bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating the proportion of intracranial aneurysms likely to be amenable to treatment with the pipeline embolization device
Authors: Brinjikji Waleed , Cloft Harry J , Fiorella David , Lanzino Giuseppe , Kallmes David F
Published: December 2011

Objective

A study was undertaken to estimate the fraction of intracranial aneurysms that might be amenable to treatment with the pipeline embolization device (PED), a current flow diverter device, and to determine the types of aneurysms that are probably not amenable to treatment with this device.

Methods

A retrospective analysis of 200 consecutive intracranial aneurysms as seen on three-dimensional rotational angiography images was conducted. Based on aneurysm and parent artery morphology, four independent observers experienced in the use of the PED judged the likelihood that a given aneurysm could theoretically be treated with one or more PED using a 5-point scale: grades 1 and 2 indicated amenability to treatment with multiple devices; grade 3 indicated amenability to treatment with one device; and grades 4 and 5 indicated the aneurysm would not be amenable to treatment with the PED. Aneurysms were analyzed on the basis of anatomical factors only. Rupture status was not considered. Interobserver agreement was determined.

Results

94 of 200 aneurysms (47%) were judged to be likely to be amenable to treatment with the PED; 50 cases (25%) were judged to be amenable to the use of multiple overlapping devices while, in 44 cases (22%), coverage with a single device was preferred. There was a significant relationship between the location of the aneurysm and the grade of the aneurysm (p<0.0001).

Conclusion

On the basis of anatomical configuration, nearly half of the aneurysms in this study were likely to be amenable to treatment with the PED.
Lameness scoring system for dairy cows using force plates and artificial intelligence
Authors: Ghotoorlar S. Mokaram , Ghamsari S. Mehdi , Nowrouzian I. , Ghotoorlar S. Mokaram , Ghidary S. Shiry
Published: December 2011

Lameness scoring is a routine procedure in dairy industry to screen the herds for new cases of lameness. Subjective lameness scoring, which is the most popular lameness detection and screening method in dairy herds, has several limitations. They include low intra‐observer and inter‐observer agreement and the discrete nature of the scores which limits its usage in monitoring the lameness. The aim of this study is to develop an automated lameness scoring system comparable with conventional subjective lameness scoring by means of artificial neural networks. The system is composed of four balanced force plates installed in a hoof‐trimming box. A group of 105 dairy cows was used for the study. Twenty‐three features extracted from ground reaction force (GRF) data were used in a computer training process which was performed on 60 per cent of the data. The remaining 40 per cent of the data were used to test the trained system. Repeatability of the lameness scoring system was determined by GRF samples from 25 cows, captured at two different times from the same animals. The mean sd was 0.31 and the mean coefficient of variation was 14.55 per cent, which represents a high repeatability in comparison with subjective vision‐based scoring methods. Although the highest sensitivity and specificity values were seen in locomotion score groups 1 and 4, the automatic lameness system was both sensitive and specific in all groups. The sensitivity and specificity were higher than 72 per cent in locomotion score groups 1 to 4, and it was 100 per cent specific and 50 per cent sensitive for group 5.
Heterosis for carotenoid concentration and profile in maize hybrids
Authors: Burt Andrew J. , Grainger Christopher M. , Shelp Barry J. , Lee Elizabeth A.
Published: December 2011

Production of high-lutein maize grain is of particular interest as a value-added feed source to produce high-lutein eggs. In this paper, it is demonstrated that heterosis for total carotenoid concentration and for the ratio of lutein to zeaxanthin (L:Z ratio), or profile type, exists infrequently in yellow dent crosses. However, yellow dent inbred maize lines A619 and CG102, both possessing high-lutein profiles, produce F1seed with a classic overdominant expression of lutein levels (i.e., 49 µg/g dry weight (DW) above the high-parent value). Reciprocal crosses of A619 and CG102 with one another and with two high-zeaxanthin (i.e., low lutein), high-carotenoid lines both suggest that the A619 and CG102 high-lutein phenotypes are achieved by different and complementary genotypes. The contribution of CG102 to the heterotic response was examined using a QTL-based approach that involved phenotyping the mapping population in a testcross to A619. Significant QTL were found at loci known to be involved in the carotenoid pathway but also at loci proximate to, but separate from, known carotenoid pathway steps. Exploiting an overdominant heterotic response for lutein and total carotenoids should be given strong consideration as a viable method of producing high-carotenoid hybrid maize lines.
Interaction of carbon monoxide with small metal clusters: a DFT, electrochemical, and FTIR study
Authors: Adams Brian D. , Asmussen Robert M. , Chen Aicheng , Mawhinney Robert C.
Published: December 2011

