bluuebunny/crossref_metadata_2025_split huggingface dataset:
Constructing views of science tied to issues of equity and diversity: A study of beginning science teachers
Authors: Bianchini Julie A. , Solomon Eric M. 
Published: December 2002

AbstractIn this study, we examined the discursive and social practices of a teacher educator (the first author) and her eight beginning science teachers in a course on the nature of science and issues of equity and diversity. We focused our investigation on beginning science teachers' views of science and science teaching, as well as the grounds they offered for their views. We organized our discussion of the nature of science, teacher learning, and grounds for views along three dimensions: personal, social, and political. We found that beginning teachers routinely drew from only one of these three dimensions to support their views of the nature of science and ways to represent science to all students. In our implications, we recommend that teacher educators encourage teacher learners to examine personal, social, and political grounds carefully and critically in the process of constructing or revising their views. We argue that attention to these three dimensions of grounds for views will assist beginning teachers in adopting nature of science positions that are broad and complex, that more clearly reflect the goals of equity and excellence, and thus, that hold greater promise for achieving a science education inclusive of all students. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 53–76, 2003
Contrasting landscapes: A comparison of the impact of different induction programs on beginning secondary science teachers' practices, beliefs, and experiences
Authors: Luft Julie A. , Roehrig Gillian H. , Patterson Nancy C. 
Published: December 2002

AbstractInduction programs are essential in addressing the unique pedagogical and content needs of secondary science teachers. Yet most secondary science teachers have little access to general induction programs, and even less opportunity to participate in specialized science induction programs. This study examines the impact of three different induction programs on secondary science teachers. The teachers were matched by grade level among three groups; one group participated in a science‐focused support program, another participated in a general support program, and a third had no formal support. All teachers were monitored during the spring semester to understand their teaching beliefs, instructional practices, and experiences in the classroom. The analysis of data revealed that the secondary science teachers in the science‐focused support program implemented more student‐centered inquiry lessons, held beliefs aligned with student‐centered practices, and felt fewer constraints in their teaching than did the other two groups of teachers. This study reinforces the importance of induction programs for teachers, suggests there is a need for specialized support programs for beginning science teachers, and recommends that universities and school districts work together to develop such programs. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 77–97, 2003
Software Radio—a key technology for adaptive access
Authors: Noll Josef , Buracchini Enrico 
Published: December 2002

AbstractThe paper provides a vision of an adaptive wireless access for next‐generation services. Depending on the requirements of the applications and the user situation, an optimum access method has to be selected. Software (SW) radio is the key enabling technology in this field. The functionality of a SW radio is described, and the challenges for future developments are identified. A major advantage of SW radio is the on‐the‐fly upgrade capabilities, both of terminals and of base stations. The paper concludes with a presentation of future trends, hybrid fibre distribution of radio signals and mechanisms for control of the various access networks. Copyright © 2002 John Wiley & Sons, Ltd.
A software radio–based reconfigurable transponder for space applications
Authors: Mondin Marina , Presti Letizia Lo , Scova Alessandro 
Published: December 2002

AbstractA novel approach to space communications is represented by the Software Radio (SR) concept, a new technology currently deeply investigated by the scientific community, especially for wireless applications such as mobile communications or wireless network access. The SR approach leads to the definition of a new generation of radio equipment, whose communication functions are almost completely defined by means of software modules. The main outcome of the deployment of this technology is the great flexibility of the radio interface. As a matter of fact the communication standards can be easily reconfigured by simply replacing the corresponding software modules.This paper describes the SDRsat research project that aims at designing a complete software radio reconfigurable regenerative transponder for space applications. Copyright © 2002 John Wiley & Sons, Ltd.
Vancomycin Acts Synergistically with Gentamicin against Penicillin-Resistant Pneumococci by Increasing the Intracellular Penetration of Gentamicin
Authors: Cottagnoud P. , Cottagnoud M. , Täuber M. G. 
Published: December 2002

ABSTRACT
Vancomycin and gentamicin act synergistically against penicillin-resistant pneumococci in vitro and in experimental rabbit meningitis. The aim of the present study was to investigate the underlying mechanism of this synergism. The intracellular concentration of gentamicin was measured by using the following experimental setting. Bacterial cultures were incubated with either gentamicin alone or gentamicin plus vancomycin for a short period (15 min). The gentamicin concentration was determined before and after grinding of the cultures by using the COBAS INTEGRA fluorescence polarization system (Roche). The grinding efficacies ranged between 44 and 54%, as determined by viable cell counts. In the combination regimen the intracellular concentration of gentamicin increased to 186% compared to that achieved with gentamicin monotherapy. These data suggest that the synergy observed in vivo and in vitro is based on an increased intracellular penetration of the aminoglycoside, probably due to the effect of vancomycin on the permeability of the cell wall.
Bacteremia Due to
Bacteroides fragilis
Group: Distribution of Species, β-Lactamase Production, and Antimicrobial Susceptibility Patterns
Authors: Aldridge Kenneth E. , Ashcraft Deborah , O'Brien Megan , Sanders Charles V. 
Published: December 2002

