Estradiol valerate and tibolone: effects upon brain oxidative stress and blood biochemistry during aging in female rats.

Estrogen compounds have been described as important brain protectors. This study investigated the effects of estradiol valerate (EV--0.3 mg/kg) and two concentrations of tibolone (TB1=0.5 mg/kg and TB2=1 mg/kg) on brain oxidative stress parameters and blood biochemistry in ovariectomized female rats, of three different age groups (young--2 months, adult--8 months, and old--20 months). In the brain cortex, young and old TB2-treated and old no-hormone-replacement (NR) females showed lower lipid hydroperoxide (LPO) levels compared to young Sham and adult TB1 animals (P<0.05). Also in the cortex, both tibolone doses produced higher (P<0.05) total antioxidant capacity (TOSC) levels compared to EV-treated adult females. Ovariectomized adult females (NR, EV, TB1 and TB2) showed lower (P<0.05) TOSC levels in the hippocampus compared to the Sham control. Reactive oxygen species (ROS) were higher (P<0.05) in old females compared to all younger ones. TB2-treated adults showed higher plasma glucose (P<0.05) levels compared to old animals. Regardless of age, TB2 treatment increased female (P<0.05) LDL levels compared to Sham and EV-treated animals. In old females, TB2 significantly increased HDL levels compared to Sham controls, and decreased triglyceride levels were shown in EV, TB1 and TB2 compared to Sham old females. The Atherogenic Index of Plasma was higher (P<0.05) in adult tibolone-treated females compared to both young and old TB2-treated females. These results suggest that the effects of gonad steroid on brain and blood physiology change significantly with aging, and that evaluating hormonal treatment types and doses could be the key factor in the potential use of a specific hormone therapy.

The benefits and drawbacks of nicotine exposure in the cortex and hippocampus of old rats.

Nicotine is the main alkaloid of tobacco and possesses well-established stimulant effects. Previous reports show that nicotine at low doses improves memory functions, while high doses impair memory. This study aims to analyze the effects of nicotine (NIC) on inhibitory avoidance task and on DNA damage, reactive oxygen species (ROS) concentration, total antioxidant capacity, and lipid peroxidation in cortex and hippocampus of old rats. Male Wistar rats of 24-26 months old (620-700g) were exposed i.p. to two doses (0.3 and 1mg/kg) of NIC daily during 9 days. The treatment NIC 0.3 enhanced long-term memory (p<0.05), whereas NIC 1 improved both short and long-term memories (p<0.05). DNA damage was observed only in hippocampus (p<0.05) after NIC 1 exposure. A similar result was obtained for ROS: higher levels were detected at NIC 1 treatment in hippocampus (p<0.05). No alterations in the total antioxidant capacity were verified after NIC exposure (0.3 and 1mg/kg) in both tissues (p>0.05). Finally, evidence of oxidative damage was observed in terms of lipid peroxides levels, being higher at NIC 1 in hippocampus (p<0.05). Overall the results indicate that deleterious effects paralleled the improved short and long-term memories at the highest NIC dose, since augmented DNA damage, ROS concentration and lipid peroxides levels were registered.

Estradiol valerate and tibolone: effects on memory.

This study investigated the effects of estradiol valerate (EV) and tibolone (TB) treatments on some memory parameters of ovariectomized young (2 months), adult (8 months) and old (20 months) female rats. A Sham-operated group was used as control and the animals were treated daily, by oral gavage, with saline (Sham and placebo NR group), EV (0.3 mg/kg) or TB (0.5 or 1 mg/kg, TB1 and TB2, respectively). In step-down inhibitory avoidance task, the latency of old TB2-treated females in the short-term test was significantly inferior (p<0.05), compared to TB2 adults. In the elevated plus maze, adult NR females spent significantly less time (p<0.05) in the open arms as compared with EV and TB2-treated animals. Additionally, adult TB2-treated females spent significantly less time in the closed arms compared to Sham, NR and TB1 groups. Finally, in the water maze retention test, young TB1-treated animals performed worse when compared to Sham, EV and TB2 females. In the old animals, EV treatment hampered subject performance as compared to all other treatments. Taken together, these results indicate that ovarian hormones differently affect female memory in an age-dependent manner.

Catabolism of 1,3-dinitrobenzene by Rhodococcus sp. QT-1.

The 1,3-dinitrobenzene-degrading Rhodococcus strain QT-1 was isolated under nitrogen limiting conditions from contaminated soil samples. Experimental data indicate tha 1,3-dinitrobenzene is metabolized via 4-nitrocatechol. Both compounds were oxidized by resting cells and nitro groups were completely eliminated as nitrite. Strain QT-1 utilizes both 1,3-dinitrobenzene and 4-nitrocatechol as source of nitrogen in the absence as well as in the presence of high amounts of ammonia. Growth on 4-nitrocatechol does not induce the enzyme(s) for the initial oxidation of 1,3-dinitrobenzene.