bluuebunny/crossref_metadata_2025 huggingface dataset:
An exotic plantation crop as a keystone resource for an endemic megachiropteran, Pteropus rufus, in Madagascar
Authors: Long Emma , Racey Paul A.
Published: July 2007

The single most important food source for Pteropus rufus at Berenty, in south-east Madagascar, is the pollen of Agave sisalana, a commercial species introduced to the area 60 y ago, which was widely available and constantly eaten by the bats during this 28-mo study. The diet of the bats at this site is unique in this respect when compared with P. rufus elsewhere in Madagascar and with other Pteropus species. The dietary breadth of P. rufus at Berenty is narrow, consisting of only 14 plant species, identified through microsopic faecal analysis and direct field observations, and three unidentified ones. The bats also eat locally cultivated and introduced fruits (Mangifera indica, Psidium cf. cattleianum, Sclerocarya caffra, Cordia sinensis and Hylocereus species) and native and endemic forest species (Tamarindus indica, Celtis philippensis, Ficus megapoda, F. grevei, F. pachyclada and Grewia species). The majority of the plant species used by P. rufus for food are located within the gallery forests of the Mandrare valley. No evidence of adjacent endemic spiny forest species was identified in their diet. Thus, conservation of the remaining gallery forest as well as retention of the sisal plantations is important to maintain the food sources of P. rufus at this site.
Effects of tree cover and season on soil nitrogen dynamics and microbial biomass in an African savanna woodland dominated by Colophospermum mopane
Authors: Mlambo Donald , Mwenje Eddie , Nyathi Petros
Published: July 2007

The objective of this study was to investigate the effects of tree cover and season on soil N dynamics and microbial biomass in a semi-arid southern African savanna in Zimbabwe. We used a randomized complete block design with five blocks of 100 × 100 m, demarcated in a 10-ha pocket of Colophospermum mopane-dominated woodland protected from grazing and fire. In each block, we randomly selected three mopane trees with large canopies (8.3 m crown diameter) and another three with small canopies (2.7 m crown diameter). We determined soil organic carbon and nutrient concentrations, litterfall N and C inputs, microbial biomass and N transformations beneath large and small mopane trees as well as in the intercanopy areas. Soil organic carbon, microbial biomass, N, P and K were more than twice those beneath large trees than in the intercanopy areas. Rainy-season net mineral N accumulation rate in the surface soil (0–10 cm) ranged from 3.71 μg g−1 mo−1 in the intercanopy areas to 8.80 μg g−1 mo−1 beneath large trees; correspondingly, net nitrate accumulation rate ranged from 1.33 to 3.60 μg g−1 mo−1. Dry-season net mineral N and net nitrate accumulation rates were similar across sampling sites and did not exceed 2 and 0.4 μg g−1 mo−1, respectively. Litterfall N inputs were positively and significantly correlated with soil N availability, microbial biomass N and N transformations. At all sampling sites, microbial biomass and mineral N pools in the dry season were maximum when soil moisture (∼5%) and N transformations were minimum. In contrast, when soil moisture (9–13%) and N transformations were maximum in the rainy season, microbial biomass and mineral N pools were minimum. It is concluded that the improved soil conditions beneath isolated trees in semi-arid savannas may enhance herbaceous biomass yield especially of canopy shade-tolerant species.
EU law and regulation of private health insurance
Authors: THOMSON SARAH , MOSSIALOS ELIAS
Published: July 2007

The influence of European Union (EU) law on private health insurance has not received as much attention as its impact on other parts of the health system (Hervey, 2007). Now is a good time to redress this relative neglect, as growing interest in private health insurance – in particular, its potential to relieve pressure on public budgets and enhance choice – raises questions about how best to create or expand and shape markets to achieve specific aims. There are no easy answers to these questions, but one thing seems clear: if policy makers intend to use private health insurance to achieve a particular objective, they must be able to direct market behaviour appropriately. Otherwise, the type of market most likely to emerge is one that simply provides access to acute care in the private sector for wealthier people. However, in newer markets lack of regulatory capacity often presents a barrier to effective policy direction (Thomson et al., 2007 forthcoming). In the established markets of the EU, many of the constraints facing policy makers come from single market legislation. Here we use the case of the Third Non-Life Insurance Directive to illustrate some of these constraints and to show how they can undermine the achievement of health policy goals such as financial protection, equity of access to health care and quality or efficiency in the organization, administration, and delivery of health services.
Silicic acid leakage from the Southern Ocean: Opposing effects of nutrient uptake and oceanic circulation
Authors: Crosta X. , Beucher C. , Pahnke K. , Brzezinski M. A.
Published: July 2007

Studies invoking the silicic acid leakage hypothesis to explain events of high biogenic opal deposition at low latitudes did not consider variations in formation rate of Southern Ocean intermediate waters. Comparison of δ30Si records from the Southern Ocean to records of biogenic opal accumulation from low‐latitude upwelling systems indicates a strong negative correlation between the silicic acid content of Southern Ocean surface waters and opal deposition at low latitudes during the last 80 kyr BP. This implies that Si leakage was somehow rendered ineffective when the silicic acid content of Southern Ocean waters was high. Comparison of opal accumulation records with records of intermediate water formation rates suggests that lower rates of intermediate water formation offset the higher silicic acid content of these water masses during glacial periods. This indicates that physical processes that control intermediate water transport dominate over biological processes that set the silicic acid content of Antarctic surface waters in determining the magnitude of silicic acid leakage from the Southern Ocean.
Modeling long‐term stability of the Ferrar Glacier, East Antarctica: Implications for interpreting cosmogenic nuclide inheritance
Authors: Johnson Jesse V. , Staiger Jane W.
Published: July 2007

