bluuebunny/crossref_metadata_2025 huggingface dataset:
Signaling Via the T Cell Receptor
Authors: Singer Andrew L. , Jordan Martha S. , Judd Barbi A. , Myung Peggy S. , Newbrough Sally A. , Nichols Kim E. , Olenchock Benjamin A. , Peterson Erik J. , Wu Jennifer N. , Zhong Xiao-Ping , Koretzky Gary A.
Published: September 2003

Upon T cell receptor (TCR) engagement, Lck (a member of the Src family of protein tyrosine kinases) phosphorylates immunoreceptor tyrosine-based activation motifs (ITAMs) contained within the cytoplasmic domains of the chains of the CD3 complex. Subsequently, Zap70 (a member of the Syk family of kinases) is recruited by binding of its Src homology 2 (SH2) domains to the phosphorylated ITAM sites. Activated Zap70 propagates signal transduction through the phosphorylation of downstream targets, including the adaptor molecules LAT and SLP-76. These adaptors facilitate phospholipase C-γ1 (PLCγ1) activation, resulting in the cleavage of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P
2
] to inositol 1,4,5-trisphosphate (IP
3
) and diacylglycerol (DAG). The known signaling pathways that lead to T cell activation upon TCR engagement rely on IP
3
and DAG second messengers. IP
3
triggers calcium mobilization, which leads to activation of the transcription factor nuclear factor of activated T cells (NF-AT). DAG activates Ras guanine nucleotide-releasing protein (RasGRP) and protein kinase C θ (PKCθ), which in turn lead to activation of the Ras-mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways, respectively. CD45 and Csk have been identified as key proximal regulators of T cell signal transduction by modulating phosphorylation and, hence, enzymatic activity of the Src family kinases. The Connections Maps Pathway emphasizes the signaling events that lead to changes in gene expression in response to T cell activation.

Science Viewpoint

A. L. Singer, G. A. Koretzky, Control of T cell function by positive and negative regulators.
Science
296
, 1639-1640 (2002). [
Abstract
] [
Full Text
]
The Ins and Outs of STAT1 Nuclear Transport
Authors: McBride Kevin M. , Reich Nancy C.
Published: September 2003

There is an inherent elegance in being in the right place at the right time. The STAT1 transcription factor possesses regulatory signals that ensure its distribution to the right cellular location at the right time. Latent STAT1 resides primarily in the cytoplasm, and there it responds to hormone signaling through tyrosine phosphorylation by Janus kinases or growth factor receptors. After phosphorylation, STAT1 dimerizes, and this conformational change reveals a nuclear import signal that is recognized by a specific nuclear import carrier. In the nucleus, the STAT1 dimer dissociates from the import carrier and binds to specific DNA target sites in the promoters of regulated genes. STAT1 is subsequently dephosphorylated in the nucleus by a constitutively active tyrosine phosphatase, leading to its dissociation from DNA. A nuclear export signal of STAT1 appears to be masked when dimers are bound to DNA, but it becomes accessible to the CRM1 export carrier after dissociation from DNA. CRM1 binds STAT1 and transports the transcription factor back to the cytoplasm. Studies show that the regulatory trafficking signals that guide the nuclear import and export of STAT1 reside within its DNA binding domain. The location of these signals indicates that their function has coevolved with the ability of STAT1 to bind DNA and regulate gene expression. The nuclear import and subsequent recycling of STAT1 to the cytoplasm are integral to its function as a signal transducer and activator of transcription.
The JAK-STAT Pathway
Authors: Aaronson David S. , Horvath Curt M.
Published: September 2003

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway transmits information received from extracellular polypeptide signals, through transmembrane receptors, directly to transcription factors that bind target gene promoters in the nucleus. This process provides a mechanism for transcriptional regulation without second messengers. Evolutionarily conserved in eukaryotic organisms from slime molds to humans, JAK-STAT signaling appears to be an early adaptation to facilitate intercellular communication that has coevolved with myriad cellular signaling events. This coevolution has given rise to highly adapted, ligand-specific signaling pathways that control gene expression. In addition, the JAK-STAT signaling pathways are regulated by a vast array of intrinsic and environmental stimuli, which can add plasticity to the response of a cell or tissue. The Connections Map provides a generalized view of this JAK-STAT signaling, with additional Connections Maps highlighting the components that are activated by type I interferons (IFN-α/β), IFN-γ, and interleukins and growth factors that activate STAT3.

Science Viewpoint

D. S. Aaronson, C. M. Horvath, A road map for those who don't know JAK-STAT.
Science
296
, 1653-1655 (2002).[
Abstract
] [
Full Text
]
The Type I Interferon Pathway
Authors: Aaronson David S. , Horvath Curt M.
Published: September 2003

The type I interferon (IFN-α/β) signal transduction pathway is not only the first-characterized Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, but one of the best studied in molecular detail. IFN-α-stimulated gene factor 3 (ISGF3) is atypical for STAT-containing complexes, because it requires interaction with an additional factor, IFN regulatory factor 9 (IRF9), to provide specific DNA binding. Type I IFN is the main innate antiviral cytokine, and the outcome of ISGF3 activation is establishment of the cellular antiviral state, in which cells are able to inhibit the replication of a broad range of virus types providing a general resistance to infection. It is increasingly evident that other branches of the innate and adaptive immune systems activate IFN-α/β signaling, indicating its importance in various stress responses. The Connections Map provides an overview of this canonical pathway, with an interpathway relation to the Toll-like Receptor Pathway, which stimulates the production of type I interferons in response to microbial pathogens.

