bluuebunny/crossref_metadata_2025 huggingface dataset:
An Application of Optimization Methods to Evaluate Conditioning Intervals
Authors: Repperger D. W. , Luciani R. J. , Frazier J. W.
Published: July 2009

A decision rule is obtained to determine when exercise is beneficial. The term beneficial used in this context refers to the extension of lifetime based on studies of cardiovascular conditioning. Models are used to characterize changes in heart rate with intense exercise. In addition, it is necessary to consider a model involving a heartbeat bank to help determine the conditioning interval. Optimization procedures are used to develop the decision rule, to examine the assumptions in the problem, and to point out when a unique solution exists. This procedure is applied to empirical data for one individual (inter-subject study) and a unique conditioning interval is obtained.
Active Contractions of Ureteral Segments
Authors: Zupkas P. F. , Fung Y. C.
Published: July 2009

The first step in the analysis of the biomechanics of any organ is to obtain its constitutive equation. In pursuit of a constitutive equation describing the peristalsis of the ureter, we measured the relationship between the length of the muscle, the velocity of contraction, and the active tension development of isolated ureter segments. The results of length-tension measurements (giving the maximum tension developed in isometric contraction of a ureter segment of specific length) were similar to those obtained by previous investigators and reflected the behavior of length-tension relationships for other smooth muscles. Two aspects of the force-velocity relationship of the ureter were examined: the effect of releasing the ureter at different times after stimulation, and that at different levels of afterload. Measurements were analyzed using the hyperbolic Hill’s equation in the form T/T0=(1−v/v0)(1+cv/v0)−1 where v is the velocity of contraction, v0 is the velocity of contraction when T = 0, T is the tension in the muscle after release, T0 is the tension in the muscle immediately prior to c is the dimensionless constant. The results of force-velocity measurements showed that the so-called “maximum” velocity v0, is the largest if the tension is released at a time of contraction, early in the rise portion of the contraction cycle. Further, if tension is released from an isometric contraction at a fixed time in the rise portion of the contraction cycle, the largest value of v0 is obtained when the muscle length is in the range of 0.85–0.90 Lmax. Interestingly, the in vivo length of the ureter lies also in this range, 0.85–0.90 Lmax.
A Circle of Willis Simulation Using Distensible Vessels and Pulsatile Flow
Authors: Kufahl R. H. , Clark M. E.
Published: July 2009

The development of a one-dimensional numerical (finite-difference) model of the arterial network surrounding the circle of Willis is described based on the full Navier-Stokes and conservation of mass equations generalized for distensible vessels. The present model assumes an elastic wall defined by a logarithmic pressure-area relation obtained from the literature. The viscous term in the momentum equation is evaluated using the slope of a Karman-Pohlhausen velocity profile at the vessel boundary. The afferent vessels (two carotids and two vertebrals) are forced with a canine physiologic pressure signature corresponding to an aortic site. The network associated with each main efferent artery of the circle is represented by a single vessel containing an appropriate amount of resistance so that the mean flow through the system is distributed in accordance with the weight of brain irrigated by each vessel as determined from a steady flow model of the same network. This resistance is placed a quarter wave-length downstream from the heart to insure proper reflection from the terminations, where the quarter wavelength is determined using the frequency corresponding to the first minimum on an input impedance-frequency diagram obtained at the heart. Computer results are given as time histories of pressure and flow at any model nodal point starting from initial conditions of null flow and constant pressure throughout the model. Variations in these pressure and flow distributions caused by the introduction of pathologic situations into the model illustrate the efficacy of the simulation and of the circle in equalizing and redistributing flows in abnormal situations.
A Steady-State Filtration Model for Transluminal Water Movement in Small and Large Blood Vessels
Authors: Tzeghai G. , Weinbaum S. , Pfeffer R.
Published: July 2009

It is now generally accepted that the intercellular cleft between adjacent endothelial cells is the primary pathway for the transluminal movement of water and small ions in the vasculature. A steady-state theoretical model has been developed to show quantitatively how the geometry of the intercellular cleft between adjacent endothelial cells is related to both the water movement and pressure distribution in the subendothelial space and to examine how the existence of a subendothelial interaction layer affects the hydraulic resistance of the media of vessels of varying wall thickness. The velocity and pressure fields in the media are described using porous matrix theory based on Darcy’s law and a lubrication-type analysis is used to describe the flow in a variable geometry intercellular cleft. These two equations are solved simultaneously to determine the unknown pressure distribution beneath the endothelium and the flow in the arterial media. Application of this model shows that, when the tight junction in the cleft is 26 Å or less, more than half of the total hydraulic resistance of the wall occurs across the endothelial cell monolayer, for a vessel whose wall thickness is less than 0.02 cm. This finding is in good agreement with the experimental findings of Vargas, et al. (1978) for rabbit aorta. Contrary to previous belief, the model shows that the filtration resistance of an arterial wall with intact endothelium does not scale linearly with wall thickness due to the highly nonlinear resistance of the endothelial interaction layer.
A Biomechanical Model of the Posterior Knee Capsule of the Cat
Authors: Hoffman A. H. , Grigg P. , Flynn D. M.
Published: July 2009