The adsorption of CO molecules onto small metal clusters was studied using density functional theory (DFT) calculations, and experimental electrochemical and attenuated total reflection-Fourier transform infrared spectroscopic (ATR-FTIR) techniques were used to examine CO adsorbed onto nanostructures of similar composition. The adsorption strengths and CO vibrational stretching frequencies were calculated and analyzed for clusters of the form M–CO for all of the period 4, 5, and 6 d-block transition metals. A direct link between the νCO and the population of d orbitals of the metal was observed. All possible binding sites for CO on clusters of the form Pd4–CO, Pd2Pt2–CO, and Pd2Au2–CO were determined and the corresponding adsorption energies and CO stretching frequencies were examined. Pure Pd and bimetallic PdPt and PdAu nanostructures were fabricated and used as catalysts for the adsorption and electrochemical oxidation of CO. The relative quantities of CO molecules adsorbed to surface of the catalysts decrease in the order of PdPt > Pd > PdAu, consistent with our DFT results. The location of νCO bands of CO adsorbed onto the nanostructured catalysts were determined by means of ATR-FTIR spectroscopy and were found to have values close to that predicted by DFT. This paper shows that DFT calculations on very small metal clusters Mn–CO (n ≤ 4) can be a simple but effective way of screening catalysts for their adsorbing properties.
Density functional theory calculations for the interaction of Li+ cations and PF6– anions with nonaqueous electrolytes
Authors: Bhatt Mahesh Datt , Cho Maenghyo , Cho Kyeongjae
Published: December 2011

The interaction of lithium (Li+) cation and hexafluorophosphate (PF6–) anion with nonaqueous electrolytes is studied by using density functional theory at the B3LYP/6–311++G(d,p) level in the gas phase in terms of the coordination of Li+ and PF6– with these solvents. Ethylene carbonate (EC) coordinates with Li+ and PF6– most strongly and reaches the anode and cathode most easily because of its highest dielectric constant among all the solvent molecules, resulting in its preferential reduction on the anode and oxidation on the cathode. For cyclic carbonates EC and propylene carbonate (PC), the structure Li+(S)4 is found to be the most stable. However, for linear carbonates dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), the formation of PF6–(S)n=1–3 is not favorable. Such analysis may be useful in applications for lithium ion batteries.
Volatile organic compounds analyzed by direct insertion probe mass spectrometry
Authors: Li Jian Jun
Published: December 2011

A modified approach for analyzing volatile organic compounds through standard direct insertion probe mass spectrometry is presented. With aluminum oxide or silica powder packed in a capillary tube, the sample’s evaporative loss in a high vacuum instrument chamber is significantly reduced and the retention time is increased accordingly. With this technique, organic compounds with lower boiling points (e.g., 2-butanol at 99 °C) can be readily detected and analyzed.
Is the risk of nest predation heterospecifically density-dependent in precocial species belonging to different nesting guilds?
Authors: Elmberg Johan , Pöysä Hannu
Published: December 2011

Nest predation is a key source of mortality and variation in fitness, but the effect co-occurring species belonging to different nesting guilds have on each other’s nest success is poorly understood. By using artificial nests, we tested if predation on cavity nests of Common Goldeneyes ( Bucephala clangula (L., 1758)) is increased in the presence of ground nests of Mallards ( Anas platyrhynchos L., 1758) and vice versa. Specifically, by adding ground nests in the vicinity of cavity nests, we tested the hypothesis that predation on cavity nests is heterospecifically density-dependent. A shared predator, the pine marten ( Martes martes (L., 1758)), was intensively hunted in one of the study areas, but not in the other, leading to most individuals in the former being naïve immigrants. Cavity-nest fate was not affected by addition of ground nests. Similarly, ground-nest survival did not decrease when nearby cavity nests were depredated. Fate of nests in a given nest cavity was highly predictable between years in the study area with minimal removal of pine martens, but not in the one with intensive removal. Predation rate was higher on cavity nests than on ground nests. Predation on ground nests was lower in the study area with intensive removal of pine martens. We conclude there was neither apparent competition between guilds nor heterospecific density-dependence in predation risk.
Is sperm viability independent of ejaculate size in the house cricket (Acheta domesticus)?
Authors: Gress Brian E. , Kelly Clint D.
Published: December 2011

Assessing sperm viability is a popular means of testing hypotheses related to ejaculate quality. This technique has produced interesting results; however, the sperm viability assay itself may kill sperm. This is a serious pitfall, as assay-related mortality could confound results and produce artificially low estimates of viability. To avoid spurious results, it has been recommended that investigators include sperm number in their viability analyses. Unfortunately, studies conducted to date on internal fertilizers have not included sperm counts in their analyses, so it is not possible to assess whether this factor can indeed produce artefactual results. In this paper, we use male house crickets ( Acheta domesticus (L., 1758)) to show that sperm viability is dependent on sperm number and exclusion of this factor from statistical analyses affects our interpretation of experimental treatment results. We show that mechanically rupturing a spermatophore significantly reduces sperm viability, but this does not appear to drive the nonindependent relationship between viability and number. Instead, our study shows that nonindependence is due to processes other than differential physical damage to the sperm during collection. We also show that allowing a spermatophore to evacuate its sperm without rupturing for 10 min maximizes both sperm number and viability.
Roosts and home ranges of spotted bats (Euderma maculatum) in northern Arizona
Authors: Chambers Carol L. , Herder Michael J. , Yasuda Kei , Mikesic David G. , Dewhurst Stephen M. , Masters W. Mitchell , Vleck David
Published: December 2011

