بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. CELL INJUREYby biological agents BY Dr Abdul Aziz Djamal MSc.DTM&H.SpMK(K)

3. CELL INJURY AND ADAPTATION Causes of cell injury: 1. Hypoxia(deficiency of oxygen) due to: (i) Ischaemia (ii) decrease of oxygen carrying capacity of blood due to anaemia, cardiac or respiratory failure and CO poisoning. 2. Physical agent:burns, deep cold, radiation, mechanical trauma and electric shock. 3. Biological agentse.g. viruses, bacterial toxins, fungi and parasites. 4. Chemical agentsand drugs e.g. alkalis, acids, insecticides, alcohol and narcotic drugs & air pollutants et.. 5. Endogenous toxinsas in case of uremia, jaundice and diabetic ketosis. 6. Immunologic reactions (hypersensitivity). 7. Nutritional imbalancesuch as protein calorie malnutrition, starvation, obesity, diabetes mellitus and deficiency of other substances and vitamins. 8. Genetic abnormalitiesas in Down syndrome & sickle cell anemia.

4. Hypoxic and ischemic injury to the cells occur through:- a)- ATP depletion b)- over production of oxygen – derived free radicals due to imbalance between free radicals generation and radical defense system. Other mechanisms caused by all forms of cell injury include:- a) - Defect in membrane selective permeability b)- Increased intracellular ca+ and loss of ca+ homeostasis that result from damage of both cell membrane & mitochondrial membrane and ER.The increased intracellular Ca+ cause activation of degenerative cellular enzymes as protease,ATpase, phospholipase and endonuclease. (that cause damage & mutation of the nucleus) . - Pathogenesis of cell injury:

5. Mechanism Of Bacterial And Viral Injury • a) By production of cytotoxic lymphokins & activation of lytic complement substance • b) Direct effect of bacterial toxins on the cell membrane & mitochondrial damage, through incorporation of viral genome to cell DNA and their alteration • c) Irreversible mitochondrial damage.

6. Biological agentsthat can caused Human CelIular Injury Bacteria Virus Fungi Protozoa/Parasite.

7. Biological Products Produced that caused Cellular Injury Toxin : Exotoxin Endotoxin. Enzymes Exported Proteins. Structural Products Triggering the Pathologic Immune response.

8. Mechanism of Bacterial Injury to the Human cell 1. Direct. Diphtheria Toxin to Respiratory Tract lining cells. Toxin- receptor protein- pinocytosis- inactivate the Elongation factor 2 (EF2) – Stop translation- cell death. 2. Indirect : Complement activation. Cytokine activation.

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11. CAUSES OF CELL INJURY

12. CAUSES OF CELL INJURY

13. Cellular Reaction PatternTo Stress Depends On: 1. Type, duration, and severity of stress. 2. Type, state and adaptability of cell. I-Irreversible Cell Injury: Severe stimuli leads tonecrosis .& Apoptosis II-Reversible Cell Injury: Mild stress for short duration leads to biochemical change or mild form of morphologic change in the affected cells ( hydropic swelling).

17. III-Persistent prelethal stress leads to cellular adaptation. 1-Adaptation of growth. a) Increased growthand cellular activity e. g.Hypertrophy &Hyperplasia b) Decreased growth and cellular activity e.g. Atrophy. 2-Disturbances of cellular differentiation and morphology e.g.Metaplasia,& Dysplasia. 3-Intra and Extra cellular accumulations e. g. a) Lipids as infatty change & Cholesterol deposits. b) Proteins as inHyaline change& Amyloidosis. c) Pigments as inPathologic pigmentation. d) Calcium as inPathologic Calcification e) Enzymatic metabolic deficiency as in Gout&lyzosomal storage disease.

18. IRREVERSIBLE CELL INJURY NECROSIS Necrosis Definition: Necrosis is local death of cells while the individual is a life followed by morphological changes in the surrounding living tissue, (cell placed immediately in fixative are dead but not necrotic). Causes of cell necrosis: See before, but the most common causes of cell death are viruses, ischaemia, bacterial toxins, hypersensitivity, and ionizing radiation. Morphologic change in necrosis: The changes don’t appear in the affected cells by light microscopy before 2-6 hours according to the type of the affected tissue.

