The destruction of spores of Bacillus subtilis by the combined effects of hydrogen peroxide and ultraviolet light

Ultraviolet light irradiation of bacterial spores in the presence of hydrogen peroxide has been shown to produce synergistic kills when compared with ultraviolet light (u.v.) and hydrogen peroxide used sequentially. This use in combination has been patented for the commercial sterilization of packaging before filling with UHT-processed products. Previous results have shown that lamps producing u.v. light with a maximum output at about 254 nm were extremely effective. Results obtained using a Synchrotron radiation source to produce a narrow band of irradiation now shows that the greatest kill of spores of Bacillus subtilis in the presence of hydrogen peroxide is obtained with radiation at ˜270 nm. Such results suggest that the action of the u.v. light is not directly on the spore DNA but may be related to the production of free hydroxyl radicals from hydrogen peroxide.     

COVID-19 and “natural” experiments arising from physical distancing: a hypothetical case study from chronobiology

ABSTRACT

With countless “natural” experiments triggered by the COVID-19-associated physical distancing, one key question comes from chronobiology: “When confined to homes, how does the reduced exposure to natural daylight arising from the interruption of usual outdoor activities plus lost temporal organization ordinarily provided from workplaces and schools affect the circadian timing system (the internal 24 h clock) and, consequently, health of children and adults of all ages?” Herein, we discuss some ethical and scientific facets of exploring such natural experiments by offering a hypothetical case study of circadian biology.     

Growth of B95-8 cells and expression of Epstein-Barr virus lytic phase in serum-free medium.

Epstein-Barr virus (EBV)-transformed tamarin (Saguinus oedipus) cells (B95-8) were selected for growth in medium with reduced serum and then transferred to serum-free medium which consisted of RPMI 1640 supplemented with insulin, transferrin, and selenium. Serum-free cells in continuous passage for 1 year had a morphology, growth rate, and culture density which approached those of B95-8 cells grown with serum. The cells expressed virus-induced antigens, including the EBV-associated DNA polymerase. Cells exposed to EBV-inducing agents, n-butyric acid and phorbol 12-myristate-13-acetate, produced transforming virus with titers comparable to those of cultures grown with serum. These findings demonstrate that serum is neither required for the growth of B95-8 cells nor necessary for induction or full expression of the EBV lytic phase in these cells.     

Acetaldehyde-mediated hepatic lipid peroxidation: role of superoxide and ferritin

Evidence in alcoholics as well as in experimental models support the role of hepatic lipid peroxidation in the pathogenesis of alcohol-induced liver injury, but the mechanism of this injury is not fully delineated. Previous studies of the metabolism of ethanol by alcohol dehydrogenase revealed iron mobilization from ferritin that was markedly stimulated by superoxide radical generation by xanthine oxidase. Peroxidation of hepatic lipid membranes (assessed as malondialdehyde production) was studied during in vitro alcohol metabolism by alcohol dehydrogenase. Peroxidation was initiated by acetaldehyde-xanthine oxidase, stimulated by ferritin, and inhibited by superoxide dismutase or chelation or iron with desferrioxamine. In conclusion, lipid peroxidation may be initiated during the metabolism of ethanol by alcohol dehydrogenase by an iron-dependent acetaldehyde-xanthine oxidase mechanism.     

Catabolism of neurotensin in the epithelial layer of porcine small intestine

The mammalian small intestine is both a source and a site of degradation of neurotensin. Metabolites produced by incubation of the peptide with dispersed enterocytes from porcine small intestine were isolated by high-performance liquid chromatography and identified by amino-acid analysis. The principal sites of cleavage were at the Tyr-11-Ile-12 bond, generating neurotensin-(1-11), and at the Pro-10-Tyr-11 bond, generating neurotensin-(1-10). The corresponding COOH-terminal fragments, neurotensin-(11-13) and -(12-13) were metabolized further. Formation of neurotensin-(1-11) and -(1-10) was completely inhibited by phosphoramidon (Ki = 6 nM), an inhibitor of endopeptidase 24.11, but not by captopril, an inhibitor of peptidyl dipeptidase A. Incubation of neurotensin with purified endopeptidase 24.11 from pig stomach also resulted in cleavage of the Tyr-11-Ile-12 and Pro-10-Tyr-11 bonds. A minor pathway of cell-surface-mediated degradation was the phosphoramidon-insensitive cleavage of the Tyr-3-Glu-4 bond, generating neurotensin-(1-3) and neurotensin-(4-13). No evidence for specific binding sites (putative receptors) for neurotensin was found either on the intact enterocyte or on vesicles prepared from the basolateral membranes of the cells. Neurotensin-(1-8), the major circulating metabolite, was not formed when neurotensin(1-13) was incubated with cells, but represented a major metabolite (together with neurotensin-(1-10] when neurotensin-(1-11) was used as substrate. The study has shown that degradation of neurotensin in the epithelial layer of the small intestine is mediated principally through the action of endopeptidase 24.11, but this enzyme is probably not responsible for the production of the neurotensin fragments detected in the circulation.