5-erythropoiesis and RBC destruction

					                       Hematology-
                       The study of Blood


                          Hematopoiesis
                          Production of Blood Cells


Erythropoiesis
             Production of Red Blood Cells


    Chapter 32 and pages 861-864
1
         Lecture outline
    I. Functions of blood
    II. Properties of whole blood
    III. Whole blood components
               A. Plasma
                          i. Components of plasma
               B. Formed elements
                          i. Site of hematopoiesis
                          ii. Hemocytoblast- determined but not differentiated
                          iii. Erythropoiesis
                                       a. ―Ingredients‖
                                       b. Process
     IV. Red blood cell characteristics
               A. General ―need to know‖ information, indices
               B. Components within a red blood cell
                          i. Hemoglobin
                                       a. Globin chains
                                       b. Pyrrole groups
                                       c. iron
2
          C. Steady-state maintenance of RBC counts
                   i. Erythropoietin
                   ii. Removal/destruction of RBC
                             a. jaundice
V.       RBC pathologies
          A. Polycythemia
                   i. Primary
                   ii. secondary
         B. Anemia
                   i. Defective RBC production
                             a. Iron deficiency
                             b. Aplastic anemia
                             c. megaloblastic
                   ii. Blood loss
                             a. Hemorrhagic (chronic, acute)
                             b. Acquired (transfusion, venom, drugs)
                             c. Inherited (thalassemia, sickle cell, hereditary
                                       spherocytosis, G6PD deficiency)


     3
       Anemia: a reduced carrying capacity of
       oxygen
     Anemia is not a reduced hematocrit (Hct), because you can have
      less O2 for other reasons.You can be anemic with normal levels
      of RBC’s if the hemoglobin is abnormal, and has less iron.




4
    Functions of Blood
• Transportation
   – Gases, nutrients,
     hormones, wastes,
     antibodies.
• Regulation
   – Body fluid volume
   – Body fluid pH         These red blood cells function
   – Body T°               in oxygen transport

   – Electrolyte levels
• Protection from
  pathogens and bleeding        Used with permission given by A. Imholtz
                                http://academic.pg.cc.md.us/~aimholtz/
5
     Blood transports O2, CO2, nutrients, wastes,
      hormones, lipids, etc. The blood also regulates body
      temperature. Hormones can adjust blood volume, urine
      output, and maintain pH (which needs to be 7.40). A
      person with blood pH of 7.35 or 7.45 will not feel well,
      act strangely. There are buffers in the blood to keep the
      pH steady, and lungs and kidneys help with this. We also
      have WBCs in our blood for immune system function,
      and platelets for clotting.


6
                    Blood – Physical
                    Characteristics
     Adult ♂ contains 5-6L
     Adult ♀ contains 4-5L
     T is about 100.4 F
     5 times as viscous as water
       What accounts for its viscosity?
     pH ranges from 7.35 – 7.45 (slightly
      alkaline)                               Without O2                      With O2
       What happens at either extreme?
     Color ranges—oxygen poor vs.
      oxygen rich
                                             Used with permission given by A. Imholtz
                                             http://academic.pg.cc.md.us/~aimholtz/
7
     Adults have 4-6 liters of blood (Let’s call it 5 liters for this
      class). The heart pumps all of it every 60 seconds. The
      temperature of our core is higher than the superficial
      temperature. Blood is 5x thicker than water because of the
      RBC’s. Increase the numbers of RBC’s, and you will increase
      viscosity, increase heart workload.




8
     The color of blood is bright red or dark burgundy, depending on
      oxygenation. Blood is intracellular fluid (RBC’s, 45%) and extra
      cellular fluid (plasma, 55%). In plasma is mostly water, plus
      dissolved hormones, proteins, electrolytes. Don’t memorize the
      next two slides that show everything in the blood; just understand
      that there are many things in the blood. Water is the solvent. 7g%
      of the plasma is protein, albumin is the most abundant. Albumin
      helps keep the water in the plasma by keeping the particle count
      high. Problems with water leaving the vascular compartment will
      lead to ascites, so albumin in the blood acts as osmotic
      support.


9
                    Whole Blood


         Plasma                  Formed Elements
          (55%)                           (45%)


 1. Water (92%)            1. Red Blood Cells-erythrocytes
                              (99.9%)
 2. Plasma Proteins (7%)
                           2. Platelets- thrombocytes                            (0.1%)
 3. Other Solutes (1%)
                           3. White Blood Cells- leukocytes

                                      Used with permission given by A. Imholtz
                                      http://academic.pg.cc.md.us/~aimholtz/
10
                                            Transports, organic and inorganic
                 Water (92%)                molecules, formed elements, and heat

                                               Albumins (60%): Contribute to plasma
                                               osmotic pressure; Transport lipids,
Plasma                                         steroid hormones

                                               Globulins (35%): Transport ions,
                   Plasma                      hormones, lipids; Immune function
                   Proteins (7g%)
                                               Fibrinogen (4%): Essential component
                                               of clotting system
 Other Solutes (1%)                 Regulatory Proteins (<1%): Enzymes, Hormones

                 Electrolytes: Ions necessary for vital cellular activity. Contribute to
                 osmotic pressure of body fluids. Major electrolytes are Na+
                 (140meq/L),K+ (3-5 mEq/L), Ca2+, Mg2+, Cl-, HCO3-, HPO42-, SO42-
                 Organic Nutrients: Used for ATP production, cell growth and maintenance;
                 Includes lipids (800mg %) , carbohydrates (80-120mg%) , cholesterol
                 (200mg%) and amino acids
  Organic Wastes: Carried to sites of breakdown or excretion; Includes urea, uric
11acid, creatinine, bilirubin, and ammonium ions
      Besides albumin, there are other proteins in the blood,
       such as fibrinogen (inactive form of fibrin). Fibrin is the
       fiber that grows across a cut and makes a scab. Other
       proteins include regulatory and proteolytic enzymes.
       Other substances in blood include glucose, lipids,
       cholesterol, bilirubin (waste product of RBC
       destruction), and creatinine (waste product of kidney).
       We check those levels in the blood to ascertain kidney
       function. There are lots of solutes in the blood!


12
     BLOOD ANALYSIS TERMINOLOGY
      You need to measure hematocrit (Hct), hemoglobin (Hgb), and do a RBC count. With
        this information, you can then calculate MCV, MCH, and MCHC. By the way, RBC =
        corpuscle.
      MCV(mean corpuscular volume) calculated as MCV = Hct / RBC count. Normal is 80-
        100 µm
      MCH (mean corpuscular hemoglobin) calculated as MCH = Hb / RBC count. Normal
        is 32 pcicograms (10 -12 micrograms). There is not much, but hemoglobin is still the
        most abundant protein in RBC’s.
      MCHC (mean corpuscular hemoglobin concentration) is the ratio of MCH to MCV. It is
        calculated as MCHC = Hb/Hct. Normal is 34%
      MCD (mean corpuscular diameter) normal is 7-8 µm wide, 2 µm thick.




