The buccal mucosa is an inner lining exposed to frequent friction caused by teeth occlusion and therefore, a vulnerable site to lesions such as stomatitis, leukoplakia, lichen planus and cancer. Although it is considered an important tissue in the field of oral surgery, not enough information regarding the buccal mucosa is available. In this study, we characterized the buccal mucosa in the oral cavity using imaging mass spectrometry (IMS). Tissues such as epithelium, lamina propria and muscle were identified in rat buccal mucosa by HE staining. Moreover, IMS data of high-intensity ions were classified into 4 groups according to their distribution. In a previous IMS analysis of mouse tongue tissue, we detected linoleic acid-containing phosphatidyl choline (PC)(diacyl 16:0/18:2), oleic acid-containing PC (diacyl 16:0/18:1) and DHA-containing PC (diacyl 16:0/22:6) as major PCs. In the present work, we analyzed buccal mucosa tissue with emphasis on the aforementioned PC by IMS and showed that the investigated PCs existed in the layers of epithelium, lamina propria, and muscle at different ratios. This is the first study to analyze by IMS the buccal mucosa. The results presented here are likely to provide the perspective on understanding oral environments and to develop treatments for oral disorders.

Background: Reverse triiodothyronine (rT3) has useful clinical applications, such as differentiating euthyroid sick syndrome from hypothyroidism. However, rT3 measurement is unavailable in the clinical setting in Japan. Therefore, we assessed the feasibility of using liquid chromatography–tandem mass spectrometry (LC–MS/MS) for measuring serum rT3 levels in outpatients.

Method: MS/MS detection was performed in the positive ionization mode on a tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The precursor–product ion pairs of rT3 (m/z 652→508) and ¹³C₆-rT3 (m/z 658→514) were selected. Quantification was performed via selected reaction monitoring using peak areas. The serum from 89 patients (age, 8.1±8.1 years) who visited Aichi Medical University was collected. Patients diagnosed with thyroid disease were excluded. rT3 was extracted from 100 μL of patient serum by liquid–liquid extraction. ¹³C₆-rT3 was used as the internal standard. Serum rT3 levels were also determined using a radioimmunoassay (RIA) kit.

Result: The lower limit of rT3 quantification was 0.02 ng/mL. The relative standard deviation and relative error were <9% and <4%, respectively, indicating an acceptable level of reproducibility. Compared with RIA, LC–MS/MS exhibited superior linearity (0.99872 versus 0.99999). rT3 levels in the patient serum samples were in the range of 0.038–0.853 ng/mL.

Conclusion: The LC–MS/MS technique reliably measured rT3 in the serum of 89 outpatients.

Pathogenesis of autism spectrum disorder (ASD) remains unclear and there are still no proper clinical diagnosis biomarkers or effective medical therapy methods for ASD. Previous studies have implicated physiological and metabolic abnormalities in ASD. Here we performed a metabolome analysis of urine and dry blood spot samples from 90 ASD patients and 90 age-matched controls from China using mass spectrometry. To our certain knowledge, this is the first study investigating ASD patients’ urinary and blood metabolites at the same time. Abnormalities in urinary and blood amino acids, organic acids and acylcarnitines showed a similar tendency to the reported physiological and metabolic abnormalities in ASD patients. This thesis aimed at detailing the metabolome information of Chinese ASD patients, hoping to help the study of ASD pathology, quantitative diagnosis or therapy methods.