Roosting ecology and foraging behavior of spotted bats ( Euderma maculatum (J.A. Allen, 1891)) are poorly known. We captured 47 spotted bats at three locations in northern Arizona and attached radio transmitters to 16 bats to identify roosts and home ranges. We identified 14 roosts for 12 bats. Female roosts faced south; males did not select a roost aspect. Bats used a mean of 1.4 roosts during 10 days. Mean distances from capture site and nearest perennial water source to roosts were 15.1 and 5.8 km, respectively. Maximum and minimum distances from capture to roost site were 36.3 and 2.3 km, respectively. Home ranges (95% use, minimum convex polygon method) for bats averaged 297 km2, which was much larger than reported for spotted bats elsewhere in their range and other insectivorous bats. Maximum flight speed was 53 km/h. Most foraging locations were in desert scrub vegetation, but bats also used woodlands and forests, perhaps seeking seasonal prey or cooler sites to reduce water stress. Maternity roosts were remote, difficult to access, and within protected areas in northern Arizona. Foraging areas and ponds used for drinking, however, included private and public lands managed for a variety of uses.
Mid-crustal controls on episodic stress-field rotation around major reverse, normal and strike-slip faults
Authors: Nüchter Jens-Alexander , Ellis Susan
Published: December 2011

Numerical models are used to investigate the geometry of coseismic stress-field perturbation in the crust surrounding a reverse fault, a normal fault and a strike-slip fault. The results predict a coseismic stress drop in the upper crust and loading to high stress below the brittle–ductile transition (BDT) due to the taper-off in fault slip. Coseismic stress deflections occur for each fault type as a result of the coseismic stress redistribution and is at a maximum in the middle crust where fault slip tapers-off. The zone of high-stress deflection extends downwards to the base of the crust. During the post-seismic interval, the stress-field geometry recovers towards the pre-earthquake stress state, but simple stress-field geometries cannot be re-established. The numerical results indicate that: (1) stress deflection due to slip taper-off below the BDT is important for the stress perturbation throughout the crust; (2) predictions for coseismic stress deflection exclusively based on the fault-parallel shear-stress drop ratio systematically underestimate stress deflection in the entire crust; (3) stress rotation is persistent throughout the crust in seismically active regions; and (4) the geometry of secondary faults is expected to be affected by the perturbed stress field.
Formation of fault-related calcite precipitates and their implications for dating fault activity in the East Anatolian and Dead Sea fault zones
Authors: Nuriel P. , Rosenbaum G. , Uysal T. I. , Zhao J. , Golding S. D. , Weinberger R. , Karabacak V. , Avni Y.
Published: December 2011

Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Turkey) and Dead Sea (Israel) fault zones were investigated structurally, geochemically and geochronologically. The results indicate major differences in the nature of calcite precipitates and temporal relationship to faulting. In the Düziçi Fault, calcite-filled veins and hydraulic fractures precipitated co-seismically during three consecutive faulting events. Calcite precipitated in veins at the Har Zefiyya Fault was controlled by near-surface karst processes. Initial opening of the veins occurred prior to about 500 ka and may represent the onset of an east–west contractional deformation. In the Carmel Fault Zone the calcite coating the fault plane precipitated by karst processes, with no evidence of subsequent deformation. Calcite fault gouge from the same site are a mix of host-rock gouge and newly formed authigenic calcite, and their overall geochemistry suggests pervasive fluid–rock interaction in the fault zone. In the Baraq Fault Zone the precipitation of calcite within syntectonic tension gashes and veins occurred prior to 540 ka by the pervasive infiltration of meteoric water into the fault zone. The results demonstrate that geochemical and structural analyses, combined with U–Th geochronology, can shed light on co-seismic and inter-seismic fault activity, and can potentially provide precise age constraints on the timing of brittle deformation.
Reproduction of thermal pressurization and fluidization of clay-rich fault gouges by high-velocity friction experiments and implications for seismic slip in natural faults
Authors: Ujiie Kohtaro , Tsutsumi Akito , Kameda Jun
Published: December 2011

We examine the frictional properties and microstructures of clay-rich fault gouges subjected to thermal pressurization and fluidization, generated in high-velocity friction experiments under dry and wet conditions. In the dry tests, slip weakening occurs by thermal pressurization, which is marked by a fault-gouge expansion associated with a water-phase transition from liquid to vapour. The water is derived from dehydration of clay minerals by frictional heating. The resulting microstructure in the gouge layer is a random distribution of spherical clay–clast aggregates in the matrix, and mixing of different gouge constituents without shear surfaces. In the wet tests, slip weakening is caused by pore-fluid pressurization resulting from shear-enhanced compaction of the water-saturated gouge and frictional heating. Compared to the dry tests, the wet tests show smaller dynamic stress drops and slip weakening distance. The steady-state shear stress in the wet tests is almost independent of normal stress, suggesting a fluid-like behaviour of the fault gouge during high-velocity shearing. The microstructures after the wet tests show that the foliated zone is accompanied by grain-size segregation in the gouge layer. The grain-size segregation is attributed to the Brazil-nut effect resulting from the difference in dispersive pressure in the granular-fluid shear flow at high shear rates, indicating a fluidization of fault gouge. Our results obtained at seismic slip rates imply that the propagation of an earthquake rupture can be enhanced by fluid pressurization and frictional heat, potentially leaving characteristic microstructures resulting from water vaporization by frictional heating or flow sorting at high slip rates.
Fault-zone geology: lessons from drilling through the Nojima and Chelungpu faults
Authors: Boullier Anne-Marie
Published: December 2011

