mRNA localization mechanisms in Trypanosoma cruzi

Asymmetric mRNA localization is a sophisticated tool for regulating and optimizing protein synthesis and maintaining cell polarity. Molecular mechanisms involved in the regulated localization of transcripts are widespread in higher eukaryotes and fungi, but not in protozoa. Trypanosomes are ancient eukaryotes that branched off early in eukaryote evolution. We hypothesized that these organisms would have basic mechanisms of mRNA localization. FISH assays with probes against transcripts coding for proteins with restricted distributions showed a discrete localization of the mRNAs in the cytoplasm. Moreover, cruzipain mRNA was found inside reservosomes suggesting new unexpected functions for this vacuolar organelle. Individual mRNAs were also mobilized to RNA granules in response to nutritional stress. The cytoplasmic distribution of these transcripts changed with cell differentiation, suggesting that localization mechanisms might be involved in the regulation of stage-specific protein expression. Transfection assays with reporter genes showed that, as in higher eukaryotes, 3'UTRs were responsible for guiding mRNAs to their final location. Our results strongly suggest that Trypanosoma cruzi have a core, basic mechanism of mRNA localization. This kind of controlled mRNA transport is ancient, dating back to early eukaryote evolution.

Conjunctival flora, Schirmer's tear test, intraocular pressure, and conjunctival cytology in neotropical primates from Salvador, Brazil

BACKGROUND

This study aimed to establish reference values for selected ophthalmic diagnostic tests in healthy neotropical primates from Salvador, Brazil.

METHODS

A total of 73 intact adults, including Callithrix jacchus (n = 31), Callithrix penicillata (n = 8), Cebus sp. (n = 22), and Cebus xanthosternos (n = 9) were used to evaluate the normal conjunctival bacterial flora. Cebus xanthosternos (n = 12) were used to evaluate tear production with Schirmer's tear test (STT), intraocular pressure (IOP), and conjunctival cytology.

RESULTS

For all animals evaluated, Gram-positive bacteria were predominant. Results of the diagnostic tests in Cebus xanthosternos were as follows: STT: 14.92 ± 5.46 mm/minutes, IOP: 19.62 ± 4.57 mmHg, and conjunctival cytology revealed intermediate squamous epithelial cells in great quantities.

CONCLUSIONS

These ophthalmic reference values will be particularly useful to diagnose discrete or unusual pathological changes in the neotropical primates eye.