bluuebunny/crossref_metadata_2025 huggingface dataset:
Diurnal evolution of cycling biomechanical parameters during a 60‐s Wingate test
Authors: Lericollais R. , Gauthier A. , Bessot N. , Davenne D.
Published: August 2010

The purpose of this study was to assess the evolution of pedaling kinetics and kinematics during a short‐term fatigue cycling exercise at two times of day. Twenty active male subjects were asked to perform a 60‐s Wingate test against a constant braking resistance during two experimental sessions at 06:00 and 18:00 hours, i.e., very close to the hours of core temperature values, which are, respectively, the lowest and the highest. The results showed that the fatigue index was higher (P<0.05) at 18:00 hours (71.4%) than at 06:00 hours (69.2%) and power output was higher (P<0.05) in the evening than in the morning during the first 20 s of the test, after which no difference was observed. Taken together, these results showed a greater progression of fatigue in the evening than in the morning. The diurnal variations in performance and fatigue were associated (P<0.001) with diurnal changes in cycling kinematic parameters, characterized by a reduction in the range of motion of the ankle angle in the evening. These findings show that a time‐of‐day effect on movement patterns occurs during an anaerobic cycling exercise and that this phenomenon has a direct influence on performance and fatigue.
Injury incidence in hip hop dance
Authors: Ojofeitimi S. , Bronner S. , Woo H.
Published: August 2010

Hip hop dance has rapidly become a popular international art form. There is limited information on injury patterns in this population. The purpose of this study was to determine injury incidence and patterns among three groups of hip hop dancers. Three hundred and twelve intermediate, advanced, and expert hip hop dancers were recruited at battles, dance conferences, clubs, and on dance related web sites within the United States and internationally. A Web‐based survey was conducted over a 6‐month period. Inclusion criteria included intermediate and advanced level dancers over the age of 13. Dancers were divided into three main categories: Breakers, Popper/Lockers, and New Schoolers. Separate analysis of variances were used to compare injury pattern differences between groups. Two hundred and thirty‐two dancers reported a total of 738 injuries. Five hundred and six of these (sustained by 205 dancers) were time‐loss (TL) injuries. Annual injury incidence was 237% (162% involving TL). Lower extremity injuries were 52% and upper extremity injuries 32% of total injuries. Breakers had a higher injury incidence compared with Popper/Lockers, and New Schoolers. Hip hop dancers report injury rates that are higher than other dance forms but similar to gymnastics. These dancers should be educated concerning injury prevention, biomechanics, and use of protective equipment.
The N‐terminal hybrid binding domain of RNase HI from Thermotoga maritima is important for substrate binding and Mg2+‐dependent activity
Authors: Jongruja Nujarin , You Dong‐Ju , Kanaya Eiko , Koga Yuichi , Takano Kazufumi , Kanaya Shigenori
Published: August 2010

Thermotoga maritima ribonuclease H (RNase H) I (Tma‐RNase HI) contains a hybrid binding domain (HBD) at the N‐terminal region. To analyze the role of this HBD, Tma‐RNase HI, Tma‐W22A with the single mutation at the HBD, the C‐terminal RNase H domain (Tma‐CD) and the N‐terminal domain containing the HBD (Tma‐ND) were overproduced in Escherichia coli, purified and biochemically characterized. Tma‐RNase HI prefers Mg2+ to Mn2+ for activity, and specifically loses most of the Mg2+‐dependent activity on removal of the HBD and 87% of it by the mutation at the HBD. Tma‐CD lost the ability to suppress the RNase H deficiency of an E. coli rnhA mutant, indicating that the HBD is responsible for in vivo RNase H activity. The cleavage‐site specificities of Tma‐RNase HI are not significantly changed on removal of the HBD, regardless of the metal cofactor. Binding analyses of the proteins to the substrate using surface plasmon resonance indicate that the binding affinity of Tma‐RNase HI is greatly reduced on removal of the HBD or the mutation. These results indicate that there is a correlation between Mg2+‐dependent activity and substrate binding affinity. Tma‐CD was as stable as Tma‐RNase HI, indicating that the HBD is not important for stability. The HBD of Tma‐RNase HI is important not only for substrate binding, but also for Mg2+‐dependent activity, probably because the HBD affects the interaction between the substrate and enzyme at the active site, such that the scissile phosphate group of the substrate and the Mg2+ ion are arranged ideally.
Peptide Amphiphile Nanofiber Delivery of Sonic Hedgehog Protein to Reduce Smooth Muscle Apoptosis in the Penis After Cavernous Nerve Resection
Authors: Bond Christopher W. , Angeloni Nicholas L. , Harrington Daniel A. , Stupp Samuel I. , McKenna Kevin E. , Podlasek Carol A.
Published: August 2010

Introduction

Erectile dysfunction (ED) is a serious medical condition that affects 16–82% of prostate cancer patients treated by radical prostatectomy and current treatments are ineffective in 50–60% of prostatectomy patients. The reduced efficacy of treatments makes novel therapeutic approaches to treat ED essential. The secreted protein Sonic hedgehog (SHH) is a critical regulator of penile smooth muscle and apoptosis that is decreased in cavernous nerve (CN) injury and diabetic ED models. Past studies using Affi-Gel beads have shown SHH protein to be effective in suppressing apoptosis caused by CN injury.

Aim

We hypothesize that SHH protein delivered via novel peptide amphiphile (PA) nanofibers will be effective in suppressing CN injury-induced apoptosis.

