Modifications in the Release of Rat Growth Hormone in vitro and the Morphology of Rat Anterior Pituitaries Incubated in Various Ionophores

The ionophore A23187 increased the release of rat growth hormone in the presence of a phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine; a second ionophore X537A inhibited growth hormone release induced by the methylxanthine. A23187 did not alter rat growth hormone release in the absence of 3-isobutyl-1-methylxanthine, but X537A enhanced hormone release in the absence of calcium or in the presence or somatostatin. These findings provide further evidence that both calcium and cyclic AMP are important in the regulation of growth hormone release. Tissue incubated in X537A combined electronlucent vesicles apparently derived from the Golgi apparatus, swollen granules and mitochondria with dense matrices. Tissue incubated in the presence of valinomycin or A23187 did not show altered morphology of either secretory granules or the Golgi complex. Possible mechanisms of these changes are discussed.     

A23187诱导K562细胞分化为树突细胞的实验研究

目的 体外探讨A23187快速将人慢性白血病K562细胞定向诱导分化为树突细胞(DC)的实验方法.方法 K562细胞在含有A23187或细胞因子的条件下诱导分化为DC,倒置显微镜下观察细胞形态的变化,流式细胞术检测DC表面标志的改变,逆转录-聚合酶链反应(RT-PCR)检测各表面标志mRNA水平的变化,四甲基偶氮唑蓝(...     

Comparative study of the effects of salinomycin and monensin on electrophysiologic and contractile properties of canine myocardium

The effects of the monocarboxylic ionophore, salinomycin (K⁺-selective), on isometric twitcches, high K⁺-induced contracture and transmembrane action potentials were compared with those of the monocarboxylic ionophore, monensin (Na⁺-selective), in isolated canine right ventricular muscle. In a concentration (5 × 10⁻⁶) which did not produce changes in resting force, salinomycin increased peak active force ( P₀, + 170 ± 36%, mean % change from control ±S.D., P< 0.01). and relaxation and maximal rates of force development (dP/dt_max, + 123 ± 33%, P < 0.01) and relaxation (−dP/dt_max, + 180 ± 40%, P < 0.01) of the isometric twitch. A similar response pattern was found for 5 × 10⁻⁶ M monensin (P₀, + 90 ± 24%, P < 0.01; dP/dt_max, + 137 ± 19%, P < 0.01; −dP/dt_max, + 145 ± 20%, P < 0.01). In contrast to their effects on isometric twitches, salinomycin reduced peak K⁺ contracture force (P_c, −35 ± 14%, P < 0.01) whereas monensin increased it (P_c, +30 ± 12%, P < 0.02). Ventricular muscle action potential duration was shortened similarly by the ionophores. β-Adrenergic receptor blockade with nadolol diminished salinomycin's effects on the isometric twitch and K⁺ contracture, but not its effect to shorten the action potential. Monensin's actions were unaffected by nadolol. These results suggest that salinomycin's effects arise from both a direct modulation of K⁺ movement and the release of endogenous catecholamine. In contrast, monensin may act to alter intracellular Na⁺ which in turn leads to Na⁺---Ca²⁺ exchange and Ca²⁺ -mediated modulation of K⁺ movement.     

Release of noradrenaline from the ligated cat hypogastric nerve

After in vivo ligation for 24 h of the cat hypogastric nerve, large amounts of noradrenaline (NA) and dopamine β-hydroxylase (DBH) accumulated in the nerve segment immediately proximal to the ligature (P₁). In vitro incubation of 24-h-ligated nerves (segments P₁ and P₂) in oxygenated Krebs solution at 37% C in the presence of the ionophore X537A or high K⁺ concentrations caused a marked release of endogenously accumulated NA into the incubation medium. High-K⁺-evoked release was entirely dependent on extracellular Ca²⁺. Electrical nerve stimulation caused an 80% tissue NA loss, but the transmitter could not be found in the medium as intact NA. These results suggest that the in vivo ligated cat hypogastric nerve may serve as a useful model of adrenergic nerve terminals free of effector cells.     

Calcium enhancement of alcohol and drug-induced sleeping time in mice and rats

Calcium injected intracerebroventricularly (IVT) at various times before a hypnotic dose of ethanol significantly enhanced the duration of sleeping time (loss of righting reflex, LRR) in mice and rats. This cation also enhanced the duration of LRR induced by t-butanol and chloral hydrate, but not that induced by sodium pentobarbital. Other cations injected IVT (manganese, cadmium, and zinc) also enhanced ethanol-induced LRR. The synergistic effects of the ionophores X537A and A23187 on calcium-enhanced LRR, and the antagonism of ethanol-induced LRR by EDTA and EGTA suggest the involvement of a membrane-associated calcium pool in the hypnotic effect of ethanol. These studies show that generality of cation enhancement of alcohol-induced sleeping time in mice and rats, and confirm earlier reports which suggested that calcium is involved with the central nervous system depressant effects of alcohols.     

