Haematopoiesis

BONE MARROW STRUCTURE

• Principal organ of adult haematopoiesis
• Formed element of the blood
• RBC, WBC, PLT
• Produced in the bone marrow from a common pluripotent stem cell
• Stem cell: Self-renewal. Differentiates.
• Regulators: Complex microenvironment of stromal cells, growth factors
• Bone marrow
• Haematopoietic cells. Fat cells. Stromal cells
• Different places, different times
• 6w feral life: yolk sac
• 6-14w fetal life: liver & spleen
• 24w feral life onwards: bone marrow
• Children
• Active haematopoiesis in axial skeleton and lon bones
• Marrow more cellular
• Adults
• Fat replaces cellular bone marrow
• Haematopoiesis: Axial skeleton
• 1/2 marrow for blood cell production
• 1/2 marrow taken up by fat
• Disease states
• Marrow cellularity increased
• Long bone active again in haematopoiesis
• Extramedullary haematopoiesis
• Liver and spleen recruited into blood cell production as in feral life
• Organomegaly
• e.g. Myeloproliferative disorders. Thalassaemias (intermedia, major)

THE HAEMOPOIETIC PROCESS

• Bone marrow
• Stem cell
• Common pluripotent. Self-renewal
• Progenitor cells
• In presence of growth factors
• Maturation
• Peripheral blood
• Red cell lose nucleus prior to release into blood
• Platelets from megakaryocyte
• Role of growth factors
• Regulators: Cell-cell and cell-matrix interactions. Growth factors.
• Growth factors
• From endothelial cells, fibroblasts, monocytes, lymphocytes
• Early stage haematopoiesis
• Stem cell factors (SCF)
• Promotes stem cell proliferation
• Affect all cell lines
• Mature cells
• Lineage specifics
• Granulocyte colony-stimulating factor (G-CSF)
• Colony stimulating factors
• G-CSF. GM-CSF
• Shorten duration of neutropenia
• Erythropoietin (EPO)
• Control erythropoiesis
• Produced in kidneys
• Reduced O2 delivery ￫ Cortex of kidney ￫ Erythropoietin
• Controlled by negative feedback loop
• Reduced O2 delivery
• Anaemia: Increased red cell until Hb concentration increases and O2 delivery to kidney back to normal
• Hypoxia ￫ Reduced oxygen to peritubular cells ￫ EPO release ￫ Increased RBC without anaemia ￫ Polycythaemia
• Renal tumour ￫ EPO ￫ Polycythaemia

Cell Cycle and Apoptosis

BASIC PRINCIPLES OF THE CELL CYCLE

• Quiescent phase (G0)
• Cells stop proliferating
• Duration varies
• Most cells in normal tissue of adults
• First gap phase (G1)
• Prior to initiation to DNA synthesis
• Separate M and S phases
• Cells preparing for DNA duplication
• Cells receptive to growth signal
• DNA synthesis(s)
• Second gap phase (G2)
• After DNA synthesis
• Before mitosis and completion of cell cycle
• Repair errors
• Mitosis (M)

REGULATIONS OF THE CELL CYCLE 

APOPTOSIS (PROGRAMMED CELL DEATH)

CANCER AND THE CEL CYCLE

Cancer and the Cell Cycle

• Cells escaped growth control mechanisms
• Stages
• Accumulation of somatic mutations
• Genes for proteins for detection or repair of damaged DNA
• Increases mutation rate
• Development of genetic instability
• Changes in genes in cancer cells
• Duplications, deletions of parts of chromosomes, DNA translocation

ONCOGENES

• Initially identified as viral gene
• Proto-oncogenes
• Genes within normal DNA of every cell
• Mutatated, activated ￫ Product ￫ Tumour
• Influence is direct or indirect 
• e.g. mitogen-activated protein kinase (MAPK) pathway
• Amino acid substitutions @ 21 or 61 in Ras
• Activating ERK MAPK pathway

TUMOUR SUPPRESSOR GENES

• Mutations ￫ Loss of function that restrains cell growth
• RB gene
• Normal: non-phosphorylated RB prevents cell proliferation
• Phosphorylation by CDK ￫ S phase
• Retinoblastoma
• p53
• Tumour suppressor 
• Loss or mutated in >50% all human cancers
• Damage to DNA ￫ Nuclear phosphoprotein ￫ Blocking progression through cell cycle or apoptosis
• Direct mutation. Mutations of other genes affecting p53 expression or function.

