On-Shell Description of Unsteady Flames

The problem of non-perturbative description of unsteady premixed flames with arbitrary gas expansion is solved in the two-dimensional case. Considering the flame as a surface of discontinuity with arbitrary local burning rate and gas velocity jumps given on it, we show that the front dynamics can be determined without having to solve the flow equations in the bulk. On the basis of the Thomson circulation theorem, an implicit integral representation of the gas velocity downstream is constructed. It is then simplified by a successive stripping of the potential contributions to obtain an explicit expression for the vortex component near the flame front. We prove that the unknown potential component is left bounded and divergence-free by this procedure, and hence can be eliminated using the dispersion relation for its on-shell value (i.e., the value along the flame front). The resulting system of integro-differential equations relates the on-shell fuel velocity and the front position. As limiting cases, these equations contain all theoretical results on flame dynamics established so far, including the linear equation describing the Darrieus-Landau instability of planar flames, and the nonlinear Sivashinsky-Clavin equation for flames with weak gas expansion.Comment: 21 pages, 3 figures; extended discussion of causality, new references adde

Evaluation of immune responses of cattle as a means to identify high or low responders and use of a human microarray to differentiate gene expression

An immune response (IR) index to identify cows with high (H) and low (L) antibody-mediated immune responses (AMIR) had been previously devised. High AMIR associated with decreased mastitis and improved response to vaccination. Measurement of cell-mediated immune response (CMIR) was not included in the index; therefore various antigen/adjuvant combinations were evaluated as inducers of DTH to be added to the IR-index. The Bacillus Calmette Guérin (BCG)-induced/purified protein derivative (PPD)-elicited tuberculin skin test is a reliable measure of DTH; however, its use to identify livestock with high CMIR may be confounded due to previous exposure to Mycobacteria tuberculosis. DTH to BCG/PPD was therefore compared with that induced by Mycobacteria phlei (saprophyte) and its derivative phlein as the test antigen. Antibody to OVA was also evaluated. The results indicated that BCG/PPD and M. phlei/phlein induced similar DTH, but cross reaction to PPD was evident following induction of DTH using M. phlei making it a less than ideal alternative for testing livestock. Nonetheless, cows could be ranked for both AMIR and CMIR. RNA from two cows with the highest and lowest IR ranks was then used to probe a human 1.7 kD microarray to determine the ability of a human array to provide information on bovine genes associated with H and L

Cytokines in Pigs Bred Selectively for High and Low Immune Response [abstract only]

Yorkshire pigs have been bred for high (H) and low (L) immune response based on selection for multiple antibody (Ab) and cell mediated immune response traits. High responders have better production and larger litter size when compared with controls and low responders. The ability of high and low line pigs to resist M. hyorhinis infection has been tested. The high responders had more rapid and higher Ab response and the severity of the disease was less, as judged by clinical and postmortem signs. However, arthritis was found to be relatively more severe in high responders. We hypothesized that the immune response differences between genetically different lines could be attributed to either dominant or differential cytokine expression. To test the above hypothesis, quantitative RNA PCR (Q.RNA PCR), to quantitate the porcine cytokines at the mRNA level, was developed by constructing an internal control. Two synthetic oligos, namely 5\u27 construct (FPC) and 3\u27 construct (TPC), were designed based on the nt sequences of porcine cytokine genes. FPC represented the upstream primer sequences of nine cytokines sequentially in the order IL-1, IL-4, IL-6, IL-8, IL-2, IL-1O, TNF-α, TNF-β and IFN-γ, and TPC, the downstream primer sequences in the same order. The primers were designed such that when cRNA and target RNA were amplified, they give two non-overlapping products. FPCs and TPCs were constructed by overlapping and the extension method of PCR amplification utilizing six oligos for each, and were cloned into pSP 64 poly A vector. The application of Q.RNA PCR has been tested for determining quantitatively the cytokines in peripheral blood mononuclear cells in H-L line pigs. Preliminary study indicated differential expression of cytokines, namely IL-1, IL-6, IL-1O, TNF-α and IFN-γ, in naive animals. Expression of other cytokines, namely IL-2, IL-4, IL-8 and TNF-β, was absent in the pigs tested. Future studies involve the determination of cytokines in the context of immunization to the antigens (HEWL, BCG, etc.) as well as during infection (ex: M. hyorhinis) in conjunction with cytokine expression regulation strategies, namely MAbs and/or antisense ODNs or gene therapy

Impact of heat stress on dairy cattle and selection strategies for thermotolerance: a review

Climate change is a problem that causes many environmental issues that impact the productivity of livestock species. One of the major issues associated with climate change is an increase of the frequency of hot days and heat waves, which increases the risk of heat stress for livestock species. Dairy cattle have been identified as being susceptible to heat stress due to their high metabolic heat load. Studies have shown heat stress impacts several biological processes that can result in large economic consequences. When heat stress occurs, dairy cattle employ several physiological and cellular mechanisms in order to dissipate heat and protect cells from damage. These mechanisms require an increase and diversion in energy toward protection and away from other biological processes. Therefore, in turn heat stress in dairy cattle can lead numerous issues including reductions in milk production and reproduction as well as increased risk for disease and mortality. This indicates a need to select dairy cattle that would be thermotolerant. Various selection strategies to confer thermotolerance have been discussed in the literature, including selecting for reduced milk production, crossbreeding with thermotolerant breeds, selecting based on physiological traits and most recently selecting for enhanced immune response. This review discusses the various issues associated with heat stress in dairy cattle and the pros and cons to the various selection strategies that have been proposed to select for thermotolerance in dairy cattle