Methods

Adult Sprague Dawley rats (n = 50) were used to optimize PA injection in vivo. PA with SHH protein (n = 16) or bovine serum albumin (BSA) (control, n = 14) was injected into adult rats that underwent bilateral CN cut. Rats were sacrificed at 2, 4, and 7 days. Alexa Fluor-labeled SHH protein was used to determine the target of SHH signaling (n = 3).

Main Outcome Measures

Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and semiquantitative immunohistochemical analysis for SHH protein and cluster differentiation protein three (CD3) were performed.

Results

SHH-PA caused a 25% and 16% reduction in apoptosis at 4 and 7 days after CN injury and a 9.3% and 19% increase in SHH protein at 4 and 7 days after CN injury. CD3 protein was not observed in SHH-PA-treated penis. In vitro, 73% of SHH protein diffused from PA within 6 days. Labeled SHH was observed in smooth muscle.

Conclusions

PA technology is effective in delivering SHH protein to the penis and SHH is effective in suppressing CN injury-induced apoptosis. These results suggest substantial translational potential of this methodology and show that only a short duration of SHH treatment is required to impact the apoptotic index.
THE OCCURRENCE AND UTILIZATION OF THE CLADOCERAN Moina macrocopa (STRAUS) IN A KRAFT PULP MILL TREATMENT LAGOON
Authors: Norman Karen E. , Blakely Julie B. , Chew Kenneth K.
Published: August 2010

Moina macrocopa (Crustacea: Cladocera) is a seasonal inhabitant of a kraft pulp waste treatment lagoon operated by the Weyerhaeuser Corporation in Washington. Both laboratory and field studies were initiated to determine M. macrocopa impact on pollution abatement, its seasonal abundance, and its potential as an aquaculture feed.

M. macrocopa were found to significantly reduce total suspended solids in laboratory pulp effluent studies. In the field, Moina were associated with lower levels of biochemical oxygen demand and total suspended solids.

Mass harvest methods were evaluated as to expense, labor involvement, equipment costs, and capture efficiency. During optimum conditions, more than 50 kg of M. macrocopa were harvested per hour.

Nutritional analyses indicated that M. macrocopa in a frozen state could be utilized as a fish feed. A survey of local tropical fish stores revealed a strong market potential. Wholesale prices for frozen Moina were estimated at $.50 to $2/kg. Retail prices were estimated at $2.50 to $7.50/kg.

Although these data are preliminary, it appears M. macrocopa has future potential in aquaculture as both an aid in pollution abatement and as a marketable fish food.
FATTY ACID METABOLISM IN JUVENILE LOBSTERS (Homarus americanus) FED A DIET LOW IN METHIONINE AND HISTIDINE
Authors: Castell John D. , Boghen Andrews D.
Published: August 2010

Juvenile lobsters were fed diets supplemented with 9% hydrogenated coconut oil (HCO) alone or 8% HCO with 1% 18:3ω3, 1% mixed 18:3ω3/18:2ω6 (2/1) or 1% 22:6ω3. After the experiment was started, it was discovered that the protein (purified from shrimp tail meat, Pandalus borealis) was low in both methionine (0.9%) and histidine (0.2%). Essential amino acid deficiency probably accounted for the high mortality (50% by week 5 or 6) in all groups. In spite of the high mortality, a number of interesting effects of dietary lipids on fatty acid metabolism and storage in lobsters were observed.

When lobsters were fed 18:3ω3 or 22:6ω3 with HCO in the absence of dietary fatty acids of the ω6 series, they produced unusually high levels of 20:3ω3 and 16:1ω3. This could be an attempt to retain the ω3 structure with minimal unsaturation. High levels of more unsaturated fatty acids would result in greatly reduced viscosity of lipids in lobsters held at 20°C. The levels of 20:4ω6, 20:5ω3 and 22:6ω3, the typical essential fatty acids (EFA), remained relatively constant in the lobster lipids for all dietary treatments. Dietary 18:2ω6 resulted in a significant decrease in the production of both 16:1ω3 and 20:3ω3 from dietary 18:3ω3.
DEVELOPMENT AND CHARACTERIZATION OF GENETIC STOCKS AND THEIR HYBRIDS IN Macrobrachium rosenbergii: PHYSIOLOGICAL RESPONSES AND LARVAL DEVELOPMENT RATES
Authors: Sarver D. , Onizuka D. , Malecha S.
Published: August 2010

Several genetic stocks of Macrobrachium rosenbergii were examined with respect to their physiological responses to different laboratory culture environments as juveniles and their development rates as larvae. Results indicate that physiological genetic differences exist between these genotypes and that these differences may be important for genetic improvement. Early growth rates for Thai, Sarawak, and Australian stocks were compared to those for the Anuenue stock (originally brought from Malaysia) at 19, 23, and 29°C. Growth at 19°C was very poor for all genotypes. At 23 and 29°C the Anuenue strain grew faster than the Thai and Australian strains and about equal to the Sarawak strain.

Growth of Anuenue, Australian, Thai and Sarawak strains at 0, 5, and 10 ppt salinities was also compared. The Anuenue and Thai strains grew as well at 5 ppt as in freshwater while 10 ppt significantly depressed growth. In the Australian and Sarawak groups growth was depressed in both 5 and 10 ppt treatments.

Temperature tolerance was found to increase with age for all strains although the Anuenue strain appeared to be the most tolerant to low temperatures. The prawns were tested just after metamorphosis at two weeks post‐metamorphosis and one month post‐metamorphosis.

Tolerance to high pH was tested for the Anuenue and found to increase with age. Mortality at a pH of 9.5 at 29°C went from 80% for newly metamorphosed juveniles to 43% for two‐week‐old animals and 50% for one‐month‐old animals.

