bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Small-Molecule Inhibitors of Nucleoside Triphosphate Hydrolase in
Toxoplasma gondii
Authors: Asai Takashi , Takeuchi Tsutomu , Diffenderfer Jeff , Sibley L. David 
Published: July 2002

ABSTRACT

Approximately 150,000 small-molecule compounds were tested by a robotic screening assay for their ability to inhibit nucleoside triphosphate hydrolase (NTPase), a novel enzyme of the tachyzoite form of
Toxoplasma gondii
. Five unrelated species of compounds were found to inhibit the activities of both NTPase isoforms (NTPase isoform I [NTPase-I] and NTPase-II). The 50% inhibitory concentrations (IC
50
s) ranged from 0.1 to 20 μM, and in general, the IC
50
s were similar for both NTPase isoforms. However, the activity of NTPase-I was 20 times more sensitive than the activity of NTPase-II to one of the inhibitors: 9-hydroxy-10-(pentachlorophenoxy)stearic acid. The five compounds identified also prevented tachyzoite replication in vitro, with IC
50
s ranging from ∼7 to ≥50 μM. The most effective of these initial compounds, 2-phenylthio-indole, was used to identify six additional, structurally related compounds, which were tested for their inhibitory effects on enzyme activities and tachyzoite replication. Surprisingly, these compounds were competitive inhibitors of NTPase-I but noncompetitive inhibitors of NTPase-II. Modifications to the indole and phenol rings resulted in alterations of activity, thus providing insight into the structural features that are important for inhibition of
T. gondii
NTPases.
Mutations in Cytochrome
b
Resulting in Atovaquone Resistance Are Associated with Loss of Fitness in
Plasmodium falciparum
Authors: Peters Jennifer M. , Chen Nanhua , Gatton Michelle , Korsinczky Michael , Fowler Elizabeth V. , Manzetti Sergio , Saul Allan , Cheng Qin 
Published: July 2002

ABSTRACT

Drug resistance in malarial parasites has become a major obstacle in the control of the disease. Strategies are urgently needed to control the development of resistance and to possibly reverse existing resistance. One key element required to reverse malaria drug resistance is for the parasites to “pay” a biological “cost” or suffer a loss of fitness when acquiring resistance to antimalarial drugs. Such a situation would be a disadvantage to the resistant parasites in the absence of drug pressure. We compared here the relative fitness of atovaquone-resistant
Plasmodium falciparum
K1 clones with single and double base mutations in their cytochrome
b
genes to their parent clones during erythrocytic stages in the absence of drug pressure. We found that the double amino acid mutation (M133I and G280D) is associated with a 5 to 9% loss of fitness and that the single amino acid change of M133I did not result in any detectable loss of fitness. Molecular modeling of the interaction of
P. falciparum
cytochrome
b
with ubiquinone led to the prediction that a loss of fitness of the malaria parasites would result from the G280D mutation due to its close proximity to the putative ubiquinone-binding site. This appears to have resulted in a weakening of the cytochrome
b
-ubiquinone complex, thereby causing the electron transport chain to become less efficient. Our results suggest that the prevalence of resistant parasites may decrease after the drug usage is discontinued.
Immunomodulatory and Protective Effects of Moxifloxacin againstCandida albicans-Induced Bronchopneumonia in Mice Injected with Cyclophosphamide
Authors: Shalit Itamar , Horev-Azaria Limor , Fabian Ina , Blau Hannah , Kariv Naam , Shechtman Itsak , Alteraz Hannah , Kletter Yehudith 
Published: July 2002

