Metabolism of leukotriene B4 in the monkey. Identification of the principal nonvolatile metabolite in the urine

Five milligrams of [5,6,8,9,11,12,14,15-³H₈]-leukotriene B₄ (LTB₄) (1.68 Ci/mmol) were infused into a monkey over a three hour period. Twenty-five per cent of the infused ³H-activity was recovered in the urine during the twenty hours of collection. Plasma and urinary metabolite volatility studies revealed that in contrast to previously studied eicosanoids, more than 70% per cent of the infused LTB₄³H-label was converted to tritiated water. The major nonvolatile urinary metabolite of LTB₄ representing 0.8% of the infused material was identified as 20-OH-LTB₄. LTB₄ was not excreted in the urine. Other nonvolatile metabolites of LTB₄ representing less than 0.4% each of the infused material were isolated from the urine. While there was an adequate quantity of some of these metabolites for partial characterization, there was insufficient material for structural elucidation. Further studies were performed in rabbits in which either LTB₄ or the structurally related compound 8,15-dihydroxyeicosatetraenoic acid (8,15-diHETE) were infused intravenously. In these rabbits the metabolism of LTB₄ and 8,15-diHETE was similar to that in the monkey with greater than 80% of the infused ³H-activity converted to tritiated water. These studies suggest that leukotriene B₄ and structurally related compounds undergo extensive degradation in vivo via the β-oxidation system.     

Range edges and the molecular divergence of Greya moth populations

Aim We investigated the geographical pattern of genetic divergence and demographic history in the prodoxid moth Greya obscura throughout its entire geographical range in far western North America and compared it to the geographical patterns found in a previously studied species, Greya politella, which co‐occurs over the same range, in the same habitats, and on the same host plants. Location The study included sites distributed throughout the California Floristic Province. Methods We used analysis of cytochrome c oxidase subunit I (COI) and amplified fragment length polymorphisms to evaluate the pattern and history of genetic continuity among populations. Results Greya obscura populations show a history of spatial expansion with considerable haplotype diversity in the centre of the geographical range. As with G. politella, some range‐edge populations of G. obscura are sufficiently divergent (6.7% in COI) to be considered as potentially cryptic species. Greya obscura and G. politella, however, differ in the specific range‐edge sites showing greatest genetic divergence and cryptic speciation. Main conclusions These results corroborate the view that range edges are important cradles of divergence and speciation. In addition, the results indicate that the geographical pattern of divergence at edges may differ even among closely related species occupying the same habitats and using the same hosts.     

Proliferative response of human diploid fibroblasts to intermittent light exposure

Three- to four-hour exposure to fluorescnt light, one to three times weekly, reproducibly enhanced the proliferation rate of human diploid fibroblasts. This enhancement was observed in WI-38 and a line from whole embryo mince at late population doubling level (PDL) as well as in a line from adult skin at early PDL. Single or multiple exposures of short duration stimulated proliferation, whereas exposures of long duration were cytotoxic. This proliferative response is reversible, and is mediated through the culture medium, Dulbecco Vogt's supplemented with 10% fetal bovine serum. Apparently light produces some mitogenic substance(s) in the culture medium that accumulates in the cells and is toxic or growth-stimulatory depending on its concentration per cell. Another possibility is that light produces in the medium both cytotoxic and growth-stimulatory substances.     

The Heat-Resistant Agglutinin Family Includes a Novel Adhesin from Enteroaggregative Escherichia coli Strain 60A

Heat-resistant agglutinin 1 (Hra1) is an accessory colonization factor of enteroaggregative Escherichia coli (EAEC) strain 042. Tia, a close homolog of Hra1, is an invasin and adhesin that has been described in enterotoxigenic E. coli. We devised a PCR-restriction fragment length polymorphism screen for the associated genes and found that they occur among 55 (36.7%) of the enteroaggregative E. coli isolates screened, as well as lower proportions of enterotoxigenic, enteropathogenic, enterohemorrhagic, and commensal E. coli isolates. Overall, 25%, 8%, and 3% of 150 EAEC strains harbored hra1 alone, tia alone, or both genes, respectively. One EAEC isolate, 60A, produced an amplicon with a unique restriction profile, distinct from those of hra1 and tia. We cloned and sequenced the full-length agglutinin gene from strain 60A and have designated it hra2. The hra2 gene was not detected in any of 257 diarrheagenic E. coli isolates in our collection but is present in the genome of Salmonella enterica serovar Heidelberg strain SL476. The cloned hra2 gene from strain 60A, which encodes a predicted amino acid sequence that is 64% identical to that of Hra1 and 68% identical to that of Tia, was sufficient to confer adherence on E. coli K-12. We constructed an hra2 deletion mutant of EAEC strain 60A. The mutant was deficient in adherence but not autoaggregation or invasion, pointing to a functional distinction from the autoagglutinin Hra1 and the Tia invasin. Hra1, Tia, and the novel accessory adhesin Hra2 are members of a family of integral outer membrane proteins that confer different colonization-associated phenotypes.     

