Hereditary Spherocytosis: Review of the Genetic Disorder

Hereditary Spherocytosis: Review of the Genetic Disorder Ginamar Galvan Abstract This review is on the studies of several scientists whom completed research on the genetic disorder, spherocytosis. Based on several articles in the literature, it was learned that spherocytosis is an inherited anemia caused by the dysfunction of the cell’s cytoskeleton. These articles provide information of hereditary spherocytosis comprising of the disorder on the molecular level and how the patient’s diagnosis is concluded using laboratory testing. Patients can be found to be affected on a certain level ranging from mild to severe. They are then prescribed remedial medical attention pertaining to their level. The research showed that a form of response is to undergo a splenectomy which can ease a patient’s ailment, but has been found to not correct the life span of erythrocytes unlike speculation that it did. Hereditary Spherocytosis: A Review on the Genetic Disorder Introduction Hereditary spherocytosis is an anemic disorder affecting the blood that causes erythrocytes to be produced as spheres while normal erythrocytes are shaped as concave disks. The spheroidal shape is caused by a loss of membrane surface relative to intracellular volume (Gallagher 2005). Spherocytosis is genetically based, meaning that it can be passed down from either parent who already encompasses the disorder. This disorder can be found in all racial classifications but is more prevalent in Caucasians (Oliveira et.al 2012). Spherocytosis in Northern Europe and North America have a 1 in 5000 births in reported incidences and is usually the cause of inherited chronic hemolysis (Huq et al., 2010 and Bolton-Maggs et al., 2004). In the reviewed literature, spherocytosis has been researched and discussed regarding various aspects of this disorder, including the functionality of erythrocytes and what occurs after diagnosis. Cellular Level of Spherocytosis In 1871, hereditary spherocytosis was first explained and the first splenectomy was also performed shortly after (Bolton-Maggs et al., 2004). Between family members, the expression of spherocytosis is somewhat similar but the degree of severity differs throughout. The cause of the irregular shape and lifespan of the erythrocytes is the defect of an element in the cytoskeleton which is made of proteins in which the vertical attachment of the proteins to the lipid bilayer membrane is affected and therefore it is weakened (Bolton-Maggs et al., 2004). Other elements that influence the shape of the cell includes problems with spectrin, ankyrin, band 3 and/or protein 4.2 and the severity of the disorder is influenced by how many of these proteins are affected (Bolton-Maggs et al., 2004). Sodium dodecyl sulfate-polyacrylamide gel electrophorese is used as to determine whether or not these proteins have deficiencies. The defects in the genes of spherocytosis are present in five genes in chromosomes 1, 8, 14, 15 and 17 (Oliveira et al., 2012). Dysfunctions of these genes affect the membrane of the red blood cell which can threaten the cytoskeleton which is meant to maintain the form and elasticity of the cell. When the cytoskeleton is infringed upon, the red cell becomes abnormally shaped and does not live as long as a normal healthy cell (Oliveira et al., 2012). According to the article, â€Å"Guidelines for diagnosis and management of hereditary spherocytosis†, a hundred and seventy-four individuals were recruited from a hundr ed and twenty-three families and spectrin-deficient pro-bands were a larger cause than any other protein defect in patients when compared to parents who were seemingly regular. Diagnosis of Spherocytosis Hereditary spherocytosis is usually diagnosed when the patient is a child who has a varying extent of anemia, jaundice, and splenomegaly (Bolton-Maggs et al., 2004). Family history is also very important when diagnosing because in most cases seventy-five percent of patients will have a family history of the disorder (Gallagher 2010). There are different varieties at which hereditary spherocytosis affects people and treatments can sometimes require blood transfusions. Complications may develop which include severe anemia which may cause growth delay, deferred sexual maturation, tumors, and skin ulcers and many of these patients are transfusion dependent (Gallagher 2010). The patients that participated in the clinical study at the Pediatric Hematology Center of Hospital das Clà ­nicas, Universidade Federal de Minas Gerais in the journal, â€Å"Clinical course of 63 children with hereditary spherocytosis: a retrospective study†, were followed for about 19 years and had scheduled follow ups for every three months or in some cases more often if it was deemed necessary. They were diagnosed based upon their clinical history, physical examination and tests done in the laboratory and family histories were studied. Patients were classified as mild, moderate or severe depending on their hemoglobin concentration, bilirubin concentration and reticulocyte count and were