19. Changes in the cytoplasm: i. Swelling and granularity of the cytoplasmdue to (a) Imbibition of water (ATP in the cell) (b) Coagulation of the cytoplasm. ii. Loss of cellular membrane and release of intracellular enzymes in the blood e.g. Serum Transaminase(ST )& LDH where their detection is of diagnostic value in liverand heart diseases. iii.Fusion of cellsforming homogeneous eosinophilic mass.

21. Nuclear changes:Occur due to hydrolysis of nucleoproteins: i. Pyknosis i.e. the nucleus becomes shrunken condensed and deeply stained. ii. Karyorrhexis: rupture of nuclear membrane with fragmentation of the nucleus. iii. Karyolysis: the nucleus dissolves and disappears. Finally the affected tissue changes to homogeneous eosinophilic mass with nuclear debris.

22. NUCLEAR CHANGES IN NECROSIS

23. Types of necrosis The variable types of necrosis differ as regards causes, gross and microscopic pictures. (1) Coagulative necrosis: It is mainly caused by sudden ischaemia e.g.infarction of heart, kidney and spleen. The protein of the affected tissue becomes denaturated. Grossly,it appears dry pale opaque. It is triangular ? subcapsular with the base towards the capsule of the affected organ. This is due to the fan like distribution of the supplying blood vessels. The infarct area is surrounded by narrow zone of inflammation and congestion. Microscopically,the structural outline of the affected tissue is preserved but the cellular details are lost.

24. GROSS AND MICROSCOPIC PICTURE OF NECROSIS

25. (2) Liquifactive necrosis The necrosed tissue undergoes rapid softening e.g. infarction of the nervous tissue which has abundant lysosomal enzymes. Also, this type of necrosis occurs in case of suppurativeinflammation(Abscess) where liquefaction occurs under the effect of proteolytic enzymes of PNLs liquefaction of the amoebic abscess occurs due to the effect of strong proteolytic enzymes and hyaluronidase secreted by E. Histolytica. Grossly:the affected tissue appears as homogenous amorphous substance. Microscopically:it appears as homogenous eosinophilic structure. .

27. (3) Caseous necrosis: • It is characteristic of tuberculosis. The necrotic tissue undergoes slow partial liquefaction forming yellow cheesy material. • Microscopically, it shows amorphous granular eosinophilic material lacking the cell outlines. • Unlike coagulative necrosis, the necrotic cells do not retain their cellular outlines, and do not disappear by lysis, as in liquifactive necrosi • Grossly, the caseous material resembles clumpy cheese, hence the name caseous necrosis. • The cause of necrosis in TB ishypersensitivityreaction caused by the tuberculoprotein content of the cell wall of Mycobacterium..

28. Caseous necrosis in LN. Amorphous ,granular ,eosinophilic ,necrotic center is surrounded by granulomatous inflammation.

29. T.B LUNG : (Large Area Of Caseous Necrosis) AREA ,YELLOW-WHITE AND CHESSY

30. (4) Fat necrosis it is necrosis of adipose tissue including two types: • Traumatic: caused by trauma to adipose tissue e.g. breast and subcutaneous tissue. b) Enzymatic: which occurs in case of acute haemorrhagic pancreatitis. • Obstruction of the pancreatic duct leads to release of lipase which splits the fat cells of the omentum into fatty acid (combine with Ca giving chalky white calcification) and to glycerol which is absorbed in the circulation.

31. (5) Fibrinoid necrosis This is characterized by swelling, fragmentation, increased eosinophilia of collagen fibers and accumulation of mucopolysaccharides and fibrin due to vascular exudation of fibrinogen at the site of lesion, e.g.: a)Collagen diseases(Rheumatic fever, Rheumatoid, Sclerodermia, Lupus erythematosus and Polyarteritis nodosa). b) In the wall of blood vessels in malignant hypertension

32. FIBRINOID NECROSIS

33. (6) Zenker’s necrosis: • Of the rectus abdominus muscle and diaphragm as a complication of : • bacterial infection particularly typhoid fever. • The striated muscles lose its striation, swell and fuse together in homogeneous structureless mass.

34. (7) Gangrenous necrosis: The tissue in this case have undergone ischaemic cell death and coagulative necrosis followed by liquifactive action of putrefactive organisms. When coagulative pattern is dominant the process is termed dry gangrene. When the liquifactive action of the bacteria is more pronounced it is called wet gangrene.

