bluuebunny/crossref_metadata_2025_split huggingface dataset:
Binding Site for Chitin Oligosaccharides in the Soybean Plasma Membrane
Authors: Day R. Bradley , Okada Mitsuo , Ito Yuki , Tsukada Koji , Zaghouani Habib , Shibuya Naoto , Stacey Gary 
Published: July 2002

Abstract
Affinity cross-linking of the plasma membrane fraction to an125I-labeled chitin oligosaccharide led to the identification and characterization of an 85-kD, chitin binding protein in plasma membrane-enriched fractions from both suspension-cultured soybean cells and root tissue. Inhibition analysis indicated a binding preference for larger (i.e. degrees of polymerization = 8)N-acetylated chitin molecules with a 50% inhibition of initial activity value of approximately 50 nm.N-Acetyl-glucosamine and chitobiose showed no inhibitory effects at concentrations as high as 250 μm. It is noteworthy that the major lipo-chitin oligosaccharide Nod signal produced by Bradyrhizobium japonicum was also shown to be a competitive inhibitor of ligand binding. However, the binding site appeared to recognize the chitin portion of the Nod signal, and it is unlikely that this binding activity represents a specific Nod signal receptor. Chitooligosaccharide specificity for induction of medium alkalinization and the generation of reactive oxygen in suspension-cultured cells paralleled the binding activity. Taken together, the presence of the chitin binding protein in the plasma membrane fraction and the specificity and induction of a biological response upon ligand binding suggest a role for the protein as an initial response mechanism for chitin perception in soybean (Glycine max).
Molecular confinement influences protein structure and enhances thermal protein stability
Authors: Eggers Daryl K. , Valentine Joan S. 
Published: July 2002

AbstractThe sol‐gel method of encapsulating proteins in a silica matrix was investigated as a potential experimental system for testing the effects of molecular confinement on the structure and stability of proteins. We demonstrate that silica entrapment (1) is fully compatible with structure analysis by circular dichroism, (2) allows conformational studies in contact with solvents that would otherwise promote aggregation in solution, and (3) generally enhances thermal protein stability. Lysozyme, α‐lactalbumin, and metmyoglobin retained native‐like solution structures following sol‐gel encapsulation, but apomyoglobin was found to be largely unfolded within the silica matrix under control buffer conditions. The secondary structure of encapsulated apomyoglobin was unaltered by changes in pH and ionic strength of KCl. Intriguingly, the addition of other neutral salts resulted in an increase in the α‐helical content of encapsulated apomyoglobin in accordance with the Hofmeister ion series. We hypothesize that protein conformation is influenced directly by the properties of confined water in the pores of the silica. Further work is needed to differentiate the steric effects of the silica matrix from the solvent effects of confined water on protein structure and to determine the extent to which this experimental system mimics the effects of crowding and confinement on the function of macromolecules in vivo.
Role of individual disulfide bonds in hen lysozyme early folding steps
Authors: Guez Valérie , Roux Pascale , Navon Amiel , Goldberg Michel E. 
Published: July 2002

