bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellular Localization of Isoprenoid Biosynthetic Enzymes inMarchantia polymorpha. Uncovering a New Role of Oil Bodies
Authors: Suire Claude , Bouvier Florence , Backhaus Ralph A. , Bégu Dominique , Bonneu Marc , Camara Bilal 
Published: July 2002

Abstract
Like seed plants, liverworts synthesize and accumulate a myriad of isoprenoid compounds. Using antibodies raised against several isoprenoid biosynthetic enzymes, we investigated their intracellular compartmentation by in situ immunolocalization from Marchantia polymorpha. The enzymes examined were deoxy-xylulose phosphate synthase, geranyl diphosphate synthase, farnesyl diphosphate synthase, geranylgeranyl diphosphate synthase, monoterpene synthase, geranylgeranyl diphosphate reductase, phytoene synthase, and phytoene desaturase. Our results show that liverwort oil bodies, which are organelles bound by a single unit membrane, possess isoprenoid biosynthetic enzymes similar to those found in plastids and the cytosol. We postulate that oil bodies play a dynamic role in cell metabolism in addition to their role as sites of essential oil accumulation and sequestration. The occurrence of such enzymes in different cellular compartments might be due to multiple targeting of gene products to various organelles.
Non-Targeted and Targeted Protein Movement through Plasmodesmata in Leaves in Different Developmental and Physiological States
Authors: Crawford Katrina M. , Zambryski Patricia C. 
Published: July 2002

Abstract
Plant cells rely on plasmodesmata for intercellular transport of small signaling molecules as well as larger informational macromolecules such as proteins. A green fluorescent protein (GFP) reporter and low-pressure microprojectile bombardment were used to quantify the degree of symplastic continuity between cells of the leaf at different developmental stages and under different growth conditions. Plasmodesmata were observed to be closed to the transport of GFP or dilated to allow the traffic of GFP. In sink leaves, between 34% and 67% of the cells transport GFP (27 kD), and between 30% and 46% of the cells transport double GFP (54 kD). In leaves in transition transport was reduced; between 21% and 46% and between 2% and 9% of cells transport single and double GFP, respectively. Thus, leaf age dramatically affects the ability of cells to exchange proteins nonselectively. Further, the number of cells allowing GFP or double GFP movement was sensitive to growth conditions because greenhouse-grown plants exhibited higher diffusion rates than culture-grown plants. These studies reveal that leaf cell plasmodesmata are dynamic and do not have a set size exclusion limit. We also examined targeted movement of the movement protein of tobacco mosaic virus fused to GFP, P30::GFP. This 58-kD fusion protein localizes to plasmodesmata, consistently transits from up to 78% of transfected cells, and was not sensitive to developmental age or growth conditions. The relative number of cells containing dilated plasmodesmata varies between different species of tobacco, with Nicotiana clevelandii exhibiting greater diffusion of proteins thanNicotiana tabacum.
A Biophysical Analysis of Stem and Root Diameter Variations in Woody Plants
Authors: Génard Michel , Fishman Svetlana , Vercambre Gilles , Huguet Jean-Gérard , Bussi Claude , Besset Jacques , Habib Robert 
Published: July 2002

