A measure of response to perturbation used to assess structural change in some polluted and unpolluted stream fish communities

Summary A new method for measuring structural change in sets of species which have been subjected to natural or experimental perturbation is developed and is shown to be superior to static diversity and evenness measures for this purpose. Three parameters, H, J, and X;} are shown to provide necessary and sufficient information on the severity of a perturbation as well as the uniformity of its effect on all species in the set. When positive and negative changes in species abundance are considered separately, the method is sensitive to compensatory changes which are not detected by static measures.The parameters are then calculated for some data sets on polluted and unpolluted fish communities in second and third order streams from the Clemons Fork watershed in eastern Kentucky. Results indicate that H, the diversity of change over two sampling seasons, is high for perturbed and unperturbed systems, but J the eveness of change is lower for the communities which were polluted in the second sampling season. Severe pollution results in the suppression of most major fish species, whereas more moderate pollution results in a large number of compensatory changes. The biological basis for such an outcome is discussed, and the notion of these three parameters as the vital signs of a healthy ecosystem is presented.     

The relation of proton motive force,adenylate energy charge and phosphorylation potential to the specific growth rate and efficiency of energy transduction inBacillus licheniformis under aerobic growth conditions

The magnitude of the proton motive force (p) and its constituents, the electrical () and chemical potential (-ZpH), were established for chemostat cultures of a protease-producing, relaxed (rel ^–) variant and a not protease-producing, stringent (rel ⁺) variant of an industrial strain ofBacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of p with the specific growth rate was found. The calculated intracellular pH (pH_in) was not constant but inversely related to . This change in pH_in might be related to regulatory functions of metabolism but a regulatory role for pH_in itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low and an increased value at higher . For both limitations, the ATP/ADP ratio was directly related to .The phosphorylation potential (G'p) was invariant with . From the values for G'p and p, a variable H⁺/ATP-stoichiometry was inferred: H⁺/ATP=1.83+0.52µ, so that at a given H⁺/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for =0 to _max (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of G'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.Abbreviations CCCP carbonylcyanide-p-trichloromethoxyphenylhydrazone - DW dry weight of biomass - F Faraday's constant, 96.6 J/(mV × mol) - Fo chemostat outflow-rate (ml/h) - FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - G'p phosphorylation potential, the Gibbs energy change for ATP-synthesis from ADP and P_i - G'⁰p standard Gibbs energy change at specified conditions - H⁺/ATP number of protons translocated through - ATP synthase in synthesis of one ATP - H⁺/O protons translocated during transfer of 2 electrons from substrate to oxygen - specific growth rate (1/h) - _H+ transmembrane electrochemical proton potential, J/mol - M_b molar weight (147.6 g/mol) of bacteria with general cell formula C_6.0H_10.8O_3.0N_1.2 - pH_out,in extracellular, intracellular pH - P_i (intracellular) inorganic phosphate - p proton motive force, mV - pH transmembrane pH-difference - transmembrane electrical potential, mV - P/O number of ADP phosphorylated to ATP upon reduction of one O^2– to H₂O by two electrons transferred through the electron transfer chain - P/O (H⁺/O) × (H⁺/ATP)^–1 - P/O_F, P/O_N P/O with the two electrons donated by resp. (NADH + H⁺) and FADH - q specific rate of consumption or production (mol/g DW × h) - rel ⁺,rel ^– stringent, relaxed genotype - R universal gas constant, 8.36 J/(mol × degree) - T absolute temperature - TPMP⁺ triphenylmethylphosphonium ion - TPP⁺ tetraphenyl phosphonium ion - Y growth yield, g DW/mol - Z conversion constant=61.8 mV for 310 K (37 °C) - ZpH transmembrane proton potential or chemical potential, mV     

On the nature of the uncoupling effect of fatty acids

The effect of palmitic acid on the electrical potential difference across the inner mitochondrial membrane appears to depend on the medium in which mitochondria are incubated. In medium A (cf. Luvisettoet al. (1987),Biochemistry,26, 7332–7338) decreases much more than in medium B (cf. Rottenberg and Hashimoto (1986),Biochemistry,25, 1747–1755) at concentrations of fatty acid which equally stimulate the rate of respiration in state 4. Valinomycin and NaCl were both present in medium B and absent in medium A. However, in both media the pattern of the P/O ratio as a function of antimycin in the presence of a constant amount of palmitic acid or of FCCP shows similar behaviour. We conclude that in both media palmitic acid increases the membrane conductance to protons, but for unclear reasons the assay fails to measure the decline of in medium B. However, the increase in membrane conductance induced by palmitic acid does not quantitatively account for the stimulation of the rate of respiration.     

