bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Underfill Thermomechanical Properties on Thermal Cycling Fatigue Reliability of Flip-Chip Ball Grid Array
Authors: Wang Tong Hong , Lai Yi-Shao , Wu Jenq-Dah
Published: January 2005

Plane two-dimensional finite element analysis was applied to study the effect of underfill thermomechanical properties on the potential of thermal fatigue failure for flip-chip ball grid array. Two-stage as well as constant thermomechanical properties of underfills were manipulated to represent extremes of practical underfills. The steady-state creep model was incorporated for the eutectic solder bump to represent its real behavior. It was found from the parametric studies that the underfill with high Young’s modulus, low coefficient of thermal expansion, and high glass transition temperature leads to the longest service life.
Impact of TXV and Compressor in the Stability of a High-End Computer Refrigeration System
Authors: Makwana Yasin , Agonafer Dereje , Manole Dan
Published: January 2005

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge is to limit the rise in chip temperature above the ambient. In the past, virtually all commercial computers were designed to operate at temperatures above the ambient. However, researchers have identified the advantages of operating electronics at low temperatures. Until recently, large-scale scientific computers used direct immersion cooling of single-chip modules. The current research focuses on mainframes (computer system), which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Multivariable control of compressor speed along with thermostatic expansion valve (TXV) opening can give better stability and performance. TXV is a mechanical controlling device used in the refrigeration system. The compressor is the only mechanical-working component in the refrigeration cycle that circulates refrigerant through the system continuously. Hence, controlling the compressor is an important aspect. The control objective is defined as improving the transient behavior of the vapor compression cycle for the refrigeration system operating around an evaporator set-point temperature. The system behavior is studied in two cases, TXV being the only control element in the first case, while TXV and a compressor both act as control elements in the other case.
Optimal Spacings for Mixed Convection
Authors: Bello-Ochende T. , Bejan A.
Published: January 2005

This paper completes the description of geometry optimization in stacks of parallel plates that generate heat. The spacing between plates, or the number of plates in a fixed volume, has been maximized in two limits: pure natural convection and pure forced convection. In this paper, the in-between regime of mixed convection is modeled numerically. After simulating the flow and temperature fields in configurations with a variety of spacings, this paper reports the optimal spacings and the dimensionless groups that govern them (Rayleigh number, pressure drop number, mixed convection ratio). It shows that the numerical results match the results in the limits of natural convection and forced convection. The paper constructs a correlation that bridges the gap between the two limits, and provides a single formula for optimal spacings covering the entire domain, from natural convection to forced convection.
Study of Lateral Merger of Vapor Bubbles During Nucleate Pool Boiling
Authors: Mukherjee A. , Dhir V. K.
Published: January 2005

In the present work the bubble dynamics and heat transfer associated with lateral bubble merger during transition from partial to fully developed nucleate boiling is studied numerically. Complete Navier–Stokes equation in three dimensions along with the continuity and energy equations are solved using the SIMPLE method. The liquid vapor interface is captured using the Level-Set technique. Calculations are carried out for multiple bubble mergers in a line and also in a plane and the bubble dynamics and wall heat transfer are compared to that for a single bubble. The results show that merger of multiple bubbles significantly increases the overall wall heat transfer. This enhanced wall heat transfer is caused by trapping of liquid layer between the bubble bases during merger and by drawing of cooler liquid towards the wall during contraction after merger. Good agreement with data from experiments is found in bubble growth rate and bubble shapes obtained from numerical simulations.
The Challenges of Electronic Cooling: Past, Current and Future
Authors: Chu Richard C.
Published: January 2005

This paper represents my personal recapitulation of my 4 decades of continuous involvement in all phases of electronic cooling, from conceptual design, through engineering development to product implementation. The cooling designs that we applied successfully in the past are reviewed chronologically. The challenges we are currently facing are also discussed and an attempt is made to forecast the challenges that will confront the electronics cooling community in the near and distant future. The paper includes a summary of IBM sponsored research spanning a period of 25 years at 12 universities on a wide range of topics related to electronic cooling technology.
Multidrug-Resistant
Salmonella enterica
Serovar Muenchen from Pigs and Humans and Potential Interserovar Transfer of Antimicrobial Resistance
Authors: Gebreyes Wondwossen A. , Thakur Siddhartha
Published: January 2005

