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PubMed2000

Secondary structure of chorion proteins of the teleostean fish Dentex dentex by ATR FT-IR and FT-Raman spectroscopy.

FT-Raman spectroscopy and ATR-IR spectroscopy were applied to study the secondary structure of the eggshell (chorion) proteins of the teleostean fish Dentex dentex. Raman and IR spectra clearly indicate an abundance of antiparallel beta-pleated sheet conformation in chorion proteins. This finding is further supported by analysis of the vibrational data by regression techniques and deconvolution procedures. Thus, the common morphological characteristics of D. dentex, Salmo gairdneri, and other teleostean fish chorions may be explained on the basis of common secondary structure features of their constituent proteins. A detailed understanding of the interactions that dictate the self-assembly of fish chorion proteins to form the fish eggshell awaits determination of amino acid sequences.

Animals↗
PubMed1996

Patterns, trends, and toxicological significance of chlorinated hydrocarbon and mercury contaminants in bald eagle eggs from the Pacific coast of Canada, 1990-1994.

Bald eagle (Haliaeetus leucocephalus) eggs were collected during incubation, 1990-1992, from 16 nests near three bleached-kraft pulp mills, from six nests in the Fraser River estuary and from seven nests at a reference site on the Pacific coast of Canada. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among sites. Mean concentrations of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were significantly higher in eggs collected from near three kraft pulp mill sites in the Strait of Georgia (44, 45, 84 ng/kg) than from the reference area in Johnstone Strait (15 ng/kg). There were few differences among sites in mean organochlorine pesticide levels, indicating the diffuse distribution of those chemicals and the domination of atmospheric inputs. Mean concentrations of total polychlorinated biphenyls (PCBs) were highest in eggs from the Strait of Georgia (4.86 mg/kg) and the PCB congener pattern was significantly different between that area and both the lower Fraser valley and Johnstone Strait. Mean mercury concentrations, which were mainly methyl-mercury, were significantly higher in eggs collected from the lower Fraser Valley (0.258 mg/kg) and Johnstone Strait (0.294 mg/kg) compared to the Strait of Georgia (0.188 mg/kg). Individual and regional variation in concentrations of organochlorine pesticides, PCBs and mercury in eagle eggs were thought to be influenced mainly by dietary differences. Toxicologically, in 1990, mean TCDD-toxic equivalents (TEQs) in bald eagle eggs were about two-fold greater than a lowest-observed-effect level, suggested elsewhere for this species, of 210 ng/kg TEQs. In the Strait of Georgia, PCCDs and PCDFs made a greater contribution to TEQs than non-ortho and mono-ortho PCBs, whereas the reverse was true for eggs outside the strait. Mean eggshell thickness was less than the pre-1947 value at all sites, although there was no significant relationship between eggshell thickness and DDE concentrations. Levels of other organochlorine pesticides and mercury were below those considered to be toxic.

Analysis of Variance↗
PubMed1993

Water loss from eggs of domestic fowl and calcium status of hatchlings.

Water balance in eggs of domestic fowl was manipulated by drilling holes (each 3 mm in diameter) through the calcareous layer into the air cell on day 10 of incubation. Water loss between days 0 and 18 averaged 6 g for eggs in the control group (no hole) but increased to 8, 12, and 15 g for eggs with 1, 2, or 3 holes, respectively. Hatching success was 79-87% for eggs with 0-2 holes through the eggshell but only 43% for eggs with three holes. Live mass of hatchlings declined as the number of holes drilled in the eggshell increased, but dry mass of carcasses was unaffected by the treatments. The quantity of Ca2+, Mg2+, and phosphorus in residual yolks and yolk-free carcasses of hatchlings was not influenced by the amount of water lost from eggs. Plasma Ca2+ and Mg2+ were elevated in hatchlings from eggs with high rates of water loss. The inability to regulate plasma Ca2+ may be a negative consequence of excessive water loss and could contribute to increased mortality of embryos.

Animals↗
PubMed1987

Formation by the uterus of a peripheral layer of the sheath in microfilariae of Litomosoides carinii and Brugia malayi.

