Rapid involution of the thymus was induced in SD rats after administration of high-dose estradiol benzoate. The prominent histological changes observed were as follows: (1) the thymic cortex was become thinner; (2) the corticomedullary ratio was decreased; and (3) a substantial loss of cortical lymphocytes occurred. As a consequence, marked reduction in thymus weight was caused. Under electron microscope, the epithelial reticular cells (ERCs) were found, to be a heterogenous cell group. Their responses to high-dose estradiol were different from each other, and the distinctive changes observed were: (1) cell degeneration changes in some pale ERCs were observed; (2) the other pale ERCs were found to be filled with lower density vacuoles which were very similar to secretory vacuoles; and (3) the dark ERCs were inereased obviously, and many collagen fibril bundles were seen in the vicinity of their perikarya or wrapped by their cytoplasmic processes. There were no striking ultrastructural changes in thymocytes. However, the number of ANAE positive cells in the experimental group was lower than that of the controls evidently. In addition, a large number of plasma cells were observed in the cortex of the experimental group. Based on the above mentioned observations, the possible mechanism of the estradiol effect on the thymus involution was discussed.

Objective:To assess the influence of extreme temperature events on the mortality risk of nervous system diseases in residents of Jiangsu Province and identify patients with nervous system diseases who are susceptible to extreme temperature events.Methods:Acase-crossover design was used to investigate the cumulative lagged effects of extreme temperature events on the mortality risk of nervous system disease in local residents by using the data on causes of death from nervous system diseases in Jiangsu from 2014 to 2020 with conditional logistic regression model. The final definition of extreme temperature events was established using Akaike information criterion. The heat wave was defined as 4 or more consecutive days with daily mean temperatures above the 92.5 th percentile of annual daily mean temperatures, and the cold spell was defined as 2 or more consecutive days with daily mean temperatures below the 10 th percentile of annual daily mean temperatures. Furthermore, stratified analyses was conducted to compare the effects of extreme temperature events on mortality risk in populations in different gender, age and marital status groups to identify susceptible populations to extreme temperature event. Results:Statistical results showed that the effect values of heat wave and cold spell on the mortality risk of nervous system diseases all peaked at the 7 th day of the cumulative lag, with OR of 1.60 (95% CI: 1.44-1.76) and 1.33 (95% CI: 1.13-1.56), respectively. Heat wave exposure increased mortality risk for individuals with Alzheimer's and Parkinson's diseases, while cold spell exposure increased the mortality risk for those with Alzheimer's disease. Stratified analyses showed that the mortality risk for nervous system disease and Alzheimer's disease was higher in partnerless population after heat wave exposure. Conclusions:Heat wave and cold spell were associated with increased mortality risks for nervous system disease, highlighting the need for improved early warning systems for extreme temperature event. In the context of heat wave, interventions to protect individuals with nervous system disease should prioritize partnerless population.