Characterization of spatio-temporal dynamics of the constrained network of the filamentous fungus Podospora anserina using a geomatics-based approach.

In their natural environment, fungi are subjected to a wide variety of environmental stresses which they must cope with by constantly adapting the architecture of their growing network. In this work, our objective was to finely characterize the thallus development of the filamentous fungus Podospora anserina subjected to different constraints that are simple to implement in vitro and that can be considered as relevant environmental stresses, such as a nutrient-poor environment or non-optimal temperatures. At the Petri dish scale, the observations showed that the fungal thallus is differentially affected (thallus diameter, mycelium aspect) according to the stresses but these observations remain qualitative. At the hyphal scale, we showed that the extraction of the usual quantities (i.e. apex, node, length) does not allow to distinguish the different thallus under stress, these quantities being globally affected by the application of a stress in comparison with a thallus having grown under optimal conditions. Thanks to an original geomatics-based approach based on the use of automatized Geographic Information System (GIS) tools, we were able to produce maps and metrics characterizing the growth dynamics of the networks and then to highlight some very different dynamics of network densification according to the applied stresses. The fungal thallus is then considered as a map and we are no longer interested in the quantity of material (hyphae) produced but in the empty spaces between the hyphae, the intra-thallus surfaces. This study contributes to a better understanding of how filamentous fungi adapt the growth and densification of their network to potentially adverse environmental changes.

Prediction and experimental evidence of different growth phases of the Podospora anserina hyphal network.

Under ideal conditions, the growth of the mycelial network of a filamentous fungus is monotonous, showing an ever increasing complexity with time. The components of the network growth are very simple and based on two mechanisms: the elongation of each hypha, and their multiplication by successive branching. These two mechanisms are sufficient to produce a complex network, and could be localized only at the tips of hyphae. However, branching can be of two types, apical or lateral, depending on its location on the hyphae, therefore imposing the redistribution of the necessary material in the whole mycelium. From an evolutionary point of view, maintaining different branching processes, with additional energy needs for structure and metabolism, is intriguing. We propose in this work to discuss the advantages of each branching type using a new observable for the network growth, allowing us to compare growth configurations. For this purpose, we build on experimental observations of the Podospora anserina mycelium growth, enabling us to feed and constrain a lattice-free modeling of this network based on a binary tree. First, we report the set of statistics related to the branches of P. anserina that we have implemented into the model. Then, we build the density observable, allowing us to discuss the succession of growth phases. We predict that density over time is not monotonic, but shows a decay growth phase, clearly separated from an other one by a stationary phase. The time of appearance of this stable region appears to be driven solely by the growth rate. Finally, we show that density is an appropriate observable to differentiate growth stress.

Prediction and experimental evidence of the optimisation of the angular branching process in the thallus growth of Podospora anserina.

Based upon apical growth and hyphal branching, the two main processes that drive the growth pattern of a fungal network, we propose here a two-dimensions simulation based on a binary-tree modelling allowing us to extract the main characteristics of a generic thallus growth. In particular, we showed that, in a homogeneous environment, the fungal growth can be optimized for exploration and exploitation of its surroundings with a specific angular distribution of apical branching. Two complementary methods of extracting angle values have been used to confront the result of the simulation with experimental data obtained from the thallus growth of the saprophytic filamentous fungus Podospora anserina. Finally, we propose here a validated model that, while being computationally low-cost, is powerful enough to test quickly multiple conditions and constraints. It will allow in future works to deepen the characterization of the growth dynamic of fungal network, in addition to laboratory experiments, that could be sometimes expensive, tedious or of limited scope.

Liver fibrosis staging by computed tomography: Prospective randomized multicentric evaluation of image analyses.

