bluuebunny/crossref_metadata_2025 huggingface dataset:
A strong-interaction theory for the motion of arbitrary three-dimensional clusters of spherical particles at low Reynolds number
Authors: Hassonjee Qaizar , Ganatos Peter , Pfeffer Robert
Published: April 2006

This paper contains an ‘exact’ solution for the hydrodynamic interaction of a three-dimensional finite cluster at arbitrarily sized spherical particles at low Reynolds number. The theory developed is the most general solution to the problem of an assemblage of spheres in a three-dimensional unbounded media. The boundary-collocation truncated-series solution technique of Ganatos, Pfeffer & Weinbaum (1978) for treating planar symmetric Stokes flow problems has been extensively modified to treat the non-symmetric multibody problem. The orthogonality properties of the eigenfunctions in the azimuthal direction are used to satisfy the no-slip boundary conditions exactly on entire rings on the surface of each particle rather than just at discrete points.

Detailed comparisons with the exact bipolar solutions for two spheres show the present theory to be accurate to five significant figures in predicting the translational and angular velocity components of the particles at all orientations for interparticle gap widths as close as 0.1 particle diameter. Convergence of the results to the exact solution is rapid and systematic even for unequal-sized spheres (a1/a2 = 2). Solutions are presented for several interesting and intriguing configurations involving three or more spherical particles settling freely under gravity in an unbounded fluid or in the presence of other rigidly held particles. Advantage of symmetry about the origin is taken for symmetric configurations to reduce the collocation matrix size by a factor of 64. Solutions for the force and torque on three-dimensional clusters of up to 64 particles have been obtained, demonstrating the multiparticle interaction effects that arise which would not be present if only pair interactions of the particles were considered. The method has the advantage of yielding a rather simple expression for the fluid velocity field which is of significance in the treatment of convective heat and mass transport problems in multiparticle systems.
Considerations on the moving contact-line singularity, with application to frictional drag on a slender drop
Authors: Durbin P. A.
Published: April 2006

It has previously been shown that the no-slip boundary condition leads to a singularity at a moving contact line and that this forces one to admit some form of slip. Present considerations on the energetics of slip due to shear stress lead to a yield stress boundary condition. A model for the distortion of the liquid state near solid boundaries gives a physical basis for this boundary condition. The yield stress condition is illustrated by an analysis of a slender drop rolling down an incline. That analysis provides a formula for the frictional drag resisting the drop movement. With the present boundary condition the length of the slip region becomes a property of the fluid flow.
The force exerted on a body in inviscid unsteady non-uniform rotational flow
Authors: Auton T. R. , Hunt J. C. R. , Prud'Homme M.
Published: April 2006

A general expression is derived for the fluid force on a body of simple shape moving with a velocity v through inviscid fluid in which there is an unsteady non-uniform rotational velocity field u0(x,t) in two or three dimensions. It is assumed that the radius is small compared with the scale over which the strain rate changes, though for the sphere it is also assumed that the changes in the ambient velocity field over the scale of the sphere are small compared with the velocity of the body relative to the flow. Given these approximations it is shown that the effects of the rate of change of the vorticity of the ambient flow is of second order and can be neglected. However the rate of change of the irrotational straining motion is included in the analysis. It is shown that the inertial forces derived by many authors for irrotational flow can be simply added to a generalization of the lift force derived by Auton (1987) in a companion paper. It is shown how this lift force is made up of a rotational and an inertial or added-mass component. For three-dimensional bluff bodies the latter is generally larger (by a factor of three for a sphere), and can be simply calculated from the added-mass coefficient. For illustration, the general expression is used to derive formulae for (i) the motion of a spherical bubble in a steady non-uniform flow to contrast with the motion in an unsteady flow, and (ii) the motion of rigid volumes of neutral density across an inviscid shear flow. These results show how added-mass (and lift) forces lead to different motions for a sphere and a cylinder. The general expression is useful in two-phase flow calculations, and for indicating the forces and motions of ‘lumps of fluid’ in turbulent flows.
Interaction of impulsively generated vortex pairs with bodies
Authors: Homa J. , Lucas M. , Rockwell D.
Published: April 2006

A vortex pair, impulsively generated from a planar nozzle, is shown to have a degree of vorticity concentration in good agreement with inviscid theory, providing well-posed initial conditions for interaction with basic types of bodies (cylinders and plates). The scale of these bodies ranges from the same order as, to over an order of magnitude smaller than, the scale (distance between centres) of the incident vortex pair.

The fundamental case of a (primary) vortex pair symmetrically incident upon a very small cylinder shows rapid growth of a secondary vortex pair. These secondary vortices quickly attain a circulation of the same order as that of the corresponding primary vortices within a distance smaller than the lengthscale of the primary vortex pair. At this location, the temporal variation of integrated vorticity of primary and secondary vortices attains a maximum simultaneously. This zero phase shift between arrival of vorticity maxima provides the basis for formation of counter-rotating, primary–secondary vortex pairs, where both the primary and secondary vortices move at the same phase speed.

