Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Diversification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2000

Molecular genetics of crustacean feeding appendage development and diversification.

Arthropods dominate our seas, land, and air and have done so for hundreds of millions of years. Among the arthropods, crustaceans present us with a rich history of morphological change, much of which is still represented among extant forms. Crustacea largely interact with their environment via their appendages; thus vast amounts of variation exist among the different appendages of a single individual and between appendages from different species. Comparative studies of crustacean appendage development present us with an important story regarding the evolution of morphology over both relatively short (a few million years) and relatively long (a few hundred million years) evolutionary time scales. Recent studies have used the genetic and molecular data from Drosophila development to try to understand the molecular basis for some of the variations seen in crustacean limbs. Here we review some of these data based on the expression patterns of the genes Ultrabithorax, abdominal - A, Sex combs reduced, and Distal-less.

Animals↗
PubMed1987

Common origin and phylogenetic diversification of animal hormonal systems.

The comparative view leads to the following main conclusions: Hormones are intercellular messengers in multicellular organisms. However, the receptor mechanism, the ability of forming receptors to substances in the cell's environment and the ability to synthesize most of the substances which serve as hormones in metazoans, are present in unicellular organisms, too. The main achievement of multicellular organisms in evolving hormonal mechanisms is due to their ability of differentiation. Though the whole genome and the ability to synthesize certain substances is, in principle, common to all body cells, the forming of certain substances and the ability to react to them in a certain way is delegated to certain cell groups only. This may be common to many intercellular messenger substances such as chalons, prostaglandins, morphogenetic and tissue-specific growth substances. A special feature in hormonal systems is that the two sites of release and reaction are distinct and are located at a distance from each other. Possibly this is the main or even the only difference from other intercellular messengers. However, it is of great functional importance because it enables hormones to control the temporal coordination of entirely different processes in different tissues located at a distance from each other or distributed all over the body. This feature is common to all compounds presently known as hormones. While the localization of receptors in target cells, as well as the nature of the releasing tissue or the mode of transport through the blood, may be too marrow borders for a definition (for instance in animal groups without a closed blood circulation system) the fact that there is transport over a distance is not. The fact that release and reaction sites are located at a distance from each other within the multicellular body may serve as a definition of "hormones' based on a common phylogenetic root and functional importance. On this common base different animal phyla have evolved different hormonal systems in relation to the particular problems of long distance temporal control of physiological processes posed by their special type of organization.

Animals↗
PubMed1991

Diversification of cadmium-binding proteins due to different levels of contamination in Arion lusitanicus.

Individuals of Arion lusitanicus were collected in the former mining area of Braubach (Federal Republic of Germany) which is highly polluted by various metals. The animals were transferred to the laboratory and fed contaminated litter from their original habitat. Groups of animals from a quarry near Heidelberg were reared in the laboratory and fed diets of different cadmium concentrations. Slugs fed uncontaminated food were used as controls. The concentration of cadmium in the midgut gland of cadmium-fed slugs increased in proportion with the metal concentration of the food. High amounts of zinc and copper were found in the midgut glands of slugs from Braubach. After centrifugation of homogenates, specific patterns of distribution between cytosolic components and pellets were observed for different metals. Cadmium and copper were predominantly bound to cytosolic components, whereas the main portion of zinc was associated with the pellet. In laboratory-fed slugs the increase of cadmium concentration in the food correlated with an increase of the metal content in the homogenate and in two components (supernatant, pellet) of the midgut gland. This correlation was most clearly expressed in the cytosolic components which contained 93-100% of total midgut gland cadmium. Total cadmium in control slugs was associated with components with a molecular weight of more than 15,000. In Braubach and in cadmium-loaded slugs, all the cadmium was bound to a protein with a molecular weight of 10,000, which also contained low amounts of zinc and copper. In highly contaminated individuals fed on the most concentrated cadmium diet, however, a spillover effect was observed, some cadmium being bound to an additional component with a molecular weight of more than 15,000.

Administration, Oral↗