Cosmic Black Holes

Production of high-energy gravitational objects is a common feature of gravitational theories. The primordial universe is a natural setting for the creation of black holes and other nonperturbative gravitational entities. Cosmic black holes can be used to probe physical properties of the very early universe which would usually require the knowledge of the theory of quantum gravity. They may be the only tool to explore thermalisation of the early universe. Whereas the creation of cosmic black holes was active in the past, it seems to be negligible at the present epoch.Comment: 7 pages. Essay submitted to the 2003 Gravity Research Foundation essay competition. Received an honorable mention. Accepted for publication in IJMP

Quality Characteristics of Irradiated Turkey Breast Rolls Formulated with Plum Extract

The effects of adding 1%, 2% and 3% plum extract on the quality characteristics of vacuum-packaged, irradiated RTE turkey breast rolls were determined. Turkey breast rolls were sliced, packaged and irradiated at 0 or 3 kGy using a Linear Accelerator. Lipid oxidation, volatile profiles, color, texture, proximate analysis and sensory characteristics of sliced turkey breast rolls were determined at 0 and 7 days of storage. Addition of plum extract had no detectable effect on the proximate analysis of turkey breast rolls. Plum extract increased a* and b*- values, and decreased L* value of turkey breast rolls due to the original color of plum extract. Addition of \u3e2% plum extract to turkey breast rolls was effective in controlling lipid oxidation of irradiated meat and the production of aldehydes (hexanal, heptanal, octanal, and nonanal) in nonirradiated meat at Day 0. Texture of turkey breast rolls was not influenced, but juiciness was increased by plum extract. Therefore, addition of 3% or higher of plum extract is recommended to improve mouth-feel and antioxidant effect in irradiated turkey breast rolls. However, the color of turkey breast rolls with 3% plum extract was dark and might not be appealing to consumers

Oxidization without substrate unfolding triggers proteolysis of the peroxide-sensor, PerR

Peroxide operon regulator (PerR) is a broadly conserved hydrogen peroxide sensor in bacteria, and oxidation of PerR at its regulatory metal-binding site is considered irreversible. Here, we tested whether this oxidation specifically targets PerR for proteolysis. We find that oxidizing conditions stimulate PerR degradation in vivo, and LonA is the principal AAA+ (ATPases associated with diverse cellular activities) protease that degrades PerR. Degradation of PerR by LonA is recapitulated in vitro, and biochemical dissection of this degradation reveals that the presence of regulatory metal and PerR-binding DNA dramatically extends the half-life of the protein. We identified a LonA-recognition site critical for oxidation-controlled PerR turnover. Key residues for LonA-interaction are exposed to solvent in PerR lacking metal, but are buried in the metal-bound form. Furthermore, one residue critical for Lon recognition is also essential for specific DNA-binding by PerR, thus explaining how both the metal and DNA ligands prevent PerR degradation. This ligand-controlled allosteric mechanism for protease recognition provides a compelling explanation for how the oxidation-induced conformational change in PerR triggers degradation. Interestingly, the critical residues recognized by LonA and exposed by oxidation do not function as a degron, because they are not sufficient to convert a nonsubstrate protein into a LonA substrate. Rather, these residues are a conformation-discriminator sequence, which must work together with other residues in PerR to evoke efficient degradation. This mechanism provides a useful example of how other proteins with only mild or localized oxidative damage can be targeted for degradation without the need for extensive oxidation-dependent protein denaturation.United States. Public Health Service (GM049224

Consumption of Oxidized Oil Increases Oxidative Stress in Broilers and Affects the Quality of Breast Meat

A total of 120 4-week-old broiler chickens were allotted to 12 pens and fed one of three diets including control, oxidized diet (5% oxidized oil), or antioxidant-added diet (500 IU vitamin E) for 2 weeks. Blood samples were collected at the end of feeding trial, and breast muscles were sampled immediately after slaughter. Breast meats were also collected 24 h after slaughter and used for meat quality measurements. Oxidative stress in blood, lipid and protein oxidation, and sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity of breast muscle were determined. The oxidized diet increased oxidative stress in blood and increased carbonyl content in breast meat compared with the other two dietary treatments (P \u3c 0.05). Lipid oxidation of breast muscles with the antioxidant-supplemented diet was lower than that with the oxidized and control diet groups (P \u3c 0.05). Meat from birds fed the oxidized diet showed higher drip loss after 1 and 3 days of storage and greater 0−1 h post-mortem pH decline (P \u3c 0.05). Significant differences in specific SERCA activity in breast muscles from birds fed control and oxidized diets (P \u3c 0.05) were detected. This suggested that dietary oxidized oil induced oxidative stress in live birds and increased lipid and protein oxidation in breast muscle. Decrease in SERCA activity in breast muscles due to oxidative stress in live animals accelerated post-mortem glycolysis, which sped the pH drop after slaughter and increased drip loss, indicating that oxidation of diet can cause PSE-like (pale, soft, and exudative) conditions in broiler breast muscles

Effects of Dietary Oxidation on the Quality of Broiler Breast Meat

One hundred and twenty 4-week-old broilers were randomly assigned to one of the three dietary treatments including control (none), oxidized oil (5% of diet) and antioxidants (500 IU vitamin E and 200 ppm BHT) and fed for 2 weeks. Blood samples were collected 1day before slaughter and breast muscles were sampled immediately after slaughter. Degree of lipids and protein oxidation in blood and breast muscle, and meat quality parameters were determined. Compared to control group, broilers fed diet with oxidized oil significantly increased lipid oxidation in both blood (P \u3c 0.05). Dietary oxidized oil tended to increase carbonyl content in blood and muscle (P \u3c 0.05). Addition of antioxidants significantly decreased lipid oxidation in both blood and muscle samples and arrested protein oxidation in muscle (P \u3c 0.05). Meats from oxidized oil treatment showed higher drip loss at days 1 and 3 and lower water holding capacity at day 1 than control group (P \u3c 0.05). No significant difference was found about drip loss and water holding capacity between control and antioxidant treatments. The rate of pH decline in breast meat from oxidized oil treatment was significantly higher than that of control between 0 and 1 hour after slaughter (P \u3c 0.05). However, dietary treatments did not show significant effects on body weight gain, feed consumption and feed efficiency of live birds, and cooking loss and color of breast meat. This suggested that degree of oxidation in diet increased the oxidation in blood and muscle, and the oxidative stress in live birds were related to the variations in quality parameters including pH decline, drip loss, and protein and lipid oxidation of broiler breast meat