IsletSwipe, a mobile platform for expert opinion exchange on islet graft images

We previously developed a deep learning-based web service (IsletNet) for an automated counting of isolated pancreatic islets. The neural network training is limited by the absent consensus on the ground truth annotations. Here, we present a platform (IsletSwipe) for an exchange of graphical opinions among experts to facilitate the consensus formation. The platform consists of a web interface and a mobile application. In a small pilot study, we demonstrate the functionalities and the use case scenarios of the platform. Nine experts from three centers validated the drawing tools, tested precision and consistency of the expert contour drawing, and evaluated user experience. Eight experts from two centers proceeded to evaluate additional images to demonstrate the following two use case scenarios. The Validation scenario involves an automated selection of images and islets for the expert scrutiny. It is scalable (more experts, images, and islets may readily be added) and can be applied to independent validation of islet contours from various sources. The Inquiry scenario serves the ground truth generating expert in seeking assistance from peers to achieve consensus on challenging cases during the preparation for IsletNet training. This scenario is limited to a small number of manually selected images and islets. The experts gained an opportunity to influence IsletNet training and to compare other experts' opinions with their own. The ground truth-generating expert obtained feedback for future IsletNet training. IsletSwipe is a suitable tool for the consensus finding. Experts from additional centers are welcome to participate.

Wnt/β-Catenin Signaling Promotes Differentiation of Ischemia-Activated Adult Neural Stem/Progenitor Cells to Neuronal Precursors

Modulating endogenous regenerative processes may represent a suitable treatment for central nervous system (CNS) injuries, such as stroke or trauma. Neural stem/progenitor cells (NS/PCs), which naturally reside in the subventricular zone (SVZ) of the adult brain, proliferate and differentiate to other cell types, and therefore may compensate the negative consequences of ischemic injury. The fate of NS/PCs in the developing brain is largely influenced by Wingless/Integrated (Wnt) signaling; however, its role in the differentiation of adult NS/PCs under ischemic conditions is still enigmatic. In our previous study, we identified the Wnt/β-catenin signaling pathway as a factor promoting neurogenesis at the expense of gliogenesis in neonatal mice. In this study, we used adult transgenic mice in order to assess the impact of the canonical Wnt pathway modulation (inhibition or hyper-activation) on NS/PCs derived from the SVZ, and combined it with the middle cerebral artery occlusion (MCAO) to disclose the effect of focal cerebral ischemia (FCI). Based on the electrophysiological properties of cultured cells, we first identified three cell types that represented in vitro differentiated NS/PCs – astrocytes, neuron-like cells, and precursor cells. Following FCI, we detected fewer neuron-like cells after Wnt signaling inhibition. Furthermore, the immunohistochemical analysis revealed an overall higher expression of cell-type-specific proteins after FCI, indicating increased proliferation and differentiation rates of NS/PCs in the SVZ. Remarkably, Wnt signaling hyper-activation increased the abundance of proliferating and neuron-like cells, while Wnt pathway inhibition had the opposite effect. Finally, the expression profiling at the single cell level revealed an increased proportion of neural stem cells and neuroblasts after FCI. These observations indicate that Wnt signaling enhances NS/PCs-based regeneration in the adult mouse brain following FCI, and supports neuronal differentiation in the SVZ.

A piecewise monotone subgradient algorithm for accurate L¹-TV based registration of physical slices with discontinuities in microscopy

