bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina
Authors: Paz Yakov , Shimoni Eyal , Weiss Meira , Pick Uri 
Published: May 2007

Abstract
Uptake of iron in the halotolerant alga Dunaliella salina is mediated by a transferrin-like protein (TTf), which binds and internalizes Fe3+ ions. Recently, we found that iron deficiency induces a large enhancement of iron binding, which is associated with accumulation of three other plasma membrane proteins that associate with TTf. In this study, we characterized the kinetic properties of iron binding and internalization and identified the site of iron internalization. Iron deficiency induces a 4-fold increase in Fe binding, but only 50% enhancement in the rate of iron uptake and also increases the affinity for iron and bicarbonate, a coligand for iron binding. These results indicate that iron deprivation leads to accumulation and modification of iron-binding sites. Iron uptake in iron-sufficient cells is preceded by an apparent time lag, resulting from prebound iron, which can be eliminated by unloading iron-binding sites. Iron is tightly bound to surface-exposed sites and hardly exchanges with medium iron. All bound iron is subsequently internalized. Accumulation of iron inhibits further iron binding and internalization. The vacuolar inhibitor bafilomycin inhibits iron uptake and internalization. Internalized iron was localized by electron microscopy within vacuolar structures that were identified as acidic vacuoles. Iron internalization is accompanied by endocytosis of surface proteins into these acidic vacuoles. A novel kinetic mechanism for iron uptake is proposed, which includes two pools of bound/compartmentalized iron separated by a rate-limiting internalization stage. The major parameter that is modulated by iron deficiency is the iron-binding capacity. We propose that excessive iron binding in iron-deficient cells serves as a temporary reservoir for iron that is subsequently internalized. This mechanism is particularly suitable for organisms that are exposed to large fluctuations in iron availability.
The Senescence-Induced Staygreen Protein Regulates Chlorophyll Degradation
Authors: Park So-Yon , Yu Jae-Woong , Park Jong-Sung , Li Jinjie , Yoo Soo-Cheul , Lee Na-Yeoun , Lee Sang-Kyu , Jeong Seok-Won , Seo Hak Soo , Koh Hee-Jong , Jeon Jong-Seong , Park Youn-Il , Paek Nam-Chon 
Published: May 2007

Abstract
Loss of green color in leaves results from chlorophyll (Chl) degradation in chloroplasts, but little is known about how Chl catabolism is regulated throughout leaf development. Using the staygreen (sgr) mutant in rice (Oryza sativa), which maintains greenness during leaf senescence, we identified Sgr, a senescence-associated gene encoding a novel chloroplast protein. Transgenic rice overexpressing Sgr produces yellowish-brown leaves, and Arabidopsis thaliana pheophorbide a oxygenase–impaired mutants exhibiting a stay-green phenotype during dark-induced senescence have reduced expression of Sgr homologs, indicating that Sgr regulates Chl degradation at the transcriptional level. We show that the leaf stay-greenness of the sgr mutant is associated with a failure in the destabilization of the light-harvesting chlorophyll binding protein (LHCP) complexes of the thylakoid membranes, which is a prerequisite event for the degradation of Chls and LHCPs during senescence. Transient overexpression of Sgr in Nicotiana benthamiana and an in vivo pull-down assay show that Sgr interacts with LHCPII, indicating that the Sgr-LHCPII complexes are formed in the thylakoid membranes. Thus, we propose that in senescing leaves, Sgr regulates Chl degradation by inducing LHCPII disassembly through direct interaction, leading to the degradation of Chls and Chl-free LHCPII by catabolic enzymes and proteases, respectively.
Components of theArabidopsismRNA Decapping Complex Are Required for Early Seedling Development
Authors: Goeres David C. , Van Norman Jaimie M. , Zhang Weiping , Fauver Nellie A. , Spencer Mary Lou , Sieburth Leslie E. 
Published: May 2007