A biomechanical model is presented which represents the upper edge of the posterior knee capsule in the cat as a two-segment, vertically loaded catenary suspension cable from which the capsule sheet is suspended. Data are presented which show that the upper edge of the capsule is organized as a cable, which spans the notch between the femoral condyles. When a point load is applied to the cable, measurement of the cable shape allows for calculation of the cable tension and the downward distributed loads acting on the cable. This method was used to measure the in-vivo cable tension and the distributed downward loading acting on the capsule cable. The results show that the lateral side of the posterior joint capsule sustains a higher loading than the medial side.
Long Bone Torsion: I. Effects of Heterogeneity, Anisotropy and Geometric Irregularity
Authors: Kennedy J. G. , Carter D. R.
Published: July 2009

The influences of heterogeneity, anisotropy and geometric irregularity on the unrestrained, linearly elastic torsional response of long bones are assessed. Longitudinal geometric variations contribute insignificantly to the torsional response for typical long bone geometries. Anisotropy, heterogeneity and transverse geometric irregularity significantly influence the torsional response. A procedure is discussed which uses an approximate means to characterize both heterogeneity and anisotropy in predicting the torsional response. The accuracy of circular and elliptical annulus models of the bone cross-sectional geometry are assessed by comparing the stress predictions of these simple models to those of finite element models of the bone geometry.
Long Bone Torsion: II. A Combined Experimental and Computational Method for Determining an Effective Shear Modulus
Authors: Kennedy J. G. , Carter D. R. , Caler W. E.
Published: July 2009

A technique is established which allows an effective torsional shear modulus to be determined for long bones, while remaining nondestructive to whole bone specimens. Strain gages are bonded to the diaphysis of the bone. Strains are then recorded under pure torsional loads. Theoretical stress predictions are combined with experimental strain recordings to arrive at a modulus value. Shear modulus calculations for four canine radii are reported using theoretical stress predictions from circular, elliptical and finite element models of the transverse bone geometry. The effective shear modulus, obtained from an average of the shear moduli determined at strain gage locations, serves to average the heterogeneous shear modulus distribution over the cross section. The shear modulus obtained is that associated with the “circumferential” direction in transverse planes.
The Effect of Conformity and Plastic Thickness on Contact Stresses in Metal-Backed Plastic Implants
Authors: Bartel D. L. , Burstein A. H. , Toda M. D. , Edwards D. L.
Published: July 2009

Surface damage in polyethylene components for total joint replacement is associated with large contact stresses. An elasticity solution and finite element analyses were used to determine the influence of design parameters on the stresses due to contact in metal-backed components. For nearly conforming contact surfaces, it was found that the stresses in the plastic are very sensitive to clearance, that minimum plastic thickness of 4–6 mm should be maintained for metal-backed components, and that bonding the plastic to the metal backing reduces tensile stresses in the plastic at the edge of the contact zone.
Turbulent Stresses in the Region of a Hancock Porcine Bioprosthetic Aortic Valve
Authors: Walburn F. J. , Sabbah H. N. , Stein P. D.
Published: July 2009

The purpose of this study was to measure stresses associated with turbulence (Reynolds stresses), in the region of a 29-mm-dia porcine bioprosthetic valve (Hancock, Model 242). Studies were performed in an in vitro pulse duplicating system with the valve mounted in the aortic position. The Reynolds stresses were calculated from velocities obtained with a two channel laser Doppler anemometer. The largest Reynolds shear stress and normal stress occurred at the highest stroke volume used (80 mL). Averaged over ejection they were 38 dynes/cm2 and 380 dynes/cm2, respectively. The maximal instantaneous Reynolds shear stress was 2500 dynes/cm2 and the maximal instantaneous Reynolds normal stress was 6800 dynes/cm2. Stresses of these magnitudes are in the range reported to damage platelets.
A Transient Heating Technique for the Measurement of Thermal Properties of Perfused Biological Tissue
Authors: Newman W. H. , Lele P. P.
Published: July 2009

Knowledge of tissue thermal transport properties is imperative for any therapeutic medical tool which employs the localized application of heat to perfused biological tissue. In this study, several techniques are proposed to measure local tissue thermal diffusion by heating with a focused ultrasound field. Transient as well as near steady-state heat inputs are discussed and examined for their suitability as a measurement technique for either tissue thermal diffusivity or perfusion rate. It is shown that steady-state methods are better suited for the measurement of perfusion; however the uncertainty in the perfusion measurement is directly related to knowledge of the tissue’s intrinsic thermal diffusivity. Results are presented for a transient thermal pulse technique for the measurement of the thermal diffusivity of perfused and nonperfused tissues, in vitro and in vivo. Measurements conducted in plexiglas, animal muscle, kidney and brain concur with tabulated values and show a scatter from 5–15 percent from the mean; measurements made in perfused muscle and brain compare well with the nonperfused values. An estimate of the error introduced by the effect of perfusion shows that except for highly perfused kidney tissue the effect of perfusion is less than the experimental scatter. This validation of the tissue heat transfer model will allow its eventual extension to the simultaneous measurement of local tissue thermal diffusivity and perfusion.
Finite Element Analysis of a Three-Dimensional Open-Celled Model for Trabecular Bone
Authors: Beaupre G. S. , Hayes W. C.
Published: July 2009

