bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self-regulated black hole growth via momentum deposition in galaxy merger simulations
Authors: DeBuhr Jackson , Quataert Eliot , Ma Chung-Pei , Hopkins Philip 
Published: June 2010

Abstract
We perform hydrodynamical simulations of major galaxy mergers using new methods for calculating the growth of massive black holes (BH) in galactic nuclei and their impact on the surrounding galaxy. We model BH growth by including a subgrid model for accretion produced by angular momentum transport on unresolved scales. The impact of the BH's radiation on surrounding gas is approximated by depositing momentum into the ambient gas, which produces an outward force away from the BH. We argue that these phenomenological models for BH growth and feedback better approximate the interaction between the BH and dense gas in galaxies than previous models. We show that this physics leads to self-regulated BH growth: during the peak of activity, the accretion rate on to the BH is largely determined by the physics of BH feedback, not the subgrid accretion model. The BH significantly modifies the gas dynamics in the galactic nucleus (≲300 pc), but does not generate large-scale galactic outflows. Integrated over an entire galaxy merger, BH feedback has little effect on the total number of stars formed, but is crucial for setting the BH’s mass.
Applying DNA barcoding for the study of geographical variation in host–parasitoid interactions
Authors: SANTOS ANA M. C. , BESNARD GUILLAUME , QUICKE DONALD L. J. 
Published: June 2010

AbstractStudies on the biogeography of host–parasitoid interactions are scarce, mainly because of technical difficulties associated with rearing and species identification. DNA barcoding is increasingly recognized as a valuable tool for taxon identification, allowing to link different life history stages of a species. We evaluate the usefulness of a protocol based on cytochrome oxidase I (COI) sequencing for the study of geographical variation of host–parasitoid interactions. Larvae ofAcroclita subsequana(Lepidoptera: Tortricidae) were collected in Macaronesia and dissected to search for parasitoid larvae. Both hosts and parasitoids were sequenced and assigned to molecular operational taxonomic units (MOTUs) based on pairwise genetic distances, tree‐based and similarity‐based methods. Hosts were grouped into six MOTUs, usually with an allopatric distribution, while parasitoids clustered into 12 MOTUs, each of which was mostly found attacking a single host MOTU. Available COI sequence databases failed to provide identification to species level for these MOTUs. Three challenges related to the applicability of DNA barcoding in this type of studies are identified and discussed: (i) more suitable primers need to be developed for both parasitoids and hosts; (ii) the most commonly used approaches for inferring MOTUs have different limitations (e.g. arbitrary nature of defining a threshold to separate MOTUs) and need to be improved or replaced by other techniques; and (iii) for the identification of MOTUs, it is imperative to increase the range of sequenced taxa in the currently available reference databases. Finally, in spite of these difficulties, we discuss how DNA barcoding will help ecological and biogeographical studies of host–parasitoid interactions.
Evaluation of large‐scale dissemination of Nosema ceranae spores by European bee‐eaters Merops apiaster
Authors: Valera F. , Martín‐Hernández R. , Higes M. 
Published: June 2010

SummaryIdentification of transmission routes and of factors affecting the spatial positions of pathogens, hosts and vectors is basic to an adequate disease management. Nosema ceranae is a Microsporidian recently described as a parasite of Apis mellifera honeybees and is currently considered the aetiological agent of an emergent illness named nosemosis type C. In this article we evaluate the role of a bird species, the European bee‐eater, Merops apiaster, as a large‐scale dispersive agent of N. ceranae. We found a high prevalence of viable spores of N. ceranae in pellets regurgitated by bee‐eaters in different locations in the Iberian Peninsula, Central Europe and central Asia. In contrast, spores of Nosema apis, considered till recently the most common microsporidium infecting honeybees, were detected in a single locality and Nosema bombi spores were not noticed. Since non‐viable spores were also found in bee‐eater nests from different locations, this bird species could also reduce the fraction of infected insects by withdrawing pathogens from the colonies. We conclude that bee‐eater mobility and migration may have played an important role in the transmission of the pathogen N. ceranae.
Quantification of nitrogenase in Trichodesmium IMS 101: implications for iron limitation of nitrogen fixation in the ocean
Authors: Whittaker Sherrie , Bidle Kay D. , Kustka Adam B. , Falkowski Paul G. 
Published: June 2010

