The influence of ultra-violet radiation on chicken hatching

The influence of UV-B radiation on embryonic development of chickens Hampshire breed was investigated. The set eggs with the average weight of 60.0 +/- 0.5 g were divided into six groups. The chickens in the control group C were hatched in the darkness. The chicken embryos in experimental groups were, during their incubation, influenced by UV light: in E1 (1 h a day), in E2 (2h a day), in E3 (3 h a day), in E4 (4 h a day), and in E5 (5 h a day). After the experiment, we can state that UV radiation appealing on chickens embryos of shorter time (1-2 h) was reflected in decreasing embryonic mortality in experimental group E1 (1.27 +/- 0.14%), the embryonic development was accelerated and the weight of hatched chickens was increased in group E2 (492.43 +/- 5.02 h and 47.83 +/- 2.62 g, respectively). The negative influence of UV radiation was reflected while it is longer appealing on chickens embryos (for 3-5 h), mainly by increased embryonic mortality in groups E3 (10.27 +/- 1.65%), E4 (58.09 +/- 3.12%), and E5 (100.00 +/- 0.00%). The results obtained are highly significant (p<0.001) in comparison with a control group C, as well as, with the experimental groups E1 and E2.

Dynamic patterns of expression of BMP isoforms 2, 4, 5, 6, and 7 during chicken heart development

Bone morphogentic proteins (BMPs) play an important role in cardiac development. Using an in vitro explant analysis, we show that BMPs are crucial for myocardium formation. As a first approach to identify which BMP may be involved in myocardium formation in intra- and extracardiac mesenchyme in vivo, a survey of the expression patterns of BMP2, -4, -5, -6, and -7 mRNA is prepared by in situ hybridization in chicken embryonic hearts from HH5 to 44. During recruitment of mesodermal cells to the outflow tract myocardium (HH10-23), BMP2, -4, -5, and -7 mRNA are expressed in the distal myocardial border and the flanking mesenchyme. After completion, BMP2 and -4 mRNA become restricted to the mesenchyme and BMP5 and -7 mRNA to the myocardium. At the venous pole, BMP2, -5, and -7 mRNA are expressed in the distal myocardial border of the caval vein, while BMP2, -5, -6, and -7 mRNA are expressed in the distal myocardium around the pulmonary vein. BMP4 mRNA is expressed in the adjacent mesenchyme at both sides. During muscularization of the atrioventricular cushions and the tricuspid valve, the cardiomyocytes that protrude into the mesenchyme express BMP2, -4, -5, and -7 mRNA, whereas BMP6 mRNA is expressed in the cushion mesenchyme. The myocardial protrusions formed in the mesenchymal proximal outlet septum express BMP4, -5, and -7 mRNA, while BMP2 and -6 mRNA are expressed in the mesenchyme. The spatiotemporal expression patterns of these BMPs in relation to myocardium formation at the distal ends and within the heart suggest a role for BMPs in myocardium formation. During delamination of the valves, BMP4 and -6 mRNA are expressed at the ventricular side of the forming mitral valve, BMP4 mRNA at the ventricular side of the forming tricuspid valve, and BMP2, -4, and -6 mRNA at the vascular side of the forming semilunar valves.

Cartilage canals in the chicken embryo are involved in the process of endochondral bone formation within the epiphyseal growth plate

