光对高等植物乙醇酸氧化酶的诱导

本文阐述了光对高等植物乙醇酸氧化酶活性的影响,分析了白光、光强度、光质等对酶的诱导作用,讨论了前人解释光的作用机制的几种学说,在此基础上提出了另一个光对乙醇酸氧化酶诱导机理的假说,认为光对该酶的诱导有两方面的作用,一是进行光合作用产生乙醇酸,乙醇酸诱导酶蛋白合成;二是光促进体内FMN的生物合成与还原。所合成的酶蛋白再与FMN结合成全酶而表现出催化活性。     

Fenthion induced-oxidative stress in the liver of adult rats and their progeny: Alleviation by Artemisia campestris

Fenthion (FEN) is an organophosphate insecticide used in both agricultural and urban areas throughout the world including Tunisia. Recent investigations have proved the crucial role of natural antioxidants to prevent the damage caused by toxic compounds. In this study, we investigated the role of Artemisia campestris (Ac) leaf powder in protection against oxidative damage and hepatotoxicity induced by fenthion in female rats and their pups. Female Wistar rats were divided into four groups: group I served as controls which received standard diet, group II received orally FEN 551 ppm, group III received both 551 ppm of FEN and experimental diet (5% Artemisia) and group IV received experimental diet (5% Artemisia). Oral administration 551 ppm of FEN by drinking water to adult rats caused hepatotoxicity as monitored by the increase in the levels of hepatic markers enzymes (transaminases and lactate dehydrogenase), total cholesterol (TC) and triglycerides (TG), as well as hepatic malondialdehyde (MDA) levels thus causing a drastic alteration in antioxidant defence system. Particularly, the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) and the level of reduced glutathione (GSH) increased by FEN. These biochemical alterations were accompanied by histological changes marked by leucocytes infiltration, sinusoidal dilatation (moderate peliosis), granuloma inflammatory disorders and necrosis in hepatocytes of dams. While, slight leucocytes infiltration was shown in pups. Treatment with Ac prevented the liver damage induced by FEN, as revealed by inhibition of hepatic lipid peroxidation accompanied by an improvement of liver histopathological changes, CAT and GPx activities except GSH and SOD which were not modified. It could be concluded that A. campestris is promising a protective agent against hepatotoxicity during the exposure to fenthion.     

Studies on Fe deficiency stress response in three cultivars of sunflower (helianthus annuus L.)

Iron deficiency stress was induced in cultivars, PKV‐7237, Morden and EC‐68414 of sunflower (Helianthus annuus L) by first growing them in full nutrient medium and transferring to minus Fe medium after a month. The minus Fe nutrient medium was changed again at 13 and 26 days. The change in pH and the degree of chlorosis were recorded. It was found that the pH decreased rapidly in all cultivers from 6.4 to 3.8 in 5 days. The cv. Morden was found more tolerant to the stress than others. Furthermore, the flavinlike pigments as shown by the yellow coloration of the medium were more intense in PKV than in Korden, and were very much less in EC. It was also noted that the pH reduction was non‐redumptive, a feature observed even after transferring twice to fresh minus Fe medium adjusted to pH 6.4. The results of the experiments showed that as long as Fe absorbed from the pre‐stress medium was available in the root, the chlorosis was not severe; but once it was nearly depleted, chlorosis appeared and persisted for a long time.