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Acetylcholine, a New Active Principle of Ergot.

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... One should consider that the existence of acetylcholine independent of neurons has been known for a long time before (for review see ref. [6]). Unfortunately, the scientific community has forgotten the first experiments by Ewins and Dale who investigated the effect of an extract of the ergot fungus (Claviceps purpurea) on the blood pressure in 1914 [7,8]. Ergot grows on rye particularly during rainy periods in spring and can induce serious intoxications (called "St. ...
... Anthony's Fire") which were known during the Middle Ages and were based on the vasoactive effects of the ergot alkaloids. When Ewins and Dale investigated the hemodynamic effects of an extract of this fungus, they found a depressor effect [7,8]. Later on they could attribute this depressor effect to acetylcholine [8]. ...
... When Ewins and Dale investigated the hemodynamic effects of an extract of this fungus, they found a depressor effect [7,8]. Later on they could attribute this depressor effect to acetylcholine [8]. In conclusion, the first experiments illuminating a biological role of acetylcholine, "the blood pressure lowering substance", the molecule was extracted from fungi, i.e., from nonneuronal organisms. ...
Article
The biological role of acetylcholine and the cholinergic system has been revisited within the last 25 years. Acetylcholine and the pivotal components of the cholinergic system (high affinity choline uptake, choline acetyltransferase and its endproduct acetylcholine, muscarinic and nicotinic receptors, cholinesterases) are expressed by more or less all mammalian cells, i.e., cells not innervated by neurons at all. Moreover, acetylcholine and cholinergic binding sites have been described in plants. Acetylcholine is even detected in bacteria and algae and thus represents an extremely old signaling molecule on the evolutionary time scale. The following chapter summarizes the detection of acetylcholine beyond neurons with particular emphasis on the presence of acetylcholine in so-called primitive organisms. Finally, an overview is given about the detection in mammalian non-neuronal cells. The existence of the non-neuronal cholinergic system has identified an important new target to illuminate the pathophysiological background of acute and chronic inflammatory diseases as well as heart diseases and cancer.
... He then asked a colleague, chemist Arthur J. Ewins, to purify the chemical entity that caused the hypotension, suspecting the ergot extracts had been contaminated with muscarine (see Burgen [8]). Ewins (1914) [9] succeeded in isolating a small amount of the hypotensive substance from ergot, fruiting bodies of Claviceps purpurea, an ergot fungus, and identified it physiologically and chemically as ACh. This was the first discovery of ACh in a natural organism. ...
... He then asked a colleague, chemist Arthur J. Ewins, to purify the chemical entity that caused the hypotension, suspecting the ergot extracts had been contaminated with muscarine (see Burgen [8]). Ewins (1914) [9] succeeded in isolating a small amount of the hypotensive substance from ergot, fruiting bodies of Claviceps purpurea, an ergot fungus, and identified it physiologically and chemically as ACh. This was the first discovery of ACh in a natural organism. ...
... It was about 75 years ago that acetylcholine (ACh) was discovered in non-animal cells (Ewins, 1914). Since that time it has been detected in representatives of many species of lower and higher plants as well as bacteria and fungi (Fluck & Jaffe, 1976; Hartmann & Gupta, 1989). ...
... Acetylcholine has been detected in fungal hyphae (Ewins, 1914; Heirman, 1939; Oury & Bacq, 1938), in callus cultures of bryophytes (Hartmann, 1971; Hartmann & Kilbinger, 1974a), and in the aerial parts (Hartmann & Kilbinger, 1974b; Jaffe, 1970; Kopcewicz et al., 1977; Ledeira et al., 1982a; Lin, 1957; Miura & Shih, 1984; Tretyn & Tretyn, 1989), tubers (Marquardt et al., 1952) and roots (Emmelin & Feldberg, 1947, 1949 Hartmann & Kilbinger, 1974b; Jaffe, 1970 Ledeira et al., 1982b; Miura & Shih, 1984) of higher plants (Table I). In the aerial parts of angiosperms, it has been found in stems (Emmelin & Feldberg, 1947, 1949 Hartmann & Kilbinger, 1974b; Jaffe, 1970 Ledeira et al., 1982b; Miura & Shih, 1984), hypocotyls (Hoshino, 1983b; Jaffe, 1970 Verbeek & Vendrig, 1977), leaves (Antweiler & PaUade, 1972; Appel & Werle, 1959; Collier & Chesher, 1956; Emmelin & Feldberg, 1947, 1949 Fiedler et al., 1953; Hartmann & Kilbinger, 1974b; Horton & Felippe, 1973; Jaffe, 1970, Ledeira et al., 1982b Lin, 1957; Miura & Shih, 1984; Neuwald, 1952; Satter et al., 1972; Saxena et al., 1965 Saxena et al., , 1966 Tretyn & Tretyn, 1990), apical buds (Jaffe, 1970; Lin, 1957), flowers (Fiedler et al., 1953) and seeds (Devasankaraiah et al., 1974; Ledeira et al., 1982a; Lin, 1957; Miura & Shih, 1984). ...
... Enfin, ce manuscrit se terminera par une conclusion et les prespectives de recherche envisagées. (Ewins, 1914). Les propriétés physiologiques de l'acétylcholine ont été étudiées en parallèle par Dale en 1914(Dale, 1914. ...
... La première étape dans l'identification de cette protéine réceptrice fut de la classer en fonction des réponses induites par différentes molécules. Les contractions musculaires induites par l'acétylcholine pouvaient être mimées par l'application de nicotine ou de muscarine (Ewins, 1914). Il a été mis en évidence que cette protéine réceptrice pouvait alors être de 2 types. ...
