Anti-inflammatory lipid mediators and insights into the resolution of inflammation

The pro-inflammatory signalling pathways and cellular mechanisms that initiate the inflammatory response have become increasingly well characterized. However, little is known about the mediators and mechanisms that switch off inflammation. Recent data indicate that the resolution of inflammation is an active process controlled by endogenous mediators that suppress pro-inflammatory gene expression and cell trafficking, as well as induce inflammatory-cell apoptosis and phagocytosis, which are crucial determinants of successful resolution. This review focuses on this emerging area of inflammation research and describes the mediators and mechanisms that are currently stealing the headlines.     

Light-dependent monoterpene synthesis in Pinus radiata cultures

Callus cultures of Pinus radiata that synthesized monoterpenes de novo and which were stable for at least 1 year have been established. The products differed from those of parent plants in that α-pinene (87–100%) rather than β-pinene was the main component. The best lines accumulated monoterpenes (ca 2 × 10^?3% wt/wet wt)in yields 40–20% of that in the parent stem and needles. The composition of the extractable oil depended on the light regime. After culture in total darkness toluene and acetone accumulated. These compounds also occurred (at low levels) in dark-grown seedlings and in seeds of P. radiata and a route for their formation from α-pinene is suggested. Cell-free extracts of the culture lines converted [¹⁴C] IPP into geraniol, nerol and α- and β-pinenes in up to 46% total yield. These are the most active crude extracts for monoterpene biosynthesis that have been reported from either tissue cultures or higher plants.     

The membrane-bound [NiFe]-hydrogenase (Ech) from Methanosarcina barkeri: unusual properties of the iron-sulphur clusters.

The purified membrane-bound [NiFe]-hydrogenase from Methanosarcina barkeri was studied with electron paramagnetic resonance (EPR) focusing on the properties of the iron-sulphur clusters. The EPR spectra showed signals from three different [4Fe-4S] clusters. Two of the clusters could be reduced under 101 kPa of H2, whereas the third cluster was only partially reduced. Magnetic interaction of one of the clusters with an unpaired electron localized on the Ni-Fe site indicated that this was the proximal cluster as found in all [NiFe]-hydrogenases. Hence, this cluster was assigned to be located in the EchC subunit. The other two clusters could therefore be assigned to be bound to the EchF subunit, which has two conserved four-Cys motifs for the binding of a [4Fe-4S] cluster. Redox titrations at different pH values demonstrated that the proximal cluster and one of the clusters in the EchF subunit had a pH-dependent midpoint potential. The possible relevance of these properties for the function of this proton-pumping [NiFe]-hydrogenase is discussed.     

New perspectives on the mechanical basis for airway hyperreactivity and airway hypersensitivity in asthma.

We revisit the airway wall model of Lambert et. al. (Lambert RK, Wiggs BR, Kuwano K, Hogg JC, and Pare PD. J Appl Physiol 74: 2771-2781, 1993). We examine in detail the notion of a general airway bistability such that the airway lumen can suddenly decrease from a relatively open to a relatively closed condition without needing additional increase in active airway smooth muscle (ASM) tension during the stimulation. The onset of this bistability is an emergent consequence of the balance of forces associated with airway wall properties, parenchymal tissue properties, maximum lung elastic recoil, and the maximum stress that the ASM can generate. In healthy lungs, we find that all these properties reside in conditions that largely prevent the emergence of the bistability even during maximum ASM stimulation. In asthmatic airways, however, the airway wall and ASM remodeling conditions can tip the balance so as to promote the onset of the bistability at a lower dose of ASM stimulation (enhanced sensitivity) and then work to amplify the maximum constriction reached by each airway (enhanced reactivity). Hence, a larger fraction of asthmatic airways can display overall airway hyperreactivity. Simulations studies examine the role of increasing ASM maximum tension, airway wall stiffening, reduced lung volume, and decreased parenchymal tethering. Results predict that the single most important factor causing this airway hyperreactivity is amplified maximum ASM tension and not a thickening of the airway wall per se.     