SummaryIron is widely thought to limit nitrogen fixation in the open, oligotrophic ocean due to the low solubility of Fe in oxic seawater and the high Fe demand for the nitrogenase holozyme. However, empirical evidence for Fe limitation of field populations of Trichodesmium based on either incubation experiments or molecular and physiological indicators has not quantitatively related Fe supply to the cellular Fe quotas for nitrogenase. Rather, the Fe required for N2 fixation has been inferred from in vivo catalytic activity. Using a pet14b expression vector, we cloned the nif H gene (encoding the Fe‐protein, which contains 4Fe atoms per subunit) from Trichodesmium IMS 101, and purified the His‐tagged apoprotein with which we derived a primary standard based on quantitative Western blots. Using a standard curve derived from the cloned Trichodesmium Fe apoprotein, we measured the absolute abundance of the Fe‐protein in iron‐replete cultures of this marine diazotroph. At peak expression, we calculate 0.04 mg nitrogenase mg−1 C. Assuming a conservative stoichiometry of two Fe‐protein subunits per MoFe protein (which contains 15 Fe atoms per subunit, or a total of 38 atoms of Fe per holozyme), we estimate 236 µmol Fe is bound to nitrogenase per mol cellular C. This estimate is about 10 times greater than the Fe previously calculated to support diazotrophic growth under these conditions. Our results suggest that under bloom conditions in the subtropical North Atlantic and North Pacific, as much as ∼2.22 and 0.06 µmol m−3 of Fe is bound to Trichodesmium nitrogenase respectively. Such a high quota represents between ∼50% and > 100% summer‐time average particulate Fe in surface waters, suggesting the importance of this taxon for the retention and biogeochemical cycling of Fe. Moderate growth (0.10 day−1) towards the end of these blooms would require a vertical flux as high as ∼23 µmol Fe day−1 m−2 into the mixed layer.
Physiological versus clinical consequences of left recurrent laryngeal neuropathy (LRLN)
Authors: SEEHERMAN H. J. , EHRLICH PAULA J. , MORRIS ELISABETH 
Published: June 2010

SummaryThe clinical implications of ventilatory alterations induced by left recurrent laryngeal neuropathy (LRLN) are reduced performance due to increased metabolic requirements for breathing and a reduction in peak aerobic power (V̇O2peak). To test this hypothesis, the metabolic cost of locomotion (MCL) and peak aerobic power (V̇O2peak) were measured in 4 non racing crossbred horses (low V̇O2peak) with reversibly induced LRLN using an incremental treadmill exercise test. Reversible LRLN was achieved with regional anaesthesia. These results were compared to previous measurements in 4 Thoroughbred racehorses (high V̇O2peak, Ehrlichet al.1993). No significant difference in MCL (based on V̇O2and venous lactate) was found in either group of horses at exercise intensities where V̇O2< V̇O2peak(<9 m/s). Peak aerobic power decreased by 15.3% (140.0 ± 3.2 vs. 165.3 ± 3.4 ml/kg/min ± s.e., in the Thoroughbred racehorses (high V̇O2peak) with induced LRLN but not in the non racing horses with lower V̇O2peak(135.0 ± 4.5 ml/kg/min ± s.e. The results of these 2 studies indicate that alterations in ventilation due to LRLN cause a significant reduction in V̇O2peakonly in horses with high V̇O2peak. At exercise intensities where V̇O2< V̇O2peak, MCL was not increased in either group of horses despite ventilatory alterations induced by LRLN.
Effect of head position on upper airway function in exercising horses
Authors: PETSCHE V. M. , DERKSEN F. J. , BERNEY C. E. , ROBINSON N. E. 
Published: June 2010