Salmonella
serovars are important reservoirs of antimicrobial resistance. Recently, we reported on multidrug-resistant (MDR)
Salmonella enterica
serovar Typhimurium strains among pigs with resistance to ampicillin, kanamycin, streptomycin, sulfamethoxazole, and tetracycline (resistance [R] type AKSSuT) and resistance to amoxicillin-clavulanic acid, ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (R type AxACSSuT). In the present study, 67 isolates (39 from humans and 28 from pigs) of clinically important
Salmonella
serovar Muenchen were characterized. Among the porcine isolates, 75% showed resistance to seven antimicrobials: ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, amoxicillin-clavulanic acid, and kanamycin (R type ACSSuTAxK). One isolate from humans showed resistance to 10 of the 12 antimicrobials: ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, amoxicillin-clavulanic acid, kanamycin, gentamicin, cephalothin, and ceftriaxone (R type ACSSuTAxKGCfCro). Pulsed-field gel electrophoresis revealed no clonality between the porcine and the human strains. The porcine and the human MDR strains carried class 1 integrons of 2.0 and 1.0 kb, respectively. Genes specific to the porcine strain included
aadA2
,
aphA1-Iab
, and
tetA
(B). DNA sequencing revealed that the porcine isolates carried
bla
OXA-30
on a class 1 integron. Genes specific to the human strain included
bla
TEM
,
strA
,
strB
,
cmlA
,
tetA
(A), and
aadA2
. No
bla
CMY-2
gene was detected. Serovar Muenchen strains of porcine and human origin were able to transfer resistance genes to laboratory strain
Escherichia coli
MG1655 by conjugation. Plasmid restriction with four restriction enzymes, EcoRI, BamHI, HindIII, and PstI, showed that the conjugative plasmids from porcine
Salmonella
serovar Muenchen and Typhimurium R-type MDR strains isolated from the same farms at the same time were similar on the basis of the sizes and the numbers of bands and Southern hybridization. The plasmid profiles among the
Salmonella
serovar Muenchen isolates from the two host species were different. This is the first report to show a high frequency of MDR
Salmonella
serovar Muenchen strains from pigs and a human strain that is similar to the MDR isolates with the AmpC enzyme previously reported among
Salmonella
serovars Newport and Typhimurium strains. The MDR strains from the two host species independently represent public health concerns, as
Salmonella
serovar Muenchen is among the top 10 causes of salmonellosis in humans.
Alkyl Gallates, Intensifiers of β-Lactam Susceptibility in Methicillin-ResistantStaphylococcus aureus
Authors: Shibata Hirofumi , Kondo Kyoko , Katsuyama Ryo , Kawazoe Kazuyoshi , Sato Yoichi , Murakami Kotaro , Takaishi Yoshihisa , Arakaki Naokatu , Higuti Tomihiko
Published: January 2005

We found that ethyl gallate purified from a dried pod of tara (Caesalpinia spinosa) intensified β-lactam susceptibility in methicillin-resistant and methicillin-sensitive strains ofStaphylococcus aureus(MRSA and MSSA strains, respectively). This compound and several known alkyl gallates were tested with MRSA and MSSA strains to gain new insights into their structural functions in relation to antimicrobial and β-lactam susceptibility-intensifying activities. The maximum activity of alkyl gallates against MRSA and MSSA strains occurred at 1-nonyl and 1-decyl gallate, with an MIC at which 90% of the isolates tested were inhibited of 15.6 μg/ml. At concentrations lower than the MIC, alkyl gallates synergistically elevated the susceptibility of MRSA and MSSA strains to β-lactam antibiotics. Such a synergistic activity of the alkyl gallates appears to be specific for β-lactam antibiotics, because no significant changes were observed in the MICs of other classes of antibiotics examined in this study. The length of the alkyl chain was also associated with the modifying activity of the alkyl gallates, and the optimum length was C5 to C6. The present work clearly demonstrates that the length of the alkyl chain has a key role in the elevation of susceptibility to β-lactam antibiotics.
cDNA Microarray Analysis of Differential Gene Expression in
Candida albicans
Biofilm Exposed to Farnesol
Authors: Cao Ying-Ying , Cao Yong-Bing , Xu Zheng , Ying Kang , Li Yao , Xie Yi , Zhu Zhen-Yu , Chen Wan-Sheng , Jiang Yuan-Ying
Published: January 2005

Candida albicans
biofilms are structured microbial communities with high levels of drug resistance. Farnesol, a quorum-sensing molecule that inhibits hyphal formation in
C. albicans
, has been found to prevent biofilm formation by
C. albicans
. There is limited information, however, about the molecular mechanism of farnesol against biofilm formation. We used cDNA microarray analysis to identify the changes in the gene expression profile of a
C. albicans
biofilm inhibited by farnesol. Confocal scanning laser microscopy was used to visualize and confirm normal and farnesol-inhibited biofilms. A total of 274 genes were identified as responsive, with 104 genes up-regulated and 170 genes down-regulated. Independent reverse transcription-PCR analysis was used to confirm the important changes detected by microarray analysis. In addition to hyphal formation-associated genes (e.g.,
TUP1
,
CRK1
, and
PDE2
), a number of other genes with roles related to drug resistance (e.g.,
FCR1
and
PDR16
), cell wall maintenance (e.g.,
CHT2
and
CHT3
), and iron transport (e.g.,
FTR2
) were responsive, as were several genes encoding heat shock proteins (e.g.,
HSP70
,
HSP90
,
HSP104
,
CaMSI3
, and
SSA2
). Further study of these differentially regulated genes is warranted to evaluate how they may be involved in
C. albicans
biofilm formation. Consistent with the down-regulation of the cell surface hydrophobicity-associated gene (
CSH1
), the water-hydrocarbon two-phase assay showed a decrease in cell surface hydrophobicity in the farnesol-treated group compared to that in the control group. Our data provide new insight into the molecular mechanism of farnesol against
C. albicans
biofilm formation.
Genotypic Characterization of the DNA Polymerase and Sensitivity to Antiviral Compounds of Foscarnet-Resistant Herpes Simplex Virus Type 1 (HSV-1) Derived from a Foscarnet-Sensitive HSV-1 Strain
Authors: Saijo Masayuki , Suzutani Tatsuo , Morikawa Shigeru , Kurane Ichiro
Published: January 2005

