Mycotoxin Fumonisin B1 Interferes Sphingolipid Metabolisms and Neural Tube Closure during Early Embryogenesis in Brown Tsaiya Ducks

Fumonisin B₁ (FB₁) is among the most common contaminants produced by Fusarium spp. fungus from corns and animal feeds. Although FB₁ has been known to cause physical or functional defects of embryos in humans and several animal species such as Syrian hamsters, rabbits, and rodents, little is known about the precise toxicity to the embryos and the underlying mechanisms have not been fully addressed. The present study aimed to investigate its developmental toxicity and potential mechanisms of action on sphingolipid metabolism in Brown Tsaiya Ducks (BTDs) embryos. We examined the effect of various FB₁ dosages (0, 10, 20 and 40 µg/embryo) on BTD embryogenesis 72 h post-incubation. The sphingomyelin content of duck embryos decreased (p < 0.05) in the highest FB₁-treated group (40 µg). Failure of neural tube closure was observed in treated embryos and the expression levels of a neurulation-related gene, sonic hedgehog (Shh) was abnormally decreased. The sphingolipid metabolism-related genes including N-acylsphingosine amidohydrolase 1 (ASAH1), and ceramide synthase 6 (CERS6) expressions were altered in the treated embryos compared to those in the control embryos. Apparently, FB₁ have interfered sphingolipid metabolisms by inhibiting the functions of ceramide synthase and folate transporters. In conclusion, FB₁-caused developmental retardation and abnormalities, such as neural tube defects in Brown Tsaiya Duck embryos, as well as are partly mediated by the disruption of sphingolipid metabolisms.

Decorin regulates myostatin and enhances proliferation and differentiation of embryonic myoblasts in Leizhou black duck

Skeletal muscle is one of the most important economic traits in the poultry industry whose development goes through several processes influenced by several candidate genes. This study explored the regulatory role of DCN on MSTN and the influence of these genes on the proliferation and differentiation of embryonic myoblasts in Leizhou black ducks. Embryonic myoblasts were transfected with over-expressing DCN, Si-DCN, and empty vector and cultured for 24 h, 48 h, and 72 h of proliferation and the comparative expression of DCN and MSTN were measured. The results showed that cells transfected with the over-expression DCN had a significantly (P < 0.05) higher expression of DCN mRNA than the normal group and the expression of MSTN mRNA showed a downward trend during the proliferation of myoblasts. DCN mRNA expression was lower in cells transfected with Si-DCN than the normal group in all stages of proliferation. While the expression of MSTN in the Si-DCN transfected group was higher than the normal group with a significant (P < 0.05) difference at the 72 h stage. DCN mRNA increased at the early stage of differentiation but decreased (P > 0.05) from the 6th day to the 8th day of differentiation. The level of MSTN increased gradually during the differentiation process of myoblasts until it decreased significantly on the 8th day. These results show that DCN enhances the proliferation and differentiation of Leizhou black duck myoblasts and suppresses MSTN activity.

Antioxidant activities and protective effects of duck embryo peptides against H2 O2-induced oxidative damage in HepG2 cells

Previous work showed that peptides from duck eggs incubated for 15 D presented high total antioxidant activities. Here, this work explore the antioxidant activities of different segments, ZT1 (≤3 KD), ZT2 (≤10 KD), and ZT3 (≤30 KD), derived from duck embryo peptides and their protective effects against H₂ O₂-induced oxidative damage in HepG2 cells. Peptides present no cytotoxicity to HepG2 cells. Moreover, ZT1 exhibits a higher ability to scavenge several radicals as well as stronger inhibition of H₂ O₂-induced oxidative stress than ZT2 and ZT3. The activities of catalase and glutathione peroxidase as well as total superoxide dismutase increase in a concentration-dependent manner. Peptides are isolated from ZT1 and then subjected to LC-MS/MS to identify their sequences, followed by functional annotation, bioinformatics prediction, and hot-spot motif recognition. As a result, 413 potential functional peptides are identified, with some compounds exhibiting more than 1 function. This work will help for exploring bioactive substances in duck embryo eggs and enhance the utilization value of duck or other poultry eggs.

Embryonic development of parakeratinized epithelium of the tongue in the domestic duck (Anas platyrhynchos f. domestica): LM, SEM, and TEM observations

The parakeratinized epithelium is a common and widespread type of keratinized epithelium in the oral cavity in adult birds. In contrast to orthokeratinized epithelium, which mostly covers mechanical papillae and the lingual nail, parakeratinized epithelium covers almost the entire dorsal surface of the tongue in birds. The characteristic feature of parakeratinized epithelium is the presence of nuclei in the keratinized layer. The present study aimed to investigate for the first time the micro- and ultrastructural changes of parakeratinized epithelium during embryonic development and to assess the readiness of the epithelium to serve protective functions during food transport to the esophagus. Three developmental stages were distinguished: embryonic, transformation, and pre-hatching stages. The embryonic stage lasts from the 9th to the 14th day of incubation and the epithelium is composed of undifferentiated epithelial cells. The transformation stage lasts from the 15th to the 22nd day of incubation and the epithelium undergoes transformation into stratified epithelium consisting of basal, intermediate, and superficial layers. The characteristic feature of this stage is formation of the periderm with osmophilic granules. The pre-hatching stage starts on the 23rd day, and the epithelium with a fully developed keratinized layer resembles that of the epithelium in adult animals. No periderm was observed on the epithelial surface. It was confirmed that at the time of hatching the parakeratinized epithelium is fully differentiated and ready to fulfill its function during food transport. The presence of periderm is a common feature characteristic for para- and orthokeratinized epithelium in the oral cavity of birds. However, the formation of the keratinized/cornified layer is different for these two types of keratinized epithelia.

Effect of thermal manipulation during embryogenesis on the promoter methylation and expression of myogenesis-related genes in duck skeletal muscle

Avian embryos are an ideal system to investigate the effect of incubation temperature on embryonic development, but the characteristics and mechanisms of temperature effects on poultry embryonic myogenesis are unclear. In this study, we investigated the effect of increasing the incubation temperature by 1 °C on the expression of nine myogenesis-related genes in ducks and then explored the correlation between the alteration of promoter methylation and the expression of two of the nine genes under thermal manipulation (TM). The qRT-PCR results showed that TM during embryonic days (ED) 1-10 promoted (P < 0.05) the expression of genes in breast muscle (PAX3, PAX7, MYOG, MCK, SIX1, TNNC1) and leg muscle (MYOD, MYOG, MYF5, MCK, AKIRIN2, TNNC1). TM during ED10-20 promoted the expression of PAX3, MYF5 and MCK and inhibited AKIRIN2 expression in breast muscle (P < 0.05); however, it inhibited the expression of PAX3, PAX7, MYOD, MYOG, MYF5, SIX1, AKIRIN2 and TNNC1 and promoted MCK expression in leg muscle (P < 0.05). TM during ED20-27 inhibited the expression of genes in breast muscle (PAX7) and leg muscle (MYOD, MYOG, MYF5, TNNC1) and promoted MCK expression in breast and leg muscle (P < 0.05). Furthermore, with the Sequenom MassARRAY platform, it was observed that the average methylation level of AKIRIN2 (ED10) and TNNC1 (ED20) in leg muscle decreased (P < 0.05) after TM. Notably, we found significant (P < 0.05) inverse correlations between the methylation and mRNA levels of AKIRIN2 under TM during ED1-10 (r = - 0.969) and ED10-20 (r = - 0.805). Taken together, TM during ED1-10 was more favorable for improving duck myogenesis-related gene expression than TM during ED10-20 and ED20-27. TM during duck embryogenesis seemed to have a greater effect on the development of leg muscle than breast muscle and might alter AKIRIN2 expression by changing its promoter methylation status. These findings may be helpful to understand temperature effects on the muscle development of avian embryos and to explore the role of epigenetic regulation during this process.

