Experimental dissolution of molybdenum-sulphides at low oxygen concentrations: A first-order approximation of late Archean atmospheric conditions

The abundance of atmospheric oxygen and its evolution through Earth's history is a highly debated topic. The earliest change of the Mo concentration and isotope composition of marine sediments are interpreted to be linked to the onset of the accumulation of free O2 in Earth's atmosphere. The O2 concentration needed to dissolve significant amounts of Mo in water is not yet quantified, however. We present laboratory experiments on pulverized and surface-cleaned molybdenite (MoS2) and a hydrothermal breccia enriched in Mo-bearing sulphides using a glove box setup. Duration of an experiment was 14 days, and first signs of oxidation and subsequent dissolution of Mo compounds start to occur above an atmospheric oxygen concentration of 72 ± 20 ppmv (i.e., 2.6 to 4.6 × 10−4 present atmospheric level (PAL)). This experimentally determined value coincides with published model calculations supporting atmospheric O2 concentrations between 1 × 10−5 to 3 × 10−4 PAL prior to the Great Oxidation Event and sets an upper limit to the molecular oxygen needed to trigger Mo accumulation and Mo isotope variations recorded in sediments. In combination with the published Mo isotope composition of the rock record, this result implies an atmospheric oxygen concentration prior to 2.76 Ga of below 72 ± 20 ppmv.

Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension

Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.

Effect of reduced oxygen tension and long-term mechanical stimulation on chondrocyte-polymer constructs

We have investigated the influence of long-term confined dynamic compression and surface motion under low oxygen tension on tissue-engineered cell-scaffold constructs. Porous polyurethane scaffolds (8 mm x 4 mm) were seeded with bovine articular chondrocytes and cultured under normoxic (21% O(2)) or hypoxic (5% O(2)) conditions for up to 4 weeks. By means of our joint-simulating bioreactor, cyclic axial compression (10-20%; 0.5 Hz) was applied for 1 h daily with a ceramic ball, which simultaneously oscillated over the construct surface (+/-25 degrees; 0.5 Hz). Culture under reduced oxygen tension resulted in an increase in mRNA levels of type II collagen and aggrecan, whereas the expression of type I collagen was down-regulated at early time points. A higher glycosaminoglycan content was found in hypoxic than in normoxic constructs. Immunohistochemical analysis showed more intense type II and weaker type I collagen staining in hypoxic than in normoxic cultures. Type II collagen gene expression was slightly elevated after short-term loading, whereas aggrecan mRNA levels were not influenced by the applied mechanical stimuli. Of importance, the combination of loading and low oxygen tension resulted in a further down-regulation of collagen type I mRNA expression, contributing to the stabilization of the chondrocytic phenotype. Histological results confirmed the beneficial effect of mechanical loading on chondrocyte matrix synthesis. Thus, mechanical stimulation combined with low oxygen tension is an effective tool for modulating the chondrocytic phenotype and should be considered when chondrocytes or mesenchymal stem cells are cultured and differentiated with the aim of generating cartilage-like tissue in vitro.

A 13,600-year diatom oxygen isotope record from the South Carpathians (Romania): Reflection of winter conditions and possible links with North Atlantic circulation changes

