Investigation of non-linear Mate1-mediated efflux of trimethoprim in the mouse kidney as the mechanism underlying drug-drug interactions between trimethoprim and organic cations in the kidney

The purpose of this study was to elucidate the involvement of Mate1 in the tubular secretion of trimethoprim and saturation of Mate1-mediated efflux to address the mechanisms underlying the pharmacokinetic drug interactions with trimethoprim. Trimethoprim is a more potent inhibitor of MATE2-K than MATE1 with K_i values (μM) of 0.030–0.28 and 2.4–5.9, respectively. Trimethoprim is a substrate of human MATE1 and MATE2-K with K_m values of 2.3 ± 0.9 and 0.018 ± 0.004 μM, and mouse Mate1, but not human OCT2, mouse Oct1 and Oct2. Pyrimethamine significantly reduced the renal clearance (CL_R) of trimethoprim (mL/min/kg) from 40.0 ± 5.1 to 20.1 ± 3.7 (p < 0.05). Trimethoprim was given to mice at three infusion rates (150, 500, and 1500 nmol/min/kg). Together with an increase in the plasma concentrations of trimethoprim, the CL_R (mL/min/kg) of trimethoprim decreased to 25.9 ± 3.2, 13.5 ± 5.7, and 8.92 ± 1.50 at the respective rates. Trimethoprim decreased the CL_R of rhodamine 123 in an infusion rate-dependent manner: 11.5 ± 1.3 (control), 5.17 ± 1.55, 1.31 ± 0.50, and 0.532 ± 0.180. These results suggest that Mate1 mediates the tubular secretion of trimethoprim, and at therapeutic doses, MATEs-mediated efflux can be saturated, and thereby, cause drug interactions with other MATE substrates.     

Muscle relaxant action of excitatory amino acid antagonists

Antagonists of neuronal excitation induced by dicarboxylic amino acids were tested in genetically spastic rats of the Han-Wistar strain. These animals exhibit an increased muscle tone which can be measured as a spontaneous tonic activity in the electromyogram of the gastrocnemius-soleus muscle. Compounds that block excitation due to N-methyl-D-aspartic acid reduced the spontaneous activity measured in the electromyogram in a dose-related manner. The most potent compounds, 2-amino-7-phosphonoheptanoic and kynurenic acids were effective muscle relaxants when given either intraperitoneally or intracerebroventricularly. 2-Amino-5-phosphonopentanoic acid possessed much weaker muscle relaxant activity, while L-glutamic acid diethylester was inactive by either route. The results suggest that blockade of N-methyl-D-aspartic acid receptors results in a myorelaxant effect. Specific antagonists of excitation at N-methyl-D-aspartic acid receptors may provide a new class of muscle relaxants.     

Sustained Release of Minocycline From Minocycline-Calcium-Dextran Sulfate Complex Microparticles for Periodontitis Treatment

It is important to address the periodontitis-associated bacteria in the residual subgingival plaque after scaling and root planing to successfully treat periodontitis. In this study, we explored the possibility of exploiting the ion pairing/complexation of minocycline, Ca²⁺, and sulfate/sulfonate-bearing biopolymers to develop an intrapocket delivery system of minocycline as an adjunct to scaling and root planing. Minocycline-calcium-dextran sulfate complex microparticles were synthesized from minocycline, CaCl₂, and dextran sulfate. They were characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. An in vitro release study was conducted to evaluate the release kinetics of minocycline from these microparticles. Agar disk diffusion assays and biofilm-grown bacteria assays were used to assess antibacterial capability. High loading efficiency (96.98% ± 0.12%) and high loading content (44.69% ± 0.03%) for minocycline were observed for these complex microparticles. Mino-Ca-DS microparticles achieved sustained release of minocycline for at least 9 days at pH 7.4 and 18 days at pH 6.4 in phosphate-buffered saline, respectively. They also demonstrated potent antimicrobial effects against Streptococcus mutans and Aggregatibacter actinomycetemcomitans in agar disk diffusion and biofilm assays. These results suggested that the ion pairing/complexation of minocycline, Ca²⁺, and sulfonate/sulfate-bearing biopolymers can be exploited to develop complex microparticles as local delivery systems for periodontitis treatment.     