AbstractTo probe the role of individual disulfide bonds in the folding kinetics of hen lysozyme, the variants with two mutations, C30A,C115A, C64A,C80A, and C76A,C94A, were constructed. The corresponding proteins, each lacking one disulfide bond, were produced in Escherichia coli as inclusion bodies and solubilized, purified, and renatured/oxidized using original protocols. Their enzymatic, spectral, and hydrodynamic characteristics confirmed that their conformations were very similar to that of native wild‐type (WT) lysozyme. Stopped‐flow studies on the renaturation of these guanidine‐unfolded proteins with their three disulfides intact showed that, for the three variants, the native far‐UV ellipticity was regained in a burst phase within the 4‐ms instrument dead‐time. The transient overshoots of far‐UV ellipticity and tryptophan fluorescence that follow the burst phase, as well as the kinetics of transient 8‐anilino‐1‐naphthalene‐sulfonic acid (ANS) binding, were diversely affected depending on the variant. Together with previous reports on the folding kinetics of WT lysozyme carboxymethylated on cysteines 6 and 127, detailed analysis of the kinetics showed that (1) none of the disulfide bonds were indispensable for the rapid formation (<4 ms) of the native‐like secondary structure; (2) the two intra‐α‐domain disulfides (C6‐C127 and C30‐C115) must be simultaneously present to generate the trapped intermediate responsible for the slow folding population observed in WT lysozyme; and (3) the intra‐β‐domain (C64‐C80) and the inter‐αβ‐domains (C76‐C94) disulfides do not affect the kinetics of formation of the trapped intermediate but are involved in its stability.
The X‐ray structure determination of bovine carbonmonoxy hemoglobin at 2.1 Å resoultion and its relationship to the quaternary structures of other hemoglobin crystal forms
Authors: Safo Martin K. , Abraham Donald J. 
Published: July 2002

AbstractCrystallographic studies of the intermediate states between unliganded and fully liganded hemoglobin (Hb) have revealed a large range of subtle but functionally important structural differences. Only one T state has been reported, whereas three other quaternary states (the R state, B state, and R2 or Y state) for liganded Hb have been characterized; other studies have defined liganded Hbs that are intermediate between the T and R states. The high‐salt crystal structure of bovine carbonmonoxy (CO bovine) Hb has been determined at a resolution of 2.1 Å and is described here. A detailed comparison with other crystallographically solved Hb forms (T, R, R2 or Y) shows that the quaternary structure of CO bovine Hb closely resembles R state Hb. However, our analysis of these structures has identified several important differences between CO bovine Hb and R state Hb. Compared with the R state structures, the β‐subunit N‐terminal region has shifted closer to the central water cavity in CO bovine Hb. In addition, both the α‐ and β‐subunits in CO bovine Hb have more constrained heme environments that appear to be intermediate between the T and R states. Moreover, the distal pocket of the β‐subunit heme in CO bovine Hb shows significantly closer interaction between the bound CO ligand and the Hb distal residues Val 63(E11) and His 63(E7). The constrained heme groups and the increased steric contact involving the CO ligand and the distal heme residues relative to human Hb may explain in part the low intrinsic oxygen affinity of bovine Hb.
The Onset of Flow Instability in Uniformly Heated Horizontal
Microchannels
Authors: Kennedy J. E. , Roach G. M. , Dowling M. F. , Abdel-Khalik S. I. , Ghiaasiaan S. M. , Jeter S. M. , Quershi Z. H. 
Published: July 2002

Abstract
Onset of nucleate boiling and onset of flow instability in uniformly heated microchannels with subcooled water flow were experimentally investigated using 22-cm long tubular test sections, 1.17 mm and 1.45 mm in diameter, with a 16-cm long heated length. Important experimental parameter ranges were: 3.44 to 10.34 bar channel exit pressure; 800 to 4500 kg/m2s mass flux (1 to 5 m/s inlet velocity); 0 to 4.0 MW/m2 channel wall heat flux; and 7440–33,000 Peclet number at the onset of flow instability. Demand curves (pressure drop versus mass flow rate curves for fixed wall heat flux and channel exit pressure) were generated for the test sections, and were utilized for the specification of the onset of nucleate boiling and the onset of flow instability points. The obtained onset of nucleate boiling and onset of flow instability data are presented and compared with relevant widely used correlations. [S0022-1481(00)02101-0]
In Vivo Activities of Evernimicin (SCH 27899) against Vancomycin-Susceptible and Vancomycin-Resistant Enterococci in Experimental Endocarditis
Authors: Souli Maria , Thauvin-Eliopoulos Claudie , Eliopoulos George M. 
Published: July 2002