Abstract
A comprehensive model of stem and root diameter variation was developed. The stem (or root) was represented using two coaxial cylinders corresponding with the mature xylem and the extensible tissues. The extensible tissues were assumed to behave as a single cell separated from the mature xylem by a virtual membrane. The mature xylem and the extensible tissues are able to dilate with temperature and grow. Moreover, the extensible tissues are able to shrink and swell according to water flow intensity. The model is mainly based on the calculation of water volume flows in the “single cell” that are described using the principles of irreversible thermodynamics. The elastic response to storage volume and plastic extension accompanying growth are described. The model simulates diameter variation due to temperature, solute accumulation, and xylem, water potential. The model was applied to the peach (Prunus persica) stem and to the plum (Prunus domestica × Prunus spinosa) root. The simulation outputs corresponded well with the diameter variation observed. The model predicts that variations of turgor pressure and osmotic potential are smaller than the variations of xylem water potential. It also demonstrates correlations between the xylem water potential, the turgor pressure, the elastic modulus, and the osmotic potential. The relationship between the diameter and the xylem water potential exhibits a subtential hysteresis, as observed in field data. A sensitivity analysis using the model parameters showed that growth and shrinkage were highly sensitive to the initial values of the turgor pressure and to the reflection coefficient of solutes. Shrinkage and growth were sensitive to elastic modulus and wall-yielding threshold pressure, respectively. The model was not sensitive to changes in temperature.
Novel Patterns of Ectopic Cell Plate Growth and Lipid Body Distribution in the Arabidopsis gemini pollen1Mutant
Authors: Park Soon Ki , Twell David 
Published: July 2002

Abstract
The nature of aberrant gametophytic cell divisions and altered pollen cell fate in the gemini pollen1(gem1) mutant was investigated through ultrastructural analysis. The earliest noticeable defect in gem1 was the appearance of extended membrane profiles at the early bicellular stage. These were replaced by ectopic internal walls, which divided the cytoplasm into twin or multiple cell compartments. Complete or partial internal walls were callosic with highly complex profiles, indicating failed guidance or deregulated cell plate growth. Extended membrane profiles and delayed callose synthesis at division sites further suggested a novel pattern of cell plate assembly ingem1. Multiple cell compartments in gem1adopted vegetative cell fate with regard to lipid body distribution. In the wild type, lipid bodies appear specifically in the vegetative cell, whereas in gem1, lipid bodies accumulated in all cytoplasmic compartments. Our results support the hypothesis that altered pollen cell fate in gem1 results from abnormal inheritance of cell fate determinants as a result of disturbed cytokinesis.
BIN2, a New Brassinosteroid-Insensitive Locus in Arabidopsis
Authors: Li Jianming , Nam Kyoung Hee , Vafeados Dionne , Chory Joanne 
Published: July 2002

Abstract
Brassinosteroids (BRs) play important roles throughout plant development. Although many genes have been identified that are involved in BR biosynthesis, genetic approaches in Arabidopsis have led to the identification of only one gene, BRI1, that encodes a membrane receptor for BRs. To expand our knowledge of the molecular mechanism(s) of plant steroid signaling, we analyzed many dwarf and semidwarf mutants collected from our previous genetic screens and identified a semidwarf mutant that showed little response to exogenous BR treatments. Genetic analysis of the bin2(BR-INSENSITIVE 2) mutant indicated that the BR-insensitive dwarf phenotype was due to a semidominant mutation in the BIN2 gene that mapped to the middle of chromosome IV between the markers CH42 and AG. A direct screening for similar semidwarf mutants resulted in the identification of a second allele of the BIN2 gene. Despite some novel phenotypes observed with the bin2/+ mutants, the homozygousbin2 mutants were almost identical to the well-characterized bri1 mutants that are defective in BR perception. In addition to the BR-insensitive dwarf phenotype,bin2 mutants exhibited BR insensitivity when assayed for root growth inhibition and feedback inhibition of CPDgene expression. Furthermore, bin2 mutants displayed an abscisic acid-hypersensitive phenotype that is shared by thebri1 and BR-deficient mutants. A gene dosage experiment using triploid plants suggested that the bin2 phenotypes were likely caused by either neomorphic or hypermorphic gain-of-function mutations in the BIN2 gene. Thus, the two bin2 mutations define a novel genetic locus whose gene product might play a role in BR signaling.
Effect of the N1 residue on the stability of the α‐helix for all 20 amino acids
Authors: Cochran Duncan A.E. , Penel Simon , Doig Andrew J. 
Published: July 2002

