Apoptosis

APOPTOSIS : APOPTOSIS Apoptosis—Coordinated and internally programmed cell death in physiological and pathological conditions. Differs from necrosis No inflammatory reaction

Apoptosis seen in : Apoptosis seen in Physiological During embryogenesis Hormone dependant-endometrial shedding, lactating breast after weaning Atrophy of thymus Pathological Injury due to heat, Radiation, Cytotoxic drugs, for cancer, Tumour cells, Autoimmune diseases

Morphological changes : Morphological changes Involves single cell or cluster of cells Oval masses with intensely pink cytoplasm Nuclear chromatin condensed and aggregated peripherally under nuclear membrane in various shapes and sizes Ultimately karyorrhexis occurs

Slide 4 : With E.M. it appears as fragmentation of DNA into nucleosome like pieces formed due to activation of endonucleases Cells shrink, form cytoplasmic buds and fragment into apoptotic bodies There is no inflammatory reaction but apoptotic bodies are phagocytosed by macrophages

Mechanism of apoptosis : Mechanism of apoptosis Signalling- A) An intrinsic programmed event-eg.-lack of growth factor, specific ligand –receptor interactions, release of enzymes from T cells or selected injurious agent B) These signals may either suppress preexisting death programs or initiate a death cascade

Slide 6 : Control and integration- Done by specific proteins that connect the original death signals to the final execution programme There are two broad pathways 1) signals by specific adapter proteins 2) regulation of mitochondrial permeability by the members of BCL-2 family of proteins ( controlled by BAD, BAX & BID genes)

Slide 7 : Receptor-CD95 + Signal (Ligand) = Specific adapter protein Procuspase 8 Cuspase 3----Death inducing signal Activates cleavage of DNA or other substitutes