AIM: Liver fibrosis staging is essential. We prospectively evaluated the liver fibrosis staging performance of computed tomography (CT). METHODS: 70 hepato-gastroenterology clinicians were randomized into three stratified groups with different image analyses of radiological semiology, i.e., on raw images (group 1) and on expert-annotated (group 2) and computerized-morphometry-enriched (group 3) images. Radiological fibrosis staging based on seven simple descriptors into four stages equivalent to Metavir stages (F0/1, F2, F3, F4=cirrhosis) was determined at baseline and after image analyses in 10 patients with chronic liver diseases (two per F) concordant for four independent fibrosis stagings including Metavir. 23,800 CT images were analysed, providing 1400 fibrosis stagings. RESULTS: Fibrosis staging: overall (3 groups) accuracy (correct classification rate) was, baseline: 43%, post-analysis: 60% (p < 0.001) without significant progression in group 1 (6%, p = 0.207) contrary to groups 2 (34%, p < 0.001) and 3 (13%, p = 0.007). Cirrhosis diagnosis: overall accuracy was, baseline: 84%, post-analysis: 89% (p < 0.001) without significant progression in group 1 (0%, p = 1) contrary to groups 2 (8%, p = 0.009) and 3 (7%, p = 0.015). Baseline AUROCs were good (≥0.83) for marked fibrosis (F≥3 or cirrhosis) in all groups. Post-analysis AUROCs became excellent (≥0.89) in group 2 for all diagnostic targets (≥0.98 for F≥3 and cirrhosis) and in group 3 for cirrhosis. In post-analysis group 2, discrimination between all F was excellent (especially, F1 from F0) with an Obuchowski index at 0.87. Negative and positive predictive values for marked fibrosis were 98% and 95%, respectively. CONCLUSION: Simple CT descriptors accurately discriminate all Metavir liver fibrosis stages.

Core level shifts as indicators of Cr chemistry on hydroxylated α-Al2O3(0001): a combined photoemission and first-principles study.

The Cr/α-Al2O3(0001) interface has been explored by X-ray photoemission spectroscopy, X-ray absorption spectroscopy (XAS) and ab initio first-principles calculations of core level shifts including final state effects. After an initial oxidation via a reaction with residual surface OH but no reduction of the alumina substrate, Cr grows in a metallic form without any chemical effect on the initially oxidized Cr. However, Cr metal lacks crystallinity. Long-range (reflection high energy electron diffraction) and short-range (XAS) order are hardly observed. Thus photoemission combined with atomistic simulations becomes a unique tool to explore the chemistry and environment at the Cr/alumina interface. Cr 2p, O 1s and Al 2s shifted components are all explained by the formation of moieties involving Cr3+ and/or Cr4+ and of metallic Cr0, which supports the previously found Cr buffer mechanism for poorly adhesive metals. Beyond the situation under study, the present data demonstrate the ability of a combined experimental and theoretical approach of core-level shifts to exhaustively describe the general case of disordered metal/oxide interfaces.

Gait Monitoring and Walk Distance Estimation With an Accelerometer During 6-Minute Walk Test.

BACKGROUND: The 6-min walk test (6MWT) encompasses potential and untapped information related to exercise capacity. However, this test does not yield any information about gait pattern. Recently, we used a ventilatory polygraph to reveal respiratory adaptation during the 6MWT with subjects having high or low body mass index (BMI). In this study, we aimed to determine gait parameters with the same device, which integrates an accelerometer. METHODS: Using a 30-m corridor, steps and U-turns were detected with a custom-made algorithm, compared to video recordings as a reference method, and analyzed offline. From the vertical acceleration signal, we were able to determine cadence and step length, and we could calculate the total distance covered in 6 min (6MWD). We then compared these variables between subjects with low BMI (n = 13 subjects) or high BMI (n = 29 subjects). RESULTS: Steps and U-turn detection correlated with video results (r = 0.99, P < .001 for both). The 6MWD calculation was also in line with classical measurements (r = 0.99, P < .001). High BMI subjects had a significantly lower 6MWD, cadence, and step length than controls (P < .001 for each). Walking speed was more closely correlated with step length (r = 0.92) than with cadence (r = 0.64) for both groups. CONCLUSION: Our results demonstrated that a ventilatory polygraph with an embedded accelerometer can be used to detect steps and U-turns, and to calculate 6MWD. This method is sufficiently sensitive to characterize significant BMI-dependent differences in gait pattern during a 6MWT and appears to be a promising tool for routine clinical use.

Validity of thoracic respiratory inductive plethysmography in high body mass index subjects.

We aim to evaluate thoracic respiratory inductive plethysmography (RIP) in high body mass index (BMI) subjects with a pneumotachometer (PT) as a reference. We simultaneously evaluated spontaneous breathing by RIP and PT in 10 low and 10 high BMI subjects at rest and in moderate exercise. We then recorded RIP amplitude with different excursions mimicking respiratory thoracic deformation, with different sizes of RIP belts surrounding cylinders of different perimeters with or without deformable foam simulating adipose tissue. RIP responses correlated with PT values in low and high BMI groups for inspiratory time (r=0.86 and r=0.91, respectively), expiratory time (r=0.96 and r=0.91, respectively) and amplitude (r=0.82 for both) but with a bias (-0.23±0.25L) for high BMI subjects. ANOVA revealed the effects of perimeter and simulated adiposity (p<0.001 for both). We concluded that thoracic perimeter and deformity of adipose tissue are responsible for biases in RIP response in high BMI subjects.

