Evolutionary dynamics of whole-body regeneration across planarian flatworms

Regenerative abilities vary dramatically across animals. Even amongst planarian flatworms, well-known for complete regeneration from tiny body fragments, some species have restricted regeneration abilities while others are almost entirely regeneration incompetent. Here, we assemble a diverse live collection of 40 planarian species to probe the evolution of head regeneration in the group. Combining quantification of species-specific head-regeneration abilities with a comprehensive transcriptome-based phylogeny reconstruction, we show multiple independent transitions between robust whole-body regeneration and restricted regeneration in freshwater species. RNA-mediated genetic interference inhibition of canonical Wnt signalling in RNA-mediated genetic interference-sensitive species bypassed all head-regeneration defects, suggesting that the Wnt pathway is linked to the emergence of planarian regeneration defects. Our finding that Wnt signalling has multiple roles in the reproductive system of the model species Schmidtea mediterranea raises the possibility that a trade-off between egg-laying, asexual reproduction by fission/regeneration and Wnt signalling drives regenerative trait evolution. Although quantitative comparisons of Wnt signalling levels, yolk content and reproductive strategy across our species collection remained inconclusive, they revealed divergent Wnt signalling roles in the reproductive system of planarians. Altogether, our study establishes planarians as a model taxon for comparative regeneration research and presents a framework for the mechanistic evolution of regenerative abilities.

Content aware image restoration improves spatiotemporal resolution in luminescence imaging

Luminescent reporters are due to their intrinsically high signal-to-noise ratio a powerful labelling tool for microscopy and macroscopic in vivo imaging in biomedical research. However, luminescence signal detection requires longer exposure times than fluorescence imaging and is consequently less suited for applications requiring high temporal resolution or throughput. Here we demonstrate that content aware image restoration can drastically reduce the exposure time requirements in luminescence imaging, thus overcoming one of the major limitations of the technique.

Spontaneous senescence in the MDA-MB-231 cell line

Normal human somatic cells have a limited division potential when they grow in vitro. It is believed that shortening of telomeres, specialized structures at the ends of chromosomes, controls cell growth. When one telomere achieves a critical minimal length, the cell cycle control mechanism recognizes it as DNA damage and causes the cell's exit from the cycle in G1-phase. Because it is not possible to extend telomeres in normal cells, this non-dividing state is prolonged indefinitely, and is known as cellular senescence. The immortal cell line MDA-MB-231 has active telomerase, which prevents telomere shortening and allows cells' permanent divisions. However, there is a fraction of cells that do not divide over several days in culture as documented for some other tumour cell lines. Combination of methods has made it possible to isolate these non-growing cells and compare them with the fraction of fast-growing cells from the same culture. Although the non-growing fraction contains a significant percentage of typical senescent cells, both fractions have equal telomerase activity and telomere length. In this paper we discuss possible mechanisms that cause the appearance of this non-growing fraction of cells in cultures of MDA-MB-231, which indicate stress and genome instability rather than variation in telomerase activity or telomere shortening to affect individual cells.

[Etiopathogenesis of varicosities of the lower extremities]

This study was performed to validate the importance of heredity in the development of varicosities of lower extremities and to establish the correlation between the sclerotherapy and the pathological changes on the perforating and deep veins. The aim was also to determine the share of trauma in the development of insufficiency of the perforating veins of the lower leg. The author studied 484 hospitalized patients. By application of modern diagnostic procedures, pathological changes in the system of veins were discovered and located and varicose veins were classified into five groups. A positive family history was found in 64.5% of the treated patients. The relationship between the heredity and the pathological changes in the venous system has been given in tables. Of all the treated patients, 12.2% underwent sclerotherapy earlier. Among these patients, 50.8% showed pathological changes on the perforating veins; in 22% pathological changes, however, were found on the deep veins as well. One hundred and thirty-five patients were operated on due to insufficiency of the communicating veins. Of those patients, 21.4% stated a positive trauma in their past history, while 14.1% showed some degenerative changes in the fatty-connective tissue of the deep fascia of leg. In conclusion these results tissue of the deep fascia of leg. In conclusion these results confirm the hypothesis that trauma of lower extremities may lead to insufficiency of the communicating veins.

[Etiopathogenesis of varicosities of the lower extremities]

To investigate the significance of heredity in the development of varicosities of the lower extremities, and to establish the association between the sclerotherapy and the pathologic changes of the perforating and deep veins as well as the share of trauma in the development of perforating venous insufficiency of the lower part of the leg, the author studied 484 hospitalized patients. By using modern diagnostic procedures, the pathologic changes of the venous system were identified and located and varicosities were classified into five groups. A positive family anamnesis was found in 64.5% of the treated patients. The relationship between the heredity and the pathologic changes of the venous system is shown in tables. Of all the treated patients, 12.2% underwent sclerotization before the admission to the hospital. In 50.8% of these patients, the author found pathologic changes of the perforating veins and in 22% pathologic changes of the deep veins, as well. Due to perforating venous insufficiency 135 patients were operated. Among these patients, 21.4% reported positive history of trauma, while in 14.1% of surgically treated patients some degenerative changes of the fatty-connective tissue of the crural fascia were found. This speaks in favour of the assumption that trauma of the lower extremities may lead to perforating venous insufficiency.