Peter Karlson

Der Ecdysontiter während der Insektenentwicklung—II. Die postembryonale Entwicklung der Schmeissfliege Calliphora erythrocephala Meig.

Abstract In the third larval instar of Calliphora the ecdysone titre is very low. It rises to a level of 7 to 8 Calliphora units per gram fresh weight only shortly before puparium formation. The maximum is attained 5 to 6 hr after puparium formation, i.e. 15 to 20 hr before the pupal ecdysis. A second maximum occurs on the 11th to 13th day, i.e. during imaginal development. These values are compared with some preliminary data of ecdysone levels in lepidopteran development.

Zum tyrosinstoffwechsel der insekten IX. Kontrolle des tyrosinstoffwechsels durch ecdyson

Abstract Changes in tyrosine metabolism have been observed during development of Calliphora larvae. In younger larvae (early III. instar), tyrosine is mainly transaminated, while in older larvae conversion to 3,4-dihydroxyphenylalanine and decarboxylation to 3,4-dihydroxyphenylaethylamine is predominant. This metabolinc shift is prevented by ligation (elimination of the ecdysone-producing ring gland). In ligated abdomens as well as in intact animals, decarboxylase activity is enhanced by injection of ecdysone. It is concluded that one of the characteristic biochemical effects of ecdysone is the induction of the decarboxylating enzyme, possibly by interaction with the genetic material.

Zum tyrosinstoffwechsel der insekten VII. Der katabolische abbau des tyrosins und die biogenese der sklerotisierungssubstanz, N-acetyl-dopamin

Abstract Tyrosine metabolism of insects VII. The catabolic degradation of tyrosine and the biogenesis of the sclerotizing agent N-acetyldopamine In early third instar Calliphora larvae, tyrosine is transaminated to p -hydroxyphenyl-pyruvic acid and further metabolized to p -hydroxyphenylpropionic acid. The transaminase is a pyridoxal phosphate-dependent enzyme and can transfer the amino group to α-ketoglutarate. In the late third instar (just before pupation), tyrosine is hydroxylated to DOPA. The action of a DOPA decarboxylase was further demonstrated; in vivo the dopamine formed is rapidly acetylated to N -acetyldopamine. This metabolite serves as sclerotizing agent in puparium formation. The findings are discussed in connection with the mode of action of the metamorphosis hormone, ecdyson.

Der Ecdysontiter während der Insektenentwicklung—I. Eine Methode zur Bestimmung des Ecdysongehalts

Abstract A method for the estimation of ecdysone in insect material is described. It is based on a standardized extraction procedure and the Calliphora bioassay. For single determinations 10–15 g insect material are needed.

Zum Tyrosinstoffwechsel der Insekten—XVI. Der Tyrosinstoffwechsel der Heuschrecke Schistocerca gregaria Forsk.☆

Abstract In Schistocerca tyrosine is metabolized by two main pathways. The catabolism is initiated by transamination and the resulting p -hydroxyphenyl-pyruvate is then converted to p -hydroxyphenylpropionate and p -hydroxybenzoate. The second pathway leads to tyramine and dopamine, the precursors of the tanning agents; these amines are then N -acetylated. The fate of tyrosine depends on the stage in development. Between the moults, phenolic acids are the main metabolites. Production of dopamine and tyramine prevails at the moult; the activity of the corresponding decarboxylases shows maxima shortly before and after moulting.

Zum Tyrosinstoffwechsel der Insekten—VIII: Die Sklerotisierung der Cuticula bei der Wildform und der Albinomutante von Schistocerca gregaria Forsk.☆

Abstract The albino strain of Schistocerca differs from the wild type in having no melanin while the sclerotization of the cuticle is virtually unaltered. A preliminary survey of the tyrosine metabolism in the mutant and in wild strain revealed that there are no qualitative but only minor quantitative differences in tyrosine content, phenoloxidase activity, and incorporation of radioactive precursors into the sclerotin of the cuticle. It is concluded that the mutation to albino influences only processes in melanized parts of the cuticle, and that the main pathway of tyrosine metabolism, i.e. sclerotization and tanning of the cuticle, is not affected. Some observations on the incorporation of metabolites into the ecdysial membrane are reported and discussed.

Ein biologischer Test zur quantitativen Bestimmung der Juvenilhormon-Aktivität von Insektenextrakten

Abstract An assay method for the quantitative evaluation of juvenile hormone in very small volumes of insect extracts is described. The Tenebrio unit (TE) is defined as a juvenile hormone activity unit. The use of the method is demonstrated in one of the steps involved in concentrating juvenile hormone.

Zum wirkungsmechanismus der hormone ☆: IV. Der einfluss des ecdysons auf den nucleinsaeurestoffwechsel von Calliphora-larven

Abstract Injection of ecdysone into larvae of the blow fly Calliphora erythrocephala results in the stimulation of ribonucleic acid turnover. By 4–7 hours after hormone injection, the incorporation of inorganic phosphate into RNA has increased by 50–80%. The results corroborate the postulated mechanism of hormone action via activation of genes and stimulation of messenger-RNA synthesis.

Zum Tyrosinstoffwechsel der Insekten—XIII. Radioautographische Lokalisation von Tyrosinmetaboliten in der Cuticula von Schistocerca gregaria Forsk.

Abstract Labelled tyrosine was injected into fourth-instar larvae of Schistocerca gregaria Forsk. After moulting, radioactivity was mainly found in the outer layers of the cuticle. The amount is dependent (1) on the degree of sclerotization, (2) on the time interval between injection and moulting. When 14 C-tyrosine is injected 70-15 hr before moulting, the incorporation of radioactivity into the cuticle is high, and there is no difference between the albino and normal strain. It is presumed that 70-15 hr before moulting precursors of the sclerotizing substances are formed and that these metabolic processes are controlled by the moulting hormone, ecdysone. After injection 10-2 hr prior to the moult, very little radioactivity is incorporated into the cuticle of the albino mutant whereas in the normal strain the melanin patches are selectively labelled. This shows that the metabolism ending in melanin occurs much later than the production of the sclerotizing agents. Tryptophane metabolites are not incorporated into the cuticle, which proves that tryptophane does not participate in sclerotization and pigmentation of the cuticle.

Zum Tyrosinstoffwechsel der Insekten—XIV. Radioautographische Lokalisation der Sklerotisierungssubstanz im Puppentönnchen von Calliphora erythrocephala

Abstract When labelled tyrosine, dopamine, or N-acetyl-dopamine is injected into mature larvae of Calliphora erythrocephala , the radioactivity appears mainly in the sclerotized parts of the puparium. There is no difference in the picture after administration of (α- 14 C)-dopamine or N-(1- 14 C-acetyl)-dopamine. It is concluded that the tanning agent, i.e. N-acetyldopamine, is incorporated as a whole entity. The tanning agent is also present though in lower concentration in the outer endocuticle. It is presumably transported from the haemolymph through the epidermal cells into the exocuticle. This renders the concept of ‘self-tanning cuticular proteins’ unlikely.