bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protein disulfide isomerase, but not binding protein, overexpression enhances secretion of a non‐disulfide‐bonded protein in yeast
Authors: Smith Jason D. , Tang Benjamin C. , Robinson Anne Skaja 
Published: January 2004

AbstractIn eukaryotes, secretory proteins are folded and assembled in the endoplasmic reticulum (ER). Many heterologous proteins are retained in the ER due to suboptimal folding conditions. We previously reported that heterologous secretion of Pyrococcus furiosus β‐glucosidase in Saccharomyces cerevisiae resulted in the accumulation of a large fraction of inactive β‐glucosidase in the ER. In this work, we determine the effect of introducing additional genes of ER‐resident yeast proteins, Kar2p (binding protein [BiP]) and protein disulfide isomerase (PDI), on relieving this bottleneck. Single‐copy expression of BiP and PDI worked synergistically to improve secretion by ∽60%. In an effort to optimize BiP and PDI interactions, we created a library of β‐glucosidase expression strains that incorporated four combinations of constitutively or inducibly‐expressed BiP and PDI genes integrated to random gene copynumbers in the yeast chromosome. Approximately 15% of the transformants screened had secretion level improvements higher than that seen with single BiP/PDI gene overexpression, and the highest secreting strain had threefold higher β‐glucosidase levels than the control. Nineteen of the improved strains were re‐examined for β‐glucosidase secretion as well as BiP and PDI levels. Within the improved transformants BiP and PDI levels ranged sevenfold and tenfold over the control, respectively. Interestingly, increasing BiP levels decreased β‐glucosidase secretion, whereas increasing PDI levels increased β‐glucosidase secretion. The action of PDI was unexpected because β‐glucosidase is not a disulfide‐bonded protein. We suggest that PDI may be acting in a chaperone‐like capacity or possibly creating mixed disulfides with the β‐glucosidase's lone cysteine residue during the folding and assembly process. © 2004 Wiley Periodicals, Inc.
Exogenous cadherin microdisplay can interfere with endogenous signaling and reprogram gene expression in cultured hepatocytes
Authors: Brieva Thomas A. , Moghe Prabhas V. 
Published: January 2004

AbstractWe recently found that the basal micro substrate presentation of E‐cadherin, a key cell–cell adhesion molecule in the liver, can modulate hepatocellular proliferative potential and differentiated function (Brieva and Moghe, in press). In the current study, we established a similar experimental model involving rat hepatocytes cultured on collagen and incorporated 5 μm polystyrene microbeads functionalized with Protein A‐anchored E‐cadherin/human lgG Fc chimeric fusion constructs. We investigated the cadherin governed dose‐response of cell proliferative potential and quantified the underlying changes in intracellular gene signaling processes. Hepatocellular proliferative potential was found to be intensified with an increase in the microdisplay of acellular cadherins and this effect was offset by increased cell seeding density. Notably, we report that following overnight exposure to acellular cadherins, the expression of genes known to mediate the control of cell proliferation, cyclin D1 and c‐myc, was upregulated, while the expression of differentiation‐related genes, namely albumin and cytochrome P450 II B1, was reduced. The exposure of cell cultures to exogenous cadherins was found to markedly disrupt the localization of endogenous E‐cadherin and β‐catenin to junctions at cell–cell contacts and cause a quantitative decrease in the endogenous cadherin protein levels. Based on all of our observations, we propose that the acellular presentation of E‐cadherin chimeras competitively disrupts endogenous cadherin containing complexes at cell–cell junctions and increases intracellular cadherin turnover, thereby promoting β‐catenin mediated signaling, which ultimately engenders an increase in cell proliferative potential and a decrease in differentiated function. © 2004 Wiley, Periodicals, Inc.
Penicillin acylase‐catalyzed synthesis of β‐lactam antibiotics in highly condensed aqueous systems: Beneficial impact of kinetic substrate supersaturation
Authors: Youshko Maxim I. , Moody Harold M. , Bukhanov Alexander L. , Boosten Wilhelmus H. J. , Švedas Vytas K. 
Published: January 2004

