Cell Viability Under Anoxic Conditions WAGNER, Stephanie; POHL, Jakob; HACKBARTH, Steffen
Photodiagnosis and photodynamic therapy,
March 2023, 2023-03-00, Letnik:
41
Journal Article
Recenzirano
PDT relies on the availability of oxygen to generate cytotoxic ROS and singlet oxygen in particular. Yet, after photosensitizer illumination, the oxygen in the direct vicinity is consumed very ...quickly through reactions with biological material, especially in the hypoxic environment caused by the increased metabolism of tumour cells. 1 Considering these facts, the illumination regimes currently used in clinical PDT should be investigated for the extent to which they promote or even hinder generation of singlet oxygen in tumour tissue. Assuming the latter, the question arises of whether illumination induced anoxia might lead to reliable cell death. For this purpose, the correlation between the oxygen available to the cells and their short-, medium- and long-term survival rates was examined.
Using the adherent cell line FaDu as a tumour model, the atmospheric oxygen concentration inside an incubator is adjusted with a gas composition system developed in the group. To determine both the oxygen concentration actually available to the cells and their consumption 2, a simulation of oxygen diffusion in culture medium 3, 4 was derived. The survival rate of the cells was checked with fluorescence-based vitality assays both during and after exposure to anoxia.
Using oxygen consumption achieved through illumination of a photosensitizer in solution in the presence of extracellular quenchers as a first measurement, the determined results compared well with the numerical simulation.
In the series of experiments, it became clear that even at normal atmospheric pressure, significantly less oxygen than expected is available, especially for adherent cells. Accordingly, every system above anoxia is in a highly dynamic state in which the oxygen concentration at the level of the cells differs significantly from the oxygen concentration above the medium. For this reason, the simulation of this complex system, which considers cell respiration and growth as well as oxygen diffusion through the culture medium, was compared with first results of the viability assays.
Although the current experiments included only two cell lines, the model provides deep insights into the role of anoxia in PDT. Furthermore, the model can be easily adapted to the particular metabolisms of different tumours. Thus, it is an important tool to inform future case-based decisions about the potential targeted use of localized anoxia as an alternative therapy.
Patterns of uranium–molybdenum covariation in marine sediments have the potential to provide insights regarding depositional conditions and processes in paleoceanographic systems. Specifically, such ...patterns can be used to assess bottom water redox conditions, the operation of metal-oxyhydroxide particulate shuttles in the water column, and the degree of water mass restriction. The utility of this paleoenvironmental proxy is due to the differential geochemical behavior of U and Mo: (1) uptake of authigenic U by marine sediments begins at the Fe(II)–Fe(III) redox boundary (i.e., suboxic conditions), whereas authigenic Mo enrichment requires the presence of H2S (i.e., euxinic conditions), and (2) transfer of aqueous Mo to the sediment may be enhanced through particulate shuttles, whereas aqueous U is unaffected by this process. In the present study, we examine U–Mo covariation in organic-rich sediments deposited mostly in the western Tethyan region during oceanic anoxic events (OAEs) of Early Jurassic to Late Cretaceous age. Our analysis generally confirms existing interpretations of redox conditions in these formations but provides significant new insights regarding water mass restriction and the operation of particulate shuttles in depositional systems. These insights will help to address contentious issues pertaining to the character and origin of Mesozoic OAEs, such as the degree to which regional paleoceanographic factors controlled the development of the OAEs.
► We examine U–Mo covariation in Tethyan, organic-rich sediments of Mesozoic OAEs. ► We provide new insights regarding water mass restriction in some depositional systems. ► We provide new insights regarding the operation of particulate shuttles. ► These insights regard issues pertaining to the character and origin of Mesozoic OAEs.
