Retinohypothalamic pathway in the duck (Anas platyrhynchos)

Summary Retinohypothalamic connections were studied in the duck after unilateral optic nerve transection using both light and electron microscopic techniques. Degenerated endings of optic fibers were found only in a circumscribed part of the anterior hypothalamic area, i.e. the ventral region of the contralateral suprachiasmatic nucleus. Images of degenerating boutons were observed in frozen sections (method according to Johnstone-Bowsher), and their presence confirmed by electron microscopic examination. These degenerating boutons make synaptic contacts with dendrites or dendritic spines of neurons of the suprachiasmatic nucleus.In the same material, the decussation of the optic chiasma was studied with the light microscope. Uncrossed retinal fibers were found in the marginal optic tract, the basal optic root and occasionally also in the isthmo-optic tract.Dedicated to Professor Dr. W. Bargmann on the occasion of his 70th birthdaySupported by the DGRST and European Training Program Brain and Behaviour ResearchI wish to express my gratitude to Professor Andreas Oksche, who repeatedly offered me the scientific facilities at the Department of Anatomy of the University of Giessen, and who provided me with valuable neuroanatomical suggestions throughout the progress of these studies.     

Precipitating antibodies of the duck (Anas platyrhynchos)

1. Ducks do not usually produce precipitating antibodies. However, when hyperimmunized with the dinitrophenyl (DNP)-human IgG (HIgG) conjugate, ducks made precipitating antibodies to the HIgG carrier, though not to the DNP hapten. 2. Precipitation did not require NaCl and occurred over a wide range of molarities and pH. 3. Antigenic and polyacrylamide gel analysis of affinity-purified antibodies, indicated that the major constituent of the antibody population was electrophoretically homogeneous 5.7S IgG. 4. The Ig heavy chains were in two populations, viz MW 37,000 and 41,000; non-precipitating duck 5.7S IgG antibodies to HIgG had only the MW 37,000 heavy chains. 5. It is suggested that duck precipitins belong to a previously unrecognized subclass of duck 5.7S IgG, with minor physical and antigenic differences from their non-precipitating counterparts.     

Description of the mallard duck (Anas platyrhynchos) karyotype

The karyotype of the mallard duck, Anas platyrhynchos, was characterised on the basis of R and C bands. Chromosomal preparations obtained from in vitro blood lymphocyte cultures were RBG- and CBG-stained. The structures of nine and 14 pairs of chromosomes were analysed by the RBG and CBG chromosome banding techniques, respectively. The location of R bands, as well as the size and arrangement of constitutive heterochromatin blocks were determined. Ideograms of R and C banded patterns of the analysed chromosomes were drawn. The morphological makeup of the analysed chromosomes was assessed.     

Cutaneous herpesvirus infection in a mallard duck (Anas platyrhynchos)

Investigations of mortalities involving wild mallard ducks (Anas platyrhynchos) revealed the presence of a herpesvirus associated with skin lesions on the plantar surface of the foot web of one duck. Ultrastructurally, the paracrystalline arrays of viral core particles and unencapsidated nucleoids in the nucleus, and the enveloped viruses in cytoplasmic vacuoles are compatible with a herpesvirus. This appears to be the first report of cutaneous lesions in a mallard duck attributable to a herpesvirus. Whether this lesion is due to duck virus enteritis (DVE), suggesting that cutaneous shedding is possible, or due to another uncharacterized herpesvirus of ducks is unclear.     

Isolation,culture and differentiation of duck (Anas platyrhynchos) preadipocytes

In the present study, we isolated preadipocytes from the adipose tissue of Peking duck and subsequently cultured them in vitro. Cell counting kit-8 assay was employed to establish the growth curve of duck primary preadipocytes. Meanwhile, after the cells reaching full confluency, they were induced to differentiate into mature adipocytes by the addition of a cocktail containing dexamethasone, insulin, 3-isobutyl-1-methylxanthine, and oleic acid for 8 days. Successful differentiation was demonstrated by the development of lipid droplets and the expression of key marker genes including peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer binding protein-α (CEBP/α) and adipocyte fatty acid-binding protein (FABP4). Our results showed that duck primary preadipocytes began to adhere 12 h after seeding as short spindle shapes or litter triangles, which grew quickly 3 days post attachment and maintained stable after day 7. After 8 days the preadipocytes were induced to differentiate into mature adipocytes, which were stained red by oil red O. Additionally, it showed that during preadipocyte differentiation PPARγ mRNA was highly expressed at day 3, while CEBP/α and FABP4 mRNA peaked at day 5 and 8, respectively. These results indicate that we have successfully isolated and cultured Peking duck preadipocytes and successfully induced them to differentiate into mature adipocytes. This work could lay a foundation for further research into waterfowl adipogenesis.     

