bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective breeding of mice for different susceptibilities to high fat diet‐induced glucose intolerance: Development of two novel mouse lines, Selectively bred Diet‐induced Glucose intolerance‐Prone and ‐Resistant
Authors: Nagao Mototsugu , Asai Akira , Kawahara Momoyo , Nakajima Yasushi , Sato Yuki , Tanimura Kyoko , Okajima Fumitaka , Takaya Makiyo , Sudo Mariko , Takemitsu Shuji , Harada Taro , Sugihara Hitoshi , Oikawa Shinichi
Published: November 2011

Aims/Introduction:  The development of type 2 diabetes is primarily due to lifestyle and environmental factors, as well as genetics, as shown by familial clustering. To establish mouse lines for evaluating heritable factors determining susceptibility to diet‐induced diabetes, we performed selective breeding for differences in high fat diet (HFD)‐induced glucose intolerance.

Materials and Methods:  Selective breeding was performed using hybrid mice of C57BL/6J, C3H/HeJ and AKR/N backgrounds. After 5‐week HFD feeding, mice showing high and low 2‐h blood glucose levels in an oral glucose tolerance test (OGTT) were selected and bred over 14 generations to produce lines prone and resistant to diet‐induced glucose intolerance (designated Selectively bred Diet‐induced Glucose intolerance‐Prone [SDG‐P] and ‐Resistant [SDG‐R]).

Results:  At 5 weeks of age (pre HFD feeding), SDG‐P mice showed higher blood glucose levels both in the OGTT and insulin tolerance test as compared to SDG‐R mice. After receiving HFD, the glucose intolerance of SDG‐P mice became more evident without hyper insulin secretion. In addition, SDG‐P mice had greater body weight gain and lower HDL‐cholesterol levels as compared to SDG‐R mice. In comparison with C57BL/6J, a well‐known strain prone to HFD‐induced glucose intolerance, SDG‐P mice showed significantly higher glucose levels in OGTT after the 5‐week HFD feeding.

Conclusions:  Susceptibility to HFD‐induced glucose intolerance was transmitted over generations and was intensified by selective breeding. The newly established mouse lines, SDG‐P and SDG‐R, may be useful in investigating the pathophysiology of type 2 diabetes through elucidating the crucial factors for determining the susceptibility to HFD‐induced glucose intolerance. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00175.x, 2011)
Oral piercings and their dental implications: a mini review
Authors: Singh Amrinder , Tuli Avantika
Published: November 2011

Oral piercing has become common in young adults in recent years. Adolescents are characterized by a compulsive tendency to distinguish themselves from the rest; differences in clothes, hairstyle, or “decorative” details are used to this effect, based on highly‐diverse criteria. Dental health‐care professionals need to be aware of the procedures and risks involved with oral piercings and the social and psychological reasons that lead people to engage in this practice, regardless of the risks. The present article addresses oral mutilation practices, specifically from the oral health perspective, as it is of concern to dental professionals due to the health risks and oral complications associated with such practices. The various oral ornaments, piercing sites, and their implications, orally, as well as systemically, have been discussed.
Influences on blockade by t‐butylbicyclo‐phosphoro‐thionate of GABAA receptor spontaneous gating, agonist activation and desensitization
Authors: Othman Nidaa A. , Gallacher Michael , Deeb Tarek Z. , Baptista‐Hon Daniel T. , Perry David C. , Hales Tim G.
Published: November 2011

Non‐technical summary  The convulsant t‐butylbicyclophosphorothionate (TBPS) is considered a GABAA receptor (GABAAR) open channel blocker. However, the relationship between the functional state of the receptor and TBPS binding remains unclear. Radiolabelled [35S]TBPS binds to GABAARs in the absence of GABA, suggesting that access to the binding site is independent of activation. Furthermore, low concentrations of GABA enhance [35S]TBPS binding, while higher concentrations reduce binding. Using either bicuculline or the α1(K278M) mutant GABAAR subunit to disrupt function, we demonstrate roles for spontaneous gating, GABA‐evoked channel activation and desensitization in the three phases of [35S]TBPS binding. These findings provide a framework for using [35S]TBPS binding to identify deficits in GABAAR function.
Phosphodiesterase 4 inhibition attenuates plasma volume loss and transvascular exchange in volume‐expanded mice
Authors: Lin Yueh‐Chen , Adamson Roger H. , Clark Joyce F. , Reed Rolf K. , Curry Fitz‐Roy E.
Published: November 2011

Non‐technical summary  When vascular volume is expanded, atrial natriuretic peptide (ANP) released from the heart acts to restore plasma volume by increasing renal water excretion, causing vasodilatation and increasing vascular permeability to water and macromolecules. Previous experiments using mice with selective deletion of ANP receptors in vascular endothelial cells emphasized the importance of vascular permeability regulation by ANP in plasma volume restoration because this genetic manipulation of ANP action on vascular permeability limited the restoration of vascular volume after an acute increase in plasma volume. Here we demonstrate retention of intravenously infused fluid in wild‐type mice in which the response to endogenous ANP was attenuated by the pharmacological agent rolipram that stabilized the endothelial barrier by tightening adhesion between adjacent endothelial cells. The strategy may provide novel approaches to the clinical problem of maintenance of vascular volume after acute intravenous fluid infusion.
Chronic imaging of cortical sensory map dynamics using a genetically encoded calcium indicator
Authors: Minderer Matthias , Liu Wenrui , Sumanovski Lazar T. , Kügler Sebastian , Helmchen Fritjof , Margolis David J.
Published: November 2011