ABSTRACTIn a previous study, moxifloxacin was shown to ameliorate immunosuppression and enhance cytokine production in several tissues, including the lungs of cyclophosphamide-injected mice. We examined here the effects of moxifloxacin onCandida albicanslung infection in cyclophosphamide-injected mice. Mice were injected on day 0 with 250 mg of cyclophosphamide/kg, and on days 1 to 4 they were given moxifloxacin at 22.5 mg/kg/day compared to controls given ceftazidime at 75 mg/kg/day or saline. On day 6,C. albicans(10 7 CFU/mouse) was inoculated intratracheally, and animals were observed for the development of bronchopneumonia, weight loss, mortality, the presence ofC. albicans, and lung cytokine production. Histopathology on day 10 postinoculation revealed bronchopneumonia in 50, 67, and 0% of saline-, ceftazidime-, and moxifloxacin-treated mice, respectively (P < 0.05). The mortality rates were 28, 17, and 5%, respectively (P < 0.05), and weight loss occurred at 20, 32, and 0%, respectively (P < 0.05). By day 15,C. albicanswas eliminated from all moxifloxacin-treated mice but was still isolated from lung homogenates of 50 to 60% of the saline- and ceftazidime-treated groups. Among the cytokines tested on days 0 to 15, we found an increased production of tumor necrosis factor alpha, KC (functional interleukin-8), and gamma interferon in the lungs of ceftazidime- and saline-treated controls compared to the moxifloxacin pretreatment that abolished their secretion. In conclusion, moxifloxacin protected cyclophosphamide-injected mice fromC. albicans-induced lung infection and significantly reduced pneumonia, weight loss, and mortality despite the lack of direct antifungal activity. This is most likely due to an immunomodulating activity conferred by moxifloxacin, as shown in this model and in our previous studies. Its potential protective role should be studied in patients undergoing chemotherapy and immune suppression.
Overexpression of Sbe2p, a Golgi Protein, Results in Resistance to Caspofungin in
Saccharomyces cerevisiae
Authors: Osherov Nir , May Gregory S. , Albert Nathaniel D. , Kontoyiannis D. P. 
Published: July 2002

ABSTRACT

Caspofungin inhibits the synthesis of 1, 3-β-
d
-glucan, an essential cell wall target in fungi. Genetic studies in the model yeast
Saccharomyces cerevisiae
have shown that mutations in
FKS1
and
FKS2
genes result in caspofungin resistance. However, direct demonstration of the role of gene overexpression in caspofungin resistance has been lacking. We transformed wild-type
S. cerevisiae
with an
S. cerevisiae URA3
-based
GAL1
cDNA library and selected transformants in glucose synthetic complete plates lacking uracil (glucose SC minus uracil plates). We then moved the transformants to galactose SC minus uracil plates containing caspofungin (1 μg/ml) and looked for caspofungin-resistant colonies. We retested the candidates (true positives were sensitive on glucose caspofungin and resistant on galactose caspofungin media, respectively). We identified 16 caspofungin-resistant candidates. Restriction analysis and hybridization confirmed that 15 of the 16 clones were identical. We sequenced one of the cDNA clones and found that it contained the cDNA for
SBE2. SBE2
has been described in
S. cerevisiae
to encode a Golgi protein involved in the transport of cell wall components (B. Santos and M. Snyder, Mol. Biol. Cell,
11:
435-452, 2000). The
SBE2
cDNA plasmid conferred again galactose-dependent caspofungin resistance when transformed back into the wild-type
S. cerevisiae
. Finally, the
SBE2
deletion mutant was hypersensitive to caspofungin. In conclusion, overexpression of Sbe2p under the regulated control of the
GAL1
promoter results in caspofungin resistance in
S. cerevisiae
. This transport pathway may provide insight into the tolerance or lack of sensitivity to caspofungin of some pathogenic fungi.
Efficacies of Entecavir against Lamivudine-Resistant Hepatitis B Virus Replication and Recombinant Polymerases In Vitro
Authors: Levine S. , Hernandez D. , Yamanaka G. , Zhang S. , Rose R. , Weinheimer S. , Colonno R. J. 
Published: July 2002

ABSTRACT
Entecavir (ETV) is a potent and selective inhibitor of hepatitis B virus (HBV) replication in vitro and in vivo that is currently in clinical trials for the treatment of chronic HBV infections. A major limitation of the current HBV antiviral therapy, lamivudine (3TC), is the emergence of drug-resistant HBV in a majority of treated patients due to specific mutations in the nucleotide binding site of HBV DNA polymerase (HBV Pol). To determine the effects of 3TC resistance mutations on inhibition by ETV triphosphate (ETV-TP), a series of in vitro studies were performed. The inhibition of wild-type and 3TC-resistant HBV Pol by ETV-TP was measured using recombinant HBV nucleocapsids, and compared to that of 3TC-TP. These enzyme inhibition studies demonstrated that ETV-TP is a highly potent inhibitor of wild-type HBV Pol and is 100- to 300-fold more potent than 3TC-TP against 3TC-resistant HBV Pol. Cell culture assays were used to gauge the potential for antiviral cross-resistance of 3TC-resistant mutants to ETV. Results demonstrated that ETV inhibited the replication of 3TC-resistant HBV, but 20- to 30-fold higher concentrations were required. To gain further perspective regarding the potential therapeutic use of ETV, its phosphorylation was examined in hepatoma cells treated with extracellular concentrations representative of drug levels in plasma in ETV-treated patients. At these concentrations, intracellular ETV-TP accumulated to levels expected to inhibit the enzyme activity of both wild-type and 3TC-resistant HBV Pol. These findings are predictive of potent antiviral activity of ETV against both wild-type and 3TC-resistant HBV.
Antileishmanial Activity of the Antiulcer Agent Omeprazole
Authors: Jiang Suping , Meadows Juliana , Anderson Steven A. , Mukkada Antony J. 
Published: July 2002

