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I Angel

Publications and source records attributed to I Angel.

61 records · Page 4Linked to original sources
PubMed1981

Saturable acetylcholine transport into purified cholinergic synaptic vesicles.

The uptake of [3H[acetylcholine ([3H]AcCho) into cholinergic synaptic vesicle ghosts purified from Torpedo electric organ was studied at concentration of [3H]AcCho ranging from 0.1 to 10 mM. The accumulated [3H]AcCho can be released either by hypoosmotic buffer or by low levels of the detergent Triton X-100. Kinetic analysis of the initial rate of [3H]AcCho uptake reveals temperature-dependent saturation kinetics which are best fitted by high-affinity (KTh approximately 0.3 mM) and low-affinity (KT) approximately 10 mM) vesicular [3H]AcCho transport systems. Several lines of evidence suggest that [3H]AcCho transport is mediated by vesicle-associated transport systems and not by a contaminant of other subcellular moieties such as the plasma membrane choline transport system. (i) The specific activity of the [3H]AcCho transport systems is higher in the purest vesicular fraction than in the less-pure fractions. (ii) Ghosts prepared from isolated synaptosomes manifest only low levels of low-affinity [3H]AcCho transport and no high-affinity [3H]AcCho transport. (iii) The vesicular AcCho transport systems lack some of the typical characteristics of synaptosomal choline transport, such as Na+ activation. (iv) The ratio of uptakes of [3H]AcCho and [3H]choline (10 microM) is about 5-fold higher in the pure vesicles than in isolated synaptosomal membranes. Addition of Mg2+-ATP decreases the rate of vesicular [3H]AcCho uptake by about 50%. The simultaneous addition of NaHCO3 and Mg2+-ATP results in activation of [3H]AcCho uptake to about 125% (relative to control), which is a 2.5-fold enhancement relative to the rate observed with Mg2+-ATP. The present findings demonstrate the presence of novel vesicle-associated AcCho transport systems. Their physiological role in the life cycle of the cholinergic synaptic vesicle and nerve terminal are discussed.

Acetylcholine↗
PubMed1980

ATP-stimulated Ca2+ transport into cholinergic Torpedo synaptic vesicles.

Activation of the Ca2+/Mg2+ ATPase associated with highly purified Torpedo synaptic vesicles results in 45Ca2+ uptake. The accumulated 45Ca2+ is released by hypoosmotic buffer and by the Ca2+ ionophore A23187. Density-gradient centrifugation and permeation chromatography reveal that vesicular acetylcholine and the membrane-bound 45Ca2+ co-migrate, thus implying that 45Ca2+ is transported into cholinergic vesicles. ATP-dependent 45Ca2+ uptake follows saturation kinetics, with KmCa2+ = 50 microM, and Vmax = 3 +/- 0.3 nmol Ca2+/mg protein/min. Treatment of the vesicles with mersalyl, dicyclohexylcarbodiimide, and quercetin leads to inactivation of the Ca2+/Mg2+ ATPase and to comparable inhibition of 45Ca2+ transport. Ruthenium red and ouabain have no effect on either of these activities. Nigericin in the presence of external K+ is a potent inhibitor of 45Ca2+ translocation, whereas gramicidin activates transport. The proton translocator carbonylcyanide p-trifluoromethoxy-phenylhydrazone (FCCP) and FCCP + the ionophore valinomycin partially inhibit 45Ca2+ transport. By contrast, the above ionophores do not affect Ca2+/Mg2+ ATPase activity. Tentative mechanisms for ATP-dependent Ca2+ transport into cholinergic synaptic vesicles and the physiological significance of this process are discussed.

Acetylcholine↗
PubMed1980

On the regulation of acetylcholine release: a study utilizing Torpedo synaptosomes and synaptic vesicles.

1. Addition of ATP to isolated highly purified Torpedo synaptic vesicles results in 45Ca2+ uptake. 2. Ca2+ dependent ACh release from Torpedo synaptosomes is accompanied by the phosphorylation of a specific protein with an apparent subunit molecular weight of about 100,000 (band alpha). 3. Activation of the presynaptic muscarinic receptors by an agonist inhibits Ca2+-dependent ACh release from Torpedo synaptosomes. This process seems to be mediated through an interference with the phosphorylation of the band alpha protein, and not by blocking the voltage-dependent presynaptic Ca2+ channel.

Acetylcholine↗
PubMedDate not supplied

Impairment of glucostatic, adrenergic and serotoninergic feeding parallels the lack of glucoprivic signals in the golden hamster.

The administration of 2-deoxyglucose (2-DG) to several animal species, including humans, results in reduction of cellular glucose availability which evokes sympathoadrenal activation, hyperglycemia and stimulation of food intake. We have investigated the effects in the hamster of several drugs which are known to stimulate food intake and induce hyperglycemic response in other species. Golden hamsters pretreated with either 2-DG (0.5 g/kg IP), the alpha-2 adrenoceptor agonist UK-14304 (0.3 mg/kg IP) or the 5-HT1A selective agonist 8-OH-DPAT (0.03 mg/kg IP), have a significant hyperglycemic response, which is similar to the response in mice or rats. However, neither 2-DG, UK-14304 nor 8-OH-DPAT were capable of stimulating food intake in these hamsters. Previous studies in rats and mice demonstrated that hyperglycemic conditions result in activation of a hypothalamic anorectic recognition site, labeled with [3H]mazindol, as well as alpha-2 adrenoceptors, labeled with [3H]idazoxan. No such activation of [3H]mazindol nor [3H]idazoxan binding was observed in the hypothalamus of hamsters treated with 2-DG, despite a normal glycemic response. Thus, in this species an uncoupling between feeding responses and glucoprivic signals may represent a lack of ischymetric regulation of feeding.

8-Hydroxy-2-(di-n-propylamino)tetralin↗