Come back Marshall, all is forgiven? : Complexity, evolution, mathematics and Marshallian exceptionalism

Marshall was the great synthesiser of neoclassical economics. Yet with his qualified assumption of self-interest, his emphasis on variation in economic evolution and his cautious attitude to the use of mathematics, Marshall differs fundamentally from other leading neoclassical contemporaries. Metaphors inspire more specific analogies and ontological assumptions, and Marshall used the guiding metaphor of Spencerian evolution. But unfortunately, the further development of a Marshallian evolutionary approach was undermined in part by theoretical problems within Spencer's theory. Yet some things can be salvaged from the Marshallian evolutionary vision. They may even be placed in a more viable Darwinian framework.Peer reviewedFinal Accepted Versio

A median fin derived from the lateral plate mesoderm and the origin of paired fins

The development of paired appendages was a key innovation during evolution and facilitated the aquatic to terrestrial transition of vertebrates. Largely derived from the lateral plate mesoderm (LPM), one hypothesis for the evolution of paired fins invokes derivation from unpaired median fins via a pair of lateral fin folds located between pectoral and pelvic fin territories1. Whilst unpaired and paired fins exhibit similar structural and molecular characteristics, no definitive evidence exists for paired lateral fin folds in larvae or adults of any extant or extinct species. As unpaired fin core components are regarded as exclusively derived from paraxial mesoderm, any transition presumes both co-option of a fin developmental programme to the LPM and bilateral duplication2. Here, we identify that the larval zebrafish unpaired pre-anal fin fold (PAFF) is derived from the LPM and thus may represent a developmental intermediate between median and paired fins. We trace the contribution of LPM to the PAFF in both cyclostomes and gnathostomes, supporting the notion that this is an ancient trait of vertebrates. Finally, we observe that the PAFF can be bifurcated by increasing bone morphogenetic protein signalling, generating LPM-derived paired fin folds. Our work provides evidence that lateral fin folds may have existed as embryonic anlage for elaboration to paired fins

Addressing gang-related violence in Glasgow:A preliminary pragmatic quasi-experimental evaluation of the Community Initiative to Reduce Violence (CIRV)

Youth gang-related violence is a public health concern in Glasgow. The Community Initiative to Reduce Violence aims to address physical violence and weapon carriage among gang-related youths in a deprived area of Glasgow. It offers access to diversionary activity, personal development, and employment preparedness in exchange for adherence to a “no violence, no weapon“ pledge. A preliminary post hoc before-and-after quasi-experimental design compared rates of criminal offending (including violent and non-violent offenses) for the 167 male youths (aged 16-29) who engaged with the initiative with data for one or two years follow-up for age-matched gang-involved youths from an equally deprived area of the city. Violent offending reduced across all groups over the time of the study. In the cohort followed for 2-years the rate reduction was greater in the intervention group (52%) than the comparison group (29%). The reduction in the rate of physical violence was not significantly different between the intervention group and the comparison group; however, the rate of weapons carrying was reduced more in the intervention group than the comparison group (84% vs 40% respectively in the 2-year follow-up cohort). The study suggests that adopting a public health approach with gang-related youth was associated with reduced weapon carriage, which can prevent consequences for victims, offenders, and society

Evaluation of exon-skipping strategies for Duchenne muscular dystrophy utilizing dystrophin-deficient zebrafish

Duchenne muscular dystophy (DMD) is a severe muscle wasting disease caused by mutations in the dystrophin gene. By utilizing antisense oligonucleotides, splicing of the dystrophin transcript can be altered so that exons harbouring a mutation are excluded from the mature mRNA. Although this approach has been shown to be effective to restore partially functional dystrophin protein, the level of dystrophin protein that is necessary to rescue a severe muscle pathology has not been addressed. As zebrafish dystrophin mutants (dmd) resemble the severe muscle pathology of human patients, we have utilized this model to evaluate exon skipping. Novel dmd mutations were identified to enable the design of phenotype rescue studies via morpholino administration. Correlation of induced exon-skipping efficiency and the level of phenotype rescue suggest that relatively robust levels of exon skipping are required to achieve significant therapeutic ameliorations and that pre-screening analysis of exon-skipping drugs in zebrafish may help to more accurately predict clinical trials for therapies of DMD

Muscle stem cells undergo extensive clonal drift during tissue growth via meox1-mediated induction of G2 cell-cycle arrest

Organ growth requires a careful balance between stem cell self-renewal and lineage commitment to ensure proper tissue expansion. The cellular and molecular mechanisms that mediate this balance are unresolved in most organs, including skeletal muscle. Here we identify a long-lived stem cell pool that mediates growth of the zebrafish myotome. This population exhibits extensive clonal drift, shifting from random deployment of stem cells during development to reliance on a small number of dominant clones to fuel the vast majority of muscle growth. This clonal drift requires Meox1, a homeobox protein that directly inhibits the cell-cycle checkpoint gene ccnb1. Meox1 initiates G2 cell-cycle arrest within muscle stem cells, and disrupting this G2 arrest causes premature lineage commitment and the resulting defects in muscle growth. These findings reveal that distinct regulatory mechanisms orchestrate stem cell dynamics during organ growth, beyond the G0/G1 cell-cycle inhibition traditionally associated with maintaining tissue-resident stem cells.Phong Dang Nguyen, David Baruch Gurevich, Carmen Sonntag, Lucy Hersey, Sara Alaei, Hieu Tri Nim ... al et

Structural chemistry and electronic properties of Sr₂FeIrO₆

A polycrystalline sample of Sr2FeIrO6 has been synthesized and shown by a combination of X-ray diffraction, neutron diffraction, magnetometry, and Mössbauer spectroscopy to be a triclinic (space group I¯1; a = 5.54996(3) Å, b = 5.57847(3) Å, c = 7.84165(3) Å, α = 89.990(1)°, β = 90.059(1)°, γ = 90.079(1)°) perovskite, with a partially ordered (0.928 : 0.072(4)) distribution of transition metal cations over the six-coordinate sites. The predominant oxidation states are Fe3+ and Ir5+, although the Mössbauer data suggest that ~4% Fe4+ is present. The compound is a Type II antiferromagnet below 120 K, with an ordered magnetic moment on the Fe-dominated sites of 3.67(3) µB per Fe3+ cation. The spins associated with the antisite defects are frustrated and do not take part in the long-range magnetic ordering, consequently giving rise to hysteresis in the magnetic susceptibility below 40 K. The possible location of the Fe4+ cations is discussed briefly.