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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↗
PubMedDate not supplied

Secretion of a novel developmentally regulated chitinase (family 19 glycosyl hydrolase) into the perivitelline fluid of the parasitic nematode, Ascaris suum.

The early development of the parasitic nematode, Ascaris suum, occurs within a chitinous eggshell and an abundant chitinase (As-p50) has been identified in the perivitelline fluid (PVF) surrounding the infective larva prior to hatching. A cDNA encoding As-p50 was cloned, sequenced and the protein expressed in Escherichia coli. As-p50 is a member of glycosyl hydrolase family 19, previously identified only in plants, making the characterization of As-p50 the first family 19 glycosyl hydrolase from any animal species. As expected, the chitinase activity of recombinant As-p50 or isolated PVF was insensitive to allosamidin. As-p50 expression was developmentally regulated. As-p50 mRNA appeared between days 5 and 8 of development prior to the formation of the first-stage larva (L1). The As-p50 protein and chitinase activity appeared later between days 8 and 15 and remained at constant levels until hatching. GFP-promoter constructs of C08B6.4, the most closely related Caenorhabditis elegans As-p50 homologue, were expressed in hypodermal cells of 3-fold stage larvae and L1s with a timing similar to that of As-p50 and the fusion protein was secreted into the space between the hypodermis and the cuticle. Taken together, these results suggest that As-p50 is involved in the formation of the L1 cuticle and/or the initial molt; however, As-p50 may be multifunctional and also responsible for the digestion of the eggshell during hatching.

Amino Acid Sequence↗
PubMed1983

Scanning electron microscopy of the scabies burrow and its contents, with special reference to the Sarcoptes scabiei egg.

An entire burrow of a female Sarcoptes scabiei (var. hominis) mite was examined by scanning electron microscopy during serial transverse sectioning. The elevated roof and the wall were composed of compacted corneocytes. The floor had a smooth surface except at the anterior end. Here it was made up of nucleated stratum granulosum cells, etched in appearance, presumably having been chewed by the mite. The female mite, the larvae, scybala, and eggs were also examined. The ultrastructure of the eggshell surface revealed it to have a distinctive geometric patterning. Cross-sectioning showed this shell or chorion to be composed of an outer layer of minute, closely packed penta- and hexahedrons resting on a thin inner homogenous layer. The polyhedric surface pattern was exactly replicated in the cement substance which attached the egg to the burrow floor. Observations were made on the embryonic positioning which permitted the larvae to emerge from the eggshells in a uniform manner.

Female↗
PubMed2001

Separase is required for chromosome segregation during meiosis I in Caenorhabditis elegans.

BACKGROUND: Chromosome segregation during mitosis and meiosis is triggered by dissolution of sister chromatid cohesion, which is mediated by the cohesin complex. Mitotic sister chromatid disjunction requires that cohesion be lost along the entire length of chromosomes, whereas homolog segregation at meiosis I only requires loss of cohesion along chromosome arms. During animal cell mitosis, cohesin is lost in two steps. A nonproteolytic mechanism removes cohesin along chromosome arms during prophase, while the proteolytic cleavage of cohesin's Scc1 subunit by separase removes centromeric cohesin at anaphase. In Saccharomyces cerevisiae and Caenorhabditis elegans, meiotic sister chromatid cohesion is mediated by Rec8, a meiosis-specific variant of cohesin's Scc1 subunit. Homolog segregation in S. cerevisiae is triggered by separase-mediated cleavage of Rec8 along chromosome arms. In principle, chiasmata could be resolved proteolytically by separase or nonproteolytically using a mechanism similar to the mitotic "prophase pathway." RESULTS: Inactivation of separase in C. elegans has little or no effect on homolog alignment on the meiosis I spindle but prevents their timely disjunction. It also interferes with chromatid separation during subsequent embryonic mitotic divisions but does not directly affect cytokinesis. Surprisingly, separase inactivation also causes osmosensitive embryos, possibly due to a defect in the extraembryonic structures, referred to as the "eggshell." CONCLUSIONS: Separase is essential for homologous chromosome disjunction during meiosis I. Proteolytic cleavage, presumably of Rec8, might be a common trigger for the first meiotic division in eukaryotic cells. Cleavage of proteins other than REC-8 might be necessary to render the eggshell impermeable to solutes.

Animals↗
PubMed2002

Development of cardiac rhythms in birds.