ABSTRACT

The benzimidazole compound omeprazole, used widely for the treatment of peptic ulcer disease, inhibits the growth of
Leishmania donovani
, the causative agent of visceral leishmaniasis. Promastigotes cultured at acidic pH and amastigotes within infected macrophages are reduced 90% or more with 150 μM omeprazole. Antiparasitic action of the drug is due to its inhibition of the P-type K
+
,H
+
-ATPase on the surface membrane. This enzyme is important for pH homeostasis and the maintenance of proton motive force across the membrane in
Leishmania.
The drug is effective only at acidic pH, a condition that mimics the in vivo environment within the phagolysosomal vesicles where the amastigote form of the parasite resides. Omeprazole deserves consideration as an alternative to currently available chemotherapeutics, which have severe toxic side effects.
Ciprofloxacin in Polyethylene Glycol-Coated Liposomes: Efficacy in Rat Models of Acute or Chronic
Pseudomonas aeruginosa
Infection
Authors: Bakker-Woudenberg Irma A. J. M. , ten Kate Marian T. , Guo Luke , Working Peter , Mouton Johan W. 
Published: July 2002

ABSTRACT

In a previous study in experimental
Klebsiella pneumoniae
pneumonia, the therapeutic potential of ciprofloxacin was significantly improved by encapsulation in polyethylene glycol-coated (“pegylated”) long-circulating (STEALTH) liposomes. Pegylated liposomal ciprofloxacin in high doses was nontoxic and resulted in relatively high and sustained ciprofloxacin concentrations in blood and tissues, and hence an increase in the area under the plasma concentration-time curve (AUC). These data correspond to data from animal and clinical studies showing that for fluoroquinolones the AUC/MIC ratio is associated with favorable outcome in serious infections. Clinical failures and the development of resistance are observed for marginally susceptible organisms like
Pseudomonas aeruginosa
and for which sufficient AUC/MIC ratios cannot be achieved. In the present study the therapeutic efficacy of pegylated liposomal ciprofloxacin was investigated in two rat models of
Pseudomonas aeruginosa
pneumonia. In the acute model pneumonia developed progressively, resulting in a rapid onset of septicemia and a high mortality rate. Ciprofloxacin twice daily for 7 days was not effective at doses at or below the maximum tolerated dose (MTD). However, pegylated liposomal ciprofloxacin either at high dosage or given at low dosage in combination with free ciprofloxacin on the first day of treatment was fully effective (100% survival). Obviously, prolonged concentrations of ciprofloxacin in blood prevented death of the animals due to early-stage septicemia in this acute infection. However, bacterial eradication from the left lung was not effected. In the chronic model, pneumonia was characterized by bacterial persistence in the lung without bacteremia, and no signs of morbidity or mortality were observed. Ciprofloxacin administered for 7 days at the MTD twice daily resulted in killing of more than 99% of bacteria in the lung; this result can also be achieved with pegylated liposomal ciprofloxacin given once daily. Complete bacterial eradication is never observed.
Three-Dimensional Quantitative Structure-Activity Relationship and Comparative Molecular Field Analysis of Dipeptide Hydroxamic Acid
Helicobacter pylori
Urease Inhibitors
Authors: Mishra Hetal , Parrill Abby L. , Williamson John S. 
Published: July 2002

ABSTRACT

A homology model of
Helicobacter pylori
urease was developed by using the crystal structure of urease from
Klebsiella aerogenes
(EC 3.5.1.5) as a template. The acetohydroxamic acid moiety was docked into the active pocket of the enzyme model, followed by relaxation of the complex by use of molecular dynamics. The resulting conformation was used as a template to construct 24 potential dipeptide hydroxamic acid inhibitors with which comparative molecular field analysis (CoMFA) was performed. The resulting model provided a cross-validation correlation coefficient (
q
2
L00
) of 0.610, a conventional
r
2
value of 0.988, and an
F
(Fisher indication of statistical significance) value of 294.88. We were able to validate the CoMFA model by using the 50% inhibitory concentrations of six compounds that were not included in the construction of the model. A very good structural correlation was observed between the amino acids in the model urease's active pocket and the contour maps derived from the CoMFA model. This correlation, accompanied by the validation supplied by use of the CoMFA data, illustrates that the model can aid in the prediction and design of novel
H. pylori
urease inhibitors.
Salicylate Reduces Susceptibility of
Mycobacterium tuberculosis
to Multiple Antituberculosis Drugs
Authors: Schaller Alain , Sun Zhonghe , Yang Yongping , Somoskovi Akos , Zhang Ying 
Published: July 2002

