bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformational solution studies of the SDS micelle‐bound 11‐28 fragment of two Alzheimer's β‐amyloid variants (E22K and A21G) using CD, NMR, and MD techniques
Authors: Rodziewicz‐Motowidło Sylwia , Juszczyk Paulina , Kołodziejczyk Aleksandra S. , Sikorska Emilia , Skwierawska Agnieszka , Oleszczuk Marta , Grzonka Zbigniew
Published: May 2007

The β‐amyloid (Aβ) is the major peptide constituent of neuritic plaques in Alzheimer's disease (AD) and its aggregation is believed to play a central role in the pathogenesis of the disease. Naturally occurring mutations resulting in changes in the Aβ sequence (pos. 21‐23) are associated with familial AD‐like diseases with extensive cerebrovascular pathology. It was proved that the mutations alter the aggregation ability of Aβ and its neurotoxicity. Among five mutations at positions 21–23 there are two mutations with distinct clinical characteristics and potentially distinct pathogenic mechanism—the Italian (E22K) and the Flemish (A21G) mutations. In our studies we have examined the structures of the 11‐28 fragment of the Italian and Flemish Aβ variants. The fragment was chosen because it has been shown to be the most important for amyloid fibril formation. The detailed structure of both variants Aβ(11‐28) was determined using CD, 2D NMR, and molecular dynamics techniques under water‐SDS micelle conditions. The NMR analysis revealed two distinct sets of proton resonances for the peptides. The studies of both peptides pointed out the existence of well‐defined α‐helical conformation in the Italian mutant, whereas the Flemish was found to be unstructured with the possibility of a bent structure in the central part of the peptide. © 2007 Wiley Periodicals, Inc. Biopolymers 87: 23–39, 2007.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Der Einfluß verschiedener politischer Systeme auf Ungarns Wissenschaft im 20. Jahrhundert
Authors: Szabadváry Ferenc
Published: May 2007

WÄRE ICH IM JAHRE 1823 in Ungarn geboren worden und hätte man mich vor 100 Jahren, also 1896, gefragt, wie die Politik meine naturwissenschaftlichen Forschungen beeinflußt habe, so hätte ich erstaunt geantwortet: Wieso diese Frage, was haben denn die beiden miteinander zu tun?
Associations ofABCB1, ABCC2, andABCG2polymorphisms with irinotecan‐pharmacokinetics and clinical outcome in patients with advanced non‐small cell lung cancer
Authors: Han Ji‐Youn , Lim Hyeong‐Seok , Yoo Yeon‐Kyeong , Shin Eun Soon , Park Yong Hoon , Lee Sung Young , Lee Jong‐Eun , Lee Dea Ho , Kim Heung Tae , Lee Jin Soo
Published: May 2007

BACKGROUND.

The authors investigated whetherABCB1, ABCC2,andABCG2genetic polymorphisms affect pharmacokinetics (PK) of irinotecan and treatment outcome of patients with advanced nonsmall cell lung cancer (NSCLC).

METHODS.

Blood samples from 107 NSCLC patients treated with irinotecan and cisplatin chemotherapy were used for genotypingABCB1(1236C > T, 2677G > T/A, 3435C > T),ABCC2(−24C > T, 1249G > A, 3972C > T), andABCG2(34G > A, 421C > A) polymorphisms. Genotypes were correlated with irinotecan‐PK, toxicity, tumor response, and survival.

RESULTS.

Among 8 polymorphisms, 3435TT and 2677TT were associated with AUCSN‐38Gand CLSN‐38G. When haplotypes are assigned, 2677TT/3435TT carriers showed significantly lower AUCSN‐38G(P= .006), whereas 2677GG/3435CC carriers showed significantly higher AUCSN‐38(P= .039). These findings suggest that 2677TT and 3435TT variants are associated with higher efflux activity. In toxicity, the 2677G/T or A was associated with grade 4 neutropenia. The 2677GG carriers showed significantly lower absolute neutrophil count during the 1stcycle (P= .012) as well as entire course of chemotherapy (P= .042). The 3435TT was associated with higher frequency of grade 3 diarrhea (P= .047). In tumor response,ABCC2−24TT and 3972TT genotypes were associated with higher response rates (P= .031 and .046, respectively) and longer progression‐free survival (P= .035 and .038, respectively), which was sustained in haplotype analysis.

CONCLUSIONS.

Specific polymorphisms ofABCB1andABCC2can influence disposition and tumor response to irinotecan by regulating transporter activity. These findings may help to individualize irinotecan‐based chemotherapy in patients with advanced NSCLC. Cancer 2007. © 2007 American Cancer Society.
Fused Donor–Acceptor Ligands in RuII Chemistry: Synthesis, Electrochemistry and Spectroscopy of [Ru(bpy)3−n(TTF‐dppz)n](PF6)2
Authors: Goze Christine , Leiggener Claudia , Liu Shi‐Xia , Sanguinet Lionel , Levillain Eric , Hauser Andreas , Decurtins Silvio
Published: May 2007

