Application of the combination index (CI)-isobologram equation to study the toxicological interactions of lipid regulators in two aquatic bioluminescent organisms

Pharmaceuticals in the aquatic environment do not appear singly and usually occur as complex mixtures, whose combined effect may exhibit toxicity to the aquatic biota. We report an environmental application of the combination index (CI)-isobologram equation, a method widely used in pharmacology to study drug interactions, to determine the nature of toxicological interactions of three fibrates toward two aquatic bioluminescent organisms, Vibrio fischeri and the self-luminescent cyanobacterial recombinant strain Anabaena CPB4337. The combination index-isobologram equation method allows computerized quantitation of synergism, additive effect and antagonism. In the Vibrio test, the fibrate combinations showed antagonism at low effect levels that turned into an additive effect or synergism at higher effect levels; by contrast, in the Anabaena test, the fibrate combinations showed a strong synergism at the lowest effect levels and a very strong antagonism at high effect levels. We also evaluated the nature of the interactions of the three fibrates with a real wastewater sample in the cyanobacterial test. We propose that the combination index-isobologram equation method can serve as a useful tool in ecotoxicological assessment.     

Concentrations of selected metals in honey consumed in Nigeria

The concentration of metals, cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), and zinc (Zn) was measured in selected samples of honey in Nigeria with a view to providing information on the regional concentration profile of metals in these honeys. The honey samples were digested with a mixture of acids and analysed for metal concentrations using atomic absorption spectrophotometry. The concentrations of metals (mg kg^?1) in these honeys ranged from < 0.3 for Cd,<0.50–39.75 for Pb,<0.25–6.98 for Ni,<0.25–55.25 for Cr,<0.25–71.25 for Cu,<0.25–3.50 for Co,<5.0–163.15 for Fe,<11.0–31.75 for Mn and 1.0–31.0 for Zn. The concentrations of metals were relatively high but lower than their respective permissible limits in food except for Pb and Cu in some samples. The regional distribution patterns of metals indicated that honey samples from the Niger Delta region of Nigeria had higher mean concentrations of Ni, Cr, Co, Fe and Zn than honey samples from other regions. The honey samples from the northern region had higher mean concentrations of Pb and Cu.     

Effect of polypyrrole film on the stability and electrochemical activity of fluoride based graphite intercalation compounds in HF media

Fluoride intercalation/deintercalation cycles on commercially available high purity graphite electrodes leads to powder formation and electrode damage. Formation of polypyrrole films of optimum thickness by potential cycling on the graphite surface before fluoride intercalation leads to good mechanical stability to the electrode during intercalation/deintercalation cycles. The intercalation potential shifts by 200 mV in the positive direction. The intercalation and deintercalation charges (Q _a, Q _c) also decrease slightly. However the charge recovery ratio (Q _c/Q _a) improves significantly. Since the polypyrrole layer is compact on the graphite surface, the present study indicates that the film offers mechanical stability to the graphite film without affecting the electronic conductivity of the surface. F^– ion transport through the film also occurs with a small overvoltage.     

Quantum Dot‐Based Thermal Spectroscopy and Imaging of Optically Trapped Microspheres and Single Cells

Laser‐induced thermal effects in optically trapped microspheres and single cells are investigated by quantum dot luminescence thermometry. Thermal spectroscopy has revealed a non‐localized temperature distribution around the trap that extends over tens of micrometers, in agreement with previous theoretical models besides identifying water absorption as the most important heating source. The experimental results of thermal loading at a variety of wavelengths reveal that an optimum trapping wavelength exists for biological applications close to 820 nm. This is corroborated by a simultaneous analysis of the spectral dependence of cellular heating and damage in human lymphocytes during optical trapping. This quantum dot luminescence thermometry demonstrates that optical trapping with 820 nm laser radiation produces minimum intracellular heating, well below the cytotoxic level (43 °C), thus, avoiding cell damage.     

Low-Temperature Bainite: A Thermal Stability Study

The thermal stability of nanobainitic structures obtained by heat treating two different high-carbon high-silicon steels at temperatures between 200 °C and 600 °C has been investigated by means of three complementary techniques, i.e., field emission gun-scanning electron microscopy, X-ray diffraction, and high-resolution dilatometry. Three main stages have been established, each of them characterized by a distinctive microstructure. Furthermore, the nanocrystalline structure generated by the bainite reaction confers the steel with an extraordinary tempering resistance.     

Increased hepatic fatty acid polyunsaturation precedes ectopic lipid deposition in the liver in adaptation to high-fat diets in mice

Objective

We monitored hepatic lipid content (HLC) and fatty acid (FA) composition in the context of enhanced lipid handling induced by a metabolic high-fat diet (HFD) challenge and fasting.

Materials and methods

Mice received a control diet (10% of kilocalories from fat, N = 14) or an HFD (45% or 60% of kilocalories from fat, N = 10 and N = 16, respectively) for 26 weeks. A subset of five mice receiving an HFD (60% of kilocalories from fat) were switched to the control diet for the final 7 weeks. At nine time points, magnetic resonance spectroscopy was performed in vivo at 14.1 T, interleaved with glucose tolerance tests.

Results

Glucose intolerance promptly developed with the HFD, followed by a progressive increase of fasting insulin level, simultaneously with that of HLC. These metabolic defects were normalized by dietary reversal. HFD feeding immediately increased polyunsaturation of hepatic FA, before lipid accumulation. Fasting-induced changes in hepatic lipids (increased HLC and FA polyunsaturation, decreased FA monounsaturation) in control-diet-fed mice were not completely reproduced in HFD-fed mice, not even after dietary reversal.

Conclusion

A similar adaptation of hepatic lipids to both fasting and an HFD suggests common mechanisms of lipid trafficking from adipose tissue to the liver. Altered hepatic lipid handling with fasting indicates imperfect metabolic recovery from HFD exposure.

     

Harnessing methane generated from livestock manure in Ghana, Nigeria, Mali and Burkina Faso

Methane emission from livestock manure is increasingly contributing to the global green house gas emissions. In this paper the methane emission from cattle, pig, sheep, goat and chicken manure in four West African countries; Nigeria, Ghana, Burkina Faso and Mali were estimated. A systematic estimation of the methane emission was done based on the livestock production projections by FAO from 1998 to 2008 and guidelines provided by the Intergovernmental Panel on Climate Change (IPCC). During this period, cattle were found to have emitted more methane followed by pigs, goats, sheep and chicken in that order. A total of about 845 Gg of methane was emitted by the livestock during the period of which cattle contributed about 40%, whereas pigs, goats, sheep and chicken contributed 21.2%, 18.7%, 13.1% and 6.6% respectively. The methane emission from manure management in these countries increased from 64.1 Gg in 1998 to 90.5 Gg in 2008, with an annual growth rate of 3.4% y⁻¹. The methane estimated from livestock manure over the period was shown to be consistent with the linear group model which predicts that in 2018, 2.4 Mt CO₂-eq will be emitted increasing to 3.0 Mt CO₂-eq in 2028 if the mechanism of manure management remains unchanged. This paper reveals that generating methane from the manure produced by the livestock under controlled conditions could supplement the energy needs, increase Gross Domestic Product (GDP) and consequently reduce the direct impact of methane on climate change.