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151.
Angela B. Lange Ian Orchard William Lam 《Archives of insect biochemistry and physiology》1987,5(4):285-295
Proctolin increases the frequency and amplitude of myogenic contractions and results in a sustained contraction of the oviducts of Locusta migratoria. The possible mode of action of proctolin receptors on this visceral muscle has been investigated. Calcium-free saline, containing either 20 mM magnesium ions or 100 μM EGTA, inhibited myogenic contractions, lowered basal tension, and abolished all the effects of proctolin following a 20 min incubation. These effects were reversible upon washing with normal saline. Similar results were obtained with normal saline containing 10 mM cobalt ions. Nifedipine at 50 μM lowered basal tension, abolished myogenic contractions, and reduced the proctolin-induced sustained contraction by 42-62% at 0.5 nM proctolin and by 33-37% at 5 nM proctolin. Similar results were obtained with 100 μM verapamil. Proctolin was still capable of eliciting considerable contractions (25-67% of controls) in preparations depolarized with 100 mM potassium saline. The removal of calcium from the high-potassium saline reversibly abolished the potassium-induced contraction and reversibly blocked the action of proctolin. Nifedipine was ineffective in blocking the action of proctolin in high-potassium saline. Neither cyclic AMP levels nor cyclic GMP levels of the lateral oviducts were elevated by proctolin in the presence of a phosphodiesterase inhibitor. The results indicate that proctolin mediates its effects via an influx of external calcium ions. This calcium appears to enter through two channels, a voltage-dependent channel and a receptor-operated channel. Cyclic nucleotides do not appear to be involved in the action of proctolin in this visceral muscle. 相似文献
152.
Jacques de Keyser Hiljle Walraevens Guy Ebinger Georges Vauquelin 《Journal of neurochemistry》1989,53(4):1096-1102
D1 dopamine receptors were identified in membranes of human nucleus caudatus, nucleus accumbens, amygdala, and globus pallidus, by the specific binding of [3H](+)-R-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-benzazepine-7 -ol [( 3H]SCH 23390). In these four brain regions, dopamine/[3H]SCH 23390 competition binding curves were computer-analyzed to a two-site model, distinguishing a high- (RH) and low- (RL) affinity site for dopamine. The ability of guanine nucleotides (0.4 mM GTP or 0.1 mM 5'-guanylylimidodiphosphate) to provoke a conversion of RH into RL was different between these brain regions. In amygdala, a complete conversion was seen, whereas there was no guanine nucleotide-effect on RH in globus pallidus. In nucleus caudatus and nucleus accumbens, guanine nucleotides provoked only a partial conversion of RH into RL, suggesting that these brain regions may contain guanine nucleotide-sensitive and -insensitive receptors. Heating of the membranes at 60 degrees C for 5 min had the same effect as guanine nucleotides. The pharmacological profiles of the guanine nucleotide-sensitive and -insensitive D1 receptors were similar, suggesting that D1 receptors in human brain are heterogeneous only with respect to their effector-coupling mechanism: guanine nucleotide-sensitive receptors, which are capable of undergoing functional coupling with Gs, and guanine nucleotide-insensitive receptors, which are not.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
153.
Comparison of a sugar beet with a forage beet variety shows that, during germination, the seedlings have the same nucleoside triphosphate content, but those of sugar beet contain more sucrose and less UDPG than those of forage beet. 相似文献
154.
155.
Daisuke Yamamoto Sachiyo Ishikawa 《Archives of insect biochemistry and physiology》1991,18(4):265-272
Octopamine was found to decrease extrajunctional, but not junctional glutamate responses, in mealworm neuromuscular preparations. This action of octopamine was mimicked by forskolin, 8-(4-chlorophenylthio)-adenosine 3′:5′-cyclic monophosphate (CPT-cyclic AMP), and 8-bromoguanosine 3′:5′-cyclic monophosphate (8-bromo-cyclic GMP), but not by 1,2-oleoylacetylglycerol (OAG), a protein kinase C activator. We suggest that the octopamine-induced reduction in the glutamate sensitivity of extrajunctional membranes may enable the muscle to more closely follow its neuronal input by preventing a depolarization (and hence a conductance increase) due to the discharge of unsequestered transmitter molecules at nonsynaptic sites. 相似文献
156.
《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1595-1598
Abstract A number of different energy transfer dye labeled-cassettes were synthesized using aminoacid based trifunctional linkers and coupled to the propargylamino-substituted dideoxynucleoside-5′-triphosphates (ddNTPs). These terminators were evaluated for their energy transfer efficiency and DNA sequencing potential using thermostable DNA polymerase. 相似文献
157.