Several drilling projects have been conducted through active faults with the aim of learning about the geology of the fault zones and tentatively correlating the structure and mineralogy of the fault zones with their seismological behaviour during recent earthquakes. Here we present the major results obtained from structural and mineralogical studies of core samples retrieved from the dextral reverse strike-slip Nojima Fault (Japan) within granitic rocks following the Kobe earthquake (1995), and from the Chelungpu Thrust Fault (Taiwan) within alternating silts and shales following the Chi-chi earthquake (1999). We show how these projects, despite not fullfilling all their objectives, have still contributed to a better geological knowledge of the fault zones, to a better characterization of the slip zones related to the recent earthquakes particularly of their thickness, microstructures and deformation mechanisms, and to a better understanding of the nature and role of fluids within the fault zone. They have also led to new questions, and to new approaches, for studying fault-rock samples. For all of these reasons, they have stimulated international scientific research into fault-zone geology.
Deep rock damage in the San Andreas Fault revealed by P- and S-type fault-zone-guided waves
Authors: Ellsworth William L. , Malin Peter E.
Published: December 2011

Damage to fault-zone rocks during fault slip results in the formation of a channel of low seismic-wave velocities. Within such channels guided seismic waves, denoted by F
g
, can propagate. Here we show with core samples, well logs and F
g
-waves that such a channel is crossed by the SAFOD (San Andreas Fault Observatory at Depth) borehole at a depth of 2.7 km near Parkfield, California, USA. This laterally extensive channel extends downwards to at least half way through the seismogenic crust, more than about 7 km. The channel supports not only the previously recognized Love-type- (F
L
) and Rayleigh-type- (F
R
) guided waves, but also a new fault-guided wave, which we name F
Φ
. As recorded 2.7 km underground, F
Φ
is normally dispersed, ends in an Airy phase, and arrives between the P
-
and S
-
waves. Modelling shows that F
Φ
travels as a leaky mode within the core of the fault zone. Combined with the drill core samples, well logs and the two other types of guided waves, F
Φ
at SAFOD reveals a zone of profound, deep, rock damage. Originating from damage accumulated over the recent history of fault movement, we suggest it is maintained either by fracturing near the slip surface of earthquakes, such as the 1857 Fort Tejon
M
7.9, or is an unexplained part of the fault-creep process known to be active at this site.
Geology of the seismogenic subduction thrust interface
Authors: Fagereng Åke
Published: December 2011

A microseismically active layer of underthrust sediments is commonly inferred along subduction thrust interfaces. The exhumed Chrystalls Beach Complex, in the Otago Schist, New Zealand, may be analogous to an actively deforming underthrust rock assemblage. The complex contains asymmetric competent lenses of sandstone, chert and basalt enclosed in a cleaved mudstone matrix. Continuous fabrics such as folds, boudins and asymmetric phacoids formed by distributed cataclasis and dissolution–precipitation creep. Discontinuous deformation is evident in an extensive fault-fracture mesh involving mutually cross-cutting subvertical extension veins and subhorizontal slickenfibre shear surfaces.

The Hikurangi margin provides an example of along-strike variations in seismic style, possibly related to heterogeneous fluid-pressure state and interface geology. In both the ancient and active subduction-related shear zone, fluid-pressure state appears to be a critical control on frictional failure, which primarily occurs on weak, fluid-overpressured discontinuities. Continuous, aseismic deformation occurs where other mineral deformation mechanisms, such as dissolution–precipitation creep, are preferred. The geometry and composition of the underthrust rock assemblage appear to be first-order controls on megathrust fluid-pressure distribution, bulk rheology and dominant deformation mechanism, and thus may be significant controls on megathrust seismic style.
Textural record of the seismic cycle: strain-rate variation in an ancient subduction thrust
Authors: Rowe Christie D. , Meneghini Francesca , Moore J. Casey
Published: December 2011

Active faults slip at different rates over the course of the seismic cycle: earthquake slip (
c
. 1 m s
−1
), interseismic creep (
c
. 10–100 mm year
−1
) and intermediate rate transients (e.g. afterslip and slow slip events). Studies of exhumed faults are sometimes able to identify seismic slip surfaces by the presence of frictional melts, and slow creep by textures diagnostic of rate-limited plastic processes. The Pasagshak Point Thrust preserves three distinct fault rock textures, which are mutually cross-cutting, and can be correlated to different strain rates. Ultrafine-grained black fault rocks, including pseudotachylyte, were formed during seismic slip on layers up to 30 cm thick. Well-organized
S
–
C
cataclasites 7–31 m thick were formed by slow creep, with pressure solution as a dominant, rate-limiting mechanism. These must have formed at strain rates consistent with long-term plate-boundary motion, but solution-creep healing acted to reduce porosity of the cataclasites and eventually restricted fluid connectivity such that creep by this mechanism could not continue. Disorganized, non-foliated, rounded clast cataclasites were formed at shear rates faster than solution creep and are interpreted as representing shear at intermediate strain rates. These could have formed during afterslip or delocalization of slip associated with an earthquake rupture.

