The effects of some ions on the membrane potential of the giant axon of Myxicola

The effects of various ions on the resting membrane potential of the giant axons of Myxicola were determined. The mean resting potential in artificial sea water is 69 mv, inside negative. The membrane potential decreases with incresing external potassium concentrations, while changes in the sodium and chloride concentrations have little or no effect. For potassium concentrations greater than 50 mM/L the relation between membrane potential and concentration approximates that of a perfectly selective potassium electrode. The data for the whole range of concentrations examined can be well fitted by the equation: It was pointed out that the Myxicola giant axons can be studied under space voltage clamp and can be made available in the laboratory for 12 months out of the year. Myxicola then should become a very useful preparation for the study of membrane phenomena.     

Ionic and non-ionic compounds in the germination of spores of bacillus megaterium texas

Summary Germination requirements of suspensions of spores of Bacillus megaterium, Texas strain, an l-alanine-inosine type, have been examined employing a decrease in optical density as the criterion of germination. In deionized water, l-alanine and inosine were devoid of germinative powers. They were effective only in conjunction with any one of a large variety of salts. Data are given for germination by the monovalent and divalent alkali metal chlorides. The potassium halides were germinative; potassium fluoride was the best. Salts of organic acids, including fatty acids and polycarboxylic acids, were germinative. The need for inosine could be bypassed by various salts, e.g., ammonium propionate or salts of dipicolinic acid. Also, l-alanine was replaceable by a variety of amino acids, provided suitable ions were present. In the presence of magnesium chloride, sodium dipicolinate could substitute for either inosine or l-alanine, but not both. Salts of n-hexylamine and n-heptylamine bypassed the need for both l-alanine and inosine. A primary role for ions in germination is proposed and a secondary, augmentative action is attributed to l-alanine and inosine.     

Sodium currents in toad cardiac pacemaker cells

Cells in the pacemaker region of toad (Bufo marinus) sinus venosus had spontaneous rhythmic action potentials. The rate of firing of action potentials, the rate of diastolic depolarization and the maximum rate of rise of action potentials were reduced by TTX (10 nm to 1 m). Currents were recorded with the whole cell, tight seal technique from cells enzymatically dissociated from this region. Cells studied were identified as pacemaker cells by their characteristic morphology, spontaneous rhythmic action potential activity that could be blocked by cobalt but not by TTX and lack of inward rectification. When calcium, potassium and nonselective cation currents (I_f) activated by hyperpolarization were blocked, depolarization was seen to generate transient and persistent inward currents. Both were sodium currents: they were abolished by tetrodotoxin (10 to 100 nm), their reversal potential was close to the sodium equilibrium potential and their amplitude and reversal potential were influenced as expected for sodium currents when extracellular sodium ions were replaced with choline ions. The transient sodium current was activated at potentials more positive than –40 mV while the persistent sodium current was obvious at more negative potentials. It was concluded that, in toad pacemaker cells, TTX-sensitive sodium currents contributing both to the upstroke of action potentials and to diastolic depolarization may play an important role in setting heart rate.We thank the Australian National Heart Foundation for their support. D.A.S. is an NHMRC Senior Research Officer.     

Metabolic products of microorganisms

Summary Boromycin, at a concentration of 0.05 g/ml inhibits the synthesis of protein, RNA and DNA in whole cells of Bacillus subtilis. It is being antagonised by surface active compounds and is being bound to lipoprotein. Binding of the boromycin within the cell especially takes place at the cytoplasmic membrane.The inhibitory effect to Bacillus subtilis is being reversed by high concentration of potassium salts (e.g. 0.2 m KCl). The reversion is specific of potassium salts. After the adding of boromycin a discharge of potassium ions from the cells can be observed. The K⁺-Na⁺-activated ATP-ase of the cytoplasmic membrane is not influenced by boromycin. On an artificial membrane of carbon tetrachloride boromycin shows a low selectivity for potassium ions compared with sodium and lithium ions.The degradation of boromycin through alkaline and acid hydrolysis leads to a loss of antibiotic activity, due to the splitting off the boric acid from the molecule.76. Information: W. Pache u. H. Zähner: Arch. Mikrobiol. 66, 281–288 (1969).     

