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At least 613 records · Page 34Linked to original sources
PubMed1994

A new member to the astacin family of metalloendopeptidases: a novel 1,25-dihydroxyvitamin D-3-stimulated mRNA from chorioallantoic membrane of quail.

1,25-Dihydroxyvitamin D-3 is essential for the utilization of eggshell calcium by avian embryo through the chorioallantoic membrane (CAM). A cDNA library was constructed from poly(A)+ RNA extracted from vitamin D-deficient CAMs given 1,25-dihydroxyvitamin D-3. Screening this library by differential hybridization yielded a full-length (approximately 1.8 kb) cDNA, whose corresponding mRNA is increased 3-fold 2.5 h after a single injection of 1,25-(OH)2D3. The complete nucleotide sequence for the full-length cDNA has been determined. An open-reading frame, corresponding to a 310 amino acid, 41 kDa protein was found. Searching protein sequence data bases revealed a strong similarity to the following proteases: astacin, a crayfish digestive protease, Oryzias latipes hatching enzyme constituent protease (Orz), Xenopus laevis developmentally regulated UVS.2 protein secreted by the hatching gland of embryos, the NH2-terminal domain of human bone morphogenetic protein (BMP-1) and Drosophila dorsal-ventral patterning tolloid. The cDNA has approximately 36% overall identity with astacin and BMP-1, and is more than 60% identical to either Orz or UVS.2. Moreover, multiple alignment analysis indicates that 37 residues, including 3 cysteine residues, are strictly conserved in the complete 200-amino acid astacin sequence. All 6 proteins contain a zinc-binding motif (HEXXH), found at the active site of most metalloendopeptidases. This motif is found within an extended sequence of HEXXHXXGFXHE that is unique to this subgroup of metalloendopeptidases. In addition, the 6 proteins have 50% identity (including the present cDNA) and 79% are conserved in 4 of these proteins in a 24-amino acid sequence that includes the putative active site. The level of mRNA for the new protein reaches a maximum at day 12 of embryonic life and declines thereafter. It is suggested that this clone corresponds to an mRNA encoding for a protease that may play a role in the degradation of eggshell matrix.

Allantois↗
PubMed1984

Changes in activity of chicken medullary bone cell populations in relation to the egg-laying cycle.

Osteoblastic and osteoclastic activity was studied in avian medullary bone in vivo. During the active period of eggshell calcification, medullary bone active resorption surface increased ninefold. This correlated with a sevenfold increase in the percentage of active osteoclasts. Osteoblast activity is also increased during the active period, as demonstrated by a twofold increase in the active osteoblastic surface. These findings and our observation that the medullary bone volume remains the same (+/- 13%) whether the eggshell is being formed (active period) or not (inactive period) led to the conclusion that the activities of osteoblasts and osteoclasts rapidly return to balance.

Animals↗
PubMed1993

Accumulation of organochlorine contaminants in double-crested cormorants.

Cormorant eggs and lipid samples from juvenile Cormorants were analyzed for 14 organochlorine contaminants. Low concentrations (geometric mean < 0.05 microg/g) of hexachlorobenzene (HCB), lindane, oxy-chlordane, heptachlor epoxide, dieldrin, endrin, mirex, DDD and DDT in eggs primarily reflected the wintering-ground origin of organochlorine contaminants. Overall geometric mean concentrations of DDE and PCBs in Cormorant eggs were 3.90 and 2.22 microg/g egg respectively, and would not affect reproduction or eggshell thickness. Eggshells averaged 0.44 mm in thickness and no correlation (r2 = 0.17) with log-transformed DDE residues in Cormorant eggs was evident. Only DDE and PCBs were detected in lipid samples from 5- to 8-week-old Cormorants (geometric mean approximately 1.0 microg/g lipid for each compound). The PCB: DDE ratios in Cormorant lipid from some individual colonies were 2-3.5 times greater than the ratio in eggs from the same colony, suggesting an accumulation of PCBs related to local diet. Juvenile Cormorants might serve as regional indicators of chemical residue contamination in Alberta, and provide a temporal perspective on changes in contaminant burdens in aquatic ecosystems.

Journal Article↗
PubMed1995

Reduced breeding success of Cormorants (Phalacrocorax carbo sinensis) in relation to persistent organochlorine pollution of aquatic habitats in The Netherlands.

