bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mechanism of Rhythmic Ethylene Production in Sorghum. The Role of Phytochrome B and Simulated Shading1
Authors: Finlayson Scott A. , Lee In-Jung , Mullet John E. , Morgan Page W. 
Published: July 2002

Abstract
Mutant sorghum (Sorghum bicolor [L.] Moench) deficient in functional phytochrome B exhibits reduced photoperiodic sensitivity and constitutively expresses a shade-avoidance phenotype. Under relatively bright, high red:far-red light, ethylene production by seedlings of wild-type and phytochrome B-mutant cultivars progresses through cycles in a circadian rhythm; however, the phytochrome B mutant produces ethylene peaks with approximately 10 times the amplitude of the wild type. Time-course northern blots show that the mutant's abundance of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase mRNA SbACO2 is cyclic and is commensurate with ethylene production, and that ACC oxidase activity follows the same pattern. Both SbACO2 abundance and ACC oxidase activity in the wild-type plant are very low under this regimen. ACC levels in the two cultivars did not demonstrate fluctuations coincident with the ethylene produced. Simulated shading caused the wild-type plant to mimic the phenotype of the mutant and to produce high amplitude rhythms of ethylene evolution. The circadian feature of the ethylene cycle is conditionally present in the mutant and absent in the wild-type plant under simulated shading. SbACO2 abundance in both cultivars demonstrates a high-amplitude diurnal cycle under these conditions; however, ACC oxidase activity, although elevated, does not exhibit a clear rhythm correlated with ethylene production. ACC levels in both cultivars show fluctuations corresponding to the ethylene rhythm previously observed. It appears that at least two separate mechanisms may be involved in generating high-amplitude ethylene rhythms in sorghum, one in response to the loss of phytochrome B function and another in response to shading.
Fluxes of Reserve-Derived and Currently Assimilated Carbon and Nitrogen in Perennial Ryegrass Recovering from Defoliation. The Regrowing Tiller and Its Component Functionally Distinct Zones1
Authors: Schnyder Hans , de Visser Ries 
Published: July 2002

Abstract
The quantitative significance of reserves and current assimilates in regrowing tillers of severely defoliated plants of perennial ryegrass (Lolium perenneL.) was assessed by a new approach, comprising13C/12C and 15N/14N steady-state labeling and separation of sink and source zones. The functionally distinct zones showed large differences in the kinetics of currently assimilated C and N. These are interpreted in terms of ”substrate” and ”tissue” flux among zones and C and N turnover within zones. Tillers refoliated rapidly, although C and N supply was initially decreased. Rapid refoliation was associated with (a) transient depletion of water-soluble carbohydrates and dilution of structural biomass in the immature zone of expanding leaves, (b) rapid transition to current assimilation-derived growth, and (c) rapid reestablishment of a balanced C:N ratio in growth substrate. This balance (C:N, approximately 8.9 [w/w] in new biomass) indicated coregulation of growth by C and N supply and resulted from complementary fluxes of reserve- and current assimilation-derived C and N. Reserves were the dominant N source until approximately 3 d after defoliation. Amino-C constituted approximately 60% of the net influx of reserve C during the first 2 d. Carbohydrate reserves were an insignificant source of C for tiller growth after d 1. We discuss the physiological mechanisms contributing to defoliation tolerance.
Mtsym6, a Gene ConditioningSinorhizobium Strain-Specific Nitrogen Fixation inMedicago truncatula
Authors: Tirichine Leı̈la , de Billy Françoise , Huguet Thierry 
Published: July 2002

Abstract
The availability of a wide range of independent lines for the annual medic Medicago truncatula led us to search for natural variants in the symbiotic association with Sinorhizobium meliloti. Two homozygous lines, Jemalong 6 and DZA315.16, originating from an Australian cultivar and a natural Algerian population, respectively, were inoculated with two wild-type strains ofS. meliloti, RCR2011 and A145. Both plant lines formed nitrogen-fixing (effective) nodules with the RCR2011 strain. However, the A145 strain revealed a nitrogen fixation polymorphism, establishing an effective symbiosis (Nod+Fix+) with DZA315.16, whereas only small, white, non-nitrogen fixing nodules (Nod+Fix−) were elicited on Jemalong 6. Cytological studies demonstrated that these non-fixing nodules are encircled by an endodermis at late stages of development, with no visible meristem, and contain hypertrophied and autofluorescent infection threads, suggesting the induction of plant defense reactions. The non-fixing phenotype is independent of growth conditions and determined by a single recessive allele (Mtsym6), which is located on linkage group 8.
Tissue-Specific and Developmental Pattern of Expression of the Rice sps1 Gene
Authors: Chávez-Bárcenas Ana T. , Valdez-Alarcón Juan J. , Martı́nez-Trujillo Miguel , Chen Lilly , Xoconostle-Cázares Beatriz , Lucas William J. , Herrera-Estrella Luis 
Published: July 2002

