bluuebunny/crossref_metadata_2025 huggingface dataset:
Model‐independent, multimodality deformable image registration by local matching of anatomical features and minimization of elastic energy
Authors: Söhn Matthias , Birkner Mattias , Chi Yuwei , Wang Jian , Yan Di , Berger Bernhard , Alber Markus
Published: March 2008

With respect to the demands of adaptive and 4D‐radiotherapy applications, an algorithm is proposed for a fully automatic, multimodality deformable registration that follows the concept of translational relocation of regularly distributed image subvolumes governed by local anatomical features. Thereby, the problem of global deformable registration is broken down to multiple independent local registration steps which allows for straightforward parallelization of the algorithm. In a subsequent step, possible local misregistrations are corrected for by minimization of the elastic energy of the displacement field under consideration of image information. The final displacement field results from interpolation of the subvolume shift vectors. The algorithm can employ as a similarity measure both the correlation coefficient and mutual information. The latter allows the application to intermodality deformable registration problems. The typical calculation time on a modern multiprocessor PC is well below 1 min, which facilitates almost‐interactive, “online” usage. CT‐to‐MRI and CT‐to‐cone‐beam‐CT registrations of head‐and‐neck data sets are presented, as well as inhale‐to‐exhale registrations of lung CT data sets. For quantitative evaluation of registration accuracy, a virtual thorax phantom was developed; additionally, a landmark‐based evaluation on four lung respiratory‐correlated CT data sets was performed. This consistently resulted in average registration residuals on the order of the voxel size or less (3D‐residuals ). Summarizing, the presented algorithm allows an accurate multimodality deformable registration with calculation times well below 1 min, and thus bears promise as a versatile basic tool in adaptive and 4D‐radiotherapy applications.
Evaluation of beam wobbling methods for heavy‐ion radiotherapy
Authors: Yonai Shunsuke , Kanematsu Nobuyuki , Komori Masataka , Kanai Tatsuaki , Takei Yuka , Takahashi Osamu , Isobe Yoshiharu , Tashiro Mutsumi , Koikegami Hajime , Tomita Hideki
Published: March 2008

The National Institute of Radiological Sciences (NIRS) has extensively studied carbon‐ion radiotherapy at the Heavy‐Ion Medical Accelerator in Chiba (HIMAC) with some positive outcomes, and has established its efficacy. Therefore, efforts to distribute the therapy to the general public should be made, for which it is essential to enable direct application of clinical and technological experiences obtained at NIRS. For widespread use, it is very important to reduce the cost through facility downsizing with minimal acceleration energy to deliver the HIMAC‐equivalent clinical beams. For the beam delivery system, the requirement of miniaturization is translated to reduction in length while maintaining the clinically available field size and penetration range for range‐modulated uniform broad beams of regular fields that are either circular or square for simplicity. In this paper, we evaluate the various wobbling methods including original improvements, especially for application to the compact facilities through the experimental and computational studies. The single‐ring wobbling method used at HIMAC is the best one including a lot of experience at HIMAC but the residual range is a fatal problem in the case of a compact facility. On the other hand, uniform wobbling methods such as the spiral and zigzag wobbling methods are effective and suitable for a compact facility. Furthermore, these methods can be applied for treatment with passive range modulation including respiratory gated irradiation. In theory, the choice between the spiral and zigzag wobbling methods depends on the shape of the required irradiation field. However, we found that it is better to use the zigzag wobbling method with transformation of the wobbling pattern even when a circular uniform irradiation field is required, because it is difficult to maintain the stability of the wobbler magnet due to the rapid change of the wobbler current in the spiral wobbling method. The regulated wobbling method, which is our improvement, can well expand the uniform irradiation field and lead to reducing the power requirement of the wobbler magnets. Our evaluations showed that the regulated zigzag wobbling method is the most suitable method for use in currently designed compact carbon‐therapy facilities.
A computational implementation and comparison of several intensity modulated proton therapy treatment planning algorithms
Authors: Li Haisen S. , Romeijn H. Edwin , Fox Christopher , Palta Jatinder R. , Dempsey James F.
Published: March 2008

The authors present a comparative study of intensity modulated proton therapy (IMPT) treatment planning employing algorithms of three‐dimensional (3D) modulation, and 2.5‐dimensional (2.5D) modulation, and intensity modulated distal edge tracking (DET) [A. Lomax, Phys. Med. Biol. 44, 185–205 (1999)] applied to the treatment of head‐and‐neck cancer radiotherapy. These three approaches were also compared with 6 MV photon intensity modulated radiation therapy (IMRT). All algorithms were implemented in the University of Florida Optimized Radiation Therapy system using a finite sized pencil beam dose model and a convex fluence map optimization model. The 3D IMPT and the DET algorithms showed considerable advantages over the photon IMRT in terms of dose conformity and sparing of organs at risk when the beam number was not constrained. The 2.5D algorithm did not show an advantage over the photon IMRT except in the dose reduction to the distant healthy tissues, which is inherent in proton beam delivery. The influences of proton beam number and pencil beam size on the IMPT plan quality were also studied. Out of 24 cases studied, three cases could be adequately planned with one beam and 12 cases could be adequately planned with two beams, but the dose uniformity was often marginally acceptable. Adding one or two more beams in each case dramatically improved the dose uniformity. The finite pencil beam size had more influence on the plan quality of the 2.5D and DET algorithms than that of the 3D IMPT. To obtain a satisfactory plan quality, a 0.5 cm pencil beam size was required for the 3D IMPT and a 0.3 cm size was required for the 2.5D and the DET algorithms. Delivery of the IMPT plans produced in this study would require a proton beam spot scanning technique that has yet to be developed clinically.
A generalized a priori dose uncertainty model of IMRT delivery
Authors: Jin Hosang , Palta Jatinder , Suh Tae‐Suk , Kim Siyong
Published: March 2008

