Sinking rates, orientation, and behavior of pennate diatoms.

Phytoplankton cells are now recognized as dynamic entities rather than as passive and isolated particles because they can actively modulate impacts of selection factors (nutrients, light, turbidity, and mixing) through a wide range of adaptations. Cell shape and/or chain length modulation is one of these processes but has predominantly been studied as an adaptation or an acclimatation to a specific growth limitation (light, nutrients, predation, etc.). In this study we have demonstrated that cell shape and size may have greater roles than previously known in phytoplankton ecology and species adaptation by permitting cell-to-cell signaling and more complex ecological processes that result from it. By exploring microscale biophysical interactions that lead to specific cell reorientation processes, we demonstrated that cell geometry not only modulates cell sinking rates but can also provide fast sensor responses to the cells' environment. Although gyrotaxis has been described in detail for motile phytoplankton cells, our findings illustrate that the reorientation process described here can occur even in non-motile cells within their natural environment. An additional consistent behavior was also recently described for a diatom species (Pseudo-nitzschia delicatessima), and with this study, we extend this observation to Pseudo-nitzschia pungens and Pseudo-nitzschia fraudulenta. Our observations emphasize the generality of this process, which adds a new level of complexity to our understanding of cellular interactions and their network of sensors.

3D analysis of gerbil cochlea with cochlear implant.

OBJECTIVES: To assess a clearing protocol using ethyl cinnamate, an organic substance which is non-toxic for humans, and its value in light-sheet microscopy study of post-implantation cochlear damage in the Mongolian gerbil. MATERIAL AND METHODS: The animals underwent right cochlear implantation in the round window by a retroauricular approach. They were then euthanized 10 weeks after implantation (electrode array in place). The cochleae were prepared according to a 29-day protocol including steps of fixation, microdissection, decalcification, permeabilization, blocking, fluorescent immunolabeling, dehydration and finally clearing in ethyl cinnamate solution. Acquisition of transparent cochleae was performed by light-sheet microscopy. Imaris software was then used for 3D analysis. RESULTS: The transparent cochleae had not undergone any shrinkage or any significant architectural changes. Six cochleae were acquired by light-sheet microscopy, allowing good visibility of the whole cochlea. 3D immunofluorescence analysis of the cochlea provided sufficient image resolution for analysis of the spiral ganglion neurons and assessment of the fibrotic tissue reaction surrounding the electrode array. CONCLUSION: The ethyl cinnamate clearing protocol was effective for light-sheet microscopy analysis of the whole Mongolian gerbil cochlea with the implant left in situ. This technique is suitable for the study of post-implantation cell and tissue damage in the same sample, without the potential toxicity of other methods described to date.

Mitochondrial alterations triggered by repeated exposure to fine (PM2.5-0.18) and quasi-ultrafine (PM0.18) fractions of ambient particulate matter.

Nowadays ambient particulate matter (PM) levels still regularly exceed the guideline values established by World Health Organization in most urban areas. Numerous experimental studies have already demonstrated the airway toxicity of the fine fraction of PM (FP), mainly triggered by oxidative stress-induced airway inflammation. However, only few studies have actually paid close attention to the ultrafine fraction of PM (UFP), which is likely to be more easily internalized in cells and more biologically reactive. Mitochondria are major endogenous sources of reactive oxygen species (ROS) through oxidative metabolism, and coordinate many critical cellular signaling processes. Mitochondria have been often studied in the context of PM toxicity and generally associated with apoptosis activation. However, little is known about the underlying adaptation mechanisms that could occur following exposure at sub-apoptotic doses of ambient PM. Here, normal human bronchial epithelial BEAS-2B cells were acutely or repeatedly exposed to relatively low doses (5 µg.cm-2) of FP (PM2.5-0.18) or quasi-UFP (Q-UFP; PM0.18) to better access the critical changes in mitochondrial morphology, functions, and dynamics. No significant cytotoxicity nor increase of apoptotic events were reported for any exposure. Mitochondrial membrane potential (ΔΨm) and intracellular ATP content were also not significantly impaired. After cell exposure to sub-apoptotic doses of FP and notably Q-UFP, oxidative phosphorylation was increased as well as mitochondrial mass, resulting in increased production of mitochondrial superoxide anion. Given this oxidative boost, the NRF2-ARE signaling pathway was significantly activated. However, mitochondrial dynamic alterations in favor of accentuated fission process were observed, in particular after Q-UFP vs FP, and repeated vs acute exposure. Taken together, these results supported mitochondrial quality control and metabolism dysfunction as an early lung underlying mechanism of toxicity, thereby leading to accumulation of defective mitochondria and enhanced endogenous ROS generation. Therefore, these features might play a key role in maintaining PM-induced oxidative stress and inflammation within lung cells, which could dramatically contribute to the exacerbation of inflammatory chronic lung diseases. The prospective findings of this work could also offer new insights into the physiopathology of lung toxicity, arguably initiate and/or exacerbate by acutely and rather repeated exposure to ambient FP and mostly Q-UFP.

