Electroantennogram responses of the oriental fruit fly, Dacus dorsalis, to a spectrum of alcohol and aldehyde plant volatiles

Electroantennograms (EAGs) were recorded from unmated, laboratory-reared, male and female oriental fruit flies, Dacus dorsalis, in response to a range of between C₁ and C₁₂ carbon chain-length saturated and unaturated aliphatic alcohols and aldehydes, most all of which are known host-plant volatiles. Only two of the 35 compounds tested elicited significantly larger EAGs from female than male antennae. For the two functional-group series tested, aldehydes elicited responses greater than or equal to the responses to the alcohols. In general, the unsaturated alcohols did not elicit responses significantly different from the saturated alcohols. However, the unsaturated aldehydes, (E)-2-hexenal and 10-undecenal, elicited larger amplitude EAGs than their saturated analogs. EAGs were significantly greater for a particular carbon chain-length, with responsiveness to primary alcohols peaking at C₆ and aldehydes peaking at C₇. The (E)-2- monoenic alcohols peaked at C₆, while the (E)-3-alcohols plateaued between C₅ and C₈. The greatest EAG responses of all compounds tested were elicited by the saturated and unsaturated C₆ alcohols and aldehydes which are constitutents of the general green-leaf volatile complex that emanates from most plants. The potential adapative benefit of selective sensitivity to green-leaf volatiles is discussed in regards to foraging behaviors of oriental fruit flies.

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Résumé Des électroantennogrammes (EAG) ont enregistré les réponses, en élevages de femelles et mâles vierges de Dacus dorsalis, à une gamme de chaînes de carbones de C₁ à C₁₂ saturés et non-saturés d'alcools aliphatiques et d'aldéhydes, dont beaucoup sont connus comme substances volatiles des végétaux. Seulement 2 des 35 composés examinés ont provoqué des EAG significativement plus importants chez les femelles que chez les mâles. Pour les séries des deux groupes fonctionnels examinés, les aldéhydes ont provoqué des réponses supérieures ou égales aux alcools. En général, les réponses aux alcools nonsaturés n'étaient pas significativement différentes des réponses aux alcools saturés. Cependant, les aldéhydes non-saturés, (E)-2-hexénal et 10-undécénal, ont induit des EAG de plus grande ampleur que leurs analogues saturés. Les EAG étaient significativement les plus importants pour une chaîne de longueur particulière, la réponse aux alcools primaires culminant en C₆ et les aldéhydes en C₇. Les alcools monoéniques (E)-2- culminaient en C₆, tandis que les alcools (E)-3- étaient étales entre C₅ et C₈. Les EAG les plus importants ont été obtenus pour tous les composés examinés avec les alcools et aldéhydes en C₆ qui appartiennent à l'odeur verte complexe émise par beaucoup de plantes. Le bénéfice adaptatif potentiel de la sensibilité sélective à l'odeur verte des feuilles est examinée en fonction du comportement de prospection de D. dorsalis.

     

Ultraviolet photoproducts at the ochre suppressor mutation site in the glnU gene of Escherichia coli: relevance to "mutation frequency decline"

Summary Ochre suppressor mutations induced by UV in the Escherichia coli glnU tRNA gene are CG to TA transitions at the first letter of the anticodon-encoding triplet, CAA. Premutational UV photoproducts at this site have long been known to exhibit an excision repair anomaly (mutation frequency decline or MFD), whereby post-irradiation inhibition of protein synthesis enhances their excision and reduces suppressor mutation yields ten-fold. We sought to clarify the basis of this unique repair response by determining the spectrum of UV photoproducts on both strands of a 36 by region of glnU which includes the anticodon-encoding triplet. We found that four different photolesions are produced within the 3 by sequence corresponding to the tRNA anticodon: (i) on the transcribed strand, TC (6–4) photoproducts and TC cyclobutane dimers are formed in equal numbers at the site of the C to T transition, indicating that this site is a hotspot for the usually less frequent (6–4) photoproduct; (ii) on the nontranscribed strand, TT dimers are found opposite the second and third letters of the anticodon-encoding triplet, adjacent to the mutation site; and (iii) on the nontranscribed strand, an alkali-sensitive lesion other than a (6–4) photoproduct is formed, apparently at the G in the mutation site. We suggest that mutation frequency decline may reflect excision repair activity at closely spaced UV lesions on opposite strands, resulting in double-strand breaks and the death of potential mutants.     

