bluuebunny/crossref_metadata_2025 huggingface dataset:
A new model for the prediction of Dst on the basis of the solar wind
Authors: Temerin M. , Li Xinlin
Published: October 2003

An explicit model for predicting Dst based on solar wind data for the years 1995–1999 gives a good fit with a prediction efficiency of 88%, a linear correlation coefficient between the Dst index and the model of 0.94, and a RMS error of 6.4 nT. The same model applied to the first half of 2000 gave a prediction efficiency of 91%, a linear correlation coefficient of 0.95, and a RMS error of 7.9 nT. The modeled Dst is a sum of three terms that have growth and decay, a dynamic pressure term, an interplanetary magnetic field term, and some offset terms. The main innovations are that the decay terms have different time constants ranging from 5 days to 1 hour and that all the terms except the offsets depend on the angle of the Earth's dipole with respect to the solar wind velocity. This result shows that the magnetosphere is highly predictable and that chaotic behavior within the magnetosphere has little influence on the large‐scale currents that determine Dst.
Dislocation creep of calcite
Authors: Renner Jörg , Evans Brian , Siddiqi Gunter
Published: October 2003

When the power law equation, ∝ σnexp(−Q/RT), which relates strain rate (), stress (σ), gas constant (R), and temperature (T), is used to describe thermally activated dislocation creep of calcite rocks, the stress sensitivity (n) and temperature sensitivity or apparent activation energy (Q) differ greatly from rock to rock. To better constrain parameters of a mechanical equation of state, we performed triaxial deformation experiments on dense synthetic aggregates of polycrystalline calcite at temperatures of 873–1073 K and strain rates between 5 × 10−7 and 3 × 10−3 s−1 to strains <0.20. The strength of the marbles decreases with increasing temperature or decreasing strain rate. Combining microstructure analysis with mechanical data indicates that strength decreases with increasing grain size (d) following a Hall‐Petch relation. A detailed analysis of the data revealed systematic dependence of n and Q on stress, grain size, and temperature. The variations in n and Q can be accommodated by using a Peierls law, = APσ2 exp(σ/σP)exp(−QP/RT). The resistance to glide, σP, is composed of an intrinsic Peierls stress and a grain size dependent back stress and is given by σP = (ΣP,0 + Kd−0.5)(Tm − T), where Tm denotes the melting temperature. The following parameters seem to apply to all calcite rocks: AP ≈ 10±0.5 MPa−2 s−1, QP ≈ 200 kJ/mol, ΣP,0 ≈ 7.8 MPa kK−1, and K ≈ 115 MPa kK−1 μm0.5. Under some laboratory conditions, dislocation creep may operate simultaneously with grain size sensitive diffusion creep, complicating the quantification of the individual flow laws. More accurate flow laws will need to include the evolution of microstructure in composite flow laws, perhaps requiring a statistical description of a microstructure variable yet to be specified exactly.
Postglacial rebound and Earth's viscosity structure from GRACE
Authors: Velicogna Isabella , Wahr John
Published: October 2003

The Gravity Recovery and Climate Experiment (GRACE) satellite mission was launched in March 2002 and has an expected 5‐year lifetime. One potential application of GRACE measurements of time‐variable gravity will be to isolate the postglacial rebound signal, which can then be used to estimate the Earth's viscosity structure. In this paper we present a sensitivity analysis of simulated GRACE data, designed to assess the accuracy with which those data can be used to recover a simple model of Earth viscosity. We find that without combining with any other data type, but ignoring complications caused by uncertainties in the global ice loading history, GRACE data alone would allow us to determine the viscosity of a uniform lower mantle layer and an upper mantle/transition zone layer to within ±30–40% and to estimate lithospheric thickness to within ±15–20%. GRACE will have a harder time differentiating between the separate viscosities of the transition zone and upper mantle, but accuracies of within a factor of 2 might still be achievable for those parameters. Errors in the ice loading history could significantly degrade these viscosity estimates, particularly for the transition zone and upper mantle. The accuracy of recovery of the true Earth viscosity will depend in part on how well the model parameterization used for the grid search can represent the true Earth structure. However, combining GRACE data with data from other more traditional measurements of postglacial rebound has the potential of dramatically improving viscosity estimates throughout the Earth, particularly in the lower mantle.
The turbulent kinetic energy budget in the marine atmospheric surface layer
Authors: Sjöblom Anna , Smedman Ann‐Sofi
Published: October 2003

The terms in the turbulent kinetic energy (TKE) budget have been analyzed according to stability, wave age, and wind speed, using long‐term measurements over the sea. The measurements were performed at the island Östergarnsholm in the middle of the Baltic Sea. The results show that there is an imbalance between normalized production and normalized dissipation, also in neutral conditions, and that this imbalance depends not only on stability, which has been previously suggested, but also on wave age and wind speed. For small wave ages and high wind speeds, production is larger than dissipation at neutral conditions. For saturated waves and moderate wind speeds, the sea surface resembles a land surface, while for swell and low wind speeds, dissipation strongly exceeds production. The normalized pressure transport becomes significant during swell conditions, and is not balanced by the normalized turbulent transport. “Inactive” turbulence, where energy is being brought down to the surface from higher levels, is probably the reason for these high values of the pressure transport. The traditional “inertial dissipation method,” where the sum of the transport terms is assumed small and neglected, therefore needs to be corrected for an imbalance between production and dissipation.
A laboratory investigation of Alfvén wave refraction in a parallel gradient
Authors: Mitchell C. C. , Maggs J. E. , Vincena S. T. , Gekelman W. N.
Published: October 2003