Utilization of lactose in non-respiring cells of the yeast Debaryomyces polymorphus

The facultative anaerobic yeast Debaryomyces polymorphus ferments glucose and galactose but does not utilize the disaccharide lactose under anaerobic conditions. The activity of the intracellulary located -galactosidase was not affected by anaerobiosis. Hence, the transport of lactose appears to be limiting for lactose utilization. The uptake of lactose (and of its metabolizable analogue, 4-nitrophenol--d-galactoptranoside) was mediated by an inducible transport system and it was strictly dependent on metabolic energy. Anaerobic conditions inhibited the transport of lactose completely as did the uncoupler carbonylcyanide-m-chlorophenyl-hydrazone, the electron transport chain inhibitors rotenone, antimycin A, potassium cyanide and the ATPase inhibitor diethylstilbestrol under aerobic conditions. Transport inhibited by antimycin A was resumed by adding ascorbate+tetramethyl-p-phenylenediamine. Glucose was taken up by a constitutive transport system, even in anaerobic cells it was still about five times faster than the uptake of lactose in respiring cells. Thus, monosaccharides can energize their uptake by glycolysis and represent, in contrast to lactose, fermentable, substrates in D. polymorphus.Abbreviations 4NPßgal 4-nitrophenol--d-galactopyranoside - TMPD tetramethyl-p-phenylenediamine Dedicated to Professor Augustin, Betz at the occassion of his 65th birthday.     

The effect of respiratory inhibitors on the fermentative ability of Pichia stipitis,Pachysolen tannophilus and Saccharomyces cerevisiae under various conditions of aerobiosis

Summary The growth and ethanol production by the d-xylose-fermenting yeasts Pichia stipitis and Pachysolen tannophilus under various conditions of aerobiosis responded similarly to the addition of the respiratory inhibitors potassium cyanide (KCN), antimycin A (AA), sodium azide and rotenone. However, the d-glucose-fermenting yeast Saccharomyces cerevisiae differed markedly from these yeasts in response to the inhibitors. In general the growth of the d-xylose-fermenting yeasts was inhibited by the respiratory inhibitors while ethanol production was either stimulated (especially when oxygen was available) or unaffected or inhibited by rotenone or AA or KCN and sodium azide, respectively. However, by exception KCN and AA stimulated ethanol production under aerobic conditions by Pichia stipitis and Pachysolen tannophilus respectively. Stimulatory or inhibitory effects by respiratory inhibitors were less marked in S. cerevisiae. These data suggest that unimpaired mitochondrial function is necessary for growth on d-xylose and optimal d-xylose fermentation. A requirement for membrane generated energy during d-xylose utilisation is indicated by 2,4-dinitrophenol inhibition of growth and fermentation.     

Aerobic and sequential anaerobic fermentation to produce xylitol and ethanol using non-detoxified acid pretreated corncob

Background

For economical bioethanol production from lignocellulosic materials, the major technical challenges to lower the production cost are as follows: (1) The microorganism should use efficiently all glucose and xylose in the lignocellulose hydrolysate. (2) The microorganism should have high tolerance to the inhibitors present in the lignocellulose hydrolysate. The aim of the present work was to combine inhibitor degradation, xylitol fermentation, and ethanol production using a single yeast strain.

Results

A new process of integrated aerobic xylitol production and anaerobic ethanol fermentation using non-detoxified acid pretreated corncob by Candida tropicalis W103 was proposed. C. tropicalis W103 is able to degrade acetate, furfural, and 5-hydromethylfurfural and metabolite xylose to xylitol under aerobic conditions, and the aerobic fermentation residue was used as the substrate for ethanol production by anaerobic simultaneous saccharification and fermentation. With 20% substrate loading, furfural and 5-hydroxymethylfurfural were degraded totally after 60 h aerobic incubation. A maximal xylitol concentration of 17.1 g l^-1 was obtained with a yield of 0.32 g g^-1 xylose. Then under anaerobic conditions with the addition of cellulase, 25.3 g l^-1 ethanol was produced after 72 h anaerobic fermentation, corresponding to 82% of the theoretical yield.

Conclusions

Xylitol and ethanol were produced in Candida tropicalis W103 using dual-phase fermentations, which comprise a changing from aerobic conditions (inhibitor degradation and xylitol production) to anaerobic simultaneous saccharification and ethanol fermentation. This is the first report of integrated xylitol and ethanol production from non-detoxified acid pretreated corncob using a single microorganism.

     

Anaerobic growth and potential for amino acid production by nitrate respiration in <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations (0.5% O₂), while no visible colonies were formed in the absence of O₂. However, in the presence of nitrate (), the organism exhibited limited growth anaerobically with production of nitrite (), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate respiration. Agar piece assays using l-lysine- and l-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating the potential of C. glutamicum for anaerobic amino acid production.     