Apoptosis (Programmed Cell Death)

• Suicide of the cell
• Cells become more compact
• Blebbing at membranes. Chromatin condensed. DNA fragmented to 180bp

TRIGGERS

• Ligand
• Cytotoxic lymphocyte attacks target
• Withdrawal of necessary growth factor
• Irradiation
• Glucocorticoids

FAS RECEPTOR (Fas or FasR)

• Trigger for apoptosis
• Fas
• Cell-surface receptor related to tumour necrosis factor (TNF) receptor
• Homomeric trimer. Death domain. 
• Fas ligand (FasL)
• Transmembrane protein related to TNF
• Fas + FasL
• Fas trimers ￫ Large aggregates ￫ Activate apoptosis
• TNF + its receptor (TNF-R1) ￫ Apoptosis

DOWNSTREAM FROM THE FAS RECEPTOR

• Classical pathway for apoptosis
• Fas + FasL. TNF + TNF-R1.
• Members of caspase family (cysteine aspartate proteases): Important downstream components
• Pathway involving kinase JNK
• Protein c-Jun ￫ Proteases
• Not blocked by Bcl2

Regulations of the cell cycle

CHECKPOINTS 

• Control progress through cell cycle
• Prevent cells entering next stage until previous stage completed
• G1: DNA damage
• S: Incomplete replication
• G2: DNA damage
• M: Ensure all necessary earlier events been performed

MECHANISMS OF REGUATION

• Regulators: Phosphorylation. Dephosphorylation
• M-phase kinase
• Regulates mitosis
• 2 forms. Phosphorylation of proteins
• Activation at G2/M 
• Inactivation before end of M
• 2 subunits
• Catalytic
• Cdc2
• Kinase phosphorylates serine and threonine
• Modification ￫ Triggers G2 to M
• Regulatory
• Cyclin
• Necessary for catalytic kinase to function on right substrates
• Destruction by proteolysis ￫ Inactivation of M-phase kinase
• Substrate: H1 histone
• Checkpoint pathways 
• Prevent progression if DNA is damaged
• Recognition of DNA damage
• Apoptosis. Block cell cycle. Transcribe response genes. Repair damage
• Appropriate progress made
• Replication before division. Kinetochores paired before metaphase finished
• Proteins involved
• Sensor
• Recognise event that triggers checkpoint pathway
• Transducer
• Activated by sensors
• Amplification function
• Effector
• Activated by transducer kinases
• Correct the event triggered the checkpoint pathway
• Protein kinase ATM. Ataxia telangiectasia
• Cyclin-dependent kinases (CKDs) 
• Progression of cell cycle regulated by kinases that interact with cyclins
• Inhibitors
• Cyclin-dependent kinase inhibitors (CKIs)
• Retinoblastoma gene product phosphorylated by cdm-cyclin D complex
• Action of CKI of INK4 family
• Action of CKI of Kip family
• Mutations ￫ Cancers

Receptors and intracellular signalling

BASIC PRINCIPLES OF CELL-CELL SIGNALLING

• Generator cell produces a chemical signal (or ligand)
• Ligand binds with receptors
• Initiation of intracellular events.
• Intracellular messenger 
• Limited receptors. Specific response.
• Dual function of receptors
• Ligand binding 
• Signal transduction
• Patterns of intracellular communication
• Endocrine
• Specialised cells
• Hormone
• Circulate in bloodstream
• Distant target cells
• Integrating ad harmonising responses in disparate cells and tissues
• Growth. Puberty. Pregnacy
• Paracrine
• Ligand
• Diffuses locally
• Adjacent cells 
• Within organs or tissues
• Tubuloglomerular feedback in kidney
• Synaptic
• Interneuronal or neuromuscular synaptic transmission
• Close physical proximity of generator and target cells 