Image registration tasks are often formulated in terms of minimization of a functional consisting of a data fidelity term penalizing the mismatch between the reference and the target image, and a term enforcing smoothness of shift between neighboring pairs of pixels (a min-sum problem). Most methods for deformable image registration use some form of interpolation between matching control points. The interpolation makes it impossible to account for isolated discontinuities in the deformation field that may appear, e.g., when a physical slice of a microscopy specimen is ruptured by the cutting tool. For registration of neighboring physical slices of microscopy specimens with discontinuities, Janácek proposed an L¹-distance data fidelity term and a total variation (TV) smoothness term, and used a graph-cut (GC) based iterative steepest descent algorithm for minimization. The L¹-TV functional is nonconvex; hence a steepest descent algorithm is not guaranteed to converge to the global minimum. Schlesinger presented transformation of max-sum problems to minimization of a dual quantity called problem power, which is--contrary to the original max-sum functional--convex. Based on Schlesinger's solution to max-sum problems we developed an algorithm for L¹-TV minimization by iterative multi-label steepest descent minimization of the convex dual problem. For Schlesinger's subgradient algorithm we proposed a novel step control heuristics that considerably enhances both speed and accuracy compared with standard step size strategies for subgradient methods. It is shown experimentally that our subgradient scheme achieves consistently better image registration than GC in terms of lower values both of the composite L¹-TV functional, and of its components, i.e., the L¹ distance of the images and the transformation smoothness TV, and yields visually acceptable results even in cases where the GC based algorithm fails. The new algorithm allows easy parallelization and can thus be sped up by running on multi-core graphic processing units.

Nonrigid registration of CLSM images of physical sections with discontinuous deformations

When biological specimens are cut into physical sections for three-dimensional (3D) imaging by confocal laser scanning microscopy, the slices may get distorted or ruptured. For subsequent 3D reconstruction, images from different physical sections need to be spatially aligned by optimization of a function composed of a data fidelity term evaluating similarity between the reference and target images, and a regularization term enforcing transformation smoothness. A regularization term evaluating the total variation (TV), which enables the registration algorithm to account for discontinuities in slice deformation (ruptures), while enforcing smoothness on continuously deformed regions, was proposed previously. The function with TV regularization was optimized using a graph-cut (GC) based iterative solution. However, GC may generate visible registration artifacts, which impair the 3D reconstruction. We present an alternative, multilabel TV optimization algorithm, which in the examined samples prevents the artifacts produced by GC. The algorithm is slower than GC but can be sped up several times when implemented in a multiprocessor computing environment. For image pairs with uneven brightness distribution, we introduce a reformulation of the TV-based registration, in which intensity-based data terms are replaced by comparison of salient features in the reference and target images quantified by local image entropies.

Compensation of inhomogeneous fluorescence signal distribution in 2D images acquired by confocal microscopy

In images acquired by confocal laser scanning microscopy (CLSM), regions corresponding to the same concentration of fluorophores in the specimen should be mapped to the same grayscale levels. However, in practice, due to multiple distortion effects, CLSM images of even homogeneous specimen regions suffer from irregular brightness variations, e.g., darkening of image edges and lightening of the center. The effects are yet more pronounced in images of real biological specimens. A spatially varying grayscale map complicates image postprocessing, e.g., in alignment of overlapping regions of two images and in 3D reconstructions, since measures of similarity usually assume a spatially independent grayscale map. We present a fast correction method based on estimating a spatially variable illumination gain, and multiplying acquired CLSM images by the inverse of the estimated gain. The method does not require any special calibration of reference images since the gain estimate is extracted from the CLSM image being corrected itself. The proposed approach exploits two types of morphological filters: the median filter and the upper Lipschitz cover. The presented correction method, tested on images of both artificial (homogeneous fluorescent layer) and real biological specimens, namely sections of a rat embryo and a rat brain, proved to be very fast and yielded a significant visual improvement.

Testate amoebae examined by confocal and two-photon microscopy: implications for taxonomy and ecophysiology

Testate amoebae (TA) are a group of free-living protozoa, important in ecology and paleoecology. Testate amoebae taxonomy is mainly based on the morphological features of the shell, as examined by means of light microscopy or (environmental) scanning electron microscopy (SEM/ESEM). We explored the potential applications of confocal laser scanning microscopy (CLSM), two photon excitation microscopy (TPEM), phase contrast, differential interference contrast (DIC Nomarski), and polarization microscopy to visualize TA shells and inner structures of living cells, which is not possible by SEM or environmental SEM. Images captured by CLSM and TPEM were utilized to create three-dimensional (3D) visualizations and to evaluate biovolume inside the shell by stereological methods, to assess the function of TA in ecosystems. This approach broadens the understanding of TA cell and shell morphology, and inner structures including organelles and endosymbionts, with potential implications in taxonomy and ecophysiology.