This study provides a continuous lateglacial and Holocene record of diatom silica oxygen isotope changes (delta O-18(DIAT)) in a subalpine lake sediment sequence obtained from the Retezat Mts (Taul dintre Brazi, 1740 m a.s.l.). This through-flow, shallow, high-altitude lake with a surface area of only 0.4 ha has short water residence time and is predominantly fed by snowmelt and rainwater. Its delta O-18(DIAT) record principally reflects the oxygen isotope composition of the winter and spring precipitation, as diatom blooms occur mainly in the spring and early summer. Hence, changes in delta O-18(DIAT) are interpreted as seasonal scale changes: in the amount of winter precipitation. Low oxygen isotope values (27-28.5 parts per thousand) occurred during the lateglacial until 12,300 cal BP, followed by a sharp increase thereafter. In the Holocene delta O-18(DIAT) values ranged from 29 to 31 parts per thousand until 3200 cal BP, followed by generally lower values during the late Holocene (27-30 parts per thousand). Short-term decreases in the isotopic values were found between 10,140-9570, 9000-8500, 7800-7300, 6300-5800, 5500-5000 and at 8015, 4400, 4000 cal BP. After 3200 cal BP a decreasing trend was visible with the lowest values between 3100-2500 and after 2100 cal BP The general trend in the record suggests that contribution of winter precipitation was generally lower between 11,680 and 3200 cal BP, followed by increased contribution during the last millennia. The late Holocene decrease in delta O-18(DIAT) shows good agreement with the speleothem delta O-18, lake level and testate amoebae records from the Carpathian Mountains that also display gradual delta O-18 decrease and lake level/mire water table level rise after 3200 cal BR Strong positive correlation with North Atlantic circulation and solar activity proxies, such as the Austrian and Hungarian speleothem records, furthermore suggested that short-term increases in the isotopic ratios in the early and mid Holocene are likely connectable to high solar activity phases and high frequency of positive North Atlantic Oscillation indexes that may have resulted in decreased winter precipitation in this region.

Human melanocytes can be isolated, propagated and expanded from plucked anagen hair follicles

Herein, we report a technically simple method for isolation and culture of human follicular melanocytes based on explant cultures of epilated hair follicles. This technique does not require any surgical intervention and allows the isolation and cultivation of follicular melanocytes from a comparatively small amount of raw material. Generally, 30-60 human anagen hair follicles have been plucked from the scalp of healthy donors and cultivated under low oxygen pressure (5%). After a short period of time cells of various types were growing out from the outer root sheath (ORS) of the hair follicles. Under the selected culture conditions, most of the cells other than melanocytes have been eliminated and a nearly 100% pure population of melanocytes has been achieved, as confirmed by immunohistochemical analyses for melanocyte-specific markers, for example, Tyrosinase-1, S-100 and premelanosomal antigens. These melanocytes derived from the ORS were proliferating for up to 2 months.

Hypoxic expansion promotes the chondrogenic potential of articular chondrocytes

For cell-based cartilage repair strategies, an ex vivo expansion phase is required to obtain sufficient numbers of cells needed for therapy. Although recent reports demonstrated the central role of oxygen for the function and differentiation of chondrocytes, a beneficial effect of low oxygen concentrations during the expansion of the cells to further improve their chondrogenic capacity has not been investigated.Therefore, freshly harvested bovine articular chondrocytes were grown in two-dimensional monolayer cultures at 1.5% and 21% O2 and redifferentiation was subsequently induced in three-dimensional micromass cultures at 1.5%, 5%, and 21% O2. Cells expanded at 1.5% O2 were characterized by low citrate synthase (aerobic energy metabolism)--and high LDH (anaerobic energy metabolism-activities,suggesting an anaerobic energy metabolism. Collagen type II mRNA was twofold higher in cells expanded at 1.5% as compared to expansion at 21% O2. Micromass cultures grown at 21% O2 showed up to a twofold increase in the tissue content of glycosaminoglycans when formed with cells expanded at 1.5% instead of 21% O2. However, no differences in the levels of transcripts and in the staining for collagen type II protein were observed in these micromass cultures. Hypoxia (1.5% and 5% O2) applied during micromass cultures gave rise to tissues with low contents of glycosaminoglycans only. In vivo, the chondrocytes are adapted to a hypoxic environment. Taking this into account, by applying 1.5% O2 in the expansion phase in the course of cell-based cartilage repair strategies, may result in a repair tissue with higher quality by increasing the content of glycosaminoglycans.

