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81.
Bruce R. Johnson Jack H. Peck Ronald M. Harris-Warrick 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(2):201-209
Summary The anterior burster neuron of the lobster (Panulirus interruptus) stomatogastric ganglion is a conditional burster that functions as the primary pacemaker for the pyloric motor network. When modulatory inputs to this cell are blocked, it loses its bursting properties and becomes quiescent. Applications of the monoamines, dopamine, octopamine or serotonin restore rhythmic bursting in this cell (Flamm and Harris-Warrick 1986). At 15 °C, serotonin- and octopamine-induced oscillations depend critically upon sodium entry (blocked by low sodium saline or tetrodotoxin); dopamine-induced oscillations depend upon calcium entry (blocked by reduced extracellular calcium; Harris-Warrick and Flamm 1987). We show here that the ionic dependence of amine-induced oscillations in the anterior burster cell differs at 15 and 21 °C. At 21 °C, all amines have the potential to induce rhythmic oscillations in saline containing tetrodotoxin. At the elevated temperature and in tetrodotoxin, both calcium and sodium currents are essential for the maintenance of dopamine-induced oscillaions; serotonin-induced oscillations do not depend upon either calcium or sodium alone; octopamine-induced oscillations do not depend upon calcium and show a variable dependence upon sodium. Thus, multiple ionic mechanisms, which vary with both the modulator and the ambient temperature, can be recruited to support rhythmic activity in a conditional burster neuron.Abbreviations
AB
anterior burster
-
PD
pyloric dilator
-
PY
pyloric constrictor
-
DA
dopamine
-
5HT
serotonin
-
Oct
octopamine
-
STG
stomatogastric ganglion
-
TTX
tetrodotoxin
-
GSP
graded synaptic potential 相似文献
82.
A 46,XY female patient with streak gonads and a large deletion of Yp is described. The deletion included the Y chromosomal genes SRY, ZFY, and RPS4Y. The patient did not display any Turner stigmata, such as webbing of the neck, cardiac or other abnormalities. The findings argue against an important role of RPS4Y in the prevention of Turner stigmata in males and are consistent with a role of SRY in testis differentiation in humans. 相似文献
83.
Bruce A. Menge 《Oecologia》1991,88(1):1-8
Summary Petraitis (1990) recently critized previous generalizations regarding the effects of predation in the New England rocky intertidal region (e.g., Menge 1976; Lubchenco and Menge 1978). Contrary to Lubchenco's and my conclusions, Petraitis concluded that (1) barnacles and not mussels are the favored prey of dogwhelks and (2) barnacles and not dogwhelks control mussel abundances in the mid and low rocky intertidal region. I provide evidence that these criticisms are unwarranted. First, Lubchenco and I never claimed that diet composition reflected prey preference. Moreover, predators can influence prey abundance without preferring the prey. Hence, claims regarding preferences have no bearing on our conclusions. Second, Petraitis' experiments do not invalidate Lubchenco's and my experimental results. Reanalyses of our experimental data support the earlier conclusion that at wave-sheltered sites, whelks reduce the abundance of mussels independently of barnacle abundances. Further, at all but one of Lubchenco's and my study sites, predator densities were higher than at Petraitis' site. Thus, the absence of a predator effect in Petraitis's study was most likely due to low predator density rather than a lack of generality of our earlier results. This reevaluation therefore suggests that within a broader conceptual framework, Petraitis' apparently divergent results are actually consistent with ours. 相似文献
84.
Morphological Responses of Wheat to Changes in Phytochrome Photoequilibrium 总被引:5,自引:0,他引:5 下载免费PDF全文
Wheat plants (Triticum aestivum L.) were grown at the same photosynthetic photon flux (PPF), 200 micromoles per square meter per second, but with phytochrome photoequilibrium ([unk]) values of 0.81, 0.55, and 0.33. Plants grown at [unk] values of 0.55 and 0.33 tillered 43 and 56%, less compared with plants grown at [unk] of 0.81. Main culm development (Haun stage) was slightly more advanced at lower values of [unk], and leaf sheaths, but not leaf lamina, were longer at lower [unk]. Dry-mass accumulation was not affected by different levels of [unk]. Three levels of PPF (100, 200, and 400 micromoles per square meter per second) and two lamp types, metal halide and high pressure sodium, were also tested. Higher levels of PPF resulted in more dry mass, more tillering, and a more advanced Haun stage. There was no difference in plant dry mass or development under metal halide versus high pressure sodium lamps, except for total leaf length, which was greater under high pressure sodium lamps (49.5 versus 44.9 centimeters, P < 0.01). 相似文献
85.
P700 is rapidly, but only transiently photooxidized upon illuminating dark-adapted leaves. Initial oxidation is followed by a reductive phase even under far-red illumination which excites predominantly photosystem (PS) I. In this phase, oxidized P700 is reduced by electrons coming from PSII. Charge separation in the reaction center of PSI is prevented by the unavailability of electron acceptors on the reducing side of PSI. It is subsequently made possible by the opening of an electron gate which is situated between PSI and the electron acceptor phosphoglycerate. Electron acceptors immediately available for reduction while the gate is closed corresponded to 10 nmol · (mg chlorophyll)–1 electrons in geranium leaves, 16 nmol · (mg chlorophyll)–1 in sunflower and 22 nmol · (mg chlorophyll)–1 in oleander. Reduction of NADP during the initial phase of P700 oxidation showed that the electron gate was not represented by ferredoxin-NADP reductase. Availability of ATP indicated that electron flow was not hindered by deactivation of the thylakoid ATP synthetase. It is concluded that NADP-dependent glyceraldehydephosphate dehydrogenase is completely deactivated in the dark and activated in the light. The rate of activation depends on the length of the preceding dark period. As chloroplasts contain both NAD- and NADP-dependent glyceraldehydephosphate dehydrogenases, deactivation of the NADP-dependent enzyme disconnects chloroplast NAD and NADP systems and prevents phosphoglycerate reduction in the dark at the expense of NADPH and ATP which are generated by glucose-6-phosphate oxidation and glycolytic starch breakdown, respectively.Abbreviations Chl
chlorophyll
- P700
electron donor pigment in the reaction center of photosystem I
Cooperation of the Institute of Botany of the University of Würzburg with the Institute of Astrophysics and Atmospheric Physics of the Estonian Academy of Sciences in Tartu was supported by the Deutsche Forschungsgemeinschaft and the Estonian Academy of Sciences. This work was performed within the Sonderforschungsbereich 251 of the University of Würzburg. 相似文献
86.
