bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of human erythropoietin secretion from MLV‐infected human primary fibroblasts used for encapsulated cell therapy
Authors: Schwenter F. , Déglon N. , Aebischer P.
Published: March 2003

Background

The transplantation of encapsulated cells genetically engineered to secrete human erythropoietin (hEpo) represents an alternative to repeated injections of the recombinant hormone for the treatment of Epo‐responsive anemia. In the present study, the ability of primary human foreskin fibroblasts to secrete high levels of hEpo and the importance of cis‐acting elements and infection conditions on transgene expression level were assessed.

Methods

The transduction efficiency was first evaluated with β‐galactosidase (LacZ)‐encoding retroviral vectors derived from the murine leukemia retrovirus (MLV) pseudotyped either with an amphotropic envelope or with the G glycoprotein of vesicular stomatitis virus (VSV‐G). Human fibroblasts were then infected with an amphotropic hEpo‐expressing retroviral vector, which was modified by insertion of a post‐transcriptional regulatory element from the woodchuck hepatitis virus (WPRE) and a Kozak consensus sequence (KZ). Human Epo production was further optimized by increasing the multiplicity of infection and by selecting high producer cells. The survival and the transgene expression of these fibroblasts were finally evaluated in vivo. The cells were encapsulated into microporous hollow fibers and subcutaneously implanted in nude mice.

Results

A secretion level of approximately 5 IU hEpo/106 cells/day was obtained with the basal vector. A 7.5‐fold increase in transgene expression was observed with the insertion of WPRE and KZ elements. Finally, according to the optimization of infection conditions, we obtained a 40‐fold increase in hEpo secretion, reaching approximately 200 IU hEpo/106 cells/day. The in vivo experiments showed an increase in the hematocrit during the first 2 weeks and elevated levels exceeding 60% were maintained over a 6‐week period.

Conclusions

These results indicate that primary human fibroblasts represent a promising source for encapsulated cell therapy. Copyright © 2003 John Wiley & Sons, Ltd.
The in vivo use of chloroquine to promote non‐viral gene delivery to the liver via the portal vein and bile duct
Authors: Zhang Xiaohong , Sawyer Greta J. , Dong Xuebin , Qiu Ying , Collins Louise , Fabre John W.
Published: March 2003

Background

Assistance with exit from endocytic vesicles is a key factor for non‐viral gene delivery, and is a particular challenge in vivo. We have evaluated the in vivo use of chloroquine administered systemically, orally and/or locally for gene delivery to the liver.

Methods

The DNA vector (polylysine‐molossin) is a 31 amino acid bifunctional synthetic peptide, incorporating an amino terminal chain of 16 lysines for electrostatic binding of DNA. Gene delivery was to the right lateral lobes of the liver by branches of the bile duct or portal vein.

Results

Single intraperitoneal injections of 8, 25 and 75 mg/kg of chloroquine (the maximum tolerated single intraperitoneal dose) resulted in increasing levels of luciferase reporter gene expression, following gene delivery via the bile duct. 100 mg/kg of chloroquine orally was equivalent to 25 mg intraperitoneally. A 3‐day course of intraperitoneal and oral chloroquine gave ∼10–30‐fold higher gene expression than an optimal single dose, and resulted in a scattering of positive hepatocytes in the lobule. Gene delivery via the bile duct was much more effective than via the portal vein. Serum chloroquine levels at the time of gene delivery showed a highly significant correlation with gene expression, but the maximum achievable levels in vivo (∼1–2 µM) were much lower than those required for optimal in vitro gene delivery. Chloroquine (0.2–5 mM) was also given locally in the bile duct with vector/DNA complexes. Maximum gene expression was obtained with 0.5 mM local chloroquine, but the level of gene expression was only equivalent to the 25 mg intraperitoneal dose.

Conclusions

The in vivo use of chloroquine is effective for promoting gene delivery to the liver, but requires multiple dosing and is limited by systemic toxicity. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and biphenyls by gas chromatography/mass spectrometry in the negative chemical ionization mode with different reagent gases
Authors: Chernetsova Elena S. , Revelsky Alexander I. , Revelsky Igor A. , Mikhasenko Ilya A. , Sobolevsky Tim G.
Published: March 2003