Heart rate (HR) in avian embryos developing inside an eggshell has been measured by various means while maintaining adequate gas exchange through the eggshell. This is an important requirement in order to avoid adverse effects of impeding gas exchange on the cardiac rhythms of developing embryos. The present report is a review of our ontogenetic study on embryonic HR, which was measured with fulfillment of the above requirement and also hatchling HR measured non-invasively. Firstly, we reviewed measurements of daily changes (developmental patterns) in embryonic mean heart rate (MHR), which were determined from a short-term measurement of HR once a day, in 34 species of altricial and precocial birds. The allometric relationship between the MHR during pipping in altricial birds and their fresh egg masses was the same as that between the MHR at 80% of incubation duration and fresh egg masses in pre-cocial birds. Secondly, we presented the developmental patterns of MHR in chick embryos and hatchlings, which were determined from long-term, continuous measurement of HR before, during and after hatching. The ultradian and circadian rhythms of HR were clearly shown in embryos and hatchlings, respectively. Thirdly, we summarized instantaneous HR fluctuations: HR variability and HR irregularities, in chick embryos and hatchlings. The distinctive patterns were shown in pre-pipped and pipped embryos and newly hatched chicks, individually, which were partly related to autonomic nervous functions and physiological functions.

Analysis of Variance↗
PubMed2001

In vivo modulation of nonylphenol-induced zonagenesis and vitellogenesis by the antiestrogen, 3,3'4,4'-tetrachlorobiphenyl (PCB-77) in juvenile fish.

Zonagenesis and vitellogenesis (eggshell zona radiata protein (Zrp) and vitellogenin (Vtg) production, respectively), are two estrogen-regulated processes in oviparous vertebrates that are crucial for oocyte maturation. Treatment of juvenile Atlantic salmon (Salmo salar) with nonylphenol (NP; 25 mg kg(-1)) alone or in combination with 3,3',4,4'-tetrachlorobiphenyl (TCB; 0.1 mg kg(-1)) resulted in pronounced elevations of plasma eggshell Zrp and Vtg and their respective liver mRNA levels in two separate experiments. TCB treatment alone caused the elevation of CYP1A mRNA, protein and enzyme levels (7-ethoxyresorufin O-deethylase (EROD)). In experiment 3, which also included the time factor, exposure of juvenile salmon to 10 and 25 mg NP per kg in combination with TCB generally resulted in reduced plasma Zrp and Vtg levels, compared with NP treatments alone. In a fourth experiment, juvenile salmon were exposed to different doses of TCB either 2 days before or 2 days after a single dose (25 mg kg(-1)) of NP. Samples were always collected 5 days after the NP exposure and analyzed for mRNA and protein levels. Generally, TCB doses given 2 days after NP exposure resulted in the elevation of Vtg and Zrp protein and mRNA levels. Vtg and Zrp mRNA levels were also elevated in the groups treated with 0.1 mg TCB 2 days before NP exposure. In all experiments, TCB injection resulted in the induction of liver CYP1A mRNA, CYP1A protein and EROD activity, but no Zrp or Vtg protein/mRNA inductions were observed when given alone. The present study documents for the first time the apparent stimulation of xenoestrogen-induced responses by an antiestrogenic CYP1A-inducer, in fish or any other lower vertebrate. However, the stimulatory or inhibitory effect of TCB on NP-induced responses appear to be dependent on the ratio of NP and TCB doses, and temporal sequence of exposure. Fish hepatic zonagenesis and vitellogenesis continue to provide interesting models for further studies on the mechanisms and possible interactions between endocrine disruptors and CYP1A-inducers, their antiestrogenic and/or estrogen potentiating effects.

Journal Article↗
PubMed1986

Chemical nature and mode of stabilization of eggshell/capsule of some cyclophyllidean cestodes.

The chemical nature and mode of stabilization of the eggshell/capsule of Moniezia expansa, Avitellina lahorea and Stilesia globipunctata have been investigated using histochemical techniques. In M. expansa where vitelline glands are present, the eggshell is stabilized by -S-S and -S-H linkages whereas in A. lahorea and S. globipunctata, the vitelline glands are absent and the double membranes, fibrous capsule and paruterine organ contain mainly elastokeratin-type structural protein. The possible role of the vitellaria in the presence or absence of eggshell and its thickness is discussed.

Animals↗
PubMed1986

Chitin synthesis in zygotes of Ascaris suum.