The Ferrar Glacier extends from the Taylor Dome, through the Royal Society Range, to the Ross Sea. Its pathway is strongly influenced by large‐scale topographic features. Ice thins and flows over these features, like water over a dam. Recently acquired evidence demonstrates that the profile of the Ferrar Glacier has been relatively static for the last ∼4 million years. This long record of stability is in sharp contrast to numerous other features in Antarctica and motivates an exploration of the stability with a numerical model. Large variations in ice thickness along the Ferrar profile make necessary a thermomechanically coupled model which includes higher‐order stress terms. Such a model is presented here and then is used to investigate (1) glacial ice flow patterns, (2) stress fields, and (3) sensitivity to climate forcing. In all three cases, the Ferrar Glacier is shown to be generally insensitive to the changes and to have stability consistent with cosmogenic nuclide evidence. The modeling is novel in that the Ferrar Glacier is a member of a class of glaciers which has never before been modeled. Ice flow results indicate that curious flow patterns arise in the glacier, producing very old ice (∼100,000 years) near the surface up glacier of thinning points. This flow pattern is demonstrated to be of consequence when interpreting the inheritance of cosmogenic nuclides in two ways. First, the velocity field is used to determine the maximum time a cobble found on the glacier surface could have been exposed to cosmic radiation. Second, the flow entrains supraglacial material from the glacier's surface, shielding it from cosmic rays for a period, and then deposits the material at the surface down glacier. Both flow effects are discussed in relation to cosmogenic nuclide inheritance and are quantified. The sensitivity of the results to past climates and glacier surfaces is also considered.
The Reproducibility of Lists of Differentially Expressed Genes in Microarray Studies
Authors: Shi Leming , Jones Wendell , Jensen Roderick , Harris Stephen , Perkins Roger , Goodsaid Federico , Guo Lei , Croner Lisa , Boysen Cecilie , Fang Hong , Amur Shashi , Bao Wenjun , Barbacioru Catalin , Bertholet Vincent , Cao Xiaoxi Megan , Chu Tzu-Ming , Collins Patrick , Fan Xiao-hui , Frueh Felix , Fuscoe James , Guo Xu , Han Jing , Herman Damir , Hong Huixiao , Kawasaki Ernest , Li Quan-Zhen , Luo Yuling , Ma Yunqing , Mei Nan , Peterson Ron , Puri Raj , Qian Feng , Shippy Richard , Su Zhenqiang , Sun Yongming Andrew , Sun Hongmei , Thorn Brett , Turpaz Yaron , Wang Charles , Wang Sue-Jane , Warrington Janet , Willey James , Wu Jie , Xie Qian , Zhang Liang , Zhang Lu , Zhong Sheng , Chen James , Wolfinger Russell , Tong Weida
Published: July 2007

Reproducibility is a fundamental requirement in scientific experiments and clinical contexts. Recent publications raise concerns about the reliability of microarray technology because of the apparent lack of agreement between lists of differentially expressed genes (DEGs). In this study we demonstrate that (1) such discordance may stem from ranking and selecting DEGs solely by statistical significance (P) derived from widely used simple t-tests; (2) when fold change (FC) is used as the ranking criterion, the lists become much more reproducible, especially when fewer genes are selected; and (3) the instability of short DEG lists based on P cutoffs is an expected mathematical consequence of the high variability of the t-values. We recommend the use of FC ranking plus a non-stringent P cutoff as a baseline practice in order to generate more reproducible DEG lists. The FC criterion enhances reproducibility while the P criterion balances sensitivity and specificity.
Function, structure and therapeutic potential of complement C5a receptors
Authors: Monk P N , Scola A‐M , Madala P , Fairlie D P
Published: July 2007

Complement fragment (C)5a is a 74 residue pro‐inflammatory polypeptide produced during activation of the complement cascade of serum proteins in response to foreign surfaces such as microorganisms and tissue damaged by physical or chemical injury. C5a binds to at least two seven‐transmembrane domain receptors, C5aR (C5R1, CD88) and C5L2 (gpr77), expressed ubiquitously on a wide variety of cells but particularly on the surface of immune cells like macrophages, neutrophils and T cells. C5aR is a classical G protein‐coupled receptor that signals through Gαi and Gα16, whereas C5L2 does not appear to couple to G proteins and has no known signalling activity. Although C5a was first described as an anaphylatoxin and later as a leukocyte chemoattractant, the widespread expression of C5aR suggested more general functionality. Our understanding of the physiology of C5a has improved significantly in recent years through exploitation of receptor knockout and knockin mice, C5 and C5a antibodies, soluble recombinant C5a and C5a analogues and newly developed receptor antagonists. C5a is now also implicated in non‐immunological functions associated with developmental biology, CNS development and neurodegeneration, tissue regeneration, and haematopoiesis. Combined receptor mutagenesis, molecular modelling, structure‐activity relationship studies and species dependence for ligand potency on C5aR have been helpful for identifying ligand binding sites on the receptor and for defining mechanisms of receptor activation and inactivation. This review will highlight major developments in C5a receptor research that support C5aR as an important therapeutic target. The intriguing possibilities raised by the existence of a non‐signalling C5a receptor are also discussed.

