The role of the slope of oxygen consumption and EMG activity on freely chosen pedal rate selection

The objective of this study was to verify the following hypothesis: the pedal rate that minimizes root mean square (RMS) slope and the slow component amplitude of oxygen consumption could be close to the freely chosen pedal rate (FCPR) used by well-trained cyclists. Nine male competitive cyclists performed a 21 min submaximal exercise on a cycle ergometer at a workload of 65% of their respective peak aerobic power. For each session, the subject's pedal rate was freely chosen or assigned to 60, 75, 90 or 105 rev min(-1). When pedal rates were imposed, the electromyographic root mean square slope, the oxygen uptake during the third minute and the 20th min, and the slow component amplitude of oxygen consumption were used in the analysis. In order to determine the optimal pedal rate (OPR), a quadratic function was fitted to the data by regression, for each variable measured. The mean values of OPR relative to oxygen uptake during the third min (71+/-9 rev min(-1)) were lower than the mean values of the OPR relative to the slow component amplitude of oxygen consumption (82+/-8 rev min(-1)), the electromyographic root mean square slope (80+/-7 rev min(-1)) and freely chosen pedal rate (86+/-13 rev min(-1)). Freely chosen pedal rate was not significantly different from the OPR in reference to the amplitude of the slow component of oxygen consumption, electromyographic root mean square slope, and oxygen uptake during the 20th min. OPR for RMS slope was correlated (R=0.72) to FCPR. Expert cyclists were likely to use a spontaneous pedal rate that minimizes neuromuscular fatigue.     

Vestibulo-ocular reflex and motion sickness in figure skaters

In order to determine the effect of figure skating on the functional plasticity of the vestibular system, we quantified vestibulo-ocular reflex (VOR) and motion sickness (MS) intensity in 11 female figure skaters and 11 matched control subjects. Vestibular stimulation consisted of three cycles of sinusoidal rotation (0.025 Hz, ±60°/s) and two velocity steps of 60°/s (acceleration 60°/s²). Nauseogenic stimulation consisted of a constant velocity (60°/s) off vertical axis rotation (OVAR) using a 15° tilt angle. Subjective sickness symptoms were rated immediately after OVAR with the Pensacola diagnostic index. During sinusoidal stimulations, the skaters’ VOR, as compared with that of the controls, demonstrates a gain that is 27% lower (0.44 ± 0.12 vs. 0.58 ± 0.10; P < 0.01) and a phase advance (10 ± 12° vs. −0.3 ± 6.4°; P < 0.05). During velocity steps, the VOR gain is 32% lower among the skaters (0.52 ± 0.14 vs. 0.71 ± 0.12; P < 0.01), but there is no difference in time constant (10.8 ± 1.8 s vs. 10.5 ± 2.7 s; P = 0.78). Nauseogenic stimulation evokes significantly less MS in figure skaters than in control subjects (2.8 ± 2.8 vs. 16.2 ± 13.7; P < 0.01). Quantitative alterations in VOR parameters observed in figure skaters probably result from vestibular habituation induced by repeated unusual stimulations when practicing figure skating.     

Inter-individual differences in habitual sleep timing and entrained phase of endogenous circadian rhythms of BMAL1, PER2 and PER3 mRNA in human leukocytes

