1/6 Murphy Cell Injury: Death

Front 1

How does the cytoplasm of a necrotic cell stain with H&E compared to a healthy one? Why?

Back 1

Deep pink compared to healthy pale pink.

More avid binding of eosin to denatured cytoplasmic proteins

Front 2

What are the 3 cytoplasmic changes to note in a necrotic cell?

Back 2

Eosinophilia
Vacuolization (enzymatic digestion of organelles)
calcification

Front 3

Compare what you're looking for when you look at necrotic cells vs necrotic tissues.

Back 3

Necrotic cells: cytoplasmic changes and nuclear changes

Necrotic tissues: looking for patterns in a mass of cells (coagulative, liquefactive, or caseous necrosis)

Front 4

What nuclear changes may you see in necrotic cells?

Back 4

Pick one:
karyolysis
pyknosis
karyorrhexis

Until 2 days after onset of necrotic cell death-- nucleus simply disappears

Front 5

What is karyolysis?

Back 5

DNA-ases have degraded DNA. When stained with H&E, the nucleus is pale blue rather than a health dark blue.

Front 6

What is pyknosis?

Back 6

Nucleus shrinks and DNA condensates- H&E stains very dark blue (darker than healthy dark blue)

Front 7

What is karyorrhexis?

Back 7

nucleus undergoes framentation

Front 8

How long before necrotic cell's nucleus disappears?

Back 8

2 days

I bet L&O SVU labs know that

Front 9

You suspect tissue death from hypoxia/ischemia- what necrotic tissue pattern do you expect to see microscopically? Describe.

Back 9

Coagulative necrosis
Outlines of every necrotic cell preserved and recognizable-- retained because denaturation of cellular proteins (ENZYMES) predominates. No autolysis.

Front 10

You suspect tissue death from a focal bacterial infection- what necrotic tissue pattern do you expect to see microscopically? Describe.

Back 10

Liquefactive necrosis
Cells appear liquefied due to digestion and lysis by enzymes coming from either the cells' own lysosomes (autolysis) or from local WBC (activated leukocytes; heterolysis)

Front 11

You suspect a pt has TB- what necrotic tissue pattern do you expect to see microscopically on biopsy? Describe.

Back 11

caseous necrosis
Tissue GROSSly appears "cheesy" (image is gross appearance, not microscopic)
Microscopically: necrotic focus of fragmented cells and granular cellular debris surrounded by border of granulomatous inflammation (explained in different lecture)

Front 12

When they say "programmed cell death, type I" or "type II" what are those?

Back 12

type I = apoptosis
type II = autophagy

Front 13

What's the general overview of the apoptotic process?

Back 13

Initiation phase: intracellular "suicide program" gets activated (either intrinsically or extrinsically)

Execution phase: Activates intracellular enzymes -> degrade nucleus and cytoplasmic proteins

Front 14

In what kinds of situations would cells apoptose?

Back 14

For physiologic reasons: during embryogenesis/development, replacing immature cells with /matoor/ cells. Hormonal dependent involution- menstruation.

For pathologic reasons: TNF -> in tumors. Viral diseases (hepatitis). Etc, etc, etc.

Front 15

What is the goal of the initiation phase?

Back 15

Activate the "initiator caspase cascade"

Front 16

Initiation phase: Intrinsic pathway

aka?

What is the end game here to get that caspase cascade going?

Back 16

mitochondrial pathway

Make mitochondria spill cytochrome c to get apoptosomes formed which bind and activate initiator caspase 9

Front 17

How is the intrinsic apoptotic pathway initiated?

Back 17

Certain stressors (like radiation or deprivation of relevant hormone) activate intracytoplasmic sensor proteins-- a subfamily of Bcl-2 called "BH3-only" which includes Bim, Bid, and Bad

Front 18

What role do Bim, Bid, Bad and related BH3-only proteins play?

Back 18

These are sensor proteins. When their spidey-senses tingle, they activate Bax and Bak (pro-apoptotic proteins)

Front 19

What do Bax and Bak do?

Back 19

They polymerize into oligomers and insert themselves in the mitochondrial membrane making channels to release proteins (most notably cytochrome c) from the inner mitochondrial membrane.

They also inhibit anti-apoptotic proteins including Bcl-x and certain Bcl-2 proteins

Front 20

Bonus question: we learned about Bcl-2 before-- what was it?

Back 20

An oncogene that gets upregulated in follicular lymphoma after it's put behind an immunoglobulin promoter in B lymphocytes. That's a slow growing cancer since the oncogene is for not dying instead of explosive growth.

Front 21

What happens after cytochrome c gets released from mitochondria?

Back 21

It binds to Apaf-1 (APoptosis-Activating Factor-1) which forms a hexamer called The Apoptosome which binds and activates caspase-9 which activates other caspase-9 molecules and then initiator caspase cascade is off and running.

Front 22

What happens in the extrinsic apoptosis initiation pathway?

What's another name for this pathway?

Back 22

death receptor pathway- cell has these receptors for apoptotic signal delivery. Examples: TNFR1 and Fas.

When ligands bind these it activates caspases 8 and 10 -> trigger others and initiator caspase cascade takes off.

Front 23

Ok. So you've activated the initiator caspase cascade. Now what?

Back 23

The cascade activates The Executioner caspases like caspase 3 and 6 -> degradation of DNA, nuclear proteins; cytoskeletal decoupling makes for blebbing -> death

Front 24

What happens to apoptotic cells' remains?

Back 24

Get phagocytosed by macrophages or other phagocytic cells

Front 25

What type of inflammation do the apoptotic cells elicit?

Back 25

Neither type- they don't elicit inflammatory response because of the rapidity of phagocytosis

Front 26

this is not necrosis- how do I know that? i.e. what are the morphological characteristics of apoptosis? 5

Back 26

involves single cells or a small group of cells
minimal membrane damage
nuclear chromatin condenses
pronounced blebbing (membrane-bound apoptotic bodies)
no inflammatory response

Front 27

When do you go the programmed cell death type II route?

Back 27

autophagy is for cell that are nutritionally deprived-- an autophagic vacuole with organelles inside fuses with a lysosome => autophagolysosome which digests the materials and releases them back into cytoplasm to provide nutrients in desperate situations

does that make this like ethical cannibalism?

autophagy also has role in defense of viral/bacterial infections

Front 28

If the autophagy pathway gets upregulated too much it's bad. What types of diseases is it seen in? Name 2 specifically.

Back 28

It destroys too many organelles -> cell death

Degenerative diseases of nerve and muscle
Alzheimer's disease
ALS (amyotrophic lateral sclerosis)

Front 29

What genes regulate autophagy?

Back 29

Atg genes

Front 30

What do they mean when they say it's unclear whether autophagy is the direct cause of cell death?

Back 30

Is that the real problem - that just that pathway is going crazy in and of itself- as opposed to another stressor driving the death as well as the autophagy

Front 31

Show time.

What are the 5 major ways necrosis and apoptosis differ?

Back 31