Properties of monovalent nickel complexes with tetraaza-macrocyclic ligands in aqueous solutions

The effects of N-alkylation on the redox potential of the couples NiLⁱ²⁺/NiLⁱ⁺, L = tetraaza-14-membered-macrocyclic ligands, and on the properties of the monovalent nickel complexes in aqueous solutions are reported for 14 complexes. The spectra and lifetimes of the NiLⁱ⁺ complexes are reported. The self-exchange rates for the couples NiLⁱ²⁺/NiLⁱ⁺ were determined. Two of the ligands were synthesized for the first time for this study. Cyclic voltammetry and pulse radiolysis were used. The results point out that: (i) N-alkylation always shifts the redox potential to a less cathodic one; this effect stems to a large degree from the decrease in the solvation energy of the complex caused by the N-alkylation of the ligand. (ii). The lifetime of the monovalent complexes is not linearly related to the redox potential of the NiLⁱ²⁺/NiLⁱ⁺ couples. (iii) The NiLⁱ⁺ complexes exist in several isomeric forms; the rate of the isomerization depends on the structure of the ligand. (iv) Different isomers of NiLⁱ⁺ may be formed when the complex NiLⁱ²⁺ is reduced by different reagents; therefore, the pulse-radiolytically formed NiLⁱ⁺ complexes might have different properties than those formed electrochemically.     

Boundaries of the pSC101 minimal replicon are conditional.

The DNA segment essential for plasmid replication commonly is referred to as the core or minimal replicon. We report here that host and plasmid genes and sites external to the core replicon of plasmid pSC101 determine the boundaries and competence of the replicon and also the efficiency of partitioning. Missense mutations in the plasmid-encoded RepA protein or mutation of the Escherichia coli topoisomerase I gene enable autonomous replication of a 310-bp pSC101 DNA fragment that contains only the actual replication origin plus binding sites for RepA and the host-encoded DnaA protein. However, in the absence of a repA or topA mutation, the DNA-bending protein integration host factor (IHF) and either of two cis-acting elements are required. One of these, the partitioning (par) locus, is known to promote negative DNA supercoiling; our data suggest that the effects of the other element, the inverted repeat (IR) sequences that overlap the repA promoter, are mediated through the IR's ability to bind RepA. The concentrations of RepA and DnaA, which interact with each other and with plasmid DNA in the origin region (T. T. Stenzel, T. MacAllister, and D. Bastia, Genes Dev. 5:1453-1463, 1991), also affect both replication and partitioning. Our results, which indicate that the sequence requirements for replication of pSC101 are conditional rather than absolute, compel reassessment of the definition of a core replicon. Additionally, they provide further evidence that the origin region RepA-DnaA-DNA complex initiating replication of pSC101 also mediates the partitioning of pSC101 plasmids at cell division.     

Interaction of workplace demands and cardiovascular reactivity in progression of carotid atherosclerosis: population based study.

OBJECTIVE: To examine the combined influence of workplace demands and changes in blood pressure induced by stress on the progression of carotid atherosclerosis. DESIGN: Population based follow up study of unestablished as well as traditional risk factors for carotid atherosclerosis, ischaemic heart disease, and other outcomes. SETTING: Eastern Finland. SUBJECTS: 591 men aged 42-60 who were fully employed at baseline and had complete data on the measures of carotid atherosclerosis, job demands, blood pressure reactivity, and covariates. MAIN OUTCOME MEASURES: Change in ultrasonographically assessed intima-media thickness of the right and left common carotid arteries from baseline to 4 year follow up. RESULTS: Significant interactions between workplace demands and stress induced reactivity were observed for all measures of progression (P < 0.04). Men with large changes in systolic blood pressure (20 mm Hg or greater) in anticipation of a maximal exercise test and with high job demands had 10-40% greater progression of mean (0.138 v 0.123 mm) and maximum (0.320 v 0.261 mm) intima-media thickness and plaque height (0.347 v 0.264) than men who were less reactive and had fewer job demands. Similar results were obtained after excluding men with prevalent ischaemic heart disease at baseline. Findings were strongest among men with at least 20% stenosis or non-stenotic plaque at baseline. In this subgroup reactive men with high job demands had more than 46% greater atherosclerotic progression than the others. Adjustment for atherosclerotic risk factors did not alter the results. CONCLUSIONS: Men who showed stress induced blood pressure reactivity and who reported high job demands experienced the greatest atherosclerotic progression, showing the association between dispositional risk characteristics and contextual determinants of disease and suggesting that behaviourally evoked cardiovascular reactivity may have a role in atherogenesis.     

Effects of the pSC101 partition (par) locus on in vivo DNA supercoiling near the plasmid replication origin.