AbstractAdvantages of performing penicillin acylase‐catalyzed synthesis of new penicillins and cephalosporins by enzymatic acyl transfer to the β‐lactam antibiotic nuclei in the supersaturated solutions of substrates have been demonstrated. It has been shown that the effective nucleophile reactivity of 6‐aminopenicillanic (6‐APA) and 7‐aminodesacetoxycephalosporanic (7‐ADCA) acids in their supersaturated solutions continue to grow proportionally to the nucleophile concentration. As a result, synthesis/hydrolysis ratio in the enzymatic synthesis can be significantly (up to three times) increased due to the nucleophile supersaturation. In the antibiotic nuclei conversion to the target antibiotic the remarkable improvement (up to 14%) has been gained. Methods of obtaining relatively stable supersaturated solutions of 6‐APA, 7‐ADCA, and D‐p‐hydroxyphenylglycine amide (D‐HPGA) have been developed and syntheses of ampicillin, amoxicillin, and cephalexin starting from the supersaturated homogeneous solutions of substrates were performed. Higher synthetic efficiency and increased productivity of these reactions compared to the heterogeneous “aqueous solution‐precipitate” systems were observed. The suggested approach seems to be an effective solution for the aqueous synthesis of the most widely requested β‐lactam antibiotics (i.e., amoxicillin, cephalexin, cephadroxil, cephaclor, etc.). © 2004 Wiley Periodicals, Inc.
Poly‐3‐hexyl thiophene Langmuir‐Blodgett films for application to glucose biosensor
Authors: Singhal Rahul , Chaubey Asha , Kaneto Keiichi , Takashima W. , Malhotra B. D. 
Published: January 2004

AbstractLangmuir‐Blodgett films of poly(3‐hexyl thiophene) have been prepared by simultaneous entrapment of glucose oxidase and transferred onto the indium‐tin‐oxide coated glass plates. The films have been characterized by FTIR spectroscopy and detailed response studies have been performed with respect to glucose concentration, temperature, and storage time. These P3HT/SA/GOX electrodes have been utilized for glucose estimation from 100–500 mg/dL by amperometric method. The electrodes have been found to have sensitivity of 0.75 nA/mg/dL detection limit of 50 mg/dL and shelf life of about 75 days at 4°C. © 2004 Wiley Periodicals, Inc.
On‐line monitoring of important organoleptic methyl‐branched aldehydes during batch fermentation of starter culture Staphylococcus xylosus reveal new insight into their production in a model fermentation
Authors: Petersen Christian de Vos , Beck Hans C. , Lauritsen Frants R. 
Published: January 2004

AbstractA small fermentor (55 mL) was directly interfaced to a membrane inlet mass spectrometer for continuous on‐line monitoring of oxygen and volatile metabolites during batch fermentations of the starter culture Staphylococcus xylosus. Using this technique, we were able to correlate production of the very important flavor compounds 2‐methylbutanal, 3‐methylbutanal, and 2‐methylpropanal with various growth conditions. We found that the aldehydes were present in the culture broth only as transient metabolites. They were produced in the exponential growth phase, reached a maximum concentration when the culture became anaerobic, and then they rapidly disappeared from the culture medium. This general pattern was observed for three different strains of S. xylosus and S. carnosus. Small amounts of inoculum or increased exposure to oxygen were found to favor production of the aldehydes as a result of a longer aerobic growth period. Growing S. xylosus under conditions resembling those in a fermented sausage revealed that NaCl (5%) increased aldehyde production considerably, whereas KNO3 (0.03%) or NaNO2 (0.03%) had little effect. A lowering of pH from 7.2 to 6.0 reduced cell density, but had a minor affect on aldehyde production. © 2004 Wiley Periodicals, Inc.
Affinity purification of plasmid DNA by temperature‐triggered precipitation
Authors: Kostal Jan , Mulchandani Ashok , Chen Wilfred 
Published: January 2004

AbstractThis report describes a new plasmid DNA purification method, which takes advantage of the DNA‐binding affinity and specificity of the bacterial metalloregulatory protein MerR, and of the temperature responsiveness of elastin‐like proteins (ELPs). Upon increasing the temperature, ELP undergoes a reversible phase transition from water‐soluble forms into aggregates, and this property was exploited for the precipitation of plasmid DNA containing the MerR recognition sequence by a simple temperature trigger. In one purification step, plasmid DNA was purified from E. coli cell lysates to a better purity than that prepared by a standard alkaline purification method, with no contaminating chromosomal DNA and cellular proteins. This protein‐based approach, in combination with the reversible phase transition feature of ELP, makes the outlined method a promising candidate for large‐scale purification of plasmid DNA for sensitive applications such as nonviral gene therapy or DNA vaccines. © 2004 Wiley Periodicals, Inc.
Transglutaminase‐mediated modification of glutamine and lysine residues in native bovine β‐lactoglobulin
Authors: Nieuwenhuizen Willem F. , Dekker Henk L. , Gröneveld Toos , de Koster Chris G. , de Jong Govardus A. H. 
Published: January 2004

