Lecture 7: Disturbances of Growth/Cellular Adaptation

Question 1

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

1. Fractured ribs and blood in the thoracic cavity (hemothorax)

What does that mean?

Answer 1

1. Fractured ribs and blood in the thoracic cavity (hemothorax)

What does that mean?

Rib fracture was likely due to trauma (hit by a car) resulting in bleeding into the thorax which likely caused death by not allowing the lungs to adequately inflate leading to hypoxia. If mild, blood in the thorax would be removed by phagocytosis of cellular component and lymphatic absorption of fluid components. Ribs would have healed by callus formation.

Question 2

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

2. Avulsion of nerves of the brachial plexus of the right foreleg.

What does that mean?

Answer 2

Avulsion of nerves of the brachial plexus of the right foreleg

Detachment of nerves of more than a few millimeters is usually irreversible. Some peripheral nerve regeneration does take place but within limits. The avulsion would have caused neurogenic atrophy to the affected muscles of the foreleg.

Question 3

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

3. Atrophy of muscles of the right foreleg

What does that mean?

Answer 3

3. Atrophy of muscles of the right foreleg

This is due to loss of nervous supply. Neurogenic atrophy. It is potentially reversible if nerve supply can be restored. Paralysis of this limb would result.

Question 4

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

4. Unilateral agenesis of the right kidney and enlargement of left kidney

What does that mean?

Answer 4

4. Unilateral agenesis of the right kidney and enlargement of left kidney

Congenital lack of development of the right kidney will cause compensatory hypertrophy of the opposite kidney

Question 5

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

5. Diffuse increase in thickness of endometrium with numerous small cysts

What does that mean?

Answer 5

5. Diffuse increase in thickness of endometrium with numerous small cysts

This is cystic hyperplasia of the endometrium. It is due simplistically to increased response to progesterone. It is often accompanied by bacterial infection and inflammation. It is potentially reversible if hormone levels are restored to appropriate levels.

Question 6

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

6. Left ventricular myocardial hypertrophy

What does that mean?

Answer 6

6. Left ventricular myocardial hypertrophy

This may be a protective or adaptative response to increased function (e.g. in athletic animals) and is reversible if there is prolonged inactivity. Hypertrophy can also occur inappropriately for a variety of causes, some idiopathic such as in cardiomyopathy.

Question 7

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

7. Serous atrophy of fat of perirenal and coronary fat

What does that mean?

Answer 7

7. Serous atrophy of fat of perirenal and coronary fat

An indication of caloric deficiency and suggests you need to find the cause. It is reversible. There are the last fat stores to be absorbed when an animal is starving.

Question 8

History: A 7 year old female coonhound had been lost during a hunting expedition. She was found dead by the side of the highway after being gone for 2 weeks.

Necropsy Findings:

8. Thymic involution

What does that mean?

Answer 8

8. Thymic involution

Normal for the age of the animal and can be reversed with growth hormone in some cases.

Question 9

What are some ways that cells can accumulate an excess amount of “stuff”?

Answer 9

What are some ways that cells can accumulate an excess amount of “stuff”?

• Abnormal metabolism
• Defect in protein folding or transport
• Lack of an enzyme
• Ingestion of indigestible materals

Question 10

Abnormal metabolism in a cell leads to…

Answer 10

Abnormal metabolism in a cell leads to Fatty liver.

This is most likely a systemic process, or multiple problems are going on in the animal, resulting in the altered metabolism of glycose, or lipid. That may result in the appearance of hepatic lipidosis, or glycogen degeneration of the liver.

Question 11

A defect in protein folding or transport leads to…?

Answer 11

A defect in protein folding or transport leads to accumulation of abnormal proteins.

Example: Prion diseases. Still being worked out what’s going on there.

Basically, we know that they misfold and that’s it.

Question 12

A lack of an enzyme in a cell leads to…?

Answer 12

A lack of an enzyme in a cell leads to lysosomal storage disease; the accumulation of endogenous materials.