AbstractN1 is the first residue in an α‐helix. We have measured the contribution of all 20 amino acids to the stability of a small helical peptide CH3CO‐XAAAAQAAAAQAAGY‐NH2 at the N1 position. By substituting every residue into the N1 position, we were able to investigate the stabilizing role of each amino acid in an isolated context. The helix content of each of the 20 peptides was measured by circular dichroism (CD) spectroscopy. The data were analyzed by our modified Lifson‐Roig helix‐coil theory, which includes the n1 parameter, to find free energies for placing a residue into the N1 position. The rank order for free energies is Asp−, Ala > Glu− > Glu0 > Trp, Leu, Ser > Asp0, Thr, Gln, Met, Ile > Val, Pro > Lys+, Arg, His0 > Cys, Gly > Phe > Asn, Tyr, His+. N1 preferences are clearly distinct from preferences for the preceding N‐cap and α‐helix interior. pKa values were measured for Asp, Glu, and His, and protonation‐free energies were calculated for Asp and Glu. The dissociation of the Asp proton is less favorable than that of Glu, and this reflects its involvement in a stronger stabilizing interaction at the N terminus. Proline is not energetically favored at the α‐helix N terminus despite having a high propensity for this position in crystal structures. The data presented are of value both in rationalizing mutations at N1 α‐helix sites in proteins and in predicting the helix contents of peptides.
Three‐dimensional structures of the three human class I alcohol dehydrogenases
Authors: Niederhut Monica S. , Gibbons Brian J. , Perez‐Miller Samantha , Hurley Thomas D. 
Published: July 2002

AbstractIn contrast with other animal species, humans possess three distinct genes for class I alcohol dehydrogenase and show polymorphic variation in the ADH1B and ADH1C genes. The three class I alcohol dehydrogenase isoenzymes share ∼93% sequence identity but differ in their substrate specificity and their developmental expression. We report here the first three‐dimensional structures for the ADH1A and ADH1C*2 gene products at 2.5 and 2.0 Å, respectively, and the structure of the ADH1B*1 gene product in a binary complex with cofactor at 2.2 Å. Not surprisingly, the overall structure of each isoenzyme is highly similar to the others. However, the substitution of Gly for Arg at position 47 in the ADH1A isoenzyme promotes a greater extent of domain closure in the ADH1A isoenzyme, whereas substitution at position 271 may account for the lower turnover rate for the ADH1C*2 isoenzyme relative to its polymorphic variant, ADH1C*1. The substrate‐binding pockets of each isoenzyme possess a unique topology that dictates each isoenzyme's distinct but overlapping substrate preferences. ADH1*B1 has the most restrictive substrate‐binding site near the catalytic zinc atom, whereas both ADH1A and ADH1C*2 possess amino acid substitutions that correlate with their better efficiency for the oxidation of secondary alcohols. These structures describe the nature of their individual substrate‐binding pockets and will improve our understanding of how the metabolism of beverage ethanol affects the normal metabolic processes performed by these isoenzymes.
Kinetic properties and inhibition of the dimeric dUTPase‐dUDPase from Leishmania major
Authors: Hidalgo‐Zarco Fernando , Camacho Ana G. , Bernier‐Villamor Victor , Nord Johan , Ruiz‐Pérez Luis Miguel , González‐Pacanowska Dolores 
Published: July 2002

