bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large‐scale field sampling: Fixed nitrogen and dry deposition of phosphorus
Authors: Baker A. R. , Lesworth T. , Adams C. , Jickells T. D. , Ganzeveld L.
Published: July 2010

Atmospheric nitrogen inputs to the ocean are estimated to have increased by up to a factor of three as a result of increased anthropogenic emissions over the last 150 years, with further increases expected in the short‐ to mid‐term at least. Such estimates are largely based on emissions and atmospheric transport modeling, because, apart from a few island sites, there is very little observational data available for atmospheric nitrogen concentrations over the remote ocean. Here we use samples of rainwater and aerosol we obtained during 12 long‐transect cruises across the Atlantic Ocean between 50°N and 50°S as the basis for a climatological estimate of nitrogen inputs to the basin. The climatology is for the 5 years 2001–2005, during which almost all of the cruises took place, and includes dry and wet deposition of nitrate and ammonium explicitly, together with a more uncertain estimate of soluble organic nitrogen deposition. Our results indicate that nitrogen inputs into the region were ∼850–1420 Gmol (12–20 Tg) N yr−1, with ∼78–85% of this in the form of wet deposition. Inputs were greater in the Northern Hemisphere and in wet regions, and wet regions had a greater proportion of input via wet deposition. The largest uncertainty in our estimate of dry inputs is associated with variability in deposition velocities, while the largest uncertainty in our wet nitrogen input estimate is due to the limited amount and uneven geographic distribution of observational data. We also estimate a lower limit of dry deposition of phosphate to be ∼0.19 Gmol P yr−1, using data from the same cruises. We compare our results to several recent estimates of N and P deposition to the Atlantic and discuss the likely sources of uncertainty, such as the potential seasonal bias introduced by our sampling, on our climatology.
Seismic reflector alignment along the volcanic front in northeastern Honshu, Japan
Authors: Hasemi Akiko , Horiuchi Shigeki
Published: July 2010

We found seismic reflectors aligned along the east side of the volcanic front in northeastern Honshu, Japan, by analyzing seismograms of intermediate‐depth earthquakes recorded at High Sensitivity Seismograph Network Japan stations. We identified an unusual high‐frequency later phase on the seismograms, which arrives after the direct S waves and continues for >5 s. The characteristics of the waveforms suggest that this later phase is an S wave incidence. We plotted envelope waveforms and identified later phase arrivals on envelope waveforms. To estimate the location of the source of the later phases, we defined an event group that consisted of six to eight events distributed in a region of ∼50 km3. The source of the later phases was located by a combination of a station and an event group using later phase travel times. If we assume that later phases arriving at a station from an event group are generated by a common source, then we can use the observed travel times in a grid search to obtain the source location. The sources of the later phase were found to be aligned along the east side of a volcanic front at a depth of 20–30 km. The averaged ratio of the amplitudes of the later phases to the amplitudes of the incident waves on the later phase source was estimated to be ∼0.6. This result suggests the existence of unusual reflectors spread in the lower crust beneath the fore‐arc region. It may be possible that the later phase sources are steeply inclined bodies filled with fluid.
Multiphase electrokinetic coupling: Insights into the impact of fluid and charge distribution at the pore scale from a bundle of capillary tubes model
Authors: Jackson Matthew D.
Published: July 2010

A bundle of capillary tubes model is used to investigate multiphase electrokinetic coupling during the flow of water and an immiscible second phase such as air or oil. The charge on the surface of each capillary is assumed constant, and the impact of charge distribution at the pore scale is investigated by calculating the relative streaming potential coupling coefficient assuming that the diffuse part of the electrical double layer is (1) much less than the capillary radius (“thin”) and (2) comparable to the capillary radius (“thick”). The relative coupling coefficient generally decreases with decreasing water saturation, falling to zero at the irreducible water saturation. In the limit of a thin double layer, the relative coupling coefficient at partial saturation is independent of capillary size distribution and depends upon the wettability of the capillaries only if surface electrical conductivity is significant and the irreducible water saturation is small. In the limit of a thick double layer, the relative coupling coefficient depends upon the capillary size distribution and wettability. If water is the only phase that contains an excess of charge, the relative coupling coefficient can be described in terms of the water relative permeability, relative electrical conductivity, and relative excess countercharge density transported by the water. This latter quantity increases with decreasing water saturation in water‐wet models and decreases with decreasing water saturation in oil‐wet models. It does not scale inversely with water saturation as has been assumed previously and depends upon the pore scale distribution of fluid and charge.
Dynamic responses of terrestrial ecosystems structure and function to climate change in China
Authors: Tao Fulu , Zhang Zhao
Published: July 2010

