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31.
Weerasinghe A Sekikawa H Watanabe H Mannoor K Morshed SR Halder RC Kawamura T Kosaka T Miyaji C Kawamura H Seki S Abo T 《Cellular immunology》2001,207(1):28-35
Mice were infected with Plasmodium (P.) yoelii blood-stage parasites. Both the liver and spleen were the sites of inflammation during malarial infection at the beginning of day 7. The major expanding cells were found to be NK1.1(-) intermediate alphabetaTCR (alphabetaTCR(int)) in the liver and spleen, although the population of NK1.1(+) alphabetaTCR(int) cells remained constant or slightly increased. These TCR(int) cells are of extrathymic origin or are generated by an alternative intrathymic pathway and are distinguished from conventional T cells of thymic origin. During malarial infection, the population of conventional T cells did not increase at all. TCR(int) cells purified from the liver of mice which had recovered from P. yoelii infection protected mice from malaria when they were transferred into 6.5-Gy-irradiated mice. Interestingly, the immunity against malaria seemed to disappear as a function of time after recovery, namely, mice which had recovered from malaria 1 year previously again became susceptible to malarial infection. The present results suggest that TCR(int) cells are intimately associated with protection against malarial infection and, therefore, that mice which had recovered from malaria 1 year previously lost such immunity. 相似文献
32.
Leaf isoenzymes of Pericopsis mooniana from twenty-one trees at forest plantation were evaluated for their use in identification of elite trees among heterogeneous
population. Trees were grouped morphologically, before leaf extracts were separated by one-dimensional polyacrylamide gel
electrophoresis. Isoenzyme analysis were carried out for peroxidase, esterase, alcohol dehydrogenase, formate dehydrogenase,
acid phosphatase, aspartate aminotransferase, isocitrate dehydrogenase, malate dehydrogenase, leucine aminopeptidase, phosphoglucoisomerase,
phosphogluconate dehydrogenase, phosphoglucomutase, and shikimate dehydrogenase. From the thirteen enzymes studied only four
gave distinct banding patterns. Level of significance of appearing particular band for each enzyme of a given category was
investigated using χ2-test, followed by cluster analysis for categorization. The isozyme type A of formate dehydrogenase showed promising results
that could be used for differentiating trees of categories investigated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
33.
We examined brain phospholipase A2 (PLA2) activity and the expression of enzymes metabolizing arachidonic acid (AA) in cytosolic PLA2 knockout () mice to see if other brain PLA2 can compensate for the absence of cPLA2 alpha and if cPLA2 couples with specific downstream enzymes in the eicosanoid biosynthetic pathway. We found that the rate of formation of prostaglandin E2 (PGE2), an index of net cyclooxygenase (COX) activity, was decreased by 62% in the compared with the control mouse brain. The decrease was accompanied by a 50-60% decrease in mRNA and protein levels of COX-2, but no change in these levels in COX-1 or in PGE synthase. Brain 5-lipoxygenase (5-LO) and cytochrome P450 epoxygenase (cyp2C11) protein levels were also unaltered. Total and Ca2+-dependent PLA2 activities did not differ significantly between and control mice, and protein levels of type VI iPLA2 and type V sPLA2, normalized to actin, were unchanged. These results show that type V sPLA2 and type VI iPLA2 do not compensate for the loss of brain cPLA2 alpha, and that this loss has significant downstream effects on COX-2 expression and PGE2 formation, sparing other AA oxidative enzymes. This suggests that cPLA2 is critical for COX-2-derived eicosanoid production in mouse brain. 相似文献
34.
Odhran S. O'sullivan Mary A. Heskel Peter B. Reich Mark G. Tjoelker Lasantha K. Weerasinghe Aurore Penillard Lingling Zhu John J. G. Egerton Keith J. Bloomfield Danielle Creek Nur H. A. Bahar Kevin L. Griffin Vaughan Hurry Patrick Meir Matthew H. Turnbull Owen K. Atkin 《Global Change Biology》2017,23(1):209-223
High‐temperature tolerance in plants is important in a warming world, with extreme heat waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high‐temperature tolerance are documented in animals, but generally not in plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high‐temperature tolerance of leaf metabolism, we quantified Tcrit (high temperature where minimal chlorophyll a fluorescence rises rapidly and thus photosystem II is disrupted) and Tmax (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper canopy leaves of 218 plant species spanning seven biomes. Mean site‐based Tcrit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For Tmax, the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. Tcrit and Tmax followed similar biogeographic patterns, increasing linearly (?8 °C) from polar to equatorial regions. Such increases in high‐temperature tolerance are much less than expected based on the 20 °C span in high‐temperature extremes across the globe. Moreover, with only modest high‐temperature tolerance despite high summer temperature extremes, species in mid‐latitude (~20–50°) regions have the narrowest thermal safety margins in upper canopy leaves; these regions are at the greatest risk of damage due to extreme heat‐wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat‐wave events for 2050 and accounting for possible thermal acclimation of Tcrit and Tmax, we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat‐wave events become more severe with climate change. 相似文献
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36.