Binding of polonium-210 to liver metallothionein 总被引:1,自引:0,他引:1
The interactions of 210Po at the molecular level in biological systems have received little study even though this alpha-emitting radionuclide occurs widely in nature. Polonium-210 was given subcutaneously to rats and found to be incorporated into liver metallothionein as judged by a number of criteria including heat stability, acetone precipitation, and chromatography. In vitro studies confirmed this binding. The binding of 210Po to metallothionein has implications that may help explain some of the radiation damage 210Po causes intracellularly. 相似文献
87.
88.
Helmut Bäumlein Istvan Nagy† Raimundo Villarroel Dirk Inzé Ulrich Wobus 《The Plant journal : for cell and molecular biology》1992,2(2):233-239
A 2.4 kb fragment containing the 5'-flanking region and the 5'-noncoding sequence of the Vicia faba legumin gene LeB4 mediates high level seed-specific expression in transgenic tobacco plants. Deleted derivatives of this legumin upstream sequence were fused to the npt-II reporter gene to determine the tissue-specific activity of the chimeric constructs in stably transformed tobacco plants. The results indicate the presence of positive regulatory, enhancer-like cis elements within 566 bp of the upstream sequence. Most importantly, however, these elements are only fully functional in conjunction with the core motif CATGCATG of the legumin box around position -95, since destruction of the motif by a 6 bp deletion in an otherwise intact 2.4 kb upstream sequence drastically reduces expression in seeds. At the same time, low level expression in leaves is observed. The occurrence of similar CATGCATG consensus cis elements with alternating purine and pyrimidine base pairs in front of several other plant genes suggests a functional role of the motif in a wider range of plant promoters. 相似文献
89.
A Balland T Faure D Carvallo P Cordier P Ulrich B Fournet H de la Salle J P Lecocq 《European journal of biochemistry》1988,172(3):565-572
A stable transformed cell line constitutively expressing human factor IX has been established. Wild-type Chinese hamster ovary cells (CHO cells) were transformed using a polycistronic expression vector carrying a previously isolated factor IX cDNA and a selection gene encoding the Escherichia coli xanthine-guanine phosphoribosyl transferase. One clone, CHO 622.4, contains a high number of genomically integrated plasmids and secretes 1-3 mg factor IX l-1 day-1 into the culture medium with a biological activity ranging from 25% to 40%. The recombinant molecule was purified either by conventional chromatography or by immunoaffinity chromatography using antibodies specific to a calcium-induced factor IX conformer. The purified recombinant protein migrates as a single band with the same mobility as that of natural factor IX on SDS/polyacrylamide gels. N-terminal sequencing shows tow differently processed forms of recombinant factor IX: whereas the majority of the zymogen is correctly processed, approximately 20% of the purified recombinant molecule contains an 18-amino-acid NH2-extension corresponding to the precursor form of factor IX. Analysis of the 4-carboxyglutamic acid content indicates a high but incomplete carboxylation (70%) of the recombinant molecule as compared to natural factor IX. The carbohydrate composition of both the natural and recombinant molecules has been determined. Both molecules have a N-glycan structure of similar complexity, indicating that factor IX contains all the information to direct the same glycosylation pattern in human liver cells and in an unrelated cell line such as CHO-K1. 相似文献
90.
Peter Berthold und Ulrich Querner 《Journal of Ornithology》1988,129(3):372-375
Summary In 9 hand-raised Garden Warblers, Zugunruhe was continuously recorded in registration cages with movable perches on microswitches in a constant 12:12 hr light-dark cycle throughout the first fall migratory period. In addition, video-records were taken during 23 nights under infrared illumination involving more than 150 hours. The main results are: (1) infrared illumination did not affect Zugunruhe or other events and thus is a useful method, (2) over 90 % of the Zugunruhe recorded with video is wing whirring (i. e. intense wing beating in a sitting position), the rest is hopping and flying, (3) an interval of the customarily used half-an-hour-with-Zugunruhe equals 14.1 min of wing whirring, (4) 35.9 % of the Zugunruhe recorded as wing whirring is missed in a registration cage with one movable perch. This loss is reduced to about 5 % if two movable perches are used, (5) the experimental birds produced in the average 352.1 ± 170.51 (SD) hours with Zugunruhe which equals about 165 hrs of wing whirring. When this value is multiplied by the average flight speed of the species during migration (about 25–30 km/h) a theroretical flight distance of about 4800 km is obtained. This is just the distance from the south German breeding grounds via Spain to the estuary of the river Niger which is situated within the center of the population-specific winter quarters. Zugunruhe in that species thus appears with some restrictions to be wandering by wing whirring in a sitting position. 相似文献