FGF and TGFβ signaling link form and function during jaw development and evolution

How does form arise during development and change during evolution? How does form relate to function, and what enables embryonic structures to presage their later use in adults? To address these questions, we leverage the distinct functional morphology of the jaw in duck, chick, and quail. In connection with their specialized mode of feeding, duck develop a secondary cartilage at the tendon insertion of their jaw adductor muscle on the mandible. An equivalent cartilage is absent in chick and quail. We hypothesize that species-specific jaw architecture and mechanical forces promote secondary cartilage in duck through the differential regulation of FGF and TGFβ signaling. First, we perform transplants between chick and duck embryos and demonstrate that the ability of neural crest mesenchyme (NCM) to direct the species-specific insertion of muscle and the formation of secondary cartilage depends upon the amount and spatial distribution of NCM-derived connective tissues. Second, we quantify motility and build finite element models of the jaw complex in duck and quail, which reveals a link between species-specific jaw architecture and the predicted mechanical force environment. Third, we investigate the extent to which mechanical load mediates FGF and TGFβ signaling in the duck jaw adductor insertion, and discover that both pathways are mechano-responsive and required for secondary cartilage formation. Additionally, we find that FGF and TGFβ signaling can also induce secondary cartilage in the absence of mechanical force or in the adductor insertion of quail embryos. Thus, our results provide novel insights on molecular, cellular, and biomechanical mechanisms that couple musculoskeletal form and function during development and evolution.

Neural crest and the origin of species-specific pattern

For well over half of the 150 years since the discovery of the neural crest, the special ability of these cells to function as a source of species-specific pattern has been clearly recognized. Initially, this observation arose in association with chimeric transplant experiments among differentially pigmented amphibians, where the neural crest origin for melanocytes had been duly noted. Shortly thereafter, the role of cranial neural crest cells in transmitting species-specific information on size and shape to the pharyngeal arch skeleton as well as in regulating the timing of its differentiation became readily apparent. Since then, what has emerged is a deeper understanding of how the neural crest accomplishes such a presumably difficult mission, and this includes a more complete picture of the molecular and cellular programs whereby neural crest shapes the face of each species. This review covers studies on a broad range of vertebrates and describes neural-crest-mediated mechanisms that endow the craniofacial complex with species-specific pattern. A major focus is on experiments in quail and duck embryos that reveal a hierarchy of cell-autonomous and non-autonomous signaling interactions through which neural crest generates species-specific pattern in the craniofacial integument, skeleton, and musculature. By controlling size and shape throughout the development of these systems, the neural crest underlies the structural and functional integration of the craniofacial complex during evolution.

Laying sequence interacts with incubation temperature to influence rate of embryonic development and hatching synchrony in a precocial bird

Incubation starts during egg laying for many bird species and causes developmental asynchrony within clutches. Faster development of late-laid eggs can help reduce developmental differences and synchronize hatching, which is important for precocial species whose young must leave the nest soon after hatching. In this study, we examined the effect of egg laying sequence on length of the incubation period in Wood Ducks (Aix sponsa). Because incubation temperature strongly influences embryonic development rates, we tested the interactive effects of laying sequence and incubation temperature on the ability of late-laid eggs to accelerate development and synchronize hatching. We also examined the potential cost of faster development on duckling body condition. Fresh eggs were collected and incubated at three biologically relevant temperatures (Low: 34.9°C, Medium: 35.8°C, and High: 37.6°C), and egg laying sequences from 1 to 12 were used. Length of the incubation period declined linearly as laying sequence advanced, but the relationship was strongest at medium temperatures followed by low temperatures and high temperatures. There was little support for including fresh egg mass in models of incubation period. Estimated differences in length of the incubation period between eggs 1 and 12 were 2.7 d, 1.2 d, and 0.7 d at medium, low and high temperatures, respectively. Only at intermediate incubation temperatures did development rates of late-laid eggs increase sufficiently to completely compensate for natural levels of developmental asynchrony that have been reported in Wood Duck clutches at the start of full incubation. Body condition of ducklings was strongly affected by fresh egg mass and incubation temperature but declined only slightly as laying sequence progressed. Our findings show that laying sequence and incubation temperature play important roles in helping to shape embryo development and hatching synchrony in a precocial bird.

Deep RNA sequencing of pectoralis muscle transcriptomes during late-term embryonic to neonatal development in indigenous Chinese duck breeds

Pectoral muscle (PM) comprises an important component of overall meat mass in ducks. However, PM has shown arrested or even reduced growth during late embryonic development, and the molecular mechanisms underlying PM growth during the late embryonic to neonatal period in ducks have not been addressed. In this study, we characterized potential candidate genes and signaling pathways related to PM development using RNA sequencing of PM samples selected at embryonic days (E) 21 and 27 and 5 days post-hatch (dph) in two duck breeds (Gaoyou and Jinding ducks). A total of 393 differentially expressed genes (DEGs) were identified, which showed higher or lower expression levels at E27 compared with E21 and 5 dph, reflecting the pattern of PM growth rates. Among these, 43 DEGs were common to all three time points in both duck breeds. These DEGs may thus be involved in regulating this developmental process. Specifically, KEGG pathway analysis of the 393 DEGs showed that genes involved with different metabolism pathways were highly expressed, while genes involved with cell cycle pathways showed lower expression levels at E27. These DEGs may thus be involved in the mechanisms responsible for the phenomenon of static or decreased breast muscle growth in duck breeds during the late embryonic period. These results increase the available genetic information for ducks and provide valuable resources for analyzing the mechanisms underlying the process of PM development.

Health-promoting bioactivities of betalains from red dragon fruit (Hylocereus polyrhizus (Weber) Britton and Rose) peels as affected by carbohydrate encapsulation

BACKGROUND

Betalains, which are red-purple and yellow pigments, are ideal alternatives to synthetic colorants as they possess strong coloring potential and excellent health-contributing properties. However, the instability of betalains toward normal storage and biological conditions, in addition to the limited number of betalain sources, impedes their food application and diminishes their bioactivities. This study aimed to evaluate the health-promoting bioactivities of betalains from red dragon fruit (Hylocereus polyrhizus (Weber) Britton and Rose) peels as affected by encapsulation in maltodextrin-gum Arabic and maltodextrin-pectin matrices.

RESULTS

Encapsulation in maltodextrin-gum Arabic and maltodextrin-pectin matrices afforded dry betalain powders after lyophilization. Optical microscopy imaging showed that the betalain powders consisted of matrix-type and shard-like microparticles. ABTS antioxidant assay revealed that maltodextrin-gum Arabic-betalain (MGB) and maltodextrin-pectin-betalain (MPB) microparticles possessed higher antioxidant capacities (195.39 ± 8.63 and 201.76 ± 4.06 µmol Trolox g^-1 microparticles respectively) than the non-encapsulated betalain extract (151.07 ± 2.57 µmol Trolox g^-1 extract). Duck embryo chorioallantoic membrane (CAM) vascular irritation assay showed that the anti-inflammatory activity of encapsulated betalains was five- to six-fold higher than that of non-encapsulated betalains (P ≤ 0.05). Antiangiogenic activity, as evaluated by duck embryo CAM assay, was enhanced two- to four-fold by carbohydrate encapsulation. Glutathione S-transferase (GST)-inducing activity of betalains was likewise improved four- to five-fold.

CONCLUSION

The study showed that the antioxidant, anti-inflammatory, antiangiogenic and GST-inducing activities of betalains from red dragon fruit peels were enhanced through carbohydrate encapsulation. © 2016 Society of Chemical Industry.

Altered immune response in mallard ducklings exposed to lead through maternal transfer in the wild

Lead (Pb) poisoning has caused significant mortality in waterfowl populations worldwide. In spite of having been banned since 2003, prevalence of Pb shot ingestion in mallards (Anas platyrhynchos) from the Ebro delta was still 15.5% in 2011-12. We collected mallard eggs from this area to study the effects of maternally transferred Pb on eggshell properties and on immune response and oxidative balance of ducklings. Eggshell Pb levels were positively correlated with Pb levels in the blood of ducklings. Ducklings with blood Pb levels above 180 ng mL(-1) showed reduced body mass and died during the first week post hatching. Blood Pb levels positively correlated with humoral immune response, endogenous antioxidants and oxidative stress biomarkers, and negatively correlated with cellular immune response. Pb shot ingestion in birds can result in maternal transfer to the offspring that can affect their developing immune system and reduce their survival in early life stages.

