Investigation of bacteriophage MS2 viral dynamics using model discrimination analysis and the implications for phage therapy

Lytic phages infect their bacterial hosts, use the host machinery to replicate, and finally lyse and kill their hosts, releasing progeny phages. Various mathematical models have been developed that describe these phage-host viral dynamics. The aim of this study was to determine which of these models best describes the viral dynamics of lytic RNA phage MS2 and its host Escherichia coli C-3000. Experimental data consisted of uninfected and infected bacterial cell densities, free phage density, and substrate concentration. Parameters of various models were either determined directly through other experimental techniques or estimated using regression analysis of the experimental data. The models were evaluated using a Bayesian-based model discrimination technique. Through model discrimination it was shown that phage-resistant cells inhibited the growth of phage population. It was also shown that the uninfected bacterial population was a quasispecies consisting of phage-sensitive and phage-resistant bacterial cells. When there was a phage attack the phage-sensitive cells died out and the phage-resistant cells were selected for and became the dominant strain of the bacterial population.     

Temperature acclimation in a biochemical model of photosynthesis: a reanalysis of data from 36 species

The Farquhar et al. model of C(3) photosynthesis is frequently used to study the effect of global changes on the biosphere. Its two main parameters representing photosynthetic capacity, V(cmax) and J(max), have been observed to acclimate to plant growth temperature for single species, but a general formulation has never been derived. Here, we present a reanalysis of data from 36 plant species to quantify the temperature dependence of V(cmax) and J(max) with a focus on plant growth temperature, i.e. the plants' average ambient temperature during the preceding month. The temperature dependence of V(cmax) and J(max) within each data set was described very well by a modified Arrhenius function that accounts for a decrease of V(cmax) and J(max) at high temperatures. Three parameters were optimized: base rate, activation energy and entropy term. An effect of plant growth temperature on base rate and activation energy could not be observed, but it significantly affected the entropy term. This caused the optimum temperature of V(cmax) and J(max) to increase by 0.44 degrees C and 0.33 degrees C per 1 degrees C increase of growth temperature. While the base rate of V(cmax) and J(max) seemed not to be affected, the ratio J(max) : V(cmax) at 25 degrees C significantly decreased with increasing growth temperature. This moderate temperature acclimation is sufficient to double-modelled photosynthesis at 40 degrees C, if plants are grown at 25 degrees C instead of 17 degrees C.     

Molecular characterization of porcine hyaluronidase genes 1, 2, and 3 clustered on SSC13q21

Hyaluronidase genes (HYAL) encode hyaluronidase enzymes required for hyaluronan degradation. Both in humans and in mouse, clustered hyaluronidase genes have been identified. Here, the porcine hyaluronidase cluster consisting of genes HYAL1, HYAL2 and HYAL3 was characterized. The porcine cDNA sequences and proteins share homologies to human orthologs of 85 and 81% for HYAL1, 87 and 89% for HYAL2 and 86 and 83% for HYAL3, respectively. The porcine hyaluronidase proteins approximately share a 40% homology with each other. Furthermore, genes FUS1 and FUS2 were found within this cluster, which was assigned to SSC13q21. A total of seven SNPs were detected in the genes (four in HYAL1, two in HYAL2 and one in HYAL3). Three of the four SNPs in HYAL1 led to amino acid exchanges (C622G --> Asp24 to Glu; C633T --> Pro28 to Leu, and G1298T --> Ala250 to Ser). The amino acid replacements induce putative changes in the extended strand at Asp24, in the extended strand and the random coil at Pro28, and finally in the random coil and the alpha helix at Ala250. Frequency estimations for four SNPs located in genes HYAL1 and HYAL3 using animals (n = 295) of nine European and six Chinese pig breeds indicated several significant deviations. For example, there were no significant differences in allele frequencies between pigs representing breeds Hampshire and Jiangquhai at SNP C633T (HYAL1), but between Hampshire respectively Jiangquhai animals and Rongchang pigs. Analysis of the same breeds at SNP C588T (HYAL3) indicates significant differences between Hampshire and Jiangquhai respectively Rongchang, but not between Jiangquhai and Rongchang. The breed G?ttingen Minipig displayed significant differences concerning two SNPs with respect to the other European pig breeds tested. For all three hyaluronidase genes, N-glycosylation sites are typical. For HYAL2 the lysosomal character was proven. The catalytic site responsible for HAase activity is conserved in the three enzymes. Expression of hyaluronidases was determined by RT-PCR and quantitative PCR. Broad gene expression was observed in different tissues for the three genes, respectively.     