Non‐technical summary  Optical imaging is widely used to map functional areas of the cerebral cortex. We present a method for fast fluorescence imaging of map‐level cortical activity using a calcium indicator protein. Sensory‐evoked neuronal activity can be imaged repeatedly in the same mouse over weeks, enabling new opportunities for the longitudinal study of cortical function and dysfunction. We hope this method will be flexibly applied across different cortical areas and to a variety of newly developed genetically encoded calcium and voltage sensors.
Postsynaptic BDNF signalling regulates long‐term potentiation at thalamo‐amygdala afferents
Authors: Meis S. , Endres T. , Lessmann V.
Published: November 2011

Non‐technical summary  Long‐term potentiation (LTP) in the lateral amygdala (LA) is a widely accepted cellular correlate of fear learning. In the present study we analysed the involvement of the neurotrophin brain‐derived neurotrophic factor (BDNF) in amygdala LTP by stimulating selectively thalamic or cortical sensory inputs into the LA. In heterozygous BDNF knockout mice we observed that LTP in the cortico‐amygdala pathway remained intact, whereas LTP in the thalamo‐amygdala pathway was abolished. Likewise, acute interference with BDNF/TrkB signalling in wild‐type mice by application of a BDNF scavenger (TrkB‐IgG) led to inhibition of LTP in this pathway. In addition, postsynaptic inhibition of TrkB receptors, which mediate BDNF effects, blocked LTP in the thalamic pathway. Thus, our data demonstrate for the first time a crucial role for postsynaptic BDNF signalling in mediating LTP selectively in the thalamo‐amygdala pathway in the LA.
Physiological characterization and functional heterogeneity of narrow‐field mammalian amacrine cells
Authors: Pang Ji‐Jie , Gao Fan , Wu Samuel M.
Published: November 2011

Non‐technical summary  Retina is the first neural station of the visual system, and visual images falling onto the retina are encoded and processed by three layers of neurons. Amacyine cells are a major class of third‐order retinal neurons that serve important visual functions, including shape recognition, motion detection and directional selectivity. Here we show for the first time a systematic examination of light‐evoked electrical responses, cell morphology and relative rod/cone inputs of the narrow‐field amacrine cells in the mouse retina. Results from this study provide a functional description of how retinal neurons are interconnected and how visual information is processed in the retinal synaptic network.
Dynamic Hydroelastic Scaling of the Underwater Shock Response of Composite Marine Structures
Authors: Bachynski Erin E. , Motley Michael R. , Young Yin L.
Published: November 2011

The hydroelastic scaling relations for the shock response of water-backed, anisotropic composite marine structures are derived and verified. The scaling analysis considers the known underwater explosion physics, previously derived analytical solutions for the underwater shock response of a water-backed plate, and elastic beam behavior. To verify the scaling relations, the hydroelastic underwater shock response of an anisotropic composite plate at several different scales is modeled as a fully coupled fluid-structure interaction (FSI) problem using the commercial Lagrangian finite element software ABAQUS/Explicit. Following geometric and Mach similitude, as well as proper scaling of the FSI parameter, scaling relations for the structural natural frequencies, fluid and structural responses are demonstrated for a variety of structural boundary conditions (cantilevered, fixed-fixed, and pinned-pinned). The scaling analysis shows that the initial response scales properly for elastic marine structures, but the secondary bubble pulse reload caused by an underwater explosion does not follow the same scaling and may result in resonant response at full scale.
Sandwich Beams With Corrugated and Y-frame Cores: Does the Back Face Contribute to the Bending Response?
Authors: St-Pierre L. , Fleck N. A. , Deshpande V. S.
Published: November 2011

Stainless steel sandwich beams with a corrugated core or a Y-frame core have been tested in three-point bending and the role of the face-sheets has been assessed by considering beams with (i) front-and-back faces present, and (ii) front face present but back face absent. A fair comparison between competing beam designs is made on an equal mass basis by doubling the front face thickness when the back face is absent. The quasi-static, three-point bending responses were measured under simply supported and clamped boundary conditions. For both end conditions and for both types of core, the sandwich beams containing front-and-back faces underwent indentation beneath the mid-span roller whereas Brazier plastic buckling was responsible for the collapse of sandwich beams absent the back face. Three-dimensional finite element (FE) predictions were in good agreement with the measured responses and gave additional insight into the deformation modes. The FE method was also used to study the effect of (i) mass distribution between core and face-sheets and (ii) beam span upon the collapse response of a simply supported sandwich panel. Sandwich panels of short span are plastically indented by the mid-span roller and the panels absent a back face are stronger than those with front-and-back faces present. In contrast, sandwich panels of long span undergo Brazier plastic buckling, and the presence of a back face strengthens the panel.
Wave Motion in Periodic Flexural Beams and Characterization of the Transition Between Bragg Scattering and Local Resonance
Authors: Liu Liao , Hussein Mahmoud I.
Published: November 2011

