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1.
Since the introduction of an African subspecies into Brazil in the mid-1950's1, descendent Africanized honey bees (Apis mellifera L.) have spread throughout the Neotropics and into temperate North America. Restriction enzyme analysis of 422 feral honey bee colonies collected from non-Africanized areas in the southern United States revealed that over 21% of them had mitochondrial DNA (mtDNA) derived from a European race established in North America by the 17th century, 77% of them had mtDNA common in honey bees maintained by beekeepers and about 1% exhibited African mtDNA. Further analysis revealed that the African mtDNA was derived from a north African subspecies imported to the US in the 19th century. 相似文献
2.
K. Nielsen J. Sheppard W. Holmes I. Tizard 《Cellular and molecular life sciences : CMLS》1978,34(1):118-119
Summary Rats infected withTrypanosoma lewisi or decomplemented by injection of cobra venom factor or complement activating factor of trypanosomes were found to be more susceptible to infection withSalmonella typhimurium. Decomplemented rats subsequently infected withT. lewisi developed higher blood parasitemia than did normalT. lewisi infected rats.This project is supported by the National Research Council of Canada grant A 0068 and a grant from the International Development Research Center. 相似文献
3.
Loss of integrin alpha(v)beta6-mediated TGF-beta activation causes Mmp12-dependent emphysema 总被引:16,自引:0,他引:16
Morris DG Huang X Kaminski N Wang Y Shapiro SD Dolganov G Glick A Sheppard D 《Nature》2003,422(6928):169-173
Integrins are heterodimeric cell-surface proteins that regulate cell growth, migration and survival. We have shown previously that the epithelial-restricted integrin alpha(v)beta6 has another critical function; that is, it binds and activates latent transforming growth factor-beta (TGF-beta). Through a global analysis of pulmonary gene expression in the lungs of mice lacking this integrin (Itgb6 null mice) we have identified a marked induction of macrophage metalloelastase (Mmp12)--a metalloproteinase that preferentially degrades elastin and has been implicated in the chronic lung disease emphysema. Here we report that Itgb6-null mice develop age-related emphysema that is completely abrogated either by transgenic expression of versions of the beta6 integrin subunit that support TGF-beta activation, or by the loss of Mmp12. Furthermore, we show that the effects of Itgb6 deletion are overcome by simultaneous transgenic expression of active TGF-beta1. We have uncovered a pathway in which the loss of integrin-mediated activation of latent TGF-beta causes age-dependent pulmonary emphysema through alterations of macrophage Mmp12 expression. Furthermore, we show that a functional alteration in the TGF-beta activation pathway affects susceptibility to this disease. 相似文献
4.
W. S. Sheppard G. J. Steck B. A. McPheron 《Cellular and molecular life sciences : CMLS》1992,48(10):1010-1013
Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly were found to vary among introduced populations in the Neotropics. The survey included samples from 15 established natural populations and 5 laboratory cultures from Hawaii, Central America, South America and West Africa and samples from recent California infestations (1989, 1991). Based on restriction fragment length polymorphisms from 2 enzymes, Hawaii is an unlikely source for the 1989 and 1991 California infestations. Interpopulational variation in mtDNA demonstrates the potential for the technique to trace the process of colonization (geographic spread) by this insect. 相似文献
5.
J. J. Chart H. Sheppard M. J. Allen W. L. Bencze R. Gaunt 《Cellular and molecular life sciences : CMLS》1958,14(4):151-152
Zusammenfassung 2-Methyl-1,2-bis-(3-pyridyl)-1-propanon (Su 4885) hemmt beim Hund die Ausscheidung von 17-OH-Steroiden aus den Nebennieren und hemmtin vitro ähnlich wie Amphenon den ACTH-Effekt auf Ratten-, Meerschweinchen-und Hunde-Nebennieren.In situ bei der Ratte hat es jedoch keine Amphenon-Wirkung, von dem es sich auch sonst unterscheidet. 相似文献
6.
Rats infected with Trypanosoma lewisi or decomplemented by injection of cobra venom factor or complement activating factor of trypanosomes were found to be more susceptible to infection with Salmonella typhimurium. Decomplemented rats subsequently infected with T. lewisi developed higher blood parasitemia than did normal T. lewisi infected rats. 相似文献
7.
8.
R. C. Sheppard 《Cellular and molecular life sciences : CMLS》1963,19(3):125-126
Zusammenfassung Es wird die Synthese des Laktons (III) von Glykokoll-L-leucyl-L-prolin (IV) beschrieben. Spektroskopische Untersuchungen zeigen, dass das Lakton (III) eine durch Säure katalysierte transannulare Reaktion unter Bildung des Cyclol-Peptid-Derivats (II) durchläuft. 相似文献
9.
H Sheppard 《Nature》1970,228(5271):567-568
10.
A. M. L. Azeredo-Espin R. F. W. Schroder M. D. Huettel W. S. Sheppard 《Cellular and molecular life sciences : CMLS》1991,47(5):483-485
Summary This study demonstrates variability in restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) among four popalations of Colorado potato beetle (CPB). A suite of three enzymes (EcoRI,HpaI,PstI) was sufficient to discriminate among the populations tested. Individuals heteroplasmic for restriction enzyme patterns were found in some populations. Variability in CPB mtDNA should prove useful in efforts to trace the origin and dispersal of the species in North America. 相似文献