Among the “pure” strains only the Australian strain showed significantly faster development times in replicated trials. The first Australian postlarvae appeared after an average of 15.5 days and 95% metamorphosed after 20.5 days compared to 24 and 32 days for the Anuenue strain. In unreplicated trials involving hybrids between Anuenue stocks and over two dozen other stocks only the Australian‐Anuenue hybrid showed faster larval development times with time to 95% settling at 35 days compared to 47 days for the Anuenue controls.
Influence of the Photostabilizer in the Photoprotective Effects of a Formulation Containing UV‐Filters and Vitamin A
Authors: Benevenuto Carolina Gomes , Sala Di Matteo Miguel A. , Maia Campos Patrícia M. B. G. , Gaspar Lorena Rigo
Published: August 2010

Vitamin A palmitate has been used in cosmetics; however, studies report that this substance shows photoreactivity that can lead to loss of safety and efficacy. On the other hand, photostabilizers have been used to increase sunscreen photostability and consequently their safety and effectiveness. Thus, this study aimed to evaluate the influence of photostabilizers on the photoprotective effects of a cosmetic formulation containing UV‐filters and vitamin A palmitate. The formulation containing UV‐filters was supplemented with vitamin A palmitate and the photostabilizers diethylhexyl 2,6‐naphthalate (DEHN), bumetrizole and benzotriazolyl dodecyl p‐cresol (BTDC). Hairless mice were treated daily by topical applications and irradiated (UVA/B). Erythema index, transepidermal water loss, histological/histometric analysis and number of sunburn cells (SBC) were evaluated. The results showed that all formulations protected from UV‐induced enhancement of erythema and SBC but there was no difference among them. The formulation with no stabilizers reduced viable epidermis thickness due to atrophy induced by UV radiation. Thus, it can be concluded that the presence of photostabilizers influenced the effects of formulations containing UV‐filters and vitamin A palmitate, which could be seen by histological and histometric analysis. Furthermore, the formulations containing the stabilizers DEHN and BTDC showed better protective effects on hairless mice skin.
Determinants of Right Ventricular Failure in Patients Admitted With Acute Left Heart Failure
Authors: Berkowitz Robert , Alhaj Eyad , Manchikalapudi Rama Bindu , Satya Kumar , Dadfarmay Sina , Zakir Ramzan
Published: August 2010

Pulmonary hypertension, which may lead to right ventricular (RV) failure, increases with left ventricular (LV) diastolic dysfunction severity. The prevalence and determinants of RV failure were analyzed in 120 patients admitted with acute left heart (LH) failure. Patients were divided into RV failure (n=50) and non–RV failure (n=70) groups. The prevalence of RV failure was found to be 42%. In both groups, two thirds of the patients had isolated LV diastolic dysfunction and the rest had combined LV systolic and diastolic dysfunction. Patients in the RV failure group were characterized by higher LV diastolic grade (2.2±0.6 vs 1.84±0.7; P=.0070), pulmonary artery systolic pressure (PASP; 57.8±15.3  vs 50.14±12.1 mm Hg; P=.0028), right atrial enlargement (92% vs 25.7%; P=.000001), and more‐than‐moderate tricuspid regurgitation (58% vs 27.1%; P=.0006). RV failure is a frequent finding in patients with advanced LH failure. It is strongly associated with the severity of LV diastolic dysfunction and the severity of PASP. Congest Heart Fail. 2010;16:243–248. © 2010 Wiley Periodicals, Inc.
A Retrospective Economic Analysis of the Ontario Red Fox Oral Rabies Vaccination Programme
Authors: Shwiff S. A. , Nunan C. P. , Kirkpatrick K. N. , Shwiff S. S.
Published: August 2010

Ontario initiated a red fox (Vulpes vulpes) oral rabies vaccination (ORV) programme in 1989. This study utilized a benefit‐cost analysis to determine if this ORV programme was economically worthwhile. Between 1979 and 1989, prior to ORV baiting, the average annual human post‐exposure treatments, positive red fox rabies diagnostic tests and indemnity payments for livestock lost to rabies were 2248, 1861 and $246 809, respectively. After baiting, from 1990 to 2000, a 35%, 66% and 41% decrease in post‐exposure treatments, animal rabies tests and indemnity payments was observed, respectively. These reductions were viewed as benefits of the ORV programme, whereas total costs were those associated with ORV baiting. Multiple techniques were used to estimate four different benefit streams and the total estimated benefits ranged from $35 486 316 to $98 413 217. The annual mean ORV programme cost was $6 447 720, with total programme costs of $77 372 637. The average benefit‐cost ratios over the analysis period were .49, 1.06, 1.27 and 1.36, indicating overall programme efficiency in three of the four conservative scenarios.
QA procedures for multimodality preclinical tumor drug response testing
Authors: Lee Yongsook C. , Goins Beth A. , Fullerton Gary D.
Published: August 2010

Purpose:

There are growing expectations that imaging biomarkers for tumor therapeutic drug response assessment will speed up preclinical testing of anticancer drugs in rodent models. The only imaging biomarker presently approved by the U.S. Food and Drug Administration is tumor size measurement based on either World Health Organization (WHO) criteria or Response Evaluation Criteria in Solid Tumors (RECIST). Frequently, preclinical data are accumulated from multiple research centers on multiple continents using scanners from different manufacturers and sometimes even using different imaging modalities. Very expensive cancer drug response studies can be compromised by inadequate controls to assure precision and accuracy of tumor size measurements. This project was undertaken to develop standardized quality assurance (QA) procedures using a multimodality preclinical tumor response phantom to validate the accuracy of tumor size measurements based on WHO criteria, RECIST, or global tumor volume criteria for evaluation of cytostatic drugs.

