The autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose.Xanthan strongly inhibited the peroxidation of soybean oil containing tocopherols but showed no antioxidant activity on soybean oil without tocopherols in the emulsion. Xanthan did not have hydrogendonating ability but expressed Fe2+-binding activity. The Fe2+-binding activity corresponded to the pyruvate content of xanthan. Depyruvated xanthan did not inhibit effectively the autoxidation of soybean oil. The Fe2+-chelating structure of xanthan is discussed.

There has been much current interest in the long-range oxidative damage to DNA through the DNA duplex caused by one-electron oxidations. 1 Hole (radical cation) migration through the DNA duplex has been suggested to play a crucial role in mutagenesis and carcinogenesis caused by carcinogenic agents, ionizing radiation, and high-intensity laser irradiation. 1,2 As is well-known, guanine (G) is the most easily oxidized base, 3 and the electron-loss center created in duplex DNA ultimately ends up at G residues via hole migration through the DNA duplex. Several years ago, we demonstrated both experimentally and by ab initio calculations that 5′-G residues of 5′-GG-3′ steps in B-form DNA are the most easily oxidized due to the GG stacks and can act as thermodynamic sinks in hole migration across the DNA π stack. 4 We also demonstrated that the highest occupied molecular orbital (HOMO) of a GG stack is especially high in energy and concentrated on the 5′-G. 4b Thereafter, examples of 5′-G selective oxidations have been reported in many different systems. These include (i) photooxidation using different types of DNA-binding agents such as Rh(III)-metallointercalators, 1a-c,f substituted anthraquinones, 1d,e,5 riboflavin, 6 naphthalimide derivatives, 4 a p-cyano-substituted benzophenone, 7 and pterins; 8 (ii) chemical oxidation by Ru(III)-metallointercalators 1c,9 and Ni(II)ligand/sulfite system; 10 (iii) two-photon photoionization of DNA with a high-intensity laser pulse (266 nm); 11 and (iv) direct irradiation with a powerful 193-nm excimer laser. 12 Notably, the 5′-G selectivity of 5′-GG-3′ steps is irrelevant to the structural

The bactericidal activity of phlorotannins from brown algae against food-borne pathogenic bacteria (25 strains), methicillin-resistant Staphylococcus aureus (MRSA) (nine strains) and Streptococcus pyogenes (one strain) was examined and compared with that of catechins. In addition, the effect of the oral administration of phlorotannins on mice was investigated. Phlorotannins, which are oligomers of phloroglucinol, were extracted from thalli of the brown alga Ecklonia kurome and prepared by silicic acid chromatography. The bactericidal activity of polyphenols was determined using a broth microdilution method. Of the bacteria tested, Campylobacter spp. were the most susceptible to the phlorotannins. The MBCs of the crude phlorotannins, dieckol and 8,8'-bieckol (hexamers), and that of epigallocatechin gallate (EGCG) against Campylobacter jejuni were 50 mg/L, 0.03 micromol/mL and 0.03 micromol/mL, respectively. On the whole, the bactericidal effects of the phlorotannins were more pronounced than those of the catechins. The phlorotannins were as effective against MRSA as against the other bacteria tested. At twice the MBCs, all Vibrio parahaemolyticus were killed within 0.5-2 h. However, at the same concentration, catechins showed little bactericidal activity within 4 h. No effect on mice was observed with oral administration of the phlorotannins under the conditions tested.

No abstract

Spontaneous regression of hepatocellular carcinoma is a rare phenomenon. Abscopal regression of tumours resulting from the eVect of irradiation of a tissue on a remote non-irradiated tissue is also rare. The case of a 76 year old Japanese man with hepatocellular carcinoma that regressed after radiotherapy for thoracic vertebral bone metastasis is described. Serum levels of tumour necrosis factorincreased after radiotherapy. The findings suggests that such abscopal related regression may be associated with host immune response, involving cytokines such as tumour necrosis factor-. (Gut 1998;43:575-577)

IVIM imaging may be helpful for differentiation between benign and malignant salivary gland tumors.

No abstract

Previously, we reported two types of neutral ceramidase in mice, one solubilized by freeze-thawing and one not. The former was purified as a 94-kDa protein from mouse liver, and cloned (Tani, M., Okino, N., Mori, K., Tanigawa, T., Izu, H., and Ito, M. (2000) J. Biol. Chem. 275, 11229 -11234). In this paper, we describe the purification, molecular cloning, and subcellular distribution of a 112-kDa membrane-bound neutral ceramidase of rat kidney, which was completely insoluble by freeze-thawing. The open reading frame of the enzyme encoded a polypeptide of 761 amino acids having nine putative N-glycosylation sites and one possible transmembrane domain. In the ceramidase overexpressing HEK293 cells, 133-kDa (Golgi-form) and 113-kDa (endoplasmic reticulum-form) Myc-tagged ceramidases were detected, whereas these two proteins were converted to a 87-kDa protein concomitantly with loss of activity when expressed in the presence of tunicamycin, indicating that the N-glycosylation process is indispensable for the expression of the enzyme activity. Immunohistochemical analysis clearly showed that the ceramidase was mainly localized at the apical membrane of proximal tubules, distal tubules, and collecting ducts in rat kidney, while in liver the enzyme was distributed with endosome-like organelles in hepatocytes. Interestingly, the kidney ceramidase was found to be enriched in the raft microdomains with cholesterol and GM1 ganglioside.Over the past decade, sphingolipids and their metabolites have emerged as a new class of lipid biomodulators of various cell functions (1, 2). Ceramide (N-acylsphingosine; Cer), 1 a common lipid backbone of sphingolipids, functions as a second messenger in a variety of cellular events including apoptosis and cell differentiation (3, 4). Sphingosine (Sph) has bifunctional effects on cell growth, i.e. it exerts mitogenic (5) and apoptosis inducing (6) activities, depending on the cell type and cell cycle. Sph-1-phosphate (S1P) was found to function as an intra-and intercellular second messenger to regulate cell growth (7), motility (8), and morphology (9). Interestingly, S1P inhibits the apoptosis induced by Cer and Fas ligand (10), indicating that the balance of Cer/Sph/S1P affects cell phenotype. Ceramidase (CDase, EC 3.5.1.23) is an enzyme that catalyzes hydrolysis of the N-acyl linkage of Cer to produce Sph, which can be phosphorylated to S1P by sphingosine kinase (11). Sph is not produced by de novo synthesis (12), and thus the activity of CDase is crucial not only for switching off the Cer-induced signaling but also for generation of Sph and S1P. CDase is classified into two categories: acid and neutral/alkaline enzymes depending on pH optimum. Acid CDase is thought to be a housekeeping enzyme to catabolize Cer in lysosomes. The enzyme was purified from human urine (13), and cDNA encoding the enzyme was isolated from cDNA libraries of human (14) and mouse (15). A deficiency of the enzyme could cause Farber disease in which Cer is accumulated in lysosomes (16). Neutral/alkaline CDase seems...