Visualization shows that the mode of secondary vortex formation is highly sensitive to the degree of symmetry of the initial encounter of the incident vortex pair with the body. The symmetrical mode of (in-phase) secondary vortex formation shows very rapid growth of large-scale secondary vortices; their development is relatively independent of the particulars of body shape and scale. On the other hand, the antisymmetrical mode takes two basic forms: large-scale secondary vortex formation, with the phase shift between their formation determined by the lengthscale of the body; and small-scale, antisymmetrical shedding of secondary vortices from the body occurring for a body lengthscale an order of magnitude smaller than that of the incident vortex pair. Correspondingly, there are several types of distortion of the cores and trajectories of the primary (incident) vortices.
Dissociative charge transfer and collision induced dissociation of Ar2+ and Ar3+ clusters in collisions with argon atoms at keV energies
Authors: Ismail I. M. , Lepère V. , Barat M. , Fayeton J. A. , Picard Y. J. , Wohrer K.
Published: April 2006

The dynamics of dissociative charge transfer and collision induced dissociation of Ar2+ and Ar3+ clusters colliding with Ar atoms at 4.8keV has been investigated using a novel multifragment detection scheme that maps the postcollision vectors of all particles simultaneously. Estimation of internal energies and measurement of pre- and postcollision vectors enables a full description of reaction dynamics. The prominence of electronic excitation in defining the dynamics of these collision systems is demonstrated. The dissociation dynamics of Ar3+ clusters is distinctly different from that of Ar2+. This is attributed to a combination of lower internal energies and predominantly triangular T-shape structure of the Ar3+ ion.
Double-decker femtosecond electron beam accelerator for pulse radiolysis
Authors: Yang Jinfeng , Kondoh Takafumi , Yoshida Akira , Yoshida Youichi
Published: April 2006

A new concept of double-decker electron beam accelerator based on a photocathode radio-frequency (rf) gun was proposed for studying chemical kinetics and primary processes or reactions of radiation chemistry. The synchronized double-decker electron beams with time interval of 1.4ns were generated in the rf gun by injecting two laser beams on the photocathode. The double-decker electron beams were accelerated by a booster linear accelerator (linac) up to 31.8MeV with energy-phase correlation and compressed into femtosecond by rotating the bunch in the energy-phase distribution in magnetic fields. The normalized transverse emittance of both beams downstream of the linac was obtained to be 2.5±0.6mmmrad for the up beam with bunch charge of 0.47nC and 3.6±0.7mmmrad for the down beam with bunch charge of 0.65nC. The minimum relative energy spread was (0.14±0.03)% for the two beams. The compressed bunch length was obtained to be 430±25fs for the up bunch and 510±20fs for the down bunch.
Integrative prototype B-scan photoacoustic tomography system based on a novel hybridized scanning head
Authors: Yang Diwu , Xing Da , Tan Yi , Gu Huaimin , Yang Sihua
Published: April 2006

A prototype B-scan photoacoustic tomography system is developed. It integrates pumping fiber, ultrasound coupling medium, and a transducer array into a novel hybridized scanning head. By moving the scanning head a photoacoustic tomography can be obtained in the reflection mode. Concentration-adjustable glycerite is used as the ultrasonic coupling medium to match the ultrasonic velocities in tissues, reducing the acoustic reflection, eliminating the acoustic refraction, and rectifying the acoustic path difference. This system is used to image graphite phantom in tissue and human blood vessels. Our experimental results show that this integrative system has the potential for fast photoacoustic imaging.
Electrical characterization of p-type N-doped ZnO films prepared by thermal oxidation of sputtered Zn3N2 films
Authors: Nakano Yoshitaka , Morikawa Takeshi , Ohwaki Takeshi , Taga Yasunori
Published: April 2006

We report on p-type conduction in N-doped ZnO (ZnO:N) films that were prepared by oxidative annealing of sputtered Zn3N2 films at temperatures between 500 and 800°C in flowing O2 gas. Room-temperature Hall-effect measurements show a significant improvement of p-type doping characteristics by the oxidative annealing at temperatures between 700 and 800°C, where more N acceptors are activated and the oxidation state is enhanced, as confirmed by deep-level optical spectroscopy and secondary ion mass spectrometry measurements. Therefore, the high-temperature oxidation of Zn3N2 is effective in moderating the self-compensation effect in ZnO:N from the viewpoint of oxygen vacancy annihilation.
Histone chaperone Asf1 is required for histone H3 lysine 56 acetylation, a modification associated with S phase in mitosis and meiosis
Authors: Recht J. , Tsubota T. , Tanny J. C. , Diaz R. L. , Berger J. M. , Zhang X. , Garcia B. A. , Shabanowitz J. , Burlingame A. L. , Hunt D. F. , Kaufman P. D. , Allis C. D.
Published: April 2006

Histone acetylation affects many nuclear processes including transcription, chromatin assembly, and DNA damage repair. Acetylation of histone H3 lysine 56 (H3 K56ac) in budding yeast occurs during mitotic S phase and persists during DNA damage repair. Here, we show that H3 K56ac is also present during premeiotic S phase and is conserved in fission yeast. Furthermore, the H3 K56ac modification is not observed in the absence of the histone chaperone Asf1.
asf1
Δ and H3 K56R mutants exhibit similar sensitivity to DNA damaging agents. Mutational analysis of Asf1 demonstrates that DNA damage sensitivity correlates with (
i
) decreased levels of H3 K56ac and (
ii
) a region implicated in histone binding. In contrast, multiple
asf1
mutants that are resistant to DNA damage display WT levels of K56ac. These data suggest that maintenance of H3 K56 acetylation is a primary contribution of Asf1 to genome stability in yeast.
Rofecoxib is a potent inhibitor of cytochrome P450 1A2: studies with tizanidine and caffeine in healthy subjects
Authors: Backman Janne T. , Karjalainen Marjo J. , Neuvonen Mikko , Laitila Jouko , Neuvonen Pertti J.
Published: April 2006

Aims

Case reports suggest an interaction between rofecoxib and the CYP1A2 substrate tizanidine. Our objectives were to explore the extent and mechanism of this possible interaction and to determine the CYP1A2 inhibitory potency of rofecoxib.