Methods:

A tumor response phantom containing five low contrast test objects designed to simulate animal tumor models was made of tissue‐mimicking materials. Imaging of the phantom was performed using three modalities in two institutions to evaluate size measurement of tumor‐simulating test objects.

Results:

Evaluation of tumor measurements from the three commonly used imaging devices in two different institutions for monitoring tumor size changes showed that a single phantom for multiple modalities was feasible. The tumor response phantom validated precision and accuracy of tumor response data input from ultrasound, computed tomography, and/or magnetic resonance imaging devices.

Conclusions:

Measurement results show that the standardized QA procedures using the tumor response phantom can provide a rationale check of data that excludes input from poorly maintained instruments, inadequate measurement protocols, or random operator error that frequently introduce unacceptable variability or systematic error in multiple institutions trials.
SPECT region of interest reconstruction with truncated transmission and emission data
Authors: Zeng Gengsheng L. , Gullberg Grant T.
Published: August 2010

Purpose:

The aim of this article is to propose an exact SPECT region of interest (ROI) reconstruction method using truncated transmission and truncated emission data.

Methods:

Recently, the authors published two articles in Physics in Medicine and Biology with two results in SPECT ROI emission image reconstruction. The first result states that if the transmission data are truncated but the emission data are not truncated, the emission image can be exactly reconstructed, provided the entire emission image is inside the region where the transmission data are not truncated. The second result states that if the transmission data are not truncated, the emission ROI can be exactly reconstructed with truncated emission data. This article combines these two results and obtains a new result that the emission ROI can be exactly reconstructed if both transmission and emission data are truncated.

Results:

Computer simulations are performed to verify the proposed ROI image reconstruction algorithm.

Conclusions:

Exact SPECT ROI image reconstruction is possible using truncated transmission and emission projections with some prior information about the attenuator and the emission distribution.
Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs
Authors: Grissom William A. , Rieke Viola , Holbrook Andrew B. , Medan Yoav , Lustig Michael , Santos Juan , McConnell Michael V. , Pauly Kim Butts
Published: August 2010

Purpose

: Magnetic resonance thermometry using the proton resonance frequency (PRF) shift is a promising technique for guiding thermal ablation. For temperature monitoring in moving organs, such as the liver and the heart, problems with motion must be addressed. Multi‐baseline subtraction techniques have been proposed, which use a library of baseline images covering the respiratory and cardiac cycle. However, main field shifts due to lung and diaphragm motion can cause large inaccuracies in multi‐baseline subtraction. Referenceless thermometry methods based on polynomial phase regression are immune to motion and susceptibility shifts. While referenceless methods can accurately estimate temperature within the organ, in general, the background phase at organ/tissue interfaces requires large polynomial orders to fit, leading to increased danger that the heated region itself will be fitted by the polynomial and thermal dose will be underestimated. In this paper, a hybrid method for PRF thermometry in moving organs is presented that combines the strengths of referenceless and multi‐baseline thermometry.

Methods

: The hybrid image model assumes that three sources contribute to image phase during thermal treatment: Background anatomical phase, spatially smooth phase deviations, and focal, heat‐induced phase shifts. The new model and temperature estimation algorithm were tested in the heart and liver of normal volunteers, in a moving phantom HIFU heating experiment, and in numerical simulations of thermal ablation. The results were compared to multi‐baseline and referenceless methods alone.

Results

: The hybrid method allows forin vivo temperature estimation in the liver and the heart with lower temperature uncertainty compared to multi‐baseline and referenceless methods. The moving phantom HIFU experiment showed that the method accurately estimates temperature during motion in the presence of smooth main field shifts. Numerical simulations illustrated the method's sensitivity to algorithm parameters and hot spot features.

Conclusions

: This new hybrid method for MR thermometry in moving organs combines the strengths of both multi‐baseline subtraction and referenceless thermometry and overcomes their fundamental weaknesses.
Standardized evaluation methodology for 3D/2D registration based on the Visible Human data set
Authors: Markelj Primož , Likar Boštjan , Pernuš Franjo
Published: August 2010

Purpose:

A new image database with a reference‐based standardized evaluation methodology for objective evaluation and comparison of three‐dimensional/two‐dimensional (3D/2D) registration methods has been introduced.

Methods:

Computed tomography (CT) images of a male and female from the Visible Human Project were used and 16 subvolumes, each containing one of vertebrae T3‐T12 and L1‐L5 and the pelvis, were defined from the CTs. Six pairs of 2D fluoroscopic x‐ray images from different views, showing the thoracic, lumbar, and pelvic regions, were rendered from the CT data using a ray‐casting algorithm with an energy conversion function. Furthermore, a single 13‐gauge needle was analytically simulated and projected onto the 2D images. By the novel standardized evaluation methodology, a 3D/2D registration method is evaluated by four evaluation criteria: Accuracy, reliability, robustness, and algorithm complexity.

Results:

To demonstrate the usefulness of the proposed data set and the standardized evaluation methodology, a part of the data set was used in an evaluation study of two gradient‐based 3D/2D registration methods. It was shown that the use of a failure criterion to calculate the registration accuracy and reliability is not required, since all the information about a registration method can be determined from the estimated distribution of registration errors.