Expression Pattern of Calcitonin Gene-related Peptide-like Immunoreactivity in the Duck Thymus During Embryonic and Postembryonic Development

OBJECTIVE

To study the expression pattern of calcitonin gene-related peptide (CGRP)-like immunoreactivity (-ir) in the duck thymus during the embryonic and postembryonic development.

STUDY DESIGN

Studies were carried out on Tianfu ducks on 12, 14, 16, 18, 20, 22, 24, and 26 days of age prehatching, and at 0 (hatching), 1, 3, 5, 8, 14, 17, 20, 26, 29, and 32 weeks of age posthatching using high-sensitivity immunocytochemistry.

RESULTS

CGRP-ir was detected in the neuron-like cells, the lymphocytes, the vascular smooth muscle cells, as well as the reticular epithelial cells of Hassall's corpuscle and diffuse forms of Hassall's corpuscle. CGRP-ir cells were predominantly distributed in the medulla and very rarely in the cortex. The distribution density of CGRP-ir cells in the medulla increased progressively from 24 days of age prehatching to 5 weeks of age posthatching, and thereafter showed a tendency to decrease. CGRP-ir nerves, mainly running along the blood vessels, were recognized during the postembryonic development of the thymus.

CONCLUSION

The expression pattern of CGRP-ir showed obvious age-related changes during the embryonic and postembryonic development of the duck thymus, which might be related to thymus growth and involution.

Effects of the regulation of follistatin mRNA expression by IGF-1 in duck (Anas platyrhynchos) skeletal muscle

The IGF-1 and TGF-β pathways have been shown to be involved in regulating muscle development. Many mediators that are associated with the regulation of muscle development have been found to participate in the cross-talk between these two pathways. To research the relationships between IGF-1 and the follistatin-mediated TGF-β pathways in duck skeletal muscle development, a series of studies were conducted. The results showed that follistatin had similar expression patterns to IGF-1 during duck embryonic muscle development. The in ovo feeding of IGF-1 to duck eggs was shown to increase follistatin expression in the duck skeletal muscle. Thus, IGF-1 may induce the mRNA expression of follistatin. These results suggest that follistatin may be a key regulator of multiple signaling cascades responding to the cross-talk between the IGF-1 and TGF-β pathways.

Identification and profiling of microRNAs in the embryonic breast muscle of pekin duck

MicroRNAs (miRNAs) regulate gene expression by fully or partially binding to complementary sequences and play important roles in skeletal muscle development. However, the roles of miRNAs in embryonic breast muscle of duck are unclear. In this study, we analyzed the miRNAs profiling in embryonic breast muscle of Pekin duck at E13 (the 13(th) day of hatching), E19, and E27 by high-throughput sequencing. A total of 382 miRNAs including 359 preciously identified miRNAs 23 novel miRNA candidates were obtained. The nucleotide bias analysis of identified miRNAs showed that the miRNAs in Pekin duck was high conserved. The expression of identified miRNAs were significantly different between E13 and E19 as well as between E27 and E19. Fifteen identified miRNAs validated using stem-loop qRT-PCR can be divided into three groups: those with peak expression at E19, those with minimal expression at E19, and those with continuous increase from E11 to E27. Considering that E19 is the fastest growth stage of embryonic Pekin duck breast muscle, these three groups of miRNAs might be the potential promoters, the potential inhibitors, and the potential sustainer for breast muscle growth. Among the 23 novel miRNAs, novel-miRNA-8 and novel-miRNA-14 had maximal expression at some stages. The stem-loop qRT-PCR analysis of the two novel miRNAs and their two targets (MAP2K1 and PPARα) showed that the expression of novel-mir-8 and PPARα reached the lowest points at E19, while that of novel-mir-14 and MAP2K1 peaked at E19, suggesting novel-miRNA-8 and novel-miRNA-14 may be a potential inhibitor and a potential promoter for embryonic breast muscle development of duck. In summary, these results not only provided an overall insight into the miRNAs landscape in embryonic breast muscle of duck, but also a basis for the further investigation of the miRNAs roles in duck skeletal muscle development.

Embryotoxicity of weathered crude oil from the Gulf of Mexico in mallard ducks (Anas platyrhynchos)

Weathered crude oil in the Gulf of Mexico can result from oil spills such as the Deepwater Horizon incident that occurred on April 20, 2010 or from natural seeps. Adult waterbirds of the Gulf Coast region may become exposed to weathered crude oil while foraging, wading, or resting, and residues can then be transferred to nests, eggs, and hatchlings. Although the toxicity of many types of crude oil to avian embryos has been thoroughly studied, the effects of weathered crude oil on developing avian embryos are not well characterized. The objective of the present study was to examine embryotoxicity of weathered crude oil collected from the Gulf of Mexico in June 2010 using mallard ducks (Anas platyrhynchos) as a model species. Weathered crude oil was applied to fertilized mallard duck eggs by paintbrush in masses ranging from 0.1 to 99.9 mg on day 3 of incubation. Mortality occurred as early as day 7 and the conservatively derived median lethal application of weathered crude oil was 30.8 mg/egg (0.5 mg/g egg) or 30.7 µl/egg (0.5 µl/g egg). Body mass, liver and spleen mass, crown-rump and bill lengths, and frequency of deformities were not significantly different among hatchlings from oiled and control eggs. In comparison to published reports of fresh crude oil embryotoxicity, weathered crude oil was considerably less toxic. We conclude that avian toxicity varies according to the degree of crude oil weathering and the stage of embryonic development at the time of exposure. Results indicate bird eggs exposed to weathered crude oil from the Gulf of Mexico during summer 2010 may have had reduced hatching success.

Teratogenic effects of injected methylmercury on avian embryos

Controlled laboratory studies with game farm mallards (Anas platyrhynchos) and chickens (Gallus gallus) have demonstrated that methylmercury can cause teratogenic effects in birds, but studies with wild species of birds are lacking. To address this need, doses of methylmercury chloride were injected into the eggs of 25 species of birds, and the dead embryos and hatched chicks were examined for external deformities. When data for controls were summed across all 25 species tested and across all types of deformities, 24 individuals out of a total of 1,533 (a rate of 1.57%) exhibited at least one deformity. In contrast, when data for all of the mercury treatments and all 25 species were summed, 188 deformed individuals out of a total of 2,292 (8.20%) were found. Some deformities, such as lordosis and scoliosis (twisting of the spine), misshapen heads, shortening or twisting of the neck, and deformities of the wings, were seldom observed in controls but occurred in much greater frequency in Hg-treated individuals. Only 0.59% of individual control dead embryos and hatchlings exhibited multiple deformities versus 3.18% for Hg-dosed dead embryos and hatchlings. Methylmercury seems to have a widespread teratogenic potential across many species of birds.

Toxicity of polybrominated diphenyl ethers (DE-71) in chicken (Gallus gallus), mallard (Anas platyrhynchos), and American kestrel (Falco sparverius) embryos and hatchlings

Embryonic survival, pipping and hatching success, and sublethal biochemical, endocrine, and histological endpoints were examined in hatchling chickens (Gallus gallus), mallards (Anas platyrhynchos), and American kestrels (Falco sparverius) following air cell administration of a pentabrominated diphenyl ether (penta-BDE; DE-71) mixture (0.01-20 microg/g egg) or polychlorinated biphenyl (PCB) congener 126 (3,3',4,4',5-pentachlorobiphenyl; 0.002 microg/g egg). The penta-BDE decreased pipping and hatching success at concentrations of 10 and 20 microg/g egg in kestrels but had no effect on survival endpoints in chickens or mallards. Sublethal effects in hatchling chickens included ethoxyresorufin-O-dealkylase (EROD) induction and histological changes in the bursa, but these responses were not observed in other species. Polychlorinated biphenyl congener 126 (positive control) reduced survival endpoints in chicken and kestrel embryos and caused sublethal effects (EROD induction, reduced bursal mass and follicle size) in chickens. Mallards were clearly less sensitive than the other species to administered penta-BDE and PCB 126. In a second experiment, the absorption of penta-BDE (11.1 microg/g egg, air cell administered during early development) into the contents of chicken and kestrel eggs was determined at various intervals (24 h postinjection, midincubation, and pipping). By pipping, 29% of the penta-BDE administered dose was present in the egg contents in chickens, and 18% of the administered dose was present in kestrel egg contents. Based on uptake in kestrels, the lowest-observed-effect level on pipping and hatching success may be as low as 1.8 microg total penta-BDE/g egg, which approaches concentrations detected in eggs of free-ranging birds. Because some penta-BDE congeners are still increasing in the environment, the toxic effects observed in the present study are cause for concern in wildlife.