Supplementary material:

Detailed map of Pasagshak Peninsula is available at
http://www.geolsoc.org.uk/SUP18493
.
Integrating an open-source course management system (Moodle) into the teaching of a first-year medical physiology course: a case study
Authors: Seluakumaran Kumar , Jusof Felicita Fedelis , Ismail Rosnah , Husain Ruby
Published: December 2011

Educators in medical schools around the world are presently experimenting with innovative ways of using web-based learning to supplement the existing teaching and learning process. We have recently used a popular open-source course management system (CMS) called the modular object-oriented dynamic learning environment (Moodle) to construct an online site (DPhysiol) to facilitate our face-to-face teaching of physiology to a group of first-year students in the Bachelor of Medicine and Bachelor of Surgery program. The integration of the Moodle site into our teaching was assessed using online log activity, student examination marks, and feedback from students. The freely available Moodle platform was simple to use, helped to effectively deliver course materials, and has features that allowed cooperative learning. Students who used the CMS throughout their academic year and commented favorably regarding its use as a complement to the face-to-face classroom sessions. The group of students used the CMS obtained significantly higher scores in the final examination compared with the previous class that did not use the CMS. In addition, there was a significant correlation between student participation and performance in online quizzes and their final examination marks. However, students' overall online usage of the CMS did not correlate with their examination marks. We recommend Moodle as a useful tool for physiology educators who are interested in integrating web-based learning into their existing teaching curriculum.
Exploring first-year undergraduate medical students' self-directed learning readiness to physiology
Authors: Abraham Reem Rachel , Fisher Murray , Kamath Asha , Izzati T. Aizan , Nabila Saidatul , Atikah Nik Nur
Published: December 2011

Medical students are expected to possess self-directed learning skills to pursue lifelong learning. Previous studies have reported that the readiness for self-directed learning depends on personal attributes as well as the curriculum followed in institutions. Melaka Manipal Medical College of Manipal University (Karnataka, India) offers a Bachelor of Medicine and Bachelor of Surgery (MBBS) twinning program that is of 5 yr in duration. Keeping in mind the amount of time that the curriculum has devoted for self-directed learning, we explored the self-directed learning readiness of first-year MBBS students ( n = 130) using a self-directed learning readiness scale (SDLRS) and explored the correlation between SDLRS scores of high achievers, medium achievers, and low achievers with their academic performance in physiology examinations. Students were requested to respond to each item of the SDLRS on a Likert scale. Median scores of the three scales of the SDLRS were compared across the three groups of students using a Kruskall-Wallis test. SDLRS scores of the students ( n = 130) were correlated with their marks in theory papers of first, second, and third block-end examinations using Spearmann's correlation coefficient. The mean item score for desire for learning was found to be higher followed by self-control and self-management. Data analyses showed significantly high ( P < 0.03) median scores for self-control for high achievers compared with medium and low achievers. Between the groups, high achievers had a higher score for all the three scales of the SDLRS followed by low and medium achievers. SDLRS scores and academic performance of the three groups of students were found to exhibit a weak correlation. This study threw light on the fact that despite having a high desire for learning and ability of self-control, students need to be supported in their self-management skills.
Explorations in statistics: regression
Authors: Curran-Everett Douglas
Published: December 2011

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of Explorations in Statistics explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive connection. Regression helps us answer three questions: does some variable Y depend on another variable X; if so, what is the nature of the relationship between Y and X; and for some value of X, what value of Y do we predict? Residual plots are an essential component of a thorough regression analysis: they help us decide if our statistical regression model of the relationship between Y and X is appropriate.
Enhancing learning through optimal sequencing of web-based and manikin simulators to teach shock physiology in the medical curriculum
Authors: Cendan Juan C. , Johnson Teresa R.
Published: December 2011

The Association of American Medical Colleges has encouraged educators to investigate proper linkage of simulation experiences with medical curricula. The authors aimed to determine if student knowledge and satisfaction differ between participation in web-based and manikin simulations for learning shock physiology and treatment and to determine if a specific training sequencing had a differential effect on learning. All 40 second-year medical students participated in a randomized, counterbalanced study with two interventions: group 1 ( n = 20) participated in a web-based simulation followed by a manikin simulation and group 2 ( n = 20) participated in reverse order. Knowledge and attitudes were documented. Mixed-model ANOVA indicated a significant main effect of time ( F1,38 = 18.6, P < 0.001, ηp2 = 0.33). Group 1 scored significantly higher on quiz 2 (81.5%) than on quiz 1 (74.3%, t19 = 3.9, P = 0.001), for an observed difference of 7.2% (95% confidence interval: 3.3, 11.0). Mean quiz scores of group 2 did not differ significantly ( quiz 1: 77.0% and quiz 2: 79.7%). There was no significant main effect of group or a group by time interaction effect. Students rated the simulations as equally effective in teaching shock physiology ( P = 0.88); however, the manikin simulation was regarded as more effective in teaching shock treatment ( P < 0.001). Most students (73.7%) preferred the manikin simulation. The two simulations may be of similar efficacy for educating students on the physiology of shock; however, the data suggest improved learning when web-based simulation precedes manikin use. This finding warrants further study.
Are faculty predictions or item taxonomies useful for estimating the outcome of multiple-choice examinations?
Authors: Kibble Jonathan D. , Johnson Teresa
Published: December 2011

