Kinetics of anaerobic biodegradation of glycerol by sulfate-reducing bacteria

A kinetic model has been developed and kinetic parameters of anaerobic degradation of glycerol, an abundant by-product of biofuel manufacturing, by a consortium of sulfate reducing bacteria (SRB) in a closed system have been determined. The following main species of SRB has been identified in the consortium: Desulfovibrio baarsii, Desulfomicrobium sp., and Desufatomaculum sp. The proposed model included processes of glycerol degradation, sulfate reduction, and inhibition by metabolic products, as well as effects of pH and temperature. The suggested equation for the anaerobic glycerol degradation was based on Edward and Andrew’s equation. The following kinetic parameters of the anaerobic glycerol degradation were obtained for the initial glycerol concentration from 0.15 to 4 ml/l and sulfate concentration of 2760 mg/l at 22°C: maximum specific growth rate of SRB μ_max = 0.56 day⁻¹, economic coefficient of ashless biomass from glycerol of 0.08 mol SRB/mol COC, and yield of ashless biomass from sulfate of 0.020 mol SRB/mol SO₄. It was shown that the optimum molar ratio of $ {{C_{Gl} } \mathord{\left/ {\vphantom {{C_{Gl} } {C_{SO_4 } }}} \right. \kern-\nulldelimiterspace} {C_{SO_4 } }} $ {{C_{Gl} } \mathord{\left/ {\vphantom {{C_{Gl} } {C_{SO_4 } }}} \right. \kern-\nulldelimiterspace} {C_{SO_4 } }} for SRB growth was 0.8. Initial boundary concentration of inhibition by undissociated hydrogen sulfide was 70 mg/l. Dependence of the specific growth rate of bacteria on the temperature was approximated by the Arrhenius equation in the temperature range of 20–30°C with the goodness of fit R² = 0.99.     

Summer nutrient dynamics in the Middle Atlantic Bight: primary production and utilization of phytoplankton carbon

In late summer, production and utilization of carbon in thestratified water of the Middle Atlantic Bight appears to approachsteady-state conditions. In the euphotic zone there is a paniculateorganic carbon (POC) pool of {small tilde}6000 mg Cm^–2.Primary production adds {small tilde}350 mg C m^–2 d^–1,while zooplankton ingestion removes {small tilde}450 mg C m^–2d^–1, of which {small tilde}135 mg C m^–2 d^–1are returned to the POC pool as feces. Sinking of POC averages{small tilde}240 mg C m ^–2 d^–1. Thus, there is anet loss from the euphotic zone of {small tilde}200 mg C m^–2d^–1, which represents a removal rate from the POC poolof {small tilde}3%d^–1. However, sinking losses of phytoplanktoncarbon from the POC pool were small ({small tilde}12 mg C m^–2d^–1), which suggests that most of the primary productionenters the pelagic food chain. This is in sharp contrast tothe conditions in early spring, when the POC pool increasessubstantially, and the main loss is sinking rather than heterotrophicconsumption. ^*This research was supported by the U.S. Department of Energyunder Contract No. DE-AC02-76CH000I6.     

pH and oxidation-reduction potential change of environment during growth of lactic acid bacteria: Effects of oxidizers and reducers

Decrease of pH and dropping of oxidation-reduction potential have been observed during growing Lactobacillus salivarius 1588 and 3823, Lactobacillus acidophilus 101E, and Lactococcus lactis 3690 in anaerobic conditions in medium with glucose fermentation. These parameters and membrane proton permeability of bacteria ($ C_m^{H^ + } $ C_m^{H^ + } ) changed in the mediums with different pH. Oxidizer ferrycianide and reducer DL-dithiothreitol affected the bacterial growth and their changed H⁺ extrusion from the cells and K⁺ uptake by the cells in experiment conditions. Application of oxidizers and reducers are suggested for regulation of growth related with H⁺ ion transport in lactic acid bacteria.     

