bluuebunny/crossref_metadata_2025 huggingface dataset:
Aldose Reductase and AGE‐RAGE Pathways: Key Players in Myocardial Ischemic Injury
Authors: KANEKO MICHIYO , BUCCIARELLI LOREDANA , HWANG YUYING C. , LEE LARISEE , YAN SHI FANG , SCHMIDT ANN MARIE , RAMASAMY RAVICHANDRAN
Published: July 2005

Abstract: Cardiovascular disease represents the major cause of morbidity and mortality in patients with diabetes mellitus. The impact of cardiac disease includes increased sensitivity of diabetic myocardium to ischemic episodes and diabetic cardiomyopathy, manifested as a subnormal functional response of the diabetic heart independent of coronary artery disease. In this context, we were to our knowledge the first to demonstrate that diabetes increases glucose flux via the first and key enzyme, aldose reductase, of the polyol pathway, resulting in impaired glycolysis under normoxic and ischemic conditions in diabetic myocardium. Our laboratory has been investigating the role of the polyol pathway in mediating myocardial ischemic injury in diabetics. Furthermore, the influence of the aldose reductase pathway in facilitating generation of key potent glycating compounds has led us to investigate the impact of advanced glycation end products (AGEs) in myocardial ischemic injury in diabetics. The potent impact of increased flux via the aldose reductase pathway and the increased AGE interactions with its receptor (RAGE) resulting in cardiac dysfunction will be discussed in this chapter.
Advanced Glycation End Products and Bone Loss during Aging
Authors: ODETTI PATRIZIO , ROSSI SIMONA , MONACELLI FIAMMETTA , POGGI ALESSIA , CIRNIGLIARO MARIA , FEDERICI MARCELLO , FEDERICI ALBERTO
Published: July 2005

Abstract: It is well known that bone mass density decreases with age. Age‐related bone mass loss is ascribed to several factors. Nonenzymatic glycation has been proposed as a new potential factor in the loss of bone during aging. In this study we evaluated the concentration of pentosidine, an advanced glycation end product, in cortical and trabecular bone and in the plasma of subjects undergoing orthopedic surgery. The relationship between these parameters and a clinical index of osteoporosis was also studied. Samples of bone and plasma of 104 nondiabetic subjects (74 women and 30 men), 72 ± 1 years old, were studied. Pentosidine was determined by HPLC after decalcification and hydrolysis. The radiologic Singh index was evaluated blindly by orthopedic surgeons to provide the degree of osteoporosis. Pentosidine concentration of cortical bone shows a significant exponential increase with age (r= 0.610, P < 0.001). This increase, however, is not seen in the trabecular bone, which is characterized by a large spread in the data. Interestingly the concentration of cortical pentosidine is also related to the Singh score (rs=−0.274, P < 0.01). Plasma pentosidine has a significant exponential correlation with age (r=+0.339, P < 0.001) and a linear correlation with the cortical bone pentosidine (r=+0.248, P < 0.05). This study demonstrates that pentosidine increases exponentially in cortical bone during aging, and is thus a good biomarker for the degree of bone mass density loss. The trabecular bone concentration of pentosidine is more variable, probably because of the turnover rate and the local environment; plasma pentosidine might provide information on the bone turnover rate.
Increased Protein Glycation in Cirrhosis and Therapeutic Strategies to Prevent It
Authors: AHMED NAILA , LÜTHEN REINHARD , HÄUSSINGER DIETER , ŠEBEKOVÁ KATARÍNA , SCHINZEL REINHARD , VOELKER WOLFRAM , HEIDLAND AUGUST , THORNALLEY PAUL J.
Published: July 2005

Abstract: Glycation of liver proteins by reactive aldehydes formed from the metabolism of ethanol and lipid peroxidation has been implicated in the development of both alcoholic and nonalcoholic liver cirrhosis. Modified proteins are targeted to the proteasome for proteolysis. Release of glycation‐free adducts into the circulation may provide a diagnostic “signature” of hepatic protein damage. We quantitatively screened protein glycation, oxidation, and nitrosation adduct residues and free adducts in portal, hepatic, and peripheral venous blood plasma of cirrhotic patients; we also screened the hepatic and peripheral venous blood plasma of control subjects by liquid chromatography‐mass spectrometry. There was a remarkable 14‐16‐fold increase of glyoxal‐derived, hydroimidazolone‐free adduct in portal and hepatic venous plasma of cirrhotic patients with respect to normal controls. There was only a twofold increase of glycation adduct residues in plasma proteins in cirrhotic patients, which was attributed mainly to decreased albumin turnover. Therapeutic strategies to decrease dicarbonyl compounds may be beneficial, such as dicarbonyl scavengers, glutathione repleting agents, and high‐dose thiamine therapy.
Advanced Glycation End Products in Human Cancer Tissues: Detection of Nε‐(Carboxymethyl)lysine and Argpyrimidine
Authors: VAN HEIJST JEROEN W. J. , NIESSEN HANS W. M. , HOEKMAN KLAAS , SCHALKWIJK CASPER G.
Published: July 2005

Abstract: Tumors are generally characterized by an increased glucose uptake and a high rate of glycolysis. Since one consequence of an elevated glycolysis is the nonenzymatic glycation of proteins, we studied the presence of advanced glycation end products (AGEs) in human cancer tissues. We detected the presence of the AGEs Nε‐(carboxymethyl)lysine (CML) and argpyrimidine in several human tumors using specific antibodies. Because AGEs have been associated with the etiology of a variety of different diseases, these results suggest that CML and argpyrimidine could be implicated in the biology of human cancer.
Advanced Glycation End Product Free Adducts Are Cleared by Dialysis
Authors: AGALOU S , AHMED N , THORNALLEY P J , DAWNAY A
Published: July 2005

