An open-access volume electron microscopy atlas of whole cells and tissues.

Understanding cellular architecture is essential for understanding biology. Electron microscopy (EM) uniquely visualizes cellular structures with nanometre resolution. However, traditional methods, such as thin-section EM or EM tomography, have limitations in that they visualize only a single slice or a relatively small volume of the cell, respectively. Focused ion beam-scanning electron microscopy (FIB-SEM) has demonstrated the ability to image small volumes of cellular samples with 4-nm isotropic voxels1. Owing to advances in the precision and stability of FIB milling, together with enhanced signal detection and faster SEM scanning, we have increased the volume that can be imaged with 4-nm voxels by two orders of magnitude. Here we present a volume EM atlas at such resolution comprising ten three-dimensional datasets for whole cells and tissues, including cancer cells, immune cells, mouse pancreatic islets and Drosophila neural tissues. These open access data (via OpenOrganelle2) represent the foundation of a field of high-resolution whole-cell volume EM and subsequent analyses, and we invite researchers to explore this atlas and pose questions.

Correlative three-dimensional super-resolution and block-face electron microscopy of whole vitreously frozen cells.

Within cells, the spatial compartmentalization of thousands of distinct proteins serves a multitude of diverse biochemical needs. Correlative super-resolution (SR) fluorescence and electron microscopy (EM) can elucidate protein spatial relationships to global ultrastructure, but has suffered from tradeoffs of structure preservation, fluorescence retention, resolution, and field of view. We developed a platform for three-dimensional cryogenic SR and focused ion beam-milled block-face EM across entire vitreously frozen cells. The approach preserves ultrastructure while enabling independent SR and EM workflow optimization. We discovered unexpected protein-ultrastructure relationships in mammalian cells including intranuclear vesicles containing endoplasmic reticulum-associated proteins, web-like adhesions between cultured neurons, and chromatin domains subclassified on the basis of transcriptional activity. Our findings illustrate the value of a comprehensive multimodal view of ultrastructural variability across whole cells.

Palpebral portion of the orbicularis oculi muscle to repetitive nerve stimulation testing: A potential assessment indicator in patients with generalized myasthenia gravis.

Repetitive nerve stimulation (RNS) is a valuable diagnostic method for myasthenia gravis (MG). However, its association with clinical severity was scarcely studied. We reviewed medical records and retrospectively enrolled 121 generalized MG patients. Sensitivity of different muscles to RNS and clinical scoring systems was evaluated. RNS testing revealed facial muscles have the highest positive rate, followed by proximal muscles and distal muscles, with the palpebral portion of the orbicularis oculi muscle most sensitive. Amplitude decrement of compound muscle action potential (CMAP) in the palpebral portion of the orbicularis oculi muscle is related to quantitative myasthenia gravis (QMG) scores, MG-specific manual muscle testing (MMT) scores and myasthenia gravis-related activities of daily living (MG-ADL) scores. We suggest that RNS testing of the palpebral portion of the orbicularis oculi muscle is a potential assessment indicator in patients with generalized MG.

Responsiveness to low-dose rituximab in refractory generalized myasthenia gravis.

We aim to investigate the effect of a low dose of rituximab (RTX) in improving the clinical symptoms of refractory generalized myasthenia gravis (MG). Eight patients with refractory generalized MG were treated with a low dose of 600mg RTX. Patients were evaluated by serial clinical scales, flow cytometry of peripheral blood B, T and NK cells, immunoglobulin, complement levels and antibody titer. The quantitative MG score (QMGS), manual muscle testing (MMT), MG-related activities of daily living (MG-ADL) and MG-specific quality-of-life (QOL) were recorded at baseline as well as 1, 3, and 6months after RTX infusion. The initial improvement was recorded at 1month after treatment. QMGS, MMT and MG-ADL were significantly improved and the average steroid dosage reduction was 43% (p=0.018) at 6months. 600mg RTX was sufficient to deplete B cells and maintain low B-cell counts until 6months after infusion. Treatment with RTX did not result in a significant change in the percentage of CD4+, CD8+ T-cells while an average increase in the percentage of NK cells. Our study found successful B cell depletion was parallel to symptoms remission and change in serum C3 and C4 levels. Serum AChR antibody levels were independent of clinical response and not influenced by RTX. Therefore, low dose of 600mg RTX may be sufficient in depleting B cells, maintaining low B-cell counts and improving the clinical symptoms of MG in 6months.