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PubMed1984

Comparison of the effect of DDE on the Ca metabolism of the eggshell gland and its subcellular fractions of the duck and the domestic fowl.

In a strain of ducks sensitive to the eggshell-thinning effect of p-p'-DDE, administration of 40 mg kg of the compound in the food for 45 days reduced the eggshell index (EI) by 13% and the content of calcium in the fluid of the shell gland forming an eggshell by 36%, and raised the calcium content of the shell gland mucosa by 19%, compared with the control values. DDE inhibited the translocation (secretion) of calcium between the gland mucosa and the uterine cavity. The ATP-dependent binding of Ca2+ to the subcellular fractions of the gland mucosa was reduced in DDE-treated ducks. The Ca2+ binding to a microsomal subfraction (FI) rich in fragments of the plasma membrane was reduced by 16%, whereas that to a subfraction FIII which bound Ca2+ at a very high rate was reduced by 36%. The latter may contain calcium-secreting granules of the gland. In the mitochondrial fraction the Ca2+ binding was reduced by 35%. In the domestic fowl DDE did not lower EI or interfered with the translocation of calcium between the shell gland mucosa and uterine cavity. DDE administration increased the Ca2+ binding to FI by 26%; the binding to other subfractions was not changed significantly. DDE may interfere with the stimulus-secretion mechanism of the eggshell gland in ducks through its effect on Ca2+ binding.

Adenosine Triphosphate↗
PubMed1988

Small gene family encoding an eggshell (chorion) protein of the human parasite Schistosoma mansoni.

We have isolated six independent genomic clones encoding schistosome chorion or eggshell proteins from a Schistosoma mansoni genomic library. A linkage may of five of the clones spanning 35 kilobase pair (kbp) of the S. mansoni genome was constructed. The region contained two eggshell protein genes closely linked, separated by 7.5 kbp of intergenic DNA. The two genes of the cluster were arranged in the same orientation, that is, they were transcribed from the same strand. The sixth clone probably represents a third copy of the eggshell gene that is not contained within the 35-kbp region. The 5' end of the mRNA transcribed from these genes was defined by primer extension directly off the RNA. The ATCAT cap site sequence was homologous to a silkmoth chorion PuTCATT cap site sequence, where Pu indicates any purine. DNA sequence analysis showed that there were no introns in these genes. The DNA sequences of the three genes were very homologous to each other and to a cDNA clone, pSMf61-46, differing only in three or four nucleotides. A multiple TATA box was located at positions -23 to -31, and a CAAAT sequence was located at -52 upstream of the eggshell transcription unit. Comparison of sequences in regions further upstream with silkmoth and Drosophila sequences revealed several very short elements that were shared. One such element, TCACGT, recently shown to be an essential cis-regulatory element for silkmoth chorion gene promoter function, was found at a similar position in all three organisms.

Amino Acid Sequence↗
PubMed1992

Effects of ascorbic acid on plasma thyroxine concentrations and eggshell quality of Leghorn chickens treated with dietary thiouracil.

Because ascorbic acid (AA) and the thyroid hormones are known to influence eggshell formation, the effects of AA on body weight, total plasma thyroxine (T4), egg production, and eggshell quality of Single Comb White Leghorn (SCWL) hens concurrently and previously treated with thiouracil (TU) were determined. Hens were provided feed containing either 0 or 100 ppm AA from 47 to 67 wk of age and either 0 or .1% TU from 47 to 57 wk of age. A three-way split-plot analysis was employed to test for the effects of AA, TU, and time, and their interactions. Dietary TU increased body weight between 53 and 59 wk, and increased thyroid weight at 67 wk; however, TU only depressed plasma T4 level at 51 wk. Dietary TU depressed egg production from 50 to 56 wk and egg weight at 49, 51, and 57 wk. Dietary TU depressed eggshell weight per unit surface area at 49 wk. There was no significant effect due to AA and no AA by TU interaction for any of the parameters examined. It was concluded that .1% dietary TU from 47 to 57 wk of age did not alter eggshell quality and that dietary AA at the 100 ppm level did not influence the effects of .1% TU on body weight, egg production, or egg weight of SCWL hens.