13
Red blood cell-
need to know information


  Hematocrit: % volume of blood that is red
     cells
      Men ~45% (42-52%)
      Women ~40% (37-47%)
  Hemoglobin concentration -Wt of Hb in 100
     ml blood                                  100 ml
      15-16 (male) gm Hb/100 ml blood
      13-14 (female) gm Hb/100 ml blood
  Oxygen carrying capacity:
      gm Hb/100 ml blood * 1.34 ml O2/gm Hb
      ~21 ml O2/ 100 ml blood for men
      ~19 ml O2/ 100 ml blood for women




14
     Red Blood Cell “Indices”
  Mean Corpuscular Volume
    MCV 80-100 m3
  Mean Corpuscular Hemoglobin
    32g (10-12; picogram)
    Wt of Hb in a single RBC
  Mean Corpuscular Hemoglobin Concentration
    34%
    Concentration of Hb to volume in a single RBC (i.e., solute/solvent).
  Mean Corpuscular Diameter
    MCD 7-8 m
  Color Index
    CI 0.9 – 1.1

                                             A “corpuscle”
15
      COLOR (Chromasia; indicates how much Hgb is there)
       Normal is 1.0
      Normochromic is 1
      Hypochromic is less than 1. Can’t have hyperchromic RBC’s. A
       disorder that appears hyperchromic is

      Hereditary Spherocytosis. It is the most common inherited
       disorder that affects the RBC membrane. RBC comes out of
       marrow normal, but with time, the membrane is lost, but none of
       the contents are lost, RBC gets smaller and concentrated, looks
       redder. Thus, it could look hyperchromatic.

16
      SIZE
      Normocytic is normal size.
      Microcytic (small)
      Macrocytic or Megaloblastic (big)


      SHAPE
      Poikilocytosis is abnormal shapes, such as sickled or
       sphaerocytes. Cells with abnormal size or shape will be
       removed from circulation faster, get anemia.

17
     Terminology
 Chromasia- indication of
     MCH
      Hyper/hypochromic
      normochromic
 Anisocytosis – cells of
     abnormal size; indication of MCV
      Microcytic
      Macrocytic/ Megalocytic
      normocytic
 Poikilocytosis – cells of
     abnormal shape
      Spherocytosis
      Sickle cell
      Echinocyte


18
     CELL COUNTS
      We have 5 liters of blood, 25 trillion RBC’s, 4.5 million in one microliter. We
        need the rate of old blood cells that die to match the rate of new ones being
        made. RBC’s are made by stem cells in bone marrow. Too many RBC’s is
        polycythemia, too few is anemia. RBC shape should be biconcave because
        that increases surface area for O2 binding and allows it to be flexible to get
        through capillaries. When a RBC gets older, its membrane is less flexible, gets
        stuck in liver and is detected and destroyed. Because of the shape increasing
        surface area, there is rapid gas exchange across cell membranes for wastes and
        O2.You know that hemoglobin binds O2, but CO2 can also bind to
        hemoglobin, but only if O2 is not there.




19
     SITES OF HEMOPOIETIC ACTIVITY
      An embryo (< 3 months) makes blood in yolk sac
      Fetus (> 3 months) makes blood in the liver
      At birth, makes blood in the bone marrow
      Blood that is made in the bone marrow is specifically
       made in the axial and appendicular skeleton until the age
       of 20. Thereafter, it can only be made in the axial
       skeleton, mainly in the sternum and iliac crest.




20
       Let’s talk about formed elements-
       Sites Of Hemopoietic Activity

                               Bone marrow
     Yolk sac
                                                         Vertebra
                    Liver

                                                             Sternum
                                                                        Axial
                                                                        skeleton


                                                              Rib

                    Spleen
                                                       Femur
                                                                    Appendicular
                                             Tibia                  skeleton

                3                                       20
           1
                FETAL MONTHS                         ADULT
21
     ERYTHROPOIESIS (MAKING A RBC)
      A stem cell that is completely undifferentiated yet is called a
       pleuripotent stem cell.
      A pleuripotent stem cell can differentiate into any cell
       type: nerve, muscle, blood, etc. Since we are discussing
       blood cell formation, we will focus on a pleuripotent stem
       cell that differentiates into a Hemocytoblast.




22
     Hematopoiesis
 The ―pluripotent hemopoietic stem
     cell‖ or ―hemocytoblast‖ is the
     precursor of all blood cells.
    Found in bone marrow.
    Undergoes mitotic divisions
    daughter cells differentiate
    This is the source of all new blood    Myeloid stem cell

     cells.
      The ―colony-forming unit, myeloid
        stem cell line‖
      The ―colony forming unit, lymphoid
        stem cell line‖



23
      Hemocytoblasts can differentiate into any blood cell
      type. Therefore, they are not pleuripotent anymore, but they
      are still multipotent (they are “determined”, but not
      completely differentiated). A hemocytoblast will
      continue to differentiate into one of two cell types:
        Lymphoid line generates B and T cells
        Myeloid line generates red and all other blood cells.
       Scientists doing stem cell research have found a way to turn a
         multipotent cell back into a pleuripotent cell by just Inserting four
         genes into a multipotent cell!




24
      To make a good RBC, you need to start with good
       ingredients: a good hemocytoblast, proper nucleotides, folic
       acid, vitamin B12, and other vitamins.You also need growth
       inducers, differentiation markers (signals), amino acids
       (Adenine, Thymine, cytosine, guanine), heme (a pyrrole ring
       and globin proteins), and iron.




25
     The Recipe for Normal
     Erythropoiesis
                 Healthy stem cells
                 Growth inducers (interleukins)
                 Differentiation inducers
                 Cell Division (Mitosis)
                   DNA replication- vitamin B12 and folic
                    acid coenzymes
                   building blocks of DNA
                     (Adenine, Thymine, Cytosine, Guanine)
                 Hemoglobin Synthesis
                   amino acids, heme and iron


26
      Newly formed red blood cells have to get from the bone marrow into a blood
       vessel. To do this, they squeeze through the endothelial cells of the vessel, but
       their nucleus cannot fit, so it gets pinched off. The new RBC in the bloodstream
       has a little bit of endoplasmic reticulum and bits of DNA deposits left over from
       where the nucleus was pinched off, so a brand new (immature) RBC in the
       bloodstream is called a reticulocyte. Thus, RBC’s are in an immature state
       when they are released into the bloodstream. It takes about 1-2 days for these
       endoplasmic bits to dissolve. Until then, you can see the difference between a
       reticulocyte and a mature RBC under the microscope when looking at a blood
       smear. Reticulocytes are immature red blood cells. Only about 1% of the RBC’s
       should be reticulocytes. If there are more, it indicates a problem.




27
  Hemocytoblast            Pluripotent stem cell      Erythropoiesis-5-7
                                                      days
  Myeloid Stem Cell            Could become an RBC or several types of WBC


                         Destined to become an RBC; “more” determined but still
                         not differentiated




                        Various stages. Actively synthesize Hb



                       Just lost its nucleus. Enters the circulation – should be no
                       more than 1% among all RBCs.


                         Mature RBC--Differentiated. (After a reticulocyte
                         has been in the blood stream for 1-2 days)
28What   is a functional advantage of the fact that the RBC lacks mitochondria?
      As long as a RBC is flexible, it can weave around the web of reticular fibers in
         the liver and spleen without getting stuck. Those that get stuck are phagocytized
         by macrophages. RBC’s that are old or hemoglobin abnormalities (sickle cells)
         tend to be less flexible, and are caught in reticular fibers and destroyed. This can
         also happen to reticulocytes.
     
      This process takes 7 days: hemocytoblast  myeloid stem cell 
         reticulocyte  RBC
     
      Up until the reticulocyte is released, it retains its shredded endoplasmic
         reticulum, trying to undergo protein synthesis to make hemoglobin as much as
         possible.