ABSTRACT

To assess the potential efficacy of evernimicin (SCH 27899) against serious enterococcal infections, we used a rat model of aortic valve endocarditis established with either a vancomycin-susceptible
Enterococcus faecalis
or a vancomycin-resistant
Enterococcus faecium
strain. Animals infected with either one of the test strains were assigned to receive no treatment (controls) or 5-day therapy with one of the following regimens: evernimicin 60-mg/kg of body weight intravenous (i.v.) bolus once daily, 60-mg/kg i.v. bolus twice daily (b.i.d.), 60 mg/kg/day i.v. by continuous infusion, or 120 mg/kg/day i.v. by continuous infusion. These regimens were compared with vancomycin at 150 mg/kg/day. In animals infected with
E. faecalis
, evernimicin at 120 mg/kg/day by continuous infusion significantly reduced bacterial counts in vegetations (final density, 5.75 ± 3.38 log
10
CFU/g) compared with controls (8.51 ± 1.11 log
10
CFU/g). In animals infected with 0.5 ml of an 8 × 10
7
-CFU/ml inoculum of the vancomycin-resistant
E. faecium
, both 60-mg/kg bolus once a day and b.i.d. dose regimens of evernimicin were very effective (viable counts, 3.45 ± 1.44 and 3.81 ± 1.98 log
10
CFU/g, respectively). Vancomycin was unexpectedly active against infections induced with that inoculum. In animals infected with a 10
9
-CFU/ml inoculum of the vancomycin-resistant
E. faecium
, the evernimicin 60-mg/kg i.v. bolus b.i.d. reduced viable counts in vegetations compared with controls (6.27 ± 1.63 versus 8.34 ± 0.91 log
10
CFU/g;
P
< 0.05), whereas vancomycin was ineffective. Although resistant colonies could be selected in vitro, we were not able to identify evernimicin-resistant clones from cardiac vegetations. An unexplained observation from these experiments was the great variability in final bacterial densities within cardiac vegetations from animals in each of the evernimicin treatment groups.
Contribution of Dithiol Ligands to In Vitro and In Vivo Trypanocidal Activities of Dithiaarsanes and Investigation of Ligand Exchange in an Aqueous Solution
Authors: Loiseau Philippe M. , Lubert Patrick , Wolf Jean-Gerard 
Published: July 2002

ABSTRACT

Twelve new dithiaarsanes were evaluated for their in vitro and in vivo trypanocidal properties in regard to their three parent molecules, 4-amino-phenylarsenoxide, melarsenoxide, and 4-dansylamino-phenylarsenoxide. The most potent dithiaarsane, compound 2b, had a minimum effective concentration of 1.5 nM after 48 h of incubation and at a dose of 0.39 μmol/kg of body weight (0.2 mg/kg) administered subcutaneously cured 100% of mice acutely infected with
Trypanosoma brucei brucei
CMP. With this model, the chemotherapeutic index of compound 2b was 512, compared to 256 for melarsamine dihydrochloride (Cymelarsan) under the same conditions. With a chronic infection produced by
T. brucei brucei
GVR, compound 2b cured 100% of mice after treatment at a dose of 25 μmol/kg (12.5 mg/kg) for 4 consecutive days, whereas melarsamine dihydrochloride and potassium melarsonyl (Trimelarsan) cured less than 50% mice at this dose. For both acute and late-stage infections, dithiaarsanes having a melaminophenyl ring exhibited the most-potent trypanocidal activity. Compound 2b is thus one of the most active organoarsenicals described in a mouse trypanosomiasis model. Considering that the main intracellular targets of organoarsenicals are thiol groups, we studied the possibility of ligand exchange between Cymelarsan and several dithiols. In aqueous solution, we observed a rapid exchange of cysteamine from melarsamine with free cysteamine and also with various dithiols always in favor of more stable cyclic derivatives. These ligand exchanges suggest the ability of trivalent organoarsenicals to react with targets such as trypanothione and dihydrolipoic acid. Among several ligands, a 1,3-dimercaptopropane moiety appeared the most suitable for trypanocidal activity.
Comparative Efficacies of Terbinafine and Fluconazole in Treatment of Experimental Coccidioidal Meningitis in a Rabbit Model
Authors: Sorensen Kevin N. , Sobel Raymond A. , Clemons Karl V. , Calderon Leilani , Howell Kimberley J. , Irani Plomarz R. , Pappagianis Demosthenes , Williams Paul L. , Stevens David A. 
Published: July 2002

