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At least 19 recordsLinked to original sources
PubMed1992

Inhibition of eggshell formation in domestic fowl by indomethacin: relation to calcium and prostaglandin metabolism in the eggshell gland mucosa.

1. The involvement of prostaglandins in eggshell formation in the domestic fowl was investigated by considering the effects of the drug indomethacin on the calcium metabolism on the eggshell gland. Egglaying birds were given a single dose (100 mg) of indomethacin at the beginning of shell calcification. Fourteen hours later the birds were sacrificed and the effects of the drug were determined. There was a 21% reduction in the shell thickness of the egg present in the shell gland at the time of slaughter (P < 0.01). The calcium content of the eggshell gland mucosa was increased to 153% (P < 0.01) of the controls. In the treated birds, there was 43% more calcium (P < 0.05) present in the shell gland lumen (recovered by rinsing with Tris buffer) than in the gland lumen of control birds. Total calcium in blood plasma was decreased by 15% (P < 0.05). In homogenate and three subcellular fractions (MIII, FI and FIII) of eggshell gland mucosa, 45Ca uptake was significantly reduced (i.e. by 29%, 25%, 17% and 35%, respectively). A significant reduction (62-66%) was also observed in the synthesis of PGF2 alpha, PGE2 and TxB2 by eggshell gland mucosa homogenate. 2. The effects of indomethacin treatment on the calcium metabolism of the avian eggshell gland are discussed and compared with p,p-DDE-induced alterations in calcium metabolism and prostaglandin synthesis by the eggshell gland.

Animals↗
PubMed1992

Eggshells as an index of aedine mosquito production. 1: Distribution, movement and sampling of Aedes taeniorhynchus eggshells.

The distribution of Aedes taeniorhynchus eggshells in Florida mangrove basin forests was determined and used to design a sampling plan. Eggshells were found in 10/11 sites (91%), with a mean +/- SE density of 1.45 +/- 0.75/cc; density did not change significantly year to year. Highest densities were located on the sloping banks of hummocks, ponds and potholes. Eggshells were less clumped in distribution than eggs and larvae and thus required a smaller sample size for a given precision level. While eggshells were flushed from compact soil that was subject to runoff during heavy rain, mangrove peat, the dominant soil of eggshell-bearing sites, was less dense and had little runoff or eggshell flushing. We suggest that eggshell surveys could be used to identify Ae. taeniorhynchus oviposition sites and oviposition patterns.

Aedes↗
PubMed1992

Eggshells as an index of aedine mosquito production. 2: Relationship of Aedes taeniorhynchus eggshell density to larval production.

To test if eggshell density could be used as an index of aedine mosquito production, we compared eggshell density with the larval production of Aedes taeniorhynchus in Florida mangrove basin forests. Quantitative (n = 7) and categorical (n = 34) estimates of annual larval production were regressed against the number of eggshells per cc of soil. Significant regressions were obtained in both instances. Larval production was concentrated in zones with the highest eggshell density. We suggest that eggshell density and distribution can be used to identify oviposition sites and the sequence of larval appearance.

Aedes↗
PubMed1985

Relation between Ca metabolism and ATPase activities in the subcellular fractions from duck eggshell gland mucosa after DDE administration during different stages of eggshell formation.

The ATP-dependent Ca2+ uptake by and the Ca2+-Mg2+-activated ATPase activity in the subcellular fractions from the eggshell gland of two varieties of ducks, Indian Runner ducks (IRD) and the cross-breed of Swedish and Rouen ducks (SRD), showed functional changes during eggshell formation in relation to the values in the resting state. DDE inhibited the Ca2+ uptake (Ca) but increased the Ca2+-Mg2+-ATPase activity (P) of fractions from active but not of those from resting glands. DDE reduced the Ca/P ratio of several fractions from active glands. DDE inhibited the functional increase in Ca2+-Mg2+-ATPase in the IRD homogenate, however. The effect of DDE on the eggshell index of mature eggshell was greater in IRD than in SRD, the reason for this being that the effect was exerted during a shorter time period in the latter variety.

Animals↗
PubMed1992

Furosemide decreases eggshell thickness and inhibits 45Ca2+ uptake by a subcellular fraction of eggshell gland mucosa of the domestic fowl.

