Sustained remission of systemic lupus erythematosus related calciphylaxis.

Calciphylaxis continues to present a clinical challenge for patient management. As in this case, it can be associated with connective tissue disease (CTD) such as systemic lupus erythematosus (SLE). Unlike previous reported cases, long-term remission has been attained. This provides some insight into methods of therapy as well as potential pathogenic models for this disease.

The use of rats associated with a human faecal flora as a model for studying the effects of diet on the human gut microflora.

The activities of four bacterial biotransformation enzymes (beta-glucosidase, beta-glucuronidase, nitrate reductase and nitroreductase) were measured in the caecal contents of conventional flora rats or germ-free rats contaminated with a mixed, human faecal flora and compared with activities present in a fresh human stool preparation. Both the conventional flora rats and the rats inoculated with a human flora exhibited an enzyme profile generally similar to that of human faeces, although the conventional rat flora exhibited negligible nitrate reductase activity. The enzyme profile remained essentially unaltered in both human flora preparations following supplementation of the diet with pectin, whereas the conventional rat flora responded to this plant cell wall carbohydrate with a significant increase in nitrate reductase activity. The results demonstrate that enzymic activities of the human faecal microflora can be simulated in rats associated with a mixed population of human intestinal bacteria.

Dietary modification of intestinal bacterial enzyme activities--potential formation of toxic agents in the gut.

The bacterial population colonising the large intestine is able to metabolise a variety of ingested or endogenously produced substances to products, some of which possess toxic, mutagenic or carcinogenic properties. Dietary components, resistant to digestion and absorption in the upper alimentary tract, may influence these reactions by altering the environment of the gut or through the provision of nutrients to the flora. Evidence for the involvement of bacterial enzymes in the formation of toxic products in vivo has come largely from animal studies, particularly where fermentable plant cell-wall components are present in the diet. The role of diet in the modification of toxicologically important bacterial biotransformation processes will be discussed. Preliminary data will also be presented from a study demonstrating changes in the enzymic activity of the human faecal flora induced by pectin and bran. The significance of these changes to the disposition of chemicals in the gut will be discussed.

Effect of mixtures of dietary fibres on the enzyme activity of the rat caecal microflora.

The enzyme activity of the caecal microflora from weanling rats was determined after feeding 1 of 3 basal diets (purified fibre-free; purified plus cellulose; and stock), with or without additional dietary fibre (pectin, i-carrageenan or carboxymethylcellulose 5% w/w). The wet weight of caecal contents and total bacterial numbers were similar for the purified fibre-free and purified plus cellulose diets, yet were significantly higher in animals fed the stock diet. Pectin supplementation of the basal diets had no effect of caecal bacterial numbers, but significantly increased total nitrate reductase activity per caecum except when added to stock diet. Carrageenan decreased caecal bacterial numbers and most enzyme activities with both purified diets, and to a lesser extent with the stock diet. Carboxymethylcellulose increased bacterial numbers and enzyme activities, particularly beta-glucosidase and nitrate reductase when added to the purified diet but not when added to either the purified diet plus cellulose or the stock diet. The results demonstrate that the effects of dietary fibre components on the rat caecal microflora are dependent upon the initial fibre content of the diet base.

Solubilisation, purification and reconstitution of hepatic microsomal azoreductase activity.

Microsomal NADPH-cytochrome c (P-450) reductase and cytochrome P-450 were purified from the livers of phenobarbitone-treated rats. Purified NADPH-cytochrome c (P-450) reductase effected the NADPH-dependent reduction of FMN and FAD under anaerobic conditions in a non-enzymic manner, but was unable to reduce directly the azo dye, amaranth. In the presence of FMN, the purified reductase effected reduction of amaranth through the production of reduced FMN. Incorporation of NADPH-cytochrome c (P-450) reductase into the microsomal fraction increased the azoreductase activity of liver preparations from phenobarbitone-treated rats, but had no effect on azoreductase activity in preparations from control animals. Azoreductase activity was reconstituted into dilauroyl phosphatidylcholine vesicles containing purified cytochrome P-450 and purified NADPH-cytochrome c (P-450) reductase. In the absence of supplementary FMN, amaranth reduction was completely dependent upon all three components, but in the presence of FMN, the omission of any one component failed to abolish completely azoreductase activity.