Pre-natal development of the adrenal gland in the mallard duck (Anas platyrhynchos)

Summary The differentiating nephrotome in the 10-day-old mallard duck embryo is able to synthesize corticosterone, aldosterone and deoxycorticosterone even though an adrenal anlage cannot be identified histologically until the 12th day of incubation. At this time, sudanophilic cells containing much smooth endoplasmic reticulum and numerous mitochondria with tubular cristae are located adjacent to the developing mesonephros. Chromaffm cells appear in this region on about the 14th day of embryogenesis. A discrete glandular structure containing measurable quantities of corticosteroids can be identified on the 15th day, and during the next 2 days the tissue becomes encapsulated. Concomitantly, the ACTH-inducible rates of corticosteroid hormone synthesis increase several fold. The corticotropic responsiveness of the developing adrenal steroidogenic tissue increases progressively during the remainder of embryogenesis.This work was supported by grants to James Cronshaw and W.N. Holmes from the University of California Committee on Research and the National Science Foundation (DIR-8820923), Washington, DC, USA     

Urocortin-like immunoreactivity in the primary lymphoid organs of the duck (Anas platyrhynchos)

Urocortin (UCN) is a 40 aminoacid peptide which belongs to corticotropin-releasing factor (CRF) family. This family of peptides stimulates the secretion of proopiomelanocortin (POMC)-derived peptides, adrenocorticotropic hormone (ACTH), β-endorphin and melanocyte-stimulating hormone (MSH) in the pituitary gland. In the present study, using Western blotting and immunohistochemistry, the distribution of UCN in the primary lymphoid organs of the duck was investigated at different ages. In the cloacal burse and thymus, Western blot demonstrated the presence of a peptide having a molecular weight compatible with that of the mammalian UCN. In the cloacal burse, immunoreactivity was located in the medullary epithelial cells and in the follicular associated and corticomedullary epithelium. In the thymus, immunoreactivity was located in single epithelial cells. Double labelling immunofluorescence studies showed that UCN immunoreactivity completely colocalised with cytokeratin immunoreactivity in both the thymus and cloacal burse. Statistically significant differences in the percentage of UCN immunoreactivity were observed between different age periods in the cloacal burse. The results suggest that, in birds, urocortin has an important role in regulating the function of the immune system.Key words: cloacal burse, thymus, cytokeratin, medullary reticular epithelial cells, CRFUrocortin (UCN) is a 40-amino acid peptide belonging to the mammalian corticotropin- releasing hormone (CRH) family which was first discovered in the rat midbrain (Vaughan et al., 1995). On the basis of its selective ability to bind CRH-receptor type 2 (CRH-R2), different types of UCN, i.e. UCN1, UCN2 and UCN3, have been identified (Lewis et al., 2001; Reyes et al., 2001). In mammals, UCN has been found in the central nervous (Vaughan et al., 1995), digestive (Muramatsu et al., 2000) and immune systems (Bamberger et al., 1998; Kageyama et al., 1999; Baigent et al., 2000), and in genital organs (Petraglia et al., 1996). UCN has also been found to play a role in regulating some CRH-receptor-mediated effects (Turnbull et al., 1999). While UCN2 and UCN3 selectively bind to CRH-R2, UCN1 binds to both CRH-R1 and CRH-R2 and shows a greater affinity to CRH-R2 than CRH alone (Chalmers et al., 1996). Despite the ability to interact with the same receptors, different functions are attributed to UCN and CRH. CRH is the primary neuroregulator of the vertebrate stress response in so far as it has been shown to be the major hypothalamic releasing factor for pituitary adrenocorticotropic hormone, whereas UCN seems not to be involved in the activation of the hypothalamus- hypophysis-adrenal axis (Turnbull et al., 1999). Conversely, UCN influences the function of the cardiovascular and nervous systems by increasing anxiety, decreasing appetite and influencing behavioral activity (Latchman, 2001). In non-mammalian vertebrates, few data have been reported on the presence and the role of UCN.The molecule, however, may have been conserved during vertebrate evolution, given that it has also been detected in amphibians and birds (Kozicz et al., 2002; Cavani et al., 2003; Boorse et al., 2005; Calle et al., 2005). In amphibians, UCN and CRH receptors have been found in the brain as well as in many other organs and tissues, including the pituitary gland, heart, kidney and alimentary canal (Kozicz et al., 2002; Boorse et al., 2005, 2006); thus suggesting a potential role for diverse actions in tissue maintenance and function. In Xenopus laevis, UCN injected in the third ventricle has been found to suppress food intake (Boorse et al. 2005). Moreover, it has been found to act as a cytoprotective factor in tadpole tail during metamorphosis (Boorse et al. 2006). In birds, UCN-ir has been found in neurons of the pigeon paramedian subgriseal mesencephalon which appear to be part of the brain circuitry involved in sympathetic nervous system-mediated behavioral responses to stress (Cavani et al. 2003; Cunha et al., 2007). Intracerebroventricular administered UCN, moreover, has been reported to decrease food intake in the chicken (Zhang et al., 2001). Up until now, however, no data are available regarding the presence and role of UCN in tissues and organs of birds outside the central nervous system (CNS). Since UCN and its receptors have been reported to be extensively expressed in immune tissues and addressed to play important roles in the regulation of the immune response (Baigent, 2001), the present study has investigated the presence and distribution of UCN in the primary lymphoid organs of the duck by means of Western blotting and immunohistochemistry. In addition, in order to verify if UCN also plays a role in the maturation of bird primary lymphoid organs, UCN expression was evaluated at different age periods.     

