CHOLINE UPTAKE BY CHOLINERGIC NEURON CELL SOMAS

The cellular compartments of ciliary ganglia take up choline by a single, saturable process with K_m=7.1 × 10^?5 M and V_max= 4.66 pmol/min per ganglion: Denervation of the ganglia and the resultant degeneration of nerve terminals caused no significant decrease of the rate of accumulation of choline by the ganglia. This indicates that the measured uptake is by the postganglionic ncurons and nonneural elements (NNE: glial and connective tissue cells) in the ganglia. This uptakc is not dependent on metabolic energy and is not affectcd by lowcring Na⁺ or raising K⁺ concentrations in the incubating mcdia but is depressed in the presence of ouabain and hemicholinium-3. The presence or Na⁺-dependent. rapidly saturable uptake in the preganglionic nerve terminals which is not detectablc kinetically is, however, inferred from a decrease in ACh synthesis in dcncrvatcd prcparations and a similar decrcasc in intact ganglia incubated in low Na+ solution.     

SELECTIVE LOCALIZATION OF A HIGH AFFINITY CHOLINE UPTAKE SYSTEM AND ITS ROLE IN ACh FORMATTON IN CHOLINERGIC NERVE TERMINALS

The avian iris-ciliary nerve preparation exhibits two distinct choline uptake systems. One component, a sodium dependent, high affinity system Km-2 am and Vmax - 0.5 pmolpin per preparation is confined to nerve terminals. The other component is localized in muscle cells. It is sodium independent and low affinity system (Km - 200 am and Vmax - 16 pmol/min per muscle). The high affinity uptake of choline and the synthesis of ACh in the nerve terminals are coupled. Vmax Ach formation -0.5 pmol/min. is the same as Vmax for choline transport; however. with the external choline concentration equal to that of avian plasma only -50% of choline taken up is converted to ACh. In contrast to the nerve terminals, the cell bodies of the same neurons are deficient in the high affinity uptake-ACh synthesis coupled system. This indicates a nerve terminal membrane specialization related to neuro-transmitter synthesis.     

SELECTIVE PREDATION BY TWO SWIFTS AND A SWALLOW IN CENTRAL AMERICA

Samples of flying insects were made at three sites and during dry and wet seasons in Costa Rica and at two sites during the wet season in Panama. Compared with these were the diets of three aerially foraging birds: the Band-rumped Swift Chaetura spinicauda and Rough-winged Swallow Stelgidopteryx ruficollis in Costa Rica and the Short-tailed Swift Chaetura brachyura in Panama. Among insects flying, Diptera accounted for between 52 and 75%, with smaller numbers of Hymenoptera (mean = 15%) and Coleoptera (10%). In bird stomach contents, however, Hymenoptera predominated (59–81%), Coleoptera were less common (mean = 18.5%) and Diptera least common (3.4%) of the three orders. The discrepancy between diets and samples of flying insects could not be accounted for solely on the basis of differential digestion. The composition of the swift and swallow diets was similar; there were no significant seasonal differences in the taxonomic composition of the diet of Chaetura spinicauda. Size distributions of beetle prey fitted log-normal distributions in every case. Mean size of prey was significantly larger than that of insects available in all comparisons. Although there was no seasonal difference in the mean size of prey of Chaetura spinicauda, the variance in prey size, used as a measure of niche width, was significantly larger in the wet than in the dry season. Although insect densities may be higher, foraging time is reduced and the wet season is likely the worse season. This result therefore supports Emlen's hypothesis of narrower niches under optimal conditions and broader niches under suboptimal conditions. For increasing altitude above ground published data show a decrease in the density of insects flying, a decrease in the proportions of taxa favoured by the birds, and a significant decrease in the mean size of beetles. None of these trends can explain the differences between the birds' diets and the samples of flying insects. Preference of prey by these birds is concluded not to be a function of prey size alone, but to involve interaction among prey size, ease of capture, and local density. Because of different flight abilities, insect taxa will differ in ease of capture and, consequently, in mean size preferred by the predator, as well as proportions in the diet. This factor favours Hymenoptera and Coleoptera over Diptera as prey. Local concentrations of winged ants, bees and social wasps, and fig wasps make these prey differentially easy to exploit and explain the preference of Hymenoptera over Coleoptera. Large species of swifts are hypothesized to be the evolutionary consequence of the tendency of aerially foraging birds to exploit local concentrations of single prey species.     

