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Biomedical subjects

Richard A Dixon

Publications and source records attributed to Richard A Dixon.

2 recordsLinked to original sources

Pancreatic neuroendocrine tumors in patients with tuberous sclerosis: a multicenter study and systematic review.

INTRODUCTION: Pancreatic neuroendocrine tumors (pNETs) are a recognized feature of tuberous sclerosis complex (TSC). The current evidence suggests that pNETs occurring in TSC may exhibit a different clinical course from sporadic cases, but their natural history remains poorly characterized. OBJECTIVE: This study aimed to characterize the demographics, clinical presentation, management, and long-term outcomes of TSC-associated-pNETs and to propose possible guidelines for surveillance and management. MATERIALS AND METHODS: We conducted a multicenter retrospective review of TSC-pNET patients from 6 UK TSC specialist clinics and from 3 NET referral centers, from 2008 to 2024. Data on demographics, tumor characteristics, management, and outcomes, were collected. A systematic review of the literature from 2009 to 2026 on TSC-pNETs was also performed. RESULTS: We identified a total of 26 consecutive cases with the TSC-pNET-association in our cohort: 21 cases of pNETs from TSC specialist clinics (1.1% of the population), and 5 cases of TSC-pNETs from the NET referral centers (0.25% of the population). An additional 80 cases were identified from the published literature. We observed a wide spectrum of clinical phenotypes, with the majority being nonfunctioning pNETs (n = 24; 92%), whereas 2 patients were diagnosed with glucagonomas. Surgical intervention was the mainstay initial treatment, the indication being either functional pNETs, or large or symptomatic nonfunctioning pNETs. CONCLUSION: TSC-pNETs are rare and mostly nonfunctioning tumors with variable clinical behavior. Due to their uncertain malignant potential, we suggest that baseline pancreatic imaging should be incorporated into TSC surveillance, and we emphasize the need for heightened pNET surveillance and updated management recommendations.

TS complex

Factors underlying a latitudinal gradient in the S/G lignin monomer ratio in natural poplar variants.

The chemical composition of wood plays a pivotal role in the adaptability and structural integrity of trees. However, few studies have investigated the environmental factors that determine lignin composition and its biological significance in plants. Here, we examined the lignin syringyl-to-guaiacyl (S/G) ratio in members of a Populus trichocarpa population sourced from their native habitat and conducted a genome wide association study to identify genes linked to lignin formation. Our results revealed many significant associations, suggesting that lignin biosynthesis is a complex polygenic trait. Additionally, we found an increase in the S/G ratio from northern to southern geographic origin of the trees sampled, along with a corresponding metabolic and transcriptional reprogramming of xylem cell wall biosynthesis. Further molecular analysis identified a mutation in a cell wall laccase genetically associated with higher S/G ratios that predominate in trees from warmer lower latitudes. Collectively, our findings suggest that lignin heterogeneity arises from an evolutionary process enabling poplar adaptation to different climatic challenges.

Populus