Transmission of Salmonella enterica serotype Typhimurium in poultry with and without antimicrobial selective pressure

AIMS: To determine the effect of antimicrobial selective pressure on the transmission of antimicrobial resistant and sensitive strains of Salmonella in poultry. METHODS AND RESULTS: Eight pens housed 12 broiler chicks each. Two chicks in four of the pens were inoculated with a Salm. Typhimurium strain resistant to 12 antimicrobials (including tetracycline), and two chicks in each of the four other pens were inoculated with a strain sensitive to all antimicrobials tested. Two pens inoculated with each strain were treated with chlortetracycline and two were not. Chicks were killed on day 7 and caeca were cultured for Salmonella. Experiments were performed independently twice. Chicks exposed to pen mates inoculated with the resistant strain and treated with tetracycline were 90% positive for Salmonella; whereas 60% of chicks given no antimicrobials were positive. Chicks exposed to the sensitive strain were 95% positive with tetracycline treatment and 90% positive without treatment. CONCLUSIONS: A multidrug-resistant Salm. Typhimurium strain had significantly increased transmission when chicks were treated with tetracycline. Transmission of a sensitive strain was not inhibited by antimicrobial selective pressure at recommended therapeutic dose. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates that antimicrobial usage may influence the transmission of antimicrobial-resistant pathogens in poultry.     

Morphological and functional changes in cardiac myocytes isolated from mice overexpressing TNF-alpha

Transgenic (TG) TNF1.6 mice, which cardiac specifically overexpress tumor necrosis factor-alpha (TNF-alpha), exhibit heart failure (HF) and increased mortality, which is markedly higher in young (<20 wk) males (TG-M) than females (TG-F). HF in this model may be partly caused by remodeling of the extracellular matrix and/or structure/function alterations at the single myocyte level. We studied left ventricular (LV) structure and function using echocardiography and LV myocyte morphometry, contractile function, and intracellular Ca(2+) (Ca(i)(2+)) handling using cell edge detection and fura 2 fluorescence, respectively, in 12-wk-old TG-M and TG-F mice and their wild-type (WT) littermates. TG-F mice showed LV hypertrophy without dilatation and only a small reduction of basal fractional shortening (FS) and response to isoproterenol (Iso). TG-M mice showed a large LV dilatation, higher mRNA levels of beta-myosin heavy chain and atrial natriuretic factor versus TG-F mice, reduced FS relative to both WT and TG-F mice, and minimal response to Iso. TG-F and TG-M myocytes were similarly elongated (by approximately 20%). The amplitude of Ca(i)(2+) transients and contractions and the response to Iso were comparable in WT and TG-F myocytes, whereas the time to 50% decline (TD(50%)) of the Ca(i)(2+) transient, an index of the rate of sarcoplasmic reticulum Ca(2+) uptake, was prolonged in TG-F myocytes. In TG-M myocytes, the amplitudes of Ca(i)(2+) transients and contractions were reduced, TD(50%) of the Ca(i)(2+) transient was prolonged, and the inotropic effect of Iso on Ca(i)(2+) transients was reduced approximately twofold versus WT myocytes. Protein expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 and phospholamban was unaltered in TG versus WT hearts, suggesting functional origins of impaired Ca(2+) handling in the former. These results indicate that cardiac-specific overexpression of TNF-alpha induces myocyte hypertrophy and gender-dependent alterations in Ca(i)(2+) handling and contractile function, which may at least partly account for changes in LV geometry and in vivo cardiac function in this model.     

Isolation and culture of rat microvascular endothelial cells

The purpose of this study is to identify the separation techniques that result in pure cultures of rat microvascular endothelial cells (MECs). A multistep process is used to optimize the separation of the cells from rat epididymal fat pads, obtaining as pure a culture as possible within a relatively short processing time. The process initially employs the digestion, filtration, and density gradient separation steps. We further describe the use of an attachment phase that allows the differential adherence of contaminating cell types. Immunomagnetic purification is the final step in the process and is performed using anti-PECAM-1 (CD31) monoclonal antibody-labeled DynaBeads.     