Abstract
Sucrose-phosphate synthase (SPS) is one of the key regulatory enzymes in carbon assimilation and partitioning in plants. SPS plays a central role in the production of sucrose in photosynthetic cells and in the conversion of starch or fatty acids into sucrose in germinating seeds. To explore the mechanisms that regulate the tissue-specific and developmental distribution of SPS, the expression pattern of rice (Oryza sativa) sps1 (GenBank accession no. U33175) was examined by in situ reverse transcriptase-polymerase chain reaction and the expression directed by the sps1promoter using the β-glucuronidase reporter gene. It was found that the expression of the rice sps1 gene is limited to mesophyll cells in leaves, the scutellum of germinating seedlings, and pollen of immature inflorescences. During leaf development, thesps1 promoter directs a basipetal pattern of expression that coincides with the distribution of SPS activity during the leaf sink-to-source transition. It was also found that during the vegetative part of the growth cycle, SPS expression and enzymatic activity are highest in the youngest fully expanded leaf. Additionally, it was observed that the expression of the sps1 promoter is regulated by light and dependent on plastid development in photosynthetic tissues, whereas expression in scutellum is independent of both light and plastid development.
Local and Systemic Induction of Two Defense-Related Subtilisin-Like Protease Promoters in Transgenic Arabidopsis Plants. Luciferin Induction of PR Gene Expression
Authors: Jordá Lucia , Vera Pablo 
Published: July 2002

Abstract
Following a pathogenic attack, plants are able to mount a defense response with the coordinated activation of a battery of defense-related genes. In this study we have characterized the mode of expression of the P69B and P69C genes from tomato (Lycopersicon esculentum Mill.), which encodes two closely related subtilisin-like proteases associated with the defense response. We have compared the mode of gene regulation in heterologous transgenic Arabidopsis plants harboring promoter-β-glucuronidase (GUS) and promoter-luciferase (LUC) gene fusions for these two genes. These studies revealed that the P69B and P69C promoters are induced by salicylic acid as well as during the course of both a compatible and an incompatible interaction with Pseudomonas syringae. Furthermore, P69B andP69C expression takes place in both the local and the distal (noninoculated) leaves upon inoculation with bacteria but following different and unique tissue-specific patterns of expression that are also different to that described for most other classicalPR genes. Also, we report that luciferin, the substrate for the reporter luciferase (LUC) gene, is able to activate expression of PR genes, and this may pose a problem when using this gene reporter system in studies related to plant defense.
Genes That Are Uniquely Stress Regulated in Salt Overly Sensitive (sos) Mutants
Authors: Gong Zhizhong , Koiwa Hisashi , Cushman Mary Ann , Ray Anamika , Bufford Davi , Kore-eda Shin , Matsumoto Tracie K. , Zhu Jianhua , Cushman John C. , Bressan Ray A. , Hasegawa Paul M. 
Published: July 2002

Abstract
Repetitive rounds of differential subtraction screening, followed by nucleotide sequence determination and northern-blot analysis, identified 84 salt-regulated (160 mm NaCl for 4 h) genes in Arabidopsis wild-type (Col-0 gl1) seedlings. Probes corresponding to these 84 genes and ACP1,RD22BP1, MYB2, STZ, andPAL were included in an analysis of salt responsive gene expression profiles in gl1 and the salt-hypersensitive mutant sos3. Six of 89 genes were expressed differentially in wild-type and sos3 seedlings; steady-state mRNA abundance of five genes (AD06C08/unknown, AD05E05/vegetative storage protein 2 [VSP2],AD05B11/S-adenosyl-l-Met:salicylic acid carboxyl methyltransferase [SAMT],AD03D05/cold regulated 6.6/inducible2 [COR6.6/KIN2], and salt tolerance zinc finger [STZ]) was induced and the abundance of one gene (AD05C10/circadian rhythm-RNA binding1 [CCR1]) was reduced in wild-type plants after salt treatment. The expression of CCR1, SAMT,COR6.6/KIN2, and STZ was higher insos3 than in wild type, and VSP2 andAD06C08/unknown was lower in the mutant. Salt-induced expression of VSP2 in sos1 was similar to wild type, and AD06C08/unknown, CCR1,SAMT, COR6.6/KIN2, and STZwere similar to sos3. VSP2 is regulated presumably bySOS2/3 independent of SOS1, whereas the expression of the others is SOS1 dependent.AD06C08/unknown and VSP2 are postulated to be effectors of salt tolerance whereas CCR1,SAMT, COR6.6/KIN2, and STZare determinants that must be negatively regulated during salt adaptation. The pivotal function of the SOS signal pathway to mediate ion homeostasis and salt tolerance implicatesAD06C08/unknown, VSP2,SAMT, 6.6/KIN2, STZ, andCCR1 as determinates that are involved in salt adaptation.
Chloroplast Biogenesis. Regulation of Lipid Transport to the Thylakoid in Chloroplasts Isolated from Expanding and Fully Expanded Leaves of Pea
Authors: Andersson Mats X. , Kjellberg J. Magnus , Sandelius Anna Stina 
Published: July 2002

