bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo pharmacodynamic interactions between two drugs used in orthostatic hypotension – midodrine and dihydroergotamine
Authors: Jourdan Géraldine , Verwaerde Patrick , Pathak Atul , Tran Marie‐Antoinette , Montastruc Jean‐Louis , Senard Jean‐Michel
Published: December 2006

A combination of midodrine and dihydroergotamine (DHE) is frequently used clinically in patients suffering from severe orthostatic hypotension (OH). Whereas midodrine acts as a selective, peripheral alpha1‐receptor agonist, DHE displays complex pharmacology and can behave as an alpha‐adrenergic receptor agonist or antagonist. Surprisingly, the consequences of such a combination on blood pressure have never been investigated. The present study was performed in order to evaluate the pressor effects induced by the administration of both midodrine and DHE in old conscious dogs (n = 6) in experimental condition reproducing autonomic failure‐related baroreflex dysfunction (atropine 0.1 mg/kg). For this purpose, we first studied the relative potency and intrinsic activity of each agonist and noradrenaline (NA) for the alpha1‐adrenergic receptor. The orders of potency obtained in our study were 0.35, 11 and 400 μg/kg for NA, DHE and midodrine, and intrinsic activity: NA > midodrine > DHE. These results strongly suggest that DHE really acts in vivo as an alpha1‐adrenoceptor partial agonist. Afterwards, the pressor effects of coadministration of midodrine (0.4 mg/kg) and DHE (15 μg/kg) were investigated: in one setting, midodrine was first administered, followed by DHE; in another, DHE was first administered, followed by midodrine. Our results show that in conscious dogs, the combination of midodrine and DHE leads to near‐complete abolition of the pressor effect induced by the first administered drug. This in vivo proof of such antagonistic effects on blood pressure could explain clinical observations of worsening of OH in humans administered midodrine plus DHE. Although in vivo results obtained in conscious healthy dogs need to be experimentally and clinically confirmed in humans suffering from OH, these results strongly suggest that a midodrine–DHE combined treatment should be avoided in clinical practice.
CO2 elimination at varying inspiratory pause in acute lung injury
Authors: Aboab J. , Niklason L. , Uttman L. , Kouatchet A. , Brochard L. , Jonson B.
Published: December 2006

Previous studies have indicated that, during mechanical ventilation, an inspiratory pause enhances gas exchange. This has been attributed to prolonged time during which fresh gas of the tidal volume is present in the respiratory zone and is available for distribution in the lung periphery. The mean distribution time of inspired gas (MDT) is the mean time during which fractions of fresh gas are present in the respiratory zone. All ventilators allow setting of pause time, TP, which is a determinant of MDT. The objective of the present study was to test in patients the hypothesis that the volume of CO2 eliminated per breath, VTCO2, is correlated to the logarithm of MDT as previously found in animal models. Eleven patients with acute lung injury were studied. When TP increased from 0% to 30%, MDT increased fourfold. A change of TP from 10% to 0% reduced VTCO2 by 14%, while a change to 30% increased VTCO2 by 19%. The relationship between VTCO2 and MDT was in accordance with the logarithmic hypothesis. The change in VTCO2 reflected to equal extent changes in airway dead space and alveolar PCO2 read from the alveolar plateau of the single breath test for CO2. By varying TP, effects are observed on VTCO2, airway dead space and alveolar PCO2. These effects depend on perfusion, gas distribution and diffusion in the lung periphery, which need to be further elucidated.
Reliability and validity of the lung volume measurement made by the BOD POD body composition system
Authors: Davis James A. , Dorado Silvia , Keays Kathleen A. , Reigel Kimberly A. , Valencia Kristoffer S. , Pham Patrick H.
Published: December 2006

The BOD POD Body Composition System uses air‐displacement plethysmography to measure body volume. To correct the body volume measurement for the subject's lung volume, the BOD POD utilizes pulmonary plethysmography to measure functional residual capacity (FRC) at mid‐exhalation as that is the subject's lung volume during the body volume measurement. Normally, FRC is measured at end‐exhalation. The BOD POD FRC measurement can be corrected to an end‐exhalation volume by subtracting approximately one‐half of the measured tidal volume. Our purpose was to determine the reliability and validity of the BOD POD FRC measurement at end‐exhalation. Ninety‐two healthy adults (half female) underwent duplicate FRC measurements by the BOD POD and one FRC measurement by a traditional gas dilution technique. The latter method was used as the reference method for the validity component of the study. The order of the FRC measurements by the two methods was randomized. The test–retest correlation coefficients for the duplicate BOD POD FRC measurements for the male and female subjects were 0·966 and 0·948, respectively. The mean differences between the BOD POD FRC trial #1 measurement and gas dilution FRC measurement for the male and female subjects were −32 and −23 ml, respectively. Neither difference was statistically significant. The correlation coefficients for these two measurements in the male and female subjects were 0·925 and 0·917, respectively. Based on these results, we conclude that the BOD POD FRC measurement in healthy males and females is both reliable and valid.
Disturbed glucose metabolism is associated with left ventricular dysfunction using tissue Doppler imaging in patients with myocardial infarction
Authors: Henareh Loghman , Lind Britta , Brodin Lars‐Åke , Agewall Stefan
Published: December 2006

Aims:  To investigate the association between glucose abnormalities and left ventricular (LV) function assessed by tissue Doppler imaging (TDI) in patients with previous history of myocardial infarction and without known diabetes mellitus.

Patients and methods:  In a cross‐sectional study, 123 patients, aged 31–80 years, with a history of previous myocardial infarction and without known diabetes mellitus were examined with TDI echocardiography. A standard oral glucose test (OGTT) with 75 g of glucose was performed.

