bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of characteristics for calculating ionospheric electrodynamics from multisatellite and ground‐based radar data
Authors: Amm O.
Published: October 2003

Multisatellite missions like the recently launched Cluster II spacecraft provide for the first time the possibility to instantaneously obtain spatially distributed measurements of field‐aligned currents (FAC). We present the “FAC‐based method of characteristics” that combines such measurements mapped to the ionosphere with two‐dimensional data of the ionospheric electric field, as it can be obtained from coherent scatter radars, to calculate distributions of ionospheric conductances and actual (not equivalent) currents, given an estimate of the Hall to Pedersen conductance ratio. The applicability of the method is demonstrated for a passage of the Cluster II spacecraft over the MIRACLE network of ground‐based instruments in northern Fennoscandia on 1 February 2001, using preliminary but realistic orbit parameters. The geophysical situation of ionospheric electrodynamic parameters that we model during this passage refers to a real event of a plasma vortex propagating eastwards over the MIRACLE field of view, as studied by Kosch et al. [2000]. The application of the method of characteristics on the simulated radar and satellite measurements calculated from this model shows that the modeled Hall and Pedersen conductances, as well as the ionospheric currents, can be reconstructed by the method to good accuracy.
Reconnection onset in the tail of Earth's magnetosphere
Authors: Sitnov M. I. , Sharma A. S. , Guzdar P. N. , Yoon P. H.
Published: October 2003

We present the nonlocal kinetic linear stability analysis of the self‐consistent isotropic collisionless plasma equilibrium with strongly stretched magnetic field lines (the so‐called modified Harris sheet) with respect to the tearing mode, which provides the onset of laminar reconnection in the system. The stability problem is solved using the finite element technique and the drift‐kinetic description for the electron species with additional averaging over the bounce motion of the trapped electrons. The mode is found unstable for ion‐to‐electron temperature ratios typical for the tail current sheet of Earth's magnetosphere when this sheet is sufficiently long, so that the electrons leaving it may be treated as transient particles. Comparison of the theory with earlier fluid modeling shows that the onset of reconnection is controlled by the Hall effect and a purely kinetic effect arising from different responses of the trapped and transient electrons. Geophysical implications such as the formation of the near‐Earth neutral line and thin current sheets during substorms are discussed.
Radar observation of kinetic effects at meter scales for Farley‐Buneman plasma waves
Authors: Haldoupis Christos , Schlegel Kristian , Hussey Glenn C. , Koehler James A.
Published: October 2003

Coherent backscatter Doppler measurements, made simultaneously at 144 MHz and 50 MHz from a common volume in the midlatitude E region ionosphere, were analyzed in order to study the phase velocity ratio of type 1 plasma irregularities at 1 m and 3 m wavelengths. In the analysis, high‐resolution Doppler spectrograms were used first to identify the type 1 events and then to estimate the mean and spectral peak velocities from averaged power Doppler spectra. The simultaneous spectrogram signatures of type 1 echoes suggested a somewhat higher threshold for instability excitation at 144 MHz than at 50 MHz. Statistically, the measured 144 MHz to 50 MHz velocity ratios attain values above unity, mostly in the range from 1.05 to 1.14 with an overall average of 1.10. This 10% difference in the type 1 velocities at 144 MHz and 50 MHz was attributed to kinetic effects at short plasma wavelengths. For comparison, a linear kinetic model of the Farley‐Buneman instability, which includes also a destabilizing plasma density gradient, was used to provide numerical estimates of type 1 phase velocities. It was found that the theoretical predictions for gradient‐free Farley‐Buneman waves agreed well with the observations, under the suppositions that the strongest type 1 echoes come from E region altitudes where conditions for instability are optimal and that type 1 waves have their phase velocities limited at threshold values equal to the plasma ion acoustic speed. The present study has confirmed the accuracy of the kinetic theory of the Farley‐Buneman instability, which strengthens its validity and suitability for meter‐scale E region irregularity studies.
Global hybrid simulation of the Kelvin–Helmholtz instability at the Venus ionopause
Authors: Terada N. , Machida S. , Shinagawa H.
Published: October 2003

The Kelvin–Helmholtz (K‐H) instability at the Venus ionopause is investigated using a two‐dimensional global hybrid (particle ions, massless fluid electrons) model for the case where the interplanetary field is oriented transverse to the flow. In order to self‐consistently study the kinetic processes at the Venus ionopause, we calculate the entire Venus ionopause–solar wind interaction region kinetically, including the ionosphere, ionopause transition layer, magnetosheath, and solar wind regions, by applying boundary‐fitted coordinates to the particle‐in‐cell code. Calculations are done for the unmagnetized ionospheric condition. It is found that the distribution of ionopause surface waves generated by the K‐H instability exhibits a clear asymmetry between hemispheres of upward and downward solar wind motional electric fields. In the hemisphere where the motional electric field points away from the ionosphere, our two‐dimensional model observes the development of the instability from the subsolar location, where the Venus ionopause has been thought to be stable due to small velocity shear and stabilizing effects such as gravity stabilization. Ionospheric filaments (streamers) are highly elongated in this hemisphere, and perturbations on the scale of the planetary radius are observed at the flank of the ionotail. In the opposite hemisphere, the instability develops only in a limited region between solar zenith angles (SZA) of ∼40° and 90°, and the surface of the ionotail appears rather smooth except for some special cases. The wavelength of the dominant mode is very long (2000–3000 km) in this hemisphere due to the finite Larmor radius (FLR) stabilizing effect. We show that the process operating at the ionopause is not a localized one but is important for the dynamics of the ionosphere and other regions. The asymmetrical momentum transport across the ionopause yields an asymmetrical convection pattern of the ionosphere. Our model also shows the dynamic nature of the interaction. The dynamic ion removal process associated with the K‐H instability is found to play a significant role in the ion escape from the planet (O+ removal rate of approximately several times 1025 particles per second).
Simultaneous middle and upper atmosphere radar and ionospheric sounder observations of midlatitude E region irregularities and sporadic E layer
Authors: Ogawa T. , Takahashi O. , Otsuka Y. , Nozaki K. , Yamamoto M. , Kita K.
Published: October 2003