ABSTRACT

A rabbit model of coccidioidal meningitis was used to compare the therapeutic efficacies of terbinafine (TBF) and fluconazole (FCZ). Hydrocortisone acetate-treated New Zealand White male rabbits were infected intracisternally with either 2.2 × 10
4
or 6.4 × 10
4
Coccidioides immitis
arthroconidia. Oral treatment with polyethylene glycol 200 (PEG) twice daily (
n
= 8), TBF twice daily (
n
= 9; 200 mg/kg of body weight/day), or FCZ once daily (
n
= 8; 80 mg/kg/day) began on day 5 and continued for 21 days. Mean survival times were 20, 24, and 32 days for rabbits treated with PEG, TBF, and FCZ, respectively. All of the FCZ-treated animals (100%;
P
= 0.003), 56% of the TBF-treated animals (
P
= 0.4), and 25% of the PEG-treated animals survived the length of the study. Both FCZ and TBF were effective at reducing the incidence of paresis. Only FCZ was effective at reducing most neurological and systemic signs. FCZ treatments resulted in lower cerebrospinal fluid (CSF) protein concentrations and leukocyte counts and faster clearing of CSF fungal cultures compared with those for PEG-treated controls, but TBF treatments had no significant effect on these parameters. Neither drug affected CSF glucose levels. Mean serum TBF levels by bioassay were within the range of 3.5 to 6.2 μg/ml at 1, 2, and 4 h postdosing and 0.35 to 7.0 μg/ml at 14 h postdosing. No TBF was detected in CSF. Mean FCZ levels (24 to 25.5 h postdosing) by bioassay were 16.4 to 19.2 and 13.5 to 19.2 μg/ml in serum and CSF, respectively. The reduction in the numbers of CFU in the spinal cord and brain was over 100-fold (
P
= 0.0005) in FCZ-treated animals and 2-fold (
P
≤ 0.2) in TBF-treated animals compared with those in PEG-treated animals. Histopathologic severity (semiquantitative scoring system) was significantly attenuated by FCZ treatment (
P
= 0.05) and was slightly attenuated by TBF treatment compared with that for the controls. In conclusion, TBF appeared to have a slight effect on survival, histology, and reduction of the numbers of CFU in tissue; however, these effects were not significant. FCZ was effective at controlling coccidioidal meningitis.
Simultaneous Quantitation of Intracellular Zidovudine and Lamivudine Triphosphates in Human Immunodeficiency Virus-Infected Individuals
Authors: Rodriguez Jose F. , Rodriguez Jorge L. , Santana Jorge , García Hermes , Rosario Osvaldo 
Published: July 2002