British Journal of Pharmacology (2007) 152, 429–448; doi:10.1038/sj.bjp.0707332; published online 2 July 2007
A functional comparison of recombinant and native somatostatin sst2 receptor variants in epithelia
Authors: Holliday N D , Tough I R , Cox H M
Published: July 2007

Background and purpose.

Somatostatin (SRIF‐14) exerts broad spectrum antisecretory effects by activating the somatostatin 2 (sst2) receptor. The rat (r) sst2 receptor exists in ‘long’ (sst2a) and ‘short’ (sst2b) forms that differ in their C termini, while a single human (h) sst2a exists. This study compares the characteristics of recombinant rsst2a, rsst2b and hsst2a activation in human epithelia, and with native sst2 responses in rat colon.

Experimental approach.

Epithelial layers of each clone or rat colon were placed in Ussing chambers and short‐circuit current (ISC) measured in response to SRIF‐14 and chosen analogues. The relative potencies and ability to cause desensitization to SRIF‐14 were assessed, and the affinities of the sst2 antagonist, D‐Tyr8 CYN154806 for hsst2a, rsst2a and native rat colon sst2 receptors were established.

Key results.

Basolateral SRIF‐14 responses were transient in hsst2a and rsst2a epithelia, but prolonged in rsst2b‐expressing cells. Activation of rsst2a resulted in significant desensitization to SRIF‐14 and receptor phosphorylation, whereas the rsst2b receptor did neither. Sst2‐preferred agonists (BIM23190C and BIM23027) reduced Isc with similar potency and both caused complete desensitization to SRIF‐14. CYN154806 antagonized hsst2a and rsst2a receptors with pKB values of 7.9 and 7.8, respectively. In rat colon mucosa, CYN154806 blocked SRIF‐14 responses with a pA2 value of 8.2, and BIM23190C responses with a pKB of 8.4.

Conclusions and implications.

SRIF‐14 caused rapid rsst2a receptor phosphorylation and desensitization of epithelial antisecretory responses, neither of which occurred with the rsst2b receptor. These mechanisms are most likely to be a prerequisite for sensitivity to sst2‐analogues with radiotherapeutic potential.

British Journal of Pharmacology (2007) 152, 132–140; doi:10.1038/sj.bjp.0707365
Heart rate variability measures: a fresh look at reliability
Authors: Pinna Gian Domenico , Maestri Roberto , Torunski Antoni , Danilowicz-Szymanowicz Ludmila , Szwoch Malgorzata , La Rovere Maria Teresa , Raczak Grzegorz
Published: July 2007

Despite its extensive use in physiological and clinical research, the analysis of HRV (heart rate variability) is still poorly supported by rigorous reliability studies. The main aim of the present study was to perform an in-depth assessment of absolute and relative reliability of standard indexes of HRV from short-term laboratory recordings. In 39 healthy subjects [mean age (min–max): 38 (26–56) years; 18 men and 21 women] we recorded 5 min of supine ECG during spontaneous and paced (15 breaths/min) breathing. The test was repeated on the next day under the same conditions. From the RR intervals we computed standard indexes of HRV: SDNN (S.D. of RR interval values), RMSSD (root-mean-square of successive RR interval differences), LF (low frequency) and HF (high frequency) power (absolute and normalized units) and LF/HF. Absolute reliability was assessed by 95% limits of random variation; relative reliability was assessed by the ICC (intraclass correlation coefficient). The sample size needed to detect a mean difference ≥30% of the between-subject S.D. was also estimated. Although there was no significant mean change between the two tests, we found that in individual subjects the second measurement was as high/low as 1.9/0.5 times (SDNN, best case) and 3.5/0.3 times (LF/HF, worst case) the first measurement, due to pure random variation. For most parameters the ICC was >0.8 (range 0.65–0.88). The estimated sample size ranged from 24–98 subjects. Reliability indexes tended to improve during paced breathing. We conclude that short-term HRV parameters are subject to large day-to-day random variations. Random error, however, represents a limited part of the between-subject variability; therefore observed differences between individuals mostly reflect differences in the subjects' error-free value rather than random error. Overall, paced breathing improves reliability.
Expression and extracellular release of Trx80, the truncated form of thioredoxin, by TNF-α- and IL-1β-stimulated human synoviocytes from patients with rheumatoid arthritis
Authors: Lemarechal Hervé , Anract Phillippe , Beaudeux Jean-Louis , Bonnefont-Rousselot Dominique , Ekindjian Ohvanesse G. , Borderie Didier
Published: July 2007

