Electroantennogram responses of the European corn borer,Ostrinia nubilalis,to (Z)- and (E)-11-tetradecenyl acetates

Antennal responses of male European corn borer moths, Ostrinia nubilalis, to their two pheromone components, (Z)- and (E)-11-tetradecenyl acetates (tda), were studied. The electroantennogram (EAG) response was highest when the ventral side and lowest when the dorsal side of the antenna faced the air stream carrying the chemical stimulus. Repetitive stimulation with one of the isomers resulted in adaptation which affected the amplitude of response in subsequent tests of both (Z)- and (E)-11-tda. This suggested that the receptors for the two tda isomers are either identical or highly interactive. Mixtures of the two pheromone components did not elicit higher responses than the major component, (Z)-11-tda. A significant difference was observed between London and New York strains of this insect in their relative responses to (Z)- and (E)-11-tda. EAG responses of hybrids of these two strains resembled those for the New York strain.     

The determination of the instantaneous velocity of axonally transported organelles from filmed records of their motion

A computational procedure is described for obtaining reproducible, low noise estimates of the instantaneous velocity of axonally transported organelles. Axonally transported organelles were detected in myelinated nerve fibers from Xenopus laevis by dark-field microscopy. The motion of the organelles was recorded on motion picture film at 3 frames/s, and the position of organelles travelling in the retrograde direction was obtained as a pair of x (axial) and y (transverse) coordinates at each 0.33-s interval. THe trend in organelle movement with time was calculated for each of the series of x and y coordinates by linear regression. This trend was removed from the measurements of x and y to yield sets of trend-free displacements. The trend yielded a measure of the mean velocity of the organelle in each of the two orthogonal directions. Power spectra of the deviations in x and y about the trend were calculated. For 133 particles studied, 99% of the power in the trend-free deviations occurred at frequencies below 0.3 Hz. The peak power in the x and y deviations occurred at a frequency of 0.1 Hz or less. Positional deviations about the trend were treated with a discrete 21-term differentiating filter that attenuated frequencies above 0.3 Hz. Instantaneous velocities for the organelles were obtained by adding the result of the band-limited differentiation to the appropriate estimates of mean velocity. The 21-term method was compared with a commonly used 2-term approximation to a differentiator and was shown to produce velocity estimates with about one order of magnitude less error. Estimates of organelle velocity obtained with the 21-term method indicate that saltatory particle motion may be viewed either as a smooth variation of particle velocity with respect to time or as an irregular, or discontinuous, variation of velocity with respect to particle position.     

Rapid detection and identification of Erwinia carotovora subsp. atroseptica by a conjugated Staphylococcus aureus slide agglutination test

A. MCLEOD AND M.C.M. PEROMBELON. 1992. A conjugated Staphylococcus aureus slide agglutination test was used to detect and identify the potato blackleg pathogen, Erwinia carotovora subsp. atroseptica. Agglutination was obtained with > 10⁸ cfu/ml of the homologous strain with a polyclonal antiserum (171) against E.c. atroseptica serogroup I which is the predominant E.c. atroseptica serogroup on potatoes in Scotland. The titre of antiserum 171 against live cells of E.c. atroseptica groups I and XXII was 2000 whereas that of other serogroups was considerably less; only 1 and 4 out of 22 serogroups of E. carotovora subsp. carotovora reacted at 1:1500 and 1:1000 antiserum dilutions, respectively and one of the three less common other E.c. atroseptica serogroups reacted at 1:1000. When tested against 24 different bacterial species including E. chrysanthemi and saprophytic bacteria present in potato tuber rots, negative results were obtained with 1:1000 antiserum dilution. The titre against heat-treated (1 h, 70°C) cells of E.c. atroseptica serogroups I and XXII was1700–2000 whereas it was < 10 against other bacteria including E.c. carotovora. Detection of E.c. atroseptica serogroups I and XXII in diseased potato tissues was achieved directly by the slide agglutination test, but lower antiserum dilutions (1:700–1000) were needed. Still lower antiserum dilutions were needed with heat-treated test material for E.c. atroseptica identification.     

Toxoplasma gondii: lymphocyte function during acute infection in mice

T-cell function during acute Toxoplasma gondii infection was evaluated in murine models. Blastogenic response to the T-cell mitogen concanavalin A (Con A) was not depressed during infection with either the C37 or the C56 strain of T. gondii in either $\text{BALB}\text{c}$ or $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice that were inoculated either intravenously or intraperitoneally with varying doses of tachyzoites 7, 14, or 30 days earlier. In evaluation of lymphocytes from individual mice, utilization of a range of concentrations of Con A was found to be important for correct interpretation of results. There was variability in the magnitude of response of individual mice and in the concentration of mitogen that produced an optimal response among the inbred mice. The T-cell-dependent, primary antibody response to sheep red blood cells (SRBC) was not depressed in $\text{BALB}\text{c}$ mice infected with the C37 strain of Toxoplasma 1 and 8 days prior to inoculation with SRBC. A lower blastogenic reponse to Con A of lymphocytes from $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice compared with that of $\text{BALB}\text{c}$ mice appeared to correlate with increased susceptibility of $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice to low-challenge inocula of T. gondii.     

Advances in approaches to seagrass restoration in Australia

Three case studies involving two temperate Australian seagrass species – Pondweed (Ruppia tuberosa) and Ribbon Weed (Posidonia australis) – highlight different approaches to their restoration. Seeds and rhizomes were used in three collaborative programmes to promote new approaches to scale up restoration outcomes.