Express Your LOV: An Engineered Flavoprotein as a Reporter for Protein Expression and Purification

In this work, we describe the utility of Light, Oxygen, or Voltage-sensing (LOV) flavoprotein domains from plant phototropins as a reporter for protein expression and function. Specifically, we used iLOV, an enhanced and more photostable variant of LOV. A pET-based plasmid for protein expression was constructed, encoding a C terminal iLOV-octahistidine (His8)-tag and a HRV 3C protease cleavage recognition site. Ten different proteins, with various sub-cellular locations, were cloned into the plasmid, creating iLOV-His8 tag fusions. To test protein expression and how iLOV could be used as a reporter, the proteins were expressed in three different cell lines, in four different culture media, at two different temperatures. To establish whether the presence of the iLOV tag could have an impact on the functionality, one of the proteins, EspG, was over-expressed and purified. EspG is an “effector” protein normally produced by enterohemorrhagic E. coli strains and “injected” into host cells via the T3SS. We tested functionality of EspG-iLOV fusion by performing functional studies of EspG in mammalian host cells. When EspG-iLOV was microinjected into the host cell, the Golgi apparatus was completely disrupted as had previously been observed for EspG.     

Spontaneous gallbladder pathology in baboons

Background Gallbladder pathology (GBP) is a relatively uncommon, naturally occurring morbidity in both baboons and humans. Methods A retrospective analysis was performed on 7776 necropsy reports over a 20 year period to determine the prevalence of baboon GBP. Results Ninety‐seven cases of GBP were identified, yielding a 20 year population prevalence of 1.25%. GBP is more common in adult female baboons, occurring with a female to male ratio of nearly 2:1. Among gallbladder pathologies, cholecystitis (35.1%) and cholelithiasis (29.9%) were the most prevalent abnormalities, followed by hyperplasia (16.5%), edema (15.5%), amyloidosis (5.2%), fibrosis (4.1%), necrosis (4.1%), and hemorrhage (1.0%). Conclusion Many epidemiologic similarities exist between GBP in baboons and humans suggesting that the baboon may serve as a reliable animal model system for investigating GBP in humans.     

Thermal ecology and baseline energetic requirements of a large‐bodied ectotherm suggest resilience to climate change

1. Most studies on how rising temperatures will impact terrestrial ectotherms have focused on single populations or multiple sympatric species. Addressing the thermal and energetic implications of climatic variation on multiple allopatric populations of a species will help us better understand how a species may be impacted by altered climates.
2. We used eight years of thermal and behavioral data collected from four populations of Pacific rattlesnakes (Crotalus oreganus) living in climatically distinct habitat types (inland and coastal) to determine the field‐active and laboratory‐preferred body temperatures, thermoregulatory metrics, and maintenance energetic requirements of snakes from each population.
3. Physical models showed that thermal quality was best at coastal sites, but inland snakes thermoregulated more accurately despite being in more thermally constrained environments. Projected increases of 1 and 2°C in ambient temperature result in an increase in overall thermal quality at both coastal and inland sites.
4. Population differences in modeled standard metabolic rate estimates were driven by body size and not field‐active body temperature, with inland snakes requiring 1.6× more food annually than coastal snakes.
5. All snakes thermoregulated with high accuracy, suggesting that small increases in ambient temperature are unlikely to impact the maintenance energetic requirements of individual snakes and that some species of large‐bodied reptiles may be robust to modest thermal perturbations under conservative climate change predictions.

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The Nuffield Council’s green light for genome editing human embryos defies fundamental human rights law

In July 2018, the Nuffield Council on Bioethics released the report Genome editing and human reproduction: Social and ethical issues, concluding that human germline modification of human embryos for implantation is not ‘morally unacceptable in itself’ and could be ethically permissible in certain circumstances once the risks of adverse outcomes have been assessed and the procedure appears ‘reasonably safe’. The Nuffield Council set forth two main principles governing anticipated uses and envisions applications that may include health enhancements as a public health measure. This essay provides a critique of three aspects in the Nuffield Council’s Report: its presumption of therapeutic efficacy, its inflation of parental rights to create a certain type of child, and its reliance on a specially commissioned report that appears to distort key definitions in international law.     

Can reintroductions to degraded habitat succeed? A test using the common brushtail possum

Habitat degradation contributes to species decline, and habitat quality is an important factor influencing reintroduction success globally. Habitat quality can include a range of physical resources such as nest sites and food resources but also anything that can restrict the use of these resources such as predation risk or competition. In arid Australia, introduced predators are thought to be the primary cause of mammal extinction and reintroduction failure although habitat clearance and alteration are also major causes of population decline. Common brushtail possums are one arid Australian marsupial close to regional extinction. To understand whether habitat quality was limiting their recovery, we reintroduced 148 possums into an area where introduced red foxes were controlled but historic overgrazing had degraded the habitat. We measured both direct (hollow availability, midstorey cover and high‐quality plant foods) and indirect (survival, condition, reproduction, movement) measures of habitat quality. Sixty‐seven released possums and 26 post‐release recruits were radiocollared for up to 2 years after release. Post‐release survival of radiocollared possums was high after 12 months (0.70), and there were no deaths from starvation. Predation by feral cats was the most common cause of mortality, and the open, degraded habitat may have exacerbated predation risk. Continuous breeding, good body condition and comparative home ranges with other sites suggested that food resources were not limiting. Possums used natural tree hollows in Eucalyptus spp. with no use of artificial nest boxes. Results suggest that historically degraded habitat was not a barrier to short‐term reintroduction success when foxes were controlled and natural tree hollows were plentiful. However, demographic data on hollow‐bearing tree species suggest a possible future decline in availability of hollows. These factors, combined with the unknown effects of drought, and synergistic effects of predation and poor quality habitat, suggest long‐term reintroduction success may require improved habitat and cat control.