Omega-3 fatty acids deprivation affects ontogeny of glutamatergic synapses in rats: Relevance for behavior alterations

Essential omega-3 polyunsaturated fatty acids (ω3) are crucial to brain development and function, being relevant for behavioral performance. In the present study we examined the influence of dietary ω3 in the development of the glutamatergic system and on behavior parameters in rats. Female rats received isocaloric diets, either with ω3 (ω3 group) or a ω3 deficient diet (D group). In ontogeny experiments of their litters, hippocampal immunocontent of ionotropic NMDA and AMPA glutamatergic receptors subunits (NR2 A\B and GluR1, respectively) and the alpha isoform of the calcium-calmodulin protein kinase type II (αCaMKII) were evaluated. Additionally, hippocampal [³H]glutamate binding and uptake were assessed. Behavioral performance was evaluated when the litters were adult (60 days old), through the open-field, plus-maze, inhibitory avoidance and flinch-jump tasks. The D group showed decreased immunocontent of all proteins analyzed at 02 days of life (P2) in comparison with the ω3 group, although the difference disappeared at 21 days of life (except for αCaMKII, which content normalized at 60 days old). The same pattern was found for [³H]glutamate binding, whereas [³H]glutamate uptake was not affected. The D group also showed memory deficits in the inhibitory avoidance, increased in the exploratory pattern in open-field, and anxiety-like behavior in plus-maze. Taken together, our results suggest that dietary ω3 content is relevant for glutamatergic system development and for behavioral performance in adulthood. The putative correlation among the neurochemical and behavioral alterations caused by dietary ω3 deficiency is discussed.     

Intraperitoneal delivery of human natural killer cells for treatment of ovarian cancer in a mouse xenograft model

Background aimsThere is an urgent need for novel therapeutic strategies for relapsed ovarian cancer. Dramatic clinical anti-tumor effects have been observed with interleukin (IL)-2 activated natural killer (NK) cells; however, intravenous delivery of NK cells in patients with ovarian cancer has not been successful in ameliorating disease. We investigated in vivo engraftment of intraperitoneally (IP) delivered NK cells in an ovarian cancer xenograft model to determine if delivery mode can affect tumor cell killing and circumvent lack of NK cell expansion.MethodsAn ovarian cancer xenograft mouse model was established to evaluate efficacy of IP-delivered NK cells. Tumor burden was monitored by bioluminescent imaging of luciferase-expressing ovarian cancer cells. NK cell persistence, tumor burden and NK cell trafficking were evaluated. Transplanted NK cells were evaluated by flow cytometry and cytotoxicity assays.ResultsIP delivery of human NK cells plus cytokines led to high levels of circulating NK and was effective in clearing intraperitoneal ovarian cancer burden in xenografted mice. NK cells remained within the peritoneal cavity 54 days after injection and had markers of maturation. Additionally, surviving NK cells were able to kill ovarian cancer cells at a rate similar to pre-infusion levels, supporting that in vivo functionality of human NK cells can be maintained after IP infusion.ConclusionsIP delivery of NK cells leads to stable engraftment and antitumor response in an ovarian cancer xenograft model. These data support further pre-clinical and clinical evaluation of IP delivery of allogeneic NK cells in ovarian cancer.