Previous work has shown that deletion of the partition (par) locus of plasmid pSC101 results in decreased overall superhelical density of plasmid DNA and concommitant inability of the plasmid to be stably inherited in populations of dividing cells. We report here that the biological effects of par correlate specifically with its ability to generate supercoils in vivo near the origin of pSC101 DNA replication. Using OsO4 reactivity of nucleotides adjoining 20 bp (G-C) tracts introduced into pSC101 DNA to measure local DNA supercoiling, we found that the wild type par locus generates supercoiling near the plasmid's replication origin adequate to convert a (G-C) tract in the region to Z form DNA. A 4 bp deletion that decreases par function, but produces no change in the overall superhelicity of pSC101 DNA as determined by chloroquine/agarose gel analysis, nevertheless reduced (G-C) tract supercoiling sufficiently to eliminate OsO4 reactivity. Mutation of the bacterial topA gene, which results in stabilized inheritance of par-deleted plasmids, restored supercoiling of (G-C) tracts in these plasmids and increased OsO4 reactivity in par+ replicons. Removal of par to a site more distant from the origin decreased supercoiling in a (G-C) tract adjacent to the origin and diminished par function. Collectively, these findings indicate that par activity is dependent on its ability to produce supercoiling at the replication origin rather than on the overall superhelical density of the plasmid DNA.     

Rapid analysis of amino acids using pre-column derivatization

A new approach to the pre-column derivatization and analysis of amino acids is described. The method is based upon formation of a phenylthiocarbamyl derivative of the amino acids. The derivatization method is rapid, efficient, sensitive, and specific for the analysis of primary and secondary amino acids in protein hydorlyzates. The liquid chromatographic system allows for the rapid, bonded-phase separation with ultraviolet detection of the common amino acids with 12-min analysis time and a 1-pmol sensitivity.     

The mechanism of inhibition of ureogenesis by acidosis

In perfused rat liver a decrease of cytosol pH, determined with pH-sensitive microelectrodes7 from 7.2 to 6.85 is associated with a 50% fall in ureogenesis from ammonium chloride. In isolated rat hepatocytes the fall in ureogenesis due to acidosis is associated with decrease in the mitochondrial and cytosolic concentration of citrulline. Limitation of carbamoyl phosphate synthesis and thus citrulline supply could be responsible for the inhibition of ureogenesis observed.     

Ultrastructure and enzyme digestion of nucleoli and associated structures in hypothalamic nerve cells viewed in resinless sections

Estrogen has been shown to affect ventromedial hypothalamic (VMH) nerve cell nucleoli in ovariectomized rats, by causing an increase in the number of electron-dense aggregates associated with nucleoli. In order to characterize these nucleolus-associated structures and other nuclear components, we examined the ultrastructure of ventromedial hypothalamic nucleoli and nuclei revealed by enzyme digestions (pepsin, RNase and DNase) in resinless thin sections. Digestion by pepsin did not cause obvious alterations in the morphology of the nucleolus or its related structures. Pepsin treatment followed by RNase, however, reduced the density of the nucleolus, while that of the nucleolus-associated structure and other related structures remained unchanged. Conversely pepsin treatment followed by DNase, reduced the density of nucleolus-associated and other chromatin structures, but had no effect on the density of the nucleolus. Pepsin treatment followed by RNase and then DNase treatment, reduced the density of the nucleolus and nucleolus-associated structures. A residual nucleolus and nucleolus-associated structure remained after this treatment. Stereo viewing of resinless sections shows that the nucleolus, its associated structures, and other related structures, are associated with fine filaments that may comprise the nuclear matrix. The nucleolus-associated structure containing DNA may direct RNA synthesis at an increased rate in estrogen-treated hypothalamic cells.     

Febrile Gastroenteritis Due to Salmonella thompson—Report of an Outbreak

Salmonella thompson, a common pathogen of poultry, has received scant attention as a cause of human gastroenteritis. At least 45 persons were infected with S thompson in Sacramento, California, after eating at a chicken restaurant and 38 became symptomatic. Ten required admission to hospital, and all were treated with antibiotics and improved. In 19 cases cultures of stool specimens for S thompson over a 60-day period showed slower but statistically insignificant differences in salmonellal elimination in 7 patients who received antibiotics when compared with 12 who were untreated. We report this outbreak to increase awareness of the virulence and prevalence of gastroenteritis due to S thompson.     

Analogs of arachidonic acid methylated at C-7 and C-10 as inhibitors of leukotriene biosynthesis

The syntheses and biological activity of (all )-7,7-dimethyl-5-8,- 11,14-eicosatetraenoic acid, (all )-7,7,-dimethyl-5,8,11-eicosatrienoic acid, ( , -7,7-dimethyl-5,8-eicosadienoic acid, (all )-10,10-dimetyl- 5,8,11,14-eicosatetraenoic acid, (all -10,10-dimethyl-5,8,11-eicosatrienoic acid, and .-( , -15-hydroxy-7,7-dimethyl-5,8-eicosadienoic acid are described. These arachidonic acid analogs are all inhibitors of ionophore-induced SRS-A biosynthesis in rat peritoneal cells. Their mode of action may involve inhibition of phospholipase A₂ rather than Δ⁵-lipoxygenase. These compounds failed to exhibit significant activity in an model designed to detect inhibitors of antigen-induced, leukotriene-mediated bronchoconstriction is sensitized guinea pigs.