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31.
More than a 600-fold variation in nitrogen dioxide assimilation among 217 plant taxa 总被引:4,自引:0,他引:4
H. Morikawa A. Higaki M. Nohno M. Takahashi M. Kamada M. Nakata G. Toyohara Y. Okamura K. Matsui S. Kitani K. Fujita K. Irifune & N. Goshima 《Plant, cell & environment》1998,21(2):180-190
Assimilation of nitrogen dioxide in response to fumigation with 15 N-labelled nitrogen dioxide was studied in 217 plant taxa. The taxa included 50 wild herbaceous plants collected from roadsides (42 genera, 15 families), 60 cultivated herbaceous plants (55 genera, 30 families) and 107 cultivated woody plants (74 genera, 45 families). Two parameters, the 'NO2 -N content', or NO2 -derived reduced nitrogen content in fumigated plant leaves (mg N g–1 dry weight), and the 'NO2 -utilization index', or percentage of the NO2 -derived reduced nitrogen in the total reduced nitrogen, were determined. The NO2 -N content differed 657-fold between the highest ( Eucalyptus viminalis ; 6·57) and lowest ( Tillandsia ionantha and T. caput-medusae ; 0·01) values in the 217 taxa; 62-fold in a family (Theaceae) and 26-fold in a species ( Solidago altissima ). Nine species had NO2 -utilization indices greater than 10%, of which Magnolia kobus , Eucalyptus viminalis , Populus nigra , Nicotiana tabacum and Erechtites hieracifolia had NO2 -N contents > 4·9. These plants can be considered 'NO2 -philic' because in them NO2 -nitrogen has an important function(s). The Compositae and Myrtaceae had high values for both parameters, whereas the monocots and gymnosperms had low ones. These findings suggest that the metabolic pathway of NO2 -nitrogen differs among plant species. The information presented here will be useful for creating a novel vegetation technology to reduce the atmospheric concentration of nitrogen dioxide. 相似文献
32.
Yasuhiro Ohshima Mitsutoshi Tsukimoto Takato Takenouchi Hitoshi Harada Akina Suzuki Mitsuru Sato Hiroshi Kitani Shuji Kojima 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010
Background
Ionizing irradiation causes not only growth arrest and cell death, but also release of growth factors or signal transmitters, which promote cancer malignancy. Extracellular ATP controls cancer growth through activation of purinoceptors. However, there is no report of radiation-induced ATP release from cancer cells. Here, we examined γ-irradiation-induced ATP release and its mechanism in B16 melanoma.Methods
Extracellular ATP was measured by luciferin–luciferase assay. To investigate mechanism of radiation-induced ATP release, we pharmacologically inhibited the ATP release and established stable P2X7 receptor-knockdown B16 melanoma cells using two short hairpin RNAs targeting P2X7 receptor.Results
Cells were exposed to 0.5–8 Gy of γ-rays. Extracellular ATP was increased, peaking at 5 min after 0.5 Gy irradiation. A selective P2X7 receptor channel antagonist, but not anion transporter inhibitors, blocked the release of ATP. Further, radiation-induced ATP release was significantly decreased in P2X7 receptor-knockdown cells. Our results indicate that γ-irradiation evokes ATP release from melanoma cells, and P2X7 receptor channel plays a significant role in mediating the ATP release.General Significance
We suggest that extracellular ATP could be a novel intercellular signaling molecule released from cancer cells when cells are exposed to ionizing radiation. 相似文献33.
Abe T Kakehata S Kitani R Maruya S Navaratnam D Santos-Sacchi J Shinkawa H 《The Journal of membrane biology》2007,215(1):49-56
The development of motor protein activity in the lateral membrane of the mouse outer hair cell (OHC) from postnatal day 5
(P5) to P18 was investigated under whole-cell voltage clamp. Voltage-dependent, nonlinear capacitance (C
v), which represents the conformational fluctuations of the motor molecule, progressively increased during development. At
P12, the onset of hearing in the mouse, C
v was about 70% of the mature level. C
v saturated at P18 when hearing shows full maturation. On the other hand, C
lin, which represents the membrane area of the OHC, showed a relatively small increase with development, reaching steady state
at P10. This early maturation of linear capacitance is further supported by morphological estimates of surface area during
development. These results, in light of recent prestin knockout experiments and our results with quantitative polymerase chain
reaction, suggest that, rather than the incorporation of new motors into the lateral membrane after P10, molecular motors
mature to augment nonlinear capacitance. Thus, current estimates of motor protein density based on charge movement may be
exaggerated. A corresponding indicator of motor maturation, the motor’s operating voltage midpoint, V
pkcm, tended to shift to depolarized potentials during postnatal development, although it was unstable prior to P10. However,
after P14, V
pkcm reached a steady-state level near −67 mV, suggesting that intrinsic membrane tension or intracellular chloride, each of which can modulate V
pkcm, may mature at P14. These developmental data significantly alter our understanding of the cellular mechanisms that control
cochlear amplification and provide a foundation for future analysis of genetic modifications of mouse auditory development. 相似文献
34.
