On the mechanism of trap closure of Venus flytrap (Dionaea muscipula Ellis)

The rapid trap closure of Dionaea muscinula Ellis has been explained by either a loss of turgor pressure of the upper epidermis, which should thus become flexible, or by a sudden acid-induced wall loosening of the motor cells. According to our experiments both explanations are doubtful. Objections against the turgor mechanism come from the determination by extracellular measurements from the upper epidermis of action-potential amplitudes before and after trap closure. Neither time course nor amplitude of the action potentials are altered by trap closure. In contrast a rise in the apoplastic concentration of K⁺ or Na⁺, which are the only ions present in the trap in osmotically significant concentrations, from 1 to 10 mM reduces the action-potential amplitudes by 25% and 15%, respectively. Furthermore, after trap closure the upper epidermal cells retain a considerable cell sap osmolality of 0.41 mol·kg^-1 which equals that of the mesophyll cells as determined by incipient plasmolysis. A sudden cell-wall acidification causing movement is improbable since an acidification of the apoplast from pH 6 to pH 4 reduces action-potential amplitudes by 33% whereas the amplitudes measured extracellylarly from the mesophyll and lower epidermis remain unchanged by trap closure. In addition, buffering the apoplast at pH 6 does not prevent movement in traps which have been incised several times from the margin to the midrib to facilitate buffer diffusion into the mesophyll. Even an alkalinization of cell walls of plasmolysed leaf segments to pH 9 does not prevent considerable extensions of the mesophyll and subsequent movement of the specimens during deplasmolysis.These experiments make it very likely that the mesophyll cells are already extensible but are kept compressed in the open trap, thus developing tissue tension. The mechanism which prevents their extension as long as the trap is open can so far only be explained for traps which have been paralysed by a long-term incubation in 1 mM La³⁺. Leaf strips taken from stimulated, closed traps, comprising the lower epidermis and some mesophyll, prove to be highly extensible if they are stretched perpendicular to the midrib on a constant-load extensiometer. By contrast, strips taken from the lower side of paralysed traps are as rigid as those from the upper side of both stimulated and paralysed traps. From observations of semithin cross sections in a polarizing microscope, it is concluded that the extensibilities of these tissue strips are mainly determined by the cell walls of the upper epidermis plus a layer of adjacent mesophyll and by the lower epidermis, respectively, since these are the only cell walls with a preferential microfibril orientation in the direction of the applied stress.Abbreviations E _m membrane potential - E _s surface potential - Mes 2-(N-morpholino)ethanesulfonic acid - Tris 2-amino-2(hydroxymethyl)-1,3-propanediol     

Progress of ethylene action mechanism and its application on plant type formation in crops

BackgroundThe plant hormone ethylene exerts a huge influence in the whole life cycle of plants, especially stress-resistance responses. With the development of functional genomics, that the action mechanism of ethylene takes part in mediated plant architecture has been clarified gradually, such as plant roots, stems, leaves, fiber elongation and so on. Accordingly, the application of ethylene on crops chemical control and genetic improvement is greatly expanded. From the view of ethylene mediated plant architecture in crops, here reviewed advances in ethylene biosynthesis and signal transduction pathway, stress-resistance responses and the yield potential enhance of crops in recently 20 years. On these grounds, the objectives of this paper were to provide scientific reference and a useful clue for the crop creation of ideal plant type.     

Monoclonal Antibodies Against the Voltage-Sensitive Sodium Channel from Rat Skeletal Muscle: Mapping Antibody Binding Sites

Twenty-one monoclonal antibodies specific for the rat skeletal muscle voltage-sensitive sodium channel have been characterized according to subunit reactivity, recognition of carbohydrates, and mutual binding interactions. All antibodies recognize the 260-kDa alpha-subunit of the sodium channel on immunoblots. N-Acetylneuraminic acid inhibited the binding of five antibodies in a concentration-dependent manner, but five other monosaccharides known to be components of the channel had no effect on antibody binding. Competition studies using biosynthetically labeled antibodies separated these 21 antibodies into groups recognizing at least nine distinct domains. Through common interactions between domains, these could in turn be associated into two larger topologically related regions. One region encompasses seven interacting domains and 16 antibodies. This region is probably extracellular by virtue of the interaction of one subgroup with N-acetylneuraminic acid, and may represent a particularly immunogenic region on this channel protein.     

