Multiplication of Pseudomonas syringae pv. phaseolicola"in planta"

In the compatible combination of the halo blight disease of bean Pseudomonas phaseolicola was able to colonize large areas of the intercellular space of leaves, such that these confluent water congested areas became visible as water-soaked spots. Most of the plant cell walls in the infected region maintained their normal shape, even when the cytoplasm had collapsed. Some inward bending of plant cell walls preceded their rather slow degradation and final replacement by bacterial masses. Neighbouring plant cells appeared to be metabolically active. In resistant leaves no indications of active bacterial attachment or encapsulation could be observed. However, bacteria appeared to be more densely packed in resistant leaves, and relatively more plant cells completely collapsed as compared with susceptible leaves. From 8—14 days after inoculation, the bacterial concentration did not change much in susceptible or resistant leaves, indicating the absence of bactericidal components. Even Pseudomonas pisi snowed some multiplication in bean leaves (immune reaction), but its growth stopped earlier than that of P. phaseolicola. in the resistant cultivars, probably due to a different mechanism of resistance. Although less bacteria were determined in the intercellular washing fluid (IF) compared with leaf homogenates, the high bacterial concentrations in the IF supported our observation that an effective encapsulation of bacteria in resistant leaves did not occur.     

The stereochemical course of phospho transfer catalyzed by adenylosuccinate synthetase. A reaction pathway via a phosphorylated intermediate with net inversion

The stereochemical course of phospho transfer in the reaction catalyzed by adenylosuccinate synthetase from rat muscle has been determined with chiral [gamma-17O,18O]GTP gamma S as a substrate. The stereochemical configuration of the product, inorganic thiophosphate, was determined by 31P NMR after the compound was stereospecifically incorporated into ATP beta S. The reaction goes with net inversion of configuration, which is the course for a single phospho transfer, even though 6-phospho-IMP is probably an intermediate on the normal reaction pathway (Liebermann, I. (1956) J. Biol. Chem. 223, 327-339). The breakdown of this intermediate goes by C-O bond cleavage and so is not a true phospho transfer step. Thus, inversion of configuration during the course of this ligase reaction is consistent with a single phospho transfer step in the overall reaction, the formation of the phosphorylated intermediate.     

Removal of positioned nucleosomes from the yeast PHO5 promoter upon PHO5 induction releases additional upstream activating DNA elements.

The chromatin fine structure in the promoter region of PHO5, the structural gene for a strongly regulated acid phosphatase in yeast, was analyzed. An upstream activating sequence 367 bp away from the start of the coding sequence that is essential for gene induction was found to reside in the center of a hypersensitive region under conditions of PHO5 repression. Under these conditions three related elements at positions -469, -245 and -185 are contained within precisely positioned nucleosomes located on both sides of the hypersensitive region. Upon PHO5 induction the chromatin structure of the promoter undergoes a defined transition, in the course of which two nucleosomes upstream and two nucleosomes downstream of the hypersensitive site are selectively removed. In this way approximately 600 bp upstream of the PHO5 coding sequence become highly accessible and all four elements are free to interact with putative regulatory proteins. These findings suggest a mechanism by which the chromatin structure participates in the functioning of a regulated promoter.     

Disinhibition of oocyte growth in adult,virgin Periplaneta americana by corpus allatum denervation: Age dependency and relatedness to mating

Unilateral section of the nervi corporis allati I (NCA-1) of isolated, starved, adult, virgin Periplaneta americana disinhibited oocyte growth during a specific period following their adult emergence. The effect required that the corpus allatum (CA) be free of NCA-1 innervation for 4 days beyond the time the females were 7–8 days old. The onset of this sensitive period corresponds to when most isolated, starved virgins become sexually receptive. The results suggest that NCA-1 inhibition of CA activity, initiated about 7 days, is relieved by mating. When done on sexually receptive, starved virgins, unilateral NCA-1 section was as effective as insemination for stimulating growth and chorionation of the first generation of oocytes. Neural inhibition of juvenile hormone (JH) secretion by the CA may also explain diminished production of oocytes by isolated, fed virgins, for during 30 days following unilateral NCA-1 section they produced 2.6 to 5 times more oothecae than did controls with a single CA removed or after the sham operation. The number of oothecae deposited by fed virgins was similarly increased after bilateral NCA-1 section, but to a lesser extent than when the operation was done on fed, inseminated females of the same age. Specificity of the response of the CA to denervation was substantiated by experiments in which the CA were extirpated and reimplanted, by topically applying C₁₆JH, and by experiments in which the nervus corporis cardiaci 1 and 2 on the right or left side were severed.     

Survey of Chemical Compounds Tested In Vitro against Rumen Protozoa for Possible Control of Bloat

Over 170 chemical agents were screened for antiprotozoal action in bovine ruminal fluid. Compounds were tested at 0.1 and 0.05% concentrations. Tested compounds included inorganic compounds, antibiotics, biocides, neuromuscular agents, arsenicals, plant and animal hormones, antimalarials, surface-active agents, anthelmintics, and many others. The most active compounds were cupric sulfate, nickel sulfate, nitrofurazone, hydrogen peroxide, dodecyl sodium sulfate, pelargonic acid, iodoacetic acid, 1-diethylaminoethylamino-4-methylthiaxanthrone, sodium arsanilate, sodium arsenate, bismuth glycolyl arsanilate, 1-β-hydroxyethyl-2-methyl-5-nitroimidazole, and p-nitroaniline. Copper ion was not particularly effective against entodinia; nickel ion had no effect on holotrichs. Hydrogen peroxide and iodoacetic acid were effective at a concentration of 0.005%. Anionic surface-active agents were very effective, especially long-chain sulfates and phosphates. These antiprotozoal agents warrant further in vivo studies for possible use in treating or curing bloat in ruminants.     