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Bien que l’utilisation des insecticides contre les insectes ravageurs de culture ait permis d’accomplir des progrès en matière de rendements agricoles, leur utilisation a également entrainé l’apparition d’insectes résistants. Alors que les mécanismes de résistance sont bien connus, peu de données sont disponibles sur l’effet d’une exposition des insectes à une dose sublétale d’insecticide. L’objectif de cette étude est donc de caractériser les modifications cellulaires et moléculaires développées chez la blatte P. americana exposée à une dose sublétale d’un insecticide : l’Imidaclopride. Nous avons montré qu’après une exposition pendant 30 jours à une dose sublétale d’Imidaclopride, les blattes devenaient moins sensibles à cet insecticide et que cette modification de la sensibilité des blattes était maintenue 30 jours après l’arrêt du traitement à l’Imidaclopride. Grâce à des analyses biochimiques et moléculaires, nous avons démontré que les principaux acteurs dans ce phénomène sont les récepteurs nicotiniques (nAChRs) qui sont les cibles moléculaires de l’Imidaclopride. De plus, dans le but de développer de nouvelles stratégies de lutte contre les insectes nuisibles, nous avons rendu de nouveau sensibles à l’Imidaclopride les blattes accommodées aux traitements en ciblant les nAChRs par l’interférence ARN. Étant donné que ces récepteurs jouent un rôle primordial dans l’accommodation des blattes à l’Imidaclopride et que l’expression et l’activité de ces récepteurs peuvent être régulées par de nombreuses protéines, nous avons entrepris un séquençage à haut-débit du transcriptome (RNA-seq) issu du dernier ganglion abdominal de la blatte afin de déterminer l’ensemble des gènes différentiellement exprimés après traitement des blattes à l’Imidaclopride ainsi que 30 jours après l’arrêt de ce traitement. L’ensemble de ces travaux de thèse contribue au développement de nos connaissances sur les effets des doses sublétales sur les insectes et sur les mécanismes d’accommodation afin de pouvoir les prendre en considération dans les stratégies de lutte contre les insectes nuisibles.
... Acetylcholine (ACh) is one of the most exemplary neurotransmitters (Wessler et al. 2001). It was first revealed in non-animal organisms (Ewins 1914). Since then, it has been found in all types of plants as well as in bacteria and fungi (Fluck and Jaffe 1976). ...
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Acetylcholine (ACh) is one of the important neurotransmitters, involved in signal transduction function in human and animal brain. However, the influence of ACh treatment on salt-stress tolerance in plants is yet unknown. Salt stress caused a reduction in gas-exchange parameters, chlorophyll content, antioxidant enzyme activities, and leaf relative water content of Nicotiana benthamiana plants. However, the above inhibitions could be significantly alleviated by application of leaf spray or root application of ACh. Exogenous ACh reduced the accumulation of malondialdehyde by enhancing activities of antioxidant enzymes such as peroxidase and superoxide dismutase. In addition, enhanced accumulation of organic osmolytes including soluble sugars and proline possibly regulated the signal mechanisms related to stress. Application of ACh could also improve gas-exchange parameters and photosynthetic pigment accumulation in leaves of salt-stressed plants. These effects of ACh were beneficial for maintaining better water status in plants, the concentration of 10 µM ACh applied both in the form of leaf spray or root application was the most effective. Therefore, our findings provided a stronger evidence for a physiological role of ACh and its potential use at optimal concentration by leaf or root application to alleviate damage caused by salt-stress in plants.
... In plants ACh has so far been found only in ergot, Claviceps purpurea (Ewins 1914), and in the nettles Urtica urens and Urtica diocia (Emmelin and Feldberg 1947). The present communication reports another rich plant source of ACh-the seed and leaf of the Malayan jackfruit, Artocarpus integra. ...
Article
Jackfruit (Artocarpus heterophyllus Lam.) is an ancient fruit that is widely consumed as a fresh fruit. The use of jackfruit bulbs and its parts has also been reported since ancient times for their therapeutic qualities. The beneficial physiological effects may also have preventive application in a variety of pathologies. The health benefits of jackfruit have been attributed to its wide range of physicochemical applications. This review presents an overview of the functional, medicinal, and physiological properties of this fruit.
... ACh is the first neurotransmitter being identified by Sir Henry Dale and his colleague Arthur Ewins in 1914 [17]. Comprising acetyl coenzyme A, ChAT, vesicular acetylcholine transporter, cholinergic receptors and AChE, the cholinergic system plays a crucial role in regulating neuronal functions. ...
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The melanosome is an organelle that produces melanin for skin pigmentation, which is synthesized by epidermal melanocytes, subsequently transported, and internalized by epidermal keratinocytes. Exposure to ultraviolet (UV) from sunlight radiation is a major stimulator of melanosome uptake by keratinocytes. Acetylcholine (ACh) is known to be released by keratinocytes under UV exposure, which regulates melanin production in melanocytes by participating in which has been named as “skin synapse”. Here, the role of cholinergic molecules, i.e., ACh and α7 nicotinic acetylcholine receptor (nAChR), in regulating melanosome uptake through phagocytosis by keratinocytes was illustrated. In cultured keratinocytes (HaCaT cells), the fluorescent beads at different sizes imitating melanosomes, or melanosomes, were phagocytosed under UV exposure. The UV‐induced phagocytosis in keratinocytes was markedly increased by applied ACh, an acetylcholinesterase (AChE) inhibitor, or an α7 nAChR agonist. In contrast, the antagonist of α7 nAChR was able to fully block the UV‐induced phagocytosis, suggesting the role of α7 nAChR in this event. The intracellular Ca++ mobilization was triggered by UV exposure, accounting for the initiation of phagocytosis. The blockage of UV‐mediated Ca++ mobilization, triggered by BAPTA‐AM or α7 nAChR antagonist, resulted in a complete termination of phagocytosis. Besides, the phosphorylation of cofilin, as well as expression and activation of RhoA, accounting for phagocytosis was induced by UV exposure: the phosphorylation was blocked by BAPTA‐AM or α7 nAChR antagonist. The result suggests that cholinergic system, especially α7 nAChR, is playing a regulatory role in modulating melanosome uptake in keratinocytes being induced by UV exposure.
... Acetylcholine (ACh) was the first neurotransmitter to be discovered [1]. It is an essential mediator of both the central and the peripheral nervous system [2,3]. ...
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Background: Our aim was to investigate the role of nicotinic acetylcholine receptors (nAChRs) in in-vitro osteoclastogenesis and in in-vivo bone homeostasis. Methods: The presence of nAChR subunits as well as the in-vitro effects of nAChR agonists were investigated by ex vivo osteoclastogenesis assays, real-time polymerase chain reaction, Western blot and flow cytometry in murine bone marrow-derived macrophages differentiated in the presence of recombinant receptor activator of nuclear factor kappa B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). The bone phenotype of mice lacking various nAChR subunits was investigated by peripheral quantitative computed tomography and histomorphometric analysis. Oscillations in the intracellular calcium concentration were detected by measuring the Fura-2 fluorescence intensity. Results: We could demonstrate the presence of several nAChR subunits in bone marrow-derived macrophages stimulated with RANKL and M-CSF, and showed that they are capable of producing acetylcholine. nAChR ligands reduced the number of osteoclasts as well as the number of tartrate-resistant acidic phosphatase-positive mononuclear cells in a dose-dependent manner. In vitro RANKL-mediated osteoclastogenesis was reduced in mice lacking α7 homomeric nAChR or β2-containing heteromeric nAChRs, while bone histomorphometry revealed increased bone volume as well as impaired osteoclastogenesis in male mice lacking the α7 nAChR. nAChR ligands inhibited RANKL-induced calcium oscillation, a well-established phenomenon of osteoclastogenesis. This inhibitory effect on Ca(2+) oscillation subsequently led to the inhibition of RANKL-induced NFATc1 and c-fos expression after long-term treatment with nicotine. Conclusions: We have shown that the activity of nAChRs conveys a marked effect on osteoclastogenesis in mice. Agonists of these receptors inhibited calcium oscillations in osteoclasts and blocked the RANKL-induced activation of c-fos and NFATc1. RANKL-mediated in-vitro osteoclastogenesis was reduced in α7 knockout mice, which was paralleled by increased tibial bone volume in male mice in vivo.