There may be a lack of an enzyme, or a non-functional enzyme that doesn’t allow for the complete metabolism of the substrate. That will accumulate in the cell somewhere, often in a lysosome.

So, there’s lots of mucopolysaccharide diseases (Examples of some: Ceroid-lipofuscinosis, Krabbe Disease, Pompe Disease, Niemann-Pick), lots of lysosomal storage diseases out there. Helps to understand microbiology; you see what happens when one small organelle, one small enzyme isn’t working. Can have a disastrous effect on the cell, and thus the whole organ.

Question 13

The ingestion of indigestible materials in a cell leads to…?

Answer 13

The ingestion of indigestible materials in a cell leads to the accumulation of exogenous materials.

Examples: Asbestos, Carbon, Silica

Question 14

What is Fatty Degeneration (Fatty Change)?

Answer 14

Fatty Degeneration is the accumulation of a lipid within the cell, although triglycerides is a more appropriate term.

What are some ways that cells can accumulate an excess amount of “stuff”?

Abnormal metabolism - Fatty degeneration
Defect in protein folding or transport
Lack of an enzyme
Ingestion of indigestible materals

Question 15

What organs are most typically affected by Fatty Degeneration?

Answer 15

What organs are most typically affected by Fatty Degeneration?

• Liver (Not only can the liver store lipid, it’s the organ that processes lipid. Central to lipid metabolism)
• Kidney
• Skeletal/cardiac muscle

What are some ways that cells can accumulate an excess amount of “stuff”?

Abnormal metabolism - Fatty degeneration
Defect in protein folding or transport
Lack of an enzyme
Ingestion of indigestible materals

Question 16

What are the three standard routes of Fatty Degeneration of the Liver?

Answer 16

Three standard routes of Fatty Degeneration of the Liver:

1. Excess delivery of fatty acids (FA) to liver
2. Blockage of FA oxidation
3. Interference with export of triglycerides

Question 17

Of the three standard routes of Fatty Degeneration of the Liver (excess delivery of fatty acids to liver, blockage of FA oxidation, or interference with export of triglycerides)…

Tell me more about excess delivery of fatty acids (FA) to liver.

Examples?

Answer 17

Excess delivery of fatty acids (FA) to liver

Can have excess of delivery of fat to the liver that overwhelm its capacity to metabolize it

Examples:

Caloric deficiency, starvation, diabetes mellitus

Question 18

Of the three standard routes of Fatty Degeneration of the Liver (excess delivery of fatty acids to liver, blockage of FA oxidation, or interference with export of triglycerides)…

Tell me more about the blockage of FA oxidation.

Answer 18

Blockage of FA oxidation

If you have a breakdown/decreased oxidation/overwhelming use of the enzymes, you end up with oxidations of the ketone bodies from fatty acids.

This results in mitochondrial damage.

Question 19

Of the three standard routes of Fatty Degeneration of the Liver (excess delivery of fatty acids to liver, blockage of FA oxidation, or interference with export of triglycerides)…

Tell me more the interference with export of triglycerides.

Examples?

Answer 19

Interference with export of triglycerides

You have impaired synthesis of apoproteins, then you don’t have the correct folding mechanisms of proteins that help triglycerides leave the cell. Will result in the impaired release of those lipoproteins as well.

End result will be lipid accumulation within the hepatocytes

Examples: Decreased protein synthesis, Carbon tetrachloride, Aflatoxin

Question 20

Think back to Lab 1 and CCL4 toxicity in a mouse liver.

What were the two changes you saw?

How does CCL4 act on the cell?

Answer 20

Saw examples in the first lab of CCL4 toxicity, and its effect on the mouse liver

Saw two changes there:

• Acute cell swelling at the perimeter of the lesion
• Centralobularly, saw necrosis of hepatocytes (Pale, swollen cells and more deeply pink cells toward the center of the lobule)

CCl4 is a particularly strong toxin in that it causes lipid peroxidation, it can cause immediate necrosis of the cells

Is also can result in the accumulation of lipid in the cells through this process of damage through the rER, ribosomes then detach and then you have decreased protein synthesis, and that is your mechanism of losing apoproteins.