AbstractBovine β‐lactoglobulin (BLG) is a major component in whey and its physical properties are important for the texture of many dairy‐based foods. Modification of proteins with transglutaminase from Streptoverticillium mobaraense (MTGase) can be used to alter their physical properties. MTGase‐mediated modification of native BLG was until now, however, not effective. Here we report a method that allows for the enzymatic modification of native BLG with MTGase. Lysines 8, 77, and 141 were modified with α‐N‐carbobenzyloxy‐glutamine‐glycine and glutamines 35, 59, 68,and 155 were modified with 6‐aminohexanoic acid under nonreducing and nondenaturing conditions. MTGase‐mediated BLG crosslinking is hampered by the low reactivity of the lysines and enzymatic deamidation of the glutamines prevails. Modification of BLG with poly‐lysine yields a BLG derivative with increased affinity for the water–air interface and stronger surface tension lowering capacities than normal BLG. Hence, this modification method offers the opportunity to change the functional properties of BLG and to prepare novel protein foods. © 2004 Wiley Periodicals, Inc.
Genome‐wide transcriptional response of a Saccharomyces cerevisiae strain with an altered redox metabolism
Authors: Bro Christoffer , Regenberg Birgitte , Nielsen Jens 
Published: January 2004

AbstractThe genome‐wide transcriptional response of a Saccharomyces cerevisiae strain deleted in GDH1 that encodes a NADP+‐dependent glutamate dehydrogenase was compared to a wild‐type strain under anaerobic steady‐state conditions. The GDH1‐deleted strain has a significantly reduced NADPH requirement, and therefore, an altered redox metabolism. Identification of genes with significantly changed expression using a t‐test and a Bonferroni correction yielded only 16 transcripts when accepting two false‐positives, and 7 of these were Open Reading Frames (ORFs) with unknown function. Among the 16 transcripts the only one with a direct link to redox metabolism was GND1, encoding phosphogluconate dehydrogenase. To extract additional information we analyzed the transcription data for a gene subset consisting of all known genes encoding metabolic enzymes that use NAD+ or NADP+. The subset was analyzed for genes with significantly changed expression again with a t‐test and correction for multiple testing. This approach was found to enrich the analysis since GND1, ZWF1 and ALD6, encoding the most important enzymes for regeneration of NADPH under anaerobic conditions, were down‐regulated together with eight other genes encoding NADP(H)‐dependent enzymes. This indicates a possible common redox‐dependent regulation of these genes. Furthermore, we showed that it might be necessary to analyze the expression of a subset of genes to extract all available information from global transcription analysis. © 2004 Wiley Periodicals, Inc.
Detection, isolation, and characterization of exopolysaccharide produced by a strain of Phormidium 94a isolated from an arid zone of Mexico
Authors: Vicente‐García Valeria , Ríos‐Leal Elvira , Calderón‐Domínguez Georgina , Cañizares‐Villanueva Rosa Olivia , Olvera‐Ramírez Roxana 
Published: January 2004

AbstractPhormidium 94a, a cyanobacteria that produces extracellular polymeric substances (EPS), was isolated from arid soils of Mexico. Microscopic localization, using histochemical techniques like the Toluidine blue technique, was done in order to demonstrate the presence of EPS. Acetone was added to precipitate the EPS. In this study we characterized the EPS by GC, HPLC, and IR techniques. The highest fraction of EPS had a molecular weight of 2,000 kDa. The sugar composition was galactose, mannose, galacturonic acid, arabinose, and ribose in the three main fractions, and the sugar ratio found was different in each fraction. The low EPS concentrations had a Newtonian behavior, when the concentrations were increased, the behavior changed to pseudoplastic. The EPS rheulogical behavior is similar to low viscosity arabic gum. Also, it was found that an increase in viscosity occurred at longer hydration time. More rheological and toxicological studies are required in order to analyze its possible application in food industries. © 2004 Wiley Periodicals, Inc.
Absolute stability of a class of neural networks with unbounded delay
Authors: Zhang Jiye 
Published: January 2004