Science Viewpoint

D. S. Aaronson, C. M. Horvath, A road map for those who don't know JAK-STAT.
Science
296
, 1653-1655 (2002). [
Abstract
] [
Full Text
]
Intrinsic Macrolide Resistance in
Mycobacterium smegmatis
Is Conferred by a Novel
erm
Gene,
erm
(38)
Authors: Nash Kevin A.
Published: September 2003

High-level, acquired macrolide resistance in mycobacteria is conferred by mutation within the 23S rRNA gene. However, several mycobacteria are naturally resistant to macrolides, including the
Mycobacterium smegmatis
group and
Mycobacterium tuberculosis
complex. Thus, the aim of this study was to characterize this resistance. Intrinsic macrolide resistance in
M. smegmatis
was inducible and showed cross-resistance to lincosamides but not to streptogramin B (i.e., ML resistance). A similar phenotype was found with
Mycobacterium microti
and macrolide-resistant
Mycobacterium fortuitum
. A search of the DNA sequence data for
M. smegmatis
strain mc
2
155 identified a novel
erm
gene,
erm
(38), and expression analysis showed that
erm
(38) RNA levels increased >10-fold after a 2-h incubation with macrolide. Inducible ML resistance was not expressed by an
erm
(38) knockout mutant, and complementation of this mutant with intact
erm
(38) in
trans
resulted in high-level ML resistance (e.g., clarithromycin MIC of >512 μg/ml). Thus, the results indicate that
erm
(38) confers the intrinsic ML resistance of
M. smegmatis
. Southern blot analysis with an
erm
(38)-specific probe indicated that a similar gene may be present in macrolide-resistant
M. fortuitum
. This finding, with the presence of the
erm
(37) gene (Rv1988) in the
M. tuberculosis
complex, suggests that such genes are widespread in mycobacteria with intrinsic macrolide resistance.
Antibiotic-Dependent Induction of
Pseudomonas putida
DOT-T1E TtgABC Efflux Pump Is Mediated by the Drug Binding Repressor TtgR
Authors: Terán Wilson , Felipe Antonia , Segura Ana , Rojas Antonia , Ramos Juan-Luis , Gallegos María-Trinidad
Published: September 2003

Pseudomonas putida
is well known for its metabolic capabilities, but recently, it has been shown to exhibit resistance to a wide range of antibiotics. In
P. putida
DOT-T1E, the TtgABC efflux pump, which has a broad substrate specificity, extrudes antibiotics such as ampicillin, carbenicillin, tetracycline, nalidixic acid, and chloramphenicol. We have analyzed the expression of the
ttgABC
efflux pump operon and its regulatory gene,
ttgR
, in response to several structurally unrelated antibiotics at the transcriptional level and investigated the role of the TtgR protein in this process.
ttgABC
and
ttgR
are expressed in vivo at a moderate basal level, which increases in the presence of hydrophobic antibiotics like chloramphenicol and tetracycline. In vitro experiments show that, in the absence of inducers, TtgR binds to a palindromic operator site which overlaps both
ttgABC
and
ttgR
promoters and dissociates from it in the presence of chloramphenicol and tetracycline. These results suggest that the TtgR repressor is able to bind to structurally different antibiotics, which allows induction of TtgABC multidrug efflux pump expression in response to these antimicrobial agents. This is the first case in which the expression of a drug transporter of the resistance-nodulation-division family has been shown to be regulated directly by antibiotics.
Antimony Uptake Systems in the Protozoan Parasite
Leishmania
and Accumulation Differences in Antimony-Resistant Parasites
Authors: Brochu Christian , Wang Jingyu , Roy Gaétan , Messier Nadine , Wang Xiao-Yan , Saravia Nancy G. , Ouellette Marc
Published: September 2003

The first line drug against leishmaniasis consists of pentavalent antimony [Sb(V)], but there is general belief that the active form of the metal is the trivalent form [Sb(III)]. In this study, we have quantified the accumulation of Sb(V) and Sb(III) in
Leishmania
by using inductively coupled plasma mass spectrometry. The accumulation was studied in three
Leishmania
species at various life stages, sensitive or resistant to antimony. Both Sb(III) and Sb(V) are accumulated in promastigote and amastigote parasites, but through competition experiments with arsenite, we found that the routes of entry of Sb(V) and Sb(III) are likely to differ in
Leishmania
. The level of accumulation of either Sb(III) or Sb(V), however, was not correlated with the susceptibility of wild-type
Leishmania
cells to antimony. This suggests that other factors may also be implicated in the mode of action of the drugs. In contrast to metal susceptibility, resistance to Sb(III) correlated well with decreased antimony accumulation. This phenotype was energy dependent and highlights the importance of transport systems in drug resistance of this protozoan parasite.
Multilaboratory Comparison of Proficiencies in Susceptibility Testing of
Helicobacter pylori
and Correlation between Agar Dilution and E Test Methods
Authors: Best L. M. , Haldane D. J. M. , Keelan M. , Taylor D. E. , Thomson A. B. R. , Loo V. , Fallone C. A. , Lyn P. , Smaill F. M. , Hunt R. , Gaudreau C. , Kennedy J. , Alfa M. , Pelletier R. , Veldhuyzen van Zanten S. J. O.
Published: September 2003