糠醛—油,N—甲基—2—吡咯烷酮—油汽液平衡和虚拟组分法研究

用改进的Ｅｌｌｉｓ平衡釜，采用化学分析、微型萃取和气相色谱模拟实沸点蒸馏相结合的方法，测定了糠醛－提余油，糠醛－抽出油，Ｎ－甲基－２－吡咯烷酮提余油，Ｎ－甲基－２－吡咯烷酮－抽出油四个系统在常压下的汽液平衡数据。应用虚拟组分法，采用Ｃｈａｏ－Ｓｅａｄｅｒ混合模型对实验数据进行了关联，取得了较好结果。     

东风桔化学成分的研究

从东风桔根中分离到一种新的吖啶酮类生物硷。根据紫外,红外,核磁共振谱和质谱等证明其结构为N-甲基-1,4,5-三羟基-3,6-二甲氧基吖啶酮-9,命名为东风桔碱B。     

Neurotoxic effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the cat. Tyrosine hydroxylase immunohistochemistry

N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces substantia nigra pars compacta (SNc) cell death in several species including the mouse, dog and monkey. MPTP is presently shown to cause apparent nigral cell death in the SNc of the cat as noted by a long-lasting decrease in tyrosine-hydroxylase (TH)-like cell staining. A transient loss of TH-like staining is also observed in the ventral tegmental area, locus coeruleus and retrorubral area. These latter areas appear normal 1.5-5.0 months after MPTP administration. The caudate nucleus (CD) showed a greater TH depletion than the nucleus accumbens (ACC) and only recovered slightly over time. After 7 days of MPTP, an apparent axonopathy, characterized by lightly staining fibers with large TH-positive varicosities, is seen in the CD and to a lesser extent, in the ACC. These findings demonstrate that MPTP is toxic to the cat's nigrostriatal dopaminergic system and suggests that the cat is a good intermediate species in which to study the responses of dopaminergic neurons to MPTP.     

NMDA和非NMDA受体参与介导猫脊髓内脏伤害性信息传递(英文)

目的:研究NMDA(N-methyl-D-aspartic acid)和非NMDA受体在介导脊髓内脏痛传入中的作用,方法:气球膨胀(3-15 kPa,20 s)麻醉猫结-直肠诱发脊髓背角痛敏神经元发放,结果:1)扩张结-直肠引起神经元发放增加的为兴奋性型:17个SLA型(短潜伏期突然增加);11个SLS型(短潜伏期渐增);9个LL型(长潜伏期),15个神经元属于抑制性的Inh型,2)67.6％,78.4％和59.5％的膨胀肠诱发兴奋的神经元,分别被微电泳NMDA、使君子酸(QA)和海人藻酸(KA)激活;60％,86.7％和53.3％的Inh神经元也分别被3个酸激活.3)微电泳NMDA受体拮抗剂d,l-2-amino-5-phosphonovalemte(APV)和非NMDA受体拮抗剂6,7-dinitro-quinoxaline-2,3-dione(DNQX),分别使兴奋性反应减少35％±10％和65％±14％,DNQX明显强于APV(P<0.05).DNQX使3/7个Inh神经元抑制翻转30％-50％,而APV无效,结论:NMDA和非NMDA受体均参与介导脊髓内脏伤害性信息传递,而非NMDA受体的作用更强。 (责任编辑 李颖)     

东风桔吖啶酮生物碱

自东风桔(Atalantia buxifolia)根分得11个化合物。经光谱分析和化学反应证明其中—新化合物结构为N-甲基-1,3-二羟基-2,5,6-三甲氧基吖啶酮-9,命名为东风桔碱。     

Mg dependence of membrane resistance increases evoked by NMDA in hippocampal neurones

The response of granule cells and CA1 pyramidal neurones to NMDA was studied in the presence of and absence of Mg²⁺ using an in vitro slice preparation. In the absence of Mg²⁺ the depolarizing response of hippocampal neurones to NMDA is accompanied by a decrease in input resistance. In the presence of Mg²⁺ ions, however, the response to NMDA is always associated with an apparent increase in input resistance. These results indicate that the action of NMDA is by a classical mechanism of conductance increase and are in agreement with the suggestion that the apparent increase in input resistance associated with NMDA depolarizations is the result of voltage-dependent channel block by Mg²⁺ of the NMDA evoked current.