Pathology – Lecture 6Tuesday 5-10-2010Done By: Lujain Shomali

In The Name of Allah

Before starting the lecture.. The CR had an announcement about the internal labs:

1) You need to study for the Micro lab only the manual and the handouts of these labs .. there's no need to have the slides coz they're only headlines

2) About Patho lab ,you are going to have your copy of Web Path CD for the first week lab about " Cell Injury ", and it's about 29 slides .. and every week you will be told about the new slides of the next lab.

3) for the Genetics lab there's a manual + available slides every Monday in "Al Jam3yya "..

*P.S : Micro & Patho labs examinations don't have a special "Mid-Term" exam ,instead they're included with their material theoretical exams( first, second, final ), while Genetics lab exam is considered as "Mid-Term" one & is going to be held at 8/11/2010 -iA- .

Now let's begin ..

In the last lecture we started talking about cell death and we know that it's an irreversible process that includes Necrosis and Apoptosis and Autolysis.

Autolysis (تفسخ), is the death of tissue and starts after cell death .It's a path process dealing with enzymes which break down the cell body and it involves the process of auto digestion and lysis in the presence of living cells.

We started to talk about necrosis which is an irreversible change & it's dissolution of local groups of cells.

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Remember: Apoptosis happens to a Single cell while necrosis is to a group of cells.

These processes of cell death increases the eosinophilia which means the dead cells are more pink than other living ones.

Pyknosis is a change which involves the nucleus, and the nucleus becomes smaller and darker (more basophilic). (In fact, the eosinophilia deals with the cytoplasmic part of the cell).

Karyorrhexis means break down of the nucleus to small fragments.

Karyolysis means the dissolution of the nucleus (it disappears).

* Remember the difference between autolysis and heterolysis .

Why should this occur ?

The process of Necrosis consists of two things. There's enzymatic digestion of the cell, and denaturing of proteins.

There are various types of necrosis including the Coagulative, Liquefactive, Caseous, Fat, Gummatous, and Fibrinoid necrosis.

We won't take a look at Gummatous or Fibrinoid necrosis. (Basically the Gummatous is a syphilitic infection producing what's called a Granuloma and we'll hear more about that later on. As for Fibrinoid necrosis, most of it is seen in the blood vessel wall & many of it is related to severe hyper tension. Most of the vessels become necrotic, eosinophilic, and infiltrated by inflammatory cells)

Now what happens after necrosis? (sequels of necrosis) :

- The dead cells are autolysed by their enzymes.

- Phagocytosis (macrophages attack the necrotic tissue)

- Organization & fibrous repair: there's usually a fibrous scar left in the area of necrotic tissue.

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-Dystrophic calcification (sometimes after cells death they're followed by Dystrophic calcification not metastatic. Remember that won't happen always)

(1) Coagulative necrosis :

The commonest type of necrosis & most of it is due to ischemia, so that sometimes it is called ischemic infarction .

×it is seen in the kidney, adrenals, and it's typical for the heart myocardial infarction( القلبية العضلة واحتشاء الجلطة ). Gross appearance: very firm.

× in ischemic and hypoxic injury a large amount of calcium ions enter the cells so they cause cell death, that's why it's suspected that high levels of intracellular calcium plays a role in coagulative necrosis (calcification).

×it also results in denaturing all proteins in the cell and also includes enzymes since many of them are proteins.

×Histological: there will be preservation of the tissue’s basic architecture & cellular outlines since the cells are not completely digested (and it’s important to remember this since it is different from other types of necrosis). When using (H&E) staining the tissue appears faint (pale) and more eosinophlic, but you can recognize the hazy (blurred) appearance of the dead cells, and because they're dead they will be devoid of nuclei.

This picture shows a kidney with a wedge-shaped (triangular) necrotic area. It's quite solid. Notice that necrosis follows the pattern of blood supply. It's large toward the periphery where the blood is less, and it's smaller where there is better supply toward the center. So in highly vascularized tissue, necrosis is smaller and less spread and vice versa.

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(2) Liquefactive necrosis:

Liquefactive necrosis is different, Autolysis predominates and results in liquefaction. So what really happens is instead of being solid it's like a cystic area has an abscess, like what results in bacterial infections. It is especially seen in hypoxia of the brain when the large amounts of lipids there are denaturing to form a very soft area.

×Brain cells have a large amount of hydrolytic digestive enzymes (hydrolases). These enzymes cause the neural tissue to become soft and liquefied.

× Liquefactive necrosis is what causes pus (collection of acute inflammatory cells and necrotic tissue) to form. Neutrophils have many enzymes (e.g. Hydrolytic enzymes ) which are secreted in regard to

abscess, and destroy the tissue; that's why infections are generated.