We present a laboratory investigation of Alfvén wave refraction due to a gradient in the plasma beta along the magnetic field. Theoretically, it is expected that perpendicular wave refraction occurs when the Alfvén wave changes from kinetic to inertial, as occurs along a typical auroral field line. The change in propagation characteristics is expected to produce a focusing of the wave energy. In the Earth's magnetosphere it is thought that this refractive property may play a key role in the field line resonance process. This effect is observed in the laboratory by creating a plasma with a parallel gradient of 100 per 105 Debye lengths. An Alfvén wave is then launched with an antenna, and the field patterns of the wave are observed at several axial locations.
Ion and neutral motions observed in the winter polar upper atmosphere
Authors: Heelis R. A. , McEwen D. , Guo W.
Published: October 2003

Continuous samples of the ion drift are made near 800‐km altitude from the DMSP satellite and compared with remote measurements of the F region neutral winds made from the ground at Eureka in the northern polar cap. These measurements are compared with each other and with variations in the interplanetary magnetic field and solar wind. Over a 6‐day period, linear relationships between the north‐south component of the IMF and the noon‐midnight components of the ion and neutral drifts are used to determine the response times of the gas motions to changes in the solar wind driver. When the IMF is southward or weakly northward, the ion and neutral gas response begins almost immediately following a change in the solar wind driver. The time constant for the ion response is about 20 min, while for an F peak density of about 5 × 105 cm−3 the neutral time constant is 75 min. While significant variability exists, the 55‐min time difference between the response times is consistent with the neutral‐ion collision time prevailing in the F region at the time and location of the measurements. In the quasi‐equilibrium state, antisunward ion drifts in excess of 150 m s−1 drive the neutral gas antisunward with speeds about 60% of the ion drift.
The 6.5‐day wave in the mesosphere and lower thermosphere: Evidence for baroclinic/barotropic instability
Authors: Lieberman R. S. , Riggin D. M. , Franke S. J. , Manson A. H. , Meek C. , Nakamura T. , Tsuda T. , Vincent R. A. , Reid I.
Published: October 2003

A westward propagating zonal wave number 1 wave with a period near 6.5 days was a prominent feature in the mesosphere and lower thermosphere (MLT) during the 1994 equinoxes. The meridional structure of the wave in the upper stratosphere and the MLT is consistent with the 5‐day wave structure predicted by normal mode theory. However, the amplitude increases sharply above 80 km, where the wave exhibits a highly organized baroclinic circulation. The eddy fluxes and the background state suggest that the wave is amplified by instability of the mesospheric winds.
Gyrophase‐restricted 100 keV–2 MeV ion beams near the foreshock boundary
Authors: Meziane K. , Wilber M. , Lin R. P. , Parks G. K.
Published: October 2003

We report on gyrophase‐restricted ion beams with energies extending from ∼100 keV up to ∼2 MeV, observed by Wind in the Earth's distant (∼65 RE) foreshock. The ion gyrophases seen were nearly constant during periods when the distance to the shock contact point could be expected to vary by several RE, when there was no significant wave activity. At times the distributions had two peaks ∼180° apart in gyrophase. These were consistent with a remotely‐sensed energetic ion foreshock region having a thickness <2 gyroradii (∼1.5 RE for 0.5 MeV protons with pitch‐angle α = 30°). In this picture, gaps in phase space would correspond to particles with guiding centers outside of the energetic foreshock region. Similar observations over a decade of energies (100 keV–2 MeV) suggest that the region thickness scales with gyroradius. According to this interpretation, we have determined a rough range of geometries for which energetic particle production is favored. (Eg., θBn ∼70–80° for 500 keV ions with α = 30°.)
A simple electrodynamic model of a dust devil
Authors: Farrell William M. , Delory Greg T. , Cummer Steven A. , Marshall John R.
Published: October 2003

We present an electrodynamic model of a dust devil applying a similar methodology as performed previously for charging in terrestrial thunderstorms. While thunderstorm processes focus on inductive charging between large graupel and smaller ice and water droplets, we tailor the model to focus on the electric charge transfer between dust grains of different sizes and compositions. We specifically compare and contrast the triboelectric dust charging processes presented previously in Melnik and Parrot [1998] and Desch and Cuzzi [2000] in the development of macroscopic dust devil electric fields. We find that large vertical E‐fields (∼20 kV/m) can develop in the devil.
Kimberlite from Rajmahal magmatic province: Sr‐Nd‐Pb isotopic evidence for Kerguelen plume derived magmas
Authors: Kumar Anil , Dayal A. M. , Padmakumari V. M.
Published: October 2003

Previous studies showed that the Rajmahal‐Sylhet‐Bengal (RSB) flood basalt province (117 ± 2 Ma) in eastern India was spatially close to the active Kerguelen hotspot about 118 Ma ago. Yet, it could not be unequivocally correlated to this hotspot due to wide variation in isotopic compositions of both the RSB and Kerguelen plateau basalts. However, we report Sr‐Nd‐Pb isotopic compositions (87Sr/86Sri: 0.70535 to 0.70561; εNd(T): −2.6 to −3.2; 206Pb/204Pbi: 17.88 to 18.07) of a co‐eval (116 ± 2 Ma) Group II kimberlite from this flood basalt province that is identical to recently identified pristine Kerguelen plume basalts from the Kerguelen Plateau/Archipelago and Broken Ridge. This suggests that the Kerguelen hotspot could indeed be responsible for the ∼117 Ma magmatic activity in Eastern India.
The microbiota of periodontal pockets with different depths in therapy‐resistant periodontitis
Authors: Edwardsson Stig , Bing Ma , Axtelius Björn , Lindberg Birgitta , Söderfeldt Björn , Attström Rolf
Published: October 2003

