Tissue engineeringTissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose but is not limited to applications involving cells and tissue scaffolds.
CD4In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells. It was discovered in the late 1970s and was originally known as leu-3 and T4 (after the OKT4 monoclonal antibody that reacted with it) before being named CD4 in 1984. In humans, the CD4 protein is encoded by the CD4 gene.
Callus (cell biology)Plant callus (plural calluses or calli) is a growing mass of unorganized plant parenchyma cells. In living plants, callus cells are those cells that cover a plant wound. In biological research and biotechnology callus formation is induced from plant tissue samples (explants) after surface sterilization and plating onto tissue culture medium in vitro (in a closed culture vessel such as a Petri dish). The culture medium is supplemented with plant growth regulators, such as auxin, cytokinin, and gibberellin, to initiate callus formation or somatic embryogenesis.
HaptenHaptens (derived from the Greek haptein, meaning “to fasten”) are small molecules that elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself. The mechanisms of absence of immune response may vary and involve complex immunological interactions, but can include absent or insufficient co-stimulatory signals from antigen-presenting cells.
Plant tissue culturePlant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues, or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used, to produce clones of a plant in a method known as micropropagation. Different techniques in plant tissue culture may offer certain advantages over traditional methods of propagation, including: The production of exact copies of plants that produce particularly good flowers, fruits, or other desirable traits.
ChemotaxisChemotaxis (from chemo- + taxis) is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming toward the highest concentration of food molecules, or to flee from poisons (e.g., phenol). In multicellular organisms, chemotaxis is critical to early development (e.g.
