共查询到20条相似文献,搜索用时 15 毫秒
1.
Terry W. Moody Nguyen B. Thoa Thomas L. ODonohue David M. Jacobowitz 《Life sciences》1981,29(22):2273-2279
Bombesin-like peptides were characterized in rat spinal cord by radio-immunoassay. The density of bombesin-like peptides was eight-fold greater in the dorsal than ventral horn or white matter of the spinal cord. Using high pressure liquid chromatography fractionation techniques, the main peak of immunoreactivity coeluted with synthetic bombesin. Also, the mechanism of release spinal cord peptides was determined. K+ and veratridine stimulated release of immunoreactive bombesin in a Ca++-dependent mechanism. These data indicate that bombesin-like peptides may function as a unique class of neuroregulatory agents in mammalian spinal cord. 相似文献
2.
J P Burbach J G Loeber J Verhoef E R de Kloet D de Wied 《Biochemical and biophysical research communications》1979,86(4):1296-1303
β-Endorphin (β-LPH 61–91), γ-endorphin (61–77), des-tyrosine-γ-endorphin (62–77), α-endorphin (61–76), and β-LPH 61–69 either labeled with [125I] at the N-terminal 61-tyrosine residue or unlabeled were incubated with a crude synaptosomal plasma membrane fraction of rat brain or in human serum. At different time intervals the release of [125I]-tyrosine or the change in immunoreactivity of the endorphins was determined. The cSPM preparation displayed both high aminopeptidase and endopeptidase activities. In contrast, human serum mainly contained aminopeptidase activity. The data suggest that functional endorphin metabolism may occur at the synaptosomal plasma membrane. These membranes may potentially be involved in the formation of behaviorally active endorphin fragments. 相似文献
3.
PROPERTIES OF THE UPTAKE AND RELEASE OF GLUTAMIC ACID BY SYNAPTOSOMES FROM RAT CEREBRAL CORTEX 总被引:7,自引:6,他引:1
G. Takagaki 《Journal of neurochemistry》1976,27(6):1417-1425
Abstract– (1) The uptake and release of glutamic acid by guinea-pig cerebral cortex slices and rat synaptosomal fractions were studied, comparing the naturally occurring l - and non-natural d -isomers. Negligible metabolism of d -glutamic acid was observed in the slices. (2) Whereas in the cerebral slices the accumulation of glutamic acid was almost the same for the two isomers, d -glutamic acid was accumulated into the synaptosomal fraction at a markedly lower rate than was the L-isomer. (3) The uptake systems for d -isomer into the slices and synaptosomal fraction were found to be of single component, in contrast with the two component systems, high and low affinity components, for the uptake of l -glutamic acid. The apparent Km values for the uptake of d -glutamic acid into the slices and synaptosomal fraction were comparable with those reported for the low affinity components for l -isomer. The uptake systems for d -glutamic acid were dependent on the presence of Na+ ions in the medium, like those for l -glutamic acid and GABA. (4) The evoked release of radioactive preloaded d -glutamic acid was observed both from the slices and synaptosomal fraction following stimulation by high K+ ions in the medium. From these observations, it is evident that the evoked release of an amino acid by depolarization in vitro is not necessarily accompanied by a high affinity uptake process. (5) The uptake of l -glutamic acid, expecially into the synaptosomal fraction, was highly resistant to ouabain. On the other hand, the uptake rate of d -glutamic acid and GABA into the synaptosomal fraction was inhibited by varying concentrations of ouabain in accordance with the inhibition for brain Na-K ATPase. (6) The uptake of l -glutamic acid into subfractions of the P2 fraction was studied in relation to the distribution of the ‘synaptosomal marker enzymes’. An attempt to correlate the activities of enzymes of glutamic acid metabolism with the uptake of l -glutamic acid into the synaptosomal fraction from various parts of brain was unsuccessful. The high affinity uptake of l -glutamic acid was found to be very active in the synaptosomal fraction from any part of brain examined. 相似文献
4.
