bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross talk between DevS sensor kinase homologue, Rv2027c, and DevR response regulator of Mycobacterium tuberculosis
Authors: Saini Deepak Kumar , Malhotra Vandana , Tyagi Jaya Sivaswami
Published: April 2004

Rv2027c is a putative orphan histidine sensor kinase that bears strong homology to DevS of the hypoxia‐responsive DevR–DevS two‐component system in M. tuberculosis. The cytosolic C‐terminal domain of Rv2027c protein (Rv2027c194) was overexpressed in E. coli and biochemically characterized. Rv2027c194 underwent autophosphorylation at a conserved His392 residue and engaged in phosphotransfer with DevR response regulator. The rates of autophosphorylation and the stabilities of the phosphorylated species were broadly similar in Rv2027c and DevS. However, unlike DevS, Rv2027c utilized Ca2+ as an alternative divalent ion during autophosphorylation. In contrast to DevS which completed phosphotransfer to DevR in 5–10 min, phosphotransfer from Rv2027c∼P was only partial at 30 min. Unlike devS transcription that was hypoxia‐responsive, Rv2027c transcript levels were not upregulated from basal levels during hypoxia. The differential regulation of devS and Rv2027c genes, the ability of Rv2027c to utilize Ca2+ as a divalent cation in autophosphorylation at physiological concentrations and to engage in phosphotransfer with DevR suggests that the DevR regulon could be modulated by more than one environmental cue relayed through DevS and Rv2027c.
Ribosomal crystallography: a flexible nucleotide anchoring tRNA translocation, facilitates peptide‐bond formation, chirality discrimination and antibiotics synergism
Authors: Agmon Ilana , Amit Maya , Auerbach Tamar , Bashan Anat , Baram David , Bartels Heike , Berisio Rita , Greenberg Inbal , Harms Joerg , Hansen Harly A.S. , Kessler Maggie , Pyetan Erez , Schluenzen Frank , Sittner Assa , Yonath Ada , Zarivach Raz
Published: April 2004

The linkage between internal ribosomal symmetry and transfer RNA (tRNA) positioning confirmed positional catalysis of amino‐acid polymerization. Peptide bonds are formed concurrently with tRNA‐3′end rotatory motion, in conjunction with the overall messenger RNA (mRNA)/tRNA translocation. Accurate substrate alignment, mandatory for the processivity of protein biosynthesis, is governed by remote interactions. Inherent flexibility of a conserved nucleotide, anchoring the rotatory motion, facilitates chirality discrimination and antibiotics synergism. Potential tRNA interactions explain the universality of the tRNA CCA‐end and P‐site preference of initial tRNA. The interactions of protein L2 tail with the symmetry‐related region periphery explain its conservation and its contributions to nascent chain elongation.
Infections after Endoscopic Polypectomy Using Nasal Steroids
Authors: Bross‐Soriano Daniel , Arrieta‐Gómez Jose R. , Prado‐Calleros Héctor
Published: April 2004

BACKGROUND

Topical nasal steroids such as beclomethasone dipropionate and fluticasone propionate have been widely used in the treatment of rhinitis and polyposis. An increase in infection has occurred with the use of fluticasone propionate after endoscopic polypectomy.

OBJECTIVE

The purpose of this study was to determine the prevalence of nasal and paranasal infections with the use of topic nasal steroids after endoscopic polypectomy and to compare the recurrence rates of the polyposis.

DESIGN AND SETTING

We conducted a prospective, comparative, open, experimental, longitudinal study at an academic tertiary referral medical center.

METHODS

One hundred sixty‐two patients in whom endoscopic polypectomy had been indicated were randomly divided into 3 groups of 54 patients each. The patients from the first group were treated with saline lavage only. Patients from the second group also received fluticasone propionate 400 μg/day in nasal spray after lavage. Patients from the third group received beclomethasone dipropionate 600 μg/day after lavage. The prevalence of infections and recurrence of polyposis was compared in the 3 groups.

RESULTS

Three patients, 2 in the placebo group and 1 in the beclomethasone group, developed infections during the first 3 months after surgical procedure. The recurrence of polyps in the group without steroids was 44%. In contrast, 15% from the patients treated with fluticasone showed recurrence of polyposis; furthermore, 26% of the patients treated with beclomethasone showed recurrence of polypsosis, with a minimum follow‐up of 12 months.

CONCLUSIONS

The use of nasal steroids does not seem to increase the prevalence of infections after endoscopic polypectomy. (Otolaryngol Head Neck Surg 2004;130:319–22.)
Radiofrequency Treatment of Turbinate Hypertrophy: A Randomized, Blinded, Placebo‐Controlled Clinical Trial
Authors: Nease Carey J. , Krempl Greg A.
Published: April 2004

OBJECTIVES

We sought to evaluate the short‐term efficacy of radiofrequency volumetric tissue reduction (RFVTR) in treating nasal obstruction in subjects with inferior turbinate hypertrophy.

STUDY DESIGN AND SETTING

We conducted a prospective, randomized, single‐blinded, placebo‐controlled trial with crossover option, involving 32 patients and performed in a clinical office setting at the University of Oklahoma Medical Center.

RESULTS

The outcomes were measured using 10‐cm visual analog scales (VASs) before treatment and at 8 weeks and 6 months posttreatment. Improvement was shown in frequency of obstruction, severity of obstruction, and overall ability to breathe for both the placebo and RFVTR treatment arms at 8 weeks (P < 0.05). The amount of improvement, however, was significantly better in the treatment arm compared with placebo for the severity of obstruction and overall ability‐to‐breathe categories. At 6 months, the mean improvement scores were significantly better than the pretreatment scores for all 3 categories.