Multileaf collimator‐based intensity modulated radiation therapy (IMRT) is complex because each intensity modulated field consists of hundreds of subfields, each of which is associated with an intricate interplay of uncertainties. In this study, the authors have revised the previously introduced uncertainty model to provide an a priori accurate prediction of dose uncertainty during treatment planning in IMRT. In the previous model, the dose uncertainties were categorized into space‐oriented dose uncertainty (SOU) and nonspace‐oriented dose uncertainty (NOU). The revised model further divided the uncertainty sources into planning and delivery. SOU and NOU associated with a planning system were defined as inherent dose uncertainty. A convolution method with seven degrees of freedom was also newly applied to generalize the model for practical clinical cases. The model parameters were quantified through a set of measurements, accumulated routine quality assurance (QA) data, and peer‐reviewed publications. The predicted uncertainty maps were compared with dose difference distributions between computations and 108 simple open‐field measurements using a two‐dimensional diode array detector to verify the validity of the model parameters and robustness of the generalized model. To examine the applicability of the model to overall dose uncertainty prediction in IMRT, a retrospective analysis of QA measurements using the diode array detector for 32 clinical IM fields was also performed. A scatter diagram and a correlation coefficient were employed to investigate a correlation of the predicted dose uncertainty distribution with the dose discrepancy distribution between calculation and delivery. In addition, a test was performed to correlate failed regions in dose verification with the dose uncertainty map. The quantified model parameters well correlated the predicted dose uncertainty with the probable dose difference between calculations and measurements. It was visually validated with the scatter diagrams. The average correlation coefficient between uncertainty and dose difference of 108 verification measurements was , indicating a strong linear correlation. In the clinical IM field studies, the dose uncertainty map mimicked the probable dose difference distribution. The average correlation coefficient between the overall dose uncertainty and the dose difference of 32 QA measurements (total 13 184 comparison points) was , which also indicated a strong linear correlation between them. The failed regions of the test remarkably corresponded to relatively high dose uncertainty. In conclusion, the dose uncertainty map was able to highlight high dose uncertainty regions, where more care should be taken during the treatment plan. The a priori accurate prediction of dose uncertainty in IMRT will significantly improve the treatment plan evaluation process, thus improving the quality of radiation treatments.
Accurate patient dosimetry of kilovoltage cone‐beam CT in radiation therapy
Authors: Ding George X. , Duggan Dennis M. , Coffey Charles W.
Published: March 2008

The increased utilization of x‐ray imaging in image‐guided radiotherapy has dramatically improved the radiation treatment and the lives of cancer patients. Daily imaging procedures, such as cone‐beam computed tomography (CBCT), for patient setup may significantly increase the dose to the patient's normal tissues. This study investigates the dosimetry from a kilovoltage (kV) CBCT for real patient geometries. Monte Carlo simulations were used to study the kV beams from a Varian on‐board imager integrated into the Trilogy accelerator. The Monte Carlo calculated results were benchmarked against measurements and good agreement was obtained. The authors developed a novel method to calibrate Monte Carlo simulated beams with measurements using an ionization chamber in which the air‐kerma calibration factors are obtained from an Accredited Dosimetry Calibration Laboratory. The authors have introduced a new Monte Carlo calibration factor,, which is determined from the calibration procedure. The accuracy of the new method was validated by experiment. When a Monte Carlo simulated beam has been calibrated, the simulated beam can be used to accurately predict absolute dose distributions in the irradiated media. Using this method the authors calculated dose distributions to patient anatomies from a typical CBCT acquisition for different treatment sites, such as head and neck, lung, and pelvis. Their results have shown that, from a typical head and neck CBCT, doses to soft tissues, such as eye, spinal cord, and brain can be up to 8, 6, and 5 cGy, respectively. The dose to the bone, due to the photoelectric effect, can be as much as 25 cGy, about three times the dose to the soft tissue. The study provides detailed information on the additional doses to the normal tissues of a patient from a typical kV CBCT acquisition. The methodology of the Monte Carlo beam calibration developed and introduced in this study allows the user to calculate both relative and absolute absorbed doses.
Evaluation of residual patient position variation for spinal radiosurgery using the Novalis image guided system
Authors: Jin Jian‐Yue , Ryu Samuel , Rock Jack , Faber Kathleen , Chen Qing , Ajlouni Munther , Movsas Benjamin
Published: March 2008

