Being immune privileged, the central nervous system (CNS) is constituted by unique parenchymal and non-parenchymal tissue-resident macrophages, namely, microglia and border-associated macrophages (BAMs), respectively. BAMs are found in the choroid plexus, meningeal and perivascular spaces, playing critical roles in maintaining CNS homeostasis while being phenotypically and functionally distinct from microglial cells. Although the ontogeny of microglia has been largely determined, BAMs need comparable scrutiny as they have been recently discovered and have not been thoroughly explored. Newly developed techniques have transformed our understanding of BAMs, revealing their cellular heterogeneity and diversity. Recent data showed that BAMs also originate from yolk sac progenitors instead of bone marrow-derived monocytes, highlighting the absolute need to further investigate their repopulation pattern in adult CNS. Shedding light on the molecular cues and drivers orchestrating BAM generation is essential for delineating their cellular identity. BAMs are receiving more attention since they are gradually incorporated into neurodegenerative and neuroinflammatory disease evaluations. The present review provides insights towards the current understanding regarding the ontogeny of BAMs and their involvement in CNS diseases, paving their way into targeted therapeutic strategies and precision medicine.

The secondary sex ratio (SSR), indicating the ratio of male to female live births, has garnered considerable attention within the realms of reproductive biology and public health. Numerous factors have been posited as potential trendsetters of the SSR. Given the extensive research on the impact of daily behaviors and habits on individuals’ reproductive health, there is a plausible suggestion that lifestyle choices may also influence the SSR. By synthesizing the existing literature on the current research field, this comprehensive review indicates that an elevated SSR has been associated with an increased intake of fatty acids and monosaccharides, proper nutrition, higher educational levels, financial prosperity, and favorable housing conditions. On the other hand, a decreased SSR may be linked to undernutrition, socioeconomic disparities, and psychological distress, aligning with the Trivers–Willard hypothesis. Occupational factors, smoking habits, and cultural beliefs could also contribute to trends in the SSR. Our review underscores the significance of considering the aforementioned factors in studies examining the SSR and emphasizes the necessity for further research to unravel the mechanisms underpinning these connections. A more profound comprehension of SSR alterations due to lifestyle holds the potential to adequately develop public health interventions and healthcare strategies to enhance reproductive health and overall well-being.

The secondary sex ratio (SSR), defined as the ratio of male to female births in a population, has long been a subject of scientific inquiry due to its potential as a health indicator. The interplay between catastrophic events and the delicate balance of male and female births presents a nuanced and compelling study area. Natural disasters, such as earthquakes, hurricanes, floods, and volcanic eruptions, have been known to disrupt ecosystems and human populations, leading to both short-term and long-term consequences. Studies have suggested a potential influence of these disasters on the SSR, with varying degrees of impact observed across different regions and disaster types. Similarly, nuclear accidents, such as the infamous Chernobyl disaster, have sparked interest in their potential effects on human health and development. The release of radioactive materials into the environment can have far-reaching consequences, including impacts on reproductive outcomes. Through a rigorous examination of the existing literature, the present review aims to synthesize current knowledge on the impacts of natural disasters and nuclear accidents on the SSR and unravel the mechanisms that explain SSR fluctuations. By shedding light on the diverse influences shaping the SSR, this narrative review contributes to a deeper appreciation of the intricate interplay between environmental, biological, and societal factors that determines the SSR, calling for targeted strategies to mitigate potential adverse effects on sex ratios in the aftermath of such events.

The secondary sex ratio (SSR), which reflects the proportion of male to female offspring at birth, is influenced by a complex interplay of multiple factors. This review delves into the current understanding of how infections and genetics contribute to variations in the SSR. The effects of infections on the SSR represent an intriguing intersection of biology and epidemiology. Research indicates that several infectious diseases, such as toxoplasmosis, coronavirus disease 2019, Spanish flu, acquired immunodeficiency syndrome and tuberculosis, can impact the SSR through mechanisms that are only partially understood. Genetics are also scrutinized in this review. Although their involvement in determining the SSR is debatable, various genetic factors have been studied. The influences of the Rhesus D heterozygous phenotype, major histocompatibility complex, corticosteroid-binding globulin deficiency, ethnicity, and consanguinity on SSR have been delineated. By amalgamating findings from diverse disciplines, this review aims to offer a comprehensive overview of the multifaceted impact of infections and genetics on SSR, pinpointing potential implications for reproductive biology and public health.

The secondary sex ratio (SSR), defined as the ratio of male to female live births in a population, is a crucial indicator of reproductive and public health. External factors, such as lifestyle, natural disasters, environmental chemicals and infections, have been examined as potential trendsetters of the SSR. Several global challenges have emerged in recent years, such as climate change, wars, terrorist attacks and stressful political events. These aspects can potentially impact reproductive health outcomes, fertility rates, and the overall well-being of individuals. With respect to this, they may also affect the SSR. Through an in-depth examination of the existing literature, this manuscript elucidates the complex interconnections between global challenges and the SSR. Indeed, terrorist attacks and stressful political events have been linked to a decrease in the SSR. In contrast, high temperatures and warfare have shown a propensity to elevate the SSR in numerous scenarios. However, these associations require further validation through additional studies. The precise mechanisms through which these determinants exert their influence need to be elucidated. Understanding the unseen influences of global challenges on the SSR is crucial for understanding population trends and ensuring effective public health interventions.