Cell ageing & death Flashcards
does necrosis require energy?
no
is necrosis pathological or physiological?
always pathological - never physiological phenomenem
describe coagulative necrosis?
- preservation of cell outlines
- dead cells are consumed by various enzymatic processes & cells
- microenvironment too toxic for proteolysis etc
- common
- often seen in cardiac muscle - MI (occurs when blood flow stops)
describe liquefactive necrosis?
- liquid viscous mass - no cell structure remains
- pus
- associated with localised bacterial & fungal infections
- necrosis within the brain
describe caseous necrosis
- cheesy necrosis
- microscopic
- usually associated with tuberculosis
- granulomatous inflammation with central necrosis
how do you determine caseous necrosis?
r culture, PCR, look for result of Ziehl Neelson stain
when is apoptosis physiological?
- when we need cells to die off
- counter-intuitively it may be part of normal growth →like development of toes & fingers
- removal of self-reactive lymphocytes
- hormonal-dependant evolution
when is apoptosis pathological?
- in response to injury
- radiation (including UV light)
- chemotherapy
- viral infection - hepatitis
- cancers
- graft Vs host disease
what are the 2 mechanisms of apoptosis and what do they rely on?
extrinsic & intrinsic
= all mechanisms rely on activating caspases
what happens in extrinsic pathway of apoptosis?
- death receptor initiated pathway
- cell membrane receptors with death domains
what are death receptor examples in extrinsic apoptosis?
- tumour necrosis factor (TNF)
- Fas
what is TNF?
tumour necrosis factor = complex but induces apoptosis in association with inflammatory conditions = cell surface receptor
*note: different from TNF alpha - TNF alpha is cytokine in immune response
what is Fas?
= a cell surface receptor involved in extrinsic apoptosis
subgroup of TNF that triggers apoptosis of lymphocytes
= people with Fas mutations often get autoimmune diseases
what happens in intrinsic pathway of apoptosis?
- mitochondrial pathway
- growth signals promote anti-apoptotic molecules in mitochondrial membrane
- when removed, replaced by Bax, Bak (they are both proteins of same family that change conformation and affect mitochondria permeability)
- increase permeability of mitochondria
- release of proteins like cytochrome C that leads to cascade and then stimulates caspases
what is pyknosis?
cells nucleus shrinks and chromatin that’s within the nucleus becomes more dense & clumped
= occurs during apoptosis