The eggshells of young developmental stages in the uterus are rather thin and homogenous. In the brezel stage of Brugia malayi they are 35 nm thick and 20 nm in Litomosoides carinii. In young developmental stages up to brezel stages the eggshells bind the lectins WGA, DBA and PNA labelled with colloidal gold. This shows that GlcNAc, GalNAc and Gal residues are present at the surface of the sheath. In intrauterine microfilariae of B. malayi the original sheath is reduced to a thickness of 7 nm. It is reinforced by secretions from a specialized area of the epithelium of the uterus which do not appear as a homogeneous layer but look like a string of pearls. This layer may be called the "uterine layer". It has a thickness of 40-80 nm. In the microfilaria of L. carinii, the thickness of the original sheath is reduced to 2-3 nm and the uterine layer has a thickness of 7 nm. The uterine layer does not react with any of the lectins, which shows that the surface lacks N-acetylglucosamine, N-acetylgalactosamine and galactose residues. The uterine layer appears to be an ancestral (plesiomorphic) feature which is present in free-living nematodes and the highly specialized bloodforms of filariae. The uterine layer seems to protect and disguise the original sheath against the immune reactions of the host.

Animals↗
PubMed1995

Immunoelectron microscopical localization of a circulating antigen in the excretory system of Schistosoma mansoni. Ultrastructural localization studies of the excretory system of S. mansoni.

In this study the excretory system of Schistosoma mansoni was ultrastructurally examined with a recently described monoclonal antibody (mAb) against a circulating antigen. In previous studies this mAb was found to have affinity for the excretory system. Strong immunoreactivity was found on the flagella of the flame cells and of the collecting ducts throughout the worm. The eggshell and the space between the miracidium and the eggshell showed strong reactivity with a declining gradient towards the exterior, suggesting a secretion process. In cercariae, immunoreactivity was restricted to the tegument, whereas in schistosomula the labeling pattern resembled that of the adult worm, demonstrating positive reactivity of the flame cells and no immunostaining of the tegument. This stage-dependent differential expression of different antigens in the excretory system and in the tegument could suggest a maturation process of the excretory system.

Animals↗
PubMed1976

Lead in tissues of mallard ducks dosed with two types of lead shot.

Mallard ducks (Anas platyrhynchos) were sacrificed one month after ingesting one number 4 all-lead shot or one number 4 lead-iron shot. Livers, kidneys, blood, wingbones, and eggs were analyzed for lead by atomic absorption. Necropsy of sacrificed ducks failed to reveal any of the tissue lesions usually associated with lead poisoning in waterfowl. Lead levels in ducks given all-lead shot averaged about twice those in ducks given lead-iron shot, reflecting the amount of lead in the two types of shot. Lead in the blood of ducks dosed with all-lead shot averaged 0.64 ppm, and 0.28 ppm in ducks given lead-iron shot. Lead residues in livers and kidneys of females given all-lead shot were significantly higher than in males. In both dosed groups, lead levels in wingbones of females were about 10 times those in males, and were significantly correlated with the number of eggs laid after dosage. Lead levels in contents and shells of eggs laid by hens dosed with all-lead shot were about twice those in eggs laid by hens dosed with lead-iron shot. Eggshells were found to best reflect levels of lead in the blood. Our results indicate that mallards maintained on a balanced diet and dosed with one lead shot may not accumulate extremely high lead levels in the liver and kidney. However, extremely high lead deposition may result in the bone of laying hens after ingesting sublethal amounts of lead shot as a result of mobilization of calcium from the bone during eggshell formation.

Animals↗
PubMed1983

Effect of the substratum on the growth of CFU-c in continuous marrow culture.

The effect of the substratum on the maintenance of granulocyte-macrophage progenitors (CFU-c) was studied in continuous mouse marrow culture. Glass and decalcified eggshell membrane were found preferable to plastic, providing better adherence of stromal cells. Eggshell membrane consists of a meshwork of branching fibers suitable for the adherence of stromal cells. The glass surface with its high surface pH may provide an electrostatic attraction for the negatively charged surface of stromal cells.

Animals↗
PubMed1975

The effect of mirex on reproduction of Japanesequail and on characteristics of eggs from Japanese quail and chickens.