Animals↗
PubMed1979

Structure of the schistosome eggshell: amino acid analysis and incorporation of labelled amino acids.

Preparations of eggshells of Schistosoma mansoni and S. japonicum were hydrolyzed and analyzed for amino acid composition. Both species showed great similarities in the proportions of each residue found. The predominant amino acid in shell hydrolysates was found to be glycine, which accounted for 37% of S. mansoni and 45% of S. japonicum amino acids. Four components (glycine, aspartic acid, lysine, and serine) totalled 68--75% of amino acids in the eggshells. Other individual amino acids were present in relatively small proportions ranging from 5.2--0.01%. Less than 1% of the amino acid residues were identified as tyrosine, and bityrosine was detected at a level not exceeding 1 in 1,600 residues. Carbohydrates were estimated to comprise 7.5--10% of the eggshell weight, based on hexose assay, and glucosamine was identified as the principal amino sugar in shell hydrolysates. In vivo labelling of the S. mansoni eggshell was demonstrated following injection of C14-glycine and C14-tyrosine into infected mice and subsequent purification of the shells of eggs recovered from their liver.

Amino Acids↗
PubMed1991

Eggshell morphology of the small eggs of human trematodes in Thailand.

Light and scanning electron micrographs of Opisthorchis viverrini, Haplorchis taichui, H. pumilio, A Phaneropsolus bonnei, and Prosthodendrium molenkampi eggs were studied. Under light microscopy. O. viverrini eggs had rough eggshells and prominent shoulders. H. taichui, H. pumilio were similar in shape and had smooth eggshells and prominent shoulders. H. pumilio eggs were bigger than H. taichui eggs. P. bonnei and P. molenkampi eggs had smooth eggshells and indistinct shoulders. P. bonnei eggs were thinner and bigger than P. molenkampi eggs. Some deformed eggs of O. viverrini and Haplorchis sp. were found and they had no embryos and indistinct opercula. Under scanning electron microscopy, O. viverrini eggs looked like musk-melon skin; they had prominent shoulders and long knobs. H. taichui eggs had curly, thread-like ridges and prominent shoulders and knobs. H. pumilio eggs had streched ridges, like Chinese bitter mormodica, and prominent shoulders. P. bonnei and P. molenkampi eggs had smooth eggshells and small shoulders and knobs.

Animals↗
PubMed1979

Effects of organochlorine residues on eggshell thickness, reproduction, and population status of brown pelicans (Pelecanus occidentalis) in South Carolina and Florida, 1969--76.

Shells of brown pelican (Pelecanus occidentalis) eggs collected in South Carolina from 1969 through 1975 and in Florida during 1969, 1970, and 1974 were significantly thinner (P greater than 0.05) than eggshells collected before 1947. Thickness of South Carolina eggshells increased in 1975, and mean thickness of eggshells collected in Florida during 1974 was greater than that of eggshells collected during 1969 and 1970, primarily in Gulf Coast colonies. Residues of 13 organochlorines were found in eggs and tissues of pelicans found dead during 1974 and 1975, although residues in brains of these specimens were not high enough to cause death. Residues of organochlorines, except PCBs, declined through 1975. PCBs increased in eggs from Atlantic Coast colonies. Reproductive success and population status of brown pelicans in South Carolina have improved markedly since authors began their studies in 1969. Good reproductive success was reported in 3 of 5 years from 1973 through 1977.

Animals↗
PubMed1991

Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. I. Macracanthorhynchus hirudinaceus (Archiacanthocephala).

