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PubMed1995

Electrophoretical and histochemical characterization of Schistosoma mansoni phenol oxidases.

The phenol oxidase system, which is thought to play a central role in eggshell formation, was analyzed by means of electrophoretic and histochemical techniques. In contrast to current beliefs, our data show that males also express the phenol oxidase activity. The analysis of the electrophoretic pattern from males and females shows differences: adult males present a major band and a faint band, migrating slightly below. Adult females express a more complex pattern composed of four bands. Histochemical studies revealed that female phenol oxidase is concentrated in the vitelline cells, is inhibited by DDC, and this inhibition is correlated with disruption of female egg production. The present studies, in agreement with other reports, reveal that female phenol oxidase may be involved in sclerotization of the S. mansoni eggshell.

Animals↗
PubMed1994

Biotechnological applications of research on animal pigmentation.

The implications of primary research on pigmentation for the colour manipulation of animal species of economic importance, and the facilitation of specific processes in biotechnology are discussed. Pigment technologists, especially poultry and fish nutritionists, are concerned with achieving the often specific type and degree of coloration demanded by consumers of various products (notably egg yolk, eggshell, broiler skin and salmon flesh). In most instances involving melanin (pelage, plumage and integument) and porphyrin (eggshell) pigments, the desired coloration is achieved through the use of alternate alleles at gene loci controlling the characters of interest. In contrast, coloration involving carotenoids is controlled primarily through pigment supplementation in the diet. The difference between carotenoids and other pigments involves the strict dietary origin of the former. Factors other than pigment availability, such as body condition, hormonal status and genetic constitution, also affect coloration. Although day-old chicks can be sexed by visual inspection of their genitalia, matings resulting in sex-associated phenotypes are in wide use. The genetic markers involved affect the colour of the plumage. The cloning of genes involved in pigmentation offers the prospect of deciphering the genetic control of animal pigmentation and modifying it to meet specific pigmentation needs.

Journal Article↗
PubMed2004

Pentachlorophenol (PCP) bioaccumulation and effect on heat production on salmon eggs at different stages of development.

In this study, pentachlorophenol (PCP) bioaccumulation and its effect on heat dissipation was studied in eggs of the lake salmon (Salmo salar m. sebago). In bioaccumulation studies, the eggs were exposed to low concentrations (0.051-0.056 micromol/l, 13.583-14.915) of waterborne [14C]-labeled PCP at two developmental stages: (1) 3 weeks after fertilization, and (2) just before hatching. The effect of PCP on egg heat dissipation was measured by a microcalorimeter after exposing the eggs to gradual concentrations (0-0.992 micromol/l) of PCP for 48 h. After both the bioaccumulation and heat dissipation experiments, the eggs were dissected and the concentrations of PCP in tissue were determined separately for eggshell, yolk and embryo. The bioaccumulation studies showed that PCP accumulates more in the eggs at the late developmental stage. Bioconcentration factors (BCF) for different tissues were 3-42 times higher for the eggs at the late developmental stage compared with the eggs that were incubated only for 3 weeks. In early developmental stage, the eggshell adsorbs a large portion of the chemical. In late developmental stage, the actual embryo accumulated both proportionately and totally more than other dissected tissues in the beginning of the exposure, but eventually the yolk accumulated highest total amount of the chemical. A probable reason for the higher PCP body burden in the late developmental stage is that the respiration rate and metabolic activity of the embryo increases as it grows. The salmon eggs responded to an exposure to PCP with an elevated rate of heat dissipation. The threshold concentration above which the embryo heat dissipation was amplified was 29.64 micromol/kg embryo wet weight (ww) or 0.28 micromol/l. The highest embryo heat production was measured at the exposure concentration of 0.992 micromol/l. At higher exposure concentrations the heat dissipation decreased. The basic findings of the study are that PCP accumulates in growing embryonic tissue and is able to change the physiology of developing embryo.

