Development of an Arterio‐venous Difference Method to Study the Metabolic Physiology of the Femoral Adipose Tissue Depot

Gluteofemoral adipose tissue (AT) has interesting positive associations with metabolic health, yet little is known of its metabolic physiology. Here, we describe a technique for cannulation of a vein draining the femoral fat depot. Using ultrasound guidance, a cannula was introduced into a superficial branch of the great saphenous vein. We also obtained arterialized blood and, for comparison, blood representing drainage from forearm muscle and from subcutaneous abdominal AT. We measured appropriate biomarkers of skeletal muscle (creatinine) and AT (nonesterified fatty acids (NEFAs), glycerol, leptin) drainage. Blood obtained in this way from the saphenous vein did not show creatinine release (creatinine concentration 100.5 ± 0.4%, mean ± s.e.m., of that in arterialized blood), whereas creatinine concentrations in blood draining forearm muscle averaged 121 ± 1% of those in arterialized blood. Fatty acid release from the tissue drained was suppressed after feeding and increased during β‐adrenergic stimulation. We also demonstrated leptin secretion. These findings suggest that blood so obtained is representative of AT drainage with little apparent contribution of skeletal muscle. We believe this technique will facilitate physiological studies of a lower‐body fat depot in humans.     

The evolution of bacterial mutation rates under simultaneous selection by interspecific and social parasitism

Many bacterial populations harbour substantial numbers of hypermutable bacteria, in spite of hypermutation being associated with deleterious mutations. One reason for the persistence of hypermutators is the provision of novel mutations, enabling rapid adaptation to continually changing environments, for example coevolving virulent parasites. However, hypermutation also increases the rate at which intraspecific parasites (social cheats) are generated. Interspecific and intraspecific parasitism are therefore likely to impose conflicting selection pressure on mutation rate. Here, we combine theory and experiments to investigate how simultaneous selection from inter- and intraspecific parasitism affects the evolution of bacterial mutation rates in the plant-colonizing bacterium Pseudomonas fluorescens. Both our theoretical and experimental results suggest that phage presence increases and selection for public goods cooperation (the production of iron-scavenging siderophores) decreases selection for mutator bacteria. Moreover, phages imposed a much greater growth cost than social cheating, and when both selection pressures were imposed simultaneously, selection for cooperation did not affect mutation rate evolution. Given the ubiquity of infectious phages in the natural environment and clinical infections, our results suggest that phages are likely to be more important than social interactions in determining mutation rate evolution.     

Physiological consequences of defects in ERCC1-XPF DNA repair endonuclease

ERCC1-XPF is a structure-specific endonuclease required for nucleotide excision repair, interstrand crosslink repair, and the repair of some double-strand breaks. Mutations in ERCC1 or XPF cause xeroderma pigmentosum, XFE progeroid syndrome or cerebro-oculo-facio-skeletal syndrome, characterized by increased risk of cancer, accelerated aging and severe developmental abnormalities, respectively. This review provides a comprehensive overview of the health impact of ERCC1-XPF deficiency, based on these rare diseases and mouse models of them. This offers an understanding of the tremendous health impact of DNA damage derived from environmental and endogenous sources.     

DNA extraction method affects microbial community profiles from soils and sediment

To evaluate whether different deoxyribonucleic acid (DNA) extraction procedures can affect estimates of bacterial community composition, based on the 16S ribosomal ribonucleic acid gene denaturing gradient gel electrophoresis (DGGE) profiles, we compared four in situ lysis procedures using three soils and one marine sediment. Analysis of DGGE profiles, generated by polymerase chain reaction of purified DNA extracts, demonstrated that the choice of DNA extraction method significantly influenced the bacterial community profiles generated. This was reflected both in the number of bands or ribotypes detected from each sample and in subsequent principle coordinate analysis and unweighted-pair group method using arithmetic average analyses. The methods also differed significantly in their robustness, i.e. reproducibility across multiple analyses. Two methods, both based on bead beating, were demonstrated to be suitable for comparative studies of a range of soil and sediment types. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Measurement of S-nitrosothiols in extracellular fluids from healthy human volunteers and rheumatoid arthritis patients, using electron paramagnetic resonance spectrometry

