Pathology Flashcards
What are the 4 types of amyloid?
AA (amyloid-associated) (seen in chronic inflammation)
AL (amyloid light chain)
B-amyloid protein
Islet amyloid polypeptide (cats)
What is platelet rolling mediated by?
P-selectin (on endothelium) or von Willebrand factor (on extracellular matrix)
For what 3 reasons may buccola mucosal bleeding time be abnormal?
Thrombocytopenia (check first)
Platelet dysfunction
Vascular disorders
When calculating buccola mucosal bleeding time, how soon after making the incision should pressure be applied?
10 mins
When performing a clot retraction test, an abnormal shrinkage result plus a normal platelet count is indicative of what?
Thrombocytopathia
What converts soluble fibrinogen to insoluble fibrin?
Thrombin
What are the 3 groups of coagulation factors?
What are they activated by?
Contact group (activated by contact with collagen)
Vitamin K dependant group (activated by other factors)
Highly labile fibrinogen group (activated by thrombin)
Where are most coagulation factors produced?
Liver
What is the average half life of most coagulation factors?
1-2 days
Which factor starts the intrinsic pathway?
XII
What is the end product of secondary hemostasis?
Cross-linked fibrin
What colour tube (and anticoagulant) is used most commonly for coagulation testing?
Blue top (citrate)
What test is performed for testing the extrinsic pathway?
Prothrombin time (PT)
What is the fibrinolytic pathway mediated by?
Plasmin
What can you measure that specifically indicates the breakdown of cross-linked fibrin?
D-dimers
Are clotting factors present in plasma or serum?
Plasma
What is albumin produced by?
Hepatocytes
What are globulins produced by?
Hepatocytes, B lymphocytes and plasma cells
Give 3 causes of decreased production of albumin
- Chronic liver disease (lack of hepatocytes to make albumin)
- Prolonged malnutrition (lack of precursor nutrients)
- Maldigestion (pancreatic enzyme deficiency; cannot digest precursor nutrients)
Give 3 causes of increased loss of albumin
- Kidney-glomerular leakage of albumin
- GI loss
- Burns
What happens to chylomicron remnants?
Travel to liver for uptake and degradation
Where is HDL formed?
Liver and intestinal epithelium
Lipaemia is primarily caused by increases in which two types of lipoprotein?
Chylomicrons
VLDLs
What are the functions of chaperones?
Interact with proteins
Aid with proper folding and transport
Facilitate degradation of proteins
What is the function of white blood cells (leukocytes)?
Destruction of microorganisms and removal of dead or damaged tissues
What is the function of platelets?
Haemostasis (stop bleeding)
Which blood cells live the longest?
Lymphocytes live weeks to years and may recirculate
RBCs live 1to >5 months
Which blood cell components have the shortest lifespan?
Why is it important to remember this?
Why should we care?
Neutrophils live 10 hours in the blood, and 24-48 hours in tissues
If there is a sudden arrest in haemopoiesis (formation of blood), neutropenia is the first thing we’d notice
A critical neutropenia may impair ability to fight infections
How long do the following live for? RBC PLT Lymphocytes Monocytes Neutrophils
RBC=1 to >5 months depending on species (160d cow, 150d sheep, 145d horse, 110d dog, 86d pig, 70d cat)
PLT=10 days
Lymphocytes=weeks to years, may recirculate
Monocytes=days
Neutrophils=10 hours in blood, 24-48 hours in tissues
What are the products of extravascular and intravascular lysis of RBCs?
Extravascular= bilirubin Intravascular= free haemoglobin
Give examples of haemopoietic tissue
Haemopoietic islands in yolk sac and aorta-gonad-mesonephros of embyro
Bone marrow
Liver, spleen, kidneys
Which cytokine plays a key role in growth, differentiation and activation of eosinophils?
IL-5 (interleukin-5)
What is the name of the hormone that controls erythropoiesis?
Erythropoietin (Epo)
Where is erythropoietin released from?
What does it stimulate?
Kidneys
Stimulates red bone marrow to produce RBCs
What name is given to juvenile red blood cells?
