bluuebunny/crossref_metadata_2025 huggingface dataset:
Westerly wind events and precipitation in the eastern Indian Ocean as predictors for El Niño: Climatology and case study for the 2002–2003 El Niño
Authors: Curtis Scott , Adler Robert F. , Huffman George J. , Gu Guojun
Published: October 2004

This study expands on recent work linking intraseasonal‐to‐seasonal variability in observed precipitation and wind from September to March in the eastern Indian Ocean with the initiation of El Niño events during the last 25 years. First, westerly wind burst (WWB) events are defined as days when westerly wind speeds averaged over 5°–15°S and 70°–100°E were greater than 1.5 standard deviations from the mean. The number of WWB days from September to March was high before the onset of the 1982–1983, 1991–1992, 1997–1998, and 2002–2003 El Niño events, but not the 1986–1987 El Niño. This study suggests that for the 1979–2002 period, variations in precipitation in the eastern Indian Ocean is a more robust predictor of El Niño onset than analyzed winds. On the basis of the work of Curtis et al. [2002], a real‐time precipitation‐based El Niño Onset Index is presented, which during the austral summer of 2001–2002 successfully predicted the 2002–2003 El Niño. The index focuses on the magnitude of 30–60 day oscillations and mean conditions in the precipitation field. Case studies of high‐resolution satellite‐based data sets of precipitation, wind, and sea surface temperature (SST) for the 2001–2002 season are examined to better understand how events in the Indian Ocean are linked to Pacific Ocean wind disturbances and SST changes. Twice during this season maxima in precipitation and zonal winds propagated eastward, the first near the equator and the second to the south. For the southern case, warm waters preceded heavy precipitation in the eastern Indian Ocean, which preceded strong westerly winds. A cooling of the sea surface followed the wind‐rain system. This sequence of events moved through the ocean passage between Indonesia and Australia, suggesting a coupling of convection, wind, and sea surface temperatures on the timescale of days. These case studies provide a basis for how the east Indian Ocean variations are linked to subsequent events in the Pacific Ocean, including the initiation of El Niño events.
Effects of film‐forming compounds on the growth of giant cloud condensation nuclei: Implications for cloud microphysics and the aerosol indirect effect
Authors: Medina Jeessy , Nenes Athanasios
Published: October 2004

The presence of giant cloud condensation nuclei (GCCN) within stratocumulus clouds can help the formation of drizzle by acting as collector drops. We propose that the presence of film‐forming compounds (FFCs) on GCCN may decrease their growth enough to cease this drizzle formation mechanism. We systematically explore the accommodation properties and amount of FFCs necessary to have a significant impact on GCCN size under realistic conditions of growth inside typical stratocumulus clouds. It is found that even low mass fractions (as low as 0.2%) of FFCs with a modest effect on water vapor accommodation can significantly reduce GCCN size and their potential to act as collector drops. Our conclusions apply to both pristine and polluted aerosol conditions, which suggest that in the presence of FFCs, GCCN may be influencing the microphysical evolution of clouds to a lesser extent than previously thought.
Chemistry of sea‐salt particles and inorganic halogen species in Antarctic regions: Compositional differences between coastal and inland stations
Authors: Hara Keiichiro , Osada Kazuo , Kido Mizuka , Hayashi Masahiko , Matsunaga Katsuji , Iwasaka Yasunobu , Yamanouchi Takashi , Hashida Gen , Fukatsu Toru
Published: October 2004

Observations of aerosol constituents and acidic gases in the Antarctic area were carried out at Syowa (39.58°E, 69.00°S) in 1997 and 1998 and Dome Fuji stations (39.62°E, 77.37°S) in 1997. Sea‐salt concentrations decreased to background levels in the summer at both Syowa (Na+, ≤4 nmol m−3) and Dome Fuji (Na+, ∼0.44 nmol m−3 on average). During the winter, blizzard and strong wind may cause an increase of sea‐salt particles at Syowa, whereas long‐range transport from the boundary layer at midlatitudes and coastal Antarctic regions may contribute significantly to the increase in sea‐salt particles observed at Dome Fuji. Particulate Cl− and Br− are liberated preferentially from sea‐salt particles at Syowa and Dome Fuji in the summer. The molar ratio of Cl−/Na+ and Br−/Na+ at Syowa decreased to ∼0.5 and ≈0, respectively, in summer. At Dome Fuji more Cl− tend to be liberated from sea‐salt particles thorough heterogeneous NO3− formation. The concentrations of gaseous chlorine species (mostly HCl) and bromine species ranged from 0.2 to 5.3 nmol m−3 and below detection limit (BDL) to 1.5 nmol m−3, respectively, corresponding to sea‐salt modification. In the present study, SO42− depletion due to mirabilite formation was observed not only at Syowa but also at Dome Fuji. This evidence suggests that SO42− depletion might occur through sublimation on snow surfaces in addition to seawater freezing. At Syowa, sea‐salt fractionation relating to Mg2+, K+, and Ca2+ was also observed mostly under strong wind conditions.
Climate‐related vegetation characteristics derived from Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index and normalized difference vegetation index
Authors: Zhang Ping , Anderson Bruce , Barlow Mathew , Tan Bin , Myneni Ranga B.
Published: October 2004

