Aspects of the demetalation and remetalation of ceruloplasmin

This study dealt with the demetalation and remetalation chemistry of the copper-containing protein ceruloplasmin. For the enzyme from human plasma, dialysis against cyanide at 4°C readily removed copper. Although the apoprotein took up copper(I) at the same temperature, the characteristic blue color of the native protein did not return to any significant extent. However, excellent reconstitution occurred when we added copper(I) at room temperature. With porcine ceruloplasmin, it was more practical to carry out the copper removal step at room temperature, but the reconstitution went smoothly at 4°C. With either source of ceruloplasmin, the binding of the six essential copper ions was generally a highly cooperative process, but the results were different when we combined the apoprotein with Hg(II). After the protein took up 2 mercury ions, it would take up only 1–2 more metal ions even after exposure to a large excess of copper(I). In order to accomodate the various experimental results, we have proposed that a reversible conformational change must occur during the demetalation and remetalation processes. During the remetalation process, it is therefore important that metal uptake occurs in the proper sequence.     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

The role of β- and α-adrenoreceptors on blood flow and temperature of brown adipose tissue and involvement of nitric oxide in their effects

1. o

2. 1. Isoproterenol increased interscapular brown adipose tissue (BAT) blood flow and temperature.

3. 2. Phenylephrine increased BAT temperature, but did not affect blood flow. The effect was completely suppressed by N^ω-nitro- -arginine methyl ester ( -NAME), an inhibitor of endogenous NO synthesis.

4. 3. Isoproterenol plus phenylephrine increased BAT blood flow and temperature earlier than isoproterenol alone.

5. 4. CL316,243 increased BAT blood flow and temperature. These effects were also inhibited by -NAME.

6. 5. These data suggest that BAT blood flow as well as thermogenesis is regulated mainly by β-adrenoreceptors and partly by α₁-adrenoreceptors, and NO may be a common mediator for their regulations.

     

Measurement of field scale N2O emission fluxes from a wheat crop using micrometeorological techniques

Measurements of N₂O emission fluxes from a 3 ha field of winter wheat were measured using eddy covariance and relaxed eddy accumulation continuously over 10 days during April 1994. The measurements averaged fluxes over approximately 10⁵ m² of the field, which was fertilised with NH₄NO₃ at a rate of 43 kg N ha^-1 at the beginning of the measurements. The emission fluxes became detectable after the first heavy rainfall, which occured 4 days after fertiliser application. Emissions of N₂O increased rapidly during the day following the rain to a maximum of 280 ng N m^-2s^-1 and declined over the following week. During the period of significant emission fluxes, a clear diurnal cycle in N₂O emission was observed, with the daytime maximum coinciding with the soil temperature maximum at 12 cm depth. The temperature dependence of the N₂O emission was equivalent to an activation energy for N₂O production of 108 kJ mol^-1. The N₂O fluxes measured using relaxed eddy accumulation, averaged over 30 to 270 min, were in agreement with those of the eddy covariance system within 60%. The total emission of N₂O over the period of continuous measurement (10 days) was equivalent to about 10 kg N₂O-N, or 0.77% of the N fertiliser applied.     

Evaluation of three herbaceous index plant species for bioavailability of soil cadmium, chromium, nickel and vanadium

Uncultivated plants growing on disturbed sites may be useful for assessing the bioavailability of some metals in soils, and thus the potential for metal mobilization up the terrestrial food chain, an important element in ecological risk assessment. A planted chicory cultivar (Cichorium intybus L. var. foliosum Hegi.) and the uncultivated plants horseweed (Canada fleabane) (Erigeron canadensis L.) and dogfennel (Eupatorium capillifolium (Lam.) Small) were evaluated for their ability to act as index plant species for soil Cd, Cr, Ni, and V at two field sites where these metals had been applied five yr previously to two highly weathered sandy Ultisols. Soil Cd was available to all analyzed plant tissues of all three plant species at both sites, particularly on the sandier Blanton soil. Chicory was an effective index plant for Cd on the finer textured Orangeburg soil but functioned as an indicator plant (toxicity symptoms were observed) on the sandier Blanton soil. Horseweed and dogfennel were effective index plants for Cd in both contaminated soils. Soil Cr, Ni, and V were less bioavailable than soil Cd and plant metal uptake was more sensitive to residual soil Cr, Ni, and V than was soil extraction with double acid. Horseweed and chicory may have potential as index plants for soil Cr. Chicory may have potential as a Ni index plant. Chicory and dogfennel may have potential as V index plants.     

