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1.
Rodrigo A. Cunha E. Milusheva †E. S. Vizi J. A. Ribeiro A. M. Sebastião 《Journal of neurochemistry》1994,63(1):207-214
Abstract: The modulation by adenosine analogues and endogenous adenosine of the electrically evoked release of [3H]acetylcholine ([3H]ACh) was compared in subslices of the three areas of the rat hippocampus (CA1, CA3, and dentate gyrus). The mixed A1/A2 agonist 2-chloroadenosine (CADO; 2–10 µM) inhibited, in a concentration-dependent manner, the release of [3H]ACh from the three hippocampal areas, being more potent in the CA1 and CA3 areas than in the dentate gyrus. The inhibitory effect of CADO (5 µM) on [3H]ACh release was prevented by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 50 nM) in the three hippocampal areas and was converted in an excitatory effect in the CA3 and dentate gyrus areas. The A2A agonist CGS-21680 (30 nM) produced a greater increase of the evoked release of [3H]ACh in the CA3 than in the dentate gyrus areas, whereas no consistent effect was found in the CA1 area or in the whole hippocampal slice. The excitatory effect of CGS-21680 (30 nM) in the CA3 area was prevented by the adenosine receptor antagonist 3,7-dimethyl-1-propargylxanthine (10 µM). Both adenosine deaminase (2 U/ml) and DPCPX (250 nM) increased the evoked release of [3H]ACh in the CA1 and CA3 areas but not in the dentate gyrus. The amplitude of the effect of DPCPX and adenosine deaminase was similar in the CA1 area, but in the CA3 area DPCPX produced a greater effect than adenosine deaminase. It is concluded that the electrically evoked release of [3H]ACh in the three areas of the rat hippocampus can be differentially modulated by adenosine. In the CA1 area, only A1 inhibitory receptors modulate ACh release, whereas in the CA3 area, both A2A excitatory and A1 inhibitory adenosine receptors modulate ACh release. In the dentate gyrus, both A1 inhibitory and A2A excitatory adenosine receptors are present, but endogenous adenosine does not activate them. 相似文献
2.
Carmen Fernández-Galaz Allan E. Herbison Richard G. Dyer 《Journal of neurochemistry》1993,60(5):1806-1815
Abstract: Present techniques are unable to provide a sensitive and accurate index of noradrenergic activity in the rat preoptic area. In this study, we have examined the brainstem A1 noradrenergic input to the preoptic area using a new technique whereby [3H]noradrenaline is preloaded into the preoptic area and release of radioactivity from this region is measured subsequently using microdialysis in vivo. Electrical stimulation of the ipsilateral A1 area for 20 min at 5, 10, and 15 Hz evoked significant increases in dialysate radioactivity that were repeatable and frequency-dependent. After removal of calcium from the perfusion medium, basal release of radioactivity was markedly reduced and the effect of A1 stimulation abolished. Changing to a 100 mM K+ medium evoked an increase in the release of radioactivity that was sixfold greater than that seen after A1 stimulation. Separation of the dialysate with HPLC showed that 33% of the increase in measured radioactivity after A1 stimulation was directly attributable to [3H]noradrenaline and the remainder to the metabolites vanillylmandelic acid, 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylglycol. In contrast, the increase in radioactivity after K+ depolarization was due almost completely to [3H]noradrenaline. Addition of 10 μM clonidine to the perfusion medium markedly reduced basal release of radioactivity, but had no effect on evoked release following A1 stimulation. Conversely, perfusion with 10 μM yohimbine had no effect on basal release, but significantly increased evoked release after A1 stimulation. These results now provide a characterization of noradrenergic activity in the preoptic area and indicate the importance of the A1 noradrenergic input to this region. The technique of measuring radioactivity with microdialysis after preloading with [3H]noradrenaline provides a relatively simple, sensitive index of noradrenergic activity in vivo with good temporal resolution. 相似文献
3.