Abstract: Plasma advanced glycation end product (AGE) free adducts are increased up to 50‐fold among patients on dialysis. We examined the ability of hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) to clear these compounds. The AGE free adducts Nε‐carboxymethyl‐lysine (CML) and Nε‐(1‐carboxyethyl)lysine (CEL) and the hydroimidazolones derived from glyoxal (G‐H1), methylglyoxal (MG‐H1), and 3‐deoxyglucosone (3DG‐H) were determined by LC‐MS/MS and pentosidine by HPLC with fluorimetric detection in ultrafiltrates of plasma, urine, or PD effluent as appropriate from patients on HD (n= 8) or PD (n= 8), and from healthy controls (n= 8). Among patients on HD, all free AGEs predialysis were significantly higher than in controls and were decreased with dialysis. The removal of MG‐H1 and 3DG‐H was comparable to that of urea, whereas that of CML and pentosidine was some 20% higher; in contrast, the removal of CEL and G‐H1 was 25% lower. Among patients on CAPD, free AGEs in PD effluent increased with increasing dwell time. The combined renal and peritoneal 24‐h excretion rates of CML (4.7 μmol), CEL (6.5 μmol), 3DG‐H (16.6 μmol), and pentosidine (0.08 μmol) were twofold higher than the amount excreted in healthy controls, whereas MG‐H1 was ninefold higher (59 μmol); the combined clearances of all free AGEs except pentosidine were lower than in healthy controls. Impaired renal clearance contributes to increased plasma free AGEs in uremia, but the increased excretion rate among patients on PD demonstrates that there was also an increased synthesis of free AGEs. Both HD and PD are able to remove free AGEs.
From Molecular Footprints of Disease to New Therapeutic Interventions in Diabetic Nephropathy
Authors: MIYATA TOSHIO , YAMAMOTO MAKOTO , IZUHARA YUKO
Published: July 2005

Abstract: Proteins are particularly attractive targets for product analysis, which is used to understand pathology. Protein modifications, such as advanced glycation end products (AGEs), serve as footprints of biochemical processes and also help in the search for novel agents that efficiently inhibit protein damage. Interestingly, several medical agents that are used clinically interfere with oxidative protein damage through different mechanisms characteristic of their chemical structures. We recently found that angiotensin II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) lower the in vitro formation of the AGEs pentosidine and carboxymethyllysine. Their inhibition for AGE formation is more striking than aminoguanidine. Unlike aminoguanidine, ARBs and ACEIs do not trap reactive carbonyl precursors of AGEs. Rather, they inhibit AGE formation, possibly as a result of their potent ability to scavenge hydroxyl radicals and to chelate the transition metals necessary for the Fenton reaction. We tested their AGE‐lowering ability in vivo in a unique type‐2 diabetic model with nephropathic SHR/NDmcr‐cp rats, which exhibits the metabolic syndrome (obesity, hyperglycemia, hyperlipidemia, hyperinsulinemia) in addition to hypertension. Obesity and associated metabolic derangements, in addition to hypertension, markedly accelerate renal injury. Expectedly, correction of hyperglycemia and hyperinsulinemia partially but significantly improves renal injury. A low‐calorie diet greatly improves renal injury despite persistent hypertension. Among antihypertensive agents, ARBs, unlike nifedipine and atenolol, are renoprotective despite persistent metabolic syndrome, but their action is independent of blood pressure lowering and is observed in a dose‐dependent manner despite the complete blockade of angiotensin II receptor. Interestingly, the improvement of renal injury by ARBs as well as a low‐calorie diet is associated with a significant reduction in local oxidative stress and AGE formation in the kidney. During the characterization of the AGE‐lowering profile of our chemical compound libraries (∼2000), we identified several inhibitors of oxidative stress and advanced glycation. They are indeed renoprotective, independently of correction of hypertension and metabolic syndrome, in experimental diabetic nephropathy and other nephritis models. Altogether, our data are in good agreement with the recent therapeutic concept for diabetic nephropathy that multiple risk factor interventions are critical in the treatment of diabetic renal injury, and further implicate a therapeutic potential of inhibition of oxidative stress and advanced glycation.
Can Advanced Glycation End Product Inhibitors Modulate More than One Pathway to Enhance Renoprotection in Diabetes?
Authors: COUGHLAN MELINDA T. , COOPER MARK E. , FORBES JOSEPHINE M.
Published: July 2005

Abstract: Although advanced glycation end products (AGEs) have been postulated to contribute to diabetic nephropathy in their own right, advanced glycation is clearly only one pathway by which renal injury may be induced in diabetes. The interaction between metabolic and hemodynamic factors amplifies the deleterious effects of the diabetic milieu, thereby reducing the threshold for microvascular injury via common mechanisms. This includes interactions between AGE‐mediated pathways and the renin angiotensin system, oxidative stress, protein kinase C, and growth factors, which play a significant role in the development and progression of diabetic renal disease. As it is likely that the future of preventive therapy will not involve a single “cure‐all” agent, it seems that a highly relevant question in diabetic nephropathy should be, which pathogenic pathways are already addressed by currently available therapies? Combination therapies that target multiple pathways may ultimately be more successful than those that modify a single pathway. Therefore, research into synergistic interactions among the various pathogenic pathways leading to diabetic complications is critical in order to develop interventions that confer optimal end‐organ protection.
High‐Dose Thiamine Therapy Counters Dyslipidemia and Advanced Glycation of Plasma Protein in Streptozotocin‐Induced Diabetic Rats
Authors: KARACHALIAS NIKOLAOS , BABAEI‐JADIDI ROYA , KUPICH CHRISTIAN , AHMED NAILA , THORNALLEY PAUL J.
Published: July 2005