Multi-loop representation of the segmental muscle stretch reflex

Bees were trained to react to differences both in the size and in the degree of greyness of discs. To measure the differential sensitivity on these parameters, differences in size and shade of grey (-intervals) were established such as lead to a specific choice reaction (Fig. 3). The -intervals may be described for both parameters by Weber's rule (Fig. 4). The main result is the following relationship between the differential sensitivity and the equivalence curve as defined by cross modality matching. The bee treats two discs, which differ from a reference disc in diameter or in degree of greyness, as equivalent when both differ from the reference disc by an equal number of -intervals (Fig. 6). The choice reactions between the reference disc and the discs of the equivalent pair are the same for these parameters. This does not hold for another parameter (Fig. 7A and B). Problems of infering from the -intervals to the differential sensitivity are then discussed.     

Interaction of cytochrome c L with methanol dehydrogenase from Methylophaga marina 42:

The reaction of methanol dehydrogenase with cytochrome c _L from Methylophaga marina and the reactions of the non-physiological substrates, Wurster's blue and ascorbic acid, with both proteins were studied as a function of temperature (4–32 °C), pressure (1–2000 bar) and ionic strength using the optical high pressure stopped-flow method. The thermodynamic parameters H, S and V were determined for all reactions where electron transfers are involved. These data allowed the determination of the Maxwell relationships which proved the internal thermodynamic consistency of the system under study. A conformational change on the cytochrome c _L level was deduced from both breaks in the Arrhenius plots and the variation of the V with temperature.Abbreviations MOPS 4-morpholinepropanesulfonic acid - CHES 2-(cyclohexylamino)ethanesulfonic acid - MDH methanol dehydrogenase - EDTA ethylenedinitrilotetraacetic acid disodium salt - BTB bromothymol blue (3,3-dibromothymolsulfoneph-thalein) - PQQ 2,7,9-tricarboxy-lH-pyrrolo-[2,3f]quinoline-4,5-dione - cytochrome c _HH mammalian horse heart cytochrome c     

Protonmotive force driven 6-deoxyglucose uptake by the oral pathogen,Streptococcus mutans Ingbritt

Streptococcus mutans Ingbritt was grown in glucose-excess continuous culture to repress the glucose phosphoenolpyruvate phosphotransferase system (PTS) and allow investigation of the alternative glucose process using the non-PTS substrate, (³H) 6-deoxyglucose. After correcting for non-specific adsorption to inactivated cells, the radiolabelled glucose analogue was found to be concentrated approximately 4.3-fold intracellularly by bacteria incubated in 100 mM Tris-citrate buffer, pH 7.0. Mercaptoethanol or KCl enhanced 6-deoxyglucose uptake, enabling it to be concentrated internally by at least 8-fold, but NaCl was inhibitory to its transport. Initial uptake was antagonised by glucose but not 2-deoxyglucose. Evidence that 6-deoxyglucose transport was driven by protonmotive force (p) was obtained by inhibiting its uptake with the protonophores, 2,4-dinitrophenol, carbonylcyanide m-chlorophenylhydrazine, gramicidin and nigericin, and the electrical potential difference () dissipator, KSCN. The membrane ATPase inhibitor, N,N¹-dicyclohexyl carbodiimide, also reduced 6-deoxyglucose uptake as did 100 mM lactate. In combination, these two inhibitors completely abolished 6-deoxyglucose transport. This suggests that the driving force for 6-deoxyglucose uptake is electrogenic, involving both the transmembrane pH gradient (pH) and . ATP hydrolysis, catalysed by the ATPase, and lactate excretion might be important contributors to pH.Abbreviations DNP 2,4-dinitrophenol - CCCP carbonylcyanide m-chlorophenylhydrazone - DCCD N,N¹-dicyclohyxyl carbodiimide - p protonmotive force - pH transmembrane pH gradient - transmembrane electrical potential difference     

Measurements of electrical potential differences across yeast plasma membranes with microelectrodes are consistent with values from steady-state distribution of tetraphenylphosphonium inPichia humboldtii