The immunohistochemical distribution of bombesin-like immunoreactivity in the central nervous system of the rat was revealed using a rabbit antibody against [Glu7]bombesin(6–14). In radioimmunoassay, the antibody had minimal cross reactivity with substance P thereby enhancing the significance of histochemical controls proving that the immunoreactivity detected was related to bombesin but not to substance P. Bombesin-immunoreactive neurons were detected in several brain structures including the hypothalamus, interpeduncular nucleus, central grey, dorsolateral tegmental nucleus, dorsal parabrachial nucleus, nucleus of the solitary tract and trigeminal complex. In the spinal cord, intense immunoreactivity was found in the superficial layers of the posterior horn. Since in this area the reaction diminished after rhizotomy the location of the peptide in afferent neurons was considered. In the anterior horn the bombesin-like immunoreactivity located in nerve terminal-like structures was unchanged after rhizotomy suggesting that the cell bodies were located in CNS. 相似文献
5.
The effect of depolarizing potassium concentration on the release of [14C]glycine, [3H]GABA, and [35S]taurine was investigated in the whole chick retina and in a synaptosomal fraction prepared from the chick retina. In the whole retina, increasing potassium concentration above 40 mM resulted in an increased release of the three amino acids. The release of glycine was the most stimulated and that of taurine, the least. The potassium-evoked release of glycine and GABA was calcium dependent. In the synaptosomal fraction, 68.5 mM potassium significantly stimulated the efflux of GABA and glycine by a calcium-dependent mechanism. The release of taurine from this fraction was unaffected by high potassium. 相似文献
6.
Distribution of bombesin-like peptides in the alimentary canal of several vertebrate species 总被引:2,自引:0,他引:2
G H Greeley M Partin A Spannagel T Dinh F L Hill J Trowbridge M Salter H F Chuo J C Thompson 《Regulatory peptides》1986,16(2):169-181
The objective of this study was to quantitate and characterize the variants of bombesin-like immunoreactivity in the alimentary canal of the rat, rabbit, hawk, owl, dog, monkey and human. Bombesin-like immunoreactivity was found throughout the entire gastrointestinal tract of all species studied. In the rat, the highest concentration of bombesin-like immunoreactivity was found in the colon. Gel chromatography showed that bombesin-like immunoreactivity corresponded to gastrin-releasing peptide (GRP-27) and GRP-10. In the dog, the greatest concentration of bombesin-like immunoreactivity was observed in the mucosal layer of the fundus, whereas the concentration of bombesin-like immunoreactivity in the muscle layer of the dog did not vary significantly from region to region. Gel chromatography showed that bombesin-like immunoreactivity in the dog corresponded to GRP-27, bombesin, GRP-10, and a smaller fragment. In the human, the concentration of bombesin-like immunoreactivity did not vary significantly from region to region in the mucosal and muscular layers. Gel chromatography of human fundal mucosa showed that bombesin-like immunoreactivity peaks occur in the regions of GRP-27, bombesin and GRP-10. These findings substantiate the observation that bombesin-like peptides play a variety of roles in the regulation of gut function. 相似文献
7.
The release of preloaded [3H]dopamine by the synaptosomal fraction prepared from rat forebrain was examined in the presence and absence of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a calmodulin inhibitor. The release induced by high K+ was blocked by W-7 in a concentration-dependent manner after the pretreatment with and in the presence of the inhibitor. The inhibition by W-7 may specifically involve calmodulin, because little effects were seen with N-(6-aminohexyl)-naphthalenesulfonamide, an analog of W-7 with only a low affinity for calmodulin. W-7 may not affect the voltage-dependent Ca2+ channel of synaptosomal plasmalemma, since the inhibitor produced no change in the synaptosomal 45Ca2+ uptake induced by high K+ depolarization. Thus, calmodulin may play a role in transmitter release and may function at the step(s) after the increase of free Ca2+ concentration in the cytosol of the nerve terminal. W-7 affected only to a small extent [3H]dopamine release in the presence of A23187 plus Ca2+. 相似文献
8.