Optimised immunofluorescence method on cleared intact Mongolian gerbil cochlea.

Immunofluorescence on cleared intact cochlea allows detailed analysis of the cochlear ultrastructure, while avoiding the problems of dissection and serial sections. Protocols have been developed for mice and Mongolian gerbils. This technical note proposes a detailed and optimised immunofluorescence protocol in the Mongolian gerbil comprising significant quantitative and qualitative improvements. This protocol sequentially comprises: fixation (1 day), decalcification (6 days), pre-treatment (7.5hours), immunolabelling (42hours), dehydration and clearing (23hours), followed by mounting and laser scanning confocal microscopy acquisition. This protocol has been optimised in terms of duration (10 days versus 13 days) with a reduction of the number of steps, improvement of the specificity of immunolabelling and optimisation of the quality of the results obtained. This technical note provides a detailed description of this protocol.

Imaging and cell count in cleared intact cochlea in the Mongolian gerbil using laser scanning confocal microscopy.

OBJECTIVES: To draw up a clearing protocol for Mongolian gerbil cochlea, and to assess the feasibility of quantifying and analyzing 3D cell architecture in the transparent cochleae. MATERIALS AND METHODS: Freshly dissected inner ears were prepared on a 13-day protocol: fixation, microdissection, post-fixation, decalcification, pretreatment (signal enhancement, permeabilization and blocking), fluorescent labeling (indirect immunolabeling and direct labeling), dehydration, clearing in Spalteholz solution (MSBB: methyl salicylate and benzyl benzoate) and mounting. Image acquisition used laser scanning confocal microscopy. ImageJ software was used to measure the length of the organ of Corti thus available for analysis and to count inner and outer hair cells. RESULTS: Four cochleas underwent imaging. 3D reconstruction enabled organ of Corti length to be measured, at a mean 1269±346µm. Mean inner and outer hair-cell count per organ of Corti length was 142±44 and 400±122, respectively. CONCLUSION: Cochlear clearing by MSBB was feasible in Mongolian gerbils and provided high-resolution immunofluorescence-labeled inner-ear images. To our knowledge, this was the first application of the technique in this species. Cell count could thus be performed along the organ of Corti length without traumatic dissection.

[Primary esophageal localization of non-Hodgkin's lymphoma. Apropos of a case]. / Localisation oesophagienne primitive de lymphome non hodgkinien. A propos d'un cas.

Authors present a case of primary oesophageal lymphoma, in view of the great rarity of the neoplasm in this place.

[Mediofacial necrosis and malignant centrofacial granuloma. Apropos of 8 cases and 1 with atypical localizations]. / Nécroses médio-faciales et granulome malin centro-facial. A propos de 8 cas et d'une localisation atypique.

Since the first descriptions by McBride and then Stewart, and later reports by wegener, numerous publications have contained data emphasizing the diagnostic and classification difficulties of these affections, 450 cases having been documented up to the present times. Findings clearly demonstrate that mediofacial necrosis differs greatly by its pathological, etiopathogenic and out come features, and particularly the localization of the lesions. Eight case were investigated, and conclusions drawn that it was important to identify the different affections grouped under the term "mediofacial necrosis", in order to isolate cases of pure malignant centrofacial granuloma, which have no detectable etiology and cannot be integrated in another nosological framework.

[Value of immediate prosthetic technics in hemiresections of the face]. / Intérêts des techniques prothétiques immédiates dans les hémi-résections du massif facial.

A brief historical survey is completed by the presentation of a technique for immediate prosthetic rehabilitation during facial hemiresections for malignant tumors. The method presents multiple advantages when compared to typical drainage procedures from the physiological, mechanical and psychological points of view. A detailed description of the introduction of this prosthesis is followed by a brief summary of postoperative sequelae and the advantages the method supplies due to its extreme simplicity in application.