THE STUDY OF SEVERAL PROTEINS SYNTHESIZED AT VARIOUS STAGES OF CHICK DEVELOPMENT
Fraser, Ian Hugh
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A method was developed for the assay of very small quantities of radioactively-labelled peptide chains of human hemoglobin based upon the formation of complex with porcine haptoglobin, and subsequent precipitation of the complex with antiserum to the haptoglobin. Attempts to apply the method to a kinetic study of synthesis of the globin chains of embryonic chick hemoglobins in explanted chick blastodiscs were unsuccessful. Exploratory studies indicated one of the reasons for this failure is probably a relatively low affinity of the embryonic chick Hbs for porcine haptoglobin. Although the plasma of 8 week old chicks contained a haptoglobin, no evidence was obtained for the presence of this protein in the circulation of the 10 day embryo and supporting membranes. Reports in the literature indicate that levels of aminolevulinate synthetase enzyme present in individual chick blastodiscs are sufficient for assay by highly sensitive radiochemical methods. However activity was not detectable by the most sensitive method of assay currently available and prior positive observations reflect artefacts of the assay method used. The course of development of serotonin N-acetyltransferase activity in the chick pineal during development to 18 days post hatch had no appreciable effect upon the course of increase in activity. However, a diurnal cycle in levels of activity was observed with birds examined at 16 days post hatch. Preliminary studies of organ cultures of embryonic chick pineal gland indicate that the developmental increase in serotonin N-acetyltransferase activity is probably not induced solely in response to norepinephrine.