Purpose: The Novalis system has been demonstrated to achieve accurate target localization on anthropomorphic phantoms. However, other factors, such as rotational deviation, patient intrafraction motion, and image fusion uncertainty due to patient body deformation, could contribute additional position uncertainty for actual patients. This study evaluates such position uncertainty for spinal radiosurgery patients. Materials and Methods: Fifty‐two consecutive spinal radiosurgery patients were included in the study. Rotational deviation was evaluated from 6‐deg of freedom (6D) fusion results for all patients. The combined uncertainty of patient motion and image fusion was determined from fusion results of additional kV x‐ray images acquired before, during, and after treatment for 25 of the 52 patients. The uncertainty of image fusion was also evaluated by performing 6D fusion ten different times with various regions of interest in the images selected for fusion. This was performed for two patients with L3 and T2 lesions, respectively, for comparison. Results: The mean rotational deviation was , , and along the yaw, roll, and pitch directions, respectively. The combined uncertainty from patient motion and image fusion was , , and in the anteroposterior (AP), longitudinal, and lateral directions, respectively. The uncertainty (standard deviation) due to image fusion was less than 0.28 mm in any direction for the L3 lesion and 0.8 mm in the AP direction for the T2 lesion. Conclusion: Overall position uncertainty for spinal radiosurgery patients has been evaluated. Rotational deviation and patient motion were the main factors contributed to position uncertainty for actual patient treatment.
Experimental verification and clinical implementation of a commercial Monte Carlo electron beam dose calculation algorithm
Authors: Fragoso Margarida , Pillai Sushakumari , Solberg Timothy D. , Chetty Indrin J.
Published: March 2008

This study describes the modeling and the experimental verification and clinical implementation of the alpha release of Monte Carlo (MC) electron beam dose calculation algorithm for patient‐specific treatment planning. The MC electron beam modeling was performed for beam energies ranging from 6 to 18 MeV from a Siemens (Primus) linear accelerator using standard‐shaped electron applicators and 100 cm source‐to‐surface distance (SSD). The agreement between MC calculations and measurements was, on average, within and 2 mm for all applicator sizes. However, differences of the order of were noted in the off‐axis dose profiles for the largest applicator modeled and for all energies. Output factors were calculated for standard electron cones and square cutouts inserted in the applicator for different SSDs and were found to be within of measured data. Experimental verification of the MC electron beam model was carried out using an ionization chamber and film in solid‐water slab and anthropomorphic phantoms containing bone and lung materials. Agreement between calculated and measured dose distributions was within . Clinical comparison was performed in four patient treatment plans with lesions in highly irregular anatomies, such as the ear, face, and breast, where custom‐designed bolus and field shaping blocks were used in the patient treatments. For comparison purposes, treatment planning was also performed using the conventional pencil beam (PB) algorithm with the treatment planning system. Differences between MC and PB dose calculations for the patient treatment plans were significant, particularly in anatomies where the target was in close proximity to low density tissues, such as lung and air cavities. Concerning monitor unit calculations, the largest differences obtained between MC and PB algorithms were between 4.0% and 5.0% for two patients treated with oblique beams and involving highly irregular surfaces, i.e., breast and cheek. Clinical results are reported for overall uncertainty values (averaged over voxels with doses ) ranging from to and calculations were performed using cubic voxels with side 0.3 cm. Timing values ranged from 2 min to 24.5 h, depending on the field size, beam energy, number, and thickness of computed tomography slices used to define the patient's anatomy for the overall uncertainty values mentioned above.
A detailed study on the use of polynomial functions for modeling geometric distortion in magnetic resonance imaging
Authors: Wang Deming , Yang Zhengyi
Published: March 2008

The use of polynomial functions for modeling geometric distortion in magnetic resonance imaging (MRI) that arises from scanner's hardware imperfection is studied in detail. In this work, the geometric distortion data from four representative MRI systems were used. Modeling of these data using polynomial functions of the fourth, fifth, sixth, and seventh orders was carried out. In order to investigate how this modeling performed for different size and shape of the volume of interest, the modeling was carried out for three different volumes of interest (VOI): a cube, a cylinder, and a sphere. The modeling's goodness was assessed using both the maximum and mean absolute errors. The modeling results showed that (i) for the cube VOI there appears to be an optimal polynomial function that gives the least modeling errors and the sixth order polynomial was found to be the optimal polynomial function for the size of the cubic VOI considered in the present work; (ii) for the cylinder VOI, all four polynomials performed approximately equally well but a trend of a slight decrease in the mean absolute error with the increasing order of the polynomial was noted; and (iii) for the sphere VOI, the maximum absolute error showed some variations with the order of the polynomial, with the fourth order polynomial producing the smallest maximum absolute errors. It is further noted that extrapolation could lead to very large errors so any extrapolation needs to be avoided. A detailed analysis on the modeling errors is presented.
Classification of breast computed tomography data
Authors: Nelson Thomas R. , Cerviño Laura I. , Boone John M. , Lindfors Karen K.
Published: March 2008

Differences in breast tissue composition are important determinants in assessing risk, identifying disease in images and following changes over time. This paper presents an algorithm for tissue classification that separates breast tissue into its three primary constituents of skin, fat and glandular tissue. We have designed and built a dedicated breast CT scanner. Fifty‐five normal volunteers and patients with mammographically identified breast lesions were scanned. Breast CT voxel data were filtered using a median filter and the image histogram was computed. A two compartment Gaussian fit of histogram data was used to provide an initial estimate of tissue compartments. After histogram analysis, data were input to region‐growing algorithms and classified as to belonging to skin, fat or gland based on their value and architectural features. Once tissues were classified, a more detailed analysis of glandular tissue patterns and a more quantitative analysis of breast composition was made. Algorithm performance assessment demonstrated very good or excellent agreement between algorithm and radiologist observers in 97.7% of the segmented data. We observed that even in dense breasts the fraction of glandular tissue seldom exceeded 50%. For most individuals the composition is better characterized as being a 70% (fat)–30% (gland) composition than a 50% (fat)–50% (gland) composition.
Development of Physics Applied to Medicine in the UK, 1945–1990. Vol. 28
Authors: Basran Parminder S.
Published: March 2008

