Cholesterol sulfate (CholSO4) was found to be a useful substitute of sulfatide for the preparation of negatively charged liposomes entrapping adriamycin (ADM). Liposomes composed of egg phosphatidylcholine, cholesterol, and CholSO4 in a molar ratio of 6:3:1 entrapped ADM efficiently and reduced the leakage of the entrapped ADM from the liposomes to the same degree as found for sulfatide-containing liposomes. The novel liposomes induced neither haemolysis nor platelet aggregation
Cholera toxin (CT) has been reported to bind specifically to GM1 ganglioside on cell surface plasma membranes and activates adenylate cyclase. We examined whether or not GM1 ganglioside (galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosyl-glucosylceramide) accumulates in plasma membranes of cultured skin fibroblasts from GM1 gangliosidosis patients by measuring cyclic AMP (adenosine 3′, 5′-cyclic monophosphate; cAMP) production elicited by CT. Optimal conditions for the assay were determined to be 1μg/ml of CT and 1h incubation at 37°C. The responses of intracellular cAMP level to a direct activator of adenylate cyclase, forskolin, and to phorbol 12-myristate 13-acetate (PMA) were not different between patients and controls. Insertion of exogenous GM1 ganglioside into the cell membrane caused a linear increase in the cAMP production triggered by CT in control cells. Under the optimal conditions, intracellular cAMP production in response to CT was estimated as 544.3±16.3pmol/h per mg protein in the patients' cells and 284.8±46.8pmol/h per mg protein in the control ones. These data are the first indication of the accumulation of GM1 ganglioside in cell surface membranes of patients with GM1 gangliosidosis.
Low density lipoprotein (LDL) subfractions, LDL-1, LDL-2, and LDL-3, separated from rabbit hypercholesterolemic serum and normal LDL from normal rabbit serum were modified by exposure to air in the absence or presence of Cu2+ at 37°C. When these LDLs were incubated in the presence of Cu2+, the lipid peroxide level and the mobility in agarose gel electrophoresis were increased in the following order: LDL-1>LDL-2>LDL-3>normal LDL. In the absence of Cu2+, the increases were also remarkable for LDL-1, less for LDL-2, but nonexistent for LDL-3 and normal LDL. Incubation in the presence of Cu2+ brought about the degradation of apo B-100 and the formation of fluorescent substances in these samples, but such did not occur in the absence of Cu2+. LDL samples modified in the presence of Cu2+ were taken up by rat peritoneal macrophages to the following extents: LDL-1>LDL-2>LDL-3>normal LDL. This tendency was supported by fluorescence microscopic observation using 1, 1′-dioctadecyl 3, 3, 3′, 3′-tetra-methylindocarbocyanine perchloride-labeled samples, and by the contents of total cholesterol in macrophages. These results indicate that LDL-1, which was identified as the main component of intermediate density lipoprotein, is more susceptible to lipid peroxidation-mediated modification and is more atherogenic than other subfractions of LDL.
Dietary deprivation of fat in male Swiss mice for 6 weeks resulted in a decrease in cytochrome c-reductase (Cyt.c-red.) activity without alteration of the activities of arylhydrocarbon hydroxylase (AHH), aminopyrene demethylase (APD), and cytochrome P-450 (Cyt. P-450) in the liver, whereas levels of glutathione-S-transferase (GST) and reduced glutathione (GSH) were significantly increased by fat-free diet feeding. Following N-nitrosodiethylamine (NDEA) administration, AHH, APD, and Cyt. P-450 significantly declined, whereas GST and GSH were stimulated in the liver of control as well as fat-deficient mice. NDEA treatment decreased the activities of AHH and APD, and increased the GST activity in the lungs of fat-deficient mice only. The higher levels of GST and/or GSH in fat deficiency may have a protective role in chemical carcinogenesis.
Feeding of ellagic acid, one of the naturally occurring plant phenols, at varying dose levels through drinking water for eight weeks resulted in a dose-dependent significant increase in the hepatic glutathione-S-transferase activity as well as in the hepatic and pulmonary reduced glutathione levels. However, the pulmonary glutathione-S-transferase activity was not affected. Glutathione-S-transferase inhibition curve, obtained at different concentrations of ellagic acid in the 10, 000×g hepatic supernatant using 1-chloro-2, 4-dinitrobenzene as substrate, suggests two types of isoenzymes of glutathione-S-transferase, ellagic acid-binding (isoenzymes to which ellagic acid is prone to bind) and ellagic acid-non binding (isoenzymes to which ellagic acid does not bind). I50 for ellagic acid-binding isoenzymes was found to be 35μM. Kinetic studies revealed that ellagic acid inhibited glutathione-S-transferase activity non-competitively with respect to 1-chloro-2, 4-dinitro-benzene as a substrate, with a Ki of 450μM and Ks of 322μM.
