Search results
Results from the WOW.Com Content Network
The transition from non-life to life has never been observed experimentally, but many proposals have been made for different stages of the process. The study of abiogenesis aims to determine how pre-life chemical reactions gave rise to life under conditions strikingly different from those on Earth today.
Crawling is one form of amoeboid movement which starts when an extension of the moving cell binds tightly to the surface. [ 9 ] [ 10 ] The main bulk of the cell pulls itself toward the bound patch. By repeating this process the cell can move until the first bound patch is at the very end of the cell, at which point it detaches.
Stem cell infusion therapy is a type of infusion therapy in which stem cells are infused into the blood. These stem cells then exit the blood vessels and preferentially migrate to damaged tissue as part of the regeneration process. [12] Angiopellosis has been shown to be the mechanism by which stem cells extravasate and reach damaged tissue [13 ...
A scenario is a set of related concepts pertinent to the origin of life (abiogenesis), such as the iron-sulfur world. Many alternative abiogenesis scenarios have been proposed by scientists in a variety of fields from the 1950s onwards in an attempt to explain how the complex mechanisms of life could have come into existence. These include ...
Rearward membrane flow was also observed in Dictyostelium discoideum cells. [30] These observations provide strong support for models of cell movement which depend on a rearward cell surface membrane flow (Model B, above). The migration of supracellular clusters has also been found to be supported by a similar mechanism of rearward surface flow ...
A wheeled buffalo figurine—probably a children's toy—from Magna Graecia in archaic Greece [1]. Several organisms are capable of rolling locomotion. However, true wheels and propellers—despite their utility in human vehicles—do not play a significant role in the movement of living things (with the exception of the corkscrew-like flagella of many prokaryotes).
Often expressed in cm/s. This value is inversely related to the total cross-sectional area of the blood vessel and also differs per cross-section, because in normal condition the blood flow has laminar characteristics. For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall.
The eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. DNA-bearing organelles like mitochondria and chloroplasts are remnants of ancient symbiotic oxygen-breathing bacteria and cyanobacteria, respectively, where at least part of the rest of the cell may have been derived from an ancestral archaean prokaryote ...