bluuebunny/crossref_metadata_2025_split huggingface dataset:
Safety and Pharmacokinetics of Single Doses of (+)-Calanolide A, a Novel, Naturally Occurring Nonnucleoside Reverse Transcriptase Inhibitor, in Healthy, Human Immunodeficiency Virus-Negative Human Subjects
Authors: Creagh Terri , Ruckle Jon L. , Tolbert Dwain T. , Giltner Jeremy , Eiznhamer David A. , Dutta Bipul , Flavin Michael T. , Xu Ze-Qi 
Published: July 2002

ABSTRACT(+)-Calanolide A is a novel, naturally occurring, nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase first isolated from a tropical tree (Calophyllum lanigerum) in the Malaysian rain forest. Previous studies have demonstrated that (+)-calanolide A has specific activity against the reverse transcriptase of HIV-1 and a favorable safety profile in animals. In addition, (+)-calanolide A exhibits a unique HIV-1 resistance profile in vitro. The safety and pharmacokinetics of (+)-calanolide A was examined in four successive single-dose cohorts (200, 400, 600, and 800 mg) in healthy, HIV-negative volunteers. In this initial phase I study, the toxicity of (+)-calanolide A was minimal in the 47 subjects treated. Dizziness, taste perversion, headache, eructation, and nausea were the most frequently reported adverse events. These events were not all judged to be related to study medication nor were they dose related. While 51% of subjects reported mild and transient dizziness, in many cases this appeared to be temporally related to phlebotomy. Calculation of the terminal-phase half-life (t1/2) was precluded by intrasubject variability in the 200-, 400-, and 600-mg dose cohorts but was approximately 20 h for the 800-mg dose group. (+)-Calanolide A was rapidly absorbed following administration, with time to maximum concentration of drug in plasma (Tmax) values occurring between 2.4 and 5.2 h postdosing depending on the dose. Plasma levels of (+)-calanolide A at all dosing levels were quite variable; however, both the mean concentration in plasma (Cmax), and the area under the plasma concentration-time curve increased proportionately in relation to the dose. Although raw plasma drug levels were higher in women than in men, when doses were normalized for body mass, the pharmacokinetic profiles were virtually identical with those observed for males. In general, levels of (+)-calanolide A in human plasma were higher than would have been predicted from animal studies, yet the safety profile remained benign. In conclusion, this study demonstrated the safety and favorable pharmacokinetic profile of single doses of (+)-calanolide A in healthy, HIV-negative individuals.
Proinflammatory Activity of a Cecropin-Like Antibacterial Peptide fromHelicobacter pylori
Authors: Bylund Johan , Christophe Thierry , Boulay Francois , Nyström Thomas , Karlsson Anna , Dahlgren Claes 
Published: July 2002

ABSTRACTHelicobacter pylori, the bacterial pathogen associated with gastritis and peptic ulcers, is highly successful in establishing infection in the human gastric mucosa, a process typically associated with massive infiltration of inflammatory cells. Colonization of the mucosa is suggested to be facilitated byH. pylori-produced cecropin-like peptides with antibacterial properties, giving the microbe a competitive advantage over other bacteria. We show that a cecropin-like antibacterial peptide fromH. pylori, Hp(2-20), not only has a potent bactericidal effect but also induces proinflammatory activities in human neutrophils, e.g., upregulation of integrins (Mac-1), induction of chemotaxis, and activation of the oxygen radical producing NADPH-oxidase. Furthermore, we show that these effects are mediated through binding of Hp(2-20) to the promiscuous, G-protein-linked lipoxin A4receptor–formyl peptide-like receptor 1.
d
-Ala:
d
-Ala Ligase Gene Flanking the
vanC
Cluster: Evidence for Presence of Three Ligase Genes in Vancomycin-Resistant
Enterococcus gallinarum
BM4174
Authors: Ambúr Ole-Herman , Reynolds Peter E. , Arias Cesar A. 
Published: July 2002