Developmental changes in insulin-like growth factor (IGF)-I and -II mRNA abundance in extra-embryonic membranes and small intestine of avian embryos

OBJECTIVE

Numerous researchers have evaluated the insulin-like growth factors (IGF) influence on mammalian fetal development. Although IGF has been explored in the avian system, questions remain on the role of IGF in avian development. Therefore, the current study evaluated the mRNA abundance of IGF in the amnion and allantoic membranes and developing small intestine in the chicken, duck, and turkey during the incubation and post-hatch period.

DESIGN

Broiler, duck, and turkey eggs were incubated with small intestinal, allantoic, and amniotic membranes collected in the final days of incubation and 1 week post-hatch. RNA was extracted using Trizol and qRT-PCR was utilized to compare differences during embryo development within and across species.

RESULTS

The expression of the IGF mRNA varied between species in the final days of incubation in the amniotic and allantoic membranes. The turkey had higher (0.38-1.72 log) transcript abundance of IGF-I and IGF-II in the amnion and allantois compared to the chicken and duck. Evaluating the mRNA abundance within the chicken duodenum, jejunum, and ileum, the duodenum had the lowest expression of IGF-I and IGF-II (P<0.05) at day -4 of incubation compared to the jejunum and ileum. Focusing on differences in jejunal IGF expression among the three species, the turkey had the lowest IGF-I abundance at day -4 of incubation and highest IGF-I abundance at day of hatch (P<0.05). Transcript abundance of both IGF-II and IGF-R was highest in the turkey at day of hatch and day 1 post-hatch compared to the duck and chicken. The whole tissue versus the mucosal expression of the IGF mRNA abundance was evaluated during the post-hatch period. Duodenal, jejunal, and ileal segments had higher IGF-I transcript abundance (P<0.05) at day 1, day 3, and day of hatch, respectively. No differences were observed between segment and mucosa for IGF-II in the post-hatch period. The duodenal and jejunal mucosa IGF-R transcript abundance was greater (P<0.05) at day of hatch compared to the intestinal segment. The duck IGF mRNA in the jejunal mucosa was higher than the whole segment and decreased from day of hatch to day 3 post-hatch while the IGF mRNA abundance increased in the whole segment during the same time period. The turkey IGF-I transcript abundance decreased in both the segment and mucosa following hatch while the IGF-II mRNA expression increased by 1.5 logs from hatch to day 1 post-hatch.

CONCLUSION

The transcript abundance of the IGF axis in the extra-embryonic membranes and gastrointestinal tissue of the developing chicken, duck, and turkey are influenced by embryonic age and species. A better understanding of the IGF axis in the small intestine during embryonic development may allow for increasing the optimal growth of both the gastrointestinal tract and the neonate.

The genesis of cartilage size and shape during development and evolution

How do cartilaginous elements attain their characteristic size and shape? Two intimately coupled processes underlie the patterned growth of cartilage. The first is histogenesis, which entails the production of cartilage as a discrete tissue; the second is morphogenesis, which pertains to the origins of three-dimensional form. Histogenesis relies on cues that promote the chondrogenic differentiation of mesenchymal cells, whereas morphogenesis requires information that imbues cartilage with stage-specific (e.g. embryonic versus adult), region-specific (e.g. cranial versus appendicular) and species-specific size and shape. Previous experiments indicate that early programmatic events and subsequent signaling interactions enable chondrogenic mesenchyme to undergo histogenesis and morphogenesis, but precise molecular and cellular mechanisms that generate cartilage size and shape remain unclear. In the face and jaws, neural crest-derived mesenchyme clearly plays an important role, given that this embryonic population serves as the source of chondrocytes and of species-specific patterning information. To elucidate mechanisms through which neural crest-derived mesenchyme affects cartilage size and shape, we made chimeras using quail and duck embryos, which differ markedly in their craniofacial anatomy and rates of maturation. Transplanting neural crest cells from quail to duck demonstrates that mesenchyme imparts both stage-specific and species-specific size and shape to cartilage by controlling the timing of preceding and requisite molecular and histogenic events. In particular, we find that mesenchyme regulates FGF signaling and the expression of downstream effectors such as sox9 and col2a1. The capacity of neural crest-derived mesenchyme to orchestrate spatiotemporal programs for chondrogenesis autonomously, and to implement cartilage size and shape across embryonic stages and between species simultaneously, provides a novel mechanism linking ontogeny and phylogeny.

[Studies on the propagation characteristics of duck plague virulent virus in duck embryo fibroblasts]

The propagation characteristics of virulent duck plague virus (DPV) in duck embryo fibroblast (DEF) were studied by the method of light microscopy observation of DEF cell culture monolayer, electron microscopy observation of infected DEF cell culture, real-time PCR detecting virus propagation. The results demonstrated that on duck embryo fibroblast a number of plaques were formed by DPV 42 h postinfection. Electron microscopy of the ultrathin section of infected duck embryo fibroblasts demonstrated that the nucleic acid of DPV was round in shape with diameter of 35-45 nm and was often in a cluster in the nucleus of DEF. The nucleocapsid of DPV was round in shape with diameter of 90-100 nm and could be observed both in nucleus and cytoplasm of DEF. The mature DPV which had the structures of envelop and tegument was spherical in shape with diameter of 150-300 nm and was located in cytoplasmic vacuoles. DPV penetrated the DEF cell membrane by direct fusion between the viral envelop and the plasma membrane. Progeny viral nucleic acid was produced in the nucleus and the assembled nucleocapsids obtained the structure of tegument in the cytoplasm and obtained the structure of envelop by budding into the cytoplasmic vesicles. The mature DPV particles were released out of the cell through exocytosis of the cytoplasmic vesicles. Detection of DPV by real-time PCR demonstrated that virus in DEF began its obvious propagation 10 h postinfection and virus amount tended to increase until 30 h postinfection. DPV began to be released into the supernatant 22 h postinfection and the DPV amount peaked 50 h postinfection, when the virus content in DEF and supernatant both underwent approximately 10(3) fold increase. DPV mainly existed in the DEF and the virus content in DEF was 10(2)-10(3) fold than the supernatant.

[Preliminary study on apoptosis of DEF cells induced by new type gosling viral enteritis virus (NGVEV) infection]

The characteristics changes of apoptosis of Duck Embryo Fibroblasts (DEF) cells induced by New type gosling viral enteritis virus, NGVEV) were observed by means of HE staining, electron microscopy and Annexin V-FITC/PI fluorescent staining. During 24-48 h post infection (pi), the difference of morphological change between infected DEF cells and the mock infected cells was invisible. At 72 h pi, the nuclear chromatin was getting condensed through HE staining; apoptotic morphological change such as abnormal shape of the nucleus, condensation of the cytoplasm and chromatin were observed under electron microscope; and the early apoptotic cells (Annexin V-FITC positive and PI negative) were detected under fluorescence microscope. At 96-120 h pi, by means of HE staining and electron microscopy, the advanced morphological change of apoptosis such as formation of different kinds of apoptotic bodies, and shrink of the DEF cells and nucleus were detected; under fluorescence microscope the different stages of the apoptotic DEF can be easily distinguished: early apoptotic cells (Annexin V-FITC postive and pi negative), advanced or late apoptotic cells (both Annexin V-FITC and PI positive), necrosis cells or dead cells (Annexin V-FITC negative and PI positive). This investigation shows that NGVEV might induce apoptosis and form characteristic apoptotic morphological changes in the DEF cells. NGVEV inducement of apoptosis may be an important mechanism of efficient dissemination of virus progeny.

