Browsing by Author "Perez, A"

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    Glyphosate-resistant Lolium multiflorum in Chilean orchards
    (BLACKWELL PUBLISHING LTD, 2003) Perez, A; Kogan, M
    Lolium multiflorum (Italian ryegrass) seeds suspected of being resistant to glyphosate were collected from fruit orchards at two locations, San Bernardo (SB) and Olivar (OL), Chile, that had been treated an average of three times per year with the isopropylamine salt of glyphosate during the previous 8-10 years. Laboratory experiments were conducted for each orchard population and a susceptible population, a commercial cultivar called Tama (TM), using Petri dishes containing filter paper saturated with 5 mL of glyphosate solution (0-160 mg a.e. L-1 ). Pot dose-response experiments were also conducted in the greenhouse. The three L. multiflorum populations were treated with glyphosate (0.00-4.32 kg a.e. ha(-1) ). The dose needed to reduce shoot length (Petri dish experiment) and fresh weight (pot dose-response experiment) by 50% was determined for each population. Compared with the TM population, the Petri dish experiment found that the SB and OL populations were five- and sixfold, respectively, more resistant to glyphosate, whereas the pot dose-response experiment found that the SB and OL populations were two- and fourfold, respectively, more resistant to glyphosate. These results confirm a new case of glyphosate resistance in a novel species, L. multiflorum , and correspond to the first case of glyphosate resistance reported from South America.
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    Increased aortic NADPH oxidase activity in rats with genetically high angiotensin-converting enzyme levels
    (LIPPINCOTT WILLIAMS & WILKINS, 2005) Jalil, JE; Perez, A; Ocaranza, MP; Bargetto, J; Galaz, A; Lavandero, S
    In humans and rats, angiotensin I-converting enzyme activity is significantly determined by a gene polymorphism. Homozygous Brown Norway rats have higher plasma angiotensin I-converting enzyme activity and circulating angiotensin II (Ang II) levels than Lewis rats. Because Ang II induces NAD(P) H oxidase activation, we hypothesized here that Brown Norway rats have higher vascular NAD(P) H oxidase activity and superoxide anion production than Lewis rats. Homozygous Brown Norway (n = 15) and Lewis (n = 13) male rats were used. Plasma angiotensin I-converting enzyme activity (by fluorimetry), Ang II levels (by high-performance liquid chromatography and radioimmunoassay), and aortic NAD(P) H oxidase activity, as well as superoxide anion production ( by chemiluminescence with lucigenin) were measured. Plasma angiotensin I-converting enzyme activity and Ang II levels were 100% higher in Brown Norway rats than in Lewis rats (P < 0.05). Aortic angiotensin I-converting enzyme, but not Ang II, was elevated (P < 0.05). Aortic superoxide anion production and NAD(P) H oxidase activity were 300% and 260% higher in Brown Norway than in Lewis rats, respectively (P < 0.05), which was not observed in Brown Norway rats treated with candesartan (10 mg/kg per day for 7 days). Endothelial NO synthase activity in the aorta from Brown Norway rats was significantly lower than in Lewis rats. However, inducible NO synthase activity and both endothelial NO synthase and inducible NO synthase mRNA and protein levels were similar in both genotypes. In summary, Brown Norway rats have higher vascular NAD(P) H oxidase activity and superoxide anion production than Lewis rats, suggesting the presence of a higher level of vascular oxidative stress in rats with genetically higher angiotensin I-converting enzyme levels. This effect is mediated through the angiotensin I receptor.