CONCLUSIONS

RFVTR is an effective alternative for the treatment of patients with nasal obstruction due to inferior turbinate hypertrophy.

SIGNIFICANCE

This is the first randomized trial that demonstrates that RFVTR is significantly better than placebo in treating nasal obstruction due to inferior turbinate hypertrophy. (Otolaryngol Head Neck Surg 2004;130:291–9.)
Revision Endoscopic Frontal Sinus Surgery with Surgical Navigation
Authors: Chiu Alexander G. , Vaughan Winston C.
Published: April 2004

BACKGROUND

Revision surgery of the frontal sinus remains one of the most difficult operations for the endoscopic surgeon. Most agree that knowledge and recognition of its complex anatomy and sparing of frontal recess mucosa are keys to a successful operation. The use of surgical navigation systems may allow for more precise dissections and greater rates of frontal recess patency.

METHODS

Retrospective review of all patients undergoing revision endoscopic frontal sinus surgery with surgical navigation was performed with a minimum 24‐month follow‐up.

RESULTS

Sixty‐seven patients underwent revision endoscopic frontal sinus surgery with surgical navigation. The average follow‐up was 32 months. Fifty‐eight (86.6%) had a patent frontal recess and significant subjective improvement in symptoms. No patient underwent external frontal sinus obliteration, and there were no major complications.

CONCLUSIONS

Endoscopic techniques with surgical navigation are effective in revision frontal sinus cases. The dissection of remnant agger nasi, obstructing frontal and supraorbital cells are necessary to widen the anterior‐posterior as well as the medial‐lateral dimensions of the recess. Computer navigational systems appear to serve as a valuable adjunct in preoperative planning and safe intraoperative dissection. (Otolaryngol Head Neck Surg 2004;130:312–8.)
Imaging the Internal Structure of the Rat Cochlea Using Optical Coherence Tomography at 0.827 μm and 1.3 μm
Authors: Wong Brian J. F. , Zhao Yonghua , Yamaguchi Mark , Nassif Nader , Chen Zhongping , De Boer Johannes F.
Published: April 2004

OBJECTIVE

The purpose of this study was to use high‐speed optical coherence tomography (OCT) to obtain cross‐sectional images of the rat cochlea.

STUDY DESIGN AND METHODS

The cochleae of Sprague‐ Dawley rats were imaged within 2 to 4 hours after death. Specimens were prepared by removing the bulla to expose the mesotympanum; some images were obtained in intact temporal bones removed from the cranium. The central element of an OCT imaging device is a Michelson interferometer combined with a low‐coherence light source. This study used 2 OCT systems with different light sources: 1) a semiconductor optical amplifier operating and 2) a superluminescent diode with peak emissions wavelengths of 1.3 μm and 827 nm, respectively. Images (1.87 × 2.00 mm or 1.87 × 1.00 mm, 10 × 10 μm pixel resolution) were acquired at a frame rate of 1 Hz. Cross‐sectional images at 100‐μm increments were obtained from a medial‐to‐lateral direction.

RESULTS

The scala vestibuli, scala media, scala tympani, modiolus, spiral ligament, and several turns of the cochlea were identified.

CONCLUSION

These images reflect the ability of OCT to provide images of the internal cochlea structure with micron scale resolution and at near‐real time frame rates. (Otolaryngol Head Neck Surg 2004;130:334–38.)
Patterns of Mold Sensitivity in the Subtropical Gulf Coast
Authors: Calhoun Karen H.
Published: April 2004

OBJECTIVES

We sought to determine the patterns of mold‐ and nonmold positive skin tests in a subtropical Gulf Coast climate and to determine whether any particular positive skin tests predict “allergic versus nonallergic” status as shown on the full panel of skin testing.

STUDY DESIGN AND SETTING

We conducted a retrospective evaluation of serial endpoint allergy skin test results in 75 consecutive patients from a tertiary referral medical center.

RESULTS

Of the 67 evaluable patients, 58 (86.6%) had a positive skin test to at least 1 antigen. The most common positive skin tests were in response to cockroach, Dermatophygoides farinae, Bermuda grass, false ragweed, mesquite, Stemphylium, Curvularia, short ragweed, and Timothy grass. There were no identifiable groups of antigens that tended to occur together. Screening with a panel of 6 antigens (cockroach, dust mite, cat, rough marsh elder, Timothy grass, and Stemphylium) would have correctly predicted whether the patient would react to any or none of the full panel of antigens.

CONCLUSION

Cockroach, dust mite, and a grass were the most common positive skin tests among our patients, with many patients also having positive skin tests to molds. Although there is evidence that cross‐reactivity exists among different mold species, we were unable to identify any clusters of mold reacting together in individual patients. In our patient population, a 6‐allergen screening panel (cockroach, dust mite, cat, rough marsh elder, Timothy grass, and Stemphylium) would have accurately distinguished “allergic” from “nonallergic” patients, as demonstrated on the full panel of skin testing.