A detailed study of so-called communicating cartilage canals, which penetrate deeply up into the lower hypertrophic zone of the epiphyseal growth plate in the embryonic chicken femur (E20), was carried out with the aim to clarify whether or not these canals are involved in the bone-forming process. In addition, we examined the manner in which cartilage canals are formed and compare the present data with our previous data. The canals were investigated by means of light microscopy, electron microscopy, immunohistochemistry (VEGF, VEGFR2/Flk1, type I collagen), and 3D reconstruction. Some communicating canals deeply penetrate into the upper hypertrophic zone where they terminate, showing electron-dense cells at their end. Subcellular characteristics of these cells are hardly detectable and we suppose that they undergo cell death. Other canals pass down deeper into the lower hypertrophic zone. The upper segment of these canals is composed of capillaries, mesenchymal cells, and macrophage-like cells. Precursors of osteoblasts are adjacent to the canals. The lower segment of communicating canals is composed of bone matrix or osteoid, which contains type I collagen fibrils and cells having the typical subcellular features of osteoblasts. No vessels are found in these segments. Immunohistochemistry shows that the matrix of the canals labels positively for type I collagen. In addition, staining with sirius red demonstrates that bone matrix is formed in these parts. We assume that the osteoblast-like cells of the lower segments of communicating canals originate either from mesenchymal cells or even from hypertrophic chondrocytes. Our immunohistochemical data also reveal that vascular endothelial growth factor (VEGF) and the corresponding receptor VEGFR2/Flk1 (VEGF receptor 2/Flk1) are localized in cartilage canals of the reserve zone, the proliferative zone, and the hypertrophic zone. The receptor is found in the endothelial cells of the vessels. Furthermore, VEGF is present in hypertrophic chondrocytes. The results of our study suggest that cartilage canals penetrate actively into the cartilage anlage and that bone is formed in the lower segments of the communicating canals where no vessels are detectable.

The Effect of Ethanol Exposure on Extraembryonic Vascular Development in the Chick Area Vasculosa

The effect of ethanol (EtOH) exposure on extraembryonic vascular development was examined using the chick embryo area vasculosa (AV) in shell-less culture. Embryos were placed in cultures at Hamburger Hamilton (HH) stage 11/12 and a single dose of EtOH (10, 30 or 50%) was applied to the center of the blastodisc. Untreated/sodium-chloride-treated controls showed normal embryonic growth and well-developed extraembryonic vessels at 24/48 h of treatment. At doses of 30 and 50%, the mortality rate was significantly increased, and survivors demonstrated significant growth retardation and inhibition of normal vascular development in a dose-dependent manner. Immunostaining for vascular endothelial growth factor (VEGF) showed that mesenchymal cells continued to differentiate into angioblasts to form blood islands, but their assembly into primitive vessels was perturbed in a dose-dependent manner. Northern blot analyses of basic fibroblast growth factor, VEGF, Flt-1 and Flk-1 mRNA expression supported these findings and showed a dose-dependent decrease in EtOH-treated cultures compared to controls. Co-treatment with alpha-tocopherol (0.05 M) or all-trans-retinoic acid (10(-8) M) significantly decreased the mortality rate and improved both embryonic growth and extraembryonic vascular development in the cultures. On the other hand, almost all embryos treated with 10% EtOH survived the first 48 h after treatment. However, the complexity of the vascular tree measured as the relative vasculogenesis index, the surface area of the AV and the mRNA expression of vasculogenic molecules were increased during the first 24 h. This acute effect disappeared 48 h after treatment and the vascular tree continued to develop parallel to the controls. No significant growth retardation was observed in this group. These results suggest that, in terms of extraembryonic vascular development, an early, single, low-dose EtOH exposure may have an acute, short-term positive effect, whereas moderate- or high-dose EtOH exposure may severely perturb this process disabling the necessary absorption of the nutrients for the embryo to develop properly. The mechanisms of action of EtOH on extraembryonic vascular development may involve the establishment of reactive oxygen species, resulting in the initiation of oxidative stress and perturbation of retinoic acid signaling and alterations in the expression of growth-regulatory vasculogenic factors and their receptors.

Anterior identity is established in chick epiblast by hypoblast and anterior definitive endoderm

Previous studies of head induction in the chick have failed to demonstrate a clear role for the hypoblast and anterior definitive endoderm (ADE) in patterning the overlying ectoderm, whereas data from both mouse and rabbit suggest patterning roles for anterior visceral endoderm (AVE) and ADE. Based on similarity of gene expression patterns, fate and a dual role in 'protecting' the prospective forebrain from caudalising influences of the organiser, the chick hypoblast has been suggested to be the homologue of the mouse anterior visceral endoderm. In support of this, when transplanted to chick embryos, the rabbit AVE induces anterior markers in the chick epiblast. To reevaluate the role of the hypoblast/ADE (lower layer) in patterning the chick ectoderm, we used rostral blastoderm isolates (RBIs) as an assay, that is, rostral regions of blastoderms transected at levels rostral to the node. RBIs are, therefore, free from the influences of Hensen's node and ingressing axial mesoderm - tissues that are able to induce Ganf, the earliest specific marker of anterior neural plate. We demonstrate, using such RBIs (or RBIs dissected to remove the lower layer with or without tissue replacement), that the hypoblast/ADE (lower layer) is required and sufficient for patterning anterior positional identity in the overlying ectoderm, leading to expression of Ganf in neuroectoderm. Our results suggest that patterning of anterior positional identity and specification of neural identity are separable events operating to pattern the rostral end of the early chick embryo. Based on this new evidence we propose a revised model for establishing anteroposterior polarity, neural specification and head patterning in the early chick that is consonant with that occurring in other vertebrates.

