Multiple processes drive genetic structure of humpback whale (Megaptera novaeangliae) populations across spatial scales

Elucidating patterns of population structure for species with complex life histories, and disentangling the processes driving such patterns, remains a significant analytical challenge. Humpback whale (Megaptera novaeangliae) populations display complex genetic structures that have not been fully resolved at all spatial scales. We generated a data set of nuclear markers for 3575 samples spanning the seven breeding stocks and substocks found in the South Atlantic and western and northern Indian Oceans. For the total sample, and males and females separately, we assessed genetic diversity, tested for genetic differentiation between putative populations and isolation by distance, estimated the number of genetic clusters without a priori population information and estimated rates of gene flow using maximum‐likelihood and Bayesian approaches. At the ocean basin scale, structure is governed by geographical distance (IBD P < 0.05) and female fidelity to breeding areas, in line with current understanding of the drivers of broadscale population structure. Consistent with previous studies, the Arabian Sea breeding stock was highly genetically differentiated (F_ST 0.034–0.161; P < 0.01 for all comparisons). However, the breeding stock boundary between west South Africa and east Africa was more porous than expected based on genetic differentiation, cluster and geneflow analyses. Instances of male fidelity to breeding areas and relatively high rates of dispersal for females were also observed between the three substocks in the western Indian Ocean. The relationships between demographic units and current management boundaries may have ramifications for assessments of the status and continued protections of populations still in recovery from commercial whaling.     

Escherichia coli O157:H7 colonization in small domestic ruminants

Enterohaemorrhagic Escherichia coli O157:H7 was first implicated in human disease in the early 1980s, with ruminants cited as the primary reservoirs. Preliminary studies indicated cattle to be the sole source of E. coli O157:H7 outbreaks in humans; however, further epidemiological studies soon demonstrated that E. coli O157:H7 was widespread in other food sources and that a number of transmission routes existed. More recently, small domestic ruminants (sheep and goats) have emerged as important sources of E. coli O157:H7 human infection, particularly with the widespread popularity of petting farms and the increased use of sheep and goat food products, including unpasteurized cheeses. Although the colonization and persistence characteristics of E. coli O157:H7 in the bovine host have been studied intensively, this is not the case for small ruminants. Despite many similarities to the bovine host, the pathobiology of E. coli O157:H7 in small domestic ruminants does appear to differ significantly from that described in cattle. This review aims to critically review the current knowledge regarding colonization and persistence of E. coli O157:H7 in small domestic ruminants, including comparisons with the bovine host where appropriate.     

NDPK-A (but not NDPK-B) and AMPK alpha1 (but not AMPK alpha2) bind the cystic fibrosis transmembrane conductance regulator in epithelial cell membranes

Cystic fibrosis (CF) results from mutations within the cystic fibrosis transmembrane-conductance regulator (CFTR) protein. The AMP-activated protein kinase (AMPK) is a heterotrimer composed of different isoforms of the alphabetagamma subunits, where the alpha1 catalytic subunit binds CFTR. Nucleoside diphosphate kinase (NDPK, NM23/awd) converts nucleoside diphosphates to nucleoside triphosphates but also acts as a protein kinase. We recently showed that AMPK alpha1 binds NDPK-A in lung epithelial cytosol. Here we report that in the plasma membrane of human airway epithelial cells, NDPK-A and AMPK alpha1 associate with the plasma membrane via CFTR. We show that the regulatory domain of CFTR binds NDPK-A whereas AMPK gamma1 or gamma2 bind the first nucleotide binding domain (NBD1) and AMPK alpha1 binds the second (NBD2) of CFTR. We also show that NDPK-A specifically binds AMPK alpha1 and AMPK gamma2 subunits, thereby specifying the isozyme of AMPK heterotrimer that associates with CFTR at the membrane. Thus, the combined data provide novel insight into the subunit composition of the epithelial CFTR/AMPK/NDPK complex, such that: CFTR interacts specifically with AMPK alpha1, gamma2 and NDPK-A and not NDPK-B or AMPK gamma1.     

Plant processes important for the transformation and degradation of explosives contaminants

Environmental contamination by explosives is a worldwide problem. Of the 20 energetic compounds, 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) are the most powerful and commonly used. Nitroamines are toxic and considered as possible carcinogens. The toxicity and persistence of nitroamines requires that their fate in the environment be understood and that contaminated soil and groundwater be remediated. This study, written as a minireview, provides further insights for plant processes important for the transformation and degradation of explosives. Plants metabolize TNT and the distribution of the transformation products, conjugates, and bound residues appears to be consistent with the green liver model concept. Metabolism of TNT in plants occurs by reduction as well as by oxidation. Reduction probably plays an important role in the tolerance of plants towards TNT, and, therefore a high nitroreductase capacity may serve as a biochemical criterion for the selection of plant species to remediate TNT. Because the activities and the inducibilities of the oxidative enzymes are far lower than of nitroreductase, reducing processes may predominate. However, oxidation may initiate the route to conjugation and sequestration leading ultimately to detoxification of TNT, and, therefore, particularly the oxidative pathway deserves more study. It is possible that plants metabolize RDX also according to the green liver concept. In the case of plant metabolism of HMX, a conclusion regarding compliance with the green liver concept was not reached due to the limited number of available data.     

The screening of selected microorganisms for use as models of mammalian drug metabolism

Summary Fifty fungi and two Streptomyces species were screened for their ability to metabolise the probe substrates aminopyrine, diazepam, testosterone, theophylline and warfarin. The metabolism of the ¹⁴C-labelled substrates by whole growing cells was compared with that by rat liver microsomes using TLC-autoradiography. Testosterone, warfarin and diazepam were readily metabolised by most microorganisms, and aminopyrine and theophylline were only metabolised by a few. A relationship between substrate lipophilicity and number of microorganisms able to biotransform the substrate was observed, lipophilic substrates being favoured for metabolism, analogous to mammalian cytochrome P-450. A wide variety of metabolites were produced by the screened cultures, with a significant number co-chromatographing with mammalian metabolites. Most microorganisms appeared to exhibit cytochrome P-450-type oxidative reactions such as hydroxylation and N-demethylation, similar to mammalian hepatic microsomal cytochrome P-450 systems. Offprint requests to: D. A. Griffiths     

Production of inositol trisphosphates and inositol tetrakisphosphate in stimulated pancreatic islets

Glucose and carbamylcholine caused concentration-dependent increases in the production of total [3H]inositol phosphates in [3H]inositol-labelled rat pancreatic islets. When extracts from islets stimulated with glucose, carbamylcholine or depolarising concentrations of K+ were analysed using anion-exchange high performance liquid chromatography, increased production of [3H]Ins1,4,5-P3 was detected, and in addition, elevated levels of two other labelled compounds which co-chromatographed with Ins1,3,4-P3 and Ins1,3,4,5-P4. In the case of carbamylcholine and high K+, such an effect was apparent within 20 s, whereas glucose appeared to cause a delayed response. In the presence of 5 mM LiCl, the accumulation of Ins1,3,4-P3 was more marked. The presence of LiCl had no major influence on the levels of Ins1,4,5-P3 or Ins1,3,4,5-P4. It is suggested that the stimulation of pancreatic islets with glucose, carbamylcholine or high K+ results in the hydrolysis of inositol lipids with the production of Ins1,4,5-P3 and in addition, Ins1,3,4-P3 and Ins1,3,4,5-P4. The physiological functions of these novel inositol phosphates in islets remain to be established.