We showed that applications of cobalt and zinc salicylates lead to restoration of the impulse activity of a PPa1 neuron of
the snail, Helix pomatia, under conditions of the blockade of synaptic transmission by cadmium ions. In the case where a PPa1 neuron demonstrated
no background activity and/or under conditions of total isolation of this cell, the above-mentioned salicylates initiate generation
of action potentials, as well as exert an excitatory effect on “silent” non-identified cells of the parietal and visceral
ganglia. Based on the data obtained, we conclude that the activating effect of cobalt and zinc salicylates on the PPa1 cell
is similar to that of the so-called initiating factor (IF), which initiates generation of the burst activity. These effects
are independent of the inward calcium current. Using an activator of cAMP phosphodiesterase, imidazole, we showed that the
effects of the above salicylates (similar to the effect of IF) are related to the influence of these agents on the system
of cyclic nucleotides.
Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 11–17, January–February, 2006. 相似文献
158.
Optimal extraction conditions for high-performance liquid chromatographic determination of nucleotides in yeast 总被引:5,自引:0,他引:5
Different extraction methods of nucleotides from the yeast Saccharomyces cerevisiae were compared. A new extraction solution--formic acid saturated with 1-butanol--was found to be more effective than the commonly used solutions of trichloroacetic acid, perchloric acid, or formic acid alone. Using this solution the optimal extraction conditions were established. Nucleotide recovery was evaluated by adding standard nucleotides to the extraction medium and carrying them together with the cells through the whole extraction procedure. Nucleotides were separated and quantitated by high-performance liquid chromatography on an anion-exchange column. 相似文献
159.
Marcel H. N. Hoefnagel Frank Van Iren Kees R. Libbenga Linus H. W. Van der Plas 《Physiologia plantarum》1994,90(2):269-278
In Cathuranthus roseus (L.) G. Don cells the cyanide-resistant pathway is engaged after phosphate or nitrogen starvation. Re-addition of these nutrients disengaged it again. Re-addition of phosphate leads to a transient disengagement which becomes only permanent after a second addition of phosphate. Disengagement after re-addition of nitrogen is slow: it takes 9 days before the activity has disappeared. In this system the mechanism of engagement of the cyanide-resistant pathway was studied. Addition of phosphate to phosphate-starved cells induced cell division within 24 h. The disengagement of the cyanide-resistant pathway was probably only an indirect effect of phosphate because the cellular P, content, which increased rapidly after addition, was low again before the cyanide-resistant pathway was disengaged. A better correlation was observed between high ADP and adenylate content of the cells and disengagement of the cyanide-resistant pathway. In addition it appeared that the engagement of the cyanide-resistant pathway was not the result of a limited carrier capacity of the cytochrome pathway. It is tentatively concluded that the engagement of the cyanide-resistant pathway in phosphate-starved cells was the result of a limited adenylate content. After nitrogen addition to N-starved cells, it took 5 days until the first growth occurred. Before the cyanide-resistant pathway was disengaged, its activity increased with the increased respiration rate which preceded growth. Within 72 h a higher ADP content was observed, which was still high after 10 days. The stimulation of the cytochrome pathway by uncoupler was small and more or less the same with and without added nitrogen, as long as the cyanide-resistant pathway was engaged. After disengagement the stimulation by uncoupler was significantly larger. It is suggested that the engagement during N-starvation was the result of a limited carrier capacity of the cytochrome pathway. Stimulation of the metabolism by re-addition of phosphate, nitrogen or sucrose resulted in a rapid increase in the levels of uracil nucleotides and uridine diphosphoglucose (UDPG) which are involved in sucrose metabolism. 相似文献
160.
To cope with medium acidity, Lactococcus lactis has evolved a number of inducible mechanisms commonly referred as acid stress response. To better understand the molecular basis of this response, several mutants constitutively tolerant to acidity were previously obtained by insertional random mutagenesis of L. lactis MG1363. Mutants in which the GMP synthase gene (i.e. guaA), the (p)ppGpp synthase gene (i.e. relA*) or the high affinity phosphate transport system (i.e. pstS) are inactivated are further characterized in this study. 2-DE was performed and showed that 42, 26, and 35 protein spots are positively deregulated in the guaA, relA*, and pstS mutants, respectively, as compared to the wild-type strain. Most of these proteins were identified by MS. Proteomes comparison of the mutants guaA, relA*, and pstS as well as the acid adaptation proteome of the wild-type strain revealed (i) the presence of numerous overlaps and (ii) that only five proteins were overexpressed in the four conditions, suggesting that these proteins play a crucial role in the constitutive acid stress tolerance of the mutants and in the acid tolerance response of the wild-type strain. 相似文献