Our understanding of the structure and function of China's terrestrial ecosystems, particularly their responses to transient climate change on timescales of decades to centuries, can be further improved by dynamic vegetation models that include vegetation dynamics as well as biogeochemical processes. Here, the Lund‐Potsdam‐Jena dynamic global vegetation model was calibrated to reasonably capture the general patterns of vegetation distribution across China's terrestrial ecosystems. New parameter values were used for bioclimatic limits, and the model was validated against satellite, in situ, and inventory data for net primary production (NPP), leaf area index, and carbon storage simulations. Dynamic responses of China's terrestrial ecosystems to rising atmospheric CO2 concentration ([CO2]) and climate change in the 20th and 21st centuries were then simulated. Simulations were driven by eight climate scenarios consisting of combinations of two general circulation models and four emission scenarios from Intergovernmental Panel on Climate Change Special Report Emission Scenarios ranging from low emission to fossil intensive emission. We derived possible temporal and spatial change patterns of vegetation distribution, carbon flux, and carbon pools across China. Simulations showed that regional changes in temperature and precipitation would cause substantial vegetation changes in northern, northeastern, and western China. Such vegetation dynamics, and associated mechanisms such as responses of NPP and heterotrophic respiration to rising [CO2] and regional climate change, would lead to corresponding changes in temporal and spatial patterns of carbon flux and carbon pools. As a result, some regional ecosystems could switch from carbon sinks to carbon sources or vice versa by the end of the 21st century. China's terrestrial ecosystems have an average carbon uptake of 0.12 to 0.20 Gt C yr−1 over the period of 1981–2100; however, the rate of increase in carbon sinks is projected to decrease after about 2040, particularly under the fossil intensive emission scenario.
Direct and indirect effects of increasing dissolved organic carbon levels on pH in lakes recovering from acidification
Authors: Erlandsson Martin , Cory Neil , Köhler Stephan , Bishop Kevin
Published: July 2010

In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (∼75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in this study was to model pH in 2008 from DOC, acid neutralizing capacity, pCO2 (partial carbon dioxide pressure), and Al speciation, using both the DOC observed in 2008 and the “unelevated” DOC of 1990. Furthermore, we consider the indirect effects of increasing DOC on acidity, i.e., the ancillary effects from DOC on pCO2, Al transport and speciation, and release of base cations (BCs). Our results indicate that the DOC increase in the latest decades has retarded the recovery from acidification by 0.13 pH units (median for all lakes) and by more than 1 unit for individual lakes. The effects of elevated pCO2 and BC concentrations accompanying the DOC increase compensated for each other for the average lake, whereas the effects of higher Al transport on pH were minor. The estimate of the amount of BCs released with the organic anions is however uncertain, and further studies on this topic are needed.
Effect of bioclogging in porous media on complex conductivity signatures
Authors: Abdel Aal Gamal Z. , Atekwana Estella A. , Atekwana Eliot A.
Published: July 2010

Flow through sand columns inoculated with Pseudomonas aeruginosa were used to investigate the effect of bioclogging on the complex conductivity and flow and transport properties. Complex conductivity (0.1–1000 Hz), the bulk hydraulic conductivity (K), volumetric flow rate (Q), dispersivity (D), and microbial cell concentrations were monitored over time. Environmental scanning electron microscope images of the sands were obtained at the end of the experiment. Bioclogging resulting from increases in microbial cell concentration and the production of exopolymeric substances (EPS) had a large impact on the imaginary conductivity (σ″), K, Q, D, and porosity (Φ). Changes in electrical and transport properties developed in three stages: an initial stage 1 with no significant changes in all measured parameters (Days 1–8), which we attribute to the reversible and irreversible attachment of microbial cells to the sand. In stage 2a (Days 9–16), bioclogging caused by the growth of biomass either as microcolonies filling pore throats and/or as uniform covering on the sand surfaces resulted in maximum decrease in Q and K, but with only moderate increases in σ″. In stage 2b (Days 17–24), significant production of EPS substances and increase in biofilm thickness resulted in a higher rate of increase in σ″ compared to stage 2a. In stage 3 (Days 25–32), biofilm growth reached a quasi steady state and insignificant changes are observed in all measured parameters. The results of this study suggest that σ″ can provide complimentary information in the assessment of bioclogging in porous media.
Ensemble evaluation of hydrological model hypotheses
Authors: Krueger Tobias , Freer Jim , Quinton John N. , Macleod Christopher J. A. , Bilotta Gary S. , Brazier Richard E. , Butler Patricia , Haygarth Philip M.
Published: July 2010

It is demonstrated for the first time how model parameter, structural and data uncertainties can be accounted for explicitly and simultaneously within the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. As an example application, 72 variants of a single soil moisture accounting store are tested as simplified hypotheses of runoff generation at six experimental grassland field‐scale lysimeters through model rejection and a novel diagnostic scheme. The fields, designed as replicates, exhibit different hydrological behaviors which yield different model performances. For fields with low initial discharge levels at the beginning of events, the conceptual stores considered reach their limit of applicability. Conversely, one of the fields yielding more discharge than the others, but having larger data gaps, allows for greater flexibility in the choice of model structures. As a model learning exercise, the study points to a “leaking” of the fields not evident from previous field experiments. It is discussed how understanding observational uncertainties and incorporating these into model diagnostics can help appreciate the scale of model structural error.
Modeling aquifer systems with analytic elements and subdomains
Authors: Fitts C. R.
Published: July 2010

A new approach for analytic element (AE) modeling of groundwater flow is presented. The approach divides the modeled region into polygonal subdomains, each with its own analytic flow model and its own local isotropic or anisotropic aquifer parameters. This allows analytic modeling of systems where the anisotropy ratio and direction vary spatially, an AE capability not possible without subdomains. It also allows for flexible layering in a model, with more layers in the area of interest abutting fewer layers in the far field. The approach is demonstrated in a model with seven subdomains and a mix of single‐layer and triple‐layer areas. Checks of the model indicate that the inter‐subdomain boundary conditions can be approximated well, and where the differential equation is approximated (multilayer areas and transient flow), that approximation can be quite accurate.
Sequence diversity and novelty of natural assemblages of picoeukaryotes from the Indian Ocean
Authors: Massana Ramon , Pernice Massimo , Bunge John A , del Campo Javier
Published: July 2010

