芳香烃羟化酶活性与苯并[a]芘中间代谢产物生成关系的研究

100mg香烟烟油,多氯联苯诱导大鼠肝S_9组分中芳香烃羟化酶代谢B[a]P为3-OH-B[a]P的活性分别升高约40,20倍,而代谢B[a] P生成6-OXY-B [a]P自由基产物却仅由多氯联苯诱导的S_9组分作用中才被观察到。     

Synthesis of 3-(3-pyridyl)- and 3-(3-benzo[b]thienyl)-D-alanine

The DL-arylamino acid ethyl ester derivatives of β-(3-pyridyl)-DL-alanine, and β-(3-benzo[b]thienyl)-DL-alanine were synthesized by diethyl acetamidomalonate condensation with the respective arylmethyl halides followed by partial hydrolysis to the monoethyl ester and decarboxylation. Each derivative was enzymatically resolved to a separable mixture of the corresponding N-acetyl-L-amino acid and the unchanged D amino acid derivative. Acidic hydrolysis of the latter gave the corresponding D-amino acid, the optical purity of which was established by HPLC analysis of the 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (GITC) derivative. The free D amino acids were converted to D-BOC derivatives by reaction with di-tert-butyldicarbonate in tert-butyl alcohol, water and sodium hydroxide.     

Biochemical and ultrastructural alterations produced by miconazole and econazole in Trypanosoma cruzi

Miconazole and econazole, two fungicide imidazole derivatives, completely inhibited growth of Trypanosoma cruzi (Tulahuen strain) at concentrations of about 20 muM. Culturing of T. cruzi in the presence of lower doses of imidazole derivatives produced: decrease of 5,7-diene sterol content in epimastigotes (including ergosterol); disappearance of the nuclear chromatin, vacuolization and decrease in the electron density of the cytoplasm; selective surface alterations as revealed by an increased response to wheat-germ- and phytohemagglutinin. At variance with the effect of miconazole on Candida (De Nollin et al. (1977) Antimicrobial. Agents Chemother. 11, 500-513), miconazole and econazole, under the experimental conditions used, did not increase the rate of hydrogen peroxide generation by T. cruzi.     

Effect of Carbamazepine on Dopamine Release and Reuptake in Rat Striatal Slices

Carbamazepine has been shown to enhance dopaminergic agonist behavioral effects, but not to displace [3H]spiroperidol binding. To verify if carbamazepine acts presynaptically on dopaminergic neurons, reuptake and release of [3H]dopamine were measured in rat striatal slices in vitro. It was observed that carbamazepine blocked 20% of the reuptake of [3H]dopamine, while cocaine blocked 82% of the reuptake, compared with control. Carbamazepine released 62% and tyramine released 92% of the accumulated [3H]dopamine, compared with control. It was concluded that carbamazepine acts presynaptically on striatal neurons, mainly through enhancement of dopamine release. This finding can be related to some behavioral effects described for carbamazepine; however, the importance of its effects in epileptic and manic-depressive patients remains to be clarified.     

以杯[4]芳烃衍生物为载体的钾离子选择电极的研究

目的：研制新的以杯[4]芳烃衍生物为载体的PVC膜钾离子选择电极。方法：以3种杯[4]芳烃衍生物为载体，癸二酸二辛酯或邻苯二甲酸二辛酯为增塑剂，四（4－氯）苯硼钾为离子定域体制得了PVC膜钾离子选择电极，测试了该类电极对钾离子的响应性能和对7种阳离子的选择性系数。结果：以5，11，17，23－四叔丁基－25，26，27，28－四[2-(乙氧基羰基）苄氧基]杯[4]芳烃为载体所制得的电极（电极Ⅰ）对钾离子有良好的能斯特响应，该电极的选择性系数优于电极Ⅱ和Ⅲ。分别用电极Ⅰ，Ⅱ，Ⅲ对青霉素V钾中的钾含量进行了测定，其结果均与原子吸收法基本一致。结论：所制得的上述电极是一类新的钾离子选择电极，有实用价值。     

Positron emission tomographic investigations of central muscarinic cholinergic receptors with three isomers of [76Br]BrQNP