35. Obtraction of blood supply to bowel is alrmost followed by Gangrene

36. Fate and local effects OF NECROSIS : 1. A small area undergoes repair: A) The products of the necrotic cells irritate the surrounding tissue forming a zone of inflammation. B) The accumulated neutrophils in the zone of inflammation soften the necrotic tissue and make its removal by macrophages and blood stream easy and help the process of healing. C) Repair by regeneration or fibrosis depends upon the type of cells affected (labile-stable-permanent).

37. 2. If the necrotic area is wide, its products can’t be removed and a fibrous capsule form around it in order to separate it from the living tissue. Areas of necrotic softening in the brain become surrounded by proliferated neuroglia (gliosis). 3. Old unabsorbed caseous lesions and fat necrosis usually becomes heavily calcified (dystrophic calcification). 4-when the necrotic tissue is infected with putrefactive Organism------Gangrine

38. General effects of necrosis 1. Release of enzymes from the breakdown tissue into the blood forms the basis of clinical tests for diagnosis e.g. detection of transamenase in myocardial infarction and liver necrosis in hepatitis. 2. Absorption of dead products into the circulation leads to leukocytosis and fever (Not diagnostic).

40. N.B.: I. Necrosis of: 1) Of small groups of cells is called focal necrosis. 2) Of large groups of cells is called confluent necrosis. 3) Of extensive areas of an organ is called massive necrosis. II. Somatic death means death of the individual. III. Post-mortum autolysis of the tissue occurring after death can be differentiated from necrosis by the absence of inflammatory zone around the affected tissue (inflammation is reaction of living tissue to an injury).

41. Apoptosis Definition: • It is programmed death of cells in living tissues. It is an active process differing from necrosis by the following points: • Occurs in both physiological and pathological conditions. • Starts by nuclear changes in the form of chromatin condensation and fragmentation followed by cytoplasmic budding and then phagocytosis of the extruded apoptotic bodies. • Plasma membrane are thought to remain intact during apoptosis until the last stage so does not initiate inflammatory reaction around it.

43. Death by Committing SuicideAPOPTOSIS While committing suicide cells: • Shrink • Chromatin Degraded • Mitochondria Break Down • Break into Membrane-bound Fragments • Phosphatidylserine Exposed • Phagocytic Receptors • Inflammation Inhibition

44. Microscopically: In the tissue stained with H & E apoptosis affects single or small clusters of cells and apoptotic cell appears as round mass of intensely eosinophilic cytoplasm with dense nuclear chromatin fragments.

45. Major criteria of Apoptosis 1- Morphological changes 2- Chromatin condensation 3- DNA fargmentation 4- Cell death

47. Initiation for apoptosisFactors predisposes to apoptosis 1- Nontoxic stimulican lead to apoptosis . 2- loss ofgrowth factors. 3- Direct action of cytokines (e.g., tumor necrosis factor) 4- Immune system action (e.g., natural killer cells or cytotoxic T lymphocytes). 5- Viral infection. 6- Adult tissue homeostasis . 7- Sublethal damage to the cells (e.g., by ionizing radiation, hyperthermia, toxins.) 8- Loss of cell-cell or cell-matrix attachments.

48. Examples of physiologic and pathologic cases accompanied with apoptosis: 1. Programmed cell death during embryogenesis. 2. Hormone dependent cell involution in case of endometrial cell break down during menstrual cycle. 3. Cell death in tumours during regression induced by cytotoxic drugs or irradiation. 4. In some viral disease e.g. viral hepatitis in which apoptotic cells are known as councilman bodies.

49. ROLE (VALUE)OF APOPTOSIS 1-Defense: Against nonself multicellular organisms (cell commits suicide wheninfected by a virusmay protect other cells from further spread of the virus) 2-Digestion: The cellular DNAdestroy thegenetic informationof any external stimulus. 3-Protecting: Protection of the organism fromunregulated growth of individual cells

50. Necrosis Cells swell and burst, releasing their intracellular contents Damaging to surrounding cells Causes inflammation Apoptosis vs. Necrosis • Apoptosis • Cells shrink and condense • Release small membrane bound bodies • Small fragments are engulfed by surrounding cells