29
Red Blood Cell physical
properties and components
  Most abundant blood cells – ¼ of
     body cells
  4.5 - 5.5 x 10 6 cells / mm3
  Why a biconcave disc?
    Provides a large surface area for O2   Rate of Production
                                            Bone Marrow
     entry/exit
    Enables them to bend and flex when                   Steady
     entering small capillaries                            State
  simply membranous bags of
     hemoglobin, a protein found in         Rate of
     extreme abundance in RBCs, which       Removal

     binds and transports O2 and CO2        Liver,
                                            Spleen

30
      Erythropoiesis is stimulated by a hormone
       called EPO, which is secreted by the kidney.
      In conditions where there are not enough RBC’s in the
       body (e.g. Erythroblastosis Fetalis), oxygen levels will
       decrease. The kidneys will sense that, and produce EPO,
       which stimulates stem cells to divide faster, and hastens
       the release of immature RBCs into the bloodstream, so
       we will see more reticulocytes in a blood smear.



31
      When the RBC is fully mature, it lacks organelles. This is
       good, because it can transport more O2 if it does not
       contain any mitochondria, which consume oxygen.
       However, there is a disadvantage, to not having a nucleus
       and other organelles: a RBC can’t repair any damage or
       express new proteins. That’s why they only live 120 days;
       they accumulate damage, lose their flexibility, and get
       destroyed. A true RBC count should be at a steady state,
       new ones replace dying ones.


32
 I want my
 oxygen!




       O2



             O2




33
      A Hemoglobin molecule consists of three parts
      Globin chains (proteins from gene expression)
      Heme Group
                                  Heme Group
      Pyrrole ring Iron




34
Hemoglobin
 Large protein consisting
      of 4 polypeptides
   2  chains and 2 β chains
 Each chain contains a single
  molecule of heme, an iron-
  containing pigment
   The iron ion in heme is able to reversibly
    bind an oxygen molecule thanks to the
    surrounding globin chains.                    Note the 2  chains and 2 β
   Meaning, O2 can bind to Hb at the lungs and   chains. Notice how each has
    then be released at the tissues               an associated heme molecule
                                                  with an iron atom.
                                                  •Based on the above, how
                                                  many molecules of O2 can
                                                  each Hb protein bind?


 35
     GLOBIN CHAINS
      To make the globin chains, we need genes. If there is a defect in the gene, the
        globin chains are defective, as in the case of sickle cell disease. Since it is the
        iron that binds the oxygen, why do we need globin at all? Because iron binds to
        oxygen so strongly, it will never let go unless hemoglobin is there to move its
        structure to block the magnetism of the iron. We need for iron to bind strongly
        to the oxygen in the lungs. When there is no oxygen on a hemoglobin molecule,
        the globin chains move a little, exposing the iron so it can grab some oxygen
        while in the lungs. Once the iron is bound to oxygen, the globin chains move a
        little, decreasing the hold of iron onto the oxygen, so that the first oxygen-
        depleted cell that it comes close to can pull the oxygen molecule off of the
        hemoglobin complex. This is considered reversible binding of oxygen;
        hemoglobin has an affinity for oxygen in lungs, and low affinity to oxygen in the
        tissues.



36
      There are different types of globin chains. In an adult, there are 2 alpha globin chains and
        2 beta chains. Therefore, adult hemoglobin is called A2B2. Since each globin chain
        is a protein, and there are four proteins bound to each other, hemoglobin has quaternary
        structure. An embryo has embryonic hemoglobin, called A2E2. An embryo does
        not have working blood vessels yet, since oxygen is coming in from the placenta.
        Therefore, an embryo needs Hgb with a higher affinity for oxygen than mom’s A2B2, to
        rip the oxygen off mom’s hemoglobin. When the embryo develops into a fetus, its blood
        vessels get bigger, have closer proximity to mom’s blood vessels, needs a little less
        affinity than embryonic hemoglobin, but the fetus still needs to have hemoglobin that has
        a higher affinity for oxygen than A2B2, so fetal hemoglobin is A2G2. Around the
        time of birth, the baby’s hemoglobin becomes A2B2. Once a baby is breathing on its
        own, it needs hemoglobin with lower affinity. Therefore, the order of affinity for oxygen
        of the different types of hemoglobin is HgbE (A2E2), HgbF (A2G2), then HgbA (A2B2).




37
 Globin Chains
  Why not just use iron/heme group?
  Determine Hb’s affinity for oxygen
  Are expression products of different genes (chromosomes 11,
   16)
  Different genes are expressed throughout life and have
     different affinities for oxygen
      Embryonic Hb (HbE) 22 (before 3 months gestation)
      Fetal (HbF) 22       (replaced within 6 months of birth)

      Adult (HbA) 22
        = heme group (+ iron)

             = alpha chain

38
              = Beta chain
     HEME GROUP
      Within each globin chain is a heme group. A heme group
       consists of a pyrrole ring, with an iron atom in the middle.
       Since there are four globin chains per hemoglobin molecule,
       each Hgb has 4 irons.




39
     MAKING HEMOGLOBIN
      Hemoglobin is made in the mitochondria of the
       erythrocyte while it is developing (in the proerythroblast
       stage). Once iron is added to the pyrrole ring, the entire
       structure is called heme. When you add the four globin
       chains to heme, it is now called hemoglobin. When a
       macrophage phagocytizes a RBC, the hemoglobin is
       taken apart into its components. The iron and globin are
       recycled, but the pyrrole group is cannot be reused, so it
       needs to be eliminated from the body as a waste product.


40
  The making of a pyrrole ring in
  proerythroblast mitochondria




  Alpha and Beta Globin polypeptide chains are synthesized
  at the ribosome in the cytoplasm.
   Completed porphyrin rings are sent to meet them in the
41
   cytoplasm, where they all bind to form Hb.
      We get iron from our diet. It is absorbed from the intestine and released into
       the plasma, where it binds to a plasma protein called apotransferrin (when
       it is not bound to iron) or transferrin (when it is bound to iron).
       Since we have said that the plasma protein has bound to the iron, we will now
       call it transferrin. The transferrin protein takes the iron to cells in the body that
       need iron, or the iron is stored intracellularly in two different forms.
         Ferritin is a protein within a cell that has bound onto the iron. This same protein, when
          unbound, is called apoferritin.
         Hemosiderin is a complex in cells that binds to iron and does not release it for use very easily;
          it is very insoluble. Macrophages that phagocytize RBC’s tend to accumulate hemosiderin
          deposits. Too much hemosiderin in a cell or in tissues is toxic.




42
 Obtained in the diet
      Released into plasma
      Binds to protein called ―apotransferrin‖        Iron
      Travels in circulation as transferrin
      Delivered to cells needing iron or stored
     intracellularly in two different forms
   Apoferritin- to form iron- bound ferritin
   Hemosiderin-extremely insoluble; toxic to cells;
     iron over-load
 Ferrous (reduced; +2) form binds indirectly to
  oxygen
 Ferric (oxidized; +3) form cannot bind oxygen
 Hb with iron in ferric form is called
  methemoglobin




43
     IRON HAS SEVERAL DIFFERENT STATES
      Ferrous (reduced +2) form binds indirectly to oxygen.
       We need it in this state.
      Ferric (oxidized +3) form cannot bind to oxygen. Hgb
       with iron in ferric form is called methemoglobin.

      We have proteins to convert iron from its ferric to the ferrous
       state. There are some household products and pesticides that
       change ferrous to ferric, and our body may not enough available
       energy to convert it back to the ferrous form we can use.




44
     ERYTHROPOIETIN (EPO)
      EPO (erythropoietin) is a hormone; 90% of EPO is
      made in the kidney, 10% is made in the liver. It
      stimulates all the stem cells of blood, many of which
      develop into RBCs. The RBCs are ready to exit the bone
      marrow and enter the circulation in 5 days, plus another
      2 days of maturation within the circulatory system. If
      you lose kidney function, you can become
      anemic. EPO is released by the kidney in response to
      low oxygen levels in the tissues (hypoxia).