AbstractTo understand the mechanisms controlling vein patterning in Arabidopsis thaliana, we analyzed two phenotypically similar mutants, varicose (vcs) and trident (tdt). We had previously identified VCS, and recently, human VCS was shown to function in mRNA decapping. Here, we report that TDT encodes the mRNA-decapping enzyme. VCS and TDT function together in small cytoplasmic foci that appear to be processing bodies. To understand the developmental requirements for mRNA decapping, we characterized the vcs and tdt phenotypes. These mutants were small and chlorotic, with severe defects in shoot apical meristem formation and cotyledon vein patterning. Many capped mRNAs accumulated in tdt and vcs mutants, but surprisingly, some mRNAs were specifically depleted. In addition, loss of decapping arrested the decay of some mRNAs, while others showed either modest or no decay defects, suggesting that mRNAs may show specificity for particular decay pathways (3′ to 5′ and 5′ to 3′). Furthermore, the severe block to postembryonic development in vcs and tdt and the accompanying accumulation of embryonic mRNAs indicate that decapping is important for the embryo-to-seedling developmental transition.
TomatoBRASSINOSTEROID INSENSITIVE1Is Required for Systemin-Induced Root Elongation inSolanum pimpinellifoliumbut Is Not Essential for Wound Signaling
Authors: Holton Nicholas , Caño-Delgado Ana , Harrison Kate , Montoya Teresa , Chory Joanne , Bishop Gerard J. 
Published: May 2007

AbstractThe tomato Leu-rich repeat receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1) has been implicated in both peptide (systemin) and steroid (brassinosteroid [BR]) hormone perception. In an attempt to dissect these signaling pathways, we show that transgenic expression of BRI1 can restore the dwarf phenotype of the tomato curl3 (cu3) mutation. Confirmation that BRI1 is involved in BR signaling is highlighted by the lack of BR binding to microsomal fractions made from cu3 mutants and the restoration of BR responsiveness following transformation with BRI1. In addition, wound and systemin responses in the cu3 mutants are functional, as assayed by proteinase inhibitor gene induction and rapid alkalinization of culture medium. However, we observed BRI1-dependent root elongation in response to systemin in Solanum pimpinellifolium. In addition, ethylene perception is required for normal systemin responses in roots. These data taken together suggest that cu3 is not defective in systemin-induced wound signaling and that systemin perception can occur via a non-BRI1 mechanism.
Canonical Signal Recognition Particle Components Can Be Bypassed for Posttranslational Protein Targeting in Chloroplasts
Authors: Tzvetkova-Chevolleau Tzvetelina , Hutin Claire , Noël Laurent D. , Goforth Robyn , Carde Jean-Pierre , Caffarri Stephano , Sinning Irmgard , Groves Matthew , Teulon Jean-Marie , Hoffman Neil E. , Henry Ralph , Havaux Michel , Nussaume Laurent 
Published: May 2007

Abstract
The chloroplast signal recognition particle (cpSRP) and its receptor (cpFtsY) target proteins both cotranslationally and posttranslationally to the thylakoids. This dual function enables cpSRP to utilize its posttranslational activities for targeting a family of nucleus-encoded light-harvesting chlorophyll binding proteins (LHCPs), the most abundant membrane proteins in plants. Previous in vitro experiments indicated an absolute requirement for all cpSRP pathway soluble components. In agreement, a cpFtsY mutant in Arabidopsis thaliana exhibits a severe chlorotic phenotype resulting from a massive loss of LHCPs. Surprisingly, a double mutant, cpftsy cpsrp54, recovers to a great extent from the chlorotic cpftsy phenotype. This establishes that in plants, a new alternative pathway exists that can bypass cpSRP posttranslational targeting activities. Using a mutant form of cpSRP43 that is unable to assemble with cpSRP54, we complemented the cpSRP43-deficient mutant and found that this subunit is required for the alternative pathway. Along with the ability of cpSRP43 alone to bind the ALBINO3 translocase required for LHCP integration, our results indicate that cpSRP43 has developed features to function independently of cpSRP54/cpFtsY in targeting LHCPs to the thylakoid membranes.
Carbon dynamics in a model grassland with functionally different soil communities
Authors: BRADFORD M. A. , TORDOFF G. M. , BLACK H. I. J. , COOK R. , EGGERS T. , GARNETT M. H. , GRAYSTON S. J. , HUTCHESON K. A. , INESON P. , NEWINGTON J. E. , OSTLE N. , SLEEP D. , STOTT A. , JONES T. HEFIN 
Published: May 2007

