Blastema


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blastema

[bla′stēma]
(embryology)
A mass of undifferentiated protoplasm capable of growth and differentiation.

Blastema

 

in the study of regeneration, the accumulation of homogeneous, nonspecialized cells on the surface of a wound after amputation of an organ. Tissues of the organ that is being restored are formed from blastemas in the course of regeneration.

In embryology: (1) a group of cells from which a new individual develops by asexual reproduction in some multicellular animals (Coelenterata, worms, Ascidia, and others); (2) the surface layer of cytoplasm in the cen-trolecithal ova of many arthropods. By means of fine outgrowths the blastema is connected to the cytoplasm, which surrounds the nucleus situated in the center of the ovum.

References in periodicals archive ?
The mature epidermal cap is suspected to be a source of growth factors that stimulate the formation and maintenance of the function of the regenerating blastema (a proliferative mass of pluripotent progenitor cells), as there is no regeneration in the absence of the epidermal cap (Goss, 1991).
In embryonic life the kidney develops from the metanephric blastema.
Next, the regeneration blastema is formed as the mesenchymal cells propagate and accumulate.
A year ago, Dr Mark Keating, who studies regeneration in zebra fish (which can re-grow fins, scales, spinal cord and part of its heart), identified a gene essential for initiating blastema formation when the fish's tail fin is cut.
Es una malformacion congenita rara que se presenta en lactantes y ninos pequenos, aunque existe reporte de un caso de un paciente de 30 anos, (11) la teoria propuesta es un defecto embriologico que evita la conexion de los tubulos de la rete testis (que se originan del blastema gonadal) y los conductos deferentes (derivados del conducto mesonefrico).
Otros autores mencionan que se requiere la presentacion de tres alteraciones adicionales para ser llamada displasia renal: mesenquima persistente, ductos metanefricos persistentes y metaplasia disontogenica (Picut y Lewis, 1987); sin embargo, la persistencia de tejido pobremente diferenciado (glomerulos fetales) y estructuras anomalas (epitelio tubular atipico) implican una induccion del blastema metanefrico que fallaron en recibir una diferenciacion completa (Potter et al.
The resulting blastema, a mass of unspecialized cells, proliferates rapidly to form a limb bud.
The metanephrogenic blastema forms glomeruli, proximal tubules, and distal tubules.
Moreover, the ingrowth of the branching ureteric buds into the metanephric blastema results in the characteristic lobulated appearance of the definitive kidney.
3,4) From a pathophysiology standpoint, horseshoe kidney occurs during the second and sixth week of gestation when the inferior portion of the metanephric blastema fuses to form an isthmus, commonly in the lower renal pole (90%) and anteriorly to the aorta and vena cava.
The occurrence of the MURCS association is sporadic, (4) and the etiology is still not clear; one hypothesis is that it results from an alteration of the blastema of the lower cervical and upper thoracic somites and pronephric ducts, which have an intimate spatial relationship in the fourth week of fetal development.
Before the fish's fins regenerate, the wound is closed with multiple layers of tissue, and the cells beneath the stump then lose their identity and form what is called blastema.