Reticulocytes
Which hormone mediates thrombopoiesis? (production of thrombocytes/platelets)
Where is it produced?
Thrombopoietin (TPO)
Liver
What effect does IL-6 (inflammation) and iron deficiency have on platelet production?
Increases it
When restraining an animal, why should you be quick and avoid the animal struggling?
To avoid platelet clumping and blood clots
What is the function of commensal bacteria?
Where are they found?
Prevent attachment of pathogenic bacteria and hence block their invasion and infection
Found on skin, and mucosal surfaces esp. GI and respiratory tracts
What name is given to the part of an antigen that the immune system recognises?
Epitope
Which 3 thymic hormones are produced in the cortex of the thymus?
Which cells produce them?
Thymosin, thymulin, thymopoietin
Producxed by reticular epithelial cells
Where does lymph flow?
Red bone marrow, lymphatic tissue and lymphatic vessels
What is the function of plasma?
Carries nutrients and waste products
Maintains fluidity
Which cell is the common precursor for all blood cells?
What does it immediately differentiate into?
Pluripotent stem cell
Lymphoid stem cell or myeloid stem cell
What cells are found in the storage pool?
Mature neutrophils
Which cells are found in the proliferative pool?
Monoblasts, myeloblasts, megakaryoblasts, rubriblasts
Which cells would you find in the maturation pool?
Monocytes, metamyelocytes, neutrophils, basophils, eosinophils, metarubricytes, reticulocytes, megakaryocytes
What is a metarubricyte?
Nucleated RBC
How are platelets produced?
Fragmentation of megakaryocyte cytoplasm and shedding into blood
A complete haemogram should include which 3 lab tests?
Centrifugation of microhaematocrit tube
Blood counts
Blood smear evaluation
Iron deficiency causes which type of anaemia?
Microlytic anaemia (small erythrocytes)
When does cell division of erythrocytes stop?
When optimal intracellular Hb concentration is reached
Why are smaller red blood cells produced in iron deficiency?
An extra cell division occurs before the critical cytoplasmic Hb concentration is reached that is necessary to stop DNA synthesis and cell division
Where is red bone marrow found in large mammals?
Spine, vertebrae, sternum and hip bones
What doe CFU stand for?
Colony-forming unit
Give rise to blasts which eventually evolve into mature cells
Which cells are granulocytes?
Neutrophils, eosinophils, basophils
Name the 3 primary growth factors which cause differentiation of granulocytes and monocytes
GM-CSF (granulocyte and monocyte differentiation)
M-CSF (monocyte development)
G-CSF (granulocyte development)
If basophils are seen in circulation, what are they usually seen with?
Eosinophils
Describe the regulation of erythropoiesis
Hypoxia due to reduced RBC count, decreased availability of O2 to blood or increased tissue demand for O2.
Kidney releases erythropoietin
This stimulates red bone marrow to produce RBCs
Increases O2 carrying ability of the blood
How many days does it take from RBC stem cell to reticulocyte release?
5 days
Do juvenile RBCs contain a nucleus?
No, but they do contain residual RNA and organelles
Where do reticulocytes migrate to?
Through transient apertures in endothelial cells into venous sinuses
Mature after 24 hours in blood
What morphological changes would we see with accelerated erythropoiesis?
Polychromasia, reticulocytosis
How is thrombopoietin production and clearance controlled?
Produced constantly, mainly by liver
Cleared by receptor-mediated uptake and destruction by platelets and megakaryocytes
However, interleukin 6 can increase TPO synthesis, independent of PLT numbers. Iron deficiency increases thrombopoiesis independently of TPO
What is MCV?
Mean corpuscular volume
Average erythrocyte size
What is MCHC?
Mean corpuscular Hb concentration
Average erythrocyte Hb concentration
What is MCH?
Mean corpuscular Hb
Average erythrocyte Hb per cell
Hb/RBC
What kind of anaemia is present if there is raised MCV?
What about reduced MCV?
Macrocytic anaemia (presence of larger cells which are usually juvenile RBCs-regenerative anaemia) Microcytic anaemia (production of small erythrocytes, likely due to less haemoglobin available for erythropoiesis caused by iron deficiency)
What kind of anaemia is seen with reduced MCHC?
