Augustine Ocloo

The basal proton conductance of mitochondria depends on adenine nucleotide translocase content

The basal proton conductance of mitochondria causes mild uncoupling and may be an important contributor to metabolic rate. The molecular nature of the proton-conductance pathway is unknown. We show that the proton conductance of muscle mitochondria from mice in which isoform 1 of the adenine nucleotide translocase has been ablated is half that of wild-type controls. Overexpression of the adenine nucleotide translocase encoded by the stress-sensitive B gene in Drosophila mitochondria increases proton conductance, and underexpression decreases it, even when the carrier is fully inhibited using carboxyatractylate. We conclude that half to two-thirds of the basal proton conductance of mitochondria is catalysed by the adenine nucleotide carrier, independently of its ATP/ADP exchange or fatty-acid-dependent proton-leak functions.

Proton conductance and fatty acyl composition of liver mitochondria correlates with body mass in birds.

The proton conductance of isolated liver mitochondria correlates significantly with body mass in mammals, but not in ectotherms. To establish whether the correlation in mammals is general for endotherms or mammal-specific, we measured proton conductance in mitochondria from birds, the other main group of endotherms, using birds varying in mass over a wide range (nearly 3000-fold), from 13 g zebra finches to 35 kg emus. Respiratory control ratios were higher in mitochondria from larger birds. Mitochondrial proton conductance in liver mitochondria from birds correlated strongly with body mass [respiration rate per mg of protein driving proton leak at 170 mV being 44.7 times (body mass in g)(-0.19)], thus suggesting a general relationship between body mass and proton conductance in endotherms. Mitochondria from larger birds had the same or perhaps greater surface area per mg of protein than mitochondria from smaller birds. Hence, the lower proton conductance was caused not by surface area changes but by some change in the properties of the inner membrane. Liver mitochondria from larger birds had phospholipid fatty acyl chains that were less polyunsaturated and more monounsaturated when compared with those from smaller birds. Phospholipid fatty acyl polyunsaturation correlated positively and monounsaturation correlated negatively with proton conductance. These correlations echo those seen in mammalian liver mitochondria, suggesting that they too are general for endotherms.

Structure and Function of Mitochondria in Hepatopancreas Cells from Metabolically Depressed Snails

Mitochondria in cells isolated from the hepatopancreas of aestivating land snails (Helix aspersa) consume oxygen at 30% of the active control rate. The aim of this study was to investigate whether the lower respiration rate is caused by a decrease in the density of mitochondria or by intrinsic changes in the mitochondria. Mitochondria occupied 2% of cellular volume, and the mitochondrial inner membrane surface density was 17 μm−1, in cells from active snails. These values were not different in cells from aestivating snails. The mitochondrial protein and mitochondrial phospholipid contents of cells were also similar. There was little difference in the phospholipid fatty acyl composition of mitochondria isolated from metabolically depressed or active snails, except for arachidonic acid, which was 18% higher in mitochondria from aestivating snails. However, the activities of citrate synthase and cytochrome c oxidase in mitochondria isolated from aestivating snails were 68% and 63% of control, respectively. Thus the lower mitochondrial respiration rate in hepatopancreas cells from aestivating snails was not caused by differences in mitochondrial volume or surface density but was associated with intrinsic changes in the mitochondria.

Anti-melanoma, tyrosinase inhibitory and anti-microbial activities of gold nanoparticles synthesized from aqueous leaf extracts of Teraxacum officinale

There has been a tenacious search for pharmaceuticals of natural origin, as they are cost‐effective and are noted for having little or no side effects. The rate at which diseases are developing resistance to synthetic drugs is quite alarming, and the side effects of these drugs remain an excruciating agony to the pharmaceutical industry. Gold nanoparticles (AuNPs) have wide applications in current technology. However, their use in medicine has not been adequately explored. Chemical methods for the synthesis are associated with environmental benignity and tissue toxicity on in vivo administration. For the first time, we have synthesized AuNPs from leaf extracts of Teraxacum officinale that were found to have significant anti‐melanoma, tyrosinase inhibitory and anti‐microbial effects, and hence stand as promising candidates for use in cosmetics medical and food industries.

Antioxidant Activity of Solvent Fractions of Taraxacum officinale (Dandelion) Leaves

Methanolic crude extract of dandelion (Taraxacum officinale) leaves was fractionated in solvents and antioxidant activity evaluated. The ethyl acetate and butanol fractions showed high antioxidant activities in all the assays. Methylene chloride and water fractions demonstrated moderate activity, whereas the hexane fraction had relatively lower activity.

Isolation and characterisation of theobromine-degrading filamentous fungi

Strategies for achieving global food security include identification of alternative feedstock for use as animal feed, to contribute towards efforts at increasing livestock farming. The presence of theobromine in cocoa pod husks, a major agro-waste in cocoa-producing countries, hinders its utilisation for this purpose. Cheap treatment of cocoa pod husks to remove theobromine would allow largescale beneficial use of the millions of metric tonnes generated annually. The aim of this study was to isolate theobromine-degrading filamentous fungi that could serve as bioremediation agents for detheobromination of cocoa pod husks. Filamentous fungi were screened for ability to degrade theobromine. The most promising isolates were characterized with respect to optimal environmental conditions for theobromine degradation. Secretion of theobromine-degrading enzymes by the isolates was investigated. Theobromine degradation was monitored by HPLC. Of fourteen theobromine-degrading isolates collected and identified by rDNA 5.8S and ITS sequences, seven belonged to Aspergillus spp. and six were Talaromyces spp. Based on the extent of theobromine utilization, four isolates; Aspergillus niger, Talaromyces verruculosus and two Talaromyces marneffei, showed the best potential for use as bioagents for detheobromination. First-time evidence was found of the use of xanthine oxidase and theobromine oxidase in degradation of a methylxanthine by fungal isolates. Metabolism of theobromine involved initial demethylation at position 7 to form 3-methylxanthine, or initial oxidation at position 8 to form 3,7-dimethyuric acid. All four isolates degraded theobromine beyond uric acid. The data suggest that the four isolates can be applied to substrates, such as cocoa pod husks, for elimination of theobromine.