Parametric Maximum Parsimonious Reconstruction on Trees

We give a formal study of the relationships between the transition cost parameters and the generalized maximum parsimonious reconstructions of unknown (ancestral) binary character states {0,1}\{\mathtt{0},\mathtt{1}\} over a phylogenetic tree. As a main result, we show there are two thresholds l¹_n\lambda^{\mathtt{1}}_{n} and l⁰_n\lambda^{\mathtt{0}}_{n}, generally confounded, associated to each node n of the phylogenetic tree and such that there exists a maximum parsimonious reconstruction associating state 1\mathtt{1} to n (resp. state 0\mathtt{0} to n) if the ratio “10\mathtt{1}\mathtt{0}-cost”/“01\mathtt{0}\mathtt{1}-cost” is smaller than l¹_n\lambda^{\mathtt{1}}_{n} (resp. greater than l⁰_n\lambda^{\mathtt{0}}_{n}). We propose a dynamic programming algorithm computing these thresholds in a quadratic time with the size of tree.     

An evolutionary analytical model of a complementary circular code simulating the protein coding genes, the 5′ and 3′ regions

The self-complementary subset ∪{AAA,TTT} with = {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} of 22 trinucleotides has a preferential occurrence in the frame 0 (reading frame established by the ATG start trinucleotide) of protein (coding) genes of both prokaryotes and eukaryotes. The subsets ∪{CCC} and ∪{GGG} of 21 trinucleotides have a preferential occurrence in the shifted frames 1 and 2 respectively (frame 0 shifted by one and two nucleotides respectively in the 5′-3′ direction). and are complementary to each other. The subset contains the subset which has the rarity property (6 × 10⁻⁸) to be a complementary maximal circular code with two permutated maximal circular codes and in the frames 1 and 2 respectively. is called a C³ code. A quantitative study of these three subsets in the three frames 0, 1, 2 of protein genes, and the 5′ and 3′ regions of eukaryotes, shows that their occurrence frequencies are constant functions of the trinucleotide positions in the sequences. The frequencies of in the frame 0 of protein genes are 49, 28.5 and 22.5% respectively. In contrast, the frequencies of in the 5′ and 3′ regions of eukaryotes, are independent of the frame. Indeed, the frequency of in the three frames of 5′ (respectively 3′) regions is equal to 35.5% (respectively 38%) and is greater than the frequencies and , both equal to 32.25% (respectively 31%) in the three frames. Several frequency asymmetries unexpectedly observed (e.g. the frequency difference between and in the frame 0), are related to a new property of the subset involving substitutions. An evolutionary analytical model at three parameters (p, q, t) based on an independent mixing of the 22 codons (trinucleotides in frame 0) of with equiprobability (1/22) followed by t ≈ 4 substitutions per codon according to the proportions p ≈ 0.1; q ≈ 0.1 and r = 1 − p − q ≈ 0.8 in the three codon sites respectively, retrieves the frequencies of observed in the three frames of protein genes and explains these asymmetries. Furthermore, the same model (0.1, 0.1, t) after t ≈ 22 substitutions per codon, retrieves the statistical properties observed in the three frames of the 5′ and 3′ regions. The complex behaviour of these analytical curves is totally unexpected and a priori difficult to imagine.     

Über Romanowsky-Farbstoffe und den Romanowsky-Giemsa-Effekt

Zusammenfassung Es wurden analysenreine Proben der Romanowsky-Farbstoffe Eosin Y, Erythrosin B und Tetrachlorfluoreszein hergestellt.Im DC der Farbstoffproben konnten keine Verunreinigungen nachgewiesen werden. Die Absorptionsspektren der Farbstoffdianionen in wäßriger alkalischer Lösung und der Farbstoffsäuren in 95%igem Ethanol wurden bei sehr kleinen Farbstoffkonzentrationen gemessen und der molare Extinktionskoeffizient der längstwelligen Absorptionsbande der monomeren Farbstoffspezies bestimmt (Tabelle 1). Die Extinktionskoeffizienten können zur Standardisierung von Farbstoffproben verwendet werden. Die Absorptionsspektren von Eosin Y hängen in wäßriger Lösung von der Farbstoffkonzentration ab. Aus der Konzentrationsabhängigkeit wurden mit einem neuen, sehr empfindlichen Verfahren zwei Assoziationsgleichgewichte ermittelt. Bereits in sehr verdünnter Lösung bilden sich Dimere, bei erhöhter Konzentration Tetramere, Die Dissoziationskonstante der DimerenD in MonomereM beträgt bei pH=12, 293K:K ₂₁=2,9 × 10^–5 M; der TetramerenQ in DimereD:K ₄₂=2,4 × 10^–3 M. Aus den gemessenen Spektren von Eosinlösungen verschiedener Konzentration, pH=12, und den GleichgewichtskonstantenK ₂₁,K ₄₂ haben wir die Spektren der reinen Monomeren, Dimeren und Tetrameren bestimmt.M hat eine langwellige Absorptionsbande: , _M =1,03 x 10₅ M_-1 cm_-1;D eine Bande: , _D =1,74 x 10₅ M_-1 cm_-1;Q zwei Banden: , , _Q1=1,65 x 10⁵, _Q2=1,96 x 10⁵ M^-1 cm^-1. Das Absorptionsspektrum der Dimeren wird quantenmechanisch interpretiert.

