Suppression of drain conductance in InP-based HEMTs by eliminating hole accumulation

We have developed planar-type InP-based high-electron mobility transistors (HEMTs) that significantly suppress the frequency dispersion of drain conductance (g/sub d/) and the kink phenomena, and have examined the physical mechanisms of these phenomena. These phenomena appear to be caused by hole accumulation at the extrinsic source due to impact ionization. Our planar structure includes alloyed ohmic contacts that eliminate the hole barrier at the interface between the carrier-supply layer and the channel in the source and drain region to suppress hole accumulation. Therefore, the planar structure effectively eliminated hole accumulation at the extrinsic source, and suppressed g/sub d/ frequency dispersion to 25% and the kink phenomena to 50% compared with conventional structure HEMTs.     

Suppression of leukotriene formation in RBL-2H3 cells that overexpressed phospholipid hydroperoxide glutathione peroxidase

The overexpression of phospholipid hydroperoxide glutathione peroxidase (PHGPx) by RBL-2H3 cells was used as the basis for an investigation of the effects of PHGPx on the formation of leukotrienes. The rates of production of leukotriene C4 (LTC4) and leukotriene B4 (LTB4) in cells that overexpressed PHGPx were 8 times lower than those in a control line of cells. The reduction in rates of production of leukotrienes apparently resulted from the increase in the PHGPx activity since control rates of formation of leukotrienes could be achieved in PHGPx-overexpressing cells upon inhibition of PHGPx activity by diethyl malate. The conversion of radioactively labeled arachidonic acid to intermediates in the lipoxygenase pathway, such as 5-hydroxyeicosatetraenoic acid (5-HETE), LTC4, and LTB4, was strongly inhibited in PHGPx-overexpressing cells that had been prelabeled with [14C]arachidonic acid. PHGPx apparently inactivated the 5-lipoxygenase that catalyzed the conversion of arachidonic acid to 5-hydroperoxyeicosatetraenoic acid (5-HPETE) since 5-HPETE is a common precursor of 5-HETE, LTC4, and LTB4. The rates of formation of LTC4 and LTB4 in PHGPx-overexpressing cells returned to control rates upon the addition of a small amount of 12-HPETE. Flow cytometric analysis revealed that the rapid burst of formation of lipid hydroperoxides induced by A23187 was suppressed in PHGPx-overexpressing cells as compared with the control lines of cells. Subcellular fractionation analysis showed that the amount of PHGPx associated with nuclear fractions from PHGPx-overexpressing cells was 3.5 times higher than that from the control line of cells. These results indicate that PHGPx might be involved in inactivation of 5-lipoxygenase via reductions in levels of the fatty acid hydroperoxides that are required for the full activation of 5-lipoxygenase. Thus, in addition to its role as an antioxidant enzyme, PHGPx appears to have a novel function as a modulator of the production of leukotrienes.     

Ventral pancreatic resection for adenoma and low-grade malignancies of the head of the pancreas

The head of the pancreas can be anatomically divided into two sections, one drained by the duct of the Santorini system, and the other drained by the ventral pancreatic duct. This study was undertaken to determine whether independent resection of the ventral pancreas drained by the ventral pancreatic duct could be performed safely and effectively, by employing the following method in four patients. First, the duodenum and pancreas were sufficiently separated preserving the mesoduodenum and the posterior pancreaticoduodenal artery. Next, the main pancreatic duct was divided at the papillary portion, and sectioned at its junction with the duct of Santorini, ensuring preservation of the intrapancreatic bile duct. After the ventral pancreas had been detached from the glistening intrapancreatic bile duct, the ventral pancreas was connected with the dorsal pancreas by only the pancreatic parenchyma. The ventral pancreatic resection was completed following the incision of this border. A pancreatic fistula developed in one patient postoperatively, but this healed within 30 days. The hospital stay after surgery ranged from 35 to 58 days, and a good quality of life was maintained in all four patients. Thus, we conclude that ventral pancreatic resection can be safely performed and is especially valuable for treating the increasingly frequent adenomas and borderline malignancies in the main pancreatic duct system of the head of the pancreas.     