We studied the potential of three radiobrominated isomers of BrQNP, (Z(-,-)-[⁷⁶Br]BrQNP,E(-,-)-[⁷⁶Br]BrQNP andE(-,+)-[⁷⁶Br]BrQNP), as suitable radioligands for imaging of central muscarinic cholinergic receptors in the human brain. These radioligands were stereospecifically prepared by electrophilic radiobromodestannylation of the respective tributylstannyl precursors using no-carrier-added [⁷⁶Br]BrNH₄ and peracetic acid. Preliminary pharmacological characterizations were determined by biodistribution, autoradiography, competition, displacement and metabolite studies in rats. The (-,-)-configuration presented important specific uptakes in brain muscarinic cholinergic receptor (mAChR)-rich structures and in heart, low metabolization rates and an apparent M₂ selectivity. The (-,+)-configuration revealed more rapid clearance, lower uptake, a higher metabolization rate and an apparent M₁ selectivity. Reversibility of the binding was confirmed for the three radiotracers. Positron emission tomography in the living baboon brain revealed high and rapid uptake in the brain and accumulation in the mAChR-rich structures studied. At 30 min p.i., theE(-,-)-radiotracer reached a plateau in cortex, pons and thalamus with concentrations of 29%, 24% and 19% ID/l, respectively.Z(-,-)-[⁷⁶Br]BrQNP also accumulated in these structures, reaching a maximal uptake (27% ID/l) in the cortex 2 h p.i. At 5 min p.i. a plateau (17% ID/l) was only observed in the cortex for theE(-,+)-[⁷⁶Br]BrQNP; by contrast, the other structures showed slow washout. After 3 weeks, the (-,-)-radiotracers were studied in the same baboon pretreated with dexetimide (1 mg/kg), a well-known muscarinic antagonist. In all the mAChR structures, the highly reduced uptake observed after this preloading step indicates that these radiotracers specifically bind to muscarinic receptors.Z(-,-)-[⁷⁶Br]BrQNP, which is displaced in higher amounts from M₂ mAChR-enriched structures, reveals an M₂ affinity. The two isomers having the (-,-)-configuration are potential probes for investigating central muscarinic receptors. The absolute configuration on the acetate chiral centre influences their muscarinic subtype selectivity and thecis-trans isomerism of the vinyl moiety affects their specific fixation.     

Synthesis and cytotoxic activity of new alkyl[3-(2-chloroethyl)ureido]benzene derivatives

Several alkyl[3-(2-chloroethyl)ureido] (CEU) benzene derivatives were prepared as potential anticancer agents. These new compounds were readily prepared in good yields by addition of anilines to 2-chloroethylisocyanate. Their cytotoxic activity was evaluated on human breast cancer (MDA-MB-231), human colon adenocarcinoma (LoVo) and mouse lymphocytic leukemia (P388D₁) tumor cell lines. Several new CEUs were significantly more cytotoxic than the nitrogen mustard chlorambucil. The biological activity of these aromatic urea derivatives seems to be related to the nature and position of the alkyl substituents on the aromatic ring. Substitution by branched alkyl groups on position 4 of the aromatic ring led to cytotoxic molecules which are up to 5 times more potent than the standard chlorambucil.     

Differential Stimulation of Noradrenaline Release by Reversal of the Na+/Ca2+ Exchanger and Depolarization in Chromaffin Cells

We compared the effectiveness of Ca²⁺ entering by Na⁺/Ca²⁺ exchange with that of Ca²⁺ entering by channels produced by membrane depolarization with K⁺ in inducing catecholamine release from bovine adrenal chromaffin cells. The Ca²⁺ influx through the Na⁺/Ca²⁺ exchanger was promoted by reversing the normal inward gradient of Na⁺ by preincubating the cells with ouabain to increase the intracellular Na⁺ and then removing Na⁺ from the external medium. In this way we were able to increase the cytosolic free Ca²⁺ concentration ([Ca²⁺]_c) by Na⁺/Ca²⁺ exchange to 325 ± 14 nM, which was similar to the rise in [Ca²⁺]_c observed upon depolarization with 35 mM K⁺ of cells not treated with ouabain. After incubating the cells with ouabain, K⁺ depolarization raised the [Ca²⁺]_c to 398 ± 31 nM, and the recovery of [Ca²⁺]_c to resting levels was significantly slower. Reversal of the Na⁺ gradient caused an −6-fold increase in the release of noradrenaline or adrenaline, whereas K⁺ depolarization induced a 12-fold increase in noradrenaline release but only a 9-fold increase in adrenaline release. The ratio of noradrenaline to adrenaline release was 1.24 ± 0.23 upon reversal of the Na⁺/Ca²⁺ exchange, whereas it was 1.83 ± 0.19 for K⁺ depolarization. Reversal of the Na⁺/Ca²⁺ exchange appeared to be as efficient as membrane depolarization in inducing adrenaline release, in that the relation of [Ca²⁺]_c to adrenaline release was the same in both cases. In contrast, we found that for the same average [Ca²⁺]_c, the Ca²⁺ influx through voltage-gated channels was much more efficient than the Ca²⁺ entering through the Na⁺/Ca²⁺ exchanger in inducing noradrenaline release from chromaffin ceils. This greater effectiveness of membrane depolarization in stimulating noradrenaline release suggests that there is a pool of noradrenaline vesicles which is more accessible to Ca²⁺ entering through voltage-gated Ca²⁺ channels than to Ca²⁺ entering through the Na⁺/Ca²⁺ exchanger, whereas the adrenaline vesicles do not distinguish between the source of Ca²⁺.     

