Near-Field Scanning Optical Microscope Combined with Digital Holography for Three-Dimensional Electromagnetic Field Reconstruction

International audienceNear-field scanning optical microscopy (NSOM) has proven to be a very powerful imaging technique that allows overcoming the diffraction limit and obtaining information on a scale much smaller than what can be achieved by classical optical imaging techniques. This is achieved using nanosized probes that are placed in close proximity to the sample surface, and thus allow the detection of evanescent waves that contain important information about the properties of the sample on a subwavelength scale. In particular, some aperture-based probes use a nanometer-sized hole to locally illuminate the sample. The far-field radiation of such probes is essential to their imaging properties, but cannot be easily estimated since it highly depends on the environment with which it interacts. In this chapter, we tackle this problem by introducing a microscopy method based on full-field off-axis digital holography that allows us to study in details the three-dimensional electromagnetic field scattered by a NSOM probe in different environments. We start by describing the NSOM and holography techniques independently, and continue by highlighting the advantage of combining both methods. We present a comparative study of the reconstructed light from a NSOM tip located in free space or coupled to transparent and plasmonic media. While far-field methods, such as back focal plane imaging, can be used to infer the directionality of angular radiation patterns, the advantage of our technique is that a single hologram contains information on both the amplitude and phase of the scattered light, allowing to reverse numerically the propagation of the electromagnetic field towards the source. We also present Finite Difference Time Domain (FDTD) simulations to model the radiation of the NSOM tip as a superposition of a magnetic and an electric dipole. We finally propose some promising applications that could be performed with this combined NSOM-holography technique

Characterization of metaplastic and heterotopic epithelia in the human gastrointestinal tract by the expression pattern of acyl-CoA synthetase 5

Metaplastic and heterotopic epithelia are frequently found in the human intestine. The recently cloned human acyl-CoA synthetase 5 (ACS5) is a key enzyme in providing cytosolic acyl-CoA thioesters. The aim of the study was to identify and to locate the expression of ACS5 in the gastric body and the small intestine with metaplasia or heterotopia by different methods. In the normal gastrointestinal tract, ACS5 was predominantly found in the villus epithelium of the small intestine, but not in the gastric mucosa. Of note, strong expression of ACS5 was also detectable in intestinal metaplasia of the stomach. Inversely, ACS5 expression could neither be detected in heterotopic gastric mucosa of the corpus type nor in gastric, pseudopyloric, or antral metaplasia of the small intestine. In conclusion, our data implicate that ACS5 is a suitable differentiating marker molecule in the gastrointestinal tract

Expression of clusterin in Crohn's disease of the terminal ileum

Crohn's disease (CD) is a chronic inflammatory intestinal disorder with disturbance and injury of the intestinal mucosal barrier, in which various proinflammatory molecules as well as molecules with antiinflammatory activity and cytoprotective function are found to be expressed. We investigated whether clusterin, a multifunctional cytoprotective protein, is upregulated in Crohn's disease, because augmented expression of clusterin is seen in many organs following various forms of tissue injury. Human actively and inactively inflamed ileal tissues from CD patients as well as normal intestinal specimens from control patients (normal ileum) were investigated by Western blot analysis, immunohistochemisty and in situ hybridization. As compared with controls, a strongly enhanced expression of clusterin was found in CD tissues, correlating with disease activity. Immunohistochemistry and in situ hybridization analysis revealed foci of crypts almost completely lined by clusterin expressing enterocytes in CD, a feature that was never seen in controls. Such crypts appeared especially within the morphologically intact mucosa apart from erosive or ulcerative lesions. Besides epithelia, clusterin was also expressed by inflammatory mononuclear cells. Enhanced expression of clusterin by crypt epithelia might reflect a cytoprotective function of the protein in order to prevent further injury of the intestinal mucosal barrier in CD

Distinct expression of calnexin in major human salivary glands

Calnexin (Cnx) has been characterized as a membrane-bound protein that transiently interacts in a unique chaperone system with newly synthesized glycoproteins in order to allow the establishment of their proper tertiary and, in most cases, quarternary structures. The aim of the study was to identify and to locate the expression of Cnx in the three major salivary glands of humans by different methods. Strong expression of Cnx protein and mRNA were generally found in serous salivary secretory units. With regard to mucous secretory units, expression of Cnx was only detectable at a low level in mucous acinar cells of sublingual glands, but not of submandibular glands. Expression of Cnx was always preserved in the surface epithelium of intralobar and interlobular duct segments. In addition, expression of Cnx was detected in sebaceous glands of parotid tissues, with a distribution pattern resembling that seen in sebaceous glands of the normal skin. In conclusion, production of saliva is associated with the expression of Cnx. Synthesis of molecules in mucous secretory units is not necessarily associated with a strong Cnx expression, whereas synthesis in serous secretory units apparently is. The tissue-specific Cnx expression is also paralleled by the observation that the secretions produced by the major salivary glands differ in their composition and amoun

Permian detachment faulting and syntectonic magmatism constrained by U-Pb LA-ICP-MS on zircon in the Orobic Anticline, Italy

The Grassi Detachment Fault is an Early Permian, low-angle extensional structure located in the Orobic Anticline. It separates the Variscan Basement in its footwall from the volcanic and sedimentary rocks of the Early Permian Collio Formation in its hanging wall. Its textures indicate a top-to-the-southeast displacement. The footwall basement consist of the Variscan Morbegno Gneiss and two granitoid intrusions, the Val Biandino Quarz Diorite (VBQD) and the Valle Biagio Granite (VBG). The former is syntectonic with respect to the detachment, whereas for the latter, the relation to the detachment is unknown. Volcanic rocks of the Collio Formation in the hanging wall may represent the extrusive part of the magmatic system. In the study area in the western part of the Orobic anticline, several faults and shear zones are exposed: (1) The top-SE Grassi Detachment Fault. It is truncated by the unconformably overlying, post-rift, Late Permian Verrucano Lombardo towards the NW. This reflects the eroded culmination of a Permian metamorphic core complex. (2) The Sasso Rosso Fault, a steeply NW-dipping, brittle normal in the footwall between VBQD and VBG. It is also sealed by the basal unconformity of the Verrucano Lombardo. (3) Several minor south-directed Alpine thrusts, duplicating the lithostratigraphy, including the detachment. (4) The Biandino Fault, a steeply SE-dipping Alpine backthrust, overprinting the detachment as well as the Alpine forethrusts. U-Pb zircon geochronology using LA-ICP-MS yielded concordant ages of 293.2 ± 4.9 Ma for the VBQD and 286.0 ± 4.8 Ma for the VBG. These ages coincide with the beginning of the Collio volcanism and with the emplacement of mafic melts in the lower crust of the Ivrea Zone, indicating that the volcanics, granitoids and mafic intrusions belonged to a crustal-scale magmatic system. Since structural relations indicate contemporaneity of VBQD intrusion and extensional detachment faulting, it results that the Early Permian magmatism occurred in a framework of core-complex style extension