Involvement of the hypothalamic-pituitary-thyroid axis and its interaction with the hypothalamic-pituitary-adrenal axis in the ontogeny of avian thermoregulation: a review

The emergence of thermoregulation in avian species is a complex matter in which neural as well as hormonal processes are involved. In a previous paper, the neural aspects of primary avian thermoregulation were discussed. In this paper the role of the hypothalamus-pituitary-thyroid axis (HPT-axis) and the hypothalamus-pituitary-adrenal axis (HPA-axis) in the ontogeny of avian thermoregulation is evaluated. The regulatory mechanisms and different important hormones of both axes, which have stimulatory or inhibitory effects, are discussed. Because the onset of functionality of the thermoregulatory system is of great interest, the ontogeny and functionality of the hormonal axes are clarified. There is a great difference between precocial and altricial birds in hormonal events as well as in neural processes which are involved in the emergence of thermoregulation. In precocial avian species the HPT-axis becomes functional during the mid- to late embryonic period while the same axis only becomes fully functional during the first week post-hatch in altricial avian species. As early as the sixties, the emergence of homeothermy in chickens was investigated. It was concluded that the thyroid gland plays an important role in the thermoregulatory mechanisms of newly hatched chicks. More recent studies however were not able to show any direct effect of the thyroid hormones on the thermoregulation of day-old chicks, although blocking the conversion of T4 to T3 caused a decrease in body temperature in young chicks. Thyrotropin releasing hormone (TRH) is known to act in thermoregulation in mammals and several authors have found an effect of TRH on the metabolism of young and older chicks. However, the exact mechanism still remains unclear. Because the HPT- and the HPA-axis show close relationships, the role of the HPA-axis in the ontogeny of thermoregulation is also taken into consideration in this review. In mammals as well as in birds, corticotropin releasing hormone (CRH) is involved in the primary thermoregulation. We conclude that the HPT-axis has an important role in the ontogeny of avian thermoregulation. The exact role of the HPA-axis remains largely unclear although at least CRH is definitely of some importance

Gas exchange during storage and incubation of Avian eggs: Effects on embryogenesis, hatchability, chick quality and post-hatch growth

Embryonic development is a dynamic process that requires a fine balance between several factors in order to achieve an optimum hatchability and chick quality. These factors include the background of the embryo, such as genetic line of the breeders, the age of the breeder, egg weight, and factors related to the environment in which the egg is stored and incubated, such as temperature, humidity, gas levels and altitude. Gas exchanges are of fundamental importance for embryonic development during incubation and may affect the livability of the embryo. This paper reviews the roles of the gaseous environment (i.e. O 2 and CO2) around hatching eggs during storage and during incubation and the effect it might have on the survival of the developing embryos and the chicks that hatch. The state of the art on the different attempts to establish the optimum requirements of different gases that promote the optimal developmental trajectories at different periods during incubation is presented. The roles and consequences of different levels of O2 and CO2 during storage and incubation on hatchability, incubation duration, hatching process, embryo growth, embryo mortality, organ development and morphology, metabolism, blood acid-base balance, chick quality and chick post-hatch growth are reviewed. © 2007 World's Poultry Science Association

Ontogeny of avian thermoregulation from a neural point of view

The ontogeny of thermoregulation differs among (avian) species, but in all species both neural and endocrinological processes are involved. In this review the neural processes in ontogeny of thermoregulation during the prenatal and early postnatal phase are discussed. Only in a few avian species (chicken, ducklings) the ontogeny of some important neural structures are described. In the early post hatching phase, peripheral and deep-body thermoreceptors are present and functional, even in altricial species, in which the thermoregulation is still immature at hatch. It is suggested that the development of peripheral and deep-body thermoreceptors is not responsible for the inability to maintain a stable body temperature at cold ambient temperatures during early postnatal phase, although studies examined the ontogeny of thermoreception only in an indirect manner. Thus, other factors, such as volume to surface ratio and rate of insulation are important. Studies regarding the ontogeny of hypothalamic cold- and warm-sensitivity neurons in precocial species demonstrate that maturation of the hypothalamic temperature sensitivity takes place during the late prenatal and early postnatal period, with a relatively high cold sensitivity of the hypothalamus during the transition from poikilotherm to homeotherm. In addition, incubation temperatures are demonstrated to influence postnatal hypothalamic thermosensitivity. Brain temperature regulation is found to maturate during avian ontogeny as well and is demonstrated to coincide with the ontogenic pattern of general thermoregulation in several avian species. Relevant information of the ontogeny of the spinal cord and effector pathways related to the development of avian thermoregulation is lacking. We concluded that both prenatal and early postnatal temperature affects hypothalamic thermosensitivity and consequently condition thermoregulation in later life