There's a large number of Pyogenic microorganisms (antigens, bacterial, occasionally fungal infections) that produces pus too (e.g. the staph, the strept, and so on ).

×In the figure :

1- part of the brain and you can see that the reddish area which is soft (not solid like the coagulative

necrosis)cavity filled with liquids. Later on this will be replaced by gliosis and never by fibrosis (we'll hear about it in the future)

2-a lung abscess; it could be a bacterial or fungal infection. Whatever it is, it leads to the same thing. (Look at the middle of the superior lobe)

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3-a histological appearance of a liver abscess. All these dark colored cells are neutrophils which release a lot of enzymes which digest the tissue and produce these cavities.

(3) Caseous necrosis:

Caseous necrosis is a special type of necrosis mostly seen in tuberculosis (TB: bacterial infection) but it can be seen in some fungal infections that may behave like TB.

× Caseous comes from cheese; the white cheese which breaks down into small white soft pieces just like ceaseous necrosis.

× Histologically: it has white cheesy material in the center and is surrounded by Epitheloid cells (they are cells which look like epithelium but they're really macrophages). Macrophages play a role in TB, they engulf the microbacteria. The microbacteria after that remain inside the macrophages, and sometimes the macrophages come together to form a multi-nucleated cell that is called "Langhans giant cell" (we will hear about it more when we take the chronic inflammation which is a very specific chronic inflammatory process)

× caseous necrosis is a modified coagulative necrosis, and this small modification is caused by the lipopolysaccharide capsule of TB bacilli.

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- left: you can see the caseous necrosis as the yellow material ( this should be white but the snapshot make it yellow ).

-right: (histological view) at the top right border there's Acellular necrotic tissue rimmed by inflammatory cells ( it may show also multi nucleated giant cells ). Here we have caseous necrosis of TB, but this condition can be seen in other diseases.

(4) Fat necrosis :

Fat necrosis is not related to an inflammatory process nor ischemia. Fat necrosis is one of two:

Traumatic Fat necrosis occurs usually in fatty tissue it can be seen in the fat female breast, in the gluteal region and other areas which have trauma.

× it's presented as a hard lump (mass) in the breast or wherever, the destroyed fat related to trauma is released and engulfed again by macrophages producing a foreign body giant cell reaction not the Langerhans, it's a different type of giant cell which is called the foreign body giant cell. It engulfs the fat and it could engulf anything, for example it may be related to a surgical process engulfing part of sutures or if you pricked your hand by a small piece of wood that won't get out, your giant cells will take it (or by

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macrophages which changed to giant cells ). And this process may result in dystrophic calcification later on.

Enzymatic fat necrosis, the commonest cause is acute pancreatitis. As you know, the pancreas has many powerful enzymes so when the pancreas becomes acutly inflammated (which is a very dangerous process and a medical emergency that has to be treated quickly!), the enzymes there are released into the abdominal cavity and peritoneum and other organs and start the digestion of the peritoneal fat. You'll have the same appearance of foreign body giant cell inflammation in the fat. And in this case the areas which are involved in the active digestion become soft, saponificated and also calcified.

× saponification areas are those which look like soap bubbles

×note : in either of the two types the picture is very similar( the histology)! So pictures won't help in identify the type.

Remember : calcification grossly looks yellowish white, while microscopically using H&E staining it looks blue !

- left side : normal fat │ right side : saponified fat │and in between there's the reaction with acute inflammatory cells and fibrosis that follows calcification.

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Gangrene:

Gangrene is necrosis with putrefaction (تعفن) but the rest of the organ is normal. There are two types of gangrene:

a. Wet gangrene: a type of coagulative necrosis usually due to ischemia, and after that liquefactive necrosis due to a superimposed infection (a strong bacterial infection)

Q: A girl asks: "What do we mean by Superimposed ? "

A: We mean by it " that things lay on other things and come later on" for example if a soldier has a very bad wound in his leg in a war, after a few days it becomes bluish and this leg gradually dies because of a strong bacterial infection which destroys it and releases toxins all over the body and he will die unless his leg was amputated. And sometimes it could happen in operating theatres (surgery room) and then the operating theatre is closed due to the danger of infections.

b. Dry gangrene: is total ischemia to the tissue without superimposed infections. It's especially seen in severe atherosclerosis because the blood supply does not come to the limbs properly, and you can see it in uncontrolled diabetes patients. Sometimes they get blue toes and the toes just fall off! You can see many of diabetes patients on a wheel chairs. Why? Because they have amputation of their legs or feet or something like that!

× In this case the dead tissue just dry off. Again it’s a form of coagulative necrosis, and it's usually associated with peripheral vascular disease. Peripheral vascular disease is related to atherosclerosis and diabetes. It's

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a very known complication of diabetes. That's why diabetics always have to protect their feet.

