Parallelism, It\u27s Evolutionary Origin and Systematic Significance

Parallelism as one of the forms of biological similarity is investigated in the light of recent findings from developmental and molecular biology. From the organismic point of view, functional constraints and evolutionary canalization are well established as causes of parallelism. To these may be added, from the molecular perspective, (a) erratic activations of repressed genes; (b) activations of alternative pathways under the influence ofhomoeotic genes; and (c) horizontal gene transfer, for which a simple mechanism is proposed. The control of gene expression through the action oftransposable elements, reversible to some degree, appears to be an evolutionarily important and frequent phenomenon, which may account for many cases formerly interpreted as losses or irreversible changes of genes. It is suggested that this mechanism, which seems to be optimized in angiosperms, may account for the great evolutionary plasticity of this plant group. It may also provide an explanation for so-called reversals which appear as artifacts of character analyses and are biologically barely explicable. Events of horizontal gene transfer, creative for evolution but disturbing for classification, appear less frequent, or otherwise the structure of the taxonomic hierarchy would not be perceptible. Increasing knowledge in the fields of molecular and developmental biology tends to blur the borderline between homology, homoiology, parallelism, and perhaps convergence, phenomena formerly thought to be more or less distinct

Vitality of bog pine and colonising Norway spruce along environmental gradients within a bog

Bog pine is an endangered species in Europe as drainage of bogs permits colonisation by Norway spruce, resulting in severe bog pine habitat loss in marginal bog forests, and a habitat shift towards the bog centre where growing conditions are extreme. Thus, we investigated the physiological causes that limit bog pine regeneration at the bog margins and growth in the centre. We measured needle nitrogen concentration, chlorophyll content, photosynthetic capacity and the morphological traits of bog pine and spruce along transects from the centre to the margin of a bog in the Black Forest, Germany. Needle nitrogen and chlorophyll contents in the bog pine increased from the centre to the margin. However, photosynthesis was independent of chlorophyll content indicating that other factors, such as light rather than nutrients, may limit regeneration of bog pine. Vitality of bog pine was highest at the edge of the bog centre. This zone appears to be a compromise between nutrient limitation and shallow water levels on the one hand, and light limitation caused by spruce on the other. Therefore, in order to conserve bog pine, it is necessary to maintain wet and open bog forests that cannot be colonised by spruce

ISPAD Clinical Practice Consensus Guidelines 2022: The delivery of ambulatory diabetes care to children and adolescents with diabetes

info:eu-repo/semantics/publishedVersio

In vivo tumor cell adhesion in the pulmonary microvasculature is exclusively mediated by tumor cell - endothelial cell interaction

<p>Abstract</p> <p>Background</p> <p>Metastasis formation is the leading cause of death among colon cancer patients. We established a new in-situ model of in vivo microscopy of the lung to analyse initiating events of metastatic tumor cell adhesion within this typical metastatic target of colon cancer.</p> <p>Methods</p> <p>Anaesthetized CD rats were mechanically ventilated and 10⁶human HT-29LMM and T84 colon cancer cells were injected intracardially as single cell suspensions. Quantitative in vivo microscopy of the lung was performed in 10 minute intervals for a total of 40 minutes beginning with the time of injection.</p> <p>Results</p> <p>After vehicle treatment of HT-29LMM controls 15.2 ± 5.3; 14.2 ± 7.5; 11.4 ± 5.5; and 15.4 ± 6.5 cells/20 microscopic fields were found adherent within the pulmonary microvasculature in each 10 minute interval. Similar numbers were found after injection of the lung metastasis derived T84 cell line and after treatment of HT-29LMM with unspecific mouse control-IgG. Subsequently, HT-29LMM cells were treated with function blocking antibodies against β1-, β4-, and αv-integrins wich also did not impair tumor cell adhesion in the lung. In contrast, after hydrolization of sialylated glycoproteins on the cells' surface by neuraminidase, we observed impairment of tumor cell adhesion by more than 50% (p < 0.05). The same degree of impairment was achieved by inhibition of P- and L-selectins via animal treatment with fucoidan (p < 0.05) and also by inhibition of the Thomson-Friedenreich (TF)-antigen (p < 0.05).</p> <p>Conclusions</p> <p>These results demonstrate that the initial colon cancer cell adhesion in the capillaries of the lung is predominantly mediated by tumor cell - endothelial cell interactions, possibly supported by platelets. In contrast to reports of earlier studies that metastatic tumor cell adhesion occurs through integrin mediated binding of extracellular matrix proteins in liver, in the lung, the continuously lined endothelium appears to be specifically targeted by circulating tumor cells.</p

Cardiovascular development: towards biomedical applicability: Epicardium-derived cells in cardiogenesis and cardiac regeneration

During cardiogenesis, the epicardium grows from the proepicardial organ to form the outermost layer of the early heart. Part of the epicardium undergoes epithelial-mesenchymal transformation, and migrates into the myocardium. These epicardium- derived cells differentiate into interstitial fibroblasts, coronary smooth muscle cells, and perivascular fibroblasts. Moreover, epicardium-derived cells are important regulators of formation of the compact myocardium, the coronary vasculature, and the Purkinje fiber network, thus being essential for proper cardiac development. The fibrous structures of the heart such as the fibrous heart skeleton and the semilunar and atrioventricular valves also depend on a contribution of these cells during development. We hypothesise that the essential properties of epicardium-derived cells can be recapitulated in adult diseased myocardium. These cells can therefore be considered as a novel source of adult stem cells useful in clinical cardiac regeneration therapy

Enhanced sensitivity of a mountain bog to climate change as a delayed effect of road construction

Trees of Pinus rotundata (bog pine) characterise many bogs in the mid-altitude mountains of central Europe (Switzerland, East and South Germany, Czech Republic). The research described here focuses on recent changes in the growth of bog pine on the Ennersbacher Moor, a mountain mire in the Black Forest (south-west Germany). An increase in the cover of bog pine is usually caused by drainage and subsequent drawdown of the water table. However, this bog has not been drained or directly disturbed in any other way. One possible explanation is that a road constructed in 1983 along one margin of the bog has diverted part of its water supply. Even though the road was designed to conduct potentially salt-contaminated drainage water away from the bog, its construction did not cause an immediate vegetation response in the 1980s and 1990s. Therefore, I hypothesise that it enhanced the sensitivity of the bog to climatic stress, predisposing it to a succession that was eventually triggered by a series of drought years in 2009–2011. Data collected near the centre of the bog over the period 1998–2014 indicate not only a distinct change in the relationship between height and trunk circumference of the trees, but also an increase of dwarf shrub cover and changes in the composition of Sphagnum communities. Although the pH of near-surface water may have increased slightly over this period, pH and EC values remain within typical ranges for raised bogs in the Black Forest. Examination of peat profiles reveals that the peat is more highly humified now than it was in 2002, and water table records from 2012–2014 show a greater amplitude of fluctuation than water table data collected in 1998–2001. Even though its mean level is only 105 mm below the ground surface, the water table is now observed to fall rapidly to depths of at least 350 mm during both wet and dry summers. Mapping surface (meso)topography and flow lines from the adjacent slope shows that the Ennersbacher Moor is not domed in this direction, so that water arriving from upslope would reach the bog centre if the road were not present. Overall, the results support the hypothesis that the observed succession is a delayed effect of construction of the road