Results:  Two‐hour plasma glucose were significantly and negatively associated with TDI parameters such as LV ejection time; early diastolic filling velocity (E′‐v); ratio of the early to late diastolic filling velocity (E′/A′) and positively associated with regional myocardial performance index (MPI) (P<0·05). Left ventricular ejection time and MPI were significantly higher; E′/A′ and E′‐v were significantly lower in patients with disturbed glucose metabolism compared with patients with normal glucose tolerance (P<0·01). These differences remain significant also when the patients with DM were excluded.

Conclusions:  The present study demonstrates that disturbed glucose metabolism is associated with more pronounced LV dysfunction using TDI in patients with myocardial infarction. These abnormalities in LV function were more common not only in subjects with diabetes, but also in patients with prediabetic condition, impaired glucose intolerance.
Disjoining Pressure Effects in Ultra-Thin Liquid Films in Micropassages—Comparison of Thermodynamic Theory With Predictions of Molecular Dynamics Simulations
Authors: Carey V. P. , Wemhoff A. P.
Published: December 2006

The concept of disjoining pressure, developed from thermodynamic and hydrodynamic analysis, has been widely used as a means of modeling the liquid-solid molecular force interactions in an ultra-thin liquid film on a solid surface. In particular, this approach has been extensively used in models of thin film transport in passages in micro evaporators and micro heat pipes. In this investigation, hybrid μPT molecular dynamics (MD) simulations were used to predict the pressure field and film thermophysics for an argon film on a metal surface. The results of the simulations are compared with predictions of the classic thermodynamic disjoining pressure model and the Born-Green-Yvon (BGY) equation. The thermodynamic model provides only a prediction of the relation between vapor pressure and film thickness for a specified temperature. The MD simulations provide a detailed prediction of the density and pressure variation in the liquid film, as well as a prediction of the variation of the equilibrium vapor pressure variation with temperature and film thickness. Comparisons indicate that the predicted variations of vapor pressure with thickness for the three models are in close agreement. In addition, the density profile layering predicted by the MD simulations is in qualitative agreement with BGY results, however the exact density profile is dependent upon simulation parameters. Furthermore, the disjoining pressure effect predicted by MD simulations is strongly influenced by the allowable propagation time of injected molecules through the vapor region in the simulation domain. A modified thermodynamic model is developed that suggests that presence of a wall-affected layer tends to enhance the reduction of the equilibrium vapor pressure. However, the MD simulation results imply that presence of a wall layer has little effect on the vapor pressure. Implications of the MD simulation predictions for thin film transport in micro evaporators and heat pipes are also discussed.
Evaporation/Boiling in Thin Capillary Wicks (II)—Effects of Volumetric Porosity and Mesh Size
Authors: Li Chen , Peterson G. P.
Published: December 2006

Presented here is the second of a two-part investigation, designed to systematically identify and investigate the parameters affecting the evaporation from and boiling within, thin capillary wicking structures with a range of volumetric porosities and mesh sizes. The experimental studies were investigated under steady-state conditions at atmospheric pressure. Part I of the investigation described the wicking fabrication process and experimental test facility, and focused on the effects of the capillary wick thickness (ASME J. Heat Transfer., 128, pp. 1312–1319). In Part II, we examine the effects of variations in the volumetric porosity and the mesh size. The experimental results presented here indicate that the critical heat flux (CHF) was strongly dependent on both the mesh size and the volumetric porosity; while the evaporation/boiling heat transfer coefficient was significantly affected by mesh size, but not strongly dependent on the volumetric porosity. The experimental results further illustrate that the menisci at the CHF are located in the corners, formed by the wire and the heated wall and between the wires in both the vertical and horizontal directions. The minimum value of these three menisci determined the maximum capillary pressure generated through the capillary wick. The experimental results and observations are systematically presented and analyzed, and the local bubble and liquid vapor interface dynamics are examined theoretically. Based on the relative relationship between the heat flux and superheat, classic nucleate boiling theory, and the visual observations of the phase-change phenomena, as well as by combining the results obtained here with those obtained in Part I of the investigation, the evaporation/boiling heat transfer regimes in these capillary wicking structures are identified and discussed.
Operating Characteristic Investigations in Pulsating Heat Pipe
Authors: Cai Qingjun , Chen Chung-lung , Asfia Julie F.
Published: December 2006

Pulsating heat pipe (PHP) is an interesting heat transfer device. In this paper we focus on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both the total temperature differences (from the evaporator to condenser) and the evaporator temperature fluctuations are relevant to operating temperature. The minimal total temperature difference and temperature fluctuation appear at an operating temperature ranging from 120°Cto160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large total temperature difference and temperature fluctuation. Phase change proportion increases at the optimal operating temperature. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus the operating temperature.
Numerical Study of an Evaporating Meniscus on a Moving Heated Surface
Authors: Mukherjee Abhijit , Kandlikar Satish G.
Published: December 2006

The present study is performed to numerically analyze an evaporating meniscus bounded between the advancing and receding interfaces on a moving heated surface. The numerical scheme developed for analyzing interface motion during bubble growth in pool boiling has been applied. A column of liquid is placed between a nozzle outlet and a moving wall, and calculations are done in two dimensions with a fixed distance between the nozzle and the wall. The results show that the wall velocity creates a circulation near the meniscus base, resulting in transient heat conduction. The local wall heat transfer is found to vary significantly along the meniscus base, the highest being near the advancing contact line. The heat transfer coefficient is found to depend on the advancing contact angle and wall velocity but is independent of the wall superheat. Reasonable agreement is observed when the meniscus profile and heat transfer results obtained from the numerical simulation are compared to the experimental data.
Dynamic Anti-Integrator-Windup Controller Design for Linear Systems With Actuator Saturation
Authors: Kanamori Mitsuru , Tomizuka Masayoshi
Published: December 2006