Regulation of mitochondrial function by hypoxia and inflammation in sepsis: A putative role for hypoxia inducible factor

Sepsis-related organ failure is the leading cause of mortality in European intensive care units (ICU). Although the inflammatory cascade of mediators in response to infection is well known, the relationships between regional inflammation, microvascular heterogeneity, hypoxia and hypoxia-inducible gene expression, and finally, organ dysfunction, are unknown. Growing evidence suggests that not only low oxygen supply to the tissues secondary to macrovascular and microvascular alterations, but also altered cellular oxygen utilization is involved in the development of multiorgan dysfunction [1]–[3]. Microbial products and innate and adaptive dysregulated immune response to infection directly affect parenchymal cells of organs and may contribute to multiorgan dysfunction.

Thermoreversible hyaluronan-based hydrogel supports in vitro and ex vivo disc-like differentiation of human mesenchymal stem cells

BACKGROUND CONTEXT The fate of human mesenchymal stem cells (hMSCs) supplied to the degenerating intervertebral disc (IVD) is still not fully understood and can be negatively affected by low oxygen, pH, and glucose concentration of the IVD environment. The hMSC survival and yield upon injection of compromised IVD could be improved by the use of an appropriate carrier and/or by predifferentiation of hMSCs before injection. PURPOSE To optimize hMSC culture conditions in thermoreversible hyaluronan-based hydrogel, hyaluronan-poly(N-isopropylacrylamide) (HA-pNIPAM), to achieve differentiation toward the disc phenotype in vitro, and evaluate whether preconditioning contributes to a better hMSC response ex vivo. STUDY DESIGN In vitro and ex vivo whole-organ culture of hMSCs. METHODS In vitro cultures of hMSCs were conducted in HA-pNIPAM and alginate for 1 week under hypoxia in chondropermissive medium alone and with the supplementation of transforming growth factor β1 or growth and differentiation factor 5 (GDF-5). Ex vivo, hMSCs were either suspended in HA-pNIPAM and directly supplied to the IVDs or predifferentiated with GDF-5 for 1 week in HA-pNIPAM and then supplied to the IVDs. Cell viability was evaluated by Live-Dead assay, and DNA, glycosaminoglycan (GAG), and gene expression profiles were used to assess hMSC differentiation toward the disc phenotype. RESULTS The HA-pNIPAM induced hMSC differentiation toward the disc phenotype more effectively than alginate: in vitro, higher GAG/DNA ratio and higher collagen type II, SOX9, cytokeratin-19, cluster of differentiation 24, and forkhead box protein F1 expressions were found for hMSCs cultured in HA-pNIPAM compared with those cultured in alginate, regardless of the addition of growth factors. Ex vivo, direct combination of HA-pNIPAM with the disc environment induced a stronger disc-like differentiation of hMSCs than predifferentiation of hMSCs followed by their delivery to the discs. CONCLUSIONS Hyaluronan-based thermoreversible hydrogel supports hMSC differentiation toward the disc phenotype without the need for growth factor supplementation in vitro and ex vivo. Further in vivo studies are required to confirm the suitability of this hydrogel as an effective stem cell carrier for the treatment of IVD degeneration.

Ocean (De)oxygenation Across the Last Deglaciation: Insights for the Future

Anthropogenic warming is expected to drive oxygen out of the ocean as the water temperature rises and the rate of exchange between subsurface waters and the atmosphere slows due to enhanced upper ocean density stratification. Observations from recent decades are tantalizingly consistent with this prediction, though these changes remain subtle in the face of natural variability. Earth system model projections unanimously predict a long-term decrease in the global ocean oxygen inventory, but show regional discrepancies, particularly in the most oxygen-depleted waters, owing to the complex interplay between oxygen supply pathways and oxygen consumption. The geological record provides an orthogonal perspective, showing how the oceanic oxygen content varied in response to prior episodes of climate change. These past changes were much slower than the current, anthropogenic change, but can help to appraise sensitivities, and point toward potentially dominant mechanisms of change. Consistent with the model projections, marine sediments recorded an overall expansion of low-oxygen waters in the upper ocean as it warmed at the end of the last ice age. This expansion was not linearly related with temperature, though, but reached a deoxygenation extreme midway through the warming. Meanwhile, the deep ocean became better oxygenated, opposite the general expectation. These observations require that significant changes in apparent oxygen utilization occurred, suggesting that they will also be important in the future.