SummaryThe objective of the present study was to determine the effect of head and neck position on upper airway flow mechanics in exercising horses. Five Standardbred horses (452 ± 16.5 kg bwt; 4.7 ± 0.9 years [mean ± s.e.]) were exercised at 75% (Period A) and at 100% of maximal heart rate (Period B) with head and neck unrestrained, extended, or flexed. Airflow was measured using a facemask mounted pneumotachograph, while tracheal pressure during inhalation and exhalation (PUIand PUE) was measured using a nasotracheal catheter. With head and neck unrestrained, PUI, PUE, inspiratory and expiratory impedance (ZI, ZE), respiratory frequency (f) and indices describing the tidal breathing flow‐volume loops (TBFVLs) were similar to those previously reported. There were no significant changes in the extended position, except that expiratory time (Te) and ratio of peak expiratory flow and peak inspiratory flow (PEF/PIF) were significantly increased inPeriods AandB, respectively. In contrast, in the flexed position, ZIwas significantly increased inPeriod B.Also, inspiratory flow at 50% of tidal volume (IF50) was significantly decreased, and PEF/PIF and EF50/IF50were significantly increased. At period A, PUIwas increased and Te was prolonged. We conclude that during strenuous exercise head and neck extension has little effect on upper airway flow mechanics, but that head and neck flexion causes upper airway obstruction.
Ventilatory responses of horses to prolonged submaximal exercise
Authors: BAYLY W. , II H. SCHOTT , SLOCOMBE R. 
Published: June 2010

SummaryWhile prolonged submaximal exercise is associated with an increase in core body temperature, the role of ventilation in the dissipation of this heat load is unclear. We examined airway mechanics in 5 horses exercising on a treadmill at 40% V̇O2maxfor 60 min or until fatigued, in order to study the ventilatory response to prolonged low intensity exercise. Respiratory tract mechanics, pH and arterial blood gases were recorded at rest and at regular intervals during exercise. Mean ± s.d. run time was 51.7 ± 5.9 min. No changes in ventilatory mechanics were seen in the first 12–15 min of exercise. Mean breathing frequency (fb) did not change during the test (109 ± 11), however, tidal volume (VT) and fbvaried considerably in individual horses over the course of the run. Some animals freely interchanged their breathing pattern between shallow tachypnoea and regular tidal breathing with fbranging from 76 to 171. Minute ventilation was not affected by breathing pattern but increased from 935 ± 119 l/min after 12–15 min to 1365 ± 343 l/min at the end of exercise. This was associated with a rise in pulmonary arterial blood temperature (BT) from 39.2 ± 0.2°C to 41.8 ± 0.4°C and an increase in work of breathing (Wrm) from 214 ± 30 to 475 ± 122 kg/cm. Wrm/min/l and kg·min increased 1.98‐, 1.28‐ and 1.87‐fold, respectively, in the same period. VTand each expression of Wrmwere logarithmically correlated with BT. PCO2decreased from 41.2 ± 1.7 Torr after 12–15 min to 30.6 ± 1.3 Torr after 57–60 min, while pH increased from 7.43 ± 0.03 to 7.56 ± 0.03 in the same period. We conclude that while the thermoregulatory role of the equine respiratory system may be unclear, horses mount a concerted hyperventilatory response during prolonged submaximal exercise. This response may be associated with rises in core temperature and intermittent tachypnoea, is characterised by increases in Wrmand may be physiologically costly and inefficient.
Assessment of anaerobic capacity using maximal accumulated oxygen deficit in fit Thoroughbreds
Authors: EATON M. D. , ROSE R. J. , EVANS D. L. , HODGSON D. R. 
Published: June 2010

SummaryTwenty‐three Thoroughbred racehorses that were presented for a standard incremental exercise test also performed a test at an intensity equivalent to 115% V̇O2max in an effort to evaluate their anaerobic capacity by measuring the maximal accumulated oxygen deficit (MAOD). Submaximal V̇O2 values for speeds 3 to 10 m/s and V̇O2max were determined for horses exercising on a treadmill inclined at a 10% slope. An individual regression equation of speed and V̇O2 was used to calculate the speed for each horse to exercise at 115% V̇O2max and the energy demand for exercise at this intensity. The horses underwent a warm‐up period consisting of 5 min at 50% V̇O2max followed by walking for 5 min at 1.5 m/s. The treadmill was then acclerated as rapidly as possible until a speed of 115% V̇O2max was attained. During the test, expired gas samples were collected at 0, 15, 30, 45, 60 s and every 30 s until fatigue. MAOD was calculated by subtracting the measured oxygen uptake from the calculated oxygen demand. A 5 min post exercise blood sample was collected for measurement of plasma [lactate]. The MAOD values ranged from 36 to 94 mlO2 equivalents/kg and the V̇O2max values ranged from 128 to 170 ml/kg/min. The mean ± s.e. MAOD values were 59 ± 3 mlO2 equivalents/kg and mean V̇O2max was 146 ± 2 ml/kg/min. Mean plasma [lactate] was 23.0 ± 1.2 mmol/l. MAOD was weakly correlated with V̇O2max (r = 0.514, P < 0.05), but was not correlated with run time, plasma lactate or treadmill work. The test of MAOD was suitable for use during clinical exercise testing.
Flow cytometric studies of equine phagocytes following strenuous exercise
Authors: ADAMSON ELISABETH J. , SLOCOMBE R. F. 
Published: June 2010