The present paper is concerned with the design of dynamic anti-integrator-windup controllers for critically stable linear systems with a single pole at the origin. The constant gain term in the conventional anti-windup controller is extended to have dynamics represented by a transfer function. The proposed dynamic anti-windup compensator is similar to the one based on co-prime factorization of the plant. The overall controller includes an internal model for constant signals and achieves regulation for constant disturbance and reference inputs as long as the asymptotic control input stays within the saturation limits. The effectiveness of the proposed method is demonstrated on a one-link flexible arm through simulations and experiments.
Model-Based Fuel Optimal Control of Hybrid Electric Vehicle Using Variable Structure Control Systems
Authors: Wei X. , Guzzella L. , Utkin V. I. , Rizzoni G.
Published: December 2006

Hybrid electric vehicles provide promising alternatives to conventional engine-powered vehicles with better fuel economy and less emission. Realization of these benefits depends, in part, on proper control of the vehicle. This paper examines a variable structure control that switches between two operating points. The resulting sliding optimal control provides a better energy management strategy than that obtained conventionally from Pontryagin’s minimum principle. Since one of the operating points is at zero engine power, this sliding optimal control is also referred to as engine start-stop strategy. Contrary to the general understanding that the engine should only stop at low speeds or during decelerations, it is shown that engine start-stop also improves fuel economy during highway cruising. The main contribution of this paper is to theoretically prove that this “duty-cycle” operation mode is indeed optimal using Pontryagin’s minimum principle.
Intake Air Path Diagnostics for Internal Combustion Engines
Authors: Franchek Matthew A. , Buehler Patrick J. , Makki Imad
Published: December 2006

Presented is the detection, isolation, and estimation of faults that occur in the intake air path of internal combustion engines during steady state operation. The proposed diagnostic approach is based on a static air path model, which is adapted online such that the model output matches the measured output during steady state conditions. The resulting changes in the model coefficients create a vector whose magnitude and direction are used for fault detection and isolation. Fault estimation is realized by analyzing the residual between the actual sensor measurement and the output of the original (i.e., healthy) model. To identify the structure of the steady state air path model a process called system probing is developed. The proposed diagnostics algorithm is experimentally validated on the intake air path of a Ford 4.6L V-8 engine. The specific faults to be identified include two of the most problematic faults that degrade the performance of transient fueling controllers: bias in the mass air flow sensor and a leak in the intake manifold. The selected model inputs include throttle position and engine speed, and the output is the mass air flow sensor measurement.
Robust Fault Detection Observer Design: Iterative LMI Approaches
Authors: Wang H. B. , Wang J. L. , Lam J.
Published: December 2006

This paper deals with the Robust Fault Detection (RFD) problem with the aid of the H∞ norm and H− index optimization techniques and the LMI approach. First, a necessary and sufficient condition is proposed for the design of RFD observers in the nominal case. Then, the RFD problem for systems with structured uncertainties in the system matrices is considered. Approaches are proposed to design robust fault detection observers to enhance the fault detection and to attenuate the effects due to unknown inputs and uncertainties. Furthermore, the design of the threshold of fault detection is investigated. We also consider the fault sensitivity over finite frequency range in which case no constraint is required on D being of full column rank for a system (A,B,C,D). Numerical examples are employed to demonstrate the effectiveness of the proposed methods.
Refined Stability Conditions for Linear Uncertain Systems With Multiple Time-Varying Delays
Authors: Huang Chih-Peng
Published: December 2006

This paper mainly proposes distinct criteria for the stability analysis and stabilization of linear uncertain systems with time-varying delays. Based on the Lyapunov theorem, a sufficient condition of the unforced systems with single time-varying delay is first derived. By involving a memoryless state feedback controller, the condition will be extended to treat with the resulting closed-loop system. These explicit criteria can be reformulated in LMIs forms, so we will readily verify the stability or design a stabilizing controller by the current LMI solver. Furthermore, the considered systems with multiple time-varying delays are similarly addressed. Numerical examples are given to demonstrate that the proposed approach is effective and valid.
New Results in Quasi-Optimum Control
Authors: Friedland Bernard
Published: December 2006

A technique of quasi-optimum control, developed by the author in 1966, has as its goal to permit one to use the apparatus of optimum control theory without having to solve the two-point boundary value problem for the actual problem. This is achieved by assuming the actual problem is “near” a simplified problem the solution of which was known. In this case, the control law adds a linear correction to the costate of the simplified problem. The linear correction is obtained as the solution of a matrix Riccati equation. After a review of the theory, several new applications of the technique are provided. These include mildly nonlinear processes, processes with bounded-control, and processes with state-variable constraints.
Discussion: “Analysis of a System of Linear Delay Differential Equations” (Asl, F. M., and Ulsoy, A. G., 2003, ASME J. Dyn. Syst., Meas., Control, 125, pp. 215–223)
Authors: Zafer Naci
Published: December 2006

This work presents a commentary of the article published by Asl and Ulsoy (2003, ASME J. Dyn. Syst., Meas., Control, 125, pp. 215–223). We show by an example that their method leads to inaccurate results and is therefore erroneous.
Amoxicillin Is Effective against Penicillin-ResistantStreptococcus pneumoniaeStrains in a Mouse Pneumonia Model Simulating Human Pharmacokinetics
Authors: Abgueguen Pierre , Azoulay-Dupuis Esther , Noel Violaine , Moine Pierre , Rieux Veronique , Fantin Bruno , Bedos Jean-Pierre
Published: December 2006

