bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloning and Characterization of a Gibberellin-Induced RNase Expressed in Barley Aleurone Cells1
Authors: Rogers Sally W. , Rogers John C. 
Published: July 2002

AbstractWe cloned a cDNA for a gibberellin-induced ribonuclease (RNase) expressed in barley (Hordeum vulgare) aleurone and the gene for a second barley RNase expressed in leaf tissue. The protein encoded by the cDNA is unique among RNases described to date in that it contains a novel 23-amino acid insert between the C2 and C3 conserved sequences. Expression of the recombinant protein in tobacco (Nicotiana tabacum) suspension-cultured protoplasts gave an active RNase of the expected size, confirming the enzymatic activity of the protein. Analyses of hormone regulation of expression of mRNA for the aleurone RNase revealed that, like the pattern for α-amylase, mRNA levels increased in the presence of gibberellic acid, and its antagonist abscisic acid prevented this effect. Quantitative studies at early times demonstrated that cycloheximide treatment of aleurone layers increased mRNA levels 4-fold, whereas a combination of gibberellin plus cycloheximide treatment was required to increase α-amylase mRNA levels to the same extent. These results are consistent with loss of repression as an initial effect of gibberellic acid on transcription of those genes, although the regulatory pathways for the two genes may differ.
Sieve Tube Unloading and Post-Phloem Transport of Fluorescent Tracers and Proteins Injected into Sieve Tubes via Severed Aphid Stylets
Authors: Fisher Donald B. , Cash-Clark Cora E. 
Published: July 2002

Abstract
A variety of fluorescent tracers and proteins were injected via severed aphid stylets into the sieve tubes of wheat (Triticum aestivum L.) grains to evaluate the dimensions of plasmodesmal channels involved in sieve element/companion cell (SE/CC)unloading and post-phloem transport. In the post-phloem pathway, where diffusion is the predominant mode of transport, the largest molecule to show mobility was 16-kD dextran, with a Stokes radius of 2.6 nm. This suggests that the aqueous channels for cell-to-cell transport must be about 8 nm in diameter. Even the largest tracer injected into the sieve tubes, 400-kD fluorescein-labeled Ficoll with a Stokes radius of about 11 nm, was unloaded from the SE/CC complex. However, in contrast to smaller tracers (≤3 kD, with a Stokes radius ≤ 1.2 nm), the unloading of fluorescein-labeled Ficoll and other large molecules from the SE/CC complex showed an irregular, patchy distribution, with no further movement along the post-phloem pathway. Either the plasmodesmal channels involved in SE/CCunloading are exceptionally large (perhaps as much as 42 nm in diameter), with only a very small fraction of plasmodesmata being conductive, or the larger tracers damage the plasmodesmata in some way, enlarging smaller channels.
Biliverdin Reductase-Induced Phytochrome Chromophore Deficiency in Transgenic Tobacco
Authors: Montgomery Beronda L. , Franklin Keara A. , Terry Matthew J. , Thomas Brian , Jackson Stephen D. , Crepeau Marc W. , Lagarias J. Clark 
Published: July 2002

AbstractTargeted expression of mammalian biliverdin IXα reductase (BVR), an enzyme that metabolically inactivates linear tetrapyrrole precursors of the phytochrome chromophore, was used to examine the physiological functions of phytochromes in the qualitative short-day tobacco (Nicotiana tabacum cv Maryland Mammoth) plant. Comparative phenotypic and photobiological analyses of plastid- and cytosol-targeted BVR lines showed that multiple phytochrome-regulated processes, such as hypocotyl and internode elongation, anthocyanin synthesis, and photoperiodic regulation of flowering, were altered in all lines examined. The phytochrome-mediated processes of carotenoid and chlorophyll accumulation were strongly impaired in plastid-targeted lines, but were relatively unaffected in cytosol-targeted lines. Under certain growth conditions, plastid-targeted BVR expression was found to nearly abolish the qualitative inhibition of flowering by long-day photoperiods. The distinct phenotypes of the plastid-targeted BVR lines implicate a regulatory role for bilins in plastid development or, alternatively, reflect the consequence of altered tetrapyrrole metabolism in plastids due to bilin depletion.
Na+/H+ Antiporter fromSynechocystis Species PCC 6803, Homologous to SOS1, Contains an Aspartic Residue and Long C-Terminal Tail Important for the Carrier Activity
Authors: Hamada Akira , Hibino Takashi , Nakamura Tatsunosuke , Takabe Teruhiro 
Published: July 2002