Rocío Salceda 《Neurochemical research》1989,14(1):49-54
The uptake of [14C]glycine and the effect of depolarizing potassium concentrations on its release was investigated in the whole frog retina and its synaptosomal fractions. The uptake of [14C]glycine in retina and synaptosomal fractions was found to be saturable as well as energy and Na+-dependent. TheK
m value for glycine uptake was found to be 46 M for P2 fraction and 100 M for P1 fraction, with aV
max of 3.5 and 3.8 nmol/mg protein/min respectively. The release of [14C]glycine from P1 and P2 synaptosomal fractions was markedly increased by raising potassium concentration in the medium, in a partially Ca2+-dependent manner. Evoked glycine release was 50% reduced when calcium was omitted from the medium. The K+-stimulated release of glycine from P2 fraction was significantly reduced in the presence of TTX. The cellular origin of the P1 and P2 synaptosomal fractions releasing glycine is discussed. 相似文献
9.
UPTAKE OF [3 H-METHYL]CHOLINE BY MICROSOMAL, SYNAPTOSOMAL, MITOCHONDRIAL AND SYNAPTIC VESICLE FRACTIONS OF RAT BRAIN 总被引:1,自引:0,他引:1
Abstract— Microsomal, mitochondrial, synaptosomal and synaptic vesicle fractions of rat brain took up [3H-methyl]choline by a similar carrier-mediated transport system. The apparent Km for the uptake of [3H-methyl]choline in these subcellular fractions was about 5 × 10?5 M. Choline uptake was also observed in microsomal fractions prepared from liver and skeletal muscle. Virtually identical kinetic properties for [3H-methyl]choline transport were found in the synaptosomal fractions prepared from the whole brain, cerebellum or basal ganglia. Countertransport of [3H-methyl]choline from the synaptosomal fraction was demonstrated against a concentration gradient. HC-3 was a competitive inhibitor of the uptake of [3H-methyl]choline in brain microsomal, synaptosomal and mitochondria] fractions with respective values for Ki of 4.0, 2.1 and 2.3 × 10?5 M. HC-15 was a competitive inhibitor of the transport of [3H-methyl]choline in the synaptosomal fraction, with a Ki of 1.7 × 10?4 M. Upon entry into the microsomal fraction, 74 per cent of the radioactivity could be recovered as unaltered choline, 10 per cent as phosphorylcholine, 1.5 per cent as acetylcholine and 2.5 per cent as phospholipid. Choline acetyltransferase (EC 2.3.1.6) was assayed with [14C]acetylCoA in synaptosomal fractions prepared from basal ganglia and cerebellum, and in the 31,000 g supernatant fraction of a rat brain homogenate. Enzyme activity was 11-fold greater in the synaptosomal fraction from the basal ganglia than in that from the cerebellum. HC-3 did not inhibit choline acetyltransferase and there was no evidence for acetylation of HC-3. Our findings suggest that choline uptake is a ubiquitous property of membranes in the CNS and cannot serve to distinguish cholinergic nerve endings and their synaptic vesicles. 相似文献
10.
Exchange release has previously been proposed as the mechanism by which dopamine is transported over the synaptosomal membrane. An increase in carrier-mediated dopamine release should therefore result in an enhanced rate of synaptosomal dopamine uptake. In order to test this hypothesis, rat striatal synaptosomes were incubated with 14C-dopamine until equilibrium. Then, the 14C-dopamine concentration in the medium was reduced in order to elicit various rates of net dopamine efflux, while influx was monitored using tracer amounts of 3H-dopamine. Dopamine release was concentration dependent and saturable and thus may be carrier-mediated. In contrast to that expected for a mechanism of exchange release, dopamine influx was depressed as compared to equilibrium conditions. Furthermore, nomifensine, a specific inhibitor of dopamine influx, did not attenuate dopamine efflux. It is concluded that dopamine transport over the synaptosomal membrane may not be via a mechanism of strict exchange release. 相似文献
11.
