Gas chromatographic determination of low concentrations of benzoic acid in human plasma and urine

A method for the determination of benzoic acid down to concentrations of 10 ng/ml in plasma or urine is described. After addition of an internal standard, benzoic acid is extracted at acid pH into diethyl ether. Both compounds are derivatized with pentafluorobenzyl bromide. The derivatives are determined by gas chromatography using a ⁴³Ni electron-capture detector. Hippuric acid is hydrolysed in plasma and urine and total benzoic acid is determined by the same technique.     

The cya gene region of Erwinia chrysanthemi B374: organisation and gene products

Summary A DNA fragment containing the cya gene region of Erwinia chrysanthemi, B374 was cloned in vivo and transferred into cells of E. coli using a plasmid pULB113 derived from RP4 followed by subcloning in vitro into the vector pBR322. The cya gene encodes a 95 kDal protein that complemented E. coli cya mutants. Apparently, cya genes truncated at the 3 end could still produce proteins complementing cya-defective strains, thus showing that adenylate cyclase truncated at its carboxy-terminal end could synthesise cAMP. A protein of unknown function (40 kDal) is encoded by a gene that is transcribed divergently from the control region of the adenylate cyclase gene.     

Detailed cell cycle analysis in human lymphocytes; Application to γ-irradiated cells

Summary A method based on BrdU incorporation for analyzing in detail the kinetics of the cell cycle is described. The S phase has been subdivided into five subphases, each recognizable by their BrdU incorporation pattern at metaphase. The method can be useful for the study of abnormal cell cycles, and may have particular application in mutagenesis studies concerning the various subphases of the S phase, without using synchronization techniques. An application of the method is described, showing that -irradiation, during the course of the S phase, leads to a lack of cells which were in early S phase at the time of irradiation. This finding can be related either to a higher lethality at this stage of the cell cycle or to a delay in completion of DNA replication after irradiation.Hoider of a C.E.C. scholarship     

Foraging behaviour at multiple temporal scales in a wild alpine equid

Forage abundance, forage quality, and social factors are key elements of the foraging ecology of wild herbivores. For non-ruminant equids, forage-limited environments are likely to impose severe constraints on their foraging behaviour. We used a multi-scale approach to study foraging behaviour in kiang (Equus kiang), a wild equid inhabiting the high-altitude rangelands of the Tibetan Plateau. Using behavioural observations and vegetation sampling, we first assessed how patterns of plant abundance and quality affected (i) the instantaneous forage intake rate (fine scale) and (ii) the proportion of time spent foraging (coarse scale) across seasons. We also tested whether foraging behaviour differed among group types, between sex in adults, and between females of different reproductive status. At a fine scale, intake rate increased linearly with bite size and increased following a type II curvilinear function with biomass on feeding sites. Forage intake rate also increased linearly with plant quality. Male and female kiangs had similar intake rates. Likewise, gravid and lactating females had similar intake rates as barren and non-lactating females. At a coarse scale, kiangs spent longer time feeding in mesic than in xeric habitats, and spent more time feeding in early summer and fall than in late summer. Groups of adults with foals spent less time feeding than male groups and groups of adults without foals. Our findings suggest that kiangs use flexible foraging behaviours in relation to seasonal variations of vegetation quality and abundance, a likely outcome of the extreme seasonal conditions encountered on the Tibetan Plateau.     

Genomic organization and primary structure of five homologous pairs of intron-less genes encoding secretory globins from the insect Chironomus thummi thummi

From a Chironomus thummi thummi genomic library we have isolated two distinct recombinant phages, CttG-1 and CttG-3, each carrying a cluster of five homologous globin genes. In addition to the previously reported nucleotide sequence of globin gene D (Antoine and Niessing, 1984) we present the chromosomal arrangement, primary structure and predicted amino acid sequence of nine globin genes. The divergently transcribed globin genes all lack introns, they encode secretory preglobins each containing a highly conserved signal peptide. The amino acid sequences deduced from the globin genes correspond to globin III and variants thereof, to globin IV, and to a novel globin, whose direct amino acid sequence has not yet been reported.     

Caspase-1 activation by Salmonella

Salmonella is an interesting example of how the selective pressure of host environments has led to the evolution of sophisticated bacterial virulence mechanisms. This microbe exploits the first-line of defence, the macrophage, as a crucial tool in the initiation of disease. After invasion of intestinal macrophages, a virulence protein secreted by Salmonella specifically induces apoptotic cell death by activating the cysteine protease caspase-1. The pro-apoptotic capability is necessary for successful pathogenesis. The study of mechanisms by which Salmonella induces programmed cell death offers new insights into how pathogens cause disease and into general mechanisms of activation of the innate immune system.     

Dissecting the genetic components of adaptation of Escherichia coli to the mouse gut

While pleiotropic adaptive mutations are thought to be central for evolution, little is known on the downstream molecular effects allowing adaptation to complex ecologically relevant environments. Here we show that Escherichia coli MG1655 adapts rapidly to the intestine of germ-free mice by single point mutations in EnvZ/OmpR two-component signal transduction system, which controls more than 100 genes. The selective advantage conferred by the mutations that modulate EnvZ/OmpR activities was the result of their independent and additive effects on flagellin expression and permeability. These results obtained in vivo thus suggest that global regulators may have evolved to coordinate activities that need to be fine-tuned simultaneously during adaptation to complex environments and that mutations in such regulators permit adjustment of the boundaries of physiological adaptation when switching between two very distinct environments.