Acetylcholine in plants: presence, metabolism and mechanism of action

Acetylcholine (ACh) has been detected in representatives of many taxonomic groups throughout the plant kingdom. The site of its synthesis in plants is probably young leaves. In some plant species choline acetyltransferase (CHAT) activity has been found. This enzyme showing properties similar to animal CHAT, probably participates in ACh synthesis from its precursors, choline and acetyl-Coenzyme A. Acetylcholinesterase (ACHE) activity has also been found in many plant tissues. This enzyme decomposes ACh and exhibits properties similar to animal ACHE. The presence of both ChAT and AChE in plant tissues suggests that ACh undergoes similar metabolism in plants as it does in animals. Exogenous ACh affects phytochrome- controlled plant growth and development. Mimicking red light (R), ACh stimulates adhesion of root tips to a glass surface and influences leaf movement and membrane permeability to ions. It also affects seed germination and plant growth. Moreover, ACh can modify some enzyme activity and the course of some metabolic processes in plants. Acetylcholine in the presence of calcium ions (Ca:+), like R stimulates swelling of protoplast isolated from etiolated wheat leaves. It is proposed that the primary mechanism of action of ACh in plant cells is via the regulation of membrane permeability to protons (H+), potassium ions (K+), sodium ions (Na +) and Ca :+ .Acetylcholin (ACh) wurde in Vertretern vieler taxonomischer Gruppen des Pflanzreiches gefunden. Es wird wahrscheinlich inden jungen Bltittern synthetisiert. In einigen Pflanzen hat man daneben Cholin-Acetyltransferase (ChAT)-Activit~t nachweisen k6nnen; dieses Enzym ziegt tihnliche Eigenschaften wie tierische ChAT und ist offenbar an der ACh-Synthese aus sienen Vorstufen Cholin und Acetyl-Coenzym A beteiligt. Acetylcholineesterase (AChE)-Activit~t wurde ebenfalls in vielen Pflanzengeweben gefunden; dieses Enzym spaltet ACh und ziegt ~ihnliche Eigenschaften wie tierische ACHE. Die Anwesenheit yon ChAT und AChE in pflanzlichem Gewebe ltil3t vermuten, dal3 ACh in Pflanzen einem ~ihnlichen Metabolismus unterliegt wie im tierischen System. ~,hnlich wie Rotlicht stimuliert ACh die Anheftung von Wurzelspitzen an Glasoberfltichen und beeinflul3t Blattbewegung und Membranpermeabilit~t far Ionen; dariiber hinaus beeinflul3t es Samenkeimung und pflanzliches Wachstum. Des weiteren kann ACh Enzym-Aktivit~ten modifizieren und dadurch den Ablauf einiher metabolischer Prozesse in Pflanzen. SchlieBlich stimuliert ACh in Gegenwart von Calcium-Ionen (Ca2§ ~ahnlich wie Rotlicht, das Schwellen von Protoplasten etiolierter Weizenbl~itter. Es wird vermutet, dal3 die Primiirwirkung von ACh in Pflanzenzellen durch Regulation der Membranpermeabilit~it far Protonen (H§ Kaliumionen (K§ Natriumionen (Na § und Ca 2§ erfolgt

Cytochemical and histochemical characterization of cotyledonary bodies from Pharbitis nil seedlings

Cytological and histochemical characterization of the structures from which an obscure substance is secreted via open stomata to the abaxial surface of Japanese morning glory (Pharbitis nil Choisy cv. Violet) cotyledons has been carried out. Observation of intact cotyledons using the light microscope revealed randomly distributed semi-transparent structures. These structures, which were shown to be the same as those previously described as giant oil cells are referred to here as cotyledonary bodies. These bodies can be eas- ily isolated and purified after enzymatic digestion of the cotyledons. Using different staining procedures we have confirmed that each cotyledonary body originates from an individual mesophyll cell dur- ing embryo development. Purified bodies consist of (i) a thick shell- like envelope; (ii) a transparent, hydrophilic zone; (iii) a hydropho- bic core. Hydrophobic contents of the bodies were readily extracted with methanol and shown to contain fatty acids and phenolic com- pounds using the gas chromatography/mass spectrometry (GC/MS) technique. Methanolic extracts of cotyledonary bodies showed high fluorescence with two excitation and emission maxima. Using a flu- orescence microscope we have shown that the bodies isolated from seedlings grown in continuous light, conditions non-inductive for flowering, and those grown under conditions inductive for flowering (a single 16 h, long dark period) have different fluorescence emis- sion spectra. Different levels of free Ca 2+ inside cotyledonary bodies isolated from light-grown and single dark-period treated P. nil seed- lings were found using the fluorescent calcium indicator dye Fluo-3 under a confocal scanning laser microscope. On the basis of these observations we speculate that cotyledonary bodies could be in- volved in floral induction