ABSTRACT

Salicylate induces multiple antibiotic resistance in various bacterial species. Here we investigated the effect of salicylate on the susceptibility of
Mycobacterium tuberculosis
to a range of antituberculosis (anti-TB) drugs. In the presence of salicylate, the killing effects of isoniazid (INH), rifampin (RMP), ethambutol (EMB), streptomycin (STR), and
p
-aminosalicylate (PAS) were reduced, as shown with a tetrazolium redox dye viability assay and a bacterial survival assay. Salicylate-induced resistance was more pronounced for PAS, STR, and EMB but was not apparent for INH and RMP when salicylate and the anti-TB agents were incorporated into 7H11 plates. The significance of these findings for TB treatment needs to be further evaluated in vivo.
Resazurin Microtiter Assay Plate: Simple and Inexpensive Method for Detection of Drug Resistance in
Mycobacterium tuberculosis
Authors: Palomino Juan-Carlos , Martin Anandi , Camacho Mirtha , Guerra Humberto , Swings Jean , Portaels Françoise 
Published: July 2002

ABSTRACT

A method for detecting multidrug-resistant
Mycobacterium tuberculosis
by using a reduction of resazurin is described. Eighty clinical isolates were evaluated against isoniazid and rifampin; results at 7 days were compared with those of the proportion method. Specificity and sensitivity were excellent. The method is simple, inexpensive, and rapid and might be used with other antituberculosis drugs.
Airborne Microbial Flora in a Cattle Feedlot
Authors: Wilson S. C. , Morrow-Tesch J. , Straus D. C. , Cooley J. D. , Wong W. C. , Mitlöhner F. M. , McGlone J. J. 
Published: July 2002

ABSTRACT

A total of 1,408 cattle held in eight commercial feedlot pens were used to examine the quantity and diversity of microorganisms in cattle feedlot air. The effect of two feeding patterns on the generation of airborne dust and the total numbers of microorganisms was also examined (four feedlot pens/treatment). Microbial samples were collected, and dust particles that were 2.5 μm or less in diameter were measured with a Dustrak monitor during the evening dust peak for 4 days at sites both upwind and downwind of the feedlot pens. An Andersen biological cascade sampler was employed with different medium and incubation combinations for the capture and identification of bacteria and fungi. The results showed that when bacteria were considered, only nonpathogenic gram-positive organisms were recovered. However, gram-negative bacteria may have been present in a viable but nonculturable state. Fungi were recovered in smaller numbers than bacteria, and none of the fungi were pathogenic. The Dustrak results showed that one feeding pattern resulted in cattle behavior that generated levels of downwind dust lower (
P
= 0.04) than the levels generated by the behavior resulting from the other feeding pattern. However, the Andersen sampler results showed that there were no differences between feeding patterns with regard to the total number or diversity of microorganisms. The disparity may have been due to the different operating principles of the two systems. The overall numbers of microorganisms recovered were lower than those reported in studies of intensively housed farm animals in which similar recovery techniques were used.
Functional Production and Characterization of a Fibrin-Specific Single-Chain Antibody Fragment fromBacillus subtilis: Effects of Molecular Chaperones and a Wall-Bound Protease on Antibody Fragment Production
Authors: Wu Sau-Ching , Yeung Jonathan C. , Duan Yanjun , Ye Ruiqiong , Szarka Steven J. , Habibi Hamid R. , Wong Sui-Lam 
Published: July 2002

ABSTRACTTo develop an ideal blood clot imaging and targeting agent, a single-chain antibody (SCA) fragment based on a fibrin-specific monoclonal antibody, MH-1, was constructed and produced via secretion fromBacillus subtilis. Through a systematic study involving a series ofB. subtilisstrains, insufficient intracellular and extracytoplasmic molecular chaperones and high sensitivity to wall-bound protease (WprA) were believed to be the major factors that lead to poor production of MH-1 SCA. Intracellular and extracytoplasmic molecular chaperones apparently act in a sequential manner. The combination of enhanced coproduction of both molecular chaperones andwprAinactivation leads to the development of an engineeredB. subtilisstrain, WB800HM[pEPP]. This strain allows secretory production of MH-1 SCA at a level of 10 to 15 mg/liter. In contrast, with WB700N (a seven-extracellular-protease-deficient strain) as the host, no MH-1 SCA could be detected in both secreted and cellular fractions. Secreted MH-1 SCA from WB800HM[pMH1, pEPP] could be affinity purified using a protein L matrix. It retains comparable affinity and specificity as the parental MH-1 monoclonal antibody. This expression system can potentially be applied to produce other single-chain antibody fragments, especially those with folding and protease sensitivity problems.
Survival of GacS/GacA Mutants of the Biological Control Bacterium
Pseudomonas aureofaciens
30-84 in the Wheat Rhizosphere
Authors: Chancey Scott T. , Wood Derek W. , Pierson Elizabeth A. , Pierson Leland S. 
Published: July 2002