Foscarnet is widely used for the treatment of acyclovir-resistant herpesvirus infections, and foscarnet-resistant herpesvirus infections are a serious concern in immunocompromised patients. Twenty-seven single-plaque isolates of herpes simplex virus type 1 (HSV-1) resistant to foscarnet were selected from foscarnet- and acyclovir-sensitive HSV-1 strain TAS by exposure to foscarnet, and the DNA polymerase genes were analyzed. The sensitivities of these mutants to foscarnet, cidofovir, S2242, acyclovir, ganciclovir, and penciclovir were determined. A single amino acid substitution, double amino acid substitutions, and a combination of a single amino acid substitution with a deletion or insertion of amino acid residues in the viral DNA polymerase were demonstrated in 21, 4, and 2 isolates, respectively. Of the 27 isolates, an amino acid substitution of serine for asparagine at amino acid position 724 in the DNA polymerase (724 S-N) was detected in 8 isolates. An amino acid substitution in conserved region II was demonstrated in these eight isolates as well as four other isolates. The mutation in the DNA polymerase responsible for resistance to foscarnet was located between the pre-IV region and conserved region V, especially within conserved region II. All the isolates were sensitive or hypersensitive to cidofovir and ganciclovir. Seven, 5, and 15 of the 27 isolates were also sensitive to S2242, acyclovir, and penciclovir, respectively. Thus, most of the foscarnet-resistant HSV-1 isolates were sensitive or hypersensitive to cidofovir and ganciclovir.
Bactericidal Action of Gatifloxacin, Rifampin, and Isoniazid on Logarithmic- and Stationary-Phase Cultures of
Mycobacterium tuberculosis
Authors: Paramasivan C. N. , Sulochana S. , Kubendiran G. , Venkatesan P. , Mitchison D. A.
Published: January 2005

The bactericidal activity of gatifloxacin, alone and in combination with isoniazid and rifampin, was studied on both exponential- and stationary-phase cultures of
Mycobacterium tuberculosis
strain H37Rv. On log-phase cultures, the bactericidal activity of gatifloxacin at 4 μg/ml was rapid and was very similar to that of isoniazid. At concentrations of 0.25 and 4 μg/ml, gatifloxacin enhanced the activity of isoniazid. Killing of the stationary-phase culture was biphasic. During the first 2 days, gatifloxacin at 4 μg/ml slightly increased the limited bactericidal activities of isoniazid and rifampin. However, no further additional bactericidal activity was found during further incubation with isoniazid alone or when gatifloxacin was added to either isoniazid or rifampin. This suggested that the stationary-phase culture contained a mixture of occasionally dividing bacilli that were killed during the first 2 days and true static persisters in the residual population that mimicked those in human lesions. In view of the failure of gatifloxacin to add to the sterilizing activity of isoniazid or rifampin during days 2 to 6 of exposure in the stationary-phase culture, it is unlikely to be a sterilizing drug that can be used to shorten the duration of treatment appreciably when it is added to present treatment regimens.
Interaction between Posaconazole and Amphotericin B in Concomitant Treatment against
Candida albicans
In Vivo
Authors: Cacciapuoti Anthony , Gurnani Maya , Halpern Judith , Norris Christine , Patel Reena , Loebenberg David
Published: January 2005

The interaction of posaconazole and amphotericin B was evaluated in concomitant treatment of
Candida albicans
systemic infections in immunocompetent mice by using four strains of
C. albicans
with different susceptibilities to fluconazole. Posaconazole and amphotericin B were each tested at four dose levels alone and in all possible combinations against each
C. albicans
strain. Survival curves of mice treated with combinations of posaconazole and amphotericin B were statistically compared with those of mice treated with the component monotherapies. Of the 64 total combinations evaluated against the
C. albicans
strains (16 combinations per strain), 20.3% were more effective in prolonging mouse survival than both of the monotherapies, 45.3% were more effective than one of the monotherapies, and 32.8% were similar to both monotherapies. No evidence of antagonism was observed between posaconazole and amphotericin B in this mouse model, consistent with in vitro results against the same strains.
Clinical Pharmacokinetics of Nelfinavir and Its Metabolite M8 in Human Immunodeficiency Virus (HIV)-Positive and HIV-Hepatitis C Virus-Coinfected Subjects
Authors: Regazzi Mario , Maserati Renato , Villani Paola , Cusato Maria , Zucchi Patrizia , Briganti Elena , Roda Rinaldo , Sacchelli Luca , Gatti Francesca , Delle Foglie Palma , Nardini Giulia , Fabris Paolo , Mori Fernanda , Castelli Paula , Testa Lucia
Published: January 2005

In order to evaluate the potential risk of nelfinavir (NFV) accumulation in human immunodeficiency virus (HIV)-hepatitis C virus (HCV)-coinfected patients with liver disease, we investigated the concentrations of NFV and M8, the active metabolite of NFV, in plasma HIV-positive (HIV+) patients coinfected with HCV. A total of 119 HIV+ subjects were included in our study: 67 HIV+ patients, 32 HIV+ and HCV-positive (HCV+) patients without cirrhosis, and 20 HIV+ and HCV+ patients with cirrhosis. Most of the enrolled patients (chronically treated) were taking NFV at the standard dosage of 1,250 mg twice a day. To assay plasma NFV and M8 concentrations, patients underwent serial plasma samplings during the dosing interval at steady state. Plasma NFV and M8 concentrations were measured simultaneously by a high-performance liquid chromatography method with UV detection. The HIV+ and HCV+ patients with and without cirrhosis had significantly lower NFV oral clearances than the HIV+ and HCV-negative individuals (28 and 58% lower, respectively;
P
< 0.05), which translated into higher areas under the concentration-time curves for cirrhotic and noncirrhotic patients. The NFV absorption rate was significantly lower in cirrhotic patients, resulting in a longer time to the maximum concentration in serum. The mean ratios of the M8 concentration/NFV concentration were significantly lower (
P
< 0.05) in HIV+ and HCV+ subjects with cirrhosis (0.06 ± 0.074) than in the subjects in the other two groups. The mean ratios for M8 and NFV were not statistically different between HIV+ and HCV-negative patients (0.16 ± 0.13) and HIV+ and HCV+ patients without cirrhosis (0.24 ± 0.17), but the interpatient variability was high. Our results indicate that the pharmacokinetics of NFV and M8 are altered in HIV+ and HCV+ patients, especially those with liver cirrhosis. Therefore, there may be a role for therapeutic drug monitoring in individualizing the NFV dosage in HIV-HCV-coinfected patients.
Mefloquine versus Quinine plus Sulphalene-Pyrimethamine (Metakelfin) for Treatment of Uncomplicated Imported Falciparum Malaria Acquired in Africa
Authors: Matteelli Alberto , Saleri Nuccia , Bisoffi Zeno , Gregis Giampietro , Gaiera Giovanni , Visonà Raffaella , Tedoldi Simona , Scolari Carla , Marocco Stefania , Gulletta Maurizio
Published: January 2005

