The N-terminal sequence of ribosomal protein L10 from the archaebacterium Halobacterium marismortui and its relationship to eubacterial protein L6 and other ribosomal proteins

The amino-terminal sequence of ribosomal protein L10 from Halobacterium marismortui has been determined up to residue 54, using both a liquid- and a gas-phase sequenator. The two sequences are in good agreement. The protein is clearly homologous to protein HcuL10 from the related strain Halobacterium cutirubrum. Furthermore, a weaker but distinct homology to ribosomal protein L6 from Escherichia coli and Bacillus stearothermophilus can be detected. In addition to 7 identical amino acids in the first 36 residues in all four sequences a number of conservative replacements occurs, of mainly hydrophobic amino acids. In this common region the pattern of conserved amino acids suggests the presence of a beta-alpha fold as it occurs in ribosomal proteins L12 and L30. Furthermore, several potential cases of homology to other ribosomal components of the three ur-kingdoms have been found.     

Homology of Saccharomyces cerevisiae ADH4 to an iron-activated alcohol dehydrogenase from Zymomonas mobilis

Summary Insertion of the transposable element Ty at the ADH4 locus results in increased levels of a new alcohol dehydrogenase (ADH) activity in Saccharomyces cerevisiae. The DNA sequence of this locus has been determined. It contains a long open reading frame which is not homologous to the other ADH isozymes that have been characterized in S. cerevisiae nor does it show obvious homology to Drosophila ADH. The hypothetical ADH does, however, show strong homology to the sequence of an iron-activated ADH from the bacterium Zymomonas mobilis. Thus ADH4 appears to encode an ADH structural gene which, along with the Zymomonas enzyme, may define a new family of alcohol dehydrogenases.Now The Plant Cell Research Institute, Inc., 6560 Trinity Court, Dublin, CA 94568, USA     

Effect of supercooling and freezing on photosynthesis in freezing tolerant leaves of Afroalpine ‘giant rosette’ plants

Summary The effect of supercooling and freezing on the photosynthetic capability of representatives of the permanent frost hardy giant rosette plants Dendrosenecio keniodendron, D. brassica and Lobelia telekii, of the tropical alpine regions was investigated with the non-invasive chlorophyll a fluorescence technique. While supercooling, normal chlorophyll a fluorescence kinetics exhibiting the sequence 0, I, (D), P, S, M, were recorded, however with some retardation of both, the fast and the slow characteristics as compared to those obtained at day-time temperature. As long as the leaves remained unfrozen, the rise of the variable fluorescence F from the level 0 to P was inversely related to a drop of the temperature from about 0°C to-8°C. The increase of F with lower temperature is understood to result from a decrease of the velocity of the quenching reactions while photoreduction of the primary electron acceptor appeared to be unimpeded. The second fluorescence maximum (M), usually interpreted to indicate the commencement of the biochemical reactions of photosynthesis was consistenly to be observed during supercooling. Fluoescence induction kinetics of frozen leaves showed only fast rise to presumably F _max which was not followed by a significant decay for as long as 4 min. The lack of substantial quenching indicates that in the freeze-dehydrated state neither reoxidation of the primary acceptor nor energetization of the thylakoid membrane was accomplished. This effect however was immediately and fully reserved upon thawing of the leaves when the usual fluorescence induction kinetics as well as normal rates of CO₂-uptake were observed. Thus the permanent frost-hardy afroalpine plants do not exhibit any even short-term memory effect of the nocturnal frost on such a delicate process as is photosynthesis.     

The effect of grass maturing and root decay on N2O production in soil

The N₂O flux from the surface of grass-covered pots was only significant following grass maturing. Removal of the above-ground plant material resulted in an immediate and long-lasting increase in N₂O production in the soil. The results suggest that easily available organic matter from the roots stimulates the denitrification when the plants are damaged. Grass cutting might therefore result in a marked nitrogen loss through denitrification. The quantitative effect was equal in soil with and without succinate added. The size of the anaerobic zone around the roots is therefore sufficient to allow for denitrification activity mediated by increased organic matter availability because of plant cutting.     

Genetic demonstration of bidirectionality in the high affinity purine base transporter of mutant mouse S49 cells

A mutant cell line was selected from wild type S49 lymphoblasts that expressed a novel high affinity purine base transport system not found in parental cells or any other mammalian cell line (Aronow, B., Toll, D., Patrick, J., Hollingsworth, P., McCartan, K., and Ullman, B. (1986) Mol. Cell. Biol. 6, 2957-2962). In order to determine whether this nucleobase transport system was bidirectional, mutant cell lines possessing this high affinity base transport capability were derived from a nucleoside transport-deficient derivative of an adenylosuccinate synthetase-deficient S49 cell line. The resulting progeny excreted significantly greater amounts of purine into the cell culture medium than parental cells. This purine was identified as hypoxanthine. These results demonstrate genetically that the high affinity purine base transport system can mediate both the influx and efflux of hypoxanthine.     

Vertical distributions and relations of euphausiid populations off Elephant Island,March 1984

Summary Distributional relationships are described for post-larval and larval Euphausia superba and Thysanoessa sp. (probably macrura) and post-larval Euphausia frigida collected in 0–70/80 m and 0–175/200 m depth ranges with a MOCNESS sampler north of Elephant Island (61°S, 55°W) during 17–23 March 1984. Larval E. superba (predominantly calyptopes stage 2 and 3) were rare shallower than 80 m at night. Day catches of post-larval E. suberba were small and night catches were primarily near the top of the thermocline above 50 m depth. Thysanoessa sp. occurred throughout the 0–200 m depth range and was abundant in the upper 80 m both night and day. E. frigida migrated to the upper 80 m at night from deeper day depths. Larval stages of E. superba and bost-larval stages of all three species demonstrated independent and variable vertical distribution patterns both night and day. Changes in E. superba abundance and distributional patterns could to a certain extent be associated with observed environmental changes. An increase in larval and decrease in post-larval E. superba abundances between 0–80 m was associated with an intrusion of cold water at depth. At night, vertically restricted concentrations of post-larval E. superba were associated with shallow mixed layer depths, and a significant vertical separation of developmental stages and size categories was observed only during periods of stratification in the upper 80 m. Fluctuations in the distribution and abundance of Thysanoessa sp. and distribution of E. frigida did not appear to be influenced by physical parameters within the upper 80 m. Within the 0–80 m depth range, the distributions of these two species differed from each other and from E. superba and showed large tow to tow variability that could not be related to physical parameters in the upper water column.     

HIV testing: changing trends at a clinic for sexually transmitted diseases in London.

Trends in human immunodeficiency virus (HIV) counselling and antibody testing at a London clinic for sexually transmitted diseases showed substantial changes over a 12 month period. From around 100 a month in the summer of 1986 the numbers of people attending rose substantially to 276 in October 1986 and 475 in November at the time of the campaign in the popular press. They rose further still, to 700, at the time of AIDS (acquired immune deficiency syndrome) week in March 1987. In April they fell to the levels seen six months previously. Apart from this increase in overall numbers the proportions of women and heterosexual men who were seen increased.