Transient Activity of Excitatory Cl− Channels in Chara: Evidence for Quantal Release of a Gating Factor

In attached patches on the plasma membrane of nonexcited Chara corallina cells, randomly activating, transient Cl⁻ currents with variable amplitudes were recorded. The peak amplitudes of these currents could be grouped into distinct populations with approximately equidistant mean peak currents. Generally, the mean current of the smallest population measured about half of the distance between the means of subsequent populations. Currents of the smallest population occurred most frequently at all voltages; the frequency of observations decreased with increasing amplitudes of the currents. At all voltages transient currents from different populations were similar in duration with the exception of the smallest currents, which lasted only 0.6 times as long as larger currents. Furthermore, transient currents were most frequent at positive voltages, but once initiated at a positive conditioning pulse they were also observed during subsequent pulses to negative voltages. The results are consistent with the idea that Chara contains Ca²⁺ stores in the vicinity of the plasma membrane, which are indirectly filled from the external medium. Upon quantal Ca²⁺ discharge from adjacent stores, a process independent of membrane voltage, the concentration of Ca²⁺ in the cytoplasm increases transiently. Depending on the number of discharging stores, distinct numbers of Ca²⁺-stimulated Cl⁻ channels activate, giving rise to the macroscopic excitatory Cl⁻ current in these cells. Received: 27 October 1997/Revised: 26 February 1998     

Distinct pharmacological profiles of ORAI1, ORAI2, and ORAI3 channels

The ubiquitous Ca²⁺ release-activated Ca²⁺ (CRAC) channel is crucial to many physiological functions. Both gain and loss of CRAC function is linked to disease. While ORAI1 is a crucial subunit of CRAC channels, recent evidence suggests that ORAI2 and ORAI3 heteromerize with ORAI1 to form native CRAC channels. Furthermore, ORAI2 and ORAI3 can form CRAC channels independently of ORAI1, suggesting diverse native CRAC stoichiometries. Yet, most available CRAC modifiers are presumed to target ORAI1 with little knowledge of their effects on ORAI2/3 or heteromers of ORAIs. Here, we used ORAI1/2/3 triple-null cells to express individual ORAI1, ORAI2, ORAI3 or ORAI1/2/3 concatemers. We reveal that GSK-7975A and BTP2 essentially abrogate ORAI1 and ORAI2 activity while causing only a partial inhibition of ORAI3. Interestingly, Synta66 abrogated ORAI1 channel function, while potentiating ORAI2 with no effect on ORAI3. CRAC channel activities mediated by concatenated ORAI1-1, ORAI1-2 and ORAI1-3 dimers were inhibited by Synta66, while ORAI2-3 dimers were unaffected. The CRAC enhancer IA65 significantly potentiated ORAI1 and ORAI1-1 activity with marginal effects on other ORAIs. Further, we characterized the profiles of individual ORAI isoforms in the presence of Gd³⁺ (5μM), 2-APB (5 μM and 50 μM), as well as changes in intracellular and extracellular pH. Our data reveal unique pharmacological features of ORAI isoforms expressed in an ORAI-null background and provide new insights into ORAI isoform selectivity of widely used CRAC pharmacological compounds.     

Benzoxazolinone aryl sulfonamides as potent,selective Nav1.7 inhibitors with in vivo efficacy in a preclinical pain model

Studies on human genetics have suggested that inhibitors of the Na_v1.7 voltage-gated sodium channel hold considerable promise as therapies for the treatment of chronic pain syndromes. Herein, we report novel, peripherally-restricted benzoxazolinone aryl sulfonamides as potent Na_v1.7 inhibitors with excellent selectivity against the Na_v1.5 isoform, which is expressed in the heart muscle. Elaboration of initial lead compound 3d afforded exemplar 13, which featured attractive physicochemical properties, outstanding lipophilic ligand efficiency and pharmacological selectivity against Na_v1.5 exceeding 1000-fold. Key structure-activity relationships associated with oral bioavailability were leveraged to discover compound 17, which exhibited a comparable potency/selectivity profile as well as full efficacy following oral administration in a preclinical model indicative of antinociceptive behavior.     