Three ruthenium(II) polypyridine complexes of general formula [Ru(bpy)3−n(TTF‐dppz)n](PF6)2 (n=1‐3, bpy=2,2′‐bipyridine), with one, two or three redox‐active TTF‐dppz (4′,5′‐bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2‐a:2′,3′‐c]phenazine) ligands, were synthesised and fully characterised. Their electrochemical and photophysical properties are reported together with those of the reference compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2 and [Ru(bpy)2(dppz)](PF6)2 and the free TTF‐dppz ligand. All three complexes show intraligand charge‐transfer (ILCT) fluorescence of the TTF‐dppz ligand. Remarkably, the complex with n=1 exhibits luminescence from the Ru2+→dppz metal‐to‐ligand charge‐transfer (3MLCT) state, whereas for the other two complexes, a radiationless pathway via electron transfer from a second TTF‐dppz ligand quenches the 3MLCT luminescence. The TTF fragments as electron donors thus induce a ligand‐to‐ligand charge‐separated (LLCS) state of the form TTF‐dppz−‐Ru2+‐dppz‐TTF+. The lifetime of this LLCS state is approximately 2.3 μs, which is four orders of magnitude longer than that of 0.4 ns for the ILCT state, because recombination of charges on two different ligands is substantially slower.
Syntheses, Structures and Coordination Modes of Acetatopalladium(II) Complexes with 1,3‐Bis(2‐arylimino)isoindoline Ligands of Different Steric Influence
Authors: Bröring Martin , Kleeberg Christian , Cónsul Tejero Esther
Published: May 2007

Acetatopalladium(II) complexes of four different 1,3‐bis(2‐arylimino)isoindoline ligands (bai's) with different degrees of steric congestion have been prepared and were characterized by NMR and XRD with respect to nuclearity and coordination mode. In particular, the propensity for heteroaryl ring rotation and C–H activation has been investigated. Palladium(II) ions bind to bai ligands in different coordination modes, either as classical Werner‐type N,N,N bonded complexes or―after pyridyl ring rotation and C–H activation―as carbometalated C,N,N chelates. In the latter case two (bai*)Pd(OAc) subunits have been found to dimerize via two bridging Pd(OAc) moieties in the solid and in solution. These stable and electroneutral tetranuclear species are of low solubility in non‐donor solvents, but break up into soluble dinuclear species of unknown composition upon the addition of DMSO, azide or cyanide. Attempts to activate C–C bonds by this strategy were not successful. Surprisingly, the exchange of the terminal pyridines by pyrimidines does not result in the formation of oligonuclear or oligomeric species. Besides the degree of steric hindrance, three more factors, solubility of the products, stoichiometry of metal precursor and charge compensation, have been identified to govern the outcome of the metalation of these bai ligands.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Simple Synthesis of 6‐(Trifluoromethyl)‐2,4,5,6‐tetrahydropyrazolo[3,4‐b]pyran Derivatives by One‐Pot, Three‐Component Reactions
Authors: Li Dong‐Mei , Song Li‐Ping , Li Xian‐Fu , Xing Chun‐Hui , Peng Wei‐Min , Zhu Shi‐Zheng
Published: May 2007

One‐pot, three‐component condensation reactions of aromatic aldehydes 1, 3‐methylpyrazol‐5‐one (2) and ethyl trifluoroacetoacetate (3) provided an efficient methodology for the preparation of ethyl (4S*,5R*)‐4‐aryl‐6‐hydroxy‐3‐methyl‐6‐(trifluoromethyl)‐2,4,5,6‐tetrahydropyrazolo[3,4‐b]pyran‐5‐carboxylate derivatives (4). The reactions gave moderate to good yields under mild conditions. These new products 4 were fully characterized by spectral methods and single‐crystal X‐ray diffraction analysis. A plausible reaction pathway for the formation of 4 is presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Estimating the cost‐effectiveness of an intervention in a clinical trial when partial cost information is available: a Bayesian approach
Authors: Lambert Paul C. , Billingham Lucinda J. , Cooper Nicola J. , Sutton Alex J. , Abrams Keith R.
Published: May 2007

There is an increasing need to establish whether health‐care interventions are cost effective as well as clinically effective. It is becoming increasingly common for cost studies to be incorporated into clinical trials, either on all patients or more usually on a subset of patients. Establishing the total cost per patient is complex, as it requires information on resource use, which may come from a variety of different sources. This complexity may lead to considerable missing data, and can result in some patients only having partial cost information.

In this paper we consider a clinical trial consisting of 351 patients with advanced non‐small cell lung cancer comparing chemotherapy with standard palliative care. A subset of 115 patients was selected for the cost sub‐study. Total cost was split into four components, for which resource use was collected. Complete resource data were available on 82 patients. For the remaining patients at least one of the cost components was missing.

The objective of this paper is to develop a Bayesian approach which simultaneously models both the clinical effectiveness data and the cost data, by modelling the individual components. This also provides estimates of the cost‐effectiveness in terms of the Incremental Net Monetary Benefit (INMB) and Cost‐Effectiveness Acceptability Curves (CEAC). We compare a number of different models of increasing complexity. The models estimate the interrelationships between the four cost components and survival, and thus enable a predictive distribution for each missing cost item to be obtained. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of canopy density on snow distribution in a temperate mountain range
Authors: López‐Moreno J. I. , Latron J.
Published: May 2007

We analyse spatial variability and different evolution patterns of snowpack in a mixed beech–fir stand in the central Pyrenees. Snow depth and density were surveyed weekly along six transects of contrasting forest cover during a complete accumulation and melting season; we also surveyed a sector unaffected by canopy cover. Forest density was measured using the sky view factor (SVF) obtained from digital hemispherical photographs. During periods of snow accumulation and melting, noticeable differences in snow depth and density were found between the open site and those areas covered by forest canopy. Principal component analysis provided valuable information in explaining these observations. The results indicate a high variability in snow accumulation within forest areas related to differences in canopy density. Maximum snow water equivalent (SWE) was reduced by more than 50% beneath dense canopies compared with clearings, and this difference increased during the melting period. We also found significant temporal variations: when melting began in sectors with low SVF, most of the snow had already thawed in areas with high SVF. However, specific conditions occasionally produced a different response of SWE to forest cover, with lower melting rates observed beneath dense canopies. The high values of correlation coefficients for SWE and SVF (r > 0·9) indicate the reliability of predicting the spatial distribution of SWE in forests when only a moderate number of observations are available. Digital hemispherical photographs provide an appropriate tool for this type of analysis, especially for zenith angles in the range 35–55 . Copyright © 2007 John Wiley & Sons, Ltd.
Estimating nutrient and sediment flood loads in a small Mediterranean river
Authors: Salles Christian , Tournoud Marie George , Chu Yin
Published: May 2007