MODIS‐based leaf area index (LAI) and normalized difference vegetation index (NDVI) are used to examine detailed information regarding actual growing season and total annual production for various regions. Overall, MODIS LAI has larger variability and demonstrates more information regarding the evolution and structure of the seasonal vegetation characteristics. In contrast, the NDVI saturates around 0.7 and tends to overestimate the growing season in regions where it is already long. Next, a climatic impact index (CII) is derived to provide additional information regarding the potential sensitivity of vegetation to changes in climatic variables by accounting for the length of growing season. By normalizing the growth rate to the biome‐average growth rate, this index can identify fractional loss of annual production, as opposed to the absolute loss which may be strongly weighted by the overall growth rate for different ecosystems. Our index provides a quantitative framework for assessing the importance of the length of the growing season in determining climatic vulnerability. In the last part of the paper, we use the long time series AVHRR products as a substitute for the MODIS products and test the temporal characteristics of the CII. Major drought events are well‐captured by the CII, suggesting potential use as a monitoring and evaluation tool. Furthermore, the strong positive correlation between the CII and the vegetation condition index (VCI) suggests that the CII can quantitatively identify the effects of climatic variability upon vegetation activity.
Absolute values of gravity wave momentum flux derived from satellite data
Authors: Ern Manfred , Preusse Peter , Alexander M. Joan , Warner Christopher D.
Published: October 2004

Temperature data obtained by the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) are analyzed for gravity waves (GWs). Amplitude, phase and vertical wavelength are determined from detrended temperature height profiles. The retrieved phases are utilized to estimate the horizontal wavelengths. At 25 km altitude an equatorial maximum of horizontal wavelength with a decrease toward mid and high latitudes is found. Simultaneous estimates of both horizontal and vertical wavelengths and temperature amplitudes allow the direct calculation of GW momentum flux (MF) from satellite observations for the first time. However, histograms of horizontal wavelength distributions indicate severe undersampling which prevents the retrieval of the propagation directions of the waves, and suggests our MF estimates may be too low, particularly at the high latitudes. Therefore an empirical aliasing correction has been applied. A world map of MF at 25 km altitude shows high variability and pronounced source regions and deviates in structure from a map of GW variances at the same altitude. Results from the Warner and McIntyre GW parameterization scheme (three‐part model) show better agreement with CRISTA MF estimates than with CRISTA squared GW amplitudes. Best agreement is found for low model launch levels. Large error ranges of the estimated MF values obtained in this paper could be substantially reduced by improved horizontal sampling in future satellite missions.
On the relevance of accurate correction and validation procedures in the analysis of AVHRR‐NDVI time series for long‐term monitoring
Authors: Simoniello T. , Cuomo V. , Lanfredi M. , Lasaponara R. , Macchiato M.
Published: October 2004

The effects of solar zenith angle (SZA) changes, short‐wave calibration instability, and satellite switches on the interannual vegetation variability inferred from 1‐km advanced very high resolution radiometer–normalized difference vegetation index (AVHRR‐NDVI) were evaluated. The annual maximum value composite (MVC) of NDVI over middle and southern Italy was processed from afternoon viewings of NOAA 9, 11, and 14 for the period 1985–1999. MVCs were computed from imagery relative to the period of maximum photosynthetic activity. Raw data were compared with data corrected according to a procedure we recently developed and validated. Our results show that the SZA changes cause an error that increases as the NDVI value decreases. The maximum magnitude is 6.2% for forests and up to 41.8% for lakes. Calibration and intercalibration anomalies modify NOAA 11 NDVI values of 7–8% for all classes except for lakes and artificial surfaces, which show a variation of almost 11–12%; the NOAA 14 NDVI anomalies are set on about 11% with the exception of artificial surfaces (∼17%) and sparsely vegetated areas (∼9%). We also evaluated the improvement obtained from the use of the last update of calibration coefficients of NOAA 14. The positive impact of these coefficients is apparent for all the considered land covers, but a persistent overestimation of NOAA 14 calibration coefficients was still found. Altogether, the artificial anomalies can induce a relative error on NDVI variations up to 130%. This result strongly points out the relevance of performing an accurate correction of systematic errors and a careful validation before drawing conclusions from multitemporal AVHRR‐NDVI analyses focused on the detection of long‐term vegetation changes.
Temporal variability of dust mobilization and concentration in source regions
Authors: Luo Chao , Mahowald Natalie , Jones Charles
Published: October 2004