Ultrasonic telemetry was used to compare post‐release survival and movements of Atlantic sharpnose sharks Rhizoprionodon terraenovae in a coastal area of the north‐east Gulf of Mexico. Ten fish were caught with standardized hook‐and‐line gear during June to October 1999. Atlantic sharpnose sharks were continuously tracked after release for periods of 0·75 to 5·90 h and their positions recorded at a median interval of 9 min. Individual rate of movement was the mean of all distance and time measurements for each fish. Mean ± s.e . individual rate of movement was 0·45 ± 0·06 total lengths per second (LT s?1) and ranged from 0·28 to 0·92 LT s?1 over all fish. Movement patterns did not differ between jaw and internally hooked Atlantic sharpnose sharks. Individual rate of movement was inversely correlated with bottom water temperature at capture (r2 = 0·52, P ≤ 0·05). No consistent direction in movement was detected for Atlantic sharpnose sharks after release, except that they avoided movement towards shallower areas. Capture‐release survival was high (90%), with only one fish not surviving, i.e. this particular fish stopped movement for a period of 10 min. Total rate of movement was total distance over total time (m min?1) for each Atlantic sharpnose shark. Mean total rate of movement was significantly higher immediately after release at 21·5 m min?1 over the first 1·5 h of tracking, then decreased to 11·2 m min?1 over 1·5–6 h, and 7·7 m min?1 over 3–6 h (P ≤ 0·002), which suggested initial post‐release stress but quick recovery from capture. Thus, high survival (90%) and quick recovery indicate that the practice of catch‐and‐release would be a viable method to reduce capture mortality for R. terraenovae. 相似文献
4.
Two strains of Dunaliella salina (Dunal) Teod., UTEX 1644 and UTEX 200, were cultured under different growth regimes, including 10 mM NO3? or NH4+, 1.5 or 3.0 M NaCl, and low (0.035%) or high (5%) CO2 in air. The release of 14C-labeled dissolved organic carbon (DOC), expressed as a rate and as a percentage of photosynthetic 14CO2 assimilation, was subsequently determined. The percentage of DOC released was inversely related to cell density in the assay medium, but photosynthesis on a per-cell basis was not. Release of DOC was low, in the range of 1–5% of photosynthesis, but during acclimation to growth on NH4+, it rose to 11%. The presence of NH4+ rather than NO3? in the growth medium increased the rate of release by both strains, but the percentage release was stimulated only in UTEX 200 cells, because their photosynthetic rate was depressed by NH4+. For UTEX 1644, high, as compared to low, CO2-grown cells, had somewhat higher rates and percentages of DOC release, but release from UTEX 200 cells was unaffected by the growth-CO2. The rate of DOC release by high CO2-grown cells was not enhanced at a low concentration of dissolved inorganic carbon, indicating that the released material did not originate from the photorespiratory pathway. The effects of NaCl on DOC release varied with strain and growth conditions. For UTEX 200, the cells in NO3?, but not NH4+, exhibited a doubling or more in percentage of release with a doubling in NaCl concentration, irrespective of growth-CO2. With UTEX 1644 the low CO2-grown cells showed the greatest enhancement in 3.0 M NaCl. Organic matter accumulated on the external surface of the cell membrane and constituted a well-defined cell-coat, which was more dense in NH4+ than in NO3?-grown cells. Microtubules, which may play a role in maintaining cell shape, were observed just below the plasma membrane. From a practical viewpoint, the presence of organic material in the hypersaline ponds of salt-works is detrimental to salt production. When D. salina cells become abundant in such ponds, the attendant, continuous release of DOC may make a significant contribution to the problem. 相似文献
5.