SIGNIFICANCE

A small (6‐antigen) screening panel accurately predicted “allergic” versus “nonallergic” as shown by our full panel of skin testing. This is useful clinically when an “allergic versus nonallergic” etiology of sinonasal symptoms affects treatment choices. (Otolaryngol Head Neck Surg 2004; 130:306–11.)
Smallpox: What Every Otolaryngologist Should Know
Authors: Tennyson Heath C. , Mair Eric A.
Published: April 2004

OBJECTIVE

In light of recent terrorist events and the potential threat of smallpox as a biological agent, we present information concerning smallpox to better inform the otolaryngologist concerning this disease and its prevention.

STUDY DESIGN

We performed a review of the smallpox and smallpox vaccination literature over the past 200 years using MEDLINE, PREMEDLINE, Centers for Disease Control and Prevention Internet site, World Health Organization Internet site, and references found in previous publications not found in MEDLINE or PREMEDLINE. Our search focused on the pathogenesis, clinical presentation, course, unique manifestations in the head and neck, diagnosis, and treatment of smallpox, as well as the method of smallpox vaccination, vaccination contraindications, and complications.

RESULTS

Smallpox is a viral disease with a high mortality rate. Its clinical course, manifestations, and methods of prevention are carefully analyzed in light of otolaryngology practice.

CONCLUSION

Smallpox manifestations in the head and neck often presented as acute airway obstruction and also as long‐term sequelae such as ectropion, nasal vestibular stenosis, conductive hearing loss, and blindness. Most chronic sequelae involve the head and neck. Smallpox vaccination is effective but not without potential serious risks. (Otolaryngol Head Neck Surg 2004;130:323–33.)
Vaccine‐Preventable Pediatric Postmeningitic Sensorineural Hearing Loss in Southern India
Authors: Cherukupally Shilpa Reddy , Eavey Roland
Published: April 2004

OBJECTIVE

The study goal was to assess vaccine‐preventable pediatric postmeningitic sensorineural hearing loss in southern India.

STUDY DESIGN AND SETTING

We conducted a prospective pilot study from January through March 2001 in a tertiary pediatric hospital in southern India.

RESULTS

Sixty‐five patients were studied. Thirty‐five (54%) patients had positive cerebrospinal fluid cultures, with the most common organisms being Streptococcus pneumoniae and Haemophilus influenzae. An additional 10 (15%) patients were diagnosed with tuberculous meningitis. Of 28 patients who could comply with audiometric evaluations, 8 (28%) had sensorineural hearing loss.

CONCLUSIONS

The etiologic organisms of bacterial meningitis in this study population are similar to those organisms in the developed world, with the minority exception of tuberculous meningitis. Further, a similar prevalence of postmeningitic sensorineural hearing loss occurred.

SIGNIFICANCE

An effective vaccination program against S. pneumoniae and H. influenzae type b should reduce the prevalence of sensorineural hearing loss due to bacterial meningitis in developing countries with similar bacterial profiles. (Otolaryngol Head Neck Surg 2004;130:339–343.)
Melt segregation under compaction and shear channeling: Application to granitic magma segregation in a continental crust
Authors: Rabinowicz Michel , Vigneresse Jean‐Louis
Published: April 2004

We present a model of melt segregation in a mush submitted to both compaction and shear. It applies to a granitic melt imbedded within a partially molten continental crust, able to sustain large stress values. The mathematical derivation starts with the equations for melt and plastic flow in a mush. They are manipulated to obtain equations for the mean flow field and for the separation velocity. Assuming that the mean flow field is simple shear, a specific set of equations for the melt flow in a shear field is obtained. After simplifying the equations, they finally reduce to two systems of coupled equations. One is the well‐known equation for compaction. The other is new and describes melt channelling during shear in a mush with a constant viscosity plastic matrix. Three free parameters are observed. One is the usual compaction length, and the other two are functions of the stress and strain amplitude during shear. Compaction instabilities lead to the development of spherical pockets rich in melt while shear channelling instability segregates melt in parallel veins. The size of the pockets and the distance between veins remain close to the compaction length. Actually, the viscosity ratio between the matrix and its melt controls the compaction length L, which is found metric or submetric. The two types of instability segregate melt. However, the compaction process is generally so sluggish that it cannot compete with the channelling one. The channelling time is controlled by the amount of intergranular melt present in the system and of the amplitude of the shear stresses. During each channelling cycle, lasting for about 30 to 300 kyr, the intergranular melt is completely squeezed out from the volume in between veins. As melting progresses, the successive batches of melt, as well as the residual solid matrix, are increasingly more dehydrated. As a result, both phases progressively stiffen without changing their viscosity contrast and the associated compaction length. The segregation process stops when the dehydration process clamps the deformation of the solid matrix.
Daily rainfall analysis for South America from a regional climate model and station observations
Authors: Seth A. , Rojas M. , Liebmann B. , Qian J.‐H.
Published: April 2004

Seasonal rainfall prediction, while useful for some planning, does not have the temporal resolution required for many applications. Information regarding sub‐seasonal variations in rainfall is often needed for water management and agriculture sector decisions. Daily station observations are used to characterize rainfall frequency and intensity and to verify a regional climate model (RegCM). The model is driven by reanalyses and by general circulation model ensemble realizations for two anomalous seasons in South America. Rainfall distributions simulated by the RegCM slightly overestimate smaller events at the expense of large events in the Northeast and Amazon, yet the smallest rainfall events are generally well represented. Importantly, the RegCM captures the shift in the rainfall distribution which occurs between 1983 (more small events) and 1985 (more large events). The sensitivity of these results to periodic reinitialization show some promise. These results imply that regional models may provide useful statistics on the subseasonal character of rainfall, however, longer nested integrations are needed.
Coseismic deformations detectable by satellite gravity missions: A case study of Alaska (1964, 2002) and Hokkaido (2003) earthquakes in the spectral domain
Authors: Sun Wenke , Okubo Shuhei
Published: April 2004

