Olfactory coding by lepidopterous larvae

Extracellular electrophysiological recording from olfactory receptors in the antennae of tobacco hornworm larvae (Manduca sexta (Johan.)) has revealed that cells respond differentially to different odors by changing latency, rate of increase of frequency of firing, rate of adaptation, and alternation of frequency increase and decrease. The resulting temporal patterns of spike activity could function as a code to allow for discrimination among various plant odors.

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Zusammenfassung Extrazelluläre elektrophysiologische Erregungsableitungen von Geruchsrezeptoren in den Antennen von Tabakschwärmer-Raupen (Manduca sexta (Johan.)) ergaben, daß die Zellen auf verschiedene Duftstoffe unterschiedlich mit Änderung der Latenzzeit, der Zunahmerate der Erregungsfrequenz, der Anpassungsrate sowie der Änderung der Frequenz-Zunahme und-Abnahme reagieren. Die sich daraus ergebenden Zeitmuster der Spike-Aktivität könnten als Code dienen und so die Unterscheidung zwischen verschiedenen Pflanzendüften ermöglichen.

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This research was supported by National Science Foundation Grant GB-1472.     

Bacterial oxidation of polythionates: determination of tetrathionate with an ion-selective electrode.

A commercially available ion-selective electrode for nitrate was used to continuously monitor tetrathionate oxidation by Thiobacillus dentrificans. The electrode was much more sensitive to tetrathionate than to nitrate. The same electrode could also be used for the determination of trithionate.     

The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets

1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5.0-9.2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively.     

Genetics of NAD metabolism in Salmonella typhimurium and cloning of the nadA and pnuC loci.

The nadA and pnuC loci of S. typhimurium were cloned and found to reside within a 2.2-kilobase region. Two-dimensional O'Farrell gel electrophoresis of the proteins produced after chloramphenicol amplification and subsequent release from chloramphenicol inhibition revealed NadA and PnuC to be 43,000- and 25,000-molecular-weight proteins, respectively. The data indicated that nadA and pnuC represent two distinct genes.     

The signal sequence suffices to direct export of outer membrane protein OmpA of Escherichia coli K-12.

We studied whether information required for export is present within the mature form of the Escherichia coli 325-residue outer membrane protein OmpA. We had previously analyzed overlapping internal deletions in the ompA gene, and the results allowed us to conclude that if such information exists it must be present repeatedly within the membrane part of the protein encompassing amino acid residues 1 to 177 (R. Freudl, H. Schwarz, M. Klose, N. R. Movva, and U. Henning, EMBO J. 4:3593-3598, 1985). A deletion which removed the codons for amino acid residues 1 to 229 of the OmpA protein was constructed. In this construct the signal sequence was fused to the periplasmic part of the protein. The resulting protein, designated Pro-OmpA delta 1-229, was processed, and the mature 95-residue protein accumulated in the periplasm. Hence, information required for export does not exist within the OmpA protein.