CPR1 - Biochemistry {1.01, 1.03a, 1.04-1.06, 1.17-1.18,2.02}

What is anemia?

Low Hb value on the CBC, low RBC number

What is Erythropoiesis?

Process of making new RBCs

Where does Erythropoiesis exclusively occur?

In bone marrow

What are the major sites of Erythropoiesis in adults?

vertebrae and pelvis, lower rates in sternum and ribs

What are the major sites of Erythropoiesis in children?

Tibia and femur

What are the major sites of Erythropoiesis in the early fetus?

localized to yolk sac followed by localization to liver and spleen by the 4th month

What gives rise to all the different blood cells?

Hematopoietic Stem Cell (HSC)

What cells provide a meshwork of ECM material that support the cells of the marrow?

Stromal cells

What are blood sinuses in the bone marrow?

Thin-walled blood vessels in which newly formed cells are released into

What cells are myeloid cells?

RBCs, Platelets, monocytes and granulocytes (neutrophils, eosinophils, basophils)

What cells are lymphoid cells?

B cells, T cells and NK cells

Where do macrophages and osteoclasts differentiate?

Outside of the bone marrow

What is GATA-1 in hematopoiesis?

Gene required for terminal differentiation of RBCs

What are most mutations in GATA-1 associated with in RBCs and Platelets?

Morphological abnormalities

What is survival in Hematopoiesis?

Evading apoptosis

What is proliferation in Hematopoiesis?

Cell division

What is differentiation in Hematopoiesis?

Becoming a specific cell type, typically permanently losing the ability to divide

What happens to hematopoietic cells in the absence of the support cells or signals?

May die by apoptosis or prematurely commit to differentiation

What are colony stimulating factors (CSF)?

extracellular signaling molecules that drive cells towards differentiation

What is function of erythropoietin (EPO)?

inhibit apoptosis and promote survival of CFU-E cells

What are RBCs primarily dependent on for energy?

Anaerobic glycolysis

What removes senescent RBCs?

Macrophages in the spleen and liver

What cytokine to BFU-E cells require for survival and proliferation?

IL-3

What do BFU-E cells mature to after multiple rounds of cell division?

CFU-E cells

What can BFU-E cells only ultimately become?

RBCs

What is the first recognizable cell type in Erythropoiesis?

Proerythroblast (Pronormoblast)

What are the characteristics of Proerythroblasts (Pronormoblasts)?

Large nucleus, basophilic cytoplasm, very high RNA content, Massive generation of free ribosomes for Hb synthesis

What are the stages of erythropoiesis?

BFU-E→CFU-E→Proerythroblast→BE→PoE→OE→Reticulocyte→Erythrocyte

What do Proerythroblasts (Pronormoblasts) become after maturation?

Basophilic Erythroblast (BE)

What are the characteristics of Basophilic Erythroblast (BE)?

Intense basophilia, Nucleus still pretty large, Cell size begins to decrease, some chromatin condensation/clumping

What do Basophilic Erythroblast (BE) become after maturation?

Polychromatic Erythroblast (PoE)

What are the characteristics of Polychromatic Erythroblasts (PoE)?

Cytoplasmic mixture of basophilia and eosinophilia, Additional chromatin clumping/condensation, Cell size decreases

What do Polychromatic Erythroblasts (PoE) become after maturation?

Orthochromatophilic Erythroblast (OE) (Normoblast)

What are the characteristics of Orthochromatophilic Erythroblasts (OE) (Normoblasts)?

Much increased Eosinophilia, Nucleus becomes condensed pyknotic, Much smaller cells

What is basophilic staining?

Darker regions of blue/purple

What eosinophilic?

Lighter region of pink/red

What do Orthochromatophilic Erythroblasts (OE) (Normoblasts) become after maturation?

Reticulocytes

How do Orthochromatophilic Erythroblasts (OE) (Normoblasts) become Reticulocytes?

Ejection of nucleus

How are expelled nuclei from Orthochromatophilic Erythroblasts (OE) dealt with in Erythropoiesis?

Macrophages

What are the characteristics of Reticulocytes?

Contain about 80% of the Hb content of mature RBCs, no nucleus

How does hypoxia relate to EPO release?

Lack of oxygen stimulates kidneys to release EPO

How does chronic kidney disease relate to Erythropoiesis?

Damaged kidneys lead to reduced EPO release leading to anemia

What is the function of the JAK-STAT pathway Erythropoiesis?

EPO acts as a Growth Factor (GF) inducing the pathway and leads to alterations in gene transcription

What does activation of the Ras/Raf/MAPK pathway lead to in Erythropoiesis?

Increases survival and proliferation

What is the staining pattern of early Erythroid Precursors?

basophilic (lots of RNA/ribosomes)

What is the staining pattern of middle Erythroid Precursors?

mixed staining (RNA + Hb)

What is the staining pattern of late Erythroid Precursors?

eosinophilic (Hb dominates; ribosomes diluted)

What is the lifespan of RBCs?

about 120 days

How many RBCs are removed by the spleen/liver every day?

about 160 billion/day

What is the most EPO sensitive cell?

CFU-E

How does high altitude relate to Erythropoiesis?