... there is no available report on the presence of ACh or Ch in these spices. The presence of ACh in ergot (Ewins, 1914) is the earliest reference to its presence in plant sources. ACh has also been reported to be present in the hairs of the nettle plant Urtica urcns (Emmelin and Feldberg, 1949) and in the roots of the mung bean Phaseolus aureus (Jaffe, 1970). ...
Article
Aqueous extracts obtained from seven commonly used spices (cardamon, coriander, cumin, black pepper, red pepper, anise and fennel) showed cholinomimetic effects when tested on rat blood pressure, rat jejunum and frog rectus abdominis preparations. This effect was observed mostly when the spices were roasted. Chemical estimation using gas chromatography/mass spectrometry confirmed the presence of large amounts of acetylcholine and its precursor choline.
... However, cholinergic signaling has probably been established from the beginning of life, as a non-neuronal communication mechanism in micro-organisms and plants [20]. Although first evidence for this hypothesis was obtained early in the 20th century [47,48], the importance of non-neuronal acetylcholine as a paracrine and autocrine hormone in mammalian cells and tissues was appreciated only by the end of the century and has immensely broadened the biological role of this mediator [49,50]. Initial studies by the group of Wessler et al. [51,52], demonstrated the expression of the acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) and acetylcholine production by bronchial epithelial cells. ...
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Since ancient times, anticholinergics have been used as a bronchodilator therapy for obstructive lung diseases. Targets of these drugs are G-protein-coupled muscarinic M(1), M(2) and M(3) receptors in the airways, which have long been recognized to regulate vagally-induced airway smooth muscle contraction and mucus secretion. However, recent studies have revealed that acetylcholine also exerts pro-inflammatory, pro-proliferative and pro-fibrotic actions in the airways, which may involve muscarinic receptor stimulation on mesenchymal, epithelial and inflammatory cells. Moreover, acetylcholine in the airways may not only be derived from vagal nerves, but also from non-neuronal cells, including epithelial and inflammatory cells. Airway smooth muscle cells seem to play a major role in the effects of acetylcholine on airway function. It has become apparent that these cells are multipotent cells that may reversibly adopt (hyper)contractile, proliferative and synthetic phenotypes, which are all under control of muscarinic receptors and differentially involved in bronchoconstriction, airway remodeling and inflammation. Cholinergic contractile tone is increased by airway inflammation associated with asthma and COPD, resulting from exaggerated acetylcholine release as well as increased expression of contraction related proteins in airway smooth muscle. Moreover, muscarinic receptor stimulation promotes proliferation of airway smooth muscle cells as well as fibroblasts, and regulates cytokine, chemokine and extracellular matrix production by these cells, which may contribute to airway smooth muscle growth, airway fibrosis and inflammation. In line, animal models of chronic allergic asthma and COPD have recently demonstrated that tiotropium may potently inhibit airway inflammation and remodeling. These observations indicate that muscarinic receptors have a much larger role in the pathophysiology of obstructive airway diseases than previously thought, which may have important therapeutic implications.
... First synthesized in 1867 by von Baeyer, who acetylated choline using acetylchloride, ACh was left on the chemical list for several decades without exploration of its biological activity [see a review by Burgen (1)]. In 1914, however, Ewins (2) identified ACh as the active principle in ergot that exerts an inhibitory effect on the heart but a stimulatory effect on intestinal muscle. This was the first discovery of ACh in a life form. ...
Article
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T and B cells express most cholinergic system components—e.g., acetylcholine (ACh), choline acetyltransferase (ChAT), acetylcholinesterase, and both muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively). Using ChATBAC-eGFP transgenic mice, ChAT expression has been confirmed in T and B cells, dendritic cells, and macrophages. Moreover, T cell activation via T-cell receptor/CD3-mediated pathways upregulates ChAT mRNA expression and ACh synthesis, suggesting that this lymphocytic cholinergic system contributes to the regulation of immune function. Immune cells express all five mAChRs (M1–M5). Combined M1/M5 mAChR-deficient (M1/M5-KO) mice produce less antigen-specific antibody than wild-type (WT) mice. Furthermore, spleen cells in M1/M5-KO mice produce less tumor necrosis factor (TNF)-α and interleukin (IL)-6, suggesting M1/M5 mAChRs are involved in regulating pro-inflammatory cytokine and antibody production. Immune cells also frequently express the α2, α5, α6, α7, α9, and α10 nAChR subunits. α7 nAChR-deficient (α7-KO) mice produce more antigen-specific antibody than WT mice, and spleen cells from α7-KO mice produce more TNF-α and IL-6 than WT cells. This suggests that α7 nAChRs are involved in regulating cytokine production and thus modulate antibody production. Evidence also indicates that nicotine modulates immune responses by altering cytokine production and that α7 nAChR signaling contributes to immunomodulation through modification of T cell differentiation. Together, these findings suggest the involvement of both mAChRs and nAChRs in the regulation of immune function. The observation that vagus nerve stimulation protects mice from lethal endotoxin shock led to the notion of a cholinergic anti-inflammatory reflex pathway, and the spleen is an essential component of this anti-inflammatory reflex. Because the spleen lacks direct vagus innervation, it has been postulated that ACh synthesized by a subset of CD4+ T cells relays vagal nerve signals to α7 nAChRs on splenic macrophages, which downregulates TNF-α synthesis and release, thereby modulating inflammatory responses. However, because the spleen is innervated solely by the noradrenergic splenic nerve, confirmation of an anti-inflammatory reflex pathway involving the spleen requires several more hypotheses to be addressed. We will review and discuss these issues in the context of the cholinergic system in immune cells.