Based on a regular array of cubic unit cells, each containing a body-centered spherical void, we created an idealized three-dimensional model for both subchondral trabecular bone and a class of porous foams. By considering only face-to-face stacking of unit cells, the inherent symmetry was such that, except at the surface, the displacements and stresses within any one unit cell were representative of the entire porous structure. Using prescribed displacements the model was loaded in both uniaxial compressive strain and uniaxial shear strain. Based on the response to these loads, we found the tensor of elastic constants for an equivalent homogeneous elastic solid with cubic symmetry. We then compared the predicted modulus with our experimental values for bovine trabecular bone and literature values for an open-celled latex rubber foam.
Experimental Investigation of Branch Flow Ratio, Angle, and Reynolds Number Effects on the Pressure and Flow Fields in Arterial Branch Models
Authors: Cho Y. I. , Back L. H. , Crawford D. W.
Published: July 2009

An experimental investigation was carried out to acquire an understanding of local pressure changes and flow along the main lumen of arterial branch models similar to the femoral artery of man with three different branch angles (30, 60, and 90 deg) and side branch to the main lumen diameter ratio of 0.4. Effects of branch to main lumen flow rate ratios and physiological Reynolds numbers were found to be significant on the local pressure changes, while that of branch angle was also found to be important. The flow visualization study revealed that the flow separated in the main lumen near the branch junction when the pressure rise coefficient along the main lumen was above a critical value (i.e., 0.35 ∼ 0.46), which was observed to be a function of the Reynolds number. The critical value of the branch to main lumen flow rate ratio was found to be about 0.38 ∼ 0.44 also depending on the Reynolds number. Time averaged pressure distributions for pulsatile flow were similar in trend to steady flow values although they differed somewhat in detail in the main lumen in the branch region.
The Response of Living Tissue to Pulses of a Surgical CO2 Laser
Authors: Armon E. , Laufer G.
Published: July 2009

The response of living tissue to surgical lasers was studied numerically. An algorithm computed the crater boundaries formed by a single laser pulse and the thermochemical damage around this crater. Heat conduction and beam attenuation by tissue vapors were found to be the major factor in the reduction of cutting efficiency.
A General Method for Determining the Functional Role of a Muscle
Authors: Andrews J. G.
Published: July 2009

This paper presents a general classification method for determining the functional role of any muscle, and a procedure for determining the sensitivity of that role to small changes in system parameters. The classification method is based on the premise that the system model, when acted upon solely by the muscle of interest, will depart from any initial rest configuration in such a way as to decrease the muscle’s length. This method is particularly useful for multiple-joint muscles, and is illustrated by examining a slider-crank mechanism and straight line muscle model to determine the functional role of the hamstrings during a constrained leg flexion motion.
Influence of Hypothermia and Circulatory Arrest on Cerebral Temperature Distributions
Authors: Olsen R. W. , Hayes L. J. , Wissler E. H. , Nikaidoh H. , Eberhart R. C.
Published: July 2009

A finite element model of the bioheat transfer equation has been developed to simulate the temperature distribution in the head of a subhuman primate. Simulations were made of the induction of deep hypothermia and of subsequent hypothermic circulatory arrest (HCA). Simulations of the circulatory arrest phase were performed with different values of surface heat transfer coefficient and tissue metabolic heat generation. Numerical results were compared with experimental data for the same procedure. The simulations indicate the brain cools rapidly to a near isothermal condition in response to an infusion of cold arterial blood. However, extracerebral structures cool much more slowly. The bulk of heat gain by the brain during HCA is due to heat transfer from these warmer extra-cerebral tissues. These results suggest extended cooling by cardiopulmonary bypass (CPB) combined with surface cooling pads should reduce or even prevent the rise of brain temperatures during HCA.
The Mechanics of Terminal Lymph Flow
Authors: Miller G. E. , Seale J. L.
Published: July 2009

The effects of external pressure on the terminal lymphatic clearance rate are studied. Sulfur colloid tagged with 99mTc is injected into the subcutaneous tissue in the hind thigh of canines. The activity of the tracer is measured over the injection site for 90 min to determine the lymphatic clearance rate of the sulfur colloid. Several experiments are performed at different external pressures applied to the surface of the canine thigh. A two-compartment model is defined to determine both the terminal lymphatic flow rate per unit volume of tissue and the diffusion constant (sulfur colloid/interstitial fluid) from the raw data. Experimental results indicate that increases in the external pressure applied to the skin cause terminal lymphatic clearance rates to increase until the pressure reaches 60 mm Hg. At this level, some test results showed reduced levels of clearance. At 75 mm Hg, the lymphatic clearance of sulfur colloid from the subcutaneous tissue was stopped suggesting occlusion of the vessels resulting from vessel collapse.
Thermoelasticity with Second Sound: A Review
Authors: Chandrasekharaiah D. S.
Published: July 2009

Thermoelasticity theories predicting a finite speed for the propagation of thermal signals have come into existence during the past 20 years. In contrast to the conventional thermoelasticity theory, these nonclassical theories involve a hyperbolic-type heat transport equation, and are motivated by experiments exhibiting the actual occurrence of wave-type heat transport (second sound). Several authors have formulated these theories on different grounds, and a wide variety of problems revealing characteristic features of the theories has been investigated. This article presents a fairly self-contained bibliographical review of the relevant literature. Novelties involved in the formulations of the theories are emphasized, and concise derivations of the governing equations presented. Results concerned with solutions of initial-boundary value problems are summarized, and salient aspects of the theories illustrated. The list of references is exhaustive and up-to-date.
Boundary Layer Interactions With Compliant Coatings: An Overview
Authors: Gad-el-Hak Mohamed
Published: July 2009