I.
Introduction
374

II.
Approaches to Selective and Sensitive GC/MS Determination of PCDD, PCDF, and PCB
374

A. Most Prevalent Ionization Modes in GC/MS
374

B. Sensitive Detection: Negative Chemical Ionization with Different Reagent Gases
375

   1. Determination of Polychlorinated Dibenzo‐p‐dioxins (PCDDs) and Dibenzofurans (PCDFs) with Different
Reagent Gases
376

     a. CH4 as reagent gas
376

     b. O2 as reagent gas
377

     c. O2 as reagent gas [atmospheric pressure chemical ionization (APCI)]
378

     d. CH4/O2 as reagent gas
379

     e. CH4/N2O as reagent gas
380

     f. i‐C4H10/CH2Cl2/O2 as reagent gas
380

     g. Ar/CH4, CH4, i‐C4H10 as reagent gases
381

     h. H2 as reagent gas
381

     i. Ar, Xe, SF6, H2, and He as reagent gases
381

   2. Determination of Polychlorinated Biphenyls (PCBs) with Different Reagent Gases
382

     a. CH4 and CH4/O2 as reagent gases
382

     b. O2 as reagent gas [atmospheric pressure chemical ionization (APCI)]
382

     c. CH4 and NH3 as reagent gases
383

     d. CH4/O2, Ar/O2, CH4/H2O, and CH4 as reagent gases
383

III.
Conclusion and Actual Problems
383

References
385

Reagent gases that are used in mass spectrometry in the NCI mode for the determination of polychlorinated dibenzo‐p‐dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) are discussed. Ion‐molecule reactions and respective characteristic ions that form while using reagent gases (CH4, O2, i‐C4H10, NH3, H2, He, Ar, Xe, SF6) or gas mixtures (CH4/O2, Ar/CH4, CH4/H2O, Ar/O2, i‐C4H10/CH2Cl2/O2) are reviewed. It is shown that only CH4, O2, CH4/O2, and CH4/N2O are widely used and well studied, even though—in the case of these reagent gases—there are contradictions between the publications of various authors. Such reagent gases as NH3 and He are not well studied, but further investigations of their use for the determination of organochlorine pollutants could be of interest. The possibilities of more sensitive and selective determination of PCDDs, PCDFs, and PCBs are discussed. © 2003 Wiley Periodicals, Inc., Mass Spec Rev 21:373–387, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mas.10037
Characterization of transcription factors by mass spectrometry and the role of SELDI‐MS
Authors: Forde Cameron E. , McCutchen‐Maloney Sandra L.
Published: March 2003

I.
Introduction
419

  II.
Genomics, Proteomics, and MS
420

 III.
Regulatory Networks and the Traditional Study of Transcription Factors
421

  IV.
Identification of Transcription‐Factor Complexes
422

   V.
Structural Characterization of Transcription Factors
423

  VI.
Determination of Binding Sites and Stoichiometry of Binding
423

 VII.
Post‐Translational Modifications
426

VIII.
Assessing Metal Binding and Activity
427

  IX.
Affinity Capture and Identification of Transcription Factors Using MS
429

   X.
Role of SELDI‐MS to Characterize Transcription Factors
430

  XI.
Other Applications of SELDI‐MS
433

 XII.
Conclusion and Future Prospects
434

Acknowledgments
434

References
434

Over the last decade, much progress has been made in the field of biological mass spectrometry, with numerous advances in technology, resolution, and affinity capture. The field of genomics has also been transformed by the sequencing and characterization of entire genomes. Some of the next challenges lie in understanding the relationship between the genome and the proteome, the protein complement of the genome, and in characterizing the regulatory processes involved in progressing from gene to functional protein. In this new age of proteomics, development of mass spectrometry methods to characterize transcription factors promises to add greatly to our understanding of regulatory networks that govern expression. However, at this time, regulatory networks of transcription factors are mostly uncharted territory. In this review, we summarize the latest advances in characterization of transcription factors by mass spectrometry including affinity capture, identification of complexes of DNA‐binding proteins, structural characterization, determination of protein–DNA and protein–protein interactions, assessment of modification sites and metal binding, studies of functional activity, and the latest chip technologies that use SELDI‐MS that allow the rapid capture and identification of transcription factors. © 2003 Wiley Periodicals, Inc., Mass Spec Rev 21:419–439, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mas.10040
Inhibition of proteasome‐dependent degradation of Wee1 in G2‐arrested Hep3B cells by TGFβ1
Authors: Hashimoto Osamu , Ueno Takato , Kimura Rina , Ohtsubo Motoaki , Nakamura Toru , Koga Hironori , Torimura Takuji , Uchida Sanae , Yamashita Katsumi , Sata Michio
Published: March 2003

Transforming growth factor β1 (TGFβ1)‐induced G2 arrest was observed when a proliferation inhibitory function of the retinoblastoma protein (Rb) was compromised, but the mechanism underlying the G2 arrest was poorly characterized compared with that of G1 arrest. In the present study, we characterized G2 arrest induced by TGFβ1 (1 ng/mL) in the Rb‐negative hepatoma cell line (Hep3B) and compared with G1 arrest in the Rb‐positive hepatoma cell line (Huh7). Activities of cyclin‐dependent kinases (CDK) 2 and cell division cycle (CDC) 2 were markedly decreased at 24 h, the time when cell‐cycle arrest became apparent in both cell lines. However, considerable amounts of inactive CDC2‐cyclinB1 complexes were present in the nucleus of G2‐arrested Hep3B but were not present in G1‐arrested Huh7. The inhibitory phosphorylation of CDC2 on Tyr‐15 was significantly elevated at 12–24 h, and its levels gradually declined during G2 arrest in Hep3B. In particular, augmentation of CDK inhibitors p21cip1 and p27kip1 and Wee1 kinase and diminution of CDC25C phosphatase coincided with induced Tyr‐15 phosphorylation and inhibition of CDC2. Wee1 in Hep3B was unstable and was degraded in a proteasome‐dependent manner, but it became substantially stabilized within 6 h of TGFβ1 treatment. Moreover, a Wee1 inhibitor, PD0166285, abrogated the TGFβ1‐induced G2 arrest in Hep3B. These findings suggest that TGFβ1 induced G2 arrest in Hep3B at least in part through stabilization of Wee1 and subsequent increase in Tyr‐15 phosphorylation and inhibition of CDC2. © 2003 Wiley‐Liss, Inc.
Mutational analysis of Ctnnb1 and Apc in tumors from rats given 1,2‐dimethylhydrazine or 2‐amino‐3‐methylimidazo[4,5‐f]quinoline: Mutational ‘hotspots’ and the relative expression of β‐catenin and c‐jun
Authors: Blum Carmen A. , Tanaka Tomoko , Zhong Xiaoying , Li Qingjie , Dashwood Wan‐Mohaiza , Pereira Clifford , Xu Meirong , Dashwood Roderick H.
Published: March 2003

