High dose remifentanil increases myocardial oxidative stress and compromises remifentanil infarct-sparing effects in rats.

Chronic administration of high dose opioids such as morphine is known to create intracellular oxidative stress via an opioid receptor dependent mechanism and this can interfere with cellular function. This study aimed at examining whether such changes can occur following short term exposure to high concentration of remifentanil, a potent short acting opioid. We conducted a experimental study using rat myocardium and systematically quantified tissue levels of superoxide anions, malondialdehyde (MDA) and nitrotyrosine following exposure to increasing duration (15 min, 1 or 2 h) or escalating doses of remifentanil (1 µg, 5 µg, 10 µg or 20 µg/kg/min). Concurrently the susceptibility of the heart to ischaemia reperfusion injury was assessed under the similar conditions. For any given duration of remifentanil infusion, there was increasing superoxide anions generated as the dose of remifentanil was increased. MDA concentrations were significantly increased when the animal was exposed to 10 µg/kg/min for 2h or 20 µg/kg/min for any duration. There was a trend towards an increased nitrotyrosine concentration with increasing dose of remifentanil, becoming significant when the dose was 20 µg/kg/min. The infarct limiting ability of remifentanil was compromised when the dihydroethidium fluorescence positive cell percentage exceeded 50%, MDA concentration greater than 2 nmol/mg of protein and nitrotyrosine content exceeding 1.5 µg/mg of protein. Short term high dose opioid exposure can induce oxidative changes seen previously only with chronic opioid use and this high oxidative stress environment corrupts the heart's sensitivity to be preconditioned by opioids.

[FTIR research on the modification of plant oil pitch binders by polyester waste].

Various plant oil pitchs (cottonseed pitch, bean oil pitch, and mixed plant oil pitch) were used to prepare the plant oil pitch binders for casting. They were treated by polyester waste and processed by several technics such as esterifying. In the mean time, FTIR and TG were adopted to learn the structure, property, and sclerous mechanism of the binders. From the comparison with synthetic fat binder, the authors can see that the treated binders have similar components. They also have many excellent properties such as higher dry tensile strength and slower deflation velocity, which equal to or even exceed the properties of synthetic fat binder. Therefore, the treated binders, which were cheaper, can be used to make class I mold and core binders.