45
     Steady state RBC count-Erythropoietin
     (EPO)
  What is it? A hormone
  What is its source? 90% from kidney, 10%
   from liver
  Conditions for its secretion? Kidney senses
   hypoxemia (low oxygen; is most essential
   regulatory of RBC production)
  Erythropoietin is always present in the
   plasma we would be anemic without it!
  What are its actions?
         Promotes release of reticulocytes
         Stimulates stem cell mitosis
         Increase in red cell number in 5 days
         Synthetic EPO /Recombinant Human EPO—
          ‖Ecrit‖ ―Eprex‖ ―Dynepo‖


46
      Chemotherapy for cancer patients targets rapidly dividing cells, especially the hair
        (causes hair loss), stomach lining (causes nausea), and the bone marrow (causing low
        RBC count, and fatigue). They are given artificial EPO to offset the anemia. Athletes
        might take EPO (illegally) for ―blood doping‖. It causes an increase in RBC production,
        leads to more O2, more ATP, more energy, but it thickens blood, can cause heart attack.
        Sports authorities have been using a drug test on athletes who use a form of EPO made
        from bacteria; the bacterial particles are detectable on blood tests. Now, these
        unscrupulous athletes are getting clever: someone has manufactured human EPO that
        cannot be detected in these drug tests. This human EPO is approved for medicinal use in
        Europe, and it is in America on the Black Market. So now, sports authorities do a RBC
        count. If the RBCs are present in excess of set limit before the race starts, they are
        disqualified. Some of these athletes get away with it by training with human EPO and
        donating blood before the race.




47
      If you want to climb a high mountain, you can’t just
       climb to the top in one day. There is less oxygen pressure
       at high altitudes, so RBCs can’t bind oxygen as well.
       What you do is go to a base camp, part way up the
       mountain, and stay there for 2 weeks, so the kidney can
       release EPO to stimulate RBC production. Then you go
       up the mountain to the next base camp for 2 weeks.
       Then you can go to the top, when the new cells can bind
       to oxygen better.


48
RBC
Removal
 Lifespan approx. 120 days
 RBCs are subjected to incredible
  mechanical stress.
   Narrow capillaries
 Limited ATP stores for replacement
                                                     Above, we have a macrophage
  of worn parts                                      phagocytizing multiple RBCs
   Why are they unable to synthesize replacements
                                                        How many RBCs did it engulf?
      for damaged parts?
 Membrane fragility
 Macrophages in liver and spleen
  remove old RBCs
 Contents destroyed or recycled

 49
     Three different cells participate in
     destruction of RBCs
      RBC
      Macrophage
      Hepatocyte




50
        When a RBC is old, it gets trapped in the reticular fibers of the spleen or liver, where a macrophage
         detects it and engulfs it. Within the macrophage, the globin chains, porphyrrin ring, and iron are detached
         from each other and liberated. What happens to each of these segments?
        The Iron is released into plasma, apoferrin binds to it (so now the apoferrin is called transferring), it is
         taken into cells that can use or store it. The iron is stored as ferritin or Hemosiderin.
        The globin chains (proteins) are hydrolyzed into amino acids (the building blocks of proteins), which
         are used for synthesis of any other proteins wherever they are needed.
        The porphyrin ring is converted in the macrophage to pre-bilirubin (uncongugated). It is released into
         blood, and since it is hydrophobic, it needs albumin as a protein carrier. It is taken to the liver, and enters
         a hepatocyte (liver cell). Within the hepatocyte, it is conjugated it with glucuronic acid, which makes it
         hydrophilic. It is then released into the bile duct, enters the intestines. The bilirubin undergoes further
         conversion before it becomes part of the feces, and is responsible for the brown color. If there is a
         blockage of the bile duct, it can only exit the body by the urine; it undergoes a different type of
         conversion, and the urine will be a deep orange-yellow color. Without the brown color in the feces, they
         will look white. White stools indicate obstruction in the bile duct.


        Know what parts of a RBC can be recycled: Not all of the heme, but the globin chains, and the iron.




51
 Heme Group Modification and Excretion
                                     Amino acids
                                                    glucuronic acid
                    globin

                                                1               2       3         Into
                heme
                                                                                  bile
                    Free bilirubin                Free         conjugated
Senescent
                                                bilirubin       bilirubin   Converted to
 red cell                                                                   stercobilinog
                    iron                                                       ens and
                                                                            urobilinogens
                                                                            and excreted
              macrophage              albumin                                  in feces
                                                        hepatocyte
      transferrin                                   1. Uptake
                                                    2. Conjugation
                                                    3. Excretion (rate limiting)
                Stored as ferritin or
52              hemosiderin
      There are several different problems that occur
       when bilirubin is not excreted: all types lead to
       jaundice.
      A newborn baby has to make new RBC’s in the liver, and
       is not able to deal with hemolysis. Hepatocytes are not
       mature enough to add the glucouronic acid to the
       porphyrin ring to conjugate it. Adults who have a gall
       bladder obstruction, causes conjugated bilirubin to be
       reabsorbed; they need the kidney to deal with it, and the
       urine becomes orange.

53
     Jaundice
        Hemolytic jaundice: Free bilirubin levels
         rise- RBCs are hemolyzed more quickly
         than hepatocytes can conjugate
        Obstructive Jaundice due to clogged bile
         ducts (portal hypertension): rate of
         bilirubin formation is normal, but can not
         pass from blood to intestines. Most of
         the bilirubin is the conjugated type.
            Feces can be clay colored




                                    Consider a bruise. The initial color is due
                                    to blood in the interstitial spaces.
                                         As a bruise turns green and yellow,
                                         what must be occurring?
54                                       What must be occurring as the yellow
                                         color fades away?
      How conjugated bilirubin is broken down and excreted
      When conjugated bilirubin leaves the bile duct and enters the
       intestines, bacteria in the colon convert it to another type of
       bilirubin: urobilinogen, which is further metabolized to
       stercobilinogen, and finally oxidized to stercobilin. This
       stercobilin gives feces its brown color. If there is unconjugated
       bilirubin that arrives in the intestine (from an obstruction in the
       bile duct), it will be absorbed back into the bloodstream (causing
       jaundice), and the rest is filtered by kidney, converted to another
       type of bilirubin (urobilin), which causes the urine to turn orange.



55
        BRUISES
      What happens when a bruise goes from purple to green to yellow?
      When a blood vessel breaks, RBC’s leak out, and macrophages
       phagocytize them. The macrophage breaks down the hemoglobin in
       the blood cells into the heme portion, and the globin portion. The
       globin portion (made of proteins) is broken down into amino acids,
       which are transported to wherever in the body they are needed to
       make new proteins. The heme portion is broken down into iron
       (which is sent to storage or transported to where it is needed) and the
       pyrrole ring is released into the tissues. There, it is converted to
       biliverdin, a green type of bilirubin. The biliverdin is then reduced to
       unconjugated bilirubin (yellow).


56
      The unconjugated bilirubin then travels to the liver through the bloodstream. Because
       this bilirubin is not soluble, however, it is transported through the blood bound to serum
       albumin. Once it arrives at the liver, it is conjugated with glucuronic acid (to form
       conjugated bilirubin) to become more water soluble.
      This conjugated bilirubin is excreted from the liver into the gallbladder and becomes
       part of bile. Intestinal bacteria convert the bilirubin into urobilinogen. From here the
       urobilinogen can take two pathways. It can either be further converted into
       stercobilinogen, which is then oxidized to stercobilin and passed out in the feces, or it
       can be reabsorbed by the intestinal cells, transported in the blood to the kidneys, and
       passed out in the urine as the oxidized product urobilin. Stercobilin and urobilin are the
       products responsible for the color of feces and urine, respectively.

