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Wood density is the product of carbon allocation for structural growth and reflects the trade-off between mechanical support and water conductivity. We tested a conceptual framework based on the assumption that micro-density depends on direct and indirect relationships with endogenous and exogenous factors. The dynamics of wood formation, including timings and rates of cell division, cell enlargement, and secondary wall deposition, were assessed from microcores collected weekly between 2002 and 2016 from five black spruce stands located along a latitudinal gradient in Quebec, Canada. Cell anatomy and micro-density were recorded by anatomical analyses and X-ray measurements. Our structural equation model explained 80% of micro-density variation within the tree-ring with direct effects of wall thickness (σ = 0.61), cell diameter (σ = -0.51), and photoperiod (σ = -0.26). Wood formation dynamics had an indirect effect on micro-density. Micro-density increased under longer periods of cell-wall deposition and shorter durations of enlargement. Our results fill a critical gap in understanding the relationships underlying micro-density variation in conifers. We demonstrated that short-term responses to environmental variations could be overridden by plastic responses that modulate cell differentiation. Our results point to wood formation dynamics as a reliable predictor of carbon allocation in trees.

International audience; The objective was to compare eight methods for estimation of dairy goat body composition, by calibrating against chemical composition (water, lipid, protein, mineral and energy) measured post-mortem. The methods tested on 20 Alpine goats were body condition score (BCS), 3-dimension imaging (3D) automatic assessment of BCS or whole body scan, ultrasound, computer tomography (CT), adipose cell diameter, deuterium oxide dilution space (D 2 OS) and bioelectrical impedance spectroscopy (BIS). Regressions were tested between predictive variates derived from the methods and empty body (EB) composition. The best equations for estimation of EB lipid mass included BW combined with i) perirenal adipose tissue mass and cell diameter (R 2 = 0.95, residual standard deviation, rSD = 0.57 kg), ii) volume of fatty tissues measured by CT (R 2 = 0.92, rSD = 0.76 kg), iii) D 2 OS (R 2 = 0.91, rSD = 0.85 kg), and iv) resistance at infinite frequency from BIS (R 2 = 0.87, rSD = 1.09 kg). The D 2 OS combined with BW provided the best equation for EB protein mass (R 2 = 0.97, rSD = 0.17 kg), whereas BW alone provided a fair estimate (R 2 = 0.92, rSD = 0.25 kg). Sternal BCS combined with BW provided good estimation of EB lipid and protein mass (R 2 = 0.80 and 0.95, rSD = 1.27 and 0.22 kg, respectively). Compared to manual BCS, BCS by 3D slightly decreased the precision of the predictive equation for EB lipid (R 2 = 0.74, rSD = 1.46 kg), and did not improve the estimation of EB protein compared with BW alone. Ultrasound measurements and whole body 3D imaging methods were not satisfactory estimators of body composition (R 2 ≤ 0.40). Further developments in body composition techniques may contribute for high-throughput phenotyping of robustness.

International audience; Cells usually grow to a certain size before they divide. The fission yeast Schizosaccharomyces pombe is an established model to dissect the molecular control of cell size homeostasis and cell cycle. In this chapter, we describe two simple methods to: (1) precisely compute geometrical parameters (cell length, diameter, surface, and volume) of single growing and dividing fission yeast cells with image analysis scripts and (2) manipulate cell diameter with microfabricated chambers and assess for cell size at division. We demonstrate the strength of these approaches in the context of growing spores, which constantly change size and shape and in deriving allometric relationships between cell geometrical parameters associated with G2/M transition. We emphasize these methods to be useful to investigate problems of growth, size, and division in fungal or bacterial cells.

International audience; The paper presents the interest of on-line permittivity monitoring to estimate the density of Vero cells growing on microcarriers (MCs), even when high cell densities were reached in perfusion bioreactors (4.5 x 10(6) cells ml(-1)). Cultures were performed with various MCs concentrations in a reactor equipped with a settling tube. A linear correlation between on-line permittivity and off-line volumetric cell concentration was observed provided that MCs are not fully covered by cells. High permittivities such as 250 pF cm(-1) could be measured without signal saturation of the Fogale Biomass system (R). The correlation was no longer linear when cell density per carrier exceeded 100% cell confluency corresponding to 150 cells MC-1 (0.15 x 10(6) cells cm(-2)). This behaviour was attributed to the decrease of cell volume when cells saturated MCs surface. It mainly happened when low MCs concentration and continuous medium renewing were used. Therefore, permittivity sensor can be considered as a reliable tool to monitor on-line adherent cell densities not exceeding total cell confluency. Moreover, it could be useful to detect when cell confluency occurs.