During the past five years, several research programs have been conducted to reexamine the subject of boundary layer interactions with compliant coatings. One of the objectives of the research was to answer the question: Can compliant coatings delay transition and/or significantly reduce turbulence skin friction on bodies at high Reynolds numbers? Several significant developments have been achieved by the many investigators participating in these studies. The purpose of this article is to review the progress in our understanding of compliant coating interactions with laminar, transitional, and turbulent boundary layers. The paper will include some work done prior to the recent five year period and available in the open literature, but will emphasize more recent work, some of which is not as yet published.
Buckling and Postbuckling of Imperfect Cylindrical Shells: A Review
Authors: Simitses George J.
Published: July 2009

Thin-walled cylinders of various constructions are widely used in simple or complex structural configurations. The round cylinder is commonly found in tubing and piping, and in offshore platforms. Depending on their use, these cylinders are subjected (in service) to individual and combined application of external loads. In resisting these loads the system is subject to buckling, a failure mode which is closely associated with the establishment of its load-carrying capacity. Therefore, the system buckling and postbuckling behavior have been the subject of many researchers and investigators both analytical and experimental. The paper is a state-of-the-art survey of the general area of buckling and postbuckling of thin-walled, geometrically imperfect, cylinders of various constructions, when subjected to destabilizing loads. The survey includes discussion of imperfection sensitivity and of the effect of various defects on the critical conditions.
Mechanics-Related Problems of Magnetic Recording Technology and Ink-Jet Printing
Authors: Bogy D. B. , Talke F. E.
Published: July 2009

In this paper, mechanical aspects of magnetic recording technology and nonimpact printing are discussed. In the recording area, theoretical and experimental aspects of air bearing theory, head/disk dynamics, and head/disk tribology are studied. Flutter of rotating disks is investigated, the flow field between rotating disks is described, and nonrepeatable run-out of disk file spindles is studied. Furthermore, the head/disk interface for flexible media is discussed and dimensional stability of flexible substrate is examined. In the printing area, experimental and theoretical investigations using continuous and drop-on-demand fluid jets are presented, and numerical calculations of the drop formation process in drop-on-demand fluid jets are described.
Practical Aspects of Finite Element Computations in Solid Mechanics
Authors: Hibbitt H. D.
Published: July 2009

The paper focuses on practical aspects of the prospective use of finite element methods in problems in solid mechanics. It looks briefly at the computer and computer language environment in which the methods are used, and at the computational aspects of the numerical method itself. The fundamental algorithmic problems (spatial and temporal discretization, and the modeling of realistic material behaviors) are reviewed from an applications viewpoint, and some areas where further work is needed are mentioned.
Applied Mechanics Problems in Automotive Engineering
Authors: Howell L. J.
Published: July 2009

The automotive industry is undergoing a technological revolution unparalleled since its infancy. Increased foreign competition, particularly in terms of product cost, has created a need for technological innovation both in automotive products and in automotive manufacturing and assembly processes. Applied mechanics research has become a critical element in many of the areas which can promote improved products and process efficiency. Several major research programs which are underway at General Motors will be reviewed and used to motivate the discussion of important applied mechanics problems. Research examples will include automated vehicle design technology, advanced materials, and mechanics of manufacturing processes. Suggested research spans the entire range of the applied mechanics field, from basic theory to numerical applications. Experimental research is as vital to further progress as is analytical research. Considerably more emphasis should be given to relating mechanical performance of the finished product to its fabrication.
Thermal Management of Electronic Equipment: A Review of Technology and Research Topics
Authors: Nakayama Wataru
Published: July 2009

Increasing miniaturization of microcircuits on chips of increasing size and new schemes of electrical connection, such as flip-chip bonding and surface mounting, are setting more demanding criteria regarding the thermal field within electronic equipment. While the search for a solution to meet a set of prescribed design criteria is becoming more complex, the body of available data needed to perform such a search is quite small. This article describes the two primary functions to be implemented by electronic heat transfer research: the definition of thermal design criteria and the establishment of a thermal packaging database. Examples of actual designs of packages are drawn from recent publications to illustrate the points of technical importance. The examples are packages of DRAM chips, flat-leaded packages of logic chips, and modules with dismountable heat sinks. These examples are used to address thermal stress problems, the problems of fin design, and thermal interface management, respectively. In the section on natural convection cooling, the effects of various factors on the uncertainties pertaining to heat transfer coefficient are assessed in light of the correlations proposed in the current literature. The section on forced convection cooling deals with the problem of heat transfer from an array of packages in a parallel-plate channel. The final section is devoted to the research topics of nucleate boiling heat transfer enhancement, from the surface of a small component, and microchannel cooling.
On Experimental Studies of Longitudinal and Flexural Wave Propagations: An Annotated Bibliography
Authors: Al-Mousawi M. M.
Published: July 2009