There is growing interest in β‐catenin and its role in various human cancers. We recently reported that 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ)‐ and 1,2‐dimethylhydrazine (DMH)‐induced colon tumors in the rat contain mutations in Ctnnb1, the gene for β‐catenin, but the mutation spectrum was influenced by postinitiation exposure to chlorophyllin (CHL) and indole‐3‐carbinol (I3C) [Blum et al., Carcinogenesis 2001;22:315–320]. The present paper describes a follow‐up study in which all of the target organs for IQ‐ and DMH‐induced tumorigenesis were screened; Ctnnb1 mutations were found in 44 of 119 DMH‐induced colon tumors, six of 13 IQ‐induced colon tumors, 28 of 81 DMH‐induced small intestine tumors, none of five IQ‐induced small intestine tumors, four of 106 IQ‐induced liver tumors, none of 14 DMH‐induced Zymbal's gland tumors, none of 24 IQ‐induced Zymbal's gland tumors, and none of 29 IQ‐induced skin tumors. In tumors from rats given carcinogen alone, or carcinogen plus CHL or I3C, Ctnnb1 mutations frequently substituted amino acids adjacent to Ser33, a critical Ser/Thr residue in the glycogen synthase kinase‐3β regulatory domain of β‐catenin. However, substitution of critical Ser/Thr residues themselves was detected in only three of 24 (12.5%) of the tumors from rats given carcinogen alone, compared with 23 of 58 (40%) of the tumors from rats given carcinogen and treated postinitiation with I3C or CHL (P < 0.02). More than 50 of the colon tumors with wild‐type β‐catenin were examined further for their Apc status; the overall frequency of Apc mutations was <10%, and these genetic changes occurred exclusively in the ‘Mutation Cluster Region’ of Apc. A subset of colon tumors also was examined for expression of β‐catenin and c‐jun; these proteins were overexpressed in all tumors containing Ctnnb1 mutations, but the expression was highest in tumors with Ctnnb1 mutations affecting Thr41 and Ser45 residues in the glycogen synthase kinase‐3β region of β‐catenin. Thus, Ctnnb1 mutations occurred more frequently than Apc mutations in colon and small intestine tumors of the rat, and certain mutations upregulated β‐catenin/T‐cell factor target genes more effectively than others, perhaps influencing the response to phytochemicals administered postinitiation. © 2003 Wiley‐Liss, Inc.
The phytochemical profile and identification of main phenolic compounds from the leaf exudate of Aloe secundiflora by high‐performance liquid chromatography–mass spectroscopy
Authors: Rebecca Waihenya , Kayser Oliver , Hagels Hansjörg , Zessin Karl‐H , Madundo Mtambo , Gamba Nkwengulila
Published: March 2003

The phytochemical profile of Aloe secundiflora (Aloeaceae) and the identity of eight major compounds, including the two main constituents, have been determined from the leaf exudate of this ethnoveterinary used species from Kenya and Tanzania. Analytical HPLC‐MS studies of the exudate have revealed that ­it comprises a mixture of phenolic compounds, mainly anthrones (aloenin, aloenin B, isobarbaloin, barbaloin and other aloin derivatives), chromones and phenylpyrones with a low content of polysaccharides and aliphatic compounds. The high percentage of anthrones in the exudate could provide a first line of evidence for the use of the plant in ethnoveterinary practices. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of carbohydrates and amino acids in vegetable waste waters by ion chromatography
Authors: Arienzo Michele , De Martino Antonio , Capasso Renato , Di Maro Antimo , Parente Augusto
Published: March 2003

High‐performance anion exchange chromatography coupled with pulsed amperometric detection was used for the quantitative determination of total and free sugars in olive oil mill waste waters (OMWW). Automated amino acid ion chromatography was employed to analyse total and free amino acids in the same OMWW. Sugars were analysed in samples pre‐purified by means of a three‐step purification procedure involving: (i) methanol precipitation of OMWW; (ii) dialysis of the obtained solid and liquid fractions; and (iii) chromatographic purification on RP18 phase followed by Amberlite resin. The amino acids were determined directly in samples obtained from the first two steps performed for sugar analysis. The analysis carried out with the reported methodologies allowed the quantitative determination of total sugars and amino acids and the differentiation between their free and bound forms. The sugars determined were arabinose, fructose, galactose, glucose, rhamnose, xylose, galacturonic and glucuronic acids, and the amino acids were Asp, Glu, Thr, Ser, Pro, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Arg and Cys. Asn, Gln, and Trp were not detected. The technological, biotechnological and environmental advantages arising from this analytical methodology applied to OMWW are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd.
On‐line identification of unstable catalpol derivatives from Jamesbrittenia fodina by LC‐MS and LC‐NMR
Authors: Cogne A.‐L. , Queiroz E. F. , Wolfender J.‐L. , Marston A. , Mavi S. , Hostettmann K.
Published: March 2003