Conclusions:

The proposed simulated image data set with quite realistic synthetic 2D images, depicting soft tissues and outliers, is especially suitable for preliminary testing of 3D/2D registration algorithms. Since the aim of this article is to provide objective comparison and unbiased evaluation of 3D/2D registration methods, the standardized evaluation methodology is available upon request from the authors.
An MCNPX Monte Carlo model of a discrete spot scanning proton beam therapy nozzle
Authors: Sawakuchi Gabriel O. , Mirkovic Dragan , Perles Luis A. , Sahoo Narayan , Zhu X. Ron , Ciangaru George , Suzuki Kazumichi , Gillin Michael T. , Mohan Radhe , Titt Uwe
Published: August 2010

Purpose:

The purposes of this study were to validate a discrete spot scanning proton beam nozzle using the Monte Carlo (MC) codeMCNPX and use the MC validated model to investigate the effects of a low‐dose envelope, which surrounds the beam's central axis, on measurements of integral depth dose (IDD) profiles.

Methods:

An accurate model of the discrete spot scanning beam nozzle from The University of Texas M. D. Anderson Cancer Center (Houston, Texas) was developed on the basis of blueprints provided by the manufacturer of the nozzle. The authors performed simulations of single proton pencil beams of various energies using the standard multiple Coulomb scattering (MCS) algorithm within theMCNPX source code and a new MCS algorithm, which was implemented in the MCNPX source code. The MC models were validated by comparing calculated in‐air and in‐water lateral profiles and percentage depth dose profiles for single pencil beams with their corresponding measured values. The models were then further tested by comparing the calculated and measured three‐dimensional (3‐D) dose distributions. Finally, an IDD profile was calculated with different scoring radii to determine the limitations on the use of commercially available plane‐parallel ionization chambers to measure IDD.

Results:

The distance to agreement, defined as the distance between the nearest positions of two equivalent distributions with the same value of dose, between measured and simulated ranges was within 0.13 cm for both MCS algorithms. For low and intermediate pencil beam energies, the MC simulations using the standard MCS algorithm were in better agreement with measurements. Conversely, the new MCS algorithm produced better results for high‐energy single pencil beams. The IDD profile calculated with cylindrical tallies with an area equivalent to the area of the largest commercially available ionization chamber showed up to 7.8% underestimation of the integral dose in certain depths of the IDD profile.

Conclusions:

The authors conclude that a combination of MCS algorithms is required to accurately reproduce experimental data of single pencil beams and 3‐D dose distributions for the scanning beam nozzle. In addition, the MC simulations showed that because of the low‐dose envelope, ionization chambers with radii as large as 4.08 cm are insufficient to accurately measure IDD profiles for a 221.8 MeV pencil beam in the scanning beam nozzle.
Intensity modulated dose calculation with an improved experimental pencil‐beam kernel
Authors: Azcona Juan Diego , Burguete Javier
Published: August 2010

Purpose:

This article presents an improved pencil‐beam dose calculation formalism based on an experimental kernel obtained by deconvolution. The new algorithm makes it possible to calculate the absorbed dose for all field sizes.

Methods:

The authors have enhanced their previous work [J. D. Azcona and J. Burguete, Med. Phys. 35, 248–259 (2008)] by correcting the kernel tail representing the contribution to the absorbed dose far from the photon interaction point. The correction was performed by comparing the calculated and measured output factors. Dose distributions and absolute dose values calculated using the new formalism have been compared to measurements. The agreement between calculated and measured dose distributions was evaluated according to the ‐index criteria. In addition, 35 individual intensity‐modulated radiation therapy (IMRT) fields were calculated and measured in polystyrene using an ionization chamber. Furthermore, a series of 541 IMRT fields was calculated using the algorithm proposed here and using a commercial IMRT optimization and calculation software package. Comparisons were made between the calculations at single points located at the isocenter for all the beams, as well as between beams grouped by anatomic location.

Results:

The percentage of points passing the‐index criteria (3%, 3 mm) when comparing calculated and measured dose distributions is generally greater than 99% for the cases studied. The agreement between the calculations and the experimental measurements generally lies in the ±2% interval for single points, with a mean value of 0.2%. The agreement between calculations using the proposed algorithm and using a commercial treatment planning system is also between ±5%.

Conclusions:

An improved algorithm based on an experimental pencil‐beam kernel obtained by deconvolution has been developed. It has been validated clinically and promises to be a valuable tool for IMRT quality assurance as an independent calculation system for monitor units and dose distributions. An important point is that the algorithm presented here uses an experimental kernel, which is therefore independent of Monte‐Carlo‐calculated kernels.
Characterization of the ringing artifacts in rotator‐based reconstruction with Monte Carlo‐based resolution compensation for PET
Authors: Zhang Long , Staelens Steven , Van Holen Roel , Verhaeghe Jeroen , Vandenberghe Stefaan
Published: August 2010

Purpose:

Studies have shown that Monte Carlo‐based reconstruction could effectively improve the image quality of positron emission tomography. The authors have previously used a Gaussian rotator‐based algorithm to efficiently reduce the computational cost for system matrix (SM) calculation and to meet the large memory requirements for SM storage. However, pronounced ringing artifacts were observed in the reconstructed image. In this article, the authors investigated and characterized these artifacts.

Methods:

The authors proposed an “ideal” rotator and used it as a baseline in the artifacts evaluation. This ideal rotator produces perfectly rotated images. The Gaussian rotator method was evaluated by a full system model and a partial system model without positron range and acolinearity, which could be compensated for by the blurring of the Gaussian rotator for studies. Noiseless data, Monte Carlo simulation data, as well as acquired experimental data were used to quantitatively characterize the behavior of the artifacts.