SummaryImpacts of environmental changes on carbon cycling in terrestrial ecosystems are typically correlated with shifts in the composition, biomass and activity of soil faunal communities. Given the role of soil fauna in decomposition, shifts in soil faunal communities may further modify the carbon dynamics of a perturbed system.To test this possibility, we manipulated soil community composition in model grassland ecosystems and used a13CO2‐tracer to follow the assimilation, retention and pathways of recent, photosynthetically fixed carbon. The community treatments formed a nested hierarchy of functional complexity: (1) microbiota only; (2) microbiota and mesofauna; (3) microbiota, mesofauna and macrofauna.These treatments significantly affected the rate of decline in13C‐label respiration rate and the amount of13C‐label retained by the communities: while the rate of decline in13C‐label respiration rate was greatest in the microbiota treatment, the treatment with both micro‐ and mesofauna retained less13C‐label than either the more functionally complex or simple treatments. The presence of macrofauna altered the utilization of13C‐label by Collembola and Enchytraeidae: they decreased the mass of13C‐label utilized by Collembola and increased that utilized by Enchytraeidae.Our results suggest that soil community composition may play a key role in regulating the dynamics of recent, photosynthetically fixed carbon.
Carbon dioxide uptake, water relations and drought survival for Dudleya saxosa, the ‘rock live‐forever’, growing in small soil volumes
Authors: NOBEL P. S. , ZUTTA B. R. 
Published: May 2007

Summary

Although many plants grow in rock crevices and other regions of small soil volume, including over 20 000 epiphytic and hemi‐epiphytic species, analyses of the actual soil volume occupied, the water availability in that soil, the water‐storage capacity in the shoots and underground organs, and the photosynthetic pathway utilized have rarely been combined.
Dudleya saxosa (M.F. Jones) Britton and Rose (Crassulaceae), growing in the Sonoran Desert, has very shallow roots that occupied soil volumes averaging only 43 × 10−6 m3 per medium‐sized plant. This volume of soil can hold about the same amount of water (10 g) as can be stored in the leaves, corm and roots combined (11 g), but at a sufficiently high water potential for transfer to the plant for less than 1 week after a substantial rainfall.
About 80% of the net carbon dioxide uptake by D. saxosa over a 24‐h period occurred during the daytime (C3) under wet conditions, the daily total decreasing by 34% and the pattern shifting to nocturnal net CO2 uptake (CAM) after 46 days’ drought. Seventy‐seven days’ drought eliminated its daily net CO2 uptake.
Stomatal frequency was only 67 mm−2 on the adaxial (upper) surface and twofold lower on the abaxial surface. The cuticle was thick, 34 µm for the adaxial surface. Leaves had 24 mesophyll cell layers, leading to a high mesophyll cell surface area per unit leaf area of 142.
The three leaf anatomical features plus utilization of CAM increased net CO2 uptake per unit of water transpired, and helped D. saxosa thrive in a small soil volume, with the underground corm being a major supplier of water to the succulent leaves during 2.5 months of drought. The maximum water‐holding capacity of the soil explored by the roots closely matched the maximum water‐holding capacity of the plant, reflecting the conservative strategy used by D. saxosa in a stressful semi‐arid environment.
Cytokine‐mediated control of lipopolysaccharide‐induced activation of small intestinal epithelial cells
Authors: Lotz Michael , König Till , Ménard Sandrine , Gütle Dominique , Bogdan Christian , Hornef Mathias W. 
Published: May 2007

SummaryCytokines with anti‐inflammatory properties have been implicated in the prevention of inappropriate immune activation by commensal bacteria in the intestinal tract. Here, we analysed receptor expression, cellular signalling, and the inhibitory activity of interleukin (IL)‐4, ‐10, ‐11, and ‐13 as well as of transforming growth factor‐β on lipopolysaccharide‐mediated small intestinal epithelial cell activation. Only IL‐4 and IL‐13 had a significant inhibitory effect on chemokine secretion and nitric oxide (NO) production in differentiated and polarized cells. Reverse transcription–polymerase chain reaction of primary intestinal epithelial cells obtained by laser‐microdissection confirmed expression of the type II IL‐4 receptor consisting of the IL‐4 receptor α and the IL‐13 receptor α1. Also, IL‐4 or IL‐13 led to rapid signal transducer and activator of transcription 6 phosphorylation, diminished inducible NO synthase expression, and enhanced the antagonistic arginase 1 activity. In conclusion, cytokines such as IL‐4 and IL‐13 affect intestinal epithelial cells and exhibit a modulating activity on Toll‐like receptor‐4‐mediated epithelial cell activation.
Effectiveness of two nickel‐titanium rotary instruments and a hand file for removing gutta‐percha in severely curved root canals during retreatment: an ex vivo study
Authors: Gergi R. , Sabbagh C. 
Published: May 2007