High-dose oral amoxicillin (3 g/day) is the recommended empirical outpatient treatment of community-acquired pneumonia (CAP) in many European guidelines. To investigate the clinical efficacy of this treatment in CAP caused byStreptococcus pneumoniaestrains with MICs of amoxicillin ≥2 μg/ml, we used a lethal bacteremic pneumonia model in leukopenic female Swiss mice with induced renal failure to replicate amoxicillin kinetics in humans given 1 g/8 h orally. Amoxicillin (15 mg/kg of body weight/8 h subcutaneously) was given for 3 days. We used fourS. pneumoniaestrains with differing amoxicillin susceptibility and tolerance profiles. Rapid bacterial killing occurred with an amoxicillin-susceptible nontolerant strain: after 4 h, blood cultures were negative and lung homogenate counts under the 2 log10CFU/ml detection threshold (6.5 log10CFU/ml in controls,P< 0.01). With an amoxicillin-intermediate nontolerant strain, significant pulmonary bacterial clearance was observed after 24 h (4.3 versus 7.9 log10CFU/ml,P< 0.01), and counts were undetectable 12 h after treatment completion. With an amoxicillin-intermediate tolerant strain, 24-h bacterial clearance was similar (5.4 versus 8.3 log10CFU/ml,P< 0.05), but 12 h after treatment completion, lung homogenates contained 3.3 log10CFU/ml. Similar results were obtained with an amoxicillin-resistant and -tolerant strain. Day 10 survival rates were usually similar across strains. Amoxicillin with pharmacokinetics simulating 1 g/8 h orally in humans is bactericidal in mice with pneumonia due toS. pneumoniaefor which MICs were 2 to 4 μg/ml. The killing rate depends not only on resistance but also on tolerance of theS. pneumoniaestrains.
Optimal Antimicrobial Catheter Lock Solution, Using Different Combinations of Minocycline, EDTA, and 25-Percent Ethanol, Rapidly Eradicates Organisms Embedded in Biofilm
Authors: Raad Issam , Hanna Hend , Dvorak Tanya , Chaiban Gassan , Hachem Ray
Published: December 2006

Antimicrobial lock solutions may be needed to salvage indwelling catheters in patients requiring continuous intravenous therapy. We determined the activity of minocycline, EDTA, and 25% ethanol, alone or in combination, against methicillin-resistant
Staphylococcus aureus
and
Candida parapsilosis
catheter-related bloodstream infection strains in two established models of biofilm colonization. Biofilm-colonized catheter segments from a modified Robbins device and a silicone disk biofilm colonization model were exposed to these antimicrobial agents for 15 or 60 min, respectively. After exposure, segments were sonicated and cultured. To determine regrowth after incubation at 37°C, following the brief exposure to the antimicrobial agents, an equal number of segments were washed, reincubated for 24 h, and then sonicated and cultured. The triple combination of minocycline-EDTA (M-EDTA) in 25% ethanol was the only antimicrobial lock solution that completely eradicated
S. aureus
and
C. parapsilosis
in biofilm of all segments tested in the two models, and it completely prevented regrowth. In addition, M-EDTA in 25% ethanol was significantly more effective in rapidly eradicating the growth or regrowth of methicillin-resistant
S. aureus
and
C. parapsilosis
biofilm colonization in the two models than the other solutions—minocycline, EDTA, M-EDTA, 25% ethanol, and EDTA in ethanol. We conclude that M-EDTA in 25% ethanol is highly effective at rapidly eradicating
S. aureus
and
C. parapsilosis
embedded in biofilm adhering to catheter segments.
Antibiotic Susceptibility Profile of Bifidobacteria as Affected by Oxgall, Acid, and Hydrogen Peroxide Stress
Authors: Kheadr E. , Dabour N. , Le Lay C. , Lacroix C. , Fliss I.
Published: December 2006

The effects of acid, oxgall, and H
2
O
2
on susceptibilities to antibiotics and nisin were examined for 13 strains of bifidobacteria. Susceptibilities to ampicillin, cloxacillin, penicillin, vancomycin, kanamycin, neomycin, paramomycin, streptomycin, chloramphenicol, erythromycin, tetracycline, and nisin A were assayed by a microdilution broth method. Acid-, oxgall- and H
2
O
2
-stressed variants were produced and assayed. Exposure to a pH of 2.0 for 60 min reduced susceptibilities to cloxacillin and nisin A but increased susceptibilities to ampicillin, vancomycin, aminoglycosides, chloramphenicol, and erythromycin in a strain-dependent manner. Exposure to oxgall (0.3%) for 90 min increased susceptibilities to cell wall-directed antibiotics and aminoglycosides but increased resistances to tetracycline and nisin A. Oxidative stress increased the susceptibilities of 70% of the strains to ampicillin and chloramphenicol, of 50% of the strains to cloxacillin and tetracycline, and of 40% of the strains to erythromycin but did not affect susceptibilities to vancomycin, kanamycin, and nisin A. This study shows that exposure of bifidobacteria to stressful conditions resembling those in the gastrointestinal tract may substantially modify their susceptibilities to antibiotics and may thus affect their probiotic capacities, especially when they are used for the management of intestinal infections and antibiotic-associated diarrhea.
Effect of Carbapenem Administration on Establishment of Intestinal Colonization by Vancomycin-Resistant Enterococci and
Klebsiella pneumoniae
in Mice
Authors: Stiefel Usha , Pultz Nicole J. , Donskey Curtis J.
Published: December 2006