Thioredoxin (Trx) plays several important roles, through changes to sulfhydryl reactions and protein interactions, in controlling cellular signalling processes in RA (rheumatoid arthritis). Trx80, the 10 kDa C-terminal truncated form of Trx, is a potent mitogenic cytokine and is involved in the Th1 response. In the present study, we have investigated the ability of synoviocytes from five RA patients to induce Trx80 after ex vivo stimulation by the pro-inflammatory cytokines IL-1β (interleukin-1β) and TNF-α (tumour necrosis factor-α) or by H2O2. Synoviocytes from five OA (osteoarthritis) patients were used as controls. Immunoprecipitation assays using two different antibodies showed that RA, but not OA, cells expressed intact Trx80 protein in culture even when not stimulated. Treatment with pro-inflammatory cytokines alone or in combination enhanced this basal production and induced the extracellular release of Trx80 by all of the RA cells tested. Under our experimental conditions, the rate of Trx80 release from RA cells was approx. 30% of the total Trx produced. In contrast, Trx80 was not detected in response to H2O2 in RA or OA synoviocyte lysates and their respective culture supernatants, indicating that the oxidative process induced by H2O2 in synoviocytes was unable to modify Trx80 release. Moreover, Trx80 induced synoviocyte proliferation as evaluated by [3H]thymidine incorporation. These results highlight the effect of the inflammatory process on the release of both Trx and Trx80 from RA synoviocytes, and suggest that the cytokine-induced increase in Trx80 cell release may constitute a link between inflammation and the immune system in RA.
The Geometrical Model for Microfibril Deposition and the Influence of the Cell Wall Matrix
Authors: Emons A. M. C. , Schel J. H. N. , Mulder B. M.
Published: July 2007

Abstract: A theory for cell wall deposition has been formulated consistent with present day experimental data on cell walls and cellular processes. This theory has a generic origin, geometrical constraints, as the underlying cause for the cell wall architecture. The theory has been worked out as a fully mathematical model, allowing for specific predictions of a qualitative and quantitative nature. The key point of the geometrical theory is the coupling of the trajectory of the cellulose microfibril synthases, i.e., rosettes, to their density. This coupling provides the cell with a mechanism for manipulating the cell wall texture by creating controlled local variations in the number of active synthases. In the present paper we show that the geometrical model can explain the helicoidal, crossed polylamellate, helical and axial wall textures, which are the basic textures found in plant cell walls. In addition, we discuss the role of cortical microtubules in the wall deposition process and how the cell wall matrix contributes to cell wall texture determination.
Three‐Dimensional Reconstruction of the Stomatal Complex in Pinus canariensis Needles Using Serial Sections
Authors: Zellnig G. , Peters J. , Jiménez M. S. , Morales D. , Grill D. , Perktold A.
Published: July 2007

Abstract: The three‐dimensional (3D) morphology of the stomata in leaves of Pinus canariensis is described with respect to the spatial arrangement of guard cells, subsidiary cells, polar and lateral cells. Serial semi‐thin sections of the stomatal apparatus were digitally reconstructed and analysed with regard to the position, shape and size of the cell types involved. The stomatal complex consists of 16 cells with uniquely shaped polar and lateral cells. The polar cells form a kind of roof above the epistomatal chamber thereby reducing the surface aperture. The structural features of the stomatal complex differ from other Pinus species and are presumed to be an adaptation to extreme environmental conditions.
Space-time contours to treat intense field-dressed molecular states. II. Applications
Authors: Sarkar Biplab , Adhikari Satrajit , Baer Michael
Published: July 2007

This second article in the two back-to-back articles presents a numerical application to support and strengthen two theoretical findings extensively discussed in the previous article (article I). In I, we found that introducing the space-time contours enables to distinguish between N, the number of nuclear Schrödinger equations to be solved, and L, the number of field-free states that become populated by the external field (in the ordinary, perturbative approaches this distinction is not apparent). In the numerical study we show, employing the electronic transition probability matrix P(s,t) [which closely is related to the transformation matrix ω(s,t)—see Eqs. (21) and (25) in I], that the N=L case is rare and in most cases we have N<L. Since the perturbative approach can be shown to follow when N=L (see Sec. III C in I) the numerical study implies that in most cases the perturbative approach is not reliable. The second issue that is studied is related to the diabatization process. It is shown, numerically, that the N<L case, in general, does not lead to field-dressed diabatic potentials which are single valued. However, if N is chosen to be identical to the number of field-free states that yield field-free single-valued diabatic potentials in a given spatial region then the corresponding N field-dressed states also yield single-valued (field-dressed) diabatic potentials. This result is independent of L. The numerical study is carried out for an eigenvalue problem based on the Mathieu equation.
In search of definitive signatures of the elusive NCCO radical
Authors: Simmonett Andrew C. , Evangelista Francesco A. , Allen Wesley D. , Schaefer Henry F.
Published: July 2007

Previous experimental assignments of the fundamental vibrational frequencies of NCCO have been brought into question by subsequent unsuccessful attempts to observe IR signatures of this radical at these frequencies. Here we compute the fundamental vibrational frequencies by applying second-order vibrational perturbation theory to the complete quartic force field computed at the all-electron (AE) coupled cluster singles, doubles, and perturbative triples level [CCSD(T)] with the correlation-consistent, polarized core-valence quadruple-zeta (cc-pCVQZ) basis set, which has tight functions to correctly describe core correlation. The AE-CCSD(T)/cc-pCVQZ geometric parameters are re(N–C)=1.1623Å, re(C–C)=1.4370Å, re(C–O)=1.1758Å, θe(N–C–C)=168.55°, and θe(C–C–O)=132.22°. Our CCSD(T)/cc-pCVQZ values of the characteristic stretching frequencies ν1 and ν2 are 2171 and 1898cm−1, respectively, in stark contrast to the experimentally derived values of 2093 and 1774cm−1. Finally, focal-point extrapolations using correlation-consistent basis sets cc-pVXZ (X=D,T,Q,5,6) and electron correlation treatments as extensive as full coupled cluster singles, doubles, and triples (CCSDT) with perturbative accounting of quadruple excitations [CCSDT(Q)] determine the vibrationless barrier to linearity of NCCO and the dissociation energy (D0) of NCCO→NC+CO to be 8.4 and 26.5kcalmol−1, respectively. Using our precisely determined dissociation energy, we recommend a new 0K enthalpy of formation for NCCO of 50.9±0.3kcalmol−1.
Spin blockade in the conduction of colloidal CdSe nanocrystal films
Authors: Guyot-Sionnest Philippe , Yu Dong , Jiang Pei-hsun , Kang Woowon
Published: July 2007