Results:

The study of the noiseless data indicated that the artifacts were mainly attributed to the rotator, which further blurred the simulated system responses. The simulation study suggested that the artifacts become less pronounced and not quantitatively significant in practice. This result is consistent with the experimental data study. Better contrast recovery was achieved with an overcompensated system model. Traditionally, an undercompensated system model was preferred to avoid artifacts. The authors’ studies suggest that the Gaussian rotator with the full system model yields the best image quality among the evaluated methods with considerably reduced quantitative error and quantitatively insignificant artifacts in practice.

Conclusions:

The authors’ investigation indicated that a moderately overcompensated system model (about 2 mm FWHM in this study) yielded better contrast recovery and quantitatively insignificant artifacts in practice.
Direction‐dependent localization errors in SPECT images
Authors: Roper Justin , Bowsher James , Yin Fang‐Fang
Published: August 2010

Purpose:

Single photon emission computed tomography (SPECT) is being investigated for imaging inside radiation therapy treatment rooms to localize biological targets. Here, computer simulations were used to analyze locational and directional dependencies in localization errors and to assess the effects of spatial resolution modeling and observer normalization on localization performance.

Methods:

SPECT images of the XCAT phantom, containing 12 hot tumors, were reconstructed with detector response function compensation (DRC) and without DRC (nDRC). Numerical observers were forced to select the most suspicious tumor location, using normalized cross correlation (NXC) or un‐normalized cross correlation (XC), from 3 cm diameter search volumes that each contained only one tumor. For each tumor site, localization was optimized as a function of the iteration number and postreconstruction smoothing. Localization error, the distance between true and estimated tumor positions, was calculated across the ensembles of 80 images. Direction‐dependent localization bias and precision were estimated from the image ensemble.

Results:

For the six superficial tumors in close proximity to the detector trajectory, mean localization errors were and were lowest or comparable using DRC‐NXC, though differences from DRC‐XC and nDRC‐NXC were not statistically significant. DRC‐NXC did provide statistically significantly better localization than nDRC‐XC for five of these six tumors. At the other six sites where attenuation was more severe and the distance was generally greater between the tumor and detector, DRC typically did not show better localization than nDRC. Observer normalization improved the localization substantially for a tumor near the hotter heart. Localization errors were anisotropic and dependent on tumor location relative to the detector trajectory.

Conclusions:

This computer‐simulation study compared localization performance for normalized and un‐normalized numerical observers, which were used to estimate tumor positions in SPECT images, reconstructed with and without DRC. For tumors localized to on average, which are good candidates for SPECT‐guided radiation therapy, localization performance typically improved by compensating for the detector response function and by using a normalized observer. The observed direction‐dependent localization errors have important implications for radiation therapy and are relevant to SPECT imaging in general.
Overcorrection of iodinated contrast attenuation in SPECT‐CT: Phantom studies
Authors: Bonta Dacian V. , Wahl Richard L.
Published: August 2010

Purpose:

The authors investigated the effects of iodinated contrast agents on the quantification of radioactivity obtained using a combined single photon emission tomography (SPECT) and high resolution 16 slice computed tomography (CT) scanner.

Methods:

Two conditions were evaluated: Contrast media mixed with radioisotope and the contrast media, and the radioisotope solution confined in adjacent but distinct volumes. Phantoms containing combinations of, , and solutions in normal saline and contrast solutions in normal saline corresponding to the two conditions were prepared and scanned. Images were reconstructed by iterative reconstruction (ordered subset expectation maximization), with and without CT‐derived attenuation maps. The reconstructed counts encoded in the reconstructed images were compared.

Results:

Compared to normal saline, the presence of an iodinated contrast agent resulted in the underestimation of reconstructed counts in all nonattenuation corrected SPECT images. Compared to normal saline, the presence of a contrast agent resulted in the overestimation of reconstructed counts in all attenuation corrected SPECT images. The largest underestimation of reconstructed counts was 12.8% and the largest overestimation value was 35.9%.

Conclusions:

High concentrations of a contrast agent caused errors in the measurement of actual radiotracer reconstructed counts in phantoms. These errors could have important consequences for the use of oral and intravenous contrast in both diagnostic (qualitative) and dosimetric (quantitative) SPECT‐CT imaging. The authors’ findings suggest that noncontrast imaging or alternative contrast‐specific attenuation correction approaches should be considered for optimal SPECT activity quantification.
Freezing Tolerance in Plants Requires Lipid Remodeling at the Outer Chloroplast Membrane
Authors: Moellering Eric R. , Muthan Bagyalakshmi , Benning Christoph
Published: August 2010

Freezing Tolerance Explained

Freezing temperatures exact a toll on plant cells through various mechanisms, including disruption of water balances as ice crystals form. Cellular and organelle lipid bilayers are also put under stress.

Moellering
et al.