ABSTRACT

A retrospective analysis of susceptibility data on 542 blood isolates of the
Bacteroides fragilis
group tested from 1987 to 1999 by the same NCCLS-recommended broth microdilution method throughout is presented. Metronidazole, β-lactam-β-lactamase inhibitor combinations, carbapenems, and trovafloxacin were the most active agents (susceptibility of ≥93%). Among the cephalosporin-cephamycins, the order of activity was cefoxitin > ceftizoxime > cefotetan = cefotaxime = cefmetazole > ceftriaxone. All isolates were resistant to penicillin G, and 22% were resistant to clindamycin. The susceptibility rates to piperacillin-tazobactam, imipenem, and meropenem were affected least among isolates resistant to cefoxitin or clindamycin. Except for piperacillin-tazobactam, imipenem, and meropenem, the
B. fragilis
species was more susceptible than were the non-
B. fragilis
species. These data underscore the importance of susceptibility testing of the
B. fragilis
group and can serve as a guide in the choice of empirical antimicrobial therapy.
In Vitro Activities of Cethromycin (ABT-773), a New Ketolide, against
Streptococcus pneumoniae
Strains That Are Not Susceptible to Penicillin or Macrolides
Authors: Mason Edward O. , Lamberth Linda B. , Wald Ellen R. , Bradley John S. , Barson William J. , Kaplan Sheldon L. 
Published: December 2002

ABSTRACT

Pneumococcal resistance to antimicrobials presents problems to physicians for empirical treatment of acute otitis media (AOM). Three hundred thirty-three isolates of
Streptococcus pneumoniae
selected for nonsusceptibility to penicillin (MIC >0.1 μg/ml) from the middle ear (
n
= 325) or mastoid (
n
= 8) of children seen between 1994 and 2000 at four children's hospitals in the United States were tested by broth microdilution for susceptibility to nine antibiotics. Using NCCLS 2002 breakpoints, resistance to the following drugs was as indicated: amoxicillin, 1%; azithromycin, 71%; cefprozil, 71%; ceftriaxone, 2%; cefdinir, 98%; erythromycin, 70%; levofloxacin, 0%; and trimethoprim-sulfamethoxazole, 93%. Of the penicillin- and erythromycin-nonsusceptible isolates, 97% were inhibited by cethromycin (ABT-773) and 83% were inhibited by telithromycin at a concentration of ≤0.125 μg/ml. Macrolide resistance among penicillin-nonsusceptible pneumococci increased from 44 to 80% in the 6 years of the study from which the isolates were selected; however, the proportion of isolates with M or MLS
B
phenotypes remained constant over the time period (53 and 18%, respectively). Prior treatment with a macrolide or clindamycin alone or in combination with a β-lactam resulted in 94 or 85% of isolates causing infections being macrolide and or clindamycin resistant. No prior individual macrolide (azithromycin, erythromycin, or clarithromycin) resulted in more macrolide resistance or in a more prevalent resistance phenotype. The ketolides appear to be active antimicrobials against penicillin- and macrolide-resistant pneumococci.
Simple In Vitro Assay for Determining the Sensitivity of
Plasmodium vivax
Isolates from Fresh Human Blood to Antimalarials in Areas where
P. vivax
Is Endemic
Authors: Russell Bruce M. , Udomsangpetch Rachanee , Rieckmann Karl H. , Kotecka Barbara M. , Coleman Russell E. , Sattabongkot Jetsumon 
Published: December 2002