Laying White Leghorn chickens were fed mirex at 0, 5, 10, 20, 40, 80, and 160 ppm for 12 weeks, and laying Japanese quail were fed mirex at 0, 5, 40, and 80 ppm for 12weeks. The data suggest that dietary mirex at these levels did not affect egg production, egg weight, shell thickness, shell calcium, the proportion of broken eggs, or the proportion of soft-shelled eggs of either chickens or quail. Statistical significance (P greater than 0.05) associated with dietary mirex was detected in the analysis of eggshell weight for chickens; however, because a dose-response relationship of shell weight vs. level of mirex fed was not evident, this observation was attributed to chance. The data suggest that dietary mirex did not affect eggshell weight, fertility, or hatchability of quail. Mirex accumulation in eggs and carcasses of both species was proportional to dose and was slightly higher in quail than in chickens.

Analysis of Variance↗
PubMed1982

Inductive specificity of mineralized bone matrix in ectopic osteoclast differentiation.

The present report describes the first in a series of studies designed to identify the factor or factors responsible for eliciting osteoclast differentiation. Particles of mineralized and demineralized bone, hydroxyapatite (HA), and eggshell were grafted onto the chorioallantoic membranes (CAMs) of chick embryos. After 3 of 6 days, portions of CAMs with associated grafts were harvested, processed for light and electron microscopy, and examined for the presence of multinucleated giant cells with the morphological characteristics of osteoclasts. Light microscopic examination revealed that, within only 3 days, many particles of mineralized materials had become surrounded or engulfed by multinucleated giant cells. Ultrastructurally, all such cells possessed a vacuolated and mitochondria-enriched cytoplasm, but they differed in the nature of the contacts formed at the cell-particle interface. With eggshell, the cells developed filopodia but lacked clear zones and ruffled membranes. With HA, clear zones were evident but cytoplasmic extensions and membrane ruffling were absent. Implants of mineralized bone, however, elicited the formation of giant cells with prominent clear zones and ruffling of the plasma membrane like that observed in bonafide osteoclasts. In contrast, grafts of demineralized bone did not evoke giant cell formation but rather recruited two cell types morphologically akin to either fibroblasts or macrophages. We conclude that the factor(s) responsible for osteoclast differentiation resides specifically within bone matrix and is intimately associated with the mineral phase. Further, in response to such a factor(s), osteoclast differentiation can occur ectopically, outside of the developing vertebrate body.

Allantois↗
PubMed2001

Disrupted carbonic anhydrase distribution in the avian shell gland following in ovo exposure to estrogen.

Eggshell thinning among wild birds has been an environmental concern for almost half a century and the underlying mechanisms are still not fully understood. Previously we showed that exposure of quail embryos to ethynylestradiol (EE2) caused disorganization of the tubular glands in the shell gland of adult birds. In this study, we have examined the effect of in ovo exposure to EE2 on carbonic anhydrase (CA) localization, especially in the shell gland, because CA is required for shell formation. In the control birds, CA was localized in the cell membranes of the tubular gland cells of the shell gland, whereas the surface epithelium was always devoid of CA. In ovo treatment with 20ng EE2/g egg resulted in a loss of CA activity in the tubular glands while the surface epithelium showed strong induction of both membrane bound and cytoplasmic CA activity in 49+/-1% of the cells. The dose 2ng EE2/g egg resulted in partial loss of tubular gland CA and strong induction of CA activity in 2.5+/-0.5% of the surface epithelial cells and weaker induction in 22+/-2% of the epithelial cells. In conclusion, this study shows that embryonic exposure to a xenoestrogen disrupts CA distribution in the adult shell gland. We propose that eggshell thinning in avian wildlife could reflect a functional malformation in the shell gland, already induced by xenoestrogen during embryonic development rather than being caused solely by exposure of the adult bird.

Animals↗
PubMed2000

Variability of mercury and selenium levels in clutches of Audouin's gulls (Larus audouinii) breeding at the Chafarinas Islands, Southwest Mediterranean.

We determined mercury and selenium in 43 eggs (eggshell, albumen, and yolk) which belong to different clutch sizes of Audouin's gull from the Chafarinas Islands. The results were compared with those obtained previously with the same species at the Ebro Delta. Both, the intra- and the interclutch sources of variability have been examined. There is an effect of the female on mercury and selenium concentrations in a clutch, which supports the use of eggs as monitoring tools. The distribution pattern of mercury among albumen, yolk and eggshell, the dynamics of this element during the laying process, as well as data concerning egg formation strategies suggest that the mercury in the albumen corresponds mainly to the mercury acquired by the female while feeding in the breeding area. The mercury and selenium levels of the eggs from the Chafarinas Islands were lower than those of the Ebro Delta, which can be due to differences in both the marine contamination and the diet in the two colonies.

