Agricultural Activities of a Meadow Eliminated Plant Litter from the Periphery of a Farmland in Inner Mongolia,China

The purpose of our investigation was to clarify the effects of agriculture on the process of loss of litter at the periphery of a farmland. This study revealed the generation process of an ecologically unusual phenomenon that is observed around cropland in semi-arid regions. We hypothesized that the vegetation around a farmland cannot supply plant litter to the ground surface because the ecological structure has been changed by agricultural activities. The study was conducted at Xilingol steppe, Xilingol League, Inner Mongolia Autonomous Region, China. Four study lines were established from the edge of an arable field to the surrounding meadow and parallel to the wind direction during the strong wind season. Key measurement for each line was set at the border between the farmland and steppe. Four study sites were set at intervals along each line. Plant litter, soil particle size distribution, plant species composition, plant volume, and species diversity were investigated. Despite using the same mowing method at the meadows of all study sites, the litter at the only periphery of the farmland completely disappeared. Soil particle size distribution in steppe, which was adjacent to the farmland, was similar to that of the farmland. Plant community structure at the periphery of the farmland was different from that of the far side from the farmland. This implies that soil scattered from the farmland affected the species composition of the steppe. Consequently, the change in plant community structure induced litter loss because of mowing. We concluded that plant litter was lost near the farmland because of the combined effects of farming and mowing. The results support our hypothesis that the vegetation around a farmland cannot supply plant litter because the ecological structure has been changed by agricultural activities.     

Isolation and Chemical Structure of New Oxidation Product of 5-Ketogluconic Acid,and a Hypothetical Pathway from Glucose to Tartaric Acid through this New Compound

In the course of study on the mechanism of the tartaric acid formation from 5-ketogluconic acid, a new intermediary substance with mauve color to Abdel-Akhel and Smith’s reagent was isolated from intact cell culture liquid. The chemical structure of this substance was determined as 1,2-dihydroxyethyl hydrogen L(+) tartrate from the results of hydrolysis experiments and from the identifications of the constituents of the molecule, and named “pretaric acid.” Tartaric acid was evidently produced from pretaric acid by intact cell culture. Clearly, then, pretaric acid appears to be an intermediate in the formation of tartaric acid from 5-ketogluconic acid. The authors assumed that in the formation of pretaric acid from 5-ketogluconic acid, a Baeyer-Villiger type oxidation occurred.     

Secondary structure of 5S RNA: NMR experiments on RNA molecules partially labeled with nitrogen-15

A method has been found for reassembling fragment 1 of Escherichia coli 5S RNA from mixtures containing strand III (bases 69-87) and the complex consisting of strand II (bases 89-120) and strand IV (bases 1-11). The reassembled molecule is identical with unreconstituted fragment 1. With this technique, fragment 1 molecules have been constructed 15N-labeled either in strand III or in the strand II-strand IV complex. Spectroscopic data obtained with these partially labeled molecules show that the terminal helix of 5S RNA includes the GU and GC base pairs at positions 9 and 10 which the standard model for 5S secondary structure predicts [see Delihas, N., Anderson, J., & Singhal, R. P. (1984) Prog. Nucleic Acid Res. Mol. Biol. 31, 161-190] but that these base pairs are unstable both in the fragment and in native 5S RNA. The data also assign three resonances to the helix V region of the molecule (bases 70-77 and 99-106). None of these resonances has a "normal" chemical shift even though two of them correspond to AU or GU base pairs in the standard model. The implications of these findings for our understanding of the structure of 5S RNA and its complex with ribosomal protein L25 are discussed.     

Methylation strongly enhances DNA bending in the replication origin region of the Escherichia coli chromosome

Summary Two-dimensional gel electrophoresis, at high and low temperatures, and gel mobilities of circularly permuted DNA segments showed a large bending locus about 50 bp downstream from the right border of the 245 by oriC box, a minimal essential region of autonomous replication on the Escherichia coli chromosome. Bending was strongly enhanced by Dam methylation. In DNA from a Dam^– strain, the mobility anomaly arising from altered conformation was much reduced, but was raised to the original level by methylation in vivo or in vitro. Enhancement of the mobility anomaly was also observed by hybrid formation of the Dam^– strand with the Dam⁺ strand. Near the bending center, GATC, the target of Dam methylase, occurs seven times arranged essentially on the same face of the helix with 10.5 by per turn. We concluded that small bends at each Dam site added up to the large bending detectable by gel electrophoresis.     