Summary Electrical potential differences across the plasma membrane () of the yeastPichia humboldtii were measured with microelectrodes (filled with 0.1m KCl) inserted into cells immobilized in microfunnels. The registered signals were reproducible and stable for several minutes. On attainment of stable reading for the specific membrane resistanceR _sp was determined by applying square-current pulses to the preparation. Both andR _sp were pH dependent and displayed equal but opposite deflection, reaching its maximal value of –88±9 mV (n=13) andR _sp its minimal value of 10 k·cm² (maximal conductance) at pH 6.5. Uncouplers and the polyene antibiotic nystatin depolarized the cells, decreasing to –21±15 mV (n=10) with concomitant decrease ofR _sp. Comparison of values from microelectrode measurements with those calculated from the steady-state distribution of tetraphenylphosphonium ions agreed within 10 mV under all physiological conditions tested, except at pH values above 7.0. During microelectrode insertion transient voltage signals (a few msec long) were detected by means of an oscilloscope. These voltage signals were superimposed on the stable recordings described above. These short voltage signals disappeared in uncoupled cells. The closely related values obtained by two independent methods (direct measurements with microelectrodes and calculation from steady-state distribution of a lipophilic cation) provide evidence that these values reffect the true membrane potential of intact cells.     

Characterization of a structurally and functionally diverged acyl-acyl carrier protein desaturase from milkweed seed

A cDNA for a structurally variant acyl-acyl carrier protein (ACP) desaturase was isolated from milkweed (Asclepias syriaca) seed, a tissue enriched in palmitoleic (16:1⁹)* and cis-vaccenic (18:1¹¹) acids. Extracts of Escherichia coli that express the milkweed cDNA catalyzed ⁹ desaturation of acyl-ACP substrates, and the recombinant enzyme exhibited seven- to ten-fold greater specificity for palmitoyl (16:0)-ACP and 30-fold greater specificity for myristoyl (14:0)-ACP than did known ⁹-stearoyl (18:0)-ACP desaturases. Like other variant acyl-ACP desaturases reported to date, the milkweed enzyme contains fewer amino acids near its N-terminus compared to previously characterized ⁹-18:0-ACP desaturases. Based on the activity of an N-terminal deletion mutant of a⁹ -18:0-ACP desaturase, this structural feature likely does not account for differences in substrate specificities.     

A dominant mutation for high oleic acid content in sunflower (Helianthus annuus L.) seed oil is genetically linked to a single oleate-desaturase RFLP locus

Pervenets is a sunflower mutant with a seed oil oleic acid content greater than 65%. It was obtained after mutagenesis treatment on VNIIMK 8931. Several commercial varieties derived from Pervenets and breeding materials with a high oleic acid content have been marketed. However, the genetics of this trait are still not fully understood by breeders. To characterize the Pervenets mutation, we studied RFLP in relation to high oleic acid content. We performed diversity analyses on 239 genotypes with cDNA sequences coding for 9- and 12-desaturases as probes. The 12 RFLPs enabled us to identify at least two independent loci. One 12 RFLP allele (12HOS) was strictly correlated to high oleic acid content, whereas no correlation was found between 9-desaturase polymorphism and high oleic acid content. These results enabled to us estimate the genetic distance between the marker and the Pervenets mutation loci. An F₂ segregating population of 107 plants confirmed the correlation between high oleic acid content and 12HOS, indicating tight genetic linkage. The nature of the Pervenets dominant mutation and the complexity of the high oleic acid content trait are discussed.     

Comparative Study of Effects of Various Sterols and Triterpenoids on Permeability of Model Lipid Membranes

Using permeability to labeled glucose as a criterion of stability for liposomal membranes, a comparative study on stabilizing properties of different sterols and triterpenes in phospholipid bilayer has been carried out as well as on structural peculiarities of sterols responsible for membranolytic properties of cucumarioside G₁ from the cucumaria Eupentacta fraudatris. Stabilizing action of the studied sterols and triterpenoides incorporated in the bilayer decreases in the following order: cholesterol sulfate > cholesterol > ⁵-sterols > -sitosterol > ergosterols > ⁷-sterols > epicholesterol > pregnane > androstane > coprosterol > 14-methylcholest-9(11)-en-3-ol > 4, 14-dimethylcholest-9(11)-en-3-ol > holothurinogenin A₁ > glucoside of cholesterol > -xylosidase of ⁷-sterols > betulin > protopanaxatriol > phosphatidylcholine liposomes without sterol > protopanaxadiol > oleanolic acid. Sterol-dependent membranolytic cucumarioside G₁ practically loses its ability to increase permeability of phospholipid membranes containing sterols obtained from this holothuria as well as coprosterol, epicholestrol, sulfated and glycosylated forms of sterols. The obtained results confirm the sterol hypothesis of the mechanism of membranotropic action of holothuria glycosides and of resistance to them of holothuria cell membranes.     

