Effects of Kainic Acid on Brain Calcium Fluxes Studied In Vivo and In Vitro

The effect of in vivo administration of kainic acid into the rabbit hippocampus was studied with brain dialysis and subsequent determination of the Ca2+ concentration in the dialysate. When included in the perfusing medium, kainic acid as well as veratridine induced a decrease in extracellular Ca2+. The effect of kainic acid (but not of veratridine) was insensitive to tetrodotoxin. In vitro studies revealed no effect of kainic acid on 45Ca2+ uptake by isolated astrocytes, but showed an enhancement of synaptosomal 45Ca2+ accumulation. This was, however, only 25% of the stimulatory effect of high K+ depolarization. Glutamate activated synaptosomal Ca2+ uptake, whereas dihydrokainate had no effect. The uptake evoked by kainate and glutamate was independent of the K+ level in the medium which indicates the involvement of other than voltage-sensitive Ca2+ channels. The results confirm previous finding that kainic acid promotes the uptake of Ca2+ in brain cells. Kainate affects Ca2+ fluxes pre- and postsynaptically. Presynaptic Ca2+ influx may be mediated by chemically gated mechanisms.     

Inability to produce a model of dialysis encephalopathy in the rat by aluminum administration

We attempted to produce a rat model of brain aluminum toxicity in order to explore whether or not aluminum accumulation produces the neurochemical changes observed in brains of patients who die with dialysis encephalopathy. Daily subcutaneous injection of Al(OH)₃ caused marked elevation of serum aluminum concentrations, but did not increase brain aluminum contents, either in rats with normal renal function, or in rats with unilateral or 5/6 nephrectomies. LiCl pretreatment, which has been reported to cause irreversible renal failure, did not impair renal function nor aid in achieving elevated brain aluminum contents. No reductions in brain contents of -aminobutyric acid (GABA) or in glutamic acid decarboxylase (GAD, E.C.4.1.1.15) and choline acetyltransferase (ChAT, E.C.2.3.1.6) activities were observed in aluminum-treated rats. We conclude that the rat is not a suitable laboratory animal to explore the role of aluminum toxicity in causing the GABA and ChAT deficits present in brains of hemodialyzed human patients.     

Thymidine phosphorylase and uridine phosphorylase of Lactobacillus casei

Abstract Comparison of the whole cell protein profiles of Staphylococcus epidermidis grown in pooled human peritoneal dialysate (HPD) with those of cells grown in nutrient broth (NB) revealed proteins of 27, 39, 45, 54 and 98 kDa which were absent or poorly expressed in NB-grown cells. IgG, but not transferrin, was detected bound to the surface of bacteria grown in HPD. Immunoblotting experiments revealed that IgG antibodies present in pooled HPD recognised staphylococcal protein antigens of 16, 27, 35, 39, 45, 54 and 98 kDa. The 16-, 35- and 39-kDa antigens which were associated with the cytoplasmic membrane were repressed following growth in NB or in HPD supplemented with excess iron.     

Differential Control by N-Methyl-D-Aspartate and Kainate of Striatal Dopamine Release In Vivo: A Trans-Striatal Dialysis Study

Using the technique of trans-striatal dialysis in halothane-anesthetized rats, we have studied the effects of intrastriatally infused N-methyl-D-aspartate (NMDA), kainate, and quisqualate on the liberation of endogenous striatal dopamine. The striatal infusion of NMDA (10(-3)-10(-2) M) or kainate (10(-4)-10(-2) M) but not of quisqualate (up to 10(-2) M) for one 20-min fraction provoked a dramatic increase in striatal dopamine efflux up to a maximum of 1,200 and 3,400% of basal levels for NMDA and kainate, respectively. NMDA (10(-3) M) evoked liberation of striatal dopamine was totally blocked by coinfusion of 2-amino-5-phosphonovalerate (2-APV; 5 X 10(-4) M) and by the systemic injection of phencyclidine (3 mg/kg i.p.). The effects of NMDA (10(-3) M) were also totally antagonized in a dose-dependent manner by the striatal coinfusion of atropine (10(-7)-10(-4) M), and abolished in rats that had received bilateral striatal ibotenate lesions (10 micrograms/1 microliter) 1 week prior to implantation of the dialysis fiber. The striatal infusion of tetrodotoxin (10(-6) M) reduced basal dopamine efflux by 60-70% and abolished the NMDA (10(-3) M)-evoked liberation of striatal dopamine. The effects of kainate (10(-3) M) on striatal dopamine efflux were only partially reduced by doses of 2-APV or atropine that totally blocked the NMDA response, and were also partially resistant to tetrodotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increases in Striatal and Hippocampal Impedance and Extracellular Levels of Amino Acids by Cardiac Arrest in Freely Moving Rats

