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991.
992.
The kinetics of changes in photosystem I (PSI), photosystemII (PSII), and whole chain (PSII and PSI) electron transport,chlorophyll fluorescence parameters, the capacity to bind atrazineand the polypeptide profiles of thylakoids isolated from wheatleaves on exposure to a photon flux density of 2000 µmolm2 s1 were determined. Severe and similar levelsof photo-inhibitory damage to both PSII and whole chain electrontransport occurred and were correlated with decreases in theratio of variable to maximal fluorescence, the proportionalcontribution of the rapid a phase of the fluorescence kineticsand the capacity to bind atrazine. Severe photo-inhibition ofelectron transport was not associated with a major loss of chlorophyllor total thylakoid protein. However, a small decrease in a 70kDa polypeptide together with increases in a number of low molecularmass polypeptides (824 kDa) occurred. Phosphorylation of thylakoid polypeptides alleviated photo-inhibitionof PSII electron transport but stimulated photoinhibitory damageto whole chain electron transport. The consequences of suchphosphorylation-induced effects on photoinhibition in vivo areconsidered. Key words: Chlorophyll fluorescence, electron transport, photo-inhibition, protein phosphorylation, thylakoid membranes, wheat (Triticum aestivum) 相似文献
993.
Milena Z. Živković Stošić Niko S. Radulović Marija S. Genčić Vladimir N. Ranđelović 《化学与生物多样性》2021,18(7):e2100285
Herein n-, iso- and anteiso-series of very-long-chained (VLC) alkanes (C21–C35), fatty acid benzyl esters (FABEs; C20–C32), and 2-alkanones (C23–C35) were identified in the wax of Primula veris L. and P. acaulis (L.) L. (Primulaceae). For the very first time in a sample of natural origin, the presence of iso- and anteiso-VLC FABEs and 2-alkanones was unequivocally confirmed by synthetic work, derivatization, and NMR. It should be noted that the studied species produced unusually high amounts of branched wax constituents (e. g., >50 % of 2-alkanones were branched isomers). The domination of iso-isomers, probably biosynthesized from leucine-derived starters, is a unique feature in the Plant Kingdom. The plant organ distribution of these VLC compounds in P. acaulis samples (different habitats and phenological phases) pointed to their possible ecological value. This was supported by a eutectic behavior of binary blends of FABEs and alkanes, as well as by high UV-C absorption by FABEs. 相似文献
994.
995.
S Y Yan Z R Mao H Y Yang M A Tu S H Li G P Huang G S Li L Guo G Q Jin R F He 《The International journal of developmental biology》1991,35(4):429-435
The nucleus of a blastula cell from Tilapia (Oreochromis nilotica, family Cichlidae, order Perciformes) was transplanted into an enucleated egg of Loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes). From among 3747 nucleo-cytoplasmic hybrid (NCH) eggs two NCH larval fish (0.05%) were obtained; one died on the 6th day and the other died on the 12th day after the operation. Morphological examinations showed that both NCH larval fish had developed normally with an opened mouth except they could not take food after complete utilization of their egg yolk on the 5th day of development. The possible mechanisms for obtaining such inter-order NCH larval fish are discussed. This is the first report indicating that inter-order NCH larval fish can be obtained in spite of their evolutionary divergence. 相似文献
996.
Floral development and expression of floral homeotic genes are influenced by cytokinins 总被引:3,自引:1,他引:3
J.J. Estruch A. Granell G. Hansen E. Prinsen P. Redig H. Van Onckelen Z. Schwarz-Sommer H. Sommer A. Spena 《The Plant journal : for cell and molecular biology》1993,4(2):379-384
Tobacco plants that are somatic mosaics for the expression of a cytokinin-synthesizing gene have viviparous leaves. Epiphyllous buds can be either vegetative or floral. Floral adventitious buds can be either normal or abnormal. Abnormalities of floral development correlate with: (i) a local activation of the cytokinin-synthesizing gene, (ii) a drastic increase in floral cytokinin content, and (iii) a decrease in the steady-state levels of mRNA homologues of the homeotic genes DEFA , GLO and PLENA of Antirrhinum majus . Thus, these data show in planta that cytokinins, a class of phytohormones, are able to alter the development of floral organs and to decrease the expression of three homeotic floral genes. 相似文献
997.
998.