Intratumoral hypoxia as the genesis of genetic instability and clinical prognosis in prostate cancer

Intratumoral hypoxia is prevalent in many solid tumors and is a marker of poor clinical prognosis in prostate cancer. The presence of hypoxia is associated with increased chromosomal instability, gene amplification, downregulation of DNA damage repair pathways, and altered sensitivity to agents that damage DNA. These genomic changes could also lead to oncogene activation or tumor suppressor gene inactivation during prostate cancer progression. We review here the concept of repair-deficient hypoxic tumor cells that can adapt to low oxygen levels and acquire an aggressive "unstable mutator" phenotype. We speculate that hypoxia-induced genomic instability may also be a consequence of aberrant mitotic function in hypoxic cells, which leads to increased chromosomal instability and aneuploidy. Because both hypoxia and aneuploidy are prognostic factors in prostate cancer, a greater understanding of these biological states in prostate cancer may lead to novel prognostic and predictive tests and drive new therapeutic strategies in the context of personalized cancer medicine.

Interplay between receptor tyrosine kinases and hypoxia signaling in cancer.

Deregulated signaling via receptor tyrosine kinase (RTK) pathways is prevalent in numerous types of human cancers and is commonly correlated with worst prognosis, resistance to various treatment modalities and increased mortality. Likewise, hypoxic tumors are often manifested by aggressive mode of growth and progression following an adaptive genetic reprogramming with consequent transcriptional activation of genes encoding proteins, which support tumor survival under low oxygen-related conditions. Consequently, both the hypoxia-inducible factor (HIF) system, which is the major mediator of hypoxia-related signaling, and numerous RTK systems are considered critical molecular targets in current cancer therapy. It is now evident that there is an intricate molecular crosstalk between RTKs and hypoxia-related signaling in the sense that hypoxia can activate expression of particular RTKs and/or their corresponding ligands, while some RTK systems have been shown to trigger activation of the HIF machinery. Moreover, signaling regulation of some RTK systems under hypoxic conditions has also been documented to take place in a HIF-independent manner. With this review we aim at overviewing the most current observations on that topic and highlight the importance of the potential co-drugging the HIF system along with particular relevant RTKs for better tumor growth control.

Assessment of bovine adipose-derived stem cells osteogenic and adipogenic differentiation in Normoxic and hypoxic conditions

Background: The differentiation of ADSC is regulated by many factors, including oxygen tensions. Evidences have suggested that low oxygen tension or hypoxia is involved in the osteogenic, adipogenic differentiations of MSCs. Expansion and induction of ADSCs under hypoxia generally result in enhanced osteogenic, differentiation. Therefore, we analyzed bovine ADSC differentiations in Normoxia and hypoxia conditions Methodology: Recently (<8h) cow tail from a slaughterhouse, take out some fat from the tail and fat cells was isolated by using for isolation of ADSC protocol, the expansion cells were put into osteogenic and adipogenic medium for 3 weeks in hypoxia and normoxia conditions separately and characterized by Von kossa, Alizarin red and Oil red O staining and further by using real-time PCR by using primers of osteocalcin, Collagen type1, cbfa1/runx2, ALP, ostepontin, osteonectin, BMP2, BMP24, BMP27, noggin, gremlin, Nestin and HIF1A,VEGFA,PPARG,Leptin. Results: Our experiment results show hypoxia promotes osteogenesis but suppresses adipogenesis.

Angiopoietin-1 receptor Tie2 distinguishes multipotent differentiation capability in bovine coccygeal nucleus pulposus cells.