Methods

In a randomized, double‐blind, two‐phase cross‐over study, nine healthy subjects took 25 mg rofecoxib or placebo daily for 4 days and, on day 4, each ingested 4 mg tizanidine. Plasma concentrations and the urinary excretion of tizanidine, its metabolites (M) and rofecoxib, and pharmacodynamic variables were measured up to 24 h. On day 3, a caffeine test was performed to estimate CYP1A2 activity.

Results

Rofecoxib increased the area under the plasma concentration–time curve (AUC0–∞) of tizanidine by 13.6‐fold [95% confidence interval (CI) 8.0, 15.6;P < 0.001), peak plasma concentration (Cmax) by 6.1‐fold (4.8, 7.3;P < 0.001) and elimination half‐life (t1/2) from 1.6 to 3.0 h (P < 0.001). Consequently, rofecoxib markedly increased the blood pressure‐lowering and sedative effects of tizanidine (P < 0.05). Rofecoxib increased several fold the tizanidine/M‐3 and tizanidine/M‐4 ratios in plasma and urine and the tizanidine/M‐5, tizanidine/M‐9 and tizanidine/M‐10 ratios in urine (P < 0.05). In addition, it increased the plasma caffeine/paraxanthine ratio by 2.4‐fold (95% CI 1.4, 3.4;P = 0.008) and this ratio correlated with the tizanidine/metabolite ratios. Finally, the AUC0−25of rofecoxib correlated with the placebo phase caffeine/paraxanthine ratio (r = 0.80,P = 0.01).

Conclusions

Rofecoxib is a potent inhibitor of CYP1A2 and it greatly increases the plasma concentrations and adverse effects of tizanidine. The findings suggest that rofecoxib itself is also metabolized by CYP1A2, raising concerns about interactions between rofecoxib and other CYP1A2 substrate and inhibitor drugs.
Pharmacokinetics and systemic endocrine effects of the phyto‐oestrogen 8‐prenylnaringenin after single oral doses to postmenopausal women
Authors: Rad M. , Hümpel M. , Schaefer O. , Schoemaker R. C. , Schleuning W‐D. , Cohen A. F. , Burggraaf J.
Published: April 2006

Aims

Pre‐clinical data suggest that the racemic phyto‐oestrogen 8‐prenylnaringenin (8‐PN) may have beneficial effects in postmenopausal women and may become an alternative to classical hormone replacement therapy (HRT) treatment regimes. The aim of this study was to investigate the pharmacokinetics, endocrine effects and tolerability of chemically synthesized 8‐PN in postmenopausal women.

Methods

The study was performed using a randomized, double‐blind, placebo‐controlled, dose‐escalation design with three groups of eight healthy postmenopausal women. In each group six subjects received 8‐PN and two subjects placebo. 8‐PN was given orally in doses of 50, 250 or 750 mg. Drug concentrations in serum, urine and faeces were measured up to 48 h and follicle‐stimulating hormone/luteinizing hormone (LH) concentrations up to 24 h.

Results

All treatments were well tolerated and associated with a low incidence of (drug unrelated) adverse events. Serum concentrations of free 8‐PN showed rapid drug absorption and secondary peaks suggestive of marked enterohepatic recirculation. Independent of the treatment group, approximately 30% of the dose was recovered in excreta as free compound or conjugates over the 48‐h observation period. The first Cmax and AUC0−48 h showed dose linearity with ratios of 1 : 4.5 : 13.6 (Cmax) and 1 : 5.2 : 17.1 (AUC). The750‐ mg dose decreased LH concentrations by 16.7% (95% confidence interval 0.5, 30.2).

Conclusion

Single oral doses of up to 750 mg 8‐PN were well tolerated by postmenopausal women. The pharmacokinetic profile of 8‐PN was characterized by rapid and probably complete enteral absorption, high metabolic stability, pronounced enterohepatic recirculation and tight dose linearity. The decrease in LH serum concentrations found after the highest dose demonstrates the ability of 8‐PN to exert systemic endocrine effects in postmenopausal women.
Influence of a single dose of 20 mg tadalafil, a phosphodiesterase 5 inhibitor, on ambulatory blood pressure in subjects with hypertension
Authors: Patterson Dean , McInnes Gordon T. , Webster John , Mitchell Malcolm M. , MacDonald Thomas M.
Published: April 2006

Aims

To test the non‐inferiority of a single dose of tadalafil 20 mg compared with placebo with respect to 26‐h mean ambulatory systolic and diastolic blood pressure in treated and untreated hypertensive subjects.

Methods

A multicentre, randomized, double‐blind, placebo‐controlled crossover study in 114 subjects with hypertension (36 subjects on no therapy with daytime mean ambulatory blood pressure ≥ 140/85 mmHg; 38 subjects on two to four classes of antihypertensive agents with daytime mean ambulatory blood pressure ≥140/85 mmHg and 40 subjects on two to four classes of antihypertensive agents with ambulatory blood pressure < 140/85 mmHg).

Results

Overall tadalafil reduced mean ambulatory blood pressure monitor systolic and diastolic blood pressure by 4.8 mmHg [95% confidence interval (Cl) 3.7, 5.9; P < 0.01] and 2.9 mmHg (95% CI 1.9, 3.6; P < 0.01), respectively, compared with placebo. In hypertensive subjects with uncontrolled blood pressure on two to four classes of antihypertensive agents (n = 36) tadalafil reduced mean ABPM systolic and diastolic blood pressure by 7.5 mmHg (95% CI 5.4, 9.6; P < 0.01) and 4.3 mmHg (95% CI 6.1, 8.9; P < 0.01) compared with placebo.

