bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulus set effects in the similarity ratings of unfamiliar complex sounds
Authors: Allen Prudence , Scollie Susan
Published: July 2002

This study examined the effect of the distribution of values for various acoustic properties on the similarity ratings obtained in a paired-comparison study of complex sounds. Listeners rated the similarity of tones and tone complexes in one of four sets. Across the four sets both component frequency and the number of components in the stimuli were drawn from distributions that were either categorical or noncategorical. Other acoustic properties were distributed similarly in all sets. Solutions suggested that frequency was most important to the ratings, followed by the number of components in each critical band. Results suggest that when the values of an acoustic property are distributed categorically, its importance to similarity ratings increases relative to that observed with a less categorical distribution.
Vowel intelligibility in clear and conversational speech for normal-hearing and hearing-impaired listeners
Authors: Ferguson Sarah Hargus , Kewley-Port Diane
Published: July 2002

Several studies have demonstrated that when talkers are instructed to speak clearly, the resulting speech is significantly more intelligible than speech produced in ordinary conversation. These speech intelligibility improvements are accompanied by a wide variety of acoustic changes. The current study explored the relationship between acoustic properties of vowels and their identification in clear and conversational speech, for young normal-hearing (YNH) and elderly hearing-impaired (EHI) listeners. Monosyllabic words excised from sentences spoken either clearly or conversationally by a male talker were presented in 12-talker babble for vowel identification. While vowel intelligibility was significantly higher in clear speech than in conversational speech for the YNH listeners, no clear speech advantage was found for the EHI group. Regression analyses were used to assess the relative importance of spectral target, dynamic formant movement, and duration information for perception of individual vowels. For both listener groups, all three types of information emerged as primary cues to vowel identity. However, the relative importance of the three cues for individual vowels differed greatly for the YNH and EHI listeners. This suggests that hearing loss alters the way acoustic cues are used for identifying vowels.
Climate Warming and Disease Risks for Terrestrial and Marine Biota
Authors: Harvell C. Drew , Mitchell Charles E. , Ward Jessica R. , Altizer Sonia , Dobson Andrew P. , Ostfeld Richard S. , Samuel Michael D.
Published: July 2002

Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming, a subset of pathogens might decline with warming, releasing hosts from disease. Recently, changes in El Niño–Southern Oscillation events have had a detectable influence on marine and terrestrial pathogens, including coral diseases, oyster pathogens, crop pathogens, Rift Valley fever, and human cholera. To improve our ability to predict epidemics in wild populations, it will be necessary to separate the independent and interactive effects of multiple climate drivers on disease impact.
Tumor Regression by Targeted Gene Delivery to the Neovasculature
Authors: Hood John D. , Bednarski Mark , Frausto Ricardo , Guccione Samira , Reisfeld Ralph A. , Xiang Rong , Cheresh David A.
Published: July 2002

Efforts to influence the biology of blood vessels by gene delivery have been hampered by a lack of targeting vectors specific for endothelial cells in diseased tissues. Here we show that a cationic nanoparticle (NP) coupled to an integrin αvβ3–targeting ligand can deliver genes selectively to angiogenic blood vessels in tumor-bearing mice. The therapeutic efficacy of this approach was tested by generating NPs conjugated to a mutant
Raf
gene,

ATP
μ
-Raf

, which blocks endothelial signaling and angiogenesis in response to multiple growth factors. Systemic injection of the NP into mice resulted in apoptosis of the tumor-associated endothelium, ultimately leading to tumor cell apoptosis and sustained regression of established primary and metastatic tumors.
Covariation of Synaptonemal Complex Length and Mammalian Meiotic Exchange Rates
Authors: Lynn Audrey , Koehler Kara E. , Judis LuAnn , Chan Ernest R. , Cherry Jonathan P. , Schwartz Stuart , Seftel Allen , Hunt Patricia A. , Hassold Terry J.
Published: July 2002

Analysis of recombination between loci (linkage analysis) has been a cornerstone of human genetic research, enabling investigators to localize and, ultimately, identify genetic loci. However, despite these efforts little is known about patterns of meiotic exchange in human germ cells or the mechanisms that control these patterns. Using recently developed immunofluorescence methodology to examine exchanges in human spermatocytes, we have identified remarkable variation in the rate of recombination within and among individuals. Subsequent analyses indicate that, in humans and mice, this variation is linked to differences in the length of the synaptonemal complex. Thus, at least in mammals, a physical structure, the synaptonemal complex, reflects genetic rather than physical distance.
Super ENSO and Global Climate Oscillations at Millennial Time Scales
Authors: Stott Lowell , Poulsen Christopher , Lund Steve , Thunell Robert
Published: July 2002

The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (δ
18
O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite δ
18
O record into components of temperature and local water δ
18
O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Niño–Southern Oscillation (ENSO). El Niño conditions correlate with stadials at high latitudes, whereas La Niña conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO
2
, N
2
O, and CH
4
during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Niño.
An Alternative Flavin-Dependent Mechanism for Thymidylate Synthesis
Authors: Myllykallio Hannu , Lipowski Gerard , Leduc Damien , Filee Jonathan , Forterre Patrick , Liebl Ursula
Published: July 2002