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Romanowsky dyes and Romanowsky-Giemsa effect. 2. Eosin Y, Erythrosin B, tetrachlorofluorescein, Spectroscopic characterization of pure dyes, association of Eosin Y

Summary Analytically pure smaples of the Romanowsky dyes eosin y, erythrosin b and tetrachlorofluorescein are prepared. DC of the dye samples shows no contaminations. We measured the absorption spectra of the dye dianions in alkaline aqueous solution and of the dye acids in 95% ethanol at very low dye concentrations. The molar extinction coefficients of the long wavelength absorption of the monomeric dye species are determined (Table 1). The extinction coefficients may be used for standardisation of dye samples. The absorption spectra of eosin y in aqueous solution are dependend on concentration. Using a new very sensitive method it was possible to identify two association equilibria from the concentration dependency of the spectra. Dimers are formed even in very dilute solutions, at higher concentrations tetramers. The dissociation constant of the dimersD in monomersM at 293 K, pH=12, isK ₂₁=2,9×10^–5 M; of the tetramersQ in dimersDK ₄₂=2,4×10^–3 M. From the experimental spectra of eosin solutions at various concentrations, pH=12, and the equilibrium constantsK ₂₁,K ₄₂ the absorption spectra of the pure monomers, dimers and tetramers are calculated. M has one long wavelength absorption band, , _M =1,03 x 10₅ M_-1 cm_-1;D also one absorption band, , _D =1,74 x 10₅ M_-1 cm_-1;Q two absorption bands, , , _Q1=1,65 x 10⁵, _Q2=1,96 x 10⁵ M^-1 cm^-1. The absorption spectrum of the dimers is discussed by quantum mechanics.

     

Genetic effects of forest fragmentation in high-density Araucaria angustifolia populations in Southern Brazil

Araucaria angustifolia is an endangered tropical/subtropical coniferous of great interest for conservation due its economical, ecological, and social value. Only 3% of original Araucaria forests remain, which are generally confined to small forest fragments. Forest fragmentation can have serious consequences on genetic process in tree population, affecting long-term fitness and adaptability. To investigate the effects of forest fragmentation on genetic diversity and the structure of A. angustifolia populations, the genetic diversity of eight microsatellite loci was compared in four small fragmented populations (<22 ha), four tree groups (five to 11 trees) occurring in pastures and in three plots in a large continuous population. The clearest effect of fragmentation was the loss of rare alleles (p ≤ 0.05) in fragmented populations (19.4% to 47.2%) and intermediate frequency (0.05 < p ≤ 0.25) and rare alleles (p ≤ 0.05) in tree groups (19% to 86.1%) in comparison to continuous populations. Fragmented populations have significant higher fixation index ( [^(F)]_\textIS = 0.121 \widehat{F}_{\text{IS}} = 0.121 , P < 0.05) than continuous populations ( [^(F)]_\textIS = 0.083 \widehat{F}_{\text{IS}} = 0.083 , P < 0.05). High genetic differentiation was detected among tree groups ( [^(G)]_\textST^￠ = 0.258 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.258 , P < 0.01) and low among fragments ( [^(G)]_\textST^￠ = 0.031 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.031 , P < 0.05) and continuous populations ( [^(G)]_\textST^￠ = 0.026 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.026 , P < 0.05), showing a significant bottleneck effect in tree groups. Evidence that forest fragments have experienced a recent bottleneck was confirmed in at least two studied fragments. The implications of the results for conservation of the fragmented A. angustifolia populations are discussed.     

