The development of superficial infraslow potential oscillations of the brain in chick embryos.

The development of superficial infraslow potential oscillations (ISPO) of brain hemispheres, cerebellum and optic lobes was studied in chick embryos between day 9 and 21 of incubation. The ISPO were firstly registered in brain hemispheres at day 10 of incubation, i.e. 5 days before the onset of spontaneous EEG activity. The ISPO in 10-day-old embryos had an average frequency of 9.9 c/min and an amplitude of 0.14 mV. During further development till hatching the frequency decreased to 7.5 c/min and the amplitude increased to 1.39 mV. Similar ISPO with the same developmental trend were also registered from the surface of the cerebellum and optic lobes. Superficial ISPO were not synchronized either between both hemispheres or between different fields of the same hemisphere.     

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.     

Toxic effects of phencyclidine on developing chick embryo brain

We studied the effects of Phencyclidine (PCP, Angel Dust) on the developing chick embryo brain. In Group-1, the eggs were injected with PCP on the 7th day of incubation and the embryo brains were studied on the 10th day. In Group-2, eggs were injected twice; first on the 7th day and then on the 10th day of incubation. Group-2 brains were then studied on the 16th day of incubation. PCP significantly depressed the development of embryo brains. Cerebral hemisphere weight, total protein and total DNA were significantly lower on day 10 of incubation in Group-1. Similar results were observed in Group-2. Concomitantly, the concentration of brain serotonin at day 10 was also significantly reduced when PCP was injected into the eggs on the 7th day of incubation. Since serotonin has been reported to influence development of the chick embryo brain, the present finding of the effect of PCP on brain development might be a secondary phenomenon. The possible implications of the effects of PCP on human brain development are also discussed.     

Phosphorylation of brain specific membrane proteins of developing chick embryo

Phosphorylation of plasma membrane proteins in various tissues of chick embryos was investigated during the development. A polypeptide of Mr 22,000 was found to be the major phosphorylated plasma membrane protein in embryonic brain; this protein was absent in embryonic muscle, liver, and gizzard tissues. Extraction of plasma membranes with Triton X-100 (1%) or Nonidet p40 (1%) or sodium deoxycholate (1%) resulted in the solubilization of most membrane proteins including the 22 KDa phosphoprotein suggesting that the 22 KDa protein is a membrane-bound protein. Maximum phosphorylation of the 22 KDa protein by [gamma-32P]ATP was observed at 0.01 mM Ca2+. Higher concentrations of Ca2+ (2.5 mM) inhibited the phosphorylation of the 22 KDa protein whereas 3.5 mM Mg2+ stimulated the phosphorylation.     

Hyaluronidase activity and hyaluronate content of the developing chick embryo heart.

Hyaluronidase activity and hyaluronate content were measured in the developing chick heart from embryonic day 3 through posthatching stages. High levels of both enzyme and substrate were found during the earliest stages examined. Hyaluronidase activity gradually declined to 63% of the initial (day 3) level by embryonic day 16. Enzyme activity decreased more sharply during the next 4 days to 30% of the initial level and remained constant through 2 weeks after hatching. Low levels of enzyme activity (about 10% initial levels) were still detectable in 10-week-old chicken hearts. The heart hyaluronidase is an endoglycosidase with an estimated molecular weight of 62,000, which degrades hyaluronate and, to a lesser extent, chondroitin sulfate at an acid pH optimum. Hyaluronate constituted approximately 50% of the total glycosaminoglycan content at embryonic day 5. Between embryonic days 5 and 12, the concentration of hyaluronate decreased to 25–30% of the initial level and remained constant thereafter. The level of other glycosaminoglycans decreased more gradually than hyaluronate and did not reach a constant level until hatching. This pattern of hyaluronidase activity and hyaluronate concentration presumably reflects the extensive tissue remodeling which transforms the developing heart from a thin-walled tube containing extensive regions of extracellular matrix to a compact, thick-walled myocardium having a limited extracellular compartment.     

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.     

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.     

Detection of endogenous epidermal growth factor-like activity in the developing chick embryo

Epidermal growth factor-like activity has been detected by radioreceptor assay and radioimmunoassay in the developing chick embryo. Very little activity could be detected prior to Day 8 of embryonic life (hatching is at Day 21). A peak of EGF activity was detectable by both assays over Days 10 to 12. The EGF activity then fell to virtually undetectable levels during Days 14 to 17. A later rise in RRA detectable EGF like activity was then observed over Days 18-20. The EGF activity from a Day 11 embryo chromatographed on high-performance liquid chromatography as a single peak, with very high recovery of activity, at a later elution position than mouse EGF or human EGF.