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41.
Nitrogen-fixing (acetylene-reducing) activity of intact saplings ofAlnus maximowiczii was measured under natural conditions in the subalpine zone of Mt Fuji. The nitrogen-fixing activity was detected from the
middle of June when expansion of leaves had just begun to the end of October when the shedding of leaves was almost completed.
Diurnal changes in the activity were almost parallel with those of ground temperature. The measured nitrogen-fixing activity
was related to ground temperature and total leaf area. Using this relation, annual nitrogen fixation was estimated from the
data of ground temperature and leaf area measured in the field. The amount of annual nitrogen fixation was almost the same
as that of nitrogen used for annual growth. It was concluded that nitrogen fixation by nodules made a considerable contribution
to the nitrogen economy in the saplings ofA. maximowiczii. 相似文献
42.
Tan Kah-Siew; Hoson Takayuki; Masuda Yoshio; Kamisaka Seiichiro 《Plant & cell physiology》1992,33(2):103-108
Irradiation of white fluorescent light (5 W m2) inhibitedthe growth of Oryza coleoptiles. Light irradiation increasedstress-relaxation parameters of coleoptile cell walls, minimumstressrelaxationtime and relaxation rate, and decreased cellwall extensibility (strain/load). Under light conditions, thecontents of ferulic and diferulic acids ester-linked to thehemicellulosic arabinose residue in cell walls increased andcorrelated with the modification of the cell wall mechanicalproperties. These results suggest that light irradiation enhancesthe formation of diferulic acid bridges in hemicelluloses, makingcell walls mechanically rigid and thus inhibits cell elongationin rice coleoptiles. Also, irrespective of coleoptile age orthe presence of light, the ratio of diferulic acid to ferulicacid was almost constant, suggesting that the rate limitingstep in the formation of diferulic acid bridges in Oryza cellwalls is in the step of feruloylation. (Received September 24, 1991; Accepted December 3, 1991) 相似文献
43.
Aiko Kiso Koushi Hidaka Tooru Kimura Yoshio Hayashi Azin Nezami Ernesto Freire Yoshiaki Kiso 《Journal of peptide science》2004,10(11):641-647
Plasmepsin (Plm) has been identified as an important target for the development of new antimalarial drugs, since its inhibition leads to the starvation of Plasmodium falciparum. A series of substrate-based dipeptide-type Plm II inhibitors containing the hydroxymethylcarbonyl isostere as a transition-state mimic were synthesized. The general design principle was provision of a conformationally restrained hydroxyl group (corresponding to the set residue at the P2' position in native substrates) and a bulky unit to fit the S2' pocket. 相似文献
44.
45.
H. Akagi A. Nakamura R. Sawada M. Oka T. Fujimura 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(7-8):948-951
Twelve Japanese rice cultivars were converted to CMS by asymmetric protoplast fusion with MTC-5A, the cytoplasm of which was derived from an indica rice, Chinsurah Boro II. With the exception of the cybrids that had a nucleus from Hoshiyutaka, most of these cybrid plants were sterile. The unique sequence downstream from the mitochondrial atp6 of MTC-5A was specifically amplified in the sterile cybrid plants by PCR. All progenies of the cybrid plants carrying this unique sequence were sterile. On the other hand, in some of the sterile cybrid plants in which the unique sequence was not amplified by PCR, fertility was recovered in their progenies. Somaclonal mutation may have caused sterility in these cybrids. Only the cybrid plants that had the unique sequence detected by PCR were CMS. Thus, the CMS plants can be selected rapidly and easily by PCR, at an early stage of plant regeneration. Soon after transplanting the regenerated plants to a green house, fertile cybrids and sterile cybrids produced by somaclonal mutation can be removed. These findings also show that the unique region downstream from atp6 is tightly linked with the CMS phenotype. 相似文献
46.
Concanavalin A (Con A) suppresses auxin-induced elongation ofsurface-abraded segments from both dicotyledonous and poaceousplants. In coleoptile segments of rice (Oryza sativa L.), theauxin-induced decrease in the minimum stress-relaxation timeand increase in the mechanical extensibility of the cell wallswere also inhibited by Con A, indicating that the lectin suppresseselongation by inhibiting the cell wall loosening. Auxin causeda decrease in the level of (1 3), (1 4)-ß-D-glucansin the cell walls of rice coleoptile segments, and this decreasewas also inhibited by the lectin. Con A suppressed the autolytichydrolysis of the glucans, as well as their breakdown in vitroby a protein fraction that had been extracted from the cellwalls of rice coleoptiles with 1 M NaCl. Furthermore, most ofthe glucan-hydrolyzing activity of the wall proteins bound toa Con A-Sepharose column, suggesting that glycoprotein enzymesare involved in the hydrolysis. Although Con A also affectedthe hydrolysis of other wall polysaccharides, the present data,when considered in combination with the inhibitory effects ofglucan-specific or glucanasespecific antibodies, support theview that the breakdown of (1 3),(1 4)-ß-D-glucansis associated with the cell wall loosening that is responsiblefor auxin-induced elongation in Poaceae. (Received August 17, 1994; Accepted February 15, 1995) 相似文献
47.