Despite the ecological importance of marine pico-size eukaryotes, the study of their in situ diversity using molecular tools started just a few years ago. These studies have revealed that marine picoeukaryotes are very diverse and include many novel taxa. However, the amount and structure of their phylogenetic diversity and the extent of their sequence novelty still remains poorly known, as a systematic analysis has been seldom attempted. In this study, we use a coherent and carefully curated data set of 500 published 18S ribosomal DNA sequences to quantify the diversity and novelty patterns of picoeukaryotes in the Indian Ocean. Our phylogenetic tree showed many distant lineages. We grouped sequences in OTUs (operational taxonomic units) at discrete values delineated by pair-wise Jukes–Cantor (JC) distances and tree patristic distances. At a distance of 0.01, the number of OTUs observed (237/242; using JC or patristic distances, respectively) was half the number of sequences analyzed, indicating the existence of microdiverse clusters of highly related sequences. At this distance level, we estimated 600–800 OTUs using several statistical methods. The number of OTUs observed was still substantial at higher distances (39/82 at 0.20 distance) suggesting a large diversity at high-taxonomic ranks. Most sequences were related to marine clones from other sites and many were distant to cultured organisms, highlighting the huge culturing gap within protists. The novelty analysis indicated the putative presence of pseudogenes and of truly novel high-rank phylogenetic lineages. The identified diversity and novelty patterns among marine picoeukaryotes are of great importance for understanding and interpreting their ecology and evolution.
Phylogenetic and metabolic diversity of bacteria associated with cystic fibrosis
Authors: Guss Adam M , Roeselers Guus , Newton Irene L G , Young C Robert , Klepac-Ceraj Vanja , Lory Stephen , Cavanaugh Colleen M
Published: July 2010

In patients afflicted with cystic fibrosis (CF), morbidity and mortality are primarily associated with the adverse consequences of chronic microbial bronchial infections, which are thought to be caused by a few opportunistic pathogens. However, recent evidence suggests the presence of other microorganisms, which may significantly affect the course and outcome of the infection. Using a combination of 16S rRNA gene clone libraries, bacterial culturing and pyrosequencing of barcoded 16S rRNA amplicons, the microbial communities present in CF patient sputum samples were examined. In addition to previously recognized CF pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus, >60 phylogenetically diverse bacterial genera that are not typically associated with CF pathogenesis were also detected. A surprisingly large number of fermenting facultative and obligate anaerobes from multiple bacterial phyla was present in each sample. Many of the bacteria and sequences found were normal residents of the oropharyngeal microflora and with many containing opportunistic pathogens. Our data suggest that these undersampled organisms within the CF lung are part of a much more complex microbial ecosystem than is normally presumed. Characterization of these communities is the first step in elucidating potential roles of diverse bacteria in disease progression and to ultimately facilitate advances in CF therapy.
Human RASSF7 regulates the microtubule cytoskeleton and is required for spindle formation, Aurora B activation and chromosomal congression during mitosis
Authors: Recino Asha , Sherwood Victoria , Flaxman Amy , Cooper Wendy N. , Latif Farida , Ward Andrew , Chalmers Andrew D.
Published: July 2010

RASSF7, a member of the N-terminal Ras association domain family, has increased expression in various cancers and, on the basis of our previous work in Xenopus embryos, may be a regulator of mitosis. In the present study, we address, for the first time, the role of human RASSF7 in mitosis. We demonstrate that RASSF7 is expressed in a broad range of different cell types and that this expression could be enhanced following exposure to hypoxia. Knocking down RASSF7 in human cell lines inhibited cell growth and induced defects in mitosis, including aberrant spindle formation and a failure in chromosomal congression. In order to understand the molecular basis of the defects in more detail, we analysed the activity of mitotic signalling proteins and found that activation of Aurora B did not occur in cells in which RASSF7 was knocked down. We also show that endogenous RASSF7 protein localizes to the centrosome and demonstrate using microtubule-regrowth assays that RASSF7 is an important regulator of microtubule dynamics. On the basis of these observations, we propose that, owing to its key role in regulating the microtubule cytoskeleton, RASSF7 is required for mitosis in human cells.
MEK/ERK pathway mediates cytoprotection of salvianolic acid B against oxidative stress‐induced apoptosis in rat bone marrow stem cells
Authors: Lu Biyan , Ye Zhizhong , Deng Yubin , Wu Hongfu , Feng Jianqiang
Published: July 2010

To improve the survival and/or differentiation of grafted BMSCs (bone marrow stem cells) represents one of the challenges for the promising cell‐based therapy. Considerable reports have implicated Sal B (salvianolic acid B), a potent aqueous extract of Salvia miltiorrhiza, in enhancing the survival of cells under various conditions. In this study, we investigated the effect of Sal B on H2O2‐induced apoptosis in rat BMSCs, focusing on the survival signalling pathways. Results indicated that the MEK [MAPK (mitogen‐activated protein kinase)/ERK (extracellular‐signal‐regulated kinase) kinase] inhibitor (PD98059) and 10 μM Sal B remarkably prevented BMSCs from H2O2‐induced apoptosis through attenuating caspase‐3 activation, which is accompanied by the significant up‐regulation of Bcl‐2. In addition, the ROS (reactive oxygen species) accumulation was also reduced after Sal B treatment. Furthermore, Sal B inhibited the ERK1/2 phosphorylations stimulated by H2O2. Taken together, our results showed that H2O2‐induced apoptosis in BMSCs via the ROS/MEK/ERK1/2 pathway and Sal B may exert its cytoprotection through mediating the pathway.
Development of Verbal Passive in Williams Syndrome
Authors: Perovic Alexandra , Wexler Kenneth
Published: July 2010

Purpose

To experimentally investigate knowledge of passives of actional (
hold
) and psychological (
love
) verbs in children with Williams syndrome (WS). Passives are usually reported to be in line with mental age in WS. However, studies usually focus on passives of actional verbs only.