Susceptibility testing was performed at seven Canadian microbiology laboratories and the Helicobacter Reference Laboratory, Halifax, Nova Scotia, Canada, to assess susceptibility testing proficiency and the reproducibility of the results for clarithromycin and metronidazole and to compare the Epsilometer test (E test) method to the agar dilution reference method. Control strain
Helicobacter pylori
ATCC 43504 (American Type Culture Collection) and 13 clinical isolates (plus duplicates of four of these strains including ATCC 43504) were tested blindly. The National Committee for Clinical Laboratory Standards (NCCLS) guidelines for agar dilution testing were followed, and the same suspension of organisms was used for agar dilution and E test. Antimicrobials and E test strips were provided to the investigators. Methods were provided on a website (
www.Helicobactercanada.org
). Each center reported MICs within the stated range for strain ATCC 43504. Compared to the average MICs, interlaboratory agreements within 2 log
2
dilutions were 90% (range, 69 to 100%) for clarithromycin by agar dilution, with seven very major errors [VMEs], and 85% (range, 65 to 100%) by E test, with three VMEs. Interlaboratory agreements within 2 log
2
dilutions were 83% (range, 50 to 100%) for metronidazole by agar dilution, with six VMEs and eight major errors (MEs), and 75% (range, 50 to 94%) by E test, with four VMEs and four MEs. At lower and higher concentrations of antibiotic, E test MICs were slightly different from agar dilution MICs, but these differences did not result in errors. When a standardized protocol based on NCCLS guidelines was used, most participants in this study correctly identified clarithromycin- and metronidazole-susceptible and -resistant strains of
H. pylori
93% of the time by either the agar dilution or E test method, and the numbers of errors were relatively equivalent by both methods.
Antifungal Susceptibility Survey of 2,000 Bloodstream
Candida
Isolates in the United States
Authors: Ostrosky-Zeichner Luis , Rex John H. , Pappas Peter G. , Hamill Richard J. , Larsen Robert A. , Horowitz Harold W. , Powderly William G. , Hyslop Newton , Kauffman Carol A. , Cleary John , Mangino Julie E. , Lee Jeannette
Published: September 2003

Candida
bloodstream isolates (
n
= 2,000) from two multicenter clinical trials carried out by the National Institute of Allergy and Infectious Diseases Mycoses Study Group between 1995 and 1999 were tested against amphotericin B (AMB), flucytosine (5FC), fluconazole (FLU), itraconazole (ITR), voriconazole (VOR), posaconazole (POS), caspofungin (CFG), micafungin (MFG), and anidulafungin (AFG) using the NCCLS M27-A2 microdilution method. All drugs were tested in the NCCLS-specified RPMI 1640 medium except for AMB, which was tested in antibiotic medium 3. A sample of isolates was also tested in RPMI 1640 supplemented to 2% glucose and by using the diluent polyethylene glycol (PEG) in lieu of dimethyl sulfoxide for those drugs insoluble in water. Glucose supplementation tended to elevate the MIC, whereas using PEG tended to decrease the MIC. Trailing growth occurred frequently with azoles. Isolates were generally susceptible to AMB, 5FC, and FLU. Rates of resistance to ITR approached 20%. Although no established interpretative breakpoints are available for the candins (CFG, MFG, and AFG) and the new azoles (VOR and POS), they all exhibited excellent antifungal activity, even for those strains resistant to the other aforementioned agents.
Clinical Isolates of
Streptococcus pneumoniae
with Different Susceptibilities to Ceftriaxone and Cefotaxime
Authors: Karlowsky James A. , Jones Mark E. , Draghi Deborah C. , Sahm Daniel F.
Published: September 2003

Ceftriaxone and cefotaxime are extended-spectrum cephalosporins previously demonstrated to possess very similar in vitro activities against
Streptococcus pneumoniae
. Anecdotal reports of isolates with divergent in vitro susceptibilities to ceftriaxone and cefotaxime have been published. To determine the prevalence of pneumococcal isolates with divergent ceftriaxone and cefotaxime susceptibilities, we tested 1,000 clinical isolates collected by U.S. laboratories in 2001-2002 by broth microdilution and E-test. The percentages of isolates susceptible to ceftriaxone and cefotaxime were significantly different by both broth microdilution (98.6 and 96.6%, respectively;
P
< 0.05) and E-test (98.3 and 95.8%;
P
< 0.001). The differences observed were due solely to the activities of the two agents against penicillin-resistant isolates. Twenty-six of 188 penicillin-resistant isolates (13.8%) demonstrated different ceftriaxone and cefotaxime MIC interpretative phenotypes when tested by broth microdilution; 18 isolates were concurrently ceftriaxone susceptible and cefotaxime intermediate, 6 were ceftriaxone intermediate and cefotaxime resistant, and 2 were ceftriaxone susceptible and cefotaxime resistant (1.1% of penicillin-resistant isolates; 0.2% of all isolates tested). Sixteen of the 26 isolates (65%) were from southern U.S. states. The 26 isolates had serogroups and serotypes (6, 9, 14, 19, and 23) commonly associated with penicillin-resistant isolates;
Sma
I pulsed-field gel electrophoresis identified 18 isolates (69%) dispersed among five subtype groups and 8 isolates that were unrelated to any of the other isolates. We conclude that certain isolates of penicillin-resistant pneumococci are less susceptible to cefotaxime than to ceftriaxone and that these isolates are not the result of the spread of a single clone. Whether such isolates have increased in prevalence over time remains unknown.
In Vitro Activities of New Antifungal Agents against
Chaetomium
spp. and Inoculum Standardization
Authors: Serena Carolina , Ortoneda Montserrat , Capilla Javier , Pastor F. Javier , Sutton Deanna A. , Rinaldi Michael G. , Guarro Josep
Published: September 2003