Conclusions

In patients with uncontrolled hypertension on multiple agents the addition of tadalafil 20 mg lowered mean 26‐h blood pressure.
Hydroxychloroquine potentiates Fas-mediated apoptosis of rheumatoid synoviocytes
Authors: Kim W-U , Yoo S-A , Min S-Y , Park S-H , Koh H-S , Song S-W , Cho C-S
Published: April 2006

Inadequate apoptosis may contribute to the synovial hyperplasia associated with rheumatoid arthritis (RA). The Fas-associated death domain protein (FADD)-like interleukin (IL)-1β-converting enzyme (FLICE)-inhibitory protein (FLIP), which is an apoptotic inhibitor, has been implicated in the resistance to Fas-mediated apoptosis of synoviocytes. This study investigated whether hydroxychloroquine (HCQ), an anti-rheumatic drug, induces the apoptosis of rheumatoid synoviocytes, and modulates the expression of FLIP. Fibroblast-like synoviocytes (FLS) were prepared from the synovial tissues of RA patients, and were cultured with various concentrations of HCQ in the presence or absence of the IgM anti-Fas monoclonal antibodies (mAb) (CH11). Treatment with HCQ, ranging from 1 to 100 µM, induced the apoptosis of FLS in a dose- and time-dependent manner. The increase in synoviocytes apoptosis by HCQ was associated with caspase-3 activation. A combined treatment of HCQ and anti-Fas mAb increased FLS apoptosis and caspase-3 activity synergistically, compared with either anti-Fas mAb or HCQ alone. The Fas expression level in the FLS was not increased by the HCQ treatment, while the FLIP mRNA and protein levels were decreased rapidly by the HCQ treatment. Moreover, time kinetics analysis revealed that the decreased expression of FLIP by HCQ preceded the apoptotic event that was triggered by HCQ plus anti-Fas mAb. Taken together, HCQ increases the apoptosis of rheumatoid synoviocytes by activating caspase-3, and also sensitizes rheumatoid synoviocytes to Fas-mediated apoptosis. Our data suggest that HCQ may exert its anti-rheumatic effect in rheumatoid joints through these mechanisms.
A rare RET gene exon 8 mutation is found in two Greek kindreds with familial medullary thyroid carcinoma: implications for screening
Authors: Kaldrymides Philippos , Mytakidis Nikolaos , Anagnostopoulos Theodore , Vassiliou Manolis , Tertipi Athanasia , Zahariou Maria , Rampias Theodoros , Koutsodontis Giorgos , Konstantopoulou Irene , Ladopoulou Angela , Bei Thalia , Yannoukakos Drakoulis
Published: April 2006

Objective  Familial medullary thyroid carcinoma (FMTC) is caused by germ‐line mutations in the RET proto‐oncogene. These mutations concern mainly cysteine residues in exons 10 and 11, whereas noncysteine mutations in exons 13–16 are rare. Mutations in other exons have been reported only in isolated families. In this study we have analysed the RET gene in two FMTC families negative for mutations in the above exons.

Design  We have analysed exons 7–19 and 21 in one index patient from each family using DNA sequencing.

Patients  Twenty‐eight subjects from both families were clinically assessed and subsequently molecularly analysed for the presence of RET gene mutations.

Results  We have found the mutation c.1597G→T (Gly533Cys) in two Greek families with FMTC. The mutation was detected in all seven MTC patients of both families as well as in 13 asymptomatic relatives in the heterozygote state, although one of the patients was also a homozygote due to consanguinity. The mutation shows a wide clinical heterogeneity, as there are carrier patients with age of diagnosis ranging from 23 to 88 years.

Conclusions  It is likely that this mutation causes FMTC, as no other mutation was found in the RET gene, the mutation co‐segregates with FMTC, and family members without the mutation are clinically unaffected. As the same point mutation was previously found in a large Brazilian family, it may be present in other populations as well. Therefore, exon 8 of RET should be screened in FMTC families with no identified common RET mutations.
E‐learning for healthcare students: developing the communities of practice framework
Authors: Moule Pam
Published: April 2006

Aim.  This paper presents research considering whether healthcare students were able to develop characteristics of communities of practice when engaged in an online module.

Background.  Little is known about whether the communities of practice framework can be applied to online learning, with no previous consideration of its potential use within healthcare education.

Methods.  Using a case study approach the research, completed in 2004, had two phases. A questionnaire was administered to a group of 109 healthcare students to gain information on which to base sampling for the subsequent phase. Phase 2 employed three strands of data collection: five students completed an online diary, the online interactions of seven students were captured on a discussion board and three students were interviewed. Data were analysed using a form of pattern matching.

Findings.  Students were able to develop essential elements of communities of practice: mutual engagement, joint enterprise and shared repertoire, though this was not uniformly seen. Particular issues emerged for the online community, including enabling access to the online environment to support mutual engagement. The development of trust was also threatened by difficulties of presenting identities online. Joint enterprise was hampered by the online situation, although the virtual classroom proved essential for supporting endeavour. Not all students were committed to their groups. There was some evidence of group members developing shared repertoire, as routines of group working emerged. Professional understanding and computer skills were also enhanced.

Conclusion.  The framework can be applied to supporting online learning internationally amongst students and has applicability to professional groups. Those intending to employ the framework should ensure that students can gain access to the community and have the computer skills to engage. Course design should be considered to ensure support for developing the essential components of communities of practice.
Microclimate, light adaptation and desiccation tolerance of epiphytic bryophytes in two Venezuelan cloud forests
Authors: León‐Vargas Yelitza , Engwald Stefan , Proctor Michael C. F.
Published: April 2006

Aim  Analysis of microclimate factors and physiological responses determining survival and growth of epiphytic bryophytes in the lower canopy and trunk space of north‐Andean cloud forests.

