Determinants of macaques' space use: A test for the ecological constraints model using GPS collars.

As a central topic in Behavioral Ecology, animal space use involves dynamic responses to social and ecological factors. We collared 22 rhesus macaques (Macaca mulatta) from six groups on Neilingding Island, China, and collected 80,625 hourly fixes over a year. Using this high-resolution location data set, we quantified the macaques' space use at the individual level and tested the ecological constraints model while considering various environmental and human interfering factors. As predicted by the ecological constraints model, macaques in larger groups had longer daily path lengths (DPLs) and larger home ranges. We found an inverted U-shape relationship between mean daily temperatures and DPLs, indicating that macaques traveled farther on mild temperature days, while they decreased DPLs when temperatures were too high or too low. Anthropogenic food subsidies were positively correlated to DPLs, while the effect of rainfall was negative. Macaques decreased their DPLs and core areas when more flowers and less leaves were available, suggesting that macaques shifted their space use patterns to adapt to the seasonal differences in food resources. By applying GPS collars on a large number of individuals living on a small island, we gained valuable insights into within-group exploitation competition in wild rhesus macaques.

Caffeine-induced neurotoxicity mediated by Nrf2 pathway in PC12 cells and zebrafish larvae.

Caffeine is one of the most widely used psychostimulants in the world and possesses central excitative, anti-depressive, and neuroprotective properties. However, excessive ingestion or abuse of caffeine can lead to intoxication. Many toxic effects are attributed to oxidative damage, and nuclear factor erythroid 2-related factor 2 (Nrf2) is a critical intracellular regulator of the oxidative stress response. Here, we investigated the neurotoxicity of caffeine in rat pheochromocytoma PC12 cells and zebrafish larvae. It was found that caffeine inhibited the viability of PC12 cells in a dose- and time-dependent manner. Furthermore, it induced PC12 cell apoptosis and elevated reactive oxygen species (ROS) production. Quantitative polymerase chain reaction (qPCR) and western blotting revealed that caffeine also inhibited the expression levels of Nrf2 mRNA and protein and its target genes (e.g., NADPH quinone oxidoreductase 1 [NQO1]). Furthermore, Nrf2 silencing attenuated the toxic effects of caffeine. In addition, zebrafish larvae were treated with different doses of caffeine. Behavioral experiments showed that a low dose of caffeine (0.05 to 0.3 mM) increased the average distance of movement and promoted excitation. Survivorship curves showed that caffeine (0.2 to 1.5 mM) caused lethality. Finally, qPCR revealed that a higher dose of caffeine inhibited mRNA levels in the Nrf2 pathway. Based on these results, this study identified for the first time that overuse of caffeine can induce neurotoxicity by inhibiting the Nrf2 pathway. These results will provide a new perspective for studies on caffeine toxicity.