Vascular action of circulating and local natriuretic peptide systems is potentiated in obese/hyperglycemic and hypertensive rats

Hypertension is commonly associated with diabetes mellitus. The aim of the present study was to explore the pathophysiological significance of the natriuretic peptide (NP) system in hypertension associated with genetically obese/hyperglycemic Wistar fatty rats. The messenger RNA (mRNA) levels of the two biologically active NP receptors, NP-A receptor [more specific for atrial natriuretic peptide (ANP)] and NP-B receptor [more specific for C-type natriuretic peptide (CNP)], and CNP mRNA levels were determined in the aorta and kidney by ribonuclease protection assay. Plasma ANP levels were determined by RIA. Both NP-A and NP-B receptor mRNA levels in the aortae of Wistar fatty rats were double those in Wistar lean rats. Plasma ANP levels and CNP mRNA levels in the aorta of Wistar fatty rats were also significantly higher than those in Wistar lean rats. In contrast, there was no significant difference in renal levels of the mRNA for both NP receptors and CNP between the two strains. Administration of a NP-A and -B receptor antagonist, HS-142-1, to Wistar fatty rats resulted in a significant increase in systolic blood pressure and a larger decrease in plasma cGMP level than that in Wistar lean rats, with no difference in the extents of decrease in urine volume and urinary sodium excretion between the two strains. These results suggest that both the ANP/NP-A system and the CNP/NP-B system in vessels are up-regulated at the level of gene expression and may, thus, play an important role in counteracting the hypertension associated with diabetes mellitus.     

An asymmetrical lightly doped source cell for virtual groundhigh-density EPROMs

An EPROM cell structure with asymmetrically doped source and drain junctions, which is suitable for a virtual ground array architecture, is described. The asymmetric cell can eliminate a write disturb to an adjacent cell, which is inherent in virtual ground designs, in the write mode. In the read mode, the cell provides higher read current and substantial soft-write lifetime, along with optimization of the lightly doped n⁺ region concentration. Virtual ground designs using the cell have been implemented. A planarized process to improve manufacturability is discussed. These reliable, scalable cell and array structures are judged promising for the next generation of high-density EPROMs     

A method for rapid and complete substitution of the circulating erythrocytes in SCID mice with bovine erythrocytes and use of the substituted mice for bovine hemoprotozoa infections

We have previously developed an in vivo experimental system for a bovine hemoprotozoan parasite, in which SCID mice were periodically transfused with bovine red blood cells (Bo-RBCs), followed by infection with the parasite. The SCID mice prepared by the original method, however, had both mouse and bovine RBCs in the circulation, and their proportion always fluctuated significantly. In the present study, we aimed to deplete the mouse RBCs circulating in SCID mice and, thereby, to create SCID mice having complete Bo-RBC substitution. An anti-erythropoietin rabbit serum, an anti-mouse RBC rabbit serum and 23 monoclonal anti-mouse RBC rat antibodies were prepared for this purpose. They were examined, after administration into SCID mice, for their ability to decrease hematocrit value and also for any other adverse effect. A monoclonal antibody, clone 2E11, was found to have potent ability to induce clearance of the mouse RBCs in SCID mice without causing toxic effects. SCID mice receiving this antibody together with periodic transfusion of Bo-RBCs had their circulating RBCs completely substituted with Bo-RBCs. Infection of Bo-RBC-SCID mice with bovine hemoprotozoan parasites demonstrated that elimination of the mouse RBCs from Bo-RBC-SCID mice resulted in augmentation of parasite growth.     

Real time observation of the binding of herpes simplex virus type 1 (HSV-1) to immobilized heparan sulfate and the neutralization of HSV-1 by sulfonated human immunoglobulin

A real time biomolecular interaction assay system involving an optical sensor was applied to quantitative analysis of the binding of herpes simplex virus type 1 (HSV-1) to immobilized heparan sulfate, a cellular receptor component of HSV-1, and the neutralization antibody titer against this virus with a commercially available sulfonated human immunoglobulin preparation. The virus titer in a viral solution and the neutralizing antibody titer in the human immunoglobulin preparation could be successfully estimated in a short time with this system without any difficult cell culture.