STUDY OBJECTIVES: Individual sleep timing differs and is governed partly by circadian oscillators, which may be assessed by hormonal markers, or by clock gene expression. Clock gene expression oscillates in peripheral tissues, including leukocytes. The study objective was to determine whether the endogenous phase of these rhythms, assessed in the absence of the sleep-wake and light-dark cycle, correlates with habitual sleep-wake timing. DESIGN: Observational, cross-sectional. SETTING: Home environment and Clinical Research Center. PARTICIPANTS: 24 healthy subjects aged 25.0 +/- 3.5 (SD) years. MEASUREMENTS: Actigraphy and sleep diaries were used to characterize sleep timing. Circadian rhythm phase and amplitude of plasma melatonin, cortisol, and BMAL1, PER2, and PER3 expression were assessed during a constant routine. RESULTS: Circadian oscillations were more robust for PER3 than for BMAL1 or PER2. Average peak timings were 6:05 for PER3, 8:06 for PER2, 15:06 for BMAL1, 4:20 for melatonin, and 10:49 for cortisol. Individual sleep-wake timing correlated with the phases of melatonin and cortisol. Individual PER3 rhythms correlated significantly with sleep-wake timing and the timing of melatonin and cortisol, but those of PER2 and BMAL1 did not reach significance. The correlation between sleep timing and PER3 expression was stronger in individuals homozygous for the variant of the PER3 polymorphism that is associated with morningness. CONCLUSIONS: Individual phase differences in PER3 expression during a constant routine correlate with sleep timing during entrainment. PER3 expression in leukocytes represents a useful molecular marker of the circadian processes governing sleep-wake timing.     

Gene deletion and allelic replacement in the filamentous fungus <Emphasis Type="Italic">Podospora anserina</Emphasis>

Gene replacement via homologous recombination is a fundamental tool for the analysis of gene function. However, this event is rare in organisms like the filamentous fungus Podospora anserina. We show here that deletion of the PaKu70 gene is an efficient strategy for improving gene manipulation in this organism. By using the ΔPaKu70 strain, it is now possible (1) to produce deletion mutants with an efficiency of 100%, (2) to achieve allelic exchange by introducing a mutated allele associated with a selection cassette at the locus, (3) to introduce a mutation in a gene without co-insertion of a selectable marker and without any modification of the target locus.     

Decision technologies as normative instruments: exposing the values within

OBJECTIVE: Describe some of the implicit normative and value judgments made in decision technologies development and use. METHODS: Using conceptual analysis of published models, we first outline some of the background assumptions of the knowledge translation/evidence-based medicine view of decision technologies. We then describe how normative judgments are embedded in decision technology development and use, drawing from empirical normative analysis of qualitative interviews with clinical practice guidelines developers (n=18) and users (n=17) in Canada and the UK. RESULTS: Normative judgments are made in at least three stages of decision technologies' "life cycle": (1) in the identification of contexts where decisions are seen as requiring support; (2) in determining what type of information and options should be part of the content of decision technologies; (3) in the negotiation between different actors regarding how effectiveness of decision technologies should be judged. These findings contrast with the knowledge translation/evidence-based medicine picture of decision technologies as neutral carriers of facts, or 'pure' synthesis of research evidence. CONCLUSION: Normative judgments are at play throughout the life cycle of decision technology development and use. References to scientific notions of truth and validity in the knowledge translation/evidence-based medicine model tend to overlook the socio-political dimension of decision technology development and implementation, as well as the contested nature of what "good decision" these technologies aim to support. PRACTICE IMPLICATIONS: Empirical normative analysis is an important research tool to better understand the values, interests and power relationships embedded in decision technologies. Such lines of inquiry could foster a more open debate among stakeholders - including patients and members of the public - regarding the norms promoted by practice guidelines and patient decision aids. It also offers new insights in understanding the problem of implementing decision technologies in clinical practice.     

Quality control assessment of human immunodeficiency virus type 2 (HIV-2) viral load quantification assays: results from an international collaboration on HIV-2 infection in 2006

Human immunodeficiency virus type 2 (HIV-2) RNA quantification assays used in nine laboratories of the ACHI(E)V(2E) (A Collaboration on HIV-2 Infection) study group were evaluated. In a blinded experimental design, laboratories quantified three series of aliquots of an HIV-2 subtype A strain, each at a different theoretical viral load. Quantification varied between laboratories, and international standardization of quantification assays is strongly needed.     