MEMBRANE-BOUND RECEPTORS AND SIGNAL TRANSDUCTION

CYTOSOLIC RECEPTORS

Cytosolic receptors

• Steroids ￫ Cytosolic receptors ￫ Modify gene transcription
• Lipid soluble ligand + Receptor ￫ Dimerisation ￫ Translocation of ligand-receptor complex into nucleus ￫ Specific binding of complex to promoter or enhancer elements of genes ￫ Modulation of gene transcription.
• Receptor monomers
• Ligand-binding domain. Highly homologous domains.
• DNA binding. Transciption activation
• De novo gene transcription & protein synthesis
• Slow onset. Long lasting

Membrane-bound receptors and signal transduction

• Receptors
• On cell surface. Anchored in plasma membrane
• Ionotropic receptor (With integral ion channel function)
• G protein coupled receptors
• Receptors with integral enzymatic function
• Growth factors, Insulin, ANP
• In cytoplasma
• Steroid hormones. Lipophilic substances
• Phosphorylation
• Effector proteins
• Serine. Threonine.
• Intracellular messengers
• Kinase enzymes
• Protein kinase A (cAMP)
• Protein kinase G (cGMP)
• Protein kinase C (diacylglycerol)
• Activation
• Ion channels. Enzymes. Transporter

IONOTROPIC RECEPTORS

• e.g. nAChR, GABAa, 5HT3
• Rapid (milisecond) opening of integral receptor ion channel
• Changes in membrane potential
• Biological response
• Neurotransmission. Muscle transmission

G PROTEIN-COUPLED RECEPTORS

• e.g. mAChR, alpha and beta adrenoreceptors, dopamine, 5HT, opiate, peptides
• Extracellular N-terminus. Intracellular C-terminus. 7-membrane spanning domains
• Ligand binds to domain (extracellular)
• Conformational change
• Guanine nucleotide-binding  (G) protein binds with cytoplasmic domain
• Families characterised by relatedness of alpha subunits
• Gi
• Alpha i
• Inhibits adenylate cyclase
• Activates K channels
• Gq
• Activates phospholipase C
• Catalyse formation of DAG, IP3
• Signal transduction
• Intracellular messengers (proteins)
• cAMP
• Phosphorylation of serine and threonine
• Activates protein kinase A
• Inositol 1,4,5-triphosphate (IP3)
• Binds to receptor on endoplasmic reticulum
• Release of stored Ca ions
• Intracellular signal
• Diacylglycerol (DAG)
• Diffuses freely
• Activates protein kinase C (PKC)
• Malfunctions
• Cholera
• Cholera toxins catalysing ADP-ribosylation of alpha s subunit of Gs in enterocytes
• Gs unable to hydrolyse guanosine triphosphate (GTP)
• GTP needed to terminate Gs activation
• High level cAMP. High Na and H2O efflux into lumen. Watery diarrhoea. 

RECEPTORS WITH INTEGRAL ENZYMATIC FUNCTION

• Tyrosine kinase-linked receptors
• Insulin, growth factors, receptor guanylate cyclases (receptors for natriuretic peptides)
• Large extracellular N-terminal (ligand binding). Membrane spanning helix. Intracellular C-terminal (enzymatic activity)