The purpose of this study was to evaluate whether multiple-choice item difficulty could be predicted either by a subjective judgment by the question author or by applying a learning taxonomy to the items. Eight physiology faculty members teaching an upper-level undergraduate human physiology course consented to participate in the study. The faculty members annotated questions before exams with the descriptors “easy,” “moderate,” or “hard” and classified them according to whether they tested knowledge, comprehension, or application. Overall analysis showed a statistically significant, but relatively low, correlation between the intended item difficulty and actual student scores (ρ = −0.19, P < 0.01), indicating that, as intended item difficulty increased, the resulting student scores on items tended to decrease. Although this expected inverse relationship was detected, faculty members were correct only 48% of the time when estimating difficulty. There was also significant individual variation among faculty members in the ability to predict item difficulty (χ2 = 16.84, P = 0.02). With regard to the cognitive level of items, no significant correlation was found between the item cognitive level and either actual student scores (ρ = −0.09, P = 0.14) or item discrimination (ρ = 0.05, P = 0.42). Despite the inability of faculty members to accurately predict item difficulty, the examinations were of high quality, as evidenced by reliability coefficients (Cronbach's α) of 0.70–0.92, the rejection of only 4 of 300 items in the postexamination review, and a mean item discrimination (point biserial) of 0.37. In conclusion, the effort of assigning annotations describing intended difficulty and cognitive levels to multiple-choice items is of doubtful value in terms of controlling examination difficulty. However, we also report that the process of annotating questions may enhance examination validity and can reveal aspects of the hidden curriculum.
Coexpression of ecto-5′-nucleotidase/CD73 with specific NTPDases differentially regulates adenosine formation in the rat liver
Authors: Fausther Michel , Lecka Joanna , Soliman Elwy , Kauffenstein Gilles , Pelletier Julie , Sheung Nina , Dranoff Jonathan A. , Sévigny Jean
Published: December 2011

Ectonucleotidases modulate purinergic signaling by hydrolyzing ATP to adenosine. Here we characterized the impact of the cellular distribution of hepatic ectonucleotidases, namely nucleoside triphosphate diphosphohydrolase (NTPDase)1/CD39, NTPDase2/CD39L1, NTPDase8, and ecto-5′-nucleotidase/CD73, and of their specific biochemical properties, on the levels of P1 and P2 receptor agonists, with an emphasis on adenosine-producing CD73. Immunostaining and enzyme histochemistry showed that the distribution of CD73 (protein and AMPase activity) overlaps partially with those of NTPDase1, -2, and -8 (protein levels and ATPase and ADPase activities) in normal rat liver. CD73 is expressed in fibroblastic cells located underneath vascular endothelial cells and smooth muscle cells, which both express NTPDase1, in portal spaces in a distinct fibroblast population next to NTPDase2-positive portal fibroblasts, and in bile canaliculi, together with NTPDase8. In fibrotic rat livers, CD73 protein expression and activity are redistributed but still overlap with the NTPDases mentioned. The ability of the observed combinations of ectonucleotidases to generate adenosine over time was evaluated by reverse-phase HPLC with the recombinant rat enzymes at high “inflammatory” (500 μM) and low “physiological” (1 μM) ATP concentrations. Overall, ATP was rapidly converted to adenosine by the NTPDase1+CD73 combination, but not by the NTPDase2+CD73 combination. In the presence of NTPDase8 and CD73, ATP was sequentially dephosphorylated to the CD73 inhibitor ADP, and then to AMP, thus resulting in a delayed formation of adenosine. In conclusion, the specific cellular cocompartmentalization of CD73 with hepatic NTPDases is not redundant and may lead to the differential activation of P1 and P2 receptors, under normal and fibrotic conditions.
Expression profiling identifies novel gene targets and functions forPdx1in the duodenum of mature mice
Authors: Chen Chin , Sibley Eric
Published: December 2011

Transcription factor pancreatic and duodenal homeobox 1 (Pdx1) plays an essential role in the pancreas to regulate its development and maintain proper islet function. However, the functions of Pdx1 in mature small intestine are less known. We aimed to investigate the intestinal role of Pdx1 by profiling the expression of genes differentially regulated in response to inactivation of Pdx1 specifically in the intestinal epithelium. Pdx1 was conditionally inactivated in the intestinal epithelium of Pdx1flox/flox;VilCre mice. Total RNA was isolated from the first 5 cm of the small intestine from mature Pdx1flox/flox;VilCre and littermate control mice. Microarray analysis identified 86 probe sets representing 68 genes significantly upregulated or downregulated 1.5-fold or greater in Pdxflox/flox;VilCre mice maintained under standard conditions. Ingenuity Pathway Analysis revealed that functions of the differentially expressed genes are significantly associated with metabolism of nutrients including lipids and iron. Network analysis examining the interactions among the differentially expressed genes further supports the notion that Pdx1 may modulate metabolism of lipids and iron from mature intestinal epithelium. Following forced oil feeding, Pdx1flox/flox;VilCre mice showed diminished lipid staining in the duodenal epithelium and decreased serum triglyceride levels, indicating reduced lipid absorption compared with control duodenal epithelium. Blood samples from Pdx1flox/flox;VilCre mice have significantly lower mean values for mean corpuscular volume and mean corpuscular hemoglobin, consistent with iron deficiency. The absence of nonheme iron in the villous epithelium and lamina propria of Pdx1flox/flox;VilCre duodenum indicates that the duodenal epithelium lacking Pdx1 may have defects in importing iron through enterocytes, resulting in iron deficiency in Pdx1flox/flox;VilCre mice.
Adaptive response of vascular endothelial cells to an acute increase in shear stress magnitude
Authors: Zhang Ji , Friedman Morton H.
Published: December 2011

