Lecture 3

CFU-GEMM which in turn gives rise to BFU-E

Burst forming unit - erythroid (BFU-E)
Colony forming unit - erythroid (CFU-E)

Less responsive to EPO, only a few EPO receptors
larger colonies in culture

Under the influence of IL-3, GM-CSF, TPO, KITL

5 divisions

Highly response to and dependent on EPO (for survival)
Many EPO receptors
Smaller colonies in culture

BFU-E to CFU-E to…
1. Pronormoblast
2. Basophils normoblast
3. Polychromatic normoblast
4. Orthrochromic normoblast
5. Reticulocyte
6. Erythrocyte

1 week

1 week

1 week

18-21 days

8-32 mature RBCs

Nucleus and cytoplasm

Size, chromatin pattern, nucleoli

Amount, degree of basophilia, granularity

Cell diameter (size) decreases

Size of the nucleus will decrease, decrease in N/C ratio

Chromatin becomes coarser / denser
space in between chromatin and parachromatin becomes less obvious
nucleus is highly dense (pyknotic)

Cytoplasmic basophilia decreases«
(more Hb in cytoplasm rather than RNA)

Polychromatic normoblast

Orthochromatic normoblast

Yes

No, ends in orthochromatic stage

Polychromatic normoblast

Cell size, nucleus, cytoplasm

Chromatin pattern
size
N:C ratio
nucleoli

Color

Polychromatic normoblast

Round / oval, open chromatin, N:C 8:1, 1-2 nucleoli

Deeply basophilic, high RNA content, Golgi zone may be apparent

Usually 1 (could be more)

ONLY in bone marrow

24 hrs

Starts making glob in chains
Req items of Hb production (enzymes for heme) are synthesized

Chromatin denser / clumps,
open parachromatin area
nucleoli may or may not be there
N:C 6:1

Deep blue, (bluer than PNB)

Could be >1

Only in BM

24 hrs

Hb is detectable but obscured by heavy cytoplasmic basophilia

Chromatin a little open in early stage but becomes dense at the end (nucleus gets smaller)
N:C :4:1 -> 1:1 (end)
no nucleoli

Combination of blue (RNA) and Hb (acid / eosin) makes blue-gray pattern (polychromatic, multi colors)
last stage of cell division

Only in BM

30 hrs

Hb production prominent,
RNA (ribosomes) are still present (blue color)

Pyknotic
N:C ratio low (close to 1:2)

Close to salmon pink, bluish hue (RNA still there)

48 hrs, not able to do division

Only in the BM

Continues making Hb (remants of mRNA)
nucleus ejected at the end and Englishmen by BM mq

No nucleus

At ortho -> mostly salmon pink with bluish, but at the end similar to RBC with salmon pink cytoplasmic
larger than mature RBC
not biconcave disk yet, lumpy

Methylene blue (Supra vital staining)

Polychromasia

1-2 days in BM, 1 day in peripheral blood to become mature RBC (spleen processes membrane, pit out inclusions)

In BM / peripheral blood, it cont to make Hb using remnants of RNA

MB, BCB - Brilliant Cresyl Blue

No

Salmon pink

None

Peripheral blood

120 days

Gas exchange / transfer
O2 lungs -> tissues, CO2 body -> lungs

Hypoxia

1. Early release of reticulocytes
2. Inhibition of apoptosis
3. Reduced marrow transit time

Glycoprotein, true hormone

Cytokines by mq

Extravascular and intravascular hemolysis

Ab-coated or irregular RBC that goes through phagocytosis releasing globin and heme;
heme gets put into bilirubin metab while globin become AA

Outside the vessels (in the tissues)

Inside the vessels

RBC in circulation becomes exposed to stress, toxins, complement and break into free hemoglobin that binds to haptogoblin

Glycolysis (anaerobic)

Use plasma glucose to generate ATP, generating 4 molecules of ATP

ATP level is low

Detoxifies accumulated peroxider

Diverts Glucose-6-phosphate (G6P) to Penrose phosphate by the action of glucose-6-phosphate dehydrogenase (G6PD)

Glucose-6-phosphate dehydrogenase

G6PD

Degmacytes (bite cell) and Heinz body (inclusions)

Oxidizing agents put the hemoglobin (Fe2+) under oxidative stress, turning it into methemoglobin (Fe3+)

Cytochrome b5 reductase
NADPH methemoglobin reductase

Rare dominant hereditary disorder where glutamate replaces valine in pos 67 on beta chain of hemoglobin molecule

Methemoglobin to 15-30%

Cyanosis but do not exhibit any other symptoms

2,3-BPG diversion from glycolysis pathway through 1,3-BPG and then back to glycolysis through 3-PG

Binds to globin chains of Hb:
1. Maintains Hb in deoxygenated form
2. Facilitates O2 delivery to tissues

Harsh conditions like acidosis and low ATP (low pH and low ATP)

2 ATP

Inhibit the mutate and activate the phosphatase

1,3-BPG retained in EMP
2,3-DPG returned to glycolysis path

6-8 um in diameter, 90 fl volume, 140 um surface area, biconcave discoid shape with 40% excess surface area

Can stretch up to 2.5 times their normal resting diameter when passing through 3um microvessel in spleen

Deformability

Broad surface area for close contact with lung vascular bed and tissues enhancing gas transporting efficiency

52% protein, 8% CHO, 40% lipids

Equal proportions of cholesterol and PL, PL bilayer as a barrier, dynamic fluidity, self-sealing property, maintaining osmotic pressure

Hydrophilic and hydrophobic

Hydrophilic polar head groups orientated outward (plasma and cytoplasm sides)

Hydrophobic no polar acyl tails facing canter of the membrane (hidden from plasma / cytoplasm)

Cholesterol, phospholipids, glycolipids, proteins

Membrane gets stronger but not deformable

Symmetric distribution

RBCs will transform to codocyte (target cell) or acanthocyte (spur cell)

Asymmetric distribution

Phosphatidylcholine (PC) and sphingomyelin

Phosphatidylserine (PS) and phosphatidylethanolamine (PE)

Cover outside of membrane (glycocalyx)

Mostly protective function
also carry blood group ags (ABH, Lewis)

Forming complexes with skeletal proteins to maintain membrane vertical stability

Receptors, transporters, adhesion sites

Ankyrin complex and actin junction complex (or protein 4.1 complex)

Band 3 and protein 4.2 link lipid bilayer to the spectrum cytoskeleton through ankyrin

Band 3, protein 4.2, adducin and actin link lipid bilayer to the spectrum cytoskeleton through protein 4.1

Filamentous alpha-spectrin and beta-spectrin;
form lateral heterodimers

Key regulators of membrane elasticity and mechanical stability

Hereditary elliptocytosis

Leads to hereditary spherocytosis

Loss of ability to rebound after deformability

Up to 2.5 times their resting diameter (as they pass through narrow capillaries and splenic pores)

RBCs able to stretch 2.5X their diameter

Lose deformability and are unable to pass through splenic pores and are destroyed by mq

RBC membrane impermeable to cations (Na+ K+ Ca2+ but preamble to water, CL- and HC3-)

With aquaporins

NA+ATPase regulate intracellular concentrations of Na and K cations

cation pumps maintain IC / EC ratios of 1:12 and 25:1 respectively)

Expels Ca form the cell, maintaining low IC levels of 30-60 nM (compared to 1.8 mM in the plasma)

Ca and K influx with water following, resulting in swelling and lysis

Overhydrated stomatocytosis

Ca influx happens due to pump dmg by polymerized Hb contributing to hemolysis