Abstract: The streptozotocin‐induced (STZ) diabetic rat experimental model of diabetes on insulin maintenance therapy exhibits dyslipidemia, mild thiamine deficiency, and increased plasma protein advanced glycation end products (AGEs). The reversal of thiamine deficiency by high‐dose thiamine and S‐benzoylthiamine monophosphate (benfotiamine) prevented the development of incipient nephropathy. Recently, we reported that high‐dose thiamine (but not benfotiamine) countered diabetic dyslipidemia. To understand further the differences between the effects of thiamine and benfotiamine therapy, we quantified the levels of the AGEs in plasma protein. We found hydroimidazolone AGE residues derived from glyoxal and methylglyoxal, G‐H1 and MG‐H1, were increased 115% and 68% in STZ diabetic rats, with respect to normal controls, and were normalized by both thiamine and benfotiamine; whereas N‐carboxymethyl‐lysine (CML) and N‐carboxyethyl‐lysine (CEL) residues were increased 74% and 118% in STZ diabetic rats and were normalized by thiamine only. The lack of effect of benfotiamine on plasma CML and CEL residue concentrations suggests there may be important precursors of plasma protein CML and CEL residues other than glyoxal and methylglyoxal. These are probably lipid‐derived aldehydes.
Post‐Amadori AGE Inhibition as a Therapeutic Target for Diabetic Complications: A Rational Approach to Second‐Generation Amadorin Design
Authors: KHALIFAH RAJA G. , CHEN YING , WASSENBERG JAMES J.
Published: July 2005

Abstract: Aminoguanidine and pyridoxamine (Pyridorin™), two major inhibitors of advanced glycation end product (AGE) formation, have entered clinical trials for diabetic nephropathy. They share no structural similarity and are believed to inhibit AGE formation by entirely different mechanisms. Pyridoxamine is a post‐Amadori AGE inhibitor—that is, an “Amadorin”—whereas aminoguanidine primarily scavenges reactive dicarbonyl precursors to AGEs. However, pyridoxamine also has a limited potential to react with dicarbonyls. We thus embarked on an effort to develop second‐generation Amadorins with low nucleophilicity. Our hypothesis was that we could improve specificity for inhibiting the post‐Amadori pathway by minimizing the potential for scavenging small dicarbonyl intermediates. This mechanism‐based strategy has led to a rational drug design program that has successfully produced candidate Amadorins, among them the novel compound BST‐4997. This Amadorin has greater post‐Amadori potency than pyridoxamine but possess no dicarbonyl scavenging activity. Prototypical inhibitors like BST‐4997 provide a unique tool to help identify relevant AGE pathways that contribute to diabetic complications. Targeting AGE inhibition differs significantly from traditional approaches to drug discovery and thus represents a new paradigm for the drug industry that should be recognized.
Pyridoxamine: The Many Virtues of a Maillard Reaction Inhibitor
Authors: VOZIYAN PAUL A. , HUDSON BILLY G.
Published: July 2005

Abstract: Pyridoxamine (PM) is one of three natural forms of vitamin B6. It is a critical transient intermediate in catalysis of transamination reactions by vitamin B6‐dependent enzymes. The discovery eight years ago that PM can inhibit the Maillard reaction stimulated new interest in this B6 vitamer as a prospective pharmacological agent for treatment of complications of diabetes. PM application in diabetic nephropathy has now progressed to a phase III clinical trial. Investigation of the PM mechanism of action demonstrated that PM inhibits post‐Amadori steps of the Maillard reaction by sequestering catalytic metal ions and blocking oxidative degradation of Amadori intermediate. PM also has the capacity to scavenge toxic carbonyl products of sugar and lipid degradation, and to inhibit reactive oxygen species. These multiple activities position PM as a promising drug candidate for treatment of multifactorial chronic conditions in which oxidative reactions and/or carbonyl compounds confer pathogenicity.
Tissue‐Specific Variation in Glycation of Proteins in Diabetes: Evidence for a Functional Role of Amadoriase Enzymes
Authors: BROWN SARAH M. , SMITH DELLA M. , ALT NADJA , THORPE SUZANNE R. , BAYNES JOHN W.
Published: July 2005

Abstract: The Amadori product fructoselysine (FL), an intermediate in the formation of many advanced glycation end products, may be deglycated by various pathways. These include spontaneous chemical degradation or enzymatic deglycation by amadoriases. This study was designed to compare changes in FL in various tissues in response to changes in glycemia, thereby testing tissue‐specific deglycation. FL content in skin collagen, red cell hemoglobin, and total muscle, liver, and brain protein was analyzed by isotope dilution gas chromatography‐mass spectrometry. Mean blood glucose increased over fourfold in diabetic versus control rats, whereas changes in glycation of proteins varied from fivefold in collagen to no change in the liver and brain. These results suggest significant differences among tissues in the activity of deglycating enzymes and/or protein turnover.
Some Clues as to the Regulation, Expression, Function, and Distribution of Fructosamine‐3‐Kinase and Fructosamine‐3‐Kinase‐Related Protein
Authors: CONNER JAMES R. , BEISSWENGER PAUL J. , SZWERGOLD BENJAMIN S.
Published: July 2005

