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

Across mammalian skin, structurally complex and diverse mechanosensory end organs respond to mechanical stimuli and enable our perception of dynamic, light touch. How forces act on morphologically dissimilar mechanosensory end organs of the skin to gate the requisite mechanotransduction channel Piezo2 and excite mechanosensory neurons is not understood. Here, we report high-resolution reconstructions of the hair follicle lanceolate complex, Meissner corpuscle, and Pacinian corpuscle and the subcellular distribution of Piezo2 within them. Across all three end organs, Piezo2 is restricted to the sensory axon membrane, including axon protrusions that extend from the axon body. These protrusions, which are numerous and elaborate extensively within the end organs, tether the axon to resident non-neuronal cells via adherens junctions. These findings support a unified model for dynamic touch in which mechanical stimuli stretch hundreds to thousands of axon protrusions across an end organ, opening proximal, axonal Piezo2 channels and exciting the neuron.

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 Aβ low-threshold mechanoreceptors (Aβ 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 Aβ 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 Aβ 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 Aβ 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 Aβ 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 Aβ RA-LTMR activation in which axon protrusions anchor Aβ 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.

Immediate Catheter Directed Thrombolysis for Thromboembolic Stroke During Carotid Endarterectomy

Background

Carotid artery endarterectomy (CEA) is a common procedure undertaken by vascular surgeons with over 5,000 procedures performed annually worldwide. Published rates of perioperative stroke range from 1.3% to 6.3%.

Case report

A case is presented in which on-table intra-cranial angiography and catheter directed thrombolysis were used for a thromboembolic occlusion of the distal internal carotid artery (ICA) and proximal middle cerebral artery (MCA). An 83-year-old lady developed a dense right hemiparesis while undergoing a CEA under local anaesthetic (LA). Immediate re-exploration of the endarterectomy did not reveal technical error. Intraoperative duplex scanning of the internal carotid artery revealed no detectable diastolic flow. On-table angiogram showed complete occlusion of the distal ICA and proximal MCA. Catheter directed administration of TPA was undertaken. The entire ICA and MCA were completely clear on a completion angiogram. The patient made a full neurological recovery.

Discussion and conclusion

Prompt diagnosis and treatment with intraoperative catheter directed thrombolysis can resolve thromboembolic occlusion of the ICA/MCA. It is argued that performing CEA under LA is useful for immediate recognition of perioperative stroke. Furthermore, the advantage is highlighted of vascular surgeons having both the resources and skillset to perform on-table angiography and thrombolysis.

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Post-CEA stroke can be effectively treated with catheter directed thrombolysis.

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It is important to diagnose and treat distal or intracranial thromboembolism.

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Rapid stroke recognition during CEA can be aided by performance under local anaesthetic.

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Vascular surgeons should be able to perform intraoperative angiography and thrombolysis.

Mesocaval shunt inhibits primary and metastatic hepatoma growth and enhances apoptosis

BACKGROUND

Previous reports indicate that hepatocyte growth factor and other hepatic trophic factors reach the liver presumably by portal venous inflow and stimulate experimental hepatic tumor growth, invasion, and metastasis. This study tests this hypothesis by evaluating whether a mesocaval shunt (MCS) alters hepatic tumor growth, the mitotic rate, apoptosis, and incidence and growth of lung metastasis in rats with implanted hepatoma.

METHODS

Morris hepatoma (1 x 10(5)) cells were implanted intrahepatically in 19 ACI rats. One week after implantation, 10 rats underwent MCS operation and nine controls a sham operation. Rats were killed 21 days after the operation to assess tumor volume, tumor cell mitosis, apoptosis, area of tumor necrosis, pulmonary metastases and percentage of lung tumor area.

RESULTS

Mesocaval shunt induced a significant increase in the rate of tumor apoptosis (25 +/- 5 v 14 +/- 6, P < .01) and the percentage of area of tumor necrosis (29% +/- 17% v 13% +/- 8%, P < .05), a decreased tumor volume (839 +/- 1,195 v 2,909 +/- 2,572, P < .05), a reduction in tumor mitosis (70 +/- 28 v 93 +/- 11, P < .05) and decreased percentage area of pulmonary metastatic tumor (9.8 +/- 6.8 v 18.8 +/- 14, P < .05).

