Identification of type of threading dislocation causing reverse leakage in GaN p-n junctions after continuous forward current stress.

Power devices are operated under harsh conditions, such as high currents and voltages, and so degradation of these devices is an important issue. Our group previously found significant increases in reverse leakage current after applying continuous forward current stress to GaN p-n junctions. In the present study, we identified the type of threading dislocations that provide pathways for this reverse leakage current. GaN p-n diodes were grown by metalorganic vapor phase epitaxy on freestanding GaN(0001) substrates with threading dislocation densities of approximately 3 × 105 cm-2. These diodes exhibited a breakdown voltage on the order of 200 V and avalanche capability. The leakage current in some diodes in response to a reverse bias was found to rapidly increase with continuous forward current injection, and leakage sites were identified by optical emission microscopy. Closed-core threading screw dislocations (TSDs) were found at five emission spots based on cross-sectional transmission electron microscopy analyses using two-beam diffraction conditions. The Burgers vectors of these dislocations were identified as [0001] using large-angle convergent-beam electron diffraction. Thus, TSDs for which b = 1c are believed to provide current leakage paths in response to forward current stress.

Real world long-term outcomes in patients with mucopolysaccharidosis type II: A retrospective cohort study.

We investigated the decline of activities of daily living with symptomatic progression in patients with mucopolysaccharidosis type II (MPS II) and investigated the associated factors. Clinical data were retrospectively collected from the medical records of 28 patients with MPS II who visited our hospital between October 2007 and August 2019. Activities of daily living were assessed over time using a 5-point scale (from stage 1, indicating independent, to stage 5, indicating total assistance + medical care); the relationships of the interval years from stage 2 (mild symptoms) to stage 4 (total assistance) with therapeutic intervention, anti-drug antibodies (ADA), urinary glycosaminoglycans (uGAG), and genotypes were analyzed. Eight are attenuated types, and 20 are severe types. Further, 20 underwent enzyme replacement therapy (ERT) alone, 5 underwent hematopoietic stem cell transplantation (HSCT) alone, and 3 underwent both therapy. The mean interval years (standard deviation) from stage 2 to 4 was 3.5 (0.7) and 7.3 (3.3) in patients who started undergoing ERT (n = 6) and HSCT (n = 3) at stage 2, respectively, whereas it was 3.1 (1.5) in patients who received no treatment until they reached stage 4 (n = 8). The study findings revealed the process of changes in the activities of daily living over a long duration in patients with MPS II undergoing different treatments. In severe type, the activity deteriorated regardless of the stage at which ERT was initiated. The activity declined slower in patients who received HSCT at an early stage.

Divergent developmental trajectories in two siblings with neuropathic mucopolysaccharidosis type II (Hunter syndrome) receiving conventional and novel enzyme replacement therapies: A case report.

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked recessive lysosomal storage disease caused by a mutation in the IDS gene and characterized by systemic accumulations of glycosaminoglycans. Its somatic symptoms can be relieved by enzyme replacement therapy (ERT) with idursulfase, but because the enzyme cannot cross the blood-brain-barrier (BBB), it does not address the progressive neurodegeneration and subsequent central nervous system (CNS) manifestations seen in patients with neuropathic MPS-II. However, pabinafusp alfa, a human iduronate-2-sulfatase (IDS) fused with a BBB-crossing anti-transferrin receptor antibody, has been shown to be efficacious against both the somatic and CNS symptoms of MPS II. We report two cases of MPS-II in Japanese siblings sharing the same G140V mutation in the IDS gene, who showed markedly contrasting developmental trajectories following enzyme replacement therapy (ERT). Sibling 1 was diagnosed at 2 years of age, started undergoing conventional ERT shortly afterward, and scored a developmental quotient (DQ) of 53 on the Kyoto Scale of Psychological Development (KSPD) at 4 years of age. Sibling 2 was diagnosed prenatally and received conventional ERT from the age of 1 month through 1 year and 11 months, when he switched to pabinafusp alpha. He attained a DQ of 104 at age 3 years and 11 months, along with significant declines in heparan sulfate concentrations in the cerebrospinal fluid. This marked difference in neurocognitive development highlights the importance of early initiation of ERT with a BBB-penetrating enzyme in patients with neuropathic MPS-II.

Identification of glycosylated exendin-4 analogue with prolonged blood glucose-lowering activity through glycosylation scanning substitution.

Exendin-4, a glucagon-like peptide 1 receptor agonist, is a potent therapeutic xenopeptide hormone for the treatment of type 2 diabetes. In order to further improve in vivo activity, we examined the introduction of sialyl N-acetyllactosamine (sialyl LacNAc) to exendin-4. The glycosylated analogue having sialyl LacNAc at position 28 was found to have improved in vivo activity with prolonged glucose-lowering activity.