Abstract: Fructosamine‐3‐kinase (FN3K) and the more recently discovered fructosamine‐3‐kinase‐related protein (FN3KRP) appear to protect proteins from nonenzymatic glycation. To gain a better understanding of these enzymes we performed a series of investigations including (1) in silico comparisons of their promoters; (2) real‐time PCR analysis of their expression in human tissues; (3) effects of hyperglycemia, interleukin‐1β (IL‐1β), and nuclear factor kappa‐B (NFκB) activation on their mRNA levels; (4) effects of small interfering RNA (siRNA) suppression of FN3K expression (knockdown) in cultured cells and (5) search of FN3K and FN3KRP homologs in available genomic and EST (expressed sequence tag) databases. Our results indicate that (1) both FN3K and FN3KRP promoters are TATA‐less and CAAT‐less and contain several homologous CpG islands and Sp1 binding sites. (2) Both genes are expressed in all human tissue examined, with FN3K showing significantly higher levels in tissues susceptible to nonenzymatic glycation and diabetic complications. (3) Treatment of fibroblasts with high glucose, IL‐1β, and activation of NFκB does not affect the expression of either FN3K or FN3KRP. (4) Knockdown of FN3K in cultured cells inhibits or arrests their growth. (5) FN3K‐like genes are widely distributed in nature, with the notable exception of insects and yeasts. These data suggest that FN3K and FN3KRP are constitutive “housekeeping” genes and that they play an important role in cell metabolism, possibly as deglycating enzymes.
Substrate Specificity of Amadoriase I from Aspergillus fumigatus
Authors: MENNELLA CARMELA , BORRELLI ROSA CINZIA , VINALE FRANCESCO , RUOCCO MICHELINA , FOGLIANO VINCENZO
Published: July 2005

Abstract: Generation of Amadori products is the major single modification by the Maillard reaction in vivo and a source of biologically active glycoxidation products leading to protein cross‐linking in biological tissues. Amadoriase I from Aspergillus fumigatus cleaves Amadori products into deoxyglucosone, hydrogen peroxide, and the corresponding primary amine. It has been reported that Amadori products formed on free amino acids are a good substrate for amadoriase I, whereas the enzyme is unable to cleave Amadori products formed on whole proteins. This work aims to investigate the affinity of amadoriase I for oligopeptides and small proteins. Recombinant amadoriase I was expressed in E. coli and purified by Ni His‐tag affinity chromatography. Di‐, tri‐, and tetrapeptides were derivatized with glucose, and the corresponding Amadori products were purified by TLC and HPLC. Glycated β‐lactoglobulin was also used as a substrate. In both cases the formation of Amadori products was monitored by electrospray ionization‐mass spectrometry (ESI‐MS). The Km of amadoriase for glycated‐l‐lysine was 4.2 mM, which is in accordance with the literature. Km decreases with the length of peptide, being slightly reduced for dipeptides, and is around 10 mM for tri‐ and tetrapeptides. Glycated proteins are not substrates of the enzyme; but when amadoriase I was added during the glycation reaction, a significant reduction of Amadori product formation was observed on both peptides and proteins. Data confirm the hypothesis that steric hindrance is critical for amadoriase I activity, indicating that oligopeptides up to four amino acids in length are good substrates. Moreover, these data show that, at least in some experimental conditions, amadoriase I is able to reduce the formation of protein‐bound Amadori product.
Transglycation—A Potential New Mechanism for Deglycation of Schiff's Bases
Authors: SZWERGOLD BENJAMIN S. , HOWELL SCOTT K. , BEISSWENGER PAUL J.
Published: July 2005

Abstract: Nonenzymatic glycation is believed to play a major role in the development of diabetic complications. Over the past several years we and others have shown that in cells this nonenzymatic process can be reversed by an ATP‐dependent reaction catalyzed by fructosamine‐3‐kinase (FN3K) and possibly by its isozyme, fructosamine‐3‐kinase‐related protein (FN3KRP). In this study we provide the first evidence that this FN3K‐dependent deglycation, acting on the Amadori products, is complemented by another deglycation process operating on the very first product of nonenzymatic glycation, glucosylamines (Schiff's bases). We postulate that the first step in this Schiff's‐base deglycation process occurs by transfer of the sugar moiety from macromolecule‐bound glucosylamine to one of the low‐molecular weight intracellular nucleophiles—in particular, glutathione. We term this reaction transglycation, and in this study we demonstrate that it occurs readily and spontaneously in vitro. We further propose that one of the spontaneously formed glucose‐glutathione adduct(s) is subsequently removed from cells by a multidrug‐resistance pump (MRP, MDR‐protein, ATP‐binding‐cassette protein), metabolized, and excreted in urine. In support of this latter contention, we show that at least one transglycation product, glucose‐cysteine, is found in human urine and that its concentrations are increased in diabetes.
Proteins of Thermus thermophilus Are Resistant to Glycation‐Induced Protein Precipitation: An Evolutionary Adaptation to Life at Extreme Temperatures?
Authors: MÜNCH GERALD , BERBAUM KATRIN , URBAN CHRISTIN , SCHINZEL REINHARD
Published: July 2005