Although deoxythymidylate cannot be provided directly by ribonucleotide reductase, the gene encoding thymidylate synthase ThyA is absent from the genomes of a large number of nonsymbiotic microbes. We show that ThyX (Thy1) proteins of previously unknown function form a large and distinct class of thymidylate synthases.
ThyX
has a wide but sporadic phylogenetic distribution, almost exclusively limited to microbial genomes lacking
thyA
. ThyX and ThyA use different reductive mechanisms, because ThyX activity is dependent on reduced flavin nucleotides. Our findings reveal complexity in the evolution of thymidine in present-day DNA. Because ThyX proteins are found in many pathogenic microbes, they present a previously uncharacterized target for antimicrobial compounds.
Regulation of Hypoxic Death in
C. elegans
by the Insulin/IGF Receptor Homolog DAF-2
Authors: Scott Barbara A. , Avidan Michael S. , Crowder C. Michael
Published: July 2002

To identify genetic determinants of hypoxic cell death, we screened for hypoxia-resistant (Hyp) mutants in
Caenorhabditis elegans
and found that specific reduction-of-function (rf) mutants of
daf-2
, an insulin/insulinlike growth factor (IGF) receptor (INR) homolog gene, were profoundly Hyp. The hypoxia resistance was acutely inducible just before hypoxic exposure and was mediated through an AKT-1/PDK-1/forkhead transcription factor pathway overlapping with but distinct from signaling pathways regulating life-span and stress resistance. Selective neuronal and muscle expression of
daf-2
(+) restored hypoxic death, and
daf-2
(rf) prevented hypoxia-induced muscle and neuronal cell death, which demonstrates a potential for INR modulation in prophylaxis against hypoxic injury of neurons and myocytes.
Leg Patterning Driven by Proximal-Distal Interactions and EGFR Signaling
Authors: Galindo M. I. , Bishop S. A. , Greig S. , Couso J. P.
Published: July 2002

wingless
and
decapentaplegic
signaling establishes the proximal-distal axis of
Drosophila
legs by activating the expression of genes such as
Distalless
and
dachshund
in broad proximal-distal domains during early leg development. However, here we show that
wingless
and
decapentaplegic
are not required throughout all of proximal-distal development. The tarsus, which has been proposed to be an ancestral structure, is instead defined by the activity of
Distalless
,
dachshund
, and a distal gradient of epidermal growth factor receptor (EGFR)–Ras signaling. Our results uncover a mechanism for appendage patterning directed by genes expressed in proximal-distal domains and possibly conserved in other arthropods and vertebrates.
Adhesion and Friction Mechanisms of Polymer-on-Polymer Surfaces
Authors: Maeda Nobuo , Chen Nianhuan , Tirrell Matthew , Israelachvili Jacob N.
Published: July 2002

The adhesion and friction of smooth polymer surfaces were studied below the glass transition temperature by use of a surface forces apparatus. The friction force of a crosslinked polymer was orders of magnitude less than that of an uncrosslinked polymer. In contrast, after chain scission of the outermost layers, the adhesion hysteresis and friction forces increase substantially. These results show that polymer-polymer adhesion hysteresis and friction depend on the dynamic rearrangement of the outermost polymer segments at shearing interfaces, and that both increase as a transition is made from crosslinked surfaces to surfaces with long chains to surfaces with quasi-free ends. The results suggest new ways for manipulating the adhesion and friction of polymer surfaces by adjusting the state of the surface chains.
Maps of Subsurface Hydrogen from the High Energy Neutron Detector, Mars Odyssey
Authors: Mitrofanov I. , Anfimov D. , Kozyrev A. , Litvak M. , Sanin A. , Tret'yakov V. , Krylov A. , Shvetsov V. , Boynton W. , Shinohara C. , Hamara D. , Saunders R. S.
Published: July 2002

After 55 days of mapping by the High Energy Neutron Detector onboard Mars Odyssey, we found deficits of high-energy neutrons in the southern highlands and northern lowlands of Mars. These deficits indicate that hydrogen is concentrated in the subsurface. Modeling suggests that water ice–rich layers that are tens of centimeters in thickness provide one possible fit to the data.
Phagocytosis Affects Biguanide Sensitivity of
Acanthamoeba
spp
Authors: Noble Judith A. , Ahearn Donald G. , Avery Simon V. , Crow Sidney A.
Published: July 2002

The incidence of
Acanthamoeba
keratitis, a disease associated with contact lens wear, has been in apparent decline with the advent of multipurpose contact lens solutions. The concentrations of the biguanides chlorhexidine digluconate (CHX) and particularly polyhexamethylene biguanide (PHMB) included in multipurpose solutions (MPSs) are sublethal for amoebae. We evaluated by flow cytometry the effects of these two biguanides on phagocytosis of particles and the survival of trophozoites of
Acanthamoeba castellanii
and
A. polyphaga
. Trophozoites of
A. castellanii
and
A. polyphaga
(10
6
/ml) were exposed to solutions of 5 and 50 μg of PHMB and CHX per ml in the presence and absence of particles (i.e., heat-killed yeasts and bacteria and latex beads). In addition, trophozoites were exposed to particles treated with these concentrations of the two biguanides. In the absence of particles, trophozoites of
A. polyphaga
appeared to be more resistant to the biguanides than those of
A. castellanii
. In the presence of particles, the rates of survival of both species were decreased. In most instances, particles treated with sublethal concentrations of both biguanides that were adsorbed onto the particles reduced the incidence of phagocytosis. Particles present in MPSs in contact lens cases may be involved in the decreased incidence of
Acanthamoeba
keratitis.
Design and Activity of Antimicrobial Peptides against Sporogonic-Stage Parasites Causing Murine Malarias
Authors: Arrighi Romanico B. G. , Nakamura Chikashi , Miyake Jun , Hurd Hilary , Burgess J. Grant
Published: July 2002