... As early as 1914, Ewins provided the first evidence for non-neuronal ACh synthesized in ergot fungi [1], but in the following decades the biological role of ACh was predominantly focussed on its action as a neurotransmitter operating within the nervous system. During the past two decades our knowledge about the expression and functions of ACh outside the nervous system has been markedly extended. ...
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The worldwide use of neonicotinoid pesticides has caused concern on account of their involvement in the decline of bee populations, which are key pollinators in most ecosystems. Here we describe a role of non-neuronal acetylcholine (ACh) for breeding of Apis mellifera carnica and a so far unknown effect of neonicotinoids on non-target insects. Royal jelly or larval food are produced by the hypopharyngeal gland of nursing bees and contain unusually high ACh concentrations (4-8 mM). ACh is extremely well conserved in royal jelly or brood food because of the acidic pH of 4.0. This condition protects ACh from degradation thus ensuring delivery of intact ACh to larvae. Raising the pH to ≥5.5 and applying cholinesterase reduced the content of ACh substantially (by 75-90%) in larval food. When this manipulated brood was tested in artificial larval breeding experiments, the survival rate was higher with food supplemented by 100% with ACh (6 mM) than with food not supplemented with ACh. ACh release from the hypopharyngeal gland and its content in brood food declined by 80%, when honeybee colonies were exposed for 4 weeks to high concentrations of the neonicotinoids clothianidin (100 parts per billion [ppb]) or thiacloprid (8,800 ppb). Under these conditions the secretory cells of the gland were markedly damaged and brood development was severely compromised. Even field-relevant low concentrations of thiacloprid (200 ppb) or clothianidin (1 and 10 ppb) reduced ACh level in the brood food and showed initial adverse effects on brood development. Our findings indicate a hitherto unknown target of neonicotinoids to induce adverse effects on non-neuronal ACh which should be considered when re-assessing the environmental risks of these compounds. To our knowledge this is a new biological mechanism, and we suggest that, in addition to their well documented neurotoxic effects, neonicotinoids may contribute to honeybee colony losses consecutive to a reduction of the ACh content in the brood food.
... However, the genes encoding these enzymes have not been identified. Interestingly, acetylcholine, a naturally occurring ChE substrate, has been detected in the extract of the ergot fungus, Claviceps purpurea, more than a hundred years ago [71]. ...
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Cholinesterases (ChE), the enzymes whose primary function is the hydrolysis of choline esters, are widely expressed throughout the nature. Although they have already been found in plants and microorganisms, including ascomycete fungi, this study is the first report of ChE-like activity in fungi of the phylum Basidiomycota. This activity was detected in almost a quarter of the 45 tested aqueous fungal extracts. The ability of these extracts to hydrolyse acetylthiocholine was about ten times stronger than the hydrolytic activity towards butyrylthiocholine and propionylthiocholine. In-gel detection of ChE-like activity with acetylthiocholine indicated a great variability in the characteristics of these enzymes which are not characterized as vertebrate-like based on (i) differences in inhibition by excess substrate, (ii) susceptibility to different vertebrate acetylcholinesterase and butyrylcholinesterase inhibitors, and (iii) a lack of orthologs using phylogenetic analysis. Limited inhibition by single inhibitors and multiple activity bands using in-gel detection indicate the presence of several ChE-like enzymes in these aqueous extracts. We also observed inhibitory activity of the same aqueous mushroom extracts against insect acetylcholinesterase in 10 of the 45 samples tested; activity was independent of the presence of ChE-like activity in extracts. Both ChE-like activities with different substrates and the ability of extracts to inhibit insect acetylcholinesterase were not restricted to any fungal family but were rather present across all included Basidiomycota families. This study can serve as a platform for further research regarding ChE activity in mushrooms.
... N one of the myriad neuromuscular blocking drugs, their antagonists, and the entire industry of medical neuromuscular monitoring devices might be available today, were it not for the experiments by Sir Henry Hallett Dale in 1913 and Otto Loewi in 1921. 2 These two pioneers were awarded the 1936 Nobel Prize for "the discovery of chemical synaptic transmission." 3 In 1941, Eccles, Katz, and Kuffler demonstrated that in the presence of curare, there was a decrease in the end-plate potential at the postsynaptic muscle membrane such that the action potential could no longer be propagated in response to motor nerve stimulation. ...
Article
Over the past five decades, quantitative neuromuscular monitoring devices have been used to examine the incidence of postoperative residual neuromuscular block in international clinical practices, and to determine their role in reducing the risk of residual neuromuscular block and associated adverse clinical outcomes. Several clinical trials and a recent meta-analysis have documented that the intraoperative application of quantitative monitoring significantly reduces the risk of residual neuromuscular blockade in the operating room and postanesthesia care unit. In addition, emerging data show that quantitative monitoring minimizes the risk of adverse clinical events, such as unplanned postoperative reintubations, hypoxemia, and postoperative episodes of airway obstruction associated with incomplete neuromuscular recovery, and may improve postoperative respiratory outcomes. Several international anesthesia societies have recommended that quantitative monitoring be performed whenever a neuromuscular blocking agent is administered. Therefore, a comprehensive review of the literature was performed to determine the potential benefits of quantitative monitoring in the perioperative setting.
... The first demonstration of non-neuronal acetylcholine (ACh) was published in 1914 by A.J. Ewins, when he extracted ACh from ergot, the fungus Claviceps purpurea [1]. In the following decades multiple reports presented data about the presence of ACh in non-nervous tissues (for review see [2]), but during the subsequent decades the biological role of ACh was restricted mainly to the topic of neurotransmission. ...
Article
Acetylcholine (ACh) was created by nature as one of the first signaling molecules, expressed already in procaryotes. Based on the positively charged nitrogen, ACh could initially mediate signaling in the absence of receptors. When evolution established more and more complex organisms the new emerging organs systems, like the smooth and skeletal muscle systems, energy-generating systems, sexual reproductive system, immune system and the nervous system have further optimized the cholinergic signaling machinery. Thus, it is not surprising that ACh and the cholinergic system are expressed in the vast majority of cells. Consequently, multiple common interfaces exist, for example, between the nervous and the immune system. Research of the last 20 years has unmasked these multiple regulating mechanisms mediated by cholinergic signaling and thus, the biological role of ACh has been revised. The present article summarizes new findings and describes the role of both non-neuronal and neuronal ACh in protecting the organism from external and internal health threats, in providing energy for the whole organism and for the individual cell, controling immune functions to prevent inflammatory dysbalance, and finally, the involvement in critical brain functions, such as learning and memory. All these capacities of ACh enable the organism to attain and maintain homeostasis under changing external conditions. However, the existence of identical interfaces between all these different organ systems complicates the research for new therapeutic interventions, making it essential that every effort should be undertaken to find out more specific targets to modulate cholinergic signaling in different diseases.