The time‐varying properties of dust mobilization and concentration variability in source areas are studied in model simulations to understand the processes that control entrainment of dust into the atmosphere. Two different meteorological reanalysis data sets (National Centers for Environmental Prediction/National Center for Atmospheric Research and NASA Data Assimilation Office) and two different source parameterizations are used for the analysis, which is done for six different main dust source regions. The results show that ∼35–70% variance of dust mobilization is associated with diurnal variability of dust mobilization in the major dust sources regions, and this is similar using different meteorological analyses and source parameterizations. Synoptic‐scale variability is responsible for 6–50% of the dust mobilization, with more variation between different meteorology and parameterizations. The variability of dust concentrations in source regions is very sensitive to source meteorology and parameterization, with the synoptic variability responsible for 30–50% of the variability in some configurations or 6–40% in other configurations. Diurnal variability in concentrations varies from 20–50 to 25–80% depending on the model configuration. Analyses suggest that dust mobilization and dust concentration are more influenced by synoptic variability in Australia and east Asia than in North Africa and Arabian dust source regions, consistent with observations of cold fronts and cyclone movements systems driving dust mobilization and transport in Australia and east Asia source regions. Differences in variability between different meteorological data sets and source parameterizations suggest that possible dust feedbacks onto the dust cycle may be sensitive to source parameterization and model.
Simultaneous determination of continental surface emissivity and temperature from NOAA 10/HIRS observations: Analysis of their seasonal variations
Authors: Chédin A. , Péquignot E. , Serrar S. , Scott N. A.
Published: October 2004

Continental surface infrared emissivity strongly depends on the wavelength and on the type of the surface. Emissivity values as low as 0.7 may be observed around 8–10 μm or, at shorter wavelengths, around 4 μm, particularly over desert regions. Satellite observations are very sensitive to emissivity variations: At 11 μm an uncertainty as small as 2% may lead to a variation of up to 0.5K in brightness temperature. An accurate and coherent, i.e., simultaneous, determination of surface temperature and emissivity is essential to greatly improve the estimation of the longwave surface energy budget and, consequently, to improve the performance of surface‐atmosphere interaction models. On the basis of a space differential approach and a nonlinear regression inference method, 4 years of NOAA 10 observations (July 1987 to June 1991) over northern Africa (5°N–30°N and 20°W–60°E) have been interpreted in terms of surface emissivity at three wavelengths, namely, 11.1 μm, 8.3 μm, and 4 μm, corresponding to atmospheric windows, and surface temperature, actually, “skin” temperature. Emissivity maps at a resolution of 1° × 1° and 1 month reveal strong signatures of sand at 8.3 and 4.0 μm and of carbonates at 11.1 μm. Time series of zonal means may bring into evidence important seasonal variations as, for example, over regions of savannas: from 5% at 11.1 μm (peak to peak) to 15% at 4 μm. They are shown to be in phase with the precipitation and 1 month ahead of the Normalized Difference Vegetation Index time series. The mean uncertainty may be theoretically estimated on the order of less than 2% for the emissivity at 11.1 μm and of 1.6K for the surface temperature.
Transport of biomass burning emissions from southern Africa
Authors: Sinha Parikhit , Jaeglé Lyatt , Hobbs Peter V. , Liang Qing
Published: October 2004

The transport of biomass burning emissions from southern Africa to the neighboring Atlantic and Indian Oceans during the dry season (May–October) of 2000 is characterized using ground, ozonesonde, and aircraft measurements of carbon monoxide (CO) and ozone (O3) in and around southern Africa, together with the GEOS‐CHEM global model of tropospheric chemistry. The model shows a positive bias of ∼20% for CO and a negative bias of ∼10–25% for O3 at oceanic sites downwind of fire emissions. Near areas of active fire emissions the model shows a negative bias of ∼60% and ∼30% for CO and O3, respectively, likely due to the coarse spatial (2° × 2.5°) and temporal (monthly) resolution of the model compared to that of active fires. On average, from 1994 to 2000, ∼60 Tg of carbon monoxide (CO) from biomass burning in southern Africa was transported eastward to the Indian Ocean across the latitude band 0°–60°S during the 6 months of the dry season. Over the same time period, ∼40 Tg of CO from southern African biomass burning was transported westward to the Atlantic Ocean over the latitudes 0°–20°S during the 6‐month dry season, but most of that amount was transported back eastward over higher latitudes to the south (21°–60°S). Eastward transport of biomass burning emissions from southern Africa enhances CO concentrations by ∼4–13 ppbv per month over the southern subtropical Indian Ocean during the dry season, with peak enhancements in September. Carbon monoxide from southern African and South American biomass burning is seen in the model simulations as far away as Australia, contributing ∼8 ppbv and ∼12–15 ppbv CO, respectively, and thus explaining the ∼20–25 ppbv observed enhancement of CO over Melbourne in mid‐September 2000.
Interaction between a bubble plume and the near field in a stratified lake
Authors: McGinnis D. F. , Lorke A. , Wüest A. , Stöckli A. , Little J. C.
Published: October 2004

A steady state bubble‐plume model is evaluated using full‐scale temperature, salinity, and dissolved oxygen data collected in a Swiss lake. The data revealed a plume‐generated near‐field environment that differed significantly from the ambient far‐field water column properties. A near‐field torus of reduced stratification developed around the plume, the extent of which is on the same lateral scale as the horizontal dislocations generated by persistent first‐mode seiching. The plume fallback water was found to penetrate much deeper than expected, thereby maintaining reduced vertical gradients in the near‐field torus. The plume entrains a portion of the fallback water leading to short‐circuiting, which generates a complex plume‐lake interaction and reduces far‐field downwelling relative to the upward plume flow. As the integral plume model incorporates the entrainment hypothesis, it is highly sensitive to the near‐field environmental conditions. After identifying appropriate near‐field boundary conditions the plume model predictions agree well with the field observations.
Edge plasma measurements near the minimum-B anchor cell of GAMMA10 using Langmuir probe and calorimeter arrays
Authors: Nakashima Y. , Islam M. K. , Natori T. , Katanuma I. , Ohki T. , Watanabe K. , Higashizono Y. , Cho T. , Ishimoto Y.
Published: October 2004

