Gram-Negative Marine Bacteria: Structural Features of Lipopolysaccharides and Their Relevance for Economically Important Diseases

Gram-negative marine bacteria can thrive in harsh oceanic conditions, partly because of the structural diversity of the cell wall and its components, particularly lipopolysaccharide (LPS). LPS is composed of three main parts, an O-antigen, lipid A, and a core region, all of which display immense structural variations among different bacterial species. These components not only provide cell integrity but also elicit an immune response in the host, which ranges from other marine organisms to humans. Toll-like receptor 4 and its homologs are the dedicated receptors that detect LPS and trigger the immune system to respond, often causing a wide variety of inflammatory diseases and even death. This review describes the structural organization of selected LPSes and their association with economically important diseases in marine organisms. In addition, the potential therapeutic use of LPS as an immune adjuvant in different diseases is highlighted.     

High photostabilization of Zn<Superscript>2+</Superscript> chelating spironaphthoxazine

The chelation of spirooxazines with Zn (NO₃)₂ and zinc salt of 2-hydroxybenzoic acid (ZnHB) upon UV irradiation induced considerable retardation of the thermal discoloration rate in the dark. The excellent stability of the spirooxazine compound SPO2 having a carboxylate moiety at 5′ position of the naphthalene ring with ZnHB was found.     

Photoisomerization and photo-induced optical anisotropy of polymethacrylate containing aminonitroazobenzene chromophores in the side chain

Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy.Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiation of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal (LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.     

GPCR engineering yields high-resolution structural insights into beta2-adrenergic receptor function

The beta2-adrenergic receptor (beta2AR) is a well-studied prototype for heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) that respond to diffusible hormones and neurotransmitters. To overcome the structural flexibility of the beta2AR and to facilitate its crystallization, we engineered a beta2AR fusion protein in which T4 lysozyme (T4L) replaces most of the third intracellular loop of the GPCR ("beta2AR-T4L") and showed that this protein retains near-native pharmacologic properties. Analysis of adrenergic receptor ligand-binding mutants within the context of the reported high-resolution structure of beta2AR-T4L provides insights into inverse-agonist binding and the structural changes required to accommodate catecholamine agonists. Amino acids known to regulate receptor function are linked through packing interactions and a network of hydrogen bonds, suggesting a conformational pathway from the ligand-binding pocket to regions that interact with G proteins.     

Trophic cascades in a formerly cod-dominated ecosystem

Removal of top predators from ecosystems can result in cascading effects through the trophic levels below, completely restructuring the food web. Cascades have been observed in small-scale or simple food webs, but not in large, complex, open-ocean ecosystems. Using data spanning many decades from a once cod-dominated northwest Atlantic ecosystem, we demonstrate a trophic cascade in a large marine ecosystem. Several cod stocks in other geographic areas have also collapsed without recovery, suggesting the existence of trophic cascades in these systems.     

Neurons containing NADPH-diaphorase are selectively resistant to quinolinate toxicity

Exposure of cultures of cortical cells from mouse to either of the endogenous excitatory neurotoxins quinolinate or glutamate resulted in widespread neuronal destruction; but only in the cultures exposed to quinolinate, an N-methyl-D-aspartate agonist, was there a striking preservation of the subpopulation of neurons containing the enzyme nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d). Further investigation revealed that neurons containing NADPH-d were also resistant to the toxicity of N-methyl-D-aspartate itself but were selectively vulnerable to the toxicity of either kainate or quisqualate. Thus, neurons containing NADPH-d may have an unusual distribution of receptors for excitatory amino acids, with a relative lack of N-methyl-D-aspartate receptors and a relative preponderance of kainate or quisqualate receptors. Since selective sparing of neurons containing NADPH-d is a hallmark of Huntington's disease, the results support the hypothesis that the disease may be caused by excess exposure to quinolinate or some other endogenous N-methyl-D-aspartate agonist.     

Effect of potential multimicrobe probiotic product processed by high drying temperature and antibiotic on performance of weanling pigs