ABSTRACT
Highly active antiretroviral therapy (HAART) is the standard treatment for infection with human immunodeficiency virus (HIV). The most common HAART regimen consists of the combination of at least one protease inhibitor (PI) with two nucleoside reverse transcriptase inhibitors (NRTIs). Contrary to PIs, NRTIs require intracellular activation from the parent compound of their triphosphate moiety to suppress HIV replication. Simultaneous intracellular determination of two NRTI triphosphates is difficult to accomplish due to their relatively small concentrations in peripheral blood mononuclear cells (PBMCs), requiring large amounts of blood from HIV-positive patients. Recently, we described a method to determine intracellular zidovudine triphosphate (ZDV-TP) concentrations in HIV-infected patients by using solid-phase extraction and tandem mass spectrometry. The limit of quantitation (LOQ) for ZDV-TP was 0.10 pmol, and the method was successfully used for the determination of ZDV-TP in HIV-positive patients. In this study, we enhanced the aforementioned method by the simultaneous quantitation of ZDV-TP and lamivudine triphosphate (3TC-TP) in PBMCs from HIV-infected patients. The LOQ for 3TC-TP was 4.0 pmol, with an interassay coefficient of variation and an accuracy of 7 and 12%, respectively. This method was successfully applied to the simultaneous in vivo determination of the ZDV-TP and 3TC-TP pharmacokinetic profiles from HIV-infected patients receiving HAART.
Early Bactericidal Activity of Paromomycin (Aminosidine) in Patients with Smear-Positive Pulmonary Tuberculosis
Authors: Donald P. R. , Sirgel F. A. , Kanyok T. P. , Danziger L. H. , Venter A. , Botha F. J. , Parkin D. P. , Seifart H. I. , Van de Wal B. W. , Maritz J. S. , Mitchison D. A. 
Published: July 2002

ABSTRACT

The early bactericidal activity of the aminoglycoside paromomycin (aminosidine) in doses of 7.5 and 15 mg/kg of body weight was measured in 22 patients with previously untreated smear-positive pulmonary tuberculosis. The fall in log
10
CFU per milliliter of sputum per day during the first 2 days of treatment for 7 patients receiving a paromomycin dosage of 7.5 mg/kg/day was 0.066, with a standard deviation (SD) of 0.216 and confidence limits from −0.134 to 0.266, and that for 15 patients receiving 15 mg/kg/day was 0.0924, with an SD of 0.140 and confidence limits from 0.015 to 0.170. The difference between the mean and zero was not significant for the 7.5-mg/kg dose group but was significant for the 15-mg/kg dose group (
t
= 2.55,
P
= 0.023). Since paromomycin has no cross-resistance with streptomycin and has no greater toxicity than other aminoglycosides, these results suggest that it has the potential to substitute for streptomycin in antituberculosis regimens and may be a particularly valuable addition to the drug armamentarium for the management of multidrug-resistant tuberculosis.
In Vitro Development of Resistance to Telithromycin (HMR 3647), Four Macrolides, Clindamycin, and Pristinamycin in
Streptococcus pneumoniae
Authors: Davies Todd A. , Dewasse Bonifacio E. , Jacobs Michael R. , Appelbaum Peter C. 
Published: July 2002

ABSTRACT

The ability of 50 sequential subcultures in subinhibitory concentrations of telithromycin (HMR 3647), azithromycin, clarithromycin, erythromycin A, roxithromycin, clindamycin, and pristinamycin to select for resistance was studied in five macrolide-susceptible and six macrolide-resistant pneumococci containing
mefE
or
ermB
. Telithromycin selected for resistance less often than the other drugs.
Pharmacokinetics and Safety of Ascending Single Doses of DZ-2640, a New Oral Carbapenem Antibiotic, Administered to Healthy Japanese Subjects
Authors: Tanaka Makoto , Kato Kinuyo , Hakusui Hideo , Murakami Yoichi , Sato Kenichi , Ito Yasushi , Kawamoto Keiji 
Published: July 2002