Insects produce several types of peptides to combat a broad spectrum of invasive pathogenic microbes, including protozoans. However, despite this defense response, infections are often established. Our aim was to design novel peptides that produce high rates of mortality among protozoa of the genusPlasmodium, the malaria parasites. Using existing antimicrobial peptide sequences as templates, we designed and synthesized three short novel hybrids, designated Vida1 to Vida3. Each has a slightly different predicted secondary structure. The peptides were tested against sporogonic stages of the rodent malaria parasitesPlasmodium berghei(in vitro and in vivo) andP. yoelii nigeriensis(in vitro). The level of activity varied for each peptide and according to the parasite stage targeted. Vida3 (which is predicted to have large numbers of β sheets and coils but no α helices) showed the highest level of activity, killing the early sporogonic stages in culture and causing highly significant reductions in the prevalence and intensity of infection ofP. bergheiafter oral administration or injection inAnopheles gambiaemosquitoes. The secondary structures of these peptides may play a crucial role in their ability to interact with and kill sporogonic forms of the malaria parasite.
Antifungal Triazoles and Polymorphonuclear Leukocytes Synergize To Cause Increased Hyphal Damage toScedosporium prolificansandScedosporium apiospermum
Authors: Gil-Lamaignere Cristina , Roilides Emmanuel , Mosquera Juan , Maloukou Avgi , Walsh Thomas J.
Published: July 2002

Scedosporium prolificansandScedosporium apiospermum(Pseudallescheria boydii) cause pulmonary and disseminated infections refractory to most currently used antifungal agents in immunocompromised patients. We therefore investigated the potential antifungal activities of the triazoles itraconazole (ITC), voriconazole (VRC), and posaconazole (PSC) in combination with human polymorphonuclear leukocytes (PMNs) against the hyphae of these fungal pathogens. A colorimetric assay with (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]2H-tetrazolium-5-carboxanilide) sodium salt was used for the measurement of hyphal damage as an indicator of antifungal activity. We found that the newer triazoles VRC and PSC displayed synergistic effects with PMNs againstS. prolificanshyphae after 24 h (P< 0.05), whereas the effect of ITC in combination with PMNs was additive (P< 0.01). All three triazoles displayed additive antifungal activities in combination with PMNs againstS. apiospermumhyphae (P< 0.05). The synergistic or additive effects that these triazoles exhibited, combined with the antifungal activities of human PMNs, may have important therapeutic implications for the management of infections due toS. prolificansandS. apiospermum.
In Vitro Antiviral Interaction of Lopinavir with Other Protease Inhibitors
Authors: Molla Akhteruzzaman , Mo Hongmei , Vasavanonda Sudthida , Han Lixin , Lin C. Thomas , Hsu Ann , Kempf Dale J.
Published: July 2002

The in vitro inhibition of wild-type human immunodeficiency virus (HIV) by combinations of lopinavir and six other protease inhibitors over a range of two-drug combination ratios was evaluated. Combinations of lopinavir with indinavir, nelfinavir, amprenavir, tipranavir, and BMS-232632 generally displayed an additive relationship. In contrast, a consistent, statistically significant synergistic inhibition of HIV type 1 replication with combinations of lopinavir and saquinavir was observed. Analysis of the combination indices indicated that lopinavir with saquinavir was synergistic over the entire range of drug combination ratios tested and at all levels of inhibition in excess of 40%. Cellular toxicity was not observed at the highest drug concentrations tested. These results suggest that administration of combinations of the appropriate dose of lopinavir with other protease inhibitors in vivo may result in enhanced antiviral activity with no associated increase in cellular cytotoxicity. More importantly, the observed in vitro synergy between lopinavir and saquinavir provides a theoretical basis for the clinical exploration of a novel regimen of lopinavir-ritonavir and saquinavir.
Influence of Clarithromycin on Early Atherosclerotic Lesions after
Chlamydia pneumoniae
Infection in a Rabbit Model
Authors: Fong Ignatius W. , Chiu Brian , Viira Esther , Jang Dan , Mahony James B.
Published: July 2002

Chlamydia pneumoniae
may play a role in atherogenesis and vascular diseases, and antibiotics may prove useful in these conditions. Three groups of New Zealand White rabbits (24 per group) were infected via the nasopharynx with
C. pneumoniae
on three separate occasions (2 weeks apart). Group I was untreated and sacrificed at 12 weeks; group II received clarithromycin at 20 mg/kg/day for 8 days, beginning 5 days after each inoculation (early treatment); and group III received a similar dose of clarithromycin starting 2 weeks after the third inoculation and continued for 6 weeks thereafter (delayed treatment). To test for a possible anti-inflammatory effect of clarithromycin, two other groups of uninfected rabbits (12 animals in each) were fed 0.5% cholesterol-enriched chow, and one of these groups was treated with clarithromycin at 30 mg/kg/day for 6 weeks. Of 23 untreated infected rabbits, 8 developed early lesions of atherosclerosis, whereas 2 of the 24 early-treated group II had similar changes (
P
= 0.036 [75% efficacy]). However, in the delayed-treatment group, group III, 3 of 24 rabbits developed early lesions of atherosclerosis, thus demonstrating 62.5% reduction compared to the untreated controls (
P
= 0.07 [trend to statistical significance]).
C. pneumoniae
antigen was detected in 8 of 23 group I (untreated) rabbits versus 1 of 24 of the early-treated (group II) rabbits and 4 of 24 animals in the delayed group III (
P
= 0.009 and 0.138, respectively). All of the untreated, cholesterol-fed rabbits had moderate to advanced atherosclerosis (grade III or IV); clarithromycin had no effect on reducing the prevalence of but did reduce the extent of atherosclerosis in the cholesterol-fed rabbits by 17% compared to untreated controls. Thus, clarithromycin administration modified
C. pneumoniae
-induced atherosclerotic lesions and reduced the ability to detect organism in tissue. Early treatment was more effective than delayed treatment.
Potent and Selective Inhibition of Human Cytomegalovirus Replication by 1263W94, a Benzimidazole
l
-Riboside with a Unique Mode of Action
Authors: Biron Karen K. , Harvey Robert J. , Chamberlain Stanley C. , Good Steven S. , Smith Albert A. , Davis Michelle G. , Talarico Christine L. , Miller Wayne H. , Ferris Robert , Dornsife Ronna E. , Stanat Sylvia C. , Drach John C. , Townsend Leroy B. , Koszalka George W.
Published: July 2002

