Structural Changes of the Paraflagellar Rod during Flagellar Beating in Trypanosoma cruzi

, the agent of Chagas disease, is a protozoan member of the Kinetoplastidae family characterized for the presence of specific and unique structures that are involved in different cell activities. One of them is the paraflagellar rod (PFR), a complex array of filaments connected to the flagellar axoneme. Although the function played by the PFR is not well established, it has been shown that silencing of the synthesis of its major proteins by either knockout of RNAi impairs and/or modifies the flagellar motility.Here, we present results obtained by atomic force microscopy (AFM) and transmission electron microscopy (TEM) of replicas of quick-frozen, freeze-fractured, deep-etched and rotary-replicated cells to obtain detailed information of the PFR structures in regions of the flagellum in straight and in bent state. The images obtained show that the PFR is not a fixed and static structure. The pattern of organization of the PFR filament network differs between regions of the flagellum in a straight state and those in a bent state. Measurements of the distances between the PFR filaments and the filaments that connect the PFR to the axoneme as well as of the angles between the intercrossed filaments supported this idea.Graphic computation based on the information obtained allowed the proposal of an animated model for the PFR structure during flagellar beating and provided a new way of observing PFR filaments during flagellar beating

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others

Fine structure and cytochemistry of the nucleus and the kinetoplast of epimastigotes of Trypanosoma cruzi

6 p.-18 fig.Ultrastructural cytochemical techniques were used to analyze the nucleus and the kinetoplast of epimastigotes of Trypanosoma cruzi. With the use of ethanolic phosphotungstic acid, which detects basic proteins, reaction product was seen in the chromatin and at the periphery of the kinetoplast. Thallium alcoholate, which interacts with DNA, stained strongly the whole kinetoplast and the chromatin. With the use of a silver impregnation method that detects acidic nucleolar proteins, silver granules were seen preferentially located in the central region of the nucleolus. With the EDTA method, which reveals the presence of ribonucleoproteins, staining was observed in the nuclear pores. Also 6–8 nm fibrils, 25 nm and 40 nm granules, which correspond to the perichromatin fibers, interchromatin granules and the perichromatin granules, respectively, were identified in the nucleus. The EDTA method also revealed the presence of 40 nm granules in the kinetoplast. These granules were seen mainly at the two extremities of the kinetoplast. Freeze-fracture images indicate that the nuclear membrane contains ca. 9 pores/μm2 of nuclear surface area. The mean diameter of the pores was 80 nm. All these results suggest that epimastigotes of T. cruzi have a very active nucleus and a high rate of nucleocytoplasmic interchange.This work has been supported by CSIC-CNPq interchange, Comission Assessora para Investigação Cientifica e Técnica de Espanha, FINEP and WHO.Peer reviewe