SYP and appendicitis: Apparently normal appendices removed from patients with a clinical presentation of acute appendicitis present changes in substance P neuroendocrine markers, vasoactive intestinal polypeptide, gastric inhibitory polypeptide, calcium-binding protein, cyclooxygenases 1 and 2, tumor necrosis factor, prostaglandin E2, mast cell tryptase, nitric oxide synthase, CD8 lymphocytes, protein gene product 9.5, vascular endothelial growth factor, class 2 histocompatibility complex, synaptophysin, enolase, and S100 protein [[20], [21], [22], [23], [24]].