Benzimidazole nucleosides have been shown to be potent inhibitors of human cytomegalovirus (HCMV) replication in vitro. As part of the exploration of structure-activity relationships within this series, we synthesized the 2-isopropylamino derivative (3322W93) of 1H-β
-d-
ribofuranoside-2-bromo-5,6-dichlorobenzimidazole (BDCRB) and the biologically unnatural
l-
sugars corresponding to both compounds. One of the
l
derivatives, 1H-β
-l-
ribofuranoside-2-isopropylamino-5,6-dichlorobenzimidazole (1263W94), showed significant antiviral potency in vitro against both laboratory HCMV strains and clinical HCMV isolates, including those resistant to ganciclovir (GCV), foscarnet, and BDCRB. 1263W94 inhibited viral replication in a dose-dependent manner, with a mean 50% inhibitory concentration (IC
50
) of 0.12 ± 0.01 μM compared to a mean IC
50
for GCV of 0.53 ± 0.04 μM, as measured by a multicycle DNA hybridization assay. In a single replication cycle, 1263W94 treatment reduced viral DNA synthesis, as well as overall virus yield. HCMV mutants resistant to 1263W94 were isolated, establishing that the target of 1263W94 was a viral gene product. The resistance mutation was mapped to the UL97 open reading frame. The pUL97 protein kinase was strongly inhibited by 1263W94, with 50% inhibition occurring at 3 nM. Although HCMV DNA synthesis was inhibited by 1263W94, the inhibition was not mediated by the inhibition of viral DNA polymerase. The parent benzimidazole
d-
riboside BDCRB inhibits viral DNA maturation and processing, whereas 1263W94 does not. The mechanism of the antiviral effect of
l-
riboside 1263W94 is thus distinct from those of GCV and of BDCRB. In summary, 1263W94 inhibits viral replication by a novel mechanism that is not yet completely understood.
Assessment of Azithromycin in Combination with Other Antimalarial Drugs against
Plasmodium falciparum
In Vitro
Authors: Ohrt Colin , Willingmyre George D. , Lee Patricia , Knirsch Charles , Milhous Wilbur
Published: July 2002

Initial field malaria prophylaxis trials with azithromycin revealed insufficient efficacy against falciparum malaria to develop azithromycin as a single agent. The objective of this in vitro study was to determine the best drug combination(s) to evaluate for future malaria treatment and prophylaxis field trials. In vitro, azithromycin was tested in combination with chloroquine against 10 representative
Plasmodium falciparum
isolates. Azithromycin was also assessed in combination with eight additional antimalarial agents against two or three multidrug-resistant
P. falciparum
isolates. Parasite susceptibility testing was carried out with a modification of the semiautomated microdilution technique. The incubation period was extended from the usual 48 h to 68 h. Fifty percent inhibitory concentrations (IC
50
s) were calculated for each drug alone and for drugs in fixed combinations of their respective IC
50
s (1:1, 3:1, 1:3, 4:1, 1:4, and 5:1). These data were used to calculate fractional inhibitory concentrations and isobolograms. Chloroquine-azithromycin studies revealed a range of activity from additive to synergistic interactions for the eight chloroquine-resistant isolates tested, while an additive response was seen for the two chloroquine-sensitive isolates. Quinine, tafenoquine, and primaquine were additive to synergistic with azithromycin, while dihydroartemisinin was additive with a trend toward antagonism. The remaining interactions appeared to be additive. These results suggest that a chloroquine-azithromycin combination should be evaluated for malaria prophylaxis and that a quinine-azithromycin combination should be evaluated for malaria treatment in areas of drug resistance.
Chemiosmotic Mechanism of Antimicrobial Activity of Ag
+
in
Vibrio cholerae
Authors: Dibrov Pavel , Dzioba Judith , Gosink Khoosheh K. , Häse Claudia C.
Published: July 2002

Although the antimicrobial effects of silver salts were noticed long ago, the molecular mechanism of the bactericidal action of Ag
+
in low concentrations has not been elucidated. Here, we show that low concentrations of Ag
+
induce a massive proton leakage through the
Vibrio cholerae
membrane, which results in complete deenergization and, with a high degree of probability, cell death.
Efficacy of Orally Delivered Cochleates Containing Amphotericin B in a Murine Model of Aspergillosis
Authors: Delmas G. , Park S. , Chen Z. W. , Tan F. , Kashiwazaki R. , Zarif L. , Perlin D. S.
Published: July 2002

