1a on agonist-stimulated Ca2+ release was insurmountable in the presence of phenethylamine- or imidazoline-type agonists. Ten mutations in the orthosteric binding pocket of the α1A-adrenoceptor were evaluated for alterations in ρ-Da1a affinity. The D1063.32A and the S1885.42A/S1925.46A receptor mutations reduced toxin affinity moderately (6 and 7.6 times, respectively), while the F862.64A, F2886.51A and F3127.39A mutations diminished it dramatically by 18- to 93-fold. In addition, residue F862.64 was identified as a key interaction point for 125I-HEAT, as the variant F862.64A induced a 23-fold reduction in HEAT affinity. Unlike the M1 muscarinic acetylcholine receptor toxin MT7, ρ-Da1a interacts with the human α1A-adrenoceptor orthosteric pocket and shares receptor interaction points with antagonist (F862.64, F2886.51 and F3127.39) and agonist (F2886.51 and F3127.39) ligands. Its selectivity for the α1A-adrenoceptor may result, at least partly, from its interaction with the residue F862.64, which appears to be important also for HEAT binding. 相似文献
6.
Marta Marchetti Delphine Capela Renaud Poincloux Nacer Benmeradi Marie-Christine Auriac Aurélie Le Ru Isabelle Maridonneau-Parini Jacques Batut Catherine Masson-Boivin 《PloS one》2013,8(2)
Rhizobia are symbiotic soil bacteria able to intracellularly colonize legume nodule cells and form nitrogen-fixing symbiosomes therein. How the plant cell cytoskeleton reorganizes in response to rhizobium colonization has remained poorly understood especially because of the lack of an in vitro infection assay. Here, we report on the use of the heterologous HeLa cell model to experimentally tackle this question. We observed that the model rhizobium Sinorhizobium meliloti, and other rhizobia as well, were able to trigger a major reorganization of actin cytoskeleton of cultured HeLa cells in vitro. Cell deformation was associated with an inhibition of the three major small RhoGTPases Cdc42, RhoA and Rac1. Bacterial entry, cytoskeleton rearrangements and modulation of RhoGTPase activity required an intact S. meliloti biosynthetic pathway for queuosine, a hypermodifed nucleoside regulating protein translation through tRNA, and possibly mRNA, modification. We showed that an intact bacterial queuosine biosynthetic pathway was also required for effective nitrogen-fixing symbiosis of S. meliloti with its host plant Medicago truncatula, thus indicating that one or several key symbiotic functions of S. meliloti are under queuosine control. We discuss whether the symbiotic defect of que mutants may originate, at least in part, from an altered capacity to modify plant cell actin cytoskeleton. 相似文献
7.
P Almasio C Marchetti F Piovella M M Ricetti E Ascari 《Bollettino della Società italiana di biologia sperimentale》1983,59(10):1544-1550
Electron microscope technique was used to investigate the passage across the endothelial monolayer by murine tumor lines. After the initial adhesion, cancer cells induce a retraction of endothelium and migrate under vascular intima. Subsequently they spread on basement membrane showing a flattened shape, meanwhile endothelial cells reconstitute the monolayer. The four tumor lines show a similar behaviour being able to induce endothelial retraction and exposure of extracellular matrix and cross through the monolayer. The technique appears useful to study in details this multi-step process. 相似文献
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9.
Fangyuan Cheng Qian Wang Pierpaolo Maisano Delser Chenhong Li 《Ecology and evolution》2019,9(21):12202-12215
Freshwater fish evolved from anadromous ancestors can be found in almost all continents. The roles of paleogeographic events and nature selection in speciation process often are under focus of research. We studied genetic diversity of anadromous and resident tapertail anchovies (Coilia nasus species complex) in the Yangtze River Basin using 4,434 nuclear loci, and tested the history of freshwater invasion of C. nasus. We found that both C. brachygnathus and C. nasus were valid species, but the resident C. nasus taihuensis and the anadromous C. nasus were not different genetically based on Bayes factor species delimitation (BFD*). Maximum likelihood tree, Network, PCA and STRUCTURE analyses all corroborated the results of BFD*. Two independent freshwater invasion events of C. nasus were supported, with the first event occurring around 4.07 Ma and the second happened around 3.2 Ka. The time of the two freshwater invasions is consistent with different paleogeographic events. Estimation showed that gene flow was higher within ecotypes than between different ecotypes. F‐DIST analyses identified 120 disruptive outliers by comparing C. brachygnathus to anadromous C. nasus, and 21 disruptive outliers by comparing resident C. nasus to anadromous C. nasus. Nine outliers were found to be common between the two comparisons, indicating that independent freshwater invasion of C. nasus might involve similar molecular pathways. The results of this study suggest that adaptation to landlocked freshwater environment of migratory fish can evolve multiple times independently, and morphology of landlocked ecotypes may cause confusion in their taxonomy. 相似文献
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