Relationship between the microcirculation and the pathological changes in the spradic and variant forms of Creutzfeldt-Jakob Disease (CJD)

This chapter is concerned with the influence of the brain microcirculation on the development of the pathological changes in Creutzfeldt-Jakob disease (CJD). Hence, the spatial correlations between the vacuolation, prion protein (PrP) deposits, and the blood vessel profiles were studied in immunolabelled sections of the cerebral cortex, hippocampus, and cerebellum in two subtypes of CJD, viz., sporadic Creutzfeldt-Jakob disease (sCJD) and variant CJD (vCJD). In sCJD, both the vacuolation and the ‘synaptic-type’ PrP deposits were spatially correlated with the blood vessels; the PrP deposits being the more strongly correlated than the vacuoles. In vCJD, there were no significant spatial correlations between either the vacuolation or the diffuse-type of PrP deposit and the microvessels. By contrast, a consistent pattern of spatial correlation was observed in gyri of the cerebral cortex between the florid PrP deposits and blood vessels. In both sCJD and vCJD, the frequency of positive spatial correlations was similar in the different gyri of the cerebral cortex and in the upper compared with the lower laminae. In conclusion, the microcirculation appears to be more significantly involved in determining the pathological changes in sCJD than in vCJD. The spatial correlations of the florid PrP deposits in vCJD and the synaptic deposits in sCJD and the blood vessels may be attributable to factors associated with the microcirculation which enhance the aggregation of PrP molecules rather than representing a possible haematogenous spread of the disease.

Quantitative microscopic analysis of histological sections of brain tissue

This article reviews methods for quantifying the abundance of histological features in thin tissue sections of brain such as neurons, glia, blood vessels, and pathological lesions. The sampling methods by which quantitative measures can be obtained are described. In addition, methods are described for determining the spatial pattern of an object and for measuring the degree of spatial correlation between two or more histological features.

Methods of studying the planar distribution of objects in histological sections of brain tissue

This article reviews the statistical methods that have been used to study the planar distribution, and especially clustering, of objects in histological sections of brain tissue. The objective of these studies is usually quantitative description, comparison between patients or correlation between histological features. Objects of interest such as neurones, glial cells, blood vessels or pathological features such as protein deposits appear as sectional profiles in a two-dimensional section. These objects may not be randomly distributed within the section but exhibit a spatial pattern, a departure from randomness either towards regularity or clustering. The methods described include simple tests of whether the planar distribution of a histological feature departs significantly from randomness using randomized points, lines or sample fields and more complex methods that employ grids or transects of contiguous fields, and which can detect the intensity of aggregation and the sizes, distribution and spacing of clusters. The usefulness of these methods in understanding the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease is discussed. © 2006 The Royal Microscopical Society.

Objective clinical performance of ‘comfort-enhanced' daily disposable soft contact lenses

Purpose: To examine the objective clinical performance of ‘comfort-enhanced’ daily disposable contact lenses over a 16-h day. Methods: Four contact lenses (Hilafilcon B, Etafilcon A Plus, Nelfilcon A and Nelfilcon A Plus) were evaluated in an investigator masked, open label trial at the end of a week’s bilateral wear. Pre-lens noninvasive tear break-up time (PL-NITBUT), tear prism height, bulbar hyperaemia and ocular surface temperature (OST) were measured with the lens in situ at 8, 12 and 16 h of wear. Results: There was no difference between how many hours the lenses types were worn each day (F = 0.90, p = 0.44). The PL-NITBUT decreased with the duration of daily lens wear (F = 32.0, p < 0.001) and was more stable with Nelfilcon A Plus (F = 6.00, p = 0.002) than with the other lenses evaluated. Bulbar blood vessels increased in coverage (F = 11.5, p < 0.001) but not overall redness (F = 0.0, p = 0.99) with the duration of daily lens wear, but there was no difference between the lenses (p > 0.05). The tear prism height decreased with the duration of daily wear (F = 27.0, p < 0.001) and differed between lenses (F = 2.9, p = 0.04). The OST decreased with the duration of lens wear (F = 119.7, p < 0.001) and was reduced by daily disposable lens wear (F = 7.88, p < 0.001), but did not differ between lenses (F = 0.88, p = 0.45). Conclusions: Objective measures of tear film indicated a difference between the lenses evaluated for PLNITBUT and tear prism height, but not for wearing time or bulbar conjunctival hyperaemia. Therefore clinical benefits of daily disposable ‘comfort enhancing’ contact lenses can be measured, but challenges remain in producing contact lenses that do not compromise anterior eye physiology over the whole day. 2010 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Measuring the degree of spatial correlation between histological features in thin sections of brain tissue