Method

Twenty-six children with WS, ages 6–16, and 3 groups of typically developing controls, ages 3;6–14;4 (years;months), individually matched to the WS group on nonverbal reasoning, receptive vocabulary, or grammar, participated. Their comprehension of actives and short and long passives (with and without the by-phrase) was tested using a sentence–picture-matching task.

Results

Children with WS performed well above chance on passives of actional verbs but extremely poorly on passives of psychological verbs (short and long). Furthermore, their performance on both types of passives was worse than that of matched controls.

Conclusions

The results reveal a previously unreported deficiency in the domain of syntax in WS, suggesting a particular difficulty with the structure of the verbal passive, not directly related to general levels of nonverbal abilities, receptive vocabulary, or general comprehension of grammar. It is argued that the difficulty in the formation of verbal passives in WS stems from a deficit in forming argument chains.
Preferential prescribing of oral corticosteroids in Irish male asthmatic children
Authors: Williams David , Kelly Alan , Feely John
Published: July 2010

Aims  To determine if there is a gender difference in the prescription of oral corticosteroids in asthmatic children (< 15 years).

Methods  8072 asthmatics were identified on the basis that they received a prescription for either an inhaled β‐adrenoceptor agonist, an inhaled corticosteroid, inhaled cromoglycate/nedocromil sodium, oral xanthines or leukotriene antagonist. Odds ratios (OR) and 95% confidence intervals (CI) were determined for the different asthma treatments for males compared with females.

Results and conclusions  Male asthmatic children were more likely (OR = 1.37, 95% CI = 1.21,1.55, P < 0.001) to receive a prescription for an oral corticosteroid compared with their female counterparts suggesting a possible increased severity of their condition, rather than a different management of their disease. Male asthmatic children were less likely to be prescribed an antibiotic over the study period (OR = 0.85, 95% CI = 0.77, 0.93, P < 0.001).
Temporo‐mandibular joint kinetics and chewing cycles in children. A 3‐year follow‐up
Authors: Bodin C. , Lodetti G. , Marinone M. G.
Published: July 2010

Summary. Objectives. To report the temporo‐mandibular joint (TMJ) kinetics and masticatory function in healthy children.

Design. Temporo‐mandibular joint palpation and electrognathographic registrations of chewing cycles were repeated for 3 years in order to evaluate changes.

Setting. Healthy children without systemic pathologies, decayed cavities and previous dental treatment.

Sample and methods. Electrognathographic (EGN) registration of masticatory cycles and TMJ palpation were carried out on 52 patients (mean age: 5 years 8 months, range: 5 years 1 month, 6 years 8 months), by two university researchers, once a year for 3 consecutive years. TMJ palpation, differentiated TMJ synchronism (simultaneous bilateral opening movement) and TMJ asynchronism (not simultaneous bilateral opening movement), TMJ subluxation and click were observed. Electrognathographic registrations differentiated normal and abnormal jaw chewing cycles, and narrow and large cycles.

Results. Temporo‐mandibular joint asynchronism was evident in 34 of 52 patients in the primary dentition, in 42 of 52 patients after the eruption of the first permanent molar, and in 31 of 52 patients after the eruption of the permanent incisors. TMJ subluxation increased during the full period of observation. Three temporomandibular clicks appeared after the eruption of the permanent incisors. Altered mastication was not always associated with TMJ disorders.

Conclusions. In children, normal chewing cycles can coexist with occlusal discrepancies, cranio‐facial growth and TMJ alterations.
The effects of combined treatment with β1‐selective receptor antagonists and lipid‐lowering drugs on fat metabolism and measures of fatigue during moderate intensity exercise: a placebo‐controlled study in healthy subjects
Authors: Eagles C. J. , Kendall M. J.
Published: July 2010

Aims
 We examined the effects of different combinations of β1‐selective adrenoceptor blockers and lipid‐lowering drugs, on fat metabolism and fatigue during moderate intensity exercise in 14 healthy young volunteers.

Methods
 The study was a randomized crossover design, each subject completing 5, 90 min walks at 50% of predetermined maximal oxygen uptake (VO2 max), one following each 3 day treatment period with either: atenolol 100 mg and bezafibrate 400 mg, atenolol 100 mg and fluvastatin 40 mg, metoprolol CR 100 mg and bezafibrate 400 mg, metoprolol CR 100 mg and fluvastatin 40 mg, or placebo.