Phenotypic and functional reversal within the early human hematopoietic compartment

The fate of phenotypically defined human hematopoietic stem cells (hHSCs) in culture and the link between their surface marker expression profile and function are still controversial. We studied these aspects of hHSC biology by relating the expression of the early lineage markers (ELM) CD33, CD38, and CD71 on the surface of human umbilical cord blood (UCB) CD34(+) cells to their long-term nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse repopulation activity (LT-SRA). In uncultured UCB samples, LT-SRA was largely confined to the small CD34(+)ELM(-) cell fraction. CD34(+) cells expressing ELM markers at their surface usually lacked LT-SRA. After culturing UCB CD34(+) cells for 6 days in serum-free medium and on a feeder layer of Rat2 cells, the number of CD34(+)ELM(-) cells stayed roughly the same or showed a slight increase and the LT-SRA was preserved, suggesting a close association between LT-SRA and the CD34(+)ELM(-) phenotype. Indeed, transplantation of CD34(+)ELM(-) cells isolated from cultured UCB CD34(+) cells resulted in long-term hematopoietic reconstitution of conditioned NOD/SCID mice, whereas CD34(+)ELM(+) cells derived from the same cultures were devoid of LT-SRA. Remarkably, roughly 1% of the cells recovered from cultures initiated with isolated CD34(+)ELM(+) cells had lost ELM surface expression. Concurrently, the cultured CD34(+)ELM(+) cells acquired LT-SRA, suggesting that hematopoietic stem cells (HSCs) may arise by the dedifferentiation of early hematopoietic progenitor cells. The latter finding challenges the paradigm of unidirectional hematopoietic differentiation and opens new opportunities for HSC expansion prior to transplantation.     

Mutually exclusive redox forms of HMGB1 promote cell recruitment or proinflammatory cytokine release

Tissue damage causes inflammation, by recruiting leukocytes and activating them to release proinflammatory mediators. We show that high-mobility group box 1 protein (HMGB1) orchestrates both processes by switching among mutually exclusive redox states. Reduced cysteines make HMGB1 a chemoattractant, whereas a disulfide bond makes it a proinflammatory cytokine and further cysteine oxidation to sulfonates by reactive oxygen species abrogates both activities. We show that leukocyte recruitment and activation can be separated. A nonoxidizable HMGB1 mutant in which serines replace all cysteines (3S-HMGB1) does not promote cytokine production, but is more effective than wild-type HMGB1 in recruiting leukocytes in vivo. BoxA, a HMGB1 inhibitor, interferes with leukocyte recruitment but not with activation. We detected the different redox forms of HMGB1 ex vivo within injured muscle. HMGB1 is completely reduced at first and disulfide-bonded later. Thus, HMGB1 orchestrates both key events in sterile inflammation, leukocyte recruitment and their induction to secrete inflammatory cytokines, by adopting mutually exclusive redox states.     

Mineralocorticoid receptor is involved in rat and human ocular chorioretinopathy

Central serous chorioretinopathy (CSCR) is a vision-threatening eye disease with no validated treatment and unknown pathogeny. In CSCR, dilation and leakage of choroid vessels underneath the retina cause subretinal fluid accumulation and retinal detachment. Because glucocorticoids induce and aggravate CSCR and are known to bind to the mineralocorticoid receptor (MR), CSCR may be related to inappropriate MR activation. Our aim was to assess the effect of MR activation on rat choroidal vasculature and translate the results to CSCR patients. Intravitreous injection of the glucocorticoid corticosterone in rat eyes induced choroidal enlargement. Aldosterone, a specific MR activator, elicited the same effect, producing choroid vessel dilation -and leakage. We identified an underlying mechanism of this effect: aldosterone upregulated the endothelial vasodilatory K channel KCa2.3. Its blockade prevented aldosterone-induced thickening. To translate these findings, we treated 2 patients with chronic nonresolved CSCR with oral eplerenone, a specific MR antagonist, for 5 weeks, and observed impressive and rapid resolution of retinal detachment and choroidal vasodilation as well as improved visual acuity. The benefit was maintained 5 months after eplerenone withdrawal. Our results identify MR signaling as a pathway controlling choroidal vascular bed relaxation and provide a pathogenic link with human CSCR, which suggests that blockade of MR could be used therapeutically to reverse choroid vasculopathy.