Chemoenzymatic synthesis of glycosylated glucagon-like peptide 1: effect of glycosylation on proteolytic resistance and in vivo blood glucose-lowering activity.

Glucagon-like peptide 1 (7-36) amide (GLP-1) has been attracting considerable attention as a therapeutic agent for the treatment of type 2 diabetes. In this study, we applied a glycoengineering strategy to GLP-1 to improve its proteolytic stability and in vivo blood glucose-lowering activity. Glycosylated analogues with N-acetylglucosamine (GlcNAc), N-acetyllactosamine (LacNAc), and alpha2,6-sialyl N-acetyllactosamine (sialyl LacNAc) were prepared by chemoenzymatic approaches. We assessed the receptor binding affinity and cAMP production activity in vitro, the proteolytic resistance against dipeptidyl peptidase-IV (DPP-IV) and neutral endopeptidase (NEP) 24.11, and the blood glucose-lowering activity in diabetic db/db mice. Addition of sialyl LacNAc to GLP-1 greatly improved stability against DPP-IV and NEP 24.11 as compared to the native type. Also, the sialyl LacNAc moiety extended the blood glucose-lowering activity in vivo. Kinetic analysis of the degradation reactions suggested that the sialic acid component played an important role in decreasing the affinity of peptide to DPP-IV. In addition, the stability of GLP-1 against both DPP-IV and NEP24.11 incrementally improved with an increase in the content of sialyl LacNAc in the peptide. The di- and triglycosylated analogues with sialyl LacNAc showed greatly prolonged blood glucose-lowering activity of up to 5 h after administration (100 nmol/kg), although native GLP-1 showed only a brief duration. This study is the first attempt to thoroughly examine the effect of glycosylation on proteolytic resistance by using synthetic glycopeptides having homogeneous glycoforms. This information should be useful for the design of glycosylated analogues of other bioactive peptides as desirable pharmaceuticals.

Histamine regulates growth of malignant melanoma implants via H2 receptors in mice.

The present study examined the effect of histamine H2-receptor antagonists and exogenous histamine on growth of malignant melanoma implant in mice. Drugs were administered to B16BL6 malignant-melanoma-implanted syngeneic mice, and the tumor volume was measured throughout the experiments. Cell proliferation was assessed by MTT assay and mRNA expression was determined by RT-PCR. Both roxatidine and cimetidine significantly suppressed growth of B16BL6 implant compared with vehicle. On the other hand, systemically administered histamine significantly stimulated growth of B16BL6 implants. In addition, the histamine-stimulated B16BL6 implant growth was markedly suppressed by co-administration of cimetidine in a dose-dependent manner. H2-receptor antagonists, however, failed to affect in vitro proliferation of B16BL6 cells. H2-receptor mRNA was detected in B16BL6 implants but not in the cell line. These results indicated that both endogenous and exogenous histamine have ability to stimulate growth of malignant melanoma implants via H2 receptors expressed in host cells.

Exogenous histamine stimulates colorectal cancer implant growth via immunosuppression in mice.

Results from a limited number of studies suggest a potential role for endogenous histamine in regulating tumor growth in immunocompetent cells. The present study examined the effects of exogenous histamine on colorectal cancer growth and the immune response against tumor tissue in mice. Histamine was administered for 21 days to Colon 38 mouse colon adenocarcinoma-implanted syngeneic mice and tumor volume was measured throughout the experiment. Systemic administration of histamine for 21 days caused a significant increase in tumor implant growth compared with the vehicle. At the end of histamine administration, the interferon (IFN)-gamma / interleukin (IL)-4 ratio in peripheral lymphocytes, as well as histamine and cytokine levels in tumor implants were determined. Histamine levels in tumor implants remained unchanged after exogenous histamine delivery. Mice with tumor implants exhibited significantly elevated IFN-gamma / IL-4 ratios compared with mice lacking tumors. Nonetheless, the increased IFN-gamma / IL-4 ratios were markedly suppressed by histamine administration compared with vehicle. In addition, histamine delivery significantly decreased IFN-gamma and IL-12 mRNA expression, but increased IL-10 mRNA expression in tumor implants. It was concluded that exogenous histamine dysregulates the balance between T-helper 1 (Th1) and T-helper 2 (Th2) cells, attenuating anti-tumor cytokine expression in the tumor microenvironment, thus resulting in stimulated colorectal cancer growth.

Roxatidine- and cimetidine-induced angiogenesis inhibition suppresses growth of colon cancer implants in syngeneic mice.

