Ammonia addedin vitro,but not moderate hyperammonemiain vivo,stimulates glutamate uptake and H+-ATPase activity in synaptic vesicles of the rat brain

The uptake of radiolabelled neurotransmitters: glutamate (GLU), GABA, and dopamine (DA) and the activity of the vacuolar type H⁺-pumping ATPase (H⁺-ATPase), were measured in crude synaptic vesicles treatedin vitro with a neurotoxic (3 mM) dose of NH₄ ⁺ (acetate or chloride), or isolated from rats with a moderate increase of brain ammonia (to 0.6 mM) induced by i.p. administration of ammonium acetate (HA rats) or a hepatotoxin-thioacetamide (HE rats).In vitro treatment with ammonium salts increased the sodium-independent, chloride-dependent uptake of GLU but did not stimulate the uptake of GABA or DA. Thein vitro treatment also stimulated the H⁺-ATPase activity. Since H⁺-ATPase generates the electrochemical gradient driving synaptic vesicular neurotransmitter transport, its stimulation by ammonia may have facilitated GLU uptake. However the GLU specificity of the effect must be related to other factors differentially affecting GLU uptake and the uptake of other neurotransmitters. Enhanced GLU accumulation in the synaptic vesicles may contribute to the increase of synaptic GLU exocytosis previously reported to accompany acute increases of brain ammonia to toxic levels. However, GLU uptake and H⁺-ATPase activity, but also the uptake of GABA and DA, were unchanged in synaptic vesicles prepared from rats with HA or HE. This indicates that changes in GLU and/or GABA release reported for moderate hyperammonemic conditions must be elicited by factors unrelated to the synaptic vesicular transport of the amino acids.     

分光光度法测定拉氧头孢的含量

本文采用钒酸铵作为氧化剂和显色剂，分光光度法测定拉氧头孢的含量，线性范围６０～１８０ｕｇ／ｍｌ（ｒ＝０．９９９９），平均回收率在９９％以上，变异系数小于０．９％。本法简便、准确。适用于拉氧头孢的快速含量测定。     

Approach to the patient with metabolic acidosis: Newer concepts

Summary: A new classification for patients with metabolic acidosis is provided: a pathophysiological classification. to recognize an overproduction of acids which results in a hydrogen ion (H⁺) gain the number of new anions retained in the body is added to those excreted in the urine when the cation accompanying them was not H⁺ or ammonium (NH₄⁺). the first tools are to recognize new anions that were added during the overproduction of acids. the nature of these anions can be recognized by assessing their fractional excretion. the second set of tools focuses on an assessment of NH₄⁺ in the urine using urine anion and osmolar gaps. the clinical approach suggested focuses on detecting an emergency (severity of H⁺ accumulation, toxic alcohols and/or dyskalaemias). the second step analyzes the expected responses to acidaemia; here the focus is on the P_CO2 in vital organs and the rate of excretion of ammonium. the principles used for diagnosis and treatment of metabolic acidosis are illustrated by a case example.     

壳聚糖季铵盐的合成及结构表征

用异相法合成了水溶性壳聚糖季铵盐衍生物，并用红外光谱及核磁共振谱进行结构表征。结果表明：在中性反应条件下，壳聚糖分子的季铵盐衍生化反应主要发生于亲该中心Ｃ２位的氨基上，所合成的壳聚糖季铵盐衍生物可直接溶解于水。其水溶液可以任意比例与乙醇、丙二醇、甘油等混溶。     

重组巴斯德毕赤酵母高密度培养中铵离子浓度的影响

采用Mut^s表型的重组毕赤酵母生产血管生长抑制素，表达阶段流加甘油—甲醇混合碳源以提高菌体密度和血管生长抑制素的表达水平，菌体密度可达174g／L，约是表达阶段采用甲醇为单一碳源的发酵过程的3倍。菌体密度的提高导致表达阶段发酵液中铵离子浓度下降很快，当发酵液中的铵离子浓度低至40mmol／L时，影响了血管生长抑制素的表达。改变pH调节方式并在发酵后期添加25mmol／L(NH4)2SO4使发酵液中铵离子浓度维持在150mmol／L以上，血管生长抑制素的表达产量达到108mg／L。     

Studies of urease-induced crystallisation in undiluted human urine using the Coulter counter technique

Summary Urease-induced crystallisation was studied in different human urine samples after urease incubation. The studies were performed using the Coulter counter technique, which enables determination of the number and size of particles in a solution and calculation of the total particle volume. The crystallization took place in three consecutive but overlapping steps: (1) nucleation, (2) growth and (3) aggregation. The maximal number of particles obtained in the different samples varied little, but there was a great variation in particle size and total particle volume. The variation in particle size appeared to be mainly due to differences in particle growth, a factor that might be of importance for stone formation.     

Investigations into the regioselective C‐deuteriation of enolates using a diisopropylammonium salt

Results are reported on the regioselective C‐deuteriation of 2‐methyl tetralone using a series of diisopropylamine derived D‐sources. The results presented further aid the understanding of kinetic deuteriation of both ‘base‐containing’ and ‘base‐free’ enolates. Copyright © 2002 John Wiley & Sons, Ltd.     

Haemodynamic Effects of the Quaternary Ammonium Compound QX 572 in Anaesthetized Cats. II. Studies on the Mechanism for the Cardiac Chronotropic Effects

Abstract The antiarrhythmic compound, QX 572, has been shown to increase heart rate both in patients and experimental animals. In anaesthetized cats the positive cardiac chronotropic effects were mainly due to increased sympathetic activity. The present experiments were designed to localize the active sites within the sympathetic nerve system. It was found that QX 572 caused an increased heart rate in response to electrical stimulation of the cardiac sympathetic nerves, but this was not due to effects on the CNS, the sympathetic ganglia or the cardiac adrenergic beta-receptors. It is concluded that QX 572 by some action increased the amount of noradrenaline released from the cardiac sympathetic nerve endings. The mechanism for this effect has not been clarified.     

甘草酸铵的免疫调节作用(英文)

甘草酸铵100 mg/(kg·d)po连续7 d明显影响PGE_2,PGF_(2α),cAMP,cGMP等多种免疫调节介质的药理作用,表明甘草酸铵能影响免疫调节系统.其详细机理及免疫应答的调控是否依赖前列腺素尚待阐明.     

Cations differentially affect subpopulations ofl-glutamate receptors in rat synaptic plasma membranes

Several cations were examined for their ability to specifically affect one of the 3l-glutamate (l-Glu) binding sites in rat forebrain synaptic plasma membranes (i.e. Na⁺-dependent, Cl⁻-dependent and Cl⁻-independent). Na⁺-dependent binding was potently inhibited by K⁺ and NH₄⁺ ions. Other monovalent cations testedd (Cs⁺, Li⁺, triethylammonium) had no effect on this binding site. Polyvalent cations (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Cr³⁺) also had little effect on the Na⁺-dependentl-Glu binding site. Cl⁻-dependentl-Glu binding was potently inhibited by Na⁺ ions but was not affected by other monovalent ions. All of the divalent cations were potent inhibitors of both Cl⁻-dependent and -independent binding. The results show that these binding sites ofl-Glu can be distinguished by their response to cations and suggest possible novel modes of regulation in vivo.