The anti-Parkinsonian drug selegiline delays the nucleation phase of α-synuclein aggregation leading to the formation of nontoxic species

Parkinson's disease (PD) is a movement disorder characterized by the loss of dopaminergic neurons in the substantia nigra and the formation of intraneuronal inclusions called Lewy bodies, which are composed mainly of α-synuclein (α-syn). Selegiline (Sel) is a noncompetitive monoamino oxidase B inhibitor that has neuroprotective effects and has been administered to PD patients as monotherapy or in combination with l-dopa. Besides its known effect of increasing the level of dopamine (DA) by monoamino oxidase B inhibition, Sel induces other effects that contribute to its action against PD. We evaluated the effects of Sel on the in vitro aggregation of A30P and wild-type α-syn. Sel delays fibril formation by extending the lag phase of aggregation. In the presence of Sel, electron microscopy reveals amorphous heterogeneous aggregates, including large annular species, which are innocuous to a primary culture enriched in dopaminergic neurons, while their age-matched counterparts are toxic. The inhibitory effect displayed by Sel is abolished when seeds (small fibril pieces) are added to the aggregation reaction, reinforcing the hypothesis that Sel interferes with early nuclei formation and, to a lesser extent, with fibril elongation. NMR experiments indicate that Sel does not interact with monomeric α-syn. Interestingly, when added in combination with DA (which favors the formation of toxic protofibrils), Sel overrides the inhibitory effect of DA and favors fibrillation. Additionally, Sel blocks the formation of smaller toxic aggregates by perturbing DA-dependent fibril disaggregation. These effects might be beneficial for PD patients, since the sequestration of protofibrils into fibrils or the inhibition of fibril dissociation could alleviate the toxic effects of protofibrils on dopaminergic neurons. In nondopaminergic neurons, Sel might slow the fibrillation, giving rise to the formation of large nontoxic aggregates.     

力竭运动及恢复期大鼠纹状体5-HT、DA及其代谢物浓度的动态变化研究

目的:观察一次性力竭运动过程及恢复期大鼠纹状体细胞外液中多巴胺(DA)和5-羟色胺(5-HT)及其代谢物浓度的动态变化规律。方法:采用活体微透析结合毛细管电泳-激光诱导技术,连续观察清醒大鼠在一次性力竭运动过程及恢复期纹状体细胞外液中酪氨酸(Tyr)、5-HT、5-羟吲哚乙酸(5-HIAA)、色氨酸(Trp)和DA浓度的动态变化。结果:大鼠纹状体细胞外液中Trp、5-HT、5-HIAA水平运动初期均未见显著变化(P>0.05),运动后期、力竭及恢复期均显著高于安静水平(P<0.05,P<0.01);DA、Tyr水平在运动后期、力竭及恢复期显著高于安静水平(P<0.05,P<0.01);DA/5-HT运动初期显著升高(P<0.05,P<0.01),运动后期出现下降趋势,力竭前15 min降至最低点,而恢复期略有回升,但运动后期、力竭及恢复期与安静状态相比均无显著差异。结论:力竭运动过程中大鼠纹状体细胞外液中DA和5-HT的动态变化具有阶段性特征,运动疲劳过程中状体内DA和5-HT两种神经递质的代谢水平均显著增强,而其中以5-HT的作用占优。     

Qualitative analysis of constitutive heterochromatin and primate evolution

The results of qualitative heterochromatin analysis in 16 species of primates: Homo sapiens , Pan troglodytes and Gorilla gorilla (F. Hominidae), Hylobates syndactilus (F. Hylobatidae), Macaca fascicularis , M. tibetana , Mandrillus sphinx , M. leucophaeus , Cercopithecus aethiops , C. sabaeus and C. albogularis (F. Cercopithecidae), Cebus apella , Ateles belzebuth hybridus , Aotus azarae , Saimiri sciureus and Lagothrix lagothricha (F. Cebidae) are presented in this work. We characterized heterochromatin using: (a) in situ digestion with restriction enzymes AluI, HaeIII, RsaI and Sau3A, and (b) chromosome staining with DA/DAPI on unbanded chromosomes, on C-banded chromosomes and on sequentially G-C-banded chromosomes. The aim of this work was to relate the qualitative characteristics of constitutive heterochromatin observed with the cytogenetic evolutive processes in the primate group. Results obtained show that (1) in the family Cercopithecidae, Papionini species do not present chromosomal rearrangements when their karyotypes are compared and the heterochromatin characteristics are uniform, while Cercopithecini species show a high number of chromosomal reorganizations, but they have the same heterochromatic characteristics; (2) the Platyrrhini species analysed show variability in their karyological and heterochromatic characteristics; (3) the Hominoidea present two different situations: Pan , Gorilla and Homo with few chromosomal reorganizations among their karyotypes but with a high variability in their heterochromatin characteristics, and Hylobates with low heterochromatin variability and a highly derived karyotype. Speciation processes related to chromosome changes and heterochromatin variations in different groups of primates are discussed.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 107–124.     