Gene expression of FK506-binding proteins 12.6 and 12 during chicken development

FKBPs are cytosolic receptors for the immunosuppressive drug FK506. FKBP12.6 and FKBP12 associate with cardiac and skeletal muscle isoforms of ryanodine receptors and thereby regulate intracellular Ca(2+) release. The amino acid sequences of FKBP12.6 and FKBP12 are highly conserved among mammals and chicken. The expression profiles of FKBP12.6 and FKBP12 genes during chicken development were compared by Northern blot and in situ hybridization analyses. Transcripts of the FKBP12 gene were abundant throughout the embryo at early stages of development but subsequently underwent gradual down-regulation. Expression of the FKBP12.6 gene was mostly restricted to the heart during early embryogenesis and also underwent subsequent down-regulation, becoming localized to the atrium after hatching. Treatment of early embryos with FK506 had no apparent effect on embryogenesis. Retinoic acid induced marked abnormalities in cardiogenesis, but it did not affect FKBP gene expression. These results suggest that, even though FKBP12.6 and FKBP12 genes are expressed in chick embryos, FK506-sensitive functions of the encoded proteins do not appear to contribute to early embryogenesis or cardiogenesis.

Exposure to cold or heat during incubation on developmental stability of broiler embryos

An experiment was conducted to measure the effects of exposure to heat or cold during incubation on the size of skeletal bilateral traits (face, wings, shank, tibia, and femur) and weights of heart and lungs of broiler embryos. Measurements were obtained at 10 and 18 d of incubation and at hatch on d 21. Treatments consisted of eggs incubated at 37.8 degrees C throughout (control; C), cooled to 36.9 degrees C for 6 h daily from d 0 to 8 (C0-8), heated to 39.6 degrees C for 6 h daily from d 0 to 8 (H0-8), cooled to 21.0 degrees C for 24 h on d 14 (C14), cooled to 36.9 degrees C for 6 h daily from d 10 to 18 (C10-18), and heated to 39.6 degrees C for 6 h daily from d 10 to 18 (H10-18). Although cooling and heating of eggs during incubation influenced growth of the skeletal traits on d 10 and 18, compensation generally occurred by the time of hatch. The developmental stability of bilateral traits varied with the specific trait, with those observed earlier in incubation tending to decrease by hatch.

Embryonic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in chickens: effects of dose and embryonic stage on hatchability and growth

Chicken embryos (Gallus domesticus) were injected with 0, 8, 20 or 50 ng tetrachlorodibenzo-p-dioxin (TCDD) per egg at embryonic day (ED) 4, 8 or 12 to investigate the effects of differential periods of sensitivity to TCDD exposure. At hatch, all chicks were weighed, sexed and examined macroscopically to identify possible malformations. Liver, bursa, heart and spleen masses were recorded from a number of chicks. The remaining chicks were raised until 6 weeks of age and body and organ masses, plasma concentrations of thyroid hormones, triglycerides and glucose were measured. Dose and stage during embryonic development at which injection was performed affected hatchability. Fifty nanogram of TCDD was highly toxic for 4-day-old chicken embryos. TCDD was less toxic for chicken embryos of 8- and especially 12-days old. One-day-old chick and organ weights were not different between TCDD doses at all injection days. However, injection performed at ED4 or ED8 with 20 and 50 ng, respectively, significantly depressed post-hatch body mass gain. Moreover, body mass gain in males was more depressed than in females. The delayed growth in TCDD treated chickens was accompanied by changes in T(3)/T(4) ratio that at some ages were significantly higher compared to control animals. No pronounced changes in plasma triglycerides or glucose concentrations during postnatal life were observed. Absolute and relative organ masses of 6-week-old chickens showed no remarkable changes.