AbstractIn this paper, the existence and uniqueness of the equilibrium point and absolute stability of a class of neural networks with partially Lipschitz continue activation functions are investigated. The neural networks contain both variable and unbounded delays. Using the matrix property, the necessary and sufficient condition for the existence and uniqueness of the equilibrium point of the neural networks is obtained. By constructing proper vector Liapunov functions and non‐linear integro‐differential inequalities involving both variable delays and unbounded delay, the sufficient conditions for absolute stability (global asymptotic stability) are obtained. Copyright © 2004 John Wiley & Sons, Ltd.
A matrix pencil approach to the local stability analysis of non‐linear circuits
Authors: Riaza Ricardo 
Published: January 2004

AbstractThis paper addresses local stability issues in non‐linear circuits via matrix pencil theory. The limitations of the state–space approach in circuit modelling have led to semistate formulations, currently framed within the context of differential‐algebraic equations (DAEs). Stability results for these DAE models can be stated in terms of matrix pencils, avoiding the need for state–space reductions which are not advisable in actual circuit simulation problems. The stability results here presented are applied to electrical circuits containing non‐linear devices such as Josephson junctions or MOS transistors. Copyright © 2004 John Wiley & Sons, Ltd.
An interval algorithm for finding all solutions of non‐linear resistive circuits
Authors: Yamamura Kiyotaka , Igarashi Naoya 
Published: January 2004

AbstractIn this letter, an efficient algorithm is proposed for finding all solutions of non‐linear (not piecewise‐linear) resistive circuits. This algorithm is based on interval analysis, the dual simplex method, and the contraction methods. By numerical examples, it is shown that the proposed algorithm could find all solutions of systems of 500–700 non‐linear circuit equations in acceptable computation time. Copyright © 2004 John Wiley & Sons, Ltd.
The vasodilatory actions of insulin on resistance and terminal arterioles and their impact on muscle glucose uptake
Authors: Clerk Lucy H. , Vincent Michelle A. , Lindner Jonathan R. , Clark Michael G. , Rattigan Stephen , Barrett Eugene J. 
Published: January 2004

AbstractWhether a discrete vascular action of insulin in skeletal muscle integrally participates in insulin‐mediated glucose disposal has been extensively examined but remains a contentious issue. Here, we review some of the data both supporting and questioning the role of insulin‐mediated increases in limb blood flow in glucose metabolism. We advance the hypothesis that controversy has arisen, at least in part, from a failure to recognize that insulin exerts at least three separate actions on the peripheral vasculature, each with its own characteristic dose and time responsiveness. We summarize how, viewed in this manner, certain points of contention can be resolved. We also advance the hypothesis that an action on the precapillary arteriole may play the dominant role in mediating perfusion‐dependent effects of insulin on glucose metabolism in muscle. Copyright © 2003 John Wiley & Sons, Ltd.
Soluble adhesion molecules in Finnish schoolchildren with signs of preclinical type 1 diabetes
Authors: Toivonen Anna , Kulmala Petri , Rahko Jukka , Ilonen Jorma , Knip Mikael 
Published: January 2004

AbstractBackgroundWe measured the circulating concentrations of the soluble forms of intercellular adhesion molecule‐1, ICAM‐1 (sCD54) and L‐selectin (sCD62L) in 104 non‐diabetic Finnish schoolchildren testing positive for one or more diabetes‐associated autoantibodies and in 104 autoantibody‐negative children to elucidate the relationship between soluble adhesion molecules and humoral, genetic and metabolic markers of preclinical type 1 diabetes.MethodsSpecific enzyme‐linked immunosorbent assays were used to analyse serum sICAM‐1 and sL‐selectin concentrations.ResultsThe sICAM‐1 and sL‐selectin levels were comparable in the autoantibody‐positive and control children, even when comparing children with multiple autoantibodies with those having one or no autoantibodies. The IA‐2A titres in children testing positive for this autoantibody correlated with the sICAM‐1 concentrations (rs = 0.62, P = 0.05), but otherwise no significant associations were seen between the autoantibody specificities and the concentrations of soluble adhesion molecules. Control children with HLA DQB1 genotypes conferring a low or decreased risk of type 1 diabetes had higher levels of sL‐selectin than those with high or moderate risk genotypes (P = 0.04). sL‐selectin concentrations were significantly increased in the autoantibody‐positive children with a first‐phase insulin response (FPIR) below the 5th (n = 11;P = 0.026) or 10th percentiles (n = 17;P = 0.009) relative to the children with a normal FPIR. No associations were observed between sICAM‐1 concentrations and DQB1 genotypes or FPIR.ConclusionsThe data indicate that there are a few conspicuous signs of endothelial/leukocyte activation reflected in increased circulating levels of soluble adhesion molecules in schoolchildren who are positive for markers of preclinical type 1 diabetes. The correlation between sICAM‐1 concentrations and IA‐2A levels in the IA‐2A‐positive children suggests that the former may increase in late preclinical type 1 diabetes, as IA‐2A are the last autoantibodies to appear in the prediabetic process. Increased sL‐selectin concentrations in subjects with impaired β‐cell function may reflect an active destructive insulitis process. Copyright © 2004 John Wiley & Sons, Ltd.
The role of the sodium hydrogen exchanger‐1 in mediating diabetes‐induced changes in the retina
Authors: Cukiernik Mark , Hileeto Denise , Downey Donal , Evans Terry , Ali Khan Zia , Karmazyn Morris , Chakrabarti Subrata 
Published: January 2004

