Lipoxygenbase-derived products of arachidonic acid mediate stimulation of hexose uptake in human polymorphonuclear leukocytes

The titration of metal-freed bovine α-lactalbumin with Mg²⁺ ions causes a two-stepped decrease in the tryptophan fluorescence quantum yield and a pronounced spectral shift towards shorter wavelengths, which seems to be a result of the binding of two magnesium ions to the protein molecule. The magnesium binding constants evaluated from the fluorimetric Mg²⁺-titration are 2·10³ and 2·10² M^?1. Mg²⁺ ions in millimolar concentrations almost do not influence the binding of Ca²⁺ ions to the protein.     

A respiration-dependent primary sodium extrusion system functioning at alkaline pH in the marine bacterium Vibrioalginolyticus

The membrane potential generated at pH 8.5 by K⁺-depleted and Na⁺-loaded $\text{Vibrio}\text{alginolyticus}$ is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na⁺-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na⁺ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na⁺-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na⁺ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na⁺ chemical gradient.     

High resolution vertical profiles of pH in recent sediments

High resolution (0.1 cm sampling interval) profiles of pH were obtained from some recent estuarine (Long Island Sound, Chesapeake Bay) and freshwater (Lake Erie) sediments and from laboratory microcosms containing homogenized Lake Erie sediment (both with and without tubificid oligochaetes) by incrementally precessing a micro-pH electrode downward through the sediment. These profiles revealed that hydrogen ion undergoes chemical reactions on a scale smaller than can be resolved using classic 1 cm sampling intervals, and that the vertical distribution of hydrogen ion is affected by bioturbation. In all sediments examined, a local pH minimum occurred immediately below the oxidized zone. In estuarine sediments, a second deeper pH minimum was observed. The presence of tubificids prevented profound pH changes from developing in microcosm sediments treated with a layer of activated sewage sludge and resulted in more modest alterations of pH profile in microcosm sediments lacking such a layer. The technique used in this study is by no means limited to pH. In principal, any chemical species that can be directly determined by electrodes (e.g. O₂, S^-2) may be studied. Microelectrode techniques could be especially useful in the study of chemical gradients around animal burrows and in time series studies of whole core diagenesis.     

Dissolved oxygen dependent phosphorus release from profundal sediments of Lake Constance (Obersee)

Phosphorus release rates from profundal sediments of Lake Constance (Obersee) have been determined in D.O., pH regulated sediment-water systems. Above 10% O₂ saturation (> 1.2 ppm D. O.) and with pH as in situ, no net release could be found. Sedimentations of diatom sludge (Asterionella formosa) and carbonate-phosphate coprecipitate (CaCO₃.CaHPO₄) increased the release to 0.5 mg × m^–2 × d^–1 which, however, will not be relevant to the P balance in Obersee. The annual phosphorus accumulation in profundal Obersee and Ueberlingersee is, therefore, observed as due to sinking of phosphorus-bound detritus during the stagnation period.The experimental work was carried out at the Limnological Institute of the University of Freiburg/Breisgau (West Germany) and has been supported by the Industrieverband Körperpflege und Waschmittel e.V. and the Gernan Research Council (DFG)The experimental work was carried out at the Limnological Institute of the University of Freiburg/Breisgau (West Germany) and has been supported by the Industrieverband Körperpflege und Waschmittel e.V. and the Gernan Research Council (DFG)     

An ecological study of the rare rotifer species Trochosphaera solstitialis (Thorpe 1893) and the first report of the male

An ecological study of the rotifer species Trochosphaera solstitialis (Thorpe, 1893) was conducted for a period of eight months in a temporary pond in eastern Texas, U.S.A. The pond was found to be environmentally stressed and contained large amounts of decomposing vegetation. Physico-chemical factors contributing to the stressed conditions were low dissolved oxygen concentrations, low pH values, high ammonia concentrations, and high color values caused by large concentrations of iron, tannin and lignin. Large concentrations of iron, tannin, and lignin seem to be highly correlated with T. solstitialis populations. Physicochemical conditions probably eliminated predators of the rotifer, such as fish. Males of T. solstitialis were observed which never left the body cavity of the female. Males probably do not feed with an apparent rudimentary digestive system.     

