Oral colistin sulfate in pigs: pharmacokinetics and effect on fecal Escherichia coli excretion of weaned pigs challenged with Escherichia coli F4 (K88)

Colistin sulfate (CS), a polymyxin antibiotic, is used in Canada for the treatment of post-weaning diarrhea in pigs as an alternative to neomycin. The aim of the present study was to evaluate some pharmcokinetics parameters of CS and its effect on the evolution of the intestinal Escherichia coli population in pigs challenged with enterotoxigenic E. coli (ETEC): F4

Impacts of colistin sulfate on fecal Escherichia coli resistance and on growth performance of piglets in a post-weaning diarrhea model

Colistin sulfate (CS) is used in Canada for the treatment of post weaning diarrhea (PWD), to overcome conventional therapeutic antibiotics failures. The aim of the present study was to determine the effect of a conventional oral regimen of CS for the treatment of PWD, on the development of E. coli CS resistance and to evaluate the effect of ETEC: F4 infection on CS intestinal absorption. A total of 48 pigs were used, challenge was carried out by oral administration of 109CFU of a hemolytic ETEC: F4 strain resistant to nalidixic acid. CS was administered at a dose of 50.000 UI/kg twice a day for 5 days. Feces were examined clinically and bacteriologically before and after challenge to evaluate presence of diarrhea and E. coli fecal excretion. ETEC: F4 virulence factors were monitored and CS plasma concentrations were quantified by an HPLC-MS/MS. From one until six days after CS administration, a significant reduction in the fecal excretion of ETEC: F4, total E. coli, ETEC: F4 virulence factors and in diarrhea scores was observed in the challenged treated group compared to the challenged untreated group (p\u3c0.0001). No significant difference in growth performances was observed in treated compared to non-treated pigs (p\u3e0.71). A significant selection pressure on E. coli total population was observed following CS treatment (p\u3c0.0001). Challenge with ETEC: F4 resulted in an increase in intestinal absorption of CS. Our study is the first to demonstrate in an experimental model of PWD, that CS at a dose of 50,000 IU/kg is effective in reducing fecal excretion of E. coli. However, this regimen was associated with a selection pressure on E. coli CS resistance, and did not improve growth performance in challenged pigs. Thus, the use of this antibiotic in pig should be revised

Neutron to proton ratios of quasiprojectile and midrapidity emission in the 64^{64}Zn + 64^{64}Zn reaction at 45 MeV/nucleon

Simultaneous measurement of both neutrons and charged particles emitted in the reaction $^{64}$Zn + $^{64}$Zn at 45 MeV/nucleon allows comparison of the neutron to proton ratio at midrapidity with that at projectile rapidity. The evolution of N/Z in both rapidity regimes with increasing centrality is examined. For the completely re-constructed midrapidity material one finds that the neutron-to-proton ratio is above that of the overall $^{64}$Zn + $^{64}$Zn system. In contrast, the re-constructed ratio for the quasiprojectile is below that of the overall system. This difference provides the most complete evidence to date of neutron enrichment of midrapidity nuclear matter at the expense of the quasiprojectile

Red Clover Improves the Energy to Protein Balance of Lucerne-Grass Herbage

Low ratio of readily fermentable carbohydrate to soluble protein concentrations in lucerne (Medicago sativa L.) leads to inefficient use of herbage N by ruminants. To improve the energy to protein balance in lucerne-grass herbage, four proportions of lucerne:red clover (Trifolium pratense L.) were compared in mixtures with and without grasses: timothy (Phleum pratense L.) and tall fescue (Schedonorus arundinaceus Schreb. Dumort.) in Quebec (QC, Canada). In the first post-seeding year, red clover proportion averaged (across grasses and four harvests) 0, 37, 59, and 74% in herbage mixtures. Increasing the proportion of red clover caused a slight but significant decrease in herbage total nitrogen (TN) concentration (32 to 31 g kg-1 DM) but substantial decreases in non-protein N (PA), rapidly (PB1) and moderately (PB2) degraded protein fractions, and a significant increase in the slowly degraded protein fractions (PB3+PC) (157 to 308 g kg-1 TN). With the inclusion of 74% of red clover, the ratio of soluble sugar to crude protein (CP) in herbage increased from 0.25 to 0.36 because of the increase in the soluble sugar concentration (48 to 66 g kg-1 DM). The inclusion of red clover in mixture with lucerne improved the energy to CP balance compared to lucerne alone, and caused a linear increase in the herbage in vitro neutral detergent fiber digestibility from 568 to 639 g kg-1 aNDF with similar herbage dry matter yield (10.3 Mg ha-1)

Addition of Red Clover or Birdsfoot Trefoil in Alfalfa-based Mixtures to Improve the Forage Energy to Protein Balance

The low ratio of sugars (S) to crude proteins (CP) in alfalfa (AL, Medicago sativa L.) leads to inefficient use of nitrogen by ruminants. The objective was to determine if adding red clover (RC, Trifolium pratense L.) or birdsfoot trefoil (BT, Lotus corniculatus L.) with or without a grass species to AL improved the forage S/CP ratio. Treatments were 100% AL (control) or AL-based mixtures with RC or BT in three proportions (75, 50, or 25% of seeded legumes) with either no grass or with timothy (Phleum pratense L.) or tall fescue (Schedonorus arundinaceus Schreb. Dumort.), resulting in 21 treatments assigned to a randomized complete block design with four replications at three sites in Canada (Agassiz, BC; St-Anne-de-Bellevue, QC; StAugustin-de-Desmaures, QC). Species contribution and nutritive attributes measured at each harvest were weighted for yield as a proportion of the seasonal yield and expressed yearly for the first two post-seeding years. Regression analyses showed that forage S concentration increased, CP concentration tended to decrease, and the S/CP ratio increased from 0.3 to 0.5 (y = 0.002 x + 0.3; P = 0.003, R2 = 0.53) with the addition of up to 92% RC or up to 66% BT to AL-based mixtures. The addition of up to 61% TI or 55% TF did not impact the S/CP ratio of AL-based mixtures. Further studies are needed to determine if the improved forage S/CP ratio following the addition of RC or BT to AL-based mixtures leads to an improved N-use efficiency in ruminants

Variable-spectral-response optical waveguide Bragg grating filters for optical signal processing

A simple method is described that permits the spectral response (spectral width, shape, and center resonant wavelength) of an optical waveguide Bragg grating to be controlled accurately in a prescribed manner. The control methodology consists of bonding the Bragg grating along the length of a mechanical support structure, which is then loaded with an appropriate force distribution. The function of the support structure is to transfer the strain induced by loading to the grating, thus modifying the grating’s spectral response in accordance with the variation in effective optical pitch induced by the strain transfer. We design and demonstrate a support structure that provides independent control over the spectral width and center wavelength of a Bragg grating

Correlation effects on electronic transport through dots and wires

We investigate how two-particle interactions affect the electronic transport through meso- and nanoscopic systems of two different types: quantum dots with local Coulomb correlations and quasi one-dimensional quantum wires of interacting electrons. A recently developed functional renormalization group scheme is used that allows to investigate systems of complex geometry. Considering simple setups we show that the method includes the essential aspects of Luttinger liquid physics (one-dimensional wires) as well as of the physics of local correlations, with the Kondo effect being an important example. For more complex systems of coupled dots and Y-junctions of interacting wires we find surprising new correlation effects.Comment: to appear in "Advances in Solid State Physics" Volume 46, Ed. R. Haug (Springer, 2006