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21.
Takayuki Hoson Seiichiro Kamisaka Yoshio Masuda Masamichi Yamashita 《Journal of plant research》1992,105(1):53-70
We developed a three-dimensional (3-D) clinostat to simulate a microgravity environment and studied the changes in plant growth processes under this condition. The rate of germination of cress (Lepidium sativum), maize (Zea mays), rice (Oryza sativa), pea (Pisum sativum), or azuki bean (Vigna angularis) was not affected on the clinostat. The clinostat rotation did not influence the growth rate of their roots or shoots, except for a slight promotion of growth in azuki roots and epicotyls. On the contrary, the direction of growth of plant organs clearly changed on the 3-D clinostat. On the surface of the earth, roots grow downward while shoots upward in parallel to the gravity vector. On the 3-D clinostat, roots of cress elongated along the direction of the tip of root primordia after having changed the direction continuously. Rice roots also grew parallel to the direction of the tip of root primordia. On the other hand, roots of maize, pea, and azuki bean grew in a random fashion. The direction of growth of shoots was more controlled even on the 3-D clinostat. In a front view of embryos, shoots grew mostly along the direction of the tip of primordia. In a side view, rice coleoptiles showed an adaxial (toward the caryopsis) while coleoptiles of maize and epicotyls of pea and azuki bean an abaxial curvature. The curvature of shoots became larger with their growth. Such an autotropism may have an important role in regulation of life cycle of higher plants under a microgravity environment. 相似文献
22.
Kah-Siew Tan Takayuki Hoson Yoshio Masuda Seiichiro Kamisaka 《Physiologia plantarum》1991,83(3):397-403
Rice ( Oryza sativa L. cv. Sasanishiki) coleoptiles grown under water achieved greater length than those grown either in air or under water with constant air bubbling. The extensibility of cell walls in coleoptiles grown under water was larger than that in the other treatments. Per unit length of the coleoptile, the content of ferulic and diferulic acids ester-linked to hemicelluloses was higher in air and bubbling type coleoptiles than in water type ones. The extensibility of the coleoptile cell walls correlated with the content of diferulic acids per unit length and per hemicellulose, suggesting that the enhancement of the formation of diferulic acid bridges in hemicelluloses in air or under water with air bubbling makes the cell walls mechanically rigid; thereby inhibiting cell elongation in rice coleoptiles. In addition, the ratio of diferulic acid to ferulic acid was almost constant irrespective of coleoptile age, zone and growth conditions, suggesting that the feruloylation of hemicelluloses is rate-limiting in the formation of diferulic acid bridges in the cell walls of rice coleoptiles. 相似文献
23.
Inhibition of auxin-induced elongation and xyloglucan breakdown in azuki bean epicotyl segments by fucose-binding lectins 总被引:3,自引:0,他引:3
Auxin-induced elongation of epicotyl segments of azuki bean ( Vigna angularis Ohwi and Ohashi cv. Takara) was suppressed by fucose-binding lectins from Tetragonolobus purpureus Moench and Ulex europaeus L. These lectins also inhibited auxin-induced cell wall loosening (decrease in the minimum stress-relaxation time of the cell walls) of segments. Auxin caused a decrease in molecular mass of xyloglucans extracted with 24% KOH from the cell walls. The lectins inhibited auxin-induced changes in molecular mass of the xyloglucans. The autolytic release of xylose-containing products from the pectinase-treated cell walls was also suppressed by the lectins. Fucose-binding lectins pretreated with fucose exhibited little or no inhibitory effect on auxin-induced elongation, cell wall loosning, or breakdown of xyloglucans. These results support the view that the breakdown of xyloglucans is involved in the cell wall loosening responsible for auxin-induced elongation in dicotyledons. 相似文献
24.
Xyloglucan nonasaccharide (XG9) is recognized as an inhibitorof 2,4-D-induced long-term growth of segments of pea stems.In the presence of 105 M 2,4-D, inhibition by 109M XG9 of elongation of third internode segments of pea seedlingswas detected within 2 h after the start of incubation, in someexperiments. Analysis by double-reciprocal (Lineweaver-Burk)plots of elongation in the presence of various concentrationsof 2,4-D, with or without XG9, gave parallel lines, indicatingthat XG9 inhibited 2,4-D-induced elongation in an uncompetitivemanner. XG9 did not influence the 2,4-D-induced cell wall loosening.Thus, XG9 does not fulfill the proposed definition of an "antiauxin". XG9 at 1011 to 106 M did not influence IAA-inducedelongation of segments from pea third internodes, azuki beanepicotyls, cucumber hypocotyls, or oat coleoptiles. Inhibitionof IAA-induced elongation by XG9 was not observed even whenthe segments from pea or azuki bean were abraded. Furthermore,fucosyl-lactose at 1011 to 104 M did not affectthe IAA-induced elongation of segments of pea internodes orof azuki bean epicotyls. XG9 may be incapable of inhibitingthe IAA-induced cell elongation (especially in oat) or, alternatively,the endogenous levels of XG9 may be so high that exogenouslyapplied XG9 has no inhibitory effect on IAA-induced elongation. (Received February 28, 1991; Accepted May 25, 1991) 相似文献
25.