Band gaps appear in the frequency spectra of periodic materials and structures. In this work we examine flexural wave propagation in beams and investigate the effects of the various types and properties of periodicity on the frequency band structure, especially the location and width of band gaps. We consider periodicities involving the repeated spatial variation of material, geometry, boundary and/or suspended mass along the span of a beam. In our formulation, we implement Bloch’s theorem for elastic wave propagation and utilize Timoshenko beam theory for the kinematical description of the underlying flexural motion. For the calculation of the frequency band structure we use the transfer matrix method, derived here in generalized form to enable separate or combined consideration of the different types of periodicity. Our results provide band-gap maps as a function of the type and properties of periodicity, and as a prime focus we identify and mathematically characterize the condition for the transition between Bragg scattering and local resonance, each being a unique wave propagation mechanism, and show the effects of this transition on the lowest band gap. The analysis presented can be extended to multi-dimensional phononic crystals and acoustic metamaterials.
The Refined Theory of Plane Problems for One-Dimensional Quasicrystalline Bodies
Authors: Gao Yang , Ricoeur Andreas
Published: November 2011

Without employing ad hoc assumptions, various equations and solutions for plane problems of one-dimensional quasicrystals are deduced systematically. A method for the exact solution of three-dimensional equations is presented under homogeneous and nonhomogeneous boundary conditions. The equations and solutions are used to construct the refined theory of thick plates for both an in-plane extensional deformation regime and a normal or shear surface loading. With this method, the refined theory can now be explicitly established from the general solution of quasicrystals and the Lur’e method. In two illustrative examples of infinite plates with a circular hole, it is shown that explicit expressions of analytical solutions can be obtained by using the refined theory.
Modeling of Initially Curved Beam Structures for Design of Multistable MEMS
Authors: Williams Matthew D. , Keulen Fred van , Sheplak Mark
Published: November 2011

This article describes a mathematical model and two solution methodologies for efficiently predicting the equilibrium paths of an arbitrarily shaped, precurved, clamped beam. Such structures are common among multistable microelectromechanical systems (MEMS). First, a novel polynomial-based solution approach enables simultaneous solution of all equilibrium configurations associated with an arbitrary mechanical loading pattern. Second, the normal flow algorithm is used to negotiate the particularly complex nonlinear equilibrium paths associated with electrostatic loading and is shown to perform exceptionally well. Overall, the techniques presented herein provide designers with general and efficient computational frameworks for studying the effects of loading, shape, and imperfections on beam behavior. Sample problems motivated from switch and actuator applications in the literature demonstrate the methodologies’ utility in predicting the nonlinear equilibrium paths for structures of practical importance.
Out-of-Plane Pipe Whip for a Bent Cantilever Pipe: Comparison Between Experiment and FEM Models
Authors: Reid S. R. , Aleyaasin M. , Wang B.
Published: November 2011

The three-dimensional, dynamic, elastic-plastic response of a right-angle bent cantilever pipe, with an initially uniform, circular cross section, subjected to out-of-plane loading is examined using finite element beam and shell models in ABAQUS. The large-deflection behavior involves both bending and torsional elastoplastic deformations of the pipe, phenomena which have not been previously studied in the context of the dynamic problem of pipe whip. Initially, neglecting ovalization and local collapse (kinking), the bent pipe is modeled as a beam, using spatial beam elements in ABAQUS. This enables the basic three-dimensional kinematic behavior of the pipe to be analyzed. A similar, but potentially more accurate, analysis was then performed using shell elements. It is shown that there is no significant difference in the global dynamic plastic response. However the ovalization of the pipe cross section and formation and movement of the plastic zones (hinges) can be captured by using shell elements. This provides data which could form the basis for examining local failures in the pipe run. Previously unpublished experimental results, obtained in an earlier study by some of the present authors, are compared with the simulated results. Good agreement is observed and it is concluded that a nonlinear dynamic model using finite elements provides a rigorous approach for estimating the hazard zone (HZ) and, also, for treating the kinematics of a whipping pipe for this complex three-dimensional situation.
Development of a Portable Tissue Micro Array Instrument
Authors: Tan K. K. , Putra A. S. , Pham L. P. , Lee T. H. , Salto-Tellez M. , Kim L. G.
Published: November 2011

Tissue micro array (TMA) is based on the idea of applying miniaturization and a high throughput approach to hybridization-based analyses of tissues. It facilitates biomedical research on a large scale in a single experiment; thus representing one of the most commonly used technologies in translational research. A critical analysis of the existing TMA instruments indicates that there are potential constraints in terms of portability, apart from costs and complexity. This paper will present the development of an affordable, configurable, and portable TMA instrument to allow an efficient collection of tissues, especially in instrument-to-tissue scenarios. The purely mechanical instrument requires no energy sources other than the user, is light weight, portable, and simple to use.
Evaluating Design of Abdominal Aortic Aneurysm Endografts in a Patient-Specific Model Using Computational Fluid Dynamics
Authors: Segalova Polina A. , Xiong Guanglei , Venkateswara Rao K. T. , Zarins Christopher K. , Taylor Charles A.
Published: November 2011

