Biochemical studies on a 12-lipoxygenase in human uterine cervix

Human uterine cervix possesses a high 12-lipoxygenase activity; this enzyme has been isolated in a purified form from the squamous epithelial region of human cervix and its major properties have been investigated. Enzyme activity was present in all subcellular fractions obtained by centrifugation; the highest specific activity was associated with the microsome fraction (160,000 X g pellet). Purification of the enzyme was achieved by acetone precipitation, ion exchange chromatography on CM-cellulose and affinity chromatography on linoleyl-aminoethyl-Sepharose. The product from the incubation of sodium [1-14C]arachidonate with crude enzyme extracts co-chromatographed with authentic 12-hydroxyeicosatetraenoic acid, but the purified enzyme gave a product that behaved like the 12-hydroperoxy derivative. The enzyme had optimum activity at pH 6.5, a Km of 15 microM for arachidonic acid and was stimulated by ATP and Ca2+. Enzyme activity was inhibited by esculetin, nordihydroguaiaretic acid, eicosatetraynoic acid, detergents at concentrations greater than 0.1% (w/v) and preincubation of substrate with GSH and GSH peroxidase. The occurrence of a high 12-lipoxygenase activity is discussed in relation to the specific physiological functions of this tissue.     

The partition of glycosaminoglycan-quarternary ammonium complexes II. The effects of polymer molecular weight and sulfation

Previous results have shown the possibility for obtaining high-resolution separations of glycosaminoglycans by partition in butanol/aqueous two-phase systems containing quarternary ammonium salts. In this paper, the effects on partition behavior of both polymer molecular weight and sulfation were examined. Two series of fractioned chondroitin sulfate polymers were isolated in which the molecular weight and sulfation varied systematically. In the molecular weight series the six samples, spanned the range from 3200 ± 300 to 19 700 ± 500 and each sample carried 0.8 sulfate groups per uronic acid residue. In the sulfation series, each sample had an essentially constant molecular weight of 13 000, but the sulfation varied from 0.58 to 0.88 sulfate groups per uronic acid. The $\text{C}{}_{50}{}^1$ of each of these samples was determined in the 1-butanol/aqueous NaCl phae system containing 1% hexadecylpyridinium chloride. In the series wherein the molecular weight varied, the C₅₀ increased with molecular weight up to 12 000 where a limiting value was reached. In the series wherein the sulfation varied, a linear relationship was found between the C₅₀ and the square of the number of anionic substituents per disaccharide. These results show that fractionation by partition techniques will be sensitive to the anionic nature of the polymer, but for the common connective tissue glycosaminoglycan, there will be no fractionation according to molecular weight.     

Recombination confounds interpretations of Wolbachia evolution.

Wolbachia are vertically transmitted bacteria known from arthropods and nematode worms, which are maintained in host populations because they either physiologically benefit infected individuals or parasitically manipulate their reproduction. The different manipulation phenotypes are scattered across the Wolbachia phylogeny, suggesting that there have been multiple evolutions of similar phenotypes. This conclusion relies on the assumption of an absence of recombination between bacterial strains, so that the gene used to reconstruct the phylogeny reflects the evolutionary history of the genes involved in the trait. We tested for recombination by reconstructing the phylogeny of two Wolbachia genes from seven B-subdivision strains. The two genes produced mutually incompatible topologies, indicating that these lineages are subject to genetic recombination. This means that many evolutionary patterns inferred from Wolbachia phylogenies must be re-evaluated. Furthermore, recombination may be an important feature both in the evolution of the manipulation phenotypes and avoidance of Müller's ratchet. Finally, we discuss the implications of recombination for attempts to genetically engineer Wolbachia for use in the control of crop pests and human pathogens.     

Q&A: Friends (but sometimes foes) within: the complex evolutionary ecology of symbioses between host and microbes

Over the past decade, there has been a pronounced shift in the study of host–microbe associations, with recognition that many of these associations are beneficial, and often critical, for a diverse array of hosts. There may also be pronounced benefits for the microbes, though this is less well empirically understood. Significant progress has been made in understanding how ecology and evolution shape simple associations between hosts and one or a few microbial species, and this work can serve as a foundation to study the ecology and evolution of host associations with their often complex microbial communities (microbiomes).     

Assisted Suicide in Switzerland: Clarifying Liberties and Claims

Assisting suicide is legal in Switzerland if it is offered without selfish motive to a person with decision‐making capacity. Although the ‘Swiss model’ for suicide assistance has been extensively described in the literature, the formally and informally protected liberties and claims of assistors and recipients of suicide assistance in Switzerland are incompletely captured in the literature. In this article, we describe the package of rights involved in the ‘Swiss model’ using the framework of Hohfeldian rights as modified by Wenar. After outlining this framework, we dissect the rights involved in suicide assistance in Switzerland, and compare it with the situation in England and Germany. Based on this approach, we conclude that in Switzerland, claim rights exist for those requesting suicide assistance, and for those who are considering providing such assistance, even though no entitlements exist toward suicide assistance. We then describe the implementation of the ‘Swiss model’ and difficulties arising within it. Clarifying these issues is important to understand the Swiss situation, to evaluate what features of it may or may not be worth correcting or emulating, and to understand how it can impact requests for suicide assistance in other countries due to ‘suicide tourism’. It is also important to understand exactly what sets Switzerland apart from other countries with different legislations regarding suicide assistance.     

Influence of aerobic microorganisms upon virus survival in soil

Survival of human poliovirus type 1 in a sandy loam soil appeared to be deleteriously influenced by aerobic microorganisms. This effect was determined by comparing the survival of virus in soil under four different possible combinations of aerobic versus anaerobic (H2-CO2) atmosphere and sterile versus nonsterile condition. Storage of samples was done in humid chambers to prevent soil desiccation. The effect attributed to aerobic microorganisms was measurable and statistically significant at all three incubation temperatures used in the study (1, 23, and 37 degrees C), with the increase in inactivation rate attributable to aerobic microorganisms generally being two to threefold. No comparable effect was observed to occur for anaerobic microorganisms under the sets of conditions employed in the study.     

Thermodynamics of mucopolysaccharide–dye binding. III. Thermodynamic and cooperativity parameters of acridine orange–heparin system

Binding isotherms for acridine orange (AO)–heparin systems can be evaluated solely on the basis of quantitative fluorescence spectroscopic measurements. The evaluation of thermodynamic parameters indicates that the interactions of AO with heparins from several animal sources are similar to each other in magnitude. Binding is highly exothermic (ΔH = ?6 kcal mol^?1) and is stabilized by dye–polymer and dye–dye (coopertive) interactions, as well as by entropic factors (ΔS = +7 e.u.). The predominant stabilizing factor appears to be the electrostatic attraction between the AO cation and the heparin polyanion, although the other factors are important as well. At 24°C the value of the cooperative binding constants for the various heparins range from 8.8 to 11.3 × 10⁵M^?1, corresponding to a free energy of ?8 kcal mol^?1. The degree of cooperativity, which is a direct measure of dye–dye interaction, varies with polymer:dye ratio; the theoretical basis for this variation remains to be elucidated. Electrophoretic data indicate that each heparin sample consists of a mixture of species, each with its own charge density. This precludes definitive interpretation of observed small differences in the values of the thermodynamic parameters among the various samples until each sample can be resolved into its components.