Development of Physics Applied to Medicine in the UK, 1945–1990. Vol. 28 Christie D. A. and Tansey E. M. Wellcome Trust Centre for the History of Medicine at UCL, London, 2006, $10.00. ISBN: 0 85484 108 3 and 978 085484 108 0, 172 pp.
A biphasic theory for the viscoelastic behaviors of vocal fold lamina propria in stress relaxation
Authors: Zhang Yu , Czerwonka Lukasz , Tao Chao , Jiang Jack J.
Published: March 2008

In this study, a biphasic theory is applied to investigate the viscoelastic behaviors of vocal fold lamina propria during stress relaxation. The vocal fold lamina propria tissue is described as a biphasic material composed of a solid phase and an interstitial fluid phase. The biphasic theory reveals the interaction between the solid and the fluid. For the one-dimensional case, the analytical solutions of solid displacement, fluid velocity, and stress are derived. The biphasic theory predicts the stress relaxation of the vocal fold lamina propria. The quasilinear viscoelastic model as well as its higher-order elastic parameters can be derived from this biphasic theory. Furthermore, the fluid is found to support the majority of the stress at the early stage of stress relaxation; however, when the time becomes sufficiently large, the solid eventually bears all the stress. The early fluid stress support is much higher than the eventual solid support and may be important for understanding the effects of dehydration on tissue damage. By considering the solid-fluid structure of the vocal fold lamina propria, the biphasic theory allows for a more physical theory of tissue viscoelasticity than a single phase solid description and may provide a valuable physical mechanism for the observed vocal fold rheologic behaviors.
Characterization of high intensity focused ultrasound transducers using acoustic streaming
Authors: Hariharan Prasanna , Myers Matthew R. , Robinson Ronald A. , Maruvada Subha H. , Sliwa Jack , Banerjee Rupak K.
Published: March 2008

A new approach for characterizing high intensity focused ultrasound (HIFU) transducers is presented. The technique is based upon the acoustic streaming field generated by absorption of the HIFU beam in a liquid medium. The streaming field is quantified using digital particle image velocimetry, and a numerical algorithm is employed to compute the acoustic intensity field giving rise to the observed streaming field. The method as presented here is applicable to moderate intensity regimes, above the intensities which may be damaging to conventional hydrophones, but below the levels where nonlinear propagation effects are appreciable. Intensity fields and acoustic powers predicted using the streaming method were found to agree within 10% with measurements obtained using hydrophones and radiation force balances. Besides acoustic intensity fields, the streaming technique may be used to determine other important HIFU parameters, such as beam tilt angle or absorption of the propagation medium.
Rectangular plate with velocity feedback loops using triangularly shaped piezoceramic actuators: Experimental control performance
Authors: Aoki Yohko , Gardonio Paolo , Elliott Stephen J.
Published: March 2008

This paper presents experimental results on the implementation of decentralized velocity feedback control on a new smart panel in order to produce active damping. The panel is equipped with 16 triangularly shaped piezoceramic patch actuators along its border and accelerometer sensors located at the top vertex of the triangular actuators. The primary objective of this paper is to demonstrate the vibration and sound radiation control using the new smart panel. Narrow frequency band experimental results highlight that the 16 control units can produce reductions up to 15dB at resonance frequencies between 100 and 700Hz in terms of both structural vibration and sound power radiation.
Small-scale seismic inversion using surface waves extracted from noise cross correlation
Authors: Gouédard Pierre , Roux Philippe , Campillo Michel
Published: March 2008

Green’s functions can be retrieved between receivers from the correlation of ambient seismic noise or with an appropriate set of randomly distributed sources. This principle is demonstrated in small-scale geophysics using noise sources generated by human steps during a 10-min walk in the alignment of a 14-m-long accelerometer line array. The time-domain correlation of the records yields two surface wave modes extracted from the Green’s function between each pair of accelerometers. A frequency–wave-number Fourier analysis yields each mode contribution and their dispersion curve. These dispersion curves are then inverted to provide the one-dimensional shear velocity of the near surface.
Efficacies of Ceftobiprole Medocaril and Comparators in a Rabbit Model of Osteomyelitis Due to Methicillin-Resistant
Staphylococcus aureus
Authors: Yin Li-Yan , Calhoun Jason H. , Thomas Jacob K. , Shapiro Stuart , Schmitt-Hoffmann Anne
Published: March 2008