LC‐UV‐MS analysis of the methanol extract of Jamesbrittenia fodina O. M. Hilliard (Scrophulariaceae) revealed the presence of cinnamic ester derivatives. Two isomeric pairs of these constituents were detected, but could not be isolated. In order to identify these unstable compounds, LC‐1H‐NMR spectra were obtained for each individual isomer and standard NMR measurements were performed in‐mixture. The spectra clearly demonstrated that the fractions consisted of mixtures of cis and trans cinnamoyl catalpol glycoside esters. Copyright © 2003 John Wiley & Sons, Ltd.
Composition of volatiles of banana cultivars from Madeira Island
Authors: Nogueira J. M. F. , Fernandes P. J. P. , Nascimento A. M. D.
Published: March 2003

The composition of the volatiles of banana fruit from various cultivars grown on Madeira Island has been determined. Using GC‐MS, the volatiles were shown to be complex mixtures of several classes of components, mainly esters, alcohols, aldehydes, ketones and acids. The average contents of the total volatiles from cultivars “Dwarf Cavendish”, “Giant Cavendish”, “Robusta” and “Williams” were 93.0, 116.5, 157.3 and 157.0 mg/kg, respectively. The ester and alcoholic fractions appear to play a decisive role in the organoleptic characteristics of banana fruit, presenting a substantial content ranging from 57.2 to 89.8 mg/kg and 19.0 to 47.7 mg/kg, respectively, in all cultivars from Madeira Island studied. 3‐Methyl butyl butanoate ester was the major constituent. Copyright © 2003 John Wiley & Sons, Ltd.
Identification of lipophilic flavones and flavonols by comparative HPLC, TLC and UV spectral analysis
Authors: Greenham Jenny , Harborne Jeffrey B. , Williams Christine A.
Published: March 2003

The identification of lipophilic flavones and flavonols using a combination of high performance liquid chromatography, thin layer chromatography and UV spectral analysis is discussed. Data are provided for the flavones, apigenin, luteolin and tricetin and twelve of their methyl ethers, 8‐hydroxyluteolin, 6‐hydroxyluteolin and scutellarein and fourteen of their methyl ethers, and some 6,8‐dihydroxyapigenin and 6,8‐dihydroxyluteolin derivatives. Data for some forty two flavonols with extra 6‐ and/or 8‐hydroxylation, mostly 6‐hydroxykaempferol and quercetagetin derivatives, are also presented. The remaining compounds analysed include fourteen 5‐deoxyflavones, four 5‐methoxyflavones and five 5‐deoxyflavonols plus further 5‐hydroxylated flavones and flavonols without B‐ring oxidation or with 2′‐, 5′‐ or 6′‐hydroxylation. Copyright © 2003 John Wiley & Sons, Ltd.
Reactions of 1,2,5‐thiadiazole 1,1‐dioxide derivatives with nitrogenated nucleophiles. Part 1—Addition of amines and amides to 3,4‐diphenyl‐1,2,5‐thiadiazole 1,1‐dioxide
Authors: Caram José Alberto , Aimone Silvia Lucía , Mirífico María Virginia , Vasini Enrique Julio
Published: March 2003

The addition reactions of some amides and aromatic amines to a CN double bond of 3,4‐diphenyl‐1,2,5‐thiadiazole 1,1‐dioxide (1) were studied in aprotic solvent solutions [N,N‐dimethylformamide (DMF) and acetonitrile (MeCN)]. Equilibrium constants for the reactions of 1 with acetamide, 2‐fluoroacetamide, butyramide, benzamide, aniline and 3‐aminopyridine were measured using a previously reported cyclic voltammetric (CV) method. Aliphatic amines gave unstable solutions, probably owing to reactions of anionic species derived from 1. Other N nucleophiles tested (formamide, succinimide, thioacetamide and cyanamide) yielded different products that have not yet been characterized. DMF, N,N‐dimethylacetamide (DMA) and N‐methylacetamide did not react. The addition thiadiazoline produced in the reaction of acetamide with 1 was characterized by IR and 1H and 13C RMN NMR spectroscopy as a prototype compound. For this system, the equilibrium constant could also be measured by a standard UV–VIS method and was found to be in agreement with the value obtained by CV. The reaction of 1 with urea produced a bicyclic product, identified as 3a,6a‐diphenyltetrahydroimidazo[4,5‐c]‐1,2,5‐thiadiazol‐5‐one 2,2‐dioxide. Copyright © 2003 John Wiley & Sons, Ltd.
Algorithmic, geometric and graphs issues in wireless networks
Authors: Li Xiang‐Yang
Published: March 2003

We present an overview of the recent progress of applying computational geometry techniques to solve some questions, such as topology construction and broadcasting, in wireless ad hoc networks. Treating each wireless device as a node in a two‐dimensional plane, we model the wireless networks by unit disk graphs in which two nodes are connected if their Euclidean distance is no more than one. We first summarize the current status of constructing sparse spanners for unit disk graphs with various combinations of the following properties: bounded stretch factor, bounded node degree, planar, and bounded total edges weight (compared with the minimum spanning tree). Instead of constructing subgraphs by removing links, we then review the algorithms for constructing a sparse backbone (connected dominating set), that is, subgraph from the subset of nodes. We then review some efficient methods for broadcasting and multicasting with theoretic guaranteed performance. Copyright © 2003 John Wiley & Sons, Ltd.
Robust position‐based routing in wireless ad hoc networks with irregular transmission ranges
Authors: Barrière Lali , Fraigniaud Pierre , Narayanan Lata , Opatrny Jaroslav
Published: March 2003

