Studies on chemical transmission in taste fibre endings. 3. The action of acetylcholine and 2-dimethylaminoethanol on the taste fibre endings

Determination of isoform-specific RNA structure with nanopore long reads

Current methods for determining RNA structure with short-read sequencing cannot capture most differences between distinct transcript isoforms. Here we present RNA structure analysis using nanopore sequencing (PORE-cupine), which combines structure probing using chemical modifications with direct long-read RNA sequencing and machine learning to detect secondary structures in cellular RNAs. PORE-cupine also captures global structural features, such as RNA-binding-protein binding sites and reactivity differences at single-nucleotide variants. We show that shared sequences in different transcript isoforms of the same gene can fold into different structures, highlighting the importance of long-read sequencing for obtaining phase information. We also demonstrate that structural differences between transcript isoforms of the same gene lead to differences in translation efficiency. By revealing isoform-specific RNA structure, PORE-cupine will deepen understanding of the role of structures in controlling gene regulation.

Acetylcholine increases intracellular Ca2+ in taste cells via activation of muscarinic receptors

Previous studies suggest that acetylcholine (ACh) is a transmitter released from taste cells as well as a transmitter in cholinergic efferent neurons innervating taste buds. However, the physiological effects on taste cells have not been established. I examined effects of ACh on taste-receptor cells by monitoring [Ca2+]i. ACh increased [Ca2+]i in both rat and mudpuppy taste cells. Atropine blocked the ACh response, but D-tubocurarine did not. U73122, a phospholipase C inhibitor, and thapsigargin, a Ca2+-ATPase inhibitor that depletes intracellular Ca2+ stores, blocked the ACh response. These results suggest that ACh binds to M1/M3/M5-like subtypes of muscarinic ACh receptors, causing an increase in inositol 1,4,5-trisphosphate and subsequent release of Ca2+ from the intracellular stores. A long incubation with ACh induced a transient response followed by a sustained phase of [Ca2+]i increase. In Ca2+-free solution, the sustained phases disappeared, suggesting that Ca2+ influx is involved in the sustained phase. Depletion of Ca2+ stores by thapsigargin alone induced Ca2+ influx. These findings suggest that Ca2+ store-operated channels may be present in taste cells and that they may participate in the sustained phase of [Ca2+]i increase. Immunocytochemical experiments indicated that the M1 subtype of muscarinic receptors is present in both rat and mudpuppy taste cells.

The distribution of acetylcholinesterase in buds of the rat vallate papilla as determined by electron microscope histochemistry

The distribution of acetylcholinesterase (AChE) in the rat vallate papillary bud was investigated by histochemical electron microscopy. Previous reports of specific AChE activity around subgemmal and intragemmal nerves and between some taste bud cells have been confirmed. In addition we have consistently observed dense precipitation between microvilli in the taste pore. The studies suggest that the neurotransmitter, acetylcholine, may be involved in early events in the taste process which are believed to occur in the pore.