The P2X7 receptor (P2X7R) is an ATP-gated ion channel highly expressed in microglia. P2X7R plays important roles in inflammatory responses in the brain. However, little is known about the mechanisms regulating its functions in microglia. Lysophosphatidylcholine (LPC), an inflammatory phospholipid that promotes microglial activation, may have some relevance to P2X7R signaling in terms of microglial function. In this study, we examined its effects on P2X7R signaling in a mouse microglial cell line (MG6) and primary microglia. LPC facilitated the sustained increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)) through P2X7R channels activated by ATP or BzATP. The potentiated increase in [Ca(2+)](i) was actually inhibited by P2X7R antagonists, brilliant blue G and oxidized ATP. The potentiating effect of LPC was not observed with P2Y receptor systems, which are also expressed in MG6 cells. G2A, a receptor for LPC, was expressed in MG6 cells, but not involved in the facilitating effect of LPC on the P2X7R-mediated change in [Ca(2+)](i). Furthermore, LPC enhanced the P2X7R-associated formation of membrane pores and the activation of p44/42 mitogen-activated protein kinase. These results suggest that LPC may regulate microglial functions in the brain by enhancing the sensitivity of P2X7R. 相似文献
35.
36.
Mutations in the helix termination motif of mouse type I IRS keratin genes impair the assembly of keratin intermediate filament 总被引:1,自引:0,他引:1
Tanaka S Miura I Yoshiki A Kato Y Yokoyama H Shinogi A Masuya H Wakana S Tamura M Shiroishi T 《Genomics》2007,90(6):703-711
Two classical mouse hair coat mutations, Rex (Re) and Rex wavy coat (Re(wc)), are linked to the type I inner root sheath (IRS) keratin genes of chromosome 11. An N-ethyl-N-nitrosourea-induced mutation, M100573, also maps close to the type I IRS keratin genes. In this study, we demonstrate that Re and M100573 mice bear mutations in the type I IRS gene Krt25; Re(wc) mice bear an additional mutation in the type I IRS gene Krt27. These three mutations are located in the helix termination motif of the 2B alpha-helical rod domain of a type I IRS keratin protein. Immunohistological analysis revealed abnormal foam-like immunoreactivity with an antibody raised to type II IRS keratin K71 in the IRS of Re/+ mice. These results suggest that the helix termination motif is essential for the proper assembly of types I and II IRS keratin protein complexes and the formation of keratin intermediate filaments. 相似文献
37.
38.
Yano S Suyotha W Honda A Takagi K Rattanakit-Chandet N Wakayama M Tachiki T 《Bioscience, biotechnology, and biochemistry》2011,75(2):299-304
Chitinase I (CHI1) of Bacillus circulans KA-304 forms protoplasts from Schizophyllum commune mycelia when the enzyme is combined with α-1,3-glucanase of B. circulans KA-304. CHI1 consists of an N-terminal unknown region and a C-terminal catalytic region classified into the glycoside hydrolase family-19 type. An N-terminal region-truncated mutant of CHI 1 (CatCHI1), which was expressed in Escherichia coli Rosetta-gami B (DE3), lost colloidal chitin- and powder chitin-binding activities. The colloidal chitin- and the powder chitin-hydrolyzing activities of CatCHI1 were lower than those of CHI1, and CatCHI1 was not effective in forming the protoplast. A fusion protein of the N-terminal region of CHI1 and green fluorescent protein (Nterm-GFP) was expressed in E. coli, and the fusion protein was adsorbed to colloidal chitin, powder chitin, and chitosan. Fluorescence microscopy analysis showed that Nterm-GFP bound to the S. commune cell-wall. 相似文献
39.
Yano S Haruta H Ikeda T Kikuchi T Murakami M Moriguchi M Wakayama M 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2011,879(29):3247-3252
D-Aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (AxD-NAase) offers a novel biotechnological application, the production of D-amino acid from the racemic mixture of N-acyl-DL-amino acids. However, its substrate specificity is biased toward certain N-acyl-D-amino acids. To construct mutant AxD-NAases with substrate specificities different from those of wild-type enzyme, the substrate recognition site of the AxD-NAase was rationally manipulated based on computational structural analysis and comparison of its primary structure with other D-aminoacylases with distinct substrate specificities. Mutations of amino acid residues, Phe191, Leu298, Tyr344, and Met346, which interact with the side chain of the substrate, induced marked changes in activities toward each substrate. For example, the catalytic efficiency (k(cat)/K(m)) of mutant F191W toward N-acetyl-D-Trp and N-acetyl-D-Ala was enhanced by 15.6- and 1.5-folds, respectively, compared with that of the wild-type enzyme, and the catalytic efficiency (k(cat)/K(m)) of mutant L298A toward N-acetyl-D-Trp was enhanced by 4.4-folds compared with that of the wild-type enzyme. Other enzymatic properties of both mutants, such as pH and temperature dependence, were the same as those of the wild-type enzyme. The F191W mutant in particular is considered to be useful for the enzymatic production of D-Trp which is an important building block of some therapeutic drugs. 相似文献
40.