Effects of d-amphetamine on behavior maintained by signaled and unsignaled delays to reinforcement

Four pigeons responded under a progressive-delay procedure. In a signaled-delay condition, a chained variable interval (VI) 30-s progressive time (PT) 4-s schedule was arranged; in an unsignaled-delay condition, a tandem VI 30-s PT 4-s schedule was arranged. Two pigeons experienced a signaled-unsignaled-signaled sequence; whereas, two pigeons experienced an unsignaled-signaled-unsignaled sequence. Effects of saline and d-amphetamine were determined under each condition. At intermediate doses (1.0 and 1.78 m/kg) delay functions were shallower, area under the curve was increased, and, when possible, break points were increased compared to saline; these effects were not systematically related to signaling conditions. These effects on control by delay often were accompanied by decreased response rates at 0 s. These results suggest that stimulus conditions associated with the delay may not play a crucial role in effects of d-amphetamine and other stimulants on behavior controlled by reinforcement delay.     

Phylogeny and evolution of sexually selected tail ornamentation in widowbirds and bishops (Euplectes spp.)

Despite similar ecology, mating systems and female preferences for supernormal tails, the 17 species of African widowbirds and bishops (Euplectes spp.) show astonishing variation in male tail ornamentation. Whereas bishops retain their brown nonbreeding tails in nuptial plumage, widowbirds grow black nuptial tails, varying in length from a few centimetres in E. axillaris to the extreme half metre train of E. progne. Here, we phylogenetically reconstruct the evolution of the discrete trait, nuptial tail and the continuous trait, tail length, using a molecular phylogeny of 33 Euplectes subspecies. Unlike many recent findings of labile evolution of plumage ornaments, our results suggest that the nuptial tail of Euplectes is a derived and phylogenetically conserved ornamental trait that, once gained, shows directional evolution in its expression. Directionality is demonstrated in the trivial sense of a short‐tailed ancestor, and by contingency and randomization tests suggesting that branches with increasing tail length are overrepresented. This supports an early origin and strong retention of directional female mate choice in widowbirds and bishops, as previously indicated by empirical and experimental results, and provides a less labile, yet rapid scenario of sexually selected diversification.     

The valve movement response of mussels: a tool in biological monitoring

Biological sensors are becoming more important to monitor the quality of the aquatic environment. In this paper the valve movement response of freshwater (Dreissena polymorpha) and marine (Mytilus edulis) mussels is presented as a tool in monitoring studies. Examples of various methods for data storage and data treatment are presented, elucidating easier operation and lower detection limits. Several applications are mentioned, including an early warning system based on this valve movement response of mussels.     

Seismic signal transmission between burrows of the Cape mole-rat,Georychus capensis

Summary Both seismic and auditory signals were tested for their propagation characteristics in a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by alternately drumming its hind legs on the burrow floor. Signal production in this species is sexually dimorphic, and mate attraction is likely mediated primarily by seismic signalling between individuals in neighboring burrows. Measurements within, and at various distances away from, natural burrows suggest that seismic signals propagate at least an order of magnitude better than auditory signals. Moreover, using a mechanical thumper which could be triggered from a tape recording of the mole-rat's seismic signals, we established that the vertically-polarized surface wave (Rayleigh wave) propagates with less attenuation than either of the two horizontally-polarized waves. Thus, we tentatively hypothesize that Rayleigh waves subserve intraspecific communication in this species.Abbreviations PPM pulses per min - SB simulated burrow - SD standard deviation - SPL sound pressure level     

Structure of the Bombyx mori fibroin light-chain-encoding gene: upstream sequence elements common to the light and heavy chain.