The conduction of thin films of n-type CdSe colloidal quantum dots is studied at low temperature and under magnetic field. At medium and high magnetic fields (10T), the films exhibit positive magnetoresistance consistent with the variable range hopping model. At low magnetic field(<0.3T) but in the strong electric field regime, there is a narrower magnetoresistance of order 10%–15%. The magnetoresistance shows a strong bias dependence, small and positive at low bias, increasing but still positive at higher bias, and turning negative at the highest bias. A similar behavior has been reported recently for thin film organics. Weak localization effects are ruled out. The explanation for the observations is based on spin blockade relaxed by the hyperfine interaction. The weak magnetoresistance at low bias is attributed to the diffusing paths taken by the hopping electrons. At higher bias, the more directed motion of electrons leads to increasingly positive magnetoresistance due to the more effective spin blockade. At the highest bias, the magnetoresistance becomes negative, which is attributed to the increased exchange interaction associated with the shorter tunneling distance.
Ballistic electron and photocurrent transport in Au-molecular layer-GaAs diodes
Authors: Li W.-J. , Kavanagh K. L. , Talin A. A. , Clift W. M. , Matzke C. M. , Hsu J. W. P.
Published: July 2007

We present a study on hot electron transport through Au∕molecule∕n-GaAs(001) diodes via ballistic electron emission microcopy (BEEM). The molecules in the structure form a monolayer of either octanedithiol [HS–(CH2)8–SH] or hexadecanethiol [HS–(CH2)15–CH3]. For the dithiol case, the presence of the molecular interlayer leads to undetectable BEEM transmission. Whereas a small photoinduced collector current is detected at random locations at a forward (reverse) scanning tunneling microscopy (STM) tip voltage of −1.43±0.01V (+1.50±0.02V). In comparison, with monothiol diodes, or diodes where the molecules are sandwiched between two Au films (Au∕molecule∕Au∕GaAs), the BEEM transmission remains a significant fraction of the reference diode signal (30%–80%) with a slight increase in the ballistic transport threshold voltage (−1.0to−1.1V) from that of the reference Au∕GaAs diodes (−0.89V). Auger depth profiling and cross-sectional transmission electron microscopy show that Au-molecule intermixing occurs in Au/hexadecanethiol/GaAs but not in Au/octanedithiol/GaAs diodes. The suppression of BEEM signal and the detection of STM-induced photocurrent in the Au/octanedithiol/GaAs case are consistent with an insulating monolayer containing pinholes or recombination centers with densities of 1 every 25×25nm2 or ∼2000μm−2.
Theoretical study of the electrical transport of nickel nanowires and a single atomic chain
Authors: Li H. , Zhang X. Q. , Sun F. W. , Li Y. F. , Liew K. M. , He X. Q.
Published: July 2007

Five kinds of nanowires and a nanochain that is embedded in a carbon nanotube have been optimized by density function theory, and the electronic transport properties through these nanowires and nanochain are studied. Our results indicate that the transmission spectra exhibit size-dependent oscillations. We observe and study the nonlinear contribution to the I-V characteristic (current-voltage) curves that is due to the quantum size effect. The I-V curve of the single chain is different from that when the chain is embedded in a carbon nanotube. The results provide valuable information on the correlation between the transport properties of nanowires and their microstructures.
Preparation and photoinduced wettability conversion of superhydrophobic β-Ga2O3 nanowire film
Authors: Gao L. Y. , Zheng M. J. , Zhong M. , Li M. , Ma L.
Published: July 2007

High-yield uniform β-Ga2O3 nanowire films with mesh structure on GaP substrate have been synthesized via heat treating porous GaP preevaporated Au under low vacuum. The single-crystalline β-Ga2O3 nanowires have uniform diameters of about 100nm and a preferential [001] growth direction along the axis. The as-prepared β-Ga2O3 nanowire film reveals a superhydrophobic property. The remarkable photoinduced surface wettability conversion at β-Ga2O3 nanowire film was found, which can be explained by the cooperation of the surface photosensitivity and the special nanostructure.
Instabilities of the flow in a curved channel with compliant walls
Authors: Guaus Anaïs , Bottaro Alessandro
Published: July 2007

The linear stability of flows in curved compliant channels is examined. The walls bounding the fluid are modelled as thin cylindrical shells supported by a rigid outer frame through arrays of springs and dampers; this is often referred to as Kramer-type coating. Sufficiently soft compliant walls have an influence on the large-scale streamwise vortices produced in the channel by the centrifugal force, although the effect is limited to modes of large enough spanwise wavelengths. For even longer wavelengths, a spanwise-periodic surface-based wave precedes the onset of the streamwise vortex instability. Longitudinal or oblique travelling-wave flutter modes may appear and dominate the transition scenario, for sufficiently compliant walls, depending on the receptivity conditions.
Isotope-Coded Affinity Tagging of Proteins
Authors: Aebersold Ruedi , Griffin Timothy J. , Donohoe Sam
Published: July 2007