26.
Reverse effect of gram-positive bacteria vs. gram-negative bacteria on adjuvant-induced arthritis in germfree rats 总被引:5,自引:0,他引:5
O Kohashi Y Kohashi T Takahashi A Ozawa N Shigematsu 《Microbiology and immunology》1985,29(6):487-497
Germfree (GF) F344 rats developed severe adjuvant-induced arthritis with a 100% incidence after a single intradermal injection of heat-killed Mycobacterium bovis (BCG). Specific pathogene-free (SPF) rats developed less severe arthritis with a lower incidence. The rats colonized with Escherichia coli or Bacteroides developed mild disease comparable to that in SPF rats. The rats colonized with Bifidobacterium, Propionibacterium acnes, Lactobacillus casei, L. fermentum, L. murini, and L. acidophilus developed more severe disease than that in GF rats. Furthermore, the rats colonized with a mixture of E. coli and the above lactobacilli developed very mild disease similar to that in SPF rats. These results suggest that gram-negative bacteria, such as E. coli and Bacteroides, may suppress the disease, possibly through their lipopolysaccharides, and may be responsible for the lower susceptibility of SPF rats; gram-positive bacteria, such as Bifidobacterium, P. acnes, and lactobacilli, may enhance the disease, possibly through their peptidoglycans; and E. coli may play a dominant role in modulating the development of adjuvant-induced arthritis. 相似文献
27.
Summary The effect of cholecystokinin (CCK) and internal Ca2+ on outward K+ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 × 10–10
M) applied to the bath evoked a marked increase in the outward K+ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca2+. When strongly buffered Ca2+-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca2+ concentration ([Ca2+]
i
) from 5 × 10–10
M to 10–7 and 5 × 10–7
M mimicked the effect of CCK. It would appear therefore that CCK controls K+ conductance in the acinar cells via changes in the internal free ionized Ca2+ concentration. 相似文献
28.
Binding sites for atrial natriuretic peptide, ANP-(99-126) were studied in lymphoid organs of the rat with quantitative autoradiography. Tissue sections were incubated in the presence of 0.13 nM 125I-ANP-(99-126) followed by autoradiography using [3H]-Ultrofilm, and the results were analyzed by computerized densitometry and comparison to 125I-standards. Specific ANP binding sites were localized in the medulla and the cortex of the rat thymus and in the white pulp of the rat spleen, with apparent binding sites concentrations of 93, 65, and 126 fmol/mg protein, respectively. The presence of ANP binding sites in areas related to the maturation and function of lymphocytes, and to the production of thymic hormones, suggests the possibility of a role of circulating ANP in the modulation of the immune response. 相似文献
29.
Yoshiya Shigematsu Ken Tsukahara Tomoaki Tanaka Michio Takeuchi Dr. Eiji Ichishima 《Current microbiology》1986,13(1):43-46
The molecular properties, such as molecular weight, N-and C-terminal amino acids, amino acid composition, and circular dichroism, of 1,2--mannosidase isolated from the culture filtrate ofAspergillus saitoi were determined.The enzyme had aK
m of 0.67 mM andk
cat of 1.27/s with mannobiose at pH 50.0 and 30°C. The anomeric configuration of the reaction products of the enzyme was examined by studying the -anomer. A single Manl2Man linkage in intact Taka-amylase A fromAspergillus oryzae was hydrolyzed, producing free mannose. 相似文献
30.
Conformations of the cyclic tetrapeptide cyclo(L -Pro-Sar)2 in solution were studied by 1H- and 13C-nmr spectrometry and model building. The nmr data provide definite evidence that this cyclic peptide exists chiefly in two conformations, namely, a C2-symmetric conformation and an asymmetric structure. The former was demonstrated to be predominant in polar solvents (100% in Me2SO-d6). This structure contains all cis-peptide bond linkages and all trans′ Pro Cα?CO bonds. It represents the first cyclic tetrapeptide in which all four peptide bonds have been found in the cis-conformation. As the polarity of the solvent decreases, the population of C2-symmetric conformers decreases (88% in CD3CN and 65% in CDCl3). At the same time, a minor asymmetric conformer, characterized by cis-cis-cis-trans peptide bond sequences (two cis Sar-Pro bonds, one cis Pro-Sar bond, and one trans Pro-Sar bond), is seen to increase (9% in CD3CN and 30% in CDCl3). A proposed predominant conformation in solution for cyclo(L -Pro-Sar)2 was compared with a crystal structure, as reported in an accompanying paper. Both structures show striking overall similarities. 相似文献