also screened by ultrasonography to see if they had cholelithiasis. Splenectomy happened when there is an increase in the size of the organ and hemoglobin is decreased while reticulocyte count increased. Ones that needed a spleen sequestration were given immunizations and penicillin. When hemoglobin and reticulocyte count both decreased the patient was categorized to be in aplastic crisis. Most patients have somewhat balanced hemolysis accompanied by slight to average anemia. Anemia can be asymptomatic except for some fatigue and jaundice occurs in patients about half of the time which is usually in association with viral infections (Gallagher 2010). When some patients’ erythrocytes are stressed, patients may notice symptoms because their body is compensating with amplified erythropoiesis for their hemolysis (Gallagher 2010). In the journal, â€Å"Guidelines for diagnosis and management of hereditary spherocytosis†, several laboratory tests were used for diagnosis which includes osmotic fragility, acidified glycerol lysis test, osmotic gradient ektacytometry, and eosin-5-maleimide binding. Osmotic fragility is affected by elevated reticulocyte count while acidified glycerol lysis test detects autoimmune hemolytic anemia, hereditary persistence of fetal haemoglobin, pyruvate kinase and glucose-6-phosphate dehydrogenase deficiency as well as chronic renal failure. The osmotic gradient ektacytometry measures red cell deformability and the eosin-5-maleimide binding shows distinct histograms for red blood cells of spherocytosis. And in the journal, â€Å"Clinical course of 63 children with hereditary spherocytosis: a retrospective study†, the tests in the laboratory include the patient’s complete blood count, smear, reticulocyte count, concentration of bilirubin, positive osmotic fragility test and negative direct antiglobulin test. The osmotic fragility of the patients’ looked at the red blood cells in tubes that were washed in mixtures of increasing sodium chloride concentrations that were either put in incubation for 24 hours or not. Treatment of Spherocytosis There are ways to manage hereditary spherocytosis such as using folate therapy if the patient is severe, routine observation, frequent blood tests and in some cases splenectomy. Splenectomy can improve anemia in most patients including even the most severe. The splenectomy can be performed laproscopically and is the more preferred method because it causes less discomfort after the surgery, quicker recovery time, shorter hospitalization, and decreased costs. Splenectomy complications can occur including infection, bleeding and pancreatitis (Gallagher 2010). This operation used to be considered routine in hereditary spherocytosis patients but now is being reconsidered concerning the complications that can arise. The patients that usually receive a splenectomy are diagnosed to be severe or are older patients whose vital organs are inhibited vascularly (Gallagher 2010). Moderate patients possess more options and may not need a splenectomy. In â€Å"Clinical course of 63 children with hereditary spherocytosis: a retrospective study†, when patients were followed up, thirty-five patients needed transfusions and the need for them was more common in the severity group. Fourteen needed spleen sequestration, three had aplastic crisis, twenty-two had a splenectomy, seventeen developed cholelithiasis and ten had a cholecystectomy. Patients had different degrees of jaundice and anemia while most had some enlargement of the spleen. About 2/3 of the patients were anemic and seventy percent had splenomegaly. Patients that were classified as severe were younger and needed more blood transfusions than the other groups. A viral infection could lead to an overestimated severe classification because anemia level rises. All the patients were told and arranged to take folic acid. Does Splenetomy return Red Cell life span to normal? In some patients, anemia, reticulocytosis, and hyperbilirubinemia may disappear and cause some to infer that the patient no longer has problems with their red cell survival rate (Chapman 1968). Using a micro-hematocrit the hematocrit was determined, the reticulocytes were found in a methylene blue contained cover slip smear, and the red cell was counted by an electronic counter (Chapman 1968). The red cells that were being circulated were labeled with Diisopropyl fluorophosphates. DF32P were given to eleven patients that had a splenectomy two to twenty seven years before. The mean cellular hemoglobin content and concentration were higher in males than females. The concentration was of a normal degree in the females and above normal in all but one of the males (Chapman 1968). Mean red blood cell life spans were determined by the disappearance of radioactivity from the circulating blood by calculating linear regression. From the evidence the life span of the red blood cells seems to be somewhat dependent on age after their splenectomy. Patients that are within the same family do not show any consistency of the degree of spherocytosis expression. The red blood cell life span