INTRODUCTION

Quantitative proteomics has traditionally been performed using 2D gel electrophoresis, where quantitation is accomplished by recreating differences in the staining patterns of proteins derived from two states of cell populations or tissues from a similar biological system. More recently, mass spectrometry (MS) methods based on stable isotope quantitation have been developed that show significant potential for differential expression proteomic studies. One such in vitro method, described in this protocol, involves the use of isotope-coded affinity tags (ICATs) with three functional moieties: a cysteine reactive moiety, a linker with either eight hydrogens (the light form of the reagent) or eight deuteriums (the heavy form of the reagent, having an isotope code or mass tag of 8 Da), and a biotin moiety (the affinity tag). Using this technique, the cysteine side chains in complex mixtures of proteins from two different states of a cell population (e.g., normal vs. disease) are reduced and alkylated using the light form of the reagent (d0-labeled tag) in one cell state and the heavy form of the reagent (d8-labeled tag) for proteins in the second cell state. The two mixtures (d0 and d8 labeled) are then combined and subjected to proteolytic digestion (typically, with trypsin and/or Lys-C). Generated cysteine-containing peptides are affinity-purified using an avidin column, resulting in a “simplified” mixture of peptides that contains ~10-fold fewer peptides than the original mixture. These peptides are analyzed by MS, and quantitation information based on the relative abundance of the d0 and d8 isotopes is obtained. The identification of proteins is obtained from the peptide molecular mass and MS/MS-derived amino acid sequence.
Genome Modification by Inclusion of loxP Transgene Sequences: Figure 1.
Authors: Ohtsubo Kazuaki , Marth Jamey D.
Published: July 2007

INTRODUCTION

We describe here a procedure for introducing loxP sites into the mammalian genome. A typical gene-targeting approach to create a conditional null allele is presented, in which the initial placement of loxP sites is not deleterious to allele function. This can be modified to include knock-ins of point mutations, with such mutations flanked by loxP sites that can then be recombined by Cre expression. The choice of sequence or regulatory element to modify is dependent on the experimental design. Consideration must be given to the possible production of truncated and altered gene sequence products, or otherwise aberrantly functioning alleles.
Long-Term Two-Photon Transcranial Imaging of Synaptic Structures in the Living Brain
Authors: Grutzendler Jaime , Gan Wen-Biao
Published: July 2007

INTRODUCTION

This is a detailed protocol for long-term transcranial imaging of neuronal structures in the brains of living mice, using two-photon microscopy. It has been used to image individual dendritic spines and axonal varicosities in various mouse brain areas, such as visual, somatosensory, motor, and frontal cortices, over intervals of up to 4 months. This long-term transcranial imaging approach allows detailed structural and functional changes of synapses to be monitored during learning and memory processes, as well as in neurological disease models. It also provides a sensitive tool to detect the effects of various pharmacological and therapeutic interventions on cells in the living brain.
Differential Interference Contrast (DIC) Imaging of Living Cells: Figure 1.
Authors: Ziv Noam E. , Schiller Jackie
Published: July 2007

INTRODUCTION

This protocol describes the use of electronically enhanced, differential interference contrast (DIC) imaging techniques for the study of living cells. Methods for DIC imaging of cells using an inverted microscope and for infrared (IR) imaging of brains slices using an upright microscope are presented. DIC microscopy (also known as Nomarski microscopy) is extremely useful for resolving individual cells and cellular organelles in live, unstained tissue. The data obtained are valuable in their own right, as well as for complementing fluorescence microscopy data. DIC microscopy can be applied to cell culture, brain slices, and even intact organisms (such as embryos). High-quality images of living cells in brain slices can also be obtained using a combination of DIC optics and IR video microscopy.
Sagittal Explant Culture for 3D Confocal Time-Lapse Analysis of Chick Peripheral Nervous System Formation: Figure 1.
Authors: Kasemeier-Kulesa Jennifer C. , Lefcort Frances , Kulesa Paul M.
Published: July 2007

INTRODUCTION

The peripheral nervous system (PNS) regulates key events within the body including breathing, heart rate, and pain and temperature sensation. In the trunk of the developing embryo, neural crest (NC) cells that follow a ventro-medial pathway form the dorsal root ganglia (DRG) and sympathetic ganglia (SG) of the PNS. The cellular and molecular mechanisms that mediate the formation of the PNS are not completely understood due to the lack of a model system to monitor NC cell migratory behaviors deep within the embryo. Here, we describe a unique sagittal explant culture technique that allows for visualization of DRG and SG formation in the relatively intact chick embryo to assess potential molecules and signals influencing the formation of the PNS. By making a midline cut down the chick antero-posterior axis, each half of the embryo is an explant that can be imaged either from the medial perspective, to reveal events occurring deep within the embryo (SG formation), or from the lateral surface, to image events occurring in the dorso-lateral plane (DRG formation).
Conditional Mutagenesis of the Genome Using Site-Specific DNA Recombination: Figure 1.
Authors: Ohtsubo Kazuaki , Marth Jamey D.
Published: July 2007