Ontogenetic Development of 5-HT1D Receptors in Human Brain: An Autoradiographic Study

The pattern of pre- and postnatal appearance of 5-HT_1D receptors throughout the different areas of the human brain was studied by quantitative in vitro autoradiography, using [¹²⁵I]GTI (serotonin O -carboxymethyl-glycyl-[¹²⁵I]tyrosinamide) as a ligand. The anatomical distribution of 5-HT_1D receptors in neonatal, infant and children's brain was in good agreement with that observed in the adult, the basal ganglia and substantia nigra being the most intensely labelled areas. The development of these receptors throughout the human brain was mainly postnatal: low densities of [¹²⁵I]GTI binding sites were observed at the fetal/neonatal stage in most regions analyzed, in contrast with the high levels of labelling found in infant and children's brains. Indeed, in a number of regions, including the globus pallidus, substantia nigra and visual cortex, a peak of overexpression of 5-HT_1D receptors was observed in the first decade of life. Such overexpression could support a regulatory role for 5-HT_1D receptors in advanced periods of the CNS developmental process. Our results also indicate that the administration of drugs acting on 5-HT_1D receptors during the early postnatal period of life could result in modifications of their properties, as these receptors are already functional in this period.     

Quantitative autoradiography of 5-HT1D and 5-HT1E binding sites labelled by [H]5-HT, in frontal cortex and the hippocampal region of the human brain

In human cortex and hippocampus area, [³H]5-HT (5 nM) labels 5-HT_1A, 5-HT_1D and 5-HT_1E sites. After masking 5-HT_1A receptors by 0.1 μM 8-OH-DPAT, the binding displaced by 0.1 μM 5-CT presumably represented 5-HT_1D sites and the remaining binding 5-HT_1E sites. In frontal cortex, 5-HT_1A receptors represented the main binding in layers II and VI and a lower fraction on other layers. 5-HT_1D and 5-HT_1E sites, were more homogeneously distributed in layers II to VI (21–34% of specific [³H]5-HT binding). 5-HT_1E sites were of similar affinities (K_D close to 6–8 nM) in the cortical layers II to VI. In CA1 field of hippocampus, (pyramidal layer, stratum radiatum, molecular layer), CA2 and dentate gyrus, 5-HT_1A receptors represented the major fraction, 5-HT_1D sites a significant fraction and 5-HT_1E a minor fraction of the specific [³H]5-HT binding. In CA3–CA4 fields, 5-HT_1A receptors were less densely present, 5-HT_1D sites were predominant and 5-HT_1E sites represented a significant fraction (27%). The highest densities of 5-HT_1E sites have been measured in subiculum, where 5-HT_1A, 5-HT_1D, and 5-HT_1E binding sites were equally represented and in entorhinal cortex where 5-HT_1E sites represented the major binding in layer III. They were also present in layers II and IV (29 and 24%) and, to a lesser extent, in layers V and VI. 5-HT_1A sites were predominant in layer VI, II and V and were less abundant in other layers. 5-HT_1D were homogeneously present in layers II, III, IV and were present in low amounts in other layers. No 5-HT_1E were detected in choroid plexus, where [³H]5-HT was dramatically reduced by mesulergine (5-HT_2C receptors). No significant displacement of [³H]5-HT by mesulergine was measured in other structures.