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991.
Summary Specimen preparation protocols that allow field emission scanning electron microscope imaging of microtubules in plant cells were developed, involving simultaneous permeabilization with saponin and stabilization of microtubules with taxol. All categories of microtubule array were observed in onion root tip cells and in tobacco BY-2 cells grown in suspension culture and synchronized to provide high frequencies of mitotic stages. Cortical arrays consist of overlapping microtubules with free ends; individual microtubules directly overlie individual microfibrils in the cell wall. Preprophase bands and spindle microtubule bundles were also imaged. Phragmoplasts revealed early stages of wall deposition in the included cell plates and features interpreted as relating to high rates of microtubule turnover at the growing margins. It was possible to combine high resolution three-dimensional imaging with immunogold labelling of microtubules. Individual gold particles were readily distinguished decorating microtubules in the preparations; the method should be vaulable for studying many features of plant cell microtubules and their associated macromolecules.Abbreviations FESEM
field emission gun scanning electron microscope
- MTSB
microtubule stabilising buffer
Dedicated to Professor Eldon H. Newcomb in recognition of his contributions to cell biology 相似文献
992.
Oleosin genes in maize kernels having diverse oil contents are constitutively expressed independent of oil contents 总被引:2,自引:0,他引:2
Julie T. L. Ting Keunmyoung Lee Chandra Ratnayake Kathryn A. Platt Ronald A. Balsamo Anthony H. C. Huang 《Planta》1996,199(1):158-165
In seeds, the subcellular storage oil bodies have a matrix of oils (triacylglycerols) surrounded by a layer of phospholipids embedded with abundant structural proteins called oleosins. We used two maize (Zea mays L.) strains having diverse kernel (seed) oil contents to study the effects of varying the oil and oleosin contents on the structure of the oil bodies. Illinois High Oils (IHO, 15% w/w oils) and Illinois Low Oils (ILO, 0.5%) maize kernels were the products of breeding for diverse oil contents for about 100 generations. In both maize strains, although the genes for oil synthesis had apparently been modified drastically, the genes encoding oleosins appeared to be unaltered, as revealed by Southern blot analyses of the three oleosin genes and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with immunoblotting of the oleosins. In addition, both strains contained the same three oleosin isoforms of a defined proportion, and both accumulated oils and oleosins coordinately. Oleosins in both strains were restricted to the oil bodies, as shown by analyses of the various subcellular fractions separated by sucrosedensity-gradient centrifugation. Electron microscopy of the embryos and the isolated organelles revealed that the oil bodies in IHO were larger and had a spherical shape, whereas those in ILO were smaller and had irregular shapes. We conclude that in seeds, oleosin genes are expressed independent of the oil contents, and the size and shape of the oil bodies are dictated by the ratio of oils to oleosins synthesized during seed maturation. The extensive breeding for diverse oil contents has not altered the apparent mechanism of oil-body synthesis and the occurrence of hetero-dimer or -multimer of oleosin isoforms on the oil bodies.Abbreviations IHO
Illinois High Oils
- ILO
Illinois Low Oils
This work was supported by a USDA NRICGP grant. We thank Dr. J.W. Dudley of the University of Illinois for the IHO and ILO maize kernels, and Dr. W. Thomson for discussion on the stereological method. 相似文献
993.
Inhibition of Neuronal Nitric Oxide Synthase by 7-Nitroindazole Protects Against MPTP-Induced Neurotoxicity in Mice 总被引:25,自引:4,他引:21
Jörg B. Schulz Russell T. Matthews Miratul M. K. Muqit Susan E. Browne M. Flint Beal 《Journal of neurochemistry》1995,64(2):936-939
Abstract: Several studies suggest that nitric oxide (NO• ) contributes to cell death following activation of NMDA receptors in cultured cortical, hippocampal, and striatal neurons. In the present study we investigated whether 7-nitroindazole (7-NI), a specific neuronal nitric oxide synthase inhibitor, can block dopaminergic neurotoxicity seen in mice after systemic administration of MPTP. 7-NI dose-dependently protected against MPTP-induced dopamine depletions using two different dosing regimens of MPTP that produced varying degrees of dopamine depletion. At 50 mg/kg of 7-NI there was almost complete protection in both paradigms. Similar effects were seen with MPTP-induced depletions of both homovanillic acid and 3,4-dihydroxyphenylacetic acid. 7-NI had no significant effect on dopamine transport in vitro and on monoamine oxidase B activity both in vitro and in vivo. One mechanism by which NO• is thought to mediate its toxicity is by interacting with superoxide radical to form peroxynitrite (ONOO− ), which then may nitrate tyrosine residues. Consistent with this hypothesis, MPTP neurotoxicity in mice resulted in a significant increase in the concentration of 3-nitrotyrosine, which was attenuated by treatment with 7-NI. Our results suggest that NO• plays a role in MPTP neurotoxicity, as well as novel therapeutic strategies for Parkinson's disease. 相似文献
994.
