Influence of Environmental Factors on Interstrain Competition in Rhizobium japonicum

The effect of several biotic and abiotic factors on the pattern of competition between two strains of Rhizobium japonicum was examined. In two Minnesota soils, Waseca and Waukegan, strain USDA 123 occupied 69% (Waseca) and 24% (Waukegan) of the root nodules on Glycine max L. Merrill cv. Chippewa. USDA 110 occupied 2% of the root nodules in the Waseca soil and 12% of the nodules in the Waukegan soil. Under a variety of other growth conditions—vermiculite, vermiculite amended with Waseca soil, and two Hawaiian soils devoid of naturalized Rhizobium japonicum strains—USDA 110 was more competitive than USDA 123. The addition of nitrate to or the presence of antibiotic-producing actinomycetes in the rhizosphere of soybeans did not affect the pattern of competition between the two strains. However, preexposure of young seedings to USDA 110 or USDA 123 before transplantation into soil altered the pattern of competition between the two strains significantly. In the Waseca soil, preexposure of cv. Chippewa to USDA 110 for 72 h increased the percentage of nodules occupied by USDA 110 from 2 to 55%. Similarly, in the Hawaiian soil Waimea, nodule occupancy by USDA 123 increased from 7 to 33% after a 72-h preexposure.     

Effects of short-term administration of sex hormones on normal and autoimmune mice

The effects of short-term administration (2 to 4 wk) of sex hormones on the immune system of normal (C57BL/6) and autoimmune (C57BL/6-lpr, C3H/lpr, B/W) strains of mice were investigated. Both estrogen (E2) and testosterone (Te) had significant effects on the numbers of T and B cells as well as on the density of cell surface antigens as demonstrated by flow cytometry. For example, Te depleted Thy-1.2+ thymocytes in normal mice and brought about a shift to lower density cells. Lyt-2+ cells appeared to be the main target cells of hormonal modulation in normal and autoimmune mice. Both sex hormones significantly depleted these cells in the thymus but had differential effects in the peripheral lymphoid organs, particularly in the spleen. In general, E2 depleted Lyt-2+ cells, whereas Te increased or maintained this subpopulation of cells in spleen and lymph nodes. Similarly, the suppressor cell activity and IL 2 production on a per cell basis in E2-treated animals was diminished, whereas Te-treated animals had normal or enhanced activity. The relevance of these findings to differential sex susceptibility in autoimmune diseases is discussed.     

Inhibition of plasma prolactin in the rat by amantadine

A single iv injection of 15 or 30 but not 7.5 mg/kg BW of an antiviral drug, amantadine, significantly (P less than 0.05) decreased plasma prolactin (PRL) concentrations in male rats. This effect was dose-dependent, with the highest dose producing a longer-lasting decrease in plasma PRL. The amantadine-induced decrease was unaffected by a simultaneous injection of 5-hydroxytryptophan (30 mg/kg BW) but was completely blocked by a simultaneous injection of haloperidol (0.05 mg/kg BW). It is concluded that this novel effect of amantadine on PRL is produced by an interaction with the dopaminergic system.     

Asplenetin,a flavone and its glycoside from Launaea asplenifolia

A new flavone, asplenetin, has been isolated from Launea asplenifolia and characterized as 5,7,3′,4′,5′-pentahydroxy-3-(3-methylbutyl)flavone. Its glycoside, asplenetin 5-O-neohesperidoside, is also reported.     

Solvent influence on rate and mechanism of oxidation of ethylenediaminetetraacetatocobaltate(II) by periodate

The kinetics of the oxidation of Co^II(EDTA)²⁻ by IO₄⁻ were studied in various ethanol + water mixtures covering the range 7.9 to 58.0 wt% ethanol, at five different temperatures in the range 15–35 °C. The effect of solvent on the rate and mechanism of the reaction was investigated. An inner-sphere mechanism for the reaction was proposed and supported by the calculated activation parameters.     

A rapid procedure for DNA sequencing using transposon-promoted deletions in Escherichia coli

A simple procedure has been developed for sequencing long fragments of DNA. The fragment (which can be several kb in length) is cloned in pAA3.7X, and subdivided into many overlapping segments by Tn9-promoted deletions. The deletions are isolated by positive selection for galactose resistance. A rapid plasmid preparation from several hundred galactose-resistant colonies is fractionated by agarose gel electrophoresis to pick a series of deletions terminating at approx. 200-bp intervals across the entire length of the fragment. Selected plasmids are purified by rapid alkaline extraction, and used directly for supercoil sequencing with a primer derived from IS1. Sequences of adjacent deletions contain overlaps which are used to connect individual sequences to give the complete sequence.     

Analysis of the shape of P vs I curves of a natural phytoplankton assemblage during the year in the mesotrophic Lake Maarsseveen (I), The Netherlands

Production versus light response curves were made of natural phytoplankton assemblages during the year in an incubator at 8 different light intensities ranging from 60 to 1500 Einstein.m^–2.sec^–1. The shape of these curves is analyzed in relation to the sensitivity for photo-inhibition. At the end of the month of April, there is a sudden shift in this sensitivity at higher light intensities. The algal assemblage becomes less sensitive for photo-inhibition. The influence of light-adaptation, temperature, nutrient limitation and species composition is discussed.     

Phosphoglucose isomerase isozymes in teleostean fishes from the Arabian Gulf

Two phosphoglucose isomerases (PGI) with different electrophoretic mobilities have been found in all groups of teleostean fishes studied, with the exception of the Clupeomorpha. PGI proved to be a good taxonomic criterion to differentiate members of the Nemipteridae, Sciaenidae, Platycephalidae and Stromateidae from the other teleost families.     

Spectral shifting by dyes to enhance algae growth

The photosynthetic growth action spectrum of a green alga at three bands of visible light (blue, orange, and red) at fixed quanta input and under light-limiting conditions was measured in a batch cultivation system. Quantum efficiencies (biomass dry weight increment per quanta absorbed) were better in the yellow-red region than in the blue region. Results served as a basis for the design and optimization of a dye system that would shift the energy of solar radiation to the required wavelength range by absorbing ultraviolet to blue radiation and emitting in the yellow-red, thus enhancing algae growth. Direct incorporation of dyes into the growth medium, although theoretically expected to enhance growth, in fact resulted in dye decomposition, toxicity to algae and consequently in growth inhibition. Indirect application of dyes in a double tubular reactor (algae inside and dye solution outside) demonstrated growth enhancement for certain dyes with high quantum yields and stability, which had suitable absorption/emission spectra for artificial light sources used. The maximum indirect growth enhancement was obtained using rhodamine 6G at a concentration of 3x10(-5)M with tungsten filament lamp sources.