Various methods were evaluated for estimating the loads of total suspended sediments and particulate associated and dissolved nutrients during floods. The six selected methods were compared using field data from two carefully sampled floods at the outlet of a small Mediterranean catchment. Water samples were available during floods at short time intervals (i.e. from 1 to 6 h time steps) and discharge was measured every 5 min. In the first step, the load estimators were compared on the basis of available data. Despite a fine description of the species concentration, there were significant differences in load estimates between the six methods. In the second step the sampling sensitivity of the methods was compared. For the two floods, 3000 random sub‐samples were generated from Monte Carlo simulations. The estimates derived from the random sub‐samples were compared to the load estimated by using the entire record. The results show that bias and precision are affected by the sample size and the transport phase of the species. Generally speaking, two methods allow reliable load estimation as long as a detailed water flow and at least three to four samples per day are available. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding
Authors: Descloitres Marc , Ruiz Laurent , Sekhar M. , Legchenko Anatoly , Braun Jean‐Jacques , Mohan Kumar M. S. , Subramanian S.
Published: May 2007

A groundwater recharge process of heterogeneous hard rock aquifer in the Moole Hole experimental watershed, south India, is being studied to understand the groundwater flow behaviour. Significant seasonal variations in groundwater level are observed in boreholes located at the outlet area indicating that the recharge process is probably taking place below intermittent streams. In order to localize groundwater recharge zones and to optimize implementation of boreholes, a geophysical survey was carried out during and after the 2004 monsoon across the outlet zone. Magnetic resonance soundings (MRS) have been performed to characterize the aquifer and measure groundwater level depletion. The results of MRS are consistent with the observation in boreholes, but it suffers from degraded lateral resolution. A better resolution of the regolith/bedrock interface is achieved using electrical resistivity tomography (ERT). ERT results are confirmed by resistivity logging in the boreholes. ERT surveys have been carried out twice—before and during the monsoon—across the stream area. The major feature of recharge is revealed below the stream with a decrease by 80% of the calculated resistivity. The time‐lapse ERT also shows unexpected variations at a depth of 20 m below the slopes that could have been interpreted as a consequence of a deep seasonal water flow. However, in this area time‐lapse ERT does not match with borehole data. Numerical modelling shows that in the presence of a shallow water infiltration, an inversion artefact may take place thus limiting the reliability of time‐lapse ERT. A combination of ERT with MRS provides valuable information on structure and aquifer properties respectively, giving a clue for a conceptual model of the recharge process: infiltration takes place in the conductive fractured‐fissured part of the bedrock underlying the stream and clayey material present on both sides slows down its lateral dissipation. Copyright © 2007 John Wiley & Sons, Ltd.
Rainfall partitioning into throughfall, stemflow, and interception within a single beech (Fagus sylvatica L.) canopy: influence of foliation, rain event characteristics, and meteorology
Authors: Staelens Jeroen , De Schrijver An , Verheyen Kris , Verhoest Niko E. C.
Published: May 2007

While the hydrological balance of forest ecosystems has often been studied at the annual level, quantitative studies on the factors determining rainfall partitioning of individual rain events are less frequently reported. Therefore, the effect of the seasonal variation in canopy cover on rainfall partitioning was studied for a mature deciduous beech (Fagus sylvatica L.) tree over a 2‐year period. At the annual level, throughfall amounted to 71% of precipitation, stemflow 8%, and interception 21%. Rainfall partitioning at the event level depended strongly on the amount of rainfall and differed significantly (p < 0·001) between the leafed and the leafless period of the year. Therefore, water fluxes of individual events were described using a multiple regression analysis (ra2 > 0·85, n = 205) with foliation, rainfall characteristics and meteorological variables as predictor variables. For a given amount of rainfall, foliation significantly increased interception and decreased throughfall and stemflow amounts. In addition, rainfall duration, maximum rainfall rate, vapour pressure deficit, and wind speed significantly affected rainfall partitioning at the event level. Increasing maximum hourly rainfall rate increased throughfall and decreased stemflow generation, while higher hourly vapour pressure deficit decreased event throughfall and stemflow amounts. Wind speed decreased throughfall in the growing period only. Since foliation and the event rainfall amount largely determined interception loss, the observed net water input under the deciduous canopy was sensitive to the temporal distribution of rainfall. Copyright © 2007 John Wiley & Sons, Ltd.
Unexpected paracrine action of prostate cancer cells harboring a new class of androgen receptor mutation—A new paradigm for cooperation among prostate tumor cells
Authors: Lapouge Gaëlle , Erdmann Eva , Marcias Gemma , Jagla Monika , Monge Audrey , Kessler Pascal , Serra Sebastian , Lang Hervé , Jacqmin Didier , Bergerat Jean‐Pierre , Céraline Jocelyn
Published: May 2007

