Long-Lived C. elegans daf-2
The daf-2 mutant retained extended lon- gevity relative to wild-type mutants whenpropagated on B. subtilis (Fig. 1B), but the Mutants Are Resistant to
fractional extension in life-span was modest(76 Ϯ 9%) compared with the fractional ex- Bacterial Pathogens
tension observed on pathogenic bacteria [E.
, 325 Ϯ 57%; S. aureus, 514 Ϯ189%; P. aeruginosa, 118% Ϯ 14%; and E. Danielle A. Garsin,1,3 Jacinto M. Villanueva,1,3 Jakob Begun,1,3 coli, 110 Ϯ 11% (9)]. The age-1 mutant also Dennis H. Kim,1,3 Costi D. Sifri,2,4 Stephen B. Calderwood,2,4 lived longer on B. subtilis (table S1). The extended survival of the daf-2 and age-1mutants on the relatively innocuous B. subti-lis suggests that additional factors beyond table S1) under the experimental conditions pathogen resistance are likely involved in nisms of aging (1, 2) and immune function assayed. In these experiments, the daf-2(e1370) life-span regulation. However, when feeding (3) in Caenorhabditis elegans. Herein we allele was more resistant to bacterial pathogens on pathogenic bacteria, especially Gram-pos- show that the mechanisms that govern these than the daf-2(1368) allele and the age- itive ones, mechanisms underlying pathogen 1(hx546) allele (Fig. 1A; table S1). This is most resistance appear to be the dominant contrib- likely a consequence of differences in allele utor to the overall longevity of daf-2 and gens Pseudomonas aeruginosa and Salmonella strengths of the daf-2 and age-1 mutants, all of enterica and the Gram-positive pathogens En- which are partial loss-of-function mutants.
Our data suggest that the insulin signaling terococcus faecalis and Staphylococcus aureus Because C. elegans daf-2 and age-1 mu- pathway modulates both inherent longevity kill C. elegans by an infection-like process with tants were identified in screens using Esche- and pathogen resistance to affect overall sur- remarkable overlap between the bacterial fac- richia coli strain OP50 as the food source and vival in a manner dependent on the pathoge- tors required for virulence in mammals and because E. coli may also be pathogenic to C. nicity of the bacteria on which C. elegans is killing in nematodes (4, 5). Additionally, a p38 elegans (57 ), the enhanced longevity phe- feeding. The linkage of longevity and patho- notype of daf-2 and age-1 could reflect ac- gen resistance to the same signaling pathway signaling cascade is a key component of the quired resistance to E. coli– mediated killing.
may have general relevance to the observa- C. elegans innate immune response, as it is Indeed, nematodes lived considerably longer tion that most organisms become more sus- in mammals (3). These experiments estab- when feeding on the Gram-positive bacteri- lish C. elegans as a useful model for study- um Bacillus subtilis, a common soil bacteri- ing bacterial pathogenicity and host immu- um that C. elegans is likely to feed on in the References and Notes
nity. Here we show that certain long-lived wild (Fig. 1B) (8). It is not likely that B. 1. C. E. Finch, G. Ruvkun, Annu. Rev. Genomics Hum. Genet. 2, 435 (2001).
C. elegans mutants are highly resistant to subtilis is simply more nutritious or more 2. C. A. Wolkow, K. D. Kimura, M.-S. Lee, G. Ruvkun, readily digestible than E. coli because the rate Science 290, 147 (2000).
of growth, egg to egg generation time, and 3. D. H. Kim et al., Science 297, 623 (2002).
4. A. Aballay, F. M. Ausubel, Curr. Opin. Microbiol. 5, 97
tween longevity and pathogen resistance, we number of eggs laid were the same whether tested whether C. elegans daf-2 and age-1 feeding on B. subtilis or E. coli (fig. S1).
5. D. A. Garsin et al., Proc. Natl. Acad. Sci. U.S.A. 98,
mutants exhibit enhanced resistance to E. 6. D. Garigan et al., Genetics 161, 1101 (2002).
faecalis, S. aureus, and P. aeruginosa. daf-2 7. G. V. Mallo et al., Curr. Biol. 12, 1209 (2002).
encodes an insulin-like receptor that functions 8. The difference in life-span between feeding on E. coli upstream of the phosphatidylinositol 3-kinase OP50 and B. subtilis PY79 was particularly dramatic when the longevity assays were carried out at 27°C (PI 3– kinase) encoded by age-1, and partial loss rather than at 25°C; the worms lived almost 100% of function mutations in daf-2 or age-1 result in longer on B. subtilis then they did on E. coli (table S1).
a long-lived phenotype (1). Both daf-2 and age-1 9. Fractional life-span extension was calculated based mutants were resistant to killing by E. faecalis, S. aureus, and P. aeruginosa (Fig. 1A; table S1). 10. We thank S. Lee and R. Feinbaum for helpful discussions Most dramatic was the five- and sixfold in- and critical reading of the manuscript. D.A.G. and J.M.V.
creased survival of the daf-2(e1370) mutants are supported by postdoctoral fellowships from the Irv- ington Institute for Immunological Research. C.D.S. and relative to wild-type C. elegans when exposed to D.H.K. are supported by postdoctoral fellowships from the Gram-positive pathogens E. faecalis and S. the Howard Hughes Medical Institute. This work was aureus, respectively (Fig. 1A; table S1).
supported by NIH grant GM48707 (to F.M.A.).
Supporting Online Material insulin-signaling pathway in C. elegans oc- curs by de-repression of the forkhead tran- Fig. 1. Pathogen resistance of the C. elegans
scription factor DAF-16, which is normally daf-2(e1370) mutant. (A) Survival of N2, daf-
under negative regulation by DAF-2. There- 2(e1370), daf-16 (mgDf47), a nd daf-2;daf-16 C. 5 November 2002; accepted 28 February 2003 fore, strong loss-of- function alleles of daf-16 elegans feeding on E. faecalis strain OG1RF. (B)
such as mgDf47 suppress the long-lived phe- Adult life-span of N2 and daf-2(e1370) C. el- notype of daf-2 mutants (2). daf-16(mgDf47) egans when feeding on B. subtilis (PY79) or E. coli Department of Genetics, 2Department of Microbiology (OP50) grown on NG (nematode growth) medi- and Molecular Genetics, Harvard Medical School, 3De- also suppressed the pathogen-resistant pheno- partment of Molecular Biology, 4Division of Infectious um with FUDR (5-Fluoro-2-deoxyuridine). Assays type of daf-2(e1370) (Fig. 1A; table S1). Inter- Diseases, Massachusetts General Hospital, Boston, MA were carried out as previously described (2, 5).
estingly, the daf-16 mutant exhibited a compa- STATA 6 statistical software (Stata, College Sta- rable degree of susceptibility to pathogen- tion, TX ) was used to plot survival by the Kaplan- *To whom correspondence should be addressed. E- mediated killing as wild-type worms (Fig. 1A; SCIENCE VOL 300 20 JUNE 2003


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