Isolation and identification of alpha-methyloctanylcarnitines from human urine

Medium-chain acylcarnitines were isolated from human urine using a combination of chloroform-methanol extraction, silicic acid column and molecular sieving chromatography and preparative HPLC. Three purified acylcarnitines were analyzed by fast atom bombardment mass spectrometry and were also saponified and the free fatty acids analyzed by gas chromatography and mass spectrometry. Combined electron impact mass spectrometry and fast atom bombardment mass spectrometry and periodate oxidation for location of double bonds, demonstrated the occurrence of delta 6-octenylcarnitine, 2-methyloctanylcarnitine and 2-methyl-delta 6-octenylcarnitine. These acylcarnitines were present in the thirteen urines obtained from normal humans, but were not detected in urines from three individuals who had been on total parenteral nutrition for more than a year. The occurrence of alpha-methyl medium-chain acylcarnitines in human urine indicates a role for carnitine in excretion (detoxification) of these acyl derivatives.     

Habitat properties and plant traits interact as drivers of non‐native plant species’ seed production at the local scale

To answer the long‐standing question if we can predict plant invader success based on characteristics of the environment (invasibility) or the invasive species (invasiveness), or the combination of both, there is a need for detailed observational studies in which habitat properties, non‐native plant traits, and the resulting invader success are locally measured. In this study, we assess the interaction of gradients in the environmental and trait space on non‐native species fitness, expressed as seed production, for a set of 10 invasive and noninvasive non‐native species along a wide range of invaded sites in Flanders. In our multidimensional approach, most of the single environmental gradients (temperature, light availability, native plant species diversity, and soil fertility) and sets of non‐native plant traits (plant size, photosynthesis, and foliar chemical attributes) related positively with invader seed production. Yet correlation with seed production was much stronger when several environmental gradients were assessed in interaction, and even more so when we combined plant traits and habitat properties. The latter increased explanatory power of the models on average by 25% for invasive and by 7% for noninvasive species. Additionally, we report a 70‐fold higher seed production in invasive than in noninvasive species and fundamentally different correlations of seed production with plant traits and habitat properties in noninvasive versus invasive species. We conclude that locally measured traits and properties deserve much more attention than they currently get in invasion literature and thus encourage further studies combining this level of detail with the generality of a multiregion and multispecies approach across different stages of invasion.     

Studies of an acidic cardiotoxin isolated from the venom of Mojave rattlesnake (Crotalus scutulatus).

A major lethal protein was isolated from the venom of Mojave rattlesnake (Crotalus scutulatus) by successive purification in DEAE column chromatography and isoelectric focusing. This homogeneous and monomeric form of toxin is designated as "Mojave toxin". Unlike basic neurotoxins or cytotoxins isolated from venoms of cobras, kraits and sea snakes, the Mojave toxin is an acidic protein with an isoelectric point of 4.7. The toxin is also different from crotoxin (from Crotalus durissus terrificus) which consists of both acidic and basic components. The molecular weight determined by Sephadex G-75 column chromatography resulted in a value of about 22 000. A singel protein band with a molecular weight of about 12 000, was observed after sodium dodecyl sulfate gel electrophoresis of the reduced Mojave toxin. Isoelectric focusing gel in the presence of 8 M urea also showed a single protein band, suggesting that the toxin is composed of subunits. Unlike the neurotoxic nature of the basic proteins from the venoms of Elapidae and sea snakes (Hydrophiidae) and crotoxin, Mojave toxin is cardiotoxic rather than neurotoxic. It is very likely that venoms of all rattlesnakes from North and Central America contain Mojave toxin as the common toxin.     

Quantitation of the efflux of acylcarnitines from rat heart, brain, and liver mitochondria

The efflux of individual short-chain and medium-chain acylcarnitines from rat liver, heart, and brain mitochondria metabolizing several substrates has been measured. The acylcarnitine efflux profiles depend on the substrate, the source of mitochondria, and the incubation conditions. The largest amount of any acylcarnitine effluxing per mg of protein was acetylcarnitine produced by heart mitochondria from pyruvate. This efflux of acetylcarnitine from heart mitochondria is almost 5 times greater with 1 mM than 0.2 mM carnitine. Apparently the acetyl-CoA generated from pyruvate by pyruvate dehydrogenase is very accessible to carnitine acetyltransferase. Very little acetylcarnitine effluxes from heart mitochondria when octanoate is the substrate except in the presence of malonate. Acetylcarnitine production from some substrates peaks and then declines, indicating uptake and utilization. The unequivocal demonstration that considerable amounts of propionylcarnitine or isobutyrylcarnitine efflux from heart mitochondria metabolizing alpha-ketoisovalerate and alpha-keto-beta-methylvalerate provides evidence for a role (via removal of non-metabolizable propionyl-CoA or slowly metabolizable acyl-CoAs) for carnitine in tissues which have limited capacity to metabolize propionyl-CoA. These results also show propionyl-CoA must be formed during the metabolism of alpha-ketoisovalerate and that extra-mitochondrial free carnitine rapidly interacts with matrix short-chain aliphatic acyl-CoA generated from alpha-keto acids of branched-chain amino acids and pyruvate in the presence and absence of malate.     

Primary structure of hemoglobins of the musk rat (Ondatra zibethica, Rodentia)

The amino-acid sequence for the hemoglobin of the musk-rat (Ondatra zibethica) was determined. The sequence of both chains was established by automatic Edman-Begg degradation of the tryptic peptides and, in the case of the beta-chains additionally of the prolyl-peptide. The complete primary structure of the alpha-chains differs at 22, that of the beta-chains at 36 positions from the adult human hemoglobin. There are no changes in the heme-binding residues, the alpha 1--beta 2 contact positions and the allosteric regulator sites. In the heme-pocket we found beta 44 Ser leads to His and 8 positions changed within the alpha 1--beta 1 contact regions. These changes are discussed with respect to the function of the respective regions.