Avian characteristics

Birds evolved from a group of reptiles known as the dinosaurs (order Dinosauria), which first appeared during the late Triassic period (which ended about 210 million years ago). The earliest bird known in the fossil record is Archaeopteryx, from the mid-Jurassic period about 160 million years ago. These extremely early birds had many typical avian characteristics, such as feathers and a homy beak, and were very likely warm-blooded, but they also had reptilian features, such as teeth. In fact, modem birds and dinosaurs still have many characteristics in common, and some biologists and paleontologists believe that birds should be viewed, and classified, as living dinosaurs. ... 

T-tubule is a transverse invagination of the plasma membrane, which occurs at the specified sites characteristic to animal species and organs, i.e. at the Z-line in cardiac ventricle muscle and non-mammalian vertebrate skeletal muscle and at the A-I junction in mammalian skeletal muscle. It is absent in all avian cardiac cells, all cardiac conduction cells, many mammalian atrial cells and most smooth muscle cells. T-tubule serves as an inward conduit for the action potential. 

What are the characteristics that make the influenza virus, for example, avian influenza, a potential pandemic agent ... 

Worker and environmental safety Atrazine and simazine are safe to apply according to the directions on the label. Nontarget safety margins are good because atrazine is nonvolatile and has low specific activity. In addition, avian, mammalian, and aquatic toxicities are low. Relative safety to nontarget plant species is a positive characteristic that is not always found in alternative products. 

Castanospermine s antitumor potential continues to receive attention. Recent in vitro studies have examined inhibition of tyrosinase activity in human melanoma cells (181), effects on intracellular transport of an avian erythroblastosis oncoprotein (277), and consequences for biosynthesis, maturation, and transport of ai-antitrypsin in the human hepatoma HepG2 cell line (257,272). The latter study was the first to show the inability of 239 to permeate the plasma membrane in intact HepG2 cells. In vivo experiments with nude mice proved that the alkaloid altered the glycosylation of endothelial cells, prevented angiogenesis, and inhibited tumor growth (273). However, recent in vivo studies failed to reveal cytotoxicity towards two rat prostate adenocarcinoma cell lines, or effects on cell characteristics related to metastatic potential (274). Uptake and metabolism of the more lipophilic 6-0-butanoylcastanospermine in tumor cell lines and after oral administration to mice was traced with C-labeled material, and showed rapid conversion into the parent alkaloid, which is undoubtedly the active metabolite (275). Multiple dosing in mice produced additive results. 

The transferrins are a class of iron-binding glycoproteins which have been found in the blood serum of a variety of vertebrates and are presumably also present in moth hemolymph [see (74) and references therein], These proteins would appear to mediate the absorption and distribution of iron (75), and could play some role in the movement of carbon dioxide in the body (76). Proteins of similar characteristics, lactoferrin and conalbumin, have been isolated from milk and avian egg white respectively. It has been proposed (77) that conalbumin could prevent bacterial contamination of the egg yolk by removing free iron. A similar bacteriostatic action could be performed by lactoferrin in milk, and it is possible that this protein is involved in controlling the intestinal flora in infants (78). 

Nakanishi, Y., Okuda, S., Tsuji, M, and Suzuki, S., The occurrence of uridine diphosphate N-acetylgalactosamine 6-sulfate in quail egg white and characteristic distrihution of sul ted sugar nucleotides in different avian eggs. Biochim. Biophys. Acta 564, 8-14 (1979b). 

Numerous ultrastructural and histochemical studies have now demonstrated conclusively that many of the epithelial cells in the thymus have the characteristics of secretory cells (Singh, 1981). Cortical as well as medullary thymic epithelial cells may exhibit membrane-bound, electron-dense granules, which are also found in a variety of endocrine organs. Epithelial cells containing membrane-bound, electron-dense granules have now been identified in avian (Frazier, 1973 Hakason et al., 1974 Kendall and Frazier,... 

The complexity and plasticity of BBB properties called for experimental dissection of the disrnption process in both in vitro and in vivo conditions. Multiple cell and organ cnltnres, animal models, and measurement techniques have been developed, each of which addresses some of the issues involved. The development of research into BBB characteristics was initially approached in avian embryos, where transplanted endothelial quail cells invaded a developing chick chimera. A simpler cell culture model of the BBB was developed by Rubin and co-workers. More recently, an immortalized cell line created from vascular endothelial cells was used to develop another model of the BBB in co-cultures with glioma cells and was used to demonstrate nitric oxide-induced perturbations of these cells. hi another cell culture model, hypoxia was shown to increase the susceptibility to oxidative stress and intercellular permeability. ... 

Duff, R.G. and Vogt, P.K. 1969. Characteristics of two new avian tumor vims subgroups. Virology 39, 18-30. 

Qasses III and V have not been included since their existence and characteristics in avian species are in doubt. 

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