In this study, the effect of a potential multimicrobe probiotic subjected to high-temperature drying was investigated. Potential multimicrobe probiotics produced by solid substrate fermentation were dried at low (LT, 40°C for 72 h) or high (HT, 70°C for 36 h) temperature. In Exp. 1, 288 weaned pigs (BW, 6.43 ± 0.68 kg) were allotted to 4 treatments on the basis of BW (4 pens per treatment with 18 pigs in each pen). Dietary treatments were negative control (NC; basal diet without any antimicrobial), positive control (PC; basal diet + 0.1% chlortetracycline), basal diet with 0.3% probiotic LT, and basal diet with 0.3% probiotic HT. Diets were fed in 2 phases, phase I (d 0 to 14) and phase II (d 15 to 28); and growth performance, apparent total tract digestibility (ATTD, d 28), and fecal microflora (d 14 and 28) were evaluated. Over the 28-d trial, pigs fed PC and probiotic diets had greater ADG (P < 0.001), ADFI (P < 0.05), and G:F (P < 0.01) than pigs fed NC diet. The ATTD of DM and GE was greater (P < 0.05) in pigs fed probiotic diets when compared with pigs fed the NC diet. At d 28, fewer Clostridia (P < 0.01) were identified in the feces of pigs fed PC and probiotic diets than pigs fed the NC diet. However, the performance, ATTD of DM and GE, and fecal Clostridia population were similar among pigs fed probiotic LT and HT diets. In Exp. 2, 288 weaned pigs (initial BW, 5.84 ± 0.18 kg) were allotted to 4 treatments in a 2 × 2 factorial arrangement on the basis of BW. The effects of 2 levels of probiotic HT (0.30 or 0.60%), each with or without antibiotic (chlortetracycline, 0 or 0.1%), on performance, ATTD, intestinal morphology, and fecal and intestinal microflora were investigated. Feeding of 0.60% probiotic HT diet improved (P < 0.05) overall ADG, ATTD of DM and GE, and Lactobacillus population in the feces and intestine, and reduced the population of Clostridium and coliforms in feces (d 14) and ileum. Inclusion of antibiotic improved (P < 0.05) the overall ADG, ADFI, and ATTD of DM at d 14 and reduced fecal Clostridium population at d 28. Increased (P < 0.05) villus height at jejunum and ileum, and villus height:crypt depth at the ileum was noticed in pigs fed 0.60% probiotic HT and antibiotic diets. In conclusion, high drying temperature had no effect on the efficacy of potential multimicrobe probiotic product. However, the probiotic product dried at high temperature was more effective at 0.60% inclusion, whereas inclusion of an antibiotic improved pig performance but did not show any interaction with probiotics.     

Cholecystokinin mediates depression of feed intake in dairy cattle fed high fat diets

Two experiments were conducted to investigate the effects of 1) different concentrations of dietary fat and 2) i.v. administration of a cholecystokinin receptor antagonist (MK-329) on feed intake and plasma concentrations of hormones and metabolites in dairy cattle. In Experiment 1, 4 lactating Holstein cows were used in a 4 x 4 Latin square design. Treatments were diets with 1) no fat added, 2) 30 g fat/kg feed (calcium salts of long-chain fatty acids as fat supplement), 3) 60 g fat/kg, and 4) 90 g fat/kg added. Cows were fed once daily a diet of concentrate, corn silage, alfalfa haylage, and alfalfa pellets. Dry matter intake decreased linearly with increasing concentrations of dietary fat (P < 0.0001). Overall plasma concentrations of nonesterified fatty acids (P < 0.0001), triacylglycerol (P < 0.0006), and cholecystokinin (P < 0.02), increased linearly with each level of dietary fat, but there was a linear decrease in plasma insulin (P < 0.0008). In Experiment 2, 4 nonpregnant and nonlactating Holstein heifers were used in a cross-over design in a 2 x 2 factorial arrangement of treatments. Treatments were diet (fatty acids, 27 g/kg vs 103 g/kg diet dry matter) and i.v. injections (MK-329 vs vehicle). Heifers were fed once daily a total mixed ration of corn silage, cracked corn and soybean meal with or without fat supplement. Diets were switched by period and either MK-329 (70 microg/kg body weight) or its vehicle was injected i.v. at 2 hr postfeeding. Daily dry matter intake was decreased by feeding the high fat diet (P < 0.02) but was not affected by injections. Injection of MK-329, however, increased dry matter intake by 92% in heifers fed the high fat diet during the first 2 hr postinjection compared to vehicle injection. Plasma pancreatic polypeptide concentration was increased by the high fat diet at 2 hr postfeeding (P < 0.02) but was lowered by MK-329 at 1 hr postinjection (P < 0.001). Plasma insulin was lowered by the high fat diet (P < 0.01) but was not affected by injections. The elevated plasma cholecystokinin concentration may have mediated depressed feed intake of dairy cattle fed the high fat diets.     

Evidence of supersolidity in rotating solid helium

Supersolidity, the appearance of zero-viscosity flow in solids, was first indicated in helium-4 torsional oscillator (TO) experiments. In this apparatus, the irrotationality of the superfluid component causes it to decouple from the underlying normal solid, leading to a reduction in the resonant period of the TO. However, the resonant period may be altered for reasons other than supersolidity, such as the temperature dependence of the elastic modulus of solid helium. Superimposing rotation onto oscillatory measurements may distinguish between supersolidity and classical effects. We performed such simultaneous measurements of the TO and the shear modulus, and observed substantial change in the resonant period with rotational speed where the modulus remained unchanged. This contrasting behavior suggests that the decrease in the TO period is a result of supersolidity.