measures of biological diversity overview and unified framework

A variety of statistical measures of diversity have been employed across biology and ecology, including Shannon entropy, the Gini-Simpson index, so-called effective numbers of species (aka Hill's measures), and more besides. I will review several major options and then present a comprehensive formalism in which all these can be embedded as special cases, depending on the setting of two parameters, labelled degree and order. This mathematical framework is adapted from generalized information theory. A discussion of the theoretical meaning of the parameters in biological applications provides insight into the conceptual features and limitations of current approaches. The unified framework described also allows for the development of a tailored solution for the measurement of biological diversity that jointly satisfies otherwise divergent desiderata put forward in the literature

Intrinsic factors and the embryonic environment influence the formation of extragonadal teratomas during gestation

Background: Pluripotent cells are present in early embryos until the levels of the pluripotency regulator Oct4 drop at the beginning of somitogenesis. Elevating Oct4 levels in explanted post-pluripotent cells in vitro restores their pluripotency. Cultured pluripotent cells can participate in normal development when introduced into host embryos up to the end of gastrulation. In contrast, pluripotent cells efficiently seed malignant teratocarcinomas in adult animals. In humans, extragonadal teratomas and teratocarcinomas are most frequently found in the sacrococcygeal region of neonates, suggesting that these tumours originate from cells in the posterior of the embryo that either reactivate or fail to switch off their pluripotent status. However, experimental models for the persistence or reactivation of pluripotency during embryonic development are lacking. Methods: We manually injected embryonic stem cells into conceptuses at E9.5 to test whether the presence of pluripotent cells at this stage correlates with teratocarcinoma formation. We then examined the effects of reactivating embryonic Oct4 expression ubiquitously or in combination with Nanog within the primitive streak (PS)/tail bud (TB) using a transgenic mouse line and embryo chimeras carrying a PS/TB-specific heterologous gene expression cassette respectively. Results: Here, we show that pluripotent cells seed teratomas in post-gastrulation embryos. However, at these stages, induced ubiquitous expression of Oct4 does not lead to restoration of pluripotency (indicated by Nanog expression) and tumour formation in utero, but instead causes a severe phenotype in the extending anteroposterior axis. Use of a more restricted T(Bra) promoter transgenic system enabling inducible ectopic expression of Oct4 and Nanog specifically in the posteriorly-located primitive streak (PS) and tail bud (TB) led to similar axial malformations to those induced by Oct4 alone. These cells underwent induction of pluripotency marker expression in Epiblast Stem Cell (EpiSC) explants derived from somitogenesis-stage embryos, but no teratocarcinoma formation was observed in vivo. Conclusions: Our findings show that although pluripotent cells with teratocarcinogenic potential can be produced in vitro by the overexpression of pluripotency regulators in explanted somitogenesis-stage somatic cells, the in vivo induction of these genes does not yield tumours. This suggests a restrictive regulatory role of the embryonic microenvironment in the induction of pluripotency

Psychological and Biomechanical Aspects of Patient Adaptation to Diabetic Neuropathy and Foot Ulceration

© 2017, Springer Science+Business Media, LLC. Purpose of Review: The purpose of this review was to elucidate how psychological and biomechanical factors interrelate in shaping patients’ experience with diabetic symmetric polyneuropathy (DSPN) and its sequela-diabetic foot ulceration (DFU). Recent Findings: Recent findings emphasize the importance not only of neuropathic pain but also of other DSPN symptoms, such as unsteadiness. We highlight the negative spiral between unsteadiness, falls, and psychological distress. Moreover, unsteadiness is a key determinant of non-adherence to offloading resulting in the delayed DFU healing. While depression is an established predictor of incident DFU, findings linking depression and DFU healing remain inconclusive. Examination of physical activity in DFU development and healing represents the most recent application of research to this field. Summary: Research evidence indicates that DSPN markedly impairs physical and emotional functioning and suggests that there is an unmet need for the development of multifaceted interventions that address both psychological distress and biomechanical challenges experienced by patients with this debilitating complication of diabetes

Hölder-conditioned hypsometry: A refinement to a classical approach for the characterization of topography

©2020. American Geophysical Union. All Rights Reserved. The effective characterization of topographic surfaces is a central tenet of geomorphology. Differences in land surface properties reveal variations in structural controls and the nature and efficacy of Earth-shaping processes. In this paper, we employ the Hölder exponents, α, characterizing the local scaling behavior of topography and commonly used in the study of the (multi)fractal properties of landscapes and show that the joint probability distribution of the area of the terrain with a given elevation and α contains a wealth of information on topographic structure. The conditional distributions of the hypsometric integrals as a function of α, that is, Ihyp|α, are shown to capture this structure. A multivariate analysis reveals three metrics that summarize these conditional distributions: Strahler's original hypsometric integral, the standard deviation of the Ihyp|α, and the nature of any trend of the Ihyp|α against α. An analysis of five digital elevation models (DEMs) from different regions of the United States shows that only one is truly described by the hypsometric integral (Mettman Ridge from central Oregon). In the other cases, the new metrics clearly discriminate between instances where topographic roughness is more clearly a function of elevation, as captured by the conditional variables. In a final example, we artificially sharpen the ridges and valleys of one DEM to show that while the hypsometric integral and standard deviation of Ihyp|α are invariant to the change, the trend of Ihyp|α against α captures the changes in topography