Adult neurogenesis and specific replacement of interneuron subtypes in the mouse main olfactory bulb

Background  

New neurons are generated in the adult brain from stem cells found in the subventricular zone (SVZ). These cells proliferate in the SVZ, generating neuroblasts which then migrate to the main olfactory bulb (MOB), ending their migration in the glomerular layer (GLL) and the granule cell layer (GCL) of the MOB. Neuronal populations in these layers undergo turnover throughout life, but whether all neuronal subtypes found in these areas are replaced and when neurons begin to express subtype-specific markers is not known.     

Delayed contrast enhancement of MRI in hypertrophic cardiomyopathy

Fibrotic lesions in the myocardium exhibit delayed contrast enhancement (DCE) on MR images. On the other hand, plexiform fibrosis is observed in hypertrophic cardiomyopathy (HCM), indicating an association of this condition with the pathogenesis of heart failure and arrhythmia. To examine the occurrence and extent of DCE and its relation to cardiac function and arrhythmia in HCM, we studied 59 patients with HCM who had undergone MRI. The relationship of DCE to cardiac function and arrhythmia was further investigated. DCE occurred in 45 (76.3%) of the 59 patients with HCM, with a high frequency of localization in regions, where the right ventricle is attached. As for the relationship of DCE to cardiac function, a significant decrease (P=0.007) in cardiac function was observed in the group in which 4 or more segments exhibited DCE, compared with the group in which DCE was observed in 3 or less segments. Regarding the relationship of DCE to arrhythmia, both the occurrence of DCE and the extent of DCE were significantly larger (p<0.05, p=0.026, respectively) in the group with VT. These results indicate that DCE may save to identify severe cases of HCM on the basis of cardiac function, arrhythmia, and pathophysiological aspects.     

Image enhancement by adjusting the contrast of spatial frequencies

We demonstrate a brand-new method for image enhancement by adjusting the contrast of different spatial frequencies. Fine characteristics of an image are well enhanced with negligible side effects. This method is easy to implement owing to its simple optical basis.     

Perceptual contrast enhancement with dynamic range adjustment

Recent years, although great efforts have been made to improve its performance, few Histogram equalization (HE) methods take human visual perception (HVP) into account explicitly. The human visual system (HVS) is more sensitive to edges than brightness. This paper proposes to take use of this nature intuitively and develops a perceptual contrast enhancement approach with dynamic range adjustment through histogram modification. The use of perceptual contrast connects the image enhancement problem with the HVS. To pre-condition the input image before the HE procedure is implemented, a perceptual contrast map (PCM) is constructed based on the modified Difference of Gaussian (DOG) algorithm. As a result, the contrast of the image is sharpened and high frequency noise is suppressed. A modified Clipped Histogram Equalization (CHE) is also developed which improves visual quality by automatically detecting the dynamic range of the image with improved perceptual contrast. Experimental results show that the new HE algorithm outperforms several state-of-the-art algorithms in improving perceptual contrast and enhancing details. In addition, the new algorithm is simple to implement, making it suitable for real-time applications.     

Diffraction-induced edge contrast enhancement for terahertz imaging

Contrast enhancement is particularly important for imaging of weakly absorbing materials. We demonstrate the inherent contrast-enhancement effect at the edges of a transparent object by using a conventional pulsed terahertz imaging setup without additional modification of the system design. We provide both experimental and theoretical evidence suggesting that this effect is a consequence of the frequency-dependent energy loss of the terahertz radiation induced by edge diffraction. The influence of the phase step of the broadband terahertz pulses on the edge contrast is discussed.     

Impaired adult olfactory bulb neurogenesis in the R6/2 mouse model of Huntington's disease

Background  

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder linked to expanded CAG-triplet nucleotide repeats within the huntingtin gene. Intracellular huntingtin aggregates are present in neurons of distinct brain areas, among them regions of adult neurogenesis including the hippocampus and the subventricular zone/olfactory bulb system. Previously, reduced hippocampal neurogenesis has been detected in transgenic rodent models of HD. Therefore, we hypothesized that mutant huntingtin also affects newly generated neurons derived from the subventricular zone of adult R6/2 HD mice.     

Phase contrast enhancement in microscopy using spiral phase filtering

We demonstrate two methods based on Fourier plane filtering using (a) a fractional spiral phase plate (SPP) and (b) an off-axial SPP for phase contrast enhancement in optical microscopy. In comparison to previous works, a spatially incoherent LED is used in the Köhler illumination as the light source to illuminate the biological specimen. We demonstrate that both these methods can transform the phase specimen into a relief-like view even under such illumination. The degree and orientation of enhancement can be controlled by changing the phase structure of the filter. The SPP is displayed on a phase-only spatial light modulator, and can be integrated into the optical path of standard microscopes.     

Effective contrast enhancement method for color night vision

Image fusion refers to the techniques that integrate complementary information from multiple image sensors’ data in a way that makes the new images more suitable for human visual perception. The paper focuses on the low color contrast problem of linear fusion algorithms with color transfer method. Firstly, the contrast of infrared and visible images is enhanced using local histogram equalization and median filter. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To enhance the color contrast between the target and the background, the scaling factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot and cold targets are all popped out with intense colors while the background details present natural color appearance. Target detection experiments through target recognition area, detection rate, target-background discrimination also show that the presented method has a better performance than the former methods.     