Coseismic deformations observed on the Earth surface or modeled by conventional dislocation theory cannot be compared directly with those observed by gravity satellite missions because of the spatial resolution limit of the missions and the signal attenuation of the gravity field. Coseismic deformations in the spectrum domain should be considered instead. For this purpose the conventional dislocation theory [e.g., Sun and Okubo, 1993] for a spherical Earth model can be used because it is expressed in the form of a spherical harmonic. In this study, analytical expressions of degree variances of the coseismic geoid and gravity changes for shear and tensile sources are derived and calculated for three real earthquakes. Those results are compared with expected errors of the Gravity Recovery and Climate Experiment (GRACE) to elucidate whether or not coseismic geoid and gravity changes are detectable by gravity satellite missions. Behaviors of the degree variances for four independent seismic sources are investigated. Results indicate that both the gravity and geoid changes are near two orders of magnitude larger than the precession of the gravity missions in low harmonic degrees. On the basis of these results, we derived the minimum magnitudes of earthquakes detectable by GRACE. We concluded that coseismic deformations for an earthquake with a seismic magnitude above m = 7.5 are expected to be detected by GRACE.
Temporal and spatial variations of shallow subsurface temperature as a record of lateral variations in groundwater flow
Authors: Bense V. F. , Kooi H.
Published: April 2004

In the present paper it is shown how profiles consisting of closely spaced (≤10 m) temperature measurements at shallow depth, obtained at several instances during one season, provide a detailed record of lateral variations in vertical groundwater flow. This is illustrated by a field study around the Peel Boundary Fault zone that cuts through the unconsolidated, siliciclastic deposits that occur in the southeastern part of Netherlands. This regionally important fault forms at many locations a strong barrier to horizontal groundwater flow and therefore induces complex groundwater flow patterns. Temperature anomalies (over 2°C) are observed over short distances. These anomalies reverse over the season. Numerical modeling of coupled groundwater flow and heat transport demonstrates how the temporal and spatial variations of subsurface temperature are the result of the interaction between seasonal fluctuations in surface temperature and spatial variations in groundwater flow. In addition to the horizontal profiles, temperature‐depth profiles obtained in groundwater observation wells were used to constrain the larger‐scale characteristics of the groundwater flow system. In order to simulate the observed geothermal patterns it appeared to be essential to account for the long‐term changes in surface temperature. Although groundwater temperature data are commonly used to constrain groundwater flow fields on regional scale or to calculate vertical groundwater velocities at point locations beneath small streams, the present study is one of the first to integrate these different scales and incorporate the impact of recent climate change.
Fluid flow in compressive tectonic settings: Implications for midcrustal seismic reflectors and downward fluid migration
Authors: Connolly J. A. D. , Podladchikov Y. Y.
Published: April 2004

Beneath the brittle‐ductile transition of the Earth's crust, the dilational deformation necessary to create fluid pathways requires fluid pressure that is near to rock confining pressure. Although the deformation may be brittle, it is rate limited by the ductile compaction process necessary to maintain elevated fluid pressure; thus the direction of fluid expulsion is dictated by the mean stress gradient. The paradox posed by the conditions required to maintain high fluid pressure simultaneously with lower crustal rock strength can be explained by a model whereby fluids are localized within self‐propagating hydraulic domains. Such domains would behave as weak inclusions imbedded within adjacent fluid‐poor rocks. Because the mean stress gradient in a weak inclusion depends on its orientation with respect to far‐field stress, the direction of fluid flow in such domains is sensitive to tectonic forcing. In compressional tectonic settings, this model implies that fluid flow may be directed downward to a depth of tectonically induced neutral buoyancy. In combination with dynamic propagation of the brittle‐ductile transition, this phenomenon provides a mechanism by which upper crustal fluids may be swept into the lower crust. The depth of neutral buoyancy would also act as a barrier to upward fluid flow within vertically oriented structural features that are normally the most favorable means of accommodating fluid expulsion. Elementary analysis based on the seismogenic zone depth and experimental rheological constraints indicates that tectonically induced buoyancy would cause fluids to accumulate in an approximately kilometer thick horizon 2–4 km below the brittle‐ductile transition, an explanation for anomalous midcrustal seismic reflectivity.
Acoustic imaging of gas hydrate and free gas at the Storegga Slide
Authors: Bünz Stefan , Mienert Jürgen
Published: April 2004

Analysis of P wave velocities of an ocean‐bottom cable (OBC) data set demonstrates the existence of gas hydrates and free gas on the northern flank of the Storegga Slide. The distribution and concentration of gas hydrates and free gas show significant variation over the length of the OBC. Average gas hydrate saturation of pore space is 5%, when modeled by effective‐medium theory with hydrates as a sediment‐frame component. Average gas saturation is 0.45% assuming homogeneous distribution. The bottom‐simulating reflector (BSR) is generally identified as termination of enhanced reflection but in some places appears as a reflection proper. Amplitude anomalies related to the BSR are primarily caused by the gas and not the hydrates. The gas hydrates at the Storegga Slide develop from gas‐rich fluids migrating into the gas‐hydrate stability zone (GHSZ) from the sediments below. Development of polygonal faults and the related expulsion of formation water might drive the fluid flow in the area. The physical and geological properties of the sediments control the distribution and concentration of gas, which migrates predominantly along strata rather than along the base of the GHSZ. This migration mechanism controls the flux of gas‐rich fluids into the GHSZ and hence the distribution of gas hydrates and the variation in gas hydrate concentration.
The role of tides in beach cusp development
Authors: Coco Giovanni , Burnet Tom K. , Werner B. T. , Elgar Steve
Published: April 2004