COMPARISONS OF NITRATE UPTAKE, STORAGE, AND REDUCTION IN MARINE DIATOMS AND FLAGELLATES 总被引:1,自引:0,他引:1
Diatoms, but not flagellates, have been shown to increase rates of nitrogen release after a shift from a low growth irradiance to a much higher experimental irradiance. We compared NO3 ? uptake kinetics, internal inorganic nitrogen storage, and the temperature dependence of the NO3 ? reduction enzymes, nitrate (NR) and nitrite reductase (NiR), in nitrogen‐replete cultures of 3 diatoms (Chaetoceros sp., Skeletonema costatum, Thalassiosira weissflogii) and 3 flagellates (Dunaliella tertiolecta, Pavlova lutheri, Prorocentrum minimum) to provide insight into the differences in nitrogen release patterns observed between these species. At NO3 ? concentrations <40 μmol‐N·L ? 1, all the diatom species and the dinoflagellate P. minimum exhibited saturating kinetics, whereas the other flagellates, D. tertiolecta and P. lutheri, did not saturate, leading to very high estimated K s values. Above ~60 μmol‐N·L ? 1, NO3 ? uptake rates of all species tested continued to increase in a linear fashion. Rates of NO3 ? uptake at 40 μmol‐N·L ? 1, normalized to cellular nitrogen, carbon, cell number, and surface area, were generally greater for diatoms than flagellates. Diatoms stored significant amounts of NO3 ? internally, whereas the flagellate species stored significant amounts of NH4 + . Half‐saturation concentrations for NR and NiR were similar between all species, but diatoms had significantly lower temperature optima for NR and NiR than did the flagellates tested in most cases. Relative to calculated biosynthetic demands, diatoms were found to have greater NO3 ? uptake and NO3 ? reduction rates than flagellates. This enhanced capacity for NO3 ? uptake and reduction along with the lower optimum temperature for enzyme activity could explain differences in nitrogen release patterns between diatoms and flagellates after an increase in irradiance. 相似文献
6.
Many conclusions concerning plant responses to CO2 enrichment have been based on assumptions of increased leaf size derived from observations of average leaf area measured at some time well into the growth period. The objectives of this study were to study the effect of elevated CO2 on 1) the timing of mainstem leaflet appearance, 2) the rate and duration of leaflet expansion, and 3) the final area of individual leaflets of soybeans (Glycine max [L.] Merr. cv. Bragg) grown from seed at 348, 502, and 645 μl 1–1 CO2 concentrations. Central leaflet areas from mainstem trifoliolates 1–6 were measured every two days from time of appearance to full expansion. Leaflets tended to appear earlier in elevated CO2 treatments; leaflets 2 through 6 appeared an average of 0.4 days earlier in the 502 μl 1–1 treatment and 1.2 days earlier in the 645 μl 1–1 treatment than in the 349 μl 1–1 treatment. Relative rates of expansion were different among leaflets in their response to elevated CO2; expansion rates of leaflets 1 and 4 were significantly higher at the highest CO2 concentration. However, final area of leaflets was not affected by CO2, or (in leaflet 5 only) was slightly smaller at the highest CO2 treatment. Apparently, higher expansion rates of leaflets 1 and 4 at high CO2 were offset by a tendency for decreased duration of expansion. It appears that there are morphological constraints on final leaflet area in soybean seedlings which limit the effects of elevated CO2 on the early development of mainstem leaf area. 相似文献
7.
Kazumasa Ohkuma Kunio Abe Manabu Kagaya Kazuyuki Yamaya Motokazu Okukawa Masa-aki Watanabe Takeo Yamamoto 《Journal of fish biology》2020,97(5):1560-1563
We released five adult masu salmon (Oncorhynchus masou) tagged with external transmitters to track their ascending behaviour. The signals of all specimens were recorded in the upper area of the river system. Two patterns of ascending behaviour were recognized: ascending upward immediately after release and ascending during increased river discharge. The fastest ascending speed was about 1000 m h–1. Active movements were detected at night. The signal recording duration at each receiver for each fish was generally brief. Most fish did not stay at the pools where the receivers were installed. 相似文献
8.