Abstract. This study presents the composition of the cultivable microbiota colonising periodontal pockets of different depths among 2 patient‐groups classified as non‐responsive (NR‐group; 11 participants) or responsive (R‐group; 10 participants) to periodontal treatment. Microbiological samples from three types of pocket (<4 mm deep A‐samples; 4–5 mm B‐samples; >5 mm C‐samples) were analysed by cultural methods for putative periodontitis pathogens, microbial groups constituting ≥5% of the total cultivable flora and opportunistic pathogens. Actinomyces naeslundii, A. israelii, Bacteroides forsythus, Fusobacterium spp, Porphyromonas gingivalis, Prevotella intermedia, Peptostreptococcus micros, anaerobic streptococci and facultative anaerobic streptococci were most prevalent. Actinobacillus actinomycetemcomitans, Staphylococcus aureus, enteric rods and yeasts were less prevalent. The periodontitis pathogens Bacteroides forsythus, Fusobacterium spp, Porphyromonas gingivalis, Prevotella intermedia and Peptostreptococcus micros constituted together (on average) ≤23% of the viable counts in the A‐ and B‐samples of both patient groups and in the C‐samples of the Rgroup. In the C‐samples of the NR‐group their mean counts were 45%. Correlations were found between smoking habits and the five pathogens in the Csamples and in pooled pocket depth samples. The results show that groups of periodontopathogens should be considered a causal factor in therapy‐resistant periodontitis. Further, smoking and deep pockets can enhance a shift in the balance of the subgingival microflora predisposing a site to disease and a susceptible host may be the pre‐requisite to therapy‐resistant periodontitis.
Comparative antiplaque effectiveness of an essential oil and an amine fluoride/stannous fluoride mouthrinse
Authors: Riep B. G. , Bernimoulin J.‐P. , Barnett M. L.
Published: October 2003

Abstract. The adjunctive use of antimicrobial mouthrinses to help control supragingival plaque and gingivitis has been shown to contribute significantly to patients' daily oral hygiene regimens. This controlled clinical study used an observer‐ blind, randomized, cross‐over design in a 4‐day plaque regrowth model to determine the relative efficacies of an essential oil‐containing mouthrinse (Listerine® Antiseptic) and an amine fluoride/stannous fluoride‐containing mouthrinse (Meridol®) in inhibiting the development of supragingival plaque. A 0.1% chlorhexidine mouthrinse (Chlorhexamed®‐Fluid) was used as a positive control, and a 5% hydroalcohol solution was used as a negative control. Dosing for each of the test mouthrinses was based on the manufacturers' label directions. Because the volume and rinse time for each of the test mouthrinses were different, each test mouthrinse had its own negative control group. On day 1 of each test period, subjects received an oral soft and hard tissue examination and a dental prophylaxis to remove all plaque, calculus, and extrinsic stain. Starting the same day, subjects refrained from all mechanical oral hygiene procedures for the next 4 days and rinsed 2× daily under supervision with their randomly‐assigned mouthrinse. On day 5, each subject received a plaque assessment as well as an oral examination to assess side effects. Each test period was separated by a 2‐week washout period. 23 volunteers with a median age of 26 years completed the study. Compared to the respective placebos, the median percent plaque reductions at 5 days were 23.0%, 12.2%, and 38.2% for the essential oil, amine/stannous fluoride, and chlorhexidine rinses, respectively. The plaque reductions seen in the essential oil and chlorhexidine rinse groups were statistically significant (p<0.001), while the plaque reduction in the amine/stannous fluoride rinse group was not statistically significant (p>0.05). Additionally, the essential oil rinse was significantly more effective (p<0.001) than the amine/stannous fluoride rinse in inhibiting plaque accumulation in this clinical model.
Development and validation of a short‐term clinical model for assessing calculus inhibitory agents
Authors: Santos Sylvia L. , Putt Mark S. , Feinberg Carol A. , Fernandez Patricia M.
Published: October 2003

Abstract. The purpose of this project was to develop and validate an efficient, short‐term clinical model for assessing topically‐applied anticalculus agents. In this model, calculus development occurred within 14 days on both labial and lingual surfaces of the mandibular anterior teeth. Because of documented longterm clinical efficacy, pyrophosphate dentifrices were used to investigate the validity of the short‐term calculus model for evaluating anticalculus agents. This paper provides the results of the final 3 studies conducted during the development of this model. For each study, the design consisted of two 14‐day phases, i.e., a control phase and a treatment phase, separated by a 7‐day washout phase. At the start of each phase, a prophylaxis was performed on the mandibular anterior teeth to remove all plaque and calculus. At the end of each phase, supragingival calculus formation on the labial and lingual surfaces of these same teeth was measured using the VMI scoring method. Twice a day during the control phase, subjects applied a control dentifrice undiluted to the test teeth with a custom‐fitted toothshield and brushed only the exposed teeth with the same dentifrice. For the treatment phase, subjects were randomly assigned to groups balanced on the basis of control‐phase calculus scores and then delivered the dentifrices using the toothshield as in the first phase. After 14 days, calculus formation occurred in all groups. However, the pyrophosphate dentifrice groups had significantly less calculus (16–30%) than the control dentifrice group. These studies demonstrated that this methodology permitted rapid formation of dental calculus, and by substantiating with anticalculus systems documented to have activity in long‐term human trials, it is concluded that this short‐term clinical model is valid for assessing anticalculus agents.
Prediction and diagnosis of attachment loss by enhanced chemiluminescent assay of crevicular fluid alkaline phosphatase levels
Authors: Chapple I. L. C. , Garner I. , Saxby M. S. , Moscrop H. , Matthews J. B.
Published: October 2003