Computer modeling of blood flow in patient-specific anatomies can be a powerful tool for evaluating the design of implantable medical devices. We assessed three different endograft designs, which are implantable devices commonly used to treat patients with abdominal aortic aneurysms (AAAs). Once implanted, the endograft may shift within the patient’s aorta allowing blood to flow into the aneurismal sac. One potential cause for this movement is the pulsatile force experienced by the endograft over the cardiac cycle. We used contrast-enhanced computed tomography angiography (CTA) data from four patients with diagnosed AAAs to build patient-specific models using 3D segmentation. For each of the four patients, we constructed a baseline model from the patient’s preoperative CTA data. In addition, geometries characterizing three distinct endograft designs were created, differing by where each device bifurcated into two limbs (proximal bifurcation, mid bifurcation, and distal bifurcation). Computational fluid dynamics (CFD) was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, and displacement forces on the endograft surface were calculated. The curvature and surface area of each device was quantified for all patients. The magnitude of the total displacement force on each device ranged from 2.43 N to 8.68 N for the four patients examined. Within each of the four patient anatomies, the total displacement force was similar (varying at least by 0.12 N and at most by 1.43 N), although there were some differences in the direction of component forces. Proximal bifurcation and distal bifurcation geometries consistently generated the smallest and largest displacement forces, respectively, with forces observed in the mid bifurcation design falling in between the two devices. The smallest curvature corresponded to the smallest total displacement force, and higher curvature values generally corresponded to higher magnitudes of displacement force. The same trend was seen for the surface area of each device, with lower surface areas resulting in lower displacement forces and vise versa. The patient with the highest blood pressure displayed the highest magnitudes of displacement force. The data indicate that curvature, device surface area, and patient blood pressure impact the magnitude of displacement force acting on the device. Endograft design may influence the displacement force experienced by an implanted endograft, with the proximal bifurcation design showing a small advantage for minimizing the displacement force on endografts.
Development of an Automatic Adjustable Colonoscope
Authors: Litten Jonathan D. , Choi JungHun , Drozek David
Published: November 2011

Colonoscopy can be associated with many problems, such as mechanical trauma due to the distal tip contacting the colon wall or health issues due to the extended use of anesthesia. In order to eliminate these complications, an automatic adjustable colonoscope was designed. This device uses sensors, actuators, and a control system to automatically position the distal tip in the center of the colon lumen. The sensors were tested to determine their ability to accurately sense the distance from the tip to the surface. The actuators were tested to determine the correlation between motor rotation and displacement of the distal tip. The control system was tested to assess the ability of the device to position the tip in the center of the test tube and the ability to navigate through a flat test course. It was determined that the sensors could accurately determine distances from 0 to 15 mm from the test surface in all test conditions. The motors for up-down movement and left-right movement of the colonoscope had response times of 0.57 s and 0.69 s, respectively, when the motors were rotated from 0 deg to 90 deg. The control system was able to safely move the colonoscope tip away from all walls of the test apparatus. It was also able to navigate through the flat test course without coming in contact with the walls. The automatic adjustable colonoscope has demonstrated that it can safely and effectively position the distal tip to avoid contact with the walls of the test surface.
Quality factor enhancement on nanomechanical resonators utilizing stiction phenomena
Authors: Ashiba Hiroki , Kometani Reo , Warisawa Shin’ichi , Ishihara Sunao
Published: November 2011

A simple method of applying tensile stress to nanomechanical resonators was proposed and demonstrated. Two parallel beams were fabricated by wet etching. The beams then stuck to each other due to surface tension caused by the rinse solution and formed a stiction resonator. The stuck beams were stressed because of the deformation caused by the sticking. The stiction resonators were modeled to estimate the sticking length and evaluate the strain of the resonators. The maximum resonator strain obtained in this study was over 0.3%. The quality factors of the stiction resonators were then experimentally evaluated. Results showed that tensile stress had a significant effect on the quality factor enhancement. Using stiction is an effective, useful, and widely applicable method for the tensile stress application.
Spatial correlation of proton irradiation‐induced activity and dose in polymer gel phantoms for PET/CT delivery verification studies
Authors: Lopatiuk‐Tirpak Olena , Su Zhong , Li Zuofeng , Hsi Wen , Meeks Sanford , Zeidan Omar
Published: November 2011

Purpose: This work demonstrates a novel application of BANG3‐Pro2 polymer gel dosimeter as a dosimetric phantom able to accurately capture both dose and induced activity.Methods: BANG3‐Pro2 dosimeters were irradiated with a clinical proton beam using an unmodulated beam and a spread‐out Bragg peak (SOBP) modulation, the latter with a Lucite compensator to introduce a range offset in one quadrant of the circular field. The dosimeters were imaged in a nearby positron emission tomography/computed tomography (PET/CT) unit starting within 5 min of beam‐off. Induced positron emission (PE) activity along the central axis of the beam was compared to analytical calculations. Dose distributions were read out using an optical CT scanner and were validated against ion chamber measurements and the treatment plan. The offset between the distal fall‐off of dose and activity (50% level) was determined over the entire irradiated field. Lateral profiles of PE were correlated to measured dose for the unmodulated beam delivery.Results: Measured profiles of PE activity along the central beam axis were found to be within 10% of the predictions of analytical calculations. The depth‐dose profiles agreed with the reference values (ion chamber or treatment plan) within 3%. The offset between the depth profiles of dose and activity for the unmodulated beam was 8.4 ± 1.4 mm. For the compensator‐based SOBP delivery, the distribution of offsets throughout the field was found to be bimodal, with the mean of 8.9 ± 2.8 mm for the thinner region of the compensator and 4.3 ± 2.5 mm for the thicker region. For the pristine beam delivery, lateral profiles of dose and activity were found to exhibit fair spatial correlation throughout the beam range, with the mean 2D gamma index of 0.42 and 91% of the evaluated pixels passing the test.Conclusions: This work presents the first demonstration of simultaneous and accurate experimental measurement of three‐dimensional distributions of dose and induced activity and lays the groundwork for further investigations using BANG3‐Pro2 as a dosimetric phantom in PET/CT delivery verification studies.
Potential of high‐Z contrast agents in clinical contrast‐enhanced computed tomography
Authors: Nowak Tristan , Hupfer Martin , Brauweiler Robert , Eisa Fabian , Kalender Willi A.
Published: November 2011