We made middle and upper atmosphere (MU) radar observations of midlatitude E region field‐aligned irregularities (FAIs) in the summer of 1999 and 2000. Sporadic E (Es) layer was monitored with a routine ionosonde, and its altitude was measured with an FM‐CW sounder (FCS). In this paper we draw attention to two findings. First, we show that quasiperiodic (QP) radar echoes appearing before 0200 LT are more enhanced with increasing foEs − fbEs, which means that the FAI generation is closely related to localized density gradients within Es, and extend from 100 to 130 km in altitude, while Es altitudes determined from the FCS soundings are between 100 and 110 km. The latter fact suggests that existing models for the QP echo generation, which require a deep modulation of Es altitude, are not applicable to our observational results. We propose a new working model for generating QP echoes in which polarization electric fields originated from high‐density plasma clouds within Es are mapped upward along the geomagnetic field to produce relatively weak irregularities above the Es layer. Second, we show new findings obtained from the current observations, namely, two types of QP echoes that occur below 100 km in the morning: one is the morning QP (MQP) echoes with periods of 4‐8 min, and the other is the QP echoes with periods of ∼1 min. The latter type can be categorized as low‐altitude QP echoes that were found from previous nighttime MU radar observations. Until now the MU radar QP echoes have been believed to occur above 100 km for the period from sunset to midnight. Although we do not know the generation mechanisms of the low‐altitude MQP echoes, we suppose that these echoes might be caused by a weak Es that exists below 100 km.
Evidence for tidal triggering of earthquakes as revealed from statistical analysis of global data
Authors: Tanaka Sachiko , Ohtake Masakazu , Sato Haruo
Published: October 2003

We observe tidal triggering of earthquakes by measuring the correlation between the Earth tide and earthquake occurrence. We used the times, locations, and focal mechanisms of the 9350 globally distributed earthquakes with magnitude 5.5 or larger from the Harvard centroid moment tensor catalog. The tidal stress was theoretically computed by using the Preliminary Reference Earth Model and a recent ocean tide model, NAO.99b. We considered the shear stress on the fault plane and the trace of stress tensor, J1. Defining the tidal phase angle at the occurrence time for each earthquake, we statistically tested the phase selectivity using the Schuster's method. For all the earthquakes, no significant correlation is found between the Earth tide and earthquake occurrence both for the shear stress and for J1. By classifying the data set according to fault types, however, we find a high correlation with the shear stress for reverse fault type. The correlation is particularly clear for shallow and smaller earthquakes of this type. Significant correlation with J1 also appears for larger earthquakes of reverse fault type and for shallow and larger ones of normal fault type. We find no correlation for strike‐slip type. For all the cases of high correlation, earthquakes tend to occur when the tidal stress accelerates the fault slip, indicating that high correlation is not coincidental but is physically justified. This result strongly suggests that a small stress change due to the Earth tide encourages earthquake occurrence when the stress in the future focal area is near a critical condition.
Global distribution and dynamics of colored dissolved and detrital organic materials
Authors: Siegel D. A. , Maritorena S. , Nelson N. B. , Hansell D. A. , Lorenzi‐Kayser M.
Published: October 2003

Colored dissolved organic matter (CDOM), also referred to as gelbstoff, gilvin, or yellow matter, has long been known to be an important component of the optical properties of coastal and estuarine environments. However, an understanding of the processes regulating its global distribution and variability, its relationship to the total pool of dissolved organic carbon (DOC), and its influence on light availability remain largely unexplored. Satellite imagery from the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) is used to characterize the global distribution of light absorption due to colored detrital and dissolved materials (CDM). The quantity CDM is considered as it is not yet possible to differentiate CDOM and detrital particulate absorption from ocean color spectra on a routine basis. Nonetheless, analysis of an extensive field data set indicates that detrital particulates make only a small contribution to CDM. A comparison of coincident field observations of CDM with SeaWiFS retrievals shows good agreement, indicating that the present procedures perform well. To first order, the basin‐scale CDM distribution reflects patterns of wind‐driven vertical circulation of the gyres modulated by a meridional trend of increasing CDM toward higher latitudes. The global CDM distribution appears regulated by a coupling of biological, photochemical, and physical oceanographic processes all acting on a local scale, and greater than 50% of blue light absorption is controlled by CDM. Significant differences in both CDM concentration and its contribution to blue light absorption are found spatially among the major ocean basins and temporally on variety of timescales. Significant impacts of riverine discharges can be discerned, although their effects are largely localized. Basin‐scale distributions of CDM and DOC are largely unrelated, indicating that CDM is a small and highly variable fraction of the global DOC pool. This first view of the global CDM distribution opens many new doors for the quantification of global marine photoprocesses using satellite ocean color data.
Fracture roughness and gouge distribution of a granite shear band
Authors: Amitrano David , Schmittbuhl Jean
Published: October 2003