The photosynthetic behavior of leaves and twigs was compared in Hymenoclea salsola T. and G., a subshrub of the Mohave and Sonoran deserts, in which both leaves and green twigs make substantial contributions to whole-plant carbon gain. Light saturated photosynthesis in twigs was 0.62 times that of leaves (36.9 μmol m-2 s-1) when plants were well watered. Similar ratios were consistently observed in contrasting the photosynthetic responses of the two organ types to light, temperature, and intercellular CO2, regardless of whether rates were compared under saturating or highly limiting conditions of light or intercellular CO2. These scalar differences in photosynthetic rate between leaves and green twigs under a wide range of conditions were correlated with contrasting anatomical features such as chlorenchyma volume per projected area. Under normal ambient CO2 concentrations (350 μl 1-1), twigs on well watered plants operated at lower intercellular CO2 concentrations than the leaves. Possible causes of this difference are discussed with respect to performance under well-watered conditions, organ lifespans, and contrasting anatomical constraints. Twigs require larger investments than do leaves of both carbon and nitrogen per projected area of the respective organs, yet they realize lower photosynthetic rates per intercepted light. Twigs, however, fulfill additional roles besides photosynthesis such as structural support and vascular transport which does not allow them to be as anatomically specialized as leaves for photosynthesis. Twigs also have a longer expected lifespan than leaves with a larger fraction of them surviving the summer drought period. This was correlated with a greater tolerance of twig than leaf photosynthesis to low plant water potentials. 相似文献
9.
A new test method has been developed to estimate the required release rate of hydrogen peroxide (H2O2) to prevent marine biofouling. The technique exploits a well-defined concentration gradient of biocide across a cellulose acetate membrane. A controlled flux of H2O2, an environmentally friendly biocide, was obtained. Larvae of the barnacle, Balanus improvisus, were subjected to known release rates of H2O2 from a surface, under laboratory conditions. It was found that the distribution of settled larvae was not significantly different from the controls when H2O2 fluxes of 5–8 μg cm?2 day?1 were applied. However, release rates of 40 μg cm?2 day?1 significantly displaced the distribution of settled larvae towards the area of the chamber farthest away from the membrane. Membrane tests in seawater (Jyllinge Harbour, Denmark) for over 16 weeks showed that release rates of H2O2 of approximately 2800 μg cm?2 day?1 deterred biofouling efficiently. A H2O2 release rate of about 224 μg cm?2 day?1 resulted in some slime formation, but it was less than that on the H2O2-free control. It appears that to obtain efficient resistance to biofouling in natural seawater requires much higher membrane release rates of H2O2 (factor of between 5 and 50) than laboratory membrane exposure assays using barnacle larvae. 相似文献
10.
《Electromagnetic biology and medicine》2013,32(1):21-42
Theoretical analysis of peculiarities of reception of weak extremely low-frequency periodic signals by calcium-dependent intracellular regulatory systems was performed on the reduced “minimal” model for calcium oscillations suggested by Goldbeter et al. (Proc. Natl. Acad. Sci. USA 87, 1461–1465, 1990). The model considered the following calcium-dependent processes: the rise in intracellular free calcium concentration ([Ca2+]i) due to calcium ionophore A23187 action on a cell, activation of the Ca2+ entry through calcium channels in the plasma membrane by the initial rise in [Ca2+]i, and the Ca2+ release from intracellular stores by the calcium-induced calcium release mechanism. Calcium channels of plasma membrane were chosen as a target for the modulating signal and an additive noise influence in the model. An increase in [Ca2+]i under the influence of the modulating signal was demonstrated to depend not only on the amplitude and frequency of this signal, but also on the phase of the signal with respect to a momentary chemical stimulation of the cell. Such an effect was found only at high strengths of chemical stimulation and with a particular sequence of delivery of the chemical and electromagnetic stimuli. An increase in noise intensity led to magnification of the mean level of [Ca2+]i in a narrow frequency range by the mechanism of stochastic resonance. Under the influence of a modulating periodic signal, the gradual increase in strength of chemical stimulation induced a system transition from regular to chaotic behavior, and then to induced periodic oscillations. A boundary of the transition from chaotic to periodic oscillations corresponded to a “threshold” of sensitivity of calcium-dependent intracellular signaling systems on [Ca2+]i to the influence of the modulating signal. Results of the theoretical analysis led us to conclude that the narrow-band response of a system to an external electromagnetic signal is determined purely by nonlinear properties of the system. 相似文献
11.
