H17 blood cell formation

Sinuses of BM structure

1) Can be viewed as specialized capillaries b/w arteries and veins 2) Endothelium here is simple squamous epithelium with thin basal lamina 3) Discontinuous endothelium

Precursor cells (Blasts) definition

Definition: first stage in differentiation of committed progenitor cells where can make morphologic distinctions

steel and ckit interaction

a) Ckit and steel are needed for the PSC to survive b) Steel i) Comes in several forms ii) Can be transmembrane bound as part of adventicial cell c) Steel bound to adventicial cell keeps the PSC bound to eat through the ckit receptor bound to the PSC d) This interraction is needed for the PSC to continue dividing and survive

Pluripotent stem cell

a. Pluripotent stem cell = all blood cells arise from this i. Normally always gives rise to one of itself and one that can do something else and differentiate further ii. Stem cell - an undifferentiated cell that can continue to divide indefinitely and its daughter cells, in a proper environment, can form specific differentiated cells. iii. Pluripotent - all the different specific cell types of both the lymphoid and myeloid lines form from this stem cell. 1) Only a small number, less than one in a million of the nucleated blood cells in the marrow are pluripotent stem cells.

macrophage development line of cells:

a. Pluripotent stem cell-->myeloid stem cell--> CFC mix-->CFC-GM-->monoblast-->promonocyte-->monocyte-->macrophage

neutrophil differentiation line of cells

a. Pluripotent stem cell-->myeloid stem cell--> CFC mix-->CFC-GM-->myeloblast-->promyelocyte (neutrophilic)-->neutrophilic myelocyte-->metamyelocyte-->band cell--> neutrophil

Irradiated mouse experiment just the steps, not the discovery

a. Step 1: Irradiate mouse to just the point that it can no longer produce blood cells (found that people after Hiroshima got sick about one month later b/c unable to produce leukocytes b. Step 2: Transfuse littermate's bone marrow into the irradiated mouse c. Step 3: Mouse recovers. Sacrifice mouse and look at liver :( d. Liver observations after BM transplant

Existence of one pluripotent stem cell experiment steps

a. Step 1: take BM, mash it up and put it in a test tube b. Step 2: put in a retrovirus which will insert into various places in the cells i. The idea is that each cell will have the retrovirus inserted into a different location in the DNA c. Step 3: Transfuse this bone marrow into another sad irradiated mouse

colony-forming cell (CFC) or a colony -forming unit (CFU)

b. A cell that can divide many times and produce visible colonies of cells either in an animal (in vivo) or in the laboratory (in vitro) is called a colony-forming cell (CFC) or a colony -forming unit (CFU).

Mesoblastic period

b. Mesoblastic period (first phase) = i. 2nd/3rd week - third month ii. primitive erythrocytes form in blood islands in wall of yolk sac

platelet development line of cells:

b. Pluripotent stem cell-->myeloid stem cell-->CFC-MEG (called MEP in Ross table)-->megakaryoblast-->promegakaryocyte-->megakaryocyte-->platelets

Hepatic Period

c. Hepatic Period (second phase) = i. Second fetal month until birth ii. Hematopoiesis occurs mainly in liver Some hematopoiesis in spleen and lymph nodes as while continue as minot sites after birth

Multipotent stem cells

c. Multipotent stem cells = daughter cells of pluripotent stem cell can become these i. a lymphoid multipotent stem cell 1) ii. a myeloid multipotent stem cell iii. multipotent stem cells can not become pluripotent stem cells. iv. one in one-thousand nucleated blood cells in the marrow are multipotent myeloid stem cells. v. Because the multipotent stem cell can divide indefinitely, it is also a CFC.

c. One BFC-E gives rise to over ____ mature erythrocytes or ____ cells (___ rounds of division)

c. One BFC-E gives rise to over 2000 mature erythrocytes or 2^11 cells (11 rounds of division)

