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PubMed1991

Identification of a putative eggshell precursor protein of the female Schistosoma japonicum.

In adult worms of Schistosoma japonicum, a prominent radiolabelled female-specific protein (34 kDa) was demonstrated on fluorography of SDS gels with the pulse incorporation of 14C-tyrosine in vitro, though it was difficult to detect major female-specific proteins by direct staining methods. This female-specific protein was demonstrated to localize exclusively in the vitelline cells by indirect immunofluorescence using the rabbit anti-34 kDa female protein antiserum. It was shown that 14C-tyrosine was selectively incorporated into the vitelline cells by the pulse labelled autoradiographs. Two days after the exposure of worms to radio-tyrosine, the shells of eggs in the uterus were demonstrated to have become radioactive, indicating that 14C-tyrosine-labelled protein was used as a material for the eggshell. In the fluorograph of proteins extracted from newly laid eggs in vitro, the prominent band was not found at the 34 kDa region, but a lot of radioactivity appeared at higher than 100 kDa. The results suggested that a 34 kDa female protein was a precursor of the eggshell and became a much larger protein molecule as a result of cross-linking during eggshell hardening.

Animals↗
PubMed1986

Gene regulation and evolution in the chorion locus of Bombyx mori. Structural and developmental characterization of four eggshell genes and their flanking DNA regions.

We report on the detailed structural and developmental characterization of four chorion genes and a truncated pseudogene located within a 9.5 X 10(3) base chromosomal segment. These genes belong to the A and B multigene families and, like previously characterized moth chorion genes, are arranged in tightly linked pairs, which are divergently transcribed (A/B.L11 and A/B.L12). On the basis of their high degree of sequence divergence, the A genes define two distinct subfamilies, while the more homologous B genes represent different copies of the same gene type. The A.L11 and B.L11 introns are much longer, in each case because of a single inserted DNA segment that is missing from A.L12 or B.L12. The 2.1 X 10(3) base insertion in A.L11 is the first retrovirus-like transposable element characterized in Bombyx mori. The very short 5' flanking sequences of A/B.L11 and A/B.L12 (277 and 276 base-pairs) are distinct as shown by hybridization but both recur in additional chorion gene pairs, forming two respective classes that are expressed during distinctly different developmental periods. The divergently transcribed genes of each pair, which border the same 5' flanking sequence, are expressed co-ordinately, during the same developmental period. Detailed comparisons of the 5' flanking regions, and of the corresponding region of the Drosophila s15-1 chorion gene, revealed numerous, very short sequence elements that are shared. One such element, T-C-A-C-G-T, is also associated with all five sequenced Drosophila chorion genes. Some elements are repeated in a dyad symmetrical pattern, i.e. are associated with each of the two genes in a pair, while others, including T-C-A-C-G-T, occur only once per 5' flanking region, and, if functionally important, would presumably act bi-directionally on both genes of the pair.

Animals↗
PubMed1976

Effects of ambient pressures, He and Sf6 on O2 and CO2 transport in the avian egg.

The CO2 and O2 tnesions were determined in the air cells of 14-16 day old chicken eggs before and after transfer to a 21% O2 in He or SF6 atmosphere. In the former gas mixture the air-cell PCO2 (which reflects the arterialized blood PCO2) fell rapidly from 32 torr in air to 17 torr in He-O2 attaining a new steady state in 2-4 h. In the SF6-O2 mixture PCO2 rose from 36 torr in a similar period. A similar PCO2 increase was also observed when eggs were compressed to 2 atm of air while exposure to 0.5 atm with a 40% O2-N2 mixture decreased PCO2. Since gas transport across the eggshell is by gas phase diffusion, these findings can be explained by the changes in the diffusion coefficient of CO2 which increase in the presence of He and decrease in SF6. Furthermore, the diffusion coefficient is also inversely related to the absolute pressure. Quantitative prediction of the changes of PCO2 in the He and SF6 mixture cannot be made, since the binary diffusion coefficients are not necessarily applicable in a ternary gas mixture. However, effective diffusion coefficients in these multicomponent mixtures can be derived on the basis of the observed PCO2 changes.

Animals↗
PubMed1986

Eggshell conductance--Fick's or Stefan's law?

The diffusion of gases through the avian eggshell has usually been interpreted as an example of Fick's law, and this appears to be the best explanation for gas exchange through narrow long pores. Many eggshells, however, contain more elaborate pores, of which the funnel-shaped type is the most common. It is suggested that most of the resistance to diffusion through these types of pores is best explained by Stefan's law of diffusion through apertures. The implications of this theory to the understanding of pore functions are discussed.