Cochleates containing amphotericin B (CAMB) were administered orally at doses ranging from 0 to 40 mg/kg of body weight/day for 14 days in a murine model of systemic aspergillosis. The administration of oral doses of CAMB (20 and 40 mg/kg/day) resulted in a survival rate of 70% and a reduction in colony counts of more than 2 logs in lungs, livers, and kidneys. Orally administered CAMB shows promise for the treatment of aspergillosis.
Topoisomerase Mutations Associated with In Vitro Selection of Resistance to Moxifloxacin in
Streptococcus pneumoniae
Authors: Houssaye Serge , Gutmann Laurent , Varon Emmanuelle
Published: July 2002

We analyzed the frequencies of selection, the order of acquisition, and the mutations selected on moxifloxacin in two wild-type pneumococcal strains, R6 and 5714. The first selection step showed either a single GyrA mutation or no mutation in any of the quinolone resistance-determining regions. Second-step mutants selected had either a second mutation in ParC or in ParE. Moxifloxacin could belong to these fluoroquinolones, which preferentially target GyrA though probably acting equally through both gyrase and topoisomerase IV.
Potential Repair of
Escherichia coli
DNA following Exposure to UV Radiation from Both Medium- and Low-Pressure UV Sources Used in Drinking Water Treatment
Authors: Zimmer J. L. , Slawson R. M.
Published: July 2002

The increased use of UV radiation as a drinking water treatment technology has instigated studies of the repair potential of microorganisms following treatment. This study challenged the repair potential of an optimally grown nonpathogenic laboratory strain of
Escherichia coli
after UV radiation from low- and medium-pressure lamps. Samples were irradiated with doses of 5, 8, and 10 mJ/cm
2
from a low-pressure lamp and 3, 5, 8, and 10 mJ/cm
2
from a medium-pressure UV lamp housed in a bench-scale collimated beam apparatus. Following irradiation, samples were incubated at 37°C under photoreactivating light or in the dark. Sample aliquots were analyzed for up to 4 h following incubation using a standard plate count. Results of this study showed that
E. coli
underwent photorepair following exposure to the low-pressure UV source, but no repair was detectable following exposure to the medium-pressure UV source at the initial doses examined. Minimal repair was eventually observed upon medium-pressure UV lamp exposure when doses were lowered to 3 mJ/cm
2
. This study clearly indicates differences in repair potential under laboratory conditions between irradiation from low-pressure and medium-pressure UV sources of the type used in water treatment.
Klebsiella pneumoniae
Produces No Histamine:
Raoultella planticola
and
Raoultella ornithinolytica
Strains Are Histamine Producers
Authors: Kanki Masashi , Yoda Tomoko , Tsukamoto Teizo , Shibata Tadayoshi
Published: July 2002

Histamine fish poisoning is caused by histamine-producing bacteria (HPB).
Klebsiella pneumoniae
and
Klebsiella oxytoca
are the best-known HPB in fish. However, 22 strains of HPB from fish first identified as
K. pneumoniae
or
K. oxytoca
by commercialized systems were later correctly identified as
Raoultella planticola
(formerly
Klebsiella planticola
) by additional tests. Similarly, five strains of
Raoultella ornithinolytica
(formerly
Klebsiella ornithinolytica
) were isolated from fish as new HPB.
R. planticola
and
R. ornithinolytica
strains were equal in their histamine-producing capabilities and were determined to possess the
hdc
genes, encoding histidine decarboxylase. On the other hand, a collection of 61 strains of
K. pneumoniae
and 18 strains of
K. oxytoca
produced no histamine.
Large Fraction of Dead and Inactive Bacteria in Coastal Marine Sediments: Comparison of Protocols for Determination and Ecological Significance
Authors: Luna G. M. , Manini E. , Danovaro R.
Published: July 2002

It is now universally recognized that only a portion of aquatic bacteria is actively growing, but quantitative information on the fraction of living versus dormant or dead bacteria in marine sediments is completely lacking. We compared different protocols for the determination of the dead, dormant, and active bacterial fractions in two different marine sediments and at different depths into the sediment core. Bacterial counts ranged between (1.5 ± 0.2) × 10
8
cells g
−1
and (53.1 ± 16.0) × 10
8
cells g
−1
in sandy and muddy sediments, respectively. Bacteria displaying intact membrane (live bacterial cells) accounted for 26 to 30% of total bacterial counts, while dead cells represented the most abundant fraction (70 to 74%). Among living bacterial cells, nucleoid-containing cells represented only 4% of total bacterial counts, indicating that only a very limited fraction of bacterial assemblage was actively growing. Nucleoid-containing cells increased with increasing sediment organic content. The number of bacteria responsive to antibiotic treatment (direct viable count; range, 0.3 to 4.8% of the total bacterial number) was significantly lower than nucleoid-containing cell counts. An experiment of nutrient enrichment to stimulate a response of the dormant bacterial fraction determined a significant increase of nucleoid-containing cells. After nutrient enrichment, a large fraction of dormant bacteria (6 to 11% of the total bacterial number) was “reactivated.” Bacterial turnover rates estimated ranged from 0.01 to 0.1 day
−1
but were 50 to 80 times higher when only the fraction of active bacteria was considered (on average 3.2 day
−1
). Our results suggest that the fraction of active bacteria in marine sediments is controlled by nutrient supply and availability and that their turnover rates are at least 1 order of magnitude higher than previously reported.
Fungal Fragments as Indoor Air Biocontaminants
Authors: Górny Rafał L. , Reponen Tiina , Willeke Klaus , Schmechel Detlef , Robine Enric , Boissier Marjorie , Grinshpun Sergey A.
Published: July 2002