Exchange of NO and NO2 between wheat canopy monoliths and the atmosphere

The fluxes of NO and NO₂ between wheat canopy monoliths and the atmosphere were investigated with the dynamic chamber technique. For this purpose monoliths were dug out at different plant growth stages from a field site, transported to the institute, and placed in an environmental growth chamber. The wheat canopy monoliths were exposed over a period of four days to the average ratios of atmospheric NO₂ and NO measured at the field site, i.e. NO₂ concentration of about 18 mL L^-1 plus NO concentration lower than 0.5 nL L^-1. Under these conditions NO emission into the atmosphere and NO₂ deposition into canopy monoliths was observed. Both fluxes showed diurnal variation with maximum rates during the light and minimum rates during darkness. NO₂ fluxes correlated with soil temperature as well as with light intensity. NO fluxes correlated with soil temperature but not with light intensity. From the investigation performed the diurnal variation of the NO and NO₂ compensation points, the maximum rates of NO and NO₂ emission, and the total resistances of NO and NO₂ fluxes were calculated. Under the assumption that the measured data are representative for the whole vegetation period, annual fluxes of NO and NO₂ were estimated. Annual NO emission into the atmosphere amounted to 87 mg N m^-2 y^-1 (0.87 kg ha^-1 y^-1), annual NO₂ deposition into canopy monoliths amounted to 1273 mg N m^-2 y^-1 (12.73 kg ha^-1 y^-1). Apparently, the uptake of atmospheric nitrogen by the wheat field from NO₂ deposition is about 15 times higher than the loss of nitrogen from NO emission. It can therefore be assumed that even in rural areas wheat fields are a considerable sink for atmospheric nitrogen. The annual sink strength estimated in the present study is ca. 12 kg N ha^-1 y^-1. The possible origin of the NO emitted and the fate of atmospheric NO₂ taken up by the wheat canopy monoliths are discussed.Preliminary results of this paper were presented at the Joint Workshop COST 611/Working Party 3 and EUROTRAC in Delft, The Netherlands (Ludwig et al., 1991).     

Culture of rat mesenteric arteriolar smooth muscle cells: effects of platelet-derived growth factor, angiotensin, and nitric oxide on growth

We cultured smooth muscle cells as explants from rat mesenteric arterioles (40–200m in diameter) obtained by injecting a suspension of iron oxide intraarterially and magnetically separating the arterioles after collagenase digestion of adventitial tissue. In third-passaged cells we ascertained smooth muscle purity of >98% by characteristic morphology, contraction responses, and specific immunofluorescence staining. Treatment of growth-arrested (in 0.4% fetal calf serum) cells with platelet-derived growth factor (0.3–7.5 nM) or angiotensin II (0.001–1000 nM) induced ³H-thymidine incorporation and cell proliferation in a dose-dependent manner (P<0.01). S-nitroso-N acetylpencillamine (0.05–0.5 mM), a nitric oxide-generating compound, inhibited 10% fetal calf serum-induced ³H-thymidine incorporation (P<0.05) and cell proliferation (P<0.01). The antimitogenic effect of S-nitroso-N-acetylpencillamine was significantly reduced by hemoglobin and potentiated by superoxide dismutase (P<0.01). In addition to a new technique for culturing mesenteric arteriolar smooth muscle cells, these findings provide evidence that platelet-derived growth factor, angiotensin II, and nitric oxide may be involved in their growth control.     

Is there a gas (general adaptation syndrome) response to various types of environmental stress?

A hypothesis of existence of a general adaptation syndrome (GAS), in which different types of stress evoke similar coping mechanisms, resulting in adaptations, is tested for plants. As stress coping mechanisms, oxy-free radical scavengers and antioxidants, osmoregulation, the role of abscisic acid, jasmonates, nitric oxide, synthesis of heat shock proteins and phytochelatins as heavy metal detoxifiers are discussed. The authors would like to thank the Netherlands Organization for Scientific Research (NWO) which enabled their collaboration and the formulation of some of the concepts here presented.     

Regulation of gap junction coupling in the developing neocortex

In the developing mammalian, neocortex gap junctions represent a transient, metabolic, and electrical communication system. These gap junctions may play a crucial role during the formation and refinement of neocortical synaptic circuitries. This article focuses on two major points. First, the influence of gap junctions on electrotonic cell properties will be considered. Both the time-course and the amplitude of synaptic potentials depend,inter alia, on the integration capabilities of the postsynaptic neurons. These capabilities are, to a considerable extent, determined by the electrotonic characteristics of the postsynaptic cell. As a consequence, the efficacy of chemical synaptic inputs may be crucially affected by the presence of gap junctions. The second major topic is the regulation of gap junctional communication by neurotransmitters via second messenger pathways. The monoaminergic neuromodulators dopamine, nordrenaline, and serotonin reduce gap junction coupling via activation of two different intracellular signaling cascades—the cAMP/protein kinase A pathway and the IP₃/Ca²⁺/protein kinase C pathway, 013 respectively. In addition, gap junctional communication seems to be modulated by the nitric oxide (NO)/cGMP system. Since NO production can be stimulated by glutamate-induced calcium influx, the NO/cGMP-dependent modulation of gap junctions might represent a functional link between developing glutamatergic synaptic transmission and the gap junctional network. Thus, it might be of particular importance in view of a role of gap junctions during the process of circuit formation.