Several papers considered the problem of routing inad hocwireless networks using the positions of the mobile hosts. Perimeter routing1,2gives an algorithm that guarantees delivery of messages in such networks without the use of flooding of control packets. However, this protocol is likely to fail if the transmission ranges of the mobile hosts vary because of natural or man‐made obstacles. It may fail because either some connections are not considered, which effectively results in a disconnection of the network, or because some crossing connections are used, which could misdirect the message. In this paper, we describe a robust routing protocol, a variant of perimeter routing, which tolerates up to 40% of variation in the transmission ranges of the mobile hosts. More precisely, our protocol guarantees message delivery in a connected ad hoc wireless network without the use of message flooding whenever the ratio of the maximum transmission range to the minimum transmission range is at most √2. Copyright © 2003 John Wiley & Sons, Ltd.
Forward‐node‐set‐based broadcast in clustered mobile ad hoc networks
Authors: Wu Jie , Lou Wei
Published: March 2003

A taxonomy of broadcast protocols in mobile ad hoc networks (MANETs) is given where protocols are classified into four groups: global, quasi‐global, quasi‐local, and local. The taxonomy also divides protocols based on the nature of algorithms: probabilistic and deterministic. The locality of maintenance also plays an important role in evaluating the protocol. An important objective in designing a broadcast protocol is to reduce broadcast redundancy to save scarce resources such as energy and bandwidth and to avoid the broadcast storm problem. This objective should be achieved without introducing excessive overhead and time delay, measured by sequential rounds of information exchanges. This is done by choosing a small forward node set that forms a connected dominating set (CDS) to carry out a broadcast process. In this paper, a clustered network model is proposed in which each node is a clusterhead in the clustered architecture. Clusterheads are connected by carefully selecting non‐clusterhead nodes locally at each clusterhead to connect clusterheads within the 2.5‐hop coverage, a novel notion proposed in this paper. Information of neighbor clusterheads is piggybacked on the broadcast packet to further reduce each forward node set. It is shown that this approach is quasi‐local with locality of maintenance. In addition, this approach has a constant approximation ratio to the minimum connected dominating set (MCDS) and generates a small forward node set in the average case. Comparisons are also done through simulation with representative protocols from each of the four groups of protocols based on the proposed taxonomy. We also simulate the proposed broadcast protocol in a dynamic network and analyze its performance. Copyright © 2003 John Wiley & Sons, Ltd.
Constructing optimal virtual cellular networks for nonuniformly distributed base stations
Authors: Fan Guangbin , Zhang Jingyuan
Published: March 2003

In a cellular network, the cell size varies from area to area, and the base stations may not be uniformly distributed. For example, in a well‐populated city, the cell size may be smaller than that in a rural area. It is harder to study the performance of a nonuniform cellular network. By imposing a virtual uniform cellular network on the nonuniform cellular network, some performance issues of the nonuniform network can be studied using the imposed virtual one. In the imposed virtual cellular network, each virtual cell cannot contain more than one base station. This paper has proposed algorithms to construct optimal virtual cellular networks for nonuniformly distributed base stations. The constructed virtual cellular networks are optimal in the sense that their corresponding uniform cell sizes reach the largest possible. The main advantage of constructing the optimal virtual cellular network is that the number of virtual cells required to cover the service area is minimized. The algorithm works for mesh networks as well as for honeycomb networks. On the basis of a novel concept, referred to as the projection locus, both kinds of optimal virtual cellular networks can be constructed in O(nlog n) time for n nonuniformly distributed base stations. Copyright © 2003 John Wiley & Sons, Ltd.
Admission control in TD‐CDMA networks
Authors: Mišić Jelena , Tang Yat‐Kwan , Mišić Vojislav B
Published: March 2003

Quality of service (QoS) at the call or flow level in Time Division Code Division Multiple Access (TD‐CDMA) networks is an important topic that has not yet received much attention. In this paper, we propose a two‐tier admission and scheduling policy. The scheduling policy is comprised of two procedures, theUser Prioritizer Procedure(UPP) andPacket Allocator Procedure(PAP). TheUPPis used to determine the serving priority of users. The task ofPAPis to allocate packets to a time slot without violating the outage probability by invoking the tier 1 and tier 2 admission control. The tier 1 admission keeps the probability of violating the Bit Error Rate (BER) limits for new call arrivals below a specified threshold. The tier 1 admission allocates bandwidth for newly arrived calls on the basis of the outage probability threshold. The tier 2 admission reserves bandwidth in all surrounding sectors for future handoff events, which minimizes the probability that the handoff call from one sector will cause an outage condition in the target sector. The performance of the proposed policy is evaluated through simulations in the presence of voice and data traffic types. We show that the proposed scheme can provide satisfactory quality for a call or data flow during its lifetime. Copyright © 2003 John Wiley & Sons, Ltd.
The use of the simulated annealing algorithm for channel allocation in mobile computing
Authors: Zomaya Albert Y. , Smith Aidan , Seredynski Franciszek
Published: March 2003

