Opposing Actions of Thrombin and Protease Nexin-1 on Amyloid β-Peptide Toxicity and on Accumulation of Peroxides and Calcium in Hippocampal Neurons

Abstract: Amyloid β-peptide (Aβ) is the principal component of neuritic plaques in the brain in Alzheimer's disease (AD). Recent studies revealed that Aβ can be neurotoxic by a mechanism involving free radical production and loss of cellular ion homeostasis, thus implicating Aβ as a key factor in the pathogenesis of AD. However, other proteins are present in plaques in AD, including the protease thrombin and protease nexin-1 (PN1), a thrombin inhibitor. We therefore tested the hypothesis that thrombin and PN1 modify neuronal vulnerability to Aβ toxicity. In dissociated rat hippocampal cell cultures the toxicity of Aβ was significantly enhanced by coincubation with thrombin, whereas PN1 protected neurons against Aβ toxicity. Aβ induced an increase in levels of intracellular peroxides and calcium. Thrombin enhanced, and PN1 attenuated, the accumulation of peroxides and calcium induced by Aβ. Taken together, these data demonstrate that thrombin and PN1 have opposing effects on neuronal vulnerability to Aβ and suggest that thrombin and PN1 play roles in the pathogenesis of neuronal injury in AD.     

Gas phase composition effects on suspension cultures of Taxus cuspidata

The effect of different concentrations and combinations of oxygen, carbon dioxide, and ethylene on cell growth and taxol production in suspension cultures of Taxus cuspidata was investigated using several factorial design experiments. Low head space oxygen concentration (10% v/v) promoted early production oftaxol. High carbon dioxide concentration (10% v/v) inhibited taxol production. The most effective gas mixture composition in terms of taxol production was 10% (v/v) oxygen, 0.5% (v/v) carbon dioxide, and 5 ppm ethylene. Cultures grown underambient concentration of oxygen had a delayed uptake of glucose and fructose compared to cultures grown under 10% (v/v) oxygen. Average calcium uptake rates into the cultured cells decreased and average phosphate uptake rates increased as ethylene was increased from 0 to 10 ppm. These results may indicate that gas composition alters partitioning of nutrients, which in turn affects secondary metabolite production. (c) 1995 John Wiley & Sons, Inc.     

Improvement of Escherichia coli microaerobic oxygen metabolism by Vitreoscilla hemoglobin: New insights from NAD(P)H fluorescence and culture redox potential

On-line NAD(P)H fluorescence and culture redox potential (CRP) measurements were utilized to investigate the role of Vitreoscilla hemoglobin (VHb) in perturbing oxygen metabolism of microaerobic Escherichia coli Batch cultures of a VHb-synthesizing E. coli strain and the iso-genic control under fully aerated conditions were subject to several high/low oxygen transitions, and the NAD(P)H fluorescence and CRP were monitored during these passages. The presence of VHb decreased the rate of net NAD(P)H generation by 2.4-fold under diminishing oxygen tension. In the absence of aeration, the strain producing VHb maintained a steady NAD(P)H level 1.8-fold less than that of the control, indicating that the presence of VHb keeps E. coli in a more oxidized state under oxygen-limited conditions. Estimated from CRP, the oxygen uptake rates near anoxia were 25% higher for cells with VHb than those without. These results suggest that VHb-expressing cells have a higher microaerobic electron transport chain turnover rate. To examine how NAD(P)H utilization of VHb-expressing cells responds to rapidly changing oxygen tension, which is common in large-scale fermentations, we pulsed air intermittently into a cell suspension and recorded the fluorescence response to the imposed dissolved oxygen (DO) fluctuation. Relative to the control, cells containing VHb had a sluggish fluorescence response to sudden changes of oxygen tension, suggesting that VHb buffers intracellular redox perturbations caused by extracellular DO fluctuations.(c) John Wiley & Sons, Inc.     

Elimination of heparan sulfate by heparitinases induces abnormal mesodermal and neural formation in Xenopus embryos

The expression of heparan sulfate glycosaminoglycan (HS-GAG) was examined in Xenopus embryos during the developmental stages. Chemical analysis showed the existence of HS-GAG in the ³⁵S-labeled embryos. By western blot analysis using a specific anti-HS monoclonal antibody, HS-GAG related epitope was found after the neurulation on two protein bands, whose molecular weights were approximately 90 kDa and 100 kDa, respectively. Immunohistochemistry revealed that HS-GAG occurred exclusively in the animal hemisphere in early gastrulae, and then appeared predominantly on the sheath of the neural tube, the notochord and epithelium. To address whether HS-GAG chains contribute to Xenopus embryonic development, we eliminated the embryonic HS-GAG by injecting purified Flavobacterium heparitinases (HSase) into their blastocoels. Most of the injected embryos were aberrant in mesodermal and neural formation, and became acephalic. Histological examination showed that these embryos were completely devoid of the central nervous system and the mesodermal tissues. Neither heat-inactivated heparitinase nor chondroitinase showed such abnormality. The HS-GAG-eliminated embryos showed decreased expression of both muscular and neural-specific markers. These results suggest that HS-GAG plays an indispensable role in establishing the fundamental body plan during early Xenopus development.     