Chaetomium
is an unusual etiological agent of human infections, but the mortality rate among immunocompromised patients is considerably greater than that among nonimmunocompromised individuals. We investigated the in vitro antifungal susceptibilities to novel antifungal agents of 19 strains belonging to three species of
Chaetomium
which have been involved in human infections, i.e.,
Chaetomium globosum
,
C. atrobrunneum
, and
C. nigricolor
, and one strain of the closely related species
Achaetomium strumarium
. A modification of the NCCLS reference microdilution method (M38-A) was used to evaluate the in vitro activities of ravuconazole, voriconazole, albaconazole, and micafungin. Micafungin was not active at all, while the geometric mean MICs and minimum effective concentrations of the three triazoles were less than 0.5 and 0.4 μg/ml, respectively.
Cyclic AMP Signaling Pathway Modulates Susceptibility of
Candida
Species and
Saccharomyces cerevisiae
to Antifungal Azoles and Other Sterol Biosynthesis Inhibitors
Authors: Jain Pooja , Akula Indira , Edlind Thomas
Published: September 2003

Azoles are widely used antifungals; however, their efficacy is compromised by fungistatic activity and selection of resistant strains during treatment. Recent studies demonstrated roles for the protein kinase C and calcium signaling pathways in modulating azole activity. Here we explored a role for the signaling pathway mediated by cyclic AMP (cAMP), which is synthesized by the regulated action of adenylate cyclase (encoded by
CDC35
in
Candida albicans
and
CYR1
in
Saccharomyces cerevisiae
) and cyclase-associated protein (encoded by
CAP1
and
SRV2
, respectively). Relative to wild-type strains,
C. albicans
and
S. cerevisiae
strains mutated in these genes were hypersusceptible to fluconazole (>4- to >16-fold-decreased 48-h MIC), itraconazole (>8- to >64-fold), or miconazole (16- to >64-fold). Similarly, they were hypersusceptible to terbinafine and fenpropimorph (2- to >16-fold), which, like azoles, inhibit sterol biosynthesis. Addition of cAMP to the medium at least partially reversed the hypersusceptibility of Ca-
cdc35
and Sc-
cyr1
-
2
mutants. An inhibitor of mammalian adenylate cyclase, MDL-12330A, was tested in combination with azoles; a synergistic effect was observed against azole-susceptible and -resistant strains of
C. albicans
and five of six non-
C. albicans Candida
species. Analysis of cAMP levels after glucose induction in the presence and absence of MDL-12330A confirmed that it acts by inhibiting cAMP synthesis in yeast. RNA analysis suggested that a defect in azole-dependent upregulation of the multidrug transporter gene
CDR1
contributes to the hypersusceptibility of the Ca-
cdc35
mutant. Our results implicate cAMP signaling in the yeast azole response; compounds similar to MDL-12330A may be useful adjuvants in azole therapy.
Inhibition of Gene Expression inEscherichia coliby Antisense Phosphorodiamidate Morpholino Oligomers
Authors: Geller B. L. , Deere J. D. , Stein D. A. , Kroeker A. D. , Moulton H. M. , Iversen P. L.
Published: September 2003

Antisense phosphorodiamidate morpholino oligomers (PMOs) were tested for the ability to inhibit gene expression inEscherichia coli.PMOs targeted to either a myc-luciferase reporter gene product or 16S rRNA did not inhibit luciferase expression or growth. However, in a strain with defective lipopolysaccharide (lpxAmutant), which has a leaky outer membrane, PMOs targeted to the myc-luciferase or acyl carrier protein (acpP) mRNA significantly inhibited their targets in a dose-dependent response. A significant improvement was made by covalently joining the peptide (KFF)3KC to the end of PMOs. In strains with an intact outer membrane, (KFF)3KC-myc PMO inhibited luciferase expression by 63%. A second (KFF)3KC-PMO conjugate targeted tolacImRNA induced β-galactosidase in a dose-dependent response. The end of the PMO to which (KFF)3KC is attached affected the efficiency of target inhibition but in various ways depending on the PMO. Another peptide-lacI PMO conjugate was synthesized with the cationic peptide CRRRQRRKKR and was found not to induce β-galactosidase. We conclude that the outer membrane ofE. coliinhibits entry of PMOs and that (KFF)3KC-PMO conjugates are transported across both membranes and specifically inhibit expression of their genetic targets.
Uptake of Nitrobenzylthioinosine and Purine β-
l
-Nucleosides by Intracellular
Toxoplasma gondii
Authors: Al Safarjalani Omar N. , Naguib Fardos N. M. , el Kouni Mahmoud H.
Published: September 2003

Intracellular
Toxoplasma gondii
grown in human foreskin fibroblast cells transported nitrobenzylthioinosine {NBMPR; 6-[(4-nitrobenzyl)mercapto]-9-β-
d
-ribofuranosylpurine}, an inhibitor of nucleoside transport in mammalian cells, as well as the nonphysiological β-
l
-enantiomers of purine nucleosides, β-
l
-adenosine, β-
l
-deoxyadenosine, and β-
l
-guanosine. The β-
l
-pyrimidine nucleosides, β-
l
-uridine, β-
l
-cytidine, and β-
l
-thymidine, were not transported. The uptake of NBMPR and the nonphysiological purine nucleoside β-
l
-enantiomers by the intracellular parasites also implies that
Toxoplasma
-infected cells can transport these nucleosides. In sharp contrast, under the same conditions, uninfected fibroblast cells did not transport NBMPR or any of the unnatural β-
l
-nucleosides. β-
d
-Adenosine and dipyridamole, another inhibitor of nucleoside transport, inhibited the uptake of NBMPR and β-
l
-stereoisomers of the purine nucleosides by intracellular
Toxoplasma
and
Toxoplasma
-infected cells. Furthermore, infection with a
Toxoplasma
mutant deficient in parasite adenosine/purine nucleoside transport reduced or abolished the uptake of β-
d
-adenosine, NBMPR, and purine β-
l
-nucleosides. Hence, the presence of the
Toxoplasma
adenosine/purine nucleoside transporters is apparently essential for the uptake of NBMPR and purine β-
l
-nucleosides by intracellular
Toxoplasma
and
Toxoplasma
-infected cells. These results also demonstrate that, in contrast to the mammalian nucleoside transporters, the
Toxoplasma
adenosine/purine nucleoside transporter(s) lacks stereospecificity and substrate specificity in the transport of purine nucleosides. In addition, infection with
T. gondii
confers the properties of the parasite's purine nucleoside transport on the parasitized host cells and enables the infected cells to transport purine nucleosides that were not transported by uninfected cells. These unique characteristics of purine nucleoside transport in
T. gondii
may aid in the identification of new promising antitoxoplasmic drugs.
Inhibition of Aminoglycoside 6′-
N
-Acetyltransferase Type Ib-Mediated Amikacin Resistance by Antisense Oligodeoxynucleotides
Authors: Sarno Renee , Ha Hongphuc , Weinsetel Natalia , Tolmasky Marcelo E.
Published: September 2003