Respirational activity of Chlorella fusca monitored by in vivo P-31 NMR

Energy metabolism during dark respiration of the green alga Chlorella fusca was investigated by ³¹P NMR spectroscopy. The kinetics of the transition from anaerobic to aerobic conditions (and vice versa) was followed with a temporal resolution of 16 s. This transition is accompanied by a shift of the cytoplasmic pH from 6.8 to 7.4, while the vacuolar pH remains constant. Simultaneously, an increase in the concentration of nucleoside-triphosphates and a decrease in the concentration of cytoplasmic orthophosphate take place, as well as the formation of mobile polyphosphates. The concentration of ATP and P _i reach steady-state levels within 30 s. Upon the reverse transition, from aerobic to anaerobic conditions, steady-state concentrations are obtained only after 3 min.     

Protonmotive force in freshwater sulfate-reducing bacteria,and its role in sulfate accumulation in Desulfobulbus propionicus

The protonmotive force in several sulfate-reducing bacteria has been determined by means of radiolabelled membrane-permeant probes (tetraphenyl-phosphonium cation, TPP⁺, for , and benzoate for pH). In six of ten freshwater strains tested only the pH gradient could be determine, while the membrane potential was not accessible due to nonspecific binding of TPP⁺. The protonmotive force of the other four strains was between –110 and –155 mV, composed of a membrane potential of –80 to –140 mV and a pH gradient between 0.25 and 0.8 (inside alkaline) at pH_out=7. In Desulfobulbus propionicus the pH gradient decreased with rising external pH values. This decrease, however, was compensated by an increasing membrane potential. Sulfate, which can be highly accumulated by the cells, did not affect the protonmotive force, if added in concentrations of up to 4 mM. The highest sulfate accumulation observed (2500-fold), which occurred at external sulfate concentrations below 5 M, could be explained by a symport of three protons per sulfate, if equilibrium with the protonmotive force was assumed. At higher sulfate concentrations the accumulation decreased and suggested an electroneutral symport of two protons per sulfate. At sulfate concentrations above 500 M, the cells stopped sulfate uptake before reaching an equilibrium with the protonmotive force.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - MOPS morpholinopropanesulfonic acid - TPP⁺ tetraphenylphosphonium cation - EDTA ethylenediaminetetraacetic acid - pH transmembrane pH gradient (pH_in-pH_out) - transmembrane electrical potential difference     

Near Neutral pH Redox Flow Battery with Low Permeability and Long‐Lifetime Phosphonated Viologen Active Species

A highly stable phosphonate‐functionalized viologen is introduced as the redox‐active material in a negative potential electrolyte for aqueous redox flow batteries (ARFBs) operating at nearly neutral pH. The solubility is 1.23 m and the reduction potential is the lowest of any substituted viologen utilized in a flow battery, reaching ?0.462 V versus SHE at pH = 9. The negative charges in both the oxidized and the reduced states of 1,1′‐bis(3‐phosphonopropyl)‐[4,4′‐bipyridine]‐1,1′‐diium dibromide ( BPP?Vi ) effect low permeability in cation exchange membranes and suppress a bimolecular mechanism of viologen decomposition. A flow battery pairing BPP?Vi with a ferrocyanide‐based positive potential electrolyte across an inexpensive, non‐fluorinated cation exchange membrane at pH = 9 exhibits an open‐circuit voltage of 0.9 V and a capacity fade rate of 0.016% per day or 0.00069% per cycle. Overcharging leads to viologen decomposition, causing irreversible capacity fade. This work introduces extremely stable, extremely low‐permeating and low reduction potential redox active materials into near neutral ARFBs.     

Water pH and metabolic parameters in silver catfish (Rhamdia quelen)

This study evaluated the effects of an acute change in water pH (from pH 7.5 to 4.0, 5.0, 6.0, 7.5, 8.0 or 9.0) on several biochemical parameters in juveniles of the silver catfish, Rhamdia quelen. Ammonia levels decreased in the liver and increased in the muscle with increasing water pH. In the kidney, lower ammonia levels were observed at neutral pH. An increase in water pH decreased the glucose, glycogen and lactate levels in the liver and kidney (except for glycogen levels in the kidney and lactate levels in the liver, which presented lower levels at neutral pH). In muscle, the glucose and glycogen levels decreased with increasing water pH, whereas lactate levels tended to be lower at neutral pH. Gill and kidney Na⁺/K⁺-ATPase activities tended to increase in alkaline water, and the highest value was observed in fish exposed to pH 9.0. The optimal levels of the analyzed biochemical parameters occurred at neutral pH. In conclusion, exposure to acidic and alkaline pH changes the metabolic parameters of silver catfish as well as gill Na⁺/K⁺-ATPase activity.