The time course of changes in the tissue impedance and the levels of extracellular transmitter and non-transmitter amino acids was studied in the striatum and hippocampus of the unanesthetized rat after cardiac arrest. Electrodes were implanted for the continuous measurement of tissue impedance so that a measure of the volume of extracellular space was provided. Alternatively, bilateral dialysis probes were used for monitoring levels of extracellular amino acids in subsequent 30-s samples using an automated precolumn derivatization technique for reversed-phase HPLC analysis and fluorimetric detection. The impedance started to rise approximately 1.2 min following cardiac arrest, increased rapidly during the first 5 min, and increased almost linearly thereafter. After 15 min, a decrease of approximately 50% in the extracellular space was calculated. The impedance rose more steeply in the striatum than in the hippocampus. The extracellular levels of taurine, which increased greater than 300% within 5 min after cardiac arrest, most closely resembled the time course of the change in impedance. Glutamate and aspartate levels did not increase until 5 min after circulatory arrest, and at 15 min they had risen to a level of 465 and 265% for the striatum and 298 and 140% for the hippocampus of the resting release, respectively. The release of gamma-aminobutyric acid (GABA) was multiphasic and did not resemble that of any of the other--putative--transmitter amino acids. Fifteen minutes after cardiac arrest, the levels of GABA were 617 and 774% of the resting release in the striatum and hippocampus, respectively. Glycine and alanine efflux substantially increased (232 and 151% in striatum and 141 and 154% in hippocampus, respectively) 15 min postmortem, whereas the glutamine level was slightly increased and levels of asparagine, histidine, threonine, ethanolamine, serine, arginine, and tyrosine were inconsistently higher in the two brain regions. At this time, the extracellular levels of glutamate, GABA, and aspartate were only slightly lower, as expected from the tissue levels and from levels of the other amino acids, an observation indicating that all the amino acids may diffuse through postmortem brain tissue to a nearly similar extent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Calcium-Dependent, Tetrodotoxin-Sensitive Stimulation of Cortical Serotonin Release After a Tryptophan Load

The effect of intraperitoneal administration of tryptophan (50, 100, or 200 mg/kg) on extracellular concentrations of tryptophan, serotonin (5-hydroxytryptamine, 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) was studied in the cortex of freely moving rats by transcerebral dialysis. Rats were implanted with dialysis probes in the frontal cortex, and experiments were performed 24 h later. Tryptophan, 5-HT, and 5-HIAA were quantified in 20-min samples of dialysate by HPLC with electrochemical detection after separation on reverse-phase columns. Tryptophan administration resulted in a significant increase of tryptophan, 5-HT, and 5-HIAA levels in dialysates. The maximal increase of 5-HT and 5-HIAA output was approximately 150% over basal values. Perfusion with Ringer's solution containing tetrodotoxin (1 microM) reduced 5-HT output by 90% and prevented the increase of 5-HT and 5-HIAA content after 100 mg/kg of tryptophan. Similar results were obtained after perfusion with Ringer's solution without Ca2+. The results indicate that a tryptophan load stimulates the physiological release of 5-HT.     