In a mouse model, ertapenem inhibited the anaerobic intestinal microflora and promoted overgrowth of enterococci, whereas imipenem-cilastatin had no effect on the indigenous microflora. Ertapenem, but not imipenem-cilastatin, promoted modest overgrowth of vancomycin-resistant enterococci when exposure occurred during treatment. Neither agent promoted colonization with extended-spectrum beta-lactamase-producing
Klebsiella pneumoniae
.
The 6-Fluoro-8-Methoxy Quinolone Gatifloxacin Down-Regulates Interleukin-8 Production in Prostate Cell Line PC-3
Authors: Takeyama Koh , Mitsuzawa Hiroaki , Nishitani Chiaki , Shimizu Takeyuki , Sano Hitomi , Kunishima Yasuharu , Takahashi Satoshi , Hotta Hiroshi , Matsukawa Masanori , Shibata Ken-ichiro , Tsukamoto Taiji , Kuroki Yoshio
Published: December 2006

Fluoroquinolones exhibit immunomodulatory effects on monocytes and macrophages, in addition to their bactericidal activities. It remains unknown even whether the quinolones act directly on the prostate. This study was based on the understanding of the molecular mechanisms of the actions of the fluoroquinolones that can be used for the treatment of chronic prostatitis/chronic pelvic pain syndrome. We investigated whether the 6-fluroro-8-methoxy quinolone gatifloxacin (GFLX) affected the production and secretion of interleukin-8 (IL-8) in the prostate cell line PC-3. GFLX decreased the level of IL-8 release from unstimulated PC-3 cells. GFLX also attenuated IL-8 secretion from PC-3 cells stimulated with peptidoglycan,Mycoplasma hominis, phorbol ester, and tumor necrosis factor alpha (TNF-α), indicating that GFLX exhibits an anti-inflammatory effect on the prostate cell line. However, GFLX failed to alter activation of the NF-κB and AP-1 elicited by these stimulants. GFLX significantly attenuated the expression of IL-8 mRNA in TNF-α-stimulated PC-3 cells and down-regulated the transcriptional activity of the 5′-flanking region of the IL-8 gene from −1481 to +44 bp. The deletion construct without the 5′-flanking region from −1481 to −170 bp but not the construct without the region from −1481 to −188 bp reversed the suppressive effect of GFLX on IL-8 promoter activity. These results demonstrate that GFLX suppresses IL-8 expression in the prostate cell line by decreasing the promoter activity of the IL-8 gene.
Pharmacokinetics and Disposition of CS-023 (RO4908463), a Novel Parenteral Carbapenem, in Animals
Authors: Shibayama Takahiro , Matsushita Yoko , Kawai Kenji , Hirota Takashi , Ikeda Toshihiko , Kuwahara Shogo
Published: December 2006

The distribution, metabolism, and excretion of CS-023 (RO4908463), a new carbapenem, were investigated in rats and monkeys after a single intravenous administration of [
14
C]CS-023. In addition, the drug's pharmacokinetics were examined in rats, dogs, and monkeys. Whole-body autoradioluminograms of rats indicated that the radioactivity is distributed throughout the body immediately after administration except for the central nervous system and testes. The highest radioactivity was found in the kidneys, which are responsible for the excretion of CS-023. R-131624 with an open β-lactam ring, the pharmacologically inactive form, was detected in the plasma and urine as the major metabolite. In rat plasma, the R-131624 levels became higher than CS-023 levels at 30 min postdose and thereafter, while in monkey plasma, CS-023 accounted for most of the radioactivity, with low levels of R-131624. More than 80% of the radioactivity administered was recovered in the urine, and CS-023 and R-131624 accounted for 29.6% and 31.4%, respectively, of the dose in rats and 51.2% and 18.5%, respectively, of the dose in monkeys. The faster metabolism to R-131624 in rats than in monkeys was likely due to the metabolism by dehydropeptidase I in rat lungs. The plasma elimination half-life of CS-023 was 0.16 h in rats, 0.75 h in dogs, and 1.4 h in monkeys. There were no appreciable interspecies differences among the animals tested in either volume of distribution (172 to 259 ml/kg) or serum protein binding (5.0 to 15.6%). The total clearance in monkeys (1.62 ml/min/kg) was lower than that in rats (15.1 ml/min/kg) or dogs (4.19 ml/min/kg).
Human β-Defensins Kill
Candida albicans
in an Energy-Dependent and Salt-Sensitive Manner without Causing Membrane Disruption
Authors: Vylkova Slavena , Nayyar Namrata , Li Wansheng , Edgerton Mira
Published: December 2006