Histological features visible in thin sections of brain tissue, such as neuronal perikarya, blood vessels, or pathological lesions may exhibit a degree of spatial association or correlation. In neurodegenerative disorders such as AD, Pick's disease, and CJD, information on whether different types of pathological lesion are spatially correlated may be useful in elucidating disease pathogenesis. In the present article the statistical methods available for studying spatial association in histological sections are reviewed. These include tests of interspecific association between two or more histological features using χ2 contingency tables, measurement of 'complete' and 'absolute' association, and more complex methods that use grids of contiguous samples. In addition, the use of correlation matrices and stepwise multiple regression methods are described. The advantages and limitations of each method are reviewed and possible future developments discussed.

Does the neuropathology of human patients with variant Creutzfeldt-Jakob disease reflect haematogenous spread of the disease?

To test the hypothesis that the distribution of the pathology in variant Creutzfeldt-Jakob disease (vCJD) represents haematogenous spread of the disease, we studied the spatial correlation between the vacuolation, prion protein (PrP) deposits, and the blood vessel profiles in the cerebral cortex, hippocampus, dentate gyrus, and cerebellum of 11 cases of the disease. In the majority of areas, there were no significant spatial correlations between either the vacuolation or the diffuse type of PrP deposit and the blood vessels. By contrast, a consistent pattern of spatial correlation was observed between the florid PrP deposits and blood vessels mainly in the cerebral cortex. The frequency of positive spatial correlations was similar in different anatomical areas of the cerebral cortex and in the upper compared with the lower laminae. Hence, with the exception of the florid deposits, the data do not demonstrate a spatial relationship between the pathological features of vCJD and blood vessels. The spatial correlation of the florid deposits and blood vessels may be attributable to factors associated with the blood vessels that promote the aggregation of PrP to form a condensed core rather than reflecting the haematogenous spread of the disease. © 2003 Elsevier Ireland Ltd. All rights reserved.

Diffuse beta-amyloid (A beta) deposits and neurons: in situ secretion or diffusion of A beta?

The association between diffuse-type beta -amyloid (AP) deposits and neuronal cell bodies in Alzheimer's disease (AD) and Down's syndrome (DS) could result from the secretion of AP from clusters of neurons in situ or the diffusion of A beta from cell processes, glial cells or blood vessels. To decide between these hypotheses, spatial pattern analysis was used to study the relationship between the degree of clustering of neuronal cell bodies and the presence of diffuse deposits in the temporal lobe of patients with DS. Significant clustering of neuronal cell bodies was present in 17/24 (71%) of brain areas studied. in addition, in 23/24 (96%) of brain areas, there was a positive correlation between the presence of diffuse deposits and the density of neurons. Hence, the data support the hypothesis that diffuse deposits develop in situ mainly as a result of the secretion of A beta by local clusters of neurons rather than by significant diffusion. Furthermore, the size of a diffuse deposit is likely to be determined by the number of neurons within a cluster which secrete A beta. The number and density of neurons could also be a factor determining the evolution of a diffuse into a mature amyloid deposit.

Celiac disease IgA modulates vascular permeability in vitro through the activity of transglutaminase 2 and RhoA

Celiac disease is characterized by the presence of specific autoantibodies targeted against transglutaminase 2 (TG2) in untreated patients' serum and at their production site in the small-bowel mucosa below the basement membrane and around the blood vessels. As these autoantibodies have biological activity in vitro, such as inhibition of angiogenesis, we studied if they might also modulate the endothelial barrier function. Our results show that celiac disease patient autoantibodies increase endothelial permeability for macromolecules, and enhance the binding of lymphocytes to the endothelium and their transendothelial migration when compared to control antibodies in an endothelial cell-based in vitro model. We also demonstrate that these effects are mediated by increased activities of TG2 and RhoA. Since the small bowel mucosal endothelium serves as a "gatekeeper" in inflammatory processes, the disease-specific autoantibodies targeted against TG2 could thus contribute to the pathogenic cascade of celiac disease by increasing blood vessel permeability.

