APOA5 polymorphisms influence plasma triglycerides in young, healthy African Americans and whites of the CARDIA Study

Genetic variation in the apolipoprotein A-V gene (APOA5) has been associated with variation in plasma triglyceride (TG) levels in African American and white females and males older than 40 years and/or at increased risk of coronary artery disease. We have examined whether plasma TG levels are associated with 16 APOA5 polymorphisms in young (18-30 years) African American (1,075 females and 783 males) and white (1,041 females and 932 males) individuals of the Coronary Artery Risk Development in Young Adults (CARDIA) Study selected without regard to health. Plasma TG was significantly (P < 0.01) associated with markers 27376 and 28837 (-3A/G) in both white females and males, with 27709 (-1131T/C) and 29085 in white males, with 29009 (S19W) in African American females and white males, and with 30966 in African American females. No statistically significant associations were observed in African American males. These six single-nucleotide polymorphisms individually accounted for 0-0.78% of lnTG variation among white females, 0-2.46% among white males, and 0-0.69% among African American females. The results of our study suggest a small but replicable context-dependent influence of the APOA5 gene region on plasma TG levels in young, healthy individuals.     

A dominant role of Toll-like receptor 4 in the signaling of apoptosis in bacteria-faced macrophages

Conserved bacterial components potently activate host immune cells through transmembrane Toll-like receptors (TLRs), which trigger a protective immune response but also may signal apoptosis. In this study, we investigated the roles of TLR2 and TLR4 as inducers of apoptosis in Yersinia enterocolitica-infected macrophages. Yersiniae suppress activation of the antiapoptotic NF-kappaB signaling pathway in host cells by inhibiting inhibitory kappaB kinase-beta. This leads to macrophage apoptosis under infection conditions. Experiments with mouse macrophages deficient for TLR2, TLR4, or both receptors showed that, although yersiniae could activate signaling through both TLR2 and TLR4, loss of TLR4 solely diminished Yersinia-induced apoptosis. This suggests implication of TLR4, but not of TLR2, as a proapoptotic signal transducer in Yersinia-conferred cell death. In the same manner, agonist-specific activation of TLR4 efficiently mediated macrophage apoptosis in the presence of the proteasome inhibitor MG-132, an effect that was less pronounced for activation through TLR2. Furthermore, the extended stimulation of overexpressed TLR4 elicited cellular death in epithelial cells. A dominant-negative mutant of Fas-associated death domain protein could suppress TLR4-mediated cell death, which indicates that TLR4 may signal apoptosis through a Fas-associated death domain protein-dependent pathway. Together, these data show that TLR4 could act as a potent inducer of apoptosis in macrophages that encounter a bacterial pathogen.     

Accelerated rates of glycolysis in the hypertrophied heart: are they a methodological artifact?

Glycolysis, measured by (3)H(2)O production from [5-(3)H]glucose, is accelerated in isolated working hypertrophied rat hearts. However, nonglycolytic detritiation of [5-(3)H]glucose via the nonoxidative pentose phosphate pathway (PPP) could potentially lead to an overestimation of true glycolytic rates, especially in hypertrophied hearts where the PPP may be upregulated. To address this concern, we measured glycolysis using [5-(3)H]glucose and a second, independent method in isolated working hearts from halothane-anesthetized, sham-operated and aortic-constricted rats. Glycolysis was accelerated in hypertrophied hearts compared with control hearts regardless of the method used. There was also excellent concordance in glycolytic rates between the different methods. Moreover, activity of glucose-6-phosphate dehydrogenase and expression of transaldolase, enzymes controlling key steps in the oxidative and nonoxidative PPP, respectively, were not different between control and hypertrophied hearts. Thus nonglycolytic detritiation of [5-(3)H]glucose in the PPP is insignificant, and (3)H(2)O production from [5-(3)H]glucose is an accurate means to measure glycolysis in isolated working normal and hypertrophied rat hearts. Furthermore, the PPP does not appear to be increased in cardiac hypertrophy induced by abdominal aortic constriction.     

The nature of illusory contour computation

Neural correlates of illusory contour perception have been found in both the early and the higher visual areas. But the locus and the mechanism for its computation remain elusive. Psychophysical evidence provided in this issue of Neuron shows that perceptual contour completion is likely done in the early visual cortex in a cascade manner using horizontal connections.     