Modelling based method for pharmacokinetic hypotheses test

The aim of this work is to propose methods to test mechanism of synergy of toxic agents in bees. A synergy between prochloraz, an imidazole fungicide, and deltamethrin, a pyrethroid insecticide, was demonstrated experimentally. The hypothesis is that prochloraz modifies the penetration or the metabolism of deltamethrin. This hypothesis is tested using a pharmacokinetic box model. A previous experimental work showed that bee instantaneous mortalities were higher, from the time t ₁ to the time t ₂ after spraying, in groups sprayed with deltamethrin at dose D ₀ in the presence of prochloraz (+P) than in those sprayed with deltamethrin alone at a dose time as high (). We postulate that accrued mortality is proportional to the cumulated internal deltamethrin (ID ₂). ID ₂ of treatment (+P) had to be greater than ID ₂ of treatment () during the period from t ₁ to t ₂ so that the hypothesis would be consistent with the experimental data. The limit, for which the hypothesis is conceivable, is the ID ₂₍₎ = ID _2(+P ) curve. We study, in particular, the asymptotic behaviour of the limit curve when different parameters of the kinetic model tend to 0 or . These limits allow to verify quickly and easily whether a mechanism is conceivable or not As the limits are calculated with algebraic values, the test can be used for other synergies.     

ATP-induced ΔpH formation in chloroplast ATP synthase proteoliposomes

Summary A procedure to reconstitute CF₀CF₁ proteoliposomes by gel filtration through a Sephadex-column pre-equilibrated with valinomycin and potassium is described. Proteoliposomes reconstituted by this procedure catalyze an ATP-induced pH of 2.5 to 3.5 units. pH was measured with either 9-aminoacridine or with the pH indicator pyranine trapped inside the proteoliposomes. CF₀CF₁ proteoliposomes prepared by conventional techniques catalyzed an ATP-induced formation, but were unable to catalyze an ATP-induced pH even in the presence of valinomycin.The ATP-induced pH was sensitive to uncouplers and energy transfer inhibitors and was increased at low temperatures. It is suggested that ATP-induced pH was observed in these proteoliposomes due to the efficient removal of intravesicular ammonium introduced with the CF₀CF₁ preparation. The ammonium acted as an internal buffer, and thus prevented an observable pH formation.     

Preparation of a series of sulfated tetrasaccharides from shark cartilage chondroitin sulfate D using testicular hyaluronidase and structure determination by 500 MHz1H NMR spectroscopy

Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz¹H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All the seven tetrasaccharides shared the common core structure GlcA1-3GalNAc1-4GlcA1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GlcA1-3GalNAc(4-sulfate) and/or GlcA1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA1-3GalNAc(4-or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum -N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.Abbreviations NFU National formulary unit - COSY correlation spectroscopy - HOHAHA homonuclear Hartmann-Hahn - 1D or 2D one- or two-dimensional - IdoA l-iduronic acid - GlcA d-gluco-4-enepyranosyluronic acid - Di-0S GlcA1-3GalNAc - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-diS _d GlcA(2-sulfate)1-3GalNAc(6-sulfate) - Di-diS_E GlcA1-3GalNAc(4, 6-disulfate) - U G, U, 2S, 4S, and 6S represent GlcA, GalNAc, GlcA, 2-O-sulfate, 4-O-sulfate, and 6-O-sulfate, respectively     

Theoretical stability diagram of solvent-containing black lipid films

Recently, we have developed an analytical, semi-microscopic theory for the macroscopic behavior of a solvent-containing black lipid film subjected to an electric cross film voltage, . Here we employ the theoretical expressions derived for the disjoining pressure, _D, the film elasticity, _F, and the film tension, _F, to construct the stability diagram of the film, in the _D-. Depending on its state (_D, ), the film is stable or is prone to squeezing or bending deformations. For a monooleate film we show how the destruction of the plane film due to a periodic thickness fluctuation (squeezing) is facilitated by two mechanisms: i) lowering of _D at fixed ; ii) lowering of at fixed _D, provided that the film is in a stable state characterized by _D<–7.03×10³ dyne/cm² and >0 mV. Bending of a low tension film (single interface tension _s 0.025 dyne/cm¹) can be achieved only for >170 mV and _D > –8.7 × 10⁴ dyne/cm². Finally, we demonstrate the existence of a marginal state ( _D ⁰ , ⁰) where the film is predicted to exhibit strong fluctuations both in the squeezing and in the bending mode.     

