Short-term effects of a large dam decommissioning on biofilm structure and functioning

Aging dams and the rising efforts to restore stream ecosystems are increasing the number of dam decommissioning programs. Although dam decommissioning aims at improving in-stream habitat, biodiversity, and ecosystem functioning in the long term, it might also cause ecological impacts in the short term due to the mobilization of the sediment accumulated in the reservoir. Benthic biofilm in particular can be impaired by episodes of high turbidity and scouring. We conducted a multiple before-after/control-impact experiment to assess the effects of the drawdown of a large dam (42 m tall), a first step to its decommissioning, on biofilm structure (biomass and chlorophyll-a) and functioning (metabolism, nutrient uptake, and organic matter breakdown). Our results show that the reservoir drawdown reduced the autotrophic biofilm biomass (chlorophyll-a) downstream from the dam, which in turn lowered metabolism. However, nitrogen and phosphorus uptake by the biofilm was not affected. Organic matter breakdown was slower below the dam than in nearby undammed reaches before and during drawdown. All drawdown effects quickly disappeared and reaches downstream from the dam approached values found in nearby undammed reaches. Thus, our results indicate that the effects of reservoir drawdown on stream biofilms exist but may be small and disappear rapidly.     

Interaction of cadmium and zinc during prenatal development in the rat

Cadmium chloride, zinc chloride, or a mixture of the two, labeled with 115m-Cd or 65-Zn was administered intraperitoneally to Wistar rats on day 9 of gestation. On day 20 fetuses of Cd-treated rats exhibited malformations, but those of rats given zinc or zinc plus cadmium did not. No radioactive cadmium was recovered in the fetuses or fetal membranes, although some was found in the placentas. Simultaneous administration of zinc did not alter the distribution of cadmium, but cadmium significantly increased the amount of zinc in the fetus and placenta. In a second experiment, cadmium or cadmium plus zinc was administered on day 9 of gestation and embryonic units were removed on days 10, 11, and 12. On day 10 cadmium was found in the embryonic unit and maternal uterus, and cadmium in both was significantly reduced by simultaneous administration of zinc. The cadmium concentration in uterus and embryonic units decreased sharply on day 11 and 12 and by day 12 did not differ in animals treated with cadmium or with cadmium plus zinc. It is concluded that cadmium reaches the placenta or embryo at an organogenetically sensitive time, and that zinc may protect the embryo by decreasing the exposure to cadmium this time.     

Activation with CpG-A and CpG-B oligonucleotides reveals two distinct regulatory pathways of type I IFN synthesis in human plasmacytoid dendritic cells

Two different CpG oligonucleotides (ODN) were used to study the regulation of type I IFN in human plasmacytoid dendritic cells (PDC): ODN 2216, a CpG-A ODN, known to induce high amounts of IFN-alpha in PDC, and ODN 2006, a CpG-B ODN, which is potent at stimulating B cells. CpG-A ODN showed higher and prolonged kinetics of type I IFN production compared with that of CpG-B ODN. In contrast, CpG-B ODN was more active than CpG-A ODN in stimulating IL-8 production and increasing costimulatory and Ag-presenting molecules, suggesting that CpG-A and CpG-B trigger distinct regulatory pathways in PDC. Indeed, CpG-A ODN, but not CpG-B ODN, activated the type I IFNR-mediated autocrine feedback loop. PDC were found to express high constitutive levels of IFN regulatory factor (IRF)7. IRF7 and STAT1, but not IRF3, were equally up-regulated by both CpG-A and CpG-B. CD40 ligand synergistically increased CpG-B-induced IFN-alpha independent of the IFNR but did not affect CpG-B-induced IFN-beta. In conclusion, our studies provide evidence for the existence of two distinct regulatory pathways of type I IFN synthesis in human PDC, one dependent on and one independent of the IFNR-mediated feedback loop. The alternate use of these pathways is based on the type of stimulus rather than the quantity of IFN-alphabeta available to trigger the IFNR. Constitutive expression of IRF7 and the ability to produce considerable amounts of IFN-alpha independent of the IFNR seem to represent characteristic features of PDC.     

