The biochemical ecology of Biomphalaria glabrata, a snail host of Schistosoma mansoni: short chain carboxylic and amino acids as phagostimulants.

1. A buccal mass olfactometer was used to investigate the responses of the fresh-water pulmonate snail Biomphalaria glabrata to carboxylic and amino acids. 2. The snails proved very discriminating as only 6 (14.6%) of the 41 chemical species tested were effective as phagostimulants. These are ranked as follows in order of potency:- butanoate greater than propanoate greater than D-malate greater than 2-hydroxybutanoate = L-tartrate = L-aspartate. 3. The structure-activity relationships of the active compounds, and their significance to the ecology and control of the snails are discussed.

Free radical-mediated damage during myocardial ischemia and reperfusion and protection by carnitine esters.

Ischemic injury may be exacerbated by readmission of oxygen into the myocardium, probably due to the formation of free radicals and their interaction with membrane lipids. We tested the hypothesis that ischemic myocardial damage is potentiated during reperfusion with excess free fatty acids in the globally ischemic rat heart, and in parallel studies, we investigated the protective effects of carnitine derivatives. Intermittent ischemia, i.e. three 20 min periods of ischemia followed by 10 min reperfusion each, was induced in isolated working rat hearts perfused with either glucose (11 mM) alone or glucose with palmitate (11 mM and 1.2 mM). The ischemic coronary flow was reduced to 1.1 ml/min in a low-flow group and equalled 0 ml/min in a no-flow group. Loss of functional recovery in the low-flow and no-flow group was more pronounced when palmitate was present in the perfusate. This was associated with increased levels of long-chain acyl-CoA esters in the palmitate perfused hearts. Malondialdehyde, an indicator of free radical formation, was elevated in both low-flow and no-flow groups when either substrate was used. We therefore suggest that free radical formation contributes to myocardial injury in intermittent ischemia. The mechanism of free radical formation and their sites of action have not yet been completely elucidated - the peroxidation of membrane lipids is probably involved, particularly in the presence of high palmitate. The protective effect of the carnitine derivatives D-propionylcarnitine, L-propionylcarnitine and propionylcarnitine taurine amide was studied in the no-flow hearts (Table 2).(ABSTRACT TRUNCATED AT 250 WORDS)

The carboxylic and amino acid chemoreception niche of Bulinus rohlfsi (Clessin), the snail host of Schistosoma haematobium.

The response of the freshwater snail, Bulinus rohlfsi, to gradients of carboxylic acids, amino acids and some related compounds was investigated by means of diffusion olfactometers. The snails proved to be very discriminating in their responses to the chemical species tested and there were also very marked ontogenetic differences. Although 15 distinctive types of amino and carboxylic acids proved to be attractants and arrestants, only octanoic acid proved effective for snails of all ages. Possible mechanisms involved in the chemoreception of active compounds, the ecological, physiological and biochemical relevance of the responses and possible application to controlled release technology are discussed.

Effect of diet on serum accumulation and renal excretion of aryl acids and secretory activity in normal and uremic man.

The influence of diet on aryl acid metabolism was determined in normal and azotemic subjects. Aryl acid content of serum and urine was estimated by fluorometry in relation to hippuric acid as a standard (FI-Hipp). Secretory activity, a reflection of the biological potency of aromatic acids in serum and urine, was determined by bioassay. The urinary excretion of FI-Hipp and secretory activity of five normal persons on an ad lib diet was 0.78 and 2.25 mM/day, respectively; similar values were observed in two subjects with chronic renal insufficiency. Subjects were fed prunes and cranberries, since these foods contain abundant quantities of hippurate precursors. Prunes 1.5 g/kg body weight, caused the urinary excretion of both FI-Hipp and secretory activity to increase about tenfold in normal and azotemic subjects. Prune feeding caused the serum levels of FI-Hipp and secretory activity to increase about threefold. Cranberries increased the renal excretion of FI-Hipp and secretory activity as did the ingestion of a beverage containing benzoate as a preservative. On the basis of these studies it is clear that diet is an important determinant of the load of aryl acids for urinary excretion; in patients with renal insufficiency the ingestion of foods containing precursors may cause serum level of biologically active aryl acids to increase strikingly.