Edge plasma diagnostic system equipped in minimum-B anchor cell of the GAMMA10 tandem mirror is described together with the measured results. Several sets of the diagnostic element consisting of a Langmuir probe and a calorimeter are placed in array on the conducting plates installed in the east anchor cell. This diagnostic system is designed to be capable of precisely investigating the spatial dependence of the edge plasma parameters. In typical ion cyclotron range of frequency-heated plasmas, detailed behavior of the edge plasma in the anchor transition regions has been measured by using this system. From these measurements a significant asymmetry of spatial profile was observed in the floating potentials. Heat flow profiles also showed the similar dependence to the probe signals. In this region there exists a strong gradient of the magnetic field strength and the direction of the observed shift is found to be consistent with that of gradient B drift for ions.
Arrangement of emissive and cold probes for fluctuation and Reynolds stress measurements
Authors: Ioniţă C. , Balan P. , Schrittwieser R. , Figueiredo H. F. C. , Silva C. , Varandas C. A. F. , Galvão R. M. O.
Published: October 2004

An arrangement of three emissive probes and one cold probe was used to simultaneously determine the Reynolds stress and the fluctuation-induced flux in the edge region of the tokamak ISTTOK. The emissive probes are arranged in a 90º triangle and inserted into the tokamak so that two of the probes are separated radially and two are separated in the poloidal direction, with one probe being used for both directions. Since emissive probes deliver a better measure of the plasma potential than cold probes, with this arrangement the radial and the poloidal electric field and their fluctuations can be measured simultaneously, so that the Reynolds stress Re can be derived from the data. This setup is radially movable so that also the radial gradient of Re can be determined. In addition, a cold probe is inserted close to one of the outer emissive probes. The fluctuation-induced flux can be determined from a simultaneous measurement of the poloidal field fluctuations and those of the ion saturation current.
Separatrix radius measurement of field-reversed configuration plasma in FRX-L
Authors: Zhang S. Y. , Tejero E. M. , Taccetti J. M. , Wurden G. A. , Intrator T. P. , Waganaar W. J. , Perkins R.
Published: October 2004

Magnetic pickup coils and single turn flux loops are installed on the FRX-L device. The combination of the two measurements provides the excluded flux radius that approximates the separatrix radius of the field-reversed configuration (FRC) plasma. Arrays of similar probes are used to map out local magnetic field dynamics beyond both ends of the theta-coil confinement region to help understand the effects of cusp locations on flux trapping during the FRC formation process. Details on the probe design and system calibrations are presented. The overall system calibration of excluded flux radius measurement is examined by replacing FRC plasma with a known radius aluminum conductor cylinder.
Myelin proteolipid protein-specific CD4+CD25+regulatory cells mediate genetic resistance to experimental autoimmune encephalomyelitis
Authors: Reddy Jayagopala , Illes Zsolt , Zhang Xingmin , Encinas Jeffrey , Pyrdol Jason , Nicholson Lindsay , Sobel Raymond A. , Wucherpfennig Kai W. , Kuchroo Vijay K.
Published: October 2004

SJL mice are highly susceptible to experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) peptide 139-151, whereas H-2 congenic B10.S mice are resistant. Immunodominance and susceptibility to EAE are associated with a high precursor frequency of PLP 139-151-specific T cells in the naïve repertoire of SJL mice. To understand the mechanism of EAE resistance in B10.S mice, we determined the precursor frequency of PLP 139-151-reactive T cells in both strains by using IAs/PLP 139-151 tetramers. SJL and B10.S mice had similar frequencies of tetramer-reactive T cells in the naïve peripheral repertoire. However, in SJL mice, the majority of PLP 139-151 tetramer-positive cells were in the CD4+CD25-population, whereas there were more tetramer-positive cells in the CD4+CD25+population of B10.S mice. Depletion of CD4+CD25+cellsin vivofacilitated the expansion of PLP 139-151-reactive cells with production of T helper 1 cytokines in EAE-resistant B10.S mice. Furthermore, anti-CD25 Ab treatment before immunization resulted in EAE induction in these otherwise resistant mice. These data indicate an important role for autoantigen-specific CD4+CD25+cells in genetic resistance to autoimmunity.
Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic
Authors: Heiri Oliver , Tinner Willy , Lotter André F.
Published: October 2004

We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of ≈1°C are inferred at ≈10,700–10,500 and 8,200–7,600 calibrated
14
C years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermohaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermohaline circulation reductions have led to summer-temperature declines of up to 1°C in central Europe.
Total synthesis of long DNA sequences: Synthesis of a contiguous 32-kb polyketide synthase gene cluster
Authors: Kodumal Sarah J. , Patel Kedar G. , Reid Ralph , Menzella Hugo G. , Welch Mark , Santi Daniel V.
Published: October 2004

