Influence of different chemical treatments on transport of Alcaligenes paradoxus in porous media.

Seven chemicals, three buffers, and a salt solution known to affect bacterial attachment were tested to quantify their abilities to enhance the penetration of Alcaligenes paradoxus in porous media. Chemical treatments included Tween 20 (a nonionic surfactant that affects hydrophobic interactions), sodium dodecyl sulfate (an anionic surfactant), EDTA (a cell membrane permeabilizer that removes outer membrane lipopolysaccharides), sodium PPi (a surface charge modifier), sodium periodate (an oxidizer that cleaves surface polysaccharides), lysozyme (an enzyme that cleaves cell wall components), and proteinase K (a nonspecific protease that cleaves peptide bonds). Buffers included MOPS [3-(N-morpholino)propanesulfonic acid], Tris, phosphate, and an unbuffered solution containing only NaCl. Transport characteristics in the porous media were compared by using a sticking coefficient, alpha, defined as the rate at which particles stick to a grain of medium divided by the rate at which they strike the grain. Tween 20 reduced alpha by 2.5 orders of magnitude, to alpha = 0.0016, and was the most effective chemical treatment for decreasing bacterial attachment to glass beads in buffered solutions. Similar reductions in alpha were achieved in unbuffered solutions by reducing the solution ionic strength to 0.01 mM. EDTA, protease, and other treatments designed to alter cell structures did not reduce alpha by more than an order of magnitude. The number of bacteria retained by the porous media was decreased by treatments that made A. paradoxus more hydrophobic and less electrostatically charged, although alpha was poorly correlated with electrophoretic mobility and hydrophobicity index measurements at lower alpha values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diisopropylfluorophosphate-interacting proteinases of nuclei of rat testis cells

Nuclei and chromatin of seminiferous epithelial cells of rat testis contain acid-extractable and non-extractable proteins which interact readily with [³H]DFP (diisopropylfluorophosphate). Proteinase activity is closely associated with these DFP-interacting proteins, and the proteinase activities are inhibited by DFP and PMSF. DFP-interacting proteins of testis chromatin increase greatly in amount at 26–32 days after birth when spermatids are appearing in increasing numbers. In nuclei separated by zonal centrifugation on sucrose gradients, the DFP-labeled proteins are highest in activity in the elongated spermatids at the stage in spermiogenesis at which histones are being replaced by testis-specific proteins and protamines. Electrophoresis in SDS-polyacrylamide gels reveals the presence of three species of DFP-interacting proteins in nuclei of seminiferous epithelial cells of the testis. The chromatin of epididymal spermatozoa of the rat contains three or four species of DFP-interacting proteins by SDS-polyacrylamide electrophoresis and some of these labeled proteins co-migrate with two of the three basic proteins which are observed during electrophoresis on polyacrylamide gels in Triton-urea.     

Thermal stratification and benthic foraging patterns of white sucker

Abundances of white sucker, 100–500 mm FL, were not significantly different among the epilimnia, metalimnia and portions of the hypolimnia shallower than 20 m in each of two lakes. However, small suckers < 200 mm were captured most frequently in the epilimnion and no white suckers were captured in the deepest region, 20–38 m, of the two lakes. White suckers consumed prey from all three temperature zones in each lake. Prominent food items were Hyalella azteca and the chironomid larvae Heterotrissocladius, Djalmabatista and Procladius. Despite differences in relative densities of benthic invertebrates among thermal zones of the two lakes, suckers in neither lake foraged exclusively on prey of epilimnetic origin. Suckers captured in the metalimnia foraged on invertebrates that were common to all three thermal zones. And, only 0–4% of the suckers captured in the hypolimnia of the two lakes contained prey that were unique to the epilimnia. Suckers caught in the hypolimnia mainly consumed deep water invertebrates; 83% of the suckers foraged in the metalimnion and hypolimnion of Islets Lake and 45% foraged in the hypolimnion in Burnt Island Lake. Consequently there was little evidence of a massive inshore feeding migration followed by a post-feeding return to the hypolimnion. Northern pike and lake trout rarely fed on white suckers in these lakes and thus piscivory was an unlikely factor in the observed distribution of suckers.     

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.     

Side chain and backbone assignments in isotopically labeled proteins from two heteronuclear triple resonance experiments.

Two multi-dimensional heteronuclear NMR experiments are described for assigning the resonances in uniformly 15N- and 13C-labeled proteins. In one experiment (HCNH-TOCSY), the amide nitrogen and proton are correlated to the side-chain protons and carbons of the same and preceding residue. In a second triple resonance experiment (HC(CO)NH-TOCSY), the amide nitrogen and proton of one residue is correlated exclusively with the side-chain proton and carbon resonances of the preceding residue by transferring magnetization through the intervening carbonyl. The utility of these two experiments for making sequential resonance assignments in proteins is illustrated for [U-15N,13C]FKBP (107 residues) complexed to the immunosuppressant, ascomycin.     

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.