Isolation and the structure of deoxopinguisone from the liverwort Ptilidium ciliare

A pure substance has been isolated from the liverwort Ptilidium ciliare of composition C₁₅H₂₂O. On the basis of the correlation of its IR and PMR spectra with those of pinguisone (I), it has been assigned structure of deoxopinguisone (II). This was confirmed by comparison with synthetic deoxopinguisone prepared from authentic pinguisone isolated from Aneura pinguis.     

Lipid composition of maturing and elongate liverwort sporophytes

The setae of Lophocolea heterophylla sporophytes undergo rapid cell elongation with no net loss of lipid. Glycerolipids and sterol esters are the predominant lipids present in unelorigate setae. Phospho- and glycolipids increase dramatically with respect to total lipid during elongation and thus reflect membrane increases. Unusual polyunsaturated fatty acids (arachidonic and eicosapentaenoic) are conspicuous constituents of these lipids.     

Vacuolar ion channels in the liverwort Conocephalum conicum

As a liverwort Conocephalum conicum belongs to the oldest terrestrial plants¹ and is phylogenetically located between green algae and higher plants. Recent patch-clamp recordings on Conocephalum vacuoles^2,3 demonstrate ion channels very similar to higher plants and clearly different from vacuolar ion channels described in green algae. Here we summarize the features of a vacuolar cation channel and a vacuolar anion channel that both are common in terrestrial plants but are not detected in green algae, and we speculate about the molecular identity of these channels in the liverwort Conocephalum.Key words: vacuole, SV channel, anion channel, Conocephalum conicum, Embryophyta     

Effects of acetyl-L-carnitine on the formation of fatty acid ethyl esters in brain and peripheral organs after short-term ethanol administration in rat

Increasing evidence suggests that Fatty acid ethyl esters (FAEE) play a central role in ethanol induced organ damage. In the current study we measured FAEE formation in rats after short-term oral administration of ethanol, in the presence and absence of pre-treatment with acetyl-L-carnitine. Ethanol treatment caused a significant increase in the levels of FAEE, particularly in the brain and heart, but also in the kidney and liver. Increases in FAEE were associated with a significant increase in FAEE synthase activity, GSH transferase activity, and lipid hydroperoxide levels. Pre-treatment with acetyl-L-carnitine resulted in a significant reduction of FAEE accumulation, decrease in FAEE synthase and GSH transferase activities, and lipid hydroperoxide levels. Administration of acetyl-L-carnitine greatly reduced the metabolic abnormalities due to non-oxidative ethanol metabolism, through an increment in lipid metabolism/turnover and by the modulation of the activities of enzymes associated with FAEE synthesis. These results suggest a potentially important pharmacological role for acetyl-L-carnitine in the prevention of alcohol-induced cellular damage.     

Light-triggered action potentials in the liverwort Conocephalum conicum

The response to light of a liverwort, Conocephalum conicum L., measured as a change in the resting potential, consists of two stages. The first stage is a slight depolarization dependent on light intensity. This plays the role of a generator potential (GP) which induces the second stage - an action potential of the all-or-none character. Action potentials induced by light and by electrical stimuli have the same properties, i.e. identical time course, propagation velocity, and refractory periods. A summation occurs of sub threshold light stimuli and of light and electrical stimuli. The presence of 5⋅10-⁻⁶ M DCMU cancelled the light response and blocked - by inhibition of the electron transport chain - the mechanism leading to GP generation. However, this effect did not produce any change in the response to electrical stimuli.     

