Polyamine als Stimulatoren von Genaktivitäten Eine autoradiographische Studie an Riesenchromosomen von Chironomus thummi

Zusammenfassung Inaktive Riesenchromosomen der Speicheldrüsen ausgewachsener Chironomus thummi-Larven zeigten nach 60 min Inkubation mit 0,05 N Putrescin-, Spermidin-oder Spermin-Lösung erneute Syntheseaktivitäten, die sich im Einbau von radioaktiv markiertem Uridin autoradiographisch zu erkennen geben. Diese Beobachtung wird im Zusammenhang mit der bekannten genaktivierenden Wirkung von Mg⁺⁺ diskutiert. Auf der Basis zahlreicher biochemisch analoger Wirkungen von Polyaminen und Mg⁺⁺ wird ein ursprünglich für die genaktivierende Wirkung von Mg⁺⁺ postuliertes Modell auf Polyamine übertragen.

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Stimulation of gene activities by polyamines an autoradiographic study with giant chromosomes of Chironomus thummi

Summary Inactive salivary gland giant chromosomes of full grown Chironomus thummi larvae showed after 60 min of incubation in 0.05 N putrescine, spermidine or spermine solutions autoradiographically demonstrable incorporation of radioactiv labelled uridine caused by a reactivation of RNA synthesis. This observations is discussed in relation to the known gene activating effect of Mg⁺⁺, and, since polyamines and Mg⁺⁺ have numerous effects in common, it is suggested that polyamines affect gene activity in a way similar to Mg⁺⁺.

     

Formation of hybrid anthranilate synthetase in vitro from components of Aspergillus and Neurospora

Glutamine-dependent anthranilate synthetase was produced in vitro by mixing the extracts of a trypA and a trypC mutant of Aspergillus nidulans. Neither mutant alone possessed this activity. The enzyme formed in the mixture had the properties of the wild-type anthranilate synthetase which, together with N-(5-phosphoribosyl) anthranilate (PRA) isomerase and indole 3-glycerol phosphate (InGP) synthetase, is found in a 10S multienzyme complex. Extracts of the trypA69 mutant contained a 6.5S protein as the active component—presumably the trypC ⁺ product—which in addition showed PRA isomerase and InGP synthetase activity. Extracts of the trypC801 mutant lacked all three enzyme activities but contained a 4.5S component—the trypA ⁺ gene product—which in vitro showed ammonia-dependent anthranilate synthetase activity. These mutants are analogous in their properties to certain tryp-2 and tryp-1 mutants of Neurospora. When complementary extracts of the two genera were mixed (Aspergillus trypA with Neurospora tryp-1 or Aspergillus trypC with Neurospora tryp-2), a hybrid glutamine-dependent anthranilate synthetase was obtained which showed less than half the activity produced in homologous combinations.This study was supported by Grant GB 22655 from the National Science Foundation to J.A.DeM.     

Der hemmende Einfluß gleichzeitig bewegter Beuteattrappen auf das Beutefangverhalten der Erdkröte (Bufo bufo L.)

Zusammenfassung Durch simultane visuelle Bewegungsreize, die von mehreren Beutetieren (z.B. Mehlkäferlarven) ausgehen, wird der Beutefang der Erdkröte (Bufo bufo L.) gehemmt. An diese Verhaltensheobaehtung anknüpfend, wurde die Abhängigkeit dieses inhibitorischen Umfeldeffektes von verschiedenen visuellen Reizparametern im Attrappen versuch quantitativ gemessen: Im frontalen Gesichtsfeld der Kröte rotierte vor dunklem Hintergrund eine weiße, rechteckige, 2,5 × 20° große Beuteattrappe (Zentralattrappe, z) mit dem Rechteckzentrum im Drehpunkt. Zusätzlich konnten mehrere Kreisscheiben von 5 bzw. 10° (Peripherattrappen, p) um die Zentralattrappe bewegt werden.Die Beutefangaktivität R _z [Beutefangreaktionen x min^–1] auf die allein gebotene Zentralattrappe war bei einer Sehwinkelgeschwindigkeit v _s der distalen Attrappenkanten 10v _s30 [grad x see^–1] maximal und sank für kleinere oder größere Winkelgeschwindigkeiten wieder ab. Eine mit v _s=25 [grad x sec^–1] allein bewegte Peripherattrappe löste maximale Beutefangaktivität R _p aus. Mit zunehmender Anzahl n _p simultan bewegter Peripherattrappen sank die Beutefangaktivität ab.Mehrere, um den gleichen Drehpunkt bewegte Peripherattrappen, deren Abstand untereinander =10° betrug, blieben von der Kröte unbeantwortet. Sie bildeten ein inhibitorisches Umfeld und hemmten dadurch die Reaktion auf die gleichzeitig bewegte Zentralattrappe z. — Die im Simultanreizungsversuch gemessene Beutefangaktivität R _zp war abhängig vom Abstand [grad] zwischen Zentralattrappe und Peripherattrappen ( : Kürzester Abstand zwischen z und p): Für =10° war R _zp0 und stieg für >10° an. — Kontrollversuche, die jeweils auf die Simultanreizung mit z allein folgten (R _z), ließen eine -abhängige Nachhemmung erkennen. — Die hemmende Wirkung auf die Beantwortung von z war auch von der Sehwinkelgeschwindigkeit v _s der Peripherattrappen abhängig; sie war bei derjenigen Sehwinkelgeschwindigkeit (v _s=25 [grad × sec^–1]) maximal, mit der die Zentralattrappe, allein geboten, maximale Beutefangaktivität auslöste; für v _sg25 [grad × sec^–1] nahm die Hemmung wieder ab.Die Versuchsergebnisse lassen auf inhibitorische Verknüpfungen innerhalb des zentralen visuellen Systems schließen. Es wird vermutet, daß die Reiz-Verhaltens-reaktionsbeziehungen in den visuellen Simultanreizungsversuchen durch eine Art zentrale laterale Inhibition bestimmt werden.