Localization of deformation during fracture mechanical tests leads to the development of shear bands. We performed triaxial tests using Sidobre granite at four different confining pressures (from 20 to 80 MPa). We compared two sets of tests: one set was stopped immediately after the formation of the shear band; a second one included additional shear deformation. From the analysis of thin sections of these laboratory samples, we characterize the typical microstructures in the shear band (mode I and II cracks, Riedel cracks, cataclastic flow). Statistical properties of rupture surface roughness and gouge grain size reveals scaling invariance. Using a mechanical profiler, the fracture roughness is measured along parallel profiles and shown to be correctly described over up to 3 orders of magnitude by self‐affine geometry with a roughness exponent close to ζ = 0.80. This property is very similar to tensile crack even if local processes are different. The influence of the slip is observed. Fracture surfaces are rougher along the slip direction (ζ = 0.74) than perpendicular to it (ζ* = 0.80). The confining pressure is shown to have a weak effect on the fracture roughness. It smoothes the surface: slight increase of the roughness exponent. Gouge particles extracted from the shear band present a power law distribution with an exponent ranging from 1.44 to 1.91. This exponent appears to increase with the shearing displacement and the confining pressure. When a significant shear of the band is combined with a high confining pressure (i.e., impeded dilation of the band), the hallmark of fragmentation is observed for the particle distribution and related to a smoothing of the band boundary.
An in‐vitro evaluation of a dental subtraction radiography system using bone chips on dried human mandibles
Authors: Rawlinson Andrew , Ellwood Roger P. , Davies Robin M.
Published: October 2003

Abstract. The aim of this in vitro study was to evaluate the ability of digital subtraction radiography to detect small differences in bone density between 2 dental images captured with the DigoraA radiographic imaging system. 5 dried human mandibles were held in a fixed position and cortical bone chips were superimposed on the alveolar bone between the 1st molar and 2nd premolar teeth. For each mandible, a reference image was obtained without bone chip placement. Subsequently, another image without a bone chip and a series of 10 images with bone chips ranging from 1.2 to 35.3 mg, were recorded. Each of the initial images of the 5 mandibles was then compared to the 11 subsequent images using digital subtraction radiography. The difference in density between the 2 images, at the site between the 1st molar and 2nd premolar, was calculated and represented as a volume equivalent of aluminium. Regression analysis demonstrated a close relationship between the weight of the bone chips and the aluminium equivalent density difference between the 2 radiographs (r2=0.96). Good results were obtained with the smaller bone chips that more closely resembled the dimensions of bone changes likely to be of clinical interest (1–8 mg). It is concluded that this subtraction radiography system is suitable for clinical investigations of localised small changes in alveolar bone and for the diagnosis and monitoring of destructive forms of periodontal diseases.
Relationship between periodontal pocket sulfide levels and subgingival species
Authors: Torresyap G. , Haffajee A. D. , Uzel N. G. , Socransky S. S.
Published: October 2003

Background: Many species implicated in the pathogenesis of periodontal disease produce volatile sulfur compounds (VSC). This investigation examined the relationship between levels of sulfide and subgingival bacterial species in the same periodontal pockets.

Material and Methods: Twenty chronic periodontitis subjects were measured clinically at six sites per tooth for plaque, gingivitis, bleeding on probing, suppuration, pocket depth and attachment level. Subgingival plaque samples, taken from the mesial aspect of each tooth, were individually analyzed for their content of 40 bacterial species using checkerboard DNA–DNA hybridization. Sulfide levels were measured at the same sites using a Diamond Probe/Perio 2000 system. Clinical and microbiological data were averaged for sulfide‐positive and ‐negative sites separately in each subject and then averaged across subjects. Significance differences in clinical and microbial parameters between sulfide‐positive and ‐negative sites were sought using the Wilcoxon signed ranks test.

Results: Mean total DNA probe counts (×105, ±SEM) at sulfide‐negative and ‐positive sites were 44.0±9.9 and 65.0±13.3, respectively (p<0.01). Seventeen species were found at significantly higher levels in sulfide‐positive than ‐negative sites. These included abundant producers of VSC such as members of the genera Fusobacterium, Campylobacter, Prevotella, Treponema and Eubacterium, and Bacteriodes forsythus, Selenomonas noxia and Propionibacterium acnes. Prevotella intermedia, Bacteriodes forsythus, Prevotella nigrescens, Fusobacterium nucleatum ss vincentii and Treponema denticola exhibited the greatest difference in mean counts between sulfide‐negative and ‐positive sites. Orange and red complex species were at higher counts at shallow (<4 mm) sulfide‐positive than shallow sulfide‐negative sites. Although not statistically significant, mean clinical parameters were somewhat higher at sulfide‐positive than sulfide‐negative sites.