was averaged at about ninety-six days when normal life span is about one hundred twenty-three days (Chapman 1968). The range of life span between the patients ranged from seventy-six to one hundred eighteen days. From these results it is inferred that splenectomy does not repair red blood cell life span. Conclusion Hereditary spherocytosis is often identified in a patient’s childhood or early adult life, although, spherocytosis can be diagnosed at any age conditional to the entirety. This molecular disorder impacts their quality of life regarding aspects of treatment, finances, stress and recovery. As discoveries are made in this area of research, individuals will have a greater knowledge of spherocytosis and advancement in the treatment of this disorder including more options. References Bolton-Maggs, P. H. B., Stevens, R. F., Dodd, N. J., Lamont, G., Tittensor, P., KIng, M. -. (2004). Guidelines for the diagnosis and management of hereditary spherocytosis.British Journal of Haematology, (126), 455-474. Retrieved from http://www.bloodmed.com/contentimage/guidelines/2121.pdf Chapman, R. G. (1968). Red cell life span after splenectomy in hereditary spherocytosis.The Journal of Clinical Investigation,47(10), 2263–2267. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC297390/ Gallagher, P. (2005). Red Cell Membrane Disorders. Hematology 2005, 2005(1), 13-18. Retrieved , from http://asheducationbook.hematologylibrary.org/content/2005/1/13.long Huq, S., Pietroni, M. A. C., Rahman, H., Alam, M. T. (2010). Hereditary spherocytosis.J Health Popul Nutr.,28(1), 107-109. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2975852/ Oliveira, M. C. L. A., Fernandes, R. A. F., Rodrigues, C. L., Ribeiro, D. A., Giovanardi, M. F., Viana, M. B. (2012). Clinical course of 63 children with hereditary spherocytosis: a retrospective study.Rev Bras Hematol Hemoter,34(1), 9-13. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3459613/pdf/rbhh-34-009.pdf What Is The Importance Of Chelates In Biology? What Is The Importance Of Chelates In Biology? Chelation is the formation or presence of two or more separate bindings between a polydentate (multiple bonded) ligand and a single central atom. Usually these ligands are organic compounds, and are called chelants, chelators, chelating agents, or sequestering agents. The ligand forms a chelate complex with the substrate. Chelate complexes are contrasted with coordination complexes composed of monodentate ligands, which form only one bond with the central atom. The denticity of a central atom, of course, refers to the number of bonds formed by the central atom. Chelants, according to ASTM-A-380, are chemicals that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale. The chelate effect. The chelate effect describes the enhanced affinity of chelating ligands for a metal ion compared to the affinity of a collection of similar nonchelating (monodentate) ligands for the same metal. Consider the two equilibria, in aqueous solution, between the copper(II) ion, Cu2+ and ethylenediamine (en) on the one hand and methylamine, MeNH2 on the other. Cu2+ + en [Cu(en)]2+ (1) Cu2+ + 2 MeNH2 [Cu(MeNH2)2]2+ (2) In (1) the bidentate ligand ethylene diamine forms a chelate complex with the copper ion. Chelation results in the formation of a five-membered ring. In (2) the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of formation of Cu-N bonds is approximately the same in the two reactions. Under conditions of equal copper concentrations and when the concentration of methylamine is twice the concentration of ethylenediamine, the concentration of the complex (1) will be greater than the concentration of the complex (2). The effect increases with the number of chelate rings so the concentration of the EDTA complex, which has six chelate rings, is much much higher than a corresponding complex with two monodentate nitrogen donor ligands and four monodentate carboxylate ligands. Thus, the phenomenon of the chelate effect is a firmly established empirical fact. Cu2+ complexes with methylamine (left) and ethylenediamine (right) The thermodynamic approach to explaining the chelate effect considers the equilibrium constant for the reaction: the larger the equilibrium constant, the higher the concentration of the complex. Ethylene diamine tetra acetic acid, Widely abbreviated as EDTA is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve scale. Its usefulness arises because of its role as a hexadentate (six-toothed) ligand and chelating agent, i.e. its ability to sequester metal ions such as Ca2+ and Fe3+. After being bound by EDTA, metal ions remain in solution but exhibit diminished reactivity. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA. EDTA is used to bind metal ions in chelation therapy, e.g., for mercury and lead poisoning. It is used in a similar manner to remove excess iron from the body. This therapy is used to treat the complication of repeated blood transfusions, as would be applied to treat thalassaemia. EDTA acts as a powerful antioxidant to prevent free radicals from injuring blood vessel walls. Dentists use EDTA solutions to remove inorganic debris (smear layer) and prepare root canals for obturation. It serves as a preservative (usually to enhance the action of another preservative such as benzalkonium chloride or thiomersal) in ocular preparations and eyedrops. In evaluating kidney function, the complex [Cr(edta)]- is administered intravenously and its filtration into the urine is monitored. This method is useful for evaluating glomerular filtration rate. EDTA is used extensively in the analysis of blood. It is an anticoagulant for blood samples for CBC/FBEs (complete blood count also known as full blood examination). Laboratory studies also suggest that EDTA chelation may prevent collection of platelets on the lining of the vessel [such as arteries] (which can otherwise lead to formation of blood clots, which itself is associated with atheromatous plaque formation or rupture, and thereby ultimately disrupts blood flow). These ideas are theoretical, and have so far been proven ineffective; however, a major clinical study of the effects of EDTA on coronary arteries is currently (2008) proceeding. EDTA played a role in the O.J. Simpson trial when the defense alleged that one of the blood samples collected from Simpsons estate was found to contain traces of the compound. In nature Virtually all biochemicals exhibit the ability to dissolve certain metal cations. Thus, proteins, polysaccharides, and polynucleic acids are excellent polydentate ligands for many metal ions. In addition to these adventitious chelators, several biomolecules are produced to specifically bind certain metals . Histidine, malate and phytochelatin are typical chelators used by plants. Histidine (abbreviated as His or H) is one of the 22 proteinogenic amino acids. In terms of nutrition, histidine is considered an essential amino acid in human infants. After reaching several years of age, humans begin to synthesize it, at which point it becomes a non-essential amino acid. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. This carboxylic diacid is the active ingredient in many sour or tart foods. Malic acid is found mostly in unripe fruits. Malic acid has two stereoisomers, a left-handed L-enantiomer and a right-handed D-enantiomer, but only the L isomer exist naturally. The salts and esters of malic acid are known as malates. The malate anion is an intermediate in the citric acid cycle. Phytochelatins are oligomers of glutathione, produced by the enzyme phytochelatin synthase. They are found in plants, fungi, nematodes and all groups of algae including cyanobacteria. Phytochelatins act as chelators, and are important for heavy metal detoxification.They are abbreviated PC2 through PC11. A mutant Arabidopsis thaliana lacking phytochelatin synthase is very sensitive to cadmium, but it grows just as well as the wild-type plant at normal concentrations of zinc and copper, two essential metal ions, indicating that phytochelatin is only involved in resistance to metal poisoning. Phytochelatin seems to be transported into the vacuole of plants, so that the metal ions it carries are stored safely away from the proteins of the cytosol. In biochemistry and microbiology Virtually all metalloenzymes feature metals that are chelated, usually to peptides or cofactors and prosthetic groups. Such chelating agents include the porphyrin rings in hemoglobin and chlorophyll. Many microbial species produce water-soluble pigments that serve as chelating agents, termed siderophores. For example, species of Pseudomonas are known to secrete pycocyanin and pyoverdin that bind iron. Enterobactin, produced by E. coli, is the strongest chelating agent known. Porphyrins are a group of organic compounds of which many occur in nature. One of the best-known porphyrins is heme, the pigment in red blood cells. Heme is a cofactor of the protein hemoglobin. They are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at their ÃŽÂ ± carbon atoms via methine bridges (=CH-). Porphyrins are aromatic Hemoglobin (also spelled haemoglobin and abbreviated Hb or Hgb) is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates and the tissues of some invertebrates. Hemoglobin in the blood is what transports oxygen from the lungs or gills to the rest of the body (i.e. the tissues) where it releases the oxygen for cell use. In mammals the protein makes up about 97% of the red blood cells dry content, and around 35% of the total content (including water). Hemoglobin has an oxygen binding capacity between 1.36 and 1.37 ml O2 per gram of hemoglobin, which increases the total blood oxygen capacity seventyfold. Hemoglobin is involved in the transport of other gases: it carries some of the bodys respiratory carbon dioxide (about 10% of the total) as carbaminohemoglobin, in which CO2 is bound to the globin protein. The molecule also carries the important regulatory molecule nitric oxide bound to a globin protein thiol group, releasing it at the same time as oxygen. Heme group Chlorophyll (also chlorophyl) is a green pigment found in almost all plants, algae, and cyanobacteria. Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. However, it is a poor absorber of green and near-green portions of the spectrum, hence the green color of chlorophyll-containing tissues. Chlorophyll was first isolated by Joseph Bienaimà © Caventou and Pierre Joseph Pelletier in 1817. In geology In earth science, chemical weathering is attributed to organic chelating agents, e.g. peptides and sugars, that extract metal ions from minerals and rocks. Most metal complexes in the environment and in nature are bound in some form of chelate ring, e.g. with a humic acid or a protein. Thus, metal chelates are relevant to the mobilization of metals in the soil, the uptake and the accumulation of metals into plants and micro-organisms. Selective chelation of heavy metals is relevant to bioremediation, e.g. removal of 137Cs from radioactive waste. Applications Chelators are used in chemical analysis, as water softeners, and are ingredients in many commercial products such as shampoos and food preservatives. Citric acid is used to soften water in soaps and laundry detergents. A common synthetic chelator is EDTA. Phosphonates are also well known chelating agents. Chelators are used in water treatment programs and specifically in steam engineering, e.g., boiler water treatment system: Chelant Water Treatment system. Heavy metal detoxification. Chelation therapy is the use of chelating agents to detoxify poisonous metal agents such as mercury, arsenic, and lead by converting them to a chemically inert form that can be excreted without further interaction with the body, and was approved by the U.S. Food and Drug Administration in 1991. In alternative medicine, chelation is used as a treatment for autism, though this practice is controversial due to no scientific plausibility, lack of FDA approval, and its potentially deadly side-effects. Though they can be beneficial in cases of heavy metal poisoning, chelating agents can also be dangerous. The U.S. CDC reports that use of disodium EDTA instead of calcium EDTA has resulted in fatalities due to hypocalcemia. Other medical applications Antibiotic drugs of the tetracycline family are chelators of Ca2+ and Mg2+ ions. EDTA is also used in root canal treatment as a way to irrigate the canal. EDTA softens the dentin facilitating access to the entire canal length and to remove the smear layer formed during instrumentation. Chelate complexes of gadolinium are often used as contrast agents in MRI scans. Copper-64 is a radioactive nuclide of copper which has unique decay properties making it useful in nuclear medicine for both imaging and therapy. 64Cu-ATSM (diacetyl-bis(N4-methylthiosemicarbazone)) has been shown to increase the survival time of tumor-bearing animals with no acute toxicity. Areas of low oxygen retention have been shown to be resistant to radiotherapy because hypoxia reduces the lethal effects of ionizing radiation. 64Cu was believed to kill these cells because of its unique decay properties. In this experiment, animal models having colorectal tumors with and without induced hypoxia were administered Cu-ATSM. Cu-ATSM is preferentially taken up by hypoxic cells over normoxic cells. The results demonstrated that this compound increased survival of the tumor bearing hamsters compared with controls. In the control groups, death due to tumor burden occurred within 4 weeks while animals with a dose greater than 6 mCi of the radioisotope tumor growth was inhibited and survival increased. The results also suggested that multiple doses and a single dose of 10 mCi were equally effective while the multiple dose regimen i s safer for non-target tissue. Radiotherapy of cancer cells using 64Cu can be applied in medical research and clinical practice. The advantages of radiotherapy with beta emitters of this energy are that there is enough to do substantial damage to the target cells but the mean range in tissue is less than a millimeter so non target tissues are unlikely to be harmed. In addition, 64Cu is a positron emitter making it a viable PET imaging radionuclide which can give real time images of the physiological processes in the system. These abilities in conjunction enable accurate monitoring of drug distribution and biokinetics simultaneously. Radiotherapeutic efficacy of Copper-64 depends highly upon the radioligand delivery to the target cells, so the development of bifunctional chelates is central to development of 64Cus potential as a radiopharmaceutical. With sufficient development, 64Cu is likely to become a central element in nuclear medicine in the years to come. A preliminary study of the bio availability of iron- and zinc-glycine chelates Groups of rats were fed diets containing marginal levels of Fe and Zn as glycine chelates (tradename Chelazome, Albion Laboratories, Verona, New Jersey, USA), or the same level of mineral as ferrous sulphate or zinc carbonate. The Fe diets were fed to weanling rats for 4 weeks and the Zn diets to young adult rats for 5 weeks. Blood Hb concentrations were significantly higher in the group fed Fe-chelazome than ferrous sulphate, 149 and 128 g/l respectively (P