Postsynaptic neuromuscular dysfunction in organophosphate induced intermediate syndrome

A 65-year-old Caucasian female developed an intermediate syndrome seven days after an acute cholinergic crisis, caused by the ingestion of fenthion. Cholinesterase activity in the blood, plasma and red cells was monitored daily by the method according to Nenner and serial serum fenthion levels were measured by capillary gas chromatography. Electromyographic studies showed fade on tetanic stimulation by means of surface electrodes at 20 Hz of the left M. abductor digiti quinti at day 7, which could no longer be observed at day 19. Fade on low-frequency stimulation and post-tetanic facilitation were both absent. A biopsy of the N. suralis was normal. A biopsy of the M. tibialis anterior revealed a limited rhabdomyolysis with a very weak staining for cholinesterase. It is hypothesized that the pathophysiologic process underlying the syndrome is the result of a time-confined phenomenon, which includes both changes in the postsynaptic structures by a desensitization process and a gradually restoring ratio of acetycholine to acetylcholinesterase. This hypothesis is suggested by the similarity in the EMG-findings of this patient and those in myasthenia gravis, which is known to be characterized by a postsynaptic transmission defect

Crispy on the Outside, Raw on the Inside: Impact-Induced Melting and Fragmentation of C-Type Asteroid Regolith Documented in a Ryugu Sample

The surfaces of airless planetary bodies are continually exposed to hypervelocity impacts of micrometeoroids and influx of solar-wind ions. Collectively known as space weathering, these processes gradually alter the morphologies, microstructures, and chemical compositions of regolith grains exposed to space [1]. Because these changes also affect the optical properties of space-weathered grains [1], understanding space weathering is critical for interpretation of remote-sensing data obtained from airless planetary surfaces and for matching meteorites to parent bodies. While the effects of space weathering on anhydrous regolith materials is well understood and documented in samples returned from the Moon [1, 2] or S-type asteroid Itokawa [3, 4], space weathering of hydrous, carbonaceous chondrite-like (C-type) planetary surfaces is poorly understood. To better understand the role of micrometeoroid impacts in space weathering on C-type asteroids (cf. [5, 6]), we investigated a population of micrometeoroid impact craters on a large regolith particle resembling CI (Ivuna-type) carbonaceous chondrites that was recently returned from C-type asteroid Ryugu by JAXA’s Hayabusa2 mission (e.g., [7])