AbstractKinetic properties of the dimeric enzyme dUTPase from Leishmania major were studied using a continuous spectrophotometric method. dUTP was the natural substrate and dUMP and PPi the products of the hydrolysis. The trypanosomatid enzyme exhibited a low Km value for dUTP (2.11 μM), a kcat of 49 s−1, strict Michaelis–Menten kinetics and is a potent catalyst of dUDP hydrolysis, whereas in other dUTPases described, this compound acts as a competitive inhibitor. Discrimination is achieved for the base and sugar moiety showing specificity constants for different dNTPs similar to those of bacterial, viral, and human enzymes. In the alkaline range, the Km for dUTP increases with the dissociation of ionizable groups showing pKa values of 8.8, identified as the uracil moiety of dUTP and 10, whereas in the acidic range, Km is regulated by an enzyme residue exhibiting a pKa of 7.1. Activity is strongly inhibited by the nucleoside triphosphate analog α‐β‐imido‐dUTP, indicating that the enzyme can bind triphosphate analogs. The existence of specific inhibition and the apparent structural and kinetic differences (reflected in different binding strength of dNTPs) with other eukaryotic dUTPases suggest that the present enzyme might be exploited as a target for new drugs against leishmaniasis.
A Dynamical Systems Approach to Damage Evolution Tracking, Part 2:
Model-Based Validation and Physical Interpretation
Authors: Cusumano Joseph P. , Chelidze David , Chatterjee Anindya 
Published: July 2002

Abstract
In this paper, the hidden variable damage tracking method developed in Part 1 is analyzed using a physics-based mathematical model of the experimental system: a mechanical oscillator with a nonstationary two-well potential. Numerical experiments conducted using the model are in good agreement with the experimental study presented in Part 1, and explicitly show how the tracking metric is related to the slow hidden variable evolution responsible for drift in the fast system parameters. Using the idea of averaging, the slow flow equation governing the hidden variable evolution is obtained. It is shown that the solution to the slow flow equation corresponds to the hidden variable trajectory obtained with the experimental tracking method. Thus we establish in principle the relationship of our algorithm to any underlying physical process. Based on this result, we discuss the application of the tracking method to systems with evolving material damage using the results of some preliminary experiments.
A Free Cyclotrigermenium Cation with a 2π-Electron System
Authors: Sekiguchi Akira , Tsukamoto Masanori , Ichinohe Masaaki 
Published: July 2002

The reaction of tetrakis(tri-
tert
-butylsilyl)cyclotrigermene with trityl tetraphenylborate in benzene produces tris(tri-
tert
-butylsilyl)cyclotrigermenium tetraphenylborate [(
tert
-Bu
3
SiGe)
3
+
BPh
4
−
], which can be isolated as a yellow solid that is stable in the absence of air. The crystal structure of the cyclotrigermenium ion reveals a free germyl cation with a 2π

-electron system. The three germanium atoms form an equilateral triangle similar to the carbon analog, the cyclopropenium ion.
Hepatitis B or Hepatitis C Virus Infection Is a Risk Factor for Severe Hepatic Cytolysis after Initiation of a Protease Inhibitor-Containing Antiretroviral Regimen in Human Immunodeficiency Virus-Infected Patients
Authors: Savès Marianne , Raffi François , Clevenbergh Philippe , Marchou Bruno , Waldner-Combernoux Anne , Morlat Philippe , Le Moing Vincent , Rivière Catherine , Chêne Geneviève , Leport Catherine ,   The APROCO Study Group
Published: July 2002

ABSTRACTIn a cohort of 1,047 human immunodeficiency virus type 1-infected patients started on protease inhibitors (PIs), the incidence of severe hepatic cytolysis (alanine aminotransferase concentration five times or more above the upper limit of the normal level ≥ 5N) was 5% patient-years after a mean follow-up of 5 months. Only positivity for hepatitis C virus antibodies (hazard ratio [HR], 7.95;P< 10−3) or hepatitis B virus surface antigen (HR, 6.67;P< 10−3) was associated with severe cytolysis. Before starting patients on PIs, assessment of liver enzyme levels and viral coinfections is necessary.
Role of the PDR Gene Network in Yeast Susceptibility to the Antifungal Antibiotic Mucidin
Authors: Michalkova-Papajova Dana , Obernauerova Margita , Subik Julius 
Published: July 2002