... The cholinergic system plays an important role in global brain homeostasis and plasticity [280]. Acetylcholine (ACh), the first neurotransmitter to be identified [281], is used by all cholinergic neurons and has a critical important role in the peripheral and CNS [282]. ACh is synthesized from choline and acetyl-coenzyme A (acetyl-CoA) via the enzyme choline acetyltransferase (ChAT) and then transferred by vesicular acetylcholine transporter (VAChT) [283,284]. ...
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The nervous system is important, because it regulates the physiological function of the body. Neurons are the most basic structural and functional unit of the nervous system. The synapse is an asymmetric structure that is important for neuronal function. The chemical transmission mode of the synapse is realized through neurotransmitters and electrical processes. Based on vesicle transport, the abnormal information transmission process in the synapse can lead to a series of neurorelated diseases. Numerous proteins and complexes that regulate the process of vesicle transport, such as SNARE proteins, Munc18-1, and Synaptotagmin-1, have been identified. Their regulation of synaptic vesicle secretion is complicated and delicate, and their defects can lead to a series of neurodegenerative diseases. This review will discuss the structure and functions of vesicle-based synapses and their roles in neurons. Furthermore, we will analyze neurotransmitter and synaptic functions in neurodegenerative diseases and discuss the potential of using related drugs in their treatment.
... It exists not only in the nervous systems of mammals, but also in those of many other organisms [10,11]. Ewins [12] first discovered it as a natural blood pressure-lowering compound through intravenous injections of ergot. Loewi [13] then found that ACh is a chemical transmitter that affects neural activity. ...
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Choline is an essential nutrient and choline esters are potential functional food ingredients. We aimed to analyze the choline compound content in 19 cultivated fruits and vegetables and identify those with high acetylcholine content. We utilized liquid chromatography with tandem mass spectrometry to quantify choline compounds according to the standard addition method. Choline compounds were extracted from lyophilized fruit/vegetable powders and passed through a weakly acidic cation exchange column, resulting in a concentrated solution of choline compounds. The compounds were separated on a pentafluorophenyl column and then analyzed using positive mode electrospray ionization. Results showed that acetylcholine and choline were the primary choline compounds in all agricultural products; propionylcholine and butyrylcholine were minor compounds in 17 and 12 agricultural products, respectively. The acetylcholine concentration was 2900-fold higher in eggplants (6.12 mg/100 g fresh weight [FW]) than in other agricultural products (average: 2.11 × 10−3 mg/100 g FW). The concentration of acetylcholine differed only 2-fold between eggplant cultivars with the highest (′Higomurasaki′: 5.53 mg/100 g FW) and lowest (′Onaga nasu′: 2.79 mg/100 g FW) concentrations. The half-life of acetylcholine in eggplants was approximately 16 days, which is longer the shelf life of eggplants. Thus, eggplants can be a good source of acetylcholine.
... Another substance that was known only as a product of laboratory synthesis was acetylcholine. In 1913, however, a sample of ergot being tested at the WPRL by Dale was contaminated with a substance subsequently identified chemically as acetylcholine [34]. Dale tested it further using physiological techniques and wrote excitedly to Elliott: "We got that thing out of our silly ergot extract. ...
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This paper provides a review of some of the major historical developments in synaptic research and neurotransmission since the first appearance of the word 'synapsis' in 1895. The key contributions and inter-relationships of several significant scientists and Nobel Laureates, including Charles Sherrington, Henry Dale, Edgar Adrian and John Eccles are highlighted, and the influence of others such as John Langley and Thomas Elliott is stressed. A recurrent theme is the importance of language and the creation of new words.
... The first report in which ACh was isolated from a microorganism occurred in Claviceps purpurea, an ergot fungi, more than one hundred years ago [210]. Recently, through radioimmunoassay a substantial amount of ACh in Saccharomyces cerevisiae (2384.7 pmol/g) was detected and its production was insensitive to cholinergic enzyme inhibitors, suggesting the presence of an enzyme different from ChAT and CarAT in fungi [204]. ...
Chapter
Due to its widespread expression, acetylcholine has been termed the ‘universal cytotransmitter’. The cholinergic system regulates the synthesis, actions and degradation of acetylcholine. This phylogenetically ancient signaling system is present in vertebrate and invertebrate organisms. In mammals, acetylcholine has generally been regarded as a classical neurotransmitter, despite the fact that it was first identified in the spleen, an immune organ. Acetylcholine regulates numerous immune functions through stimulation of muscarinic and nicotinic acetylcholine receptors. In fact, the presence of cholinergic system components has also been demonstrated in microbes, but their function in these organisms remains largely unexplored. Furthermore, during viral, bacterial, fungal and parasitic infections, the cholinergic system of the host is significantly altered, suggesting that it holds an important role in their pathogenesis. It is therefore essential to better understand cholinergic interactions during infection to develop novel forms of therapy. This chapter attempts to summarize the current literature on the topic.
... In 1906, Reid Hunt and René de M. Taveau discovered that ACh in small doses decreases blood pressure [6]. The story of NNACh started in 1914 when Arthur J. Ewins extracted ACh from ergot, the fungus Claviceps purpurea, and identified it as a blood pressure decreasing agent [7]. Later in 1914, Henry Hallett Dale characterized physiologic effects of ACh, compared to choline, and identified differences between muscarinic and nicotinic effects of ACh [8]. ...
Article
The “5th International Symposium on Non-neuronal Acetylcholine: from bench to bedside” was held on September 27–29, 2019 in Hyatt Regency, Long Beach, CA, USA. Approximately 50 scientists from 11 countries over 6 continents participated in this meeting. The major topics included an overall biologic significance of non-neuronal acetylcholine (ACh) and the roles of the non-neuronal cholinergic systems in mucocutaneous, respiratory, digestive, immunologic, endocrine, cardiovascular, musculoskeletal and kidney diseases, and cancer. This meeting facilitated continued work to advance the fundamental science and translational aspects of the interdisciplinary studies on non-neuronal ACh. The progress made has opened a new chapter in the field of cholinergic pharmacology, and advanced our knowledge beyond regulation of individual cell- and tissue-types, defining a new paradigm of selective pharmacological regulation of vital function of practically all types of non-neuronal cells. It is now clear that the autocrine and paracrine control of non-neuronal cells by non-neuronal ACh is implemented through synergistic, additive, and reciprocal effects triggered by two different cholinergic receptor classes. Each biologic effect of ACh is determined by a unique combination of cholinergic receptors subtype expressed at each stage of cell development and differentiation. The plasticity of the non-neuronal cholinergic system helps adjust homeostasis to new environmental conditions.