Single-channel analysis of the potassium permeability in HeLa cancer cells: Evidence for a calcium-activated potassium channel of small unitary conductance

Summary Cell-attached and inside-out patch-clamp experiments (O.P. Hamill et al.,Pfluegers Arch. 391: 85–100, 1981) were undertaken in order to characterize the molecular mechanisms responsible for the calcium-dependent potassium permeability observed in HeLa cancer cells. Our result essentially indicate that the HeLa cell external membrane contains potassium channels whose activity can be triggered within an internal calcium concentration range of 0.1 to 1 m. This particular channel was found to behave as an inward rectifier in symmetrical 200mm KCl with a conductance of 50 and 10 pS at large negative and large positive membrane potentials, respectively.I/V curves were also measured in 10, 20, 75, 200 and 300mm KCl and the data interpreted in terms of a one-site-two-barrier model. The channel activity appeared to be nearly voltage independent within the voltage range –100 to +100mV, an increase ofP _o, the open channel probability, being observed at large negative potentials only. In addition, the results obtained from inside-out experiments on the relationship betweenP _o and the cytoplasmic freecalcium concentration have led to conclude that four calcium ions are probably required in order to open the channel. In this regard it was found that an increase of the internal free-calcium level affects more the number of channel openings per second than the actual channel mean lifetime. Finally, it is concluded following a time interval distribution analysis, that this particular channel has at least three closed states and two open states.     

Evidence for interactions between the energy-dependent transport of sugars and the membrane potential in the yeastRhodotorula gracilis (Rhodosporidium toruloides)

Summary A membrane potential (inside negative) across the plasma membrane of the obligatory aerobic yeastRhodotorula gracilis is indicated by the intracellular accumulation of the lipid-soluble cations tetraphenylphosphonium and triphenylmethylphosphonium. The uptake of these ions is inhibited by anaerobic conditions, by uncouplers, by addition of diffusible ions, or by increase of the leakiness of the membrane caused by the polyene antibiotic nystatin. The membrane potential is strongly pH-dependent, its value increasing with decreasing extracellular proton concentration. Addition of transportable monosaccharides causes a depolarization of the electrical potential difference, indicating that the H⁺-sugar cotransport is electrogenic. The effect on the membrane potential is enhanced by increasing the sugar concentration. The half-saturation constants of depolarization ford-xylose andd-galactose were comparable to those of the corresponding transport system for the two sugars. All agents that depressed the membrane potential inhibited monosaccharide transport; hence the membrane potential provides energy for active sugar transport in this strain of yeast.     

Perturbation of monovalent cation composition in Ulva lactuca by cadmium, copper and zinc

Discs of thallus cut from the macroalga Ulva lactuca were incubated in filtered seawater containing cadmium, zinc, copper or cobalt (30 m). The metal uptake rates differed for each metal in the order Cu > Zn > Cd > Co. Exposure of the macroalga to metals resulted in a disruption of intracellular monovalent cation composition. Intracellular potassium was irreversibly lost and sodium was accumulated by cadmium- or copper-treated U. lactuca, which was assumed to indicate irreversible disruption of the plasmalemma. Exposure to zinc caused an increase in sodium concentrations, whereas potassium concentrations were not significantly different from the controls, suggesting that the integrity of the plasmalemma had been maintained at the zinc concentration used. Intracellular magnesium was also lost from copper-treated algae, which again indicated a loss of integrity of the cell membrane.     

Further photophysical and photochemical characterization of flavins associated with single-shelled vesicles