The emergence of mutations in the androgen receptor (AR) gene is a recurrent event during progression of prostate cancer (PCa) on androgen ablation therapy. In this study, we show that nonsense mutations that lead to carboxyl‐terminal end truncated ARs are found at high frequency in metastatic PCas. Transcriptional activities of the Q640X mutant AR in the androgen‐sensitive LNCaP cell line differ to those of the wild‐type AR. Indeed, this mutant AR exhibits strong and ligand‐independent transcriptional activities from an artificial promoter construct containing two repeats of androgen‐responsive elements, but is inactive on the human PSA gene promoter. Nevertheless, the expression of the Q640X mutant AR in LNCaP cells is accompanied by an increase in the level of PSA protein, and by an increase in the expression of the endogenous AR gene. This enhanced expression of the endogenous AR gene is not limited to the sole transfected cells, but is observed in non‐transfected neighboring cells. Additionally, in co‐cultures of transfected and non‐transfected LNCaP cells, the Q640X mutant AR leads to an unpredicted nuclear localization of the endogenous AR protein in the two cellular populations and this, in the absence of androgen. These data indicate that cells expressing the Q640X mutant AR acquire the property to emit a signal that activates the AR in neighboring cells by a paracrine mechanism and in a ligand‐independent manner. Our data strongly support the notion of cooperation among tumor cells in PCa and could be of relevance for the understanding of progression on androgen ablation therapy. © 2007 Wiley‐Liss, Inc.
Carbaryl exposure and incident cancer in the Agricultural Health Study
Authors: Mahajan Rajeev , Blair Aaron , Coble Joseph , Lynch Charles F. , Hoppin Jane A. , Sandler Dale P. , Alavanja Michael C.R.
Published: May 2007

Carbaryl is a carbamate insecticide with a broad spectrum of uses in agricultural, commercial and household settings. It has previously been linked with non‐Hodgkin lymphoma (NHL) but studies of cancer risk in humans are limited. We examined occupational carbaryl use and risk of all cancers in the Agricultural Health Study, a prospective study of a cohort of pesticide applicators in North Carolina and Iowa. This analysis included 21,416 subjects (1,291 cases) enrolled from 1993–1997 and followed for cancer incidence through 2003. Pesticide exposure and other data were collected using self‐administered questionnaires. Poisson regression was used to calculate rate ratios (RRs) and 95% confidence intervals (CIs) while controlling for potential confounders. Carbaryl was not associated with cancer risk overall. Relative to subjects who never used carbaryl, melanoma risk was elevated with >175 lifetime exposure‐days (RR = 4.11; 95%CI, 1.33–12.75; p‐trend = 0.07), >10 years of use (RR = 3.19; 95%CI, 1.28–7.92; p‐trend = 0.04), or ≥10 days of use per year (RR = 5.50; 95%CI, 2.19–13.84; p‐trend < 0.001). Risk remained after adjusting for sunlight exposure. Although not significant, there appeared to be a trend of decreasing prostate cancer risk with increasing level of exposure. A small increase in NHL risk was observed using some, but not all, exposure measures. No associations were observed with other examined cancer sites. Because the observed results were not hypothesized a priori and because of limited study of their biological plausibility, they should be interpreted with caution. © 2007 Wiley‐Liss, Inc.
Adenovirus‐mediated small hairpin RNA targeting Bcl‐XL as therapy for colon cancer
Authors: Zhu Hongbo , Zhu Yuping , Hu Jingzi , Hu Wenxian , Liao Yongqiang , Zhang Jun , Wang Da , Huang Xuefeng , Fang Bingliang , He Chao
Published: May 2007

Bcl‐XL, an anti‐apoptotic protein of Bcl‐2 family, is overexpressed in colon cancers. To determine Bcl‐XL's potential feasibility as a therapeutic target, we constructed a recombinant adenovirus that expressed a U6 promoter‐driven small hairpin RNA (shRNA) targeting Bcl‐XL (Ad/Bcl‐XL shRNA) and evaluated the vector's ability to induce RNA interference in vivo and alter apoptosis induction in colon cancer cells and tumours. Ad/Bcl‐XL shRNA effectively knocked down Bcl‐XL expression in colon cancer cells and decreased their viability. Treatment with Ad/Bcl‐XL shRNA but not control vectors led to dramatically increased cleavage of cellular apoptosis‐related enzymes caspase‐9, caspase‐3 and poly(ADP‐ribose) polymerase. Ad/Bcl‐XL shRNA also significantly suppressed the growth of subcutaneous tumours derived from DLD1 cells in a nude mouse model and did so without causing any obvious damage to normal tissues or normal human fibroblasts. Together, our results support the feasibility of using adenovirus‐mediated RNA interference therapy targeting Bcl‐XL against colon cancers and warrant further studies of its safety and efficacy. © 2007 Wiley‐Liss, Inc.
Tandem enzyme‐catalysed reduction/ cis‐dihydroxylation of 2,2,2‐trifluoroace‐ tophenone: chemoenzymatic routes to new enantiopure phenol and benzylic alcohol reagents
Authors: Boyd Derek R. , Sharma Narain D. , Ljubez Vera , Malone John F. , Allen Christopher C. R.
Published: May 2007

Factors that control the competition between toluene dioxgenase‐catalysed arene cis‐dihydroxylation and dehydrogenase‐catalysed ketone reduction have been studied, using whole cells of Pseudomonas putida UV and three alkylaryl ketones. The triol metabolite, obtained from 2,2,2‐trifluoroacetophenone, has been used in the synthesis of single enantiomer chiral phenols and benzylic alcohols. Potential applications of the methylether derivatives of the chiral phenols and benzylic alcohols, as resolving agents, have been found. Copyright © 2007 Society of Chemical Industry
Optimized production and concentration of lentiviral vectors containing large inserts
Authors: Yacoub Nadya al , Romanowska Malgorzata , Haritonova Natalie , Foerster John
Published: May 2007