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Inhibitory effect of simultaneously moved prey dummies on the prey catching behaviour of the common toad (Bufo bufo L.)

Summary The prey catching behaviour of the toad (Bufo bufo L.) is generally inhibited by simultaneously visual moving stimuli caused by a group of prey animals (mealworms). According to this behavioural observation the dependence of this inhibitory effect on several visual parameters were quantitatively measured in dummy experiments: in the frontal visual field of the toad a white rectangular prey dummy of 2,5×20° (central dummy, z) was rotating in a centre against dark background. In addition several disks of 5 or 10° diameter (peripheral dummies, p) could simultaneously rotate around the central dummy (Figs. 1 and 7).The prey catching activity R _z [catching reactions x min^–1] released by rotation of only the central dummy z increased with increasing angular velocity v _s of the stimulus distal edges, reaching a maximum for 10v_s30 [degrees x sec^–1] and decreasing for v _s>30 [degrees x sec^–1] (Fig. 5).A single peripheral dummy p, moved at v _s=25 [degrees x sec^–1], released maximal catching activity R _p. The activity R _p decreased with the increasing number n _p of simultaneously offered dummies (Fig. 6).The prey catching behaviour of the toad was inhibited, when several peripheral dummies p were moved around the centre with a distance =10° from each other. They caused an inhibitory field and they also inhibited the response to a simultaneously moved central dummy z. The prey catching activity, measured in experiments in which z and p rotated simultaneously, depends on the distance [degrees] between z and p ( being the shortest distance between z and p). For =10°, R _zp was zero; R _zp increased for >10° (Figs. 9 and 10). — Control experiments carried out with z allone — after having applied the simultaneous stimulation — showed a - dependent after-inhibition (Fig. 9). — The inhibitory effect on the response to z also depended on the angular velocity v _s of p; the inhibition was at a maximum for v _s25 [degrees x sec^–1], and it decreased for v _s25 [degrees x sec^–1] (Fig. 11).The experimental results suggest inhibitory interactions within the central visual system. It is supposed that the relation between stimulus and behavioural reaction in simultaneous stimulating experiments results from some kind of central nervous lateral inhibition.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5).     

Morphologic der seeigelzähne II. Die gekielten Zähne der echinacea (Echinodermata,echinoidea)

Structure and growth of a keeled tooth are discussed with Paracentrotus lividus as the main example. The microscopic structure of the tooth skeletons of other sea urchins was compared, considering at least one member of each family with the exception of Saleniidae. Attention is called to the necessary revision of the system of sea urchins.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Changes in the composition of winter rape oil during seed maturation

The course of biosynthesis of fatty acids in the seeds of winter rape (Brassica napus L. ssp.oleifera, f.biennis cv. T?ebí?ská) was investigated. After the termination of flowering seed samples were taken at five intervals, the seeds were divided into 4 fractions according to size, and their weight, water content, oil content and fatty acid composition were determined. The oil content was found to increase in all size categories with time, with the exception of a minute drop when complete maturity is reached. Larger seeds contained more oil. The fatty acid composition changes with time in the individual size fractions almost continuously. The same holds for differences between seed sizes of the same sample. The main change in oil composition consists in the decrease of C₁₈ acids in favour of C₂₂ acids. Greatest decrements during maturation were found with oleic acid, less with linoleic acid. In absolute amounts the quantity of all synthesized acids rises, the greatest rise being observed with C₂₂ acids (i.e. predominantly erucic acid). It follows from the mean rates of synthesis of the individual groups (C₁₆, C₁₈, C₂₀, C₂₂) of fatty acids that the fraction of C₂₂ rate of synthesis increases, while that of the C₁₈ acids decreases with the same speed. The results indicate that the fatty acid synthesis is most intense during the second half of seed maturation, the main role being played by accelerating the synthesis of higher acids, especially of erucic acid.     

Heterogeneous production of laccase by mycelium of white-rot fungi

Mycelium of white-rot fungi secretes laccase into the medium. It was found by cultivation on malt-agar plates that the mycelium does not produce laccase equally in all its parts. The youngest hyphae at the margins of the colony represent usually the maximum producers, whereas older hyphae produce less or none at all. An exception here isCollybia velutipes which is the weakest producer of laccase of all the fungi studied and where only the older hyphae begin to secrete it. Manometric estimation of laccase showed that maximum specific activity of laccase is achieved at the boundary between the phases of initial and linear growth and i₁₁ some cases during the first half of linear growth. Ageing of the mycelium characterized by certain changes in its metabolism is reflected in changes of enzyme production by fungal hypha of different age.