Gas gangrene : this is also wound contamination, even worse than wet gangrene ! Because it's an infection by a certain type of bacteria –Clostridia- which produces a lot of toxins. This actually is what is seen in wars and operating theatres.

Q: A guy asks : " Is it possible that dry gangrene spreads ?"

A: Well, gangrene if it is untreated it will spread whether it was dry, wet, or gas gangrene. So if there's gangrene in the toes and it wasn't amputated, it will gradually extend to the whole foot then the whole leg and extends more and more. In dry gangrene there's no infection but the dead tissue spreads spontaneously! So that when surgeon want to get rid of gangrene, he looks at where there's a change of the color and takes a safety margin, not exactly where the color has changed.

Dr. Samir al Basheer said there's no need to go over the book for the gangrene subject.

Apoptosis :

apoptosis is different from necrosis in that it's a programmed process. it's called "Programmed Cell Death by Suicide".. the cell kills itself ! after the cell dies it remains intact ( not like the other cases )( by the way, this is a common question in the exam .. so take care of it ! :D )

×it's characterized by the death of a single cell or small clusters of cells resulting in cell shrinkage not lysis or swelling because the cell will remain as is, as you'll see later on. Apoptosis is unlike necrosis where there's death of large amounts of tissue with inflammatory reaction and it's always pathological, while apoptosis is often physiological and occasionally pathological.

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× Apoptosis is an active process ( needs energy; not passive ) which depends on signals which will cause protein break down within the cell causing the cell death. Apoptosis involves cell shrinkage, the chromatin will condense and this cell produces some blebs which will be taken up as apoptotic bodies by phagocytosis.

× Now there are two main pathways where apoptosis will be triggered. One is called the Intrinsic pathway which is related to mitochondria, and the Extrinsic which depends on certain receptors on the cell surface which trigger cell death.

1. Intrinsic pathway : there's a set of genes which control this process in the mitochondria, they belong to the Bcl-2 family. Bcl-2 genes send signals if there's any harm to the cell (e.g. UV, trauma, infection or whatever).These signals monitors the mitochondrial permeability, and once this is altered, Cytochrome c which is inside the mitochondria is released. This is called Pro-apoptotic (it initiates apoptosis).

2. Extrinsic pathway: signals come from outside the cell, and then end up finally triggering apoptosis. A set of enzymes are activated, these are called Caspases and they're many subtypes (two sets): Pro-apoptotic, and Anti-apoptotic ( anti-apoptotic include Bcl-2 itself and Bcl-xL .)

× Things to know :

-Cytochrome c activates caspase-9 that triggers apoptosis .(this is important)

-FAS (Fas Ligand) and TNF1 (Tumor Necrosis Factor type I ) are examples on extrinsic apoptotic receptors .

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-at the left side : (1) is injury of the cell like radiation, toxins, free radicals that enter the cell and cause DNA damage. (2) the Bcl-2 family are also activated. when that is activated, the p53 gene, which is related to one of the protein triggering apoptosis, is also activated. then the pro-apoptotic molecules go to the initiator caspases (which initiate the whole process). the extrinsic dead receptors also trigger the initiator caspases. then both of these signals along with the initiator caspases activates the Executioner caspases. (3) that will cause the activation of the breakdown of cytoskeleton, and endonucleasis , so that they breakdown the cell.

× if you read about it in the book it's a bit complicated but this is governed by sets of genes all of them belongs to the Bcl-2 family and some of them are Pro-apoptotic and others are not. There's always in every system in the body a Trigger and a Counter-Trigger, like for example hemolysis , and a lysis of the thrombus.

Physiologic apoptosis

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1) during development and embryogenesis. when you read embryology you see that tissues change continuosaly from conception(fertilization) till adulthood. Through this period things which transform will close off, regress, and maybe disappear !

(2) Homeostatic mechanism to maintain cell population. There are many cells in the body which continuously divid, so if all the cells have lived you would have over production of cells ! this is compensated by programmed death of cells . for example if you looked at mucosa of the intestine there are many many mitotic figures, it's always changing. the same thing for the epidermis.

(3) immune reaction - defense mechanism : elimination of self reacting lymphocytes. there're many antigens in the body and sometimes there is an abnormal immune responses in that the T lymphocytes which becomes auto-reactive, and they destroy the body's cells. So this is prevented by apoptosis. another example, some lymphocytes become lymphotoxic cells which means they contain a lot of harmful toxins, so they must die by apoptosis whatever the pathway is.

(4) In aging

(5) Shedding of menstrual endometrium : involution of formal dependent tissue such as the menstrual cycle of the female every month, the endometrium is completely lost and then replaced and this is a hormonal dependent process.

(6) Regression of the breast after weaning (فطام): after weaning the breasts reduce in size by a combination of hypotrophy and hypoplasia involving a lot of apoptotic processes.