The adaptation of vascular endothelial cells to shear stress alteration induced by global hemodynamic changes, such as those accompanying exercise or digestion, is an essential component of normal endothelial physiology in vivo. An understanding of the transient regulation of endothelial phenotype during adaptation to changes in mural shear will advance our understanding of endothelial biology and may yield new insights into the mechanism of atherogenesis. In this study, we characterized the adaptive response of arterial endothelial cells to an acute increase in shear stress magnitude in well-defined in vitro settings. Porcine endothelial cells were preconditioned by a basal level shear stress of 15 ± 15 dyn/cm2 at 1 Hz for 24 h, after which an acute increase in shear stress to 30 ± 15 dyn/cm2 was applied. Endothelial permeability nearly doubled after 40-min exposure to the elevated shear stress and then decreased gradually. Transcriptomics studies using microarray techniques identified 86 genes that were sensitive to the elevated shear. The acute increase in shear stress promoted the expression of a group of anti-inflammatory and antioxidative genes. The adaptive response of the global gene expression profile is triphasic, consisting of an induction period, an early adaptive response (ca. 45 min) and a late remodeling response. Our results suggest that endothelial cells exhibit a specific phenotype during the adaptive response to changes in shear stress; this phenotype is different than that of fully adapted endothelial cells.
Reduced mitochondrial Ca2+ loading and improved functional recovery after ischemia-reperfusion injury in old vs. young guinea pig hearts
Authors: Rhodes Samhita S. , Camara Amadou K. S. , Heisner James S. , Riess Matthias L. , Aldakkak Mohammed , Stowe David F.
Published: December 2011

Oxidative damage and impaired cytosolic Ca2+ concentration ([Ca2+]cyto) handling are associated with mitochondrial [Ca2+] ([Ca2+]mito) overload and depressed functional recovery after cardiac ischemia-reperfusion (I/R) injury. We hypothesized that hearts from old guinea pigs would demonstrate impaired [Ca2+]mito handling, poor functional recovery, and a more oxidized state after I/R injury compared with hearts from young guinea pigs. Hearts from young (∼4 wk) and old (>52 wk) guinea pigs were isolated and perfused with Krebs-Ringer solution (2.1 mM Ca2+ concentration at 37°C). Left ventricular pressure (LVP, mmHg) was measured with a balloon, and NADH, [Ca2+]mito (nM), and [Ca2+]cyto (nM) were measured by fluorescence with a fiber optic probe placed against the left ventricular free wall. After baseline (BL) measurements, hearts were subjected to 30 min global ischemia and 120 min reperfusion (REP). In old vs. young hearts we found: 1) percent infarct size was lower (27 ± 9 vs. 57 ± 2); 2) developed LVP (systolic-diastolic) was higher at 10 min (57 ± 11 vs. 29 ± 2) and 60 min (55 ± 10 vs. 32 ± 2) REP; 3) diastolic LVP was lower at 10 and 60 min REP (6 ± 3 vs. 29 ± 4 and 3 ± 3 vs. 21 ± 4 mmHg); 4) mean [Ca2+]cyto was higher during ischemia (837 ± 39 vs. 541 ± 39), but [Ca2+]mito was lower (545 ± 62 vs. 975 ± 38); 5) [Ca2+]mito was lower at 10 and 60 min REP (129 ± 2 vs. 293 ± 23 and 122 ± 2 vs. 234 ± 15); 6) reduced inotropic responses to dopamine and digoxin; and 7) NADH was elevated during ischemia in both groups and lower than BL during REP. Contrary to our stated hypotheses, old hearts showed reduced [Ca2+]mito, decreased infarction, and improved basal mechanical function after I/R injury compared with young hearts; no differences were noted in redox state due to age. In this model, aging-associated protection may be linked to limited [Ca2+]mito loading after I/R injury despite higher [Ca2+]cyto load during ischemia in old vs. young hearts.
Magnitude of length-dependent changes in contractile properties varies with titin isoform in rat ventricles
Authors: Patel Jitandrakumar R. , Pleitner Jonathan M. , Moss Richard L. , Greaser Marion L.
Published: December 2011

The effects of differential expression of titin isoforms on sarcomere length (SL)-dependent changes in passive force, maximum Ca2+-activated force, apparent cooperativity in activation of force ( nH), Ca2+ sensitivity of force (pCa50), and rate of force redevelopment ( ktr) were investigated in rat cardiac muscle. Skinned right ventricular trabeculae were isolated from wild-type (WT) and mutant homozygote (Ho) hearts expressing predominantly a smaller N2B isoform (2,970 kDa) and a giant N2BA-G isoform (3,830 kDa), respectively. Stretching WT and Ho trabeculae from SL 2.0 to 2.35 μm increased passive force, maximum Ca2+-activated force, and pCa50, and it decreased nH and ktr. Compared with WT trabeculae, the magnitude of SL-dependent changes in passive force, maximum Ca2+-activated force, pCa50, and nH was significantly smaller in Ho trabeculae. These results suggests that, at least in rat ventricle, the magnitude of SL-dependent changes in passive force, maximum Ca2+-activated force, pCa50, nH, and ktr is defined by the titin isoform.
PVN adenovirus-siRNA injections silencing either NOX2 or NOX4 attenuate aldosterone/NaCl-induced hypertension in mice
Authors: Xue Baojian , Beltz Terry G. , Johnson Ralph F. , Guo Fang , Hay Meredith , Johnson Alan Kim
Published: December 2011