Animals↗
PubMed1988

Development of the chick embryo: effects of egg mass.

We asked to what extent, within a species, differences in egg mass, hence in eggshell surface area and O2 conductance, could affect the development of the avian embryo. Large (L, about 70 g) and small (S, about 55 g) fertile chicken eggs were simultaneously incubated and the embryos studied at day 18, i.e. before the onset of lung ventilation. Embryo mass and O2 consumption (VO2) (measured with a manometric technique) normalized per mass of the freshly laid egg were higher in S than in L, while no differences occurred after normalization by egg surface area (S.A.). Egg water vapour conductance, which is proportional to O2 conductance, was also found to be directly proportional to egg S.A. Hence, the mass and VO2 of the embryo are more closely related to the O2 conductance of the eggshell than to egg mass, giving support to the concept that the avian embryo's VO2 is not an invariable species characteristic, but a variable dependent on O2 availability. Hatching and viability did not differ between L and S, and the specific mass of heart and lung and their cellular (DNA) concentration were also similar between the two groups of embryos. Therefore, differentiation of tissues and organogenesis do not seem to be affected by the differences in total O2 availability determined by the differences in egg mass, while they are probably more important than total tissue mass in setting the time of hatching.

Animals↗
PubMed1994

Calcium deficient diet, acetazolamide and gas exchange characteristics of avian eggshells.

The effects of calcium deficient diet and acetazolamide on the gas exchange characteristics of avian eggshells were independently investigated in two groups of unmated hens (Gallus domesticus). In one group, eggs were collected during both a normal diet (3.00% Ca) and a calcium deficient diet (0.34% Ca). In another group, eggs were collected both before and after acetazolamide administration (200 mg/kg) per os. Eggshell water vapor conductance (GH2O) increased 30% during the calcium deficient diet and was accompanied by a 21% decrease in eggshell thickness (L). Eggshell GH2O increased 200% one day after acetazolamide administration and was not only accompanied by a 36% decrease in L, but also by an 89% increase in total functional pore area (Ap). We conclude that a calcium deficient diet increases GH2O by eggshell thinning with little effect on Ap. On the other hand, acetazolamide profoundly increases GH2O, not only by eggshell thinning but also by a remarkable increase in Ap.

Acetazolamide↗
PubMed1990

Geographical distribution of contaminants and productivity measures of herring gulls in the Great Lakes: Lake Erie and connecting channels 1978/79.

The distribution and size of colonies, residue levels of DDE, DDT, HCB, dieldrin, mirex and PCBs in eggs, productivity and eggshell thickness were determined for herring gulls at 14 sites in Lake Erie and connecting channels. The centre of distribution for breeding herring gulls was the Western Basin where approximately 90% of the 6200 nests in the study area were located. Seven of 22 colonies showed an average annual population increase of 48.3%. Most of the increase in breeding herring gulls on Lake Erie is directly associated with sites that have undergone habitat modification by man. Levels of PCBs and DDE ranged from 35 to 140 ppm (wet weight) and from 2.8 to 9.4 ppm, respectively; all other residues were less than 0.49 ppm. Most organochlorine residue levels were highest in eggs from colonies in or near the Niagara or Detroit Rivers. Mirex residues were greatest in the Niagara River and decreased significantly to the west. PCB residues were greatest in the Detroit River and decreased significantly to the east. The lowest levels generally came from colonies in the Sandusky Basin and near Pelee Island in western Lake Erie. Discriminant function analysis of six organochlorine contaminants correctly classified 90% or more of the eggs from up to four colonies in one or more years. Levels of PCBs and HCB appeared to have the greatest discriminating power. Herring gull productivity at all colonies (1-1.7 young gulls/pair) was normal and showed no significant geographical variation. Eggshell thickness was greatest in colonies in the Sandusky Basin and least in colonies in the Detroit River and extreme west end of the lake; mean eggshell thickness was 0.350 +/- 0.02 mm (6.7% thinning), which was weakly, but significantly correlated to DDE concentration. The variation in contaminants in herring gull eggs on a Basin basis (i.e., Western, Eastern, Sandusky, etc.) paralleled those known for sediments, water and fish. Thus, we suggest that in addition to its role as an indicator of lake-wide contamination of the Great Lakes, the herring gull, under some circumstances, may function as an indicator of "regional" contamination. This is an important distinction as it improves the geographical specificity of the herring gull as an indicator species on the Great Lakes, where it is a non-migratory species.

Animals↗