143 research outputs found
Surface and deep water variations during MIS 11-15 at IODP Site U1313 in the Mid-Latitude North Atlantic : insights into Mid-Pleistocene rapid climate change
AGU Fall Meeting, S. Francisco (USA), 19-14 December 200
Efeitos de disrupção endócrina dos substitutos do Bisfenol A (Bisfenol F e Bisfenol S) na artéria umbilical humana
O bisfenol F (BPF) e o bisfenol S (BPF) sĂŁo dois compostos quĂmicos que nos Ăşltimos anos
tĂŞm vindo a ser utilizados em diversos produtos do quotidiano para substituir o bisfenol A
(BPA), pois a exposição a este foi associada ao desenvolvimento de diversas patologias,
nomeadamente as cardiovasculares. Contudo, estudos recentes também têm vindo a
relacionar também a exposição aos substitutos do BPA com o desenvolvimento de várias
doenças, como neurológicas, tiroideias, comportamentais e cardiovasculares. Deste modo,
têm vindo a ser levantadas questões quanto à segurança dos substitutos do BPA para a saúde
humana. Preocupantemente, alguns estudos referem que os substitutos podem exercer
efeitos disruptivos tĂŁo ou mais graves que o BPA. No entanto, os estudos existentes ainda
sĂŁo pouco vastos e conclusivos, nomeadamente, ao nĂvel dos efeitos cardiovasculares.
Deste modo, o objetivo principal deste trabalho foi estudar os efeitos do BPA, BPF e BPS no
tĂłnus arterial e analisar quais os possĂveis mecanismos envolvidos nesses efeitos. AlĂ©m
disso, pretendeu-se perceber se os efeitos provocados pelos substitutos do BPA (BPF e BPS)
sĂŁo mais ou menos adversos do que os causados pelo BPA.
Os resultados deste trabalho parecem demonstrar que o BPA, BPS e BPF exercem efeitos
relaxantes rápidos (não genómicos) e independentes de endotélio nas artérias umbilicais
humanas (HUAs). Estes efeitos tambĂ©m foram observados para o BPF e BPS a nĂvel celular,
isto Ă©, em cĂ©lulas musculares lisas das artĂ©rias umbilicais humanas (HUASMCs). A nĂvel
dos efeitos a longo prazo, os resultados parecem demonstrar que o mecanismo contrátil das
HUAs incubadas durante 24 horas com BPA estava alterado, ao contrário do que se
verificava nas HUAs incubadas com BPF. PorĂ©m, ainda a nĂvel genĂłmico, constatou-se que
tanto o BPA como o BPF podem interferir com os principais mecanismos responsáveis pela
relaxação das HUAs, interferindo com a via NO/sGC/cGMP/PKG e modulando a atividade
dos canais de Ca2+ do tipo L (LTCC), sendo que os resultados parecem demonstrar que o
BPF altera mais a resposta vasorelaxante do que o BPA. Deste modo, a substituição do BPA
pelos seus análogos não parece ser benéfica para a saúde humana cardiovascular. Assim,
futuramente, os efeitos vasculares destes bisfenĂłis devem continuar a ser avaliados de modo
clarificar os seus modos de ação e implicações futuras na saúde materno-fetal.In recent years, the chemical compounds bisphenol F (BPF) and bisphenol S (BPS) have
been used in several everyday products to replace bisphenol A (BPA), since exposure to BPA
has been associated with the development of several pathologies, including cardiovascular
diseases. However, recent studies have also been associating exposure to BPA substitutes
with the development of various pathologies, such as neurological, thyroid, behavioral, and
cardiovascular diseases. Therefore, questions have been raised about the safety of BPA
substitutes for human health. Worryingly, some studies reported that BPA substitutes may
cause disruptive effects as harmful, or even more severe, than BPA. However, the existing
literature is still limited and inconclusive, particularly concerning cardiovascular effects.
In this sense, the aim of the present work was to study the effects of BPA, BPF, and BPS on
arterial tone and to analyze the possible mechanisms involved in these effects. Furthermore,
it was aimed to understand whether the effects caused by BPA substitutes (BPF and BPS)
are more, or less, adverse than those caused by BPA.
Our results seem to demonstrate that BPA, BPS, and BPF exert rapid (non-genomic) and
endothelium-independent relaxant effects in human umbilical arteries (HUAs). These
effects were also observed for BPF and BPS at the cellular level, i.e., in human umbilical
artery smooth muscle cells (HUASMCs). Regarding the long-term effects, the results seem
to demonstrate that in HUAs incubated for 24 hours with BPA, the contractile mechanism
was altered, in contrast to HUAs incubated with BPF. However, also at the genomic level, it
was found that both BPA and BPF can disturb the main mechanisms responsible for the
relaxation of HUAs, by interfering with the NO/sGC/cGMP/PKG pathway and modulating
the activity of L-type Ca2+ channels (LTCC). Moreover, our results seem to demonstrate that
BPF alters more the vasorelaxant response than BPA. Therefore, replacing BPA with its
analogs does not seem to be beneficial for human cardiovascular health. Thus, in the future,
the vascular effects of these bisphenols should continue to be evaluated to clarify their
modes of action and future implications for maternal-fetal health
Phytoplankton biogeography and community stability in the ocean
BACKGROUND: Despite enormous environmental variability linked to glacial/interglacial climates of the Pleistocene, we have recently shown that marine diatom communities evolved slowly through gradual changes over the past 1.5 million years. Identifying the causes of this ecological stability is key for understanding the mechanisms that control the tempo and mode of community evolution. METHODOLOGY/PRINCIPAL FINDINGS: If community assembly were controlled by local environmental selection rather than dispersal, environmental perturbations would change community composition, yet, this could revert once environmental conditions returned to previous-like states. We analyzed phytoplankton community composition across >10(4) km latitudinal transects in the Atlantic Ocean and show that local environmental selection of broadly dispersed species primarily controls community structure. Consistent with these results, three independent fossil records of marine diatoms over the past 250,000 years show cycles of community departure and recovery tightly synchronized with the temporal variations in Earth's climate. CONCLUSIONS/SIGNIFICANCE: Changes in habitat conditions dramatically alter community structure, yet, we conclude that the high dispersal of marine planktonic microbes erases the legacy of past environmental conditions, thereby decreasing the tempo of community evolution
Impact of Manganese, Copper and Zinc Ions on the Transcriptome of the Nosocomial Pathogen Enterococcus faecalis V583
Mechanisms that enable Enterococcus to cope with different environmental stresses and their contribution to the switch from commensalism to pathogenicity of this organism are still poorly understood. Maintenance of intracellular homeostasis of metal ions is crucial for survival of these bacteria. In particular Zn2+, Mn2+ and Cu2+ are very important metal ions as they are co-factors of many enzymes, are involved in oxidative stress defense and have a role in the immune system of the host. Their concentrations inside the human body vary hugely, which makes it imperative for Enterococcus to fine-tune metal ion homeostasis in order to survive inside the host and colonize it. Little is known about metal regulation in Enterococcus faecalis. Here we present the first genome-wide description of gene expression of E. faecalis V583 growing in the presence of high concentrations of zinc, manganese or copper ions. The DNA microarray experiments revealed that mostly transporters are involved in the responses of E. faecalis to prolonged exposure to high metal concentrations although genes involved in cellular processes, in energy and amino acid metabolisms and genes related to the cell envelope also seem to play important roles
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