Analysis of Variance↗
PubMed2006

Selenium distribution in eggs of avian species.

We studied the effect of egg mass of eight different avian species on Se distribution between egg components and the effect of incubation on Se accumulation by chicken eggshell and shell membrane. Eight groups of birds received a diet without Se supplementation. Unfertile eggs were collected after 35 days of feeding; yolk, albumen, shell and shell membrane were assayed separately for Se. All avian species studied showed identical Se concentration in yolk-albumen complex equal to 38.7 microg Se/100 g, reflecting a linear correlation between yolk-albumen mass and Se content. Shells and shell membrane Se accumulation showed quadratic correlation with the appropriate mass thus explaining unusually high Se concentration in ostrich shell and shell membrane, that reached values 1785 and 1904 microg Se/kg respectively. Incubation of fertile eggs decreased eggshell Se content, the effect being more expressed in eggs from hens fed sodium selenite compared to organic Se utilization (Sel-Plex). It was concluded that shell might be an additional Se source for an embryo.

Animals↗
PubMed2006

Concentration of organochlorine in egg yolk and reproductive success of Egretta garzetta (Linnaeus, 1758) at Wat Tan-en non-hunting area, Phra Nakhorn Si Ayuthaya Province, Thailand.

Contaminant analyses in animal eggs have illustrated the benefit of wildlife as indicators of xenobiotic contamination in natural habitats. In 2002, concentrations of 16 organochlorine insecticides were measured in egg yolk and the reproductive success of the little egret, Egretta garzetta, was studied in a population at Wat Tan-en non-hunting area Bang Pahan District, Phra Nakhorn Si Ayuthaya Province, Thailand. Only 4,4'-dichloro diphenylethane (4,4'-DDE) was detected in the yolk of all samples (n=12) at the concentrations ranging from 33.4 to 116.0 ng/gwetwt. Mean eggshell thickness (n=24) was 0.261+/-0.005 mm. Relationships between the concentrations of 4,4'-DDE and eggshell thickness as well as the reproductive success at all stages were not found (P>0.05). Rather, major factors potentially influencing the decline of reproductive success observed during the field study may include strong wind, predators, intraspecific and interspecific competitions.

Animals↗
PubMed2005

Brominated flame retardants and organochlorine pollutants in eggs of little owls (Athene noctua) from Belgium.

Residues of brominated diphenylethers (PBDEs), organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) were measured in 40 eggs of little owls (Athene noctua), a terrestrial top predator from Belgium. The major organohalogens detected were PCBs (median 2,600 ng/g lipid, range 790-23 000 ng/g lipid). PCB 153,138/163, 170, 180 and 187 were the predominant congeners and constituted 71% of total sum PCBs. PBDEs were measurable in all samples, but their concentrations were much lower than for PCBs, with a range from 29-572 ng/g lipid (median 108 ng/g lipid). The most prevalent PBDE congeners in little owl egg samples were BDE 47, 99 and 153. This profile differs from the profile in marine bird species, for which BDE 47 was the dominant congener, indicating that terrestrial birds may be more exposed to higher brominated BDE congeners than marine birds. The fully brominated BDE 209 could be detected in one egg sample (17 ng/g lipid), suggesting that higher brominated BDEs may accumulate in terrestrial food chains. Brominated biphenyl (BB) 153 was determined in all egg samples, with levels ranging from 0.6 to 5.6 ng/g lipid (median 1.3 ng/g lipid). Additionally, hexabromocyclododecane (HBCD) could be identified and quantified in only two eggs at levels of 20 and 50 ng/g lipid. OCPs were present at low concentrations, suggesting a rather low contamination of the sampled environment with OCPs (median concentrations of sum DDTs: 826 ng/g lipid, sum chlordanes: 1,016 ng/g lipid, sum HCHs: 273 ng/g lipid). Hexachlorobenzene (HCB) and octachlorostyrene (OCS) were also found at low median levels of 134 and 3.4 ng/g lipid, respectively. Concentrations of most analytes were significantly higher in eggs collected from deserted nests in comparison to addled (unhatched) eggs, while eggshell thickness did not differ between deserted and addled eggs. No significant correlations were found between eggshell thickness and the analysed organohalogens.