Abstract
A putative Na+/H+ antiporter gene whose deduced amino acid sequence was highly homologous to the NhaP antiporter from Pseudomonas aeruginosa and SOS1 antiporter from Arabidopsis was isolated fromSynechocystis sp. PCC 6803. TheSynechocystis NhaP antiporter (SynNhaP) was expressed inEscherichia coli mutant cells, which were deficient in Na+/H+ antiporters. It was found that the SynNhaP complemented the salt-sensitive phenotype of the E. coli mutant. Membrane vesicles prepared from the E. coli mutant transformed with the SynNhaP exhibited the Na+/H+ and Li+/H+antiporter activities, and their activities were insensitive to amiloride. Moreover, its activity was very high between pH 5 and 9. The replacement of aspartate-138 in SynNhaP with glutamate or tyrosine inactivated the SynNhaP antiporter activity. The deletion of a part of the long C-terminal hydrophilic tail significantly inhibited the antiporter activity. A topological model suggests that aspartate-138 in SynNhaP is conserved in NhaP, SOS1, and AtNHX1 and is involved in the exchange activity. Thus, it appeared that the SynNhaP would provide a model system for the study of structural and functional properties of eucaryotic Na+/H+antiporters.
Molecular Interactions between the Specialist HerbivoreManduca sexta (Lepidoptera, Sphingidae) and Its Natural Host Nicotiana attenuata. II. Accumulation of Plant mRNAs in Response to Insect-Derived Cues
Authors: Schittko Ursula , Hermsmeier Dieter , Baldwin Ian T. 
Published: July 2002

Abstract
The transcriptional changes in Nicotiana attenuataTorr. ex Wats. elicited by attack from Manduca sextalarvae were previously characterized by mRNA differential display (D. Hermsmeier, U. Schittko, I.T. Baldwin [2001] Plant Physiol 125: 683–700). Because herbivore attack causes wounding, we disentangled wound-induced changes from those elicited by M. sexta oral secretions and regurgitant (R) with a northern analysis of a subset of the differentially expressed transcripts encoding threonine deaminase, pathogen-induced oxygenase, a photosystem II light-harvesting protein, a retrotransposon homolog, and three unknown genes. R extensively modified wound-induced responses by suppressing wound-induced transcripts (type I) or amplifying the wound-induced response (type II) further down-regulating wound-suppressed transcripts (type IIa) or up-regulating wound-induced transcripts (type IIb). It is interesting that although all seven genes displayed their R-specific patterns in the treated tissues largely independently of the leaf or plant developmental stage, only the type I genes displayed strong systemic induction. Ethylene was not responsible for any of the specific patterns of expression. R collected from different tobacco feeding insects, M. sexta,Manduca quinquemaculata, and Heliothis virescens, as well as from different instars of M. sexta were equally active. The active components of M. sexta R were heat stable and active in minute amounts, comparable with real transfer rates during larval feeding. Specific expression patterns may indicate that the plant is adjusting its wound response to efficiently fend off M. sexta, but may also be advantageous to the larvae, especially when R suppress wound-induced plant responses.
Two Loci Control Phytoglycogen Production in the Monocellular Green Alga Chlamydomonas reinhardtii
Authors: Dauvillée David , Colleoni Christophe , Mouille Gregory , Buléon Alain , Gallant Daniel J. , Bouchet Brigitte , Morell Matthew K. , d'Hulst Christophe , Myers Alan M. , Ball Steven G. 
Published: July 2002

Abstract
The STA8 locus of Chlamydomonas reinhardtii was identified in a genetic screen as a factor that controls starch biosynthesis. Mutations of STA8 cause a significant reduction in the amount of granular starch produced during nutrient limitation and accumulate phytoglycogen. The granules remaining in sta8 mutants are misshapen, and the abundance of amylose and long chains in amylopectin is altered. Mutations of the STA7 locus, which completely lack isoamylase activity, also cause accumulation of phytoglycogen, althoughsta8 and sta7 mutants differ in that there is a complete loss of granular starch in the latter. This is the first instance in which mutations of two different genetic elements in one plant species have been shown to cause phytoglycogen accumulation. An analytical procedure that allows assay of isoamylase in total extracts was developed and used to show that sta8mutations cause a 65% reduction in the level of this activity. All other enzymes known to be involved in starch biosynthesis were shown to be unaffected in sta8 mutants. The same amount of total isoamylase activity (approximately) as that present insta8 mutants was observed in heterozygous triploids containing two sta7 mutant alleles and one wild-type allele. This strain, however, accumulates normal levels of starch granules and lacks phytoglycogen. The total level of isoamylase activity, therefore, is not the major determinant of whether granule production is reduced and phytoglycogen accumulates. Instead, a qualitative property of the isoamylase that is affected by thesta8 mutation is likely to be the critical factor in phytoglycogen production.
Dynamics of a Flexible Beam Contacting a Linear Spring at Low Frequency Excitation: Experiment and Analysis
Authors: Fegelman Karen J. L. , Grosh Karl 
Published: July 2002