Neuropharmacological potential of various morphological parts of Camellia sinensis L.

Camellia sinensis L. has long been used as a therapeutic agent for the Central nervous system (CNS) due to the presence of flavonoids. The present study aimed to evaluate the dose-dependent Neuropharmacological behavioral potential of Camellia sinensis seed and leaf extracts on mice. To evaluate the differential potential of leaf and seed extract various doses were prepared and examined in open field, head dip, rearing, cage cross, swimming and traction tests. One-way ANOVA set at P* < 0.05 followed by POST HOC LSD (P* < 0.01) was applied to evaluate the significant difference among the treatments. Herein both seed and leaf extract showed significant results at high doses. Interestingly leaf extract at high dose showed significant effect on mice CNS in open field and head dip test, while seed at high dose revealed significant stimulus on mice CNS in rearing, cage cross, swimming and traction tests. Overall results showed that seed produced more stimulant effect and less calmness as compared to leaf extract was. Tea leaves had already known as potential CNS stimulant drugs; current investigation suggests that tea seed can be used as an alternative CNS stimulant agent with more effective stimulant action.     

Bergenia crassifolia (L.) Fritsch – Pharmacology and phytochemistry

PurposeBergenia crassifolia (L.) Fritsch, a species in the Bergenia genus belongs to the family Saxifragaceae, is valuated for its medicinal application. The review focuses on the medicinal uses, phytochemistry, and the biological activities of B. crassifolia to explore its benefits and potential uses.MethodsIn this review, we summarized data, published in Russia and in other countries related to B. crassifolia.ResultsRhizomes and leaves of this plant are in use as traditional remedies for the treatment of different disorders in the folk medicine systems of Russia and Asia. The plant is a potential source of tannins, benzanoids, flavonoids, polysaccharides and other active compounds. Due to the presence of a multitude of bioactives, a wide array of pharmacological activities have been ascribed to different parts of this herb and individual compounds, which include adaptogenic, antiinflammatory, antihypertensive, antimicrobial, antioxidant, antiobesity, antitussive, cerebro-protective, hepatoprotective, immunomodulating, and diuretic.ConclusionThe review highlights the potential of B. crassifolia for further development of herbal medicines on its base.     

Electrical activity of the liverwort Conocephalum conicum: The all-or-nothing law, strength-duration relation, refractory periods and intracellular potentials

The characteristics of the potential changes caused by excitation of the thallus of Conocephalum conicum L. were investigated and compared with the basic criteria of an action potential. Electrical stimulation (square DC pulses) was applied, and extraand intracellular potentials were recorded. The all-or-nothing law, strength-duration relation, refractory periods, and general characteristics of the changes of transmembrane potential difference were examined. The electrical phenomena occurring during the excitation of Conocephalum fulfil the basic criteria of an action potential. The results contribute additional evidence for the hypothesis that action potentials occur both in plants and in animals.     

Evidence for multiple molecular weight forms of the chick intestinal 1,25-dihydroxyvitamin D3 receptor

Studies from many laboratories have reported apparent molecular weights for the chick intestinal 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] receptor varying from 47,000 to 67,000 daltons. We report here that in the presence of the protease inhibitor phenylmethylsulfonyl fluoride (PMSF, 0.3 mM) and in the presence or absence of ligand, the apparent molecular weight of the receptor is 99,700 ± 9,400 (SD) daltons (as determined by gel filtration). In the absence of PMSF, however, the unoccupied receptor migrates with an apparent molecular weight of 51,400 ± 5,700 (SD) daltons. This smaller form of the 1,25(OH)₂D₃ receptor, upon incubation with [³H]-1,25(OH)₂D₃ in the presence of PMSF, then migrates with an apparent molecular weight of 95,900 ± 7,300 (SD) daltons. These results suggest the presence of heretofore unappreciated multiple molecular forms of the chick intestinal 1,25(OH)₂D₃ receptor.