Purpose: Currently, only iodine‐ and barium‐based contrast media (CM) are used in clinical contrast‐enhanced computed tomography (CE‐CT). High‐Z metals would produce a higher contrast at equal mass density for the x‐ray spectra used in clinical CT. Using such materials might allow for significant dose reductions in CE‐CT. The purpose of this study was to quantify the potential for dose reduction when using CM based on heavy metals.Methods: The contrast‐to‐noise ratio weighted by dose (CNRD) was determined as a function of scan protocol by means of measurements and simulations on a clinical CT scanner. For simulations, water cylinders with diameters 160, 320, 480, and 640 mm were used to cover a broad range of patient sizes. Measurements were conducted with 160 and 320 mm water‐equivalent plastic cylinders. A central bore of 13 mm diameter was present in all phantoms. The tube voltage was varied from 80 to 140 kV for measurements and from 60 to 180 kV for simulations. Additional tin filtration of thicknesses 0.4, 0.8, and 1.2 mm was applied in the simulation to evaluate a range of spectral hardness. The bore was filled with a mixture of water and 10 mg/ml of pure iodine, holmium, gadolinium, ytterbium, osmium, tungsten, gold, and bismuth for the simulations and with aqueous solutions of ytterbium, tungsten, gold, and bismuth salts as well as Iopromid containing 10 mg/ml of the pure materials for the measurements. CNRDs were compared to iodine at phantom size‐dependent reference voltages for all high‐Z materials and the resulting dose reduction was calculated for equal contrast‐to‐noise ratio.Results: Dose reduction potentials strongly depended on phantom size, spectral hardness, and tube voltage. Depending on the added filtration, a dose reduction of 19%–60% could be reached at 80 kV with gadolinium for the 160 mm phantom, 52%–69% at 100 kV with holmium for the 320 mm phantom, 62%–78% with 120 kV for hafnium and the 480 mm phantom and 74%–86% with 140 kV for gold and the 640 mm phantom. While gadolinium might be considered at 160 mm diameter, hafnium showed the best overall performance for phantom sizes of 320 mm and above. The measurements conducted on the clinical CT scanner showed very good agreement with simulations with deviations in the order of 5 to 10%.Conclusions: The results of this study encourage the development and use of CM based on high‐Z materials, especially for adipose patients, where high tube voltages are necessary to reach sufficiently short scan times. Hafnium proved to be the best compromise for average‐size and for adipose patients. Even higher‐Z materials such as gold and bismuth showed a good overall performance in conjunction with high tube voltage, large patients or strong added filtration and may be recommended for scans under these conditions.
Complete Sequence of Broad-Host-Range Plasmid pRIO-5 Harboring the Extended-Spectrum-β-Lactamase Gene
bla
BES-1
Authors: Bonnin Rémy A. , Poirel Laurent , Sampaio Jorge Luiz Mello , Nordmann Patrice
Published: November 2011

Broad-host-range plasmid pRIO-5, harboring the extended-spectrum β-lactamase
bla
BES-1
gene in
Serratia marcescens
, was fully sequenced. Analysis of the 12,957-bp sequence of this IncP6-type plasmid revealed that the
bla
BES-1
gene was associated with two copies of the insertion sequence IS
26
. The promoter responsible for the
bla
BES-1
expression was hybrid, made of a −35 box located inside the inverted repeat of IS
26
and a −10 box inside a remnant of an insertion sequence.
Prospective Investigation of Nasal Mupirocin, Hexachlorophene Body Wash, and Systemic Antibiotics for Prevention of Recurrent Community-Associated Methicillin-Resistant Staphylococcus aureus Infections
Authors: Miller Loren G. , Tan Jennifer , Eells Samantha J. , Benitez Esther , Radner Allen B.
Published: November 2011

Recurrent community-associated methicillin-resistant
Staphylococcus aureus
(CA-MRSA) skin infections are an increasingly common problem. However, there are no data on the efficacy of decolonization regimens. We prospectively evaluated 31 patients with recurrent CA-MRSA skin infections who received nasal mupirocin, topical hexachlorophene body wash, and an oral anti-MRSA antibiotic. The mean number of MRSA infections after the intervention decreased significantly from baseline (0.03 versus 0.84 infections/month,
P
= <0.0001). This regimen appears promising at preventing recurrent CA-MRSA infections.
In Vitro
and
In Vivo
Activity of Solithromycin (CEM-101) against Plasmodium Species
Authors: Wittlin Sergio , Ekland Eric , Craft J Carl , Lotharius Julie , Bathurst Ian , Fidock David A. , Fernandes Prabhavathi
Published: November 2011