Abstract. The current study aimed to apply a novel enhanced chemiluminescence assay in the analysis of gingival crevicular fluid (GCF) alkaline phosphatase (ALP) levels from patients with untreated adult periodontitis. 3666 sites in 25 patients were monitored prior to and after attachment loss was detected with a Florida disc probe. Parameters assessed were, relative attachment level, probing pocket depth, occurrence of bleeding on probing (single episode), GCF volume (μl), total ALP levels (μIU/30 s sample time) and ALP concentration (IU/l). After recruiting patients to the study, all measures were taken at baseline and 3 months later, prior to the institution of non‐surgical periodontal therapy at active sites. Thresholds for determining attachment loss were calculated using a modification of the tolerance method. The mesio‐buccal sites of all teeth had GCF samples collected. The size of individual patient thresholds used to define whether attachment loss had occurred, was dependent upon the discomfort felt by that patient during electronic probing, with a positive correlation existing between discomfort on probing (10 cm visual analogue scale) and threshold size (R=0.52, p<0.049). A total of 274 sites (7.5%) experienced attachment loss of which 39 sites had GCF samples available for analysis. Total ALP levels were significantly higher at baseline for sites that progressed to attachment loss than paired controls (p<0.003), but all other parameters showed no differences (p>0.1). There were significant increases in total ALP levels and GCF volumes for active sites between baseline and 3 month measures (p<0.01), but not for control sites or test site ALP concentration (p>0.8). The diagnostic accuracy for GCFALP as a predictor of future attachment loss (threshold 900 μIU/30 s) was 64%, with +ve and −ve predictive values of 62% and 68%. When a threshold of 1300 μIU/30 s was selected for ALP as a marker of recent or currently active disease, diagnostic accuracy and +ve/−ve predictive values were 77% and 77%/76%, respectively. These results indicate that total GCF ALP levels may serve as a predictor of future or current disease activity.
Periodontal conditions in patients with juvenile idiopathic arthritis
Authors: Miranda Letícia A. , Fischer Ricardo G. , Sztajnbok Flávio R. , Figueredo Carlos Marcelo S. , Gustafsson Anders
Published: October 2003

Objective: Our aim was to compare the periodontal conditions in a group of juvenile idiopathic arthritis (JIA) patients with those in a control group of healthy subjects (CTR).

Material and Methods: Thirty‐two patients with JIA and 24 controls were selected. The measurements used to diagnose periodontal disease included plaque and bleeding scores, probing depths (PDs) and clinical attachment loss (CAL). Laboratory indicators of JIA activity included the erythrocyte sedimentation rate (ESR) and capsule‐reactive protein (CRP). The Mann–Whitney test was used to evaluate the data (α=0.05).

Results: The mean ages were 15.9 (±2.7) years and 14.7 (±2.3) years for groups JIA and CTR, respectively. The median ESR was 42 mm/h in the JIA group and 13 mm/h in the CTR group (p=0.032) and the median CRP was 1.9 and 0.4 mg/l, respectively (p=0.001). The prevalence of patients with a proximal attachment loss of 2 mm or more in the JIA group was 25% and in controls it was 4.2%. The mean percentages of visible plaque and marginal bleeding were similar in the JIA (54±22 and 30±16, respectively) and CTR groups (44±18 and 29±11, respectively). The mean percentages of sites with PD4 mm were significantly higher in the JIA group (3±4.7) than in the CTR group (0.4±1.7) (p=0.012). The mean percentages of sites with proximal CAL2 mm were 0.7 (±1.4) in the JIA group and 0.001 (±0.2) in the CTR group (p=0.022).

Conclusion: Adolescents with JIA present more periodontal attachment loss than healthy controls, in spite of similar plaque and marginal bleeding levels.
Bacterial colonization during de novo plaque formation
Authors: Ramberg Per , Sekino Satoshi , Uzel Naciye Guzin , Socransky Sigmund , Lindhe Jan
Published: October 2003

Objective: To determine microbial changes that occur during plaque formation in a dentition free of gingival inflammation.

Material and Methods: Ten subjects were recruited. The study included one preparatory period (2 weeks) and a plaque accumulation period (4 days). The volunteers exercised proper tooth cleaning methods, were scaled and received repeated professional mechanical tooth cleaning during the preparatory period. During the plaque accumulation period, the participants abstained from plaque control measures. Plaque was scored on the approximal surfaces of maxillary and mandibular premolars on Days 0, 1, 2 and 4 using a scale from 0 to 5 and according to the criteria of the Quigley and Hein Plaque Index (QHI). Supragingival plaque samples were obtained from the same intervals and surfaces and evaluated using a checkerboard DNA–DNA hybridization technique.

Results: The mean QHI increased from 0 to 1.6 (Day 4). The total number of organisms on Day 0 averaged 140×105 and increased to about 210×105 after 4 days without oral hygiene.

