A description of defensive hiss types in the flat horned hissing cockroach (Aeluropoda insignis)

Acoustic communication can inform studies of behaviour and phylogeny in insect species. Despite there being 4600 described species of cockroach, few studies have focused on their ability to communicate acoustically. Cockroaches have been found to produce sound in a variety of ways. Species within the tribe Gromphadorhini produce sound through modified spiracles, often referred to as hisses. Sound parameters have been described for the species Gromphadorhina portentosa and Elliptorhina chopardi. Aeluropoda insignis, within the same tribe, produces sound and is morphologically similar to these two species, but no research has been published describing its acoustic signals. Our study explores the defensive acoustic signals of this species and indicates that A. insignis is capable of producing three classes of acoustic signals (whistles, whistle–hisses and hisses) associated with defensive behaviour. Sexes differed in the entropy and the frequency of their signals, with males producing signals with lower entropy and at higher frequency than females. Future studies on acoustic communication within Blattodea could give more insight into the complexity of signals and their relationship to behavioural context.     

Identification of cell asymmetry and orientation by light scattering.

Light scattering from chicken red blood cells has been used as a model system to identify the asymmetry of cells. The histogram for forward angle light scattering for these cells is bimodal, the signal size being dependent on the cell orientation. A dual orthogonal scatter system is used to conclusively demonstrate this orientational variation in signal. A third scattering system, using a single incident beam with two orthogonal detectors, is used to further characterize the orientational variation of the scatter signal. In this third system it is shown that the signal in a detector set 90 degrees from the incident beam collects light reflected from the cell surface. The optical selection of cells in specific orientations using these systems may circumvent the need to physically orient cell in flow systems.     

Evidence for oxidative metabolism in the genotoxicity of the atmospheric reaction product 2-nitronaphthalene in human lymphoblastoid cell lines.

2-Nitronaphthalene (2NN) has been identified as a mutagenic atmospheric reaction product of naphthalene in the Ames bacterial reversion assay. Recent experiments have shown this nitroarene to be genotoxic in a human lymphoblastoid cell line (MCL-5) transfected with plasmids encoding epoxide hydrolase and four cytochrome P450 monooxygenase activities. The present study investigated the genotoxicity of 2NN in two related human B-lymphoblastoid cell lines, h1A1v2 containing a single P450 isozyme (cytochrome P450 1A1) and L3 cells which are isogenic with MCL-5 cells and are distinguished only by the absence of transfected plasmids. The results indicate that 2NN-induced mutagenesis at the heterozygous thymidine kinase (tk) locus was dependent on metabolic activities provided by the transfected plasmids in MCL-5; no significant induction of mutants was observed in L3 cells studied in parallel. A similar induction of mutation was observed in h1A1v2 and MCL-5 cell lines at the tk locus and no induction was observed at the hemizygous hypoxanthine phosphoribosyl transferase (hprt) locus. The induction of mutations in h1A1v2 cells suggests that cytochrome P450 1A1 alone can activate 2NN to a mutagenic species, however, this interpretation may be confounded by differences between the h1A1v2 and MCL-5 cell lines. The observed genotoxic activity induced by 2NN prompted testing of the amino analogue, beta-naphthylamine (betaNA), to investigate potential similarities in the metabolic activation pathways of the two compounds. The negative response of betaNA in all cell lines suggests that 2NN and betaNA are not activated in these human cells by similar metabolic pathways.     

Airborne movement of anthrax spores from carcass sites in the Etosha National Park, Namibia

Tests for airborne movement of anthrax spores downwind from three heavily contaminated carcass sites were carried out under a range of wind conditions. Anthrax spores were detected in just three of 43 cyclone or gelatin filter air samples taken at distances of 6, 12 and 18 m from the sites. In addition, nine positives resulted during sampling sessions in which the site was mechanically disturbed, with a further five positives being found in sessions subsequent to those in which the site had been disturbed. The three positive samples not related to man-made disturbance were associated with the highest winds experienced during the study. Despite colony counts exceeding 100 on the culture plates in three instances, calculations showed that these represented very low worst case probable spore inhalation rates for animals or humans exposed to such levels. The low number of positives, the clear pattern of rapidly declining numbers of anthrax spores with distance downwind from the centres of the sites apparent on settle plates, and the persisting levels of contamination despite wind and rain, collectively suggest that the anthrax spores were associated with fairly heavy particles, although this was not seen by electron microscopy on soil samples from the sites. Overall, the findings are interpreted as indicating that it is very unlikely that Etosha animals contract anthrax by the inhalation route while simply in transit near or across a carcass site. The significance of the observations in relation to weather conditions in the Etosha, other studies on particulate aerosols in the region, and reports of long-distance airborne movement of microbes, is discussed.     

Modulation of yeast plasma membrane composition of a yeast sterol auxotroph as a function of exogenous sterol

Plasma membranes isolated from a yeast sterol auxotroph (RD5-R) grown on 1, 5, and 15 micrograms ml-1 exogenous concentrations of sterol showed no discontinuity in plots of steady-state fluorescence anisotropy. Liposomes constructed from phospholipid and sterol extracted from RD5-R grown on different sterols indicated that exogenously supplied sterol modulated cellular phospholipids such that lipid-phase transitions were avoided. Liposomes derived from sterol and phospholipid extracted from the same culture exhibited no lipid-phase transitions. However, when phospholipid extracted from a culture grown on a specific sterol was mixed with sterol extracted from a heterologous culture grown on a different sterol to form liposomes, discontinuities were detected in the anisotropy measurements of the liposomes produced. Quantitative analyses revealed that the exogenously supplied sterol coordinately regulated specific phospholipid species, fatty acid composition, and sterol to phospholipid ratios in yeast auxotrophs.