Cytokines in \u3ci\u3eMycoplasma hyorhinis\u3c/i\u3e-Induced Arthritis in Pigs Bred Selectively for High and Low Immune Responses

Yorkshire pigs were bred selectively for high and low immune responses (H and L pigs, respectively) based on multiple antibody (Ab) and cell-mediated immune response traits. In a previous experiment, generation 4 (G4) pigs of each line were infected with Mycoplasma hyorhinis. High responders had a more rapid and higher Ab response and less polyserositis, but arthritis was more severe in H pigs than in L pigs. To test the hypothesis that line differences were attributable to differential expression of cytokines, M. hyorhinis infection was induced in pigs of G8. Arthritis was more severe clinically (P, ≤0.05) and postmortem (P, ≤0.001) when M. hyorhinis CFU were more numerous in synovial fluid (SF) of H pigs than of L pigs (P, ≤0.03). In H pigs but not L pigs, CFU and lesion scores were correlated positively. In H pigs, infection increased the frequency of expression of mRNAs for interleukin-8 (IL-8), IL-10, and tumor necrosis factor alpha (TNF-α) in mononuclear cells from synovial membranes (SM). In L pigs, IL-1a, IL-6, IL-10, and TNF-a mRNAs were increased in frequency of expression. The quantity of the cytokine message for IL-6 was increased in infected H pigs. For L pigs, infection increased the cytokine message for IL-1 α, IL-6, IL-10, and TNF-a. IL-6 in SM and gamma interferon (IFN-ϒ) in SF were produced at a higher copy number in H pigs than in L pigs after infection. For H pigs, there were no positive rank correlations between lesion or CFU scores and cytokines. For L pigs, IL-1 α, IL-8, IL-10, and TNF- α in SM correlated with CFU, while IL-6, TNF- β, and IFN-ϒ in SF correlated with CFU. Lesion score in L pigs correlated with IL-1 α in SF. While these results indicate that H and L pigs differ in the cytokine response to M. hyorhinis infection, they do not confirm a characteristic cytokine response in association with the relative susceptibility to infection and arthritis observed in H pigs

Analysis of gene expression patterns by microarray hybridization in blood mononuclear cells of SLA-DRB1 defined Canadian Yorkshire pigs

<p>Abstract</p> <p>Background</p> <p>The Swine Leukocyte Antigen (SLA) system encodes molecules for self-nonself discrimination and is associated with immune responses and disease resistance. Three lines of pigs defined by their SLA-DRB1 alleles were developed at the University of Guelph for xenotransplantation and immune response studies. The aim of this project was to explore the potential association between defined SLA-DRB1 alleles and gene transcriptional patterns of other immune-related genes in blood mononuclear cells.</p> <p>Findings</p> <p>Three SLA-DRB1 alleles were characterized using a RT-PCR-based sequencing method. The loci represented included a new allele, DRB1*04ns01. Next, microarray heterologous (bovine-porcine) hybridization together with qPCR were used to explore differential gene expression between SLA-DRB1-defined groups. Microarray analysis showed significant (p < 0.01) differential expression for 5 genes, mostly related to inflammation. Genes varied according to the comparison analyzed. Further testing with qPCR revealed the same trend of differential expression for 4 of the genes, although statistical significance was reached for only one.</p> <p>Conclusion</p> <p>A new SLA-DRB1 allele was characterized. A potential association was found between SLA-DRB1 alleles and inflammation-related genes. However, the influence of other genes cannot be ruled out. These preliminary findings agree with other studies linking MHC haplotypes and inflammation processes, including autoimmune disease. The study provides an initial view of the biological interactions between the SLA complex and other immune-related genes. Future studies will focus on characterization of SLA-haplotypes associated with these particular alleles and the dynamics of the immune response to antigenic challenges.</p

Growth differentiation factor 15 increases in both cerebrospinal fluid and serum during pregnancy

AIM:Growth differentiation factor 15 (GDF15) increases in serum during pregnancy to levels not seen in any other physiological state and is suggested to be involved in pregnancy-induced nausea, weight regulation and glucose metabolism. The main action of GDF15 is regulated through a receptor of the brainstem, i.e., through exposure of GDF15 in both blood and cerebrospinal fluid (CSF). The aim of the current study was to measure GDF15 in both CSF and serum during pregnancy, and to compare it longitudinally to non-pregnant levels. METHODS: Women were sampled at elective caesarean section (n = 45, BMI = 28.1±5.0) and were followed up 5 years after pregnancy (n = 25). GDF15, insulin and leptin were measured in CSF and serum. Additional measurements included plasma glucose, and serum adiponectin and Hs-CRP. RESULTS: GDF15 levels were higher during pregnancy compared with follow-up in both CSF (385±128 vs. 115±32 ng/l, P<0.001) and serum (73789±29198 vs. 404±102 ng/l, P<0.001). CSF levels correlated with serum levels during pregnancy (P<0.001), but not in the non-pregnant state (P = 0.98). Both CSF and serum GDF15 were highest in women carrying a female fetus (P<0.001). Serum GDF15 correlated with the homeostatic model assessment for beta-cell function and placental weight, and CSF GDF15 correlated inversely with CSF insulin levels. CONCLUSION: This, the first study to measure CSF GDF15 during pregnancy, demonstrated increased GDF15 levels in both serum and CSF during pregnancy. The results suggest that effects of GDF15 during pregnancy can be mediated by increases in both CSF and serum levels