Cascade reservoirs affect mercury concentrations in fish from Teles Pires river, Brazilian Amazon.

Hydroelectric reservoirs favor mercury contamination in biota, but the contamination in cascade reservoirs is not yet clear. We investigated total mercury (THg) contamination in fish in four cascade reservoirs in the Brazilian Amazon between August 2022 and April 2023. Overall, downstream predatory fish showed higher mercury concentrations than those upstream.

Trypanosoma cruzi strains in the Calomys callosus: parasitemia and reaction of intracellular forms with stage-specific antibodies in the acute and chronic phase of infection and after immunosuppression.

An experimental model for chronic Chagas disease was developed to investigate whether reactivation is influenced by the genetic origin of Trypanosoma cruzi isolates. In addition, we examined whether the distribution of T. cruzi stage-specific epitopes, as defined by monoclonal antibodies (Mab), raised against mammalian-stage parasite forms, exhibited comparable distribution patterns in Calomys callosus myocardium during the acute phase and after reactivation of the infection.

Host cell actin remodeling in response to Trypanosoma cruzi: trypomastigote versus amastigote entry.

Trypanosoma cruzi is the protozoan parasite that causes Chagas' disease, a highly prevalent vector-borne disease in Latin America. Chagas' disease is a major public health problem in endemic regions with an estimated 18 million people are infected with T. cruzi and another 100 million at risk (http://www.

Distribution of Trypanosoma cruzi stage-specific epitopes in cardiac muscle of Calomys callosus, BALB/c mice, and cultured cells infected with different infective forms.

To examine whether distinct parasite infective forms or the mammalian host could affect the distribution of Trypanosoma cruzi stage-specific epitopes defined by monoclonal antibodies (Mabs) raised against mammalian-stage parasite forms, immunofluorescence studies followed the intracellular life cycle of the parasite in the cardiac muscle of Calomys callosus and BALB/c mice in the acute phase of the disease and in LLC-MK(2) cultured cells. Animals and cells were infected either with tissue-culture derived trypomastigotes (TCT) or bloodstream trypomastigotes (BT) from the Y strain of T. cruzi.

Disruption of myofibrillar proteins in cardiac muscle of Calomys callosus chronically infected with Trypanosoma cruzi and treated with immunosuppressive agent.

Calomys callosus (Rodentia: Cricetidae) chronically infected with CL strain of Trypanosoma cruzi undergo recrudescence of the acute phase when treated with the immunosuppressor cyclophosphamide. The distribution of cytoskeletal proteins in cardiac tissue of immunosuppressed animals was mapped by immunofluorescence and electron microscopy to evaluate myofibrillar distribution during the intracellular life cycle of T. cruzi.

Mammalian cell invasion and intracellular trafficking by Trypanosoma cruzi infective forms.

Trypanosoma cruzi, the etiological agent of Chagas disease, occurs as different strains or isolates that may be grouped in two major phylogenetic lineages: T. cruzi I, associated with the sylvatic cycle and T. cruzi II, linked to the human disease.

Diterpenoids from Azorella compacta (Umbelliferae) active on Trypanosoma cruzi.

The anti-Trypanosoma cruzi activity of natural products isolated from Azorella compacta was evaluated, with particular emphasis on their effect against intracellular amastigotes. Five diterpenoids from A. compacta derived from mulinane and azorellane were isolated and identified.

Towards a more precise assay of sperm function in egg binding.

Historically, the treatment of severe male factor infertility has relied on donor sperm insemination. A decade ago the option of treating severe male factor infertility with partner sperm became a viable alternative. With the introduction of intracytoplasmic sperm injection (ICSI) in conjunction with in vitro fertilization (IVF), only men who produce no sperm are denied the option of fathering their own children.

Acquisition of arylsulfatase A onto the mouse sperm surface during epididymal transit.

Arylsulfatase A (AS-A) is localized to the sperm surface and participates in sperm-zona pellucida binding. We investigated how AS-A, usually known as an acrosomal enzyme, trafficked to the sperm surface. Immunocytochemistry of the mouse testis confirmed the existence of AS-A in the acrosomal region of round and elongating spermatids.

Cytotoxic and genotoxic effects of megazol, an anti-Chagas' disease drug, assessed by different short-term tests.

Cyto- and genotoxicity induced by drugs can limit the dose and duration of treatment, can adversely affect patient quality of life, and may be life-threatening. Two drugs are currently being used for treatment of the acute phase of Chagas' disease and both have serious undesirable effects. In this research, cyto- and genotoxic activity of the nitroimidazole-tiadiazole derivative CL 64855 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole (megazol), a promising alternative drug, was evaluated in vitro with different short-term tests: (a) induction of recombination events and mutation in the yeast Saccharomyces cerevisiae D7 strain, with and without induction of cytochrome P-450; DNA damage (single and double strand breaks, alkali-labile sites, etc.