AbstractA detailed study of one-, two-, and three-impact per period motion of a vibro-impacting, pinned beam is presented involving experimental results, as well as one- and multi-degree-of-freedom theoretical models. The details of the impact event are examined and correlated to the qualitative appearance of the frequency response. In addition, it is noted that the multi-degree-of-freedom model is necessary in order to predict response at high frequencies. This study is unique in that the model system includes a pinned boundary condition, the forcing frequency is considerably lower than the fundamental in-contact natural frequency, and the frequency analysis extends into a range important for acoustic predictions.
Abstract: SIMS—a useful complement to other depth profiling techniques
Authors: Baun W. L. , McDevitt N. T. 
Published: July 2002

Secondary ion mass spectroscopy (SIMS) used alone has been shown to be a powerful tool for elemental surface characterization.1,2 Used in conjunction with another technique such as ion scattering spectroscopy (ISS) or Auger electron spectroscopy (AES), SIMS becomes even more powerful. SIMS has been combined in our laboratory with both of the above techniques using quadrupole mass analyzers from two different manufacturers.
The complementary nature of SIMS−ISS and SIMS−AES make them especially useful when they are used together. The weakness of one is generally the strength of the other. Specific examples of this strength−weakness relationship are shown. Interesting SIMS results at ion beam accelerating energies of as low as 100 V are discussed for materials studied in research on adhesive bonding.
Adsorption and decomposition of trichlorosilane and trichlorogermane on porous silicon and Si(100)2×1 surfaces
Authors: Dillon A. C. , Wise M. L. , Robinson M. B. , George S. M. 
Published: July 2002

The adsorption and decomposition of trichlorosilane (SiHCl3) and trichlorogermane (GeHCl3) on silicon surfaces were studied using Fourier transform infrared (FTIR) spectroscopy and temperature programmed desorption investigations. The FTIR transmission spectroscopy experiments were performed in situ in an ultrahigh vacuum chamber on high surface area porous silicon samples. The FTIR spectra revealed that SiHCl3 dissociatively adsorbed at 200 K and formed SiH, SiClx, ClSiH, and Cl2SiH surface species. The presence of ClxSiH species indicated incomplete decomposition of SiHCl3 upon adsorption at 200 K. GeHCl3 also dissociatively adsorbed at 200 K and formed SiH and SiClx species. The absence of an infrared absorption in the Ge–H stretching region suggests complete transfer of hydrogen from Ge to surface Si atoms at 200 K.
The thermal stabilities of the surface species were then studied with annealing experiments. The ClxSiH species deposited by SiHCl3 exposure at 200 K decomposed between 200 and 590 K and formed additional SiH and SiCl species. The SiClx (x=2 or 3) species deposited by either GeHCl3 or SiHCl3 dissociative adsorption converted to silicon monochloride species between 200 and 600 K. The SiH surface species subsequently decreased at temperatures between 680 and 780 K as H2 desorbed from the silicon surface. FTIR spectroscopy was also utilized to monitor the adsorption of SiHCl3 and GeHCl3 on porous silicon at different surface temperatures. These adsorption studies were in agreement with the thermal annealing experiments. Temperature programmed desorption (TPD) studies were performed following saturation SiHCl3 and GeHCl3 exposures on Si(100)2×1. After SiHCl3 adsorption, the only desorption species were H2, HCl, and SiCl2, and they were observed at 810, 850, and 970 K, respectively. Following GeHCl3 adsorption, the TPD experiments monitored H2, HCl, SiCl2, and Ge at 810, 850, 950, and 1200 K, respectively. The adsorption kinetics of SiHCl3 and GeHCl3 were also measured on Si(100)2×1 and initial reactive sticking coefficients of S0≊.019 for SiHCl3 and S0≊1 for GeHCl3 were determined at 500 K. These experiments provide insight into the surface chemistry of chlorosilanes and chlorogermanes during Si, Ge, and Si1−xGex chemical vapor deposition on silicon surfaces.
Genetic Diversity of Carbapenem-Hydrolyzing Metallo-β-Lactamases from
Chryseobacterium
(
Flavobacterium
)
indologenes
Authors: Bellais Samuel , Poirel Laurent , Leotard Sophie , Naas Thierry , Nordmann Patrice 
Published: July 2002