CONCLUSION

These observations show that growth of intrahepatic tumor is influenced by portal venous inflow and suggest that MCS or other methods of regulating portal vein flow may be useful as adjunctive therapy in the treatment of advanced hepatoma.

Antibody recognition of an immunogenic influenza hemagglutinin-human leukocyte antigen class II complex

The A/Japan/57 influenza hemagglutin (HA) peptide HA 128-145, when bound by human histocompatibility leukocyte antigen-DRw11 cells, is recognized by the human CD4+ T cell clone V1. A rabbit antiserum has been raised against HA 128-145 which recognizes not only the free peptide, but also the HA 128-145/DRw11 complex on a solid matrix, in solution, or on the surface of viable cells. The detection of these complexes on viable cells was shown to be class II specific, DRw11 restricted, and commensurate with the level of DRw11 expression. The identity of DRw11 as the cell surface molecule binding HA 128-145 was confirmed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and tryptic peptide mapping. Using this antiserum HA 128-145/DRw11 complexes could be detected on the cell surface as soon as 30 min after the peptide was added, and increased up to 24 h. Dissociation kinetics showed these complexes were long-lived, with a half-life of approximately 14 h. This anti-HA peptide antiserum represents the first direct means of studying antigenic peptide-human leukocyte antigen class II complexes on the surface of living cells without the addition of a non-amino acid moiety to the peptide. The properties of this antiserum thus provide the potential to study naturally processed antigenic peptides as well as the mechanism of processing itself in a physiologically relevant system.

Clonal analysis of Hemophilus influenzae isolated from children from Pakistan with lower respiratory tract infections

The clonal diversity of 105 Hemophilus isolates from the blood of children with lower respiratory tract infection in Pakistan was analyzed. Ten isolates were identified as H. parainfluenzae and 95 as H. influenzae. Of the H. influenzae isolates, 61 (64%) were serotype b and 34 (36%) were nontypable; 95% of the type b isolates were members of a single clonal group (as defined by multilocus enzyme electrophoresis, SDS-PAGE outer membrane protein profile, and biotype). This clone is rarely observed among type b strains recovered from patients with invasive type b disease in the USA or Europe. The nontypable isolates in Islamabad also were clonally restricted: 9 clonal groups were found among 34 isolates, with just 5 clonal groups accounting for most (82%) of the strains. Children infected with type b strains were hospitalized more often than those with nontypable H. influenzae disease (64% vs. 41%, P = .06), but no other clinical or demographic features distinguished children infected by type b and nontypable strains.

Host and bacterial factors associated with Haemophilus influenzae type b disease in Minnesota children vaccinated with type b polysaccharide vaccine

Host and bacterial factors were evaluated among 86 Minnesota children with Haemophilus influenzae type b disease detected by active surveillance after introduction of type b polysaccharide vaccine in the state. Children were 2-6 y of age. Thirty-three (38%) had been vaccinated. There was no significant difference between the frequency of low serum concentrations of IgM, IgA, IgG, or IgG2 in the vaccinated and nonvaccinated subjects (13% vs. 8%, P = .5). The presence of the Gm immunoglobulin allotype phenotype (1,3,17;23;5,13,21), previously associated with a lower relative risk of vaccine failure in children from other states, was associated with a fourfold decrease in the relative risk of vaccine failure in Minnesota (P less than .07). Haemophilus isolates from 58 of the children were available for clonal characterization by multilocus electrophoresis and outer membrane protein subtyping. There were no significant differences between the clone distribution of the strains causing disease in vaccinated and nonvaccinated patients, and nearly all disease-producing clones in Minnesota also are known to cause disease in other areas of the country. Thus, vaccine failure in Minnesota is infrequently associated with hypogammaglobulinemia or with infection by unusual clones of a H. influenzae type b. Also, the Gm phenotype associated with protection against vaccine failure in other areas of the USA appears to be protective in Minnesota.