We conducted a multicenter, randomized, open-label trial to compare mefloquine with a 3-day quinine plus sulphalene-pyrimethamine (SP) regimen for the treatment of imported uncomplicated malaria acquired in Africa. The end points of the study were efficacy, tolerability, and length of hospital stay. From July 1999 to February 2003, 187 patients were enrolled in five centers in Italy, of whom 93 were randomized to receive mefloquine (the M group) and 94 were randomized to receive quinine plus SP (the QSP group). Immigrants and visiting relatives and friends represented 90% of the cases and were mainly from western African countries. A slightly increased proportion of cases in the QSP group had abnormal alanine aminotransferase levels at the baseline. The early cure rate was similar in the two groups: 98.9% (confidence interval [CI] = 97 to 100%) in the M group and 96.8% (CI = 93 to 100%) in the QSP group. The extended follow-up was completed by 135 subjects (72.2%), and no case of recrudescence was detected. There were no differences in the parasite clearance time, but patients in the M group had shorter mean fever clearance time (35.9 h versus 44.4 h for the QSP group;
P
= 0.05) and a shorter mean hospital stay (3.9 days versus 4.6 days for the QSP group;
P
= 0.007). The overall proportions of reported side effects were similar in the two groups, but patients in the M group had a significantly higher rate of central nervous system disturbances (29.0% versus 9.6% for the QSP group;
P
< 0.001).
Mechanisms of Azole Resistance in Clinical Isolates of
Candida glabrata
Collected during a Hospital Survey of Antifungal Resistance
Authors: Sanguinetti Maurizio , Posteraro Brunella , Fiori Barbara , Ranno Stefania , Torelli Riccardo , Fadda Giovanni
Published: January 2005

The increasing use of azole antifungals for the treatment of mucosal and systemic
Candida glabrata
infections has resulted in the selection and/or emergence of resistant strains. The main mechanisms of azole resistance include alterations in the
C. glabrata ERG11
gene (
CgERG11
), which encodes the azole target enzyme, and upregulation of the
CgCDR1
and
CgCDR2
genes, which encode efflux pumps. In the present study, we evaluated these molecular mechanisms in 29 unmatched clinical isolates of
C. glabrata
, of which 20 isolates were resistant and 9 were susceptible dose dependent (S-DD) to fluconazole. These isolates were recovered from separate patients during a 3-year hospital survey for antifungal resistance. Four of the 20 fluconazole-resistant isolates were analyzed together with matched susceptible isolates previously taken from the same patients. Twenty other azole-susceptible clinical
C. glabrata
isolates were included as controls. MIC data for all the fluconazole-resistant isolates revealed extensive cross-resistance to the other azoles tested, i.e., itraconazole, ketoconazole, and voriconazole. Quantitative real-time PCR analyses showed that
CgCDR1
and
CgCDR2
, alone or in combination, were upregulated at high levels in all but two fluconazole-resistant isolates and, to a lesser extent, in the fluconazole-S-DD isolates. In addition, slight increases in the relative level of expression of
CgSNQ2
(which encodes an ATP-binding cassette [ABC] transporter and which has not yet been shown to be associated with azole resistance) were seen in some of the 29 isolates studied. Interestingly, the two fluconazole-resistant isolates expressing normal levels of
CgCDR1
and
CgCDR2
exhibited increased levels of expression of
CgSNQ2
. Conversely, sequencing of
CgERG11
and analysis of its expression showed no mutation or upregulation in any
C. glabrata
isolate, suggesting that
CgERG11
is not involved in azole resistance. When the isolates were grown in the presence of fluconazole, the profiles of expression of all genes, including
CgERG11
, were not changed or were only minimally changed in the resistant isolates, whereas marked increases in the levels of gene expression, particularly for
CgCDR1
and
CgCDR2
, were observed in either the fluconazole-susceptible or the fluconazole-S-DD isolates. Finally, known ABC transporter inhibitors, such as FK506, were able to reverse the azole resistance of all the isolates. Together, these results provide evidence that the upregulation of the
CgCDR1
-,
CgCDR2
-, and
CgSNQ2
-encoded efflux pumps might explain the azole resistance in our set of isolates.
Pharmacokinetic Study of Tenofovir Disoproxil Fumarate Combined with Rifampin in Healthy Volunteers
Authors: Droste J. A. H. , Verweij-van Wissen C. P. W. G. M. , Kearney B. P. , Buffels R. , vanHorssen P. J. , Hekster Y. A. , Burger D. M.
Published: January 2005