The most dominant species on Day 0 were members of the genus Actinomyces. These organisms comprised almost 50% of the microbiota evaluated. None of the Actinomyces species increased significantly during the 4 days. Some Streptococcus species increased significantly over time as well as species of the genera Capnocytophaga, Campylobacter, Fusobacteria and Actinomyces actinomycetemcomitans.

Conclusion: In the present investigation, the preparatory phase established a situation with minimal gingival inflammation and close to zero amounts of dental plaque. The Day 0 plaque samples exhibited high proportions of Actinomyces species. During the 4 days of no oral hygiene, there was a small increase in total numbers of organisms as well as a modest increase in the proportion of “disease‐associated” taxa such as species of the “orange complex” species.
A study comparing the effectiveness of conventional training and virtual reality simulation in the skills acquisition of junior dental students
Authors: Quinn Frank , Keogh Paul , McDonald Ailbhe , Hussey David
Published: October 2003

The use of virtual reality (VR) in the training of operative dentistry is a recent innovation and little research has been published on its efficacy compared to conventional training methods. Two groups of dental students, with no experience in operative dentistry, were trained solely by either VR or conventional training in the preparation of conventional class 1 cavities. The subjects all used the same operative armamentarium and phantom heads, and were allocated the same duration of practice periods. At the completion of these training periods, both groups produced two class 1 cavities on the lower left first molar, which were subsequently coded and blindly scored for the traditional assessment criteria of outline form, retention form, smoothness, cavity depth and cavity margin angulation. An ordinal score of 0–3 or 0–4 was assigned for each assessment criterion: the higher the score, the worse the evaluation. After initial independent scoring, the two examiners discussed any notable differences until an agreed score was reached. Once the codes were broken, non‐parametric analyses were performed on the data. Wilcoxon Tests for the semiquantitative scores indicated significant differences between the VR and conventional training groups for outline form, depth and smoothness but not for retention or cavity margin angulation at P < 0.05 level, with the VR group receiving the higher, i.e. worse, scores. Cavity margin angulation approached significance with a P‐value of 0.0536. The results indicated that VR‐based skills acquisition is unsuitable for use as the sole method of feedback and evaluation for novice students.
The connection between in vitro water uptake and in vivo skin moisturization
Authors: Sagiv Assaf E. , Marcus Yizhak
Published: October 2003

Background/purpose: Humectancy or hygroscopy is the water absorption tendency of a substance from the surroundings. Our interest, from the clinical point of view, consists of correlating this tendency in vitro and its effect in vivo for the development of drugs and formulations for the treatment of dry skin syndrome or diseases accompanied by dry skin.

Method: In vitro, water absorption was measured using the comparative isopiestic method. This method is based on bringing the vapor of the water to isothermal equilibrium between a reference system and the material to be studied. The in vivo model on guinea‐pigs for the dry skin syndrome tested the therapeutic ability of mono‐, di‐ and tri‐glycerols to provide moisture to dry skin leading to healing. The moisture content in the stratum corneum was measured with a Corneometer CM 825® PC that measures merely the presence of high dielectric material (humectant or water), whereas the Mexameter MX 16® measures a pathological parameter – the erythema.

Results: Adding hydroxyl groups to a consecutive set of polyhydroxyalkanes increases the humectancy of the polyols in vitro. This elevation was found to be linear at low relative humidities (Relative humidity=31.9% and 37°C). In vivo, moisture was returned to normal within a week in all three groups.

However, only glycerol managed to abolish the erythema within 7 days.

Conclusion: A rise in water absorption ability in vitro, at a rate of about 0.25 mol water per hydroxyl group was revealed in a consecutive set of glycerols (mono‐, di‐ and tri‐glycerols). One would expect that the better humectant is a material, i.e. in which the higher its physical ability to hold water in vitro the more effective it will be in recovering skin dryness. We have found, however, that glycerol, which has the lowest humectant activity in vitro, from the set of glycerols, di‐ and tri‐glycerol, has been proven to be the best for eliminating the signs of skin dryness. Accordingly, we propose to distinguish between the in vitro humectancy (i.e. the water uptake of a material), and its in vivo moisturizing effect, i.e. its ability to cure skin dryness and erythema. This finding supports our conclusion that the connection between in vitro humectancy and in vivo moisturization is not a simple correlation.
Reflectance spectroscopy can quantify cutaneous haemoglobin oxygenation by oxygen uptake from the atmosphere after epidermal barrier disruption
Authors: Heise H. M. , Lampen P. , Stücker M.
Published: October 2003

Background: The supply of oxygen to the viable skin tissue within the upper layers is not only secured by the cutaneous blood vascular system, but to a significant part also by oxygen diffusion from the atmosphere through the horny layer. The aim of this study was to examine whether changes in haemoglobin oxygenation can be observed within the isolated perfused bovine udder skin used as a skin model by removing the upper horny layer by adhesive tape stripping.

Methods: Diffuse reflectance spectroscopy in the visible spectral range was used for non‐invasive characterisation of haemoglobin oxygenation in skin under in vitro conditions. Mid‐infrared attenuated total reflectance spectroscopy was employed for analysing the surface layer of the stratum corneum with respect to keratin, water and lipid components. Skin barrier disruption was achieved by repeated stripping of superficial corneocyte layers by adhesive tape.