The pharmacokinetics and distribution into bone tissue of ceftobiprole in uninfected New Zealand White rabbits were determined after subcutaneous administration of the prodrug ceftobiprole medocaril. Serum exposure (maximum concentration of the drug in serum, trough concentration, area under the concentration-time curve) to ceftobiprole at 20 and 80 mg/kg was dose proportional, and there was no accumulation of ceftobiprole following repeated (every 6 h [q6h]) injections of the antibiotic. Ceftobiprole titers in the tibial matrix and marrow were 3.2 ± 1.3 μg/g and 11.2 ± 6.5 μg/g, respectively, in uninfected animals treated with 20 mg/kg of the antibiotic and 13.4 ± 7.3 μg/g and 66.3 ± 43.2 μg/g, respectively, in uninfected animals treated with 80 mg/kg of the antibiotic. No differences in ceftobiprole titers were observed between right and left tibiae for either bone matrix or marrow. The efficacies of 4 weeks of treatment with ceftobiprole (40 mg/kg administered subcutaneously [s.c.] q6h), vancomycin (30 mg/kg administered s.c. q12h), or linezolid (60 mg/kg administered orally q8h) were compared, using a rabbit model of methicillin-resistant
Staphylococcus aureus
tibial osteomyelitis. After treatment with ceftobiprole, the bacterial titers in all infected left tibiae from evaluable rabbits were below the level of detection, whereas only 73% of infected left tibiae from vancomycin- or linezolid-treated animals had bacterial titers below the level of detection; the mean titers of ceftobiprole were 3 to 5 times higher in infected left tibiae than in uninfected right tibiae. These results indicate that ceftobiprole provided effective parenteral treatment of osteomyelitis in this rabbit model.
Mouse Beta-Defensin-14, an Antimicrobial Ortholog of Human Beta-Defensin-3
Authors: Hinrichsen Kerstin , Podschun Rainer , Schubert Sabine , Schröder Jens M. , Harder Jürgen , Proksch Ehrhardt
Published: March 2008

Searching the database for mouse homologs of the antimicrobial peptide human beta-defensin-3 (hBD-3) revealed highest identity (69%) to mouse beta-defensin-14 (mBD-14). Recombinant mBD-14 exhibited broad-spectrum, nanomolar microbicidal activity. Treatment of keratinocytes with gamma interferon or transforming growth factor alpha increased mBD-14 gene expression. These data suggest that mBD-14 is the functional ortholog of hBD-3.
Development of a Comprehensive Human Immunodeficiency Virus Type 1 Screening Algorithm for Discovery and Preclinical Testing of Topical Microbicides
Authors: Lackman-Smith Carol , Osterling Clay , Luckenbaugh Katherine , Mankowski Marie , Snyder Beth , Lewis Gareth , Paull Jeremy , Profy Albert , Ptak Roger G. , Buckheit Robert W. , Watson Karen M. , Cummins James E. , Sanders-Beer Brigitte E.
Published: March 2008

Topical microbicides are self-administered, prophylactic products for protection against sexually transmitted pathogens. A large number of compounds with known anti-human immunodeficiency virus type 1 (HIV-1) inhibitory activity have been proposed as candidate topical microbicides. To identify potential leads, an in vitro screening algorithm was developed to evaluate candidate microbicides in assays that assess inhibition of cell-associated and cell-free HIV-1 transmission, entry, and fusion. The algorithm advances compounds by evaluation in a series of defined assays that generate measurements of relative antiviral potency to determine advancement or failure. Initial testing consists of a dual determination of inhibitory activity in the CD4-dependent CCR5-tropic cell-associated transmission inhibition assay and in the CD4/CCR5-mediated HIV-1 entry assay. The activity is confirmed by repeat testing, and identified actives are advanced to secondary screens to determine their effect on transmission of CXCR4-tropic viruses in the presence or absence of CD4 and their ability to inhibit CXCR4- and CCR5-tropic envelope-mediated cell-to-cell fusion. In addition, confirmed active compounds are also evaluated in the presence of human seminal plasma, in assays incorporating a pH 4 to 7 transition, and for growth inhibition of relevant strains of lactobacilli. Leads may then be advanced for specialized testing, including determinations in human cervical explants and in peripheral blood mononuclear cells against primary HIV subtypes, combination testing with other inhibitors, and additional cytotoxicity assays. PRO 2000 and SPL7013 (the active component of VivaGel), two microbicide products currently being evaluated in human clinical trials, were tested in this in vitro algorithm and were shown to be highly active against CCR5- and CXCR4-tropic HIV-1 infection.
The Antimicrobial Peptide NK-2, the Core Region of Mammalian NK-Lysin, Kills Intraerythrocytic
Plasmodium falciparum
Authors: Gelhaus Christoph , Jacobs Thomas , Andrä Jörg , Leippe Matthias
Published: March 2008

In a time of dramatically increasing resistance of microbes to all kinds of antibiotics, natural antimicrobial peptides and synthetic analogs thereof have emerged as compounds with potentially significant therapeutical applications against human pathogens. Only very few of these peptide antibiotics have been tested against protozoan pathogens that are a major cause of morbidity and mortality in large parts of the world. Here, we studied the effect of NK-2, a peptide representing the cationic core region of the lymphocytic effector protein NK-lysin, on the malaria parasite
Plasmodium falciparum
. Whereas noninfected red blood cells were hardly affected, human erythrocytes infected with the parasite were rapidly permeabilized by NK-2 in the micromolar range. Loss of plasma membrane asymmetry and concomitant exposure of phosphatidylserine upon infection appears to be the molecular basis for the observed target preference of NK-2, as can be demonstrated by annexin V binding. The peptide also affects the viability of the intracellular parasite, as evidenced by the drop in DNA content of cultured parasites. Accumulated evidence derived from permeabilization assays using parasites and liposomes as targets and from fluorescence microscopy of infected erythrocytes treated with fluorescently labeled NK-2 indicates that the positively charged peptide electrostatically interacts with the altered and negatively charged plasma membrane of the infected host cell and traverses this membrane as well as the parasitophorous vacuole membrane to reach its final target, the intracellular parasite. The apparent affinity for foreign membranes that resulted in the death of a eukaryotic parasite residing in human host cells makes NK-2 a promising template for novel anti-infectives.
Antibacterial Efficacy of R-Type Pyocins towards
Pseudomonas aeruginosa
in a Murine Peritonitis Model
Authors: Scholl Dean , Martin David W.
Published: March 2008

