[ effect of thymoquinone on short-term spatial memory, passive avoidance learning and memory of diabetic rats and the involvement of hippocampal oxidative stress]

Chronic diabetes mellitus accompanies disturbance in learning, memory, and cognitive skills. With regard to anti-diabetic and antioxidant activity of thymoquinone [TQ], the effect of its chronic administration on learning and memory of diabetic rats was investigated. In this experimental study, male rats were divided into control, high dose TQ-treated control, diabetic, and low and high dose TQ- treated diabetic groups. TQ was administered i.p. at doses of 2.5 and 5 mg/kg one week after diabetes induction by streptozotocin, for 5 weeks. For evaluation of learning and memory, initial [IL] and step-through latencies [STL] were determined at the end of the study using passive avoidance test, and alternation behavior percentage was obtained using Y maze. In addition, hippocampal homogenate malondialdehyde [MDA] level was measured. STL significantly decreased in diabetic [p<0.01] and TQ-treated diabetic groups [p<0.001]; TQ treatment did not improve it in any of its doses. Alternation percentage was significantly lower in the diabetic group compared to the control [p<0.005]. TQ-treated diabetic group [at a dose of 5 mg/kg] showed a significantly higher score compared with diabetic group [p<0.01]. Diabetic rats also showed a significant increase in tissue level of malondialdehyde [p<0.01] and TQ treatment significantly reduced the level of MDA [p<0.05]. Although chronic treatment of diabetic rats with TQ could not enhance the capability of consolidation and recall in diabetic rats, it could improve spatial memory in them; part of its effect is via attenuation of lipid peroxidation

Altitudinal genetic variations among the Fagus orientalis Lipsky populations in Iran

Nuclear simple sequence repeats [nSSRs], together with 16 different enzyme loci, were used to analyze genetic diversity and differentiation among beech [Fagus orientalis Lipsky] populations along two altitudinal gradients in Hyrcanian forests of Iran. Both enzymes and nSSR analyses revealed a high level of genetic diversity in natural populations of F. orientalis. The genetic diversity, estimated by expected heterozygosity, was 0.19 [by enzymes] and 0.65 [by nSSRs]. Genetic variation across both markers did not reveal genetic structuring along altitudinal transects. There was less genetic variation among altitudinal gradients within transects compared to transect sites. Differentiation assays and analysis of molecular variance [AMOVA] indicated that there was a relatively low genetic differentiation among populations, and just 1% and 5% of the genetic variation occurred among populations by nSSR and enzyme data, respectively. Mantel tests showed that there was not a significant correlation between the genetic distances among populations and the distance of elevation. The results of the present study indicate that the relatively low genetic differentiation among F. orientalis populations at different elevations was not caused by ecological factors. These patterns suggest that higher rates of gene flow along altitudinal gradients within transects, than between transects; a process that could question altitudinal adaptation