Chap 10: Platelet Production, Structure and Function

Question 1

Nonnucleated blood cells that circulate at a concentration of 150 to 400 x10^9/L

Answer 1

Platelets

Question 2

Platelets that arise from unique bone marrow cells are called

Answer 2

Megakaryocytes

Question 3

Are the largest cells in the bone marrow and possess multiple chromosome copies (polyploid)

Answer 3

Megakaryocytes

Question 4

Megakaryocytes account for less than what percentage of all bone marrow cells?

Answer 4

0.5%

Question 5

Responding to the growth factor thrombopoietin (TPO), megakaryocyte progenitors are recruited from

Answer 5

Common myeloid progenitors

Question 6

T/F: Megakaryocytes are also found in the lungs

Answer 6

TRUE

Question 7

Megakaryocyte progenitors arise from the common myeloid progenitor under the influence of what transcription gene product?

Answer 7

GATA-1 regulated by cofactor FOG1

Question 8

GATA-1 stands for

Answer 8

Globin transcription factor-1

Question 9

FOG1 stands for

Answer 9

“Friend of GATA” (a product of the ZFPM1 (zinc finger protein multitype 1) gene)

Question 10

Three megakaryocyte lineage-committed progenitor stages, defined by their in vitro culture colony characteristics arise from

Answer 10

Common Myeloid Progenitor

Question 11

Least mature progenitor

Answer 11

Burst-forming unit (BFU-Meg)

Question 12

Intermediate progenitor

Answer 12

Colony-forming unit (CFU-Meg)

Question 13

More mature progenitor

Answer 13

Light-density CFU (LD-CFU-Meg)

Question 14

These two are diploid and undergo normal mitosis to maintain a viable pool of megakaryocyte progenitor

Answer 14

BFU-Meg and CFU-Meg

Question 15

All three progenitor stages resemble lymphocytes and CANNOT be distinguished by

Answer 15

Wright-stained light microscopy

Question 16

Undergoes endomitosis

Answer 16

LD-CFU-Meg

Question 17

A partially characterized form of mitosis unique to megakaryocytes in which DNA replication and cytoplasmic maturation are normal but cells lose their capacity to divide

Answer 17

Endomitosis

Question 18

Forrm of mitosis that lacks telophase and cytokinesis (separation into daughter cells)

Answer 18

Endomitosis

Question 19

Megakaryocyte progenitors leave the proliferative phase and enter

Answer 19

Terminal differentiation

Question 20

Series of membrane-lined channels that invade from the plasma membrane and grow inward to subdi- vide the entire cytoplasm

Answer 20

Demarcation System (DMS)

Question 21

Biologically identical to the megakaryocyte plasma membrane and ultimately delineates the individual platelets during thrombocytopoiesis.

Answer 21

Demarcation System (DMS)

Question 22

Nuclear lobularity first becomes apparent as an indentation at the 4N replication stage, rendering the cell identifiable as an

Answer 22

MK-II stage, or promegakaryocyte

Question 23

Ploidy levels are measured using _, a nucleic acid dye in megakaryocyte flow cytometry

Answer 23

Propidium iodide

Question 24

The process of platelet shedding

Answer 24

Thrombocytopoiesis

Question 25

A single megakaryocyte may shed

Answer 25

2000 t0 4000 platelets

Question 26

Lifespan of platelets

Answer 26

8-9 days

Question 27

First to appear on megakaryocyte progenitors and remains present throughout maturation

Answer 27

CD34 marker (along with CD36, CD42 and CD62)

Question 28

A viral oncogene associated with murine myeloproliferative leukemia.

Answer 28

MPL

Question 29

T/F: The plasma concentration of TPO is inversely proportional to platelet and megakaryocyte mass

Answer 29

TRUE

Question 30

Elevate the platelet count in patients being treated for a variety of cancers, including acute leukemia.