SummaryThe objective of this study was to determine if strenuous exercise in unconditioned horses impaired function of neutrophils and alveolar macrophages. Flow cytometry was used to assess the effects of a single bout of strenuous exercise on these cells. Bronchoalveolar lavage and venous blood sampling were performed 30 min, 1 and 5 days after exercise. Exercise consisted of 2 min at 2,4 and 6 m/s and then 1 min at 1 m/s incremental speeds until exhaustion, on a level treadmill. Intracellular oxidation of the fluorochrome dye DCFH‐DA was stimulated by PMA and detected by a flow cytometer. Size and granularity of the 2 cell preparations were also measured. The respiratory burst induced in granulocytes was significantly inhibited 30 min after exercise (480 ± 182) compared to that prior to exercise (2359 ± 456). Inhibition at 1 and 5 days after exercise was less than at 30 min and did not differ significantly from either control values. No change in size or granularity was seen as a result of exercise. The alveolar macrophage population remained unchanged in size, granularity and fluorescent responses following exercise. Several cell samples taken before exercise exhibited peripheral blood eosinophilia. In these samples, granulocyte size was markedly reduced and DCFH‐DA oxidation was depressed; viability did not alter. This study suggests that strenuous exercise impairs the respiratory burst of granulocytes for several days. Other factors associated with peripheral eosinophilia also have suppressive effects on granulocytes.
Effects of low intensity training on gas exchange at the start of exercise
Authors: BELLENGER SARAH , DAVIE A. J. , EVANS D. L. , HODGSON D. R. , ROSE R. J. 
Published: June 2010

SummaryWe tested the hypothesis that training would result in more rapid increase in V̇O2 and V̇CO2 following the onset of submaximal exercise. Six Standardbred horses were used and trained at submaximal intensities for 5 weeks. Horses were trained 6 days per week on an inclined treadmill (10% slope) at intensities between 40 and 70% V̇CO2max. At the onset of training horses ran 2600 m/day which progressively increased to 4500 m/day by week 5. Testing was carried out before training and after weeks 3 and 5 of training. The test involved exercise at 2 speeds, 4 m/s and 8 m/s, both for 3 min with one h recovery between the 2 speeds. All horses performed at both speeds but the initial speed was randomly allocated. An open flow gas collection system was used to measure V̇O2 and V̇CO2 every 15 s for the first min of exercise and every 30 s thereafter. After 5 weeks training, mean body weight and V̇O2max (mean ± s.e.) of the group had altered from 433 ± 5 kg to 430 ± 8 kg (P > 0.05) and from 104 ± 5 ml/kg/bwt/min to 116 ± 6 ml/kg/bwt/min (P < 0.05), respectively. There were no significant training effects on the rate of change of V̇O2 or V̇CO2 at either of the test speeds. By 45 s, the V̇O2 and V̇CO2 values had reached 85 to 95% of mean steady state values at both intensities of exercise. In general, steady state V̇O2 and V̇CO2 values were evident by 60 s of exercise. We conclude that horses have rapid increases in gas exchange at the start of exercise and these are not influenced by low intensity training.
Effects of exercise intensity and training on bronchoalveolar lavage cytology
Authors: McKANE S. A. , ROSE R. J. 
Published: June 2010

SummaryAlthough bronchoalveolar lavage (BAL) has become a commonly used technique for evaluation of pulmonary cytology and there have been many reports on horses at rest and in race training, there have ben no longitudinal studies where cytological results have been assessed during a training programme which involved increases in training intensity. In this study, 10 Thoroughbred horses were trained on a treadmill for a period of 12 weeks and were divided into 2 groups, one group (FAST) being trained at intensities to produce whole blood lactate concentrations in the range 4–8 mmol/l while the other group (SLOW) were trained at half the intensity of the FAST group. The training speeds for the FAST group ranged from 8–11 m/s whereas that for the slow group ranged from 3–6 m/s. Horses were trained for 6 days/week over daily distances of 1000–3600 m. Bronchoalveolar lavage samples were collected from each horse during weeks 1, 3, 6, 8, 10 and 12. The BAL samples were analysed and compared with respect to changes in cytology occurring throughout the period of training. The results of the study indicated that intensity and duration of exercise may have an effect on the development and severity of exercise induced pulmonary haemorrhage (EIPH), as determined by the absolute count and the percentage of erythrocytes returned in a BAL sample. This appears to be especially true when training at high intensities. However, the low levels of EIPH detected in the horses were not sufficienttocause a measurable loss of exercise performance or lowering of the horses' maximal oxygen uptake during exercise. Low intensity training was noted to have very little effect on the observed BAL cytology.
Tracheal pressure in horses with signs of dorsal displacement of the soft palate
Authors: ROETHLISBERGER‐HOLM KARIN 
Published: June 2010