Experimental investigations in the field of longitudinal wave propagation in beams are plentiful; however, experimental studies of flexural wave propagation problems are scarce and are restricted mainly to uniform and infinite structures where the effects of reflected waves are not generally included. This review is mostly restricted to low velocity impact and does not cover the so-called high velocity impact such as those of bullets and explosives. In addition to a brief survey of classical work related to impact, this article covers publications related to experimental studies of longitudinal and flexural elastic waves due to impact. This includes the longitudinal, central as well as eccentric impact and transverse impact of two bars and the impact achieved by sphere impinging on a beam. Many workers used experimental findings to study the adequacy of various theoretical solutions of the wave propagation problem such as those by Pochhammer and Chree, Euler–Bernoulli, and the Timoshenko beam theory. The revival of interest in the recent years is due to, among other things, the advancement of experimental equipment and measurement techniques for data acquisition of stress waves and associated signals. An important application of transient waves is their use for the determination of material properties under various loading conditions and strain rates that can be studied by the split Hopkinson pressure bar techniques. The problem of longitudinal and flexural waves in bars with discontinuities of cross section are covered, and some publications on fracture of materials due to bending waves are also included. Experimental investigations demonstrate the effect of abrupt change of cross section and/or material properties on reflected and transmitted waves where reflections are to be taken into consideration when estimating the level of stresses and strains in finite beam with discontinuities. In the field of flexural wave propagation, comparison of theoretical predictions with experimental results verified and validated the adequacy of the Timoshenko theory for the determination of bending strain in finite structures, a one-dimensional theory that takes into account the effect of shear deformation and rotatory inertia.
Inverse Problems in Vibration
Authors: Gladwell Graham M. L.
Published: July 2009

This article concerns infinitesimal free vibrations of undamped elastic systems of finite extent. A review is made of the literature relating to the unique reconstruction of a vibrating system from natural frequency data. The literature is divided into two groups—those papers concerning discrete systems, for which the inverse problems are closely related to matrix inverse eigenvalue problems, and those concerning continuous systems governed either by one or the other of the Sturm–Liouville equations or by the Euler–Bernoulli equation for flexural vibrations of a thin beam.
Hidden (A)Symmetries of Elastic and Plastic Bifurcation
Authors: Hunt G. W.
Published: July 2009

Buckling at a distinct bifurcation point is more often than not symmetric, in the sense that equal and opposite amplitudes of the single buckling mode give identical physical shapes and hence energy levels. It is also commonly the case that combinations of modes break such symmetries, so that when critical loads are close (and sometimes when they are not), the preferred buckling involves a strong interaction between more than one mode. A single cubic cross-term of potential energy, readily identifiable from certain symmetry tests, then dominates the early (unstable) post-buckling, which later may be restabilized by positive quartic terms. In such instances the equilibrium paths over large deflections frequently exhibit a specific looping form, with an accompanying remote bifurcation, which was first predicted from a specialized application of the theorems underlying catastrophe theory. A number of well-known, and quite different, structural examples are given. A simple spring and link model due to Budiansky and Hutchinson, with a close similarity to the well-known Shanley model, shows that the latter can be interpreted in this manner, despite its being a problem of plastic bifurcation. Interactive buckling in sandwich panels, and in the long axially-loaded cylinder, provide two practical examples, others also being identified. A pilot scheme of perturbation analysis specifically designed to handle such problems is described, and used with considerable accuracy on the two link models, as demonstrated by comparison with exact solutions.
Inhibition of Intracellular Growth of
Salmonella enterica
Serovar Typhimurium in Tissue Culture by Antisense Peptide-Phosphorodiamidate Morpholino Oligomer
Authors: Mitev Georgi M. , Mellbye Brett L. , Iversen Patrick L. , Geller Bruce L.
Published: July 2009

Two types of phosphorodiamidate morpholino oligomers (PMOs) were tested for inhibition of growth of
Salmonella enterica
serovar Typhimurium. Both PMOs have the same 11-base sequence that is antisense to the region near the start codon of
acpP
, which is essential for lipid biosynthesis and viability. To the 3′ end of each is attached the membrane-penetrating peptide (RXR)
4
XB (R, X, and B indicate arginine, 6-aminohexanoic acid, and β-alanine, respectively). One peptide-PMO (AcpP PPMO) has no charge on the PMO moiety. The second PPMO has three cations (piperazine) attached to the phosphorodiamidate linkages (3+Pip-AcpP PPMO). A scrambled-sequence PPMO (Scr PPMO) was synthesized for each type of PMO. The MICs of AcpP PPMO, 3+Pip-AcpP PPMO, and either one of the Scr PPMOs were 1.25 μM (7 μg/ml), 0.156 μM (0.94 μg/ml), and >160 μM (>900 μg/ml), respectively. 3+Pip-AcpP PPMO at 1.25 or 2.5 μM significantly reduced the growth rates of pure cultures, whereas AcpP PPMO or either Scr PPMO had no effect. However, the viable cell count was significantly reduced at either concentration of 3+Pip-AcpP PPMO or AcpP PPMO, but not with either Scr PPMO. In other experiments, macrophages were infected intracellularly with
S. enterica
and treated with 3 μM 3+Pip-AcpP PPMO. Intracellular bacteria were reduced >99% with 3+Pip-AcpP PPMO, whereas intracellular bacteria increased 3 orders of magnitude in untreated or Scr PPMO-treated cultures. We conclude that either AcpP PPMO or 3+Pip-AcpP PPMO inhibited growth of
S. enterica
in pure culture and that 3+Pip-AcpP PPMO reduced intracellular viability of
S. enterica
in macrophages.
Contribution of
dfrA
and
inhA
Mutations to the Detection of Isoniazid-Resistant
Mycobacterium tuberculosis
Isolates
Authors: Ho Yu Min , Sun Yong-Jiang , Wong Sin-Yew , Lee Ann S. G.
Published: July 2009