Eggshells of Macracanthorhynchus hirudinaceus (Archiacanthocephala) were investigated for their fine structure as well as their chemical composition. The acanthor larvae are surrounded by four eggshells (E1-4) separated by interstices of low electron density (G1-4). As these envelopes are secreted in different sequences and are reinforced to different degrees, their appearance varies throughout development. The outermost eggshell (E1) of this species has a tripartite appearance; it contains neither chitin nor keratin. Keratin appears in E2 and E3. It was localized electron microscopically using anti-keratin and, for the first time by fluorescence microscopy with the bromobimane reaction. Keratin occurs in two forms: in the second envelope (E2) it consists of twisted struts of filaments, whereas in the innermost sublayer of the third envelope (E3) it shows a conspicuous cross-striation; in the first and second sublayers of E3, neither keratin nor a discernible structure is present. Chitin occurs in the innermost layer (E4). The interstices G1, G3 and G4 seem to contain glycoproteins, whereas interstice G3 seems to contain some type of carbohydrate. After the extraction of proteins including keratin with sodium dodecyl sulfate (SDS) and dithiothreitol (DTE) only layers E1 and E4 remained.

Acanthocephala↗
PubMed1992

Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. III. Eoacanthocephala.

Eggshells of the eoacanthocephalans Neoechinorhynchus rutili (Neoechinorhynchidae) and Paratenuisentis ambiguus (Tenuisentidae) were investigated for their fine structure and their chemical composition. The acanthor larvae of P. ambiguus are surrounded by four eggshells (E1-E4) separated by electron-lucent interstices (G1-G4). This resembles the stratification of the eggshells of archiacanthocephalans and palaeacanthocephalans. However, an additional outer envelope (E0) exists in N. rutili. In mature eggs of this species, the broad interstice between E0 and E1 is densely packed with polysaccharides, but the other interstices also showed an intense Thiéry label. In both species, E2 along with its outer protuberances contains keratin, as does E2 in archiacanthocephalans and palaecanthocephalans, whereas E4 does not contain chitin, which contrasts with findings in the eggs of the two other classes of acanthocephalans. The results are discussed with respect to the classification of the Acanthocephala and to their transmission to the intermediate hosts.

Acanthocephala↗
PubMed1978

Influence of dietary calcium selenium and methylmercury on eggshell thickness in Japanese quail.

A high Ca, semi-purified diet promoted greater egg production with thicker shells in Japanese quail hens. 7 ppm of dietary Se depressed egg weights with no effect on eggshell thickness. The addition of 20 ppm of MHg to either a low or high Ca diet containing Se depressed both egg production and eggshell thickness. Se residues of liver, kidney, and brain in Se-MHg fed quail were significantly higher than in Se treated quail, probably reflecting the ability of Se to bind with Hg. CA, an enzyme required for the formation of the carbonate radical of Ca carbonate in eggshells, was not reduced in the Se-MHg treated Japanese quail hens' blood or oviducts.

Animals↗
PubMed1976

P,p-DDT and p,p'-DDE effects on egg production, eggshell thickness, and reproduction of Japanese quail.

p,p' -DDT and p,p' -DDE were investigated for effects on egg production and eggshell thickness in Japanese quail. p,p' -DDT was examined for effects on hatchability and fertility. DDE was tested at 0, 2, 10, 40, and 200 ppm in the diet. No evidence suggested that DDE affected number of eggs laid, egg weight, or eggshell thickness at any level of DDE tested. DDT was tested at 1,2.5, 10 and 40 ppm in the diet. In one experiment, quail fed DDT at 40 ppm and caged in male-female pairs broke more eggs than quail caged similarly but fed lower amounts of DDT or than quail fed an equal amount of DDT but caged alone. DDT did not detectably reduce eggshell thickness, number of eggs laid, fertility, or hatchability. However, paired quail laid fewer eggs than did single quail in two experiments and laid eggs with thinner shells in one experiment.

Animals↗
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↗
PubMed1992

Incorporation of radiolabelled amino acids by adult Schistosoma japonicum: further characterization of a putative eggshell precursor protein.