1. Administration of furosemide to egg-laying domestic fowl (single p.o. dose 100 mg/bird) caused a decrease in the thickness of the shell of eggs laid the next day. 2. Furosemide administration in vivo caused a 37% decrease in the uptake of 45Ca2+ by a subcellular fraction of the eggshell gland mucosa (mainly composed of cell fragments and plasma membranes). 3. Furosemide treatment did not affect calcium concentrations in plasma or shell gland fluid but did cause a significant increase in the calcium concentration in shell gland mucosa. 4. It is concluded that the eggshell-thinning effect of furosemide is localized to an inhibitory effect on plasma membrane calcium transport in the eggshell gland mucosa. 5. These findings are discussed and compared with the effects of other drugs and toxic substances known to influence eggshell formation in birds.

Animals↗
PubMed1992

Schistosoma mansoni p48 eggshell protein gene: characterization, developmentally regulated expression and comparison to the p14 eggshell protein gene.

Egg production by worm pairs is a major cause of pathogenesis in schistosomiasis. To further the understanding of female reproductive development, we have isolated and characterized a complete copy of an eggshell protein precursor gene, p48. Sequence analysis reveals that the gene has 3 open reading frames and does not contain an intron. One of the open reading frames, ORF1, encodes a polypeptide of 50 kDa which shows strong homology to insect chorion proteins. Determination of the position of the mRNA cap-site facilitated identification of putative regulatory elements in the 5' upstream region of the gene. Some of these elements (e.g., TCACGT) have been shown to play a role in the regulation of chorion gene expression in insects. p48 mRNA is detectable only in mature female worms and the ability to detect the mRNA coincides temporally with worm pairing. Quantitative comparisons, during female reproductive development, of p48 transcripts to those from another eggshell protein precursor gene, p14, show that the p48 mRNA is significantly less abundant than p14 mRNA. In mature female worms, p48 mRNA can only be detected in vitelline cells. Antibodies made against the polypeptide sequence deduced from ORF1 of the p48 gene recognize a 50-kDa molecule in extracts from mature female worms, but not in extracts from immature females or males.

Amino Acid Sequence↗
PubMed1987

Methyl mercury decreases the eggshell thickness and inhibits the Ca2+ uptake in a homogenate of the eggshell gland mucosa and its subcellular fractions from the domestic fowl.

In the domestic fowl 20 mg of methyl mercuric chloride (MeHg) in a single oral dose given a day before egg-laying reduced the eggshell index by 35% and decreased the Ca content of the eggshell by 31% compared with those in the eggs laid on the previous days. The plasma concentration of Ca was reduced by MeHg by 50% in comparison with controls. The Ca concentration in the shell gland mucosa was not decreased by MeHg in relation to the control value. The rate of ATP-dependent Ca2+ binding by the homogenate of the mucosa was reduced by 33% by MeHg in relation to the control rate. The activity of Ca2+-Mg2+-ATPase was not changed.

Adenosine Triphosphatases↗
PubMed1992

Partial biochemical and immunochemical characterization of avian eggshell extracellular matrices.

There is evidence to suggest that extracellular matrix molecules, such as proteoglycans, are involved in the regulation of mineral deposition in calcifying tissues. One mineralizing system which is characterized by extremely rapid mineralization is the hen eggshell. This eggshell consists of a pair of nonmineralized eggshell membranes subjacent to the calcified eggshell proper; the eggshell proper is organized into palisades (columns) of mineralized matrix separated by pores. Between the membranes and the shell proper are compacted foci of tissue called mammillary knobs, which are thought to be sites where mineralization is initiated. Previous work from this laboratory has shown the presence of types I, V, and X collagen in the shell membranes. To address the question of the possible role of proteoglycans and glycosaminoglycans in mineralization of the eggshell, two approaches were used. First, immunohistochemistry was performed with monoclonal antibodies to various proteoglycan and glycosaminoglycan epitopes. This analysis indicates that different glycosaminoglycans are localized to discrete regions within the eggshell. Dermatan sulfate is present within the matrix of the shell proper and, to a lesser extent, the mammillary knobs and the outer portion of the shell membranes. In contrast, keratan sulfate is found in the shell membranes and prominently in the mammillary knobs. Interestingly, different keratan sulfate antibodies immunostain distinct regions of the eggshell, which suggests that various types of keratan sulfate are distributed differently. The second approach utilized was to extract the eggshell membranes and recover anionic molecules by anion-exchange chromatography. This resulted in the extraction of material which was recognized by antibodies to keratan sulfate, but not to chondroitin sulfate. This material was very large, as evidenced by its elution in the void volume of a Sepharose CL-2B column. The large size may be due to the extensive cross-links known to occur in the eggshell. If eggshell membranes are extracted at elevated temperature, the material recovered is of much smaller size. These results indicate that molecules recognized by antibodies to glycosaminoglycans are present in the eggshell, and their localized distribution relative to the calcified matrix suggests that they may be involved in the regulation of mineral deposition.