Low-temperature induced transmembrane potential changes in the liverwort Conocephalum conicum

Intracellular microelectrode measurements revealed that the liverwort Conocephalum conicum generates all-or-none action potentials (APs) in response to a sudden temperature drop. In plants with anion and potassium conductance blocked, dose-dependent voltage transients (VTs) were evoked by cold stimuli. These VTs did not propagate. When the external concentration of Ca(2+) was decreased or calcium channel inhibitors (La(3+), Gd(3+), verapamil, Mg(2+), Mn(2+)) were used, inhibition of VTs was observed. Amplitudes of both APs and VTs grew when Sr(2+) ions, known to release calcium from internal stores, were added to the medium. Neomycin, which suppresses phospholipase C and indirectly affects inositol triphosphate formation, caused substantial inhibition of both APs and VTs. It is concluded that a temperature drop elucidated membrane potential changes due to calcium influx both from external and internal stores.     

Characteristics of the light-induced generator potentials in the liverwort Conocephalum conicum

Light-induced generator potentials were examined in the liverwort Conocephalum conicum L. by applying sub-threshold light stimuli (400–750 nm). The fluenceresponse dependence was determined for various wavelengths. At low values of quantum flux density (less than 1 μmol m⁻² s⁻¹) the plant reacts to the light pulses with hyperpolarization which, with a rise in the pulse intensity, is masked by the depolarization of the transmembrane potential. The action spectrum of depolarization shares many features with the absorption specturm of photosynthetic pigments. Application of inhibitors and electron donors showed a predominant role of photosystem II in the formation of the generator potential. No significant Emerson enhancement was observed after simultaneous illumination with light beams of 650 and 700 nm.     

Characteristics of anion channels in the tonoplast of the liverwort Conocephalum conicum

Isolated vacuoles of the liverwort Conocephalum conicum thallus cells were investigated using the patch-clamp technique. At high cytosolic Ca(2+) activities, slowly activating currents were evoked by positive potentials. The currents were conducted by the SV (slow-vacuolar) channel. When isolation of vacuoles was carried out at high Mg(2+) and low Ca(2+) concentration and the same proportion of the cations was kept in the bath, currents were recorded at negative potentials. Once activated, these currents persisted even after replacing Mg(2+) with K(+) in the bath. Sr(2+) and Ba(2+) were also effective activators of the currents. With a Cl(-) gradient, 10 mM in the bath and 100 mM in the lumen, currents were significantly reduced and the current-voltage characteristics shifted towards the reversal potential of Cl(-), indicating Cl(-) selectivity. Currents almost vanished after substituting Cl(-) with gluconate. They were strongly reduced by anion channel inhibitors 4,4'-diisothicyanatostilbene-2,2'-disulfonic acid (DIDS; 1 mM), anthracene-9-carboxylic acid (A9C; 2 mM) and ethacrinic acid (0.5 mM). Single-channel recordings revealed a 32 pS channel activating at negative voltages. It is concluded that the currents at negative potentials are carried by anion channels suitable for conducting anions from the cytosol to the vacuole. The anion channels were weakly calcium dependent, remaining active at physiological calcium concentration. The channels were almost equally permeable to Cl(-), NO3(-) and SO4(2-), and much less permeable to malate(2-). Anion channels did not respond to ATP addition. cAMP (10 microM) had a weak effect on anion channels. Protein kinase A (0.4 U) added to the medium caused no significant effect on anion channels.     

Sesquiterpene hydrocarbons of the liverwort Scapania ornithopodioides

The liverwort, Scapania ornithopodioides, was investigated for sesquiterpene hydrocarbons by utilizing GC and GCIMS and 17 components were identified. Among these, the major component, aromadendrene, and two minor ones, cyclosativene and α-farnesene are reported for the first time as constituents of liverworts. In addition, aromadendrene also occurred in three other Taiwanese liverworts examined.     

Extra- and intracellular measurements of action potentials in the liverwort Conocephalum conicum

Action potentials induced by electrical stimuli were recorded from the thalli of tfie liverwort, Conocephalum conicum L. An analysis of an equivalent circuit of Conocephalum conicum thallus in situ has shown that the multiphasic time course of extracellular recordings is caused by a branching of extracellular conduction layers and by an overlapping of action currents. As compared to the velocity of excitation propagation without short-circuiting, more than 10 times higher rates of action potential conduction have been recorded when the plants are immersed in a low resistaace solution. Furthermore, simultaneous extra- and intracellular recordings from thalli in situ are presented.     