Amikacin has been very useful in the treatment of infections caused by multiresistant bacteria because it is refractory to the actions of most modifying enzymes. However, the spread of AAC(6′)-I-type acetyltransferases, enzymes capable of catalyzing inactivation of amikacin, has rendered this antibiotic all but useless in some parts of the world. The aminoglycoside 6′-
N
-acetyltransferase type Ib, which is coded for by the
aac
(
6′
)-
Ib
gene, mediates resistance to amikacin and other aminoglycosides. RNase H mapping and computer prediction of the secondary structure led to the identification of five regions accessible for interaction with antisense oligodeoxynucleotides in the
aac
(
6′
)
-Ib
mRNA. Oligodeoxynucleotides targeting these regions could bind to native mRNA with different efficiencies and mediated RNase H digestion. Selected oligodeoxynucleotides inhibited AAC(6′)-Ib synthesis in cell-free coupled transcription-translation assays. After their introduction into an
Escherichia coli
strain harboring
aac
(
6′
)
-Ib
by electroporation, some of these oligodeoxynucleotides decreased the level of resistance to amikacin. Our results indicate that use of antisense compounds could be a viable strategy to preserve the efficacies of existing antibiotics to which bacteria are becoming increasingly resistant.
Sensitization ofStaphylococcus aureusandEscherichia colito Antibiotics by the Sesquiterpenoids Nerolidol, Farnesol, Bisabolol, and Apritone
Authors: Brehm-Stecher Byron F. , Johnson Eric A.
Published: September 2003

The sesquiterpenoids nerolidol, farnesol, bisabolol, and apritone were investigated for their abilities to enhance bacterial permeability and susceptibility to exogenous antimicrobial compounds. Initially, it was observed by flow cytometry that these sesquiterpenoids promoted the intracellular accumulation of the membrane-impermeant nucleic acid stain ethidium bromide by live cells ofLactobacillus fermentum, suggesting that enhanced permeability resulted from disruption of the cytoplasmic membrane. The ability of these sesquiterpenoids to increase bacterial susceptibility to a number of clinically important antibiotics was then investigated. In disk diffusion assays, treatment with low concentrations (0.5 to 2 mM) of nerolidol, bisabolol, or apritone enhanced the susceptibility ofStaphylococcus aureusto ciprofloxacin, clindamycin, erythromycin, gentamicin, tetracycline, and vancomycin. Nerolidol and farnesol also sensitizedEscherichia colito polymyxin B. Our results indicate the practical utility of sensitizing bacteria to antimicrobials with sesquiterpenoids that have traditionally been used as flavorants and aroma compounds in the food and perfume industries.
In Vitro Interaction of Flucytosine with Conventional and New Antifungals against
Cryptococcus neoformans
Clinical Isolates
Authors: Schwarz Patrick , Dromer Françoise , Lortholary Olivier , Dannaoui Eric
Published: September 2003

Combinations of flucytosine with conventional and new antifungals were evaluated in vitro against 30 clinical isolates of
Cryptococcus neoformans
. Synergy determined by checkerboard analysis was observed with combinations of fluconazole, itraconazole, voriconazole, amphotericin B, and caspofungin with flucytosine against 77, 60, 80, 77, and 67% of the isolates, respectively. Antagonism was never observed. Killing curves showed indifferent interactions between triazoles and flucytosine and synergy between amphotericin B and flucytosine.
Activity of Megazol, a Trypanocidal Nitroimidazole, Is Associated with DNA Damage
Authors: Enanga Bertin , Ariyanayagam Mark R. , Stewart Mhairi L. , Barrett Michael P.
Published: September 2003

DNA damage associated with the trypanocidal activity of megazol [2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole] was shown in experiments in which DNA repair-deficient RAD51
−/−
Trypanosoma brucei
mutants were found to be hypersensitive to the drug. Parasites resistant to megazol were selected and showed modest cross-resistance to other trypanocides, although neither drug efflux nor changes to intracellular thiols correlated with resistance.
Health status as a potential effect modifier of the relation between noise annoyance and incidence of ischaemic heart disease
Authors: Babisch W , Ising H , Gallacher J E J
Published: September 2003

Aims:Traffic noise is a psychosocial stressor. Epidemiological studies suggest chronic noise stress to be a risk factor for cardiovascular disorders.

Methods:In a prospective cohort study, the association between annoyance and disturbances due to road traffic noise and the incidence of ischaemic heart disease (IHD) was studied in 3950 middle aged men.

Results:Depending on the questionnaire item, non-significant odds ratios for IHD incidence ranging from 0.9 to 1.4 were found for the highly noise annoyed/disturbed subjects when compared with the less annoyed/disturbed subjects, over the six year follow up period. However, this relation was strongly modified by the prevalence of pre-existing chronic diseases. In subjects free of any chronic disease at the beginning of the follow up, significant odds ratios between 1.7 and 3.0 were seen. In the subgroup with chronic diseases no such noise effects were seen. This surprising result of no effect in the group of people with a potential risk, due to pre-existing health problems, may be because of the dilution of the true effect due to recall bias.