In human tissues, S-nitrosothiols (RSNOs) are generated by the nitric oxide (NO.)-dependent S-nitrosation of thiol-containing species. Here, a novel electron paramagnetic resonance spectrometry assay for RSNOs is described, together with its application to studies of human health and disease. The assay involves degrading RSNOs using N-methyl-d-glucamine dithiocarbamate (MGD) at high pH and spin trapping the NO. released using (MGD)2-Fe2+. Because dietary nitrate might contribute to tissue RSNOs, the assay was used to monitor the effect of Na15NO3 ingestion on plasma and gastric juice RSNOs in healthy human volunteers. Na15NO3 ingestion (2 mmol) increased gastric RS15NO concentrations (p<0.01), but there was no significant effect on plasma RS15NO concentrations. Having established that dietary nitrate was not a confounding factor, we applied the RSNO assay to matched plasma and knee-joint synovial fluid (SF) from rheumatoid arthritis (RA) patients, with healthy subjects as controls. Clinical markers of RA inflammatory disease activity were quantified, as were plasma and SF NO2- and NO3-. Median RSNO concentrations were 0 (interquartile range 68) nM, 109 (282) nM, and 309 (470) nM in normal plasma, RA plasma, and SF, respectively. The median RSNO concentration was significantly elevated in RA SF compared with RA plasma (p<0.05) and in RA plasma compared with normal plasma (p<0.05). SF RSNO concentrations correlated positively with SF neutrophil counts (rs=0.55, p<0.05) and inversely with blood hemoglobin concentrations (rs=-0.52, p<0.05), but not with NO2- or NO3-. Thus the raised levels of RSNOs in RA SF correlate with some established markers of inflammation, suggesting the described RSNO assay may have applications in rapid clinical monitoring of NO metabolism in human inflammatory conditions.     

No effect of intraspecific relatedness on public goods cooperation in a complex community

Many organisms—notably microbes—are embedded within complex communities where cooperative behaviors in the form of excreted public goods can benefit other species. Under such circumstances, intraspecific interactions are likely to be less important in driving the evolution of cooperation. We first illustrate this idea with a simple theoretical model, showing that relatedness—the extent to which individuals with the same cooperative alleles interact with each other—has a reduced impact on the evolution of cooperation when public goods are shared between species. We test this empirically using strain of Pseudomonas aeruginosa that vary in their production of metal‐chelating siderophores in copper contaminated compost (an interspecific public good). We show that nonsiderophore producers grow poorly relative to producers under high relatedness, but this cost can be alleviated by the presence of the isogenic producer (low relatedness) and/or the compost microbial community. Hence, relatedness can become unimportant when public goods provide interspecific benefits.     

Fat King Penguins Are Less Steady on Their Feet

Returning to the shore after a feeding sojourn at sea, king penguins often undertake a relatively long terrestrial journey to the breeding colony carrying a heavy, mostly frontal, accumulation of fat along with food in the stomach for chick-provisioning. There they must survive a fasting period of up to a month in duration, during which their complete reliance on endogenous energy stores results in a dramatic loss in body mass. Our aim was to determine if the king penguin’s walking gait changes with variations in body mass. We investigated this by walking king penguins on a treadmill while instrumented with an acceleration data logger. The stride frequency, dynamic body acceleration (DBA) and posture of fat (pre-fasting; 13.2 kg) and slim (post fasting; 11 kg) king penguins were assessed while they walked at the same speed (1.4km/h) on a treadmill. Paired statistical tests indicated no evidence for a difference in dynamic body acceleration or stride frequency between the two body masses however there was substantially less variability in both leaning angle and the leaning amplitude of the body when the birds were slimmer. Furthermore, there was some evidence that the slimmer birds exhibited a decrease in waddling amplitude. We suggest the increase in variability of both leaning angle and amplitude, as well as a possibly greater variability in the waddling amplitude, is likely to result from the frontal fat accumulation when the birds are heavier, which may move the centre of mass anteriorly, resulting in a less stable upright posture. This study is the first to use accelerometry to better understand the gait of a species within a specific ecological context: the considerable body mass change exhibited by king penguins.