Jean-Claude David

Octopamine distribution in the Locusta migratoria nervous and non-nervous systems

Abstract 1. Octopamine distribution has been studied in the central and sympathetic nervous system, in endocrine glands and some other tissues of the locust Locusta migratoria L. in gregarious phase. 2. High amounts of octopamine were found in all the nervous system and in some endoctrine glands such as the glandular parts of the corpora cardiaca and the corpora allata . Octopamine was also shown to be associated with oviduct and spermiduct. 3. The significance of this distribution is discussed.

Enzymes involved in DNA replication in the axolotl. II. Control of DNA ligase activity during very early development.

Abstract The light form of DNA ligase (6 S) present in the unfertilized egg of the axolotl undergoes a rapid decay as the egg enters cleavage. At the same time a heavy form of ligase (8.2 S) appears and becomes prominent. This change occurs progressively between 3 and 9 hr of development, and its control has been studied here by experimental analysis. The modification can be brought about by artificial activation of the eggs as well as by normal fertilization. The phenomenon is sensitive to cycloheximide, actinomycin D, α-amanitin, and injury of the female pronucleus by uv irradiation. These results lead to the conclusion that the shift in ligase form involves de novo protein synthesis and transcription of an intact maternal genome. The paternal genome is unable to govern a similar change in haploid androgenetic embryos. The control of ligase replacement appears, therefore, to be the consequence of a direct gene expression revealed for the first time in an egg before cleavage. This expression is differential for paternal and maternal genomes in the same cytoplasm.

Enzymes involved in DNA replication in the axolotl: I. Analysis of the forms and activities of DNA polymerase and DNA ligase during development☆

Abstract DNA polymerases and DNA ligases have been studied during development of the amphibian, axolotl. Three forms of DNA polymerase, I, II, and III, with sedimentation coefficients in sucrose of 9, 6, and 3.1 S, respectively, have been found in the axolotl egg. The activity of these three DNA polymerases is unchanged during early embryonic development. The activity of DNA polymerase III then increases significantly, beginning at the tailbud stage, while the activity of DNA polymerase II increases at the larval stage. DNA polymerase I does not show significant variations during this time. On the basis of their catalytic properties, it appears that DNA polymerases I and II are α-type DNA polymerases whereas DNA polymerase III is a β-type enzyme. Two different DNA ligases are found in the axolotl, one showing a sedimentation coefficient in sucrose of 8.2 S (heavy form) and the other, 6 S (light form). The 6 S enzyme is the major DNA ligase activity found in the egg before and after fertilization. Its activity then decreases during embryonic development. It can be observed again, as the only DNA ligase activity, in some adult tissues. The 8.2 S enzyme appears during the first division cycle of the fertilized egg, is present at all stages of embryonic development, and is absent from the adult tissues tested. Properties of the two DNA ligases at different stages of embryonic development have also been compared.

Evidence for a DNA ligase change related to early cleavage in axolotl egg

A definite change in the forms of DNA ligase appears when the axolotl egg enters cleavage. Sucrose gradient and phosphocellulose chromatography show that the a 6S form of DNA ligase exists before division, i.e. in unfertilised and fertilised egg, and a 8.2S form is present at the first division. N-ethylmaleimide sensitivity and heat stability are different for the two forms. The possible significance of this early change is discussed.

Low molecular weight DNA ligase of chick embryo

Abstract A nuclear DNA ligase from chick embryos was isolated by the non-aqueous method and partially purified. Its activity is several fold lower than that of the enzyme found in the cytoplasmic fraction of the chick embryos. The pH dependance curve shows a single optimum for the nuclear enzyme activity, over a very narrow pH range. The molecular weight of the nuclear enzyme is 82000 and the activity is inhibited with a low K I by d-ATP.

Tryptophan decarboxylation: A quantitatively significant route of tryptophan metabolism

We have previously presented findings which indi. cated that decarboxylation of the aromatic amino acids becomes a major pathway for their metabolism when their tissue levels are raised [1,2]. This conclusion was based in part on the finding that the plasma levels attained following oral administration of large amounts of one of these amino acids could be further elevated (over two-fold) by administrating an aromaticI_,amino acid decarboxylase inhibitor [1 ]. Subsequently more direct and quantitative studies were reported on the contribution of decarboxylation to the metabolism of tyrosine [2]. It was shown that in mice the proportion of tyrosine metabolized via decarboxylation increased up to 42% of the dietary intake with increasing intake of the amino acid. At higher levels of intake decarboxylation was quantitatively more significant than transamination. The present experiments were designed to obtain a quantitative measure of the role of decarboxylation in the metabolism of tryptophan.

Inhibition of chick embryo DNA ligase by dATP: Its use in enzyme purification

Abstract Highly purified chick embryo DNA ligase (EC.6.5.1.1) obtained in our laboratory using classical methods, mainly column chromatographies shows a bimodal pH activity and an high affinity inhibition by dATP. A single step passage of crude extract containing DNA ligase through an anion exchange resin (Dowex AG1X2) saturated with dATP allows an important purification of the enzyme retained on the column at pH 7.5 and eluted at pH 8.6. Specific activity of the purified enzyme preparation is more than 600 fold higher than that of the crude extract. Analysis of the eluant by polyacrylamide gel electrophoresis shows a main protein containing the enzyme activity.

Octopamine metabolism in the cephalic ganglion of Locusta migratoria L.

Abstract Octopamine contents in the cephalic ganglia of the locust Locusta migratoria have been determined in male and female late larval and in adult stages. The animals have been pretreated with intra-abdominal administration of p -tyrosine or p -tyramine alone or following the administration of reserpine. 1. p -Octopamine levels were higher at the 7th day than at the 5th day in the fourth larval stage. At this stage a significant difference was observed in male and female cephalic ganglia. 2. The administration of p -tyrosine and p -tyramine resulted in ganglia. 3. The pretreatment with reserpine resulted in an almost complete depletion in p -octopamine. 4. This depletion was partially abolished by p -tyrosine or more efficiently by p -tyramine administration. 5. Eventually, the p -octopamine levels were considerably decreased by the administration of the decarboxylase inhibitor, R04-4602, of the dopamine β -hydroxylase inhibitor, fusaric acid, and of the false neurotransmitter 6-hydroxydopamine.

Dexamethasone induced changes in DNA ligases in chick embryo thymus.

Abstract When injected into the egg at the 16th day of incubation, dexamethasone was found to produce in thymus a complete replacement of the 8.2 S form of DNA ligase by the 6.2 S form, with a 8-fold increase in activity. A decrease in α - and γ -DNA polymerase activity was observed while β -DNA polymerase was found to be unaffected.

Increase of cyclic adenosine monophosphate in Ba++-induced automaticity of frog heart apex

Abstract Tritium cAMP-binding-protein technique was used and demonstrated that the amount of cAMP of the cardiac apex of the frog submitted to the automatogenic action of BaCl 2 in Ringer solution is increased and even doubled when CaCl 2 is also present. Ca ++ elevated also the duration of the Ba ++ -induced cardiac apex automatism. Mathieu (1) and Abderhalden and Gellhorn (2) have demonstrated that after a few minutes lag, Ba ++ induced, at 1 mM to 1.2 mM, automatic contractions of the isolated apex of the frog heart immersed into Ringer fluid. Previous experiments made by one of us (3) have indicated a possible relationship between the amount of cyclic adenosine monophosphate (cAMP) and automatogenic activity. The results we report are based on a sensitive and specific cAMP protein binding method (4).