Animals↗
PubMed2001

Organochlorine contaminants and biomarker response in double-crested cormorants nesting in Green Bay and Lake Michigan, Wisconsin, USA.

Double-crested cormorant (Phalacrocorax auritus) eggs at pipping and sibling 10-day-old chicks were collected from two colonies in Green Bay, WI, one colony in Lake Michigan, WI, and reference colonies in South Dakota and Minnesota. Egg contents and chicks were analyzed for organochlorine contaminants including polychlorinated biphenyl (PCB) congeners. Livers of embryos and chicks were assayed for hepatic microsomal ethoxyresorufin-O-dealkylase (EROD) activity. Eggshell thickness and the physical dimensions of embryo brains were measured. Concentrations of organochlorines, including p,p'-DDE (p,p'-dichlorodiphenyldichloroethylene), PCBs, and PCB congeners were generally an order of magnitude higher in eggs and chicks from Wisconsin than from reference locations. Total PCBs averaged 10-13 microg/g wet weight in eggs from three Wisconsin colonies compared to 0.9 microg/g PCBs from reference locations. Double-crested cormorant chicks accumulated on average 33-66 microg PCBs/day and 7-12 microg p,p'-DDE/day in the Wisconsin colonies compared to 0 microg PCBs/day and 1 microg p,p'-DDE/day in the reference colonies. At pipping, EROD activity in the livers of cormorant embryos was significantly higher in the Wisconsin colonies and significantly correlated with PCBs and the toxic equivalents (TEQs) of aryl hydrocarbon-active PCB congeners relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, in 10-day-old chicks EROD activity was not consistently different among colonies and was not correlated with PCBs or TEQs. A significant negative relationship between embryo brain asymmetry and the size of the egg suggested that physical constraint might be an important factor influencing the response of this bioindicator. Thinner eggshells in two colonies located near Door County, Wisconsin, suggested that historic p,p'-DDE residues associated with orchards are still an important source of p,p'-DDE in the local environment.

Abnormalities, Drug-Induced↗
PubMed1997

Syncytial organization of acanthors of Polymorphus minutus (Palaeacanthocephala), Neoechinorhynchus rutili (Eoacanthocephala), and Moniliformis moniliformis (Archiacanthocephala) (Acanthocephala).

The fine structures of immature and of developed shelled acanthors of three species belonging to the three subgroups of the Acanthocephala were investigated. Acanthors are surrounded by four eggshells (embryonic envelopes) and are composed of three syncytia: a frontal syncytium, a central syncytium, and an epidermal syncytium. Neither a sense organ nor a nervous system has been found. The central syncytium shows a mass of condensed nuclei and 12 decondensed nuclei and gives rise to 10 anterior/posterior subepidermal myofibrillar systems and 2 oblique retractor muscles. Circular muscles are missing. A single decondensed nucleus can be assigned to each of the 12 muscular systems. The epidermal syncytium embeds the other two syncytia and forms the wrinkled epidermis, which shows an extracellular glycocalyx and intrasyncytial condensations. Prominent recurved hooks, which mark the anterior end of each acanthor, and body spines are intraepidermal differentiations. Partly branched tubular infoldings of the epidermal plasma membrane of the acanthor exist and represent precursors of the pore ducts typical of the adult epidermis. Autapomorphies in the ground pattern of the monophylum Acanthocephala are the four eggshells, the early development of three syncytia, the condensed nuclei in the central syncytium, and the differentiation of ten longitudinal muscle bands and two muscle retractors and of intraepidermal hooks and spines. The syncytial organization of the epidermis with intraepidermal skeletal condensations and infoldings of the apical plasma membrane are characteristics inherited from a stem species common to Acanthocephala, Seison, and Rotifera.

Acanthocephala↗
PubMed2000

Comparative ultrastructure of eggs in Echinostoma paraensei, E. caproni, and E. trivolvis (Trematoda: Echinostomatidae).

The 37-collar-spined echinostomes Echinostoma paraensei, E. caproni, and E. trivolvis are digeneans that live in the intestine of small mammals and birds. Comparative studies of the eggs of these species were done using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The egg of E. caproni was the largest of the three species studied, whereas the egg of E. trivolvis was the smallest in both length and width. The SEM study showed differences in the aboperculum region of the eggs in all three species. The TEM study showed that the eggshell of all three species consisted of three layers, but no difference in eggshell structure was observed in any species.