ABSTRACT

The aim of this study was to develop a simple, field-practical, and effective in vitro method for determining the sensitivity of fresh erythrocytic
Plasmodium vivax
isolates to a range of antimalarials. The method used is a modification of the standard World Health Organization (WHO) microtest for determination of
P. falciparum
drug sensitivity. The WHO method was modified by removing leukocytes and using a growth medium supplemented with AB
+
serum. We successfully carried out 34 in vitro drug assays on 39
P. vivax
isolates collected from the Mae Sod malaria clinic, Tak Province, Thailand. The mean percentage of parasites maturing to schizonts (six or more merozoites) in control wells was 66.5% ± 5.9% (standard deviation). This level of growth in the control wells enabled rapid microscopic determination (5 min per isolate per drug) of the MICs of chloroquine, dihydroartemisinin, WR238605 (tafenoquine), and sulfadoxine.
P. vivax
was relatively sensitive to chloroquine (MIC = 160 ng/ml, 50% inhibitory concentration [IC
50
] = 49.8 ng/ml) and dihydroartemisinin (MIC = 0.5 ng/ml, IC
50
= 0.47 ng/ml). The poor response of
P. vivax
to both tafenoquine (MIC = 14,000 ng/ml, IC
50
= 9,739 ng/ml) and sulfadoxine (MIC = 500,000 ng/ml, IC
50
= 249,000 ng/ml) was due to the slow action of these drugs and the innate resistance of
P. vivax
to sulfadoxine. The in vitro assay developed in our study should be useful both for assessing the antimalarial sensitivity of
P. vivax
populations and for screening new antimalarials in the absence of long-term
P. vivax
cultures.
In Vitro Activities of 7-Substituted 9-Chloro and 9-Amino-2-Methoxyacridines and Their Bis- and Tetra-Acridine Complexes against
Leishmania infantum
Authors: Di Giorgio Carole , Delmas Florence , Filloux Nathalie , Robin Maxime , Seferian Laetitia , Azas Nadine , Gasquet Monique , Costa Muriel , Timon-David Pierre , Galy Jean-Pierre 
Published: December 2002

ABSTRACT

9-Chloro and 9-amino-2-methoxyacridines bearing different substituents in position 7, as well as their corresponding unsubstituted dimeric and tetrameric complexes, were investigated for in vitro antiproliferative properties against
Leishmania infantum
compared to toxicity towards human monocytes. The results clearly confirmed that several compounds of the 2-methoxyacridine series, together with their corresponding dimeric and tetrameric derivatives, had strong in vitro antiparasitic properties. Antileishmanial activity was shown to depend on the nature of both 7- and 9-substituted groups in monoacridines, while it varied according to the nature of the 9-substituted group and the length of the linker among bis- and tetra-acridines. The effects of acridine derivatives on DNA synthesis raised the hypothesis that DNA metabolism constituted their main target in
Leishmania
promastigotes; however, secondary effects on other biochemical pathways, including protein and lipid metabolism, were observed, suggesting that acridine compounds could be considered multitarget drugs.
Exploring the Structure and Function of the Mycobacterial KatG Protein Using
trans
-Dominant Mutants
Authors: DeVito Joseph A. , Morris Sheldon 
Published: December 2002

ABSTRACT

In order to probe the structure and function of the mycobacterial catalase-peroxidase enzyme (KatG), we employed a genetic approach using dominant-negative analysis of
katG
merodiploids. Transformation of
Mycobacterium bovis
BCG with various
katG
point mutants (expressed from low-copy-number plasmids) resulted in reductions in peroxidase and catalase activities as measured in cell extracts. These reductions in enzymatic activity usually correlated with increased resistance to the antituberculosis drug isoniazid (INH). However, for the N138S
trans
-dominant mutant, the catalase-peroxidase activity was significantly decreased while the sensitivity to INH was retained.
trans
-dominance required
katG
expression from multicopy plasmids and could not be demonstrated with
katG
mutants integrated elsewhere on the wild-type
M. bovis
BCG chromosome. Reversal of the mutant phenotype through plasmid exchange suggested the catalase-peroxidase deficiency occurred at the protein level and that INH resistance was not due to a second site mutation(s). Electrophoretic analysis of KatG proteins from the
trans
-dominant mutants showed a reduction in KatG dimers compared to WT and formation of heterodimers with reduced activity. The mutants responsible for these defects cluster around proposed active site residues: N138S, T275P, S315T, and D381G. In an attempt to identify mutants that might delimit the region(s) of KatG involved in subunit interactions, C-terminal truncations were constructed (with and without the D381G dominant-negative mutation). None of the C-terminal deletions were able to complement a Δ
katG
strain, nor could they cause a dominant-negative effect on the WT. Taken together, these results suggest an intricate association between the amino- and carboxy-terminal regions of KatG and may be consistent with a domain-swapping mechanism for KatG dimer formation.
Activity and Diffusion of Tigecycline (GAR-936) in Experimental Enterococcal Endocarditis
Authors: Lefort Agnès , Lafaurie Matthieu , Massias Laurent , Petegnief Yolande , Saleh-Mghir Azzam , Muller-Serieys Claudette , Le Guludec Dominique , Fantin Bruno 
Published: December 2002