A mobile network is a distributed communication system that uses radio signals as its information medium. Since the popularization of mobile networks, the rate of connectivity has soared and the subsequent load on the networks is much more significant than original projections. Hence, resource management becomes an important issue when designing mobile networks. This work concentrates on the most important resource available to mobile networks, that is, the limited allocated bandwidth. With the given amount of bandwidth, the network is expected to meet a minimum quality of service, to provide subscribers with access to the network. As the network is based on a cellular design, the way to improve utilization of the bandwidth is to reuse frequencies or channels. However, this reuse comes at a cost. The allocation of reused channels must be subject to the avoidance of interference between allocated channels. This is known as the channel allocation problem (CAP). It will be shown that the problem can be formalized into an optimization problem, for which there are many solution methodologies. In order to meet the demands of solution quality and algorithm efficiency, the decision of which method to use is critical. Biologically inspired techniques provide effective search strategies that enable the discovery of near optimal solutions. They are ideal for problems with large and complex solution spaces such as the CAP. However, the performance of these algorithms in terms of solution quality and efficiency varies greatly with the problems to which they are applied. Copyright © 2003 John Wiley & Sons, Ltd.
MHMR: mobility‐based hybrid multicast routing protocol in mobile ad hoc wireless networks
Authors: An Beongku , Papavassiliou Symeon
Published: March 2003

The field of mobile ad hoc networking has enjoyed dramatic increase in popularity over the last few years. However, owing to the fact that such networks have dynamic, sometimes rapidly changing, random, multihop topologies, the development of efficient and applicable multicast routing protocols presents many issues and challenges. In this paper we propose a Mobility‐based Hybrid Multicast Routing (MHMR) protocol suitable for mobile ad hoc networks. The main features that our proposed protocol introduces are the following: (i) mobility‐based clustering and group‐based hierarchical structure, in order to effectively support stability and scalability; (ii) group‐based (limited) mesh structure and forwarding tree concepts, in order to support the robustness of the mesh topologies, which provides ‘limited’ redundancy and the efficiency of tree forwarding simultaneously; and (iii) combination of proactive and reactive concepts that provide low route acquisition delay and low overhead. The use of dynamic mobility‐based clustering as the underlying structure is motivated by the observation that in mobile ad hoc networks communications are often among teams that tend to coordinate their movements, and as a result we can dynamically and adaptively partition the network into several groups, each with its own mobility characteristics and behaviors. In our protocol we support the creation of a limited mesh structure based on the clusterheads of the various created clusters, and not among all the members that participate in the multicast session and route, thereby reducing significantly the complexity of the created mesh topology. The performance evaluation of the proposed protocol is achieved via modeling and simulation. The corresponding results demonstrate the proposed multicast protocol's efficiency in terms of packet delivery ratio, scalability, control overhead, end‐to‐end delay as a function of mobility, packet transmission rate, and multicast group size. Copyright © 2003 John Wiley & Sons, Ltd.
A node scheduling scheme for energy conservation in large wireless sensor networks
Authors: Tian Di , Georganas Nicolas D.
Published: March 2003

In wireless sensor networks that consist of a large number of low‐power, short‐lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performances (sensing coverage and sensing reliability). In this paper, we propose a node‐scheduling scheme, which can reduce system overall energy consumption, therefore increasing system lifetime, by identifying redundant nodes in respect of sensing coverage and then assigning them an off‐duty operation mode that has lower energy consumption than the normal on‐duty one. Our scheme aims to completely preserve original sensing coverage theoretically. Practically, sensing coverage degradation caused by location error, packet loss and node failure is very limited, not more than 1% as shown by our experimental results. In addition, the experimental results illustrate that certain redundancy is still guaranteed after node‐scheduling, which we believe can provide enough sensing reliability in many applications. We implement the proposed scheme in NS‐2 as an extension of the LEACH protocol and compare its energy consumption with the original LEACH. Simulation results exhibit noticeably longer system lifetime after introducing our scheme than before. Copyright © 2003 John Wiley & Sons, Ltd.
The failure of new entrants in commercial banking markets: a split‐population duration analysis
Authors: DeYoung Robert
Published: March 2003

Almost one in four of the new commercial banks chartered in the United States during the 1980s failed. This study uses a split‐population duration model to examine failure patterns and failure determinants for these banks and compares the results to a benchmark model estimated for small established banks. The results are consistent with a “life cycle” pattern of new bank failure: compared to small established banks, newly chartered banks are initially less likely, then substantially more likely, and finally equally likely to fail. These patterns were most extreme for banks chartered just prior to the banking recession of the late 1980s or early 1990s.
Do credit unions use their tax advantage to benefit members? Evidence from a cost function
Authors: Scott Frame W , Karels Gordon V , McClatchey Christine A
Published: March 2003

This paper examines whether the credit union income tax subsidy is passed along to members or consumed by managers. To that end, we estimate a translog cost function for credit unions and mutual thrifts that is tailored to the unique objectives of mutually owned depository institutions. We find that credit unions with residential common bonds have higher costs than mutual thrifts, but single common bond occupational and associational credit unions are more cost efficient. Thus, it appears that residential credit unions engage in expense preference behavior and hence redirect some portion of their tax benefit away from members.
Market structure, consumer banking, and optimal level of service quality
Authors: Jackson William E. , Nandakumar Purushottaman , Roth Aleda V.
Published: March 2003

In this article, we use a very simple game theoretic model to investigate the influence of differing market structures, or competitive conditions, on a bank's decision to increase the level of quality of the retail, or consumer, services that it markets. The results from our model suggest that the optional level of a bank's service quality depends critically on the competitive structure of the market in which the bank operates, the degree of demand interaction between banks, and the ease of imitation of competitors' service quality innovations.