Animals↗
PubMed2001

Nematode chitin synthases: gene structure, expression and function in Caenorhabditis elegans and the plant parasitic nematode Meloidogyne artiellia.

Although the presence of chitin in nematodes is well documented little is known about its synthesis in this phyletic group. The recently completed genome sequence of Caenorhabditis elegans predicts two sequences with homology to chitin synthases (chitin-UDP acetyl-glucosaminyl transferase; EC 2.4.1.16). We show that these genes are differentially expressed in a pattern that may reflect different functional roles. One gene is expressed predominantly in the adult hermaphrodite (the main egg-producing stage in the nematode) and later larval stages, which is consistent with a role in production of chitin for the eggshell. The other gene, however, is expressed in the cells that form the pharynx, and only in the period directly preceding a moult. These data suggest that the product of this gene is involved in synthesis of the feeding apparatus, which is replaced during each moult. We have also isolated a full-length genomic sequence of a chitin synthase orthologue from the plant parasitic nematode Meloidogyne artiellia. The single gene present in M. artiellia shows an expression pattern that is consistent with a role for the protein in production of the eggshell.

Animals↗
PubMed1994

The role of vitamin D in chorioallantoic membrane calcium transport.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) is essential for the transport of eggshell calcium to the embryo across the chorioallantoic membrane (CAM). CAM contains the vitamin D receptor that increases following 1,25-(OH)2D3 injection into embryos at day 10 of incubation. Further, a single injection of 100 ng of 1,25-(OH)2D3 into vitamin D-deficient quail eggs at day 10 of incubation resulted in a significant increase in both body and yolk calcium. This is accompanied by an increase in carbonic anhydrase from low levels in deficiency to normal levels. Acetazolamide (AZ), a specific carbonic anhydrase inhibitor injected into the quail embryos, caused hypocalcemia and hyperphosphatemia. This is similar to the hypocalcemia and hyperphosphatemia found in vitamin D-deficient embryos. These results suggest that one mechanism of action of vitamin D in the mobilization of eggshell calcium is the activation of carbonic anhydrase that acidifies the calcium carbonate shell.

Acetazolamide↗
PubMed1983

Isolation of germ line-dependent female-sterile mutation that affects yolk specific sequestration and chorion formation in Drosophila.

Two loci on the X chromosome have been implicated in choriogenesis by in situ hybridization of poly A-containing RNA from choriogenic eggchambers to Drosophila polytene chromosomes (A.C. Spradling and A.P. Mahowald (1979). Cell 16, 589-598): 7E and 12E. At least two genes coding for major eggshell proteins map to region 7E (A.C. Spradling, M.E. Digan, A.P. Mahowald, M. Scott, and E.A. Craig (1980). Cell 19, 905-914). In an effort to elucidate the functional role of the 12E gene product, 3600 EMS-treated X chromosomes were screened for recessive female-sterile mutations that mapped within the region 11F10-12F1. Four independent female-sterile mutations were recovered, three of which fell into one complementation group (fs29, fs117, and fs445). Mapping by analysis of recombinant progeny as well as of trans heterozygotes utilizing other deficiency chromosomes showed that the three noncomplementing mutations all mapped to region 12E1-12F1. Studies comparing chorion morphology and protein synthesis indicate localized perturbations in the extracellular assembly of eggshell components in mutant eggchambers. The germ line dependence of the mutations was established using germ line mosaics constructed by pole cell transplantation. Analysis of eggchamber protein accumulation patterns showed reduced amounts of yolk polypeptides (YPs) in the mutants. The elevated concentrations of YPs found in mutant hemolymph coupled with the normal YP biosynthetic patterns and active uptake of trypan blue by mutant oocytes suggest that 12E sequences play a role in yolk-specific sequestration.

Animals↗
PubMed1984

Localization of a gene for a minor chorion protein in Drosophila melanogaster: a new chorion structural locus.

A minor chorion protein (called s70) with an approximate molecular weight of 70,000 D has been characterized in Drosophila melanogaster. The Staket geographic strain was found to carry an electrophoretic variant of this eggshell component and was used to determine the chromosomal location of the s70 gene. Our results establish a new locus for a chorion gene near yellow on the X chromosome and represent the first mapping of a quantitatively minor eggshell protein.

Animals↗