O. L. Marenicheva S. A. Zabelinskii M. A. Chebotareva V. P. Ivanova V. B. Kostkin A. I. Krivchenko 《Journal of Evolutionary Biochemistry and Physiology》2001,37(6):611-616
The effect of elevated heliox pressure (101 ATA) on activity of Na+,K+-ATP-ase and some characteristics of fatty acid composition was studied in membrane phospholipids of trout and rat brain synaptosomal and mitochondrial fractions. The Na+,K+-ATP-ase activity was shown to decrease by 25% in both fractions of the rat brain; in mitochondrial fraction of the trout brain it decreased by 47%, while in synaptosomal fraction, only by 11%. It has also been established that under experimental conditions, the unsaturation index of fatty acids of phosphatidylcholine and phosphatidylethanolamine of trout synaptosomes decreased, with no changes in these lipids in mitochondrial fraction. The phosphatidylcholine unsaturation index in rats did not practically change in both fractions, while in rat phosphatidylethanolamine it increased in mitochondrial fraction and slightly decreased in synaptosomal fraction. Thus, under conditions of high pressure the reduction of the enzyme activity is also determined, specifically, by peculiarities of the phospholipid fatty acid composition in the subcellular fractions studied. A possibility of changes of the enzyme activity as a result of transition of its lipid component from the liquid crystalline to the gel state under effect of an enhancement of lipid peroxidation under conditions of elevated pressure is discussed. 相似文献
12.
Glutamate, the main excitatory neurotransmitter in the mammalian central nervous system (CNS), plays important role in brain physiological and pathological events. Quinolinic acid (QA) is a glutamatergic agent that induces seizures and is involved in the etiology of epilepsy. Guanine-based purines (GBPs) (guanosine and GMP) have been shown to exert neuroprotective effects against glutamatergic excitotoxic events. In this study, the influence of QA and GBPs on synaptosomal glutamate release and uptake in rats was investigated. We had previously demonstrated that QA “in vitro” stimulates synaptosomal L-[3H]glutamate release. In this work, we show that i.c.v. QA administration induced seizures in rats and was able to stimulate synaptosomal L-[3H]glutamate release. This in vivo neurochemical effect was prevented by i.p. guanosine only when this nucleoside prevented QA-induced seizures. I.c.v. QA did not affect synaptosomal L-[3H]glutamate uptake. These data provided new evidence on the role of QA and GBPs on glutamatergic system in rat brain. 相似文献
13.
Exposure of a crude synaptosomal fraction to K+ concentrations ranging from 25 to 100 mM evokes the release of [3H]taurine and [3H]GABA. These high concentrations of K+ induce, besides depolarization, a marked synaptosomal swelling, which is prevented by replacing chloride in the solutions with the largely impermeant anion gluconate. The depolarizing effect of K+ is unaffected by omission of chloride. The K+-evoked release of taurine seems related to K+-induced changes in synaptosomal volume rather than to a depolarizing effect, since it is totally calcium-independent but is abolished by reducing chloride and by making solutions hypertonic with mannitol. The release of [3H]GABA, in contrast is unaffected in chloride-free or hypertonic solutions. 相似文献
14.