Abstract: In thermophilic bacteria, formation of Maillard products may occur at increased rates because this reaction is favored at higher temperatures. Therefore, specific protective mechanisms against glycation‐induced protein precipitation are likely to exist in thermophilic bacteria. Indeed, Thermus thermophilus proteins remained soluble when a cell‐free extract of T. thermophilus was incubated at 37°C in the presence of glucose, fructose, or methylglyoxal; whereas E. coli proteins precipitated. In E. coli cell‐free extracts, sugar‐induced precipitation was accelerated by the addition of 5 μM Fe2+ and inhibited by metal chelators, suggesting that glycoxidation processes are involved in the formation of the precipitate. A low lysine content, endogenous small scavenger molecules, or enzymatic “antiglycation” mechanisms for the degradation of AGEs or their precursors could be excluded as possible causes for the resistance to protein precipitation in T. thermophilus. Therefore, the resistance to glycation‐mediated protein precipitation is an endogenous property of thermophilic proteins that was acquired during evolution in environments with high glycation activity.
Maillard Reaction Products Derived from Thiol Compounds as Inhibitors of Enzymatic Browning of Fruits and Vegetables: The Structure‐Activity Relationship
Authors: BILLAUD C , MARASCHIN C , PEYRAT‐MAILLARD M‐N , NICOLAS J
Published: July 2005

Abstract: Some thiol‐derived Maillard reaction products (MRPs) may exert antioxidant activity, depending on the reaction conditions as well as on the sugar and the sulphydryl compound. Recently, we reported that MRPs derived from glucose or fructose with cysteine (CSH) or glutathione (GSH) mixtures greatly inhibited polyphenoloxidases (PPOs), oxidoreductases responsible for discoloration of fresh or minimally processed fruits and vegetables. Glucose and GSH were shown to be the most active in producing inhibitory MRPs. Therefore, we examined the way in which the nature of the reactants affected their synthesis, in order to establish a structure‐activity relationship for the inhibitory products. Various aqueous (0.083 M, 0.125 M, or 0.25 M) mixtures of a sugar (hexose, pentose, or diholoside) with either a CSH‐related compound (CSH, GSH, N‐acetyl‐cysteine, cysteamine, cysteic acid, methyl‐cysteine, cysteine methyl ester), an amino acid (γ‐glutamic acid, glycine, methionine), or other sulfur compound (thiourea, 1,4‐dithiothreitol, 2‐mercaptoethanol) were heated at 103°C for 14 h. Soluble MRPs were compared for their ability to inhibit apple PPO activity. In the presence of CSH, the rated sugars (same molar concentration) ranked as to inhibitory effect were pentoses > sucrose > hexoses ≥ maltose. In the presence of glucose, the simultaneous presence of an amino group, a carboxyl group, and a free thiol group on the same molecule seemed essential for the production of highly inhibitory compounds.
The Maillard Reaction in Eye Diseases
Authors: STITT ALAN W.
Published: July 2005

Abstract:Diabetes and age‐related eye disorders remain leading causes of blindness worldwide. While defined pathogenic mechanisms for many of these diseases remain elusive, there is increasing evidence that products of the Maillard reaction may play an important role in their etiology. Advanced glycation end products (AGEs) form though a range of pathways within Maillard chemistry, and there is evidence to suggest that these adducts accumulate in the intracellular and/or extracellular environment of ocular structures. This review evaluates the ever‐growing literature on AGEs in biological systems and draws relevant links to diseases such as diabetic retinopathy, age‐related macular degeneration, and cataract formation. It also outlines recent pharmaceutical strategies to inhibit Maillard reaction products and provides links to how these may serve to limit ocular cell dysfunction.
Effects of Advanced Glycation End Products on Ezrin‐Dependent Functions in LLC‐PK1 Proximal Tubule Cells
Authors: BACH LEON A. , GALLICCHIO MARISA A. , McROBERT E ANNE , TIKOO ANJALI , COOPER MARK E.
Published: July 2005

Abstract: We have recently shown that advanced glycation products (AGEs) bind to the ERM (ezrin, radixin, moesin) family of proteins. ERM proteins act as cross‐linkers between cell membrane proteins and the actin cytoskeleton. They are also involved in signal transduction pathways. They therefore have a critical role in normal cell processes, including modulation of cell shape, adhesion, and motility. We postulate that AGEs may contribute to diabetic complications by disrupting ERM function. In support of this hypothesis, AGEs inhibit ezrin‐dependent tubulogenesis of proximal tubule cells. Phosphorylation is an important activating mechanism for ERM proteins, and AGEs inhibit ezrin phosphorylation mediated by the epidermal growth factor receptor.
An allelic series reveals essential roles for FY in plant development in addition to flowering-time control
Authors: Henderson Ian R. , Liu Fuquan , Drea Sinead , Simpson Gordon G. , Dean Caroline
Published: July 2005

The autonomous pathway functions to promote flowering in Arabidopsis by limiting the accumulation of the floral repressor FLOWERING LOCUS C (FLC). Within this pathway FCA is a plant-specific, nuclear RNA-binding protein, which interacts with FY, a highly conserved eukaryotic polyadenylation factor. FCA and FY function to control polyadenylation site choice during processing of the FCAtranscript. Null mutations in the yeast FY homologue Pfs2p are lethal. This raises the question as to whether these essential RNA processing functions are conserved in plants. Characterisation of an allelic series of fymutations reveals that null alleles are embryo lethal. Furthermore, silencing of FY, but not FCA, is deleterious to growth in Nicotiana. The late-flowering fy alleles are hypomorphic and indicate a requirement for both intact FY WD repeats and the C-terminal domain in repression of FLC. The FY C-terminal domain binds FCA and in vitro assays demonstrate a requirement for both C-terminal FY-PPLPP repeats during this interaction. The expression domain of FY supports its roles in essential and flowering-time functions. Hence, FY may mediate both regulated and constitutive RNA 3′-end processing.
Cellular mechanisms of dendrite pruning inDrosophila: insights from in vivo time-lapse of remodeling dendritic arborizing sensory neurons
Authors: Williams Darren W. , Truman James W.
Published: July 2005