Animals↗
PubMed1992

Effects of p,p'-DDE and some other chlorinated hydrocarbons on the formation of prostaglandins by the avian eggshell gland mucosa.

Some structurally related chlorinated hydrocarbons were investigated for their effects on the production of prostaglandins by the eggshell gland mucosa of ducks and domestic fowl. Formation of PGF2 alpha, PGE2 and TxB2 by homogenates of domestic fowl eggshell gland mucosa was significantly inhibited by in vitro addition of p,p'-DDE, Arochlor 1242 and, to a lesser extent, Arochlor 1260, but not by p,p'-DDT and o,p'-DDE. Comparatively, in duck eggshell gland mucosa homogenates, synthesis of the same prostaglandins was somewhat more sensitive to inhibition by 5 microM p,p'-DDE added in vitro. Eggshell gland mucosa synthesized significantly more PGF2 alpha, PGE2 and TxB2 than did the mucosa of the magnum and isthmus regions of the oviduct. Duck eggshell gland mucosa homogenates synthesized significantly more prostaglandins than similar homogenates from the domestic fowl, and, considering the former synthesis of PGF2 alpha was significantly higher when ducks were slaughtered at 08:00 than at 16:00 hours. In ducks, dietary administration of 40 ppm, p,p'-DDE for 45 days resulted in 21% eggshell thinning compared to the contemporary control values. This treatment also resulted in notable effects in homogenates of the eggshell gland mucosa, as compared to controls: Ca2+ uptake was reduced by 43%, synthesis of PGF2 alpha, PGE2 and TxB2 was reduced by 26%, 38% and 53%, respectively; the Ca content was increased to 145%. The role of p,p'-DDE in inhibiting prostaglandin formation in the eggshell gland is discussed as a mechanism of the eggshell thinning action of this chlorinated hydrocarbon.

Animals↗
PubMed1991

Schistosoma mansoni: eggshell formation is regulated by pH and calcium.

The protein precursors of the schistosome eggshell are synthesized and packaged into secretory vesicles in the vitelline cells. These vesicles appear to contain an emulsion of eggshell precursor material. Evidence is presented to show that these secretory vesicles are acidic as in other systems and that this acidity stabilizes the emulsion and prevents the eggshell cross-linking reactions from occurring. Alkalinizing treatments trigger eggshell formation within the secretory vesicles as shown by (1) the induction of autofluorescence and (2) by electron microscopy which shows that the eggshell precursors have aggregated within the secretory vesicles into spherical particles bearing microspines. These aggregates formed in the secretory vesicles were isolated and shown to have the same protease resistance and amino acid composition as authentic eggshell. The calcium ionophore A23187 induces scattered autofluorescence in intact female worms which electron micrographs show to be due to exocytosis of eggshell material. Based on these observations we propose a model for the formation of schistosome eggshell and suggest that it may apply to all trematodes in which the eggshell precursors are present as stable emulsions in the secretory vesicles of the vitelline cells.

Ammonium Chloride↗
PubMed1990

The major structural proteins of cod (Gadus morhua) eggshells and protein crosslinking during teleost egg hardening.

The highly hydrophobic protein aggregate which constitutes the fish eggshell has for the first time been quantitatively solubilized. This study shows that the nonactivated eggshell from cod is composed primarily of only three protein monomers, designated alpha (74 kDa) beta (54 kDa) and gamma (47 kDa). Protein extraction studies of the eggshells before and after egg activation demonstrate that egg hardening is accompanied by a 10-fold decline in total protein solubility, which is due to nonextraction of the alpha, beta, and gamma chains. When present during the egg activation process monodansylcadaverine (MDC-a fluorescent lysine analog) inhibits eggshell hardening and at the same time becomes covalently incorporated into the eggshell. This MDC incorporation is calcium-dependent and suggests the induction of a perivitelline transglutaminase activity after egg activation. (Transglutaminases catalyze the formation of an amide bond (isopeptide bond) between the gamma-carbonyl group of glutamine and the epsilon-amino group of lysine with release of ammonia. Crosslinks between proteins are generated when the two amino acid residues are located on different proteins.) Protein solubilization studies and NaDodSO4 gel analysis of the eggshell proteins from eggs subjected to 5 mM MDC during egg activation, reveal that when eggshell hardening is blocked by MDC, the three main eggshell proteins remain extractable even after egg activation. Simultaneously we observed a covalent incorporation of MDC into the gamma protein.