Generation of high titer lentiviral stocks and efficient virus concentration are central to maximize the utility of lentiviral technology. Here we evaluate published protocols for lentivirus production on a range of transfer vectors differing in size (7.5–13.2 kb). We present a modified virus production protocol robustly yielding useful titers (up to 107/ml) for a range of different transfer vectors containing packaging inserts up to 7.5 kb. Moreover, we find that virus recovery after concentration by ultracentrifugation depends on the size of the packaged inserts, heavily decreasing for large packaged inserts. We describe a fast (4 h) centrifugation protocol at reduced speed allowing high virus recovery even for large and fragile lentivirus vectors. The protocols outlined in the current report should be useful for many labs interested in producing and concentrating high titer lentiviral stocks. Copyright © 2007 John Wiley & Sons, Ltd.
Optimization of short‐term transgene expression by sodium butyrate and ubiquitous chromatin opening elements (UCOEs)
Authors: de Poorter Jolanda J. , Lipinski Kai S. , Nelissen Rob G. H. H. , Huizinga Tom W. J. , Hoeben Rob C.
Published: May 2007

Background

Predictable and adequate transgene expression is essential for clinical gene therapy. Several studies have focused on optimization of transgene expression. In this study the effect of sodium butyrate (NaB) and a ubiquitous chromatin opening element (UCOE) on short‐term gene expression after adenovirus‐mediated gene transfer in fibroblastic interface cells from periprosthetic tissue in loosened orthopedic implants is investigated.

Methods

Cultures of diploid human interface cells from four patients were infected with an adenovirus type‐5 vector that carries the luciferase gene driven by the cytomegalovirus (CMV) promoter as a reporter. In addition, viruses with a UCOE were evaluated. Twenty‐four hours after infection NaB was added in concentrations of 0 to 9 mM. Luciferase activity was tested after a further 24 h.

Results

NaB in a concentration of 6 mM caused a 7‐ to 16‐fold increase in reporter gene expression compared to control condition. There was no difference in reporter gene expression when cells were infected with Ad.1.5UCOE‐CMV.Luc compared to Ad.CMV.Luc. A combination of NaB and a UCOE had no advantage over NaB alone.

Conclusions

Addition of NaB results in a marked increase in transgene expression in cultured cells. This would allow the enhancement of the expression of the transgene, without requiring a higher vector dose. Butyrate administration could not be substituted by inclusion of UCOEs in the vector. It remains to be established whether the effective concentrations of butyrate can be obtained in vivo. Copyright © 2007 John Wiley & Sons, Ltd.
Gene expression and internalization following vector adsorption to immobilized proteins: dependence on protein identity and density
Authors: Bengali Zain , C.Rea Jennifer , Shea Lonnie D.
Published: May 2007

Background

Gene delivery by non‐specific adsorption of non‐viral vectors to protein‐coated surfaces can reduce the amount of DNA required, and also increase transgene expression and the number of cells expressing the transgene. The protein on the surface mediates cell adhesion and vector immobilization, and functions to colocalize the two to enhance gene delivery. This report investigates the mechanism and specificity by which the protein coating enhances gene transfer, and determines if the protein coating targets the vector for internalization by a specific pathway.

Methods

Proteins (FBS, BSA, fibronectin, collagen I, and laminin) were dried onto culture dishes, followed by PEI/DNA complex adsorption for surface delivery. Reporter genes were employed to characterize transfection as a function of the protein identity and density. Vector immobilization was measured using radiolabeled plasmid, and internalization was quantified in the presence and absence of the endocytosis inhibitors chlorpromazine and genistein.

Results

Fibronectin coating yielded the greatest expression for PEI/DNA polyplexes, with maximal expression at intermediate protein densities. Expression in control studies with bolus delivery was independent of the protein identity. Substrate binding was independent of the protein identity; however, internalization was greatest on surfaces coated with fibronectin and collagen I. Inhibition of caveolae‐mediated endocytosis reduced gene expression more than clathrin‐mediated endocytosis. Similarly, inhibition of caveolae‐mediated endocytosis significantly reduced the intracellular levels of DNA.

Conclusions

Fibronectin at intermediate densities mediated the highest levels of transgene expression, potentially by targeting internalization through caveolae‐mediated endocytosis. Substrate modifications, such as the identity and density of proteins, provide an opportunity for modification of biomaterials for enhancing gene expression. Copyright © 2007 John Wiley & Sons, Ltd.
On the distance matrix of a directed graph
Authors: Graham R. L. , Hoffman A. J. , Hosoya H.
Published: May 2007

In this note, we show how the determinant of the distance matrix D(G) of a weighted, directed graph G can be explicitly expressed in terms of the corresponding determinants for the (strong) blocks Gi of G. In particular, when cof D(G), the sum of the cofactors of D(G), does not vanish, we have the very attractive formulamagnified image.
Some applications of graph contractions
Authors: Babai László
Published: May 2007

Results in diverse areas, such as the Nielsen‐Schreier theorem on subgroups of free groups and a proof of A. T. White's conjecture on the genus of subgroups are shown to be immediate consequences of a lemma which has already proved useful in investigating topological properties and automorphism group of graphs.
Total matchings and total coverings of graphs
Authors: Alavi Y. , Behzad M. , Lesniak‐Foster L. M. , Nordhaus E. A.
Published: May 2007