The effects of nutrient enrichment on the release of dissolved organic carbon and nitrogen (DOC and DON, respectively) from
the coral Montipora digitata were investigated in the laboratory. Nitrate (NO3
−) and phosphate (PO4
3−) were supplied to the aquarium to get the final concentrations of 10 and 0.5 μmol l−1, respectively, and the corals were incubated for 8 days. The release rate of DON per unit coral surface area significantly
decreased after the nutrient enrichment, while the release rate of DOC was constant. Because the chlorophyll a (chl a) content of zooxanthellae per unit surface area increased, the release rate of DOC significantly decreased when normalized
to unit chl a. These results suggested that the incorporation of NO3
− and PO4
3− stimulated the synthesis of new cellular components in the coral colonies and consequently, reduced extracellular release
of DOC and DON. Actually, significant increase in N and P contents relative to C content was observed in the coral’s tissue
after the nutrient enrichment. The present study has concluded that inorganic nutrient enrichment not only affects coral-algal
metabolism inside the colony but also affects a microbial community around the coral because the organic matter released from
corals functions as energy carrier in the coral reef ecosystem. 相似文献
12.
A. Kunzmann 《Polar Biology》1990,11(1):9-18
Summary Gill dimensions of 27 juvenile and adult Pleuragramma antarcticum from the southern Weddell Sea and of 28 juvenile and adult Notothenia gibberifrons from the South Orkney and South Shetland Islands were estimated. The unit gill area (UGA) of P. antarcticum ranged from 75 to 167 mm2/g (mean=105); gill area index (GAI) and water-blood distance (WBD) were found to be 1.38 cm2 and 3.3 m, respectively. The exponent dg in the relationship total gill area to weight was found to be 0.90. It is concluded that P. antarcticum belongs to sluggish species and, although pelagic, its routine energy costs tend to be low. However, the closely packed lamellae (NL/mm=21) indicate more active behaviour in comparison with N. gibberifrons. A preliminary estimation of growth parameters (P, k) is presented. The sluggish behaviour of N. gibberifrons, as expected from its benthic mode of life, is reflected by the gill parameters: the very low UGA ranged from 39 to 118 mm2/g; GAI and dg were found to be 0.73 cm2 and 0.98, respectively. Comparing gill dimensions and general respiration characteristics of fish from antarctic, temperate and tropical waters it is concluded that antarctic fish have increased their scope for activity. 相似文献
13.
MARIA ANGÉLICA CARRASCO YVETTE MOROT GAUDRY-TALARMAIN JORDI MOLGO 《Neurochemistry international》1996,29(6):637-643
The aim of the present study was to investigate possible changes of inositol 1,4,5-trisphosphate (IP3) mass in Torpedo cholinergic synaptosomes in conditions promoting stimulated acetylcholine (ACh) release. For this purpose, we used a radioreceptor IP3 mass assay and a chemiluminescent method for ACh detection. Torpedo cholinergic synaptosomes have consistent IP3 mass levels under resting conditions. The IP3 mass was neither modified by changes in external Ca2+ nor by a Ca2+-free medium containing EGTA. IP3 mass and ACh release, measured in the same conditions and in parallel, were increased by depolarization with high K+ and by the ionophores A-23187 and gramicidin-D in a manner dependent on external Ca2+ emphasizing that Ca2+ entry, independently of the influx mechanism involved, leads to an IP3 increase. The phospholipase Cβ inhibitors U-73122 and U-73343 reduced K+-stimulated IP3 levels while K+-evoked ACh release was almost completely blocked suggesting an additional effect of these drugs on depolarization-neurotransmitter secretion coupling. The effect reported showing an increase of IP3 by agents that stimulate ACh release may suggest a possible link between IP3 metabolism and the neurotransmitter release mechanism. However, such a link is probably not a direct one as implied by the results obtained with the inhibitors of phospholipase C. Copyright © 1996 Elsevier Science Ltd 相似文献
14.
