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61.
Kenji Kato Su-wan Oh Hiroyuki Yamamoto Takayuki Hanazato Ikuko Yasuda Akira Otuki Masayuki Takahashi 《Ecological Research》1992,7(3):267-276
In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted
in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the
different enclosures ranged from 1.2 to 2.7×107 cells mL−1 throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was
6.3×105 cells mL−1 h−1. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed
a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures
then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not
less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria
shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already
stocked in the water column, though it is not known whether the dominant bacteria were the same. 相似文献
62.
A novel and efficient method for enzymatic synthesis of high purity maltose using moranoline (1-deoxynojirimycin). 总被引:1,自引:0,他引:1
S Maruo H Yamashita K Miyazaki H Yamamoto Y Kyotani H Ogawa M Kojima Y Ezure 《Bioscience, biotechnology, and biochemistry》1992,56(9):1406-1409
A transglycosylation reaction with moranoline (1-deoxynojirimycin) was done with soluble starch as the glucosyl donor and Bacillus macerans amylase as a cyclodextrin glycosyltransferase [EC 2.4.1.19]. The resultant transglycosylation products with moranoline, obtained by treating the reaction mixture with a strong cation exchange resin, were hydrolyzed by beta-amylase [EC 3.2.1.2] from sweet potatoes. The hydrolysate was treated with a strong cation exchange resin, and high purity maltose was obtained. 相似文献
63.
The gap theory in forest dynamics 总被引:4,自引:0,他引:4
Shin-Ichi Yamamoto 《Journal of plant research》1992,105(2):375-383
Since the late 1970s, ecologists interested in forest dynamics have focused their attention to the responses of individuals,
populations and communities to “gaps” which are openings created in the forest canopy. This review intended to introduce some
collective knowledge on major subjects of the gap theory in forest dynamics, in relation to gap-disturbance regimes, tree
regeneration behaviour and community structure. 相似文献
64.
Kunio Nakagawa Norio Omori Kahoko Hashimoto Tetsuya Yamamoto Takashi Tsunoda Tadao Nose 《Biotherapy》1992,4(2):109-115
Thein vitro effect of a combined treatment with lymphokine activated killer (LAK) cell and radiation therapy on rat brain tumor was examined using51Cr release assay. The tumor cell-line used in this experiment was 9L rat brain tumor derived from a Fischer 344 rat. LAK cells were obtained by culturing rat lymphocytes with recombinant human interleukin 2 for at least 3 days. The cytotoxic activity of the LAK cells was examined by51Cr release assay. Irradiation was done by exposing the microtiter plate in which the15Cr labeled 9L cells and LAK cells were cultured to a137Cs gamma cell unit. Without irradiation, there was 18% cytotoxicity in the 1:100 tumor-to-LAK cell ratio specimen after 24 hrs cocultivation. However, if 5 Gy of irradiation was given, followed by 12 hrs incubation, the cytotoxicity was enhanced significantly at the same cell ratio (30%). This enhancement effect was the most prominent when the cell ratio was 1:100 and the irradiation dose was 5 Gy. To generate the enhancement effect, an incubation time of over 8 hrs both before and after irradiation was required. The supernatant of the LAK cells showed 19.8% and 11.4% cytotoxicity with and without irradiation, respectively. This result indicates the participation of a cytotoxic factor released from LAK cells.This work is supported in part by grant from Univeristy of Tsukuba Project Research. 相似文献
65.
Formation of Nitrosylleghemoglobin in Nodules of Nitrate-Treated Cowpea and Pea Plants 总被引:1,自引:0,他引:1
The formation of nitrosylleghemoglobin (LbNO) was examined incowpea and pea nodules in relation to the inhibition of nitrogenfixation by nitrate. Leghemoglobin was of the ferrous type andwas mainly converted to LbNO in cowpea nodules when the acetylene-reducingactivity decreased to 45% of control values as a result of thesupply of nitrate. In nodules of nitrate-treated pea plants,leghemoglobin was also of the ferrous type and LbNO was a minorcomponent of leghemoglobin. The levels of LbNO isolated fromnodules corresponded to the levels of LbNO calculated from equilibriumconstants for LbNO and the concentration of nitrite in nodules.The dissociation rate constants for LbNO from both cowpea andpea were much smaller than those for LbO2 or LbCO, as is alsothe case in soybean. These results indicate that the inhibition of the functionsof leghemoglobin, due to the accumulation of LbNO, induces adecrease in nitrogen fixation in cowpea nodules, and that theinhibition of nitrogen fixation in pea nodules is not relatedto the formation of LbNO. (Received July 2, 1990; Accepted October 9, 1990) 相似文献
66.