Human β-defensin 2 (hBD-2) and hBD-3 have potent fungicidal activity in the micromolar range. Although little is known about their mechanism of action against
Candida
species, some similarities to the antifungal mechanism of salivary peptide histatin 5 (Hst 5) seem to exist. Since hBD-2 and hBD-3 have been reported to cause direct disruption of target cell membranes, we compared the effects of hBD-2 and hBD-3 on
Candida albicans
membrane integrity. Incubation of calcein-loaded
C. albicans
cells with a dose of hBD-2 lethal for 90% of the strains tested (LD
90
) resulted in a maximal dye efflux of only 10.3% ± 2.8% at 90 min, similar to that induced by Hst 5. In contrast, an LD
90
of hBD-3 more than doubled calcein release from cells yet did not result in more than 24% of total release, showing that neither peptide caused gross membrane damage. As for Hst 5, killing of
C. albicans
cells by hBD-2 and hBD-3 was salt sensitive; however, Ca
2+
and Mg
2+
inhibited hBD-2 but not hBD-3 fungicidal activity. Pretreatment of
C. albicans
cells with sodium azide resulted in significantly decreased ATP release and susceptibility of cells to hBD-2 and hBD-3. However, hBD-3 killing was partially restored at concentrations of ≥0.8 μM, showing energy-independent mechanisms at higher doses.
C. glabrata
resistance to Hst 5, hBD-2, and hBD-3 is not a result of loss of expression of cell wall Ssa proteins. The candidacidal effects of hBD-2-hBD-3 and Hst 5-hBD-2 were additive, while the index of interaction between Hst 5 and hBD-3 was 0.717 (
P
< 0.05). Thus, the candidacidal action of hBD-2 shows many similarities to that of Hst 5 in terms of salt sensitivity, ion selectivity, and energy requirements while hBD-3 exhibits biphasic concentration-dependent mechanisms of candidacidal action complementary to those of Hst 5.
Hepatitis C Virus (HCV) NS5B Nonnucleoside Inhibitors Specifically Block Single-Stranded Viral RNA Synthesis Catalyzed by HCV Replication Complexes In Vitro
Authors: Yang Wengang , Sun Yongnian , Phadke Avinash , Deshpande Milind , Huang Mingjun
Published: December 2006

Replication complexes of hepatitis C virus synthesized two major species of viral RNA in vitro, double stranded and single stranded. NS5B nonnucleoside inhibitors inhibited dose dependently the synthesis of single-stranded RNA but not double-stranded RNA. Moreover, replication complexes carrying a mutation resistant to a nonnucleoside inhibitor lost their susceptibilities to the inhibitor.
Pharmacokinetics of Intravenous Linezolid in Cerebrospinal Fluid and Plasma in Neurointensive Care Patients with Staphylococcal Ventriculitis Associated with External Ventricular Drains
Authors: Beer Ronny , Engelhardt Klaus W. , Pfausler Bettina , Broessner Gregor , Helbok Raimund , Lackner Peter , Brenneis Christian , Kaehler Stefan T. , Georgopoulos Apostolos , Schmutzhard Erich
Published: December 2006

The pharmacokinetic profile of linezolid in cerebrospinal fluid (CSF) in five neurointensive care patients with staphylococcal ventriculitis was studied. The mean area under concentration-time curve (± standard deviation) was 63 ± 18.9 mg · h/liter, with a CSF-to-plasma ratio of 0.8 ± 0.3. Times above MIC in CSF were 99.8% and 57.2% for pathogens with MICs of 2 mg/liter and 4 mg/liter, respectively.
Molecular Characterization of Increasing Fluoroquinolone Resistance in
Streptococcus pneumoniae
Isolates in Canada, 1997 to 2005
Authors: Adam Heather J. , Schurek Kristen N. , Nichol Kimberly A. , Hoban Chris J. , Baudry Trish J. , Laing Nancy M. , Hoban Daryl J. , Zhanel George G.
Published: December 2006

Molecular characterization of fluoroquinolone-resistant
Streptococcus pneumoniae
in Canada was conducted from 1997 to 2005. Over the course of the study, 205 ciprofloxacin-resistant isolates were evaluated for ParC and GyrA quinolone resistance-determining region (QRDR) substitutions, substitutions in the full genes of ParC, ParE, and GyrA, reserpine sensitivity, and serotype and by pulsed-field gel electrophoresis. Rates of ciprofloxacin resistance of
S. pneumoniae
increased significantly, from less than 1% in 1997 to 4.2% in 2005. Ciprofloxacin resistance was greatest in people >64 years of age and least in those <16 years of age. Significant increases were also noted in rates of resistance to gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin, to the current rates of 1.6%, 1.0%, 1.1%, and 1.0%, respectively. The most common genotype observed consisted of QRDR substitutions in GyrA (Ser81Phe) and ParC (Ser79Phe). Substitutions outside the QRDR of GyrA, ParC, and ParE were not associated with fluoroquinolone resistance in this study. Overall, 21% of isolates were reserpine-sensitive and were thus assumed to be efflux positive. The ciprofloxacin-resistant isolates belonged to 35 different serotypes, but 10 (19F, 11A, 23F, 6B, 22F, 12F, 6A, 14, 9V, and 19A) accounted for 72% of all isolates. The majority of the isolates were found to be genetically unrelated by pulsed-field gel electrophoresis. Within the observed clusters, there was considerable genetic heterogeneity with regard to fluoroquinolone resistance mechanisms and serotypes. Continued surveillance and molecular analysis of fluoroquinolone-resistant
S. pneumoniae
in Canada are essential for appropriate empirical treatment of infections and early detection of novel resistance mechanisms.
Identification of CTX-M-Type Extended-Spectrum-β-Lactamase Genes Using Real-Time PCR and Pyrosequencing
Authors: Naas Thierry , Oxacelay Cynthia , Nordmann Patrice
Published: December 2006