Mineralocorticoid excess increases superoxide production by activating NADPH oxidase (NOX), and intracerebroventricular infusions of NADPH oxidase inhibitors attenuate aldosterone (Aldo)/salt-induced hypertension. It has been hypothesized that increased reactive oxygen species (ROS) in the brain may be a key mechanism in the development of hypertension. The present study investigated the brain regional specificity of NADPH oxidase and the role of NOX2 and NOX4 NADPH oxidase subunits in the hypothalamic paraventricular nucleus (PVN) in Aldo/salt-induced hypertension. PVN injections of adenoviral vectors expressing small interfering (si)RNA targeting NOX2 (AdsiRNA-NOX2) or NOX4 (AdsiRNA-NOX4) mRNAs were used to knock down NOX2 and NOX4 proteins. Three days later, delivery of Aldo (0.2 mg·kg−1·day−1 sc) via osmotic pump commenced and 1% NaCl was provided in place of water. PVN injections of either AdsiRNA-NOX2 or AdsiRNA-NOX4 significantly attenuated the development of Aldo/NaCl-induced hypertension. In an additional study, Aldo/salt-induced hypertension was also significantly attenuated in NOX2 (genomic) knockout mice compared with wild-type controls. When animals from both functional studies underwent ganglionic blockade, there was a reduced fall in blood pressure in the NOX2 and NOX4 knockdown/knockout mice. Western blot analyses of the PVN of siRNA-NOX2- or siRNA-NOX4-injected mice confirmed a marked reduction in the expression of NOX2 or NOX4 protein. In cultured PVN neurons, silencing either NOX2 or NOX4 protein production by culturing PVN cells with siRNA-NOX2 or siRNA-NOX4 attenuated Aldo-induced ROS. These data indicate that both NOX2 and NOX4 in the PVN contribute to elevated sympathetic activity and the hypertensivogenic actions induced by mineralocorticoid excess.
Mapping 3-D functional capillary geometry in rat skeletal muscle in vivo
Authors: Fraser Graham M. , Milkovich Stephanie , Goldman Daniel , Ellis Christopher G.
Published: December 2011

We have developed a novel mapping software package to reconstruct microvascular networks in three dimensions (3-D) from in vivo video images for use in blood flow and O2 transport modeling. An intravital optical imaging system was used to collect video sequences of blood flow in microvessels at different depths in the tissue. Functional images of vessels were produced from the video sequences and were processed using automated edge tracking software to yield location and geometry data for construction of the 3-D network. The same video sequences were analyzed for hemodynamic and O2 saturation data from individual capillaries in the network. Simple user-driven commands allowed the connection of vessel segments at bifurcations, and semiautomated registration enabled the tracking of vessels across multiple focal planes and fields of view. The reconstructed networks can be rotated and manipulated in 3-D to verify vessel connections and continuity. Hemodynamic and O2 saturation measurements made in vivo can be indexed to corresponding vessels and visualized using colorized maps of the vascular geometry. Vessels in each reconstruction are saved as text-based files that can be easily imported into flow or O2 transport models with complete geometry, hemodynamic, and O2 transport conditions. The results of digital morphometric analysis of seven microvascular networks showed mean capillary diameters and overall capillary density consistent with previous findings using histology and corrosion cast techniques. The described mapping software is a valuable tool for the quantification of in vivo microvascular geometry, hemodynamics, and oxygenation, thus providing rich data sets for experiment-based computational models.
GM-CSF provides autocrine protection for murine alveolar epithelial cells from oxidant-induced mitochondrial injury
Authors: Sturrock Anne , Seedahmed Elfateh , Mir-Kasimov Mustafa , Boltax Jonathan , McManus Michael L. , Paine Robert
Published: December 2011

Exposure of mice to hyperoxia induces alveolar epithelial cell (AEC) injury, acute lung injury and death. Overexpression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the lung protects against these effects, although the mechanisms are not yet clear. Hyperoxia induces cellular injury via effects on mitochondrial integrity, associated with induction of proapoptotic members of the Bcl-2 family. We hypothesized that GM-CSF protects AEC through effects on mitochondrial integrity. MLE-12 cells (a murine type II cell line) and primary murine type II AEC were subjected to oxidative stress by exposure to 80% oxygen and by exposure to H2O2. Exposure to H2O2induced cytochrome c release and decreased mitochondrial reductase activity in MLE-12 cells. Incubation with GM-CSF significantly attenuated these effects. Protection induced by GM-CSF was associated with Akt activation. GM-CSF treatment also resulted in increased expression of the antiapoptotic Bcl-2 family member, Mcl-1. Primary murine AEC were significantly more tolerant of oxidative stress than MLE-12 cells. In contrast to MLE-12 cells, primary AEC expressed significant GM-CSF at baseline and demonstrated constitutive activation of Akt and increased baseline expression of Mcl-1. Treatment with exogenous GM-CSF further increased Akt activation and Mcl-1 expression in primary AEC. Conversely, suppression of AEC GM-CSF expression by use of GM-CSF-specific small interfering RNA resulted in decreased tolerance of oxidative stress, Furthermore, silencing of Mcl-1 prevented GM-CSF-induced protection. We conclude that GM-CSF protects alveolar epithelial cells against oxidative stress-induced mitochondrial injury via the Akt pathway and its downstream components, including Mcl-1. Epithelial cell-derived GM-CSF may contribute to intrinsic defense mechanisms limiting lung injury.