Changes of Endogenous Antioxidant Enzymes during Ischemic Tolerance Acquisition

The purpose of this study was to investigate the role of superoxide dismutase (SOD) and catalase (CAT) in brain ischemic tolerance induced by ischemic preconditioning. Forebrain cerebral ischemia was induced in rat by four vessel occlusion. The activities of the antioxidant enzymes CuZn-SOD, Mn-SOD and CAT were measured in the hippocampus, striatum and cortex after 5 min of ischemia used as a preconditioning and subsequent reperfusion, by spectrophotometric methods. In all ischemia-reperfusion groups (5 h, 1 and 2 days of reperfusion), CuZn-SOD activities were found to be increased if compared to the sham operated controls. The increase was significant (P < 0.05) in all reperfusion groups, particularly after 5 h of reperfusion (3 times) in all studied brain regions; the largest increase was detected in the more vulnerable hippocampus and striatum. Very similar changes were found in Mn-SOD activity. The activity of CAT was increased too, but reached the peak of postischemic activity 24 h after ischemia. Our attempt to understand the mechanisms of increased SOD and CAT activities by application of protein synthesis inhibitor cycloheximide showed that this increase was caused by de novo synthesis of enzymes during first hours after ischemia. Our findings indicate that both major endogenous antioxidant enzymes SOD and CAT are synthesized as soon as 5 h after ischemia. In spite of significant upregulation of these enzymes a large number of neurons in selectively vulnerable CA1 region of hippocampus undergoes to neurodegeneration within 7 days after ischemia.     

Modular antenna of photosystem I in secondary plastids of red algal origin: a <Emphasis Type="Italic">Nannochloropsis oceanica</Emphasis> case study

Photosystem I (PSI) is a multi-subunit integral pigment–protein complex that performs light-driven electron transfer from plastocyanin to ferredoxin in the thylakoid membrane of oxygenic photoautotrophs. In order to achieve the optimal photosynthetic performance under ambient irradiance, the absorption cross section of PSI is extended by means of peripheral antenna complexes. In eukaryotes, this role is played mostly by the pigment–protein complexes of the LHC family. The structure of the PSI-antenna supercomplexes has been relatively well understood in organisms harboring the primary plastid: red algae, green algae and plants. The secondary endosymbiotic algae, despite their major ecological importance, have so far received less attention. Here we report a detailed structural analysis of the antenna-PSI association in the stramenopile alga Nannochloropsis oceanica (Eustigmatophyceae). Several types of PSI-antenna assemblies are identified allowing for identification of antenna docking sites on the PSI core. Instances of departure of the stramenopile system from the red algal model of PSI-Lhcr structure are recorded, and evolutionary implications of these observations are discussed.     

Variabilität und Verbreitung desAceri-Carpinetum in der Tschechischen Sozialistischen Republik

Die phytozönologische Variabilität und die Verbreitung desAceri-Carpinetum wurden aufgrund von Analyse und Synthese eines umfangreichen Aufnahmenmaterials festgestellt. DasAceri-Carpinetum umfasst Schuttwälder der Eichen-Hainbuchenwald-Stufe auf das gegliederte Relief der Fluss- und Bachtäler gebunden; es ist auf ökologisch adäquaten Standorten des Hochlandes ?eská vyso?ina (Böhmisches Hochland) und des Aussenkarpaten-Systems verbreitet. Diese Assoziation wird in vier Subassoziationen gegliedert, u. zw.Aceri-Carpinetum aegopodietosum, Aceri-Carpinetum aconitetosum vulpariae, Aceri-Carpinetum abietetosum undAceri-Carpinetum festucetosum altissimae.     

Failure to form antibodies following transfer of nucleoprotein fractions to chick embryos

В серии опытов, посвященных исследованиям роли нуклеопротеидов в процессе образования антител (Šterzl, Hrubešová 1955; Hrubešová, Askonas, Humphrey 1959; Šterzl, Hrubešová 1959; Hrubešová 1961) мы пользовались методом переноса фракций 3–5-дневным крольчатам. Для проверки результатов, полученных после переноса нуклеопротеидов, выделенных из селезенки взрослого кролика после его иммунизации одной дозой антигена Brucella suis (Hrubešová 1961), мы в настоящей работе в качестве реципиента применяли 18-дневные куриные эмбрионы, новорожденных цыплят и цыплят в возрасте 48 часов. Донорами клеток селезенки были взрослые куры, которых мы иммунизировали 1 мл антигена Brucella suis (7,5×10⁹ микробов), инактивированной протреванием за 24 или 48 час. до обескровливания. Приготовление и анализы нуклеопротеидов (РНП, ДНП) производились теми же методами, как и в предшествовавших работах. ДНК мы приготовляли по Schwander и Signer (1950), РНК—по Kirby (1956). После переноса ДНП, РНП, РНК и ДНК, выделенных через 24 и 48 час. после иммунизации взрослой курицы, нам не удавалось определить противобруцеллезные антитела в сыворотках реципиентов. Только в контрольном опыте переноса целых клеток селезенки, выделенных через 48 час. после иммунизации, мы находили антитела к Brucella suis с максимальным титром 1∶64. Обсуждается расхождение результатов при применении различных антигенов.      