Summary In order to investigate whether the loop diuretic sensitive, sodium-chloride cotransport system described previously in shark rectal gland is in fact a sodium-potassium chloride cotransport system, plasma membrane vesicles were isolated from rectal glands ofSqualus acanthias and sodium and rubidium uptake were measured by a rapid filtration technique. In addition, the binding of N-methylfurosemide to the membranes was investigated. Sodium uptake into the vesicles in the presence of a 170mm KCl gradient was initially about five-fold higher than in the presence of a 170mm KNO₃ gradient. In the presence of chloride, sodium uptake was inhibited 56% by 0.4mm bumetanide and 40% by 0.8mm N-methylfurosemide. When potassium chloride was replaced by choline chloride or lithium chloride, sodium uptake decreased to the values observed in the presence of potassium nitrate. Replacement of potassium chloride by rubidium chloride, however, did not change sodium uptake. Initial rubidium uptake into the membrane vesicles was about 2.5-fold higher in the presence of a 170mm NaCl gradient than in the presence of a 170mm NaNO₃ gradient. The effect of chloride was completely abolished by 0.4mm bumetanide. Replacement of the sodium chloride gradient by a lithium chloride gradient decreased rubidium uptake by about 40%; replacement by a choline chloride gradient reduced the uptake even further. Rubidium uptake was also strongly inhibited by potassium. Sodium chloride dependence and bumetanide inhibition of rubidium flux were also found in tracer exchange experiments in the absence of salt gradients. The isolated plasma membranes bound³[H]-N-methylfurosemide in a dose-dependent manner. In Scatchard plots, one saturable component could be detected with an apparentK _D of 3.5×10^–6 m and a number of sitesn of 104 pmol/mg protein. At 0.8 m, N-methylfurosemide binding decreased 51% when sodium-free or low-potassium media were used. The same decrease was observed when the chloride concentration was increased from 200 to 600mm or when 1mm bumetanide or furosemide were added to the incubation medium. These studies indicate that the sodium-chloride cotransport system described previously in the rectal gland is in fact a sodium-potassium chloride cotransport system. It is postulated that this transport system plays an essential role in the secondary active chloride secretion of the rectal gland.     

Presence of a sodium-dependentd-glucose transport system in the kidney of the atlantic hagfish (Myxine glutinosa)

Summary A membrane fraction, rich in brushborder membranes, was prepared from the archinephric duct of the atlantic hagfish (Myxine glutinosa) and the uptake ofd-glucose and other sugars into the membrane vesicles was investigated by a rapid filtration technique. Uptake ofd-glucose was found to be sodium-dependent, phloridzin-inhibitable and osmotically sensitive. A sodium gradient dependent overshoot was demonstrated at 25° C as well as at the more physiological temperature of 4°C. The sodium dependentd-glucose transport was inhibited by -methyl-d-glucoside, but not by 2-deoxy-d-glucose. Furthermore at the same concentration of sugars the initial uptake ofd-glucose was 7.2-fold higher thanl-glucose uptake.d-glucose transport across the membrane in the presence of a sodium gradient was stimulated when SCN^– replaced Cl^– and inhibited when gluconate replaced Cl^–.d-glucose uptake in the presence of a sodium- and potassium gradient was decreased by the addition of valinomycin. In addition, the presence of ad-glucose gradient enhanced sodium uptake into the vesicles as compared to a mannitolgradient. Phloridzin inhibited thed-glucose dependent sodium flux. Thus an electrogenic stereospecific sodium glucose co-transport system, with properties similar to that found in the kidney of higher vertebrates is present in this primitive vertebrate and might participate in secondary-active sugar reabsorption in the archinephric duct.     

Die Bedeutung einiger anorganischer Komponenten des Seewassers für die Turgorregulation vonChaetomorpha linum (Cladophorales)

Zusammenfassung 1. Die negative Turgorregulation vonChaetomorpha linum nach Herabsetzung des Salzgehaltes im Außenmedium beruht in der Hauptsache auf einer Erniedrigung des osmotischen Potentials des Zellsaftes durch Abgabe von K^. und Cl.2. Während der positiven Turgorregulation nach Erhöhung des Salzgehaltes im Außenmedium konnte umgekehrt eine starke Speicherung von K^. und Cl beobachtet werden.3. Das Natrium als wichtigstes Kation des Seewassers ist für beide Prozesse osmotisch kaum von Bedeutung. Die Änderung des Natriumgehaltes im Versuchsmaterial betrug in beiden Fällen nur etwa 10% der Änderung seines Chloridwertes und nur etwa 5% der Änderung seines osmotischen Gesamtpotentials.4. Kalziummangel im Außenmedium führte zu einer starken Abgabe von KCl durch die Versuchspflanzen, welche dabei einen beträchtlichen Turgorverlust erlitten.5. Die ebenfalls durch Kalziummangel bewirkte starke Verquellung der Zellwände wird im Zusammenhang mit der sprughaften Abnahme des Kalziumgehaltes der Versuchspflanzen auf einen Ionenaustauschvorgang zurückgeführt, bei dem das Zellwand-Kalzium durch Natrium ersetzt werden dürfte.