Hydrocolloid food additives and rat caecal microbial enzyme activities.

Agar, carboxymethylcellulose, carrageenan, guar gum, gum acacia, locust-beam gum or pectin (50 g/kg diet), given to weanling rats for 4 wk, increased the weight of the caecal wall and the caecal contents. Feeding carboxymethylcellulose, guar gum or pectin significantly increased, and feeding carrageenan decreased, the total bacterial population of the caecum. Feeding carboxymethylcellulose significantly increased in vitro activity of bacterial azoreductase, beta-glucosidase, beta-glucuronidase, nitrate reductase, nitroreductase and urease. Guar gum, gum acacia and locust-bean gum each increased at least three of these activities. In contrast, feeding carrageenan greatly decreased all microbial enzyme activities, while agar decreased beta-glucosidase, beta-glucuronidase and nitroreductase activities.

A comparison of the activity of five microbial enzymes in cecal content from rats, mice, and hamsters, and response to dietary pectin.

Rats, mice, and hamsters were fed a fiber-free purified diet for 30 days and the activity of a number of cecal microbial enzymes was determined. Expressed per gram cecal content, azoreductase activity was greatest in preparations from the hamster and least from the mouse, and beta-glucosidase and beta-glucuronidase activities were least active from the rat. Nitroreductase was less active and nitrate reductase more active from the hamster in comparison to the other species. When expressed per kilogram body weight, bacterial activities were always greatest from the hamster. When the basal diet was supplemented with pectin (50 g/kg diet), nitrate reductase activity was increased six- to sevenfold per gram cecal content for rats and mice (tenfold when expressed per kilogram body weight), but there was no effect on the nitrate reductase activity of hamster microflora. Pectin also significantly increased beta-glucuronidase activity in rats, but significantly reduced the activities of the other enzymes in at least one of the three species.

Effect of dietary carrageenan and pectin on the reduction of nitro-compounds by the rat caecal microflora.

Rats were fed either a basal purified diet, or that diet supplemented with 50 g/kg pectin or iota carrageenan for 50 days, and caecal microbial nitroreductase activity determined using p-nitrobenzoic acid, p-nitrophenol, 2,4-dinitrotoluene, nitrofurantoin and metronidazole as substrates. Both pectin and carrageenan increased the weight of caecal contents, and pectin also increased the number of bacteria per caecum. In contrast, carrageenan decreased the caecal bacterial population. Pectin significantly increased the rate of reduction of metronidazole and the rate of conversion of p-nitrobenzoic acid to p-aminobenzoic acid, while carrageenan significantly decreased the rate of reduction of every compound studied. The results demonstrate that microbial reduction of the nitro-group may be altered by diet, although the response found with one nitro-compound may differ from that seen with another substrate.

Interaction between pectin and rat hindgut microflora.

The contents of the lower alimentary tract from rats fed a semisynthetic, pectin-supplemented diet showed increased nitrate reductase activity and an increase in the amount of luminal contents in the intestine and cecum. Nitrate reductase activity was associated with the insoluble fraction of the gut contents which was sedimented by centrifugation (5,100 X g,20 min) and was abolished after treating the animals with streptomycin, neomycin, and bacitracin for 7 days. The pectin-dependent increase in cecal size and microbial nitrate reduction were reversed when animals were transferred from a pectin-supplemented onto a control semisynthetic diet. Polygalacturonic acid (pectic acid) was without effect on either cecal size or cecal microbial nitrate reductase activity. The studies demonstrate that pectin influences microbial metabolism in the alimentary tract.