In Ascaris suum chitin is formed in the zygote immediately after oocyte fertilization, and its synthesis is completed in the eggs from the distal half of the uterus. Incorporation of radiocarbon [14C] glucose into chitin of the eggshell was 40-fold higher than incorporation of [14C] glucosamine. The same rank order also holds for the incorporation of label from these isotopes into the glycogen of the ovaries. A large part of the radiolabel was incorporated first into oocyte glycogen and only after fertilization was it incorporated into eggshell chitin. Actinomycin D inhibited chitin synthesis in the eggs from the distal half of the uterus and it significantly reduced incorporation of radiocarbon from glucose into chitin.

Animals↗
PubMed2001

Development of the vitellaria of the liver fluke, Fasciola hepatica in the rat host.

The development of the vitellaria of Fasciola hepatica within the liver of its rat host was studied by means of whole-mount stained preparations and transmission electron microscopy, together with light and electron immunocytochemistry using an antibody to vitelline protein B, an eggshell precursor protein synthesized by F. hepatica. No vitelline cells could be identified in flukes recovered from the liver parenchyma, by any of the methods used. In contrast, follicles were present in flukes at the earliest time of recovery from the bile duct, namely, 5 weeks 3 days post-infection. The vitellaria in these flukes formed a row of small follicles on either side of the body. Development of the follicles was rapid: by 6 weeks 3 days, the vitellaria resembled those in the adult fluke and eggs were present in the uterus. Immunolabelling was confined to the shell protein globules in the vitelline cells, confirming the packaging of the eggshell protein within the shell globule clusters.

Animals↗
PubMed2003

Effect of cholecalciferol-enriched hen feed on egg quality.

Eggs are one of the most important sources of vitamin D in the human diet, and their vitamin D content can be further increased by adding more vitamin D to hen feed. To investigate this issue more closely, we performed two feeding experiments. In both, zero egg samples were collected while the hens were fed regular feeds with a vitamin D content of 1720 or 4280 IU/kg. In experiment 1, egg samples were collected 2, 4, 7, 9, 11, 13, 16, 23, and 30 days after beginning the high-cholecalciferol (11 200 IU/kg) feeding period. In experiment 2, samples were collected 2, 4, 6, 8, 13, 28, 56, 84, 112, 140, and 168 days after beginning the high-cholecalciferol (12 000 IU/kg) diet. The egg samples were then assayed for their cholecalciferol content, and some samples, also for the presence of 25-hydroxycholecalciferol by an HPLC method. Further, the vitamin D-fortified eggs were compared with the controls by a sensory evaluation, by conducting fatty acid and functional analyses (emulsion capacity, gel forming capacity, foaming properties) and by measuring eggshell strength. Because vitamin D can be toxic in high doses, we also performed histopathological tests on the hens at the end of experiment 2. The top cholecalciferol contents in egg yolk (ca. 30 microg/100 g) were reached 8-13 days from starting the high-cholecalciferol diet. After 112 days feeding the cholecalciferol content gradually decreased to ca. 22 microg/100 g. When added to eggs as described above, vitamin D did not affect their sensory or functional properties or their fatty acid composition. Moreover, the cholecalciferol levels used in this study appeared not to affect eggshell strength or to be harmful for hens.

Animal Feed↗
PubMed2000

Process of egg formation in the female body cavity and fertilization in male eggs of Phytoseiulus persimilis (Acari: Phytoseiidae).

The process of egg formation in the body cavity of a phytoseiid mite, Phytoseiulus persimilis, was observed to examine fertilization of male eggs. After insemination, one of the ova at the periphery of the ovary began to expand, taking up yolk. Two pronuclei appeared in the expanded egg, located dorsally in the ovary, and yolk granules were formed gradually. After the egg became filled with yolk granules the two pronuclei fused. The egg moved via the narrow entrance at the ventral region into the oviduct, where the eggshell was formed. When the eggshell was complete, and while embryogenesis proceeded, the egg was deposited. In the meantime some ova began to expand sequentially and two joining pronuclei appeared in expanding eggs. The joining pronuclei in the first egg proved male diploidy. This is additional evidence of pseudo-arrhenotoky in this phytoseiid mite species, since the first eggs developed into males.

Animals↗
PubMedDate not supplied

Chlorinated hydrocarbon contamination in osprey eggs and nestlings from the Canadian Great Lakes basin, 1991-1995.