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The importance of some inorganic components of sea water for the turgor-regulation ofChaetomorpha linum (Chladophorales)

Some algae of the intertidal zone are capable of regulating their turgor pressure. In 1896Drevs had already shown that this process is affected primarily by accumulation (positive turgor-regulation) or extrusion (negative turgor-regulation) of mineral salts and that transformation of stock material (e. g. starch) into osmotic active substances (e. g. sucrose) and vice versa plays no important role. His results are being confirmed by the present paper. InChaetomorpha linum (Müller)Kützing, lowering of salinity resulted in a significant release of potassium and chlorine (negative turgor-regulation). Changes in sodium content were only small. In algae exposed to a salinity of 30, the total sodium concentration was only about 10% that of the external medium. Salinity increase led to a marked accumulation (positive turgor-regulation) of potassium and chlorine. Even in this process sodium was engaged only to a small degree — despite its high concentration in the surrounding medium. In both cases internal changes in sodium content amounted only to about 5% of the total osmotic changes in the external medium. After transfer from 30 salinity into isosmotic artificial sea water without Ca^··, a rapid loss of potassium and chlorine was observed. The abrupt decrease of the calcium content accompanied by a marked swelling of cell walls, leading to a significant reduction of cell space, is interpreted as ion exchange process changing the cell wall Ca^.. against Na^..

     

The effect of ionophores on proton flux in the ruminal bacterium,streptococcus bovis

NonenergizedStreptococcus bovis cells, which were washed in potassium-phosphate buffer and incubated in Tris buffer containing 200mm potassium chloride (pH 6.5), did not take up tetraphenylphosphonium ion (TPP⁺), but the same cells took up TPP⁺ when they were incubated in Tris buffer lacking potassium. This result indicated that passive potassium diffusion was creating an electrical potential () across the cell membrane. Neither cells took significant amounts of 9-aminoacridine (9-AA), an intracellular pH marker. Cells that were incubated in Tris buffer and treated with carbonyl cyanidem-chlorophenylhydrazone (CCCP) took up 9-AA, and this result indicated that this protonophore was facilitating proton influx. The ionophores monensin and lasalocid also caused 9-AA uptake, and it appeared that they were responsible for or responsive to potassium/proton antiport. However, there was also a rapid accumulation of 9-AA when the cells were treated with valinomycin, a potassium uniporter that cannot translocate protons. This latter result indicated that potassium efflux was associated with another avenue of proton influx (e. g., potassium/proton symport). Because cells treated with dicyclohexyl carbodiimide (DCCD) also exhibited valinomycin-dependent 9-AA uptake, it is unlikely that the F₁F₀ATPase or ATP formation was responsible for proton flux across the cell membrane.     

Regulation of passive potassium transport of normal and transformed 3T3 mouse cell cultures by external calcium concentration and temperature

Summary Regulation of passive potassium ion transport by the external calcium concentration and temperature was studied on cell cultures of 3T3 mouse cells and their DNA-virus transformed derivatives. Upon lowering of external calcium concentration, passive potassium efflux generally exhibits a sharp increase at about 0.1mm. The fraction of calcium-regulated potassium efflux is largely independent of temperature in the cases of the transformed cells, but shows a sharp increase for 3T3 cells upon increasing temperature above 32°C. In the same range of temperature, the 3T3 cells exhibit the phenomenon of high-temperature inactivation of the residual potassium efflux at 1mm external calcium. At comparable cellular growth densities, the transformed cell lines do not show high-temperature inactivation of residual potassium efflux. These results are consistent with the notion of a decisive role of the internal K⁺ concentration in the cell-density dependent regulation of cell proliferation. In particular, the growth-inhibiting effect of lowering the external Ca²⁺ concentrations is considered as largely due to a rise of passive K⁺ efflux and a subsequent decrease of internal K⁺ concentration. The experimental data on the Ca²⁺ dependence of passive K⁺ flux are quantitatively described by a theoretical model based on the constant field relations including negative surface charges on the external face of the membrane, which cooperatively bind Ca²⁺ ions and may concomitantly undergo a lateral redistribution. The present evidence is consistent with acidic phospholipids as representing these negative surface charges.This work is dedicated to the memory of Max Delbrück (deceased March 10, 1981), in whose laboratory in 1966 the earlier version of the present theoretical model was developed by one of the authors.     