Hyperactivity and alteration of the midbrain dopaminergic system in maternally stressed male mice offspring

We recently demonstrated that prolonged maternal stress produces profound and long-lasting deficits in brain functions by programming a subset of target genes. We have now examined the possible effects of prenatal stress on the motility of adult offspring and dopamine (DA)-related gene expression in their midbrains, one of the target brain regions of stress hormones. Maternally stressed adult male mice showed impaired response habituation to novelty, and increased wheel-running activity associated with altered responses to DA receptor and DA transporter (DAT) blockers. Along with the behavioral changes, the expression profiles of several genes of the midbrain DAergic system appeared to be altered. Expression of DAT was reduced and expression of DA receptors and striatal DA-regulated neuropeptide genes was also affected. Taken together, the present findings indicate that maternal stress can cause hyperactivity in adult offspring associated with alterations in the midbrain DAergic system suggestive of a functional hyperdopaminergic state.     

The enzymatic activity from the sediment of the Gilau dam reservoir - Cluj county

The enzymological studies on the sediment of the accumulation lake that has the main purpose of supplying drinking water to the city of Cluj-Napoca and the nearby villages, were aimed at the comprehensive understanding of the complex processes that happen in these habitats of special significance. In the sediment samples the following enzymatic activities have been quantitatively determined: phosphatase, actual and potential dehydrogenase, catalase, urease and protease. Non-enzymatic catalytic activity was also measured. Based on the relative values for the enzymatic activities, the enzymatic indicator of the sediment quality (EISQ) was calculated (ranging from 0.1 to 0.7). The enzymatic activities have been qualitatively determined for maltase, saccharase, lactase, cellobiase, amylase, dextranase, levanase, cellulase and inulinase. The correlation between the enzymatic and bacteriologic potential was statistically calculated.     

Low molecular weight chitosans—Preparation with the aid of pronase,characterization and their bactericidal activity towards Bacillus cereus and Escherichia coli

The homogeneous low molecular weight chitosans (LMWC) of molecular weight 9.5–8.5 kDa, obtained by pronase catalyzed non-specific depolymerization (at pH 3.5, 37 °C) of chitosan showed lyses of Bacillus cereus and Escherichia coli more efficiently (100%) than native chitosan (< 50%). IR and ¹H-NMR data showed decrease in the degree of acetylation (14–19%) in LMWC compared to native chitosan (∼ 26%). Minimum inhibitory concentration of LMWC towards 10⁶ CFU ml^− 1 of B. cereus was 0.01% (w/v) compared to 0.03% for 10⁴ CFU ml^− 1 of E. coli. SEM revealed pore formation as well as permeabilization of the bacterial cells, as also evidenced by increased carbohydrate and protein contents as well as the cytoplasmic enzymes in the cell-free supernatants. N-terminal sequence analyses of the released proteins revealed them to be cytoplasmic/membrane proteins. Upon GLC, the supernatant showed characteristic fatty acid profiles in E. coli, thus subscribing to detachment of lipopolysaccharides into the medium, whereas that of B. cereus indicated release of surface lipids. The mechanism for the observed bactericidal activity of LMWC towards both Gram-positive and Gram-negative bacteria has been discussed.     

Molecular mechanism of 2-APB-induced Ca influx in external acidification in PC12

2-Aminoethoxydiphenyl borate (2-APB) is used as a pharmacological tool because it antagonizes inositol 1,4,5-trisphosphate receptors and store-operated Ca²⁺ (SOC) channels, and activates some TRP channels. Recently, we reported that 2-APB enhanced the increase in cytotoxic [Ca²⁺]_i, resulting in cell death under external acidic conditions in rat pheochromocytoma cell line PC12. However, the molecular mechanism and functional role of the 2-APB-induced Ca²⁺ influx in PC12 have not been clarified. In this study, to identify the possible target for the action of 2-APB we examined the pharmacological and molecular properties of [Ca²⁺]_i and secretory responses to 2-APB under extracellular low pH conditions. 2-APB dose-dependently induced a [Ca²⁺]_i increase and dopamine release, which were greatly enhanced by the external acidification (pH 6.5). [Ca²⁺]_i and secretory responses to 2-APB at pH 6.5 were inhibited by the removal of extracellular Ca²⁺ and SOC channel blockers such as SK&F96365, La³⁺ and Gd³⁺. PC12 expressed all SOC channel molecules, Orai 1, Orai 2 and Orai 3. When we used an siRNA system, downregulation of Orai 3, but not Orai 1 and Orai 2, attenuated both [Ca²⁺]_i and secretory responses to 2-APB. These results suggest that 2-APB evokes external acid-dependent increases of [Ca²⁺]_i and dopamine release in PC12 through the activation of Orai 3. The present results indicate that 2-APB may be a useful pharmacological tool for Orai channel-related signaling.     

多巴胺神经系统显像分子探针研究

多巴胺神经系统在神经退行性疾病和精神紊乱中充当了主要角色,比如帕金森病、亨廷顿病、迟发性运动障碍、精神分裂症。以多巴胺能神经系统为靶点的PET显像可以了解多巴胺合成、受体密度和状态改变,为神经系统疾病的早期诊断、疗效监测、发病机制以及脑认知功能的研究等方面提供客观、科学的观察手段。本文综述了以多巴胺受体、多巴胺转运体及囊泡单胺转运体为靶点的PET显像剂的研究进展。