Modeling Temperature-Dependent Sex Determination in Oviparous Species Using a Dynamical Systems Approach

Systems Engineering Approach to Modeling and Analysis of Chronic Obstructive Pulmonary Disease Part II: Extension for Variable Metabolic Rates

Recently, we developed a systems engineering model of the human cardiorespiratory system [Kurian et al. ACS Omega2023, 8 (23), 20524-20535. DOI: 10.1021/acsomega.3c00854] based on existing models of physiological processes and adapted it for chronic obstructive pulmonary disease (COPD)-an inflammatory lung disease with multiple manifestations and one of the leading causes of death in the world. This control engineering-based model is extended here to allow for variable metabolic rates established at different levels of physical activity. This required several changes to the original model: the model of the controller was enhanced to include the feedforward loop that is responsible for cardiorespiratory control under varying metabolic rates (activity level, characterized as metabolic equivalent of the task-Rm-and normalized to one at rest). In addition, a few refinements were made to the cardiorespiratory mechanics, primarily to introduce physiological processes that were not modeled earlier but became important at high metabolic rates. The extended model is verified by analyzing the impact of exercise (Rm > 1) on the cardiorespiratory system of healthy individuals. We further formally justify our previously proposed adaptation of the model for COPD patients through sensitivity analysis and refine the parameter tuning through the use of a parallel tempering stochastic global optimization method. The extended model successfully replicates experimentally observed abnormalities in COPD-the drop in arterial oxygen tension and dynamic hyperinflation under high metabolic rates-without being explicitly trained on any related data. It also supports the prospects of remote patient monitoring in COPD.

Sexual Development and the Environment: Conclusions from 40 Years of Theory

In this review, we consider the insight that has been gained through theoretical examination of environmental sex determination (ESD) and thermolability - how theory has progressed our understanding of the ecological and evolutionary dynamics associated with ESD, the transitional pathways between different modes of sex determination, and the underlying mechanisms. Following decades of theory on the adaptive benefits of ESD, several hypotheses seem promising. These hypotheses focus on the importance of differential fitness (sex-specific effects of temperature on fitness) in generating selection for ESD, but highlight alternative ways differential fitness arises: seasonal impacts on growth, sex-specific ages of maturation, and sex-biased dispersal. ESD has the potential to generate biased sex ratios quite easily, leading to complex feedbacks between the ecology and evolution of ESD. Frequency-dependent selection on sex acts on ESD-related traits, driving local adaptation or plasticity to restore equilibrium sex ratio. However, migration and overlapping generations ("mixing") diminish local adaptation and leave each cohort/population with the potential for biased sex ratios. Incorporating mechanism into ecology and evolution models reveals similarities between different sex-determining systems. Dosage and gene regulatory network models of sexual development are beginning to shed light on how temperature sensitivity and thresholds may arise. The unavoidable temperature sensitivity in sex-determining systems inherent to these models suggests that evolutionary transitions between genotypic sex determination (GSD) and temperature-dependent sex determination, and between different forms of GSD, are simple and elegant. Theoretical models are often best-served by considering a single piece of a puzzle; however, there is much to gain from reflecting on all of the pieces together in one integrative picture.