Field measurements of morphology and swash flow during three episodes of beach cusp development indicate that tides modulate the height and cross‐shore position of beach cusps. During rising tide, beach cusp height decreases as embayments accrete more than horns and the cross‐shore extent of beach cusps decreases. During falling tide, beach cusp height increases as embayments erode more than horns and cross‐shore extent increases. A numerical model for beach cusp formation based on self‐organization, extended to include the effects of morphological smoothing seaward of the swash front and infiltration into the beach, reproduces the observed spacing, position, and tidal modulation. During rising tide, water particles simulating swash infiltrate, preferentially in embayments, causing enhanced deposition. During falling tide, exfiltration of water particles combined with diversion of swash from horns causes enhanced erosion in embayments. Smoothing of beach morphology in the swash zone seaward of the swash front and in the shallow surf zone accounts for most of the observed tidal modulation, even in the absence of infiltration and exfiltration. Despite the qualitative, and in some cases quantitative, agreement of the model and measurements, the model fails to reproduce observed large deviations of horn orientation from shore normal, some aspects of beach cusp shape, and deviations from the basic tidal modulation, possibly because of the simplified parameterization of cross‐shore sediment transport and the neglect of the effects of sea surface gradients on flow.
Polar stratospheric clouds observed during the Airborne Polar Experiment–Geophysica Aircraft in Antarctica (APE‐GAIA) campaign
Authors: Cairo Francesco , Adriani Alberto , Viterbini Maurizio , Di Donfrancesco Guido , Mitev Valentin , Matthey Renaud , Bastiano Maurizio , Redaelli Gianluca , Dragani Rossana , Ferretti Rossella , Rizi Vincenzo , Paolucci Tiziana , Bernardini Livio , Cacciani Marco , Pace Giandomenico , Fiocco Giorgio
Published: April 2004

In this work, observations of polar stratospheric clouds (PSC) carried out during one flight of the stratospheric research aircraft Geophysica deployed in the Airborne Polar Experiment–Geophysica Aircraft in Antarctica (APE‐GAIA) campaign in September–October 1999 are presented. An analysis of data from the two lidars and a backscatter sonde on board the Geophysica aircraft is presented, coupled with temperature measurements. The observations are analyzed with the aid of a mesoscale model to provide air mass thermal histories and a microphysical box model to simulate PSC formation. The results obtained from this comparison are discussed in view of the theories for PSC formation processes.
Constraints on the sources of tropospheric ozone from 210Pb‐7Be‐O3 correlations
Authors: Liu Hongyu , Jacob Daniel J. , Dibb Jack E. , Fiore Arlene M. , Yantosca Robert M.
Published: April 2004

The 210Pb‐7Be‐O3 relationships observed in three aircraft missions over the western Pacific (PEM‐West A and B, TRACE‐P) are simulated with a global three‐dimensional chemical tracer model (GEOS‐CHEM) driven by assimilated meteorological observations. Results are interpreted in terms of the constraints that they offer on sources of tropospheric ozone (O3). Aircraft observations of fresh Asian outflow show strong 210Pb‐O3 correlations in September–October, but such correlations are only seen at low latitudes in February–March. Observations further downwind over the Pacific show stronger 210Pb‐O3 correlations in February–March than in September–October. The model reproduces these results and attributes the seasonal contrast to strong O3 production and vertical mixing over east Asia in September–October, seasonal shift of convection from China in September–October to Southeast Asia in February–March, and slow but sustained net O3 production in Asian outflow over the western Pacific in February–March. Seasonal biomass burning over Southeast Asia in February–March is responsible for the positive 210Pb‐O3 correlations observed at low latitudes. The model reproduces the observed absence of 7Be‐O3 correlations over the western Pacific during September–October, implying strong convective and weak stratospheric influence on O3. Comparison of observed and simulated 7Be‐O3 correlations indicates that the stratosphere contributes less than 20–30% of O3 in the middle troposphere at northern midlatitudes even during spring.
Chemical retention during dry growth riming
Authors: Stuart A. L. , Jacobson M. Z.
Published: April 2004

Partitioning of volatile chemicals among the gas, liquid, and solid phases during the conversion of liquid water to ice in clouds can impact distributions of chemicals in precipitation and in the poststorm troposphere. In this paper, we extend a theoretical scaling model of chemical retention during hydrometeor freezing to all dry growth riming conditions. We account for spreading of drops upon impact with an ice‐phase hydrometeor using the spread height as the mass and heat transfer length scale. To account for heat loss to the ice substrate, we use an iterative solution to calculate the total freezing time. Using this augmented development, we calculate a theoretical dimensionless retention indicator λ under the conditions of several experimental studies and compare the retention indicator to the measured retention fraction Γ. Experimental retention compares well with the retention indicator. Empirically fitting the retention indicator to the experimental data provides the first parameterization for the retention coefficient, Γ = 1 − exp (−0.002λ), that is applicable to a range of chemicals and dry growth riming conditions. The analysis and model presented in this paper can be used to improve experimental design and parameterization of retention in cloud models.
Sea ice control of water isotope transport to Antarctica and implications for ice core interpretation
Authors: Noone David , Simmonds Ian
Published: April 2004

