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31.
Associations between δ13C values and leaf gas exchanges and tree-ring or needle growth, used in ecophysiological compositions, can be complex depending
on the relative timing of CO2 uptake and subsequent redistribution and allocation of carbon to needle and stem components. For palaeoenvironmental and
dendroecological studies it is often interpreted in terms of a simple model of δ13C fractionation in C3 plants. However, in spite of potential complicating factors, few studies have actually examined these relationships in mature
trees over inter- and intra-annual time-scales. Here, we present results from a 4 years study that investigated the links
between variations in leaf gas-exchange properties, growth, and dated δ13C values along the needles and across tree rings of Aleppo pine trees growing in a semi-arid region under natural conditions
or with supplemental summer irrigation. Sub-sections of tissue across annual rings and along needles, for which time of formation
was resolved from growth rate analyses, showed rapid growth and δ13C responses to changing environmental conditions. Seasonal cycles of growth and δ13C (up to ~4‰) significantly correlated (P<0.01) with photosynthetically active radiation, vapour pressure deficit, air temperature, and soil water content. The irrigation
significantly increased leaf net assimilation, stomatal conductance and needle and tree-ring growth rate, and markedly decreased
needle and tree-ring δ13C values and its sensitivity to environmental parameters. The δ13C estimates derived from gas-exchange parameters, and weighted by assimilation, compared closely with seasonal and inter-annual
δ13C values of needle- and tree-ring tissue. Higher stomatal conductances of the irrigated trees (0.22 vs. 0.08 mol m−2 s−1 on average) corresponded with ~2.0‰ lower average δ13C values, both measured and derived. Derived and measured δ13C values also indicated that needle growth, which occurs throughout the stressful summer was supported by carbon from concurrent,
low rate assimilation. For Aleppo pine under semi-arid and irrigated conditions, the δ13C of tree-ring and needle material proved, in general, to be a reasonable indicator of integrated leaf gas-exchange properties. 相似文献
32.
pSAT vectors: a modular series of plasmids for autofluorescent protein tagging and expression of multiple genes in plants 总被引:2,自引:0,他引:2
Tzfira T Tian GW Lacroix B Vyas S Li J Leitner-Dagan Y Krichevsky A Taylor T Vainstein A Citovsky V 《Plant molecular biology》2005,57(4):503-516
Autofluorescent protein tags represent one of the major and, perhaps, most powerful tools in modern cell biology for visualization
of various cellular processes in vivo. In addition, advances in confocal microscopy and the development of autofluorescent proteins with different excitation and
emission spectra allowed their simultaneous use for detection of multiple events in the same cell. Nevertheless, while autofluorescent
tags are widely used in plant research, the need for a versatile and comprehensive set of vectors specifically designed for
fluorescent tagging and transient and stable expression of multiple proteins in plant cells from a single plasmid has not
been met by either the industrial or the academic communities. Here, we describe a new modular satellite (SAT) vector system
that supports N- and C-terminal fusions to five different autofluorescent tags, EGFP, EYFP, Citrine-YFP, ECFP, and DsRed2.
These vectors carry an expanded multiple cloning site that allows easy exchange of the target genes between different autofluorescence
tags, and expression of the tagged proteins is controlled by constitutive promoters, which can be easily replaced with virtually
any other promoter of interest. In addition, a series of SAT vectors has been adapted for high throughput Gateway recombination
cloning. Furthermore, individual expression cassettes can be assembled into Agrobacterium binary plasmids, allowing efficient transient and stable expression of multiple autofluorescently tagged proteins from a
single vector following its biolistic delivery or Agrobacterium-mediated genetic transformation.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
33.
Dagon Y Avraham Y Magen I Gertler A Ben-Hur T Berry EM 《The Journal of biological chemistry》2005,280(51):42142-42148
Although adequate nutrition is essential for optimal neural activity and survival, mild energy restriction may improve cognition and prolong longevity. Energy status is monitored by the cellular AMP-activated protein kinase (AMPK) system, whereas leptin regulates total energy balance. We investigated the roles of AMPK and leptin in cognition and survival under diet restriction (DR). Hippocampal AMPK activity increases with energy restriction. Modest activation (DR to 60%) induces neurogenesis and improves cognition. However, DR to 40% augmented AMPK activity, reduced cognition and catecholamines, and increased neural apoptosis and mortality. Leptin signaling is preserved only in DR to 60%, countering the effects of AMPK "overactivation" by preventing neuroapoptosis, restoring noradrenergic activity and behavioral performance, and increasing longevity. The balance between leptin and AMPK is crucial in determining neuronal fate, cognitive ability, and survival. Should these findings extend to Man, then controlled activation of AMPK may improve neurodegenerative diseases, and leptin may have a new role in treating stress-associated malnutrition. 相似文献
34.