Results and conclusion: Significant changes in skin haemoglobin oxygenation were observed for skin areas with reduced lipid concentration and a reduced stratum corneum layer, as determined from the quantitative evaluation of the diffuse reflectance skin spectra. The result can be interpreted as an increase of oxygen diffusion after the removal of the upper horny layer.
SkinChip®, a new tool for investigating the skin surface in vivo
Authors: Lévêque Jean Luc , Querleux Bernard
Published: October 2003

Background/aims: Non‐invasive methods used for characterizing skin micro‐relief and skin surface hydration were developed in the 1980s. Although they allowed some progress in the knowledge of skin properties, they are not completely satisfactory in many aspects. Today, new technologies are emerging that may address such issues.

Methods: We adapted the technology produced by the ST Microelectronics Company for sensing fingerprint for the measurement of skin surface properties. Accordingly, we developed acquisition software for obtaining routinely the distribution of skin surface capacitance along different body sites. Image analysis softwares were also processed for collecting both the main orientations of the micro‐relief lines and their density. The average value of skin capacitance is also obtained.

Results: The images allow a highly precise observation of the skin topography that can be easily quantified in terms of line density and line orientation. The mean gray levels of the images appear much closely correlated to the Corneometer values.

Conclusion: This new device appears to be a very convenient way for characterizing the properties of the skin surface. With regard to hydration, it usefully provides both the average value and the hydration chart of the investigated skin zones.
Amoebapores and NK-lysin, members of a class of structurally distinct antimicrobial and cytolytic peptides from protozoa and mammals: a comparative functional analysis
Authors: BRUHN Heike , RIEKENS Beate , BERNINGHAUSEN Otto , LEIPPE Matthias
Published: October 2003

Amoebapores, the pore-forming polypeptides of the protozoan parasite Entamoeba histolytica, and NK-lysin, an effector molecule of porcine NK (natural killer) and cytotoxic T cells, belong to the same protein family, the saposin-like proteins. As both types of protein are implicated in the killing of microbes in vivo, it appears that phylogenetically diverse organisms such as amoebae and mammals use similar effector molecules to fulfil a comparable task. However, structural features have led to the assumption that the proteins display their activities according to different modes of action. To address this question, we analysed the antibacterial, cytotoxic and pore-forming activities of these proteins in parallel and in comprehensive detail. Interestingly, the comparison of activities revealed significant differences. Whereas NK-lysin, recombinantly expressed, is efficient at a broad range of pH values, the amoebapores exhibited a pronounced pH dependence of all their activities, with markedly decreased activity at pH values above 6. Moreover, increasing salinity affects amoebapores more drastically than NK-lysin. All of the proteins compared were found to be potently active against Gram-positive bacteria, but only NK-lysin was equally efficient against Gram-negative bacteria. However, the amoebapores displayed five times higher pore-forming activity than NK-lysin, which is in accordance with the more hydrophobic character of the amoebapores compared with the essentially cationic NK-lysin.
Serine acetyltransferase of Escherichia coli: substrate specificity and feedback control by cysteine
Authors: HINDSON V. John
Published: October 2003

Although SAT (serine acetyltransferase) of Escherichia coli, which catalyses the first step in cysteine synthesis, proceeds via a random-order ternary complex reaction mechanism [Hindson and Shaw (2003) Biochemistry 42, 3113–3119], it has been suggested that the nearly identical enzyme from Salmonella typhimurium might involve an acetyl-enzyme intermediate [Leu and Cook (1994) Protein Peptide Lett. 1, 157–162]. In this study the alternative acetyl acceptor threonine and the alternative acyl donor, propionyl-CoA were used to further investigate the reaction mechanism of SAT from E. coli. Steady-state kinetic data and dead-end inhibition studies were again diagnostic of a random-order ternary complex reaction mechanism for alternative substrates. Since earlier kinetic studies with SAT from S. typhimurium suggested that cysteine competes with acetyl-CoA for binding, rather than serine with which it is isostructural, the specificity of the serine-binding pocket was assessed with three substrate mimics; β-hydroxypropionic acid, glycine and ethanolamine. The data show that SAT interacts productively with the amino and hydroxymethyl moieties of serine, whereas the carboxyl group provides an essential contribution to binding strongly, supporting a view that cysteine will interact productively at the serine-binding site. Furthermore, since the hydroxymethyl contact region of the serine-binding site appears able to accommodate the methylene and acetyl moeties of threonine and O-acetyl-serine respectively, the site is unlikely to provide obligatory short-range contacts with the hydroxyl group of serine, a prerequisite for exclusion of cysteine. Such a proposal is supported by the results of micro-calorimetric studies which show that cysteine competes with serine for binding to SAT rather than with CoA. It follows that tight binding of cysteine at the serine-binding site near the catalytic centre may be the effector of a substantial reduction in the affinity of SAT for CoA, yielding the observed pattern of steady-state inhibition and the mechanism by which cysteine mediates effective end-product control of its synthesis.
Co-incident signalling between μ-opioid and M3 muscarinic receptors at the level of Ca2+ release from intracellular stores: lack of evidence for Ins(1,4,5)P3 receptor sensitization
Authors: SAMWAYS Damien S. K. , LI Wen-hong , CONWAY Stuart J. , HOLMES Andrew B. , BOOTMAN Martin D. , HENDERSON Graeme
Published: October 2003

