Carbonic anhydrases (CAs) are Zn-containing metalloenzymes that catalyse the reversible hydration of CO2. We investigated the a CA and b CA families in Arabidopsis, which contain eight aCA (AtaCA1-8) and six b CA genes (AtbCA1-6). Analyses of expressed sequence tags (ESTs) from The Arabidopsis Information Resource (TAIR) database indicate that all the b CA encoding sequences, but only three of the Ata CA, are expressed. Using semiquantitative PCR experiments, functional CA genes were more strongly expressed in green tissue, but strong expression was also found in roots for b CA3, b CA6 and a CA2. Two a CA genes were shown to respond to the CO2 environment, while the others were unresponsive. Using the green fluorescent reporter protein gene fused with cDNA sequences coding for b CAs, we provided evidence that b CAs were targeted to specific subcellular compartments: b CA1 and b CA5 were targeted to the chloroplast, b CA2 and b CA3 to the cytosol, b CA4 to the plasma membrane and b CA6 to the mitochondria. The targeting and the pattern of gene expression suggest that CA isoforms play specific roles in subcellular compartments, tissues and organs. The data indicate that other CA isoforms than the well-characterized b CA1 may contribute to the CO2 transfer in the cell to the catalytic site of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco).

This study aimed to compare physiological and perceptual responses to Nordic walking (NW) in obese women to those of walking (W), and to assess if these responses were modified by a learning period of NW technique. Eleven middle-aged obese women completed exercise trials (5 min each) at 4 km/h, inclinations of -5, 0 and +5%, with and without poles. Ventilation (V(E)) oxygen consumption V(O)(2) energy cost (EC), heart rate (HR), rating of perceived exertion (RPE) and cycle length were measured before and after a 4-week learning period (12 sessions). V(E), V(O)(2), EC, HR and cycle length were significantly higher (P < 0.001) during NW trials than W trials. RPE was significantly diminished (pole x inclination interaction, P = 0.031) when using NW poles compared to W uphill. Significant pole x inclination interactions were observed for V(O)(2) (P = 0.022) and EC (P = 0.022), whereas significant pole x time interaction was found for EC (P = 0.043) and RPE (P = 0.039). Our results confirmed that use of NW poles increased physiological responses at a given speed but decreased RPE in comparison with W during inclined level. Moreover, this is the first study showing that a learning period of NW technique permitted to enhance the difference between EC with NW poles versus the W condition and to decrease the RPE when using NW poles. Thus, although it requires a specific learning of the technique, the NW might be considered like an attractive physical activity with an important public health application.

The effects of a Nordic walking (NW) program compared to those of a walking (W) program on physiological and perceptual variables in obese middle-aged women were investigated. Subjects (n=12 NW group, n=11 W group) trained over 12 weeks 3 times.week (-1). Body mass, body mass index (BMI), body fat, heart rate (HR), resting blood pressure, peak oxygen consumption (V˙O (2peak)) were measured before and after the training period. Moreover, HR, rating of perceived exertion (RPE) and adherence were recorded during all training sessions. After the training period body mass, body fat and diastolic blood pressure decreased in both groups (P<0.05) whereas V˙O (2peak) increased in the NW group (+3.7 ml.min (-1).kg (-1); P=0.005). During the training sessions, mean HR (P=0.021), HR at preferred walking speed (P=0.020) and % of time at high intensity (P=0.031) were higher in NW than in the W group. Finally, RPE was not influenced by the modality of exercise and NW group showed a higher rate of adherence (91±19% vs. 81±29%; P=0.011). To conclude, NW activity in obese women allows an increase in exercise intensity and adherence to a training program without increasing the perception of effort leading to enhanced aerobic capacity.

