Friedrich Feyrter: a precise intellect in a diffuse system.
Prior to the contributions of Friedrich Feyrter (1895-1973), the regulation of gastrointestinal function was an ill-understood field that was polarized by a combination of the inability of clinical scientists to perceive the relationship between the cellular elements of 'nervism' and the newly recognized chemical messenger system. Feyrter, an Austrian pathologist of luminescent intellect and possessed of rigorous analytic capacity, recognized the interface of the divergent elements (neural and endocrine) and established the concept of the diffuse neuroendocrine system. His pathological descriptions of the specialized neuroendocrine cells producing biologically active substances and regulating homeostasis by a network functioning via endocrine, paracrine, and neuracrine mechanisms laid the basis for contemporary understanding of gut function. In 1938, Feyrter identified Helle Zellen (clear cells) of the pancreas and gastrointestinal tract, which was later incorporated into the amine precursor uptake decarboxylation concept of endocrine cells by A.G.E. Pearse (1916-2003). Feyrter proposed a diffuse network as a functional regulatory system as opposed to the then current doctrine of 'organ' regulation in his 1938 manuscript Uber diffuse endokrine epitheliale Organe. In addition to this seminal contribution, the prodigious intellect of Feyrter produced an array of novel observations including benign and malignant tumors of the skin, gastrointestinal tract, and eyes, carcinoid tumors and the carcinoid syndrome, the genesis of the nevus, the transformation of lipids and disorders of cellular metabolism. Sadly, the contributions of Feyrter were obscured in the catastrophe of wartime Germany and his accomplishments little recognized. We describe the life and times of this gifted scientist, teacher, and pathologist, often referred to as the 'Father of Neuroendocrinology'.