R-type pyocins are high-molecular-weight bacteriocins carried within the chromosomes of some bacterial species, such as
Pseudomonas aeruginosa
, and almost certainly evolved from lysogenic bacteriophages of the
Myoviridae
family. They contain no head structures and no DNA and are used as defense systems, usually against other strains of the same bacterial species. They bind with their tail fibers to targeted bacterial surface molecules and then kill by inserting a core or needle that dissipates the bacterial membrane potential. Their mechanism of action, high bactericidal potency (one pyocin particle can kill one bacterium), and focused spectrum suggest that R-type pyocins could be developed as antibacterial agents. In a lethal mouse peritonitis model, submicrogram quantities of pyocin prevent death from 90% lethal dose inocula of a pyocin-sensitive, clinical isolate of
P. aeruginosa
. We show here the dose response curves, treatment windows, or periods of response after infection and the several-log-unit acute reduction of bacterial load in blood and spleen samples, suggesting that R-type pyocins have several characteristics that one would expect from an effective therapeutic.
Efficacy of Benzoxazinorifamycins in a Mouse Model of
Chlamydia pneumoniae
Lung Infection
Authors: Campbell Lee Ann , Kuo Cho-Chou , Suchland Robert J. , Rothstein David M.
Published: March 2008

The efficacy of rifalazil and other benzoxazinorifamycins was tested in a mouse model of lung infection against
Chlamydia pneumoniae
. Rifalazil and six related new chemical entities all showed efficacy after one dose per day for 3 days at either 3 or 1 mg/kg of body weight.
Anamnestic Protective Immunity to
Bacillus anthracis
Is Antibody Mediated but Independent of Complement and Fc Receptors
Authors: Harvill Eric T. , Osorio Manuel , Loving Crystal L. , Lee Gloria M. , Kelly Vanessa K. , Merkel Tod J.
Published: March 2008

The threat of bioterrorist use of
Bacillus anthracis
has focused urgent attention on the efficacy and mechanisms of protective immunity induced by available vaccines. However, the mechanisms of infection-induced immunity have been less well studied and defined. We used a combination of complement depletion along with immunodeficient mice and adoptive transfer approaches to determine the mechanisms of infection-induced protective immunity to
B. anthracis
. B- or T-cell-deficient mice lacked the complete anamnestic protection observed in immunocompetent mice. In addition, T-cell-deficient mice generated poor antibody titers but were protected by the adoptive transfer of serum from
B. anthracis
-challenged mice. Adoptively transferred sera were protective in mice lacking complement, Fc receptors, or both, suggesting that they operate independent of these effectors. Together, these results indicate that antibody-mediated neutralization provides significant protection in
B. anthracis
infection-induced immunity.
Functional Analysis of Effector and Regulatory T Cells in a Parasitic Nematode Infection
Authors: Rausch Sebastian , Huehn Jochen , Kirchhoff Dennis , Rzepecka Justyna , Schnoeller Corinna , Pillai Smitha , Loddenkemper Christoph , Scheffold Alexander , Hamann Alf , Lucius Richard , Hartmann Susanne
Published: March 2008

Parasitic nematodes typically modulate T-cell reactivity, primarily during the chronic phase of infection. We analyzed the role of CD4-positive (CD4+) T effector (Teff) cells and regulatory T (Treg) cells derived from mice chronically infected with the intestinal nematodeHeligmosomoides polygyrus. Different CD4+T-cell subsets were transferred into naïve recipients that were subsequently infected withH. polygyrus. Adoptive transfer of conventional Teffcells conferred protection and led to a significant decrease in the worm burdens ofH. polygyrus-infected recipients. Roughly 0.2% of the CD4+T cells wereH. polygyrusspecific based on expression of CD154, and cells producing interleukin 4 (IL-4) and IL-13 were highly enriched within the CD154+population. In contrast, adoptive transfer of Tregcells, characterized by the markers CD25 and CD103 and the transcription factor Foxp3, had no effect on the worm burdens of recipients. Further analysis showed that soon after infection, the number of Foxp3+Tregcells temporarily increased in the inflamed tissue while effector/memory-like CD103+Foxp+Tregcells systemically increased in the draining lymph nodes and spleen. In addition, Tregcells represented a potential source of IL-10 and reduced the expression of IL-4. Finally, under in vitro conditions, Tregcells from infected mice were more potent suppressors than cells derived from naïve mice. In conclusion, our data indicate that small numbers of Teffcells have the ability to promote host protective immune responses, even in the presence of Tregcells.
Murine Model for Assessment of
Plasmodium falciparum
Transmission-Blocking Vaccine Using Transgenic
Plasmodium berghei
Parasites Expressing the Target Antigen Pfs25
Authors: Mlambo Godfree , Maciel Jorge , Kumar Nirbhay
Published: March 2008

