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.     

Diurnal variations in abscisic acid content and stomatal response to applied abscisic acid in leaves of irrigated and non-irrigated Arbutus unedo plants under naturally fluctuating environmental conditions

Summary Endogenous abscisic acid content (ABA) of Arbutus unedo leaves growing under natural conditions in a macchia near Sobreda, Portugal, was very high (0.25 to 2.3 g g¹ fresh weight). Highest concentrations were found during the very early morning hours and at midday. During the late morning hours and in the late afternoon ABA concentrations decreased to between one-third and one-fourth of peak values. The samples for ABA content were obtained from both irrigated ( between-10 and-25 bar) and non-irrigated plants experiencing natural water stress during the dry season ( of-50 bar). During the course of the measurement day, stomatal conductance was relatively constant and conductance of watered plants was 50 to 100% greater than that of unwatered plants. No clear correlations between ABA content and stomatal conductance and/or xylem water potential were observed. Despite large differences in water potential and differences in degree of stomatal opening, absolute concentrations of ABA were not found to differ.Small quantities (8–14 pmoles cm² leaf area) of ABA were applied to leaves of irrigated and non-irrigated Arbutus unedo plants by injection into the petiole. These extremely small ABA doses resulted in transient reductions in stomatal conductance. The effectiveness with which injected ABA closed stomata was highest during the morning and decreased substantially at midday. Increased sensitivity to injected ABA may again occur in the late afternoon but recent measurements suggest that this may depend on long-term drought experience of the plants. The characteristics of the response to injected ABA were similar in irrigated and non-irrigated plants although irrigated plants responded in general more strongly.     

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.     

Social competition among gynes in halictine bees: The influence of bee size and pheromones on behavior

Solitary gynes of two species of social bees, Lasioglossum (Evylaeus) malachurumand L. (E.) pauxillum(Hymenoptera: Halictidae), were observed in the field and in the laboratory during the solitary (spring) phase of their life cycles. Fighting over nests among gynes of the former species is common when nests are being provisioned and can result in serious injury or even death to one or both interactants. The payoff is occasional acquisition of a nest. In contrast, fighting was never observed in the field among gynes of L. pauxillum.Several factors determine the outcome of such fights in L. malachuram,these include relative sizes of the two opponents as well as nest ownership. Dyadic interactions in the laboratory reveal that size influences the behavioral strategies of the gynes of both species, with the larger of two individuals in a dyadic interaction being on average more aggressive. Furthermore, in a second experimental series with L. malachurum,application to the smaller gyne of synthetically derived macrocyclic lactones found in the species' Dufour's gland pheromone mixture significantly decreased the aggressive tendencies of the larger such that its behavior was no longer significantly different from that for the smaller gyne. Therefore, among gynes, aggressive pheromonal signaling, coupled with other possible signal modalities, is probably an integral part in the communication system.