Increased EPO→Increased reticulocytes→Increased RBC mass

Basophilic → Polychromatic → Orthochromatophilic: progression corresponds to ____ Hb and ______ ribosomes

Rising; Decreasing

What is the hemoglobin range to be considered anemic?

Males: < 13 g/dL; Females: < 12 g/dL

How is blood plasma attained?

supernatant after centrifugation; anticoagulant added

How is blood serum obtained?

no anticoagulant added; allowed to clot before spinning down → supernatant devoid of clotting factors.

What is microcytic anemia?

Smaller RBCs

What is macrocytic anemia?

Larger RBCs

What is the result of EPO on reticulocytes?

stimulates premature release of Reticulocytes into blood

What is Reticulocyte Production Index (RPI)?

A determination of whether a patient’s bone marrow is able to respond adequately to anemia

What does an RPI > 2 mean?

A patient is mounting an adequate response to the anemia by increasing the rate of Erythropoiesis

What is the formula for RPI?

reticulocyte % x [(Patient HCT/Mean normal HCT)/maturation correction factor] or CR/maturation correction factor

What does an RPI of < 2 indicate?

This would be a strong indication that the patient’s anemia is caused by faulty Erythropoiesis

What is MCV?

Mean Cell Volume (units: femtoliters [fLs])

What is the normal range for MCV?

80-100

What is MCH?

Mean Corpuscular Hemoglobin (mass of Hb in average RBC; units:picograms [pg])

How is MCH calculated?

(HGB/RBC) x 10⁷

What is MCHC?

Mean Corpuscular Hemoglobin Concentration (units: g/dL)

How is MCHC calculated?

(MCH/MCV) x100

What are the fundamental causes of anemia?

Acute blood loss or premature hemolysis, Ineffective Erythropoiesis, Impaired DNA synthesis caused by Folate or Vitamin B12 deficiencies, Impaired Hb synthesis caused by Iron deficiency

What does an MCHC below the reference range indicate?

Hypochromatic (pale) RBCs

What is RDW?

Statistical measure of the distribution of cell volumes across a sample of RBCs, healthy shows a tight, symmetrical distribution with a clear peak at MCV

What is a common cause of elevated RDWs?

Nutritional deficiencies

How is observed reticulocyte count (OR) calculated?

[(Absolute # of reticulocytes/microL)/RBC] x 100

How do you calculate corrected reticulocyte count (CR)?

OR x (patient HCT/mean normal HCT)

What are the early signs of iron deficiency?

Pallor, irritability, rapid pulse, dyspnea, headache, fatigue, dizziness

What is anisocytosis?

variation in the size of RBCs

How do humans eliminate excess iron from the body?

Humans have no way of eliminating excess iron from the body

How does Fe leave enterocytes?

Through ferroportin then binds to transferrin

A patient has a low MCV, low MCHC, high RDW, low RPI, and a primary defect in Hb synthesis. What is the most likely diagnosis?

Iron deficiency

A patient has high MCV, normal MCHC, high RDW, low RPI, and a primary defect of DNA synthesis. What is the most likely diagnosis?

B12/folate deficiency

A patient has a normal MCV, normal MCHC, high RDW, high RPI, and a primary defect of RBC destruction. What is the most likely diagnosis?

Hemolysis/acute blood loss

A patient has normal/mildly low MCV, normal MCHC, normal/slightly high RDW, low RPI and a primary defect of iron utilization and cytokine effects. What is the most likely diagnosis?

Anemia of chronic disease

How are Fe/Transferrin complexes taken up by cells?

Receptor-mediated endocytosis

What is the function of hephaestin?

Enzyme that oxidizes Fe²⁺ to Fe³⁺ so that iron can be carried on transferrin

What isotope of Fe can transferrin only recognize?

Fe³⁺

What is ferritin?

Large, hollow protein ball capable of holding up to 4,500 Fe³⁺ atoms

What is the function of hepcidin?

Binds to ferroportin causing internalization/destruction to protect body cells from damage from excess iron

What is hepcidin released from?

Liver

What cytokine increases hepcidin in chronic inflammation?

IL-6

What is hereditary hemochromatosis?

Iron overload disorder caused by lack of functional hepcidin

What is the concentration of blood ferritin in iron overload?

Increased ferritin

What is the concentration of blood ferritin with low iron?

Decreased ferritin

How is ferritin unintentionally released into the blood?

Cell damage/lysis, inflammation induced secretion, simple leakage

What is total iron binding capacity (TIBC)?

Measure of total transferrin reserve capacity to bind additional iron now

What is the formula for % saturation in assessing microcytic anemias?

Serum iron/TIBC x 100

What are the characteristics of stage I iron deficiency?

Negative iron balance, body drawing on reserves, serum ferritin levels decline, transferrin receptor may upregulate

What are the characteristics of stage II iron deficiency?

Serum iron noticeably decreased, more transferrin receptor in blood, % saturation less than 15-20%

What are the characteristics of stage III iron deficiency?

Full-on clinical anemia, significant # of RBCs microcytic/hypochromatic, low transferrin saturation, high transferrin receptor in blood

What does free iron activate in the heme biosynthesis pathway?

ALAS2

Why is Hb synthesis decreased in iron deficient RBC precursors?

Cells shut down production of ALAS2 slowing down the assembly line