Feather pattern development

Experiments on skin development in amniotes have shown conclusively that the pattern of cutaneous appendages is determined by the dermis. The following concept of feather pattern formation is proposed. The diameter of feather rudiments and the dermal cell density inside the dermal feather condensations are genetically fixed, region-specific parameters. The first feather rudiment is established along the middorsal line (in the lumbar region) as soon as a sufficient width of dense dermis is available. This occurs at about 6 1/2 days in the chick embryo. The next rudiments are formed in front of and behind the first one, within the longitudinal band of dense dermis. They are laid down as close as possible to the first one, given rudiment diameter and dermal condensation cell density. In other words, as they form, the middorsal rudiments are tangent circles.. Later they become separated from one another due to longitudinal growth. As progressively more dense dermis becomes available to the sides of the middorsal row of rudiments, new rudiments are being laid down lateral to the middorsal row, in successive longitudinal rows, until, by 9 or 10 days, all the available dense dermis has been used up. Again, the rudiments in the lateral rows, given their diameter and dermal condensation cell density, develop as close as possible to those of the preceding row, i.e. tangentially to two neighbouring rudiments of the preceding row, thus generating a hexagonal pattern.

Development of One-Step Reverse Transcriptase–Polymerase Chain Reaction to Detect Duck Hepatitis Virus Type 1

A one-step reverse transcriptase-polymerase chain reaction (RT-PCR) method was developed and optimized for the detection of duck hepatitis virus type 1 (DHV-1) using the Viral Gene-spin viral DNA/RNA extraction kit. A pair of DHV-1-specific primers was designed against the gene encoding RNA-dependent RNA polymerase (3D gene). Using RNA prepared from duckling liver samples infected with two reference and seven Korean field isolates of DHV-1, one-step RT-PCR with DHV1-specific primers amplified a 467-bp fragment. Under the same conditions, no amplification was observed for 14 other avian pathogenic viruses and bacteria. Using RNA prepared from serial dilutions of the DHV-1 with the supernatant of the uninfected duckling liver homogenate (10% w/v), the one-step RT-PCR assay was found to be sensitive to 10 50% egg lethal dose (ELD50) 0.1 ml(-1) of DHV-1. Furthermore, this method detected DHV-1 from the livers and allantoic fluid of duck embryos dying before 3 days postinoculation (PI) and of chicken embryos that were chilled at 3 days PI. Therefore, this one-step RT-PCR method is rapid, sensitive, and reliable, and can be readily adapted for detection of DHV-1 from other clinical samples.

Morphoregulation of avian beaks: comparative mapping of growth zone activities and morphological evolution

Avian beak diversity is a classic example of morphological evolution. Recently, we showed that localized cell proliferation mediated by bone morphogenetic protein 4 (BMP4) can explain the different shapes of chicken and duck beaks (Wu et al. [2004] Science 305:1465). Here, we compare further growth activities among chicken (conical and slightly curved), duck (straight and long), and cockatiel (highly curved) developing beak primordia. We found differential growth activities among different facial prominences and within one prominence. The duck has a wider frontal nasal mass (FNM), and more sustained fibroblast growth factor 8 activity. The cockatiel has a thicker FNM that grows more vertically and a relatively reduced mandibular prominence. In each prominence the number, size, and position of localized growth zones can vary: it is positioned more rostrally in the duck and more posteriorly in the cockatiel FNM, correlating with beak curvature. BMP4 is enriched in these localized growth zones. When BMP activity is experimentally altered in all prominences, beak size was enlarged or reduced proportionally. When only specific prominences were altered, the prototypic conical shaped chicken beaks were converted into an array of beak shapes mimicking those in nature. These results suggest that the size of beaks can be modulated by the overall activity of the BMP pathway, which mediates the growth. The shape of the beaks can be fine-tuned by localized BMP activity, which mediates the range, level, and duration of locally enhanced growth. Implications of topobiology vs. molecular blueprint concepts in the Evo-Devo of avian beak forms are discussed.

Polymorphisms in the repeat long regions of oncogenic and attenuated pathotypes of Marek's disease virus 1

The nucleotide sequences of the terminal repeat long (TR(L)) and internal repeat long regions (IR(L)) in the genomes of 13 strains of Marek's disease virus type 1 (MDV-1) were determined and represent the largest collection of sequencing data from a contiguous region (12.8 kb) in the serotype 1 genomes. The collection of strains used in this study has been well characterized with respect to their virulence and contains members of each pathotype (4 attenuated, 1 mildly virulent, 3 virulent, 2 very virulent and 3 very virulent plus). It has previously been reported that two loci (meq and RLORF4) in the RL regions are likely to encode virulence factors based on comparative genomic studies involving vaccine and virulent strains. Additional studies using knockout mutants have provided stronger evidence that indeed RLORF4 and meq or the overlapping genes 23 kD and RLORF6 are involved in virulence. In this report, we provide evidence that additional open reading frames (ORFs) in the RL regions differ significantly between the extremes of the pathotypes (attenuated vs. nonattenuated). A deletion of 10 base pairs has been identified in RLORF12 from two attenuated strains CVI988 BP-5, p48 and RM-1, p40; and the lower virulence strain JM/102W. A deletion of 40 bp was also identified in RLORF4 of the attenuated strain R2/23, passage 106. A 177 bp insertion within the meq loci has been identified in most of the attenuated strains examined. Interestingly, R2/23 did not contain this insertion but instead truncated proteins are predicted for the three overlapping ORFs (meq, 23 kD and RLORF6) due to a frameshift mutation. Single nucleotide polymorphisms (SNPs), which loosely partition between attenuated and nonattenuated strains, have been identified in the ORFs encoding RLORF12, RLORF8, meq, 23 kD, RLORF6, RLORF4, RLORF3 and ICP0 and three previously unidentified short ORFs: MHLS, MLHG and MPSG. Although no single nucleotide polymorphism in the RL regions could predict virulence, their overall contribution to virulence can now be examined in defined mutants containing additional insertions or deletions in ORFs, suspected of encoding virulence factors, identified by this research.

Effects of Anti-Bursin Monoclonal Antibody on Immunosuppression in the Duck (Cherry Valley Duck)

To study the immunologic function of bursin, we analyzed the effects of anti-bursin monoclonal antibody (mAb) on the immunosuppression in ducks (Cherry Valley duck) by injecting various doses of the anti-bursin mAb into 13-d duck embryos. After hatch, cell-mediated immune activity and humoral responses were studied using lymphocyte proliferation test, tube agglutination test, and indirect enzyme-linked immunosorbent assay to detect anti-Escherichia coli antibodies and antibodies to Riemerella anatipestifer, respectively. Simultaneously, relative weights (BW-adjusted) of bursa of Fabricius (BF), spleen, and thymus were determined. Additionally, the morphology of BF, spleen, and thymus was examined at various ages using conventional histology. Follicle morphology of BF was analyzed by image analysis. The results indicated that anti-bursin mAb markedly decreased duck lymphocyte proliferation, the antibody-producing ability to bacteria, as well as the relative BF weight. Moreover, the anti-bursin mAb hindered the development of BF follicles.

Yolk sac, body dimensions and hatchling quality of ducklings, chicks and poults

1. One-day-old chicks of Pekin duck, turkey, layer fowl and broiler fowl were examined for bacteria in the yolk sac and yolk fluid. 2. Whole hatchling, yolk-free hatchling and yolk sac weights were recorded for all species along with crown-rump length and beak-tip to toe-tip length. 3. Bacteriology revealed positive results for the whole yolk sacs of 43 to 64% of the birds in the sample of ducklings, poults and layer chicks. Broiler chicks had a 6.6% incidence of bacteria isolated from the whole yolk sac. By contrast, there were very few positive results from swabs of yolk fluid for any of the bird types. 4. The presence of bacteria in the yolk sac of hatchlings suggests that there is colonisation, rather than infection, of the yolk sac membrane during the hatching period or the first few hours post-hatching. Isolation of bacteria from the yolk sacs of young chicks might no longer be considered as solely indicative of yolk sac infection but further research is required to confirm this result. 5. Contrary to what is being suggested in commercial practice relationships between linear dimensions and hatchling weight suggest that measurement of chick length is at best a very crude measure of chick quality.