The synthesis patterns of female-specific proteins of Schistosoma japonicum were further investigated with particular reference to the 34 kDa putative eggshell precursor protein. Adult male and female worms of S. japonicum were metabolically labelled with 14C-tyrosine, 14C-glycine and 35S-methionine in vitro. The rates of amino acid incorporation for female worms were significantly higher than for males in all radiolabelling experiments. Labelled proteins were resolved by two-dimensional gel electrophoresis and visualized by fluorography. By using 14C-tyrosine and 14C-glycine, the 34 kDa female protein band resolved into three major spots with pI 6.0, 5.8 and 5.6. On the other hand, labelling studies using 35S-methionine failed to reveal synthesis of any corresponding spots at Mr 34 kDa. These results, together with the observations that eggshell hydrolysates are very rich in glycine but poor in methionine, suggested that the 34 kDa putative eggshell precursor protein of S. japonicum consists of at least three isoelectric forms. In addition, we have demonstrated several other female-specific polypeptides synthesized by this worm.

Amino Acids↗
PubMed1985

Pores in avian eggshells: gas conductance, gas exchange and embryonic growth rate.

The number of pores (N) in eggshells of birds were counted in 161 species ranging in egg mass (W) from 0.9 to 500 g. In addition the water vapor conductance of the shell (G) mg X (d X Torr)-1, the water loss in the nest (M) mg X d-1, the incubation duration (I) d, and the shell thickness or pore length (L) micron are listed for each species when available. Allometric equations for all variables are given when regressed on egg mass. When log G is regressed on log N the slope is essentially 1.0 indicating that the G X N-1 for average pores in bird eggshells is 1.5 micrograms H2O X (d X Torr)-1 regardless of egg mass or incubation duration. According to Fick's law of diffusion such pores have a cross-sectional area to pore length ratio of 0.67 micron 2 X micron-1. Further analysis show that N, G, M, and the rate of oxygen consumption at the pre-internal pipping stage, are all directly proportional to the absolute mean growth rate of embryos (defined as 0.67 [W/I], g X d-1). Thus, single pores of typical eggshells not only have a similar conductance G X N-1, but also the metabolic rate and rate of water loss are matched to the pore conductance so that O2, CO2 fluxes per pore at the pre-internal pipping stage and water vapor flux per pore are similar among species, namely 68, 49 and 50 microliters X d-1, respectively. The partial pressure differences across the shell at the same stage are 42, 40 and 27 Torr, respectively. Ecological as well as taxonomical variation may alter some of the relationships predicted for the 'typical' egg in order to conserve a typical overall diffusive water loss.

Animals↗
PubMed1989

Changes in eggshell water vapour conductance during shell formation in the chicken.

Time-related changes in shell porosity and eggshell water vapour conductance were measured in uterine eggs of the domestic fowl (Gallus domesticus) from 10 h in uterus to oviposition. Measurements were carried out in artificially-aborted eggs. It was found that the eggshell water vapour conductance decreased to a minimum level at 15 h in uterus. This coincided with increases in shell thickness and shell porosity as power functions of uterine time. From that time on, water vapour conductance increased as a power function of uterine time to the final value prior to oviposition. Thus, eggshell water vapour conductance is determined by different rates of dynamic changes in shell porosity and shell thickness in the course of shell calcification. The final conductance is reached about 2 h before oviposition.

Animals↗
PubMed1992

CO2 and avian eggshell formation at high altitude.

We tested the hypothesis that altitude-induced hypocapnia in hens reduces eggshell conductance to water vapor (GH2O). Seven laying hens (Gallus domesticus) native to 1200 m were chronically exposed to high altitude (3800 m), and then to high altitude with sufficient inspired CO2 to relieve hypocapnia (3800 m + CO2). Egg GH2O was measured gravimetrically, shell thickness was measured with a micrometer, and aggregate pore area was calculated from measured values using Fick's law. Comparing results at 1200 m (n = 118) and 3800 m (n = 102), GH2O was reduced from 13.9 +/- 0.2 to 12.6 +/- 0.2 mg/(d.Torr)(mean +/- SE), shell thickness was reduced from 0.297 +/- 0.003 mm to 0.287 +/- 0.003 mm, and calculated aggregate pore area per egg was reduced from 1.97 +/- 0.03 mm2 to 1.72 +/- 0.03 mm2. When hypocapnia was relieved at 3800 m + CO2 (n = 82), GH2O was reduced even further to 11.1 +/- 0.2 mg/(d.Torr), shell thickness increased to 0.305 +/- 0.003 mm, and aggregate pore area was reduced to 1.61 +/- 0.03 mm2. Based on these results we reject our hypothesis. We conclude that hypocapnia is responsible for thin eggshells at altitude. Other physiological stimuli must cause the reductions in eggshell GH2O and pore area.

