Tìm thấy 12+ kết quả cho từ khóa "Disorders of Hemoglobin"
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Disorders of Hemoglobin. Disorders of Hemoglobin: Introduction. Hemoglobin is critical for normal oxygen delivery to tissues. Hemoglobinopathies are disorders affecting the structure, function, or production of hemoglobin. Each consists of a tetramer of globin polypeptide chains: a pair of α- like chains 141 amino acids long and a pair of β-like chains 146 amino acids long.. The α-like genes (α,s) are encoded on chromosome 16;. the β-like genes (β,γ,δ,ε) are encoded on chromosome 11.
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Disorders of Hemoglobin. Low-affinity hemoglobins should be considered in patients with cyanosis or. Methemoglobin should be suspected in patients with hypoxic symptoms. who appear cyanotic but have a Pa O2 sufficiently high that hemoglobin should be fully saturated with oxygen. freshly drawn blood can be a critical clue. Intravenous injection of 1 mg/kg of methylene blue is effective emergency therapy.
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Acquired hemoglobinopathies include modifications of the hemoglobin molecule by toxins (e.g., acquired methemoglobinemia) and abnormal hemoglobin synthesis (e.g., high levels of HbF production in preleukemia and α-thalassemia in myeloproliferative disorders).. Table 99-1 Classification of Hemoglobinopathies. Structural hemoglobinopathies—hemoglobins with altered amino acid sequences that result in deranged function or altered physical or chemical properties.
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Thalassemias are the most common genetic disorders in the world, affecting nearly 200 million people worldwide. About 15% of American blacks. α-thalassemia trait (minor) occurs in 3% of. American blacks and in 1–15% of persons of Mediterranean origin. Β- Thalassemia has a 10–15% incidence in individuals from the Mediterranean and Southeast Asia and 0.8% in American blacks. The number of severe cases of thalassemia in the United States is about 1000.
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Heterozygotes are often symptomatic because a significant Heinz body burden can develop even when the unstable variant accounts for a portion of the total hemoglobin. Symptomatic unstable hemoglobins tend to be β-globin variants, because sporadic mutations affecting only one of the four α-globins would generate only 20–30% abnormal hemoglobin.. Hemoglobins with Altered Oxygen Affinity. High-affinity hemoglobins [e.g., Hb Yakima (β 99Asp ->.
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To date, these genome screening efforts have not yielded modifying genes, other than those known to affect the hemoglobin profile directly: e.g., persistence of fetal hemoglobin in adult life, α- thalassemia, or co-inheritance of other hemoglobin structural variants. The complexity of the data obtained thus far undermines the expectation that genome-. For example, genes affecting the inflammatory response or cytokine expression appear to be modifying candidates.
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Hydrops fetalis. homozygous α- thal-1. a When both α-alleles on one chromosome are deleted, the locus is called α- thal-1. when only a single α-allele on one chromosome is deleted, the locus is called α-thal-2.. b 90–95% of the hemoglobin is hemoglobin Barts (tetramers of γ-chains).. α-Thalassemia-2 trait is an asymptomatic, silent carrier state. α- Thalassemia-1 trait resembles β-thalassemia minor.
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Genetic counseling of the persons at risk for HbE should focus on the interaction of HbE with β-thalassemia rather than HbE homozygosity, a condition. No deleterious effects are apparent, even when all of the hemoglobin produced is HbF. These rare patients demonstrate convincingly that prevention or reversal of the fetal to adult hemoglobin switch would provide effective therapy for sickle cell anemia and β-thalassemia..
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DeSimone J et al: Maintenance of elevated fetal hemoglobin levels by decitabine during dose interval treatment of sickle cell anemia. Steinberg MH: Pathophysiologically based drug treatment of sickle cell disease. Switzer JA et al: Pathophysiology and treatment of stroke in sickle-cell disease: Present and future. Ware RE et al: Predictors of fetal hemoglobin response in children with sickle cell anemia receiving hydroxyurea therapy. Clasta S, Vichinsky EP: Managing sickle cell disease.
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The hemoglobin tetramer can bind up to four molecules of oxygen in the iron-containing sites of the heme. Salt bridges are broken, and each of the globin molecules changes its conformation to facilitate oxygen binding. Proper oxygen transport depends on the tetrameric structure of the proteins, the proper arrangement of the charged amino acids, and interaction with protons or 2,3-BPG..
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They should eschew empirical use of iron. yet iron deficiency can develop during pregnancy or from chronic bleeding.. Persons with α-thalassemia trait may exhibit mild hypochromia and microcytosis usually without anemia. HbA 2 and HbF levels are normal. Affected individuals usually require only genetic counseling. HbH disease resembles β- thalassemia intermedia, with the added complication that the HbH molecule behaves like moderately unstable hemoglobin.
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The most significant advance in the therapy of sickle cell anemia has been the introduction of hydroxyurea as a mainstay of therapy for patients with severe symptoms. Hydroxyurea (10–30 mg/kg per day) increases fetal hemoglobin and may also exert beneficial affects on RBC hydration, vascular wall adherence, and suppression of the granulocyte and reticulocyte counts. dosage is titrated to maintain a white cell count between 5000 and 8000 per µL.
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Qualitative Disorders of Platelet Function. Inherited Disorders of Platelet Function. Inherited Disorders of Platelet Dysfunction: Treatment. Acquired Disorders of Platelet Function
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Disorders of Granulocytes and Monocytes. Metabolic disorders—ketoacidosis, acute renal failure, eclampsia, acute poisoning. Inherited and acquired abnormalities of phagocyte function are listed in Table 61-3. The resulting diseases are best considered in terms of the functional defects of adherence, chemotaxis, and microbicidal activity. features of the important inherited disorders of phagocyte function are shown in Table 61-4.. Table 61-3 Types of Granulocyte and Monocyte Disorders.
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Disorders of Smell, Taste, and Hearing. Disorders of the Sense of Taste. Disorders of the sense of taste are caused by conditions that interfere with the access of the tastant to the receptor cells in the taste bud (transport loss), injure receptor cells (sensory loss), or damage gustatory afferent nerves and central gustatory pathways (neural loss) (Table 30-2)..
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Disorders of the Eye (Part 22). Descending cortical inputs mediating horizontal gaze ultimately converge at the level of the pons. They project directly to the ipsilateral abducens nucleus.
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Disorders of Granulocytes and Monocytes. Disorders of Adhesion. Two main types of leukocyte adhesion deficiency (LAD) have been described, LAD 1 and LAD 2. Both are autosomal recessive traits and result in the inability of neutrophils to exit the circulation to sites of infection, leading to leukocytosis and increased susceptibility to infection (Fig.
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Approach to the Patient: Disorders of the Sense of Taste. Electric taste testing (electrogustometry) is used clinically to identify taste deficits in specific quadrants of the tongue. The history of the disease and localization studies provide important clues to the causes of the taste disturbance.
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Disorders of Platelets and Vessel Wall. Disorders of production may be either inherited or acquired. In evaluating a patient with thrombocytopenia, a key step is to review the peripheral blood smear and to first rule out "pseudothrombocytopenia,".
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Disorders of the Eye (Part 1). Disorders of the Eye. The visual system provides a supremely efficient means for the rapid assimilation of information from the environment to aid in the guidance of behavior. The act of seeing begins with the capture of images focused by the cornea and lens upon a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain, banished to the periphery to serve as.