Abstract
To study the regulation of lipid transport from the chloroplast envelope to the thylakoid, intact chloroplasts, isolated from fully expanded or still-expanding pea (Pisum sativum) leaves, were incubated with radiolabeled lipid precursors and thylakoid membranes subsequently were isolated. Incubation with UDP[3H]Gal labeled monogalactosyldiacylglycerol in both envelope membranes and digalactosyldiacylglycerol in the outer chloroplast envelope. Galactolipid synthesis increased with incubation temperature. Transport to the thylakoid was slow below 12°C, and exhibited a temperature dependency closely resembling that for the previously reported appearance and disappearance of vesicles in the stroma (D.J. Morré, G. Selldén, C. Sundqvist, A.S. Sandelius [1991] Plant Physiol 97: 1558–1564). In mature chloroplasts, monogalactosyldiacylglycerol transport to the thylakoid was up to three times higher than digalactosyldiacylglycerol transport, whereas the difference was markedly lower in developing chloroplasts. Incubation of chloroplasts with [14C]acyl-coenzyme A labeled phosphatidylcholine (PC) and free fatty acids in the inner envelope membrane and phosphatidylglycerol at the chloroplast surface. PC and phosphatidylglycerol were preferentially transported to the thylakoid. Analysis of lipid composition revealed that the thylakoid contained approximately 20% of the chloroplast PC. Our results demonstrate that lipids synthesized at the chloroplast surface as well as in the inner envelope membrane are transported to the thylakoid and that lipid sorting is involved in the process. Furthermore, the results also indicate that more than one pathway exists for galactolipid transfer from the chloroplast envelope to the thylakoid.
Toward Improved Film Cooling Prediction
Authors: Medic G. , Durbin P. A. 
Published: July 2002

Abstract
Computations of flow and heat transfer for a film-cooled high pressure gas turbine rotor blade geometry are presented with an assessment of several turbulence models. Details of flow and temperature field predictions in the vicinity of cooling holes are examined. It is demonstrated that good predictions can be obtained when spurious turbulence energy production by the turbulence model is prevented.
Determination of band offsets in AlGaAs/GaAs and InGaAs/GaAs multiple quantum wells
Authors: Ji G. , Huang D. , Reddy U. K. , Unlu H. , Henderson T. S. , Morkoç H. 
Published: July 2002

The determination of valence band offsets Qv by fitting the optical transmission spectra for AlxGa1−xAs/GaAs and InyGa1−yAs/GaAs multiple quantum wells (MQWs) is discussed. The valence band offset Qv is defined as Qv =ΔEv/(ΔEv+ΔEc), where ΔEv and ΔEc are the valence and conduction band discontinuities at the heterojunction. For AlxGa1−xAs/GaAs (Type I for both heavy holes and light holes, i.e., electrons, heavy holes, and light holes are located in the same layers) the energy separation ΔE between the first light and heavy hole subbands in the valence band is used to determine the valence-band offset Qv. In order to improve the precision, MQWs with narrow well widths and higher Al mole fraction x should be used. Further, the inclusion of coupling between the valence and conduction subbands in Kane’s three-band model is also essential. However, Qv is still not determined uniquely by the above energy difference ΔE. Different combinations of Qv and heavy hole effective masses mhh in GaAs can lead to the same ΔE. The forbidden transition E13h in a narrow well can be used to identify the actual values of mhh and Qv. [The designation Enmh(l) refers to the energy separation of the nth conduction subband and mth heavy (light) hole subband.] Following such a procedure, we find that Qv =0.33 and mhh =0.34 m0 for AlxGa1−xAs/GaAs MQWs (x&lt;0.37). For InyGa1−yAs MQWs (Type I for heavy holes and Type II for light holes, i.e., both electrons and heavy holes are located in the same layers, but the light holes are in different layers), the transition energies between the conduction subbands and the light hole valence subbands are much better parameters to determine the band offsets in comparison with the transitions involving the heavy holes. Both the optical measurements and the calculations including the strain effect show that E11l between
the first conduction subband and the first light hole valence subband in the MQWs with wider well widths is a sensitive enough parameter to determine the band offsets. By comparing with the optical measurements we obtained Qvh =0.30 and Qvl =−0.23 (Type II) (for 0.13&lt;y&lt;0.19) for the heavy hole and light hole valence band offsets, respectively.
Molecular-beam epitaxy investigation of interface disorder effects in magnetic II–VI quantum wells
Authors: Hagston W. E. , Harrison P. , Hogg J. H. C. , Jackson S. , Nicholls J. E. , Stirner T. , Lunn B. , Ashenford D. E. 
Published: July 2002