ABSTRACT

An open reading frame located 230 nucleotides downstream from the stop codon of
vanS

c

and in the opposite direction relative to the other genes of the
vanC
cluster was identified in
Enterococcus gallinarum
BM4174. This gene (designated
ddl2
) encoded a protein of 343 amino acids that had significant predicted structural similarity to
d
-Ala:
d
-Ala ligases and displayed 33 and 35% amino acid identity to VanC-1 and the previously reported partial sequence of Ddl from
E. gallinarum
, respectively. Biochemical characterization by thin-layer chromatography confirmed that Ddl2 is a
d
-Ala:
d
-Ala ligase with no detectable
d
-Ala:
d
-Ser ligase activity. The vancomycin dependence of
Enterococcus faecalis
BM4320 (
ddl
mutant) was lost on electroporation of a plasmid construct expressing
ddl2
constitutively. The latter strain was able to grow in the absence of vancomycin, and peptidoglycan precursor analysis under the same conditions indicated the synthesis of pentapeptide[
d
-Ala] as the main precursor, confirming the activity of Ddl2 in vivo. Expression of
ddl
and
ddl2
in BM4174 was tested by reverse transcription-PCR: results suggested that both
d
-Ala:
d
-Ala ligases were expressed concomitantly. Our findings indicate that vancomycin-resistant
E. gallinarum
BM4174 is likely to express one
d
-Ala:
d
-Ser and two
d
-Ala:
d
-Ala ligase genes.
Oxidative Modifications of Kynostatin-272, a Potent Human Immunodeficiency Virus Type 1 Protease Inhibitor: Potential Mechanism for Altered Activity in Monocytes/Macrophages
Authors: Davis David A. , Read-Connole Elizabeth , Pearson Kara , Fales Henry M. , Newcomb Fonda M. , Moskovitz Jackob , Yarchoan Robert 
Published: July 2002

ABSTRACTPrevious studies have indicated that human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs) are less active at blocking viral replication in HIV-1 infected peripheral blood monocytes/macrophages (M/M) than in HIV-1-infected T cells. We explored the hypothesis that oxidative modification and/or metabolism of the PIs in M/M might account for this reduced potency. We first tested the susceptibility of several PIs (kynostatin-272 [KNI-272], saquinavir, indinavir, ritonavir, or JE-2147) to oxidation after exposure to hydrogen peroxide (H2O2): only KNI-272 was highly susceptible to oxidation. Treatment of KNI-272 with low millimolar concentrations of H2O2resulted in mono-oxidation of the sulfur in theS-methyl cysteine (methioalanine) moiety, as determined by reversed-phase high-performance liquid chromatography and mass spectrometry (RP-HPLC/MS). Higher concentrations of H2O2led to an additional oxidation of the sulfur in the thioproline moiety of KNI-272. None of the PIs were metabolized or oxidized when added to T cells and cultured for up to 12 days. However, when KNI-272 was added to M/M, the concentration of the original KNI-272 steadily decreased with a corresponding increase in the production of three KNI-272 metabolites as identified by RP-HPLC/MS. The structures of these metabolites were different from those produced by H2O2treatment. The two major products of M/M metabolism of KNI-272 were identified as isomeric forms of KNI-272 oxidized solely on the thioproline ring. Both metabolites had reduced capacities to inhibit HIV-1 protease activity when tested in a standard HIV-1 protease assay. These studies demonstrate that antiviral compounds can be susceptible to oxidative modification in M/M and that this can affect their antiviral potency.
1
H Nuclear Magnetic Resonance Study of Oxazolidinone Binding to Bacterial Ribosomes
Authors: Zhou Casey Chun , Swaney Steven M. , Shinabarger Dean L. , Stockman Brian J. 
Published: July 2002