With the emergence of
Plasmodium falciparum
infections exhibiting increased parasite clearance times in response to treatment with artemisinin-based combination therapies, the need for new therapeutic agents is urgent. Solithromycin, a potent new fluoroketolide currently in development, has been shown to be an effective, broad-spectrum antimicrobial agent. Malarial parasites possess an unusual organelle, termed the apicoplast, which carries a cryptic genome of prokaryotic origin that encodes its own translation and transcription machinery. Given the similarity of apicoplast and bacterial ribosomes, we have examined solithromycin for antimalarial activity. Other antibiotics known to target the apicoplast, such as the macrolide azithromycin, demonstrate a delayed-death effect, whereby treated asexual blood-stage parasites die in the second generation of drug exposure. Solithromycin demonstrated potent
in vitro
activity against the NF54 strain of
P. falciparum
, as well as against two multidrug-resistant strains, Dd2 and 7G8. The dramatic increase in potency observed after two generations of exposure suggests that it targets the apicoplast. Solithromycin also retained potency against azithromycin-resistant parasites derived from Dd2 and 7G8, although these lines did demonstrate a degree of cross-resistance. In an
in vivo
model of
P. berghei
infection in mice, solithromycin demonstrated a 100% cure rate when administered as a dosage regimen of four doses of 100 mg/kg of body weight, the same dose required for artesunate or chloroquine to achieve 100% cure rates in this rodent malaria model. These promising
in vitro
and
in vivo
data support further investigations into the development of solithromycin as an antimalarial agent.
Characterization of CIA-1, an Ambler Class A Extended-Spectrum β-Lactamase from Chryseobacterium indologenes
Authors: Matsumoto Takehisa , Nagata Mika , Ishimine Nau , Kawasaki Kenji , Yamauchi Kazuyoshi , Hidaka Eiko , Kasuga Eriko , Horiuchi Kazuki , Oana Kozue , Kawakami Yoshiyuki , Honda Takayuki
Published: November 2011

An Ambler class A β-lactamase gene,
bla
CIA-1
, was cloned from the reference strain
Chryseobacterium indologenes
ATCC 29897 and expressed in
Escherichia coli
BL21. The
bla
CIA-1
gene encodes a novel extended-spectrum β-lactamase (ESBL) that shared 68% and 60% identities with the CGA-1 and CME-1 β-lactamases, respectively.
bla
CIA-1
-like genes were detected from clinical isolates. In addition to the metallo-β-lactamase IND of Ambler class B,
C. indologenes
has a class A ESBL gene,
bla
CIA-1
, located on the chromosome.
Genetic Features of the Widespread Plasmid Coding for the Carbapenemase OXA-48
Authors: Poirel Laurent , Bonnin Rémy A. , Nordmann Patrice
Published: November 2011

Complete sequencing of plasmid pOXA-48a carrying the
bla
OXA-48
gene from a
Klebsiella pneumoniae
isolate was performed. Its backbone corresponded to that of an IncL/M-type plasmid, in which the
bla
OXA-48
gene had been integrated through the acquisition of the Tn
1999
composite transposon without any other antibiotic resistance gene. Molecular epidemiology using a collection of international OXA-48 producers revealed the wide diffusion of pOXA-48a or closely related plasmids.
Inactivation of the Lipopeptide Antibiotic Daptomycin by Hydrolytic Mechanisms
Authors: D'Costa Vanessa M. , Mukhtar Tariq A. , Patel Tejal , Koteva Kalinka , Waglechner Nicholas , Hughes Donald W. , Wright Gerard D. , De Pascale Gianfranco
Published: November 2011

The lipopeptide daptomycin is a member of the newest FDA-approved antimicrobial class, exhibiting potency against a broad range of Gram-positive pathogens with only rare incidences of clinical resistance. Environmental bacteria harbor an abundance of resistance determinants orthologous to those in pathogens and thus may serve as an early-warning system for future clinical emergence. A collection of morphologically diverse environmental actinomycetes demonstrating unprecedented frequencies of daptomycin resistance and high levels of resistance by antibiotic inactivation was characterized to elucidate modes of drug inactivation.
In vivo
studies revealed that hydrolysis plays a key role, resulting in one or both of the following structural modifications: ring hydrolysis resulting in linearization (in 44% of inactivating isolates) or deacylation of the lipid tail (29%). Characterization of the mechanism in actinomycete WAC4713 (a
Streptomyces
sp. with an MIC of 512 μg/ml) demonstrated a constitutive resistance phenotype and established daptomycin's circularizing ester linkage to be the site of hydrolysis. Characterization of the hydrolase responsible revealed it to be likely a serine protease. These studies suggested that daptomycin is susceptible to general proteolytic hydrolysis, which was further supported by studies using proteases of diverse origin. These findings represent the first comprehensive characterization of daptomycin inactivation in any bacterial class and may not only presage a future mechanism of clinical resistance but also suggest strategies for the development of new lipopeptides.
Blood, Tissue, and Intracellular Concentrations of Erythromycin and Its Metabolite Anhydroerythromycin during and after Therapy
Authors: Krasniqi S. , Matzneller P. , Kinzig M. , Sörgel F. , Hüttner S. , Lackner E. , Müller M. , Zeitlinger M.
Published: November 2011