Abstract: The effects of nitroprusside and S -nitrosocysteine, compounds that generate nitric oxide (NO), on synaptosomal energy-producing pathways and energy level were investigated. The decrease in respiration was much faster and more pronounced with S -nitrosocysteine than with nitroprusside. S -Nitrosocysteine, at 10 µ M , inhibited by 80% respiration with glucose and succinate (plus rotenone) in intact synaptosomes and with ascorbate/cytochrome c in broken preparations. Oxygenated hemoglobin reversed and/or prevented the inhibition, whereas glutathione (GSH) prolonged it. Under aerobic conditions, the synaptosomal energy level (creatine phosphate/creatine and ATP/ADP ratios) was reduced by the presence of S -nitrosocysteine, whereas lactate generation was enhanced. The effects on energy parameters were greater at 5 min than at 15 min of incubation and were more pronounced in the presence of GSH. Under strictly anaerobic conditions, lactate production was reduced by the NO-generating compounds in a concentration-dependent manner. It is concluded that (a) inhibition of oxidative phosphorylation by NO leads to a fall in the synaptosomal energy level, which in turn stimulates glycolysis; (b) glycolysis can be inhibited by higher concentrations of the radical; and (c) inhibitory effects on the energy-generating pathway and ATP level could contribute to NO toxicity under some in vivo situations. 相似文献
995.
林麝妊娠期和哺乳期的能量代谢特征 总被引:17,自引:5,他引:12
本文对饲养条件下林麝妊娠期和哺乳期的能量需要和行为特征进行了研究。结果表明,妊娠初期和妊娠后期能量摄取量分别比孕前增加了48.9%和95.6%。哺乳期总摄入能比妊娠期分别高2.27倍(双胎)和1.89倍(单胎)。根据在繁殖期对麝的行为观察,我们推断:麝是通过增加采食时间来增加能量的摄取,并通过减少活动,增加躺卧时间来减少能量消耗,以此满足繁殖期的能量需要。这些将结果为制定麝繁殖期的饲养标准和管理措施提供了依据。 相似文献
996.
肌球蛋白微丝在高压力下的解离和重组 总被引:1,自引:0,他引:1
高压力下肌球蛋白微丝的解离研究表明,在1-650bar压力下肌球蛋白微丝的解离是完全可逆的,在5℃时其解离平衡常数的对数lgK=-129,解离标准体积变化为2088ml/mol。研究还指出,由肌球蛋白聚合成肌球蛋白微丝的熵是+148.5kcal/mol(20℃),表明这是一熵驱动的自发过程,连续二次加压解离动力学研究结果暗示,肌球蛋白二体是肌球蛋白微丝解离过程中的中间体。 相似文献
997.
998.
Y Shimazaki E. Eguchi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(5):661-671
1. | After the intact compound eyes of the butterflyPapilio xuthus were adapted to darkness, white, blue ( max 460 nm) or orange light ( max 580 nm), the eyes were separated into the distal (primary pigment cells, the dioptric apparatus and ca. 30% of retinal tissue) and the proximal layers (the rest of the retinal tissues). Each layer was separated into a supernatant and a precipitate. Both in white and blue light-adapted eyes, the amount of 11-cis 3-hydroxyretinal increased in the supernatant of the distal layer (Sup-DL) much more than it did in dark-adapted eyes. No increase was observed in the Sup-DL of orange light-adapted eyes. |
2. | When all-trans retinol (non-native chemical) was added to the Sup-DL, it was converted to all-trans retinal under the darkness, and to all-trans and 11-cis retinal by blue light irradiation. When all-trans retinal was added to the Sup-DL, the isomerization of all-trans retinal to 11-cis retinal was accelerated by the blue light. |
3. | The Sup-DL was separated into ammonium sulfate soluble (AS-sup) and insoluble (AS-ppt) fractions. The AS-ppt fraction contained 3-hydroxyretinal but no 3-hydroxyretinol. Blue light irradiation to the AS-ppt fraction induced an increase in 11-cis 3-hydroxyretinal, with a concomitant decrease in all-trans 3-hydroxyretinal. |
999.
Summary Conidia ofFusarium oxysporum f. sp.vasinfectum started to germinate on the roots of cotton (Gossypium barbadense L.) 6 h after inoculation and formed a compact mycelium covering the root surface. 18 h later, penetration hyphae branched off and infected the root. The number of penetration hyphae increased with the number of conidia used for inoculation. The optimal temperature for penetration was between 28 and 30 °C. The highest numbers of penetration hyphae were found in the meristematic zone, 40 percent less in the elongation and root hair zones, and none in the lateral root zone. The fine structure of the infection process was studied in protodermal cells of the meristematic zone and in rhizodermal cells of the elongation zone. The penetration hyphae were well preserved after freeze substitution and showed a Golgi equivalent consisting of three populations of smooth cisternae. Plant reactions were found already during fungal growth on the root surface. In the meristematic zone, a thickening of the plant cell wall due to an apposition of dark and lightly staining material below the hyphae occurred. This wall apposition increased in size around the hypha invading the plant cell and led to the formation of a prominent wall apposition with finger-like projections into the host cytoplasm. In the elongation zone, the deposits around the penetration hypha appeared less thick and the dark inclusions were less pronounced. High pressure freezing of infected cells revealed, thatF. oxysporum penetrates and grows within the host cells without inducing damages such as plasmolysis, cell degeneration or even host necrosis. We suggest thatF. oxysporum has an endophytic or biotrophic phase during colonization of the root tips.Abbreviation Ph
penetration hyphae 相似文献
1000.