Results
 Plasma free fatty acid (FFA) concentration during exercise was significantly reduced on all treatments, in comparison with placebo, P=0.0001. Following 90 min of exercise FFA levels were as follows: placebo 573 μmol l−1 (105–1041), metoprolol CR+fluvastatin 277 μmol l−1 (0–647), metoprolol CR+bezafibrate 182 μmol l−1 (0–396), atenolol+fluvastatin 211 μmol l−1 (0–511), and atenolol+bezafibrate 123 μmol l−1 (0–352). Total fat oxidation during exercise was also reduced on all treatments in comparison with placebo: 38.1% (2–74), compared with 29.1% (0–61) on metoprolol CR+fluvastatin, P=0.02, 26.2% (2–51) on metoprolol CR+bezafibrate, P=0.002, 25.5% (3–48) on atenolol+fluvastatin, P=0.009, and 22.8% (0–47) on atenolol+bezafibrate treatment, P=0.0002. Plasma ammonia concentration was elevated on all treatments during exercise in comparison with placebo. After 90 min of exercise, plasma ammonia levels were as follows: placebo 37 μmol l−1 (0–84), metoprolol CR+fluvastatin 56 μmol l−1 (2–110), metoprolol CR+bezafibrate 79 μmol l−1 (0–167), atenolol+fluvastatin 90 μmol l−1 (10–170), and atenolol+bezafibrate 100 μmol l−1 26–174). In comparison with placebo, metoprolol CR+fluvastatin had the least adverse impact on measures of perceived exertion and the ‘feeling scale’ during exercise. Metoprolol CR+bezafibrate, atenolol+fluvastatin, and atenolol+bezafibrate treatments had greater adverse effects, particularly on perceived ‘cardiorespiratory effort’ and ‘feeling scale’ scores.

Conclusions
 In healthy volunteers, combinations of β1‐selective blockers and lipid‐lowering drugs were associated with significant reductions in fat metabolism, increased plasma ammonia levels, and raised the perception of effort during exercise, in comparison with placebo. Metoprolol CR+fluvastatin had the least effect, combinations metoprolol CR+bezafibrate and atenolol+fluvastatin had intermediate effects, and atenolol+bezafibrate had the most adverse effect.
Neuroendocrine Suppression of Female Courtship in a Wild Passerine: Corticotropin‐Releasing Factor and Endogenous Opioids
Authors: Maney Donna L. , Wingfield John C.
Published: July 2010

During emergencies in their natural environments, vertebrates initiate coping mechanisms that redirect behavior away from nonessential activities and towards survival. Reproductive behaviors are suppressed. Evidence from field studies on passerine birds shows that this inhibition may not depend on the suppression of gonadal sex steroids, since during the breeding season they remain elevated despite activation of the stress response. We hypothesize that an alternate, central mechanism mediates the inhibition of reproductive behavior during stress in passerines. In this study, we tested the intracerebroventricular effects of endogenous opioids and corticotropin‐releasing factor (CRF), neuropeptides implicated in the stress response, on courtship behavior in wild‐caught female white‐crowned sparrows. β‐endorphin (β‐EN) significantly inhibited copulation solicitation, an estrogen‐dependent courtship display, 30 min after treatment. Naloxone, an opioid antagonist, enhanced the behavior. CRF caused a suppression of solicitation that was reversible by pretreatment with naloxone, suggesting an intermediary role for endogenous opioids in CRF‐induced suppression of courtship. The effects of β‐EN and CRF on solicitation appear to be independent of any general effects on locomotor activity. These results support our hypothesis that stress neuropeptides orchestrate coping behaviors in wild birds.
Circulating Angiotensin II Activates Neurones in Circumventricular Organs of the Lamina Terminalis That Project to the Bed Nucleus of the Stria Terminalis
Authors: Sunn N. , McKinley M. J. , Oldfield B. J.
Published: July 2010

The aim of this study was to determine, in conscious rats, whether elevated concentrations of circulating angiotensin II activate neurones in both the subfornical organ and organum vasculosum of the lamina terminalis (OVLT) that project to the bed nucleus of the stria terminalis (BNST). The strategy employed was to colocalize retrogradely transported cholera toxin B subunit (CTB) from the BNST, with elevated levels of Fos protein in response to angiotensin II. Circulating angiotensin II concentrations were increased by either intravenous infusion of angiotensin II or subcutaneous injection of isoproterenol. Neurones exhibiting Fos in response to angiotensin II were present in the subfornical organ, predominantly in its central core but with some also seen in its peripheral aspect, the dorsal and lateral margins of the OVLT, the supraoptic nucleus and the parvo‐ and magnocellular divisions of the paraventricular nucleus. Fos‐labelling was not apparent in control rats infused with isotonic saline intravenously or injected with either CTB or CTB conjugated to gold particles (CTB‐gold) only. Of the neurones in the subfornical organ that were shown by retrograde labelling to project to BNST, approximately 50% expressed Fos in response to isoproterenol. This stimulus also increased Fos in 33% of neurones in the OVLT that project to BNST. Double‐labelled neurones were concentrated in the central core of the subfornical organ and lateral margins of the OVLT in response to increased circulating angiotensin II resulting from isoproterenol treatment. These data support a role for circulating angiotensin II acting either directly or indirectly on neurones in subfornical organ and OVLT that project to the BNST and provide further evidence of functional regionalization within the subfornical organ and the OVLT. The function of these pathways is yet to be determined; however, a role in body fluid homeostasis is possible.
Sensitivity of Galanin‐ and Melanin‐Concentrating Hormone‐Containing Neurones to Nutritional Status: An Immunohistochemical Study in the Ovariectomized Ewe
Authors: Chaillou E. , Baumont R. , Fellmann D. , Tramu G. , Tillet Y.
Published: July 2010

