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Long-standing Question (long-standing + question)
Selected AbstractsRESURRECTING THE ROLE OF TRANSCRIPTION FACTOR CHANGE IN DEVELOPMENTAL EVOLUTIONEVOLUTION, Issue 9 2008Vincent J. Lynch A long-standing question in evolutionary and developmental biology concerns the relative contribution of cis- regulatory and protein changes to developmental evolution. Central to this argument is which mutations generate evolutionarily relevant phenotypic variation? A review of the growing body of evolutionary and developmental literature supports the notion that many developmentally relevant differences occur in the cis -regulatory regions of protein-coding genes, generally to the exclusion of changes in the protein-coding region of genes. However, accumulating experimental evidence demonstrates that many of the arguments against a role for proteins in the evolution of gene regulation, and the developmental evolution in general, are no longer supported and there is an increasing number of cases in which transcription factor protein changes have been demonstrated in evolution. Here, we review the evidence that cis- regulatory evolution is an important driver of phenotypic evolution and provide examples of protein-mediated developmental evolution. Finally, we present an argument that the evolution of proteins may play a more substantial, but thus far underestimated, role in developmental evolution. [source] The Diffusion of Rights: From Law on the Books to Organizational Rights PracticesLAW & SOCIETY REVIEW, Issue 3 2006Jeb Barnes How does law change society? To gain new leverage on this long-standing question, this article draws on two lines of research that often ignore each other: political science research on the mobilization of law, and sociological research on the diffusion of organizational practices. Our insights stem from six case studies of diverse organizations' responses to the accommodation provisions in the Americans with Disabilities Act and related state laws. We found that different modes of exposure to the law combined with organizational attributes to produce distinct "rights practices",styles of standard operating procedures and informal routines that reflect the understanding of legal requirements within an organization. The diversity of the organizational responses challenges simple dichotomies between compliance/noncompliance, change through deterrence/change through norms, and mobilization/nonmobilization, and it underscores the importance of combining political science and sociological perspectives on law and social change. [source] Compensation for light loss due to filtering by macular pigment: relation to hue cancellationOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2007James M. Stringham Abstract Background:, A long-standing question in colour vision research is how the visual system is able to correct for the significant absorbance of short wave light by the crystalline lens and macular pigment (MP). Such compensation must be required in order to maintain colour constancy across the retina where MP levels are changing quickly and dramatically. Objective:, We studied this compensation mechanism by measuring MP spatial density profiles and hue cancellation functions across the central retina in a sample of six young healthy subjects. Method:, Yellow (Y, 575 nm)/blue (B, 440 nm) and red (R, 600 nm)/green (G, 501 nm) cancellation functions were obtained at 0, 1, 1.75, 3 and 7° eccentricity. The MP optical density at 460 nm was measured at these same eccentricities using heterochromatic flicker photometry. One subject was assessed repeatedly over a 4-month period during daily supplementation with 30 mg of lutein (L). Results:, Hue cancellation values for the Y/B system did not change across the retina (r = 0.09). In contrast, R/G sensitivity changed as a direct function of MP absorbance (r = 0.99). The Y/B values did not change in the one subject supplemented with 30 mg L daily, despite increases in MP of about 50% over 4 months. Conclusions:, Despite large variations in MP across the retina, hue cancellation values for the Y-B system across the central retina were constant. For example, one subject's MP density declined from a central peak of 0.99 to near zero at 7° (near 90% transmission difference) yet thresholds for the Y/B system were unaffected. In contrast, the G lobe of the R/G system was directly correlated with MP density. Taken together, these results confirm that the Y/B system compensates for MP density, but the R/G system does not. [source] Effects of Administrators' Aspirations, Political Principals' Priorities, and Interest Groups' Influence on State Agency Budget RequestsPUBLIC BUDGETING AND FINANCE, Issue 2 2007JAY EUNGHA RYU This article addresses a long-standing question in public budgeting: What factors influence bureau/agency budget request decisions? Empirical results confirm the complexity of variables that explain different levels of budget requests by over 1,000 state administrative agencies. The expected significant influence of administrator (agency head) aspirations was clearly present. But other important sources enter into the decision of agencies to satisfy rather than maximize. These include the strategic roles, activities, and priorities of governors, legislatures, and interest groups. These political principals' influence operates to constrain, discipline, or even augment agency budget requests. [source] ,Bubble chamber model' of fast atom bombardment induced processesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2003Marina V. Kosevich A hypothesis concerning FAB mechanisms, referred to as a ,bubble chamber FAB model', is proposed. This model can provide an answer to the long-standing question as to how fragile biomolecules and weakly bound clusters can survive under high-energy particle impact on liquids. The basis of this model is a simple estimation of saturated vapour pressure over the surface of liquids, which shows that