We find that banks in low demand interaction markets will adopt different strategies, inducing each bank to develop its own “unique” brand of quality. It is not necessarily the case that the leading banks will lead in quality improvements. This may partially explain why some of the largest banks do not have the highest levels of consumer service quality.
An analysis of advisor choice, fees, and effort in mergers and acquisitions
Authors: Hunter William C. , Jagtiani Julapa
Published: March 2003

This paper investigates the choice of financial advisors in mergers and acquisitions, the fees that the targets and the acquiring firms pay to these advisors, and the speed with which advisors complete transactions. Our sample includes 5337 merger deals announced during the period January 1995 to June 2000, that involved publicly traded targets and acquirers. We find that top‐tier advisors are more likely to complete deals and to complete them in less time than lower tier advisors. However, the synergistic gains realized by the acquirers declined when top advisors were used. We also find that contingent fees play a significant role in expediting the deal completion. Surprisingly, we find that deals that are initiated by the advisors do not seem to take less time to complete. Our results suggest that the payment of larger advisory fees do not play an important role in determining the likelihood of completing the deal, but they are associated with greater acquisition gains realized by the acquirer. In addition, these synergistic gains are also associated with the switching by acquirers of their financial advisors within the same tier.
The determination of commercial bank reserve requirements
Authors: Lown Cara S. , Wood John H.
Published: March 2003

Excess reserve ratios have been studied extensively and are believed to be endogenously determined. In contrast, required reserve ratios are conventionally treated as exogenous. However, there are public policy reasons for a positive response of reserve requirements to interest rates. These are opposed by private incentives to secure lower requirements when their cost rises with interest rates. Several kinds of evidence support the hypothesis that reserve requirements are inverse functions of interest rates, sometimes with long lags that reflect the political process. The results also suggest that banks are not passive creatures of regulation but mold their environment.
The Basel Committee proposals for a new capital accord: implications for Italian banks
Authors: Sironi Andrea , Zazzara Cristiano
Published: March 2003

Following a few general considerations on the recently proposed revision of the Basel Agreement on capital adequacy, this paper focuses on the first pillar of the Basel Committee proposals, the handling of capital requirements for credit risk in the banking book. The Basel Committee envisages an approach alternatively based on external ratings or on internal rating systems for the determination of the minimum capital requirement related to bank loan portfolios. This approach supports a system of capital requirements that is more sensitive to credit risk. On the basis of specific assumptions, these requirements provide a measure of the value at risk (VaR) produced by models used by major international banks. We first address the impact of the standardised and (internal ratings‐based) IRB foundation approach using general data on Italian banks loans' portfolios default rates. We then simulate the impact of the proposed new rules on the corporate loan portfolios of Italian banks, using the unique data set of mortality rates recently published by the Bank of Italy. Three main conclusions emerge from the analysis: (i) the standardised approach implicitly penalizes Italian banks in their interbank funding as their rating is generally below AA/Aa, (ii) the average default rate experienced by Italian banks is higher than the one implied in the benchmark risk weight (BRW) proposed by the Basel Committee for the IRB foundation approach, thereby potentially leading to an increase in the regulatory risk weights, and (iii) the risk‐weight is based on an average asset correlation that is significantly higher than the one historically recorded within the Italian banks' corporate borrowers. These findings support the need for a significant revision of the basic inputs and assumptions of the Basel proposals. Finally, in relation to the conditions that allow the capital market to effectively discipline banks, we comment on the proposals advanced in relation to the third pillar of the new capital adequacy scheme.
Kinetic studies of rat liver hexokinase D (glucokinase) in non-co-operative conditions show an ordered mechanism with MgADP as the last product to be released
Authors: MONASTERIO Octavio , CÁRDENAS María Luz
Published: March 2003

The kinetic mechanism of rat liver hexokinase D ('glucokinase') was studied under non-co-operative conditions with 2-deoxyglucose as substrate, chosen to avoid uncertainties derived from the co-operativity observed with the physiological substrate, glucose. The enzyme shows hyperbolic kinetics with respect to both 2-deoxyglucose and MgATP2-, and the reaction follows a ternary-complex mechanism with Km = 19.2±2.3mM for 2-deoxyglucose and 0.56±0.05mM for MgATP2-. Product inhibition by MgADP- was mixed with respect to MgATP2- and was largely competitive with respect to 2-deoxyglucose, suggesting an ordered mechanism with 2-deoxyglucose as first substrate and MgADP- as last product. Dead-end inhibition by N-acetylglucosamine, AMP and the inert complex CrATP [the complex of ATP with chromium in the 3+ oxidation state, i.e. Cr(III)—ATP], studied with respect to both substrates, also supports an ordered mechanism with 2-deoxyglucose as first substrate. AMP appears to bind both to the free enzyme and to the E·dGlc complex. Experiments involving protection against inactivation by 5,5′-dithiobis-(2-nitrobenzoic acid) support the existence of the E·MgADP- and E·AMP complexes suggested by the kinetic studies. MgADP-, AMP, 2-deoxyglucose, glucose and mannose were strong protectors, supporting the existence of binary complexes with the enzyme. Glucose 6-phosphate failed to protect, even at concentrations as high as 100mM, and MgATP2- protected only slightly (12%). The inactivation results support the postulated ordered mechanism with 2-deoxyglucose as first substrate and MgADP- as last product. In addition, the straight-line dependence observed when the reciprocal value of the inactivation constant was plotted against the sugar-ligand concentration supports the view that there is just one sugar-binding site in hexokinase D.
Interactions between plant RING-H2 and plant-specific NAC (NAM/ATAF1/2/CUC2) proteins: RING-H2 molecular specificity and cellular localization
Authors: GREVE Krestine , COUR Tanja LA , JENSEN Michael K. , POULSEN Flemming M. , SKRIVER Karen
Published: March 2003

