Grieving from the Margins: Black Canadian Men Navigating the Invisible Burden of Perinatal Loss and Masculine Expectations.

Trillions of microbes reside in the intestine, forming the gut microbiota, which plays pivotal roles in gastrointestinal homeostasis, basic physiological processes, and central nervous system (CNS) functions. These microbes communicate with the brain through neural, immune, endocrine, and microbiota-derived metabolites. Germ-free mice exhibit abnormal brain development, function, and behavior. In both animal models and humans, modulation of the microbiota—through the administration of specific bacterial strains, fecal microbiota transplantation, or antibiotic exposure—has been shown to alter behavior and exert long-term effects on the brain, spinal cord, and enteric nervous system. Additionally, infections disrupt gut-brain communication and contribute to neurophysiological symptoms. An imbalance or structural change in the gut microbiota has been documented in various mental disorders and neurodegenerative diseases. Moreover, the microbiome, along with its metabolites and components, can influence an individual’s susceptibility to neurological conditions. Given its importance in disease, there is growing interest in understanding the composition and function of the gut microbiome. However, the multidimensionality of host-microbiome interactions and the individual variability of gut flora pose significant challenges in interpreting disease-related shifts in microbiome composition and function. In recent years, specific bacterial strains that influence brain activity and cognitive behavior through neurotransmitters and neurotrophic factors have garnered increasing attention. Evidence suggests that certain microbes, including , , , , , , and , can directly or indirectly modulate receptors, transporters, and specific targets of dopaminergic pathways. These neurotransmitters activate ganglia in the myenteric plexus and submucosal plexus of the ENS, and they are important mediators in the interface between the gut and the brain through the gut-brain axis. Although functional strains or probiotics are closely associated with the plasticity of the central nervous system, further research is needed to elucidate underlying mechanisms. Due to population aging and various environmental factors, Parkinson’s disease (PD) has become one of the fastest-growing neurodegenerative disorders worldwide. Its etiology stems from the combined effects of genetics, environment, aging, inflammation, and oxidative stress. α-Synuclein (α-syn) accumulation and dopaminergic neuron loss lead to hallmark motor symptoms, including rigidity, resting tremor, and bradykinesia. The “ascending anatomy theory,” which proposes that PD pathology propagates from the intestine to the brain, has gained considerable attention, positing that intestinal α-syn may be transported to the brain via the vagus nerve in a prion-like fashion. Notably, many PD patients experience gastrointestinal dysfunction or constipation before motor symptoms. The intestinal microbiota has drawn increasing interest in PD pathogenesis, and beneficial bacteria or functional strains emerge as a promising PD prevention and treatment strategy. However, most current research has focused on probiotics and their capacity to alleviate PD-related motor and gastrointestinal dysfunction, as well as reshape intestinal microecology, leaving the characteristics of functional strains and their mechanisms less explored. High-altitude environments such as the Qinghai–Tibet Plateau impose chronic hypobaric hypoxia, low temperatures and intense ultraviolet irradiation, which profoundly remodel gut microbial communities and metabolites and are tightly linked to oxidative stress, barrier dysfunction and neurocognitive symptoms in humans and animal models. These extreme conditions are thought to select for microbial taxa with enhanced stress resistance, antioxidant capacity and immunomodulatory properties that facilitate host adaptation to plateau hypoxia, making plateau-derived strains an underexplored reservoir of candidate microbiota-based therapeutics.