Reorientation of Cortical Microtubules in the Sub-Apical Region during Tuberization in Single-Node Stem Segments of Potato in Culture 总被引:6,自引:0,他引:6
The initial events in tuberization were examined in single-nodestem segments of potato, in which the tuberization was easilyregulated in culture. The addition of 8% sucrose to the culturemedium caused the cessation of elongation of lateral shootsand the swelling of the sub-apical region of each shoot. Swellingwas first induced by lateral cell expansion, which was followedby periclinal cell division. The divided cells then expandedlaterally. The alteration in the direction of growth was accompaniedby the reorientation of arrays of cortical microtubules (MTs),which was monitored by immunofluorescence microscopy. Cellsin the sub-apical region of elongating shoots had prominenttransverse arrays of MTs. The MTs in swelling cells were orientedlongitudinally with respect to the axis of the shoot. Finally,the arrays of MTs became completely disorganized. By contrast,the elongation of lateral shoots continued in GA3-treated segmentsand the cells in the sub-apical region of such shoots retainedconspicuous transverse arrays of MTs during culture, even inthe presence of a high concentration (8%) of sucrose. (Received July 2, 1994; Accepted May 19, 1995) 相似文献
48.
Kunio Koshimura Yasutaka Takagi Soichi Miwa †Tsuneo Kido ‡Yasuyoshi Watanabe Yoshio Murakami Yuzuru Kato Tomoh Masaki 《Journal of neurochemistry》1995,65(2):827-830
Abstract: 6R-l -erythro-Tetrahydrobiopterin (6R-BH4) is a cofactor for aromatic l -amino acid hydroxylases and nitric oxide synthase. Recently, we have reported that independently of its cofactor activities, 6R-BH4 acts from the outside of neurons in the brain to enhance the release of monoamine neurotransmitters such as dopamine. To characterize the pharmacological properties of the action, we examined the effects of 6S-BH4, a diastereoisomer of 6R-BH4, on dopamine release in the rat striatum by using brain microdialysis and compared its effects with those of 6R-BH4. Perfusion of 6S-BH4 or 6R-BH4 through the dialysis probe increased extracellular dopamine levels (an index of in vivo dopamine release) concentration dependently; the maximal increase by 6S-BH4, was one-sixth of that by 6R-BH4. 6S-BH4 increased extracellular DOPA levels in the presence of NSD 1015, an inhibitor of aromatic l -amino acid decarboxylase (an index of in vivo tyrosine hydroxylase activity), to an extent similar to the increase induced by 6R-BH4. The increase in the DOPA levels induced by either of the pteridines was abolished after pretreatment of rats with α-methyl-p-tyrosine (an inhibitor of tyrosine hydroxylase). Under the same conditions, the 6S-BH4-induced dopamine release was abolished, but most of the 6R-BH4-induced increase persisted. Coadministration of 6S-BH4 with 6R-BH4 inhibited the increase in dopamine release induced by 6R-BH4 alone. These results show that 6R-BH4 stimulates dopamine release by acting at the specific recognition site on the neuronal membrane, and that 6S-BH4 acts as an antagonist of 6R-BH4 at this site, although it has cofactor activities. 相似文献
49.
Shigeki Furuya Miho Sera Rie Tohno-oka Kazuyuki Sugahara Koichiro Shiokawa Yoshio Hirabayashi 《Development, growth & differentiation》1995,37(3):337-346
The expression of heparan sulfate glycosaminoglycan (HS-GAG) was examined in Xenopus embryos during the developmental stages. Chemical analysis showed the existence of HS-GAG in the 35 S-labeled embryos. By western blot analysis using a specific anti-HS monoclonal antibody, HS-GAG related epitope was found after the neurulation on two protein bands, whose molecular weights were approximately 90 kDa and 100 kDa, respectively. Immunohistochemistry revealed that HS-GAG occurred exclusively in the animal hemisphere in early gastrulae, and then appeared predominantly on the sheath of the neural tube, the notochord and epithelium. To address whether HS-GAG chains contribute to Xenopus embryonic development, we eliminated the embryonic HS-GAG by injecting purified Flavobacterium heparitinases (HSase) into their blastocoels. Most of the injected embryos were aberrant in mesodermal and neural formation, and became acephalic. Histological examination showed that these embryos were completely devoid of the central nervous system and the mesodermal tissues. Neither heat-inactivated heparitinase nor chondroitinase showed such abnormality. The HS-GAG-eliminated embryos showed decreased expression of both muscular and neural-specific markers. These results suggest that HS-GAG plays an indispensable role in establishing the fundamental body plan during early Xenopus development. 相似文献
50.
Rika Morishita Shinsuke Saga Noriko Kawamura †Yoshio Hashizume ‡Toshiaki Inagaki Kanefusa Kato Tomiko Asano 《Journal of neurochemistry》1997,68(2):820-827
Abstract: The localization of two forms of the γ subunit of G proteins, γ3 and γ12, was examined in the mammalian brain. Concentrations of these two γ subunits increased markedly, as did those of glial fibrillary acidic protein, during postnatal development in the rat cerebral cortex. In aged human brains, by contrast, the concentration of γ3 tended to decrease with age, whereas that of γ12 in the temporal cortex increased slightly. An immunohistochemical study of human brains revealed that γ3 was abundant in the neuropil, whereas γ12 was localized in glial cells. In the hippocampal formation of aged human brains, levels of γ12-positive cells, as well as levels of glial fibrillary acidic protein- and vimentin-positive astrocytes, increased, in particular in the CA1 subfield and the prosubiculum, in which there was a decrease in the number of pyramidal cells. The appearance of γ12-positive cells associated with the loss of pyramidal cells was also observed in the hippocampus of rats that had been treated with kainic acid. These results indicate that γ12 is strongly expressed in reactive astrocytes. In a study of cultured neural cells, we found that γ12 was predominant in glioma cells, such as C6 and GA-1 cells, in contrast with the specific localization of γ3 in PC12 pheochromocytoma cells, which are neuron-like cells. Taken together, the results indicate that γ3 and γ12 are selectively expressed in neuronal and glial cells, respectively, and that concentrations of γ3 and γ12 in the brain are related to the numbers and/or extent of maturation of these cells. 相似文献