ABSTRACT

The oxazolidinones are a novel class of antibiotics that inhibit initiation of protein synthesis in bacteria. In order to investigate their novel mechanism of action, the interactions of several oxazolidinones with bacterial 70S ribosomes, 50S subunits, and 30S subunits have been characterized by
1
H nuclear magnetic resonance (NMR) line-broadening analyses and transferred nuclear Overhauser enhancement (TRNOE) experiments. PNU-177553 and PNU-100592 (eperezolid) and their corresponding enantiomers, PNU-184414 and PNU-107112, were studied. The dissociation constants were determined to be 94 ± 44 μM and 195 ± 40 μM for PNU-177553 and eperezolid, respectively. There was a ∼4-fold decrease in affinity for their corresponding enantiomers. The NMR-derived dissociation constants are consistent with their antibacterial activity. PNU-177553 and eperezolid were found to bind only to the 50S subunit, with similar affinity as to the 70S ribosome, and to have no affinity for the 30S subunit. Specific binding of PNU-177553 was further confirmed in TRNOE experiments in which positive NOEs observed for the small molecule alone were changed to negative NOEs in the presence of bacterial 70S ribosomes. The observed NOEs indicated that PNU-177553 did not adopt a significantly different conformation when bound to the 70S ribosome, compared to the extended conformation that exists when free in solution. Since this is likeliest the case for each of the four compounds included in this study, the A ring C5 side chain may be positioned in the proper orientation for antibacterial activity in PNU-177553 and eperezolid but not in their inactive enantiomers.
Pharmacodynamic Assessment of Clarithromycin in a Murine Model of Pneumococcal Pneumonia
Authors: Tessier Pamela R. , Kim Myo-Kyoung , Zhou Wen , Xuan Dawei , Li Chonghua , Ye Min , Nightingale Charles H. , Nicolau David P. 
Published: July 2002

ABSTRACT

The pharmacodynamic profile of clarithromycin (CLR) was evaluated with a murine model of pneumonia. Eight
Streptococcus pneumoniae
isolates, including three macrolide-sensitive and five macrolide-resistant strains, were inoculated intratracheally into immunocompromised ICR mice as 10
8
-CFU bacterial suspensions. Orally administered CLR daily doses ranging from 5 to 600 mg/kg of body weight were given over 5 days, during which animal survival was monitored. The bacterial density in lung tissues was examined after 24 h of CLR treatment and in control groups. Pharmacokinetic analysis of CLR in mice demonstrated that the regimen of 150 mg/kg twice a day was representative of human pharmacokinetics and was used to compare the efficacy of CLR against sensitive and resistant
S. pneumoniae
strains. Immunocompetent CBA/J mice were also infected and treated as described above and evaluated for bacterial density and survival to assess the effect of the presence of leukocytes. All three pharmacodynamic parameters, the duration (percent) of the time that serum CLR concentrations remain above the MIC (%T>MIC), the ratio of the area under the concentration-time curve from 0 to 24 h (AUC
0-24
) to the MIC, and the ratio of the maximum concentration of drug in serum to the MIC, were found to be closely correlated to CLR bacterial efficacy (
P
< 0.001). Furthermore, all parameters had close correlation to bacterial density (
r
2
= 0.72 to 0.82), median survival (
r
2
= 0.93 to 0.94), and total percent survival (
r
2
= 0.91 to 0.92). These in vivo data suggest that the bacterial activity of CLR is closely correlated with all three parameters over a wide range of exposures and, as a consequence of parameter interdependency, AUC
0-24
/MIC is the most reasonable predictor of antibiotic efficacy. In this neutropenic pneumonia model, CLR was less efficacious against
S. pneumoniae
strains for which MICs were ≥4 μg/ml. However, the presence of leukocytes in the immunocompetent mice resulted in improved bactericidal activity, relative to that in the neutropenic animals, despite an MIC of 4 μg/ml.
Association of Metronidazole Resistance and Natural Competence in
Helicobacter pylori
Authors: Yeh Yu-Ching , Chang Kai-Chin , Yang Jyh-Chin , Fang Chi-Tai , Wang Jin-Town 
Published: July 2002