Animals↗
PubMed2004

Molecular characterization of a novel peroxidase involved in Aedes aegypti chorion protein crosslinking.

Peroxidase-catalyzed chorion or eggshell protein crosslinking is an important biochemical event contributing to the formation of a protective chorion or eggshell in insects. Although the survival of the developing or developed embryo in the environment before hatching relies on the protection of the chorion, the identity of the peroxidative enzyme responsible for mediating chorion protein crosslinking has never been identified in any insect species. In this report, we describe the determination of partial peptide sequences of a novel mosquito chorion peroxidase through LC/MS/MS of a trypsin-digested chorion peroxidase active fraction, specific localization of the enzyme in the chorion through histochemical analysis, proteolytic processing of chorion peroxidase through comparison of the accurate mass of its intact mature enzyme with molecular mass of its deduced amino acid sequence, isolation of its cDNA based on chorion peroxidase partial amino acid sequences, evaluation of its transcriptional profile in developing ovaries, and application of the primary mosquito chorion peroxidase sequence in predicting potential chorion peroxidases in other species.

Aedes↗
PubMed2006

Herbimycin A suppresses mitotic activity and egg production of female Schistosoma mansoni.

The eggs of the endoparasite Schistosoma are the causative agent of schistosomiasis, an important disease of humans, which is endemic in (sub-) tropical regions. The absence of a vaccine with sufficient protective qualities and increasing resistance to approved and established drugs like praziquantel, justify the exploration of novel ways to fight schistosomes. Our strategy is based on interference with the sexual maturation of the female. Prerequisites for gonad development in adult females are a continuous pairing contact with the male and significantly increased mitotic activity. In this study we show that the male governs sexual maturation of the female, as the separation of couples causes a clear reduction of female mitotic activity and, consequently, egg production. We demonstrate that treatment of schistosomes with Herbimycin A, an inhibitor of protein tyrosine kinases (PTKs), mimics the separation of couples as the drug blocks mitotic activity and egg production of paired females. However, the synthesis of the eggshell precursor protein p14 is elevated. Furthermore, we show for the first time in invertebrates that Herbimycin A decreases tyrosine phosphorylation and PTK stability in schistosomes. Summarised, our data provide evidence that PTKs have key functions in regulating gonad development, eggshell gene expression and, consequently, egg production. Therefore, we suggest envisaging schistosome PTKs as novel targets for strategies to combat schistosomiasis.

Animals↗
PubMed2004

Peptide mapping by capillary electrophoresis with Pluronic F127.

Separation of peptides and proteins by capillary zone electrophoresis suffers from the interaction of these solutes with the capillary wall which results in the formation of broad peaks and low resolution. To minimize the protein/peptide-capillary wall interaction we tried to use Pluronic F127, a triblock copolymer of the general formula (polyethylene oxide)(x)(polypropylene oxide)(y)(polyethylene oxide)(z) when x=106, y=70 and z=106 which can be considered a surfactant capable of self-association both into isotropic and anisotropic gels. The analytes studied were enzymatic digests (obtained by trypsin or pepsin treatment) of insoluble matrix proteins from avian eggshell. The best separations were obtained by a system exploiting 10% Pluronic F127 in 20 mmol/l phosphate buffer, pH 2.5. Electrophoretic peptide profiles obtained were very complex owing to the complicated nature of the samples (the exact composition of the proteinous insoluble part of the eggshell is still unknown). The separation in phosphate buffer only offered complex maps of incompletely resolved peaks. The use of Pluronic F127 distinctly improved the separation with a considerably better resolution regarding both the number of peaks obtained and the quality of the separation.