Conclusions: Intra‐pocket sulfide levels reflect the levels of sulfide‐producing species and may provide useful diagnostic information.
Analysis of the relationship between the severity of periodontal destruction and proteoglycan metabolism of gingiva and gingival crevicular fluid
Authors: Huri Cenk Basil , Yamalik Nermin , Kilinç Kamer , Kilinç Asuman , Etikan Ilker , Eratalay Kenan
Published: October 2003

Background: Although it is well‐described that proteoglycans (PGs) are among the major non‐collagenous components of the matrix which are degraded during periodontal diseases, the relationship between PG metabolism and seventy of periodontal breakdown, the extent of degradation of PGs together with the resulting end‐products, and the elimination pathways of these catabolic end‐products is likely to need further clarification.

Objective: The main aim of the present study was to analyze the possible impact of severity of periodontal destruction on PG metabolism of gingiva and gingival crevicular fluid (GCF).

Material and methods: For this purpose, gingiva and GCF samples obtained from patients (n=45) exhibiting sites (n=57) with moderate periodontal breakdown (MP) or severe periodontal breakdown (SP) were analyzed for PG metabolism via spectrophotometric determination of uronic acid levels. Gingiva and GCF samples were obtained from the same sites in every patient to analyze the possible relationship between uronic acid content of gingival tissue and GCF.

Results: No significant differences were found in uronic acid levels between sites with MP and SP (p>0.05). The uronic acid content of GCF and gingiva showed significant overlaps between MP and SP sites and uronic acid levels did not present any constant correlation with the clinical parameters (p>0.05). In a similar manner, uronic acid content of GCF and gingival tissue was not correlated (p>0.05).

Conclusion: The lack of a significant correlation between the uronic acid content of gingival tissue and GCF may suggest that the passage of PG metabolites from gingiva to GCF is likely to be under the influence of multifactorial interactions rather than being linear. As a general measure of PG metabolism, uronic acid levels do not seem to be related with the severity of periodontal destruction and tend to act as different measures when compared to traditional clinical parameters.
Comprehensive validation of competencies for dental vocational training and general professional training
Authors: Prescott L. , Hurst Y. , Rennie J. S.
Published: October 2003

This paper outlines a study designed to validate competencies for dental vocational training (DVT) and general professional training (GPT) in order to ensure their accuracy and acceptability. A highly inclusive approach is described whereby all trainers in Scotland were invited to participate in the exercise. The 168 individuals recruited were drawn from all branches of the dental services and all regions in Scotland. Using online or paper questionnaires, quantitative and qualitative data were collected for each competency statement over 9 months, after which focus groups discussed and decided which changes should be made. A high response rate was observed and from the 160 competencies originally identified, almost half (47.5%) were redrafted as a direct result of the validation process. Sections of the competency document that required most attention are discussed, as are the nature of changes made to the competencies. As a result of this study, a fully validated competency document for DVT and GPT has been produced and will allow a high degree of standardization of training through the provision of essential consistent information to trainers and VDPs.
Tribological testing of skin products: gender, age, and ethnicity on the volar forearm
Authors: Sivamani Raja K. , Wu Gabriel C. , Gitis Norm V. , Maibach Howard I.
Published: October 2003

Background/purpose: Few studies have focused on the simultaneous measurement of the friction and electrical properties of skin. This work investigates the feasibility of using these measurements to differentiate between the effects of chemicals commonly applied to the skin. In addition, this study also compares the condition of the skin and its response to application of chemicals across gender, ethnicity, and age at the volar forearm.

Method: Friction and electrical tests were performed on 59 healthy volunteers with the UMT Series Micro‐Tribometer (UMT). A 13‐mm‐diameter copper cylindrical friction/electrical probe was pressed onto the skin with a weight of 20 g and moved across the skin at a constant velocity of 0.4 mm/s. Each volunteer served as his or her own control. The friction and electrical impedance measurements were performed for polyvinylidene chloride occlusion and for the application of glycerin and petrolatum.

Results: No differences were found across age, gender, or ethnicity at the volar forearm. Polyvinylidene chloride (PVDC) occlusion showed a small increase in the friction and a small decrease in the electrical impedance; petrolatum increased the friction by a greater amount but its effect on the impedance was comparable to PVDC occlusion; glycerin increased the friction by an amount comparable to petrolatum, but it decreased the impedance to a much greater degree than petrolatum or the PVDC occlusion. An amplitude/mean measurement of the friction curves of glycerin and petrolatum showed that glycerin has a significantly higher amplitude/mean than petrolatum.

Conclusion: The properties of the volar forearm appear to be independent of age, gender, and ethnicity. Also, the simultaneous measurement of friction and electrical impedance was useful in differentiating between compounds administered to the skin.
Objective assessment of involved surface area in patients with psoriasis
Authors: Yune Young‐Min , Park Sang Yong , Oh Hyun Sook , Kim Dong‐Jun , Yoo Dong‐Su , Kim Il‐Hwan , Moon Jong‐Sub , Kim Min‐Ki , Oh Chil‐Hwan
Published: October 2003

Background/aims: Although difficult, it is essential to assess the disease severity of psoriasis objectively. The visual grading method currently used for assessing the involved surface area in patients with psoriasis, which is included on the Psoriasis Area and Severity Index (PASI) scoring system, is a subjective method. The aim of this study was to establish the reliable objective method, in estimating the involved surface area in patients with psoriasis.