ABSTRACT

To study whether the capability of horizontal DNA transfer is associated with metronidazole resistance in
Helicobacter pylori
, a total of 81 clinical isolates were tested for MICs of metronidazole (MTZ). The MIC assays were performed by using the E-test and reconfirmed by the agar dilution method. Natural competence assays were performed by transferring a chloramphenicol acetyltransferase cassette and a 23S rRNA gene from a clarithromycin-resistant strain (with an A-to-G mutation at nucleotide 2143) by using natural transformation. Of the 81 isolates, 65 (80.2%) were naturally competent while 16 were not. Among the 65 naturally competent strains, 39 (60%) were highly resistant to MTZ (MICs, >32 μg/ml) while only 2 of 16 (12.5%) noncompetent strains were highly MTZ resistant (
P
, <0.001). Therefore, there is an association between natural competence and MTZ resistance.
Internal Thiols and Reactive Oxygen Species in Candidacidal Activity Exerted by an N-Terminal Peptide of Human Lactoferrin
Authors: Lupetti Antonella , Paulusma-Annema Akke , Senesi Sonia , Campa Mario , van Dissel Jaap T. , Nibbering Peter H. 
Published: July 2002

ABSTRACTWe previously showed that the energized mitochondrion and extracellular ATP are essential for the candidacidal activity of the N-terminal peptide of human lactoferrin, subsequently referred to as hLF(1-11). The present study focuses on the involvement of internal thiols and reactive oxygen species (ROS) in the candidacidal activity exerted by hLF(1-11). Our results reveal that hLF(1-11) reduced the internal thiol level ofCandida albicansby 20%. In agreement,N-acetyl-l-cysteine (NAC), which is a precursor of glutathione and an ROS scavenger, inhibited the candidacidal activity of hLF(1-11). In addition, azodicarboxylic acid bis(N,N-dimethylamide) (diamide), which oxidizes internal thiols, was candidacidal. Furthermore, hLF(1-11) increased the level of ROS production byC. albicansin a dose-dependent manner, and a correlation between ROS production and candidacidal activity was found. 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), which is an ROS scavenger, partially inhibited the hLF(1-11)-induced, but not the diamide-triggered, candidacidal activity. It is of interest that hLF(1-11) and diamide acted synergistically in killingC. albicansand in ROS production. In agreement, oxidized ATP, an irreversible inhibitor of extracellular ATP receptors, partially blocked the hLF(1-11)-induced, but not the diamide-triggered, candidacidal activity. Finally, the hLF(1-11)-induced activation of mitochondria was inhibited by NAC, indicating that internal thiols and ROS affect mitochondrial activity. Therefore, the candidacidal activity of hLF(1-11) involves both generation of ROS and reduction of internal thiols.
Use of Two-Dimensional Electrophoresis To Study Differential Protein Expression in Divercin V41-Resistant and Wild-Type Strains of
Listeria monocytogenes
Authors: Duffes Frederique , Jenoe Paul , Boyaval Patrick 
Published: July 2002

