Hydrophobic interactions at subsite S1′ of human dipeptidyl peptidase IV contribute significantly to the inhibitory effect of tripeptides

Functional inhibitory peptides of human dipeptidyl peptidase 4 (hDPP4) have been highly anticipated as the active ingredient of functional food for type II diabetes; however, the molecular mechanism of hDPP4 inhibition remains unclear. In this study, we focused on dipeptides and tripeptides, which display structure-function correlations that are relatively easy to analyze, and examined their interactions with hDPP4 on an atomic level using a combination of docking studies and an hDPP4 inhibition assay. First, we performed comprehensive binding mode analysis of the dipeptide library and demonstrated that the formation of a tight interaction with the S1 subsite composing part of the substrate pocket is essential for dipeptides to compete with the substrate and strongly inhibit hDPP4. Next, we synthesized tripeptides by adding various amino acids to the C-terminus of Ile-Pro and Val-Pro, which have especially high inhibitory activity among compounds in the dipeptide library, and measured the hDPP4 inhibitory activity of the tripeptides. When hydrophobic amino acids (Ile, Met, Val, Trp) were added, the inhibitory activity increased several-fold. This phenomenon could be explained as follows: the C-terminal amino acid of the tripeptide formed hydrophobic interactions with Tyr547 and Trp629, which compose the S1′ subsite located relatively outside the substrate pocket, thereby stabilizing the hDPP4-peptide binding. The structural information on the interaction between hDPP4 and peptide inhibitors attained in this study is anticipated to be useful in the development of a more potent hDPP4 competitive inhibitor

Gastric Carcinoid with Hypergastrinemia: Report of Three Cases

We report 3 cases of gastric carcinoids with hypergastrinemia. Case 1: A 60-year-old man had a 2 cm carcinoid of the stomach and underwent partial resection. Involvement of the muscularis propria and lymph nodes metastasis were observed microscopically. Follow-up gastroscopy revealed another carcinoid lesion and total gastrectomy was performed. Case 2: A 67-year-old woman with multiple carcinoids of the entire stomach underwent antrectomy. No growth of residual tumors has been detected so far. Case 3: A 61-year-old man had a tumor near the esophagogastric junction and underwent total gastrectomy. Carcinoid component was diffusely intermingled with adenocarcinoma in the tumor and invaded into the subserosa. In all 3 cases, the serum gastrin level was high and atrophic gastritis was microscopically observed. Carcinoid tumor in Case 3 was different from those in Cases 1 and 2 and interestingly, gastric carcinoid with hypergastrinemia showed various types of appearance

Double radiofrequency ablation is more extensive with a spherical zone shape compared to single ablation in a pig liver model

Objective : We compared the duration of ablation and the area of coagulation necrosis between a single ablation method (SAM) and a double ablation method (DAM) with a ’multitined expandable’ electrode (LeVeen 2cm) for radiofrequency ablation (RFA) using pig liver. Method : In the SAM group, ablation was completed after the first roll-off. In the DAM group, an additional ablation was performed to achieve a second roll-off. The comparison was made of the time required for roll-off and the extent of coagulation necrosis between the both groups. The Ellipticity index (EI) quantitatively describes the shape of the general RF ablation zone in the axial plane. Results : There was no statistically significant difference in the interval until the first roll-off between both groups (SAM group : 100.7±24.7 seconds vs DAM group : 103.2±37.7 seconds, P=0.43). In the DAM group, the interval from the start of the additional ablation until the second roll-off was 154.0±86.9 seconds, longer than the interval for the first roll-off (P=0.023). The extent of coagulation necrosis was significantly more extensive in the DAM group (axial diameter, mean±SD, 26.2±2.8 mm)×(maximal diameter : 29.3±1.6 mm)× (minimal diameter : 26.5±3.6 mm) compared to the SAM group with (23.0±3.3 mm)×(23.7± 3.1 mm)×(20.0±2.5 mm), respectively. Although there was no statistically significant difference in the EI between both groups, macroscopically, the shape of coagulation necrosis tended to be non-spherical in the SAM group and spherical in the DAM group. Conclusions : The DAM with a ’multitined expandable’ electrode was more extensive with a spherical zone shape compared to the SAM

Identification and Modulation of the Key Amino Acid Residue Responsible for the pH Sensitivity of Neoculin, a Taste-Modifying Protein

Neoculin occurring in the tropical fruit of Curculigo latifolia is currently the only protein that possesses both a sweet taste and a taste-modifying activity of converting sourness into sweetness. Structurally, this protein is a heterodimer consisting of a neoculin acidic subunit (NAS) and a neoculin basic subunit (NBS). Recently, we found that a neoculin variant in which all five histidine residues are replaced with alanine elicits intense sweetness at both neutral and acidic pH but has no taste-modifying activity. To identify the critical histidine residue(s) responsible for this activity, we produced a series of His-to-Ala neoculin variants and evaluated their sweetness levels using cell-based calcium imaging and a human sensory test. Our results suggest that NBS His11 functions as a primary pH sensor for neoculin to elicit taste modification. Neoculin variants with substitutions other than His-to-Ala were further analyzed to clarify the role of the NBS position 11 in the taste-modifying activity. We found that the aromatic character of the amino acid side chain is necessary to elicit the pH-dependent sweetness. Interestingly, since the His-to-Tyr variant is a novel taste-modifying protein with alternative pH sensitivity, the position 11 in NBS can be critical to modulate the pH-dependent activity of neoculin. These findings are important for understanding the pH-sensitive functional changes in proteinaceous ligands in general and the interaction of taste receptor–taste substance in particular

