Principle of relative positioning of structures in the human body

The arrangement of various biological structures should generally ensure the safety of crucial structures and increase their working efficiency; however, other principles governing the relative positions of structures in humans have not been reported. The present study therefore investigated other principles using nerves and their companion vessels in the human body as an example. Nerves and blood vessels usually travel together and in the most direct way towards their targets. Human embryology, histology, and gross anatomy suggest that there are many possible positions for these structures during development. However, for mechanical reasons, tougher or stronger structures should take priority. Nerves are tougher than most other structures, followed by arteries, veins, and lymphatic vessels. Nerves should therefore follow the most direct route, and be followed by the arteries, veins, and lymphatic vessels. This general principle should be applicable to all living things.     

Automated analysis of rabbit knee calcified cartilage morphology using micro-computed tomography and deep learning

Structural dynamics of calcified cartilage (CC) are poorly understood. Conventionally, CC structure is analyzed using histological sections. Micro-computed tomography (µCT) allows for three-dimensional (3D) imaging of mineralized tissues; however, the segmentation between bone and mineralized cartilage is challenging. Here, we present state-of-the-art deep learning segmentation for µCT images to assess 3D CC morphology. The sample includes 16 knees from 12 New Zealand White rabbits dissected into osteochondral samples from six anatomical regions: lateral and medial femoral condyles, lateral and medial tibial plateaus, femoral groove, and patella (n = 96). The samples were imaged with µCT and processed for conventional histology. Manually segmented CC from the images was used to train segmentation models with different encoder–decoder architectures. The models with the greatest out-of-fold evaluation Dice score were selected. CC thickness was compared across 24 regions, co-registered between the imaging modalities using Pearson correlation and Bland–Altman analyses. Finally, the anatomical CC thickness variation was assessed via a Linear Mixed Model analysis. The best segmentation models yielded average Dice of 0.891 and 0.807 for histology and µCT segmentation, respectively. The correlation between the co-registered regions was strong (r = 0.897, bias = 21.9 µm, standard deviation = 21.5 µm). Finally, both methods could separate the CC thickness between the patella, femoral, and tibial regions (p < 0.001). As a conclusion, the proposed µCT analysis allows for ex vivo 3D assessment of CC morphology. We demonstrated the biomedical relevance of the method by quantifying CC thickness in different anatomical regions with a varying mean thickness. CC was thickest in the patella and thinnest in the tibial plateau. Our method is relatively straightforward to implement into standard µCT analysis pipelines, allowing the analysis of CC morphology. In future research, µCT imaging might be preferable to histology, especially when analyzing dynamic changes in cartilage mineralization. It could also provide further understanding of 3D morphological changes that may occur in mineralized cartilage, such as thickening of the subchondral plate in osteoarthritis and other joint diseases.     

Osteohistology of Greererpeton provides insight into the life history of an early Carboniferous tetrapod

The vertebrate transition to land is one of the most consequential, yet poorly understood periods in tetrapod evolution. Despite the importance of the water–land transition in establishing modern ecosystems, we still know very little about the life histories of the earliest tetrapods. Bone histology provides an exceptional opportunity to study the biology of early tetrapods and has the potential to reveal new insights into their life histories. Here, we examine the femoral bone histology from an ontogenetic series of Greererpeton, an early tetrapod from the Middle-Late Mississippian (early Carboniferous) of North America. Thin-sections and micro-CT data show a moderately paced rate of bone deposition with significant cortical thickening through development. An interruption to regular bone deposition, as indicated by a zone of avascular tissue and growth marks, is notable at the same late juvenile stage of development throughout our sample. This suggests that an inherent aspect to the life history of juvenile Greererpeton resulted in a temporary reduction in bone deposition. We review several possible life history correlates for this bony signature including metamorphosis, an extended juvenile phase, environmental stress, and movement (migration/dispersal) between habitats. We argue that given the anatomy of Greererpeton, it is unlikely that events related to polymorphism (metamorphosis, extended juvenile phase) can explain the bony signature observed in our sample. Furthermore, the ubiquity of this signal in our sample indicates a taxon-level rather than a population-level trait, which is expected for an environmental stress. We conclude that movement via dispersal represents a likely correlate, as such events are a common life history strategy of aquatically bound vertebrates.     

Hepatocellular carcinoma: a practical review for the surgical pathologist

Hepatocellular carcinoma causes significant human morbidity and mortality worldwide. In Western Europe and North America, the rising prevalence of nonalcoholic steatohepatitis is a major contributor to chronic liver disease and, ultimately, hepatocellular carcinoma. In some cases, a definitive diagnosis of hepatocellular carcinoma can be rendered in the absence of histologic confirmation; needle core biopsies may be taken for small and/or indeterminate liver lesions. Pathologists continue to provide important clinical care through the diagnosis, staging, and molecular understanding of this malignancy. This article summaries the epidemiology, imaging, histopathology, and targeted immunohistochemical profile of hepatocellular carcinoma in adults with a focus on practical knowledge for daily use.     

大隐静脉瓣膜的形态特点及其意义

目的:为临床诊断和治疗大隐静脉曲张、构建组织工程静脉瓣提供形态学基础。方法:34侧大隐静脉股段标本按自身比例均分为近、中和远3段,手术显微镜下解剖、观察瓣膜的形态,测量相关数值,分析瓣膜与静脉属支的关系。对新鲜瓣膜行Masson三色改良染色和H-E染色。结果:大隐静脉股段瓣膜数为(3.18±0.94)个,瓣膜以半月形双叶瓣为主,瓣膜方位无显著性差异,隐-股点主要位于属支汇入处的远心端(Ⅲ型)。瓣膜的窦面和腔面均覆着一层内皮细胞,在管腔面内皮下层覆着数层网状的弹力纤维,瓣膜主要由胶原纤维构成。结论:通过对大隐静脉瓣膜形态学研究,获取了其基本形态学特点及数据,为进一步临床研究及组织工程构建人工瓣膜提供形态学参考。     

Cell layers and neuropil: contrast‐enhanced MRI of mouse brain in vivo

Contrast‐enhanced T₁‐ and T₂‐weighted MRI at 9.4 T and in‐plane resolutions of 25 and 30 µm has been demonstrated to differentiate between neural tissues in mouse brain in vivo, including granule cell layers, principal cell layers, general neuropil, specialized neuropil and white matter. In T₁‐weighted MRI of the olfactory bulb, hippocampus and cerebellum, contrast obtained by the intracranial administration of gadopentetate dimeglumine (Gd‐DTPA) reflects the extra‐ and intracellular spaces of gray matter in agreement with histological data. General neuropil areas are highlighted, whereas other tissues present with lower signal intensities. The induced contrast is similar to that in plain T₂‐weighted MRI, but offers a 16–30‐fold higher contrast‐to‐noise ratio. Systemic administration of manganese chloride increases the signal‐to‐noise ratio in T₁‐weighted MRI to a significantly greater extent in principal cell layers and specialized neuropil than in granule cell layers, whereas gadolinium‐enhanced MRI indicates no larger intracellular spaces in these tissues. Granule cell layers are enhanced no more than general neuropil by manganese, whereas gadolinium‐enhanced MRI indicates significantly larger intracellular spaces in the cell layers. These discrepancies suggest that the signal increase after manganese administration reflects cellular activity which is disproportionate to the intracellular space. As a result, principal cell layers and specialized neuropil become highlighted, whereas granule cell layers, general neuropil and white matter present with lower signal intensities. Copyright © 2013 John Wiley & Sons, Ltd.