Analysis of spatial patterns in histological sections of brain tissue using a method based on regression

A method of determining the spatial pattern of any histological feature in sections of brain tissue which can be measured quantitatively is described and compared with a previously described method. A measurement of a histological feature such as density, area, amount or load is obtained for a series of contiguous sample fields. The regression coefficient (β) is calculated from the measurements taken in pairs, first in pairs of adjacent samples and then in pairs of samples taken at increasing degrees of separation between them, i.e. separated by 2, 3, 4,..., n units. A plot of β versus the degree of separation between the pairs of sample fields reveals whether the histological feature is distributed randomly, uniformly or in clusters. If the feature is clustered, the analysis determines whether the clusters are randomly or regularly distributed, the mean size of the clusters and the spacing of the clusters. The method is simple to apply and interpret and is illustrated using simulated data and studies of the spatial patterns of blood vessels in the cerebral cortex of normal brain, the degree of vacuolation of the cortex in patients with Creutzfeldt-Jacob disease (CJD) and the characteristic lesions present in Alzheimer's disease (AD). Copyright (C) 2000 Elsevier Science B.V.

Analysis of spatial patterns in histological sections of brain tissue

A method is described which enables the spatial pattern of discrete objects in histological sections of brain tissue to be determined. The method can be applied to cell bodies, sections of blood vessels or the characteristic lesions which develop in the brain of patients with neurodegenerative disorders. The density of the histological feature under study is measured in a series of contiguous sample fields arranged in a grid or transect. Data from adjacent sample fields are added together to provide density data for larger field sizes. A plot of the variance/mean ratio (V/M) of the data versus field size reveals whether the objects are distributed randomly, uniformly or in clusters. If the objects are clustered, the analysis determines whether the clusters are randomly or regularly distributed and the mean size of the clusters. In addition, if two different histological features are clustered, the analysis can determine whether their clusters are in phase, out of phase or unrelated to each other. To illustrate the method, the spatial patterns of senile plaques and neurofibrillary tangles were studied in histological sections of brain tissue from patients with Alzheimer's disease.

Factors determining the morphology of β-amyloid (Aβ) deposits in Down's syndrome

Immunostained preparations of the medial temporal lobe from patients with Down's syndrome (DS) were counterstained with cresyl violet to reveal the β-amyloid (Aβ) deposits and their associated cell populations. Aβ deposits in the cornu Ammonis (CA) of the hippocampus were, on average, more strongly stained, less often directly associated with neurons and more often associated with glial cells than the adjacent areas of cortex. Cored deposits were more frequently recorded in sulci rather than gyri and were associated with more glial cells than the uncored deposits. Multiple regression analyses suggested there was a positive correlation in the cortex between Aβ deposit size and the frequency of closely associated neurons, the correlation being most significant with larger (>25 μm) neurons. The morphology of Aβ deposit was also correlated with the location of deposits in the cortex, CA and dentate gyrus but this factor was of lesser importance. No significant variation in the morphology of the Aβ deposits was associated with the presence of blood vessels within or adjacent to the deposit. The data suggest that neuronal cell bodies are important in the initial formation of Aβ deposits and glial cells with the development of more mature amyloid deposits.

Measuring the degree of spatial correlation between pathological lesions in Alzheimer's disease

The pathological lesions characteristic of Alzheimer's disease (AD), viz., senile plaques (SP) and neurofibrillary tangles (NFT) may not be randomly distributed with reference to each other but exhibit a degree of sptial association or correlation, information on the degree of association between SP and NFT or between the lesions and normal histological features, such as neuronal perikarya and blood vessels, may be valuable in elucidating the pathogenesis of AD. This article reviews the statistical methods available for studying the degree of spatial association in histological sections of AD tissue. These include tests of interspecific association between two or more histological features using chi-square contingency tables, measurement of 'complete' and 'absolute' association, and more complex methods that use grids of contiguous samples. In addition, analyses of association using correlation matrices and stepwise multiple regression methods are described. The advantages and limitations of each method are reviewed and possible future developments discussed.

Analysis of population dispersion in histological sections

Stereology and other image analysis methods have enabled rapid and objective quantitative measurements to be made on histological sections. These mesurements may include total volumes, surfaces, lengths and numbers of cells and blood vessels or pathological lesions. Histological features, however, may not be randomly distributed across a section but exhibit 'dispersion', a departure from randomness either towards regularity or aggregation. Information of population dispersion may be valuable not only in understanding the two-or three-dimensional structure but also in elucidating the pathogenesis of lesions in pathological conditions. This article reviews some of the statistical methods available for studying dispersion. These range from simple tests of whether the distribution of a histological faeture departs significantly from random to more complex methods which can detect the intensity of aggregation and the sizes, distribution and spacing of the clusters.