Receptor tyrosine kinases

• Ligand + receptor tyrosine kinases ￫ conformational change ￫ receptor dimerisation ￫ Activation integral tyrosine kinase activity ￫ Cytoplasmic domain ￫Autophosphorylation ￫ Expose binding site to cytosolic protein with SH2 (src homology 2) domain
• Phosphatidylinositol 3-kinase, GTPase-activating protein, Phospholipase C-gamma
• Intracellular processes
• Enzyme activation & alterations in gene transcription
• Overactive receptor tyrosine kinase
• Multiple endocrine neoplasia type 2
• Medullary thyroid carcioma, phaeochromocytoma, hyperparathyroidism
• Mutations in the RET gene on chromosome 10
• Protein product: Membrane-bound tyrosine kinase
• Constitutive receptor activation ￫ Unchecked growth signal, tumour formation
• Proto-oncogenes
• Encode components of signal transduction pathways
• Mutations ￫ cancers
• Monoclonal recombinant antibodies
• Trastuzamab vs HER2
• Invasive breast cancers 
• 25% over express the epidermal growth factor receptor tyrosine kinase, HER2
• Adverse prognosis
• Erlotinib, Geftinib vs different class epidermal growth factor receptor
• Non-small cell lung cancer

Receptor guanylate cyclases

• Receptors for atrial natriuretic peptides (ANPs)
• Ligand + Extracellular domain of receptor ￫ Guanylate cyclase activity ￫ Activation of intracellular domain ￫ GTP ￫ cGMP ￫ Protein kinase G ￫ Phosphorylates & activates intracellular effector proteins ￫ Biological response
• Nitric oxide
• Paracrine mediator
• From endothelial cells, some neurones and inflammatory cells
• Lacks classical receptor
• Unique mechanism of action
• NO ￫ Diffuses freely into cells ￫ Activates soluble cytosolic form of guanylate cyclase ￫ Rise in cGMP
• Exogenous NO
• Nitrovasodilator drugs 
• Glyceryl trinitrate, Sodium nitroprusside
• Rise in cGMP in vascular smooth muscle cells ￫ Relaxation of blood vessels 

Ion Transport: Basic principles of ion transport

ION CHANNELS

• Subunits
• Different proteins
• Multiple copies of same protein
• Ion-conducting pore
• Electrical and chemical gradients

ION CARRIERS

• Binding
• Conformational changes
• Moves ion
• Energy driven
• Active transport
• Hydrolysis of ATP
• Secondary active transport
• Gradient generated by other transporter
• Carries
• One ion
• Two or more ions, same direction
• Two or more ions, opposite directions
• Charged neutral

TYPES OF IONS MOVED BY TRANSPORT PROTEINS

• Simple actions
• Anions
• Larger ionised molecules

Ion Transport: Ion Carriers

CARRIERS THAT UTILISE ATP (PUMPS)

• Na/K ATPase
• Alpha and beta subunit
• Alpha
• Coordinate cation transport
• 3Na efflux, 2K influx
• Maintain Na K concentration gradient
• In epithelial cells
• Drive Na and K transport
• In non-epithelial cells
• Determine resting membrane potential
• Allow depolarisation
• Allow electrical signalling
• Bind and hydrolyse ATP to release energy to drive transport
• Drugs targeting Na/K ATPase
• Digoxin
• Increasing cardiac contractility
• Inhibits ATPase enzyme of Na/K ATPase
• Preventing hydrolysis
• Removes energy supply
• Inhibit Na efflux, K influx
• Rise in intracellular Na
• Rise in intracellular Ca
• Enhancing actin-myosin interaction
• Increasing cardiac contractility
• ?Significant inotropic in heart failure treatment
• Enhances vagal activity
• Slow conduction via atrioventricular node
• Used in rate control in atrial fibrillation