Hypochromic anaemia
Seen with regeneration (juvenile RBCS have lower Hb concentration) or iron deficiency
Which stains could you use to identify reticulocytes?
Routine Wright’s
New Methylene Blue (stains RNA in ribosomes)
How do you calculate an absolute reticular count?
% retic x RBC (10^12/L) x 10
Which values for absolute reticular count in dogs and cats are a sign of non-regenerative anaemia?
Dog
What is the general term for abnormal RBC shape?
Poikilocytosis
What are the causes of regenerative anaemia?
Blood loss
Haemolysis (destruction of RBCs)
What are the causes of non-regenerative anaemia?
Decreased production
Lack of erythropoietin
Chronic inflammation
What is blood loss anaemia?
Proportional loss of all blood components (plasma and cells)
Can be acute or chronic
1. Initial decrease of blood volume, while proportion of plasma and cells is maintained. Hct and TP are unchanged
2. Within a few hours, activation of mechanisms to maintain volaemia -> influx of H2O from extracellular space -> dilution -> reduction of Hct and total protein
(Hct-ratio of volume of RBCs to a given volume of blood)
What are 2 causes of blood loss anaemia?
Haemorrhage
Blood-sucking parasites
Presence of spherocytes is strongly supportive of what?
Immune-mediated haemolytic anaemia
Macrophages partially phagocytise RBCs at the part of the membrane where the antigen-antibody complex is, causing loss of the discoid shape
What is agglutination?
Antibody-mediated clumping of RBCs
Stongly supportive of immune-mediated haemolytic anaemia
What is rouleaux formation?
What is it caused by?
In which species is it normal?
Stacking of RBCs due to increased plasma proteins coating RBCs
Caused by inflammation, cancer
Horses and cats
How can you differentiate between agglutination and rouleaux formation?
Saline agglutination test
Add 9 drops of saline to 1 drop of blood. Rouleaux formation will disappear, whereas agglutination persists
Which values for WBC in a single field are indicative of leucopenia and leucocytosis?
If 50 WBC in a single LPF10x field then likely leucocytosis
What do we look for at the tail end of a blood smear?
Platelets
Erythrocytes will be ruptured here
Give some causes of neutropenia
Severe inflammation Bone marrow disease eg neoplasia, immune-mediated destruction of precursors Overwhelming tissue demand Reduced bone marrow production Increased destruction of neutrophils
What is left shift?
What causes it?
Increased number of juvenile neutrophils (band or earlier stages) released from bone marrow
Due to severe acute inflammation
(Also bacterial infection, immune-mediated disease (e.g. IMHA))
What causes monocytosis? (monocyte count above upper reference limit)
Chronic inflammation / tissue damage / necrosis (usually combined with neutrophilia)
‘Stress leucogram’ or steroid administration (combined with neutrophilia, lymphopenia and eosinopenia)
Leukaemia
What causes lymphocytosis? (Lymphocyte count above upper reference limit)
Chronic inflammation
Adrenaline release in cats
Leukaemia
What causes lymphopenia? (lymphocyte count below upper reference limit)
Chronic inflammation (seen with neutrophilia) Stress leucogram (effect of prolonged steroid in blood) Viral disease eg FIV, FIP
What causes eosinophilia? (eosinophil count above upper reference limit)
Parasitic disease
Allergy
What is toxic change?
What is it due to?
Increased basophilia (blue colour) of the cytoplasm, blue granules (Dohle bodies), vacuoles (foamy appearance) Due to reduced maturation time because of intense stimulation of myelopoiesis. Seen in overwhelming inflammation
What is the average value for platelet count?
150-500 x 109/L
Platelet clumps are most common in which species?
Feline and bovine
Give 4 causes of thrombocytopenia
Increased destruction Increased consumption (intravascular coagulation) Decreased production (destruction of megakaryocytes in bone marrow) Redistribution/sequestration (splenomegaly-abnormal enlargement of the spleen-platelets are temporarily entrapped within the spleen but are still able to bind Thrombopoietin, so bone marrow is not stimulated)
What is immunomodulation?