Screening of 127 isoniazid (INH)-resistant
Mycobacterium tuberculosis
isolates from Singapore for mutations within the
dfrA
and
inhA
genes revealed mutations in 0 and 5 (3.9%) isolates respectively, implying that mutations in
dfrA
do not contribute to the detection of INH-resistant
M. tuberculosis
and that mutations within
inhA
are rare. Thirty-seven (29%) of the 127 isolates had no mutations in any of the genes implicated in INH resistance (
katG
,
kasA
, and
ndh
;
inhA
and
ahpC
promoters), suggesting that there are new INH targets yet to be discovered.
Combination Chemotherapy against
Clonorchis sinensis
: Experiments with Artemether, Artesunate, OZ78, Praziquantel, and Tribendimidine in a Rat Model
Authors: Keiser Jennifer , Xiao Shu-Hua , Smith Thomas A. , Utzinger Jürg
Published: July 2009

Caused by the Chinese liver fluke
Clonorchis sinensis
, clonorchiasis is of growing public health importance. Treatment and control of the disease rely on a single drug, praziquantel, and little information regarding combination chemotherapy is available. Here, we evaluated the in vivo efficacy of praziquantel combined with artemether, artesunate, OZ78, and tribendimidine, as well as an artesunate-tribendimidine combination against
C. sinensis
, in a rat model. Data from previous experiments were included, and negative binomial regression analyses were carried out to determine dose-response relationships and to study the effect of drug combination. All drugs given in monotherapy were efficacious in killing the worms; doses of 16 and 70 mg/kg of body weight of artesunate, for example, reduced worm burden by 50% and 95%, respectively. Artemether and OZ78 (12.5 to 50 mg/kg) showed dose-dependent killing of worms but no significant drug interactions when given with 150 mg/kg praziquantel, suggesting independent additive effects. In contrast, artesunate and tribendimidine (12.5 to 50 mg/kg) showed synergistic interactions with 150 mg/kg praziquantel. When low doses of 3.1 and 6.25 mg/kg OZ78 and artemether, respectively, were combined with praziquantel (150 mg/kg) an increased worm survival, above the level observed with praziquantel monotherapy, was noted. A similar antagonism was seen when praziquantel (75 mg/kg) was combined with several of the companion drugs at various doses. In conclusion, in vivo efficacy of praziquantel, the artemisinins, OZ78, and tribendimidine against
C. sinensis
is confirmed, and combination chemotherapy with praziquantel produces synergistic and antagonistic effects depending on the doses administered. Further preclinical investigations are warranted.
Intravenous Doripenem at 500 Milligrams versus Levofloxacin at 250 Milligrams, with an Option To Switch to Oral Therapy, for Treatment of Complicated Lower Urinary Tract Infection and Pyelonephritis
Authors: Naber K. G. , Llorens L. , Kaniga K. , Kotey P. , Hedrich D. , Redman R.
Published: July 2009

The prospective, multicenter, double-blind study presented in this report evaluated whether or not intravenous (IV) administration of doripenem, a carbapenem with bactericidal activity against gram-negative and gram-positive uropathogens, is inferior to IV administration of levofloxacin in the treatment of complicated urinary tract infection (cUTI). Patients (
n
= 753) with complicated lower UTI or pyelonephritis were randomly assigned to receive IV doripenem at 500 mg every 8 h (q8h) or IV levofloxacin at 250 mg q24h. Patients in both treatment arms were eligible to switch to oral levofloxacin after 3 days of IV therapy to complete a 10-day treatment course if they demonstrated significant clinical and microbiological improvements. The microbiological cure rate (primary end point) was determined at the test-of-cure (TOC) visit occurring 5 to 11 days after the last dose of antibiotic. For the microbiologically evaluable patients (
n
= 545), the microbiological cure rates were 82.1% and 83.4% for doripenem and levofloxacin, respectively (95% confidence interval [CI] for the difference, −8.0 to 5.5%); in the microbiological modified intent-to-treat cohort (
n
= 648), the cure rates were 79.2% and 78.2%, respectively. Clinical cure rates at the TOC visit were 95.1% in the doripenem arm and 90.2% in the levofloxacin arm (95% CI around the difference in cure rates [doripenem cure rate minus levofloxacin cure rate], 0.2% to 9.6%). Both treatment regimens were generally well tolerated. Doripenem was found not to be inferior to levofloxacin in terms of therapeutics and is now approved for use in the United States and Europe for the treatment of adults with cUTI, including pyelonephritis. As fluoroquinolone resistance increases, doripenem may become a more important option for successful treatment of cUTIs, including treatment of pyelonephritis.
In Vitro Activities of Telavancin and Six Comparator Agents against Anaerobic Bacterial Isolates
Authors: Finegold Sydney M. , Bolanos Mauricio , Sumannen Paula H. , Molitoris Denise R.
Published: July 2009

The antimicrobial activities of telavancin and six comparators were evaluated against 460 isolates of anaerobic bacteria. Telavancin demonstrated excellent activity against gram-positive anaerobes (MIC
90
, 2 μg/ml) and was the most potent agent tested against
Clostridium difficile
(MIC
90
, 0.25 μg/ml). As expected, gram-negative isolates were not inhibited by telavancin.
Impact of Therapeutic Treatment with β-Lactam on Transfer of the
bla
CTX-M-9
Resistance Gene from
Salmonella enterica
Serovar Virchow to
Escherichia coli
in Gnotobiotic Rats
Authors: Faure Stéphanie , Perrin-Guyomard Agnès , Delmas Jean-Michel , Laurentie Michel
Published: July 2009