For macrolides, clinical activity but also the development of bacterial resistance has been attributed to prolonged therapeutic and subtherapeutic concentrations. Although erythromycin is a long-established antimicrobial, concomitant determination of the pharmacokinetics of erythromycin and its metabolites in different compartments is limited. To better characterize the pharmacokinetics of erythromycin and its anhydrometabolite (anhydroerythromycin [AHE]) in different compartments during and after the end of treatment with 500 mg of erythromycin four times daily, concentration-time profiles were determined in plasma, interstitial space of muscle and subcutaneous adipose tissue, and white blood cells (WBCs) at days 1 and 3 of treatment and 2 and 7 days after end of therapy. In WBCs, concentrations of erythromycin exceeded those in plasma approximately 40-fold, while free concentrations in plasma and tissue were comparable. The observed delay of peak concentrations in tissue might be caused by fast initial cellular uptake. Two days after the end of treatment, subinhibitory concentrations were observed in plasma and interstitial space of both soft tissues, while 7 days after the end of treatment, erythromycin was not detectable in any compartment. This relatively short period of subinhibitory concentrations may be advantageous compared to other macrolides. The ratio of erythromycin over AHE on day 1 was highest in plasma (2.81 ± 3.45) and lowest in WBCs (0.27 ± 0.22). While the ratio remained constant between single dose and steady state, after the end of treatment the concentration of AHE declined more slowly than that of the parent compound, indicating the importance of the metabolite for the prolonged drug interaction of erythromycin.
Penetration of Doripenem into Skeletal Muscle and Subcutaneous Adipose Tissue in Healthy Volunteers
Authors: Burian Bernhard , Zeitlinger Markus , Donath Oliver , Reznicek Gottfried , Sauermann Robert
Published: November 2011

Sufficient antibiotic concentrations at the infection site are a prerequisite for good bacterial killing. This study was performed to determine pharmacokinetics of doripenem in soft tissues and saliva. Six healthy male volunteers received a single intravenous infusion of 500 mg doripenem over 1 h. The concentrations of doripenem were measured over 8 h in saliva, plasma, and extracellular space fluid of skeletal muscle and subcutaneous adipose tissue employing
in vivo
microdialysis. Unbound drug concentrations were determined using ultra-high-performance liquid chromatography-tandem mass spectrometry. Maximum concentrations of doripenem were 15.3 ± 6.0 mg/liter in plasma, 9.9 ± 2.3 mg/liter in subcutaneous adipose tissue, 6.6 ± 2.9 mg/liter in skeletal muscle, and 0.5 ± 0.2 mg/liter in saliva. Areas under the concentration-time curve (AUC) from 0 to infinity were 26.3 ± 10.1, 20.4 ± 3.8, 12.8 ± 3.0, and 1.0 ± 0.5 mg · h/liter in plasma, adipose tissue, skeletal muscle, and saliva, respectively. Ratios of AUC in adipose tissue, skeletal muscle, and saliva to those in plasma were 0.84 ± 0.28, 0.53 ± 0.19, and 0.04 ± 0.03, respectively. In all six volunteers, a threshold of ≥40% for “time above MIC,” an index indicative of good antimicrobial activity, was exceeded in adipose tissue for MICs of ≤2 mg/liter and in skeletal muscle for MICs ≤1.5 mg/liter. Doripenem penetrates well into interstitial space fluid of skeletal muscle and adipose tissue, suggesting good antimicrobial activity in infected soft tissues, whereas it is detectable in relatively low concentrations in saliva.
Phenotypic and Genotypic Analysis of
In Vitro
-Selected Artemisinin-Resistant Progeny of Plasmodium falciparum
Authors: Tucker Matthew S. , Mutka Tina , Sparks Kansas , Patel Janus , Kyle Dennis E.
Published: November 2011

Emergence of artemisinin resistance in Cambodia highlights the importance of characterizing resistance to this class of drugs. Previously, intermediate levels of resistance in
Plasmodium falciparum
were generated
in vitro
for artelinic acid (AL) and artemisinin (QHS). Here we expanded on earlier selection efforts to produce levels of clinically relevant concentrations, and the resulting lines were characterized genotypically and phenotypically. Recrudescence assays determined the ability of resistant and parent lines to recover following exposure to clinically relevant levels of drugs. Interestingly, the parent clone (D6) tolerated up to 1,500 ng/ml QHS, but the resistant parasite, D6.QHS340×3, recovered following exposure to 2,400 ng/ml QHS. Resistant D6, W2, and TM91c235 parasites all exhibited elevated 50% inhibitory concentrations (IC
50
s) to multiple artemisinin drugs, with >3-fold resistance to QHS and AL; however, the degree of resistance obtained with standard methods was remarkably less than expected for parasite lines that recovered from 2,400-ng/ml drug pressure. A novel assay format with radiolabeled hypoxanthine demonstrated a greater degree of resistance
in vitro
than the standard SYBR green method. Analysis of merozoite number in resistant parasites found D6 and TM91c235 resistant progeny had significantly fewer merozoites than parent strains, whereas W2 resistant progeny had significantly more. Amplification of
pfmdr1
increased proportionately to the increased drug levels tolerated by W2 and TM91c235, but not in resistant D6. In summary, we define the artemisinin resistance phenotype as a decrease in susceptibility to artemisinins along with the ability to recover from drug-induced dormancy following supraclinical concentrations of the drug.
Interplay between Single Resistance-Associated Mutations in the HIV-1 Protease and Viral Infectivity, Protease Activity, and Inhibitor Sensitivity
Authors: Henderson Gavin J. , Lee Sook-Kyung , Irlbeck David M. , Harris Janera , Kline Melissa , Pollom Elizabeth , Parkin Neil , Swanstrom Ronald
Published: November 2011