Numerous, highly conserved RING-H2 domains are found in the model plant Arabidopsis thaliana (thale cress). To characterize potential RING-H2 protein interactions, the small RING-H2 protein RHA2a was used as bait in a yeast two-hybrid screen. RHA2a interacted with one of the plant-specific NAC [NAM ('no apical meristem'), ATAF1/2, CUC2 ('cup-shaped cotyledons 2')] transcription factors, here named ANAC (abscisic acid-responsive NAC). The core RING-H2 domain was sufficient for the interaction. The ability of 11 structurally diverse RING-H2 domains to interact with ANAC was then examined. Robust interaction was detected for three of the domains, suggesting multi-specificity for the interaction. The domains that interacted with ANAC contain a glutamic acid residue in a position corresponding to a proline in many RING-H2 domains. Conversion of this glutamic acid residue into proline in RHA2a decreased its ability to interact with ANAC, most likely by changing the interaction surface. This suggested that a short, divergent region in RING-H2 domains modulate interaction specificity. ANAC contains a degenerate bipartite nuclear localization signal (NLS), while RHG1a, also identified as an ANAC interaction partner, contains a basic NLS. Both signals localized β-glucuronidase reporter fusions to the nucleus. N-terminally truncated RHA2a also directed nuclear localization, apparently dependent on basic amino acids in the RING-H2 domain. Nuclear co-localization of the RING-H2 proteins and ANAC may enable their interaction in vivo to regulate the activity of the ANAC transcription factor.
Human mismatch-repair protein MutL homologue 1 (MLH1) interacts with Escherichia coli MutL and MutS in vivo and in vitro: a simple genetic system to assay MLH1 function
Authors: QUARESIMA Barbara , ALIFANO Pietro , TASSONE Pierfrancesco , AVVEDIMENTO Enrico V. , COSTANZO Francesco S. , VENUTA Salvatore
Published: March 2003

A simple genetic system has been developed to test the effect of over-expression of wild-type or mutated human MutL homologue 1 (hMLH1) proteins on methyl-directed mismatch repair (MMR) in Escherichia coli. The system relies on detection of Lac+ revertants using MMR-proficient or MMR-deficient E. coli strains carrying a lac +1 frameshift mutation expressing hMLH1 proteins. We report that expression of wild-type hMLH1 protein causes an approx. 19-fold increase in mutation rates. The mutator phenotype was due to the ability of hMLH1 protein to interact with bacterial MutL and MutS proteins, thereby interfering with the formation of complexes between MMR proteins and mismatched DNA. Conversely, expression of proteins encoded by alleles deriving from hereditary-non-polyposis-colon-cancer (HNPCC) families decreases mutation rates, depending on the specific amino acid substitutions. These effects parallel the MutL-and MutS-binding and ATP-binding/hydrolysis activities of the mutated proteins.
Identification and characterization of Gbeta3s2, a novel splice variant of the G-protein beta3 subunit
Authors: ROSSKOPF Dieter , MANTHEY Iris , HABICH Christiane , KIELBIK Marzena , EISENHARDT Andreas , NIKULA Christiane , URBAN Melanie , KOHNEN Stefanie , GRAF Eva , RAVENS Ursula , SIFFERT Winfried
Published: March 2003

The T-allele of a polymorphism (C825T) in the gene for the G-protein β3 subunit (GNB3) is associated with cardiovascular and metabolic disorders, distinct cellular features and altered drug responses. The molecular mechanisms that give rise to this complex phenotype have been linked to the occurrence of Gβ3s, a splice variant of GNB3. Gβ3s is predominantly expressed in cells with the 825T-allele. In the present study we describe the identification and characterization of an additional Gβ3 splice variant referred to as Gβ3s2. Its mRNA is expressed in heart, blood cells and tumour tissue, and its expression is also tightly associated with the GNB3 825T-allele. Gβ3s2 is generated by alternative splicing using non-canonical splice sites. Gβ subunits belong to the family of propeller proteins and consist of seven regular propeller blades. Transcripts for Gβ3s2 are lacking 129bp of the coding sequence of the wild-type Gβ3 protein. Thus the predicted structure consists of only six propeller blades, which resembles the structure of Gβ3s. Co-immunoprecipitation analyses indicated that Gβ3s2 dimerizes with different Gγ subunits, e.g. Gγ5, Gγ8C and Gγ12. In Sf9 insect cells, expression of Gβ3s2 together with Gγ12 enhances receptor-stimulated activation of Gαi2. Expression of Gβ3s2 in mammalian cells activated the mitogen-activated protein kinase cascade. Together, these results suggest that Gβ3s2 is a biologically active Gβ variant which may play a role in the manifestation of the complex phenotype associated with the 825T-allele.