(p.
226
, published online 26 August; see the Perspective by

Browse

) analyzed the function of a protein in the model plant,
Arabidopsis thaliana
that, when disrupted, leaves plants more susceptible to damage by freezing. The protein, SENSITIVE TO FREEZING 2 (SFR2), shifts and swaps lipid headgroups, altering the chemistry of the chloroplast lipid bilayer membranes to stabilize them during freezing.
Prevalence of Antimicrobial-Resistant Pathogens in Canadian Hospitals: Results of the Canadian Ward Surveillance Study (CANWARD 2008)
Authors: Zhanel George G. , DeCorby Melanie , Adam Heather , Mulvey Michael R. , McCracken Melissa , Lagacé-Wiens Philippe , Nichol Kimberly A. , Wierzbowski Aleksandra , Baudry Patricia J. , Tailor Franil , Karlowsky James A. , Walkty Andrew , Schweizer Frank , Johnson Jack , Hoban Daryl J.
Published: August 2010

A total of 5,282 bacterial isolates obtained between 1 January and 31 December 31 2008, inclusive, from patients in 10 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2008) underwent susceptibility testing. The 10 most common organisms, representing 78.8% of all clinical specimens, were as follows:
Escherichia coli
(21.4%), methicillin-susceptible
Staphylococcus aureus
(MSSA; 13.9%),
Streptococcus pneumoniae
(10.3%),
Pseudomonas aeruginosa
(7.1%),
Klebsiella pneumoniae
(6.0%), coagulase-negative staphylococci/
Staphylococcus epidermidis
(5.4%), methicillin-resistant
S. aureus
(MRSA; 5.1%),
Haemophilus influenzae
(4.1%),
Enterococcus
spp. (3.3%),
Enterobacter cloacae
(2.2%). MRSA comprised 27.0% (272/1,007) of all
S. aureus
isolates (genotypically, 68.8% of MRSA were health care associated [HA-MRSA] and 27.6% were community associated [CA-MRSA]). Extended-spectrum β-lactamase (ESBL)-producing
E. coli
occurred in 4.9% of
E. coli
isolates. The CTX-M type was the predominant ESBL, with CTX-M-15 the most prevalent genotype. MRSA demonstrated no resistance to ceftobiprole, daptomycin, linezolid, telavancin, tigecycline, or vancomycin (0.4% intermediate intermediate resistance).
E. coli
demonstrated no resistance to ertapenem, meropenem, or tigecycline. Resistance rates with
P. aeruginosa
were as follows: colistin (polymyxin E), 0.8%; amikacin, 3.5%; cefepime, 7.2%; gentamicin, 12.3%; fluoroquinolones, 19.0 to 24.1%; meropenem, 5.6%; piperacillin-tazobactam, 8.0%. A multidrug-resistant (MDR) phenotype occurred frequently in
P. aeruginosa
(5.9%) but uncommonly in
E. coli
(1.2%) and
K. pneumoniae
(0.9%). In conclusion,
E. coli
,
S. aureus
(MSSA and MRSA),
P. aeruginosa
,
S. pneumoniae
,
K. pneumoniae
,
H. influenzae
, and
Enterococcus
spp. are the most common isolates recovered from clinical specimens in Canadian hospitals. The prevalence of MRSA was 27.0% (of which genotypically 27.6% were CA-MRSA), while ESBL-producing
E. coli
occurred in 4.9% of isolates. An MDR phenotype was common in
P. aeruginosa.
In Vitro
Profiling of Pramiconazole and
In Vivo
Evaluation in
Microsporum canis
Dermatitis and
Candida albicans
Vaginitis Laboratory Models
Authors: de Wit Kelly , Paulussen Caroline , Matheeussen An , van Rossem Koen , Cos Paul , Maes Louis
Published: August 2010

The triazole antifungal pramiconazole (Stiefel, a GSK company) was compared with itraconazole, miconazole, and terbinafine
in vitro
and
in vivo
. Potent
in vitro
activities against
Candida
spp. (50% inhibitory concentration [IC
50
], 0.04 to 1.83 μM) and
Microsporum
and
Trichophyton
spp. (IC
50
, 0.15 to 1.34 μM) were obtained but not, however, against other filamentous molds and zygomycetes. In the
M. canis
guinea pig model and
C. albicans
vulvovaginitis rat model, pramiconazole was superior to the reference compounds after oral and topical administration.
Loss of the Group A
Streptococcus
Regulator Srv Decreases Biofilm Formation
In Vivo
in an Otitis Media Model of Infection
Authors: Roberts Amity L. , Connolly Kristie L. , Doern Christopher D. , Holder Robert C. , Reid Sean D.
Published: August 2010

Group A
Streptococcus
(GAS) is a common causative agent of pharyngitis, but the role of GAS in otitis media is underappreciated. In this study, we sought to test the hypothesis that GAS colonizes the middle ear and establishes itself in localized, three-dimensional communities representative of biofilms. To test this hypothesis, the middle ears of chinchillas were infected with either a strain of GAS capable of forming biofilms
in vitro
(MGAS5005) or a strain deficient in biofilm formation due to the lack of the transcriptional regulator Srv (MGAS5005 Δ
srv
). Infection resulted in the formation of large, macroscopic structures within the middle ears of MGAS5005- and MGAS5005 Δ
srv
-infected animals. Plate counts, scanning electron microscopy, LIVE/DEAD staining, and Gram staining revealed a difference in the distributions of MGAS5005 versus MGAS5005 Δ
srv
in the infected samples. High numbers of CFU of MGAS5005 Δ
srv
were isolated from the middle ear effusion, and MGAS5005 Δ
srv
was found randomly distributed throughout the excised macroscopic structure. In contrast, MGAS5005 was found in densely packed microcolonies indicative of biofilms within the excised material from the middle ear. CFU levels of MGAS5005 from the effusion were significantly lower than that of MGAS5005 Δ
srv
early during the course of infection. Allelic replacement of the chromosomally encoded streptococcal cysteine protease (
speB
) in the MGAS5005 Δ
srv
background restored biofilm formation
in vivo
. Interestingly, our results suggest that GAS naturally forms a biofilm during otitis media but that biofilm formation is not required to establish infection following transbullar inoculation of chinchillas.
Vascular Endothelial Growth Factor Receptor 1 Contributes toEscherichia coliK1 Invasion of Human Brain Microvascular Endothelial Cells through the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway
Authors: Zhao Wei-Dong , Liu Wei , Fang Wen-Gang , Kim Kwang Sik , Chen Yu-Hua
Published: August 2010

