Climate change: contraction and convergence: myth and reality.
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Carbon Dioxide↗
Biomedical subjects
Peter F Smith
Publications and source records attributed to Peter F Smith.
Mouse cristin/R-spondin family proteins are novel ligands for the Frizzled 8 and LRP6 receptors and activate beta-catenin-dependent gene expression.
Wnt signaling plays critical biological roles during normal embryonic development and homeostasis in adults. In the canonical pathway, binding of Wnt ligands to the Frizzled (Fzd) receptor and the low density lipoprotein-related receptor (LRP) 5 or LRP6 coreceptor initiates downstream signaling events leading to gene activation by beta-catenin and the T-cell factor (TCF)-lymphoid enhancer factor (LEF) family transcription factor complex. In this study, we provide several lines of evidence that the mouse Cristin/R-spondin family proteins function as Fzd8 and LRP6 receptor ligands and induce the canonical Wnt/beta-catenin signaling pathway, leading to TCF-dependent gene activation. First, conditioned medium containing Cristin/R-spondin proteins effectively induced reporter activity in a TCF-binding site-dependent manner. Second, stimulation of cells with Cristin/R-spondin was accompanied by stabilization of endogenous beta-catenin proteins and induction of canonical Wnt target genes. Third, Cristin/R-spondin proteins physically interacted with the extracellular domains of the LRP6 and Fzd8 receptors in vivo and in vitro. Interestingly, unlike canonical Wnt ligands, Cristin/R-spondin failed to form a ternary complex with both LRP6 and Fzd8 receptors, suggesting that R-spondin may activate the canonical Wnt signaling pathway by different mechanisms. Furthermore, Cristin/R-spondin proteins possess an intriguing positive modulatory activity on Wnt ligands, possibly through a direct interaction. Our findings expand the repertoire of ligands that induce beta-catenin/TCF-dependent gene activation and implicate the presence of active beta-catenin-dependent gene activation in a Wnt-free biological context.
Amino Acid Sequence↗
Louis Stromeyer (1804-76): German orthopaedic and military surgeon and his links with Britain.
Louis Stromeyer was a pioneer of orthopaedic surgery and military medicine in Germany. The 200th anniversary of his birth was celebrated on 6 March 2004. He was much admired in Britain, which he visited on three occasions and where he met many of the country's leading surgeons. He was a friend and colleague of the London surgeon W J Little (1810-94), whose clubfoot he corrected by the operation he developed, and which Little introduced to Britain: subcutaneous tenotomy. A bibliography of Stromeyer's publications is appended.
Germany↗
Direct detection of weakly interacting massive particles using non-cryogenic techniques.
A flux of weakly interacting neutral particles incident on the Earth would produce occasional nuclear-recoil events in any material. These could be detected as scintillation or ionization pulses in suitable target materials. Expected rates are in the range 1-10(-4) events kg(-1) d(-1). These must be distinguished from much higher rates due to backgrounds from gamma and beta background, even in deep underground locations. Methods of uniquely identifying nuclear recoils are described using crystal scintillators, scintillation and ionization processes in liquid xenon, and ionization tracks in gases. World progress on these techniques and future prospects are summarized. A possible future weakly interacting massive particle detector based on mechanical recoil of suspended microgranules is proposed which, with advances in nanotechnology, could eventually be extended to the detection of low-energy relic neutrinos.
Journal Article↗
Hybrid origin of a cichlid population in Lake Malawi: implications for genetic variation and species diversity.
The importance of species recognition to taxonomic diversity among Lake Malawi cichlids has been frequently discussed. Hybridization - the apparent breakdown of species recognition - has been observed sporadically among cichlids and has been viewed as both a constructive and a destructive force with respect to species diversity. Here we provide genetic evidence of a natural hybrid cichlid population with a unique colour phenotype and elevated levels of genetic variation. We discuss the potential evolutionary consequences of interspecific hybridization in Lake Malawi cichlids and propose that the role of hybridization in generating both genetic variability and species diversity of Lake Malawi cichlids warrants further consideration.
Animals↗
Phylogeography of Lake Malawi cichlids of the genus Pseudotropheus: significance of allopatric colour variation.
One of the most compelling features of the cichlid fishes of the African Great Lakes is the seemingly endless diversity of male coloration. Colour diversification has been implicated as an important factor driving cichlid speciation. Colour has also been central to cichlid taxonomy and, thus, to our concept of species diversity. We undertook a phylogeographical examination of several allopatric populations of the Lake Malawi cichlid Pseudotropheus zebra in order to reconstruct the evolutionary history of the populations, which exhibit one of two dorsal fin colours. We present evidence that populations with red dorsal fins (RT) are not monophyletic. The RT population defining the northern limit of the distribution has evidently originated independently of the southern RT populations, which share a common ancestry. This evidence of species-level colour convergence is an important discovery in our understanding of cichlid evolution. It implies that divergence in coloration may accompany speciation, and that allopatric populations with similar coloration cannot be assumed to be conspecific. In addition to this finding, we have observed evidence for introgression, contributing to current evidence that this phenomenon may be extremely widespread. Thus, in species-level phylogenetic reconstructions, including our own, consideration must be given to the potential effects of introgression.
Alleles↗
Allele frequencies for three STR loci RT24, RT09, and BM1225 in northern New England white-tailed deer.
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Alleles↗