Genes for tryptophan biosynthesis in the halophilic archaebacterium Haloferax volcanii: the trpDFEG cluster.

Tryptophan auxotrophs of the archaebacterium Haloferax volcanii define a cluster of overlapping genes homologous to eubacterial-eukaryotic trpD, -F, -E, and -G, linked in that order and each preceded by a possible ribosome binding site. Residues involved in feedback inhibition of eubacterial anthranilate synthetases are conserved.     

Patterns of abundance variation in reef fishes near an artificial reef at Guam

Synopsis Development of the fish community on a submerged 16 m barge and variation in fish abundance on nearby transects were surveyed twice monthly for twenty months. A steady increase in abundance was observed for certain fishes on the barge, whereas a few species exhibited distinct seasonal variation on both the barge and transects. Most of the seasonal species settled between March and May.Some seasonal species appeared to be site selective in their settlement and consequently settled juveniles were clumped in their distribution. An abundance of preferred topographical features may be why settlement was relatively high at the study site and indirectly why predators became significantly (r₃ = 7.67^***, N = 37) more abundant at the study area during the months of maximum prey settlement. Concurrent settlement of several species during the same few months may be important because juveniles become an abundant food source to predators during those few months only. Periodic swamping of predators by abundant juvenile prey may improve the chances for individuals of rarer prey species to be overlooked and therefore be succesfully recruited.     

Regulation of amino acid transport in L6 muscle cells: I. Stimulation of transport system a by amino acid deprivation

The regulation of amino acid transport in L6 muscle cells by amino acid deprivation was investigated. Proline uptake was Na⁺-dependent, saturable and concentrative, and was predominantly through system A. Proline uptake was inhibited by alanine, α-amino isobutyric acid (AIB), and by α-methylamino isobutyric acid, but not by lysine or valine. At 25°C, Km of proline uptake was 0.5 mM. Amino acid-deprivation resulted in a progressive increase in the rate of proline uptake, reaching up to 6-fold stimulation after 6 hours. The basal and stimulated transport were equally Na⁺-dependent, and both were inhibited by competition with the same amino acids. Kinetic analysis showed that Km decreased by a factor of 2.4 and Vmax increased 1.9-fold in deprived cells. Amino acid-deprivation did not stimulate amino acid uptake through systems other than system A. This suggests that the higher Km in proline-supplemented cells is not due to release of intracellular amino acids into unstirred layers surrounding the cells. The presence of amino acids which are substrates of system A (including AIB) during proline-deprivation, prevented stimulation of proline uptake, whereas those transported by systems Ly⁺ or L exclusively were ineffective. The stimulation of the transport-rate in deprived cells could be reversed by subsequent exposure to proline or other substrates of system A. L6 cells, deprived of proline for 6 hours, retained the stimulation of transport after detachment from the monolayers with trypsin. Uptake rates were comparable in suspended and attached cells in monolayer culture. Thus, amino acid-depreivation of L6 cells results in an adaptive increase in proline uptake, which is not due to unstirred layers but appears to be mediated by other mechanisms of selective transport regulation.     

Abortion and the NHS: the first decade.

Analysis of statistics published since the Abortion Act showed that from 1972 about half the abortions carried out on residents of England and Wales had been performed within the National Health Service. Regional variations in the proportions of abortions performed within the NHS had persisted. In some health regions fewer abortions were being carried out than before. In 1975 about 40% of abortions on single women and women with no existing children were performed within the NHS. Trends in the concurrent sterilisation rate, gestational age at operation, duration of stay in hospital, and mortality and complication rates suggested a steady improvement in the effectiveness and efficiency of abortion services. Nevertheless, the NHS still compares poorly with the private sector and some other countries.     

Failure of phenobarbitone to prevent febrile convulsions.

One-hundred-sixty-five children without known neurological disorder who presented with their first febrile convulsion between the ages of six months and three years were assigned to daily phenobarbitone treatment or to a control group and followed up at a special clinic for six months. One-hundred-and-sixty-one-one children completed the trial, and of the 88 children assigned to phenobarbitone treatment 10 had further convulsions during this period compared with 14 of the 73 control children. Only 49 of those assigned to phenobarbitone took the drug regularly throughout the trial, and four of these had further febrile convulsions, a proportion not significantly different from that in the controls. All four had mean plasma phenobarbitone concentrations over 69 mumol/l (16 mug/ml) during the trial and in three the plasma concentration was at or over this figure within eight hours over 69 mumol/l (16 mug/ml) during the trial and in three the plasma concentration was at or over this figure within eight hours of the repeat convulsion. Regular phenobarbitone does not seem to prevent febrile convulsions. Attention should instead be directed to organising emergency services to allow early termination of fevrile convulsions, whether first or subsequent, to prevent irreversible brain damage.     