AbstractAim  To evaluate ex vivo the effectiveness of hand files, ProTaper and R‐Endo rotary instruments when removing gutta‐percha from curved root canals.Methodology  Ninety severely curved teeth were divided into three groups. The root canals were accessed, prepared and filled with vertically condensed gutta‐percha and sealer. Removal of gutta‐percha was performed with the following devices and techniques: Hedström files (Vereinigte Dentalwerke, Munich, Germany), ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) and R‐Endo (Micro‐Mega, Besançon, France). All techniques were used with the solvent eucalyptol. The amount of filling material debris remaining on root canal walls was assessed radiographically from two directions: mesio‐distal and bucco‐lingual. The images were digitized and analysed with autocad 2000 software. Total canal area, area of the cervical, middle and apical thirds, and area of remaining filling material from both directions were outlined by two different operators and calculated. Statistical analysis of remaining filling material within each third of the canals was performed by the Kruskal–Wallis test.Results  Comparisons of the percentages of remaining filling material in the entire canal did not reveal any significant differences between the methods of removal. However, the canal third was of relevance in all groups; the apical third had the most remaining filling material compared with the middle and cervical thirds (P = 0.0012).Conclusion  All instruments left filling material inside the root canal. ProTaper and R‐Endo rotary instruments were inadequate for the complete removal of filling material from the root canal system.
Fatigue testing of a NiTi rotary instrument. Part 2: fractographic analysis
Authors: Cheung G. S. P. , Darvell B. W. 
Published: May 2007

AbstractAim  To examine the topographic features of the fracture surface of a NiTi instrument after fatigue failure, and to correlate the measurements of some features with the cyclic load.Methodology  A total of 212 ProFile rotary instruments were subjected to a rotational‐bending test at various curvatures until broken. The fracture surface of all fragments was examined by SEM to identify the crack origins. The crack radius, i.e. extent of the fatigue‐crack growth towards the centroid of the cross‐section, was also measured, and correlated with the strain amplitude for each instrument.Results  All fracture surfaces revealed the presence of one or more crack origins, a region occupied by microscopic striations, and an area with microscopic dimples. The number of specimens showing multiple crack origins was significantly greater in the group fatigued under water than in air (P < 0.05). A linear relationship between the reciprocal of the square root of the crack radius and the strain amplitude was discernible (P < 0.001), the slopes of which were not significantly different for instruments fatigued in air and water.Conclusions  The fractographic appearance of NiTi engine‐files that had failed because of fatigue is typical of that for other metals. The fatigue behaviour of NiTi instruments is adversely affected by water, not only for the low‐cycle fatigue life, but also the number of crack origins. There appears to be a critical extent of crack propagation for various strain amplitudes leading to final rupture (akin to the Griffith's criterion for brittle materials).
Comparison of root canal preparation with two rotary NiTi instruments: ProFile .04 and GT Rotary
Authors: Rödig T. , Hülsmann M. , Kahlmeier C. 
Published: May 2007