      Know what happens during hemoglobin breakdown: what happens to all its parts, where
        does bilirubin go?




57
     JAUNDICE
      When a person has jaundice, is it high levels of conjugated or unconjugated bilirubin? It
        depends on what is causing the jaundice.
      Pre-hepatic jaundice is caused by anything which causes an increased rate of hemolysis
        (breakdown of red blood cells). This can be caused by such things as malaria, sickle cell
        anemia, Hereditary Spherocytosis, Hemolytic Disease of the Newborn (HDN), glucose
        6-phosphate dehydrogenase deficiency (G6DH). Pre-hepatic jaundice will have
        increased unconjugated bilirubin in the serum.
      Post-hepatic jaundice, also called obstructive jaundice, is caused by a blockage in
        the bile duct (portal hypertension), usually by gallstones. Post-hepatic jaundice will
        have increased conjugated bilirubin in the serum.
      Hepatic jaundice is from the inability of hepatocytes to conjugate and excrete bilirubin.
        This includes acute hepatitis, hepatotoxicity and alcoholic liver disease. Hepatic jaundice
        will have increased unconjugated bilirubin in the serum. In alcoholics, their
        conjugated bilirubin can also be high.



58
      In alcoholics, their unconjugated bilirubin levels are high in the
       serum because their hepatocytes are damaged. Their conjugated
       bilirubin levels are high because they also lack albumin, ascites
       occurs, and the abdominal fluid puts pressure on bile duct, so the
       conjugated bilirubin is not removed from body. It gets reabsorbed
       by intestines, and the serum levels of conjugated bilirubin are also
       increased. Treatment for ascites is to drain it out and take a
       diuretic. Gotta get the melon tapped!




59
     RBC PATHOLOGY
      Polycythemia (too many RBC’s)
      Anemia (too few RBC’s)
         Defective
            Iron Deficiency Anemia
            Aplastic Anemia (cells are not generated)
            Megaloblastic Anemia
            Thalassemia
            Hereditary Spherocytosis
            Sickle Cell Anemia
            G6PD Deficiency (Glucose 6 Phosphate Deficiency)
         Blood Loss (Hemorrhagic Anemia)
            Traumatic hemorrhage
            Hemolytic anemia (crosses over into the defective category)
                 Extrinsic (Acquired)
                 Intrinsic (Inherited)

60
     POLYCYTHEMIA
      This condition is too many RBC’s, affects viscosity and
       blood flow, and causes an increased work load for the
       heart. The heart needs a more forceful
       contraction, becomes enlarged over time. It is
       something to be concerned about, since there is an
       underlying problem that keeps the RBC’s developing too
       quickly. The heart can only enlarge safely to a certain
       limit; after that, it cannot pump properly, and the person
       can get heart failure. Types of polycythemia:


61
     Types of Polycythemia
      Relative Polycythemia
      Absolute Polycythemia
        Primary
        Secondary




62
     Relative Polycythemia
      This is a decrease in the plasma volume (dehydration), but
       the RBC count is normal. The hematocrit will be high,
       and EPO is normal, since it is the ratio of RBC’s/plasma.
       Before thinking it is primary polycythemia, check the heart
       rate, urine output, and ask about dehydration. A dehydrated
       person will have high hematocrit, low blood pressure, high
       heart rate, and low urine output.




63
     Absolute Polycythemia
      This is the overproduction of red blood cells, and may be due
       to a primary process in the bone marrow (a
       myeloproliferative syndrome), or it may be a reaction to
       chronically low oxygen levels.




64
          Primary Polycythemia
          (Polycythemia Vera, or idiopathic polycythemia)

 Problem with myeloproliferation: There is a problem with stem cells replicating too
     much (can also affect WBCs). If the problem is in the hemocytoblasts, all cells
     increased. If just the myelogenous stem cell is a problem , the lymphocytes are not
     elevated. The hematocrit is high and EPO levels will be low because the
     kidneys are satisfied with enough oxygen, but the stem cells don’t obey the negative
     feedback. Kidneys are normal. Treatment is to donate blood frequently, and replace
     with IV of isosmotic solution.




65
        Secondary polycythemia
 Problem is a reaction to chronically low oxygen levels, such as during pregnancy,
  or living in high altitudes. In this case, hematocrit is high and EPO level
  is high. The kidneys are normal. Treatment is just to monitor the situation for
  secondary problems: these people need the extra oxygen.
 Problem in the kidneys, causing inappropriate increase in EPO. May be caused by
  kidney disorder, tissue hypoxia (from heart or lung disease, including smoking),
  hepatic problems, or athletes’ blood doping. Hematocrit is high and EPO is
  high.Treatment is low flow oxygen.




66
   RBC pathology--Polycythemia- An elevated
   hematocrit --an increase in the number of erythrocytes in the blood.

  How does polycythemia affect blood viscosity and
  thus affect blood flow?

Three Pathophysiological Categories of Polycythemia
1.Relative Polycythemia (Red Blood Cell Mass Normal,
Plasma Volume Decreased) – re-hydrate patient

                    2. Polycythemia Vera               3. Secondary Polycythemia

  Pathophysiology   Stem Cell Disorder- genetic        Tissue hypoxia increasing EPO production
                    problem or cancer                  or due to renal or hepatic disease causing
                                                       inappropriate increase in EPO production,
                                                       respiratory, or cardiac failure, high altitudes,
                                                       pregnancy, etc.

  CBC               Hct and often WBC and platelets    Only Hct is increased
                    are increased (total blood
                    volume)
  EPO level         Decreased or low normal            Normal or increased


67Treatment         Blood let and add istonic saline   Low flow oxygen if necessary
ANEMIA
 Anemia is any condition that causes a reduced oxygen
  carrying capacity.
 It is not defined as a low Hct, since that is only one type of
  anemia.
Two categories of anemia:
 Defective RBC Production
    Dietary
    Genetic
 Blood Loss (Hemorrhagic Anemia)
    Traumatic
    Hemorrhagic
     Defective RBC Production
      Dietary (will get better when diet improves)
          Iron Deficiency Anemia (abnormal Hgb)
          Megaloblastic Anemia (abnormal cell size)
      Genetic
        Aplastic Anemia (cells are not generated)
        Thalassemia (abnormal Hgb)
        Hereditary Spherocytosis (abnormal membrane)
        Sickle Cell Anemia (abnormal Hgb)
        G6PD (Glucose 6 Phosphate) Deficiency (cannot repair own
          damage)


69
     Blood Loss
     (Hemorrhagic Anemia)
      Blood Loss (Hemorrhagic Anemia)
        Traumatic Hemorrhage
        Hemolytic Anemia (genetic defect in Hgb, but considered in this
         category)
          Extrinsic (Acquired)
          Intrinsic (Inherited)




70
                                      Anemia
         A Condition where the blood has an abnormally low oxygen-
                 carrying capacity from low Hb concentration
       •Why are anemic individuals often short of breath, fatigued, and chilly?

                   Blood loss                                      Defective RBC production

     Hemolytic                       Hemorrhagic                          Iron deficiency
                                                                          Low MCH, MCHC
                                            Chronic                       and MCV
                                            (leads to iron def.)
acquired                inherited
                                            acute                         aplastic
      Transfusion                                                        megaloblastic
      incompatibility        Thalassemia-
                             MHC and MCV
                             low
        venom
                             Sickle Cell-
        drugs
                             Hereditary spherocytosis-loss of
                             spectrin normal MHC and
                             increased MCHC
71                            G6PD deficiency
     REVIEW
     MCH/MCV = MCHC
      MCV is the blood volume of the blood cell (small =microcytic, large =megaloblastic)
      MCH is the amount of Hgb in a RBC (low =hypochromic)
      MCHC is the concentration of Hgb compared to the entire volume of the cell.