Spatial and Temporal variations of mangrove fish assemblages in Martinique (French West Indies)

A study of the mangrove fish fauna in a bay of Martinique Island (French West Indies) was carried out at different seasons during two consecutive years. fishes were sampled with specific hoop-nets in the coastal areas at 8 stations.A total of 87 species was collected in the bay. Most individuals were represented by small-size specimens and juveniles. The overall species richness varied according to the stations and the sampling periods. The biomass and number of individuals were variable according to the location but remained stable in time. A factor correspondence analysis and a hierarchical clustering with median links were used to follow the evolution of the stations in space and time. Two types of stations were differentiated: the stations characterized by the mangrove and those under the influence of seagrass beds. A seasonal cycle, opposing the dry periods to the others, was observed.Thus, it seems that the use of the mangrove habitat by the fishes is optimized through a complete reorganization of communities in terms of species composition whereas the overall number and biomass remain stable. This model remains valid even for the most constraining biota of the mangrove ecosystem inhabited by a small number of well adapted species.     

Environmental and macroinvertebrate dynamics in the Lower Rhône River and a lateral dike field: a study matching two functioning descriptors

Environmental variables and macroinvertebrate communities are studied in two sites of the Lower Rhône River, the main channel and a lateral, occasionally connected dike field. Environmental variables and faunistic communities allow discrimination the two compartments. The environmental and faunistic differences the two sites change over time. The physical and chemical differences are significantly correlated with water discharge of the main channel. The faunistic ones are significantly correlated with the temperature of the dike field water. The connections between the main channel and the dike field could be very important to maintain a high heterogeneity of the habitat, and for recolonization of the main channel after a perturbation.     

Glutathione disulfide as an index of oxidative stress during postischemic reperfusion in isolated rat hearts

The objectives of this study were to determine 1) whether reactive oxygen species generated upon postischemic reperfusion lead to oxidative stress in rat hearts, and 2) whether an exogenous prooxidant present in the early phase of reperfusion causes additional injury. Isolated buffer-perfused rat hearts were subjected to 30 min of hypothermic no-flow ischemia followed by 30 min of reperfusion. Increased myocardial content of glutathione disulfide (GSSG) and increased active transport of GSSG were used as indices of oxidative stress. To impose a prooxidant load, cumene hydroperoxide (20 M) was administered during the first 10 min of reperfusion to a separate group of postischemic hearts. Reperfusion after 30 min of hypothermic ischemia resulted in a recovery of myocardial ATP from 28% at end-ischemia to 50–60%, a release of 5% of total myocardial LDH, and an almost complete recovery of both coronary flow rate and left ventricular developed pressure. After 5 and 30 min of reperfusion, neither myocardial content of GSSG nor active transport of GSSG were increased. These indices were increased, however, if cumene hydroperoxide was administered during early reperfusion. After stopping the administration of cumene hydroperoxide, myocardial GSSG content returned to control values and GSH content increased, indicating an unimpaired glutathione reductase reaction. Despite the induction of oxidative stress, reperfusion with cumene hydroperoxide did not cause additional metabolic, structural, or functional injury when compared to reperfusion without cumene hydroperoxide. We conclude that reactive oxygen species generated upon postischemic reperfusion did not lead to oxidative stress in isolated rat hearts. Moreover, even a superimposed prooxidant load during early reperfusion did not cause additional injury.     

On the Modeling of Some Anti-inflammatory and Anti-thrombotic Drugs by AM1

Two families of autacoids from cell membrane phospholipids have been identified. The first, the icosanoids, which are formed from arachidonic acid, include prostaglandins and leukotrienes. The other includes modified phospholipids, as the platelet aggregating factor (PAF). These compounds are related to inflammatory and cardiovascular diseases. We review in this paper some of the work that has been done in our laboratories in the last few years relating to the modeling of new potential thromboxane synthase (TXS) and 5-lipoxygenase (5-LO) and cyclooxygenase (COX) inhibitors, and TXA₂ receptor antagonists derived from nitrogenated heterocycles. We include the results of the modeling of a group of proposed PAF antagonists, and compare their structures with PAF itself and with a recently proposed PAF antagonist model. This revised version was published online in June 2006 with corrections to the Cover Date.     

Rehabilitating degraded forests in Central Europe into self–sustaining forest ecosystems

There is a need for a consistent forest restoration strategy for the `Black Triangle', Central Europe. In the past 50 years, forests in this area have been heavily affected by industrial pollution. Recently, the amount of pollutants has decreased. This means that effective forest restoration programmes can be started. Forest decline must be seen as an ecological disturbance which cannot be solved by applying technical measures only. An ecosystem approach to forest restoration must be introduced into restoration policy and management. Basic principles and working methods of such an approach are briefly described and proposals are made for forest restoration policy, management and research in the area.