In Vitro Phosphorylation of Proteins in IAA-Treated Mesocotyls in Zea mays

Five-mm sections of elongation zones of Zea mesocotyls wereincubated for designated periods with various concentrationsof IAA. In vitro protein phosphorylation in the soluble fraction(85,000 x g supernatant) prepared from the sections was analyzedby sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The phosphorylation of proteins in the soluble fraction thathad been prepared from sections incubated for 20 min in thepresence of 10{small tilde}^s M IAA was greater than that inthe sections incubated for 20 min without IAA. The amount ofphosphorylation of proteins per protein became higher when higherconcentrations increased (10{small tilde}⁸—10{small tilde}⁵M).The growth of sections incubated in the presence of 10{smalltilde}⁸ M IAA or higher concentrations was greater than thatof sections incubated in the absence of IAA. The promotion ofgrowth by IAA was greater at higher concentrations of IAA. Proteinsin the soluble fraction, prepared from sections incubated for20 min in the presence of 10{small tilde}⁵ M IAA, were phosphorylatedin the presence of either 10 fM cAMP, 10 µM cGMP, 100µM W-7, 100 µM W-5, 20 µM H-7 or 20 µMHA1004. The calmodulin antagonist, W-7, and the inhibitor ofprotein kinase C, H-7, inhibited the phosphorylation of proteinsstimulated by incubation with IAA. These results suggest thatIAA promotes cell elongation via protein phosphorylation thatdepends on calmodulin-dependent protein kinase and protein kinaseC. (Received November 29, 1995; Accepted May 20, 1996)     

Thermodynamic,Equilibrium and Kinetic Study of the Biosorption of Basic Blue 41 using Bacillus maceran

Thermodynamic, kinetic and equilibrium studies during the biosorption of Basic blue 41(BB 41) from aqueous solution using Bacillus macerans were carried out with a focus on pH, contact time, temperature, biomass dosage and initial dye concentration. The maximum adsorption capacity was found to be 89.2 mg/g under optimal conditions of pH (10.0) and temperature (25 °C). The biosorption rates obtained were consistent with the pseudo‐second order kinetic models. The equilibrium data were analyzed using linearized forms of Langmuir and Freundlich isotherms, and the Langmuir isotherm was found to provide the best correlation of the experimental data for the biosorption of BB 41. The equilibrium time for the removal of BB 41 by the biomass was attained within 90 min. Thermodynamic parameters such as free energy (<$>\Delta G<$>), enthalpy (<$>\Delta H<$>), and entropy (<$>\Delta S<$>) were also calculated. The results indicate that biosorption is spontaneous and exothermic in nature. The negative value of entropy confirms the decreased randomness at the solid‐liquid interface during the adsorption of BB 41 onto Bacillus macerans.     

Effects of viral mutation on cellular dynamics in a monte carlo simulation of HIV immune response model in three dimensions

Summary The cellular dynamics of HIV interaction with the immune system is explored in three-dimensions using a direct Monte Carlo simulation. Viral mutation with probability, Pmut, is considered with immobile and mobile cells. With immobile cells, the viral population becomes larger than that of the helper cells beyond a latency period Tcrit and above a mutation threshold Pcrit. That is at Pmut ≥ Pcrit, { }, with γ ⋍ 0.73 in three dimensions and γ ⋍ 0.88 in 2-D. Very little difference in Pcrit is observed between two and three dimensions. With mobile cells, no power-law is observed for the period of latency, but the difference in Pcrit between two and three dimensions is increased. The time-dependency of the density difference between Viral and Helper cell populations (ρV − ρH) is explored and follows the basic pattern of an immune response to infection. This is markedly more defined than in the 2-D case, where no clear pattern emerges.     

Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?