CARRIERS THAT UTILISE SECONDARY ACTIVE TRANSPORT MECHANISMS

• Energy from electrochemical gradient of one ion
• Na/K/2Cl cotransporter
• Mediates Na transport across epithelia
• Thick ascending limb of the loop of Henle
• Reabsorption 25% Na
• Drugs targeting Na/K/2Cl co transporter
• Loop diuretics (frusemide)
• Causes natriuresis
• Block Na/K/2 Cl cotransporter
• Reducing Na and K reabsorption
• Disease caused by abnormal Na/K/2Cl co transporter
• Bartter's syndrome
• Rare
• Profound hypokalaemia in infancy
• Na/Cl co-transporter
• Mediates Na transport across epithelia
• Distal tubule
• Reabsorption of 10% Na
• Drugs targeting Na/Cl co-transporters
• Thiazide diuretics
• Causes natriuresis
• Blocks Na/Cl co-transporter
• Reducing Na and Cl reabsorption
• Disease caused by abnormal Na/Cl co-transporters
• Gitelman's syndrome
• Hypokalaemia in adults

Ion Transport: Ion Channels

FACTORS DETERMINING TRANSPORT THROUGH ION CHANNELS

• Selectivity
• Structure
• Size
• Charge
• Conductance
• Rapid/ high: non-selective
• Slow/ low: highly-selective
• Gating
• Voltage
• Coordination of ion channel activity and cell function

ION CHANNELS IN EPITHELIAL CELLS

• Epithelial cells
• An interphase
• Polarised
• Apical (luminal)
• Basolateral (interstitial)
• Epithelial sodium channel
• ENaC
• Apical membrane
• Absorptive epithelia
• Alpha, beta, gamma subunits
• Cytoplasm, cell membrane,  large extracellular loop, cytoplasm
• Na conducting pore
• Reabsorption of Na. Urine into interstitium. Down chemical gradient.  Na pump in basolateral membrane. 
• Hormonal control
• Aldosterone: Na retaining. Na reabsorption. K excretion. 
• ANP: Natriuresis. Auppress ENaC. 
• Liddle's syndrome
• Rare
• Autosomal dominant
• Hypertension
• Mutation beta gamma
• Pull Na out of apical membrane to cytoplasm
• Reducing ENaC activity
• Stucked channel
• Increases Na reabsorption
• Na overload. Hypertension.  Suppression renin-aldosterone system.  Hypokalaemia.
• Pseudohypoaldosteronism type 1
• Opposite to Liddle
• Didruption of pore-forming region
• Loss ENaC activity.  Salt wasting. Potassium retention.
• Hypotension. Activation renin-aldosterone. Hyperkalaemia.
• Cystic fibrosis transmembrane conductance regulators
• Large continuous protein
• 2 repeating structures
• Each cross membrane 6x
• In epithelial cells . airways, duct of pancreas, sweat glands
• Functions
• Cl function
• Regulators of other ion transporter. 
• ENaC suppressed by CFTR
• Cystic fibrosis
• In the airway
• CFTR mutations
• Decreased Cl secretion
• Increased absorption Na
• Fluid thick & viscous, blocking bronchi, bronchioles. Bronchoectasis. Recurrent lung infections esp pseudomonas
• Die prematurely from respiratory failure
• In the pancreatic duct
• Secretion Cl and HCO3, water
• Failure of secretion
• Viscous
• Block ducts. Auto digestion. Pancreatic destruction.
• CF features: pancreatic insuff, malab. weifgt loss, failure to thrive
• Replace pancreatic enzymes, high calorie diet
• Insulin deficiency. diabetes mellitus
• In the sweat duct
• Cl reabsorption in sweats
• Unable to conserve Cl. High cl conc in sweat. Sweat test.
• Vulnerable to dehydration. Not able to reduce Cl, Na, H2O lost in sweat