Profiles of mRNA expression of genes related to sex differentiation of the gonads in the chicken embryo

Sex is determined genetically in birds. The homogametic sex is male (ZZ), whereas the heterogametic sex is female (ZW). According to the genetic sex, gonads develop into testes or ovary. In this study, we performed experiments to reveal mRNA expression patterns in the gonad between d 5.5 and 8.5 of incubation and examined a possible role of Dss-Ahc critical region on the X chromosome 1 (Dax1), Steroidogenic factor 1 (Sf1), P450aromatase (P450arom), Estrogen receptor alpha (ER alpha), doublesex and mab3 related transcription factor 1 (Dmrt1), Sry-related HMG box gene 9 (Sox9), Gata binding protein 4 (Gata4), and anti-müllerian hormone (Amh) in sex differentiation in chicken embryonic gonads using RNase protection assay. In embryonic chicken gonads, Dax1 mRNA was expressed in both sexes but was higher in females than in males at d 6.5 and 7.5 of incubation. The Sf1 mRNA was expressed in both sexes, but it was expressed more in males at d 5.5 than in females but more in females than in males at d 7.5 and 8.5 of incubation. The P450arom mRNA was expressed only in female gonads from d 5.5 of incubation. The ER alpha mRNA was expressed in both sexes, but it did not show a sex difference. On the other hand, the Dmrt1 mRNA was expressed in both sexes, but it showed a male-specific expression pattern. The male-specific expression pattern was observed in Sox9 mRNA, but it was not expressed in female gonads. The Gata4 mRNA was expressed in both sexes, and sex differences were not revealed throughout the observational period. Amh mRNA was expressed in both sexes, but it had male-specific mRNA expression pattern at d 6.5 to 8.5 of incubation. These results indicate that Dax1, Sf1, and P450arom have possible roles in ovary formation, whereas Dmrt1, Sox9, and Amh are related to testis formation in differentiating chicken gonads at d 5.5 to 8.5 of incubation.

Effect of stevioside and steviol on the developing broiler embryos

At day 7 of incubation, fertile broiler eggs were injected with different amounts of stevioside and steviol of 0.08, 0.8, or 4 mg stevioside/egg and 0.025, 0.25, or 1.25 mg steviol/egg. At hatch (day 21) and 1 week later, not any influence of the different treatments could be found on embryonic mortality, body weight of the hatchlings, deformations (e.g., bone, beak, and head malformations, abnormal feathering, open vent), or abnormal development of the gonads. No stevioside or steviol could be detected in the blood of the hatchlings. The hatchlings developed normally. It is concluded that prenatal exposure to stevioside and steviol is not toxic for the chicken embryo.

A non-mitochondrial carboxylase, related to glutamate action is synthesized in the retina of the chick embryo

SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot of chick retinal proteins at 21 days after intravitreal injection with 5 or 10 microM/eye Glu showed decreases in 37, 42, 53 and 57 kDa proteins and increases in 35, 72 and >94 kDa proteins. These proteins were carboxylases except for the 35 and 37 kDa proteins. With > or =15 microM/eye Glu, non-specific loss of retinal proteins was observed. In embryonic retinas, the 42 kDa protein was seen a few days before hatching, with biotin incorporation on days 3-6 after hatching. Immunohistochemistry indicated that this protein was a component of both the inner nuclear layer and the photoreceptor. Immunocytochemistry located it to the cell surface.

