Root cap size and shape influence responses to the physical strength of the growth medium in Arabidopsis thaliana primary roots.

During the progression of root in soil, root cap cells are the first to encounter obstacles and are known to sense environmental cues, thus making the root cap a potential mechanosensing site. In this study, a two-layered growth medium system was developed in order to study root responses to variations in the physical strength of the medium and the importance of the root cap in the establishment of these responses. Root growth and trajectory of primary roots of Arabidopsis seedlings were investigated using in vivo image analysis. After contact with the harder layer of the medium, the root either penetrated it or underwent rapid curvature, thus enabling reorientation of growth. We initially hypothesized that the root-cap structure would affect apex penetration and reorientation, with pointed caps facilitating and domed caps impeding root penetration. This hypothesis was investigated by analysing the responses of Arabidopsis mutants with altered root caps. The primary root of lines of the fez-2 mutant, which has fewer root-cap cell layers and a more pointed root cap than wild-type roots, showed impaired penetration ability. Conversely, smb-3 roots, which display a rectangular-shaped cap, showed enhanced penetration abilities. These results, which contradict our original hypothesis, reveal a role for resistance to buckling in determining root penetration abilities.

A new scenario for gravity detection in plants: the position sensor hypothesis.

The detection of gravity plays a fundamental role during the growth and evolution of plants. Although progress has been made in our understanding of the molecular, cellular and physical mechanisms involved in the gravity detection, a coherent scenario consistent with all the observations is still lacking. In this special issue article, we discuss recent experiments showing that the response to inclination of shoots is independent of the gravity intensity, meaning that the gravity sensor detects an inclination and not a force. This result questions some of the commonly accepted hypotheses and leads to propose a new 'position sensor hypothesis'. The implications of this new scenario are discussed in light of the different observations available in the literature.

Assessment of the global two-stage method to EC50 determination.

Preclinical studies of a new drug supply sets of concentration-effect observations. For each experiment, EC50 is estimated through fitting of the Emax model. Naive pooling of these individual estimates, also called the Standard Two-Stage method (STS), is usually performed. A better combination is obtained by the Global Two-Stage method (GTS) which takes into account the variability of the nonlinear regression estimation errors. The performances of STS and GTS are compared on real and simulated data. The results show that GTS performs better than STS in terms of bias or RMSE, especially in case of poorly designed experiments. Degradation of the quality of STS results in simulations appears to be mainly due to some experiments that are usually rejected by experimenters. Such rejections are avoided when using GTS, which hence is particularly suitable for systematic treatment of this kind of data.

[Bilateral optic neuropathy revealing systemic sarcoidosis]. / Neuropathie optique bilatérale révélatrice d'une sarcoïdose systémique.

INTRODUCTION: Although ocular involvement concerns about 25 to 60% of patients with systemic sarcoidosis, papilledema is a rare event. EXEGESIS: A 43-year-old man presented with left visual loss related to papillitis. Despite high-dose corticosteroids, visual loss became rapidly bilateral. Thoracic CT-scan showed mediastinal and parenchymal involvement. Histological study of lung, bronchial and lymphadenopathy biopsies displayed giant-cells granuloma without necrosis. Diagnosis of sarcoidosis complicated with optic neuropathy was made. Therapy combining prednisone, methotrexate and infliximab was started without significant improvement of visual acuity. CONCLUSION: This report underlines the potential severity of optic neuropathy in sarcoidosis.

[Clinical and biological efficacy of tocilizumab in giant cell arteritis: report of three patients and literature review]. / Efficacité clinique et biologique du tocilizumab au cours de la maladie de Horton : à propos de trois observations et revue de la littérature.

INTRODUCTION: Treatment of giant cell arteritis is based on prolonged corticosteroid therapy but adverse side effects are common especially in the elderly. CASE REPORTS: We report three patients with giant cell vasculitis treated by tocilizumab, an interleukin-6 receptor antibody, owing to resistance or intolerance to corticosteroid therapy. A favorable outcome was rapidly observed both on clinical and biological data allowing a corticoid therapy sparing. CONCLUSION: Tocilizumab is a promising treatment of giant cell arteritis but controlled trials are needed to confirm its efficacy.

[Immune-mediated necrotizing myopathy associated with antibodies to hydroxy-methyl-glutaryl-coenzyme A reductase]. / Myopathie nécrosante auto-immune associée aux anticorps anti-hydroxy-méthyl-glutaryl-coenzyme A réductase.

INTRODUCTION: Statins or 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (HMGCR) are among the most commonly prescribed treatment in France. They may be responsible for muscular intolerance with variable severity. They have been recently involved in the occurrence of an acquired inflammatory myopathy associated with anti-HMGCR antibodies. This new type of toxic myopathy remains poorly known by clinicians. OBSERVATION: We report a 61-year-old woman treated with a statin for many years who developed a lower and upper limb disabling myopathy with a rapid unfavourable course despite treatment withdrawal. Clinical history and investigations, especially including an assay for anti-HMGCR antibodies led to the diagnosis of autoimmune necrotizing myopathy with anti-HMGCR antibodies. Subsequent initiation of an immunosuppressive treatment by corticosteroids and methotrexate was effective. CONCLUSION: Statins may unmask or cause an autoimmune necrotizing myopathy associated with the presence of anti-HMGCR antibodies. Their identification is now routinely available. An immunosuppressive treatment is necessary and justified by the autoimmune nature of the disease.