Methods: Thirty patients with psoriasis participated in this study. The skin lesions of each patient were estimated using the visual grading method and an image analysis system.

Results: The differences between five dermatologists' estimates of the involved surface area obtained from the visual grading method were highly significant (P<0.05, Kruskal–Wallis test). The comparison between the visual grading method and the image analysis system showed that the involved areas measured by the visual grading method were significantly higher than those from the image analysis (P<0.05, Wilcoxon signed rank test).

Conclusions: The visual grading method was neither objective nor reproducible. On the other hand, the image analysis system can be used as an objective method of measuring the involved surface area of patients with psoriasis. Therefore, the image analysis system can be used as a standard for the assessment of the involved area of patients with psoriasis.
Melanoma and seborrheic keratosis differentiation using texture features
Authors: Deshabhoina Srinivas V. , Umbaugh Scott E. , Stoecker William V. , Moss Randy H. , Srinivasan Subhashini K.
Published: October 2003

Purpose: To explore texture features in two‐dimensional images to differentiate seborrheic keratosis from melanoma.

Methods: A systematic approach to consistent classification of skin tumors is described. Texture features, based on the second‐order histogram, were used to identify the features or a combination of features that could consistently differentiate a malignant skin tumor (melanoma) from a benign one (seborrheic keratosis). Two hundred and seventy‐one skin tumor images were separated into training and test sets for accuracy and consistency. Automatic induction was applied to generate classification rules. Data analysis and modeling tools were used to gain further insight into the feature space.

Result and Conclusions: In all, 85–90% of seborrheic keratosis images were correctly differentiated from the malignant skin tumors. The features correlation_average, correlation_range, texture_energy_average and texture_energy_range were found to be the most important features in differentiating seborrheic keratosis from melanoma. Over‐all, the seborrheic keratosis images were better identified by the texture features than the melanoma images.
Free fatty acids induce cell differentiation to infective forms in Trypanosoma cruzi
Authors: WAINSZELBAUM Marisa J. , BELAUNZARÁN María L. , LAMMEL Estela M. , FLORIN-CHRISTENSEN Mónica , FLORIN-CHRISTENSEN Jorge , ISOLA Elvira L. D.
Published: October 2003

Intestinal extracts of Triatoma infestans induce cell differentiation of Trypanosoma cruzi epimastigotes into the infective metacyclic form. Part of this effect can be explained by the presence of haemoglobin fragments, which stimulate trypanosomal adenylate cyclase. In this work we examined the metacyclogenic activity of lipids present in this intestinal extract. We found that lipid extracts of the intestinal extract have significant stimulatory effects that reside with the free-fatty-acid fraction, especially oleic acid. These compounds stimulate de novo diacylglycerol formation and protein kinase C activity in the parasite. Moreover, metacyclogenesis is stimulated by phorbol esters and cell-permeant diacylglycerol, while protein kinase C down-regulation or incubation with inhibitors of this kinase abrogates this effect. These results indicate that free fatty acids are a novel signal, inducing metacyclogenesis, acting through a pathway involving diacylglycerol biosynthesis and protein kinase C activation.
Interferon-γ regulates nucleoside transport systems in macrophages through signal transduction and activator of transduction factor 1 (STAT1)-dependent and -independent signalling pathways
Authors: SOLER Concepció , FELIPE Antonio , GARCÍA-MANTEIGA José , SERRA Maria , GUILLÉN-GÓMEZ Elena , CASADO F. Javier , MacLEOD Carol , MODOLELL Manuel , PASTOR-ANGLADA Marçal , CELADA Antonio
Published: October 2003

The expressions of CNT and ENT (concentrative and equilibrative nucleoside transporters) in macrophages are differentially regulated by IFN-γ (interferon-γ). This cytokine controls gene expression through STAT1-dependent and/or -independent pathways (where STAT1 stands for signal transduction and activator of transcription 1). In the present study, the role of STAT1 in the response of nucleoside transporters to IFN-γ was studied using macrophages from STAT1 knockout mice. IFN-γ triggered an inhibition of ENT1-related nucleoside transport activity through STAT1-dependent mechanisms. Such inhibition of macrophage growth and ENT1 activity by IFN-γ is required for DNA synthesis. Interestingly, IFN-γ led to an induction of the CNT1- and CNT2-related nucleoside transport activities independent of STAT1, thus ensuring the supply of extracellular nucleosides for the STAT1-independent RNA synthesis. IFN-γ up-regulated CNT2 mRNA and CNT1 protein levels and down-regulated ENT1 mRNA in both wild-type and STAT1 knockout macrophages. This is consistent with a STAT1-independent, long-term-mediated, probably transcription-dependent, regulation of nucleoside transporter genes. Moreover, STAT1-dependent post-transcriptional mechanisms are implicated in the regulation of ENT1 activity. Although nitric oxide is involved in the regulation of ENT1 activity in B-cells at a post-transcriptional level, our results show that STAT1-dependent induction of nitric oxide by IFN-γ is not implicated in the regulation of ENT1 activity in macrophages. Our results indicate that both STAT1-dependent and -independent pathways are involved in the regulation of nucleoside transporters by IFN-γ in macrophages.
Adipocyte differentiation of 3T3-L1 preadipocytes is dependent on lipoxygenase activity during the initial stages of the differentiation process
Authors: MADSEN Lise , PETERSEN Rasmus K. , SØRENSEN Morten B. , JØRGENSEN Claus , HALLENBORG Philip , PRIDAL Lone , FLECKNER Jan , AMRI Ez-Zoubir , KRIEG Peter , FURSTENBERGER Gerhard , BERGE Rolf K. , KRISTIANSEN Karsten
Published: October 2003