Location  Two cloud forests at 2000–2400 m in the northern Andes near Mérida, Venezuela.

Methods  Data‐logging of dry and wet‐season temperature, relative humidity (r.h.) and photosynthetically‐active radiation (PAR) for month‐long periods, and laboratory measurements of desiccation tolerance and light responses of selected epiphytic bryophytes.

Results  Rainfall averages 20 mm or less in January and February, and 200 mm or more from August to October, but is very variable at all seasons. The proportion of time ‘wet’ (continuous 100% r.h.) in the months sampled ranged from 8.5% to 52.2% or more; a dry/wet‐season range between 20% and 40% is probably commoner. The length of ‘wet’ and ‘dry’ periods approximated log‐normal distributions, with mid‐points for wet periods ranging from 2.8 to 10.7 h, and dry periods from 6.2 to 17.1 h. The longest recorded dry period was 143 h. Humidity typically rose during the night to > 90% r.h., reaching 100% for significant periods (implying cloudwater (fog) deposition) on about one night in two in all seasons. Of six bryophytes of pendulous growth form, all survived periods of at least a few days’ desiccation; most recovered better from high than low humidities. Measured 95% light‐saturation values ranged from 110 to 256 μmol m−2 s−1, somewhat but not greatly higher than ambient light levels

Main conclusions  Environmental conditions in the cloud forests are probably near‐optimal for epiphytic bryophytes, but in even the wettest forest these plants must tolerate at least short periods of drying at any time of year, and longer periods seasonally. Interception of cloudwater droplets from moving air is likely to be an important source of water for bryophytes of pendant and other diffuse life forms, especially in periods of low rainfall. Absorption of water from near‐saturated air is probably of little physiological significance. Bryophytes of these life‐forms are notably conspicuous in tropical‐montane cloud forests. They remain prominent into humid temperate regions such as southern Chile, New Zealand and Macaronesia, but progressively disappear at higher latitudes with the stresses of increasing seasonality.
Dependence of Hyperpolarisation‐Activated Cyclic Nucleotide‐Gated Channel Activity on Basal Cyclic Adenosine Monophosphate Production in Spontaneously Firing GH3 Cells
Authors: Kretschmannova K. , Gonzalez‐Iglesias A. E. , Tomić M. , Stojilkovic S. S.
Published: April 2006

The hyperpolarisation‐activated cyclic nucleotide‐gated (HCN) channels play a distinct role in the control of membrane excitability in spontaneously active cardiac and neuronal cells. Here, we studied the expression and role of HCN channels in pacemaking activity, Ca2+ signalling, and prolactin secretion in GH3 immortalised pituitary cells. Reverse transcriptase‐polymerase chain reaction analysis revealed the presence of mRNA transcripts for HCN2, HCN3 and HCN4 subunits in these cells. A hyperpolarisation of the membrane potential below − 60 mV elicited a slowly activating voltage‐dependent inward current (Ih) in the majority of tested cells, with a half‐maximal activation voltage of −89.9 ± 4.2 mV and with a time constant of 1.4 ± 0.2 s at −120 mV. The bath application of 1 mM Cs+, a commonly used inorganic blocker of Ih, and 100 µM ZD7288, a specific organic blocker of Ih, inhibited Ih by 90 ± 4.1% and 84.3 ± 1.8%, respectively. Receptor‐ and nonreceptor‐mediated activation of adenylyl and soluble guanylyl cyclase and the addition of a membrane permeable cyclic adenosine monophosphate (cAMP) analogue, 8‐Br‐cAMP, did not affect Ih. Inhibition of basal adenylyl cyclase activity, but not basal soluble guanylyl cyclase activity, led to a reduction in the peak amplitude and a leftward shift in the activation curve of Ih by 23.7 mV. The inhibition of the current was reversed by stimulation of adenylyl cyclase with forskolin and by the addition of 8‐Br‐cAMP, but not 8‐Br‐cGMP. Application of Cs+ had no significant effect on the resting membrane potential or electrical activity, whereas ZD7288 exhibited complex and Ih‐independent effects on spontaneous electrical activity, Ca2+ signalling, and prolactin release. These results indicate that HCN channels in GH3 cells are under tonic activation by basal level of cAMP and are not critical for spontaneous firing of action potentials.
Phylogeny of the subgenus Culicoides and related species in Italy, inferred from internal transcribed spacer 2 ribosomal DNA sequences
Authors: Gomulski L. M. , Meiswinkel R. , Delécolle J.‐C. , Goffredo M. , Gasperi G.
Published: April 2006

Abstract.  Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) include vectors for the economically important animal diseases, bluetongue (BT) and African horse sickness (AHS). In the Mediterranean Basin, these diseases are transmitted by four species of Culicoides: the first three belong in the subgenus Avaritia Fox and are Culicoides imicola Kieffer, Culicoides obsoletus (Meigen) and Culicoides scoticus Downes and Kettle; the fourth is Culicoides pulicaris (Linnaeus) in the subgenus Culicoides Latreille. In the Palaearctic Region, this subgenus (usually referred to as the C. pulicaris group) now includes a loose miscellany of some 50 taxa. The lack of clarity surrounding its taxonomy stimulated the present morphological and molecular study of 11 species collected in Italy. Phylogenetic analysis of nuclear ribosomal DNA internal transcribed spacer 2 (ITS2) sequence variation demonstrated a high degree of divergence. These results, combined with those from a parallel morphological study, disclosed: (1) that some previously described taxa should be resurrected from synonymy; (2) that there are new species to be described; (3) that the subgenus Culicoides (as currently employed) is a polyphyletic assemblage of four lineages – the subgenus Culicoides sensu stricto, the subgenus Silvicola Mirzaeva and Isaev, the subgenus Hoffmania Fox and the hitherto unrecognized Fagineus species complex. Each is discussed briefly (but not defined) and its constituent Palaearctic taxa listed. Strong congruence between morphological and molecular data holds promise for resolving many of the difficult taxonomic issues plaguing the accurate identification of vector Culicoides around the world.
Role of FNR and FNR‐regulated, sugar fermentation genes in Neisseria meningitidis infection
Authors: Bartolini Erika , Frigimelica Elisabetta , Giovinazzi Serena , Galli Giuliano , Shaik Yazdani , Genco Caroline , Welsch Jo Anne , Granoff Dan M. , Grandi Guido , Grifantini Renata
Published: April 2006