Altitude↗
PubMed1989

Predicted structure of a major Schistosoma mansoni eggshell protein.

The complete sequence for a major Schistosome mansoni eggshell protein gene has been determined from a genomic DNA fragment. The use of an open reading frame encoding a glycine-rich polypeptide was confirmed by in vitro translation of schistosome mRNA in the presence of [3H]glycine and comparison with the amino acid composition of purified, schistosome eggshells. Apart from the extraordinary abundance of glycine and tyrosine which are evenly distributed throughout the polypeptide chain, the most striking features of the deduced amino acid sequence are the presence of five well-conserved tandem repeats of 16-18 residues in the N-terminal region and the asymmetrical distribution of charged residues. Acidic residues (Asp) are confined to the N-terminal region, while basic residues (Lys, His), with the exception of a single histidine, are found in the C-terminal region. A model structure composed of short anti-parallel beta-strands is proposed, in which glycines and residues with small side chains lie within the strands and tyrosines and cysteines are arranged at the bends, where they would be available for cross-linking. Four such strands form one of the tandem repeats which are predicted in turn to form a stack of five closely packed beta-sheets, each of three strands and linked by the more variable fourth strand. The C-terminal region may form a similar but less compact structure. The ordered structure demonstrated by birefringence studies of the schistosome eggshell [Kusel, J. (1970) Parasitology 60, 79-88] could be formed by packing of the polypeptides such that the N-terminal domain contributes counter ions or cross-links to the C-terminal domain of adjacent molecules.

Amino Acid Sequence↗
PubMed1990

The gene family encoding eggshell proteins of Schistosoma japonicum.

The four closely related genes encoding eggshell proteins in the human parasite Schistosoma japonicum are described. A cDNA and a genomic DNA library were constructed and members of the eggshell protein gene family isolated. The four genes in this family do not contain introns, and differ in organization and nucleotide sequence from the related set of genes in Schistosoma mansoni and Schistosoma haematobium. The coding sequences of two of the S. japonicum genes and their flanking regions were determined. Transcription start sites for these genes were shown by primer extension analysis to occur 47 and 50 nucleotides in front of the start codon. A female-specific component in nuclear extracts binds to a DNA fragment containing conserved sequences upstream of the transcription start sites. The deduced protein sequences of 207 and 212 amino acids are composed of 50% glycine with continuous glycine regions as long as 11 residues. In vitro translations of male and female RNAs revealed female-specific translation products, the sizes of which were consistent with the eggshell proteins.

Amino Acid Sequence↗
PubMed1986

Effect of lindane on eggshell characteristics and calcium level in the domestic duck.

Adult laying domestic ducks (Anas platyrhynchos domesticus) were forced fed lindane (gamma-hexachlorocyclohexane) 20 mg/kg body weight daily, thrice/week and twice/week for 8 weeks. Significant shell thinning (18-21%) was observed in ducks with daily and thrice/week lindane feeding. SEM studies of thinned eggshells revealed reduced and tightly clustered mammillae with apparent decrease in intermammillary spaces and signs of inhibition of calcite formation. Such structural changes of thinned shells were associated with a significant reduction in the level of calcium both of the plasma and of shell gland of the ducks. Simultaneously, density of the pore in the shell and pore area/cm2 of the shell in these birds were drastically reduced, presumably because of total absence of 'large' pores in such shells. Such porosity change is suggestive of reduced conductivity of eggshell implying impaired hatching success. Diethyl stilboestrol post-treatment neutralized all the adverse effects of lindane on duck eggshell, indicating induced estrogen deficiency in such birds by lindane.

Animals↗