Paleomagnetic evidence for the evolution of Meso- to Neo-proterozoic glaciogenic rocks in central-eastern Brazil

Paleomagnetic studies on basic dikes in the eastern São Francisco Craton which have isotopic ages of 1.0–1.1 Ga, define an apparent polar wander path for South America over this time interval. The data indicate that the São Francisco Craton was at paleolatitudes between 40° and 65° at the time of emplacement of these dikes. Neo-Proterozoic sedimentary glaciogenic rocks, the Macaúbas Group, Bebedouro Formation, Ibiá Formation and Carandai Formation, crop out in central-eastern Brazil. An age of about 1.0 Ga has been proposed for these glacial deposits. Paleogeographical reconstructions of South America show a continental movement coherent with paleoenvironmental models proposed for the Macaúbas Group and suggest that the glacial period may have occurred between 1.01 and 1.08 Ga.     

Respiratory Rate as a Regulatory Factor in the Biosynthesis of the Denitrification Pathway of the Bacterium Paracoccus denitrificans

The decrease in the electron flow of the aerobic respiratory chain of the bacterium Paracoccus denitrificans, owing to either the drop in the saturation of terminal oxidases by oxygen or to the inhibition of the rate of respiration by azide or nitrite, resulted in the synthesis of dissimilatory nitrate reductase and nitrite reductase. The dependence of the resulting activities of the two enzymes (after a three-hour adaptation) on the initial value of the parameter V_max/k_La (oxidase activity of the volume unit of the culture divided by the volumetric oxygen transfer coefficient) or on the concentrations of the inhibitors had a similar form, characterized by the appearance of a maximum. The increasing parts of the obtained curves reflect the synthesis of enzymes, probably initiated by the increase in the intracellular degree of reduction, the subsequent drop being evidently in connection with the lack of metabolic energy for biosynthesis. The possible mechanisms of the effect of nitrogenous terminal acceptors (NO^-₃ and NO^-₂) on the formation of the denitrification pathway are discussed.     

Mivazerol, a Novel α2-Agonist and Potential Anti-Ischemic Drug, Inhibits KCl-Stimulated Neurotransmitter Release in Rat Nervous Tissue Preparations

Abstract: In this study, we have investigated the effect of mivazerol, [3-(1H-imidazol-4-yl)methyl-1]-2-hydroxy-benzamide hydrochloride, a new α₂-agonist lacking hypotensive properties and a potential anti-ischemic drug, on the evoked release of norepinephrine, aspartate, and glutamate in tissue preparations from hippocampus, spinal cord T1–T5 section, rostrolateral ventricular medulla, and nucleus tractus solitarii of the brainstem of rat. A simple and efficient in vitro procedure to study pharmacologically the release of norepinephrine and glutamate is described. Tissues were chopped into (0.3 × 0.2 × 0.2 mm³) sections and the resulting minces were used for this study. Exposure to KCl (10–75 mM) for 5 min served as a stimulus for the release response. One, S (for aspartate and for glutamate release), or two such stimuli, S₁ and S₂ (for norepinephrine release) were conducted. The release of norepinephrine (+150% above baseline) was inhibited in a dose-dependent manner by mivazerol in hippocampus (IC₅₀ = 1.5 × 10^?8M), spinal cord (IC₅₀ = 5 × 10^?8M), rostrolateral ventricular medulla (IC₅₀ = 10^?7M), and nucleus tractus solitarii (IC₅₀ = 7.5 × 10^?8M), and by clonidine in hippocampus (IC₅₀ = 5 × 10^?8M), spinal cord (IC₅₀ = 4.5 × 10^?8M), rostrolateral ventricular medulla (IC₅₀ = 2.5 × 10^?7M), and nucleus tractus solitarii (IC₅₀ = 10^?7M). This effect was counteracted by the selective α₂-antagonists yohimbine and rauwolscine. A significant glutamate and aspartate release response was also induced by KCl (35 mmol/L) in hippocampus (+250 and +135%, respectively) and spinal cord (+120 and +55%, respectively), in vitro. However, neither mivazerol nor clonidine, at doses up to 10 µM, had any significant effect on KCl-induced glutamate release in spinal cord, whereas mivazerol blocked completely the release of both amino acids in hippocampus and only the release of aspartate in spinal cord. On the other hand, clonidine (1 µM) was only effective in reducing by 40% the release of aspartate in hippocampus. These data indicate that (1) inhibition of KCl-induced norepinephrine release by mivazerol is mediated by its action on α₂-adrenergic receptors; (2) at concentrations selective for α₂-adrenergic receptors, only mivazerol was effective in blocking the KCl-induced glutamate release in hippocampal tissue; and (3) at the same concentrations, both mivazerol and clonidine were unable to inhibit glutamate release in the spinal cord. These data suggest that prevention of hyperadrenergic activity by mivazerol in perioperative patients may be mediated through its effect on the release of norepinephrine and/or the release of glutamate and aspartate in regions of the CNS that are involved in the control of cardiovascular homeostasis.     

