Three-dimensional reconstructions of mechanosensory end organs suggest a unifying mechanism underlying dynamic, light touch.

Specialized mechanosensory end organs within mammalian skin-hair follicle-associated lanceolate complexes, Meissner corpuscles, and Pacinian corpuscles-enable our perception of light, dynamic touch 1 . In each of these end organs, fast-conducting mechanically sensitive neurons, called Aß low-threshold mechanoreceptors (Aß LTMRs), associate with resident glial cells, known as terminal Schwann cells (TSCs) or lamellar cells, to form complex axon ending structures. Lanceolate-forming and corpuscle-innervating Aß LTMRs share a low threshold for mechanical activation, a rapidly adapting (RA) response to force indentation, and high sensitivity to dynamic stimuli 1-6 . How mechanical stimuli lead to activation of the requisite mechanotransduction channel Piezo2 7-15 and Aß RA-LTMR excitation across the morphologically dissimilar mechanosensory end organ structures is not understood. Here, we report the precise subcellular distribution of Piezo2 and high-resolution, isotropic 3D reconstructions of all three end organs formed by Aß RA-LTMRs determined by large volume enhanced Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) imaging. We found that within each end organ, Piezo2 is enriched along the sensory axon membrane and is minimally or not expressed in TSCs and lamellar cells. We also observed a large number of small cytoplasmic protrusions enriched along the Aß RA-LTMR axon terminals associated with hair follicles, Meissner corpuscles, and Pacinian corpuscles. These axon protrusions reside within close proximity to axonal Piezo2, occasionally contain the channel, and often form adherens junctions with nearby non-neuronal cells. Our findings support a unified model for Aß RA-LTMR activation in which axon protrusions anchor Aß RA-LTMR axon terminals to specialized end organ cells, enabling mechanical stimuli to stretch the axon in hundreds to thousands of sites across an individual end organ and leading to activation of proximal Piezo2 channels and excitation of the neuron.

Protocol for preparation of heterogeneous biological samples for 3D electron microscopy: a case study for insects.

Modern morphological and structural studies are coming to a new level by incorporating the latest methods of three-dimensional electron microscopy (3D-EM). One of the key problems for the wide usage of these methods is posed by difficulties with sample preparation, since the methods work poorly with heterogeneous (consisting of tissues different in structure and in chemical composition) samples and require expensive equipment and usually much time. We have developed a simple protocol allows preparing heterogeneous biological samples suitable for 3D-EM in a laboratory that has a standard supply of equipment and reagents for electron microscopy. This protocol, combined with focused ion-beam scanning electron microscopy, makes it possible to study 3D ultrastructure of complex biological samples, e.g., whole insect heads, over their entire volume at the cellular and subcellular levels. The protocol provides new opportunities for many areas of study, including connectomics.

Treatment of xenografted ovarian carcinoma using paclitaxel-loaded ultrasound microbubbles.

RATIONALE AND OBJECTIVES: The aim of this study was to explore the antitumor effects on mice xenografted ovarian carcinoma using the technique of ultrasound-mediated drug release from paclitaxel-loaded lipid microbubbles (PLMs). MATERIALS AND METHODS: Twenty-five ovarian cancer-bearing nude mice were randomly divided into five groups of five mice each. Each group received a unique kind of treatment once a day. These treatments were PLMs combined with ultrasound, intravenous paclitaxel administration, non-drug-loaded microbubbles combined with ultrasound, intravenous PLM administration, and normal saline administration (the control group). After 7 days of consecutive treatment, all mice were sacrificed, and their tumors were harvested to measure volumes and weights. The tumor inhibition rate was calculated by weight. Expressions of vascular endothelial growth factor (VEGF) and p53 in tumor tissues were detected by immunohistochemical staining. RESULTS: Mean tumor volume and weight were the lowest in the first group (PLMs combined with ultrasound), so this group's tumor inhibition rate was the highest (P < .05). On immunohistology, VEGF and p53 expression levels were lowest (P < .05) in the first group. CONCLUSION: Ultrasound irradiation mediates PLM destruction so that the drug is released from the vehicles at the same time. It helps achieve targeted chemotherapy in tumor tissues. This technique has potential to be adopted as a novel tool for ovarian cancer chemotherapy.