Damaging effects of polychlorinated biphenyls on chicken primordial germ cells

This work describes the effects of a commercial polychlorinated biphenyl (PCB) mixture, Aroclor 1254, as well as 17beta-oestradiol (E2) and testosterone on numbers and histomorphological changes of primordial germ cells (PGCs) in gonadal regions of Day 5 Hyline chicken embryos. The oestrogen receptor antagonist, clomiphen, alone or with PCBs was used in an attempt to protect the developing gonad from oestrogen-like effects of chemical PCBs. The results were as follows: (i) PCBs delayed embryonic development independently of dose (1 microg/egg, P<0.05; 10 microg/egg, P<0.01; 100 microg/egg, P<0.001 v. the control) and caused a dose-independent increase in mortality compared with the control group (10 microg/egg, P<0.01; 100 microg/egg, P<0.05); maximal mortality was observed in the 1 microg/egg group (P<0.001); (ii) PCBs decreased PGC numbers dose dependently (P<0.001) and caused a swollen nucleus with hyperchromatism (pyknosis) or cytoplasm vacuolation as signs of gonadal PGC degeneration in all PCB groups, or even complete disappearance in the 100 microg/egg group; (iii) after PCB treatment, the index of gonadal lesion increased significantly with the decrease of gonadal PGC number (1, 10 and 100 microg/egg, P<0.001); (iv) there were no observed effects of E2, testosterone and clomiphen on PGCs in the experiments; and (v) clomiphen failed to block the damaging effects of PCBs. These results suggest that the adverse effects of PCBs on chicken gonadal and germ cell development were initiated during the early stages of incubation through direct toxic effects, rather than through oestrogen-mimicking actions. As PGC numbers in the gonads decrease and the index of gonadal lesion increases, one may expect reproductive function to be compromised.

Expression of cVg1 mRNA during chicken embryonic development

Using degenerated PCR-primers to identify known and novel BMPs that are expressed in the developing chicken heart, we identified not only BMP2, -4, and -7 mRNA, but also the TGFbeta superfamily member cVg1. The expression pattern of cVg1 mRNA was determined during chicken development from HH4 to HH44. In early developmental stages, cVg1 mRNA is expressed in the primitive streak, paraxial mesoderm, developing somites, and developing neural tube. Subsequently, cVg1 mRNA is expressed in the developing central and peripheral nervous system, retina, auditory vesicle, notochord, lung alveoli, and olfactory mucosa. In the heart, cVg1 is initially expressed through the linear heart tube, but becomes restricted to the forming chamber myocardium, in an expression domain similar to that of atrial natriuretic factor (ANF) mRNA.

Spatial and temporal pattern of Wnt-6 expression during chick development

The WNT family of proteins is composed of several members. In the present study we isolated the full length chick Wnt-6 cDNA and analyzed its expression pattern by in situ hybridization during chick development. Wnt-6 expression is observed in the ectoderm from HH-stage 4 onwards. At HH-stages, 7-16 expression can be seen in the ectoderm overlying the segmental plate and the epithelial somite, while the ectoderm overlying the compartmentalized somite is Wnt-6 negative. Expression is also observed at the heart outflow tract and in the ectoderm overlying the pharyngeal arches. From HH-stages 17 to 27, expression is also observed at limb level, both in the dorsal and ventral ectoderm and a stronger expression in the dorsoventral boundary. Furthermore, expression in the ectoderm delimiting the somitic boundaries in the anteroposterior and mediolateral axis at limb level was observed, as well as in the ventral body wall. Expression becomes evident in the inner ear. From HH-stage 30 onwards, expression is restricted to the feather buds and to the gastrointestinal tract.

Vibration analysis on incubating eggs and its relation to embryonic development

Coucke (1998) was the first to use acoustic resonance analysis to monitor embryo development in chicken eggs. He remarked that at around 100 hours of incubation, the course of the resonant frequency and damping changed abruptly in the case of fertile eggs. He also showed that these changes were related to a physiologic event during early embryonic development. The objective of our study is to monitor the course of the vibration parameters during the early incubation of chicken eggs and to relate these changes to egg and embryo characteristics. A total of 72 Hybro eggs were incubated vertically in a small incubator at standard conditions. Several egg parameters were measured before incubation. During the early stages of incubation the vibration behavior of these eggs was monitored. The time at which the damping of the vibration suddenly changed, the diameter of the eggs and their interaction were found to be significant explanatory variables in order to predict hatching time. A correlation coefficient r of 0.72 was obtained.