Thermodynamics of Mn2+-binding to goat α-lactalbumin

By means of reaction calorimetry we measured the apparent enthalpy change, H^app, of the binding of Mn²⁺-ions to goat -lactalbumin as a function of temperature. The observed H^app can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat -lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (H, G, S, C_p) into the binding and conformational contributions. By circular dichroism we showed that NH ₄ ⁺ -ions, upon binding to bovine a-lactalbumin, induce the same conformational change as do Na⁺ and K⁺: the binding constant equals 98 ± 9 M^–1.Abbreviations BLA bovine -lactalbumin - GLA goat -lactalbumin - HLA human -lactalbumin - CD circular dichroism Offprint requests to: H. Van DaelDeceased     

The occurrence of the chloroplast pyrenoid is correlated with the activity of a CO2-concentrating mechanism and carbon isotope discrimination in lichens and bryophytes

The organic-matter carbon isotope discrimination () of lichens with a wide range of photobiont and/or cyanobiont associations was used to determine the presence or absence of a carbon-concentrating mechanism (CCM). Two groups were identified within the lichens with green algal photobionts. One group was characterised by low, more C₄-like values ( < 15), the other by higher, more C₃-like values ( > 18). Tri-partite lichens (lichens with a green alga as the primary photobiont and cyanobacteria within internal or external cephalodia) occurred in both groups. All lichens with cyanobacterial photobionts had low values ( < 15). The activity of the CCM, organic-matter values, on-line values and gas-exchange characteristics correlated with the presence of a pyrenoid in the algal chloroplast. Consistent with previous findings, lichens with Trebouxia as the primary photobiont possessed an active CCM while those containing Coccomyxa did not. Organic values for lichens with Stichococcus as the photobiont varied between 11 and 28. The lichen genera Endocarpon and Dermatocarpon (Stichococcus + pyrenoid) had C₄-like organic values ( = 11 to 16.5) whereas the genus Chaenotheca (Stichococcus — pyrenoid) was characterised by high C₃-like values ( = 22 to 28), unless it associated with Trebouxia ( = 16). Gas-exchange measurements demonstrated that Dermatocarpon had an affinity for CO₂ comparable to those species which possessed the CCM, with K_0.5 = 200–215 1 · 1^–1, compensation point () = 45–48 l · l^–1, compared with K_0.5 = 195 1 · 1^–1, = 441 · 1^–1 for Trebouxioid lichens. Furthermore, lichens with Stichococcus as their photobiont released a small pool (24.2 ± 1.9 to 34.2 ± 2.5 nmol · mg^–1 Chl) of inorganic carbon similar to that released by Trebouxioid lichens [CCM present, dissolved inorganic carbon (DIC) pool size = 51.0 ± 2.8 nmol · mg^–1 Chl]. Lichens with Trentepohlia as photobiont did not possess an active CCM, with high C₃-like organic values ( = 18 to 23). In particular, Roccella phycopsis had very high on-line values ( = 30 to 33), a low affinity for CO₂ (K_0.5 = 400 1 · 1^–1, = 120 1 · ^–1) and a negligible DIC pool. These responses were comparable to those from lichens with Coccomyxa as the primary photobiont with Nostoc in cephalodia (organic = 17 to 25, on-line = 16 to 21, k_0.5 = 388 1 · 1^–1, = 85 1 · 1^–1, DIC pool size = 8.5 ± 2.4 nmol · mg^–1 Chl). The relative importance of refixation of respiratory CO₂ and variations in source isotope signature were considered to account for any variation between on-line and organic . Organic was also measured for species of Anthocerotae and Hepaticae which contain pyrenoids and/or Nostoc enclosed within the thallus. The results of this screening showed that the pyrenoid is correlated with low, more C₄-like organic values ( = 7 to 12 for members of the Anthocerotae with a pyrenoid compared with = 17 to 28 for the Hepaticae with and without Nostoc in vesicles) and confirms that the pyrenoid plays a fundamental role in the functioning of the CCM in microalgal photobionts and some bryophytes.Abbreviations and Symbols CCM carbon-concentrating mechanism - DIC dissolved inorganic carbon (CO₂ + HCO ₃ ^- + CO ₃ ^2- ) - DW dry weight - K_0.5 external concentration of CO₂ at which half-maximal rates of CO₂ assimilation are reached - photobiont photosynthetic organism present in the lichen - Rubisco ribulose-1,5-bisphosphate carboxylase-oxygenase - carbon isotope discrimination (%) - ¹³C carbon isotope ratio (%) This research was funded by Natural Environment Research Council grant no. GR3/8313. The authors would also like to thank Dr. B. Coppins, Royal Botanic Gardens Edinburgh and Prof. A. Roy Perry, National Museum of Wales, for access to herbarium collections, Dr. T. Booth for confocal microscopy work and Dr. A.J. Richards, University of Newcastle upon Tyne and Dr. O.L. Gilbert, University of Sheffield for identifying bryophytes and lichens respectively. E.S. would particularly like to thank Dr. M. Broadmeadow, The Forestry Authority, Farnham, Surrey, and Cristina Máguas, Universidade de Lisboa, for their advice and expertise at the beginning of the project.     