Activation of Gi/Go-coupled opioid receptors increases [Ca2+]i (intracellular free-Ca2+ concentration), but only if there is concomitant Gq-coupled receptor activation. This Gi/Go-coupled receptor-mediated [Ca2+]i increase does not appear to result from further production of InsP3 [Ins(1,4,5)P3] in SH-SY5Y cells. In the present study, fast-scanning confocal microscopy revealed that activation of μ-opioid receptors alone by 1 μM DAMGO ([d-Ala, NMe-Phe, Gly-ol]-enkephalin) did not stimulate the InsP3-dependent elementary Ca2+-signalling events (Ca2+ puffs), whereas DAMGO did evoke Ca2+ puffs when applied during concomitant activation of M3 muscarinic receptors with 1 μM carbachol. We next determined whether μ-opioid receptor activation might increase [Ca2+]i by sensitizing the InsP3 receptor to InsP3. DAMGO did not potentiate the amplitude of the [Ca2+]i increase evoked by flash photolysis of the caged InsP3 receptor agonist, caged 2,3-isopropylidene-InsP3, whereas the InsP3 receptor sensitizing agent, thimerosal (10 μM), did potentiate this response. DAMGO also did not prolong the rate of decay of the increase in [Ca2+]i evoked by flash photolysis of caged 2,3-isopropylidene-InsP3. Furthermore, DAMGO did not increase [Ca2+]i in the presence of the cell-membrane-permeable InsP3 receptor agonist, InsP3 hexakis(butyryloxymethyl) ester. Therefore it appears that μ-opioid receptors do not increase [Ca2+]i through either InsP3 receptor sensitization, enhancing the releasable pool of Ca2+ or inhibition of Ca2+ removal from the cytoplasm.
Modulation of NAADP (nicotinic acid–adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations
Authors: DICKINSON George D. , PATEL Sandip
Published: October 2003

NAADP (nicotinic acid–adenine dinucleotide phosphate) mediates Ca2+ release from intracellular Ca2+ stores in a wide variety of cell types. In sea urchin eggs, subthreshold concentrations of NAADP can cause full inactivation of NAADP-induced Ca2+ release, an effect that may be related to the ability of the target protein to bind its ligand in an essentially irreversible manner. In the present study, we found that K+ ions inhibit dissociation of NAADP from sea urchin egg homogenates. In low K+-containing media, an addition of excess unlabelled NAADP effectively displaced bound radioligand whereas dilution of radioligand initiated only partial dissociation. The inhibitory effects of K+ on dissociation of NAADP were concentration dependent, reversible and persisted after detergent solubilization. Lowering [K+] of the medium decreased the sensitivity of NAADP receptors for their ligand in stimulating Ca2+ release, but it did not affect inactivation of NAADP-induced Ca2+ release by subthreshold concentrations of NAADP. Our results are consistent with the observation of multiple conformations of the NAADP receptor that are readily revealed in low K+-containing media.
Ceramide induces a loss in cytosolic peroxide levels in mononuclear cells
Authors: PHILLIPS Darren C. , GRIFFITHS Helen R.
Published: October 2003

Ceramide (a sphingolipid) and reactive oxygen species are each partly responsible for intracellular signal transduction in response to a variety of agents. It has been reported that ceramide and reactive oxygen species are intimately linked and show reciprocal regulation [Liu, Andreieu-Abadie, Levade, Zhang, Obeid and Hannun (1998) J. Biol. Chem. 273, 11313–11320]. Utilizing synthetic, short-chain ceramide to mimic the cellular responses to fluctuations in natural endogenous ceramide formation or using stimulation of CD95 to induce ceramide formation, we found that the principal redox-altering property of ceramide is to lower the [peroxide]cyt (cytosolic peroxide concentration). Apoptosis of Jurkat T-cells, primary resting and phytohaemagglutinin-activated human peripheral blood T-lymphocytes was preceded by a loss in [peroxide]cyt, as measured by the peroxide-sensitive probe 2′,7′-dichlorofluorescein diacetate (also reflected in a lower rate of superoxide dismutase-inhibitable cytochrome c reduction), and this was not associated with a loss of membrane integrity. Where growth arrest of U937 monocytes was observed without a loss of membrane integrity, the decrease in [peroxide]cyt was of a lower magnitude when compared with that preceding the onset of apoptosis in T-cells. Furthermore, decreasing the cytosolic peroxide level in U937 monocytes before the application of synthetic ceramide by pretreatment with either of the antioxidants N-acetyl cysteine or glutathione conferred apoptosis. However, N-acetyl cysteine or glutathione did not affect the kinetics or magnitude of ceramide-induced apoptosis of Jurkat T-cells. Therefore the primary redox effect of cellular ceramide accumulation is to lower the [peroxide]cyt of both primary and immortalized cells, the magnitude of which dictates the cellular response.
Quantitative screening of advanced glycation endproducts in cellular and extracellular proteins by tandem mass spectrometry
Authors: THORNALLEY Paul J. , BATTAH Sinan , AHMED Naila , KARACHALIAS Nikolaos , AGALOU Stamatina , BABAEI-JADIDI Roya , DAWNAY Anne
Published: October 2003