THE EFFECTS OF OUABAIN AND THE ACTIVATION OF NEURAL MEMBRANE ATPase BY BIOGENIC AMINES

Abstract— The effects of 10⁻⁵ m -noradrenaline (NA), 5-hydroxytryptamine (5-HT) and dopamine (DA) on the activities of Na⁺-K⁺ ATPase (EC 3.6.1.3) were studied in synaptic membranes from 6 regions of the rabbit brain. NA and 5-HT stimulated the synaptic membrane Na⁺-K⁺ ATPase from the cerebrum, but none of the amines influenced the activity of this enzyme in the other brain regions. The Na⁺-K⁺ ATPase activity of the cerebral synaptic membrane isolated at the 0.8/0.9 m & 0.9/1.0 m interphase of a sucrose density gradient was increased two-fold by 10⁻⁵ m -NA and 5-HT. The Na⁺-K ⁺ ATPase recovered at the 1.0/1.2 m interphase was not influenced by NA, DA or 5-HT. NA, DA and 5-HT did not activate the Mg ATPase of synaptic membranes from any of the 6 brain regions or whole brain synaptic vesicles. The cortex synaptic membrane (Na⁺-K⁺) ATPase is postulated to have a direct role in the uptake of the biogenic amines. An indirect role is proposed for this enzyme in amine uptake into brain stem.     

Transformations and fate of sheep urine-N applied to an upland U.K. pasture at different times during the growing season

The fate of sheep urine-N applied to an upland grass sward at four dates representing widely differing environmental conditions, was followed in soil (0–20 cm) and in herbage. Urine was poured onto 1-m² plots to simulate a single urination in August 1984 (warm and dry), May (cool), July and August 1985 (cool and wet) at rates equivalent to 40–52 g N m⁻². The transformation of urine-N (61–69% urea-N) in soil over a 6–7 week period followed the same general pattern when applied at different times during the season; rapid hydrolysis of urea, the appearance of large amounts of urine-N as ammonium in soil extracts, and the appearance of nitrate about 14 days after application. The magnitude of “apparent” nitrification however differed markedly with environmental conditions, being greatest in May 1985 when a maximum of 76% of the inorganic soil N was in the form of nitrate. At all other application dates nitrate levels were relatively low. With the August 1984 application soil inorganic N returned to control levels (given water only) after 31 days but considerable amounts remained in soil for 60–90 days with the other applications. Weekly cuts to 3-cm indicated that increases in herbage dry matter and N yields in response to urine application were greatest in absolute terms after the May 1985 application and continued for at least 70 days with all applications. Relative to control plots the May application resulted in a 3-fold increase in herbage DM compared with corresponding values of 6-, 5-, and 7-fold increases with the August 1984, July and August 1985 applications. Recovery of urine-N in herbage was poor averaging only 17% of that applied at different dates, while recovery in soil extracts was incomplete. The exact routes of loss (volatilisation, leaching, denitrification or immobilisation) were not quantified but it is evident that substantial amounts of urine-N can be lost from the soil-plant system under upland conditions.     

Change in microbial communities in acetate- and glucose-fed microbial fuel cells in the presence of light

Power densities produced by microbial fuel cells (MFCs) in natural systems are changed by exposure to light through the enrichment of photosynthetic microorganisms. When MFCs with brush anodes were exposed to light (4000 lx), power densities increased by 8–10% for glucose-fed reactors, and 34% for acetate-fed reactors. Denaturing gradient gel electrophoresis (DGGE) profiles based on the 16S rRNA gene showed that exposure to high light levels changed the microbial communities on the anodes. Based on 16S rRNA gene clone libraries of light-exposed systems the anode communities using glucose were also significantly different than those fed acetate. Dominant bacteria that are known exoelectrogens were identified in the anode biofilm, including a purple nonsulfur (PNS) photosynthetic bacterium, Rhodopseudomonas palustris, and a dissimilatory iron-reducing bacterium, Geobacter sulfurreducens. Pure culture tests confirmed that PNS photosynthetic bacteria increased power production when exposed to high light intensities (4000 lx). These results demonstrate that power production and community composition are affected by light conditions as well as electron donors in single-chamber air-cathode MFCs.     

Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities

Considerable uncertainty remains over how increasing atmospheric CO₂ and anthropogenic climate changes are affecting open‐ocean marine ecosystems from phytoplankton to top predators. Biological time series data are thus urgently needed for the world's oceans. Here, we use the carbon stable isotope composition of tuna to provide a first insight into the existence of global trends in complex ecosystem dynamics and changes in the oceanic carbon cycle. From 2000 to 2015, considerable declines in δ¹³C values of 0.8‰–2.5‰ were observed across three tuna species sampled globally, with more substantial changes in the Pacific Ocean compared to the Atlantic and Indian Oceans. Tuna recorded not only the Suess effect, that is, fossil fuel‐derived and isotopically light carbon being incorporated into marine ecosystems, but also recorded profound changes at the base of marine food webs. We suggest a global shift in phytoplankton community structure, for example, a reduction in ¹³C‐rich phytoplankton such as diatoms, and/or a change in phytoplankton physiology during this period, although this does not rule out other concomitant changes at higher levels in the food webs. Our study establishes tuna δ¹³C values as a candidate essential ocean variable to assess complex ecosystem responses to climate change at regional to global scales and over decadal timescales. Finally, this time series will be invaluable in calibrating and validating global earth system models to project changes in marine biota.