Fjord migration and survival of wild and hatchery-reared Atlantic salmon and wild brown trout post-smolts 总被引:1,自引:1,他引:0
Eva B. Thorstad Finn Økland Bengt Finstad Rolf Sivertsgård Núria Plantalech Pål Arne Bjørn R. Scott McKinley 《Hydrobiologia》2007,582(1):99-107
The behaviour of wild (n = 43, mean LT = 152 mm) and hatchery-reared (n = 71, mean LT = 198 mm) Atlantic salmon and wild anadromous brown trout (n = 34, mean LT = 171 mm) post-smolts with acoustic transmitters was compared in a Norwegian fjord system. There was no difference in survival
between wild and hatchery reared salmon from release in the river mouth to passing receiver sites 9.5 km and 37.0 km from
the release site. Mortality approached 65% during the first 37 km of the marine migration for both groups. There was no difference
between wild and hatchery-reared salmon either in time from release to first recording at 9.5 km (mean 135 and 80 h), or in
the rate of movement through the fjord (mean 0.53 and 0.56 bl s−1). Hatchery-reared salmon reached the 37 km site sooner after release than the wild salmon (mean 168 and 450 h), but rate
of movement in terms of body lengths per second did not differ (mean 0.56 and 0.77 bl s−1). The brown trout remained a longer period in the inner part of the fjord system, with much slower rates of movement during
the first 9.5 km (mean 0.06 bl s−1). 相似文献
15.
Methane release from stands of water horsetail (
Equisetum fluviatile
) in a boreal lake 总被引:1,自引:0,他引:1
1. Annual and diel variations in methane (CH4) release in stands of Equisetum fluviatile were measured from June to November in Lake Pääjärvi, southern Finland, where E. fluviatile is the dominant emergent macrophyte. An estimate of total annual release of CH4 from stands of E. fluviatile in this lake was also made. Diel variation was measured twice (June and August), whereas measurements for annual variation were performed monthly. The hypothesis that a relationship exists between the productivity of stands and CH4 release was also tested, whereupon net ecosystem exchange (NEE) of CO2 as well as standing stock of E. fluviatile were determined, in addition to simultaneous recordings of air temperature and solar radiation. 2. Seasonal variations in CH4 release were pronounced, with the highest release rate of 813 mg m–2 day–1 measured in July and the lowest 6.5 mg m–2 day–1 in November, when the shoreline was already frozen. 3. Methane release rates were strongly correlated with mean air temperature in the measuring chambers and with total solar radiation. There was no significant correlation between the instantaneous radiation and CH4 release rates. 4. The seasonal patterns of CH4 release and NEE of CO2 resembled each other, except in July when NEE suddenly dropped. The decrease in NEE coincided with the highest CH4 release rate measured and the highest temperature during the measuring period, i.e. 32 °C outside and 37 °C inside the chamber. Excluding this date, daily CH4 release was strongly correlated with NEE (r2 = 0.971). 5. No diel changes in CH4 release rates were detected. In June and August the maximum release rates were 11.4 and 16.8 mg CH4 m–2 h–1, respectively. 6. The standing stock of E. fluviatile at different times of the growing season was not correlated with CH4 efflux; the CH4 release rates could be related neither to the number of shoots, i.e. sufficient conduits for gas transport were always present, nor to the shoot biomass in the measuring chambers. 7. For an estimate of the annual release, the monthly values measured at noon were integrated over the entire growing season; this resulted in 43.7 g CH4 m–2 for the annual emission. The total annual emission of CH4 from the area covered with E. fluviatile in Lake Pääjärvi was calculated to be ≈ 5000 kg. 8. Significant amounts of CH4 are released from stands of E. fluviatile in boreal lakes. The CH4 release rate follows a seasonal pattern but there is no diel pattern. Methane release rate can be related to temperature, solar radiation and NEE of CO2, but not to the standing stock of E. fluviatile or the number of shoots. 相似文献
16.
