Erythropoiesis in the developing chick embryo

The types of erythroid cells of chick embryos developing in ovo have been correlated with the hemoglobins of the embryos. Prior to 5 days, when primitive cells constitute the only erythroid cells, two hemoglobins can be resolved by polyacrylamide gel electrophoresis. The two adult hemoglobins and a minor hemoglobin found only in embryos and young chicks first appear simultaneously with initiation of definitive erythropoiesis.     

Alpha-fetoprotein expression in intra- and extraembryonic fluids of developing chick embryo

The ontogeny of alpha-fetoprotein (AFP) has been studied in the chicken (from 7 days of incubation until 2 days after hatching) using (1) the two-dimensional immunoelectrophoresis technique, (2) the polyacrylamide gel electrophoresis, and (3) the high resolution two-dimensional polyacrylamide gel electrophoresis. The molecular weight of AFP was estimated at 71,000. AFP was seen as a heterogeneous population composed of four isoforms which slightly differ by their isoelectric points. Up to the 18th day of development, qualitative changes in AFP heterogeneity do not occur. Only traces of the two alkaline isoforms were observed in plasma of 2 days post-hatching chickens. AFP has been identified in allantoic and cerebrospinal fluids but is not present in amniotic fluid. At 7 days of embryonic age, all the plasma AFP species are present in cerebrospinal fluid.     

The spatial and temporal distribution of polarizing activity in the flank of the pre-limb-bud stages in the chick embryo

The presence of polarizing activity in the limb buds of developing avian embryos determines the pattern of the anteroposterior axis of the limbs in the adult. Maps of the spatial distribution and the strength of the signal within limb buds of different stages are well documented. Polarizing activity can also be found in Hensen's node in the early embryo. We have mapped the distribution of polarizing activity as it emerges from Hensen's node and spreads into the flank tissue of the embryo. There is a clear change in the local pattern of expression of polarizing activity between stage 8 and 18. Almost no activity is measured for stages 8 and 9. More or less uniform levels of around 10% are spread along the flank lateral to the unsegmented somitic mesoderm from somite position 12 to 22 in stage 10 embryos. Some 6 to 8 h later at stage 12, there is a distinct peak of activity at somite position 18, the middle of the wing field. This peak increases at stages 13 to 15 and its position traverses to the posterior edge of the wing field. Full strength of activity is reached shortly before the onset of limb bud formation at stage 16 to 17. Stages 16 to 18 were investigated for polarizing activity in the wing and the leg field. Low levels of polarizing activity are present in the anterior leg field at stages 16 and 17 but have disappeared by stage 18 and all activity is confined to the posterior part of the leg bud.     

Expression pattern of LINGO-1 in the developing nervous system of the chick embryo

We isolated a chick homologue of LINGO-1 (cLINGO-1), a novel component of the Nogo-66 receptor (NgR)/p75 neurotrophin receptor (NTR) signaling complex, and examined the expression of cLINGO-1 in the developing brain and spinal cord of the chick embryo by in situ hybridization and immunohistochemistry. cLINGO-1 was expressed broadly in the spinal cord, including the ventral portion of the ventricular zone, and motor neurons. cLINGO-1 was also expressed in the dorsal root ganglion and boundary cap cells at dorsal and ventral roots. In the early embryonic brain, cLINGO-1 was first expressed in the prosencephalon and the ventral mesencephalon, and later in the telencephalon, the rostral part of the mesencephalon and some parts of the hindbrain. cLINGO-1 was also expressed in the ventral part of the neural retina and trigeminal and facial nerves. We also found that cLINGO-1, cNgR1 and p75NTR were expressed in overlapped patterns in the spinal cord and the dorsal root ganglion, but that these genes were expressed in distinct patterns in the early embryonic brain.     

Expression pattern of BM88 in the developing nervous system of the chick and mouse embryo

We isolated a chick homologue of BM88 (cBM88), a cell-intrinsic nervous system-specific protein and examined the expression of BM88 mRNA and protein in the developing brain, spinal cord and peripheral nervous system of the chick embryo by in situ hybridization and immunohistochemistry. cBM88 is widely expressed in the developing central nervous system, both in the ventricular and mantle zones where precursor and differentiated cells lie, respectively. In the spinal cord, particularly strong cBM88 expression is detected ventrally in the motor neuron area. cBM88 is also expressed in the dorsal root ganglia and sympathetic ganglia. In the early neural tube, cBM88 is first detected at HH stage 15 and its expression increases with embryonic age. At early stages, cBM88 expression is weaker in the ventricular zone (VZ) and higher in the mantle zone. At later stages, when gliogenesis persists instead of neurogenesis, BM88 expression is abolished in the VZ and cBM88 is restricted in the neuron-containing mantle zone of the neural tube. Association of cBM88 expression with cells of the neuronal lineage in the chick spinal cord was demonstrated using a combination of markers characteristic of neuronal or glial precursors, as well as markers of differentiated neuronal, oligodendroglial and astroglial cells. In addition to the spinal cord, cBM88 is expressed in the HH stage 45 (embryonic day 19) brain, including the telencephalon, diencephalon, mesencephalon, optic tectum and cerebellum. BM88 is also widely expressed in the mouse embryonic CNS and PNS, in both nestin-positive neuroepithelial cells and post-mitotic betaIII-tubulin positive neurons.     