THE GENETIC BASIS OF THE TRADE-OFF BETWEEN CALLING AND WING MORPH IN MALES OF THE CRICKET GRYLLUS FIRMUS

Wing dimorphisms exist in a wide range of insects. In wing-dimorphic species one morph is winged has functional flight muscles (LW), and is flight-capable, whereas the other has reduced wings (SW) and cannot fly The evolution and maintenance of wing dimorphisms is believed to be due to trade-offs between flight capability and fitness-related traits. Although there are well-established phenotypic trade-offs associated with wing dimorphism in female insects, there only exist two studies that have established a genetic basis to these trade-offs. The present study provides the first evidence for a genetically based trade-off in male insects, specifically in the sand cricket Gryllus firmus. Because they have to expend energy to maintain the flight apparatus (especially flight muscles), LW males are predicted to call less and therefore to attract fewer females. To be of evolutionary significance, call duration wing morph, and wing muscle condition (size and functionality) should all have measurable heritabilities and all be genetically correlated. Differences between morphs in male G. firmus in the likelihood of attracting a female were tested in the laboratory using a T-maze where females chose between a LW male and a SW male. Call duration for each male was recorded on the sixth day of adult life. A significant difference in call duration was found between SW and LW males (SW = 0.86 ± 0.01, LW = 0.64 ± 0.01 h). SW males attracted significantly more females than did LW males (63% vs. to 37%). All the traits involved in the trade-off had significant heritabilities (call = 0 75 ± 0 33; wing morph = 0.22 ± 007; muscle weight = 0.38 ± 0.09) and genetic correlations (call and wing morph = -0.46 ± 0.20 for SW, -0.68 ± 0.16 for LW; LW call and muscle weight = -0.80 ± 0.14). These results provide the first documented evidence that trade-offs between a dimorphic trait and a fitness-related character in males has a genetic basis and hence can be of evolutionary significance.     

Stereocontrol in Diels-Alder cycloaddition to unsaturated sugars: reactivities of acyclic seven-carbon trans dienophiles dervied from aldopentoles

Acyclic trans-2,3-unsaturated aldoheptonate derivatives (1–9) obtained from -aldopentoses by Witting chain-extension served as dienophiles for a detailed comparative study of their asymmetric Diels-Alder cycloaddition with cyclopentadiene. Cycloaddition under uncatalyzed thermal conditions gave mixtures of the four possible stereoisomeric norbornene adducts. The endo:exo ratios and the diastereofacial selectivities in the formation of the adducts were determined by NMR spectroscopy and by chemical transformations. The quantitative distribution of adducts as a function of stereochemistry of the dienophile is discussed.     

Gene Knockouts and Murine Development

A considerable quantity of data has been generated using the technique of in vivo gene knockout in mice, much of which is of relevance to the developmental biologist. Null mutations in Hox genes at the 3'-end of the clusters create complex irregularities at the rostral end of the embryo, including defects in the middle ear and the large blood vessels, suggesting that Hox genes may be involved in pattern specification of these structures in addition to the anteroposterior axis. Null mutations in oncogenes either cause wide pleiotropic effects, or act in a restricted manner on the haematopoietic system. Null mutations in growth factors and related molecules cause failure of proliferation in restricted areas of the embryo in some cases, but have little phenotype in others. There is as yet no null mutation which supports the idea that growth factors are involved in mesoderm induction in mammals. A surprising variety of genes have no null phenotype, or one less severe than might have been previously predicted on the basis of their known function in vitro and pattern of expression. This leads to the possibility that genetic redundancy exists in development.     

Analysis of isethionic acid in mammalian tissues

A gas-liquid chromatographic assay has been developed to measure isethionic acid after methylation with diazomethane. The identity of the products of methylation has been confirmed by mass-spectrometry and nuclear magnetic resonance spectroscopy. The method was used to measure isethionic acid in rat heart, dog heart and rat brain. The assay was validated by measuring isethionic acid on squid axoplasm. We have been able to detect only trace amounts of isethionic acid in rat brain (0.2 mg/100g) and rat heart (0.1 mg/ 100g). None was found in dog heart.     

Biosynthesis of (+)-car-3-ene in Pinus species

Degradation of (+)-car-3-ene biosynthesized from MVA-[2-¹⁴C] in Pinus palustris or Pinus sylvestris proved that the C-4 atom of the monoterpene is derived from C-2 of MVA rather than C-4 as has been hitherto assumed. The pro-2S hydrogen of MVA is stereospecifically lost in the formation of the Δ³-double bond. These results delineate possible routes for the biosynthesis of the carane skeleton.