Effects in sedentary and exercised rats of allopurinol (a xanthine oxidase activity inhibitor) administration on lipid peroxidation and antioxidants were investigated by measurement of malondialdehyde (MDA), as well as α-tocopherol, β-tocopherol, γ-tocopherol, and total glutathione, concentration in plasma and liver, and comparison with those in untreated sedentary and exercised rats. Liver lipid peroxide concentration as measured by MDA in the exercised control group was significantly (p<0.05) increased by 104.2% compared with that of the sedentary control group. In the allopurinol-treated groups, the liver lipid peroxide concentration was 57.0% greater in the exercised group than in the sedentary group. Plasma lipid peroxide concentration in the exercised control and exercised allopurinol-treated groups increased over those of the respective sedentary groups. Plasma tocopherol (vitamin E) levels were greater in exercised groups than in corresponding sedentary groups. However, liver vitamin E levels of exercised control rats were significantly (p<0.05) decreased compared with those of sedentary control rats. Plasma total glutathione level in the exercised control group was decreased compared with that in the sedentary control group, and liver total glutathione level in the exercised control group was significantly (p<0.01) decreased compared with that in the sedentary control group. These results suggest that intensive exercise induced greater generation of oxygen radicals and enhanced lipid peroxidation in blood and liver. In addition, these results indicate that antioxidants as vitamin E located in cell membranes may be consumed by reactions that inhibit lipid peroxidation following exercise. This response to allopurinol treatment indicates that sources of oxygen radicals are not only the electron transport system in mitochondria but also the activation of xanthine oxidase during intensive exercise.
Soybean oligosaccharide extract (SOE) containing galactooligosaccharides like raffinose and stachyose has a sweet taste similar to that of sucrose. When ingested, these galactooligosaccharides are neither digested nor absorbed, but promote the growth of bifidobacteria in the human intestine. It therefore has the potential to be an alternative sweetener in dietary treatment for metabolic disorders. However, the indigestible oligosaccharides, in general, often cause diarrhea when taken beyond a specific amount. To determine the maximum non-effective dose (NEDmax) and the 50% effective dose (ED50) of SOE on diarrhea, we conducted a single blind comparative study on 106 adult healthy volunteers with an average age of 29±12 years. They were randomly chosen to ingest either SOE in a concentration 1, 2, 4, 6, 8, or 10 times the standard dose of 0.16g/kg body weight, or the equivalent proportions of sucrose as the control. The NEDmax was found to be 0.64g/kg for males and 0.96g/kg for females, while the ED50 was 0.88g/kg for men and 2.41g/kg for women. These values assure, for both genders, that man can ingest SOE at least four times the standard dosage per ingestion without intestinal disturbances.
Experiments were carried out to assess Spirulina fusiformis, a blue-green alga, as a source of vitamin A in preschool children. The absorption of total carotenes and β-carotene from a single dose of Spirulina containing 1, 200μg of β-carotene was examined in apparently healthy children aged 3 to 5 years. After stabilization on an almost carotene-free diet taken for 7 days, a bolus dose of Spirulina was fed along with the meal. Fecal excretion of total carotene and β-carotene for 4 days prior to the supplementation and 4 days after supplementation were examined. The effect of daily supplementation of either Spirulina or of vitamin A for one month on serum retinol levels was also examined. The mean absorption of total carotene was found to be 72.3%; and that of β-carotene, 75.2%. Serum retinol showed a significant improvement in both the Spirulina- and vitamin A-supplemented groups, the increase being slightly better in the vitamin A-supplemented group. On withdrawal of the supplements, serum retinol levels returned to presupplementation levels by 1 to 3 months in both groups. The bioavailability of carotenes from Spirulina is thus comparable to that from other sources such as carrots and green leafy vegetables, thus suggesting the potential use of this alga as a dietary source of provitamin A.
Because of the controversy among reports as to whether dietary fiber interferes with mineral absorption or not, we investigated the effect of dietary citrus pectin in a low-caloric, processed formula on serum calcium (Ca), zinc (Zn), copper (Cu), and iron (Fe) in 14 healthy obese Egyptian women undergoing weight reduction over a four-week period. The total caloric supply was 1, 000kcal/day. There was no difference between pre- and post-study values in the serum Ca. This was ascribed to the fact that water-soluble dietary fibers are fermented in the colon with the generation of short-chain fatty acids, which besides being absorbed, also enhance colonic divalent cation absorption. There was a numerical non significant decrease well within the reference values of Zn (-4.87%), Cu(-6.42%), and Fe(-19.65%). These results were discussed in light of the suggestion that the Zn, Cu, and Fe status is one aspect of an integrated acute-phase response. The response might have been triggered earlier by obesity, and later on augmented by the nutritional and psychological stress superimposed by the slimming diet. Hence, we conclude that dieters should be supplemented with minerals to replenish the body resources before embarking on low-energy diets. These diets should be of short duration, and must be interrupted by periods of normal alimentation if the need calls for their repetition.