Buffers↗
PubMed2006

Development of endothermic metabolic response in embryos and hatchlings of the emu (Dromaius novaehollandiae).

During hatching, there is a maturation of the mechanisms controlling the respiratory physiology involved in endotherm in precocial avian species. Here we examined the timing of the development of an endothermic response of oxygen uptake (MO2) to an alteration of ambient temperature (T(a)) in a model precocial species, the preterm and hatching emu (Dromaius novaehollandiae). Late stage pre-pipped and pipped embryos and hatchlings were measured for responses of MO2 and shell or skin temperature (T(s)) to altered T(a) (DeltaT(a)). MO2 remained unchanged in pre-pipped and internally pipped (IP) embryos at the end of 1.5h exposure to DeltaT(a) of +/-10 degrees C. Externally pipped (EP) embryos responded to a cooling and a warming exposure with marked increase and decrease in MO2, as hatchlings responded to DeltaT(a) with an endothermic change in MO2. The demonstration of the endothermic inverse metabolic response first appearing in EP embryos suggests that pre-EP embryos may also possess the ability to produce the endothermic inverse metabolic response, but they are restricted by the eggshell gas conductance. Late pre-pipped and IP embryos were measured again for responses of [Formula: see text] to DeltaT(a) in air and then in a 40% O(2) environment. The metabolic response of pre-pipped embryos at 90% of incubation was partially altered by switching from air to hyperoxia. IP embryos responded to DeltaT(a) in 40% O(2) with apparent inverse changes in MO2. The late stage emu embryo possesses the ability to produce an endothermic metabolic response at an earlier stage of development than in chickens, but this response is limited by the eggshell gas conductance.

Animals↗
PubMed2005

Oviductal morphology in relation to hormonal levels in the snapping turtle, Chelydra serpentina.

Microscopic and in situ visual observations were used to relate circulating hormone levels to morphological changes in the oviduct of the snapping turtle Chelydra serpentina throughout the ovarian cycle. Increase in levels of progesterone (P), estradiol (E2) and testosterone (T) levels coincide with an increase in number and growth of endometrial glands, luminal epithelial cells and secretory droplets throughout the oviduct. Testosterone and estradiol levels rose significantly (P < 0.05) after the May-June period and remained high throughout the rest of the summer. Progesterone levels remained stable throughout the summer, with a brief decline in July due to luteolysis. Hormonal values declined significantly (P < 0.001) at the end of the ovarian cycle in the fall. In situ visual observation of fresh oviducts at different stages of gravidity in recently ovulated turtles revealed that proteinaceous like components from the endometrial glands were released into the lumen to form fibers. The morphological features of the oviduct remained active throughout the summer months even though the snapping turtle is a monoclutch species which deposits all the eggs in late-May to mid-June. The high steroid levels correlate with and may be responsible for the secretory activity present throughout the summer and their decline correlates with change to low secretory activity in the fall. Calcium deposition accompanied by morphological changes in luminal cells are suggestive of secretory activity. In the egg-bearing turtles, uterine Ca2+ concentrations measured by flame atomic absorption spectrophotometry revealed significantly higher Ca2+ concentrations (P < 0.001) in eggs with soft shell than eggs without shell. There was a significant increase in calcium granules and proteinaceous fibers in luminal surface of the uterus during the period of eggshelling. This supports the fact that in the snapping turtle like in other reptiles, eggshelling process occurs in the uterus.

Animals↗
PubMed2005

The Drosophila shell game: patterning genes and morphological change.

What are the mechanisms that convert cell-fate information into shape changes and movements, thus creating the biological forms that comprise tissues and organs? Tubulogenesis of the Drosophila dorsal eggshell structures provides an excellent system for studying the link between patterning and morphogenesis. Elegant genetic and molecular analyses from over a decade provide a strong foundation for understanding the combinatorial signaling events that specify dorsal anterior cell fates within the follicular epithelium overlying the oocyte. Recent studies reveal the morphogenetic events that alter that flat epithelial sheet into two tubes; these tubes form the mold for synthesizing the dorsal appendages--eggshell structures that facilitate respiration in the developing embryo. This review summarizes the mutant analyses that give insight into these patterning and morphogenetic processes.