The Mechanism of Calcium Action on Flower Induction in Pharbitis nil

Calcium ions, calcium ionophores A23187 and ionomycin, as well as caffeine, stimulated the flowering of Pharbitis nil when applied just before and 2 h after starting a subinductive, 14-h long dark period. Effectiveness of all the mentioned compounds decreased over successive hours and when used from 6 h after the onset of the dark period they had no effect or inhibited flowering. Intracellular calcium modulators, ryanodine and thapsigargicin, which are active in animal cells had no effect on flowering. These results suggest that an increase in free Ca2 + before and during the first 2 h of the dark period increases the flowering responses, whereas after the 6th hour it decreases it. We postulate that the targets for calcium action are stomata, which are open before the dark period and remain closed during the first 4 - 5 h of the dark period. The significance of stomata in flower induction was confirmed in experiments with abscisic acid (ABA), a plant hormone which regulates stomatal movements. Treating the cotyledons of plants with ABA at the 8th and 10th hour of the dark period, resulted in plants with about 50 % less flower buds than the control, however, this phytohormone had no effect on flowering when used before the subinductive dark period

Transplantation in children

Kidney transplantation in very young children, less than 2 years of age, has usually failed, mainly because of difficulties maintaining these patients on hemodialysis long enough to permit retransplantation after loss of the original graft. Liver replacement in the very young child has been associated with a higher frequency of vascular and biliary obstruction than in the older child, due to the small size of these structures. Such accidents have contributed to unsatisfactory results with biliary atresia. Transplantation of kidney or liver into older children has been more successful than transplantation of these organs into adults. Related or cadaveric kidney transplantation in the child has been followed by at least a 60 per cent patient survival for 6 to 13 years and a very acceptable quality of life. Liver replacement for diseases other than biliary atresia has been followed by a 56 per cent 1 year survival rate, and two children have survived for more than 5 years

Core handling and processing for the WAIS Divide ice-core project

On 1 December 2011 the West Antarctic Ice Sheet (WAIS) Divide ice-core project reached its final depth of 3405 m. The WAIS Divide ice core is not only the longest US ice core to date, but is also the highest-quality deep ice core, including ice from the brittle ice zone, that the US has ever recovered. The methods used at WAIS Divide to handle and log the drilled ice, the procedures used to safely retrograde the ice back to the US National Ice Core Laboratory (NICL) and the methods used to process and sample the ice at the NICL are described and discussed

Core handling and processing for the WAIS Divide ice-core project

On 1 December 2011 the West Antarctic Ice Sheet (WAIS) Divide ice-core project reached its final depth of 3405 m. The WAIS Divide ice core is not only the longest US ice core to date, but is also the highest-quality deep ice core, including ice from the brittle ice zone, that the US has ever recovered. The methods used at WAIS Divide to handle and log the drilled ice, the procedures used to safely retrograde the ice back to the US National Ice Core Laboratory (NICL) and the methods used to process and sample the ice at the NICL are described and discussed

Photomorphogenic mutants of tomato

Photomorphogenesis of tomato is being studied with the aid of mutants which are either modified in their photore- ceptor composition or in their signal transduction chain(s) . Several mutants affecting the phytochrome family of photoreceptors, some of which appear deficient for specific genes encoding phytochrome apoproteins have been isolated . In addition, other mutants, including transgenic lines overexpressing phytochrome A, exhibit exaggerated photomorphogenesis during de-etiolation . Anthocyanin biosynthesis and plastid development are being used as model systems for the dissection of the complex interactions among photomorphogenic photoreceptors and to elucidate the nature of their transduction chains