DEGENERATION OF CENTRAL AND PERIPHERAL NORADRENALINE NEURONS PRODUCED BY 6-HYDROXY-DOPA

—The effects of systemically administered 2,4,5-trihydroxyphenylalanine (6-OH-DOPA) on endogenous noradrenaline, [³H]amine uptake and fluorescence morphology has been investigated in mouse brain, heart and iris. 6-OH-DOPA in a dose of 100 mg/kg intraperitoneally caused practically no changes in these parameters. Pretreatment with a potent monoamine oxidase inhibitor (nialamide) led to a pronounced long-lasting 6-OH-DOPA induced reduction in endogenous noradrenaline, [ ³ H]amine uptake and nerve density of noradrenaline nerve terminals both in the central and peripheral nervous system. Histochemically accumulations of noradrenaline were observed in non-terminal axons. These results strongly support the view that 6-OH-DOPA can produce degeneration of both central and peripheral noradrenaline neurons. The degeneration is mediated by decarboxylation of 6-OH-DOPA to 6-OH-DA, since the effects could be abolished by decarboxylase inhibition. The effect of 6-OH-DOPA was selective on noradrenaline neurons in the brain, since neither 5-hydroxytryptamine nor dopamine neurons were affected, opening up new possibilities for studies on central noradrenaline transmitter mechanisms. In the brain there were pronounced accumulations of noradrenaline in the ascending noradrenaline axons making 6-OH-DOPA a powerful tool in the mapping of central noradrenaline pathways.     

CHOLINE ACETYLTRANSFERASE ACTIVITY IN LARGE VENTRAL SPINAL NEURONS

Abstract— Up to approx 3 pmol of acetylcholine (ACh)/h/cell body was synthesized by perikarya of large spinal neurons isolated in bulk fractions from bovine ventral spinal cord. Many of the cell bodies are probably derived from motoneurons. A medium of low ionic strength and pH was used to minimize losses of soluble acetyl CoA:choline- o -acetyltransferase (ChAc; EC 2.3.1.6) from the neurons, whose permeability properties were altered. Such a medium also increased the retention of other soluble proteins by the cell bodies. The maximal rate of hydrolysis of ACh by the isolated neurons exceeded that of its synthesis by a factor of at least 100. It was estimated that ChAc and acetylcholinesterase (AChE; EC 3.1.1.7) each represent less than 0.01% by weight of the total protein in these cell bodies and that as little as 10% of each enzyme in the ventral spinal cord is located within the large neuronal somata and their proximal processes.     

胎儿胃肌间神经节胆碱能神经元的研究

本文采用胆碱乙酰转移酶（ＣｈＡＴ）和乙酰胆碱酯酶（ＡＣｈＥ）酶组织化学方法和显微图像分析技术对３２周～４０周胎儿胃底部、胃体部、胃窦部及胃幽门管部的肌间神经节内胆碱能神经元进行光镜定位定量观察。结果表明：胆碱能神经元的分布,细胞大小及酶活性在胃各部有所不同,胆碱能神经元数量由胃底至幽门管部逐渐递增;胃痛和胃体部以中小型神经元为主,胃窦和胃幽门管部以大中型神经元为主;胃各区酶活性强度不一,胃底部和胃体部酶活性显著高于胃幽门部,胃体部酶活性最强。提示胃各部的运动功能和代谢功能有所不同。     

FORMATION OF SEROTONIN BY ISOLATED SEROTONIN-CONTAINING NEURONS AND BY ISOLATED NON-AMINE-CONTAINING NEURONS

Isolated giant serotonin-containing neurons of the cerebral ganglia of Helix pomatia were shown to produce serotonin when incubated with 5-hydroxytryptophan (5-HTP) whereas cells of the buccal ganglia, which are non-amine-containing cells did not. The rate of production was comparable to that for Ach in the isolated neurons of Aplysia. The significance of these results is discussed.     