Analysis and three-dimensional visualization of collagen in artificial scaffolds using nonlinear microscopy techniques

Extracellularly distributed collagen and chondrocytes seeded in gelatine and poly-ɛ-caprolactone scaffolds are visualized by two-photon excitation microscopy (TPEM) and second-harmonic generation (SHG) imaging in both forward and backward nondescanned modes. Joint application of TPEM and SHG imaging in combination with stereological measurements of collagen enables us not only to take high-resolution 3-D images, but also to quantitatively analyze the collagen volume and a spatial arrangement of cell-collagen-scaffold systems, which was previously impossible. This novel approach represents a powerful tool for the analysis of collagen-containing scaffolds with applications in cartilage tissue engineering.

Methods for compensation of the light attenuation with depth of images captured by a confocal microscope

A confocal laser scanning microscope (CLSM) enables us to capture images from a biological specimen in different depths and obtain a series of precisely registered fluorescent images. However, images captured from deep layers of the specimen may be darker than images from the topmost layers because of light loss distortions. This effect causes difficulties in subsequent analysis of biological objects. We propose a solution using two approaches: either an online method working already during image acquisition or an offline method assisting as a postprocessing step. In the online method, the gain value of a photomultiplier tube of a CLSM is controlled according to the difference of mean image intensities between the reference and currently acquired image. The offline method consists of two stages. In the first stage, a standard histogram maintaining relative frequencies of gray levels and improving brightness and contrast is created from all images in the series. In the second stage, individual image histograms are warped according to this standard histogram. The methods were tested on real confocal image data captured from human placenta and rat skeletal muscle specimens. It was shown that both approaches diminish the light attenuation in images captured from deep layers of the specimen.

General practice. Catch a falling star

A panel set up to identify and support poorly performing GPs in one health authority relies on patients and health professionals to raise their concerns. Doctors from small and single-handed practices account for many of those investigated. The average length in practice of those investigated was 28 years. Panel members believe the system is working reasonably well but does not provide quick solutions to problems of poor performance.

Alignment of adjacent picture frames captured by a CLSM

Mosaicking a picture from its adjacent parts (called picture frames or tiles) is encountered in different fields of research and technology, e.g., photogrammetry, remote sensing, microscopy, etc. It is applied whenever the object of investigation is too large for the field of view of the sensor, e.g. a microscope. We describe mosaicking with a confocal laser-scanning microscope (CLSM) Bio-Rad, MRC 600 (U.K.). Aligning neighboring picture tiles was accomplished by registering the overlapped border areas of these tiles. Such registration procedures are constrained by: 1) the limited size of the registered samples (windows); 2) anisotropy of the form of the windows (usually narrow rectangles); and 3) the content of the windows, including changes of their intensity scale. Focusing on the latter problem, methods of registration were discussed and the robustness of the following three similarity based methods was studied with regard to the distortions of the intensity scales of the tiles to be registered: 1) the sum of absolute valued differences (SAVD); 2) normalized correlation coefficient (NCC); and 3) the mutual information function (MIF). Pilot experiments were extended to three-dimensional (3-D) stacks of pictures encountered in the framework of 3-D object rendering and visualization. MIF was found in most cases to be the most robust; however, it also demanded the most computational power. It is discussed how to choose a cost-effective method of the registration with regard to the content (texture, contrast, intensity scale distortion) of the tiles.

