| rdfs:comment
| - Das Hämoglobin Barts besteht aus vier gamma-Ketten. Es ist schwer löslich und reichert sich deshalb in den roten Blutkörperchen an. Zudem hat es eine extrem hohe Affinität zu Sauerstoff, was dazu führt, dass im Gewebe fast kein Sauerstoff mehr vorhanden ist. Hämoglobin Barts wird bei einer Erkrankung an α-Thalassämie produziert; in der schwerwiegendsten Form dieser Krankheit ist es die einzige Art von Hämoglobin, die sich noch im Körper befindet. In dieser Situation würde sich ein Hydrops fetalis entwickeln und dieser normalerweise vor oder kurz nach der Geburt sterben, außer es wird eine intrauterine Bluttransfusion durchgeführt. (de)
- Hemoglobin Barts, abbreviated Hb Barts, is an abnormal type of hemoglobin that consists of four gamma globins. It is moderately insoluble, and therefore accumulates in the red blood cells. Hb Barts has an extremely high affinity for oxygen, so it cannot release oxygen to the tissue. Therefore, this makes it an inefficient oxygen carrier. As an embryo develops, it begins to produce alpha-globins at weeks 5–6 of development. When both of the HBA1 and HBA2 genes which code for alpha globins becomes dysfunctional, the affected fetuses will have difficulty in synthesizing a functional hemoglobin. As a result, gamma chains will accumulate and form four gamma globins. These gamma globins bind to form hemoglobin Barts. It is produced in the disease alpha-thalassemia and in the most severe of cases (en)
- L'hémoglobine Barts, couramment abrégée Hb Barts, est une variante anormale d'hémoglobine constituée de quatre sous-unités γ-globine, c'est-à-dire qu'elle a pour formule γ4. Elle est assez peu soluble et s'accumule par conséquent dans les érythrocytes. Son affinité pour l'oxygène est très élevée, de sorte qu'elle ne libère pratiquement pas d'oxygène dans les tissus. Elle doit son nom au St Bartholomew's Hospital de Londres, surnommé St Barts, où elle a été découverte. (fr)
- L'emoglobina di Barts è una variante patologica di emoglobina tipica dell'α-talassemia, nella forma con tutti e quattro i geni della catena α mutati (--/--). Durante lo sviluppo intra-uterino si formano tetrameri γ (l'emoglobina fetale presenta due catene α associate a due catene γ: queste verranno sostituite dalle catene β a sviluppo completato) non funzionali perché presentano elevata affinità per l'ossigeno e difficoltà nel rilasciarlo a livello tissutale. La condizione non è vitale e il quadro clinico presenta epatosplenomegalia ed edema generalizzato con morte per idrope fetale. (it)
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| has abstract
| - Das Hämoglobin Barts besteht aus vier gamma-Ketten. Es ist schwer löslich und reichert sich deshalb in den roten Blutkörperchen an. Zudem hat es eine extrem hohe Affinität zu Sauerstoff, was dazu führt, dass im Gewebe fast kein Sauerstoff mehr vorhanden ist. Hämoglobin Barts wird bei einer Erkrankung an α-Thalassämie produziert; in der schwerwiegendsten Form dieser Krankheit ist es die einzige Art von Hämoglobin, die sich noch im Körper befindet. In dieser Situation würde sich ein Hydrops fetalis entwickeln und dieser normalerweise vor oder kurz nach der Geburt sterben, außer es wird eine intrauterine Bluttransfusion durchgeführt. Da Hämoglobin Barts durch alpha-Thalassämie erhöht wird, kann es, als gemessener Wert, für einen nützlichen Screening-Test zu dieser Krankheit sehr hilfreich sein. Diese Variante des Hämoglobins wurde so benannt, da sie im St Bartholomew’s Hospital in London entdeckt wurde. Das Krankenhaus hat den Spitznamen „St. Barts“, sodass man das Hämoglobin schließlich Hämoglobin Barts nannte. (de)
- Hemoglobin Barts, abbreviated Hb Barts, is an abnormal type of hemoglobin that consists of four gamma globins. It is moderately insoluble, and therefore accumulates in the red blood cells. Hb Barts has an extremely high affinity for oxygen, so it cannot release oxygen to the tissue. Therefore, this makes it an inefficient oxygen carrier. As an embryo develops, it begins to produce alpha-globins at weeks 5–6 of development. When both of the HBA1 and HBA2 genes which code for alpha globins becomes dysfunctional, the affected fetuses will have difficulty in synthesizing a functional hemoglobin. As a result, gamma chains will accumulate and form four gamma globins. These gamma globins bind to form hemoglobin Barts. It is produced in the disease alpha-thalassemia and in the most severe of cases, it is the only form of hemoglobin in circulation. In this situation, a fetus will develop hydrops fetalis and normally die before or shortly after birth, unless intrauterine blood transfusion is performed. Since hemoglobin Barts is elevated in alpha thalassemia, it can be measured, providing a useful screening test for this disease in some populations. The ability to measure hemoglobin Barts makes it useful in newborn screening tests. If hemoglobin Barts is