Escherichia coliis the most common Gram-negative organism causing neonatal meningitis. Previous studies demonstrated thatE. coliK1 invasion of brain microvascular endothelial cells (BMEC) is required for penetration into the central nervous system, but the microbe-host interactions that are involved in this process remain incompletely understood. Here we report the involvement of vascular endothelial growth factor receptor 1 (VEGFR1) expressed on human brain microvascular endothelial cells (HBMEC) inE. coliK1 invasion of HBMEC. Our results showed that treatment of confluent HBMEC with pan-VEGFR inhibitors significantly inhibitedE. coliK1 invasion of HBMEC. Immunofluorescence results indicated the colocalization of VEGFR1 withE. coliK1 during bacterial invasion of HBMEC. TheE. coli-induced actin cytoskeleton rearrangements in HBMEC were blocked by VEGFR inhibitors but not by VEGFR2-specific inhibitors. The small interfering RNA (siRNA) knockdown of VEGFR1 in HBMEC significantly attenuatedE. coliinvasion and the concomitant actin filament rearrangement. Furthermore, we found an increased association of VEGFR1 with the p85 subunit of phosphatidylinositol 3-kinase (PI3K) in HBMEC infected withE. coliK1 and thatE. coliK1-triggered Akt activation in HBMEC was blocked by VEGFR1 siRNA and VEGFR inhibitors. Taken together, our results demonstrate that VEGFR1 contributes toE. coliK1 invasion of HBMEC via recruitment of the PI3K/Akt signaling pathway.
Transcriptional Response ofLeptospira interrogansto Iron Limitation and Characterization of a PerR Homolog
Authors: Lo Miranda , Murray Gerald L. , Khoo Chen Ai , Haake David A. , Zuerner Richard L. , Adler Ben
Published: August 2010

Leptospirosis is a globally significant zoonosis caused byLeptospiraspp. Iron is essential for growth of most bacterial species. Since iron availability is low in the host, pathogens have evolved complex iron acquisition mechanisms to survive and establish infection. In many bacteria, expression of iron uptake and storage proteins is regulated by Fur.L. interrogansencodes four predicted Fur homologs; we have constructed a mutation in one of these,la1857. We conducted microarray analysis to identify iron-responsive genes and to study the effects ofla1857mutation on gene expression. Under iron-limiting conditions, 43 genes were upregulated and 49 genes were downregulated in the wild type. Genes encoding proteins with predicted involvement in inorganic ion transport and metabolism (including TonB-dependent proteins and outer membrane transport proteins) were overrepresented in the upregulated list, while 54% of differentially expressed genes had no known function. There were 16 upregulated genes of unknown function which are absent from the saprophyteL. biflexaand which therefore may encode virulence-associated factors. Expression of iron-responsive genes was not significantly affected by mutagenesis ofla1857, indicating that LA1857 is not a global regulator of iron homeostasis. Upregulation of heme biosynthetic genes and a putative catalase in the mutant suggested that LA1857 is more similar to PerR, a regulator of the oxidative stress response. Indeed, thela1857mutant was more resistant to peroxide stress than the wild type. Our results provide insights into the role of iron in leptospiral metabolism and regulation of the oxidative stress response, including genes likely to be important for virulence.
Interaction between Pathogenic Bacteria and Intrauterine Leukocytes Triggers Alternative Molecular Signaling Cascades Leading to Labor in Women
Authors: Estrada-Gutierrez Guadalupe , Gomez-Lopez Nardhy , Zaga-Clavellina Veronica , Giono-Cerezo Silvia , Espejel-Nuñez Aurora , Gonzalez-Jimenez Marco Antonio , Espino y Sosa Salvador , Olson David M. , Vadillo-Ortega Felipe
Published: August 2010

Increased risk of preterm labor has been linked to cervicovaginal infection with
Ureaplasma urealyticum
and group B streptococci. Although various experimental models have been developed to study the role of amniochorion infection in preterm labor, they typically exclude the initial interaction between intrauterine leukocytes (recruited from decidual vessels into the avascular fetal membranes) and infecting bacteria. In this work, we ascertained whether inflammatory molecules secreted by bacterium-activated intrauterine leukocytes stimulate the amniochorion production of mediators involved in human labor. Using a two-step process beginning with placental circulating leukocytes as a proxy for intrauterine leukocytes, we found that coincubation of amniochorion explants with plasma from placental whole blood preincubated with group B streptococci resulted in a significant increase in tumor necrosis factor alpha (TNF-α) and matrix metalloproteinase 9 (MMP-9) levels in tissue. Extensive changes in the connective tissue arrangement and a decrease in collagen content demonstrated the degradation of the extracellular matrix following this treatment. In contrast, plasma from blood preconditioned with
U. urealyticum
induced a highly significant secretion of interleukin-1β (IL-1β) and prostaglandin E
2
(PGE
2
) by the amniochorion without changes in the extracellular matrix organization or content. These data demonstrate that group B streptococci induce degradation of the amniochorion as a result of MMP-9 production, probably via TNF-α, whereas
U. urealyticum
stimulates the secretion of PGE
2
, probably via IL-1β, potentially stimulating myometrial contraction. Our study provides novel evidence that the immunological cells circulating within the uterine microenvironment respond differentially to an infectious agent, triggering alternative molecular signaling pathways leading to human labor.