Conclusions:Annoyance and disturbance due to road traffic noise is associated with a higher incidence of IHD. Prevalence of disease can be an important effect modifier of the relation between noise annoyance and health outcomes.
Time To Pregnancy and occupational lead exposure
Authors: Joffe M , Bisanti L , Apostoli P , Kiss P , Dale A , Roeleveld N , Lindbohm M-L , Sallmén M , Vanhoorne M , Bonde J P
Published: September 2003

Background:Lead exposure is known to be harmful to the male reproductive system, including impairment of fertility. However, it is unclear whether currently existing low levels of exposure have this effect.

Aims:To study retrospectively current workers in lead using industries (battery manufacture, smelting, etc), and in non-lead using control industries, in four European countries, with Time To Pregnancy as the outcome variable, as part of the EU funded Asclepios Project.

Methods:Exposure assessment was mainly by blood lead values, which were available from the late 1970s, supplemented by imputed values where necessary. Three exposure models were studied: (1) short term (recent) exposure; (2) total duration of work in a lead using industry; and (3) cumulative exposure. A Cox proportional hazards model with discrete ties was used for the statistical analysis, with covariates for both partners.

Results:A total of 1104 subjects took part, of whom 638 were occupationally exposed to lead at the relevant time. Blood lead levels were mainly less than 50 μg/dl. No consistent association of Time To Pregnancy with lead exposure was found in any of the exposure models, although reduced fertility was observed in one category each in models (2) and (3).

Conclusions:This basically negative result is unlikely to be due to the misclassification of key variables, to insufficient statistical power, or to bias, for example, response bias. If any impairment of male reproductive function exists at the levels of occupational lead exposure now current, it does not appear to reduce biological fertility.
Synergistic effect of hepatitis virus infection and occupational exposures to vinyl chloride monomer and ethylene dichloride on serum aminotransferase activity
Authors: Hsieh H-I , Wang J-D , Chen P-C , Cheng T-J
Published: September 2003

Aims:To study the synergistic effect of occupational chemical exposure and hepatitis virus infection on serum aminotransferase activity.

Methods:A total of 568 male workers who were employed in five polyvinyl chloride (PVC) or four vinyl chloride monomer (VCM) manufacturing factories were studied. Information relating to current job title, alcohol consumption, and cigarette smoking was obtained. Exposure level of chemical mixtures was classified by hygienic effect (a summation of personal time weighted average/reference permissible exposure level of each chemical) into high, moderate, and low exposure groups. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and anti-hepatitis C antibody were assayed.

Results:Hepatitis virus infection and increased body mass index were associated with abnormal serum aminotransferase activity. In workers with hepatitis virus infection, those with high exposure had a higher prevalence of abnormal AST and ALT compared to low exposure; among those without hepatitis virus infection, the differences of prevalence of abnormal AST and ALT were not significant between different chemical exposure groups. There was a significant trend of increasing risks of increased AST and ALT in moderate and high exposure groups with hepatitis virus infection. Such a synergistic effect was more prominent among HBeAg-positive workers.

Conclusions:Mixed exposures to 1,2-ethylene dichloride and VCM have a positive synergistic effect with hepatitis virus infection on liver damage. Assessment of fitness for work should be considered in workers with hepatitis B and C infection, when they have potential exposure to hepatotoxins in the workplace.
Cancer risk in offspring of male pesticide applicators in agriculture in Sweden
Authors: Rodvall Y , Dich J , Wiklund K
Published: September 2003

Aims:To explore cancer risk from date of birth until 1994 in children, born 1958 or later, of Swedish male pesticide applicators.

Methods:Records of male pesticide applicators licensed 1965–76 were linked to the Multigeneration Register. The records of their offspring were then linked to the Swedish Cancer Registry and the Cause of Death Register.

Results:In total 51 cases of cancer were observed, which is significantly lower than the expected 73.0 (standardised incidence ratio (SIR) 0.70, 95% CI 0.52 to 0.92). Tumours of the nervous system was most common, amounting to 20 cases, 39% of all cancer cases (SIR 1.01, 95% CI 0.62 to 1.56). A statistically significant reduced risk for leukaemia was found (SIR 0.43, 95% CI 0.19 to 0.86). For non-Hodgkin’s lymphoma, three cases were observed and 4.8 expected (SIR 0.63, 95% CI 0.13 to 1.83). For Hodgkin’s disease, five cases were observed versus 3.7 expected (SIR 1.36, 95% CI 0.44 to 3.17). Two cases of testicular cancer were observed and 1.7 expected (SIR 1.19, 95% CI 0.13 to 4.28).

Conclusions:None of the a priori hypotheses of increased risk of tumours of the nervous system, kidney cancer, leukaemia, lymphoma, soft tissue sarcoma, and testicular cancer in children of male pesticide applicators could be confirmed.
Simvastatin Modulates Expression of the
PON1
Gene and Increases Serum Paraoxonase
Authors: Deakin Sara , Leviev Ilia , Guernier Sophie , James Richard W.
Published: September 2003

Background—

The HDL-associated enzyme paraoxonase protects LDLs from oxidative stress. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) appear to favorably influence the atherosclerotic process by different mechanisms. The present study examined the influence of simvastatin on paraoxonase expression and serum paraoxonase levels.