Koelliker haemoglobins in developing chick embryo

1. Three Koelliker haemoglobins, HbKE, HbKA and HbKH, derived from a post-translational loss of alpha-Arg-141, were isolated from red cells of chicken embryos. HbKE is typical of embryos up to 7 days of incubation, HbKA and HbKH are found in mature embryos. 2. All the precursor haemoglobins contain alpha A chains. HbKA derives from adult haemoglobin A whose globin composition is alpha A2 beta 2, HbKH from embryonic haemoglobin H with a globin composition alpha A2 beta H2 and HbKE from embryonic haemoglobin E with globin composition alpha A2 epsilon 2. 3. No Koelliker derivatives of haemoglobins with alpha-like chains other than alpha A were observed.     

NGF Retards apoptosis in chick embryo bursal cell in vitro

Abstract. Recent studies have demonstrated that the action of nerve growth factor (NGF) is not restricted to neuronal cells but also affects cells of the immune system. In a previous work on the effect of NGF on the chick embryo bursa of Fabricius both in vivo and in vitro, we observed that NGF prolongs bursal cell survival in vitro. In the present study we report that the increase of viable cells in NGF-treated cultures is not due to a proliferative effect of NGF on bursal cells but to a reduction of cell mortality. The morphological analysis revealed that bursal cells in cultures die by apoptosis, which was also shown by the typical pattern of DNA fragmentation, a hallmark of this cell death process. It is concluded that NGF, with an action similar to that described in sympathetic neurons and PC12, could retard bursal cell death by influencing apoptosis.     

Alcohol dehydrogenase activity in the developing chick embryo

Before day 9 of incubation, chick embryos contain no measurable alcohol dehydrogenase (ADH) activity. Following day 9 of incubation, chick embryo liver ADH activity increases as a linear function of liver mass. A single dose of ethanol given at the start of incubation is cleared only slowly prior to day 9 of incubation but is completely cleared by day 13. Chick embryo liver ADH has two detectable isozymes throughout development. The percentage contribution of each isozyme to total ADH activity does not change significantly during development. The Km apparent of chick liver ADH is significantly increased shortly after hatching relative to the Km apparent of embryonic ADH. Ethanol exposure during incubation has no effect on the development of ADH activity or isozyme distribution.     

The excretion of salt load by the developing chick embryo

Salt loads (0.17 or 0.34 mmol Na+; 6 M NaCl solution labelled with 24Na) were administered into the amnion of 7-day-old chick embryos. The 24Na distribution in embryonic blood, amniotic and allantoic fluids was measured in 1, 2, 4, 8, 12 and 24 h intervals to assess the kinetics of salt load movements in particular egg compartments. The aim was to estimate the efficiency of the embryonic homeostatic apparatus to maintain ionic balance in the internal environment of the embryonic body. The Na+ concentration in amniotic fluid was expected to rise after salt loading by about 275 and 400 mM, respectively. More than 10% of the salt dose per ml appeared in the embryonic blood 2 h after salt load administration while only 0.2% were found in the urine (collected as allantonic fluid). The maximal rise of 24Na activity in the blood of salt-loaded embryos reached 11%-12% of the dose which corresponded to an increase of Na+ concentration by 19 and 41 mM, respectively. The maximum of 24Na activity appeared in the allantoic fluid with a delay of several hours and indicated an increment of Na+ concentration by 6% and 9% of the dose per ml in the case of salt-loaded embryos. The Na+ concentration in the allantoic fluid (urine) never exceeded that in the blood. The final Na+ activity (estimated in the blood 24 h after salt loading) was equal to 5% of the dose per ml in both cases, indicating a persistent elevation of Na+ concentration by 8.6 and 17.2 mM, respectively.     

Patterning in time and space: HoxB cluster gene expression in the developing chick embryo

The developing embryo is a paradigmatic model to study molecular mechanisms of time control in Biology. Hox genes are key players in the specification of tissue identity during embryo development and their expression is under strict temporal regulation. However, the molecular mechanisms underlying timely Hox activation in the early embryo remain unknown. This is hindered by the lack of a rigorous temporal framework of sequential Hox expression within a single cluster. Herein, a thorough characterization of HoxB cluster gene expression was performed over time and space in the early chick embryo. Clear temporal collinearity of HoxB cluster gene expression activation was observed. Spatial collinearity of HoxB expression was evidenced in different stages of development and in multiple tissues. Using embryo explant cultures we showed that HoxB2 is cyclically expressed in the rostral presomitic mesoderm with the same periodicity as somite formation, suggesting a link between timely tissue specification and somite formation. We foresee that the molecular framework herein provided will facilitate experimental approaches aimed at identifying the regulatory mechanisms underlying Hox expression in Time and Space.