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.     

Apical trehalase expression associated with cell patterning after inducer treatment of LLC-PK1 monolayers

Trehalase, a differentiation-specific marker of renal proximal tubule brush border membrane, is expressed in confluent long-term cultures of the renal epithelial cell line LLC-PK1. The level of trehalase is greatly increased after treatment of cultures with differentiation inducers such as hexamethylene bisacetamide (HMBA), accompanied by increases in other apical membrane-associated differentiated functions (Yoneyama and Lever: J. Cell. Physiol. 121: 64-73, 1984). In the present study, we utilize a polyclonal antibody specific for renal trehalase to demonstrate that trehalase expression induced in LLC-PK1 cultures after HMBA treatment is localized in cells forming a three-dimensional network of strands across the confluent monolayer. The antitrehalase antibody recognized an apical membrane antigen of apparent molecular weight 100-110 kD both in LLC-PK1 cultures and in the corresponding pig renal brush border membranes. Strand formation and total trehalase activity increased in parallel as a function of inducer concentration and duration of exposure. Strand formation and trehalase expression were also greatly enhanced in monolayers grown on a Nuclepore filter support even in the absence of inducer. Strand formation was not a prerequisite for induced trehalase expression in culture, since strands did not develop in cultures treated with N, N'-dimethylformamide (DMF) and equally potent inducer of trehalase expression. In this case, cells which expressed increased levels of trehalase were dispersed at random over the monolayer. Induction of strand formation and trehalase expression by HMBA required a minimum exposure period of 48 hr and persisted up to a week after removal of inducer. By contrast, the response to DMF required continuous presence of inducer. Levels of trehalase declined even in the continuous presence of inducer in local regions of low cell density created by wound-repair of the monolayer. In addition to the membrane-bound form, trehalase activity was also recoverable from the culture medium, but release of trehalase was not affected by inducers. These observations are consistent with the view that a cell type committed to express a program of differentiation after HMBA treatment or growth on a permeable support is organized in specific cell patterns visible as strands over the confluent cell monolayer.     

Decrease of palmitoyl-CoA elongation in platelets and leukocytes in the patient of hereditary methemoglobinemia associated with mental retardation

Effect of the deficiency of NADH-cytochrome b5 reductase on fatty acid elongation was studied in the platelets and leukocytes taken from a patient of hereditary methemoglobinemia associated with mental retardation. The activity of fatty acid elongation was determined by measuring the incorporation of [2-14C]malonyl-CoA into palmitoyl-CoA. The de novo biosynthesis of fatty acids was blocked by the addition of phosphotransacetylase, and the elongation system could be assayed in the homogenates separated from de novo biosynthesis. As compared to normal subjects approximately 40% decrease of fatty acid elongation was observed both in the platelets and leukocytes from the patient.     

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.     

Transgenic tobacco resistant to a bacterial disease by the detoxification of a pathogenic toxin

Summary Some plant pathogens produce toxins which cause disease in infected plants. One of the pathogenic toxins, tabtoxin, is produced by Pseudomonas syringae pv. tabaci, which causes wildfire of tobacco. A tabtoxin resistance gene (ttr) coding for an acetyltransferase isolated from Pseudomonas syringae pv. tabaci was fused to the 35S promoter of the cauliflower mosaic virus (CaMV) to construct a chimeric gene for introduction into tobacco cells by Agrobacterium-mediated transformation. The transgenic tobacco plants showed high specific-expression of the ttr gene and no chlorotic symptoms caused by tabtoxin treatment or with infection by Pseudomonas syringae pv. tabaci. These results demonstrate a successful approach to obtain disease-resistant plants by detoxification of the pathogenic toxins which play an important role in pathogenesis.     

Variations in the Natural Abundance of 15N in Nitrogenous Fractions of Komatsuna Plants Supplied with Nitrate

Komatsuna (Brassica campestris L. var. rapa) plants were grownhydroponically under various conditions with respect to thesupply of nitrate, and the variations in levels of natural ¹⁵Nabundance (¹⁵N) in nitrogenous fractions of leaf blades, petiolesplus midribs, and roots in these plants were analyzed. The fractionation of nitrogen isotopes during uptake of nitratewas null irrespective of the concentrations of nitrate in theculture medium. The roots had lower ¹⁵N values than that inthe nitrate applied to plants. The nitrate in the three tissuesexamined had higher ¹⁵N values than that in the nitrate applied:the values were highest in the leaf blades which were presumedto have highest activities in terms of reduction of nitrate.In contrast, the amino acids and residual fractions had lower¹⁵N values than those in the nitrate applied. These resultssuggest that reduction of nitrate is a critical step in thefractionation of nitrogen isotopes in plant tissues in vivo. ¹Permanent address: Fukuoka Agricultural Experiment Station,Yoshiki 587, Chikushino, 818 Japan. (Received March 10, 1989; Accepted July 10, 1989)     

Functional alterations induced by fusarium T-2 toxin in Madin-Darby bovine Kidney (MDBK) and primary fetal bovine Kidney (PFBK) cultures

We recently reported that primary fetal bovine Kidney (PFBK) cells were consistently more sensitive to the cytotoxic effects of fusarium T-2 toxin than Madin-Darby bovine kidney (MDBK) cells in culture. The present report examined the influence of T-2 on selected biochemical parameters of these two culture types. T-2 toxin inhibited incorporation of labeled thymidine, uridine, and leucine in both culture types; at lower concentrations of the toxin, PFBK cells were affected to a greater extent than MDBK cells. T-2 toxin inhibited both the transport of thymidine as well as thymidine incorporation into macromolecules in MDBK cells during initial periods, but did not affect uridine incorporation. The cellular enzymes, K⁺- dependent phosphatase and succinic dehydrogenase were inhibited in MDBK but not in PFBK cultures; acid phosphatase was not influenced in either culture types. In a cell-free system none of the above enzymes were affected by T-2 until the toxin concentration exceeded 10^?5M.