Tenofovir disoproxil fumarate (tenofovir DF) was studied in combination with rifampin in 24 healthy subjects in a multiple-dose, open-label, single-group, two-period study. All subjects were given tenofovir DF at 300 mg once a day (QD) from days 1 to 10 (period 1). From days 11 to 20 the subjects received tenofovir DF at 300 mg combined with rifampin at 600 mg QD (period 2). The multiple-dose pharmacokinetics of tenofovir (day 10 and 20) and rifampin (day 20) were assessed. The drug-related adverse events (AEs) experienced during this study were mostly mild. Only one grade 3 AE possibly or probably related to the treatment (raised liver enzyme levels) occurred during period 2; the subject was withdrawn from the study. Pharmacokinetic data for 23 subjects were thus evaluable. Point estimates for the mean ratios of tenofovir with rifampin versus tenofovir alone for the area under the concentration-time curve from time zero to 24 h (AUC
0-24
), the maximum concentration of drug in plasma (
C
max
), and the minimum concentration of drug in plasma (
C
min
) were 0.88, 0.84, and 0.85, respectively. The 90% classical confidence intervals for AUC
0-24
,
C
max
, and
C
min
were 0.84 to 0.92, 0.78 to 0.90, and 0.80 to 0.91, respectively, thus suggesting pharmacokinetic equivalence. Similarly, coadministration of rifampin and tenofovir DF did not result in changes in the values of the tenofovir pharmacokinetic parameters. For rifampin, the values of the pharmacokinetic parameters found in this study were comparable to those found in the literature, indicating that tenofovir DF has no effect on the pharmacokinetics of rifampin. In conclusion, adaptation of either the rifampin or the tenofovir DF dose for the simultaneous treatment of tuberculosis and human immunodeficiency virus (HIV) infection in HIV-infected patients is probably not required.
Levofloxacin plus Metronidazole Administered Once Daily versus Moxifloxacin Monotherapy against a Mixed Infection of
Escherichia coli
and
Bacteroides fragilis
in an In Vitro Pharmacodynamic Model
Authors: Hermsen Elizabeth D. , Hovde Laurie B. , Sprandel Kelly A. , Rodvold Keith A. , Rotschafer John C.
Published: January 2005

Moxifloxacin has been suggested as an option for monotherapy of intra-abdominal infections. Recent data support the use of a once-daily metronidazole regimen. The purpose of this study was to investigate the activity of levofloxacin (750 mg every 24 h [q24h]) plus metronidazole (1,500 mg q24h) compared with that of moxifloxacin (400 mg q24h) monotherapy in a mixed-infection model. By using an in vitro pharmacodynamic model in duplicate,
Escherichia coli
and
Bacteroides fragilis
were exposed to peak concentrations of 8.5 mg of levofloxacin/liter q24h, 32 mg of metronidazole/liter q24h, and 2 mg for moxifloxacin/liter q24h for 24 h. The activities of levofloxacin, metronidazole, moxifloxacin, and levofloxacin plus metronidazole were evaluated against
E. coli
,
B. fragilis
, and
E. coli
plus
B. fragilis
. The targeted half-lives of levofloxacin, metronidazole, and moxifloxacin were 8, 8, and 12 h, respectively. Time-kill curves were analyzed for time to 3-log killing, slope, and regrowth. Pre- and postexposure MICs were determined. The preexposure levofloxacin, metronidazole, and moxifloxacin MICs for
E. coli
and
B. fragilis
were 0.5 and 1, >64 and 0.5, and 1 and 0.25 mg/liter, respectively. Levofloxacin and moxifloxacin achieved a 3-log killing against
E. coli
and
B. fragilis
in all experiments, as did metronidazole against
B. fragilis
. Metronidazole did not decrease the starting inoculum of
E. coli
. The area under the concentration-time curve/MIC ratios for
E. coli
and
B. fragilis
were 171.7 and 85.9, respectively, for levofloxacin and 26 and 103.9, respectively, for moxifloxacin. Levofloxacin plus metronidazole exhibited the fastest rates of killing. The levofloxacin and moxifloxacin MICs for
B. fragilis
increased 8- to 16-fold after the organism was exposed to moxifloxacin. No other changes in the postexposure MICs were found. Levofloxacin plus metronidazole administered once daily exhibited activity similar to that of moxifloxacin against the mixed
E. coli
and
B. fragilis
infection. A once-daily regimen of levofloxacin plus metronidazole looks promising for the treatment of intra-abdominal infections.
Novel
Plasmodium vivax dhfr
Alleles from the Indonesian Archipelago and Papua New Guinea: Association with Pyrimethamine Resistance Determined by a
Saccharomyces cerevisiae
Expression System
Authors: Hastings Michele D. , Maguire Jason D. , Bangs Michael J. , Zimmerman Peter A. , Reeder John C. , Baird J. Kevin , Sibley Carol Hopkins
Published: January 2005

In plasmodia, the dihydrofolate reductase (DHFR) enzyme is the target of the pyrimethamine component of sulfadoxine-pyrimethamine (S/P).
Plasmodium vivax
infections are not treated intentionally with antifolates. However, outside Africa, coinfections with
Plasmodium falciparum
and
P. vivax
are common, and
P. vivax
infections are often exposed to S/P. Cloning of the
P. vivax dhfr
gene has allowed molecular comparisons of
dhfr
alleles from different regions. Examination of the
dhfr
locus from a few locations has identified a very diverse set of alleles and showed that mutant alleles of the vivax
dhfr
gene are prevalent in Southeast Asia where S/P has been used extensively. We have surveyed patient isolates from six locations in Indonesia and two locations in Papua New Guinea. We sequenced
P. vivax dhfr
alleles from 114 patient samples and identified 24 different alleles that differed from the wild type by synonymous and nonsynonymous point mutations, insertions, or deletions. Most importantly, five alleles that carried four or more nonsynonymous mutations were identified. Only one of these highly mutant alleles had been previously observed, and all carried the 57L and 117T mutations.
P. vivax
cannot be cultured continuously, so we used a yeast assay system to determine in vitro sensitivity to pyrimethamine for a subset of the alleles. Alleles with four nonsynonymous mutations conferred very high levels of resistance to pyrimethamine. This study expands significantly the total number of novel
dhfr
alleles now identified from
P. vivax
and provides a foundation for understanding how antifolate resistance arises and spreads in natural
P. vivax
populations.
Mutations in the
Pneumocystis jirovecii DHPS
Gene Confer Cross-Resistance to Sulfa Drugs
Authors: Iliades Peter , Meshnick Steven R. , Macreadie Ian G.
Published: January 2005