ABSTRACT

The use of bacteriocins from food-grade lactic acid bacteria to fight against the food-borne pathogen
Listeria monocytogenes
has been gaining interest. However, the emergence of resistant cells is frequently reported when
Listeria
is exposed to such antibacterials. A two-dimensional electrophoresis study of whole-cell protein expression of
Listeria monocytogenes
variants sensitive or resistant to the action of a bacteriocin produced by
Carnobacterium divergens
V41, divercin V41, is reported in this paper. The resistant variant obtained from the sensitive strain of
L. monocytogenes
P was also resistant to piscicocins V1 and SF668, but remained sensitive to nisin. Its growth rate was 50% less than the sensitive strain, and the MIC for it was 10
4
times higher. No reversion of the resistance was observed after 20 successive cultures in the absence of divercin V41. Comparison of the protein patterns by two-dimensional gel electrophoresis analysis showed clear differences. In the resistant variant pattern, at least nine spots had disappeared and eight new ones were observed. One of the newly synthesized proteins was identified as a flagellin of
L. monocytogenes
. Direct interaction between flagellin and divercin V41 was not evidenced. Intracellular synthesis of flagellin is probably an indirect effect of a modification in transcriptional regulation with widespread effects through a sigma factor. An intense protein, only present in the sensitive strain, was identified as a non-heme iron-binding ferritin displaying strong similarities to Dps proteins. Common modifications in the transcriptional regulation for these two proteins are discussed.
Persistence of Selected
Spartina alterniflora
Rhizoplane Diazotrophs Exposed to Natural and Manipulated Environmental Variability
Authors: Bagwell Christopher E. , Lovell Charles R. 
Published: July 2002

ABSTRACT

Rhizoplane-rhizosphere nitrogen-fixing microorganisms (diazotrophs) are thought to provide a major source of biologically available nitrogen in salt marshes dominated by
Spartina alterniflora
. Compositional and functional stability has been demonstrated for this important functional group; however, the quantitative responses of specific diazotroph populations to environmental variability have not been assessed. Changes in the relative abundances of selected rhizoplane diazotrophs in response to long-term fertilization were monitored quantitatively by reverse sample genome probing. Fertilization stimulated
Spartina
, with plant height nearly tripling after 1 year. Fertilization also resulted in significant changes in interstitial porewater parameters. Diazotrophic activity (acetylene reduction assay) was sensitive to the fertilization treatments and was inhibited in some plots on several sampling dates. However, inhibition was never consistent across all of the replicates within a treatment and activity always recovered. The rhizoplane diazotrophs were quite responsive to environmental variability and to experimental treatments, but none were displaced by either environmental variability or experimental treatments. All strains were detected consistently throughout this study, and extensive spatial heterogeneity in the distribution patterns of these organisms was observed. The physiological traits that differentiate the diazotroph populations presumably support competitiveness and niche specialization, resulting in the observed resilience of the diazotroph populations in the rhizosphere.
A Gene Encoding a Novel Multidomain β-1,4-Mannanase from
Caldibacillus cellulovorans
and Action of the Recombinant Enzyme on Kraft Pulp
Authors: Sunna Anwar , Gibbs Moreland D. , Chin Charles W. J. , Nelson Peter J. , Bergquist Peter L. 
Published: July 2002

ABSTRACT

Genomic walking PCR was used to obtained a 4,567-bp nucleotide sequence from
Caldibacillus cellulovorans
. Analysis of this sequence revealed that there were three open reading frames, designated ORF1, ORF2, and ORF3. Incomplete ORF1 encoded a putative C-terminal cellulose-binding domain (CBD) homologous to members of CBD family IIIb, while putative ORF3 encoded a protein of unknown function. The putative ManA protein encoded by complete
manA
ORF2 was an enzyme with a novel multidomain structure and was composed of four domains in the following order: a putative N-terminal domain (D1) of unknown function, an internal CBD (D2), a β-mannanase catalytic domain (D3), and a C-terminal CBD (D4). All four domains were linked via proline-threonine-rich peptides. Both of the CBDs exhibited sequence similarity to family IIIb CBDs, while the mannanase catalytic domain exhibited homology to the family 5 glycosyl hydrolases. The purified recombinant enzyme ManAd3 expressed from the cloned catalytic domain (D3) exhibited optimum activity at 85°C and pH 6.0 and was extremely thermostable at 70°C. This enzyme exhibited high specificity with the substituted galactomannan locust bean gum, while more substituted galacto- and glucomannans were poorly hydrolyzed. Preliminary studies to determine the effect of the recombinant ManAd3 and a recombinant thermostable β-xylanase on oxygen-delignified
Pinus radiata
kraft pulp revealed that there was an increase in the brightness of the bleached pulp.
Growth of
Escherichia coli
O157:H7 in Bruised Apple (
Malus domestica
) Tissue as Influenced by Cultivar, Date of Harvest, and Source
Authors: Dingman Douglas W. 
Published: July 2002