In graph theory, the related problems of deciding when a set of vertices or a set of edges constitutes a maximum matching or a minimum covering have been extensively studied. In this paper we generalize these ideas by defining total matchings and total coverings, and show that these sets, whose elements in general consist of both vertices and edges, provide a way to unify these concepts. Parameters denoting the maximum and the minimum cardinality of these sets are introduced and upper and lower bounds depending only on the order of the graph are obtained for the number of elements in arbitrary total matchings and total coverings. Precise values of all the parameters are found for several general classes of graphs, and these are used to establish the sharpness of most of the bounds. In addition, variations of some well known equalities due to Gallai relating covering and matching numbers are obtained.
A digest of the four color theorem
Authors: Bernhart Frank R.
Published: May 2007

A major event in 1976 was the announcement that the Four Color Conjecture (4CC) had at long last become the Four Color Theorem (4CT). The proof by W. Haken, K. Appel, and J. Koch is published in the Illinois Journal of Mathematics, and their two‐part article outlines the nature and reliability of the solution. The first section is a readable and informative historical survey. The reminder will appeal chiefly to specialists in graph theory. Although the logic of attack is relatively simple, the need to examine an immense number of individual cases is frustrating. Hopefully this first breakthrough will pave the way for a short elegant proof. For the second section, 1200 hours of computer time was required to verify the 4‐color reducibility of nearly 1900 configurations. At this time there is no good way to condense the proof. In this digest we offer an exposition of the main ideas. The first and the last parts are intended for a general audience, but the intermediate sections assume more knowledge of graph theory proper. The usual statement of the 4CC goes as follows: “All maps on the sphere or plane can be colored with four colors so that neighboring regions are never colored alike.” The form in which the 4CT was proved is “There exists an unavoidable set of reducible configurations, relative to triangulations of the plane.” The initial part of our task is to explain how the 4CC comes to be expressed in such jargon. The next step is to show how one finds simple finite sets of unavoidable configurations. Then comes the question of how to prove reducibility, followed by a consideration of the known obstacles to reduction. Our concluding remarks and criticisms include a consideration of prospects for the future.
Chromatic polynomials and whitney's broken circuits
Authors: Bari Ruth A. , Hall Dick Wick
Published: May 2007

The theorem of Hassler Whitney, which gives the chromatic polynomial of a graph in terms of “broken circuits,” is used to derive a new formula for the coefficients of chromatic polynomials.
Enumeration of graphs with signed points and lines
Authors: Harary Frank , Palmer Edgar M. , Robinson Robert W. , Schwenk Allen J.
Published: May 2007

Our object is to enumerate graphs in which the points or lines or both are assigned positive or negative signs. We also treat several associated problems for which these configurations are self‐dual with respect to sign change. We find that the solutions to all of these counting problems can be expressed as special cases of one general formula involving the concatenation of the cycle index of the symmetric group with that of its pair group. This counting technique is based on Pólya's Enumeration Theorem and the Power Group Enumeration Theorem. Using a suitable computer program, we list the number of graphs of each type considered up to twelve points. Sharp asymptotic estimates are also obtained.
Wright's formulae for the number of connected sparsely edged graphs
Authors: Gray P. M. D. , Murray A. M. , Young N. A.
Published: May 2007

We have written computer programs to determine exactly the coefficients in Wright's formula for f(n, n + k), the number of connected sparsely edged labeled graphs (see preceding paper), and used them up to k = 24. We give the results up to k = 7.
A property of trees in terms of unique connected subgraphs
Authors: Hedetniemi Stephen T. , Spresser Diane M.
Published: May 2007

The following theorem is proved: Let G be a graph with p ≥ 3 points such that for some n, 3 ≤ n ≤ p, any n points lie on a unique smallest connected subgraph. Then G = Cn+1 or G is a tree, and conversely.
On ramsey numbers for books
Authors: Rousseau C. C. , Sheehan J.
Published: May 2007

For n = 1, 2, …, let Bn = K2 + K̄n. We pose the problem of determining the Ramsey numbers r(Bm, Bn) and demonstrate that in many cases critical colorings are avialable from known examples of strongly regular graphs.
On the eulericity of a graph
Authors: Matthews K. R.
Published: May 2007

The eulericity ϵ(G) of a bridgeless graph G is defined as the least number of eulerian subgraphs of G which together cover the lines of G. A 1–1 correspondence is shown to exist between the k‐tuples of eulerian subgraphs of G and the proper flows (mod2k) on a given network based on G. The inequality ϵ(G) ⩽ 3 them follows from a result of Jaeger.
Matroidal families of finite connected nonhomeomorphic graphs exist
Authors: Andreae Thomas
Published: May 2007

A matroidal family is a nonempty set ℱ of connected finite graphs such that for every arbitrary finite graph G the edge sets of the subgraphs of G which are isomorphic to an element of ℱ form a matroid on the edge set of G. In the present paper the question whether there are any matroidal families besides the four previously described by Simões‐Pereira is answered affirmatively. It is shown that for every natural number n ⩾ 2 there is a matroidal family that contains the complete graph with n vertices. For n = 4 this settles Simões‐Pereira's conjecture that there is a matroidal family containing all wheels.
Graph Decompositions Satisfying Extremal Degree Constraints
Authors: Catlin Paul A.
Published: May 2007

We show that the vertex set of any graph G with p⩾2 vertices can be partitioned into non‐empty sets V1, V2, such that the maximum degree of the induced subgraph 〈Vi〉 does not exceed

where pi = |Vi|, for i=1, 2. Furthermore, the structure of the induced subgraphs is investigated in the extreme case.
An infinite family of octahedral crossing numbers
Authors: Gross Jonathan L.
Published: May 2007

This paper calculates some crossing numbers for certain octahedral graphs. Precisely, if the number p is a prime power congruent to 1 modulo 4, then the crossing number of the p‐dimensional octahedral graph in the orientable surface of genus (p–1)(p‐4)/4 is (p2–p)/2. The key step is the construction of a self‐dual imbedding of the complete graph on p vertices such that no face boundary contains a repeated vertex.
Counterexamples to faudree and schelp's conjecture on hamiltonian‐connected graphs
Authors: Thomassen Carsten
Published: May 2007