Adipocytes play a central role in whole-body energy homoeostasis. Complex regulatory transcriptional networks control adipogensis, with ligand-dependent activation of PPARγ (peroxisome proliferator-activated receptor γ) being a decisive factor. Yet the identity of endogenous ligands promoting adipocyte differentiation has not been established. Here we present a critical evaluation of the role of LOXs (lipoxygenases) during adipocyte differentiation of 3T3-L1 cells. We show that adipocyte differentiation of 3T3-L1 preadipocytes is inhibited by the general LOX inhibitor NDGA (nordihydroguaiaretic acid) and the 12/15-LOX selective inhibitor baicalein. Baicalein-mediated inhibition of adipocyte differentiation was rescued by administration of rosiglitazone. Treatment with baicalein during the first 4 days of the differentiation process prevented adipocyte differentiation; supplementation with rosiglitazone during the same period was sufficient to rescue adipogenesis. Accordingly, we demonstrate that adipogenic conversion of 3T3-L1 cells requires PPARγ ligands only during the first 4 days of the differentiation process. We show that the baicalein-sensitive synthesis of endogenous PPARγ ligand(s) increases rapidly upon induction of differentiation and reaches a maximum on days 3–4 of the adipocyte differentiation programme. The conventional platelet- and leucocyte-type 12(S)-LOXs and the novel eLOX-3 (epidermis-type LOX-3) are expressed in white and brown adipose tissue, whereas only eLOX-3 is clearly expressed in 3T3-L1 cells. We suggest that endogenous PPARγ ligand(s) promoting adipocyte differentiation are generated via a baicalein-sensitive pathway involving the novel eLOX-3.
Stable dimeric assembly of the second membrane-spanning domain of CFTR (cystic fibrosis transmembrane conductance regulator) reconstitutes a chloride-selective pore
Authors: RAMJEESINGH Mohabir , UGWU Francisca , LI Canhui , DHANI Sonja , HUAN Ling Jun , WANG Yanchun , BEAR Christine E.
Published: October 2003

Structural information is required to define the molecular basis for chloride conduction through CFTR (cystic fibrosis transmembrane conductance regulator). Towards this goal, we expressed MSD2, the second of the two MSDs (membrane-spanning domains) of CFTR, encompassing residues 857–1158 in Sf9 cells using the baculovirus system. In Sf9 plasma membranes, MSD2 migrates as expected for a dimer in non-dissociative PAGE, and confers the appearance of an anion permeation pathway suggesting that dimeric MSD2 mediates anion flux. To assess directly the function and quaternary structure of MSD2, we purified it from Sf9 cells by virtue of its polyhistidine tag and nickel affinity. Reconstitution of MSD2 into liposomes conferred a 4,4′-di-isothiocyanostilbene-2,2′-disulphonate-inhibitable, chloride-selective electrodiffusion pathway. Further, this activity is probably mediated directly by MSD2 as reaction of its single cysteine residue (Cys866) with the thiol modifying reagent, Nα(3-maleimidylpropionyl)biocytin, inhibited chloride flux. Only MSD2 dimers were labelled by Nα(3-maleimidylpropionyl)biocytin, supporting the idea that only dimeric MSD2 can mediate anion flux. As a further test of this hypothesis, we conducted a second purification procedure, wherein purified dimeric and monomeric MSD2 proteins were reconstituted separately. Only proteoliposomes containing stable MSD2 dimers mediated chloride electrodiffusion, providing direct evidence that dimeric MSD2 mediates chloride channel function. In summary, we have shown that the second membrane domain of CFTR can be purified and functionally reconstituted as a chloride channel, providing a tool for probing the structural basis of chloride conduction through CFTR.
Trafficking of Kv1.4 potassium channels: interdependence of a pore region determinant and a cytoplasmic C-terminal VXXSL determinant in regulating cell-surface trafficking
Authors: ZHU Jing , WATANABE Itaru , GOMEZ Barbara , THORNHILL William B.
Published: October 2003