Populations of osprey (Pandion haliaetus) in the Great Lakes basin declined dramatically during the 1950s-1970s due largely to adverse effects of persistent chlorinated hydrocarbons, ingested in their fish prey, on eggshell thickness and adult survival. Nevertheless, these contaminants were not measured in osprey tissues during the decades of decline on the Canadian Great Lakes. Between 1991 and 1995, we monitored recovering osprey populations on the Great Lakes, including Georgian Bay and the St. Marys River area on Lake Huron and the St. Lawrence Islands National Park, as well as at two inland sites within the basin. Current OC levels, even from the most contaminated lakes, were typically lower than those associated with reproductive effects. DDE levels in fresh eggs averaged 1.2-2.9 microg/g, well below the 4.2 microg/g level associated with significant eggshell thinning and shell breakage. Nevertheless, a proportion of eggs from all study areas did exceed this level. PCB levels in eggs seldom exceeded 5 microg/g except in one lake of high breeding density in the Kawartha Lakes inland study area, where the mean sum PCB level was 7.1 microg/g and the maximum concentration measured was 26.5 microg/g. On average, mean reproductive output (0.78-2.75 young per occupied nest) of breeding populations in Great Lakes basin study areas exceeded the threshold of 0.8 young thought necessary to maintain stable populations. We concluded that, although eggs and especially nestling plasma, are useful in reflecting local contaminant levels, ospreys are relatively insensitive, at least at the population level, to health effects of current levels of chlorinated hydrocarbons on the Canadian Great Lakes.

Animals↗
PubMed2002

The origin of lactation as a water source for parchment-shelled eggs.

Available evidence indicates that mammary gland secretions first evolved in synapsids that laid parchment-shelled eggs. Unlike the rigid-shelled eggs of birds and some other sauropsids, parchment-shelled eggs lose water very rapidly when exposed to ambient air of lower vapor pressure, whether due to differences in relative humidity or to differences in temperature. This precludes endothermic incubation of parchment-shelled eggs in an open nest. Synapsids may have avoided egg desiccation by incubating eggs in a pouch, but this would limit maternal activity. Parchment-shelled eggs are able to take up liquid water across the eggshell. I propose that mammary secretion originally evolved as a means of supplying water to eggs, and as such was essential to the evolution of endothermy among the egg-laying cynodonts that were ancestral to mammals. It is possible that synapsid eggs, like parchment-shelled squamate eggs, were also capable of uptake of some nutrients, such as sodium and ionic calcium. Living monotremes still produce parchment-shelled eggs. The porous eggshell and bilaminar yolk sac membrane of these eggs permit substantial uptake of uterine secretions during the intrauterine period, and might also facilitate uptake of mammary secretions during egg incubation. In its simplest form, mammary secretion may be an ancient trait of egg-laying synapsids, having had an important role long before milk became obligatory for suckling young.

Animals↗
PubMed1999

The effect of pentosan polysulphate on bone healing of rat cranial defects.

The purpose of the study was to determine the efficacy of pentosan polysulphate, used in combination with guided bone regeneration on rat skull defects. The study was conducted on 45 adult Wistar rats. On each animal two symmetrical 6 mm wide, full-thickness, skull defects were created in the parietal regions. The right defect was chosen as the experimental site and the left one was left empty to provide a control. Each experimental site was covered by an inner and outer polytetrafluoroethylene membrane. The 45 rats were divided into 3 groups: in group I (n = 15), carboxymethyl cellulose, used as a delivery vehicle, was injected between the two membranes; in group II (n = 15), 1 mg of pentosan polysulfate was added to the carboxymethyl cellulose vehicle; in group III (n = 15), purified micronized eggshell powder was added to the mixture of pentosan polysulfate and carboxymethyl cellulose between the two membranes. In each group, the animals were sacrificed at 42 days. The harvested specimens were processed for contact radiography and standard histological examination. The results were assessed by a Fisher's exact test. All animals, except one, healed uneventfully. In group I, partial bone healing was observed in 14 out of 15 animals. In group II, partial bone healing was observed in 13 out of 15 animals, and complete bone healing in 1 out of 15 cases. In group III, partial resorption of the eggshell implant was observed with a partial bone healing in only 2 cases (P < 0.001). In conclusion, significant bone regeneration was observed with the membranes alone. The use of pentosane polysulphate did not result in additional bone gain. The use of particulate material as a space maintainer is also questionable.

Absorbable Implants↗