Nicholas Rolston Adam D. Printz Jared M. Tracy Hasitha C. Weerasinghe Doojin Vak Lew Jia Haur Anish Priyadarshi Nripan Mathews Daniel J. Slotcavage Michael D. McGehee Roghi E. Kalan Kenneth Zielinski Ronald L. Grimm Hsinhan Tsai Wanyi Nie Aditya D. Mohite Somayeh Gholipour Michael Saliba Michael Grätzel Reinhold H. Dauskardt 《Liver Transplantation》2018,8(9)
Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5‐aminovaleric acid is reported. A trade‐off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single‐crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO2/ZrO2/C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability. 相似文献
37.
Nicholas G. Smith Trevor F. Keenan I. Colin Prentice Han Wang Ian J. Wright Ülo Niinemets Kristine Y. Crous Tomas F. Domingues Rossella Guerrieri F. Yoko Ishida Jens Kattge Eric L. Kruger Vincent Maire Alistair Rogers Shawn P. Serbin Lasse Tarvainen Henrique F. Togashi Philip A. Townsend Meng Wang Lasantha K. Weerasinghe Shuang‐Xi Zhou 《Ecology letters》2019,22(3):506-517
Earth system models (ESMs) use photosynthetic capacity, indexed by the maximum Rubisco carboxylation rate (Vcmax), to simulate carbon assimilation and typically rely on empirical estimates, including an assumed dependence on leaf nitrogen determined from soil fertility. In contrast, new theory, based on biochemical coordination and co‐optimization of carboxylation and water costs for photosynthesis, suggests that optimal Vcmax can be predicted from climate alone, irrespective of soil fertility. Here, we develop this theory and find it captures 64% of observed variability in a global, field‐measured Vcmax dataset for C3 plants. Soil fertility indices explained substantially less variation (32%). These results indicate that environmentally regulated biophysical constraints and light availability are the first‐order drivers of global photosynthetic capacity. Through acclimation and adaptation, plants efficiently utilize resources at the leaf level, thus maximizing potential resource use for growth and reproduction. Our theory offers a robust strategy for dynamically predicting photosynthetic capacity in ESMs. 相似文献
38.
Strong thermal acclimation of photosynthesis in tropical and temperate wet‐forest tree species: the importance of altered Rubisco content 下载免费PDF全文
Benedict M. Long Nur H. A. Bahar Lasantha K. Weerasinghe Danielle Creek John R. Evans Peter B. Reich Owen K. Atkin 《Global Change Biology》2017,23(7):2783-2800
Understanding of the extent of acclimation of light‐saturated net photosynthesis (An) to temperature (T), and associated underlying mechanisms, remains limited. This is a key knowledge gap given the importance of thermal acclimation for plant functioning, both under current and future higher temperatures, limiting the accuracy and realism of Earth system model (ESM) predictions. Given this, we analysed and modelled T‐dependent changes in photosynthetic capacity in 10 wet‐forest tree species: six from temperate forests and four from tropical forests. Temperate and tropical species were each acclimated to three daytime growth temperatures (Tgrowth): temperate – 15, 20 and 25 °C; tropical – 25, 30 and 35 °C. CO2 response curves of An were used to model maximal rates of RuBP (ribulose‐1,5‐bisphosphate) carboxylation (Vcmax) and electron transport (Jmax) at each treatment's respective Tgrowth and at a common measurement T (25 °C). SDS‐PAGE gels were used to determine abundance of the CO2‐fixing enzyme, Rubisco. Leaf chlorophyll, nitrogen (N) and mass per unit leaf area (LMA) were also determined. For all species and Tgrowth, An at current atmospheric CO2 partial pressure was Rubisco‐limited. Across all species, LMA decreased with increasing Tgrowth. Similarly, area‐based rates of Vcmax at a measurement T of 25 °C (Vcmax25) linearly declined with increasing Tgrowth, linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf N. The decline in Rubisco constrained Vcmax and An for leaves developed at higher Tgrowth and resulted in poor predictions of photosynthesis by currently widely used models that do not account for Tgrowth‐mediated changes in Rubisco abundance that underpin the thermal acclimation response of photosynthesis in wet‐forest tree species. A new model is proposed that accounts for the effect of Tgrowth‐mediated declines in Vcmax25 on An, complementing current photosynthetic thermal acclimation models that do not account for T sensitivity of Vcmax25. 相似文献
39.