Two overlapping genomic clones containing the fibroin light-chain (Fib-L)-encoding gene (Fib-L) were obtained from the cosmid library of the silkworm, Bombyx mori J-139, by hybridization with the Fib-L cDNA clone. Sequencing of the 14.6-kb region revealed that Fib-L was 13472 bp long containing seven exons, and that the gene contained a large first intron which occupied about 60% of the gene. Comparison of restriction patterns of the J-139 Fib-L with those of eight other B. mori breeds producing normal-level fibroin demonstrated that considerable restriction-fragment length polymorphisms were present in regions containing the first intron and the 3′-flanking sequence. However, sizes of the Fib-L mRNA and the Fib-L polypeptide were very similar among the nine breeds tested, suggesting that the exon sequences and the splice signals were all well conserved. 5′-Flanking regions of Fib-L and the fibroin heavy-chain (Fib-H)-encoding gene (Fib-H) compared in this study contained three 18-30-bp sequences of high similarity and many 8-10-bp common elements, six of which coincided with the binding sites of homeodomain proteins. Gel retardation assays with the nuclear extracts of the posterior and middle silk glands suggested that protein factors present in the posterior silk-gland nuclei could bind to a set of those common upstream elements.     

Pyrazines as warning odour components in the Monarch butterfly, Danaus plexippus, and in moths of the genera Zygaena and Amata (Lepidoptera)

2-Methoxy-3-alkylpyrazines have been identified as odour components in Danaus plexippus, Zygaena lonicerae and an Australian Amata species, by means of coupled gas chromatography/mass spectrometry, with selected ion monitoring. Wide variability in pyrazine content was observed with D. plexippus and this was correlated with similar variability in the larval food-plants, Asclepias spp., which are presumed to be the odour sources for this butterfly. The importance of pyrazines in the biology of aposematic insects and their role as ingredients of a generalized warning system are discussed.     

C-terminal polypeptides are necessary and sufficient for in vivo targeting of transiently-expressed proteins to peroxisomes in suspension-cultured plant cells

Summary The potential of tobacco BY-2 suspension-cultured cells for examining in vivo targeting and import of proteins into plant peroxisomes was shown recently in our laboratory. In the current study, the necessity and sufficiency of putative C-terminal targeting signals on cottonseed malate synthase and bacterial chloramphenicol acetyl-transferase (CAT) were examined in BY-2 cells. Cotton suspension cells also were evaluated as another in vivo peroxisome targeting system. Ultrastructural views of BY-2 cells showed that the peroxisomes were relatively small (0.1-0.3 m diameter), a characteristic of so-called unspecialized peroxisomes, Peroxisomes in cotton and tobacco cells were identified with anti-cottonseed catalase IgGs as distinct immunofluorescent particles clearly distinguishable from abundant immunofluorescent mitochondria and plastids, marked with antibodies to -ATPase and stearoyl-ACP 9 desaturase, respectively. The C-terminal ser-lys-leu (SKL) motif is a well-established peroxisome targeting signal (PTS 1) for mammals and yeasts, but not for plants. Antiserum raised against SKL peptides recognized proteins only in peroxisomes in cotton and tobacco cells. The necessity of SKL-COOH for targeting of proteins to plant peroxisomes had not been demonstrated; we showed that SKL-COOH was necessary for directing cottonseed malate synthase to BY-2 peroxisomes. KSRM-COOH, a conservative modification of SKL-COOH, was shown by others to be sufficient for redirecting CAT in stably-transformed Arabidopsis plants to the leaf peroxisomes. Here we show with the same CAT constructs (e.g., pMON316CAT-KSRM) that KSRM is sufficient for targeting transiently-expressed passenger proteins to unspecialized BY-2 peroxisomes. These results provide new direct evidence for the necessity of SKL-COOH (a type 1 PTS) and sufficiency of a conservative modification of the PTS 1 (KSRM-COOH) for in vivo, heterologous targeting of proteins to plant peroxisomes.Abbreviations CAT chloramphenicol acetyltransferase - CHO cells Chinese hamster ovary cells - DAB 3,3-diaminobenzidine - GUS -glucuronidase - ICL isocitrate lyase - KSRM lysine-serine-arginine-methionine - MS malate synthase - PBS phosphate-buffered saline - PTS peroxisome targeting signal - SKL serine-lysine-leucine - tobacco BY-2 Bright Yellow-2 Dedicated to Professor Eldon H. Newcomb in recognition of his contributions to cell biology