Ecological analyses of nesting success in evening grosbeaks

Summary We studied the nesting success of Evening Grosbeaks (Coccothraustes vespertinus) inhabiting two areas of the Front Range of the Rocky Mountains of Colorado from 1983–1987. Sixty-four nests were followed during building, incubating, brooding, and fledging; 54.7% were successful (young fledged). The largest number of nests failed during incubation. Nests started later were more successful than nests begun earlier in the season. Failure was most likely due to severe weather, abandonment during building, or predation. Specific habitat characteristics of grosbeak nesting sites and where nests were placed in trees were consistently associated with nesting success. Successful nests, when compared with nests that failed, were: (1) built in more open areas characterized by dispersed vegetation and a higher minimum canopy, (2) oriented in more southerly directions, (3) built closer to the main trunk of the nest tree, and (4) built in larger trees. Current ideas about whether or not birds actually select nest-sites are briefly discussed. We conclude that some grosbeaks optimally select nest sites where the likelihood of producing fledglings is higher than in other areas.     

Identification of a cysteine residue at the active site of Escherichia coli isocitrate lyase.

Escherichia coli isocitrate lyase was inactivated by iodacetate in a pseudo-first-order process. Complete inactivation was associated with the incorporation of only one carboxymethyl group per enzyme subunit. The substrate and products of the enzyme protected against inactivation, suggesting that the reactive group may be located at the active site. Isolation and sequencing of a carboxymethylated peptide showed that the modified residue was a cysteine, in the sequence Cys-Gly-His-Met-Gly-Gly-Lys. The reactivity of isocitrate lyase to iodoacetate declined with pH, following a titration curve for a group of pKa 7.1. The Km of the enzyme for isocritrate declined over the same pH range.     

Multielement analysis of biological samples by inductively coupled plasma-mass spectrometry

Interest in the biological behavior of a growing number of elements, along with increasing recognition of the importance of interactions among them, demands a versatile and reliable technique for multielement analysis of biological samples. Significant improvements over the sensitivity achieved with conventional inductively coupled plasma (ICP) optical emission spectrometries have been realized with the introduction of quadrupole mass spectrometry (MS) for detection of ions in the plasma. The hybrid technique of ICP-MS promises to be a method of rapid multielement analysis, at detection limits that approach or surpass those of other technologies. However, the application of ICP-MS to analyses of biological interest is truly in its infancy. Here we report the use of ICP-MS for the determination of more than 30 elements of biological interest in a tissue and a biological fluid (rat liver and serum, respectively). Experimental values of the elements serve as a basis for discussion of analytical protocols, performance criteria, and certain problems peculiar to ICP-MS.     

The glue protein of ribbed mussels (Geukensia demissa): a natural adhesive with some features of collagen

