Objective-The distribution of atherosclerosis around branch sites changes with age in human and rabbit aortas. We tested whether that reflects a change in the pattern of wall shear stress by examining shear-dependent morphological features of endothelial cells. Methods and Results-Endothelial cells and their nuclei align and elongate with applied shear. These parameters were examined in the descending thoracic aorta of immature and mature rabbits. The use of Häutchen preparations, fluorescent stains, and automated image analysis allowed nuclear morphology to be mapped reliably at high resolution over large areas. Cells and their nuclei were most elongated downstream of branch ostia in immature aortas but upstream of them in mature aortas. Elongation was generally greater in mature animals, and nuclei aligned toward the ostia more in these animals, consistent with a greater flow into the branch. Morphology away from branches was indicative of helical flow in the aorta, with greatest shear on the dorsal wall, at both ages. Key Words: atherosclerosis Ⅲ blood flow Ⅲ endothelium Ⅲ shear stress T he prevalence of atherosclerosis varies greatly from one region of the arterial system to another. This patchy distribution is particularly striking near branch points and in curved vessels, consistent with the development of disease depending on mechanical factors. The current consensus is that lesions occur most frequently where blood flow exerts a low, oscillatory shear stress on the wall. 1,2 We have drawn attention to age-related changes in the pattern of lesions around branch ostia in the human aorta, 3 and we have demonstrated similar changes in the pattern of spontaneous 4 and diet-induced 5-7 lesions in rabbits. These changes could reflect alteration of the mechanical stresses acting on the wall or alteration of the relationship between mechanical stress and lesion development; the latter would imply that the low shear stress hypothesis cannot be valid at all ages. Conclusion-TheBlood flow velocity near the wall cannot be measured in vivo with sufficient spatial resolution to determine whether the pattern of wall shear stress around branch points changes with age. However, local wall shear stress can be inferred from endothelial morphology. In vitro studies have shown that endothelial cells and their nuclei align with the predominant flow direction and elongate with increasing shear stress. 8 -11 This relationship also seems to hold in vivo: patterns of cell morphology seen near branches correlate with the flow visualized in models of the branches, 12-14 and if flow or the orientation of the endothelium is altered, cells and their nuclei adjust their shape and alignment accordingly. [15][16][17][18] In a preliminary study using endothelial morphology to determine whether the pattern of shear stress near branches changes with age, 19 we measured nuclear orientation and elongation around the origins of intercostal arteries in aortas from immature and mature rabbits. Changes with age in the pattern of nuclear elongatio...
This paper presents an automatic detection method for thin boundaries of silver-stained endothelial cells (ECs) imaged using light microscopy of endothelium mono-layers from rabbit aortas. To achieve this, a segmentation technique was developed, which relies on a rich feature space to describe the spatial neighbourhood of each pixel and employs a Support Vector Machine (SVM) as a classifier. This segmentation approach is compared, using hand-labelled data, to a number of standard segmentation/thresholding methods commonly applied in microscopy. The importance of different features is also assessed using the method of minimum Redundancy, Maximum Relevance (mRMR), and the effect of different SVM kernels is also considered. The results show that the approach suggested in this paper attains much greater accuracy than standard techniques; in our comparisons with manually labelled data, our proposed technique is able to identify boundary pixels to an accuracy of 93%. More significantly, out of a set of 56 regions of image data, 43 regions were binarised to a useful level of accuracy. The results obtained from the image segmentation technique developed here may be used for the study of shape and alignment of ECs, and hence patterns of blood flow, around arterial branches.
Child abuse is a preventable phenomenon of considerable concern resulting in significant child mortality and morbidity. We analyze various abuse lesions such as radiological (visceral and skeletal lesions and those associated with head trauma) and cutaneous (burns, bruises, bites, etc.) to enhance streamlined identification of injuries in cases of physical child abuse. For effective results, it is essential to remain mindful of all background factors, such as the caregiver setting and the prevalence of child maltreatment in the concerned community while acknowledging the possibility of natural causes (genetic diseases such as osteogenesis imperfecta and hemophilia, or acquired abnormalities) that can mimic NAT and cause confusion in diagnosis and treatment. The margin of error in cases of abuse is negligible, therefore, making its diagnosis a momentous as well as challenging clinical task. An ineffective diagnosis can have detrimental emotional consequences for the family and may even expose the child to future potentially fatal episodes of abuse. Hence, there is a need to direct special focus on the importance of accurate history taking and immediate, responsible reporting to authorities, as well as to child protective services. Therefore, considering the multifactorial approach this subject requires, this review aims to delve into prevalence statistics, various risk factors, and their effect on psychological health to offer a near-complete regulation to ensure an effective understanding of NAT on part of doctors, social workers, and other relevant authorities.
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