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61.
Vaccination with purified microgamete antigens prevents transmission of rodent malaria 总被引:2,自引:0,他引:2
Malaria vaccination with preparations of microgametes has been shown to inhibit transmission of Plasmodium spp. to the mosquito vectors of avian, rodent and simian parasites. This transmission-blocking immunity results from the induction of microgamete-agglutinating antibodies in the vaccinated host which, when ingested in a mosquito blood meal, react with exflagellating microgametes in the midgut to prevent fertilization and oocyst development. Here we have passively transferred the immunity with gamete-specific monoclonal antibodies raised against the rodent malaria parasite Plasmodium yoelii nigeriensis, and an IgG2a isotype monoclonal antibody from a hybridoma cell line, PYG-1, has been used to identify the target antigens on the gametes and to affinity-purify sufficient quantities of specific gamete antigen to facilitate vaccination studies. This transmission-blocking monoclonal antibody immunoprecipitated microgamete antigens of apparent relative molecular mass (Mr), 67K (67,000), 59K, 57K, 42K and 35K. Immunization of mice with these proteins before infection and mosquito feeding led to a 85-99.7% reduction in transmission to the mosquito vector; vaccination via intravenous or intramuscular routes was equally effective and did not require an adjuvant. 相似文献
62.
Observations of the 21-centimetre line of atomic hydrogen in the early Universe directly probe the history of the reionization of the gas between galaxies. The observations are challenging, though, because of the low expected signal strength (~10?mK), and contamination by strong (>100?K) foreground synchrotron emission in the Milky Way and extragalactic continuum sources. If reionization happened rapidly, there should be a characteristic signature visible against the smooth foreground in an all-sky spectrum. Here we report an all-sky spectrum between 100 and 200?MHz, corresponding to the redshift range 6?相似文献
63.
Two Earth-sized planets orbiting Kepler-20 总被引:1,自引:0,他引:1
Fressin F Torres G Rowe JF Charbonneau D Rogers LA Ballard S Batalha NM Borucki WJ Bryson ST Buchhave LA Ciardi DR Désert JM Dressing CD Fabrycky DC Ford EB Gautier TN Henze CE Holman MJ Howard A Howell SB Jenkins JM Koch DG Latham DW Lissauer JJ Marcy GW Quinn SN Ragozzine D Sasselov DD Seager S Barclay T Mullally F Seader SE Still M Twicken JD Thompson SE Uddin K 《Nature》2012,482(7384):195-198
Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R(⊕)), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R(⊕)) and the other smaller than the Earth (0.87R(⊕)), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere. 相似文献
64.
65.
H. J. Rogers 《Cellular and molecular life sciences : CMLS》1972,28(4):435-437
Zusammenfassung Es wird gezeigt, dass Chlorpromazin keine Veränderung der Konzentration von Aminosäuren erzeugt, wohl aber die Inkorporation des Isotopen14C-Glukose im säurelöslichen Anteil des Mäusegehirns temperaturabhängig vermehrt.
Governors' Research Scholar, Guy's Hospital Medical School. 相似文献
Governors' Research Scholar, Guy's Hospital Medical School. 相似文献
66.
Summary Several N-1-alkyl-, 3-, and 4-carbamidopyridinium halides were synthesized and determined to be inhibitors of mitochondrial oxidative phosphorylation. L-Glutamate respiration was most depressed by N-1-dodecylpyridinium bromide whereas succinate respiration was most depressed by N-1-dodecylisonicotinamide bromide. Combination of inhibitors with mitochondrial sites may involve lipophilic interactions as modified by steric restrictions. 相似文献
67.
Hay SI Cox J Rogers DJ Randolph SE Stern DI Shanks GD Myers MF Snow RW 《Nature》2002,415(6874):905-909
The public health and economic consequences of Plasmodium falciparum malaria are once again regarded as priorities for global development. There has been much speculation on whether anthropogenic climate change is exacerbating the malaria problem, especially in areas of high altitude where P. falciparum transmission is limited by low temperature. The International Panel on Climate Change has concluded that there is likely to be a net extension in the distribution of malaria and an increase in incidence within this range. We investigated long-term meteorological trends in four high-altitude sites in East Africa, where increases in malaria have been reported in the past two decades. Here we show that temperature, rainfall, vapour pressure and the number of months suitable for P. falciparum transmission have not changed significantly during the past century or during the period of reported malaria resurgence. A high degree of temporal and spatial variation in the climate of East Africa suggests further that claimed associations between local malaria resurgences and regional changes in climate are overly simplistic. 相似文献
68.
Dinosaurian growth patterns and rapid avian growth rates 总被引:5,自引:0,他引:5
Did dinosaurs grow in a manner similar to extant reptiles, mammals or birds, or were they unique? Are rapid avian growth rates an innovation unique to birds, or were they inherited from dinosaurian precursors? We quantified growth rates for a group of dinosaurs spanning the phylogenetic and size diversity for the clade and used regression analysis to characterize the results. Here we show that dinosaurs exhibited sigmoidal growth curves similar to those of other vertebrates, but had unique growth rates with respect to body mass. All dinosaurs grew at accelerated rates relative to the primitive condition seen in extant reptiles. Small dinosaurs grew at moderately rapid rates, similar to those of marsupials, but large species attained rates comparable to those of eutherian mammals and precocial birds. Growth in giant sauropods was similar to that of whales of comparable size. Non-avian dinosaurs did not attain rates like those of altricial birds. Avian growth rates were attained in a stepwise fashion after birds diverged from theropod ancestors in the Jurassic period. 相似文献
69.