     If you got 50/100 on an exam, your score is 50%. Let’s say this is normal:
      MCH = 40
      MCV = 80
      Then MCHC is 40/80 = 50%




72
      If cells are megaloblastic (elevated MCV) and normotonic (MCHC is normal), the cell got
        bigger, but the amount of Hgb must have increased as the cell enlarged. This is the case with
        megaloblastic anemia. The MCV might be 80 (elevated), the MCV might be 160 (elevated) but
        the MCHC is 80/160 = 50% (normal).


      What happens to the MCHC if cells are microcytic (low MCH) and hypochromic (low MCV)?
      Ratio may be 20/60, so MCHC is low (33%). This is seen in thalassemia and iron deficiency
        anemia.


      In some diseases, the person starts out with normochromic and normocytic cells, but with
        time, the cell shrinks, but hemoglobin stays the same. This will be a low MCH, normal MCV,
        low MCHC.
      Example: 20/80 = 25% MCHC.


      Be mindful of the size, amount of hemoglobin, and how the MCHC will change.




73
     IRON DEFICIENCY ANEMIA
      Either the person does not eat enough iron, or cannot absorb iron
       from the intestine, or not enough iron is in storage. This causes the
       hemoglobin to not be made correctly. Cells become
       microcytic, hypochromic, and low MCH, MCV, MCHC.
       Children and pregnant women often get this form of anemia.
       NOTE: Iron pills are bright red, look like candy; be careful!
       Children can get them and overdose. Iron deficiency anemia often
       causes weird cravings for things like dirt and charcoal. They often
       like to chew ice all the time. Anemia is there because there is not
       enough iron, can’t carry the oxygen. When the cells are too small,
       their membranes are not properly flexible, get hung up on
       reticulocytes, and destroyed.

74
Defective- Iron Deficiency
      almost always blood loss (chronic)
      exceptions (children, pregnancy)
      Understand iron metabolism- transport
       and storage of iron (apotransferrin to
       transferrin; apoferritin to ferritin;
       hemosiderin)
      Cells can be hypochromic and microcytic
       and poikilocytotic (too little Hemoglobin)
       due to insufficiency
      Decreased, MCH, MCHC and MCV
       (microcytic)
      Pica




75
     MEGALOBLASTIC ANEMIA
      Caused by lack of dietary vitamin B12 and folic acid
      A coenzyme is a non-protein chemical compound that binds to a protein and
       is required for the protein's biological activity. Coenzymes are called "helper
       molecules" since they assist in biochemical transformations. They help an
       enzyme to be more efficient. Coenzymes are not proteins, they don’t have
       amino acids to provide a binding site, unlike an enzyme (which is a catalyst).
       Many coenzymes are vitamins, or made from vitamins. The coenzyme binds
       to a different area on the enzyme and causes the enzyme to shift so
       that its substrate binding site opens up to allow the substrate to
       bind.The enzyme’s amino acids have to be in correct order to allow the proper
       binding site for its substrate. The coenzyme does not change.




76
      Megaloblastic
      anemias-
      Defective

 deficiency in dietary Folic acid or Vitamin B12
 Coenzymes in synthesis of thymidine; DNA synthesis is halted and therefore
  mitosis rates are low
 RNA production is elevated, Elevated rates of protein synthesis
 Cells become megaloblastic, irregularly shaped (poikilocytotic) and have
  fragile membranes so they are removed sooner (hemolytic)
 Increased MCV, increased MCH and normal MCHC (increased Hb synthesis)


 77
     Vitamin B12 and folic acid
     are coenzymes
      They are important for synthesis of thymine (a DNA nucleotide).
       Lack of thymine still allows DNA replication, but the cell cannot
       divide, so it gets bigger. Since the cell can use its RNA, the focus is
       on protein synthesis. Megaloblastic cells get larger, can’t divide,
       but protein synthesis continues, so there is an increase in Hgb in
       the cell. MCH and MCV go up, but proportionally to each
       other. Can get 50/100 and 100/200. Stem cells stay locked in the
       growth phase.




78
        What is a coenzyme?
 This is the missing
 fragment of the enzyme.
 When this is vacant, the
 apoenzyme doesn’t have                                    Substrate
 the proper conformation                                   A+ B
 to function.                                        X
                              Enzyme                     This is the
                                                         enzyme’s active
                                                         site, the working
                                                         end of any
                                                         enzyme.


                            This is the coenzyme.          Product C
                            Our vitamins are
                            coenzymes, linking to
                            particular apoenzymes.
79
     Folic acid
      Folic acid is actually another B vitamin (B9). It is found in
       vegetables (especially green leafy ones), fortified grains, and
       fruits. The liver has several months’ storage for folic
       acid. People who are often deficient in folic acid are children
       and pregnant women, people with poor nutrition,
       alcoholism, or sprue (iliac disease, loss of microvilli in small
       intestine, don’t absorb as much).




80
     Vitamin B12
      Vitamin B12 can only be synthesized by bacteria and is found primarily in meat, eggs and
        dairy products. Because strict vegetarians (vegans) don’t eat these products, they are
        often deficient in vitamin B12, unless they take it in pill form. Vitamin B12 cannot be
        absorbed from the intestines to the bloodstream without intrinsic factor, which is
        secreted by the parietal cells in the stomach. People who have had a gastrectomy also
        lose their parietal and chief cells. Remember, parietal cells release intrinsic factor and
        HCL (P  I + HCL … don’t get into a ―pickle‖ on a test). Chief cells in the stomach
        make pepsinogin, and HCl converts that to pepsin (digestive enzyme). Intrinsic factor
        is needed to allow the small intestine can absorb vitamin B12. People who lack
        of intrinsic factor from gastric surgery will need weekly vitamin B12 shots for life. They
        can’t take it orally because it cannot be absorbed without the intrinsic factor. A person
        who has megaloblastic anemia from a lack of intrinsic factor is said to have a particular
        type of megaloblastic anemia, called pernicious anemia. The liver has several
        years’ storage of vitamin B12 (3-5 years).




81
   Megaloblastic Anemias
  • Folic acid
       –Leafy green veggies
       –Greater demand during pregnancy for neural tube
       closure.
       –Stored supply (liver-6-9 months)
       –Poor nutrition, alcoholism, sprue, and anti-cancer
       drugs interfere
 Vitamin B12
   Meat, dairy, eggs
   Stomach mucosa; parietal cells produce intrinsic factor, a glycoprotein
    which is necessary for Vitamin B12 absorption. Join in stomach, then Vit
    B12 released and absorbed in the ileum.
   Seen with poor nutrition and strict vegetarians/ gastritis or gastrectomy,
    gastric atrophy, when lack IF
   Stored supply (liver 3-5 years)


82http://www.nlm.nih.gov/medlineplus/ency/article/000569.htm
     APLASTIC ANEMIA
     (CELLS NOT GENERATED)
     Primary aplastic anemia is idiopathic (unknown cause). Stem cells are not replicating
        enough. Need stem cell transplant.
     Secondary aplastic anemia can be caused by several things.
      Drugs like antibiotics (chloramphenicol) might cause loss of stem cell production
      Chemicals (pesticides with benzenes)
      Radiation
      A virus
      Malignancy
      Immune suppression
      Decreased EPO from any of the following: Problem with kidney. Rena disease, AIDS,
        chronic infections, hypometabolic state with protein deprivation, or hypopituitarism.