Application of plasmonic silver films in histology for contrast enhancement

We have studied the absorption spectra and micrographs of sections of cells of the epithelium and andenocarcinoma of the large intestine, immobilized between standard glass slides and cover glasses and plasmonic silver films. We have shown that when we use a microtome technique and specially selected plasmonic silver films, we can achieve enhancement of the image contrast in analysis of the cell morphology as a result of the increase in the light absorption and scattering cross sections with the contrasting stains hematoxylin and eosin.     

On enhancement of spectral contrast in speech for hearing-impaired listeners

A digital processing method is described for altering spectral contrast (the difference in amplitude between spectral peaks and valleys) in natural utterances. Speech processed with programs implementing the contrast alteration procedure was presented to listeners with moderate to severe sensorineural hearing loss. The task was a three alternative (/b/,/d/, or /g/) stop consonant identification task for consonants at a fixed location in short nonsense utterances. Overall, tokens with enhanced contrast showed moderate gains in percentage correct stop consonant identification when compared to unaltered tokens. Conversely, reducing spectral contrast generally reduced percent correct stop consonant identification. Contrast alteration effects were inconsistent for utterances containing /d/. The observed contrast effects also interacted with token intelligibility.     

Infrared dim small target enhancement using toggle contrast operator

A new infrared dim small target enhancement algorithm based on toggle contrast operator is proposed. Toggle contrast operator is modified and used to construct operators using the image features derived from dilation and erosion operators. Then, based on the constructed operators, the operators which could be used to estimate the clutter background of the original infrared dim small target image are proposed using the same strategy as the definition of opening. Finally, the infrared dim small target is well enhanced through subtracting the estimated background from the original image. Experimental results on infrared images with different types of targets verified that the proposed method could effectively enhance infrared dim small target, which would be very useful for infrared dim small target detection and tracking.     

Fast color contrast enhancement method for color night vision

The increasing availability and deployment of imaging sensors operating in multiple spectral bands has led to a large research effort in color image fusion, resulting in a plethora of pixel-level image fusion algorithms. In this study a simple and fast fusion approach for color night vision is presented. The contrast of infrared and visible images is adjusted by local histogram equalization. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To obtain false color images possessing a natural day-time color appearance, this paper adopts an approach which transfers color from the reference to the fused images in a simplified Lab space. To enhance the contrast between the target and the background, a stretch factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot targets are popped out with intense colors while the background details present natural color appearance. Target detection experiments also show that the presented method has a better performance than the former methods, owing to the target recognition area, detection rate, color distance and running time.     

Protein expression differs between neural progenitor cells from the adult rat brain subventricular zone and olfactory bulb

Background  

Neural progenitor cells can be isolated from various regions of the adult mammalian brain, including the forebrain structures of the subventricular zone and the olfactory bulb. Currently it is unknown whether functional differences in these progenitor cell populations can already be found on the molecular level. Therefore, we compared protein expression profiles between progenitor cells isolated from the subventricular zone and the olfactory bulb using a proteomic approach based on two-dimensional gel electrophoresis and mass spectrometry. The subventricular zone and the olfactory bulb are connected by the Rostral Migratory Stream (RMS), in which glial fibrillary acidic protein (GFAP)-positive cells guide neuroblasts. Recent literature suggested that these GFAP-positive cells possess neurogenic potential themselves. In the current study, we therefore compared the cultured neurospheres for the fraction of GFAP-positive cells and their morphology of over a prolonged period of time.     

Multi-scale retinex-based contrast enhancement method for preserving the naturalness of color image

Optical Review - For images with insufficient visibility, image processing is required. Retinex theory is often implemented for image contrast enhancement for images with this characteristic. This...     

Ultrashort pulse temporal contrast enhancement based on noncollinear optical-parametric amplification

A pulse clean technique in time domain combining noncollinear optical-parametric amplification and second-harmonic generation is demonstrated. The measurement-limited >10(10) temporal contrast ratio of the 0.5?mJ/40?fs pulse near 800?nm is obtained over a large temporal range extending from <1?ps before the main pulse. The contrast ratio enhancement as fourth power of the initial contrast is demonstrated. The total efficiency is >6% for the 8.2?mJ/40?fs initial incident femtosecond pulse.     

Image contrast enhancement using adjacent-blocks-based modification for local histogram equalization

Infrared images usually have some non-ideal characteristics such as weak target-to-background contrast and strong noise. Because of these characteristics, it is necessary to apply the contrast enhancement algorithm to improve the visual quality of infrared images. Histogram equalization (HE) algorithm is a widely used contrast enhancement algorithm due to its effectiveness and simple implementation. But a drawback of HE algorithm is that the local contrast of an image cannot be equally enhanced. Local histogram equalization algorithms are proved to be the effective techniques for local image contrast enhancement. However, over-enhancement of noise and artifacts can be easily found in the local histogram equalization enhanced images. In this paper, a new contrast enhancement technique based on local histogram equalization algorithm is proposed to overcome the drawbacks mentioned above. The input images are segmented into three kinds of overlapped sub-blocks using the gradients of them. To overcome the over-enhancement effect, the histograms of these sub-blocks are then modified by adjacent sub-blocks. We pay more attention to improve the contrast of detail information while the brightness of the flat region in these sub-blocks is well preserved. It will be shown that the proposed algorithm outperforms other related algorithms by enhancing the local contrast without introducing over-enhancement effects and additional noise.