Sea ice in the Southern Ocean is important for Antarctic climate and hydrology. The dependence of water isotope abundance (δ18O and deuterium excess) on the winter sea ice state is examined with the isotopic version of the Melbourne University general circulation model. Reductions in the ice concentration provide warmer temperatures in winter and allow higher precipitation totals further south, while the reverse occurs with increased ice extent. The model shows clear demarcation between the changes in the isotopic conditions over the sea ice pack, where local changes in surface exchange dominate, and those of the continent interior, which depend on the long‐ranged transport aloft. While less sensitive to the forcing, the interior response is influenced by changes in turbulent mixing over the ice pack and modification of the vertical transport associated with diabatic heating. The interior deuterium excess response is more strongly affected by sea ice as it captures changes in temperature over the ice rather than just the final vapor mass. Traditional reconstruction of temperature from a single isotopic nuclide would give erroneous interpretation of change in the global mean temperature unless the sea ice changes in parallel; instead, the spatial structure of the sea ice response gives some hope for extracting past sea ice conditions from multicore analysis. This study begins to explore the role of entropy production during transport such that the isotopic interpretation is more closely tied to the dynamics of the atmosphere than is expressed by idealized parcel analysis.
Form and flow of the Devon Island Ice Cap, Canadian Arctic
Authors: Dowdeswell J. A. , Benham T. J. , Gorman M. R. , Burgess D. , Sharp M. J.
Published: April 2004

In this study, 3370 km of 100 MHz ice‐penetrating radar data were acquired from Devon Ice Cap, Arctic Canada. Bed returns were obtained from >90% of flight tracks. Mean crossing point errors in ice surface elevation and ice thickness were 7–8 m. Digital elevation models of ice cap surface and bed elevation, and ice thickness, were produced and can be used as boundary conditions in numerical modeling. Devon Ice Cap, including 1960 km2 of contiguous stagnant ice to its west, is 14,010 km2. The ice cap proper is 12,050 km2. Its largest drainage basin is 2630 km2. The ice cap crest has a maximum measured elevation of 1921 m. Maximum recorded ice thickness is 880 m. Ice cap volume is 3980 km3 (about 10 mm sea level equivalent). The bed, 8% of which lies below sea level, is an upland plateau dissected by steep‐sided valleys that control the locations of the major outlet glaciers which dominate ice cap drainage. About 73 km, 4%, of the ice cap margin ends in tidewater. The margin is not floating. Icebergs of <100 m were observed offshore. Only a single outlet glacier showed signs of past surge activity. All major outlet glaciers along the eastern ice cap margin have retreated 1–3 km since 1960. Synthetic aperture radar‐interferometic velocity structure shows slow, undifferentiated flow predominating in the west and center, with fast‐flowing outlet glaciers and intervening slow‐flowing ridges typical elsewhere. Outlet glacier velocities are 7–10 times higher than in areas of undifferentiated flow. This velocity structure, of fast‐flowing units within slower‐flowing ice, appears typical of many large (103 km2) Arctic ice caps.
Nighttime removal of NOx in the summer marine boundary layer
Authors: Brown S. S. , Dibb J. E. , Stark H. , Aldener M. , Vozella M. , Whitlow S. , Williams E. J. , Lerner B. M. , Jakoubek R. , Middlebrook A. M. , DeGouw J. A. , Warneke C. , Goldan P. D. , Kuster W. C. , Angevine W. M. , Sueper D. T. , Quinn P. K. , Bates T. S. , Meagher J. F. , Fehsenfeld F. C. , Ravishankara A. R.
Published: April 2004

The nitrate radical, NO3, and dinitrogen pentoxide, N2O5, are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction of NO2 reacts to form NO3 and N2O5 during the course of a night, their fate is an important determining factor to the overall fate of NOx (=NO and NO2). As a comprehensive test of nocturnal nitrogen oxide chemistry, concentrations of O3, NO, NO2, NO3, N2O5, HNO3 and a host of other relevant compounds, aerosol abundance and composition, and meteorological conditions were measured in the marine boundary layer from the NOAA research vessel Ronald H. Brown off the East Coast of the United States as part of the New England Air Quality Study (NEAQS) during the summer of 2002. The results confirm the prominent role of NO3 and N2O5 in converting NOx to HNO3 at night with an efficiency on par with daytime photochemical conversion. The findings demonstrate the large role of nighttime chemistry in determining the NOx budget and consequent production of ozone.
Sensitivity of Asian dust storm to natural and anthropogenic factors
Authors: Gong S. L. , Zhang X. Y. , Zhao T. L. , Barrie L. A.
Published: April 2004

The impacts of natural and anthropogenic factors on sand and dust storm distribution of 2001 in East Asia have been investigated by using the most up‐to‐date desertification map in China and desert reversal scenarios in natural precipitation zones. Here we show that although desertification in China has only increased total area of desert by ∼2%–7% since 1950s [Zhong, 1999; Zhu and Zhu, 1999], it has generated disproportionably large areas with dust storm production potentials. Depending on the degree of desertification, newly formed deserts covered 15% to 19% of the original desert areas and would generate more dust storm, ranging from 10% to 40%, under the same meteorological conditions for spring 2001. Among the natural factors, the restoration of vegetation covers in the Chinese deserts within the 200 mm/y and 400 mm/y precipitation zones was found to decrease the surface mass concentrations by 10–50 % in most regions. It is also found that the contributions of surface concentrations from non‐Chinese deserts account for up to 60% in Northeast China and up to 50% in Korea and Japan.
3D electron‐acoustic solitary waves introduced by phase space electron vortices in magnetized space plasmas
Authors: Shukla P. K. , Mamun A. A. , Eliasson B.
Published: April 2004

