Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Mitochondrial and Oxidative Stress Aspects in Hippocampus of Rats Submitted to Dietary n-3 Polyunsaturated Fatty Acid Deficiency After Exposure to Early Stress

Neurochemical Research - Chronic dietary long-chain polyunsaturated fatty acids (PUFAs) deficiency may lead to changes in cortex and hippocampus neuronal membrane phospholipids, and may be linked...     

Chronic Stress Causes Sex-Specific and Structure-Specific Alterations in Mitochondrial Respiratory Chain Activity in Rat Brain

Chronic restraint stress (CRS) induces a variety of changes in brain function, some of which are mediated by glucocorticoids. The response to stress occurs in a sex-specific way, and may include mitochondrial and synaptic alterations. The synapse is highly dependent on mitochondrial energy supply, and when mitochondria become dysfunctional, they orchestrate cell death. This study aimed to investigate the CRS effects on mitochondrial respiratory chain activity, as well as mitochondrial potential and mass in cell body and synapses using hippocampus, cortex and striatum of male and female rats. Rats were divided into non-stressed (control) and stressed group (CRS during 40 days). Results showed that CRS increased complex I–III activity in hippocampus. We also observed an interaction between CRS and sex in the striatal complex II activity, since CRS induced a reduction in complex II activity in males, while in females this activity was increased. Also an interaction was observed between stress and sex in cortical complex IV activity, since CRS induced increased activity in females, while it was reduced in males. Glucocorticoid receptor (GR) content in cortex and hippocampus was sexually dimorphic, with female rats presenting higher levels compared to males. No changes were observed in GR content, mitochondrial potential or mass of animals submitted to CRS. It was concluded that CRS induced changes in respiratory chain complex activities, and some of these changes are sex-dependent: these activities are increased in the striatal mitochondria by CRS protocol mainly in females, while in males it is decreased.

     

Na+, K+ ATPase Activity Is Reduced in Amygdala of Rats with Chronic Stress-Induced Anxiety-Like Behavior

In this study, we examined the effects of two chronic stress regimens upon anxiety-like behavior, Na⁺, K⁺-ATPase activity and immunocontent, and oxidative stress parameters (antioxidant enzymes and reactive oxygen species production) in the amygdala. Male rats were subjected to chronic unpredictable and to chronic restraint stress for 40 days. Subsequently, anxiety-like behavior was examined. Both stressed groups presented increased anxiety-like behavior. Reduced amygdalal Na⁺, K⁺-ATPase activity in the synaptic plasma membranes was also observed, without alterations in the amygdala immunocontent. In addition, when analyzing oxidative stress parameters, only superoxide dismutase activity was decreased in the amygdala of animals subjected to unpredictable stress. We conclude that both models of chronic stress lead to anxiety-like behavior and decreased amygdalal Na⁺, K⁺-ATPase activity, which appears not to be related to oxidative imbalance. The relationship between this decreased activity and anxiety-like behavior remains to be studied.     

Maternal Hypermethioninemia Affects Neurons Number,Neurotrophins Levels,Energy Metabolism,and Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase Expression/Content in Brain of Rat Offspring

In the current study, we verified the effects of maternal hypermethioninemia on the number of neurons, apoptosis, nerve growth factor, and brain-derived neurotrophic factor levels, energy metabolism parameters (succinate dehydrogenase, complex II, and cytochrome c oxidase), expression and immunocontent of Na⁺,K⁺-ATPase, edema formation, inflammatory markers (tumor necrosis factor-alpha and interleukin-6), and mitochondrial hydrogen peroxide levels in the encephalon from the offspring. Pregnant Wistar rats were divided into two groups: the first one received saline (control) and the second group received 2.68 μmol methionine/g body weight by subcutaneous injections twice a day during gestation (approximately 21 days). After parturition, pups were killed at the 21st day of life for removal of encephalon. Neuronal staining (anti-NeuN) revealed a reduction in number of neurons, which was associated to decreased nerve growth factor and brain-derived neurotrophic factor levels. Maternal hypermethioninemia also reduced succinate dehydrogenase and complex II activities and increased expression and immunocontent of Na⁺,K⁺-ATPase alpha subunits. These results indicate that maternal hypermethioninemia may be a predisposing factor for damage to the brain during the intrauterine life.     

Interactions Between Chronic Stress and Chronic Consumption of Caffeine on the Enzymatic Antioxidant System

We studied the effect of chronic caffeine on parameters related to oxidative stress in different brain regions of stressed and non-stressed rats. Wistar rats were divided into three groups: control (receiving water), caffeine 0.3 g/L and caffeine 1.0 g/L (in the drinking water). These groups were subdivided into non-stressed and stressed (repeated restraint stress during 40 days). Lipid peroxide levels and the total radical-trapping potential were assessed, as well as antioxidant enzyme activities superoxide dismutase, gluthatione peroxidase, and catalase in hippocampus, striatum and cerebral cortex. Results showed interactions between stress and caffeine, especially in the cerebral cortex, since caffeine increased the activity of some antioxidant enzymes, but not in stressed animals. We concluded that chronic administration of caffeine led, in some cases, to increased activity of antioxidant enzymes. However, these effects were not observed in the stressed animals.     

The effects of hypercaloric diets on glucose homeostasis in the rat: influence of saturated and monounsaturated dietary lipids

Consumption of energy-dense/high-fat diets is strongly and positively associated with overweight and obesity, which are associated with increase in the prevalence of certain chronic diseases. We evaluated the effect of hypercaloric/fat or normocaloric diets on some biochemical parameters in rats. Seventy-two rats were divided into four groups that were fed for 16 weeks with diets: normocaloric [9.12% soy oil, normocaloric soy oil (NSO)], hypercaloric olive oil [43.8% olive oil, hypercaloric olive oil (HOO)], hypercaloric saturated fat [43.8% saturated fat, hypercaloric saturated fat (HSF)] and normocaloric saturated fat [43.8% saturated fat, normocaloric saturated fat (NSF)]. HSF rats consumed more calories daily than the others and gained more retroperitoneal fat, although HSF and HOO rats had higher body weight. In liver, glycogen synthesis and concentration were higher in rats HSF and NSF. In plasma, total cholesterol (TC) levels were higher in HSF rats than in the others, and triacylglycerol (TAG) levels were lower in HOO and higher in HSF rats in relation to the others. In liver, TC and TAG were elevated in HSF, NSF and HOO rats. Paraoxonase 1 activity, which is related to high-density lipoprotein cholesterol and has anti-atherogenic role was lower in rats HSF. In HOO rats, glucose tolerance test was altered, but insulin tolerance test was normal. These results suggest that consumption of energy-dense/high-fat diets, both saturated or monounsaturated, causes damaging effects. However, more studies are necessary to understand the mechanisms by which these diets cause the metabolic alterations observed.