Why would we want to use it?
Modification of the immune response
Reduce inflammatory response Reduce allergic response Treat neoplasia of the immune system Enhance immune response to infection Suppress inappropriate immune response (immune mediated diseases)
How does an immune mediated disease occur?
Something happens to prevent recognition of self-antigens
Immune response is directed towards own tissues
If no detected underlying cause, can be referred to as ‘autoimmune’
Which immune system does immunosuppressive drugs act on?
What do they do?
Adaptive
Reduce lymphocyte proliferation or limit their effect
What are the 3 main groups of immunosuppressive drugs?
Drugs which inhibit DNA synthesis
Drugs which inhibit IL-2 production/action
Drugs which inhibit cytokine gene expression
What is IL-2 produced by?
What does it do?
Th cells (CD4+)
Stimulates:
Clonal proliferation of T cells, humoral immunity (B cell activity) and innate immune cells (macrophages, NK cells)
What is cyclosporin used for?
What is it metabolised by? Excretion?
Immunosuppressive drug. Inhibits IL-2 and therefore causes decreased proliferation of cytotoxic cells, decreased B cell responses and decreased T cell function in hypersensitivity reactions.
Metabolised by liver (cytochrome P450). Metabolites excreted in bile.
Glucocorticoids are synthetic versions of what?
What do they do?
Cortisol
Stimulate neogenesis
Suppress inflammation. Immunosuppressive.
Reduce clonal proliferation of CD4+ cells (T helper cells)
Binds intracellular receptor which migrates to nucleus and modifies transcription-reduces transcription of IL-2 gene and other cytokine genes
Why must glucocorticoid treatment be withdrawn very slowly?
Glucocorticoids suppress the HPA (hypothalamus-pituitary-adrenal gland) axis; recovery of adrenal function can take months
What is the function of drugs which inhibit DNA synthesis?
Give 3 examples
Inhibit synthesis of purines and/or pyrimidines
Suppress B and T cells
Azathioprine (inhibits DNA and RNA synthesis-disrupts mitosis and cell metabolism)
MMF (mycophenolate mofetil) (selective suppression of B and T cell proliferation)
Leflunomide (inhibits T and B cell proliferation)
What is carprofen?
NSAID
What is histamine produced by?
What is its release caused by?
Basophils and mast cells
Release is caused by IgE binding to Fc receptors on mast cells
What is the function of COX-1 and COX-2?
Enzyme involved in prostaglandin biosynthesis. Converts free arachidonic acid to prostaglandin
Present at sites of inflammation. Promotes production of mucus in stomach and reduces acid secretion.
Inhibited by NSAIDs eg aspirin
What is the difference between COX-1 and COX-2?
COX-1 is produced under any conditions. It has protective uses like production of stomach mucus, secretion of bicarbonate and reducing gastric acid secretion. Found in the stomach, kidney, platelets.
COX-2 is only produced under certain conditions like inflammation. It causes production of prostaglandins which cause pain and inflammation, and pyrexia. Located in monocytes, macrophages, leukocytes.
Why would we want to inhibit COX enzymes?
COX enzymes convert arachidonic acid to prostaglandins
Prostaglandins play a key role in development of pain and inflammation
Therefore by inhibiting COX, we get relief from pain and inflammation
Give some examples of NSAIDs
Oxicans (eg meloxicam) Coxibs (eg celecoxib) Propionates (eg carprofen) Pyrazolones (eg phenylbutazone) Salicylates (eg aspirin) P-aminophenols (paracetamol)
What are the adverse effects of NSAIDs?
Stomach ulcers
GI bleeding
Anaemia
What is metastasis?
Movement of cancerous cells to other parts of the body
Why are smaller tumours more sensitive to chemotherapy?
Cells are dividing more quickly so are more sensitive
Larger tumours have more G0 cells (not dividing) so are less sensitive
Explain the 2 theories as to why some tumours are resistant to chemotherapy?
