ABSTRACT
Chagas disease is a parasitic infection caused by Trypanosoma cruzi, whose motility is not only important for localization, but also for cellular binding and invasion. Current animal models for the study of T. cruzi allow limited observation of parasites in vivo, representing a challenge for understanding parasite behavior during the initial stages of infection in humans. This protozoan has a flagellar stage in both vector and mammalian hosts, but there are no studies describing its motility in vivo.The objective of this project was to establish a live vertebrate zebrafish model to evaluate T. cruzi motility in the vascular system. Transparent zebrafish larvae were injected with fluorescently labeled trypomastigotes and observed using light sheet fluorescence microscopy (LSFM), a noninvasive method to visualize live organisms with high optical resolution. The parasites could be visualized for extended periods of time due to this technique's relatively low risk of photodamage compared to confocal or epifluorescence microscopy. T. cruzi parasites were observed traveling in the circulatory system of live zebrafish in different-sized blood vessels and the yolk. They could also be seen attached to the yolk sac wall and to the atrioventricular valve despite the strong forces associated with heart contractions. LSFM of T. cruzi-inoculated zebrafish larvae is a valuable method that can be used to visualize circulating parasites and evaluate their tropism, migration patterns, and motility in the dynamic environment of the cardiovascular system of a live animal.
Subject(s)
Chagas Disease/diagnosis , Trypanosoma cruzi/pathogenicity , Animals , Cell Movement , Disease Models, Animal , Humans , Larva , ZebrafishABSTRACT
Macroorchidism is a rare condition in children and is usually associated with fragile X syndrome. Other possible etiologies of macroorchidism are long-standing primary hypothyroidism, adrenal remnants in congenital adrenal hyperplasia, follicle stimulating hormone (FSH)-secreting pituitary macroadenomas, local tumors, lymphomas, and aromatase deficiency. Bilateral macroorchidism can be a normal variant in adult men. We report the case of an 11.5-year-old boy who was referred to our hospital for evaluation of marked bilateral testicular enlargement in the previous few months. Physical examination revealed a testicular volume larger than 30 ml. Complementary investigations allowed us to rule out all hitherto reported etiologies of bilateral macroorchidism and therefore a diagnosis of idiopathic macroorchidism was established. The increased number of Sertoli cells found on biopsy, without elevated plasma FSH levels, prompted us to speculate about a hypothetical FSH receptor hyperfunction as a possible cause of the exaggerated testicular enlargement in this patient.