History of the Pasteur effect and its pathobiology

Summary Long before the mechanism of fermentation was understood,Pasteur discovered an important regulatory phenomenon of carbohydrate metabolism. He observed that yeast consumes more sugar anaerobically than aerobically. This so-called Pasteur effect has been subject of many controversies and an analysis of the development of the concepts has been presented. Among the key errors made in the early evaluations was to emphasize the control of end product formation rather than of hexose utilization.The Pasteur phenomenon as understood at present is a complex coordinated control mechanism which operates at several levels. The basic phenomenon is a competition between glycolysis and oxidative phosphorylation for the available ADP and inorganic phosphate. Superimposed are allosteric controls of hexokinase (glucose-6-phosphate) and of phosphofructokinase (ATP). However, in some cells glucose-6-phosphate is not an inhibitor of hexokinase and ATP levels do not change significantly during transition from aerobic to anaerobic conditions. It is therefore clear that other secondary allosteric effectors such as inorganic phosphate play a significant role. The major conclusion is that there are multiple and different control mechanisms participating in the Pasteur effect in different cells.A loss of control in tumor cells gives rise to a high aerobic glycolysis. The history and possible significance of this in malignancy is described.     

Intensification of alcoholic fermentation upon dehydration-rehydration of the yeast Saccharomyces cerevisiae

Summary In comparison with intact yeast, dehydrated-rehydrated cells of Saccharomyces cerevisiae show significantly higher ethanol production from exogenous substrate under both anaerobic and aerobic conditions, particularly when low concentration (0.1%) of glucose are used. For populations with a higher percentage of viable rehydrated cells (above 70%) a more notable decrease in the Pasteur effect (the difference between the quantity of ethanol formed under anaerobic and aerobic conditions) is observed.     

Effect of calcium on brain metabolism in vitro

In attempts to distinguish between direct and indirect effects of Ca on brain cell metabolism, respiration, glycolysis, ATP, phosphocreatine, incorporation of [¹⁴C] leucine into protein, and accumulation of⁴⁵Ca was determined in brain slices. Incubation was carried out in normal salt-balanced medium, in high-potassiumor ouabain-containing medium under aerobic and anaerobic conditions. Calcium ions inhibited slightly glycolysis and respiration in normal medium and activated amino acid incorporation into proteins. Levels of ATP and phosphocreatine remained normal. These effects were interpreted as due to a stabilization of plasma membranes by Ca ions to prevent their spontaneous depolarization. Incubation of slices in high-potassium and ouabain media in aerobic conditions in the presence of Ca resulted in activation of respiration and glycolysis, decrease of ATP and phosphocreatine levels, and inhibition of amino acid incorporation into proteins. The disturbances in energy metabolism, caused by the respiration-linked Ca uptake in brain mitochondria and concomitant inhibition of oxidative phosphorylation, may lead to the inhibition of amino acid incorporation into proteins. An increase in Ca levels in the cytoplasm may only be expected in anaerobic conditions during the incubation in high-potassium and ouabain media. This is manifested by a direct inhibition of glycolysis by Ca ions and a drastic decrease of ATP and phosphocreatine in slices. The results suggest that stimulation of aerobic glycolysis and inhibition of anaerobic glycolysis by Ca may explain the unknown mechanism of the so-called reversed Pasteur effect of brain slices incubated in high-potassium media.     

Stimulation of the anaerobic growth ofSalmonella typhimurium by reduction ofl-carnitine,carnitine derivatives and structure-related trimethylammonium compounds

In view of the development of al-carnitine deficiency, the metabolism ofl-carnitine and structure-related trimethylammonium compounds was studied inSalmonella typhimurium LT₂ by means of thin-layer chromatography (TLC).l-Carnitine, crotonobetaine and acetyl-l-carnitine stimulated the anaerobic growth in a complex medium significantly. The stimulation depended on the formation of -butyrobetaine. The reduction ofl-carnitine proceeded in two steps: (1) Dehydration of thel-carnitine to crotonobetaine, (2) hydrogenation of crotonobetaine to -butyrobetaine. The reduction of crotonobetaine was responsible for the growth stimulation. Terminal electron acceptors of the anaerobic respiration such as nitrate and trimethylamine N-oxide, but not fumarate, suppressed the catabolism ofl-carnitine completely. Glucose fermentation, too, inhibited the reduction ofl-carnitine but optimal growth with a high carnitine catabolism was achieved byd-ribose. The esters of carnitine with medium- and long-chain fatty acids inhibited the growth considerably because of their detergent properties.Abbreviations TLC thin-layer chromatography