The effect of ammonia and calcium on the activity of monoamine oxidase (MAO) was studied. The enzyme activity in nonsynaptic brain mitochondria isolated from the rats treated with ammonium acetate was estimated from the release of H2O2using spectrophotometry. The effect of calcium on MAO was assayed directly after adding Ca2+to the nonsynaptic mitochondria isolated from the forebrain of control rats. Both ammonium acetate injectionin vivoand Ca2+additionin vitrostimulated the activity of MAO A but not that of MAO B in mitochondria. This is the first evidence for ammonia and Ca2+regulation of MAO A in the forebrain nonsynaptic mitochondria and for their contribution to oxidative stress in the neurons via MAO A activation. 相似文献
17.
Various parameters of the Tanada effect (Proc. Natl. Acad. Sci. U.S. 59: 376–380. 1968) have been defined. This phenomenon, in which root tips of Phaseolus aureus L. adhere to a negatively charged glass surface when they are irradiated with 660 nm (red) light and release under 730 nm (far-red) light, has been characterized as follows. Secondary roots, whether etiolated or light grown exhibit photoreversible adhesion. Primary roots do not. Tips from 6–8 mm secondary roots exhibit the best response to red light, whereas tips from 3 mm roots respond best to far-red light. Red light saturetes the adhesion system at about 50 μ W/cm2xnm and far-red light, release system at about 150 ü W/cm2 xnm. The adhesion effect begins to show escape from far-red reversibility within 60–90 seconds, an observation quite different from other “typical” long term de- etiolation effects. In addition, root tips irradiated with red light begin to release spontaneously in the dark after 10 min, and have nearly completed release after 50 min. Tips irradiated with continuous red light show gradual release after 15 minutes of exposure. Whether these data indicate an extremely rapid dark reversion of Pfr to Pr or decay of Pfr under continuous red light is not known at this time. In order to study tip adhesion and release, the glass beaker surface may be negatively charged with thiocyanate (SCN-), nitrate (NO3-), sulfate (SO42-), chloride (Cl-), phosphate (PO43-), citrate (C6H5O73-), oxalate (C2O42-) or glutamine (C5H8NO4-). Benzoate (C7H5O2-) and acetate (CH3COO-) were found to be relatively ineffective for red light adhesion, however when citrate and oxalate were used release was inhibited. This was apparently due to a chelation of Ca2+since release began immediately as excess Ca+2 was added to the bathing solution. Substitution of GTP, ITP, UTP, or CTP for ATP resulted in only 20 to 40% adhesion and release for GTP, ITP and UTP, CTP showed normal adhesion kinetics under red light but very slow release kinetics under far-red light. The effects of red and far-red light in the numbers of secondary roots are that red light inhibits root initiation while far-red light partially reverses the red light effect. 相似文献
18.
A possible role for protein kinases in the regulation of GABA exocytosis in nerve endings was investigated. The effect on the release of the radioactive neurotransmitter ([3H]GABA) from mouse brain synaptosomes of several protein kinase inhibitors was estimated after treatment with 37 mM K+ in the absence of external Na+, a condition under which [3H]GABA release is completely Ca2+ dependent. Among the inhibitors one group inhibit the kinases by binding to the catalytic site (i.e. staurosporine and H7) and others (TFP, sphingosine and W7) act on the regulatory site of protein kinases. The compounds of the second group, which are reported to inhibit calmodulin dependent events and the increase in cytosolic Ca2+ (Ca
i
) induced by high K+ depolarization, were the most efficient inhibitors of [3H]GABA release. The selective inhibitor of CaMPK II, KN-62, also markedly diminished [3H]GABA release as well as the increase in Ca
i
induced by high K+. The kinase inhibitors from the first group that are unable to diminish the increase in Ca
i
induced by high K+ were also less efficient inhibitors of [3H]GABA release even at high concentrations. The present results indicate that at the doses tested all the drugs inhibit to some extent the release of the Ca2+ dependent fraction of [3H]GABA perhaps by inhibiting a CaMPK II mediated phosphorylation step triggered by depolarization and facilitated by the elevation of Ca
i
. In addition, the second group of antagonists and KN-62 inhibit the elevation of Ca
i
to high K+ thus exhibiting a higher efficiency on [3H]GABA release than the first group of antagonists. 相似文献
19.