The stable carbon isotopic compositions of carbonate sediments (δ13Ccarb) have been widely used to reconstruct the global carbon cycle and as a stratigraphic correlation tool. This work investigates ...a δ13Ccarb record of marine organic-rich, mixed siliciclastic‐carbonate mudstones accumulated from the Tithonian (late Jurassic) to the early Valanginian (early Cretaceous) in a retro-arc basin connected to the Proto-Pacific Ocean (Neuquén Basin, Argentina). The high-resolution record of δ13Ccarb values of these strata from outcrops at various locations in the basin differ from those in the coeval pelagic strata of the Tethys. The δ13Ccarb profile in the Puerta Curaco area shows an overall increasing trend from average values of −7‰ (early Tithonian) to approximately 0‰ (early Valanginian). The negative δ13Ccarb values occur in a ~ 400 m thick TOC-rich succession (TOC > 2%) and are arranged in 3 large-scale increasing-decreasing cycles. Although absolute values are offset, main trends are similar in other outcrops and in subsurface wells. The co-occurrence of the highest U/Th (>1.4) and the most negative δ13Ccarb values suggests that the major trends in the δ13Ccarb profile might be modulated by oscillations in oxygen content within the basin probably driven by sea-level changes. Clastic-dominated transgressive hemicycles have higher TOC and more negative δ13Ccarb values while the opposite occurs in carbonate-rich regressive hemicycles. A trend from “normal” Tithonian surface-water values (avg. +2‰) in the southern shelf to increasingly negative δ13Ccarb values towards the basin center indicates a mixing between platform-derived carbonate material unaffected by diagenesis and carbonate precipitated or altered in a dysoxic/anoxic basin. The δ13Ccarb profile in the Tethyan realm does not record this episode of high burial of organic carbon occurred in the Neuquén basin during the Tithonian and Berriasian but display a slightly decreasing trend between +2.5 and +1.5‰.
•High-resolution Tithonian-Berriasian δ13Ccarb curve in marine retro-arc setting.•Mixed carbonate-siliciclastic environment with thick TOC-rich succession.•δ13Ccarb trends controlled by alternating anoxia-dysoxia in well-stratified basin.•Local basinal negative δ13Ccarb values due to precipitation of authigenic carbonate.•Diagenetic & Corg burial processes produce trends that do not reflect global C cycle.
Severe global climate change led to the deterioration of environmental conditions in the oceans during the Toarcian Stage of the Jurassic. Carbonate platforms of the Western Tethys Ocean exposed in ...Alpine Tethyan mountain ranges today offer insight into this period of environmental upheaval. In addition to informing understanding of climate change in deep time, the effect of ancient carbon cycle perturbations on carbonate platforms has important implications for anthropogenic climate change; the patterns of early Toarcian environmental deterioration are similar to those occurring in modern oceans. This study focuses on the record of the early Toarcian Oceanic Anoxic Event (ca 183.1 Ma) in outcrops of the north‐west Adriatic Carbonate Platform in Slovenia. Amidst environmental deterioration, the north‐west Adriatic Platform abruptly transitioned from a healthy, shallow‐water environment with diverse metazoan ecosystems to a partially drowned setting with low diversity biota and diminished sedimentation. An organic carbon‐isotope excursion of −2.2‰ reflects the massive injection of CO2 into the ocean‐atmosphere system and marks the stratigraphic position of the Toarcian Oceanic Anoxic Event. A prominent dissolution horizon and suppressed carbonate deposition on the platform are interpreted to reflect transient shoaling of the carbonate compensation depth to unprecedentedly shallow levels as the dramatic influx of CO2 overwhelmed the ocean’s buffering capacity, causing ocean acidification. Trace metal geochemistry and palaeoecology highlight water column deoxygenation, including the development of photic‐zone anoxia, preceding and during the Toarcian Oceanic Anoxic Event. Ocean acidification and reduced oxygen levels likely had a profoundly negative effect on carbonate‐producing biota and growth of the Adriatic Platform. These effects are consistent with the approximate doubling of the concentration of CO2 in the ocean‐atmosphere system from pre‐event levels, which has previously been linked to a volcanic triggering mechanism. Mercury enrichments discovered in this study support a temporal and genetic link between volcanism, the Toarcian Oceanic Anoxic Event and the carbonate crisis.
