Schematic drawing of custom-made bite force device set up.

<p>Schematic drawing of custom-made bite force device set up.</p

Mean ± SE values of postural parameters.

<p>Mean and standard error values of center of pressure (COP) path length (A), area (B), velocity (C), and length function of surface (LFS) (D) during control period (BDC-3), the first day (R0) and the second day of recovery period (R+1) for the different test conditions: dental intercuspidal position (ICP) (white bars) and mandibular rest position (RP) (black bars), eyes open and eyes closed. * and ** significant differences compared with BDC-3 value. (Respectively <i>p</i> < 0.05 and <i>p</i> < 0.01; ANOVA for repeated measures).</p

Combined (left and right) changes in jaw and cervical muscles stiffness, frequency and relaxation time before, during and after dry immersion.

<p>Combined (left and right) changes in jaw and cervical muscles stiffness, frequency and relaxation time before, during and after dry immersion.</p

Maximal molar bite force before and after dry immersion.

<p>Maximal molar bite force before and after dry immersion.</p

Body temperature, body weight, plasma volume, systolic and diastolic pressure, and heart rate before and after dry immersion.

<p>Body temperature, body weight, plasma volume, systolic and diastolic pressure, and heart rate before and after dry immersion.</p

Nighttime (NT) and daylight (DL) spontaneous locomotor activity.

<p>Activity was measured in standard cages (BL) and during 14 days (d1–d14) for control (<b>A</b>), isolated-control (<b>B</b>), isolated (<b>C</b>), attached (<b>D</b>), and unloaded (<b>E</b>) rats. Data are given as a mean ± SEM. *- P < 0.05 <i>versus</i> basal level (BL).</p

Effects of short-term dry immersion on bone remodeling markers, insulin and adipokines

<div><p>Background</p><p>Dry immersion (DI), a ground-based model of microgravity previously used in Russia, has been recently implemented in France. The aim of this study was to analyze early events in a short-term DI model in which all conditions are met to investigate who is first challenged from osteo- or adipo-kines and to what extent they are associated to insulin-regulating hormones.</p><p>Methods</p><p>Twelve healthy men were submitted to a 3-day DI. Fasting blood was collected during pre-immersion phase for the determination of the baseline data collection (BDC), daily during DI (DI_24h, DI_48H and DI_72h), then after recovery (R_+3h and R_+24h). Markers of bone turnover, phosphocalcic metabolism, adipokines and associated factors were measured.</p><p>Results</p><p>Bone resorption as assessed by tartrate-resistant acid phosphatase isoform 5b and N-terminal crosslinked telopeptide of type I collagen levels increased as early as DI_24h. At the same time, total procollagen type I N- and C-terminal propeptides and osteoprotegerin, representing bone formation markers, decreased. Total osteocalcin [OC] was unaffected, but its undercarboxylated form [Glu-OC] increased from DI_24h to R_+3h. The early and progressive increase in bone alkaline phosphatase activities suggested an increased mineralization. Dickkopf-1 and sclerostin, as negative regulators of the Wnt-β catenin pathway, were unaltered. No change was observed either in phosphocalcic homeostasis (calcium and phosphate serum levels, 25-hydroxyvitamin D, fibroblast growth factor 23 [FGF23]) or in inflammatory response. Adiponectemia was unchanged, whereas circulating leptin concentrations increased. Neutrophil gelatinase-associated lipocalin [lipocalin-2], a potential regulator of bone homeostasis, was found elevated by 16% at R_+3h compared to DI_24h. The secretory form of nicotinamide phosphoribosyl-transferase [visfatin] concentrations almost doubled after one day of DI and remained elevated. Serum insulin-like growth factor 1 levels progressively increased. Fasting insulin concentrations increased during the entire DI, whereas fasting glucose levels tended to be higher only at DI_24h and then returned to BDC values. Changes in bone resorption parameters negatively correlated with changes in bone formation parameters. Percent changes of ultra-sensitive C-reactive protein positively correlated with changes in osteopontin, lipocalin-2 and fasting glucose. Furthermore, a positive correlation was found between changes in FGF23 and Glu-OC, the two main osteoblast-/osteocyte-derived hormones.</p><p>Conclusion</p><p>Our results demonstrated that DI induced an unbalanced remodeling activity and the onset of insulin resistance. This metabolic adaptation was concomitant with higher levels of Glu-OC. This finding confirms the role of bone as an endocrine organ in humans. Furthermore, visfatin for which a great responsiveness was observed could represent an early and sensitive marker of unloading in humans.</p></div

Design of the experimental cages.

<p>Control (<b>A</b>), isolated-control (<b>B</b>), isolated (<b>C</b>), attached (<b>D</b>), and unloaded (<b>E</b>) rats.</p

Heart rate and blood pressure during treadmill running.

<p>Heart rate (left) and mean arterial pressure (right) during a treadmill running test before (<b>PRE</b>) and after (<b>POST</b>) 14-days of control (<b>A</b>), isolation-control (<b>B</b>), isolation (<b>C</b>), attachment (<b>D</b>), and unloading (<b>E</b>). Cage: in experimental cage. TM1: in the treadmill cage, at rest, before exercise. EX: during treadmill running. TM2: in the treadmill cage, at rest, after exercise. Data are given as a mean ± SEM. *and # - P < 0.05 <i>versus</i> respective TM1 level.</p

Heart rate changes.

<p>Nighttime (NT) and daylight (DL) heart rate measured in standard cages (BL) and during 14 days (d1–d14) for control (<b>A</b>), isolated-control (<b>B</b>), isolated (<b>C</b>), attached (<b>D</b>), and unloaded (<b>E</b>) rats. Data are given as a mean ± SEM. *- P < 0.05 <i>versus</i> basal level (BL).</p