ABSTRACT

The activity of tigecycline (GAR-936), a novel glycylcycline, was investigated in vitro and in experimental endocarditis due to the susceptible
Enterococcus faecalis
JH2-2 strain, its VanA type transconjugant BM4316, and a clinical VanA type strain,
E. faecium
HB217 resistant to tetracycline. MICs of GAR-936 were 0.06 μg/ml for the three strains. In vitro pharmacodynamic studies demonstrated a bacteriostatic effect of GAR-936 that was not enhanced by increasing concentrations to more than 1 μg/ml and a postantibiotic effect ranging from 1 to 4.5 h for concentrations of 1- to 20-fold the MIC. Intravenous injection of [
14
C]GAR-936 to five rabbits with enterococcal endocarditis sacrificed 30 min, 4 h, or 12 h after the end of the infusion evidenced a lower clearance of GAR-936 from aortic vegetations than from serum and a homogeneous diffusion of GAR-936 into the vegetations. In rabbits with endocarditis, GAR-936 (14 mg/kg of body weight twice a day [b.i.d.]) given intravenously for 5 days was bacteriostatic against both strains of
E. faecalis
. Against
E. faecium
HB217, bacterial counts in vegetations significantly decreased during therapy (
P
< 0.01), and the effect was similar with GAR-936 at 14 mg/kg b.i.d., 14 mg/kg once a day (o.d.), and 7 mg/kg o.d., which provided concentrations in serum constantly above the MIC. Mean serum elimination half-life ranged from 3.3 to 3.6 h. No GAR-936-resistant mutants were selected in vivo with any regimen. We concluded that the combination of prolonged half-life, significant postantibiotic effect, and good and homogeneous diffusion into the vegetations may account for the in vivo activity of GAR-936 against enterococci susceptible or resistant to glycopeptides and tetracyclines, even when using a o.d. regimen in rabbits.
Chemotherapy with Benznidazole and Itraconazole for Mice Infected with Different
Trypanosoma cruzi
Clonal Genotypes
Authors: Toledo Max Jean de Ornelas , Bahia Maria Terezinha , Carneiro Cláudia M. , Martins-Filho Olindo Assis , Tibayrenc Michel , Barnabé Christian , Tafuri Washington Luis , de Lana Marta 
Published: December 2002

ABSTRACT

The benznidazole (BZ) and itraconazole (ITC) susceptibilities of a standard set of
Trypanosoma cruzi
natural stocks were evaluated during the acute phase and the chronic phase of experimental chagasic infection in BALB/c mice. Twenty laboratory-cloned stocks representative of the total phylogenetic diversity of
T. cruzi
, including genotypes 20 and 19 (
T. cruzi
I) and genotypes 39 and 32 (
T. cruzi
II), were analyzed. Our results demonstrate important differences among stocks that could be pointed out as markers of biological behavior. Members of the
T. cruzi
I group were highly resistant to both BZ and ITC, whereas members of the
T. cruzi
II group were partially resistant to both drugs, despite their susceptibilities to ITC during the chronic phase of infection. The resistance to BZ observed for
T. cruzi
I was mainly triggered by genotype 20 isolates, whereas resistance to ITC was due to both genotype 20 and 19 isolates. Two polar patterns of response to BZ observed for genotype 39 isolates had a major impact on the partial resistance pattern observed for members of the
T. cruzi
II group. Genotype 32 isolates showed a typical profile of susceptibility. The correlation between the response to treatment and phylogenetic classification of
T. cruzi
stocks was clearer for ITC than for BZ. In conclusion, the data presented show a correlation between phylogenetic divergence among
T. cruzi
stocks and their susceptibilities to chemotherapeutic agents in vivo. Our results warn of the necessity to take into account the lesser genetic subdivisions of
T. cruzi
stocks since the upper subdivisions (
T. cruzi
I and II) show a great deal of heterogeneity for in vivo drug susceptibility.
Enzymatic Assay for Measurement of Intracellular DXG Triphosphate Concentrations in Peripheral Blood Mononuclear Cells from Human Immunodeficiency Virus Type 1-Infected Patients
Authors: Kewn Stephen , Wang Laurene H. , Hoggard Patrick G. , Rousseau Franck , Hart Robert , MacNeela John P. , Khoo Saye H. , Back David J. 
Published: December 2002