While it is generally accepted that anaerobic metabolism is required during infection, supporting experimental data have only been described in a limited number of studies. To provide additional evidence on the role of anaerobic metabolism in bacterial pathogens while invading mammalian hosts, we analysed the effect of the inactivation of FNR, the major regulatory protein involved in the adaptation to oxygen restrictive conditions, and of two of the FNR‐regulated genes on the survival of Neisseria meningitidis serogroup B (MenB) in vivo. We found that fnr deletion resulted in more than 1 log reduction in the meningococcal capacity to proliferate both in infant rats and in mice. To identify which of the FNR‐regulated genes were responsible for this attenuated phenotype, we defined the FNR regulon by combining DNA microarray analysis and FNR–DNA binding studies. Under oxygen‐restricted conditions, FNR positively controlled the transcription of nine transcriptional units, the most upregulated of which were the two operons NMB0388‐galM and mapA‐pgmβ implicated in sugar metabolism and fermentation. When galM and mapA were knocked out, the mutants were attenuated by 2 and 3 logs respectively. As the operons are controlled by FNR, from these data we conclude that MenB survival in the host anatomical sites where oxygen is limiting is supported by sugar fermentation.
Primary glioma spheroids maintain tumourogenicity and essential phenotypic traits after cryopreservation
Authors: Sundlisæter E. , Wang J. , Sakariassen P. Ø. , Marie M. , Mathisen J. R. , Karlsen B. O. , Prestegarden L. , Skaftnesmo K. O. , Bjerkvig R. , Enger P. Ø.
Published: April 2006

Tumour spheroids initiated from glioma biopsy specimens provide a valuable three‐dimensional cell culture system that share several biological features of malignant brain tumours in situ. Upon xenotransplantation in immunodeficient rats, tumours derived from such spheroids exhibit a highly infiltrative growth. Successful cryopreservation of spheroid specimens therefore represents an excellent tool for future comparative studies of tumour growth and progression. Thus, if frozen stocks of human glioma spheroids can be established, similar to those obtained from cancer cell lines, it would ease the planning of biopsy‐based experiments. In this context, it is crucial that cryopreservation does not alter the biological behaviour of the tumour spheroids. The biopsy spheroids were frozen to −40°C, stored for 1 week at −196°C, thawed rapidly and cultured for 1 week. The viability of the spheroids was compared against controls using a two‐colour fluorescence assay, which demonstrated that cryopreservation was well tolerated. Using an in vitro invasion assay, it is shown that the freezing procedures did not affect the spheroids ability to invade a collagen gel. Cryopreserved and control tumour spheroids were equally tumourogenic, and produced overlapping survival curves when transplanted into the brains of immunocompromised rats. Immunohistochemical analyses showed no significant changes regarding microvessel density or proliferation index. Furthermore, gene expression profiling using a macroarray system detected no significant changes following cryopreservation. The present data show that cryopreservation is well tolerated, and represent a methodologically reliable storage method for biopsy spheroids that can be used in experimental studies at later time points.
The CBF1‐dependent low temperature signalling pathway, regulon and increase in freeze tolerance are conserved in Populus spp.
Authors: BENEDICT CATHERINE , SKINNER JEFFREY S. , MENG RENGONG , CHANG YONGJIAN , BHALERAO RISHIKESH , HUNER NORMAN P. A. , FINN CHAD E. , CHEN TONY H. H. , HURRY VAUGHAN
Published: April 2006

The meristematic tissues of temperate woody perennials must acclimate to freezing temperatures to survive the winter and resume growth the following year. To determine whether the C‐repeat binding factor (CBF) family of transcription factors contributing to this process in annual herbaceous species also functions in woody perennials, we investigated the changes in phenotype and transcript profile of transgenic Populus constitutively expressing CBF1 from Arabidopsis (AtCBF1). Ectopic expression of AtCBF1 was sufficient to significantly increase the freezing tolerance of non‐acclimated leaves and stems relative to wild‐type plants. cDNA microarray experiments identified genes up‐regulated by ectopic AtCBF1 expression in Populus, demonstrated a strong conservation of the CBF regulon between Populus and Arabidopsis and identified differences between leaf and stem regulons. We studied the induction kinetics and tissue specificity of four CBF paralogues identified from the Populus balsamifera subsp. trichocarpa genome sequence (PtCBFs). All four PtCBFs are cold‐inducible in leaves, but only PtCBF1 and PtCBF3 show significant induction in stems. Our results suggest that the central role played by the CBF family of transcriptional activators in cold acclimation of Arabidopsis has been maintained in Populus. However, the differential expression of the PtCBFs and differing clusters of CBF‐responsive genes in annual (leaf) and perennial (stem) tissues suggest that the perennial‐driven evolution of winter dormancy may have given rise to specific roles for these ‘master‐switches’ in the different annual and perennial tissues of woody species.
Exogenous supply of glutamine and active cytokinin to the roots reduces NO3–uptake rates in poplar
Authors: DLUZNIEWSKA PAULINA , GESSLER ARTHUR , KOPRIVA STANISLAV , STRNAD MIROSLAV , NOVÁK ONDŘEJ , DIETRICH HENRIETTE , RENNENBERG HEINZ
Published: April 2006