We derive a multi‐dimensional nonlinear equation for electron‐acoustic waves in magnetized plasmas composed of stationary ions, magnetized cold electrons with a significant fraction of electron beams, and magnetized hot electrons which have a non‐isothermal vortex‐like distribution. We find three‐dimensional (3D) electron‐acoustic solitary waves which have a stronger nonlinearity (in comparison with that associated with the traditional harmonic generation) due to the trapping of hot electrons in the localized electron‐acoustic wave potential. The relevance of our investigation to nonlinear structures (e.g., the bipolar parallel electric fields) in the Earth's magnetosphere is discussed.
Tissue engineering of blood vessels: characterization of smooth‐muscle cells for culturing on collagen‐and‐elastin‐based scaffolds
Authors: Buijtenhuijs Paula , Buttafoco Laura , Poot Andre A. , Daamen Willeke F. , Van Kuppevelt Toin H. , Dijkstra Pieter J. , De Vos Rob A. I. , Sterk Lotus M. Th. , Geelkerken Bob R. H. , Feijen Jan , Vermes Istvan
Published: April 2004

Tissue engineering offers the opportunity to develop vascular scaffolds that mimic the morphology of natural arteries. We have developed a porous three‐dimensional scaffold consisting of fibres of collagen and elastin interspersed together. Scaffolds were obtained by freeze‐drying a suspension of insoluble type I collagen and insoluble elastin. In order to improve the stability of the obtained matrices, they were cross‐linked by two different methods. A water‐soluble carbodi‐imide, alone or in combination with a diamine, was used for this purpose: zero‐ or non‐zero‐length cross‐links were obtained. The occurrence of cross‐linking was verified by monitoring the thermal behaviour and the free‐amino‐group contents of the scaffolds before and after cross‐linking. Smooth‐muscle cells (SMCs) were cultured for different periods of time and their ability to grow and proliferate was investigated. SMCs were isolated from human umbilical and saphenous veins, and the purity of the cultures obtained was verified by staining with a specific monoclonal antibody (mAb). Cultured cells were also identified by mAbs against muscle actin and vimentin. After 14 days, a confluent layer of SMCs was obtained on non‐cross‐linked scaffolds. As for the cross‐linked samples, no differences in cell attachment and proliferation were observed between scaffolds cross‐linked using the two different methods. Cells cultured on the scaffolds were identified with an anti‐(α‐smooth‐muscle actin) mAb. The orientation of SMCs resembled that of the fibres of collagen and elastin. In this way, it may be possible to develop tubular porous scaffolds resembling the morphological characteristics of native blood vessels.
Aspergillus niger mstA encodes a high-affinity sugar/H+ symporter which is regulated in response to extracellular pH
Authors: vanKUYK Patricia A. , DIDERICH Jasper A. , MacCABE Andrew P. , HERERRO Oscar , RUIJTER George J. G. , VISSER Jaap
Published: April 2004

A sugar-transporter-encoding gene, mstA, which is a member of the major facilitator superfamily, has been cloned from a genomic DNA library of the filamentous fungus Aspergillus niger. To enable the functional characterization of MSTA, a full-length cDNA was expressed in a Saccharomyces cerevisiae strain deficient in hexose uptake. Uptake experiments using 14C-labelled monosaccharides demonstrated that although able to transport d-fructose (Km, 4.5±1.0 mM), d-xylose (Km, 0.3±0.1 mM) and d-mannose (Km, 60±20 µM), MSTA has a preference for d-glucose (Km, 25±10 µM). pH changes associated with sugar transport indicate that MSTA catalyses monosaccharide/H+ symport. Expression of mstA in response to carbon starvation and upon transfer to poor carbon sources is consistent with a role for MSTA as a high-affinity transporter for d-glucose, d-mannose and d-xylose. Northern analysis has shown that mstA is subject to CreA-mediated carbon catabolite repression and pH regulation mediated by PacC. A. niger strains in which the mstA gene had been disrupted are phenotypically identical with isogenic reference strains when grown on 0.1–60 mM d-glucose, d-mannose, d-fructose or d-xylose. This indicates that A. niger possesses other transporters capable of compensating for the absence of MSTA.
A proximal tissue-specific module and a distal negative regulatory module control apolipoprotein(a) gene transcription
Authors: NEGI Sarita , SINGH Saurabh K. , PATI Nirupma , HANDA Vikas , CHAUHAN Ruchi , PATI Uttam
Published: April 2004