Structurally distinct external solvent-exposed domains drive replication of major human prions

There is a limited understanding of structural attributes that encode the iatrogenic transmissibility and various phenotypes of prions causing the most common human prion disease, sporadic Creutzfeldt-Jakob disease (sCJD). Here we report the detailed structural differences between major sCJD MM1, MM2, and VV2 prions determined with two complementary synchrotron hydroxyl radical footprinting techniques—mass spectrometry (MS) and conformation dependent immunoassay (CDI) with a panel of Europium-labeled antibodies. Both approaches clearly demonstrate that the phenotypically distant prions differ in a major way with regard to their structural organization, and synchrotron-generated hydroxyl radicals progressively inhibit their seeding potency in a strain and structure-specific manner. Moreover, the seeding rate of sCJD prions is primarily determined by strain-specific structural organization of solvent-exposed external domains of human prion particles that control the seeding activity. Structural characteristics of human prion strains suggest that subtle changes in the organization of surface domains play a critical role as a determinant of human prion infectivity, propagation rate, and targeting of specific brain structures.     

Brain to blood efflux as a mechanism underlying the neuroprotection mediated by rapid remote preconditioning in brain ischemia

Glutamate represents the main excitatory neurotransmitter in the mammalian brain; however, its excessive elevation in the extracellular space is cytotoxic and can result in neuronal death. The ischemia initiated brain damage reflects changes in glutamate concentration in peripheral blood. This paper investigated the role of the brain in blood efflux of the glutamate in an improved tolerance of the brain tissue to ischemic conditions. In the rat model of focal brain ischemia, the neuroprotection was initiated by rapid remote ischemic preconditioning (rRIPC). Our results confirmed a strong neuroprotective effect of rRIPC. We observed reduced infarction by about 78% related to improved neuronal survival by about 70% in the ischemic core. The level of tissue glutamate in core and penumbra dropped significantly and decreased to control value also in the core region of the contralateral hemisphere. Despite significant improvement of blood–brain barrier integrity (by about 76%), the additional gain of glutamate content in the peripheral blood was caused by rRIPC. Based on our results, we can assume that neuroprotection mediated by rapid remote ischemic preconditioning could lie in the regulated, whole-brain release of glutamate from nerve tissue to the blood, which preserves neurons from the exposure to glutamate toxicity and results in reduced infarction.

     

Therapeutic lithium alters polar head-group region of lipid bilayer and prevents lipid peroxidation in forebrain cortex of sleep-deprived rats

Lithium is regarded as a unique therapeutic agent for the management of bipolar disorder (BD). In efforts to explain the favourable effects of lithium in BD, a wide range of mechanisms was suggested. Among those, the effect of clinically relevant concentrations of lithium on the plasma membrane was extensively studied. However, the biophysical properties of brain membranes isolated from experimental animals exposed to acute, short-term and chronic lithium have not been performed to-date. In this study, we compared the biophysical parameters and level of lipid peroxidation in membranes isolated from forebrain cortex (FBC) of therapeutic lithium-treated and/or sleep-deprived rats. Lithium interaction with FBC membranes was characterized by appropriate fluorescent probes. DPH (1,6-diphenyl-1,3,5-hexatriene) and TMA-DPH (1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulphonate) were used for characterization of the hydrophobic lipid core and Laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) for the membrane-water interface. Lipid peroxidation was determined by immunoblot analysis of 4-HNE-(4-hydroxynonenal)-protein adducts. The organization of polar head-group region of FBC membranes, measured by Laurdan generalized polarization, was substantially altered by sleep deprivation and augmented by lithium treatment. Hydrophobic membrane interior characterized by steady-state anisotropy of DPH and TMA-DPH fluorescence was unchanged. Chronic lithium had a protective effect against peroxidative damage of membrane lipids in FBC. In summary, lithium administration at a therapeutic level and/or sleep deprivation as an animal model of mania resulted in changes in rat FBC membrane properties.