Mathematical model for the ecosystem response of Lake Ladoga to phosphorus loading

The ecosystem response model described in this paper combines an ecosystem model and a three-dimensional circulation model of Lake Ladoga developed earlier by the authors. The ecosystem model describes the process of Lake Ladoga eutrophication, and its biological submodel describes changes in the phyto- and zooplankton. In the earlier model version, lake circulation was determined using a two-dimensional hydrodynamical model which was not completely adequate. The present model allows calculation of the distributions of phyto- and zooplankton and mineral phosphorus and nitrogen. One of its main advantages is that reliable computations of the ecosystem dynamics over an extended period of time are possible. The response of the ecosystem to different levels of phosphorus pollution loading and to weather conditions is studied.     

Relationship between radiation induced adaptive response in human fibroblasts and changes in chromatin conformation

Chromatin conformation changes in the normal human fibroblasts VH-10 were studied by the method of anomalous viscosity time dependence (AVTD). Gamma-irradiation of cells in a dose range of 0.1–3 Gy caused an increase in maximal viscosity of cell lysates. Conversely, irradiation of cells with low doses of 0.5 or 2 cGy resulted in a decrease in the AVTD peaks with a maximum effect approximately 40 min after irradiation. The same exposure conditions were used to study a possible adaptive effect of low doses, measured by changes in cell survival. A primary dose of 2 cGy caused significant modification of cell response to a challenge dose. Approximately 20% protection to challenge doses of 0.5 Gy (p < 0.003), 2 Gy (p < 0.02) and 2.5 Gy (p < 0.002) was observed. However, the direction of this effect (adaptation or synergism) was found to be dependent on a challenge dose. The combined effect of 2 cGy and 1 Gy was significantly synergistic, while no modification was observed for 1.5 Gy and 3 Gy. A partial correlation was found between the AVTD changes and cell survival when the combined effect of a primary dose of 2 cGy and challenge dose was examined. The dose of 2 cGy alone increased survival by 16% (p < 0.0003). These results suggest that the low-dose induced effects on survival may be related to chromatin reorganization.     

Attenuation effects on the kerma rates in air after cesium depositions on grasslands

Since the reactor accident of Chernobyl, cesium depth profiles and nuclide-specific kerma rates in air have been determined for various grassland sites in south Bavaria and in Ukraine. The sites are described by soil characteristics, annual precipitation, distance from release point, mode of deposition, and activity per unit area. The effects of surface roughness and migration of cesium into the soil on the kerma rate in air over grasslands was determined by two methods. The kerma rates in air obtained by the evaluations of in situ gamma-ray spectrometry results and of measured activity distributions in the soil showed only negligible differences for the observation period of 6 years after deposition. For the sites in Ukraine the kerma rate in air per activity per unit area was found to be systematically 40% higher than in Bavaria. The results from Bavaria on the attenuation of the kerma rate and a data set, including experiences from the weapons test fallout, are analytically approximated as a function of time up to 25 years after deposition.     

Activation of murine macrophages by hydrogen peroxide

Hydrogen peroxide at concentrations from 0.1 to 20 μM enhances phagocytosis and oxidative burst of murine peritoneal macrophages. The activation of these macrophage functions is paralled by prolonged hyperpolarization and a transient increase in cytoplasmic free calcium concentration. All the effects are dose- and time-dependent. The results obtained for H₂O₂ are compared with those for a natural activator, peptide N-formyl-methionyl-leucly-phenylalanine. The data demonstrate the ability of small doses of hydrogen peroxide to stimulate macrophages through the intracellular mechanisms of ion transduction.     

Effect of oxygen on ubiquinone-10 production by Paracoccus denitrificans

Summary Ubiquinone-10 (Q₁₀) production was measured in batch cultures of Paracoccus denitrificans grown for 8 h at increasing oxygen concentrations (0–21 % O₂ in the sparging gas). Whereas the cellular level of Q₁₀ decreased monotonically from 1.2 to 0.5 mol/g d.w., the total yield of Q₁₀ was maximal at 2.5 % O₂ and amounted to 350 nmol (0.3 mg) per L of culture.     

The Chemiluminescence Assay of Lipid Peroxidation Products in Human Blood Plasma Lipoproteins

A chemiluminescence (CL) flash kinetics on the addition of Fe²⁺ ions into oxidized low density lipoprotein (LDL) suspension has been studied. LDL oxidation was carried out at 37°C without and in the presence of 5 or 50 μM of Cu.²⁺ It has been found that under certain experimental conditions (the addition of excess iron ions, more than 1 mM) the amplitude of CL flash depended almost linearly (1) on the concentration of oxidized LDL and (2) on the extent of LDL oxidation measured as diene conjugates (DC) and 2-thiobarbituric acid-reactive substance (TBARS) accumulation. The corresponding correlation coefficients were: for TBARS - 0.94 and for DC - 0.97, in the case of LDL autooxidation; 0.72 and 0.98, in the case of copper-induced LDL oxidation. A sensitivity of the CL method was shown to be significantly enhanced (by more than two orders) in the presence of CL sensitizer - 2, 3,5, 6-lH,4H-tetrahydro-9-(2' -benzoimidazolyl)-quinolizin-(9, 9a, 1 -gh)coumarin.