Odontocetes have an exceptional range in body mass spanning 10³ kg across species. Because, size influences oxygen utilization and carbon dioxide production rates in mammals, this lineage likely displays an extraordinary variation in oxygen store management compared to other marine mammal groups. To examine this, we measured changes in the partial pressures of respiratory gases ( P_\textO2 P_{{{\text{O}}_{2} }} , P_\textCO2 P_{{{\text{CO}}_{2} }} ), pH, and lactate in the blood during voluntary, quiescent, submerged breath holds in Pacific white-sided dolphins (Lagenorhynchus obliquidens), bottlenose dolphins (Tursiops truncatus), and a killer whale (Orcinus orca) representing a mass range of 96–3,850 kg. These measurements provided an empirical determination of the effect of body size on the variability in blood biochemistry during breath hold and experimentally determined aerobic dive limits (ADL) within one taxonomic group (odontocetes). For the species in this study, maximum voluntary breath-hold duration was positively correlated with body mass, ranging from 3.5 min in white-sided dolphins to 13.3 min for the killer whale. Variation in breath-hold duration was associated with differences in the rate of change for P_\textO2 P_{{{\text{O}}_{2} }} throughout breath hold; P_\textO2 P_{{{\text{O}}_{2} }} decreased twice as fast for the two smaller species (−0.6 mmHg O₂ min⁻¹) compared to the largest species (−0.3 mmHg O₂ min⁻¹). In contrast, the rate of increase in P_\textCO2 P_{{{\text{CO}}_{2} }} during breath hold was similar across species. These results demonstrate that large body size in odontocetes facilitates increased aerobic breath-hold capacity as mediated by decreased mass-specific metabolic rates (rates of change in P_\textO2 P_{{{\text{O}}_{2} }} served as a proxy for oxygen utilization). Indeed the experimentally determined 5 min ADL for bottlenose dolphins was surpassed by the 13.3 min maximum breath hold of the killer whale, which did not end in a rise in lactate. Rather, breath hold ended voluntarily as respiratory gases and pH fell within a narrow range for both large and small species, likely providing cues for ventilation.     

The annual cycle of Mesodinium rubrum in the waters surrounding the Isles of Shoals, Gulf of Maine

Mesodinium rubrum was collected in Kemmerer bottles, fixed inBouin's solution and protargol stained. Cell volume showed aseasonal change of over an order of magnitude, being largest(3.25x10⁴ µm³) in the early spring and smallest in thesummer. Cell abundance was highest in the spring and lowestin the summer. Biomass followed a similar trend ranging from{small tilde}1 to 147 J m^–3 Production, estimated by amultiple regression that incorporated ambient temperature andcell volume, was 2.5 kJ m^–3 day^–1 This is {smalltilde}0.3% of the primary production.     

A study of the effects of water carbonate alkalinity on some parameters of blood acid-base status in rainbow trout (Salmo gairdneri R.)

Summary The effects of two levels of water carbonate alkalinity (CA=0.3–0.5 meq·l⁻¹ and CA=12–13.5 meq·l⁻¹) on arterial blood acid-base status ( , pHa, [HCO ₃ ⁻ ]+[CO ₃ ⁻⁻ ]), oxygen consumption ( ) and plasma ionic composition (Na⁺, K⁺, Cl⁻) were investigated in trout living in normoxic-normocapnic water at 15°C. The results show that a high level of carbonate alkalinity induced a decrease in and a situation of mixed respiratory and metabolic acidosis compared to that in low CA water. These changes are accompanied by significant changes in ionic composition but the levels of oxygen consumption are unchanged. The role of the different capacitance coefficients of water for CO₂ and the effects of the different ionic composition of water on ionic and gascous exchanges are discussed. Equipe de Recherche associée au CNRS N° 070622     

Apparent molar volumes and tastes of molecules with more than one sapophore

The taste qualities of molecules known to generate more thanone type of taste (multisapophoric molecules) or known to containmore than one sapophore (potentially multisapophoric molecules)have been examined by physical methods in an attempt to explaintheir dominant taste response. The physical parameters examinedwere intrinsic viscosity, Huggins constant, apparent molar volumeand apparent specific volume. The apparent specific volume wasfound to discriminate between the four basic tastes (salt <{small tilde}0.33, sour {small tilde}0.33 to {small tilde}0.52,sweet {small tilde}0.52 to {small tilde}0.71 and bitter {smalltilde}0.71 to {small tilde}0.93) when applied to 48 unisapophoricmolecules. The corresponding values for 18 multisapophoric moleculeslie close to the appropriate primary taste interface. The apparentlyanomalous behaviour of six other molecules is discussed. Itis suggested that in order to elicit a particular basic tastea molecule must contain the appropriate sapophore and interactwith water so as to achieve a critical specific volume. Theseresults are consistent with the idea that specific receptorsfor the four taste modalities reside at different layers ofthe taste epithelium.     

