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71.
A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean 总被引:70,自引:0,他引:70
Coale KH Johnson KS Fitzwater SE Gordon RM Tanner S Chavez FP Ferioli L Sakamoto C Rogers P Millero F Steinberg P Nightingale P Cooper D Cochlan WP Landry MR Constantinou J Rollwagen G Trasvina A Kudela R 《Nature》1996,383(6600):495-501
The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability. 相似文献
72.
Insect motion detectors matched to visual ecology 总被引:1,自引:0,他引:1
To detect motion, primates, birds and insects all use local detectors to correlate signals sampled at one location in the image with those sampled after a delay at adjacent locations. These detectors can adapt to high image velocities by shortening the delay. To investigate whether they use long delays for detecting low velocities, we compared motion-sensitive neurons in ten species of fast-flying insects, some of which encounter low velocities while hovering. Neurons of bee-flies and hawkmoths, which hover, are tuned to lower temporal frequencies than those of butterflies and bumblebees, which do not. Tuning to low frequencies indicates longer delays and extends sensitivity to lower velocities. Hoverflies retain fast temporal tuning but use their high spatial acuity for sensing low-velocity motion. Thus an unexpectedly wide range of spatio-temporal tuning matches motion detection to visual ecology. 相似文献
73.
S. F. Wang J. C. Braekman D. Daloze J. Pasteels P. Soetens N. V. Handjieva P. Kalushkov 《Cellular and molecular life sciences : CMLS》1996,52(6):628-630
The isolation of N-quinaldyl-L-arginine·HCl (1) from the CoccinellidaeSubcoccinella-24-punctata is reported. The structure, first established on the basis of the analysis of the spectral properties of1, has been confirmed by synthesis. The alkaloid is of endogenous origin and markedly deterrent to ants. 相似文献
74.
75.
Summary The intensity of sound-induced convulsions in the genetically epilepsy-prone rat (GEPR) was reduced in a dose related fashion by intracerebroventricular administration of dobutamine, (1 agonist), terbutaline (2 agonist) or phenylephrine (1 agonist). BHT-920 (2 agonist) did not cause a dose-related decrease in sound-induced convulsion intensity. Binding studies showed that whole brain and receptor densities (Bmax) were normal while the Kd was increased for the ligand in GEPR brain.Acknowledgment. We are most grateful to Boehringer Ingelheim for generously supplying BHT 920. We are also indebted to Ciba-Geigy Corporation for the gift of terbutaline hydrochloride and phentolamine hydrochloride. The work was supported in part by NIH grant NS 16829. 相似文献
76.
F. M. Goñi J. M. Valpuesta M. C. Barbero E. Rial J. I. G. Gurtubay J. M. Macarulla 《Cellular and molecular life sciences : CMLS》1984,40(2):193-195
Summary The solubilizing effect of Triton X-100 on beef heart submitochondrial particles (ETPH) has been studied under various physiological conditions. Coupled, uncoupled and azide-inhibited ETPH particles have been studied. Quantitative and qualitative differences are found in the proteins solubilized by the detergent from ETPH particles under the various conditions tested.Acknowledgments: This work was supported in part by a grant from a Spanish Comisión Asesora para la Investigación Cientifica y Técnica. M.C. Barbero was recipient of a scholarship from the Basque Government. 相似文献
77.
C. N. Powell 《Cellular and molecular life sciences : CMLS》1978,34(11):1450-1451
Summary 9 groups of 6 female rats were used in an experiment using fraction 3 ofTrypanosoma rhodesiense. 500 g gave 100% immunoprotection and 1000 and 1500 g gave 66% immunoprotection when challenged with 5×102
T. brucei. 2 groups of 10 female rats were tested for a short period inoculation immune response. In this, 750 g of fraction 3 ofT. rhodesiense gave 70% immunoprotection when challenged withT. brucei.I thank the University of Zambia for support; Dr M. A. Q. Awan, Mazabuka, Zambia, forT. rhodesiense andT. brucei; Prof. J. W. Kibukamusoke, Dr O. Okong'o and Dr W. W. Anokbonggo for advice; Mr L. Nyaliti for technical help. 相似文献
78.
C Torrossian 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(9):693-696
The oxygen consumption of "hibernating" ants shows a grouping effect translated by a significant decrease in the level of oxygen consumption as a function of grouping effect. The general relation between oxygen consumption and the living body mass is the same, if the living material belongs to a single animal, or a social community of ants. 相似文献
79.
The spontaneous conversion of mammalian cyclic GMP-dependent protein kinase (G-PK) into modulator-dependent protein kinase (type II) (M-PKII) in the absence of cGMP or histone was observed in vitro. The findings, together with similarity in substrate protein specificity, suggest that M-PKII is the catalytic subunit of mammalian G-PK. 相似文献
80.
Summary The effects of selected -agonists and -antagonists on theophylline-induced lipolysis were investigate in isolated hamster white fat cells 2-Agonists (tramazoline, clonidine) inhibited theophylline-induced lipolysis while an 2-agonist (methoxamine) was without any effect. The inhibitory effect of 2-agonists was suppressed by yohimbine (2-antagonist), whereas 2-antagonists were inefficient. This result implies that the -adrenergic receptor of hamster fat cells is of the 2-type, although located postsynaptically.Acknowledgments. This work was supported by grants from CNRS (ERA 412) and DGRST (grant No. 787 1078). We thank M. Dauzats for excellent technical assistance. We thank Prof. H. Schmitt for tramazoline and AR-C 239 and for helpful discussion. 相似文献