Sodium ions are necessary for growth and energy transduction in the marine cyanobacterium Oscillatoria brevis

The maximal growth rate of the marine cyanobacterium Oscillatoria brevis was reached at 200–400 mM NaCl and pH 9.0–9.6. NaCl was found (i) to stimulate the rate of the light-supported generation across the cytoplasmic membrane of the cells and (ii) to decrease the sensitivity of level and motility of the O. brevis trichomes to protonophorous uncouplers. The Na⁺/H⁺ antiporter, monensin, increased both and the uncoupler sensitivity of the cells. The data obtained agree with the assumption that O. brevis possesses a primary Na⁺ pump in its cytoplasmic membrane.Abbreviations ATP adenosine-5-triphosphate - TTFB tetrachlortrifluoromethylimidazol - CCCP carbonyl cyanide m-chlorophenylhydrazone - Na⁺ transmembrane electrochemical potential differences of Na⁺ - transmembrane electric potential difference - pNa transmembrane pNa difference     

Screening for naturally occurring apolipoprotein A-I variants: apo A-I(ΔK107) is associated with low HDL-cholesterol levels in men but not in women

Isoelectric focussing (IEF) in carrier ampholyte-generated pH gradients and hybrid isoelectric focussing (HIEF) in immobilized pH gradients under nondenaturing conditions were used in parallel to screen 5,500 plasma samples for naturally occurring variants of apolipoprotein A-I (apo A-I). The following defects were identified in four unrelated subjects heterozygous for apo A-I variants: apo A-I(K107)(2 ×), apo A-I(K107M)(1 ×), and apo A-I(E41R)(1 ×). The later variant is a novel finding. Family studies did not reveal any association of apo A-I(K107M) and apo A-I(E41R) with dyslipidemia, but identified several heterozygotes for apo A-I(K107) who had low levels of high density lipoprotein (HDL)cholesterol. Therefore, and since the apo A-I(K107) is the most frequent apo A-I variant in Germany (1 5,000) we evaluated our data and that reported from 11 families with 32 heterozygous carriers and 30 unaffected controls. This analysis revealed that apo A-I(K107) is associated with lower HDL-cholesterol (-30%) and higher triglycerides (+ 48%) in men but not in women as compared with unaffected family members as well as with controls from the Prospective Cardiovascular Münster (PROCAM) study. Moreover, 11 of 15 male apo AI(K107) heterozygotes but only 2 of 17 female apo AI(K107) heterozygotes had HDL-cholesterol levels below the 20th percentile of sex-matched controls from the PROCAM study. We conclude that heterozygosity for apo A-I(K107) decreases HDL-cholesterol and increases triglycerides in men but not in women.     

Conformational transitions in closed circular DNA molecules I. Topological and energetical considerations

A theory of conformational transitions in closed circular DNA as a function of topological linking number of the molecule () is elaborated taking into account topological and energetical considerations. The theory predicts a step-like dependence of a number of superhelical turns in DNA molecules () on . Thus, the number of superhelical turns = for small values of . For a large (when conformational transitions begin to occur) =–_ij, where _ij is the total angle of conformational transitions for a given . This prediction is in good agreement with published data on the dependence of the sedimentation coefficient of circular DNA molecules on their topological linking number. The results also allow to explain the disagreement between a number of titratable superhelical turns in circular DNA molecules and a number of supercoiles seen on electron micrographs for molecules with sufficiently large .