The glycogen body in neonate birds of the order Psittaciformes and its role in neonate mortality
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The glycogen body (GB) is a specific structure of the spinal cord of birds, localized betweenthe third lumbar vertebrae and the first sacral vertebrae in the fossa rhomboidea spinalis. It iscomposed of astroglial cells specialized in storing large amounts of glycogen derivatives. Thefactors that control filling and the release of glycogen derivatives by the structure are stillunknown. The function of the GB is uncertain, and different hypotheses have been proposed,such as energy storage for the nervous tissue and the cerebrospinal fluid, a role in myelinsynthesis, a nonfunctional remnant from reptilian ancestors, etc.The pattern of activity of the thyroid gland (TG) differs between altricial and precocialhatchlings, although its development is the same. The altricial neonates do not have the perihatchpeak of thyroid hormones (TH) and thermoregulation response during the first week of life whichis typical of precocial chicks. The egg contains a low content of glucose, and gluconeogenesis in the liver of the embryo isthe only possible pathway for obtaining glucose from lipids and proteins. Gluconeogenesis isbiotin-dependant because one of its key enzymes, pyruvate carboxylase (PC), is biotindependant.Between the 1st of January and the 31st of October of 2003, all dead chicks (up to one month)and embryos in the last period of incubation in the Loro Parque parrot collection were collected. The study is the first study of the GB in psittaciformes and also tried to find out the causes ofempty / hypotrophic GBs reported in previous observations in the same collection. Completenecropsy, microbiological and histopathological studies (using PAS, Turnbull s blue and HEstains) were performed to diagnose the cause of death of all chicks. Finally, the database wascomposed of 110 animals, mainly from the nursery. The clinical picture mainly described werestunted chicks with dry and pale skin, globose head and sudden deaths during the first week oflife. The GB was found inside the lumbosacral spinal cord between the nervous tissue andpresented and inverted triangular shape in the transversal sections. It was mainly composed ofone type of irregular, large and polygonal cell. The major part of the cells was occupied by storesof glycogen derivatives, which stained bright red pink using the PAS stain. It was wellvascularized and the central canal passed through it.The GBs were only found to be normal in seven (6.4%) cases, the rest (93.6%) presenteddeficiencies in the glycogen filling of the astroglial cells. Problems of athyroidism andhypothyroidism were diagnosed in 86.1% of the birds in which the TG were studied. Immaturity ofsome organs, retarded yolk sac, unphysiological fatty livers, underdeveloped lungs and retardedextramedullary haematopoiesis were some of the other histopathological findings observed inthese chicks. It is suggested that possible factors interfering with gluconeogenesis during the embryonicperiod, such as eggs with a low biotin content laid by hens with subclinical biotin deficiencies,may be the cause of empty and hypotrophic GBs. Empting of the structure prior to death (by anunknown pathway) as an attempt to save the chicks life is also suspected. A lack of colloid insidethe follicles of the TG has also been noted. A direct relationship of the GB with the TG has notbeen observed, but more studies are necessary.Verknüpfung zu Publikationen oder weiteren Datensätzen
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Giessen : VVB Laufersweiler 2006