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 ?
Low levels or absence of WT1 is confined to areas of stromal differentiation and terminal epithelial differentiation, whereas high levels of WT1 are seen in areas of blastemal and early epithelial differentiation [29, 30].
However, approximately 1% of infants at birth retain residual blastemal within their kidney [37, 38].
Maintenance of blastemal proliferation by functionally diverse epidermis in regenerating zebrafish fins.
Mpsl defines a proximal blastemal proliferative compartment essential for zebrafish fin regeneration.
This is to say that probably doses of 20 and 30 mg.[L.sup.-1] did not interfere in the expression of the genes required to the formation of the epidermal cap and the blastema, but could have interfered, momentarily, during transcriptions or translations or even complexing with proteins inhibiting their expression as an enzyme or structural functions as a protein in the process of blastemal cells differentiation on the cells responsible for the synthesis and deposition of actinotrichia and lepidotrichia, or even in the necessary signalling to differentiated cells to trigger the synthesis of the components of the dermal skeleton.
Blastomas can be biphasic with epithelial and sarcomatous elements; however, carcinosarcomas do not show a primitive blastemal component.
MORPHOLOGY: Wilms' tumor is an embryonic tumor typically composed of variable admixture of blastemal, epithelial and stromal components.
Classification of Hepatoblastoma Major categories Epithelial Fetal, well differentiated (mitotically inactive with minimal mitotic rate of [less than or equal to]2 mitoses per 10, x40 objective fields) Fetal, mitotically active (>2 mitoses per 10, x40 objective fields) Embryonal Macrotrabecular Small cell, undifferentiated Rhabdoid Mixed stroma having osteoid features; rarely striated muscle, cartilage, or minor components as follows: Cholangioblastic (ductal) Intestinal glandular epithelium (teratoid) Neuroid-melanocytic (teratoid) Rhabdomyoblastic Chondroid Blastemal
Heterologous differentiation, blastemal elements, nephrogenic rests favor diagnosis of Wilms tumor.
Skeletal muscle and blastemal elements were also absent.
Multiple histologic sections of the tumor (in excess of 1 per centimeter of tumor) showed the presence of necrotic tissue admixed with epithelial structures and focal aggregates of undifferentiated blastemal tissue (Figure 2).
In young children, the most important differential diagnosis is with Wilms tumor (nephroblastoma), and any cystic tumor encountered in children should be extensively sampled for the presence of blastemal elements, which strongly suggests the diagnosis of Wilms tumor.