Regressive events that refine exuberant or inaccurate connections are critical in neuronal development. We used multi-photon, time-lapse imaging to examine how dendrites of Drosophila dendritic arborizing (da) sensory neurons are eliminated during early metamorphosis, and how intrinsic and extrinsic cellular mechanisms control this deconstruction. Removal of the larval dendritic arbor involves two mechanisms: local degeneration and branch retraction. In local degeneration, major branch severing events entail focal disruption of the microtubule cytoskeleton, followed by thinning of the disrupted region, severing and fragmentation. Retraction was observed at distal tips of branches and in proximal stumps after severing events. The pruning program of da neuron dendrites is steroid induced; cell-autonomous dominant-negative inhibition of steroid action blocks local degeneration,although retraction events still occur. Our data suggest that steroid-induced changes in the epidermis may contribute to dendritic retraction. Finally, we find that phagocytic blood cells not only engulf neuronal debris but also attack and sever intact branches that show signs of destabilization.
Hedgehog regulated Slit expression determines commissure and glial cell position in the zebrafish forebrain
Authors: Barresi Michael J. F. , Hutson Lara D. , Chien Chi-Bin , Karlstrom Rolf O.
Published: July 2005

Three major axon pathways cross the midline of the vertebrate forebrain early in embryonic development: the postoptic commissure (POC), the anterior commissure (AC) and the optic nerve. We show that a small population of Gfap+astroglia spans the midline of the zebrafish forebrain in the position of, and prior to, commissural and retinal axon crossing. These glial `bridges' form in regions devoid of the guidance molecules slit2 and slit3,although a subset of these glial cells express slit1a. We show that Hh signaling is required for commissure formation, glial bridge formation, and the restricted expression of the guidance molecules slit1a, slit2, slit3 and sema3d, but that Hh does not appear to play a direct role in commissural and retinal axon guidance. Reducing Slit2 and/or Slit3 function expanded the glial bridges and caused defasciculation of the POC, consistent with a `channeling' role for these repellent molecules. By contrast, reducing Slit1a function led to reduced midline axon crossing, suggesting a distinct role for Slit1a in midline axon guidance. Blocking Slit2 and Slit3, but not Slit1a, function in the Hh pathway mutant yot (gli2DR) dramatically rescued POC axon crossing and glial bridge formation at the midline, indicating that expanded Slit2 and Slit3 repellent function is largely responsible for the lack of midline crossing in these mutants. This analysis shows that Hh signaling helps to pattern the expression of Slit guidance molecules that then help to regulate glial cell position and axon guidance across the midline of the forebrain.
Wnt signalling mediated by Tbx2b regulates cell migration during formation of the neural plate
Authors: Fong Steven H. , Emelyanov Alexander , Teh Cathleen , Korzh Vladimir
Published: July 2005

During gastrulation, optimal adhesion and receptivity to signalling cues are essential for cells to acquire new positions and identities via coordinated cell movements. T-box transcription factors and the Wnt signalling pathways are known to play important roles in these processes. Zebrafish tbx2b, a member of the TBX2 family, has previously been shown to be required for the specification of midline mesoderm. We show here that tbx2b transcripts are present during mid-gastrula before its expression is detected by whole-mount in situ hybridization. Isolated ectodermal cells deficient in Tbx2b have altered cell surface properties and the level of cadherins in these cells is lower. In chimaeric embryos generated by cell transplantation and single blastomere injections, Tbx2b-deficient cells are defective in cell movement in a cell-autonomous manner, resulting in their exclusion from the developing neural plate. Using this `exclusion'phenotype as a screen, we show that Tbx2b acts within the context of Fz7 signalling. The exclusion of cells lacking T-box proteins in chimeras during development was demonstrated with other T-box genes and may indicate a general functional mechanism for T-box proteins.
The cell adhesion molecule NrCAM is crucial for growth cone behaviour and pathfinding of retinal ganglion cell axons
Authors: Zelina Pavol , Avci Hasan X. , Thelen Karsten , Pollerberg G. Elisabeth
Published: July 2005

We investigated the role of the cell adhesion molecule NrCAM for axonal growth and pathfinding in the developing retina. Analysis of the distribution pattern of NrCAM in chick embryo retina sections and flat-mounts shows its presence during extension of retinal ganglion cell (RGC) axons; NrCAM is selectively present on RGC axons and is absent from the soma. Single cell cultures show an enrichment of NrCAM in the distal axon and growth cone. When offered as a substrate in addition to Laminin, NrCAM promotes RGC axon extension and the formation of growth cone protrusions. In substrate stripe assays, mimicking the NrCAM-displaying optic fibre layer and the Laminin-rich basal lamina, RGC axons preferentially grow on NrCAM lanes. The three-dimensional analysis of RGC growth cones in retina flat-mounts reveals that they are enlarged and form more protrusions extending away from the correct pathway under conditions of NrCAM-inhibition. Time-lapse analyses show that these growth cones pause longer to explore their environment, proceed for shorter time spans, and retract more often than under control conditions; in addition, they often deviate from the correct pathway towards the optic fissure. Inhibition of NrCAM in organ-cultured intact eyes causes RGC axons to misroute at the optic fissure; instead of diving into the optic nerve head,these axons cross onto the opposite side of the retina. Our results demonstrate a crucial role for NrCAM in the navigation of RGC axons in the developing retina towards the optic fissure, and also for pathfinding into the optic nerve.
Drosophila Cks30Ainteracts with Cdk1 to target Cyclin A for destruction in the female germline
Authors: Swan Andrew , Barcelo Gail , Schüpbach Trudi
Published: July 2005