Resistance-associated mutations in the HIV-1 protease modify viral fitness through changes in the catalytic activity and altered binding affinity for substrates and inhibitors. In this report, we examine the effects of 31 mutations at 26 amino acid positions in protease to determine their impact on infectivity and protease inhibitor sensitivity. We found that primary resistance mutations individually decrease fitness and generally increase sensitivity to protease inhibitors, indicating that reduced virion-associated protease activity reduces virion infectivity and the reduced level of per virion protease activity is then more easily titrated by a protease inhibitor. Conversely, mutations at more variable positions (compensatory mutations) confer low-level decreases in sensitivity to all protease inhibitors with little effect on infectivity. We found significant differences in the observed effect on infectivity with a pseudotype virus assay that requires the protease to cleave the cytoplasmic tail of the amphotropic murine leukemia virus (MuLV) Env protein. Additionally, we were able to mimic the fitness loss associated with resistance mutations by directly reducing the level of virion-associated protease activity. Virions containing 50% of a D25A mutant protease were 3- to 5-fold more sensitive to protease inhibitors. This level of reduction in protease activity also resulted in a 2-fold increase in sensitivity to nonnucleoside inhibitors of reverse transcriptase and a similar increase in sensitivity to zidovudine (AZT), indicating a pleiotropic effect associated with reduced protease activity. These results highlight the interplay between enzyme activity, viral fitness, and inhibitor mechanism and sensitivity in the closed system of the viral replication complex.
Antiviral Breadth and Combination Potential of Peptide Triazole HIV-1 Entry Inhibitors
Authors: McFadden Karyn , Fletcher Patricia , Rossi Fiorella , Kantharaju  , Umashankara Muddagowda , Pirrone Vanessa , Rajagopal Srivats , Gopi Hosahudya , Krebs Fred C. , Martin-Garcia Julio , Shattock Robin J. , Chaiken Irwin
Published: November 2011

The first stage of human immunodeficiency virus type 1 (HIV-1) infection involves the fusion of viral and host cellular membranes mediated by viral envelope glycoprotein gp120. Inhibitors that specifically target gp120 are gaining increased attention as therapeutics or preventatives to prevent the spread of HIV-1. One promising new group of inhibitors is the peptide triazoles, which bind to gp120 and simultaneously block its interaction with both CD4 and the coreceptor. In this study, we assessed the most potent peptide triazole, HNG-156, for inhibitory breadth, cytotoxicity, and efficacy, both alone and in combination with other antiviral compounds, against HIV-1. HNG-156 inhibited a panel of 16 subtype B and C isolates of HIV-1 in a single-round infection assay. Inhibition of cell infection by replication-competent clinical isolates of HIV-1 was also observed with HNG-156. We found that HNG-156 had a greater than predicted effect when combined with several other entry inhibitors or the reverse transcriptase inhibitor tenofovir. Overall, we find that HNG-156 is noncytotoxic, has a broad inhibition profile, and provides a positive combination with several inhibitors of the HIV-1 life cycle. These results support the pursuit of efficacy and toxicity analyses in more advanced cell and animal models to develop peptide triazole family inhibitors of HIV-1 into antagonists of HIV-1 infection.
Decoding the Functional Roles of Cationic Side Chains of the Major Antimicrobial Region of Human Cathelicidin LL-37
Authors: Wang Guangshun , Epand Raquel F. , Mishra Biswajit , Lushnikova Tamara , Thomas Vinai Chittezham , Bayles Kenneth W. , Epand Richard M.
Published: November 2011

Human cathelicidin LL-37 is a critical cationic antimicrobial peptide for host defense against infection, immune modulation, and wound healing. This article elucidates the functional roles of the cationic side chains of the major antimicrobial region of LL-37, corresponding to residues 17 to 32 (designated GF-17). Antimicrobial assays, killing kinetics studies, and vesicle leakage experiments all indicate that a conversion of lysines to arginines affected the ability of the peptide to kill the Gram-positive
Staphylococcus aureus
strain USA300. Alanine scanning experiments show that
S. aureus
is less sensitive than
Escherichia coli
to a single cationic residue mutation of GF-17. Among the five cationic residues, R23 appears to be somewhat important in killing
S. aureus
. However, R23 and K25 of GF-17 are of prime importance in killing the Gram-negative organism
E. coli
. In particular, R23 is essential for (i) rapid recognition, (ii) permeation of the
E. coli
outer membrane, (iii) clustering of anionic lipids in a membrane system mimicking the
E. coli
inner membrane, and (iv) membrane disruption. Bacterial aggregation (i.e., rapid recognition via charge neutralization) is the first step of the peptide action. Structurally, R23 is located in the interface (i.e., the first action layer), a situation ideal for the interactions listed above. In contrast, residues K18, R19, and R29 are on the hydrophilic surface of the amphipathic helix and play only a secondary role. Mapping of the functional spectrum of cationic residues of GF-17 provides a solid basis for engineering bacterium-specific antimicrobials using this highly potent template.