BACKGROUND The intervertebral disc (IVD) has limited self-healing potential and disc repair strategies require an appropriate cell source such as progenitor cells that could regenerate the damaged cells and tissues. The objective of this study was to identify nucleus pulposus-derived progenitor cells (NPPC) and examine their potential in regenerative medicine in vitro. METHODS Nucleus pulposus cells (NPC) were obtained from 1-year-old bovine coccygeal discs by enzymatic digestion and were sorted for the angiopoietin-1 receptor Tie2. The obtained Tie2- and Tie2+ fractions of cells were differentiated into osteogenic, adipogenic, and chondrogenic lineages in vitro. Colony-forming units were prepared from both cell populations and the colonies formed were analyzed and quantified after 8 days of culture. In order to improve the preservation of the Tie2+ phenotype of NPPC in monolayer cultures, we tested a selection of growth factors known to have stimulating effects, cocultured NPPC with IVD tissue, and exposed them to hypoxic conditions (2 % O2). RESULTS After 3 weeks of differentiation culture, only the NPC that were positive for Tie2 were able to differentiate into osteocytes, adipocytes, and chondrocytes as characterized by calcium deposition (p < 0.0001), fat droplet formation (p < 0.0001), and glycosaminoglycan content (p = 0.0095 vs. Tie2- NPC), respectively. Sorted Tie2- and Tie2+ subpopulations of cells both formed colonies; however, the colonies formed from Tie2+ cells were spheroid in shape, whereas those from Tie2- cells were spread and fibroblastic. In addition, Tie2+ cells formed more colonies in 3D culture (p = 0.011) than Tie2- cells. During expansion, a fast decline in the fraction of Tie2+ cells was observed (p < 0.0001), which was partially reversed by low oxygen concentration (p = 0.0068) and supplementation of the culture with fibroblast growth factor 2 (FGF2) (p < 0.0001). CONCLUSIONS Our results showed that the bovine nucleus pulposus contains NPPC that are Tie2+. These cells fulfilled formally progenitor criteria that were maintained in subsequent monolayer culture for up to 7 days by addition of FGF2 or hypoxic conditions. We propose that the nucleus pulposus represents a niche of precursor cells for regeneration of the IVD.

Incidence of low central venous oxygen saturation during unplanned admissions in a multidisciplinary intensive care unit: an observational study

INTRODUCTION: It has been shown that early central venous oxygen saturation (ScvO2)-guided optimization of hemodynamics can improve outcome in septic patients. The early ScvO2 profile of other patient groups is unknown. The aim of this study was to characterize unplanned admissions in a multidisciplinary intensive care unit (ICU) with respect to ScvO2 and outcome. METHODS: Ninety-eight consecutive unplanned admissions to a multidisciplinary ICU (median age 63 [range 19 to 83] years, median Simplified Acute Physiology Score [SAPS II] 43 [range 11 to 92]) with a clinical indication for a central venous catheter were included in the study. ScvO2 was assessed at ICU arrival and six hours later but was not used to guide treatment. Length of stay in ICU (LOSICU) and in hospital (LOShospital) and 28-day mortality were recorded. RESULTS: ScvO2 was 70% +/- 12% (mean +/- standard deviation) at admission and 71% +/- 10% six hours later (p = 0.484). Overall 28-day mortality was 18%, LOSICU was 3 (1 to 28) days, and LOShospital was 19 (1 to 28) days. Patients with an ScvO2 of less than 60% at admission had higher mortality than patients with an ScvO2 of more than 60% (29% versus 17%, p < 0.05). Changes in ScvO2 during the first six hours were not predictive of LOSICU, LOShospital, or mortality. CONCLUSION: Low ScvO2 in unplanned admissions and high SAPS II are associated with increased mortality. Standard ICU treatment increased ScvO2 in patients with a low admission ScvO2, but the increase was not associated with LOSICU or LOShospital.