The development of fibrocartilage in the elastic tendon of the chicken wing

The elastic tendon of the chicken wing has five morphologically distinct regions. One of these regions is a distally located fibrocartilage from which fibrous connections extend to the capsule of the distal radius. In adult birds, this region shows the characteristics of a tendon-compressed fibrocartilage, with an accumulation of proteoglycans between thick collagen bundles arranged in a basket-weave formation. Here we study the development of this fibrocartilage in order to of compare it with other tendon fibrocartilages and try to identify the factors involved in fibrocartilage differentiation. This fibrocartilage initially developed by cell enlargement and accumulation of vimentin, with simultaneous deposition of proteoglycans in the extracellular matrix and an increase in the amount and thickness of collagen bundles. Elastic fibers were minor components associated with the collagen bundles. Cells could be classified into two main types. One was typically fibrocartilaginous and the other was fibroblast-like, the latter occurring in close association with the collagen bundles. These results establish the steps in the development of the elastic tendon fibrocartilage and provide a basis for future studies.

Effects of egg storage time on spread of hatch, chick quality, and chick juvenile growth

A total of 1,800 incubating eggs produced by a commercial flock of Cobb broiler breeders was used to determine the effects of storage duration (3 or 18 d) on spread of hatch and chick quality. Chick relative growth (RG) at the end of 7 d of rearing was also determined as a measure of the chick performance. Chick quality was defined to encompass several qualitative characteristics and scored according to their importance. Eggs stored for 3 d hatched earlier than those stored for 18 d (P < 0.05). Hatching was normally distributed in both categories of eggs, and the spread of hatch was not affected by storage time (P = 0.69). Storage duration of 18 d reduced the percentage of day-old chick with high quality as well as average chick quality score (P < 0.05). RG varied with length of egg storage, quality of day-old chick, and the incubation duration (P < 0.05). Eighteen-day storage of eggs not only resulted in longer incubation duration and lower quality score but also depressed RG. Chick quality as defined in this study was correlated to RG and storage time. It was concluded that day-old chick quality may be a relatively good indicator of broiler performance. The results suggest however that in order to improve performance prediction power of chick quality, it would be better to define it as a combination of several qualitative aspects of the day-old chick and the juvenile growth to 7 d.

Effects of storage time on incubating egg gas pressure, thyroid hormones, and corticosterone levels in embryos and on their hatching parameters

Incubating eggs (1,800 total) produced by a commercial flock of Cobb broiler breeders were used to determine the effects of storage duration (3 and 18 d) on gas partial pressure, thyroid hormones, and hatching parameters. Partial pressure of oxygen (pO2) and carbon dioxide (pCO2) were measured on d 18 and at internal pipping (IP) during incubation. Blood samples were collected for determination of triiodothyronine (T3), thyroxine (T4), and corticosterone concentrations in the embryos at IP and in newly hatched chicks. From 464 to 510 h of incubation, eggs were checked individually every 2 h to determine the timing and duration of IP, external pipping (EP), and total hatching time. At 18 d of incubation and at IP, pCO2 was greater in air cell of eggs stored for 3 d compared to those stored for 18 d (P < 0.05), but pO2 was greater in eggs stored for 18 d. At IP, T3 and corticosterone levels were higher in plasma of the embryos of eggs stored for 3 d compared to those stored for 18 d, but it was the reverse in newly hatched chicks (P < 0.05). Embryos from eggs stored for 18 d required more time to complete IP compared to embryos of eggs stored for only 3 d (P < 0.05), whereas the duration of EP was not affected by storage. The overall longer incubation was, however, not only due to prolonged IP but also to later occurrence of IP. It was concluded that prolonged IP as a result of long storage may be related to the late increase in corticosterone level, which may be a necessary stimulus for higher T3/T4 ratio, late increase in pCO2 level, and decrease in pO2. The effect of long storage was a delay in hatching and a continuous increase in T3 due to higher corticosterone levels between IP and hatching, which may be an indication of the more stressful event of hatching of embryos from eggs stored longer. Differences in pCO2, pO2, T3, T4, and corticosterone levels in the incubating eggs may be manifestations of these changes culminating in altered hatching parameters and consequently differences in chick quality and growth potentials.