Glycation of proteins forms fructosamines and advanced glycation endproducts. Glycation adducts may be risk markers and risk factors of disease development. We measured the concentrations of the early glycation adduct fructosyl-lysine and 12 advanced glycation endproducts by liquid chromatography with tandem mass spectrometric detection. Underivatized analytes were detected free in physiological fluids and in enzymic hydrolysates of cellular and extracellular proteins. Hydroimidazolones were the most important glycation biomarkers quantitatively; monolysyl adducts (Nε-carboxymethyl-lysine and Nε-1-carboxyethyl-lysine) were found in moderate amounts, and bis(lysyl)imidazolium cross-links and pentosidine in lowest amounts. Quantitative screening showed high levels of advanced glycation endproducts in cellular protein and moderate levels in protein of blood plasma. Glycation adduct accumulation in tissues depended on the particular adduct and tissue type. Low levels of free advanced glycation endproducts were found in blood plasma and levels were 10–100-fold higher in urine. Advanced glycation endproduct residues were increased in blood plasma and at sites of vascular complications development in experimental diabetes; renal glomeruli, retina and peripheral nerve. In clinical uraemia, the concentrations of plasma protein advanced glycation endproduct residues increased 1–7-fold and free adduct concentrations increased up to 50-fold. Comprehensive screening of glycation adducts revealed the relative and quantitative importance of α-oxoaldehyde-derived advanced glycation endproducts in physiological modification of proteins–particularly hydroimidazolones, the efficient renal clearance of free adducts, and the marked increases of glycation adducts in diabetes and uraemia–particularly free advanced glycation endproducts in uraemia. Increased levels of these advanced glycation endproducts were associated with vascular complications in diabetes and uraemia.
Structure and transcriptional regulation of the Nat2 gene encoding for the drug-metabolizing enzyme arylamine N-acetyltransferase type 2 in mice
Authors: BOUKOUVALA Sotiria , PRICE Naomi , PLANT Kathryn E. , SIM Edith
Published: October 2003

Arylamine N-acetyltransferases (NATs) are polymorphic enzymes, well-known for their role in the metabolism of drugs and carcinogens. Mice have three NAT isoenzymes, of which NAT2 is postulated to be involved in endogenous, as well as xenobiotic, metabolism. To understand expression of the murine Nat2 gene, we have analysed its structure and transcriptional regulation. We have accurately mapped the transcription initiation site 6.5 kb upstream of the coding region of the gene, adjacent to a recently described non-coding exon. Transcription was demonstrated to start from this region in embryonic and adult liver, spleen, submaxillary gland, kidney, brain, thymus, lung and placenta, but not in the heart. Database searches and analyses of cDNA by PCR suggested alternative splicing of the single 6.2 kb intron of Nat2, and determined the position of the polyadenylation signal at 0.44 kb downstream of the coding region of the gene. Examination of the 13 kb sequence flanking the coding and non-coding exons of Nat2 revealed a single promoter, located close to the transcription-initiation site, and indicated regions likely to harbour control elements. The Nat2 promoter consists of an atypical TATA box and a Sp1 [SV40 (simian virus 40) protein 1] box identical with that found in many housekeeping gene promoters. Activity of the Nat2 promoter was severely reduced by deletion or mutation of either of these two elements, whereas the region of the Sp1 box bound cellular protein and resisted DNase I digestion. Finally, the ability of the promoter region to bind cellular protein was reduced by competition with oligonucleotides bearing the Sp1 consensus sequence.
Site-directed mutagenesis of the active site of diacylglycerol kinase α: calcium and phosphatidylserine stimulate enzyme activity via distinct mechanisms
Authors: ABE Takahiro , LU Xiaolan , JIANG Ying , BOCCONE Clark E. , QIAN Shaomin , VATTEM Krishna M. , WEK Ronald C. , WALSH James P.
Published: October 2003

Diacylglycerol kinases (DAGKs) catalyse ATP-dependent phosphorylation of sn-1,2-diacylglycerol that arises during stimulated phosphatidylinositol turnover. DAGKα is activated in vitro by Ca2+ and by acidic phospholipids. The regulatory region of DAGKα includes an N-terminal RVH motif and EF hands that mediate Ca2+-dependent activation. DAGKα also contains tandem C1 protein kinase C homology domains. We utilized yeast, Saccharomyces cerevisiae, which lacks an endogenous DAGK, to express DAGKα and to determine the enzymic activities of different mutant forms of pig DAGKα in vitro. Six aspartate residues conserved in all DAGKs were individually examined by site-directed mutagenesis. Five of these aspartate residues reside in conserved blocks that correspond to sequences in the catalytic site of phosphofructokinases. Mutation of D434 (Asp434) or D650 abolished all DAGKα activity, whereas substitution of one among D465, D497, D529 and D697 decreased the activity to 6% or less of that for wild-type DAGKα. Roles of homologous residues in phosphofructokinases suggested that the N-terminal half of the DAGK catalytic domain binds Mg-ATP and the C-terminal half binds diacylglycerol. A DAGKα mutant with its entire regulatory region deleted showed a much decreased activity that was not activated by Ca2+, but still exhibited PS (phosphatidylserine)-dependent activation. Moreover, mutations of aspartate residues at the catalytic domain had differential effects on activation by Ca2+ and PS. These results indicate that Ca2+ and PS stimulate DAGKα via distinct mechanisms.
Regulation and organization of adenylyl cyclases and cAMP
Authors: COOPER Dermot M. F.
Published: October 2003

Adenylyl cyclases are a critically important family of multiply regulated signalling molecules. Their susceptibility to many modes of regulation allows them to integrate the activities of a variety of signalling pathways. However, this property brings with it the problem of imparting specificity and discrimination. Recent studies are revealing the range of strategies utilized by the cyclases to solve this problem. Microdomains are a consequence of these solutions, in which cAMP dynamics may differ from the broad cytosol. Currently evolving methodologies are beginning to reveal cAMP fluctuations in these various compartments.