A subset of ocular adnexal marginal zone lymphomas may arise in association with IgG4-related disease

We previously suggested a relationship between ocular immunoglobulin (Ig)G4-related disease (IgG4-RD) and marginal zone lymphomas (MZLs). However, the cytokine background associated with these disorders and whether it differs between ocular adnexal MZLs with (IgG4-associated MZL) and without (IgG4-negative MZL) numerous IgG4+ plasma cells are unknown. In this study, we identified the mRNA expression pattern of Th2 and regulatory T-cell (Treg) cytokines in IgG4-RD and in IgG4-associated MZL and IgG4-negative MZL using real-time polymerase chain reaction analysis. Ocular IgG4-RD and IgG4-associated MZL exhibited significantly higher expression ratios of interleukin (IL)-4/β-actin, IL-10/β-actin, IL-13/β-actin, transforming growth factor (TGF) β1/β-actin, and FOXP3/β-actin than did IgG4-negative MZL (p < 0.05). This finding further supports our prior observations that a significant subset of ocular MZLs arises in the setting of IgG4-RD. Furthermore, the presence of a different inflammatory background in IgG4-negative MZLs suggests that IgG4-associated MZLs may have a different pathogenesis

Influence of an artificial pleural effusion technique on cardio-pulmonary function and autonomic activity

Objective : Percutaneous treatment of hepatocellular carcinoma (HCC) located directly under the diaphragm is problematic because ultrasonic imaging is difficult, and the lung may be injured during the procedure. It has been reported that an infusion of 5% glucose solution into the thoracic cavity enables percutaneous treatment in such cases. However, the safety aspects of this have not been investigated. In this study, variations in heart rate and changes in circulatory and respiratory dynamics were examined during the infusion of artificial pleural effusion directly under the diaphragm in patients with HCC. Method : The subjects were 13 patients with an HCC directly under the diaphragm. About 500 ml of a 5% glucose solution was infused into the thoracic cavity, and mean blood pressure, heart rate, and oxygen saturation were measured. Holter electrocardiography was simultaneously recorded to evaluate autonomic nerve function. To analyze variations in heart rate, the low-frequency waves (LF : 0.04-0.15 Hz), high-frequency waves (HF : 0.15-0.40 Hz, an index of parasympathetic nerve activity), and the LF/HF ratio (index of sympathetic nerve activity) were examined. The above parameters were measured before, during (when infusion of the half the planned volume was complete), and after infusion were compared. Results : No significant changes in the mean blood pressure or heart rate were found. Oxygen saturation was significantly decreased during and after the infusion. The HF value was slightly higher after infusion and the LF value was significantly increased during infusion. The LF/HF ratio was significantly increased during infusion, and this increase persisted after infusion. Conclusions : The infusion of artificial pleural effusion had no effect on circulatory dynamics, but transiently affected respiratory functions. It was also revealed that infusion stimulated the parasympathetic nerves

Interferon-α enhances biological defense activities against oxidative stress in cultured rat hepatocytes and hepatic stellate cells

Oxidative stress has been implicated as a cause of hepatic fibrosis, and hepatic stellate cells (HSCs), which are the most important collagen-producing cell types, have been reported to be activated by lipid peroxidation products. Antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) provide a defense system that plays a critical role in protecting the cell from free radical damage, particularly lipid peroxidation. To elucidate the antioxidant activity of interferon-α (IFN-α), the effects of IFN-α on rat hepatocytes undergoing oxidative stress and HSCs in primary culture as well as isolated rat liver mitochondria were examined. IFN-α was observed to dose-dependently increase the immunoreactive protein levels of copper, zinc-and manganese-dependent SOD as well as the enzyme activities of GPx, and decrease the lipid peroxidation product levels and oxidative burst both in stressed hepatocytes and activated HSCs GPx activities, however, were not detected in the latter cells. IFN-α also inhibited HSC activation and lipid peroxidation in liver mitochondria. These findings suggest that IFN-α may enhance biological defense activities against oxidative stress and function as a potent fibrosuppressant by protecting hepatocytes and hepatic stellate cells from lipid peroxidation in vivo

Upgraded millimeter-wave interferometer for measuring the electron density during the beam extraction in the negative ion source

The upgraded millimeter-wave interferometer with the frequency of 70 GHz is installed on a large-scaled negative ion source. Measurable line-averaged electron density is from 2×1015to 3×1018m−3in front of the plasma grid. Several improvements such as the change to shorter wavelength probing with low noise, the installation of special ordered horn antenna, the signal modulation for a high accuracy digital phase detection, the insertion of insulator, and so on, are carried out for the measurement during the beam extraction by applying high voltage. The line-averaged electron density is successfully measured and it is found that it increases linearly with the arc power and drops suddenly at the beam extraction

MRI Appearance of Prostatic Stromal Sarcoma in a Young Adult

Prostatic stromal sarcoma (PSS) is quite rare. Herein, we describe magnetic resonance imaging (MRI) features of a PSS identified in a 26-year-old man with dysuria and hematuria. MRI clearly depicted the extent and multinodular appearance of the tumor, which was mainly located in the central zone of the prostate. The tumor appeared as a heterogeneously signal-hyperintense mass with a pseudocapsule on T2-weighted imaging. Contrast-enhanced T1-weighted MRI showed necrotic portions in the gradually enhanced solid mass, and diffusion-weighted imaging permitted the accurate assessment of the local extent of the tumor. Thus, the appearance on MRI was quite different from that of adenocarcinoma of the prostate