Pneumocystis jirovecii
is a major opportunistic pathogen that causes
Pneumocystis
pneumonia (PCP) and results in a high degree of mortality in immunocompromised individuals. The drug of choice for PCP is typically sulfamethoxazole (SMX) or dapsone in conjunction with trimethoprim. Drug treatment failure and sulfa drug resistance have been implicated epidemiologically with point mutations in dihydropteroate synthase (DHPS) of
P. jirovecii. P. jirovecii
cannot be cultured in vitro; however, heterologous complementation of the
P. jirovecii
trifunctional folic acid synthesis (PjFAS) genes with an
E. coli DHPS
-disrupted strain was recently achieved. This enabled the evaluation of SMX resistance conferred by
DHPS
mutations. In this study, we sought to determine whether
DHPS
mutations conferred sulfa drug cross-resistance to 15 commonly available sulfa drugs. It was established that the presence of amino acid substitutions (T
517
A or P
519
S) in the DHPS domain of PjFAS led to cross-resistance against most sulfa drugs evaluated. The presence of both mutations led to increased sulfa drug resistance, suggesting cooperativity and the incremental evolution of sulfa drug resistance. Two sulfa drugs (sulfachloropyridazine [SCP] and sulfamethoxypyridazine [SMP]) that had a higher inhibitory potential than SMX were identified. In addition, SCP, SMP, and sulfadiazine (SDZ) were found to be capable of inhibiting the clinically observed drug-resistant mutants. We propose that SCP, SMP, and SDZ should be considered for clinical evaluation against PCP or for future development of novel sulfa drug compounds.
Antistaphylococcal Activity of Dalbavancin, an Experimental Glycopeptide
Authors: Lin Gengrong , Credito Kim , Ednie Lois M. , Appelbaum Peter C.
Published: January 2005

Dalbavancin, tested against 146 staphylococci, was more potent than other drugs tested, with an MIC at which 50% of staphylococci were inhibited of 0.03 μg/ml and an MIC at which 90% of staphylococci were inhibited of 0.06 μg/ml by microdilution. For all strains, MICs of vancomycin, linezolid, ranbezolid, oritavancin, daptomycin, and quinupristin-dalfopristin were ≤4.0 μg/ml. Dalbavancin was bactericidal at four times the MIC against all six strains tested.
Plasmid-Mediated Quinolone Resistance in Isolates Obtained in German Intensive Care Units
Authors: Jonas Daniel , Biehler Klaus , Hartung Doris , Spitzmüller Bettina , Daschner Franz D.
Published: January 2005

Screening of 703 isolates of
Enterobacteriaceae
, obtained from 34 German intensive care units (ICUs), revealed
qnr
-positive, integron-containing isolates of
Enterobacter
sp. and
Citrobacter freundii
from four patients in 2 German ICUs. This is one of the first reports of
qnr
-positive strains obtained from patients in Europe.
Simple Fibroblast-Based Assay To Test the Pyrazinamide Susceptibility of
Mycobacterium tuberculosis
Authors: Takii Takemasa , Hamasaki Sonomi , Hirano Kazue , Abe Chiyoji , Onozaki Kikuo
Published: January 2005

A simple fibroblast-based assay (SFA) was found to be efficient in evaluating the susceptibilities of clinical isolates of
Mycobacterium tuberculosis
to pyrazinamide (PZA). Forty-five clinical isolates were examined. The MICs of PZA for susceptible strains in an SFA were between 3.13 and 12.5 μg/ml, and the MICs of PZA for resistant strains were more than 100 μg/ml.
Combination Therapy with Amphotericin B Lipid Complex and Caspofungin Acetate of Disseminated Zygomycosis in Diabetic Ketoacidotic Mice
Authors: Spellberg Brad , Fu Yue , Edwards John E. , Ibrahim Ashraf S.
Published: January 2005

We studied the combination of amphotericin B lipid complex (ABLC) and caspofungin in mice with disseminatedRhizopus oryzae. Combination therapy improved survival compared to that of mice given monotherapy and that of untreated controls (P< 0.05) but did not improve organ clearance. In addition, prophylactic combination therapy was not more effective than prophylactic ABLC alone.
Dissemination of Sulfonamide Resistance Genes (
sul1
,
sul2
, and
sul3
) in Portuguese
Salmonella enterica
Strains and Relation with Integrons
Authors: Antunes Patrícia , Machado Jorge , Sousa João Carlos , Peixe Luísa
Published: January 2005