The present study shows for the first time the influence of exogenously applied amino acids and cytokinin on the physiological and molecular aspects of N metabolism in poplar trees. In a short‐term feeding experiment, glutamine ortrans‐zeatin riboside (tZR) was added directly to the nutrient solution. NO3–net uptake declined significantly in response to both treatments. Feeding with glutamine brought about an increase in concentrations of different amino compounds in the roots (glutamine, glutamate, alanine,γ‐amino butyric acid (GABA) and NH4+, which negatively correlated with the net NO3–uptake. The plants showed a reduction of cytosolic glutamine synthetase 1 (GS1) transcript level in the roots. In addition, glutamine feeding changed the root‐to‐shoot distribution on N assimilation in favour of the leaves and plant internal N cycling.tZR treatment resulted in expansion of zeatin‐type (Z‐type) cytokinins in the roots and increased nitrate reductase (NR)–mRNA level. The results indicate that both particular amino acids and active cytokinins are involved in the feedback regulation of N uptake and metabolism in poplar. We propose that inhibition of N uptake by cytokinins in poplar is more complex than that mediated by amino compounds, and other effectors are involved in this regulation.
Fusarium confers protection against several mycelial pathogens of pepper plants
Authors: Díaz J. , Silvar C. , Varela M. M. , Bernal A. , Merino F.
Published: April 2006

Inoculation of nonhost pepper (Capsicum annuum) plants with the tomato wilt pathogen, Fusarium oxysporum f.sp. lycopersici (FOL), caused no symptoms and the fungus was not recovered from any part of the plant. FOL, however, partially protected pepper plants from subsequent infection with Phytophthora capsici, Verticillium dahliae or Botrytis cinerea by significantly reducing the percentage of diseased plants and the appearance and intensity of symptoms. FOL did not inhibit the mycelial growth of these pathogens in vitro. The protection induced by FOL against Botrytis was inhibited by 1‐methylcyclopropene (MCP), an inhibitor of ethylene perception, suggesting the involvement of this hormone in the signalling of FOL‐induced resistance. The activities of β‐1,3‐glucanase and peroxidase 48 h after FOL induction were similar to those in control plants. Chitinase activity, however, was higher in the stems of plants inoculated with FOL. A study of the levels of phenolic compounds revealed that cell‐wall‐bound phenolics were more abundant in plants treated with FOL, especially in stems, while soluble phenolic contents did not differ.
Two‐hybrid protein–protein interaction analysis in Arabidopsis protoplasts: establishment of a heterodimerization map of group C and group S bZIP transcription factors
Authors: Ehlert Andrea , Weltmeier Fridtjof , Wang Xuan , Mayer Caroline S. , Smeekens Sjef , Vicente‐Carbajosa Jesús , Dröge‐Laser Wolfgang
Published: April 2006

In vivo protein–protein interactions are frequently studied by means of yeast two‐hybrid analysis. However, interactions detected in yeast might differ considerably in the plant system. Based on GAL4 DNA‐binding (BD) and activation domains (AD) we established an Arabidopsis protoplast two‐hybrid (P2H) system. The use of Gateway®‐compatible vectors enables the high‐throughput screening of protein–protein interactions in plant cells. The efficiency of the system was tested by examining the homo‐ and heterodimerization properties of basic leucine zipper (bZIP) transcription factors. A comprehensive heterodimerization matrix of Arabidopsis thaliana group C and group S bZIP transcription factors was generated by comparing the results of yeast and protoplast two‐hybrid experiments. Surprisingly, almost no homodimerization but rather specific and selective heterodimerization was detected. Heterodimers were preferentially formed between group C members (AtbZIP9, ‐10, ‐25, ‐63) and members of group S1 (AtbZIP1, ‐2, ‐11, ‐44, ‐53). In addition, significant but low‐affinity interactions were detected inside group S1, S2 or C AtbZIPs, respectively. As a quantitative approach, P2H identified weak heterodimerization events which were not detected in the yeast system. Thus, in addition to cell biological techniques, P2H is a valuable tool for studying protein–protein interaction in living plant cells.
Highly salted food and mountain herbs elevate the risk for stomach cancer death in a rural area of Japan
Authors: Kurosawa Michiko , Kikuchi Shogo , Xu Jun , Inaba Yutaka
Published: April 2006

Background:  Although many case–control and experimental studies have shown that highly salted foods are risk factors for stomach cancer, only a few cohort studies have supported the relationship.

Methods:  In a cohort study conducted in a rural area of Japan, 8035 residents aged over 30 years (approx. 55% were female) filled out a questionnaire. Seventy‐six of them died from stomach cancer during an 11‐year follow‐up period. In the questionnaire, intake frequencies of 29 food items, smoking and drinking habits were investigated. Tsukemono (pickled vegetables) and tsukudani (foods deep boiled in soy sauce) are highly salted foods in the area. Frequency of each food item intake was classified into three levels, and age‐ and sex‐adjusted risks were calculated using proportional hazard models.

Results:  In the final model obtained by backward elimination, frequent intake of tsukemono and tsukudani and that of mountain herbs remained as significant risk factors. Compared with the least frequent intake, risk (95% confidence interval) of the most frequent intake was 5.4 (1.8–16.3) for highly salted foods (P for trend < 0.01) and 3.7 (1.4–9.6) for mountain herbs (P for trend = 0.04).