INTRODUCTION

Altering the genome of intact cells and organisms by site-specific DNA recombination has become an important gene-transfer methodology. DNA modifications produced by gene transfer and homologous recombination are typically static once integrated among target cell chromosomes. In contrast, the inclusion of exogenous recombinase target sequences within transferred DNA segments allows subsequent modifications to previously altered genomic structure that increase the utility of gene transfer and enhance experimental design. Creating tissue- and cell-type-specific genetic lesions in animal models, indelibly marking progenitors for cell fate mapping, inducing large-scale chromosomal rearrangements, and complementing gene defects in studies of phenotypic maintenance and reversion are all possible by directing recombinase expression using gene transfer among experimentally modified genomes. Moreover, this approach is effective in providing controlled data establishing genotype-phenotype relationships and allows for the excision of introduced marker genes that can affect neighboring chromatin structure and function. Although early work involved the yeast Flp recombinase, most studies in mammalian systems have used the Cre recombinase derived from bacteriophage P1. Both enzymes are members of the integrase family of recombinases but bind to distinct DNA target signals. Cre recombinase operates on the 34-bp loxP sequence and, like Flp, performs conservative recombination involving DNA segments positioned among these target sites.
The Combination of B‐Type Natriuretic Peptide and C‐Reactive Protein Provides Incremental Prognostic Value Among Older Patients Referred for Cardiac Catheterization
Authors: Stolker Joshua M. , Rich Michael W.
Published: July 2007

Recent clinical studies have demonstrated the utility of B‐type natriuretic peptide (BNP) and C‐reactive protein (CRP) for predicting cardiovascular outcomes. The authors hypothesized that a combined biomarker score would provide incremental prognostic value among older individuals. Clinical data, biomarkers, and echocardiograms were obtained in 200 geriatric patients referred for cardiac catheterization. Tertile score was defined as the sum of an individual's BNP tertile plus CRP tertile within the study population, for a total score from 2 to 6. The primary end point was cardiovascular hospitalization or death at 6 months. Univariate predictors of events included prior heart failure, atrial fibrillation, left ventricular systolic dysfunction, functional class, significant mitral regurgitation, BNP, CRP, and the tertile score. In contrast to BNP or CRP alone, the tertile score consistently provided incremental value when added to clinical predictors in multivariate models. A simple summation score may help clinicians predict outcomes in symptomatic geriatric patients beyond standard clinical variables.
Outcomes of Unexplained Syncope in the Elderly
Authors: Roussanov Oleg , Estacio Greta , Capuno Maribeth , Hill Judith , Kovesdy Csaba , Jarmukli Nabil
Published: July 2007

The objective of this study was to determine whether syncope of unknown etiology (SUE) influences mortality in the elderly. Patients with SUE at 65 years or older were identified retrospectively and their outcomes were compared with an age‐, sex‐, and comorbidity‐matched group of patients drawn from the same population. All‐cause 3‐year mortality was analyzed using the Kaplan‐Meier method and the log‐rank test. SUE was identified in 150 of 304 patients (49%) with syncope. Patients with SUE and controls experienced mortality rates (1/1000 person‐years [95% confidence interval]) of 147.8 (112.6–193.9) and 153.4 (117.5–200.3), P=.7, respectively. Of all the recorded characteristics of SUE, only the inpatient status was associated with higher all‐cause mortality (Cox model adjusted hazard ratio [95% confidence interval] of inpatients vs outpatients with SUE: 2.2 [1.1–4.1], P=.017). New‐onset SUE is not an independent predictor of mortality in elderly patients.
Age‐Related Vascular Stiffness and Left Ventricular Size After Myocardial Infarction
Authors: Hirsch Glenn A. , Ingkanisorn W. Patricia , Schulman Steven P. , Gerstenblith Gary , Dyke Christopher K. , Rhoads Kenneth L. , Thompson Richard , Aletras Anthony H. , Arai Andrew E.
Published: July 2007

Aortic stiffness increases with age and may contribute to adverse remodeling after myocardial infarction (MI). The authors examined whether vascular stiffness affects left ventricular (LV) size after MI using contrast‐enhanced cardiac magnetic resonance imaging. Despite similar infarct sizes, patients aged 60 years or older (n=30) had a lower ejection fraction (42±15 vs 53±11%, P<.01) and greater end‐systolic volume index (75±47 vs 44±18 mL/m2, P<.01) than younger patients (n=19). As infarct size increased, LV end‐systolic volumes (P<.0001) and ejection fraction (P<.0001) in the older participants were progressively greater. Participants with greater aortic stiffness had greater end‐systolic volume indices (P<.0001) and lower ejection fraction (P<.0001) with increasing infarct size. Using multivariate analysis, MI size (P<.001) and aortic distensibility (P=.02) were significant predictors of end‐systolic volume index. Older patients have increased LV size after MI compared with younger patients, possibly related to age‐related decreases in aortic distensibility affecting LV remodeling.
Regulation of ligands for the activating receptor NKG2D
Authors: Mistry Anita R. , O'Callaghan Chris A.
Published: July 2007