all liquids ever tested by fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (SIMS) were in the superheated state under the experimental conditions applied. The result of the interaction of the energetic particles with superheated liquids is known to be qualitatively different from that with equilibrium liquids. It consists of initiation of local boiling, i.e., in formation of vapour bubbles along the track of the energetic particle. This phenomenon has been extensively studied in the framework of nuclear physics and provides the basis for construction of the well-known bubble chamber detectors. The possibility of occurrence of similar processes under FAB of superheated liquids substantiates a conceptual model of emission of secondary ions suggested by Vestal in 1983, which assumes formation of bubbles beneath the liquid surface, followed by their bursting accompanied by release of microdroplets and clusters as a necessary intermediate step for the creation of molecular ions. The main distinctive feature of the bubble chamber FAB model, proposed here, is that the bubbles are formed not in the space and time-restricted impact-excited zone, but in the nearby liquid as a ,normal' boiling event, which implies that the temperature both within the bubble and in the droplets emerging on its burst is practically the same as that of the bulk liquid sample. This concept can resolve the paradox of survival of intact biomolecules under FAB, since the part of the sample participating in the liquid,gas transition via the bubble mechanism has an ambient temperature which is not destructive for biomolecules. Another important feature of the model is that the timescale of bubble growth is no longer limited by the relaxation time of the excited zone (,10,12,s), but rather resembles the timescale characteristic of common boiling, sufficient for multiple interactions of gas molecules and formation of clusters. Further, when the bubbles burst, microdroplets are released, which implies that FAB processes are similar to those in spraying techniques. Thus, two processes contribute to the ion production, namely, release of volatile solvent clusters from bubbles and of non-volatile solute from sputtered droplets. This view reconciles contradictory views on the dominance of either gas-phase or liquid-phase effects in FAB. Some other effects, such as suppression of all other ions by surface-active compounds, are consistent with the suggested model. Copyright © 2003 John Wiley & Sons, Ltd. [source] Conjugation mediates transfer of the Ll.LtrB group II intron between different bacterial speciesMOLECULAR MICROBIOLOGY, Issue 5 2004Kamila Belhocine Summary Some self-splicing group II introns (ribozymes) are mobile retroelements. These retroelements, which can insert themselves into cognate intronless alleles or ectopic sites by reverse splicing, are thought to be the evolutionary progenitors of the widely distributed eukaryotic spliceosomal introns. Lateral or horizontal transmission of introns (i.e. between species), although never experimentally demonstrated, is a well-accepted model for intron dispersal and evolution. Horizontal transfer of the ancestral bacterial group II introns may have contributed to the dispersal and wide distribution of spliceosomal introns present in modern eukaryotic genomes. Here, the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis was used as a model system to address the dissemination of introns in the bacterial kingdom. We report the first experimental demonstration of horizontal transfer of a group II intron. We show that the Ll.LtrB group II intron, originally discovered on an L. lactis conjugative plasmid (pRS01) and within a chromosomally located sex factor in L. lactis 712, invades new sites using both retrohoming and retrotransposition pathways after its transfer by conjugation. Ll.LtrB lateral transfer is shown among different L. lactis strains (intraspecies) (retrohoming and retrotransposition) and between L. lactis and Enterococcus faecalis (interspecies) (retrohoming). These results shed light on long-standing questions about intron evolution and propagation, and demonstrate that conjugation is one of the mechanisms by which group II introns are, and probably were, broadly disseminated between widely diverged organisms. [source] Invasive ants in Australia: documented and potential ecological consequencesAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008Lori Lach Abstract A growing number of species are being transported and introduced by humans to new locations and are establishing self-sustaining populations outside their native ranges. Since ants play many ecological roles, introduction of an invasive ant species, and subsequent disruption of Australia's rich and abundant native ant fauna, has the potential for numerous adverse consequences. Over 6700 ants representing 105 species from 73 genera have been intercepted at Australian ports of entry in the last 20 years and all six of the world's most destructive invasive ants have become established in the country. Here we review the current and potential consequences of these ants on Australia's natural and agricultural environments. To date, several studies, most involving the big-headed ant, Pheidole megacephala, and the Argentine ant, Linepithema humile, have documented a decline in native ant species richness. The displacement of native ants by these invaders could have multiple consequences for the native flora and fauna. Since few of these have been investigated in Australia, we combine knowledge from invasions elsewhere, the ecology of the interactions, and data on current and predicted geographic ranges of introduced ants to hypothesise about likely indirect effects of invasive ants in Australia. Further investigations that are aimed at testing these predictions will also aid in justifying and prioritising national prevention and control efforts, and will contribute to some of the long-standing questions about ant invasions globally. [source] | ||||||||||