The conjugative transfer of the plasmid carrying the
bla
CTX-M-9
gene from
Salmonella enterica
serovar Virchow isolated from a chicken farm to a recipient
Escherichia coli
strain was evaluated in vitro and in axenic rats inoculated with both strains, with or without selective pressure due to therapeutic doses of cefixime. The transfer of the
bla
CTX-M-9
gene of
S. enterica
serovar Virchow to
E. coli
was confirmed in vitro, at a low frequency of 5.9 × 10
−8
transconjugants/donors. This transfer rate was higher in gnotobiotic rats and reached ∼10
−5
transconjugants/donors without selective pressure. This frequency was not affected by the addition of therapeutic doses of cefixime. Thus, estimates of in vitro transfer underestimated potential transfer in the digestive tract, and therapeutic doses of cefixime did not increase the selection for transconjugants.
Norovirus Distribution within an Estuarine Environment
Authors: Gentry Jennifer , Vinjé Jan , Guadagnoli Dominic , Lipp Erin K.
Published: July 2009

Human norovirus (NoV) has been studied extensively as an important cause of gastroenteritis outbreaks worldwide. While oysters are a primary vehicle for infection, few studies have examined the wider distribution of NoV in the estuarine environment. Active shellfish-harvesting areas in Georgia were examined for the prevalence, genotype diversity, and concentrations of NoV in a variety of estuarine sample types over the course of 1 year. Of the 225 samples (9 oyster, 72 water, 72 63- to 200-μm plankton, and 72 >200-μm plankton) collected from 12 stations across two estuaries, 21 samples (9.3%) tested positive for NoV. By sample type, 55.0% (5/9) of oysters, 8.3% (6/72) of water samples, 11.1% (8/72) of 63- to 200-μm plankton samples, and 2.8% (2/72) of >200-μm plankton samples were positive for human NoV. The two NoV-positive >200-μm plankton samples, which contained mainly zooplankton, had the greatest quantity of NoV genomes (3.5 × 10
13
and 1.7 × 10
15
genomes g
−1
) of any sample tested. The majority, 90.5% (19/21), of the samples tested positive for genogroup I NoV, and only 9.5% (2/21) of the samples tested positive for genogroup II. The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human NoV in the water environment.
Establishment of
Agrobacterium tumefaciens
-Mediated Transformation of an Oleaginous Fungus,
Mortierella alpina
1S-4, and Its Application for Eicosapentaenoic Acid Producer Breeding
Authors: Ando Akinori , Sumida Yosuke , Negoro Hiroaki , Suroto Dian Anggraini , Ogawa Jun , Sakuradani Eiji , Shimizu Sakayu
Published: July 2009

Gene manipulation tools for an arachidonic-producing filamentous fungus,
Mortierella alpina
1S-4, have not been sufficiently developed. In this study,
Agrobacterium tumefaciens
-mediated transformation (ATMT) was investigated for
M. alpina
1S-4 transformation, using the uracil-auxotrophic mutant (
ura5
−
strain) of
M. alpina
1S-4 as a host strain and the homologous
ura5
gene as a selectable marker gene. Furthermore, the gene for ω3-desaturase, catalyzing the conversion of n-6 fatty acid to n-3 fatty acid, was overexpressed in
M. alpina
1S-4 by employing the ATMT system. As a result, we revealed that the frequency of transformation surpassed 400 transformants/10
8
spores, most of the integrated T-DNA appeared as a single copy at a random position in chromosomal DNA, and most of the transformants (60 to 80%) showed mitotic stability. Moreover, the accumulation of n-3 fatty acid in transformants was observed under the conditions of optimal ω3-desaturase gene expression. In particular, eicosapentaenoic acid (20:5n-3), an end product of n-3 fatty acids synthesized in
M. alpina
1S-4, reached a maximum of 40% of total fatty acids. In conclusion, the ATMT system was found to be effective and suitable for the industrial strain
Mortierella alpina
1S-4 and will be a useful tool for basic mutagenesis research and for industrial breeding of this strain.
Characterization of Mundticin L, a Class IIa Anti-
Listeria
Bacteriocin from
Enterococcus mundtii
CUGF08
Authors: Feng Guoping , Guron Giselle K. P. , Churey John J. , Worobo Randy W.
Published: July 2009

Enterococcus mundtii
CUGF08, a lactic acid bacterium isolated from alfalfa sprouts, was found to produce mundticin L, a new class IIa bacteriocin that has a high level of inhibitory activity against the genus
Listeria
. The plasmid-associated operons containing genes for the mundticin L precursor, the ATP binding cassette (ABC) transporter, and immunity were cloned and sequenced. The fifth residue of the conservative consensus sequence YGNGX in the mature bacteriocin is leucine instead of valine in the sequences of the homologous molecules mundticin KS (ATO6) and enterocin CRL35. The primary structures of the ABC transporter and the immunity protein are homologous but unique.
Tolerance of theRalstonia eutrophaClass I Polyhydroxyalkanoate Synthase for Translational Fusions to Its C Terminus Reveals a New Mode of Functional Display
Authors: Jahns Anika C. , Rehm Bernd H. A.
Published: July 2009