The present article describes the results of a combined theoretical and experimental investigation into the quality of the interfaces of II–VI quantum well structures grown by molecular-beam epitaxy (MBE). Detailed information is presented on the dilute magnetic semiconductor system CdTe/Cd1−xMnxTe in which the CdTe forms the well and the Cd1−xMnxTe forms the barrier. Structures are grown routinely in which both the photoluminescence (PL) and photoluminescence excitation (PLE) linewidths are narrow (∼1–2 meV). This is indicative of high quality material, a feature which is confirmed by the x-ray data in which Pendellösung fringes can be seen. However, in spite of this, it is found that although the same growth conditions are nominally employed quantum well structures are obtained which show either (i) different discernible structures in the PL and the PLE spectra, or (ii) marked differences in the Stokes’ shift between the PLE and PL from one sample to the next. A related feature concerns observations of an asymmetrical magnetic field splitting of the heavy-hole exciton states in the barriers.
The results of theoretical calculations of the exciton energy levels and their associated linewidths are presented. A comparison of theory with the experimental observations shows that the above effects can be accounted for in terms of interface disorder and magnetic field dependent interface potentials. Thus in case (i) above, the relative intensity of the components in the PLE is different from that in the PL. This is consistent with large island growth in the plane of the well, large here meaning that the island diameters exceed those of the exciton diameter (∼140–150 Å). Observations of a Stokes’ shift, even though the absorption and emission lines are narrow, can be accounted for theoretically if the concept of smaller scale disorder is introduced, i.e., island sizes that are small compared with the diameter of the exciton. Finally, results are presented which show a remarkable asymmetry in the Zeeman splitting of the heavy-hole exciton lines. It is shown that this can be accounted for by introducing deep, short-range interface potentials (∼1 or 2 monolayers). The latter are magnetic field dependent, the source of the asymmetry being attributed to band-gap renormalization effects. The implications of all these results for MBE growth conditions are described.
Effect of a Cellulose Acetate Phthalate Topical Cream on Vaginal Transmission of Simian Immunodeficiency Virus in Rhesus Monkeys
Authors: Manson Kelledy H. , Wyand Michael S. , Miller Christopher , Neurath A. Robert 
Published: July 2002

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1) infection continues to spread in developing countries, mostly through heterosexual transmission. The development of a safe and cost-effective topical microbicide, effective against a range of STDs including HIV-1, would greatly impact the ongoing epidemic. When formulated in a vehicle, a micronized form of cellulose acetate phthalate (CAP), which is an inactive pharmaceutical excipient, has been shown to inactivate HIV-1, herpes simplex virus types 1 and 2, cytomegalovirus,
Neisseria gonorrhoeae
,
Trichomonas vaginalis
,
Haemophilus ducreyi
, and
Chlamydia trachomatis
in vitro. Formulated CAP was also shown to be effective against herpes simplex virus type 2 in vivo. Here we show that a formulation of CAP protected four of six rhesus monkeys from vaginal infection with simian immunodeficiency virus. Thus, CAP may be a candidate for use as a topical microbicide for preventing HIV-1 infection in humans.
Isolation and Characterization of Tetracycline-Resistant Clinical Isolates of
Helicobacter pylori
Authors: Kwon Dong H. , Kim J. J. , Lee M. , Yamaoka Y. , Kato M. , Osato M. S. , El-Zaatari F. A. K. , Graham David Y. 
Published: July 2002