Currently, there is no animal model for
Plasmodium falciparum
challenge to evaluate malaria transmission-blocking vaccines based on the well-established Pfs25 target antigen. The biological activity of transmission-blocking antibodies is typically assessed using an assay known as the membrane feeding assay (MFA). It is an in vitro method that involves mixing antibodies with cultured
P. falciparum
gametocytes and feeding them to mosquitoes through an artificial membrane followed by assessment of infection in the mosquitoes. We genetically modified
Plasmodium berghei
to express Pfs25 and demonstrated that the transgenic parasites (TrPfs25Pb) are susceptible to anti-Pfs25 antibodies during mosquito-stage development. The asexual growth kinetics and mosquito infectivity of TrPfs25Pb were comparable to those of wild-type parasites, and TrPfs25Pb displayed Pfs25 on the surface of ookinetes. Immune sera from nonhuman primates immunized with a Pfs25-based vaccine when passively transferred to mice blocked transmission of TrPfs25Pb to
Anopheles stephensi
. Furthermore, mice immunized with Pfs25 DNA vaccine and challenged with TrPfs25Pb displayed reduced malaria transmission compared to mice immunized with wild-type plasmid. These studies describe development of an animal malaria model alternative to the in vitro MFA and show that the model can facilitate
P. falciparum
transmission-blocking vaccine evaluation based on the target antigen Pfs25. We believe that an animal model to test transmission-blocking vaccines would be superior to the MFA, since there may be additional immune factors that synergize the transmission-blocking activity of antibodies in vivo.
Interleukin-1β Modulates Proinflammatory Cytokine Production in Human Epithelial Cells
Authors: Eskan Mehmet A. , Benakanakere Manjunatha R. , Rose Beate G. , Zhang Ping , Zhao Jiawei , Stathopoulou Panagiota , Fujioka Daisuke , Kinane Denis F.
Published: March 2008

Periodontitis is a chronic human inflammatory disease initiated and sustained by dental plaque microorganisms. A major contributing pathogen is
Porphyromonas gingivalis
, a gram-negative bacterium recognized by Toll-like receptor 2 (TLR2) and TLR4, which are expressed by human gingival epithelial cells (HGECs). However, it is still unclear how these cells respond to
P. gingivalis
and initiate inflammatory and immune responses. We have reported previously that HGECs produce a wide range of proinflammatory cytokines, including interleukin-6 (IL-6), IL-8, granulocyte-macrophage colony-stimulating factor, tumor necrosis factor alpha (TNF-α), and IL-1β. In this study, we show that IL-1β has a special role in the modulation of other inflammatory cytokines in HGECs challenged with
P. gingivalis
. Our results show that the increased production of IL-1β correlates with the cell surface expression of TLR4, and more specifically, TLR4-normal HGECs produce fourfold more IL-1β than do TLR4-deficient HGECs after challenge. Moreover, blocking the IL-1β receptor greatly reduces the production of “secondary” proinflammatory cytokines such as IL-8 or IL-6. Our data indicate that the induction of IL-1β plays an important role in mediating the release of other proinflammatory cytokines from primary human epithelial cells following challenge with
P. gingivalis
, and this process may be an inflammatory enhancement mechanism adopted by epithelial cells.
Breadth and Magnitude of Antibody Responses to MultiplePlasmodium falciparumMerozoite Antigens Are Associated with Protection from Clinical Malaria
Authors: Osier Faith H. A. , Fegan Gregory , Polley Spencer D. , Murungi Linda , Verra Federica , Tetteh Kevin K. A. , Lowe Brett , Mwangi Tabitha , Bull Peter C. , Thomas Alan W. , Cavanagh David R. , McBride Jana S. , Lanar David E. , Mackinnon Margaret J. , Conway David J. , Marsh Kevin
Published: March 2008

Individuals living in areas where malaria is endemic are repeatedly exposed to many different malaria parasite antigens. Studies on naturally acquired antibody-mediated immunity to clinical malaria have largely focused on the presence of responses to individual antigens and their associations with decreased morbidity. We hypothesized that the breadth (number of important targets to which antibodies were made) and magnitude (antibody level measured in a random serum sample) of the antibody response were important predictors of protection from clinical malaria. We analyzed naturally acquired antibodies to five leadingPlasmodium falciparummerozoite-stage vaccine candidate antigens, and schizont extract, in Kenyan children monitored for uncomplicated malaria for 6 months (n= 119). Serum antibody levels to apical membrane antigen 1 (AMA1) and merozoite surface protein antigens (MSP-1 block 2, MSP-2, and MSP-3) were inversely related to the probability of developing malaria, but levels to MSP-119and erythrocyte binding antigen (EBA-175) were not. The risk of malaria was also inversely associated with increasing breadth of antibody specificities, with none of the children who simultaneously had high antibody levels to five or more antigens experiencing a clinical episode (17/119; 15%;P= 0.0006). Particular combinations of antibodies (AMA1, MSP-2, and MSP-3) were more strongly predictive of protection than others. The results were validated in a larger, separate case-control study whose end point was malaria severe enough to warrant hospital admission (n= 387). These findings suggest that under natural exposure, immunity to malaria may result from high titers antibodies to multiple antigenic targets and support the idea of testing combination blood-stage vaccines optimized to induce similar antibody profiles.
Mycolactone Is Responsible for the Painlessness of
Mycobacterium ulcerans
Infection (Buruli Ulcer) in a Murine Study
Authors: En Junichiro , Goto Masamichi , Nakanaga Kazue , Higashi Michiyo , Ishii Norihisa , Saito Hajime , Yonezawa Suguru , Hamada Hirofumi , Small Pamela L. C.
Published: March 2008