The sensitivities of galanin and melanin‐concentrating hormone (MCH) neuronal systems to nutrition are poorly understood in sheep compared to rodents. The aim of this study was to describe the changes in the numbers of galanin and MCH neurones in ovariectomized ewes submitted to different nutritional levels. In the first experiment, ewes were fed ad libitum or food deprived for 24 h. In the second experiment, two groups of ewes were fed at maintenance level (group 100) or undernourished (group 40) for 167 days, after which one‐half of each group was killed or refed ad libitum (group 100R and 40R) for 4 days. The MCH neuronal population located in the lateral hypothalamic area was not affected by these nutritional changes. Long‐term undernutrition enhanced the number of galanin neurones located in the infundibular nucleus and the dorsal hypothalamic area (DHA), refeeding resulted in an increase of neurones in the DHA and preoptic area, but short‐term starvation had no effect on any galanin subpopulations. Our data suggest that the sensitivity of MCH neuronal populations to nutrition in sheep differs from that of rodents. Various populations of galanin‐containing neurones differ in sensitivity in ewes subjected to long undernutrition and refeeding but not to short starvation.
Chronic Excess of Corticosterone Increases Serotonergic Fibre Degeneration in Aged Rats
Authors: Nyakas C. , Mulder J. , Felszeghy K. , Keijser J. N. , Mehra R. , Luiten P. G. M.
Published: July 2010

Evidence is presented for the potentiating role of corticosterone on axonal degeneration of serotonergic neurones during ageing. Aged rats, 24 months old, were implanted subcutaneously with 2 × 100 mg pellets of corticosterone. Serotonergic and cholinergic (ChAT‐ and NADPHd‐positive) fibre degenerations in the anteroventral thalamic nucleus (AVT) were measured 2 months after corticosterone implantation. Numbers of immunoreactive serotonergic raphe and mesolimbic cholinergic neurones were also quantified. Basal plasma corticosterone and adrenocorticotropin (ACTH) concentrations were assayed at 2, 4, 6, and 8 weeks after implantation in the plasma and at 1, 2, 4 and 6 weeks in urine. The degree of serotonergic fibre aberrations in the AVT increased significantly after corticosterone exposure, while that of ChAT‐positive and NADPHd‐stained axon aberrations showed a modest but nonsignificant increase. A positive correlation between the magnitudes of serotonergic and cholinergic fibre aberrations appeared in the AVT, but only in the corticosterone‐treated rats. The number of serotonin immunopositive neurones in the raphe nuclei after corticosterone decreased marginally, while that of mesopontine ChAT‐positive neurones was not influenced. Measurements of basal plasma corticosterone and ACTH, as well as urine corticosterone, revealed that the steroid implantation increased the plasma corticosterone level for at least 4 weeks and decreased ACTH level for at least 6 weeks. By the week 8, the pituitary‐adrenal function was apparently restored. However, at sacrifice, both the weight of adrenal glands and that of thymus remained reduced, indicating the long‐lasting effects of corticosterone on target tissues. It is concluded that the raphe serotonergic neurones and their projecting fibres are sensitive to corticosterone excess in aged rats and become more vulnerable to degeneration processes than under normal ageing conditions. Cholinergic neurones of brainstem origin, which also express massive NADPHd activity, are more resistant against corticosterone, but their axon degeneration correlates to serotonergic fibre degeneration.
Pups Presence Eliminates the Stress Hyporesponsiveness of Early Lactating Females to a Psychological Stress Representing a Threat to the Pups
Authors: Deschamps S. , Woodside B. , Walker C.‐D.
Published: July 2010

Blunted neuroendocrine responses to stress are reported in lactating females after exposure to various stressors. However, many of the stimuli used in these studies have little ethological relevance for maternal protection of the litter in a threatening environment. The question that arises is whether the relevance of the stressor to the infant is critical in the ‘gating’ of the neuroendocrine response. We hypothesized that the presence of pups with their mothers at the time of exposure to an intruder or a predator odour is an effective way to increase the emotional salience of the psychological stressor, thus eliminating the stress hyporesponsiveness in lactating females. We first compared neuroendocrine responses [corticotropin‐releasing factor (CRF) mRNA in the paraventricular nucleus of the hypothalamus (PVN) and central nucleus of the amygdala (CeA), plasma adrenocorticotropic hormone (ACTH) and corticosterone] between early (EL, PPD3‐5), late (LL, PPD 15) lactating and virgin (V) females to a male intruder in the home cage. We next investigated the effect of pups' presence at the time of stressor exposure on the magnitude of the hormonal response to a male intruder in the home cage or to a predator odour (fox urine) in a novel environment. In the male intruder paradigm, levels of CRF mRNA expression in the PVN and CeA were lower in LL compared to EL or V females and plasma ACTH and corticosterone secretion was not as elevated in LL compared to EL females. Aggression towards the intruder was high in EL females in the presence of their pups and a positive correlation was found with the integrated ACTH response. Aggression rapidly declined after pup separation (2.5 h or 48 h) or in LL nursing females. In EL females, the presence of the pups with their mothers (EL + pups) at the time of stress significantly increased plasma ACTH and corticosterone responses to either male intruder or predator odour compared to EL females without their pups for 2.5 h or 48 h (EL − pups). Plasma ACTH response to fox urine in EL + pups females was comparable to that of virgin females, suggesting that increasing the salience of emotionally relevant stimuli by keeping the pups present in the cage could eliminate the hyporesponsiveness detected for EL females without their pups. These studies indicate the critical role of the pups in modulating the maternal response to stressors that represent a threat for the litter. We hypothesize that the amygdala, because of its ability to process olfactory stimuli and stimuli with affective properties, might play an essential role in ‘gating’ the neuroendocrine response to stress during lactation.
Selective Roles of Protein Kinase C Isoforms on Cell Motility of GT1 Immortalized Hypothalamic Neurones
Authors: Choe Y. , Jung H. , Khang I. , Kim K.
Published: July 2010