CHOLINE: HIGH AFFINITY UPTAKE IN VIVO BY RAT HIPPOCAMPUS

Abstract— [³H]Choline uptake has been measured in vivo in the rat hippocampus. Pharmacological agents and lesions which profoundly affect sodium-dependent, high-affinity [³H]choline uptake in vivo similarly affect [³H]choline uptake measured in vitro. Pentobarbital (65 mg/kg) and oxotremorine (0.75 mg kg) cause a decrease in [³H]choline uptake. Scopolamine (5 mg/kg) and iontophoretically applied extracellular potassium cause an increase in [³H]choline uptake. Septal lesions cause a decrease in [³H]choline uptake. Application of the general method may allow direct examination of presynaptic function and neural integration in the undisrupted living mammalian brain.     

ADENOSINE UPTAKE BY CHOLINERGIC SYNAPTOSOMES FROM TORPEDO ELECTRIC ORGAN

Pure cholinergic synaptosomes prepared from the electric organ of Torpedo are able to take adenosine up efficiently and convert it to ATP. The apparent K_m of the adenosine uptake is 2.4 μM and the V_m: 518 pmol/30′/mg prot. The uptake system exhibits a high specificity towards adenosine, as shown by the lack of competition with analogues. Tubercidin blocks the uptake competitively and dipyridamole is a very potent non competitive inhibitor (K_i= 4 × 10^-8 M). Considering that during nerve activity ATP is released extracellularly and can modulate transmitter release, the physiological significance of adenosine uptake is discussed as a possible mechanism to terminate the ATP action.     

CF-Ⅰ细菌富集铀的研究

研究了 CF—Ⅰ细菌富集溶液中铀。对铀的最大富集量达360mg/g 干菌以上,在较短时间内可吸附溶液中98％的铀;pH、细胞生长状态、细胞膜表面电位等对其富集铀作用影响较大,pb~(2+)等重金属离子能干扰细胞对铀的富集。电镜及能谱结果表明,富集的铀绝大郭分以四价态存在于 CF-Ⅰ细胞膜表面。     

爪蟾胚胎脊髓胆碱能神经元上两类非去极化激活的钙通道

用膜片箝方法,在标定的爪蟾胚胎脊髓胆碱能神经细胞膜上记录钙离子单通道电流。结果显示,在静息膜电位时钙通道即有开放活动。根据通道的电导及动力学等特性,我们将其分为两种类型:NS 型钙通道,斜率电导7.5pS,静息膜电位时平均开放时间0.58ms,其活动受牵张膜片的影响;NL 型钙通道,斜率电导16.7pS,静息膜电位时二级平均开放时间分别是2ms 和19.3ms。鉴于它们在膜静息以及负电位相的显著活动,我们推测这两类钙通道可能参与神经元静息膜电位时钙依赖的细胞活动过程。     

THE ACCUMULATION OF ELECTROLYTES : XI. ACCUMULATION OF NITRATE BY VALONIA AND HALICYSTIS

The nitrate concentration in the sap of Valonia macrophysa, Kütz., is at least 2000 times that of the sea water, and in Halicystis Osterhoutii, Blinks and Blinks, at least 500 times that of the sea water.     

THE ACCUMULATION OF ELECTROLYTES : X. ACCUMULATION OF IODINE BY HALICYSTIS AND VALONIA

Analyses of the sap of Halicystis Osterhoutii and of Valonia macrophysa for iodide indicate accumulations of the order of 1000 to 10,000-fold in the first case, and 40 to 250-fold in the second case. The chemical potential of KI, NaI, HI, and CaI₂ is greater inside than outside.     