The aerosolization process of fungal propagules of three species (
Aspergillus versicolor
,
Penicillium melinii
, and
Cladosporium cladosporioides
) was studied by using a newly designed and constructed aerosolization chamber. We discovered that fungal fragments are aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces. Concentration measurements with an optical particle counter showed that the fragments are released in higher numbers (up to 320 times) than the spores. The release of fungal propagules varied depending on the fungal species, the air velocity above the contaminated surface, and the texture and vibration of the contaminated material. In contrast to spores, the release of fragments from smooth surfaces was not affected by air velocity, indicating a different release mechanism. Correlation analysis showed that the number of released fragments cannot be predicted on the basis of the number of spores. Enzyme-linked immunosorbent assays with monoclonal antibodies produced against
Aspergillus
and
Penicillium
fungal species showed that fragments and spores share common antigens, which not only confirmed the fungal origin of the fragments but also established their potential biological relevance. The considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human health effects that have been detected in buildings with mold problems but had no scientific explanation until now. This study suggests that future fungal spore investigations in buildings with mold problems should include the quantitation of fungal fragments.
Identification of theEnterococcus faecalisTyrosine Decarboxylase Operon Involved in Tyramine Production
Authors: Connil Nathalie , Le Breton Yoann , Dousset Xavier , Auffray Yanick , Rincé Alain , Prévost Hervé
Published: July 2002

Screening of a library ofEnterococcus faecalisinsertional mutants allowed isolation of a mutant affected in tyramine production. The growth of this mutant was similar to that of the wild-typeE. faecalisJH2-2 strain in Maijala broth, whereas high-performance liquid chromatography analyses showed that tyramine production, which reached 1,000 μg ml−1for the wild-type strain, was completely abolished. Genetic analysis of the insertion locus revealed a gene encoding a decarboxylase with similarity to eukaryotic tyrosine decarboxylases. Sequence analysis revealed a pyridoxal phosphate binding site, indicating that this enzyme belongs to the family of amino acid decarboxylases using this cofactor. Reverse transcription-PCR analyses demonstrated that the gene (tdc) encoding the putative tyrosine decarboxylase ofE. faecalisJH2-2 is cotranscribed with the downstream gene encoding a putative tyrosine-tyramine antiporter and with the upstream tyrosyl-tRNA synthetase gene. This study is the first description of a tyrosine decarboxylase gene in prokaryotes.
Effects of Psychological Stress and Alprazolam on Development of Oral Candidiasis in Rats
Authors: Núñez M. J. , Balboa J. , Riveiro P. , Liñares D. , Mañá P. , Rey-Méndez M. , Rodríguez-Cobos A. , Suárez-Quintanilla J. A. , García-Vallejo L. A. , Freire-Garabal M.
Published: July 2002

Psychological stress has been found to suppress cell-mediated immune responses that are important in limiting the proliferation of
Candida albicans
. Since anxiolytic drugs can restore cellular immunity in rodents exposed to stress conditions, we designed experiments conducted to evaluate the effects of alprazolam (1 mg/kg of body weight/day), a central benzodiazepine anxiolytic agonist, on the development of oral candidiasis in Sprague-Dawley rats exposed to a chronic auditory stressor. Animals were submitted to surgical hyposalivation in order to facilitate the establishment and persistence of
C. albicans
infection. Application of stress and treatment with drugs (placebo or alprazolam) were initiated 7 days before
C. albicans
inoculation and lasted until the end of the experiments (day 15 postinoculation). Establishment of
C. albicans
infection was evaluated by swabbing the inoculated oral cavity with a sterile cotton applicator on days 2 and 15 after inoculation, followed by plating on YEPD (yeast extract-peptone-dextrose) agar. Tissue injury was determined by the quantification of the number and type (normal or abnormal) of papillae on the dorsal tongue per microscopic field. A semiquantitative scale was devised to assess the degree of colonization of the epithelium by fungal hyphae. Our results show that stress exacerbates
C. albicans
infection of the tongues of rats. Significant increases in
Candida
counts, the percentage of the tongue's surface covered with clinical lesions, the percentage of abnormal papillae, and the colonization of the epithelium by fungal hyphae were found in stressed rats compared to those found in the unstressed rats. Treatment with alprazolam significantly reversed these adverse effects of stress, showing that, besides the psychopharmacological properties of this anxiolytic drug against stress, it has consequences for
Candida
infection.
NF-κB Family of Transcription Factors: Central Regulators of Innate and Adaptive Immune Functions
Authors: Caamaño Jorge , Hunter Christopher A.
Published: July 2002

Transcription factors of the Rel/NF-κB family are activated in response to signals that lead to cell growth, differentiation, and apoptosis, and these proteins are critical elements involved in the regulation of immune responses. The conservation of this family of transcription factors in many phyla and their association with antimicrobial responses indicate their central role in the regulation of innate immunity. This is illustrated by the association of homologues of NF-κB, and their regulatory proteins, with resistance to infection in insects and plants (M. S. Dushay, B. Asling, and D. Hultmark, Proc. Natl. Acad. Sci. USA93:10343-10347, 1996; D. Hultmark, Trends Genet.9:178-183, 1993; J. Ryals et al., Plant Cell9:425-439, 1997). The aim of this review is to provide a background on the biology of NF-κB and to highlight areas of the innate and adaptive immune response in which these transcription factors have a key regulatory function and to review what is currently known about their roles in resistance to infection, the host-pathogen interaction, and development of human disease.
Proteasomal Degradation of Cytotoxic Necrotizing Factor 1-Activated Rac
Authors: Lerm Maria , Pop Marius , Fritz Gerhard , Aktories Klaus , Schmidt Gudula
Published: July 2002