Methods and Results—

Simvastatin upregulated in a dose-dependent manner the activity of the promoter of the paraoxonase gene in expression cassettes transfected into HepG2 cells. Upregulation could be blocked by mevalonate and other intermediates of the cholesterol biosynthetic pathway. Simvastatin increased nuclear factors, notably sterol regulatory element–binding protein-2, capable of binding to the paraoxonase promoter; this was also blocked by mevalonate. Sterol regulatory element–binding protein-2 upregulated promoter activity in vitro. Patients treated with statin showed a significant increase in serum concentrations and activities of paraoxonase.

Conclusions—

The data indicate that simvastatin can modulate expression in vitro of the antioxidant enzyme paraoxonase and is associated with increased serum paraoxonase concentration and activity. It is consistent with effects of simvastatin treatment, which have the potential to influence beneficially antiatherogenic mechanisms at the HDL level. The study provides evidence for 1 molecular mechanism by which paraoxonase gene expression could be regulated.
Molecular Mechanism and Role of Endothelial Monocyte Chemoattractant Protein-1 Induction by Vascular Endothelial Growth Factor
Authors: Yamada Motoko , Kim Shokei , Egashira Kensuke , Takeya Motohiro , Ikeda Tomohiro , Mimura Osamu , Iwao Hiroshi
Published: September 2003

Objective—

We investigated the role of monocyte chemoattractant protein-1 (MCP-1) in vascular endothelial growth factor (VEGF)–induced angiogenesis and vascular permeability and the underlying molecular mechanism of VEGF-induced endothelial MCP-1 expression in vitro and in vivo.

Methods and Results—

We used an anti–MCP-1 neutralizing antibody for specific inhibition of MCP-1. VEGF increased tubule formation in the angiogenesis assay and vascular permeability in the Miles assay, and these effects were markedly inhibited by anti–MCP-1 antibody. Using a luciferase MCP-1 promoter-gene assay, we found that the activator protein-1 (AP-1) binding site of the MCP-1 promoter region contributes to the increase in MCP-1 promoter activity by VEGF. To specifically inhibit AP-1, we used recombinant adenovirus containing a dominant-negative c-Jun (Ad-DN-c-Jun). Ad-DN-c-Jun inhibited VEGF-induced endothelial MCP-1 mRNA expression and promoter activity in vitro. In vivo gene transfer of DN-c-Jun into rat carotid artery, with the hemagglutinating virus of the Japan liposome method, significantly blocked VEGF-induced MCP-1 and macrophage/monocyte (ED1) expression in endothelium.

Conclusions—

These results reveal that endothelial MCP-1 induced by VEGF seems to participate in angiogenesis, vascular leakage, or arteriosclerosis. AP-1 plays a critical role in the molecular mechanism underlying induction of MCP-1 by VEGF.
Vascular Remodeling Induced by Naturally Occurring Unsaturated Lysophosphatidic Acid In Vivo
Authors: Yoshida Kenji , Nishida Wataru , Hayashi Ken’ichiro , Ohkawa Yasuyuki , Ogawa Akira , Aoki Junken , Arai Hiroyuki , Sobue Kenji
Published: September 2003

Background—

We previously identified unsaturated (16:1, 18:1, and 18:2) but not saturated (12:0, 14:0, 16:0, and 18:0) lysophosphatidic acids (LPAs) as potent factors for vascular smooth muscle cell (VSMC) dedifferentiation. Unsaturated LPAs strongly induce VSMC dedifferentiation via the coordinated activation of the extracellular signal–regulated kinase (ERK) and p38 mitogen–activated protein kinase (p38MAPK), resulting in the proliferation and migration of dedifferentiated VSMCs. Here, we investigated the effects of 18:1 and 18:0 LPAs (as representative unsaturated and saturated LPAs, respectively) on the vasculature in vivo.

Methods and Results—

Rat common carotid arteries (CCAs) were treated transiently with 18:1 or 18:0 LPA and then examined by histological and biochemical analyses. The 18:1 but not 18:0 LPA potently induced vascular remodeling that was composed primarily of neointima. The incorporation of [
3
H]18:1 LPA into the CCAs revealed that a sufficient amount of unmetabolized [
3
H]18:1 LPA to induce VSMC dedifferentiation was present in the vascular wall. The 18:1 LPA–induced neointimal formation in vivo was also dependent on the coordinated activation of ERK and p38MAPK. Unlike balloon-injured CCAs, the 18:1 LPA–treated CCAs showed a histological similarity to human atherosclerotic arteries.

Conclusions—

This is the first report demonstrating a role for a naturally occurring unsaturated LPA in inducing vascular remodeling in vivo and provides a novel animal model for neointimal formation.
Long-Term Survival of Xenografted Neonatal Cardiomyocytes by Adenovirus-Mediated CTLA4-Ig Expression and CD40 Blockade
Authors: Li Tao-Sheng , Ito Hiroshi , Kajiwara Koji , Hamano Kimikazu
Published: September 2003

Background—

Prolonged survival of xenografted neonatal cardiomyocytes was achieved by blocking the CD28/B7 costimulatory pathway via CTLA4-Ig gene transfer. We examined the long-term survival of xenografted neonatal cardiomyocytes by adenovirus-mediated CTLA4-Ig expression and transient CD40 blockade with anti-CD40L monoclonal antibody (MR1).

Methods and Results—

Neonatal cardiomyocytes derived from Dark Agouti rats were infected with CTLA4-Ig-expressing adenovirus vectors and injected directly into the normal myocardium of C3H/He mice. Mice were also given an intraperitoneal injection of 500 μg MR1 (CTLA+MR group, n=30) or control immunoglobulin (CTLA group, n=30) 1 hour before and 1, 3, and 7 days after cardiomyocyte implantation. As a control, cells infected with β-Gal-expressing adenovirus vector (RL group, n=15) and cells without infection (control group, n=15) were injected into additional mice. Mice from all groups were killed 2, 4, and 8 weeks after xenotransplantation, and mice from the CTLA+MR and CTLA groups were killed 4 and 6 months after xenotransplantation. Neonatal cardiomyocytes were successfully infected by adenovirus vectors. Immunohistochemical analysis showed that the xenografted cardiomyocytes survived and expressed CTLA4-Ig for 6 months in all mice from the CTLA+MR and CTLA groups. A gap junction between the xenografted and host cardiomyocytes was also confirmed. Conversely, neonatal cardiomyocytes did not survive for even 2 weeks after xenotransplantation in the mice from the RL and control groups.

