Potential of ultraviolet radiation for control of american cockroach populations

Populations of Periplaneta americana (L.) were exposed for 8–20 week periods in specially designed rooms to 254 nm UV at low intensity (50–115 ergs sec^–1cm^–2), high intensity (160–220 ergs sec^–1cm^–2), or to white light. The rooms contained tables and chairs to simulate occupied space, with food and water placed in positions exposed to UV radiation. General irradiation (where the whole room was exposed to UV) at 115 ergs sec^–1cm^–2 and above was effective in producing high mortality in all stages except 8–10th instar nymphs and adults. Hot-spots irradiation (where UV lamps were placed behind table and chair harborages) produced high mortality only in 1 st-3rd instar nymphs which would result in slower elimination of a population. Crude aggregation pheromone was not successful in holding cockroaches close to radiation sources or substantially increasing mortality under the conditions of the experiments.

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Zusammenfassung Populationen von Periplaneta americana (L.), die hinsichtlich ihrer Alterszusammensetzung (2.–3.; 5–6.; 8.–10. und adultes Stadium) und der Anzahlen in jedem Stadium festgelegt waren, wurden für 8–20 Wochenperioden in speziell dafür entworfenen Räumen einer 254 nm UV-Bestrahlung mit geringer (50–115 erg sec^–1cm^–2) oder hoher (160–220 erg sec^–1cm^–2) Intensität oder weißem Licht (als Kontrolle) ausgesetzt. Die Räume enthielten Tische und Stühle, um bewohnten Raum mit natürlichen Zufluchtsstätten mit Nahrung und Wasser an Stellen, die der UV-Bestrahlung unterlagen, zu simulieren. Ganzraumbestrahlung mit 115 erg sec^–1cm^–2 und darüber erzeugte hohe Mortalität bei 1.–3. und 5.–6.-Larvenstadien, örtliche Bestrahlung (UV-Lampen hinter Tisch- und Stuhl-Zufluchtsstätten) dagegen nur beim 1.–3.-Stadium, was zu einer langsameren Ausrottung einer Population führen würde. Ungereinigtes Aggregationspheromon als Zusatz, um Schaben dicht an die UV-Quellen zu locken und sie hier zu halten, war offenbar unwirksam, da eben die Mortalität nicht signifikant zunahm. Dieses Versagen war in erster Linie auf die Konkurrenz mit der Fülle von natürlichem Pheromon, das von den gewohnten Zufluchtsstätten ausging, zurückzuführen, verbunden mit der dem UV-Licht innewohnenden Abschreckung. Dennoch darf man annehmen, daß UV-Bestrahlung einen bedeutsamen Wert für die Verhinderung eines Populationswachstums (durch Ausschalten junger Larvenstadien) besitzt, besonders dort, wo chemische Bekämpfung aus Gesundheits- und Sicherheitsgründen oder wegen gesetzlichen Einschränkungen nur begrenzt möglich ist.

     

Dark inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase in legumes: A biosystematic study

2-carboxyarabinitol 1-phosphate (CA 1-P) is a naturally occurring inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Members of the Fabaceae exhibit a particularly wide range in the extent of CA 1-P accumulation during darkness and include Phaseolus vulgaris, whose dark/light regulation of Rubisco activity is principally achieved by synthesis/degradation of CA 1-P. An extensive survey of the degree of dark inhibition of Rubisco was undertaken for the subfamily Papilionoideae to elucidate evolutionary patterns in the occurrence of this regulatory mechanism. Seventy-five species from 21 tribes were examined. Dark inhibition of Rubisco was found in ancestral tribes such as the Sophoreae, but was substantially reduced or absent in representative species of three more recently evolved tribes, Cicereae, Hedysareae and Vicieae. We conclude that regulation of Rubisco by CA 1-P is neither of recent origin nor of restricted distribution among the Papilionoideae. On the contrary, it becomes lost or less pronounced only in a minority of the more evolutionarily advanced species in this important subfamily.     

Structural requirements for the binding of AMP to the allosteric site of NAD-specific isocitrate dehydrogenase from bakers' yeast

The specificity of yeast NAD-specific isocitrate dehydrogenase for the structures of the allosteric effector 5'-AMP was examined with analogues modified in the purine ring, pentosyl group, and 5'-phosphate group. An unsubstituted 6-amino group was essential for activation as was the phosphoryl group at the 5'-position. Activity was retained when an oxygen function of the 5'-phosphoryl was replaced by sulfur (Murry & Atkinson, 1968) or by nitrogen (phosphoramidates). 2-NH2-AMP, 2-azido-AMP, and 8-NH2-AMP were active; 8-azido-AMP and 8-Br-AMP were inactive. The configuration or nature of substituents about carbons 2' and 3' of the pentosyl portion of AMP was not critical for allosteric activation since AMP analogues containing, e.g., 2',3'-dideoxyribose or the bulky 2',3'-O-(2,4,6-trinitrocyclo-hexadienylidene) substituent (TNP-AMP) were active. TNP-AMP was bound to the enzyme with fluorescence enhancement and had an S0.5 for activation similar to the S0.5 for AMP. Positive effector activity was decreased when the pentosyl moiety of 5'-AMP was replaced by the six-membered nitrogen-containing morpholine group, indicating that the pentosyl group may be critical as a spacer for the proper geometry of binding to enzyme at the 6-amino and 5'-phosphoryl groups of 5'-AMP. A comparison of molecular models of 5'-AMP with 8,5'-cycloAMP suggests that the species of 5'-AMP required for binding to the enzyme contains the purine and ribose moieties in an anti conformation and positioning of the 5'-phosphate trans with respect to carbon 4'.(ABSTRACT TRUNCATED AT 250 WORDS)     

The photoreaction center of Rhodospirillum rubrum mutant strain F24.1

Rhodospirillum rubrum strain F24.1 is a spontaneous revertant of nonphototrophic mutant F24 derived from wild-type strain S1. Strain F24 shows no detectable photochemical activity and contains, at most, traces of the photoreaction center polypeptides. Strain F24.1 has a phototrophic growth rate close to that of the wild-type strain (Picorel, R., del Valle-Tascón, S. and Ramírez, J.M. (1977) Arch. Biophys. Biochem. 181, 665–670) but shows little photochemical activity. Light-induced absorbance changes in the near-infrared, photoinduced EPR signals and ferricyanide-elicited absorbance changes indicate that strain F24.1 has a photoreaction center content of 7–8% as compared to strain S1. Polyacrylamide gel electrophoresis of isolated F24.1 chromatophores shows the photoreaction center polypeptides to be present in amounts compatible with this value. Photoreaction center was prepared from strain F24.1 and showed no detectable difference with that of strain S1. It is concluded that strain F24.1 photosynthesis is due entirely to its residual 7–8% of typical photoreaction center.