Human SIR2 deacetylates p53 and antagonizes PML/p53-induced cellular senescence

The yeast Sir2 protein mediates chromatin silencing through an intrinsic NAD-dependent histone deacetylase activity. Sir2 is a conserved protein and was recently shown to regulate lifespan extension both in budding yeast and worms. Here, we show that SIRT1, the human Sir2 homolog, is recruited to the promyelocytic leukemia protein (PML) nuclear bodies of mammalian cells upon overexpression of either PML or oncogenic Ras (Ha-rasV12). SIRT1 binds and deacetylates p53, a component of PML nuclear bodies, and it can repress p53-mediated transactivation. Moreover, we show that SIRT1 and p53 co-localize in nuclear bodies upon PML upregulation. When overexpressed in primary mouse embryo fibroblasts (MEFs), SIRT1 antagonizes PML-induced acetylation of p53 and rescues PML-mediated premature cellular senescence. Taken together, our data establish the SIRT1 deacetylase as a novel negative regulator of p53 function capable of modulating cellular senescence.     

Mitochondrial gene order is not conserved in arthropods: prostriate and metastriate tick mitochondrial genomes

The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes encode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are basal members of Ixodidae and have the same gene order as Limulus polyphemus. In contrast, in R. sanguineus, a block of genes encoding NADH dehydrogenase subunit 1 (ND1), tRNA(Leu)(UUR), tRNA(Leu)(CUN), 16S rDNA, tRNA(Val), 12S rDNA, the control region, and the tRNA(Ile) and tRNA(Gln) have translocated to a position between the tRNA(Glu) and tRNA(Phe) genes. The tRNA(Cys) gene has translocated between the control region and the tRNA(Met) gene, and the tRNA(Leu)(CUN) gene has translocated between the tRNA(Ser)(UCN) gene and the control region. Furthermore, the control region is duplicated, and both copies undergo concerted evolution. Primers that flank these rearrangements confirm that this gene order is conserved in all metastriate ticks examined. Correspondence analysis of amino acid and codon use in the two ticks and in nine other arthropod mitochondrial genomes indicate a strong bias in R. sanguineus towards amino acids encoded by AT-rich codons.      

Nucleotide polymorphism at the alcohol dehydrogenase locus of pocket gophers, genus Geomys

Using the strictly neutral model as a null hypothesis, we tested for deviations from expected levels of nucleotide polymorphism at the alcohol dehydrogenase locus (Adh-1) within and among four species of pocket gophers (Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G. attwateri). The complete protein-encoding region was examined, and 10 unique alleles, representing both electromorphic and cryptic alleles, were used to test hypotheses (e.g., the neutral model) concerning the maintenance of genetic variation. Nineteen variable sites were identified among the 10 alleles examined, including 9 segregating sites occurring in synonymous positions and 10 that were nonsynonymous. Several statistical methods, including those that test for within-species variation as well as those that examine variation within and among species, failed to reject the null hypothesis that variation (both within and between species of Geomys) at the Adh locus is consistent with the neutral theory. However, there was significant heterogeneity in the ratio of polymorphism to divergence across the gene, with polymorphisms clustered in the first half of the coding region and fixed differences clustered in the second half of the gene. Two alternative hypotheses are discussed as possible explanations for this heterogeneity: an old balanced polymorphism in the first half of the gene or a recent selective sweep in the second half of the gene.      

Effects of hypophysectomy and thyroidectomy on salt balance in the plethodontid salamanders,Desmognathus fuscus andDesmognathus monticola

Summary Hypophysectomy significantly reduced serum sodium levels inDesmognathus fuscus andD. monticola. Prolactin, corticosterone or aldosterone replacement failed to restore serum sodium to control levels. Hypophysectomy also led to decreases in in vitro integumental potential difference and shortcircuit current, which were not restored to control levels by prolactin or corticosterone. Thyroidectomy significantly reduced the level of serum sodium inD. monticola, but it increased in vitro potential difference and short-circuit current. Thyroxine treatment of either hypophysectomized or thyroidectomizedD. monticola completely restored serum sodium, potential difference and short-circuite current to control levels.