Colony Stimulating factors

d. Colony Stimulating factors (CFCs) = facotrs that affect hematopoietic growth i. Frequently also serve other functions ii. Often exist in the blood serum iii. Stimulate or inhibit mitosis, cell division, differentiation, development, cell functions, survival

what was found in the liver after the irradiated mouse experiment?

d. Liver observations after BM transplant i. Colony forming cells/units were observed in little islands in the liver 1) Note that this means the cell had to undergo at least 6 divisions to form a colony ii. Some large colonies were a big mix of things while others were much more specific Suspected that larger colonies were the pluripotent stem cell (PSC) --

Myeloid period

d. Myeloid period (third phase) = i. 4th fetal month -- ii. Hematopoiesis occurs in the bone marrow

Progenitor cells

d. Progenitor cells = daughter cells of myeloid multipotent stem cells can become these i. Not a stem cell ii. Irreversibly destined to give rise to only one or two blood cell types iii. Can undergo rapid mitosis iv. Cannot replenish themselves v. Form colonies of a limited number of cells vi. Nomenclature: due to specific blood cell type 1) Ie erythroid CFC or CFC-E

findings of the pluripotent stem cell experiment (how did they know the PSC exists from the retroviral experiment)

d. Study the various blood cell lines i. Found that retrovirus was in the same place in the DNA in all blood cell lines ii. This means that all those cells had to come from the same pluripotent cell, so this proved the existence of a pluripotent cell capable of differentiating into any blood cell

Metamyelocyte (neutrophil)

e. Metamyelocyte = i. Defined by: when nucleus begins to deform ii. No longer capable of mitosis

what role do receptors for growth factors in blood development play?

e. Recptors on cells: i. Must have receptor to respond to growth factor ii. Pathways of cell growth are really regulated by the receptors on the cell, NOT really by the growth factors in the blood iii. A PSC daughter cell that wants to commit will change its receptors so it's more reponsive to growth factors

If the steel is not bound to a membrane

i) If the steel is not bound to a membrane, it will become inactivated and the cell would not continue getting the signal it needs

(XIII) Eosinophils and Basophils a. Their maturation is the same as for neutrophils with the following differences:

i. Arise from CFC-Eosin and CEC-Bas ii. No band cell stage iii. Metamyelocytes are distinguished from myelocytic phase by deformation and lobulation of the nucleus

Megakaryoblasts

i. Arise from CFC-Meg ii. Undergo only several rounds of division before turning into promegakaryocytes

describe the role of IL-3 in erythrocyte production

i. BFC-E expansion = IL-3 (CSF, colony stimulating factor) stimulates BFC-E to undergo 6 rounds of division 1) Does not require CSF erythropoietin 2) Cell must have the appropriate receptor or it will die 3) As the population changes it develops the receptor for erythropoietin

d. Promegakaryocytes

i. Both the cytoplasm and nucleus begin to enlarge ii. Mitoses occur but without the cytoplasm actually dividing (cell does not divide) 1) Ploidy goes from 16-64n iii. Cytoplasmic granules begin to form

platelet budding mechanism, and location

i. Bud off from megakaryocyte in a continuous process ii. Interaction of megakaryocyte with endothelial cells in blood sinuses of marrow is necessary here iii. Mechanism of budding: megakaryocyte extends processes through endothelial lining and platelets are pinched off directly into blood

Neutrophilic myelocyte (neutrophil)

i. Defined by: ability to see specific granules that make it look different than those of other granulocytes ii. Last cell capable of mitosis iii. Generates specific granules iv. Morphology: 1) First that is distinguishable from other granulocyte types (and in fact that is what defines it as a myelocyte)

Band cell

i. Defined by: nucleus forming a U shape; very very deformed ii. Nucleus starts to pinch off

monocyte

i. Develop azurophilic granules ii. Exit marrow and remains in blood for 16 hr. iii. Enters connective tissue

Promonocyte

i. Develops in bone marrow Capable of several divisions before monocyte maturation