ABSTRACT

DZ-2640 is the ester-type oral carbapenem prodrug of an active parent compound, DU-6681. The pharmacokinetics and safety of DU-6681 were investigated in six studies after oral administration of a single dose of DZ-2640 to healthy male Japanese volunteers at doses of 25, 50, 100, 200, and 400 mg (as the equivalents of DU-6681) in the fasted state. The same volunteers received the drug at a dose of 100 mg in the fasted and fed states to examine the effect of food intake on the bioavailability of DZ-2640. The concentrations of DU-6681 in plasma and urine were determined by a validated high-performance liquid chromatography method and a bioassay. A good correlation between both methods was seen, indicating an absence of major active metabolites. The mean maximum concentrations of DU-6681 in plasma (
C
max
) ranged from 0.263 μg/ml (25-mg dose) to 2.489 μg/ml (400-mg dose) and were reached within 1.5 h following drug administration. After reaching the
C
max
, plasma DU-6681 concentrations declined in a monophasic manner, with a half-life of 0.47 to 0.89 h. The area under the concentration-time curve (AUC) and
C
max
increased almost linearly with the dose up to the 200-mg dose. The AUC and
C
max
increased less than proportionally after administration of the 400-mg dose, suggesting a reduction in drug absorption. The plasma protein binding of DU-6681 was in the range of 23.3 to 25.6%. The cumulative urinary recoveries (0 to 24 h) were in the range of 31.9 to 44.9%. The AUC was slightly but statistically significantly reduced by food intake. However, the
C
max
, half-life, and recovery in urine were not affected by food intake. The renal clearance (402 to 510 ml/min) was much greater than the mean glomerular filtration rate (ca. 120 ml/min), which indicated active tubular secretion of the drug. A mild transient and moderate diarrhea was observed in two of six volunteers in the study with a single dose of 25 mg. Mild soft stools were observed in two of six volunteers who received a 400-mg dose of the drug.
SHV-13, a Novel Extended-Spectrum β-Lactamase, in
Klebsiella pneumoniae
Isolates from Patients in an Intensive Care Unit in Amsterdam
Authors: Yuan Meifang , Hall Lucinda M. C. , Savelkoul Paul H. M. , Vandenbroucke-Grauls Christina M. J. E. , Livermore David M. 
Published: July 2002

ABSTRACT

Eleven clonally related
Klebsiella pneumoniae
isolates were examined. These had been isolated at an intensive care unit in Amsterdam in 1994. Their resistance was associated with a conjugative 170-kb plasmid which encoded a novel SHV β-lactamase designated SHV-13. The SHV-13 enzyme had two substitutions compared with SHV-1: Leu35Gln and Gly238Ala. It hydrolyzed cefotaxime much more rapidly than ceftazidime or aztreonam.
Effect of Fluconazole on the Pharmacokinetics of Doxorubicin in Nonhuman Primates
Authors: Warren Katherine E. , McCully Cynthia M. , Walsh Thomas J. , Balis Frank M. 
Published: July 2002

ABSTRACT
Antifungal prophylaxis in cancer patients who are undergoing chemotherapy is associated with prolonged neutropenia. We measured the effect of fluconazole on doxorubicin pharmacokinetics in nonhuman primates to determine if neutropenia is related to a pharmacokinetic interaction that delays the clearance of the chemotherapeutic agent. Fluconazole pretreatment had no effect on doxorubicin pharmacokinetics.
Postantifungal Effects of Echinocandin, Azole, and Polyene Antifungal Agents against
Candida albicans
and
Cryptococcus neoformans
Authors: Ernst Erika J. , Klepser Michael E. , Pfaller Michael A. 
Published: July 2002

ABSTRACT

The postantifungal effect (PAFE) of fluconazole, MK-0991, LY303366, and amphotericin B was determined against isolates of
Candida albicans
and
Cryptococcus neoformans
. Concentrations ranging from 0.125 to 4 times the MIC were tested following exposure to the antifungal for 0.25 to 1 h. Combinations of azole and echinocandin antifungals (MK-0991 and LY303366) were tested against
C. neoformans
. Fluconazole displayed no measurable PAFE against
Candida albicans
or
Cryptococcus neoformans
, either alone or in combination with either echinocandin antifungal. MK-0991, LY303366, and amphotericin B displayed a prolonged PAFE of greater than 12 h against
Candida
spp. when tested at concentrations above the MIC for the organism and 0 to 2 h when tested at concentrations below the MIC for the organism.