ABSTRACT

Four of five apple cultivars (Golden Delicious, Red Delicious, McIntosh, Macoun, and Melrose) inoculated with
Escherichia coli
O157:H7 promoted growth of the bacterium in bruised tissue independent of the date of harvest (i.e., degree of apple ripening) or the source of the apple (i.e., tree-picked or dropped fruit). Apple harvest for this study began 4 September 1998 and ended 9 October, with weekly sampling. Throughout this study, freshly picked (<2 days after harvest) McIntosh apples usually prevented the growth of
E. coli
O157:H7 for 2 days. Growth of
E. coli
O157:H7 did occur following 6 days of incubation in bruised McIntosh apple tissue. However, the maximum total cell number was approximately 80-fold less than the maximum total cell number recovered from Red Delicious apples. When fruit was stored for 1 month at 4°C prior to inoculation with
E. coli
O157:H7, all five cultivars supported growth of the bacterium. For each apple cultivar, the pH of bruised tissue was significantly higher and °Brix was significantly lower than the pH and °Brix of undamaged tissue regardless of the source. In freshly picked apples, changes in the pH did not occur over the harvest season. Bruised Golden Delicious, McIntosh, and Melrose apple tissue pHs were not significantly different (tree-picked or dropped), and the °Brix values of McIntosh, Macoun, and Melrose apple tissue were not significantly different. Single-cultivar preparations of cider did not support growth of
E. coli
, and the cell concentration of inoculated cider declined over an 11-day test period. The rate of decline in
E. coli
cell concentration in the McIntosh cider was greater than those in the other ciders tested. The findings of this study suggested that the presence of some factor besides, or in addition to, pH inhibited
E. coli
growth in McIntosh apples.
Importance of Cry1 δ-Endotoxin Domain II Loops for Binding Specificity in
Heliothis virescens
(L.)
Authors: Jurat-Fuentes Juan Luis , Adang Michael J. 
Published: July 2002

ABSTRACT

We constructed a model for
Bacillus thuringiensis
Cry1 toxin binding to midgut membrane vesicles from
Heliothis virescens
. Brush border membrane vesicle binding assays were performed with five Cry1 toxins that share homologies in domain II loops. Cry1Ab, Cry1Ac, Cry1Ja, and Cry1Fa competed with
125
I-Cry1Aa, evidence that each toxin binds to the Cry1Aa binding site in
H. virescens
. Cry1Ac competed with high affinity (competition constant [
K
com
] = 1.1 nM) for
125
I-Cry1Ab binding sites. Cry1Aa, Cry1Fa, and Cry1Ja also competed for
125
I-Cry1Ab binding sites, though the
K
com
values ranged from 179 to 304 nM. Cry1Ab competed for
125
I-Cry1Ac binding sites (
K
com
= 73.6 nM) with higher affinity than Cry1Aa, Cry1Fa, or Cry1Ja. Neither Cry1Ea nor Cry2Aa competed with any of the
125
I-Cry1A toxins. Ligand blots prepared from membrane vesicles were probed with Cry1 toxins to expand the model of Cry1 receptors in
H. virescens
. Three Cry1A toxins, Cry1Fa, and Cry1Ja recognized 170- and 110-kDa proteins that are probably aminopeptidases. Cry1Ab and Cry1Ac, and to some extent Cry1Fa, also recognized a 130-kDa molecule. Our vesicle binding and ligand blotting results support a determinant role for domain II loops in Cry toxin specificity for
H. virescens
. The shared binding properties for these Cry1 toxins correlate with observed cross-resistance in
H. virescens.