AbstractBackgroundThe sodium hydrogen exchanger (NHE) is a transmembrane protein responsible for alkalinization and control of intracellular acidosis by the removal of hydrogen and the subsequent influx of sodium. Our investigation attempts to determine the role of NHE‐1 in the pathogenesis of early retinal microangiopathy due to diabetes.MethodsDiabetes was induced in male Sprague–Dawley rats with a single intravenous streptozotocin injection (65 mg/kg). To examine the duration‐dependent changes in NHE‐1 expression, retinas from 1‐, 6‐ and 12‐week diabetic animals were analyzed. To examine the functional consequences of NHE‐1 inhibition in comparison with good blood glucose control, diabetic rats were randomly assigned to poorly controlled diabetic, well‐controlled diabetic, poorly controlled diabetic with cariporide groups and were compared with nondiabetic controls after six weeks. Cariporide is an orally active inhibitor of NHE‐1 (6000 ppm in rat chow). At the end of the treatment period, color Doppler ultrasound was used to determine the resistivity index (RI) of the central retinal artery. The mRNA expression of endothelin (ET) isoforms 1 and 3, inducible and endothelial nitric oxide synthase (iNOS and eNOS respectively) and NHE‐1 were examined. NHE‐1 distribution was localized with immunohistochemistry.ResultsAll diabetic animals showed hyperglycemia, increased glycated hemoglobin and lower body weight gain compared to nondiabetic controls. Diabetes caused an increased RI, indicative of retinal vasoconstriction, which was corrected by both cariporide treatment and good glucose control. NHE‐1 was localized in the endothelium of the retinal microvasculature and the neuronal and glial components. NHE‐1 mRNA expression was unchanged after 1 week and increased after 6 and 12 weeks of diabetes. Furthermore, a diabetes‐induced upregulation of ET‐1 and ET‐3 mRNA expression after six weeks was corrected with cariporide treatment. NHE‐1 inhibition of diabetic animals upregulated iNOS mRNA levels, although expression of eNOS and iNOS mRNA were not altered in poorly controlled diabetes. Improved blood glucose control with higher doses of insulin also corrected diabetes‐induced increased RI by upregulating eNOS and iNOS mRNA expression.ConclusionsThe results of the study suggest that NHE‐1 may be involved in the regulation of several vasoactive modulators that contribute to functional alterations in diabetic retinal microangiopathy. Copyright © 2004 John Wiley & Sons, Ltd.
Dynamic approach to learning disability assessment: DLD test
Authors: Dwairy Marwan 
Published: January 2004

AbstractA severe discrepancy between intellectual ability and achievement is one major criterion for diagnosis of learning disability (LD). This manuscript describes the shortcomings of this paradigm and offers a new dynamic approach for LD assessment based on evaluation of LD during a standard learning process of how to read and write a new language. The dynamic learning disability (DLD) test, K‐ABC IQ test, and K‐ABC reading test were administered to 56 normal 4th grade students and to 48 LD students. It was hypothesized that the results using the conventional criteria may mismatch the results of DLD, and that DLD predicts the progress of students in a long‐term group learning process better. The results indicated that LD students, as a group, manifested significant difficulties in the DLD test. Among 48 students who meet the conventional criteria for LD diagnosis 14 students (29.16%) were able to learn a new language in the DLD test (Inconsistent LD sub‐group). From the 14 students who have low achievement in reading without serious indications of cognitive difficulties, six students (42.857%) manifested serious difficulties in learning a new language in the DLD test (Latent LD sub‐group). The DLD test as well as the labels of the sub‐groups was validated by the amount of progress in the long‐term group learning process. The DLD test proved to have high reliability and predictive validity coefficients. It is suggested that it become part of the diagnostic battery of tests of LD. Copyright © 2004 John Wiley & Sons, Ltd.