83
Defective- Aplastic
anemia

     • Primary
        idiopathic
     • Secondary
        Drugs - chemotherapy, antibiotics,
                                                          Compare the 2 slides of red bone marrow.
        Chemicals - benzene                              Blue dots indicates developing blood cells.
        Radiation                                        Left-hand slide is during aplastic anemia;
                                                          right-hand slide is almost back to normal
        Immune suppression of stem cell
        Malignancy
        Hypoproliferative from reduced
         erythropoietin                                                     Therapy?
             Renal Disease, AIDS, chronic infections,
              Hypometabolic state--protein deprivation,
              hypothyroidism, hypopituitarism

84
     THALASSEMIA
      Alpha Thalassemia
      Beta Thalassemia
        Major Beta Thalassemia
        Minor Beta Thalassemia




85
     Alpha Thalassemia
      Alpha Thalassemia is a mutation in one or more of the gene that makes the alpha
        globin chains of hemoglobin.You need two alpha globin chains in each hemoglobin
        molecule. If there are not enough, the Hgb molecule substitutes another beta globin
        chain, so the hemoglobin is now A1B3 or just A0B4, both of which will precipitate out of
        solution, interfering with DNA replication, gene expression, and development. Cells
        from alpha thalassemia are microcytic, hypochromic. Low MCV low MCH, but not
        proportionally. There are three genes that code for alpha globin, so alpha thalassemia
        is not common. You get two of these genes from one parent, and two from the other
        parent. If you have a mutation in one gene, there are three other genes that
        can make the alpha globin, so there are no problems. But if there are
        mutations in two of the genes, might have mild episodes of anemia, never
        diagnosed as thalassemia. If you have 3 genes damaged, will have chronic
        problem. All 4 genes damaged, will die in utero.




86
     Beta Thalassemia
      Beta Thalassemia has only two genes that code for beta globin.You get one gene from
        one parent, one from the other parent. A mutation in just one gene can be a problem, so
        beta thalassemia is more common than alpha thalassemia. Beta thalassemia interferes
        with cell function. Cells are microcytic, hypochromic, and MCV, MCH, and
        MCHC are all low. Because these defective cells are phagocytized in the liver and
        spleen, person gets hepatosplenomegaly. Because these cells are removed from
        circulation, EPO levels are high, more RBC’s are made, and this causes expansion of
        intermedulary cavity (where Erythropoiesis is going on), and this causes skeletal
        abnormalities; also get iron overload and cellular toxicity. In severe cases,
        there will be reversal to fetal hemoglobin: the gene for gamma globulin chains is
        turned on again, and the fetal hemoglobin will take the place of the missing alpha chains.
        Fetal hemoglobin has less affinity for oxygen, but it’s better than nothing.
          Thalassemia Major (Cooley’s anemia): both genes are mutated (homozygous)
          Thalassemia Minor: one gene is mutated (heterozygous).




87
     What are the Thalassemias?
 A group of diseases characterized by
     defects in synthesis of one or more
     globin chains (-, -thalassemia)
    Some severe, others mild
    Unaffected chain is in excess and
     accumulates in erythropoietic cell
     and causes impaired DNA synthesis
    Hypochromic, microcytic
    Organ failure
    Splenomegaly/hepatomegaly




88                             http://sickle.bwh.harvard.edu/menu_thal.html
     Thalassemia- 2
      Thalassa (Greek) = Sea
      -Thal or Thal. major
       (Cooley’s anemia)
        Shortened RBC lifespan, early
           removal (hemolysis)
          Expansion of intramedullary spaces
           (erythropoiesis)
          Skeletal abnormalities
          Increased iron absorption, iron
           overload and its consequences
          HbF can persist



89
     HEREDITARY SPHEROCYTOSIS (HS)
      HS is the most common inherited blood membrane disorder.
       Initially, all three values of MCV, MCH, and MCHC are normal.
       People with HS lack a certain protein, so the membrane
       becomes smaller, all inside becomes smaller, and since
       membrane is also an abnormal shape, the cells are phagocytized.
       MCV decreases, MCH stays the same, MCHC decreases. If
       the room collapses with the same 100 people in it, everything
       inside is more concentrated. Know just the end result.




90
     Hereditary spherocytosis
     • Spherocytosis (membrane)-microcytic
      (MCV ), normochromic, and spherical
      (poikilocytic). Easily ruptured. MCHC is
      INCREASED!
       • Most common inherited blood membrane
         disorder
       • Autosomal dominant
       • Gradual loss of membrane, so MCHC increases Photo credit:
       • Treat with splenectomy                      http://www.nlm.nih.gov/medlin
                                                    eplus/ency/images/ency/fullsiz
                                                    e/1220.jpg




91
     SICKLE CELL ANEMIA
      Sickle Cell Anemia is from a gene mutation that causes a defect in the beta
       globin chain, not the same mutation as thalassemia. Glutamic acid (polar,
       hydrophilic amino acid) is replaced by Valine (nonpolar amino
       acid) in position 6. At first, all three values are normal for MCV, MCH,
       MCHC. There are no problems as long as the RBC does not sickle. It sickles
       from being near hypoxic tissue; causes the beta globin chains line up
       in long rods (change in shape). When the cells are in this sickle shape, it
       blocks blood vessels, impedes blood flow, generates even more hypoxia, and
       more sickling. Things that cause tissue hypoxia include being at high altitudes
       (airplane or mountain climbing), scuba diving, sleeping (breathing is more
       shallow while sleeping), respiratory or other illness, overexertion. These
       conditions lead to a sickle crisis, which is very painful. The cells are caught in
       reticular fibers and removed, resulting in a reduced RBC count, and anemia.



92
Sickle cell trait (heterozygous) vs. Disease (homozygous)
         The defective gene is on chromosome 11; you get one chromosome 11 from mom and one from dad.
         If both parents are heterozygous and you inherit two normal chromosomes (25% chance), both beta
          globin chains are normal, you do not have sickle cell disease or sickle cell trait, and you can make A2B2.
         However, if you live in Africa, you might die from malaria. That’s why there are not a lot of people in
          Africa that have both normal chromosomes.
      
         Sickle Cell Disease (HgbSS) is when you inherit both abnormal chromosomes (25% chance of this
          happening from two heterozygous parents). This form is deadly; they tend to die from anemia.
      
         Sickle Cell Trait (HgbSA) is when you inherit one normal chromosome and one abnormal (50%
          chance), you can make a mixture of hemoglobin: some will be A2B2 (normal) and some will have normal
          alpha chains but the beta chain is affected. This is Sickle Cell Trait, and is not as severe as Sickle Cell
          Disease. The heterozygous form is often seen in Africans, those from a country that has a lot of malaria.
          Those who have one bad copy can survive malaria. Those who have two good copies die of malaria. Those
          with two bad copies die of anemia.




 93
         Sickle Cell
         Anemia-
         hemolytic/inherited
 Gene defect; defect in code for  chain leads to HbS
 Nucleotide mutation leads to amino acid substitution
 Valine (nonpolar) is substituted in place of glutamic
      acid (polar) in position #6
 When peptide chain folds, it doesn’t take on the proper
      shape (conformation)!
     β chains link together and become stiff rods under low-
      O2 conditions.
     RBCs to become sickle-shaped
     clog small blood vessels.
     Sickle cell (hemoglobin) HbS; normochromic,
      normocytic poikilocytic, during episode
     Easily ruptured- hemolysis



    94
    http://www.dnai.org/text/mediashowcase/index2.html?id=609
     Review of Mendelian Genetics
             For any gene, carry two copies (alleles), one from each of our parents.