Pathologic apoptosis

(1) Prostatic ‘atrophy’ after castration : the prostate gradually shrinks after removal of the testes for any reason, let's say a tumor.

(2) Death of inflammatory cells after inflammation : if there's an acute inflammatory process with a lot of neutrophils, the neutrophils themselves die after the infusion.

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(3) When cells are damaged by disease or injurious agents:

a. DNA damage e.g. radiation, chemotherapy, Cytotoxic drugs: In cancer the aim of these therapies is to induce apoptosis and to kill as many cells as possible to induce apoptosis. Sometimes apoptosis is accompanied by rapidly proliferating cells. In fact the chemotherapy triggers death to the newly dividing cells. The more rapidly dividing the tissue is, the more sensitive the cells are to radiation or chemotherapy. For example, if the lower part of a male body is exposed to radiation, the sperms generated in the testes are affected the most and killed rapidly so the male become finally sterile. the same thing is applied on the bone marrow.

b. Viral infections e.g. viral hepatitis (A, B or C), papilloma viruses (HPV), targets different individual cells in the body.

c. Neoplasia & malignancy: tumors that regress or involute, in fact, the more rapidly dividing they are the more you see apoptosis in them, and it can be induced.

d. Deletion of auto reactive T cells in thymus

e. rejection of transplants : if somebody has a new kidney and it may die because of rejection and apoptotic activity.

× erythrophoresis is a process where there is breakdown of certain components e.g. the cytoplasm, the plasma, urine, or whatever. it's done in the lab and an electric current passes through this and breakdown the sub types.

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- this is the erythrophoresis for the DNA.(A) The shortest one is the normal cell. (B) is DNA with a step-ladder shape. (C) is a diffused DNA.

×now you see that apoptosis is a step-ladder because it's a programmed process, and the smudged one is due to necrosis.

now here I want to summarize the differences between apoptosis and necrosis :

This table is taken directly from the book. Dr. Samir said it's important to look over it plus the other table listed below..

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Aging and Cellular Death :

× Theories

- Aging is caused by accumulations of injurious events

- Aging is the result of a genetically controlled developmental program. (this program is not cell death, it's Aging)

× Mechanisms

1. Genetic, environmental, and behavioral

2. Changes in regulatory mechanisms

3. Degenerative alterations

× the genetic factors are various you can see many people of the same family live for a 100 years, while in other families they only live around 60 years ! that's really genetically oriented, and it may be involved in failure of repair mechanisms. There's some genes are called "Clock genes" which time our lives. "Telomerase" which are present at the end of chromosomes, and when the cells divide over and over, chromosomes become SHORTER with each cycle! the shorter they are,

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the less is the life of the cell. So, there's a continuous shortening of the chromosomes till the cell dies.( we're going to talk about telomerase later in the "neoplasia" chapter ).

× Environmental mechanism is really related to the generation of a lot of Free Radicals (FR) which ultimately ends in accumulation of lipofuscin pigment. This will be seen in aging tissues.

× the last thing, there will be an accumulation of abnormal proteins, these are a complicated protein with certain glucose, and both of these produces a complicated glycosylation age products. These are called "AGES". The more AGES you form, the shorter is your life. And that's present very much in uncontrolled diabetic patients and ends up in cell death.

Finally I apologize if there's a lot of mistakes.

Best Wishes to all of You

And good luck in your exams): ..

This hand out is done by : Lujain Ali Al-Shomali

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Aجه?ما قالA الس?ماءF كئيبـــــةB وAت

?جهLمF في السIما Aكفي الت ــــت ابتسم ي Qـ قFل

QقAمRا عتني عAل ?يـــالي جAر? قــالA الل

QقAما ـتA العAل Qعـ AرAج QنW Aئ مQ وAل WسA قلـــــتF ابت

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Aما ةW مAغQن AشاشA Wالب رF ب AسQخA ــــــــتA ت Qـ AمQ أن أ

QنA فAتيكA أ Aعلى ش BرAطAال خ WاحAيا ص

AحAط?ما Aت ــــــــــــــهW أنQ ي QجAل?ما، والوA Aث Aت ت

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QجFما Aن ــــــــبL األ WحF ــــــــــذا ن Aـ ، وAك BمWالطA مFت

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غAما QرFم FبAهQنيــــا ويذLأتـــي إلى الدA ي

دAى AكA والر? Qن Aي مQ ما دامA ب WسA قلتF ابت

Aبس?ما Aت AنQ ت ـــــــدF ل QعـA ـــــــــــك ب Iـ QرB فإن ب Wش

- إيليا أبو ماضي -

"If you don't like something, change it. If you can't change it , then change your attitude..

DON'T COMPLAIN !!

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