To exploit the huge potential of whole-genome sequence information, the ability to efficiently synthesize long, accurate DNA sequences is becoming increasingly important. An approach proposed toward this end involves the synthesis of ≈5-kb segments of DNA, followed by their assembly into longer sequences by conventional cloning methods [Smith, H. O., Hutchinson, C. A., III, Pfannkoch, C. & Venter, J. C. (2003)
Proc. Natl. Acad. Sci. USA
100, 15440–15445]. The major current impediment to the success of this tactic is the difficulty of building the ≈5-kb components accurately, efficiently, and rapidly from short synthetic oligonucleotide building blocks. We have developed and implemented a strategy for the high-throughput synthesis of long, accurate DNA sequences. Unpurified 40-base synthetic oligonucleotides are built into 500- to 800-bp “synthons” with low error frequency by automated PCR-based gene synthesis. By parallel processing, these synthons are efficiently joined into multisynthon ≈5-kb segments by using only three endonucleases and “ligation by selection.” These large segments can be subsequently assembled into very long sequences by conventional cloning. We validated the approach by building a synthetic 31,656-bp polyketide synthase gene cluster whose functionality was demonstrated by its ability to produce the megaenzyme and its polyketide product in
Escherichia coli
.
The Accountability of Para-governmental Organizations (bonyads): The Case of Iranian Foundations
Authors: Saeidi Ali A.
Published: October 2004

This paper attempts to explain the emergence and development of para-governmental organizations (bonyads) in Iran and demonstrate their contradictory position in the Iranian political economy. These organizations represent the dual power structure in Iran which reinforces the financial authority of religious leaders without accountability. By analyzing the functions of these organizations, the paper sets out to probe their economic policies in line with the government's populist macroeconomic policies. The paper demonstrates the adverse effects of these organizations on political development and economic reforms in the post-Khomeini era when the struggle for accountability soared.
Possible Mechanisms Underlying the Testicular Toxicity of Oxfendazole in Rats
Authors: Okamura Miwa , Watanabe Takao , Kashida Yoko , Machida Noboru , Mitsumori Kunitoshi
Published: October 2004

To clarify the mechanisms underlying the testicular toxicity of oxfendazole (OX), adult Wistar rats were orally administered a dose of 100 mg/kg/day for 3, 7, or 14 days. Assays of sex-related hormones showed a significant decrease in only the estradiol serum level at days 3 and 7, as compared with the control group. Histopathologically, marked degeneration of meiotic spermatocytes was observed in stage XIV—I seminiferous tubules from day 3 onwards, and these spermatocytes gave positive results on terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL). Abnormalities of spermiogenesis such as megakaryospermatids and binucleated spermatids were also observed in the testes of OX-treated rats. Under the electron microscope, lipid accumulation and dilatation of the endoplasmic reticulum were frequently found in the cytoplasm of the Sertoli cells on day 3. These results strongly suggest that OX induces both apoptosis of meiotic spermatocytes, most probably due to disruption of the microtubules, and degeneration of the Sertoli cells, characterized by distended endoplasmic reticulum and prominent cytosolic lipid accumulation.
Articular Chondromatosis and Chrondroid Metaplasia in Transgenic TAg Mice
Authors: Verschoyle Richard D. , Edwards Richard , Nolan Barbara , Greaves Peter
Published: October 2004

The C3(1)/SV40 T antigen transgenic mouse model for which rapid mammary and prostate tumor development has been documented uses the FVB/N mouse as a background strain. In this study, where the background strain used was the C57BL/6J mouse, neither mammary nor prostate tumors developed over periods of up to 40 weeks. However, a disturbance of hyaline cartilage in joints was observed similar to that found in synovial chondromatosis in humans. In addition, cartilage thickening in the external ears and cartilaginous metaplasia of the ascending aorta also occurred. This suggests that rearrangement of the transgene occurred in breeding on the C57BL background, thus modifying its expression. It raises the possibility that the genetic changes induced by the SV40 T antigen transforming sequence are important in cartilage homeostasis.
Subchronic Exposure to Arsenic Through Drinking Water Alters Expression of Cancer-Related Genes in Rat Liver
Authors: Xing Cui  , Song Li  , Shraim Amjad , Kobayashi Yayoi , Hayakawa Toru , Kanno Sanae , Yamamoto Megumi , Hirano Seishiro
Published: October 2004