Here, the class I polyhydroxyalkanoate synthase (PhaC) fromRalstonia eutrophawas investigated regarding the functionality of its conserved C-terminal region and its ability to tolerate translational fusions to its C terminus. MalE, the maltose binding protein, and green fluorescent protein (GFP) were considered reporter proteins to be translationally fused to the C terminus. Interestingly, PhaC remained active only when a linker was inserted between PhaC and MalE, whereas MalE was not functional. However, the extension of the PhaC N terminus by 458 amino acid residues was required to achieve a functionality of MalE. These data suggested a positive interaction of the extended N terminus with the C terminus. To assess whether a linker and/or N-terminal extension is generally required for a functional C-terminal fusion, GFP was fused to the C terminus of PhaC. Both fusion partners were active without the requirement of a linker and/or N-terminal extension. A further reporter protein, the immunoglobulin G binding ZZ domain of protein A, was translationally fused to the N terminus of the fusion protein PhaC-GFP and resulted in a tripartite fusion protein mediating the production of polyester granules displaying two functional protein domains.
Cloning of a Novel Pyrethroid-Hydrolyzing Carboxylesterase Gene from
Sphingobium
sp. Strain JZ-1 and Characterization of the Gene Product
Authors: Wang Bao-zhan , Guo Peng , Hang Bao-jian , Li Lian , He Jian , Li Shun-peng
Published: July 2009

A novel esterase gene,
pytH
, encoding a pyrethroid-hydrolyzing carboxylesterase was cloned from
Sphingobium
sp. strain JZ-1. The gene contained an open reading frame of 840 bp. Sequence identity searches revealed that the deduced enzyme shared the highest similarity with many α/β-hydrolase fold proteins (20 to 24% identities). PytH was expressed in
Escherichia coli
BL21 and purified using Ni-nitrilotriacetic acid affinity chromatography. It was a monomeric structure with a molecular mass of approximately 31 kDa and a pI of 4.85. PytH was able to transform
p
-nitrophenyl esters of short-chain fatty acids and a wide range of pyrethroid pesticides, and isomer selectivity was not observed. No cofactors were required for enzyme activity.
DYF-1 Is Required for Assembly of the Axoneme in
Tetrahymena thermophila
Authors: Dave Drashti , Wloga Dorota , Sharma Neeraj , Gaertig Jacek
Published: July 2009

In most cilia, the axoneme can be subdivided into three segments: proximal (the transition zone), middle (with outer doublet microtubules), and distal (with singlet extensions of outer doublet microtubules). How the functionally distinct segments of the axoneme are assembled and maintained is not well understood. DYF-1 is a highly conserved ciliary protein containing tetratricopeptide repeats. In
Caenorhabditis elegans
, DYF-1 is specifically needed for assembly of the distal segment (G. Ou, O. E. Blacque, J. J. Snow, M. R. Leroux, and J. M. Scholey. Nature. 436:583-587, 2005). We show that
Tetrahymena
cells lacking an ortholog of DYF-1, Dyf1p, can assemble only extremely short axoneme remnants that have structural defects of diverse natures, including the absence of central pair and outer doublet microtubules and incomplete or absent B tubules on the outer microtubules. Thus, in
Tetrahymena
, DYF-1 is needed for either assembly or stability of the entire axoneme. Our observations support the conserved function for DYF-1 in axoneme assembly or stability but also show that the consequences of loss of DYF-1 for axoneme segments are organism specific.
Further Characterization of the
epa
Gene Cluster and Epa Polysaccharides of
Enterococcus faecalis
Authors: Teng Fang , Singh Kavindra V. , Bourgogne Agathe , Zeng Jing , Murray Barbara E.
Published: July 2009

We previously identified a gene cluster,
epa
(for
e
nterocococcal
p
olysaccharide
a
ntigen), involved in polysaccharide biosynthesis of
Enterococcus faecalis
and showed that disruption of
epaB
and
epaE
resulted in attenuation in translocation, biofilm formation, resistance to polymorphonuclear leukocyte (PMN) killing, and virulence in a mouse peritonitis model. Using five additional mutant disruptions in the 26-kb region between
orfde2
and OG1RF_0163, we defined the
epa
locus as the area from
epaA
to
epaR
. Disruption of
epaA
,
epaM
, and
epaN
, like prior disruption of
epaB
and
epaE
, resulted in alteration in Epa polysaccharide content, more round cells versus oval cells with OG1RF, decreased biofilm formation, attenuation in a mouse peritonitis model, and resistance to lysis by the phage NPV-1 (known to lyse OG1RF), while mutants disrupted in
orfde2
and OG1RF_163 (the
epa
locus flanking genes) behaved like OG1RF in those assays. Analysis of the purified Epa polysaccharide from OG1RF revealed the presence of rhamnose, glucose, galactose, GalNAc, and GlcNAc in this polysaccharide, while carbohydrate preparation from the
epaB
mutant did not contain rhamnose, suggesting that one or more of the glycosyl transferases encoded by the
epaBCD
operon are necessary to transfer rhamnose to the polysaccharide. In conclusion, the
epa
genes, uniformly present in
E. faecalis
strains and involved in biosynthesis of polysaccharide in OG1RF, are also important for OG1RF shape determination, biofilm formation, and NPV-1 replication/lysis, as well as for
E. faecalis
virulence in a mouse peritonitis model.