Cks is a small highly conserved protein that plays an important role in cell cycle control in different eukaryotes. Cks proteins have been implicated in entry into and exit from mitosis, by promoting Cyclin-dependent kinase(Cdk) activity on mitotic substrates. In yeast, Cks can promote exit from mitosis by transcriptional regulation of cell cycle regulators. Cks proteins have also been found to promote S-phase via an interaction with the SCFSkp2 Ubiquitination complex. We have characterized the Drosophila Cks gene, Cks30A and we find that it is required for progression through female meiosis and the mitotic divisions of the early embryo through an interaction with Cdk1. Cks30A mutants are compromised for Cyclin A destruction, resulting in an arrest or delay at the metaphase/anaphase transition, both in female meiosis and in the early syncytial embryo. Cks30A appears to regulate Cyclin A levels through the activity of a female germline-specific anaphase-promoting complex,CDC20-Cortex. We also find that a second closely related Cks gene, Cks85A, plays a distinct, non-overlapping role in Drosophila, and the two genes cannot functionally replace each other.
The VAB-1 Eph receptor tyrosine kinase and SAX-3/Robo neuronal receptors function together duringC. elegansembryonic morphogenesis
Authors: Ghenea Simona , Boudreau Jeffrey R. , Lague Nicholas P. , Chin-Sang Ian D.
Published: July 2005

Mutations that affect the single C. elegans Eph receptor tyrosine kinase VAB-1 cause defects in cell movements during embryogenesis. Here, we provide genetic and molecular evidence that the VAB-1 Eph receptor functions with another neuronal receptor, SAX-3/Robo, for proper embryogenesis. Our analysis of sax-3 mutants shows that SAX-3/Robo functions with the VAB-1 Eph receptor for gastrulation cleft closure and ventral epidermal enclosure. In addition, SAX-3 functions autonomously for epidermal morphogenesis independently of VAB-1. A double-mutant combination between vab-1 and slt-1 unmasks a role for the SLT-1 ligand in embryogenesis. We provide evidence for a physical interaction between the VAB-1 tyrosine kinase domain and the juxtamembrane and CC1 region of the SAX-3/Robo receptor. Gene dosage, non-allelic non-complementation experiments and co-localization of the two receptors are consistent with a model in which these two receptors form a complex and function together during embryogenesis.
Laser-marking process for liquid-crystal display light guide panel
Authors: Kim Gyung-Dong , Kang Hyuk Jin , Ahn Sung-Hoon , Song Chul Ki , Back Chang , Lee Caroline S
Published: July 2005

A light guide panel is an element of the liquid-crystal display backlight unit, which is extensively used for display devices. In this study, a laser-marking process is applied to the fabrication of light guide panels, and the new fabrication process may replace existing manufacturing methods such as silk screen printing, stamping, or V-cutting methods. The objective of this research is to evaluate the feasibility of the laser patterning system. A series of light guide patterns were made with a 50 W CO2 laser (continuous wave) to understand the effects of laser power and scanning speed on the geometry of groove patterns. The width and depth of the fabricated grooves increased with increasing laser power and decreasing scanning speed. In order to analyse surface geometry, scanning electron microscopy (SEM) photography was used and, for luminance measurement, a Topcon-BM7 was used. As a result, the marking conditions of the laser patterning, 5W and 0.4m/s, were suggested.
Development of a STEP-compliant inspection framework for discrete components
Authors: Ali L , Newman S T , Petzing J
Published: July 2005

The measurement and inspection of manufactured parts play a vital role in manufacturing industry and is considered an integral part of the quality control. Though this is recognized, the state of the art in measurement and inspection of components is still recognized as a separate island of automation with no formal overall integration of standards and specifications. Although the introduction of probing has enabled automated inspection processes to become commonplace, the solutions for the in-process gauging at CNC machine tools and the programming of coordinate measuring machines is still vendor specific.

The introduction of new standards for data exchange, such as STEP, AP219, and STEP-NC, has influenced the future direction of the inspection process. In light of current research in this field, a STEP compliant inspection framework for a component is presented. This framework aims to provide a capability to establish standardized measuring and inspection across the total CAx chain. It will facilitate the use of information downstream in the chain, such as an inspection workplan, workingsteps, and a mechanism to close the loop and feedback of inspection results to component model design. In order to achieve this integration STEP-NC (ISO14649) along with AP219 has been used in this research to provide the basis of a STEP-compliant inspection framework.
Integrated design of turbomachinery through a STEP-XML platform for data exchange
Authors: Cascini G , Giovani G , Rissone P , Rotini F
Published: July 2005