Amino Acids↗
PubMed1977

Effects of DDT on eggshell quality and calcium adenosine triphosphatase.

Adult mallard ducks were fed a diet containing 50 ppm DDT for 6 months. Eggs laid during this period were collected and eggshell weight, thickness, and calcium were determined. Chronic ingestion of DDT resulted in production of eggshells that were significantly thinner and lighter than those of controls. Total calcium of thinned eggshells was also reduced; however, calcium per gram of eggshell was not altered, indicating that other eggshell constituents were not incorporated as well. Calcium adenosine triphosphatase activity in the microsomal fraction of eggshell gland epithelium was assayed in control and DDT-fed ducks. Enzyme activity in DDT-fed ducks was reduced to 65% of control values. Since Ca-ATPase has been shown to be associated with calcium transport, enzyme inhibition may be responsible for decreased eggshell weight and thickness. Electron microscopic evaluation of microsomal fractions showed elements of the plasma membrane, including cilia and microvilli, as well as rough and smooth endoplasmic reticulum. Inhibition of calcium transport at the plasma membrane of mucosal epithelium is proposed as a possible mechanism of DDT-induced eggshell thinning.

Adenosine Triphosphatases↗
PubMed1989

Schistosoma haematobium: analysis of eggshell protein genes and their expression.

Eggshell protein genes of Schistosoma mansoni that encode a 14 kDa protein have been shown to be highly conserved and expressed in a sex-, tissue-, and temporal-specific manner. To initiate studies on the eggshell protein genes of S. haematobium, a cDNA probe, pSMf 61-46, representing a S. mansoni eggshell protein mRNA was used to screen a S. haematobium genomic library. Of the seven independent recombinant clones isolated, two (lambda SH 2-1 and lambda SH 6-1) were analyzed and compared to those of S. mansoni. lambda SH 2-1 and lambda SH 6-1 each contain a different genomic copy of the gene encoding a 19.8 and 17.6 kDa protein, respectively. This is due to an additional 78 bp present in the coding region of lambda SH 2-1 relative to lambda SH 6-1. The rest of the coding sequences are identical, and the 5' and 3' untranslated regions are nearly identical. The deduced amino acid sequences of S. haematobium eggshell proteins are very rich in glycine (47 and 50%) when compared to 43.5% glycine in the protein encoded by S. mansoni. Long stretches of glycines, as many as 15 in a row, occur in the S. haematobium sequence. DNA comparison of the eggshell protein genes of the two schistosome species yielded an overall homology of 83.1%. The homology is much higher in the 5' and 3' untranslated regions than in the protein-coding regions. Genomic clones of both species contained second open reading frames, which appeared to be kept open as a consequence of the amino acid composition of the other. There are no introns in S. haematobium or S. mansoni eggshell protein genes, and the genomic Southern data indicated a similar arrangement of these genes in the genome of both species. Primer extension experiments and dideoxynucleotide sequencing of the RNA determined the mRNA cap site sequence as ATCAT and ATCAC in lambda SH 2-1 and lambda SH 6-1, respectively. Northern blot analysis determined the size of the mRNA to be about 1.0 kp. Expression of the RNA from these genes appears to be regulated in a manner similar to the corresponding genes in S. mansoni. mRNA is found only in mature females and first appears at 70 days after infection of hamsters. DNA sequence comparisons of the 5' flanking regions of S. haematobium and S. mansoni eggshell protein genes to each other and to those of silkmoth and Drosophila revealed several short sequence elements that are shared.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Eggshell zona radiata-proteins from cod (Gadus morhua): extra-ovarian origin and induction by estradiol-17 beta.