If you lose apoproteins, then those lipid globules can never exit the cell.

Question 21

What are the gross changes to a liver that’s damaged by excessive fat storage?

Answer 21

What are the gross changes to a liver that’s damaged by excessive fat storage?

• It’s enlarged
• It would feel almost greasy, because there’s so much lipid within the structure
• Would have rounded edges (compared to the well-defined, pointed edges of a normal liver)
• Soft, friable, easy to damage
• Diffusely yellow or tan (Much different than the expected mahogany color)
• It would float in water.

Question 22

What are the microscopic changes to a liver that’s damaged by excessive fat storage?

Answer 22

Histologically, cells are large, swollen, describe them as having vacuoles.

Any time you have an enlarged hepatocyte, there can be the presence of water in the cytosol, it can be due to glycogen storage, or it can be lipid

• Not always distinguishable by light microscopy
• Sometimes there are extra stains we need to do, to distinguish what kind of structures those are.

Generally, when you’re looking at a lipid vacuole, you’re looking at something that’s really large. It might be a single vacuole or it may be many. It will be clear, and often has a crisp margin.

• Vs glycogen and water, which tends to have a ragged, unclear lining. Your eye can’t determine where the clear starts and the pink begins. But with lipid? Very clear demarcation

The cell can be so full with lipid droplets that the nucleus gets pushed off to the side. If you have a cell that normally has a centrally located nucleus (like a hepatocyte) and instead you can barely see the nucleus and see one or several well-defined, clear spaces, that’s a pretty good sign that that’s lipid storage

Question 23

What is this small, crappy image an example of?

Answer 23

This is a gross example of a fatty liver.

Here, we see an enhance lobular pattern, that’s what the reticulated pattern is

Each of these is indicating a hepatic lobule.

Question 24

Is fatty infiltration is the same as fatty change?

Answer 24

No, fatty infiltration is not the same as fatty change.

Fatty infiltration refers to the fatty infiltration of the stroma. So, the space in between muscle cells vs Fatty change, which is when the lipid is in the cell itself

One thing you may see in hearts and skeletal muscle as a form of atrophy is that the interstitium may take on increased adipose tissue. This is fatty infiltration.

Question 25

What is glycogen degeneration?

Where does it occur?

What causes it?

What disease do you commonly see this in?

Answer 25

Glycogen degeneration is the deposition of carbs, starches, glycogen within primarily the liver and the kidney.

Caused by prolonged periods of hyperglycemia; increased glucose in the blood.

Not uncommon to see this in Cushing’s Disease, or hyperadrenocorticism. Or in any situation that would cause the need for increased gluconeogenesis

Question 26

Expound upon Cushing’s Disease and glycogen degeneration.

Answer 26

Not uncommon to see glycogen degeneration in Cushing’s Disease, or in any situation that would cause the need for increased gluconeogenesis (like phases of diabetes mellatus, when an animal would have been hyperglycemic and then dropped suddenly to being hypoglycemic)

There a variety of ways that that could occur, but anything that results in the unregulated increase in gluconeogenesis, in increasing the blood sugar, is going to put an unusual amount of glucose into the bloodstream, which will be taken out by the liver. That results in storage as glycogen within hepatocytes.

This is ok on a temporary basis, long term presents some challenges

Question 27

What’s the stain used to confirm the presence of glycogen in a cell?

Answer 27

To confirm glycogen degeneration, we could do a PAS stain

Clear areas of cell would stain a fuchsia or magenta color. We would say that it was PAS positive, if we saw the clear material staining as purple.

Question 28

Can you think of two other examples of when things get stored in cells in ways that messes with cell function?

Answer 28

Two other storage issue examples:

• Spongiform encephalopathy (scrapie), sheep. Will see vacuolated neurons.
• Lysosomal storage diseases. Will see excessive glycogen/carbohydrates in neurons. Markedly enlarged neurons at the periphery of the cell by small clear spaces

Question 29

What’s a challenge of histopathology, in the sectioning process when going from a water-based structure to an alcohol-based structure?