Recently, we demonstrated that activation of the protein kinase C (PKC) signalling pathway promoted morphological differentiation of GT1 hypothalamic neurones via an increase in β‐catenin, a cell‐cell adhesion molecule, indicating a possible involvement of PKC in cellular motility. In this study, we explored the differential roles of PKC isoforms in GT1 cell migration. First, we transiently transfected GT1 cells with enhanced green fluorescence protein (EGFP)‐tagged actin to monitor the dynamic rearrangement of filamentous‐actin (F‐actin) in living cells. Treatment with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), a PKC activator, markedly promoted lamellipodia formation, while safingol (a PKCα‐selective inhibitor) blocked the TPA‐induced lamellipodial actin structure. Both wound‐healing and Boyden migration assays showed that TPA treatment promoted neuronal migration of GT1 cells; however, cotreatment of TPA with safingol or rottlerin (a PKCδ‐selective inhibitor) clearly blocked this TPA effect, indicating that both PKCα and PKCδ may be positive regulators of neuronal migration. By contrast, PKCγ‐EGFP‐expressing GT1 cells exhibited decreased cellular motility and weak staining for actin stress fibres, suggesting that PKCγ may act as a negative mediator of cell migration in these neurones. Among the PKC downstream signal molecules, p130Cas, a mediator of cell migration, and its kinase, focal adhesion kinase (FAK), increased following TPA treatment; phosphorylation of p130Cas was induced in a PKCα‐dependent manner. Together, these results demonstrate that PKCα promotes GT1 neuronal migration by activating focal adhesion complex proteins such as p130Cas and FAK.
Role of Specific Adrenergic Receptors in Mediating the Adrenocorticotropic Hormone Response to Increased Nitric Oxide Levels
Authors: Seo D. O. , Lee S. , Rivier C.
Published: July 2010

We investigated the role played by catecholamine‐dependent pathways in modulating the ability of the nitric oxide (NO) donor 3‐morpholino‐sydnonimine (SIN‐1) to release adrenocorticotropic hormone (ACTH) following its intracerebroventricular (i.c.v.) or intravenous (i.v.) injection. We first showed that the nonspecific adrenergic agonist noradrenaline, the α‐ or β‐adrenergic agonists phenylephrine or dobutamine, or the noradrenergic uptake inhibitor desipramine, all significantly stimulated ACTH secretion by freely moving, nonanaesthetized rats. We then observed that destruction of noradrenergic nerve endings with the neurotoxin 6‐hydroxydopamine, respectively abolished and significantly decreased the ACTH response to the i.c.v. or i.v. administration of SIN‐1. Finally, we sought to identify the type of adrenergic receptor(s) mediating the influence of catecholamines. β‐Adrenergic receptors did not appear to be involved in the stimulatory effect of SIN‐1 regardless of its route of injection. By contrast, α2‐adrenergic receptors played an important role in the ACTH response to i.v. or i.c.v. administered SIN‐1. Collectively, these results indicate that while hypothalamic α1‐ and β‐adrenergic receptors are important for hypothalamic‐pituitary‐adrenal (HPA) axis activity, only α2‐adrenergic receptors are involved in modulating the ability of NO to release ACTH. Our laboratory and others have previously reported that NO increased hypothalamic noradrenaline levels, while conversely noradrenaline up‐regulated levels of NO synthase, the enzyme responsible for NO formation; and that injection of corticotropin‐releasing factor into the brain ventricles releases catecholamines and stimulates NO formation. Taken together with these observations, our results point to complex functional relationships between NO, catecholamines and the HPA axis.
Lipopolysaccharide Inhibits Luteinizing Hormone Release Through Interaction with Opioid and Excitatory Amino Acid Inputs to Gonadotropin‐Releasing Hormone Neurones in Female Rats: Possible Evidence for a Common Mechanism Involved in Infection and Immobilization Stress
Authors: He D. , Sato I. , Kimura F. , Akema T.
Published: July 2010