Faudree and Schelp conjectured that for any two vertices x, y in a Hamiltonian‐connected graph G and for any integer k, where n/2 ⩽ k ⩽ n − 1, G has a path of length k connecting x and y. However, we show in this paper that there are infinitely many exceptions to this conjecture and we comment on some problems on path length distribution raised by Faudree and Schelp.
Full 4‐colorings of 4‐regular maps
Authors: Berman Kenneth A. , Shank H.
Published: May 2007

A full coloring of a planar map is a face coloring such that all the faces at ech vertex are colored differently. In this paper the planar 4‐regular maps which have a full 4‐coloring are characterized. This leads to a characterization of the planar maps (not necessarily 4‐valent) which have a coupled 4‐coloring.
Enumeration of graphs by degree sequence
Authors: Hanlon Phil
Published: May 2007

The degree sequence (d0, d1, …, dp‐1) of a graph G of order p is defined by dk = the number of points of G of degree k. Methods of Robinson are extended to produce a generating function F(x0, x1, x2, …) where the coefficient of x…x is the number of graphs of order p having degree sequence (d0, …, dp‐1).
A bibliography of graph equations
Authors: Cvetković Dragoš M. , Simić Slobodan K.
Published: May 2007

Graph equations are equations in which the unknowns are graphs. Many problems and results in graph theory can be formulated in terms of graph equations. Here we offer a classification and a large bibliography of graph equations.
Orthogonal latin square graphs
Authors: Lindner Charles C. , Mendelsohn E. , Mendelsohn N. S. , Wolk Barry
Published: May 2007

An orthogonal latin square graph (OLSG) is one in which the vertices are latin squares of the same order and on the same symbols, and two vertices are adjacent if and only if the latin squares are orthogonal. If G is an arbitrary finite graph, we say that G is realizable as an OLSG if there is an OLSG isomorphic to G. The spectrum of G [Spec(G)] is defined as the set of all integers n that there is a realization of G by latin squares of order n. The two basic theorems proved here are (1) every graph is realizable and (2) for any graph G, Spec G contains all but a finite set of integers. A number of examples are given that point to a number of wide open questions. An example of such a question is how to classify the graphs for which a given n lies in the spectrum.
Generating all planer graphs regular of degree four
Authors: Manca Paolo
Published: May 2007

All planar connected graphs regular of degree four can be generated from the graph of the octahedron, using four operations.
On the number of hamiltonian cycles in a maximal planar graph
Authors: Hakimi S. L. , Schmeichel E. F. , Thomassen C.
Published: May 2007

We consider the problem of the minimum number of Hamiltonian cycles that could be present in a Hamiltonian maximal planar graph on p vertices. In particular, we construct a p‐vertex maximal planar graph containing exactly four Hamiltonian cycles for every p ≥ 12. We also prove that every 4‐connected maximal planar graph on p vertices contains at least p/(log2 p) Hamiltonian cycles.
Three‐regular subgraphs of four‐regular graphs
Authors: Chvátal V. , Fleischner H. , Sheehan J. , Thomassen C.
Published: May 2007

Berge conjectured that every finite simple 4‐regular graph G contains a 3‐regular subgraph. We prove that this conjecture is true if the cyclic edge connectivity λc(G) of G is at least 10. Also we prove that if G is a smallest counterexample, then λc(G) is either 6 or 8.
Concept of a vertex in a matroid and 3‐connected graphs
Authors: Kelmans A. K.
Published: May 2007

The concept of a matroid vertex is introduced. The vertices of a matroid of a 3‐connected graph are in one‐to‐one correspondence with vertices of the graph. Thence directly follows Whitney's theorem that cyclic isomorphism of 3‐connected graphs implies isomorphism. The concept of a vertex of a matroid leads to an equally simple proof of Whitney's theorem on the unique embedding of a 3‐connected planar graph in the sphere. It also leads to a number of new facts about 3‐connected graphs. Thus, consideration of a vertex in a matroid that is the dual of the matroid of a graph leads to a natural concept of a nonseparating cycle of a graph. Whitney's theorem on cyclic isomorphism can be strengthened (even if the nonseparating cycles of a graph are considered, the theorem is found to work) and a new criterion for planarity of 3‐connected graphs is obtained (in terms of nonseparating cycles).
Triangular embeddings of K((i‐2) n, n,…,n)
Authors: Jackson Brad
Published: May 2007

For complete i‐partite graphs of the form K(n1, n, n, …, n) the largest value of n1 that allows the graph to be triangularly‐embedded into a surface is (i‐2)n. In this paper the author constructs triangular embeddings into surfaces of some complete partite graphs of the form K((i‐2)n, n, …, n). The embeddings are exhibited using embedding schemes but the surfaces into which K((i‐2)n, n, …, n) are triangularly embedded can be seen to be particularly nice branched covers of a surface into which K(i‐2, 1, 1,…,1) is triangularly embedded.
Centers of maximal outerplanar graphs
Authors: Proskurowski Andrzej
Published: May 2007

The center of a graph is defined to be the subgraph induced by the set of vertices that have minimum eccentricities (i.e., minimum distance to the most distant vertices). It is shown that only seven graphs can be centers of maximal outerplanar graphs.
Conservative graphs
Authors: Bange David W. , Barkauskas Anthony E. , Slater Peter J.
Published: May 2007