Answer 30

Synthetic TPO Mimetics

Question 31

A nonimmunogenic oligopeptide that is effective in raising the platelet count in patients with chronic immune thrombocytopenic purpura (ITP)

Answer 31

Commercial TPO mimetic, romiplostim (NPlate, Amgen)

Question 32

Cytokines that function with TPO to stimulate mega- karyocytopoiesis include

Answer 32

IL-3, IL-6 and IL-11

Question 32

Cytokines that function with TPO to stimulate mega- karyocytopoiesis include

Answer 32

IL-3, IL-6 and IL-11

Question 33

Factors inhibit in vitro megakaryocyte growth, which indicates that they may have a role in the control of megakaryocytopoiesis in vivo

Answer 33

Ptelet factor 4 (PF4), B-thromboglobulin, neutrophil- activating peptide 2, IL-8,

Question 34

Sometimes known as stress platelets, appear in compensation for thrombocytopeni

Answer 34

Reticulated platelets

Question 35

Essential plasma surface-oriented glycosylated receptors that respond to cellular and humoral stimuli

Answer 35

Ligands or agonists

Question 36

The plasma membrane surface that absorbs albumin, fibrinogen, and other plasma proteins, in many instances transporting them to internal storage organelles using a process called endocytosis

Answer 36

Glycocalyx

Question 37

The plasma membrane invades the platelet interior, producing a unique _

Answer 37

Surface-connected canalicular system (SCCS

Question 38

A condensed remnant of the rough reticulum

Answer 38

Dense tubular system (DTS)

Question 39

DTS sequesters Ca2􏰆 and bears a number of enzymes that support platelet activation including

Answer 39

Phospholipase A2, cyclooxygenase, and thromboxane synthetase

Question 40

Contractile in platelets (as in muscle) and anchors the plasma membrane glycoproteins and proteoglycans

Answer 40

Actin

Question 41

Granules that are filled with proteins, some endocytosed, some synthesized within the mega- karyocyte and stored in platelets

Answer 41

Alpha granules

Question 42

An integrin that binds the subendothelial collagen that becomes exposed in the damaged blood vessel wall, promoting adhesion of the platelet to vessel wall

Answer 42

A2B1

Question 43

A key collagen receptor that also binds the adhesive protein thrombospondin

Answer 43

GP IV

Question 44

Leucine-rich-repeat family CAM

Answer 44

GP Ib/IX/V

Question 45

These platelet “agonists” are ligands for seven-transmembrane repeat receptors (STRs), so named for their unique membrane- anchoring structure

Answer 45

- Thrombin - Thrombin receptor activation peptide (TRAP), - Adenosine diphosphate (ADP), - Epinephrine - Serotonin, - Thromboxane A2 (TXA2) - Other prostaglandins)

Question 46

Leads to an increase in intracellular calcium levels and contributes to initial platelet activation, shape change, and the formation of small reversible aggregates

Answer 46

P2Y1 signaling

Question 47

Leads to a decrease in cyclic adenosine monophosphate (cAMP) levels and supports the formation of irreversible plate- let aggregates

Answer 47

P2Y12

Question 48

A low-affinity receptor for the immunoglobulin Fc portion that plays a role in a dangerous condition called heparin-induced thrombocytopenia

Answer 48

FcyIIA (CD32)

Question 49

An integrin that facilitates platelet binding to endothelial cells, leukocytes, and one another

Answer 49

P-selectin (CD62)

Question 50

Platelet aggregation is a key part of primary hemostasis, which in arteries may end with the formation of a

Answer 50

White clot

Question 51

White clot is composed primarily of

Answer 51

Platelets and vWf

Question 52

Fibrin and red blood cells deposit around and within the platelet syncytium to form a bulky

Answer 52

Red clot

Question 53

Red clot is essential to wound repair, but it may also be characteristic of inappropriate coagulation in venules and veins, resulting in

Answer 53

Deep vein thrombosis and pulmonary embolism

Question 54

The polar phospholipid on which the factor IX/VIII (tenase) and factor X/V (prothrombinase) complexes assemble

Answer 54

Phosphatidylserine

Question 55

Are membrane-derived vesicles that form in response to an activating stimulus that increases the platelet intracellular concentration of calcium

Answer 55

Microparticles