362 research outputs found
Regeneration in Echinoderms: repair, regrowth, cloning
No full textRegenerative potential is expressed to a maximum extent in echinoderms. It is a commonphenomenon in all the classes, extensively employed to reconstruct external appendages and internalorgans often subjected to amputation, self-induced or traumatic, rapidly followed by completesuccessful re-growth of the lost parts. Regeneration has been studied in adult individuals as well as inlarvae. In armed echinoderms, regeneration of arms is obviously frequent: in many cases, thedetached body fragments can undergo phenomena of partial or total regeneration independently of thedonor animal, and, in a few cases (asteroids), the individual autotomised arms can even regenerate toproduce new complete adults, offering superb examples of cloning strategies. In the species examinedso far most results throw light on aspects related to wound healing, growth, morphogenesis anddifferentiation, even though in most cases many crucial questions remain unanswered. The presentpaper provides an overview of the current understanding of the phenomenon and covers the mainbiological aspects of regeneration giving an idea of the “state of the art” across the phylum in terms ofexperimental approaches and representative models
Electron and ion microscopy and micromanipulation: common principles and advanced methods in applied sciences : proceedings of summer school 2008 & 2009, Milano, Italy
No full textZ-line and supercontraction in the hydraulic muscular systems of insect larvae
No full textAn electron microscopic study has been made on the body wall muscles from Lepidoptera (Noctua pronuba, Philosamia cynthia) and Diptera larvae (Tipula tipula), whose locomotion is based on a hydraulic muscle antagonism. All the fibers examined had interrupted Z‐bands, formed of single dense bodies, irregularly placed around the sarcomere; myosin filaments could pass through the spaces between one Z‐body and the next, making it possible for the sarcomere to shorten its resting length by up to 60%. In supercontracted muscles, both the thick and the thin filaments pass through the Z‐line; since these actin filaments are very long, they can overlap and interact with the myosin filaments of the adjacent sarcomeres. The muscles examined can be placed in the category of supercontracting muscles and can be considered a type of striated muscle, with morphological and functional characteristics similar to those of helical or smooth muscle
Il potenziale rigenerativo negli echinodermi: dalla riparazione tissutale alla clonazione
No full textEvidence for the 'cellular calcium regulation hypothesis' from 'simple' mutable collagenous structure: the brachial and cirral syzygial ligaments of Antedon mediterranea (Lam.)
No full textRegenerative response and Endocrine Disrupters in crinoid Echinoderms: an old experimental model, a new ecotoxicological test
No full textThe regenerative phenomena that reproduce developmental processes in adult organisms and are regulated by endocrine and neurohumoral mechanisms can provide new sensitive tests for monitoring the effects of exposure to anthropogenic chemicals such as endocrine disrupter (ED) contaminants. These pollutants in fact can be bioaccumulated by the organisms, causing dysfunctions in steroid hormone production/metabolism and activities and inducing dramatic effects on reproductive competence, development and growth in many animals, man included. Current research is exploring the effects of exposure to different classes of compounds well known for their ED activity, such as polychlorinated biphenyls (PCBs), nonylphenols and organotins, on regenerative potential of echinoderms, a relatively unexplored and promising applied approach which offers the unique chance to study physiological developmental processes in adult animals. The selected test species is the crinoid Antedon mediterranea, which represents a valuable experimental model for investigation into the regenerative process from the macroscopic to the molecular level. The present study employs an integrated approach which combines exposure experiments, chemical analysis and biological analysis utilizing classical methods of light (LM) and electron (TEM and SEM) microscopy and immunocytochemistry. The experiments were carried out on experimentally induced arm regenerations in controlled conditions with exposure concentrations comparable to those of moderately polluted coastal zones in order to reproduce common conditions of exposure to environmental contaminants. The results of the exposure tests were analysed in terms of effects at the whole organism, at the tissue and cellular level, and possible sites of action of EDs. Our results show that prolonged exposure to these compounds significantly affects the regenerative mechanisms by inducing appreciable anomalies in terms of regeneration times, overall growth, general morphology and histological and cellular pattern. A concentration/effect relationship could be found for all substances. Interestingly, contrasting results in terms of inhibition or acceleration of regeneration phenomenon were obtained for different chemicals
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