Volatiles from Merino fleece evoke antennal and behavioural responses in the Australian sheep blow fly Lucilia cuprina

To identify flystrike‐related volatile compounds in wool from Merino sheep, the attractiveness of wool to Lucilia cuprina Wiedmann (Diptera: Calliphoridae) was examined. First, a selection of wool samples guided by previous knowledge of sheep lines, predicted to be more susceptible or more resistant to flystrike, was tested. The attractiveness of the 10 samples selected was not associated with field susceptibility: two samples from the more resistant line were identified as most attractive and two samples from the more susceptible line were identified as least attractive, based on the behavioural assays with gravid flies. Comparison of the headspace volatiles of these samples, using solid phase microextraction and gas chromatography‐mass spectrometry‐electroantennographic detection, revealed octanal and nonanal to be present in the attractive wool samples that elicited responses from the fly antenna. Furthermore, the two compounds were not present in wool that was least attractive to L. cuprina. In laboratory bioassays, octanal and nonanal evoked antennal and behavioural responses in gravid L. cuprina, thus confirming their potential role as semiochemicals responsible for attracting L. cuprina to Merino sheep.     

Activation, inactivation and recovery in the sodium channels of the squid giant axon dialysed with different solutions.

Comparisons were made between families of ion currents recorded in voltage-clamped squid axons dialysed with 20 mM NaF and 330 mM CsF or TMAF, and bathed in a solution in which four fifths of the Na was replaced by Tris. The permeability coefficient PNa,fast for the fast-inactivating current in the initial open state was calculated as a function of test potential from the size of the initial peak of INa. The permeability coefficient PNa,non for the non-inactivating open state was calculated from the steady-state INa that persisted until the end of the test pulse. Dialysis with TMA had no direct effect on the QV curve for gating charge. The reversal potential for INa,non was always lower than that for INa,fast, the mean difference being about -9 mV when dialysing with Cs, but only about -1 mV with TMA. Except close to threshold, PNa,fast was roughly halved by dialysis with TMA as compared with Cs, but PNa,non was substantially increased. The time constant tau h inactivation of the sodium system was slightly increased during dialysis with TMA in place of Cs, and there were small shifts in the steady-state inactivation curve, but the rate of recovery from inactivation was not measurably altered. The flattening off of the tau h curve at increasingly positive test potentials corresponded to a steady reduction of the apparent inactivation charge until a value of about 0.2e was reached for pulses to 100 mV. The instantaneous I-V relationship in the steady state was also investigated. The results have a useful bearing on the effects of dialysis with TMA, on the differences between the initial and steady open states of the sodium channel, and on the relative voltage-dependences of the transitions in each direction between the resting and inactivated states.     

Offspring allocation in structured populations with dimorphic males

Summary Many fig wasp species have dimorphic males. These males often mate in different localities; one typically disperses before mating whereas the other does not disperse. In 1979 a model was developed for offspring allocation in dimorphic fig wasps, but it assumed that females only lay a single egg per fig. This assumption is not realistic and precludes any effects local mate competition (LMC) may exert on morph abundance. I develop a model without these restrictions and show that the optimal proportions of each morph is determined by two parameters. Firstly, the proportion of the non-dispersing morph is affected by the mean number of females that oviposit in a patch. This effect is due to the negative correlation between LMC between brothers and the number of females that oviposit in a patch. Secondly, the proportions of both male morphs correlate with the expected proportion of females which will mate with each morph. The separation of the two parameters generalizes the model to any other species which is spatially structured and which has two male morphs or even two alternative mating strategies. A comparison of two models shows that parent—offspring conflict involving morph ratios will not have far reaching consequences. I test these models using the 1979 model's data and both models accurately predict the variation in morph ratios in six species of dimorphic fig wasps.     

The effect of tetrodotoxin on the sodium gating current in the squid giant axon.

The effect of tetrodotoxin (TTX) on the sodium gating current in the squid giant axon was examined by recording the current that flowed at the pulse potential at which the ionic current fell to zero, first in the absence and then in the presence of TTX. The addition of 1 microM TTX to the bathing solution had no consistent effect on the size of the initial peak of the gating current, but resulted in small changes in the timecourse of its subsequent relaxation which were mainly caused by a reduction of about one quarter in the component that has a delayed onset and may possibly arise from changes in the state of ionization of groups in the channel wall when the lumen fills with water. Our findings suggest that the binding of TTX at the outer face of the sodium channel does not interfere with the mechanisms of activation and inactivation by the voltage sensors, but has an allosteric effect on the access of internal cations to the inside of the channel.     

Long-term effects of graduated compression stockings on cardiorespiratory performance

The use of graduated compression stockings (GCS) in sport has been increasing in the last years due to their potential positive effects for athletes. However, there is little evidence to support whether these types of garments actually improve cardiorespiratory performance. The aim of this study was to examine the cardiorespiratory responses of GCS during running after three weeks of regular use. Twenty recreational runners performed three tests on different days: test 1) – a 5-min maximal effort run in order to determine the participants’ maximal aerobic speed; and tests 2) and 3) – a fatigue running test of 30 minutes at 80% of their maximal aerobic speed with either GCS or PLACEBO stockings at random. Cardiorespiratory parameters (minute ventilation, heart rate, relative oxygen consumption, relative carbon dioxide production, ventilatory equivalents for oxygen and carbon dioxide, and oxygen pulse) were measured. Before each test in the laboratory, the participants trained with the randomly assigned stockings (GCS or PLACEBO) for three weeks. No significant differences between GCS and PLACEBO were found in any of the cardiorespiratory parameters. In conclusion, the present study provides evidence that running with GCS for three weeks does not influence cardiorespiratory parameters in recreational runners.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Proof-of-concept human laboratory study for protracted abstinence in alcohol dependence: effects of gabapentin

There is a need for safe medications that can effectively support recovery by treating symptoms of protracted abstinence that may precipitate relapse in alcoholics, e.g. craving and disturbances in sleep and mood. This proof-of-concept study reports on the effectiveness of gabapentin 1200 mg for attenuating these symptoms in a non-treatment-seeking sample of cue-reactive, alcohol-dependent individuals. Subjects were 33 paid volunteers with current Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence and a strength of craving rating 1 SD or greater for alcohol than water cues. Subjects were randomly assigned to gabapentin or placebo for 1 week and then participated in a within-subjects trial where each was exposed to standardized sets of pleasant, neutral and unpleasant visual stimuli followed by alcohol or water cues. Gabapentin was associated with significantly greater reductions than placebo on several measures of subjective craving for alcohol as well as for affectively evoked craving. Gabapentin was also associated with significant improvement on several measures of sleep quality. Side effects were minimal, and gabapentin effects were not found to resemble any major classes of abused drugs. Results suggest that gabapentin may be effective for treating the protracted abstinence phase in alcohol dependence and that a randomized clinical trial would be an appropriate next step. The study also suggests the value of cue-reactivity studies as proof-of-concept screens for potential antirelapse drugs.