Salt tolerance of the reed plant Phragmites communis

Reed plants ( Phragmites communis Trinius) were grown at NaCl concentrations up to 500 m M and their growth, mineral contents and leaf blade osmotic potential were determined. Addition of NaCl up to 300 m M did not affect growth significantly. Sucrose, Cl^-and Na⁺ concentrations in the shoots increased with the salinity of the medium and the shoot water content decreased. K⁺ always contributed most to the leaf osmotic potential. Even in the presence of 250 m M NaCl in the rooting medium, the leaf blade contained only 50 mM Na⁺, suggesting that the plants have an efficient mechanism for Na⁺ exclusion. ²²Na⁺ uptake experiments suggested that the retranslo-cation of absorbed Na⁺ from shoots to the rooting medium lowered the uptake of Na⁺.     

Immuno-Gold Localization of Nitrogenase in Root Nodules of Elaeagnus pungens Thunb

The molybdenum-iron component of nitrogenase (Mo-Fe component)was purified from soybean nodule bacteroids and antibody wasraised against it in rabbits. Antibody raised against the 53kDa polypeptide which was the major protein in the Mo-Fe componentfraction of soybean nitrogenase was confirmed to be specificto the nitrogenase by immunodiffusion and immunotitration. Thenitrogenase from root nodules of Elaeagnus pungens cross-reactedwith the antibody and appeared from the results of the immunodiffusionto be partially identical to soybean nitrogenase. Using the antibody, we examined intracellular localization ofnitrogenase in root nodules of Elaeagnus pungens, in which Frankiais present as a symbiont, by immuno-gold labelling. Thin sectionsof nodules of Elaeagnus pungens were first treated with anti-nitrogenasespecific antibody and then with colloidal gold-protein A asa marker. The gold particles were observed to be concentratedin the vesicles of the endophyte Frankia. This provides strongsupport for the existence E of nitrogenase in the vesicles.Furthermore, our results suggested that nitrogenase localizesin the hyphae of the endophyte Frankia in Elaeagnus pungensnodules. ¹Present address: Iwata Experiment Station, Japan Tobacco Inc.,Iwata-gun, Shizuoka 438, Japan. (Received March 9, 1988; Accepted July 28, 1988)     

Prerequisite for the induction of lymphokine-activated killer cells from T lymphocytes

Human blood mononuclear cells were separated into Leu-11+7-NK, Leu-11-7+, and Leu-11-7-T cells by means of a combination of the Percoll gradient method and C-mediated cytolysis using mAb. When purified Leu-11+7-NK, Leu-11-7+, and Leu-11-7-T cells were cultured with rIL 2 (500 U/ml) for 6 days in a medium supplemented with 10% FCS, Leu-11+7-NK cells responded at the maximum level and Leu-11-7+ cells responded moderately as shown by both cell-proliferation response and cytotoxic activity generated. On the other hand, Leu-11-7-T cells did not respond at all to rIL-2. However, when Leu-11-7-T cells were cultured with rIL-2 in a medium supplemented with 10% autologous serum, they showed considerable responsiveness to rIL-2. In addition, much greater response to Leu-11-7-T cells were produced by the addition of monocytes. Monocyte cytokines, neither IL 1, IFN-gamma, TNF, nor their combination were able to substitute for monocytes in the induction culture. In contrast, the response level of Leu-11+7- NK cells remained unchanged irrespective of supplementation with autologous serum to medium or the addition of monocytes to the culture. These results indicated that culture conditions in the experiments significantly affected the results as to determination of lymphokine-activated killer cell precursors, especially the result pertaining to the conversion of T lymphocytes to lymphokine-activated killer cells. Under appropriate conditions, not only NK cells but also T cells are important precursors of lymphokine-activated killer cells.