ION CHANNELS IN NON-EPITHELIAL CELLS

• Muscle, nerve cells 
• Ion channels regulate pass of ions
• Transmembrane potential difference 
• Signal between cells. Alter intracellular calcium
• Cell membrane potential
• Ohms's law 
• Potential difference
• Proportional to the current (number of ions moving across the membrane)
• Ion movement depends on 
• Type
• Electrical and chemical gradient
• Nernst potential
• Resting cell potential
• K channels
• intracellular K 140, extracellular K 4
• K moves out
• Nernst potential for K 90mV
• Potential different is electrically negative (inside negative with respect to outside)
• Changes in membrane potential
• Cell membrane potential: negative inside 
• Hyperpolarisation
• Inside becomes more negative
• Cations efflux
• Anion influx
• Depolarisation
• Inside more positive
• Anions efflux
• Cation influx
• Voltage gated sodium channels
• Alpha subunit
• 1 or more beta subunits
• Rapid changes in membrane potential
• Action potentials
• Resting
• Voltage-gated Na closed
• Depolarisation
• Rapid channel opening
• Na influx (Inside 140, outside 10)
• Na influx depolarises 
• Rapid inactivation of Na
• Na/K-ATPase
• Resting state restored by K channels
• Na channels
• Open
• Inactivated
• Cannot be reopen for a period of time
• Allows excitable cells to hyperpolarise before next action potential starts
• Closed
• Hyperpolarisation is complete
• Skeletal muscle cells
• Voltage-gated Na 
• Activation
• Depolarisation
• Increase intracellular Ca
• Muscle contraction
• Inactivation & closure
• Hyperpolarisation
• Fall in intracellular Ca
• Muscle relaxation
• Mutations of alpha subunit
• No inactivation
• Persistent inward Na
• Hyperexcitability of skeletal muscle
• Myotonia
• Syndrome of impaired muscle relaxation
• Difficulty opening the hand after clenching a fist or opening the eyes after shutting them tightly.
• Paralysis
• Action potential cannot be generated
• Syndrome of hyperkalaemic periodic paralysis
• Intermittent attack of muscle weaknesss
• Spontaneously
• Precipitated by exercise, stress, K rich food.
• Cardiac mucle cells
• Action potential
• Opening NA channles
• Na influx
• Rapid depolarisation
• Na quickly inactivated
• Depolarisation maintained by Ca influx (plateau phase)
• Hyperpolarisation by K efflux
• Long QT syndrome
• Mutations
• Slow Na inactivation
• persistent Na influx
• Delay hyperpolarisation
• Prolong action potential
• Increase QT interval in ECG
• Torsades de pointes
• Sudden dysrhythmias in Long QT syndrome
• Sudden death
• Unknown mechanisms
• Mutant Na channels 
• Failed to inactivated 
• Reipen during prolonged hyperpolarisation 
• Early after depolarisations
• Additional action potentials at multiple loci
• Nerve cells 
• Familial epilepsy
• Mutation beta1 subunit
• Rate of activation
• Speed of recovery from inactivation
• Neuronal hyperexcitability and seizures.
• Drugs targeting voltage-gated Na channels
• Membrane stabilisers in dysrhythmias and epilepsy
• Restrict Na influx
• Slow cell depolarisation
• Limit cel responsiveness to excitation
• Class 1 antiarrhythmics
• Quinidine, disopyramide, lidocaine, flecainide
• Antiepileptics 
• Phenytoin and carbamazepine

