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排序方式: 共有540条查询结果,搜索用时 15 毫秒
1.
Tazawa Masashi; Kurosawa Sachiko; Amino Shin-ichi; Tominaga Yoshito; Sakano Katsuhiro; Matsumoto Tomotaka 《Plant & cell physiology》1991,32(2):253-260
Rotational cytoplasmic streaming in leaves of Egeria densa wasinduced by light as well as by L-histidine (L-His). During bothtreatement with light and with L-His chloroplasts on the periclinalface were dislodged and moved to the anticlinal face where rotationalcytoplasmic streaming occurred. The effective concentrationof L-His was about 0.01 mM and the effect was almost saturatedat 0.1 mM. A derivative of L-His, 3-methyl-L-histidine, wasslightly less effective than L-His. By contrast, 1-methyl-L-histidinewas almost ineffective for induction of streaming, not onlyin Egeria but also in Vallisneria. Our resutlts are in markedcontrast to Fitting's result (1936) that 1-M-L-His is more effectivethan L-His. In Egeria, 1-methyl-L-His counteracted the stimulativeeffect of L-His. 1-Methyl-L-His penetrated into leaf cells ofEgeria to the same extent as 3-methyl-L-His and to a greaterextent than L-His. This observation excludes the possibilitythat the impermeability of leaves to 1-M-L-His might be responsiblefor its ineffectiveness. 1-M-L-His did not interfere with photodinesis.Differences in the mechanism of induction of rotational streamingby L-His and by light are discussed.
4 Present address: Fukui Institute of Technology, Gakuen, Fukui,910 Japan (Received July 16, 1990; Accepted December 20, 1990) 相似文献
2.
Tominaga Yoshito; Kuchitsu Kazuyuki; Katsuhara Maki; Tazawa Masashi; Miyachi Shigetoh 《Plant & cell physiology》1991,32(2):261-268
Rotational streaming of the cytoplasm including chloroplastswas induced by L-histidine, as well as by light, on the anticlinalface of leaf cells of Egeria densa. In the case of treatmentwith L-histidine some of the chloroplasts remained stationaryon the periclinal face of cells after rotational cytoplasmicstreaming was initiated. However, these chloroplasts were easilydislodged and translocated to the centrifugal end of the histidine-treatedcells by application of a centrifugal force that barely affectedthe location of chloroplasts in cells incubated in the darkwithout L-histidine. This result indicates that the anchoringof chloroplasts was weakened by L-histidine. Thus only the releaseof chloroplasts from anchoring was not enough for initiationof their streaming. The cytoplasmic pH (pHc) and vacuolar pH(pHv) were noninvasively monitored by in vivo 31P-nuclear magneticresonance (NMR) spectroscopy. Compared with the dark controlvalue, both illumination and treatment with L-histidine increasedthe pHc by 0.3 units. In contrast, pHv changed only a littlewith both illumination and treatment with L-histidine. Releaseof chloroplasts from anchoring and initiation of cytoplasmicstreaming are discussed in relation to the increase in pHc inducedby both light and L-histidine.
4 Present address: Department of Cell Biology, National Instituteof Agrobiological Resources, Kannondai, Tsukuba, Ibaraki, 305Japan
5 Present address: Marine Biotechnology Institute Co., Ltd.,Head Office, 2-35-10 Hongo, Bunkyo-ku, Tokyo, 113 Japan (Received July 16, 1990; Accepted December 20, 1990) 相似文献
3.
A series of isogenic transformable strains of Bacillus subtilis carrying the uvr-19 or rec-43 mutation or both were constructed. Both mutations made competent cells defective in repairing UV-irradiated cellular or transforming DNA, and their effects were additive in a doubly deficient strain, suggesting that two repair processes, requiring uvr-19+ and rec-43+ gene products, are independently functional in competent cells of B. subtilis. 相似文献
4.
Summary Sporulation and competent cell formation have been studied in four Bacillus subtilis strains, carrying septum-initiation mutations of different loci, div-31, div-341, div-12 and div-355 which exhibit filamentous growth at 45° C. The div-31 mutant was found to be defective in competence development at 30°–40°C whereas the div-12 mutant was affected only slightly. The div-341 and div-355 mutants showed lower competence, particularly at the higher temperatures. The four div mutant strains all showed poor sporulation at higher temperatures compared to the wild-type strain. We propose that some of the initial steps of septation are involved both in sporulation (possibly in forespore septum formation) and in competent cell formation and that these two processes share certain common features distinct from those in vegetative cell division. 相似文献
5.