Summary The Atlantic ribbed musselGeukensia (Modiolus)demissa attaches itself to the roots of cord grass and other hard objects in tidal salt marshes by spinning adhesive byssal threads. The precursor of a protein apparently present in the adhesive plaques of the threads was isolated in quantity from the foot of the mussel. The protein has an apparent molecular weight of 130000, a pI of 8.1, and contains a high proportion of Gly, Glu/Gln, Lys and 3,4-dihydroxyphenyl-l-alanine (DOPA). Sequence of tryptic peptides suggests a pattern of repeated motifs, such as: Gly-DOPA-Lys, and X-Gly-DOPA-Y-Z-Gly-DOPA/Tyr-Lys, where X is Thr or Ala in octapeptides and Gln-Thr in nonapeptides. Y is variable, but more often than not hydrophobic; and Z is frequently Pro or 4-trans-hydroxyproline (Hyp). The presence of Pro-Gly and Hyp-Gly sequences of -hydroxylysine in the protein is reminiscent of typical collagens; however, the protein is not labile to clostridial collagenase, nor does collagen cross-react with antibodies raised against the mussel protein. Unlike typical collagens, Gly probably occurs only at every 4th or 5th residue in this unusual mussel protein.Abbreviations Anti-Gdfp anti-G. demissa foot protein - Dopa 3,4-dihydroxyphenylalanine - CTAB cetyltrimethylammonium bromide - HPLC high performance liquid chromatography - PAGE polyacrylamide gel electrophoresis Supported by grants from the National Science Foundation (DMB 8500301) and the Office of Naval Research (N00014-86K-0717)     

Electroantennogram responses of the Mediterranean fruit fly, Ceratitis capitata to identified volatile constituents from calling males

Fifty-six compounds from the odor of calling, sexually mature, laboratory reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) were isolated by headspace trapping on Tenax columns and identified using GC/MS techniques (69 total compounds were detected). Electroantennogram responses (EAGs) to 54 of the 56 identified compounds as well as 5 analogs were tested on both sexes. Significant differences between the sexes in their responsiveness were found in 9 of the 54 identified compounds tested. There was no correlation between the amplitude of the EAG response and the relative abundance of compound identified from headspace analysis. Of the five major identified components, three elicited relatively small EAG responses, while two elicited large EAGs compared to the hexan-1-ol standard. The relative ranking of EAG responses were: methyl and ethyl hexenoates and hexanoates > C₄–C₆ esters and/or acetates > ethyl and methyl octenoates > monoterpenes > sesquiterpenes > C₂–C₅ acetates, alcohols and ketones. Behavioral bioassays on each of the five major identified components as well as a blend of six of the compounds showed some degree of attractancy to virgin females which in some cases approached the response to a pheromonal standard (male odors absorbed onto filter paper). These results are discussed in relationship to the insect's antennal sensitivity to putative pheromone components and/or allomonal components and to other reported C. capitata pheromone studies.

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Résumé Cinquante-six composés de l'odeur de mâles de C. capitata Weidemann, élevés en laboratoire, sexuellement mûrs et en appel, ont été isolés par piégeage sur colonnes tenax et identifiés par la technique GC/MS (69 composés avaient été détectés en tout). Les électroantennogrammes (EAGs) ont été examinés chez les deux sexes pour 54 des 56 composés identifiés et 5 de leurs analogues. Des différences significatives entre les sexes ont été observées pour 9 des 54 composés identifiés. Il n'y avait pas de corrélation entre l'ampleur de l'EAG et l'abondance relative du composé lors de son isolement. Pour les 5 principaux composés identifiés, 3 ont induit des EAGs relativement faibles, tandis que 2 étaient importants, par comparaison avec l'Hexane-1-ol utilisé comme témoin. Le classement relatif des EAG a été: hexénoates et hexanoates d'éthyl et de méthyl C₄–C₆ esters et/ou acétates octénoates d'éthyl ou de méthyl monoterpènes sesquiterpènes C₂–C₅ acétates, alcools et kétones. Les expériences de comportement avec chacun des 5 composés principaux identifiés, comme avec des mélanges de 6 composés ont mis en évidence une attraction des femelles vierges qui dans quelques cas avoisine la réponse à la phéromone témoin (odeur du mâle absorbée sur papier filtre). Ces résultats sont discutés en fonction de la sensibilité de l'antenne d'insexte aux composés supposés de la phéromone et aux composés allomonaux, et en fonction des autres études connues sur les phéromones de C. capitata.