Cormorants (Phalacrocorax carbo sinensis) breeding in the heavily contaminated sedimentation area of the rivers Rhine and Meuse have a severely reduced breeding success as compared to several other Dutch colonies. A detailed analysis of reproductive performance in combination with chemical analysis of eggs and food from colonies in differently contaminated aquatic habitats is presented. The differences in breeding success between colonies are caused mainly in the egg-stage of breeding. Eggshell thinning and increased embryonic mortality cause the differences in hatching success. The observed effects seem to be related to chlorinated hydrocarbons. Significant correlations are found for concentrations of DDE with eggshell thinning and for concentrations of PCBs with hatching and breeding success. The correlations between concentrations of chlorinated hydrocarbons in eggs and biological effects measured in the field are established both on colony and individual clutch level.

Journal Article↗
PubMed1989

Blood plasma catecholamine concentration of poult embryos during the transition from diffusive to convective respiration.

1. Plasma catecholamines were determined in turkey embryos. 2. Decreased eggshell permeability depressed dopamine and epinephrine, but increased permeability also depressed epinephrine. 3. Norepinephrine (NE) was greatest before transition to convective respiration when hypoxia occurs. 4. NE was associated inversely with eggshell permeability. 5. Catecholamines appear to assist the embryo during hatching hypoxia.

Animals↗
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↗
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↗
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↗
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↗
PubMed2001

Restriction of prenatal gas exchange impairs memory consolidation in the chick.

Our aim was to assess the effects of restricting gas exchange during incubation on postnatal memory formation and growth in the chick. Gas exchange across the eggshell was restricted by covering 50% of the eggshell with an impermeable membrane for 4 or 8 days, commencing at days 14 and 10, respectively, of a 21-day incubation. Memory formation was examined postnatally at 1-2 days using a one-trial discriminated bead task, and at 5-6 days using a discriminated wheat task. For both tasks, chicks from eggs wrapped from days 14 to 18 had impaired memory retention at 60 min after training, although learning and labile memory were not impaired. Chicks from eggs wrapped from days 10-18 appeared to be poorer in their ability to form memories, and did not discriminate as well as controls in any of the tasks. Body weights of chicks from wrapped eggs were reduced from 2 days after hatching; chicks from eggs wrapped from day 10 had lower body weights at hatching. We conclude that a period of altered prenatal gas exchange can impair memory consolidation in the chick soon after hatching. The ability to form memories may be permanently altered, as this impairment is still apparent at 5-6 days after hatching. Pre- and postnatal growth was also impaired in the chicks from wrapped eggs. Our results suggest that the extent to which postnatal neurological function and growth is impaired depends on the timing and possibly the duration of the prenatal insult.

Animals↗
PubMed2000

Chitin synthase in the filarial parasite, Brugia malayi.

Fragments of putative chitin synthase (chs) genes from two filarial species (Brugia malayi and Dirofilaria immitis) were amplified by PCR using degenerate primers. The full genomic and cDNA sequences were obtained for the B. malayi chs gene (Bm-chs-1); the predicted amino acid sequence is highly similar, over a large region, to two CHS sequences of the nematode Caenorhabditis elegans and also to two insect CHS sequences. Bm-chs-1 is abundantly transcribed in B. malayi adult females, independent of their fertilization status, but is also expressed in males and microfilariae. Oocytes and early embryos contain large amounts of Bm-chs-1 transcript by in situ hybridization, but later stage embryos within the maternal uterus show little or no Bm-chs-1 transcript. No specific hybridization could be demonstrated in maternal somatic tissues. Polyclonal antibodies were raised against a peptide expressed from a recombinant cDNA fragment of Bm-chs-1; immunostaining detected CHS protein in oocytes and early to midstage embryos. These studies characterize a gene that is likely to be essential to oogenesis and embryonic development in a parasitic nematode. Because chitin synthesis and eggshell formation begin after fertilization, the presence of CHS protein in early oocytes suggests that the enzyme must be activated as a result of fertilization. These studies also demonstrate that chitin synthesis may not be restricted to eggshell formation in nematodes, as the Bm-chs-1 gene is transcribed in life cycle stages other than adult females.

Amino Acid Sequence↗