Postural- and respiratory-related activities of abdominal muscles during post-exercise hyperventilation.

The present study focuses on the role of superficial abdominal muscles revealed by electromyographic recordings during the maintenance of a bipedal stance perturbed by post-exercise hyperventilation. Twelve healthy subjects performed six 30-s postural tests: one pre-exercise test while breathing quietly, then one test every minute for the 5 min immediately following a maximum-intensity, incremental cycling exercise test. Displacement of the centre of pressure in the sagittal plane was monitored over time. Myoelectric activities of the obliquus externus (OE), obliquus internus (OI) and rectus abdominis (RA) muscles were recorded by surface electromyography (EMG). Metabolic parameters were measured with a portable telemetric device. The change in ventilatory drive induced by exercise was accompanied by a significant increase in both postural sway parameters and EMG activities. For OE and OI, the increased EMG activities were prominent during expiration, whereas OI was silent during inspiration. OE and RA were activated during both expiration and inspiration. It is concluded that the compensation of respiratory disturbances of the erect posture appears to be less effective when minute ventilation increases. The patterns of muscle activity suggest that abdominal muscles are controlled differentially and that their functional coordination is dependent on the respiratory demand.

Isokinetic testing of evertor and invertor muscles in patients with chronic ankle instability.

Ankle sprains are among the most common sport-related injuries and can lead to chronic ankle instability. Impaired sensorimotor function of the ankle musculature is often suggested as a cause. The current study sought to assess and compare the isokinetic performance and electromyographic patterns of evertor and invertor muscles in patients with chronic ankle instability and in a control group. Twelve patients with chronic ankle instability and twelve healthy subjects were included. Isokinetic eccentric and concentric testing at various angular velocities was performed for eversion and inversion movements. The corresponding myoelectric activities of the fibularis longus and tibialis anterior muscles were quantified from surface electromyographic recordings by computing average root mean square values. Patients had lower myoelectric activity of the evertor and invertor muscles than controls did; this difference could account for the eccentric weakness associated with ankle instability. Functional strength ratios revealed a dynamic strength imbalance in unstable ankle patients and that may contribute to recurrent injury. Our findings suggest that rehabilitation programs for unstable ankle patients must be focused on the motor control of eccentric contractions of the ankle evertors and invertors, to boost these muscles' contribution to ankle stabilization.

Postural control and ventilatory drive during voluntary hyperventilation and carbon dioxide rebreathing.

The present study sought to establish links between hyperventilation and postural stability. Eight university students were asked to stand upright under two hyperventilation conditions applied randomly: (1) a metabolic hyperventilation induced by 5 min of hypercapnic-hyperoxic rebreathing (CO(2)-R); and, (2) a voluntary hyperventilation (VH) of 3 min imposed by a metronome set at 25 cycles per min. Recordings were obtained with eyes open, with the subjects standing on a force plate over 20-s periods. Ventilatory response, displacements in the centre of pressure in both the frontal and sagittal planes and fluctuations in the three planes of the ground reaction force were monitored in the time and frequency domains. Postural changes related to respiratory variations were quantified by coherence analysis. Myoelectric activities of the calf muscles were recorded using surface electromyography. Force plate measurements revealed a reduction in postural stability during both CO(2)-R and VH conditions, mainly in the sagittal plane. Coherence analysis provided evidence of a ventilatory origin in the vertical ground reaction force fluctuations during VH. Electromyographic analyses showed different leg muscles strategies, assuming the existence of links between the control of respiration and the control of posture. Our results suggest that the greater disturbing effects caused by voluntary hyperventilation on body balance are more compensated when respiration is under automatic control. These findings may have implications for understanding the organisation of postural and respiratory activities and suggest that stability of the body may be compromised in situations in which respiratory demand increases and requires voluntary control.

[On frailty as a geriatric concept]. / Remarques sur le concept gériatrique de fragilité

Frailty as a geriatric concept has been considered as the beginning of a rapid downward spiral towards death. Nevertheless, the French word "fragilité" is different from frailty - and probably an erroneous translation. Furthermore, frailty can be considered as belonging to the human condition as such.

Effects of a 12-week Tai Chi Chuan program versus a balance training program on postural control and walking ability in older people.