Novel Technique for Measuring Tissue Firmness within Tomato (Lycopersicon esculentum Mill.) Fruit
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Developmental changes of tomato (Lycopersicon esculentum) fruit tissues during maturation were analyzed by a physically defined method (stress-relaxation analysis). The tip of a conical probe connected to a load sensor was positioned on the cut surface of a sliced tomato fruit, and the decay of the imposed stress was monitored. Stress-relaxation data thus obtained were used for the calculation of three stress-relaxation parameters. Different zones within tomato fruit harvested at six different ripening stages were analyzed. One of the stress-relaxation parameters, minimum stress-relaxation time (T0), decreased as the fruits matured. The decrease in T0 was first found in the core of the carpel junction within the endopericarp at the blossom end during the breaker stage. The decrease in T0 progressed from the blossom end, through the equatorial region and finally throughout the shoulder, as the fruit matured. In mature green fruit, T0 values within the placenta and the proximal carpel junction were lower than those by other parts of the fruit. For all measurements the maximum stress-relaxation time was not substantially changed during maturation, nor were their changes observed in different regions of the fruit. The observed relaxation rate was therefore correlated with softening. The results indicate that fruit softening may be physically associated with the stress-relaxation parameter, T0, and the extent of softening is a function of position within the fruit. Decreases in T0 value appear to be correlated with the reported regional variation in the appearance of polygalacturonase. 相似文献
67.
Zeaxanthin Formation and Energy-Dependent Fluorescence Quenching in Pea Chloroplasts under Artificially Mediated Linear and Cyclic Electron Transport 总被引:13,自引:5,他引:8
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Artificially mediated linear (methylviologen) and cyclic (phenazine methosulfate) electron transport induced zeaxanthin-dependent and independent (constitutive) nonphotochemical quenching in osmotically shocked chloroplasts of pea (Pisum sativum L. cv Oregon). Nonphotochemical quenching was quantitated as Stern-Volmer quenching (SVN) calculated as (Fm/F′m)-1 where Fm is the fluorescence intensity with all PSII reaction centers closed in a nonenergized, dark-adapted state and F′m is the fluorescence intensity with all PSII reaction centers closed in an energized state. Reversal of quenching by nigericin and electron-transport inhibitors showed that both quenching types were energy-dependent SVN. Under light-induced saturating ΔpH, constitutive-SVN reached steady-state in about 1 minute whereas zeaxanthin-SVN continued to develop for several minutes in parallel with the slow kinetics of violaxanthin deepoxidation. SVN above the constitutive level and relative zeaxanthin concentration showed high linear correlations at steady-state and during induction. Furthermore, Fo quenching, also treated as Stern-Volmer quenching (SVO) and calculated as (Fo/F′o)-1, showed high correlation with zeaxanthin and consequently with SVN (Fo and F′o are fluorescence intensities with all PSII reaction centers in nonenergized and energized states, respectively). These results support the view that zeaxanthin increases SVN above the constitutive level in a concentration-dependent manner and that zeaxanthin-dependent SVN occurs in the pigment bed. Preforming zeaxanthin increased the rate and extent of SVN, indicating that slow events other than the amount of zeaxanthin also affect final zeaxanthin-SVN expression. The redox state of the primary electron acceptor of photosystem II did not appear to determine SVN. Antimycin, when added while chloroplasts were in a dark-adapted or nonenergized state, inhibited both zeaxanthin-SVN and constitutive-SVN induced by linear and cyclic electron transport. These similarities, including possible constitutive Fo quenching, suggest that zeaxanthin-dependent and constitutive SVN are mechanistically related. 相似文献
68.
69.
The nanosecond fluorescence depolarization method was applied to measure the fluorescence lifetime () and the rotational correlation time () of bovine serum albumin (BSA) labeled with 1-dimethylaminonaphthalene-5-sulfonyl chloride (dansyl-Cl). Changes of and of dansyl BSA in the guanidine denaturation and in the thermal denaturation were examined. In parallel, the secondary structural change of dansyl BSA was followed by circular dichroism measurements. The magnitude of was almost unchanged between 1 and 2 M guanidine, where the secondary structure of the protein was predominantly disrupted; whereas that of began to increase before the disruption of secondary structure in the guanidine denaturation. In the thermal denaturation, in contrast, changes of both and occurred in a temperature range where the secondary structure was predominantly disrupted. The volume of equivalent sphere (V
e
) and the axial ratio () for the BSA were 3.6–3.8×10–19 cm3 and 3.6 at 2M guanidine as against 2.1×10–19 cm3 and 2.2 in the absence of guanidine (25°C), respectively. The magnitudes ofV
e
and were 4.9×10–19 cm3 and 4.5 at 65°C, respectively. Although the secondary structural change of dansyl BSA was irreversible in the thermal denaturation,V
e
and were reversible. 相似文献
70.