In the present study the release of bombesin-like immunoreactivity (BLI), somatostatin and gastrin was determined form the isolated perfused rat stomach. Gastric inhibitory polypeptide (GIP, 2 X 10(-9) M) had no effect on BLI while stimulating somatostatin and gastrin release. In these experiments the luminal pH of the stomach was kept at pH 7. Reduction of the luminal pH to 2 resulted in an inhibition of BLI secretion by GIP while gastrin release was abolished and somatostatin remained unaffected compared to luminal pH 7. Acetylcholine (10(-6) and 2 X 10(-6) M) elicited a dose-dependent stimulation of BLI secretion while gastrin was stimulated and somatostatin secretion suppressed independent of the administered dose. The present data demonstrate that release of bombesin-like immunoreactivity can be modulated by intestinal hormones and neurotransmitters and is integrated into the complex system of gastrointestinal neuroendocrine regulation. 相似文献
15.
M C Thorndyke J R Reeve S R Vigna 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1990,96(1):135-140
1. Ratfish (Hydrolagus colliei) intestines were boiled in water to inactivate proteases and then treated with cold 4% trifluoroacetic acid to extract bombesin-like peptides. 2. The extract was fractionated in several steps using reverse-phase and ion exchange HPLC, and bombesin-like immunoreactive peptides were detected by radioimmunoassay using an antiserum specific for the bioactive C-terminal region of bombesin. 3. A highly purified bombesin-like peptide-containing fraction stimulated amylase release in a dose-responsive fashion from rat pancreatic acini; the dose-response curve was parallel to a bombesin standard, and the ratfish peptide stimulated the same maximal rate of amylase secretion as the bombesin standard. 4. A potent, highly selective bombesin receptor antagonist completely abolished the stimulation of amylase release caused by the ratfish peptide, demonstrating the specificity of the response. 5. Estimates of the bombesin-like peptide concentration of this fraction by radioimmunoassay and by bioassay were nearly identical, indicating that ratfish bombesin is very similar biologically and antigenically to frog skin bombesin. 相似文献
16.
It is a well known fact that 3H‐panthenol (PL) has a high bioavailability, so we studied its biotransformation and its protective action against lipoperoxide activation in homogenates and mitochondrial‐synaptosomal fraction (11 000 g) of rat brain. The lipoperoxidation was initialized by Fe2+‐ascorbate complex (Fe2+‐Asc). In experiments in vivo, after 30 min, we demonstrated accumulation of intermediate products of CoA biosynthesis – pantothenic acid (PA), phospho‐PA, and phosphopantetheine – in postmitochondrial fraction of brain, by using a HPLC technique. Addition of the PL (10 mm ) to brain hemispheres homogenates or mitochondrial‐synaptosomal fraction caused a remarkable reduction of malondialdehyde production. However, 30 min preincubation with the PL, but not with PA, was ineffective. The data obtained may be a reason for a high neuroprotective activity of PL in curing brain diseases with vessel or alcohol‐induced damages. 相似文献
17.
Abstract: Adenosine transport inhibitors as enhancers of extracellular levels of endogenous adenosine would, presumably, only be effective if, for example, (1) the inhibitors block influx to a greater degree than efflux (release) of intracellular adenosine or (2) the inhibitors block equally well the influx and efflux of adenosine, but significant amounts of adenosine are formed as a result of dephosphorylation of released adenine nucleotides. Limited information is available regarding the directional symmetry of adenosine transporters in neural cells. Using rat brain crude P2 synaptosomal preparations preloaded with l -[3H]adenosine, our objectives here were to determine (1) if l -[3H]adenosine, a substrate for adenosine transporters that is more metabolically stable than physiological d -adenosine, was being released from synaptosomal preparations, (2) the optimal conditions necessary to observe the release, and (3) the degree to which this release was mediated by efflux through bidirectional nucleoside transporters. l -[3H]Adenosine release was found to be concentration and time dependent, temperature sensitive, and linear with synaptosomal protein. l -[3H]Adenosine release was inhibited dose-dependently by dipyridamole, nitrobenzylthioinosine, and dilazep; at concentrations of 100 µM inhibition was at least 40% for dipyridamole, 52% for nitrobenzylthioinosine, and 49% for dilazep. After loading with l -[3H]adenosine alone or l -[3H]adenosine plus unlabeled l -adenosine, d -adenosine, or uridine, l -[3H]-adenosine release was inhibited 42% by l -adenosine, 69% by uridine, and 81% by d -adenosine. The inhibition of l -[3H]adenosine release from the synaptosomal preparations by substrates for or inhibitors of nucleoside transporters suggests that a portion of the release was mediated by nucleoside transporters. This experimental system may prove useful for evaluating the effects of pharmacological agents on bidirectional transport of adenosine. 相似文献
18.