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The capacity to predict the heart rate (HR) and speed at the first (VT1) and second (VT2) ventilatory thresholds was evaluated during an incremental ski-mountaineering test using heart rate variability (HRV). Nine skiers performed a field test to exhaustion on an alpine skiing track. VT1 and VT2 were individually determined by visual analysis from gas exchanges (VT1V and VT2V) and time-varying spectral HRV analysis (VT1fH, VT2fH and VT2H). VT1 could not be determined with the HRV methods used. On the contrary, the VT2 was determined in all skiers. No significant difference between HR and speed at VT2H and VT2V was observed (174.3 ± 5.6 vs. 174.3 ± 5.3 bpm, and 6.3 ± 0.9 and 6.3 ± 0.9 km h(-1), respectively). Strong correlations were obtained for HR (r = 0.91) and speed (r = 0.92) at VT2H and VT2V with small limits of agreement (±3.6 bpm for HR). Our results indicated that HRV enables determination of HR and speed at VT2 during a specific ski-mountaineering incremental test. These findings provide practical applications for skiers in order to evaluate and control specific training loads, at least when referring to VT2.

Lower energy cost of running (Cr) has been reported when wearing minimal (MS) vs traditional shoes (TS) on level terrain, but the effect of slope on this difference is unknown. The aim of this study was to compare Cr, physiological, and kinematic variables from running in MS and TS on different slope conditions. Fourteen men (23.4 ± 4.4 years; 177.5 ± 5.2 cm; 69.5 ± 5.3 kg) ran 14 5-min trials in a randomized sequence at 10 km/h on a treadmill. Subjects ran once wearing MS and once wearing TS on seven slopes, from -8% to +8%. We found that Cr increased with slope gradient (P < 0.01) and was on average 1.3% lower in MS than TS (P < 0.01). However, slope did not influence the Cr difference between MS and TS. In MS, contact times were lower (P < 0.01), flight times (P = 0.01) and step frequencies (P = 0.02) were greater at most slope gradients, and plantar-foot angles - and often ankle plantar-flexion (P = 0.01) - were greater (P < 0.01). The 1.3% difference between footwear identified here most likely stemmed from the difference in shoe mass considering that the Cr difference was independent of slope gradient and that the between-footwear kinematic alterations with slope provided limited explanations.

Cellular RNA-dependent RNA polymerases (RDRs) are fundamental components of RNA silencing in plants and many other eukaryotes. In Arabidopsis thaliana genetic studies have demonstrated that RDR2 and RDR6 are involved in the synthesis of double stranded RNA (dsRNA) from single stranded RNA (ssRNA) targeted by RNA silencing. The dsRNA is subsequently cleaved by the ribonuclease DICER-like into secondary small interfering RNAs (siRNAs) that reinforce and/or maintain the silenced state of the target RNA. Models of RNA silencing propose that RDRs could use primer-independent and primer-dependent initiation to generate dsRNA from a transcript targeted by primary siRNA or microRNA (miRNA). However, the biochemical activities of RDR proteins are still partly understood. Here, we obtained active recombinant RDR2 and RDR6 in a purified form. We demonstrate that RDR2 and RDR6 have primer-independent and primer-dependent RNA polymerase activities with different efficiencies. We further show that RDR2 and RDR6 can initiate dsRNA synthesis either by elongation of 21- to 24- nucleotides RNAs hybridized to complementary RNA template or by elongation of self-primed RNA template. These findings provide new insights into our understanding of the molecular mechanisms of RNA silencing in plants.

To determine the most accurate method based on spectral analysis of heart-rate variability (SA-HRV) during an incremental and continuous maximal test involving the upper body, the authors tested 4 different methods to obtain the heart rate (HR) at the second ventilatory threshold (VT(2)). Sixteen ski mountaineers (mean ± SD; age 25 ± 3 y, height 177 ± 8 cm, mass 69 ± 10 kg) performed a roller-ski test on a treadmill. Respiratory variables and HR were continuously recorded, and the 4 SA-HRV methods were compared with the gas-exchange method through Bland and Altman analyses. The best method was the one based on a time-varying spectral analysis with high frequency ranging from 0.15 Hz to a cutoff point relative to the individual's respiratory sinus arrhythmia. The HR values were significantly correlated (r(2) = .903), with a mean HR difference with the respiratory method of 0.1 ± 3.0 beats/min and low limits of agreements (around -6 /+6 beats/min). The 3 other methods led to larger errors and lower agreements (up to 5 beats/min and around -23/+20 beats/min). It is possible to accurately determine VT(2) with an HR monitor during an incremental test involving the upper body if the appropriate HRV method is used.