Effects of HIV aspartyl-proteinase inhibitors on Leishmania sp.

In this work, we have found an antiproliferative effect on Leishmania sp. promastigotes and axenic amastigotes by the human immunodeficiency virus (HIV) aspartyl-proteinase inhibitors, Ac-Leu-Val-Phenylalaninal, Saquinavir mesylate and Nelfinavir, the latter two being used as part of antiretroviral therapy. This effect appears to be the result of cell division blockage. In addition, these drugs induced in culture a decrease in the percentage of co-infected HIV/Leishmania monocytes and amastigotes of Leishmania per macrophage. The finding of a dose-dependent inhibition of Leishmania promastigotes aspartyl-proteinase activity by these drugs allows us to propose this activity as the drug parasite target. A direct action of these HIV aspartyl-proteinase inhibitors on the parasite, would be correlated with the effect that highly active antiretroviral therapy have had in the decrease of HIV/Leishmania coinfection, opening an interesting perspective for new drugs research development based on this novel parasite proteinase family.     

Exaggerated response to mild stress in rats fed high-fat diet

It has been suggested that high-fat (HF) diet exaggerates the stress-induced release of glucocorticoids due to activation of the hypothalamic-pituitary-adrenal (HPA) axis. In an initial experiment, in which rats were fed HF diet for 4 days, we found that HF-fed controls stopped gaining weight, indicating that they were hyperresponsive to the mild stress of tail bleeding but responded the same as low-fat (LF)-fed rats to the more severe stress of restraint. A second experiment confirmed these results when rats fed a HF diet for 4 days showed an exaggerated corticosterone release in response to an intraperitoneal injection of saline and movement to a novel cage, compared with LF-fed rats. Experiment 3 tested the same parameters as experiment 2 but interchanged the diets. This allowed us to differentiate between the effects of the dietary fat and the novelty of the diet. Additionally, this experiment determined whether hyperresponsiveness to mild stress in HF-fed rats was sustained during a prolonged exposure to diet. The results confirmed that a HF diet, not novelty, exaggerated the endocrine stress response after 9 days on the diet but that the effect was no longer present after 23 days on the diet. The hyperresponsiveness of the HPA axis in HF-fed rats is similar to that observed in animals that have been exposed to a significant chronic or acute stress, suggesting that the HF diet may initially be perceived as a stressor.     

A novel rhythm of microcystin biosynthesis is described in the cyanobacterium Microcystis panniformis Komárek et al

The presence of microcystins (MCY) in the cyanobacteria Microcystis panniformis Komárek et al. is reported for the first time. This strain of cyanobacterium has been isolated from Barra Bonita, an eutrophicated water reservoir in S?o Paulo state, Brazil. The identification of M. panniformis was confirmed by both traditional morphological analysis and the phycocyanin intergenic spacer sequences. MCY-LR and [Asp(3)]-MCY-LR were identified in this strain after HPLC purification and extensive ESI-MS/MS analysis. Their levels in this strain were determined by HPLC and ranged from 0.25 to 2.75 and 0.08 to 0.75 fmol/cell, respectively. Analyzing the levels of MCY-LR and [Asp(3)]-MCY-LR in different times during the light:dark (L:D) cycle, it was found that levels of MCYs per cell were at least threefold as high during the day-phase than during the night-phase. This may be associated to the biological clock since prokaryotic cyanobacteria express robust circadian (daily) rhythms under the control of a timing mechanism that is independent of the cell division cycle. Our findings also showed the same pattern under light:light (L:L) cycle.     

Arsenic and high affinity phosphate uptake gene distribution in shallow submarine hydrothermal sediments

The toxicity of arsenic (As) towards life on Earth is apparent in the dense distribution of genes associated with As detoxification across the tree of life. The ability to defend against As is particularly vital for survival in As-rich shallow submarine hydrothermal ecosystems along the Hellenic Volcanic Arc (HVA), where life is exposed to hydrothermal fluids containing up to 3000 times more As than present in seawater. We propose that the removal of dissolved As and phosphorus (P) by sulfide and Fe(III)(oxyhydr)oxide minerals during sediment–seawater interaction, produces nutrient-deficient porewaters containing?<?2.0 ppb P. The porewater arsenite-As(III) to arsenate-As(V) ratios, combined with sulfide concentration in the sediment and/or porewater, suggest a hydrothermally-induced seafloor redox gradient. This gradient overlaps with changing high affinity phosphate uptake gene abundance. High affinity phosphate uptake and As cycling genes are depleted in the sulfide-rich settings, relative to the more oxidizing habitats where mainly Fe(III)(oxyhydr)oxides are precipitated. In addition, a habitat-wide low As-respiring and As-oxidizing gene content relative to As resistance gene richness, suggests that As detoxification is prioritized over metabolic As cycling in the sediments. Collectively, the data point to redox control on Fe and S mineralization as a decisive factor in the regulation of high affinity phosphate uptake and As cycling gene content in shallow submarine hydrothermal ecosystems along the HVA.     

Management of intraoral stents for radiotherapy during COVID-19 pandemic

Radiotherapy is being performed in many situations as a curative approach for head and neck cancer instead of surgery due to the current novel coronavirus disease (COVID-19) pandemic. A recent publication reported that even hypofractionation was being conducted in order to reduce the daily exposure of both patients and the medical staff involved in cancer therapies. As a result, dental teams may be requested more frequently than usual to fabricate intraoral stents (IOS). Given that IOS may be a potential source of COVID-19 contagion, the main purpose of the present correspondence is to offer a guide on how health professionals may be safely presented in the room, on the management of the IOS and also how to sanitize the stents.     

The case for studying tadpole autecology,with comments on strategies to study other small,fast-moving animals in nature

Two of the most fundamental questions in tadpole biology, also applicable to most small, under-studied organisms are: (1) ‘Why are they built the way they are?’ and (2) ‘Why do they live where they do?’ Regrettably, despite significant progress in most aspects of tadpole biology, the answers to these questions are not much better now than they were in the last century. We propose that an autecological approach, that is the careful observation of individuals and how they interact with the environment, is a potential path towards a fuller understanding of tadpole ecomorphology and evolution. We also discuss why more attention should be given to studying atypical tadpoles from atypical environments, such as torrential streams, water-filled cavities of terrestrial plants and wet rock surfaces neighbouring streams. Granted, tadpoles are rare in these settings, but in those unusual habitats the physical environments can be well described and characterized. In contrast, the more common ponds where tadpoles are found are typically too structurally complex to be easily delineated. This makes it difficult to know exactly what individual tadpoles are doing and what environmental parameters they are responding to. Our overall thesis is that to understand tadpoles we must see exactly what they are doing, where they are doing it, and how they are doing it. This takes work, but we suggest it is feasible and could greatly advance our understanding of how anuran larvae have evolved. The same strategies for studying tadpoles that we encourage here can be applied to the study of many other small and fast-moving animals.