Passage
Beta-thalassemia is a blood disorder caused by reduced production of the β-globin subunit of hemoglobin. The erythrocytes in patients with beta-thalassemia are abnormally small, lack sufficient functional hemoglobin, and are decreased in number. These individuals require lifelong blood transfusions to correct their erythrocyte shortage. Each unit of blood transfused contains many milligrams of iron and, consequently, blood iron levels increase due to repeated transfusions. The excess iron is then continuously deposited in the organs, leading to organ damage.Transferrin (Tf) is a protein that binds free iron in the blood and plays a key role in erythropoiesis, which requires uptake of iron from the blood in a process facilitated by Tf and its cell surface receptor (TfR). Iron-bound Tf, known as holotransferrin (holoTf), binds TfR to form a complex that is brought into the developing erythrocyte in an endosome. Acidification of the endosome triggers a conformational change in holoTf, which allows the release of free iron into the cell and the recycling of the remaining complex components to the cell surface. Non-iron-bound Tf is referred to as apotransferrin (apoTf), and due to its iron-binding capability, researchers believe that apoTf injections may help prevent deposition of excess iron in the organs of patients with beta-thalassemia.To investigate the effect of apoTf administration in a mouse model of beta-thalassemia, mice homozygous for an inactivating deletion in the murine β-globin gene (Hbb th−3 /Hbb th−3 ) were given blood transfusions followed by apoTf injection. Measurements of non-transferrin-bound iron in the blood (NTBI), plasma holoTf, and urinary holoTf were taken immediately and at 15 days post-injection. Results revealed that NTBI decreased over the tested period. Experimenters hypothesized that apoTf mediated certain regulatory changes that reduced NTBI in Hbb th−3 /Hbb th−3 mice by increasing urinary holoTf excretion.
-Individuals with beta-thalassemia are at risk for developing an enlarged spleen. The resulting impairment of spleen function in these individuals would NOT affect:

Question

Passage
Beta-thalassemia is a blood disorder caused by reduced production of the β-globin subunit of hemoglobin.  The erythrocytes in patients with beta-thalassemia are abnormally small, lack sufficient functional hemoglobin, and are decreased in number.  These individuals require lifelong blood transfusions to correct their erythrocyte shortage.  Each unit of blood transfused contains many milligrams of iron and, consequently, blood iron levels increase due to repeated transfusions.  The excess iron is then continuously deposited in the organs, leading to organ damage.Transferrin (Tf) is a protein that binds free iron in the blood and plays a key role in erythropoiesis, which requires uptake of iron from the blood in a process facilitated by Tf and its cell surface receptor (TfR).  Iron-bound Tf, known as holotransferrin (holoTf), binds TfR to form a complex that is brought into the developing erythrocyte in an endosome.  Acidification of the endosome triggers a conformational change in holoTf, which allows the release of free iron into the cell and the recycling of the remaining complex components to the cell surface.  Non-iron-bound Tf is referred to as apotransferrin (apoTf), and due to its iron-binding capability, researchers believe that apoTf injections may help prevent deposition of excess iron in the organs of patients with beta-thalassemia.To investigate the effect of apoTf administration in a mouse model of beta-thalassemia, mice homozygous for an inactivating deletion in the murine β-globin gene (Hbb th−3 /Hbb th−3 ) were given blood transfusions followed by apoTf injection.  Measurements of non-transferrin-bound iron in the blood (NTBI), plasma holoTf, and urinary holoTf were taken immediately and at 15 days post-injection.  Results revealed that NTBI decreased over the tested period.  Experimenters hypothesized that apoTf mediated certain regulatory changes that reduced NTBI in Hbb th−3 /Hbb th−3 mice by increasing urinary holoTf excretion.
-Individuals with beta-thalassemia are at risk for developing an enlarged spleen.  The resulting impairment of spleen function in these individuals would NOT affect:

Quizplus · Accepted Answer

11ecba2d_0ffb_fd33_a3bf_6d5a21376af0_MD0008_00 The spleen is the largest lymphoid organ in the body. It is situated in the upper left portion of the abdominal cavity, just above the stomach and below the diaphragm. The spleen performs the following functions: Filters senescent (worn-out/aged) or damaged red blood cells (RBCs) from the blood. In addition to destroying foreign material, macrophages in the spleen trap and phagocytize aged RBCs and recycle their parts (Choice C). (Note: The liver is also involved in the removal and reuse of aged RBCs.) Serves as a reservoir for blood, which can be released in the event of a sudden drop in blood volume (Choice D). Participates in immune function by housing macrophages that phagocytize and destroy foreign substances and by serving as a site of B cell activation (Choice A). Each B cell expresses a unique antibody that recognizes and binds a specific pathogen, preventing it from entering host cells and marking it for phagocytosis. An activated B cell (ie, one that has come in contact with its corresponding pathogen) rapidly proliferates to produce memory and effector B cells. Effector B cells (ie, plasma cells) produce antibodies against the current infection, and memory B cells are responsible for long-term defense against a similar infection in the future. Because individuals without a functional spleen cannot mount B cell responses as efficiently, their lifetime risk of infection is increased. (Choice B) The pancreas is the primary organ responsible for regulating blood glucose levels. When blood glucose is high, pancreatic beta cells release the hormone insulin to promote cells to take up glucose, which is then either metabolized for energy or stored as glycogen in muscle and liver cells. When blood glucose is low, pancreatic alpha cells release the hormone glucagon to promote the production of glucose (via gluconeogenesis) and the release of glucose from glycogen stores. Removal of the spleen does not affect pancreatic function. Educational objective: The spleen is involved in immune function, blood storage, and the filtration and removal of senescent red blood cells from the blood.

Passage Beta-Thalassemia Is a Blood Disorder Caused by Reduced Production of of the β-Globin