... Mott (1904, p. 1,556) was critical of "that hypothetical substance which McDougall has unfortunately called neurin" and in a footnote in his review of Sherrington's Integrative Action of the Nervous System, Mott (1907, p. 570) explained that the term "neurin" is unfortunate because "this term is already applied to a toxic substance which may under certain conditions arise from nerve degeneration." Thus, Mott felt that neurin was a neurotoxin, and when acetylcholine was first isolated, it was as an ergotoxine (Dale, 1914;Ewins, 1914) and in the conception of Langley and others, nicotine, curare and other drugs functioned as neurotoxins, not chemical signals. Thus, the term neurin seemed unfortunate but maybe McDougall knew something that Mott did not! ...
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Since the work of Semon was rediscovered by Schacter in 1978, there has been a renewed interest is searching for the “engram” as the locus of memory in the brain and Hebb’s cell assembly has been equated with Semon’s engram. There have been many theories of memory involving some concept of synaptic change, culminating in the “Hebb Synapse” theory in 1949. However, Hebb said that the idea that any two cells or systems of cells that are repeatedly active at the same time will tend to become “associated,” was not his idea, but an old one. In this manuscript we give an overview of some of the theories of the neural basis of learning and memory before Hebb and describe the synaptic theory of William McDougall, which appears to have been an idea ahead of its time; so far ahead of its time that it was completely ignored by his contemporaries. We conclude by examining some critiques of McDougall’s theory of inhibition and with a short discussion on the fate of neuroscientists whose ideas were neglected when first presented but were accepted as important many decades later.
Article
Abstract This special issue is focused on acetylcholine to mark the hundredth year since its discovery by Dr. Henry Hallett Dale. Some readers may be of the opinion that the available literature on acetylcholine is quite vast and, therefore, there is no scope for more interesting findings. However, when we consider the significance of its physiological roles and discuss its involvement in many severe diseases, acetylcholine remains an intriguing molecule worth to be kept in mind.
Article
Ergot occupies a special position among the drugs of our therapeutic armamentarium, not only on account of its unusual classification in the vegetable kingdom but also because of its interesting biological characteristics and the remarkable nature of its active principles. Known botanically as Claviceps purpurea, ergot is a parasitic filamentous fungus which grows on the ears of plants of the Gramineae family. It is found principally on cereals, and thrives best on the ears of rye. Ergot of rye, or Secale cornutum, is the officinal form of the pharmacopoeias and the starting material for pharmaceutical preparations.
Article
It is well known that acetylcholine represents a dominant neurotransmitter within mammalian airways and that airway functions, like smooth muscle activity and secretion, are under a continuous cholinergic tone. However, the teleology of this basal cholinergic tone, assumed to originate from neuronal activity, appears difficult to understand, whereas neuronal cholinergic reflex activity can be regarded as a rational regulatory pathway to protect the airways from injury [1-3]. Based on recent experimental observations, both phenomena may reflect two different biological roles of acetylcholine, acting first as a universal cytomolecule (non-neuronal) and second as a classical neurotransmitter (neuronal).
Article
Arthur James Ewins was born in Norwood in 1882, his father being a signalman on what was then the South Eastern Railway. The increasing value of the estate of the old Dulwich College (‘Alleyn’s College of God’s Gift’) had enabled its Governors to found, in addition, a modern secondary school, Alleyn’s School, in that neighbourhood. Ewins obtained his first important educational opportunity by winning a scholarship giving him entry to this school, at a time when its Headmaster was Dr H. B. Baker, F.R.S., who later became Professor of Inorganic Chemistry in the University of Oxford. By the time Ewins left school, therefore, in 1899, he had had a better opportunity than most lads of 17 in those days, to obtain a good grounding in chemistry, making him ready for a career in that subject. He left school, in fact, to accept such an opportunity at The Wellcome Physiological Research Laboratories, which had then recently been established in that part of London, at Brockwell Hall—a former manor house of which most of the estate had already become the public Brockwell Park, leaving the house and a few acres of land available to the Wellcome Laboratories for the remaining years of the lease.
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In 1929, Dale and Dudley described the first reported natural occurrence of acetylcholine (ACh) in an animal's body. They identified this ACh in the spleens of horses and oxen, which we now know suggests possible involvement of ACh in the regulation of lymphocyte activity and immune function. However, the source and function of splenic ACh were left unexplored for several decades. Recent studies on the source of ACh in the blood revealed ACh synthesis catalyzed by choline acetyltransferase (ChAT) in CD4(+) T cells. T and B cells, macrophages and dendritic cells (DCs) all express all five muscarinic ACh receptor subtypes (mAChRs) and several subtypes of nicotinic AChRs (nAChRs), including α7 nAChRs. Stimulation of these mAChRs and nAChRs by their respective agonists causes functional and biochemical changes in the cells. Using AChR knockout mice, we found that M1/M5 mAChR signaling up-regulates IgG1 and pro-inflammatory cytokine production, while α7 nAChR signaling has the opposite effect. These findings suggest that ACh synthesized by T cells acts in an autocrine/paracrine fashion at AChRs on various immune cells to modulate immune function. In addition, an endogenous allosteric and/or orthosteric α7 nAChR ligand, SLURP-1, facilitates functional development of T cells and increases ACh synthesis via up-regulation of ChAT mRNA expression. SLURP-1 is expressed in CD205(+) DCs residing in the tonsil in close proximity to T cells, macrophages and B cells. Collectively, these findings suggest that ACh released from T cells along with SLURP-1 regulates cytokine production by activating α7 nAChRs on various immune cells, thereby facilitating T cell development and/or differentiation, leading to immune modulation. Copyright © 2015. Published by Elsevier B.V.
Article
Extracts of sympathetic ganglionic chains contain a substance which behaves like acetylcholine biologically, chromatographically, and electrophoretically. The melting point of the tetrachloroaurate salt of this substance is identical to that of acetylcholine tetrachloroaurate. No other choline esters have been detected in these extracts. Perfusion of sympathetic ganglia with C14-choline indicates that C14-acetylcholine is released.