- Goldie-Coldman theory:
Detectable tumours are heterogenous. High likelihood that some of the cells will be resistant. Chemo can’t kill the resistant cells, which then multiply and quickly make up the majority of the population - Stem cell theory:
Chemo kills daughter cells. Stem cells naturally resistant. Tumour proliferation rate greater than chemo kill rate due to required inter-treatment recovery interval
How do you measure drug dose intensity?
Drug dose per unit time
What are the 2 broad categories of chemotherapy?
- Damages DNA (cell cycle non-specific)
2. Inhibits DNA replication (cell cycle specific)
What are the general side effects of chemotherapy?
BAG
Bone marrow-lowest WBC count typically after 7-10 days
Alopecia- uncommon except in a few breeds
Gastrointestinal-usually lasts longer than the first 4 days
What is the function of alkylators (chemotherapy drugs)?
How are they metabolised?
Give some examples
Give some possible side effects
Bind DNA and insert an alkyl group, leading to a change in structure. Inhibits transcription and replication, leading to apoptosis if the lesion is not repaired.
Metabolised by liver, excreted by kidneys
Melphalan, Cyclophosphamide, Lomustine
Side effects: Low WBC count -> GI problems, cystitis (Cyclophosphamide), hepatic toxicity (Lomustine)
What is the function of vinca-alkaloids (chemotherapy drugs)?
How are they metabolised?
Give some examples
Give some possible side effects
Either bind to or inhibit formation of microtubules thus preventing the formation of the mitotic spindle. Cell cycle specific-cells die in M phase by are most sensitive in S phase.
Metabolised to active forms in liver, excreted in bile.
Vincristine, Vinblastine.
Side effects: GI effects, low WBC counts, perivascular irritation of drug goes outside the vein
What is the function of anti-tumour antibiotics (chemotherapy drugs)?
How are they metabolised?
Give some examples
Give some possible side effects
3 mechanisms of action:
1. Topoisomerase inhibition -> DNA strand breaks
2. Intercalation with DNA -> Prevents transcription
3. Free radical formation -> DNA damage
Cycle non-specific
Metabolised to active forms in the liver (via hydrolysis), excreted in bile
Doxorubicin, Epirubicin
Side effects: Anaphylaxis, GI problems, low WBC count, severe perivascular irritation if drug goes outside the vein, kidney damage (cats), cumulative cardiotoxicity (dogs)
What is the function of platinating agents (chemotherapy drugs)?
How are they metabolised?
Give some examples
Give some possible side effects
Insert a platinum group into DNA. Transcription and replication are inhibited, cells die if lesion is not repaired
Mainly excreted unchanged by kidneys
Carboplatin
Myelosuppression, occasional GI toxicity, rare kidney toxicity
What is the function of anti-metabolites (chemotherapy drugs)?
How are they metabolised?
Give some examples
Give some possible side effects
Interact with DNA production pathways. Cell cycle specific to S phase.
Cytosine arabinoside, Methotrexate.
Cytosine arabinoside is metabolised by liver, plasma and peripheral tissues. Excreted by kidneys.
Methotrexate is metabolised by normal and malignant tissues, peripheral tissues. Excreted by kidneys.
Side effects: myelosuppression, GI side effects, hepatic dysfunction (cytosine)
Give some examples of biotherapy (cancer treatment)
Glucocorticoids, NSAIDs, receptor tyrosine kinase inhibitors, immunotherapy
How does metronomic chemotherapy work?
Targets supporting cells of a tumour (not specific tumour cells)
Reduces new blood vessel formation, and numbers of regulatory T cells supporting the tumour
Most use a combination of an NSAID with cyclophosphamide (alkylator)
List 3 chemotherapy drugs which act in a cell cycle specific manner
Vinca-alkaloids eg Vinblastine, Vincristine
Anti-metabolites eg Methotrexate, Cytosine arabinoside
List 3 chemotherapy drugs which act in a cell cycle non-specific manner
Alkylators eg Melphalan, Cyclophosphamide, Lomustine
Anti-tumour antibiotics eg Doxorubicin, Epirubicin
Platinating agents eg Carboplatin