Although arsenic exposure causes liver disease and/or hepatoma, little is known about molecular mechanisms of arsenic-induced liver toxicity or carcinogenesis. We investigated the effects of arsenic on expression of cancer-related genes in a rat liver following subchronic exposure to sodium arsenate (1, 10, 100 ppm in drinking water), by using real-time quantitative RT-PCR and immunohistochemical analyses. Arsenic accumulated in the rat liver dose-dependently and caused hepatic histopathological changes, such as disruption of hepatic cords, sinusoidal dilation, and fatty infiltration. A 1-month exposure to arsenic significantly increased hepatic mRNA levels of cyclin D1 (10 ppm), ILK (1 ppm), and p27Kip1 (10 ppm), whereas it reduced mRNA levels of PTEN (1 ppm) and β-catenin (100 ppm). In contrast, a 4-month arsenic exposure showed increased mRNA expression of cyclin D1 (100 ppm), ILK (1 ppm), and p27Kip1 (1 and 10 ppm), and decreased expression of both PTEN and β-catenin at all 3 doses. An immunohistochemical study revealed that each protein expression accords closely with each gene expression of mRNA level. In conclusion, subchronic exposure to inorganic arsenate caused pathological changes and altered expression of cyclin D1, p27Kip1, ILK, PTEN, and β-catenin in the liver. This implies that arsenic liver toxicity involves disturbances of some cancer-related molecules.
Defective function of GABA-containing synaptic vesicles in mice lacking the AP-3B clathrin adaptor
Authors: Nakatsu Fubito , Okada Motohiro , Mori Fumiaki , Kumazawa Noriko , Iwasa Hiroto , Zhu Gang , Kasagi Yasufumi , Kamiya Haruyuki , Harada Akihiro , Nishimura Kazuhiro , Takeuchi Arata , Miyazaki Taisuke , Watanabe Masahiko , Yuasa Shigeki , Manabe Toshiya , Wakabayashi Koichi , Kaneko Sunao , Saito Takashi , Ohno Hiroshi
Published: October 2004

AP-3 is a member of the adaptor protein (AP) complex family that regulates the vesicular transport of cargo proteins in the secretory and endocytic pathways. There are two isoforms of AP-3: the ubiquitously expressed AP-3A and the neuron-specific AP-3B. Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved. To address this question, we generated mice lacking μ3B, a subunit of AP-3B. μ3B−/− mice suffered from spontaneous epileptic seizures. Morphological abnormalities were observed at synapses in these mice. Biochemical studies demonstrated the impairment of γ-aminobutyric acid (GABA) release because of, at least in part, the reduction of vesicular GABA transporter in μ3B−/− mice. This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway. Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles. This work adds a new aspect to the pathogenesis of epilepsy.
Differential contribution of Bud6p and Kar9p to microtubule capture and spindle orientation in S. cerevisiae
Authors: Huisman Stephen M. , Bales Olivia A.M. , Bertrand Marie , Smeets Monique F.M.A. , Reed Steven I. , Segal Marisa
Published: October 2004

In Saccharomyces cerevisiae, spindle orientation is controlled by a temporal and spatial program of microtubule (MT)–cortex interactions. This program requires Bud6p/Aip3p to direct the old pole to the bud and confine the new pole to the mother cell. Bud6p function has been linked to Kar9p, a protein guiding MTs along actin cables. Here, we show that Kar9p does not mediate Bud6p functions in spindle orientation. Based on live microscopy analysis, kar9Δ cells maintained Bud6p-dependent MT capture. Conversely, bud6Δ cells supported Kar9p-associated MT delivery to the bud. Moreover, additive phenotypes in bud6Δ kar9Δ or bud6Δ dyn1Δ mutants underscored the separate contributions of Bud6p, Kar9p, and dynein to spindle positioning. Finally, tub2C354S, a mutation decreasing MT dynamics, suppressed a kar9Δ mutation in a BUD6-dependent manner. Thus, Kar9p-independent capture at Bud6p sites can effect spindle orientation provided MT turnover is reduced. Together, these results demonstrate Bud6p function in MT capture at the cell cortex, independent of Kar9p-mediated MT delivery along actin cables.
Gene Dosage–limiting Role ofAirein Thymic Expression, Clonal Deletion, and Organ-specific Autoimmunity
Authors: Liston Adrian , Gray Daniel H.D. , Lesage Sylvie , Fletcher Anne L. , Wilson Judith , Webster Kylie E. , Scott Hamish S. , Boyd Richard L. , Peltonen Leena , Goodnow Christopher C.
Published: October 2004

Inactivation of the autoimmune regulator (Aire) gene causes a rare recessive disorder, autoimmune polyendocrine syndrome 1 (APS1), but it is not known if Aire-dependent tolerance mechanisms are susceptible to the quantitative genetic changes thought to underlie more common autoimmune diseases. In mice with a targeted mutation, complete loss of Aire abolished expression of an insulin promoter transgene in thymic epithelium, but had no effect in pancreatic islets or the testes. Loss of one copy of Aire diminished thymic expression of the endogenous insulin gene and the transgene, resulting in a 300% increase in islet-reactive CD4 T cells escaping thymic deletion in T cell receptor transgenic mice, and dramatically increased progression to diabetes. Thymic deletion induced by antigen under control of the thyroglobulin promoter was abolished in Aire homozygotes and less efficient in heterozygotes, providing an explanation for thyroid autoimmunity in APS1. In contrast, Aire deficiency had no effect on thymic deletion to antigen controlled by a systemic H-2K promoter. The sensitivity of Aire-dependent thymic deletion to small reductions in function makes this pathway a prime candidate for more subtle autoimmune quantitative trait loci, and suggests that methods to increase Aire activity would be a potent strategy to lower the incidence of organ-specific autoimmunity.
Helicobacter pyloriModulates the T Helper Cell 1/T Helper Cell 2 Balance through Phase-variable Interaction between Lipopolysaccharide and DC-SIGN
Authors: Bergman Mathijs P. , Engering Anneke , Smits Hermelijn H. , van Vliet Sandra J. , van Bodegraven Ad A. , Wirth Hans-Peter , Kapsenberg Martien L. , Vandenbroucke-Grauls Christina M.J.E. , van Kooyk Yvette , Appelmelk Ben J.
Published: October 2004