The distributional changes and role of microtubules in Nod factor-challenged<Emphasis Type="Italic"> Medicago sativa</Emphasis> root hairs 总被引:1,自引:0,他引:1
The normal tip-growing pattern exhibited by root hairs of legumes is disrupted when the hair is exposed to Nod factors generated by compatible bacteria capable of inducing nodule formation. Since microtubules (MTs) play an important role in regulating directionality and stability of apical growth in root hairs [T.N. Bibikova et al. (1999) Plant J 17:657–665], we examined the possibility that Nod factors might affect the MT distribution patterns in root hairs of Medicago sativa L. We observed that Nod factor application caused rapid changes in the pattern of MTs starting as early as 3 min after perfusion. Within 3 to 10 min after Nod factor application, first endoplasmic and then cortical MTs depolymerised, initially at the proximal ends of cells. Twenty minutes after exposure to Nod factors, a transverse band of microtubules was seen behind the tip, while almost all other MTs had depolymerised. By 30 min, very few MTs remained in the root hair and yet by 1 h the MT cytoskeleton re-formed. When Nod factors were applied in the presence of 10 M oryzalin or 5 M taxol, the MTs appeared disintegrated while the morphological effects, such as bulging and branching, became enhanced. Compared to the treatments with oryzalin or taxol alone, the combinatory treatments exhibited higher growth rates. Since microtubule reorganization is one of the earliest measurable events following Nod factor application we conclude that microtubules have an important role in the early phases of the signalling cascade. Microtubule involvement could be direct or a consequence of Nod factor-induced changes in ion levels.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00425-003-1097-1Abbreviations BNM buffered nodulation medium - CLSM confocal laser scanning microscopy - MT microtubule 相似文献
40.
Snider NT Weerasinghe SV Iñiguez-Lluhí JA Herrmann H Omary MB 《The Journal of biological chemistry》2011,286(3):2273-2284
Keratin polypeptide 8 (K8) associates noncovalently with its partners K18 and/or K19 to form the intermediate filament cytoskeleton of hepatocytes and other simple-type epithelial cells. Human K8, K18, and K19 variants predispose to liver disease, whereas site-specific keratin phosphorylation confers hepatoprotection. Because stress-induced protein phosphorylation regulates sumoylation, we hypothesized that keratins are sumoylated in an injury-dependent manner and that keratin sumoylation is an important regulatory modification. We demonstrate that K8/K18/K19, epidermal keratins, and vimentin are sumoylated in vitro. Upon transfection, K8, K18, and K19 are modified by poly-SUMO-2/3 chains on Lys-285/Lys-364 (K8), Lys-207/Lys-372 (K18), and Lys-208 (K19). Sumoylation affects filament organization and stimulus-induced keratin solubility and is partially inhibited upon mutation of one of three known K8 phosphorylation sites. Extensive sumoylation occurs in cells transfected with individual K8, K18, or K19 but is limited upon heterodimerization (K8/K18 or K8/K19) in the absence of stress. In contrast, keratin sumoylation is significantly augmented in cells and tissues during apoptosis, oxidative stress, and phosphatase inhibition. Poly-SUMO-2/3 conjugates are present in chronically injured but not normal, human, and mouse livers along with polyubiquitinated and large insoluble keratin-containing complexes. Notably, common human K8 liver disease-associated variants trigger keratin hypersumoylation with consequent diminished solubility. In contrast, modest sumoylation of wild type K8 promotes solubility. Hence, conformational changes induced by keratin natural mutations and extensive tissue injury result in K8/K18/K19 hypersumoylation, which retains keratins in an insoluble compartment, thereby limiting their cytoprotective function. 相似文献