Kv1.4 and Kv1.1 potassium channel homomers have been shown to exhibit different intracellular trafficking programmes and cell-surface expression levels in cell lines: a determinant in the pore region of Kv1.4 and Kv1.1 [Zhu, Watanabe, Gomez and Thornhill (2001) J. Biol. Chem. 276, 39419–39427] and a cytoplasmic C-terminal VXXSL determinant on Kv1.4 [Li, Takimoto and Levitan (2000) J. Biol. Chem. 275, 11597–11602] have been described, which affected trafficking and cell-surface expression levels. In the present study, we examined whether trafficking pore determinants influenced any cytoplasmic C-terminal trafficking determinant. We found that removal of VXXSL from a Kv1.4 chimaera that contained the pore of Kv1.1 did not affect cell-surface trafficking. Therefore removal of the C-terminal VXXSL of Kv1.4 inhibited protein surface levels only in the presence of the Kv1.4 pore. In contrast, truncating the cytoplasmic C-terminus of Kv1.1 or truncating a Kv1.1 chimaera with the pore of Kv1.4, had little effect on surface protein levels. Furthermore, the subregion of the Kv1.4 pore trafficking determinant that was required for the inhibitory effect of VXXSL removal was mapped to a threonine residue in the deep pore region. Therefore the Kv1.4 pore determinant affected the trafficking and cell-surface levels directed by the C-terminal VXXSL determinant. Different Kv1 trafficking programmes would affect cell-surface expression levels either positively or negatively and also cell signalling. Cells may use differential trafficking programmes of membrane proteins as a post-translational mechanism to regulate surface protein levels and cell function.
Multifaceted roles of β-arrestins in the regulation of seven-membrane-spanning receptor trafficking and signalling
Authors: SHENOY Sudha K. , LEFKOWITZ Robert J.
Published: October 2003

β-Arrestins are cytosolic proteins that bind to activated and phosphorylated G-protein-coupled receptors [7MSRs (seven-membrane-spanning receptors)] and uncouple them from G-protein-mediated second messenger signalling pathways. The binding of β-arrestins to 7MSRs also leads to new signals via activation of MAPKs (mitogen-activated protein kinases) such as JNK3 (c-Jun N-terminal kinase 3), ERK1/2 (extracellular-signal-regulated kinase 1/2) and p38 MAPKs. By binding to endocytic proteins [clathrin, AP2 (adapter protein 2), NSF (N-ethylmaleimide-sensitive fusion protein) and ARF6 (ADP-ribosylation factor 6)], β-arrestins also serve as adapters to link the receptors to the cellular trafficking machinery. Agonist-promoted ubiquitination of β-arrestins is a prerequisite for their role in receptor internalization, as well as a determinant of the differing trafficking patterns of distinct classes of receptors. Recently, β-arrestins have also been implicated as playing novel roles in cellular chemotaxis and apoptosis. By virtue of their ability to bind, in a stimulus-dependent fashion, to 7MSRs as well as to different classes of cellular proteins, β-arrestins serve as versatile adapter proteins that regulate the signalling and trafficking of the receptors.
Binding of phosphatidylinositol 3,4,5-trisphosphate to the pleckstrin homology domain of protein kinase B induces a conformational change
Authors: MILBURN Christine C. , DEAK Maria , KELLY Sharon M. , PRICE Nick C. , ALESSI Dario R. , van AALTEN Daan M. F.
Published: October 2003

Protein kinase B (PKB/Akt) is a key regulator of cell growth, proliferation and metabolism. It possesses an N-terminal pleckstrin homology (PH) domain that interacts with equal affinity with the second messengers PtdIns(3,4,5)P3 and PtdIns(3,4)P2, generated through insulin and growth factor-mediated activation of phosphoinositide 3-kinase (PI3K). The binding of PKB to PtdIns(3,4,5)P3/PtdIns(3,4)P2 recruits PKB from the cytosol to the plasma membrane and is also thought to induce a conformational change that converts PKB into a substrate that can be activated by the phosphoinositide-dependent kinase 1 (PDK1). In this study we describe two high-resolution crystal structures of the PH domain of PKBα in a noncomplexed form and compare this to a new atomic resolution (0.98 Å, where 1 Å=0.1 nm) structure of the PH domain of PKBα complexed to Ins(1,3,4,5)P4, the head group of PtdIns(3,4,5)P3. Remarkably, in contrast to all other PH domains crystallized so far, our data suggest that binding of Ins(1,3,4,5)P4 to the PH domain of PKB, induces a large conformational change. This is characterized by marked changes in certain residues making up the phosphoinositide-binding site, formation of a short α-helix in variable loop 2, and a movement of variable loop 3 away from the lipid-binding site. Solution studies with CD also provided evidence of conformational changes taking place upon binding of Ins(1,3,4,5)P4 to the PH domain of PKB. Our data provides the first structural insight into the mechanism by which the interaction of PKB with PtdIns(3,4,5)P3/PtdIns(3,4)P2 induces conformational changes that could enable PKB to be activated by PDK1.
Short-term blood pressure variability in renovascular hypertension and in severe and mild essential hypertension
Authors: MUSSALO Hanna , VANNINEN Esko , IKÄHEIMO Risto , LAITINEN Tomi , HARTIKAINEN Juha
Published: October 2003