The cytotoxic necrotizing factor 1 (CNF1) from
Escherichia coli
has been shown to activate members of the Rho family by deamidation of glutamine 63. This amino acid is essential for hydrolysis of GTP, and any substitution results in a constitutively active Rho. Activation of Rho induces the formation of stress fibers, filopodia, and membrane ruffles due to activation of RhoA, Cdc42, and Rac, respectively. Here we show that the level of endogenous Rac decreased in CNF1-treated HEK293 and HeLa cells. The amount of mRNA remained unaffected, leaving the possibility that Rac is subject to proteolytic degradation. Treatment of cells with lactacystin, an inhibitor of the 26S proteasome, protected Rac from degradation. We have previously shown that CNF1 activates the c-Jun N-terminal kinase (JNK) only transiently in HeLa cells (M. Lerm, J. Selzer, A. Hoffmeyer, U. R. Rapp, K. Aktories, and G. Schmidt, Infect. Immun.
67:
496-503, 1998). Here we show that CNF1-induced JNK activation is stabilized in the presence of lactacystin. The data indicate that Rac is degraded by a proteasome-dependent pathway in CNF1-treated cells.
Novel 33-Kilodalton Lipoprotein fromMycobacterium leprae
Authors: Maeda Yumi , Makino Masahiko , Crick Dean C. , Mahapatra Sebabrata , Srisungnam Sopa , Takii Takemasa , Kashiwabara Yoshiko , Brennan Patrick J.
Published: July 2002

A novelMycobacterium lepraelipoprotein LpK (accession no.ML0603) was identified from the genomic database. The 1,116-bp open reading frame encodes a 371-amino-acid precursor protein with an N-terminal signal sequence and a consensus motif for lipid conjugation. Expression of the protein, LpK, inEscherichia colirevealed a 33-kDa protein, and metabolic labeling experiments and globomycin treatment proved that the protein was lipidated. Fractionation ofM. lepraedemonstrated that this lipoprotein was a membrane protein ofM. leprae. The purified lipoprotein was found to induce production of interleukin-12 in human peripheral blood monocytes. The studies imply thatM. lepraeLpK is involved in protective immunity against leprosy and may be a candidate for vaccine design.
Genes for Glycosylphosphatidylinositol Toxin Biosynthesis inPlasmodium falciparum
Authors: Delorenzi Mauro , Sexton Adrienne , Shams-Eldin Hosam , Schwarz Ralph T. , Speed Terry , Schofield Louis
Published: July 2002

About 2.5 million people die ofPlasmodium falciparummalaria every year. Fatalities are associated with systemic and organ-specific inflammation initiated by a parasite toxin. Recent studies show that glycosylphosphatidylinositol (GPI) functions as the dominant parasite toxin in the context of infection. GPIs also serve as membrane anchors for several of the most important surface antigens of parasite invasive stages. GPI anchoring is a complex posttranslational modification produced through the coordinated action of a multicomponent biosynthetic pathway. Here we present eight new genes ofP. falciparumselected for encoding homologs of proteins essential for GPI synthesis: PIG-A, PIG-B, PIG-M, PIG-O, GPI1, GPI8, GAA-1, and DPM1. We describe the experimentally verified mRNA and predicted amino acid sequences and in situ localization of the gene products to the parasite endoplasmic reticulum. Moreover, we show preliminary evidence for the PIG-L and PIG-C genes. The biosynthetic pathway of the malaria parasite GPI offers potential targets for drug development and may be useful for studying parasite cell biology and the molecular basis for the pathophysiology of parasitic diseases.
Quantitative Priming with Inactivated Pertussis Toxoid Vaccine in the Aerosol Challenge Model
Authors: Bruss Jon B. , Siber George R.
Published: July 2002

Serum antibodies to pertussis toxin (PT) have been shown to be protective against severe pertussis disease, although a specific level of anti-PT antibody that correlates with protection has not been demonstrated. Current animal models such as the intracerebral challenge model have significant limitations in correlating protection to a specific level of anti-PT antibody. This study examines the protective effects of priming with tetranitromethane-inactivated pertussis toxoid (PTx) vaccine in the aerosol challenge model and whether a measurable response to a priming dose of PTx is enough to initiate a protective secondary response when challenged with infection. The correlation of priming with markers of illness such as leukocytosis, weight loss, bacterial proliferation, and mortality after established infection with
Bordetella pertussis
was explored. BALB/c mice were immunized with PTx vaccine on day 6 of life and then challenged with
B. pertussis
using the aerosol challenge model. Data were analyzed according to the primary immunologic response, differentiating responders (anti-PT immunoglobulin G [IgG] ≥1 μg/ml) from nonresponders (anti-PT IgG <1 μg/ml). Mice that showed evidence of priming on the day of aerosol challenge were able to mount a secondary response to the challenge with a ≥2-fold rise in anti-PT IgG antibody by day 7 and a ≥10-fold rise by day 14 post-aerosol challenge. These primed mice were significantly better protected against leukocytosis, weight loss, and proliferation of
B. pertussis
in the lungs following aerosol challenge than the nonprimed group. This protection correlated with levels of anti-PT antibody in serum present on the day of aerosol challenge.
Colony-Stimulating Factor 1-Dependent Cells Protect against Systemic Infection with
Listeria monocytogenes
but Facilitate Neuroinvasion
Authors: Jin Yuxuan , Dons Lone , Kristensson Krister , Rottenberg Martin E.
Published: July 2002