AbstractAim  To compare root canal preparation using ProFile .04 and GT Rotary nickel–titanium instruments (both Dentsply Maillefer, Ballaigues, Switzerland).Methodology  Fifty extracted mandibular molars with mesial root canal curvatures between 20 and 40° were randomly divided into two groups and embedded in a muffle system. All root canals were prepared to size 45 using ProFile .04 or GT rotary instruments. The following parameters were evaluated: straightening of root canal curvature, postoperative root canal cross‐section, cleaning ability, safety issues and working time.Results  Both NiTi systems maintained curvature well; the mean degree of straightening was <1°. The majority of the root canals prepared with ProFile .04 (80.8%) and GT (84.0%) postoperatively showed a round or oval cross‐section. For debris, ProFile .04 and GT rotary achieved 67.1% and 71.6% scores of 1 and 2, respectively. Concerning the coronal region statistical analysis showed a better result for GT than for ProFile .04. For the middle and apical thirds of the root canals, results did not differ significantly. None of the two systems completely removed smear layer. Ten procedural incidents occurred with ProFile .04 compared with five with GT. Mean working time was shorter for ProFile .04 (131.8 s) than for GT (143.7 s); the difference was not significant.Conclusions  Both systems respected original root canal curvature well and were safe to use. Smear layer removal was not satisfactory with either systems.
Association of CD14, IL1B, IL6, IL10 and TNFA functional gene polymorphisms with symptomatic dental abscesses
Authors: De Sá A. R. , Moreira P. R. , Xavier G. M. , Sampaio I. , Kalapothakis E. , Dutra W. O. , Gomez R. S. 
Published: May 2007

AbstractAim  To investigate in individuals with symptomatic dental abscesses the occurrence of functional polymorphisms within five genes involved with the immune response. The functional gene polymorphisms analysed were CD14 (−260 C/T), IL1B (+3954 C/T), IL6 (−174 G/C,), IL10 (−1082 G/A) and TNFA (−308 G/A).Methodology  Genomic DNA obtained from oral swabs from individuals with symptomatic dental abscesses and asymptomatic inflammatory periapical lesions, without previous exacerbation, was submitted to restriction fragment length polymorphism (RFLP) analyses to determine each individual genotype. The chi‐square and principal components analysis tests were used for statistical analysis.Results  A significant association was observed between the occurrence of the GG genotype or the G allele expression of the polymorphic locus−174 (G/C) of the IL6 gene, and the presence of the symptomatic dental abscesses in women and in individuals ≤35 years old. The principal components analysis suggested predominance of the symptomatic dental abscesses in individuals displaying: high‐producer IL6 genotype; intermediate and high‐producer IL1B genotypes and low‐producer TNFA genotype.Conclusions  The present study suggests that genetic factors are associated with susceptibility to develop symptomatic dental abscesses.
Health literacy and the information needs and dilemmas of first‐time mothers over 35 years
Authors: Carolan Mary 
Published: May 2007

Aim and objectives.  This paper aims to highlight the information‐based dilemmas of a particular group of healthcare patients, first‐time mothers over 35 years.Background.  In recent years, there has been a proliferation of health‐related information and a move towards greater public access to health information as an important step towards patient education and empowerment. Information technologies, such as the Internet, have added considerable momentum to this trend. Many health professionals now consider the provision of detailed health information to patients as requisite for informed decision making. Within the literature there is some emphasis on the importance of patient understanding of information received; however, to date, few studies have considered information over‐consumption as problematic.Methods.  Using in‐depth interviews, a sample of 22 first‐time mothers over 35 years was interviewed over three junctures: 35 weeks gestation, 10–14 days postpartum and six to eight months postpartum. Three focus group interviews of midwives and maternal and child health nurses were also conducted. This paper was undertaken as part of a larger project to evaluate the experience of first mothering over 35 years.Results.  Mothers in this study were found to have access to large volumes of health information. This tendency was driven by both the women and the health professionals who cared for them. Midwives and maternal and child health nurses revealed a tendency to provide older first‐time mothers with considerable health information of a medical orientation, understanding that this is what the women required. However, despite common perceptions of empowerment, the consumption of medical‐type information proved frightening and many mothers described feeling overwhelmed by ‘knowing too much’.Conclusion.  This study contributes to the limited understanding of the information needs of a growing group of childbearing women, first‐time mothers over 35 years. By providing an insight into the ‘downside’ of extensive health information, nursing staff, in particular, may consider the amount and type of information they distribute. Some suggestions are offered to health professionals to ameliorate the information‐based dilemmas of these women.Relevance to clinical practice.  As the number of childbearing women over 35 years continues to grow, it is important for health professionals to understand the particular needs of this group. In doing so, doctors, midwives and maternal and child health nurses may be in a position to provide more meaningful maternal support.