ABSTRACT

DXG {[2
R
-
cis
]-2-amino-1,9-dihydro-9-[2-[hydroxymethyl]-1,3-dioxolan-4-yl]-6H-purin-6-one} and its prodrug DAPD ([2
R
-
cis
]-4-[2,6-diamino-9H-purin-9-yl]-1,3-dioxolane-2-methanol; amdoxovir) are novel 2′,3′-dideoxynucleosides (ddNs) displaying activity against human immunodeficiency virus type 1 (HIV-1). In this paper, we describe the development of an enzymatic assay for determining the intracellular active metabolite of DXG and DAPD, DXG triphosphate (DXGTP), in peripheral blood mononuclear cells (PBMCs) from HIV-infected patients. The assay involves inhibition of HIV reverse transcriptase (RT), which normally incorporates radiolabeled deoxynucleoside triphosphates (dNTPs) into a synthetic template primer. DXGTP (0.6 pmol) inhibited control product formation with or without a preincubation step. Inhibition was greatest when the template primer was most diluted. DAPDTP inhibited control product formation only at very high levels (50 pmol) and when a preincubation procedure was used. However, reduced template primer stability in assays using preincubation steps, coupled with potential interference by DAPDTP, led to the current assay method for DXGTP being performed without preincubation. Standard DXGTP inhibition curves were constructed. The presence of PBMC extracts or endogenous dGTP did not interfere with the DXGTP assay. Intracellular DXGTP and dGTP concentrations were determined in PBMCs from HIV-infected patients receiving oral DAPD (500 mg b.i.d.). Peak concentrations of DXGTP were obtained 8 h after dosing and were measurable through 48 h postdose. Levels of endogenous dGTP were also determined over 48 h. No direct relationship was observed between concentrations of DXGTP and dGTP. Quantification of DXGTP concentrations in PBMCs from patients receiving a clinically relevant dose of DAPD is possible with this enzymatic assay.
Contributions of MexAB-OprM and an EmrE Homolog to Intrinsic Resistance of
Pseudomonas aeruginosa
to Aminoglycosides and Dyes
Authors: Li Xian-Zhi , Poole Keith , Nikaido Hiroshi 
Published: December 2002

ABSTRACT

Of the six putative small multidrug resistance (SMR) family proteins of
Pseudomonas aeruginosa
, a protein encoded by the PA4990 gene (
emrE
Pae
) shows the highest identity to the well-characterized EmrE efflux transporter of
Escherichia coli
. Reverse transcription-PCR confirmed the expression of
emrE
Pae
in the wild-type strain of
P. aeruginosa
. Using isogenic
emrE
Pae
,
mexAB-oprM
, and/or
mexB
deletion mutants, the contributions of the EmrE protein and the MexAB-OprM efflux system to drug resistance in
P. aeruginosa
were assessed by a drug susceptibility test carried out in a low-ionic-strength medium, Difco nutrient broth. We found that EmrE
Pae
contributed to intrinsic resistance not only to ethidium bromide and acriflavine but also to aminoglycosides. In this low-ionic-strength medium, MexAB-OprM was also shown to contribute to aminoglycoside resistance, presumably via active efflux. Aminoglycoside resistance caused by these two pumps could not be demonstrated in high-ionic-strength media, such as Luria broth or Mueller-Hinton broth. The EmrE-dependent efflux of ethidium bromide was confirmed by a continuous fluorescence assay.
Reactivity of Reduced [2Fe-2S] Ferredoxins Parallels Host Susceptibility to Nitroimidazoles
Authors: Vidakovic Momcilo , Crossnoe Chetlen R. , Neidre Christopher , Kim Kyonghee , Krause Kurt L. , Germanas Juris P. 
Published: December 2002

ABSTRACT

The kinetics of the electron transfer reaction between reduced [2Fe-2S] ferredoxins and select nitroimidazole antimicrobial agents is reported. The ferredoxins from the protozoan
Trichomonas vaginalis
and the cyanobacterium
Anabaena
sp. strain 7120 were studied because they are the proximal electron donors to nitroimidazoles in these two organisms with significantly different nitroimidazole susceptibilities. The rates of electron transfer from
Anabaena
ferredoxin to all nitroimidazoles were 1 to 2 orders of magnitude lower than for
T. vaginalis
ferredoxin. Quantitative structure-activity analysis of the kinetic data showed that the size of the alkyl substituent on the N-1 position of the imidazole ring strongly influenced the magnitude of the electron transfer rate constant. This implies that the distance between the iron-sulfur cluster and the nitro group of the imidazole is the critical variable in determining the rate of electron transfer. A correlation between the magnitude of the one-electron transfer rate constant with the susceptibility of the host organism to the cytotoxic effects of nitroimidazoles was also discovered. These results demonstrate that reductive activation is the most crucial step in determining the toxicity of nitroimidazoles.