Blast (biology)
A blast (from ancient Greek βλαστός blastos "germ, sprout") is a young, not finally differentiated cell that divides or synthesizes functional proteins. Blasts usually differentiate into a special cell type. Some cells that have differentiated themselves can "dedifferentiate" again into blasts. In the case of tumor cells , too , one speaks of blastic tumor cells when the typical properties of the blasts are present.
Histologically, there are signs of increased metabolic performance:
- loosened chromatin (so-called euchromatin )
- enlarged nucleus
- increased endoplasmic reticulum
- increased ribosomes
- increased mitochondria
- increased energy metabolism
- increased RNA synthesis
- increased protein synthesis
- increased DNA synthesis in dividing cells
- usually a nucleolus
Examples
| cell | differentiated to | function | typical synthesis products (ex.) |
|---|---|---|---|
| Osteoblast | Osteocyte | Synthesis of the bone matrix ( osteoid ) | Osteopontin , osteonectin , osteocalcin , collagen , chondroitin |
| Chondroblast | Chondrocyte | Synthesis of the basic cartilage substance | Chondroitin , collagen , keratan sulfate, hyaluronic acid , proteoglycans (e.g. aggrecan), glycans |
| Myoblast | Myocyte | Synthesis of muscle - proteins | Myosin , actin , myoglobin |
| Myeloblast | Promyelocyte | Formation of granulocytes | DNA synthesis |
| Erythroblast | Erythrocyte | Formation of erythrocytes | DNA synthesis, hemoglobin |
| Monoblast | Monocyte | (hypothetical) precursor of monocytes | DNA synthesis |
| Neuroblast | Neuron (previously proneuron) | Formation of neurons | DNA synthesis, neurofilaments |
| Glioblast | Gliocyte | Formation of gliocytes ( astrocyte , oligodendrocyte , ependyma ) | DNA synthesis |