ABSTRACT

The class B carbapenem-hydrolyzing β-lactamase IND-1 has been characterized for
Chryseobacterium indologenes
strain 001. With internal primers for the
bla
gene for IND-1 (
bla
IND-1
) and an internal
bla
IND-1
probe, PCR amplifications failed, while hybridization results were positive when DNA from another
C. indologenes
isolate, strain CIP101026, was used as a template. Thus, a
bla
IND
-related gene was cloned from this
C. indologenes
reference strain. Sequencing of the insert of a recombinant plasmid conferring resistance to carbapenems revealed an open reading frame with a G + C content of 39.9% and coding for a 243-amino-acid preprotein named IND-2. IND-2 shared 80% amino acid identity with IND-1 and had a similar broad-spectrum resistance profile, including resistance to carbapenems. It was classified in functional subgroup 3a of class B carbapenem-hydrolyzing β-lactamases. IND-1 and IND-2, despite their genetic diversity, possessed similar kinetic parameters, except that ceftazidime was hydrolyzed less by IND-2. To obtain the entire
bla
IND
-related gene sequences of eight other
C. indologenes
isolates, PCR was performed using internal and external primers, followed by inverse PCR techniques. The likely chromosome-mediated metallo-β-lactamases of the 10
C. indologenes
isolates were divided into several groups and subgroups. IND-1, IND-2, IND-2a, IND-3, and IND-4 shared 77 to 99% amino acid identity.
Interactions between Triazoles and Amphotericin B against
Cryptococcus neoformans
Authors: Barchiesi Francesco , Schimizzi Anna M. , Caselli Francesca , Novelli Andrea , Fallani Stefania , Giannini Daniele , Arzeni Daniela , Di Cesare Simona , Di Francesco Luigi Falconi , Fortuna Moira , Giacometti Andrea , Carle Flavia , Mazzei Teresita , Scalise Giorgio 
Published: July 2002

ABSTRACT

The interaction of amphotericin B (AmB) and azole antifungal agents in the treatment of fungal infections is still a controversial issue. A checkerboard titration broth microdilution-based method that adhered to the recommendations of the National Committee for Clinical Laboratory Standards was applied to study the in vitro interactions of AmB with fluconazole (FLC), itraconazole (ITC), and the new investigational triazole SCH 56592 (SCH) against 15 clinical isolates of
Cryptococcus neoformans
. Synergy, defined as a fractional inhibitory concentration (FIC) index of ≤0.50, was observed for 7% of the isolates in studies of the interactions of both FLC-AmB and ITC-AmB and for 33% of the isolates in studies of the SCH-AmB interactions; additivism (FICs, >0.50 to 1.0) was observed for 67, 73, and 53% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively; indifference (FICs, >1.0 to ≤2.0) was observed for 26, 20, and 14% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively. Antagonism (FIC >2.0) was not observed. When synergy was not achieved, there was still a decrease, although not as dramatic, in the MIC of one or both drugs when they were used in combination. To investigate the effects of FLC-AmB combination therapy in vivo, we established an experimental model of systemic cryptococcosis in BALB/c mice by intravenous injection of cells of
C. neoformans
2337, a clinical isolate belonging to serotype D against which the combination of FLC and AmB yielded an additive interaction in vitro. Both survival and tissue burden studies showed that combination therapy was more effective than FLC alone and that combination therapy was at least as effective as AmB given as a single drug. On the other hand, when cells of
C. neoformans
2337 were grown in FLC-containing medium, a pronounced increase in resistance to subsequent exposures to AmB was observed. In particular, killing experiments conducted with nonreplicating cells showed that preexposure to FLC abolished the fungicidal activity of the polyene. However, this apparent antagonism was not observed in vivo. Rather, when the two drugs were used sequentially for the treatment of systemic murine cryptococcosis, a reciprocal potentiation was often observed. Our study shows that (i) the combination of triazoles and AmB is significantly more active than either drug alone against
C. neoformans
in vitro and (ii) the concomitant or sequential use of FLC and AmB for the treatment of systemic murine cryptococcosis results in a positive interaction.
In Vitro Activities of Linezolid against Multiple
Nocardia
Species
Authors: Brown-Elliott Barbara A. , Ward Shelby C. , Crist Christopher J. , Mann Linda B. , Wilson Rebecca W. , Wallace Richard J. 
Published: July 2002