A graph G with q edges is defined to be conservative if the edges of G can be oriented and distinctly numbered with the integers 1, 2,…, q so that at each vertex the sum of the numbers on the inwardly directed edges equals that on the outwardly directed edges. Several classes of graphs, including Kn, for n ≥4, and K2n, 2m, for n, m ≥ 2, are shown to be conservative. It is proven that the dual of a planar graceful graph is conservative, and that the converse of this result is false.
Note on the cochromatic number of several surfaces
Authors: Straight H. Joseph
Published: May 2007

The cochromatic number of a graph G, denoted by z(G), is the minimum number of subsets into which the vertex set of G can be partitioned so that each subset induces an empty or a complete subgraph of G. In an earlier work, the author considered the problem of determining z(S), the maximum cochromatic number among all graphs that embed in a surface S. The value of z(S) was found for the sphere, the Klein bottle, and for the nonorientable surface of genus 4. In this note, some recent results of Albertson and Hutchinson are used to determine the cochromatic numbers of the projective plane and the nonorientable surface of genus 3. These results lend further evidence to support the conjecture that z(S) is equal to the maximum n for which the graph Gn = K1 U K2 U … U Kn embeds in S.
Enumeration of weak isomorphism classes of signed graphs
Authors: Sozański Tadeusz
Published: May 2007

A signed graph is a graph in which each line has a plus or minus sign. Two signed graphs are said to be weakly isomorphic if their underlying graphs are isomorphic through a mapping under which signs of cycles are preserved, the sign of a cycle being the product of the signs of its lines. Some enumeration problems implied by such a definition, including the problem of self‐dual configurations, are solved here for complete signed graphs by methods of linear algebra over the two‐element field. It is also shown that weak isomorphism classes of complete signed graphs are equal in number to other configurations: unlabeled even graphs, two‐graphs and switching classes.
Line‐graphical degree sequences
Authors: Bauer Douglas
Published: May 2007

A degree sequence π = (d1, d2,…,dp), with d1 ≥ d2 ≥…≥ dp, is line graphical if it is realized by the line graph of some graph. Degree sequences with line‐graphical realizations are characterized for the cases d1 = p ‐ 1, d1 = p ‐ 2, d1 ≤ 3, and d1 = dp. It is also shown that if a degree sequence with d1 = p‐1 is line graphical, it is uniquely line graphical. It follows that with possibly one exception each line‐graphical realization of an arbitrary degree sequence must have either C5, 2K1, + K2, K1 + 2K2, or 3K1, as an induced subgraph.
On ramsey numbers of forests versus nearly complete graphs
Authors: Chartrand Gary , Gould Ronald J. , Polimeni Albert D.
Published: May 2007

A formula is presented for the ramsey number of any forest of order at least 3 versus any graph G of order n ≥ 4 having clique number n ‐ 1. In particular, if T is a tree of order m ≥ 3, then r(T, G) = 1 + (m ‐ 1)(n ‐ 2).
A Ramsey property for graph invariants
Authors: Buckley Fred
Published: May 2007

We consider the problem of which graph invariants have a certain property relating to Ramsey's theorem. Invariants which have this property are called Ramsey functions. We examine properties of chains of graphs associated with Ramsey functions. Methods are developed which enable one to prove that a given invariant is not a Ramsey function. Results for several familiar invariants are presented.
A new planarity criterion for 3‐connected graphs
Authors: Kelmans Alexander K.
Published: May 2007

Direct proofs of some planarity criteria are presented.
The λ‐complete multigraphs
Authors: Gardner M. L.
Published: May 2007

Let E1……Em be the edges of a hypergraph. Assume each element in the union of the edges occurs in at least two of E1……Em. Assume further that every pair of distinct edges, E1, and E1, intersect in at most one element and that for each such pair there are exactly λ other edges Ek such that E1 and E1 both intersect Ek. We characterize the hypergraphs for which each |E1| ≤ 2. These are the λ‐complete multigraphs.
Chromatic numbers of hypergraphs and coverings of graphs
Authors: Miller Zevi , Müller Heinrich
Published: May 2007

Burr recently proved [3] that for positive integers m1, m2……mk, and any graph G we have X(G)

if and only if G can be expressed as the edge disjoint union of subgraphs Fi satisfying X(Fi) ≤ mi. This theorem is generalized to hypergraphs. By suitable interpretations the generalization is then used to deduce propositions on coverings of graphs.
A census of maximum uniquely hamiltonian graphs
Authors: Barefoot Curtiss A. , Entringer R. C.
Published: May 2007

We show that there are 2[n/2]‐4 largest graphs of order n ≥ 7 having exactly one hamiltonian cycle. a recursive procedure for constructing these graphs is described.
Meyniel's theorem for strongly (p, q) ‐ Hamiltonian digraphs
Authors: Wojda A. P.
Published: May 2007

We give the following theorem: Let D = (V, E) be a strongly (p + q + 1)‐connected digraph with n ≥ p + q + 1 vertices, where p and q are nonnegative integers, p ≤ n ‐ 2, n ≥ 2. Suppose that, for each four vertices u, v, w, z (not necessarily distinct) such that {u, v} ∩ {w, z} = Ø, (w, u) ∉ E, (v, z) ∉ E, we have id(u) + od(v) + od(w + id(z) ≥ 2 (n + p + q)) + 1. Then D is strongly (p, q)‐Hamiltonian.
Nonseparating cycles in K‐Connected graphs
Authors: Thomassen Carsten
Published: May 2007

We show that every k‐connected graph with no 3‐cycle contains an edge whose contraction results in a k‐connected graph and use this to prove that every (k + 3)‐connected graph contains a cycle whose deletion results in a k‐connected graph. This settles a problem of L. Lovász.