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Mechanisms of disease > mechanisms of disease II > Flashcards

mechanisms of disease II Flashcards

1
Q

what are the functions of necrosis

A

removes damaged cells from an organism

failure to do so = chronic inflammation
necrosis causes acute inflammation to clear cell debris via phagocytosis

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2
Q

causes of necrosis

A

lack of blood supply

injury 
infection
cancer
infarction
inflammation
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3
Q

necrosis step by step

A
  1. result of an injurious agent or event
  2. initial events are reversible, later ones aren’t
  3. lack of oxygen prevents ATP production
  4. cells swell due to influx of water (ATP required for ion pumps to work)
  5. lysosomes rupture, enzymes degrade other organelles and nuclear material haphazardly
  6. cellular debris released, triggers inflammation
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4
Q

microscopic appearance of necrosis

  1. nuclear changes
A

nuclear changes =

  • chromatin condensation/shrinkage
  • fragmentation of nucleus
  • dissolution of chromatin by DNAse
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5
Q

microscopic appearance of necrosis

  1. cytoplasmic changes
A
  1. opacification = protein denaturation and aggregation

2. complete digestion of cells by enzymes causing cell to liquify

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6
Q

microscopic appearance of necrosis

  1. biochemical changes
A
  1. release of enzymes such as creatine kinase or lactate dehydrogenase
  2. release of other proteins such as myoglobin
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7
Q

functions of apoptosis

A
  • selective process for deletion of superfluous infected or transformed cells

involved in:

  • embryogenesis
  • metamorphosis
  • normal tissue turnover
  • endocrine dependent tissue atrophy
  • variety of pathological conditions
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8
Q

apoptosis step by step

A
  1. programmed cell death of one or a few cells
  2. events are irreversible and energy dependent
  3. cells shrink as cytoskeleton is disassembled
  4. orderly packaging of organelles and nuclear fragments into membrane bound vesicles
  5. new molecules are expressed on vesicle membrane that stimulate phagocytosis without inflammatory response
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9
Q

appearance of apoptosis

  1. cytoplasmic changes
A
  1. shrinkage of cell. organelles packaged into membrane vesicle
  2. cell fragmentation. membrane bound vesicles bud off
  3. phagocytosis of cell fragments by macrophage and adjacent cell
  4. no leakage of cytosolic components
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10
Q

appearance of apoptosis

  1. nucelar changes
  2. biochemical changes
A
  1. nuclear chromatin condenses on nuclear membrane and DNA cleavage
  2. expression of charged sugar molecules on outer surface of cell membranes and protein cleavage by proteases, caspases
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11
Q

difference of survival vs apoptosis

A

survival:

  • cell-cell or cell-matrix contacts
  • growth factors
  • cytokines

apoptosis:

  • disruption of cell-cell or cell-matrix contacts
  • lack of growth factors
  • DNA damaging agents
  • death domain ligands
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12
Q

what are caspases

A

point of convergence for causes of apoptosis

caspases are cytosine protases

caspases form activation cascade, where one cleaves and one activates the next

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13
Q

death by a thousand cuts: substrates and functions

A

Lamin A and B = nuclear envelope

PARP = DNA repair

DNA-PK = DNA repair

topoisomerase II = DNA replication

Raf-1 = signalling

Akt/PKB = cell survival

STAT1 = signalling

elf4 = translation

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14
Q

effect of caspase activation

A

results to characteristic morphological changes

includes shrinkage, chromatin condensation, DNA fragmentation and plasma membrane blabbing

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15
Q

how do we activate the initiator caspases

A
  • initiator caspases activate themselves when in close proximity
  • activation = bringing initiator caspases together
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16
Q

describe extrinsic apoptosis

A

induced by ligand binding to receptors causing receptor dimerisation

17
Q

ligand induced multimerisaion - the players

A
  1. receptor
  2. death adaptor
  3. procaspase-8
18
Q

describe TNF as an example

A
  1. tumor necrosis factor
  2. tumour necrosis factor receptor
  3. FAS-associated protein with death domain
  4. procaspase-8

auto proteolysis

19
Q

describe intrinsic apoptosis

A

induced by cytochrome c released from mitochondria

20
Q

describe cytochrome C

A

mitochondrial matrix protein

known for many years to be released in response to oxidative stress by permeability transition

any inducers of permeability transition also eventually induce apoptosis

21
Q

cytochrome c induced apoptosis: the players

A
  • cytochrome c

- procaspase-9

22
Q

how is the release of cytochrome c from the mitochondria regulated

A
  • a pore made of BCL-2 family proteins
  • BCL 2 proteins can be pro or anti-apoptotic

anti-apoptotic (bcl-2, bcl-XL, others) = repress cytochrome c release

pro-apoptotic (Bax, bad, bid, others) = facilitate cytochrome c release

  • some are not membrane proteins
  • all have BH3 domain used to form dimers
23
Q

if BCL-2 family proteins regulate cytochrome c release from mitochondria , what regulates BCL-2 proteins?

A

transcription driven by TP53

Mechanisms of disease (29 decks)

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