Factors Affecting Ultrastructural Quality in the Prefrontal Cortex of the Postmortem Human Brain

Abstract

Electron microscopy (EM) studies of the postmortem human brain provide a level of resolution essential for understanding brain function in both normal and disease states. However, processes associated with death can impair the cellular and organelle ultrastructural preservation required for quantitative EM studies. Although postmortem interval (PMI), the time between death and preservation of tissue, is thought to be the most influential factor of ultrastructural quality, numerous other factors may also influence tissue preservation. The goal of the present study was to assess the effects of pre-and postmortem factors on multiple components of ultrastructure in the postmortem human prefrontal cortex. Tissue samples from 30 subjects were processed using standard EM histochemistry. The primary dependent measure was number of identifiable neuronal profiles, and secondary measures included presence and/or integrity of synapses, mitochondria, and myelinated axonal fibers. Number of identifiable neuronal profiles was most strongly affected by the interaction of PMI and pH, such that short PMIs and neutral pH values predicted the best preservation. Secondary measures were largely unaffected by preand postmortem factors. Together, these data indicate that distinct components of the neuropil are differentially affected by PMI and pH in postmortem human brain. (J Histochem Cytochem 67:185-202, 2019)

Optimization of ultrastructural preservation of human brain for transmission electron microscopy after long post-mortem intervals

“…Both procedures increased the contrast or structural preservation, but did not improve the results in our hands, as was shown in initial experiments (data not shown). While hybrid freezing helped preserve the myelin sheaths, we could show that the PMI remains a key factor regarding the quality of the ultrastructural preservation, which is in agreement with Glausier et al [7], and is especially important for human brain biopsy samples [17]. The longer the PMI, the more signs of autolysis were visible, such as an increase in vacuoles that are void of structural material, as described by Xu et al [37].…”

“…In human samples, for ethical reasons, the PMI can range from a few hours up to 100 h [10, 13, 16, 39], during which the degradation of the tissue continues until fixation. The PMI is one of the key factors for the preservation of the neuronal profiles [7]. However, interestingly, longer PMIs do not have an effect on the proportion of myelin proteins [1].…”

Three-dimensional synaptic organization of layer III of the human temporal neocortex

“…In the present study, although we used the same fixative solution, biopsies were fixed immediately after removal, while tissue from the autopsies was fixed up to 4h post-mortem. A long- postmortem delay for the fixation of brain tissue samples can interfere with synaptic identification (Glausier et al 2019). Additionally, the dimensions of the brain tissue blocks in biopsies are generally smaller than those from autopsies, which could also influence the penetration of the fixative, such that the fixation in smaller blocks is better (Glausier et al 2019).…”

“…A long- postmortem delay for the fixation of brain tissue samples can interfere with synaptic identification (Glausier et al 2019). Additionally, the dimensions of the brain tissue blocks in biopsies are generally smaller than those from autopsies, which could also influence the penetration of the fixative, such that the fixation in smaller blocks is better (Glausier et al 2019). The above-mentioned reports from Huttenlocher and Dabholkar (1997) and Tang et al (2001) used brain tissue samples with a postmortem delay of up to 22 hours and 60 hours, respectively.…”

Neurexin and Neuroligins Jointly Regulate Synaptic Degeneration at the Drosophila Neuromuscular Junction based on TEM Studies

“…At present, ultrastructural phenotype analysis of type I boutons has mainly focused on T-bars, synaptic vesicles and the SSR [42,43], and few studies ( [44]) have analyzed ghost boutons, which are indicators of poor bouton development; hypogenetic boutons; or satellite boutons, which are indicators of synaptic overgrowth. Electron microscopy is a powerful tool to study synapse structure [55]. In the present study, we describe the ultrastructural characteristics of Drosophila larval NMJ bouton degeneration, primarily based on the dark electron density observed via electron microscopy.…”