C Luo X Yao J Li B He Q Liu H Ren F Liang M Li H Lin J Peng T F Yuan Z Pei H Su 《Cell death & disease》2016,7(3):e2160
Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality. The mechanisms underlying its pathological complications have not been fully identified. Here, we investigate the potential involvement of the glymphatic system in the neuropathology of SAH. We demonstrate that blood components rapidly enter the paravascular space following SAH and penetrate into the perivascular parenchyma throughout the brain, causing disastrous events such as cerebral vasospasm, delayed cerebral ischemia, microcirculation dysfunction and widespread perivascular neuroinflammation. Clearance of the paravascular pathway with tissue-type plasminogen activator ameliorates the behavioral deficits and alleviates histological injury of SAH. Interestingly, AQP4−/− mice showed no improvements in neurological deficits and neuroinflammation at day 7 after SAH compared with WT control mice. In conclusion, our study proves that the paravascular pathway dynamically mediates the pathological complications following acute SAH independently of glymphatic control.Cerebral aneurysm rupture causes subarachnoid hemorrhage (SAH), which is associated with a high mortality due to its secondary complications, including hemorrhage, hydrocephalus and delayed cerebral ischemia (DCI).1, 2, 3 Therapeutic interventions against the secondary complications, especially DCI, are yet limited, as the pathological mechanism underlying that is not fully understood.2, 3, 4, 5, 6, 7 Current hypotheses of the development of the secondary complications mainly include cerebral vasospasm (CVS) and the microcirculation disturbance, as well as parenchymal arterial lesions, microthrombosis and neuroinflammation.1, 2, 4, 7, 8, 9Previous studies have shown that the blockade of cerebral lymphatic drainage deteriorated the secondary cerebral ischemia after SAH, suggesting that the cerebral lymphatic drainage pathway could be involved in the pathological mechanism of SAH.10, 11 However, the central nervous system (CNS) was considered lack of a conventional lymphatic drainage system in the past. Recently, several studies have shown that the brain has in fact the proper lymphatic system, including sinus-associated lymphatic vessels and the glymphatic system (GS).12, 13, 14, 15 Sinus-associated lymphatic vessels express all of the molecular hallmarks of lymphatic endothelial cells, contain cerebrospinal fluid (CSF) and immune cells, and drain into the deep cervical lymph nodes.12, 13There is a histologically defined space in the brain, the Virchow–Robin space, where the subarachnoid space meets the paravascular space (or perivascular space in somewhere, PVS).16 The GS is a specialized brain-wide anatomic structure locating at the PVS surrounding the brain vasculature, which is ensheathed with the astroglial endfeet and astroglial water channel aquaporin-4 (AQP4).14, 15 The GS facilitates the efficient lymphatic clearance of extracellular solutes and fluid in the brain through astroglial-mediated interstitial fluid bulk flow.14Impairment of GS involves neurological conditions including traumatic brain injuries,17 ischemic stroke18 and aged brain.19 Interestingly, brain imaging study with magnetic resonance imaging reported weakened GS perfusion following acute stroke or SAH.18, 20 However, little is known about whether the GS is involved in the secondary complications of SAH. Here, we examined the potential involvement of GS in SAH-associated pathology progression with in vivo two-photon microscopy and CLARITY technique.21, 22 Our data showed that subarachnoid blood flowed into the brain parenchyma rapidly through the PVS, causing CVS, vasculitis, widespread microinfraction and neuroinflammation in the animal model of SAH and SAH patients. Prevention of CVS with Fasudil23 did not improve the neurological impairment nor alleviated the pathology, while the PVS clearance with tissue-type plasminogen activator (tPA) infusion improved the behavioral recovery and reduced neuroinflammation in the brain. Interestingly, AQP4−/− mice showed no improvements in neurological deficits and neuroinflammation at day 7 after SAH compared with WT control mice. Our study therefore suggested that the paravacular pathway dynamically mediates the pathological complications following acute SAH independently of glymphatic control. 相似文献
999.
Abstract: Estimates have been made of the amounts and rates of uptake of radioactive branched-chain i-amino acids, L-phenylalanine, and L-glutamine into incubated rat brain cortex slices. Estimates have also been made of the binding of these amino acids to brain cell fragments. It is shown that such binding, as well as the process of passive diffusion, is not affected by the presence of ouabain (0.2 mM), which suppresses the energy-dependent concentrative uptakes of the amino acids investigated. The maximum specific binding of L-glutamine is about three times that of the other amino acids and amounts to about 11% of the total uptake of the amino acid by rat brain cortex slices in 12 min from a medium containing 0.25 mM-glutamine. The sodium-ion concentration of the medium appears not to play a significant role in determining the rate of L-glutamine uptake in brain slices except at relatively low concentrations (<20 mequiv./l). The presence of Na+ , however, is essential for the attainment of a tissue-to-medium concentration ratio greater than 2.0 for L-glutamine. At relatively low concentrations (0.25 mM) the rapidity of uptake of L-glutamine into a suspension of nerve terminals exceeds that into brain cortex slices. The uptakes of L-glutamine (Km 's = 0.66 mM and 2.25 mM) and of the branched chain L-amino acids (Km 's approx. 0.3 mM and 2 mM) by rat brain cortex slices are characterized by a double affinity system, but that of L-phenylalanine has only one affinity system (Km = 0.23 mM). The Km 's have been calculated after subtracting the ouabain-insensitive passive uptakes of the amino acids from the total observed uptakes. 相似文献
1000.
Brucella abortus catalase is a periplasmic protein lacking a standard signal sequence. 总被引:1,自引:2,他引:1 下载免费PDF全文
A periplasmic catalase has been purified and cloned from Brucella abortus. The functional enzyme is a tetramer with a subunit molecular weight of 55,000. All evidence indicates that a typical N-terminal signal sequence is not associated with the export of this protein to the periplasm. 相似文献