Cell Biology

• Ion transport
• Ion channels 
• Ion channels in epithelial cells 
• Epithelial sodium channel (ENaC)
• Liddle's syndrome
• Pseudohypoaldosteronism type 1
• Cystic fibrosis transmembrane conductance regulators
• Cystic fibrosis
• Ion channels in non-epithelial cells
• Cell membrane potential
• Voltage gated sodium channels
• Skeletal muscle cells
• Myotonia
• Paralysis
• Syndrome of hyperkalaemic periodic paralysis
• Cardiac mucle cells
• Long QT syndrome
• Torsades de pointes
• Nerve cells 
• Familial epilepsy
• Class 1 antiarrhythmics
• Quinidine, disopyramide, lidocaine, flecainide
• Antiepileptics 
• Phenytoin and carbamazepine
• Ion carriers
• Carriers that utilise ATP (pumps)
• Na/K ATPase
• Digoxin
• Carriers that utilise secondary active transport mechanisms
• Na/K/2Cl cotransporter
• Loop diuretics (frusemide)
• Bartter's syndrome
• Na/Cl co-transporter
• Thiazide diuretics
• Gitelman's syndrome
• Receptors and intracellular signalling
• Ligand binding. Signal transduction
• Endocrine. Paracrine. Synaptic
• Phosphorylation
• Serine. Threonine.
• Intracellular messengers
• Kinase enzymes
• Protein kinase A (cAMP)
• Protein kinase G (cGMP)
• Protein kinase C (diacylglycerol)
• Membrane-bound receptors and signal transduction
• Receptors on cell surface.
• Ionotropic receptor (With integral ion channel function)
• e.g. nAChR, GABAa, 5HT3
• G protein coupled receptors
• e.g. mAChR, alpha and beta adrenoreceptors, dopamine, 5HT, opiate, peptides
• Gi. Adenylate cyclase
• Gq. Phospholipase C. DAG, IP3
• cAMP. Serine and threonine. Protein kinase A
• Inositol 1,4,5-triphosphate (IP3). Ca
• Diacylglycerol (DAG). Protein kinase C (PKC).
• Cholera
• Receptors with integral enzymatic function
• Receptor tyrosine kinases
• SH2 (src homology 2) domain
• Multiple endocrine neoplasia type 2. RET gene. Chromosome 10
• Proto-oncogenes. Trastuzamab vs HER2. Erlotinib, Geftinib. 
• Receptor guanylate cyclases
• ANP
• Nitric oxide
• Receptors in cytoplasma
• Steroid hormones. Lipophilic substances
• Cell cycle and apoptosis
• Phases: 
• Quiescent phase (G0)
• First gap phase (G1)
• DNA synthesis(S)
• Second gap phase (G2)
• Mitosis (M)
• Mechanisms of regulation
• M-phase kinase
• Catalytic (Cdc2)
• Regulatory (Cyclin)
• Substrate (H1 histone)
• Checkpoint pathways 
• Recognition of DNA damage
• Apoptosis. Block cell cycle. Transcribe response genes. Repair damage
• Appropriate progress made
• Replication before division. Kinetochores paired before metaphase finished
• Proteins involved
• Sensor. Transducer. Effector (Protein kinase ATM. Ataxia telangiectasia)
• Cyclin-dependent kinases (CKDs) 
• Cyclin-dependent kinase inhibitors (CKIs)
• Retinoblastoma gene product phosphorylated by cdm-cyclin D complex
• Apoptosis/ programmed cell death
• Fas receptor (Fas or FasR)
• Fas. Death domain
• Fas ligand (FasL)
• Fas + FasL
• TNF + its receptor (TNF-R1) ￫ Apoptosis
• Downstream from the Fas receptor
• Classical pathway for apoptosis
• Fas + FasL. TNF + TNF-R1. 
• ]Caspase family (cysteine aspartate proteases)
• Pathway involving kinase JNK. 
• c-Jun. Bcl2.
• Cancer and the cell cycle
• Oncogenes. Proto-oncogenes
• Tumour-suppressor genes
• RB gene
• p53
• Haematopoiesis
• Bone marrow structure
• The haematopoietic process
• Bone marrow
• Stem cell
• Progenitor cells
• Maturation
• Peripheral blood
• Role of growth factors
• Stem cell factors (SCF)
• Granulocyte colony-stimulating factor (G-CSF)
• Erythropoietin (EPO)

Cell Death

There are two mechanisms for cell death: necrosis, which is a passive response to injury, and apoptosis, a mechanism of programmed cell death for removing excess cells produced during development or for removing cells that are functionally impaired, deficient or abnormal.

Apoptosis can result from multiple stimuli or the removal of survival factors such as hormones or growth factors. p53 is an important initiator following cellular injury.

The process of apoptosis involves a rapid and sustained increase in intracellular calcium that triggers endonuclease activation, leading to cleavage of DNA into fragments of about 180 base pairs. These can be detected as a DNA ‘ladder’ on gel electrophoresis.