EFFECTS OF TETRODOTOXIN, CALCIUM AND MAGNESIUM ON THE RELEASE OF AMINO ACIDS FROM SLICES OF GUINEA-PIG CEREBRAL CORTEX 总被引:11,自引:9,他引:2
S. J. Potashner 《Journal of neurochemistry》1978,31(1):187-195
Abstract— Tetrodotoxin, Ca2+-deprivation and high-Mg2+ were used in an effort to identify the portion of the evoked release of endogenous amino acids, labelled via metabolism of [14C]-glucose, and several exogenous labelled amino acids, that came from nerve terminals when slices of guinea pig cerebral cortex were superfused with glucose-free solutions and stimulated electrically. With some exceptions, spontaneous release of labelled amino acids was decreased by 2 μm -tetrodotoxin but increased in Ca2+-free medium and in solutions containing an extra 24 mm -MgCl2. Tetrodotoxin suppressed 85–90% of the stimulated release of almost all labelled amino acids, but had a smaller effect on the release of endogenous 14C-labelled threonine-serine-glutamine (unseparated). In Ca2+-free solution, the stimulated release of endogenous 14C-labelled glutamate, aspartate and GABA was suppressed by 80–90%, but that of endogenous 14C-labelled threonine-serine-glutamine was unaffected as was most of the release of the other labelled amino acids. In medium containing an extra 24mM-MgCl2, the stimulated release of endogenous 14C-labelled glutamate, aspartate and GABA was suppressed by 75-85%, that of exogenous labelled aspartate and GABA by 50–65%, but the release of the other labelled amino acids was unaffected. The control stimulated releases of endogenous 14C-labelled glutamate, aspartate and GABA were much larger than those of other labelled amino acids but were reduced by tetrodotoxin, Ca2+-deprivation and high-Mg2+ to a level similar to that of the control stimulated releases of the other labelled amino acids. These results suggest that almost all of the stimulated release of endogenous 14C-labelled glutamate, aspartate and GABA came from nerve terminals while those of the other labelled amino acids came from other tissue elements. In addition, they are in accord with a transmitter role for glutamate, aspartate and GABA in cerebral cortex. 相似文献
20.
Summary The present study was designed to examine which type of adenosine receptors was involved in enhancement of high K+-evoked taurine release fromin vivo rat hippocampus using microdialysis. Perfusion with 0.5 or 5.0 mM adenosine enhanced high K+-evoked taurine release. Perfusion with 2M R(–)-N6-2-phenylisopropyladenosine (PIA), a selective adenosine A1 receptor agonist, did not modulate taurine release. Perfusion with 1M 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), a selective adenosine A1 receptor antagonist, increased taurine release. On the other hand, perfusion with 20M 2-[4-(2-carboxyethyl)phenethylamino]-5-N-ethyl-carboxamideadenosine (CGS21680), a selective adenosine A2A receptor agonist, enhanced taurine release, while perfusion with 1 mM 3,7-dimethyl-propagylxanthine (DMPX), an adenosine A2 receptor antagonist, did not affect taurine release. These results demonstrate that adenosine enhances high K+-evoked taurine release via activation of adenosine A2A receptors from both neurons and glial cells ofin vivo rat hippocampus. 相似文献