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PubMed1992

Molecular architecture of helicoidal proteinaceous eggshells.

I will not attempt to summarize this chapter, which is already a summary. I merely wish to point out that experimental and theoretical evidence to date clearly suggests that antiparallel beta-pleated sheet dictates self-assembly in helicoidal proteinaceous eggshells. Molecular details of this process have started to become clear after the development of the specific, most probably correct, protein structural models in the case of the silkmoths, where amino acid information is available and with the help of several experimental techniques. However, for people seeking universal mechanisms the picture should still be far from complete. Several analogous systems should be studied before providing final answers.

Amino Acid Sequence↗
PubMed2004

Transgenic birds for the production of recombinant proteins.

Transgenic birds were expected to be an excellent transgenic bioreactor for the production of recombinant pharmaceutical proteins. However, the only successful transgenic bioreactors have been based on mammals. We have developed two key techniques for obtaining transgenic birds. For bird embryo culture, we identified that the low rate of hatchability of cultured embryos is caused by limited oxygen and calcium availability. In quail embryo culture using a chicken eggshell as a culture vessel, hatchability increased to 80% by the supplement of calcium lactate in addition to oxygen aeration. A fully artificial vessel for quail embryo culture using a gas-permeable Teflon membrane was also designed. Although the hatchability was lower than that of cultures using a surrogate eggshell, we succeeded in hatching of bird embryos using a fully artificial vessel. For transgene introduction, a replication-defective pantropic retroviral vector based on Moloney murine leukemia virus (MoMLV) pseudotyped with vesicular stomatitis virus G protein (VSV-G) was injected to laid embryos at the blastodermal stage, and the embryos were hatched in vitro to generate G0 birds. The viral vector sequence was detected in the tissues of all G0 birds. The germ-line transmission efficiency was more than 80%. Plural copies of the transgene were inserted into the genome of G1 transgenic progeny.

Animals↗
PubMed1995

Eggshell thickness in marine birds in the New York Bight--1970s to 1990s.

Maintaining eggshell thickness is critical for birds, as thin eggshells result in breakage during incubation, with subsequent hatching failure. Beginning in the 1960s, eggshell thickness has been used as a biomarker of exposure to chlorinated hydrocarbon pesticides, as a measure of avian population health, and as a predictor of potential reproductive failures. In this study, eggs were collected from four coastal bird species nesting in the New York Bight (Cedar Beach, NY to Barnegat Bay, NJ) in the early 1970s, early 1980s, and early 1990s, and eggshell thickness was measured. We tested the hypothesis that decreasing use of chlorinated hydrocarbons, and subsequent decreased levels of these pollutants in the New York Bight estuarine food web, should have resulted in increased eggshell thickness from the 1970s to the 1990s. Most of the variation in eggshell thickness was explained by decade and species. Eggshell thickness increased from the early 1970s (or the 1980s for some species) to the early 1990s for all four species examined: common tern (Sterna hirundo), Roseate tern (S. dougallii), least tern (S. antillarum), and black skimmer (Rynchops niger). For common terns and black skimmers, eggshell thickness increased by nearly 50% from the 1970s to the 1990s, whereas in the smallest species, the least tern, eggshell thickness increased only by 12%. In the 1990s, least terns with the smallest eggs had the thinnest eggshells, and black skimmers with larger eggs had the thickest eggshells.

Animals↗
PubMed1976

Histochemical characteristics of the egg envelopes of Acanthosentis sp. (Acanthocephala).

The histochemical and phase contrast observations on the embryonic envelopes enclosing the acanthor of Acanthosentis sp. reveal the presence of three layers. All the three layers were non-refractile during early stages of their formation, and become refringent subsequently. The outer layer loses its refractile property together with affinity for acid and basic dyes when the eggs are fully developed. This layer is neither tanned nor chitinous. The second layer consists of glyco-lipo-proteinous matrix. The polysaccharide moiety is identified to be strongly sulfated acid mucopolysaccharide. The lipid component has been characterized to be KOH resistant and esters of unsaturated fatty acid. The protein is rich in aromatic amino acids. The third and the innermost layer contains chitin and acid mucopoly-saccharides. The protein is rich in sulfur-containing amino acids. Sulphydryl groups were present during early stages of its formation, but forms disulphide cross-links subsequently. Stages in the development of acanthors were characterized with reference to the formation of envelopes. The permeability experiments carried out on fresh eggs using 0.1% aqueous solutions of bromophenol blue, methylene blue, toluidine blue, basic fuchsin and neutral red indicate that the inward diffusion of these substances is prevented subsequent to formation of disulphide groups in the innermost layer. The results further indicate that the embryo derives nutritive requirements from the fluid of pseudocoel of the female worm through th envelopes covering it.

Acanthocephala↗
PubMed1982

Transport of electrolytes and water in the upper jejunum of the fowl in vivo perfusion.

The mechanism(s) of electrolytes (JNa, JC1, JCa and JK) and water transport (JV) were studied in the upper jejunum of the laying hen by an in vivo perfusion procedure. Water secretion is modified by the difference of osmotic pressure between the lumen and plasma and we have estimated the osmotic permeability coefficient (P osm = 17.4 microliter x h-1 x mosm-1 x g-1 DW) and the reflexion coefficient (0.72). At sodium concentrations of 0 and 80 mM x 1-1 in the lumen, there is a large secretion of Na. When the water flow is modified by osmotic pressure, this secretion is markedly influenced by JV. Similarly net chloride flux occurred mainly by solvent drag. Conversely water flow does not modify the large potassium absorption along the concentration gradient and only slightly affects the flux of calcium. Transport of calcium occurred along the gradient of concentration between lumen and plasma without saturation until a lumen concentration of 20 mM x 1-1. This driving force seemed to be the main one since JCa is close to zero when there is no gradient. This observation supports the hypothesis that the variations of net Ca absorption during the laying cycle is due to a modification of concentration of soluble calcium in the contents of the intestine.

Animals↗