By using mice genomically lacking the mononuclear phagocytic growth factor colony-stimulating factor 1 and thereby deficient in macrophage and dendritic cell populations, we show that these cells play a dual role: they constitute a major defense against systemic infection but also facilitate cerebral bacterial invasion by
Listeria monocytogenes
.
cag+Helicobacter pyloriInduces Homotypic Aggregation of Macrophage-Like Cells by Up-Regulation and Recruitment of Intracellular Adhesion Molecule 1 to the Cell Surface
Authors: Moese Stefan , Selbach Matthias , Meyer Thomas F. , Backert Steffen
Published: July 2002

Infection withcag+but notcag-negativeHelicobacter pylorileads to the formation of large homotypic aggregates of macrophage-like cells. Intracellular adhesion molecule 1 is up-regulated and recruited to the cell surface of infected cells and mediates the aggregation via lymphocyte function-associated molecule 1. This signaling may regulate cell-cell interactions and inflammatory responses.
Internalization of
Staphylococcus aureus
by Human Corneal Epithelial Cells: Role of Bacterial Fibronectin-Binding Protein and Host Cell Factors
Authors: Jett Bradley D. , Gilmore Michael S.
Published: July 2002

Wild-type
Staphylococcus aureus
was observed to be capable of invading human corneal epithelial cells (HCEC) in vitro. Internalization of
S. aureus
required expression of fibronectin-binding proteins (FnBPs); the capacity of an FnBP-deficient isogenic strain to invade HCEC was reduced by more than 99%. The binding of
S. aureus
to HCEC did not require viable bacteria, since UV-killed cells were observed to adhere efficiently. Invasion of HCEC by
S. aureus
involved active host cell mechanisms; uptake was nearly completely eliminated by cytochalasin D and genistein. These data suggest that FnBPs play a key role in host-parasite interactions and may serve as an important adhesin or invasin in ulcerative keratitis caused by
S. aureus
.
Diverse Bacteria Are Pathogens of
Caenorhabditis elegans
Authors: Couillault Carole , Ewbank Jonathan J.
Published: July 2002

Practically and ethically attractive as model systems, invertebrate organisms are increasingly recognized as relevant for the study of bacterial pathogenesis. We show here that the nematode
Caenorhabditis elegans
is susceptible to a surprisingly broad range of bacteria and may constitute a useful model for the study of both pathogens and symbionts.
Characterization of Genes Involved in Modulation of Conjugal Transfer of theBacteroidesConjugative Transposon CTnDOT
Authors: Whittle Gabrielle , Shoemaker Nadja B. , Salyers Abigail A.
Published: July 2002

In previous studies we identified an 18-kb region of theBacteroidesconjugative transposon CTnDOT that was sufficient for mobilization of coresident plasmids and unlinked integrated elements, as well as self-transfer fromBacteroidestoEscherichia coli. When this 18-kb region was cloned on a plasmid (pLYL72), the plasmid transferred itself constitutively in the absence of a coresident conjugative transposon. However, when this plasmid was present in aBacteroidesstrain containing a coresident conjugative transposon, conjugal transfer was repressed in the absence of tetracycline and enhanced in the presence of tetracycline. These results suggested that a negative and a positive regulator of conjugal transfer were encoded outside the transfer region of the CTnDOT element. In this work, a minimal and inducible transfer system was constructed and used in transfer and Western blot analyses to identify the differentially regulated genes from CTnDOT responsible for the enhancement and repression of pLYL72 conjugal transfer. Both of these regulatory functions have been localized to a region of the CTnDOT element that is essential for CTn excision. In the presence of tetracycline, the regulatory protein RteC activates the expression of a putative topoisomerase gene,exc, which in turn results in an increase in transfer protein expression and a concomitant 100- to 1,000-fold increase in the frequency of pLYL72 transfer. Our results also suggest that sinceexcalone cannot result in enhancement of transfer, other factors encoded upstream ofexcare also required. Conversely, in the absence of tetracycline, a gene located near the 3′ end ofexcis responsible for the repression of transfer protein expression and also results in a 100- to 1,000-fold decrease in the frequency of pLYL72 transfer.
The PhlA Hemolysin from the Entomopathogenic Bacterium
Photorhabdus
luminescens
Belongs to the Two-Partner Secretion Family of Hemolysins
Authors: Brillard Julien , Duchaud Eric , Boemare Noël , Kunst Frank , Givaudan Alain
Published: July 2002

Photorhabdus
is an entomopathogenic bacterium symbiotically associated with nematodes of the family Heterorhabditidae. Bacterial hemolysins found in numerous pathogenic bacteria are often virulence factors. We describe here the nucleotide sequence and the molecular characterization of the
Photorhabdus
luminescens phlBA
operon, a locus encoding a hemolysin which shows similarities to the
Serratia
type of hemolysins. It belongs to the two-partner secretion (TPS) family of proteins. In low-iron conditions, a transcriptional induction of the
phlBA
operon was observed by using the chloramphenicol acetyltransferase reporter gene, causing an increase in PhlA hemolytic activity compared to iron-rich media. A spontaneous phase variant of
P. luminescens
was deregulated in
phlBA
transcription. The
phlA
mutant constructed by allelic exchange remained highly pathogenic after injection in the lepidopteran
Spodoptera littoralis
, indicating that PhlA hemolysin is not a major virulence determinant. Using the gene encoding green fluorescent protein as a reporter,
phlBA
transcription was observed in hemolymph before insect death. We therefore discuss the possible role of PhlA hemolytic activity in the bacterium-nematode-insect interactions.