The human gastric pathogen Helicobacter pylori spontaneously switches lipopolysaccharide (LPS) Lewis (Le) antigens on and off (phase-variable expression), but the biological significance of this is unclear. Here, we report that Le+ H. pylori variants are able to bind to the C-type lectin DC-SIGN and present on gastric dendritic cells (DCs), and demonstrate that this interaction blocks T helper cell (Th)1 development. In contrast, Le− variants escape binding to DCs and induce a strong Th1 cell response. In addition, in gastric biopsies challenged ex vivo with Le+ variants that bind DC-SIGN, interleukin 6 production is decreased, indicative of increased immune suppression. Our data indicate a role for LPS phase variation and Le antigen expression by H. pylori in suppressing immune responses through DC-SIGN.
Flagellar Length Control System: Testing a Simple Model Based on Intraflagellar Transport and Turnover
Authors: Marshall Wallace F. , Qin Hongmin , Brenni Mónica Rodrigo , Rosenbaum Joel L.
Published: October 2004

Flagellar length regulation provides a simple model system for addressing the general problem of organelle size control. Based on a systems-level analysis of flagellar dynamics, we have proposed a mechanism for flagellar length control in which length is set by the balance of continuous flagellar assembly and disassembly. The model proposes that the assembly rate is length dependent due to the inherent length dependence of intraflagellar transport, whereas disassembly is length independent, such that the two rates can only reach a balance point at a single length. In this report, we test this theoretical model by using three different measurements: 1) the quantity of intraflagellar transport machinery as a function of length, 2) the variation of flagellar length as a function of flagellar number, and 3) the rate of flagellar growth as a function of length. We find that the quantity of intraflagellar transport machinery is independent of length, that flagellar length is a decreasing function of flagellar number, and that flagellar growth rate in regenerating flagella depends on length and not on the time since regeneration began. These results are consistent with the balance-point model for length control. The three strategies used here are not limited to flagella and can in principle be adapted to probe size control systems for any organelle.
Dexmedetomidine Pharmacodynamics: Part I
Authors: Hsu Yung-Wei , Cortinez Luis I. , Robertson Kerri M. , Keifer John C. , Sum-Ping Sam T. , Moretti Eugene W. , Young Christopher C. , Wright David R. , MacLeod David B. , Somma Jacques
Published: October 2004

Background

Dexmedetomidine, a highly selective alpha2-adrenoceptor agonist used for short-term sedation of mechanically ventilated patients, has minimal effect on ventilation.

Methods

This study compared the respiratory effect of dexmedetomidine to that of remifentanil. The authors measured and compared respiratory responses of six healthy male volunteers during (1) a stepwise target-controlled infusion of remifentanil, (2) a stepwise target-controlled infusion of dexmedetomidine, and (3) a pseudonatural sleep session.

Results

Compared with baseline, remifentanil infusions resulted in respiratory depression as evidenced by a decrease in respiratory rate and minute ventilation, respiratory acidosis, and apnea episodes resulting in desaturations. Remifentanil disturbed the natural pattern of breathing and flattened the distribution of ventilatory timing (inspiratory time/ventilatory cycle time). The respiratory effects of dexmedetomidine markedly contrasted with those of remifentanil. When compared with baseline, during dexmedetomidine infusions, the respiratory rate significantly increased, and the overall apnea/hypopnea index significantly decreased. The distribution of inspiratory time/ventilatory cycle time showed an increased peak. In addition, dexmedetomidine seemed to mimic some aspect of natural sleep. While the subjects were breathing a 5% CO2 mixture, hypercapnic arousal phenomena (documented by the Bispectral Index, the electroencephalogram, and sudden increase in the minute ventilation) were observed during dexmedetomidine infusions. Similar phenomena during natural sleep have been reported in the literature.

Conclusions

In comparison with remifentanil, dexmedetomidine infusions (1) did not result in clinically significant respiratory depression, (2) decreased rather than increased the apnea/hypopnea index, and (3) exhibited some similarity with natural sleep.
Acute Care Skills in Anesthesia Practice
Authors: Murray David J. , Boulet John R. , Kras Joseph F. , Woodhouse Julie A. , Cox Thomas , McAllister John D.
Published: October 2004

Background

A recurring initiative in graduate education is to find more effective methods to assess specialists' skills. Life-sized simulators could be used to assess the more complex skills expected in specialty practice if a curriculum of relevant exercises were developed that could be simply and reliably scored. The purpose of this study was to develop simulation exercises and associated scoring methods and determine whether these scenarios could be used to evaluate acute anesthesia care skills.