Growth and spirolide production of the toxic dinoflagellate Alexandrium ostenfeldii (Danish strain CCMP1773) were studied in batch culture and a photobioreactor (continuous cultures). First, batch cultures were grown in 450 mL flasks without aeration and under varying conditions of temperature (16 and 22 degrees C) and culture medium (L1, f/2 and L1 with addition of soil extract). Second, cultures were grown at 16 degrees C in 8 L aerated flat-bottomed vessels using L1 with soil extract as culture medium. Finally, continuous cultures in a photobioreactor were conducted at 18 degrees C in L1 with soil extract; pH was maintained at 8.5 and continuous stirring was applied. This study showed that A. ostenfeldii growth was significantly affected by temperature. At the end of the exponential phase, maximum cell concentration and cell diameter were significantly higher at 16 degrees C than at 22 C. In batch culture, maximum spirolide quota per cell (approx. 5 pg SPX 13-desMeC eq cell(-1)) was detected during lag phase for all conditions used. Spirolide quota per cell was negatively and significantly correlated to cell concentration according to the following equation: y = 4013.9x(-0.858). Temperature and culture medium affected the spirolide profile which was characterized by the dominance of 13,19-didesMeC (29-46%), followed by SPX-D (21-28%), 13-desMeC (21-23%), and 13-desMeD (17-21%). Stable growth of A. ostenfeldii was maintained in a photobioreactor over two months, with maximum cell concentration of 7 x 10(4) cells mL(-1). As in batch culture, maximum spirolide cell quota was found in lag phase and then decreased significantly throughout the exponential phase. Spirolide cell quota was negatively and significantly correlated to cell concentration according to the equation: y = 12,858x(-0.8986). In photobioreactor, spirolide profile was characterized by higher proportion of 13,19-didesMeC (60-87%) and lower proportions of SPX-D (3-12%) and 13-desMeD (1.6-10%) as compared to batch culture. (C) 2011 Elsevier B.V. All rights reserved.

International audience; The aim of the work was to study the relationship between subcutaneous adipose tissue development and the fat firmness score attained in the carcass. For this purpose, 48 Lacaune male lambs were fed a concentrate from 23.5 +/- 0.2 to 41.4 +/- 0.2 kg live weight (63 +/- 0.7 to 122 +/- 3.2 days of age, respectively). After slaughter, the lamb carcasses were classified according to fat firmness (1: very firm to 5: very soft/oily). Subcutaneous adipose cell was measured and their overall distribution determined. Results showed that the adipose cells of the studied lambs exhibited a bimodal distribution, suggesting that a fast postnatal hyperplasic or cell proliferation process had been initiated in the subcutaneous adipocytes. In addition, the size of the small adipocyte peak was inversely correlated with the firmness of the fat (40.5, 37.7 and 30.9% of total adipocytes for groups of lambs with a firmness score of 4-5, 3 and 1-2, respectively). In this way, the average adipocyte cell diameter of the lambs with firmness scores of 4-5 (71.8 +/- 0.55 mum) was less than that for the lambs with scores of 3 (73.9 +/- 0.46 mum), and in turn, the diameter of this latter group was smaller than that of lambs with scores of 1-2 (77.6 +/- 0.59 mum). This work indicates the existence of a relationship between the intensity of the hyperplastic process undergone in the lamb subcutaneous adipose tissue and its fat firmness.

International audience; Outer hair cells (OHC) of the mammalian cochlea are quasicylindrical cells of different length, which play a major role in hearing at threshold. Their particular shape allows the use of a noninvasive laser interferometric technique of isolated cells in vitro in order to measure the organic material concentration (OMC), hence the density of each cell body. In most (95 %) of the OHCs isolated from the same guinea pig, when the cell diameter is normalized, the results show that the cell body OMC does not vary with cell length. In different animals, the respective normalized OMC mean values can vary between 70 kg/m3 and 103 kg/m3. A few OHCs with morphological particularities often possess cell body OMCs > 103 kg/m3. The results of the interferometric measurements in isolated OHCs confirm that density variations in the cell bodies are not involved in a sound frequency coding. The in vitro OMC variations of the OHCs could be related to the isolation procedure; however, they could also correlate with actual in vivo OMC variations.