Zum Ortungsverfahren von Gyrinus substriatus Steph

Zusammenfassung Die vorliegende Arbeit befaßt sich mit dem Orientierungsvermögen des Taumelkäfers (Gyrinus substriatus) im Bereich der Wasseroberfläche mit Hilfe der Antennenorgane.Der Taumelkäfer besitzt eine hohe Empfindlichkeit gegenüber Oberflächenwellen und ist in der Lage, deren Einfallsrichtung festzustellen. Im Nahbereich werden Hindernisse, die in die Wasserfläche eintauchen und einen Meniskus hochziehen, gut erkannt.Die mechanischen und elektrophysiologisohen Eigenschaften der Antennen werden ermittelt. Mechanische Erschütterungen rufen Relativbewegungen zwischen Pedicellus und dem frei in die Luft ragenden Flagellum hervor und erregen das Johnstonsehe Organ. Pedicellus und Flagellum sind als schwingungsfähiges System anzusehen, dessen Eigenfrequenz 250 Hz beträgt und dessen relatives Dämpfungsmaß etwa den Wert 0,7 hat. In dem in Frage kommenden Frequenzbereich bis 150 Hz arbeitet das Schwingungssystem vorwiegend als Beschleunigungsmesser.Die elektrophysiologischen Untersuehungsergebnisse stimmen gut mit den auf Grund der Schwingungsmessungen gefundenen Eigenschaften überein. In der vom Antennennerven abgenommenen elektrophysiologischen Signalspannung werden reizsynchrone Pulssalven beobachtet, denen sich bei steigender Erregungsfrequenz ein synchrones Summenpotential überlagert. Vergleiche mit den mechanischen Untersuchungsergebnissen zeigen, daß das Summenpotential seinen Ursprung im Johnstonschen Organ hat. Die Amplitude dieses Signals steigt proportional mit der Relativbewegung zwischen Flagellum und Pedicellus an; sie ist in einem weiten Bereich unabhängig von der Frequenz.Der Käfer ist in der Lage, äußerst feine Erschütterungen der Wasserfläche wahrzunehmen. Wasserwellen, deren Amplitude nur wenige m beträgt, bringen das Johnstonsche Organ zum Ansprechen. Die Empfindlichkeit nimmt mit steigender Frequenz zu. Hat der Käfer eine Eigengeschwindigkeit, die der Ausbreitungsrichtung eines Wellenzuges entgegengerichtet ist, so erkennt er diese Wellen auf Grund des Doppier-Effektes besser. Mit einer ähnlich guten Empfindlichkeit nimmt der Käfer in der Nähe von Hindernissen den Meniskus wahr. Die ansteigende Wasserfläche ruft infolge der Eigengeschwindigkeit des Käfers eine zeitlich sich ändernde Antennenauslenkung hervor. Bei normalen Schwimmgeschwindigkeiten ist sie bereits in der Entfernung von 0,5–1,5 cm vom Rand so groß, daß der Käfer reagiert.

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On the orientation of Gyrinus substriatus StephWhirligig beetle

Summary The orientation of whirligig beetles Gyrinus substriatus on the surface of water by means of the antennae has been investigated. Whirligig beetles are very sensitive to waves on the surface and are able to find out the direction from where the waves come. They are also able to perceive objects which dip into the water surface and form a meniscus.The antennae have been investigated mechanically and electrophysiologically. Mechanic percussions produce movements between the pedicellus and the flagellum which does not touch the surface of water (Figs. 2, 14). These movements excite the Johnston-Organ. Pedicellus and Flagellum form a vibration system; the resonance-frequency is about 250 Hz and the relative attenuation constant is about 0,7. In the interesting frequency range below 150 Hz the system is mainly measuring accelerations.The results of electrophysiological investigations show a good conformity with those found by mechanical measurements. In the electrophysiological signal, derived from the antenna nerve, groups of spikes are to be observed which are in synchronism with the exciting signal. By increasing the exciting frequency a synchronous sum potential appears which is superimposed upon the original signal (Figs. 19...21).Comparisons with mechanical investigations show that the sum potential has its origin in the Johnston-Organ. The amplitude of this signal increases proportionally to the relative motion between flagellum and pedicellus, independent of frequency in a wide range (Fig. 23).The beetle is able to perceive very small percussions of the surface of water. Waves on the surface with an amplitude of several m produce a response in the Johnston-Organ. The sensivity increases with increasing frequency (Fig. 31). If the beetle is moving against a train of waves, it will perceive them better by reason of the Doppler-Effect.The sensivity is similar when the beetle approaches the meniscus near objects. The inclined water surface produces an excursion of the antenna as a function of time depending on the velocity of the beetle. At normal velocities and in an distance of 0.5–1.5 cm this effect will be large enough to produce a response (Fig. 32).

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Der Verfasser dankt Herrn Prof. Dr.-Ing. habil. H. Tischner und Herrn Dr.-Ing. A. Schief für die Anregung zu diesen Untersuchungen und dem Herrn Ministerpräsidenten des Landes Nordrhein-Westfalen — Landesamt für Forschung — für die Bereitstellung der Mittel.