Hepatocarcinoma in the tropics

L'hépatocarcinome est un fléau important sous les tropiques où il représente une cause majeure de mortalité par cancer. Son diagnos L'hépatocarcinome est un fléau important sous les tropiques où il représente une cause majeure de mortalité par cancer. Son diagnostic est souvent tardif et les moyens thérapeutiques ne sont que palliatifs. Les facteurs déterminants de la carcinogenèse hépatique sont dominés par le virus de l'hépatite B dont la carte mondiale de prévalence se calque sur celle du cancer du foie. Il existe une susceptibilité génétique la survenue de ce cancer. D'autres facteurs sont importants ou adjuvants: le virus de l'hépatite C, l'alcool, la surcharge en fer et l'afla dans la survenue de ce cancer. D'autres facteurs sont importants ou adjuvants: le virus de l'hépatite C, l'alcool, la surcharge en fer et l'aflatoxine dont les effets mutagènes ont été prouvés. Seule la suppression du facteur principal (le virus B) par la vaccination de masse pourra réduire la prévalence de cette tumeur décimant une population jeune dans ces pays en voie de développement

Colonic complications of foreign bodies ingestion (about two cases)

Deux observations de complications coliques après ingestion de corps étrangers. L'ingestion volontaire ou accidentelle de corps étrangers entraîne exeptionnellement une expression colique pathologique. Nous rapportons deux observations originales d'ingestion accidentelle de corps étrangers passés inaperçus et de révélation bruyante tardiv

A case of duodenal metastasis of an esophageal squamous cell carcinoma

La localisation de métastases au tube digestif est rare. Leur siège est plus souvent jéjuno-iléal. Les auteurs rapportent un cas de métastase d'un carcinome épidermoïde de l'œsophage chez un homme de 47 ans qui avait été traité par radiochimiothérapie puis chirurgie deux mois auparavant. Une revue de la littérature retrouve le caractère exceptionnel de ces métastases duodénale

Spontaneous intramural haematoma of oesophagus: diagnostic attitude about one case

L'hématome intra-mural de l'œsophage (HIMO) peut survenir de façon spontanée ou lors d'un trouble de la coagulation. Son expression clinique non spécifique (douleur thoracique, dysphagie, hématémèse) ne permet pas d'affirmer le diagnostic et c'est classiquement la fibroscopie œso-gastro-duodénale associée au scanner thoracique qui amènent à un diagnostic de certitude. Nous soulignons dans cette observation l'intérêt de l'endosonographie qui permet d'affirmer le diagnostic et de préciser la localisation pariétale ainsi que l'épaisseur de l'HIM

Parasitic colitis and immunodeficiency

Les colites parasitaires au cours des immunodéficiences sont surtout observées lors de déficits de l'immunité cellulaire, dominés en fréquence par l'infection par le virus de l'immunodéficience humaine. Les parasitoses en cause sont des protozooses digestives (amibiase, blastocystose, balantidiose, dientamoebiase, cryptopsoridiose, isosporose), plus rarement extra-digestives (leishmaniose viscérale, toxoplasmose, pneumocystose). La strongyloïdose est l'unique helminthiase concernée. Ces colites ont une connotation péjorative pour plusieurs raisons: intensité du déficit immun sous-jacent; colite d'expression clinique grave, compliquée ou prolongée; dissémination de la parasitose et fréquente association à d'autres agents pathogènes ou manifestations tumorales, induits également par l'immunodéficit et qui modifient les tableaux cliniques; difficultés diagnostiques justifiant une coopération entre le clinicien, le biologiste et l'endoscopiste digestif; traitements souvent en échec justifiant le recours à des alternatives inconstamment validées