Melatonin attenuates cerebral hypoperfusion-induced hippocampal damage and memory deficits in rats by suppressing TRPM7 channels.

This study was conducted to examine if modulating transporters like transient receptor potential cation channels, subfamily M, member 7 (TRPM7) underlies the hippocampal neuroprotection afforded by melatonin (Mel) in rats exposed to cerebral hypoperfusion (CHP). Experimental groups included control, Mel-treated (1.87 g/kg), CHP, and CHP + Mel (1.87 g/kg)-treated rats. CHP was induced by the permanent bilateral occlusion of the common carotid arteries (2VO) method and treatments were conducted for 7 days, orally. Mel prevented the damage of the dental gyrus and memory loss in CHP rats and inhibited the hippocampal reactive oxygen species (ROS), lipid peroxidation levels of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6), interleukine-1 beta (IL-1ß), and prostaglandin E2 (PGE2). It also reduced the hippocampal transcription of the TRPM7 channels and lowered levels of calcium (Ca2+) and zinc (Zn2+). Mel Also enhanced the levels of total glutathione (GSH) and superoxide dismutase (SOD) in the hippocampus of the control and CHP-treated rats. In conclusion, downregulation of TRPM7 seems to be one mechanism underlying the neuroprotective effect of Mel against global ischemia and is triggered by its antioxidant potential.

Preparing for Pediatrics: Experiential Learning Helps Medical Students Prepare for Their Clinical Placement.

Despite the importance of effective communication skills in pediatrics, clinical placements may inadequately prepare undergraduate students to communicate with children. The integration of non-clinical interactions with healthy children within a pediatric curriculum has the potential to enhance learning. We designed and implemented a novel course involving experiential learning, including video-recorded consultations with simulated parents (SPs), team-based scenarios with a pediatric mannequin, interactions with healthy children through a pre-school visit and medical student led health workshops for primary school children. Medical students at the RCSI University of Medicine and Health Sciences took part in the course. We used a mixed methods approach to assess the impact of the course. We investigated medical students' perspectives through a pre- and post-intervention questionnaire and post-intervention focus group discussions (FGDs). We assessed participating children's health literacy at the start of the course. 144/279 (51.6%) of the fourth year medical student cohort on their pediatric rotation, consented to participate in the study. All 144 (100%) of consenting students completed the pre-intervention questionnaire. 59/144 (40.1%) of consenting students completed the post-intervention questionnaire. Results showed a statistically significant improvement in ratings (p < 0.05) for items related to managing a confrontational situation involving family members, completing a psychosocial assessment with an adolescent and effectiveness using evidence-based medicine (EBM) when motivating patients. There was a statistically significant decrease in how students rated their comfort at using EBM when motivating patients. Four themes relating to how students experienced the intervention were identified from eight FGDs (n = 35 students): Shaping Student Learning; Supporting Student Learning; Developing New Skills and Feeling More Prepared. 39/49 (79.6%) children completed a health literacy assessment. All questions had a high percentage of positive responses. Question 7, understanding your doctor, had the highest proportion of negative responses (27%). Ours is one of the first studies to design an educational intervention to enhance pediatrics teaching by combining interactions with healthy children outside of a clinical setting with more traditional simulation-based approaches. We conclude that this type of intervention supports students' learning of pediatric communication skills and enhances students' perceived preparation for clinical placement.

Effects of the linewidth enhancement factor on the microwave linewidth of the period-one oscillations of optically injected semiconductor lasers.

We investigate the microwave linewidth of the period-one (P1) nonlinear dynamics of an optically injected semiconductor laser as a function of the linewidth enhancement factor. Under proper conditions of optical injection, the destabilizing effect of a large value of the linewidth enhancement factor of the injected semiconductor laser is found to be unexpectedly suppressed in the P1 oscillation of the laser, thus resulting in a narrow P1 linewidth equal to that generated by a laser of a small linewidth enhancement factor. By properly choosing the operating point, P1 oscillations with microwave linewidths that are an order of magnitude narrower than the free-running optical linewidths of the master and slave lasers are observed.

Linewidth characteristics of period-one dynamics induced by optically injected semiconductor lasers.

Period-one (P1) nonlinear dynamics of optically injected semiconductor lasers exhibit periodic intensity fluctuations with operating frequencies that are tunable in the micro/millimeter-wave range. Through numerical experiments, the characteristics of the microwave linewidth of the P1 oscillation and the linewidths of its optical frequency components due to intrinsic laser noise sources are investigated. The field noise and carrier noise of the master and slave lasers are systematically considered. The contribution of the field noise of the master laser is significant; it considerably broadens the microwave linewidth of the P1 oscillation. When the operating conditions in the regions of high microwave power are properly adjusted, the microwave linewidth of the P1 oscillation becomes narrower than the free-running optical linewidths of the master and slave lasers. Regions with low sensitivity to time-dependent fluctuations in an operating parameter show reduced microwave linewidth of the P1 oscillation.

Optimizing optically injected semiconductor lasers for periodic dynamics with reduced sensitivity to perturbations.

Optically injected semiconductor lasers generate limit-cycle dynamics of period-one and period-two oscillations at microwave frequencies. At specific operating points, the periodic oscillations can be rendered insensitive to small-signal fluctuation in the operating conditions of the master and slave lasers. Periodic oscillations with low-sensitivity to fluctuation in the slave laser bias current, injection strength, or detuning frequency can be enhanced through tailoring the intrinsic laser parameters. Here, through numerical calculations, the effects of each intrinsic parameter on the various low-sensitivity operating points are demonstrated through detailed maps as functions of the operating parameters. For enhanced low sensitivity to bias-current and injection-strength fluctuations, a laser with a small linewidth enhancement factor is favored. Conversely, a large linewidth enhancement factor enhances low sensitivity to detuning-frequency fluctuations. Lasers with a more negative value of the gain saturation factor confine the regions of low sensitivity to fluctuations in the bias current and detuning frequency to the extrema of the periodic oscillation frequency. The laser relaxation rates that enhance the periodic-oscillation dynamic regions of an optically injected semiconductor laser, in turn, increases the regions of the various types of low-sensitivity operating points.

Limit-cycle dynamics with reduced sensitivity to perturbations.

Limit-cycle oscillators are used to model a broad range of periodic nonlinear phenomena. Using the optically injected semiconductor laser as a paradigmatic example, we demonstrate that at specific operating points, the period-one oscillation frequency is simultaneously insensitive to multiple perturbation sources. In our system these include the temperature fluctuations experienced by the master and slave lasers as well as fluctuations in the bias current applied to the slave laser. Tuning of the oscillation frequency then depends only on the injected optical field amplitude. Experimental measurements are in detailed quantitative agreement with numerical modeling. These special operating points should prove valuable for developing ultrastable nonlinear oscillators, such as a narrow-linewidth, frequency-tunable photonic microwave oscillator.