The apo(a) [apolipoprotein(a)] gene is responsible for variations in plasma lipoprotein(a), high levels of which are a risk factor for atherosclerosis and myocardial infarction. The apo(a) promoter stimulates the expression of reporter genes in HepG2 cells, but not in HeLa cells. In the present study, we demonstrate that the 1.4 kb apo(a) promoter comprises two composite regulatory regions: a distal negative regulatory module (positions −1432 to −716) and a proximal tissue-specific module (−716 to −616). The distal negative regulatory module contains two strong negative regulatory regions [polymorphic PNR (pentanucleotide repeat region) and NREβ (negative regulatory element β)], which sandwich the postive regulatory region PREβ (positive regulatory element β). The PNR was shown to bind to transcription factors in a tissue-specific manner, whereas the ubiquitous transcription factors hepatocyte nuclear factor 3α and GATA binding protein 4 bound to NREβ to repress gene transcription. The proximal tissue-specific module contains two regulatory elements: an activating region (PREα) that activates transcription in HepG2 cells, and NREα, which is responsible for repressing the apo(a) gene in HeLa cells. NREα binds to a HeLa-specific repressor. These multiple regulatory elements might work co-operatively to finely regulate apo(a) gene expression. Although the tissue-specific module is required for apo(a) gene activation and repression in a tissue-specific manner, the combinatorial interplay of the distal and proximal regulators might define the complex pathway(s) of apo(a) gene regulation.
Numerous transcriptional alterations in liver persist after short-term enzyme-replacement therapy in a murine model of mucopolysaccharidosis type VII
Authors: WOLOSZYNEK Josh C. , ROBERTS Marie , COLEMAN Trey , VOGLER Carole , SLY William , SEMENKOVICH Clay F. , SANDS Mark S.
Published: April 2004

The lysosomal storage disease MPS VII (mucopolysaccharidosis type VII) is caused by a deficiency in β-glucuronidase activity, and results in the accumulation of partially degraded glycosaminoglycans in many cell types. Although MPS VII is a simple monogenetic disorder, the clinical presentation is complex and incompletely understood. ERT (enzyme replacement therapy) is relatively effective at improving the clinical course of the disease; however, some pathologies persist. In order to clarify the molecular events contributing to the disease phenotype and how ERT might impact upon them, we analysed liver tissue from untreated and treated MPS VII mice at both 2 and 5 months of age using biochemical assays and microarray analysis. Overall, as the disease progresses, more genes have altered expression and, at either age, numerous transcriptional changes in multiple pathways appear to be refractory to therapy. With respect to the primary site of disease, both transcriptional and post-transcriptional mechanisms are involved in the regulation of lysosomal enzymes and other lysosome-associated proteins. Many of the changes observed in both lysosome-associated mRNAs and proteins are normalized by enzyme replacement. In addition, gene expression changes in seemingly unrelated pathways may account for the complex metabolic phenotype of the MPS VII mouse. In particular, β-glucuronidase deficiency appears to induce physiological malnutrition in MPS VII mice. Malnutrition may account for the pronounced adipose storage deficiency observed in this animal. Studying the molecular response to lysosomal storage, especially those changes recalcitrant to therapy, has revealed additional targets that may improve the efficacy of existing therapies.
Lipid dynamics in yeast under haem-induced unsaturated fatty acid and/or sterol depletion
Authors: FERREIRA Thierry , RÉGNACQ Matthieu , ALIMARDANI Parissa , MOREAU-VAUZELLE Carole , BERGÈS Thierry
Published: April 2004

In the yeast Saccharomyces cerevisiae, UFA (unsaturated fatty acids) and ergosterol syntheses are aerobic processes that require haem. We took advantage of a strain affected in haem synthesis (hem1Δ) to starve specifically for one or the other of these essential lipids in order to examine the consequences on the overall lipid composition. Our results demonstrate that reserve lipids (i.e. triacylglycerols and steryl esters) are depleted independently of haem availability and that their UFA and sterol content is not crucial to sustain residual growth under lipid depletion. In parallel to UFA starvation, a net accumulation of SFA (saturated fatty acids) is observed as a consequence of haem biosynthesis preclusion. Interestingly, the excess SFA are not mainly stored within triacylglycerols and steryl esters but rather within specific phospholipid species, with a marked preference for PtdIns. This results in an increase in the cellular PtdIns content. However, neutral lipid homoeostasis is perturbed under haem starvation. The contribution of two lipid particle-associated proteins (namely Tgl1p and Dga1p) to this process is described.
Phosphoinositides differentially regulate alpha-actinin flexibility and function
Authors: CORGAN Anne Marie , SINGLETON CoreyAyne , SANTOSO Cynthia B. , GREENWOOD Jeffrey A.
Published: April 2004

α-Actinin is a cell-adhesion and cytoskeletal protein that bundles actin microfilaments and links these filaments directly to integrin-adhesion receptors. Phosphoinositides bind to and regulate the interaction of α-actinin with actin filaments and integrin receptors. In the present study, we demonstrate that PtdIns(3,4,5)P3 inhibits and disrupts α-actinin-bundling activity, whereas PtdIns(4,5)P2 can only inhibit activity. In addition, a protease-sensitivity assay was developed to examine the flexibility of the linker region between the actin-binding domain and the spectrin repeats of α-actinin. Both phosphoinositides influenced the extent of proteolysis and the cleavage sites. PtdIns(4,5)P2 binding decreased the proteolysis of α-actinin, suggesting a role in stabilizing the structure of the protein. In contrast, PtdIns(3,4,5)P3 binding enhanced α-actinin proteolysis, indicating an increase in the flexibility of the protein. Furthermore, phosphoinositide binding influenced the proteolysis of the N- and C-terminal domains of α-actinin, indicating regulation of structure within both domains. These results support the hypothesis that PtdIns(4,5)P2 and PtdIns(3,4,5)P3 differentially regulate α-actinin function by modulating the structure and flexibility of the protein.