Cimetidine is known to suppress the growth of several tumors, including gastrointestinal cancer, in humans and animals. Nonetheless, whether other histamine H(2)-receptor antagonists exert such tumor suppressive effects remains unclear. The effect of roxatidine acetate hydrochloride (roxatidine), an H(2)-receptor antagonist, on the growth of colon cancer implanted in mice was examined and compared with that of cimetidine. Drugs were orally delivered for 26 - 29 days beginning before or after implantation of syngeneic colon cancer (Colon 38) in C57BL/6 mice. Tumor volume was determined throughout and histochemical analysis was also performed. Tumor tissue and serum vascular endothelial growth factor (VEGF) levels were measured. In vitro cell growth was assessed by the MTT assay. Both roxatidine and cimetidine significantly suppressed the growth of Colon 38 tumor implants. Histologic analysis revealed that such antagonists markedly increased necrotic areas and decreased the density of microvessels in tumor tissue. Both H(2)-receptor antagonists suppressed VEGF levels in tumor tissue and significantly decreased serum VEGF levels in Colon 38-bearing mice. Such drugs, however, failed to suppress in vitro growth of the cell line. In conclusion, both roxatidine and cimetidine were found to exert suppressive effects on the growth of colon cancer implants in mice by inhibiting angiogenesis via reducing VEGF expression.

PbCl2-induced hyperpolarization of rat thymocytes: involvement of charybdotoxin-sensitive K+ channels.

The effect of PbCl2 on membrane potential and intracellular divalent metal cation concentrations of rat thymocytes was examined by flow cytometry. PbCl2 at concentrations of 0.3 microM or higher (up to 10 microM) produced persistent, dose-dependent hyperpolarization (decrease in the intensity of di-BA-C4 fluorescence). Removal of external Ca2+ did not significantly affect the PbCl2-induced hyperpolarization. Charybdotoxin, a specific antagonist of Ca(2+)-dependent K+ conductance, greatly attenuated the PbCl2-induced hyperpolarization. PbCl2 increased the intensity of fluo-3 fluorescence under both normal Ca2+ and nominally Ca(2+)-free conditions. These results suggest that Pb2+ enters thymocytes, causing an increase in fluo-3 fluorescence, and activates Ca(2+)-dependent K+ channels, resulting in hyperpolarization. The persistent activation of K+ channels by Pb2+, leading to persistent hyperpolarization, may be one mechanism whereby Pb2+ alters immune function, as membrane potential changes influence physiological functions of lymphocytes.

Pharmacological control of gastric acid secretion for the treatment of acid-related peptic disease: past, present, and future.

Pharmacological agents, such as histamine H(2) receptor antagonists and acid pump inhibitors, are now the most frequently used treatment for such acid-related diseases as gastroduodenal ulcers and reflux esophagitis. Based on increased understanding of the precise mechanisms of gastric acid secretion at the level of receptors, enzymes, and cytoplasmic signal transduction systems, further possibilities exist for the development of effective antisecretory pharmacotherapy. Gastrin CCK(2) receptor antagonists and locally active agents appear to represent promising therapies for the future. Development of gene targeting techniques has allowed production of genetically engineered transgenic and knockout mice. Such genetic technology has increased the investigative power for pharmacotherapy for not only antisecretory agents, but also treatment of mucosal diseases, such as atrophy, hyperplasia, and cancer. Elucidation of the origin of gastric parietal cells also represents an interesting investigative target that should allow a better understanding of not only acid-related diseases, but also the evolution of the stomach as an acid-secreting organ.

Influence of Helicobacter pylori infection on healing and relapse of acetic acid ulcers in Mongolian gerbils.

Both Helicobacter pylori and NSAIDs play important roles in the healing and relapse of peptic ulcers in man. We examined how H. pylori infection, indomethacin, and their combination affects the healing of gastric ulcers and whether or not such factors provoke a relapse of healed gastric ulcers in Mongolian gerbils. Gastric ulcers were induced by serosal application of an acetic acid solution. H. pylori (ATCC43504) was orally administered once into animals with active and healed ulcers. Ulcers healed within eight weeks and remained healed for the following six months. H. pylori infection significantly delayed ulcer healing four weeks following infection. Indomethacin treatment showed a tendency to delay ulcer healing. Ulcer healing in H. pylori-infected Mongolian gerbils was significantly delayed by indomethacin. H. pylori infection resulted in a relapse of healed ulcers from one to six months after infection, with a gradual increase in size. By the fourth month following a relapse, the serum gastrin level had significantly increased. H. pylori-induced ulcers in the posterior wall coexisted with relapsed ulcers in the anterior wall five and six months later. Omeprazole markedly prevented the ulcer relapse caused by H. pylori infection. It is concluded that, in Mongolian gerbils, H. pylori infection delayed the healing of preexisting gastric ulcers and resulted in the relapse of healed ulcers, yet indomethacin had little or no effect on ulcer healing or relapse.