Animals↗
PubMed1997

Histological analysis of the egg capsule of the ovoviviparous polystomatid monogenean, Pseudodiplorchis americanus.

Transmission of Pseudodiplorchis americanus is restricted to the brief period when its host, a desert toad, enters water to spawn. The parasite accumulates its entire annual reproductive output within an elongated uterus during the 10-11-month period of host hibernation. Embryos of P. americanus, at all stages of development, are retained within the uterus which eventually becomes packed with around 150 encapsulated infective larvae. Recently formed eggs, which comprise a fertilized ovum and 2-3 vitelline cells, are closely surrounded by a primary eggshell which stains positively for acidic proteins and keratin. Initially, during passage along the proximal uterus, the egg capsule is only 60 microns in diameter, but as it passes to the distal uterus it expands to 800 microns in diameter to accommodate the growing larva. Due to chemical alterations or complete replacement of the shell, the final (secondary) egg capsule is a large sac-like structure composed of elastin. The flexible nature of this shell maximizes the numbers of infective larvae which can be stored in utero. TEM studies have revealed this capsule to be composed of multi-laminate membranes with a specialized cytoplasmic lining involved in a unique mechanism for embryo nutrition. This is the first report of an elastin-type eggshell within the Monogenea.

Animals↗
PubMed2003

Structural and biochemical analysis of the Leptinotarsa decemlineata (Coleoptera; Chrysomeloidea) crystalline chorionic layer.

The developmental aspects of the Leptinotarsa decemlineata crystalline chorionic layer (CCL) morphogenesis, its composition and its supramolecular structure were studied. The mature Leptinotarsa decemlineata eggshell consists of the vitelline membrane and the CCL, while the follicle cell remnants following their degeneration after oogenesis completion constitute the outer chorionic layer. The vitelline membrane and the CCL layers are formed through continuous material deposition from the follicular epithelium, whereas the main morphogenic factor during most insect eggshell formation, namely the follicle cell and oocyte microvilli, are seemingly involved only in vitelline membrane formation. Analysis of the CCL morphogenesis showed that this layer is assembled from a fiber-like pre-crystalline material, which accumulates at the vitelline membrane-follicle cell interface. The mature CCL is about 1 microm thick and exhibits a periodicity of approximately 10 nm, while computer image analysis studies of thin-sectioned CCL revealed the existence of crystalline layers parallel to the CCL surface. Finally, SDS-PAGE-electrophoresis of purified CCLs showed that this crystalline layer is of a proteinaceous nature and is most likely composed of 3-5 polypeptides with a molecular weight ranging in between 28-60 kDa. Overall, these data exemplify for the first time the nature and supramolecular arrangement of a crystalline layer and its constituent molecules in Coleoptera.

Animals↗
PubMed2002

Effect of regional changes to shell conductance on oxygen consumption and growth of chicken embryos.

Diffusive and perfusive gas conductances of the shell and chorioallantois of avian eggs are not homogeneous, leading to disequilibrium between the air cell gas and chorioallantoic venous blood. This study measured the embryonic ability to maintain oxygen consumption rate and growth under experimentally enhanced inhomogeneity of diffusive conductance, achieved by waxing half of the eggshell and exposing the other half to graded hyperoxia that doubled the oxygen gradient across the shell. Thus, the overall gas conductance was effectively normal but highly inhomogeneous. No differences were observed between the experimental and the control eggs in respiration, residual yolk or embryo growth rate from day 12 until day 20. The embryo was able to utilise the increase of oxygen in the environment to compensate for the loss of about half of its respiratory surface area under the wax. The results indicate that an even distribution of pores in the eggshell and uniformity of chorioallantoic perfusion are not required for successful avian development.