Immunolocalization of four antioxidant enzymes in digestive glands of mollusks and crustaceans and fish liver

The aim of this work was to determine the immunolocalization of the antioxidant enzymes catalase, Cu,Zn-superoxide dismutase (SOD), Mn-SOD, and glutathione peroxidase (GPX) in the bivalve mollusks Mytilus galloprovincialis and Crassostrea sp., the crab Carcinus maenas, and the teleostean fish Mugil cephalus. By immunoblotting, crossreactivity between antibodies and the corresponding proteins in the digestive gland/hepatopancreas of invertebrates and the fish liver was demonstrated. Immunohistochemical studies showed that the stomach epithelium was strongly immunostained for catalase in mollusks. In crabs, ducts showed stronger immunostaining than tubules and in mullet hepatocytes the reaction appeared in discrete granules corresponding to peroxisomes. With regard to Cu,Zn-SOD, the apex of the tubule cells in mussels and crabs was distinctly immunostained, whereas in oysters the reaction was more marked in ducts and in mullet liver a uniform diffuse cytoplasmic staining was found. Mn-SOD was strongly positive in mollusk and crab ducts and in mullet periportal hepatocytes. Finally, GPX was not detected in mussels while in oysters a slight reaction was noted in all cell types. In crabs, connective tissue cells and the apex of duct cells were immunostained, but in mullet liver only erythrocytes appeared reactive. Immunoelectron microscopy revealed that catalase was localized in peroxisomes with a dense labeling in fish and less intense labeling in invertebrates. Cu,Zn-SOD was mainly a cytosolic protein although additional positive subcellular sites (peroxisomes, nuclei) were also observed, while Mn-SOD was restricted to mitochondria. GPX was localized in the cytosol, nucleus, and lysosomes, occurring also in peroxisomes of the fish liver. The results presented here provide a basis for future application of the immunodetection techniques to study the possible differential induction of antioxidant enzymes in aquatic organisms subjected to oxidative stress as a result of exposure to environmental pollutants.     

The role of ABA in freezing tolerance and cold acclimation in barley

The role of ABA in freezing resistance in nonacclimated and cold‐acclimated barley ( Hordeum vulgare L.) was studied. Eleven nonacclimated cultivars differed in their LT₅₀, ranging from −10.8 to −4.8°C. Sugars, free proline, soluble proteins and ABA were analyzed in nonacclimated cultivars and during cold acclimation of one cultivar. There was an inverse correlation between LT₅₀ and both ABA and sucrose contents. Exogenous ABA caused a decrease in the freezing point of leaf tissue in the cultivar with the lowest level of endogenous ABA, but not in the cultivar with the highest level, suggesting that ABA in the latter may be near the optimum endogenous level to induce freezing tolerance. Plants of cv. Aramir treated with ABA or allowed to acclimate to cold temperature increased their soluble sugar content to a similar level. The LT₅₀ of leaves of cold‐acclimated cv. Aramir decreased from −5.8 to −11.4°C, with biphasic kinetics, accumulating proline and soluble sugars with similar kinetics. The biphasic profile observed during cold acclimation could be a direct consequence of cryoprotectant accumulation kinetics. ABA and soluble protein accumulation showed a single step profile, associated mainly with the second phase of the LT₅₀ decrease. Thus, a significant increase in endogenous ABA is part of the response of barley to low temperature and may be required as a signal for the second phase of cold acclimation. Endogenous ABA contents in the nonacclimated state may determine constitutive freezing tolerance.     