Lunularic acid in cell suspension cultures of Marchantia polymorpha

Lunularic acid (LNA) was isolated from the cultured cells of the liverwort Marchantia polymorpha. Quantitative analysis by reverse phase HPLC showed that the content of LNA in the cells changed markedly during their growth, ranging from 1 to 7μg/mg dry wt. The accumulation of LNA was greatly enhanced by a deficiency of phosphate in the culture medium.     

Effects of quercetin and verapamil on membrane potential in the liverwort Conocephalum conicum

Quercetin is a very common flavonoid widely distributed in many plants. The flavonoid intake has been linked to the prevention of human diseases including cancer. Flavonoids possess also a broad spectrum of effects on plants. Quercetin is involved in Ca²⁺ transport and metabolism. The present study was designed to check the effects of quercetin alone and in combination with verapamil on the resting and action potentials in the liverwort Conocephalum conicum. The application of 59·10⁻⁶ mol·dm⁻³ quercetin caused an increase of action potential amplitudes. During the 3rd and 4th hour of treatment an increase by 20–22 % with respect to the control was observed. No changes were found in the resting potential in quercetin treated plants. Verapamil, a calcium channel inhibitor, caused gradual decrease of action potential amplitudes. Quercetin, when added together with verapamil, prevented its inhibitory effect. Interactions between quercetin and Ca²⁺ transport are discussed.     

Incorporation of [1-(13)C]1-deoxy-D-xylulose into isoprenoids of the liverwort Conocephalum conicum

The incorporation of (13)C labeled 1-deoxy-D-xylulose into the monoterpene bornyl acetate, the sesquiterpene cubebanol, and the diterpene phytol has been studied in axenic cultures of the liverwort Conocephalum conicum. Quantitative (13)C NMR spectroscopic analysis of the labeling patterns of the sesquiterpene indicated a possible degradation of 1-deoxy-D-xylulose to acetate and subsequent incorporation via the mevalonic acid pathway. In bornyl acetate, the labeling occurred only in the acetate moiety whereas the isoprene units remained unlabelled. The isoprene units of the diterpene phytol showed incorporation of intact deoxy-D-xylulose. These results indicate the involvement of both IPP biosynthetic pathways and two independently operating compartments/cell types with MEP pathway machinery. One MEP compartment is presumably the plastid where phytol is formed; the second, involved in the build-up of the isoprene part of bornyl acetate, might be located in the oil cells. The acetylation of borneol to bornyl acetate in turn occurs in a cellular compartment that is not involved in the build-up of the isoprene units of borneol.     

Measurements of intra-and extracellular pH in the liverwort Conocephalum conicum during action potentials

During action potentials triggered by electricity and light, measurements of intra- and extracellular pH in the liverwort Conocephalum conicum L. were carried out by the use of antimony-filled H⁺-sensitive microelectrodes. Intracellular pH increased transiently by about 0.05 unit in the course of an action potential, while extracellular pH, measured at the surface of the thallus, remained unchanged. Switching the light off caused a transient increase in intracellular pH by less than 0.1 unit. Turning the light on produced a fast pH decrease by about 0.15 unit followed by a slow increase. When the light was intensive enough, the action potential thus triggered caused a slight increase in intracellular pH superimposed on the phase of a slow pH increment.
The magnitude and time course of the intracellular pH changes seem insufficient for a role as messenger between action potential and the up to 100% increase in the rate of respiration that has been registered in Conocephalum conicum as a consequence of excitation.     