Soil flooding creates composite and complex stress in plants known as either submergence or waterlogging stress depending on the depth of the water table. In nature, these stresses are important ...factors dictating the species composition of the ecosystem. On agricultural land, they cause economic damage associated with long-term social consequences. The understanding of the plant molecular responses to these two stresses has benefited from research studying individual components of the stress, in particular low-oxygen stress. To a lesser extent, other associated stresses and plant responses have been incorporated into the molecular framework, such as ion and ROS signaling, pathogen susceptibility, and organ-specific expression and development. In this review, we aim to highlight known or suspected components of submergence/waterlogging stress that have not yet been thoroughly studied at the molecular level in this context, such as miRNA and retrotransposon expression, the influence of light/dark cycles, protein isoforms, root architecture, sugar sensing and signaling, post-stress molecular events, heavy-metal and salinity stress, and mRNA dynamics (splicing, sequestering, and ribosome loading). Finally, we explore biotechnological strategies that have applied this molecular knowledge to develop cultivars resistant to flooding or to offer alternative uses of flooding-prone soils, like bioethanol and biomass production.
Piecing together the history of carbon (C) perturbation events throughout Earth’s history has provided key insights into how the Earth system responds to abrupt warming. Previous studies, however, ...focused on short-term warming events that were superimposed on longer-term greenhouse climate states. Here, we present an integrated proxy (C and uranium U isotopes and paleo CO2) and multicomponent modeling approach to investigate an abrupt C perturbation and global warming event (∼304 Ma) that occurred during a paleo-glacial state. We report pronounced negative C and U isotopic excursions coincident with a doubling of atmospheric CO2 partial pressure and a biodiversity nadir. The isotopic excursions can be linked to an injection of ∼9,000 Gt of organic matter–derived C over ∼300 kyr and to near 20% of areal extent of seafloor anoxia. Earth system modeling indicates that widespread anoxic conditions can be linked to enhanced thermocline stratification and increased nutrient fluxes during this global warming within an icehouse.
Plastic waste associated with disease on coral reefs Lamb, Joleah B; Willis, Bette L; Fiorenza, Evan A ...
Science (American Association for the Advancement of Science),
2018-Jan-26, 2018-01-26, 20180126, Letnik:
359, Številka:
6374
Journal Article
Recenzirano
Plastic waste can promote microbial colonization by pathogens implicated in outbreaks of disease in the ocean. We assessed the influence of plastic waste on disease risk in 124,000 reef-building ...corals from 159 reefs in the Asia-Pacific region. The likelihood of disease increases from 4% to 89% when corals are in contact with plastic. Structurally complex corals are eight times more likely to be affected by plastic, suggesting that microhabitats for reef-associated organisms and valuable fisheries will be disproportionately affected. Plastic levels on coral reefs correspond to estimates of terrestrial mismanaged plastic waste entering the ocean. We estimate that 11.1 billion plastic items are entangled on coral reefs across the Asia-Pacific and project this number to increase 40% by 2025. Plastic waste management is critical for reducing diseases that threaten ecosystem health and human livelihoods.
Pacific hagfish (Eptatretus stoutii) are an ancient agnathan vertebrate known to be anoxia tolerant. To study their metabolic organization and the role of the mitochondria in anoxia tolerance we ...developed a novel protocol to measure mitochondrial function in permeabilized cardiomyocytes and how this is affected by one hour of anoxia followed by reoxygenation. When measured at 10 °C the mitochondria had a respiration rate of 2.1 ± 0.1pmol/s/mg WW during OXPHOS with saturating concentrations of glutamate, malate, and succinate. This is comparatively low compared to other ectothermic species. The functional characteristics of the mitochondria were quantified with mitochondrial control ratios. These demonstrated that proton leak contributed to just under 50% of the oxygen flux, with the remainder going towards ATP phosphorylation. Finally, when the preparations were exposed to an anoxia-reoxygenation protocol there was no difference in respiration compared to that of a heart sample from the same animal maintained under normoxia for the same time. When Complex I alone or Complex I and II were stimulated following one hour of anoxia there was no decline in oxygen flux observed. However, if Complex II was activated alone there was a significant decline in respiration. This decrease was however also observed in the mitochondria maintained in normoxia for one hour. In conclusion, Pacific hagfish cardiac mitochondria demonstrated a low rate of oxygen consumption, a loosely coupled electron transfer system, and a resistance to one hour of anoxia.
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•First time that mitochondrial function has been measured in hagfish.•The respiration rate of mitochondria in permeabilized hagfish heart tissue is comparatively low compared to that of other ectothermic species.•Mitochondrial proton leak contributed to just under 40% of the O2 flux, with the remainder going towards ATP phosphorylation.•There was no difference in respiration between control preparations and those exposed to one hour of anoxia followed by reoxygenation.
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