detected on a newborn screen, the patient is usually referred for further evaluation since detection of hemoglobin Barts can indicate either one alpha globin gene deletion, making the baby a silent alpha thalassemia carrier, two alpha globin gene deletions (alpha thalassemia), or hemoglobin H disease (three alpha globin gene deletions). Deletion of four alpha globin genes was previously felt to be incompatible with life, but there are currently 69 patients who have survived past infancy. Table 1: α represents the presence of α-globin gene and- represents the deletion of α-globin gene. The chance of a fetus developing Hemoglobin Bart's hydrops fetalis is dependent upon if one or both parent carries the alpha-thalassemia trait. Due to this disease being incompatible with life, diagnosis for it is done prenatally. Early detection of Hemoglobin (Hb) Bart's disease before the development of hydrops fetalis is crucial because fetuses that develop hydrops fetalis will either be stillborn or may die shortly after birth. There can be early pregnancy termination to prevent serious complications for the baby or mother. Studies shows that in 11 to 14 weeks of gestation, sonographic markers can associate affected from unaffected pregnancies. It was found that the most sensitive marker was CT ratio and MCA‐PSV. Parents at risk of having a child with Fetal Hydrops can continue their pregnancy with regular ultrasounds and intrauterine blood transfusion. Babies of such parents are born with no edema or major neurological defects, and eventually, this disease can be cured with Haematopoietic Stem Cell Transplantation. A newly developed diagnostic test, called Immunochromatography (IC) Strip Tests, uses monoclonal antibodies to detect Hemoglobin Barts in red blood cells' lysate. This diagnostic test is validated for positive and negative predictive values. It is also cheap and easy, making regular screening for alpha-thalassemia a plausible possibility. Anemia is a factor in fetuses with Hemoglobin Bart's disease as there is an "increased cardiac output" and hypovolemia as the tissues of the fetus require oxygen because of the gamma globulin's high affinity for oxygen. This deprives the tissues of receiving oxygen to function well. The symptoms of anemia occur within the first trimester. This variant of hemoglobin is so called as it was discovered at St Bartholomew's Hospital in London, often abbreviated to Barts. (en)
- L'hémoglobine Barts, couramment abrégée Hb Barts, est une variante anormale d'hémoglobine constituée de quatre sous-unités γ-globine, c'est-à-dire qu'elle a pour formule γ4. Elle est assez peu soluble et s'accumule par conséquent dans les érythrocytes. Son affinité pour l'oxygène est très élevée, de sorte qu'elle ne libère pratiquement pas d'oxygène dans les tissus. Elle doit son nom au St Bartholomew's Hospital de Londres, surnommé St Barts, où elle a été découverte. L'embryon en cours de développement commence à produire des sous-unités α à partir de la cinquième ou de la sixième semaine de gestation. Lorsque les deux gènes HBA1 et HBA2 qui codent ces sous-unités sont non-fonctionnels (thalassémine α), seules des sous-unités γ sont produites, qui s'associent pour former de l'hémoglobine Barts. Dans les cas les plus sévères de thalassémie α, l'hémoglobine Barts est la seule présente dans la circulation sanguine. Dans ce cas, le fœtus développe un hydrops fœtal et meurt généralement avant ou peu après la naissance. L'hémoglobine Barts étant plus abondante en cas de thalassémie α, la mesure de son taux peut aider à diagnostiquer cette maladie. (fr)
- L'emoglobina di Barts è una variante patologica di emoglobina tipica dell'α-talassemia, nella forma con tutti e quattro i geni della catena α mutati (--/--). Durante lo sviluppo intra-uterino si formano tetrameri γ (l'emoglobina fetale presenta due catene α associate a due catene γ: queste verranno sostituite dalle catene β a sviluppo completato) non funzionali perché presentano elevata affinità per l'ossigeno e difficoltà nel rilasciarlo a livello tissutale. La condizione non è vitale e il quadro clinico presenta epatosplenomegalia ed edema generalizzato con morte per idrope fetale. La capacità di misurare l'emoglobina Barts è utile nei test di screening neonatali. Se viene rilevato questo tipo di emoglobina, il paziente viene solitamente inviato per un'ulteriore valutazione poiché la rilevazione di emoglobina Barts può indicare una delezione del gene della globina alfa, rendendo il bambino un portatore alfa talassemico silente, due delezioni alfa della globina (alfa talassemia) o malattia dell'emoglobina H (tre delezioni del gene della globina alfa). La delezione di quattro geni alfa globinici è stata precedentemente ritenuta incompatibile con la vita, ma attualmente ci sono 69 pazienti sopravvissuti alla passata infanzia. (it)
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