Use of tree rings to study the effect of climate change on trembling aspen in Québec

In this paper, we present a new approach, based on a mixed model procedure, to quantify the tree‐ring‐based growth‐climate relationship of trembling aspen along a latitudinal gradient from 46 to 54 °N in eastern Canada. This approach allows breaking down the growth response into general intersite and local climatic responses, and analyzing variations of absolute ring width as well as interannual variations in tree growth. The final model also integrates nonclimatic variables such as soil characteristics and the occurrence of insect outbreaks into the growth predictions. Tree level random effects on growth were important as intercepts but were nonsignificant for the climatic variables, indicating that a single climate–growth relationship was justified in our case. The response of tree growth to climate showed, however, a strong dependence on the spatial scale at which the analysis was performed. Intersite variations in tree growth were mostly dependent on variations in the thermal heat sum, a variable that showed low interannual and high intersite variation. When variation for a single site was analyzed, other variables showed up to be important while the heat sum was unimportant. Finally, future growth under six different climate change scenarios was simulated in order to study the potential impact of climate change. Results suggest only moderate growth increases in the northern portion of the gradient and a growth decrease in the southern portion under future climatic conditions.     

Competence of Genetic Transformation correlated with the Occurrence of Fimbriae in Three Bacterial Species

THE involvement of bacterial fimbriae (pili) in some cases of phage infection and in bacterial conjugation has been known or presumed for some years¹. Studies in our laboratories show that fimbriae are also associated with genetic transformation in several bacterial species.     

HOW AND WHEN DO LAMBS RECOGNIZE THE BLEATS OF THEIR MOTHERS?

ABSTRACT

In domestic sheep Ovis aries, the mother and the young display a preferential bond for each other that relies on multimodal inter-individual recognition. Lambs show a preference for their own dam shortly after birth, and this is important for their survival. The role of acoustic cues in this early preference for the mother is not clear. The aim of the present work was to analyze the timing of acoustic recognition of the mother and to identify the physical parameters used in the recognition of maternal bleats by the lamb.

In a first study, we investigated the ability of lambs to discriminate between the bleats of their own mother and an alien equivalent mother in a two-choice test. Both ewes were hidden behind a canvas sheet and lambs were not allowed to approach the dams closer than 1 m, thus preventing visual as well as olfactory perception. Tests were conducted 12 hr, 24 hr or 48 hr after birth (n=19 or 20/group). An indication of vocal discrimination was already present at 24 hr and at 48 hr lambs spent significantly more time near their mother than near the alien dam.

In a second step, we investigated which physical parameters of the bleats were important for recognition. For this, we conducted playback experiments with modified bleats at two weeks postpartum. Ours results show that lambs pay attention to a combination of various time, energy and frequency parameters: timbre (distribution of energy within the spectrum), amplitude and frequency modulations appear to be the most important parameters encoding the individual signature.

We conclude that vocal recognition between the ewe and her lamb plays an important role in the display of preferential mother-young bond from very early on. Our studies also demonstrate that the encoding of the individual signature is not limited to the frequency domain but rather involves a multiparametric encoding process.     

Cell- and region-specific miR30-based gene knock-down with temporal control in the rat brain

Background  

RNA interference (RNAi) emerges as a powerful tool to induce loss-of-function phenotypes. In the context of the brain, gene manipulation is best targeted to specific subsets of cells in order to achieve a physiologically relevant outcome. Polymerase II-based viral expression systems can be used to cell-specifically express constructs incorporating flanking and loop sequences from endogenous microRNA (miRNA), which directs the designed hairpins into the endogenous gene silencing machinery. While many studies have documented non-cell-selective gene knock-down in the brain, it has not been tested whether different cell types or different areas of the central nervous system (CNS) are equally amenable to this approach. We have evaluated this issue using a tetracycline (Tet)-controllable and cell-specific miRNA 30 (miR30)-based short hairpin (shRNA) interference system.     

Vasospasm is a significant factor in cyclosporine-induced neurotoxicity: Case report

Background

The aetiology of central nervous system lesions observed in cerebral cyclosporine neurotoxicity remains controversial.

Case presentation

We report a 48-year-old woman with a non-severe aplastic anaemia who presented with stroke-like episodes while on cyclosporine treatment.Transcranial Doppler ultrasound revealed severely elevated flow velocities in several cerebral vessels, consistent with vasospasm. Immediately after reducing the cyclosporine dose, the stroke-like episodes disappeared. Only after cyclosporine withdrawal the transcranial Doppler ultrasound abnormalities fully resolved.

Conclusions

This case demonstrates a significant role of vasospasm in the pathway of cyclosporine-induced neurotoxicity. Transcranial Doppler ultrasound is an effective tool for the diagnosis and follow-up of cyclosporine-induced vasospasm.

     

Impact of different acclimation temperatures and duration on the chill coma temperature and oxygen consumption in the tenebrionid beetle Alphitobius diaperinus

When the ambient temperature is lowered to an insect's lower thermal limit, the insect enters into chill coma. Chill coma temperature and chill coma recovery can vary within species as a result of thermal acclimation, although the physiological basis of the onset of chill coma remains poorly understood. The present study investigates how the temperature of acclimation (0, 5, 10, 15 and 20 °C for 2 or 7 days) affects chill coma temperature and oxygen consumption in adult Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). It is hypothesized that the threshold decline in metabolic rate corresponds to the entry into chill coma. Oxygen consumption (as a proxy of metabolism) is measured across the chill coma temperature threshold, and a strong decline in oxygen consumption is expected at entry into chill coma. The acclimation decreases the chill coma temperature significantly from 6.6 ± 1.1 °C in control insects to 3.1 ± 0.7 °C in those acclimated to 10 °C. The change in metabolic rate (Q₁₀) after acclimation to temperatures ranging from 10 to 20 °C is 3.7. Despite acclimation, the metabolic rate of A. diaperinus conforms to Arrhenius kinetics, suggesting that the response of this beetle does not show metabolic compensation. The data suggest the existence of a threshold decline in metabolic rate during cooling that coincides with the temperature at which an insect goes into chill coma.     

Delayed setting of the photoperiodic response in recombinant clones of the aphid species Sitobion avenae

1. To explore the possible causes of apparent changes in reproductive mode from obligate to cyclical parthenogenesis over time in recombinant clones of the aphid Sitobion avenae Fabricius, all F1 progenies from various crosses were tested for several consecutive years for sexual morph production, after several weeks' exposure to a short photoperiod. 2. Variable proportions of the F1 progenies from selfing and outcrossing holocyclic clones did not produce mating females when induction was attempted in the year of hatching, but only after further induction, the following year or after. This ‘delayed setting of the photoperiodic response’ (DSPR) was much stronger in recombinants from crosses involving only clones from oceanic regions than in those involving one clone from a region with a continental climate. 3. F1 progenies resulting from crosses between one holocyclic and one intermediate clone did not show DSPR. It appeared again in the F2. 4. DSPR preferentially affected the latest hatched clones in a given progeny. 5. This phenomenon is neither an experimental artefact nor as a result of clone contamination. It appears to be because of a genetically controlled quantitative trait affecting the length of the ‘interval timer’, and may represent an adaptation of holocyclic aphid clones from oceanic regions to unpredictable winter climates.