ABSTRACT

Yeast strains disrupted in the
PDR1
,
PDR3
, or
PDR5
gene, but not in
SNQ2
, exhibited higher sensitivity to mucidin (strobilurin A) than did the isogenic wild-type strains. Different gain-of-function mutations in the
PDR1
and
PDR3
genes rendered yeast mutants resistant to this antibiotic. Mucidin induced
PDR5
expression, but the changes in the expression of
SNQ2
were only barely detectable. The results indicate that
PDR5
provides the link between transcriptional regulation by
PDR1
and
PDR3
and mucidin resistance of yeast.
A Convenient Assay for Estimating the Possible Involvement of Efflux of Fluoroquinolones by
Streptococcus pneumoniae
and
Staphylococcus aureus
: Evidence for Diminished Moxifloxacin, Sparfloxacin, and Trovafloxacin Efflux
Authors: Beyer Rebecca , Pestova Ekaterina , Millichap John J. , Stosor Valentina , Noskin Gary A. , Peterson Lance R. 
Published: July 2002

ABSTRACT

We developed a simplified assay for estimating efflux by measuring the effect of reserpine on the growth of
Streptococcus pneumoniae
and
Staphylococcus aureus
over 7 h. Reserpine enhanced ciprofloxacin and levofloxacin 17 to 68%. The hydrophobic drug trovafloxacin and the drug moxifloxacin, with a bulky C-7 substituent but hydrophilicity similar to that of levofloxacin, showed little (0 to 11%) reserpine-enhancing effect. The ease of resistant mutant strain selection correlated with efflux susceptibility.
In Vitro Activities of Telithromycin (HMR 3647) against
Rickettsia rickettsii
,
Rickettsia conorii
,
Rickettsia africae
,
Rickettsia typhi
,
Rickettsia prowazekii
,
Coxiella burnetii
,
Bartonella henselae
,
Bartonella quintana
,
Bartonella bacilliformis
, and
Ehrlichia chaffeensis
Authors: Rolain Jean-Marc , Maurin Max , Bryskier André , Raoult Didier 
Published: July 2002

ABSTRACT

In vitro activities of telithromycin compared to those of erythromycin against
Rickettsia
spp.,
Bartonella
spp.,
Coxiella burnetii
, and
Ehrlichia chaffeensis
were determined. Telithromycin was more active than erythromycin against
Rickettsia
,
Bartonella
, and
Coxiella burnetii
, with MICs of 0.5 μg/ml, 0.003 to 0.015 μg/ml, and 1 μg/ml, respectively, but was inactive against
Ehrlichia chaffeensis
.
Pharmacokinetic Interaction of Abacavir (1592U89) and Ethanol in Human Immunodeficiency Virus-Infected Adults
Authors: McDowell James A. , Chittick Gregory E. , Stevens Cristina Pilati , Edwards Kathleen D. , Stein Daniel S. 
Published: July 2002

ABSTRACT
While in vitro results at clinically relevant concentrations do not predict abacavir (1592U89) interactions with drugs highly metabolized by cytochrome P450, the potential does exist for a pharmacokinetic interaction between abacavir and ethanol, as both are metabolized by alcohol dehydrogenase. Twenty-five subjects were enrolled in an open-label, randomized, three-way-crossover, phase I study of human immunodeficiency virus-infected male subjects. The three treatments were administration of (i) 600 mg of abacavir, (ii) 0.7 g of ethanol per kg of body weight, and (iii) 600 mg of abacavir and 0.7 g of ethanol per kg. Twenty-four subjects completed the study with no unexpected adverse events reported. Ethanol pharmacokinetic parameters were unchanged with abacavir coadministration. The geometric least squares mean area under the concentration curve extrapolated to infinite time for abacavir increased 41% (from 11.07 to 15.62 μg · h/ml), and the half-life increased 26% (from 1.42 to 1.79 h) in the presence of ethanol (mean ethanol maximum concentration in plasma of 498 μg/ml). The percentages of abacavir dose recovered in urine as abacavir and its two major metabolites were each altered in the presence of ethanol, but there was no change in the total percentage (≈50%) of administered dose recovered in the 12-h collection interval. In conclusion, while a single 600-mg dose of abacavir does not alter blood ethanol concentration, ethanol does increase plasma abacavir concentrations.
Quantitation of
Candida albicans
Ergosterol Content Improves the Correlation between In Vitro Antifungal Susceptibility Test Results and In Vivo Outcome after Fluconazole Treatment in a Murine Model of Invasive Candidiasis
Authors: Arthington-Skaggs Beth A. , Warnock David W. , Morrison Christine J. 
Published: July 2002

