However, this correlation between aggregate stability and fiber growth does not explain differences in all PrPSc strains, or even in prion variants of another yeast prion. 20S-Notoginsenoside-R2 Indeed, even with the prion, there may be multiple ways to acquire phenotypically similar prion variants. Such differences highlight the remarkable conformational diversity of amyloid and the fact that there may be several ways to generate amyloid variant structures from a single polypeptide sequence. The disease is spread to humans through hematophagous insect vectors called triatomines, which are members of the Reduviidae family and the Triatominae subfamily. The dynamics of parasite-vector interactions are very complex ; different vector species show distinct geographic distributions, and certain T. cruzi strains are associated with particular insect species. Over 100 species of triatomines can act as vectors of Chagas disease in a process that involves several transmission and adaptation steps. All of these factors come into play to determine the distribution and epidemiology of the disease, for which there are still no efficacious treatment options. The cycle of T. cruzi transmission begins when a triatomine ingests the parasite during a blood meal from an infected human or animal. The parasite then passes through the triatomine digestive tract and undergoes a number of morphological differentiations that result in the production and multiplication of epimastigote parasites. During the next blood meal, the insect excretes a number of infective trypomastigote parasites in the stool and urine, and these parasites can enter their new host through the vector’s bite or directly through the mucosa. The newly infected host can then serve as a reservoir for further parasite dissemination. During this transmission cycle, the transformations experienced by T. cruzi upon entering the insect vector involve several steps. During its journey in the invertebrate host, T. cruzi must survive within the digestive constraints of the triatomine gut. In adult Rhodnius, the midgut is divided into two major regions, the stomach and intestine, which itself is further divided into anterior and posterior segments. Morphologically, the AI and PI cells from adult Rhodnius prolixus and Triatoma infestans can be separated on the basis of their shape and corresponding specific post-Atractylenolide-III feeding modifications, suggesting differences in their digestive process. Hemoglobin digestion is initiated in the AI, which is also the major region for the synthesis and secretion of digestive proteinases, such as cathepsins B and D, carboxypeptidase B, and aminopeptidase. Protein digestion takes place only in the AI, where a complex extracellular membrane layer that functions as a peritrophic membrane forms over the apical cell surface of microvilli 12�C24 hours after feeding. Initial digestion occurs inside the 
endoperitrophic membrane, intermediate digestion in the ectoperitrophic space, and final digestion at the surface of PI cells by integral microvillar enzymes or enzymes trapped in the glycocalyx. Cathepsin B, cathepsin D and carboxypeptidase B reach maximum activity 6�C7 days after feeding. The terminal digestion stage of blood proteins is carried out by an aminopeptidase retained on the microvilli and in the ECML of the intestinal cells. Because enzymatic activity increases in the lumen after feeding, extracellular membrane layer development continues until it separates the intestinal cells from the lumen 6�C7 days after feeding. The PI is clearly the major site of nutrient absorption and continues to accumulate sugars until at least 20 days after feeding. Additional hydrolase activity may also derive from obligate and facultative bacterial symbionts that are commonly found in triatomines.