They are characterized by gastric hypersecretion that results in peptic ulcers and diarrhea; this condition is known as Zollinger–Ellison syndrome (ZES). Research
Recently, research studies have been conducted to seek new medical advances in relation to gastrinoma and Zollinger–Ellison syndrome. The recent studies have shown improved understanding of pathogenesis of pancreatic neuroendocrine tumors, classifications of those tumors, new treatments/preventions to control the gastrin levels in the gastrointestinal tract, and the best and safest surgical approaches. The study concluded that the wide use of proton pump inhibitors itself might further induce hypergastrinemia (increased gastrin levels in circulatory system) by feedback inhibition. The body will try to induce further release when gastrin level is depleted. Some of the new treatments might include medication that is directed towards the liver such as embolization, chemoembolization, and radioembolization in addition to the currently offered treatments such as chemotherapy, somatostatin analogs. Other treatments that are still in phase three of clinical trials include liver transplantation and peptide-radioreceptor therapy. See also
Pancreatic endocrine tumor

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Emedicine
The vitamin B12 coenzymes are unstable in light. After consumption the cyanide ligand is replaced by other groups (adenosyl, methyl) to produce the biologically active forms. The cyanide is converted to thiocyanate and excreted by the kidney. Chemical reactions
In the cobalamins, cobalt normally exists in the trivalent state, Co(III). However, under reducing conditions, the cobalt center is reduced to Co(II) or even Co(I), which are usually denoted as B12r and B12s, for reduced and super reduced, respectively. B12r and B12s can be prepared from cyanocobalamin by controlled potential reduction, or chemical reduction using sodium borohydride in alkaline solution, zinc in acetic acid, or by the action of thiols. Both B12r and B12s are stable indefinitely under oxygen-free conditions. B12r appears orange-brown in solution, while B12s appears bluish-green under natural daylight, and purple under artificial light.B12s is one of the most nucleophilic species known in aqueous solution. This property allows the convenient preparation of cobalamin analogs with different substituents, via nucleophilic attack on alkyl halides and vinyl halides.For example, cyanocobalamin can be converted to its analog cobalamins via reduction to B12s, followed by the addition of the corresponding alkyl halides, acyl halides, alkene or alkyne. Steric hindrance is the major limiting factor in the synthesis of the B12 coenzyme analogs. For example, no reaction occurs between neopentyl chloride and B12s, whereas the secondary alkyl halide analogs are too unstable to be isolated.