Animals↗
PubMed1998

The effect of hyperoxia on embryonic and organ mass in the developing chick embryo.

It is known that hyperoxia stimulates growth late in incubation when the chick embryo outgrows the O2 diffusion capacity. We wondered whether hyperoxia could have an effect in the early period prior to the stage where metabolism exceeds the oxygen diffusion capacity of the eggshell. For this we studied four groups of chicken eggs: control group (CG; n = 100) and three test groups (TGs) exposed during 48 h to 60% O2 on days 10, 14, and 18. In the CG, embryonic and organ mass (brain, heart, lungs, liver and intestine) were measured from day 10 until day 21 of incubation. In the TGs embryonic and organ mass were obtained from 24 h after the start of hyperoxia exposure until the end of incubation. In all TGs the most striking growth rate acceleration was observed in the liver and intestine, maximum growth rate accelerations were respectively, 19 and 42% in TG1, 43 and 173% in TG2 and 39% and 84 in TG3. In contrast, the brain was little affected by the hyperoxia exposure, the maximum growth rate acceleration was 14% in TG2. The results suggest that also in the middle of the incubation period O2 availability can be a limiting factor for growth, before metabolism exceeds the oxygen diffusion capacity of the eggshell.

Animals↗
PubMed1998

Glycan vesicle formation in vitellocytes and hatching vacuoles in eggs of Echinostoma caproni and Fasciola hepatica (Digenea).

Vitelline cells, which are added to the fertilized ovum when eggs are formed in Platyhelminthes, are known to produce and secrete proteins containing vesicles for construction of the eggshell. In this study, another particular type of carbohydrate-containing vesicle is described, in the vitellocytes of Digenea. These vesicles play a role in the hatching of the miracidium from the egg. Cytochemical analysis and the binding of lectins with specificities for a variety of sugar residues revealed that the vesicles contain neutral, glycogen-like polysaccharides composed of glucosyl/mannosyl residues. The vesicles are produced at a late maturation stage of the vitellarium cells. Vitellocytes enclosed in the eggs provide nutrients for the embryo, but retain the glycan vesicles until late embryogensis. Then the vesicles merge and swell to the dimensions of the vitellocytes, and these coalesce into two vacuoles that fill the space between the embryo and the eggshell. Hatching of the miracidium is induced by exposure to light and a slight rise in temperature, i.e. conditions found in the natural environment in the morning. The eggs' internal hydrostatic pressure rises, probably due to a depolymerization of the polysaccharides that causes an osmotically driven water influx. Finally, the operculum of the egg bursts open and the miracidium escapes.

Animals↗
PubMed2000

Host-parasite interactions in Acanthocephala: a morphological approach.

In this review recent morphological and histochemical descriptions have been compiled of (mainly outer) features of all developmental stages of the Acanthocephala as well as what is known about the host's defence measures directed against these worms. From acanthors, for instance, it is documented how they escape melanization inside the haemocoel of a suitable intermediate host after they have been activated and released from their eggshell enclosure in the gut of the arthropod. Acanthors possess a complex set of eggshell-envelopes and interstices that fulfil different tasks. While the sequence of events inside the intermediate host's haemocoel is rather well known, what happens in paratenic hosts has been little studied. In final hosts the host-parasite interactions depend on the systematic affiliation of the parasite as well as the host and on the depth of penetration of each acanthocephalan species in the intestinal wall of the host. The mode of attachment also influences the microhabitat preference inside the gut. Mammals often reveal symptoms of high morbidity when infected with acanthocephalans, while fish seem to tolerate high intensities of worms deeply penetrating into their intestinal wall without showing pronounced symptoms of disease. The review also treats the subjects of host specificity, nutrient uptake and metabolism of the worms as well as their absorbance of metals and other elements. The high absorbance capacity for heavy metals suggests the usefulness of acanthocephalans as bioindicators.

Acanthocephala↗