Pharmacological Blockade of Cannabinoid CB1 Receptors in Diet-Induced Obesity Regulates Mitochondrial Dihydrolipoamide Dehydrogenase in Muscle

Cannabinoid CB₁ receptors peripherally modulate energy metabolism. Here, we investigated the role of CB₁ receptors in the expression of glucose/pyruvate/tricarboxylic acid (TCA) metabolism in rat abdominal muscle. Dihydrolipoamide dehydrogenase (DLD), a flavoprotein component (E3) of α-ketoacid dehydrogenase complexes with diaphorase activity in mitochondria, was specifically analyzed. After assessing the effectiveness of the CB₁ receptor antagonist AM251 (3 mg kg^-1, 14 days) on food intake and body weight, we could identified seven key enzymes from either glycolytic pathway or TCA cycle—regulated by both diet and CB₁ receptor activity—through comprehensive proteomic approaches involving two-dimensional electrophoresis and MALDI-TOF/LC-ESI trap mass spectrometry. These enzymes were glucose 6-phosphate isomerase (GPI), triosephosphate isomerase (TPI), enolase (Eno3), lactate dehydrogenase (LDHa), glyoxalase-1 (Glo1) and the mitochondrial DLD, whose expressions were modified by AM251 in hypercaloric diet-induced obesity. Specifically, AM251 blocked high-carbohydrate diet (HCD)-induced expression of GPI, TPI, Eno3 and LDHa, suggesting a down-regulation of glucose/pyruvate/lactate pathways under glucose availability. AM251 reversed the HCD-inhibited expression of Glo1 and DLD in the muscle, and the DLD and CB₁ receptor expression in the mitochondrial fraction. Interestingly, we identified the presence of CB₁ receptors at the membrane of striate muscle mitochondria. DLD over-expression was confirmed in muscle of CB ₁ ^-/- mice. AM251 increased the pyruvate dehydrogenase and glutathione reductase activity in C₂C₁₂ myotubes, and the diaphorase/oxidative activity in the mitochondria fraction. These results indicated an up-regulation of methylglyoxal and TCA cycle activity. Findings suggest that CB₁ receptors in muscle modulate glucose/pyruvate/lactate pathways and mitochondrial oxidative activity by targeting DLD.     

The synthesis and properties of tricyclic analogues of S6-methylthioguanine and O6-methylguanine

The syntheses of novel tricyclic pyrrolo[2,3-d]pyrimidine analogues of O(6)-methylguanine and S(6)-methylthioguanine are described. The crystal structures and pK(a) values of these analogues are reported. In a standard substrate assay with the human repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) only the oxygen-containing analogue displayed activity.     

{Omega}-3 and {omega}-6 polyunsaturated fatty acids block HERG channels

Dietary polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, which have been attributed to their availability to modulate Na⁺, Ca²⁺, and several K⁺ channels. However, their effects on human ether-a-go-go-related gene (HERG) channels are unknown. In this study we have analyzed the effects of arachidonic acid (AA, -6) and docosahexaenoic acid (DHA, -3) on HERG channels stably expressed in Chinese hamster ovary cells by using the whole cell patch-clamp technique. At 10 µM, AA and DHA blocked HERG channels, at the end of 5-s pulses to –10 mV, to a similar extent (37.7 ± 2.4% vs. 50.2 ± 8.1%, n = 7–10, P > 0.05). 5,6,11,14-Eicosatetrayenoic acid, a nonmetabolizable AA analog, induced effects similar to those of AA on HERG current. Both PUFAs shifted the midpoint of activation curves of HERG channels by –5.1 ± 1.8 mV (n = 10, P < 0.05) and –11.2 ± 1.1 mV (n = 7, P < 0.01). Also, AA and DHA shifted the midpoint of inactivation curves by +12.0 ± 3.9 mV (n = 4; P < 0.05) and +15.8 ± 4.3 mV (n = 4; P < 0.05), respectively. DHA and AA accelerated the deactivation kinetics and slowed the inactivation kinetics at potentials positive to +40 mV. Block induced by DHA, but not that produced by AA, was higher when measured after applying a pulse to –120 mV (IO). Finally, both AA and DHA induced a use-dependent inhibition of HERG channels. In summary, block induced by AA and DHA was time, voltage, and use dependent. The results obtained suggest that both PUFAs bind preferentially to the open state of the channel, although an interaction with inactivated HERG channels cannot be ruled out for AA. K⁺ channel; membrane currents; ion channels; arrhythmia; antiarrhythmics