Gavva NR Klionsky L Qu Y Shi L Tamir R Edenson S Zhang TJ Viswanadhan VN Toth A Pearce LV Vanderah TW Porreca F Blumberg PM Lile J Sun Y Wild K Louis JC Treanor JJ 《The Journal of biological chemistry》2004,279(19):20283-20295
Vanilloid receptor 1 (TRPV1), a membrane-associated cation channel, is activated by the pungent vanilloid from chili peppers, capsaicin, and the ultra potent vanilloid from Euphorbia resinifera, resiniferatoxin (RTX), as well as by physical stimuli (heat and protons) and proposed endogenous ligands (anandamide, N-arachidonyldopamine, N-oleoyldopamine, and products of lipoxygenase). Only limited information is available in TRPV1 on the residues that contribute to vanilloid activation. Interestingly, rabbits have been suggested to be insensitive to capsaicin and have been shown to lack detectable [(3)H]RTX binding in membranes prepared from their dorsal root ganglia. We have cloned rabbit TRPV1 (oTRPV1) and report that it exhibits high homology to rat and human TRPV1. Like its mammalian orthologs, oTRPV1 is selectively expressed in sensory neurons and is sensitive to protons and heat activation but is 100-fold less sensitive to vanilloid activation than either rat or human. Here we identify key residues (Met(547) and Thr(550)) in transmembrane regions 3 and 4 (TM3/4) of rat and human TRPV1 that confer vanilloid sensitivity, [(3)H]RTX binding and competitive antagonist binding to rabbit TRPV1. We also show that these residues differentially affect ligand recognition as well as the assays of functional response versus ligand binding. Furthermore, these residues account for the reported pharmacological differences of RTX, PPAHV (phorbol 12-phenyl-acetate 13-acetate 20-homovanillate) and capsazepine between human and rat TRPV1. Based on our data we propose a model of the TM3/4 region of TRPV1 bound to capsaicin or RTX that may aid in the development of potent TRPV1 antagonists with utility in the treatment of sensory disorders. 相似文献
35.
Jerry F. Tien Neil T. Umbreit Daniel R. Gestaut Andrew D. Franck Jeremy Cooper Linda Wordeman Tamir Gonen Charles L. Asbury Trisha N. Davis 《The Journal of cell biology》2010,189(4):713-723
The coupling of kinetochores to dynamic spindle microtubules is crucial for chromosome positioning and segregation, error correction, and cell cycle progression. How these fundamental attachments are made and persist under tensile forces from the spindle remain important questions. As microtubule-binding elements, the budding yeast Ndc80 and Dam1 kinetochore complexes are essential and not redundant, but their distinct contributions are unknown. In this study, we show that the Dam1 complex is a processivity factor for the Ndc80 complex, enhancing the ability of the Ndc80 complex to form load-bearing attachments to and track with dynamic microtubule tips in vitro. Moreover, the interaction between the Ndc80 and Dam1 complexes is abolished when the Dam1 complex is phosphorylated by the yeast aurora B kinase Ipl1. This provides evidence for a mechanism by which aurora B resets aberrant kinetochore–microtubule attachments. We propose that the action of the Dam1 complex as a processivity factor in kinetochore–microtubule attachment is regulated by conserved signals for error correction. 相似文献
36.
Evaluation of intrauterine antibiotic treatment of clinical metritis and retained fetal membranes in dairy cows 总被引:1,自引:0,他引:1
Retained fetal membranes (RFM) and clinical metritis (CM) are frequently diagnosed disease conditions in dairy cows and considered of major economic impact due to negative effect on reproduction and milk production. The objective of this study was to evaluate the efficacy of i.u. tetracycline for the treatment of RFM and CM in dairy cows. Affected cows were randomly assigned to two groups; treatment group animals received i.u. 5g chlortetracycline twice weekly for 2 wks, and no treatment group. A total of 1416 cows and 804 heifers in 5 herds calved during the study period. CM was diagnosed in 18.6% (inter farm range; 15.2-23.5%) and 30% (19.4-42.3%) of cows and heifers, respectively. RFM was diagnosed in 13.1% (9.4-18.1%) and 9.2% (3.6-13.8%) of cows and heifers, respectively. Conception rates after first insemination were 38.3%, 42.5% and 18% in normal, treated and non-treated CM cows, respectively. Numbers of days open were 140.5, 136.2 and 165.5 in normal, treated and non-treated CM cows, respectively. Based on 305-d corrected milk yield, cows and heifers affected by RFM and CM produced 300-500kg less milk compared with their normal herd mates. Cows treated for CM produced 654kg more milk per 305-d corrected lactation compared to non-treated control cows. Treatment of RFM had no effect on reproductive performance or milk production. In conclusion, i.u. chlortetracycline treatment was proven to prevent the detrimental effect of CM on reproductive performance in heifers and cows and on milk production in cows only. 相似文献
37.
