Nisin was first introduced commercially as a food preservative in the UK approximately 30 years ago. First established use was as a preservative in processed cheese products and since then numerous other applications in foods and beverages have been identified. It is currently recognised as a safe food preservative in approximately 50 countries. The established uses of nisin as a preservative in processed cheese, various pasteurised dairy products, and canned vegetables will be briefly reviewed. More recent applications of nisin include its use as a preservative in high moisture, hot baked flour products (crumpets) and pasteurised liquid egg. Renewed interest is evident in the use of nisin in natural cheese production. Considerable research has been carried out on the antilisterial properties of nisin in foods and a number of applications have been proposed. Uses of nisin to control spoilage lactic acid bacteria have been identified in beer, wine, alcohol production and low pH foods such as salad dressings. Further developments of nisin are likely to include synergistic action of nisin with chelators and other bacteriocins, and its use as an adjunct in novel food processing technology such as higher pressure sterilisation and electroporation. Production of highly purified nisin preparations and enhancement by chelators has led to interest in the use of nisin for human ulcer therapy, and mastitis control in cattle.

Glutathione reductase from trypanosomes and leishmanias, unlike glutathione reductase from other organisms, requires an unusual low molecular weight cofactor for activity. The cofactor was purified from the insect trypanosomatid Crithidia fasciculata and identified as a novel glutathione-spermidine conjugate, N1,N8-bis(L-gamma-glutamyl-L-hemicystinyl-glycyl)spermidine, for which the trivial name trypanothione is proposed. This discovery may open a new chemotherapeutic approach to trypanosomiasis and leishmaniasis.

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Mouse peritoneal macrophages that had ingested zymosan particles released a polar metabolite of arachidonic acid possessing slow-reacting substance activity in the guinea pig ileum assay. The metabolite was purified by solvent extraction, Sephadex G-25 column chromatography, and highpressure reverse-phase liquid chromatography. The purified metabolite absorbed light at 280 nm and contained a free amino group. When macroha ges were preincubated overnight with [3Hjarachidonic acid, [ mSIcysteine, or ['4Cloutamic acid, each radiolabel was incorporated into the compound. Direct amino acid analysis revealed glycine, glutamic acid, and cysteine at molar ratios of 0.97:1.00:0.82. The above data were consistent with the structure of leukotriene C, an adduct of arachidonic acid and glutathione. Quantification of the leukotriene C based on incorporation of [3Hlarachidonic acid or amino acid analysis indicated that 6 X 107 macrophages (3.6 mg of cell protein) released 7.5 nmol after a maximal phagocytic stimulus. The purified leukotriene C had a slow reacting substance activity of 11,500 units/nmol (1 unit has the activity of 5 ng of histamine in a guinea pig ileum contraction assay).Recent studies in this and other laboratories have shown that macrophages contain large amounts of esterified arachidonic acid (20:4) in their phospholipids (1,2) and that up to 50% of this 20:4 is released in the form of oxygenated metabolites in response to a phagocytic stimulus (1). These metabolites have been identified as prostaglandins and hydroxyicosatetraenoic acids (1). More detailed recovery experiments, however, revealed that significant quantities of a more polar species were being lost in previous fractionation procedures. The (Taconic Farms, Germantown, NY) weighing 25-30 g as described (5). Peritoneal cells (6 X 106) in alpha minimal essential medium (a-MEM, GIBCO) containing 10% fetal calf serum were added to 35-mm-diameter plastic culture dishes. After 2 hr at 37°C in 95% air/5% C02, cultures were washed three times in a-MEM to remove nonadherent cells and incubated overnight (16 hr) in fresh medium plus 10% fetal calf serum containing radiolabeled precursors as described below.Preparation of Unopsonized Zymosan. Zymosan was purchased from ICN, and stock solutions in a-MEM were prepared as described (6).Synthesis of Radiolabeled LTC by Macrophage Cultures. RPMI medium deficient in cysteine or glutamic acid and glutathione was prepared using an RPMI Select-Amine Kit (GIBCO) with replacement of RPMI vitamins with minimal essential medium vitamins. To obtain LTC labeled in the cysteine moiety, 1 ml of cysteine-deficient RPMI plus 10% fetal calf serum containing [a5S]cysteine (specific activity 284 mCi/mmol, Amersham/Searle; 1 Ci = 3.7 X 1010 becquerels) at 14.6 ,uCi/ml was added to each culture dish prior to the 16-hr incubation period. Labeling with [14C]glutamic acid was similarly performed, using glutamic acid-deficient RPMI and L-[1,2,3,4,5-14C]glutamic acid (specific activity 267 mCi/mmol, New England Nucle...

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