Micron and Microscopica Acta最新文献

Algorithms are presented for effective suppression of the quantum noise artifact that is inherent to three-dimensional confocal fluorescence microscopy images of extended spatial objects such as neurons. The specific advances embodied in these algorithms are as follows: (i) they incorporate an automatic and pattern-constrained three-dimensional segmentation of the image field, and use it to limit any smoothing to the interiors of specified image regions and hence avoid the blurring that is inevitably associated with conventional noise removal algorithms; (ii) they are ‘unsupervised’ in the sense that they automatically estimate and adapt to the unknown spatially and temporally varying noise level in the microscopy data. Fast computation is achieved by parallel computation methods, rather than by algorithmic or modelling compromises.

The quantum noise artifact is modelled using a mixture of spatially non-homogeneous Poisson point processes. The intensity of each component process is constrained to lie in specific intervals. A set of segmentation and edge-site variables are used to determine the intensity of the mixture process. Using this model, the noise-removal process is formulated as the joint optimal estimation of the segmentation labels, edge-sites and intensity of the mixture Poisson point process, subject to a combination of stochastic priors and syntactic pattern constraints. The computations proceed iteratively, starting from a set of approximate user-supplied, or default initial guesses of the underlying random process parameters. An Expectation Maximization algorithm is used to obtain a more precise characterization of these parameters, that are then input to a joint estimation algorithm.

Stereoscopic renderings of processed three-dimensional images of murine hippocampal neurons are presented to demonstrate the effectiveness of the method. The processed images exhibit increased contrast and significant smoothing and reduction of the background intensity while avoiding any blurring of the foreground neuronal structures.

An unusual type of corneal nipple pattern, with features different from the usual lower height (Group I) and greater height (Group II and III) nipples, has been detected in the corneal surface of the earwig, Forficula sp. However, the nipples show some similarities with each of the two above types possessing certain characters. The height of the nipples, their shape and arrangement in the facet suggest that the nipples may act as an anti-reflection device, and thus increase the intensity of transmitted light, thereby aiding scotopic vision of the insect.

Electron optical examination of reconstituted collagen fibrils exposed to tannic acid reveals marked changes in staining behaviour. Positive staining in solutions of tungstate salts, where uptake of the heavy metal anions occurs on the positively charged side-chains of arginyl, lysyl and hydroxylysyl residues, reveals some reduction in stain uptake following tannic acid treatment. This reduced uptake is consistent with inhibition of staining at residues known, from independent biochemical evidence, to interact with tannic acid. Negative staining shows that tannic acid introduces some additional bulk into the fibril structure, although this is not as great as that induced by glutaraldehyde fixation. Staining patterns from doubly fixed specimens, together with thermal stability measurements on collagen gels, show that tannic acid fixation does not preclude a subsequent reaction with glutaraldehyde.