ABSTRACT

Linezolid was tested by broth microdilution against 140 clinical
Nocardia
isolates belonging to seven species. The MIC at which 50% of the strains are inhibited (MIC
50
) and MIC
90
for all species other than
Nocardia farcinica
were 2 and 4 μg/ml. Linezolid is the first antimicrobial agent demonstrated to be active against all
Nocardia
species.
Emergence of a Pneumococcal Clone with Cephalosporin Resistance and Penicillin Susceptibility
Authors: Smith Anthony M. , Botha Roelof F. , Koornhof Hendrik J. , Klugman Keith P. 
Published: July 2002

ABSTRACT

We report two South African serotype 6B pneumococcal isolates with cephalosporin resistance, yet with susceptibility to penicillin. DNA fingerprinting revealed that they were clonal in origin.
pbp 2X
and
1A
genes showed major alterations typical of cephalosporin-resistant pneumococci. The
pbp 2B
gene was completely unaltered, explaining the penicillin susceptibility of the isolates.
Prediction of Abacavir Resistance from Genotypic Data: Impact of Zidovudine and Lamivudine Resistance In Vitro and In Vivo
Authors: Walter Hauke , Schmidt Barbara , Werwein Marianne , Schwingel Eva , Korn Klaus 
Published: July 2002

ABSTRACT
Abacavir is frequently used in antiretroviral combination therapies as a potent nucleoside reverse transcriptase inhibitor (NRTI). Four mutations are selected for by abacavir in vitro and in vivo: K65R, L74V, Y115F, and M184V. Abacavir resistance has also been observed in NRTI multidrug-resistant samples. Furthermore, abacavir resistance has been described in the context of zidovudine resistance. To evaluate the genetic basis of abacavir resistance, the viral genotype and phenotypic resistance were analyzed for 307 patient samples. Low- and high-level resistances were defined as 2.5- to 5.5-fold- and >5.5-fold-reduced susceptibility, respectively. If all samples with abacavir-selected and NRTI multidrug resistance-associated mutations were scored as resistant, 27.6% of the samples were misclassified, mainly due to samples falsely scored as susceptible. Therefore, the relative frequencies of other mutations were evaluated. Mutations at codons 44 and 118 were rarely detected in abacavir-susceptible samples but were overrepresented in resistant samples. Site-directed mutagenesis of E44D, V118I, and M184V resulted in low-level resistance for the double mutant 44/184 and the triple mutant. Low-level abacavir resistance was also detected for a viral clone carrying zidovudine mutations only. Additional insertion of M184V into the zidovudine background doubled the resistance, whereas 44/118 did not lead to a further increase. Incorporating combinations of zidovudine mutations and M184V into the scoring system markedly reduced the number of misclassified samples, whereas 44/118 did not improve the prediction. In conclusion, the combination of M184V with zidovudine mutations gives rise to high-level abacavir resistance, which may be clinically relevant. Thus, options for useful sequential combinations of NRTI are limited.
Sterol and Fatty Acid Composition ofCandida lusitaniaeClinical Isolates
Authors: Peyron F. , Favel A. , Calaf R. , Michel-Nguyen A. , Bonaly R. , Coulon J. 
Published: July 2002

ABSTRACTThe sterol and fatty acid compositions of four amphotericin B-resistant and of two amphotericin B-susceptibleCandida lusitaniaeclinical isolates were determined. A flow cytofluorometric susceptibility test (FCST) with a membrane potential-sensitive cationic dye was used as a complement to the conventional method for selecting the isolates. Compared to susceptible isolates, resistant ones showed a greatly reduced ergosterol content and changes in sterol composition, consistent with a defect in Δ8→7 isomerase. Within each group, no correlation between the sterol or fatty acid pattern or composition and both the degree of in vitro susceptibility and FCST MIC was found.
Stable Concentrations of Zidovudine, Stavudine, Lamivudine, Abacavir, and Nevirapine in Serum and Cerebrospinal Fluid during 2 Years of Therapy
Authors: van Praag Rieneke M. E. , van Weert Elisabeth C. M. , van Heeswijk Rolf P. G , Zhou Xiao-Jian , Sommadossi Jean-Pierre , Jurriaans Suzanne , Lange Joep M. A. , Hoetelmans Richard M. W. , Prins Jan M. 
Published: July 2002

ABSTRACT
For a number of antiretroviral drugs, prolonged suppression of viral replication is related to drug exposure. Therefore, it is important to maintain stable concentrations during prolonged therapy. While studies suggest that saquinavir concentrations decrease over time, we show that concentrations of zidovudine, stavudine, lamivudine, abacavir, and nevirapine in serum and cerebrospinal fluid are stable during 2 years of therapy.