A genetic abnormality of cardiac myocytes from the blind mutant (RC) chick heart: abnormalities of cardiac structure and choline transport

Differential Actions of Muscarinic Receptor Subtypes in Gastric, Pancreatic, and Colon Cancer

Cancers arising from gastrointestinal epithelial cells are common, aggressive, and difficult to treat. Progress in this area resulted from recognizing that the biological behavior of these cancers is highly dependent on bioactive molecules released by neurocrine, paracrine, and autocrine mechanisms within the tumor microenvironment. For many decades after its discovery as a neurotransmitter, acetylcholine was thought to be synthesized and released uniquely from neurons and considered the sole physiological ligand for muscarinic receptor subtypes, which were believed to have similar or redundant actions. In the intervening years, we learned this former dogma is not tenable. (1) Acetylcholine is not produced and released only by neurons. The cellular machinery required to synthesize and release acetylcholine is present in immune, cancer, and other cells, as well as in lower organisms (e.g., bacteria) that inhabit the gut. (2) Acetylcholine is not the sole physiological activator of muscarinic receptors. For example, selected bile acids can modulate muscarinic receptor function. (3) Muscarinic receptor subtypes anticipated to have overlapping functions based on similar G protein coupling and downstream signaling may have unexpectedly diverse actions. Here, we review the relevant research findings supporting these conclusions and discuss how the complexity of muscarinic receptor biology impacts health and disease, focusing on their role in the initiation and progression of gastric, pancreatic, and colon cancers.

Histological changes caused by the rc mutation in chickens

The rc gene represents a recessive mutation in chickens, known to cause retinal degeneration and blindness, as well as abnormal sarcolemmal membranes of cardiac myocytes associated with reduced choline transport. In this study, the visceral organs from "old" (aged 12 months) and "young" (aged 5 months) homozygous blind (rc/rc), heterozygous (Rc+/rc) and normal (Rc+/Rc+) chickens were examined histologically to investigate whether the primary effect of the mutation was on cellular structure. Homozygous birds showed enlarged thyroids with acidophilic colloids in enlarged and often ruptured follicles, macrovesicular lipid accumulation in the liver, increased numbers of nuclei in the myocardial fibres, hypertrophy of the lobular structure of the medullary portion of the thymus, cloudy swelling of the tubular epithelium of the kidney and slow maturation (in young birds) and degeneration (in old birds) of the gonads. All lesions, except for those of the thymus, were more severe in old than in young birds. Some heterozygous chickens were mildly affected and none of the normal (Rc+/Rc+) birds exhibited these abnormalities.