Using Atlantic cod (Gadus morhua) as a model organism, the aim of this report was to delineate whether teleostean eggshell zona radiata proteins have their origin, i.e., site of synthesis, in gonadal or somatic tissues. Estradiol-17 beta was administered intraperitoneally to one-year-old cod (Gadus morhua) with either undeveloped gonads or with differentiated gonads. By immunoblotting procedures estradiol-dependent protein induction was investigated using specific rabbit antisera directed against cod eggshell proteins and brown trout vitellogenin. No immunological cross-reactions were observed between the two antisera, and eggshell proteins and vitellogenin were detected in blood plasma and somatic tissues only in estradiol-treated cod. Three plasma-components were immunoreactive to antiserum directed against eggshell proteins, and these proteins possessed molecular weights of 78, 54 and 47 kDa, identical to the molecular weights of the cod eggshell alpha, beta and gamma zona radiata-proteins. These three immunoreactive plasma-components were observed after administration of estradiol-17 beta to both sexes, also in males having reached spermiation, and in juveniles of either sex without developed gonads. The data are interpreted to signify that cod eggshell zona radiata-proteins originate in an extra-ovarian tissue and are transported in the blood for deposition in the ovaries. We propose that oogenesis involves estradiol-17 beta regulation of both eggshell zona radiata-proteins and vitellogenin synthesis.

Animals↗
PubMed1992

Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. II. Palaeacanthocephala.

Eggshells of the palaeacanthocephalans Acanthocephalus anguillae, Pomphorhynchus laevis and Polymorphus minutus were investigated for their fine structure as well as their chemical composition. The acanthor larvae are surrounded by four eggshells (E1-E4) separated by interstices (G1-G4). Immature eggs do not exhibit the complete set of eggshells. The chemical composition of the outermost, thin eggshell (E1) remains unknown. E2 is supplied by outer filaments of different strength; it contains keratin, which was localized electron microscopically using anti-keratin. In P. laevis and P. minutus, E3 seems to contain glycoproteins, which could not be visualized in this eggshell of A. anguillae. The innermost eggshell (E4) uniformly contains chitin. The electron-lucent interstices of the eggs of P. laevis and P. minutus are rich in polysaccharides and/or proteoglycans, whereas those of A. anguillae contain low amounts of such substances. The differences observed in the abundance of carbohydrates are discussed with respect to the life cycles of the three acanthocephalans.

Acanthocephala↗
PubMed1991

Schistosoma japonicum: analysis of eggshell protein genes, their expression, and comparison with similar genes from other schistosomes.

As the egg of Schistosoma japonicum plays a central role in transmission and in pathogenesis, we sought to understand the molecular biology of egg formation. In this study we characterized an eggshell protein gene of S. japonicum and compared it with similar genes from S. mansoni and S. haematobium. To initiate studies on the eggshell protein genes of S. japonicum, a cloned genomic fragment containing an entire copy of a S. haematobium eggshell protein gene was used to identify three EcoRI hybridizing fragments of 2.6, 2.0, and 1.3 kbp in S. japonicum genomic DNA and to isolate three independent genomic clones from a S. japonicum genomic library. Two genomic clones, SJ 4-1 and SJ 3-1, contain at least two copies of the gene. The DNA sequence of a 2.0-kbp EcoRI fragment of clone SJ 3-1 showed two open reading frames (ORF), one of which showed a strong homology to the chorion proteins of insects. This ORF had 207 amino acids with a calculated molecular size of 18.5 kDa. The predicted peptide was glycine (50%) and tyrosine (10%) rich like other described schistosome eggshell proteins. Primer extension and the dideoxynucleotide sequence of the mRNA defined the cap site of the RNA and positioned the putative TATA and CAAAT elements and other cis-acting elements. Northern analysis demonstrated that eggshell protein mRNA was only detected in mature female parasites. The appearance of the female-specific mRNA was dependent on pairing with the male parasite and increased with egg production (as determined by hybridization intensity). A comparison of the DNA and deduced protein sequences of eggshell protein genes from S. japonicum with those of similar genes from S. mansoni and S. haematobium indicated that the genes are highly conserved, with S. mansoni and S. haematobium genes being more similar to each other than either is to S. japonicum.

Amino Acid Sequence↗
PubMed1992

Relationships between calbindin (Mr 28,000) and calcium transport by the eggshell gland.

1. Eggshell density (mg/cm2) and eggshell gland calbindin decreased in the aged hens. 2. Aged hens which laid eggs with a low shell weight and shell density had significantly lower intestinal and eggshell gland calbindin as compared with those which laid eggs with a high shell weight and shell density. 3. Significant correlations were found in aged hens between duodenal or eggshell calbindin and shell weight or shell density. 4. The results suggest that: (a) aged hens forming light shells absorbed calcium with a lower efficiency than those forming heavy shells or than young hens; (b) the decline in shell density in the aged hens is caused by a physiological calcium deficiency or by a defect in the hens' ability to alter calbindin synthesis in response to calcium needs; (c) in the aged hens, the deposition of calcium into the eggshell is dependent on, or at least associated with, eggshell gland calbindin.

Aging↗