The outcome of an encounter between a cytotoxic cell and a potential target cell depends on the balance of signals from inhibitory and activating receptors. Natural Killer group 2D (NKG2D) has recently emerged as a major activating receptor on T lymphocytes and natural killer cells. In both humans and mice, multiple different genes encode ligands for NKG2D, and these ligands are non‐classical major histocompatibility complex class I molecules. The NKG2D–ligand interaction triggers an activating signal in the cell expressing NKG2D and this promotes cytotoxic lysis of the cell expressing the ligand. Most normal tissues do not express ligands for NKG2D, but ligand expression has been documented in tumour and virus‐infected cells, leading to lysis of these cells. Tight regulation of ligand expression is important. If there is inappropriate expression in normal tissues, this will favour autoimmune processes, whilst failure to up‐regulate the ligands in pathological conditions would favour cancer development or dissemination of intracellular infection.
Viral monitoring and successful treatment of a ganciclovir‐resistant cytomegalovirus infection in a heart transplant recipient
Authors: García‐Martínez J. , Folgueira L. , Delgado R. , Hernando S. , Prieto C. , Aguado J.M. , Otero J.R.
Published: July 2007

Abstract: We reported a ganciclovir (GCV)‐resistant cytomegalovirus (CMV) infection in a heart transplant recipient. Genotypic and phenotypic susceptibility assays demonstrated an A594V mutation in the UL97 phosphotransferase gene and GCV IC50>96 μM. Low GCV concentration exposure, immunosuppressive treatment, donor‐positive/recipient‐negative CMV serostatus, viral reactivations within antiviral prophylaxis or treatment, contributed to GCV‐resistant strain selection.
Cryptosporidium parvum‐associated sclerosing cholangitis in a liver transplant patient
Authors: Denkinger C.M. , Harigopal P. , Ruiz P. , Dowdy L.M.
Published: July 2007

Abstract: Cryptosporidium parvum causes severe long‐standing diarrhea in immunocompromised patients. Sclerosing cholangitis caused by C. parvum is a rare complication in transplant recipients. We report herein the presentation of Cryptosporidium‐associated cholangitis in an adult liver transplant patient diagnosed by liver biopsy. The patient improved on treatment with azithromycin and paromomycin.
Xenogeneic human serum promotes leukocyte adhesion to porcine endothelium under flow conditions, possibly through the activation of the transcription factor NF‐κB
Authors: Morigi Marina , Zoja Carla , Colleoni Stella , Angioletti Stefania , Imberti Barbara , Remuzzi Andrea , Remuzzi Giuseppe
Published: July 2007

Abstract: Endothelial cell activation and leukocyte infiltration are a consistent feature of discordant xenograft rejection. Here we evaluated whether xenogeneic serum, as a source of xenoreactive natural antibodies and complement, induced endothelial cell activation with consequent leukocyte adhesion under flow conditions. Porcine aortic endothelial cells (PAEC) were incubated for 1 hr 30 min or 5 hr with 10% homologous porcine serum (control) or 10% xenogeneic human serum and then perfused with total human leukocytes in a parallel plate flow chamber under laminar flow (1.5 dynes/cm2). Adherent cells were counted by digital image analysis. Xenogeneic human serum significantly (P<0.01) increased the number of adherent leukocytes as compared with porcine serum. A similar adhesive response was elicited by TNFα (100 U/ml), one of the most potent inducers of endothelial cell adhesive properties, here used as positive control.

In order to elucidate possible mechanisms underlying endothelial cell activation by xenogeneic serum, we focussed on transcription factor NF‐κB, a central regulator for the induction of different genes, including adhesive molecules and chemoattractants. By confocal fluorescence microscopy, we observed a positive staining for NF‐κB (p65 subunit) in the nuclei of PAEC exposed for 1 hr 30 min to human serum, which indicated NF‐κB activation in this setting. At variance, in PAEC incubated with the homologous serum, NF‐κB was strictly localized in the cell cytoplasm. Treatment of PAEC exposed to xenogeneic serum with the NF‐κB inhibitors pyrrolidinedithiocarbamate (PDTC, 25 μM) and tosyl‐phechloromethylketone (TPCK, 25 μM) significantly (P<0.01) reduced leukocyte adhesion in respect to PAEC treated with human serum alone. Findings that xenogeneic serum promotes leukocyte‐endothelium interaction possibly through NF‐κB activation might be relevant for designing future therapeutic strategies aimed at prolonging xenograft survival.
The strength of cell‐mediated xenograft rejection in the mouse is due to the CD4+ indirect response
Authors: Chitilian Hovig V. , Laufer Terri M. , Stenger Karla , Shea Susan , Auchincloss Hugh
Published: July 2007

Abstract: Previous studies have shown that CD4+ T cells are responsible for the great strength of cell‐mediated xenograft rejection in the mouse. In vitro studies have suggested that this CD4+ response is to xenogeneic antigens that are presented indirectly. The present studies were carried out in order to determine whether the strength of cell‐mediated xenograft rejection in vivo is dependent on the CD4+ indirect response. We grafted pig skin onto mice that express class 11 MHC antigens only on their thymic epithelial cells (II‐4+ mice). These mice have normal numbers of functional peripheral CD4+ T cells; however they lack class II MHC expression on their antigen presenting cells and are thus incapable of mounting a CD4+ T cell‐mediated indirect response. Xenograft survival was prolonged on these mice. Furthermore, administration of cyclosporine and anti‐CDS monoclonal antibodies to II‐4+ recipients prolonged xenograft survival to at least the same extent as allograft survival, demonstrating that the strength of cell‐mediated xenograft rejection resides in the CD4+ indirect response. Despite the increased survival time, xenograft rejection still occurred in the absence of the indirect pathway. Depletion of the II‐4+ recipients of their CD4+ T cell population prolonged xenograft survival even further, suggesting the presence of a weaker CD4+ direct mechanism which was virtually undetectable in vitro.