Amino Acids in Rat Striatal Dialysates: Methodological Aspects and Changes After Electroconvulsive Shock

Extracellular levels of amino acids were estimated in dialysates of the rat striatum that were collected 1, 2, and/or more than 5 days after surgery, before (resting release) and during exposure to high K concentrations (50 mM) or electroconvulsive shocks. The resting release of several amino acids (Glu, Asn, Thr, Tau, Tyr, Gly, and Ala) was higher 9 days as compared to 1 day after surgery. In the 1-day preparation the resting release correlated highly with that observed with push-pull cannulas. The correlation with the tissue content of the amino acids was high only when they were divided into two groups (putative transmitters and metabolic intermediates). High K exposure produced increased output of Ala, ethanolamine (Eam), Asp, Glu, Tau, and Gly and a decrease in the egress of Gln 1 or 2 days after surgery. The effects on Asp and Glu had disappeared, and that on Gln reversed after 4-9 days. Electrically induced convulsions produced increased output of Ala, Gln, and Eam 1 or 2 days and 2 weeks after implantation of the probe. Changes were seen not only during but also (and some cases even more prominent) after the seizure. This study shows the usefulness of dialysis to monitor extracellular transmitter amino acids in the striatum of conscious rats (also bilateral dialysis was possible) for only a limited time after implantation of the probe. The dialysis method is suitable for longer time, when metabolic changes in amino acids are to be followed. In addition to transmitter release, glycolysis can be monitored by the measurement of Ala in the dialysate.     

不同透析模式对维持性血透患者残余肾功能、血脂及大中分子毒素的影响

目的:探讨不同透析模式对维持性血透患者残余肾功能、血脂及大中分子毒素的影响。方法:选取2013年3月-2014年3月期间于我院进行维持性血液透析的患者64例,采用随机数字表法随机分为研究组和对照组各32例。研究组采用高通量维持性血液透析,对照组患者采用低通量维持性血液透析。观察并比较两组患者治疗前、治疗3个月、6个月及9个月后内生肌酐清除率(Ccr)、血脂及大中分子毒素。结果:治疗后3个月、6个月、9个月两组Ccr水平较治疗前依次降低,且研究组各个时间点的Ccr均低于对照组(均P0.05)。治疗后两组患者TC、TG和LDL-C水平均显著降低,HDL-C显著上升,治疗后6个月、9个月各指标改善程度均显著优于治疗后3个月,且研究组变化更显著,差异有统计学意义(均P0.05)。治疗后两组患者血清磷、β2微球蛋白和甲状旁腺激素水平均显著降低,治疗后6个月、9个月各指标水平均显著低于治疗后3个月,且研究组明显低于对照组,两组比较差异均有统计学意义(均P0.05)。结论:高通量维持性血液透析的方式可有效清除体内的血脂和大中分子毒素,对残余肾功能影响较小。     

r-IL2工程菌透析培养研究

为了去除乙酸对rIL-2工程菌生长及基因表达的抑制作用,用医用人工肾作为透析器建立了一套透析培养装置,通过该装置对rIL-2工程菌进行了透析培养的研究,结果表明透析液、pH、透析培养的持续时间段对工程菌的生长及rIL-2的表达有较大影响。通过选择高浓度的无机盐透析液及诱导后期的透析培养方法使菌密度在50 A_(600nm)时rIL-2表达水平仍大于40％。     

Effect of pH on molecular weight and size of fulvic acids in drainage water from peaty grassland in NW Netherlands

Summary The effect of pH on the molecular weight and size of fulvic acids (FA) in a peaty ditch water was studied by dialysis, Sephadex G-25 gel filtration and ultrafiltration. The results of these techniques of fractionating according to particle size indicated that the molecular weight and size of FA decrease with decreasing pH. The ratio of the light absorbances at 250 and 365 nm (E2/E3) of ditch water increased with decreasing pH corresponding with the results of dialysis, gel filtration and ultrafiltration of FA.Our results do not correspond with the ideas of the macromolecular structure of soil FA as developed by Schnitzer¹⁶.