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.     

Glycolytic activity of rat aorta after exercise

Activities of glycolytic enzymes in the aorta were investigated in female Wistar rats. There were two groups of rats; one served as the control (sedentary rats), while the other group was forced to run on a treadmill for 10 weeks. In the control animals, the activities of hexokinase, phosphofructokinase and aldolase were relatively lower than those of the other glycolytic enzymes (phosphoglucose isomerase, lactate dehydrogenase and pyruvate kinase). After exercise, the activity of phosphofructokinase increased by 15%, whereas the other enzymatic activities were much the same as in the controls. Within the limits of the experiments, the increased percentage of phosphofructokinase was statistically significant (p less than 0.05). Since phosphofructokinase is a putative rate limiting enzyme, this enzymatic activation may indicate that glycolytic activity in the rat aorta is enhanced during and after running exercise.     

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.     

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.     

Purification and characterization of a protease from Xenopus embryos

A proteolytic enzyme was purified from Xenopus embryos. The purification procedure consisted of fractionation of an extract of embryos with acetone, gel filtration of Sephadex G-75 and chromatography on carboxymethyl-cellulose and hydroxylapatite. The preparation of enzyme appeared to be homogeneous as judged by electrophoresis in polyacrylamide gels. This protease had a molecular mass of 43-44 kDa and was composed of two subunits with molecular masses of 30 kDa and 13 kDa. The optimal pH of the reaction catalysed by the protease was approximately 4.0. This proteolytic activity was inhibited by antipain, leupeptin and iodoacetic acid; it was not affected by phenylmethylsulfonyl fluoride and pepstatin; and it was enhanced by dithiothreitol. In the presence of RNA, the optimal pH was shifted from pH 4.0 to pH 4.5. The protease was activated by addition of total RNA from Xenopus embryos, by poly(rU) or poly(rG). In contrast, after addition of tRNA or poly(rC), no activation of the protease was observed.     

A comparative study of three methods for intracellular loading of the calcium indicator aequorin in ferret papillary muscles

We compared the results of loading the bioluminescent Ca++ indicator aequorin by standard microinjection techniques to those obtained with two new chemical approaches to loading that utilize low concentrations of Ca++ chelator; i.e., 1) Immersion and 2) Macroinjection. After loading with the immersion and macroinjection methods, twitch tension returned to pre-load values indicating lack of damage to the muscles. The aequorin signals obtained with all three methods were similar and converted to similar quantitative values for [Ca++]i. Our data suggest that chemical loading (in particular macroinjection) may be preferable to microinjection, particularly in muscles with increased connective tissue content.