Effect of local shell conductance on the vascularisation of the chicken chorioallantoic membrane

The vascularisation of the chorioallantoic membrane (CAM) of avian embryos is influenced by environmental oxygen partial pressure (P(O(2))) on a global level: incubation at high P(O(2)) reduces the density of pre- and post-capillary vessels of the CAM and decelerates the thinning of the blood-gas barrier, and vice versa. This study investigates the effects of local P(O(2)) on vascular development during the formative period of days ten to fifteen, by making half of the egg hypoxic and the other half hyperoxic. The densities of arterioles, venules and capillaries were reduced under the hypoxic side, compared to untreated eggs, but not significantly changed on the hyperoxic side. Harmonic mean thickness of the tissue barrier and total CAM blood volume were not affected by the treatments. Vascular development of the CAM was therefore only partly influenced by local P(O(2)).

Expression of exogenous genes in blastodermal cells of chicken in vitro

Chicken blastodermal cells (BCs) from stage X embryos produce both somatic and germline chimeras when injected into the subgerminal cavity of recipient embryos. Transfection of the donor cells in vitro could lead to the production of chimeras capable of transmitting the transgene to their offspring. The aim of this study was to transfer and express foreign genes under control of the ovalbumin promoter in the BCs. The results showed that luciferase activity in the BCs reached a plateau value with a 2.0:1.0 or 5.0:1.0 liposome-DNA ratio and using 1 microg of DNA. Under this same condition, no difference was found in relative activity between the pGL-control and pOVALUC plasmid. The expression of other exogenous genes (green fluorescent protein and interferon alpha2a) driven by the chicken ovalbumin promoter in cultured chicken blastodermal cells in vitro is possible by this assay. Hatchability of recipient embryos after injection of 1,500 or 800 transfected BCs was compared. The advantage of using a smaller number (800) of injected transfected BCs was that early embryonic mortality was reduced and resulted in higher (P<0.01) hatchability (24.5%) than in the case of 1,500 BCs injected.

A prospective study of prenatal and postnatal development of thymus of Deshi chicken

Thymus was one of the primary lymphoid organs along with the bursa in birds. The growth of the thymus of deshi chicken (Gallus Domesticus) from prenatal embryonic day fifteen (ED15) to postnatal day ninety (D90) were studied. In macroscopic study, it was found as a paired, lobulated gland, one half of which was located on either side of the neck. Each half consists of six to eight, flattened, ovoid to elongated, pale white to yellowish white lobes of varing size and shape of lymphoid tissue lying in the sub-dermal connective tissue of the neck. Histologically, the thymus of deshi chicken at embryonic day fifteen was covered by a very thin connective tissue capsule from which septa arises and divides the gland into lobes and lobules. The lobules were homogenous, small in size and the cortex and medulla were demarcated. Lobules have developing Hassall's corpuscles and they were of uniform shape and size. The lobules become well developed with advancing age. The cortex gradually becomes thicker and was packed with large lymphocytes. Hassall's corpuscles became larger and there number increases at postnatal period (D90) in the medulla of the thymus. The growth and development of thymus at each stage of the study period were found to be significantly high. The present finding of thymus of deshi chicken was found similar to the adult hybrid chicken. The study also indicates that the chicken thymic cell population, structure & functions was similar to the human thymus histologically. It was also found that the chicken embryo allows easy experimental access to all the stages of the thymic development so the present study will be helpful for experimentation on lymphoid organs and to understand pathophysiology of immunological diseases of human.

Tissue distribution of prolactin receptor mRNA during late stage embryogenesis of the chick

Serum prolactin increases during late embryogenesis. In order to elucidate the function of prolactin at this period, tissue distribution of prolactin receptor mRNA was examined by RNase protection assay. The mRNA was detected strongly in the kidney, intestine, and allantoic membrane; weakly detected in the brain; but not detected in the liver. The expression levels of the prolactin receptor mRNA in the kidney, intestine, and allantoic membrane were retained at constant levels during later stages of embryogenesis (Days 17 and 19) and posthatch periods (2 and 28 d after hatching). These results suggest that prolactin is mainly involved in the osmoregulation during the later stage of embryogenesis and that the expression of prolactin receptor mRNA in the kidney, intestine, and allantoic membrane is regulated by a serum prolactin-independent manner.