Chapter
Acetylcholine (Ach) is an excitatory neurotransmitter formed from choline and acetic acid through the process of esterification. It is the primary neurotransmitter in the parasympathetic autonomic nervous system, a chemical transmitter at the neuromuscular junction, and a neuromodulator in the brain. This chapter outlines the history, neurochemical profile, receptor functioning, metabolism, pharmacological importance, and the clinical application of Ach.KeywordsAcetylcholineCholinergic transmissionParasympathomimeticNeurotransmitter
Article
In the folk medicine of several cultures, mushrooms have been used in religious and magical ceremonies. One of these mushrooms is the fly agaric, Amanita muscaria (Wasson, 1973). The first scientific studies of this mushroom were made by Schmiedeberg and Koppe (1869), who showed that extracts of the mushroom could slow, and at higher concentrations arrest, the beat of the frog heart. Using this action as a guide, they purified the extract using the standard alkaloid purification methods then available and obtained a crystalline aurichloride salt. Since no microanalytic data were provided by them, it is unclear whether or not this was a pure compound of the alkaloid, which they named muscarine, but later evidence suggests that it was no more than 25% pure (Eugster, 1960). It was a reliable preparation that they then used for an extensive study of its pharmacology. They showed that, in addition to its action on the heart, it contracted the smooth muscle of the stomach and intestine, stimulated the secretion of tears, saliva and mucus, constricted the pupil, caused accommodation of the lens, and also produced dyspnea. Applied to the brain and spinal cord, it produced flaccidity and weakened peripheral reflexes.
Chapter
This chapter presents information on indole alkaloids. The chapter presents a classification of various groups of alkaloids, according to the position of the substituents and the degree of substitution in the pyrrole part of the indole nucleus. The groups are extended to accommodate alkaloids, carrying substituents in the benzene ring, as well as those already specified for each group. The chapter discusses the following: (1) abrine, (2) hypaphorine, (3) gramine, (4) the ergot alkaloids, (5) the alkaloids of Peganum harmala, (6) those of Evodia rutaecarpa, (7) the yohimbe alkaloids, (8) the quebracho alkaloids, (9) the alkaloids of Rauwolfia species, (10) the alkaloids of Gelsemium species, (11) the alkaloids of Calycanthareae, (12) those of the calabar bean, (13) the iboga alkaloids, (14) the Alstonia alkaloids, (15) those of Geissospermum vellosii, (16) quinamine and cinchonamine, and (17) C-dihydrotoxiferine-I. The action of amyl alcoholic potassium hydroxide on quinamine causes rapid epimerization and three products are obtained—namely, epiquinamine, isoquinamine, and epi-isoquinamine. The chapter presents a table on the alkaloids and their transformation products.
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This volume presents a series of vibrant profiles that trace the evolution of our knowledge about the brain. Beginning almost 5,000 years ago, with the ancient Egyptian study of "the marrow of the skull", the book takes us on a fascinating journey from the classical world of Hippocrates, to the time of René Descartes and the era of Paul Broca and Santiago Ramón y Cajal, to modern researchers such as Roger W. Sperry. We meet Galen, a man of titanic ego and abrasive disposition, whose teachings dominated medicine for a thousand years; Andreas Vesalius, a contemporary of Nicolaus Copernicus, who pushed our understanding of human anatomy to new heights; Otto Loewi, pioneer in neurotransmitters, who gave the Nazis his Nobel prize money and fled Austria for England; and Rita Levi-Montalcini, discoverer of nerve growth factor, who in war-torn Italy was forced to do her research in her bedroom. For each individual, the philosophy, the tools, the books, and the ideas that brought new insights are examined. The book also looks at broader topics: How dependent are researchers on the work of others? What makes the time ripe for discovery? And what role does chance or serendipity play? Many fascinating background figures are also included, from Leonardo da Vinci and Emanuel Swedenborg to Karl August Weinhold-who claimed to have reanimated a dead cat by filling its skull with silver and zinc-and Mary Shelley, whose Frankenstein was inspired by such experiments.
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Although acetylcholine (ACh) has been shown beyond reasonable doubt to be the transmitter substance at certain cholinergic nerve endings, there are several facts which warn us against attributing a too exclusive role to this compound. First, by analogy with other transmitters (e.g., the catecholamines) the transmitter role is likely to be subserved by a group of related substances rather than by a single compound. Second, ACh occurs in non-nervous tissue and is so widely distributed in nature as to suggest a non-nervous function for it. Third, several other carboxylic esters of choline possessing related or contrasting pharmacological properties are known to occur in nature. Though so far their presence in nervous tissue has not been unequivocally demonstrated, this tissue can undoubtedly synthesize homologues of ACh in vitro (Gardiner and Whittaker 1954, Frontali 1958, Berry and Whittaker 1959) and is well equipped, by its possession of two forms of cholinesterase (ChE), to destroy them rapidly. The possibility that ACh may not be the only transmitter substance at cholinergic nerve endings or that its function may be interfered with under pathological conditions by the appearance of similar compounds must be borne in mind when considering the mode of action of anti-cholinesterase (anti-ChE) agents and justifies the inclusion of a chapter on the identification of ACh and related esters in a monograph on this subject.
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The evolutionary perspective on the universal roles of compounds known as neurotransmitters may help in the analysis of relations between all organisms in biocenosis-from microorganisms to plant and animals. This phenomenon, significant for chemosignaling and cellular endocrinology, has been important in human health and the ability to cause disease or immunity, because the "living environment" influences every organism in a biocenosis relationship (microorganism-microorganism, microorganism-plant, microorganism-animal, plant-animal, plant-plant and animal-animal). Non-nervous functions of neurotransmitters (rather "biomediators" on a cellular level) are considered in this review and ample consideration is given to similarities and differences that unite, as well as distinguish, taxonomical kingdoms.
Article
With the technical advances of the past few decades, there has been increasing emphasis in neurophysiology and neuropharmacology on studies at the cellular and subcellular levels, as illustrated by most of the chapters in the present volume. The magnitudes and sequences of the electrical signs associated with neuronal activity could be defined accurately only after the development of reliable single unit and intracellular recording techniques. At the same time, the electron microscope has yielded knowledge of the morphological details of nervous tissue well beyond its known physiological correlates. However, the chemistry of the structures and specific reactions involved in nervous function can for the most part be described only at the tissue or relatively gross cellular level, and the cytological details as to where the various reactions occur are largely conjectural.
