Isosmotic modulation of Ca2+-regulated exocytosis in guinea-pig antral mucous cells: role of cell volume

Exocytotic events and changes of cell volume in mucous cells from guinea-pig antrum were examined by video-enhanced optical microscopy.Acetylcholine (ACh) evoked exocytotic events following cell shrinkage, the frequency and extent of which depended on the ACh concentration. ACh actions were mimicked by ionomycin and thapsigargin, and inhibited by Ca2+-free solution and Ca2+ channel blockers (Ni2+, Cd2+ and nifedipine). Application of 100 μM W-7, a calmodulin inhibitor, also inhibited the ACh-induced exocytotic events. These results indicate that ACh actions are mediated by intracellular Ca2+ concentration ([Ca2+]i) in antral mucous cells.The effects of ion channel blockers on exocytotic events and cell shrinkage evoked by ACh were examined. Inhibition of KCl release (quinine, Ba2+, NPPB or KCl solution) suppressed both the exocytotic events and cell shrinkage evoked by ACh.Bumetanide (inhibition of NaCl entry) or Cl−-free solution (increasing Cl− release and inhibition of NaCl entry) evoked exocytotic events following cell shrinkage in unstimulated antral mucous cells and caused further cell shrinkage and increases in the frequency of exocytotic events in ACh-stimulated cells. However, Cl−-free solution did not evoke exocytotic events in unstimulated cells in the absence of extracellular Ca2+, although cell shrinkage occurred.To examine the effects of cell volume on ACh-evoked exocytosis, the cell volume was altered by increasing the extracellular K+ concentration. The results showed that cell shrinkage increases the frequency of ACh-evoked exocytotic events and cell swelling decreases them.Osmotic shrinkage or swelling caused the frequency of ACh-evoked exocytotic events to increase. This suggests that the effects of cell volume on ACh-evoked exocytosis under anisosmotic conditions may not be the same as those under isosmotic conditions.In antral mucous cells, Ca2+-regulated exocytosis is modulated by cell shrinkage under isosmotic conditions

Impact of low-dose sevoflurane with propofol-based anaesthesia on motor-evoked potentials in infants: protocol for a single-centre randomised controlled study

Introduction Motor-evoked potentials (MEP) are widely used to mitigate the risk of nerve injury resulting from surgical manipulation. Infants are more susceptible to anaesthetics that suppress MEP because of the immaturity of their nervous structures. Current evidence of the impact of the interaction between a small dose of sevoflurane and propofol-based total intravenous anaesthesia (TIVA) on MEP in infants is controversial. This current study aims to evaluate the impact of the coadministration of low-dose sevoflurane with propofol-based TIVA on MEP in infants.Methods and analysis A randomised controlled study will be conducted at a single tertiary care children’s hospital in Japan between July 2024 and June 2029. Children between 35 and 87 weeks of postconceptual age undergoing spinal surgery requiring MEP under general anaesthesia will be enrolled in this study. The participants will be randomly allocated into two groups: propofol+remifentanil with (intervention group) or without (control group) low-dose sevoflurane (0.10–0.15 age-adjusted minimum alveolar concentration). MEP top-to-bottom amplitudes will be measured at two chronological points: T1 (first transcranial MEP (TcMEP) recording), T2 (second TcMEP recording) in the same patient. The primary and secondary endpoints will be a reduction in MEP amplitudes (T1–T2) in the right upper and lower extremities between the control and intervention groups, respectively. The sample size was calculated to be a total of 40 based on the preliminary data of 10 infants, which showed a 35% reduction in mean values of MEP amplitudes in the right adductor muscle (SD=31) with a 10% assumed dropout rate.Ethics and dissemination The study protocol was approved by the Institutional Review Board of the Aichi Children’s Health and Medical Center (2022058). The results will be reported in a peer-reviewed journal at the relevant academic conference.Trial registration number jRCT1041230094

Effect of pH and monovalent cations on the Raman spectrum of water: Basics revisited and application to measure concentration gradients at water/solid interface in Si3N4 biomaterial

The effect of hydrogen carbonate (HCO3-) and cations (Na+, K+) solvated in water were revisited according to high spectrally resolved Raman measurements. Water solutions with different bicarbonate concentrations or added with increasing amounts of monovalent cations were examined with respect to their Raman spectra both in the bulk state and at the solid/liquid interface with a silicon nitride (Si3N4) bioceramic. Spectroscopic calibrations confirmed that the Raman emission from OH-stretching in water is sensitive to molarity variations (in the order of tens of mM). The concentration gradient developed at the solid/liquid interface in cation-added solutions interacting with a Si3N4 surface was measured and found to be peculiar to individual cations. Local variation in pH was detected in ionic solutions interacting with Si3N4 samples, which might represent a useful property for Si3N4 in a number of biomedical applications. (C) 2015 Elsevier B.V. All rights reserved