Diurnal vertical migration of Gymnodinium mikimotoi during a red tide in Hoketsu Bay, Japan

The depth, velocity and timing of the vertical migration ofGymnodinium mikimotoi were examined using fluorometric fieldobservations. Gymnodinium mikimotoi can migrate vertically {smalltilde}20 m daily at velocities of {small tilde}2.2 m h^–1     

New potent biphalin analogues containing p-fluoro-L-phenylalanine at the 4,4' positions and non-hydrazine linkers

We report the synthesis and the biological evaluation of two new analogues of the potent dimeric opioid peptide biphalin. The performed modification is based on the replacement of two key structural elements of the native biphalin, namely: the hydrazine bridge which joins the two palindromic moieties and the phenylalanine residues at the 4,4′ positions of the backbone. The new analogues 9 and 10 contain 1,2-phenylenediamine and piperazine, respectively, in place of the hydrazidic linker and p-fluoro-l-phenylalanine residues at 4 and 4′ positions. Binding values are: K_\texti^m = 0.51 \textnM K_{\text{i}}^{\mu } = 0.51\,{\text{nM}} and K_\texti^d = 12.8 \textnM K_{\text{i}}^{\delta } = 12.8\,{\text{nM}} for compound 9, K_\texti^m = 0.09 \textnM K_{\text{i}}^{\mu } = 0.09\,{\text{nM}} and K_\texti^d = 0.11 \textnM K_{\text{i}}^{\delta } = 0.11\,{\text{nM}} for analogue 10.     

Four-frequency polarizing microscope for recording plasma images in the wavelength range 0.4–1.1 μm

The optical scheme and design of a four-frequency polarizing microscope intended for simultaneous recording of plasma images in the wavelength range 0.4–1.1 μm with the spatial resolution 12 μm in the entire spectral range are described. The effectiveness of such a microscope in studies of plasmas produced on interaction of laser radiation with a target is demonstrated. The plasma images are obtained at the frequencies ω₀, (3/2)ω₀, 2ω₀, and (5/2)ω₀, where ω₀ corresponds to the frequency of heating radiation. The transformation coefficient that characterizes the efficiency of conversion of heating radiation into the 2ω₀, (3/2)ω₀, and (5/2)ω₀ harmonics generated in the plasma is determined.     

AMP-activated protein kinase plays a role in initiating metabolic rate suppression in goldfish hepatocytes

In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate ( [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O₂) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold increase in eEF2 phosphorylation, and a 24% decrease in [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O₂] (<40 μM O₂), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O₂] as assessed by estimates of cellular P₅₀ and P₉₀ values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects of AICAR on [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation, or cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must be viewed cautiously because of the known off-target effects of the pharmacological agents used.     

The effects of suspended sediment concentration on turbulence in an annular flume

The effect of suspended sediment concentrations (SSC) on fluid turbulence in an annular flume was investigated. Flow speed was held constant at 0.57 m s⁻¹, and the resulting turbulent conditions were recorded using a 3-D Acoustic Doppler Velocimeter (ADV) at height (z) of 8.5 cm above the bed. The suspended material was composed of a natural glacial clay made up of particles smaller than 6 μm. The SSC in the flume were increased from clear water to 4800 mg l⁻¹ in nine discrete increments; temporal variations of SSC were monitored using three optical backscatter sensors (OBS) mounted in the flume wall at heights of 0.03, 0.10 and 0.20 m above the flume base. The results showed that turbulent intensity ( ) and energy dissipation rate (ɛ) did not change significantly between clear water and 200 mg l⁻¹, but decreased by nearly 30% in the SSC range between 200 and 2400 mg l⁻¹. Above 2400 mg l⁻¹, no further decrease was observed. Analyses of the velocity variances over narrow frequency bands (0.2 Hz wide) from 0 to 12.5 Hz showed that most of the flow turbulent energy (~70–80%) was contained within the lower frequencies i.e. larger eddies, and that these eddies experienced the greatest decrease in energy due to turbidity. It is proposed that these patterns are the consequence of the increase in suspended sediment concentrations and of the vertical stratification of sediments for SSC >200 mg l⁻¹.     

A note on imitative behavior

In a preceding paper (Bull. Math. Biophysics,27, 175–185) the distribution function ofφ=ɛ ₁-ɛ ₂,—the difference of excitations in the two mutually inhibiting centers, has been derived in terms of the distribution functionsf ₁(ɛ ₁) andf ₂(ɛ ₂) of the two excitations. In the present note some properties of the distribution functionf(ϕ) in terms of the propertiesf ₁(ɛ ₁) andf ₂(ɛ ₂) are derived.