The deviation from linkage equilibrium with multiple loci varying in a stepping-stone cline

The balance between the creation of associations between alleles at different loci by immigration and the convergence to linkage equilibrium due to the recombination process is studied in a theoretical model. The geographical structure of the model is a stepping-stone chain of populations linking two genetically constant source populations. The model assumes an arbitrary number of autosomal loci and considers genetic variation (two alleles at each locus) that is not subject to natural selection. The gene frequencies at each locus will then show a linear cline through the stepping-stone chain of populations. The deviation from linkage equilibrium through the stepping-stone cline is characterized by an equation for linear measures that provide the linkage disequilibrium measures for a given set of loci in terms of the gene frequencies and the linkage disequilibria in the source populations and in terms of the linkage disequilibrium measures through the cline for lower numbers of loci. Numerical examples of this iterative solution are given, and it is shown that the build-up of the higher order Bennett-disequilibria through the cline is considerably more pronounced than the build-up of two-locus disequilibria.     

The structures of oligosaccharides excreted by sheep with swainsonine toxicosis

Eleven oligosaccharides were purified form the urine of sheep with swainsonine toxicosis induced by the feeding of Astragalus lentiginosus. Oligosaccharides were extracted by charcoal adsorption, chromatographed on Bio-Gel P-2, and partially fractionated by preparative-layer chromatography. Separation into individual compounds was completed by semi-preparative high pressure liquid chromatography. Structures were determined by a combination of high pressure liquid chromatography and exo- and endo- glycosidase action, methanolysis followed by gas-liquid chromatography, methylation analysis, and high resolution nuclear magnetic resonance spectroscopy. Two homologous series of oligosaccharides were identified: (a) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp+ ++-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----2)-alpha-D-Manp(1----3)-[alpha-D-Manp+ ++-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----2)-alpha-D-Manp-(1----2)-alpha-D-Manp+ ++-(1----3)-[alpha- D-Manp-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc (minor series); (b) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-alpha-D-Manp-(1----6)-beta-D-Manp -(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----6)-alpha-D-Manp-(1----6)-beta-D-Manp++ +-(1----4)-beta-D-GlcpNAc - (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-alpha-D-Manp-(1----6)-[alpha-D-Manp -(1----3)]-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)- [alpha-D-Manp-(1----3)]-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D- GlcpNAc (major series).     

Oligosaccharides from placenta: early diagnosis of feline mannosidosis

High-pressure liquid chromatography analysis of oligosaccharides from placentas allowed the diagnosis of alpha-mannosidosis in three litters of kittens. The chromatography also afforded a detailed comparison of the oligosaccharide pattern and levels in placenta, liver, brain, urine and ocular fluid of the affected animals. In all cases, two series of compounds were observed, with one or two residues of N-acetylglucosamine at the reducing terminus, respectively, and between two and nine mannose residues. This pattern is unlike that of human mannosidosis, and resembles that of ruminants, except that the major oligosaccharide contains three mannose residues instead of two.     

Comparison of ccd of F, parDE of RP4, and parD of R1 using a novel conditional replication control system of plasmid R1

A number of plasmid-encoded gene systems are thought to stabilize plasmids by killing plasmid-free cells (also termed post-segregational killing or plasmid addiction). Here we analyse the mechanisms of plasmid stabilization by ccd of F, parDE of RP4 and parD of R1, and compare them to hok/sok of R1. To induce synchronous plasmid loss we constructed a novel plasmid replication-arrest system, which possesses the advantage that plasmid replication can be completely arrested by the addition of IPTG, a non-metabolizable inducer. Using isogenic plasmid constructions we have found, for the first time, consistent correlation between the effect on steady-state loss rates and the effect on cell proliferation in the plasmid replication-arrest assay for all three systems. The parDE system had the most pronounced effect both on plasmid stabilization and on plasmid retention after replication arrest. In contrast, ccd and parD both exhibited weaker effects than anticipated from previously published results. Thus, our results indicate that the function and efficiencies of some of the systems should be reconsidered. Our results are consistent with the previously postulated hypothesis that ccd and parDE act by killing plasmid-free segregants, whereas parD seems to act by inhibiting cell division of plasmid-free segregants.     

2,4-D-Induced Changes in the K+ Uptake of Wheat Roots at Different pH Values

The effects of an auxin herbicide, 2,4-D, at a concentration of 0.01 mM, on the K⁺ uptake and efflux of excised roots of wheat (Triticum aestivum L. cv. Rannaya) were investigated at different pH values. The K⁺ movement was monitored with a K⁺ (⁸⁶Rb) tracer. In parallel experiments the ATPase activities of microsomal fractions were determined by the inorganic phosphate liberation method. 2,4-D inhibited the K⁺ uptake especially at low pH, irrespective of whether Ca²⁺ was present or not. No marked changes were observed in the K⁺ efflux properties at pH values above 4. The inhibitory effect on K⁺ uptake exhibited a correlation with the hydrocarbon solubility of the herbicide, but not with the 2,4-D-induced decrease of the ATPase activity. It is suggested that 2,4-D exerts a non-specific effect on the lipid-protein interactions, giving rise to a generalized alteration of the transport barrier properties of the plasma membrane even at as low a concentration as 0.01 mM.     

Effect of acetylcholine on growth and isoperoxidases of the lentil(Lens culinaris) root

The effects of acetylcholine (Ach) on growth, the total peroxidase activity and the isoperoxidase spectrum of the roots ofLens culinaris were studied and compared with actual and earlier results obtained with an auxin (IAA) treatment. The general growth and peroxidase activity patterns of Ach treated roots and IAA treated ones showed many important similarities.     

The cephalic arterial system in carnivores, with special reference to the systematic classification

The cephalic arterial pattern in 53 fissipeds, representing all the classical families, is described on the basis of corrosion casts prepared by means of a special plastic injection and corrosion technique. The results are discussed on an ontogenetic and phylogenetic basis and related to current theories on the systematic classification of fissipeds at a higher taxonomic level (infraorders or superfamilies). In this respect, especially the systematic position of the canids and hyaenids in relation to the felids is discussed, the greatest importance being attached to the contribution of the external carotid artery system to the intracranial circulation. Also the very specific cephalic arterial pattern in the herpestines, one of the two viverrid subfamilies studied, is emphasized.     

Real-time monitoring of cell viability and cell density on the basis of a three dimensional optical reflectance method (3D-ORM): investigation of the effect of sub-lethal and lethal injuries

Cell density and cell viability have been followed on-line by using a three-dimensional optical reflectance method (3D-ORM) probe. This method has allowed to highlight the differences between a well-mixed and a scale-down bioreactor configured in order to reproduce mixing deficiencies during a fed-batch culture of Escherichia coli. These differences have been observed both for the obscuration factor (OBF) and the coincidence probability delivered by the probe. These parameters are correlated to flow cytometry measurement based on the PI-uptake test and cell density based on optical density measurement. This first set of results has pointed out the fact that the 3D-ORM probe is sensitive to sub-lethal injuries encountered by microbial cells in process-related conditions. The effect of lethal injuries has been further investigated on the basis of additional experiments involving heat stress and a sharp increase of the OBF has been observed indicating that cells are effectively injured by the increase of temperature. However, further improvement of the probe are needed in order to give access to single-cell measurements.