M R Sadaie E Tschachler K Valerie M Rosenberg B K Felber G N Pavlakis M E Klotman F Wong-Staal 《The New biologist》1990,2(5):479-486
Ultraviolet light (UV) is known to cause activation of gene expression from the human immunodeficiency virus type 1 (HIV-1) promoter. To address the question of whether tat-defective HIV-1 provirus could be rescued by UV irradiation we examined its effect on HeLa cells containing integrated proviruses with tat mutations. Exposure of these cells to an optimal dose of UV resulted in the production of infectious viruses. The degree of UV activation and reversion to infectious virus appeared to depend on the nature of the original tat mutation. Two of the mutants required cocultivation with tat-expressing cells to fully generate replication competent viruses, while a third mutant required only cocultivation with H9 cells. Sequencing of cDNA from cells infected with this last mutant demonstrated that the parental mutant sequence was retained and that genotypic revertants to the wild-type as well as new mutant sequences were generated. These results suggest that tat-defective HIV-1 provirus can be activated by UV and can subsequently revert to wild-type virus. This study raises the possibility that UV exposure of immune cells in the skin plays a role in the activation of defective HIV-1 in vivo. 相似文献
6.
Satoshi Muraki Masahiro Yamasaki Yoshito Ehara Kunio Kikuchi Kunihiro Seki 《European journal of applied physiology and occupational physiology》1996,74(5):481-483
The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed
lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed
graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC)
were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen
uptake and peak heart rate was 1.41 ± 0.22 1·min−1 and 171.6 ± 19.2 beats·min−1, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest.
These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE. 相似文献
7.
Maria Ieda Siqueira Linhares Yoshito Eizuru Gildete Patriota de Andrade Ivailda Barbosa Fonseca Luiz Bezerra Carvalho Ivanildo Tenorio Moreira Yoichi Minamishima 《Microbiology and immunology》1994,38(6):475-478
The seroprevalence of human T cell leukemia virus type 1 (HTLV-1) infection was investigated in Brazilians (570): native inhabitants (298) and descendants from Japanese (272) living in Recife and its neighborhoods—North-east of Brazil. Furthermore, polytransfused renal transplanted patients (54) were also examined for the serological status to this virus. The seropositivity to HTLV-1, screened by enzyme-linked immunosorbent assay (ELISA), was low: 1.34% for the local population and 0.73% for the descendants from Japanese. However, the seropositivity for the renal transplanted patients was found to be 11.1%. This higher value suggests that this retrovirus infection seems to be of importance in this clinical condition. 相似文献
8.
9.
Spore coat protein synthesis in cell-free systems from sporulating cells of Bacillus subtilis.
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Cell-free systems for protein synthesis were prepared from Bacillus subtilis 168 cells at several stages of sporulation. Immunological methods were used to determine whether spore coat protein could be synthesized in the cell-free systems prepared from sporulating cells. Spore coat protein synthesis first occurred in extracts from stage t2 cells. The proportion of spore coat protein to total proteins synthesized in the cell-free systems was 2.4 and 3.9% at stages t2 and t4, respectively. The sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis patterns of immunoprecipitates from the cell-free systems showed the complete synthesis of an apparent spore coat protein precursor (molecular weight, 25,000). A polypeptide of this weight was previously identified in studies in vivo (L.E. Munoz, Y. Sadaie, and R.H. Doi, J. Biol. Chem., in press). The synthesis in vitro of polysome-associated nascent spore coat polypeptides with varying molecular weights up to 23,000 was also detected. These results indicate that the spore coat protein may be synthesized as a precursor protein. The removal of proteases in the crude extracts by treatment with hemoglobin-Sepharose affinity techniques may be preventing the conversion of the large 25,000-dalton precursor to the 12,500-dalton mature spore coat protein. 相似文献
10.
H Takamatsu S Fuma K Nakamura Y Sadaie A Shinkai S Matsuyama S Mizushima K Yamane 《Journal of bacteriology》1992,174(13):4308-4316
The putative amino acid sequence from the wild-type Bacillus subtilis div+ gene, which complements the temperature-sensitive div-341 mutation, shares a 50% identity with the sequence from Escherichia coli secA (Y. Sadaie, H. Takamatsu, K. Nakamura, and K. Yamane, Gene 98:101-105, 1991). The B. subtilis div-341 mutant accumulated the precursor proteins of alpha-amylase and beta-lactamase at 45 degrees C as in the case of sec mutants of E. coli. The div-341 mutation is a transition mutation causing an amino acid replacement from Pro to Leu at residue 431 of the putative amino acid sequence. The B. subtilis div+ gene was overexpressed in E. coli under the control of the tac promoter, and its product was purified to homogeneity. The Div protein consists of a homodimer of 94-kDa subunits which possesses ATPase activity, and the first 7 amino acids of the putative Div protein were found to be subjected to limited proteolysis in the purified protein. The antiserum against B. subtilis Div weakly cross-reacted with E. coli SecA. On the other hand, B. subtilis Div could not replace E. coli SecA in an E. coli in vitro protein translocation system. The temperature-sensitive growth of the E. coli secA mutant could not be restored by the introduction of B. subtilis div+, which is expressed under the control of the spac-1 promoter, and vice versa. The B. subtilis div+ gene is the B. subtilis counterpart of E. coli secA, and we propose that the div+ gene be referred to as B. subtilis secA, although Div did not function in the protein translocation system of E. coli. 相似文献