THE EFFECT OF ELECTRICAL STIMULATION ON THE TURNOVER OF PHOSPHATIDIC ACID IN SYNAPTOSOMES FROM GUINEA-PIG BRAIN 总被引:3,自引:1,他引:2
Synaptosomes prepared from guinea-pig cerebral cortex were suspended in a medium containing [32P]orthophosphate and subjected to electrical stimulation. When the synaptosomal phospholipids were subsequently separated, the most highly labelled was phosphatidic acid and electrical stimulation over a 10 min period increased incorporation of 32P1 into this lipid. Stimulated synaptosomes were osmotically lysed and subsynaptosomal fractions isolated. The electrically stimulated increase in phosphatidic acid labelling was localized in a fraction enriched in synaptic vesicles. This phospholipid effect was not merely a reflection of an increased specific radioactivity of synaptosomal ATP, due to the electrically stimulated increase in respiration. The time course of the phosphatidic acid effect suggests that it is synchronous with release of transmitter. 相似文献
19.
E J Peck J M Schaeffer J H Clark 《Biochemical and biophysical research communications》1973,52(2):394-400
The binding of γ-aminobutyric acid (GABA) to synaptosomal fractions of the rat cerebellar cortex has been examined at 0–4°C in the presence and absence of bicuculline, chlorpromazine, and/or Na+. A GABA-binding component has been demonstrated in the synaptosomal fraction which is competitively inhibited by bicuculline. In addition, this binding component persists in the absence of Na+ and in the presence of chlorpromazine. It seems likely that this binding component is the post-synaptic binding site or “receptor” of GABA. 相似文献
20.
D A Redburn 《Journal of neurochemistry》1978,31(4):939-945
[14C]GABA is taken up by rat brain synaptosomes via a high affinity, Na+-dependent process. Subsequent addition of depolarizing levels of potassium (56.2 MM) or veratridine (100 μM) stimulates the release of synaptosomal [14C]GABA by a process which is sensitive to the external concentration of divalent cations such as Ca2+, Mg2+, and Mn2+. However, the relatively smaller amount of [14C]GABA taken up by synaptosomes in the absence of Na+ is not released from synaptosomes by Ca2+ -dependent, K +-stimulation. [14C]DABA, a competitive inhibitor of synaptosomal uptake of GABA (Iversen & Johnson , 1971) is also taken up by synaptosomal fractions via a Na + -dependent process; and is subsequently released by Ca2+ -dependent, K+-stimulation. On the other hand, [14C]β-alanine, a purported blocker of glial uptake systems for GABA (Schon & Kelly , 1974) is a poor competitor of GABA uptake into synaptosomes. Comparatively small amounts of [14C] β-alanine are taken up by synaptosomes and no significant amount is released by Ca2+ -dependent, K+-stimulation. These data suggest that entry of [14C]GABA into a releasable pool requires external Na+ ions and maximal evoked release of [14C]GABA from the synaptosomal pool requires external Ca2+ ions. The GABA analogue, DABA, is apparently successful in entering the same or similar synaptosomal pool. The GABA analogue, β-alanine, is not. None of the compounds or conditions studied were found to simultaneously affect both uptake and release processes. Compounds which stimulated release (veratridine) or inhibited release (magnesium) were found to have minimal effect on synaptosomal uptake. Likewise compounds (DABA) or conditions (Na+-free medium) which inhibited uptake, had little effect on release. 相似文献