Evolution in eggs and phases: experimental evolution of fecundity and reproductive timing in Caenorhabditis elegans

Comparison of ARIMA, ES, GRNN and ARIMA–GRNN hybrid models to forecast the second wave of COVID-19 in India and the United States

As acute infectious pneumonia, the coronavirus disease-2019 (COVID-19) has created unique challenges for each nation and region. Both India and the United States (US) have experienced a second outbreak, resulting in a severe disease burden. The study aimed to develop optimal models to predict the daily new cases, in order to help to develop public health strategies. The autoregressive integrated moving average (ARIMA) models, generalised regression neural network (GRNN) models, ARIMA–GRNN hybrid model and exponential smoothing (ES) model were used to fit the daily new cases. The performances were evaluated by minimum mean absolute per cent error (MAPE). The predictive value with ARIMA (3, 1, 3) (1, 1, 1)₁₄ model was closest to the actual value in India, while the ARIMA–GRNN presented a better performance in the US. According to the models, the number of daily new COVID-19 cases in India continued to decrease after 27 May 2021. In conclusion, the ARIMA model presented to be the best-fit model in forecasting daily COVID-19 new cases in India, and the ARIMA–GRNN hybrid model had the best prediction performance in the US. The appropriate model should be selected for different regions in predicting daily new cases. The results can shed light on understanding the trends of the outbreak and giving ideas of the epidemiological stage of these regions.

Sex- and brain region-specific patterns of gene expression associated with socially-mediated puberty in a eusocial mammal

The social environment can alter pubertal timing through neuroendocrine mechanisms that are not fully understood; it is thought that stress hormones (e.g., glucocorticoids or corticotropin-releasing hormone) influence the hypothalamic-pituitary-gonadal axis to inhibit puberty. Here, we use the eusocial naked mole-rat, a unique species in which social interactions in a colony (i.e. dominance of a breeding female) suppress puberty in subordinate animals. Removing subordinate naked mole-rats from this social context initiates puberty, allowing for experimental control of pubertal timing. The present study quantified gene expression for reproduction- and stress-relevant genes acting upstream of gonadotropin-releasing hormone in brain regions with reproductive and social functions in pre-pubertal, post-pubertal, and opposite sex-paired animals (which are in various stages of pubertal transition). Results indicate sex differences in patterns of neural gene expression. Known functions of genes in brain suggest stress as a key contributing factor in regulating male pubertal delay. Network analysis implicates neurokinin B (Tac3) in the arcuate nucleus of the hypothalamus as a key node in this pathway. Results also suggest an unappreciated role for the nucleus accumbens in regulating puberty.