Answer 29

One of the challenges of histopathology is that in the sectioning process, and processing of the tissues, when they go from being a water based structure to an alcohol based structure, all the material that was present in the vacuoles is lost.

And we can’t tell what was there; we can’t see the fat, or misfolded protein, or whatever else was there. Because if the compound is alcohol or water soluble, it’s lost in our processing.

There’s a variety of ways around that: frozen sections, IHC stains that are available

But in routine diagnostic work, we are looking at just clear spaces. So we have to keep in our heads, what are the possibilities for this? What stains can we run to prove that?

Question 30

What is hyalin?

Answer 30

Hyalin is a term to used identify the presence of unidentified pink material that’s between cells. Could be amyloid, fibrosis…

In a pinch, you can say hyalin if you don’t know what pink material you’re looking at.

Question 31

What are we looking at?

Answer 31

This is a hyalin cast, likely albumin.

Question 32

What happens if our glomerular tufts are no longer functional?

Answer 32

Say our glomerular tufts are gone, obliterated by hyalin material.

The obliterated glomerular tufts are most likely non-functional, they’ve been expanded by the extracellular, eosinophilic material.

What would you likely see in the glomerular filtrate that you should not ever see…?

Protein. A hyalin cast; protein within the tubular lumen. It got into the lumen because there’s no effective filtering mechanism in the glomeruli anymore.

Question 33

What is amyloid?

Is it systemic or local?

What stain do we use to identify it?

Answer 33

Amyloids: It’s a variety of proteins, not just one.

It’s more defined by how it folds. The essence of amyloid is a protein that occurs as a beta-plated sheet

It can be both systemic AND local.

Congo red stain is a mechanical recognition more than anything else. The stain will detect areas of beta-pleated sheets.

(Can be frustrating, because it also recognizes fibrous tissue well, sometimes just as well as amyloid.)

Question 34

What are common sites for amyloid?

Answer 34

Common sites for amyloid in dogs:

• Renal glomerulus
• Spleen
• Liver

Common sites for amyloid in cats:

• Renal medulla
• Pancreatic islets

Side note Because amyloid is found in different places in the kidney for dogs and cats, that means it has different clinical outcomes.

Question 35

What can amyloid do to hepatocytes?

Answer 35

Amyloid causes unsolicited atrophy of hepatic cords, often due to compression of those cords.

This impairs blood flow, the entry of nutrients into the hepatocytes that likely impairs bile flow.

CRS turns amyloid material an orange color, then to confirm it we can look at it under polarized light. The light that it refracts back is a green color

Question 36

What is this?

Answer 36

This is a dog liver with amyloidosis.

These images will make more sense if you look at the full image from the lecture slides.

Question 37

What’s going down here?

Answer 37

This is a postive congo red stain. Postive for amyloid.

Question 38

OMGOMGOMG what’s happening here?

Answer 38

Lysosomal storage disease in a cat.

Don’t know which LSD, in this example

Markedly enlarged neurons at the periphery of the cell by small clear spaces

Question 39

Is there a human disease counterpart to amyloidosis?

Answer 39

Humans are different

Not common, but there is a systemic primary amyloidosis

It’s an overproduction of immunoglobulin light chains

Just know that there’s a human counterpart to the disease.

Question 40

What are some examples of localized amyloid issues?

Answer 40

Cats? See localized amyloid in the pancreatic islets.

• IAPP: Islet amyloid polypeptide. Overproduced amyloid, esp in diabetic cats. See it as a subclinical lesion.

Human? Alzheimer’s Disease. Not sure how it occurs, just a recognized phenomenon

Question 41

What issue are we seeing here?

Which circled islet is close to normal?

Answer 41

This is a cat pancreas that’s been affected by amyloidosis

The islet is effaced (replaced, expanded, somewhat destroyed) by amyloid (pale, eosinophilic material that’s between the cell)

Can see a close to a normal size islet on the tope (but still some amyloid in there, so not totally normal)

Clinical outcome to losing the islets? Hyperglycemia, diabetes