Conclusion:  Highly salted foods and mountain herbs were important risk factors for death from stomach cancer.
Combinations containing amoxicillin–clavulanate and tetracycline are inappropriate for Helicobacter pylori eradication despite high in vitro susceptibility
Authors: Cheon Jae Hee , Kim Sang Gyun , Kim Jung Mogg , Kim Nayoung , Lee Dong Ho , Kim Joo Sung , Jung Hyun Chae , Song In Sung
Published: April 2006

Background:  The purpose of the present paper was to evaluate the efficacy and tolerability of amoxicillin–clavulanate and tetracycline‐based quadruple therapy as an alternative second‐line treatment for H. pylori infection.

Methods:  The study subjects consisted of 54 patients infected with H. pylori, in whom initial triple therapy had failed. Subjects were randomized to receive the following 7‐day therapies: (i) pantoprazole 40 mg b.i.d., tripotassium dicitrate bismuthate 300 mg q.i.d., amoxicillin–clavulanate 1000 mg b.i.d., and tetracycline 500 mg q.i.d. (PBAT); or (ii) pantoprazole 40 mg b.i.d., tripotassium dicitrate bismuthate 300 mg q.i.d., metronidazole 500 mg t.i.d., and tetracycline 500 mg q.i.d. (PBMT). Eradication rates based on antibiotic susceptibility, drug compliance and side‐effect rates were evaluated and compared.

Results:  The H. pylori eradication rates were 16.0%/17.4% with PBAT and 65.5%/70.4% with PBMT by intention‐to‐treat (P < 0.001) and per‐protocol analyses (P < 0.001), respectively. In patients who received PBAT, the eradication rates were only 16.7% (2/12) for both amoxicillin and tetracycline‐susceptible H. pylori strains. Drug compliance and side‐effect rates were similar in the two groups.

Conclusions:  Despite high individual in vitro antimicrobial activity, amoxicillin–clavulanate and tetracycline‐based quadruple therapy showed low eradication rates, which strongly suggests that it should not be considered as a therapeutic option for H. pylori eradication.
Secretion of RANTES (CCL5) and interleukin‐10 from mesenteric adipose tissue and from creeping fat in Crohn’s disease: Regulation by steroid treatment
Authors: Schäffler Andreas , Fürst Alois , Büchler Christa , Paul Gisela , Rogler Gerhard , Schölmerich Jürgen , Herfarth Hans
Published: April 2006

Background:  Creeping fat represents a characteristic feature of Crohn’s disease (CD) and adipose tissue is currently being recognized as a complex compartment secreting highly active molecules. Pro‐ or anti‐inflammatory adipose tissue‐derived secretory products (adipocytokines) might play a role in the pathogenesis of CD.

Methods:  Adipose tissue specimens were obtained from creeping fat contiguous to the involved intestine of 10 patients with CD. Mesenteric adipose tissue specimens resected in 13 patients with colon cancer (CC) and in seven patients with diverticulitis (DIV) served as controls. Three fat tissue specimens per well and n = 6–8 wells per patient were incubated ex vivo for 24 h. The release of regulated on activation, T‐cell expressed and secreted (RANTES) and interleukin (IL)‐10 into the supernatant was measured by ELISA.

Results:  Both RANTES and IL‐10 secretion could be demonstrated from total adipose tissue explants. The RANTES secretion is increased from creeping fat in CD (3691 ± 597 pg/g fat per 24 h) when compared to mesenteric adipose tissue from patients with CC (1690 ± 191 pg/g fat per 24 h; P < 0.0001) or DIV (1672 ± 336 pg/g fat per 24 h; P < 0.0001). In contrast, IL‐10 secretion is downregulated significantly only in patients with DIV (1418 ± 180 pg/g fat per 24 h; P = 0.016) when compared to CC patients (2368 ± 259 pg/g fat per 24 h). Crohn’s disease patients receiving steroids had a higher secretion rate of RANTES and IL‐10.

Conclusions:  Both RANTES and IL‐10 secretion can be detected from mesenteric adipose tissue and from creeping fat. The elevated RANTES and IL‐10 secretion from creeping fat in CD is not due to a CD‐specific effect but caused by steroid treatment.
Oxidative stress in experimental liver microvesicular steatosis: Role of mitochondria and peroxisomes
Authors: Natarajan Sathish Kumar , Eapen Chundamannil E , Pullimood Anna B , Balasubramanian Kunissery A
Published: April 2006

Background: Hepatic microvesicular steatosis is a clinical manifestation seen in a number of liver diseases. Although the role of mitochondrial β‐oxidation in the development of the disease has been well studied, information on lipid peroxidative damage in liver subcellular organelles is scarce. The present study looked at oxidative stress in hepatic peroxisomes and microsomes in microvesicular steatosis, using an animal model of the disease.

Methods: Rats were given i.p. injections of sodium valproate (700 mg/kg bodyweight) to induce microvesicular steatosis, which was confirmed by histology.

Results: Oxidative stress was evident in liver in steatosis, accompanied by structural and functional alterations in hepatic mitochondria. Alterations in lipid composition, with decreased phosphatidyl choline and ethanolamine and increased lysophosphatidyl choline and ethanolamine, were seen. An increase in triglyceride content was also seen. In addition, increased lipid peroxidation was also evident in peroxisomes and microsomes from steatotic rats. Pretreatment with clofibrate results in partial reversal of changes produced by valproate.

Conclusions: These results suggest that in addition to impaired mitochondrial β‐oxidation, oxidative stress is also seen in the hepatic peroxisomes and microsomes during microvesicular steatosis.