Biomedical subjects

A G Force

Publications and source records attributed to A G Force.

4 recordsLinked to original sources

PubMed2000

Extended longevity in Drosophila is consistently associated with a decrease in developmental viability.

It has proven relatively easy to select normal-lived strains of Drosophila for extended longevity in the laboratory. Long-lived strains have not been observed in the wild as yet. Of the various life-history traits that have been investigated for their role in modulating the evolution of extended longevity, none have yet shown a consistent or convincing relationship. Other than developmental time, the traits usually investigated in this regard are those associated with the adult phase of the life cycle. We assayed developmental timing and viability in six pairs of normal- and long-lived strains, four pairs of which are from previously described strains and two pairs of which are new strains that have been independently and recently selected. We find that the life-history trait most obviously associated with all our long-lived strains is a significantly reduced developmental viability, with the long-lived strains' having as much as twice the developmental lethality as do any of the normal-lived strains. The long-lived strains also pupate closer to the food, a behavior known to decrease fitness. Thus the reduced fitness of the long-lived strains appears to be due to both physiological and behavioral factors and may well explain why long lived strains are not usually found in the wild. The extension of longevity involves costs as well as benefits that, in this case, are borne by different individuals.

Animals↗

PubMed1996

valentino: a zebrafish gene required for normal hindbrain segmentation.

Mutational analysis can serve both to identify new genes essential for patterning embryonic development and to determine their functions. Here we describe the identification and phenotypic characterization of alleles of valentino, which we recovered in a genetic screen that sought to identify mutations in the zebrafish that disrupt region-specific gene expression patterns in the embryonic brain. valentino is required for normal hindbrain segmentation and the hindbrain of valentino mutant embryos is shortened by the length of one rhombomere. We demonstrate that valentino is required cell-autonomously in the development of rhombomeres 5 and 6, and propose that valentino functions in the subdivision and expansion of a common precursor region in the presumptive hindbrain into the definitive rhombomeres 5 and 6. These results provide genetic evidence for a two-segment periodicity in the hindbrain and suggest that this periodicity arises sequentially, through the specification and later subdivision of a two-rhombomere unit, or 'protosegment'.

Animals↗

PubMed1995

Comparative biochemical and stress analysis of genetically selected Drosophila strains with different longevities.

We have performed a comparative analysis of the effects of age of reproduction on the biochemical (protein, lipid, and glycogen content) and stress resistance (ability to survive starvation, desiccation, and exogenous paraquat) parameters on 10 sister lines of five different Drosophila strains. Four pairs of these sister lines were selected under different regimens for either early or delayed reproduction; the fifth pair was maintained in a nonselected state and served as the baseline strain to which all others were compared. It is generally accepted that the early regimens give rise to short-lived phenotypes, whereas the delayed regimens give rise to long-lived phenotypes. Our results suggest that a mechanism involving lipid and starvation resistance is not operative in our long-lived strains. In addition, a mechanism involving glycogen content and desiccation resistance is only weakly supported. Finally, there is strong support for a mechanism that gives rise to enhanced paraquat resistance and therefore may involve regulatory changes in the pattern of ADS gene expression. In addition, the 15-day early age of reproduction regimen (M type) shows qualitatively similar responses to that of the late age at reproduction regimen (L type). These results suggest that correlations between biochemical traits and longevity must be interpreted with caution. We discuss possible reasons for these results, including the possibility of multiple mechanisms, each leading to a different extended longevity phenotype.

Animals↗

PubMedDate not supplied

Factors contributing to the plasticity of the extended longevity phenotypes of Drosophila.

A number of laboratories have constructed independently derived long-lived strains of Drosophila, each of which have similar but not identical patterns of variability in their adult longevity. Given the observed plasticity of longevity within each of these strains, it would be useful to review the operational and environmental factors that give rise to this phenotypic plasticity and ascertain whether they are common or strain specific. Our review of the more extensively analyzed strains suggests that the allelic composition of the initial genomes and the selection/transgene strategy employed yield extended longevity strains with superficially similar phenotypes but which are probably each the result of different proximal genetic mechanisms. This then offers a plausible explanation for the differential effects of various environmental factors on each strain's particular pattern of phenotypic plasticity. It also illustrates that the species has the potential to employ any one of a number of different proximal mechanisms, each of which give rise to a similar longevity phenotype.

Animals↗