External stimuli affecting incubation behavior and prolactin secretion in the duck (Anas platyrhynchos)

The importance of general environmental, including visual and tactile, stimuli on behavior and prolactin secretion during the incubation phase of reproduction in the duck (Anas platyrhynchos) was investigated. Nest occupancy rapidly increased at the end of egg laying and marked the initiation of incubation. Two recesses from the nest each day were synchronized to dawn and dusk; the median occurrence was 0.23 hr after dawn and 1.17 hr before dusk. Mean recess length was 36.1 +/- 1.9 min at dawn and 40.5 +/- 2.1 min at dusk. Plasma prolactin concentrations during incubation, 25.8 +/- 2.3 ng/ml, decreased to baseline levels, 10.8 +/- 1.9 ng/ml, within 24 hr after nestbox removal. The withdrawal of tactile, but not visual, stimuli of the clutch during incubation by either anesthesia or denervation of the incubation patch caused significant decreases in prolactin plasma concentrations within 24 hr. Prolactin plasma concentrations decreased rapidly at the end of incubation in ducks which successfully hatched young as well as in unsuccessful incubators. Temperature manipulations of the clutch, either above or below normal, caused decreases in plasma prolactin concentrations in parallel with temperature modification.     

Response-contigent prenatal experience of maternal calls in the Peking duck (Anas platyrhynchos)

As the time of hatching approaches, an incubating bird often vocalizes in apparent response to the movements and calls of the embryos beneath. An experiment was designed to see whether Peking duck embryos, exposed to (mallard or chicken) maternal calls presented to them in response to their foot-movements (as indicator of their motor-activity) on the day before hatching, differed in their responsiveness from other embryos exposed to the same calls but not contingent upon their own movements. The results show that response rate was significantly increased to the mallard maternal call, but not to the chiken maternal call, as a function of the contingency.     