Acute immobilization stress suppresses naloxone‐ and N‐methyl‐d‐aspartate (NMDA)‐induced, but not gonadotropin‐releasing hormone (GnRH)‐induced, luteinizing hormone (LH) release in ovariectomized oestrogen‐primed rats. To explore whether a common mechanism may underlie inhibition of gonadotropin secretion by various stressors, we examined in the present study the effect of lipopolysaccharide (LPS) on LH release induced by progesterone, GnRH, naloxone and NMDA. The effect of LPS on Fos expression in GnRH neurones was also examined in association with its effect on steroid‐induced LH release. Injection of progesterone (1 mg/rat) at noon induced an LH surge in the afternoon in ovariectomized rats pretreated with oestradiol benzoate. In these rats, the majority of hypothalamic GnRH neurones expressed Fos in the evening. Intravenous (i.v.) administration of LPS (10 µg/rat) inhibited steroid‐induced LH release and also reduced the Fos expression in GnRH neurones. In separate experiments, an i.v. injection of GnRH (50 ng/kg), naloxone (10 mg/kg) or NMDA (20 mg/kg) significantly elevated serum LH concentrations within 10 min. Pretreatment with LPS, which did not affect basal LH release or GnRH‐induced LH release, inhibited naloxone‐induced and NMDA‐induced LH release. These results show that LPS has a suprapituitary site(s) of action to suppress the activity of GnRH neurones in female rats, and suggest that LPS affects the opioid, as well as the excitatory amino acidergic regulation of GnRH neurones. The similarity of effects of LPS and immobilization stress further suggests that a common mechanism is involved in inhibition of GnRH neurones by different stressors.
Implantation of a Slow Release Corticosterone Pellet Induces Long‐Term Alterations in Serotonergic Neurochemistry in the Rat Brain
Authors: Bush V. L. , Middlemiss D. N. , Marsden C. A. , Fone K. C. F.
Published: July 2010

Many studies point to an involvement of deficits in the serotonergic nervous system and hyperactivity of the hypothalamic‐pituitary‐adrenal (HPA) axis function with depression. Indeed early life stress, involving HPA axis activation, may predispose susceptible individuals to develop depression in later life. This study investigates the effects of elevating the neuroendocrine stress hormone, corticosterone, for 1 week in adolescent rats on markers of serotonergic neurone function at adulthood. Slow release corticosterone pellets were implanted for 7 days and various serotonergic parameters, as well as plasma corticosterone levels, were measured on day 7 or on day 28 (21 days following removal of the pellet). The corticosterone implant attenuated weight gain and reduced adrenal weights compared to that in control rats implanted with a cholesterol pellet. After 7 days, with the implant still in place, the diurnal variation in plasma corticosterone was reduced so that the level was approximately at that of the evening peak throughout the day. Twenty‐one days after removal of the implant, the diurnal variation in plasma corticosterone returned. Corticosterone treatment decreased [3H] 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin binding to the 5‐hydroxytryptamine1A receptor in the cortex but not in the hippocampus. Corticosterone treatment also enhanced the circadian rhythm observed in 5‐hydroxyindoleacetic acid level and the ratio of 5‐hydroxyindoleacetic acid to the 5‐hydroxytryptamine in the frontal cortex. Despite corticosterone pellet removal 21 days earlier, there was a persistent decrease in whole body and adrenal weight, cortical 5‐hydroxytryptamine1A receptor binding and an alteration in the diurnal variation in the 5‐hydroxytryptamine ‘turnover’ in the frontal cortex.
Oestrogen‐Induced Vigorous Mounting in Female Rats Carrying Hypothalamic Knife Cuts
Authors: Ohnishi H. , Kondo Y. , Sakuma Y.
Published: July 2010

In ovariectomized Wistar rats, 1‐ or 2‐mm wide knife cuts were placed in a coronal plane from the surface of the cortex to the floor of the cranial cavity to interrupt posterior efferents of the ventromedial nucleus of the hypothalamus (VMN). Sham‐operated females had the same knife lowered to a depth of 7 mm. Ovariectomized nonoperated females were also used. After recovery, all rats received a single injection of 2 µg oestradiol benzoate, and were tested 48 h later for male and female sexual behaviour and partner preference. When placed with highly receptive stimulus females, the rats with the 2‐mm cut showed a significantly higher incidence of mounting with ejaculatory thrusts than any other groups. When placed with stud males, 1‐mm cut, as well as sham‐operated females, had increased lordosis quotients. Similarly, both 1‐mm and 2‐mm cuts and sham operation enhanced the incidence of ear wiggling. Despite the display of a transsexual behaviour (i.e. vigorous mounting), all females with the cut showed heterosexual partner preference. Thus, the cut in the present study removed the inhibitory neural effect on mounting, which presumably descends from the VMN. In the absence of this inhibition, minute amounts of oestrogen sufficed to induce vigorous mounting. Sham operation in the present study appeared to interfere with certain inhibitory neural circuitry for lordosis.
Short‐Term Effect of Oestradiol on Neurokinin B mRNA Expression in the Infundibular Nucleus of Ewes
Authors: Pillon D. , Caraty A. , Fabre‐Nys C. , Bruneau G.
Published: July 2010

In sheep, essentially all the neurokinin B (NKB) neurones of the infundibular nucleus express oestradiol receptor α, and analysis of female and male brains has revealed an exceptionally marked female‐dominant sex difference in the numbers of NKB neurones in the infundibular nucleus. This neuronal population is located in an oestradiol‐sensitive brain area involved in the control of gonadotropin‐releasing hormone (GnRH) secretion and oestrous behaviour, but its physiological role is poorly documented. The aim of the present study was to analyse NKB mRNA expression at a crucial time when the steroid has stimulated the pathways leading to the induction of these two events. After cloning a specific ovine NKB antisense riboprobe, we examined the effects of a short oestradiol treatment (4 h subcutaneously) on the expression of NKB mRNA in the caudal part of the infundibular nucleus of progesterone‐primed ovariectomized ewes. We demonstrated that oestradiol decreased both the level of NKB mRNA expression (34%) and the number of cells containing NKB mRNA (43%). Oestradiol acts strongly on these NKB cells in the short term. We suggest that this early change in NKB mRNA expression during the preovulatory period might be involved in the control of the induction of GnRH secretion or oestrous behaviour.