In 200 sulfonamide-resistant Portuguese
Salmonella
isolates, 152
sul1
, 74
sul2
, and 14
sul3
genes were detected. Class 1 integrons were always associated with
sul
genes, including
sul3
alone in some isolates. The
sul3
gene has been identified in isolates from different sources and serotypes, which also carried a class 1 integron with
aadA
and
dfrA
gene cassettes.
Stability of Fluoroquinolone Resistance in
Streptococcus pneumoniae
Clinical Isolates and Laboratory-Derived Mutants
Authors: Smith-Adam Heather J. , Nichol Kimberly A. , Hoban Daryl J. , Zhanel George G.
Published: January 2005

The stability of fluoroquinolone resistance in
Streptococcus pneumoniae
was evaluated in laboratory-derived mutants and clinical isolates. Isolates with various genotypes and phenotypes were subcultured for 20 days on antibiotic-free media and were monitored by E-tests to identify any alterations in resistance. Fluoroquinolone resistance mechanisms, whether efflux or chromosomally mediated, remained stable in both clinical and laboratory-derived mutants.
Selected Arylpiperazines Are Capable of Reversing Multidrug Resistance in
Escherichia coli
Overexpressing RND Efflux Pumps
Authors: Bohnert Jürgen A. , Kern Winfried V.
Published: January 2005

Several arylpiperazines capable of reversing multidrug resistance (MDR) in
Escherichia coli
overexpressing
acrAB
and
acrEF
but not in pump-deficient mutant strains were identified. 1-(1-Naphthylmethyl)-piperazine, one of the more active compounds, enhanced susceptibility to fluoroquinolones and other agents and increased the intracellular concentration of levofloxacin and ethidium bromide, suggesting efflux pump inhibition as the mechanism of MDR reversal.
Activity of Glycopeptides against
Staphylococcus aureus
Infection in a Rabbit Endocarditis Model: MICs Do Not Predict In Vivo Efficacy
Authors: Asseray Nathalie , Jacqueline Cedric , Le Mabecque Virginie , Batard Eric , Bugnon Denis , Potel Gilles , Caillon Jocelyne
Published: January 2005

The in vivo efficacy of vancomycin and teicoplanin against five
Staphylococcus aureus
strains with different susceptibilities to them and methicillin was studied. Rabbits were allocated at random to groups for endocarditis induction with one of these five strains and then treated for 2 days with vancomycin or teicoplanin. Each treated group was compared with a control group infected with the same strain. Vancomycin and teicoplanin showed similar activities. Low MICs did not predict better in vivo results.
Signaling through the extracellular signal-regulated kinase 1/2 cascade in cardiac myocytes
Authors: Clerk Angela , Sugden Peter H
Published: January 2005

The extracellular signal-regulated kinases 1/2 (ERK1/2) are particularly implicated in the growth response of cardiac myocytes. In these cells, the ERK1/2 pathway is potently activated by Gq protein-coupled receptor agonists (such as endothelin-1 or α-adrenergic agonists), which activate protein kinase C isoforms. Here, we review the mechanisms associated with the activation of the ERK1/2 pathway by these agonists with particular emphasis on signal integration into the pathway. Signaling to the nucleus and the regulation of transcription factor activity associated with ERK1/2 activation in cardiac myocytes are also discussed.Key words: mitogen-activated protein kinases, cardiac myocytes, intracellular signaling.
Rho GTPase function in flies: insights from a developmental and organismal perspective
Authors: Johndrow James E , Magie Craig R , Parkhurst Susan M
Published: January 2005

Morphogenesis is a key event in the development of a multicellular organism and is reliant on coordinated transcriptional and signal transduction events. To establish the segmented body plan that underlies much of metazoan development, individual cells and groups of cells must respond to exogenous signals with complex movements and shape changes. One class of proteins that plays a pivotal role in the interpretation of extracellular cues into cellular behavior is the Rho family of small GTPases. These molecular switches are essential components of a growing number of signaling pathways, many of which regulate actin cytoskeletal remodeling. Much of our understanding of Rho biology has come from work done in cell culture. More recently, the fruit fly Drosophila melanogaster has emerged as an excellent genetic system for the study of these proteins in a developmental and organismal context. Studies in flies have greatly enhanced our understanding of pathways involving Rho GTPases and their roles in development.Key words: Rho GTPases, Drosophila, development, effectors, loss-of-function mutation, dominant-negative, constitutively active.
Cardiac-specific transgenic overexpression of α1B-adrenergic receptors induce chronic activation of ERK MAPK signalling
Authors: Benoit Marie-Josée , Rindt Hansjörg , Allen Bruce G
Published: January 2005

Cardiomyocyte-specific overexpression of the wild-type α1B-adrenergic receptor (α1B-AR) produces a slowly progressing cardiomyopathy associated with clinical signs of heart failure and premature death around middle age (Lemire et al. 2001). In the heart, α1-AR activate the extracellular signal-regulated kinase (ERK) MAPK cascade. The aim of this project was to determine if cardiac-specific overexpression of the wild-type α1B-AR results in sustained activation of the ERK pathway. At 3 and 9 months, ERK activity was increased in α1B-AR overexpressing hearts relative to non-transgenic animals. Similarly, phosphorylation of MEK and p90rskwere also elevated. MAP kinase phosphatases (MKPs), which inactivate MAP kinases, are transcriptionally regulated. MKP2 mRNA levels were reduced at 3 months in α1B-AR overexpressing hearts. Interestingly, there was a general trend for reduced expression of MKP-1, -2, and -3 with increased age. In addition, expression of the modulatory calcineurin-interacting protein (MCIP) 1, an indicator of calcineurin activity, was elevated 3-fold in α1B-AR overexpressing hearts at both 3 and 9 months. These results indicate that the overexpression of the wild-type α1B-AR leads to chronic changes in the activation of signalling pathways previously shown to be associated with the hypertrophic response.Key words: cell communication, adrenergic receptor, signal transduction, heart, ERK, MKP, MCIP1.
Salicylic acid alters endothelin-1 binding in intact adult rat ventricular myocytes
Authors: Farhat Hala , Allen Bruce G
Published: January 2005