ABSTRACT

Tetracycline is an important component of combination therapies for
Helicobacter pylori
eradication. Twenty-nine tetracycline-resistant isolates requiring MICs ranging from 4 to 16 μg/ml were isolated from Korean (22 of 460) and Japanese (7 of 105) patients. Interestingly, all of the 29 tetracycline-resistant isolates exhibited cross-resistance to metronidazole, and the cross-resistance was transferred to tetracycline-sensitive
H. pylori
strains.
The Ribavirin Analog ICN 17261 Demonstrates Reduced Toxicity and Antiviral Effects with Retention of both Immunomodulatory Activity and Reduction of Hepatitis-Induced Serum Alanine Aminotransferase Levels
Authors: Tam Robert C. , Ramasamy Kanda , Bard Josie , Pai Bharati , Lim Charmaine , Averett Devron R. 
Published: July 2002

ABSTRACTThe demonstrated utility of the nucleoside analog ribavirin in the treatment of certain viral diseases can be ascribed to its multiple distinct properties. These properties may vary in relative importance in differing viral disease conditions and include the direct inhibition of viral replication, the promotion of T-cell-mediated immune responses via an enhanced type 1 cytokine response, and a reduction of circulating alanine aminotransferase (ALT) levels associated with hepatic injury. Ribavirin also has certain known toxicities, including the induction of anemia upon chronic administration. To determine if all these properties are linked, we compared thed-nucleoside ribavirin to itsl-enantiomer (ICN 17261) with regard to these properties. Strong similarities were seen for these two compounds with respect to induction of type 1 cytokine bias in vitro, enhancement of type 1 cytokine responses in vivo, and the reduction of serum ALT levels in a murine hepatitis model. In contrast, ICN 17261 had no in vitro antiviral activity against a panel of RNA and DNA viruses, while ribavirin exhibited its characteristic activity profile. Importantly, the preliminary in vivo toxicology profile of ICN 17261 is significantly more favorable than that of ribavirin. Administration of 180 mg of ICN 17261 per kg of body weight to rats by oral gavage for 4 weeks generated substantial serum levels of drug but no observable clinical pathology, whereas equivalent doses of ribavirin induced a significant anemia and leukopenia. Thus, structural modification of ribavirin can dissociate its immunomodulatory properties from its antiviral and toxicologic properties, resulting in a compound (ICN 17261) with interesting therapeutic potential.
Difference in Incidence of Spontaneous Mutations between Herpes Simplex Virus Types 1 and 2
Authors: Sarisky Robert T. , Nguyen Tammy T. , Duffy Karen E. , Wittrock Robert J. , Leary Jeffry J. 
Published: July 2002

ABSTRACT

Spontaneous mutations within the herpes simplex virus (HSV) genome are introduced by errors during DNA replication. Indicative of the inherent mutation rate of HSV DNA replication, heterogeneous HSV populations containing both acyclovir (ACV)-resistant and ACV-sensitive viruses occur naturally in both clinical isolates and laboratory stocks. Wild-type, laboratory-adapted HSV type 1 (HSV-1) strains KOS and Cl101 reportedly accumulate spontaneous ACV-resistant mutations at a frequency of approximately six to eight mutants per 10
4
plaque-forming viruses (U. B. Dasgupta and W. C. Summers, Proc. Natl. Acad. Sci. USA 75:2378–2381, 1978; J. D. Hall, D. M. Coen, B. L. Fisher, M. Weisslitz, S. Randall, R. E. Almy, P. T. Gelep, and P. A. Schaffer, Virology 132:26–37, 1984). Typically, these resistance mutations map to the thymidine kinase (TK) gene and render the virus TK deficient. To examine this process more closely, a plating efficiency assay was used to determine whether the frequencies of naturally occurring mutations in populations of the laboratory strains HSV-1 SC16, HSV-2 SB5, and HSV-2 333 grown in MRC-5 cells were similar when scored for resistance to penciclovir (PCV) and ACV. Our results indicate that (i) HSV mutants resistant to PCV and those resistant to ACV accumulate at approximately equal frequencies during replication in cell culture, (ii) the spontaneous mutation frequency for the HSV-1 strain SC16 is similar to that previously reported for HSV-1 laboratory strains KOS and Cl101, and (iii) spontaneous mutations in the laboratory HSV-2 strains examined were 9- to 16-fold more frequent than those in the HSV-1 strain SC16. These observations were confirmed and extended for a group of eight clinical isolates in which the HSV-2 mutation frequency was approximately 30 times higher than that for HSV-1 isolates. In conclusion, our results indicate that the frequencies of naturally occurring, or spontaneous, HSV mutants resistant to PCV and those resistant to ACV are similar. However, HSV-2 strains may have a greater propensity to generate drug-resistant mutants than do HSV-1 strains.