SummaryAmong the functional disorders of the upper respiratory tract, dorsal displacement of the soft palate (DDSP) is still a major diagnostic challenge. In this study, measurements of tracheal pressure were made in exercising horses with clinical signs of DDSP. Tracheal pressure was recorded via a percutaneously inserted tracheal catheter during exercise on a treadmill with an inclination of 6.25°, at speeds up to 9 m/s. Five horses with clinical signs of DDSP were compared to 20 earlier studied normal horses. In horses with signs of DDSP the tracheal pressure curve had a characteristic appearance. There were a number of short‐duration pressure peaks over a prolonged expiratory phase and an elevated peak expiratory pressure. The inspiratory pressure was within normal limits. These findings support the hypothesis that obstruction of the air passage in DDSP occurs mainly during expiration and the short peaks of the expiratory pressure curve may reflect the vibrations of the edge of the soft palate.
Pleural pressure changes during exercise do not affect measurement of mean pulmonary vascular pressures
Authors: SINHA A. K. , HAKIM T. S. , GLEED R. D. , DOBSON A. 
Published: June 2010

SummaryThis study was designed to evaluate the influence of pleural pressure on mean pulmonary vascular pressures in exercising horses. Pulmonary artery (Pa), pulmonary wedge (Pw) and oesophageal pressures (Pes) were measured with transducer tip catheters in 6 Standardbred horses at rest and during treadmill exercise at 75, 90 and 100% of maximal heart rate. Oesophageal pressure (Pes) measurements were used to estimate pleural pressure. Vascular pressures were determined in 4 ways: 1) mean transmural vascular pressure (Ptm) at Pesequal to resting end expiratory pressure; 2) mean Ptmat Pesequal to mean Pesfor the data collection period; 3) mean Ptmwithout selection of specific data points and 4) mean pulmonary vascular pressure relative to atmospheric pressure (conventional method). Despite large fluctuations associated with breathing, mean Pesduring exercise remained close to zero, suggesting that pleural pressure fluctuates equally about zero. The swings in Peswere associated with approximately equal swings in vascular pressure so that, despite the marked fluctuations, mean Paand Pwdetermined with the 4 methods were not significantly different. The results indicate that during exercise it is valid to report mean pulmonary vascular pressures without accounting for the fluctuations in pleural pressure.
Heart and spleen mass related to blood parameter changes after epinephrine injection
Authors: HANSON CHRISTINE M. , KLINE K. H. , FOREMAN J. H. , FREY L. P. , COOPER S. M. 
Published: June 2010

SummaryThe purpose of this study was to determine if splenic weight is correlated to changes in blood volume, haematocrit and haemoglobin concentration after epinephrine injection in horses. Ten mares, 5 racing type and 5 draft type, all over age 5 years were studied. Differences in plasma volume (PV), red cell volume (RCV), total blood volume (TBV) and venous haematocrit (PCV) were maximised by xylazine and epinephrine treatments to either sequester or mobilise the splenic RCV. Plasma volume was determined using an Evans Blue Dye (EBD) dilution technique, then used to calculate TBV and RCV. Horses were killed by captive bolt gun and exsanguination, and heart (HW) and spleen weights (SW) were recorded and expressed as a percentage of body weight (BW). Significant differences between breed types were found for changes in RCV and PCV between treatments. Analysis of variance found significant differences between breed types in HW/BW and SW/BW ratios. Regression analysis demonstrated a positive relationship between the change in RCV between treatments and SW/BW with significant differences (P < 0.01) between breed types in this relationship. There was no relationship between changes in RCV or PCV and HW/BW.