Megakaryocytes

i. Fully differentiated from the above promegakaryocyte form ii. Largest cells in the marrow iii. Extensive Golgi complex making large numbers of specific granules

Promyelocyte (neutrophil)

i. Morhpology: 1) Appears (but isn't) exactly like the promyelocytes for basophils and eosinophils 2) Appearance of azurophilic granules and lysosomal granules for the first time 3) Nucleus: indented 4) Increase in cell volume

Monoblast

i. Morphology: (indistinguishable from myeloblast)

f. General trends: for RBC development

i. Process takes 1 week from CEC-Ery to maturity ii. Basophilic-->eosinophilic iii. Purple blue color-->light pinkish color iv. Normal nucleus -->Condensation and decrease in nuclear size v. Organelles-->smaller/no organelles vi. mRNA, rRNA, tRNA abundant -->decrease/none vii. Low/no hemoglobin-->almost all hemoglobin viii. Large cell-->small cell

Red v. yellow marrow

i. Red marrow = active in blood cell formation ii. Yellow marrow = inactive although retains potential to ecome red

cells that are considered CFCs

i. The pluripotent stem cell is one type of CFC. ii. Multipotent stem cells are also CFCs iii. Committed progenitor cells are CFCs BUT CANNOT REPRODUCE INDEFINITELY

lymphoid multipotent stem cell

i. a lymphoid multipotent stem cell can reside in either the marrow(producing B lymphoid cells) or populate the thymus and produce T lymphoid cells or Normally always gives rise to one of itself and one that can do something else and differentiate further

describe the role of erythropoitein in erythrocyte prodcution

ii. CFC-Ery pop = 1) CFC-Ery = previous population of BFC-E population that expanded is now called this after it undergoes its rounds of division (and now that it has developed the receptor for erythropoietin) 2) This population is dependent on erythropoietin 3) Erythropoietin = with this CFC-Ery will undergo 5-6 rounds of division as it develops into mature erythrocytes a) Note that without this the CFC-Ery would just die off b) Can be taken synthetically c) Low oxygen situation like high altitude will increase this d) Production site = kidney 4) This population contains no hemoglobin

myeloid multipotent stem cell

ii. a myeloid multipotent stem cell can give rise to all the specialized blood cells produced in the marrow. Normally always gives rise to one of itself and one that can do something else and differentiate further

Islands of development in the BM

iv. Islands of development = stromal structure of bm contains these various islands because each cell has its own progenitor 1) Location is dependent on mechanism of maturation

Platelet demarcation channels

iv. Platelet demarcation channels = vast network of membrane channels; internal extensions of the plasma membrane

Reticulocyte (RBC thing)

ix. Reticulocyte 1) This is the other product from the normoblast which contains a few organelle remnants and lots of hemoglobin 2) Under high O2 demand you will see some organelles because the process was pushed forward

v. Basophilic erythroblast

v. Basophilic erythroblast 1) Cytoplasm becomes basophilic because lots of hemoglobin production requires nucleus, mRNA, rRNA, tRNA

vi. Polychromatophilic erythroblast

vi. Polychromatophilic erythroblast 1) Hemoglobin stains eosinophilic so end up with purple stained cells here (basophilic staining comes from the mRNA rRNA and tRNA and DNA still present) 2) Nucleus continues to condense 3) Last cell that is capable of dividing

orthochromatophilic erythroblast

vii. Orthochromatophilic erythroblast 1) Violet color, as cytoplasm is filled with hemoglobin it becomes more and more uniform in color 2) Nucleus is condensing and becomes no longer capable of cell division double check this

viii. Normoblast

viii. Normoblast 1) Division stops here 2) Pyknotic nucleus is finally expelled from this along with remaining organelles

x. Erythrocyte

x. Erythrocyte 1) Function: deliver O2, pick up CO2 2) Components: no nucleus or mitochondria, just hemoglobin