Sphingolipids with 2-hydroxy fatty acids aid in plasma membrane nanodomain organization and oxidative burst.

Plant sphingolipids mostly possess 2-hydroxy fatty acids (HFA), the synthesis of which is catalyzed by FA 2-hydroxylases (FAHs). In Arabidopsis (Arabidopsis thaliana), two FAHs (FAH1 and FAH2) have been identified. However, the functions of FAHs and sphingolipids with HFAs (2-hydroxy sphingolipids) are still unknown because of the lack of Arabidopsis lines with the complete deletion of FAH1. In this study, we generated a FAH1 mutant (fah1c) using CRISPR/Cas9-based genome editing. Sphingolipid analysis of fah1c, fah2, and fah1cfah2 mutants revealed that FAH1 hydroxylates very long-chain FAs (VLCFAs), whereas the substrates of FAH2 are VLCFAs and palmitic acid. However, 2-hydroxy sphingolipids are not completely lost in the fah1cfah2 double mutant, suggesting the existence of other enzymes catalyzing the hydroxylation of sphingolipid FAs. Plasma membrane (PM) analysis and molecular dynamics simulations revealed that hydroxyl groups of sphingolipid acyl chains play a crucial role in the organization of nanodomains, which are nanoscale liquid-ordered domains mainly formed by sphingolipids and sterols in the PM, through hydrogen bonds. In the PM of the fah1cfah2 mutant, the expression levels of 26.7% of the proteins, including defense-related proteins such as the pattern recognition receptors (PRRs) brassinosteroid insensitive 1-associated receptor kinase 1 and chitin elicitor receptor kinase 1, NADPH oxidase respiratory burst oxidase homolog D (RBOHD), and heterotrimeric G proteins, were lower than that in the wild-type. In addition, reactive oxygen species (ROS) burst was suppressed in the fah1cfah2 mutant after treatment with the pathogen-associated molecular patterns flg22 and chitin. These results indicated that 2-hydroxy sphingolipids are necessary for the organization of PM nanodomains and ROS burst through RBOHD and PRRs during pattern-triggered immunity.

Analysis of vestibular testing in patients with vestibular schwannoma based on the nerve of origin, the localization, and the size of the tumor.

OBJECTIVES: We aimed to analyze the factors influencing caloric response and vestibular evoked myogenic potential (VEMP) in vestibular schwannoma. SUBJECTS: The subjects comprised 130 patients with unilateral vestibular schwannoma pathologically diagnosed by surgery. METHOD: Caloric response and the amplitude and latency of VEMP were measured and analyzed based on the nerve of origin, localization, and size of the tumor. The tumors were classified into 3 types based on localization: intracanalicular, intermediate, and medial; and into 4 grades based on size: 9 mm or less, 10 to 19 mm, 20 to 29 mm, and 30 mm or greater. RESULTS: : Abnormal rates of caloric response and VEMP in patients with tumors arising from the superior vestibular nerve were not significantly different from those in patients with tumors of the inferior vestibular nerve. In the intermediate and medial type-but not in the intracanalicular type-a significant difference in tumor size was observed between patients with normal caloric response and those with canal paresis as also between patients with normal VEMP and those with abnormal VEMP. In patients with tumors that maximally measured 10 to 19 mm or of the intermediate type, the p- and n-wave latencies of VEMP were significantly prolonged compared with those in the normal opposite ear. CONCLUSION: 1) The nerve of origin of tumors cannot be predicted based on caloric response and VEMP. 2) In the intermediate and medial types, caloric response and the VEMP amplitude are significantly diminished in association with an increase in tumor size. 3) Prolonged VEMP latencies seem to be not only caused by tumor compression to the brainstem or vestibular spinal tract but also by tumor compression isolated to the inferior vestibular nerve.

[Significant factors affecting the operation time for benign parotid tumor].

Tumors of the parotid gland are fairly frequent among head and neck tumors. Parotidectomy for benign tumors is necessary for diagnosis and therapy. Furthermore, acquiring the skill for this operation is a significant step in the training course of an otolaryngologist Thus, it is useful to analyze the operation time and determine the factors affecting it to evaluate the progress in the operation skill. To measure the operation time and determine the factors affecting it, 71 cases, including 43 cases of pleomorphic adenomas and 28 cases Warthin's tumor, were retrospectively reviewed to the determine if the operation time depended on the age, sex, operated side, presence of complications, BMI, bleeding volume, tumor size, tumor location, exposure of branches of the facial nerve, and experience of the surgeon. Multivariate analysis was used to determine the factors correlated with the operation time. The results revealed that the bleeding volume, tumor size, tumor location and experience of the surgeon were significantly correlated with the operation time, whereas age, sex, operated side, presentation of complications and BMI showed no correlation with the operation time. Furthermore, surgeons with the experience of operating 20-39 cases took almost the same time for the operation as the surgeon with the experience of operating more than 40 cases. Taken together, to shorten the operation time, the inexperienced surgeon should start with smaller tumors and surgery in the superficial lobe in the initial training period, and supervision by well-experienced supervised surgeons is required until 30-40 are undertaken.

Combined effects of vestibular stimulation and gaze direction on orientation of sound lateralization.

Dichotic sound discrimination is influenced by either visual or vestibular stimulation. This study investigated the effect of simultaneous gaze and vestibular inputs on dichotic sound discrimination. The subjects (n=12) closed their eyes or gazed at a red target light placed at a distance of 50cm from their eyes, and the ITD discrimination test was simultaneously performed in either the supine or in the right lateral decubitus position, in which gravitational linear acceleration causes utricular stimulation in the lower ear. In the ITD discrimination tests, the amplitudes of saw-tooth waves in the supine position with straight gaze were significantly different from those in the lateral decubitus position with downward or upward gaze. The saw-tooth waves in the lateral decubitus position with eye closed significantly shifted toward the upper ear compared to that in the supine position with eye closed. The saw-tooth waves in the lateral decubitus position with upward and with downward gaze shifted significantly toward the upper and lower ears, respectively, as compared to that in the supine position with straight gaze. We concluded that a sound image resulting from dichotic stimulation may be more dominantly influenced by the direction of eccentric gaze than by utricular stimulation that occurs due to gravitational linear acceleration.