Influence of different concentrations of 1-methylcyclopropene on the quality of tomato harvested at different maturity stages.

BACKGROUND: A wide range of 1-methylcyclopropene (1-MCP) concentrations as well as various treatment durations have been studied in tomatoes by different researchers. However, little is known about interaction of 1-MCP doses and maturity stages of tomatoes. Therefore the effects of different concentrations of 1-MCP on storage and postharvest quality of 'Zorro' tomatoes harvested at mature green or pink maturity stages were investigated in a 2-year trial study. RESULTS: Higher concentrations of 1-MCP delayed and/or inhibited all parameters related to fruit ripening, such as lycopene, chlorophyll, surface color, polygalacturonase (PG) activity and soluble solids content/titratable acidity (SSC/TA), and these effects were greater in tomatoes harvested at the mature green stages. Lower concentrations of 1-MCP slightly reduced the loss in general quality features compared with untreated tomatoes. CONCLUSION: The results suggest that 1-MCP, especially at higher doses, is effective for delaying ripening of mature green tomatoes. Mature green fruits treated with 1000 nL L(-1) 1-MCP were stored for 35 days without significant decreases in quality characteristics such as elasticity, surface color and SSC/TA with certain physiological processes (ethylene production, PG activity, lycopene synthesis).

Temperature and exposure time during ethylene conditioning affect ripening of Bartlett pears.

Freshly harvested early- and mid-season Bartlett pears (Pyrus communis) were treated with ethylene (air plus 10 Pa C(2)H(4)) or air at 5, 10, and 20 degrees C for 24 and 48 h (experiment 1) and at 5 and 10 degrees C for 48, 72, and 96 h and at 20 degrees C for 24 h (experiment 2). Following C(2)H(4) or air treatment at different temperatures and durations, pears were transferred to 20 degrees C in air for ripening. Bartlett pears were evaluated for firmness, color, respiration, C(2)H(4) production, and activities of 1-aminocyclopropane-1-carboxylic acid synthase (ACC-S) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACC-O). Ethylene action was temperature dependent. The duration of C(2)H(4) conditioning needed to fully induce ripening was longer at lower temperatures: 72 h at 5 degrees C, 48 h at 10 degrees C, and 24 h at 20 degrees C. Cold storage in air for as little as 3-4 days at 5 or 10 degrees C appeared to hasten subsequent ripening, but to a lesser extent than pears kept for 2 weeks at -1 degrees C in air. Despite a significant increase in ACC-S activity in pears treated with C(2)H(4) at 5 degrees C, there was not a simultaneous increase in ACC-O activity, resulting in low C(2)H(4) production that was insufficient to generate the threshold endogenous levels of C(2)H(4) required for ripening. Contrary to previous findings with pears, these data indicate that ACC-O could be a rate-limiting step in C(2)H(4) biosynthesis.

Effects of hypothermia on blood endogenous endotoxin levels during cardiopulmonary bypass.

Endotoxin activates white blood cells and complement and produces a spectrum of clinical syndromes ranging from fever to septic shock. Although production of endogenous endotoxemia during cardiopulmonary bypass (CPB) has recently been reported, the role of hypothermia on endotoxemia is not clear. In this study, we evaluated the effects of moderate (24-28 degrees C) and mild (32-34 degrees C) hypothermia on blood endotoxin levels. The study population consisted of 20 patients who underwent coronary artery bypass grafting (CABG) with CPB. Moderate systemic hypothermia was applied during aortic cross-clamping in ten patients (group 1) and mild hypothermia in the remaining ten patients (group 2). The mean rectal temperatures were 26.8 +/- 1.2 degrees C in group 1 and 33.8 +/- 0.8 degrees C in group 2. The blood samples for endotoxin level measurements were obtained before CPB, during aortic cross-clamping, immediately after the release of the cross-clamp, 20 minutes after the release of the cross-clamp, after CPB, and 2 hours postoperatively. There were no endotoxins in any of the samples before CPB, but it was detected after CPB in both groups. The endotoxin levels were significantly higher in group 1 than in group 2. The present study suggests that when hypothermia is the technique of choice, the deleterious effects of endotoxemia on patients with comorbidity must be considered.