Conclusions—

Long-term survival of xenografted neonatal cardiomyocytes was achieved by adenovirus-mediated CTLA4-Ig expression and transient CD40 blockade.
Left Ventricular Performance in Patients With Severe Acute Respiratory Syndrome
Authors: Li Steven Siu-lung , Cheng Cheung-wah , Fu Chiu-lai , Chan Yiu-han , Lee Man-po , Chan Johnny Wai-man , Yiu Siu-fung
Published: September 2003

Background—

Severe acute respiratory syndrome (SARS) is characterized by an overaggressive immune response. Myocardial performance may be impaired in cytokine-mediated immune reactions.

Methods and Results—

Forty-six patients with established clinical diagnosis of SARS were studied prospectively. Transthoracic echocardiographic examinations were done at the acute stage of infection and 30 days later. Among them, 14 patients required mechanical ventilation. The clinical course, laboratory data, SARS-CoV antibody titers, and results of reverse transcriptase–polymerase chain reaction were studied. Significantly higher left ventricular index of myocardial performance (IMP) (0.42±0.13 versus 0.33±0.09,
P
<0.001), longer isovolumic relaxation time (102.9±15.7 versus 81.6±14.7 ms,
P
<0.001), lower flow propagation velocity (69.6±15.7 versus 83.8±19.7 cm/s,
P
=0.011), and Doppler-derived cardiac output (4.69±1.01 versus 5.49±1.04 L/min,
P
<0.001) were observed during acute infection when compared with those at 30 days. No significant valvular disease or pulmonary hypertension was found. At baseline, a lower mean left ventricular ejection fraction (LVEF) (65.3±12.8% versus 71.4±5.7%,
P
=0.03) and a higher mean IMP (0.51±0.11 versus 0.40±0.12,
P
=0.017) were found in patients who required mechanical ventilation. A decrease in LVEF correlated moderately with an elevated lactate dehydrogenase level (
r
=−0.605,
P
<0.001), whereas a higher IMP correlated weakly with an increase in creatine kinase level (
r
=0.38,
P
=0.016). Histological examination of the heart in the patient with the lowest EF (30.2%) revealed no interstitial lymphocytic infiltrate or myocyte necrosis.

Conclusions—

Subclinical diastolic impairment without systolic involvement was observed in patients with SARS. This impairment may be reversible on clinical recovery.
Ethics of Placebo Use in Pediatric Clinical Trials
Authors: Flynn Joseph T.
Published: September 2003

Industry-sponsored pediatric clinical trials of antihypertensive medications have greatly increased in number since passage of the Food and Drug Modernization Act of 1997. This development should ultimately benefit the treatment of hypertensive children by increasing the amount of scientific knowledge regarding the efficacy and safety of antihypertensive agents in children. However, the designs of many of these trials raise ethical questions related to the inclusion of placebo controls, a practice that has largely been abandoned in trials of antihypertensives in adults because of the well-known adverse consequences of untreated hypertension. This is an especially important issue in pediatric hypertension, as many hypertensive children have either secondary forms of hypertension or hypertension-induced target organ damage, potentially increasing the risk of harm during exposure to placebo. Against this background, and with a strong emphasis on protection of this vulnerable patient population, a strict set of conditions for use of placebos in pediatric antihypertensive trials is proposed.
Inflammation and Infections as Risk Factors for Ischemic Stroke
Authors: Lindsberg Perttu J. , Grau Armin J.
Published: September 2003

Background—

Inflammatory processes have fundamental roles in stroke in both the etiology of ischemic cerebrovascular disease and the pathophysiology of cerebral ischemia. We summarize clinical data on infection and inflammation as risk or trigger factors for human stroke and investigate current evidence for the hypothesis of a functional interrelation between traditional risk factors, genetic predisposition, and infection/inflammation in stroke pathogenesis.

Summary of Review—

Several traditional vascular risk factors are associated with proinflammatory alterations, including leukocyte activation, and predispose cerebral vasculature to thrombogenesis on inflammatory stimulation. Furthermore, accumulation of inflammatory cells, mainly monocytes/macrophages, within the vascular wall starts early during atherogenesis. During later disease stages, their activation can lead to plaque rupture and thrombus formation, increasing stroke risk. Inflammatory markers (eg, leukocytes, fibrinogen, C-reactive protein) are independent predictors of ischemic stroke. Chronic infections (eg, infection with
Chlamydia pneumoniae
or
Helicobacter pylori
) were found to increase the risk of stroke; however, study results are at variance, residual confounding is not excluded, and causality is not established at present. In case-control studies, acute infection within the preceding week was a trigger factor for ischemic stroke. Acute and exacerbating chronic infection may act by activating coagulation and chronic infections and may contribute to atherogenesis. Genetic predisposition of the inflammatory host response may be an important codeterminant for atherogenesis and stroke risk.

Conclusions—

Inflammation contributes to stroke risk via various interrelated mechanisms. Infectious diseases, traditional risk factors, and genetic susceptibility may cooperate in stimulating inflammatory pathways. Final proof of a causal role of infectious/inflammatory mechanisms in stroke pathogenesis is still lacking and will require interventional studies.