                   2 copies of                                            Gene for beta chain
                   Chromosomes #11

             We express each of these genes in a codominant fashion, that is, all the Hb in each
                erythrocyte is a mix of the products (beta chains) of our two alleles.
             ―HbB‖ is the allele for the normal ―adult‖ beta chain; ―HbS‖ is the allele for the ―sickle‖
                beta chain.
                 If our genotype is HbB/HbB, our maturing erythrocytes will fill with?
                                   HbA (adult hemoglobin- with alpha and beta chains)
                 If our genotype is HbB/HbS, our maturing erythrocytes will fill with?
                                    HbA AND HbS (a mixture of normal adult hemoglobin and the ―sickle
                   variety)
                 If our genotype is HbS/HbS, our maturing erythrocytes will fill with?
                                    HbS (alpha and ―sickle‖ beta chain)

     http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/hbb.shtml
95
     How do you tell if a person has the trait
     or the disease?
      Run their hemoglobin on electrophoresis gel (Western Blot technique). Normal
         hemoglobin will travel all the way to the end of the plate. Hemoglobin with one
         mutation will travel half way down the plate. Hemoglobin with two mutations
         will travel only part way down the plate. Therefore, heterozygous plates will
         show two bands, (one that traveled a little, and one that traveled halfway).
     
      There is no advantage to having Sickle Cell Disease, but there is one advantage
         for having Sickle Cell Trait: malaria resistance. Those with Sickle Cell Disease
         can take a drug (hydroxyuria) to switch expression of genes to make HbF.




96
     “SC Trait” vs. “SC Disease”
      Heterozygous individuals make some
       normal Hb
         Milder disease only presenting with
          hypoxia
         Not life threatening; 9% of African
          Americans
         Evolutionary advantage: malaria
          resistance

      Homozygous individuals only make
       defective Hb
         Leads to ―crisis‖—low oxygen during
          sleep, cold, infection, acidosis, etc.
         Life threatening
         Hydroxyurea to convert over to HbF




97
     Malaria Resistance
      The good thing about having Sickle Cell Trait (the heterozygous form of Sickle Cell
         Anemia)is having malaria resistance. The bad thing is dealing with frequent hypoxic
         crisis.
     
      Malaria (―bad air‖) is a disease caused by plasmodium, a protozoan that is transmitted by
         mosquitoes. Mosquitoes only live on nectar, except females when they are pregnant.
         When a mosquito bites one infected person, it takes up the plasmodium, and spreads it to
         the next person it bites. The organism travels to liver and invades RBCs, where it is
         hidden from the immune system. It can replicate in there and the immune system cannot
         detect it. However, its metabolism within the RBC creates hypoxia there, and cell with
         the Sickle Trait will sickle, get hung up on reticular fibers, and be phagocytized, killing
         the parasite. Therefore, a person with Sickle Cell Trait has a higher rate of surviving
         malaria.




98
Malaria




 Malaria (Latin) = bad air, myth, false explanation for disease
 Disease caused by infection with parasite Plasmodium
 Parasite multiplies and undergoes several different stages in its lifecycle.
  Moves to liver, then human RBC. Ruptures cells, multiplying and reinfecting
  new RBCs. High fevers.
 Evades our immune system defenses
 The vector for transmission: the female anopheles mosquito
  99
      What does this have to do with
      erythrocytes sickling?
       Parasite’s disadvantage when
        erythrocytes are rapidly
        removed from circulation
       Erythrocyte destruction means
        fewer parasite numbers!
       Easier for individual to fight the
        infection
       Advantage to humans with SS
        ―trait‖, not with SS ―disease‖




100    http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html
       http://www.youtube.com/watch?v=szlfndj0TFE
      G6PD DEFICIENCY:
      GLUCOSE 6 PHOSPHATE DEFICIENCY
         This is the most inherited enzyme defect, x-linked. RBC’s
          don’t have organelles, so they are more vulnerable to damage from
          oxidants, which cause methemoglobin and denaturation of Hgb.
          Oxidative damage can also cause proteins to cross link with each
          other, making the RBC membrane less fluid and flexible; they
          precipitates out of solution and get phagocytized. These cells also
          can’t carry oxygen because iron has to be in the ferrous 2+ form.
          Oxidative damage causes ferrous iron to lose an
          electron, becoming ferric +3, which cannot transport
          oxygen.



101
       Glutathione is an enzyme that helps remove the oxidative damage. Glutathione
        will donate an electron to reduce ferric iron (+3) to ferrous (+2). The enzyme
        is present in other cells as well, serving as an antioxidant. It is the oxidative
        damage repair man. To keep it working (it gives electrons), it needs a supply of
        electrons.You have to keep it in a reduced state. To do that, it needs glucose 6
        phosphate. If you lack that, RBC does not have the enzyme to repair oxidative
        damage, gets misshaped. People who have g6DP have to watch what they eat.
        Oxidative drugs (like antimalarials) and foods high in oxidants (such as fava
        beans) can cause serious health problems. G6PD deficiency is prevalent in the
        Middle East, where fava beans are commonly part of the diet; those with the
        enzyme deficiency have to be careful not to partake of that food.




102
      G6PD Deficiency
       Blood loss, hemolytic, inherited
       Most common inherited enzyme
          defect
         X-linked
         Many mutations (genetic variants)
         RBCs more vulnerable to oxidants and
          causes methemoglobin and
          denaturation of Hb
         Antimalarial drugs can cause hemolysis
          in African populations (10%)
         SEVERE deficiency in people of
          Mediterranean descent.
         Fava beans



103
      BLOOD LOSS ANEMIA
       HEMORRHAGIC ANEMIA
        ACUTE
        CHRONIC
       HEMOLYTIC ANEMIA
        EXTRINSIC
        INTRINSIC




104
      HEMORRHAGIC ANEMIA
       Acute hemorrhage can lead to hypovolemia and shock.
        Normocytic, normochromic, normal MCV, MCH, MCHC
        are normal
       Chronic hemorrhage (bleeding ulcer from oversecretion of HCL
        by parietal cells) can lead to microcytic, hypochromic; low
        MCV, MCH, and possibly low MCHC. RBC’s eventually have
        to be made smaller and with less hemoglobin because the stomach
        ulcer diminishes iron absorption. If iron is not absorbed fast
        enough, they get iron deficiency anemia. Considered
        hemorrhagic anemia, but can becomes iron deficiency
        anemia over time.


105
      HEMOLYTIC ANEMIA
      RBC’s rupture inside vessels.
       Extrinsic (Acquired): not a problem with RBC,
        something like snake venom is causing the problem, or
        immune reaction, blood transfusion not matching, or drug
        reaction. Normal in all three values, MCH, MCH,
        MCHC.
       Intrinsic (inherited): problem is how the RBC is made.




106
      Blood loss-hemorrhagic
       Blood Loss- normocytic,
        normochromic (normal MCV,
        MCH, MCHC)
         Acute, leads to hypovolemia, shock
         Chronic hemorrhage can lead to
          microcytic, hypochromic RBC due
          to lack of iron absorption (can’t
          absorb fast enough—iron
          deficiency anemia)
       Plastic blood? Water soluble
        paste; no refrigeration



                                               http://www.reuters.com/news/video/videoStory?videoId=54039



107
      Blood Loss-
      Hemolytic, acquired

   Acquired/ extrinsic-
      normocytic,
      normochromic (normal
      MCV, MCH, MCHC)
       • Immune responses,
        mismatch typing, HDN,
        venom, drugs

                                Image credit:
                                http://wiki.nus.edu.sg/display/Hemolysis/Overview+of
                                +Hemolysis


108

				
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