CTX-M extended-spectrum β-lactamases (ESBLs) are increasingly prevalent worldwide among
Escherichia coli
bacteria, mostly in community-acquired urinary tract infections. Finding a fast and reliable technique for identification of CTX-M enzymes is becoming a challenge for the microbiology laboratory. A fast real-time PCR amplification technique, using degenerated primers specific for all the
bla
CTX-M
alleles, coupled to real-time pyrosequencing was developed. The five CTX-M groups were unambiguously identified by pyrosequencing a 13-bp DNA region. Further sequencing of an additional 16-bp region allowed further division into subgroups. Phylogenetic trees constructed with the entire
bla
CTX-M
genes and with both pyrosequenced regions (29 bp) gave similar results, suggesting that this technique, termed the real-time detection and sequencing method, has a powerful discriminatory ability. This high-throughput technique has been evaluated by screening 48 ESBL-producing
E. coli
isolates recovered from the Bicêtre hospital (France) in 2004. Forty-four of these strains were CTX-M positive by real-time PCR detection and direct pyrosequencing of the PCR products, which identified CTX-M-15 as the main CTX-M-type β-lactamase. Pulsed-field gel electrophoresis analysis of these strains revealed that several clones, of which one CTX-M-15-positive clone was predominant (60%), were identified both in nosocomial and in community-acquired isolates. The combination of real-time PCR with pyrosequencing represents a powerful tool for epidemiological studies of CTX-M producers. This assay has the potential to be used in a diagnostic laboratory since up to 96 bacterial isolates may be screened in less than 3 h.
Library Screen for Inhibitors Targeting Norovirus Binding to Histo-Blood Group Antigen Receptors
Authors: Feng Xizhi , Jiang Xi
Published: December 2006

Human noroviruses (NVs) are a common cause of nonbacterial gastroenteritis. The disease is difficult to control due to its widespread nature and the lack of antivirals or vaccines against NVs. The recent identification of human histo-blood group antigens (HBGAs) as NV receptors opens a new way for the discovery and design of antivirals against NVs. A saliva-based enzyme immune assay (EIA) was used to screen a synthetic-compound library for inhibition of the binding of norovirus-like particles to HBGA receptors. Among 5,000 compounds tested in the first round of screening, 153 compounds exhibited >50% inhibition of the binding of VA387 (an NV that binds to A, B, and H epitopes) to the A antigen in saliva at ∼50 μg/ml, and 14 of the 153 compounds revealed strong inhibition, with a 50% effective concentration of <15 μM. Ten and 11 of the 14 compounds also revealed inhibition of the binding of VA387 to the B and H antigens, respectively. Seven and 6 of the 14 compounds also blocked the binding of the prototype Norwalk virus (A and H binder) to the A and H antigens, respectively. One compound significantly inhibited the binding of MOH (A and B binder) to the A and B antigens, but no compound revealed any inhibitory effect on the binding of a Lewis binding strain (VA207) to the Lewis antigens. The EIA is a high-throughput method for large-scale library screening for antivirals against NVs. Studies to further characterize the lead compounds and to screen additional compounds for other NVs are ongoing in our laboratory.
Multidrug Resistance Conferred by Novel DNA Polymerase Mutations in Human Cytomegalovirus Isolates
Authors: Scott Gillian M. , Weinberg Adriana , Rawlinson William D. , Chou Sunwen
Published: December 2006

The emergence of antiviral-resistant cytomegalovirus (CMV) strains is a continuing clinical problem, with increased numbers of immunocompromised patients given longer-duration antiviral prophylaxis. Two previously unrecognized CMV DNA polymerase mutations (N408K and A834P) identified separately and together in at-risk lung and kidney transplant recipients and a third mutation (L737M) identified in a liver transplant recipient were characterized by marker transfer to antiviral-sensitive laboratory strains AD169 and Towne. Subsequent phenotypic analyses of recombinant strains demonstrated the ability of mutation N408K to confer ganciclovir (GCV) and cidofovir (CDV) resistance and of mutation A834P to confer GCV, foscarnet, and CDV resistance. Mutation L737M did not confer resistance to any of the antiviral agents tested. A recombinant strain containing both N408K and A834P demonstrated increased GCV and CDV resistance compared to the levels of resistance of the virus containing only the A834P mutation. The addition of mutation N408K in combination with A834P also partially reconstituted the replication impairment of recombinant virus containing only A834P. This suggests that perturbation of both DNA polymerization (A834P) and exonuclease (N408K) activities contributes to antiviral resistance and altered replication kinetics in these mutant strains. The identification of these multidrug-resistant CMV strains in at-risk seronegative recipients of organs from seropositive donors suggests that improved prophylactic and treatment strategies are required. The additive effect of multiple mutations on antiviral susceptibility suggests that increasing antiviral-resistant phenotypes can result from different virus-antiviral interactions.
Effects of Inoculum Size and Incubation Time on Broth Microdilution Susceptibility Testing of Lactic Acid Bacteria
Authors: Egervärn Maria , Lindmark Hans , Roos Stefan , Huys Geert , Lindgren Sven
Published: December 2006

Inoculum size and incubation time were varied during broth microdilution testing of the susceptibilities of 35 strains of lactic acid bacteria to six antibiotics. An increase in either parameter resulted in elevated MICs for all species. An inoculum of 3 × 10
5
CFU/ml is recommended to assess the antibiotic susceptibilities of these bacteria by using broth microdilution.
Molecular Mechanism by Which the K70E Mutation in Human Immunodeficiency Virus Type 1 Reverse Transcriptase Confers Resistance to Nucleoside Reverse Transcriptase Inhibitors
Authors: Sluis-Cremer Nicolas , Sheen Chih-Wei , Zelina Shannon , Torres Pedro S. Argoti , Parikh Urvi M. , Mellors John W.
Published: December 2006