Human atherosclerotic plaque lipid extract impairs the antioxidant defense capacity of monocytes 总被引:1,自引:0,他引:1
Szuchman-Sapir A Etzman M Tamir S 《Biochemical and biophysical research communications》2012,423(4):884-888
Oxidative stress, induced by reactive oxygen species (ROS), is implicated in the pathogenesis of plaque formation and instability. During this ongoing oxidative process, cells in the vasculature are exposed to the atherogenicity of the plaque; previous studies have suggested that the arterial plaque, apart from being a consequence of the development of atherosclerosis, is also a cause of its progression.ObjectiveIn this study, we challenged this idea by investigating the effect of carotid plaque lipid extract on the human monocyte antioxidant system.Methods and ResultsExposure of monocytes to carotid plaque lipid extract (LE) for up to 72 h resulted in a significant increase in the ROS level (170%), with a simultaneous rise of 177% in glutathione oxidation. Experiments revealed a significant decrease, in the intracellular antioxidant enzyme activity of CAT, GPx and TRxR, (by 17, 33 and 43%, respectively). Although the activity of these enzymes subsequently returned to those of the controls, the levels of ROS did not decrease but rather continued increasing with extended LE exposure. Intriguingly, intracellular SOD activity rose significantly and remained high (176%), implying that endogenously produced H2O2, and not O2·¯ < is the factor that promotes the oxidative stress resulting from the presence of LE.ConclusionLipids from the atherosclerotic plaque may contribute to the progression of atherogenic conditions in adjacent regions by weakening the cellular antioxidant system and promoting oxidative stress, mainly through H2O2 production. 相似文献
38.
Voltage-gated ion channels are responsible for transmitting electrochemical signals in both excitable and non-excitable cells. Structural studies of voltage-gated potassium and sodium channels by X-ray crystallography have revealed atomic details on their voltage-sensor domains (VSDs) and pore domains, and were put in context of disparate mechanistic views on the voltage-driven conformational changes in these proteins. Functional investigation of voltage-gated channels in membranes, however, showcased a mechanism of lipid-dependent gating for voltage-gated channels, suggesting that the lipids play an indispensible and critical role in the proper gating of many of these channels. Structure determination of membrane-embedded voltage-gated ion channels appears to be the next frontier in fully addressing the mechanism by which the VSDs control channel opening. Currently electron crystallography is the only structural biology method in which a membrane protein of interest is crystallized within a complete lipid-bilayer mimicking the native environment of a biological membrane. At a sufficiently high resolution, an electron crystallographic structure could reveal lipids, the channel and their mutual interactions at the atomic level. Electron crystallography is therefore a promising avenue toward understanding how lipids modulate channel activation through close association with the VSDs. 相似文献
39.
Khmaladze A Matz RL Epstein T Jasensky J Banaszak Holl MM Chen Z 《Journal of structural biology》2012,178(3):270-278
Cellular volume changes play important roles in many processes associated with the normal cell activity, as well as various diseases. Consequently, there is a considerable need to accurately measure volumes of both individual cells and cell populations as a function of time. In this study, we have monitored cell volume changes in real time during apoptosis using digital holographic microscopy. Cell volume changes were deduced from the measured phase change of light transmitted through cells. Our digital holographic experiments showed that after exposure to 1 μM staurosporine for 4 h, the volumes of KB cells were reduced by ~50-60%, which is consistent with previous results obtained using electronic cell sizing and atomic force microscopy. In comparison with other techniques, digital holographic microscopy is advantageous because it employs noninvasive detection, has high time resolution, real time measurement capability, and the ability to simultaneously investigate time-dependent volume changes of both individual cells and cell populations. 相似文献
40.
Gene translation is a central process in all living organism with important ramifications to almost every biomedical field. Previous systems evolutionary studies in the field have demonstrated that in many organisms coding sequence features undergo selection to optimize this process. In the current study, we report for the first time analytical proofs related to the various aspects of this process and its optimality. Among our results we show that coding sequences with mono- tonic increasing profiles of translation efficiency (i.e., with slower codons near the 5'UTR), mathematically optimize ribosomal allocation by minimizing the number of ribosomes needed for translating a codon per time unit. Thus, the genomic translation efficiency profile reported in previous studies for many organisms is optimal in this sense. In addition, we show that improving translation efficiency of a codon in a gene may result in a decrease in the translation rate of other genes, demonstrating that the relation between codon bias and protein translation rate is less trivial than was assumed before. Based on these observations we describe an efficient heuristic for designing coding sequences with specific translation efficiency and minimal ribosomal allocation for heterologous gene expression. We demonstrate how this heuristic can be used in biotechnology for engineering a heterologous gene before expressing it in a new host. 相似文献