Contrasting effects of PACAP and carbachol on [Ca]i and inositol phosphates in human neuroblastoma NB-OK-1 cells

The effects of PACAPs on [Ca²⁺]_i were compared to those of carbachol in human neuroblastoma NB-OK-1 cells. PACAP(1–27) and PACAP(1–38) increased [Ca²⁺]_i in a biphasic manner: a transient rise and a secondary plateau. The transient phase reflected the mobilization of [Ca²⁺]_i pool(s) via the inositol phosphate pathway. The modest sustained plateau required extracellular Ca²⁺. Carbachol also increased [Ca²⁺]_i in a biphasic manner, but it mobilized intracellular Ca²⁺ pool(s) with a higher efficacy than PACAPs, then greatly increased Ca²⁺ entry, this being accompanied by a more marked and prolonged elevation of IP₃ and IP₄ than with PACAPs. It is likely that cAMP-mediated phosphorylations due to PACAPs facilitated desensitization at the PACAP receptor-phospholipase C level, so that there was less Ca²⁺ handling through PACAP receptors than with muscarinic M₁ receptors.     

Oxidative processes as indicators of chemical stress in marine bivalves

Deleterious effects of environmental contaminants could be due to enhanced prooxidant forces overcoming antioxidant defences. Before practical biomarkers based on free radical biology will be generally accepted and validated in situ, additional research is required concerning normal physiological and environmental influences on the relevant systems. The aims of this study were to evaluate in situ the importance of oxyradical production in the presence and absence of pollutants and to characterize some antioxidant systems in Mytilus edulis L. Specimens of M. edulis L. were transplanted from a reference site (Franquelin) to Baie Comeau (Baie des Anglais), on the North shore of the St. Lawrence maritime estuary, where are found aluminium and pulp and paper plants. An oxidative stress was observed in mussels submitted to a chronic exposure in the polluted environment. Variations of pro-and anti-oxidant molecules involved in oxidative processes were related in part to seasonal and physico-chemical influences. Catalase activity, malondialdehyde and glutathione concentrations will be useful as biomarkers of stress in situ since they react to anthropogenic influence and to abiotic factors such as emersion period and temperature.     

人为调节荔枝果皮有机自由基及其与果皮变褐的可能关系

荔枝果实以10ppm的6-BA、NAA、GA_3 NAA或PVP(1%) NAA处理2min,1℃贮藏8天后再于室温放2天。EPR分析表明果皮的有机自由基(g因子2.0030)比对照低9%—22%,花色素苷含量高5%—46%。离体果皮小圆片经同法浸泡1h或16h,有机自由基反而比对照高。O_2~-的捕获剂Tiron和抗氧化剂PG CA处理果皮小圆片1h,有机自由基降低8%—11%,处理16h则自由基高于对照。邻苯二酚(pH 8.4)和H_2O_2加速果色变褐,有机自由基增高10%—370%。果皮离体后自由基的EPR波谱特征也发生变化,除了一个g因子2.0026—2.0027的主峰外,尚出现另一个小峰。结果表明荔枝果皮褐变的部分原因是有机自由基增高之故。     

小鼠卵激活过程中胞质游离Ca~(2 )的变化及孤雌发育研究

乙醇和电刺激均可使小鼠MⅡ期卵母细胞激活并在体外孤雌发育至囊胚。小鼠卵对乙醇十分敏感。用7%—8%乙醇处理5min后95%以上的卵母细胞(卵龄为HCG注射后18—19h)内形成原核。3—4次电刺激后卵的激活率为71.58%;仅刺激1次卵的激活率为63.63%。乙醇刺激可诱导卵内游离Ca~(2 )浓度出现多次升高;单一电刺激仅能诱导卵内游离Ca~(2 )浓度出现1次升高;多次电刺激可诱导卵内游离Ca~(2 )浓度多次升高,而且电刺激次数与Ca~(2 )浓度升高成一一对应关系。对于电刺激,介质中足够量的Ca~(2 )对卵激活至关重要。在无Ca~(2 )的介质中,电刺激很难使卵激活。正常受精刺激诱导卵内游离Ca~(2 )浓度出现多次有规律的升高。实验结果表明,卵母细胞激活过程中胞质游离Ca~(2 )浓度重复多次升高可促使卵母细胞恢复成熟分裂。     

烧伤狗浆血游离氨基酸的动态变化

烧伤狗浆血游离氨基酸的动态变化黎君友,周幼勤,赖业馥,赵有,伊少杰ＳｅｑｕｅｎｔｉａｌＣｈａｎｇｅｓｉｎＰｌａｓｍａＦｒｅｅＡｍｉｎｏＡｃｉｄＣｏｎｃｅｎｔｒａｔｉｏｎｉｎＢｕｒｎｅｄＤｏｇｓ￥Ｌｉｊｕｎｙｏｎ;Ｚｈｏｕｙｏｕｑｉｎ;Ｌａｉｙｅｆｕ;...     