Endothelin receptors ETAR and ETBR form tight receptorligand complexes that complicate our understanding of the physiological, pharmacological, and biochemical properties of these receptors. Although radioligandbinding studies have demonstrated the binding of endothelin-1 (ET-1) to ETAR to be essentially irreversible, ETAR internalize in a ligand-dependent manner, release ET-1, and then recycle to the cell surface. Salicylic acid (SA) reduces ET-1 binding (IC50= 10 mmol/L) to recombinant ETAR in isolated membranes by promoting dissociation of [125I]ET-1. In the present study, SA (5 mmol SA/L) did not alter [125I]ET-1 binding to intact adult rat ventricular myocytes. The lack of effect was not due to internalization of receptorligand complexes. However, 100 mmol SA/L significantly reduced [125I]ET-1 binding to both intact myocytes and isolated membranes. SA induced the phosphorylation p42/44 extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase and an unidentified 40-kDa protein on the activating threonine-glutamic acid-tyrosine (T-E-Y) motif. ERK phosphorylation was reduced by a MAP kinase kinase (MEK) inhibitor, PD98059. Phosphorylation of p40 was reduced by the p38 MAP kinase inhibitor SB203580, but not PD98059. However, inhibition of ERK or p38 MAP kinases did not alter the ability of 100 mmol SA/L to induce dissociation of [125I]ET-1. These results suggest that, in the ventricular myocyte, salicylic acid alters the kinetics of ET-1 binding. The results also suggest an allosteric binding site may be present that modulates the dissociation of ET-1 receptorligand complexes in response to an as-of-yet unidentified mediator.Key words: cell communication, endothelin, endothelin receptor, inotropic agents, signal transduction, heart, ventricular myocyte.
The cardiac Na-H exchanger: a key downstream mediator for the cellular hypertrophic effects of paracrine, autocrine and hormonal factors
Authors: Fliegel Larry , Karmazyn Morris
Published: January 2005

The major mechanism by which the heart cell regulates intracellular pH is the Na+H+exchanger (NHE) with the NHE-1 isoform as the primary cardiac subtype. Although NHE-1 has been implicated in mediating ischemic injury, more recent evidence implicates the antiporter as a key mediator of hypertrophy, which is produced by various autocrine, paracrine and hormonal factors such as endothelin-1, angiotensin II, and α1adrenoceptor agonists. These agonists activate the antiporter via phosphorylation-dependent processes. NHE-1 inhibition is likely conducive to attenuating the remodelling process after myocardial infarction. These effects probably occur independently of infarct size reduction and involve attenuation of subsequent postinfarction heart failure. As such, inhibitors of NHE offer substantial promise for clinical development that will attenuate acute responses to myocardial postinfarction and chronic pos t infarction, which evolve toward heart failure. The regulation of NHE-1 is discussed as is its potential role in mediating cardiomyocyte hypertrophy.Key words: NHE-1, cardiac hypertrophy, heart failure, myocardial remodelling.
Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality
Authors: DeBell Dean S , Singleton Ryan , Gartner Barbara L , Marshall David D
Published: January 2005

Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. Growth and wood density traits of individual rings were measured via X-ray densitometry, and relationships of ring density and its components to age and growth rate were analyzed. Ring density was highest (0.49 g/cm3) near the pith, declined to 0.40 g/cm3 at age 10, remained stable to about age 25, and then increased gradually and remained between 0.43 and 0.44 g/cm3 from age 38 to 45 and beyond. A negative influence of rapid growth on whole ring density was greatest at young ages and diminished with time, becoming nonsignificant beyond age 30. Earlywood density, latewood density, and latewood proportion were all negatively related to ring width at young ages, but by age 21-25, latewood proportion was the only component of ring density that remained significantly diminished by increased growth rate. Residual differences in wood density (after age and growth rate were considered) did not appear to be related to either stand density or site class. Overall, young-growth hemlock trees are relatively uniform in wood density and likely to be more so if grown in intensively managed stands.
Allozyme variation, differentiation, and inbreeding in populations ofPinus mugoin Bulgaria
Authors: Slavov Gancho T , Zhelev Peter
Published: January 2005

Genetic variation of 17 populations of Pinus mugo Turra was studied using 10 polymorphic allozyme loci. Polymorphism and gene diversity in these populations were comparable to mean values for gymnosperm species, but slightly lower than in pines with large and continuous ranges. We did not find significant interpopulation differentiation (FST= 0.041) or isolation by distance, suggesting that gene flow might be extensive or that the time elapsed since the species range became fragmented has been too short for genetic differentiation to arise via genetic drift. We detected moderate and statistically significant levels of inbreeding (mean FIS= 0.252) for all loci in all populations. Although there are many possible explanations for this nonequilibrium population structure, we propose that the main reasons for its ubiquity are the peculiar growth form and reproductive biology of P. mugo, which promote excessive near-neighbor pollinations. Populations in Vitosha Mountain and western Stara Planina had the highest levels of inbreeding and the lowest observed heterozygosities. All populations in these mountains are small and isolated, but none of them is under a special regime of protection. Thus, the conservation status of P. mugo populations in Vitosha Mountain and western Stara Planina may deserve reevaluation. Future gene conservation efforts should focus on obtaining information on the genetic variation of adaptive traits in P. mugo.