Article
Die biogenen Amine sind niedermolekulare organische Basen, die beim Ablauf der Lebensvorgänge in tierischen und pflanzlichen Organismen entstehen. Sie umfassen aliphatische, fettaromatische und einfache cyclische Verbindungen und treten im Zellstoffwechsel als Bausteine, Zwischen- und Abbauprodukte von sehr verschiedenartiger physiologischer Bedeutung auf (Guggenheim 1951).
Article
The cholinergic system has not evoked the interest of psychopharmacologists to the same extent as the adrenergic or indoleaminergic systems of neurotransmission. It is not surprising that lay interest in hallucinogenesis has not included cholinergic agents such as the muscarinic drugs, because severe physiological reactions overlie their psychedelic effects. However, this should not have deterred a more systematic investigation by neurobiologists of the psychological effects of the naturally occurring and synthetic cholinergic agents. This deficit is balanced, to a certain extent, by the intensity with which the mechanism of synaptic transmission in the cholinergic system has been studied.
Article
To fulfil its function as a chemical transmitter, acetylcholine (ACh) must be held ready in the tissue so that it can be liberated on demand, and following its release be replaced rapidly enough for transmission to occur repetitively in response to successive nerve impulses. The question of how the ester is replaced at the release points of the synapse in available form is one which as yet can be answered only in the most general way. In tissue such as the superior cervical ganglion of mammals the amount of ACh liberated by a single volley of impulses is only a fraction of the total amount present, and one might suppose that replacement occurs from the existing store of ester; but experiment has shown that even at stimulation rates of 20 per sec the release of ACh may continue for an hour or more while the tissue stores remain normal or are increased (see Brown and Feldberg 1936 b, Mac Intosh 1959). It is evident then that resynthesis alone can account for the replacement of the ester at the synaptic release points. Evidently the situation is more complicated, however, since there are other experiments to show that when synthesis of ACh in the ganglion is prevented some release still occurs, and as much as 90% of the tissue store may be mobilized by stimulation of the preganglionic nerve continued for an hour or longer (Mac Intosh l.c.). It must be assumed therefore that both re-synthesis and translocation of ester are involved in its replacement at the release points at least over periods as long as this, although it can not be excluded that the immediate means of replacement is normally by re-synthesis. The probability of a close spatial relation between release and re-synthesis is strengthened by the evidence that whether resting or active the tissue store of ACh always remains nearly constant.
Chapter
Die in diesem Kapitel zusammengefassten Verbindungen sind charakterisiert durch das Vorhandensein einer oder mehrerer NH2 (oder NH)-Gruppen oder deren N-methylierten Verbindungen. Zahlreiche Amine d?rften in der Pflanze durch Decarboxylierung von Aminos?uren u. Betainen oder durch Abbau von Alkaloiden entstanden sein; sie kommen daher sehr oft vergesellschafiet mit diesen Muttersubstanzen vor. Die Abgrenzung gegen?ber den Alkaloiden ist ?brigens sehr unscharf; viele der im folgenden aufgef?hrten Amine werden auch meistens unter die Alkaloide eingereiht.
Chapter
In the nineteenth century the advancement of science was largely due to an organized, descriptive effort associated with a number of important discoveries. It rested on a freeing of the intellect in a way that permitted scientific empiricism; it was aided by meaningful advances in chemistry and by the use of such essential aids as microscopy. The main interest of twentieth century medicine has been in its social implications and its development of many effective means of therapy.
Chapter
Die bier zu behandelnden Amine sind organische Basen mit einer oder zwei endständigen, freien oder substituierten Aminogruppen. Es gehören dazu aliphatische, aromatische und einfache heterocyclische Verbindungen, deren pflanzenphysiologische Bedeutung noch so gut wie unbekannt ist (s. Guggenheim, 1951). Lediglich für Putrescin ist nachgewiesen, daß es einen Wuchsstoff für Bakterien [Haemophilus parainfluencae (Herbst und Snell, 1948–49) und Neisseria perflava (Martin, Pelczar und Hansen, 1952) und für eine Mutante des Schimmelpilzes Aspergillus nidulans (Sneath, 1955)] darstellt.
Chapter
Die hier behandelten Kohlensäurederivate und tierischen Basen berücksichtigen nur solche Verbindungen, die im Tierorganismus oder seinen Ausscheidungen nachgewiesen sind, also auch jene, die ihren Ursprung der Darmflora verdanken. Basen, die nur in vitro durch Bakterien oder deren Fermente entstanden oder bislang ausschließlich bei Pflanzen beobachtet sind, werden nicht erwähnt. Eine ausführliche fbersicht darüber findet sich bei GUGGENHEIM1 Bei den Basen mit unbekannter Konstitution sind ältere, die nur als Goldsalze abgetrennt wurden, ausgelassen, da die Trennung erfahrungsmäßig (s. unten) unvollständig ist und Gemische von Chlorauraten vorliegen können. Die Existenz der noch mit aufgeführten Basen Mirgelin und Kreatosin ist daher zweifelhaft.
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Drought stress promotes biochemical and physiological alterations in plant metabolism that limit growth and yield. This study investigated the accumulation of γ-aminobutyric acid (GABA) in plant tissue, the stomatal conductance (gs) and changes in leaf anatomy in Eucalyptus following drought stress situation. In this study, eight Eucalyptus clones were evaluated under normal water supply (control) and drought stress conditions (stress). For the control treatment, plants were irrigated every day with an automated system until the soil was saturated, and for the stress treatment, drought stress was imposed by non-irrigation of plants, and pots were covered using plastic sheeting to avoid rainfall and humidity. This study has shown that: (1) all clones decreased gs with increasing vapor pressure deficit (D) in both treatments. All plastics and drought-tolerant clones (except GG) presented lower stomatal sensitivity to D under stress conditions than drought-sensitive clones; (2) GABA concentrations increased fast after drought stress, but we could not find correlation with these changes and resistance to water stress; and (3) all clones increased the number of stomata and reduced leaf thickness after water stress. The finding is that GABA is a fast stress-signaling molecule in Eucalyptus, but the response of gs to D is a best physiological variable to differentiate drought-tolerant and drought-sensitive Eucalyptus clones.
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Barger (1909), J. Chem. Soc. 95, 1123. and Carr (1907), J. Chem. Soc. 91, 337. and Dale (1909), J. Physiol. 38, Proc. lxxvii. - (1910), J. Chem. Soc. 97, 2592.
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Honda (1911), Arch. exp. Path. Pharm. 65, 454. Hunt and Taveau (1911), Hygienic Bulletin, Washington. No. 73.
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Kraft (1906), Arch. Pharm. 214, 336. Nothnagel (1894), Arch. Pharm. 232, 266.