Effects of captopril treatment versus placebo on renal function in type 2 diabetic patients with microalbuminuria: a long-term study

We evaluated the renal effect of long-term antihypertensive treatment (12 months) with the angiotensin-converting enzyme inhibitor captopril compared to placebo in 15 type 2 diabetic patients with microalbuminuria. The patients were randomly allocated to captopril (n = 9) or placebo (n = 6). After 1-year therapy no significant decrease in blood pressure was demonstrated with captopril (139 +/- 17/80 +/- 9 versus 138 +/- 13/76 +/- 6 mmHg) or placebo (138 +/- 9/75 +/- 6 versus 135 +/- 14/79 +/- 10 mmHg). Only in a small hypertensive subgroup (n = 4) treated with captopril did we find a significant reduction in blood pressure (154 +/- 2/88 +/- 1 versus 142 +/- 7/78 +/- 5 mmHg, P < 0.05). The urinary albumin excretion rate did not change significantly either in the captopril group (95.6 mg/24 h, 25th percentile 138.4, 75th percentile 25.1; versus 127.8 mg/24 h, 25th percentile 29.3, 75th percentile 222) or in the placebo group (99.2 mg/24 h, 25th percentile 58.5, 75th percentile 125.8; versus 120.9 mg/24 h, 25th percentile 62.1, 75th percentile 179.7). There were also no alterations in renal blood flow or filtration rate. In the hypertensive subgroup treated with captopril a reduction in urinary albumin excretion rate after 3 and 6 months of treatment was observed (captopril 73.4 versus 24 and 41 mg/24 h, P < 0.05), but not after 12 months. Triglyceride and cholesterol levels remained constant before and after treatment while glycosylated hemoglobin decreased significantly after 12 months captopril (7.8 +/- 0.9 versus 6.9 +/- 0.7 mg%, P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term treatment with nifedipine reduces urinary albumin excretion and glomerular filtration rate in normotensive type 1 diabetic patients with microalbuminuria

The aim of the present study was to investigate the renal effects of long-term treatment with the calcium channel blocker nifedipine in normotensive type 1 diabetic patients with microalbuminuria. In a randomized, double-blind trial, 15 type 1 diabetic patients were treated with either nifedipine (n = 8; dosage 30 mg/day) or placebo (n = 7) for 12 months. At baseline and after 6 and 12 months of therapy, the albumin excretion rate (UAER, radioimmunoassay), glomerular filtration rate (GFR, chromium 51 ethylenediamine tetra-acetic acid clearance) and renal plasma flow (RPF, iodine 125 hippuran clearance) were determined. Nifedipine treatment caused a significant reduction of UAER after 6 and 12 months (median, Q1/Q3 in mg/24 h): baseline 84 (65/163); 6 months 35 (23/90), P < 0.02; 12 months 39 (15/79), P < 0.05). GFR was significantly decreased by nifedipine treatment (baseline 157 +/- 15, 6 months 122 +/- 8, 12 months 111 +/- 47 ml/min; P < 0.05, mean +/- SEM), whereas RPF remained constant. Nifedipine treatment did not influence systolic (baseline 121 +/- 7, 12 months 124 +/- 2 mmHg, mean +/- SEM) or diastolic (baseline 72 +/- 2, 12 months 74 +/- 3 mmHg) arterial blood pressure. With placebo treatment no significant alterations of UAER, GFR, RPF and arterial blood pressure were observed. Metabolic control was constant throughout the whole study period. Thus, 1 year's treatment with nifedipine reduces the UAER and GFR in normotensive type 1 diabetic patients without influencing the systemic arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated hepatic insulin extraction in essential hypertension