This study was designed to examine short-term blood pressure variability (BPV) in patients with different severity and forms of chronic medically treated hypertension. Power spectral analysis of BPV was performed from continuous finger blood pressure (Finapres) recordings. Ten patients with renovascular hypertension (RVHT), 34 with severe essential hypertension (SEHT) and 29 with mild essential hypertension (MEHT) as well as healthy age- and sex-matched control subjects were studied. The RVHT group was characterized by reduced low frequency (LF) power of both systolic and diastolic BPV (P=0.004 and P=0.003 respectively) when compared with the control group. There was also a tendency to lower total power of diastolic BPV (P=0.094). On the contrary, the SEHT group had increased total power of diastolic BPV (P=0.044). However, in the SEHT group, we found no differences in the LF and high frequency power of systolic and diastolic BPV when compared with controls. The MEHT group presented with lower LF power of systolic and diastolic BPV (P=0.028 and P=0.003 respectively) and, in addition, high frequency power of diastolic BPV was lower than in the control group (P=0.020). When the hypertensive groups were compared with each other, total power and LF power of diastolic BPV (P=0.043 and P=0.039 respectively) were lower in the RVHT group than in the SEHT group. In addition, total power of diastolic BPV was lower (P=0.030) in the MEHT group than in the SEHT group. No differences were observed in BPV between the RVHT and MEHT groups. The results show that BPV in hypertensive patients groups behaved differently. This suggests that both the aetiology and severity of hypertension have a significant influence on short-term BPV measured in laboratory conditions and that different control mechanisms are operating in these clinically distinctly different hypertension groups.
Nitric oxide donors and the skin: useful therapeutic agents?
Authors: WELLER Richard
Published: October 2003

Nitric oxide (NO) is involved in several processes in the skin, including wound healing, pigmentation and regulation of apoptosis. Pharmacological intervention with NO donors appears to be a promising treatment for conditions such as diabetic ulceration. In this issue of Clinical Science, Khan et al. describe the synthesis of a number of NO donors, based on nitrosylated thiosugars, structural changes in which altered the rate of NO release. The in vivo behaviour of one of the donors was then measured by laser Doppler blood flow measurements on the skin. The ability to tailor the pharmacokinetic behaviour of these drugs should be of interest in developing NO donors for clinical use.
Can inflammatory mediators affect fibrinolysis in the pleural space?
Authors: KURDOWSKA Anna K.
Published: October 2003

The pleural space in patients with empyema and complicated parapneumonic effusions is a stage for intensive activity representing mobilization of various host responses. Release of inflammatory mediators accompanied by influx of leucocytes as well as alternations of the fibrinolytic cascade are some of the characteristic events occurring in the pleural space during infection. The possible relationship between these two systems is the subject of the article by Alemán and co-workers in this issue of Clinical Science, and is discussed in this comment.
In vitro secreted aspartyl proteinase activity of Candida albicans isolated from oral diseases and healthy oral cavities
Authors: Kuriyama T. , Williams D. W. , Lewis M. A. O.
Published: October 2003

The in vitro secreted aspartyl proteinase (SAP) activity of Candida albicans isolated from a variety of oral conditions, including healthy oral cavities, was determined. SAP activity (units/106cells/ml, ±SD) was 0.28 ± 0.33 for pseudomembranous candidosis isolates (n = 18), 0.35 ± 0.46 for chronic erythematous candidosis isolates (n = 21) and 0.30 ± 0.32 for chronic hyperplastic candidosis isolates (n = 50). SAP activity of 0.19 ± 0.22 was recorded for isolates from squamous cell carcinoma (n = 18), 0.26 ± 0.37 for burning mouth syndrome isolates (n = 29), 0.25 ± 0.38 for isolates from xerostomia (n = 15) and 0.39 ± 0.50 for isolates from lichen planus (n = 13). The SAP activity of isolates from oral disease states was significantly (P < 0.05) higher than that recorded for 28 isolates from healthy mouths (activity of 0.04 ± 0.03). However, there was no significant difference in the SAP activity between the three forms of clinical oral candidosis (P > 0.05). SAP activity was inhibited in control samples containing the SAP inhibitor, pepstatin A. These results indicate that C. albicans strains associated with oral disease have inherently higher SAP activity.
Genetic versus environmental influence on pigment variation in the ephippia ofDaphnia pulicaria
Authors: Gerrish Gretchen A. , Cáceres Carla E.
Published: October 2003

1. The dormant eggs ofDaphnia(Crustacea: cladocera) are encased in a protective, chitonous casing known as an ephippium. Ephippia are pigmented with melanin, and the degree of pigmentation ranges from transparent to opaque. Variation in pigmentation exists within and across populations and species, raising questions about the factors that influence the natural distribution of pigmentation.

2. We used image analysis to quantify pigmentation in ephippial casings ofDaphnia pulicariathat were produced both in the field and in the laboratory. The percentage of the surface area of ephippia that is darkly pigmented ranged from 0.5 to 99.5%. The range, mean and variance of ephippial pigmentation varied across our 11 study lakes.

3. Laboratory experiments compared clonal variation (five clones/lake) and population variation (five lakes) at three temperatures (15 °C, 20 °C and 25 °C). The degree of pigment variation between clones was much greater than pigment variation between temperatures, indicating that there is a genetic component to pigmentation in the ephippia which is stronger than the effect of temperature.

4. Comparisons of pigment levels and lake characteristics were used to identify physical and biological factors associated with ephippial pigmentation. Investment in ephippial production was the strongest predictor with darker ephippia occurring more often in lakes with the highest ephippial production.