Nucleotide sequence and embryonic expression of quail and duck Sox9 genes

Sox9 is a member of the Sry-type HMG-box (Sox) gene family. It encodes a transcription factor and is thought to be important for sexual differentiation in chicken. In the present study we have isolated Sox9 cDNAs from quail and duck, and examined the expression patterns of the corresponding genes in early embryonic gonads by whole-mount in situ hybridization. We developed a polymerase chain reaction-based protocol to identify the sex of quail and duck embryos before its morphological manifestation. Sox9 expression was first detected on days 5 and 7 in the gonads of male quail and duck embryos, respectively, and was not apparent in female gonads at these stages. These expression patterns are similar to that of chicken Sox9. Our results thus suggest that the expression of quail and duck Sox9 is associated with testis differentiation.

Developmental changes in amniotic and allantoic fluid insulin-like growth factor (IGF)-I and -II concentrations of avian embryos

In the literature, IGFs in the developing embryo are usually determined by blood serum concentrations. For this study, IGF-I/-II was quantified in the amniotic and allantoic fluids of fertile commercial broiler chicken (Gallus domesticus) (n=222), Pekin duck (Anas platyrhyncha) (n=250), and turkey (Meleagridis gallopavo) eggs (n= 200) during incubation. Amniotic and allantoic fluids were collected from embryos starting at 6 days of incubation for chickens and 8 days of incubation for ducks and turkeys. IGF concentrations within the fluids were determined by radioimmunoassay. Chicken amniotic IGF-I concentration at stage 29 of development was significantly higher (P< or =0.05) than the duck or turkey. At stage 36 of development the concentration of IGF-II in the amniotic fluid was 2.8 times greater in the chicken versus the duck (P< or =0.05) and 2 times greater than in the turkey (P< or =0.05). Within species, chicken IGF-I concentration in the amniotic fluid had a cubic trend (P< or =0.001), duck IGF-I increased linearly (P< or =0.001), and turkey concentrations declined quadratically (P< or =0.001) throughout development. In all species, the IGF-II concentration was higher than the IGF-I concentration in the amniotic and allantoic fluids.

Secretion of inhibin and testicular expression of inhibin subunits in male duck embryos and newly hatched ducks

Concentrations of immunoreactive (ir-) inhibin in circulation, amniotic fluid, and testes of embryos and newly hatched ducks were determined from d 21 of incubation to d 1 of age. Plasma concentrations of FSH and LH were also determined by chicken radioimmunoassay (RIA) systems. In addition, gene expression and cellular source of inhibin were investigated by in situ hybridization and immunohistochemistry. The results showed that plasma ir-inhibin gradually declined from d 21 to d 24, followed by an increase on d 25 and remained high until d 1 after hatching. FSH in plasma was high on d 21 followed by a sharp decline toward d 25 after which FSH levels stabilized. A reverse relationship was observed between inhibin and FSH during the late stage of incubation. Embryonic testes contained high ir-inhibin levels. Testicular ir-inhibin levels were relatively high at early time points with a peak on d 23, and significantly decreased from d 23 to d 24 and stabilized thereafter. Amniotic fluid concentrations of ir-inhibin were relatively low and remained constant between d 21 and d 25. In situ hybridization demonstrated that the expression of inhibin alpha- and betaA-subunit mRNA was coexisted in the cells in the seminiferous tubules of testes on d 25. The immunoreactivity of inhibin betaA- and betaB-subunits was colocalized in the cells in the seminiferous tubules of testes on d 25. The results of dimeric inhibins determined by the ELISA method showed that inhibin B can be measured in embryonic testicular homogenate and pooled embryonic plasma. Although inhibin A was detected in testicular homogenate, it was under the detection limit in pooled embryonic plasma. In conclusion, these results indicate that cells in the seminiferous tubules of embryonic testes in ducks may secrete dimeric (bioactive) inhibins to circulation and that the FSH-inhibin feedback loop may become operational during the late stage of the incubation.

Comparison of fertility and embryo mortality following artificial insemination of common duck females (Anas Platyrhynchos) with semen from common or Muscovy (Cairina Moschata) drakes

The purpose of this study was to compare fertility and early embryo mortality rates (< or = 5 days of incubation) following artificial insemination (AI) of common duck females (Anas Platyrhynchos) with semen from either common or Muscovy (Cairina Moschata) drakes at various periods of the reproductive season (Period I, 27-35 weeks; Period II, 39-43 weeks and Period III, 49-56 weeks). Based on observations performed by stereomicroscopy on eggs laid from Days 2 to 10 after AI, we confirmed that fertility was significantly lower in the interbred compared to the purebred cross at each of the periods tested (purebred 58.1, 61.2 and 54.2 versus crossbred 31.0, 40.4 and 39.5 at Periods I, II and II, respectively; 0.01 < P < 0.001). In a complementary experiment, we demonstrated that the number of perivitelline spermatozoa (NPS) was markedly lower in mule (crossbred) eggs compared to common (purebred) eggs, a strong indication that initial sperm selection occurring in the lower oviduct is probably more intense after crossbred compared to purebred insemination. Comparison of early embryo mortality (EEM) between mule and common duck eggs indicated that increased levels of EEM in mule embryos corresponded to Stages II-IV of the Eyal-Giladi and Kochav classification (EGK). While a similar age-dependent increase in early embryo mortality was observed in eggs from both genetic origins during the latter periods of the reproductive season, it was also established that embryo mortality due to parental age was related rather to Stages X-XIV of the EGK classification in eggs from both genetic origins. It is concluded that the relative subfertility of mule compared to common duck eggs is probably the consequence of a more intense rate of selection of heterologous than homologous spermatozoa occurring in the vaginal portion of the oviduct while the causal origins of EEM in mule duck eggs can at least in part be identified on the basis of precise staging (by stereomicroscopy) of dead embryos.

Quail-duck chimeras reveal spatiotemporal plasticity in molecular and histogenic programs of cranial feather development

The avian feather complex represents a vivid example of how a developmental module composed of highly integrated molecular and histogenic programs can become rapidly elaborated during the course of evolution. Mechanisms that facilitate this evolutionary diversification may involve the maintenance of plasticity in developmental processes that underlie feather morphogenesis. Feathers arise as discrete buds of mesenchyme and epithelium, which are two embryonic tissues that respectively form dermis and epidermis of the integument. Epithelial-mesenchymal signaling interactions generate feather buds that are neatly arrayed in space and time. The dermis provides spatiotemporal patterning information to the epidermis but precise cellular and molecular mechanisms for generating species-specific differences in feather pattern remain obscure. In the present study, we exploit the quail-duck chimeric system to test the extent to which the dermis regulates the expression of genes required for feather development. Quail and duck have distinct feather patterns and divergent growth rates, and we exchange pre-migratory neural crest cells destined to form the craniofacial dermis between them. We find that donor dermis induces host epidermis to form feather buds according to the spatial pattern and timetable of the donor species by altering the expression of members and targets of the Bone Morphogenetic Protein, Sonic Hedgehog and Delta/Notch pathways. Overall, we demonstrate that there is a great deal of spatiotemporal plasticity inherent in the molecular and histogenic programs of feather development, a property that may have played a generative and regulatory role throughout the evolution of birds.

