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Matrix Expansion (matrix + expansion)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Generation, modeling, and analysis of CCII-based gyrators using the generalized symbolic framework for linear active circuits

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 3 2008
Ramy A. Saad
Abstract In this paper, CCII-based gyrators are synthesized, modeled, and analyzed using the generalized symbolic framework for linear active circuits. The systematic synthesis method using admittance matrix expansion, included in the framework, is applied to generate optimized nullor,mirror descriptions for the gyrator. The resulting CCII-based circuit representations for the gyrators, obtained from mapping nullor,mirror pairs in the ideal realizations with equivalent second-generation current conveyors (CCIIs), can be classified into two topologies according to the type of the CCII terminals handling the gyrator input and output signals. In topology I, the gyrator input and output terminals are CCIIs Y,Z -terminals, whereas in topology II, the gyrator input and output terminals are CCIIs X -terminals. The parasitic components within the synthesized circuits, associated with the actual CCIIs, are modeled and included in their expanded admittance matrices. Exact non-ideal analysis for two circuits belonging to the two topologies, involving the reduction of their expanded admittance matrices to port admittance matrices, is then carried out to investigate the practical functional performance for these circuits at their ports. The non-ideal performance analysis based on the CCII actual parasitic elements indicates that, from a practical perspective, the CCII-based gyrator circuits belonging to topology I are more efficient and suitable for the gyrator applications than those belonging to topology II in terms of bandwidth and operation at high frequencies. SPICE simulations are included to demonstrate the analytical results for the comparison between the practical performances of the two circuit topologies. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Mesangial cell proliferation inhibitors for the treatment of proliferative glomerular disease

MEDICINAL RESEARCH REVIEWS, Issue 1 2003
Yasuhisa Kurogi
Abstract Mesangial cells (MC) serve a number of functions in the renal glomerular capillary including structural support of the capillary tuft, modulation of glomerular hemodynamics, and a phagocytic function allowing removal of macromolecules and immune complexes. The proliferation of MC is a prominent feature of glomerular disease including IgA nephropathy, membranoproliferative glomerulonephritis, lupus nephritis, and diabetic nephropathy. In experimental animal models of nephritis, MC proliferation frequently precedes and is linked to the increase of extracellular matrix in the mesangium and glomerulosclerosis. Reduction of MC proliferation in glomerular disease models by treatment with heparin, low-protein diet, or antibodies to platelet-derived growth factor (PDGF), have been shown to reduce extracellular matrix expansion and glomerulosclerotic changes. Therefore, MC proliferation inhibitors may offer therapeutic opportunities for the treatment of proliferative glomerular disease. It is also known that the MC proliferation is inhibited by many kinds of pharmacological drugs, for example, angiotensin converting enzyme (ACE) inhibitors, leukotriene D4 (LTD4) antagonists, PDGF inhibitors, matrix metalloproteinases (MMP) inhibitors, 3-hydroxy-3 methyl glutaryl-coenzymeA (HMG-CoA) inhibitors, cyclin-dependent kinases (CDK) inhibitors, and others. This review summarizes the recently reported MC proliferation inhibitors with their pharmacological properties on the basis of their chemical structures. © 2002 Wiley Periodicals, Inc. Med Res Rev, 23, No. 1, 15,31, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10028 [source]

Evaluation by scanning acoustic microscopy (SAM) on glomerular lesion of IgA nephropathy

NEPHROLOGY, Issue 2001
H Kiyomoto
IgA nephropathy (IgAN) is known to commonly cause of end-stage renal failure in Japan. The glomerular lesions of IgAN have histological variations. The determination of prognosis and therapeutic strategy should be carefully done by experts because morphological information from renal biopsies using ordinary optical microscopy is usually qualitative and subjective. Moreover, the histological items for the evaluation of glomerular lesions seems to be unsatisfactory for expression of the disease condition of IgAN. The beneficial properties of scanning acoustic microscopy (SAM) include not only observation of microstructure but also quantitative measurement of acoustic propagation speed (APS), indicating the tissue elasticity. In the present study we compared the APS of glomeruli with the pathological scores that were determined by ordinary light microscopy. We used stocked human renal biopsy specimens diagnosed as IgAN (n = 12) and normal/minimal changes (n = 5). All samples were taken by renal biopsy in Kagawa Medical University Hospital during 1997,2000 under informed consent of the patients. The obtained renal tissue were immersed in 10% formalin and embedded in paraffin. A fixed specimen was consecutively cut into 4 ,m slices. One of the deparaffinized 4 ,m-specimens was directly utilized for SAM without any staining, and the others were stained with haematoxylin-eosin and Masson Trichrome for counting cell number and evaluation of collagen accumulation. For the measurement of glomerular APS, the sample line was set on the equator of the glomerulus and then scanning of the X,Z axis was carried out to obtain the interference fringes that were analysed with a computer imaging software in order to calculate the APS. In light microscopic study, pathological scores were evaluated semiquantitatively by two independent investigators who were unaware of the sample number. Glomerular lesions were scored into five grades and glomerular cell number was also counted in individual glomerulus. The computer-assisted imaging analyser Win ROOF (Mitani, Fukui, Japan) was also used for the determination of glomerular collagen content in specimens stained by Masson Trichrome. A two-dimensional image (C-mode scanning) of SAM enabled imaging of glomerulus in renal biopsy specimen compatible with findings of ordinary light microscopy without staining dye. The glomerular APS in IgAN was significantly higher than in normal/minimal changes. This alteration of glomerular APS in IgAN was positively correlated to both semiquantitative pathological scores and glomerular collagen content determined by light microscopy. However, the cell number of glomelurus did not change between IgAN and normal/minimal change. As a result, we conclude that the glomerular lesion, especially matrix expansion in IgAN, was comparable with the absolute value among specimens. Therefore, it is suggested that SAM method is a novel and useful technique for quantitative evaluation of glomerular lesion in IgAN. [source]

Mangiferin prevents diabetic nephropathy progression in streptozotocin-induced diabetic rats

PHYTOTHERAPY RESEARCH, Issue 6 2010
Xuan Li
Abstract Diabetic nephropathy is one of the most severe diabetic microangiopathies and accounting for approximately one-third of all cases of end-stage renal disease. In the present study, we investigated the effect of mangiferin, a polyphenol from Anemarrhena asphodeloides Bge. or Mangifera indica L., on diabetic nephropathy and the possible mechanisms by using a developed diabetic nephropathy rat model and cultured rat mesangial cells. Serum-advanced glycation end-products level, malonaldehyde level, sorbitol concentration of red blood cell, 24,h albuminuria excretion were significantly decreased, whereas activity of serum superoxide dismutase and glutathione peroxidase and creatinine clearance rate were increased by mangiferin. Blood glucose level remained unaffected. Mangiferin significantly inhibited glomerular extracellular matrix expansion and accumulation and transforming growth factor-beta 1 overexpression in glomeruli of diabetic nephropathy rats. Moreover, mangiferin was observed to inhibit proliferation of mesangial cells induced by high glucose and the overexpression of collagen type IV of mesangial cells induced by advanced glycation end products. In summary, mangiferin could significantly prevent progression of diabetic nephropathy and improve renal function. Copyright © 2009 John Wiley & Sons, Ltd. [source]