UNLABELLED: Lelard T, Doutrellot P-L, David P, Ahmaidi S. Effects of a 12-week Tai Chi Chuan program versus a balance training program on postural control and walking ability in older people. OBJECTIVE: To compare the respective effects of 2 balance training programs: a Tai Chi (TC) program and a balance training program on static postural control and walking ability. DESIGN: Randomized controlled trial. SETTING: General community. PARTICIPANTS: Older subjects (N=28) participated in the study. INTERVENTIONS: The TC group (n=14; mean age +/- SD, 76.8+/-5.1y) and the balance training group (n=14; 77.0+/-4.5y) were both trained for 12 weeks. MAIN OUTCOME MEASURES: Static postural control was assessed via measurement of center of pressure sway under eyes open (EO) and eyes closed (EC) conditions. Walking speed over a 10-meter course was also assessed. RESULTS: After the 12-week training period, there were no significant differences in walking speed or postural parameters in either the EO or EC conditions for the TC and balance training groups. Performance in the EC condition was lower than in the EO condition in pretest and posttest for the balance training and TC groups. The Romberg quotient (EO/EC ratio) was significantly higher after the balance training program than the TC program (P<.05). CONCLUSIONS: We cannot conclude that the balance training program has better effects than the TC program on postural control or walking ability. None of the outcome measures showed significant change posttraining in either the TC or the balance training groups. However, the differences described in the Romberg quotient after the training period between the TC and the balance training groups suggest that TC should be helpful to limit the deleterious effects of eye closure on postural balance.

Neuromuscular efficiency of the rectus abdominis differs with gender and sport practice.

The purpose of this investigation was to distinguish the abilities of the rectus abdominis (RA) muscle according to gender and sport training by means of neuromuscular parameters extracted from electromyography (EMG)-torque relationships. Thirty-eight healthy students, divided into 4 groups (i.e., 8 male runners, 10 female gymnasts, 12 male controls, and 8 female controls) were asked to perform 6 seconds of isometric trunk flexions at 20%, 25%, 75%, and 100% of their maximal voluntary contraction. Flexion torque and surface EMG of the RA muscle were recorded simultaneously to construct a EMG-torque relationship. Under maximal and submaximal conditions, an index of neuromuscular efficiency (NME) was determined to characterize the capacity of the RA muscle to develop a torque. At each level of contraction, the area of data scattering (ADS), reflecting torque and EMG fluctuations, was computed to express the capacity to maintain a constant target torque. Flexion torque, NME, and ADS values differed significantly between genders, but when data were related to anthropometric characteristics, no difference was observed. Although runners were not distinguished from male controls, gymnasts had higher flexion torque, higher NME, and lower ADS values than female controls had. These differences should reflect neural and muscular adaptations linked to the specificity of gymnastic training. These findings revealed different functional abilities of the RA muscle, according to gender and sport practices. The indices of neuromuscular capacities used in this study could constitute complementary tools to athletic trainers and professionals in sports medicine for evaluating and following, during sport-specific training programs, the abdominal muscle performance implied in force transfers with a lower cost and lower risks of back pain.

Acolhimento ou rejeição: a interpretação como relação problemática com a alteridade - acerca do verbo alemão dolmetschen / Acceptance or rejection: interpretation as a problematic relationship with alterity - about the German verb dolmetschen

Este artigo aborda o problema da comunicação, a denominada "barreira lingüística", a partir de uma reflexão sobre o termo alemão Dolmetscher, que serve para designar aquele que exerce a atividade de tradução, na grande maioria das vezes, da passagem oral de uma língua a outra. Essa atividade é considerada como apenas um dos problemas da comunicação. Por meio da investigação acerca da origem deste termo alemão, enfatiza-se uma dupla vertente relacionada a essa atividade: uma de rejeição, outra de acolhimento. Por um lado, este termo origina-se de vocábulos estrangeiros ao próprio alemão, denotando sua face de rejeição e ressaltando a incomunicabilidade. Por outro, este termo em sua origem designava não apenas o intérprete, mas o mediador ou conciliador entre duas partes adversas, assinalando a sua dimensão de acolhimento.

This article approaches the issue of communication, particularly the "linguistic barrier", based upon a reflection on the German term Dolmetscher, which designates an individual that "translates" orally one language to another. This activity is considered only one of several communication problems. By investigating the origin of the German term, we emphasize the double nature related with this activity: one of rejection, and another one of acceptance. On one hand this term originates from words that are strangers to the German language, highlighting the issues of rejection and non-communicability. On the other, this term, in its origin, designates not only the interpreter, but the mediator between adversary parts, highlighting the acceptance dimension.