高选择性kappa型阿片受体激动剂U50488H的中枢降压效应

大鼠侧脑室或脊髓蛛网膜下腔注射高选择性的 kappa 型阿片受体激动剂 U50488H50-200μg 引起血压及心率显著下降,交感神经节后纤维放电明显抑制。中枢给药的有效剂量(50μg)静脉注射并不引起心血管活动的明显变化。U50488H 的降压效应需用大剂量纳洛酮(8mg/kg,皮下注射)方可完全对抗。以上结果表明,小剂量 U50488H 可抑制交感传出冲动而降低血压,这种效应很可能是由中枢 kappa 受体介导的。当应用较大剂量 U50488H时,可能有外周降压机制参与。     

CHOLINE AND ACETYLCHOLINE IN RATS: EFFECT OF DIETARY CHOLINE

Abstract– The concentration of free choline in peripheral tissues (duodenum, heart, kidney, liver, stomach and plasma) of rats was found to be related to the amount of free choline in the diet. Under steady-state conditions, the concentration of free choline in plasma varied from a minimum of approx 6 nmol/ml (in rats fed a choline-deficient diet) to a maximum value not exceeding 21 nmol/ml. The concentration of plasma choline was elevated above 21 nmol/ml for a short time after parenteral administration of choline chloride or one of its precursors (CDP choline or phosphorylcholine), but was not affected by stress, endocrine manipulations, drug treatments or the time of day when rats were killed. The metabolism of intravenously administered [methyl-³H] choline was accelerated in peripheral tissues (except plasma) of choline-deficient rats, indicating that free choline is not preserved during choline deficiency by a reduction in its rate of turnover. Furthermore, the decrease in concentration of plasma choline that occurred in rats fed a choline-deficient diet was prevented by addition of deanol (dimethylaminoethanol) to the diet. These results indicate that free choline in peripheral tissues of rats is derived from both free choline in the diet, and from precursors of choline present within the diet. In contrast to the effects in peripheral tissues, the concentration of free choline in brain was not reduced by dietary deprivation of free choline; however, the increase in free choline that occurred when rats were decapitated was reduced in brains by deficiency of choline, suggesting a decrease in the concentration of esterified forms of cerebral choline. The concentration of acetylcholine was not reduced in the brain, duodenum, heart, kidney or stomach of 21-week old rats raised from birth on a choline-deficient diet, in the duodenum of rats given a choline-deficient diet for 1, 5 or 11 days, or in brains of rats deprived of free choline for 1 or 11 days. However, the rate of in vivo synthesis of ACh from [methyl-³H]choline was accelerated in cholinergic tissues that were depleted of free choline (i.e. duodenum, heart and stomach).     

刺激大鼠下丘脑室旁核激活的中脑中央灰质神经元对躯体传入的反应

电刺激大鼠下丘脑室旁核(PVH),在同侧中脑中央灰质(CG)内寻找逆行及顺行反应单位,然后观察它们对躯体感觉刺激的反应。实验结果表明:CG 及邻近网状结构内有10%(32/318)的单位呈逆行反应。逆行传导速度平均为0.37±0.24m/s(均数±标准差);推测这种CG→PVH 投射纤维属于细有髓或无髓神经纤维。这些单位分布于 CG 的腹外侧及背外侧亚核。50%(14/28)的逆行单位对坐骨(胫)神经的强电刺激和夹尾等损伤性刺激起反应,但对触毛或低强度的神经干刺激无明显反应。以上结果表明:外周躯体感觉,特别是损伤性信息传入 PVH 时,CG 是其中枢驿站之一。电刺激 PVH 还能顺行激活7.55(24/318)、抑制0.7%(2/318)的 CG 单位。有69%(18/26)的顺行反应单位对外周躯体神经强电刺激及夹尾起反应。提示 PVH 可能通过影响 CG神经元的活动而参与中枢痛觉的整合。