The K70E mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has become more prevalent in clinical samples, particularly in isolates derived from patients for whom triple-nucleoside regimens that include tenofovir (TNV), abacavir, and lamivudine (3TC) failed. To elucidate the molecular mechanism by which this mutation confers resistance to these nucleoside RT inhibitors (NRTI), we conducted detailed biochemical analyses comparing wild-type (WT), K70E, and K65R HIV-1 RT. Pre-steady-state kinetic experiments demonstrate that the K70E mutation in HIV-1 RT allows the enzyme to discriminate between the natural deoxynucleoside triphosphate substrate and the NRTI triphosphate (NRTI-TP). Compared to the WT enzyme, K70E RT showed 2.1-, 2.3-, and 3.5-fold-higher levels of resistance toward TNV-diphosphate, carbovir-TP, and 3TC-TP, respectively. By comparison, K65R RT demonstrated 12.4-, 12.0-, and 13.1-fold-higher levels of resistance, respectively, toward the same analogs. NRTI-TP discrimination by the K70E (and K65R) mutation was primarily due to decreased rates of NRTI-TP incorporation and not to changes in analog binding affinity. The K65R and K70E mutations also profoundly impaired the ability of RT to excise 3′-azido-2′,3′-dideoxythymidine monophosphate (AZT-MP) and other NRTI-MP from the 3′ end of a chain-terminated primer. When introduced into an enzyme with the thymidine analog mutations (TAMs) M41L, L210W, and T215Y, the K70E mutation inhibited ATP-mediated excision of AZT-MP. Taken together, these findings indicate that the K70E mutation, like the K65R mutation, reduces susceptibility to NRTI by selectively decreasing NRTI-TP incorporation and is antagonistic to TAM-mediated nucleotide excision.
Effect of Anaerobic Growth on Quinolone Lethality with
Escherichia coli
Authors: Malik Muhammad , Hussain Syed , Drlica Karl
Published: December 2006

Quinolone activity against
Escherichia coli
was examined during aerobic growth, aerobic treatment with chloramphenicol, and anaerobic growth. Nalidixic acid, norfloxacin, ciprofloxacin, and PD161144 were lethal for cultures growing aerobically, and the bacteriostatic activity of each quinolone was unaffected by anaerobic growth. However, lethal activity was distinct for each quinolone with cells treated aerobically with chloramphenicol or grown anaerobically. Nalidixic acid failed to kill cells under both conditions; norfloxacin killed cells when they were grown anaerobically but not when they were treated with chloramphenicol; ciprofloxacin killed cells under both conditions but required higher concentrations than those required with cells grown aerobically; and PD161144, a C-8-methoxy fluoroquinolone, was equally lethal under all conditions. Following pretreatment with nalidixic acid, a shift to anaerobic conditions or the addition of chloramphenicol rapidly blocked further cell death. Formation of quinolone-gyrase-DNA complexes, observed as a sodium dodecyl sulfate (SDS)-dependent drop in cell lysate viscosity, occurred during aerobic and anaerobic growth and in the presence and in the absence of chloramphenicol. However, lethal chromosome fragmentation, detected as a drop in viscosity in the absence of SDS, occurred with nalidixic acid treatment only under aerobic conditions in the absence of chloramphenicol. With PD161144, chromosome fragmentation was detected when the cells were grown aerobically and anaerobically and in the presence and in the absence of chloramphenicol. Thus, all quinolones tested appear to form reversible bacteriostatic complexes containing broken DNA during aerobic growth, during anaerobic growth, and when protein synthesis is blocked; however, the ability to fragment chromosomes and to rapidly kill cells under these conditions depends on quinolone structure.
In Vitro-Clinical Correlations for Amphotericin B Susceptibility in AIDS-Associated Cryptococcal Meningitis
Authors: Larsen R. A. , Bauer M. , Brouwer A. E. , Sanchez A. , Thomas A. M. , Rajanuwong A. , Chierakul W. , Peacock S. J. , Day N. , White N. J. , Rinaldi M. G. , Harrison T. S.
Published: December 2006

Reliable measures of antifungal drug susceptibility are needed. We tested the susceptibility of
Cryptococcus neoformans
from patients treated with amphotericin B. In vitro susceptibility employed a modified broth macrodilution method. We demonstrate a strong correlation between the quantitative measures of in vitro amphotericin B susceptibility and the quantitative response observed in patients.
Voriconazole Concentration in Human Aqueous Humor and Plasma during Topical or Combined Topical and Systemic Administration for Fungal Keratitis
Authors: Thiel Michael A. , Zinkernagel Annelies S. , Burhenne Jürgen , Kaufmann Claude , Haefeli Walter E.
Published: December 2006

Voriconazole (VRC) is an antifungal drug that effectively treats keratitis caused by yeasts and molds when administered orally. We retrospectively evaluated clinical outcomes and plasma and aqueous humor drug concentrations in five patients with fungal keratitis and one patient with posttraumatic endophthalmitis who were treated with VRC. VRC was administered either topically (1% eye drops every hour) or orally (400 mg twice a day). Plasma and aqueous humor samples from affected eyes were taken 12 h after oral administration or 1 h after eye drop application. The drug concentration was measured by liquid chromatography with UV or mass spectrometric detection. All six patients responded well to VRC treatment. The VRC concentration ranged from 2.93 to 3.40 mg/liter in the aqueous humor and from 3.20 to 4.20 mg/liter in the plasma after combined oral and topical treatment. Topical administration alone resulted in highly variable trough VRC concentrations of 0.61 to 3.30 mg/liter in the aqueous humor. VRC concentrations were above the MIC for
Candida albicans Aspergillus fumigatus
and clinical improvement was seen in all four patients with
C. albicans
and
A. fumigatus
keratitis. Combined orally and topically administered VRC resulted in aqueous humor drug concentrations of ≥2.93 mg/liter, which is above the VRC MIC for most fungi. Topical VRC treatment resulted in an aqueous humor drug concentration >0.61 mg/liter, which is above the MIC for most
Candida
species. The results from this small series of patients suggest that both topical and combined systemic and topical VRC therapy can be effective in treating fungal keratitis. Furthermore, the data provide preliminary support for initiation of VRC treatment with a combined topical and systemic administration until the causative fungus and its MIC are identified.