Fatty acids, alcohol and fatty acid ethyl esters: Toxic Ca signal generation and pancreatitis

Pancreatitis, a potentially fatal disease in which the pancreas digests itself as well as its surroundings, is a well recognized complication of hyperlipidemia. Fatty acids have toxic effects on pancreatic acinar cells and these are mediated by large sustained elevations of the cytosolic Ca²⁺ concentration. An important component of the effect of fatty acids is due to inhibition of mitochondrial function and subsequent ATP depletion, which reduces the operation of Ca²⁺-activated ATPases in both the endoplasmic reticulum and the plasma membrane. One of the main causes of pancreatitis is alcohol abuse. Whereas the effects of even high alcohol concentrations on isolated pancreatic acinar cells are variable and often small, fatty acid ethyl esters – synthesized by combination of alcohol and fatty acids – consistently evoke major Ca²⁺ release from intracellular stores, subsequently opening Ca²⁺ entry channels in the plasma membrane. The crucial trigger for pancreatic autodigestion is intracellular trypsin activation. Although there is still uncertainty about the exact molecular mechanism by which this Ca²⁺-dependent process occurs, progress has been made in identifying a subcellular compartment – namely acid post-exocytotic endocytic vacuoles – in which this activation takes place.     

Enzymatic synthesis of fatty acid ethyl esters by utilizing camellia oil soapstocks and diethyl carbonate

This study was reported on a novel process for fatty acid ethyl esters preparation by transesterification and esterification from renewable low-cost feedstock camellia oil soapstocks and friendly acyl acceptor diethyl carbonate. The main components of product were 83.9% ethyl oleate, 8.9% ethyl palmitate, 4.7% ethyl linoleate and 2.1% ethyl stearate, which could be used as eco-friendly renewable resources or additives of industrial solvent and fossil fuel. The effects of molar ratio of diethyl carbonate to soapstocks oil, lipases, organic solvent, reaction temperature and time were investigated, and process conditions were optimized. The yield was up to 98.4% in solvent-free system with molar ratio of diethyl carbonate to soapstocks oil 3:1 and 5% Novozym 435 (based on the weight of soapstocks oil) at 50 °C and 180 rpm for 24 h. Moreover, there was no obvious loss in the yield after lipases were reused for 10 batches without treatment under optimized conditions.     

The effect of excitation on the rate of respiration in the liverwort Conocephalum conicum

Simultaneous measurements were taken of the electrical activity and the rate of respiration of thalli of Conocephalum conicum L. stimulated electrically and mechanically (by cutting). The measurements of the rate of respiration employed a modified Warburg apparatus for O₂ consumption and an infra-red gas analyzer with computer recording and data processing for CO₂ evolution. The action potential, produced by either a cut (a damaging stimulus) or an electrical stimulus (a non-damaging stimulus), caused a transient rise in the rate of respiration. The course of changes in the rate of respiration depends on the character of the excitation and the area of the thallus covered by it. If stimulation does not produce excitation, the increase in the rate of respiration does not take place, regardless of the magnitude and type of the stimulus applied.     

Electrophysiological approach to examine a putative cold- and menthol-sensitive channel in the liverwort Conocephalum conicum

The mechanism of cold perception by plants is still poorly understood. It was found that temperature drop evokes changes in the activity of ion pumps and channels, which leads to plasma membrane depolarization.^1,2 The nature of the primary step of its action (alteration in membrane composition,³ transient influx of Ca²⁺ etc.,²) has not been elicited yet. Our electrophysiological experiments conducted on the liverwort Conocephalum conicum showed that its cells respond not only to sudden cooling⁴ but also to menthol, generating depolarization of the plasma membrane and action potentials (APs). Similar results are well documented in mammals; cold or “cooling compounds” including menthol cause activation of thermosenstitive channel TRPM8 permeable to Ca²⁺ and generation of AP series.⁵ TRP receptors are detected, among others, in green and brown algae. Possible existence of TRPM8-like channel-receptor in Conocephalum conicum is discussed here.Key words: action potential, cold, liverwort, menthol, thermoreceptors, voltage transient