Generation of hydrogen peroxide,superoxide anion and the hydroxyl free radical from polyphenols and active benzene metabolites: Their possible role in mutagenesis

Benzene is strongly suspected of being an animal and human carcinogen, but the mechanisms by which it induces tumors of lymphoid and hematopoietic organs are unknown. Production of active oxygen species from benzene metabolites [hydroquinone (HQ), catechol and 1,2,4-benzenetriol (1,2,4-BT) and related polyphenols (resorcinol, pyrogallol and phloroglucinol) are investigated. Pyrogallol and 1,2,4-BT can produce H₂O₂, O ₂ ^– and^·OH simultaneously, and have powerful mutagenic potential. Resorcinol and phloroglucinol cannot produce all of the active oxygen species, and show no mutagenic effects. Catechol can produce H₂O₂, but cannot produce O ₂ ^– and^·OH, and has no mutagenic activity. These data strongly support the hypothesis that benzene metabolites can cause mutagenicity via the generation of oxygen radicals. Although HQ produces H₂O₂ only, and less than produced by pyrogallol and 1,2,4-BT, the mutagenicity of HQ is higher. The results indicate that HQ may act via another mechanism to cause mutagenicity. In the presence of trace metal ions, the reactivity of polyphenols is increased. The biological significance of these phenomena are investigated and discussed.     

4-Hydroxy-2-Nonenal Levels Increase in the Plasma of Patients with Adult Respiratory Distress Syndrome as Linoleic Acid Appears to Fall

Gas chromatography-mass spectrometry has been applied to the analysis of plasma linoleic acid and one of its oxidation products, 4-hydroxy-2-nonenal (HNE), in adult patients with the acute respiratory distress syndrome (ARDS). Peak areas of total ion chromatograms showed there to be negative correlations between loss of linoleic acid and formation of HNE (measured by selective ion monitoring) in 7 out 10 patients studied. When HNE was quantitated by selective ion monitoring, with reference to a pure standard of HNE and an internal standard of nonanoic acid, ARDS patients showed significantly increased levels of HNE (0.412 ± 0.023 nmol/ml) compared with normal healthy controls (0.205 ± 0.018 nmol/ml).     

Evolution of insect-plant relationships — a devil''s advocate approach

Most hypotheses concerning the evolution of insect-plant relationships are based on the assumptions that, (1) phytophagous insects reduce plant fitness, and that (2) insect-plant relationships are the result of unconstrained selection. It can be shown, however, that there is little evidence to support these assumptions. As an alternative, it is proposed that the evolution of insect-plant relationships results primarily from autonomous evolutionary events; namely from heritable functional changes within the insects' nervous system that determine plant recognition and ultimately host plant specificity. These changes cannot be evoked by selective ecological agents. They originate from intrinsic changes (mutationssensu lato) within the insect genome. Ecological factors play a secondary role: by either supporting or preventing the establishment of the new genotype with the novel food preference. This paper has been dedicated in warm friendship to Professor Louis M. Schoonhoven, the leading scientist in sensory physiology of phytophagous insects, on the occasion of his 60th birthday.     

New method for peptide purification based on selective removal of truncation peptide impurities after SPPS with orthogonal capping

Peptide purification by high-performance liquid chromatography (HPLC) is associated with high solvent consumption, relatively large effort and lack of efficient parallelization. As an alternative, many catch-and-release (c&r) purification methods have been developed over the last decades to enable the efficient parallel purification of peptides originating from solid-phase peptide synthesis (SPPS). However, with one exception, none of the c&r systems has been widely established in industry and academia until today. Herein, we present an entirely new chromatography-free purification concept for peptides synthesized on a solid support, termed reactive capping purification (RCP). The RCP method relies on the capping of truncation peptides arising from incomplete coupling of amino acids during SPPS with a reactive tag. The reactive tag contains a masked functionality that, upon liberation during cleavage from the resin, enables straightforward purification of the peptide by incubation with a resin-bound reactive moiety. In this work, two different reactive tags based on masked thiols were developed. Capping with these reactive tags during SPPS led to effective modification of truncated sequences and subsequent removal of the latter by chemoselective reaction with a maleimide-functionalized solid support. By introducing a suitable protecting group strategy, the thiol-based RCP method described here could also be successfully applied to a thiol-containing peptide. Finally, the purification of a 15-meric peptide by the RCP method was demonstrated. The developed method has low solvent consumption, has the potential for efficient parallelization, uses readily available reagents, and is experimentally simple to perform.     

Molecular mechanisms of oxidative stress-related neonatal jaundice

Oxidative stress is a pathological condition characterized by an overload of oxidant products, named free radicals, which are not well counteracted by antioxidant systems. Free radicals induce oxidative damage to many body organs and systems. In neonatal red blood cells, free-radical mediated-oxidative stress leads to eryptosis, a suicidal death process of erythrocytes consequent to alteration of cell integrity. Neonatal red blood cells are targets and at the same time generators of free radicals through the Fenton and Haber-Weiss reactions. Enhanced eryptosis in case of oxidative stress damage may cause anemia if the increased loss of erythrocytes is not enough compensated by enhanced new erythrocytes synthesis. The oxidative disruption of the red cells may cause unconjugated idiopathic hyperbilirubinemia in neonates. High levels of bilirubin are recognized to be dangerous for the central nervous system in newborns, however, many studies have highlighted the antioxidant function of bilirubin. Recently, it has been suggested that physiologic concentration of bilirubin correlates with higher antioxidant status while high pathological bilirubin levels are associated with pro-oxidants effects. The aim of this educational review is to provide an updated understanding of the molecular mechanisms underlying erythrocyte oxidant injury and its reversal in neonatal idiopathic hyperbilirubinemia.