Parenteral supplementation with zinc in surgical patients corrects postoperative serum-zinc drop

Zinc has been known for a long time to facilitate wound healing. But, so far, supplementation trials in patients treated by major severity surgery gave either partial or controversial results. In a double-blind, randomized study including 30 patients, we show that zinc supplements (30 mg/d for 3 d) administered by a drip correct postoperative drop of serum zinc, that this correction concerns the available part of serum zinc (i.e., zinc that is bound to compounds other than alpha-2 macroglobulin in serum), and that this supplementation can improve clinical wound healing. Possible influence of increased urinary output after the intervention is discussed, and we found that serum cortisol remains stable when zinc/albumin ratio is stable, and increases sharply when the same ratio drops. Cortisol, therefore, seems to play a major role in zinc redistribution after surgery.     

Effect of taurine,l-glutamine and l-histidine addition in an amino acid glucose solution on the cellular bioavailability of zinc

Radioactive zinc was used to study the effect of a binary parenteral nutrient solution, composed of amino acids and glucose, on zinc uptake by fibroblasts. The influence of addition of taurine, l-glutamine and of the increase in l-histidine content of the admixture was assessed. The pure mixture was highly toxic for cells and so it was diluted 1/5 in tyrode buffer with 2% albumin. As compared with cells incubated in the buffer containing albumin, zinc absorption was significantly higher (P < 0.05) in the presence of the amino acids of the mixture. Amino acids thus increased bioavailability by displacing zinc bound to albumin. When the histidine concentration in the nutrient medium (4.2 mm) was doubled, inhibition was noted after 30 min of incubation and zinc uptake thereafter remained comparable to that in histidine-free medium. The addition of glutamine (4.2 mm), usually not present in binary mixtures, resulted in significant differences as compared with glutamine-free control medium. Taurine (0.8 mm), led to a constant increase in zinc uptake by fibroblasts as compared with that obtained with taurine-free mixture. However, ultrafiltration showed that taurine was not able to displace zinc from albumin.     

Differential regulation of keratin 8 and 18 messenger RNAs in differentiating F9 cells.

F9 embryonal carcinoma cells (F9EC) can be induced to differentiate in vitro into epithelial cells expressing keratin 8 (K8) and keratin 18 (K18). cDNAs corresponding to K8 and K18 mRNAs were cloned and used to study the change in the abundance of these mRNAs during differentiation of F9 cells into parietal endoderm-like cells by treatment with retinoic acid (RA) or with RA and dibutyryl cAMP (Bt2cAMP). Using an RNase protection assay, it was determined that K8 mRNA was induced slightly before K18 mRNA and that it accumulated to a greater extent than K18 mRNA. Furthermore, differentiation in presence of Bt2cAMP plus RA resulted in an earlier induction of the two mRNAs and a higher level of expression of K8 mRNA. These results indicate that K8 and K18 mRNAs are regulated differently in F9 cells.     

Ecologically based definition of seasons clarifies predator–prey interactions

Species interactions within food webs are driven by multiple constraints, including those imposed by seasonal changes in the environment. Ecologically sound definitions of seasons may therefore be a prerequisite for clarifying predator prey interactions. Most studies define biological seasons based on fixed schedules or on temporal changes in a single movement measurement. We used a novel clustering approach based on homogeneous space‐use patterns of GPS‐collared animals to reveal 7 biological seasons for caribou Rangifer tarandus caribou, and 5 for both moose Alces alces and grey wolves Canis lupus interacting in a boreal ecosystem. Subsequent evaluation of niche overlap showed that, as predicted, wolves had a stronger spatio‐temporal connection with moose, its main prey, than with caribou. Movement constraints and limiting resource distributions similarly affected all species in some instances, but also caused temporal changes in the extent of niche overlap between wolves and its two prey. The risk that caribou faced was not only linked to the niche overlap with wolves, but also to the extent of wolf‐moose niche overlap during the same period. Food‐web properties emerged from the analysis, with temporal changes in relative niche overlap reflecting the strength of trophic interactions during the year. Our study demonstrates how the study of trophic interactions can benefit from comprehensive definitions of biological seasons.     

Exogenous H(2)O(2) and catalase treatments interfere with Tri genes expression in liquid cultures of Fusarium graminearum

Effect of exogenous H(2)O(2) and catalase was tested in liquid cultures of the deoxynivalenol and 15-acetyldeoxynivalenol-producing fungus Fusarium graminearum. Accordingly to previous results, H(2)O(2) supplementation of the culture medium leads to increased toxin production. This study indicates that this event seems to be linked to a general up regulation of genes involved in the deoxynivalenol and 15-acetyldeoxynivalenol biosynthesis pathway, commonly named Tri genes. In catalase-treated cultures, toxin accumulation is reduced, and Tri genes expression is significantly down regulated. Furthermore, kinetics of expression of several Tri genes is proposed in relation to toxin accumulation. Biological meanings of these findings are discussed.     

Reaction of Mycobacterium tuberculosis truncated hemoglobin O with hydrogen peroxide: evidence for peroxidatic activity and formation of protein-based radicals

In this work, we investigated the reaction of ferric Mycobacterium tuberculosis truncated hemoglobin O (trHbO) with hydrogen peroxide. Stopped-flow spectrophotometric experiments under single turnover conditions showed that trHbO reacts with H(2)O(2) to give transient intermediate(s), among which is an oxyferryl heme, different from a typical peroxidase Compound I (oxyferryl heme pi-cation radical). EPR spectroscopy indicated evidence for both tryptophanyl and tyrosyl radicals, whereas redox titrations demonstrated that the peroxide-treated protein product retains 2 oxidizing eq. We propose that Compound I formed transiently is reduced with concomitant oxidation of Trp(G8) to give the detected oxoferryl heme and a radical on Trp(G8) (detected by EPR of the trHbO Tyr(CD1)Phe mutant). In the wild-type protein, the Trp(G8) radical is in turn reduced rapidly by Tyr(CD1). In a second cycle, Trp(G8) may be reoxidized by the ferryl heme to yield ferric heme and two protein radicals. In turn, these migrate to form tyrosyl radicals on Tyr(55) and Tyr(115), which lead, in the absence of a reducing substrate, to oligomerization of the protein. Steady-state kinetics in the presence of H(2)O(2) and the one-electron donor 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) indicated that trHbO has peroxidase activity, in accord with the presence of typical peroxidase intermediates. These findings suggest an oxidation/reduction function for trHbO and, by analogy, for other Group II trHbs.     

Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.