Insulin resistance, hyperinsulinemia, and dyslipidemia are common characteristics of patients with untreated hypertension. However, the link between the vascular and metabolic disturbances is still unclear. To provide further insights into the metabolic picture of subjects with hypertension, we evaluated insulin resistance, pancreatic secretion, and hepatic extraction of the hormone in 16 untreated patients with essential hypertension before and after 12-16 weeks of drug treatment in comparison with 16 age-, sex-, and body weight-matched normotensive control subjects. All subjects underwent an oral and a frequently sampled intravenous glucose tolerance test. Metabolic parameters were calculated by the minimal model technique. The hypertensive patients exhibited a highly reduced tissue insulin sensitivity (2.6 +/- 0.4 versus 9.6 +/- 1.9 10(4) min-1/[microunits/mL]; p < 0.001). The basal secretion rate (70 +/- 11 versus 35 +/- 5 pmol/L per minute) and the total amount of prehepatically secreted insulin (32 +/- 4 versus 16 +/- 2 nmol/L in 4 hours) were significantly increased in the hypertensive patients compared with the control subjects (p < 0.01), whereas the posthepatic insulin delivery rate was not significantly different between the two groups (4.9 +/- 0.6 versus 3.5 +/- 0.3 nmol/L in 4 hours). Hepatic insulin extraction was found to be significantly elevated in the hypertensive patients compared with control subjects (81 +/- 4% versus 69 +/- 3%, p < 0.04). Increased hepatic insulin extraction partially ameliorated B cell hypersecretion in hypertensive patients. After 12-16 weeks of drug treatment, the blood pressure was normalized, but the metabolic profile of the patients remained unchanged. We conclude that elevated insulin extraction in the liver is a specific characteristic of individuals with essential hypertension and partially compensates pancreatic B cell hypersecretion.

Effect of dexamethasone on insulin sensitivity, islet amyloid polypeptide and insulin secretion in humans

The response of islet amyloid polypeptide and insulin and their molar ratios were investigated in eight healthy volunteers before and after treatment with dexamethasone by oral and frequently-sampled intravenous glucose tolerance tests. Following dexamethasone treatment the insulin sensitivity index decreased significantly from 6.5 +/- 1.3 to 4.1 +/- 1.0 (microU.ml-1).min-1, p < 0.05. The area under the curve representing above-basal levels of insulin during oral glucose tolerance test increased significantly following dexamethasone treatment from 48132 +/- 9736 to 82230 +/- 14846 pmol.l-1 x 3 h-1, p < 0.05, the area under the curve of islet amyloid polypeptide increased from 1308 +/- 183 to 2448 +/- 501 pmol.l-1 x 3 h-1, p < 0.05. The overall insulin/islet amyloid polypeptide molar ratios calculated from the area under the curve during the 3-h period of the oral glucose tolerance test was not significantly different before and after dexamethasone treatment (42 +/- 5 vs 40 +/- 4). During the oral glucose tolerance test the insulin/islet amyloid polypeptide ratio increased significantly from baseline to 30 min (p < 0.05), then declined towards initial values before and after dexamethasone treatment. In conclusion, dexamethasone induced a significant decrease in insulin sensitivity and a significant increase in insulin secretion during the oral glucose tolerance test. However, in contrast to previous animal experiments we did not find a change in the insulin/islet amyloid polypeptide ratio before and after dexamethasone treatment.

Lymphangiography and CT in the follow-up of patients with lymphoma

One hundred twenty-six patients with the diagnosis of lymphoma underwent staging with both lymphangiography and computed tomography (CT) of the abdomen and pelvis. These patients were retrospectively studied to determine the optimal imaging modality for follow-up. Six hundred seventy-four CT scans were correlated with 138 lymphangiograms and 840 follow-up KUB (kidney, ureter, bladder) radiographs. In 21 patients there was evidence of relapse, and in 105 the disease had regressed or remained stable. In all patients with evidence of progression or regression on the CT scan, there was a concomitant change in opacified lymph nodes on the KUB radiographs. It is recommended that the initial staging of lymphoma be done with lymphangiography and CT. If the findings of both are positive, then follow-up should consist of only KUB radiography. If progression is detected, restaging with CT may also be performed. This approach will not only reduce the radiation dose but will also save time and money and enable a more efficient use of radiologic equipment.