Signaling of apoptosis through TLRs critically involves toll/IL-1 receptor domain-containing adapter inducing IFN-beta, but not MyD88, in bacteria-infected murine macrophages

TLRs are important sensors of the innate immune system that serve to identify conserved microbial components to mount a protective immune response. They furthermore control the survival of the challenged cell by governing the induction of pro- and antiapoptotic signaling pathways. Pathogenic Yersinia spp. uncouple the balance of life and death signals in infected macrophages, which compels the macrophage to undergo apoptosis. The initiation of apoptosis by Yersinia infection specifically involves TLR4 signaling, although Yersinia can activate TLR2 and TLR4. In this study we characterized the roles of downstream TLR adapter proteins in the induction of TLR-responsive apoptosis. Experiments using murine macrophages defective for MyD88 or Toll/IL-1R domain-containing adapter inducing IFN-beta (TRIF) revealed that deficiency of TRIF, but not of MyD88, provides protection against Yersinia-mediated cell death. Similarly, apoptosis provoked by treatment of macrophages with the TLR4 agonist LPS in the presence of a proteasome inhibitor was inhibited in TRIF-defective, but not in MyD88-negative, cells. The transfection of macrophages with TRIF furthermore potently promoted macrophage apoptosis, a process that involved activation of a Fas-associated death domain- and caspase-8-dependent apoptotic pathway. These data indicate a crucial function of TRIF as proapoptotic signal transducer in bacteria-infected murine macrophages, an activity that is not prominent for MyD88. The ability to elicit TRIF-dependent apoptosis was not restricted to TLR4 activation, but was also demonstrated for TLR3 agonists. Together, these results argue for a specific proapoptotic activity of TRIF as part of the host innate immune response to bacterial or viral infection.     

Characterization of flagellin expression and its role in Listeria monocytogenes infection and immunity

Flagellin is the structural component of flagella produced by many pathogenic bacteria and is a potent proinflammatory molecule that mediates these effects through Toll-like receptor (TLR) 5. In Listeria monocytogenes (LM), flagellin expression is regulated by temperature and has been described as being shut off at 37 degrees C. In this study, we demonstrate that TLR5-mediated cell activation and flagellin expression is maintained at 37 degrees C in some laboratory-adapted strains and in approximately 20% of LM clinical isolates. To determine the role of flagellin in LM infection, a targeted mutation in the structural gene for flagellin (flaA) was generated in a parental LM strain that expressed flagellin under all conditions examined. In vitro studies demonstrated that this deltaflaA mutant was (i). non-motile; (ii). not able to activate TLR5-transfected HeLa cells; and (iii). induced tumour necrosis factor (TNF)-alpha production in approximately 50% fewer CD11b+ cells in splenocytes from normal mice compared with the parental strain. However, there was no significant alteration in virulence of the deltaflaA mutant after either intravenous or oral murine infection. Similarly, there was no difference in the generation of LM-specific CD8 or CD4 T cells after intravenous or oral infection. These data indicate that flagellin is not essential for LM pathogenesis or for the induction of LM-specific adaptive immune responses in normal mice.     

Soft sensors for on-line biomass measurements

One of the difficulties encountered in control and optimisation of bioprocesses is the lack of reliable on-line sensors for their key state variables. This paper investigates the suitability of using on-line recurrent neural networks to predict biomass concentrations. Input variables of the proposed recurrent neural network are feed rate, liquid volume and dissolved oxygen. Experimental results revealed that the proposed neural network is able to predict biomass concentrations with an accuracy of ±11%.     

Evaluation of loxoprofen and its alcohol metabolites for potency and selectivity of inhibition of cyclooxygenase-2

Loxoprofen, its trans-alcohol and cis-alcohol metabolites were evaluated for selectivity of inhibition of COX-2 over COX-1. The (2S,1'R,2'S)-trans-alcohol derivative was found to be the most active metabolite and to be a potent and nonselective inhibitor of COX-2 and COX-1 in both enzyme and human whole blood assays.     

Cladistic structure within the human Lipoprotein lipase gene and its implications for phenotypic association studies

Haplotype variation in 9.7 kb of genomic DNA sequence from the human lipoprotein lipase (LPL) gene was scored in three populations: African-Americans from Jackson, Mississippi (24 individuals), Finns from North Karelia, Finland (24), and non-Hispanic whites from Rochester, Minnesota (23). Earlier analyses had indicated that recombination was common but concentrated into a hotspot and that recurrent mutations at multiple sites may have occurred. We show that much evolutionary structure exists in the haplotype variation on either side of the recombinational hotspot. By peeling off significant recombination events from a tree estimated under the null hypothesis of no recombination, we also reveal some cladistic structure not disrupted by recombination during the time to coalescence of this variation. Additional cladistic structure is estimated to have emerged after recombination. Many apparent multiple mutational events at sites still remain after removing the effects of the detected recombination/gene conversion events. These apparent multiple events are found primarily at sites identified as highly mutable by previous studies, strengthening the conclusion that they are true multiple events. This analysis portrays the complexity of the interplay among many recombinational and mutational events that would be needed to explain the patterns of haplotype diversity in this gene. The cladistic structure in this region is used to identify four to six single-nucleotide polymorphisms (SNPs) that would provide disequilibrium coverage over much of this region. These sites may be useful in identifying phenotypic associations with variable sites in this gene. Evolutionary considerations also imply that the SNPs in the 3' region should have general utility in most human populations, but the 5' SNPs may be more population specific. Choosing SNPs at random would generally not provide adequate disequilibrium coverage of the sequenced region.