ABSTRACT

MIC end point determination for the most commonly prescribed azole antifungal drug, fluconazole, can be complicated by “trailing” growth of the organism during susceptibility testing by the National Committee for Clinical Laboratory Standards approved M27-A broth macrodilution method and its modified broth microdilution format. To address this problem, we previously developed the sterol quantitation method (SQM) for in vitro determination of fluconazole susceptibility, which measures cellular ergosterol content rather than growth inhibition after exposure to fluconazole. To determine if SQM MICs of fluconazole correlated better with in vivo outcome than M27-A MICs, we used a murine model of invasive candidiasis and analyzed the capacity of fluconazole to treat infections caused by
C. albicans
isolates which were trailers (M27-A MICs at 24 and 48 h, ≤1.0 and ≥64 μg/ml, respectively; SQM MIC, ≤1.0 μg/ml), as well as those which were fluconazole sensitive (M27-A and SQM MIC, ≤1.0 μg/ml) and fluconazole resistant (M27-A MIC, ≥64 μg/ml; SQM MIC, 54 μg/ml). Compared with the untreated controls, fluconazole therapy increased the survival of mice infected with a sensitive isolate and both trailing isolates but did not increase the survival of mice infected with a resistant isolate. These results indicate that the SQM is more predictive of in vivo outcome than the M27-A method for isolates that give unclear MIC end points due to trailing growth in fluconazole.
BMS-232632, a Highly Potent Human Immunodeficiency Virus Protease Inhibitor That Can Be Used in Combination with Other Available Antiretroviral Agents
Authors: Robinson Brett S. , Riccardi Keith A. , Gong Yi-fei , Guo Qi , Stock David A. , Blair Wade S. , Terry Brian J. , Deminie Carol A. , Djang Fred , Colonno Richard J. , Lin Pin-fang 
Published: July 2002

ABSTRACTBMS-232632 is an azapeptide human immunodeficiency virus type 1 (HIV-1) protease (Prt) inhibitor that exhibits potent anti-HIV activity with a 50% effective concentration (EC50) of 2.6 to 5.3 nM and an EC90of 9 to 15 nM in cell culture. Proof-of-principle studies indicate that BMS-232632 blocks the cleavage of viral precursor proteins in HIV-infected cells, proving that it functions as an HIV Prt inhibitor. Comparative studies showed that BMS-232632 is generally more potent than the five currently approved HIV-1 Prt inhibitors. Furthermore, BMS-232632 is highly selective for HIV-1 Prt and exhibits cytotoxicity only at concentrations 6,500- to 23,000-fold higher than that required for anti-HIV activity. To assess the potential of this inhibitor when used in combination with other antiretrovirals, BMS-232632 was evaluated for anti-HIV activity in two-drug combination studies. Combinations of BMS-232632 with either stavudine, didanosine, lamivudine, zidovudine, nelfinavir, indinavir, ritonavir, saquinavir, or amprenavir in HIV-infected peripheral blood mononuclear cells yielded additive to moderately synergistic antiviral effects. Importantly, combinations of drug pairs did not result in antagonistic anti-HIV activity or enhanced cytotoxic effects at the highest concentrations used for antiviral evaluation. Our results suggest that BMS-232632 may be an effective HIV-1 inhibitor that may be utilized in a variety of different drug combinations.