Electrochemical behaviour of different binaphthalene crown ethers.: Part 2: novel strategy based on in situ removable bromine atom protecting groups for the electrosynthesis of polybinaphthalenes bearing perylene crown ethers as potentially redox switchable macromolecular hosts

The substitution of the 6 and 6′ position of binaphthalene derivatives efficiently prevents their anodic polymerization. Instead, an intramolecular coupling reaction occurs leading to perylenes. Accordingly, the anodic oxidation of a bis-binaphthalene crown ether in which one of the binaphthalene subunits has thus been protected by two bromine atoms leads to the deposition of an electroactive polymer film onto the electrode surface. By proper choice of the reaction conditions, this polymerization reaction can be accompanied by the formation of perylene subunits in the pendant crown ethers. Subsequent in situ cathodic removal of the bromine atoms has been achieved, leading to the parent conducting polymer possessing perylene moieties.     

Comparative analysis of alkali and alkaline-earth cation transfer assisted by monensin across the water ∣ 1,2-dichloroethane interface

In the first part of this paper the electrochemical transfer of alkali cations (M⁺) assisted by monensin (HX) across the water ∣ 1,2-dichloroethane (DCE) interface at pH<5, combined with a chemical exchange reaction at 5<pH<9, is proposed as the only mechanism responsible for the transfer of these cations. At pH>9 the current is voltammetrically negligible. An equation for the dependence of Δ_o^wφ_1/2 on pH and Na⁺ concentration is developed. In the second part of the paper the transfer of alkaline earth cations assisted by the same ionophore is studied. The electrochemical reactions (Me_(w)²⁺+HX_(o)?MeHX²⁺_(o)) and (Me_(w)²⁺+X^?_(o)?MeX⁺_(o)) are responsible for the peaks observed at pH<5.0 and at pH>9.0, respectively. As expected, in both cases ΔE_p=0.030 V while at intermediate pH the electrochemical exchange reaction (Me²⁺_(w)+HX_(o)?MeX⁺_(o)+H⁺_(w)) is proposed. The net charge transfer of +1 at the interface accounts for ΔE_p=0.060 V for the peak observed ΔE_p in agreement with the hyper-Nernstian slope of 60 mV found for Ca²⁺ and Ba²⁺ ISE based on antibiotics with carboxylic groups at intermediate pH values. The higher selectivity for Ba²⁺ and the tendency in selectivity at alkaline pH found in the ISEs are also observed and thus explained according to the mechanism proposed.     

Norepinephrine uptake dependent upon apparent Mg++-ATPase activity and proton transport in storage vesicles in axoplasm

A Ca++-dependent secretion of norepinephrine ([3H]NE) was evoked in adrenergic nerve endings in rat heart ventricle slices incubated in a modified Krebs-HCO3 medium containing choline Cl as the replacement for NaCl (Ch+-Ca++). Exogenous ATP inhibited secretion and lithium ion, a known inhibitor of NE uptake dependent upon Mg++-ATPase activity in vesicles (but not ouabain) prevented the response to ATP (Bogdanski, 1983,1986). It was suggested that vesicles attached to the axolemma recaptured [3H]NE from the extracellular fluid. This report indicates that other known inhibitors of uptake in isolated vesicles also inhibited the response to ATP in the attached vesicles. Included were two inhibitors of Mg++-ATPase activity, N-ethylmaleimide (NEM) and dicyclohexylcarbodiimide (DCCD), and the proton transporters 2,4-dinitrophenol (2,4-DNP 1.0 mM) and chlorpromazine (CPZ). Potassium ionophores (valinomycin with 2,4-DNP 0.1 mM, and nigericin) and a pH neutralizing reagent for vesicles (NH3 from ammonium sulfate in solution) were also effective. The uptake inhibitors, except 2,4-DNP, could also increase the rate of depletion of stored NE and its deamination in nonsecreting nerve endings incubated in Krebs-HCO3 (KRB) medium. Valinomycin by itself stimulated uptake in the presence of ATP. It is suggested that mechanisms of uptake and retention of NE in isolated vesicles (symposium (1982) Fed. Proc. 41:2742-2780) apply to the axoplasmic vesicles as well. Thus, the activity of Mg++-ATPase drives proton transport to establish the electrochemical gradients of H+, which drive the transport of NE. A lowering of the gradients can mobilize amines and evoke secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

钙离子载体A23187联合嘌呤霉素对人体外成熟卵母细胞孤雌激活作用的研究

目的：探讨钙离子载体A23187或联合嘌呤霉素（puromyein）对人类体外成熟卵母细胞的孤雌激活作用。方法：收集体外培养成熟的人卵母细胞124枚,根据体外成熟培养的时间分为24、48、72h组。分别采用A23187、A23187联合嘌呤霉素进行孤雌激活,然后应用荧光原位杂交（FISH）技术对孤雌胚胎进行性染色体分析。结果：A23187或联合嘌呤霉素能激活体外成熟的卵母细胞．激活率分别为38．9％、71．8％;二者联合应用能有效地提高孤雌胚胎的发育潜能。随着体外成熟培养的时间延长．A23187联合嘌呤霉素对卵母细胞激活率呈下降趋势;其中24、48h组成熟的卵母细胞激活率和胚胎发育潜能显高于72h组。FISH对9个孤雌胚胎的性染色体分析示,7个孤雌胚胎为XX,2个为X。结论：钙离子载体A23187联合嘌呤霉素能有效地激活人体外成熟卵母细胞．形成的孤雌胚胎核型多数为双倍体。