The chicken RaxL gene plays a role in the initiation of photoreceptor differentiation

The paired type homeodomain gene, Rax, was previously identified as a key molecule in early eye formation in mice and humans. We report the expression patterns of two Rax family members from chicken, Rax and RaxL, and on the function of RaxL in photoreceptor development. Both Rax and RaxL are expressed in early retinal progenitor cells, with Rax being expressed at a significantly higher level than RaxL. At the time that photoreceptors begin to form, RaxL appears at a relatively high level in a subset of cells within the zone of proliferating progenitor cells. Subsequently, it is expressed in cells migrating to the photoreceptor layer, where it is highly expressed during the initial, but not late, stages of photoreceptor differentiation. To test the function of RaxL, a putative dominant-negative allele of RaxL comprising a fusion of the engrailed repressor domain and a region of RaxL (EnRaxLDeltaC) was introduced in vivo into the early chick eye using a retroviral vector. EnRaxLDeltaC, but not the dominant negative Rax (EnRaxDeltaC), caused a significant reduction in expression of early markers of photoreceptor cells. Examination of the transactivation activity of RaxL on a reporter construct bearing a canonical photoreceptor-specific enhancer element showed that RaxL exhibited significant activation activity, and that this activity was severely diminished in the presence of EnRaxLDeltaC. The effect on photoreceptor gene expression in vivo was specific in that other cell types were unaffected, as was general proliferation in the retina. The reduction in numbers of cells expressing photoreceptor markers was probably due to decreased survival of developing photoreceptor cells, as there was increased apoptosis among cells of the retina expressing dominant-negative RaxL. We propose that RaxL plays a role in the initiation of differentiation, and also possibly commitment, of photoreceptor cells in the chicken retina.

The influence of non-ionic radiation on the chicken hatching

The study considers the influence of non-ionic radiation (white and monochromatic light) on the hatching of the Hampshire breed chickens. The chicken embryos were most sensitive to the white light (El), reaching the hatching time of 503.63 +/- 3.17 h, the hatchability of 95.12 +/- 3.72% and an average weight of incubated chickens 46.83 +/- 2.82 g. Of the monochromatic lights, the chicken embryos were most sensitive to yellow and green lights (E5, E4) with the hatching time of 505.22 +/- 4.03 and 507.14 +/- 3.95 h, respectively, the hatchability of 94.89 +/- 3.02 and 94.47 +/- 2.93%, respectively and the average weight of incubated chickens 45.72 +/- 1.93 and 45.05 +/- 2.66 g, respectively. The least reaction of chicken was observed with violet light (E2) with the hatching time of 510.04+/- 1.97 h, hatchability of 90.81 +/- 4.05% and the average weight of incubated chickens 42.02 +/- 3.72 g. The effect of violet light brings the same results as we observed in the case of hatching in darkness (control group C), when the hatching time was 510.41 +/- 2.82 h, hatchability 90.42 +/- 3.35% and average weight of incubated chickens 41.98 +/- 3.05 g.

Egg storage alters weight of supply and demand organs of broiler chicken embryos

Storage of fertilized eggs for more than 10 d prior to incubation decreases embryonic viability. The hypothesis was tested that embryos may grow differently following egg storage. Eggs from which embryos survived following storage (ST) were compared to eggs from a second line that did not (NOST). Three identical, independent trials were conducted using fertile eggs from both lines at two ages (peak lay and > 53 wk). Eggs were stored for 1 or 14 d prior to setting in the incubator. At 3-d intervals during development, embryos were carefully removed from the eggs, the yolks were excised and carcasses were weighed. Beginning at 12 d of incubation whole body, heart, liver and thigh tissues were weighed to assess allometric growth of supply (heart and liver) and demand (thigh muscle) tissues. Storage of eggs from both lines and from hens of both ages decreased BW differently throughout incubation. Line, Age and Storage interacted to affect embryonic BW and organ weights. Embryo weights were consistently heavier in NOST line eggs from older breeder flocks stored for 14 d than those from ST line eggs. It was concluded that extended storage of fertile eggs prior to setting affects embryonic growth to enhance survival.