Methods

Twenty-eight residents (12 junior and 16 senior) managed three intraoperative and three postoperative simulation exercises. Trainees were required to make a diagnosis and intervention in a simulation encounter designed to recreate an acute perioperative complication. The videotaped performances were scored by six raters. Three raters used a checklist scoring system. Three faculty raters measured when trainees performed three key diagnostic or therapeutic actions during each 5-min scenario. These faculty also provided a global score using a 10-cm line with scores from 0 (unsatisfactory) to 10 (outstanding). The scenarios included (1) intraoperative myocardial ischemia, (2) postoperative anaphylaxis, (3) intraoperative pneumothorax, (4) postoperative cerebral hemorrhage with intracranial hypertension, (5) intraoperative ventricular tachycardia, and (6) postoperative respiratory failure.

Results

The high correlation among all of the scoring systems and small variance among raters' scores indicated that all of the scoring systems measured similar performance domains. Scenarios varied in their overall difficulty. Even though trainees who performed well on one exercise were likely to perform well in subsequent scenarios, the authors found that there were considerable differences in case difficulty.

Conclusion

This study suggests that simulation can be used to measure more complex skills expected in specialty training. Similar to other studies that assess a broad content domain, multiple encounters are needed to estimate skill effectively and accurately.
Comparison of Cisatracurium and Vecuronium by Infusion in Neonates and Small Infants after Congenital Heart Surgery
Authors: Reich David L. , Hollinger Ingrid , Harrington Donna J. , Seiden Howard S. , Chakravorti Sephali , Cook D Ryan
Published: October 2004

Background

Neonates and infants often require extended periods of mechanical ventilation facilitated by sedation and neuromuscular blockade.

Methods

Twenty-three patients aged younger than 2 yr were randomly assigned to receive either cisatracurium or vecuronium infusions postoperatively in a double-blinded fashion after undergoing congenital heart surgery. The infusion was titrated to maintain one twitch of a train-of-four. The times to full spontaneous recovery of train-of-four without fade, extubation, intensive care unit discharge, and hospital discharge were documented after drug discontinuation. Sparse sampling after termination of the infusion and a one-compartment model were used for pharmacokinetic analysis. The Mann-Whitney U test and Student t test were used to compare data between groups.

Results

There were no significant differences between groups with respect to demographic data or duration of postoperative neuromuscular blockade infusion. The median recovery time for train-of-four for cisatracurium (30 min) was less than that for vecuronium (180 min) (P < 0.05). Three patients in the vecuronium group had prolonged train-of-four recovery: Two had long elimination half-lives for vecuronium, and one had a high concentration of 3-OH vecuronium. There were no differences in extubation times, intensive care unit stays, or hospital stays between groups.

Conclusions

Our results parallel data from adults demonstrating a markedly shorter recovery of neuromuscular transmission after cisatracurium compared with vecuronium. Decreased clearance of vecuronium and the accumulation of 3-OH vecuronium may contribute to prolonged spontaneous recovery times. Cisatracurium is associated with faster spontaneous recovery of neuromuscular function compared with vecuronium but not with any differences in intermediate outcome measures in neonates and infants.
Intravenous Emulsified Halogenated Anesthetics Produce Acute and Delayed Preconditioning against Myocardial Infarction in Rabbits
Authors: Chiari Pascal C. , Pagel Paul S. , Tanaka Katsuya , Krolikowski John G. , Ludwig Lynda M. , Trillo Raul A. , Puri Navneet , Kersten Judy R. , Warltier David C.
Published: October 2004

Background

Preconditioning against myocardial infarction by volatile anesthetics is well known. The authors tested the hypothesis that new emulsified formulations of halogenated anesthetics administered intravenously reduce myocardial infarct size when administered either 1 or 24 h before prolonged ischemia and reperfusion.

Methods

Pentobarbital-anesthetized rabbits (n = 39) were instrumented for measurement of hemodynamics and randomly assigned to receive intravenous saline (control), lipid vehicle, or infusions (3.5 ml . kg . h for 30 min) of emulsified isoflurane (6.9%), enflurane (7.1%), or sevoflurane (7.5%). Infusions were discontinued 30 min before a 30-min coronary occlusion and 3 h of reperfusion. In three additional groups, conscious rabbits (n = 21) received saline, lipid vehicle, or emulsified sevoflurane (7.5%) infusions (3.5 ml . kg . h for 30 min) 24 h before ischemia and reperfusion. Infarct size was determined using triphenyltetrazolium staining.

Results

Lipid vehicle produced transient increases in heart rate, whereas emulsified volatile anesthetics had no effect on hemodynamics before coronary occlusion. Lipid vehicle did not affect infarct size (38 +/- 2% of the area at risk; mean +/- SEM) as compared with saline control (41 +/- 4%). In contrast, emulsified isoflurane, enflurane, and sevoflurane reduced infarct size (20 +/- 3%, 20 +/- 3%, and 21 +/- 2% of the area at risk, respectively; P < 0.05). Administration of lipid vehicle or emulsified sevoflurane did not produce sedation or respiratory depression in conscious rabbits. Emulsified sevoflurane (18 +/- 2%) but not lipid vehicle (44 +/- 2%) reduced infarct size as compared with control in delayed preconditioning experiments.

Conclusions

Intravenous emulsified halogenated anesthetics produce acute and delayed preconditioning against myocardial infarction.