Yolk-sac transmission and post-hatching ontogeny of serum immunoglobulins in the duck (Anas platyrhynchos)

1. To investigate the immunoglobulin (Ig) class which is active in yolk-sac transmission of maternal antibodies in ducks, sera from laying ducks, yolks from their eggs, and sera from ducklings 0-87 days of age were examined by immunoelectrophoresis (IE), and Na2SO4-precipitated Igs from these sera and yolks were run in polyacrylamide gel electrophoresis (PAGE) under reducing conditions. 2. In yolk, 7.8S IgG was greatly enriched compared to 5.7S IgG and IgM, and was the only Ig to reach the sera of newly hatched ducklings. 3. The levels of maternally derived 7.8S IgG in duckling sera decreased after 5 days of age, reaching minimum levels at about 14 days of age. 4. Increases in the serum levels of 7.8S IgG, 5.7S IgG and IgM occurred after 20 days of age, reflecting de novo synthesis by the duckling, and the adult serum profile was achieved by 71 days of age. 5. The involvement of 7.8S rather than 5.7S IgG in yolk-sac transmission was probably determined by the additional heavy chain components of this molecule.     

Configuration of the medial and lateral segments of duck (Anas platyrhynchos) salt glands

Salt glands of the domestic duck Anas platyrhynchos differ from those of the herring gull Larus argentatus and other birds. In ducks, each salt gland consists of distinct medial and lateral segments. Centrally located drainage ducts that extend along the entire length of these medial and lateral segments collect hypertonic fluid secreted by an array of lobules. Each lobule is formed by a single mass of branched tubules in which the direction of capillary blood flow is opposite to that of the secreted fluid. This fluid drains from the medial segment through an external duct that opens into the nasal cavity at the base of the vestibular fold. A duct from the lateral segment loops and opens onto the surface of the nasal septum. The structure and function of the secretory cells is reviewed briefly within the context of our study of the configuration of duck nasal salt glands.     

Fine structure of the retinal pigment epithelium of the mallard duck (Anas platyrhynchos)

As part of a comparative morphological study, the fine structure of the retinal pigment epithelium (RPE), the choriocapillaris and Bruch's membrane (complexus basalis) has been investigated by light and electron microscopy in the mallard (Anas platyrhynchos). In this species the RPE consists of a single layer of cuboidal cells which display numerous very deep basal (scleral) infoldings and extensive apical (vitreal) processes which enclose photoreceptor outer segments. The RPE cells are joined laterally by prominent basally-located tight junctions. Internally smooth endoplasmic reticulum is the most abundant cell organelle with only small amounts of rough endoplasmic reticulum present. Polysomes are abundant as are basally-located mitochondria which often displayed a ring-shaped profile. The cell nucleus is large and vesicular. Melanosomes are plentiful only within the apical processes of the RPE cells in the light-adapted state. Myeloid bodies are large and numerous and very often have ribosomes on their outer surface. Bruch's membrane (complexus basalis) shows a pentalaminate structure but with only a poorly represented central elastic lamina. Profiles of the choriocapillaris are relatively small and the endothelium of these capillaries while extremely thin facing the retinal epithelium is but minimally fenestrated.     

Proteomic analysis of liver development of lean Pekin duck (Anas platyrhynchos domestica)

The liver plays vital roles in digestion, metabolism and immune defense. To elucidate the molecular mechanism of nutrient metabolism and antioxidation of lean Pekin duck liver from hatching to slaughter, the proteome changes were investigated using 2-DE, MS, quantitative real-time PCR and bioinformatics. A total of 59 differentially expressed proteins were identified. Proteins involved in transportation were highly up-regulated in newborn ducks whereas 37 proteins associated with metabolism, defense and antioxidation were up-regulated in adult ducks. The over-expression of proteins at the last developmental stage presumably occurs to fulfill the needs of multiple functions of the liver. However, the over-expressed proteins related to transportation during the first developmental stage are involved in maintaining the high basal metabolism of newborn ducks. The functional enrichment analysis also confirmed these results. Furthermore, the protein interaction network predicted 28 proteins acting as key nodes for liver development. The validated expression between proteins and genes provides us target genes for future genetic analyses to improve the health and performance of these ducks. These significant advanced proteome data expand our knowledge on the physiology of the duck liver, thereby providing a potentially valuable foundation for molecular breeding to enhance feed efficiency and immunity and for optimizing the feeding strategy.