ABSTRACT

GacS/GacA comprises a two-component regulatory system that controls the expression of secondary metabolites required for the control of plant diseases in many pseudomonads. High mutation frequencies of
gacS
and
gacA
have been observed in liquid culture. We examined whether
gacS/gacA
mutants could competitively displace the wild-type populations on roots and thus pose a threat to the efficacy of biological control. The survival of a
gac
mutant alone and in competition with the wild type on roots was examined in the biological control strain
Pseudomonas aureofaciens
30-84. In this bacterium, GacS/GacA controls the expression of phenazine antibiotics that are inhibitory to plant pathogenic fungi and enhance the competitive survival of the bacterium. Wheat seedlings were inoculated with strain 30-84, and bacteria were recovered from roots after 21 days in sterile or nonsterile soil to check for the presence of
gacS
or
gacA
mutants. Although no mutants were detected in the inoculum,
gacS/gacA
mutants were recovered from 29 out of 31 roots and comprised up to 36% of the total bacterial populations. Southern hybridization analysis of the recovered
gacA
mutants did not indicate a conserved mutational mechanism. Replacement series analysis on roots utilizing strain 30-84 and a
gacA
mutant (30-84.gacA) or a
gacS
mutant (30-84.A2) demonstrated that although the mutant population partially displaced the wild type in sterile soil, it did not do so in natural soil. In fact, in natural soil final rhizosphere populations of wild-type strain 30-84 starting from mixtures were at least 1.5 times larger than would be predicted from their inoculation ratio and generally were greater than or equal to the population of wild type alone despite lower inoculation rates. These results indicate that although
gacS/gacA
mutants survive in natural rhizosphere populations, they do not displace wild-type populations. Better survival of wild-type populations in mixtures with mutants suggests that mutants arising de novo or introduced within the inoculum may be beneficial for the survival of wild-type populations in the rhizosphere.
Plant-Dependent Genotypic and Phenotypic Diversity of Antagonistic Rhizobacteria Isolated from Different
Verticillium
Host Plants
Authors: Berg Gabriele , Roskot Nicolle , Steidle Anette , Eberl Leo , Zock Angela , Smalla Kornelia 
Published: July 2002

ABSTRACT

To study the effect of plant species on the abundance and diversity of bacterial antagonists, the abundance, the phenotypic diversity, and the genotypic diversity of rhizobacteria isolated from potato, oilseed rape, and strawberry and from bulk soil which showed antagonistic activity towards the soilborne pathogen
Verticillium dahliae
Kleb. were analyzed. Rhizosphere and soil samples were taken five times over two growing seasons in 1998 and 1999 from a randomized field trial. Bacterial isolates were obtained after plating on R2A (Difco, Detroit, Mich.) or enrichment in microtiter plates containing high-molecular-weight substrates followed by plating on R2A. A total of 5,854 bacteria isolated from the rhizosphere of strawberry, potato, or oilseed rape or bulk soil from fallow were screened by dual testing for in vitro antagonism towards
Verticillium
. The proportion of isolates with antagonistic activity was highest for strawberry rhizosphere (9.5%), followed by oilseed rape (6.3%), potato (3.7%), and soil (3.3%). The 331
Verticillium
antagonists were identified by their fatty acid methyl ester profiles. They were characterized by testing their in vitro antagonism against other pathogenic fungi; their glucanolytic, chitinolytic, and proteolytic activities; and their BOX-PCR fingerprints. The abundance and composition of
Verticillium
antagonists was plant species dependent. A rather high proportion of antagonists from the strawberry rhizosphere was identified as
Pseudomonas putida
B (69%), while antagonists belonging to the
Enterobacteriaceae
(
Serratia
spp.,
Pantoea agglomerans
) were mainly isolated from the rhizosphere of oilseed rape. For
P. putida
A and B plant-specific genotypes were observed, suggesting that these bacteria were specifically enriched in each rhizosphere.