Buruli ulcer is a chronic skin disease caused by
Mycobacterium ulcerans
, which produces a toxic lipid mycolactone. Despite the extensive necrosis and tissue damage, the lesions are painless. This absence of pain prevents patients from seeking early treatment and, as a result, many patients experience severe sequelae, including limb amputation. We have reported that mice inoculated with
M. ulcerans
show loss of pain sensation and nerve degeneration. However, the molecules responsible for the nerve damage have not been identified. In order to clarify whether mycolactone alone can induce nerve damage, mycolactone A/B was injected to footpads of BALB/c mice. A total of 100 μg of mycolactone induced footpad swelling, redness, and erosion. The von Frey sensory test showed hyperesthesia on day 7, recovery on day 21, and hypoesthesia on day 28. Histologically, the footpads showed epidermal erosion, moderate stromal edema, and moderate neutrophilic infiltration up to day 14, which gradually resolved. Nerve bundles showed intraneural hemorrhage, neutrophilic infiltration, and loss of Schwann cell nuclei on days 7 and 14. Ultrastructurally, vacuolar change of myelin started on day 14 and gradually subsided by day 42, but the density of myelinated fibers remained low. This study demonstrated that initial hyperesthesia is followed by sensory recovery and final hypoesthesia. Our present study suggests that mycolactone directly damages nerves and is responsible for the absence of pain characteristic of Buruli ulcer. Furthermore, mice injected with 200 μg of mycolactone showed pulmonary hemorrhage. This is the first study to demonstrate the systemic effects of mycolactone.
Type 2 Secretion Promotes Enterohemorrhagic
Escherichia coli
Adherence and Intestinal Colonization
Authors: Ho Theresa D. , Davis Brigid M. , Ritchie Jennifer M. , Waldor Matthew K.
Published: March 2008

Enterohemorrhagic
Escherichia coli
(EHEC) is a noninvasive food-borne pathogen that colonizes the distal ileum and colon. Proteins encoded in the EHEC locus of enterocyte effacement (LEE) pathogenicity island are known to contribute to this pathogen's adherence to epithelial cells and intestinal colonization. The role of non-LEE-encoded proteins in these processes is not as clear. We found that the Z2053 gene (designated
adfO
here), a gene located in a cryptic EHEC prophage, exhibits similarity to adherence and/or colonization factor genes found in several other enteric pathogens. An EHEC
adfO
mutant exhibited marked reductions in adherence to HeLa cells and in the secretion of several proteins into the supernatant. YodA, one of these secreted proteins, was found to be a substrate of the EHEC pO157-encoded type 2 secretion system (T2SS). Both the T2SS and YodA proved to be essential for EHEC adherence to cultured HeLa cell monolayers. Using an infant rabbit model of infection, we found that the
adfO
mutation did not affect colonization but that the colonization of an
etpC
(T2SS) mutant was reduced ∼5-fold. A strain deficient in YodA had a more severe colonization defect; however, this strain also exhibited a growth defect in vitro. Overall, our findings indicate that the pO157-encoded T2SS contributes to EHEC adherence and intestinal colonization and thus show that EHEC pathogenicity depends on type 2 secretion as well as type 3 secretion.
Ascophyllum and its symbionts. X. Ultrastructure of the interaction between A. nodosum (Phaeophyceae) and Mycophycias ascophylli (Ascomycetes)
Authors: Xu Haixin , Deckert Ron J. , Garbary David J.
Published: March 2008

The symbiosis of a brown alga, Ascophyllum nodosum (L.) Le Jolis and its obligate fungal symbiont, Mycophycias ascophylli (Cotton) Kohlmeyer and Volkmann-Kohlmeyer, was studied using transmission electron microscopy. A high quality of cell preservation was achieved after propane-freezing and freeze substitution; this allowed us to observe the interaction of the symbiosis without extensive artifacts. The fungus was found in the middle portion of cortical-cell walls, and at the edge of medullary cells and air-bladder filaments, but never close to host cell protoplasm. Host cell-wall modification was limited to a short distance around the hyphae. A sheath with electron-dense materials around the fungus was found in the older hyphae, but not in the hyphal tips. A range of hyphal ultrastructure was observed from cells with dense cytoplasm, absent to slight vacuolation and with well-defined organelles, to highly vacuolated cells with little cytoplasm and poorly defined organelles, to senescent cells that were often collapsed with no recognizable organelles. No sign of typical cytological resistance responses was observed in host cells, thus confirming the nonantagonistic nature of the two symbionts.
Host–pathogen specificity in postseedling reaction of Linum usitatissimum to Melampsora lini
Authors: Hoes J. A. , Kenaschuk E. O.
Published: March 2008

Eleven commercial flax cultivars and 10 race differentials, inoculated at the prebloom stage, showed significantly different levels of postseedling resistance to virulent races of flax rust. The effects of hosts and of races were significant or highly significant. Races differentiated hosts, hosts differentiated races, and host × race interaction was highly significant. Non-allelic, single-gene differences in host genotype were associated with higher levels of resistance and were ascribed to epistatic action by an L6-complex and by genes K1, M4, and N1. Epistatic action for susceptibility by gene L9 may have occurred in the race differentials Dakota (L9M) and Koto (L9P). The high aggressiveness of race 22 on 10 commercial race-differentiating hosts was correlated with possession of 26 virulence genes compared with 12–15 genes possessed by three other races. Indications are that allelism of host resistance genes and linked virulence of corresponding virulence genes, and also genetic background, were factors in host × pathogen interactions. The cultivar McGregor is a superior source of postseedling rust resistance because each of its genes K1 and L6 was associated with a high resistance level to race 22. Key words: adult plant, allelism, epistasis, flax.