Comparative development of the small intestine in the turkey poult and Pekin duckling

Turkey poults and Pekin ducklings hatch from eggs of similar weights and have the same incubation periods and body weights at hatch. The male Pekin duckling, however, can attain a market weight of 3.2 kg in approximately 6 wk, whereas at the same age, male turkeys only weigh approximately 2.1 kg. For this study, fertile turkey eggs (n = 400, mean weight: 87.2 g, range: 85 to 89.9 g) and Pekin duck eggs (n = 565, mean weight: 88.6 g, range: 85 to 92.0 g) were weighed and incubated. Embryos and hatchlings were sampled during the last week of incubation, at hatch, and through 7 d of age. Yolk-free BW of poults were 2.7 g heavier than ducklings at hatch. Yolk-free BW of ducklings, however, were greater than poults at 1 d of age (P > or = 0.06), and by 7 d of age ducklings were 140 g heavier (P < or = 0.01). Yolk sac weight was similar at 21 and 25 d of incubation, yet was significantly lower in ducks at hatch, 1, and 2 d of age (P < or = 0.05). In the duckling, jejunum and ileum weights (3.7x heavier), length (1.6x longer), and density (g/cm; 2.3x more dense) were consistently heavier than in the turkey from hatch through 7 d (P < or = 0.01). Histological sections of the distal jejunum revealed more rapid villus growth in the duck from 0 to 3 d of age. The combination of increased intestinal growth (weight and length) and maturation (villus length) allowed ducks to achieve an additional 143 g of BW gain during the critical hatch through 7 d of growth.

Programmed cell death in the embryonic vertebrate limb

The developing limb bud provides one of the best examples in which programmed cell death exerts major morphogenetic functions. In this work, we revise the distribution and the developmental significance of cell death in the embryonic vertebrate limb and its control by the BMP signalling pathway. In addition, paying special attention to the interdigital apoptotic zones, we review current data concerning the intracellular death machinery implicated in mesodermal limb apoptosis.

Molecular shaping of the beak

Beak shape is a classic example of evolutionary diversification. Beak development in chicken and duck was used to examine morphological variations among avian species. There is only one proliferative zone in the frontonasal mass of chickens, but two in ducks. These growth zones are associated with bone morphogenetic protein 4 (BMP4) activity. By "tinkering" with BMP4 in beak prominences, the shapes of the chicken beak can be modulated.

Intraembryonic avian leukosis virus subgroup C (ALV-C) inoculation producing wasting disease in ducks soon after hatching

We have studied the pathogenic changes in Khaki Campbell ducks injected in mid embryogenesis with ALV subgroup C virus td daPR-C derived from a molecular clone. The employed duck flock was shown to be highly genetically homogeneous and was controlled for the absence of current infections. Clear symptoms of wasting disease, which appeared since one week post hatching, represented the early consequence of the virus infection. They were manifested by decreased body weight, including clear involution of thymic tissue and pronounced anaemia. Microscopically, thymuses of infected animals displayed lymphatic depletion, clearly visible in the lobular cortex. Similarly, in the bursa Fabricii follicles, a marked reduction of the cortical layer and a decrease in folicullar centres was revealed. A decrease in the antibody response correlated with bursa Fabricii atrophy. The clear signs of anaemia were confirmed by haematological measurements, red blood cell count, haematocrit value and haemoglobin included. On the basis of these and additional observations we propose that inoculation of duck embryos provides a suitable model for analysis of the wasting disease produced by ALV-C.

Neural crest cells provide species-specific patterning information in the developing branchial skeleton

The skeletal elements of the branchial region are made by neural crest cells, following tissue interactions with the pharyngeal endoderm. Previous transplantation experiments have claimed that the cranial neural crest is morphogenetically prespecified in respect of its branchial skeletal derivatives, that is, that information for the number, size, shape, and position of its individual elements is already determined in these cells when they are still in the neural folds. This positional information would somehow be preserved during delamination from the neural tube and migration into the branchial arches, before being read out as a spatial pattern of chondrogenesis and osteogenesis. However, it now appears that signals from the endoderm are able to specify not only the histogenic differentiation state of neural crest cells but also the identity and orientation of the branchial skeletal elements. It is therefore important to ask whether fine details of branchial skeletal pattern such as those that exist between different species are also governed by extrinsic factors, such as the endoderm, or by the neural crest itself. We have grafted neural crest between duck and quail embryos and show that the shape and size of the resulting skeletal elements is donor derived. The ability to form species-specific patterns of craniofacial skeletal tissue thus appears to be an inherent property of the neural crest, expressed as species-specific responses to endodermal signals.

Sex ratios in mule duck embryos at various stages of incubation

Mule duck hatcheries have long reported varying degrees of unbalance in the sex ratio, with a preponderance of male mules at hatching. The aim of the present study was to assess the distributions of sex ratios at various stages of development in embryos originating from intra- and intergeneric crosses between parental lineages (Muscovy male x Muscovy female, Pekin male x Pekin female, Muscovy male x Pekin female or Mule, and Pekin male x Muscovy female or Hinny). In Experiment I, embryo sexing was performed on Days 1 and 5 of incubation (by multiplex PCR) and at hatching (by vent observation). The sex ratio was not significantly modified during the early stages of embryo development whatever the genetic origin (P>0.05, Days 1 and Day 5) but our results in mule and hinny ducklings confirmed the preponderance of males among normally hatched ducklings originating from the intergeneric lineage (58.9 and 55.4% males in mules and hinnies, respectively; P<0.05 in both cases). Sex ratio (vent sexing) in second grade (cull) ducklings revealed that 68% of these ducklings were females (P<0.05). In Experiment II, the distribution of sex ratio was also performed in mule duck eggs from 6 batches (400,000 eggs/batch) first examined for fertility (candling) on Day 18 of incubation. These results indicate that the percentage of males present in the population of normally hatched ducklings increases when fertility decreases. In addition, this experiment also revealed that 83.7-90.5% of viable male mule embryos develop up to hatching, compared to only 43.0-51.0% of female mule embryos. Given that a deviation in sex ratio during the first stages of incubation is unlikely (Experiment I), it is concluded that the skewed sex ratio of mule ducks at hatching is primarily due to increased late mortality in female mule embryos occurring between egg transfer and hatching. This mortality originated, at least in part, from the intergeneric origin of female mules, and was marked to a greater or lesser extent depending on the initial success of fertilization in a given batch, a possible indication that the initial quality of gametes may selectively exert its influence at the later stages of embryo development.

Adverse effects of (surface water pollutants) Cd, Cr and Pb on the embryogenesis of the mallard

The effects of chromium, lead and cadmium were studied on the embryogenesis, hatching success and viability of the mallard. Eggs were exposed to relatively low environmental concentrations that are characteristic to the level in polluted Hungarian surface waters. Eggs were treated by injection or immersion--prior to incubation. In study I, effects on early embryogenesis (first 10 days of incubation) were examined. Eggs were opened daily, mortality was determined and permanent slides of the embryos were made to help further external examinations. Each metal proved to be toxic to the developing mallard embryo, causing an increase in mortality and developmental anomalies. Chromium was the most teratogenic of the three heavy metals increasing the rate of malformations by 30% (P<0.001) after immersion, and 17% (P<0.01) after injection of the eggs. Cadmium proved to cause the highest rate of mortality. Embryonic death was increased by 27% (P<0.01) and 40% (P<0.001) after Cd immersion and injection, respectively. In study II, effects on hatching and viability of the ducklings were studied. The eggs were hatched, hatching and mortality rates were established, the liver of animals was histopathologically examined. However each heavy metal decreased hatching success, cadmium was found the most toxic compound, causing a 21% (P<0.01) and 47% (P<0.001) reduction in hatching success after immersion and injection, respectively. The liver of hatched ducklings showed significant lesions, dystrophy in the form of hepatic necrosis was detected in each treated animal. Each heavy metal (Cr, Pb, Cd) proved to have adverse effects on the embryonic development, hatching and viability of the mallard.

Embryotoxic thresholds of mercury: estimates from individual mallard eggs

Eighty pairs of mallards ( Anas platyrhynchos) were fed an uncontaminated diet until each female had laid 15 eggs. After each female had laid her 15th egg, the pair was randomly assigned to a control diet or diets containing 5, 10, or 20 microg/g mercury as methylmercury until she had laid a second set of 15 eggs. There were 20 pairs in each group. After the second set of 15 eggs, the pair was returned to an uncontaminated diet, and the female was permitted to lay another 30 eggs. For those pairs fed the mercury diets, the even-numbered eggs were incubated and the odd-numbered eggs were saved for possible mercury analysis. Mercury in the even-numbered eggs was estimated as the average of what was in the neighboring odd-numbered eggs. Neurological signs of methylmercury poisoning were observed in ducklings that hatched from eggs containing as little as 2.3 microg/g estimated mercury on a wet-weight basis, and deformities were seen in embryos from eggs containing about 1 microg/g estimated mercury. Although embryo mortality was seen in eggs estimated to contain as little as 0.74 microg/g mercury, there were considerable differences in the sensitivity of mallard embryos, especially from different parents, with some embryos surviving as much as 30 or more microg/g mercury in the egg.

