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51.
Inositol Phospholipid Hydrolysis in Rat Cerebral Cortical Slices: I. Receptor Characterisation 总被引:35,自引:17,他引:18
Characterisation of receptor-mediated breakdown of inositol phospholipids in rat cortical slices has been performed using a direct assay which involves prelabelling with [3H]inositol. When slices were preincubated with [3H]inositol, lithium was found to greatly amplify the capacity of receptor agonists such as carbachol, noradrenaline, and 5-hydroxytryptamine to increase the amount of radioactivity appearing in the inositol phosphates. Using a large variety of agonists and antagonists it could be shown that cholinergic muscarinic, alpha 1-adrenoceptor, and histamine H1 receptors appear to be linked to inositol phospholipid breakdown in cortex. The large responses produced by receptor agonists allowed a clear discrimination between full and partial agonists as well as quantitative analysis of competitive antagonists for each receptor. Whereas carbachol and acetylcholine (in the presence of a cholinesterase inhibitor) were full agonists, oxotremorine and arecoline were only partial agonists. Very low concentrations of atropine shifted the carbachol dose-response curve to the right and allowed inhibition constants for the antagonist to be easily calculated. The nicotinic antagonist, mecamylamine, was ineffective. Noradrenaline adrenaline were full agonists at alpha 1-adrenoceptors, but phenylephrine and probably methoxamine were partial agonists. Prazosin, but not yohimbine, potently and competitively antagonised the noradrenaline inositol phospholipid response. Mepyramine but not cimetidine competitively antagonised the histamine response. These data provide strong confirmation for the potentiating effect of lithium on neurotransmitter inositol phospholipid breakdown and emphasise the ease with which functional responses at a number of cortical receptors can be characterised. 相似文献
52.
In the cucumber ( Cucumis sativus L. cv. Straight Eight) cotyledon expansion assay, cytokinin-stimulated ethylene production was separated from cytokinin-stimulated growth through the use of potassium and calcium salts. Low concentrations of KC1, which dramatically promoted growth induced by cytokinin, inhibited ethylene evolution, while CaCl2 at a concentration that had no effect on growth, strongly promoted the cytokinin-induced ethylene evolution. In contrast to the growth response, stimulation of ethylene production was not directly related to the presence of potassium or calcium but to their relative concentrations. Concentrations of KCl and CaCl2 which promoted ethylene evolution singly, strongly inhibited it when mixed together. Low rates of exogenous ethylene had no effect on the growth response. Both the growth and ethylene responses were found to be general cytokinin phenomena. Cotyledon respiration was promoted by KC1, CaCl2 and cytokinin, but its stimulation was not correlated with either growth or ethylene production. In the presence of KClm cytokinin-induced respiration sharply lowered the content of certain sugars during the large growth response and followed KCl uptake. Analysis of KCl uptake showed that its growth promoting synergism with cytokinin was not due to osmotic effects. 相似文献
53.
Biogenic Amine-Stimulated Cyclic Adenosine-3'',5''-Monophosphate Formation in the Rat Carotid Body 总被引:3,自引:2,他引:1
The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body. 相似文献
54.
A chemiluminescent method for measuring the concentration of activated oxygen species (O22 and H2O2) is described. Its main features are: high sensitivity (10?9 M H2O2), its applicability to systems with high optical absorbance in the visible spectral region, a wide linear dynamic range, and the possibility for recording the kinetics of the processes, in which activated oxygen species are involved. 相似文献
55.
Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis 总被引:1,自引:0,他引:1
Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength.
Following testicular regression in July, the lizards are refractory to sexual stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.
Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.
The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures. Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.
Temperature also has a marked influence on appetite and growth, independent of photo-period. Weight gains are greater at 33° than at 20°C. At 33° there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C. 相似文献
Following testicular regression in July, the lizards are refractory to sexual stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.
Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.
The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures. Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.
Temperature also has a marked influence on appetite and growth, independent of photo-period. Weight gains are greater at 33° than at 20°C. At 33° there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C. 相似文献
56.
57.
Vanadate-stimulated oxidation of NAD(P)H 总被引:1,自引:0,他引:1
Vanadate stimulates the oxidation of NAD(P)H by biological membranes because such membranes contain NAD(P)H oxidases which are capable of reducing dioxygen to O2− and because vanadate catalyzes the oxidation of NAD(P)H by O2−, by a free radical chain mechanism. Dihydropyridines, such as reduced nicotinamide mononucleotide (NMNH), which are not substrates for membrane-associated NAD(P)H oxidases, are not oxidized by membranes plus vanadate unless NAD(P)H is present to serve as a source of O2−. When [NMNH] greatly exceeds [NAD(P)H], in such reaction mixtures, one can observe the oxidation of many molecules of NMNH per NAD(P)H consumed. This reflects the chain length of the free radical chain mechanism. We have discussed the mechanism and significance of this process and have tried to clarify the pertinent but confusing literature. 相似文献
58.
We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids. 相似文献
59.
Depolarisation of [3H]inositol-prelabelled slices of rat cerebral cortex with elevated extracellular K+ induced a rapid and marked increase in inositol polyphosphate accumulation. Addition of the muscarinic antagonist atropine (10 microM) markedly inhibited the K+-induced accumulation of inositol tetrakisphosphate (InsP4), with only a slight reduction in stimulated inositol bis- and trisphosphate levels. Inhibitory effects on InsP4 were noted at the earliest time period measured (30 s) and suggested the involvement of released endogenous acetylcholine in part of the response. The atropine-insensitive component of depolarisation did not appear to be secondary to release of noradrenaline, histamine, or 5-hydroxytryptamine, because addition of prazosin, mepyramine, or ketanserin was without effect on the K+ response. Furthermore, secretion of a neuropeptide that could stimulate phosphoinositide hydrolysis was unlikely, because the peptidase inhibitor bacitracin was also without effect. The results suggest that endogenous acetylcholine can stimulate phosphoinositide metabolism by interacting with muscarinic receptors and that this is particularly evident on InsP4 accumulation. Atropine-insensitive responses may be secondary to Ca2+ entry via voltage-sensitive channels. 相似文献
60.
Summary
Candida tropicalis S001 was grown on the lipid fraction of a protein-containing waste-water in order to (i) remove fat from the water, and (ii) produre yeast biomass for feed. The yeast cells were separated from the waste-water by sedimentation. Defatted waste-water was used for methane production and gave a yield of a 0.3 m3 methane/kg reduced chemical oxygen demand. The maximum specific growth rate (µmax) of C. tropicalis growing on waste-water fat at pH 4.0 was 0.35 h–1; the fat content was decreased from 8 g/l to about 0.1 g/l within 24 h. In continous culture a corresponding reduction was maintained at dilution rates up to 0.36 h–1. The effect on growth of pH, temperature and CO2 concentration was studied with triolein as the major carbon source. The µmax was nearly constant (0.16 h–1) in the pH and temperature range of 3.2–4.0 and 30°–38° C, respectively; 10% CO2 was optimal for growth. Growth on triolein resulted in a biomass yield of 0.70 g dry weight/g fat.
Offprint requests to: S. Rydin 相似文献