Design tool integration is a primary goal for any technical department in order to satisfy time constraints imposed by the market competition. While commercial products actually present valuable integration features, custom tools developed on the basis of company know-how are still lacking from this point of view. In this paper the authors describe a procedure to build an XML platform capable of integrating design tools, preserving their architecture. This database allows the storage of product configurations and its dimensional parameters in a hierarchical structure that can be easily translated into STEP format. In such a way a virtual prototype of the part can be obtained by a descriptor-based modelling system that allows design cycle automation and complete design tool integration. The work has been developed within the framework of cooperation between Nuovo Pignone, the Florentine plant of General Electric - Oil and Gas, and the University of Florence.
The polishing process of advanced ceramic balls using a novel eccentric lapping machine
Authors: Kang J , Hadfield M
Published: July 2005

The finishing process of advanced ceramic balls can be divided into two steps. The first step is lapping in which most of the stock from the ball is removed at a higher material removal rate. The second step is polishing in which the required ball surface roughness, roundness, and dimensional and geometric accuracy are achieved. In polishing, the abrasive particle size is 1 μm, and the load and speed are lower than lapping.

A novel eccentric lapping machine is used for polishing hot isostatically pressed (HIPed) silicon nitride balls. In the initial polishing stage, the polishing load is demonstrated as being most influential in the reduction of surface roughness value Ra. However, in the later polishing stages, the erosive process played a major role in the further reduction of Ra, although the high roughness peaks cannot be removed by erosive process alone. Experimental results also show that, in order to achieve desired surface roughness value, the initial surface quality of the upper plate should be reasonably high, and deep scratches on the ball surface from previous lapping processes should be avoided.

The best polishing results achieved were surface roughness values of Ra of 0.003 μm and r.m.s. ( Rq) of 0.004 μm, ball roundness of 0.08–0.09 μm. This proves that the novel eccentric lapping machine is also suitable for polishing advanced ceramic balls.
The effects of lapping load in finishing advanced ceramic balls on a novel eccentric lapping machine
Authors: Kang J , Hadfield M
Published: July 2005

Hot isostatically pressed silicon nitride ball blanks were lapped from a diameter of 13.255 mm to a diameter of 12.7 mm by a novel eccentric lapping machine. A maximum material removal rate of 68 μm/h has been achieved under a nominal lapping load of 43 N per ball. It was found that the material removal rate increased almost linearly with the lapping load within this load range. When the lapping load was higher than 43 N per ball, the material removal rate started to drop and the lapped ball roundness error started to increase. At the highest nominal lapping load of 107 N per ball, surface damage and subsurface damage were found on the lapped balls. Because of the eccentric loading effect, the actual load on an individual ball could be 25–28 per cent higher than the nominal lapping load. The surface residual stresses of lapped balls under different lapping loads were measured, and it was found that the lapping load had less effect than the previous hot isostatic pressing process. Rolling contact fatigue tests were conducted on balls lapped at nominal loads of 43 and 107 N per ball. No failure occurred on the ball lapped at 43 N per ball after 138 × 106 stress cycles. The ball lapped at 107 N per ball failed after 13.3 x 106 stress cycles with a shallow spall with a flat bottom inside. This research suggests that the lapping load for advanced ceramic balls in conventional concentric lapping could be doubled from 20 to 40 N per ball without degrading the surface quality of lapped balls.
Design of a pile-yarn-manipulating mechanism
Authors: Topalbekiroglu M , Kireçci A , Dülger Canan L
Published: July 2005

A pile-yarn-manipulating mechanism for carpet weaving was designed and implemented. The pile-yarn-manipulating mechanism served to prepare the coloured pile yarn for a knotting mechanism according to a carpet pattern used as input. Such a mechanism required two auxiliary mechanisms (a holding mechanism and a cutting mechanism) to perform its function. A model for the pile yarn manipulating mechanism is presented herein.

Important developments of weaving technology have been recorded. There are many carpet looms working at high speeds, but production methods of handmade carpets have not changed for several hundred years. The main difference between handmade and machine carpets is their texture type. The pile surface of machine carpets is produced by Jacquard's mechanism, but it is produced independently in handmade carpets by the weaver. There are basically two kinds of knot, namely the Turkish knot and the Persian knot.
Rapid prototyping methods of silicon carbide micro heat exchangers
Authors: Liu H-C , Tsuru H , Cooper A G , Prinz F B
Published: July 2005

Conventional heat exchangers are mainly constructed of metal alloys. The manufacturing process of metal alloys usually requires assembling and joining techniques such as welding and diffusion bonding. In addition, the structures are limited to simple shapes due to the restrictions of the fabrication methods. This research focused on the manufacturing of compact heat exchangers made of high thermal-conductivity ceramic material, rather than on the performance of the devices. To achieve a high surface-volume ratio in heat exchangers, a strategy was adopted that fabricates miniaturized devices with a high shape complexity.

This paper discusses an approach that uses a combination of mould shape deposition manufacturing (Mould SDM) and the gelcasting process to fabricate monolithic ceramic heat exchangers. This approach not only makes one-piece heat exchangers possible but introduces materials with superior thermal properties to the heat management applications. Silicon carbide is chosen for such applications because of its high thermal conductivity, thermal resistance, and corrosion resistance. The high chemical resistance of ceramic materials also extends the use of heat exchangers to chemical processing devices such as chemical reactors. The initial investigation of the process for micro reactors is also discussed.
A gear rattle model accounting for oil squeeze between the meshing gear teeth
Authors: Brancati R , Rocca E , Russo R
Published: July 2005

In this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (dry sump, splash, bath).

The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic motion to the driving gear.