The cellular and molecular origins of beak morphology

Cellular and molecular mechanisms underlying differences in beak morphology likely involve interactions among multiple embryonic populations. We exchanged neural crest cells destined to participate in beak morphogenesis between two anatomically distinct species. Quail neural crest cells produced quail beaks in duck hosts and duck neural crest produced duck bills in quail hosts. These transformations involved morphological changes to non-neural crest host beak tissues. To achieve these changes, donor neural crest cells executed autonomous molecular programs and regulated gene expression in adjacent host tissues. Thus, neural crest cells are a source of molecular information that generates interspecific variation in beak morphology.

Development of viral disinfectant assays for duck hepatitis B virus using cell culture/PCR

Human hepatitis B virus (HBV) is a worldwide public health problem with chronic carriers at risk for developing cirrhosis and hepatocellular carcinoma. Accidental nosocomial infections from inadequately disinfected equipment or exposure to blood and body fluids from patients are major routes. To solve such problems, disinfectants to inactivate HBV must be validated. Duck hepatitis B virus (DHBV) is accepted as a surrogate for HBV, due to their similar sensitivities to disinfectants and its safety. Ducklings are used for disinfectant efficacy assays; however, the same virus titer is obtained using duck embryonic hepatocytes. Viral titration in disinfectant efficacy assay is conducted using Southern hybridization of infected duck serum. However, this test requires radioisotopes. Therefore, disinfectant assessment protocols were developed using duck embryonic hepatocytes with polymerase chain reaction (PCR) or nested PCR. The ease of handling, lowered cost and enhanced sensitivity make PCR desirable. Chicken embryonic hepatocytes were applied to DHBV disinfectant efficacy assay. Results were consistent and could be used under certain conditions. The virucidal activities of two quaternary ammonium chloride disinfectants, n-alkyl dimethyl benzyl ammonium chloride and alkyl dimethyl benzyl ammonium chloride (10C-12C) were compared and effective concentrations were 1200 and 1800 ppm, respectively. Efficacies of these disinfectants were validated using real-time quantitative PCR. Results confirmed that the efficacy of n-alkyl dimethyl benzyl ammonium chloride was higher than alkyl dimethyl benzyl ammonium chloride (10C-12C). This assay was useful for rapid discrimination of killing potentials of disinfectants. In conclusion, these assays can be applied to other viruses that are unable to cause CPE in cell cultures and broadened the utility of DHBV as animal model for HBV.

Embryonic development from first cleavage through seventy-two hours incubation in two strains of pekin duck (Anas platyrhynchos)

Embryonic mortality is a significant problem plaguing the commercial duck industry worldwide. Yet, an objective means to stage development of the duck embryo is lacking. Such a staging procedure, which is described in this study, is essential for the critical and reproducible assessment of embryo development. The morphological features associated with duck embryo development are very similar to those of the chicken, although the duck embryo develops more slowly. The staging scheme presented here provides objective morphological criteria describing the embryonic development of the duck.

Metabolic responses of chicken and muscovy duck embryos to high incubation temperatures

Oxygen consumption, heat production (HP) and core temperature (T(af)) were measured over 3 h in 20-34-day-old Muscovy duck and 12-21-day-old chicken embryos at ambient temperature (T(a)) of 37.5 degrees C and thereafter for 3 h at T(a) of 39.0 degrees C. At 37.5 degrees C T(a), HP increased with age in avian embryos of both species, following an exponential function. In muscovy duck embryos, a plateau phase occurred between D29 and D32; in chicken embryos, a similar plateau occurred between D19 and D21. T(af) rose in accordance with HP, and the relationships between T(af) and HP could be described by significant linear regressions in both species. Mostly, HP increased in embryos of both species during heat load, but by less than calculated by the van't Hoff rule; however, there was often also a decrease in HP under these conditions. Obviously, in avian embryos high T(a) causes a down-regulation of HP mediated by active thermoregulatory mechanisms. This is in agreement with data describing the influence of hyperthermia on HP in the postnatal period of birds and mammals. Because of this, the term 'second chemical thermoregulation' defined by Gelineo [C. R. Soc. Biol. (1936) 122 337] for birds and mammals should also be used for avian embryos.

Development of heart rate responses to acoustic stimuli in Muscovy duck embryos

Heart rate (HR) of Muscovy duck embryos (Cairina moschata f. domestica) was continuously recorded from the 21st day of incubation (E21) until hatching (E35). During that period, embryos were exposed to different acoustic stimuli (species-specific maternal and duckling calls, music, rectangular and sine waves, white noise). Sudden HR changes occurred at the onset of acoustic stimulation (on-response), as well as spontaneously. From E27 onwards, the response rate was significantly higher than the rate of spontaneous HR changes. The on-response rate increased further until E30. Most responses were elicited by maternal calls and music, but rarely by duckling calls. On-responses could be classified into: HR increase (36.4%), HR decrease (37.9%) and an increase in instantaneous HR variability (23.2%). The increase in HR variability occurred only in response to sounds, but not spontaneously. HR increases were mainly observed when the baseline HR was lower than the long-term HR trend. On-response duration was no longer than 3 min in 90% of all observations. The hourly mean HR and standard deviation did not change, even during phonoperiods composed of several sound patterns and lasting several hours. We conclude that Muscovy duck embryos are able to perceive exogenous acoustic stimuli, and that the acousto-sensory-->cardiac axis is functional from E27.

Latency sites and reactivation of duck enteritis virus

Duck virus enteritis (DVE) is a contagious disease caused by herpesvirus in waterfowl populations. Recovered birds become carriers and shed the virus periodically. Reactivation of latent duck enteritis virus (DEV) has been implicated in outbreaks of DVE in domestic and migrating waterfowl populations. In this study, the sites for virus latency were determined in white Pekin ducks infected with the DEV-97 strain. At 3 wk postinfection, infectious virus was not detectable in tissues or cloacal swabs (CSs). At 7 and 9 weeks postinfection, the viral DNA was detected by polymerase chain reaction in the trigeminal ganglia (TG), suggesting that the virus is latent. Viral DNA was detected in the peripheral blood lymphocytes (PBL), spleen, thymus, bursa, and CSs only after in vitro cocultivation. In vivo virus reactivation was demonstrated when dexamethasone or a combination of dexamethasone and cyclophosphamide was inoculated in latently infected ducks. The reactivation of DEV occurred without any clinical evidence of the disease, but the virus was detected in PBL and CSs. We conclude from this study that DEV establishes latency in TG and lymphoid tissues including PBL.

Inhibition of duck hepatitis B virus replication by intrahepatic expression of an antiviral resistance gene

Resistance genes coding for inhibitors of hepadnaviral replication, such as ribozymes, antisense RNA, and dominant negative mutants have been shown to be effective in transfected hepatoma cells. In vivo studies, however, are not available to date. Here we expanded the use of the duck hepatitis B virus (DHBV) model for studying antiviral resistance genes in vivo. Animals were experimentally infected by intravenous injection of DHBV-positive serum in ovo. The use of recombinant human adenovirus type 5 and avian adenovirus CELO for gene transfer was evaluated. Adenovirus type 5 transduced more than 95% and CELO less than 1% of embryonic hepatocytes in vivo. Adenovirus type 5 interfered with DHBV replication (viral cross-talk), but this effect was moderate and did not preclude analysis of specific antiviral effects. Thus adenoviral transfer of a dominant negative mutant prior to DHBV infection (intracellular immunization) yielded 100-fold suppression of viral replication compared to the green fluorescent protein marker gene. Neither gene was toxic. These data demonstrate that a prototype anthepadnaviral resistance gene is functional in vivo. Duck embryos represent a useful model for evaluating gene therapeutic strategies in vivo without the need for large scale preparations of gene delivery vehicles.